CN112764159A - Optical waveguide element, method for producing the same, and holographic optical waveguide display device - Google Patents

Optical waveguide element, method for producing the same, and holographic optical waveguide display device Download PDF

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CN112764159A
CN112764159A CN201911002010.8A CN201911002010A CN112764159A CN 112764159 A CN112764159 A CN 112764159A CN 201911002010 A CN201911002010 A CN 201911002010A CN 112764159 A CN112764159 A CN 112764159A
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light
optical waveguide
coupling
film
present
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CN112764159B (en
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雍海波
陈淑丹
魏一振
张卓鹏
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Hangzhou Guangli Technology Co ltd
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G02B6/1221—Basic optical elements, e.g. light-guiding paths made from organic materials
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/13—Integrated optical circuits characterised by the manufacturing method
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/02—Details of features involved during the holographic process; Replication of holograms without interference recording
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/0005—Adaptation of holography to specific applications
    • G03H2001/0088—Adaptation of holography to specific applications for video-holography, i.e. integrating hologram acquisition, transmission and display

Abstract

The present invention relates to an optical waveguide element, a method of manufacturing the same, and a holographic optical waveguide display device. The optical waveguide element comprises a laminate of at least two carriers and a photopolymer film, wherein the photopolymer film is positioned between the at least two carriers; the photopolymer film having at least one light incoupling region and at least one light outcoupling region; the light coupling-in area is not connected with the light coupling-out area; and the positions of the light in-coupling region and the light out-coupling region respectively have a grating structure. The optical waveguide element has high refractive index modulation degree, diffraction efficiency, sensitivity and light transmittance, and has excellent optical waveguide imaging effect.

Description

Optical waveguide element, method for producing the same, and holographic optical waveguide display device
Technical Field
The invention belongs to the technical field of optics, particularly relates to the field of optical elements and preparation thereof, and particularly relates to an optical waveguide element in the field of augmented reality and a preparation method thereof, or holographic optical waveguide display equipment using the optical waveguide element.
Background
Near-eye display and head-mounted display technologies have been widely used in the field of augmented reality in recent years. The existing optical imaging schemes mainly include: coaxial prisms, off-axis prisms, coaxial curved surfaces, optical waveguides and the like, wherein the optical waveguides are the focus of research at the present stage. The optical waveguide couples light imaged by the optical machine into the glass substrate, transmits the light to the front of eyes by the principle of total reflection and then couples the light out, and the waveguide is only responsible for transmitting images in the process and can be understood as parallel light in and parallel light out, and is an independent optical device independent of an imaging system. By utilizing the optical waveguide technology, the size of the augmented reality glasses is equivalent to that of normal glasses, the glasses do not block the sight, and the glasses accord with human engineering, so that the wearing experience is improved.
The existing optical Waveguide can be generally classified into a Geometric Waveguide (arrayed Waveguide) and a Diffractive Waveguide (Diffractive Waveguide). The geometric optical waveguide is equivalent to a plurality of semi-transparent semi-reflecting prisms which are glued together, and semi-transparent semi-reflecting occurs once every time the geometric optical waveguide passes through one prism surface, and finally an image is formed on an eyeball. However, geometric optical waveguides are poor in mass productivity, high in cost, and not aesthetically pleasing. The diffraction optical waveguide is characterized in that light irradiates an in-coupling grating to be diffracted, the angle of the diffracted light reaches the total reflection condition of a substrate, the light is totally reflected and transmitted in the waveguide (similar to an optical fiber), and when the light is transmitted to the in-coupling grating, the light is coupled out to form an image on an eyeball.
Diffractive optical waveguides are further divided into surface relief grating optical waveguides and volume holographic grating optical waveguides. The core of the surface relief grating waveguide is composed of a plurality of sub-wavelength etching gratings, and the guiding of an image is realized through high-efficiency diffraction. The micro-nano structure form of the surface relief grating waveguide is variable, and the degree of freedom of grating combination is high; it is also biaxial pupil expansion, enabling large viewing angles, exit pupil size and eye relief. In addition, the surface relief grating waveguide has high transparency and a light and thin structure. However, the main method for preparing the surface relief grating waveguide is nanoimprint, but the nanoimprint has high cost, complex design, complex preparation of a mother board and complex production process.
The volume holographic grating optical waveguide records all information (including amplitude and phase) of object light wave in the form of interference fringes by using an interference exposure method. When the recording medium is thick (much thicker than the recorded interference fringe spacing), the two coherent beams interact within the medium to form a three-dimensional grating-like volume hologram. The light and dark fringes produced by the interference modulate the phase of the recording material (or are understood as the degree of refractive index modulation Δ n) during recording. The absorption coefficient and refractive index of the volume hologram vary periodically, and when the readout light satisfies the bragg diffraction condition, the stored information is restored in the form of diffraction imaging. However, volume holographic grating optical waveguides also have high requirements for materials, system design, and manufacturing processes.
Citation 1 discloses an optical waveguide and a display device, the optical waveguide including an optical waveguide body including a light beam coupling-in area and a light beam coupling-out area, the light beam coupling-in area being provided with a coupling-in grating configured to couple a light beam into the optical waveguide body and propagate in the optical waveguide body by total reflection; the light beam coupling-out area is provided with a coupling-out grating which is configured to couple the light beam propagating to the light beam coupling-out area out of the light waveguide body, and the light beam does not undergo secondary diffraction at the coupling-in grating and has a continuous expanded exit pupil; the light coupling grating comprises a transmission type light coupling grating and a reflection type light coupling grating which are arranged on two sides of the optical waveguide body and are parallel to the light beam propagation direction. The optical waveguide has the advantages of complex structure, higher preparation cost and single transmission mode.
Citation 2 discloses a holographic waveguide lens, a method for preparing the same, and a three-dimensional display device using the same, the lens including one, two, three, or more than three holographic waveguide lens units; the holographic waveguide lens unit is provided with three functional areas, and the functional areas are provided with nanometer diffraction gratings; respectively, a coupling-in functional area for coupling in light, a relay functional area for image diffusion in the X direction, and an emission functional area for image diffusion and output in the Y direction. The holographic waveguide lens has the advantages of complex structure, high preparation cost, complex post-treatment and small angle selectivity of grating diffraction.
It can be seen that although some degree of improvement has been made in the prior art for optical waveguide components, there is still room for further improvement in improving the overall performance of these materials.
Cited documents:
cited document 1: CN 109901298A
Cited document 2: CN 109239842A
Disclosure of Invention
Problems to be solved by the invention
In view of the above-mentioned drawbacks in the art, the present invention provides an optical waveguide element, which has the advantages of high light transmittance, high diffraction efficiency, large angle selectivity of diffraction of the optical waveguide element, excellent optical waveguide imaging effect, and the like, compared with the optical waveguide element in the prior art.
Furthermore, the invention also provides a preparation method of the optical waveguide element, which is simple, low in cost and free from complex post-treatment.
Means for solving the problems
According to the intensive research of the inventor of the present invention, it is found that the technical problems can be solved by implementing the following technical scheme:
[1] the invention firstly provides an optical waveguide element which comprises a laminated body formed by at least two carriers and a photopolymer film, wherein
The photopolymer film is positioned between at least two carriers;
the photopolymer film having at least one light incoupling region and at least one light outcoupling region;
the light coupling-in area is not connected with the light coupling-out area; and is
The positions of the light coupling-in area and the light coupling-out area are respectively provided with a grating structure.
