Holographic photopolymer materials, holographic photosensitive films, holographic optical elements, and display devices.

Abstract

Holographic photopolymer materials, holographic photosensitive films, holographic optical elements, and display devices are provided. The holographic photopolymer material comprises a polymer matrix, a photopolymerizable monomer, and a photosensitizer. The refractive index of the photopolymerizable monomer is greater than that of the polymer matrix. The molecular structure of the polymer matrix includes a linear structure, the branched chains of the polymer matrix include activating groups, and / or the molecular structure of the polymer matrix includes a crosslinked structure. Because polymer matrices with a crosslinked molecular structure have a high glass transition temperature, holographic photopolymer materials have good heat resistance. Because holographic photopolymer materials with a linear molecular structure include activating groups that can form crosslinked structures, optical elements made from holographic photopolymer materials can have crosslinked structures, i.e., optical elements can have good heat resistance. Holographic photopolymer materials have good heat resistance, or optical elements made from holographic photopolymer materials can have good heat resistance.

Description

[Technical Field]

[0001] This application relates to the field of polymer materials, and more specifically to holographic photopolymer materials, holographic photosensitive films, holographic optical elements, and display devices. [Background technology]

[0002] In optical holography, based on the principles of optical interference and diffraction, a reference light wave is introduced and interfered with the object light wave. The amplitude and phase information of the object light wave is recorded on a holographic recording medium in the form of interference fringes, and then the light wave of the original object is reconstructed by diffraction, thereby reconstructing a three-dimensional image of the original object. Holographic technology can include a holographic recording process. A holographic recording process can be understood as recording / storing the optical information of an object according to the principle of interference. Holography can include optical information such as the amplitude and phase of a light wave.

[0003] In holographic technology, holographic photosensitive films are typically used to record / store optical information, such as the amplitude and phase of light waves. The materials used in holographic photosensitive films can be referred to as holographic recording media. Holographic photopolymer materials are common holographic recording media. As a type of holographic polymer material, holographic photopolymer materials have attracted considerable attention due to their advantages, including a wide photosensitive range, ease of manufacture and transport, and good long-term storage stability.

[0004] In recent years, the application fields of holographic technology have been expanding. Some application scenarios, such as automotive displays and aerial displays, involve high temperatures. Holographic photopolymer materials disclosed in related technologies are prone to irregular movement of polymer chain segments in high-temperature environments, leading to problems such as reduced transmittance, increased haze, and diffraction peak drift in holographic optical elements / holographic photosensitive films fabricated from these materials. This limits the application of holographic photopolymer materials / holographic photosensitive films in fields such as automotive displays and aerial displays. [Overview of the project]

[0005] This application discloses a holographic photopolymer material, a holographic photosensitive film, a holographic optical element, and a display device. The holographic photopolymer material includes a polymer matrix having a crosslinked structure or includes activating groups capable of forming a crosslinked structure. The holographic photopolymer material has good heat resistance. [Means for solving the problem]

[0006] A first aspect of this application discloses a holographic photopolymer material comprising a polymer matrix, a photopolymerizable monomer, and a photosensitizer. The molecular structure of the polymer matrix includes a linear structure, the branched chains of the polymer matrix include activating groups, the activating groups are available for crosslinking reactions; and / or the molecular structure of the polymer matrix includes a crosslinked structure.

[0007] In this embodiment, the holographic photopolymer material may comprise a polymer matrix, a photopolymerizable monomer, and a photosensitizer. The polymer matrix may provide force support for the holographic photopolymer material. The photosensitizer may absorb light waves and generate an active intermediate that enables polymerization of the photopolymerizable monomer. Under irradiation with a coherent light beam, the holographic photopolymer material may be divided into a coherent light region and a coherent dark region. The photosensitizer in the coherent light region may generate an active intermediate. The active intermediate promotes the polymerization of the photopolymerizable monomer into the coherent light region, forming a monomer polymer. Ultimately, the coherent light region and the coherent dark region have different concentrations of monomer polymer. The refractive index of the photopolymerizable monomer is greater than that of the polymer matrix, and correspondingly, the refractive index of the monomer polymer is greater than that of the polymer matrix. To perform holographic recording / memory, the coherent light region and the coherent dark region have different refractive indices.

[0008] Furthermore, because polymer matrices with a cross-linked molecular structure have a high glass transition temperature, holographic photopolymer materials exhibit good heat resistance.

[0009] Holographic photosensitive films / holographic optical elements made from holographic photopolymer materials with a linear molecular structure and branched chains containing activating groups exhibit good heat resistance. Specifically, reaction conditions can be controlled so that the activating groups in the holographic photosensitive film / holographic optical element undergo a crosslinking reaction. In other words, by including a crosslinked molecular structure in the polymer matrix of the holographic photosensitive film / holographic optical element, the holographic photosensitive film / holographic optical element exhibits good heat resistance.

[0010] The holographic photopolymer material disclosed in this embodiment is found to have good heat resistance. Alternatively, a holographic photosensitive film / holographic optical element made from the holographic photopolymer material disclosed in this embodiment has good heat resistance. The holographic photopolymer material disclosed in this embodiment can be used in fields such as automotive displays and levitation displays.

[0011] Referring to the first embodiment of the first aspect, the polymer matrix comprises at least one of polymethacrylate, polymethacrylamide, polyacrylate, polyacrylamide, polyvinyl ether, polyvinyl ester, and polysiloxane.

[0012] In this embodiment, the polymer matrix has a high glass transition temperature, and a polymer matrix having a high glass transition temperature can effectively overcome the motion of polymer chain segments, and as a result, the holographic photopolymer material has good heat resistance.

[0013] Referring to a second embodiment of the first aspect, the polymer matrix comprises a copolymer containing at least two of the following substances: methacrylate, methacrylamide, acrylate, acrylamide, vinyl ether, vinyl ester, and siloxane.

[0014] In this embodiment, the polymer matrix also has a high glass transition temperature, and a polymer matrix having a high glass transition temperature can effectively overcome the motion of polymer chain segments, and as a result, the holographic photopolymer material has good heat resistance.

[0015] Referring to a third embodiment of the first aspect, the activating group comprises at least one of an epoxy group, a vinyl ether, and an N-vinyl group.

[0016] In this embodiment, the activating group may contain an epoxy group, and the epoxy group has great rigidity. The polymer matrix contains active epoxy groups with great rigidity, and the polymer matrix has a high glass transition temperature. The polymer matrix with a high glass transition temperature can effectively overcome the movement of polymer chain segments. As a result, the holographic photopolymer material has good heat resistance.

[0017] Referring to the fourth embodiment of the first aspect, the structural formula of the photopolymerizable monomer is

Chemical formula

[0018] In this embodiment, the sulfur atom, aromatic ring, and benzene ring in R2 all increase the refractive index of the photopolymerizable monomer. As a result, the photopolymerizable monomer has a high refractive index. The photopolymerizable monomer has a high refractive index, and correspondingly, the monomer polymer also has a high refractive index, ensuring that the coherent bright region and coherent dark region of the holographic photosensitive film / holographic optical element made from the holographic photopolymer material disclosed in this embodiment have a high refractive index contrast. The high refractive index contrast makes it easier to achieve both high transmittance and high diffraction efficiency of the holographic photosensitive film / holographic optical element.

[0019] Referring to the fifth embodiment of the first embodiment, the holographic photopolymer material further comprises a co-initiator. The co-initiator comprises at least one of tetrabutylammonium tetrahexylborate, tetrabutylammonium hexyltrisphenylborate, tetrabutylammonium tris(3-fluorophenyl)hexylborate, and tetrabutylammonium tris(3-chloro-4-methylphenyl)hexylborate.

[0020] In this embodiment, a co-initiator and a photosensitizer are used together, and as a result, the rate of production of the active intermediate by the photosensitizer can be increased under excitation of light waves.

[0021] Referring to the sixth embodiment of the first aspect, the infrared spectrum of the holographic photopolymer material includes a first characteristic absorption peak and a second characteristic absorption peak. The wavenumber of the first characteristic absorption peak is 877 cm⁻¹. -1 ~831cm -1 The wavenumber of the second characteristic absorption peak is 829 cm⁻¹. -1 ~787cm -1 That is the case.

[0022] In this embodiment, a holographic photopolymer material is selected whose infrared spectrum includes the following: the wavenumber of the first characteristic absorption peak is 877 cm⁻¹. -1 ~831cm -1 The range is such that the wavenumber of the second characteristic absorption peak is 829 cm⁻¹. -1 ~787cm -1 This is within the range. In this way, holographic photopolymer materials with high glass transition temperatures can be obtained.

[0023] Referring to the seventh embodiment of the first aspect, the ratio of the peak area of ​​the first characteristic absorption peak to the peak area of ​​the second characteristic absorption peak is in the range of 0.4 to 8.8.

[0024] In this embodiment, the ratio of the peak area of ​​the first characteristic absorption peak to the peak area of ​​the second characteristic absorption peak is selected to be in the range of 0.4 to 8.8, resulting in a further increase in the glass transition temperature of the polymer matrix.

