JP2001188483A - Light reflecting substrate and liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light reflecting substrate which is subjected to surface roughening by chemical etching and can emit most of incident light to the outside of a panel without total reflection thereof. SOLUTION: A resin film 23 having a maximum tilt angle ψ2 smaller than the maximum tilt angle ψ1 of a rough surface 21a of a glass substrate 21 by chemical etching is formed with a prescribed thickness on the rough surface. The resin film 23 is formed as the substrate rough surface to a light reflection film 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective or transflective liquid crystal display device of an internal diffuse reflection type, and more particularly to a light-reflective substrate.

[0002]

2. Description of the Related Art Since a reflection type liquid crystal display element requires a light source from external light, it does not require a backlight and therefore consumes less power and can be made thinner and lighter. However, the display becomes difficult to see in a dark place. To compensate for this, in the transflective type,
The light reflection film is made semi-transparent, and a backlight is used as an auxiliary light source.

[0003] In each of the models, in order to increase the viewing angle and to efficiently use the external light in many cases,
A light diffusion layer for imparting irregular reflection to the light reflection film is provided. The light reflection film and the light diffusion layer are preferably provided inside the panel in relation to the display resolution, and this method is called an internal diffuse reflection method.

As an example of the internal diffuse reflection method, conventionally, the surface of one glass substrate used for a liquid crystal display panel is chemically etched with a mixed solution of, for example, hydrofluoric acid / ammonium fluoride to form fine irregularities. Then, a light reflecting film of aluminum or the like is formed on the roughened surface.

[0005]

FIG. 4 shows a glass substrate roughened by chemical etching as described above as an electrode substrate (R plate) 51 on the back side, and a glass substrate with an electrode substrate (F plate) on the front side. 52) is a schematic enlarged cross-sectional view of a principal part of a reflective liquid crystal display panel obtained by laminating a) 52 according to a standard method.
The components such as the light reflection film, the transparent electrode, the alignment film, and the liquid crystal are not shown for convenience of drawing.

In this reflection type liquid crystal display panel, light from the outside enters the panel from the F plate 52 and is reflected by a light reflection film (not shown) formed on the rough surface (uneven surface) of the R plate 51. Out of the F plate 52.

FIG. 4 is perhaps exaggerated,
Since the irregularities due to the chemical etching on the R plate 51 side are almost bowl-shaped, the maximum inclination angle ψ1 at the edge thereof increases, and a part of the incident light is totally reflected. Note that the maximum tilt angle 、 1 is defined as the side opposite to the rough surface of the glass substrate (FIG. 4).
At the lower side).

Here, the refractive index of air is n1, the total refractive index of the liquid crystal display panel including the glass, the alignment film, the transparent electrode and the liquid crystal material is n2, and the incident angle of light to the F plate 52 from the outside is θ1, The refraction angle is θ2, F plate 5 from the reflection film
Assuming that the incident angle of the reflected light with respect to 2 is θ3 and the emission angle of the reflected light from the F plate 52 is θ4, the following relational expression holds. θ2; sin θ2 = (n1 / n2) × sin θ1 θ3 = θ2 + 2 × ψ1 θ4; sin θ4 = (n2 / n1) × sin θ3

From this relational expression, it is understood that the emission angle θ4 of the reflected light, which is a problem, largely depends on the maximum inclination angle ψ1 of the rough surface. Therefore, the maximum inclination angle of the rough surface ψ1
Is large, the emission angle θ4 of the reflected light from the rough surface becomes 90 ° or more, and as a result, part of the incident light does not exit to the outside but returns to the inside of the liquid crystal display panel. become.

In order to reduce the maximum inclination angle ψ1 of the rough surface, it is necessary to reduce the etching amount in the depth direction of the unevenness. However, as a practical matter, it is extremely difficult to control the depth by the etching amount. However, there is a problem that it is difficult to obtain the reflection characteristics.

[0011]

DISCLOSURE OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to make most of incident light into a panel while roughening the surface by chemical etching. It is an object of the present invention to provide a light-reflective substrate which can be emitted to the outside and makes effective use of external light.

Another object of the present invention is to provide a reflective or semi-transmissive liquid crystal display device having a bright display and good visibility by using such a light reflective substrate. .

In order to achieve the above object, the present invention relates to a glass substrate having one surface roughened by chemical etching and having a light reflecting film on the rough surface, wherein the liquid crystal is a reflective or semi-transmissive liquid crystal. In a light-reflective substrate used as one electrode substrate of a display element, a resin film having a maximum inclination angle ψ2 smaller than the maximum inclination angle ψ1 of the rough surface on a rough surface of the glass substrate formed by the chemical etching is provided. The light reflection film is formed on the resin film.

According to this configuration, since the rough surface has a bowl-like shape and the resin film is formed on the rough surface,
The depth of the concave portion becomes shallower. That is, the maximum inclination angle of the rough surface formed on the glass substrate surface by the chemical etching
Even if 1 is large, since the depth of the concave portion is reduced by the resin film formed thereafter, the maximum inclination angle {2} of the base rough surface of the light reflection film made of this resin film becomes the initial maximum inclination angle {2}.
It becomes smaller than 1.

