RU2541521C2 - Liquid composition for photopolymerisation-able film for hologram recording, method of composition obtaining, method of obtaining said film - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: inventions relate to liquid composition for obtaining photopolymerisation-able film for recording holograms, method of obtaining said liquid composition and method of obtaining photopolymerisation-able film. Claimed photopolymerisation-able film forms image due to refractive index modulation with exposure to activating irradiation with wavelength 325-550 nm. Composition contains from 30 to 69.45 wt % of liquid acryl monomer, which has at least one acid group COOH and belongs to carboxylic acids, from 30 to 69.45 wt % pf oligomers of mono- and diacrylates, from 0.5 to 25 wt % of nanoparticles of oxides of zinc, or silicon, or titanium or metal sulphides ZnS or CdS, covered or non-covered with organic envelopes and having size from 2 to 30 nm, from 0.05 to 5 wt % of photopolymerisation initiator.

EFFECT: increased value of refraction index modulation, increase of diffraction efficiency to 60% and increase of obtained photopolymerisation-able film thickness to 30 mcm, which is provided due to application in composition of highly-refractive nanoparticles, photostimulated diffusion of which creates refraction index modulation.

3 cl, 3 tbl, 8 ex

Description

The invention relates to organic photosensitive recording media, and in particular to methods for producing photopolymerization films for recording holograms, as well as to compositions and methods for their preparation for the manufacture of the above films. The proposed photopolymerization film forms an image due to a change in the refractive index upon exposure to the activation of irradiation with ultraviolet and visible light with a wavelength of 325-550 nm.

Known compositions for photopolymerization films and methods for producing photopolymer films for recording holograms. They can be divided into three main categories: liquid coatings containing a photoinitiator and monomers, compositions for dry films containing a photoinitiating system, a monomer and a binder polymer component forming a film, and compositions for dry films containing a crosslinking polymer and a photosensitizer or initiator.

Known composition for photopolymerization film, a method for its production and a method of manufacturing a photopolymerization film for recording holograms (RF patent No. 2325680 dated 04/22/2004, IPC G03F 7/031, G03F 7/028, G03F 7/033, G02B 5/32). The composition of the photopolymerizable recording medium consists of an unsaturated compound capable of ion-radical photopolymerization; a system providing photoactivation by radiation in the spectral region of 400-600 nm and consisting of a photochromic compound and a co-initiator. The composition contains a photochromic compound with a long photoinduced form life or a thermally irreversible photochromic compound and, optionally, a polymeric binder, a plasticizer and a non-polymerization organic liquid with a high refractive index.

The method for preparing the composition consists in preparing a solution of the solid photochromic compound ФНХ 1 in N-vinylpyrrolidone and adding to the resulting solution a mixture of polymerization compounds (OKM-2 and TATMT), as well as a DMEA co-initiator. The resulting solution was thoroughly mixed and evacuated.

A method for producing a photopolymerization-capable film includes applying the prepared solution to an Mylar film with a dividing pad of a given thickness and coating it on top with a second Mylar film. The result was triplex material.

The disadvantages of the known analogue composition for photopolymerization film: the presence of a plasticizer and non-polymerization organic liquid with a high refractive index determine the diffusion after recording and degradation of the recorded hologram, especially at elevated temperatures. The use of a complex photoactivation system, consisting of a photochromic compound and a co-initiator, and the presence of a polymer binder complicates the process chain.

The disadvantage of the method of obtaining the composition is the use of solvents, which, despite evacuation, will determine the presence of residual solvents in the films, and, therefore, their diffusion after recording and degradation of the recorded hologram, especially at elevated temperatures.

A disadvantage of the known method for producing photopolymerization-capable films for recording holograms was that the photopolymerizable layer was placed between two Dacron films separated by a 0.5 mm thick polymer gasket, the central part of which was cut out and filled with a photopolymerizable composition. A similar method does not guarantee the same thickness of the resulting films. The thickness difference is undesirable for a holographic film, since at different thicknesses there will be a different phase incursion, and, therefore, chaotic modulation of the brightness of the recorded hologram.

