Diffractive optical film with protective film, method for laser engraving diffractive optical film with protective film, and method for identifying diffractive optical film with protective film

Abstract

The invention provides a diffractive optical film with a protective film, a laser imprinting method of the diffractive optical film with the protective film, and a recognition method of the diffractive optical film with the protective film, the diffractive optical film with the protective film has an imprinting required for manufacturing, and adhesion of particles, flying materials and the like is suppressed. This diffractive optical film with a protective film comprises: a protective film laminated on at least one surface side of a diffractive optical element, the diffractive optical element comprising a birefringent layer having a local optical axis direction that changes in at least one direction along the surface of the diffractive optical element; the surface of the diffractive optical element on the side on which the protective film is provided has a mark based on at least one of modification in physical properties and change in shape of the layer constituting the diffractive optical element.

Description

Technical Field

[0001] The present invention relates to a diffractive optical film with a protective film, a laser engraving method for the diffractive optical film with a protective film, and an identification method for the diffractive optical film with a protective film. Background Art

[0002] Optical elements for controlling the direction of light are used in many optical devices or systems.

[0003] For example, in the backlight of a liquid crystal display device, AR (Augmented Reality) glasses, VR (Virtual Reality) glasses, MR (Mixed Reality) glasses, etc. head-mounted displays (HMDs (Head Mounted Displays)) such as those for overlapping and displaying virtual images and various information on the actually seen scene, head-up displays (HUDs (Head Up Displays)), projectors, beam steering devices, sensors for detecting an object and measuring the distance to the object, etc., optical elements for controlling the direction of light are used in various optical devices.

[0004] As optical elements for controlling the direction of such light, liquid crystal diffractive elements having an optically anisotropic layer formed using a liquid crystal composition containing a liquid crystal compound, and diffractive optical elements using metasurfaces, metamaterials, etc. have been proposed.

[0005] Patent Document 1 describes an optical element including a birefringent material layer having a local optical axis direction that changes in at least one direction along its surface, the local optical axis direction corresponding to an optical axis direction profile formed by changing the polarization of light from a light source between a plurality of polarized lights, focusing the light from the light source onto a spot at a focal plane, and scanning the spot along the surface of a polarization-sensitive recording medium arranged close to the focal plane in at least two dimensions such that adjacent scans substantially overlap, and the change in polarization of the polarized light and the scanning of the spot are performed independently.

[0006] Patent Document 2 describes an optical element having a plurality of stacked birefringent sub-layers configured to change the propagation direction of light passing therethrough according to the Bragg condition, each of the stacked birefringent sub-layers having a local optical axis that changes along each interface between adjacent objects in the stacked birefringent sub-layers to define a corresponding grating period. The optical element described in Patent Document 2 is an optical element that diffracts transmitted light. The following is described: By diffracting the light incident on a substrate (light guide plate) with the optical element, the light is incident at an angle of total reflection in the substrate and guided in a direction substantially perpendicular to the incident direction of the light in the substrate.

[0007] Prior art documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-532468

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2017-522601 Summary of the invention

[0011] Technical problem to be solved by the invention

[0012] When manufacturing the above-mentioned diffractive optical film, in order to give traceability such as manufacturing conditions and quality information, etc., marks (labels) are engraved on the film. Also, marks for positioning when installing these films are engraved on devices such as head-up displays and near-eye displays or modules for constructing them.

[0013] As a method of imparting such marks (engravings), conventionally, a sticker pre-printed with symbols has been used, or a method of imparting them to the front surface, back surface, or its protective film of the diffractive optical film by methods such as inkjet or laser marking has been used. However, in a precision optical system such as a near-eye display and a sensor, particles and flying objects, etc. accompanying the imparting of marks (engravings) adhere to the diffractive optical film, making it difficult to control the direction of light and possibly preventing the desired performance from being exhibited.

[0014] An object of the present invention is to solve such problems of the prior art and provide a diffractive optical film with a protective film, a laser engraving method for a diffractive optical film with a protective film, and an identification method for a diffractive optical film with a protective film, the diffractive optical film with a protective film having engravings required for manufacturing and being able to suppress the adhesion of particles and flying objects, etc. to the diffractive optical element.

[0015] Means for solving the technical problem

[0016] To solve this problem, the present invention includes the following configuration.

[0017] [1] A diffractive optical film with a protective film, comprising a protective film and a diffractive optical element, wherein,

[0018] The diffractive optical element includes a birefringent layer having a local optical axis direction that changes in at least one direction along its surface,

[0019] The protective film is laminated on at least one surface side of the diffractive optical element,

[0020] On the surface of the diffractive optical element on the side where the protective film is provided, there is at least one of a modification based on the physical properties of the layer constituting the diffractive optical element and a change in shape as a mark.

[0021] [2] The diffractive optical film with a protective film according to [1], wherein

[0022] The light transmittance of the diffractive optical element at a wavelength of 355 nm is 1 to 50%.

[0023] [3] The diffractive optical film with a protective film according to [1] or [2], wherein

[0024] The birefringent layer comprises a liquid crystal composition or a metasurface material.

[0025] [4] The diffractive optical film with a protective film according to any one of [1] to [3], wherein

[0026] The light transmittance of the birefringent layer at a wavelength of 355 nm is 1 to 50%.

[0027] [5] The diffractive optical film with a protective film according to any one of [1] to [4], wherein

[0028] The light transmittance of the protective film at a wavelength of 355 nm is 90 to 100%.

[0029] [6] A laser engraving method for a diffractive optical film with a protective film, the diffractive optical film with a protective film being a diffractive optical film with a protective film comprising a protective film and a diffractive optical element,

[0030] The diffractive optical element comprises a birefringent layer having a local optical axis direction that varies in at least one direction along its surface,

[0031] The protective film is laminated on at least one surface side of the diffractive optical element,

[0032] The laser engraving method for the diffractive optical film with a protective film comprises:

[0033] A process of irradiating the diffractive optical element with laser while maintaining the laminated state of the diffractive optical element and the protective film,

[0034] Forming a marked area by inducing at least one of a change in physical properties and shape of the layer constituting the diffractive optical element through laser irradiation,

[0035] The laser transmits through the protective film.

[0036] [7] The laser engraving method for the diffractive optical film with a protective film according to [6], wherein

[0037] The light transmittance of the diffractive optical element at a wavelength of 355 nm is 1 to 50%.

[0038] [8] The laser engraving method for the diffractive optical film with a protective film according to [6] or [7], wherein

[0039] The birefringent layer includes a liquid crystal composition or a metasurface material.

[0040] [9] The laser engraving method of the diffraction optical film with a protective film according to any one of [6] to [8], wherein,

[0041] The light transmittance of the birefringent layer at a wavelength of 355 nm is 1 to 50%.

[0042]

[10] The laser engraving method of the diffraction optical film with a protective film according to any one of [6] to [9], wherein,

[0043] The light transmittance of the protective film at a wavelength of 355 nm is 90 to 100%.

[0044]

[11] The laser engraving method of the diffraction optical film with a protective film according to any one of [6] to

[10] , wherein, in the process of irradiating the laser, the laser is irradiated on the diffraction optical element from the side of the protective film.

