Oligomer and preparation method thereof, holographic recording medium and holographic optical element

Abstract

The invention discloses a sulfur-containing isocyanate-terminated first oligomer, a preparation method of the sulfur-containing isocyanate-terminated first oligomer, a sulfur-containing hydroxyl-terminated second oligomer, a preparation method of the sulfur-containing hydroxyl-terminated second oligomer, a photopolymer type holographic recording medium and a holographic optical element. The film-forming resin comprises a sulfur-containing isocyanate-terminated first oligomer and a polyhydroxy compound, or the film-forming resin comprises a sulfur-containing hydroxyl-terminated second oligomer and a polyfunctional isocyanate. In this way, environmental pollution and damage to health of production personnel caused by volatilization of mercaptan in the preparation process of the photopolymer type holographic recording medium can be effectively avoided, and the average refractive index of the photopolymer is increased.

Description

Technical Field

[0001] The present application relates to the technical field of optical functional materials, and in particular to a sulfur-containing isocyanate-terminated first oligomer and a preparation method thereof, a sulfur-containing hydroxyl-terminated second oligomer and a preparation method thereof, a photopolymer holographic recording medium and a holographic optical element. Background Art

[0002] Augmented Reality (AR) technology based on holographic waveguide systems has great application potential. The core optical element of the holographic waveguide system is a pair of volume holographic gratings. Photopolymer is the preferred recording medium for preparing volume holographic gratings. The average refractive index of photopolymers is generally low. Due to the small molar volume and high molar refractive index of sulfur atoms, the introduction of sulfur atoms into film-forming resins in related technologies can effectively increase the refractive index of film-forming resins, thereby further increasing the average refractive index of photopolymers. However, thiols generally have high biological toxicity, and the volatilization of thiols during the production process will cause great harm to the health of production personnel and the environment. Summary of the invention

[0003] Based on this, the present application provides a sulfur-containing isocyanate-terminated first oligomer and a preparation method thereof, a sulfur-containing hydroxyl-terminated second oligomer and a preparation method thereof, a photopolymer holographic recording medium and a holographic optical element, which can effectively avoid environmental pollution caused by thiol volatilization during the preparation process and damage to the health of production personnel.

[0004] In a first aspect, the present application provides a sulfur-containing isocyanate-terminated first oligomer, wherein the first oligomer comprises a sulfur atom and a free isocyanate group, wherein the sulfur atom is formed by a thiol group being terminated by isocyanate, and the average molecular weight of the first oligomer ranges from 300 to 10,000.

[0005] In a second aspect, the present application provides a sulfur-containing hydroxyl-terminated second oligomer, wherein the second oligomer comprises a sulfur atom, an isocyanate terminated by a hydroxyl group, and a free hydroxyl group, wherein the sulfur atom is formed by a thiol group terminated by an isocyanate, and the average molecular weight of the second oligomer is in the range of 500-10000.

[0006] In a third aspect, the present application provides a method for preparing the sulfur-containing isocyanate-terminated first oligomer as described above, the method comprising:

[0007] Providing a multifunctional thiol, a multifunctional isocyanate and a first catalyst;

[0008] Providing a reaction environment for compounds without active hydrogen;

[0009] The multifunctional thiol, the multifunctional isocyanate and the first catalyst are added into the reaction environment to form a reaction system, and the sulfur-containing isocyanate-terminated first oligomer is obtained after a reaction occurs in the reaction system.

[0010] In a fourth aspect, the present application provides a method for preparing the sulfur-containing hydroxyl-terminated second oligomer as described above, the method comprising:

[0011] Providing a multifunctional thiol, a multifunctional isocyanate, a first catalyst and a polyhydroxy compound;

[0012] Providing a reaction environment for compounds without active hydrogen;

[0013] The multifunctional thiol, the multifunctional isocyanate and the first catalyst are added into the reaction environment to form a reaction system. After the reaction occurs in the reaction system, the polyhydroxy compound is added into the reaction system to continue the reaction to obtain the sulfur-containing hydroxyl-terminated second oligomer.

[0014] In a fifth aspect, the present application provides a photopolymer holographic recording medium, which includes a film-forming resin, and the film-forming resin includes the sulfur-containing isocyanate-terminated first oligomer and a polyhydroxy compound as described above, or the film-forming resin includes the sulfur-containing hydroxyl-terminated second oligomer and a polyfunctional isocyanate as described above.

[0015] In a sixth aspect, the present application provides a holographic optical element, wherein the raw material of the holographic optical element includes the photopolymer holographic recording medium as described above.

[0016] The embodiment of the present application provides a sulfur-containing isocyanate-terminated first oligomer and a preparation method thereof, a sulfur-containing hydroxyl-terminated second oligomer and a preparation method thereof, a photopolymer-type holographic recording medium and a holographic optical element. The oligomer includes a sulfur atom and a free isocyanate group, or includes a sulfur atom, an isocyanate terminated by a hydroxyl group, and a free hydroxyl group, wherein the sulfur atom is formed by a mercapto group terminated by an isocyanate; since the molecular weight of the sulfur-containing first oligomer is larger than the molecular weight of a thiol commonly used in a photopolymer, the sulfur-containing oligomer will not volatilize, thereby effectively avoiding the volatility problem of the thiol. The resulting environmental pollution and damage to the health of production personnel; since the first oligomer includes free isocyanate, the sulfur-containing first oligomer can be used together with a polyhydroxy compound to form isocyanate-alcohol as a film-forming resin for a photopolymer type holographic recording medium, or since the second oligomer includes free hydroxyl groups, the sulfur-containing second oligomer can be used together with a polyfunctional isocyanate to form isocyanate-alcohol as a film-forming resin for a photopolymer type holographic recording medium, so the sulfur atoms in the film-forming resin can effectively increase the refractive index of the film-forming resin, thereby further increasing the average refractive index of the photopolymer.

[0017] The average refractive index of the photopolymer holographic recording medium based on the above-mentioned oligomer and using isocyanate-alcohol as the film-forming resin can be increased by 0.2 to 0.5, which can effectively improve the design flexibility of optical components and reduce the refractive index difference between photopolymers and common optical lenses; when the above-mentioned oligomer is used to prepare the photopolymer holographic recording medium, the photopolymer sample has high photosensitivity and can record transmission / reflection volume holographic gratings with high diffraction efficiency (>90%). BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic flow chart of an embodiment of a method for preparing a sulfur-containing isocyanate-terminated first oligomer of the present application;

[0019] Figure 2 It is a schematic flow chart of an embodiment of a method for preparing a sulfur-containing hydroxyl-terminated second oligomer of the present application;

[0020] Figure 3 It is a schematic diagram of the reaction mechanism of isocyanate group with hydroxyl or thiol group;

[0021] Figure 4 is the holographic exposure characteristic curve of the samples in Example 3 of the present application, wherein samples 1-1, 1-2, and 1-3 record transmission gratings, and 1-4 and 1-5 record reflection gratings;

[0022] Figure 5 is the holographic exposure characteristic curve of the samples in Example 4 of the present application, wherein samples 2-1, 2-2, and 2-3 record transmission gratings, and 2-4 and 2-5 record reflection gratings;

[0023] Figure 6 It is the holographic exposure characteristic curve of the samples in Comparative Examples 1, 2, 3, and 4 of the present application, wherein Comparative Examples 2 and 4 record transmission gratings, and Comparative Examples 1 and 3 record reflection gratings. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0025] The flowcharts shown in the accompanying drawings are only examples and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps may also be decomposed, combined or partially merged, so the actual execution order may change according to actual conditions.

[0026] In the subsequent description, the suffixes such as "module", "component" or "unit" used to represent elements are only used to facilitate the description of the present application, and have no special meanings. Therefore, "module", "component" or "unit" can be used in a mixed manner.

[0027] As an important part of future digital interaction, augmented reality (AR) technology is leading a new round of technological innovation with its unique charm. With the continuous advancement of technology and the wide expansion of applications, the application prospects of AR are becoming more and more broad, and it will show great potential in many fields.

[0028] AR glasses based on holographic waveguide systems have great application potential. It can make the design of AR glasses thinner and more portable, and can bring users more realistic and natural virtual images and excellent transparency. The core optical element of the holographic waveguide system is a pair of volume holographic gratings. Photopolymer is the preferred recording medium for preparing volume holographic gratings.

[0029] Since the average refractive index of photopolymers is generally low, the critical total reflection angle in the optical waveguide is large; this means that in order to maintain the total reflection propagation of light in the waveguide, a larger incident angle is required. This limits the design flexibility of optical components and increases the complexity of optical path design, which is not conducive to the high-density integration of optical components. The refractive index difference between photopolymers and commonly used input / output couplers (such as optical fibers or other optical components) is large; when the optical signal enters the optical waveguide from the coupler or is output from the optical waveguide to the coupler, the optical signal is prone to refraction or Fresnel reflection at the interface due to the mismatch of the refractive index; this not only leads to the loss of light energy, but also may generate stray light, affecting the imaging quality; due to the refraction or Fresnel reflection of the light signal at the interface, the image is prone to "ghosting" when displayed, which will reduce the clarity and contrast of the image and affect the user experience.

[0030] Photopolymer holographic recording media usually contain a film-forming resin with a low refractive index and a writing monomer with a high refractive index. Sulfur atoms have a small molar volume and a high molar refractive index. Introducing sulfur atoms into the film-forming resin can effectively increase the refractive index of the film-forming resin, thereby further increasing the average refractive index of the photopolymer. However, since thiols generally have high biological toxicity, they can easily cause damage to the nervous system and liver and kidney functions of users during use; and photopolymer films are generally produced by scraping, casting, spin coating, printing (including screen printing, spray printing and inkjet printing), etc., and the volatilization of thiols during the production process will cause great harm to workers' health and the environment.

