JPH11119217A - Liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct the uniformity of luminance in the vertical direction caused by the dependency on visual field angle and the heat of a back light by driving the scanning electrodes of a liquid crystal panel from both sides to improve the luminance balance in the left and right direction and adjusting the luminance distribution in the up and down direction. SOLUTION: A back light is arranged on the bottom side of a liquid crystal panel. The luminance of the back light is adjusted by the shape of the reflection layer formed in the back side of a light transmission body. The reflection layer is formed on the back surface of a transparent resin light transmission body by printing high reflectivity resin in dot shapes, for example. By varying the dot sizes and the dot pitches, the luminance distribution of the back light is controlled. In the luminance distribution of the back light, the luminance distribution in the vertical direction becomes a maximum at the upper portion of the screen center section and is reduced at the top and the bottom of the screen. Thus, the uniformity of the panel luminance is improved and the irregularity of the luminance in the vicinity of the back light is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for OA equipment such as a personal computer and a display monitor.
The present invention relates to a liquid crystal display device having improved characteristics of luminance distribution with respect to a viewing angle.

[0002]

2. Description of the Related Art At present, liquid crystal displays, plasma displays, EL displays, and the like have been put into practical use as flat panel displays, and their uses have become widespread. For example, a liquid crystal panel, which is a main component of a liquid crystal display (liquid crystal display device),
Although the screen size and the number of pixels are inferior in some aspects, it can be said that it is excellent in portability in weight and volume. Current,
Liquid crystal display devices are often used in notebook computers and word processors. In the liquid crystal display devices for these applications, the size is about 10 to 12 inches, and the number of pixels is 640 × 48.
Most of them are 0 dots or 600 × 800 dots. Although the liquid crystal panel is inferior to the CRT in terms of the number of pixels, it has a functionally excellent display capability as a display.

FIG. 8 shows the structure of such a conventional liquid crystal panel (liquid crystal display element), and is a cross-sectional view of a liquid crystal panel of a simple matrix type color STN in particular. 8, a transparent electrode 4b and an alignment film layer 5b are formed on a signal electrode substrate 6.
Are formed in this order. On the scanning electrode substrate 1 facing the signal electrode substrate 6, the color filter layer 2 and the black matrix 16 are formed. Further, a transparent resin layer 3 made of an organic material is provided thereon to obtain smoothness, and a transparent electrode 4a and an alignment film layer 5a are formed in this order. The upper and lower electrode substrates configured as described above are bonded via a particulate spacer 15 with a sealing resin 14 printed on the periphery of the substrate so as to keep the gap between the electrode substrates constant. The liquid crystal 13 is sealed in the gap to form a color liquid crystal panel.

In the future, STN will develop screen sizes of 12 to 17 inches, and the display capacity will be changed from SVGA to XGA and SX.
With the evolution to GA, liquid crystal displays are becoming alternative monitors for CRTs. Therefore, the display quality is lower than before.
High levels are required.

[0005]

However, simply realizing a large screen and a high display capacity of a liquid crystal display device requires uniform brightness in a display surface due to the influence of the viewing angle of the liquid crystal panel. I can't get it. When a liquid crystal display device is used as a display device of a desktop computer or a word processor, the liquid crystal panel is generally installed almost perpendicular to the desk surface. Here, the upper part of the liquid crystal panel is referred to as an upward direction and the lower part is referred to as a downward direction as viewed from a user.

In a display state in which a voltage is not sufficiently applied to the liquid crystal layer, as in a so-called halftone display, a liquid crystal display device in which the user's viewing angle changes in the vertical direction, for example,
As shown in FIG. 9, the viewing angle depends on the vertical direction of the screen. For example, if the angle between the liquid crystal panel surface and the user's line of sight is θ, the normal line of sight (viewing angle) is below the liquid crystal panel, and when the angle θ at that time is close to 90 °, the brightness of the liquid crystal panel is Is smaller than this, and is relatively larger than when looking at the top of the screen. Thus, the angle θ
Changes, a remarkable difference appears in the luminance visually recognized by the user, causing a significant reduction in display quality.