[2] The optical waveguide element according to [1], wherein the photopolymer film has a thickness of 5 to 50 μm.
[3] The optical waveguide element according to the above [1] or [2], wherein a shortest distance between the light incoupling area and the light outcoupling area is 10mm to 10 cm.
[4] The optical waveguide element according to any one of the above [1] to [3], wherein the carrier has a thickness of 1.5mm or less and a refractive index of 1.4 to 1.6.
[5] The optical waveguide element according to any one of the above [1] to [4], wherein the photopolymer film is derived from a photopolymer composition, wherein the photopolymer composition comprises the following components:
polymerizing the reactive monomer;
a dye compound;
an initiator;
a film forming component; and
a plasticizer;
wherein the difference in refractive index (n) between the polymerizable monomer and the film-forming componentPolymerizing reactive monomers-nFilm-forming component) The value is 0.075 or more.
[6] The production method according to the above [5], wherein the polymerization active monomer is one or more selected from an acrylate monomer and an epoxy compound monomer.
[7] The preparation method of the optical waveguide element comprises the following steps:
a step of preparing a photopolymer film;
a step of composite molding the carrier and the photopolymer film;
a step of forming a grating structure, the photopolymer film having at least one light in-coupling area and at least one light out-coupling area, the light in-coupling area being unconnected to the light out-coupling area,
and a grating structure is respectively formed in the light in-coupling region and the light out-coupling region.
[8] The method for manufacturing an optical waveguide element according to the above [7], wherein the step of forming the grating structure includes a step of exposing the light incoupling region and the light outcoupling region with coherent light.
[9] The method for manufacturing an optical waveguide element according to the above [8], wherein the coherent light is coherent light having a wavelength of about 532 nm.
[10] A holographic optical waveguide display device comprising one or more optical waveguide elements according to any one of the above [1] to [6] or obtained by the method according to any one of the above [7] to [9 ].
ADVANTAGEOUS EFFECTS OF INVENTION
Through the implementation of the technical scheme, the invention can obtain the following technical effects:
the optical waveguide element disclosed by the invention not only has higher refractive index modulation degree, diffraction efficiency, sensitivity and light transmittance, but also has an excellent optical waveguide imaging effect.
Furthermore, the optical waveguide element of the present invention can also have improved dimensional shrinkage and diffraction efficiency, and the optical waveguide element has a large angle selectivity of diffraction, a wide angle selectivity, and a small influence of ambient humidity.
The optical waveguide element has the advantages of simple manufacturing process, cheap and easily-obtained raw materials, no need of complex post-treatment and easy large-scale industrial production.
Drawings
FIG. 1 shows a schematic structural view of an optical waveguide component in one embodiment of the present invention;
in fig. 1, 101: carrier, 102: photopolymer film, 103: light incoupling region, 104: a light out-coupling region.
FIG. 2 is a schematic diagram showing the light propagation path of an optical waveguide component according to an embodiment of the present invention.
FIG. 3 is a schematic diagram showing the light propagation path of an optical waveguide element according to still another embodiment of the present invention.
FIG. 4 is a schematic diagram showing the light propagation path of an optical waveguide element according to still another embodiment of the present invention.
FIG. 5 is a diagram showing the layout of the optical paths of an optical waveguide component in one embodiment of the present invention;
in fig. 5, 1: a half-wave plate; 2: a beam splitting cube; 3: a shutter; 4: a beam expander; 5: a pinhole; 6: a collimating lens; 7: a beam splitter; 8: a mirror; 9: a mirror; 10: an optical waveguide element.
Fig. 6 shows an effect display diagram of an optical waveguide element according to an embodiment of the present invention.
Detailed Description
The present invention will be described in detail below. The technical features described below are explained based on typical embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that:
in the present specification, the numerical range represented by "numerical value a to numerical value B" means a range including the end point numerical value A, B.
In the present specification, the numerical ranges indicated by "above" or "below" mean the numerical ranges including the numbers.
In this specification, the description will be made using "vicinity" to a certain wavelength of light, and it is understood that, for a specific wavelength, some error may occur from a theoretical value in use due to an instrument error or the like, and therefore, the use of "vicinity" indicates that various types of wavelengths defined in the present invention include an instrument error or the like.
In the present specification, the term "acrylate" includes the meanings of "(meth) acrylate" and "acrylate".
In the present specification, the meaning of "may" includes both the meaning of performing a certain process and the meaning of not performing a certain process.
As used herein, the term "optional" or "optional" is used to indicate that certain substances, components, performance steps, application conditions, and the like are used or not used.
In the present specification, the unit names used are all international standard unit names, and the "%" used means weight or mass% content, if not specifically stated.
In the present specification, the term "particle diameter" as used herein means an "average particle diameter" unless otherwise specified, and can be measured by a commercial particle sizer.
In the present specification, reference to "some particular/preferred embodiments," "other particular/preferred embodiments," "embodiments," and the like, means that a particular element (e.g., feature, structure, property, and/or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments.
<First aspect>
The first aspect of the present invention provides an optical waveguide element comprising a stack of at least two carriers 101 and a photopolymer film 102, wherein
The photopolymer film 102 is positioned between at least two carriers 101;
the photopolymer film 102 has at least one light incoupling region and at least one light outcoupling region;
the light in-coupling region 103 is not connected with the light out-coupling region 104; and is
The positions of the light incoupling region 103 and the light outcoupling region 104 have a grating structure, respectively.
< photopolymer film >
The optical waveguide element of the present invention is formed by sandwiching a photopolymer film 102 between at least two layers of a carrier 101.
In some specific embodiments of the present invention, the photopolymer film 102 has at least two unconnected exposure regions, which can be exposed separately or simultaneously by a set of same coherent light sources, and after post-processing, the light in-coupling region 103 and the light out-coupling region 104, which have grating structures, respectively, can be formed in one optical waveguide element.
In some specific embodiments of the present invention, the polymer film has a thickness of 5 μm or more, preferably 10 μm or more, more preferably 15 μm or more, and further preferably 20 μm or more, and further, the polymer film has a thickness of 50 μm or less, preferably 45 μm or less, and more preferably 40 μm or less. The above-mentioned thickness of the polymer film can be coordinated or matched in practice with the use of spacers, for example as described below.
Further, in order to more effectively realize diffraction imaging, the shortest distance between the light in-coupling region 103 and the light out-coupling region 104 of the present invention is 10mm or more, and preferably 15mm or more; the shortest distance between the light incoupling region 103 and the light outcoupling region 104 is 10cm or less, preferably 5cm or less, and more preferably 1cm or less.
Typically, the optical waveguide element has a regular shape to facilitate use and installation, and may be in the shape of a strip sheet, a square sheet, or a circular sheet.
In some preferred embodiments, the optical waveguide component of the present invention has the shape of an elongated strip, as shown in fig. 1. Further, the photopolymer film 102 has a light incoupling region 103 and a light outcoupling region 104 in both end regions in the longitudinal direction of the film, and grating (hologram recording) structures are formed in the light incoupling region 103 and the light outcoupling region 104, respectively.
