JP2008009061A - Backlight device and transmission type display device having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight device capable of improving characteristics at the time of wide/narrow viewing angle modes by enlarging an angular range in which a light intensity distribution is drastically changed. <P>SOLUTION: The transmission type display device 1A is provided with: a back surface light source 3A; a light control element 4A which is arranged on the light emission side of the back surface light source 3A and includes a dispersed liquid crystal material layer 4a capable of electrically switching a transparent state and a cloudy state; and a lens sheet 5A which is arranged on the light emission side of the light control element 4A and has a plurality of lenses 5L one-dimensionally or two-dimensionally arranged on at least one side surface of the lens sheet. Since the lens sheet 5A is disposed on the light emission side of the light control element 4A, the light intensity distribution at the time of the wide viewing angle mode and the light intensity distribution at the time of the narrow viewing angle mode can be changed drastically and the characteristics upon the wide/narrow viewing angle modes can be improved as compared with those in a light control element single body. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a backlight device including a light control element capable of controlling the direction of light emitted from, for example, a liquid crystal display panel, and a transmissive display device such as a liquid crystal display device including the backlight device.

  Examples of the dispersed liquid crystal material in which the transparent polymer material and the liquid crystal are dispersed in a minute region and mixed with each other include, for example, a polymer dispersed liquid crystal (PDLC) and a polymer network liquid crystal (PNLC). )It has been known. Depending on the orientation of the liquid crystal, if a material is selected such that the refractive index of the liquid crystal region takes a value close to that of the non-liquid crystal polymer region and a value not so close, the refractive index Corresponding to the difference, the composite material can take a state of scattering light (white turbidity) and a state of being transparent to light. Utilizing this property, the liquid crystal orientation can be controlled by using an electric field applied to the composite material using, for example, two electrode plates, and light can be selected from two states of scattering and transparency by electric input. Devices have been proposed.

  On the other hand, with the spread of mobile devices such as notebook computers and mobile phones in recent years, there is an increasing demand for countermeasures against anxiety that the user looks into the display screen from around the train. Also, in some cases, there is a requirement that two people want to see the same screen together, and instead of simply pasting a louver film that narrows the viewing angle on the surface of the display panel, the viewing angle can be switched reversibly. There is a need to be able to do it.

  In response, several proposals have been made to change the viewing angle of the display screen by using the electrically variable light scattering function of the above-mentioned dispersed liquid crystal material to achieve a peep prevention. For example, in Patent Document 1 below, in a display device using a light source that illuminates the display panel from the back, light that illuminates the display panel is provided by disposing a light control element including a dispersed liquid crystal material between the back light source and the display panel. A configuration for changing the angular distribution of intensity is disclosed.

  As shown in FIG. 7, the liquid crystal display device 100 includes a rear light source 101, a display panel 102, a light control element 103 as a transparent / scattering switching device disposed between the rear light source 101 and the display panel 102, The prism sheet 104 is disposed between the back light source 101 and the light control element 103. The light control element 103 is for electrically controlling the divergence angle of light from the rear light source 101 toward the display panel 104 using the transparency and scattering of the dispersed liquid crystal material, and the viewing angle is θ1 in the transparent state. And a wide viewing angle mode in which the viewing angle is θ2 in a scattering state. The prism sheet 104 has a function of collecting the light emitted from the back light source 101 and efficiently guiding it to the light control element 103.

  Further, in Patent Document 2 below, the transmission / scattering switching device as described above can easily obtain an action of widening the angular distribution of the light intensity after transmission compared to incident light. A structure using a light guide plate with a narrower divergence angle than a plate with a wider divergence angle is disclosed.

  Patent Document 3 below discloses a configuration in which the viewing angle is limited by overlapping a guest-host liquid crystal cell on the front surface of the display panel in order to switch the viewing angle between wide and narrow. When a guest-host liquid crystal cell is used to limit the viewing angle, the cell gap needs to be well controlled. Compared to this, in the case of a dispersed liquid crystal material that functions by switching between transparent / scattering, the cell gap dependency is relatively small, and there is an advantage that cells can be formed using a flexible and lightweight plastic film. Further, it is advantageous in that light absorption loss can be suppressed because it is not necessary to use a polarizing plate for the switching cell. In the following Patent Document 3, a PDLC is also arranged between the back light source and the display panel. However, this PDLC is used for switching between a reflective display and a transmissive display, and controls the viewing angle. It is not intended.

