JPH10123495A - Liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of embodying a wider visual field angle with simple constitution without the execution of intricate driving control and intricate orientation treatment. SOLUTION: The exit side of a liquid crystal element 10 is provided with a refractive diffusion plate 15 formed by densely lining up very small curvilinear projecting parts 16 curving to bulge outward on one surface in such a manner that the light emitted from the liquid crystal element 10 is refracted by the respective curvilinear projecting parts 16 of this refractive diffusion plate 15 and is diffused and emitted to a wide angle range. The visual field angle B of the liquid crystal display is thereby made wider than the visual field angle A possessed by the liquid crystal element 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art As a liquid crystal display device, TN is generally used.
(Twisted nematic) type or STN (super twisted nematic) type is used. These liquid crystal display devices have a configuration in which a planar light source generally called a backlight is arranged behind a liquid crystal element in which a pair of polarizing plates are arranged with a liquid crystal cell having a liquid crystal layer in which liquid crystal molecules are twist-aligned. ing.

In the above-mentioned TN type or STN type liquid crystal display device, the display characteristics of the liquid crystal element have directionality determined by the alignment state of liquid crystal molecules in a liquid crystal cell, and the display characteristics are changed according to the direction in which display is observed. Viewing angle (observation angle range where display can be observed with good contrast)
Has the problem of being narrow.

This is because the value of Δn · d (the product of the refractive index anisotropy Δn of the liquid crystal and the thickness d of the liquid crystal layer) of the liquid crystal cell apparently changes depending on the observation direction. Even if the applied voltage between the electrodes provided on the inner surface of the substrate is the same, that is, even if the rising angle of the liquid crystal molecules with respect to the substrate surface is the same, the light transmittance differs depending on the observation direction. The voltage-transmittance characteristic of the liquid crystal element has an observation direction dependency.

[0005] The dependence of the voltage-transmittance characteristic on the observation direction is determined by changing the voltage applied between the electrodes to the threshold voltage V of the liquid crystal.
There is also a problem when performing gradation display in which gradation is provided by controlling stepwise between th and a voltage Va at which liquid crystal molecules rise and align to a state almost perpendicular to the substrate surface. In this gradation display, the brightness of the display of the halftone greatly changes depending on the observation direction.

The liquid crystal element has a unique viewing angle (viewing angle at which display is observed in the highest contrast state) determined by the viewing direction dependence of the voltage-transmittance characteristic. Although the contrast when viewing the display from is high, when viewed from a direction deviated to some extent from the viewing angle direction, the contrast is significantly reduced, and the grayscale is inverted.

The viewing angle of the liquid crystal element is in a direction slightly inclined in one direction with respect to the front direction (perpendicular to the screen). The angle range is somewhat wide, but the viewing angle range in the opposite direction is narrow.

Therefore, conventionally, a pixel division method has been proposed as a means for improving the viewing angle of the liquid crystal display device. The pixel division method includes a voltage control method and an alignment control method.

In the voltage control method, an electrode on one substrate of a liquid crystal cell is divided into a plurality of electrodes for each pixel, and driving of different voltage values is performed between each divided electrode and an electrode on the other substrate. By applying a voltage, the rising angles of the liquid crystal molecules are made different in each region of the pixel, and the viewing angles of these regions are made different from each other.A plurality of regions having different viewing angles are synthesized and observed. Thus, the dependence of the voltage-transmittance characteristic on the observation direction is reduced.

In the alignment control method, each pixel is divided into a plurality of regions, and the alignment state of liquid crystal molecules is made different for each of the regions, so that the viewing angles of these regions are made different from each other. A plurality of regions having different angles are synthesized and observed, so that the dependence of the voltage-transmittance characteristics on the observation direction is reduced.

[0011]

However, in the above-described voltage control method, it is necessary to supply drive signals having different voltage values to each of the divided electrodes, so that the drive control of the liquid crystal display device becomes complicated. Have.

On the other hand, the alignment control method does not require complicated drive control such as a voltage control method, but the liquid crystal cell is provided with an alignment process for aligning liquid crystal molecules in different alignment states for each pixel region. Since it must be performed, there is a problem that the alignment process in the production of the liquid crystal cell is complicated and the production cost is increased.

