JP2007264321A - Video display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a video display device for diffusing light while maintaining a certain directivity of projection light from a planar light source in wide-viewing-angle mode. <P>SOLUTION: The video display device 90 comprises a plane light source 1 which a the directivity of the projection light in a specified direction, a diffusion control liquid crystal panel 2A which can be switched between a non-lens-formation state wherein the light from the planar light source 1 is transmitted while maintaining its directivity and a lens formation state wherein mainly linear polarizied light vibrating in the specified direction among the light from the planar light source 1 is diffused, and a liquid crystal display panel 3 wherein the polarized light transmission axis of a light-incident side polarizing plate is so set that linear polarized light beams vibrating in the specified direction and other directions can be guided in. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a video display device capable of controlling a viewing angle of a screen.

The following devices have been proposed as video display devices that can be electrically switched between a narrow viewing angle mode and a wide viewing angle mode. That is, an optical device is disposed between a transmissive display element and a planar light source, the planar light source is a sidelight type light source, and includes a transparent light guide plate having fine irregularities on the surface, The optical device has directivity in a specific direction, and the optical device can electrically switch reversibly between a light scattering state and a light transmitting state, and the viewing angle of display can be controlled by changing the optical device to a light scattering state. Is a device that can be larger than the viewing angle of the display in the light transmission state (see Patent Document 1).
JP 2005-257756 A

  However, the conventional video display device scatters light from the backlight uniformly in all directions when the wide viewing angle mode is set. Specifically, when the wide viewing angle mode is set, light cannot be diffused in the non-center direction of the screen while leaving some directivity on the center side of the screen. Further, the conventional video display device cannot arbitrarily change the degree of directivity maintenance on the center side of the screen and the degree of light diffusion toward the non-center direction of the screen.

  In view of the above circumstances, the present invention makes it possible to achieve diffusion of light while leaving some directivity of light emitted from a planar light source in a wide viewing angle mode, and directivity in a specific direction. It is an object to change the degree of maintenance of light and the degree of light diffusion.

  In order to solve the above-described problem, the video display device according to the present invention is a micro liquid crystal that is formed by applying a voltage to a planar light source having a directivity of light emission in a specific direction and a transparent electrode disposed with a liquid crystal layer interposed therebetween. It is configured to form a plurality of lens parts, and it mainly identifies the non-lens formation state that transmits the light while maintaining the directivity of the light from the planar light source, and the light from the planar light source A diffusion control liquid crystal panel that can switch between a lens formation state that diffuses linearly polarized light that vibrates in a direction, and linearly polarized light that is arranged to receive light from the diffusion control liquid crystal panel and vibrates in the specific direction And a liquid crystal display panel in which the polarization light transmission axis of the light incident side polarizing plate is set so that linearly polarized light oscillating in other directions can be taken in.

  If it is said structure, the said diffusion control liquid crystal panel is provided, Furthermore, in the said liquid crystal display panel, in order to be able to take in the linearly polarized light which vibrates in a specific direction and another direction, the light incident side polarizing plate of Since the polarized light transmission axis is set, the light can be diffused while leaving some directivity of the emitted light from the planar light source in the wide viewing angle mode.

The image display device of the present invention forms a plurality of minute liquid crystal lens portions by applying a voltage to a planar light source having directivity of light emission in a specific direction and a transparent electrode arranged with a liquid crystal layer interposed therebetween. A diffusion liquid crystal panel that diffuses linearly polarized light that mainly vibrates in a specific direction out of linearly polarized light by the liquid crystal lens unit;
A polarization rotating panel provided on the light exit side of the diffusion liquid crystal panel, and rotating a vibration direction of the incident polarized light by an arbitrary angle; and a liquid crystal display panel for receiving the polarized light from the polarization rotating panel. Features.

  With the above configuration, the degree of maintaining the directivity in the specific direction and the degree of light diffusion can be changed by changing the degree of angular rotation in the vibration direction by the polarization rotating panel.

