JP2000221483A - Substrate for reflection type liquid crystal display device and reflection type liquid crystal display device using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To widen the angle of a visual field independently of the position of a source of outside light when a display screen is observed and to reduce display defects such as a color mixture by laminating a flattening layer comprising a mixture of a high refractive index resin and a low refractive index resin on a scattering layer containing transparent particles dispersed in a resin different from the particles in refractive index. SOLUTION: A color filter 12, a scattering layer 13 and a flattening layer 14 are formed on a glass substrate 11 and a striped transparent substrate 15 is formed at parts corresponding to the pixels of the color filter 12. The color filter 12 consists of a red color filter 12R, a green color filter 12G and a blue color filter 12B. The scattering layer 13 is formed by dispersing transparent particles and spacer particles in a thermosetting acrylic resin whose refractive index is 1.58 and carrying out spin coating. The flattening layer 14 is formed on the scattering layer 13 by spin coating with a liquid resin prepared by mixing a thermosetting fluorine-containing acrylic resin whose refractive index is 1.44 and a thermosetting acrylic resin whose refractive index is 1.58 in a volume ratio of 2:1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD OF THE INVENTION

[0002] The present invention relates to a reflection type liquid crystal display device,
In particular, the present invention relates to a reflective liquid crystal display device substrate having no display defects and a wide viewing angle, and a reflective liquid crystal display device.

[0003]

2. Description of the Related Art Generally, a transmission type liquid crystal display device comprises a pair of substrates provided with a polarizing film and a transparent electrode, respectively, and a liquid crystal sealed between the pair of substrates. In a color liquid crystal display device that displays a color screen, a color filter is provided on one of the substrates. A backlight type or light guide type transmissive liquid crystal display device in which a light source is disposed on the back surface or side surface of a rear substrate located on the back side of the transmissive liquid crystal display device and light is incident from the rear substrate is widely used. Widespread.

A liquid crystal display device is expected to be applied to a portable display such as a mobile device utilizing the inherent feature of low power consumption. However, in a transmission type liquid crystal display device having such a built-in light source, such a liquid crystal display device is required. The power consumption of the light source is large, and it has a drawback as a portable display.
Therefore, without incorporating such a light source, external light such as indoor or outdoor is made incident from an observer-side substrate located on the observer side of the apparatus, and is reflected by, for example, a metal reflector provided on a rear substrate. A reflection type liquid crystal display device which performs a screen display using the reflected light has been studied.

As a rear substrate applied to such a reflection type liquid crystal display device, for example, as shown in FIG. 3, a TFT (32) is formed on a substrate (31), and an insulating film (33) is formed.
A metal reflection film (34) having a surface formed with irregularities for light scattering is laminated on a portion corresponding to each pixel on the
T and the metal reflection film are connected by a via hole (35) to drive the liquid crystal, or as shown in FIG.
4) is provided outside the glass substrate (41).

Generally, in this type of reflection type liquid crystal display device, when the metal reflection film (plate) reflects external light,
There is a problem that the viewing angle is limited by the position of the external light source. Further, in the rear substrate having the structure shown in FIG. 3, the formation of surface irregularities of the insulating layer for widening the viewing angle and the formation of via holes for establishing conduction with the metal reflection film are complicated, and the driving of the liquid crystal is complicated. There has been a problem that the use of the metal reflective film as an electrode is limited because the surface of the metal reflective film has large irregularities.

In the reflection type liquid crystal display device having the structure shown in FIG. 4, since the metal reflection plate is disposed on the back surface of the rear substrate, an optical path difference occurs due to the thickness of the substrate, and the light reflected by the metal reflection plate. May be transmitted through another pixel adjacent to the transmitted pixel when incident, and this may cause a display defect such as color mixing, or the incident light may be reflected on the surface of the transparent electrode (43) inside the liquid crystal. And the light is reflected by the metal reflector (44) to produce a double image.

In order to solve such a problem, the inventors of the present application have proposed a technique of disposing a light scattering layer on a viewer-side substrate in Japanese Patent Application Laid-Open No. 28055/1990. According to this technique, by forming a light scattering layer on the inner surface of a liquid crystal display device, the optical path difference is reduced, and the structure is suitable for high-definition pixel display. This light scattering layer is made of transparent resin,
It is a coating film in which transparent particles having a different refractive index from this resin are dispersed, and light scattering properties can be relatively easily secured.

