JP2009042419A - Optical control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical control deve which can be manufactured in a relatively simple method, has a high-speed responsiveness, is less restricted in composition materials, and prevents a short circuit between electrodes. <P>SOLUTION: The optical control device 8a includes a nonlinear optical layer 4 changing optical characteristics of incident light and emitting the light with changed optical characteristics, a nonconductive layer 3 having a sufficient refractive index difference from the nonlinear optical layer, and a counter electrode 5 effecting an electric field to the nonlinear optical layer 4 so as to change the optical characteristics. The counter electrode is arranged in a direction intersecting the traveling direction of light. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light control device suitable for a display device, for example.

  Conventionally, with respect to display devices such as television receivers and information terminal devices, in order to meet the demands for thinning, lightening, large screens, and high-definition display, a cathode ray tube (CRT) type with limited weight and thickness. There is a lot of development to move from display devices to flat panel display devices.

  In particular, as a flat panel display device as an information terminal device, for example, a liquid crystal display is widely used. Recently, research and development have been conducted on increasing the brightness and size of the liquid crystal display.

  Such a liquid crystal display is a display device having a structure using liquid crystal molecules. For example, liquid crystal is sealed between two glass plates, and a voltage is applied to the liquid crystal molecules to change the direction of the liquid crystal molecules, thereby transmitting light. The image is displayed by increasing / decreasing. In this structure, the liquid crystal molecules themselves do not emit light, and display is performed using reflected light in a bright place, and display is performed using light of a fluorescent lamp (backlight) prepared in the back in a dark place.

  Furthermore, there are broadly divided into a simple matrix method such as STN (super twisted nematic) method and DSTN (double-layered STN) method and an active matrix method such as TFT (thin film transistor) method, the former being cheaper. However, the latter has higher performance. Liquid crystal displays are often used as portable computers and space-saving desktop personal computers because they are thinner and lighter than other display devices such as CRT displays and plasma display panels (PDPs).

  For example, in a TN type liquid crystal display, for example, by inserting a twisted liquid crystal between two polarizing filters whose polarization directions are orthogonal to each other so that light does not pass, incident light entering through one polarizing filter can be obtained. , Twisted 90 degrees along the gap between the liquid crystal molecules, and passed through the opposing polarizing filter (light transmission state).

  On the other hand, when a voltage is applied to the liquid crystal molecules, the liquid crystal molecules stand upright and become twisted, and incident light travels between the liquid crystal molecules as they are, and cannot pass through the opposing polarizing filter (light blocking state). It will be.

  In this way, in the TN type liquid crystal display, the liquid crystal molecules in a state where the arrangement of the molecules is twisted by 90 degrees are arranged between the two polarizing filters, so that light passes when no voltage is applied, When voltage is applied, light is blocked and the screen turns black. That is, the liquid crystal molecular layer performs a light shutter function depending on whether or not a voltage is applied.

  Many flat panel displays and their manufacturing methods that make use of the characteristics of these liquid crystal molecules have been proposed.

  However, while the liquid crystal display has various advantages, there are various technical problems due to the display principle. These problems (1) to (5) are listed below.

(1) Response speed The response time of a liquid crystal panel is longer than that of a cathode ray tube display or a plasma panel. This fact is particularly clearly pointed out by using a liquid crystal panel as a television mainly for displaying moving images.

  This is mainly because the orientation change of the liquid crystal molecules is delayed from the applied waveform due to the viscosity of the liquid crystal layer and the thickness of the layer. In the case of observation as a display device including a backlight, the fact that the backlight is always lit in the display frame and an image is continuously displayed (hold drive) is also a major factor.

(2) Viewing angle A liquid crystal panel display has a narrow viewing angle compared with other displays (for example, a cathode ray tube display etc.). This is because the liquid crystal panel display uses the liquid crystal alignment for display, and the relationship between the orientation of the liquid crystal alignment and the observation direction affects the light transmittance and the light reflectance.

