JPH0216107A - Poly(n-vinylcarbazole) - Google Patents

Abstract

PURPOSE:To make it possible to produce a volume phase type hologram recording medium which can achieve a high diffraction efficiency, high transparency, low haze, prevention of the shift of diffraction peak wavelengths and high productivity by using a poly(N-vinylcarbazole) having a high molecular weight and a narrow molecular weight distribution. CONSTITUTION:A poly(N-vinylcarbazole) (hereinafter referred to as PVCz) having a weight-average molecular weight of 1,000,000 or more and a molecular weight distribution of 3 or below is provided. The PVCz is preferably one wherein the content of a PVCz having a weight-average molecular weight of 200,000 or less is 1wt.% or less of the total PVCz and the content of a PVCz having a weight-average molecular weight of 1,000,000 or more to 50wt.% or more of the total PVCz. The PVCz is useful as material for volume phase type hologram recording media, and can produce a hologram recording medium which can achieve a high diffraction efficiency, high transparency, low haze, prevention of the shift of diffraction peak wavelengths and high productivity.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to high molecular weight poly(N-vinylcarbazole) (hereinafter abbreviated as PVCz), and more specifically, to a material useful as a material for volume-phase hologram recording media. Concerning pvCz with high molecular weight and narrow molecular weight distribution.

(Prior Art) Volume phase holograms have long been considered a new optical element, and in recent years, their usefulness as a coupling element for head-up displays, for example, has attracted attention, and they are beginning to establish themselves as such.

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

Although this dichromate gelatin-based recording medium is certainly an excellent recording medium in that it can record high-performance holograms, it is inferior in heat resistance, environmental resistance, and especially moisture resistance, and recordings are easily lost due to moisture absorption. There is a problem of being exposed. Therefore, sufficient measures are required to make holograms moisture-proof.For example, when applying holograms to laser safety goggles to protect eyes from lasers, head-up display devices for automobiles, etc. It is necessary to seal with various types of sealants, which poses practical difficulties in terms of processability, safety, weight, etc.

In order to solve the above-mentioned drawbacks of dichromate gelatin-based recording media, a hologram creation technology using an iodine compound as a sensitizer in a polymer containing an aromatic compound in the molecular weight unit, such as pvCz, has been developed as a new recording medium. has been proposed (for example, see Japanese Patent Publication No. 62-14831)
. Furthermore, techniques for obtaining high-performance holograms by improving these have also been proposed (see, for example, Japanese Patent Application Laid-Open No. 101343/1983).

(Problem to be solved by the invention) The above PVCz
It is possible to provide a volume phase type hologram that is extremely excellent in recording black recording medium properties, light resistance, etc. However, in the dichromate gelatin recording medium, 99.9%
Volume phase type holograms have been created that have a diffraction efficiency of However, only a certain maximum diffraction efficiency has been achieved, and stable performance is not always obtained, and productivity is also a problem.

In addition, in the case of PVCz-based recording media, compared to dichromate gelatin-based recording media, due to the properties of PvCz, fine cracks are more likely to occur throughout the hologram during hologram development, resulting in lower transmittance. tends to decrease. In particular, when forming a type of black grating image with a narrow diffraction peak width, the thickness of the recording medium will inevitably increase as suggested by theory, so the above problem of cracking will become even more prominent, and the overall There is a problem that the transmittance decreases.

In addition, volume phase holograms using PVCz recording media can be exposed to high temperatures for long periods of time (even at temperatures below the glass transition point).
It has been observed that the peak of diffracted light tends to irreversibly shift toward shorter wavelengths when exposed to There is also the difficulty of having to do so.

Accordingly, an object of the present invention is to provide a PVCz-based recording black recording medium that maintains the advantages of the PVCz-based holographic recording medium as described above and solves the drawbacks thereof.

(Means for solving problems) The above objects are achieved by the present invention as described below.

That is, the present invention is a PVCz characterized by having a weight average molecular weight of 1 million or more and a molecular weight distribution of 3 or less.

