WO2023282063A1 - 光学表示媒体 - Google Patents
光学表示媒体 Download PDFInfo
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- WO2023282063A1 WO2023282063A1 PCT/JP2022/024956 JP2022024956W WO2023282063A1 WO 2023282063 A1 WO2023282063 A1 WO 2023282063A1 JP 2022024956 W JP2022024956 W JP 2022024956W WO 2023282063 A1 WO2023282063 A1 WO 2023282063A1
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- optical display
- display medium
- polarized light
- reflective polarizer
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
- B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
- B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
- B42D25/30—Identification or security features, e.g. for preventing forgery
- B42D25/36—Identification or security features, e.g. for preventing forgery comprising special materials
- B42D25/378—Special inks
- B42D25/391—Special inks absorbing or reflecting polarised light
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
- B32B7/02—Physical, chemical or physicochemical properties
- B32B7/023—Optical properties
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
- B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
- B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
- B42D25/30—Identification or security features, e.g. for preventing forgery
- B42D25/36—Identification or security features, e.g. for preventing forgery comprising special materials
- B42D25/364—Liquid crystals
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/20—Filters
- G02B5/22—Absorbing filters
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
Definitions
- the present invention relates to optical display media and articles that can be used for identification media, decoration media, or both, as well as methods for using optical display media.
- the identification medium is required to have anti-counterfeiting performance and identification function.
- the anti-counterfeiting performance of the identification medium referred to here is the performance that the identification medium cannot be easily duplicated by general techniques such as printing.
- the identification function of the identification medium is a function by which a genuine identification medium can be distinguished from a counterfeit identification medium forged by a general technique with high reliability by some means.
- Identification media often have a special structure that produces optical effects that cannot be seen in ordinary members.
- it can have an optical characteristic that a change in a special display state that cannot be obtained with a display medium manufactured by a general manufacturing technique can be observed due to a difference in observation mode.
- Such optical properties can also be used as properties that are excellent in appearance and exhibit design effects, apart from the function as an identification medium. Therefore, an optical display medium having the same configuration as the identification medium may be used as the identification medium and also used as the decoration medium, or an optical display medium having the same configuration as the identification medium may be used as the identification medium. In some cases, it is simply used as a decoration medium without being used.
- the identification medium that the part with the identification function is concealed, that is, the presence of the part with the identification function is not perceived by normal observation.
- the forger will not recognize the identification medium as an identification medium, but will only recognize it as a normal display medium. It does not conceive of itself to imitate the identification function of the identification medium. Therefore, an identification medium in which a part having an identification function is concealed has a low possibility of being manufactured as a forgery that mimics the identification function.
- identification media In the case of many identification media, the authenticity of identification media is determined by observation through a special viewer that includes an optical member such as a circular polarizer or linear polarizer (for example, Patent Documents 1 to 3). On the other hand, there are identification media that can be determined by observation with the naked eye without requiring a special viewer. There is a medium (for example, Patent Document 4).
- JP 2010-221650 A Japanese Patent Application Laid-Open No. 2010-113249 (corresponding publication: US Patent Application Publication No. 2010/119738) WO2005/059597 Japanese Patent No. 5915838
- the authenticity determination of the identification media of Patent Documents 1 and 2 requires a special operation of bringing the determination tool close to the identification medium. Therefore, for those identification media, the authenticity of the article in the state of normal use (state of being displayed as a product, state of being held in normal use by a user other than the identifier, etc.) , cannot be easily determined without a special operation. For example, it is not possible to determine the authenticity of an article in normal use by a simple observation such as observing it for a short period of time from a remote position.
- an object of the present invention is to provide a high anti-counterfeit performance, an identification function that can be used by simple observation without using a special judgment tool, and a confidentiality of the part having the identification function.
- An object of the present invention is to provide a high quality optical display medium.
- the present inventors have found that general equipment such as polarized sunglasses and a device that emits polarized light such as a liquid crystal display device can be used in a general manner.
- the identification function can be used by using such a general instrument in a simple observation mode that does not involve special operations. , it is possible to obtain good anti-counterfeiting performance, it is possible to improve the confidentiality of the part having the identification function, and it is possible to improve the degree of design freedom of the medium, and completed the present invention. . That is, the present invention includes the following.
- An optical display medium having a display surface, a reflective polarizer layer provided in a reflective region RL that is part or all of the display surface; a birefringent layer provided in a region RA that is provided on the viewer side of the reflective polarizer layer and that occupies a part of the reflective region RL ;
- the reflective polarizer layer is a layer that reflects incident light as circularly polarized light or linearly polarized light
- the optical display medium, wherein the birefringent layer includes a flake-shaped birefringent material and exhibits optical characteristics as a C-plate.
- the optical display medium of [1] wherein the reflective polarizer layer is a layer of a material having cholesteric regularity.
