JP2000214331A - Production of hologram filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize production of a hologram filter having high diffraction efficiency and uniform diffraction characteristic in the production of the hologram filter using an interference exposure method. SOLUTION: The interference exposure method in which nearly parallel incident light beams are obliquely radiated to a mask through a prism 11, and hologram photosensitive material 17 is exposed with a diffracted light beam and a transmitted light beam obtained through the mask is used in this production of the hologram filter. At such a time, the prism 11 used at the time of interference exposure is equipped with light absorption layers 30 and 32 absorbing partial incident light beam reflected in the prism 11 on one inclined surface opposed to another inclined surface being an incident surface on which the incident light beam is made incident.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method of manufacturing a hologram filter for diffracting and condensing incident light into a plurality of lights having different wavelength bands.

[0002]

2. Description of the Related Art Heretofore, the present applicants have developed a projection type color liquid crystal display device using a hologram lens array as a color filter. This color filter uses the hologram's diffraction spectral function to convert white light into R light.
Each color light of GB can be extracted in a predetermined direction. Unlike a normal color filter using a dye or a pigment, there is almost no loss of light due to absorption, so that high light use efficiency can be obtained in principle. Therefore, the present invention is effective in a projection type color liquid crystal display device in which improvement in brightness is particularly required.

FIG. 8 is a cross-sectional view schematically showing a structure of a spatial light modulator used in a projection type color liquid crystal display device disclosed in a prior application published by the present applicant (Japanese Patent Application Laid-Open No. Hei 9-189809). FIG.

The liquid crystal panel 111 has a silicon substrate 121
And an active matrix drive circuit 122 formed on the silicon substrate 121, and a pixel electrode layer 123 in which pixel electrodes 123r, 123g, and 123b selectively controlled and driven by the active matrix drive circuit 122 are regularly arranged. , A dielectric mirror film 124, an alignment film 125, and a light modulation layer 12 in which liquid crystal is sealed with spacers.
6, an alignment film 127, and a transparent common electrode layer 128 are sequentially laminated.

The hologram color filter 113 is formed of a so-called hologram lens array in which unit hologram lenses are regularly arranged, and diffracts read light (white light) including three primary colors of R, G, and B for each color light. It has a function of splitting the light and condensing it at the positions of the pixel electrodes 123r, 123g, and 123b corresponding to R, G, and B in the liquid crystal panel 111. Therefore, it is possible to provide a projection type color liquid crystal display device using incident light without waste. Note that, as shown in FIG.
In the case of including 4, the light collecting destination is the dielectric mirror film 124.

[0006]

FIG. 9 is a diagram showing a configuration at the time of exposure in a method of manufacturing a hologram filter using an interference exposure method.

As shown in FIG. 9, an EB substrate 213 as a hologram master substrate is tightly fixed on a thin glass 218 having a hologram photosensitive material 217 formed on the surface thereof through an oil 216 for adhesion. Further, a trapezoidal prism 211 is placed on the EB substrate 213 via a contact oil 212. Exposure light enters from one slope of the trapezoidal prism 211.

The EB substrate 213 is, as shown in the figure, a mask pattern (chrome mask 215) of a hologram master on a glass substrate 214 using an EB (electron beam) method.
Refers to the substrate on which is formed. That is, first, a metal thin film such as chromium (Cr) is formed on a glass substrate by a sputtering method or the like, and then patterning is performed using a photolithography process. When a resist is exposed, an electron beam (EB) is used.
The resist pattern is used to etch the metal thin film, and a metal mask (chrome mask 2) is used.
15) The pattern was obtained.

The chrome mask pattern is composed of a fine fringe pattern, and a part of the light incident on the mask is transmitted as it is and partly diffracted. The interference light of the two light fluxes of the transmitted light and the diffracted light forms the hologram photosensitive material 21.
7 is subjected to direct interference exposure. Thereafter, the hologram photosensitive material 21
By developing No. 7, a hologram filter can be obtained.