[0025] Referring to the eighth embodiment of the first aspect, the nuclear magnetic resonance hydrogen spectrum of the holographic photopolymer material includes a third characteristic absorption peak and a fourth characteristic absorption peak. The chemical shift of the third characteristic absorption peak is in the range of 3.2 ppm to 3.22 ppm, and the chemical shift of the fourth characteristic absorption peak is in the range of 3.5 ppm to 3.7 ppm.

[0026] In this embodiment, a holographic photopolymer material is selected in which the nuclear magnetic resonance hydrogen spectrum includes a chemical shift of a third characteristic absorption peak in the range of 3.2 ppm to 3.22 ppm and a chemical shift of a fourth characteristic absorption peak in the range of 3.5 ppm to 3.7 ppm, and as a result, a holographic photopolymer material having a high glass transition temperature can be obtained.

[0027] Referring to the ninth embodiment of the first aspect, the glass transition temperature of the polymer matrix is ​​50°C or higher.

[0028] In this embodiment, the glass transition temperature of the polymer matrix is ​​50°C or higher, and the polymer matrix has a high glass transition temperature. A polymer matrix with a high glass transition temperature can effectively overcome the motion of polymer chain segments, and as a result, the holographic photopolymer material has good heat resistance.

[0029] A second aspect of this application discloses a holographic photosensitive film comprising a protective layer and a first film layer covering the protective layer. The first film layer is made from a holographic photopolymer material disclosed in the first aspect.

[0030] For the effects achievable in the second aspect, refer to the effects achievable in any feasible embodiment of the first aspect.

[0031] The third aspect of this application discloses a holographic optical element including a protective layer and a second film layer covering the protective layer. The material used for the second film layer includes a polymer matrix and a monomer polymer. The molecular structure of the polymer matrix includes a crosslinked structure. The second film layer includes a coherent bright region and a coherent dark region, and the density of the monomer polymer in the coherent bright region is greater than the density of the monomer polymer in the coherent dark region.

[0032] For the effects achievable in the third aspect, refer to the effects achievable in any feasible embodiment of the first aspect.

[0033] Referring to the first embodiment of the third aspect, the infrared spectrum of the second film layer includes a fifth characteristic absorption peak and a sixth characteristic absorption peak. The wave number of the fifth characteristic absorption peak is 1768 cm -1 ~1692 cm -1 and the wave number of the sixth characteristic absorption peak is 1093 cm -1 ~1023 cm -1 is.

[0034] In this embodiment, a second film layer whose infrared spectrum includes the following is selected: the wave number of the fifth characteristic absorption peak is in the range of 1768 cm -1 ~1692 cm -1 and the wave number of the sixth characteristic absorption peak is in the range of 1093 cm -1 ~1023 cm -1 is. Thereby, a holographic optical element having good thermal stability can be obtained.

[0035] Referring to the second embodiment of the third aspect, the ratio of the peak area of the fifth characteristic absorption peak to the peak area of the sixth characteristic absorption peak is in the range of 1.0 to 4.4.

[0036] In this embodiment, a holographic optical element with good thermal stability can be obtained by selecting a ratio of the peak area of ​​the fifth characteristic absorption peak to the peak area of ​​the sixth characteristic absorption peak that is in the range of 1.0 to 4.4.

[0037] A fourth aspect of this application discloses a method for producing a holographic photopolymer material, comprising synthesizing a polymer matrix and mixing the polymer matrix, a photopolymerizable monomer, and a photosensitizer to obtain the holographic photopolymer material disclosed in the first aspect. The molecular structure of the polymer matrix includes a linear structure, and the branched chains of the polymer matrix include activating groups, which are available for crosslinking reactions.

[0038] For the effects that can be achieved in the fourth embodiment, please refer to the effects that can be achieved in any feasible embodiment of the first embodiment.

[0039] A fifth aspect of this application discloses a method for producing a holographic photosensitive film, comprising coating a protective layer with a holographic photopolymer material produced in a fourth aspect, and converting the holographic photopolymer material into a first film layer. The molecular structure of the polymer matrix in the first film layer includes a linear structure, the branched chains of the polymer matrix include activating groups, the activating groups are available for crosslinking reactions; and / or the molecular structure of the polymer matrix in the first film layer includes a crosslinked structure.

[0040] For the effects that can be achieved in the fifth embodiment, please refer to the effects that can be achieved in any feasible embodiment of the first embodiment.

[0041] A sixth aspect of this application discloses a method for manufacturing a holographic optical element, comprising performing a holographic treatment on a holographic photosensitive film prepared in the fifth aspect in order to convert a first film layer into a second film layer. The second film layer includes a coherent light region and a coherent dark region. The density of monomer polymer in the coherent light region is greater than the density of monomer polymer in the coherent dark region, and the monomer polymer is obtained by polymerization of photopolymerizable monomers.

[0042] For the effects that can be achieved in the sixth embodiment, please refer to the effects that can be achieved in any feasible embodiment of the first embodiment.

[0043] A seventh aspect of this application discloses a display device comprising a display and an optical element disposed on the display. The optical element includes a holographic photosensitive film as disclosed in the second aspect or a holographic optical element as disclosed in the third aspect.

[0044] For the effects that can be achieved in the seventh embodiment, please refer to the effects that can be achieved in any feasible embodiment of the first embodiment. [Brief explanation of the drawing]

[0045] [Figure 1] This is a mapping curve between the transmittance of a holographic photopolymer material and the wavelength of the irradiated light wave during a process in which the holographic photopolymer material is heated at 100°C for 6 hours, according to a feasible embodiment. [Figure 2] This is a flowchart of a method for producing a holographic photosensitive film according to a feasible embodiment. [Figure 3] This is a diagram of a holographic photosensitive film according to a feasible embodiment. [Figure 4] This is a diagram of a holographic photosensitive film according to a feasible embodiment. [Figure 5]This is a flowchart illustrating a method for fabricating a holographic optical element according to a feasible embodiment. [Figure 6] This is a diagram illustrating the principle of a reflected light path for holographic recording according to a feasible embodiment. [Figure 7] This is a diagram illustrating the principle of a transmitted light path for holographic recording according to a feasible embodiment. [Figure 8] This is a flowchart of a holographic optical element according to a feasible embodiment. [Modes for carrying out the invention]

[0046] The following describes the technical solutions in the embodiments of this application with reference to the accompanying drawings. It is clear that the embodiments described are only a selection of the embodiments of this application, and not all of them.

[0047] The following terms, such as "first," "second," etc., are used solely for explanatory purposes to distinguish between identical or similar items that have essentially the same function and features, and should not be understood as an indication or implication of relative importance, or an implicit indication of the quantity of the technical features shown. Therefore, features limited by "first," "second," etc., may explicitly or implicitly include one or more features.

[0048] In addition, in the description of this application, unless otherwise specified, “multiple” means two or three or more.

[0049] In addition, in this application, terms indicating direction, such as “up,” “down,” “left,” “right,” “horizontal,” and “vertical,” are defined in relation to the direction in which the components are schematically positioned in the accompanying drawings. These terms indicating direction are relative concepts used for relative explanation and clarification, and should be understood to change as appropriate based on changes in the direction in which the components are positioned in the accompanying drawings. Unless otherwise explicitly specified and limited, the term “connection” should be understood in a broad sense. For example, “connection” may be a fixed connection, a detachable connection, or an integrated connection, or it may be a direct connection or an indirect connection implemented via an intermediate medium.

[0050] In addition, in the embodiments of this application, terms such as “example” or “for example” indicate that an example, illustration, or explanation is being given. None of the embodiments or designs described as “example” or “for example” in the embodiments of this application are described as being more preferable or having more advantages than other embodiments or designs. More precisely, the use of terms such as “example” or “for example” is intended to present the relevant concepts in a particular way for the sake of ease of understanding.

[0051] First, the concepts in the embodiments of this application will be explained.

[0052] Interference is a phenomenon in which, when two or more waves meet in space, they either overlap or cancel each other out, thereby forming a new waveform.

[0053] Amplitude is the maximum value that a light wave's oscillation can reach.

[0054] Phase is the position of a light wave in its period at a specific moment in time.

[0055] A light beam is a form of light wave, specifically a beam-shaped light wave.

[0056] Macromolecular compounds are typically compounds with relative molecular weights ranging from several thousand to several million, and they possess excellent mechanical properties.

[0057] A linear structure is a type of polymeric compound structure. The entire molecule with a linear structure resembles a long chain.

[0058] A crosslinked structure, also known as a network structure, is a three-dimensional network structure of polymer compounds.

[0059] Diffraction efficiency (DE) is an important parameter for holographic photopolymer materials, and is the ratio of the light intensity in the diffraction direction to the intensity of the incident light.

[0060] The index-of-refraction degree of modulation is an important parameter for holographic photopolymer materials, reflecting the degree to which the material is controlled by light wave signals.

[0061] Transmittance is an important parameter of holographic photopolymer materials and can be expressed as the ratio of the light beam passing through the holographic photopolymer material to the incident light beam passing through the holographic photopolymer material.

[0062] Haze is an important parameter for holographic photopolymer materials and can be expressed as the ratio of scattered light flux to light flux passing through the holographic photopolymer material.

[0063] The glass transition temperature (Tg) is the temperature at which the glassy state changes to a highly elastic state. Tg is the lowest temperature at which molecular chains can move.