As a method for solving the above problem, there is, for example, a method disclosed in Japanese Patent Application Laid-Open No. 2-79022. Here, a proposal has been made to make the luminance distribution of the light source non-uniform.

Furthermore, in order to realize a bright display with a large screen, it is necessary to increase the luminance of the backlight. However, when the liquid crystal panel is illuminated for a long time, heat generated near the backlight lowers the threshold voltage of the liquid crystal. For this reason, the transmittance of the liquid crystal panel near the backlight increases, and luminance unevenness occurs in the vertical direction of the screen as shown in FIG. This also causes the display quality to deteriorate.

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and has a liquid crystal display capable of displaying with uniform brightness when a liquid crystal panel for displaying a large screen and a large capacity is provided. It is intended to realize the device.

[0010]

In order to solve such a problem, the invention according to claim 1 of the present application is to hold a liquid crystal layer between a signal electrode substrate and a scanning electrode substrate so that the liquid crystal layer is held from both sides of the scanning electrode. What is claimed is: 1. A liquid crystal display device comprising: a liquid crystal panel to which the same scanning signal is applied at the same timing and a main viewing angle direction is an upward direction; and a backlight that illuminates the liquid crystal panel from behind. It is characterized in that the luminance distribution in the direction perpendicular to the plane is maximum at a position above the center, and the luminance is gradually reduced in the vertical direction.

According to a second aspect of the present invention, the same scanning signal is applied at the same timing from both sides of the scanning electrode by sandwiching a liquid crystal layer between the signal electrode substrate and the scanning electrode substrate.
A liquid crystal display device comprising: a liquid crystal panel whose main viewing angle direction is downward; and a backlight that illuminates the liquid crystal panel from behind, wherein a luminance distribution in a direction perpendicular to a display surface of the liquid crystal panel is centered. It is characterized by a maximum at a lower position and a gradual decrease in luminance in the vertical direction.

[0012] The invention described in claim 3 of the present application is the first invention.
In the liquid crystal display device, the backlight has a maximum luminance distribution in a direction perpendicular to the liquid crystal panel at a position above the center of the liquid crystal panel, and the luminance gradually decreases in the vertical direction. It is characterized by the following.

According to a fourth aspect of the present invention, in the liquid crystal display device of the second aspect, the backlight is such that a luminance distribution in a direction perpendicular to the liquid crystal panel is lower than a center of the liquid crystal panel. , And the brightness gradually decreases in the vertical direction.

According to a fifth aspect of the present invention, in the liquid crystal display device of the first aspect, the liquid crystal panel has a maximum transmittance distribution in a direction perpendicular to a display surface at a position above a center, and It is characterized in that the transmittance gradually decreases in the vertical direction.

According to a sixth aspect of the present invention, in the liquid crystal display device of the second aspect, the liquid crystal panel has a maximum transmittance distribution in a direction perpendicular to the display surface at a position below the center, It is characterized in that the transmittance gradually decreases in the vertical direction.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal display according to each embodiment of the present invention will be described below with reference to FIGS.

(Embodiment 1) FIG. 1 is a perspective view showing the appearance of a liquid crystal display device according to Embodiment 1 of the present invention, in which the + Y direction is an upward direction and the -Y direction is a downward direction. FIG. 2 is a cross-sectional view showing the configuration of the liquid crystal display device in each embodiment, and the same parts as those in the conventional example are denoted by the same reference numerals.

In FIG. 2, a scanning electrode substrate 1 comprises a color filter 2, a transparent resin layer 3, a transparent electrode 4a, and an alignment film layer 5.
a is a substrate formed sequentially. Also, the signal electrode substrate 6
Is a substrate on which a transparent electrode 4b and an alignment film layer 5b are sequentially formed. The scanning electrode substrate 1 and the signal electrode substrate 6 are respectively rubbed in the rubbing direction as shown in the drawing, and the rubbing angles are bonded to each other so that the crossing angle is 70 degrees. The added liquid crystal 13 is filled and sealed with a seal resin 14. Then, as shown in FIG. 1, the signal electrode of the signal electrode substrate 6 and the scanning electrode substrate 1
Is mounted on the scanning electrodes, and a film carrier 7 on which an IC for driving signal application is mounted is connected. Further, these film carriers 7 are connected to a circuit board 8 to produce a liquid crystal panel whose viewing angle is upward. In this case, it is assumed that the angle θ described above becomes smaller in the upward direction of the liquid crystal panel. By driving the scanning electrodes simultaneously from both left and right sides, the luminance balance in the left and right direction is maintained.

