JP2798865B2 - Method for manufacturing spatial light modulator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a spatial light modulator used for a projection display.

[0002]

2. Description of the Related Art At present, three types of projection type display are being developed.
There are different approaches. Among them, a projection type display using a cathode ray tube has a limitation in the brightness of the cathode ray tube and has a drawback that the device becomes large, so that there is a limit in increasing the area of the display. In addition, in the case of a liquid crystal projection display comprising a liquid crystal panel having a thin film transistor array, the resolution of the liquid crystal panel is insufficient, the aperture ratio of the liquid crystal panel is low, and the light resistance of the thin film transistor array made of an amorphous silicon thin film. Is low.

[0003] For this reason, a projection display in which a spatial light modulator, a small display, and a light source are incorporated in an enlarged projection optical system is expected to be promising. In this method, a weak image is once written on a spatial light modulator, another read light is modulated according to this write information, and projected on a screen.

That is, write light carrying image information is applied to the photoconductive layer, and read light having a higher intensity than the write light is applied to the light modulation layer from the side opposite to the write light. For this reason, a dielectric multilayer mirror is provided between the photoconductive layer and the light modulation layer to reflect the reading light.

However, the dielectric multilayer film is formed by stacking a large number of dielectric films having different refractive indices, and has a reflectance of about ninety to ninety-nine percent at most. Since the reading light has a much higher light intensity than the writing light, if even a small part of the reading light leaks to the photoconductive layer side, the photoconductive layer is exposed,
Its resistance drops. Therefore, in order to improve the intensity ratio (amplification rate) of the read light to the write light, the read light transmitted through the dielectric multilayer film must be effectively blocked between the photoconductive layer and the light modulation layer. No.

[0006]

For this reason, the present inventor has provided a light shielding layer between the photoconductive layer and the dielectric multilayer film, and shields the read light transmitted through the light modulation layer and the dielectric multilayer film from light. Developed technology to absorb in layers. However, further study of this technology has revealed that there are difficulties, especially in the manufacturing process.

That is, the device characteristics, particularly the resolution, of the spatial light modulator largely depend on the resistivity and the light transmittance of the light shielding layer. First, when the resistivity of the light-shielding layer decreases, the contrast of the image decreases, and the resolution decreases. Further, when the light transmittance of the light-shielding layer increases, the light transmission amount increases even if the intensity of the readout light is constant. The read light transmitted through the light-shielding layer generates photocarriers in the photoconductive layer, and lowers the electric resistance throughout the photoconductive layer. As a result, the contrast of the image is reduced, and the resolution of the element is reduced. Conversely, when the light transmittance of the light shielding layer increases, it is necessary to reduce the intensity of the readout light in order to keep the resolution constant.

However, the resistivity and light transmittance of the light shielding layer are
These are mutually contradictory characteristics. That is, in order to reduce the light transmittance of the light shielding layer, it is necessary to increase the light absorbing ability. However, in a light-shielding layer having a high read-out absorption capability, the resistivity is significantly reduced due to the influence of the absorbed light energy. In such a case, the resolution of the spatial light modulator rapidly deteriorates, and the projected image becomes unclear.

An object of the present invention is to provide a spatial light modulator (SL)
The object of the present invention is to make it possible to stably produce a light shielding layer having a high resistivity and a low light transmittance when forming the light shielding layer of M).

[0010]

The present invention comprises a photoconductive layer,
One transparent electrode film provided on one surface of the photoconductive layer, a light shielding layer provided on the other surface of the photoconductive layer, and a dielectric multilayer film provided on the light shielding layer; When manufacturing a spatial light modulator having at least a light modulation layer provided on a dielectric multilayer film and another transparent electrode film provided on the surface of the light modulation layer, 12.5 to 35 atoms are used. % Germanium and 25 to 82.5 atom% carbon and 5 to 62.5%
Producing a light-shielding layer composed of an amorphous film substantially composed of atomic% of silicon by controlling high-frequency power density by plasma enhanced chemical vapor deposition. Pertains to the method.

In the above description, the high frequency power density is a value obtained by dividing the high frequency power applied between the anode and the cathode by the area of the anode and the cathode in the plasma enhanced chemical vapor deposition (CVD) method. Preferably, in the present invention, the high-frequency power density is 4.8 × 10 ⁻² W / cm ^2.
In the following cases, a favorable film can be produced.

The inventor of the present invention has proposed that a light-shielding layer made of an amorphous film containing germanium, carbon and silicon be formed by a plasma CVD method at a high frequency power density of 4.8 × 10 ⁻² W / cm ² or less. It has been found that a well-balanced light-shielding layer having high resistivity and low light transmittance can be obtained. Specifically, it has been found that when the high-frequency power density is reduced, the resistivity of the light-shielding layer increases, and the light transmittance decreases.

The high frequency power density is 4.8 × 10
^-2 (W / cm ² ) or less, the light transmittance of the light shielding layer is 0.8%.
And the resistivity becomes 3.0 × 10 ⁹ Ω · cm or more,
It was found that the resolution of the spatial light modulator became 17 lp / mm or more. When this spatial light modulator is used as a projector, the resolution of the spatial light modulator is 17 lp /
At less than mm, the image rapidly deteriorated and became unclear. This is because pixels are insufficient on the projected image.

Further, regarding the composition of the amorphous film,
Substantially composed of 12.5 to 35 atomic% germanium, 25 to 82.5 atomic% carbon and 5 to 62.5% silicon improved the resolution of the device. "Substantially" means that unavoidable impurities are acceptable.

[0015]

Hereinafter, the present invention will be described more specifically. As a liquid crystal material constituting the light modulation layer, nematic liquid crystal,
Cholesteric liquid crystals, smectic liquid crystals and polymer dispersed liquid crystals are preferred. The photoconductive layer is preferably formed of a Bi ₁₂ SiO ₂₀ single crystal, a Bi ₁₂ GeO ₂₀ single crystal, or a GaAs single crystal. Alternatively, it is preferable that the photoconductive layer be formed of a GaAs film, a hydrogenated amorphous silicon film, a hydrogenated amorphous silicon carbide film, or an amorphous selenium film.

The manufacturing process of the spatial light modulator 12A according to the embodiment of the present invention will be described step by step with reference to FIGS. In this embodiment, Bi _{12 is used} as the photoconductive layer 1A.
A single crystal of SiO _{20, a} single crystal of Bi ₁₂ GeO ₂₀ or a single crystal of GaAs is used.

First, Bi ₁₂ SiO ₂₀ , Bi ₁₂ GeO ₂₀ ,
A photoconductive layer 1A made of a single crystal of GaAs and GaAs is cut out from a single crystal wafer, and one transparent electrode film 2A is provided on one surface of the photoconductive layer 1A (FIG. 1). Then, FIG.
As shown in the figure, a light-shielding layer 3 is provided on the other surface of the photoconductive layer 1A according to the present invention. The composition and manufacturing method of the light shielding layer 3 will be described later. Next, as shown in FIG. 3, a dielectric multilayer film 4 is provided on the surface of the light shielding layer 3 by vapor deposition.

On the other hand, as shown in FIG. 4, the other transparent electrode film 2B is formed on the surface of the glass substrate 7. The dielectric multilayer film 4 and the transparent electrode film 2B are opposed to each other with a sealing material 5 including a spacer interposed therebetween. A flat space 6 is formed between the dielectric multilayer film 4, the transparent electrode film 2 </ b> B, and the sealing material 5.

In this embodiment, a polymer-dispersed liquid crystal (PDLC), which is a liquid crystal material in which liquid crystal particles are dispersed in a transparent polymer, is used. As a specific manufacturing method, a mixture of an uncured nematic liquid crystal and a resin matrix is injected from an injection port, and the injection port is sealed and then cured as in the case of a conventional ordinary twisted nematic liquid crystal. As a result, a light modulation layer 8 made of PDLC is formed in the space 6 as shown in FIG.

There is also a manufacturing method that does not use a sealing material. That is, for example, a mixture of an uncured nematic liquid crystal and a resin matrix is supplied on a substrate provided with a transparent electrode, and then, a dielectric multilayer film and a photoconductive layer to which a transparent electrode is attached are superimposed, and irradiated with light or the like. It can also be cured. Of course, after that, a sealing material may be applied to the periphery to seal the periphery. According to this manufacturing method, the mixture of the uncured nematic liquid crystal and the resin matrix may be simply supplied by roll coating, spin coating, printing, coating with a dispenser, or the like, so that the injection step is simple and the productivity is extremely high. .

In addition, the mixture of the uncured nematic liquid crystal and the resin matrix includes spacers such as ceramic particles, plastic particles, and glass fibers for controlling the gap between the substrates.
Pigments, dyes, viscosity modifiers, and other additives that do not adversely affect the performance of the liquid crystal may be added.

In a projection type display, a so-called liquid crystal light valve in which a light modulation layer is formed of a nematic liquid crystal is generally used. However, in this system, one of the P and S polarized light components of the read light phase-modulated by the liquid crystal layer passes through the polarizing beam splitter and is projected on the screen. For this reason, when the reading light is in a random polarization state, 50
% Or more is absorbed by the polarizing beam splitter. For this reason, the utilization rate of the reading light decreases, and the beam splitter generates heat.

On the other hand, polymer-dispersed liquid crystal is a liquid crystal material in which granular liquid crystal is dispersed in a transparent polymer such as acrylic. When the light modulation layer 8 is formed by the PDLC, the readout light is transmitted or scattered by the applied voltage applied to the PDLC, so that the polarization beam splitter is unnecessary and the light utilization is high. Further, since it is not necessary to provide alignment layers on both side surfaces of the liquid crystal layer, it is easy to manufacture a large-area spatial light modulator. In addition, since birefringence is not used for light modulation, even if the thickness of the liquid crystal layer is uneven, the spatial uniformity of the readout light is not significantly affected.

Next, an embodiment in which the photoconductive layer is a hydrogenated amorphous silicon film will be described with reference to FIGS. First, as shown in FIG. 6, one transparent electrode film 2A is provided on a glass substrate 17 whose surface is optically polished.

The photoconductive layer 1B made of a hydrogenated amorphous silicon film is preferably formed on the surface of the transparent electrode film 2A by a plasma chemical vapor deposition method. In this case, as described later, since the light-shielding layer 3 is formed by using a plasma enhanced chemical vapor deposition method, the photoconductive layer 1B and the light-shielding layer 3 are formed on the transparent electrode film 2A in the same film forming apparatus. It can be formed continuously. Of course, in this case, it is necessary to change the film forming gas with time.

As shown in FIG. 7, one transparent electrode film 2A
Is provided with a photoconductive layer 1B made of a hydrogenated amorphous silicon film, and a light shielding layer 3 is provided on the surface of the photoconductive layer 1B. After that, the dielectric multilayer film 4, the light modulation layer 8, the other transparent electrode film 2B, and the glass substrate 7 are provided according to the procedure described with reference to FIGS. Thus, the spatial light modulator 12B shown in FIG. 8 is obtained.

Next, the operation of such a spatial light modulator will be described with reference to the configuration example of FIG. The writing light emitted from the weak writing light source 10A passes through the liquid crystal television 11 to become input image light, and this input image light is condensed by a lens 13A, and is input to a spatial light modulator 12A, 1A.
2B is irradiated. This input image light is transmitted to the transparent electrode film 2A.
And enters the photoconductive layers 1A and 1B. On the other hand,
The read light emitted from the high-brightness read light source 10B is collected by the lens 13B, reflected by the mirror 25,
The light is adjusted by the lens 13 </ b> C and enters the light modulation layer 8.

Next, the incident light is mainly reflected by the dielectric multilayer film 4, passes through the light modulation layer 8 once again, is condensed by the lens 13C, and is projected on the screen 14 through the lens 13D.

The writing light is shaded by the liquid crystal television 11. In portions of the photoconductive layers 1A and 1B that are not exposed to light, the applied voltage between the pair of transparent electrode films 2A and 2B is mostly concentrated on the photoconductive layers 1A and 1B. Therefore, the applied voltage applied to the light modulation layer 8 does not reach the threshold voltage of the light modulation layer 8. On the other hand, the photoconductive layer 1
When light strikes A, 1B, the photoconductive layers 1A, 1A,
The electrical resistance of 1B is greatly reduced, and the voltage distributed to the light modulation layer 8 increases and exceeds its threshold.

Inside the light modulation layer 8 composed of PDLC,
When no voltage is applied to the light modulation layer 8, the liquid crystal molecules are arranged along the interface between the polymer and the liquid crystal. The shape of the liquid crystal particles is random. When the voltage applied to the light modulation layer 8 is low, the refractive indices of the liquid crystal particles and the polymer are significantly different.
The reading light changes its traveling direction many times in the light modulation layer 8 and is scattered. On the other hand, when the voltage applied to the light modulation layer 8 exceeds the threshold voltage and the liquid crystal molecules are oriented in the direction of the electric field, the read light passes through the light modulation layer 8 without being scattered.

By such a mechanism, a two-dimensional intensity distribution in the input image light is converted into a two-dimensional intensity distribution in the readout light. If the intensity of the reading light is made higher than the intensity of the writing light, the signal amplification factor becomes higher accordingly.

Further, a color moving image can be projected by using the above spatial light modulator. In this case, element 1
Three 2A and 12B are prepared and incorporated into, for example, the optical system shown in FIG.

In the optical system shown in FIG.
The writing light is modulated by 1B, 21R, and 21G to obtain each writing light image. Each of these writing light images passes through the lenses 22B, 22R, and 22G, respectively.
The light enters the spatial light modulators 20B, 20R, and 20G. Thus, writing of an image to each element is performed. On the other hand,
White light emitted from the white light source 23 is focused on the mirror 25 by the lens 24A. Of the reflected light, blue light is reflected by the dichroic mirror 26B and enters the element 20B. Visible light other than blue light passes through the dichroic mirror 26B. Next, the red light is reflected by the dichroic mirror 26R and enters the element 20R. The green light transmits through the dichroic mirror 26R and enters the element 20G.

Each of these primary color lights passes through the light modulation layer 8, is mainly reflected by the dielectric multilayer film 4, passes through the light modulation layer 8 again, and is projected on the screen 27 through the lenses 24B and 24C. You. Thereby, a full-color image is formed.

(Composition of Light-Shielding Layer) The light-shielding layer 3 is formed of an amorphous film containing germanium, carbon and silicon according to the present invention, and is 4.8 × 10 ^-2 W by plasma enhanced chemical vapor deposition. / Cm ² or less at high frequency power density. In this case, a mixed gas containing at least a germanium compound, a carbon compound and a silicon compound is used.

In particular, it is preferable to use a mixed gas of monosilane, germanium hydride, and methane, ethane or ethylene as a film forming gas. This is because if the flow rate of monosilane, germanium hydride, methane, ethane or ethylene is changed, the composition of the light shielding layer can be arbitrarily and easily changed.

(Experimental example of light-shielding layer) First, a light-shielding layer was formed on the surface of the substrate by a plasma CVD method. The flow rate of monosilane was 6.5 sccm, the flow rate of germanium hydride was 2.4 sccm, and the flow rate of ethylene was 29.5 s.
ccm. A 3.5 μm-thick light-shielding layer was formed under the conditions of a material gas pressure of 100 mtorr and a substrate temperature of 200 ° C. The composition of the light-shielding layer thus obtained has a carbon content of 56%.
Atomic%, silicon was 18 atomic%, and germanium was 26 atomic%. This composition ratio was determined by quantitative analysis using an Auger electron spectrometer.

The high-frequency power density was changed as shown in Table 2, the resistivity of each light-shielding layer was measured by a two-terminal method, and the light transmittance to light having a wavelength of 550 nm was measured by a spectrophotometer. The measurement results are shown in Table 2 and FIG.

(Experimental example of spatial light modulator) First, FIGS.
The spatial light modulator 12A was manufactured by the procedure as shown in FIG. However, the photoconductive layer 1A is formed of Bi ₁₂ SiO ₂₀ single crystal, and its size is 35 mm × 35 mm × 0.5 mm.
And The transparent electrode films 2A and 2B were formed by a vacuum evaporation method.