[0064] Holographic technology, also known as virtual imaging technology, uses interference and diffraction principles to record and reconstruct a real three-dimensional image of an object. Holographic projection technology can include holographic recording and holographic reproduction processes.

[0065] A holographic recording process can be understood as recording the optical information of an object according to the principle of interference. Specifically, a portion of a light beam illuminating the object to be photographed can form an object light beam associated with the object to be photographed; the other portion of the light beam can illuminate a holographic film (the holographic film in the embodiments of this application may also be called a holographic photopolymer material) as a reference light beam, and the reference light beam can be superimposed with the object light beam to generate interference. In this manner, the phase and amplitude of each point on the object light beam associated with the object to be photographed are converted into varying intensities in space, recording all the optical information of the object light beam (briefly called holography in the embodiments of this application) based on the contrast and spacing between interference fringes. The optical information may include phase and amplitude. In the embodiments of this application, the holographic film recording the interference fringes may be called a holographic photosensitive film.

[0066] The holographic reconstruction process can be understood as an imaging process. A hologram, also called a holographic photograph, is obtained after a holographic film that records interference fringes undergoes processing steps such as development and fixing. Specifically, a hologram can be understood as a holographic optical element. The diffracted light waves of a holographic optical element, under the illumination of a coherent light beam, can typically provide two images, specifically the original image (also called the initial image) and a conjugate image. The two images can provide the user with a realistic visual effect that conveys a strong sense of three-dimensionality. Each part of the hologram records the light information of each point of the object being photographed. Therefore, in principle, each part of the hologram can reconstruct the entire image of the object being photographed. Multiple different images may be further recorded on the same film through multiple exposures and can be displayed separately without mutual interference.

[0067] Because optical information such as the amplitude and phase of light waves can be stored, holographic technology is widely used in technological fields such as holographic optical element manufacturing, high-density holographic storage, high-end anti-counterfeiting, and additive manufacturing.

[0068] In holographic technology, holographic photosensitive films are used to record / store optical information such as the amplitude and phase of light waves. The materials used in holographic photosensitive films can be referred to as holographic recording media. Holographic polymer materials are common holographic recording media.

[0069] Holographic polymer materials use polymer compounds as a medium to store / record optical information such as the amplitude and phase of light waves.

[0070] As a type of holographic polymer material, holographic photopolymer materials have attracted widespread attention due to their advantages such as a wide photosensitive range, ease of manufacture and transport, and good long-term storage stability. Holographic photopolymer materials are described below.

[0071] The holographic photopolymer material may include a photosensitizer, a polymer matrix, and a photopolymerizable monomer.

[0072] A polymer matrix can provide force support for holographic photopolymer materials. The refractive index (index of refraction) of the polymer matrix is ​​typically low (refractive index < 1.5).

[0073] Photosensitizers can absorb the radiant energy of light waves and, through chemical changes, generate active intermediates that promote the polymerization of photopolymerizable monomers.

[0074] The refractive index of photopolymerizable monomers is typically high (refractive index > 1.5). During holographic processing, photopolymerizable monomers can polymerize under the action of active intermediates generated by a photosensitizer to form photopolymers (which may also be called monomer polymers in the embodiments of this application). The refractive index of the photopolymer is greater than that of the polymer matrix. A difference exists between the refractive indices of the photopolymer and the polymer matrix to form periodic phase separation structures and refractive index modulation.

[0075] The phase separation structure of holographic photopolymer materials can be controlled by changing parameters such as wavelength, amount of light beam, and intersection angle of coherent light beams. Typically, the main parameters used to evaluate the performance of holographic photopolymer materials include diffraction efficiency, refractive index modulation, transmittance, and haze.

[0076] Below, we describe two holographic photopolymer materials disclosed in the related technologies.

[0077] Related Technology 1 discloses a holographic photopolymer material, and the holographic photopolymer material of Related Technology 1 is (a) Polymer adhesives that can be selected from one of the following groups: polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, and polyvinyl formal, copolymers comprising their main chain segments, and mixtures thereof; (b) Unsaturated photopolymerizable monomers containing alkenes, which can be selected from one of the following groups: photopolymerizable monomers containing carbazole, and unsaturated photopolymerizable monomers containing one or more phenyl groups, phenoxy groups, naphthyl groups, naphthyloxy groups, and aromatic heterocycles containing up to three aromatic rings, chlorine, and bromine; and (c) Photoinitiator systems that can be activated by light irradiation, It may include.

[0078] The holographic photopolymer material disclosed in Related Technology 1 has excellent diffraction efficiency and refractive index modulation. However, when the holographic photopolymer material disclosed in Related Technology 1 is heated, problems such as irreversible diffraction peak wavelength drift, decreased transmittance, and increased haze occur.

[0079] Related Technology 2 discloses a holographic photopolymer material. The holographic photopolymer material is (a) Polymer matrix (aromatic, aromatic aliphatic, aliphatic, or alicyclic polyurethane); (b) Photopolymerizable monomers (acrylates / urethane acrylates with a refractive index greater than 1.50); ​​and (c) Photoinitiators (cationic dyes, anionic dyes, neutral dyes, and co-initiators) It may include.

[0080] The holographic photopolymer material disclosed in Related Technology 2 uses in-situ crosslinked polyurethane as the polymer matrix, thereby improving the heat resistance of the holographic photopolymer material to some extent. To meet the requirement of a high refractive index modulation, the holographic photopolymer material disclosed in Related Technology uses polyurethane with a low crosslinking density as the polymer matrix. As a result, the holographic photopolymer material disclosed in Related Technology 2 is also prone to problems such as irreversible diffraction peak wavelength drift, decreased transmittance, and increased haze when heated for extended periods.

[0081] The holographic photopolymer materials disclosed in the related technologies can be found to have excellent diffraction efficiency, refractive index modulation (δn), transmittance, haze, and other properties.

[0082] In recent years, the application fields of holographic photopolymer materials have been expanding. In some fields, holographic photopolymer materials are used in application scenarios such as automotive displays and aerial displays, where ambient temperatures are high. In the aforementioned application scenarios, ambient temperatures are high. Holographic optical elements obtained using holographic photopolymer materials disclosed in related technologies are prone to polymer chain segment movement in high-temperature environments, and holographic photopolymer materials have poor heat resistance. This limits the application of holographic photopolymer materials in fields such as automotive displays and aerial displays.

[0083] To improve the heat resistance of holographic photopolymer materials, one embodiment of this application discloses a holographic photopolymer material. The holographic photopolymer material may comprise a polymer matrix, a photopolymerizable monomer, and a photosensitizer.

[0084] A polymer matrix can provide force support for holographic photopolymer materials. Photopolymerizable monomers and photosensitizers are dispersed in the polymer matrix. The photosensitizer can absorb light waves and generate active intermediates that enable polymerization of the photopolymerizable monomers. Under irradiation with a coherent light beam, the holographic photopolymer material can be divided into a coherent light region and a coherent dark region. The photosensitizer in the coherent light region can generate active intermediates. These active intermediates promote polymerization of the photopolymerizable monomers into the coherent light region, forming monomer polymers. Ultimately, the coherent light region and the coherent dark region have different concentrations of monomer polymers. The refractive index of the photopolymerizable monomers is greater than that of the polymer matrix, and correspondingly, the refractive index of the monomer polymers is greater than that of the polymer matrix. Therefore, to perform holographic recording / memory, the coherent light region and the coherent dark region have different refractive indices.

[0085] Because polymer matrices with a cross-linked molecular structure have a high glass transition temperature, holographic photopolymer materials exhibit good heat resistance.

[0086] Holographic photosensitive films / holographic optical elements made from holographic photopolymer materials with a linear molecular structure and branched chains containing activating groups exhibit good heat resistance. Specifically, reaction conditions can be controlled so that the activating groups in the holographic photosensitive film / holographic optical element undergo a crosslinking reaction. In other words, by including a crosslinked molecular structure in the polymer matrix of the holographic photosensitive film / holographic optical element, the holographic photosensitive film / holographic optical element exhibits good heat resistance.

[0087] The following section further describes the components of holographic photopolymer materials.

[0088] In this embodiment of the present application, the holographic photopolymer material may include a polymer matrix.

[0089] In this embodiment of the present application, the polymer matrix comprises a polymer compound formed by linking a plurality of repeating units. The polymer matrix can provide force support for a holographic photopolymer material.

[0090] In this embodiment of the present application, repeating units can be understood as the smallest units in a polymer matrix that have the same chemical composition.

[0091] In this embodiment of the present application, the type of repeating unit is not particularly limited. Any material that can be linked to form a polymer matrix having a glass transition temperature of 50°C or higher can be used as a repeating unit in this embodiment of the present application.

[0092] In a feasible embodiment, the repeating units may include at least one of methacrylate, methacrylamide, polyacrylate, polyacrylamide, polyvinyl ether, polyvinyl ester, and polysiloxane, as well as polysiloxane, and all repeating units have polar groups. Due to the strong interactions between the polar groups, the repeating units have a high glass transition temperature, and correspondingly, the polymer matrix formed by linking the above repeating units also has a high glass transition temperature. The polar groups may include, but are not limited to, carbonyl groups, amide groups, ether groups, and silane groups.

