JPS62153936A - Liquid crystal light valve for color thermal writing - Google Patents

Abstract

PURPOSE:To obtain clock signals for controlling the position of writing from a filter of specific color of positional reference at all times regardless of change of the quantity of light of writing by constituting at least one or more kinds of diffraction grating with a diffraction grating having plural directions of grooves two-dimensionally. CONSTITUTION:Blue 21 and green 23 filters of a multicolor filter consist of diffraction grating of groove direction G124 and a red 22 filter consists of diffraction grating of groove direction G124 and groove direction G225. A liquid crystal light valve 1 carves diffraction grating 5 on a glass base 4 of writing laser light 2 side and forms a light absorbing film 6, a reflecting film 7 and a liquid crystal orientating film 8 successively. A transparent electrode film 10 and a liquid crystal orientaing film 8 are formed in another base 11, and liquid crystal 9 is held in it. + or - Primary diffracted light beams 14, 15 from diffraction grating corresponding to the red filter are different in the direction of diffraction from other + or - primary diffracted light beams 12, 13, and can be received separating by a photodetector 16. Accordingly, this can be made a clock signal of positional reference.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a color thermal writing liquid crystal light valve.

(Prior Art) In recent years, there has been a demand for displays that are highly accurate and can be partially rewritten in image processing using a converter, editing of newspaper pages, and L8I design.

As a display device with a high resolution of 2000 lines or more, there is a display that performs thermal writing using a liquid crystal laser beam.
Proceedings of the Varnish I Day (Pr.
oceeding of the 8. T.

D, ) 41978, pages 1-7 [Laser Selective Liquid Crystal Projection Display (r, ASBR-ADDRB8S
EDLIQUID CRY8TAL PROJEC'T
'ION DISPLAY) J.

According to this paper, an image can be recorded on a liquid crystal light valve 69 as shown in FIG. 6 by scanning with a laser beam 60, and a projection light 61 can be incident and reflected to display a -F image. The liquid crystal light valve 69 has a light absorption film 6
3. It has a structure in which a liquid crystal material 65 is sandwiched between a glass substrate 62 on which an aluminum reflective film 64 and a liquid crystal alignment film 68 are completely formed, and a glass substrate 67 on which a transparent electrode film 66 and a liquid crystal alignment film 68 are formed. When the laser light 60 enters the liquid crystal light valve 69, the laser light 60 is absorbed by the light absorption film 63 and converted into heat, which is transmitted through the aluminum reflection film 64 and the liquid crystal alignment film 68 to increase the temperature of the liquid crystal material 65.

A smectic liquid crystal is used as the liquid crystal material 65, and it changes to a nematic phase and a liquid phase by increasing the temperature of the smectic liquid crystal Vi, and is rapidly cooled when the laser beam 60 is removed, changing to a liquid state. The random arrangement of liquid crystal molecules is frozen, and the scattering nuclei are read out by the projection light 61 and displayed as pixels on the screen.

Since the display uses scattering, the display is a black and white pattern. A method for displaying at least three colors is described in Japanese Patent Application No. 60-1210361 entitled "Color Thermal Writing Liquid Crystal Projection Display and Writing Method Therefor". According to the above invention, the liquid crystal light valve includes three color filters made of a diffraction grating with an optical phase difference constraint λ, which are arranged periodically in a birch plane so that visible light in a specific wavelength range is diffracted in all O-order directions. It has a built-in three-color striped color filter, which can be formed with extremely fine widths and has a special feature of excellent light resistance and heat resistance.

In addition, when the laser beam is scanned with a light intensity below the threshold value for writing into the liquid crystal light valve, and all of the first-order diffracted light reflected and diffracted from the diffraction grating in the liquid crystal light valve is received, the first-order light t, Since the diffraction efficiency of the diffraction grating, which corresponds to the color filter, is different, the scanning position of the laser beam and the position of the color filter are subjected to intensity modulation in one-to-one correspondence, and the position can be determined from the electric signal obtained from the optical receiver. If all signals from a specific color filter to be used as a reference are extracted and used as a clock signal for writing position reference, writing to each color filter position is based on H1.

By providing a suitable delay time from the clock signal and giving the laser beam a sufficient amount of light to write on the liquid crystal light valve, each pixel can be written with high positional accuracy.

(Problem to be solved by the invention) However, since the first-order diffracted light that has undergone intensity modulation in one-to-one correspondence to the position of the color filter is absorbed by the light absorption film, the electric signal obtained by receiving the light is is very weak. Furthermore, the intensity modulation of the first-order diffracted light due to the difference in diffraction efficiency has a small modulation amplitude, and in order to always extract all the received light signals from a filter of a specific color regardless of changes in the amount of writing light, a gate circuit is required. Processing is complicated.

