JP2001133776A - Reflection type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection type liquid crystal display device improved in luminance and high in performance in which the light from a front light is efficiently made to enter a liquid crystal display panel. SOLUTION: In the reflection type liquid crystal display device 15, a front light 16 is disposed on a reflection type liquid crystal display panel 8. Moreover, a light source chip 33 is disposed near the corner of a light guide plate 32, and grooves 34 in a curved state are formed around the light source chip on the outer face of the light guide plate 32.

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.

Such a reflection type liquid crystal display device is shown in FIGS.
This will be described with reference to FIG. 18 is a perspective view of the front light 1, FIG. 19 is a schematic cross-sectional view of the reflection type liquid crystal display device 2 provided with the front light 1, and FIG. 20 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 including LEDs and the like provided on both ends of the light guide rod 4
It is composed of 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.

Further, a plurality of grooves 6 are formed on the peripheral surface of the light guide rod 4 along the longitudinal direction thereof, and further, the outer surface of the light guide plate 3, that is, the side opposite to the surface on which the reflective liquid crystal display panel is provided. A plurality of grooves 7 are also provided on the surface of the light guide rod 4 along the longitudinal direction of the light guide rod 4.

The front light 1 having such a configuration is shown in FIG.
As shown in FIG. 9, 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 configuration, as shown in FIG. 20, the light emitted from the two light source chips 5 enters and propagates from both end surfaces 4a of the light guide rod 4.
The light is reflected by the light-reflective member and further by the groove 6, and then enters the inside of the light guide plate 3 through one end surface 3a. 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. And
Light incident on the reflective liquid crystal display panel 8 is reflected by the reflective 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. 22 shows a front light 11 disclosed in the same publication, in which a plurality of point 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, according to the reflection type liquid crystal display device 2, there is a problem that the light emitted from the light source chip 5 cannot be used effectively because the light guide rod 4 is used.

This point will be described with reference to FIG. 21 which is a schematic longitudinal sectional view of the light guide rod 4. The light source chip 5 disposed on both end surfaces 4 a of the light guide rod 4 emits light from the light guide rod 4 in the longitudinal direction. In the direction, that is, the end faces 4a which are respectively opposed to each other
As a result, there is a problem that light is not sufficiently reflected by the groove 6, some light passes through the end face 4a, and light emitted from the light source chip 5 is not effectively used. In addition, the use of the light guide rod 4 results in an increase in size correspondingly, which further increases the cost.

The front light 11 proposed in Japanese Patent Application Laid-Open No. 10-188636 has a problem that uniform brightness cannot be obtained over the entire display area. This problem will be described with reference to FIGS. 23 and 24. . FIG. 23 is a plan view of the front light 11, and FIG.

First, as shown in FIG. 23, by arranging a plurality of point light sources 13 on the end face of the light guide plate 12, sufficient light is supplied between adjacent point light sources 13 in the light guide plate 12. A portion A where light was not emitted occurred, and thus uniform brightness was not obtained in the entire display area.

Further, as shown in FIG. 24, the light guide plate 12 has a structure in which many protrusions 14 are arranged on one side, so that a part of the light B is incident on 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.

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. It is an object of the present invention to provide a reflection type liquid crystal display device in which the light emitted from the light source chip is effectively used to increase the brightness without using a light guide rod, and the size is reduced.

Still another object of the present invention is to emit light uniformly and sufficiently to the light guide plate so that uniform luminance can be obtained over the entire display area, and high-performance reflection with increased luminance. To provide a liquid crystal display device.

[0019]

The reflection type liquid crystal display device of the present invention comprises a reflection type liquid crystal display panel having a front light comprising a rectangular light guide plate and a light source chip for making light incident on an end face of the light guide plate. And a light source chip is disposed near a corner of the light guide plate, and a substantially curved groove is formed on an outer surface of the light guide plate with the light source chip as a center.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The reflection type liquid crystal display device of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic sectional view of the liquid crystal display device 15, and FIG.
FIG. 3 is a perspective view of the front light 16, FIG. 4 is a plan view of the front light 16, and FIG. 5 is an enlarged view of a region S in FIG. 6 to 17 show front lights 16.
It is an expanded sectional view which shows the structure of the groove of FIG.