FIG. 2 is a schematic diagram showing the light propagation path of an optical waveguide component according to an embodiment of the present invention. FIG. 3 is a schematic diagram showing the light propagation path of an optical waveguide element according to still another embodiment of the present invention. Specifically, as shown in fig. 2 and fig. 3, light emitted by the optical machine enters the optical waveguide element, diffraction is generated at the position of the grating structure of the light coupling-in region 103, the angle of the diffracted light in the waveguide element satisfies the total reflection condition, the light is totally reflected inside the waveguide element, and is diffracted again after being propagated to the grating structure of the light coupling-out region 104, so that the light is coupled out, and the required visual effect is obtained.
In some specific embodiments of the present invention, the photopolymer film 102 is derived from a photopolymer composition. Specifically, the photopolymer composition comprises the following components:
polymerizing the reactive monomer;
a dye compound;
an initiator;
a film forming component; and
a plasticizer;
wherein the difference in refractive index (n) between the polymerizable monomer and the film-forming componentPolymerizing reactive monomers-nFilm-forming component) The value is 0.075 or more.
In some embodiments of the invention, the components are mixed and then used in molten or liquid form for further use.
Initiating system
In the present invention, the system for initiating polymerization of the system under irradiation with light includes a dye compound and an initiator. After the dye compound is excited by light irradiation, the initiator can react with the excited dye to generate free radicals and cause the polymerization of the polymerization-reactive monomer in the system to start.
(dye compound)
In the present invention, the dye compound is a photosensitive dye compound. The photosensitive dye compounds of the present invention may have excitation activity at around any feasible wavelength of light.
In particular, the dye compounds of the present invention may be selected according to different types of polymerizable reactive monomers. Illustrative examples include one or more of phycoerythrin B, eosin Y, erythrosine B, basic Red 2 and 2, 5-bis { [4- (diethylamino) -2-methylphenyl ] methylene } cyclopentanone, Irgacure 784, New methylene blue, thionine, basic yellow, pinacyanol chloride, rhodamine 6G, betacyanin, Ethyl Violet, Victoria blue R, azurite blue, quinaldine Red, Crystal Violet, Bright Green, basic orange G (astrazon orange G), Darrow Red (darwrend), pyronin Y, Bengal Rose Bengal, Michzone, 3.3' -carbonylbis (7-diethylaminocoumarin), iodonium pyranate I, diiodofluorescein, anthocyanidin and methylene blue, TianA, Crystal Violet (leuconitrile), or Caragave Green (leuconitrile).
In some particular embodiments of the present invention, the dye compounds of the present invention may be selected from those dyes that have an excitation activity at a wavelength of at least about 532 nm. These dye compounds can have a maximum absorption peak or can be excited to generate activity when irradiated with green (wavelength of about 532 nm) light, and as a result, energy transfer and changes in properties such as self-structure and color can be caused. In addition, the dye compound of the present invention may have an excitation activity at a wavelength of 532nm or so, and may also have an excitation activity at a wavelength of 532nm or so, in which case, it is preferable that the dye compound of the present invention has a maximum absorption peak at a wavelength of 532nm or so.
In other specific embodiments of the present invention, the dye compounds of the present invention exhibit excitation activity only at a wavelength of about 532nm, while exhibiting no significant excitation activity or no absorption peak at other wavelengths of light, which can be considered to be strong.
In a preferred embodiment of the present invention, the dye compound may be selected from one or more of erythrosin B, eosin Y, erythrosin B, basic red 2 and 2, 5-bis { [4- (diethylamino) -2-methylphenyl ] methylene } cyclopentanone.
In some specific embodiments of the present invention, the dye compound having an excitation activity at least in the vicinity of 532nm in wavelength is contained in the photopolymer composition in an amount of 70% or more, preferably 80% or more, more preferably 90% or more, and still more preferably 95% or more, based on the total weight of the dye compounds used, the dye compound having an excitation activity at a wavelength of 532 nm.
(initiator)
In the above-mentioned initiation system of the present invention, an initiator (may be referred to as a co-initiator under some conditions) is used in combination with the dye compound. Initiators suitable for use in the present invention are generally those photoinitiators which can be activated by irradiation with light and initiate polymerization of the corresponding polymerizable group, or which are capable of reacting with an excited dye to form a free radical which in turn initiates polymerization of the monomer.
Photoinitiators which can be used according to the invention can be distinguished between monomolecular initiators (type I) and bimolecular initiators (type II). They are further distinguished by their chemical characteristics as photoinitiators for free-radical, anionic, cationic or mixed polymerization types.
Photoinitiators of type I for free-radical photopolymerization (Norrish type I) cleave by a monomolecular bond when irradiated to form a free radical.
Photoinitiators of type I are, for example, triazines, such as tris (trichloromethyl) triazine, oximes, benzoin ethers, benzil ketals, α -dialkoxyacetophenones, phenylglyoxylates, bisimidazoles, 2- (4-chlorophenyl) -4, 5-diphenylimidazoles, aroylphosphine oxides (e.g., 2,4, 6-trimethylbenzoyldiphenylphosphine oxide), sulfonium and iodonium salts, and the like.
Photochemistry of these compounds has been long studied for sulfonium and iodonium salts. Iodonium salts, after excitation, first homolytically decompose and thus generate a radical and a radical cation which, by hydrogen abstraction, finally liberates a proton and thus initiates cationic polymerization (Dectar et al, J.Org.Chem.1990,55,639; J.Org.Chem.,1991, 56.1838). This mechanism makes iodonium salts equally useful for free radical photopolymerization. Here again the choice of counter ion is very important. Preference is likewise given to using SbF6-、AsF6-Or PF6-. On the other hand, this structural class is quite free in the choice of substitution on the aromatic compounds, essentially determined by the availability of suitable synthetic starter units. Sulfonium salts are compounds which decompose according to the Norrish type II mechanism (Crivello et al, Macromolecules,2000,33, 825). The choice of counter ion in the sulfonium salt is also extremely important, as it is essentially reflected in the cure rate of the polymer. In some preferred embodiments of the invention, iodonium salts are preferably used, and PF is used6-As a counter ion.
Photoinitiators of type II for free-radical polymerization (Norrish type II) undergo bimolecular reactions when irradiated, wherein the photoinitiator reacts in the excited state with a second molecule (coinitiator) to form polymerization-inducing free radicals by electron or proton transfer or direct hydrogen abstraction.
Photoinitiators of the type II are, for example, quinones, such as camphorquinone, arone compounds, such as benzophenone in combination with tertiary amines, alkylbenzophenones, halogenated benzophenones, 4,4 '-bis (dimethylamino) benzophenone (Michler's ketone), anthrone, methyl 4-dimethylaminobenzoate, thioxanthone, ketocoumarin, alpha-aminoalkylphenones or alpha-hydroxyalkylphenones.
In the present invention, photoinitiators of type I, II may be used for the UV and/or visible region.
In some particular embodiments of the invention, mixtures of these photoinitiators may also be advantageously used. Depending on the conditions of the radiation source used, the type and concentration of photoinitiator should be matched in a manner known to those skilled in the art. Other details are described, For example, in P.K.T.Oldring (Ed.), Chemistry & Technology of UV & EB Formulations For Coatings, Inks & Paints, Vol.3,1991, SITA Technology, London, pp.61-328.