In addition, the transmittance or reflectance of a color filter consisting of a diffraction grating is theoretically determined by the amount of optical phase difference depending on the depth of the diffraction grating, so there are three types of color filters, for example, red, red, green.

When configured with blue, the chromaticity of the projection light source:
Sometimes there are not enough colors on the projection screen.

The purpose of the present invention is to be able to completely separate the first-order diffracted light from a specific color filter and the first-order diffracted light from other color filters, obtain a position-based clock signal with a large width, and write. To provide a color thermal writing liquid crystal light valve capable of easily performing position control signal processing and projecting the entire screen with high visibility and chromaticity.

(Means for Solving the Problems) The color thermal writing liquid crystal light valve of the present invention has a writing-side base in which a light-absorbing film, a light-reflecting film, and a liquid crystal alignment are polished on a transparent base, and a transparent base. A transparent electrode film and a liquid crystal alignment film are sequentially laminated on the projection mil+ substrate and a liquid crystal, and has a structure in which the liquid crystal is sandwiched between both liquid crystal alignment films on the surfaces of the writing side substrate and the projection side substrate. , in a color thermal writing liquid crystal light valve in which a diffraction grating giving at least two or more types of optical phase difference is periodically formed in the writing side substrate, at least one kind of monotheism, The first diffraction grating is composed of a two-dimensional diffraction grating with a plurality of groove directions.

(Principle and operation of the invention) A multi-color filter in which at least two types of color filters are periodically arranged in a plane and output from a diffraction grating with an optical retardation metal is capable of detecting visible light in a specific wavelength range of projected light. In addition to diffracting only the laser beam and displaying color on the projection screen, the writing laser beam is scanned with a light intensity below the threshold for writing on the liquid crystal light valve, and by receiving the diffracted light, the color filter and the writing light It has the effect of being able to know the entire mutual positional relationship between the two and writing with high positional accuracy. Here, if the diffraction grating of the multi-color filter is formed to have at least one type of diffraction grating or a plurality of groove directions to be used as a position reference, the rich laser light will be directed to the liquid crystal light valve. When scanning with a light intensity below the threshold, the diffracted light from the diffraction grating that has the reference pressure at the position is also diffracted in a direction different from that of other diffraction gratings, so it can be received separately from the diffracted light from other diffraction gratings, and the The signal obtained by this method has a wider modulation width than the conventional example, and a signal from a filter of a specific color that is always used as a position reference can be obtained regardless of changes in the amount of writing light. In addition, the depth of the diffraction grating with the groove direction of the number used as the position reference can be changed for each different groove direction, so the wavelength of the writing laser beam, the refractive index of the medium, the grating It is also possible to select the entire depth of the grating so that the reflection-order diffraction light efficiency determined by the depth of the light is high, and even if there is absorption in the light-absorbing film, it is still sufficient to output the signal wire for position reference. It is possible to obtain the same amount of light. From the position-based clock signal obtained in this way, by passing the gold film through the gold film and giving the laser beam enough light to write on the liquid crystal light valve, the entire pixel can be written at the position of each color filter with high positional accuracy. It becomes possible to enter.

FIG. 7 is a diagram showing the principle of a color filter using a diffraction grating used in the present invention. In FIG. 7, a light reflecting film 7 is formed on the surface of a glass substrate 70 having rectangular irregularities with a depth a.
There is a reflection type diffraction grating coated with 1, and when white light 72 is incident on it, mainly 0th-order diffraction light 73, +1st-order diffraction light 74, and -1st-order diffraction light 75 are diffracted. The +1st-order diffracted light 74 and the -1st-order diffracted light 75 are diffracted in different directions depending on the wavelength λ, and the diffraction direction depends on the pitch of the diffraction grating. Wavelength distribution T(
λ) depends on the depth a of the grating. If the refractive index of the medium through which the light travels is fn, then the wavelength distribution of the 0th order light of the reflection type diffraction grating T(λ) is obtained by the Fi order equation.

T(λ)=cos''(2πna/λ) (1) In Figure 8, the refractive index n is 1.5 for the liquid crystal, and the depth a of the diffraction grating is (a) 290 nm, (b) 520nm
.

(c) Shows the wavelength distribution of the O-order light at 240 nm.

The colors for each case are (,1 blue, (b) green, and (C) red.