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display device which can realize a wide viewing angle with a simple configuration without performing complicated drive control and complicated alignment processing.

[0014]

According to the present invention, there is provided a liquid crystal display device comprising a liquid crystal cell having a liquid crystal layer in which liquid crystal molecules are twist-aligned, and a liquid crystal element having a pair of polarizing plates disposed on one side of a liquid crystal element. A refraction diffusion plate formed by densely arranging minute curved surface convex portions curved to the outer bulge, light emitted from the liquid crystal element is refracted by each curved surface convex portion of the refraction diffusion plate, and a wide angle range is provided. And is emitted.

According to this liquid crystal display device, the light emitted from the liquid crystal element is refracted by the respective convex portions of the refraction / diffusion plate and diffused and emitted over a wide angle range. The dependence is reduced, and the range of the viewing angle, that is, the range of the viewing angle in which the display can be observed with good contrast without inversion of the gradation and with good contrast, is wider than the viewing angle of the liquid crystal element.

In the present invention, the viewing angle is widened by providing the above-mentioned refraction / diffusion plate on the exit side of the liquid crystal element, so that complicated drive control and control like the conventional voltage control method and alignment control method are performed. A wide viewing angle can be realized with a simple configuration without performing complicated alignment processing.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a wide viewing angle by providing, on the emission side of a liquid crystal element, a refraction / diffusion plate formed on one surface of a liquid crystal element, on which fine curved convex portions curved in an outward bulge are densely arranged. It has been realized.

In the present invention, since the light emitted from the liquid crystal element is refracted by each curved convex portion of the refraction / diffusion plate and is emitted in a wide angle range and emitted, the front direction (the direction perpendicular to the screen) is obtained. However, if a non-diffuse transmission region is provided between the curved convex portions of the refraction / diffusion plate or on the top surface of each curved convex portion, the light incident on this region is diffused. Because it is emitted in the front direction without being
By compensating for the decrease in the amount of emitted light in the front direction, the brightness and contrast of the display image when viewed from the front direction can be sufficiently increased.

Each of the convex portions of the curved surface of the refraction / diffusion plate is a linear ridge, or the base has a substantially rectangular outer shape, and four side surfaces having the respective sides as bases are each formed with an outer bulge. It is preferable that the convexities are curved mountain-shaped projections, and if each of the curved convex portions is the former convex stripe, one direction is perpendicular to the diffusion plate surface and passes through a vertex of the curved convex portion. And the viewing angle can be widened in two directions opposite to each other, and if each of the curved convex portions is the latter mountain-shaped projection,
The viewing angle can be expanded in four directions.

In the case where the refraction / diffusion plate is formed such that each curved convex portion is the above-mentioned protuberance, two refraction / diffusion plates are provided on the emission side of the liquid crystal element, and the length direction of each protuberance is used. If they are arranged almost perpendicular to each other, the viewing angle can be widened in four directions.

Further, in the present invention, a planar light source is disposed behind the liquid crystal element, and a light collector for increasing the front luminance of light emitted from the light source is provided between the light source and the liquid crystal element. With this arrangement, it is possible to irradiate the liquid crystal element with high-luminance light and make the emitted light incident on the refraction / diffusion plate. Therefore, the luminance of the diffused light emitted from the refraction / diffusion plate is increased to make the screen brighter. can do.

[0022]

FIG. 1 is a side view of a liquid crystal display device according to a first embodiment of the present invention. The liquid crystal display device of this embodiment is
It comprises a liquid crystal element 10 and a refraction / diffusion plate 15 provided on the emission side of the liquid crystal element 10. A flat light source 30 for irradiating the liquid crystal element 10 with light is provided behind the liquid crystal element 10. Are arranged, and a condensing body 34 is provided between the light source 30 and the liquid crystal element 10 for increasing the front luminance of the irradiation light from the light source 30.

The liquid crystal element 10 has a pair of polarizing plates 13 and 14 sandwiched between a liquid crystal cell 11 having a liquid crystal layer in which liquid crystal molecules are twisted, and the liquid crystal cell 11 has a frame-shaped seal. Nematic liquid crystal is sealed between a pair of transparent substrates 12a and 12b joined via a material (not shown).