[0031] In order to solve the above problems, the embodiments of the present application provide a first oligomer containing sulfur and terminated by isocyanate and a preparation method thereof, a second oligomer containing sulfur and terminated by hydroxyl and a preparation method thereof, a photopolymer type holographic recording medium and a holographic optical element. The oligomer includes sulfur atoms and free isocyanate groups, or includes sulfur atoms, isocyanate terminated by hydroxyl groups and free hydroxyl groups, and the sulfur atoms are formed by the thiol groups being terminated by isocyanate. Since the molecular weight of the first oligomer containing sulfur is larger than the molecular weight of the thiol commonly used in the photopolymer, the oligomer containing sulfur will not volatilize, so the volatilization of the thiol can be effectively avoided. Since the first oligomer includes free isocyanate, the sulfur-containing first oligomer can be used together with polyhydroxy compounds to form isocyanate-alcohol as a film-forming resin for a photopolymer type holographic recording medium, or since the second oligomer includes free hydroxyl groups, the sulfur-containing second oligomer can be used together with polyfunctional isocyanate to form isocyanate-alcohol as a film-forming resin for a photopolymer type holographic recording medium, so the sulfur atoms in the film-forming resin can effectively increase the refractive index of the film-forming resin, thereby further increasing the average refractive index of the photopolymer.

[0032] The average refractive index of the photopolymer holographic recording medium based on the above-mentioned oligomer and using isocyanate-alcohol as the film-forming resin can be increased by 0.2 to 0.5, which can effectively improve the design flexibility of optical components and reduce the refractive index difference between photopolymers and common optical lenses; when the above-mentioned oligomer is used to prepare the photopolymer holographic recording medium, the photopolymer sample has high photosensitivity and can record transmission / reflection volume holographic gratings with high diffraction efficiency (>90%).

[0033] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0034] The embodiment of the present application provides a sulfur-containing isocyanate-terminated first oligomer, the first oligomer includes a sulfur atom and a free isocyanate group, the sulfur atom is formed by the thiol group being terminated by isocyanate, and the average molecular weight of the first oligomer ranges from 300 to 10000. It should be noted that the first oligomer can be a single-component substance, or a mixture of multiple components, each of the multiple components includes a sulfur atom and a free isocyanate group, the sulfur atom is formed by the thiol group being terminated by isocyanate.

[0035] The first oligomer contains sulfur atoms, and the molecular weight of the first oligomer is greater than the molecular weight of thiol commonly used in photopolymer holographic recording media. The sulfur-containing first oligomer does not volatilize, and thus can effectively avoid environmental pollution and damage to the health of production personnel caused by the volatility of thiol; the first oligomer contains free isocyanate groups, and the first oligomer can be used together with polyhydroxy compounds as isocyanate-alcohol as a film-forming resin of the photopolymer holographic recording medium, thereby providing technical support for effectively improving the refractive index of the film-forming resin and providing technical support for further improving the average refractive index of the photopolymer.

[0036] In some embodiments, the first oligomer can be obtained by reacting a multifunctional thiol with a multifunctional isocyanate.

[0037] Polyfunctional thiols may refer to compounds containing multiple thiol functional groups (-SH), generally including thiols (a class of non-aromatic compounds containing thiol functional groups, such as dithiol, trithiol, etc.), thiophenols (such as dithiol, trithiol, etc.). Polyfunctional isocyanates may refer to compounds containing multiple isocyanate groups (-NCO) (such as diisocyanates, triisocyanates, etc.).

[0038] The reaction of multifunctional thiol and multifunctional isocyanate is mainly an addition reaction between the thiol functional group (-SH) and the isocyanate group (-NCO), the hydrogen atom (H) on the thiol functional group (-SH) is added to the nitrogen atom (N) on the isocyanate group (-NCO), the sulfur atom (S) on the thiol functional group (-SH) is added to the carbon atom (C) on the isocyanate group (-NCO), and the carbon-nitrogen double bond of the isocyanate group (-NCO) is converted into a carbon-nitrogen single bond.

[0039] In some embodiments, the polyfunctional thiol includes a difunctional thiol, and the polyfunctional isocyanate includes a difunctional isocyanate.

[0040] Difunctional thiol may refer to a class of compounds containing two thiol functional groups (-SH), and difunctional isocyanate may refer to a class of compounds containing two isocyanate groups (-NCO); the embodiment of the present application adopts the reaction of difunctional thiol and difunctional isocyanate to obtain a linear sulfur-containing isocyanate-terminated first oligomer as the main product. In this way, when the linear sulfur-containing isocyanate-terminated first oligomer and the polyhydroxy compound are used as film-forming resins, it is possible to avoid the diffusion and migration of the writing monomer due to excessive crosslinking of the film-forming resin, thereby affecting the formation of volume holographic grating (VHG) and reducing the sensitivity of the material.

[0041] In some embodiments, the difunctional thiol includes at least one of 1,2-benzenedithiol, 1,3-benzenedithiol, 1,4-benzenedithiol, 2,6-naphthalenedithiol, toluene-3,4-dithiol, biphenyl-4,4'-dithiol, 4'4-dimercaptodiphenyl sulfide, ethanedithiol, 1,3-propanedithiol, 1,4-butanedithiol, 1,5-pentanedithiol, 1,6-hexanedithiol, 1,7-heptanedithiol, 1,8-octanedithiol, 1,9-nonanedithiol, 1,10-decanedithiol, 1,2-butanedithiol, 2,2'-thiobis(ethanethiol), 3,7-dithia-1,9-nonanedithiol, and 1,6-dimercapto-3-hexanethiol.

[0042] In some embodiments, the bifunctional thiol includes at least one of ethanedithiol, 1,3-propanedithiol, 1,4-butanedithiol, 1,5-pentanedithiol, 1,6-hexanedithiol, 1,7-heptanedithiol, 1,8-octanedithiol, 1,9-nonanedithiol, 1,10-decanedithiol, 1,2-butanedithiol, 2,2'-thiobis(ethanethiol), 3,7-dithia-1,9-nonanedithiol, and 1,6-dimercapto-3-hexanesulfide.

[0043] In some embodiments, the difunctional isocyanate includes at least one of hexamethylene diisocyanate, isophorone diisocyanate, trimethylhexamethylene diisocyanate, butane-1,4-diisocyanate, dicyclohexylmethane diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, 1,4-cyclohexane diisocyanate, meta-xylylene diisocyanate, ditoluene diisocyanate, p-phenylene diisocyanate, meta-phenylene diisocyanate, toluene 2,6-diisocyanate, toluene-2,5-diisocyanate, 1,4-cyclohexane dimethyl diisocyanate, and 1,3-bis(1-isocyanato-1-methylethyl)benzene.

[0044] In some embodiments, the difunctional isocyanate includes at least one of hexamethylene diisocyanate, isophorone diisocyanate, trimethylhexamethylene diisocyanate, butane-1,4-diisocyanate, dicyclohexylmethane diisocyanate, and 1,4-cyclohexanedimethyl diisocyanate.

[0045] The embodiment of the present application also provides a sulfur-containing hydroxyl-terminated second oligomer, the second oligomer includes a sulfur atom, an isocyanate terminated by a hydroxyl group, and a free hydroxyl group, the sulfur atom is formed by the thiol group being terminated by the isocyanate, and the average molecular weight of the second oligomer is in the range of 500-10000. It should be noted that the second oligomer can be a single-component substance, or a mixture of multiple components, each of the multiple components includes a sulfur atom and a free isocyanate group, the sulfur atom is formed by the thiol group being terminated by the isocyanate.

[0046] The second oligomer contains sulfur atoms, and the molecular weight of the second oligomer is greater than the molecular weight of thiol commonly used in photopolymer holographic recording media. The sulfur-containing second oligomer does not volatilize, and thus can effectively avoid environmental pollution and damage to the health of production personnel caused by the volatility of thiol; the second oligomer contains free hydroxyl groups, and the second oligomer can be used together with polyisocyanate to form isocyanate-alcohol as a film-forming resin for photopolymer holographic recording media, thereby providing technical support for effectively improving the refractive index of the film-forming resin and providing technical support for further improving the average refractive index of the photopolymer.

[0047] In some embodiments, the second oligomer can be obtained by reacting a multifunctional thiol with a multifunctional isocyanate and then reacting with a polyhydroxy compound.

[0048] Polyfunctional thiols may refer to compounds containing multiple thiol functional groups (-SH), generally including thiols (a class of non-aromatic compounds containing thiol functional groups, such as dithiol, trithiol, etc.), thiophenols (e.g., dithiol, trithiol, etc.). Polyfunctional isocyanates may refer to compounds containing multiple isocyanate groups (-NCO) (e.g., diisocyanates, triisocyanates, etc.). Polyhydroxy compounds may refer to compounds containing multiple hydroxyl groups.

[0049] The reaction of multifunctional thiol and multifunctional isocyanate is mainly an addition reaction between the thiol functional group (-SH) and the isocyanate group (-NCO), the hydrogen atom (H) on the thiol functional group (-SH) is added to the nitrogen atom (N) on the isocyanate group (-NCO), the sulfur atom (S) on the thiol functional group (-SH) is added to the carbon atom (C) on the isocyanate group (-NCO), and the carbon-nitrogen double bond of the isocyanate group (-NCO) is converted into a carbon-nitrogen single bond.

[0050] After the multifunctional thiol reacts with the multifunctional isocyanate, a first oligomer can be obtained, which includes free isocyanate groups. After adding a polyhydroxy compound, the hydroxyl group can block the free isocyanate to obtain a second oligomer, which also includes free hydroxyl groups.

[0051] In some embodiments, the polyfunctional thiol includes a difunctional thiol, and the polyfunctional isocyanate includes a difunctional isocyanate.

[0052] Difunctional thiol may refer to a class of compounds containing two thiol functional groups (-SH), and difunctional isocyanate may refer to a class of compounds containing two isocyanate groups (-NCO); the embodiment of the present application uses difunctional thiol and difunctional isocyanate to react, and the main product can be obtained as a linear sulfur-containing isocyanate-terminated first oligomer. In this way, when the linear sulfur-containing isocyanate-terminated first oligomer and the polyhydroxy compound are used as film-forming resins, it can avoid the film-forming resin being too cross-linked, which is not conducive to the diffusion and migration of the writing monomer, thereby affecting the formation of VHG and reducing the sensitivity of the material.