Next, a backlight 10A serving as a light emitting source is provided below the liquid crystal panel (in the -Z direction) to produce a liquid crystal display device. At this time, the brightness of the backlight 10A is
As shown in FIG. 2, it is adjusted by the shape of the reflective layer 11 formed on the back side of the light guide 12. The reflective layer 11 is formed on the back surface of the transparent resin light guide 12 by, for example, printing a resin having a high reflectance in a dot shape. By changing the dot size and dot pitch along the + Y and -Y directions, the luminance distribution of the backlight can be controlled. FIG. 3 shows the luminance distribution of the backlight in the liquid crystal display device according to the first embodiment. The luminance distribution in the vertical direction becomes maximum from the center of the screen to the upper part, and the luminance decreases at the upper part and the lower part of the screen. .

The thus-prepared liquid crystal display device is lit and displayed using the backlight 10A, and the display quality is evaluated. It was confirmed that the uniformity of the luminance of the liquid crystal panel was improved. Further, it was confirmed that luminance unevenness near the backlight during long-time lighting was also reduced.

(Embodiment 2) Next, a liquid crystal display device according to Embodiment 2 of the present invention will be described. The configuration of the liquid crystal display device of the present embodiment is the same as that shown in FIGS.

First, a scanning electrode substrate 1 on which a color filter 2A, a transparent resin layer 3, a transparent electrode 4a and an alignment film layer 5a are sequentially formed is provided, and a signal electrode substrate on which a transparent electrode 4b and an alignment film layer 5b are sequentially formed. 6 is provided. Then, the scanning electrode substrate 1 and the signal electrode substrate 6 are bonded together using the sealing resin 14 so that the crossing angle of the rubbing angle becomes 70 degrees.
Next, the gap is filled with a liquid crystal 13 to which a chiral additive (CM43: manufactured by Chisso Corporation) has been added, and TAB mounting is performed on the signal electrode of the signal electrode substrate 6 and the scanning electrode of the scanning electrode substrate 1. Then, the film carrier 7 on which the driving signal application IC is mounted is connected, and the film carrier 7 is further connected to the circuit board 8. In this way, a liquid crystal panel whose viewing angle direction is upward as shown in FIG. 1 is created.

At this time, when forming the color filters 2A, the line width of the black matrix 16A formed between the color filters is changed in the vertical direction of the screen. Specifically, the line width of the black matrix is minimized at a position above the center, and the line width is increased in the vertical direction. By changing the aperture ratio of the color filter 2A in the vertical direction in this way, a liquid crystal panel having a transmittance distribution in the vertical direction as shown in FIG. 4 was produced.

Next, a backlight 10 serving as a light emitting source was installed below the liquid crystal panel, and a liquid crystal display device was manufactured. In this case, unlike the backlight 10A, the backlight 10 does not need to change the reflectance of the reflecting surface in the Y direction.

The liquid crystal display device thus produced was lit and displayed, and its display quality was evaluated. The luminance dependency due to the viewing angle dependence in the plane of the liquid crystal panel was corrected by the transmittance distribution of the liquid crystal panel itself, and the luminance was corrected. It has been confirmed that the uniformity of the particles has been improved. Further, it was confirmed that luminance unevenness near the backlight during long-time lighting was also reduced.

(Embodiment 3) Next, a liquid crystal display device according to Embodiment 3 of the present invention will be described. The sectional configuration of the liquid crystal display device of the present embodiment is the same as that shown in FIG. However, the orientation direction of the liquid crystal panel is different from that shown in FIG. FIG. 5 is an external perspective view of the liquid crystal display device of the present embodiment.