The liquid crystal cell 11 is, for example, a color image display cell of an active matrix type. Although the internal structure is not shown, a plurality of pixel electrodes and these pixel electrodes are provided on the inner surface of one substrate. Corresponding switching elements (for example, thin film transistors) are arranged in a matrix and an alignment film is provided thereon. On the inner surface of the other substrate, a color filter of a plurality of colors corresponding to each pixel is formed. A sheet-like counter electrode is formed, and an alignment film is provided thereon.

The liquid crystal element 10 is, for example, a liquid crystal cell 1
1 is a TN type in which the twist angle of the liquid crystal molecules is substantially 90 °, and a pair of polarizing plates 13 and 14 are arranged so that their transmission axes are substantially orthogonal to each other or substantially parallel to each other;
In this embodiment, a design is used in which the viewing angle direction F is oriented in a direction slightly inclined toward the lower edge of the screen with respect to the front direction (direction perpendicular to the screen).

That is, in the liquid crystal element 10, the orientation direction of the liquid crystal molecules in the vicinity of the incident side substrate 12a of the liquid crystal cell 11 is approximately 45 ° clockwise with respect to the horizontal axis of the screen when viewed from the emission side. The orientation direction of the liquid crystal molecules in the vicinity of the emission side substrate 12b is set to a direction of approximately 45 ° counterclockwise when viewed from the emission side, and the liquid crystal molecules are directed from the incidence side substrate 12a to the emission side substrate 12b and viewed from the emission side to the right. Around 90 ° around
And the transmission axes of the polarizers 13 and 14 on the incident side and the exit side with respect to the orientation direction of the liquid crystal molecules in the vicinity of the incident side and the exit side substrates 12a and 12b of the liquid crystal cell 11. The viewing angle direction F of the liquid crystal element 10 is perpendicular to the screen and is a plane H along the horizontal axis of the screen (the direction perpendicular to the plane of the paper in the figure). With respect to the lower edge of the screen.

Further, the refraction diffusion plate 15 provided on the emission side of the liquid crystal element 10 has a small curved convex portion 16 which is curved to the outside bulge on one surface of a transparent film made of an allyl resin or the like. In this embodiment, the curved surface protruding portions 16 are formed as linear protruding lines along the width direction of the diffusion plate (the direction perpendicular to the paper surface in the figure). I have.

FIG. 2 is a side view of a part of the refraction / diffusion plate 15. In this embodiment, the cross-sectional shape of the curved convex portion (linear convex line) is substantially semicircular, and the curved convex portion 16 is formed. They are arranged parallel to each other without any gap.

In this embodiment, the refraction / diffusion plate 15 is formed such that the surface on which the curved convex portions are formed is opposed to the exit surface of the liquid crystal element 10 and the length direction of each curved convex portion 16 is set to the length of the liquid crystal element 10. Are arranged parallel to the horizontal axis of the screen.

The refraction / diffusion plate 15 is connected to the liquid crystal element 1.
0 even if it is provided slightly away from the exit-side polarizing plate 14,
The top of each curved convex portion 16 may be provided in contact with the outer surface of the emission-side polarizing plate 14.

On the other hand, the planar light source 30 disposed behind the liquid crystal element 10 is disposed so as to face the entire display area of the liquid crystal element 10 and both end faces of the light guide plate 31 so as to face each other. And a reflector 33 provided behind these light source lamps 32.

The light guide plate 31 is a transparent plate made of an allyl-based resin or the like having a scattering reflection surface formed on the entire back surface. Light from the light source lamp 32 is taken into the light guide plate 31 from an end face thereof and is guided by the light guide plate 31. The light is guided through the light plate 31 and emitted from the entire surface thereof as scattered light having substantially uniform light brightness.

The light collector 34 provided between the light source 30 and the liquid crystal element 10 collects light (scattered light) emitted from the light source 30 and enters the liquid crystal element 10. The irradiation light from the light source 30 has a small spread in the width direction of the light guide plate 31 (direction perpendicular to the light guide direction), and extends in the length direction of the light guide plate 31 (direction along the light guide direction). In this embodiment, since the light is a light having a large spread, a prism sheet formed by forming a strip-shaped prism portion having a fine width continuously in the width direction on the entire surface of a transparent sheet made of an allyl resin or the like is used as the light collector 34. The light collecting plate (prism sheet) 34 is provided so that the length direction of each band-shaped prism portion is substantially parallel to the width direction of the light guide plate.
Irradiation light from the light guide plate 31 is condensed so as to be less spread in the length direction of the light guide plate 31, and the front luminance of the irradiation light is increased.

