KR100818817B1 - A light control element and a display incorporating the same - Google Patents

Abstract

The light control element 15 emits light in a first polarization state in a first emission angle range, and emits light in a second polarization state different from the first polarization state in a second emission angle range larger than the first emission angle range. Let go. The light control element 15 is opaque or substantially opaque to light traveling in the direction of the first range having the first polarization state, and having a first polarization state and having a second range different from the direction of the first range. It may not be substantially opaque to light traveling in the direction of and may not be substantially opaque to the second polarization state. The angular range of light exiting from the light control element can be varied by changing the polarization state of light incident on or exiting from the element. The light control element can be integrated into the display. Alternatively, it can be used as a light control device, with a polarization switch.

Light control element, polarizer, polarization switch, transmission material, wave plate,

Description

Optical control device, optical control device and display including same, and method for manufacturing optical control device {A LIGHT CONTROL ELEMENT AND A DISPLAY INCORPORATING THE SAME}

1 shows a known light control film having a louver structure.

2 shows a known light control film having a multilayer structure.

3 illustrates the principle of a parallax-barrier autostereoscopic display.

4 shows one possible structure of the polarization-dependent light control element of the present invention.

Fig. 5 shows another structure of the polarization-dependent light control element of the present invention.

6 shows a display of the present invention that can switch between private and public viewing modes.

7 illustrates the operation of the display of FIG. 6;

(A)-(c) is a figure which shows the manufacturing method of the polarization-dependent light control element of the display of FIG.

(A)-(c) is a figure which shows the manufacturing method of another polarization-dependent light control element.

10 (a)-(d) show two ways of cutting grooves in a transparent material for the construction of a polarization-dependent light control element.

11 (a)-(b) show two alternatives for applying an alignment layer to the liquid crystal material of the polarization-dependent light control element.

12 (a)-(b) show how a polarization-dependent light control element can be constructed by removing part of an absorbing material film.

13 (a)-(f) show yet another two methods for the construction of the polarization-dependent light control element.

14 shows another display capable of switching between private and public viewing modes.

15 (a)-(b) illustrate the operation of the display of FIG.

16 shows a display of the present invention that can switch between four viewing modes.

17 (a)-(f) illustrate three operating modes of the display of FIG.

18 illustrates a display of the present invention capable of operating in an autostereoscopic personal display mode or a common display mode.

FIG. 19A shows another structure for the light control element of the display of FIG. 18; FIG.

FIG. 19B is a diagram showing manufacture of the light control element of FIG. 19A. FIG.

20 shows a display of the present invention that can present different personal images to each of two observers.

FIG. 21 shows a display of the present invention comprising a polarization-dependent light control element switchable by control of liquid crystal within the device.

22 (a)-(b) illustrate the principle of operation of one possible configuration of the display of FIG. 21;

23 (a)-(b) illustrate the principle of operation of a possible second configuration of the display of FIG. 21;

Figures 24 (a)-(b) show the principle of operation of a possible third configuration of the display of figure 21;

25A and 25B show another light control element of the present invention.

FIG. 25C is a side view of a display including the light control element of FIG. 25B. FIG.

26 is a perspective view of another light control element of the present invention.

27 (a) to 27 (b) show the principle of the light control element of FIG. 21 and the light control element according to another embodiment of the present invention.

28A, 28B, and 28C show still another light control element of the present invention;

29 and 30 show variations in the output angle range of the light control element of the present invention.

31A and 31B are a cross-sectional view and a plan view of a light control device according to still another embodiment of the present invention.

32 is a cross-sectional view of a display including a light control element according to another embodiment of the present invention.

Fig. 33 shows the effect of refractive index mismatch on the light control element of the present invention.

<Explanation of symbols for main parts of drawing>

16: area

17: transparent material

22: panel

23: polarizer

24: wave plate

The present invention relates to a light control element capable of controlling the angular range of light emitted from itself. The invention also relates to a light control device comprising such a light control element and capable of controlling to vary the angular range of the light emitted from it, and a display comprising such a light control device.

For example, electronic display devices, such as monitors used in computers and screens embedded in mobile phones and other portable information devices, are designed to have a viewing angle as wide as possible, so that images displayed by the display device are displayed. It is common to allow to see at many different viewing locations. However, there are some cases where it is desirable to see the image displayed by the display device only in a narrow range of viewing angles. For example, a person using a portable computer on a crowded train may want to reduce the viewing angle range of the computer's display screen so that documents displayed on the computer screen are not read by other passengers in the train. . For this reason, considerable effort is being made to develop an electrically switchable display device between the two modes of operation, where the display device has a wide viewing angle for general use in the 'public' display mode. The display device may be switched to a 'private' display mode having a narrow angle of view so that personal information may be displayed in a public place without being visible to anyone other than the user of the display device.

Many devices are known that limit the angle or location range in which the display can be viewed.

U. S. Patent No. 6,552, 850 discloses a method for displaying personal information on an automated teller machine (ATM). The light emitted by the display of the automated teller machine has a fixed polarization state, and the automated teller machine and its user are sheet polarizers that absorb light in the fixed polarization state but transmit light in the orthogonal polarization state. Surrounded by a large screen made. People passing by can see the user and the automated teller machine, but not the information displayed on the screen of the automated teller machine.

One known device for controlling the direction of light is the 'louvred' film shown in FIG. This film 1 is composed of alternating transparent layers 2 and opaque layers 3 provided to have a similar arrangement as the Venetian blinds. The film 1 operates on the same principle as the Venetian blinds and, as shown in the optical path 4 of FIG. 1, the light travels in a direction parallel to or almost parallel to the opaque layer 3. Allow to pass through the film. However, as shown in the optical path 5 of FIG. 1, light traveling at a wide angle with respect to the plane of the opaque layer 3 is incident on and absorbed by one of the opaque layers. Layers 2 and 3 may be perpendicular to the surface of film 1 as shown in FIG. 1, or may be at any other angle with respect to the surface of film 1.

A louver film of the type shown in FIG. 1 can be made by stacking a plurality of sheets alternately provided with a transparent material and an opaque material, and then slice-cutting the resulting block perpendicular to the layers. This method is known several years ago and is disclosed in US Pat. Nos. 2,053,173, 2,689,387, and 3,031,351.

Other manufacturing methods are also known. For example, US patent RE27617 describes a method of continuously cutting louver film from cylindrical billets of laminated layers. U. S. Patent No. 4,766, 023 discloses a method by which the optical quality and mechanical strength of the resulting film can be improved by coating the film with UV-curable monomers and then exposing the film to UV radiation. US Pat. No. 4,764,410 describes a similar method of bonding a louver sheet to a covering film using a UV-curable material.

There is another method of making a film having similar characteristics to the louver film. For example, US Pat. No. 5,147,716 describes a light control film comprising a plurality of elongated particles aligned in a direction perpendicular to the plane of the film. Thus, light rays making a wide angle to this direction are strongly absorbed, while light rays propagating in this direction are transmitted.

2 shows another example of a light control film 6, as described in US Pat. No. 5,528,319. The film 6 has a transparent body 7 embedded in its part with opaque regions 8 extending generally parallel to the plane of the film 6. The opaque regions 8 are arranged to form a stack 9, each stack 9 being spaced apart from an adjacent stack. The opaque region 8 blocks the transmission of light passing through the film in a certain direction (eg direction 1 of FIG. 2) while allowing transmission of light in another direction (eg direction 2 of FIG. 2).

Prior art light control films may be located in front of the display panel or between the transparent display panel and its backlight to limit the range of angles at which the display can be viewed. In other words, prior art light control films put the display into a 'personal' mode. However, none of the prior art light control films have the ability to switch off the personal mode function in order to be able to view the display at a wide angle.

It is reported for a display that can switch between public mode (viewing angle is wide angle) and private mode (observation angle is narrow angle). For example, in US Patent Application 2002/0158967, a light control film may be positioned on the front of the display to provide a personal mode, or mechanically retracted into a holder behind or to the side of the display to provide a common mode. It has been proposed to movably mount the light control film on the display. This method has the disadvantage of including a movable part which can break down or be damaged during use and increase the volume of the display.

The method of switching the display panel from the common mode to the personal mode without moving parts includes mounting a light control film behind the display panel and a diffuser that can be switched on and off electronically between the light control film and the display panel. To deploy. When the diffuser is inactive, the light control film limits the range of the viewing angle, so the display is in personal mode. When the diffuser is switched on, when light in the narrow angle range emitted from the light control film is incident on the diffuser, the diffuser serves to increase the angular range of light, that is, the diffuser cancels the effect of the light control film. . Thus, the display is irradiated with light moving over a wide angle range so that the display operates in a common mode. Also, the same effect can be achieved by mounting the light control film in front of the display panel and placing the switchable diffuser in front of the light control film.

Switchable privacy devices of the type described above are disclosed in US Pat. Nos. 5,831,698, 6,211,930, and 5,877,829. However, these patents indicate that the light control film always absorbs a significant portion of the light incident on it, whether the display is in shared mode or personal mode. Thus, displays are inherently inefficient in light use. In addition, since the diffuser diffuses light through wide angle in common mode, these displays are darker in common mode than in private mode (unless the backlight is brighter for compensation when the display is operating in common mode).

Another disadvantage of these display devices relates to their power consumption. These devices often use a switchable polymer-dispersed liquid crystal diffuser that does not diffuse when no voltage is applied across the liquid crystal layer and is switched on (in diffusion) by voltage application. . As such, in order to obtain a common operating mode, it is necessary to apply a voltage across the diffuser so that the diffuser is switched on. Thus, more power is consumed in shared mode than in private mode. This is a common mode most of the time and is a disadvantage for mobile devices with limited battery power.

Another method for manufacturing switchable public / private displays is disclosed in US Pat. No. 5,825,436. The structure of the light control device disclosed in this patent is similar to the louver film of FIG. However, each of the opaque elements 3 in the louver film of FIG. 1 has been replaced by a liquid crystal cell which can be electrically switched from an opaque state to a transmissive state. The light control device is disposed in front of or behind the display panel. If the cell is opaque, the display operates in private mode, and if the cell is transparent, the display operates in common mode.

One of the major drawbacks of this device is the cost and difficulty of producing a liquid crystal cell into a suitable shape. A second disadvantage is that in the personal mode, the light rays can be incident at an angle passing first through the transparent material and then through the portion of the liquid crystal cell. Such light rays may not be completely absorbed by the liquid crystal cell, thereby reducing the privacy of the display device.

Stereoscopic display achieves a three-dimensional effect by allowing the user's left eye to view a left eye image of a pair of stereoscopic image images and a right eye to view a right eye image. In stereoscopic display, this is done without the user wearing specially designed glasses. Displays that can achieve this have been known for decades, and are described, for example, in the 'Stereoscopy' book by N. A. Valyus (Focal Press, 1966). One widely used method in electronic displays is to use parallax barriers or other types of parallax optics. 3 (a) and 3 (b) show a plan view of this type of autostereoscopic image display.

In the display 10 of FIGS. 3A and 3B, the parallax barrier 11 is disposed in proximity to the image display panel 12. The parallax barrier may be located in front of the display panel 12 as shown in FIG. 3A or behind the display panel as shown in FIG. 3B. The parallax barrier 11 comprises an aperture or transparent portion 13 separated by an opaque portion 14. As schematically shown in FIGS. 3A and 3B, a left eye image and a right eye image, which are two interlaced images, are displayed on an image display panel, these figures Where the labels "L" and "R" represent pixels displaying a left eye image and a right eye image, respectively. When the user is in the proper position, the parallax barrier 11 prevents light passing through the pixels displaying the right eye image of the display from being seen through the left eye of the observer, and passes through the pixels displaying the left eye image of the display. Prevents light from being seen through the observer's right eye. In this way, the viewer perceives a three-dimensional image.

Using the same method, a display can be manufactured that allows two or more different users at different locations to view different images. This is called a 'dual-view' display. The dual observation display is in principle the same as an automatic stereoscopic image display, but displays two or more independent images rather than the left and right eye images of a stereoscopic image pair, the two or more images being multiple observers rather than the right and left eyes of one observer. The display is different so that it can be seen by the user.

The basic design of parallax barriers is well known and described, for example, by Valyus (described above). Methods for optimizing barrier design are described in "IEICE Transactions on Elctronics", vol. E83-C, no. 10, pp. 1632-1639 (2000), described by H. Yamamoto and others co-workers.

One of the problems with using parallax barriers is that parallax barriers reduce the resolution (number of pixels in an image) of an image by one half (more if more than two observed images are displayed). This is the same when using a display to represent a two-dimensional image, i.e. when the same image appears in both eyes. To avoid this problem, a switchable display has been developed which can disable or switch off the parallax barrier when displaying a two-dimensional image using the display. Such switchable parallax barrier displays are described, for example, in US Pat. No. 5,969,850, which discloses how a liquid crystal device can be used to create a switchable parallax barrier, and a patterned retarder and a switchable single wavelength plate ( US Pat. No. 6,055,103, which describes another switchable parallax barrier using a wave-plate.

Another disadvantage of the multiple viewing directional display of the type shown in FIGS. 3A and 3B is that the parallax barrier 11 must be carefully aligned with the display panel 12 in order to achieve a suitable 3D effect. Has This leads to an increase in manufacturing costs. The resolution of the display is also reduced to 1/2 when operating in the three-dimensional mode, as described above.

The second type of autostereoscopic image display avoids these drawbacks by displaying images of the left and right eyes at various points in time. For each image the full resolution of the display is used. The image is transferred to several locations using a directional backlighting system. In the first time frame, the backlight is switched such that it passes light that has passed through the display panel towards the viewer's left eye so that the left eye image is displayed. In the next time frame, the backlight is switched so that it passes the light that has passed through the display panel to the observer's right eye so that the right eye image is displayed. This sequence repeats quickly, so no flicker is detected in the image. An example of this type of display is disclosed in US Pat. No. 5,132,839. This configuration can also be used for dual observation display. A disadvantage of this type of display is that the switchable backlighting system is generally complex and expensive, which adds to the manufacturing costs.

A first aspect of the invention includes a light control element, the first angle output range and the first angle output range of the output light having a first polarization state on at least a portion of the light control element area, the first polarization state being equal to or greater than the first polarization state. Has a second angular output range of output light having a different second polarization state. The angular output range is a characteristic of the light control element. The output from this element is determined primarily by the polarization component output from the light control element, and subsequently by the output angle range of the light control element for each corresponding polarization component.

The light control element may have at least some of its area having a first polarization state and transmit or hardly transmit light traveling in the direction of the first range, having a first polarization state and different from the direction of the first range. The light traveling in the direction of the second range can be almost transmitted, and the light in the second polarization state can be transmitted.

When such a polarization-dependent light control element is located behind or in front of a transmitted display image illuminated with light in a first polarization state, the light control element limits the angular range of the light output and the image is narrowed. Displayed in degrees to allow a personal display mode to be obtained. However, when the display is illuminated with light in the second polarization state, the image is displayed in a larger angular range, thereby providing a common display mode. Switching between the common display mode and the personal display mode is performed simply by changing the polarization state of the light incident on or displayed from the displayed image and thus switching between the public display mode and the personal display mode. Can be done without a movable part. Another advantage is that in the common mode, since little or no light is absorbed by the light control element, the light efficiency is high, so that the light control element of the present invention can be produced easily and economically.

The light control element of the present invention can also be used in an emissive or reflective image. In this case, the light control element must be located between the image and the viewer.

The second polarization state may be orthogonal to the first polarization state. The two polarization states can be linear polarization states.