  In the video display device having these configurations, the pixel pitch of the liquid crystal display panel and the arrangement pitch of the transparent electrodes coincide with each other, the liquid crystal lens portions of the diffusion control liquid crystal panel or the diffusion liquid crystal panel, and the black of the liquid crystal display panel A line connecting the matrix may be orthogonal to the screen.

  Alternatively, in the video display device having these configurations, the pixel pitch of the liquid crystal display panel and the arrangement pitch of the transparent electrodes do not match, and each of the liquid crystal lens units of the diffusion control liquid crystal panel or the diffusion liquid crystal panel and the liquid crystal display panel The line connecting the black matrix may intersect in the vicinity of the standard position where the screen is observed.

  Alternatively, in the video display device having these configurations, the diffusion control liquid crystal panel or the diffusion liquid crystal panel may have stripe-shaped transparent electrodes respectively arranged so as to obliquely intersect each other with the liquid crystal layer interposed therebetween.

  According to the present invention, in the wide viewing angle mode, the light can be diffused while leaving some directivity of the emitted light from the planar light source. Further, the degree of maintaining the directivity in a specific direction and the degree of light diffusion can be changed.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  Although the video display device 90 is shown in FIG. 1, the constituent members are separated from each other for easy viewing. The video display device 90 includes a planar light source 1, a diffusion control liquid crystal panel 2 </ b> A, and a liquid crystal display panel 3. FIG. 1A shows a first state in which the directivity of light from the planar light source 1 is maintained and the light is transmitted. In FIG. 2 shows a second state in which the light is diffused in the direction of the horizontal axis of the screen (X-axis direction in FIG. 1) and the direction of the vertical axis of the screen (Y-axis direction in FIG. 1). A Z-axis direction in FIG. 1 indicates a direction perpendicular to the screen.

  The planar light source 1 is a side light type light source, and includes a light guide plate 11 and a cold cathode tube 12. The planar light source 1 has directivity of light emission in a specific direction. That is, the amount of light emitted from the planar light source 1 is generally concentrated in a specific direction. The structure and directivity of the planar light source 1 can be the same as the structure and directivity of the planar light source disclosed in Patent Document 1 described above. In this embodiment, as shown in FIG. 2, the light emitted from the planar light source 1 has a light intensity at an angle exceeding ± 20 ° with respect to the vertical direction of the screen as 30% or less of the light intensity in the vertical direction of the screen. It is trying to become. However, this is only an example, and is not limited to such a directivity range. Further, as a planar light source having directivity, a planar light source in which a pattern such as a concave pattern or a prism pattern is formed on a light guide plate is known (see Japanese Patent Laid-Open No. 9-105804). Further, in a planar light source formed by forming a pattern such as a concave pattern or a prism pattern on a light guide plate, a technique for improving the directivity of light emitted from the light guide plate is also known (see JP-A-2005-268201). ).

  As the liquid crystal display panel 3, for example, a general normally white type liquid crystal display panel 3 is used. The incident-side polarizing plate 3 and the outgoing-side polarizing plate 3 of the liquid crystal display panel 3 are arranged so that their light transmission axis directions are different from each other by 90 °. When the energization to the pixels of the liquid crystal display panel 3 is OFF, the incident light is emitted from the exit-side polarizing plate 3 with its polarization direction rotated by 90 °, so that the display is a white display. On the contrary, when the energization to the pixel is ON, since the polarization of the incident light does not rotate, the incident light cannot pass through the exit-side polarizing plate 3 and the display is black.

  FIG. 3 shows a diffusion control liquid crystal panel 2A. This diffusion control liquid crystal panel 2A includes a pair of glass substrates 21 and 21, one transparent electrode 22A and an alignment film 24A formed on one glass substrate, and the other transparent electrode formed on the other glass substrate. 23A and alignment film 24B, and a liquid crystal layer 25 filled between these glass substrates. The one-side transparent electrode 22A is a comb-shaped electrode formed long in the X direction, and the other-side transparent electrode 23A is a comb-shaped electrode formed long in the Y direction. A voltage is applied to the liquid crystal at the intersection of both comb electrodes. The pitch between the intersections may be related to the pixel interval of the liquid crystal display panel 3 or may be set independently. An example related to the pixel interval will be described later. The state shown in FIG. 3A is the first state (transmission state), and the state shown in FIG. 3B is the second state (diffusion state). When a voltage is applied between the transparent electrodes 22A and 23A, the liquid crystal turns at the intersection, and the liquid crystal having this turn has a refractive index different from that of other regions (voltage non-application region). . That is, when a voltage is applied to the diffusion control liquid crystal panel 2A, a plurality of liquid crystal lens portions appear and the second state is formed (see FIG. 1B).