In FIG. 1, the light collector 34 is provided close to the planar light source 30, but the light collector 34 is attached to the emission surface of the light source 30 (the surface of the light guide plate 31). Alternatively, it may be provided by sticking to the incident side polarizing plate 13 of the liquid crystal element 10.

The liquid crystal display device achieves a wide viewing angle by providing the refraction diffusion plate 15 on the emission side of the liquid crystal element 10. According to this liquid crystal display device,
The light emitted from the liquid crystal element is refracted by the curved convex portions 16 of the refraction / diffusion plate 15 as shown by arrows in FIG. 2 and diffuses and exits over a wide angle range. The observation direction dependency is reduced.

That is, although the voltage-transmittance characteristic of the liquid crystal element 10 has an observation direction dependency, if the refraction diffusion plate 15 is provided on the exit side of the liquid crystal element 10, the liquid crystal element 1
Since the light that has emitted 0 is diffused and emitted over a wide angle range,
The degree of change of the transmittance with respect to the change of the observation angle becomes small.

On the other hand, the liquid crystal element 10 has a unique viewing angle determined by the dependence of the voltage-transmittance characteristic on the viewing direction, and when viewed from a direction slightly deviated from the viewing angle direction F, the contrast is remarkably reduced. Although inversion of gradation occurs, the refraction / diffusion plate 15 is provided on the emission side of the liquid crystal element 10 to reduce the viewing direction dependency of the voltage-transmittance characteristic, so that the viewing angle of the liquid crystal display device, That is, the range of the viewing angle in which the display can be observed with good contrast without grayscale inversion is wider than the viewing angle of the liquid crystal element 10.

The direction in which the viewing angle is widened is the direction in which the light exiting the refraction / diffusion plate 15 is diffused.
Since each curved convex portion 16 of the refraction diffusion plate 15 is formed as a linear ridge, light emitted from the refraction diffusion plate 15 is perpendicular to the diffusion plate surface and passes through a vertex of the curved convex portion 16. Thus, the light is diffused in one direction and the other direction, and the viewing angle is increased in two opposite directions of the one direction and the other direction.

In this embodiment, since the liquid crystal element 10 is designed such that the direction F of the viewing angle is in a direction slightly inclined toward the lower edge of the screen with respect to the front direction, this liquid crystal element 10 is used. The element 10 has a viewing angle range from the front direction to the lower edge direction of the screen to some extent, and a viewing angle range to the upper edge direction of the screen is narrow. Is arranged in parallel with the horizontal axis of the screen of the liquid crystal element 10, the viewing angle of the liquid crystal display device is further widened in the lower edge direction of the screen and greatly expanded also in the upper edge direction of the screen. be able to.

In FIG. 1, A indicates the viewing angle of the liquid crystal element 10, and B indicates the viewing angle of a liquid crystal display device provided with the refractive diffusion plate 15 on the exit side of the liquid crystal element 10. The viewing angle B of the display device is also lower than the viewing angle A of the liquid crystal element 10 in the lower edge direction of the screen (the direction in which the viewing angle of the liquid crystal element 10 is present) and in the upper edge direction of the screen (the viewing angle of the liquid crystal element 10 is higher). Direction is opposite to the direction).

In this embodiment, the cross-sectional shape of each curved convex portion 16 of the refraction diffusion plate 15 is substantially semicircular, that is, a curved surface symmetrical to the left and right with the vertex of the curved convex portion 16 as a boundary. Due to the shape, the light emitted from the refraction diffusion plate 15 is diffused in substantially the same angle range in one direction and the other direction with respect to a surface perpendicular to the diffusion plate surface and passing through the apex of the curved convex portion 16. However, since the viewing angle direction F of the liquid crystal element 10 is slightly inclined with respect to the front direction, the refraction diffusion plate 1
The viewing angle B of the liquid crystal display device that has been widened by the diffusion of light by 5 is somewhat wider in the viewing angle range from the front direction to the direction in which the viewing angle of the liquid crystal element 10 is present than in the opposite direction.