[0093] The following explains the glass transition temperature of repeating units, using acrylates as an example.

[0094] The structural formula of acrylate is as follows: [ka] Acrylates have polar groups: carbonyl groups ( [ka] ) contains. Due to strong interactions between carbonyl groups, methacrylates have a high glass transition temperature.

[0095] In some feasible embodiments, the polymer matrix may contain at least one homopolymer.

[0096] Homopolymers can be understood as high-molecular-weight compounds formed by the polymerization of a single type of repeating unit. For example, the polymer matrix may contain at least one of the following: polymethacrylate (see structural formula I below), polymethacrylamide (see structural formula II below), polyacrylate (see structural formula III below), polyacrylamide (see structural formula IV below), polyvinyl ether (see structural formula V below), polyvinyl ester (see structural formula VI below), and polysiloxane (see structural formula VII below).

[0097] [ka] Structural formula I, [ka] Structural formula II, [ka] Structural formula III, [ka] Structural formula IV, [ka] Structural formula V, [ka] Structural formula VI, and [ka] Structural formula VII, where n represents the quantity of repeating units and * represents a bonding site.

[0098] It should be noted that this embodiment of the present application merely describes some examples of homopolymers that may be included in a polymer matrix. The aforementioned types of homopolymers do not constitute a particular limitation.

[0099] The polymer matrix disclosed in this embodiment has a high glass transition temperature, and a polymer matrix having a high glass transition temperature can effectively overcome the motion of polymer chain segments, and as a result, the holographic photopolymer material has good heat resistance.

[0100] In some feasible embodiments, the polymer matrix may comprise at least one copolymer. A copolymer can be understood as a high-molecular-weight compound formed by the polymerization of at least two types of repeating units. For example, the polymer matrix may comprise at least one of the copolymers comprising methacrylate and methacrylamide, copolymers comprising acrylate and polyacrylamide, and copolymers comprising vinyl ether, vinyl ester, and siloxane.

[0101] It should be noted that this embodiment of the present application merely describes some examples of copolymers that may be included in a polymer matrix. The aforementioned types of copolymers do not constitute a particular limitation.

[0102] The polymer matrix disclosed in this embodiment has a high glass transition temperature, and a polymer matrix having a high glass transition temperature can effectively overcome the motion of polymer chain segments, and as a result, the holographic photopolymer material has good heat resistance.

[0103] In some feasible embodiments, the polymer matrix may comprise at least one copolymer and at least one homopolymer. For the types of copolymers and homopolymers, please refer to the embodiments described above. Further details are not described herein.

[0104] In this embodiment of the present application, the polymer matrix comprises a polymer compound formed by linking a plurality of repeating units. In some feasible embodiments, the molecular structure of the polymer matrix may include a linear structure, and the branched chains of the polymer matrix may include activation groups. In this embodiment of the present application, the activation groups may be understood as groups that can undergo crosslinking reactions.

[0105] In a feasible embodiment, the branched chains of the polymer matrix may undergo a crosslinking reaction; that is, the molecular structure of the polymer matrix is ​​a crosslinked structure.

[0106] Polymer matrices containing crosslinked structures have a high glass transition temperature, and polymer matrices with a high glass transition temperature can effectively overcome the movement of polymer chain segments. As a result, holographic photopolymer materials have good heat resistance.

[0107] In embodiments where the polymer matrix contains activating groups, in viable embodiments, the branched chains of the polymer matrix do not need to undergo crosslinking. That is, the molecular structure of the polymer matrix is ​​linear. Polymer matrices containing linear structures have good fluidity, and the corresponding holographic photopolymer materials have excellent coating performance.

[0108] In embodiments where the polymer matrix contains activating groups, in a viable embodiment, some of the branched chains of the polymer matrix may undergo a crosslinking reaction. That is, the molecular structure of the polymer matrix includes both linear and crosslinked structures.

[0109] The type of activating group is not particularly limited in this embodiment of the present application. Any group capable of undergoing a crosslinking reaction can be used as the activating group in this embodiment of the present application.

[0110] For example, the activating group may include vinyl ether (see structural formula VIII for its structural formula) and N-vinyl group (see structural formula IX for its structural formula).

[0111] [ka] Structural formula VII and [ka] Structural formula IX, where * represents a bonding site.

[0112] It should be noted that this embodiment of the present application merely illustrates two types of activating groups, and the above-mentioned activating groups do not constitute a specific limitation.

[0113] In a viable embodiment, the photosensitizer generates an active intermediate under first conditions, and the active groups on the branched chains of the polymer matrix undergo a crosslinking reaction under second conditions, with the first and second conditions not overlapping.

[0114] In this embodiment of the present application, the first condition includes a condition for exciting a photosensitizer to produce an active intermediate. The second condition includes a condition for exciting a crosslinking reaction of the activating group. The non-overlap of the first and second conditions may be understood as the first condition not involving the crosslinking reaction of the activating group.

[0115] The first condition may include irradiation. For example, the first condition may include irradiation in the wavelength range of 400 nm to 800 nm.

[0116] The second condition is not particularly limited to the embodiments of this application.

[0117] In feasible embodiments, the second condition may include irradiation. However, it is necessary to ensure that the wavelength range of the light wave required by the second condition does not overlap with the wavelength range of the light wave required by the first condition. For example, the wavelength range required by the first condition may be 400 nm to 800 nm, while the wavelength required by the second condition may be less than 400 nm or greater than 800 nm.

[0118] In feasible embodiments, the second condition may include non-irradiation conditions. For example, non-irradiation conditions may include, but are not limited to, high temperature and electrophilic catalytic activity.

[0119] In this embodiment, the molecular structure of the polymer matrix of the holographic photopolymer material includes a linear structure, and the branched chains of the polymer matrix include activating groups. Because the molecular structure of the polymer matrix includes a linear structure, the holographic photopolymer material has good coating performance.

[0120] Holographic photosensitive films made from holographic photopolymer materials can have high data recording / storage efficiency. Specifically, the reaction conditions can be controlled so that the activating groups of the holographic photosensitive film do not undergo crosslinking during the holographic processing process. That is, during the holographic processing process, the molecular structure of the polymer matrix in the holographic photosensitive film includes a linear structure. A polymer matrix with a linear structure has low migration resistance to photopolymerizable monomers, which facilitates the migration of photopolymerizable monomers to the coherent light region. Therefore, holographic photosensitive films made from the holographic photopolymer materials disclosed in this embodiment can have high data recording / storage efficiency.

[0121] A holographic photosensitive film having holographic recording (sometimes referred to as a holographic optical element in this embodiment of the present application) can have good heat resistance. Specifically, the polymer matrix in the holographic optical element contains activating groups. Experimental conditions are controlled so that the activating groups undergo a crosslinking reaction. That is, the polymer matrix in the holographic optical element has a crosslinked structure. By using the holographic photopolymer material disclosed in this embodiment, a holographic optical element with good heat resistance can be obtained.

[0122] In feasible embodiments, the activating group may include an epoxy group.

[0123] The amount of ring-forming atoms in the epoxy group is not particularly limited in this embodiment of the present application. For example, the activating group may include a tertiary epoxy group (see structural formula X for its structural formula), a quaternary epoxy group (see structural formula XI for its structural formula), and a quintic epoxy group (see structural formula XII for its structural formula). In this embodiment of the present application, an activating group containing an epoxy group may be called an activating epoxy group.

[0124] [ka] Structural formula X, [ka] Structural formula XI, and [ka] Structural formula XII, where * represents a bonding site.

[0125] It should be noted that this embodiment of the present application merely illustrates three examples of activated epoxy groups, and these activated epoxy groups do not constitute a specific limitation.

[0126] Because the activated epoxy groups have high rigidity, the polymer matrix has high rigidity. The glass transition temperature of the polymer matrix is ​​related to the rigidity of the polymer matrix. Higher polymer matrix rigidity indicates better heat resistance of the polymer matrix. In this embodiment, the polymer matrix contains activated epoxy groups with high rigidity, and the polymer matrix has a high glass transition temperature. A polymer matrix with a high glass transition temperature can effectively suppress the movement of polymer chain segments, and as a result, the holographic photopolymer material has good heat resistance.

[0127] Holographic photopolymer materials contain epoxy group / ether bond (-O-), and as a result, the infrared spectrum of holographic photopolymer materials contains a first characteristic absorption peak. Since holographic photopolymer materials contain acrylate / carbonyl group, the infrared spectrum of holographic photopolymer materials contains a second characteristic absorption peak. The wavenumber of the first characteristic absorption peak is 877 cm⁻¹. -1 ~831cm -1 The wavenumber of the second characteristic absorption peak is 829 cm⁻¹. -1 ~787cm -1 That is the case.

[0128] A holographic photopolymer material is selected whose infrared spectrum includes the following: the wavenumber of the first characteristic absorption peak is 877 cm⁻¹. -1 ~831cm -1 The range is such that the wavenumber of the second characteristic absorption peak is 829 cm⁻¹. -1 ~787cm -1 This is within the range. In this way, holographic photopolymer materials with high glass transition temperatures can be obtained.