[0053] In some embodiments, the difunctional thiol includes at least one of 1,2-benzenedithiol, 1,3-benzenedithiol, 1,4-benzenedithiol, 2,6-naphthalenedithiol, toluene-3,4-dithiol, biphenyl-4,4'-dithiol, 4'4-dimercaptodiphenyl sulfide, ethanedithiol, 1,3-propanedithiol, 1,4-butanedithiol, 1,5-pentanedithiol, 1,6-hexanedithiol, 1,7-heptanedithiol, 1,8-octanedithiol, 1,9-nonanedithiol, 1,10-decanedithiol, 1,2-butanedithiol, 2,2'-thiobis(ethanethiol), 3,7-dithia-1,9-nonanedithiol, and 1,6-dimercapto-3-hexanethiol.

[0054] In some embodiments, the bifunctional thiol includes at least one of ethanedithiol, 1,3-propanedithiol, 1,4-butanedithiol, 1,5-pentanedithiol, 1,6-hexanedithiol, 1,7-heptanedithiol, 1,8-octanedithiol, 1,9-nonanedithiol, 1,10-decanedithiol, 1,2-butanedithiol, 2,2'-thiobis(ethanethiol), 3,7-dithia-1,9-nonanedithiol, and 1,6-dimercapto-3-hexanesulfide.

[0055] In some embodiments, the difunctional isocyanate includes at least one of hexamethylene diisocyanate, isophorone diisocyanate, trimethylhexamethylene diisocyanate, butane-1,4-diisocyanate, dicyclohexylmethane diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, 1,4-cyclohexane diisocyanate, meta-xylylene diisocyanate, ditoluene diisocyanate, p-phenylene diisocyanate, meta-phenylene diisocyanate, toluene 2,6-diisocyanate, toluene-2,5-diisocyanate, 1,4-cyclohexane dimethyl diisocyanate, and 1,3-bis(1-isocyanato-1-methylethyl)benzene.

[0056] In some embodiments, the difunctional isocyanate includes at least one of hexamethylene diisocyanate, isophorone diisocyanate, trimethylhexamethylene diisocyanate, butane-1,4-diisocyanate, dicyclohexylmethane diisocyanate, and 1,4-cyclohexanedimethyl diisocyanate.

[0057] See also Figure 1 , Figure 1 The figure is a flow diagram of an embodiment of a method for preparing a sulfur-containing isocyanate-terminated first oligomer of the present invention, wherein the sulfur-containing isocyanate-terminated first oligomer may be any of the above-mentioned sulfur-containing isocyanate-terminated first oligomers. The preparation method comprises:

[0058] Step S101: providing a multifunctional thiol, a multifunctional isocyanate and a first catalyst.

[0059] Step S102: providing a reaction environment for a compound without active hydrogen.

[0060] Since the isocyanate group is relatively active, it is easy to undergo additional side reactions with compounds containing active hydrogen, such as water vapor in the air. In order to avoid side reactions of the isocyanate group as much as possible, it is necessary to provide a reaction environment without active hydrogen compounds.

[0061] Step S103: adding the multifunctional thiol, the multifunctional isocyanate and the first catalyst into the reaction environment to form a reaction system, and reacting in the reaction system to obtain the sulfur-containing isocyanate-terminated first oligomer.

[0062] The first catalyst is used to catalyze the reaction between the thiol group and the isocyanate group. The first catalyst can be a tertiary amine catalyst and an organic metal catalyst, including but not limited to triethylenediamine, bis(dimethylaminoethyl) ether, dimethylethanolamine, 2-(2-dimethylamino-ethoxy)ethanol, trimethylhydroxyethylpropylenediamine, N,N-bis(dimethylaminopropyl)isopropanolamine, dibutyltin dilaurate, stannous octoate, potassium carboxylate catalysts and bismuth carboxylate catalysts.

[0063] In some embodiments, step S102, providing a reaction environment of a compound without active hydrogen may include:

[0064] Sub-step S1021: Adding a solvent into a sealed reaction container.

[0065] Sub-step S1022: passing an inert gas through the solvent to place the sealed reaction container and the solvent in a reaction environment free of active hydrogen compounds.

[0066] The inert gas may be a gas that does not react with isocyanate, such as nitrogen, argon, and the like.

[0067] For example, a reaction vessel is sealed with silicone oil, a solvent is added into the reaction vessel, and nitrogen is passed through the solvent from the bottom of the reaction vessel under stirring for a certain period of time, for example, 1 hour (h). This can drive the solvent, water vapor in the air, etc. out of the reaction vessel, so that the entire reaction environment is in a nitrogen environment.

[0068] At this time, step S103, wherein the multifunctional thiol, the multifunctional isocyanate and the first catalyst are added into the reaction environment to form a reaction system, and the reaction occurs in the reaction system to obtain the sulfur-containing isocyanate-terminated first oligomer, may include: adding the multifunctional thiol and the multifunctional isocyanate into the reaction container, stirring them thoroughly, and then slowly dropping a dilute solution of the first catalyst, stopping the reaction when it is detected that the thiol content in the reaction system is 0, and removing the solvent by rotary evaporation to obtain the sulfur-containing isocyanate-terminated first oligomer.

[0069] When the thiol content is 0, it indicates that there are no free thiol groups in the reaction system, and the isocyanate has completely capped the free thiol groups. At this time, free isocyanate exists in the system. Specific detection methods for the thiol content include, but are not limited to, nuclear magnetic resonance, absorbance, molecular fluorescence spectroscopy, etc. The use of nuclear magnetic resonance can achieve online and rapid detection.

[0070] See also Figure 2 , Figure 2 1 is a flow chart of an embodiment of a method for preparing a sulfur-containing hydroxyl-terminated second oligomer of the present invention, wherein the sulfur-containing hydroxyl-terminated second oligomer may be any of the above-mentioned sulfur-containing hydroxyl-terminated second oligomers. The preparation method comprises:

[0071] Step S201: providing a multifunctional thiol, a multifunctional isocyanate, a first catalyst and a polyhydroxy compound.

[0072] Step S202: providing a reaction environment for a compound without active hydrogen.

[0073] Since the isocyanate group is relatively active, it is easy to undergo additional side reactions with compounds containing active hydrogen, such as water vapor in the air. In order to avoid side reactions of the isocyanate group as much as possible, it is necessary to provide a reaction environment without active hydrogen compounds.

[0074] Step S203: adding the multifunctional thiol, the multifunctional isocyanate and the first catalyst into the reaction environment to form a reaction system. After the reaction occurs in the reaction system, adding the polyhydroxy compound into the reaction system to continue the reaction to obtain the sulfur-containing hydroxyl-terminated second oligomer.

[0075] In some embodiments, step S202, providing a reaction environment of a compound without active hydrogen may include:

[0076] Sub-step S2021: Adding a solvent into a sealed reaction container.

[0077] Sub-step S2022: passing an inert gas through the solvent to place the sealed reaction container and the solvent in a reaction environment free of active hydrogen compounds.

[0078] At this time, step S203, wherein the polyfunctional thiol, the polyfunctional isocyanate and the first catalyst are added to the reaction environment to form a reaction system, and after the reaction occurs in the reaction system, the polyhydroxy compound is added to the reaction system to continue the reaction to obtain the sulfur-containing hydroxy-terminated second oligomer, may include: adding the polyfunctional thiol and the polyfunctional isocyanate to the reaction container, stirring them thoroughly, and then slowly dropping a dilute solution of the first catalyst, and when it is detected that the thiol content in the reaction system is 0, quickly adding the polyhydroxy compound and continuing to stir, when it is detected that the isocyanate content in the reaction system is 0, stopping the reaction, and removing the solvent by rotary evaporation to obtain the sulfur-containing hydroxy-terminated second oligomer.

[0079] When the thiol content is 0, it indicates that there are no free thiol groups in the reaction system, the isocyanate has completely blocked the free thiol groups, and there are free isocyanates in the system. After adding the polyol, the hydroxyl groups block the free isocyanates. When the isocyanate content is 0, it indicates that there are no free isocyanates in the reaction system, and the hydroxyl groups have completely blocked the free isocyanates. At this time, there are free hydroxyl groups in the system. The specific detection method of the thiol content includes, but is not limited to, nuclear magnetic resonance, absorbance, molecular fluorescence spectroscopy, etc. The specific detection method of the isocyanate content includes, but is not limited to, nuclear magnetic resonance, absorbance, molecular fluorescence spectroscopy, etc. The use of nuclear magnetic resonance can achieve online and rapid detection.

[0080] In some embodiments, the solvent includes one of petroleum ether, dichloromethane, ethyl acetate, n-hexane, dimethyl sulfoxide, N,N-dimethylformamide, toluene, tetrahydrofuran, and pyridine.

[0081] In some embodiments, the polyfunctional thiol includes a difunctional thiol, and the polyfunctional isocyanate includes a difunctional isocyanate.

[0082] In some embodiments, the difunctional thiol includes at least one of 1,2-benzenedithiol, 1,3-benzenedithiol, 1,4-benzenedithiol, 2,6-naphthalenedithiol, toluene-3,4-dithiol, biphenyl-4,4'-dithiol, 4'4-dimercaptodiphenyl sulfide, ethanedithiol, 1,3-propanedithiol, 1,4-butanedithiol, 1,5-pentanedithiol, 1,6-hexanedithiol, 1,7-heptanedithiol, 1,8-octanedithiol, 1,9-nonanedithiol, 1,10-decanedithiol, 1,2-butanedithiol, 2,2'-thiobis(ethanethiol), 3,7-dithia-1,9-nonanedithiol, and 1,6-dimercapto-3-hexanethiol.

[0083] In some embodiments, the bifunctional thiol includes at least one of ethanedithiol, 1,3-propanedithiol, 1,4-butanedithiol, 1,5-pentanedithiol, 1,6-hexanedithiol, 1,7-heptanedithiol, 1,8-octanedithiol, 1,9-nonanedithiol, 1,10-decanedithiol, 1,2-butanedithiol, 2,2'-thiobis(ethanethiol), 3,7-dithia-1,9-nonanedithiol, and 1,6-dimercapto-3-hexanesulfide.