Then, the liquid crystal display device has a liquid crystal element 1
Since the viewing angle is widened by providing the refraction / diffusion plate 15 on the exit side of the light emitting element 0, it is easy to perform complicated drive control and complicated alignment processing unlike the conventional voltage control method and alignment control method. With a simple configuration, a wide viewing angle can be realized.

In the above embodiment, the planar light source 30 is disposed behind the liquid crystal element 10, and a light source for improving the front luminance of the light emitted from the light source 30 is provided between the light source 30 and the liquid crystal element 10. Since the light body (prism sheet) 34 is provided, it is possible to irradiate the liquid crystal element 10 with high-intensity light and to make the light incident on the refraction / diffusion plate 15. By increasing the luminance including the scattered light, a brighter display can be obtained.

The convex portion 16 of the refraction diffusion plate 15 has a curved surface.
May be arbitrarily selected, but it is better that the pitch is small. More preferably, the pitch of each curved convex portion 16 is made equal to the pixel pitch of the liquid crystal element 10, and the liquid crystal element 1 is formed.
It is preferable that one curved convex portion 16 is associated with each pixel of each row (or column) of 0.

Preferably, the refraction / diffusion plate 15 is provided with an antireflection coating on one or both of the entrance surface (the surface on which the curved convex portion 16 is formed in the above embodiment) and the exit surface. If an anti-reflection coating is applied to the incident surface of the refraction diffusion plate 15, the liquid crystal element 10
Can be effectively introduced into the refraction / diffusion plate 15, and if an antireflection coating is applied to the exit surface of the refraction / diffusion plate 15, surface reflection of external light can be eliminated. Image contrast can be improved.

Further, the curved convex portion 1 of the refraction diffusion plate 15 is used.
The cross-sectional shape of 6 is not limited to a substantially semicircular shape, and may be a shape whose curved surface is an elliptical surface or a paraboloid. Further, the curved convex portion 16 may have a shape having a curved surface that is asymmetrical with respect to the apex as a boundary, and if the curved convex portion 16 has such a shape, the light is emitted from the refraction diffusion plate 15. Since light is diffused in a different angle range in one direction and the other direction with respect to a plane perpendicular to the diffusion plate surface and passing through the apex of the curved convex portion 16, any one of the two opposite directions may be used. The spread of the viewing angle in the direction can be further increased.

In the above embodiment, the refraction diffusion plate 1
5 is arranged such that the length direction of the curved convex portion 16 is parallel to the horizontal axis of the screen of the liquid crystal element 10.
May be arranged such that the length direction of the curved convex portion 16 is oriented in another direction. For example, the liquid crystal element 10 may have a viewing angle in a direction slightly inclined toward the lower edge of the screen with respect to the front direction. F that is designed so that F comes
Are arranged so that the length direction of the curved convex portion 16 is parallel to the vertical axis of the screen, the viewing angle in the vertical direction of the screen becomes
Although the viewing angle is almost the same as 0, it is possible to obtain a liquid crystal display device in which the viewing angle in the left-right direction is greatly widened.

Further, in the above embodiment, the refraction diffusion plate 15
The surface on which the curved convex portion 16 is formed is disposed so as to face the emission surface of the liquid crystal element 10, and the refraction diffusion plate 15 has a surface opposite to the curved convex portion formed surface on the emission surface of the liquid crystal element 10. They may be arranged to face each other.

The refraction / diffusion plate 15 is not limited to the one described in the above embodiment, but may have the following configuration. FIG. 3 is a partial side view showing a first modified example of the refraction / diffusion plate 15. The refraction / diffusion plate 15 has a carbon film formed on an emission surface thereof so as to correspond to a boundary between the curved convex portions 16. Light-shielding mask (black mask) 17 made of
Is provided to improve the sharpness of the displayed image.

Note that, as in this modification, the refraction diffusion plate 15
In the case where light-shielding masks 17 are provided on the light-exiting surface so as to correspond to the boundary portions of the curved convex portions 16, respectively,
The thickness D including the curved convex portion 16 is not more than 1.5 times the formation pitch P of the curved convex portion 16 and the light shielding mask 17 (D ≦ 1.
5P). In this case, the spread width of the light refracted by each curved surface convex portion 16 on the emission surface is made smaller than the interval between the light-shielding masks 17, and most of the light is removed from the light-shielding masks 17. Because it can be emitted from between
The absorption of light by the light-shielding mask 17 is extremely reduced, so that it is possible to prevent a decrease in luminance of a display image due to the provision of the light-shielding mask 17.