According to the present invention, the unevenness of the rough surface is controlled by the resin film in this manner. The maximum inclination angle {2} of the resin film is preferably 5 to 20 °. This ground will be described with reference to FIG. 4 described above.

Assuming that, for example, the refractive index n1 of the air is n1 = 1.00, the refractive index n2 of the entire liquid crystal display panel is 1.50, and the incident angle θ1 of light on the F plate 52 from the outside is 30 °, The angle of refraction θ2 is 19.5 °. By calculating backward from this, the emission angle θ4 of the reflected light from the F plate 52 is 90
゜ is when the incident angle θ3 of the reflected light from the reflection film to the F plate 52 is 41.8 °. Therefore, when the maximum inclination angle of the rough surface is 11.5 ° or more, a part of the incident light is totally reflected at the interface of the F plate 52, and a loss occurs.

In the above example, the incident angle θ1 of the light with respect to the F plate 52 is 30 °. Under this condition, the total reflection of a part of the light occurs only when the maximum inclination angle of the rough surface is 11.1 °. In practice, the incident angle θ1 of the light to the F plate 52 can be sufficiently shallower than this, so that the maximum tilt angle ψ2 of the resin film is provided in the present invention with a margin. Is set to 20 °.

Incidentally, when the maximum inclination angle {2} of the base rough surface of the light reflection film made of the resin film is less than 5 °, the light emission angle is too small, and the directivity becomes too strong (light). Becomes less diffusible). Conversely, when the maximum inclination angle {2} exceeds 20 °, the amount of light that is totally reflected increases, which is not preferable in terms of light use efficiency.

As described above, even when the roughness of the rough surface of the glass substrate is controlled by the resin film, the RzD (ten-point average roughness) of the rough surface of the glass substrate is 0.3 to 5.0 μm. , S
m (pitch) is 10 to 50 μm, RzD / Sm is 3 to 1
0% and the thickness of the resin film is 0.3-5.
It is preferable that RzD / Sm is 2 to 6% at 0 μm.

Further, the liquid crystal display element of the present invention is characterized in that an electrode substrate having a transparent electrode formed on a light reflecting film of the light reflecting substrate obtained as described above via a smoothing layer is formed on one electrode substrate. According to this, a reflective or semi-transmissive liquid crystal display element having a bright display and good visibility can be obtained.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention includes both a reflection type and a transflective type, but an embodiment of a reflection type liquid crystal display device will be described with reference to the schematic sectional view of FIG.

The reflection type liquid crystal display element 1 includes a first electrode substrate 2 as an R plate and a second electrode substrate 3 as an F plate. A reflective substrate 20 is used. That is, the light reflective substrate 20 is based on a transparent glass plate 21 made of, for example, soda glass or borosilicate glass, and has an inner surface (an upper surface in FIG. 1) having a rough surface 21a having fine irregularities. I have. The back side of the transparent glass plate 21 is smooth.

The rough surface 21a is formed by chemical etching with a mixed solution of, for example, hydrofluoric acid / ammonium fluoride, and as shown in FIG.
D is 0.3 to 5.0 μm, average pitch Sm is 10 to 50
In μm, the RzD / Sm is preferably 3 to 10%. The maximum inclination angle {1} of the rough surface 21a having such a profile is 10 to 40 °. The reference plane having the maximum inclination angle ψ1 is a plane parallel to the back surface of the first electrode substrate 2.

According to the present invention, as shown in FIG. 3, the resin film 23 is formed on the rough surface 21a. In this embodiment, the resin film 23 is formed by applying an acrylic resin with a spinner or the like, and its preferable profile is that the film thickness is 0.3 to 5.0 μm and Rz
D / Sm is 2 to 6%. According to this profile, the maximum tilt angle {2} of the resin film 23 is 5 to 20 °.

A light reflecting film 24 made of a metal film is formed on the resin film 23 using the resin film 23 as a rough underlayer. In this embodiment, the light reflection film 24 is made of an aluminum film formed by a sputtering method. The thickness of the light reflection film 24 may be, for example, about 100 nm.

Referring to FIG. 1 again, a surface smoothing layer 25 formed by applying, for example, an acrylic resin by a spinner is formed on the light reflecting film 24. In the case of color display, a color filter layer may be provided on the light reflection film 24 by an electrodeposition method or the like, and a surface smoothing layer 25 may be formed thereon.

The first electrode substrate 2 has the surface smoothing layer 2
5 on which ITO (Indium Tin) is used as a transparent conductive film.
Oxide) is sputtered, and its display portion has a predetermined patterned I
A TO pattern 2a is formed.

In this embodiment, a terminal portion 31 for forming an extraction electrode is continuously provided on the second electrode substrate 3 side. The display portion and the terminal portion 31 of the second electrode substrate 3 are formed with an ITO pattern 3a as a display electrode and an extraction electrode. Although not shown, an alignment film is formed on each display electrode.