[0129] The ratio of the peak area of ​​the first characteristic absorption peak to the peak area of ​​the second characteristic absorption peak is selected to be in the range of 0.4 to 8.8, resulting in a further increase in the glass transition temperature of the polymer matrix.

[0130] Since the holographic photopolymer material contains epoxy / ether bonds, the nuclear magnetic resonance hydrogen spectrum of the holographic photopolymer material contains a third characteristic absorption peak. Since the holographic photopolymer material contains acrylate / carbonyl groups, the nuclear magnetic resonance hydrogen spectrum of the holographic photopolymer material contains a fourth characteristic absorption peak. The chemical shift of the third characteristic absorption peak is in the range of 3.2 ppm to 3.22 ppm, and the chemical shift of the fourth characteristic absorption peak is in the range of 3.5 ppm to 3.7 ppm.

[0131] Holographic photopolymer materials are selected whose nuclear magnetic resonance hydrogen spectra include a chemical shift of a third characteristic absorption peak in the range of 3.2 ppm to 3.22 ppm, and a chemical shift of a fourth characteristic absorption peak in the range of 3.5 ppm to 3.7 ppm, and as a result, holographic photopolymer materials with high glass transition temperatures can be obtained.

[0132] In feasible embodiments, the glass transition temperature of the polymer matrix is ​​50°C or higher.

[0133] In this embodiment, the glass transition temperature of the polymer matrix is ​​50°C or higher, and the polymer matrix has a high glass transition temperature. A polymer matrix with a high glass transition temperature can effectively suppress the movement of polymer chain segments, and as a result, the holographic photopolymer material has good heat resistance.

[0134] This concludes the explanation of polymer matrices.

[0135] In this embodiment of the present application, the holographic photopolymer material may include a photosensitizer.

[0136] A photosensitizer can be understood as a substance that, after being excited by a light wave, undergoes a photochemical change to produce an active intermediate.

[0137] In this embodiment of the present application, the type of photosensitizer is not particularly limited. Any substance that, after being excited by a light wave, can produce an active intermediate having the ability to induce polymerization of a photopolymerizable monomer can be used as a photosensitizer in this embodiment of the present application.

[0138] In feasible embodiments, the photosensitizer may comprise at least one of acridine orange, eosin B, erythrosine B, rose bengal, phloxine, rhodamine B, methyl blue, methylene blue, 3,3'-carbonylbis(7-diethylaminocoumarin), and 2,5-bis(4-diethylaminobenzylidene)cyclopentanone. The aforementioned photosensitizers have a stable structure, are not easily yellowed, and are easily bleached, which ensures that holographic photosensitive films / holographic optical elements fabricated using the holographic photopolymer materials disclosed in this embodiment have high transmittance.

[0139] Photosensitizers can generate active intermediates under light waves of 400 nm to 800 nm. A localized irradiation mode may be used, resulting in photosensitizers in the coherent light region generating active intermediates, while photosensitizers in the coherent dark region generating little to no active intermediates. The active intermediates promote the polymerization of photopolymerizable monomers into the coherent light region, forming monomer polymers. Ultimately, the coherent light and coherent dark regions have monomer polymers of different concentrations. To perform holographic recording / memory, the coherent light and coherent dark regions have different refractive indices.

[0140] In this embodiment of the present application, the active intermediate can be understood as an intermediate capable of inducing a polymerization reaction of a photopolymerizable monomer. The active intermediate may include, but is not limited to, free radical-active species and / or cationic-active species.

[0141] For example, free radical active species may include, but are not limited to, phenyl free radicals and alkyl free radicals.

[0142] For example, cationic active species may include, but are not limited to, protons. In this embodiment of the present application, the protons may originate from acidic substances such as hexafluorophosphate (HPH6) and hexafluoroantimonic acid (HSbF6).

[0143] To improve the holographic memory / recording efficiency of holographic photosensitive films made from holographic photopolymer materials, in feasible embodiments, the holographic photopolymer material may further contain a co-initiator.

[0144] By using a co-initiator together with a photosensitizer, the rate of activation of the active intermediate by the photosensitizer under light wave excitation can be accelerated, thereby improving the holographic memory / recording efficiency of holographic photosensitive films made from holographic photopolymer materials.

[0145] The type of co-initiator is not particularly limited in this embodiment of the present application. Any substance that can accelerate the rate of production of an active intermediate by a photosensitizer under light wave excitation can be used as a co-initiator in this embodiment of the present application.

[0146] For example, the co-initiator may include at least one of N-phenylglycine, triethanolamine, triisopropanolamine, methyldiethanolamine, chlorodiphenyliodonium salt, and hexafluorophosphate diphenyliodonium salt. The aforementioned co-initiators can accelerate the rate of active intermediate generation by the photosensitizer under light wave excitation, which may result in improved holographic memory / recording efficiency of the holographic photopolymer material.

[0147] In a viable embodiment, the co-initiator further comprises at least one of tetrabutylammonium tetrahexylborate, tetrabutylammonium hexyltrisphenylborate, tetrabutylammonium tris(3-fluorophenyl)hexylborate, and tetrabutylammonium tris(3-chloro-4-methylphenyl)hexylborate.

[0148] This concludes the explanation of photosensitizers / co-initiators.

[0149] In this embodiment of the present application, the holographic photopolymer material may include a photopolymerizable monomer.

[0150] In this embodiment of the present application, the photopolymerizable monomers are simple compounds that can be polymerized under the action of an active intermediate. The refractive index of the photopolymerizable monomer is greater than that of the polymer matrix.

[0151] In this embodiment of the present application, the compound formed by polymerization of photopolymerizable monomers can be called a monomer polymer, and the refractive index of the monomer polymer is greater than that of the holographic photopolymer material.

[0152] Under irradiation with a coherent light beam, a photosensitizer in the coherent light region may generate an active intermediate. This active intermediate promotes the polymerization of photopolymerizable monomers into the coherent light region, forming monomer polymers. Ultimately, the coherent light region and the coherent dark region have monomer polymers of different concentrations. To perform holographic recording / storage, the coherent light region and the coherent dark region have different refractive indices.

[0153] The type of photopolymerizable monomer is not particularly limited in this embodiment of the present application. Any substance that can be polymerized under the action of an active intermediate and whose refractive index is greater than that of the polymer matrix can be used as a photopolymerizable monomer in this embodiment of the present application.

[0154] In a viable embodiment, the photopolymerizable monomer may include a chlorine atom (Cl), a bromide atom (Br), an iodine atom (I), an aromatic ring, and a benzene ring. The atoms or groups can improve the refractive index of the photopolymerizable monomer, resulting in coherent bright and dark regions of the holographic optical element obtained after holographic processing having high refractive index contrast, making it easier to achieve high transmittance and high diffraction efficiency of the holographic optical element.

[0155] For example, the structural formula of a photopolymerizable monomer may include structural formula i.

[0156] [ka] Structural formula i.

[0157] In structural formula i, R1 may contain either H or CH3.

[0158] R2 may contain at least one of phenylethyl, phenoxyethyl, ortho-phenylphenethoxy, 4-(1-methyl-1-phenylethyl)phenoxyethyl, 2,4,6-tribromophenyl, 2,4,6-tribromophenoxyethyl, pentabromophenyl, pentabromophenoxy, naphthyl, and naphthoxy. The aromatic ring, benzene ring, and Br of R2 can all increase the refractive index of the photopolymerizable monomer, thus increasing the refractive index of the photopolymerizable monomer.

[0159] In a feasible embodiment, R2 in structural formula i may include 1,3-bis(thieno-2-ylthio)propan-2-yl, 1,3-bis((4-(phenylthio)phenyl)thio)propan-2-yl, and 1,3-bis((4-bromophenyl)thio)propan-2-yl. The sulfur (S) atom, aromatic ring, and benzene ring in R2 all increase the refractive index of the photopolymerizable monomer, resulting in a high refractive index for the photopolymerizable monomer. The high refractive index of the photopolymerizable monomer, and correspondingly the high refractive index of the monomer polymer, ensures that the coherent light and dark regions of the holographic photopolymer material prepared from the holographic photopolymer material disclosed in this embodiment have a high refractive index contrast, which facilitates the achievement of high transmittance and high diffraction efficiency for the holographic photopolymer material.

[0160] In feasible embodiments, the holographic photopolymer material may be completely dissolved with dichloromethane before the photoreaction, and the resulting solution may form a precipitate in n-hexane.

[0161] The heat resistance of the holographic photopolymer material disclosed in this embodiment of the application will be described below with reference to specific accompanying drawings. Figure 1 is a mapping curve between the transmittance of the holographic photopolymer material and the wavelength of the irradiated light wave in a process in which the holographic photopolymer material is heated at 100°C for 6 hours according to a feasible embodiment.

[0162] For the mapping curve between the transmittance of the holographic photopolymer material and the wavelength of the irradiated light wave at the initial (room temperature) stage, please refer to (1) in Figure 1.

[0163] For the mapping curve between the transmittance of the holographic photopolymer material and the wavelength of the irradiated light wave after heating at 100°C for 1 hour, please refer to (2) in Figure 1.

[0164] For the mapping curve between the transmittance of the holographic photopolymer material and the wavelength of the irradiated light wave after heating at 100°C for 2 hours, please refer to (3) in Figure 1.