JP-A-9-105907 JP 2005-257756 A Japanese Patent Laid-Open No. 10-197844

  However, as described in Patent Document 1, in a conventional liquid crystal display device using a light control element made of a dispersed liquid crystal material, a dispersion that can obtain a relatively high transmittance even when a scattering function is selected. Since the liquid crystal material has excellent small-angle scattering, there is a problem that the light intensity distribution can be remarkably changed only in a narrow angle range in the front direction of the display panel.

  Therefore, as proposed in the above-mentioned Patent Document 2, when a light source with a narrow angle distribution of light intensity is used as the back light source, the light control element may be switched to the scattering function and set to the wide viewing angle mode. It is difficult to widen the viewing angle before two people can see the screen at the same time. Conversely, when a light source with a wide light intensity distribution is used as the back light source, the change in intensity distribution due to the transparent / scattering switching of the light control element does not reach a level that can be recognized. It is impossible to realize a narrow viewing angle that can be achieved.

  The present invention has been made in view of the above-described problems, and a backlight device capable of enlarging an angle range in which the light intensity distribution changes remarkably and improving characteristics in a wide / narrow viewing angle mode, and a transmission type including the backlight device It is an object of the present invention to provide a liquid crystal display device as a display device as a representative example.

  In solving the above problems, the transmissive display device of the present invention includes a surface light source and a dispersed liquid crystal material that is disposed on the light emission side of the surface light source and can be electrically switched between a transparent state and a cloudy state. The light control element includes a light control element and a lens sheet that is disposed on the light emission side of the light control element and has a plurality of lenses arranged one-dimensionally or two-dimensionally on at least one surface.

  In the present invention, the lens sheet is disposed on the light emitting side of the light control element, thereby obtaining a function of expanding or reducing the divergence angle of the light emitted from the light control element with the lens on the lens sheet. As a result, the light intensity distribution in the wide viewing angle mode and the light intensity distribution in the narrow viewing angle mode can be significantly changed compared to the case of the light control element alone, and the characteristics in the wide and narrow viewing angle mode can be changed. Improvements can be made.

  The lens sheet is a lens array in which a plurality of lenses are two-dimensionally arranged in addition to a lens sheet in which a plurality of lenses are one-dimensionally arranged on one or both surfaces, such as a cylindrical lens sheet or a prism sheet. Sheet is applicable. The lens shape, lens pitch, lens height, and the like are not particularly limited, and can be set as appropriate according to the light emission characteristics of the surface light source, the light transmission characteristics of the light control element, the required viewing angle characteristics, and the like.

  A single-layer structure of a dispersed liquid crystal material layer constituting the light control element may be used, or a selective arrangement may be made corresponding to the focal position of each lens on the lens sheet. The dispersed liquid crystal material layer is sandwiched between a pair of transparent electrode layers, whereby the transparent state and the cloudy state are electrically switched. In the present invention, the dispersed liquid crystal material layer uses light transmittance in a transparent state to emit light emitted from a surface light source from a lens sheet at a first divergence angle, and has a light scattering property in a cloudy state. Utilizing this, light emitted from the surface light source is emitted from the lens sheet at a second divergence angle that is narrower than the first divergence angle. The dispersed liquid crystal material layer is not limited to a transparent state when a voltage is applied and is configured to take a white turbid state when no voltage is applied, and may be a white turbid state when a voltage is applied and a transparent state when no voltage is applied.

  And, by combining the backlight device of the present invention described above with a liquid crystal display panel, the light intensity distribution can be remarkably changed in the narrow viewing angle mode and the wide viewing angle mode, so that the wide viewing angle A wide viewing angle that allows a large number of people to view the same display screen at the same time in the mode, and a narrow viewing angle that allows only one person to view the display screen in the narrow viewing angle mode. be able to.

  As described above, according to the present invention, the light intensity distribution in the wide viewing angle mode and the light intensity distribution in the narrow viewing angle mode can be significantly changed. Improvements can be made.

  Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the following embodiments, and various modifications can be made based on the technical idea of the present invention.