The first electrode substrate 2 and the second electrode substrate 3
These display portions are attached to each other via the peripheral seal material 4 with the display portions facing each other. In addition, an in-plane spacer (not shown) for keeping the cell gap constant between the respective display portions is arranged in advance, and a predetermined liquid crystal material 6 is sealed in the cell gap.

The peripheral sealing material 4 includes a transfer material 41 made of, for example, conductive beads, and the IT material on the first electrode substrate 2 side via the transfer material 41.
The O pattern 2a is connected to a lead electrode in the terminal portion 31 on the second electrode substrate 3 side. A retardation plate 7 and a polarizing plate 8 are attached to the display surface side of the second electrode substrate 3 respectively.

In order to make a transflective liquid crystal display device,
A plurality of micro holes (micro holes) are provided in the light reflecting film, or the light reflecting film is provided as a very thin film of, for example, about 35 nm so as to have a light semi-transmissive property, and is illustrated on the back side of the first electrode substrate 2. A backlight that does not need to be provided may be provided.

[0032]

Example 1 One surface of glass D263 manufactured by Schott was roughened by chemical etching using hydrofluoric acid, ammonium fluoride or the like. The uneven profile is
RzD was 2.0 μm, Sm was 20 μm (RzD / Sm ratio = 10%), and the maximum tilt angle {1} was 33 °. Next, an acrylic resin PC manufactured by Nippon Synthetic Rubber Co., Ltd.
-405 was applied with a spinner to a thickness of 0.8 μm and cured to form a resin film. The unevenness profile of this resin film was such that RzD was 1.3 μm and Sm was 24 μm.
(RzD / Sm ratio = 5.4%), and the maximum inclination angle {2} was 15 °. On this glass substrate, aluminum was formed in a thickness of 100 nm as a light reflection film, and an acrylic resin was formed in a thickness of 2 μm as an insulating film thereon. R, G, and B color filters were formed on the other glass substrate and smoothed with an acrylic resin. Then, an ITO film was formed on both glass substrates and patterned to form a transparent electrode, and then a reflection type color liquid crystal display element was manufactured according to a standard method.

Comparative Example 1 A reflective color liquid crystal display device was produced in the same manner as in Example 1 except that a resin film was not formed on the rough surface by chemical etching.

With respect to Example 1 and Comparative Example 1, the reflection characteristics of the substrate at 30 ° incident light were measured.
Comparative Example 1 had an extremely wide half-value width of about 50 °, whereas Example 1 had a half-value width of about 35 °. In the measurement of the integrated light amount of the reflected light, the comparative example 1 was about 90% of the example 1.
% Light. This is presumably because in Comparative Example 1, the maximum inclination angle of the rough surface was as large as 33 °, and part of the incident light was absorbed in the panel by total reflection.

[0035]

As described above, according to the present invention,
A resin film having a maximum tilt angle 化学 2 smaller than the maximum tilt angle ψ1 of the rough surface is formed with a predetermined thickness on the rough surface of the glass substrate by chemical etching, and this resin film is formed as a rough underlayer of the light reflection film. By doing so, it is possible to obtain a light-reflective substrate in which most of the incident light can be emitted to the outside of the panel while the surface is roughened by chemical etching, and the external light can be used effectively.

Further, according to the present invention, by using such a light-reflective substrate, a reflective or semi-transmissive liquid crystal display device having a bright display and good visibility can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an embodiment in which the present invention is applied to a reflective liquid crystal display device.

FIG. 2 is an enlarged cross-sectional view of a light-reflective substrate used in the above embodiment after a chemical etching process.

FIG. 3 is an enlarged sectional view showing a state in which a resin film is formed on the light-reflective substrate.

FIG. 4 is a partially enlarged sectional view schematically showing a liquid crystal display panel as a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reflective liquid crystal display element 2, 3 Electrode substrate 2a, 3a Transparent electrode 20 Light reflective substrate 21 Transparent glass substrate 21a Rough surface 23 Resin film 24 Light reflective film 25 Surface smoothing layer 4 Peripheral sealing material 6 Liquid crystal material 7 Phase difference Plate 8 Polarizing plate

Claims (4)

[Claims] 1. A glass substrate having one surface roughened by chemical etching and having a light reflecting film on the rough surface, which is used as one electrode substrate of a reflective or transflective liquid crystal display element. A resin film having a maximum inclination angle ψ2 smaller than the maximum inclination angle ψ1 of the rough surface with a predetermined thickness on the rough surface of the glass substrate formed by the chemical etching; A light-reflective substrate, wherein the light-reflective film is formed on the film. 2. The maximum inclination angle ψ2 of the resin film is 5 to 20.
2. The light-reflective substrate according to claim 1, wherein ゜. 3. RzD (DIN) of the rough surface of the glass substrate
Ten-point average roughness) 0.3 to 5.0 μm, Sm (pitch)
3 to 10 μm, RzD / Sm is 3 to 10%, and the thickness of the resin film is 0.3 to 5.0 μm, and RzD / Sm is 2 to 6%. Light reflective substrate. 4. An electrode substrate having a transparent electrode formed on a light reflecting film of a light reflecting substrate according to claim 1 via a smoothing layer as one electrode substrate. A liquid crystal display device characterized by the above-mentioned.