[0084] In some embodiments, the difunctional isocyanate includes at least one of hexamethylene diisocyanate, isophorone diisocyanate, trimethylhexamethylene diisocyanate, butane-1,4-diisocyanate, dicyclohexylmethane diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, 1,4-cyclohexane diisocyanate, meta-xylylene diisocyanate, ditoluene diisocyanate, p-phenylene diisocyanate, meta-phenylene diisocyanate, toluene 2,6-diisocyanate, toluene-2,5-diisocyanate, 1,4-cyclohexane dimethyl diisocyanate, and 1,3-bis(1-isocyanato-1-methylethyl)benzene.

[0085] In some embodiments, the difunctional isocyanate includes at least one of hexamethylene diisocyanate, isophorone diisocyanate, trimethylhexamethylene diisocyanate, butane-1,4-diisocyanate, dicyclohexylmethane diisocyanate, and 1,4-cyclohexanedimethyl diisocyanate.

[0086] In some embodiments, the first catalyst includes one of triethylenediamine, bis(dimethylaminoethyl) ether, dimethylethanolamine, 2-(2-dimethylamino-ethoxy)ethanol, trimethylhydroxyethylpropylenediamine, N,N-bis(dimethylaminopropyl)isopropanolamine, dibutyltin dilaurate, stannous octoate, potassium carboxylate catalysts and bismuth carboxylate catalysts.

[0087] The molecular weight of the final first oligomer or the second oligomer can be regulated by adjusting the ratio of thiol groups to isocyanate groups. In some embodiments, the ratio of thiol groups to isocyanate groups in the reaction system is 1:1.05-5.05, for example: 1:1.05, 1:2, 1:3, 1:4, 1:5.05, etc.

[0088] In some embodiments, the ratio is 1:1.05-2, for example: 1:1.05, 1:1.5, 1:2, etc.

[0089] The embodiment of the present application also provides a photopolymer holographic recording medium, which includes a film-forming resin, and the film-forming resin includes any of the above-mentioned sulfur-containing isocyanate-terminated first oligomers and polyhydroxy compounds, or the film-forming resin includes any of the above-mentioned sulfur-containing hydroxyl-terminated second oligomers and polyfunctional isocyanates.

[0090] The sulfur-containing isocyanate-terminated first oligomer contains both sulfur atoms and free isocyanate groups, so the first oligomer and the polyhydroxy compound can form a film-forming resin with isocyanate-alcohol as a photopolymer holographic recording medium, which can effectively increase the refractive index of the film-forming resin and further increase the average refractive index of the photopolymer. The sulfur-containing hydroxyl-terminated second oligomer contains both sulfur atoms and free hydroxyl groups, so the second oligomer and the polyfunctional isocyanate can form a film-forming resin with isocyanate-alcohol as a photopolymer holographic recording medium, which can effectively increase the refractive index of the film-forming resin and further increase the average refractive index of the photopolymer.

[0091] The polyhydroxy compound can be selected from compounds with low refractive index and two or more hydroxyl functional groups, including but not limited to: tetraethylene glycol, trimethylolethane, glycerol, triethanolamine, polyester polyols with a molecular weight of 200 to 2000, polycarbonate polyols, and polyether polyols.

[0092] The multifunctional isocyanate is a compound containing multiple isocyanate groups, which can be selected from compounds with low refractive index and two or more isocyanate groups; including but not limited to: hexamethylene diisocyanate, trimethyl hexamethylene diisocyanate, (2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl)tris(hexamethylene) isocyanate, butane-1,4-diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate.

[0093] In some embodiments, the total content of the sulfur-containing isocyanate-terminated first oligomer and the polyhydroxy compound is 40%-50% by weight, for example: 40%, 42.5%, 45%, 47.5%, 50%, etc., wherein the content of the first oligomer and the polyhydroxy compound can be determined according to the content of free isocyanate in the first oligomer and the content of hydroxyl in the polyhydroxy compound. Alternatively, the total content of the sulfur-containing hydroxyl-terminated second oligomer and the multifunctional isocyanate is 40%-50%, for example: 40%, 42.5%, 45%, 47.5%, 50%, etc., wherein the content of the second oligomer and the multifunctional isocyanate can be determined according to the content of free hydroxyl in the second oligomer and the content of isocyanate groups in the multifunctional isocyanate; the photopolymer holographic recording medium further includes: a writing monomer, a photosensitive initiator system, a chain transfer agent, a second catalyst and an additive.

[0094] The writing monomer has a relatively high refractive index, including but not limited to: acrylate monomers.

[0095] The acrylic acid ester monomer can be selected from pentabromophenyl acrylate, pentachlorophenyl acrylate, phenoxyethyl acrylate, pentabromobenzyl acrylate, 2-naphthyl acrylate, 1,4-di(2-thionaphthyl)2-butyl acrylate, phenoxyethoxyethyl acrylate, bisphenol A diacrylate, tetrabromobisphenol A diacrylate, 2-phenoxyethyl acrylate, benzyl acrylate, p-chlorophenyl acrylate, 2,4,6-trichlorophenyl acrylate, p-bromophenyl acrylate, 2,4,6-tribromophenyl acrylate, propane-2,2-diylbis[(2,6-dibromo-4,1-phenylene)oxy(2-{[3,3,3-tri(4-chlorophenyl)propionyl]oxy}propane-3,1-diyl)oxyethane-2,1-diyl]diacrylate, etc.

[0096] The photosensitive initiation system may include a photosensitizer and a photoinitiator, or may not include a photosensitizer. Different wide-band responses can be achieved by adjusting the type of photosensitizer. When a photoinitiator with an adapted wavelength is selected in the raw material of the photopolymer holographic recording medium of the embodiment of the present application, the photosensitizer may not be added. The photosensitizer is a dye with a high electron transfer efficiency under light, including but not limited to cyanine dyes, fluorescein dyes, coumarin ketone dyes, nitrogen-containing aromatic heterocyclic compounds, aromatic amine compounds, benzylcycloalkane ketone compounds, or any mixture of these compounds in any proportion. Exemplarily, the photosensitizer includes one or more of new methylene blue, thionine, basic yellow, pinacol cyanol chloride, rhodamine 6G, gallocyanine, ethyl violet, Victoria blue R, lapis lazuli blue, methylene blue, Astrazon Orange G, Darrow red, pyrrole red Y, basic red 29, quinaldine red, crystal violet, ethyl violet, brilliant green, pyri11lium I, azure A, crystal violet white nitrile, malachite green white nitrile, etc.

[0097] The photoinitiator is an initiator that can be activated by actinic radiation and initiates polymerization of the corresponding polymerizable groups, including but not limited to aromatic ketone compounds, benzoin and its derivatives, benzil ketal, acylphosphine oxide, aryl ammonium borate, chromium salt, aryl diazonium salt, onium salt, organometallic compound or any mixture of these compounds. For example, it includes one or more of benzophenone, alkylbenzophenone, 4,4'-bis(dimethylamino)benzophenone, anthrone and halogenated benzophenone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bisacylphosphine oxide, phenyl dihydroxyacetate, camphorquinone, α-aminoalkylphenone, α,α-dialkoxyacetophenone, α-hydroxyalkylphenone, triphenylhexyl borate tetrabutylammonium, tri-(3-fluorophenyl)hexylborate tetrabutylammonium, tri-(3-chloro-4-methylphenyl)hexylborate tetrabutylammonium, ferrocenyl compounds, iodonium salts, sulfonium salts, hexaarylbiimidazoles, etc.

[0098] The chain transfer agent is a thiol compound, including but not limited to one or more of dodecyl mercaptan, mercaptoethanol, hexanethiol, phenylethyl mercaptan, 5-(4-pyridyl)-1,3,4-oxadiazole-2-thiol, 4-methyl-4H-1,2,4-triazole-3-thiol, etc.

[0099] The second catalyst is used to catalyze the reaction between the hydroxyl group and the isocyanate group. The second catalyst is a tertiary amine catalyst and an organic metal catalyst, including but not limited to triethylenediamine, bis(dimethylaminoethyl) ether, dimethylethanolamine, 2-(2-dimethylamino-ethoxy)ethanol, trimethylhydroxyethylpropylenediamine, N,N-bis(dimethylaminopropyl)isopropanolamine, dibutyltin dilaurate, stannous octoate, potassium carboxylate catalysts and bismuth carboxylate catalysts.

[0100] Furthermore, the additives include one or more of a defoamer, a leveling agent, a plasticizer and a dewatering agent.

[0101] The defoamer can be an organosilicon defoamer, such as BYK-011, BYK-012, BYK-014, BYK-023, BYK-051N, BYK-085, BYK-1610, BYK-1707, BYK-1740, BYK-1760 produced by BYK, DC65, AFE-7820 produced by Dow Corning, or a mixture of these defoamers in any proportion.

[0102] The leveling agent can be an organosilicon surface additive, such as BYK-302, BYK-306, BYK-307, BYK-327, BYK-329, BYK-333, BYK-356, BYK-358, BYK-378, BYK-3455, BYK-3566 produced by BYK, or a mixture of these surface additives in any proportion.

[0103] The plasticizer can be toluene, xylene, dimethylformamide, dimethylacetamide, glycerol, phthalate or a mixture of these compounds in any proportion.

[0104] The dehydrating agent includes but is not limited to p-toluenesulfonyl isocyanate, triethyl orthoformate, CUWR-WB20 dehydrating agent of Guangzhou Yourun Synthetic Materials Co., Ltd., ALT-201 dehydrating agent of Anxiang Elite Chemical Co., Ltd., PCCI dehydrating agent of Shanghai Ruhr Chemical Trading Co., Ltd., etc.

[0105] In some embodiments, the content of the writing monomer is 40%-50%, for example 40%, 42.5%, 45%, 47.5%, 50%, etc., the content of the photosensitive initiator system is 0.01%-8%, for example 0.01%, 0.05%, 1%, 3%, 5%, 6%, 7%, 8%, etc., the content of the chain transfer agent is 0.05%-5%, for example 0.05%, 1%, 2%, 3%, 4%, 5%, etc., the content of the second catalyst is 0.001%-3%, for example 0.001%, 0.005%, 0.01%, 0.05%, 1%, 2%, 3%, etc., the content of the additive is 0.1%-10%, for example 0.1%, 0.5%, 1%, 3%, 5%, 7%, 9%, 10%, etc.

