JPH07210068A - Production of surface relief type hologram - Google Patents

Abstract

PURPOSE:To obtain a hologram having desired diffraction efficiency by lessening loss of light at the time of exposure and arbitrarily controlling an exposure distribution in the production of the surface relief type hologram to be used for an optical scanner for scanning a laser beam, etc. CONSTITUTION:A hologram dry plate 10 formed of resist layer 12 and 14 consisting of plural inside and outside layers to be sensitized by light with different wavelengths is first exposed with interference fringes on the outer resist layer 14 by coherent two luminous fluxes to sensitize the outer resist layer 14 and the layer is developed. The inner resist layer 12 is then exposed by the luminous fluxes with the wavelength which does not transmit the outer resist layer 14 and sensitizes the inner resist layer 12 with the outer resist layer 14 after the development as a mask and thereafter, the outer resist layer 14 is removed and the inner resist layer 12 is developed, by which hologram patterns are obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a surface relief hologram used in an optical scanning device for scanning a laser beam.

The surface relief hologram is a transparent plate having a diffraction grating formed on the surface by unevenness, and is formed by exposing and developing an interference pattern generated by two coherent light beams.

However, such an exposure has a light intensity distribution, and the distribution of the exposure amount generated thereby causes a distribution in the depth of the unevenness, and the diffraction efficiency varies depending on the position, so that the exposure amount is uniform over the entire surface. Need to be controlled.

[0004]

2. Description of the Related Art FIG. 11 shows an interference exposure apparatus for manufacturing a conventional surface relief hologram, in which a laser beam emitted from a laser beam oscillator 101 is split into two light beams by a beam splitter 102. After being reflected by the mirrors 103, they pass through the ND filter 104 and reach the hologram dry plate 100.
The interference pattern is exposed on the resist layer on the surface of 00. Then, by developing it, a diffraction grating having a groove formed in the exposed portion is formed. Reference numeral 105 is a lens.

In such an interference exposure apparatus, the light intensity of the laser beam before entering the ND filter 104 has a distribution that becomes smaller toward the periphery, as shown in FIG.

Therefore, as shown in FIG. 13, the ND filter 104 has a smaller transmittance in the central portion. As a result, the light intensity distribution of the light flux (interference pattern) reaching the hologram dry plate 100 becomes substantially uniform as a whole as shown in FIG.

[0007]

However, if a part of the light beam is cut by the ND filter or the like as described above, the efficiency of the light is large and the efficiency is low, and it is contained in the metal film of the ND filter. Since the particles cause scattering, which becomes noise light and a minute exposure amount distribution is generated, it is impossible to manufacture a hologram having a desired diffraction efficiency distribution.

Therefore, the present invention provides a method for producing a surface relief hologram in which the loss of light at the time of exposure is small and the exposure dose distribution can be arbitrarily controlled to obtain a hologram having a desired diffraction efficiency. With the goal.

[0009]

In order to achieve the above object, a method for producing a surface relief hologram of the present invention comprises:
As shown in FIG. 1 for explaining an embodiment, a resist layer 1 composed of a plurality of inner and outer layers which are exposed to light of different wavelengths.
On the hologram dry plate 10 on which Nos. 2 and 14 are formed, first, an interference pattern is exposed to the outer resist layer 14 by two coherent light fluxes having a wavelength with which the outer resist layer 14 is exposed to develop it, and then it is developed. After the outer resist layer 14 is exposed, the inner resist layer 12 is exposed by a light flux having a wavelength that does not pass through the outer resist layer 14 and is exposed to the inner resist layer 12 using the latter outer resist layer 14 as a mask. The inner resist layer 12 is developed to obtain a hologram pattern.

The outer resist layer 14 may be mixed with a dye that absorbs light having a wavelength for exposing the inner resist layer 12. In addition, the inner resist layer 12
An intermediate layer 13 may be provided between the outer resist layer 14 and the outer resist layer 14 to prevent the layers 12 and 14 from being mixed with each other.
The intermediate layer 13 is preferably water-soluble.

Then, it is preferable that the light flux for exposing the inner resist layer 12 is made into one light flux and the exposure amount distribution thereof is controlled.