However, in order to efficiently scatter light, the diameter of the particles needs to be 0.4 to 1.0 μm or more, and if transparent particles of such a size are used, The surface of the light-scattering layer formed as a coating film has a thickness of 0.
Unevenness of about 2 to 1.0 μm occurs, which hinders the alignment of the liquid crystal in contact with the electrode. Therefore,
After that, it was proposed to form a layer of a transparent resin having a different refractive index from the light scattering layer as a flattening layer. However, the improvement of the viewing angle and the improvement of display defects such as color mixing were insufficient.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a reflective liquid crystal display device substrate provided with a light scattering film. By using the substrate, the viewing angle when observing the display screen of the obtained reflection type liquid crystal display device is widened without being limited by the position of the external light source, and the display defects such as color mixing are reduced. It is an object of the present invention to provide a reflective liquid crystal display device substrate. It is another object of the present invention to provide a reflective liquid crystal display device using the reflective liquid crystal display device substrate.

[0011]

According to the present invention, there is provided a substrate for a reflection type liquid crystal display device provided with a light scattering film, wherein the light scattering film has a laminated structure of two or more layers of resins having different refractive indexes. , At least one layer is a scattering layer in which one or more transparent particles different from the refractive index of the resin are dispersed in the resin, and another layer is a mixture of a high refractive index resin and a low refractive index resin. A flattening layer having a light scattering effect due to a difference in refractive index between the two resins, and a structure in which a flattening layer is laminated on a scattering layer.

Further, the present invention provides the reflective liquid crystal display device substrate according to the above invention, wherein the high refractive index resin of the flattening layer has a refractive index of 1.50 or more, and the low refractive index resin has a refractive index of 1 or more. 48. A substrate for a reflection type liquid crystal display device, characterized by having a thickness of .48 or less.

The present invention also provides a reflective liquid crystal display substrate according to the present invention, wherein the transparent particles have an optically isotropic crystal structure or an amorphous structure. It is an apparatus substrate.

The present invention also provides a substrate for a reflective liquid crystal display device according to the present invention, wherein the material of the transparent particles is cerium oxide.

Further, the present invention is a reflective liquid crystal display device using the substrate for a reflective liquid crystal display device according to the above invention.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below. The layer formed by laminating the scattering layer as the flattening layer in the present invention is a mixture of a high-refractive-index resin and a low-refractive-index resin, and light due to a difference in the refractive index of each resin randomly dispersed therein. It is characterized by having a scattering effect. Further, this flattening layer fills the unevenness of the surface of the scattering layer, makes the surface of the laminated layer flat, and forms a transparent electrode and an alignment film provided on the flattening layer flat and finely. It is possible to do that. As a result, display unevenness and response unevenness of the reflective liquid crystal display device can be prevented.

Further, it is possible to further improve the flatness of the surface of the flattening layer by interposing another transparent resin layer between the flattening layer and the transparent electrode. Are for liquid crystal display devices that require a high degree of flatness on the surface before forming the transparent electrode (STN, TN, O
CB, ECB, BTN liquid crystal, ferroelectric liquid crystal, etc.).

When the substrate for a reflection type liquid crystal display device according to the present invention is used as an observer-side substrate, light rays incident from the observer-side substrate are scattered by a light-scattering film to form a light-reflecting film (plate) on a rear substrate. ), And the light-reflecting film (plate) on the back substrate
Are reflected again by the light scattering film and emitted from the observer side substrate. For this reason, it is possible to observe the display screen in all directions regardless of the incident angle of the incident light beam.

In general, the refractive index of the resin is in the range of 1.3 to 1.7, and if the resin is resistant to a reflection type liquid crystal display device, it is suitable as a material for the scattering film and the flattening film. Resin combinations can be selected. For example,
When a high-refractive-index resin is used for the scattering layer, the mixing ratio of the flattening layer, which is a mixture of the high-refractive-index resin and the low-refractive-index resin, increases the ratio of the low-refractive-index resin. When a low-refractive-index resin is used, the ratio of the high-refractive-index resin to the planarizing layer, which is a mixture of the high-refractive-index resin and the low-refractive-index resin, may be increased. It is also possible to use a mixture of a high-refractive-index resin and a low-refractive-index resin for the resin used as the material of the scattering layer in which the transparent particles are dispersed.

