JP2001215494A - Liquid crystal display, and method for making the display high in contrast and wide in veiwing angle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display an image with high contrast in a wide viewing angle in a liquid crystal display. SOLUTION: An image with high contrast is obtained by collimating the light from the back light of a liquid crystal display, aligning the propagation direction of the collimated light to the center or near the center of the high contrast ratio region in the viewing angle characteristics of the liquid crystal panel, allowing the collimate light to enter the liquid crystal panel and then diffusing the light transmitted through the liquid crystal panel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of liquid crystal displays, and more particularly, to a wide viewing angle and a high contrast of a liquid crystal display.

[0002]

2. Description of the Related Art In recent years, as a display of a word processor or a personal computer, the frequency of use of a liquid crystal display (LCD) has been greatly increased due to advantages such as easy miniaturization, thinness and light weight. Also L
The CD has begun to be used as a monitor of a medical measuring device such as an ultrasonic diagnostic device, a CT diagnostic device, and an MRI diagnostic device, which has conventionally been mainly a CRT (Cathode Ray Tube).

The LCD has various display modes, and a TN mode is known as a typical display mode. As shown in FIG. 11A, two glass substrates 100 and 102 are opposed to each other, and the orientation direction is 9 between them.
A TN type liquid crystal cell in which a nematic liquid crystal 104 twisted by 0 ° is sealed, and two polarizing plates (polarizer 106 and analyzer 108) arranged on both sides of the TN type liquid crystal so that transmission axes are orthogonal to each other.
It is composed of On one glass substrate, scanning electrodes and signal electrodes are arranged in a matrix, and a thin film transistor is connected to the intersection thereof, so that a voltage can be applied independently for each pixel. As shown in FIG. 11A, the incident light that has become linearly polarized light through the polarizer 106 proceeds along the twist of the liquid crystal molecules when no voltage is applied to the liquid crystal cell, and the polarization direction is changed. Since it is rotated by 90 °, it can pass through the analyzer 108 (white display). On the other hand, when a voltage higher than the threshold is applied to the liquid crystal cell, most of the liquid crystal molecules take homeotropic alignment arranged in the direction of the electric field, except for the vicinity of the electrodes, so that the twist is eliminated and the incident light passes through the liquid crystal cell. Also, the polarization direction does not rotate and cannot pass through the analyzer 108 (black display). In this manner, in the TN mode, the display principle is to change the twist alignment of the liquid crystal by the applied voltage and control the transmittance.

[0004]

However, LCDs
Changes the brightness, contrast, color, etc., depending on the position where the display screen is viewed, and also causes inversion of the gradation.
There is a problem that the image has a so-called viewing angle dependency in which the appearance of the image changes. In particular, the LCD in the TN mode is
This viewing angle dependency is large, and the viewing angle characteristics are poor. FIG.
(A) shows the viewing angle characteristics of the TN mode LCD. In this figure, concentric circles indicate viewing angles, and radial straight lines indicate viewing directions. A hatched portion C indicates a grayscale inversion area.
Thus, in the case of the TN mode, the contrast ratio (C
The high contrast ratio region where R) is 100 or more exists slightly below the center.

[0005] It is considered that the cause of the viewing angle dependency that the color becomes lighter or the contrast is lowered by inclining the angle is caused by light leakage in the black display portion.
That is, the nematic liquid crystal used in the liquid crystal cell is optically positive uniaxial and has no effect on light incident parallel to the optical axis, but is obliquely incident on the optical axis. In this case, birefringence appears due to an increase in the refractive index in one direction according to the incident angle. Therefore, the linearly polarized light obliquely incident on the optical axis becomes elliptically polarized light due to birefringence, and a part of the light passes through the analyzer 108, resulting in light leakage at the black display portion. For this reason, the color becomes pale, the contrast is reduced, and the viewing angle characteristics such as the inversion of gradation are caused.

On the other hand, an LCD having a wide viewing angle and a high contrast ratio has an IPS mode and an MVA.
An LCD using an operation mode such as a mode is also known.
However, in the case of the MVA mode LCD, as shown in FIG. 12 (B), the viewing angle characteristic certainly has a high contrast, but a region having a high contrast ratio (for example, CR = 100 or more) exists only in the center. do not do. Also, in these LCDs, similarly to the TN mode, when the backlight light is diffused, light components in each direction are mixed, so that even when viewed straight, light leakage occurs in which light is obliquely leaked, The contrast decreases.