[0106] The embodiment of the present application also provides a holographic optical element, wherein the raw material of the holographic optical element comprises any of the above-mentioned photopolymer holographic recording media. The holographic optical element includes but is not limited to a volume holographic grating.

[0107] The embodiments of the present application are described below through specific examples.

[0108] It should be noted that the reaction between isocyanate group and hydroxyl or thiol group generates no by-products, so the product structure can be predicted from the raw materials. The reaction mechanism is as follows: Figure 3 As shown in the upper and lower reaction equations, the red circle represents the group R1 connected to -N, the blue circle represents the group R2 connected to -O, and the green circle represents the group R3 connected to -S. The hydroxyl-containing compound (R2-OH) or the thiol-containing compound (R3-SH) reacts with the isocyanate group-containing compound (R1-N=C=O) to generate R1-NH-C=OO-R2 and R1-NH-C=OO-R3.

[0109] Example 1, preparation of the first oligomer:

[0110] (1) Preparation of the first oligomer 1-1:

[0111] After adding dichloromethane to a reaction vessel sealed with silicone oil, nitrogen was passed through the dichloromethane from the bottom of the reaction vessel for 1 hour under stirring to make the entire reaction environment in a nitrogen environment. Then, ethanedithiol and hexamethylene diisocyanate were added to the reaction vessel, and after being fully stirred, a dilute solution of stannous octoate catalyst was slowly added dropwise. The reaction was stopped when the thiol content in the reaction system was 0 as detected by nuclear magnetic resonance. The solvent was removed by rotary evaporation to obtain the first isocyanate-terminated oligomer 1-1.

[0112] From the reaction mechanism, the structural formula of the first oligomer 1-1 is as follows: The isocyanate group content in the first oligomer 1-1 was tested; according to the isocyanate group content, the average molecular weight of the first oligomer 1-1 was about 9880.

[0113]

[0114] (2) Preparation of the first oligomer 1-2:

[0115] After adding ethyl acetate to a reaction vessel sealed with silicone oil, nitrogen was passed through the ethyl acetate from the bottom of the reaction vessel for 1 hour under stirring to make the entire reaction environment in a nitrogen environment. Then, 1,9-nonanedithiol and m-phenylenediisocyanate were added to the reaction vessel, and after being fully stirred, a dilute solution of catalyst dimethylethanolamine was slowly added dropwise. The reaction was stopped when the thiol content in the reaction system was 0 as detected by nuclear magnetic resonance. The solvent was removed by rotary evaporation to obtain the first isocyanate-terminated oligomer 1-2.

[0116] From the reaction mechanism, the structural formula of the first oligomer 1-2 is as follows: The isocyanate group content in the first oligomer 1-2 is tested; according to the isocyanate group content, the average molecular weight of the first oligomer 1-2 is about 7,600.

[0117]

[0118] (3) Preparation of the first oligomer 1-3:

[0119] After adding dimethyl sulfoxide to a reaction vessel sealed with silicone oil, nitrogen was passed through dimethyl sulfoxide from the bottom of the reaction vessel for 1 hour under stirring to make the entire reaction environment in a nitrogen environment. Then, 1,5-pentanedithiol and isophorone diisocyanate were added to the reaction vessel, and after being fully stirred, a dilute solution of catalyst triethylenediamine was slowly added dropwise. The reaction was stopped when the thiol content in the reaction system was 0 as detected by nuclear magnetic resonance. The solvent was removed by rotary evaporation to obtain the first isocyanate-terminated oligomer 1-3.

[0120] From the reaction mechanism, the structural formula of the first oligomer 1-3 is as follows: The isocyanate group content in the first oligomer 1-3 was tested; according to the isocyanate group content, the average molecular weight of the first oligomer 1-3 was about 4890.

[0121]

[0122] (4) Preparation of the first oligomer 1-4:

[0123] After adding petroleum ether to a reaction vessel sealed with silicone oil, nitrogen was passed through the petroleum ether from the bottom of the reaction vessel for 1 hour under stirring to make the entire reaction environment in a nitrogen environment. Then, ethanedithiol and butane-1,4-diisocyanate were added to the reaction vessel, and after being fully stirred, a dilute solution of stannous octoate catalyst was slowly added dropwise. The reaction was stopped when the thiol content in the reaction system was 0 as detected by nuclear magnetic resonance. The solvent was removed by rotary evaporation to obtain the first isocyanate-terminated oligomer 1-4.

[0124] From the reaction mechanism, the structural formula of the first oligomer 1-4 is as follows: The isocyanate group content in the first oligomer 1-4 is tested; according to the isocyanate group content, the average molecular weight of the first oligomer 1-4 is about 374.

[0125]

[0126] (5) Preparation of the first oligomer 1-5:

[0127] After adding pyridine to the reaction vessel sealed with silicone oil, nitrogen was passed through the pyridine from the bottom of the reaction vessel for 1 hour under stirring to make the entire reaction environment in a nitrogen environment. Then, 1,4-butanedithiol and 1,4-cyclohexanedimethyl diisocyanate were added to the reaction vessel, and after being fully stirred, a dilute solution of the catalyst dimethylethanolamine was slowly added dropwise. The reaction was stopped when the thiol content in the reaction system was 0 as detected by nuclear magnetic resonance. The solvent was removed by rotary evaporation to obtain the first isocyanate-terminated oligomer 1-5.

[0128] From the reaction mechanism, the structural formula of the first oligomer 1-5 is as follows: The isocyanate group content in the first oligomer 1-5 is tested; according to the isocyanate group content, the average molecular weight of the first oligomer 1-5 is about 2350.

[0129]

[0130] The determination method of the isocyanate group content and the calculation method of the average molecular weight of the first oligomer are as follows:

[0131] The isocyanate group of the first oligomer was determined by the acetone-di-n-butylamine-hydrochloric acid method. The sample was dissolved in 20 mL of anhydrous acetone solution, and 20 mL of 0.1 mol / L acetone-di-n-butylamine solution was accurately added. After sufficient vibration, 100 mL of isopropanol and 5 drops of bromocresol green indicator were added, and titrated with 0.1 mol / L HCl solution. The isocyanate value in the system was calculated by the following formula.

[0132]

[0133] Wherein, C1——isocyanate value of the first oligomer, mol / g;

[0134] C0——concentration of HCl solution, mol / L;

[0135] V2——the amount of HCl solution used to titrate the blank sample, mL;

[0136] V1——the amount of HCl solution used to titrate the oligomer, mL;

[0137] m1——Weigh the mass of the first oligomer, g.

[0138] The average molecular weight of the first oligomer is: n =2 / C1, g / mol.

[0139] Example 2, preparation of the second oligomer:

[0140] (1) Preparation of the second oligomer 2-1:

[0141] After adding N,N-dimethylformamide to the reaction vessel sealed with silicone oil, nitrogen is passed through N,N-dimethylformamide from the bottom of the reaction vessel for 1 hour under stirring to make the entire reaction environment in a nitrogen environment. Then, 1,4-butanedithiol and dicyclohexylmethane diisocyanate are added to the reaction vessel, and after being fully stirred, a dilute solution of the catalyst dibutyltin dilaurate is slowly added dropwise. When the thiol content in the reaction system is 0 as detected by nuclear magnetic resonance, propylene glycol is quickly added. Continue stirring, and stop the reaction when the isocyanate content in the reaction system is 0 as detected by nuclear magnetic resonance. The solvent is removed by rotary evaporation to obtain the hydroxyl-terminated second oligomer 2-1.

[0142] From the reaction mechanism, the structural formula of the second oligomer 2-1 is shown below. The hydroxyl group content in the second oligomer 2-1 was tested; according to the hydroxyl group content, the average molecular weight of the second oligomer 2-1 was about 9750 (the test method of the hydroxyl group content and the relationship between the hydroxyl group content and the average molecular weight of the second oligomer, please refer to the following description).

[0143]

[0144] (2) Preparation of the second oligomer 2-2:

[0145] After adding toluene to the reaction vessel sealed with silicone oil, nitrogen is passed through the toluene from the bottom of the reaction vessel for 1 hour under stirring to make the entire reaction environment in a nitrogen environment. Then, 1,2-butanedithiol and 1,4-cyclohexanedimethyl diisocyanate are added to the reaction vessel, and after being fully stirred, a dilute solution of the catalyst N,N-bis(dimethylaminopropyl)isopropanolamine is slowly added dropwise. When the thiol content in the reaction system is 0 as detected by nuclear magnetic resonance, ethylene glycol is quickly added. Continue stirring, and stop the reaction when the isocyanate content in the reaction system is 0 as detected by nuclear magnetic resonance. Remove by rotary evaporation to obtain the hydroxyl-terminated second oligomer 2-2.

[0146] From the reaction mechanism, the structural formula of the second oligomer 2-2 is as follows: The hydroxyl group content in the second oligomer 2-2 was tested; according to the hydroxyl group content, the average molecular weight of the second oligomer 2-2 was about 7630.

[0147]

[0148] (3) Preparation of the second oligomer 2-3:

[0149] After tetrahydrofuran is added to the reaction vessel sealed with silicone oil, nitrogen is passed through the tetrahydrofuran from the bottom of the reaction vessel for 1 hour under stirring to make the entire reaction environment in a nitrogen environment. Then, 1,4-benzenedithiol and butane-1,4-diisocyanate are added to the reaction vessel, and after being fully stirred, a dilute solution of the catalyst bis(dimethylaminoethyl) ether is slowly added dropwise. When the thiol content in the reaction system is 0 as detected by nuclear magnetic resonance, 1,4-butanediol is quickly added. Continue stirring, and stop the reaction when the isocyanate content in the reaction system is 0 as detected by nuclear magnetic resonance. The solvent is removed by rotary evaporation to obtain the hydroxyl-terminated second oligomer 2-3.

[0150] From the reaction mechanism, the structural formula of the second oligomer 2-3 is as follows: The hydroxyl group content in the second oligomer 2-3 was tested; according to the hydroxyl group content, the average molecular weight of the second oligomer 2-3 was about 5100.