[0045]

[12] A method for imparting traceability information to a diffraction optical film with a protective film including a protective film and a diffraction optical element to identify the diffraction optical film with a protective film, the method sequentially including the following processes:

[0046] Generating an inherent identification mark for a functional region having the diffraction effect of the diffraction optical element;

[0047] Assigning the generated identification mark or a symbol converted from the identification mark as a mark to the diffraction optical film with a protective film;

[0048] Reading the assigned mark; and

[0049] Comparing the identification mark obtained from the read mark with the information stored in the traceability database,

[0050] Wherein, the process of assigning the mark to the diffraction optical film with a protective film is to irradiate the diffraction optical element with a laser while maintaining the laminated state of the diffraction optical element and the protective film to induce at least one of the physical properties and shape changes of the layer constituting the diffraction optical element to form a mark region,

[0051] For one functional region, a plurality of marks are assigned separately from each other in the plane of the diffraction optical film with a protective film.

[0052]

[13] The method according to

[12] , wherein,

[0053] The process of reading the mark is a process performed while conveying the diffraction optical film with a protective film, and a plurality of marks are provided on a straight line parallel to the conveying direction.

[0054]

[14] According to the method described in

[12] or

[13] , wherein,

[0055] In the process of reading the mark, a plurality of imaging elements are used, and the plurality of imaging elements are arranged in such a manner that each mark passes through the imaging range of each imaging element.

[0056]

[15] According to the method described in any one of

[12] to

[14] , wherein,

[0057] The size of the unit pixel constituting the mark is set to be 9 times or more of the minimum pixel size detectable by the imaging element.

[0058] Advantageous Effects of the Invention

[0059] According to the present invention, it is possible to provide a diffractive optical film with a protective film, a laser engraving method for the diffractive optical film with a protective film, and an identification method for the diffractive optical film with a protective film, the diffractive optical film with a protective film having the engraving required for manufacturing and being able to suppress the adhesion of particles, scattered matter, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 It is a plan view conceptually showing an example of the orientation pattern of the local optical axis in the diffractive optical element of the diffractive optical film with a protective film of the present invention.

[0061] Figure 2 It is a cross-sectional view showing an example of the structure of the diffractive optical film with a protective film of the present invention.

[0062] Figure 3 It is a cross-sectional view showing another example of the structure of the diffractive optical film with a protective film of the present invention.

[0063] Figure 4 It is an example of a preferred engraving method and a method of the reading process.

[0064] Figure 5 It is a conceptual diagram for explaining an example of the laser engraving method of the present invention.

[0065] Figure 6 It is a conceptual diagram for explaining another example of the laser engraving method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0066] Hereinafter, based on the preferred embodiments shown in the drawings, a diffractive optical film with a protective film, a laser engraving method for the diffractive optical film with a protective film, and an identification method for the diffractive optical film with a protective film of the present invention will be described in detail.

[0067] In this specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value.

[0068] In this specification, "(meth)acrylate" is used in the meaning of "any one or both of acrylate and methacrylate".

[0069] In this specification, visible light is light with a wavelength that can be observed by the naked eye among electromagnetic waves, representing light in the wavelength range of 380 to 780 nm. Non-visible light is light in the wavelength range less than 380 nm and exceeding 780 nm. And, near-infrared light is light in the wavelength range of 800 to 1500 nm among non-visible light.

[0070] In this specification, Re(λ) represents the in-plane retardation at wavelength λ. Unless otherwise specified, the wavelength λ is set to 550 nm. In this specification, Re(λ) is a value measured at wavelength λ in AxoScan (manufactured by Axometrics). By inputting the average refractive index ((nx + ny + nz) / 3) and the film thickness (d(μm)) in AxoScan, the following is calculated.

[0071] Slow axis direction (°)

[0072] Re(λ) = R0(λ)

[0073] In addition, R0(λ) is represented by a numerical value calculated by AxoScan and means Re(λ).

[0074] In this specification, parallel and orthogonal respectively refer to the ranges of parallel ±5° and orthogonal ±5°, rather than strictly parallel and orthogonal in the strict sense. "Orthogonal" does not strictly represent 90°, but represents 90° ± 10°, preferably 90° ± 5°. And, regarding "parallel", it does not represent 0° in the strict sense, but represents 0° ± 10°, preferably 0° ± 5°. Moreover, the angle does not represent a strict angle, but represents a range of ±10°, preferably a range of ±5°.

[0075] [Diffractive optical film with protective film]

[0076] Use Figure 2, the diffractive optical film 1 with a protective film of the present invention is described. The diffractive optical film 1 with a protective film of the present invention is constructed to include a protective film 5 and a diffractive optical element 4. In the example shown in the figure, the diffractive optical element 4 includes a substrate 3, an adhesive layer 8 and a birefringent layer 2 in sequence. The protective film 5 has a protective film substrate 6 and a weak adhesive layer 7. The protective film 5 is laminated on at least one surface side of the diffractive optical element 4. In the example shown in the figure, the protective film 5 is laminated on the birefringent layer 2 side of the diffractive optical element 4. And, the weak adhesive layer 7 of the protective film 5 is attached to the birefringent layer 2 of the diffractive optical element 4. The birefringent layer 2 of the diffractive optical element 4 has a local optical axis direction region that changes in at least one direction along its surface (the axial direction of the birefringence in the local region changes), and the region has the function of diffracting the incident light. In the following description, such a region is also referred to as a functional region. The surface of the diffractive optical element 4 on which the protective film 5 is provided, that is, the surface of the birefringent layer 2 , has a mark 9 based on at least one of modification of the physical properties of the layer constituting the diffractive optical element 4 and change in shape.

[0077] The orientation pattern of the local optical axis formed in the birefringent layer included in the diffractive optical element of the diffractive optical film with a protective film of the present invention controls the direction of the light by applying a geometric phase distribution or an optical effect based on the Bragg diffraction condition to the irradiated light. However, if there are foreign matter such as particles in the optical path of the irradiated light, or the surface shape and / or the physical properties of the surface change due to unexpected scattered objects, the optical path changes due to these, so unexpected optical effects may occur, and the diffractive optical element cannot perform the desired function. Therefore, it is necessary to avoid particles and scattered objects adhering to the surface of the diffractive optical element as much as possible. On the other hand, from the perspective of manufacturing management, it is necessary to give marks (engravings) to the diffractive optical element. In the above-mentioned prior art, particles caused by stickers, particles and scattered objects generated during inkjet and laser marking, etc. cannot be avoided. Therefore, a protective film is provided to protect the surface of the diffractive optical element, and these marks (engravings) are given on the protective film, but since the protective film is removed at a certain stage, management based on marks (engravings) cannot be achieved after removal.

[0078] According to the structure of the present invention, by stacking a protective film and a diffractive optical element and providing a mark (engraving) on ​​the diffractive optical element, the protective film can suppress the adhesion of particles and flying objects on the diffractive optical element, and the mark (engraving) can be maintained even after the protective film is removed.

[0079] <Diffractive optical elements>

[0080] The diffractive optical element included in the present invention includes a birefringent layer having a local optical axis direction that varies in at least one direction along its surface. Further, on the surface of the diffractive optical element on the side where the protective film is provided, there is a mark based on the modification of the physical properties of the layer constituting the diffractive optical element and / or the change in shape.

[0081] {Birefringent layer}

[0082] As the birefringent material constituting the birefringent layer, a liquid crystal composition, a metasurface material, or a metamaterial can be used. As these materials, known materials can be utilized. That is, as the birefringent layer, a liquid crystal layer or a metasurface structure can be used.

[0083] In terms of being able to handle a wider wavelength region with one birefringent layer, the birefringent material is preferably a liquid crystal composition. For example, when used as an optical element assembled into an image display device such as a near-eye display, it is necessary to function in the visible light region, so it is particularly preferable to use a liquid crystal composition.