  Instead of the diffusion control liquid crystal panel 2A, a diffusion control liquid crystal panel 2B shown in FIG. 4 may be used. The diffusion control liquid crystal panel 2B includes a pair of glass substrates 21 and 21, an alignment film 24A formed on one glass substrate, a transparent electrode 23B and an alignment film 24B formed on the other glass substrate, The liquid crystal layer 25 is filled between glass substrates. The transparent electrode 23B is a strip-like electrode that is long in the direction of the screen vertical axis (Y direction, the direction perpendicular to the paper surface in FIG. 3). The voltage is applied to adjacent strip electrodes. The state shown in FIG. 4A is the first state (transmission state), and the state shown in FIG. 4B is the second state (diffusion state). When a voltage is applied between the adjacent strip electrodes of the transparent electrode 23B, the liquid crystal swirls between the adjacent strip electrodes, and the swirling liquid crystal is refracted differently from other regions (voltage non-application region). Will have a rate. That is, when a voltage is applied to the diffusion control liquid crystal panel 2B, a plurality of refraction areas whose refractive surfaces are uniform in the direction of the screen vertical axis appear in the direction of the horizontal axis of the screen (X direction) to form the second state. Is done.

  In the above diffusion control liquid crystal panel 2A, for example, the one-side transparent electrode 22A may be a solid electrode. When a solid electrode is used in this way, when a voltage is applied to the diffusion control liquid crystal panel 2A, a plurality of refraction areas whose refractive surfaces are uniform in the direction of the screen vertical axis appear in the direction of the screen horizontal axis (X direction). Thus, the second state is formed.

  Further, instead of the one side transparent electrode 22A of the diffusion control liquid crystal panel 2A described above, an oblique comb electrode 22B shown in FIG. 5 (a) is used, and instead of the other side transparent electrode 23A, shown in FIG. 5 (b). An oblique comb electrode 23C may be used. FIG. 5C shows a state where these oblique comb electrodes are overlapped. Such a diffusion-controlled liquid crystal panel using oblique comb-teeth electrodes can exhibit a plurality of refraction regions having a refractive index different from those of other regions and having a refracting surface uniform in an oblique direction. Two states (diffusion state) are obtained.

  FIG. 6 shows an arrangement structure of the diffusion control liquid crystal panel 2 </ b> A and the liquid crystal display panel 3. The liquid crystal display panel 3 is formed by forming a liquid crystal layer and a pixel electrode between a pair of glass substrates 31 and 31. For example, in an active matrix liquid crystal display panel, a black matrix (black region) 30 is formed at a TFT formation location. A light incident side polarizing plate 32A is provided on the light incident side glass substrate 31, and a light emitting side polarizing plate 32B is provided on the light emitting side glass substrate 31.

  In the structure shown in FIG. 6, the pixel pitch of the liquid crystal display panel 3 and the arrangement pitch (intersection portion pitch) of the transparent electrodes of the diffusion control liquid crystal panel 2A are made to coincide with each other. A line connecting the liquid crystal lens unit and the black matrix 30 of the liquid crystal display panel 3 is orthogonal to the screen. In other words, the liquid crystal lens portion is positioned directly below the black matrix 30. With such an arrangement, light directed to the black matrix 30 (light that is not originally used) is directed toward the pixel by refraction, and the light use efficiency is improved.