The structure of the liquid crystal display device 15 will be described with reference to FIGS.
As shown in FIG. 1, a front light 16 shown in FIG. 3 is disposed on a reflective liquid crystal display panel 8.

First, the configuration of the reflection type liquid crystal display panel 8 will be described. As the reflection type liquid crystal display panel 8, conventionally known reflection type panels having various configurations 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-type reflection plate and a scattering layer formed on the inner surface of a substrate.

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

A glass substrate 17 is covered with a light reflection layer 18 (corresponding to the reference numeral 9 in FIG. 19) made of aluminum metal, chromium metal, or the like, and a color filter 19 is formed on the light reflection layer 18 to form a color filter. The filter 19 is coated with an overcoat layer 20 made of an acrylic resin or the like, and the transparent electrode 2 made of ITO or the like is formed on the overcoat layer 20.
A plurality of 1s are arranged in a belt shape, and further covered with an alignment film 22 made of a polyimide resin rubbed in a certain direction. Also,
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, 23 are opposed to each other via a liquid crystal 26 (corresponding to a reference numeral 10 in FIG. 19) made of a chiral nematic liquid crystal twisted at an angle of, for example, 200 to 260 °. 26 is the sealing member 2
The area surrounded by 7 is filled.

Further, 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 polarizing plate 31 are sequentially formed on the outer surface of the glass substrate 23.

The light-scattering film 28 is, for example, a light-scattering film of IDS (Internal Diffusing Sheet) manufactured by Dai Nippon Printing Co., Ltd., in which beads are contained in resin. 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 16 is provided on the reflective liquid crystal panel 8 having the above-described structure. As shown in FIG. 3, the front light 16 has a light source chip 33 disposed near a corner of a rectangular light guide plate 32, and a substantially curved groove 34 on the outer surface of the light guide plate 32 around the light source chip 33. Is formed.

The light emitted from the light source chip 33 enters the inside of the light guide plate 32, and is further reflected by the groove 34.
The light is emitted from the front light 16 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, and the light scattering film 28.
The light passes through the transparent electrode 24, the alignment film 25, the liquid crystal 26, the alignment film 22, and the transparent electrode 2.
1. The light reaches the overcoat layer 20 and the color filter 19, is reflected by the light reflecting layer 18, the reflected light passes in the reverse order, and is further emitted through the front light 16. 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 and dark state.

[0033] The front light 16 and then the front light 16, will be described in more detail. A light source chip which is a point light source such as a light emitting diode (LED) or a miniature light bulb near a corner of a rectangular light guide plate 32 made of a transparent resin material such as an acrylic resin or a polycarbonate resin or a transparent inorganic material such as a glass. A groove 34 is formed on the outer surface of the light guide plate 32 with the light source chip 33 as a center.

This point will be described with reference to FIGS. FIG. 4 is a plan view of the front light 16, and FIG. 5 is an enlarged view of a region S in FIG.

When two light source chips 33 are arranged near the corners of the light guide plate 32, the grooves 34 are formed in a substantially curved shape on the outer surface of the light guide plate 32 around the respective light source chips 33. By forming a plurality of rows of curved grooves 34 corresponding to the chips 33 and similarly forming a plurality of rows of curved grooves 34 corresponding to the other light source chips 33, each light source chip 3
The light that has entered the light guide plate 32 from the third 3 is most effectively
4, the light can be efficiently emitted from the light guide plate 32 toward the reflective liquid crystal panel 8.

