JP2001147430A - Reflective liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection type liquid crystal display device having enhanced brightness and high performance by making light incident on a liquid crystal panel efficiently from a front light. SOLUTION: The reflection type liquid crystal display device 16 has the front light 15 disposed on the reflection type liquid crystal display panel 8. The front light 15 is constituted of a light guide plate 3, a light guide rod 4A provided on one end surface 3a of the light guide plate 3, light source chips 5a provided on both ends of the light guide rod 4A and light reflecting members 32 disposed on the rear surfaces of the light source chips 5a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a reflection type liquid crystal display device provided with a front light.

[0002]

2. Description of the Related Art In recent years, personal computers, word processors, televisions, digital cameras, video cameras,
Liquid crystal display devices are used in fish finder, portable positioning system (GPS), etc.
Low power consumption and applicability outdoors are required. Correspondingly, a demand for a reflection type liquid crystal display device is increasing.

However, the reflection type liquid crystal display has a problem that the display screen cannot be recognized in an environment where there is almost no external light at night or the like.

In order to solve this problem, a front light is arranged on a display screen of a reflective liquid crystal panel, light from the front light is made incident on the reflective liquid crystal panel, and the reflected light is passed through the front light. Image recognition technology has been proposed.

[0005] Such a reflective liquid crystal display device will be described with reference to FIGS. 9 is a perspective view of the front light 1, FIG. 10 is a schematic cross-sectional view of the reflection type liquid crystal display device 2 provided with the front light 1, and FIG. 11 is a plan view showing an optical path of the front light 1.

The front light 1 includes a rectangular light guide plate 3,
A light guide rod 4 provided on one end surface 3a of the light guide plate 3 and a light source chip 5 composed of an LED or the like encapsulated in a resin. Such light source chips 5 are provided at both ends of the light guide rod 4. ing. In addition, a light reflecting member (not shown) is coated on the peripheral surface of the light guide rod 4 except for the surface facing the one end surface 3a of the light guide plate 3, so that light entering the light guide rod 4 is reflected. Then, it is configured to enter one end face 3 a of the light guide plate 3.

In addition, the outer longitudinal surface 4a of the light guide rod 4
A plurality of grooves 6 are formed along the longitudinal direction of the light guide plate 3, and also on the outer surface of the light guide plate 3, that is, on the surface opposite to the surface on which the reflection type liquid crystal display panel is provided. A plurality of grooves 7 are provided in a straight line.

The front light 1 having such a configuration is shown in FIG.
As shown at 0, it is arranged on the reflective liquid crystal display panel 8. In the reflection type liquid crystal display panel 8, 9 is a reflection film, and 10 is a liquid crystal.

According to the reflection type liquid crystal display device 2 having the above structure, as shown in FIG. 11, light emitted from the two light source chips 5 enters and propagates from both end surfaces 4 a of the light guide rod 4.
The light is reflected by the light reflecting member and further by the groove 6, and the light is incident on the one end surface 3 a of the light guide plate 3 almost uniformly over the entire surface thereof, and is incident on the inside of the light guide plate 3. Then, the light is incident on the reflection type liquid crystal display panel 8 while being reflected by the groove 7 of the light guide plate 3. The light incident on the reflection type liquid crystal display panel 8 is reflected by the reflection film 9 through the liquid crystal 10, and the reflected light passes through the liquid crystal 10 again, and is recognized as image information through the front light 1.

On the other hand, in addition to the reflection type liquid crystal display device 2, other front lights have been proposed. That is, there has been proposed a configuration in which a light guide plate having a plurality of dot-like light diffusion shapes is used on the surface of a front light, and a point light source is disposed on the end face thereof (see Japanese Patent Application Laid-Open No. H10-188636).

FIG. 13 shows a front light 11 disclosed in the publication, in which a plurality of point-like light sources 13 are arranged on an end face of a light guide plate 12, and many projections 14 are arranged on one side of the light guide plate 12. There, the light emitted from the point light source 13 enters from the end face of the light guide plate 12, repeats total reflection in the light guide plate 12, and emits only from the side surface among the bottom surface and the side surface forming the projection 14, whereby Light emission from the lower surface of the front light 11 is increased.

[0012]

However, the front light 11 proposed in Japanese Patent Application Laid-Open No. Hei 10-188636 has a problem that uniform brightness cannot be obtained over the entire display area. FIG. FIG. 14 is a plan view of the front light 11, and FIG. 15 is a sectional view of a main part of the front light 11.