  FIG. 7 shows another arrangement structure of the diffusion control liquid crystal panel 2 </ b> A and the liquid crystal display panel 3. In the structure shown in FIG. 7, the pixel pitch of the liquid crystal display panel 3 and the arrangement pitch (intersection portion pitch) of the transparent electrodes of the diffusion control liquid crystal panel 2A do not coincide with each other, and each liquid crystal of the diffusion control liquid crystal panel 2A. A line connecting the lens unit and the black matrix 30 of the liquid crystal display panel 3 intersects at one point in the vicinity of the standard position for observing the screen. In general, if the liquid crystal lens portion is formed at a pitch sufficiently smaller than the pixel pitch, interference fringes generated between the lens and the pixel can be removed. However, if the arrangement structure shown in FIG. Even when the pixel pitch of the liquid crystal display panel 3 and the arrangement pitch (intersection location pitch) of the transparent electrodes of the diffusion control liquid crystal panel 2A substantially coincide with each other, generation of interference fringes can be prevented. In addition, such an arrangement structure is particularly useful for a large screen such as a notebook personal computer screen having a relatively wide screen than the screen of a mobile phone. That is, when the pitch of the interference fringes is the same, the larger the screen, the more fringes can be seen, so the removal of the interference fringes is more effective. An optical filter having a stripe-shaped opening is known in which the whole is divided into a plurality of vertical-striped cycles, and the pitch of the openings in each cycle is non-uniform (Japanese Patent Laid-Open No. 8-36145). Publication). Using this technique, the diffusion control liquid crystal panel 2A has a transparent electrode arrangement pitch that is divided into a plurality of vertically striped cycles, and the transparent electrode arrangement pitch in each cycle is made non-uniform. The lines connecting the liquid crystal lens portions of the liquid crystal panel 2A and the black matrix 30 of the liquid crystal display panel 3 almost intersect each other in the vicinity of the standard position for observing the screen.

  Now, the planar light source 1 described above has directivity of light emission in the vertical direction of the screen as shown in FIG. In addition, it is known that liquid crystal has anisotropy of refractive index (birefringence). When the diffusion control liquid crystal panel 2A is in the first state, since the liquid crystal lens portion does not appear, linearly polarized light in a certain vibration direction (hereinafter referred to as vertical polarized light) and linearly polarized light in another vibration direction. Even if there is a difference in the refractive index (hereinafter referred to as horizontally polarized light), there is not much difference in the traveling direction when transmitting through the diffusion control liquid crystal panel 2A (flat plate medium). The liquid crystal lens part appears when a region having a different refractive index is formed in the liquid crystal layer. The influence of the appearance of the liquid crystal lens part is, for example, more vertically polarized than horizontal polarized light. May become large with respect to light. In such a case, as shown in FIG. 8B, when the light passes through the diffusion control liquid crystal panel 2A in the second state (the liquid crystal lens portion appears), the vertically polarized light is mainly diffused and the horizontally polarized light The light is not diffused so much and the directivity is almost maintained. Then, as shown in FIG. 8C, the synthesized light diffuses in the peripheral direction while maintaining the directivity (light quantity) in the vertical direction of the screen to some extent.

  The polarized light transmission axis on the light incident side of the liquid crystal display panel 3 has, for example, an angle of 45 ° with respect to the vibration direction of the vertically polarized light (or horizontally polarized light) as shown in FIG. As a result, the liquid crystal display panel 3 can receive light having the same distribution as the light emission distribution (shown by the dotted line) from the diffusion control liquid crystal panel 2A, as shown by the solid line in FIG. 9B. That is, the image light emitted from the liquid crystal display panel 3 diffuses in the peripheral direction while maintaining a certain degree of directivity (light quantity) in the vertical direction of the screen. The 45 ° is an example. The composition ratio is not limited to 1: 1, and can be set to 1: 0.5 or 1: 0.7, and the polarized light transmission axis of the liquid crystal display panel 3 may be set according to the setting. .

  The alignment film in the diffusion control liquid crystal panel 2A will be described based on FIG. FIG. 10A is the same view as shown in FIG. FIG. 10B is a plan view of the alignment film 24A and the alignment film 24B. The arrow in the figure indicates the direction of the orientation vector. The orientation vectors of the orientation film 24A and the orientation film 24B are the same. Of the linearly polarized light, linearly polarized light having a vibration direction in the direction of the orientation vector is greatly affected by the liquid crystal lens unit.