As shown in FIG. 2, a scanning electrode substrate 1 on which a color filter 2, a transparent resin layer 3, a transparent electrode 4a, and an alignment film layer 5a are sequentially formed is provided.
The signal electrode substrate 6 on which b is sequentially formed is provided. Then, the scanning electrode substrate 1 and the signal electrode substrate 6 are bonded together using the sealing resin 14 so that the crossing angle of the rubbing angle becomes 70 degrees. Next, a chiral additive (CM43:
The liquid crystal 13 to which Chisso Corporation is added is filled, and TAB mounting is performed on both sides of the signal electrode of the signal electrode substrate 6 and the scanning electrode of the scanning electrode substrate 1. And I for driving signal application
The film carrier 7 carrying C is connected, and the film carrier 7 is further connected to the circuit board 8. Thus, a liquid crystal panel whose viewing angle direction is downward (−Y direction) is created as shown in FIG. It is assumed that the liquid crystal display device in this case is installed below the user's eyes.

Next, a backlight 10B, which is a light emitting source, is installed below the liquid crystal panel to produce a liquid crystal display device.
At this time, the brightness of the backlight 10B is adjusted by the shape of the reflection layer 11 on the back side of the light guide 12. Specifically, the dot size of the resin printed on the back surface of the light guide 12 is maximized from the center to the lower part of the screen, or the dot pitch is made denser from the center to the lower part of the screen. Then, the dot size is reduced in the vertical direction or the dot pitch is reduced. Thus, a vertical luminance distribution characteristic as shown in FIG. 6 was obtained.

When the liquid crystal display device thus produced was lit and displayed and its display quality was evaluated, the luminance dependence due to the viewing angle dependence in the plane of the liquid crystal panel was corrected by the backlight luminance distribution, and the uniformity of luminance was obtained. It was confirmed that the property was improved. Further, it was confirmed that luminance unevenness near the backlight during long-time lighting was also reduced.

(Embodiment 4) Next, a liquid crystal display device according to Embodiment 4 of the present invention will be described. The configuration of the liquid crystal display device of the present embodiment is the same as that shown in FIGS.

First, a scanning electrode substrate 1 on which a color filter 2B, a transparent resin layer 3, a transparent electrode 4a and an alignment film layer 5a are sequentially formed is provided, and a signal electrode substrate on which a transparent electrode 4b and an alignment film layer 5b are sequentially formed. 6 is provided. Then, the scanning electrode substrate 1 and the signal electrode substrate 6 are bonded together such that the crossing angle of the rubbing angle becomes 70 degrees. Next, a liquid crystal 13 containing a chiral additive (CM43: manufactured by Chisso Corporation) added to the gap.
And TAB mounting is performed on both sides of the signal electrode of the signal electrode substrate 6 and the scanning electrode of the scanning electrode substrate 1. And a film carrier 7 on which an IC for driving signal application is mounted.
And the film carrier 7 is connected to the circuit board 8. In this way, a liquid crystal panel whose viewing angle direction is downward is created. At this time, the black matrix 1 formed between the color filters 2B when forming the color filters 2B
The line width of 6 is minimized from the center to the lower part of the screen, and is increased in the vertical direction. Thus, the aperture ratio of the color filter 2 in the vertical direction was changed. FIG. 7 shows a vertical transmittance distribution of the liquid crystal panel of the present embodiment.

Next, a backlight 10 serving as a light emitting source was installed below the liquid crystal panel, and a liquid crystal display device was manufactured. In this case, unlike the backlight 10A, the backlight 10 does not need to change the reflectance of the reflecting surface in the Y direction.

The liquid crystal display device thus produced was lit and displayed, and its display quality was evaluated. The luminance dependence due to the viewing angle dependence in the plane of the liquid crystal panel was corrected by the transmittance distribution of the liquid crystal panel, and the uniformity of luminance was obtained. It was confirmed that the property was improved. Further, it was confirmed that luminance unevenness near the backlight during long-time lighting was also reduced.

In the first and third embodiments, the brightness distribution is formed in the vertical direction of the backlight by adjusting the reflection layer. However, a predetermined brightness distribution such as a method of inserting a filter is used. Any method may be used as long as the method is provided.

In the second and fourth embodiments, the aperture ratio of the color filter layer is changed as a method of adjusting the transmittance of the liquid crystal panel. However, the method can be realized by inserting a filter on the liquid crystal panel.