FIG. 4 is a partial side view showing a second modification of the refraction / diffusion plate 15.
The width of each curved convex portion 16 is slightly smaller than that of FIGS. 2 and 3, and a small width non-diffusion formed of a flat surface parallel to the emission surface of the diffusion plate is provided between these curved convex portions 16. The transmission region 18 is provided so that a sufficient amount of light is emitted also in the front direction of the refraction diffusion plate 15.

That is, in the above liquid crystal display device,
Since the light emitted from the liquid crystal element 10 is refracted by the respective curved convex portions 16 of the refraction / diffusion plate 15 and is diffused and emitted in a wide angle range, the amount of light emitted in the front direction (perpendicular to the screen) is limited to some extent. However, if a non-diffuse transmission area 18 is provided between the curved convex portions 16 of the refraction / diffusion plate 15 as in this modification, light incident on the area 18 is not diffused in the front direction. As a result, it is possible to compensate for a decrease in the amount of emitted light in the front direction, and therefore, it is possible to sufficiently increase the brightness and contrast of the display image when observed from the front direction.

FIG. 5 is a partial side view showing a third modification of the refraction / diffusion plate 15.
Non-diffused transmission area 18 provided between each curved convex portion 16
Is a concave surface curved in an arc shape to further improve front luminance and contrast.

That is, FIG. 6 is an enlarged view of the non-diffuse transmission area 18 of the refraction / diffusion plate 15 of the third modification.
Out of the light incident on the diffusing plate, the incident light from the direction perpendicular to the exit surface of the diffusion plate exits in the front direction, and the incident light from the oblique direction is refracted by the curved concave surface as shown by the arrow in the figure. Then, the light is emitted in the front direction, so that the brightness and contrast of the display image when observed from the front direction can be further increased.

FIG. 7 is a partial side view showing a fourth modification of the refraction / diffusion plate 15.
The top surface of each curved convex portion 16 is a flat surface parallel to the emission surface of the diffusion plate, and this flat surface is a non-diffusion transmission region 19.

By using the refraction / diffusion plate 15 of this modification,
Since the light incident on the non-diffuse transmission region 18 on the top surface of each curved surface convex portion 16 is emitted in the front direction without being diffused,
By compensating for the decrease in the amount of emitted light in the front direction, the brightness and contrast of the display image when viewed from the front direction can be sufficiently increased.

When the refraction diffusion plate 15 of the fourth modified example is used, the non-diffuse transmission of the top surface of each curved convex portion 16 of the refraction diffusion plate 15 is performed as in the example of disposition of the diffusion plate shown in FIG. Area 1
9 is provided on the outer surface of the output side polarizing plate 14 of the liquid crystal element 10 with a light refractive index substantially equal to the refractive index of the diffusing plate 15 and the polarizing plate 14 (when the refractive index of the diffusing plate 15 and the polarizing plate 14 is different, It is desirable to use a transparent adhesive 20 having a substantially intermediate refractive index).

By arranging the diffusion plate 15 in this manner, the interface between the output side polarizing plate 14 and the adhesive 20 and the interface between the adhesive 20 and the non-diffusion transmission region 19 of each curved convex portion 16 are formed. Light reflection is reduced, and the non-diffuse transmission region 19 is reduced.
Since the light incident on the light source is emitted with almost no loss, the front luminance and the contrast can be more effectively improved.

In the fourth modification, the non-diffuse transmission region 1 provided on the top surface of each curved convex portion 16 of the refraction diffusion plate 15 is provided.
Although 8 is a flat surface, the non-diffuse transmission region 18 may be a curved concave surface. In this case, incident light from an oblique direction is refracted and condensed by the curved concave surface and exits in the front direction. The brightness and contrast of the display image when observed from the front direction can be further increased. In this case, the refraction / diffusion plate 15 is slightly separated from the emission-side polarizing plate 14, or the most protruding portions (both sides of the curved concave surface) of each curved convex portion 16 are attached to the outer surface of the emission-side polarizing plate 14. What is necessary is just to provide in contact.