[0165] For the mapping curve between the transmittance of the holographic photopolymer material and the wavelength of the irradiated light wave after heating at 100°C for 3 hours, please refer to (4) in Figure 1.

[0166] For a mapping curve between the transmittance of the holographic photopolymer material and the wavelength of the irradiated light wave after heating at 100°C for 4 hours, please refer to (5) in Figure 1.

[0167] For a mapping curve between the transmittance of the holographic photopolymer material and the wavelength of the irradiated light wave after heating at 100°C for 5 hours, please refer to (6) in Figure 1.

[0168] For a mapping curve between the transmittance of the holographic photopolymer material and the wavelength of the irradiated light wave after heating at 100°C for 6 hours, please refer to (7) in Figure 1.

[0169] In the process of heating the holographic photopolymer material disclosed in this embodiment at 100°C for 6 hours, the degree of decrease in transmittance is small, indicating that the holographic photopolymer material disclosed in this embodiment of the present application has good heat resistance.

[0170] Embodiments of this application further disclose a holographic photosensitive film. The holographic photosensitive film includes a protective layer and a first film layer covering the protective layer. The first film layer is obtained by curing a holographic photopolymer material disclosed in this embodiment of this application. The first film layer includes a polymer matrix, a photopolymerizable monomer, and a photosensitizer. The polymer matrix may provide force support to the first film layer. The photosensitizer may absorb light waves and generate an active intermediate that enables polymerization of the photopolymerizable monomer. Under irradiation with a coherent light beam, the first film layer may be divided into a coherent light region and a coherent dark region. The photosensitizer in the coherent light region may generate an active intermediate. The active intermediate may promote polymerization of the photopolymerizable monomer into the coherent light region, forming a monomer polymer. Finally, the coherent light region and the coherent dark region have different concentrations of monomer polymer. The refractive index of the photopolymerizable monomer is greater than that of the polymer matrix. Correspondingly, the refractive index of the monomer polymer is greater than that of the polymer matrix. To perform holographic recording / storage, the coherent light region and the coherent dark region have different refractive indices.

[0171] In a feasible embodiment, the molecular structure of the polymer matrix in the first film layer is linear, with branched chains containing activating groups. The linear polymer matrix has low migration resistance to photopolymerizable monomers, which facilitates the migration of photopolymerizable monomers to the coherent light region. The holographic photosensitive film has high information recording / storage efficiency.

[0172] Holographic optical elements obtained by holographic recording made from the holographic photosensitive film disclosed in this embodiment have good heat resistance. Specifically, the polymer matrix in the holographic photosensitive film contains activating groups. After holographic recording is completed, the holographic photosensitive film is converted into a holographic optical element, and the polymer matrix of the holographic optical element contains activating groups. Conditions can be controlled so that the activating groups of the holographic optical element undergo a crosslinking reaction. In this way, the polymer matrix in the holographic optical element has a crosslinked structure. Holographic optical elements made from the holographic photosensitive film disclosed in this embodiment can have good heat resistance.

[0173] In feasible embodiments, the molecular structure of the polymer matrix in the holographic photosensitive film includes a crosslinked structure. Since the polymer matrix containing the crosslinked structure has a high glass transition temperature, the holographic photopolymer material has a high glass transition temperature. Correspondingly, the holographic photosensitive film has good heat resistance.

[0174] Embodiments of this application further disclose a holographic optical element comprising a protective layer and a second film layer covering the protective layer. The material used for the second film layer comprises a polymer matrix and a monomer polymer. The refractive index of the monomer polymer is greater than that of the polymer matrix. The molecular structure of the polymer matrix includes a crosslinked structure. The second film layer comprises a coherent light region and a coherent dark region, wherein the density of the monomer polymer in the coherent light region is greater than that of the monomer polymer in the coherent dark region. The monomer polymer is used to form a refractive index distribution for holographic recording. The refractive index of the region where the monomer polymer is concentrated (coherent light region) is high, and the region where the monomer polymer is not present or where the monomer polymer is not concentrated (coherent dark region) can be perceived as a background. The refractive index of the background is low, and the monomer polymer, together with the background, can form a refractive index distribution for holographic recording.

[0175] The molecular structure of the polymer matrix in the second film layer is a crosslinked structure. Because the crosslinked polymer matrix has a high glass transition temperature, the holographic optical element has good heat resistance.

[0176] Because the polymer matrix in the holographic optical element contains acrylate / carbonyl groups, the infrared spectrum of the holographic optical element contains a fifth characteristic absorption peak. Because the polymer matrix contains epoxy / ether bonds, the infrared spectrum of the holographic optical element contains a sixth characteristic absorption peak. The wavenumber of the fifth characteristic absorption peak is 1768 cm⁻¹. -1 ~1692cm -1 The wavenumber of the sixth characteristic absorption peak is 1093 cm⁻¹. -1 ~1023cm -1 That is the case.

[0177] A holographic optical element is selected whose infrared spectrum includes the following: the wavenumber of the fifth characteristic absorption peak is 1768 cm⁻¹. -1 ~1692cm-1 The wavenumber of the sixth characteristic absorption peak is 1093 cm⁻¹. -1 ~1023cm -1 This allows for the creation of holographic optical elements with good thermal stability.

[0178] By selecting a ratio of the peak area of ​​the fifth characteristic absorption peak to the peak area of ​​the sixth characteristic absorption peak within the range of 1.0 to 4.4, a holographic optical element with good thermal stability can be obtained.

[0179] In feasible embodiments, the holographic optical element may include a reflective holographic optical element and / or a transmissive holographic optical element.

[0180] Reflective holographic optical elements can be used as coupled input / coupled output elements in optical waveguides. Alternatively, reflective holographic optical elements may be used in the field of augmented reality (AR) displays. Specifically, reflective holographic optical elements can be used as optical stackers, scattering elements, etc., in direct spatial projection AR displays.

[0181] Transmissive holographic optical elements can be used as coupled input / coupled output elements in optical waveguides, etc.

[0182] Based on the same technical concept, embodiments of this application further disclose a method for producing a holographic photopolymer material, comprising synthesizing a polymer matrix and mixing the polymer matrix, a photopolymerizable monomer, and a photosensitizer to obtain the holographic photopolymer material disclosed in embodiments of this application. The molecular structure of the polymer matrix includes a linear structure, the branched chains of the polymer matrix include activating groups, the activating groups are available for crosslinking reactions, and / or the molecular structure of the polymer matrix includes a crosslinked structure.

[0183] The step of synthesizing the polymer matrix specifically involves adding a free radical initiator to repeating units to synthesize the polymer matrix. The free radical initiator is used to introduce activating groups into the branched chains of the repeating units. Free radical initiators may include azobisisobutyronitrile and dibenzoyl peroxide. Repeating units may include methyl methacrylate, ethyl acrylate, glycidyl methacrylate, tetrahydrofurfuryl methacrylate, etc.

[0184] Based on the same technical concept, embodiments of this application further disclose a method for manufacturing a holographic photosensitive film. As shown in Figure 2, the manufacturing method includes steps S201 to S203.

[0185] S201: A polymer matrix, a photopolymerizable monomer, and a photosensitizer are mixed to obtain a holographic photopolymer material.

[0186] S202: A protective layer is coated with a holographic photopolymer material.

[0187] The protective layer may include, but is not limited to, polyester film (PET), triacetyl cellulose film (TAC), glass, ceramic, and composite materials containing some of these materials.

[0188] S203: Converts the holographic photopolymer material into a first film layer.

[0189] The molecular structure of the polymer matrix in the first film layer includes a linear structure, the branched chains of the polymer matrix include activating groups, and / or the molecular structure of the polymer matrix in the first film layer includes a crosslinked structure.

[0190] Specifically, the holographic photopolymer material can be fabricated into a film by techniques such as scrape coating, curtain coating, printing, spraying, or inkjet printing to obtain a first film layer.

[0191] Steps S201 to S203 above must be completed in the dark or under safe light. The processing method for S203 includes, but is not limited to, heating in an oven, and other curing methods may be used instead.

[0192] In feasible embodiments, the molecular structure of the polymer matrix in the holographic photopolymer material is linear, and the polymer matrix in the holographic photopolymer material contains activating groups.

[0193] According to the manufacturing method disclosed in this embodiment, in the coating process, the molecular structure of the polymer matrix in the holographic photopolymer material is a linear structure. The holographic photopolymer material has good coating performance and can be uniformly coated. After the coating is completed, the reaction conditions are controlled and the branched chains of the polymer matrix undergo a crosslinking reaction to obtain a holographic photosensitive film. The molecular structure of the polymer matrix undergoing the crosslinking reaction is a crosslinked structure. Therefore, the holographic photosensitive film contains a crosslinked polymer matrix, and the crosslinked polymer matrix has a high glass transition temperature. Correspondingly, the holographic photosensitive film has good heat resistance.

[0194] In feasible embodiments, the molecular structure of the polymer matrix in the holographic photopolymer material is linear. In embodiments in which the polymer matrix in the holographic photopolymer material contains activating groups, the activating groups do not need to undergo a crosslinking reaction in step S203, and the linear polymer matrix has low migration resistance to photopolymerizable monomers, which facilitates the migration of photopolymerizable monomers to the coherent light region. Holographic photosensitive films have high information recording / storage efficiency.