The known composition for a photopolymerization film, the method for producing the composition and the method for producing the above film are selected as a prototype (RF patent No. 2331095 from 8.12.2006, IPC G03F 7/028, G03F 7/033).

The composition for a dry photopolymerization film is a liquid acrylic monomer with one (meta) acrylic group; bifunctional acrylic oligomer with two (meta) acrylic groups; thermoplastic linear polymer; photoinitiator of polymerization by activating irradiation of light with a wavelength of 350-400 nm; low boiling solvent; solvent, dissolving thermoplastic polymer-binding component.

The disadvantage of the composition of the prototype is the presence of a thermoplastic linear polymer, which complicates the process chain and reduces the thermal stability of the finished hologram.

A method of obtaining a composition includes preparing solutions by adding components to a solvent and then stirring with a magnetic stirrer until completely dissolved.

The disadvantage of the method of obtaining the composition of the prototype is the use of solvents in classical photopolymers for the preparation of films from them, which determines the presence of residual solvents in the films, and therefore their diffusion after recording and degradation of the recorded hologram, especially at elevated temperatures.

A method of obtaining a dry photopolymerization film consists in applying a composite of a low boiling solvent using a centrifuge. The solutions are applied to the glass substrate at a substrate rotation speed of 8 rpm using an applicator and a laminating machine. Then the film is dried under the foil at room temperature and finally at 70 ° C.

The disadvantage of the method of producing photopolymer films for recording holograms by centrifugation is the limitation on the thickness of the obtained films, not more than 5 microns.

The group of inventions solves the problem of increasing the modulation of the refractive index, increasing the diffraction efficiency and increasing the thickness of the obtained photopolymerization film.

The problem is achieved by using a photopolymerizable monomer composition filled with nanoparticles, the photoinduced movement of which leads to a significant value of Δη as a result of a significant difference in the refractive index of the nanoparticles and the matrix, and polymerization - to fix the recorded hologram.

The liquid composition for producing a photopolymerization film for recording a hologram, which forms an image by modulating the refractive index upon exposure to activating radiation with a wavelength of 325-550 nm, contains a mixture of from 30 to 69.45 wt.% Liquid acrylic monomer having at least , one acid group of COOH and related to carboxylic acids and from 30 to 69.45 wt.% oligomers of mono- and di-acrylates, from 0.5 to 25 wt.% of one of the types of nanoparticles ZnO, SiO ₂ , TiO ₂ , ZnS , CdS, whether or not coated with organic shells sizes ranging from 2 to 30 nm, as well as from 0.05 to 5 wt.% photopolymerization initiator, which is used as 2,2-dimethoxy-2-phenylacetophenone or bis- (5-2,4-cyclopentadiene-1-yl ) bis- [2,6-difluoro-3- (1 H-pyrrol-1-yl) phenyl] titanium.

A method of obtaining the aforementioned liquid composition for producing a photopolymerization film includes mixing and heating the above liquid composition and stirring for 2 hours at t = 90 ° C, then, with constant stirring at t = 90 ° C, the indicated amount of nanoparticles from the above list is portionwise introduced into the heated liquid composition to obtain a clear solution, after complete dispersion of the nanoparticles in the monomer mixture of the liquid composition, continuous stirring is carried out for 1 hour at t = 90 ° C, add annoe amount of photopolymerization initiator, and a liquid formulation was stirred for 1 hour at the temperature t = 90 ° C, the resulting composition was stored in a thermostat at t = 40 ° C.

A method of obtaining a photopolymerization film for recording a hologram includes applying the above liquid composition in the form of a drop on a polymer polyester film, covering it with another same film and rolling it between the rollers at a temperature of + 20 to + 60 ° C.

The essence of the claimed invention is illustrated by the following.

As a result of scientific research, the main factors that influence the optical and other important operational properties of the film are found.

The first important factor is the chemical structure of acrylic components. A necessary condition for the stabilization of nanoparticles is the presence of acid groups in at least one of the components of the composition.