In the present invention, the high refractive index resin constituting the flattening layer has a refractive index of 1.50 or more, and
The low refractive index resin preferably has a refractive index of 1.48 or less. In such a state, the light scattering effect increases.

As the high refractive index resin, a resin having a high light transmittance and a small wavelength dispersion is preferable. Such materials include, for example, acrylic resin, epoxy resin,
A polyester resin, an acrylic ester resin, a fluorene-based acrylic resin, a polyimide resin, or a copolymer resin thereof can be used. Acrylic resins widely used as resins for color filters are suitable.

As the low refractive index resin, a tetrafluoroethylene-hexafluoropropylene copolymer (n
= 1.34) or a fluorine-based acrylic resin (n = 1.34-
Fluorinated resin represented by 1.45), MOF and PCF series of Tokyo Ohka Kogyo Co., Ltd. (n = 1.46 to 1.46).
An organic silicate resin represented by 48) or a resin having a silicon group, such as an organopolysilane resin or a polysiloxane resin, can be used.

Next, in a reflection type liquid crystal display device using a polarizing film, it is not preferable to use transparent particles which cause polarization disorder or depolarization as the transparent particles, since this causes a decrease in the contrast of the display screen. That is, in a reflective liquid crystal display device using a polarizing film, it is preferable that the transparent particles have an optically isotropic crystal structure or an amorphous structure.

As the isotropic material, there are an equiaxed (cubic) material and an amorphous material. A typical high-refractive-index and equiaxed crystal is cerium oxide among metal oxides. Titanium oxide, zirconium oxide, and the like can be used if they are granulated as an amorphous oxide. As an amorphous material, mixed oxide, silicon oxide, various kinds of glass powder, or the like can be used. Alternatively, transparent particles such as resin powder, fluoride, sulfide, and nitride represented by calcium fluoride may be used.

Cerium oxide is preferred as a transparent resin having a high refractive index and being optically isotropic and having an average particle diameter near the wavelength of light.

When a color filter is provided on the substrate for a reflective liquid crystal display device according to the present invention, color display of the reflective liquid crystal display device becomes possible. Further, the formation position of the color filter may be either the observer side substrate or the rear substrate.

[0027]

Embodiments of the present invention will be described below in detail. Embodiment 1 FIG. 1 is an explanatory view showing a cross section of a reflection type liquid crystal display device using a substrate for a reflection type liquid crystal display device according to the present invention. In FIG. 1, a reflective liquid crystal display device substrate (10) has a color filter (12), a scattering layer (13), and a flattening layer (14) formed on a glass substrate (11). The transparent electrode (15) in the form of a stripe is formed at a portion corresponding to the pixel of (1).

The color filter (12) includes a red color filter (12R) and a green color filter (12R).
G), a blue color filter (12B). The opposing substrate (19) is formed by forming a metal reflection film (17) for driving liquid crystal (16) and reflecting light on a glass substrate (18).

The red color filter (12R) is formed by applying a red photosensitive resin composed of a mixture of an acrylic transparent photosensitive resin and a red pigment, forming a film thereof, exposing and developing, and exposing a portion corresponding to a red pixel. A red color filter (12R) was formed by selectively leaving the film on the substrate. Next, a green color filter (12
G) and a blue color filter (12B) were formed.

The scattering layer (13) is composed of a thermosetting acrylic resin having a refractive index of 1.58 and transparent particles (cerium oxide: particle size 1).
μm) and spacer particles (silicon oxide: particle diameter 1 μm) were dispersed and formed into a film thickness of 1.5 μm by spin coating.
Further, a thermosetting fluorine-based acrylic resin (refractive index: 1.44) and a thermosetting acrylic resin (refractive index: 1.5
8) was mixed and applied at a 2: 1 volume ratio to form a flattening layer (14) by spin coating. At this time, the color filter (12), the scattering layer (13) and the flattening layer (1)
The film thickness of 4) was formed to be about 4 μm.