The light control element may comprise a plurality of first regions that transmit or transmit little or no light in the first polarization state, and wherein each pair of adjacent first regions is a first polarization. They are spaced apart from each other by a material having transparency to light in a state and light in a second polarization state.

Each of the first regions may extend substantially parallel to a direction crossed with a plane of the display device. Alternatively, each of the first regions may extend substantially parallel to a direction perpendicular to the plane of the display device.

The light control element includes a substrate which transmits light in the first polarization state and light in the second polarization state, a plurality of recesses in the substrate, and each recess, so as not to transmit light in the first polarization state. With little transmission, the light in the second polarization state can comprise a material that transmits.

Alternatively, the light control element may be disposed in a substrate that transmits or transmits light in a first polarization state but transmits light in a second polarization state, a plurality of recesses in each of the substrates, and a first polarization state. The light in and the light in the second polarization state may comprise a material that transmits.

Each of the first regions may extend substantially parallel to the plane of the light control element, which regions may be arranged in a plurality of stacks of two or more elements, the stacks may be laterally spaced apart from each other, Each pair is separated by a material that transmits light in a first polarization state and light in a second polarization state.

The light control element comprises a personal mode on at least a portion of the light control element area having a first angular output range for light in a first polarization state and a second angular output range for light in a second polarization state; Switchable between common modes having a third angular output range above the first angular output range for light in the first polarization state on at least a portion of the. In this embodiment, the light control element is an active light control element capable of switching between the common mode and the personal mode to reduce the output angular range (for light in a specific polarization state). Rather than changing from the common mode to the private mode by switching the polarization state of the light passing through the light control element as in the previous embodiment, the light control element itself is switched to obtain the common mode or the private mode as desired.

The light control element is also switchable to a second personal mode having an angular output range for light having a first polarization state that is above the first angular output range but below the third angular output range.

Each of the first regions may be switched between a first state that does not transmit light in the first polarization state and a second state that transmits light in the first polarization state. In the second state, the light control element transmits light in two polarization states. The light control element can switch between the common mode and the private mode by switching the first region between the first state and the second state.

The light control element may further comprise a plurality of second regions, each pair of adjacent second regions being separated from each other by a material transmitting light in the first polarization state and light in the second polarization state, wherein Each of the second regions is switchable between a third state that does not transmit light in the second polarization state and a fourth state that transmits light in the second polarization state substantially. Such a light control element may have a first personal mode having an output range of narrow angles along one direction and a second personal mode having an output range of narrow angles along the other direction.

The first regions may be provided in one or more first areas of the light control element, and the second regions may be provided in one or more second areas of the light control element, and the first area and the second area do not overlap. Alternatively, the first region may be disposed on the first region. The first regions may extend substantially perpendicular to the second regions.

Each region may comprise a linear polarizer material.                         

Each of the first regions may comprise a linear polarizer material in the first state. Each of the second regions may comprise a linear polarizer material in a third state.

Each region may comprise a liquid crystal material.

The liquid crystal material may be a guest-host liquid crystal material. Such liquid crystal materials include, for example, "guest" materials, which are dyes dissolved in or chemically added to liquid crystal "host" materials.

The angular output range for light in at least one polarization state can vary over an area of the light control element. For example, the angular output range can be increased toward the opposite side edges of the light control element.

A second aspect of the present invention provides a light control device including the above-described light control element and a polarization switch disposed in an optical path passing through the light control element. The angular range of output light can be changed by using a polarization switch to control the polarization state of light incident on or output from the display. The angle range of the output light can be changed without requiring any moving parts.

The polarization switch may comprise a switchable wave plate and may comprise a switchable half wave plate arranged in series with the linear polarizer.

A third aspect of the invention provides a display comprising the above light control element.

The display may further comprise a polarization switch disposed in the optical path via the light control element. The angular range of light output from the display can be changed by controlling the polarization state of light incident on or output from the display using a polarization switch. The angle range of the light output from the display can be changed without requiring any moving parts.

The polarization switch may comprise a switchable wavelength plate. The polarization switch can also include a switchable half-wave plate disposed in series with the linear polarizer.

The light control element can form parallax optics for light in the first polarization state during use, such that the display can operate as a multi-view directional display. Thereby, the display can operate in the personal automatic stereoscopic image display mode.

A fourth aspect of the present invention provides a display comprising the first light control element described above, the second light control element described above, and a first polarization switch, wherein the first light control element for light in the first polarization state is provided. The angular output range is different from the angular output range of the second light control element with respect to the light in the first polarization state. Thus, for example, the angular range of light output from the display can be limited in both vertical and horizontal directions.

 The display may further include a second polarization switch. In this way, each of the light control elements can be operated independently, providing four kinds of display modes.

A fifth aspect of the present invention is the first light control element defined above; Opaque or nearly opaque for light having a second polarization state and moving in a direction of the third range, but not opaque for light traveling in a fourth range of directions that is different from the direction of the third range with a second polarization state A second light control element that is substantially opaque to light having a first polarization state; And a polarization switch disposed in a path of light between the first and second light control elements. In this form, one or the other of the optical control elements can be enabled at any time.

The first light control element generally outputs light of a first polarization in an angular range aligned in a first direction, and the second light control element is generally second in an angular range aligned in a second direction different from the first direction. The polarized light can be output.

The display may further comprise user manipulation means for switching the light control element between the first mode and the second mode. Alternatively, the light control element can automatically operate to switch between a first mode and a second mode of performing a predetermined operation in the display.

The predetermined operation may be the display of information classified as public or private such that the light control element is switched to common mode or private mode, respectively.

The display may include means for indicating when the light control element is in the personal mode. Alternatively, the display may be operable to display an indication that the light control element is in private mode.

When a polarization switch is used, the polarization switch may comprise a liquid crystal cell. This causes the polarization rotation effect to be switched on or off by applying an appropriate electric field to the liquid crystal cell.

The liquid crystal cell may use a Freedericksz liquid crystal mode. This has the advantage that its optical properties are weakly dependent on the viewing angle.

Alternatively, the liquid crystal cell can use twisted nematic (TN) mode. This has the advantage that the optical properties are weakly dependent on the wavelength of the light. The TN cell may operate in a system such as a Gooch-Tarry minima or a Maugin limit where the wavelength dependence of the optical properties of the cell is minimized.

Alternatively, the liquid crystal cell can use a vertically aligned nematic mode. In this case, the polarization rotation effect is switched on by applying an electric field, and there is no polarization rotation effect when no power is applied. This has the advantage of minimizing power consumption in any application.

The feature of the polarization switch can be optimized to minimize the leakage of light in the direction to block transmission through the system.

A sixth aspect of the present invention provides a method of stacking a plurality of polarizing sheets, each of the polarizing sheets including a polarizing layer and at least one light transmitting substrate; And attaching each polarizing sheet to its neighboring polarizing sheet (s). If the polarizing sheet has a suitable size, the stack can constitute the light control element of the present invention.

The method includes disposing a light curable adhesive over the first polarizing sheet, stacking the second polarizing sheet over the first polarizing sheet; And attaching the first polarizing sheet to the second polarizing sheet by irradiating the adhesive to cure the adhesive. This is a convenient way to attach the layers of the stack to each other and other methods can be used if desired.

The method may include providing a light transmitting layer between each pair of neighboring polarizing sheets. This allows the separation between the polarization regions of the light control element to be the same at the desired interval.

The method may further include removing selected regions of the polarizing layers of all the polarizing sheets of the stack. This method can be used to produce light control devices in which the polarization regions extend generally parallel to the plane of the device.

The method may further comprise cutting the stack into slices, wherein the cutting direction may be perpendicular to the plane of the polarizing sheet, or alternatively in another direction not parallel to the plane of the polarizing sheet. Each cut portion of the stack may constitute the light control element of the present invention.

According to a seventh aspect of the present invention, there is provided a method of removing a selected region of a polarizing layer of a first polarizing sheet, the polarizing sheet comprising a light transmitting substrate and a polarizing layer, stacking a second polarizing sheet on the first polarizing sheet, And removing the selected region of the polarizing layer of the second polarizing sheet. This method can also be used to make light control devices in which the polarization regions are generally parallel to the plane of the device.

An eighth aspect of the present invention provides a method for manufacturing a light control element comprising forming a plurality of recesses in a light transmitting substrate, and providing a polarizing material in the recesses.

A ninth aspect of the present invention provides a method of manufacturing a light control element comprising forming a plurality of recesses in a substrate formed of a polarizing material, and providing a light transmitting material in the recesses.                         

Forming the recess in the substrate may further include selectively irradiating the substrate.

Preferred embodiments of the present invention will be described as illustrative examples with reference to the accompanying drawings.

In the drawings, like reference numerals refer to like elements.

4 is a schematic perspective view of the light control element 15 of the present invention. The light control element comprises a plurality of regions 16 that are opaque or nearly opaque to light with a particular polarization state but are transparent to orthogonal polarization states. The light control element of FIG. 4 makes each region 16 with linear polarizing material such that each region 16 is opaque to plane-polarised light having a polarization direction that intersects the transmission axis of the region. It is convenient to implement. Thus, the regions 16 are referred to as "polarization regions", and the direction of the arrow on each region 16 in FIG. 4 indicates the direction of the transmission axis of that region. As can be seen, the polarization regions 16 are arranged such that their transmission axes are substantially parallel to each other.

In FIG. 4, the polarization regions 16 have a plate shape of a substantially constant thickness. The plates 16 are also arranged such that they are substantially parallel to each other and the neighboring plates are separated by a layer of permeable material 17. 4, the polarizing plates are arranged such that their transmission axis is substantially parallel to the upper surface of the element 15, but the present invention is not limited thereto. In fact, the present invention is not limited to the plate-shaped polarization region. The polarization regions can have any shape as long as they are effective at outputting light in one polarization state having a wide angle range and light in orthogonal polarization state having a narrow angle range.

Consider the light propagating in the z direction through the light control element 15 in FIG. 4. Here, the x, y and z directions are represented by axes in the figure. Light plane-polarized in the x direction is not absorbed by the polarization regions 16 because the polarization plane of the light is parallel to the transmission axis of the polarization region. Thus, the light polarized in the x direction, as shown by the light paths 18 and 19 in FIG. 4, is propagated along the z direction and when propagated at a predetermined angle with respect to the z direction. Pass 15).

Light that is surface polarized in the y direction and travels along the z direction or close to the z direction can pass through layers 17 of transparent material as indicated by the light path 18. However, light polarized in the y direction and incident on the light control element 15 at a predetermined angle with respect to the z direction is incident on one of the polarization regions 16, and the transmission direction of the polarization region is the polarization of the light. Because it is orthogonal to the direction, the polarization region becomes opaque to light. This is represented by the light path 20, which represents the light incident on the light control element 15 from below, as shown in FIG. 4, and is absorbed by one of the polarization regions 16. .

Therefore, the light control element 15 of FIG. 4 has a characteristic of being opaque to light in one polarization state moving in the direction of the first range but not opaque to light in the one polarization state moving in the direction of the other range (FIG. A particular embodiment of 4 is opaque to light polarized in the y direction moving at a predetermined angle with respect to the z direction, but transmits surface polarized light along the z direction or in the y direction moving close to the z direction). Moreover, the light control element 15 does not absorb light in the orthogonal polarization state (the element in FIG. 4 does not absorb light plane-polarized in parallel to the x direction). Thus, the light control element 15 of FIG. 4 can be considered to be a polarization dependent control element, since light in one polarization state is output in a wide angle range while orthogonal polarized light is output in a narrow angle range ( 4, light polarized along the y axis is transmitted only in a direction parallel to the xz plane). The angular range of the light output from the light control element 15 can be controlled by selecting the polarization of the light passing through the element using an appropriate polarization switch.

(It should be noted that the above description applies to the case of a perfect polarizer. Any real polarizer will inevitably transmit a small amount of polarization components to be blocked and will absorb a small amount of polarization components to be transmitted. Opaque, "non-absorbing", "transparent", "transparent", etc. shall not be construed as requiring complete absorption or transmission.)

In another embodiment (not shown), the polarization regions are arranged in a grid structure. For example, in addition to the polarization regions shown in FIG. 4, additional polarization regions may be provided that extend in the z and y directions but have a limited area in the x direction. The light control element of this embodiment can limit light in one polarization state propagating in the z direction to both x and y directions. Polarized regions with a grid structure can be formed by forming a grid arrangement of grooves, for example, by the methods of FIGS. 9 (a) to 9 (c) or 10 (a) to 10 (d) described below. have.

5 shows another light control element 15 'of the present invention. The light control element 15 ′ of FIG. 5 includes a plurality of regions 16 that are opaque or nearly opaque to light with a particular polarization state but are transparent to orthogonal polarization states. In the embodiment of FIG. 5, the regions 16 have a plate shape and are arranged to be substantially parallel to the top surface of the light control element 15 ′. Furthermore, the regions 16 are arranged to be stacks 21 arranged one by one up. The stacks 21 are laterally separated from each other. The area between the stacks and the plates in the stack is filled with a light transmissive material 17.

Regions 16 are arranged such that their polarization properties do not change within the stack or between different stacks. Preferably the regions 16 are made of a material which is a linear polarizer, in which case the polarization regions 16 in each stack are polarized in stacks whose transmission axes are parallel to each other and the transmission axes of the polarizing plates in one stack are different Arranged substantially parallel to the transmission axes of the plates.

The operating principle of the light control element 15 'of FIG. 5 is generally similar to the operating principle of the light control element of FIG. That is, light of one polarization passes through the light control element 15 'without being absorbed regardless of its direction of movement (in the embodiment of FIG. 5 this light is in a direction parallel to the transmission axes of the polarization regions 16). Surface polarized light). However, light in the orthogonal polarization state (ie, light polarized in a direction perpendicular to the transmission axes of the polarization regions 16) does not enter the control element 15 ′ without incident on one of the polarization regions 16. It is only transmitted if it can be transmitted, ie only if it propagates along or very close to the xz plane. Light of this polarization component moving at an angle with respect to the xz plane is incident on one of the polarization regions 16 and absorbed as shown by the light path 20 of FIG. 5. Although the light control element 15 'of FIG. 5 outputs light in one polarization state in a wide angle range, light in orthogonal polarization states is output in a narrow angle range. The angular range of the light output from the light control element 15 'can be controlled by selecting the polarization of the light passing through the element using an appropriate polarization switch.

6 shows a display 21 according to an embodiment of the invention. The display comprises an image display panel 22 driven by driving means (not shown) in use for displaying a desired image. The display panel may be any conventional image transmissive display panel such as a liquid crystal display panel. The display panel 22 is preferably a pixellated display panel.

The image display panel 22 is illuminated by the backlight 25. The backlight 25 preferably provides the display panel 22 with uniform illumination over its entire area. The backlight 25 is shown as a wide area backlight in FIG. 6, but any suitable backlight can be used. The backlight may be integrated into the display or may be a separate device.

The display 21 further comprises a light control element 15 shown in FIG. 4, and a switchable half-wave plate 24 and a linear polarizer 23 provided between the backlight 25 and the display panel 22. Polarizer 23 and half-wave plate 24 are arranged substantially parallel to the display panel face. Although the polarizer 23 is shown as a separate element in FIG. 6, the polarizer 23 is the display panel 22 when the display panel 22 has an input polarizer (eg, when the panel 22 is a liquid crystal display panel). May be an input polarizer.                     

The transmission axis of the polarizer 23 crosses the transmission axis of the polarization regions 16 of the light control element, and is preferably 90 degrees with respect to the transmission axis. The optical axis of the half-wave plate is preferably 45 degrees with respect to the transmission axis of the polarizer.