[0084] Further, as another mode, in terms of being able to selectively control the direction of light for a specific wavelength, a metasurface material can also be preferably used. When used as an optical element assembled into a sensor device such as a photoacoustic volume image sensor or a laser Doppler sensor, it has the effect of reducing noise by functioning only at a specific wavelength, so it is particularly preferable to use a metasurface material.

[0085] In the case where the birefringent layer is a liquid crystal layer composed of a liquid crystal composition, in the case of a structure having a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound continuously rotates and changes in at least one direction in the plane, it can be said that the birefringent layer has a local optical axis direction that varies in at least one direction along its surface.

[0086] On the other hand, in the case where the birefringent layer is a metasurface structure, when the unit structure constituting the metasurface structure changes at least any one of the major axis length, the minor axis length, or the in-plane direction of the major axis in at least one direction along its surface, the birefringent layer can have a local optical axis direction that changes in at least one direction along its surface.

[0087] (Liquid crystal composition)

[0088] As a liquid crystal composition that can be used, for example, the liquid crystal compositions described in the re-published patent WO2020 / 022434, the re-published patent WO2021 / 256420, and the published patent 2017-522601 can be used. As the liquid crystal composition, from the viewpoint of excellent heat resistance, durability, and operability, a polymerizable liquid crystal composition using a polymerizable liquid crystal material is preferably used. In addition, the liquid crystal composition used in the formation of the birefringent layer may further contain a surfactant, a polymerization initiator, and the like. Further, when a birefringent layer is formed using a polymerizable liquid crystal composition, the formed material sometimes does not exhibit liquid crystallinity in the strict sense, but in this specification, the formed material is also included and referred to as a liquid crystal composition.

[0089] Moreover, if the compositions described in Japanese Published Patent 2022-69310 and Japanese Published Patent 2021-102766 are used, it is not necessary to provide the subsequent alignment layer, and an alignment having a local optical axis direction that changes in at least one direction along the surface of the birefringent layer can be formed.

[0090] By laminating these liquid crystal compositions on the alignment layer, a predetermined alignment state and a liquid crystal alignment pattern can be formed. As the alignment layer used in the present invention, a photo-alignment layer is used from the viewpoint of being able to form a complex pattern and being able to reproduce a precise shape without applying physical forces such as contact and peeling to the alignment layer. The photo-alignment layer means that, by performing patterned polarized light irradiation (hereinafter, also referred to as polarized pattern irradiation) on a material as described later, a patterned alignment property can be generated according to the properties of light.

[0091] (Photo-alignment layer)

[0092] As the photo-alignment film, various known materials can be used. As the photo-alignment materials that can be used in the alignment film of the present invention, for example, azo compounds described in JP-A-2006-285197, JP-A-2007-076839, JP-A-2007-138138, JP-A-2007-094071, JP-A-2007-121721, JP-A-2007-140465, JP-A-2007-156439, JP-A-2007-133184, JP-A-2009-109831, Japanese Patent No. 3883848 and Japanese Patent No. 4151746; aromatic ester compounds described in JP-A-2002-229039; maleimide and / or alkenyl-substituted nadimide compounds having a photo-alignment unit described in JP-A-2002-265541 and JP-A-2002-317013; photo-crosslinkable silane derivatives described in Japanese Patent No. 4205195 and Japanese Patent No. 4205198; photo-crosslinkable polyimide, photo-crosslinkable polyamide and photo-crosslinkable polyester described in JP-T-2003-520878, JP-T-2004-529220 and Japanese Patent No. 4162850; and compounds capable of photo-dimerization described in JP-A-9-118717, JP-T-10-506420, JP-T-2003-505561, WO2010 / 150748, JP-A-2013-177561 and JP-A-2014-012823, particularly cinnamate compounds, chalcone compounds and coumarin compounds, etc. are exemplified as preferred examples.

[0093] Among them, azo compounds, photo-crosslinkable polyimide, photo-crosslinkable polyamide, photo-crosslinkable polyester, cinnamate compounds and chalcone compounds can be preferably used.

[0094] There is no limitation on the thickness of the alignment film, and a thickness that can obtain the required alignment function can be appropriately set according to the material for forming the alignment film.

[0095] The thickness of the alignment film is preferably 0.01 to 5 μm, more preferably 0.05 to 2 μm.

[0096] The alignment film can be provided on a support (support for the alignment film) as needed. And the function of the alignment film is to induce alignment of the liquid crystal composition. The liquid crystal composition is a polymerizable liquid crystal composition, and when the liquid crystal alignment pattern is fixed by polymerization in the state where the alignment is induced, it can be peeled off and removed from the birefringent layer.

[0097] (Support for alignment film)

[0098] As described above, the alignment film is provided on the support for the alignment film as needed.

[0099] The thickness of the support for the alignment film is not limited as long as it is appropriately set to maintain the thickness of the alignment film and the birefringent layer.

[0100] The thickness of the support for the alignment film is preferably 1 to 1000 μm, more preferably 3 to 250 μm, and further preferably 5 to 150 μm.

[0101] The support for the alignment film can be a single layer or multiple layers.

[0102] Examples of the support for the alignment film as a single layer include supports made of glass, triacetyl cellulose (TAC), polyethylene terephthalate (PET), polycarbonate, polyvinyl chloride, acrylic acid, and polyolefin. Examples of the support for the alignment film as multiple layers include supports having any one of the supports for the alignment film as described above for the single layer as a substrate and having other layers provided on the surface of the substrate.

[0103] The support for the alignment film can be peeled off and removed from the birefringent layer as needed. It can be peeled off from the birefringent layer together with the alignment film when the above alignment film is held on the support, and it can also be peeled between the alignment film and the support for the alignment film to remove only the support for the alignment film. For manufacturing reasons, in the case of using a thick and rigid material, it is preferable to transfer the birefringent layer to a thin and flexible transfer substrate after the polymerizable liquid crystal material contained in the birefringent layer is polymerized. By transferring it to a thin and flexible transfer substrate in this way, a thin and easily processable laminate can be obtained. Figure 2 In the example shown, the diffractive optical element 4 is an example of transferring the birefringent layer 2 to the substrate 3. The transfer substrate can be a protective film described later.

[0104] (Method for forming a birefringent layer using a liquid crystal composition)

[0105] As a preferred method for forming a birefringent layer using a liquid crystal composition, a forming method can be cited that is carried out through the following processes: manufacturing an alignment film; imparting a liquid crystal composition to the obtained alignment film to form a prescribed alignment state; and fixing the alignment of the liquid crystal composition. These series of processes are preferably carried out in a clean room environment.

[0106] As the process for manufacturing the alignment film, it can be carried out through the following processes: preparing a support for the alignment film as needed, laminating a material for forming the above-mentioned alignment film prepared separately on the support for the alignment film to form an alignment film composition layer; and imparting an alignment restricting force to the alignment film composition layer.

[0107] The formation of the alignment film composition layer can be carried out by known methods. For example, methods such as coating, flash plating, and transfer printing can be adopted. The formed alignment film composition layer can be irradiated with light, heated, cooled, or dried as needed, thereby changing the film quality of the layer. Typically, the following process is carried out: after removing volatile substances such as solvents contained in the alignment film composition by drying, a hard film is formed by heating or light irradiation.

[0108] A process for imparting a patterned alignment restraining force to the alignment film composition layer can also be carried out by known methods. As described above, in the case of using a photo-alignment material, a patterned alignment restraining force is imparted by irradiation with a polarized light pattern. Using Figure 1 , an example of the pattern of the alignment restraining force imparted by irradiation with a polarized pattern will be described. Figure 1 It is a diagram schematically showing a birefringent layer having a liquid crystal alignment pattern designed to exhibit the function of a lens. Figure 1 The birefringent layer 12 shown has a functional region 20 in a part of the plane. The liquid crystal alignment pattern 10 is formed in the rectangular functional region 20 so as to include the center 50 of the liquid crystal alignment pattern 10. In the functional region 20, in each direction of A1, A2, A 3- ... radially outward from the center 50, there is a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound 40 continuously rotates and changes. In the illustrated example, a rod-shaped liquid crystal compound is exemplified as the liquid crystal compound 40, and therefore the orientation of the long axis direction of the liquid crystal compound 40 is the orientation of the optical axis.

[0109] As a method of polarized light irradiation as a method for forming an alignment film having a patterned alignment restraining force for aligning a liquid crystal compound on such a liquid crystal alignment pattern, various methods can be used. As examples, the methods described in Japanese Unexamined Patent Application Publication No. 2014-016632, US Patent Publication No. US2020 / 0025987, etc. can be exemplified.

[0110] As a process for forming a predetermined alignment state by applying a liquid crystal composition onto the obtained alignment film, methods such as coating, flash evaporation coating, and transfer printing can be adopted. Regarding the coating of the liquid crystal composition, printing methods such as inkjet and roll printing, and all known methods such as spin coating, bar coating, and spray coating that can uniformly coat a liquid on a sheet can be used. In order to form an alignment state, the phase change of the isotropic layer and the liquid crystal layer can be caused by controlling the temperature of the film of the liquid crystal composition provided, thereby promoting alignment formation.

[0111] As a process for fixing the alignment of a liquid crystal composition, for example, in the case of using a polymerizable liquid crystal composition, it can be carried out by applying light or heat according to the type of polymerizable group and the polymerization initiator used. Also, in the case of using a side-chain type polymer liquid crystal, the alignment can sometimes be fixed by cooling.

[0112] In addition, for the activation of the surface of the alignment film support and / or the alignment film, surface treatments such as plasma treatment and corona treatment, and rinsing with a solvent can be performed. Also, in the case of peeling off and removing the alignment film support from the birefringent layer, it can be reused by reapplying the alignment film composition or the liquid crystal composition to the removed alignment film support and the alignment film.

[0113] (Metasurface material)

[0114] As a metasurface material that can be used as a birefringent material and its forming method, for example, the materials described in Japanese Patent Publication No. 2022-519015 and Japanese Patent Publication No. 2021-501363 can be used.

[0115] {Substrate}

[0116] If necessary, the birefringent layer can be provided on a substrate. The substrate can support the birefringent layer to make it self-supporting and improve the operability. As the material for the substrate, a flexible film made of resins such as triacetyl cellulose (TAC), polyethylene terephthalate (PET), polycarbonate, polyvinyl chloride, acrylic acid, and polyolefin is preferred. The thickness is not particularly limited, and it is only necessary to appropriately set the range with preferable processability. It is preferably 10 to 100 μm, more preferably 15 to 80 μm, and further preferably 18 to 65 μm.

[0117] In order to reduce the influence of the substrate on the light acting on the diffractive optical element, the total light transmittance of the substrate is preferably 80% or more, more preferably 90% or more, and particularly preferably 92% or more. For the same reason, the internal haze of the substrate is preferably 0.01 to 0.5, more preferably 0.02 to 0.2, and particularly preferably 0.03 to 0.1.

[0118] When the birefringent layer has polarization selectivity, in order to reduce the influence on the incident polarized light, the in-plane retardation Re(550) of the substrate is preferably 0 to 20 nm, particularly preferably in the range of 1 to 10 nm. Or, when the light emitted from the birefringent layer is polarized light and is emitted from the birefringent layer toward the substrate side, for the purpose of converting the emitted polarized light, the substrate can exhibit the characteristics of a λ / 4 plate or a λ / 2 plate.

[0119] Particularly when the birefringent layer acts in the near-infrared region, it is preferred that the substrate also has transmittance in the near-infrared region.

[0120] {Other functional layers}

[0121] The diffractive optical element can include other functional layers as needed. As such functional layers, there are exemplified a reflective layer, an antireflection layer, a refractive index matching layer, a hard coat layer, a birefringent layer, a polarization functional layer, a microlens array layer, a prism layer, a lens array layer, a color filter layer, a coloring layer, a fluorescent layer, etc. These layers and the birefringent layer can be directly laminated or laminated via an adhesive bonding layer.

[0122] {Mark}

[0123] The diffractive optical element included in the present invention has at least one mark on the surface on the side where the protective film is provided, based on the modification of the physical properties and the change in shape of the layers constituting the diffractive optical element.

[0124] The layers constituting the diffractive optical element mentioned here include the above-mentioned birefringent layer, the layers exemplified as the base material and other functional layers included in the diffractive optical element, and the adhesive bonding layer.

[0125] The change in physical properties mentioned here refers to the change induced by the irradiation of laser, and can be, for example, absorption spectral characteristics such as coloring, fluorescence characteristics, refractive index, refractive index anisotropy, wavelength dispersion of refractive index, haze, two-photon absorption characteristics, reflection characteristics. From the aspect of being able to recognize the mark by an imaging element or vision, the change in absorption spectral characteristics such as coloring, refractive index, refractive index anisotropy, haze, and reflection characteristics is preferred. Especially from the aspect of visual recognition or visual recognition by an imaging element for visible light, the change in absorption spectral characteristics such as coloring, haze, and reflection characteristics is particularly preferred.

[0126] Moreover, the change in shape can be obtained by the following method: inducing expansion, contraction or material movement of the irradiated part by the irradiation of laser, thereby generating small voids near the surface of fine irregularities or layers. Through the generation of structural birefringence, diffraction, refraction, reflection, and scattering based on such fine structures, the irradiated part can be detected as an optical mark.

[0127] These changes can occur in the state where the protective film is laminated. In this case, by being clamped between the protective film and the diffractive optical element, the generation of particles and / or flying objects from the mark part is completely suppressed. And even after removing the protective film, it can remain on the diffractive optical element.

[0128] Specific examples of the marking method will be described later.

[0129] In order to be able to engrave a mark, it is preferable that at least any one of the birefringent layer, the substrate, the layers exemplified as other functional layers included in the diffractive optical element, and the adhesive layer has a light absorption characteristic with respect to the wavelength of the irradiated laser. In particular, it is preferable that the birefringent layer has a light absorption characteristic with respect to the wavelength of the irradiated laser. When the diffractive optical element is used as a functional element in the near-infrared region or the visible region, it is preferable that there is no loss due to light absorption from the near-infrared region to the visible region. Therefore, the laser is preferably an ultraviolet laser.

[0130] More specifically, at a wavelength of 355 nm, the light transmittance of the diffractive optical element is preferably in the range of 1 to 50%, more preferably 1 to 40%, and particularly preferably 1 to 30%. By being below the upper limit, it is possible to engrave a mark with practical irradiation energy and irradiation time, and by being above the lower limit, it is easy to control the region where physical property changes and / or deformation occur. In particular, the ratio of the light transmittance of the birefringent layer at a wavelength of 355 nm to the light transmittance of the diffractive optical element at a wavelength of 355 nm is preferably 50% or less, more preferably 25% or less, and particularly preferably in the range of 10 to 1%.

[0131] The shape of the mark is not particularly limited, and the shape can be selected according to the purpose. For example, if it is for imparting traceability, a barcode, a two-dimensional code, characters, etc. can be formed as the mark. And as long as it is a mark (so-called alignment mark) for cutting and / or alignment of placement, it can be a line segment, a curve, and various figures arbitrarily formed by line segments and curves, such as figures like a circle, an ellipse, a triangle, etc., marks like an arrow, a cross mark, etc.

