JP3257825B2 - Method for producing duplicate hologram - 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 of manufacturing a surface relief type duplicate hologram used for an optical scanning device for scanning a laser beam.

A surface relief type hologram is one in which a diffraction grating is formed on the surface of a transparent plate by irregularities, but it is inefficient if a diffraction grating is formed on glass and manufactured one by one.

[0003] Therefore, a mold is taken from the hologram master formed in this way, and a large number of plastic holograms are copied.

[0004]

2. Description of the Related Art In a conventional method for producing a duplicate hologram, a liquid transparent photopolymer (light) is formed on a diffraction grating surface of a mold called a hologram stamper molded from a hologram master having a diffraction grating formed by projections and depressions. (Cured resin) is dropped thereon, a glass plate is placed thereon, and the photopolymer is cured by irradiating ultraviolet rays. After that, the cured photopolymer and the glass plate are integrally removed from the hologram stamper to obtain a duplicate hologram.

[0005]

A surface relief type hologram master from which a copy is made is formed by exposing a glass plate coated with a photosensitive resist to interference fringes and then developing. However, it is difficult to make the exposure intensity uniform between the central portion and the peripheral portion, and generally, the exposure intensity becomes lower toward the periphery.

As a result, a distribution is generated in the depth of the groove of the diffraction grating of the master hologram, and a distribution of diffraction efficiency is generated in the duplicated hologram copied therefrom as shown in FIG. Also, even if the exposure intensity becomes uniform,
If there is a distribution in the spatial frequency of the diffraction grating, a distribution occurs in the diffraction efficiency.

When a duplicate hologram having such a distribution of diffraction efficiency is used for scanning with a laser beam using an optical scanning device, a scanning line having a uniform light intensity cannot be obtained. This may cause variations in density, etc., and may cause a reading error in the vicinity of a barcode reader or the like.

Accordingly, the present invention provides a method for producing a hologram master, in which a diffraction grating formed on a master hologram has a distribution such as depth and spatial frequency.
An object of the present invention is to provide a method of manufacturing a duplicate hologram capable of producing a homogeneous duplicate hologram having a small distribution of diffraction efficiency.

[0009]

In order to achieve the above-mentioned object, a method of manufacturing a duplicate hologram according to the present invention has a diffraction grating formed by irregularities as shown in FIG. A plurality of types of liquid transparent resins 2a and 2b having different refractive indices are dropped at different positions on the diffraction grating surface 1a of the hologram stamper 1 cast from the surface relief type hologram master, and the transparent plate 3 is placed thereon. Is placed in a state where there is no gap between the plurality of types of transparent resins 2a and 2b, and the plurality of types of transparent resins 2a and 2b are placed.
b is cured in a state in which the diffraction grating surface 1a of the hologram stamper 1 is in close contact with the surface of the transparent plate 3, and then the cured transparent resins 2a and 2b and the transparent plate 3 are separated from the hologram stamper 1. It is characterized in that it is taken out integrally.

The transparent resins 2a and 2b may be photopolymers which are cured by irradiation with ultraviolet rays. A plurality of types of transparent resins are formed on the diffraction grating surface 1a of the hologram stamper 1 by changing the refractive index stepwise. The resin 2c may be dropped at different positions.

[0011]

FIG. 9 shows the relationship between the depth of the groove of the diffraction grating of the hologram and the diffraction efficiency. The figure shows the case where the hologram is formed of a material having a large refractive index. Is formed.

As shown in FIG. 9, the diffraction efficiency depends on the depth of the groove of the diffraction grating, and is greatly affected by the refractive index of the hologram material. Unless the ratio is increased, good diffraction efficiency cannot be obtained.

Therefore, a plurality of types of transparent resins 2a and 2b having different refractive indices are dropped at different positions on the surface of the hologram stamper 1 in accordance with the distribution of the depth of the grooves of the hologram master caused by variations in exposure intensity. By doing so, the diffraction efficiency can be made uniform.

By controlling the positions at which the transparent resins 2a and 2b are dropped onto the hologram stamper 1, the diffraction efficiency of the hologram can be arbitrarily controlled.

[0015]

An embodiment will be described with reference to the drawings. 1 to 3 show steps of a method for manufacturing a duplicate hologram according to a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a hologram stamper molded from a surface relief hologram master in which a diffraction grating is formed by projections and depressions. For example, a nickel plating layer whose diffraction grating surface is molded is bonded to an aluminum alloy pedestal. It has been formed.

The hologram master (not shown) is formed by applying a photosensitive photoresist to the surface of a glass plate having a smooth surface, exposing the photoresist to interference fringes, and developing the exposed photoresist. However, a distribution of diffraction efficiency occurs in the hologram master due to uneven exposure intensity and uneven interference fringes when the hologram master is created.