The light shielding layer 3 was formed by a plasma CVD method. This condition is the same as above, and the composition of the light shielding layer is also the same as above. Of course, the high frequency power density is shown in Table 2.
Was changed as shown.

The dielectric multilayer film 4 was formed by a vacuum evaporation method. The dielectric multilayer film 4 is a laminate of a TiO ₂ thin film and a SiO ₂ thin film, and a total of 20 alternately stacked. The following materials were mixed to form a PDLC, and a light modulation layer 8 having a thickness of 18 μm was obtained.

[0042]

TABLE 1 (nematic liquid crystal) mixed crystal ordinary refractive index of cyanobiphenyl n ₀ = 1.525 extraordinary refractive index n _e = 1.748 long axis of the liquid crystal molecules parallel to the direction of the relative dielectric constant = 17.6 LCD Dielectric constant in the direction perpendicular to the long axis of the molecule = 5.1 (ultraviolet curable polymer) Urethane polymer Refractive index n _p = 1.524 Curing wavelength range --- 350-380 nm (spherical spacer agent) Cured resin diameter- --------- 18μm

The spatial light modulator 12A manufactured under the conditions shown in Table 2 was set in the optical system shown in FIG. 9 or 10, an image was displayed, and the resolution was measured. The driving voltage of the element 12A is 50
And V _{rm s,} drive frequency is set to 30 Hz, the wavelength of the writing light is a 380～490Nm, the wavelength of the reading light 45
0 to 570 nm. The writing light intensity is 300 μW /
cm ² and the readout intensity was 300 mW / cm ² .
Optical amplification factor is 10 ³ times. Table 2 shows the measurement results.

[0044]

[Table 2]

As can be seen from Table 2 and FIG. 11, when the high frequency power density is decreased, the resistivity increases and the light transmittance decreases. In particular, when the high-frequency power density is 4.8 × 10 ⁻² or less, the resistivity becomes 3 × 10 ⁹ Ω · cm or more, and the light transmittance becomes 0.8% or less. As a result, the resolution becomes 17 lp /
mm or more. If the resolution is lower than this, the number of pixels is insufficient on the projection screen, and the screen becomes unclear.

When the high-frequency power density is 3.5 × 10 ⁻² W / cm ² or less, the resolution is further remarkably improved, and 1.6 × ⁻² 10 W
/ Cm ² or less is more preferable. However, when the high frequency power density is less than 1.0 × 10 ⁻⁴ W / cm ² , the plasma becomes unstable.

(Experiment 2) In the same manner as in Experiment 1, the resistivity of the light-shielding layer, the light transmittance to light having a wavelength of 550 nm, and the resolution of the spatial light modulator were measured. However, the high frequency power density when forming the light shielding layer is 4.8 × 10 ⁻² or 1.6.
× 10 ^-2 W / cm ² . Further, the respective flow rates of monosilane, germanium hydride, and ethane were adjusted, and the composition of the light-shielding layer was changed as shown in Tables 3 and 4. The results are shown in Tables 3 and 4.

[0048]

[Table 3]

[0049]

[Table 4]

As can be seen from Tables 3 and 4, in particular, when the proportion of germanium is 12.5 to 35 at%, the proportion of carbon is 25 at% or more, and the proportion of silicon is 5 at% or more. In addition, the resolution was 17 lp / mm or more, and a clear image was obtained.

[0051]

As described above, according to the present invention, a well-balanced light shielding layer having a large resistivity and a small light transmittance can be manufactured. As a result, the contrast and resolution of the spatial light modulator are improved, and a clear projected image can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state in which one transparent electrode film 2A is formed on the surface of a photoconductive layer 1A.

FIG. 2 is a cross-sectional view showing a state in which a light shielding layer 3 is provided on a photoconductive layer 1A.

FIG. 3 is a cross-sectional view showing a state in which a dielectric multilayer film 4 is provided on the surface of a light shielding layer 3.

FIG. 4 is a cross-sectional view showing a state in which a sealing material 5 is provided between a dielectric multilayer film 4 and another transparent electrode film 2B.

FIG. 5 is a sectional view showing a spatial light modulator 12A.