The second factor that affects the quality of the film is the conditions for introducing nanoparticles into the composition, which ensure desorption of water from their surface and adsorption of acrylates.

The third factor that affects the quality of the film is the method of initiating three-dimensional radical polymerization of acrylic components, which determines the initiation rate, concentration of free radicals, and rate constants of the polymerization process.

To solve this problem, it is necessary to synthesize nanocomposites suitable for producing a photopolymerization film, create a homogeneous composition of the aforementioned acrylic components and nanoparticles, choose a photoinitiator of radical polymerization of the aforementioned acrylic components when exposed to activating radiation with a wavelength in the region of 325-550 nm.

In the proposed inventions, in order to achieve the necessary properties of the aforementioned photopolymerization-capable nanocomposite film, a composition of polymerization-capable components and nanoparticles is used. In general terms, the composition consists of:

- mixtures of monomers,

- nanoparticles (ZnO, SiO ₂ and TiO ₂ ),

- initiator of photopolymerization.

A mixture of monomers plays the role of a matrix in which the distribution of nanoparticles occurs and their stabilization is observed. Carboxylic acids (2-carboxyethyl acrylate or carboxylic acid) actively interact with nanoparticles and modify their surface in such a way that they improve the compatibility of inorganic nanoparticles with an organic acrylic matrix. The presence of glycerolate bisphenol A monomer in the solution allows the formation of a polymer network. The phenoxyethyl acrylate monomer related to acrylic oligomers acts as a modifier of the mixture of acrylic monomers, which allows the viscosity of the mixture to be varied, and thus, the rate of photoinduced diffusion of nanoparticles during recording can be affected. It is important that phenoxyethyl acrylate is compatible with bisphenol A glycerolate and carboxylic acids, but does not interact with nanoparticles. The refractive index of nanoparticles is significantly different from the refractive index of the monomer matrix, which determines a significant modulation of the refractive index during the redistribution of nanoparticles.

The following monomers were used to prepare the formulations:

1.2-carboxyethyl acrylate (Aldrich No. 552348, 2Car)

2. Acrylic acid (Aldrich No. 147230, AcAc)

3. Bisphenol A glycerolate (Aldrich No. 41, 116-7, BisA)

4. Phenoxyethyl acrylate (Aldrich No. 40, 833-6, PEA)

Studies have shown that any known radical polymerization initiator can be used to cure the liquid photopolymerization composition of this invention. Specific initiators providing the best recording characteristics for specific areas of the spectrum:

1. In2 - 2,2-dimethoxy-2-phenylacetophenone (Aldrich No.19, 611-8), radiation 320-380 nm.

2. Irgacure 784 (Irg) - bis- (4-cyclopentadien-1-yl) -bis- [2,6-difluoro-3- (1H-pyrrol-1-yl) phenyl] titanium, radiation 440-532 nm.

Nanoparticles:

1. Zinc oxide (ZnO), size 30 nm. Composites were obtained based on ZnO nanoparticles, which made it possible to obtain elements with the highest diffraction efficiency.

2. Silicon oxide i (Aldrich No. 066К0110, SiO ₂ ), size 14 nm. Composites were obtained on the basis of SiO ₂ nanoparticles, which made it possible to obtain holograms with thermal stability up to 150 ° C.

The ratio of the components in the photopolymerization composition is presented in the composition table.

Example 1. The method of preparation of the composition 2Car / BisA / ZnO

The main components are 9.95 wt.% ZnO nanoparticles, 62.69 wt.% 2Car, 26.86 wt.% BisA, 0.5 wt.% Irgacure 784.

At t = 90 ° C, the 2Car / BisA composition is constantly stirred for 2 hours. Then, with constant stirring at t = 90 ° C, 9.95 wt.% ZnO are introduced into the mixture in small portions until completely dissolved in the monomer mixture to form a clear solution . The resulting composition from the moment of complete dissolution of the nanoparticles is stirred for 2 hours at a temperature of t = 90 ° C. The necessary initiator is added and mixed for 1 hour at t = 90 ° C. The initiator bis- (4-cyclopentadiene-1-yl) -bis- [2,6-difluoro-3- (1H-pyrrol-1-yl) phenyl] titanium (Irgacure 784) can be pre-dissolved before being added to the mixture for better solubility in methylene chloride.