In the above embodiment, the liquid crystal display device of the first embodiment is such that the viewing angle is widened in two opposite directions, but two refraction diffusion plates 15 used in this embodiment are used. For example, the viewing angle can be increased in four directions.

FIG. 9 is a diagram showing the arrangement of a refraction / diffusion plate according to a second embodiment of the present invention. In this embodiment, the refraction / diffusion plate (each curved surface convex portion 16 is used) used in the first embodiment is shown. A liquid crystal device (see FIG. 1) is provided with two linearly protruding strips 15 and superposing the two refraction / diffusion plates 15 in such a manner that the length directions of the respective curved convex sections 16 are orthogonal to each other. Not shown)
Are arranged on the emission surface.

According to this embodiment, the light emitted from the liquid crystal element is diffused in two opposite directions by one refraction / diffusion plate 15 and further diffused by the one refraction / diffusion plate 15 by the other refraction / diffusion plate 15. Since the light is diffused in two opposite directions along the direction orthogonal to the direction, the viewing angle can be expanded in four directions.

Further, the refraction diffusion plate 15 used in the above embodiment is used.
Is such that each curved surface convex portion 16 is formed as a linear convex ridge. However, if a refraction diffusion plate having the following configuration is used, the viewing angle can be increased in four directions only by providing one refraction diffusion plate. Can be spread.

FIG. 10 is a perspective view of a refraction / diffusion plate showing a third embodiment of the present invention. The refraction / diffusion plate 21 has a curved convex portion 22 which is substantially square in outer shape of a base portion and each side thereof. Are formed as mountain-like projections, each of which has four sides curved to the outside bulge, and the curved surface protruding portions 22 are densely arranged in a matrix in the vertical and horizontal directions.

In this embodiment as well, the pitch at which the curved convex portions 22 of the refraction / diffusion plate 21 are formed may be arbitrarily selected. The smaller the pitch, the better.
It is preferable that the pitch in the vertical direction and the horizontal direction is equal to the pixel pitch of the liquid crystal element 10 so that each pixel of the liquid crystal element 10 corresponds to one curved convex portion 22. Further, it is desirable that the refraction / diffusion plate 21 has an antireflection coating applied to one or both of the entrance surface and the exit surface.

The curved convex portion 22 of the refraction diffusion plate 21 shown in FIG. 10 has a semicircular cross section in the vertical width direction and the horizontal width direction, each having the same diameter. The cross-sectional shape in the vertical width direction and the horizontal width direction may be a shape whose curved surface is an elliptical surface or a paraboloid,
Further, the shape may have a curved surface symmetrical to the left and right with respect to the vertex, or may have a curved surface symmetrical to the left and right.

Further, the refraction diffusion plate 15 may be arranged such that the surface on which the curved convex portion 16 is formed is opposed to the exit surface of the liquid crystal element. It may be arranged to face the surface.

As in this embodiment, as the refraction / diffusion plate 21, each curved convex portion 22 has a base having a substantially rectangular outer shape, and four side surfaces each having a bottom as a base, and each of the four side surfaces is curved outwardly. If the projections are used, the viewing angle can be widened in four directions only by providing one refraction / diffusion plate 21.

The direction in which the viewing angle is widened when the refraction / diffusion plate 21 is used may be determined, for example, by setting the refraction / diffusion plate 21 in either the vertical direction or the horizontal direction to be parallel to the horizontal axis of the screen of the liquid crystal element. When placed, they are in the vertical and horizontal directions of the screen.

The refraction diffusion plate 21 shown in FIG.
The curved convex portions 22 formed of mountain-like projections are linearly arranged in the vertical direction and the horizontal direction, respectively. These curved convex portions 22 are formed by dividing the curved convex portions 22 of each row by 列 for each column.
They may be arranged by being shifted by a pitch.

Also, the refraction diffusion plate 21 of this embodiment has the same structure as that of the second to fourth modifications of the refraction diffusion plate 15 used in the first embodiment described above. Alternatively, a non-diffuse transmission area can be provided on the top surface of each curved convex portion 22. If this non-diffusion transmission area is provided, a decrease in the amount of emitted light in the front direction is compensated for, and The brightness and contrast of the display image when viewed from above can be sufficiently increased.

