JPH09145933A - Liquid crystal display - Google Patents

Abstract

(57) Abstract: The brightness of light transmitted from a backlight unit is made uniform on the display surface of a liquid crystal display panel. A liquid crystal display panel and a backlight unit for transmitting light to a display surface of the liquid crystal display panel are provided, and the backlight unit is provided with a light guide plate facing the liquid crystal display panel. A light source arranged along one end face of the light guide plate extending in the y direction, and a prism sheet is interposed between the backlight unit and the liquid crystal display panel, and the prism sheet is a transparent sheet. In a liquid crystal display device having a structure in which prism-shaped projections parallel to the y direction are arranged in parallel in the x-direction on one surface of the prism sheet, the projections of the prism sheet face the liquid crystal display panel. And the apex angle of the ridge is gradually reduced as the distance from the light source increases in the x direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a so-called backlight type liquid crystal display device.

[0002]

2. Description of the Related Art In a so-called backlight type liquid crystal display device, a backlight unit is arranged on the back surface of a liquid crystal display panel having a pair of transparent substrates arranged as opposed to each other with a liquid crystal layer therebetween as an envelope. It is configured.

On the main surface of the liquid crystal display panel, a large number of pixels capable of independently modulating the degree of light transmission in the liquid crystal layer are arranged in a matrix to form a display section. The radiated light from the backlight unit can be transmitted to the portion.

There is known a device in which a so-called prism sheet is arranged between the backlight unit and the liquid crystal display panel in order to improve the light condensing property from the backlight unit to the liquid crystal display panel. .

The backlight unit is composed of a light guide plate arranged to face the liquid crystal display panel and a light source arranged along one end face of the light guide plate extending in the y direction, for example. It is known that a plurality of dot-shaped spherical bodies are formed by printing ink on the surface of the light guide plate opposite to the liquid crystal display panel.

[0006]

However, in the liquid crystal display device configured as described above, the light emitted from the backlight unit itself has a uniform brightness over the entire irradiation region, It has been pointed out that the light transmitted from the backlight unit through the liquid crystal display panel is not uniform on the display surface of the liquid crystal display panel.

Specifically, the brightness is low at the four corners of the display surface of the liquid crystal display panel, or, as a whole, the brightness is low in the area away from the light source of the backlight unit. It is mentioned that there is.

The present invention has been made under such circumstances, and an object thereof is to provide a liquid crystal display device capable of making the brightness of light transmitted from a backlight unit uniform on the display surface of a liquid crystal display panel. Especially.

[0009]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, a liquid crystal display panel and a backlight unit for transmitting light to a display surface of the liquid crystal display panel are provided, and the backlight unit is a light guide plate arranged to face the liquid crystal display panel. A light source is arranged along one end surface of the light guide plate extending in the x direction, and a prism sheet is interposed between the backlight unit and the liquid crystal display panel, and the prism sheet is transparent. In a liquid crystal display device in which prism-shaped projections parallel to the x-direction are arranged in parallel in the y-direction on one surface of the sheet, the projections of the prism sheet are the same as those of the liquid crystal display panel. The ridges are formed on opposing surfaces, and the apex angle of the ridges is gradually reduced as the distance from the light source increases in the y direction.

In the liquid crystal display device having such a structure, the angle of the light emitted from the light guide of the backlight unit with respect to the perpendicular of the light guide increases as the distance from the light source increases. This is based on the fact that the brightness of the light transmitted through the liquid crystal display panel becomes low.

As a prism sheet interposed between the backlight unit and the liquid crystal display panel, its ridges are formed on the surface facing the liquid crystal display panel, and the apex angle of the ridges becomes further away from the light source. By sequentially reducing the size of the light, the light emitted from the light guide at an angle with respect to the normal to the light guide is incident on the ridges of the prism sheet at an angle according to the angle. The light is emitted from the prism sheet in the direction along the vertical line.

For this reason, the liquid crystal display panel has a structure in which light is transmitted through the entire area (at least the display surface) in a direction perpendicular to the liquid crystal display panel, so that the brightness of the light can be made uniform.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. FIG. 2 is an exploded perspective view showing an embodiment of the liquid crystal display device according to the present invention.