Particularly, in medical applications, an image having a high contrast ratio is required to make a diagnosis based on the density of the image. However, it is particularly required that the viewing angle is wide and the contrast ratio is high over a wide viewing angle. . In addition, in the case of medical use, the image displayed on the monitor is usually a monochrome image, and the image contrast greatly depends on the viewing angle. That is, when a plurality of doctors make a diagnosis while looking at the same LCD, the contrast ratio of the image sharply decreases depending on the direction and angle at which the LCD is viewed. If different, depending on the position of the observer, it may not be possible to properly observe the image, which may cause erroneous diagnosis or discrepancy in the diagnosis result. As described above, in the medical field, since the diagnosis is made based on the density of a monochrome image,
The demands for widening the viewing angle and increasing the contrast are severe, and current LCDs have not yet achieved sufficient performance to meet medical needs.

The present invention has been made in view of the above-mentioned conventional problems, and has a liquid crystal display having a good contrast ratio over a wide viewing angle and realizing both a wide viewing angle and a high contrast. It is another object of the present invention to provide a method for increasing a contrast and a wide viewing angle of a liquid crystal display.

[0009]

In order to solve the above-mentioned problems, a liquid crystal display according to the present invention comprises: a collimating means for using collimated light from a backlight of the liquid crystal display; and the collimated backlight is incident. A liquid crystal panel, and a backlight light incident unit and the liquid crystal panel, which are incident on the liquid crystal panel, with a traveling direction of the collimated backlight light substantially aligned with a center of a high contrast ratio region in a viewing angle characteristic of the liquid crystal panel. There is provided a liquid crystal display comprising: a diffusing unit for diffusing transmitted light.

Preferably, the high contrast ratio region is a region where the ratio of the maximum luminance to the minimum luminance is 100 or more.

The collimating means may include a transparent support, a plurality of light-transmitting spheres partially fixed to the support, and a contact portion between the support and the sphere or a light-transmitting sphere. A collimating plate or a lens substrate having an obstruction for obstructing the passage of light in a region other than the vicinity of the contact portion; a microlens arranged two-dimensionally on one surface of the microlens; A collimating plate having a light-shielding layer formed so as to cover portions other than the light-incident portion coinciding with the axis, and a diffuse reflection layer formed to cover portions other than the light-incident portion formed closer to the light-incident side than the light-shielding layer. Preferably it is.

Further, the diffusing means has a light-transmitting support and a diffusion layer in which a light-transmitting sphere is fixed to a light-absorbing binder, and the diffusion layer is visually recognizable. Light diffusion having an impossible structure, and further having a relatively low light transmittance in the non-passing region, which is the other region, compared with the passing region where the collimated light incident from the structure side mainly passes. Light having a plate or a lens substrate, microlenses arranged two-dimensionally on one surface of the lens substrate, and a light-shielding layer formed so as to cover portions other than a light emitting portion coinciding with the optical axis of the microlens. It is preferably a diffusion plate.

Further, the liquid crystal panel is a twisted nematic mode liquid crystal panel, and the backlight light incidence means causes the collimated backlight light to enter the twisted nematic mode liquid crystal panel downward by a predetermined amount. preferable.

Further, it is preferable that the liquid crystal panel is any one of a twisted nematic mode liquid crystal panel provided with an optical compensation film, a lateral electric field driving mode liquid crystal panel, and a multi-domain vertical alignment mode liquid crystal panel axisymmetric alignment mode liquid crystal panel. .

[0015] Similarly, in order to solve the above-mentioned problems,
The method for increasing the contrast and widening the viewing angle of a liquid crystal display according to the present invention is characterized in that the backlight of the liquid crystal display is used as collimated light, and the traveling direction of the collimated backlight is changed to a high contrast ratio region in the viewing angle characteristics of the liquid crystal panel. The present invention provides a method for increasing the contrast and widening the viewing angle of a liquid crystal display, wherein light is incident on the liquid crystal panel so as to be substantially aligned with the center of the liquid crystal and light transmitted through the liquid crystal panel is diffused.

