JP2000147536A - Reflecting electrode and its manufacture, and reflection type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the direction and range of reflected light and to emit reflected light which has no regularly reflected component and has many scattered and reflected components by adopting an interference pattern which is formed with scattered light of light having coherence, as an irregular pattern. SOLUTION: A transmission type diffusion plate 11 like frosted glass is lit with illumination light 15 having coherence like laser light. Diffusion light 16 diffused by the diffusion plate 11 reaches a photosensitive material 14 like a photoresist dry plate. The illumination light 15 has coherence, so a speckle pattern which is a diffraction pattern is formed on the photosensitive material 14 with the diffused light 16. This speckle pattern can be recorded by developing the photosensitive material 14. When the diffusion plate 11 is made larger vertically than horizontally, the speckle pattern becomes thinner vertically than horizontally. Thus, the diffusion plate 11 is properly sized to control the spatial frequency distribution of the pattern on the photosensitive material 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention does not require a special light source such as a backlight or an edge light, and uses ambient light as incident light, and reflects the reflected light to perform display by reflecting the light. The present invention relates to a reflective electrode mounted thereon and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, liquid crystals have been applied to various fields, and the range of application has exploded. Among them,
The number of devices driven by a battery, such as a clock and a portable terminal, has increased, and improvement in the image quality of these displays has become an issue.

At present, high-quality liquid crystals are often realized by incorporating a light source such as a backlight. However, power consumption is large, and short driving time has been a problem due to the ability of a battery.

On the other hand, in a reflection type liquid crystal display device which does not require a special light source, power consumption can be saved and driving time can be extended because ambient light is used. Can not expect.

[0005] The above-mentioned reflection type liquid crystal display device generally has a structure in which a reflection layer is arranged on the back surface (the side opposite to the viewer) of a liquid crystal panel (including electrodes on both sides of the liquid crystal layer). As the reflective layer, proposals have been made to adopt a metal plate having a roughened surface or a hologram in recent years.

On the other hand, proposals have been made on a reflection type liquid crystal display device in which the lower electrode (the side opposite to the observer) among the electrodes on both sides of the liquid crystal layer is used as a reflection layer. Hereinafter, the above-mentioned electrodes will be referred to as “reflection electrodes”. As the above proposals, Japanese Patent Application Laid-Open Nos. 8-201802 and 9-152
No. 597 is exemplified.

Japanese Patent Application Laid-Open No. Hei 8-201802 proposes that a liquid crystal layer, a transparent electrode, a color filter, and a transparent substrate are stacked in this order on a mirror reflector which also serves as an electrode for driving a liquid crystal. The display device has a configuration in which a polarizer and a scattering plate having little forward scattering characteristics and strong forward scattering characteristics (display light is scattered when emitted from the device to the observer side) are superposed in this order.

With the above configuration, an apparatus having high contrast and free from problems of visual dependency and double image is provided. In the above proposal, the advantage of using a specular reflector as the reflective electrode is that it is sufficient to dispose the polarizer on only one side of the liquid crystal layer (the problem of double image is eliminated). The emission range and direction of the display light are controlled by a scattering plate having strong forward scattering characteristics.

[0009] In a display device employing a reflective electrode, it is an important point how efficiently the display light is emitted to the observer after the ambient light is reflected by the electrode.

In the proposal according to Japanese Patent Application Laid-Open No. 9-152597, when a reflective electrode is used, an attempt is made to increase the aperture ratio of the electrode to increase the amount of reflected light, thereby realizing high-quality (high-brightness) display. It has been done.

In the description of the manufacturing of the display device disclosed in the above publication, in forming the openings of the electrodes, holes having different diameters (for example, 5 μm and 3 μm) are randomly arranged with a distance of 2 μm or more between the holes. Using a photomask having an opening pattern formed by etching, the organic insulating layer on the reflective electrode is etched to form irregularities on the surface of the reflective electrode, thereby controlling the scattering of reflected light.

According to the above method, since circular holes of different sizes are arranged so as not to be in contact with each other, a gap which becomes a mirror surface is generated in a portion corresponding to between the holes in the manufactured reflective electrode. And the component of the scattered reflected light is reduced. That is, the ratio of the regular reflection component to the scattering component is high, which means that the efficiency of light used for observation is not high.

In the above-mentioned reflector, the incident light without anisotropy is emitted as reflected light having substantially the same scattering properties in the horizontal and vertical directions. However, depending on the use environment of the display device, an appropriate observation region is different, and in order to efficiently input ambient light as display light to the observer's eyes,
According to the use environment of the display device, the reflected light of the reflective electrode is controlled anisotropically (the direction and range of the reflected light is controlled),
It is desirable to optimize the direction of the reflected light.