[0132] <Protective film>

[0133] The protective film included in the present invention is laminated on at least one surface side of the diffractive optical element.

[0134] The lamination mentioned here can be laminated in direct contact with the diffractive optical element, and can also be laminated via a weak adhesive layer or the like.

[0135] As a protective film, it preferably has the functions of preventing particles, flying objects, etc. from adhering to the surface of the diffractive optical element, and preventing deformation, damage, perforation, etc. caused by applying an external force to the diffractive optical element. The protective film can be configured to include a protective film substrate and, if necessary, a weak adhesive layer and other functional layers. In a state where the protective film is provided on the diffractive optical element, in order to form a mark on the surface of the diffractive optical element by an ultraviolet laser, the light transmittance of the protective film at a wavelength of 355 nm is preferably in the range of 90 to 100%, more preferably 95 to 100%, and particularly preferably 99 to 100%. Also, in order to control the diameter of the laser beam for marking, the haze of the protective film is preferably in the range of 0.01 to 1.0, more preferably in the range of 0.02 to 0.8, and particularly preferably in the range of 0.03 to 0.5.

[0136] (Protective film substrate)

[0137] The substrate contained in the protective film (referred to as the protective film substrate) can similarly be a substrate that can be used as the substrate of the diffractive optical element. Specifically, it is preferably a flexible film made of resins such as triacetyl cellulose (TAC), polyethylene terephthalate (PET), polycarbonate, polyvinyl chloride, acrylic acid, and polyolefin.

[0138] In order to easily capture the mark by an imaging element or the naked eye and reduce the reading error rate, the total light transmittance of the protective film substrate is preferably 80% or more, more preferably 90% or more, and particularly preferably 92% or more. For the same reason, the internal haze of the protective film substrate is preferably 0.01 to 0.5, more preferably 0.02 to 0.2, and particularly preferably 0.03 to 0.1.

[0139] In particular, when the mark is formed as a change in refractive index, refractive index anisotropy, or wavelength dispersion of refractive index, or when the laser uses beam diameter control based on polarization control, and in cases such as using a polarization camera or image contrast enhancement based on polarization separation as a detection mechanism, etc., therefore, the in-plane retardation Re(550) of the protective film substrate is preferably in the range of 0 to 20 nm, and particularly preferably in the range of 1 to 10 nm.

[0140] Also, the light transmittance of the protective film substrate at a wavelength of 355 nm is preferably in the range of 90 to 100%, more preferably 95 to 100%, and particularly preferably 99 to 100%.

[0141] (Weak adhesive layer and other layers)

[0142] As the weak adhesive layer, known materials can be used. The weak adhesive layer can be a material whose adhesion force can be changed by the action of light, heat, etc.

[0143] The weak adhesive layer preferably has a greater adhesion to the protective film substrate than to the diffractive optical film. The adhesion between the protective film substrate and the weak adhesive layer is preferably 0.5 N / 25 mm or more. Moreover, the adhesion between the weak adhesive layer and the surface of the diffractive optical element is preferably in the range of 0.02 to 0.5 N / 25 mm, more preferably in the range of 0.04 to 0.2 N / 25 mm. The adhesion can be measured in accordance with Japanese Industrial Standard JIS Z 0237:2009. Further, in the case where the weak adhesive layer is a material whose adhesion can be changed by the action of light, heat, etc., the above adhesion is measured in the changed state.

[0144] As another layer, an easy-bonding layer can be provided between the protective film substrate and the weak adhesive layer. Moreover, a hard coat layer, an antireflection layer, an anti-blocking layer, etc. can be provided on the surface of the protective film substrate on the side opposite to the weak adhesive layer side.

[0145] (Lamination of the protective film and the diffractive optical element)

[0146] Regarding the lamination of the diffractive optical element and the protective film, after they are formed respectively, they can be pressed together by known methods such as a method using a laminating device and a method using a roll laminating device to obtain the laminated structure. For example, as Figure 2 shown, the protective film 5 can be laminated on the surface of the birefringent layer 2 side of the diffractive optical element 4 including the birefringent layer 2 laminated on the substrate 3 via the adhesive layer 8.

[0147] Moreover, as Figure 3 shown, in order to further protect the surface of the substrate 3 on the side opposite to the birefringent layer 2, an additional protective film 5 can also be provided on the substrate 3 side. The lamination of the diffractive optical element 4 and the protective film 5 is preferably performed in a clean room environment.

[0148] [Laser engraving method]

[0149] In the laser engraving method of the diffractive optical film with a protective film of the present invention (hereinafter, also referred to as the laser engraving method of the present invention), the diffractive optical film with a protective film includes a protective film and a diffractive optical element, the diffractive optical element includes a birefringent layer having a local optical axis direction that changes in at least one direction along its surface, the protective film is laminated on at least one surface side of the diffractive optical element, and the laser engraving method of the diffractive optical film with a protective film includes: a process of irradiating the diffractive optical element with laser while maintaining the laminated state of the diffractive optical element and the protective film. By the laser irradiation, at least one of a change in physical properties and shape is induced in the layer constituting the diffractive optical element to form a marked area, and the laser transmits through the protective film.

[0150] Regarding the protective film and the diffractive optical element, as described above.

[0151] That is, in the laser engraving method of the present invention, a laser is irradiated onto a laminate of a protective film and a diffractive optical element before a mark is imparted, and at least one of changes in physical properties and shape on the surface of the layer constituting the diffractive optical element on the protective film side is induced to form a marked area.

[0152] Conventionally, laser marking is performed by melting or splashing a substance located on the path of an irradiation beam to form a mark. However, as described above, the melted material and / or scattered matter are not preferable for a diffractive optical element. In the laser engraving method of the present invention, since the laser transmits through the protective film, the protective film does not melt or scatter, and changes in physical properties and / or shape are induced in the layer constituting the diffractive optical element to form a marked area. Therefore, generation of particles, scattered matter, etc. is suppressed in the form of being enclosed by the protective film, and attachment of the generated particles, scattered matter, etc. to the functional area of the diffractive optical element can be prevented. Further, the surface of the diffractive optical element other than the marked area is covered with the protective film, so that attachment including particles and scattered matter other than the mark is also protected. Thus, a mark can be engraved on the diffractive optical element itself while maintaining the function of the diffractive optical element.

[0153] As the laser light source, any known laser light source can be used. As an example, YAG (yttrium aluminum garnet crystal) laser with a wavelength of 1,064 nm, each LD (laser diode) laser with wavelengths of 808 nm, 820 nm, 840 nm, 880 nm, 940 nm, green (second harmonic) laser with a wavelength of 532 nm, ultraviolet (third harmonic) laser with a wavelength of 355 nm, etc. can be used. From the aspect of excellent fineness of the mark, it is more preferable to use an ultraviolet laser (wavelength 355 nm). Further, since the diffractive optical element of the present invention is preferably transparent in the near-infrared region or visible region, engraving with ultraviolet laser is also preferable in this regard. An optical system for laser beam shaping can use known techniques.

[0154] When irradiating the laser beam, the diffractive optical film with a protective film is relatively moved with respect to the laser light source. As the moving means, the following methods can be exemplified: a method of fixing the diffractive optical film with a protective film and moving the laser light source by a robotic arm or the like; a method of fixing the laser light source and fixing the diffractive optical film with a protective film on a stage and relatively moving it; a method of moving both the laser light source and the diffractive optical film with a protective film; etc.

[0155] Regarding the formed mark, as described above.