(First embodiment)
1 and 2 are schematic configuration diagrams of a transmissive display device 1A according to a first embodiment of the present invention. The transmissive display device 1A is configured as a liquid crystal display device for mobile devices such as a notebook personal computer and a mobile phone.

  The transmissive display device 1A of the present embodiment is disposed between the liquid crystal display panel 2, the back light source 3A disposed on the back side of the liquid crystal display panel 2, and the liquid crystal display panel 2 and the back light source 3A. A light control element 4A and a lens sheet 5A are provided.

  The liquid crystal display panel 2 has a known configuration, and although not shown, a pair of transparent substrates, a liquid crystal layer sandwiched between the transparent substrates, and a polarizing plate respectively disposed on the outer surface side of the transparent substrate And.

The back light source 3A is configured by a known surface light source such as a direct type or an edge light type having a fluorescent tube, a light emitting diode or the like in a light source part. In addition, 3 A of back light sources may be comprised with planar light sources, such as an electroluminescent element.
In particular, in the present embodiment, a surface light source having a relatively low directivity (a relatively large divergence angle) is used as the back light source 3A.

  The light control element 4A is disposed between the back light source 3A and the lens sheet 5A. The light control element 4A includes a dispersed liquid crystal material layer 4a that can be electrically switched between the transparent state shown in FIG. 1 and the white turbid state shown in FIG. The light control element 4A of this embodiment has a configuration in which a plurality of dispersed liquid crystal material layers 4a and transparent resin layers 4b are alternately arranged in the same plane. The dispersed liquid crystal material layer 4 a is disposed corresponding to the focal position of each lens 5 </ b> L on the lens sheet 5.

  The dispersed liquid crystal material layer 4a can obtain a dispersed structure of liquid crystal by phase separation when the mixed liquid of liquid crystal and ultraviolet curable resin is irradiated with ultraviolet rays. Therefore, a light control element having a single layer of the dispersed liquid crystal material layer 4a can be produced by performing ultraviolet exposure on the entire surface of the mixed liquid formed in a layered manner. On the other hand, as shown in the figure, as a method of dividing the dispersed liquid crystal material layer 4a into the same plane as the transparent resin layer 4b and ensuring the consistency in the positional relationship between the arrangement of the dispersed liquid crystal material and the lens arrangement, the layer is formed in layers. The dispersed liquid crystal material layer 4a can be selectively formed only in the region corresponding to the condensing position of the lens 5L by irradiating the mixed liquid with ultraviolet rays through the lens sheet 5A.

  The dispersed liquid crystal material layer 4a and the transparent resin layer 4b have a structure sandwiched between a pair of transparent electrode layers 7a and 7b. The dispersed liquid crystal material layer 4a becomes transparent as shown in FIG. 1 when a predetermined voltage is applied between the pair of transparent electrode layers 7a and 7b, and linearly transmits the light L emitted from the back light source 3A together with the transparent resin layer 4b. On the other hand, the dispersed liquid crystal material layer 4a becomes cloudy as shown in FIG. 2 when a predetermined voltage is not applied between the pair of transparent electrode layers 7a and 7b, and scatters the light L emitted from the back light source 3A.

  One transparent electrode layer 7 a is formed on the light incident surface of the lens sheet 5 A, and the other transparent electrode layer 7 b is formed on the transparent support sheet 8. Thereby, the light control element 4A of the present embodiment is configured integrally with the lens sheet 5A. A viewing angle control circuit 11 including a voltage source 9 and a changeover switch 10 is connected to the pair of transparent electrode layers 7a and 7b.

  In the present invention, it is an essential point in the manufacturing technology that the spatial positional relationship between the lens arrangement and the discrete arrangement of the dispersed liquid crystal material is consistently formed. As one of the methods for consistently forming the positional relationship, as described above, the liquid crystal and light (or ultraviolet) curable resin mixed liquid held in a continuous layer in contact with the lens sheet is used for the lens sheet itself. There is a method of performing self-aligned exposure using a lens.