Example 2. Preparation of 2Car / BisA / PEA / ZnO

The main components are 9.95% by weight ZnO nanoparticles, 49.25% by weight 2Car, 22.39% by weight BisA, 17.91% by weight PEA, 0.5% by weight Irgacure 784.

At t = 90 ° C, 2Car / BisA is stirred for 2 hours. Then, with constant stirring at t = 90 ° C, 9.95 wt.% ZnO are introduced into the mixture in small portions until completely dissolved in the monomer mixture to form a clear solution. The resulting composition from the moment of complete dissolution of the nanoparticles is stirred for 1 h at a temperature of t = 90 ° C. Next, PEA is added and thoroughly mixed for 1 h at a temperature of t = 90 ° C. Next, the initiator is added, mixed for 1 hour at t = 90 ° C. The initiator bis- (4-cyclopentadiene-1-yl) -bis- [2,6-difluoro-3- (1H-pyrrol-1-yl) phenyl] titanium (Irgacure 784) can be pre-dissolved before being added to the mixture for better solubility in methylene chloride.

Example 3. Preparation of 2Car / BisA / PEA / SiO ₂ Formulations

The main components are 8.95 wt.% SiO ₂ nanoparticles, 49.80 wt.% 2Car, 22.64 wt. % BisA, 18.11 wt.% PEA, 0.5 wt.% Irgacure 784.

At t = 90 ° C, 2Car / BisA is stirred for 2 hours. Then, with constant stirring at t = 90 ° C, 8.95 wt.% SiO ₂ are introduced into the mixture in small portions until completely dissolved in the monomer mixture to form a clear solution. The resulting composition from the moment of complete dissolution of the nanoparticles is stirred for 1 h at a temperature of t = 90 ° C. Next, PEA is added and thoroughly mixed for 1 h at a temperature of t = 90 ° C. Next, the initiator is added, mixed for 1 hour at t = 90 ° C. The initiator bis- (4-cyclopentadiene-1-yl) -bis- [2,6-difluoro-3- (1H-pyrrol-1-yl) phenyl] titanium (Irgacure 784) can be pre-dissolved before being added to the mixture for better solubility in methylene chloride.

An example of obtaining a photopolymerization film

We apply the above photopolymerization-friendly composition (example 1) in the form of a drop on a polymer polyester film, cover it with another same film and roll it between the rollers at a temperature of + 25 ° С.

Description of the holographic recording of periodic structures on the developed nanocomposites.

Materials (with In2 and Irgacure 784 initiators) were exposed to radiation from a GKL-40 (I) helium-cadmium laser with wavelengths of 325 nm 442 nm, an output power of 15 and 50 mW at an energy density of 3 · 10 ^-2 J / cm ² , at angles between interfering beams 3 ° -45 °, exposure durations 2-700 s, layer thicknesses 20-100 microns. Transmit holograms were obtained and diffraction efficiency was determined by the ratio of the radiation intensity in the first diffraction order to the incident radiation intensity at a wavelength of 633 nm. After recording in the interference field (exposure), a mercury lamp was illuminated for five minutes. Diffraction efficiency was determined after recording in an interference field or after recording and exposure to a mercury lamp. Checked the stability of holograms during heat treatment under conditions characteristic of lamination (150 ° C for 5 min).

The following examples show the results of a holographic recording carried out on developed nanocomposites.

Example 1

1. Holograms of plane waves were recorded. For recording, materials (with the introduction of the In2 initiator) were exposed to the radiation of a GKL-40 (I) helium-cadmium laser with a wavelength of 325 nm, an output power of 15 mW at an energy density of 10 ^-2 J / cm ² , when the angle between the interfering beams varies in the range 3 ° -45 °, exposure durations 2-600 s, layer thicknesses 20-100 microns. Diffraction efficiency was determined by the ratio of the radiation intensity in the first diffraction order to the intensity of the incident radiation at a wavelength of 633 nm.