In FIG. 1, there is a liquid crystal display panel 1 first. In this liquid crystal display panel 1, a pair of transparent substrates arranged to face each other via a liquid crystal layer is used as an envelope, and a large number of pixels capable of independently modulating the degree of light transmission to the liquid crystal layer are provided on the main surface thereof. The display units are arranged in a matrix.

Further, an external circuit for modulating and driving light transmission in each of the pixels of the liquid crystal display panel 1 is provided around the liquid crystal display panel 1, and the external circuit mounts various electronic parts. It comprises a printed circuit board 2 and a plurality of liquid crystal drive ICs 3 connected between the printed circuit board 2 and the liquid crystal display panel 1.

A backlight unit 5 is arranged on the back side of the liquid crystal display panel 1 with a prism sheet 4 interposed therebetween. The backlight unit 5 serves as a light source for transmitting light from the rear side to the front side (observation side) of the display section of the liquid crystal display panel 1, and has a light guide plate 5A having substantially the same size as the liquid crystal display panel 1. And a cold cathode ray tube 5B arranged along the one end face of the light guide plate 5A, and a reflection plate for guiding light from the cold cathode ray tube 5B to the one end face side of the light guide plate 5A. 5C and.

In the backlight unit 5 as described above, the light of the cold cathode ray tube 5B introduced into the light guide plate 5 is totally reflected in the light guide plate 5 and the liquid crystal display panel 1 faces from the surface facing the liquid crystal display panel 1. It is designed to be irradiated to the side. The prism sheet 4 is provided to collect light from the light guide plate 5B on the liquid crystal display panel 1 side without scattering, and at least one surface thereof has a prism-like convex shape. It has been configured.

The liquid crystal display panel 1 is positioned and arranged from the front surface of the mold base material 6, and the prism sheet 4 and the backlight unit 5 are positioned and arranged from the rear part of the mold base material 6, thereby The positional relationship of is fixedly held.

On the other hand, the front portion of the liquid crystal display panel 1 is provided with an upper frame 7 having an opening for exposing the display portion of the liquid crystal display panel 1, and a lower frame 8 is provided on the back surface of the backlight unit 5. The upper frame 7 and the lower frame 8 are connected to each other by, for example, caulking.

FIG. 1 is a cross-sectional view taken along the line I--I of FIG. 2, showing the structure of the prism sheet 4 in relation to the backlight unit 5.

In the figure, the prismatic convex shape 4A of the prism sheet 4 is a surface facing the liquid crystal display panel (a surface opposite to the surface facing the backlight unit 5).
This ridge 4A is parallel to the direction of the cold-cathode ray tube 5B (x direction in the figure), and as it goes away from the cold-cathode ray tube 5B, its apex angle becomes an angle θ as shown in the figure. ₁
The angle is gradually decreased from the angle θ ₂ to the angle θ ₂ .

With this structure, as shown in FIG. 3, the light guided from the cold cathode ray tube 5B of the backlight unit 5 to the light guide 5A and emitted to the prism sheet 4 side is the prism sheet 4. Thus, the light can be emitted in a direction substantially along the perpendicular to the main surface of the light guide plate 5A.

Here, FIG. 4 shows a corresponding diagram showing the light path when the conventional prism sheet 4'is used.
In the figure, the light emitted from the main surface of the light guide plate 5 tends to gradually incline with respect to the normal to the main surface as it goes away from the cold cathode ray tube 5B, but this tendency is mediated by the prism sheet 4 '. It will be maintained as it is even after it is done. This is because, in the conventional prism sheet 4 ', all the apex angles of the convex shapes 4A' are constant. In such a case, it is unavoidable that the brightness is lowered in the area away from the cold cathode ray tube 5B on the surface of the liquid crystal display panel 1.

On the other hand, in this embodiment, the prism sheet 4 causes the light emitted from the light guide 5A at an angle with respect to the perpendicular of the light guide 5A to correspond to the prism sheet 4. By the convex shape 4A, the light is refracted at an angle corresponding to the angle so that the light is emitted in the direction along the perpendicular line.

Therefore, the liquid crystal display panel 1 can be configured to allow light to pass through the entire area (at least the display surface) in the direction perpendicular to the liquid crystal display panel 1, so that the brightness of the light can be made uniform.

Example 2. FIG. 5 is a main part configuration diagram showing another embodiment of the liquid crystal display device according to the present invention and corresponds to FIG.