[0072]

According to the liquid crystal display device of the present invention, the light emitted from the liquid crystal element is refracted by each curved convex portion of the refraction / diffusion plate disposed on the exit side of the liquid crystal element, and diffuses over a wide angle range. The liquid crystal element has a viewing angle range, that is, a viewing angle range in which the display can be observed with good contrast without inversion of gradation and with good contrast. It becomes wider than the viewing angle.

In the present invention, since the viewing angle is widened by providing the above-mentioned refraction / diffusion plate on the exit side of the liquid crystal element, complicated drive control and conventional control methods such as the conventional voltage control method and alignment control method are used. A wide viewing angle can be realized with a simple configuration without performing complicated alignment processing.

In the present invention, since the light emitted from the liquid crystal element is refracted by each curved convex portion of the refraction / diffusion plate and diffused and emitted in a wide angle range, the light is emitted in the front direction (the direction perpendicular to the screen). However, if a non-diffuse transmission region is provided between the curved convex portions of the refraction / diffusion plate or on the top surface of each curved convex portion, the light incident on this region is diffused. Because it is emitted in the front direction without being
By compensating for the decrease in the amount of emitted light in the front direction, the brightness and contrast of the display image when viewed from the front direction can be sufficiently increased.

Each of the convex portions of the curved surface of the refraction / diffusion plate is a linear convex, or the base has a substantially rectangular outer shape, and the four side surfaces having the respective sides as the bases are each formed with an outer bulge. It is preferable that the convexities are curved mountain-shaped projections, and if each of the curved convex portions is the former convex stripe, one direction is perpendicular to the diffusion plate surface and passes through a vertex of the curved convex portion. And the viewing angle can be widened in two directions opposite to each other, and if each of the curved convex portions is the latter mountain-shaped projection,
The viewing angle can be expanded in four directions.

[Brief description of the drawings]

FIG. 1 is a side view of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a side view of a part of the refraction diffusion plate used in the first embodiment.

FIG. 3 is a partial side view showing a first modified example of the refractive diffusion plate.

FIG. 4 is a partial side view showing a second modified example of the refractive diffusion plate.

FIG. 5 is a partial side view showing a third modification of the refractive diffusion plate.

FIG. 6 is an enlarged view of a non-diffusion transmission region of a refraction diffusion plate according to a third modification.

FIG. 7 is a partial side view showing a fourth modification of the refractive diffusion plate.

FIG. 8 is a diagram showing an example of the arrangement of diffusion plates when a refraction diffusion plate according to a fourth modification is used.

FIG. 9 is an arrangement diagram of a refraction / diffusion plate showing a second embodiment of the present invention.

FIG. 10 is a perspective view of a refraction / diffusion plate showing a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Liquid crystal element 11 ... Liquid crystal cell 13, 14 ... Polarizing plate 15, 21 ... Refraction / diffusion plate 16, 22 ... Curved surface convex part 18, 19 ... Non-diffusion transmission area 20 ... Planar light source 34 ... Condenser A ... Liquid crystal element Viewing angle B: viewing angle of liquid crystal display

Claims (5)

[Claims] 1. A small curved convex portion which is curved in an outward bulge on one surface on an emission side of a liquid crystal element having a pair of polarizing plates sandwiched between a liquid crystal cell having a liquid crystal layer in which liquid crystal molecules are twist-aligned. A liquid crystal, comprising a refraction diffusion plate formed densely arranged, wherein light emitted from the liquid crystal element is refracted by each curved surface convex portion of the refraction diffusion plate, and diffused and emitted over a wide angle range. Display device. 2. A non-diffusing transmission area is provided between each curved surface convex portion of the refractive diffusion plate.
3. The liquid crystal display device according to 1. 3. The liquid crystal display device according to claim 1, wherein a non-diffuse transmission region is provided on a top surface of each curved convex portion of the refractive diffusion plate. 4. The method according to claim 1, wherein each of the convex portions of the curved surface of the refraction diffusion plate is a linear ridge.
The liquid crystal display device according to any one of the above. 5. Each of the convex portions of the curved surface of the refraction / diffusion plate is a mountain-like projection whose base has a substantially rectangular outer shape and four side surfaces each of which has a bottom as a base. The liquid crystal display device according to claim 1, wherein: