JPH11194205A - Reflecting surface and its formation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable use even for a reflection type liquid crystal display element and to actualize display which appears to be natural, but is light. SOLUTION: A mask pattern is formed on a crystal substrate 1 which has reflectivity and in an area where the mask pattern of the crystal substrate 1 is not formed, anisotropic etching is performed by using the mask pattern as a mask to form unevenness in a right-left symmetrical mountain shape 2 of the wavelength of light to tens microns in size which is symmetrical about a center line. To lighter reflected light, a thin film of desired substance, such as Al and Ag, reflecting light is formed on the surface of the unevenness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a component utilizing light, and more particularly to an application of the aforementioned component to various display devices utilizing external light.

[0002]

BACKGROUND OF THE INVENTION The most common object that reflects light is a mirror. The mirror is made of Al or Ag that reflects light well on the back of the glass plate
Etc., and there is no particular problem in use in daily life. When extremely high-precision reflection is required, such as with a reflection-type astronomical telescope, a metal film is formed directly on the surface of the glass plate, not on the back surface, and even a small amount of light passes through the glass. To avoid being absorbed by

[0003] Even in the case of the same expression of reflection, the situation is different in a display element. For example, a liquid crystal panel performs display by controlling transmission and blocking of light in principle, so that a display light source (backlight) is installed on the back or a display plate is installed to obtain display brightness. I have. Here, there are roughly two approaches as a reflector used in the reflection method. One is a method in which a brighter display can be obtained as the light reflectance of the reflector is higher. Therefore, a reflector coated with a material having a high reflectivity such as Al or Ag is attached to the back surface of the panel. Is a method in which a scattering reflection film that incorporates light scattering rather than a mirror surface is attached.

[0004]

However, in the reflection type liquid crystal display element, the former method has a problem that a viewer cannot perceive a natural display due to the influence of metallic luster, and the latter method has a problem. There was a problem that the brightness was insufficient.

In view of the above problems, the present invention provides a reflective surface and a method for forming the same, which can be used for a reflective liquid crystal display element and realize a bright display with a natural appearance as much as possible. The purpose is to do.

[0006]

In order to achieve the above object, a reflecting surface of the present invention is provided on a reflective substrate surface.
A plurality of valley-shaped irregularities having a symmetrical shape with respect to the center line are formed, and the dimension of the valley shape is a wavelength of light to several tens of microns. According to this configuration, it is possible to provide the reflected light with directivity while maintaining a state having a certain degree of scattering.

The above-mentioned reflecting surface can be formed by the following method. That is, a mask pattern is formed on a crystal substrate having reflectivity, and anisotropic etching is performed using the mask pattern as a mask, and a region where the mask pattern is not formed on the crystal substrate is symmetrical with respect to a center line. It is only necessary to form valley-shaped irregularities having a shape of the wavelength of light to several tens of microns.

In the above configuration, when a thin film of a substance that reflects desired light is formed on the uneven surface, brighter reflected light can be obtained.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As a result of intensive studies conducted by the present inventors, the reason why a conventional reflective liquid crystal display element does not provide a bright display is that light is not reflected due to a flat reflective surface. It has been found that the light is reflected uniformly in all directions.

Therefore, the present inventor has focused on the fact that, from the viewpoint of the user of the reflection type liquid crystal display element, there is not much opportunity to look into the display device from an extremely oblique direction, and the reflected light has a characteristic. The idea was to realize a bright display by giving it the directivity of. Note that if the reflected light has too much directivity, the display itself will not look uniform, and the present inventor has given the reflected light a directivity in consideration of achieving some degree of scattering of the reflected light. A method (specifically, controlling the shape of the reflective surface) has been devised.

Next, a reflecting surface according to an embodiment of the present invention will be described with reference to the drawings. Needless to say, the reflective surface in the present embodiment is suitable for a reflective liquid crystal display device.

FIG. 1 is a sectional view of a reflecting surface according to an embodiment of the present invention. As shown in FIG. 1, a plurality of irregularities of a V-shaped valley 2 having a micro-valley shape are formed on the surface of the substrate 1. The angle 3 between the slope and the surface of the valley is uniform over the whole (that is, the valley has a symmetrical shape with respect to its center line).

Here, the interval between the V-shaped valleys (dimensions of the valleys) affects the balance between the scattering property and the reflection property of the entire reflecting surface, and is not uniquely determined to a specific value. There are regions of preferred value. For example, in relation to the wavelength of light, when the dimension of the V-shaped valley is extremely large, it looks only as if mirrors facing in different directions are lined up. The unevenness is not felt, and as a result, the light is not affected. Therefore, the dimension of the V-shaped valley is desirably about the wavelength of light to about several tens of microns.