The structure different from that shown in FIG. 1 is that the prism sheet 4 has convex ridges 4A formed on the surface facing the backlight unit 5, and the apex angle of the convex ridges 4A is in the y direction from the light source. It is getting bigger and bigger as it goes away. That is, the prism sheet 4 shown in FIG. 1 is placed inside out with the side in the x direction as the center.

Even in the case of such a configuration, similarly to the case shown in FIG. 1, since the liquid crystal display panel 1 can be configured to transmit light in the direction perpendicular to the entire area (at least the display surface) of the liquid crystal display panel 1. The brightness of the light can be made uniform.

Embodiment 3 FIG . FIG. 6 is a main part configuration diagram showing another embodiment of the liquid crystal display device according to the present invention.
FIG. 6 is a sectional view taken along line VI.

In the prism sheet 4, the central portion W and the side portions w of the prism sheet 4 in the x direction have different shapes of the ridges 4A. That is, the ridge 4A in the central portion W has a symmetrical shape with respect to the perpendicular from its apex angle, whereas the ridge 4A on both sides w has a vertical line from its apex. On the other hand, the angle on the side of the central portion W is θ
₃ , the angle on the side farther from the central portion W side is θ ₄ (> θ ₃ )
It has become. In other words, the convex stripes 4A on both sides w have a larger angle on the side farther from the central portion W side with respect to the perpendicular from the apex angle.

In this case, in the region close to the cold cathode ray tube 5B, the light is emitted from the light guide plate 5 without a large inclination from the perpendicular to the main surface thereof. In the area far from the cold cathode ray tube 5B, it is possible to prevent large refraction, and since the light is emitted with a large inclination from the perpendicular to the main surface of the light guide plate 5, the ridges 4A of the prism sheet 4 are Depending on the shape, large refraction can be caused.

From this fact, the liquid crystal display panel 1 can be configured to transmit light in the direction perpendicular to the entire area (at least the display surface), so that the brightness of the light can be made uniform. .

In this embodiment, the prism sheet 4 is used.
4A on both sides w except the central part W in the x direction
Are the same as each other, but are not limited to this, and may have a shape that takes the configuration shown in FIG. 1 into consideration. That is, as the distance from the cold cathode ray tube 5B increases, the apex angle of the convex shape 4A decreases (in this case, the angle on the side farther from the central portion W with respect to the perpendicular from the apex angle of each convex stripe increases). The conditions are left unchanged)
You may do so.

Embodiment 4 FIG . FIG. 7 is a main part configuration diagram showing another embodiment of the liquid crystal display device according to the present invention and corresponds to FIG.

The structure different from that of FIG. 1 is that the prism sheet 4 shown in FIG. 6 is arranged inside out with the side in the x direction as the center.

Even in the case of such a configuration, as in the case shown in FIG. 6, the liquid crystal display panel 1 can be configured to transmit light to the entire area (at least the display surface) in the direction perpendicular to the liquid crystal display panel 1. The brightness of the light can be made uniform.

Also in this case, it is needless to say that the apex angle of the convex portion 4A may be increased with increasing distance from the cold cathode ray tube 5B, taking into consideration the configuration shown in FIG.

Example 5. Prism sheet 4 shown in FIG.
In the area of the main surface, the extending directions of the ridges 4A are different between the areas at the four corners and the areas other than the four corners, and the ridges 4A in the four corner areas are the ridges 4A.
While the direction perpendicular to the direction along the direction is formed so as to be directed to the other area side, the ridges 4A in the other area are formed.
Are formed parallel to the y direction.

The prism sheet 4 thus constructed
Means that the light emitted from the backlight unit 5 to the liquid crystal display panel 1 side acts particularly effectively in the four corners of the backlight unit 5 when the luminance is small, and the luminance deterioration of the four corners with respect to the central portion is deteriorated. Will be able to prevent.

In the prism sheet 4 on which the ridges 4A having such a pattern are formed, the ridges 4A may face the liquid crystal display panel 1 side or the backlight unit 5 side, but in this case, 1 and 5 respectively.
It goes without saying that the configuration shown in FIG.

Example 6. FIG. 9 is a cross-sectional view showing the configuration of the backlight unit 5, and in order to efficiently guide the light from the cold cathode ray tube 5B in the light guide 5A to the liquid crystal display panel 1 side, the liquid crystal display of the light guide 5A is displayed. A plurality of light-collecting dot-shaped spherical bodies 10 formed on the main surface on the side opposite to the panel 1 are formed, and each of these spherical bodies 10 has a configuration in which light is not scattered from the light guide plate. There is.

