JPH08122760A - Spacial optical modulating element and production thereof - Google Patents

Abstract

PURPOSE: To improve the opening ratio, contrast, and light-shielding degree of a special optical modulating element compared with a conventional one by forming pixel electrodes in a pentagonal or more polygonal shape and properly selecting the rubbing direction. CONSTITUTION: For example, by patterning an Al reflection electrodes 8 into almost regular hexagons to be used as pixels, omission of pixels in the edge part is decreased and the opening rate is improved. By selecting the rubbing direction as the direction 18 which makes 85 deg. to 95 deg. angle from the one side of the hexagon, disturbance in orientation can be suppressed to the min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a projection type display,
The present invention relates to a spatial light modulator used in a holographic television or an optical arithmetic device, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, large-screen, high-definition televisions have been developed and put into practical use in various systems. In particular, the development of projection-type displays using liquid crystal technology has been active in place of the conventional CRT method. With the cathode ray tube method, the brightness of the screen is reduced and the screen becomes darker for high-density pixels. Further, it is difficult to increase the size of the cathode ray tube. On the other hand, a projection-type display using a liquid crystal element of a transistor drive system is effective but has a small aperture ratio, and the element requires a great number of steps and is expensive. A liquid crystal light valve using a cathode ray tube (hereinafter referred to as a CRT) as an input light has a simple element structure and has attracted much attention. In recent years, it has become possible to project a moving image with a large screen of 100 inches by combining a highly sensitive amorphous silicon light receiving layer and a liquid crystal. Further, a liquid crystal light valve using a ferroelectric liquid crystal, which is a liquid crystal material that responds faster than a conventional twisted nematic liquid crystal, has been attracting attention.

Although various researches and developments have been actively carried out on the structure of the spatial light modulator, as a conventional example of the spatial light modulator or the liquid crystal light valve having the structure in which the minute electrodes and the light shielding film are provided, JP-A-62-40430, JP-A-62-169120, JP-A-3-19
There is one described in Japanese Patent No. 2330, etc.

[0004]

However, since the shape of the pixel composed of the minute reflective electrode provided on the conventional photoconductive layer is square, the aperture ratio does not increase so much due to the limit of the accuracy of photolithography. Further, due to the wraparound of light during the exposure of photolithography, the corners of the pixels are rounded, which causes a reduction in the light blocking degree and the contrast. Further, when the pixel has a square shape, when the alignment film is applied and rubbing is performed, the edge portion of the pixel is 90 °, so that the fibers of the rubbing cloth do not effectively contact with each other, resulting in disordered alignment of the edge portion. Was there.

The present invention solves the above-mentioned problems of the prior art, that is, provides a spatial light modulator which not only improves the aperture ratio but also increases the light blocking degree and contrast and is free from orientation disturbance, and a method for manufacturing the same. The purpose is to do.

[0006]

In order to achieve the above object, the first spatial light modulator of the present invention comprises at least a liquid crystal layer, a light shielding layer, a photoconductive layer divided into fine electrodes, and a metal reflection layer. A film is provided, and the shape of the metal reflection film is a pentagon or more. In the above structure, it is most desirable that the pixel array is a delta array and is hexagonal.

The second spatial light modulator of the present invention comprises at least a liquid crystal layer, a light shielding layer, a photoconductive layer divided into fine electrodes, and a metal reflection film, and the shape of the metal reflection film. Are all obtuse angles and are hexagonal having two or more line symmetry axes.

As a manufacturing method, an alignment film is applied on the pixel, and an angle of 85 ° to any one side of the hexagon of the pixel is applied.
It is characterized by rubbing at an angle of 95 °.

[0009]

According to the structure of the present invention, since the shape of the metal reflection film is a polygon having a pentagonal shape or more, the angle of the apex of the polygon becomes an obtuse angle, and the edge due to the wraparound of light during exposure of photolithography. The number of missing pixels in the part is very small. Therefore, the aperture ratio is unlikely to be lowered, and the ratio of the reflection area to the entire area is increased, so that the illuminance during white display is increased and the contrast is also improved accordingly. Further, an increase in the ratio of the reflection area of Al results in a decrease in the amount of light reaching the light shielding layer and an improvement in the light shielding degree.

When the metal reflection film is hexagonal and has two or more line symmetry axes, a large number of pixels can be formed within a certain area when the delta arrangement structure is taken from the shape of the pixels. It has the feature. Further, since the shape of the edge portion of one pixel is 120 ° or more, which is a very obtuse angle, the fibers of the rubbing cloth effectively contact the pixels during rubbing after the application of the alignment film, so that the alignment disorder of the pixel edge portion occurs. It has the feature of not happening.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a conceptual cross-sectional view of a spatial light modulator according to an embodiment of the present invention, and FIG. 1B is a conceptual view of a pixel electrode of the spatial light modulator of this embodiment.

As shown in FIG. 1, glass substrate 1 and ITO
Electrode 2, amorphous silicon layer 3 (p layer 4, i layer 5,
n layer 6), a Cr electrode 7, an Al reflection electrode 8, an Al light shielding film 9, a light shielding layer 10, an alignment film 11, a liquid crystal layer 12, a spacer 13, and a glass substrate having an alignment film 14 and an ITO electrode 15. 16 is a spatial light modulation element, and it is desirable that the Al reflective electrode 8 at this time has a polygonal shape of a pentagon or more. The characteristic of being a pentagon or more is that, for example, in the case of a regular hexagon, all interior angles are 1
It is 20 °. Focusing on the apex 17 of the hexagon, the closer the angle of the apex is to 180 °, the less the pixel edge is crushed due to irregular reflection of light during photolithography, and the accuracy of photolithography is improved, and the aperture ratio is also improved. .

In Table 1, pentagon, hexagon, octagon, 10
It shows the result of patterning by photolithography with a design such that the area of one pixel of the Al electrode in the prism is 40 μm ² .

[0014]

[Table 1]

As is clear from Table 1, the design values are approached in the order of pentagon <hexagon <octagon <decagon. In other words, the greater the number of vertices, the higher the accuracy and the closer to the design value. As described above, the shape of the pixel is a polygon of pentagon or more, and the accuracy of photolithography is improved as the number of vertices is increased. However, considering the arrangement of the pixels, the hexagonal delta that allows the pixels to be arranged most densely. Most preferably, it is an array.

Further, let us consider the relationship between the hexagonal symmetry and the ease of arrangement (the easier the arrangement is, the more pixels can be included in a certain area and the aperture ratio can be increased). And, first of all, it is clear that hexagons that have no symmetry have very poor ease of arrangement. Next, considering a hexagon in which a pair of opposite sides are parallel to each other among hexagons having only one line symmetry axis, the symmetry axes are parallel to the mutually opposite sides.

That is, it is very easy to form a dense arrangement in the direction perpendicular to the axis of symmetry, while it is very difficult to arrange in a direction parallel to the axis of symmetry due to the symmetry of the pixels. In addition, in the case where the line symmetry axis is one and there is no pair of parallel sides facing each other, the arrangement is obviously poor in both the direction perpendicular to the symmetry axis and the direction parallel thereto. However, if the interior angles of the hexagon are all obtuse and there are two or more line symmetry axes, that is, if the obverse is a hexagon and all three pairs of opposite sides are parallel hexagons, then considering the pixel arrangement A very dense array structure can be obtained by adopting a vertical delta arrangement or a horizontal delta arrangement both parallel and perpendicular to the axis of symmetry. That is, the aperture ratio is greatly improved.

When rubbing after applying the alignment film and rubbing in a direction 18 close to 90 ° with respect to any one side, the fibers of the rubbing cloth first contact only one vertex of the pixel. There is no. Normally, when rubbing is performed so that only one vertex of the pixel comes into contact first, the fibers of the rubbing cloth do not rub against the vertex of the pixel, and the fiber flows laterally and an area that cannot be sufficiently rubbed appears near the vertex of the pixel. The alignment was disturbed only in that region. That is, when the rubbing method of the present invention is used, the rubbing cloth first contacts one side of the pixel instead of one point, so that the entire pixel can be rubbed uniformly. The results are shown in (Table 2).

[0019]

[Table 2]

Table 2 shows a change in the contrast of the output light of the spatial light modulator when a hexagonal metal reflection film having two or more line symmetry axes is used and the rubbing direction 18 is changed. Is. Taking the rubbing angle θ as shown in FIG. 1B, the contrast ratio is 2 when θ is 85 to 95.
It can be seen that very good rubbing is achieved when the angle is 00 or more and is between 85 ° and 95 °.

Specific examples will be described below with reference to FIGS. 2 (1) to 2 (7).
According to. (1) Optically polished glass substrate 19 (55 mm × 65 mm ×
Indium tin oxide (hereinafter referred to as ITO) is formed as a transparent conductive film 20 in a thickness of 1.1 mm by sputtering to a thickness of 1000 angstrom. Next, ITO2
Cr was vapor-deposited on the surface of No. 0 to 500 angstrom, and by photolithography, an inversion pattern of the pattern in which 2783 × 1877 vertical hexagons each having a side of 9 μm were arranged at a pitch of 24 μm, that is, the input light-shielding film 21 of chromium was formed. Formed.

(2) p-type a-Si: H layer 22 with 100 ppm of boron added by plasma CVD on the entire surface
(Film thickness 500 angstrom), i-type aS with no additive
i: H layer 23 (film thickness: 1.5 μm) and phosphorus of 1000
The n-type a-Si: H layer 24 added with ppm (film thickness 3000
3 angstroms) were successively laminated to form a photoconductive layer having a diode structure. Then Cr on the entire surface 20
The pattern was formed by photolithography by vapor-depositing 00 angstroms and arranging approximately regular hexagons each having a side of 12.5 μm at a pitch of 24 μm in a 2783 × 1877 (522,3691 total) vertical delta arrangement.

(3) Hexagonal Cr is formed by a chemical dry etching method using a mixed gas of CF4 and oxygen.
The pixel 25 is used as a mask at the time of etching, and
The exposed portion of the Si: H layer is isotropically etched. Then, when the film is etched by about 1.6 μm, a groove is dug between the Cr pixels to form a structure having a Cr eaves.
Further, the groove may be dug until the surface of the input light shielding film 21 is exposed.

(4) 5 Al is formed by electron beam evaporation
A film is formed on the entire surface of 00 to 2000 angstrom. A hexagonal Al reflection electrode 26 of 500 to 2000 angstrom is formed on the hexagonal Cr pixel 25, and an Al output light-shielding film 27 is formed on the bottom of the groove.

(5) An acrylic resin containing carbon is applied by spin coating. In this process, the resin is buried in the groove formed by etching, and Al
This resin also deposits on the electrode 26. Then, the entire surface is etched by the reactive ion etching method using oxygen to uniformly remove the resin, and the Al electrode 2
This etching is finished when the surface of 6 appears. As a result, all the resin on the surface of the Al electrode 26 is removed, but the acrylic resin layer 28 containing carbon remains in the groove.

(6) Two polyimide films 29 are used as an alignment film.
00 angstrom film is formed. Similarly, a polyimide film 32 is formed to 200 angstroms on a glass substrate 31 having an ITO electrode 30 serving as a substrate on the opposite side, and both substrates are rubbed with a nylon cloth.

(7) On the surface of the polyimide film 32 of the ITO substrate 31, spherical spacers 33 of SiO ₂ having a grain size of 0.8 μm are dispersed by a wet method and bonded to the glass substrate 19 which has been subjected to the above treatment. The liquid crystal cell thus prepared was placed in a vacuum injecting device, decompressed, and then heated to 120 ° C., and the ferroelectric liquid crystal 34 (Chisso Petrochemical Co., Ltd .: CS
-1029) was injected by capillarity.