The backlight 25 emits unpolarized light in use. The light is assumed to travel along the z axis as a whole, as shown by the axis defined in FIG. 6. The light component plane-polarized in the x direction is transmitted without large absorption by the light control element 15 as described above. Therefore, light polarized in the x direction is output by the light control element in a wide angle range. However, the light polarized in the y direction is transmitted by the light control element 15 only when it moves parallel to or close to the z direction, and thus the light control element 15 in a narrow angle range centered on the z axis. Is output from

Switchable half-wave plate 24 acts as a polarization switch in connection with polarizer 23. When the half-wave plate is switched ON, the half-wave plate has a delay of λ / 2, thus rotating the polarization plane of the plane polarized light incident thereon by twice the angle between the optical axis of the half-wave plate and the polarization plane of the incident light. Let's do it. Half-wave plate 24 is arranged such that its optical axis is about 45 degrees with respect to the x and y axes. Therefore, when the half-wave plate is switched ON, the half-wave plate rotates the polarization plane of the plane polarized light by 90 degrees in the x direction and the y direction.

A polarization switch (i.e. switchable half-wave plate 24 and polarizer 23) is disposed between the light control element 15 and the display panel in FIG. 6, but the backlight is controlled to control the polarization of light incident on the light control element. And between the light control element. In addition, the polarization switch may be integrated into the backlight 25.                     

7A and 7B show the operation of the display 21 of FIG. 6. FIG. 7A shows the operation of the display when the half-wave plate is turned on and thus rotates the x- or y-polarized polarization plane by 90 degrees. The backlight 25 is omitted in FIGS. 7A and 7B. Light plane-polarized in the y direction is represented by a short arrow in the y direction, and light plane-polarized in the x direction is represented by two concentric circles.

As described above, light polarized in the x direction incident on the light control element 15 is transmitted without being substantially absorbed. After passing through the light control element, the optical polarization plane is rotated 90 degrees by the half-wave plate 24, so that the polarization plane is parallel to the y direction and has a transmission axis arranged parallel to the y axis. The component is transmitted through the polarizer 23.

Light initially polarized along the y direction is output from the light control element within a narrow angle range. Thereafter, the polarization plane is rotated by the half-wave plate to face the x direction, so that this component is blocked by the polarizer 23. Thus, the display panel is illuminated by the light component from the backlight emitted in the plane of polarization parallel to the x direction. This is transmitted by the light control element 15 in a wide angle range, whereby the display panel 22 is illuminated with light having a wide angle range as shown in Fig. 7A. Thus, this provides a public mode of display operation.

FIG. 7B shows the operation of the display 21 when the switchable half-wave plate 24 is in the off state. When the half-wave plate 24 is in the off state, the polarization plane of light incident on the half-wave plate is not affected. The x-polarized component of the light from the backlight is transmitted by the half-wave plate 24 without changing the polarization, and thus is still polarized in the x direction to be incident on the polarizer 23. Thus, this component of the light is blocked by the polarizer 23. As a result, the display panel 22 is illuminated with this y polarization component because the y polarization component of the light from the backlight is transmitted through the polarizer 23. As described above, this is transmitted through the light control element 15 in a narrow angle range with respect to the xz plane and in a wide angle range in the vertical direction, so that the display panel is illuminated with light having only a narrow angle range in the horizontal direction. This provides a private mode of display operation since the image displayed on the display 22 is transmitted along a narrow range of directions. This is shown in Fig. 7B.

Thus, the display 21 of FIG. 6 can be switched between the common display mode and the private display mode only by switching the half-wave plate 24 between the off state and the on state with half-wave delay. This can be done electrically, so no moving parts are needed.

Switchable half-wave plate 24 may be a liquid crystal cell. For example, as described in E Lueder's "Liquid Crystal Displays: addressing schemes and electro-optic effects" in the Wiley-SID series of Display Technology (2001). Many methods are known for producing switchable half-wave plates using liquid crystal cells.

Another advantage of this display is that, as with many known switchable half-wave plates, if a voltage is not applied to the plate, the plate is turned on, and if an appropriate voltage is applied, the plate is turned off causing zero delay. This has the advantage that when the display is operating in the common display mode of Fig. 7A, the plate is turned on and thus no power is consumed by the half-wave plate. It is necessary to apply a voltage when the display should be operated only in the personal display mode.

A method of manufacturing the polarization dependent light control element of the present invention will be described.

Linear polarizer sheets are commercially available and the structure of a typical linear polarizer sheet is shown in Figure 8 (a). As can be seen here, linear polarizer sheet 26 is typically comprised of an active layer 27 that absorbs light having a particular linear polarization. The active layer 27 may be, for example, a stretched polymer layer containing an absorbing dye such as iodine. The active layer 27 is supported on both sides by a film or layer of transparent material such as, for example, cellulose acetate butyrate (CAB). The total thickness of the polarizer sheet is typically 250 μm, while the thickness of the active layer 27 is much thinner and may be 1 μm but is typically 10-20 μm.

In some commercially available linear polarizer sheets, the active layer is supported by only one transparent layer. In such a polarizer sheet, one of the transparent layers 28, 28 'of Fig. 8A will not be present.

In general, one method of manufacturing the light control element 15 of the type shown in FIG. 4 is shown in FIGS. 8B and 8C. In essence, the light control element 15 is manufactured by stacking many layers of a conventional linear polarizer sheet, such as the sheet 26 of FIG. Depending on the required separation between adjacent polarization regions 16 in the light control element, it may be necessary to provide an additional transparent spacer layer 29 between adjacent polarization sheets 26. If spacer layers 29 are provided, their refractive indices preferably match the refractive indices of the transparent substrates 28, 28 'of the polarizer. Therefore, it is desirable to manufacture the spacer layer from the same material used for the transparent substrates 28 and 28 'of the polarizing sheet, which ensures that the refractive indices of the spacer layer 29 and the substrates 28 and 28' are the same. Because. In addition, the mechanical properties of the spacer layer 29 (particularly with elastic modulus) have the advantage of matching the mechanical properties of the transparent substrates 28, 28 'of the polarizing sheet, thus providing a stack as described below. If a mechanical cutting process is used to cut into a plurality of slices, the cutting process will deform the polarizer layer and the spacer layer in the same manner and the stack will be subject to minimal distortion.

The stack layers of the polarizer sheet 26 and the transparent spacer layers 29, if provided, are attached to each other by any suitable method. This can be done, for example, using an adhesive, such as a photocurable (eg UV-curable) transparent adhesive. If such an adhesive is used, the stacks of polarizer sheet 26 and the transparent spacer layers 29, if present, have a transparent adhesive layer interposed between each pair of adjacent layers, as shown in FIG. Will be assembled. When the stack layer is assembled, the entire stack layer is irradiated with ultraviolet light to cure the adhesive.

Alternatively, each layer of adhesive can be irradiated separately before the next adhesive layer is applied. This can increase the overall time required to manufacture the stack 30, but when all the adhesive layers are irradiated in one step, the absorption of UV light in the upper layer reduces the irradiation intensity incident on the lower adhesive layer of the stack so that they are cured properly. It has the advantage of overcoming the problem of obstructing things.

The adhesive used, when cured, preferably has a refractive index as close as possible to the refractive indices of the transparent layers 28, 28 ′ of the polarizer sheet and the transparent spacer layer 29. This gives the finished element 15 good optical performance. If the refractive indices of the transparent layers 28, 28 ', 29 and the refractive indices of the adhesive layer do not coincide, refractive and reflection will occur at a plurality of boundaries in the device, thereby degrading the optical performance of the device.

Once the adhesive has cured, the block 30 can be separated into a plurality of slices 31 as shown in FIG. The block 30 can be sliced, for example by mechanical cutting. In order for the cutting step to be successful, it is desirable that the mechanical properties of the cured adhesive (especially elastic modulus) match the mechanical properties of the transparent layers 28, 28 ′, 29 of the stack 30.

It is not necessary to attach the polarizer sheets 26 and the spacer layers 29, if provided, to each other using a transparent adhesive. In principle, any suitable method can be used, for example welding.

In principle, the slice 31 cut from the block 30 can be used as the optical control element 15 of FIG. 4. In practice, however, it is desirable to provide transparent layers 32, 33 over the front and back surfaces of the slice 31, as shown in FIG. Layers 32 and 33 provide physical protection for the optical control element and also improve the quality of the optical element by planarizing the input and output faces. Layers 32 and 33 may be, for example, a cured adhesive layer. Alternatively, layers 32 and 33 may be thin polymer films that are attached to slice 31 using a UV curable adhesive.

In the variant of Figs. 8B and 8C, the sheet 26 of the linear polarizer is the same width as the preferred thickness t of the light control element (except for the transparent protective layers 32, 33). cut into strips with (w). This is shown by the broken line in Fig. 8A. These strips can then be stacked together to form a structure similar to the slice 31 shown in Fig. 8B. If desired, a strip of transparent spacer material may be interposed between adjacent strips of the polarizer sheet. The strip of polarizer sheet and, if present, the spacer material may be attached together using any suitable technique, such as for example bonding using a transparent adhesive or welding. Protective layers 32 and 33 may then be provided on the front and back of the desired stack.

An alternative method of manufacturing the light control element 15 of the present invention is shown in Figs. 9A to 9C. In this embodiment, the light control element is made of a transparent sheet 34 such as, for example, a transparent polymer film. This can be, for example, a CAB membrane.

As shown in FIG. 9B, the plurality of recesses 35 are defined in the transparent film 34. The recess 35 corresponds to the desired position of the polarization region 16 of the light control element 15 in size, shape and position. The recess may be, for example, in the form of a parallel-sided groove if the polarization region has the plate shape shown in FIG. 4. In FIG. 9B, the recess 35 extends beyond the entire depth of the transparent film 34 so that the transparent film 34 is attached to the substrate or the back sheet. The substrate 36 allows the discrete portions of the transparent film produced when the groove 35 is formed to maintain a correct relationship with each other. Substrate 36 is preferably transparent and can be mounted to the final light control element without adversely affecting the performance of the light control element. This eliminates the need to remove the substrate 36. The substrate 36 may form one of the two surface layers 32 and 33 of FIG. 8C.

In principle, it may be possible to prevent the grooves from extending through the entire depth of the transparent film 34, in which case the substrate 36 may be omitted. However, it is generally difficult to accurately control the depth of the grooves, and it is expected that placing the transparent film 34 over the substrate and forming the grooves through the entire depth of the film will provide a more reliable manufacturing process.

The recess 35 is then filled with a material 37 that absorbs light in a particular polarization state but does not absorb light in an orthogonal polarization state. This material can be, for example, a liquid crystal material comprising a dye that absorbs light of a particular linearly polarized light.

Grooves in the transparent film 34 may be formed using standard lithography techniques. One suitable technique is shown in FIGS. 10A and 10B. In the present embodiment, the transparent film 34 is a film of photosensitive material. This material is applied over the backing film 36 to provide a uniform thickness using any suitable technique such as spinning, roll coating, printing, and the like. The thickness of the photosensitive material layer 34 can be selected to be the required thickness t of the light control elements (except if the substrates 32, 33 are provided).

Next, the photosensitive material layer 34 is exposed to irradiation by ultraviolet (UV) light through the mask 38, for example, as shown in FIG. 10A. The transparent opening 39 of the mask corresponds to the position of the recess 35 required.

When the photosensitive material layer 34 is exposed, the mask is removed and the layer is washed. In the washing step, the photosensitive layer area irradiated in the irradiation step will be removed. Thus, the recess 35 is formed in the layer 34 as shown in Fig. 10B. The portion of layer 34 remaining after the irradiation and washing step forms a “wall 55” between neighboring grooves and corresponds to the transparent area in FIG. 4.

In the embodiments of FIGS. 10A and 10B, a positive photosensitive material layer 34 is used in which an area of the unirradiated layer is kept in the washing step. Alternatively, a negative photosensitive layer may be used in which the unirradiated areas are removed in the washing process. To do this it may be necessary to use a mask whose transparent openings correspond to the area of the layer for forming the wall 55.

An alternative method of forming the groove 35 is shown in Figs. 10A and 10D. Initially, a layer of transparent material is deposited over the substrate 36 with a uniform thickness corresponding to the desired thickness t of the light control element (except for this substrate, if provided). Layer 34 may be deposited again using any suitable technique, such as, for example, spinning, roll coating, printing, and the like.

10 (c) and 10 (d), the grooves are formed by removing unwanted portions of the transparent layer 34 using a high energy beam source. In this embodiment, for example, laser ablation techniques, reactive ion etching (RIE) techniques, and the like can be used. As shown in FIG. 10C, the transparent material layer 34 is exposed to the passage high energy beam source through the mask 38, and the area of the layer 34 corresponding to the opening 39 of the mask is removed. As shown in FIG. 10 (d), the recess 35 is formed.

Once the recess is formed, by the method of Figs. 10A and 10B, by the method of Figs. 10C and 10D, or by other methods, A material that transmits light in one polarization state but transmits light in an orthogonal polarization state is deposited in the recess. For example, a liquid crystal material comprising a dye that absorbs light of a particular linearly polarized light may be disposed in the groove 35 of the transparent layer 34. This liquid crystal material and dye must be aligned so that all molecules of the liquid crystal layer are oriented in the same direction. This can be accomplished by providing a polyimide alignment layer. 11 (a) and 11 (b) illustrate two possible ways of providing an alignment layer. In this embodiment of FIG. 11A, the alignment layer 40 is disposed over the entire upper surface of the substrate 36. The alignment layer 40 is then provided to have the desired alignment direction by rubbing technique or photo alignment (ie, aligned by exposure to polarized ultraviolet radiation). Next, a transparent material layer 34 is deposited on the polished alignment layer 40, and the groove 35 is formed as described above. When a liquid crystal material comprising a dye is disposed in the groove 35, this liquid crystal material will be aligned by the alignment layer 40.

In the alternative embodiment shown in FIG. 11B, the alignment layer 40 is applied after the grooves 35 are partitioned-that is, after forming the grooves of FIG. 9B and FIG. 9C. An alignment layer 40 is provided before depositing the liquid crystal material. In this embodiment, the alignment layer is deposited only on each groove 35, as shown in Fig. 11B. The alignment layer may then be provided to have the desired alignment direction, for example using polishing techniques or by optoelectronic alignment.

In another embodiment omitted from the illustration, the material of the wall 55 is used to align the liquid crystal material disposed in the recess. The sides of the wall are polished along the direction of the recess to induce alignment in the sides of the wall, which is effective for aligning the liquid crystal material deposited on the recess. This is an effective technique for, for example, a substrate formed of a soft material such as photoresist.

In order to introduce the liquid crystal material 37 into the groove 35, a second substrate or other sealing layer can be placed on the wall. The liquid crystal material, including the dye, is then introduced into the grooves 35 using capillary or vacuum techniques.

12A and 12B show another method of manufacturing the light control element 15 of the present invention. The method of FIGS. 9A-9C except that it begins with a material layer 41 that does not pass light in a given polarization state but transmits light in an orthogonal polarization state. Similar to The material is, for example, a stretched polymer such as polymerized liquid crystals doped with an absorbent dye or PVA doped with an absorbent dye. Grooves or recesses 35 are formed in this layer and filled with a transparent material. Grooves filled with a transparent material correspond to the transparent portions 17 of the light control element 15, and the remaining portions of the layer 41 of opaque material to the light of a given polarization are the regions of the light control element 15 of FIG. 4. Form the field 16.