[0151]

[0152] (4) Preparation of the second oligomer 2-4:

[0153] After adding n-hexane to the reaction vessel sealed with silicone oil, nitrogen is passed through the n-hexane from the bottom of the reaction vessel for 1 hour under stirring to make the entire reaction environment in a nitrogen environment. Then, 1,6-hexanedithiol and hexamethylene diisocyanate are added to the reaction vessel, and after being fully stirred, a dilute solution of the catalyst dimethylethanolamine is slowly added dropwise. When the thiol content in the reaction system is 0 as detected by nuclear magnetic resonance, methyl propanediol is quickly added. Continue stirring, and stop the reaction when the isocyanate content in the reaction system is 0 as detected by nuclear magnetic resonance. The solvent is removed by rotary evaporation to obtain the hydroxyl-terminated second oligomer 2-4.

[0154] From the reaction mechanism, the structural formula of the second oligomer 2-4 is as follows: The hydroxyl group content in the second oligomer 2-4 was tested; according to the hydroxyl group content, the average molecular weight of the second oligomer 2-4 was about 540.

[0155]

[0156] (3) Preparation of the second oligomer 2-5:

[0157] After adding pyridine to the reaction vessel sealed with silicone oil, nitrogen is passed through the pyridine from the bottom of the reaction vessel for 1 hour under stirring to make the entire reaction environment in a nitrogen environment. Then, 1,4-butanedithiol and 1,4-cyclohexanedimethyl diisocyanate are added to the reaction vessel, and after being fully stirred, a dilute solution of the catalyst trimethylhydroxyethylpropylenediamine is slowly added dropwise. When the thiol content in the reaction system is 0 as detected by nuclear magnetic resonance, 1,4-butanediol is quickly added. Continue stirring, and stop the reaction when the isocyanate content in the reaction system is 0 as detected by nuclear magnetic resonance. The solvent is removed by rotary evaporation to obtain the hydroxyl-terminated second oligomer 2-5.

[0158] From the reaction mechanism, the structural formula of the second oligomer 2-5 is as follows: The hydroxyl group content in the second oligomer 2-5 was tested; according to the hydroxyl group content, the average molecular weight of the second oligomer 2-5 was about 2450.

[0159]

[0160] The determination method of the hydroxyl content and the calculation method of the average molecular weight of the second oligomer are as follows:

[0161] The hydroxyl group of the second oligomer was determined by the acid anhydride pyridine potentiometric titration method. The sample was dissolved in 20 mL of pyridine solution, the hydroxyl group was esterified with acetic anhydride, the excess acetic anhydride was hydrolyzed with water, phenolphthalein was used as an indicator, and KOH solution was used to neutralize the acid produced in the esterification process and the acetic acid generated by hydrolysis. The hydroxyl value in the system was calculated by the following formula based on the difference in volume of KOH solution consumed by the titration blank and the test solution.

[0162]

[0163] Where, C3 is the concentration of KOH standard solution, mol / L;

[0164] V4 is the amount of KOH standard solution consumed in the blank test, mL;

[0165] V3 is the amount of KOH standard solution consumed by the sample, mL;

[0166] m2 is the mass of the sample (second oligomer), g;

[0167] C2 is the hydroxyl value, mg KOH / g.

[0168] The average molecular weight of the second oligomer is: n =112.2 / C2, g / mol.

[0169] Example 3: Preparation of a photopolymer holographic recording medium using the first oligomer:

[0170] (1) Preparation of photopolymer holographic recording medium 1-1, comprising the following components:

[0171] Component a) polyol: tetraethylene glycol, 0.4%;

[0172] Component b) isocyanate-terminated first oligomer 1-1, 39.6%;

[0173] The total content of tetraethylene glycol and the first oligomer 1-1 is 40%, and the molar ratio of hydroxyl groups in tetraethylene glycol to isocyanate in the first oligomer 1-1 is 1:1;

[0174] Component c) writing monomer: pentabromophenyl acrylate 50%;

[0175] Component d) photosensitive initiator system: 3% new methylene blue, 3% benzophenone;

[0176] Component e) chain transfer agent: dodecyl mercaptan 2%;

[0177] Component f) second catalyst: 1% ethylenediamine;

[0178] Component g) additives: defoamer BYK-011 0.25%, leveling agent BYK-302 0.25%, plasticizer toluene 0.25%, dewatering agent p-toluenesulfonyl isocyanate 0.25%.

[0179] (2) Preparation of photopolymer holographic recording medium 1-2, comprising the following components:

[0180] Component a) polyol: trimethylolethane, 0.2%;

[0181] Component b) isocyanate-terminated first oligomer 1-2, 42.3%;

[0182] The total content of trimethylolethane and the first oligomer 1-2 is 42.5%, and the molar ratio of the hydroxyl group in trimethylolethane to the isocyanate in the first oligomer 1-2 is 1:1;

[0183] Component c) writing monomer: pentachlorophenyl acrylate + phenoxyethyl acrylate, 47.5%;

[0184] Component d) photosensitive initiator system: 3% thionine, 3% alkyl benzophenone;

[0185] Component e) chain transfer agent: mercaptoethanol 2%;

[0186] Component f) second catalyst: bis(dimethylaminoethyl) ether 1%;

[0187] Component g) additives: defoamer BYK-012 0.25%, leveling agent BYK-306 0.25%, plasticizer xylene 0.25%, dewatering agent triethyl orthoformate 0.25%.

[0188] (3) Preparation of photopolymer holographic recording medium 1-3, comprising the following components:

[0189] Component a) polyol: glycerol, 0.3%;

[0190] Component b) isocyanate-terminated first oligomer 1-3, 44.7%;

[0191] wherein the total content of glycerol and the first oligomer 1-3 is 45%, and the molar ratio of the hydroxyl group in the glycerol to the isocyanate in the first oligomer 1-3 is 1:1;

[0192] Component c) writing monomer: phenoxyethyl acrylate + bisphenol A diacrylate + benzyl acrylate, 45%;

[0193] Component d) photosensitive initiator system: basic yellow 3%, 4,4'-bis(dimethylamino)benzophenone 3%;

[0194] Component e) chain transfer agent: hexanethiol 2%;

[0195] Component f) second catalyst: dimethylethanolamine 1%;

[0196] Component g) additives: defoamer BYK-014 0.25%, leveling agent BYK-307 0.25%, plasticizer dimethylacetamide 0.25%, dewatering agent CUWR-WB20 0.25%.

[0197] (4) Preparation of photopolymer holographic recording medium 1-4, comprising the following components:

[0198] Component a) polyol: triethanolamine, 5.6%;

[0199] Component b) isocyanate terminated first oligomer 1-4, 41.9%;

[0200] The total content of triethanolamine and the first oligomer 1-4 is 47.5%, and the molar ratio of the hydroxyl group in the triethanolamine to the isocyanate in the first oligomer 1-4 is 1:1;

[0201] Component c) writing monomer: pentabromobenzyl acrylate + 2-phenoxyethyl acrylate, 42.5%;

[0202] Component d) photosensitive initiator system: 3% of chlorinated pinacol cyanol, 3% of anthrone and halogenated benzophenone;

[0203] Component e) chain transfer agent: 2% phenylethylmercaptan;

[0204] Component f) second catalyst: dimethylethanolamine 1%;

[0205] Component g) additives: defoamer BYK-023 0.25%, leveling agent BYK-327 0.25%, plasticizer glycerol 0.25%, dewatering agent ALT-201 0.25%.

[0206] (5) Preparation of photopolymer holographic recording medium 1-5, comprising the following components:

[0207] Component a) polyol: polyethylene glycol 400, 3.9%;

[0208] Component b) isocyanate-terminated first oligomer 1-5, 46.1%;

[0209] The total content of polyethylene glycol 400 and the first oligomer 1-5 is 50%, and the molar ratio of the hydroxyl group in polyethylene glycol 400 to the isocyanate in the first oligomer 1-5 is 1:1;

[0210] Component c) writing monomer: 2-naphthyl acrylate + benzyl acrylate, 40%;

[0211] Component d) photosensitive initiator system: Rhodamine 6G 3%, 2,4,6-trimethylbenzoyldiphenylphosphine oxide 3%;

[0212] Component e) chain transfer agent: 5-(4-pyridyl)-1,3,4-oxadiazole-2-thiol 2%;

[0213] Component f) second catalyst: 2-(2-dimethylamino-ethoxy)ethanol 1%;

[0214] Component g) additives: defoamer BYK-085 0.25%, leveling agent BYK-329 0.25%, plasticizer phthalate 0.25%, dehumidifier PCCI 0.25%.

[0215] The specific components of the photopolymer holographic recording medium (1) to (5) in the above-mentioned Example 3 are shown in Table 1:

[0216] Table 1

[0217]

[0218]

[0219] Example 4: Preparation of a photopolymer holographic recording medium using a second oligomer:

[0220] (1) Preparation of photopolymer holographic recording medium 2-1, comprising the following components:

[0221] Component a) polyfunctional isocyanate: dicyclohexylmethane diisocyanate, 0.5%;

[0222] Component b) hydroxyl-terminated second oligomer 2-1: 39.5%;

[0223] The total content of dicyclohexylmethane diisocyanate and the second oligomer 2-1 is 40%, and the molar ratio of the isocyanate group in dicyclohexylmethane diisocyanate to the hydroxyl group in the second oligomer 2-1 is 1:1;

[0224] Component c) writing monomer: 2,4,6-tribromophenyl acrylate + p-bromophenyl acrylate, 50%;

[0225] Component d) photosensitive initiator system: 3% malachite green white nitrile, 3% hexaarylbisimidazole;

[0226] Component e) chain transfer agent: 4-methyl-4H-1,2,4-triazole-3-thiol 2%;

[0227] Component f) second catalyst: stannous octoate 1%;

[0228] Component g) additives: defoamer AFE-7820 0.25%, leveling agent BYK-3566 0.25%, plasticizer phthalate 0.25%, dewatering agent PCCI 0.25%.