Preferably, the liquid crystal panel is a twisted nematic mode liquid crystal panel, and the traveling direction of the collimated backlight light is directed downward by a predetermined amount to the twisted nematic liquid crystal panel.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a liquid crystal display and a method of increasing a contrast and a wide viewing angle of the liquid crystal display according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

FIG. 1 conceptually shows an example of the liquid crystal display of the present invention. A liquid crystal display (hereinafter, referred to as an LCD) 10 shown in FIG. 1 includes a liquid crystal panel 12, a backlight unit 14 for entering a parallel light beam (collimated light) as backlight light into the liquid crystal panel 12, and a liquid crystal panel 1
Light diffusion plate 16 for diffusing the light carrying the image passing through 2
And is configured. A driver (not shown) for driving the liquid crystal panel 12 is connected to the liquid crystal panel 12, and various members of the known LCD are arranged on the LCD 10 as necessary. The LCD 10 of the present invention
Since high contrast can be realized over a wide viewing angle, it can be suitably used as a monitor of a medical measurement device.

A liquid crystal panel 1 used for the LCD 10
Examples of the second type include a TN (Twisted Nematic: twisted nematic) mode provided with an optical compensation film for accurately compensating for birefringence due to liquid crystal, and IPS (Instant Nematic).
Plane Switching: Horizontal electric field drive mode, MVA mode (Multidomain Vertical Alignment: Multidomain vertical alignment) mode and ASM (Axially Symmet)
The ric Aligned Microcell (axially symmetric alignment) mode is preferably exemplified.

The backlight unit 14 can be any of various light source devices (for example, a light source of an overhead projector, etc.) as long as it can emit a parallel light beam (collimated light) having a sufficient light amount for observing an image as backlight light. Are all available. The present invention is characterized in that the collimated backlight light is incident substantially toward the center of the high contrast ratio region in the viewing angle characteristics of the liquid crystal panel. The backlight unit 14 will be described later.

Various known light diffusing plates can be used as the light diffusing plate 16. As a preferred example, a light-transmitting support, having a light-transmitting sphere and a diffusion layer formed by fixing the light-transmitting sphere to a light-absorbing binder, and having a structure in which the diffusion layer is invisible, Further, a light diffusion plate having a relatively low light transmittance in a non-passing region, which is a region other than the passing region where the collimated light incident from the structure side mainly passes, is exemplified. Further, in this light diffusion plate, the non-passing region is preferably light-absorbing (a black mask), and the reflectance is preferably 10% or less due to the function of the non-passing region. preferable.

FIG. 2A shows a conceptual diagram of an example of such a light diffusion plate. The light diffusion plate 16a shown in FIG.
A light-transmitting support sheet 18 is provided with a light-transmitting sphere (hereinafter, referred to as a bead 20) and a light-absorbing binder 2.
2 has a configuration fixed. In addition, beads 2
0 is partially in contact with the support sheet 18.

Accordingly, as shown in FIG. 2A, the collimated light (single-dot chain line) carrying the image, which has passed through the liquid crystal panel 12, is refracted by the spherical beads 20, and the beads 20 and the support sheet 18 are refracted. Is sufficiently diffused through the contact portion with the substrate. Moreover, since the binder 22 has a light absorbing property, the portion other than the contact portion between the beads 20 and the support sheet 18 becomes a black mask, and external light from the observer side is not reflected and scattered by the light diffusion plate 16. ,
There is no reduction in contrast due to this. Therefore, an LCD that can obtain a good contrast ratio over a wide viewing angle
10 can be realized.

The support sheet 18 is not particularly limited, and various materials can be used as long as the support sheet 18 has a sufficient light transmittance and a sufficient mechanical strength according to the application. Specifically, various types of glass, polyester, polyolefin, polyamide, polyether, polystyrene,
Various resin materials such as polyesteramide, polycarbonate, polyphenylene sulfide, polyetherester, polyvinyl chloride, and polymethacrylic acid ester are preferably exemplified. The light diffusing plate (collimating plate) used in the present invention including the light diffusing plate 16a
May be in the form of a rigid plate, or may be in the form of a flexible sheet or film. Therefore, depending on the required mechanical strength and application, the material and thickness of the support sheet 18 may be adjusted. You may choose.