[0014]

SUMMARY OF THE INVENTION The present invention relates to a reflective electrode having a surface having irregularities, wherein the direction and range of reflected light can be controlled, and further, there is no specular reflection component. It is a main object to provide a reflective electrode that emits reflected light having a large (or almost small) scattered reflection component.

[0015]

According to the present invention, in order to form a reflective electrode having a reflection characteristic having a desirable anisotropy, scattered light of coherent light is used as a concave / convex pattern formed on the reflective electrode. By adopting the interference pattern, the anisotropy for controlling the scattering direction and range of the reflected light and the improvement of the scattering efficiency are realized.

That is, in the reflective electrode of the present invention, in a reflector (reflective electrode) also serving as an electrode for driving liquid crystal, at least one light having coherence is provided on the surface facing the liquid crystal layer. And a concavo-convex pattern which is an interference pattern due to scattered light from the light source.

The irregularities are preferably a pattern on which speckles are recorded.

If fine irregularities are distributed on the reflection surface of the reflection electrode, the incident light causes microscopic reflection and diffraction at the reflection surface, thereby causing scattering and generating scattered reflected light.

It is known that the finer the unevenness is, the wider the spread of the scattered light is, and the rougher the unevenness is, the narrower the spread of the scattered light is.

Here, the angle of scattering is calculated by focusing on the diffraction on the uneven surface. When the concavo-convex pattern is formed with a certain degree of periodicity, the components of the spatial frequency of the concavo-convex in both the X and Y directions are fx and fy, the wavelength of light incident on the reflective electrode is λ, and the light is scattered by the reflective surface of the electrode. X, Y of light
The divergent angles in each direction are ± θx and ± θy.

At this time, these parameters have the following relationship. sin (θx) = λ · fx sin (θy) = λ · fy

From the above, when the scattering width in the X direction is changed from -θx to + θx, the spatial frequency component in the X direction of the unevenness of the reflecting surface may be changed from 0 to sin (θx) / λ. Similarly, when the scattering width in the X direction is from -θy to + θy, the spatial frequency component in the Y direction of the unevenness of the reflecting surface is from 0 to si.
n (θy) / λ.

In order to control the distribution of scattered light,
By controlling the intensity ratio of the spatial frequency component according to the angle, scattered light having an arbitrary intensity distribution can be obtained.

[0024]

Next, a description will be given of an embodiment relating to a method for producing a concave-convex pattern on a reflection surface which gives anisotropy to scattered reflected light. In the following description, “scattering” and “diffusion” are used as synonyms.

FIG. 1 is a structural view showing an optical system for producing a concave / convex pattern on a reflecting surface. FIG. 1A is a diagram of the optical system viewed from above, and FIG. 1B is a diagram of the optical system viewed from the side.

Transmission type diffusion plate 11 such as ground glass
Is illuminated with illumination light 15 having coherence such as laser light. The diffused light 16 diffused by the diffusion plate 11 reaches a photosensitive material 14 such as a photoresist dry plate.

Since the illumination light 15 has coherence, a speckle pattern which is a diffraction pattern by the diffused light 16 is generated on the photosensitive material 14. By developing the photosensitive material 14, this speckle pattern can be recorded.

By the way, the average diameter of the speckle pattern is determined in inverse proportion to the angle at which the diffusion plate 11 is viewed from the photosensitive material 14. This is described in the Optical Measurement Handbook, Asakura Shoten, Toshiharu Tada et al., Published November 25, 1994, pp.267-268.

Therefore, as shown in FIG. 1, when the size of the diffusion plate 11 is made larger in the vertical direction than in the horizontal direction,
The speckle pattern recorded on the photosensitive material 14 is finer in the vertical direction than in the horizontal direction.

By appropriately setting the size of the diffusion plate 11 in this way, it becomes possible to control the spatial frequency distribution of the pattern on the photosensitive material 14. For example,
In FIG. 1, the distance between the photosensitive material 14 and the diffusion plate 11 is 2
When the length of the diffusion plate in the vertical direction is 10 cm and the length of the diffusion plate in the horizontal direction is 3 cm, the speckle pattern recorded on the photosensitive material is as shown in FIG.

A reflector in which the above-mentioned speckle pattern is formed as unevenness of the reflection surface is arranged as shown in FIG. FIG. 2 (a) shows the state of reflection from above, and FIG. 2 (b) shows the view from the side.

