JP2710128B2 - Method for preparing photosensitive material for hologram recording and method for producing hologram - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for preparing a photosensitive material for hologram recording and a method for producing a hologram.

(Prior Art) Conventionally, a volume phase hologram has long been called a new optical element. In recent years, for example, its usefulness as a coupling element of a head-up display has attracted attention, and its position has been established.

Conventionally, as a recording medium capable of recording a high-performance volume phase hologram, gelatin sensitized with dichromic acid has been widely known and used.

Although this dichromated gelatin-based recording medium is an excellent recording medium in that it can record a high-performance hologram, it is inferior in heat resistance and environmental resistance, especially in moisture resistance, and recording is easily lost due to moisture absorption. Problem. Therefore, sufficient measures are required to make the hologram dampproof.For example, when applied to laser protective glasses for protecting eyes from laser, head-up display devices for automobiles, etc. It is necessary to seal with various sealants, workability, safety,
There were practical difficulties in terms of weight and the like.

In order to solve the above-mentioned drawbacks of the dichromated gelatin-based recording medium, an aromatic compound such as poly (N-vinylcarbazole) (hereinafter abbreviated as PVCz) is included in the molecular chain constituent unit as a new recording medium. A hologram preparation technique using an iodine compound as a sensitizer for a polymer has been proposed (for example, see Japanese Patent Publication No. 62-14831). Further, a technique for obtaining a high-performance hologram by improving them has been proposed (for example, see Japanese Patent Application Laid-Open No. 54-101343).

(Problems to be Solved by the Invention) The above-mentioned PVCz-based recording medium can provide a volume phase hologram which is extremely excellent in moisture resistance, light resistance and the like. However, while a volume phase hologram having a diffraction efficiency of 99.9% and a transmittance of 90% or more has been created in the dichromated gelatin-based recording medium, the PVCz-based recording medium has In this case, the maximum diffraction efficiency is usually achieved only 90%, and even if improved, about 98%. In addition, stable performance is not always obtained and there is a point to be improved in productivity.

In addition, in the case of a PVCz-based recording medium, compared to a dichromated gelatin-based recording medium, fine cracks tend to occur on the hologram as a whole during hologram development due to the nature of PVCz, and the transmittance is high. Tends to decrease. In particular, when forming a black grating image of a type having a narrow diffraction peak width, the thickness of the recording medium is inevitably thick as suggested by the theory, so that the above-mentioned cracking problem becomes more remarkable, and The transmittance decreases.

Also, when a volume phase hologram recorded on a PVCz-based recording medium is exposed to a high temperature (even at a temperature below the glass transition point) for a long time, the diffraction light peak tends to irreversibly shift to the shorter wavelength side. It is recognized that there is also a difficulty in that a peak shift due to a thermal history must be considered in advance in design in order to match the wavelength of the diffracted light with the specific light.

The present inventors have previously proposed PVCz having a high molecular weight and a narrow molecular weight distribution as means for solving the above problems.

In preparing a recording medium using such a high molecular weight PVCz, it is necessary to dissolve the PVCz in an organic solvent to form a film, but the viscosity of the solution increases due to the high molecular weight of PVCz. In addition, it becomes difficult to remove insoluble components such as dusts in the solution or to perform a defoaming treatment, and when dissolving an organic iodine compound as a sensitizer in the above PVCz solution, it takes a long time to form a uniform solution. When the stability of the organic iodine compound is poor, the viscosity of the solution further increases during that time, causing a problem that the film formation is significantly hindered.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a hologram recording photographic material containing PVCz, which can provide a film having a uniform film thickness which can be handled in forming a film and which can be handled stably.

(Means for Solving the Problems) The above object is achieved by the present invention described below.

That is, the present invention relates to a solution obtained by dissolving an organic iodine compound, a weight average molecular weight of 1,000,000 or more and a molecular weight distribution of 3 or more.
The following PVCz is dissolved in a solvent that does not decompose the organic iodine compound, and has a viscosity of 50 to 5,000 at 25 ° C.
A method for preparing a hologram recording light-sensitive material, which is prepared by mixing with a solution in the range of 0 cps, and a method for producing a hologram using the recording light-sensitive material.

(Function) By using PVCz having a weight average molecular weight of 1,000,000 or more and a molecular weight distribution of 3 or less as a material for forming a hologram recording medium, high diffraction efficiency, high transparency, low haze, and a diffraction peak wavelength are obtained. Is provided with high productivity, and the problem of the related art is solved.