[0156] Among them, in the process of irradiating the laser, the laser can be irradiated from the protective film side to the surface of the diffractive optical element in contact with the protective film (the interface between the diffractive optical element and the protective film), or the laser can be irradiated from the diffractive optical element side. However, from the viewpoint of suppressing damage to the diffractive optical element, etc., it is preferable to irradiate the laser L from the protective film side to the surface of the diffractive optical element in contact with the protective film to form a mark on the surface of the diffractive optical element in contact with the protective film (refer to Figure 5 ).

[0157] Moreover, when observed from the direction perpendicular to the main surface of the diffractive optical element, the formation position of the mark is preferably an edge region where no functional region is formed (refer to Figure 4 , Figure 6 etc.). That is, the mark is preferably formed at a position that does not overlap with the functional region when observed from the direction perpendicular to the main surface of the diffractive optical element.

[0158] In addition, multiple marks can be provided. This will be described in detail later.

[0159] In the manufacturing method of the diffractive optical film with a protective film, from the viewpoint of productivity, sometimes after forming a plurality of functional regions on the layer that becomes the birefringent layer, cutting is performed to manufacture a plurality of diffractive optical films with a protective film.

[0160] For example, in the case where the birefringent layer is a liquid crystal layer, after forming a coating film that becomes an optically oriented film on a long strip-shaped alignment film support, by irradiating the above-mentioned polarization light pattern to different positions in the plane of the coating film, a plurality of regions having a patterned alignment restricting force are formed in the plane of the alignment film. Then, a liquid crystal composition is coated on the alignment film, and heating, light irradiation, etc. are performed to form a liquid crystal layer (birefringent layer) having a plurality of functional regions. Then, by cutting according to each functional region, a plurality of diffractive optical films with a protective film can be manufactured.

[0161] In this case, after forming a liquid crystal layer (birefringent layer) having a plurality of functional regions and laminating the protective film, before cutting, the process of irradiating the laser is performed to form a mark. At this time, marks are formed in the edge regions near each of the plurality of functional regions corresponding to each functional region. That is, as in the example shown in Figure 6 , a mark 9a corresponding to the functional region 20a is formed near the functional region 20a, a mark 9b corresponding to the functional region 20b is formed near the functional region 20b, a mark 9c corresponding to the functional region 20c is formed near the functional region 20c, and a mark 9d corresponding to the functional region 20d is formed near the functional region 20d.

[0162] Then, cut according to each region including one functional region and the mark corresponding to the functional region, whereby a plurality of diffractive optical films with a protective film can be produced.

[0163] And, as Figure 6 shown, a plurality of marks can be formed for one functional region. In the illustrated example, three marks are formed for one functional region.

[0164] In the case of forming a plurality of marks for one functional region, the plurality of marks can be the same mark or different marks. And, in the case where the mark is for the purpose of imparting traceability such as manufacturing conditions and quality information, that is, in the case where the mark includes the identification information of the diffractive optical film with a protective film, the plurality of marks can be different-shaped marks including the same identification information.

[0165] In the case of forming a plurality of marks for one functional region, at least one of the plurality of marks can be a mark including identification information, and at least one of the others can be a mark for positioning purposes.

[0166] And, in the case where the mark is a mark including identification information, the mark can be an identifiable identification mark (for example, characters, numbers, etc.) by itself, or a symbol (barcode, two-dimensional barcode, etc.) converted from the identification information.

[0167] And, in Figure 6 the example shown, it is assumed that four functional regions are two-dimensionally arranged in one layer, but it is not limited thereto, and there can also be two or three, or five or more functional regions. And the arrangement of the plurality of functional regions is not particularly limited. For example, the plurality of functional regions can be arranged in one direction.

[0168] [Method for identifying a diffractive optical film with a protective film]

[0169] Method for identifying a diffraction optical film with a protective film (hereinafter, also referred to as the identification method of the present invention) is a method for identifying a diffraction optical film with a protective film by imparting traceability information to the diffraction optical film with a protective film including a protective film and a diffraction optical element. This method successively includes the following processes: generating an inherent identification mark for a functional region having the diffraction effect of the diffraction optical element; imparting the generated identification mark or a symbol converted from the identification mark as a label to the diffraction optical film with a protective film; reading the imparted label; and comparing the identification mark obtained from the read label with the information stored in the traceability database. Among them, the process of imparting as a label to the diffraction optical film with a protective film is as follows: while maintaining the laminated state of the diffraction optical element and the protective film, irradiating the diffraction optical element with a laser to induce at least one of the physical property and shape changes of the layer constituting the diffraction optical element to form a marked area, and for one functional region, a plurality of marks are imparted separately from each other in the plane of the diffraction optical film with a protective film.

[0170] Regarding the protective film, diffraction optical element, label, and method of forming the label, etc., as described above.

[0171] As an example of the process using the label, the process for imparting traceability to the diffraction optical film with a protective film will be described.

[0172] First, a process of generating an inherent identification mark for the diffraction optical film with a protective film to which the label is imparted is performed. The generated identification mark can further undergo a process of being converted into a symbol such as a character string or a two-dimensional code through encoding.

[0173] Furthermore, a process of imparting the generated identification mark or a symbol converted from the identification mark as a label to the diffraction optical film with a protective film by the above-described engraving method is performed.

[0174] On the other hand, a process of obtaining information on the diffraction optical film with a protective film to be the object and storing it in the traceability database is performed. The method of forming the diffraction optical film with a protective film is as described above. As information related to traceability, examples include the manufacturing lot, storage history, processing history, temperature and humidity during the formation of each layer, various parameters related to formation, physical property information, shape information, presence or absence of defects, and information related to usability obtained by inspecting the diffraction optical film with a protective film.

[0175] Information such as physical property information, shape information, and presence or absence of defects can be obtained by inspecting the obtained diffraction optical film with a protective film.

[0176] As a specific example, a method for obtaining information on the presence or absence of defects in the film described in the embodiment (note: liquid crystal lens) of International Publication Gazette WO2023 / 101002 is used to illustrate an example of obtaining information on the presence or absence of defects in a diffraction optical film with a protective film.

[0177] As an inspection device, a device can be used that sequentially arranges a light source that emits inspection light, a first circular polarizer (first polarizer, first quarter-wave plate), a diffraction optical film with a protective film to be measured, a second circular polarizer (second quarter-wave plate, second polarizer), and a light detection device, and inspects based on the amount of light of the inspection light that reaches the light detection device. At this time, the circularly polarized light transmitted by the first circular polarizer and the circularly polarized light transmitted by the second circular polarizer are set to be circularly polarized lights in the same direction.

[0178] In a region where there are no defects and the film formation has been carried out normally, the circularly polarized light incident on the diffraction optical film with a protective film is converted into circularly polarized light with left-right inversion and exits from the diffraction optical film with a protective film and is incident on the second circular polarizer and absorbed, so the inspection light does not reach the light detection device. On the other hand, in the case of defects such as poor liquid crystal alignment and foreign substances, a part of the circularly polarized light of the inspection light passing through this part is not properly converted, so light including the incident circularly polarized light component exits from the diffraction optical film with a protective film and is incident on the second circular polarizer, so a part of the inspection light passes through the second circular polarizer and reaches the light detection device. Therefore, by measuring the amount of light of the inspection light in the light detection device, it is possible to obtain information on the presence or absence of defects in the diffraction optical film with a protective film as the object.

[0179] Moreover, in the above inspection device, the structure can be such that the circularly polarized light transmitted by the first circular polarizer and the circularly polarized light transmitted by the second circular polarizer are circularly polarized lights in opposite directions.