In an embodiment of the method, the alignment layer 40 is initially deposited on the substrate 36 and then arranged using, for example, polishing or optoelectronic alignment techniques.

Next, a photosensitive material layer 41 comprising absorbent dye is deposited on the alignment layer 41. Alignment layer 40 serves to align the dye molecules of layer 41 such that layer 41 absorbs light of a particular linearly polarized light. Short lines in the alignment layer 41 of FIGS. 12A and 12B represent the alignment of the dye molecules in the layer 41.

The photosensitive layer is treated with UV or other radiation through mask 38. In the embodiment of FIG. 12A, since the layer 41 is a positive photosensitive material layer, the openings 39 of the mask correspond to the areas desired to be removed from the layer 41. Therefore, the size, shape and positions of the openings of the mask correspond to the desired shape, size and positions of the transparent areas of the light control element 15.

After the irradiation process, the mask 38 is removed and the layer 41 is washed to remove the photosensitive material from the irradiated areas. The remaining portions of the layer 41 make up the polarizer 16 of the light control element 15. The grooves 35 may be filled with a transparent material, for example a transparent polymer or a transparent resin, to form the transparent regions 17.

In a variant of the embodiment, the light control element is formed by removing unnecessary portions of the layer of material absorbing light of linearly polarized light by an ablation technique using a high energy beam source. This may be a laser ablation technique, an RIE technique. This embodiment may be used for any material that absorbs light of a given linearly polarized light, and is not limited to using a photosensitive material. In this embodiment, the alignment layer 40 may be omitted if the material absorbing light of a given linearly polarized light does not require the alignment layer. The areas of the layer removed by the removal technique may be filled with the transparent material as described above.

13 (a) and 13 (b) show another method of manufacturing the light control element of the present invention. This embodiment uses a commercially available linear polarizer sheet of the type comprising an active layer 27 disposed on a single transparent substrate 28, as shown in Fig. 13A. The second transparent substrate 28 ′ of the polarizer sheet of FIG. 8A does not exist.

Initially, selected portions of the active layer 27 of the first polarizer sheet 26a are removed using, for example, a patterned photo-etching process or a laser ablation process. The result of this process is a series of discrete regions 27 'of linear polarization material disposed on the transparent substrate 28, as shown in FIG. 13 (b). Each of the discrete regions 27 'of the polarizing material in FIG. 13 (b) corresponds to one of the polarizing regions 16 in the light control element 15' of FIG.

Next, the second polarizer sheet 26b is attached to the top surface of the first polarizer sheet 26a. This process may consist of depositing an adhesive layer, for example a UV-curing adhesive, on the top surface of the first polarizing sheet. The UV-curing adhesive acts to fill the remaining gaps by first attaching the two polarizing sheets to each other and then removing the portions of the active layer of the first polarizing sheets. The adhesive is preferably selected such that its refractive index approaches the refractive index of the transparent substrate 28 of the polarizing sheets upon curing. Stacked polarizers are irradiated to cure the adhesive.

Selected regions of the active layer of the second polarizing sheet may then be removed using patterned photo-etching techniques or laser ablation techniques again. The removed regions of the active layer of the second polarizing sheet are placed directly above the regions from which the active layer of the first polarizing sheet is removed and have the same size and shape. Conversely, the remaining regions of the active layer of the second polarizing sheet are placed directly over the remaining regions 27 'of the active layer of the first polarizing sheet 26a and have the same size and shape.

The processes of attaching another layer of polarizing sheet 26c to the stack and removing selected regions of the active layer may be repeated several times if necessary. Finally, the protective transparent layer 32 may be deposited on the best polarizer sheet to serve as a protective layer.

In this embodiment, the remaining regions 27 'of the active layer form stacks 21 of polarization regions 16 in the light control film 15' of FIG. FIG. 13D shows a light control element having three polarizing sheets 26a-26c, each stack of polarizing sheets comprising three polarizing sheets; However, the present invention is not limited only to this number of polarizing sheets.

In this embodiment, it is in principle possible to assemble the entire stack 32 and cure all adhesive layers in one process. However, it is important to ensure that each polarizer sheet is correctly aligned with the preceding polarizer sheet, and that waiting for the entire stack to be made before curing the adhesive layers may occur that the polarizer sheet may be accidentally moved when subsequent sheets are stacked. In terms of potential drawbacks. Therefore, in practice it may be highly desirable to cure each adhesive layer and then deposit the adhesive layer and polarizer sheet to prevent one polarizer sheet from moving relative to the other sheets.

13 (d) to (f) show a modification of this embodiment. In this embodiment, the polarizing sheets 26a-26c and the protective substrate 32 are initially stacked together with a layer of curable adhesive disposed between each element. The stack 42 is irradiated to cure the adhesive layers.

As shown in FIG. 13F, a plurality of recesses or grooves are formed in the stack 42. Each groove removes the active layer of each polarizing sheet 26a-26c of the stack and removes the substrates of all the polarizer sheets except the lowest position polarizer sheet, thereby removing the transparent substrate 28 of the polarizer 26a at the lowest position. It is made to have enough depth to leave only a)).

The remaining stack portion 42 'corresponds to the stack 21 of polarization regions in the light control element 15' of FIG. The position, size, and shape of the remaining portion 42 'of the stack is appropriately selected. The recesses 35 between the remaining portions 42 'will be filled with a transparent material, and if desired, a protective substrate (not shown) may be deposited over the top surface of the light control element.

14 shows a display according to another embodiment of the present invention. Like the display 21 of FIG. 6, the display 21 ′ of FIG. 14 includes the light control element 15 of the present invention. However, the light control element 15 in the display 21 'of FIG. 14 is located in front of the image display panel 22 (ie, between the display panel and the viewer) rather than the rear as in FIG. This embodiment can be applied to a display panel 22 that is an emissive display panel such as an organic light-emitting device (OLED) display, a cathode ray tube display, or a field emission display. It can also be applied to a transmissive image display panel such as a liquid crystal display panel.

The polarization switch is positioned between the display panel and the viewer to control the polarization of light reaching the viewer. In FIG. 14, the polarization switch is formed of a linear polarizer 23 and a switchable half-wave plate 24 positioned between the display panel 22 and the light control element 15. When the display panel is integrated with the output polarizer, for example, if the display panel 22 is a liquid crystal display panel, the output polarizer of the display panel may be used as the polarizer 23. The switchable half-wave plate 24 has an optical axis rotated by 45 ° with respect to the transmission axis of the linear polarizer 23 and is disposed in front of the polarizer 23.

The polarization switch may alternatively be located between the light control element and the viewer, or, in the case of a transmissive display, behind the display panel. In principle, the display may be implemented using an emissive display that emits light with controllable exiting polarization, in which case no external polarization switch would be required.

If display panel 22 is a transmissive display panel, display 21 'will require to be illuminated by light from a suitable backlight (not shown).

In the embodiment of FIG. 14, the polarization region 16 of the light control element 15 has its transmission axis parallel to the transmission axis of the polarizer 23. In this embodiment, the transmission axis of the horizontal polarizer 23 is parallel to the x-axis, and thus the polarizing plate 16 of the light control element 15 has a transmission axis parallel to the x-axis.

The operation of the display 21 is shown in Figs. 15A and 15B. Fig. 15A shows the operation of the display 21 when the switchable half-wave plate is OFF and therefore there is no retardation. In this embodiment, the horizontal polarizer 23 transmits plane-polarized light parallel to the x-axis. When the plate 24 is off, since there is no influence on the polarization plane of the light passing therethrough, the light incident on the light control element 15 is still plane-polarized light parallel to the x-axis. Since the polarizing plate 16 of the light control element has a transmission axis arranged in the x-direction, the polarizing plate 16 does not absorb light incident on the light control element 15. Thus, as shown in Fig. 15A, the light has a wide viewing angle range and is output from the light control element, thereby providing a public display mode.

FIG. 15B shows the operation of the display when switchable plate 24 is ON and provides a λ / 2 delay. In this case, the polarizer 23 passes light back plane-polarized in the x-direction. Since the optical axis of the plate is rotated by 45 ° with respect to the polarization plane of light incident thereon, when the light passes through the plate 24, the plane of light is rotated by 90 °. Thus, light incident on the light control element is plane-polarized in the y-direction, and the polarization region 16 of the light control element will absorb any light incident thereon. Accordingly, the light control element 15 outputs light having only a narrow angular range, as shown in FIG. 15B, thereby providing a private display mode.

16 shows another display 43 according to the invention. The display 43 includes two light control elements similar to the element 15 of FIG. 4. Both light control elements 15a and 15b transmit light of a specific linearly polarized light regardless of the travel direction of the light. Both light control elements 15a and 15b transmit light in an orthogonal linearly polarized state only over a range of directions, but since the two light control elements have different geometries, they are orthogonal linearly polarized. The range of ray angles through which light is transmitted differs between the two elements. Thus, the display 43 can operate in two or more display modes.

The display 43 includes an image display panel 22. This may be a transmissive display panel or an emissive display panel, as in the embodiment of FIG. 14. If the display panel is a transmissive display panel, the display requires illumination with an appropriate backlight (not shown).

The linear polarizer 23 is disposed in front of the display panel 22. If the display panel 22 has an output side linear polarizer (for example, if the display panel 22 is a liquid crystal display panel), the output side polarizer of the display panel 22 may be used as the polarizer 23.

The first light control element 15a is disposed in front of the polarizer 23. A polarization switch is provided to select the polarization of the light output from the first light control element. In Fig. 16, the first polarization switch is composed of a polarizer 23 and a first switchable wave plate 24a disposed between the polarizer and the first light control element 15a. The half-wave plate is arranged in such a manner that its optical axis is rotated 45 ° with respect to the transmission axis of the polarizer 23.

The second light control element 15b is disposed in front of the first light control element 15a. The second polarization switch is provided for selecting the polarization of the light output from the first light control element. In FIG. 16, the first polarization switch is composed of a polarizer 23 and a second switchable half-wave plate 24b disposed between the first light control element 15a and the second light control element 15b. The optical axis of the second switchable half-wave plate 24a is arranged to be in a position rotated 45 degrees with respect to the transmission axis of the polarizer 23.

The order of the elements is not limited to the order shown in FIG. For example, the elements may be arranged in the order of backlight, light control element, switchable wave plate, light control element, switchable wave plate, polarizer, and display panel.

The light control elements 15a, 15b are each configured to transmit light of linearly polarized light passed by the polarizer 23 in all directions. However, the light control elements are rotated by 90 degrees with respect to the transmission axis of the polarizer 23 and are selected such that their emission angle ranges for the plane polarized light are different from each other.

In the display shown in FIG. 16, the polarizer 23 is composed of a transmission axis parallel to the z (vertical) direction. The optical axes of the two switchable half-wave plates 24a and 24b are in parallel with each other and rotated 45 degrees with respect to the transmission axis of the polarizer 23. Since the light control elements 15a and 15b both do not have an absorption effect on the vertically polarized light, they transmit the vertically polarized light regardless of the incident angle on the light control element. The first polarization dependent light control element 15a passes the horizontally polarized light only in a direction close to the horizontal (x-y) plane and blocks the horizontally polarized light propagating at a large angle with respect to the horizontal plane. The second light control element 15b passes horizontally polarized light propagating in a direction close to the vertical (y-z) plane, but blocks light propagating at a large angle with respect to the vertical plane.

17A-17C show three of the four possible modes of operation of the display 43 of FIG. 16. FIG. 17A shows the mode of operation where both switchable waveplates 24a and 24b are off and so all provide zero delay. In this operation mode, the light emitted from the display panel 22 is plane polarized by the polarizer 23, and the polarization plane faces the vertical direction. The polarization plane is not affected by any of the switchable half-wave retarders 24a, 24b, and light propagating through the display 43 is plane polarized in the vertical direction. (The polarization direction of the light is schematically shown in Figs. 17A to 17C-vertical arrows show planar polarized light, while two concentric circles show horizontally polarized light (i.e. The light control elements 15a, 15b are transparent to vertically polarized light irrespective of the direction of propagation, so that light has a wide range in both horizontal and vertical directions. It is output from the display over the observation angle. This is schematically illustrated in FIG. 17D, which is a schematic plan view of the display.

FIG. 17B shows an operation mode of the display 43 when the first wave plate 24a is on and the second wave plate 24b is off. In this mode of operation, the polarizer 23 again outputs plane polarized light in the vertical direction, but the polarization plane is rotated by 90 degrees by the second wave plate 24a. Since the second wave plate 24b is off, it does not affect the polarization plane of light passing through it-thus, the polarization plane of light passing through the display is converted to horizontal polarization by the first wave plate 24a and The light passes through the display and then remains in horizontal polarization.

In the operation mode of FIG. 17B, light is polarized in the horizontal direction when it passes through both the light control elements 15a and 15b. The first light control element 24a passes the horizontally polarized light only in the directions close to the horizontal plane, while the second light control element 15b passes the horizontally polarized light only in the directions close to the vertical plane. Is that only light propagating in a direction close to the direction perpendicular to the display surface is transmitted through the entire system. In this mode, the display has a narrow range of observation angles in both the horizontal and vertical directions, as shown schematically in FIG. 17E, which is a schematic plan view of the display.

In Fig. 17C, both half-wave retarders 24a and 24b are on. The polarizer 23 again passes vertically polarized light, and the polarization plane is rotated by 90 degrees by the first half-wave plate so that incident light to the first polarization dependent control element 15a is horizontally polarized. However, when light passes through the second half-wave plate, the polarization plane is again rotated by 90 degrees, so that incident light to the second light control element 24b is plane polarized in the vertical direction. Therefore, in this mode, the first light control element 24a transmits only light propagating at an angle close to the horizontal plane, which is opaque to light propagating at a wide angle with respect to the horizontal plane. However, since the light reaching the second light control element 15b has been returned to be vertical plane polarized light, the second light control element 15b does not absorb light. Thus, as shown in Fig. 17F, which is a schematic plan view of the display, the output from the display has a wide viewing angle in the horizontal direction but a narrow viewing angle in the vertical direction.

Although not shown in FIG. 17, in the fourth mode, the first half-wave plate 24a is off and the second half-wave plate 24b is on. In this mode, the first light control element 15a has no absorption effect because it receives vertically polarized light, while the second light control element 15b has a large angle with respect to the vertical plane for light propagating. Opaque (because it receives horizontally polarized light). In this mode, the display has a narrow viewing angle in the horizontal direction but a wide viewing angle in the vertical direction.

Thus, the display 43 has three modes, a common display mode with a wide viewing range, and a limited viewing range.

In a modification of this embodiment, the second polarization switch can be omitted (by omitting the second wave plate 24b). In this modification, only the display modes of FIGS. 17A and 17B will be available-but such a display can be switched between the common display mode and the private display mode by appropriately switching the first wave plate 24a. Will be able to switch.

Other combinations of two light control elements and waveplates are possible. For example, modifying the embodiment of FIG. 16, the two polarization-dependent light control elements are planar polarized in one direction that is nearly parallel or nearly perpendicular to the transmission axis of the polarizer and propagates along a direction near the same plane. Light can pass through, but with different viewing angle ranges. For example, the first device can absorb horizontally polarized light at an angle greater than 20 ° with respect to the vertical plane, while the light control element is capable of absorbing horizontally polarized light at an angle of at least 10 ° with respect to the vertical plane. Can absorb. This provides a display that can be switched between a display mode with a wide viewing angle, a display mode with a horizontal viewing angle of 20 °, and a display mode with a horizontal viewing angle of 40 °.