The characteristics of the hologram filter, when used in a liquid crystal display device, largely reflect the image characteristics on a screen. If the diffraction efficiency of the hologram filter is low, the light utilization rate of the display device decreases and the screen becomes dark. If there is unevenness in the characteristics of the hologram filter depending on the location, it appears as grayscale unevenness on the screen.

A projection type liquid crystal display device is manufactured using a hologram filter manufactured by using the above-described conventional interference exposure method, and a screen screen is projected. Was noticed on the screen.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method of manufacturing a hologram filter capable of eliminating unevenness in characteristics of a hologram filter and obtaining higher diffraction efficiency.

[0013]

A first feature of the method of manufacturing a hologram filter according to the present invention is that a substantially parallel incident light is obliquely applied to a hologram master substrate via a prism and obtained through the hologram master substrate. In a method for manufacturing a hologram filter using an interference exposure method of exposing a hologram photosensitive material with diffracted light and transmitted light, the prism absorbs light on another inclined surface facing one inclined surface serving as an incident surface of the incident light. Is to have a layer.

According to the first feature of the present invention, in the interference exposure step, a part of the light incident from one inclined surface of the prism is reflected by a hologram master substrate surface or the like, and a part of the light is reflected. The light exits through the other slope of the prism. At this time, reflection occurs at the interface due to the difference in the refractive index between the prism and the air layer. However, if there is a light absorbing layer, light reaching the other inclined surface of the prism is absorbed by the light absorbing layer. Can be suppressed. Therefore, the occurrence of partial exposure fog of the hologram photosensitive material caused by the reflected light can be suppressed. As a result, unevenness in the diffraction characteristics of the hologram filter can be prevented by more uniform exposure.

A second feature of the method for manufacturing a hologram filter of the present invention is that a substantially parallel incident light is obliquely applied to a hologram master substrate, and the diffracted light and transmitted light obtained through the hologram master substrate are transparent. In a method of manufacturing a hologram filter using an interference exposure method for exposing a hologram photosensitive material formed on a surface of a support substrate, the transparent support substrate has a light absorbing layer on a back surface.

According to the second feature of the present invention, in the interference exposure step, light that has passed through the hologram photosensitive material and reaches the back surface of the support substrate can be absorbed by the light absorbing layer. Therefore,
Light reflected on the outer surface of the support substrate can be suppressed from contributing to the exposure of the hologram photosensitive material as return light. The exposure by the return light is performed from a direction completely different from the incident angle of the originally intended exposure light, so that interference exposure different from the design is performed, and as a result, the diffraction efficiency of the hologram filter is reduced. Since the presence of the light absorbing layer on the back surface of the support substrate can prevent the generation of return light due to reflection, it is possible to suppress a decrease in the diffraction efficiency of the hologram filter.

A third feature of the method of manufacturing a hologram filter according to the present invention is that a hologram master substrate having a thin film pattern formed on the back surface of a transparent substrate is irradiated with obliquely parallel incident light from an oblique direction. A method of manufacturing a hologram filter using an interference exposure method of exposing a hologram photosensitive material with diffracted light and transmitted light obtained through the hologram filter, wherein the incident angle of the exposure light to the hologram master substrate is θ, and the plate thickness of the hologram master substrate is In this case, the irradiation area of the exposure light on the hologram master substrate has a margin width of 2 dtan θ or more at the incident end.

A part of the light applied to the hologram master substrate is reflected on the back surface of the thin film pattern, and a part of the light is re-reflected on the transparent substrate surface and is incident on the hologram master substrate. It contributes to exposure of a certain area on the photosensitive material. The presence or absence of the exposure fog causes a difference in the diffraction characteristics of the hologram filter, and further affects the image characteristics of a liquid crystal display device using the same. Therefore, if there is a region where the exposure fog exists and a region where the exposure fog does not exist on the hologram photosensitive material used as the color filter, it is recognized as a gradation difference on the image. However, in the interference exposure process,
If the irradiation area of the exposure light on the hologram master substrate is adjusted so as to have a margin width of 2 dtan θ or more at the incident end, uniform exposure fog occurs over the entire effective hologram photosensitive material area used as a color filter, The diffraction characteristics can be made uniform.