  In particular, in the development of liquid crystal panel displays for television applications and the like, increasing the viewing angle is a major technical issue.

  Currently, measures are taken to increase the viewing angle by, for example, an IPS (in-plane switching) system or a VA (vertical alignment) system. These methods are designed so that the light transmittance of the liquid crystal panel display does not depend on the viewing direction as much as possible by devising a combination of orientations of liquid crystal alignment used for display (for example, bright display or dark display). Yes.

  Further, although not as effective as these methods, a device for expanding a viewing angle by arranging a retardation film using liquid crystal molecules between a polarizing filter and a liquid crystal layer has been devised.

(3) Contrast The value obtained by dividing the brightness of the bright display by the brightness of the dark display is the contrast (this is also referred to as the contrast ratio, and is usually also referred to as the dark place contrast because it is measured in a dark room). And is used as an indicator of display quality.

  The contrast of a display device with a low contrast is a very important index. In contrast, a liquid crystal panel display has a limit because it is difficult to display perfect black.

  This is because the liquid crystal panel cannot sufficiently shield the incident light from the backlight. The more detailed cause is that the polarization degree of the polarizing filter is not completely 100%, the liquid crystal layer and the color filter. For example, since the polarization is slightly canceled due to, for example, the display light leaks depending on the viewing angle, and the like can be seen.

  For this reason, when a dark screen in a movie or the like is projected by a liquid crystal panel display, it becomes difficult to express, for example, darkness of jet black, which is a technical problem in the case of using a liquid crystal panel for video applications such as a television.

  Note that the contrast (light contrast) in a room in which normal illumination is turned on is rather higher in a liquid crystal panel (for example, a transmissive liquid crystal panel) than in a PDP (plasma display panel) or the like. This is because the bright place contrast is measured simultaneously with the light reflected by the display surface in addition to the brightness due to the display, similarly to the light seen by the observer.

  The reflectance of the display surface of the liquid crystal panel display is lower than the reflectance of the PDP, and there is little decrease in bright place contrast. This is because in a liquid crystal panel, a color filter and a polarizing film that absorb light are arranged on the display surface, whereas in a PDP, the phosphor itself is white and has a high reflectance.

  Actually, the contrast in the dark place of the current liquid crystal panel is about 500 to 1000, so the contrast of the liquid crystal panel becomes a problem only when observing in a dark room, and it is a problem in an application used in a bright room. Often not.

(4) Power consumption Since the liquid crystal panel itself does not emit light (self-emission), there is a case where a light emitting source that emits a certain amount of light is required, which is more efficient than the light emitting element. It may get worse.

  This is because a polarizing filter, a color filter, and the like are arranged, so that the light transmittance of the liquid crystal panel excluding the backlight is about 5% to 10%, and most of the light from the backlight is a polarizing filter or This is because it is absorbed by the color filter. Therefore, in general, power consumption is higher than that of a plasma display panel (PDP) or the like.

  In addition, a liquid crystal panel that does not use a backlight (reflection type liquid crystal panel) is frequently used as a display element with low power consumption, but power consumption becomes a problem depending on the application. This is because the liquid crystal must be AC driven, and even when the display content is not rewritten (in the case of a still image), power for charging and discharging is necessary. In contrast, other display methods (electrophoretic display, etc.) have been developed instead of liquid crystals.

(5) Dot drop The liquid crystal panel has a very delicate structure, and in the TFT-type liquid crystal panel which is currently mainstream using thin film transistors, a huge number of transistors are formed on a glass substrate.

  Since a transistor is an electronic component that is extremely weak against contamination by foreign matters, even if dust of about several angstroms is mixed in, a malfunction occurs. As a result, a dot (image element) having an abnormality in a related electronic circuit does not function normally, so that a dot drop is generally generated.

  At present, it is said that the unit price of a liquid crystal panel will increase 10 times if a drop of about 2 to 3 dots is not allowed per LCD panel, and the manufacturer has difficulty in dealing with customers as a technical limit. is doing.