In some specific embodiments of the present invention, the initiator is selected from one or more of diphenyliodonium hexafluorophosphate, ethyl 4-dimethylaminobenzoate, N-phenylglycine, 2- (4-chlorophenyl) -4, 5-diphenylimidazole.
Polymerizing reactive monomers
In the present invention, a monomer having polymerization activity is used to perform polymerization reaction and form a crosslinked structure upon exposure. The polymerization active monomer suitable for the invention comprises one or more of acrylate monomers and epoxy compounds. In some preferred embodiments of the present invention, the polymerization-active monomer has a refractive index of 1.55 or more, preferably 1.57 or more, and more preferably 1.58 or more, from the viewpoint of improving the degree of modulation of the refractive index.
The polymerizable monomer of the present invention may include a polymerizable monomer having one or more (two or more) functional groups. The polymerizable monomer may be an acrylate monomer, an epoxy compound, or a mixture thereof. Preferably, such polymerization-reactive monomers include at least acrylate-based monomers. The content of the monomer having a plurality of functional groups is 20 to 50%, preferably 25 to 40%, based on the total weight of the polymerizable monomer, from the viewpoint of improving diffraction efficiency, dimensional stability and refractive index modulation.
As the acrylate monomer having one functional group suitable for use in the present invention, it may have a structure of the following general formula (I-1) or (I-2):
Ar-L-(X-O)n-C(O)-CH＝C(R1)2 (I-1)
Ar-L-(X-O)n-C(O)-C(CH3)＝C(R1)2 (I-2)
wherein Ar represents a group having one or more aromatic groups, preferably having 1 to 3 benzene rings, more preferably a phenyl group, a naphthyl group or a biphenyl group, and optionally, these benzene rings may be substituted or unsubstituted; l is an oxygen atom or a sulfur atom; x represents a linear or branched alkyl group having 1 to 6 carbon atoms, preferably a linear or branched alkyl group having 2 to 3 carbon atoms, which may be optionally substituted; n represents an integer of 1 to 5, preferably an integer of 1 to 3; (ii) a R1Each occurrence, which is the same or different, independently represents a hydrogen or halogen atom.
As the acrylate monomer having a plurality of functional groups suitable for use in the present invention, it may have a structure of the following general formula (II-1) or (II-2):
Figure BDA0002241622650000121
wherein R is1X, L is as defined above for (I-1) and (I-2), n is an integer of 1 to 5, preferably 1 to 3, Z is a group containing one or more aromatic groups, and Z is a substituted or unsubstituted phenyl groupOr a biphenyl group.
In the present invention, as the acrylate monomer having a refractive index of 1.55 or more, in addition to the monomers having the above-described structure, an acrylate monomer containing an aromatic group selected from one or more of phenyl, biphenyl, naphthyl and fluorenyl or substituted with halogen may be used.
In some specific embodiments, the acrylate monomer having an aromatic group may be selected from: biphenyl-containing acrylates such as [1, 1-biphenyl ] -4, 4-diylbis (2-methacrylate), 4' -biphenyldiacrylate and the like; naphthalene-containing acrylates such as 1-naphthalene methacrylate, 2 '-bis (2-acryloyloxy) -1, 1' -thiobinaphthalene, 2 '-bis [2- (2-acryloyloxyethoxy) -1, 1' -binaphthalene, 2 '-bis [ 2-acryloyloxyethoxy) -1, 1' -thiobinaphthalene and the like.
In some specific embodiments, in the acrylate substituted with halogen, the halogen includes fluorine, chlorine or bromine, preferably, the halogen is bromine. Such acrylate monomers as p-chlorophenyl acrylate, p-bromophenyl acrylate, pentachlorophenyl acrylate, pentabromophenyl acrylate, 2,4, 6-tribromophenyl acrylate, 2,4, 6-trichlorophenyl acrylate and the like can be exemplified.
Further, as the epoxy compound monomers suitable for the present invention, those having a relatively high refractive index (1.55 or more) are preferable, which is advantageous for improving dimensional stability.
In the present invention, the epoxy compound that can be used may have a structure of the following general formula (III):
Figure BDA0002241622650000131
wherein E represents an epoxy group-containing group. In some specific embodiments, each E group may contain 1 or 2 epoxy groups. Further, from the viewpoint of suppressing the dimensional shrinkage after film formation, in a preferred embodiment, each E group contains 1 epoxy group at the time of its occurrence.
The structure of the epoxy group is not particularly limited, and the epoxy group is preferably present as an aliphatic epoxy group. In other embodiments, the epoxy group or epoxy structure of the E group is bonded to Ar as described above through an ether group1The groups are linked. The ether group may be a sulfide group or an oxygen ether group, and is preferably an oxygen ether group from the viewpoint of suppressing the dimensional shrinkage after film formation.
In the general formula (III), n representing the number of E groups is an integer of 0 to 4, and each E group is the same or different. It goes without saying that the total number of n in the present invention is not 0. In some preferred embodiments, each occurrence of n is 1.
In the above general formula (III), each Ar1The same or different, independently represent an aryl-containing group. In some preferred embodiments of the invention, Ar1Represents a group having 1 or two substituted or unsubstituted benzene rings, typically Ar1May be selected from the following structures:
Figure BDA0002241622650000141
wherein X in the formula (b) is selected from a single bond, O or S atom.
In the above general formula (III), -C (R)3R4) -formation of a carbonyl group, or, R3、R4The same or different, each occurrence independently represents a hydrogen atom, an aryl group having 6 to 30 carbon atoms, or an alkyl or alkoxy group having 1 to 10 carbon atoms, and R3、R4May be connected by a single bond; preferably an alkyl group or an alkoxy group having 1 to 3 carbon atoms;
in some preferred embodiments of the present invention, the epoxy compounds suitable for use in the present invention have a structure represented by the following general formula (IV):
Figure BDA0002241622650000142
wherein R is3And R4Have the same definition as in formula (III).
R5Each occurrence is the same or different and is independently selected from hydrogen, halogen and alkyl with 1-5 carbon atoms; preferably 1 to 3 alkyl groups, and x is 0 to 4, preferably an integer of 0 or 1. The halogen may be F, Cl or a Br atom.
In a further preferred embodiment, the epoxy compound suitable for use in the present invention has a structure represented by the following general formulae (IV-1) to (IV-3):
Figure BDA0002241622650000143
Figure BDA0002241622650000151
in the present invention, one kind of the epoxy compound may be used, or a mixture of two or more kinds of the epoxy compounds may be used.
The epoxy compounds suitable for use in the present invention can be obtained by a preparation method generally used in the art, and in a typical embodiment, can be carried out using a coupling reaction of epichlorohydrin with a phenolic compound:
Figure BDA0002241622650000152
in addition, other polymerizable components may be used in the photopolymer composition of the present invention without affecting the technical effects of the present invention, in addition to the above-mentioned polymerizable active monomers such as the acrylate monomers and the epoxy compound monomers used in the present invention, and these other polymerizable components include other acrylate monomers or epoxy compound monomers, etc., which are different from the above-mentioned acrylate monomers and epoxy compound monomers.