18 shows a display 44 according to another embodiment of the present invention. This display may provide an autostereoscopic private display mode.

The structure of the display 44 of FIG. 18 is generally similar to the display structure of the display 21 ′ of FIG. 14. The structure also includes a display panel 22 and the light control element 15 of the present invention disposed in front of the display panel. A polarization switch is provided between the display panel and the viewer. The image display panel 22 may be a transmissive display panel or an emissive display panel illuminated by a backlight (not shown). In Fig. 18, a polarization switch is formed by the linear polarizer 23 and the switchable half-wave plate 24 disposed between the display panel and the light control element. In addition, the order of the elements is not limited to the order shown in FIG. 18, and the elements may be arranged in the following order, for example, a backlight, a light control element, a switchable wave plate, a polarizer, and a display panel. The order provides a rear-barrier display.

In this embodiment, the polarization regions 16 of the light control element 15 are arranged such that they can transmit plane polarized light in a direction perpendicular to the transmission axis of the polarizer 23. The optical axis of the switchable half-wave plate is arranged at 45 ° with respect to the transmission axis of the polarizer 23. In Fig. 18, the polarizer 23 has its transmission axis arranged parallel to the y-axis, and the polarizing plates 16 of the light control element have their transmission axis arranged parallel to the x-axis, but the display has this particular configuration. It is not limited to.

When the half-wave plate is on, the light polarized in the y-direction by the polarizer 23 is rotated by 90 ° by its switchable half-wave plate 24. Thus, the light leaving the switchable half-wave plate is plane polarized in the x-direction, and as a result is not affected by the light control element 15. The device therefore operates in the common display mode.

When the switchable half-wave plate is off, this does not affect the polarization plane of the light transmitted by the polarizer 23, so that the plane polarized light in the y-direction enters the light control element 15. Since the polarization regions 16 of the light control element 15 absorb plane-polarized light in the y-direction, the light control element propagates close to the xz-plane, through the transparent region 17 of the element 15. Only light that can pass through will be transmitted. The device thus operates in a personal display mode as previously described. In the display of Fig. 18, the display panel 22 is driven by any suitable driving means (not shown) to display two interlaced images. The two images are the left eye image and the right eye image of the stereoscopic image image pair. Interlaced scanning is schematically illustrated by the letters "R" and "L" in FIG. 18, which represent columns of pixels that respectively display a right eye image and a left eye image.

The thickness of the light control element 15 and the width of the transparent region 17 are selected such that the light control element 15 acts as a parallax barrier for plane polarized light parallel to the y-direction. The parallax barrier separates the two images displayed on the display panel 22 so that the observer's left eye sees the left eye image and the observer's right eye sees the right eye image. In general, the width of the transparent area of the light control element 15 is chosen so that the pitch p of the light control element / parallax barrier can ensure that the parallax barrier correctly separates the two images.

Thus, the personal display mode of the device 44 may be an automatic stereoscopic image display mode. Therefore, the display 44 is switchable between the personal automatic stereoscopic image display mode and the common two-dimensional display mode. The display of FIG. 18 may be used in personal two dimensional display mode. To accomplish this, a single image is displayed on the display panel 22 rather than two interlaced images.

18 may be applied to a rear barrier display by arranging the elements in an appropriate order as described above, or may be applied to a dual-view display.

The image display panel 22 of the display 44 will typically have a depth of tens of pixels and a width of tens of pixels. The polarization regions 16 of the light control element 15 form an opaque portion of the parallax barrier when the device is operating in its autostereoscopic image personal mode, and thus an image display panel (into the paper plane of FIG. 19). It must extend over the full depth of. Also, the opaque portion of the parallax barrier of an autostereoscopic image display typically has at least one pixel width of the image display panel of the display. Thus, the polarization regions 16 of the image control element 15 must all be wide (having the same width as at least one pixel of the display panel 22) and must be high (as many pixels as possible). Depth). If the segments of polarizing material forming polarization region 16 are made of polarizing material throughout, then as suggested in FIG. 18, the segments may have both polarization states as light passes through the entire thickness of the segment. Will absorb light, which will degrade the device's performance in common mode.

19 (a) and (b) show one way to overcome this problem. FIG. 19A shows a modified light control element 15 "of the present invention, which is generally similar to the light control element of FIG. 4 but with the polarization region 16 formed of a polarizing material throughout its width. Instead, each polarization region 16 is formed of a polarizing material arranged in a channel having a U-shaped or inverted U-shaped cross section, as shown in Fig. 19A. Is filled with a light-transmissive material 46. The polarization region 16 is again separated by the light transmission material region 17. The polarization region 16 as shown in Fig. 19A. Disposing will have no effect on the light of the polarization intended to be absorbed-this absorption will occur as well on the control element 15 "of FIG. 19 as on the control element 15 of FIG. However, since the thickness of the polarizing material is much smaller than in the embodiment of FIG. 19, the polarization region 16 of the light control element 15 ″ of FIG. 19A is not intended to be absorbed so that the light of the polarization is to a considerable extent. It will not absorb.

Fig. 19B shows one method of manufacturing the light control element 15 "in Fig. 19A. In this method, the control element 15" is made of a transparent material located on the substrate 33. Figs. Are made of layers. Selected areas of the transparent film are removed using, for example, irradiation of photoresist material or the selective removal techniques described above. The material is removed to define the U-shaped channel 47 in the transparent material. The resulting channel 47 is subsequently filled with a liquid crystal containing dye, which acts as a polarizing material to absorb the defined linearly polarized light. This liquid crystal material can be aligned by any of the methods described above with reference to Figs. 11A and 11B.

The light control element 15 "of Fig. 19A can also be made of a layer of material that blocks light in one polarization state but transmits light in an orthogonal polarization state. It is removed leaving U-shaped regions as described above with reference to 12 (b), and then a transmissive material is deposited.

20 shows another display 48 of the present invention. This may display private images to two separate observers 45A and 15B.

The display 48 includes a transmissive image display panel 22 illuminated by a backlight 25. The first light control element 15a, the second light control element 15b, and a polarization switch are disposed between the backlight 25 and the display panel 22. The polarization switch in FIG. 20 is formed of a linear polarizer 23 provided between the switchable half-wave plate 24 and the second light control element 15b and the display panel. The switchable half-wave plate has its optical axis arranged at 45 ° with respect to the transmission axis of the polarizer 23. The polarizer 23 may be an input polarizer of the display panel 22.

The first light control element blocks the first linearly polarized light propagating in some directions, but not all directions, and does not affect the second linearly polarized light perpendicular to the first polarization. The second light control element blocks the second linearly polarized light propagating in some directions, but not all directions, and does not affect the first linearly polarized light. The polarizer 23 is arranged to block either the first or second linearly polarized light.

In the embodiment of FIG. 20, the first light control element 15a is effective to control the angular range of the horizontally polarized light but has no absorption effect on the vertically plane polarized light, and the second light control element 15b. Is effective in controlling the angular range of vertically polarized light, but has no absorption effect on horizontally planar polarized light, and the polarizer 23 has its transmission axis arranged vertically. However, the present invention is not limited to this particular orientation.

In the light control element 15 of FIG. 4, the polarization region 16 is arranged parallel to the input and output surfaces of the light control element. However, the present invention is not limited to this particular orientation. In the light control element of FIG. 20, the polarization regions 16 of the first and second light control elements 15a, 15b are not arranged to be perpendicular to the input and output surfaces of these control elements. The orientation of the polarization regions 16 of the two light control elements 15a and 15b is such that the direction in which the first light control element 15a induces horizontally polarized light is vertically polarized by the second light control element. It is arranged to be different from the direction of sending the light. In the particular embodiment of FIG. 20, the first light control element 15a passes through the horizontally polarized light within a narrow angle range centered at about + 30 ° with respect to the axis of the display and the second light control element 15b. ) Passes vertically polarized light within a narrow angular range centered about -30 ° to the display axis.

The light control elements 15a and 15b of FIG. 20 can be manufactured in a similar manner to the light control element of FIG. For example, the layers of the polarizing plate may be stacked as shown in FIG. 8B, and the stack may be cut at an angle other than 90 ° with respect to the top surface of the stack.

In one mode of operation of the display 48, the switchable half-wave plate 22 is turned off. Therefore, it does not affect the polarization of the light passing therethrough. In this mode, the first polarization dependent light control element 15a is effectively disabled because it does not affect the vertically polarized light transmitted by the polarizer 23. The first light control element 15a controls the angular range of the horizontally polarized light but it is blocked by the polarizer 23. The vertically polarized light is output from the second light control element 15b and directed to the second observer 45B angle range and passes through the polarizer 23. Therefore, in this display mode, the second user 45B sees the image displayed on the display panel 22, while the first user sees the dark display panel.

When the half-wave plate 24 is turned on, it functions to rotate the polarization plane of light by 90 degrees. Thus, the horizontal plane polarized component of the light from the backlight is converted to vertical plane polarized light by the half wave plate 24 and passes through the polarizer. This light is directed to the first observer 45A by the first light control element 15a. The vertically polarized component of the light from the backlight 25 is converted into horizontally polarized light by the half-wave plate 24 and blocked by the polarizer 23. Therefore, when the half-wave plate 24 is turned on, the first user sees the image displayed on the display panel 22 while the second user sees the dark display panel.

If each user is required to display a personal image, the wavelength plate is quickly switched between on and off, and the image displayed on the panel is switched in synchronization with the switching of the half-wave plate, so that the first image while the wavelength plate is off Is always displayed and the second image is always displayed while the wavelength plate is on. If the switching runs fast enough, each user will see a different image without flickering.

In different display modes, the display 48 can display a single image to both users. This can be done by quickly switching the wavelength plate between on and off states without changing the image displayed on the display panel 22. This display mode can also be obtained by applying an intermediate control voltage to the wave plate and having a delay of zero or more and lambda / 2 or less. In this display mode, the horizontal and vertical polarization components of the light from the backlight will be converted into circular or elliptical polarized components by the switchable half-wave plate 24, so that each component is partially by the polarizer 23. Will be transmitted.

20 shows a display 48 that directs different views to different observations in order to provide a dual observation display. The display 48 may alternatively be arranged so that two different images are directed to one observer such that one eye of the observer receives one image and the other eye of the observer receives another image. In this case, the display can operate as an automatic stereoscopic image display by displaying the left eye image and the right eye image of the stereoscopic image pair on the display in chronological order.

In a variation of display 48 (not shown), the backlight is a switchable directional backlight. When the first backlight control element 15a is active, the backlight emits light mainly in the direction in which the first light control element 15a transmits light, but when the second light control element 15b is active, the backlight Mainly emits light in a direction in which the second light control element 15b transmits light. The advantage of this embodiment is that the light emitted by the backlight is used more effectively, leading to a brighter display as the same backlight. (In this specification, the term "cross-talk" refers to the visibility that the image intended for the first user (or the first eye of the user) has for the second user (or the second eye). Or vice versa).

In the embodiment of FIG. 20, the polarization switch is provided within the backlight, between the backlight and the first light control element 15a, between the first light control element 15a and the second light control element 15b, or the display panel 22. Can be optionally installed before).                     

In addition, the embodiment of FIG. 20 provides a light control element between a display panel and an observer, for example, an image display panel; Polarizers; Switchable half-wave plate; It can be implemented by installing the components in the order of the first light control element and the second light control element. When the components are arranged in this order, either an emissive display or a transmissive display (requires backlight) can be used. When the components are arranged in this order, the polarizer may be configured by the exit polarizer of the image display panel if the image display panel has an exit polarizer.

The embodiment of FIG. 20 has the additional advantage of not requiring a display panel 22 to be precisely aligned with the light control element. In a conventional display, precise registration of this component is required, but not required in this embodiment.

21 shows a display 49 according to another embodiment of the present invention. The display 49 is, in one state, an active light control element that transmits a second orthogonal polarized light while transmitting a first linearly polarized light that is opaque to the first linearly polarized light propagating in a specific direction and propagating in another direction. And 50. Thus, in this state, the light control element 50 acts in the same manner as the light control element 15 of FIG. However, in this embodiment the light control element 50 is switchable and can be switched to a second state that does not pass any linearly polarized light.

In the display 49 of FIG. 21, the light control element 50 is disposed between the backlight 25 and the transmissive display panel 22 of the display 49. The linear polarizer 23 is provided between the backlight and the display panel, which may be disposed between the light control element and the display panel or between the backlight and the light control element as shown in FIG. In the case where the polarizer 23 is disposed between the light control element 50 and the display panel 22 as shown in FIG. 21, if the display panel 22 has an input polarizer, it can be used as the polarizer 23. have.

The transmission axis of the linear polarizer 23 is arranged parallel to the transmission axis of the polarization region of the light control element 50. In FIG. 21, the transmission axis of the polarizer 23 and the transmission axis of the polarization region 16 of the light control element 50 are parallel to the x axis.

The polarization region 16 of the light control element 50 is formed of a "guest-host" liquid crystal material. For example, in this embodiment, the dye is dissolved or chemically attached to the liquid crystal material. The dye is switchable between the absorbed state and the non-absorbed state such that the polarization region is switchable between the absorbed state and the non-absorbed state.

22A and 22B show two modes of operation of the display 49 of FIG. 21. This figure shows a linear polarizer 23 disposed between the backlight 25 and the light control element 50, but this does not affect the operation of the device. The linear polarizer 23 is arranged with a transmission axis parallel to the x axis. In the mode shown in FIG. 22B, the dye molecules of the liquid crystal molecules are aligned along the x direction such that the region 16 containing the dye does not pass x polarized light. The polarizer 23 transmits light that is surface polarized along the x direction, which is absorbed in the polarization region 16. Accordingly, the light propagating along or close to the xz plane passes through the light control element as shown by path A in FIG. 22 (b), but the light propagating at a large angle with respect to the xz plane is polarized region 16. Is absorbed to obtain a personal display mode. The angular range in this mode depends on the ratio between the width of the transparent region 17 and the thickness of the light control element 50.

As shown in Figs. 22A and 22B, the optical control element 50 is provided with electrodes 51 and 52 on its upper and lower surfaces. These electrodes are used to apply an electric field across the liquid crystal layer so that the liquid crystal molecules can generally be aligned in the z direction. This allows the dye molecules to reorient themselves along with the liquid crystal molecules so that the dye molecules are also aligned along the z direction. This is represented in FIG. 22A by a short line shown in the region 16 of the liquid crystal material. Therefore, the surface polarized light in the x direction propagated by the polarizer 23 is not absorbed by the liquid crystal region 16, and a common display mode is obtained as shown in Fig. 22A.

The optical control element 50 of this embodiment can be manufactured in various ways. For example, it may be manufactured as described in Figs. 9A to 9C using the lower substrate 36 having the transparent electrode uniform over its entire area. A second substrate having a uniform transparent electrode is placed on the structure, and the liquid crystal material containing the dye is filled in the recess. The liquid crystal material having a dye may be oriented in any of the methods described above with reference to FIGS. 11A and 11B. In this configuration, the liquid crystal material may have positive dielectric anisotropy and may be homogeneously aligned, or may have negative dielectric anisotropy or may be homeotropically aligned.