Example 2

2. Materials (with initiator Irgacure 784) were exposed to the radiation of a GKL-40 (I) helium-cadmium laser with a wavelength of 442 nm, an output power of 50 mW at an energy density of 3 · 10 ^-2 J / cm ² , at angles between interfering beams 3 ° -45 °, exposure durations 2-700 s, layer thicknesses 20-100 microns. Received transmitting holograms and determined diffraction efficiency according to claim 1

Example 3

3. Materials were exposed (by items 1, 2), diffraction efficiency was determined after exposure

Example 4

4. The materials were exposed (in paragraphs 1, 2) and exposed to UV radiation of a mercury lamp with a wavelength of 365 nm at an illumination of 10 W / m ² for 5 min, diffraction efficiency was determined after exposure.

Example 5

5. The materials were exposed (according to claims 1, 2), exposed to UV radiation (according to claims 4), warmed up at a temperature of 150 ° С for 5 minutes, diffraction efficiency was determined after heating.

Table 1 shows the maximum values of diffraction efficiency for transmission holograms obtained according to paragraphs. 3-5.

Table 2 shows the sensitivity values of materials at different exposure wavelengths and initiator concentrations.

Thus, the inventive method for producing a photopolymerization film for recording a hologram, a composition for producing the above film, and a method for producing this composition provide a hologram that does not require post-exposure processing with a large Δn and, therefore, a sufficiently high diffraction efficiency of up to 60% at 30 microns thick.

The photopolymerization film and the holograms recorded on it have a number of additional advantages compared to the known materials - the high heat resistance required for lamination. The recorded hologram withstands heating up to 150 ° C for 5 minutes without loss of diffraction efficiency. This is achieved by the absence of thermoplastic components in the composition and the irreversible photoinduced movement of nanoparticles, fixed during cross-linking of the material.

The moisture resistance of the composition is significantly higher than that of known holographic polymers, due to the lack of hydrophilic in the composition and the presence of inorganic nanoparticles chemically bonded to the polymer.

Claims (3)

1. A liquid composition for producing a photopolymerization film for recording a hologram, which forms an image by modulating the refractive index during exposure by activating radiation with a wavelength of 325-550 nm, containing a mixture of liquid acrylic monomer and acrylic oligomer, as well as a photopolymerization initiator, characterized in that contains from 30 to 69.45 weight. % liquid acrylic monomer having at least one acid group COOH and related to carboxylic acids, from 30 to 69.45 weight. % oligomers of mono- and diacrylates, from 0.5 to 25 wt.% nanoparticles of ZnO, or SiO ₂ , or TiO ₂ oxides or metal sulfides ZnS or CdS, coated or not coated with organic shells and having a size of from 2 to 30 nm, from 0.05 to 5 wt.% Photopolymerization initiator, which is used as 2,2-dimethoxy-2-phenylacetophenone or bis- (5-2,4-cyclopentadiene-1-yl) bis- [2,6-difluoro-3 - (1H-pyrrol-1-yl) phenyl] titanium. 2. The method of producing a liquid composition for producing a photopolymerization film according to claim 1, comprising mixing the above components, characterized in that the above liquid composition is heated and constantly stirred for 2 hours at t = 90 ° C, then with constant stirring at t = 90 ° C, the indicated amount of nanoparticles from the specified list is portionwise introduced into the heated liquid composition until a clear solution is obtained; after the nanoparticles are completely dispersed in the monomer mixture of the liquid composition, a constant stirring for 1 hour at t = 90 ° C, add the indicated amount of photopolymerization initiator, and the liquid composition is stirred for 1 hour at a temperature of t = 90 ° C. 3. A method of producing a photopolymerization film for recording a hologram, comprising applying a liquid composition to a substrate and rolling between rollers, characterized in that the liquid composition according to claim 1 is applied in the form of a droplet onto a polymer polyester film, closed with another same film, and between the rollers rolled at a temperature of +20 to + 60 ° C.