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1A is a diagram showing a configuration at the time of exposure in a hologram filter manufacturing method using an interference exposure method according to a first embodiment.

To manufacture a hologram filter, first, a glass substrate 18 having a thickness of about 1 mm serving as a support for the filter is used.
A film-shaped hologram photosensitive material 17 having a thickness of about 3 μm to 5 μm is attached thereon. As the hologram photosensitive material 17, for example, a commercially available material such as Omnidex (trade name) manufactured by DuPont can be used. In addition, a hologram photosensitive material made of silver salt photosensitive material, photopolymer, photoresist, gelatin dichromate, or the like can be used. In addition, you may coat on a glass substrate using a liquid photosensitive material instead of a film-shaped photosensitive material.

Next, as shown in FIG. 1A, an EB substrate 1 serving as a hologram master is placed on a hologram photosensitive material 17.
Further, the trapezoidal prisms 11 are further fixed on the EB substrate 13 in the gaps via the contact oil 12, respectively.

At this time, the EB substrate 13 is mounted on the chrome mask 1
5 with hologram photosensitive material 17 and chrome mask 15
Are arranged so that they can face each other via the oil 16 for close contact. In addition, as the adhesion oils 12 and 16, a material having a refractive index close to that of the glass substrate 14 or the like is selected in order to reduce reflection.

The feature of the method of manufacturing the hologram filter according to the first embodiment is that, in the interference exposure step, the trapezoidal prism 11 is provided with a light absorption layer 30 on one of the slopes facing the exposure light incident surface. Is to form The light absorbing layer 30 may be blackboard glass, a black film or a black printed body. Any material that absorbs the wavelength of light used as exposure light may be used.

Exposure light enters from one slope of the trapezoidal prism 11 on the right in the figure and enters the EB substrate 13 from an oblique direction.
A part of the exposure light passes through the chrome mask 15 as it is, and a part is diffracted. The hologram photosensitive material 17 is subjected to interference exposure by the diffracted light and the transmitted light.

Hereinafter, the effect of the light absorbing layer 30 will be described in comparison with the case where no light absorbing layer is provided. As shown in FIG. 2, most of the light incident from one slope of the trapezoidal prism 11 is transmitted through the chrome mask 15 and is exposed to the photosensitive material as diffracted light. Due to the properties, some light is reflected at the surface. When the light absorption layer 30 is not provided on the slope of the trapezoidal prism 11, the reflected light is reflected in the direction of the other slope facing the one slope on which the incident light of the trapezoidal prism 11 is incident, and is emitted to the outside. At this time, due to the difference in the refractive index between the trapezoidal prism 11 and the air, part of the light is reflected by the slope of the trapezoidal prism 11 and returns. This return light exposes the hologram photosensitive material again through the chrome mask 15.

The chromium mask 1 irradiated with the exposure light which is directly incident on the region on the chrome mask 15 irradiated with the return light
There is an offset in the area above 5. FIG. 3 is a diagram schematically showing this. Each light incident on the chrome mask 15 is converted into hologram photosensitive material 17 as diffracted light or transmitted light.
Is exposed. Therefore, the hologram photosensitive material 17 has an area a in which fog exposure does not occur and an area b in which fog exposure occurs due to return light reflected by the slope of the trapezoidal prism 11. Such exposure unevenness results in uneven diffraction characteristics when a color filter is used.

When a liquid crystal display device is manufactured using a hologram filter having uneven diffraction characteristics, and an image is projected on the screen 40, the unevenness of the diffraction characteristics of the hologram filter shows regions A and B having a gradation difference on the screen. Will be visually recognized.