FIG. 3 is a perspective view of a diffraction grating with two types of groove directions. Wavelength distribution T1 of the 0th order light of the diffraction grating with depth al and groove direction G1 and the diffraction grating with depth It and groove direction G2, respectively
(λ) and 'rt(λ) are expressed by a comfortable equation as in equation (1).

'r+(λ) = cos2(2πnal/λ)(2)
T2(λ1-cos''(2πna27'λ) (3) When these two types of diffraction gratings are formed by overlapping each other so that the groove directions are perpendicular to each other as shown in Fig. 3, the wavelength distribution of the zero-order light T, (
λ) is obtained by the following formula.

T, (λl-'rl(λ)·'rdλ) (4) (Example) FIG. 2 is a diagram showing an example of a multicolor filter used in a color thermal writing liquid crystal light valve according to the present invention. It consists of a multicolor filter ht21, red 22, and green 23.

The filters 1121 and 23 in green are composed of diffraction gratings in the groove direction G124, and the filter in red 22 is composed of a diffraction grating in the groove direction G24 and the groove direction G225 perpendicular thereto. If the medium that provides optical retardation is gold or liquid crystal and the refractive index is 1.5,
The depth of the diffraction grating is 290 nm for Blue 21.

Green 23 is 520nm, red 22 is 240nm and 410n
It is m. The lattice constant of the diffraction grating is 2 μm and 10 μm
One pixel is entirely formed with a size of m x 30 μm. Therefore, red, green, and blue filters each having 1000x1000 pixels can be arranged on a 30 mm square substrate. Here, all the lattice constants of the diffraction gratings are made equal, but it is not always necessary to make all the lattice constants equal, for example, the lattice constants of gratings with different groove directions can be used.

To imprint the diffraction grating shown in Figure 2 on a substrate, here a glass substrate, first the diffraction grating of one type of color filter is etched to a certain depth by chemical etching and isobaric ion milling on the substrate masked with photoresist. Form with
It is sufficient to repeat this procedure by changing the position, depth, and direction of the groove.

In addition, a similar multicolor filter can be obtained by forming the entire diffraction grating by patterning IC4 photosensitive resin, or by taking a mold replica from the once formed diffraction grating and transferring it to plastic resin.

Among the above forming methods, the characteristics of the multicast filter obtained by transferring it to the acrylic resin using a mold are described below.
The chromaticity of the color filter and the diffraction efficiency of the first-order diffraction light could be increased by completely overlapping the diffraction gratings 4C [direction G, 250 diffraction gratings]. Standard C as a projection light source
When using a light source, the chromaticity coordinates of the red 22 filter (1
, the diffraction grating with depth 240 nm and groove direction G124 only has X-0, 49, Y=0.37, but when all the diffraction gratings with rC depth 410 nm and groove direction G225 are combined, X= 0.53, Y=0.35, and the chromaticity gamut area was improved by about 15 inches. Also, the depth is 410n
The diffraction grating with groove direction G and 25 had a first-order diffraction efficiency of 40 inches with respect to the wavelength of the writing laser beam of 0.83 μm. In addition, for example, if a diffraction grating with a depth of 3·l 3 nm and a groove direction of 0225 is superimposed on a green 23 diffraction grating, the chromaticity gamut area increases by 25%, and the first-order diffraction light efficiency of the writing light increases by 24%. You can get As described above, by forming all the diffraction gratings in a filter of a specific color so as to have a plurality of groove directions, a multicolor filter with good chromaticity and high first-order diffraction efficiency of one writing light can be realized.

FIG. 1 is a perspective view of one embodiment of a color thermal writing liquid crystal light valve according to the present invention. The color thermal writing liquid crystal light valve l has a diffraction grating 5 shown in FIG. 2 on the glass substrate 4 on the side of the writing laser beam 2, as compared to the liquid crystal light valve shown in FIG.
The difference is that it is engraved. An n-vi compound semiconductor film containing Cd, a Te
'fI: An IT-Vl group compound semiconductor film, a dye absorption film, and a dielectric multi-interference film including a film are formed by vapor deposition or the like, and an Al film is further vapor-deposited as a reflective film 7, and a polymer film is formed as a liquid crystal alignment film 8 thereon. or an 8i0 film by oblique deposition. In addition, ITO (indium) is used as the transparent electrode film 10 on the other substrate 11.
A liquid crystal alignment film 8 is further formed. The liquid crystal 9 is a smectish liquid crystal, for example 0.
CRP (octyl cyano bifunyl) and DCBP
(Decyl-Cyano e Bia-Niel) or a mixture thereof can be used.