[0180] In this case, since the circularly polarized light transmitted through the first circular polarizer and the circularly polarized light transmitted through the second circular polarizer are in opposite directions, in the region where there are no defects and the film is formed normally, the circularly polarized light incident on the diffraction optical film with a protective film is converted into circularly polarized light with left-right reversal, exits from the diffraction optical film, and is incident on the second circular polarizer and transmitted. Therefore, inspection light with a sufficient amount of light corresponding to the amount of light emitted from the light source reaches the light detection device. On the other hand, in the case where there are defects such as poor liquid crystal alignment and foreign matter, a part of the circularly polarized light of the inspection light passing through this part is not properly converted. Therefore, it exits from the diffraction optical film with a protective film as light containing the incident circular polarization component and is incident on the second circular polarizer. As a result, a part of the light incident on the second circular polarizer is absorbed, and the amount of light reaching the light detection device is reduced compared to the region where there are no defects and the film is formed normally. Also, in the case where light is absorbed due to defects such as foreign matter, the amount of light reaching the light detection device is similarly reduced compared to the region where there are no defects and the film is formed normally. Regarding obtaining information on whether the diffraction optical film with a protective film as the object has defects from the detection amount of the inspection light in the light detection device, it is the same as above.

[0181] In addition, in the inspection, for the purpose of improving the detection accuracy in the light detection device, etc., other optical elements (deflection elements, polarization elements, etc.) can be further combined and used.

[0182] Furthermore, in the above description, it is assumed that the light transmitted through the diffraction optical film with a protective film is detected for inspection, but it is not limited to this. The light reflected by the diffraction optical film with a protective film can also be detected for inspection.

[0183] As the light source that emits the inspection light described above, a known light source device can be used. As an example, a point light source device such as an LED or a laser can be directly used, and it can also be a light source formed by combining a lens, a prism, an aperture, etc. with these point light sources into a beam shape. Also, a planar light source device formed by combining a diffusion plate with the above point light source, a cold cathode tube, etc., or a planar light emitting device such as an OLED can be used. From the aspect of being able to select a planar inspection range, it is preferable to use a planar light source device or a planar light emitting device as the light source.

[0184] The information on whether there are defects detected in this way, etc., is associated with an identification code and stored in a traceability database.

[0185] The traceability database is composed of a PC (Personal Computer), etc., associates information related to the traceability of the diffraction optical film with a protective film and the identification mark of this diffraction optical film with a protective film, and stores (saves) them.

[0186] The inspection of the diffractive optical film with a protective film may be performed before or after the process of imparting the marking.

[0187] Furthermore, as information related to traceability, information such as processing, mounting work, and storage history performed after the mark is engraved on the diffractive optical film with a protective film can be further added at any time and stored in the traceability database.

[0188] Then, a process is performed to associate the identification number with the information stored in the traceability database.

[0189] Finally, by reading the assigned mark and comparing the identification mark obtained from the read mark with the information stored in the traceability database, the traceability of the diffractive optical film with a protective film as the object can be ensured. The method for reading the assigned mark is not particularly limited, as long as the mark is photographed and read using an imaging device (imaging element).

[0190] Specifically, for example, Figure 6 As shown, when a plurality of functional areas are formed on a birefringent layer and cut to produce a plurality of diffractive optical films with protective films, before cutting, the above-mentioned defect inspection is performed in each functional area, and the information on the presence or absence of defects in each functional area is associated with the identification mark and stored in the traceability database. After cutting, the mark of each diffractive optical film with protective film is read and checked with the traceability database, so that the information on the presence or absence of defects in the diffractive optical film with protective film can be obtained. Thus, for example, unqualified products (defective products) and qualified products can be distinguished.

[0191] When performing the process of reading the applied mark, it is preferable to further include a measure for reducing the error rate of reading when reading is performed while conveying the diffractive optical film with the protective film.

[0192] An example of a measure for reducing the reading error rate will be described one by one for each of the above processes.

[0193] As a preferred measure in the process of adding the generated identification mark or the symbol converted from the identification mark as a mark to the diffractive optical film, the size of the unit pixel constituting the mark is set to be relatively larger than the pixel size of the imaging element used in the reading process. In this way, the image information of the mark can be obtained with sufficient resolution even during transportation, thereby reducing the reading error rate.

[0194] Specifically, it is preferable that the size of a unit pixel constituting the mark be set to 9 times or more the minimum detectable pixel size of the imaging element.

[0195] Further, for example, in the case of using a two-dimensional code, it is preferable that the size of one pixel constituting the bar code is 0.2 mm square or more, more preferably 0.3 mm square or more, and particularly preferably 0.5 cm square or more. There is no particular limitation on the upper limit, but from the viewpoint of ensuring the amount of information that can be carried by each mark, it is preferably 2 mm square or less, and more preferably 1.5 mm square or less.

[0196] Further, as another preferred measure in the process of attaching the generated identification mark or the symbol converted from the identification mark to the diffractive optical film as a mark, it is possible to attach a plurality of marks to the area range of the diffractive optical film with a protective film (that is, the area that becomes the diffractive optical film with a protective film after cutting) which is a unit for attaching traceability. At this time, by setting a plurality of the same marks, error correction can be performed in the reading process described later, or a plurality of marks can be set to be different from each other, and information can be carried and error correction can be performed by complementing each other among the plurality of marks. When setting a plurality of marks, it is preferably 2 or more, and more preferably 3 or more, with respect to the area range of the film which is a unit for attaching traceability.

[0197] In the case of setting a plurality of marks, a series of marks can be dispersedly set on an imaginary straight line set with respect to the area range of the film which is a unit for attaching traceability on the diffractive optical film with a protective film, and also can be dispersedly set in a two-dimensional direction. In the case of dispersedly setting on a straight line, from the aspect of reducing reading errors, it is preferable that the straight line is parallel to the conveying direction of the diffractive optical film with a protective film when reading the marks. And this virtual straight line has a width of 2 mm, for example, and as long as it is configured such that any position of the mark passes through this straight line. That is, the plurality of marks are not limited to the marks strictly set on a straight line.

[0198] In the process of reading the attached marks, for example, in the case of using an imaging element as a reading device to obtain the marks as image information, it is preferable to use a plurality of imaging elements in the reading process so as to set the relative positions of the imaging elements and the conveying device such that each mark passes through the imaging range of each imaging element. That is, in the process of reading the marks, it is preferable to use a plurality of imaging elements arranged in parallel with the conveying direction of the diffractive optical film with a protective film, and each mark is read by a plurality of imaging elements, and one mark is read multiple times. Here, the multiple times are preferably 2 or more, and more preferably 3 or more.

[0199] Use Figure 4 , an example of the preferred arrangement method and reading process of the marks will be described. In addition, it should be noted that the figures and the description conceptually illustrate the content of a preferred example.

[0200] To simplify the drawing, the diffractive optical film 1 with a protective film only shows the area range 21 of the film as a unit for imparting traceability. The actual diffractive optical film 1 with a protective film can be in a single-leaf shape, or can be in a long-strip shape in which a plurality of area ranges 21 are continuously or intermittently connected. The diffractive optical film 1 with a protective film is conveyed in the conveying direction 62. When the diffractive optical film 1 with a protective film is in a long-strip shape, it is preferable that the long-strip direction (not shown) is parallel to the conveying direction.

[0201] A plurality of (three in the illustrated example) marks 9 formed by the above structure are provided on the diffractive optical film 1 with a protective film. At this time, the plurality of marks 9 are arranged on the edge region 30 surrounding the functional region 20 in a direction parallel to the conveying direction 62.