(Function) As a result of research to achieve the object of the present invention, the present inventors have found that conventional PVCz-based hologram recording media have high diffraction efficiency, high transparency, low haze, suppressed shift of diffraction peak wavelength, and high productivity. It has been found that the reason why the characteristics cannot be achieved is due to the properties of PVCz forming the recording medium.

In other words, volume phase hologram recording involves exposing the recording layer to interference waves from coherent light such as laser light.
Next, the recording layer is expanded with a good solvent for the recording layer, and then the same recording layer is contracted with a poor or non-solvent.

At this time, PVCz is crosslinked by light irradiation in the presence of a sensitizer and swells in a good solvent, but at this time, if the molecular weight of PVCz is low or it contains a large amount of low molecular weight components, uncrosslinked low molecular weight products and photodegradable polymers are eluted. The polymer dissolved at this time strongly depends on the polymer solubility of the solvent used, the temperature, the type of solvent, etc.

In particular, if a highly soluble solvent is used as a good solvent to increase the diffraction efficiency and swelling degree of the resulting hologram, the elution of uncrosslinked and decomposed polymers will be significant, and as a result, during the subsequent shrinkage treatment with a poor solvent, , so-called voids in polymer science are formed, and these voids cause light scattering, resulting in a cloudy appearance in the hologram.

Therefore, PV with high molecular weight and narrow molecular weight distribution
By using Cz as a recording material, many of the problems of the prior art mentioned above were solved at the same time.

Furthermore, the higher the molecular weight of a polymer, not limited to PVCz, the higher its mechanical strength. In addition, the main mechanism of volume phase hologram formation is to create strain in the polymer and freeze it, so in order to freeze the strain in the polymer caused by expansion and contraction during development, PVCz It is necessary that the molecular weight is high. They have also found that the presence of a large amount of low molecular weight components in PVCz promotes the relaxation of strain due to their plasticizing action, and therefore, the smaller the amount of low molecular weight components present, the more effective it is in freezing strain.

On the other hand, PVCz, which has been conventionally used as a hologram recording medium, has a polystyrene equivalent weight average molecular weight of 700,000 to 950,000 at most, and its molecular weight distribution is 4.
5 to 5.5, and because it has such a weight average molecular weight and molecular weight distribution, it causes the various problems mentioned above.

(Preferred Embodiments) Next, the present invention will be described in more detail by citing preferred embodiments.

PVCz in the present invention is obtained by polymerizing N-vinylcarbazole, and PVCz obtained by a conventional method or commercially available has the above-mentioned weight range average molecular weight and molecular weight distribution. PVCz having a specific ff1ffi average molecular plate and molecular weight distribution, which is the object of the present invention, can be obtained by purifying conventional PVCz, for example, by molecular fractionation using a solvent and removing low molecular weight components. In addition, the weight average molecular weight referred to in the present invention is the molecular weight in terms of polystyrene, and when tetrahydrofuran is used as a solvent,
Gel Permeation Chromatograph (Gel Permeation Chromatograph) with column temperature of 27°C.
graph) (The columns used were Showdex KF-807, KF80M, exclusion limits 2X108, 3X]O' were connected, zx+o'75
Calibrated using polystyrene as a standard up to 1.2X to3).

For the molecular weight separation, any conventionally known separation method may be used, such as a method using various solvents having different solubility for PVCz or a method of changing the concentration.

As an example, the mixing ratio of a good solvent and a poor or non-solvent for PVCz was changed, and the solubility of the mixed solvent for PVCz was changed to perform fractionation and remove low molecular weight.

In molecular weight fractionation, good solvents for PVCz include, for example, pyridine, quinoline and their derivatives, dioxane, cyclic ethers such as tetrahydrofuran, benzene, toluene, xylene (ortho form, meta form, bulk form and mixtures thereof), ethylbenzene. , n-propylbenzene, cumene, phenol, cresol, chlorobenzene, dichlorobenzene, nitrobenzene, benzyl alcohol, benzyl chloride, benzyl bromide, α-methylnaphthalene, α-chlornaphthalene and other benzene and naphthalene derivatives, bilane, dichloromethane , halogen-substituted saturated or unsaturated hydrocarbons such as chloroform, trichloroethylene, trichloroethane, dichloroethane, and bromoform; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; esters such as ethyl acetate and ethyl formate;
Other amines, amides, etc. may be mentioned, and appropriate ones are selected or used in combination from these.

In addition, examples of non- or poor solvents used for molecular weight fractionation include n-pentane, n-hexane, n-hebutane, n-
Alkanes such as octane, isooctane, cyclohexane, cycloalkanes, alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, tert-butyl alcohol, n-amyl alcohol, isoamyl alcohol, diethyl Examples include ethers such as ether, methyl ethyl ether, diisopropyl ether, etc., and appropriate ones are selected or used in combination from these.

A special solvent is prepared by mixing the above-mentioned good solvent and poor solvent in such a ratio that PVCz is sufficiently dissolved when the mixture is heated and that PVCz in the polymer range is precipitated when the mixture is cooled. PVCz is melted by heating and then cooled. At this time, the high molecular weight PVCz is precipitated and the low molecular weight content is in a dissolved state, so by separating the solution phase, a product rich in PVCz with a weight average molecular weight of 1 million or more can be obtained. By changing the type of solvent, mixing ratio, etc. as necessary, low molecular weight P V C
PVCz with a low z content and a narrow molecular weight distribution can be obtained.

According to detailed research by the present inventor, when the weight average molecular weight of purified PVCz is 1 million or more and its molecular weight distribution is 3 or less, by using it as a volume phase type hologram recording medium, the above-mentioned It has been found that various problems such as the following can be advantageously solved. In particular, those with a molecular weight distribution of 2 or less, and PV with a weight average molecular weight of 200,000 or less
The objects of the present invention can be advantageously achieved by a polymer in which the content of Cz is 1% by weight or less, and in which PVCz having a weight average molecular weight of 1 million or more accounts for 50% by weight or more of the total polymer.

Although one example of the fractionation method for obtaining the PVCz of the present invention has been described above, it is obvious that the PVCz of the present invention can be easily obtained by any purification method other than the above-mentioned fractionation method.

As an example of the use of the PVCz of the present invention, a case where it is used for hologram recording will be described.

Since PVCz does not have an optical absorption band on the wavelength side longer than 4 million m, when used as a hologram recording medium, it must be activated in advance to radiation with a halogen compound, preferably an iodine compound and/or a bromine compound. need to be.

Such a halogen compound coexists in PVCz and constitutes a recording layer having sufficient sensitivity even in the visible wavelength range, and specifically, preferable ones include carbon tetramonide, iodoform, and ethylene tetramonide. , triiodoethane, tetraiodoethane, pentaiodoethane, hexaiodoethane, carbon tetrabromide, ethylene tetrabromide, and other iodine and bromine compounds. These halogen compounds are used in an amount of, for example, 100 to 1 part by weight of the PVCzlOO.
Add in parts by weight.

If the amount of the halogen compound added is too small, the sensitivity of the resulting recording medium will be low and exposure will take a long time, which is not preferable. This is not preferable because the halogen compounds remain and it is necessary to remove all of them later, which causes voids to occur in the recording medium.

Furthermore, in the present invention, it is better not to use a plasticizer when creating a recording medium. For example, if a plasticizer is mixed, the plasticizer remaining without being eluted will swell in the same way as PVCz during the swelling and shrinking process during development. - This is because the material must be subjected to a shrinkage action, and after shrinkage, there is a possibility that a refractive index distribution other than the refractive index modulation that satisfies the Bragg condition may occur in the recording medium. Of course, this does not necessarily mean that it cannot be used as long as it does not cause the above-mentioned inconveniences.

The recording medium made of PVCz of the present invention is the above-mentioned PVCz
It can be obtained by dissolving a halogen compound and other necessary additives in a suitable solvent in a predetermined ratio or forming a dispersion, and then forming a coating film on a suitable substrate such as a glass plate or a plastic film.

The recording medium formed as described above is exposed to light using an optical system as shown in the first diagram using an object beam which is coherent visible light of up to 560 rv+ and a coherent laser beam of two beams as a reference.

Following the exposure process, the unreacted halogen is removed from the recording layer by immersing it in a solvent that hardly dissolves the PvCz constituting the recording layer, as well as the cross-linked PvCz produced by the photoreaction. The compound is almost completely eluted and removed to remove coloring.

Note that this step can also serve as the swelling step described below.

The subsequent development process consists of two steps: a swelling process and a shrinking process.

That is, the recording layer from which a hologram latent image has been formed through the exposure step and from which the halogen compound has been removed is treated with a swelling a liquid, which is a first solvent, to cause swelling in accordance with the formed hologram pattern. The subsequent treatment with the second solvent shrinks the swollen recording layer and amplifies and immobilizes the hologram according to the swollen state.

The swelling liquid, which is the first solvent in the hologram development process, is a solvent that hardly dissolves crosslinked and uncrosslinked PVCz products produced as a result of the photoreaction between PVCz and a halogen compound in a short period of time. be. As such a solvent, those having an appropriate swelling power are selected from among the good solvents listed as special solvents in the present invention, or used in combination.

The shrinking liquid, which is the second solvent, can be any solvent that does not have a swelling or dissolving effect on the recording layer and is compatible with the swelling liquid. Appropriate solvents are selected or used in combination.

In addition, processing conditions such as temperature and time for each step vary depending on the type of recording layer and solvent used, and cannot be unconditionally defined, but numerically, the temperature and time for each step are 10°C to 70°C. A sufficient effect can be achieved by treatment for several seconds to several minutes at a moderate temperature.

It goes without saying that the hologram film obtained as described above can be used while being adhered to the substrate, and furthermore, since the PVC used in the present invention has a high molecular weight, it has sufficient strength even when it is peeled off from the substrate. Therefore, it can be used for various purposes even as a hologram film peeled from a substrate.

(Effect) The volume phase hologram obtained using PVCz having the specific weight average molecular weight and molecular weight distribution of the present invention as described above has a maximum diffraction efficiency of 98% of the volume phase hologram using conventional PVCz. , it has improved to 99.9%, and the A transmittance is 80% at 600 nm.
The haze was 92%, and the haze was 1 at a thickness of 10 μm.
2% improved to below 2%, and an additional 14%
The blue shift of 20 r+m after being left at 0° C. for 2 hours was within 1 nm.

(Example) Next, the present invention will be explained in more detail by giving examples and comparative examples.

Example I PVCZ (Rubican M-170, manufactured by BASF) 20g
was added to a dioxane/isopropyl alcohol mixture (weight ratio 3/1) and dissolved by heating, and after being homogenized, it was cooled to room temperature. The precipitated PVCz was separated by decantation, and the separated PVCz was added to a dioxane/isopropyl alcohol mixture (weight ratio 3/1) and stirred to wash the polymer several times to obtain the PVCz of the present invention.

A part of it was dissolved in tetrahydrofuran, and the column temperature was 2.
Using a gel permeation chromatograph at 7°C, the column was Shodex (Showa Denko @) K.
When F-807 and KF80M were connected and the weight average molecular weight and molecular weight distribution were determined based on polystyrene,
The weight average molecular weight was 1.52 million, and the molecular weight distribution was 1.48. In addition, the content of PVCz with a molecular weight of 200,000 or less is 0.
8% by weight, and the content of PVCz with molecules (1) of 1,000,000 or more was 62% by weight.

2.5 g of the above PVCz and tetraiodine carbon were dissolved in chlorhenzene in a dark place, and coated on a cleaned glass plate using a spinner (manufactured by Kyowa Semiconductor) for ¥1. dry 7
．． A recording layer of 2 μm was formed.

This recording layer was removed using an Ar laser (488 nm).
A hologram was recorded by exposure using the optical system shown in the figure.

After exposure, it was immersed in toluene at 35°C for 2 minutes, xylene at 35°C for 2 minutes, and further immersed in hebutane at 20°C for 2 minutes, followed by drying to obtain a volume phase hologram.