  In addition, the concave / convex shape of the lens is formed on the front surface of one sheet, and the concave portion for accommodating the dispersed liquid crystal is formed on the back surface of the same sheet, whereby the positional relationship between the lens and the concave portion for accommodating the dispersed liquid crystal is formed. An integral molding method is also practical so as not to deviate. Double-sided simultaneous hot press molding or the like by a roll process can be employed. In particular, when a lenticular lens in which a lens extends in a one-dimensional direction is combined with a stripe-shaped dispersed liquid crystal accommodating recess, a melt extrusion process is suitable. If the die for lens molding and the die for forming the dispersed liquid crystal containing recess are opposed to each other and the extrusion port is formed, the positional relationship between the lens and the recess is determined by the metal die and molded on the sheet. Can be kept small.

  Further, as shown in FIG. 3, the light control element 4A in which the dispersed liquid crystal material 4d is filled in the recess formed on the surface of the transparent resin layer 4c is configured independently of the lens sheet 5A and then integrated. May be. In this case, the lens sheet and the light control element having the structure as shown in FIG. 3 are simultaneously manufactured in the roll process, and then bonded together without leaving a long time, so that the alignment can be easily performed without distorting the mutual dimensions. be able to.

  The lens sheet 5 </ b> A has a configuration in which a plurality of lenses 5 </ b> L are arranged on one surface on the light emitting side. The lens sheet 5A is for performing an action of enlarging or reducing the divergence angle of the light L of the rear light source 3A controlled by the light control element 4A. In FIGS. 1 and 2, the lens 5L is primary in the x-axis direction. Originally composed of a plurality of cylindrical lens sheets. Alternatively, the lens sheet 5A is configured by a lens array sheet in which a plurality of lenses 5L are arranged in the x-axis direction and the y-axis direction in FIGS. The cross-sectional shape of the lens 5L is not limited to the curved shape shown in the figure, and may be a prism shape.

  The back light source 3A, the light control element 4A, and the lens sheet 5A described above constitute a backlight device 6A of the liquid crystal display panel 2. In the backlight device 6A, when the dispersed liquid crystal material layer 4a of the light control element 4A is in the transparent state shown in FIG. 1, the divergence angle of the light L from the back light source 3A is enlarged or almost changed by the lens sheet 5A. The emitted light is incident on the liquid crystal display panel 2. Thereby, it becomes possible for the observer S to visually recognize the display image of the liquid crystal display panel 2 over a wide angle range centering on the front direction, and the wide viewing angle mode of the transmissive display device 1A is realized.

  For example, by using a lens having an aperture ratio (focal length / aperture) of 0.9 as the lens 5L, parallel light can be expanded to a divergence angle of 30 ° (one side from the optical axis). This angle is sufficiently larger than the divergence angle at which the dispersed liquid crystal material layer 4a can spread light alone.

  On the other hand, when the dispersed liquid crystal material layer 4a of the light control element 4A is in the cloudy state shown in FIG. 2, light L is scattered by the dispersed liquid crystal material layer 4a, and the scattered light is collected by the lens 5L and substantially parallelized. The light is incident on the liquid crystal display panel 2. Thereby, it becomes possible for the observer S to view the display image of the liquid crystal display panel 2 only in a narrow angle range near the front direction, and the narrow viewing angle mode of the transmissive display device 1A is realized.

  The formation pitch, size, shape, aspect ratio, and the like of the lens 5L on the lens sheet 5 can be appropriately set based on the intensity distribution of the light emission angle in the required wide / narrow viewing angle mode. If necessary, a lens may be formed on the other surface of the lens sheet (the surface on the light control element 4A side).

  As described above, according to the transmissive display device 1A of the present embodiment, the light intensity distribution in the wide viewing angle mode and the light intensity distribution in the narrow viewing angle mode of the liquid crystal display panel 2 can be remarkably changed. The characteristics of the wide / narrow viewing angle mode can be improved. In other words, in the wide viewing angle mode, it is possible to realize a wide light intensity distribution that allows two or more people to view the screen at the same time. In the narrow viewing angle mode, only one person can display the screen. A narrow light intensity distribution can be obtained.

(Second Embodiment)
4 and 5 are schematic configuration diagrams of a transmissive display device 1B according to the second embodiment of the present invention. In the figure, portions corresponding to those of the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  The transmissive display device 1B of the present embodiment is disposed between the liquid crystal display panel 2, the back light source 3B disposed on the back side of the liquid crystal display panel 2, and the liquid crystal display panel 2 and the back light source 3B. A light control element 4B and a lens sheet 5B are provided.

