JP2001183663A - Reflection type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection type liquid crystal display device having small thickness and hardly causing interference fringes. SOLUTION: In the reflection type liquid crystal display device 13, a front light 12 composed of a light guide plate 3 is abutted and arranged on a reflection type liquid crystal display panel 8, and an antireflection plate 16 having >=0.1 μm arithmetic mean roughness Ra is provided on the abutting face 15 of the light guide plate 3.

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 device 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 reflection type liquid crystal display device will be described with reference to FIGS. FIG. 7 is a perspective view of the front light 1,
FIG. 8 is a schematic sectional view of the reflection type liquid crystal display device 2 provided with the front light 1, and FIG. 9 is a plan view showing an optical path of the front light 1.

The front light 1 includes a rectangular light guide plate 3,
The light guide plate 3 includes a light guide rod 4 provided on one end face 3a of the light guide plate 3 and a light source chip 5 made of an LED or the like encapsulated in a resin. I have. The light guide plate 3 is provided on the peripheral surface of the light guide rod 4.
A light-reflective member (not shown) other than the surface facing the one end surface 3a
So that light entering the light guide rod 4 is reflected and enters the one end surface 3a 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.

FIG. 8 shows a front light 1 having such a structure.
Is disposed on the reflective liquid crystal display panel 8 as shown in FIG. 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. 9, the light emitted from the two light source chips 5 enters and propagates from both end surfaces 4a of the light guide rod 4, and the light reflection occurs. At the conductive member, and further reflected by the groove 6,
Then, light is incident on the one end surface 3a of the light guide plate 3 almost uniformly over the entire surface, 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.

In the reflection type liquid crystal display device 2 having such an optical path, a film-like light reflection prevention plate 11 is usually attached to the surface of the light guide plate 3 facing the reflection type liquid crystal display panel 8. When the light reflected by the groove 7 of the light guide plate 3 is emitted from the light guide plate 3 toward the reflective liquid crystal display panel 8, the light is reflected upward at the interface between the light guide plate 3 and the air layer. The glare of the light guide plate 3 is prevented.

Further, the light guide plate 3 is liable to be warped due to a change in temperature or the like.
A gap of about 1.0 mm is provided. As a result, the light guide plate 3 comes into contact with the reflective liquid crystal display panel 8 due to warpage,
Interference fringes are prevented from being generated due to a slight gap change at the contact portion.

[0012]

However, in the above-mentioned reflection type liquid crystal display device 2, a gap of about 0.5 to 1.0 mm is provided between the light reflection preventing plate 11 and the reflection type liquid crystal display panel 8. As a result, the thickness of the entire apparatus has increased correspondingly, and it has not been possible to meet the market needs for thinning in recent years.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a high-performance reflective liquid crystal display device which prevents interference fringes, achieves a reduction in thickness, and is adapted to market needs.

[0014]

According to the reflection type liquid crystal display device of the present invention, a front light constituted by a light guide plate having a light source disposed on an end face is arranged in contact with a reflection type liquid crystal display panel. Arithmetic average roughness Ra 0.1μ on the contact surface of the light guide plate
m or more.

According to another reflection type liquid crystal display device of the present invention, a front light constituted by a light guide plate having a light source disposed on an end face is arranged on a reflection type liquid crystal display panel, and the reflection type liquid crystal display device is provided. Arithmetic average roughness Ra0.1 on the contact surface of the panel
A polarizing plate having a thickness of at least μm is provided.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a reflection type liquid crystal display device of the present invention will be described with reference to FIGS. Figure 1 shows the front light 1
2, FIG. 2 is a schematic sectional view of a reflection type liquid crystal display device 13 provided with a front light 12, FIG. 3 is a plan view showing an optical path of the front light 12, and FIG.
FIG. FIG. 5 is an enlarged sectional view of a reflective liquid crystal display panel, and FIG. 6 is a schematic sectional view of another reflective liquid crystal display device 14 of the present invention. In addition, FIG.
The same parts as those of the reflection type liquid crystal display device 2 shown in FIG.

The structure of the liquid crystal display device 13 will be described with reference to FIGS. As shown in FIG. 2, the reflective liquid crystal display panel 8
The front light 12 shown in FIG. An anti-reflection plate 16 having an arithmetic average roughness Ra of 0.1 μm or more is provided on the contact surface 15 of the light guide plate 3 of the front light 12.