[0195] The polymer matrix in the holographic photosensitive film contains activating groups. After holographic recording is complete, the holographic photosensitive film is converted into a holographic optical element. The holographic optical element also contains activating groups. The conditions can be controlled so that the activating groups of the holographic optical element undergo a crosslinking reaction. Thus, the polymer matrix in the holographic optical element has a crosslinked structure, ensuring that the holographic optical element has good heat resistance. It can be seen that the holographic optical element obtained by using the holographic photosensitive film fabricated in this embodiment can have high heat resistance.

[0196] The holographic photosensitive film disclosed in this embodiment of the present application will be described below with reference to specific accompanying drawings.

[0197] For a feasible embodiment, please refer to Figure 3 for a diagram of the holographic photosensitive film. The holographic photosensitive film may include a first film layer and a protective layer. The first film layer includes a polymer matrix 31, a photopolymerizable monomer 32, and a photosensitizer 33. The polymer matrix 31 may include a main chain 311 and branched chains 312. The photopolymerizable monomer 32 and the photosensitizer 33 are dispersed in the polymer matrix 31. In this embodiment, the branched chains of the polymer matrix 31 do not undergo crosslinking. That is, the molecular structure of the polymer matrix 31 is linear.

[0198] For a feasible embodiment, please refer to Figure 4 for a diagram of the holographic photosensitive film. The holographic photosensitive film may include a first film layer and a protective layer. The first film layer includes a polymer matrix 31, a photopolymerizable monomer 32, and a photosensitizer 33. The polymer matrix 31 may include a main chain 311 and branched chains 312. The photopolymerizable monomer 32 and the photosensitizer 33 are dispersed in the polymer matrix 31. In this embodiment, the branched chains of the polymer matrix 31 undergo a crosslinking reaction. That is, the molecular structure of the polymer matrix 31 in the holographic photosensitive film is a crosslinked structure.

[0199] Based on the same technical concept, embodiments of this application further disclose a method for fabricating a holographic optical element. As shown in Figure 5, the fabrication method includes steps S501 to S504.

[0200] S501: A polymer matrix, a photopolymerizable monomer, and a photosensitizer are mixed to obtain a holographic photopolymer material.

[0201] S502: A protective layer is coated with a holographic photopolymer material.

[0202] S503: Converts the holographic photopolymer material into a first film layer.

[0203] For specific implementations of S501 to S503, please refer to the embodiments described above. Further details will not be explained in this specification.

[0204] S504: Perform holographic processing to convert the first film layer into the second film layer.

[0205] The second film layer includes a coherent light region and a coherent dark region, where the density of monomer polymers in the coherent light region is greater than the density of monomer polymers in the coherent dark region. The monomer polymers are obtained by polymerization of photopolymerizable monomers.

[0206] In this embodiment of the present application, the holographic optical element may include a reflective holographic optical element and a transmissive holographic optical element.

[0207] Figures 6 and 7 illustrate the principle of optical paths for holographic recording.

[0208] As shown in Figures 6 and 7, the holographic recording system includes a laser 61, a shutter (SH), a beam expander 62, a lens 63, a reflector 64, and a beam splitter 65.

[0209] The laser 61 is configured to generate a light beam that satisfies the coherence condition, and the shutter is configured to control the holographic exposure time.

[0210] The beam expander 62 can change the diameter and divergence angle of the light.

[0211] Lens 63 is configured to collimate the magnified light beam.

[0212] The reflector 64 is configured to control the propagation direction of the light beam so that the light beam propagates according to a set path.

[0213] The beam splitter 65 is configured to split the optical beam into coherent optical beams having the same frequency, a constant phase difference, and the same direction of vibration.

[0214] In this embodiment of the present application, the light beam emitted by the laser 61 is split into two coherent light beams by the beam splitter 65, and the two coherent light beams separately irradiate a holographic photosensitive film to perform holographic recording.

[0215] Refer to Figure 6. When two coherent light beams (66 and 67) are present on each side of the holographic photosensitive film 6 during holographic processing, a reflective holographic optical element is obtained.

[0216] Refer to Figure 7. When two coherent light beams (66 and 67) are on the same side of the holographic photosensitive film 6 during holographic processing, a transmitted holographic optical element is obtained.

[0217] In embodiments where the molecular structure of the polymer matrix in the holographic photosensitive film is linear and the polymer matrix contains activating groups, S504 may include the following:

[0218] (1) A holographic photosensitive film is exposed (irradiated) under the first condition, and as a result, the coherent light region and the coherent dark region have monomer polymers of different concentrations.

[0219] The first condition includes conditions for exciting the photosensitizer to generate an active intermediate. Under the first condition, the activating group does not undergo a crosslinking reaction.

[0220] (2) The exposed holographic photosensitive film is placed under second conditions, and as a result, the activating groups on the branched chains of the polymer matrix are crosslinked and polymerized to obtain a holographic optical element.

[0221] In this embodiment, the molecular structure of the polymer matrix in the holographic photosensitive film is linear, and the linear polymer matrix has low migration resistance to photopolymerizable monomers, which facilitates the migration of photopolymerizable monomers to the coherent light region. Therefore, the holographic photosensitive film disclosed in this embodiment can have high data recording / storage efficiency.

[0222] In this embodiment, the polymer matrix in the holographic optical element has a crosslinked structure, and the holographic optical element has good heat resistance.

[0223] The performance of the holographic optical elements disclosed in this embodiment of the present application will be described below with reference to specific embodiments.

[0224] Embodiment 1:

[0225] A free radical initiator is repeatedly added to the reaction unit, and the reaction is carried out at 60°C to 80°C for 24 hours to synthesize a polymer matrix.

[0226] 40% (wt) of polymer matrix, 60% (wt) of photopolymerizable monomer, co-initiators (1.5 wt% N-methyldiethanolamine MDEA and 0.5 wt% diphenyliodonium hexafluorophosphate DPI-PF6), and 0.3% (wt) of photosensitizer are weighed and dissolved in a solvent for later use. See Figure 8(1) for a diagram of the resulting holographic photopolymer material. It can be seen that the holographic photopolymer material may contain a polymer matrix 31, a photopolymerizable monomer 32, and a photosensitizer 33. The polymer matrix 31 may contain a main chain 311 and branched chains 312.

[0227] A holographic photopolymer material is coated onto a glass plate with a scraper height of 100 μm, and a film is obtained by scraping it at a coating speed of 200 mm / min. The obtained wet film is dried at 40°C for 2 minutes. Finally, a holographic photosensitive film with a thickness of 50 μm is coated onto the surface of the photosensitive film. See Figure 8(2) for a diagram of the holographic photosensitive film. It can be seen that the photopolymerizable monomer 32 and photosensitizer 33 are dispersed in the polymer matrix 31. In this embodiment, the branched chains of the polymer matrix do not undergo crosslinking reactions. That is, the molecular structure of the polymer matrix 31 is a linear structure.

[0228] Exposure (holographic processing) is performed on the holographic photosensitive film based on the optical path for holographic recording shown in Figure 6. The wavelength of light is 660 nm, and the exposure energy is 30 mJ / cm². 2 Next, the holographic photosensitive film is irradiated under a high-pressure mercury lamp for 5 minutes to obtain a holographic photosensitive film having a holographic record. For a diagram of the holographic photosensitive film having a holographic record, please refer to Figure 8 (3). The holographic photosensitive film having a holographic record may include a monomer polymer 34 and a polymer matrix 31. The molecular structure of the polymer matrix 31 is a linear structure, and the polymer matrix 31 includes branched chains 312. The density of the monomer polymer 34 in the coherent light region A is greater than the density of the monomer polymer 34 in the coherent dark region B, and a holographic photosensitive film having a holographic record is obtained.

[0229] The reaction conditions are adjusted so that the branched chains 312 in the holographic photosensitive film having holographic recording undergo a crosslinking reaction. For the resulting holographic optical element, please refer to (4) in Figure 8.

[0230] The holographic optical elements of Embodiments 2 to 10 have a similar structure to the holographic optical element of Embodiment 1, but differ from the holographic photopolymer material used in Embodiments 2 to 10 in terms of the components and the amount of each component added, compared to the holographic photopolymer material used in Embodiment 1. For details, please refer to the data in Table 1. The photopolymerizable monomer content can be approximately understood as the amount of photopolymerizable monomers added or the amount of photopolymerizable monomers.

[0231] The test items for the holographic optical elements disclosed in Embodiments 1 to 10 include transmittance, diffraction efficiency, and the degree of transmittance reduction at 400 nm after heating at 100°C for 6 hours. For the test results, please refer to the corresponding data in Table 1.

[0232] The testing process for each test item is as follows:

[0233] (1) The transmittance T of the holographic optical element at a wavelength of 400 nm is measured using an ultraviolet-visible spectrophotometer.

[0234] (2) The diffraction efficiency (η) of the holographic optical element is measured by an ultraviolet-visible spectrophotometer.