These other acrylate monomers that may be used include mono-and multifunctional acrylates, mono-and multifunctional urethane acrylates, and in particular:
other acrylates which may be used are, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, ethoxyethyl acrylate, ethoxyethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, t-butyl acrylate, t-butyl methacrylate, hexyl acrylate, hexyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, butoxyethyl acrylate, butoxyethyl methacrylate, dodecyl acrylate, dodecyl methacrylate.
Other useful urethane acrylates are understood to mean compounds having at least one acrylate group with at least one urethane bond. Such compounds are known to be obtainable by reacting hydroxy-functional acrylates with isocyanate-functional compounds.
For this purpose, isocyanate-functional compounds such as aromatic, araliphatic, aliphatic and cycloaliphatic di-, tri-or polyisocyanates can be used. Mixtures of such di-, tri-or polyisocyanates may also be used. Suitable di-, tri-or polyisocyanates are, for example, butylidene isocyanate, Hexamethylene Diisocyanate (HDI), isophorone diisocyanate (IPDI), 1, 8-diisocyanato-4- (isocyanatomethyl) octane, 2, 4-and/or 2,4, 4-trimethylhexamethylene diisocyanate, bis (4,4' -isocyanatocyclohexyl) methane isomers and mixtures thereof having any desired isomer content, isocyanatomethyl-1, 8-octane diisocyanate, 1, 4-cyclohexyl diisocyanate, cyclohexanedimethylene diisocyanate isomers, 1, 4-phenylene diisocyanate, 2, 4-and/or 2, 6-toluene diisocyanate, 1, 5-naphthalene diisocyanate, 2,4' -or 4,4' -diphenylmethane diisocyanate, 1, 5-naphthalene diisocyanate, m-methylthiophenyl isocyanate, triphenylmethane 4,4' -triisocyanate and tris (p-isocyanatophenyl) thiophosphate or their derivatives having a urethane, urea, carbodiimide, acylurea, isocyanurate, allophanate, biuret, oxadiazinetrione, uretdione or iminooxadiazinedione structure and mixtures thereof. Aromatic or araliphatic di-, tri-or polyisocyanates are preferred.
Hydroxy-functional acrylates or methacrylates suitable for preparing the urethane acrylates are the following compounds: 2-hydroxyethyl (meth) acrylate, polyethylene oxide mono (meth) acrylate, polypropylene oxide mono (meth) acrylate, polybutylene oxide mono (meth) acrylate, poly (. epsilon. -caprolactone) mono (meth) acrylate, for example
Figure BDA0002241622650000161
M100(Dow, Schwalbach, Germany), 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 3-hydroxy-2, 2-dimethylpropyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl acrylate, hydroxy-functional mono-, di-or tetraacrylates of polyols such as trimethylolpropane, glycerol, pentaerythritol, dipentaerythritol, ethoxylated, propoxylated or alkoxylated trimethylolpropane, glycerol, pentaerythritol, dipentaerythritol or industrial mixtures thereof. Among them, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, 4-hydroxybutyl acrylate and poly (. epsilon. -caprolactone) mono (meth) acrylate are preferable.
In the present invention, it is advantageous to add a multifunctional monomer for increasing the crosslinking density, and therefore, for the other multifunctional acrylate monomers which can be used, for example, some acrylate monomers having a functional group number of 3 or more, such as pentaerythritol tetraacrylate, an octafunctional hyperbranched monomer ETERCURE6361-100, or multifunctional urethane acrylate, etc., are preferably used.
In the acrylate monomers used in the present invention, the weight sum ratio of the acrylate monomers having the refractive index of more than 1.55 in the present invention is 80% or more, preferably 90% or more, and more preferably 95% or more, based on the total weight of all the acrylate monomers.
In addition, as for other usable epoxy compounds, it is preferable that these epoxy compounds of other structures have a certain refractive index, for example, a refractive index of 1.5 or more, preferably 1.52 or more, and more preferably 1.55 or more.
Further, other epoxy compounds such as:
Figure BDA0002241622650000171
wherein Y represents a single bond or a heteroatom such as O or S.
In some specific embodiments of the present invention, when the epoxy compound of the present invention is used in combination with an epoxy compound of another structure, the epoxy compound of the above structure (formula (III)) of the present invention is used in an amount of 80% or more, preferably 90% or more, and more preferably 95% or more, based on the total weight of the epoxy compounds.
Film-forming component
The film-forming component used in the present invention may be selected from polymers or resin materials having a molecular weight of 1000 or more and having a certain adhesiveness. Preferably, these materials have a low refractive index, and in particular embodiments, the refractive index of these materials is 1.480 or less, preferably 1.475 or less, and more preferably 1.470 or less.
In the present invention, suitable film-forming components include:
homopolymers of vinyl acetate or copolymers of vinyl acetate with acrylates, ethylene, styrene, etc.;
cellulose esters such as cellulose acetate, cellulose acetate-butyrate;
cellulose ethers such as methyl cellulose, ethyl cellulose, and benzyl cellulose, and the like;
polyvinyl alcohol;
polyvinyl acetals such as polyvinyl butyral, polyvinyl formal and the like;
polyurethanes, generally obtained by reacting polyols such as polytetrahydrofuran, polyethylene glycol, polypropylene glycol, castor oil, and isocyanates such as hexamethylene-1, 6-diisocyanate, 1, 4-cyclohexane diisocyanate, methyl-2, 4-diisocyanate;
styrene/butadiene-based block copolymers;
polyvinylpyrrolidone, and the like.
The preferred film-forming component of the present invention is selected from at least one of cellulose acetate butyrate, polyvinylpyrrolidone, polyvinyl alcohol, and polyvinyl acetate from the viewpoint of suppressing dimensional shrinkage of the final optical waveguide product, and improving diffraction efficiency and refractive index modulation.
In addition, in the present invention, it is advantageous to increase the diffraction efficiency and the refractive index modulation degree of the final hologram recording material as the refractive index of the polymerization-active monomer is higher and the difference in refractive index from the film-forming component is larger. Thus, in the present invention, the difference in refractive index (n) between the polymerizable monomer and the film-forming componentPolymerizing reactive monomers-nFilm-forming component) The value is 0.075 or more, preferably 0.078 or more, further preferably 0.080 or more, for example 0.085 or more, 0.090 or more, 0.100 or more.
Plasticizer
In the present invention, a plasticizer is used to increase the flexibility of the photopolymer composition and to alleviate the degree of dimensional shrinkage that occurs after film formation and curing.
In some particular embodiments, plasticizers suitable for use in the present invention are polymeric materials with good compatibility/dissolution characteristics, low volatility, and high boiling point. Typically, these polymeric materials may be polymeric polyols or glycidyl ethers of polymeric polyols. From the viewpoint of suppressing dimensional shrinkage, in a preferred embodiment of the present invention, the polymeric polyol may be polyethylene glycol, polypropylene glycol, or the like; the glycidyl ether of the polyhydric alcohol can be polyethylene glycol diglycidyl ether and polypropylene glycol diglycidyl ether. In addition, the plasticizer may be stabilized by adding a substance such as an acid anhydride or polyisocyanate.
Some plasticizers that may additionally be used may include small molecule plasticizers such as butylene phthalate, N-vinyl pyrrolidone, and the like.
For the plasticizer of the present invention, one kind or a combination of two or more kinds may be used.