Next, an ITO thin film is uniformly formed on the glass substrate (11) provided with the color filter (12), the scattering layer (13) and the flattening layer (14) by sputtering.
A well-known photolithography process was performed using a positive resist to form a stripe-shaped transparent electrode (15), thereby producing a reflective liquid crystal display device substrate (10).

The metal reflective film (17) is cleaned by applying a glow discharge to the surface of the glass substrate (18) and then successively forming a transparent oxide thin film (10 nm thick) and a silver thin film (150 nm thick). Was formed, the resist was applied, exposed, developed, and then etched with a mixed acid of sulfuric acid, nitric acid, and acetic acid. Then, the reflective liquid crystal display device substrate (1)
0) and the back surface of the opposing substrate (19) were bonded to each other to produce a reflection type liquid crystal display device shown in FIG.

Separately from the production of the above-mentioned substrate for a reflection type liquid crystal display device, a scattering layer is formed on a glass substrate, and a flattening layer obtained by mixing a high refractive index resin and a low refractive index resin is laminated on the scattering layer. Then, a light scattering film was produced. The scattering performance of this light-scattering film was measured using a variable-angle luminance meter (GP-200: manufactured by Murakami Color Research Laboratory). Table 1 shows the measurement results.
By using a mixed system in which the high-refractive-index resin and the low-refractive-index resin are mixed for the flattening layer, the light scattering property is improved as compared with the case where a one-component flattening layer made of one kind of resin is used. ing.

[0034]

[Table 1]

<Embodiment 2> FIG. 2 is an explanatory view showing a cross section of a reflection type liquid crystal display device using a reflection type liquid crystal display device substrate as another example of the reflection type liquid crystal display substrate according to the present invention. is there. In FIG. 2, a reflective liquid crystal display device substrate (2
No. 0) forms a scattering layer (23), a flattening layer (24), and a color filter (22) on a glass substrate (21), and further forms a striped transparent layer on a portion of the color filter (22) corresponding to a pixel. An electrode (25) is formed.

The color filter (22) includes a red color filter (22R) and a green color filter (22).
G), and a blue color filter (22B). The opposing substrate (29) is formed by forming a metal reflection film (27) for driving a liquid crystal (26) and reflecting light on a glass substrate (28).

The scattering layer (23) is composed of a thermosetting acrylic resin having a refractive index of 1.58 and transparent particles (cerium oxide: particle diameter 1).
μm) and spacer particles (silicon oxide: particle diameter 1 μm) were dispersed and formed into a film thickness of 1.5 μm by spin coating.
Further, a thermosetting fluorine-based acrylic resin (refractive index: 1.44) and a thermosetting acrylic resin (refractive index: 1.5
8) in a 2: 1 volume ratio was applied by spin coating to form a flattened layer (24). At this time, the color filter (22), the scattering layer (23) and the flattening layer (2)
The film thickness of 4) was formed to be about 2.5 μm.

Next, on a glass substrate (21) provided with the scattering layer (23) and the flattening layer (24), a red photosensitive resin composed of a mixture of an acrylic transparent photosensitive resin and a red pigment is provided. Was applied to form a film, and the film was exposed and developed to selectively leave the film at a portion corresponding to a red pixel, thereby forming a red color filter (22R). Next, a green color filter (22
G) and a blue color filter (22B) were formed.

Next, an ITO thin film is uniformly formed on the glass substrate (21) provided with the scattering layer (23), the flattening layer (24) and the color filter (22) by a sputtering method. A well-known photolithography process was performed using the resist to form a stripe-shaped transparent electrode (25), thereby producing a reflective liquid crystal display device substrate (20).

The metal reflection film (27) is cleaned by applying a glow discharge to the surface of the glass substrate (28), and then sequentially forming a transparent oxide thin film (10 nm thick) and a silver-based thin film (150 nm thick). Was formed, the resist was applied, exposed, developed, and then etched with a mixed acid of sulfuric acid, nitric acid, and acetic acid. Then, the reflective liquid crystal display substrate (2)
0) and the back surface of the opposing substrate (29) were attached to each other to produce a reflective liquid crystal display device shown in FIG.