  Similar to the back light source 3A in the first embodiment, the back light source 3B is configured by a known surface light source such as a direct type or an edge light type having a fluorescent tube, a light emitting diode, or the like in a light source unit. In particular, in the present embodiment, a surface light source having a relatively high directivity (a relatively small divergence angle) is used as the back light source 3B.

  The light control element 4B is disposed between the rear light source 3B and the lens sheet 5B in the same manner as the light control element 4A in the first embodiment described above, and the transparent state shown in FIG. 4 and the cloudiness shown in FIG. It includes a dispersed liquid crystal material layer 4a whose state can be electrically switched. Also in the present embodiment, as in the first embodiment described above, the light control element 4B has a configuration in which a plurality of dispersed liquid crystal materials 4a and transparent resin layers 4b are alternately arranged in the same plane, The dispersed liquid crystal material layer 4 a is disposed corresponding to the focal position of each lens 5 </ b> L on the lens sheet 5.

  The lens sheet 5B has a configuration in which a plurality of lenses 5L are arranged on one surface on the light emitting side. The lens sheet 5B is for performing an action of expanding or reducing the divergence angle of the light L of the rear light source 3B controlled by the light control element 4B. In FIGS. 4 and 5, the lens 5L is primary in the x-axis direction. Originally composed of a plurality of cylindrical lens sheets. Alternatively, the lens sheet 5B is configured by a lens array sheet in which a plurality of lenses 5L are arranged in the x-axis direction and the y-axis direction in FIGS. The cross-sectional shape of the lens 5L is not limited to the curved shape shown in the figure, and may be a prism shape. In particular, the lens sheet 5B of the present embodiment is provided with a flat portion 5P between two adjacent lenses 5L.

  The back light source 3B, the light control element 4B, and the lens sheet 5B described above constitute a backlight device 6B of the liquid crystal display panel 2. In the backlight device 6B, when the dispersed liquid crystal material layer 4a of the light control element 4B is in the transparent state shown in FIG. 4, the light L emitted from the back light source 3B with a relatively narrow divergence angle is formed in the region where the lens 5L is formed. The light is diverged by the light condensing action and is incident on the liquid crystal display panel 2 in the formation region of the flat portion 5P with almost no change in the divergence angle of the light L. Thereby, it becomes possible for the observer S to view the display image of the liquid crystal display panel 2 over a certain wide angle range centering on the front direction, and the wide viewing angle mode of the transmissive display device 1B is realized.

  On the other hand, when the dispersed liquid crystal material layer 4a of the light control element 4B is in the cloudy state shown in FIG. 5, the light L is scattered by the dispersed liquid crystal material layer 4a, and the scattered light is condensed by the lens 5L and substantially parallelized. The light is incident on the liquid crystal display panel 2. Further, in the flat portion 5P, the light L emitted at a relatively narrow divergence angle of the back light source 3B is transmitted as it is and is incident on the liquid crystal display panel 2. Thereby, it becomes possible for the observer S to view the display image of the liquid crystal display panel 2 only in a narrow angle range near the front direction, and the narrow viewing angle mode of the transmissive display device 1B is realized.

  Note that the formation pitch, size, shape, and formation length of the flat portion 5P of the lens 5L on the lens sheet 5B are appropriately set based on the required intensity distribution of the light emission angle in the wide / narrow viewing angle mode. be able to. In particular, the flat portion 5P is essentially a region where the light focusing action is weaker than that of the lens 5L, and does not mean that the flat portion 5P forms a geometrically strict plane. A smooth curved surface is also used in consideration of processing convenience and optical characteristics.

  As described above, according to the transmissive display device 1B of the present embodiment, the light intensity distribution in the wide viewing angle mode and the light intensity in the narrow viewing angle mode of the liquid crystal display panel 2 as in the first embodiment described above. By significantly changing the distribution, it is possible to improve the characteristics of the wide / narrow viewing angle mode.