The anti-reflection plate 16 is made of triacetyl cellulose (TAC) or polyethylene terephthalate (PE).
T) and the like, and a resin containing a filler having a particle size of several μm is applied to the surface thereof to form irregularities having an arithmetic average roughness Ra of 0.1 μm or more. Further, an antireflection film is coated on the surface, and an adhesive layer for bonding to the light guide plate 3 is formed on the back surface of the film.

Next, the configuration of the reflection type liquid crystal display panel 8 will be described with reference to FIG. As the reflection type liquid crystal display panel 8, conventionally known reflection type panels having various configurations can be used.

In addition, in order to obtain a bright display without using a backlight, it is necessary for the reflective liquid crystal panel 8 to emit light at a wide scattering angle with respect to incident light from all angles. 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 reflection 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 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.

As for 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, SiO2, AlF3, CaF2, MgF2, etc., and TiO2, ZrO2,
A laminated structure with a high refractive index layer made of SnO2 or SnO2 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. . . And so on 4
It may have a stacked structure of layers, six layers, eight layers or more.

The two substrates 17 and 23 are opposed to each other via a liquid crystal 26 (corresponding to reference numeral 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., 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 12 is provided on the reflective liquid crystal panel 8 having the above-described structure. The front light 12 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.

Further, 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 13 having the above-described structure, as shown in FIG. 2, the light emitted from the two light source chips 5a enters and propagates from both end faces 4a of the light guide rod 4A, and is transmitted through the grooves 6. The light is then reflected, and enters the inside of the light guide plate 3 through the one end face 3a. Then, the light is reflected by the groove 7 of the light guide plate 3, whereby the reflection type liquid crystal panel 8 is transmitted from the front light 12 through the light reflection preventing plate 16.
And the emitted light passes through the polarizing plate 31, the second retardation film 30, the first retardation film 29, the light-scattering film 28, and the glass substrate 23, and the transmitted light passes through the transparent electrode 24, Alignment film 25, liquid crystal 26, alignment film 22,
The light reaches 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 is further emitted from the front light 12 through the light reflection preventing plate 16. Is done. 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.

Thus, the reflection type liquid crystal display device 13 of the present invention
When the front light 12 is disposed so as to be in contact with the reflective liquid crystal display panel 8, the arithmetic mean roughness Ra is applied to the contact surface 15 of the light guide plate 3 of the front light 12.
By providing the anti-reflection plate 16 having a thickness of 0.1 μm or more, in such a contact state, the distance between the both is maintained in the air layer having a substantially constant thickness, and even if the light guide plate 3 is warped,
Interference fringes due to subtle gap changes are no longer generated.

Further, by bringing the front light 12 into contact with the reflective liquid crystal display panel 8, a reduction in thickness meeting the needs of the market has been achieved.

Further, according to the reflection type liquid crystal display device 13 of the present invention, the light source chips 5a provided at both ends of the light guide rod 4A are provided.
The light reflecting member 32 on the back surface of the light source chip 5
The emitted light of “a” effectively entered the light guide rod 4A, and the emitted light of the front light 12 increased.

Incidentally, according to an experiment conducted by the present inventor, the surface treatment of the anti-reflection plate 16 was performed with the arithmetic average roughness Ra.
At 0.1 μm, 0.5 μm, 1.0 μm, 2.0 μm
The evaluation was carried out using five types of apparatuses which were changed to m and 5.0 μm, and no interference fringes were generated even after long-term use.

However, a reflection type liquid crystal display device having the same structure as the reflection type liquid crystal display device 13 except that the surface treatment of the light reflection preventing plate 16 was made 0.07 μm in arithmetic average roughness Ra, and the other components were manufactured. However, interference fringes occurred due to long-term use.

Next, another reflection type liquid crystal display device 1 of the present invention.
4 will be described with reference to the schematic sectional view of FIG. Also in this liquid crystal display device 14, the conventional front light 1 shown in FIG. 7 is disposed on the reflective liquid crystal display panel 8 as shown in FIG. Instead of the polarizing plate 31, the contact surface 15 has an arithmetic average roughness Ra of 0.1.
A polarizing plate 33 surface-treated so as to have a thickness of not less than μm is provided.