In contrast, PVCz, which has been conventionally used as a hologram recording medium, has a weight-average molecular weight in terms of polystyrene of 700 to 950,000 even at a high molecular weight, and its molecular weight distribution is 4.5 to 5.5.
The weight average molecular weight and the molecular weight distribution have caused the above-mentioned various problems.

Further, in forming the PVCz into a film, a sensitizer is added to the PVCz solution by a specific method and the viscosity of the solution is set to a specific range, whereby a uniform hologram having a thickness of 3 to 20 μm is formed. A film with a large thickness can be easily formed.
Preparation of the photosensitive material becomes easy.

(Preferred Embodiment) Next, the present invention will be described in more detail with reference to preferred embodiments.

PVCz in the present invention is obtained by polymerization of N-vinylcarbazole, and PVCz obtained by a usual method or commercially available PVCz has a weight average molecular weight and a molecular weight distribution as described above. Conventional purification of PVCz, for example, purification by molecular weight fractionation with a solvent, and removal of low molecular weight components can provide PVCz having the specific weight average molecular weight and molecular weight distribution which are the objects of the present invention.

The weight average molecular weight referred to in the present invention is a molecular weight in terms of polystyrene, and is a value determined by gel permeation chromatography at a column temperature of 27 ° C. using tetrahydrofuran as a solvent (column used). Is Shodex KF-807, KF80
M, exclusion limit 2 × 10 ⁸ , 3 × 10 ⁷ connected, 2 × 10 ^{7 to} 1.
Up to 2 × 10 ³ polystyrene standard).

For the separation of the molecular weight, any conventionally known separation method such as a method using various solvents having different solubility in PVCz or a method of changing the concentration may be used. Typically, the dissolution-precipitation separation is carried out by mixing a good solvent / a poor solvent. Typically, a combination of dioxane / isopropyl alcohol is preferred.

Good solvent and poor solvent, PVCz when the mixture is heated
Is sufficiently dissolved, and when this is cooled, PV in the high molecular weight range
Mix it in the ratio where Cz precipitates to make a purified solvent, and in this, PV
Heat and dissolve Cz, then cool. At this time, for high molecular weight
Since PVCz precipitates out and the low molecular weight component is in a dissolved state, the solution phase is separated to obtain Pz having a weight average molecular weight of 1,000,000 or more.
You can get something rich in VCz.

According to a detailed study of the present inventors, when the weight average molecular weight of purified PVCz is 1,000,000 or more, and its molecular weight distribution is 3 or less, by using this as a volume phase hologram recording medium, It has been found that such various problems can be advantageously solved.

As described above, one of the separation methods for obtaining PVCz used in the present invention.
Although an example is described, it is obvious that PVCz using the present invention can be easily obtained by any purification method other than the above-mentioned fractionation method.

When the high molecular weight PVCz is dissolved in an organic solvent and a sensitizer is further added thereto, various problems as described above occur, and it becomes difficult to form a recording layer having a uniform thickness.

In the present invention, an organic iodine compound as a sensitizer is added as a solution to the PVCz solution, and an organic solvent of the PVCz solution that does not decompose the iodine compound is selected, and the viscosity of the solution is 50 to 5,000 cps. Preferably 300 to 2,000 cps
By doing so, the mixture of the iodine compound and PVCz can be completed in a short time, and a photosensitive material solution that can form a recording layer having a uniform thickness without excessively increasing the viscosity of the PVCz solution can be obtained.

In order to make the viscosity of the PVCz solution fall within the above range, the viscosity varies depending on the type of the solvent.
A PVCz concentration of about 14 g to 14 g is good. If the concentration exceeds the above range, it becomes difficult to remove insoluble components such as dust by filtration or the like, so that handling is inconvenient and problems arise in coatability during film formation.
On the other hand, if the concentration is too low, it becomes difficult to obtain a desired film thickness.

The solvent for the organic iodine compound and PVCz used in the present invention should not be determined solely by the solubility of PVCz,
One that does not impair the stability of the organic iodine compound and that has sufficient solubility for both the organic iodine compound and PVCz and that has excellent compatibility should be selected. Preferred examples of the organic solvent satisfying such conditions include benzene,
Examples thereof include halides thereof, aromatic solvents such as toluene and xylene, and aliphatic solvents such as chloroform. or,
The solution of the organic iodine compound and the PVCz solution may be mixed by any method.However, a method of adding a small amount of the solution of the organic iodine compound as a high-concentration solution and not changing the viscosity and concentration of the PVCz solution significantly, or both. It is also a preferable method to increase the concentration of the mixture and dilute the mixture to a predetermined viscosity and concentration after mixing them. By adopting such a method, when the organic iodine compound is directly added to the PVCz solution as a solid, it takes 3 to 5 hours to sufficiently dissolve the compound, which is reduced to within 1 hour, and the viscosity increases during or after that. Less is.

Specific examples of preferred organic iodine compounds include organic iodine compounds such as carbon iodide, iodoform, ethylene tetraiodide, triiodoethane, tetraiodoethane, pentaiodoethane, and hexaiodoethane.
The organic iodine compound to be added is 100 parts by weight per 100 parts by weight of PVCz.
The ratio is preferably from 1 to 1 part by weight.

If the addition amount of the organic iodine compound is too small, the sensitivity of the obtained recording medium is low, it takes a long time for exposure, and if it exceeds 100 parts, undecomposed organic iodine compound remains in the recording medium, You need to remove them all later,
It causes voids in the recording medium.

A hologram recording medium can be obtained by forming a coating film on a suitable substrate such as a glass plate or a plastic film using the above-mentioned light-sensitive material solution of the present invention.

The recording medium formed as described above is exposed by an optical system as shown in FIG. 1 using a coherent laser of two light beams of object light and reference light, which are coherent visible light up to 560 nm.

Subsequent to the exposure step, the recording layer is immersed in a solvent that hardly elutes a PVCz cross-linked product formed by the photoreaction, as well as the PVCz constituting the recording layer, and the unreacted organic compound is removed from the recording layer. Only iodine compounds are eluted and removed to remove coloring.
This step can also serve as the following swelling step.

The subsequent developing step includes two steps, a swelling step and a shrinking step.

That is, the recording layer from which the hologram latent image is formed by the exposure step and from which the organic iodine compound has been removed is treated with a swelling liquid as a first solvent to cause swelling according to the formed hologram pattern. In the subsequent treatment with the second solvent, the recording layer in the swollen state is contracted, and the hologram is amplified and fixed according to the swollen state.

The swelling liquid, which is the first solvent in the hologram development step, is a good solvent that hardly elutes a crosslinked or uncrosslinked product of PVCz generated as a result of a photoreaction between PVCz and an organic iodine compound.

The shrinking liquid as the second solvent does not have a swelling or dissolving action on the recording layer, and any non- or poor solvent compatible with the swelling liquid can be used.

Further, the processing conditions such as the temperature and time of each step vary depending on the type of the recording layer and the type of the solvent to be used, and cannot be specified unconditionally, but generally, each step is about 10 ° C. to 70 ° C. A sufficient effect can be obtained by treating for several seconds to several minutes at the above temperature.

(Effects) The use of the photosensitive material solution of the present invention containing PVCz having the specific weight average molecular weight and molecular weight distribution as described above and an organic iodine compound and having a viscosity in a specific range allows the use of 3 to 20%.
A hologram recording layer having a thickness of μm and a uniform thickness is formed. Further, the viscosity of the solution can be prevented by the preparation method, and a hologram recording layer having a uniform thickness can be formed even after storage for a long period of time.

The volume phase hologram obtained using the hologram recording layer described above has improved the maximum diffraction efficiency of the conventional volume phase hologram using PVCz from 98% to 99.9%. The transmittance was improved from 80% at 600 nm to 92%, and the haze from 12% at a thickness of 10 μm was improved to 2% or less.

(Examples) Next, the present invention will be described more specifically with reference to examples and comparative examples.

Example 1 PVCz (weight average molecular weight 1.43 million, molecular weight distribution 1.73, gel permeation chromatograph, and Shodex, Showa Denko KK) KF-807, KF80M as columns
5.3 g) was added to 60 ml of chlorobenzene and dissolved by stirring to prepare a PVCz solution. The viscosity of this solution was measured at 25 ° C. using an E-type viscometer (VISCONICED, manufactured by Tokyo Keiki Co., Ltd.) using a 3 mm cone, and it was 2,400 cps.