  In the present embodiment as well as in the first embodiment, when the dispersed liquid crystal is in a cloudy state, the spread angle of light rays from the backlight device to the transmissive display panel is reduced. . A conventional technique in which a dispersed liquid crystal material is arranged between a back light source such as a fluorescent tube and a display panel to control the magnitude of the light divergence angle is a type of “wide viewing angle in a cloudy state”, which is like the present invention. In addition, there is no known example in which the “narrow viewing angle in a cloudy state” is realized. The achievement of the “narrow viewing angle in the cloudy state” of the present invention is a component in which the light emitted from the back light source passes through the dispersed liquid crystal material and then passes through the lens sheet (or prism sheet) toward the display panel. Depends on the new ordering.

  The operation mode having a “narrow viewing angle in a cloudy state” has the following remarkable features. In order not to impair the brightness of the displayed image when the viewing angle is widened, the total luminous flux transmitted through the display panel is larger than that in the narrow viewing angle mode in order to send light into a large solid angle region. Must be. A light beam incident on the display panel from the back light source passes through a light control element made of a dispersed liquid crystal material. The total luminous flux transmitted through the light control element is larger when the dispersed liquid crystal is not cloudy and transparent (if the brightness of the back light source is constant). That is, the operation mode of “the narrow viewing angle in the cloudy state and the wide viewing angle in the transparent state” of the present invention avoids the disadvantageous light loss in the wide viewing angle mode.

(Third embodiment)
Subsequently, a third embodiment of the present invention will be described. FIG. 6 is a control circuit diagram of the back light source 3 and the dispersed liquid crystal cell (light control element) 4 of the backlight device 6 according to the present invention.

  In the first and second embodiments described above, when the dispersed liquid crystal material layer 4a of the light control element 4A is switched to the white turbid state and set to the narrow viewing angle mode, the display luminance is increased by the light scattering effect by the dispersed liquid crystal material layer 4a. There is a tendency to decrease. On the other hand, since the light is concentrated in a narrow solid angle range, the luminance seen from the front tends to increase at the same time. Since both contradictory actions coexist, it depends on the device which of the front luminance in the narrow viewing angle mode and the wide viewing angle mode becomes higher (when the luminance of the rear light source is kept constant). In any case, in order to keep the display brightness equal in both modes, it is preferable to compensate by increasing or decreasing the brightness of the rear light source in accordance with the viewing angle mode.

  FIG. 6 shows an example of the configuration of the light intensity control circuit 12 that varies the light intensity of the rear light source 3 in the wide viewing angle mode and in the narrow viewing angle mode. Two contacts T1 and T2 selectively connected to the changeover switch 13 are connected to a reference drive voltage source via variable resistors R1 and R2, respectively. The changeover switch 13 is switched in conjunction with the changeover switch 10 of the viewing angle control circuit 11, and is connected to the contact T1 when the switch 10 is ON (in the wide viewing angle mode), and the switch 10 is OFF (narrow viewing angle mode). Is connected to the contact T2. Then, for example, by setting the voltage drop amount of the reference voltage due to the resistors R1 and R2 so that T1 is larger than the contact T2, the light intensity in the narrow viewing angle mode is increased than in the wide viewing angle mode. be able to.

  Further, in order to achieve the low power consumption required for the mobile device, it is desirable to have the property of maintaining the state when the voltage is applied as much as possible even when no voltage is applied to the dispersed liquid crystal cell 4. In such a cell, a low duty pulse source can be used as the drive voltage source 9, which is advantageous for power saving.

  On the other hand, the dispersed liquid crystal cell 4 having the property of maintaining the state when the voltage is applied as much as possible even when no voltage is applied to the cell is compared with the followability of the state when the voltage is switched from OFF to ON. Thus, there is a drawback that the followability of the state when the voltage is switched from ON to OFF is slow. That is, the response of the dispersed liquid crystal cell 4 from the transparent state to the white turbid state is worse than the response of the dispersed liquid crystal cell 4 from the white turbid state to the transparent state. In particular, in the control example in which the light amount of the back light source 3 is increased in the cloudy state, the increase in the scattering property of the dispersed liquid crystal cell 4 when the voltage is switched from ON to OFF tends to be delayed from the increase in the light amount. This appears as an unpleasant phenomenon in which the screen viewed from the front at the time of switching shines abnormally brightly for a moment.