Preferably, as shown in FIG.
The light source chip 33 is formed by forming a line whose normal C is substantially perpendicular to the groove 34 with the light emitting portion 3 as a center.
The light further entering the light guide plate 32 is reflected to the maximum by the groove 34, whereby the reflection type liquid crystal panel 8 is reflected by the light guide plate 32.
Light can be emitted to the maximum.

Next, the structure of the groove 34 will be described with reference to FIGS. The groove 34 has a substantially triangular cross section, and the depth d is represented by the distance from the inverted triangular top as shown in FIG.

It is desirable that the depth d be in the range of 1 to 70 μm. FIG. 7 shows the state of reflection at the groove 34 under these preferable conditions. That is, light entering the light guide plate 32 from the light source chip 33 is reflected by one surface of the groove 34,
The emitted light is directed toward the reflective liquid crystal panel 8 from the front light 16.

However, when the depth d is less than 1 μm, the amount of light reflected by one surface of the groove 34 is reduced as shown in FIG. 8, so that the amount of light emitted from the front light 16 is reduced. Further, when the depth d exceeds 70 μm, the presence of the groove is easily recognized because the groove becomes large as shown in FIG. 9, so that the visibility of the front light 16 is reduced.

The pitch P of the grooves 34 is, as shown in FIG. 10, the interval between the adjacent grooves 34, and the pitch P is preferably set to 0.05 to 0.7 mm. If so, the light that has entered the light guide plate 32 from the light source chip 33 is most effectively reflected on one surface of each groove 34, and becomes appropriate outgoing light from the front light 16 toward the reflective liquid crystal panel 8.

However, this pitch P is 0.05 m
If it is less than m, the number of the grooves 34 increases, so that the display surface of the front light 16 generally becomes white, thereby lowering the contrast. In addition, when it exceeds 0.7 mm, the groove 34 is easily recognized visually.

Further, regarding the angle of the groove 34, FIG.
This will be described with reference to FIGS.

When the groove 34 has a triangular cross section of ABC as shown in FIG. 11, A is an end near the light source chip 33, and B is an end farthest from the light source chip 33. It is. C is the top of a triangular cross section. Β is an angle defined by A and C, and γ is an angle defined by B and C.

The angle β is preferably 35 to 55 °. This point will be described with reference to FIGS. 12 and 13 when the angle β is 35 °, and FIGS. 14 and 15 when the angle β is 55 °.

First, when the angle β is 35 °, as shown in FIG. 12, the incident light that reaches the groove 34 is reflected at 70 ° with respect to the incident direction, and is emitted. The direction is two directions from the front light 16 toward the reflection type liquid crystal panel 8, that is, the vertical emission direction shown in FIG.
The light is emitted with a deviation of about 0 °.

When the angle β is 55 °, FIG.
As shown in (2), the incident light reaching the groove 34 is reflected at 110 ° with respect to the incident direction, and the light is emitted. The light emitting direction is the direction to be directed from the front light 16 to the reflective liquid crystal panel 8, That is, light is emitted with a deviation of about 20 ° from the vertical emission direction shown in FIG.

By setting the deviation of about 20 ° as an allowable range, the angle β is preferably 35 to 55 °.

The angle γ does not directly affect the light emission. However, when the angle is reduced, the groove becomes large, and the groove is easily recognized.
° or more.

However, when the angle γ is increased, there is a problem in manufacturing. This will be described with reference to FIGS.

To form the groove 34 in the light guide plate 32, a molding technique using a mold is used, but a mold having a projection corresponding to the groove 34 as shown in FIG. The light guide plate 32 having the groove 34 having the required shape is obtained by the contact. However, when the angle γ is increased to around 90 °, the projection of the mold becomes acute as shown in FIG. 17, so that a groove corresponding to the projection shape is not formed. Therefore, the angle γ is preferably set in the range of 45 to 90 °.