As described above, when there is no light absorption layer, a gradation difference on an image occurs due to uneven diffraction characteristics of the hologram filter due to the presence of reflected light on the slope of the trapezoidal prism 11. On the other hand, as shown in FIG. 1A, if the light absorbing layer 30 is formed on one of the trapezoidal prisms 11 on the other slope facing the slope of the exposure light, the chrome mask 15 Light that is reflected by the surface and reaches the other inclined surface of the trapezoidal prism 11 is almost completely absorbed by the light absorbing layer 30, so that no reflection occurs, and uneven exposure due to return light as shown in FIG. 17 does not occur. As a result, it is possible to obtain a hologram filter whose diffraction characteristics are more uniform in a place, and in a liquid crystal display device using this,
The occurrence of gradation unevenness on the screen can be prevented, and the image characteristics can be improved. (Second Embodiment) FIG. 1B is a diagram showing a configuration at the time of exposure in a method of manufacturing a hologram filter using an interference exposure method according to a second embodiment.

The feature of the method of manufacturing a hologram filter according to the second embodiment is that, as shown in FIG. 1B, it becomes a support for the hologram photosensitive material 17 when the hologram photosensitive material 17 is subjected to interference exposure. That is, the light absorbing layer 32 is provided on the back surface of the thin glass 18. The light absorbing layer 32 may be any material such as black glass or black film as long as it can absorb light having an exposure wavelength. When the hologram filter is incorporated in the light modulation element of the liquid crystal display device, the light absorption layer 32 is used after being peeled off.

Hereinafter, the effect of the light absorbing layer 32 will be described in comparison with the case where the light absorbing layer 32 is not provided. As shown in FIG. 2, when the light absorbing layer 32 is not provided, a part of the light applied to the hologram photosensitive member 17 at the time of exposure passes through the thin glass 18 as it is and is emitted into the air. When emitted, some light is re-reflected at the interface due to the difference in the refractive index between glass and air. The re-reflected light exposes the hologram photosensitive material 17 from a direction opposite to the original exposure light.

As described above, the hologram photosensitive material 17 is not exposed to light incident from a predetermined direction through the hologram master substrate (EB substrate 13) but is exposed to light from a direction different from the predetermined direction. Then
The completed hologram filter does not exhibit an ideal diffraction characteristic as shown in FIG. 4A, and emits diffracted light in a direction different from the original ideal diffraction characteristic as shown in FIG. 4B. I will.

On the other hand, when the light absorbing layer 32 is provided on the back surface of the thin glass 18 at the time of exposure as in the second embodiment shown in FIG. The light that reaches the thin glass 18 is the light absorbing layer 3
2, the occurrence of reflection on the surface of the thin glass 18 is suppressed. Therefore, the influence of the exposure due to the reflected light is suppressed, and a substantial decrease in the diffraction efficiency of the hologram filter due to this can be suppressed. As a result, by using the hologram filter manufactured by this manufacturing method, the light use efficiency of the liquid crystal display device can be improved.

As shown in the first embodiment, the light absorbing layer 30 may be provided on the slope of the trapezoidal prism 11 used at the time of exposure also in the manufacturing method according to the second embodiment. (Third Embodiment) FIG. 5 is a view showing a schematic configuration at the time of exposure in a hologram filter manufacturing method using an interference exposure method according to a third embodiment. The basic configuration at the time of exposure in the hologram filter manufacturing method according to the third embodiment is the same as the first configuration shown in FIGS. 1A and 1B.
This is the same as the configuration at the time of exposure in the embodiment. Here, for convenience of explanation, a state in which light passing through the aperture 36 is transmitted through the EB substrate 13 is schematically illustrated.