Other ingredients
In the present invention, other components commonly used in the art may be used according to actual production needs as long as the technical effects of the present invention are not affected, and the components include: solvents, levelling agents, wetting agents, defoamers or tackifiers, as well as polyurethanes, thermoplastic polymers, oligomers, compounds having additional functional groups (e.g. acetals, epoxides, oxetanes, oxazolines, dioxolanes) and/or compounds having hydrophilic groups (e.g. salts and/or polyethylene oxides), can be used as additional auxiliaries and additives.
In some embodiments of the invention, the optional solvent is a volatile solvent that has good compatibility with the components of the invention, such as ethyl acetate, butyl acetate, and/or acetone. Although it is generally considered that the use of a solvent may cause a significant effect of dimensional shrinkage, in the present invention, even if a solvent is used in the provided photopolymer composition, the effect of suppressing dimensional shrinkage can be significantly observed as compared with the conventional photocurable composition.
Composition of matter
With respect to the composition of the photopolymer composition provided herein, in some preferred embodiments, it can be (based on the total weight of the composition):
the content of the polymerization active monomer may be 30 to 60%, preferably 35 to 50%, when the content is less than 30%, the shrinkage rate of the grating structure in the optical waveguide element is high, and the grating structure is easy to deform, and when the content is more than 60%, the diffraction efficiency of the grating structure is low, and the imaging quality of the optical waveguide element is deviated. In some embodiments, the polymerizable monomer has a monofunctional monomer content of 20% to 40% and a polyfunctional monomer content of 10% to 20%.
The content of the dye compound may be 0.1 to 2%, preferably 0.4 to 1%, and when the content is less than 0.1%, the efficiency of initiating insufficient photosensitivity is low, and when the content is more than 2%, the film forming processability of the photopolymer composition may be reduced, which may affect the diffraction efficiency of the finally obtained optical waveguide element.
The content of the film-forming component may be 10 to 40%, preferably 15 to 30%, and when the content is less than 10%, it is disadvantageous to the film-forming process, and when the content is more than 40%, it may cause a decrease in the refractive index modulation degree.
The content of the initiator can be 0.5-5%, and preferably 1.5-2.5%; the content of the plasticizer may be 10 to 40%, preferably 15 to 35%.
Further, the content of the other components than the above components is not particularly limited, and may be used in accordance with the amount range generally used in the art, provided that the technical effect of the present invention is not affected.
< vector >
For the carrier 101, the substrate may preferably be a layer of material or a composite of materials that is transparent in the visible spectrum (greater than 85% transmittance in the wavelength range of 400-780 nm).
Preferred materials or material composites of the substrate of the carrier 101 are based on Polycarbonate (PC), polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene, polypropylene, cellulose acetate, cellulose hydrate, cellulose nitrate, cyclic olefin polymers, polystyrene, polyepoxides, polysulfones, Cellulose Triacetate (CTA), polyamides, polymethyl methacrylate, polyvinyl chloride, polyvinyl butyral or polydicyclopentadiene or mixtures thereof. They are more preferably based on PC, PET and CTA. The material composite may be a foil laminate or a coextrusion. Preferred material composites are double or triple foils constructed according to one of the embodiments A/B, A/B/A or A/B/C. PC/PET, PET/PC/PET and PC/TPU (TPU ═ thermoplastic polyurethane) are particularly preferred.
As an alternative to the substrates of the aforementioned carrier 101, it is also possible to use flat glass plates or transparent plastic films, which can be used in particular for the precise imagewise exposure of large areas, for example for holography (holography interference lithography for integrated optics, IEEE Transactions on Electron Devices (1978), ED-25(10), 1193-.
The thickness of the support 101 suitable for the present invention may be 1.5mm or less, preferably, may be 20 μm to 1mm, and further preferably, may be 100 μm to 900 μm, for example: 200 to 400 μm, etc.
The refractive index of the carrier 101 may be 1.4 or more in the present invention, and specifically, considering that total reflection occurs only between the carrier 101 and the air (light density is very low), the refractive index of the carrier 101 is preferably 1.4 to 1.6 since the refractive index of the carrier 101 is close to that of most organic polymers and is advantageous for total reflection when the refractive index is 1.4 to 1.6. Further, the present invention preferably uses the support 101 of a larger refractive index and the photopolymer film 102 of a larger refractive index because the angle required for the total reflection condition between the support 101 and the air will be larger, i.e., the FOV (viewing angle) of the waveguide sheet can be significantly increased.
In other cases, the optical waveguide element may additionally comprise a cover layer and/or other functional layers, each optionally at least partially associated with the photopolymer film 102.
In addition, in still other cases, the support 101 may also additionally comprise a cover layer and/or other functional layers, optionally each at least partially connected to the support 101, on the side facing away from the photopolymer film 102. For example, a cover layer and/or other functional layers connected to the carrier 101 may optionally be present in some locations other than the light coupling-in region 103 and the light coupling-out region 104 of the light guide element.
The optical waveguide element obtained in the present invention may be a planar optical waveguide element or a curved optical waveguide element having a certain curvature. For the curved optical waveguide element, light can be deflected in the waveguide, the display image will be elongated, if the light source distortion is adjusted, the output image of the optical machine can be adapted to the display effect of the waveguide sheet, so as to improve the FOV (visual angle) of the waveguide sheet, as shown in fig. 4.
<Second aspect of the invention>
A second aspect of the present invention provides a method for producing an optical waveguide element of the first aspect, comprising the steps of:
a step of preparing a photopolymer film 102;
a step of composite molding the carrier 101 and the photopolymer film 102;
a step of forming a grating structure, said photo polymer film 102 having at least one light in-coupling region 103 and at least one light out-coupling region 104, said light in-coupling region 103 being unconnected to light out-coupling region 104,
a grating structure is formed in each of the light incoupling region 103 and the light outcoupling region 104.
The step of first forming the carrier 101 and the photopolymer film 102 in a composite manner and the step of first forming the grating structure are not particularly limited in the present invention, and may be a step of first forming the carrier 101 and the photopolymer film 102 in a composite manner and then forming the grating structure, or a step of first forming the grating structure and then forming the carrier 101 and the photopolymer film 102 in a composite manner, and preferably a step of first forming the carrier 101 and the photopolymer film 102 in a composite manner and then forming the grating structure.
Step of preparing the photopolymer film 102
In the present invention, a mixture is obtained by mixing the raw materials of the photopolymer film 102, and the mixture is formed into a film. Specifically, the raw material of the photopolymer film 102 may be the photopolymer composition described above.
Specifically, the compositions are mixed in proportion in an appropriate container, and mechanical stirring or the like may be employed as occasion demands to make the mixing uniform. The temperature of the mixing is not particularly limited, and in general, the mixing may be performed under ambient conditions at room temperature or under heating.
In some embodiments of the invention, the formation of a homogeneous mixture is facilitated by the use of suitable heating methods, particularly without the additional use of solvents. The heating temperature may be determined based on the activity of the components of the photopolymer composition and the desired viscosity of the system. In some conditions it is desirable to increase the mixing temperature to obtain a lower viscosity, but this is desirable to avoid excessive polymerization in unnecessary processing windows to cause difficulties in subsequent processing.