When the illumination light 65 is incident on the reflector 61, the light is scattered and reflected by the unevenness of the speckle pattern on the surface of the reflector. As shown in FIG. 1, when a diffuser plate that is longer in the vertical direction than in the horizontal direction is used, scattered reflected light having anisotropy that diffuses widely in the vertical direction is generated.

FIG. 6 shows the distribution of the scattered reflected light generated by the reflector having the speckle pattern shown in FIG. The speckle pattern in the present invention refers to a pattern in which the density or phase on the pattern shows a random value depending on the position, as described in p.266 of the above-mentioned "Light Measurement Handbook". Even if this pattern is binarized, the frequency component remains, so that the effect is not lost.

[0034]

<Embodiment 1> An embodiment of a method for manufacturing a reflective electrode according to the present invention will be described below. As shown in FIG. 3A, a photosensitive resin is applied by spin coating on the substrate 31 on which the elements for the liquid crystal reflective electrode are formed, thereby forming the organic insulating resin layer 12.

As the organic insulating layer 12, a photosensitive resin such as a photoresist is used.
The thickness was 5 μm. Next, the substrate 3 coated with the organic insulating layer 12
Prebake 1 In this embodiment, prebaking was performed at 90 ° C. for 30 minutes.

Next, as shown in FIG.
The diffusion plate 41 surrounded by 2 is disposed so as to face the organic insulating layer 12. At this time, it is preferable that the diffusion plate 41 and the organic insulating layer 12 do not adhere to each other in order to cause interference between the diffusion lights from the diffusion plate and to generate sufficient speckles, and it is better to separate the diffusion plate 41 by at least 1 mm or more. . In this state, irradiation is performed with coherent light 51 such as laser light as shown in the figure. In the present embodiment, an argon ion laser was used as this laser.

Next, for example, the concentration of TMDH 5
% Of the organic insulating layer is developed using a developing solution having a concentration of 0.1%. Thereby, as shown in FIG. 3C, a concavo-convex pattern corresponding to the speckle pattern is formed on the organic insulating film 12.
At this time, the amount of exposure and the developing time in the step of FIG.
It is desirable not to expose 1.

Thereafter, the organic insulating layer 12 in the state shown in FIG.
Then, a normal reflective electrode manufacturing process such as formation of a contact hole is performed to form a metal reflective layer on the surface. In this embodiment, the aluminum reflection layer was formed by sputtering.

<Embodiment 2> Hereinafter, a second embodiment of the method of manufacturing a reflective electrode according to the present invention will be described. As shown in FIG. 4A, a photosensitive resin is applied by spin coating on the substrate 31 on which the elements for the liquid crystal reflective electrode are formed, thereby forming the organic insulating resin layer 12.

As the organic insulating layer 12, a photosensitive resin such as a photoresist is used.
The thickness was 5 μm. Next, the substrate 3 coated with the organic insulating layer 12
Prebake 1 In this embodiment, prebaking was performed at 90 ° C. for 30 minutes.

Next, as shown in FIG. 4B, a photomask 13 is disposed on the organic insulating layer 12 side.

After the speckle pattern is recorded on the photosensitive resin in the process shown in FIG.
The one produced by removing the chromium film by etching was used. Therefore, a speckle pattern is formed on the photomask 13 in a form (shading) depending on the presence or absence of the chromium film.

Next, in the state shown in FIG.
Light 55 is irradiated from the side. In this embodiment, ultraviolet light is used.

Next, for example, the concentration of TMDH 5
% Of the organic insulating layer is developed using a developing solution having a concentration of 0.1%. Thereby, as shown in FIG. 4C, a concavo-convex pattern corresponding to the speckle pattern is formed on the organic insulating film 12.
At this time, the amount of exposure and the development time in the step of FIG.
It is desirable not to expose 1.

Thereafter, the organic insulating layer 12 in the state shown in FIG.
Then, a normal reflective electrode manufacturing process such as formation of a contact hole is performed to form a metal reflective layer on the surface. In this embodiment, the aluminum reflection layer was formed by sputtering.

In this embodiment, the speckle pattern of the photomask is recorded by photographing the speckle pattern using diffusible coherent light, but the speckle pattern is calculated by a computer and used in a semiconductor manufacturing apparatus. EB
The photomask may be manufactured using a device such as a drawing device or a laser drawing device.

In any of the above-described embodiments, FIG.
In the process of FIG. 4B or FIG. 4B, the description is made on the case where the diffused light generated from only one light is exposed and recorded on the organic insulating layer, but the present invention is not limited to this. Instead, the speckle pattern may be recorded using light different from the diffused light.