[0202] The diffractive optical film 1 with a protective film is conveyed in the conveying direction 62 and is read by the reading device 60. At this time, a plurality of (three in the illustrated example) reading devices 60 are arranged side by side, and the arrangement direction 61 thereof is parallel to the film conveying direction 62. In this way, each of the marks 9 is read by each reading device 60, and each mark is read three times in total. Since there are three marks 9 with respect to the area range 21, a total of nine readings can be performed. For example, assuming that the reading error rate of each reading of the mark 9 by the reading device 60 is 50%, since nine readings can be performed on one area range 21, the error rate can be theoretically suppressed to less than 0.2%.

[0203] The area range 21 of the film as a unit for imparting traceability may include a pattern as shown in Figure 1 that is, only includes one functional region, or may be a so-called multi-faceted form including a plurality of functional regions. In the case of including a plurality, it can be used after being singulated by cutting or the like before being installed in the device. And, in the case of including a plurality, as traceability information, information on which functional region the defect is included in each of the included functional regions can be added.

[0204] And, as an example of the process using the mark, a process of using the mark as an alignment mark when mounting the diffractive optical film on a device is also described.

[0205] First, on the diffractive optical film with a protective film obtained in the above process, a process of detecting a reference point of the diffractive optical element is performed. The reference point mentioned here means that, when the diffractive optical film with a protective film has a symmetry point or a symmetry axis of physical properties, it can be detected by optical detection thereof, and, when positioning marks are previously provided on the alignment film, the substrate, etc., it can be detected based on the mark. For example, the diffractive optical film with a protective film has a shape as shown in Figure 1In the case of a diffractive optical film having a birefringent layer with a functional region that functions as a liquid crystal lens, the center of the liquid crystal lens can be said to be the symmetry point of the physical properties of the diffractive optical film with a protective film.

[0206] Next, a process is performed in which a relative distance and an angle are set with respect to a reference point to determine the position for laser engraving. The relative distance and the angle can be determined in a rectangular coordinate system or in a polar coordinate system.

[0207] Next, a mark is imparted to the diffractive optical film with a protective film by the above-described laser engraving method.

[0208] Then, as needed, through processes such as cutting into a specified size and edge shaping, a process of mounting on a device is performed.

[0209] In the process of mounting on a device, a process of determining a reference point on the device side, a process of setting the mark imparted by the laser engraving method of the present invention and the reference point on the device side to a specified relative positional relationship, and a process of fixing the diffractive optical film with a protective film of the present invention to the device are performed. The protective film can be removed from the diffractive optical film with a protective film as needed during or after the mounting process.

[0210] The diffractive optical film with a protective film of the present invention can preferably be used as an optical component of an image display device constituting a head-mounted display such as an AR (Augmented Reality) glasses, VR glasses, MR (Mixed Reality) glasses, etc., and can preferably be used as an optical component in biosensors such as a photoplethysmography measurement device, a laser Doppler measurement device, a pulse oximeter, an eye tracking device, and measurement devices such as LIDAR. By associating the mark with traceability information, quality control becomes easy, and various high-quality devices can be stably manufactured. Also, by aligning the device and high precision through the mark, various high-quality devices can be stably manufactured.

[0211] Symbol Explanation

[0212] 1 - Diffractive optical film with a protective layer, 2 - Birefringent layer, 3 - Substrate, 4 - Diffractive optical element, 5 - Protective film, 6 - Protective film substrate, 7 - Weak adhesive layer, 8 - Adhesive layer, 9, 9a to 9d - Mark, 10 - Liquid crystal alignment pattern, 12 - Birefringent layer, 20, 20a to 20d - Functional region, 30 - Edge region, 40 - Liquid crystal compound, 50 - Center, 60 - Reading device (imaging element), 61 - Arrangement direction of the reading device, 62 - Conveying direction of the diffractive optical film with a protective film.

Claims

1. A diffractive optical film with a protective film, comprising a protective film and a diffractive optical element, wherein: The diffractive optical element includes a birefringent layer having a local optical axis direction that changes in at least one direction along the surface of the layer. The protective film is laminated on at least one surface side of the diffractive optical element, A surface of the diffractive optical element on the side where the protective film is provided has a mark based on at least one of a modification of physical properties and a change in shape of a layer constituting the diffractive optical element.

2. The diffractive optical film with a protective film according to claim 1, wherein: The diffractive optical element has a transmittance of 1 to 50% at a wavelength of 355 nm.

3. The diffractive optical film with a protective film according to claim 2, wherein: The birefringent layer includes a liquid crystal composition or a metasurface material.

4. The diffractive optical film with a protective film according to claim 3, wherein: The birefringent layer has a light transmittance of 1 to 50% at a wavelength of 355 nm.

5. The diffractive optical film with a protective film according to claim 4, wherein: The protective film has a light transmittance of 90 to 100% at a wavelength of 355 nm.

6. A laser engraving method for a diffractive optical film with a protective film, wherein the diffractive optical film with a protective film comprises a protective film and a diffractive optical element, The diffractive optical element includes a birefringent layer having a local optical axis direction that changes in at least one direction along the surface of the layer. The protective film is laminated on at least one surface side of the diffractive optical element, The laser engraving method of the diffractive optical film with a protective film includes: a process of irradiating the diffractive optical element with laser light while maintaining the stacked state of the diffractive optical element and the protective film, forming a marking region by inducing at least one of a change in physical properties and a change in shape in a layer constituting the diffractive optical element by laser irradiation, The laser light transmits through the protective film.

7. The laser marking method for a diffractive optical film with a protective film according to claim 6, wherein: The diffractive optical element has a transmittance of 1 to 50% at a wavelength of 355 nm.

8. The laser marking method for a diffractive optical film with a protective film according to claim 7, wherein: The birefringent layer includes a liquid crystal composition or a metasurface material.

9. The laser marking method for a diffractive optical film with a protective film according to claim 8, wherein: The birefringent layer has a light transmittance of 1 to 50% at a wavelength of 355 nm.

10. The laser marking method for a diffractive optical film with a protective film according to claim 9, wherein: The protective film has a light transmittance of 90 to 100% at a wavelength of 355 nm.

11. The laser marking method for a diffractive optical film with a protective film according to claim 6, wherein: In the process of irradiating the laser light, the laser light is irradiated toward the diffractive optical element from the protective film side.

12. A method for providing traceability information to a diffractive optical film with a protective film comprising a protective film and a diffractive optical element so as to identify the diffractive optical film with a protective film, the method comprising the following steps in sequence: A process for generating an inherent identification mark for a functional region having the diffraction effect of the diffraction optical element; A process of assigning the generated identification mark or a symbol converted from the identification mark as a label to the diffraction optical film with a protective film; A process of reading the assigned label; and A process of checking the identification mark obtained from the read label against information stored in a traceability database, wherein the process of assigning the label to the diffraction optical film with a protective film is a process of irradiating the diffraction optical element with a laser while maintaining the laminated state of the diffraction optical element and the protective film to induce at least one of changes in the physical properties and shape of the layers constituting the diffraction optical element to form a marked region; For one such functional region, a plurality of labels are assigned separately from each other within the plane of the diffraction optical film with a protective film.

13. The method according to claim 12, wherein, The process of reading the label is a process carried out while conveying the diffraction optical film with a protective film, wherein the plurality of labels are arranged on a straight line parallel to the conveying direction.

14. The method according to claim 13, wherein, In the process of reading the label, a plurality of imaging elements are used, and the plurality of imaging elements are arranged such that each of the labels passes through the imaging range of each of the imaging elements.

15. The method according to claim 14, wherein, The size of the unit pixel constituting the label is set to be 9 times or more the minimum pixel size detectable by the imaging element.

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