First, as shown in FIG. 14, by arranging a plurality of point light sources 13 on the end face of the light guide plate 12, a sufficient amount of light is provided between adjacent point light sources 13 in the light guide plate 12. A portion A where light was not emitted occurred, so that uniform brightness could not be obtained in the entire display area even when compared with the reflective liquid crystal display device 2 including the front light 1 including the light guide rod 4.

Further, as shown in FIG. 15, the light guide plate 12 has a structure in which many protrusions 14 are arranged on one surface, so that a part of the light B enters the inside of the protrusions 14 of the light guide plate 12. The light is reflected at 14 and leaks to the upper surface of the front light 11 (the display surface of the reflective liquid crystal display device 2), whereby the light emission from the lower surface of the front light 11 becomes insufficient, and as a result, the brightness is reduced. There are also issues.

On the other hand, according to the reflection type liquid crystal display device 2, since the light guide rods 4 are used, light can be almost uniformly incident on one end surface 3a of the light guide plate 3 over the entire surface thereof. However, on the other hand, there is a problem that the light emitted from the light source chip 5 is not effectively used.

This point will be described with reference to FIG. 12 which is a schematic longitudinal sectional view of the light guide rod 4. The light source chips 5 arranged on both end surfaces 4a of the light guide rod 4 are sealed in a mold R made of transparent resin. The light emitted from the light source chip 5 passes through the mold body R, further passes through the end face 4a, and enters the inside of the light guide rod 4, but a part of the light leaks from the mold body R and the light guide rod 4 and enters the light guide rod 4. There is a problem that the light is not sufficiently incident, and the light emitted from the light source chip 5 is not effectively used.

Accordingly, in view of the above description, the present invention has been completed by solving all the problems of both the front light 1 and the front light 11 of the reflection type liquid crystal display device 2 as described above. An object of the present invention is to provide a reflection type liquid crystal display device in which the luminance of the light guide rod is increased by effectively utilizing the light emitted from the light source chip while taking advantage of the light guide rod.

[0018]

According to the reflection type liquid crystal display device of the present invention, a front light constituted by a rectangular light guide plate is disposed on a reflection type liquid crystal display panel, and a front light is provided along an end face of the light guide plate. And a light guide rod having a light source chip disposed at an end thereof, and a light reflecting member provided on a back surface of the light source chip.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a reflection type liquid crystal display device of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view of the front light 15, FIG. 2 is a schematic sectional view of a reflection type liquid crystal display device 16 provided with the front light 15, and FIG. 3 is a plan view showing an optical path of the front light 15. FIG. 4 is a schematic sectional view showing the vicinity of the light source chip of the front light 15, and FIG. 5 is a schematic sectional view showing the configuration of the reflective liquid crystal display panel 8 forming the liquid crystal display device 16. 6 to 8 are schematic sectional views of the vicinity of a light source chip of another front light according to the present invention.
The same parts as those in the reflection type liquid crystal display device 2 shown in FIGS. 9 to 11 are denoted by the same reference numerals.

The structure of the liquid crystal display device 16 will be described with reference to FIGS. As shown in FIG. 2, the reflective liquid crystal display panel 8
The front light 16 shown in FIG. 1 is disposed on the LCD. First, the configuration of the reflective liquid crystal display panel 8 will be described.

As the reflection type liquid crystal display panel 8, various types of conventionally known reflection type panels can be used.

In the reflection type liquid crystal panel 8, it is necessary to emit light at a wide scattering angle with respect to incident light from all angles in order to obtain a bright display without using a backlight. In addition to providing a mirror-like reflector on the inner surface, there is a so-called function-separated type in which a scattering film is further provided on the front surface of the device. There are a reflection-type liquid crystal display structure of the present invention, which includes a reflection-type liquid crystal display structure in which a reflection layer is formed, or a reflection-reflection type in which a mirror-surface reflection plate and a scattering layer are formed on the inner surface of the substrate.

Therefore, the reflection type liquid crystal panel 8 of the function separation type is used.
The description will be made with reference to the reflection type structure of the color liquid crystal display of FIG.

On a glass substrate 17, a light reflecting layer 18 (reference numeral 9 in FIG.
, A color filter 19 is formed on the light reflection layer 18, an overcoat layer 20 made of an acrylic resin or the like is coated on the color filter 19, and an overcoat layer 20 made of ITO or the like is formed on the overcoat layer 20. Transparent electrode 21
Are arranged in a strip shape, and further covered with an alignment film 22 made of a polyimide resin rubbed in a certain direction. Further, a plurality of transparent electrodes 24 made of ITO or the like are arranged in a strip shape on a glass substrate 23, and further covered with an alignment film 25 made of a polyimide resin rubbed in a certain direction.