When the reflection diffraction efficiency of the above hologram was measured using a spectrophotometer (Hitachi U-3400) equipped with a reflection device, it was found to be 518
It shows a maximum reflection diffraction efficiency of 99% for light of 600 nm.
The transmittance of nm light is 87%, and the haze (total haze value) is measured using a haze meter (based on JIS K7105).
When measured using a Nippon Juishiki (trade name), it was 1.7%.

Next, after holding the hologram at 140°C for about 5 hours in a nitrogen atmosphere, the characteristics of the hologram were measured using the optical system, and no peak shift in the maximum diffraction efficiency was observed, and no change in the maximum diffraction efficiency or haze value was observed. There wasn't.

Example 2 20 g of PVCZC) L/Bican M-170) was mixed with a dioxane/isopropyl alcohol mixture (weight ratio 3/1).
), the mixture was heated and dissolved, and the mixture was allowed to cool at 28°C. The precipitated PVCz was separated by decantation, and the separated PVCz was added to a dioxane/isopropyl alcohol mixture (weight ratio 371.2) and stirred to wash the polymer several times to obtain the PVCz of the present invention.

When a part of it was measured for weight average molecular weight and molecular weight distribution in the same manner as in Example 1, the weight average molecular weight was 1,760,000, and the molecular weight distribution was 1.51. In addition, the content of PVCz with a molecular weight of 200,000 or less is 0.2% by weight, and the molecule ff
The content of pvCz of 11 million or more was 53% by weight.

The reflection diffraction efficiency of a volume phase type hologram obtained by forming a recording layer in the same manner as in Example 1 and performing exposure and development in the same manner as in Example 1, except that the film thickness was 10.2 μm using the above PVCz, was 99. 9%, transmittance is 92%, haze is 1.6%
In particular, the haze was the same even though the thickness of the recording layer was increased by 50%. Also, the same results as in Example 1 were obtained in the heat storage test.

Comparative Example 1 PVCz (Rubican M-1) before special production in Example 1
A volume phase hologram of a comparative example was obtained by forming a recording layer, exposing and developing in the same manner as in Example 1 using 2.5 g of 70 (manufactured by BASF, trade name). When this hologram was measured in the same manner as in Example 1, the diffraction efficiency was only 4%, the transmittance was poor at 68%, and it was clearly cloudy, so there was no need to measure the haze value. Moreover, after the same heating test as in Example 1, diffraction was completely lost.

In addition, the development conditions in the above were immersion in toluene at 20°C for 2 minutes, immersion in xylene at 25°C for 2 minutes, and then immersion in 20°C
When the film was immersed in hebutane for 2 minutes and developed at low temperature, the diffraction efficiency was 12% and the transmittance was 77%.
The diffraction efficiency disappeared after a 5 hour heating test at °C.

When the above-mentioned PVCz before special production was measured under the same conditions as in Example 1, the weight average molecular weight was 920,000 and the molecular weight distribution was 5.4.

Comparative Example 2 Unrefined PVC instead of special PVCz in Example 1
Z (Tubicol 2105P (manufactured by Anan Kaori ■)) 2.
A volume phase hologram of a comparative example was obtained by forming a recording layer, exposing and developing in the same manner as in Example 1, using 5 g. This hologram also has a maximum diffraction efficiency of 23% (52
00,000 m), transmittance of 73% and haze of 21%, and
After a heating test of 140°C for 5 hours, the peak wavelength was 501 nm.
m, and the maximum diffraction efficiency decreased to 6%.

When the above-mentioned PVCz before special production was measured under the same conditions as in Example 1, the weight average molecular weight was 780,000, and the molecular weight distribution was 4.6.

[Brief explanation of the drawing]

FIG. 1 shows a hologram recording optical system used in Examples.

Claims (3)

[Claims] (1) Poly(N-
vinyl carbazole). (2) The poly(N-vinylcarbazole) according to claim 1, wherein the content of poly(N-vinylcarbazole) having a weight average molecular weight of 200,000 or less is 1% by weight or less of the total weight. (3) The poly(N-vinylcarbazole) according to claim 1, wherein the content of poly(N-vinylcarbazole) having a weight average molecular weight of 1 million or more is 50% by weight or more of the total weight.
.