A comparison between the rugged reflecting surface of the present invention shown in FIG. 1 and an ordinary flat reflecting surface is as follows.
Significant differences are seen in the reflected light. Figure 2
This will be described with reference to the intensity distribution of reflected light shown in FIG. When the reflecting surface 4 is flat, a broad and uniform reflection intensity distribution as shown by 5 is exhibited. On the other hand, when the reflection surface 4 has undulations as in the present invention, a directional reflection intensity distribution as shown in 6 is obtained. Reflection of light on a flat surface does not cause a difference between the incident light distribution and the reflected light distribution because the magnitude of the incident angle and the reflection angle is constant over the entire surface, but has a special scattering property as in the present invention. Since the light is reflected by the reflecting surface so as to be condensed in a limited range, the light is brighter than the flat surface within the limited range. Further, according to the reflecting surface of the present invention, although the reflected light has directivity, it has a certain degree of scattering, so that a glare-like impression like a mirror when condensed using a concave mirror is reduced, A feeling close to a more natural brightness can be obtained.

Various methods are possible for forming the reflective surface structure of the present invention as described above, and not all of them can be listed. For example, a metal mold is formed and pressed on a deformable material surface. And a method of performing fine processing on the surface of the substrate material using an electron beam or a laser beam. Although each has advantages and disadvantages, the method of the present invention described below can relatively easily and accurately produce a desired structure.

According to the method of forming a reflective surface of the present invention, a micro-scale V-shaped valley is accurately formed by performing anisotropic etching using a specific plane orientation of a crystalline substrate. FIG. 3 shows a process sectional view of the method for forming a reflective surface according to the present invention. First, as shown in FIG. 3A, a desired pattern 12 is formed on the surface of the substrate 11 using a material having resistance to an etching solution. Next, FIG.
As shown in (b), the pattern 12
By immersing the entire substrate 11 on which the pattern is formed, the recess 14 is formed by gradually progressing the etching of the other portion only in a specific direction while leaving the portion of the pattern 12 without dissolving it. . And FIG.
As shown in (c), the depression 14 is gradually deepened, and the etching is terminated at a point defined by the width of the pattern 12 to form a V-shaped valley 15.

In the above structure, the crystalline substrate material used for the substrate 11 is, in particular, Si, Ge, G
When aAs, GaSb, GaP, InSb, InP, or the like is used, it itself reflects light to a considerable extent. Depending on the application, only surface shape processing is sufficient, but if further brightness is required, It is effective to cover the surface of the formed micro-valley-shaped V-shaped valley with a thin film of a metal having higher reflectivity. Although the method of forming this metal thin film varies widely, the flatness of the metal surface viewed microscopically,
Film formation in a vacuum is desirable from the viewpoint of purity and the like, and sputtering, vacuum evaporation, CVD, electron beam evaporation, or the like can be used.

(Embodiment 1) A GaAs substrate is used as a reflective crystalline substrate.
On the (00) plane, a stripe pattern is formed in the [01-1] direction (ie, perpendicular to the (01-1) plane) using a thin film of Al ₂ O ₃ , and etching is performed using this stripe pattern as an etching mask. Was done. An advantage of using a metal oxide such as Al ₂ O ₃ as described above is that an organic solvent can be used as an etching solution. Etchant used a mixture of Br ₂ in CH ₃ OH. Here, the mixing ratio of Br ₂ and the etching rate are related, and a certain specific value is not optimal. However, if it is about several%, it is several μm / min, and in this embodiment, it is 4%. And

The size of the V-shaped valley to be formed can be controlled by the interval between the stripe patterns. In the present embodiment, this interval is set to 10 μm.
Also, by making the width of the stripe itself 4 μm,
A surface in which V-shaped valleys were arranged at intervals of 4 μm was formed. As a result, the substrate surface, that is, the (100) plane and the slope, that is, (1)
11) The angle with the plane was 54 ゜ 44 '. Finally, using a heated H ₃ PO ₄ solution, the thin film stripe pattern of Al ₂ O ₃ used as an etching mask was removed to complete a reflective surface.

(Embodiment 2) This embodiment is different from Embodiment 1 in that an etching solution used for forming a V-shaped valley is different.

GaAs is used as a reflective crystalline substrate.
Using an s substrate, C ₃ H ₄ (OH) (COOH) ₃ .H ₂ O, H ₂ O ₂ , H ₂
A mixed solution of O is used. The advantage of this etching solution is that it does not contain an organic solvent, and a normal photoresist can be used as a mask pattern for etching.
Various types of photoresists are sold, both positive type and negative type. In this embodiment, various resists can be used. For example, OMR series and OFPR series of Tokyo Ohka Kogyo Co., Ltd. and S series of Shipley Co. , SPR series, LC series and the like can be used.