[0012]

First, the interference pattern is exposed to the outer resist layer 14 by two coherent light fluxes having a wavelength with which the outer resist layer 14 is exposed, and by developing it, the groove of the interference pattern is formed on the outer resist layer 14. Is formed so as to penetrate through.

Next, the inner resist layer 12 is exposed by using it as a mask. This exposure requires only one light flux, does not require coherence, and the exposure dose distribution can be easily adjusted during exposure.

Then, the resist layer 14 on the outer side is removed and the resist layer 12 on the inner side is developed to form a diffraction grating having unevenness of a depth corresponding to the exposure amount on the inner resist layer 12.

Further, when a dye that absorbs light having a wavelength for exposing the inner resist layer 12 is mixed with the outer resist layer 14, the light shielding action of the outer resist layer 14 when exposing the inner resist layer 12 is performed. , The diffraction efficiency can be improved by forming the diffraction grating in a deeper and cleaner shape.

Further, by providing the intermediate layer 13 between the inner and outer resist layers 12, 14, both resist layers 12, 1 are formed.
4 is prevented from mixing, and by using a water-soluble intermediate layer 13, the intermediate layer 13 can be easily washed off and removed after the inner resist layer 12 is exposed.

[0017]

Embodiments will be described with reference to the drawings. FIG. 2 shows a hologram dry plate 10 used in the first embodiment of the present invention. For example, a positive resist for i-line (wavelength 365 nm) having a sensitivity on the short wavelength side is formed of a transparent glass substrate 11.
The resist layer 12 having a thickness of, for example, 2 μm is formed on the lower side by applying the resist layer 12 thereon.

Then, a water-soluble resin having resistance to an organic solvent is applied to the surface to form the intermediate layer 13, and then, for example, g-line (wavelength 4) having sensitivity on the long wavelength side is applied to the surface.
37 nm) positive resist is applied to form an outer resist layer 14 having a thickness of 1 μm, for example. This is the hologram dry plate 10.

FIGS. 3 and 4 show the spectral sensitivity and the spectral transmittance of the inner resist layer 12. Thus, the inner resist layer 12 is sensitive to the i-line region and has a high transmittance from the i-line region to the g-line region.

FIGS. 5 and 6 show the spectral sensitivity and the spectral transmittance of the outer resist layer 14, and thus, the outer resist layer 14 is sensitive to the g-line region and the transmittance of the g-line region. Is high, but the transmittance in the i-line region is extremely low. Therefore, light having a wavelength that the inner resist layer 12 is exposed to is blocked by the outer resist layer 14.

The intermediate layer 13 is for preventing the inner resist layer 12 and the outer resist layer 14 from directly touching and mixing with each other as described above, and for example, transparent polyvinyl alcohol or the like can be used. .

FIG. 7 shows an interference exposure apparatus according to the first embodiment, in which a laser emitted from a He-Cd laser oscillator 1 which oscillates a coherent laser beam having a wavelength of 441.6 nm close to the g-line. The beam is split into two light beams by the beam splitter 2 and reflected by the mirrors 3, respectively, and then reaches the hologram dry plate 10, and the interference pattern is exposed on the resist layer 14 outside the hologram dry plate 10. 5 is a lens. Then, the outer resist layer 14
When the interference pattern exposed to the above is developed, the exposed portion becomes a groove penetrating the outer resist layer 14.

Therefore, as shown in FIG. 1, the hologram dry plate 10 is irradiated with a mercury lamp 6 which emits light having a wavelength in the i-line region, using the resist layer 14 on the outside as a mask.
Single-beam exposure is performed. Since the outer resist layer 14 has strong absorption of light having a wavelength in the i-line region, the inner resist layer 12 is exposed by the light passing through the groove portion where the outer resist layer 14 does not exist.

In the one-beam exposure using the mercury lamp 6 or the like, partial exposure can be easily performed on the exposed portion. Therefore, for example, the exposed portion is exposed by changing the time for each portion. An arbitrary exposure dose distribution can be easily given.

After the exposure is finished, the outer resist layer 14 is dissolved and removed with an organic solvent, and then the intermediate layer 13 is dissolved and removed with water. Then, the resist layer 12 on the inner side is subjected to a developing treatment with an alkali so that the exposed portion becomes a concave groove, and a hologram pattern which can be used as a diffraction grating as shown in FIG. 8 is obtained.