- the color difference ⁇ E * (N) between the region RA and the region RB of the reflective region RL other than the region RA is extremely The optical display medium according to any one of [1] to [3], which is 1 or less when observed at an angle of 0°.
- the color difference ⁇ E * ( P ) between the region RA and the region RB of the reflective region RL other than the region RA is the polar angle
- the optical display medium according to any one of [1] to [5], which is 3 or more in any one of observations in all directions of 20 to 70° and azimuth angles of 0 to 360°.
- the forgery prevention performance is high, the identification function can be used by simple observation without using a special determination tool, and the location having the identification function is highly confidential.
- An optical display medium is provided.
- FIG. 1 is a top view schematically showing an example of the optical display medium of the present invention.
- FIG. 2 is a vertical cross-sectional view of the optical display medium shown in FIG. 1 taken along line L1.
- (meth)acrylic group is a term that includes “acrylic group”, “methacrylic group” and combinations thereof. Expressions such as “(thio)epoxy group” and “iso(thio)cyanate group” are also terms having the same meaning.
- the NZ coefficient is a value represented by (nx-nz)/(nx-ny) unless otherwise specified.
- nx, ny, and nz are the principal refractive indices of the layers, and nx represents the refractive index in the direction (in-plane direction) perpendicular to the thickness direction of the layer, which gives the maximum refractive index.
- ny represents the refractive index in the in-plane direction and in the direction orthogonal to the nx direction.
- nz represents the refractive index in the thickness direction.
- d represents the thickness of the layer.
- the measurement wavelength is 550 nm unless otherwise stated.
- the oblique retardation is also described.
- the in-plane retardation Re is usually measured by optical observation from the direction of the polar angle of 0 ° of the film, while the retardation in the oblique direction is changed to the oblique direction with a polar angle of more than 0 °. It corresponds to the value of the apparent in-plane retardation when observing and assuming that the plane perpendicular to the observation direction is the plane of the film.
- the oblique phase difference observed from a certain polar angle may be indicated by adding the numerical value of the polar angle.
- an oblique phase difference observed from a direction with a polar angle of 45° may be indicated as an oblique 45° phase difference, or Re 45 , for example.
- the in-plane retardation observed from a polar angle of 0° is sometimes indicated as Re 0 , for example.
- nx' is calculated by the following formula (e2).
- the direction of the slow axis of a certain layer refers to the direction of the slow axis in the in-plane direction.
- the definition is as described above.
- the optical display medium is placed horizontally with the display surface facing upward. Therefore, the side from which the optical display medium is viewed is sometimes simply called the "upper” side, and the opposite side is sometimes called the “lower” side.
- the surface closer to the display surface of the optical display medium may be referred to as the "upper” surface.
- the direction perpendicular to the "up” and “down” directions may be referred to as the "horizontal" direction.
- the color difference indicated by the symbol ⁇ E * is the color difference ( ⁇ E * ab ) in the CIE 1976 (L * , a * , b * ) color space and is calculated using the D65 illuminant as the white point. be.
- the optical display medium of the present invention is - Unpolarized light is made incident on an optical display medium, and reflected light from the optical display medium is observed in a normal manner (a manner that does not involve special selection of polarized light components).
- - Make unpolarized light incident on an optical display medium, and selectively observe a polarized component of light reflected from the optical display medium.
- - Polarized light is incident on an optical display medium, and reflected light from the optical display medium is observed in a normal manner. It can be observed in such an observation mode.
- the first of the three aspects is “non-polarized observation”
- the second is “non-polarized-polarized observation”
- the third is It is sometimes called “polarized-nonpolarized observation”.
- observation with polarized light As a general term for the second and third methods, they are sometimes referred to as "observation with polarized light”.
- the optical display medium of the present invention has a display surface, a reflective polarizer layer provided in a reflective region RL that is a part or all of the display surface, and a reflective polarizer layer provided on the viewer side of the reflective polarizer layer. and a birefringent layer provided in a region RA that occupies part of the region RL .
- FIG. 1 is a top view schematically showing an example of the optical display medium of the present invention
- FIG. 2 is a vertical cross-sectional view of the optical display medium shown in FIG. 1 taken along line L1.
- the optical display medium 100 includes a substrate 101, a reflective polarizer layer 102 provided in contact with the upper surface 101U of the substrate 101, and a A birefringent layer 111 is provided in contact therewith.
- the top surface of the optical display medium 100 is the area entirely occupied by the reflective polarizer layer 102 and thus the reflective area RL .
- the birefringent layer 111 occupies only a partial area RA of the reflective area RL .
- the optical display medium 100 further comprises an isotropic layer 112 as an optional component.
- the isotropic layer 112 occupies a region RB other than the region RA in the reflective region RL .
- the birefringent layer 111 and the isotropic layer 112 are arranged such that their side surfaces are in contact with each other at the boundary 119 .