A second configuration of the switchable optical control element is to use a patterned alignment layer. This is illustrated in FIGS. 23A and 23B. In this embodiment, each substrate 36, 36 'of the device is provided with a transparent electrode on one surface and an alignment film (not shown) on the electrode. Once the alignment layer is patterned, the substrates are next aligned parallel to each other, separated by a distance equal to the desired thickness of the liquid crystal layer. The gap between the substrates is then filled with liquid crystal material, including the dye. Because of the patterned alignment layer, regions having two different alignments are adopted when no voltage is applied across the liquid crystal layer. In region 53, the liquid crystal molecules, and therefore the dye molecules, are aligned in the nearly z direction. However, in region 54, the liquid crystal molecules are almost aligned in the x direction (planar alignment), and therefore the dye molecules are also aligned in this direction. As a result, the region 54 operates as an absorption region for light polarized in the x direction.

When an electric field is applied across the liquid crystal layer through the electrodes 51 and 52, the liquid crystal molecules in the region 54 having the horizontal alignment are themselves redirected in the z direction, and the dye molecules are also rearranged and placed in the z direction. do. The orientation of the dye molecules does not change in the region 53 where there is already an alignment in the z direction. As a result, the entire liquid crystal layer becomes non-absorbing with respect to light polarized in the x direction as shown in Fig. 23A.

24 (a) and 24 (b) show a modified embodiment of FIGS. 23 (a) and 23 (b). In this embodiment, the electrodes 51 and 52, rather than the alignment film, are patterned. (The alignment films and the substrates are omitted in FIGS. 24A and 24B for the sake of clarity). The alignment films are arranged to generate liquid crystal alignment in the z direction (vertical alignment; homeotropic alignment) as shown in Fig. 24A. When an electric field is applied between the electrodes, the liquid crystal layer regions between the electrodes are redirected to adopt a horizontal alignment (parallel to the x direction), whereas the liquid crystal material of the regions where the electrodes are not visible has its initial vertical alignment. Keep it. This is illustrated in (b) of FIG. 24. In the region 54 of the liquid crystal layer between the electrodes, when a voltage is applied across the liquid crystal layer, the liquid crystal molecules adopt horizontal alignment, whereby the dye molecules also reorient themselves parallel to the x direction. As a result, the region 54 can absorb light polarized in the x direction when a voltage is applied across the liquid crystal layer.

In explaining the operation of the embodiments of Figs. 22A to 24B, it is assumed that the liquid crystal material contains a positive dichroic dye. The liquid crystal material may also comprise negative dichroic dyes, in which case the mode of operation of the optical control element is reversed.

As another alternative, it is also possible to use an electrode structure which generates an in-plane equilibrium electric field and rotates the dye molecules and the liquid crystal molecules of the plane parallel to the substrate by appropriately applying a voltage. In this case, the liquid crystal molecules and the dye molecules may be switched along the x direction or along the y direction.

The liquid crystal material used in the above-described embodiment may be either a nematic liquid crystal or a smectic liquid crystal material. Alternatively, a bistable liquid crystal material may be used, in which case the orientation of the liquid crystal material is stable in both operating states, so the application of voltage is necessary to switch the material from one operating state to another. It is only required.

25A is a schematic perspective view of an optical control element 55 according to a further embodiment of the present invention. The optical control element 55 of this embodiment is an active optical control element, which is a variation of the optical control element 50 shown in FIG. The control element comprises a plurality of polarization regions 16a, 16b formed of a switchable material between an absorbed state and a non-absorbed state. The polarization regions 16a and 16b are disposed between the lower substrate 56 and the upper substrate 57. Electrodes 51 and 52 are disposed on the upper substrate and the lower substrate, respectively, and these electrodes are used to apply an electric field across the liquid crystal layer to cause the polarization regions 16a and 16b to switch between their absorbed and non-absorbed states. do. The spaces between adjacent polarization regions 16a and 16b are filled with a transmissive material.

As in the embodiment of FIG. 21, the polarization regions 16a and 16b include liquid crystal and dye molecules. By applying an electric field across the polarization region, the liquid crystal molecules of the polarization regions 16a and 16b are themselves oriented in the z direction. As described above, the dye molecules are thus reoriented with the liquid crystal molecules themselves and are also aligned along the z direction. As a result, the dye molecules do not absorb the y plane polarization component or the x plane polarization component of the light passing through the control element 50. The polarization regions are then in a nonabsorbed state.

As shown in Figs. 25A and 25B, the plurality of regions A and B are defined as light control elements. In regions A, the polarization regions 16a extend along the x-direction, while the polarization regions 16b in region B extend along the y-axis. 25B shows one possible arrangement of regions A and regions B over the region of the optical control element 55. In this arrangement, regions A and regions B alternate with each other along both the x- and y-directions. However, the invention is not limited to this particular arrangement of these areas, other arrangements are possible.

If no voltage is applied between the electrodes 51 and the electrodes 52, the liquid crystal molecules align along the directions of the polarization regions 16a and 16b, and dye-molecules are also in this direction. Sort along. Therefore, in region A, the dye molecules are aligned along the x-direction, while in region B the dye molecules are aligned along the y-direction. Light propagating along the z-direction or in a direction close thereto will hardly be absorbed in regions A or B and will be transmitted through the light control element. This is so for both the x-plane polarization component and the y-plane polarization component. The optical control element is then put into a common mode with a wide angle output range.

When the polarization regions 16a and 16b are switched to the absorption mode, as described above with respect to Figs. 22A and 22B, the polarization regions 16a of the regions A are in the x-axis. It is thus opaque to plane-polarized light, since this polarization component is absorbed by the dye molecules aligned along the x-direction. Therefore, while region A transmits x-polarized light propagating along or close to the xz plane, x-polarized light propagating at a large angle with respect to the xz plane is absorbed by the polarization regions 16a. . Therefore, the area A can be switched between the common mode for passing the two polarization components in the wide angle range and the personal mode for passing the y-polarization component in the large angle range but passing the x-polarization component in the narrow angle range.

Conversely, if the polarization region 16b of regions B, in which the dye molecules are aligned along the y-direction, is switched to an absorption mode, the y-polarization component if the light propagates along or close to the yz plane Will pass. However, in the same manner as described above with reference to FIGS. 21, 22 (a) and 22 (b), the light of the y-polarized component propagating at a large angle with respect to the yz plane is polarized regions ( In 16b). Therefore, region B is switchable between the common mode in which the light of the two polarization components is transmitted in the wide angle range and the personal mode in which the y-polarization component is transmitted in the narrow angle range but the x-polarization component is transmitted in the wide angle range. .

25C shows the light control element 55 of FIGS. 25A and 25B incorporated into a display. The display includes an image display device 22 which is, for example, a liquid crystal display device. The light control element 55 is disposed in front of the display device 22, and a switchable polarization rotator 58 (eg, a switchable half-wave plate) is provided between the display device 22 and the light control element 55. Is placed on the path.

It is assumed that display device 22 incorporates an exit polarizer to emit substantially planar-polarized light, or else a linear polarizer is disposed between the display device and the polarization rotator. This light control element 55 is arranged such that the polarization plane of the light leaving the display device (or polarizer) is parallel to the direction of the polarization area of either the regions A or the regions B. In this example, assume that this display device emits plane-polarized light along the y-direction.

When a voltage is applied between the electrodes 51 and 52 of the light control element, the dyed liquid crystal is switched to lie parallel to the z axis and does not absorb the y-polarized light passing through the element. This is true for regions A and B. The display is in common mode.

When no voltage is applied between the electrodes 51 and 52 of the light control element, the dyed liquid crystals align along the louver direction (the x-axis in the region A and the y-axis in the region B). If the polarization rotator is inactive, light incident on the optical control element 55 is y-plane polarized. Therefore, regions A are nonabsorbent because polarization regions 16a of regions A do not absorb y-plane polarized light. However, polarized regions 16b of regions B absorb for y-plane polarized light and thus transmit only light propagating to or near the yz-plane. Therefore, an observer looking along the z axis sees almost no absorption and can read the information displayed on the image display device 22. An observer moving left or right (along the x direction) sees absorption from areas marked B, and these areas appear dark, making it impossible to read the information on the display. The display appears to have a 'checkerboard' light pattern and dark squares overlaid on it, which darkens the image. Therefore, the display provides privacy along the x-direction in this mode.

To obtain privacy in the y-direction, the polarization rotator is switched to rotate the polarization plane of incident light by 90 °. Light incident on the light control element 55 is now plane-polarized along the x-direction. Regions B no longer absorb, but regions A absorb light propagating at any angle to the xz-plane and only transmit light propagating at or near the xz-plane. The observer moving along the y-direction sees absorption from areas A, which areas appear dark, making it impossible to read the information on the display. The display again appears to have a 'checkerboard' light pattern and dark squares overlaid on it, which darkens the image. Therefore, the display provides privacy along the y-direction in this mode.

The order of the elements is not limited to the order shown in FIG. 25C. The light control element 55 of FIG. 25A can be disposed before the display or after the transmissive display so that the display can be switched between the common display mode and the personal display mode.

In the embodiment of FIG. 25A, since the electrodes 51, 52 are not patterned, a uniform electric field is applied across the entire area of the light control element 55. Therefore, the entire area of the light control element can be switched between the common mode and the private mode.

Patterning the directions of polarization regions is on a simple extension of the method for making the unpatterned “louver” structure of FIG. 21. The alignment direction of the liquid crystal is also patterned so that it is always parallel to the polarization regions 16a and 16b. Methods of patterning alignment layers of liquid crystal cells are also well known, and are usually on a simple extension of the alignment methods described above with reference to FIGS. 11A and 11B. Appropriate methods are also described, for example, in US Pat. Nos. 6,055,103 and 6,624,863, US Patent Application 2003/0137626, and in H. Stevenson and M.Khazova, in Korean, Seoul, Asia Display 2004 Patterned grating alignment of reactive mesogens for phase retarders'.

The display shown in FIG. 25C can be changed by replacing the switchable polarization rotator with a fixed patterned retarder. The patterned retarder includes regions that rotate the polarization plane of incident light by 90 ° and regions that have no effect on the polarization plane of incident light. The areas correspond to areas A and areas B of the light control element 55 in size, shape and location. Each and every area A of the light control element is aligned with the area of the patterned retarder that rotates the polarization plane of light by 90 °, and each and every area B of the light control element does not rotate the polarization plane of the light. The light control element and the patterned retarder are aligned such that they are aligned with the area (reversely established).

In a display where each area A of the light control element is aligned with the area of the patterned retarder that rotates the polarization plane of light by 90 °, the light passing through the areas A is plane polarized along the x-direction, Light passing through regions B is planar polarized along the y-direction (assuming light incident on the patterned retarder is y-plane polarized). If no voltage is applied to the louver layer, the regions B absorb light propagating at an angle to the yz-plane, and only light propagating at or near the yz-plane as described above. Permeate. Similarly, area A absorbs light propagating at an angle with the xz-plane and only transmits light propagating at or near the xz-plane. Thus, private mode provides privacy in both the x and y directions.

In another alternative, the alignment of liquid crystal molecules through the light control element 55 is in the same direction. The control element simultaneously provides horizontal and vertical privacy for light polarized along the liquid crystal alignment direction. For example, if the liquid crystal molecules are aligned in the y direction in both the regions A and B, the y-plane polarization propagating at an angle with the xz plane is absorbed in the region A, and the region A is y only if it propagates at or adjacent to the xz plane. It transmits polarized light. Similarly, y-plane polarization propagating at an angle with the yz plane is absorbed in region B, and region B transmits y-polarized light only when propagating at or adjacent to the yz plane. In this embodiment, the liquid crystal alignment direction is preferably parallel to the direction of the polarization region in the region A (or region B) and perpendicular to the direction of the polarization region of the region B (or region A). No additional polarization rotator is required in this embodiment.

26 is a schematic perspective view of a light control element 60 according to another embodiment of the present invention. Elements of the light control element 60 are shown separately in FIG. 26 for simplicity of explanation.

The light control element 60 of this embodiment is again an active optical control element. It can operate in one of four modes: a common mode, a mode that provides privacy in the x direction, a mode that provides privacy in the y direction, and a mode that provides privacy in both the x and y directions.                     

The light control element 60 includes two sets of polarization regions 16a and 16b similar to the polarization region 16 of the light control element 50 of FIG. 21. Polarization regions 16a and 16b are switchable between absorbed and non-absorbed states. In a preferred embodiment, the polarization regions 16a, 16b of the light control element 60 are made of a dye-containing liquid crystal material which is switchable between an absorption state (no voltage application) and a non-absorption state as described above. The space between adjacent polarization regions 16a, 16b is filled with a transmissive material.

The first set of polarization regions 16a are aligned along one direction, in this example along the x direction. These polarization regions 16a are disposed between the first electrode 52 and the lower center electrode 62. The polarization region 16a is switched between the state absorbing for the x plane polarization component and the state transmitting for the x component. In either state, the first polarization region 16a transmits the y polarization component.

The second polarization region 16b extends substantially perpendicular to the first polarization region and extends along the y direction in this example. The second polarization region 16b is disposed between the upper center electrode 61 and the second electrode 51 and may be switched between a state absorbing for y plane polarization and a state transmitting for y polarization component. In either state, the second polarization region 16b transmits light of the x polarization component.

The half-wave plate 63 is disposed between the lower center electrode 62 and the upper electrode 61.

Consider the operation of the light control element 60 when illuminated from below by the x plane polarization 64. If the first polarization region is switched to its absorption mode, then this region transmits only x polarization that propagates on or near the x-y plane. Light propagating at an angle with the x-z plane is absorbed.

The half-wave plate 63 rotates the polarization plane of light by 90 degrees. Accordingly, x-polarized light passing through the first polarization region 16a may be converted into y-polarized light by the half-wave plate 63, and y-polarized light may be absorbed by the second polarization region 16b. Thus, if the second polarization region 16b is also switched to its absorption mode, this region absorbs light propagating at an angle to the yz plane and only transmits light propagating at or near the y-z plane. Thus, if both the first polarization region and the second polarization region are switched to their absorption mode, the light control element 60 passes only the light propagating along or adjacent to the z direction. The control element 60 thus provides privacy in both the x and y directions in this mode.

The first polarization region 16a may be independently controlled from the second polarization region 16b. Thus, it is possible to put the first polarization region 16a in its absorption mode, while putting the second polarization region 16b in the non-absorption mode. In this case, the light control element absorbs light propagating at an angle with the xz plane, but does not absorb light propagating at an angle with the yz plane, thereby providing privacy only in the y direction.

Conversely, the first polarization region 16a may exhibit nonabsorbency, while the second polarization region 16b may exhibit absorptivity. In this case, light propagating at an angle with the yz plane is absorbed and the device provides privacy only in the x direction.

If both the first polarization region and the second polarization region are nonabsorbent, the optical control element 60 operates in a common mode and has a wide viewing range.

The optical control element 60 of FIG. 26 is placed either on the front of the display or on the back of the transmissive display. The linear polarizer is provided behind the optical control element 60 so that light incident on the lower substrate 56 of the optical control element is plane-polarized. When the optical control element 60 lies in front of the display device, the linear polarizer may be the exit polarizer of the display device. Alternatively, the polarizer may be provided on the back side of the light control element.

27B shows another optical control element 65 of the present invention. This optical control element is again an active control element 65 and comprises a polarization region 16 made of a dye containing liquid crystal material which is switchable between an absorption state and a non-absorption state. The space between adjacent polarization regions is filled with a transmissive material. The polarization region 16 is disposed between the lower substrate 56 and the upper substrate (not shown). The lower electrode 52 is disposed on the lower substrate 56, and the upper electrode (not shown) is disposed on the upper substrate.

In the optical control element 65 of FIG. 27B, the polarization region has a limited extent in both the x and y directions, and thus has the form of "pillars" extending along the z direction. . The "pillars" are arranged in a matrix, with pillars in one row being laterally offset relative to "pillars" in adjacent rows.