The incident light passes through the trapezoidal prism 11 to the EB
The light is obliquely incident on the substrate 13. The EB substrate 13 includes a chrome mask 15 and a glass substrate 14. The incident light is divided into light that travels straight through the light and light that is diffracted, and the hologram photosensitive material 17 is subjected to interference exposure. At this time, part of the exposure light is reflected by the metallic properties of the chrome mask 15 surface.

In the first embodiment, the light reflected by the chrome mask 15 enters the trapezoidal prism 11 and the influence of light reflected on the prism slope is considered. Consideration will be given to the influence of reflected light at the interface between the respective layers caused by a slight difference in the refractive index between the oil for use 12 and the glass substrate 14.

As shown in FIG. 6B, the aperture 36
Most of the light obliquely incident from above and to the right in the figure passes through the chrome mask 15 as it is and goes straight or is diffracted, but part of the light is reflected by the surface of the chrome mask 15. Further, a part thereof is re-reflected at the interface between the trapezoidal prism 11 and the contact oil 12 or the interface between the contact oil 12 and the glass substrate 14 and returns to the chrome mask 15. A part of this return light is transmitted or diffracted through the chrome mask 15 and contributes to the exposure of the hologram photosensitive material 17. In the drawing, only the straight transmitted light is shown for convenience. These return lights cause exposure fog in a certain area (left side in the figure) of the hologram photosensitive material 17.

FIG. 7 shows a state of an image on a screen 40 of a conventional liquid crystal display device using a hologram photosensitive material 17 produced in such an exposure mode as a color filter.

An image on the screen corresponding to the right side in the figure where the hologram photosensitive material region where the exposure fog has not occurred is used as a color filter, and an image on the screen corresponding to the hologram photosensitive material region where the exposure fog has occurred is used as the color filter In the region, a gradation difference that can be visually recognized occurs. In particular, since the line-shaped gradation difference is conspicuous, it tends to be a problem in evaluating the screen.

As is apparent from FIG. 5, the chrome mask 15 of the exposure light obliquely incident from the right hand in the drawing is shown.
The boundary of the region where the exposure fog occurs, which is reflected on the surface and further re-reflected on the surface of the glass substrate 14 or the like, depends on the incident angle when the exposure light enters the chrome mask 15 and the thickness of the EB substrate 13.

Now, assuming that the incident angle of the exposure light is θ and the thickness of the EB substrate 13 is d, the area of the chrome mask 15 where the exposure light does not fog is narrowed by the aperture 36. As a result, 2 dta from the end of the exposure area (the end of the exposure light incident side)
It corresponds approximately to the width of nθ. As shown in FIG. 1, since the chromium mask 15 and the hologram photosensitive material 17 are in contact with each other via the oil for contact, the width of the region on the hologram photosensitive material 17 where no exposure fog occurs also corresponds to approximately 2 dtan θ.

In the method of manufacturing the hologram filter according to the present embodiment, when the exposure light is incident at an incident angle θ and the thickness of the EB substrate 13 is d, as shown in FIG. The aperture is adjusted so that a region having a width of 2 dtanθ or more from the incident side end as a light irradiation region is secured as a margin region for exposure light irradiation, and a region excluding this margin region is set as an effective hologram filter region.

That is, as shown in FIG. 5, only an area having an exposure fog is used as an effective hologram filter area, and a stepwise gradation difference does not substantially appear on the screen. Can obtain a good uniform image.

Although the contents of the present invention have been described with reference to the embodiments, the present invention is not limited to the above embodiments. For example, not only can each embodiment be implemented independently, but also the first to third embodiments may be arbitrarily combined. It will be apparent to those skilled in the art that various modifications and improvements other than the above are possible.

[0043]

A first feature of the present invention is that, in the method for manufacturing a hologram filter using the interference exposure method as described above, the prism used at the time of the interference exposure has one inclined surface serving as an incident surface of the incident light. And a light absorbing layer that absorbs a part of the incident light reflected in the prism on the other inclined surface opposite to the above. According to this, the occurrence of light reflection at the interface can be suppressed due to the presence of the light absorbing layer provided on the slope of the prism. Therefore, partial exposure fog of the hologram photosensitive material caused by the reflected light can be suppressed. Since the gradation difference on the screen image caused by the partial exposure fog disappears, the image characteristics are improved.