Thus, according to the liquid crystal display device 15 of the present invention, when arranging the front light 16 on the reflective liquid crystal panel 8, the front light 16 is positioned near the corner of the rectangular light guide plate 32. And the groove 34 is formed in a substantially curved shape on the outer surface of the light guide plate 32 with the light source chip 33 as a center, so that light entering the light guide plate 32 from the light source chip 33 can be most effectively used. , Whereby the light can be efficiently emitted from the light guide plate 32 toward the reflective liquid crystal panel 8, and as a result, a high-performance reflective liquid crystal display device 15 with increased luminance is obtained.

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. For example, in the liquid crystal display device 15, the light source chips 33 are arranged at two corners of the rectangular light guide plate 3, respectively, but instead at one corner, or at three or four corners. The light source chips 33 may be arranged for the corners in the above.

[0053]

As described above, according to the reflection type liquid crystal display device of the present invention, the reflection type liquid crystal display panel includes the rectangular light guide plate and the light source chip for making the light incident on the end face of the light guide plate. A front light is arranged, and a light source chip is further arranged near a corner of the light guide plate, and a groove is formed in a substantially curved shape on the outer surface of the light guide plate with the light source chip as a center, so that the light guide plate is more separated from the light source chip. The light that has entered inside is most effectively reflected by the groove, thereby emitting light evenly and sufficiently to the light guide plate, so that uniform brightness can be obtained over the entire display area. Light can be more efficiently emitted toward the reflective liquid crystal display panel, and the high-performance brightness with increased brightness is 1.5 to 1.5 times that of the conventional product.
A high-performance reflective liquid crystal display device about twice as high can be provided.

Further, in the present invention, as compared with the conventional front light as shown in FIG. 18, no light guide rod is used, so that the light emitted from the light source chip is effectively used to increase the brightness and reduce the size. The reflection type liquid crystal display device which achieved the above was provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a liquid crystal display device of the present invention.

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

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

FIG. 4 is a plan view of a front light used in the liquid crystal display device of the present invention.

FIG. 5 is an enlarged view of a region S in FIG. 4;

FIG. 6 is an enlarged sectional view showing a groove of a front light.

FIG. 7 is an enlarged sectional view showing a groove of a front light.

FIG. 8 is an enlarged sectional view showing a groove of the front light.

FIG. 9 is an enlarged sectional view showing a groove of the front light.

FIG. 10 is an enlarged sectional view showing a groove of a front light.

FIG. 11 is an enlarged sectional view showing a groove of a front light.

FIG. 12 is an enlarged sectional view showing one surface of a groove of a front light.

FIG. 13 is an enlarged sectional view showing one surface of a groove of the front light.

FIG. 14 is an enlarged sectional view showing one surface of a groove of the front light.

FIG. 15 is an enlarged sectional view showing one surface of a groove of the front light.

FIG. 16 is an enlarged sectional view showing a groove of the front light.

FIG. 17 is an enlarged sectional view showing a groove of the front light.

FIG. 18 is a perspective view of a conventional front light.

FIG. 19 is a schematic sectional view of a conventional reflective liquid crystal display device.

FIG. 20 is a plan view showing an optical path of a conventional front light.

FIG. 21 is a schematic sectional view of a light source section of a conventional front light.

FIG. 22 is a perspective view of another conventional front light.

FIG. 23 is a plan view of another conventional front light.

FIG. 24 is an enlarged sectional view of a main part of another conventional front light.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 11, 16 Front light 2, 15 Liquid crystal display device 3 Light guide plate 5 Light source chip 6 Groove 8 Reflection type liquid crystal display panel 13 Point light source 32 Light guide plate 33 Light source chip 34 Groove

Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court II (Reference) // F21Y 101: 02 G02F 1/1335 530

Claims (1)

[Claims] 1. A reflection type liquid crystal display device comprising a reflection type liquid crystal display panel and a front light comprising a rectangular light guide plate and a light source chip for making light incident on an end face of the light guide plate. A reflection type liquid crystal display device, wherein a light source chip is arranged near a corner, and a groove is formed in a substantially curved shape on the outer surface of the light guide plate around the light source chip.