The color filter 19 is of a pigment dispersion type,
That is, a photosensitive resist prepared in advance with a pigment (red, green, blue, or the like) is applied on a substrate and formed by photolithography. A chromium metal or a black matrix of a photosensitive resist may be formed between the color filters 19.

With respect to the light reflecting layer 18, instead of a single layer of aluminum metal or chromium metal, a low refractive index layer made of, for example, SiO ₂ , AlF ₃ , CaF ₂ , MgF _2, etc. For example, TiO ₂ , Zr
A laminated structure with a high refractive index layer made of O ₂ , SnO ₂ or the like may be provided. Further, a low refractive index layer, a high refractive index layer, a low refractive index layer, and a high refractive index layer are formed on the metal layer. . . Thus, a stacked structure of four layers, six layers, eight layers or more may be used.

The two substrates 17 and 23 are opposed to each other via a liquid crystal 26 (corresponding to 10 in FIG. 2) made of a chiral nematic liquid crystal twisted at an angle of, for example, 200 to 260 °. 26 is a sealing member 27
Is filled in the area surrounded by.

Further, on the outer surface of the glass substrate 23, a light-scattering film 28, a first retardation film 29 made of polycarbonate or the like, a second retardation film 30 made of polycarbonate or the like, and an iodine-based polarizing plate 31 are sequentially formed.

The light-scattering film 28 is, for example, a light-scattering film of IDS (Internal Diffusing Sheet) manufactured by Dai Nippon Printing Co., Ltd., and is made of resin containing beads and the like. In addition, light scattering irregularities may be provided on the surface of the flat plate. By providing the light scattering film 28 between the glass substrate 23 and the first retardation film 29, the light reflected by the light reflecting layer 18 is scattered by the light scattering film 28 in directions other than the regular reflection direction. As a result, the viewing angle of the image display increases, and the recognition area of the image display increases.

A front light 15 is provided on the reflective liquid crystal panel 8 having the above-described structure. The front light 15 includes a rectangular light guide plate 3, a light guide rod 4A provided on one end surface 3a of the light guide plate 3, and a point light source such as a light emitting diode (LED) or a miniature light bulb provided at both ends of the light guide rod 4A. It is composed of a light source chip 5a as a light source and a light reflecting member 32 arranged on the back of the light source chip 5a. Light source chip 5a and light reflecting member 3
Reference numeral 2 is enclosed in a mold body R made of a transparent resin. In addition, such a light source chip 5a is provided with a light guide rod 4A.
May be provided only at one end.

Light guide plate 3, light guide rod 4A, and molded body R
Is formed of a transparent resin material such as acrylic resin and polycarbonate resin, and a transparent inorganic material such as glass.

Also, the outer longitudinal surface 4b of the light guide rod 4A
A plurality of grooves 6 are formed along the longitudinal direction of the light guide plate 3, and also on the outer surface of the light guide plate 3, that is, on the surface opposite to the surface on which the reflective liquid crystal panel 8 is disposed, in the longitudinal direction of the light guide rod 4 </ b> A. A plurality of grooves 7 are provided in a straight line.

The light reflecting member 32 has a structure in which a plate made of metal such as aluminum or chrome is bent, and the light source chip 5a is disposed inside the bent portion. Then, among the irradiation light of the light source chip 5a, the light emitted to the back surface is reflected by the light reflecting member 32. By appropriately adjusting such a bending angle, it is possible to provide directivity to the reflected light. it can. Thus, most of the reflected light can be made to enter the inside of the light guide rod 4A. Although the light reflecting member 32 has a structure in which a metal plate is bent, the light reflecting member 32 may have a conical shape or a bowl shape instead.

According to the reflection type liquid crystal display device 16 having the above structure, as shown in FIG. 2, the light emitted from the two light source chips 5 enters and propagates from both end surfaces 4a of the light guide rod 4A.
The light is reflected by the groove 6 and one end face 3a of the light guide plate 3
Through to the inside. Then, the light is reflected by the groove 7 of the light guide plate 3, and thereby the front light 15
The light is further emitted toward the reflective liquid crystal panel 8, and the emitted light is transmitted to the polarizing plate 31, the second retardation film 30, the first retardation film 29, the light scattering film 28, and the glass substrate 2.
3, and the passing light is transmitted through the transparent electrode 24, the alignment film 25,
The light reaches the liquid crystal 26, the alignment film 22, the transparent electrode 21, the overcoat layer 20, and the color filter 19, is reflected by the light reflection layer 18, the reflected light passes in the reverse order, and further passes through the front light 15. Is emitted.
At this time, when a voltage is applied between the transparent electrodes 21 and 24,
The molecular arrangement of the liquid crystal 26 is changed by ON / OFF by the application of the voltage, thereby controlling the passing light to generate a bright / dark state.