Within each pillar-shaped polarization region 16, the alignment direction of the liquid crystal is selected to be a direction along the x or y axis. The alignment direction of the liquid crystal in each pillar-shaped polarization region is defined by any prior art. For example, the direction of liquid crystal alignment is controlled by alignment layers as described above or by modifications applied to existing photoresist or polymer layers. The alignment layer is patterned by any suitable technique, and examples of suitable methods have been described above with reference to FIG. 25C.

The optical control element 65 of FIG. 27B is aligned to provide privacy in both the x and y directions. This is done by selecting such that the alignment direction of the liquid crystal molecules in each polarization region 16 is the same. For example, assume that liquid crystal molecules are aligned along the y direction in each polarization region 16, and y plane polarization is incident on the optical control element. When the polarization region 16 is switched to its absorption state, each polarization region absorbs the y polarization component. As a result, the y plane polarization can pass through the optical control element 65 only along or along the z axis. Any y-polarized light propagating at an angle with the xz plane or at an angle with the yz plane is absorbed by the polarization region 16. Thus, the control element 65 provides privacy in both the x and y directions.

When the polarization region is switched to the non-absorbed state, the y polarization component can pass through the optical control element without large absorption, providing a common mode.

In contrast, the optical control element 49 of the type shown in FIG. 21 has polarization regions 16 aligned to be parallel strips as compared to that shown in FIG. Thus, the polarization region provides privacy in only one direction-in the example shown in FIG. 27 (a) the polarization region 16 cannot limit the output angle in the yz plane-only privacy along the x axis can do.

The optical control element 65 of FIG. 27B is provided on the back of the transmissive display device or on the front of the display device. As described above, the linear polarizer must be provided in series with the optical control element, which can be the output polarizer of the display device in which the control element lies in front of the display device, or in the display device in which the control element lies in the back of the transmissive display device. It may be an inlet polarizer.

Figure 28 (a) shows another optical control element 66 according to the present invention. Optical control element 66 is an active control element and includes a region of dye containing liquid crystal material that is switchable between an absorbed state and a non-absorbed state. The region 17 between the polarization regions is filled with a transmissive material. The polarization area and the transparent area 17 are disposed between the lower substrate 56 and the upper substrate 57 (not shown). The lower electrode 52 is disposed on the lower substrate, and the upper electrode (not shown) is disposed on the upper substrate.

In the present embodiment, the transparent region 17 has a limited range in both the x and y directions, and thus has the form of a "pillar" extending along the z direction. The polarization area is defined in the gap between the transparent areas 17.

The alignment direction of the liquid crystal molecules is not uniform over the region of the optical control element 66. The alignment direction of the liquid crystal molecules is patterned such that each transparent region 17 has at least one polarization region having a first alignment direction and at least one other polarization having a second liquid crystal alignment direction substantially perpendicular to the first alignment direction. Adjacent to the area. In a preferred embodiment in which the transparent region 17 is substantially rectangular in plan view, opposite sides of the transparent region are adjacent to the polarizing region having the first liquid crystal alignment direction, and the other two opposite sides are the second liquid crystal alignment. Adjacent to the polarization region having a direction.

28B is a schematic plan view of the optical control element 66, illustrating one possible arrangement of the liquid crystal alignment direction. In this embodiment, the first and second alignment directions are parallel to the x and y directions, respectively. As shown, the left and right sides of the transparent region (as the device is shown in FIG. 28 (b)) are adjacent to the polarization region 16b where the liquid crystal molecules are aligned along the y direction (the alignment direction of the liquid crystal molecules is It is represented by the dash of FIG. 28 (b)). The upper and lower surfaces of the transparent region 17 (as the optical control element is shown in FIG. 28B) are adjacent to the polarization region 16a in which the liquid crystal molecules are aligned along the x direction.

In operation, the optical control element 66 is disposed in series with the switchable polarizing rotator. The operation of the control element 66 is described below with reference to an example where a switchable polarizing rotor is disposed behind the control element 66 and the light incident on the polarizing rotor is plane polarized along the y direction.

When the polarization rotator is deactivated, the y polarization passes through the polarization rotator and is incident on the optical control element 66. The polarization region 16b in which the liquid crystals are aligned along the y axis is absorbing with respect to the y polarization component, and when the control element is switched to its absorption mode, the y polarization propagating at an angle with the yz plane is transmitted to the polarization region 16b. Is absorbed. The polarization region 16a has liquid crystal molecules aligned along the x axis, and thus does not absorb the y polarization component largely. Thus, control element 66 provides privacy in the x direction.

When the polarization rotator is switched on, the polarization plane of the incident light is rotated 90 degrees. Thus, the original y polarized light is converted into x polarized light and is incident on the control element 66. X-polarized light is absorbed in the polarization region 16a in which liquid crystal molecules are aligned along the x direction. Light propagating at an angle with the xz plane is absorbed in the polarization region 16a, and privacy is provided for the y direction. The polarization region 16b in which the liquid crystal molecules are aligned along the y direction does not substantially absorb the x polarization component.

Thus, by switching the polarization rotator, the control element 66 can provide privacy in either the x direction or the y direction.

The control element 66 and polarization rotator may be disposed in front of the display or behind the transmissive display.

FIG. 28C is a schematic plan view of another embodiment of the control element 66, illustrating another way in which the polarization regions 16a, 16b can be aligned. Other configurations of the polarization regions 16a and 16b are also possible, but the configuration shown in Figs. 28B and 28C is good because it mimics the effect of the louver structure shown in Fig. 21. Do. When the polarization region 16a is effective, for example, it provides a louver structure in which the polarization region extends along the x axis, and conversely, when the polarization region 16b is effective, the louver structure in which the polarization region extends along the y axis is provided. to provide. These configurations are effective because the polarization region is most effective when the alignment direction of the liquid crystal molecules in the polarization region is aligned with the louver structure parallel to the direction of the louver structure.

In the above embodiment, the viewing angle provided in the personal mode is substantially the same over the entire area of the control element. This is shown in FIG. 29, which is a schematic diagram of a display having the control element 67 of the present invention disposed in front of the image display device 22. The control element 67 can be any control element of the invention, including any one of the preferred embodiments described above. It can be seen that the viewing angles are displayed for the three positions A, B, and C over the area of the control element 15, and that the viewing angle range is substantially the same at each position. This may have the disadvantage that an observer at a finite distance from the control element 67 may read part of the display but not other parts of the display. In the example of FIG. 29, the observer at position 68 located on one side of the display is within the viewing range of position C, is only within the viewing range of position B, and is outside the viewing range of position A. FIG. Thus, the observer at position 68 cannot read the entire display. Indeed, if the area of the display panel is large and the viewer is close to the display, there may be no location where the viewer can read the entire display.

This problem can be overcome by varying the observation angle of the control element over the area. 30 shows another control element 67 ′ of the present invention disposed in front of the display device 22. The control element 67 does not have a constant observation angle over the area.

In a preferred embodiment, at or near the center of the display, ie at position B, the viewing angle of the control element has a minimum θ ₁ . The viewing angle increases toward either side of the display, having a value θ ₂ at position A or position C. The observer at the observation position 68 may be within the observation ranges of positions A, B, and C to read the displayed information over the entire area of the display. The variation in the viewing angle can be symmetric about the display center.

The viewing angle need not vary symmetrically with respect to the center of the control element, but can be configured to vary in other ways. For example, if you want the display to always be visible on only one side, the viewing angle of the control element need not change symmetrically across the display. For example, assuming that the display of FIG. 30 is always observed at position 68, control element 67 'has a large viewing angle at position C (since observation position 68 is almost directly above position C). There is no need, and the viewing angle may simply increase across the control element from position C toward position A. The viewing angle may, for example, vary linearly with respect to the position across the control element from position C toward position A.

The viewing angle of the control element can be configured to vary according to the position from the left to the right of the control element and / or the vertical position from the top to the bottom of the control element.

The aforementioned control element can be modified relatively easily to provide a varying viewing angle over the area. For example, the viewing angle can be increased by increasing the ratio of the width of the transparent area to the width of the polarization area. This can be done, for example, by increasing the width of the transparent area while keeping the width of the polarization area the same. In an embodiment employing a patterned multilayer polarizer, such as the control element 15 ′ of FIG. 5, the viewing angle is defined between the lateral separation between two adjacent polarization regions 16 relative to the width of the polarization region. It can be increased by increasing the ratio.

31A is a schematic cross-sectional view of another optical control element 69 of the present invention. This embodiment is an activation control element and is generally similar to the control element 50 of FIG. It includes a plurality of liquid crystal regions 16 disposed between the upper substrate 57 and the lower substrate 56. A transparent material 17 is provided between the liquid crystal regions 16. As in the embodiment of FIG. 21, the liquid crystal region contains dye molecules. When the liquid crystal regions are switched to align the dye molecules along the z direction and also to align themselves along the z direction, the polarization region 16 is nonabsorbent with respect to either the x component or the y component of the polarized light. . When the liquid crystal molecules in the polarization area are switched to align along the horizontal direction (in this embodiment, the x direction), the dye molecules align themselves along the x direction, and the polarization area is absorptive to the x component of the surface polarized light. Control element 69 is in private mode.

31B is a schematic plan view of the lower electrode 52 of the control element 69. As can be seen, the lower electrode 52 consists of inter-digitated electrodes 52a and 52b. Each electrode includes a series of "fingers" that extend transversely from the bus line. The "finger" of the electrode is disposed adjacent to the polarization region, as shown in Fig. 31B. The polarization region 16 disposed adjacent the finger of the electrode 52a is disposed between the two polarization regions adjacent to the finger of the other sub-electrode 52b, and vice versa.

The control element 69 of FIG. 31A can be switched to one of three states. When all polarized regions are switched to their absorption state, a narrow angled personal mode is obtained. If all polarization regions are switched to their non-absorbing state, a common mode is obtained. However, as shown in Fig. 31A, it is possible to obtain a third mode by switching all other polarization regions to its absorption mode and switching the remaining polarization regions to their non-absorption modes. This provides a second personal mode with a wider viewing angle than the personal mode obtained when all polarization regions 16 are switched to their non-absorbing state. Thus, the control element 69 can operate in a narrow angle private mode, a wide angle private mode or a common mode.

In a control element in which the liquid crystal molecules are in an absorption state when no voltage is applied and are switched to a non-absorption state by applying a voltage, by applying a voltage between both the electrode 51 and the sub-electrodes 52a and 52b. A common mode is obtained. Wide angle personal mode by applying a voltage between the upper electrode 51 and one of the sub-electrodes 52a and 52b, and not applying a voltage between the electrode 51 and the other of the sub-electrodes 52a and 52b. Is obtained. In the state shown in FIG. 31A, a voltage is applied between the electrode 51 and the sub electrode 52b, but no voltage is applied between the electrode 51 and the sub electrode 52a. 31A and 31B are merely examples of control elements capable of operating in two or more individual modes having different viewing angles. Many other configurations are possible. For example, one of the electrodes can be configured as three sub-electrodes, each of which switches every third polarization region. The control element may operate in a personal mode in which every third polarization region absorbs and other polarization regions do not absorb, which is a personal mode having a wider viewing angle than the mode shown in FIG. To provide.

In all the embodiments of the invention described above, there is a compromise between the brightness of the display and the effectiveness of the personal mode. As an example, using a dye liquid crystal louver switched by an electric field, it is more complete to increase the concentration of the dye to increase the absorption of light and to prevent unwanted observers from seeing the light. There is an embodiment to decrease the brightness. The same fact applies for the concentration of absorbent material in other embodiments, and similar compromises are made for the thickness and number of layers in embodiments using laminated polarizing sheets.

Typically, if one wants to improve the brightness of a personal display, one needs to sacrifice privacy levels, i.e. to reduce the difference between the light levels visible to unwanted observers in public and private modes. Thus, when this contrast level is relatively small, a method of increasing the privacy level is useful.

This can be done by switching some areas of the display to private mode and leaving other areas corresponding to the common mode. For example, the display may be divided into square squares having approximately the same size as the characters of the text expected to be displayed. The alternating square regions of the checkerboard pattern may be switched to public and private mode, All four nearest neighbors per 'public' square area become the private square area and vice versa.

The unwanted observer in private mode then sees a checkerboard pattern of light and dark areas overlaid on the image shown on the display. This pattern can interfere with the readout of the display even with the entire display switched to the 'personal' state and made clear.

The checkerboard pattern is only one example of a pattern that may consist of "public" and "private" areas. This pattern may, for example, consist of text designed to distract viewers from the displayed personal text, or may consist of a logo or advertisement.

Switching of selected areas of the display can be accomplished in several ways. In an embodiment where switching between private and shared modes is achieved by separate switchable wavelength plates, the wavelength plate may be patterned such that only certain areas of it are valid. Here, in the case where the switchable wavelength plate comprises a liquid crystal layer, this can be done, for example, by filling certain areas with photoresist before the liquid crystal enters, so that these photoresist areas are optically in all modes of the display. It is maintained to be isotropic.

In all embodiments, the selected regions can be switched by patterning one or more electrodes used to switch devices. For example, one electrode may be divided into two conductive regions that do not form electrical contacts, while one region may be permanently switched on while the other region is switched on in private mode and shared mode. Is switched off. Alternatively, selected regions of the electrodes can be completely removed so that no electric field can be applied to these regions and they are always kept unswitched.

One possible problem with the aforementioned methods is that there may be some difference in the luminance of the public mode and the private mode even for the observer in the central position. When switching to private mode is patterned, this results in a weak pattern that overlaps on the display even for the observer in the center position. The data delivered to the display panel can be changed to solve this problem. The luminance of the pixels in the "public" area can be somewhat reduced so that the displayed gray level matches across the entire display.

A possible problem experienced by many embodiments of the present invention is that the luminance of the personal mode is relatively low. This is because the polarization dependent light control film absorbs much of the light traveling through them in the personal mode. For example, when light of the correct polarization is provided, the light control element shown in FIG. 5 will absorb more light portions than the portion absorbed by the area of each side covered by the polarizer.

To reduce this effect, lenses or other refractive elements can be placed in the plane between the backlight and the light control film. 32 is a diagram showing an example of such a display.

The display 70 of FIG. 32 has an addressable liquid crystal layer disposed between the display panel 22, for example an entrance polarizer and an exit polarizer, and illuminated by a backlight 25. The light control element of the present invention is disposed between the backlight and the display panel and in this embodiment the control element is a control element 15 'as shown in FIG. Only a stack 21 of polarizing material is shown in FIG. 32. A switchable half-wave plate 24 is disposed between the control element 15 ′ and the display panel 22. Finally, a lens array 71 is disposed between the backlight 25 and the control element 15 '.

In the personal mode of the display 70, the stacked polarizer sheet 16 of the control element 15 ′ absorbs light in a polarization state passing through the incoming polarizer of the display panel 22. The backlight 25 emits light at a wide angle, but is preferably arranged to emit light more strongly along the axis of the display device 70 than in any other direction. The lens array 71 is arranged such that the stacked polarizer 16 is close to the focal plane of the lens array 71, and the center portions of the lenses 71a of the array are aligned with the gaps between adjacent stacks 21 of the polarizer. Is arranged to be.