Further, in order to improve the observability of the LCD 10, the observation surface (the surface opposite to the beads 20) of the support sheet 18 is subjected to a known light non-reflection treatment such as an anti-reflection (AR) coat. Is preferred.

The beads 20 are light-transmissive and (substantially) spheres of a size that cannot be visually recognized by an observer. The beads 20 are fixed to the support sheet 18 by a binder 22 while partially contacting the support sheet 18. The light diffusing plate 16a is
The liquid crystal panel 12 is arranged and held with the 0 side facing the liquid crystal panel 12.

The material of the beads 20 is not particularly limited, and various materials can be used as long as they are transparent. For example, the above-mentioned materials of the sheet material 18 are variously exemplified, and particularly, the optical characteristics are good. In this respect, a (meth) acrylic resin or glass is preferably used. The size of the beads 20 is not particularly limited, and may be any size that cannot be visually recognized by an observer, depending on the use of the LCD 10 or the like.
The weight average particle diameter is preferably from 10 μm to 21 μm.

The binder 22 is not particularly limited, and various adhesives can be used as long as the beads 20 can be fixed to the support sheet 18, for example, vinyl acetate resin,
Ethylene-vinyl acetate copolymer, vinyl chloride resin, vinyl chloride-vinylidene chloride copolymer, (meth) acrylate resin, butyral resin, silicone resin, polyester, vinylidene fluoride resin, nitrocellulose resin, polystyrene, styrene Acrylic copolymers, urethane resins, polyethylene, polypropylene, polyethylene chloride, rosin derivatives, and mixtures thereof are preferably exemplified.

In this embodiment, the binder 22 has a light absorbing property. In this case, a light-absorbing material may be used as the binder 22, or a light-absorbing agent such as carbon black may be dispersed in the binder to give the binder 22 a light-absorbing property.

The method of manufacturing the light diffusion plate 16a is not particularly limited.
May be dispersed to adjust the paint, and the paint may be applied to the support sheet 18 and dried (cured), or the binder 22 may be applied to the support sheet 18 and the beads 20 may be spread over the entire surface. Then, the binder 22 may be dried. In this embodiment, since the binder 22 has a light absorbing property, the beads 20 can be uniformly fixed to the support sheet 18 over the entire surface, and the beads 20 are preferably not buried in the binder 22. It is necessary to adjust the amount of the binder so that more than half is exposed from the binder 22. If necessary, bead 20
The binder 22 may be dried after the beads 20 are brought into contact with the support sheet 18 by pressing or by settling by gravity. Note that, as described above, the light diffusion plate 16a
For example, it is preferable to have a black mask such as one using a light-absorbing binder from the viewpoint of reflection of external light, but it may be one without a black mask.

FIG. 2B shows another preferred example of the light diffusing plate 16. The light diffusion plate 16b has a microlens array 28 (hereinafter, referred to as a lens array 28) formed by two-dimensionally arranging a large number of hemispherical microlenses 28a on one surface of a plate-shaped lens substrate 26. I have. On the surface of the lens substrate 26 on the side opposite to the lens array 28, a light shielding layer 32 is entirely covered except for the light emitting portion 30 that is set to coincide with the optical axis of each micro lens 28a (on-axis). Is formed. Further, on the observation side (the upper layer of the light-shielding layer 32 based on the lens substrate 26 in the illustrated example) than the light-shielding layer 32, similarly except for the light incident portion 30, the anti-reflection layer (AR layer) is covered. ) 34 are formed.

The light diffusing plate 16b is connected to the lens array 28
It is arranged with the side facing the liquid crystal panel 12. LCD panel 1
The collimated light carrying the image passing through 2 is shown in FIG.
As schematically shown in (B), each micro lens 2
8a, is refracted, passes through the lens substrate 26, and is emitted from the light emitting unit 30 as diffused light. Light (stray light) incident on the light incident part 30 other than the light incident part 30 is shielded by the light shielding layer 32 and does not hinder observation. The light-shielding layer 32 is not particularly limited, and various known ones can be used. As an example, chromium (Cr) used for the BM of the liquid crystal panel 12 is exemplified. In a preferred embodiment, the antireflection layer 34 is formed on the observation surface side, so that good image observation is possible. The antireflection layer 34 is not particularly limited, and various known ones can be used.