The spherical body 10 is formed in this manner for the reason described below. First, FIG. 10 shows paths of light emitted from the light guide plate 5A in the prism sheet 4. As is clear from this figure, in order to improve the directivity of the light emitted from the prism sheet 4, the scattering of the light emitted from the light guide plate 5A is suppressed,
In the figure, it is preferable to leave only the luminous flux of B ₂ and eliminate the luminous flux of B ₁ .

As described above, by improving the condensing property of light emitted from the light guide plate 5A (meaning light without light scattering), the prism sheet 4 corresponding to each region on the main surface of the light guide plate 5A is improved. The effect that the shape of the ridge 4A can be uniquely determined can be exerted.

Here, as the constitution of the plurality of dot-shaped spherical bodies 10 which are not light-scattered, (1) those formed by printing of ink and containing no light-scattering substance ( For example, an acrylic resin alone) is used. (2) It is made of the same material as the light guide plate 5A and is formed integrally with the light guide plate 5A. For example,
This is a case where they are simultaneously formed when the light guide plate 5A is formed by molding. (3) It may be formed by processing the surface of the light guide plate.

FIG. 11 is a graph showing the relationship between the concentration of the light scattering agent in the ink and the distribution of light emitted from the light guide plate in the backlight unit 5 to which the above (1) is applied. Here, the light guide plate emission light distribution indicates the inclination angle θ of the emission light in the y direction of the main surface of the light guide plate 5A, and the cold cathode ray tube 5B.
The rotation angle of the side is from 0 ° to 180 °. The characteristics shown by the solid line in the figure show the case where the ink containing no light scattering agent is applied, and it is found that the light converging property is considerably improved. The characteristic indicated by the alternate long and short dash line in the figure shows the case where the conventional ink is used, and the characteristic indicated by the dotted line shows the case where the ink containing a large amount of the light scattering agent is used.

When the backlight unit 5 having such a structure is used for the purpose of suppressing light scattering, the backlight unit 5 and the liquid crystal display panel 1 are used.
It goes without saying that it is preferable to adopt a configuration in which a so-called diffusion sheet is not interposed between the above and.

[0048]

As is apparent from the above description,
According to the liquid crystal display device of the present invention, the brightness of the light transmitted from the backlight unit can be made uniform on the display surface of the liquid crystal display panel.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a main part of an embodiment of a liquid crystal display device according to the present invention.

FIG. 2 is an overall perspective view showing an embodiment of a liquid crystal display device according to the present invention.

FIG. 3 is an explanatory diagram showing an effect of the liquid crystal display device according to the present invention.

FIG. 4 is an operation diagram in a conventional configuration for comparing the effects in the description of FIG.

FIG. 5 is a cross-sectional view of an essential part showing another embodiment of the liquid crystal display device according to the present invention.

FIG. 6 is a cross-sectional view of essential parts showing another embodiment of the liquid crystal display device according to the present invention.

FIG. 7 is a cross-sectional view of essential parts showing another embodiment of the liquid crystal display device according to the present invention.

FIG. 8 is a sectional view of a main part showing another embodiment of the liquid crystal display device according to the present invention.

FIG. 9 is a cross-sectional view of a principal part showing another embodiment of the liquid crystal display device according to the present invention.

FIG. 10 is an explanatory diagram showing the reason for adopting the configuration shown in FIG.

FIG. 11 is experimental data showing an effect of the configuration shown in FIG.

[Explanation of symbols]

4 ... Prism sheet, 4A ... ridge, 5 ... Backlight unit, 5A ... Light guide plate, 5B ... Cold cathode ray tube.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor ▲ Shin Naohiro Shino 3350 Hayano, Mobara-shi, Chiba Hitachi Electric Devices Co., Ltd.