The depth of the groove of the hologram pattern thus obtained corresponds to the exposure amount for the inner resist layer 12. Therefore, by changing the exposure amount of the mercury lamp 6 for each part, the groove depth can be arbitrarily controlled and a desired diffraction efficiency distribution can be obtained.

Next, a second embodiment of the present invention will be described. Here, a dye that absorbs light having a wavelength in the i-ray region is mixed with the outer resist layer 14. Then, as shown in FIG.
As shown in, the transmittance of the outer resist layer 14 in the i-line region is further reduced.

A hologram pattern is formed using such an outer resist layer 14 in the same manner as in the first embodiment. Then, the contrast of the exposure to the inner resist layer 12 performed using the outer resist layer 14 as a mask becomes large, and as shown in FIG. 10, it is possible to obtain a hologram pattern of a deeper groove with less shape loss. .

[0029]

According to the present invention, since the resist layer for forming the hologram pattern can be exposed with an arbitrary exposure amount distribution, the groove depth can be arbitrarily controlled to obtain a desired diffraction efficiency distribution. Holograms can be manufactured with. In addition, when performing two-beam exposure to obtain an interference pattern, the coherent light beam is directly exposed to the surface of the hologram dry plate without passing through a filter or the like, so there is little exposure loss and the yield is shortened by shortening the exposure time. Has the effect of improving

[Brief description of drawings]

FIG. 1 is a process drawing of a first embodiment.

FIG. 2 is a sectional view of a hologram dry plate according to the first embodiment.

FIG. 3 is a spectral sensitivity characteristic diagram of a resist layer on the inner side of the first embodiment.

FIG. 4 is a spectral transmittance characteristic diagram of a resist layer on the inner side of the first embodiment.

FIG. 5 is a spectral sensitivity characteristic diagram of the resist layer on the outer side of the first embodiment.

FIG. 6 is a spectral transmittance characteristic diagram of a resist layer on the outer side of the first embodiment.

FIG. 7 is a schematic view of an interference exposure apparatus of the first embodiment.

FIG. 8 is a cross-sectional view of a hologram pattern obtained according to the first embodiment.

FIG. 9 is a spectral transmittance characteristic diagram of a resist layer on the outside of the second example.

FIG. 10 is a cross-sectional view of a hologram pattern obtained according to the second embodiment.

FIG. 11 is a schematic diagram of a conventional interference exposure apparatus.

FIG. 12 is a light intensity distribution characteristic diagram of a conventional example.

FIG. 13 is a transmittance distribution characteristic diagram of a conventional filter.

FIG. 14 is an exposure intensity distribution characteristic diagram of a conventional example.

[Explanation of symbols]

 10 Hologram Dry Plate 11 Glass Substrate 12 Inner Resist Layer 13 Intermediate Layer 14 Outer Resist Layer

Claims (5)

[Claims] 1. A hologram dry plate (10) on which a resist layer (12, 14) composed of a plurality of inner and outer layers which are exposed to light of different wavelengths is formed, and first, a coherent wavelength of which the outer resist layer (14) is exposed. The outer resist layer (14) is exposed to the outer resist layer (14) by two light fluxes and developed, and then the outer resist layer (14) after development is used as a mask to pass through the outer resist layer (14). Without exposing the inner resist layer (12) with a light flux having a wavelength that the inner resist layer (12) is exposed to, the outer resist layer (1) is exposed.
4) is removed and the inner resist layer (12) is developed to obtain a hologram pattern, which is a method for producing a surface relief hologram. 2. The method for producing a surface relief hologram according to claim 1, wherein the outer resist layer (14) is mixed with a dye which absorbs light having a wavelength for exposing the inner resist layer (12). 3. An intermediate layer (13) is provided between the inner resist layer (12) and the outer resist layer (14) to prevent both layers (12, 14) from mixing with each other. The method for producing a surface relief hologram according to claim 1 or 2. 4. The method for producing a surface relief hologram according to claim 3, wherein the intermediate layer (13) is water-soluble. 5. The method for producing a surface relief hologram according to claim 1, wherein the light flux for exposing the inner resist layer (12) is one light flux, and the exposure amount distribution is controlled.