In the light diffusing plate 16b, the material of the lens substrate 26 and the lens array 28 is not particularly limited, and various materials used for the lens, such as glass and various optical resins, can be used. . In addition, the lens substrate 26 and the lens array 28 may be integrally formed or fixed by combining separate members. further,
As the micro lens 28a, a shape obtained by cutting an ellipsoid (a spheroid) by a plane orthogonal to the long axis can be suitably used in addition to the hemisphere.

FIG. 3 shows the backlight unit 14 of the LCD 10.
Is shown conceptually. The backlight unit 14 includes a high-intensity lamp 38, a reflector 40, and a collimator 42. The light emitted from the high-intensity lamp 38 is directly or reflected by the reflection plate 40 and is incident on the collimating plate 42, becomes collimated backlight light, and is incident on the liquid crystal panel 12. The collimating plate 42 basically has the same configuration as the light diffusing plate 16a except that the light-shielding binder 22 is replaced with a light-diffusing and reflecting binder 44. The beads 20 are arranged toward the liquid crystal panel 12 toward the luminance lamp 38.

As the light-diffusing and reflecting binder 44, a material in which fine particles of a light-diffusing substance are dispersed in an adhesive (preferably, a transparent adhesive) for forming the above-mentioned binder 22 is preferably exemplified. . Light diffusing materials include yttrium oxide (Y ₂ O ₃ ), zirconium oxide (ZrO ₂ ), gadolinium oxide (Gd ₂ O ₃ ), lanthanum oxide (La ₂ O ₃ ), hafnium oxide (HfO ₂ ), and barium sulfate ( BaSO ₄ ), alumina (Al ₂ O ₃ )
And at least one of fine particles such as titanium oxide (TiO ₂ ).

In the collimating plate 42, the light emitted from the high-intensity lamp 38 and reflected on the light reflecting plate 40 and incident on the collimating plate 42 is opposite to the light diffusing plate 16a described above. As schematically shown in FIG. 2, only light incident on the contact point between the bead 20 and the support sheet 18 is incident on the bead 20, is refracted, and is emitted as collimated light. Further, the light other than the contact point, that is, the light incident on the binder 44, is diffused and reflected by the binder 44, is incident on the light reflection plate 40 and is reflected,
The light again enters the collimator plate 42.

The traveling direction of the collimated backlight light is approximately at the center of the high contrast ratio region in the viewing angle characteristics of the liquid crystal panel 12, preferably, approximately at the high contrast ratio region having a contrast ratio (RC) of 100 or more. It is injected to face the center. The direction of the backlight light is adjusted by the direction of the collimating plate 42. For example, in the case where the liquid crystal panel 12 is in the MVA mode and its viewing angle characteristics are as shown in FIG. 12B, the backlight light, which is collimated light, is directed toward substantially the center of the high contrast ratio region. Make it incident. In order to make the backlight light incident toward the center in this way, the collimating plate 42 may be arranged so as to be parallel to the liquid crystal panel 12.

By making the collimated backlight light incident substantially at the center of the high contrast ratio region of the liquid crystal panel 12, the collimated light is incident straight on the optical axis direction of the liquid crystal molecules. Refraction is suppressed. As a result, light leakage is prevented,
High contrast is achieved. And the liquid crystal panel 1
The high-contrast collimated light transmitted through 2 is diffused by the light diffusion plate 16. Light diffusion plate 1 of this embodiment
No. 6, as described above, achieves a wide viewing angle without reflection of external light.

FIG. 4 shows another example of a preferred collimating plate. This collimating plate 48 is a plate-shaped lens substrate 50.
On one surface, a microlens array 52 (hereinafter, referred to as a lens array 52) in which a large number of hemispherical microlenses 52a are two-dimensionally arranged is formed. A light-shielding layer 56 is formed so as to entirely cover the part other than the light incident part 54 set to coincide with the optical axis of the lens 52a, and a diffuse reflection layer 58 is similarly formed on the light incident side of the light-shielding layer 56. . FIG.
4 (B) and FIG. 4, this collimating plate 48 has basically the same configuration as the above-described light reflecting plate 16b, except that a diffusion reflecting layer 58 is formed instead of the antireflection layer 34. It has.