Claims (11)

[Claims] 1. A liquid crystal display panel, and a backlight unit for transmitting light to a display surface of the liquid crystal display panel, the backlight unit including a light guide plate arranged to face the liquid crystal display panel. A light source is arranged along one end surface of the light guide plate extending in the x direction, and a prism sheet is interposed between the backlight unit and the liquid crystal display panel, and the prism sheet is transparent. In a liquid crystal display device having a structure in which prism-shaped projections parallel to the x-direction are arranged in parallel in the y-direction on one surface of the sheet, the prism sheet has the projections and a liquid crystal display panel. A liquid crystal display device, wherein the liquid crystal display device is formed on opposing surfaces, and the apex angle of the ridges is gradually reduced as the distance from the light source increases in the y direction. 2. A liquid crystal display panel, and a backlight unit for transmitting light to a display surface of the liquid crystal display panel, wherein the backlight unit is arranged to face the liquid crystal display panel. A light source is arranged along one end surface of the light guide plate extending in the x direction, and a prism sheet is interposed between the backlight unit and the liquid crystal display panel, and the prism sheet is transparent. In a liquid crystal display device having a structure in which prism-shaped projections parallel to the x-direction are arranged in parallel in the y-direction on one surface of the sheet, the projections of the prism sheet are a backlight unit. A liquid crystal display device, wherein the liquid crystal display device is formed on opposing surfaces, and the apex angle of the ridges is gradually increased with increasing distance from the light source in the y direction. 3. A liquid crystal display panel, and a backlight unit for transmitting light to a display surface of the liquid crystal display panel, wherein the backlight unit is arranged to face the liquid crystal display panel. A light source is arranged along one end surface of the light guide plate extending in the x direction, and a prism sheet is interposed between the backlight unit and the liquid crystal display panel, and the prism sheet is transparent. In a liquid crystal display device having a structure in which prism-shaped ridges parallel to the x-direction are arranged in parallel in the y-direction on one surface of the sheet, the prism sheet has a central portion in the y-direction and both of them. The shapes of the ridges on the sides are different, and the ridges at the center have a symmetrical shape with respect to the vertical line from the apex angle, while the ridges on both sides have the ridges. Pair with the perpendicular from the corner The liquid crystal display device characterized by the angle of the side moves away from the central portion is larger Te. 4. A liquid crystal display panel, and a backlight unit for transmitting light to a display surface of the liquid crystal display panel, the backlight unit being arranged to face the liquid crystal display panel. A light source is arranged along one end face of the light guide plate extending in the x direction, and a prism sheet is interposed between the backlight unit and the liquid crystal display panel. In a liquid crystal display device having a structure in which prism-shaped convex stripes are arranged in parallel on one surface, the prism sheet has four corner areas in which the extending directions of the convex stripes are the four corners of the transparent sheet. Different from other regions except for, the ridges of the four corner regions are formed so that the direction perpendicular to the direction along the ridges is directed to the other region side. other Convex Article of range, the liquid crystal display device characterized by being formed parallel to the y-direction. 5. The liquid crystal display device according to claim 4, wherein the ridges provided at the four corners of the prism sheet have the apex angles that gradually increase toward the other region side. 6. A liquid crystal display panel, and a backlight unit for transmitting light to a display surface of the liquid crystal display panel, wherein the backlight unit is arranged to face the liquid crystal display panel. A light source is arranged along one end surface of the light guide plate extending in the x direction, and a prism sheet is interposed between the backlight unit and the liquid crystal display panel, and the prism sheet is transparent. In a liquid crystal display device having a structure in which prism-shaped ridges parallel to the x direction are arranged in parallel in the y direction on one surface of the sheet, the light guide plate is a surface opposite to the liquid crystal display panel. The liquid crystal is characterized in that a plurality of dot-shaped spherical bodies for condensing light are formed in and each of these spherical bodies is configured not to scatter light from the light guide plate. Display devices. 7. The liquid crystal display device according to claim 6, wherein the plurality of dot-shaped spherical bodies are formed by printing ink, and the ink does not contain a light scattering substance. 8. The liquid crystal display device according to claim 6, wherein the plurality of dot-shaped spherical bodies are made of the same material as the light guide plate and are formed integrally with the light guide plate. 9. The liquid crystal display device according to claim 8, wherein the plurality of dot-shaped spherical bodies are formed at the same time when the light guide plate is formed by molding. 10. The liquid crystal display device according to claim 8, wherein the plurality of dot-shaped spherical bodies are formed by processing the surface of the light guide plate. 11. The liquid crystal display device according to claim 6, wherein a diffusion sheet is not provided between the backlight unit and the liquid crystal display panel. .