- the birefringent layer is preferably arranged so that all or part of the edge side surfaces are in contact with the edge side surfaces of the isotropic layer, from the viewpoint of enhancing the confidentiality of the identification function.
- the birefringent layer and the isotropic layer may be separated from each other, but from the viewpoint of enhancing the confidentiality of the identification function, the distance when they are separated is preferably small.
- Such a distance is usually 200 ⁇ m or less, preferably 100 ⁇ m or less, more preferably 50 ⁇ m or less, even more preferably 20 ⁇ m or less, particularly preferably 10 ⁇ m or less.
- a region RA occupied by the birefringent layer 111 and a region RB other than the birefringent layer 111 are provided in the reflective region RL to form a latent image.
- a latent image is an image that is not observed by normal non-polarized light observation, but is observed only by specific observation of the optical display medium.
- the floral pattern defined by the area RA can function as a latent image in a particular observation.
- a reflective polarizer layer is a layer that reflects incident light as circularly or linearly polarized light.
- a reflective polarizer layer transmits some or all of the polarization components of incident light at certain wavelengths and reflects some or all of other polarization components.
- a reflective circular polarizer or a reflective linear polarizer can be used as the reflective polarizer layer.
- a reflective circular polarizer is an optical element that transmits one of a right-handed circularly polarized component and a left-handed circularly polarized component of incident light of a certain wavelength and reflects the other one.
- a reflective linear polarizer is an optical element that transmits one of a certain linearly polarized light component and a linearly polarized light component perpendicular to that component of incident light of a certain wavelength, and reflects the other one.
- the reflective polarizer layer is preferably a reflective circular polarizer.
- an identification function that is less dependent on the direction of the transmission axis of the linear polarizer will be developed.
- a reflective circular polarizer is used as the reflective polarizer layer 102.
- FIG. A more specific example of the material constituting the reflective circular polarizer will be described separately later.
- a birefringent layer is a layer exhibiting optical properties as a C plate.
- a C-plate is a positive C-plate or a negative C-plate.
- a negative C plate is preferable as the C plate because a high-quality negative C plate with a high degree of freedom in design can be easily manufactured using a liquid crystalline compound that can also be used as a material for a reflective circular polarizer. .
- a layer of material with cholesteric ordering some or all of whose reflection bands are outside the visible region, a layer that can function as a negative C-plate can be readily obtained.
- the in-plane retardation Re is also small, so the relationship between nx and ny in the C plate can be defined by the in-plane retardation Re.
- the in-plane retardation Re(A) 0 of the birefringent layer in the present application is preferably 30 nm or less, more preferably 15 nm or less, and ideally 0 nm.
- nz-nx when the birefringent layer is a positive C plate and the value of ny-nz when the birefringent layer is a negative C plate can be appropriately adjusted within a range in which a desired oblique retardation is obtained. .
- each of these values is preferably 0.010 or more, more preferably 0.015 or more, and is preferably 0.30 or less, more preferably 0.25 or less.
- the birefringent layer is a C plate, its diagonal retardation is larger than the front in-plane retardation.
- the oblique retardation Re(A) 45 of the birefringent layer measured from any azimuth angle with a polar angle of 45° preferably satisfies the following formula (e1).
- the oblique retardation Re(A) 45 of the birefringent layer measured from all azimuth angles with a polar angle of 45° is within the following preferred range.
- At least part of Re(A) 20-70 (that is, measured values of in-plane retardation Re(A) measured from all azimuth angles within the polar angle range of 20 to 70°) is 107. 5 nm or more and can be 167.5 nm or less. If Re(A) 20-70 satisfies such requirements, the birefringent layer is a ⁇ /4 waveplate at 550 nm, the center of the visible light wavelength, when viewed from any direction in the range of 20-70° polar angles. can function as
- the lower limit of Re 20-70 is more preferably 120 nm or more and more preferably 155 nm or less. Since the birefringent layer is a C plate and Re(A) 0 is a small value such as 30 nm or less, if Re(A) 20-70 satisfies the formula (e1) at a certain azimuth angle, all In azimuth, Re(A) 20-70 satisfies equation (e1).
- the in-plane retardation Re(A) 45 of the birefringent layer measured from any azimuth angle with a polar angle of 45° is preferably 70 nm or more, while preferably 700 nm or less.
- the birefringent layer functions as a ⁇ /4 wavelength plate at 550 nm, the center of the visible light wavelength, when viewed from any direction within the range of polar angles of 20 to 70°. can function as
- the birefringent layer is a layer containing flaky birefringent material.
- a flake birefringent material is a flake shaped particle of a film that can function as a C-plate. Such flake-shaped particles can be obtained by preparing a film that can function as a C-plate and crushing it into flat-shaped particles. A more specific example of the material forming the C plate will be described separately later.