  Among the problems described above, a decrease in response speed is a factor that significantly degrades the image quality of moving images, and is an essential item for improving display performance.

  For the above-mentioned problems, the viscosity of the liquid crystal material is reduced, the thickness of the liquid crystal layer is reduced, the device for overshooting the display drive waveform (overdrive), the insertion of black display between display frames by the display drive waveform, and Measures such as blinking of the backlight are taken.

  However, although the response speed is slightly improved, the fundamental characteristics have not been improved.

  On the other hand, a new light control device has been proposed, and a high-speed light control device using a photonic crystal having a so-called opal 3D structure has been proposed.

  However, in the above structure, it is necessary to form a 3D structure on the substrate, and the process is very complicated.

  On the other hand, in order to improve the above-mentioned problem, in the flat-type display device, a wavelength shift type light control device having a layer having a wavelength selection function and a layer having a wavelength shift function is disclosed in a prior application by the present applicant. Although proposed, this configuration makes it possible to obtain stable high-speed moving image characteristics with a simple method (see Patent Document 1 described later).

  That is, this wavelength shift type light control device is characterized in that a layer having a function of controlling light transmittance (light absorption) of a specific wavelength and a layer that transmits only light of a specific wavelength are formed on a substrate. It is said.

  Here, in the layer having a function capable of controlling the light transmittance (light absorption) of a specific wavelength on the substrate, for example, by applying a voltage to the photonic crystal, the refractive index of the component is changed, and the photo By changing the nick band wavelength, the light transmittance (light absorption) of a specific wavelength is controlled.

  FIG. 5 shows a configuration example 58 of such a wavelength shift type light control device.

In this configuration example 58, as shown in FIG. 5A, a backlight module 56 using LEDs (light emitting diodes) is used as a light source, and a transparent electrode 55 and a ferroelectric PLZT (with ferroelectricity) are formed on a glass substrate 61. A photonic crystal structure having a laminated structure with a PbLaZrTiO ₃ ) layer 57 is arranged, and color filters 52R, 52G and 52B having a wavelength selection function are arranged on the photonic crystal structure.

  FIG. 5B is a plan view showing a state in which the color filters 52R, 52G and 52B, the transparent electrode 55, and the PLZT layer 57 are arranged on the glass substrate 61 so as to have a laminated structure.

Japanese Patent Application No. 2006-116384 ([Claim 1], [Claim 4], paragraph number [0037], [FIG. 3])

  However, the structure of the invention of the prior application shown in FIG. 5 has a laminated structure of the layer 55 for applying the voltage V to the photonic crystal and the layer 57 having a wavelength shift function. Since conductivity is required, there are problems such as a limitation of materials that can be selected.

  In addition, since the conductive material has a relatively high refractive index, there is a problem that it is difficult to obtain a large difference in refractive index from the layer 57 having a wavelength shift function.

  In addition, since a laminated structure of a thin film of 100 nm or less is indispensable in order to control the wavelength in the visible region, there is a concern such as a short circuit (dielectric breakdown) between electrodes in the upper and lower parts when using a conductive material. is there.

  The present invention has been made in view of such a situation, and the object thereof is to reduce the restrictions on the constituent materials in a light control device capable of high-speed response that can be manufactured by a relatively simple method. Therefore, the difference in refractive index between adjacent layers is increased, and a short circuit between electrodes is sufficiently prevented.

  That is, the present invention provides an optical functional layer that changes the optical characteristics of incident light, emits light having the changed optical characteristics, and a counter electrode that applies an electric field to the optical functional layer in order to change the optical characteristics. The counter electrode is related to a light control device provided facing the direction crossing the light traveling direction.