The collimating plate 42 is used for the lens array 5
The two sides are arranged facing the liquid crystal panel 12. The light emitted from the high-intensity lamp 38 and directly or reflected by the light reflecting plate 40 and incident on the collimating plate 42 is opposite to the light diffusing plate 16b, as shown schematically in FIG. The light enters the lens substrate 50 from the incident portion 54, passes through, enters each micro lens 52a, is refracted, and is emitted as collimated light. By adjusting the direction of the collimating plate 48, the traveling direction of the collimated backlight light is adjusted, and the collimated light is incident substantially at the center of the high contrast ratio region of the liquid crystal panel 12, whereby the same effect as described above is obtained. can get.

The light incident to portions other than the light incident portion 54 is diffusely reflected by the diffuse reflection layer 58, is incident on the light reflection plate 40 and is reflected, and is incident again on the light collimation plate 48. high. Further, since the light that has passed through the diffuse reflection layer 58 is shielded by the light shielding layer 56, the light does not become stray light that causes a decrease in directivity of the collimated light. The method for forming the diffuse reflection layer 58 is not particularly limited, and various known methods can be used. For example, there is exemplified a method of forming the above-mentioned light-diffusing substance with a paint or the like in which fine particles of the light-diffusing substance are dispersed.

FIG. 5 shows another example of a preferred collimating plate. In FIG. 5, (A) shows a front view, and (B)
And (C) show perspective views, respectively. As shown in FIG. 5, the collimating plate 62 is configured by arranging two prism sheets 64 face to face in parallel so that the longitudinal directions of the prisms are orthogonal to each other. FIG.
The pitch of the prism indicated by p in FIG. The prism sheet 64 collects light in the direction indicated by the arrow q in FIG. 5C and keeps the light spread in the longitudinal direction of the prism indicated by the arrow r. Therefore, as shown in FIGS. 5A and 5B, collimated light can be obtained by facing the two prism sheets 64 in parallel so that the longitudinal directions of the prisms are orthogonal to each other.

By adjusting the direction of the collimating plate 62, the traveling direction of the collimated backlight is adjusted, and the collimated light is incident on the liquid crystal panel 12 so as to be substantially aligned with the center of the high contrast ratio region. The effect of is obtained.

FIG. 6 shows another example of a preferred collimating plate used in the present invention. In FIG. 6, (A)
Shows a front view, and (B) shows a plan view. The collimating plate 68 has a prism sheet 70 and a louver 72 arranged in parallel so that the directions thereof are orthogonal to each other. Thereby, collimated light can be obtained, and the same effect can be obtained by adjusting the traveling direction of the collimated backlight light to approximately the center of the high contrast ratio region of the liquid crystal panel 12.

In the combination prism sheet, since a square matrix structure is generated, the collimating plate using the beads or the lens array described above is more suitable for high definition LCD (pixel size 200 μm or less). , More effective.

FIG. 7 shows another example of the present invention. In this example, a TN mode liquid crystal panel is used. In the case of the TN mode, as shown in FIG. 12A, a high contrast ratio region having a contrast ratio of 100 or more exists slightly below the center. The traveling direction of the light is set slightly downward to match the approximate center of the high contrast area. That is, the traveling direction of the collimated backlight light is inclined downward by a predetermined angle so as to be incident on the liquid crystal panel substantially in accordance with the angle at which the center of the high contrast ratio region faces downward from the horizontal direction. As a result, the backlight light is incident straight on the optical axis of the liquid crystal molecules, thereby suppressing birefringence. As a result, light leakage is prevented, the contrast ratio is improved, and the light is diffused by the light diffusion plate 16, whereby the viewing angle characteristics are improved satisfactorily.