[0041]

According to the present invention, there is provided a substrate for a reflection type liquid crystal display device provided with a light scattering film, wherein the light scattering film has a laminated structure of two or more layers of resins having a difference in refractive index.
The layer is a scattering layer in which one or more kinds of transparent particles different from the refractive index of the resin are dispersed in the resin, and the other one layer is
It is a mixture of a high-refractive-index resin and a low-refractive-index resin, and is a flattening layer having a light scattering effect due to a difference in refractive index between the two resins. For a reflective liquid crystal display device having a structure in which a flattening layer is laminated on a scattering layer. Since the substrate is a substrate, by using this substrate for a reflective liquid crystal display device in a reflective liquid crystal display device, the viewing angle when observing the display screen of the reflective liquid crystal display device is limited by the position of the external light source. Thus, the substrate for a reflective liquid crystal display device becomes wider without any display defects such as color mixture.

Further, according to the present invention, in the above-mentioned substrate for a reflective liquid crystal display device, the high refractive index resin of the flattening layer has a refractive index of 1.50 or more, and the low refractive index resin has a refractive index of 1.48.
Therefore, the substrate for a reflective liquid crystal display device having a large light scattering effect is obtained. In addition, the present invention provides a reflective liquid crystal display device, wherein the transparent particles have an optically isotropic crystal structure or an amorphous structure in the substrate for a reflective liquid crystal display device, so that the contrast of a display screen is not reduced. Substrate. In addition, according to the present invention, since the material of the transparent particles is cerium oxide in the above reflective liquid crystal display device substrate, the reflective liquid crystal display device substrate does not cause a decrease in the contrast of the display screen.

Further, since the present invention is a reflection type liquid crystal display device using the above-mentioned substrate for a reflection type liquid crystal display device, the viewing angle when observing the display screen of the reflection type liquid crystal display device is reduced by the external light source. Wide without being limited by the position of
A reflective liquid crystal display device in which display defects such as color mixing are reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a cross section of a reflective liquid crystal display device using a substrate for a reflective liquid crystal display device according to the present invention.

FIG. 2 is an explanatory view showing a cross section of a reflective liquid crystal display device using a substrate of another example of a substrate for a reflective liquid crystal display device according to the present invention.

FIG. 3 is an explanatory diagram of a rear substrate applied to a reflective liquid crystal display device in a conventional method.

FIG. 4 is an explanatory diagram of a metal reflection plate applied to a reflection type liquid crystal display device in a conventional method.

[Explanation of symbols]

10, 20 ... substrate for reflective liquid crystal display device according to the present invention 11, 21, 18, 28, 41 ... glass substrate 12, 22 ... color filter 12R, 22R ... red color filter 12G, 22G ... green color filter 12B, 22B ... blue color filter 13, 23 ... scattering layer 14, 24 ... flattening layer 15, 25, 43 ... transparent electrode 16, 26 ... liquid crystal 17 , 27, 34: Metal reflective film 19, 29: Counter substrate 31: Substrate 32: TFT 33: Insulating film 35: Via hole 44: Metal reflective plate

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H091 FA02Y FA14Y FA31Y FB02 FB08 FB13 FC01 FD04 FD06 GA02 GA07 HA06 KA01 LA15 LA17 LA19

Claims (5)

[Claims] 1. A reflection type liquid crystal display device substrate provided with a light scattering film, wherein the light scattering film has a laminated structure of two or more layers of a resin having a difference in refractive index, and at least one layer is made of the resin. A scattering layer in which one or more kinds of transparent particles different from the refractive index of the resin are dispersed, and another layer is a mixture of a high refractive index resin and a low refractive index resin, and is formed by a refractive index difference between the two resins. A substrate for a reflection type liquid crystal display device, which is a flattening layer having a light scattering effect, wherein the flattening layer is laminated on the scattering layer. 2. The high refractive index resin of the flattening layer has a refractive index of 1.50 or more, and the low refractive index resin has a refractive index of 1.48.
2. The substrate for a reflective liquid crystal display device according to claim 1, wherein: 3. The substrate for a reflective liquid crystal display device according to claim 1, wherein the transparent particles have an optically isotropic crystal structure or an amorphous structure. 4. The substrate for a reflective liquid crystal display device according to claim 1, wherein the material of the transparent particles is cerium oxide. 5. A reflection type liquid crystal display device using the substrate for a reflection type liquid crystal display device according to claim 1.