Light emitted by the backlight 25 along the axis of the display will pass between the stacks 21 of polarizers and thus will be incident on the display panel 22. Lens array 71 directs the light emitted by the backlight at the axial angle of the display, allowing it to pass through the gaps between adjacent stacks 21 of the polarizing sheet. Accordingly, the lens array increases the amount of light in the desired polarization state passing through the control element 15 'without being propagated and absorbed along or in the z-direction as it passes through the control element 15'. This increases the brightness of the display in this personal mode.

In the common mode of the display, the switchable wavelength plate 24 is switched such that the polarization state of the light absorbed by the stacked polarizer sheets 16 is the polarization state absorbed by the incoming polarizer of the display panel 22. Accordingly, absorption of light by the polarizer sheet 16 in the common mode is not critical.

In the above-described embodiment of the present invention employing a louver structure, the refractive indices of the polarization regions 16, 16a, 16b and the transparent elements therebetween are such as to minimize Fresnel reflection at the interface between the polarization region and the neighboring transparent region. It is preferred to be selected. This is because these reflections can limit the performance of the louver structure in common mode.

The solid line curve in FIG. 33 shows the result of the transmittance calculation for the louver structure in which the refractive index of the absorbing segments is 0.15 times larger than that of the transparent segments. The curve indicated by the dotted line represents the transmittance of the same louver structure when the refractive index of the absorbing segments is the same as that of the transparent segments. As can be seen, Fresnel reflections, which occur when the refractive indices do not match, can cause large variations in undesired luminance with respect to the viewing angle in common mode. These large variations are eliminated if the refractive indices of the transparent and absorbing segments coincide.

When the display with the light control element of the present invention is switched from the common mode to the personal mode, the light distribution emitted by the backlight can also be changed to improve the personal mode. For example, the backlight can be manufactured to simply be darker in personal mode, making it more difficult for unwanted observers to read the display.

Alternatively, the operating mode of the backlight can be changed to reduce light transmission towards unwanted observers. This can be done by switching the backlight from the uncollimated mode to the focused mode. This not only improves privacy but also has the advantage of reducing the power consumption of the display.

The invention can also be applied to prevent glare (reflected ambient light) from interfering with the viewing of the display. For example, in an instrument panel display of a motor vehicle, a polarization-sensitive light control film may be placed in front of the display, thereby making the display unreadable from points higher than the normal viewing position in personal mode. In this mode, the light control film also prevents ambient light from reaching the display at a high angle, and also prevents ambient light from reflecting off the display and entering the user's field of view.

Light control may also be applied to prevent light from the display from reflecting off other sides and confused a user. For example, in an automobile, the dashboard display must be carefully arranged so that the light is not reflected from the windscreen at night and does not obstruct the driver's view on the road. The present invention can be applied to prevent light from reaching the windscreen when the light is switched to the "personal" mode under low illumination. If the ambient light level is high, this reflection is not important, so the display can be switched to the "public" mode, which can have the advantage of high brightness.

In such an application, the device can be switched automatically between the glare-reducing ('personal') mode and its normal mode or automatically according to an optical sensor that detects ambient light conditions. The brightness of the display itself may also vary automatically depending on the ambient light conditions.

In a display incorporating the active light control element of the invention, the light control element is used between its common mode and its private mode, for example,

1. Manually-the display may include a switch or other means used by the user to select the desired mode; or

2. It can be switched in a variety of ways, including by software running on a computer to cause the display to switch.

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In case 2, the software may cause the display to automatically switch when the user views personal content (eg, a secure web page or bank account information). The request for privacy may be indicated by a signal contained in an electronic file (e.g., an XML tag or icon or an image within a web page) or the request for privacy may be indicated when the web page is observed using a password or any key. It may be assumed by the display when words (eg, "password", "confidential") appear.

Any of these methods can be used for switching between personal modes where a light control element having one or more personal modes is used.

The display incorporating the active light control element of the present invention also has an indicator for indicating that the display is in personal mode. For example, an indicator such as an LED may light up next to the display, or the LED may cause the word 'individual' to light up next to the display.

Alternatively, the display may display an indication that the display is in personal mode. The term "personal" may appear on the display or in some other location on the display when the display is in personal mode. For example, an icon may be displayed on the display itself.

The light control element of the invention has been described in connection with a display. However, the light control elements of the present invention are not limited to use only for displays. Combining the light control element of the present invention with a polarization switch disposed in an optical path passing through the light control element forms a light control device having many application ranges. For example, such a light control device can be sold separately so that it can be attached to an existing display and become a switchable display between common and private modes. Such a light control device may also have other applications. As one example, it may be used to make a window that can be switched between a narrow transmission angle range and a wide transmission angle range. The window is effective to block glare when switched to have a narrow range of transmission angles. Such windows would have applications such as switchable sun visors for motor vehicles, for example.

In the above embodiments where a polarization switch is used, the polarization switch may comprise a liquid crystal cell. This allows the polarization rotation effect to be switched on or off by suitably switching the electric field applied across the liquid crystal cell.

When the polarization switch includes a liquid crystal cell, the liquid crystal of the liquid crystal cell may operate in one of a plurality of liquid crystal modes. For example, the liquid crystal cell may utilize the Freedericks mode, which has the advantage that the optical properties of the liquid crystal cell do not depend greatly on the viewing angle.

Alternatively, the liquid crystal mode used may be a twisted nematic (TN) mode. This mode has the advantage that its optical properties do not depend very much on the light wavelength. The TN cell can be operated in a region, such as a posterior-tary minimum or moggin limit, in which the dependence of the optical properties on the light wavelength is minimized.

As another alternative, a vertically oriented nematic mode can be used. In this case, the polarization rotation effect is switched on by applying an electric field and there is no polarization rotation effect when no power is applied. Use of this mode may have the advantage of minimizing power consumption in some applications.

The polarization switch including the liquid crystal cell is not limited only to the liquid crystal modes specifically mentioned above. Other liquid crystal modes can be used within the scope of the present invention.

The characteristics of the polarization switch can be optimized using known techniques to minimize light leakage through the system in directions intended to block the transmission of light, which can be achieved for any type of polarization switch and includes a liquid crystal cell. It is not limited only to the polarization switching.

When the polarization dependent light control element is located behind or in front of a transmitted display image illuminated with light in a first polarization state, the light control element limits the angular range of the light output and the image is displayed in a narrow angle range to allow the individual Allow display mode to be acquired. However, when the display is illuminated with light in the second polarization state, the image is displayed in a larger angular range, thereby providing a common display mode. Switching between the common display mode and the personal display mode is performed simply by changing the polarization state of the light incident on or displayed from the displayed image and thus switching between the public display mode and the personal display mode. Can be done without a movable part. In the common mode, since little or no light is absorbed by the light control element, the light efficiency is high, so that the light control element of the present invention can be produced easily and economically.

Claims (65)

On at least a portion of its area, a first emission angle range for outputting light in a first polarization state and a second polarization state that is greater than the first emission angle range and different from the first polarization state Light control element having a second emission angle range for emitting the light of the. The method of claim 1, wherein at least a portion of its area is opaque or substantially opaque to light traveling in the direction of the first range with the first polarization state, and having the first polarization state and A light control element that is not substantially opaque to light traveling in a direction of a second range different from the direction of the first range, and is not substantially opaque to the second polarization state. The light control element of claim 1 or 2, wherein the second polarization state is orthogonal to the first polarization state. 3. The method of claim 1, further comprising a plurality of first regions that are opaque or substantially opaque to light in the first polarization state and are transmissive to light in the second polarization state, the first adjacent region of claim 1. Each pair of regions is spaced apart from each other by a material having transparency to light in the first polarization state and light in the second polarization state. 5. The light controlling element according to claim 4, wherein each first region extends parallel to a direction intersecting a plane of the element. The light control element of claim 4 wherein each first region extends parallel to a direction perpendicular to the plane of the element. The substrate of claim 4, wherein the substrate has transparency to light in the first polarization state and light in the second polarization state, a plurality of recesses in the substrate, and substantially opaque or substantially to light in the first polarization state. And a material opaque and transmissive to light in said second polarization state and disposed within each recess. 5. The substrate of claim 4, further comprising: a substrate that is opaque or substantially opaque to light in the first polarization state and transparent to light in the second polarization state, a plurality of recesses in the substrate, And a material disposed in each recess and transmissive to light and to light in said second polarization state. The device of claim 4, wherein each first region extends parallel to the plane of the device, the first regions arranged to be a plurality of stacks each of two or more regions, the stacks of adjacent stacks. And each pair is laterally spaced apart from one another by a material having transparency to the light in the first polarization state and the light in the second polarization state. The individual of claim 1, wherein the device has a first emission angle range for light in the first polarization state and the second emission angle range for light in the second polarization state over at least a portion of its area. A light control element switchable between a private mode and a public mode having a third emission angle range greater than the first emission angle range for light in the first polarization state over at least a portion of its area. 11. The device of claim 10, wherein the device is in addition to a second personal mode having an exit angle range for the light in the first polarization state that is greater than the first exit angle range and less than the third exit angle range. Switchable light control element. delete delete delete delete delete The light control element of claim 4 wherein each region comprises a linear polarizing material. 11. The light controlling element of claim 10, wherein each first region comprises a linear polarizing material in its first state. 19. The light controlling element according to claim 18, wherein each second region comprises a linear polarizing material in its third state. The light control element of claim 10, wherein at least one of the first regions is switchable between its first state and its second state independently of at least another of the first regions. The light control element according to claim 4, wherein each region comprises a liquid crystal material. 22. The light controlling element according to claim 21, wherein said liquid crystal material is a guest-host liquid crystal material. The light control element of claim 1, wherein the emission angle range for light in at least one polarization state is varied over an area of the element. A light control device comprising the light control element according to claim 1 and a polarization switch arranged in an optical path passing through the light control element. 25. The light controlling device according to claim 24, wherein said polarization switch comprises a switchable wave-plate. 25. The light controlling device according to claim 24, wherein said polarizing switch comprises a switchable half wave-plate disposed in series with a linear polarizer. A display comprising the light control element of claim 1. 28. The display of claim 27, further comprising a polarization switch disposed in an optical path through the light control element. The display of claim 28, wherein the polarization switch comprises a switchable wave plate. 30. The display of claim 29, wherein the polarization switch comprises a switchable halfwave plate disposed in series with a linear polarizer. 30. The display as claimed in claim 27, wherein the light control element, when used, forms a parallax optic for light in the first polarization state so that the display acts as a multiple viewing direction display. Display enabled. The first light control device according to claim 1, The second light control device according to claim 1, First polarization switch Including, And wherein the emission angle range of the first light control element relative to the light in the first polarization state is different from the emission angle range of the second light control element relative to the light in the first polarization state. 33. The display of claim 32, further comprising a second polarization switch. The first light control device according to claim 1, Opaque or substantially opaque for light traveling in a direction of the third range with a second polarization state, and for light traveling in a fourth range direction different from the direction of the third range with the second polarization state A second light control element that is not substantially opaque and is not substantially opaque to light in the first polarization state; A polarization switch disposed in the optical path passing through the first and second light control elements Display comprising a. 35. The device of claim 34, wherein the first light control element emits light in the first polarization state within an angle range centered near the first direction when used, and the second light control element is used in the first direction when used. And emitting light in the second polarization state within an angle range centered in a second direction different from the second direction. A display comprising the light control element according to claim 9, The display further comprises user operating means for switching the light control element between a common mode and a private mode. A display comprising the light control element according to claim 9, And the light control element is automatically operable to switch between a common mode and a private mode following the execution of a predetermined operation on or in the display. 38. The display of claim 37, wherein the predetermined operation is an indication of information classified as public or private, the indication causing the light control element to switch to the common mode or to the personal mode, respectively. The display of claim 27 comprising means for indicating when the light control element is in a personal mode. The display of claim 27 operable to display an indication that the light control element is in a personal mode. 34. A display according to any one of claims 28, 32 or 33, wherein said or each polarizing switch comprises a separate liquid crystal cell. 43. The display of claim 41, wherein the or each liquid crystal cell uses a Freedericksz liquid crystal mode. 43. The display of claim 41, wherein the or each liquid crystal cell uses a twisted nematic mode. 42. The display of claim 41, wherein the or each liquid crystal cell uses a vertically aligned nematic mode. 42. The display of claim 41, wherein the characteristics of the or each polarization switch are selected to minimize light leakage through the display in directions intended to block transmission. 25. The light controlling device according to claim 24, wherein said polarizing switch comprises a liquid crystal cell. 47. The light controlling device according to claim 46, wherein the liquid crystal cell uses a Frederitz liquid crystal mode. 47. The light controlling device according to claim 46, wherein said liquid crystal cell uses a twisted nematic mode. 47. The light controlling device according to claim 46, wherein said liquid crystal cell uses a vertically aligned nematic mode. 47. The light control device of claim 46, wherein the properties of the polarization switch are selected to minimize light leakage through the device in directions intended to block transmission. In the light control device manufacturing method, Stacking a plurality of polarizing sheets by stacking one on top of each other, each polarizing sheet comprising a polarizing layer and at least one light transmissive substrate; and Adhering each polarizing sheet to adjacent polarizing sheet (s) Light control device manufacturing method comprising a. The method of claim 51, Disposing a photocurable adhesive over the first polarizing sheet; Stacking a second polarizing sheet on the first polarizing sheet; Irradiating the adhesive to cure the adhesive to adhere the first polarizing sheet to the second polarizing sheet. Light control device manufacturing method comprising a. 53. The method of claim 51 or 52, further comprising providing a light transmitting layer between each pair of adjacent polarizing sheets. 53. The method of claim 51 or 52, further comprising removing selected regions of the polarization layers of all polarizing sheets of the stack. 53. The method of claim 51 or 52, further comprising cutting the laminated sheets into slices, wherein the direction of cutting is perpendicular to or alternatively to the plane of the polarizing sheets. A method for manufacturing a light control element, which is another direction that is not parallel to the plane of the field. In the light control device manufacturing method, Removing selected regions of the polarizing layer of the first polarizing sheet, wherein the polarizing sheet comprises a light transmissive substrate and the polarizing layer; Stacking a second polarizing sheet on the first polarizing sheet; Removing selected regions of the polarizing layer of the second polarizing sheet Light control device manufacturing method comprising a. Forming a plurality of recesses in the light transmissive substrate, Providing a polarizing material in the recesses Light control device manufacturing method comprising a. Forming a plurality of recesses in the substrate formed of the polarizing material, Providing a light transmissive material in the recesses Light control device manufacturing method comprising a. 59. The method of claim 57 or 58, wherein the step of forming the recesses in the substrate comprises selectively irradiating the substrate. The device of claim 4, wherein the device is further configured to define the first emission angle range for light in the first polarization state and the second emission angle range for light in the second polarization state over at least a portion of its area. And a common mode having a third emission angle range greater than the first emission angle range for the light in the first polarization state, over a personal mode having and an at least a portion of its area. 61. The light control of claim 60, wherein each first region is switchable between an opaque first state for light in the first polarization state and a second state that is substantially transmissive for light in the first polarization state. device. 62. The apparatus of claim 61, further comprising a plurality of second regions, wherein each pair of adjacent second regions are separated from each other by a material that is transparent to light in the first polarization state and light in the second polarization state Wherein each second region is switchable between a third state that is opaque for light in the second polarization state and a fourth state that is substantially transmissive for light in the second polarization state. 63. The apparatus of claim 62, wherein the first regions are provided within one or more first areas of the light control element, and the second regions are provided within one or more second areas of the light control element. And the first area (s) do not overlap the second area (s). 63. The light control element of claim 62 wherein the first regions are disposed above the second regions. 66. The light control element of claim 63 wherein the first regions extend perpendicular to the second regions.

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