FIG. 6 is a cross-sectional view showing a state in which one transparent electrode film 2A is provided on the surface of a glass substrate 17.

FIG. 7 is a cross-sectional view showing a state in which a photoconductive layer 1B and a light shielding layer 3 are sequentially provided on the surface of a transparent electrode film 2A.

FIG. 8 is a cross-sectional view showing a spatial light modulator 12B.

FIG. 9 is a schematic diagram illustrating an example of a projection optical system.

FIG. 10 is a schematic diagram illustrating an example of a full-color projection optical system.

FIG. 11 is a graph showing the relationship between high-frequency power density, light transmittance, and resistivity.

[Explanation of symbols]

1A, 1B Photoconductive layer 2A One transparent electrode film 2B The other transparent electrode film 3 Light shielding layer 4 Dielectric multilayer film 7,17 Glass substrate 8 Light modulation layer made of liquid crystal material 12A, 12B, 20B, 20R, 20G Spatial light Modulation element 14 Screen 21B, 21R, 21G Liquid crystal panel 23 White light source 26B, 26R Dichroic mirror

Continued on the front page. (72) Inventor Jungo Kondo 72-7, Fujishima, Daisin-cho, Nisshin-cho, Aichi-gun, Aichi-ken No. 13 (72) Inventor Shoji Tange 3-150 Omoyama, Tenpaku-ku, Nagoya-shi, Aichi Japan Inspector Yagoto Dormitory Examiner Hiroo Ohara Hei 4-301819 (JP, A) JP-A-62-40430 (JP, A) JP-A-58-199327 (JP, A) JP-A-58-81627 (JP, A) Patent 2647779 (JP, B2) ( 58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 31/08 C23C 16/30 G02F 1/13 101 G02F 1/135

Claims (10)

(57) [Claims] 1. A photoconductive layer, one transparent electrode film provided on one surface of the photoconductive layer, a light shielding layer provided on the other surface of the photoconductive layer, and Manufactures a spatial light modulation element including at least the provided dielectric multilayer film, the light modulation layer provided on the dielectric multilayer film, and the other transparent electrode film provided on the surface of the light modulation layer. In doing so, 12.5-35 at.% Germanium and 25-82.
Producing the light-shielding layer consisting of an amorphous film substantially composed of 5 atomic% of carbon and 5 to 62.5 atomic% of silicon by controlling high frequency power density by plasma enhanced chemical vapor deposition. A method for manufacturing a spatial light modulator, comprising: 2. The method for manufacturing a spatial light modulator according to claim 1, wherein the amorphous film is formed at a high frequency power density of 4.8 × 10 ⁻² W / cm ² or less. 3. The light-shielding layer has a light transmittance of 0.8% or less for light having a wavelength of 550 nm and a resistivity of 3.0 × 10 ⁹ Ω.
3. The method for manufacturing a spatial light modulator according to claim 1, wherein the diameter is not less than cm. 4. The method for manufacturing a spatial light modulator according to claim 3, wherein a spatial light modulator having a resolution of 17 lp / mm or more is obtained. 5. The method for manufacturing a spatial light modulator according to claim 1, wherein a mixed gas of monosilane, germanium hydride, and methane is used as a film forming gas. 6. The method for manufacturing a spatial light modulator according to claim 1, wherein a mixed gas of monosilane, germanium hydride, and ethane is used as a film forming gas. 7. The method according to claim 1, wherein a mixed gas of monosilane, germanium hydride and ethylene is used as a film forming gas.
Or a method for manufacturing a spatial light modulator according to item 2. 8. The space according to claim 1, wherein the light-shielding layer and the photoconductive layer are continuously formed by plasma enhanced chemical vapor deposition inside the same film forming apparatus. A method for manufacturing a light modulation element. 9. The photoconductive layer is a hydrogenated amorphous silicon film or an amorphous silicon carbide film,
A method for manufacturing a spatial light modulator according to claim 8. 10. The spatial light modulator according to claim 1, wherein the photoconductive layer is formed of a Bi ₁₂ SiO ₂₀ single crystal, a Bi ₁₂ GeO ₂₀ single crystal, or a GaAs single crystal. Production method.