  According to the light control device of the present invention, since the counter electrode is provided so as to face in the direction intersecting the light traveling direction, the counter electrode is disposed at a position other than the light transmitting portion of the optical function layer. can do. Therefore, since the counter electrode is not laminated with the optical function layer in the light transmitting portion, the electrode constituent material can be selected from various materials without considering the refractive index difference with the optical function layer, and the counter Since the electrodes can be arranged on both side surfaces of the optical functional layer or in the vicinity thereof, even if the thickness of the light transmission portion is small, a short circuit between the counter electrodes can be prevented.

  This light control device can also form each constituent layer by a relatively simple method, and is excellent in high-speed response as an operation characteristic of the light control device.

  In the present invention, in order to fully exhibit the above-described effect, each electrode of the counter electrode is provided on one end side of one surface of the optical functional layer and the other end side of the other surface, respectively. It is desirable that they are arranged.

  Moreover, it is desirable to have a laminated structure in which the optical functional layer and the nonconductive layer are laminated.

  In this case, a plurality of the optical function layers may be laminated, and a voltage may be applied between the counter electrodes in each of the plurality of optical function layers.

  In addition, it is desirable to obtain outgoing light in which the wavelength of the incident light is changed as the optical characteristic. In this case, the transmission wavelength or absorption wavelength of the incident light may change, and the optical function layer may be opposed to the optical function layer. It is desirable to arrange a filter having wavelength selectivity in the light traveling direction.

  In this case, at least the refractive index of the optical functional layer may be controlled by applying a voltage between the counter electrodes.

  The optical functional layer preferably has a photonic crystal structure.

  In addition, a liquid crystal element may be disposed on the light path, and the light may be further modulated by the liquid crystal element.

  Further, the stacked structure forms a plurality of pixels and can be configured as a display device that performs color display by the emitted light.In this case, the incident light is obtained from a backlight light source or an external light source, The emitted light is preferably passed through the color filter.

  Next, a preferred embodiment of the present invention will be described with reference to the drawings.

First Embodiment FIGS. 1 and 2 show a light control apparatus 8a according to a first embodiment of the present invention.

As shown in FIG. 1A and FIG. 1B, a non-conductive layer (for example, a glass substrate) 11 that does not absorb light in the visible region is opposed to the backlight module 6 made of LEDs. A laminated structure in which SiO ₂ films) 3 and nonlinear optical layers (for example, nitroaniline films or PLZT layers) 4 are alternately laminated is formed. Each of the stacked structures constitutes a pixel, and the non-conductive layer 3 and the nonlinear optical layer 4 are joined with a predetermined refractive index difference so as to exhibit the target optical characteristics. .

Further, in order to apply the voltages V ₁ , V ₂ , V ₃ , and V ₄ to each nonlinear optical layer 4, a transparent electrode (for example, ITO or polyethylene dioxythiophene electrode) 5 is positioned on the upper left surface of each nonlinear optical layer 4. And at the lower end position on the right end, respectively, crossing the traveling direction of light. These transparent electrodes (counter electrodes) are arranged to face each other at a position that does not interfere with the optical axis of the backlight module 6 (a position that avoids the passage of light from the backlight). Each electrode 5 is partially embedded in the non-conductive layer 3, but is not limited thereto. Moreover, each voltage may be the same as each other, but may be different.

  By constructing this structure as a display device corresponding to the wavelength regions of the three primary colors, a flat display element capable of arbitrarily controlling the hue can be manufactured.

In the present embodiment, for example, a SiO ₂ film 3 as a non-conductive layer and ITO as a transparent electrode layer 5 to which a voltage is applied on a glass substrate 11 such as quartz as a substrate that does not absorb in the visible region. A layer and a nonlinear optical layer (for example, a PLZT film) 4 capable of controlling the refractive index by applying a voltage are laminated, for example, with 21 layers each having a thickness of 100 nm, so that light control having a wavelength shift function is achieved. The device 8a can be produced.