[0229] (2) Preparation of photopolymer holographic recording medium 2-2, comprising the following components:

[0230] Component a) Multifunctional isocyanate: 0.6% isophorone diisocyanate;

[0231] Component b) hydroxyl terminated second oligomer 2-2: 41.9%;

[0232] The total content of isophorone diisocyanate and the second oligomer 2-2 is 42.5%, and the molar ratio of the isocyanate group in isophorone diisocyanate to the hydroxyl group in the second oligomer 2-2 is 1:1;

[0233] Component c) writing monomer: 2,4,6-trichlorophenyl acrylate 47.5%;

[0234] Component d) photosensitive initiator system: 3% crystal violet nitrile, 3% sulfonium salt;

[0235] Component e) chain transfer agent: 5-(4-pyridyl)-1,3,4-oxadiazole-2-thiol 2%;

[0236] Component f) second catalyst: dibutyltin dilaurate 1%;

[0237] Component g) additives: defoamer DC65 0.25%, leveling agent BYK-3455 0.25%, plasticizer glycerol 0.25%, dewatering agent ALT-201 0.25%.

[0238] (3) Preparation of photopolymer holographic recording medium 2-3, comprising the following components:

[0239] Component a) polyfunctional isocyanate: butane-1,4-diisocyanate 0.6%;

[0240] Component b) hydroxyl terminated second oligomer 2-3: 44.4%;

[0241] The total content of butane-1,4-diisocyanate and the second oligomer 2-3 is 45%, and the molar ratio of the isocyanate group in butane-1,4-diisocyanate to the hydroxyl group in the second oligomer 2-3 is 1:1;

[0242] Component c) writing monomer: 2-phenoxyethyl acrylate + benzyl acrylate, 45%;

[0243] Component d) photosensitive initiator system: Azure A 3%, iodonium salt 3%;

[0244] Component e) chain transfer agent: 2% phenylethylmercaptan;

[0245] Component f) second catalyst: 1% N,N-bis(dimethylaminopropyl)isopropanolamine;

[0246] Component g) additives: defoamer BYK-1760 0.25%, leveling agent BYK-378 0.25%, plasticizer dimethylacetamide 0.25%, dewatering agent CUWR-WB20 0.25%.

[0247] (4) Preparation of photopolymer holographic recording medium 2-4, comprising the following components:

[0248] Component a) polyfunctional isocyanate: (2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl)tris(hexamethylene)isocyanate, 11.3%;

[0249] Component b) hydroxyl terminated second oligomer 2-4: 36.2%;

[0250] The total content of (2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl)tris(hexamethylene)isocyanate and the second oligomer 2-4 is 47.5%, and the molar ratio of the isocyanate group in (2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl)tris(hexamethylene)isocyanate and the hydroxyl group in the second oligomer 2-4 is 1:1;

[0251] Component c) writing monomer: p-bromophenyl acrylate + tetrabromobisphenol A diacrylate + 2-naphthyl acrylate, 42.5%;

[0252] Component d) photosensitive initiator system: pyri11lium I 3%, ferrocenyl compound 3%;

[0253] Component e) chain transfer agent: hexanethiol 2%;

[0254] Component f) second catalyst: 1% trimethylhydroxyethylpropylenediamine;

[0255] Component g) additives: defoamer BYK-1740 0.25%, leveling agent BYK-358 0.25%, plasticizer dimethylformamide 0.25%, dewatering agent triethyl orthoformate 0.25%.

[0256] (5) Preparation of photopolymer holographic recording medium 2-5, comprising the following components:

[0257] Component a) polyfunctional isocyanate: 2.1% trimethylhexamethylene diisocyanate;

[0258] Component b) hydroxyl terminated second oligomer 2-5: 47.9%;

[0259] The total content of trimethylhexamethylene diisocyanate and the second oligomer 2-5 is 50%, and the molar ratio of the isocyanate group in trimethylhexamethylene diisocyanate and the hydroxyl group in the second oligomer 2-5 is 1:1;

[0260] Component c) writing monomer: pentachlorophenyl acrylate + 1,4-di(2-thionaphthyl) 2-butyl acrylate, 40%;

[0261] Component d) photosensitive initiator system: 3% Brilliant Green, 3% tetrabutylammonium tris-(3-chloro-4-methylphenyl)hexylborate;

[0262] Component e) chain transfer agent: mercaptoethanol 2%;

[0263] Component f) second catalyst: 2-(2-dimethylamino-ethoxy)ethanol 1%;

[0264] Component g) additives: defoamer BYK-1707 0.25%, leveling agent BYK-356 0.25%, plasticizer xylene 0.25%, dewatering agent p-toluenesulfonyl isocyanate 0.25%.

[0265] The specific components of the photopolymer holographic recording media (1) to (5) in the above-mentioned Example 4 are shown in Table 2:

[0266] Table 2

[0267]

[0268]

[0269] Comparative Example 1

[0270] The experimental process is the same as (1) in Example 3, except that the photopolymer holographic recording medium comparative example 1 includes the following components:

[0271] Component a) Film-forming resin component 1: 8.6% tetraethylene glycol + 8.6% ethanedithiol;

[0272] Component b) Film-forming resin component 2: hexamethylene diisocyanate, 22.8%;

[0273] The total content of tetraethylene glycol + ethylene dithiol and hexamethylene diisocyanate is 40%, and the molar ratio of hydroxyl + mercapto in tetraethylene glycol + ethylene dithiol and isocyanate group in hexamethylene diisocyanate is 1:1;

[0274] Component c) writing monomer: pentabromophenyl acrylate 50%;

[0275] Component d) photosensitive initiator system: 3% new methylene blue, 3% benzophenone;

[0276] Component e) chain transfer agent: dodecyl mercaptan 2%;

[0277] Component f) second catalyst: 1% ethylenediamine;

[0278] Component g) additives: defoamer BYK-011 0.25%, leveling agent BYK-302 0.25%, plasticizer toluene 0.25%, dewatering agent p-toluenesulfonyl isocyanate 0.25%.

[0279] Comparative Example 2

[0280] The experimental process is the same as (1) in Example 4, except that the photopolymer holographic recording medium comparative example 2 includes the following components:

[0281] Component a) Film-forming resin component 1: 6.4% propylene glycol + 6.4% 1,4-butanedithiol;

[0282] Component b) Film-forming resin component 2: trimethylhexamethylene diisocyanate, 27.2%;

[0283] The total content of propylene glycol + 1,4-butanedithiol and dicyclohexylmethane diisocyanate is 40%, and the molar ratio of hydroxyl + mercapto in propylene glycol + 1,4-butanedithiol and isocyanate group in dicyclohexylmethane diisocyanate is 1:1;

[0284] Component c) writing monomer: 2,4,6-tribromophenyl acrylate + p-bromophenyl acrylate, 50%;

[0285] Component d) photosensitive initiator system: 3% malachite green white nitrile, 3% hexaarylbisimidazole;

[0286] Component e) chain transfer agent: 4-methyl-4H-1,2,4-triazole-3-thiol 2%;

[0287] Component f) second catalyst: stannous octoate 1%;

[0288] Component g) additives: defoamer AFE-7820 0.25%, leveling agent BYK-3566 0.25%, plasticizer phthalate 0.25%, dewatering agent PCCI 0.25%.

[0289] Comparative Example 3

[0290] The experimental process is the same as (1) in Example 3, except that the photopolymer holographic recording medium comparative example 3 includes the following components (compared with comparative example 1, ethylenedithiol is not included):

[0291] Component a) Film-forming resin component 1: tetraethylene glycol, 21.4%;

[0292] Component b) Film-forming resin component 2: hexamethylene diisocyanate, 18.6%;

[0293] The total content of tetraethylene glycol and hexamethylene diisocyanate is 40%, and the molar ratio of the hydroxyl group in tetraethylene glycol to the isocyanate group in hexamethylene diisocyanate is 1:1;

[0294] Component c) writing monomer: pentabromophenyl acrylate 50%;

[0295] Component d) photosensitive initiator system: 3% new methylene blue, 3% benzophenone;

[0296] Component e) chain transfer agent: dodecyl mercaptan 2%;

[0297] Component f) second catalyst: 1% ethylenediamine;

[0298] Component g) additives: defoamer BYK-011 0.25%, leveling agent BYK-302 0.25%, plasticizer toluene 0.25%, dewatering agent p-toluenesulfonyl isocyanate 0.25%.

[0299] Comparative Example 4

[0300] The experimental process is the same as (1) in Example 4, except that the photopolymer holographic recording medium comparative example 4 includes the following components (compared with comparative example 2, 1,4-butanedithiol is not included):

[0301] Component a) Film-forming resin component 1: propylene glycol, 11%;

[0302] Component b) Film-forming resin component 2: 29% trimethylhexamethylene diisocyanate;

[0303] The total content of propylene glycol and trimethylhexamethylene diisocyanate is 40%, and the molar ratio of the hydroxyl group in propylene glycol to the isocyanate group in trimethylhexamethylene diisocyanate is 1:1;

[0304] Component c) writing monomer: 2,4,6-tribromophenyl acrylate + p-bromophenyl acrylate, 50%;

[0305] Component d) photosensitive initiator system: 3% malachite green white nitrile, 3% hexaarylbisimidazole;

[0306] Component e) chain transfer agent: 4-methyl-4H-1,2,4-triazole-3-thiol 2%;

[0307] Component f) second catalyst: stannous octoate 1%;

[0308] Component g) additives: defoamer AFE-7820 0.25%, leveling agent BYK-3566 0.25%, plasticizer phthalate 0.25%, dewatering agent PCCI 0.25%.

[0309] Test example:

[0310] (1) The odors of Example 3, Example 4, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 during the preparation of the holographic recording medium were tested. The results are shown in Table 3.

[0311] Table 3

[0312]

[0313] (2) The performance of the holographic recording media of Example 3, Example 4, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 was tested. The results are as follows: Figure 4-6 , Table 4.

[0314] The test method includes the following steps:

[0315] Solid-state lasers with wavelengths of 405nm, 532nm, and 633nm were used as light sources. After passing through a beam expander, beam splitter, and half-wave plate, two beams with the same light intensity and a diameter of 8mm were obtained. The two beams intersected in the prepared holographic recording medium for exposure, and the light intensity was 2.91mW / cm 2 The detection light source is a 785nm wavelength solid laser that does not react with the recording medium. The detection light is incident on the exposure area from the Bragg angle. The transmitted light and diffracted light are monitored in real time by the photodetector. The single grating diffraction efficiency (η) of the photopolymer sample and the photosensitivity (S) of the recording medium are calculated by formulas (1) to (3).