[0235] Specifically, the minimum transmittance (TB) of the reflection peak and the baseline transmittance (TA) are determined first. The baseline transmittance is the perpendicular coordinate of the intersection of the minimum transmittance peak and the baseline, and the diffraction efficiency (η) is calculated according to the following formula:

number

[0236] (3) After heating the holographic optical element at 100°C for 6 hours, the degree of decrease in transmittance at 400 nm is measured using an ultraviolet-visible spectrophotometer.

[0237] Specifically, the transmittance (TC) of the holographic optical element is measured before heating, and the transmittance (TD) of the holographic optical element is measured after heating at 100°C for 6 hours. Then, the degree of decrease in transmittance (θ) is calculated according to the following formula:

number

[0238] [Table 1]

[0239] The components of the holographic photopolymer material in Embodiments 1 to 10, and the performance of the holographic optical element in Embodiments 1 to 10.

[0240] For the complete names of each component in Table 1, please refer to Table 2.

[0241] [Table 2]

[0242] From the decrease in transmittance corresponding to Embodiments 1 to 10 in Table 1, it can be seen that after heating the holographic optical elements disclosed in the embodiments of this application at 100°C for 6 hours, the decrease in transmittance of the holographic optical elements is all less than 35%. Except for the holographic optical element disclosed in Embodiment 6, the decrease in transmittance of the holographic optical elements disclosed in the other embodiments is about 10% after heating the holographic optical elements at 100°C for 6 hours. It can be seen that the holographic optical elements disclosed in the embodiments of this application have good heat resistance.

[0243] From the transmittances corresponding to Embodiments 1 to 10 in Table 1, it can be seen that the transmittances of all holographic optical elements disclosed in the embodiments of this application are greater than 50%, indicating that holographic optical elements have high transmittance.

[0244] From the diffraction efficiencies corresponding to Embodiments 1 to 10 in Table 1, it can be seen that the diffraction efficiencies of the holographic optical elements disclosed in Embodiments 1 to 7 are greater than 50%, indicating that the holographic optical elements disclosed in Embodiments 1 to 7 have high diffraction efficiencies.

[0245] Based on the same technical concept, embodiments of the present application further disclose a display device including the holographic optical element or the holographic photosensitive film disclosed in the embodiments of the present application. The display device is, for example, a head-up display (HUD) device.

[0246] Based on the same technical concept, embodiments of the present application further disclose a storage device including the holographic optical element or the holographic photosensitive film disclosed in the embodiments of the present application.

[0247] Based on the same technical concept, embodiments of the present application further disclose an anti-counterfeiting identifier including the holographic optical element or the holographic photosensitive film disclosed in the embodiments of the present application.

[0248] Those skilled in the art can easily understand other implementation solutions of the present disclosure after considering this specification and implementing the invention disclosed herein. This application intends to cover any variations, functions, or adaptive changes of the present disclosure. These variations, functions, or adaptive changes follow the general principles of the present disclosure and include general knowledge in the technical field not disclosed in the present disclosure or commonly used technical means. This specification and the embodiments are only regarded as examples, and the actual scope and spirit of the present disclosure are pointed out by the appended claims.

[0249] It should be understood that the present disclosure is not limited only to the exact structures described above and shown in the accompanying drawings, and modifications and changes can be made without departing from the scope of the present disclosure. The scope of the present disclosure is limited only by the appended claims.

Description of Reference Numerals

[0250] 31 Polymer Matrix 32 Photopolymerizable monomers 33 Photosensitizers 34 Monomer polymers 61 Lasers 62 Beam Expander 63 lenses 64 Reflector 65 Beam Splitter 66 Coherent Light Beams 67 Coherent light beam 311 Main chain 312 Branching chain

Claims

1. A holographic photopolymer material, Polymer matrix; A photopolymerizable monomer wherein the refractive index of the photopolymerizable monomer is greater than the refractive index of the polymer matrix; and Photosensitizer Includes, The molecular structure of the polymer matrix includes a linear structure, and the branched chains of the polymer matrix include activating groups, which are available for crosslinking reactions. and / or The polymer matrix has a molecular structure that includes a cross-linked structure, making it a holographic photopolymer material.

2. The holographic photopolymer material according to claim 1, wherein the polymer matrix comprises at least one of polymethacrylate, polymethacrylamide, polyacrylate, polyacrylamide, polyvinyl ether, polyvinyl ester, and polysiloxane.

3. The holographic photopolymer material according to claim 1 or 2, wherein the polymer matrix comprises a copolymer containing at least two of the following substances: methacrylate, methacrylamide, acrylate, acrylamide, vinyl ether, vinyl ester, and siloxane.

4. The holographic photopolymer material according to any one of claims 1 to 3, wherein the activating group comprises at least one of an epoxy group, a vinyl ether, and an N-vinyl group.

5. The structural formula of the photopolymerizable monomer is, 【Chemistry 1】 Equipped with, R 1 is H or CH 3 including; and R 2 The holographic photopolymer material according to any one of claims 1 to 4, comprising at least one of 1,3-bis(thieno-2-ylthio)propan-2-yl, 1,3-bis((4-(phenylthio)phenyl)thio)propan-2-yl, and 1,3-bis((4-bromophenyl)thio)propan-2-yl.

6. It further contains a co-initiator, The holographic photopolymer material according to any one of claims 1 to 5, wherein the co-initiator comprises at least one of tetrabutylammonium tetrahexylborate, tetrabutylammonium hexyltrisphenylborate, tetrabutylammonium tris(3-fluorophenyl)hexylborate, and tetrabutylammonium tris(3-chloro-4-methylphenyl)hexylborate.

7. The infrared spectrum of the holographic photopolymer material includes a first characteristic absorption peak and a second characteristic absorption peak. The wavenumber of the first characteristic absorption peak is 877 cm⁻¹. －1 ~831cm －1 The range is such that the wavenumber of the second characteristic absorption peak is 829 cm⁻¹. －1 ~787cm －1 A holographic photopolymer material according to any one of claims 1 to 6, which is within the range of [specified range].

8. The holographic photopolymer material according to claim 7, wherein the ratio of the peak area of ​​the first characteristic absorption peak to the peak area of ​​the second characteristic absorption peak is in the range of 0.4 to 8.

8.

9. The holographic photopolymer material according to any one of claims 1 to 8, wherein the nuclear magnetic resonance hydrogen spectrum of the holographic photopolymer material includes a third characteristic absorption peak and a fourth characteristic absorption peak, the chemical shift of the third characteristic absorption peak is in the range of 3.2 ppm to 3.22 ppm, and the chemical shift of the fourth characteristic absorption peak is in the range of 3.5 ppm to 3.7 ppm.

10. The holographic photopolymer material according to any one of claims 1 to 9, wherein the glass transition temperature of the polymer matrix is ​​50°C or higher.

11. A holographic photosensitive film comprising a protective layer and a first film layer covering the protective layer, wherein the first film layer is made from a holographic photopolymer material according to any one of claims 1 to 10.

12. A holographic optical element comprising a protective layer and a second film layer covering the protective layer, wherein the material used for the second film layer comprises a polymer matrix and a monomer polymer, and the molecular structure of the polymer matrix comprises a crosslinked structure. A holographic optical element wherein the second film layer comprises a coherent light region and a coherent dark region, and the density of the monomer polymer in the coherent light region is greater than the density of the monomer polymer in the coherent dark region.

13. The infrared spectrum of the second film layer includes a fifth characteristic absorption peak and a sixth characteristic absorption peak, and the wave number of the fifth characteristic absorption peak is 1768 cm －1 to 1692 cm －1 and the wave number of the sixth characteristic absorption peak is 1093 cm －1 to 1023 cm －1 The holographic optical element according to claim 12, wherein the range is as follows.

14. The holographic optical element according to claim 13, wherein the ratio of the peak area of ​​the fifth characteristic absorption peak to the peak area of ​​the sixth characteristic absorption peak is in the range of 1.0 to 4.

4.

15. A method for producing a holographic photopolymer material, A step of synthesizing the polymer matrix, wherein the molecular structure of the polymer matrix includes a linear structure, the branched chains of the polymer matrix include activating groups, and the activating groups are available for crosslinking reactions; The steps include: mixing the polymer matrix, a photopolymerizable monomer, and a photosensitizer to obtain the holographic photopolymer material according to any one of claims 1 to 10; Methods that include...

16. A method for producing a holographic photosensitive film, The steps include: coating a protective layer with a holographic photopolymer material obtained according to claim 15; A step of converting the holographic photopolymer material into a first film layer, The molecular structure of the polymer matrix in the first film layer includes a linear structure, the branched chains of the polymer matrix include activating groups, and the activating groups are available for crosslinking reactions; and / or The molecular structure of the polymer matrix in the first film layer includes a crosslinked structure, and Methods that include...

17. A method for fabricating a holographic optical element, A step of performing a holographic treatment on a holographic photosensitive film according to claim 16 in order to convert the first film layer into a second film layer, wherein the second film layer includes a coherent light region and a coherent dark region, the density of the monomer polymer in the coherent light region is higher than the density of the monomer polymer in the coherent dark region, and the monomer polymer is obtained by polymerization of the photopolymerizable monomer. A method that includes this.

18. A display device comprising a display and an optical element arranged on the display, A display device comprising the optical element being a holographic photosensitive film according to claim 11, or a holographic optical element according to any one of claims 12 to 14.

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