In the example shown in FIG. 7, the liquid crystal panel is a TN mode liquid crystal panel 76, and the collimating plate 42 using the beads 20 is used as the collimating plate. Also in this embodiment, the light diffusing plate 16 is used as in the above-described example, but is not shown in FIG. 7 (the same applies to the following examples). As shown in FIG. 7, the collimating plate 42 is inclined downward by a predetermined angle in accordance with the angle at which the center of the high contrast ratio region of the TN mode liquid crystal panel 76 is shifted downward from the horizontal direction. Then, the collimated backlight light is set to enter the TN mode liquid crystal panel 76 obliquely downward at a predetermined angle.

As described above, by aligning the traveling direction of the collimated backlight light with the center of the high contrast ratio region of the liquid crystal panel, the backlight light is incident straight on the optical axis of the liquid crystal molecules. Since the birefringence of molecules is suppressed to prevent light leakage in the black display portion, the contrast ratio is improved. In addition, a wide viewing angle is achieved by diffusing the collimated light carrying the high-contrast image with the light diffusion plate 16.

FIG. 8 shows another example. In this example, the collimating plate 42 of the example shown in FIG. 7 is replaced with a collimating plate 48 using the (micro) lens array 52 shown in FIG. Again, in this case,
The same effect can be obtained by setting the collimating plate 48 so that the collimated light is incident obliquely downward on the TN mode liquid crystal panel 76.

FIG. 9 shows another example. In this example, the collimating plate 42 of the example shown in FIG. 7 is replaced with the collimating plate 68 composed of the prism sheet 70 and the louver 72 shown in FIG. Again, in this case,
The same effect can be obtained by setting the collimating plate 68 so that the collimated light enters the TN mode liquid crystal panel 76 obliquely downward.

FIG. 10 shows another example. In this example, the collimator plate 42 of the example shown in FIG. 7 is replaced with a plate having an asymmetric prism sheet 78 and a louver 44. At this time, the louver 44 is arranged so as to be orthogonal to the direction of the asymmetric prism, as shown in FIG. Further, in this case, the direction of light can be changed in a fixed direction by the asymmetric prism sheet 78. Therefore, as shown in FIG. If the predetermined angle is provided, the asymmetric prism sheet 78 and the louver 44 may be arranged in parallel with the TN mode liquid crystal panel 76, and it is not necessary to tilt the collimating plate downward as in the above-described example.

Although the liquid crystal display of the present invention and the method for increasing the contrast and widening the viewing angle of the present invention have been described in detail, the present invention is not limited to the above-described examples, and is within the scope of the present invention. Of course, various improvements and changes may be made.

[0053]

As described above, according to the present invention, it is possible to improve the viewing angle characteristics of a liquid crystal display, improve the contrast ratio, and achieve both a wide viewing angle and a high contrast. .

[Brief description of the drawings]

FIG. 1 is a view conceptually showing one example of a liquid crystal display of the present invention.

FIGS. 2A and 2B are conceptual diagrams showing an example of a light diffusing plate used in the liquid crystal display of FIG.

FIG. 3 is a schematic diagram showing an example of a backlight unit of the liquid crystal display shown in FIG.

FIG. 4 is a view conceptually showing another example of a collimating plate used in the present invention.

5A and 5B are diagrams conceptually illustrating another example of the collimating plate used in the present invention, wherein FIG. 5A is a front view, FIG. 5B is a perspective view, and FIG. The perspective view of a prism sheet is each shown.

6A and 6B are diagrams conceptually illustrating another example of the collimating plate used in the present invention, wherein FIG. 6A is a front view, and FIG. 6B is a plan view.

FIG. 7 is a view conceptually showing another example of the liquid crystal display of the present invention.

FIG. 8 is a view conceptually showing another example of the liquid crystal display of the present invention.

FIG. 9 is a view conceptually showing another example of the liquid crystal display of the present invention.

FIG. 10 is a view conceptually showing another example of the liquid crystal display of the present invention.

11A and 11B are explanatory diagrams showing the operation principle of a TN mode liquid crystal display. FIG. 11A shows a case where no voltage is applied.
(B) shows the case of voltage application.

12A and 12B are diagrams showing viewing angle characteristics of a conventional liquid crystal display, wherein FIG. 12A shows a case of a TN mode, and FIG. 12B shows a case of an MVA mode.