In some preferred embodiments of the invention, the temperature used in the step of mixing is above 60 ℃, more preferably above 70 ℃ and below 115 ℃, preferably below 110 ℃. The resulting molten or liquid mixture may be used immediately or stored briefly at the processing temperature for use.
In addition, in the preferred embodiment of the present invention, the spacer is used in the photopolymer film 102 from the viewpoint of controlling the thickness of the photopolymer film 102, suppressing dimensional shrinkage of the optical waveguide element, and maintaining high diffraction efficiency, and particularly, in the case of the present invention in which two layers of the support 101 sandwich one layer of the photopolymer film 102, the use of the spacer is advantageous for process control.
For spacers, in some particular embodiments of the invention, particles that are substantially opaque to visible light may be used. These particles may be inorganic particles, organic particles or metallic particles. The inorganic particles are preferably used in the present invention from the viewpoint of suppressing the dimensional shrinkage of the optical waveguide element and the production cost.
The kind of the inorganic particles is not particularly limited, and for example, silica, titania, or the like can be used. In some specific embodiments, the inorganic particles have a substantially spherical steric shape; in other embodiments, the inorganic particles have an average particle size of 2 to 50 μm, preferably 3 to 40 μm, and the size of the spacer can be coordinated, selected or determined with the thickness of the photopolymer film 102 being formed.
As for the method of using the spacer, in the present invention, the spacer may be previously formed on the surface of the support 101, and this process may be achieved by a method of coating a dispersion system containing the spacer. In some embodiments, the spacer may be dispersed in a hydrocarbon, alcohol, or ketone solvent, for example, to form a dispersion. For these solvents, it is preferable to use a substance having a relatively low boiling point, and examples of the solvent include one or more of benzene, toluene, cyclohexane, pentane, ethanol, isopropanol, acetone, methyl ethyl ketone, and the like. The dried spacer particles (powder) may be directly dispersed in these solvents, or a sol-like substance formed by the spacers may be dispersed in these solvents.
In some embodiments of the present invention, the concentration of the spacer-containing dispersion system may be 0.1 to 3mg/mL, preferably 0.1 to 0.3mg/mL, and when the concentration is too high, the dispersion uniformity is deteriorated, and the light is scattered by the spacer during propagation in the waveguide to generate stray light, thereby forming a hazy background, resulting in a decrease in the diffraction efficiency of the optical waveguide device.
In the present invention, the spacer can be uniformly applied to the surface of the carrier 101 by a coating method, and the coating method is not particularly limited, and can be performed by a spray coating or spin coating method. After the spacers are formed on the surface of the carrier 101 by a coating method, the solvent may be removed by heating, blowing, or the like.
A step of composite molding the carrier 101 and the photopolymer film 102
In this step, a film is formed on the support 101 by using the above-obtained molten and liquid mixture. In some specific embodiments of the present invention, the photopolymer 102 film has a thickness of 5 μm or more, preferably 15 μm or more, more preferably 20 μm or more, and further, the polymer film has a thickness of 50 μm or less, preferably 40 μm or less. The above-mentioned thickness of the polymer film can be coordinated or matched in practice with the use of spacers, for example as described below.
As for the material of the support 101, the same definition as < first aspect > described above, and in a preferred embodiment, glass may be used as the support 101. Optionally, the carrier 101 is cleaned, dried, etc. prior to use.
Further, the (hot) melt or liquid obtained above is formed into a film on the surface of the side having the spacer on the support 101. For example, flat, onto the carrier 101, in which case, for example, devices known to the person skilled in the art, such as knife coating devices (medical knives, knife rollers, curved bars (Commabar), etc.) or slit nozzles, etc., can be used. Optionally, if desired, a degassing step is carried out after the coating of the film, in order to eliminate possible bubbles in the film. After coating, a photopolymer film can be obtained by cooling or the like.
In the present invention, the photopolymer film 102 described above as a holographic medium can be processed into holograms by suitable exposure operations for various optical applications. Visual holograms include all holograms which can be recorded by methods known to those skilled in the art.
Step of forming a grating structure
In the present invention, a grating structure is formed on at least two unconnected positions of the photopolymer film 102 by exposure, bleaching, etc. to form a light in-coupling region 103 and a light out-coupling region 104 having a grating structure. In this process, exposure to coherent light can be used to control the microstructure. The coherent light may have any feasible wavelength, and preferably, coherent light having a wavelength around 532nm is used.
In some preferred embodiments of the present invention, the exposure of the photopolymer film 102 can be performed with two beams of coherent light. There is no particular limitation on the source of the coherent light having a wavelength of about 532nm, and in some specific embodiments of the present invention, the green laser beam may be split into two coherent light beams having the same or different intensities by an optical element, and the resulting photopolymer film 102 may be simultaneously exposed.
By using coherent light exposure, spaced bright and dark regions may be present in the photopolymer film 102 (the two beams of coherent light produce alternating bright and dark stripes in the photopolymer film 102). The bright-area monomer is polymerized under the action of an initiator, and the concentration of the monomer is reduced; the difference in concentration between the bright and dark regions causes the monomers to phase separate, the monomers in the dark region migrate to the bright region, and the monomers in the bright and dark regionsA refractive index difference Δ n (refractive index modulation degree) is formed. With respect to the exposure intensity, it may be 5 to 30mJ/cm in some embodiments of the present invention2. The exposure sensitivity of the invention can reach 5mJ/cm2And the exposure efficiency is higher.
In some embodiments of the invention, two beams of coherent light may be exposed simultaneously from one side of the polymer film (transmissive grating structure); in other embodiments, two beams of coherent light are used to expose the polymer film from both sides (reflective grating structure).
After exposure, refractive index distribution in a sine function distribution is formed in the photopolymer film 102, and the diffraction grating structure is obtained. The difference between the sinusoidal peaks, i.e., Δ n (degree of refractive index modulation). In some specific embodiments of the present invention, Δ n may be 0.025 or more, preferably 0.030 or more, and more preferably 0.032 or more, 0.035 or more, 0.040 or more, 0.045 or more, 0.05 or more, or 0.06 or more.
From the viewpoint of improving the angular selectivity of the grating, in a preferred embodiment of the present invention, the optical waveguide element is obtained by exposing the polymer film to two coherent light beams from both sides of the polymer film to form a reflective grating structure. Such an optical waveguide element may have a large angle selection range up to ± 14 ° or even up to ± 16 °, and a diffraction efficiency of 70% or more, preferably 80% or more, and further preferably 90% or more. Thus, it is also demonstrated that the above-described photopolymer composition of the present invention is particularly suitable for use in the preparation of reflective diffractive optical waveguide elements.
As shown in fig. 5, fig. 5 shows a typical optical path layout of the present invention, a visible laser beam is split into two laser beams with the same or different intensities, and the two coherent laser beams are reflected and converged on the photopolymer film 102 by a reflector for exposure. The photopolymer film 102 is then moved so that the light is focused at other locations of the photopolymer film 102 that are not connected to the previously exposed locations and is exposed again.
After exposure, a holographic diffraction grating structure is formed in the photopolymer film 102, and the final reflective diffraction grating structure containing the photopolymer film 102 is obtained after natural light irradiation (without other complicated post-processing).