Although the method of correcting the brightness in the upward and downward directions of the liquid crystal panel has been described, when the liquid crystal panel is mounted almost horizontally as viewed from the user as in an ATM,
The downward direction is interpreted as the near side, and the upward direction is interpreted as the other side.

[0037]

As described above, according to the present invention, by driving the scanning electrodes of the liquid crystal panel from both sides, the luminance balance in the left-right direction is improved, and the luminance distribution in the vertical direction is adjusted. It is possible to correct unevenness in the vertical direction due to the angle dependence and the heat of the backlight.
Thus, a liquid crystal display device having high display uniformity can be realized.

[Brief description of the drawings]

FIG. 1 is an external view showing a configuration of a liquid crystal display device according to Embodiments 1 and 2 of the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of a liquid crystal display device according to Embodiments 1, 2, 3, and 4 of the present invention.

FIG. 3 is a vertical luminance distribution diagram of the backlight according to the first embodiment.

FIG. 4 is a vertical transmittance distribution diagram of a liquid crystal panel according to a second embodiment.

FIG. 5 is an external view illustrating a configuration of a liquid crystal display device according to Embodiments 3 and 4 of the present invention.

FIG. 6 is a vertical luminance distribution diagram of the backlight according to the third embodiment.

FIG. 7 is a vertical transmittance distribution diagram of the liquid crystal panel in the fourth embodiment.

FIG. 8 is a cross-sectional view illustrating a configuration of a conventional liquid crystal display device.

FIG. 9 shows the viewing angle dependency of halftone luminance in a conventional liquid crystal display device.

FIG. 10 shows the viewing angle dependence of halftone luminance during long-time lighting in a conventional liquid crystal display device.

[Explanation of symbols]

 Reference Signs List 1 scanning electrode substrate 2, 2A, 2B color filter 3 transparent resin layer 4a, 4b transparent electrode 5a, 5b alignment film 6 signal electrode substrate 7 film carrier 8 circuit substrate 9 diffusion plate 10, 10A, 10B backlight 11 reflection layer 12 conductive Optical body 13 Liquid crystal 14 Seal resin 15 Spacer 16 Black matrix

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideki Matsukawa 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (6)

[Claims] A liquid crystal panel having a liquid crystal layer sandwiched between a signal electrode substrate and a scanning electrode substrate, wherein the same scanning signal is applied at the same timing from both sides of the scanning electrode, and a main viewing angle direction is an upward direction; A backlight for illuminating the liquid crystal panel from behind, wherein a luminance distribution in a direction perpendicular to a display surface of the liquid crystal panel is maximum at a position above a center, and A liquid crystal display device characterized in that the brightness is gradually reduced by the following method. 2. A liquid crystal panel in which a liquid crystal layer is sandwiched between a signal electrode substrate and a scanning electrode substrate, the same scanning signal is applied at the same timing from both sides of the scanning electrode, and a main viewing angle direction is downward. A backlight that illuminates the liquid crystal panel from behind, wherein a luminance distribution in a direction perpendicular to a display surface of the liquid crystal panel is maximum at a position below a center, and in a vertical direction thereof. On the other hand, a liquid crystal display device characterized by gradually lowering the luminance. 3. The backlight according to claim 1, wherein a luminance distribution in a direction perpendicular to the liquid crystal panel becomes maximum at a position above a center of the liquid crystal panel, and the luminance gradually decreases in a vertical direction. The liquid crystal display device according to claim 1, wherein 4. The backlight according to claim 1, wherein a luminance distribution in a direction perpendicular to the liquid crystal panel is maximum at a position below a center of the liquid crystal panel, and the luminance gradually decreases in a vertical direction. 3. The liquid crystal display device according to claim 2, wherein: 5. The liquid crystal panel according to claim 1, wherein the transmittance distribution in the direction perpendicular to the display surface is maximum at a position above the center, and the transmittance gradually decreases in the vertical direction. Item 2. The liquid crystal display device according to item 1. 6. The liquid crystal panel according to claim 1, wherein the transmittance distribution in the direction perpendicular to the display surface is maximum at a position below the center, and the transmittance gradually decreases in the vertical direction. The liquid crystal display device according to claim 2.