  In this light control apparatus, since the transparent electrode 5-5 is disposed obliquely opposite to the nonlinear optical layer (electro-optic film) 4, the nonlinear optical layer 4 has a relationship between its film thickness and length. Is taken into consideration, an electric field substantially in the lateral direction of the film surface is generated. For this reason, the refractive index of the nonlinear optical layer 4 changes due to the interaction with the electric field in the lateral direction. In this case, since the nonlinear optical material has a high tendency to be oriented perpendicular to the film surface, the non-linear optical material reacts more greatly to the electric field in the lateral direction than the electric field in the direction perpendicular to the film surface, and the change in the refractive index increases.

The above-mentioned SiO ₂ film 3, ITO layer 5 and PLZT film 4 are formed, for example, by a usual sputtering method, and the PLZT film 4 is crystallized by subsequent heat treatment. Thereafter, the color filters 2R, 2B, and 2G are fixed to the back surface of the glass substrate 1 that does not absorb in the visible region as a layer having a wavelength selection function.

In FIG. 2, after the incident light L ₀ having a wavelength of λ ₁ is transmitted through the light control device 8a, it is converted into an emitted light L having a wavelength of λ ₂ and extracted through each color filter. This is because the incident light L ₀ is selectively shifted to a wavelength light corresponding to R, G, or B for each pixel, passed through each color filter, and extracted as outgoing light L.

  As a result of examining the response speed of the light control device 8a, it is 8 μsec compared with 8 msec in the case of a display element using a conventional liquid crystal, and a high-speed operation can be obtained.

  In the present embodiment, an ITO layer is used as the conductive layer 5 and PLZT, which is a material having a characteristic capable of controlling the refractive index by applying a voltage, is used as a constituent material of the nonlinear optical layer 4. Without being limited to this material, the structure and conditions can be changed as appropriate without departing from the spirit of the present invention.

For example, at least trigonal crystalline LiNbO ₃ and LiTaO ₃ , perovskite crystalline BaNaNb 5015, PbLaZrTi, PbLaLiZrTi, PbZrTi, KTiOPO ₄ and KNbO ₃ may be used as the material of the ferroelectric film.

  As another configuration example, for example, a constituent material having a photonic crystal structure includes, for example, a nitroaniline film as a wavelength-shiftable thin film 4, a SiO film as a non-conductive thin film 3, and a polyethylene dioxythiophene film as a transparent electrode 5. Can be used to form the light control device 8a.

  That is, on a substrate that does not absorb in the visible region, for example, a glass substrate 11 such as quartz, the SiO film as the non-conductive layer 3, polyethylene dioxythiophene as the electrode 5 to which the voltage is applied, and the refractive index can be reduced by applying the voltage. The controllable nitroaniline film 4 is, for example, 31 layers each having a thickness of 100 nm, whereby a layer having a wavelength shift function can be produced.

  The organic conductor layer (polyethylenedioxythiophene) 5 can be formed by, for example, a spin-on method, and the nitroaniline film can be formed by an evaporation method.

  Thereafter, the color filters 2R, 2G, and 2B are fixed on the glass substrate 1 that does not absorb in the visible region as a layer having a wavelength selection function.

  As a result of examining the response speed with the light control device having this configuration, it is 8 μsec, compared with 8 msec in the case of a display element using a conventional liquid crystal, and a high-speed operation can be obtained.

  According to the present embodiment, the electrode 5 is disposed on the layer 4 having the wavelength shift function at a position other than the light transmission portion, and a voltage is applied by the plurality of counter electrodes 5 disposed. Further, the layer 3 used in combination with the layer 4 having the wavelength shift function can be selected from non-conductive materials capable of taking a sufficient refractive index difference with the layer 4 having the wavelength shift function. It is hard to be restricted by material selection.

  For example, in conventional ITO, n = about 1.9, but in a typical silicon oxide film, n = 1.4, which can be reduced by about 0.5.

  In addition, since the material is non-conductive, problems such as short circuit and dielectric breakdown that are likely to occur between the electrodes in the laminated structure of the conductive material and the nonlinear optical film described above are less likely to occur.

  This light control device can be formed by a relatively simple method, can respond at high speed, and can obtain good characteristics.