The spatial light modulator thus manufactured is written with writing light 35 from the glass substrate 19 side,
The reading light 37 passing through the polarizer 36 is irradiated from the glass substrate 31 side, and the output light 38 reflected by the Al electrode 26 is projected as an image through the analyzer 39. The drive voltage at this time is a forward voltage of 15V for erasing and a reverse voltage of -1V for optical writing. At this time, the forward application time is 1.4 msec, and the reverse application time is 15.7 msec.
And Here, the optical writing intensity is 1000 μW / cm
When it was set to 2, a contrast ratio of 200: 1 or more was secured.

[0029]

As described above, according to the present invention, the pixel shape is a pentagonal or more polygonal shape so that the edge portion is not lost due to the light wraparound by photolithography, and the aperture ratio is improved. However, the light blocking degree and the contrast can be increased.

Further, by rubbing the rubbing direction at an angle of 85 ° to 95 ° with respect to one side of the pixel in the pixel structure of the present invention, uneven alignment of the edge portion is less likely to occur, thereby further improving the contrast. It has the excellent effect of

[Brief description of drawings]

1A is a conceptual cross-sectional view of a spatial light modulator of the present invention, and FIG. 1B is a conceptual diagram of a pixel electrode of a spatial light modulator of the present invention.

FIG. 2 is a cross-sectional view of the manufacturing process of the spatial light modulator of the present invention.

[Explanation of symbols]

 1 Glass Substrate 2 ITO Transparent Electrode 3 Amorphous Silicon Layer 4 Amorphous Silicon Layer (p Layer) 5 Amorphous Silicon Layer (i Layer) 6 Amorphous Silicon Layer (n Layer) 7 Chromium Electrode 8 Al Reflective Electrode 9 Al Light Shielding Film 10 Light Shielding Layer 11 Alignment film 12 Liquid crystal layer 13 Spacer 14 Alignment film 15 ITO electrode 16 Glass substrate 17 Position of apex of polygon 18 Rubbing direction 19 Glass substrate 20 Transparent electrode 21 Chrome input light shielding film 22 p-type a-Si: H layer 23 i-type a -Si: H layer 24 n-type a-Si: H layer 25 Chrome pixel 26 Al reflective electrode 27 Al output light-shielding film 28 Acrylic resin layer 29 Polyimide alignment film 30 ITO electrode 31 Glass substrate 32 Polyimide alignment film 33 Spacer 34 Ferroelectric Liquid crystal 35 Writing light 36 Polarizer 37 Reading Light 38 Output light 39 Analyzer

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Akio Takimoto 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Hiroshi Tsutsui, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A spatial light modulator comprising at least a liquid crystal layer, a light shielding layer, a photoconductive layer divided into minute shapes, and a metal reflection film, wherein the metal reflection film has a pentagonal shape or more. A spatial light modulator having a polygonal shape. 2. The spatial light modulator according to claim 1, wherein the metal reflection film has a hexagonal shape and the metal reflection film has a delta arrangement. 3. A spatial light modulator comprising at least a liquid crystal layer, a light-shielding layer, a photoconductive layer divided into minute shapes, and a metal reflective film, wherein the metal reflective film has an obtuse angle at all interior angles. And a spatial light modulator having a hexagonal shape having two or more line symmetry axes. 4. A hexagonal metal reflective film having at least a liquid crystal layer, a light-shielding layer, a photoconductive layer divided into fine electrodes, and having an obtuse internal angle and two or more line symmetry axes. It is a spatial light modulator, wherein an alignment film is applied on the metal reflection film, and an angle of 85 ° to any one side of the hexagonal pixel is applied.
A method of manufacturing a spatial light modulator, comprising rubbing at an angle of 95 °.