Writing in the color thermal writing liquid crystal light valve 1 constructed in this manner is performed by irradiating the laser beam 2 in the same manner as in the past. When using, for example, red, green, and blue color filters to generate a color image, in order to obtain a red image, the portions of the liquid crystal corresponding to the green and blue color filters may be written with laser light. Green, blue painting (
1 can be obtained by writing with a laser beam on the liquid crystal portions corresponding to the red and blue color filters and red and green color filters, respectively. Yellow, purple, and blue-green are obtained by additive color mixing. Further, by controlling the writing laser beam t' to give gradation, a full color image can be realized.

In order to select the position f#t of each color filter that is related to the non-linearity of the optical scanning writing optical system and write on the liquid crystal 9 by irradiating the laser beam 2, the positional relationship between the laser beam 2 and each color filter must be selected. need to know. For this purpose, the laser beam 2 scans with a constant light amount below the threshold value for writing into the liquid crystal light valve 1 during the horizontal scanning period by the optical deflector 3. Laser light 2
When scanned on a diffraction grating corresponding to blue and green filters, +1st-order diffracted light 12 and -1st-order diffracted light 13 are shown by broken lines.
When reflected and diffracted and scanned on the diffraction grating corresponding to the red filter, +1st order diffracted light 1 in different directions shown by dotted lines
4. -1st-order diffracted light 15 is also reflected and diffracted (14) ”,
.

do. In this way, the ±1st-order diffracted light 14, 15F'i and other +1st-order diffracted light 12.13 from the diffraction grating corresponding to the red filter 9, which have different diffraction directions, can be received separately by the light receiver 16. However, it is sufficient that at least one of the ±1st-order diffracted lights 14 and 15 is fully received. Since the electrical signal obtained from the photoreceiver is obtained only when the laser beam 2 is completely scanning over the red color filter used as a position reference, this can be used as a position reference clock signal. When writing to the position of each color filter, when there are red, green, and blue image signals, set an appropriate delay time from the position-based clock signal, and make sure that the laser beam has enough light intensity to write to the liquid crystal light valve. It is done by giving.

Figures 4m, (2) and 31 are diagrams showing examples of electrical signals obtained by receiving the first-order diffracted light of the writing light.

Figure 5 (+), (21, (Compared to the conventional example of (31), it was possible to obtain a clock signal for writing position control with a large image variation amplitude regardless of changes in the amount of writing light without using a gate circuit. .

(Effects of the Invention) As described in detail above, the present invention has the advantage that the clock signal for controlling the writing position can always be obtained from a filter of a specific color with the entire position as a reference, regardless of changes in the amount of incident light. It becomes possible to write to all color filter positions of each pixel with high precision, and one effect is to improve the chromaticity of the color filter.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of a color thermal writing liquid crystal light valve according to the present invention, FIG. 2 is a diagram showing an embodiment of a multicolor filter used in the color thermal writing liquid crystal light valve according to the present invention, and FIG. 4 is a perspective view of a diffraction grating having a plurality of groove directions used in the present invention, FIG. 4 is a diagram showing a receiver signal obtained by the present invention, FIG. 5 is a diagram showing a conventional receiver signal, and FIG. 6 is a diagram showing a conventional receiver signal. The cross-sectional views of conventional liquid crystal light valves, FIGS. 3 and 7, are diagrams illustrating the principle of wavelength selection of the diffraction grating used in the present invention. In the figure, 1: color thermal writing liquid crystal light valve, 2
: laser beam, 3: optical deflector, 5: diffraction grating, 12.14
:+1st order diffracted light, l 3 , t 5 knee 1st order diffracted light, 16: light received gain, respectively. 1, Hewa ＼-N+1ノν, %, %J
%m ((\to))su\toshu

Claims (2)

[Claims] (1) A writing side base in which a light absorption film, a light reflection film, and a liquid crystal alignment film are sequentially laminated on a transparent base; a transparent electrode film on the transparent base;
It consists of a projection-side substrate on which liquid crystal alignment films are sequentially laminated, and a liquid crystal, and has a structure in which the liquid crystal is sandwiched between both liquid crystal alignment films on the surfaces of the writing-side substrate and the projection-side substrate, and at least Diffraction gratings that provide two or more types of optical phase differences are periodically formed in a plane, and at least one type of the diffraction gratings is a diffraction grating that has a two-dimensional plurality of groove directions. A color thermal writing liquid crystal light bulb. (2) The diffraction grating has a plurality of two-dimensional groove directions,
The color thermal writing liquid crystal light valve according to claim 1, wherein at least one groove direction is formed with a depth such that high diffraction efficiency can be obtained with respect to the wavelength of the writing light. .