  FIG. 11 is a cross-sectional view showing the video display device 91. The video display device 91 includes a diffusion control liquid crystal panel 2A (2B or the like), a polarization rotation panel 4, and a liquid crystal display panel 3 in order from the backlight 1 side. The diffusion control liquid crystal panel 2A is always used in the second state (diffusion ON) in which a voltage is applied when the video display device is powered on. That is, the diffusion control liquid crystal panel 2A that is always used in the second state forms a plurality of minute liquid crystal lens portions by applying a voltage to the transparent electrodes arranged with the liquid crystal layer sandwiched therebetween, and linearly polarized light is generated by the liquid crystal lens portions. The diffusion liquid crystal panel mainly diffuses linearly polarized light that vibrates in a specific direction. The polarization rotating panel 4 corresponds to the diffusion control liquid crystal panel 2A in which both electrodes are solid electrodes. Specifically, the polarization rotation panel 4 is formed on a pair of glass substrates 41, 41, a solid transparent electrode (entire electrode) 42 and an alignment film 44 formed on one glass substrate, and the other glass substrate. The solid transparent electrode 43 (entire surface electrode) and the alignment film 44, and a liquid crystal layer 45 filled between the glass substrates. The polarization rotation panel 4 rotates the vibration direction of the incident polarized light by an arbitrary angle according to the voltage value applied between the electrodes. The alignment films 44 and 44 do not need to have the same orientation vector.

  The light emitted from the planar light source 1 passes through the diffusion control liquid crystal panel 2A (the liquid crystal lens unit is always exposed) as a diffusion liquid crystal panel, so that the vertically polarized light is mainly diffused and the horizontally polarized light as described above. Will not diffuse and will almost maintain the directivity. Then, as shown in FIG. 8C, the synthesized light diffuses in the peripheral direction while maintaining the directivity (light quantity) in the vertical direction of the screen to some extent. If the light having such a distribution is incident on the liquid crystal display panel 3 without rotating the vibration direction, if the polarization light transmission axis direction of the liquid crystal display panel 3 is as shown in FIG. The same operation as that of the display device 90 is obtained.

  Even when the vibration direction is rotated by 90 ° by the polarization rotating panel 4 and is incident on the liquid crystal display panel 3, the same action as that of the image display device 90 is obtained. On the other hand, when the oscillation direction is rotated 45 ° clockwise by the polarization rotating panel 4 and is incident on the liquid crystal display panel 3, the oscillation direction of vertically polarized light having a large degree of dispersion is incident on the liquid crystal display panel 3. This coincides with the side light transmission axis, and an image is displayed with the light intensity distribution shown on the left side of FIG. That is, video display is performed with the highest degree of diffusion. On the other hand, when the vibration direction is rotated 45 ° counterclockwise by the polarization rotating panel 4 and is incident on the liquid crystal display panel 3, the vibration direction of the horizontally polarized light having a small degree of dispersion is the liquid crystal display panel. 3 is coincident with the incident side light transmission axis, and an image is displayed with the light intensity distribution shown on the right side of FIG. That is, video display is performed with the lowest degree of diffusion. Of course, when the direction of vibration is rotated by a certain angle by the polarization rotation panel 4 and enters the liquid crystal display panel 3, the light intensity distribution changes according to the certain angle.

  Even when the direction of the light transmission axis on the incident side of the liquid crystal display panel 3 is different from the above, similar display switching can be performed by changing the degree of rotation by the polarization rotation panel 4.

  In addition, in the configuration shown in FIG. 11, the configuration shown in FIG. 6 or 7 can be adopted.

  In addition, you may provide a condensing lens function part in the light-projection surface of the said planar light source. The condensing lens functional unit is composed of a convex lens, a Fresnel lens, a hologram optical element, and the like. The condensing lens function unit collects light rays at a predetermined distance in the Z direction (a standard distance between the screen and the user when the user views the screen). The condenser lens functional unit may be formed by processing the surface of the light guide plate, or a condenser lens functional plate created separately from the light guide plate may be disposed on the light guide plate.