[0316]

[0317]

[0318]

[0319] Where η is the diffraction efficiency, η max is the highest diffraction efficiency, I d is the diffracted light, I t is the transmitted light, S is the photosensitivity, E is the exposure energy, and ΔE is the exposure energy when the highest diffraction efficiency is achieved.

[0320] The performance of the photopolymer holographic recording media of Examples 3-4 and Comparative Examples 1-4 was evaluated according to the above test method. The results are as follows: Figure 4-6 As shown in Table 4.

[0321] Table 4

[0322]

[0323] from Figures 4 to 6 As can be seen from Table 4, the exposure amount of the holographic recording media of Examples 3 and 4 of the present application is less than the exposure amount of Comparative Examples 1 to 4, the diffraction efficiency of the holographic recording media of Examples 3 and 4 of the present application is greater than the diffraction efficiency of Comparative Examples 1 to 4, the sensitivity of the holographic recording media of Examples 3 and 4 of the present application is greater than the sensitivity of Comparative Examples 1 to 4, and the average refractive index of the holographic recording media of Examples 3 and 4 of the present application is greater than the average refractive index of Comparative Examples 1 to 4.

[0324] It should be understood that the terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0325] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0326] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A sulfur-containing isocyanate-terminated first oligomer, characterized in that: The first oligomer includes a sulfur atom and a free isocyanate group, wherein the sulfur atom is formed by capping the mercapto group with isocyanate, and the average molecular weight of the first oligomer is in the range of 300-10000.

2. The first oligomer according to claim 1, characterized in that The first oligomer can be obtained by reacting a multifunctional thiol with a multifunctional isocyanate.

3. The first oligomer according to claim 2, characterized in that The multifunctional thiol includes a difunctional thiol, and the multifunctional isocyanate includes a difunctional isocyanate.

4. A sulfur-containing hydroxyl-terminated second oligomer, characterized in that The second oligomer includes sulfur atoms, isocyanate terminated by hydroxyl groups and free hydroxyl groups, wherein the sulfur atoms are formed by mercapto groups terminated by isocyanate, and the average molecular weight of the second oligomer is in the range of 500-10000.

5. The second oligomer according to claim 4, characterized in that The second oligomer can be obtained by reacting a multifunctional thiol with a multifunctional isocyanate and then reacting with a polyhydroxy compound.

6. The second oligomer according to claim 5, characterized in that The multifunctional thiol includes a difunctional thiol, and the multifunctional isocyanate includes a difunctional isocyanate.

7. A method for preparing a sulfur-containing isocyanate-terminated first oligomer as claimed in any one of claims 1 to 3, characterized in that: The method comprises: Providing a multifunctional thiol, a multifunctional isocyanate and a first catalyst; Providing a reaction environment for compounds without active hydrogen; The multifunctional thiol, the multifunctional isocyanate and the first catalyst are added into the reaction environment to form a reaction system, and the sulfur-containing isocyanate-terminated first oligomer is obtained after a reaction occurs in the reaction system.

8. The method according to claim 7, characterized in that The reaction environment for providing a compound without active hydrogen comprises: Add solvent to a sealed reaction vessel; Passing an inert gas through the solvent so that the sealed reaction container and the solvent are in a reaction environment of a compound without active hydrogen; The multifunctional thiol, the multifunctional isocyanate and the first catalyst are added into the reaction environment to form a reaction system, and the reaction occurs in the reaction system to obtain the sulfur-containing isocyanate-terminated first oligomer, comprising: The multifunctional thiol and the multifunctional isocyanate are added to the reaction container, and after being fully stirred, a dilute solution of the first catalyst is slowly added dropwise. When the thiol content in the reaction system is detected to be 0, the reaction is stopped, and the solvent is removed by rotary evaporation to obtain the sulfur-containing isocyanate-terminated first oligomer.

9. A method for preparing a sulfur-containing hydroxyl-terminated second oligomer according to any one of claims 4 to 6, characterized in that: The method comprises: Providing a multifunctional thiol, a multifunctional isocyanate, a first catalyst and a polyhydroxy compound; Providing a reaction environment for compounds without active hydrogen; The multifunctional thiol, the multifunctional isocyanate and the first catalyst are added into the reaction environment to form a reaction system. After the reaction occurs in the reaction system, the polyhydroxy compound is added into the reaction system to continue the reaction to obtain the sulfur-containing hydroxyl-terminated second oligomer.

10. The method according to claim 9, characterized in that The reaction environment for providing a compound without active hydrogen comprises: Add solvent to a sealed reaction vessel; Passing an inert gas through the solvent so that the sealed reaction container and the solvent are in a reaction environment of a compound without active hydrogen; The multifunctional thiol, the multifunctional isocyanate and the first catalyst are added into the reaction environment to form a reaction system, and after the reaction occurs in the reaction system, the polyhydroxy compound is added into the reaction system to continue the reaction to obtain the sulfur-containing hydroxyl-terminated second oligomer, comprising: The multifunctional thiol and the multifunctional isocyanate are added to the reaction container, and after being fully stirred, a dilute solution of the first catalyst is slowly added dropwise. When it is detected that the thiol content in the reaction system is 0, the polyhydroxy compound is quickly added and the stirring is continued. When it is detected that the isocyanate content in the reaction system is 0, the reaction is stopped, and the solvent is removed by rotary evaporation to obtain the sulfur-containing hydroxyl-terminated second oligomer.

11. The method according to claim 8 or 10, characterized in that: The solvent includes one of petroleum ether, dichloromethane, ethyl acetate, n-hexane, dimethyl sulfoxide, N,N-dimethylformamide, toluene, tetrahydrofuran and pyridine.

12. The method according to claim 7 or 9, characterized in that: The multifunctional thiol includes a difunctional thiol, and the multifunctional isocyanate includes a difunctional isocyanate.

13. The method according to claim 12, characterized in that The difunctional thiol includes at least one of 1,2-benzenedithiol, 1,3-benzenedithiol, 1,4-benzenedithiol, 2,6-naphthalenedithiol, toluene-3,4-dithiol, biphenyl-4,4'-dithiol, 4'4-dimercaptodiphenyl sulfide, ethanedithiol, 1,3-propanedithiol, 1,4-butanedithiol, 1,5-pentanedithiol, 1,6-hexanedithiol, 1,7-heptanedithiol, 1,8-octanedithiol, 1,9-nonanedithiol, 1,10-decanedithiol, 1,2-butanedithiol, 2,2'-thiobis(ethanethiol), 3,7-dithia-1,9-nonanedithiol, and 1,6-dimercapto-3-hexanesulfide; The difunctional isocyanate includes at least one of hexamethylene diisocyanate, isophorone diisocyanate, trimethylhexamethylene diisocyanate, butane-1,4-diisocyanate, dicyclohexylmethane diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, 1,4-cyclohexane diisocyanate, meta-xylyl diisocyanate, ditoluene diisocyanate, p-phenylene diisocyanate, meta-phenylene diisocyanate, toluene 2,6-diisocyanate, toluene-2,5-diisocyanate, 1,4-cyclohexane dimethyl diisocyanate, and 1,3-bis(1-isocyanato-1-methylethyl)benzene.

14. The method according to claim 13, characterized in that The difunctional thiol includes at least one of ethanedithiol, 1,3-propanedithiol, 1,4-butanedithiol, 1,5-pentanedithiol, 1,6-hexanedithiol, 1,7-heptanedithiol, 1,8-octanedithiol, 1,9-nonanedithiol, 1,10-decanedithiol, 1,2-butanedithiol, 2,2'-thiobis(ethanethiol), 3,7-dithia-1,9-nonanedithiol, and 1,6-dimercapto-3-hexanesulfide; The difunctional isocyanate includes at least one of hexamethylene diisocyanate, isophorone diisocyanate, trimethylhexamethylene diisocyanate, butane-1,4-diisocyanate, dicyclohexylmethane diisocyanate, and 1,4-cyclohexane dimethyl diisocyanate.

15. The method according to claim 7 or 9, characterized in that: The first catalyst includes one of triethylenediamine, bis(dimethylaminoethyl) ether, dimethylethanolamine, 2-(2-dimethylamino-ethoxy)ethanol, trimethylhydroxyethylpropylenediamine, N,N-bis(dimethylaminopropyl)isopropanolamine, dibutyltin dilaurate, stannous octoate, potassium carboxylate catalysts and bismuth carboxylate catalysts.

16. The method according to claim 7 or 9, characterized in that: The ratio of mercapto group to isocyanate group in the reaction system is 1:1.05-5.

05.

17. The method according to claim 16, characterized in that The ratio is 1:1.05-2.

18. A photopolymer holographic recording medium, characterized in that: The photopolymer holographic recording medium comprises a film-forming resin, wherein the film-forming resin comprises a sulfur-containing isocyanate-terminated first oligomer and a polyhydroxy compound as described in any one of claims 1 to 3, or the film-forming resin comprises a sulfur-containing hydroxyl-terminated second oligomer and a polyfunctional isocyanate as described in any one of claims 4 to 6.

19. The photopolymer holographic recording medium according to claim 18, wherein: In terms of mass percentage, the total content of the sulfur-containing isocyanate-terminated first oligomer and the polyhydroxy compound is 40%-50%, or the total content of the sulfur-containing hydroxyl-terminated second oligomer and the multifunctional isocyanate is 40%-50%; The photopolymer holographic recording medium further comprises: a writing monomer, a photosensitive initiation system, a chain transfer agent, a second catalyst and additives.

20. The photopolymer holographic recording medium according to claim 19, wherein: In terms of mass percentage, the content of the writing monomer is 40%-50%, the content of the photosensitive initiator system is 0.01%-8%, the content of the chain transfer agent is 0.05%-5%, the content of the second catalyst is 0.001%-3%, and the content of the additive is 0.1%-10%.

21. A holographic optical element, characterized in that: The raw material of the holographic optical element comprises the photopolymer holographic recording medium as claimed in any one of claims 18 to 20.

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