As a specific method of forming a reflective surface, first, a photoresist is used to form a stripe pattern in the [01-1] direction (ie, perpendicular to the (01-1) plane) using a photoresist on the (100) surface of the GaAs substrate. Form. Since the etching rate depends on the mixing ratio of each component of the etching solution,
Conditions are set according to the purpose, but extremely slow or fast conditions are not preferable from the viewpoint of productivity and pattern accuracy. C ₃ H ₄ (OH) (COOH) at room temperature
Approximately 60n when ₃ · H ₂ O: H ₂ O ₂ is approximately 1: 1
m / sec was obtained, and in this embodiment, etching was performed under this condition.

Details such as that the size of the V-shaped valley to be formed can be controlled by the interval of the stripe pattern are the same as those in the first embodiment, and a description thereof will be omitted. Finally, the stripe pattern of the resist was removed using a stripping solution specified for the resist to complete the reflection surface.

(Embodiment 3) This embodiment is different from Embodiment 1 described above in that the substrate on which the reflective surface is formed and the V
An etchant used for forming the valley shape is different.
An Si substrate is used as the reflective crystalline substrate, and S
A stripe pattern using a thin film of SiO ₂ is formed on the (100) plane of the i-substrate, and anisotropic etching of Si is performed using the SiO ₂ pattern as a mask.

A specific method of forming a reflection surface is as follows. First, a thickness of about 150 is obtained by thermal oxidation of a clean Si substrate.
A 0 ° SiO ₂ film is formed. Next, a photoresist is applied to form a stripe pattern in the [01-1] direction (that is, perpendicular to the (01-1) plane). In addition,
At this time, various resists can be used as listed in the second embodiment, and any type of resist can be used. Next, a portion of S which is not covered with the resist by the buffered hydrofluoric acid which is generally commercially available is used.
After removing the iO ₂ , anisotropic etching of Si is performed using KOH: H ₂ O: (CH ₃ ) using the SiO ₂ pattern as a mask.
_{2 This} is performed using a solution of CHOH = 20 g: 60 ml: 100 ml.

The details such as that the size of the V-shaped valley to be formed can be controlled by the interval of the stripe pattern are the same as those in the first embodiment, and a description thereof will be omitted. Finally, the thin film stripe pattern of SiO ₂ used as an etching mask was removed using buffered hydrofluoric acid to complete the reflection surface.

The present invention has been described with the embodiments. However, in any of the above-described embodiments, the case where a higher brightness is required than when the semiconductor substrate surface itself is used (desired light is required). In the case of reflection, it is effective to cover the surface of the formed micro-valley-shaped V-shaped valley with a thin film of a metal or the like having a high reflectance.

In this case, after a V-shaped valley is formed by etching using a mask, a thin film of a metal having high reflectance of visible light, for example, Al or Ag is deposited on the surface.
There are various methods of forming a film in a vacuum suitable for this, and sputtering, vacuum evaporation, CVD, electron beam evaporation and the like can be used.

[0029]

As described above, according to the present invention, by forming valley-shaped micro unevenness on the surface of a reflective substrate, it is possible to give the reflected light characteristic directivity. As a result, it is possible to guide bright reflected light while having a natural appearance in a limited visual field range.

[Brief description of the drawings]

FIG. 1 is a sectional view of a reflecting surface according to an embodiment of the present invention.

FIG. 2 is a diagram showing an intensity distribution of reflected light of light incident on a reflecting surface according to the embodiment of the present invention.

FIG. 3 is a sectional view showing a process of forming a reflective surface according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Valley shape 3 Inclination angle 4 Reflection surface 5 Light reflection intensity distribution from flat reflection surface 6 Light reflection intensity distribution from scattering reflection surface according to the present invention 11 Substrate 12 Etching mask pattern 13 Etching solution 14 Formed by progress of etching Depressed hollow 15 V-shaped shape

Claims (4)

[Claims] 1. A plurality of valley-shaped irregularities having a symmetrical shape with respect to a center line are formed on a surface of a reflective substrate, and the valley-shaped shape has a wavelength of light to several tens of microns. A reflective surface, characterized in that: 2. The valley-shaped uneven surface is covered with a thin film of a substance reflecting desired light.
The reflective surface according to 1. 3. A mask pattern is formed on a crystal substrate having reflectivity, and anisotropic etching is performed using the mask pattern as a mask. Forming a valley-shaped unevenness having a bilaterally symmetrical shape and a size of the wavelength of light to several tens of microns. 4. The method according to claim 3, wherein after forming the valley-shaped irregularities, a thin film of a substance reflecting desired light is formed on the surface.