  A directivity control film (louver) may be provided on the light emitting side of the planar light source. This directivity control film cuts light that is emitted with an angle that is wider than, for example, 60 ° about an axis perpendicular to the screen.

FIG. 1A is a perspective view showing an image display device according to an embodiment of the present invention, and FIG. 1A shows a first state in which the directivity of light from a planar light source is maintained and the light is transmitted; FIG. 1B shows a second state in which light from the planar light source is diffused in the direction of the horizontal axis of the screen. It is explanatory drawing which showed the light output distribution of the backlight. It is explanatory drawing which showed an example of the diffusion control liquid crystal panel. It is explanatory drawing which showed an example of the diffusion control liquid crystal panel. It is explanatory drawing which showed an example of the electrode structure of a diffusion control liquid crystal panel. It is explanatory drawing which showed the example of arrangement structure of a diffusion control liquid crystal panel and a liquid crystal display panel. It is explanatory drawing which showed the example of arrangement structure of a diffusion control liquid crystal panel and a liquid crystal display panel. It is explanatory drawing explaining that the grade of the spreading | diffusion of a diffusion control liquid crystal panel changes with the vibration directions of polarized light. It is explanatory drawing which showed the light transmission axis direction of the light-incidence side of a liquid crystal display panel, and the light intensity distribution of a liquid crystal display panel. It is explanatory drawing which showed the structure of the diffusion control liquid crystal panel, and the orientation vector of the orientation film. It is explanatory drawing which showed the other structural example of the video display apparatus of this application.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Planar light source 2A, 2B Diffusion control liquid crystal panel 3 Liquid crystal display panel 4 Polarization rotation panel 90, 91 Image display apparatus

Claims (5)

A planar light source having directivity of light emission in a specific direction;
A plurality of minute liquid crystal lens portions are formed by applying a voltage to a transparent electrode arranged with a liquid crystal layer in between, and the light from the planar light source is maintained and the light is transmitted. A diffusion control liquid crystal panel capable of switching between a non-lens formation state and a lens formation state that diffuses linearly polarized light mainly oscillating in a specific direction out of the light from the planar light source;
Polarized light transmission of the light incident side polarizing plate arranged to receive the light from the diffusion control liquid crystal panel and capable of capturing linearly polarized light oscillating in the specific direction and linearly polarized light oscillating in the other direction A liquid crystal display panel with axes set;
A video display device comprising: A planar light source having directivity of light emission in a specific direction;
A plurality of minute liquid crystal lens portions are formed by applying a voltage to a transparent electrode arranged with a liquid crystal layer interposed therebetween, and a straight line that vibrates mainly in a specific direction out of linearly polarized light by the liquid crystal lens portion. A diffusing liquid crystal panel that diffuses polarized light;
A polarization rotating panel that is provided on the light exit side of the diffusion liquid crystal panel and rotates the oscillation direction of the incident polarized light at an arbitrary angle;
A liquid crystal display panel that receives polarized light from the polarization rotation panel;
A video display device comprising:   3. The video display device according to claim 1, wherein a pixel pitch of the liquid crystal display panel and an arrangement pitch of the transparent electrodes coincide with each other, and each of the liquid crystal lens portions of the diffusion control liquid crystal panel or the diffusion liquid crystal panel. And a black matrix of the liquid crystal display panel is orthogonal to the screen.   3. The video display device according to claim 1, wherein a pixel pitch of the liquid crystal display panel and a disposition pitch of the transparent electrodes do not coincide with each other, and each of the liquid crystal lens portions of the diffusion control liquid crystal panel or the diffusion liquid crystal panel; An image display device, wherein a line connecting the black matrix of the liquid crystal display panel intersects in the vicinity of a standard position for observing the screen.   3. The video display device according to claim 1, wherein the diffusion control liquid crystal panel or the diffusion liquid crystal panel has stripe-shaped transparent electrodes respectively arranged so as to sandwich the liquid crystal layer so as to obliquely intersect each other. A video display device.

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