A solution in which 0.4 g of tetraiodomethane was separately dissolved in 60 ml of chlorobenzene was mixed with the above PVCz solution and stirred for 30 minutes to obtain a hologram recording light-sensitive material solution of the present invention. This PVCz5.
The viscosity of the 3 g / 120 ml solution was 920 cps.

Spinner (Mikasa 1) on a glass plate with the above solution washed
M) to form a 7.2 μm recording layer. When the uniformity of the thickness of the recording layer was measured with a spectrophotometer using a monitor wavelength of 350 nm and a mask having a hole of 5 mmφ, the thickness change was within 0.5 μm.

The recording layer was exposed to an optical system shown in FIG. 1 using an Ar laser (488 nm) to record a hologram.

After exposure, the film was immersed in toluene at 35 ° C. for 2 minutes and xylene at 35 ° C. for 2 minutes, immersed in heptane at 20 ° C. for 2 minutes, and dried to obtain a volume phase hologram.

When the reflection diffraction efficiency of the hologram was measured, 51
The maximum reflection / diffraction efficiency is 99% at the light of 8 nm, the transmittance at the light of 600 nm is 87%, and the haze (total haze value) is
Haze meter based on JISK7105 (manufactured by Nippon Denshoku Co., Ltd.)
Was 1.4%.

Example 2 4.8 g of PVCz having a weight average molecular weight of 1.69 million and a molecular weight distribution of 1.23
Was dissolved in 130 ml of ethylene dichloride to obtain a solution having a viscosity of 1,300 cps, and this was added to 20 ml of a 50 ml chlorobenzene solution in which 10 g of tetraiodomethane was dissolved and uniformly mixed to obtain a hologram recording light-sensitive material of the present invention. . The PVCz concentration of this solution is 4.
At 8 g / 150 ml, the viscosity was 1,120 cps.

Thereafter, in the same manner as in Example 1, the diffraction efficiency is 99%, and the transmittance is 88%.
And a volume phase hologram with a haze of 0.8% were obtained.

The hologram recording light-sensitive materials of the present invention of Examples 1 and 2 did not show any change in absorption spectrum even when left in the dark at 25 ° C. for 2 days. No change was observed in the hologram performance.

Comparative Example 1 When 0.5 g of tetraiodoethane was directly added to and dissolved in the PVCz solution prepared in Example 1, it took 2 hours to dissolve uniformly. The diffraction efficiency of a hologram obtained in the same manner as in Example 1 using this solution was 95%.

[Brief description of the drawings]

 FIG. 1 shows a hologram recording optical system used in the embodiment.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuro Kuwayama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroyoshi Kishi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inside the company

Claims (8)

(57) [Claims] 1. A solution prepared by dissolving an organic iodine compound and poly (N-vinylcarbazole) having a weight average molecular weight of 1,000,000 or more and a molecular weight distribution of 3 or less in a solvent which does not decompose the organic iodine compound. And a solution having a viscosity at 25 ° C. in the range of 50 to 5,000 cps. 2. The hologram recording according to claim 1, wherein said organic iodine compound is selected from carbon tetraiodide, iodoform, ethylene tetraiodide, triiodoethane, tetraiodoethane, pentaiodoethane and hexaiodoethane. Preparation method of photosensitive material. 3. The method according to claim 1, wherein said solvent is selected from benzene, halogenated benzene, toluene, xylene and chloroform. 4. A solution prepared by dissolving an organic iodine compound and poly (N-vinylcarbazole) having a weight average molecular weight of 1,000,000 or more and a molecular weight distribution of 3 or less in a solvent which does not decompose the organic iodine compound. And a solution having a viscosity in the range of 50 to 5,000 cps at 25 ° C. was prepared to prepare a hologram recording light-sensitive material, and this light-sensitive material was applied on a substrate to form a film having a thickness of 3 to 20 μm. A method for producing a hologram, comprising: forming a recording layer; and exposing and developing the recording layer. 5. The method according to claim 4, wherein the hologram is a volume phase hologram. 6. The hologram according to claim 4, wherein said organic iodine compound is selected from carbon tetraiodide, iodoform, ethylene tetraiodide, triiodoethane, tetraiodoethane, pentaiodoethane and hexaiodoethane. Production method. 7. The method according to claim 4, wherein the solvent is selected from benzene, halogenated benzene, toluene, xylene and chloroform. 8. The method according to claim 4, wherein the developing is a step of swelling and shrinking the recording layer.