A second feature of the present invention resides in that a light absorbing layer is provided on the back surface of the transparent support substrate on which the hologram photosensitive material is formed. According to this, the generation of reflected light on the outer surface of the support substrate is suppressed, the return light of these reflected light is suppressed from exposing the hologram photosensitive material, and the diffraction efficiency of the hologram filter is reduced due to unnecessary exposure. Can be suppressed.

Further, a third feature of the present invention is that, when the incident angle of the exposure light to the hologram master substrate is θ and the thickness of the hologram master substrate is d, the irradiation area of the exposure light on the hologram master substrate is 2dta at side end
has a margin width of nθ or more. According to this, an exposure fog caused by reflection generated on the hologram master substrate uniformly occurs over the entire effective hologram photosensitive material area used as a color filter. Is eliminated, and the image characteristics are improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an exposure step in a method of manufacturing a hologram filter using an interference exposure method according to first and second embodiments of the present invention.

FIG. 2 is a diagram for explaining an effect of a method of manufacturing a hologram filter according to the first and second embodiments of the present invention.

FIG. 3 is a diagram for explaining an effect of the hologram filter manufacturing method according to the first embodiment of the present invention.

FIG. 4 is a view for explaining an example of a defect in diffraction characteristics caused by receiving unnecessary exposure in an exposure step in a hologram filter.

FIG. 5 is a configuration diagram of an exposure step showing a method of manufacturing a hologram filter according to a third embodiment of the present invention.

FIG. 6 is a diagram for explaining an effect of a method of manufacturing a hologram filter according to a third embodiment of the present invention.

FIG. 7 is a diagram for explaining an effect of a method of manufacturing a hologram filter according to a third embodiment of the present invention.

FIG. 8 is a device sectional view of a conventional light modulation element using a hologram filter.

FIG. 9 is a configuration diagram in an exposure step according to a conventional method of manufacturing a hologram filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Trapezoid prism 12, 16 Adhesion oil 13 EB substrate 14 Glass substrate 15 Chrome mask 17 Hologram photosensitive material 18 Thin glass 30, 32 Light absorption layer

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 2H049 AA25 AA34 AA51 AA60 AA64 CA01 CA05 CA09 CA15 CA17 CA22 CA28 CA30 2K008 AA00 BB04 DD13 DD15 DD22 HH19 HH20 HH25

Claims (3)

[Claims] An interference exposure method in which substantially parallel incident light is obliquely applied to a hologram master substrate through a prism, and a hologram photosensitive material is exposed with diffracted light and transmitted light obtained through the hologram master substrate. A method for manufacturing a hologram filter, wherein the prism has a light absorbing layer on another slope opposite to one slope serving as an incident surface of the incident light. 2. An interference in which a hologram master substrate is obliquely irradiated with substantially parallel incident light, and the hologram photosensitive material formed on the surface of the transparent support substrate is exposed with diffracted light and transmitted light obtained through the hologram master substrate. A method of manufacturing a hologram filter using an exposure method, wherein the transparent support substrate has a light absorbing layer on a back surface. 3. A hologram master substrate on which a thin film pattern is formed on the back surface of a transparent substrate is irradiated with obliquely parallel incident light from an oblique direction, and hologram photosensitive is performed by diffracted light and transmitted light obtained through the hologram master substrate. A method of manufacturing a hologram filter using an interference exposure method of exposing a material, wherein an incident angle of exposure light to a hologram master substrate is θ,
A method for manufacturing a hologram filter, wherein, when the thickness of the hologram master substrate is d, an irradiation area of the exposure light on the hologram master substrate has a margin width of 2 dtan θ or more at an incident end.