Thus, the reflection type liquid crystal display device 16 of the present invention.
Since the light reflecting member 32 is disposed on the back of the light source chip 5a provided at both ends of the light guide rod 4A, the light emitted from the light source chip 5a effectively enters the light guide rod 4A, The light has increased.

It should be noted that the present invention is not limited to the liquid crystal display device as in the above embodiment, and various changes and improvements can be made without departing from the scope of the present invention. FIGS. 6 to 8 show other examples as (1) to (3).
This will be described below.

(1) In FIG. 6, a portion of the mold body R that comes into contact with the light guide rod 4A is formed into a convex lens 33. The directivity of the light emitted from the light source chip 5a is further improved by the convex lens 33, and the light is effectively incident inside the light guide rod 4A.

(2) In FIG. 7, the same function and effect can be obtained by coating the periphery of the mold body R with a metal film 34 of aluminum, chromium, silver or the like as a light reflecting member.

(3) FIG. 8 shows a light guide rod 4B obtained by integrally molding a mold body R and a light guide rod 4A, thereby forming a light guide rod 4 and an end face 4a like the light guide rod 4A. As a result, light reflection on the end face 4a does not occur, and as a result, the light emitted from the light source chip 5a further effectively enters the light guide rod 4B.

[0040]

As described above, according to the reflection type liquid crystal display device of the present invention, a front light is provided on the reflection type liquid crystal display panel, and the front light is provided along the end surface of the rectangular light guide plate. The light guide rod with the light source chip arranged at the end is provided, and the light reflecting member is provided on the back of the light source chip, so that the most light emitted from the light source chip enters the light guide rod. As a result, the light emitted from the front light is increased, and as a result, a high-performance reflective liquid crystal display device with increased luminance can be provided.

According to the present invention, Japanese Patent Application Laid-Open No. 10-18 / 1998
Compared with the front light proposed in No. 8636, uniform luminance was obtained over the entire display area, thereby providing a highly reliable and high-quality reflective liquid crystal display device with increased luminance.

[Brief description of the drawings]

FIG. 1 is a perspective view of a front light used for a liquid crystal display device of the present invention.

FIG. 2 is a schematic sectional view of the liquid crystal display device of the present invention.

FIG. 3 is a plan view of a front light used in the liquid crystal display device of the present invention.

FIG. 4 is a schematic sectional view showing the vicinity of a light source chip of a front light used in the liquid crystal display device of the present invention.

FIG. 5 is a schematic sectional view of a reflection type liquid crystal display panel of the liquid crystal display device of the present invention.

FIG. 6 is a schematic sectional view showing the vicinity of a light source chip of another front light used in the liquid crystal display device of the present invention.

FIG. 7 is a schematic sectional view showing the vicinity of a light source chip of another front light used in the liquid crystal display device of the present invention.

FIG. 8 is a schematic sectional view showing the vicinity of a light source chip of another front light used in the liquid crystal display device of the present invention.

FIG. 9 is a perspective view of a front light used in a conventional liquid crystal display device.

FIG. 10 is a schematic sectional view of a conventional liquid crystal display device.

FIG. 11 is a plan view of a front light used in a conventional liquid crystal display device.

FIG. 12 is a schematic sectional view showing the vicinity of a light source chip of a front light used in a conventional liquid crystal display device.

FIG. 13 is a perspective view of a conventional front light.

FIG. 14 is a plan view of a conventional front light.

FIG. 15 is an enlarged sectional view of a main part of a conventional front light.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 11, 15 Front light 2, 16 Reflection type liquid crystal display device 3 Light guide plate 4, 4A, 4B Light guide rod 5, 5a Light source chip 8 Reflection type liquid crystal display panel 9 Reflection film 10 Liquid crystal R mold body 32 Light reflection member 33 Convex lens

Claims (1)

[Claims] 1. A reflection type liquid crystal display device comprising a reflection type liquid crystal display panel and a front light constituted by a rectangular light guide plate disposed on the reflection type liquid crystal display panel, wherein a light source is provided at an end along an end surface of the light guide plate. A reflection type liquid crystal display device comprising: a light guide rod on which a chip is provided; and a light reflection member provided on a back surface of the light source chip.