[Explanation of symbols]

 Reference Signs List 10 liquid crystal display (LCD) 12 liquid crystal panel 14 backlight unit 16 (16a, 16b) light diffusion plate 18 support sheet 20 beads 22, 44 binder 26, 50 lens substrate 28, 52 (micro) lens array 30 light emitting unit 32, 56 light-shielding layer 34 anti-reflection layer 38 high-intensity lamp 40 reflecting plate 42, 48, 62, 68 collimating plate 54 light incident part 58 diffuse reflection layer 64, 70 prism sheet 72 louver 76 TN mode liquid crystal panel 78 asymmetric prism sheet 100, 102 Glass substrate 104 liquid crystal molecules 106 polarizer 108 analyzer

Claims (11)

[Claims] 1. A collimating means for using collimated backlight light of a liquid crystal display, a liquid crystal panel on which the collimated backlight light is incident, and a liquid crystal panel on which the traveling direction of the collimated backlight light is adjusted. A liquid crystal panel, comprising: a backlight light incident means for entering the liquid crystal panel in accordance with substantially the center of the high contrast ratio region in the viewing angle characteristic; and a diffusing means for diffusing light transmitted through the liquid crystal panel. display. 2. The liquid crystal display according to claim 1, wherein the high contrast ratio region is a region where the ratio of the maximum luminance to the minimum luminance is 100 or more. 3. The collimating means comprises: a transparent support;
A large number of light-transmitting spheres that are fixed by partially contacting the support, and an inhibition portion that inhibits light from passing through a contact portion between the support and the sphere or a region other than the vicinity of the contact portion. A collimating plate or a lens substrate, a microlens two-dimensionally arranged on one surface of the lens substrate, and a light-shielding layer formed so as to cover portions other than a light incident portion coinciding with an optical axis of the microlens. 3. The liquid crystal display according to claim 1, wherein the liquid crystal display is a collimating plate including: a collimating plate; and a diffuse reflection layer formed to cover a part other than the light incident part formed on the light incident side of the light shielding layer. 4. The diffusing means has a light-transmitting support and a diffusion layer formed by fixing a light-transmitting sphere to a light-absorbing binder, and the diffusion layer is visible. Light diffusion having an impossible structure, and further having a relatively low light transmittance in the non-passing region, which is the other region, compared with the passing region where the collimated light incident from the structure side mainly passes. Board,
Alternatively, a light diffusing plate having a lens substrate, microlenses arranged two-dimensionally on one surface of the lens substrate, and a light shielding layer formed so as to cover portions other than a light emitting portion coinciding with an optical axis of the microlens. The liquid crystal display according to any one of claims 1 to 3, wherein 5. The liquid crystal panel is a twisted nematic mode liquid crystal panel, and the backlight light incidence means causes the collimated backlight light to enter the twisted nematic mode liquid crystal panel downward by a predetermined amount. The liquid crystal display according to any one of claims 1 to 4. 6. The liquid crystal display according to claim 1, wherein said liquid crystal panel is a twisted nematic mode liquid crystal panel provided with an optical compensation film. 7. The liquid crystal display according to claim 1, wherein said liquid crystal panel is a horizontal electric field drive mode liquid crystal panel. 8. The liquid crystal display according to claim 1, wherein said liquid crystal panel is a multi-domain vertical alignment mode liquid crystal panel. 9. The liquid crystal display according to claim 1, wherein said liquid crystal panel is an axially symmetric alignment mode liquid crystal panel. 10. The backlight light of a liquid crystal display is used as collimated light, and the traveling direction of the collimated backlight light is incident on the liquid crystal panel such that the traveling direction of the collimated backlight light is substantially at the center of a high contrast ratio region in the viewing angle characteristics of the liquid crystal panel. A method of increasing the contrast and widening the viewing angle of a liquid crystal display, wherein light transmitted through the liquid crystal panel is diffused. 11. The liquid crystal panel according to claim 10, wherein the liquid crystal panel is a twisted nematic mode liquid crystal panel, and the traveling direction of the collimated backlight light is made to enter the twisted nematic liquid crystal panel downward by a predetermined amount. A method for increasing the contrast and widening the viewing angle of a liquid crystal display.