  In order to avoid the phenomenon as described above, in the present embodiment, in the light intensity control circuit 12 shown in FIG. 6, a resistor R3 is inserted in series with the contact T2, and between the changeover switch 13 and the rear light source 3. A capacitor C is inserted in parallel. As a result, the light intensity control circuit 12 increases the amount of light when the dispersion liquid crystal cell 4 is switched to the cloudy state or the OFF state by the magnitude of the time constant determined by the product of the resistance value of the resistor R3 and the capacitance of the capacitor C. Can be delayed. The resistor R3 and the capacitor C correspond to the “delay circuit unit” of the present invention. The resistance value of the resistor R3 and the capacitance of the capacitor C can be appropriately set according to the time required for the dispersion liquid crystal cell 4 to change from the transparent state to the cloudy state.

  Note that the delay control of the light amount increase timing of the rear light source 3 is not limited to that by the above circuit configuration, and can be controlled by, for example, a change in driving voltage from a microprocessor. The configuration of the light intensity control circuit unit 12 having the above configuration is also applicable to a backlight device in which the light control element 4 is disposed on the light exit surface side of the lens sheets 5A and 5B.

1 is a schematic configuration diagram of a transmissive display device according to a first embodiment of the present invention, and shows a wide viewing angle mode. 1 is a schematic configuration diagram of a transmissive display device according to a first embodiment of the present invention, and shows a narrow viewing angle mode. It is sectional drawing which shows the modification of a structure of the light control element which comprises the transmissive display apparatus of FIG. It is a schematic block diagram of the transmission type display apparatus by the 2nd Embodiment of this invention, and the time of wide viewing angle mode is shown. It is a schematic block diagram of the transmissive display apparatus by the 2nd Embodiment of this invention, and the time at the time of a narrow viewing angle mode is shown. It is a circuit block diagram of the backlight apparatus explaining the 3rd Embodiment of this invention. It is a schematic block diagram of the conventional transmissive display apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1A, 1B ... Transmission type display device, 2 ... Liquid crystal display panel, 3, 3A, 3B ... Back light source, 4, 4A, 4B ... Light control element, 4a ... Dispersed liquid crystal material layer, 4b ... Transparent resin layer, 5A, 5B ... Lens sheet, 5L ... Lens, 5P ... Flat part, 6, 6A, 6B ... Backlight device, 7a, 7b ... Transparent electrode layer, 8 ... Transparent support sheet, 9 ... Voltage source, 10 ... Changeover switch, 11 ... Field of view Angle control circuit, 12 ... Light intensity control circuit, 13 ... Changeover switch

Claims (6)

A surface light source;
A light control element that is disposed on the light emitting side of the surface light source and includes a dispersed liquid crystal material that can be electrically switched between a transparent state and a cloudy state;
A backlight device, comprising: a lens sheet that is disposed on a light emitting side of the light control element and on which at least one surface a plurality of lenses are arranged one-dimensionally or two-dimensionally. The backlight device according to claim 1, wherein the dispersed liquid crystal material layer is disposed corresponding to a focal position of each lens on the lens sheet. The dispersed liquid crystal material layer emits light emitted from the surface light source from the lens sheet at a first divergence angle when transparent, and emits light emitted from the surface light source from the lens sheet when clouded. The light is emitted at a second divergence angle narrower than the divergence angle of 1.
The backlight device according to claim 1. A light intensity control circuit that changes the light intensity of the surface light source according to when the dispersed liquid crystal material layer is in a transparent state and when in a cloudy state,
The light intensity control circuit increases the light intensity of the surface light source when the dispersed liquid crystal material layer is cloudy than the light intensity of the surface light source when the dispersed liquid crystal material layer is transparent. The backlight device according to claim 1. The said light intensity control circuit is provided with the delay circuit part which delays switching of the light intensity of the said surface light source for a predetermined time, when the said dispersion | distribution liquid crystal material layer switches from a transparent state to a cloudy state. Backlight device. A display panel;
A surface light source disposed on the back side of the display panel;
A light control element including a dispersed liquid crystal material disposed between the display panel and the surface light source and electrically switched between a transparent state and a cloudy state;
A transmissive display device, comprising: a lens sheet disposed between the display panel and the light control element and having a plurality of lenses arranged one-dimensionally or two-dimensionally on at least one surface thereof. .

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