Second Embodiment FIG. 3 shows a light control device 8b according to a second embodiment of the present invention, and an LCD between the color filters 2R, 2B and 2G and the uppermost non-conductive layer 3 is shown. (Liquid crystal element) 7 is the same as in the first embodiment except that 7 is arranged.

  That is, due to the presence of the LCD 7, the wavelength-shifted (converted) outgoing light obtained from the above-described laminated structure is further optically modulated, and the target wavelength light can be selectively extracted. However, the LCD 7 is schematically shown, and its structure can be adopted from known ones.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to these examples at all, and can be suitably changed in the range which does not deviate from the main point of invention.

  For example, the electrode 5 may be disposed on each end face of the non-conductive layer 3 as shown in FIGS. 4B and 4C in addition to the above-described example as shown in FIG.

  Further, the laminated structure of the non-conductive layer 3 and the nonlinear optical layer 4 is not necessarily a structure in which a plurality of layers are laminated. For example, the number may be only one, but sufficient wavelength conversion is performed. A plurality of layers are preferably stacked.

  As for the position of the backlight module 6, the distance from the substrate 11 can be changed if the emitted light from now on is sufficiently utilized. This backlight is suitable for a transmissive display device, but in the case of a reflective type, the backlight is unnecessary and the light source is external light.

  The LCD 7 may be disposed not only on the light emitting side of the light control device 8a but also on the light incident side. Further, the LCD 7 may be provided independently for each color portion (dot).

  The light control device of the present invention is suitable for a flat display device.

2A is a cross-sectional view of the light control device according to the first embodiment of the present invention, and FIG. It is sectional drawing which shows the wavelength conversion and selection condition of incident light similarly. It is sectional drawing of the light control apparatus by the 2nd Embodiment of this invention. It is sectional drawing (A), (B), (C) which shows the example of various arrangement | positioning of an electrode similarly. It is sectional drawing (A) and its top view (B) of the light control apparatus by prior invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 11 ... Board | substrate, 2R, 2G, 2B ... Color filter, 3 ... Non-conductive layer,
4 ... Nonlinear optical layer, 5 ... Transparent electrode, 6 ... Backlight module, 7 ... LCD,
8a, 8b ... Light control device

Claims (13)

  An optical functional layer that changes the optical characteristics of incident light and emits light having the changed optical characteristics, and a counter electrode that applies an electric field to the optical functional layer to change the optical characteristics. The light control device in which the electrode is provided so as to face the direction intersecting with the light traveling direction.   The light control device according to claim 1, wherein each electrode of the counter electrode is disposed on one end side of one surface of the optical functional layer and the other end side of the other surface.   The light control device according to claim 1, wherein the light control device has a laminated structure in which the optical functional layer and a non-conductive layer are laminated.   The light control device according to claim 3, wherein a plurality of the optical functional layers are laminated.   The light control device according to claim 4, wherein a voltage is applied between the counter electrodes in each of the plurality of optical functional layers.   The light control apparatus according to claim 1, wherein outgoing light in which a wavelength of the incident light is changed is obtained as the optical characteristic.   The light control apparatus according to claim 6, wherein a transmission wavelength or an absorption wavelength of the incident light is changed.   The light control device according to claim 7, wherein at least a refractive index of the optical functional layer is controlled by applying a voltage between the counter electrodes.   The light control device according to claim 1, wherein the optical functional layer has a photonic crystal structure.   The light control device according to claim 1, wherein a liquid crystal element is disposed on a path of the light, and the light is further modulated by the liquid crystal element.   The light control device according to claim 6, wherein a filter having wavelength selectivity is disposed in the light traveling direction so as to face the optical functional layer.   The light control device according to claim 3, wherein the stacked structure forms a plurality of pixels and is configured as a display device that performs color display using the emitted light.   The light control device according to claim 11, wherein the incident light is obtained from a backlight light source or an external light source, and the emitted light is passed through a color filter.

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