The diffraction grating surface of the hologram master is nickel-plated, for example, and a pedestal made of an aluminum alloy is bonded to the outer surface of the nickel plating layer and immersed in a stripping solution. Finally, the hologram stamper 1 is formed by removing the resist adhering to the diffraction grating surface cast on the nickel plating layer side.

The diffraction grating surface 1 of the hologram stamper 1
1, two types of liquid transparent photopolymers 2 having different refractive indices from each other as shown in FIG.
a and 2b are dropped.

In this embodiment, a first photopolymer 2a having a small refractive index (for example, methyl methacrylate having a refractive index of 1.491) is applied to a central portion where a deep groove is formed at a high exposure intensity when a hologram master is manufactured. The second photopolymer 2b having a large refractive index (for example, vinyl chlorobenzoate having a refractive index of 1.592) is dropped into a portion near the periphery where the depth of the groove is shallow.

Then, a glass plate 3 having a transparent and smooth surface is placed on the glass plate 3 so that there is no gap between the photopolymers 2a and 2b having different refractive indexes as shown in FIG.

Then, in a state where the photopolymers 2a and 2b are completely adhered to the diffraction grating surface 1a of the hologram stamper 1 and the surface of the glass plate 3, ultraviolet light is irradiated from a UV light source 4 to cure the photopolymers 2a and 2b. Let it.

Finally, as shown in FIG. 3, the cured photopolymers 2a and 2b and the glass plate 3 are integrally removed from the hologram stamper 1 to obtain a duplicate hologram.

FIG. 4 shows the distribution state of the diffraction efficiency of the duplicated hologram obtained in this manner. The diffraction efficiency of the peripheral portion, which had been reduced in the prior art, was increased.
It is possible to obtain a uniform diffraction efficiency as a whole.

As described above, by selecting a photopolymer material having an appropriate refractive index in accordance with the depth and the spatial frequency of the groove of the diffraction grating of the hologram master, a duplicated hologram having a uniform diffraction efficiency can be obtained.

FIGS. 5 to 7 show a second embodiment of the present invention, in which a plurality of types of photopolymers 2c... In this example, five types of photopolymers 2c... Of which the refractive index was changed stepwise were sequentially dropped on the diffraction grating surface 1a of the hologram stamper 1 while changing the positions. The other points are the same as in the first embodiment.

.. Can be produced by sequentially changing the mixing ratio of two or more materials having different refractive indices.

FIG. 8 shows the distribution of the diffraction efficiencies of the duplicate hologram obtained by the second embodiment. A duplicate hologram having a very uniform diffraction efficiency having no difference in efficiency from the central portion to the peripheral portion is shown. Obtainable.

As described above, by selecting a plurality of types of photopolymers 2c having different diffraction efficiencies and dropping them at arbitrary positions, the distribution of the diffraction efficiency of the duplicate hologram can be arbitrarily controlled.

[0030]

According to the method of the present invention for producing a duplicate hologram, a plurality of liquid transparent resins having different diffraction efficiencies are dropped onto the hologram stamper, whereby a uniform duplicate hologram having a small variation in the diffraction efficiency depending on the position. And the distribution of diffraction efficiency can be arbitrarily controlled as needed.

[Brief description of the drawings]

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

FIG. 2 is a process chart of the first embodiment.

FIG. 3 is a process chart of the first embodiment.

FIG. 4 is a diagram showing a diffraction efficiency distribution of the first embodiment.

FIG. 5 is a process chart of the second embodiment.

FIG. 6 is a process chart of the second embodiment.

FIG. 7 is a process chart of the second embodiment.

FIG. 8 is a diagram showing a diffraction efficiency distribution of the second embodiment.

FIG. 9 is a diagram showing characteristics of diffraction efficiency of a hologram.

FIG. 10 is a diagram showing a conventional diffraction efficiency distribution.

[Explanation of symbols]

 Reference Signs List 1 hologram stamper 1a diffraction grating surface 2a first photopolymer (liquid transparent resin) 2b second photopolymer (liquid transparent resin) 3 glass plate (transparent plate)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-126166 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03H 1/00-1/34

Claims (3)

(57) [Claims] 1. A plurality of types of liquid transparent resins having different refractive indices are dropped onto different positions on a diffraction grating surface of a hologram stamper molded from a surface relief type hologram master having a diffraction grating formed by irregularities. Then, a transparent plate is placed on the transparent resin, so that there is no gap between the plurality of types of transparent resins, and the plurality of types of transparent resins are placed on the diffraction grating surface of the hologram stamper and the transparent plate surface. A method for producing a duplicate hologram, wherein the cured transparent resin and the transparent plate are integrally taken out of the hologram stamper after being cured in a state where they are in close contact with each other. 2. The method for producing a duplicate hologram according to claim 1, wherein said transparent resin is a photopolymer which is cured by ultraviolet irradiation. 3. A method for producing a duplicate hologram according to claim 1, wherein a plurality of types of transparent resins are dropped on the diffraction grating surface of the hologram stamper by changing the refractive index in a stepwise manner.