In addition, the present invention is not particularly limited to the method for producing a curved optical waveguide element, and in some specific embodiments, a film may be formed on a substrate having a certain curvature by using the substrate and exposing the substrate. In other embodiments, a planar substrate may be used, and the coated film may be processed (e.g., by external force) to form a curved optical waveguide element having a curvature after exposure.
<Third aspect of the invention>
In a third aspect of the invention, the use of the above-obtained optical waveguide component of the invention is disclosed. Without limitation, one or more of the optical waveguide elements described above in the present invention may be used in various holographic optical waveguide display devices in the art, and may be used alone or in combination with other optical elements.
Further, the optical waveguide element of the present invention can be used in a holographic optical waveguide display device, and is particularly suitable for Augmented Reality (AR) head display apparatuses such as AR display eyewear devices and the like.
Examples
Hereinafter, the present invention will be described by way of specific examples.
Example 1
An optical waveguide component prepared by the steps of:
1) in a dark room or a red light environment, 10mL of polymer (obtained by heating at 100 ℃) and 2mg of silicon dioxide microsphere spacer with the average particle size of 20 mu m are mixed to form a mixture, and the mixture is heated to 100 ℃ and stirred for 4 hours until the mixture is uniformly mixed;
2) maintaining the temperature at 100 ℃, coating the mixed solution obtained in the step (1) on a glass substrate with the thickness of 1mm and the size of 20mm multiplied by 70mm under red light, then covering another glass substrate with the thickness of 1mm and the size of 20mm multiplied by 70mm on the upper surface of the mixed solution, and cooling to normal temperature to obtain a solid photopolymer dry plate;
3) subjecting one side of the dry plate obtained in the step (2) to 532nm laser beam expanding and beam splitting interference exposure (see figure 5), wherein an exposure area is 15mm multiplied by 15mm, and a holographic grating structure is formed; exposing the dry plate by adopting a high laser intensity short exposure time mode, wherein the exposure energy density is 5mJ/cm2；
4) Translating the dry plate obtained in the step (3), selecting a blank area with the size of 15mm multiplied by 15mm on the other side, repeating the step (3), and obtaining a group of optical waveguide elements of the holographic grating, wherein the distance between two exposure areas is 30 mm;
5) and (4) completely fixing and bleaching the optical waveguide element of the volume holographic grating obtained in the step (4) after natural light irradiation for about 30min, and in addition, no post-treatment is needed.
The contents of the components of the obtained photopolymer dry film are shown in the following table 1:
TABLE 1
Composition of Content (wt.)
2, 5-bis { [4- (diethylamino) -2-methylphenyl]Methylene cyclopentanone 0.2％
N-phenylglycine 0.8％
2-Phenylthioacrylate (n ═ 1.557) 28％
9, 9-bis (methyl acrylate) fluorene (n ═ 1.606) 14％
Cellulose acetate butyrate (n ═ 1.475) 28％
Polyethylene glycol 29％
The diffraction efficiency of the optical waveguide element is more than 70%, the angle selectivity reaches +/-6 degrees, and the effect display diagram of the prepared optical waveguide element is shown in fig. 6.
Example 2
Same procedure as in example 1, except that the exposure energy density was 8mJ/cm2And the contents of the components of the resultant dry film photopolymer are shown in the following table 2:
TABLE 2
Composition of Content (wt.)
Basic Red 2 0.2％
N-phenylglycine 0.8％
2- (4-chlorophenyl) -4, 5-diphenylimidazole 1％
2-Naphthalenethioethyl acrylate (n ═ 1.620) 33％
9, 9-bis (propene)Carbomethoxy) fluorene (n ═ 1.606) 11％
Cellulose acetate butyrate (n ═ 1.475) 22％
N-vinyl pyrrolidone 32％
The diffraction efficiency of the optical waveguide element obtained by the embodiment is more than 95%, the angle selectivity reaches +/-12 degrees, the exposure is sensitive, and the refractive index modulation degree reaches 0.08.
Example 3
Same as example 1, but the exposure energy density was 20mJ/cm2The contents of the components of the obtained dry film photopolymer are shown in the following table 3:
TABLE 3
Composition of Content (wt.)
Basic Red 2 0.2％
4-Dimethylaminobenzoic acid ethyl ester 0.8％
Diphenyliodonium hexafluorophosphate 1％
2-naphthyl acrylate(n＝1.608) 39％
9, 9-bis (methyl acrylate) fluorene (n ═ 1.606) 13％
Cellulose acetate butyrate (n ═ 1.475) 13％
Glutaric anhydride 7％
Polyethylene glycol 26％
In this embodiment, the diffraction efficiency of the optical waveguide element prepared by mixing glutaric anhydride modified polyethylene glycol and cellulose acetate butyrate is as high as 85%.
It should be noted that, although the technical solutions of the present invention are described by specific examples, those skilled in the art can understand that the present disclosure should not be limited thereto.
Having described embodiments of the present disclosure, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen in order to best explain the principles of the embodiments, the practical application, or improvements made to the technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.
Industrial applicability
The optical waveguide element of the present invention can be industrially produced and used in a holographic optical waveguide display device.

Claims (10)

1. An optical waveguide component, characterized by: comprising a stack of at least two carriers and a photopolymer film, wherein
The photopolymer film is positioned between at least two carriers;
the photopolymer film having at least one light incoupling region and at least one light outcoupling region;
the light coupling-in area is not connected with the light coupling-out area; and is
The positions of the light coupling-in area and the light coupling-out area are respectively provided with a grating structure.
2. The optical waveguide element of claim 1 wherein the photopolymer film has a thickness of 5 to 50 μm.
3. An optical waveguide element as claimed in claim 1 or 2, characterized in that the shortest distance between the light in-coupling area and the light out-coupling area is 10mm-10 cm.
4. The optical waveguide element according to any one of claims 1 to 3, wherein the carrier has a thickness of 1.5mm or less and a refractive index of 1.4 to 1.6.
5. An optical waveguide element as claimed in any one of claims 1 to 4 wherein the photopolymer film is derived from a photopolymer composition, wherein the photopolymer composition comprises the following components:
polymerizing the reactive monomer;
a dye compound;
an initiator;
a film forming component; and
a plasticizer;
wherein the difference in refractive index (n) between the polymerizable monomer and the film-forming componentPolymerizing reactive monomers-nFilm-forming component) The value is 0.075 or more.
6. The optical waveguide component of claim 5 wherein the polymerizable monomer is selected from one or more of acrylate monomers and epoxy monomers.
7. A method of making an optical waveguide component comprising the steps of:
a step of preparing a photopolymer film;
a step of composite molding the carrier and the photopolymer film;
a step of forming a grating structure, the photopolymer film having at least one light in-coupling area and at least one light out-coupling area, the light in-coupling area being unconnected to the light out-coupling area,
and a grating structure is respectively formed in the light in-coupling region and the light out-coupling region.
8. The method for producing an optical waveguide element according to claim 7, wherein the step of forming a grating structure includes a step of exposing the light incoupling region and the light outcoupling region with coherent light.
9. The method of manufacturing an optical waveguide element according to claim 8, wherein the coherent light has a wavelength of approximately 532 nm.
10. Holographic optical waveguide display device comprising one or more optical waveguide elements according to any of claims 1 to 6 or obtained by a method according to any of claims 7 to 9.
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