In this case, by making the light-sensitive material to be exposed and recorded incident (on-axis) diffused light having the same optical axis and another light, and recording by exposure, the diffused light having a small color change during reproduction is specified. It is preferable because the light is emitted from the pattern.

[0049]

According to the present invention, in a reflective electrode having unevenness on its surface, ambient light can be used efficiently, and the direction and range of reflected light can be controlled (display light has anisotropy). In addition, since reflected light having no (or almost no) regular reflection component and a large amount of scattered reflection component is emitted, high-quality (high-brightness) display can be realized when mounted on a reflection-type liquid crystal display device.

[0050]

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an optical system for producing a concave-convex pattern serving as a reflection surface, and FIG.
(b) is a diagram of the optical system viewed from the side.

FIG. 2 is an explanatory view showing an arrangement when a reflector having a speckle pattern formed as unevenness of a reflection surface is applied to a liquid crystal display device, and FIG. ,
FIG. 2B is a view from the side.

FIG. 3 is an explanatory view showing an example of a method for manufacturing a reflective electrode of the present invention in the order of steps.

FIG. 4 is an explanatory view showing another example of a method for manufacturing a reflective electrode of the present invention in the order of steps.

FIG. 5 is an explanatory diagram showing an example of a speckle pattern.

FIG. 6 is an explanatory diagram showing a distribution of scattered reflected light generated by a reflector having the speckle pattern of FIG. 5 on its surface.

[Explanation of symbols]

 11, 41: Diffusion plate 12: Organic insulating layer 13: Photomask 14: Photosensitive material 15: Coherent illumination light 16: Diffusion light 31: Substrate on which elements for liquid crystal reflective electrode are formed 42: Light shielding plate 51: Coherent light 61: Reflector 65: Illumination light

Claims (11)

[Claims] In a reflector (reflection electrode) serving also as an electrode for driving a liquid crystal, an interference pattern due to scattered light from at least one light having coherence is formed on a surface facing a liquid crystal layer. A reflective electrode, characterized in that a concave-convex pattern is formed. 2. The reflective electrode according to claim 1, wherein the concave / convex pattern is a pattern on which speckles are recorded. 3. The reflective electrode according to claim 2, wherein the average speckle diameter of the speckle pattern is different in two orthogonal directions on the reflecting surface. 4. A speckle pattern is recorded on the photosensitive resin in the form of fine irregularities by irradiating the photosensitive resin with diffuse transmitted light emitted by illuminating the transparent diffuser with coherent light; Then, a method of manufacturing a reflective electrode, comprising a step of forming a reflective metal layer on the uneven surface of the resin. 5. The method for manufacturing a reflective electrode according to claim 4, wherein a transparent diffuser having different sizes in a vertical direction and a horizontal direction is used. 6. A photosensitive resin is irradiated with diffuse transmitted light emitted by illuminating the transparent diffuser with coherent light, whereby a speckle pattern is recorded on the resin in a shaded form. From the speckle pattern, a photomask is produced by a photolithography process, and the photosensitive resin is irradiated with transmitted light emitted by illuminating the produced photomask, thereby forming a fine speckle pattern on the resin. Recording in the form described above, and then forming a reflective metal layer on the uneven surface of the resin. 7. A speckle pattern is recorded on the resin by sequentially forming a metal layer / photosensitive resin on a glass surface, and irradiating the resin with diffusible coherent light, and then performing a photolithography process. A method for manufacturing a reflective electrode, comprising a step of manufacturing a photomask on which a speckle pattern is recorded by partially removing a metal layer. 8. Calculating a speckle pattern by diffusible coherent light, drawing the obtained speckle pattern to produce a photomask, and transmitting transmitted light emitted by illuminating the photomask. By irradiating the photosensitive resin, a speckle pattern is recorded on the resin in the form of fine irregularities,
Forming a reflective metal layer on the concave and convex surface of the resin. 9. A metal layer / photosensitive resin is sequentially formed on a glass surface, a speckle pattern due to diffusible coherent light is calculated, and the obtained speckle pattern is used in an EB drawing apparatus or a laser drawing apparatus. Forming a photomask on which a speckle pattern is recorded by drawing on the resin and then partially removing the metal layer by a photolithography process. . 10. The photomask according to claim 6, wherein a speckle pattern formed on the photomask uses a photomask having a different average diameter of speckles in two orthogonal directions on the surface. The method for producing the reflective electrode according to the above. 11. A reflection type liquid crystal display device comprising the reflection electrode according to claim 1.