The polarizing plate 33 is a resin film made of triacetyl cellulose (TAC), polyethylene terephthalate (PET), or the like.
By applying a resin containing m filler, irregularities having an arithmetic average roughness Ra of 0.1 μm or more are formed.

Thus, the reflection type liquid crystal display device 1 having the above-described structure is provided.
As for No. 4, the front light 1 was disposed on the reflective liquid crystal display panel 8 so as to be in contact therewith, whereby the front light 1 was reduced in thickness, and the surface treatment was performed so that the arithmetic average roughness Ra became 0.1 μm or more. By arranging the polarizing plate 33 on the reflective liquid crystal display panel 8, in such a contact state, the distance between the two is maintained in the air layer having a substantially constant thickness, and even if the light guide plate 3 is warped. As a result, interference fringes due to subtle gap changes did not occur.

According to an experiment conducted by the present inventor, the surface treatment of the polarizing plate 33 was performed with an arithmetic mean roughness Ra of 0.2 μm.
m, 0.6 μm, 1.0 μm, 2.1 μm, 5.5 μm
When the evaluation was performed using five types of apparatuses changed as described above, no interference fringes were generated even when all of them were used for a long time.

When the surface treatment of the polarizing plate 33 was made to be 0.08 μm in arithmetic average roughness Ra, and a reflection type liquid crystal display device having the same structure as that of the reflection type liquid crystal display device 14 was produced. Interference fringes occurred due to long-term use.

It should be noted that the present invention is not limited to the liquid crystal display device as in the above-described embodiment, and various changes and improvements can be made without departing from the scope of the present invention. For example, the reflection type liquid crystal display panel 8 is ST
Although the description has been made with the N-type simple matrix type color liquid crystal display panel, the monochrome STN type simple matrix type liquid crystal display panel may also be used.
Alternatively, a similar effect can be obtained with a twisted nematic liquid crystal display panel such as a TN type simple matrix type liquid crystal display panel or a TN type active matrix type liquid crystal display panel.

[0044]

As described above, according to the reflective liquid crystal display device of the present invention, when the front light is placed in contact with the reflective liquid crystal display panel, the arithmetic mean roughness Ra0 is applied to the contact surface of the light guide plate. With the provision of the anti-reflection plate of 1 μm or more, in such a contact state, the distance between the both is maintained in the air layer having a substantially constant thickness, and even if the light guide plate is warped, a delicate gap is formed. Interference fringes due to the change are not generated, and as a result, a reflective liquid crystal display device having excellent long-term reliability can be provided.

According to another reflection type liquid crystal display device of the present invention, when a front light is placed on the reflection type liquid crystal display panel, the arithmetic mean roughness is applied to the contact surface of the reflection type liquid crystal display panel. Even when a polarizing plate having a Ra of 0.1 μm or more was provided, similarly, interference fringes caused by a slight gap change did not occur, and as a result, a reflective liquid crystal display device excellent in long-term reliability could be provided.

[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 of a main part of another liquid crystal display device of the present invention.

FIG. 7 is a perspective view of a front light used in a conventional liquid crystal display device.

FIG. 8 is a schematic sectional view of a conventional liquid crystal display device.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 12 Front light 2, 13, 14 Reflective liquid crystal display device 3 Light guide plate 4 Light guide rod 5 Light source chip 8 Reflective liquid crystal display panel 9 Reflective film 10 Liquid crystal 15 Contact surface 16 Light reflection preventing plate 33 Polarizing plate

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H091 FA02Y FA11X FA16Z FA23X FA35Y FA37X FA41X FA45X FB02 FB08 FB12 FC12 FC26 FD14 GA06 GA13 GA16 HA07 HA10 KA03 LA11 LA21 2K009 AA12 BB24 BB28

Claims (2)

[Claims] 1. A reflection type liquid crystal display device comprising a reflection type liquid crystal display panel and a front light constituted by a light guide plate having a light source disposed on an end face in contact with the reflection type liquid crystal display panel. A reflection type liquid crystal display device comprising a light reflection preventing plate having an average roughness Ra of 0.1 μm or more. 2. A reflection type liquid crystal display device comprising a reflection type liquid crystal display panel and a front light constituted by a light guide plate having a light source disposed on an end face in contact with the reflection type liquid crystal display panel. A reflective liquid crystal display device, comprising: a polarizing plate having an arithmetic mean roughness Ra of 0.1 μm or more on a surface.