- the optical display medium of the present invention may consist only of a birefringent layer and a reflective polarizer layer, but may also comprise optional constituents.
- optional components include isotropic layers.
- An isotropic layer is a layer that is optically isotropic, that is, a layer that has no or sufficiently small in-plane retardation and thickness retardation.
- the in-plane retardation Re(B) 0 of the isotropic layer measured from the 0° polar angle direction is preferably 30 nm or less, more preferably 15 nm or less, and ideally 0 nm.
- the thickness direction retardation Rth(B) of the isotropic layer is preferably -30 nm or more, more preferably -15 nm or more, and is preferably 30 nm or less, more preferably 15 nm or less.
- the oblique 45° retardation Re(B) 45 of the isotropic layer is preferably 30 nm or less, more preferably 15 nm or less, and ideally 0 nm.
- the isotropic layer can be provided in a region RB other than the region RA in the reflective region RL.
- the isotropic layer By providing the isotropic layer in the region RB, it is possible to reduce the difference between the appearance of the region RA and the appearance of the region RB when observed with non - polarized light, and to enhance the confidentiality of the identification function.
- the isotropic layer like the isotropic layer 112 in the examples of FIGS. preferable.
- Examples of other optional components include light absorbing layers, substrate layers, decorative members, and mounting members.
- a light absorption layer is a layer that absorbs incident light.
- the light absorbing layer can be a black layer.
- the material of the light absorbing layer may be any material, and may be, for example, a black-colored film.
- the light-absorbing layer may be provided on the back side of the reflective polarizer layer, ie, on the opposite side of the reflective polarizer layer to the viewing side.
- the reflective polarizer layer is either a reflective circular polarizer or a reflective linear polarizer, much of the incident light that is not reflected is transmitted.
- a light absorbing layer is provided on the back side of the reflective polarizer layer, the transmitted light is absorbed, and as a result, the effect of the reflected light can be visually recognized more clearly.
- the optical display medium is a see-through object. It is possible to obtain a design effect.
- a substrate layer may be provided on the back side of the reflective polarizer layer, such as substrate 101 in the examples of FIGS.
- the substrate layer may be a layer that also serves as a light absorption layer, but a substrate layer may be provided separately from the light absorption layer.
- the decorative member is a member that does not contribute to the development of the identification function of the optical display medium, but can contribute to the design effect of the optical display medium.
- An example of the decorative member is a piece having a metallic luster called lame. Such strips may, for example, be provided alongside strips of the reflective polarizer layer or may be provided overlying the top surface of the reflective polarizer layer.
- Another example of the decorative member is a transparent member such as a cover glass that covers the display surface of the optical display medium, and a member such as a tray or the like for decorating or protecting the periphery of the optical display medium. mentioned.
- a mounting member is a member that functions when an optical display medium is mounted on an article.
- a part or the whole of the mounting member may also serve as a decorative member.
- attachment members include members such as rings, clasps, hooks, wires, chains, and strings extending from the periphery of the optical display medium, and cases such as trays that also serve as decorative members.
- the mounting member may be directly attached to the reflective polarizer layer and/or the patterned retardation layer, which are essential components of the optical display medium, or may be bonded via any other member.
- the connection with the mounting member may be any of adhesion by adhesive, adhesion by welding, mechanical connection such as screwing or ligature, and the like.
- the optical display medium preferably has a small color difference ⁇ E * (N) between the regions RA and RB when viewed with non - polarized light.
- the color difference ⁇ E * (N) when observed with non-polarized light is preferably 1 or less, more preferably 0.7 or less, and ideally 0 when observed at a polar angle of 0°.
- ⁇ E * (N) is preferably 1 or less, more preferably 0.7 or less in all observations in all directions with a polar angle of 20 to 70° and an azimuth angle of 0 to 360°.
- ⁇ E * (N) satisfies the above numerical range requirements in all observations in all directions with a polar angle of 20 to 70° and an azimuth angle of 0 to 360°. Having such a small ⁇ E * (N) can enhance the confidentiality of the identification function of the optical display medium in normal observation with non-polarized light.
- the color difference ⁇ E * ( P ) between the regions RA and RB when observed with polarized light is small when observed at a polar angle of 0° and large when observed at a polar angle exceeding 0°.
- the color difference ⁇ E * (P) is preferably 1 or less, more preferably 0.7 or less, and ideally 0 when observed at a polar angle of 0°.
- the color difference ⁇ E * (P) is preferably 3 or more, more preferably 7 or more, in any one of observations in all directions with a polar angle of 20 to 70° and an azimuth angle of 0 to 360°.
- the color difference ⁇ E * (P) is preferably 3 or more, more preferably 7 or more, in all observations in all directions with a polar angle of 20 to 70° and an azimuth angle of 0 to 360°. be.
- the maximum value of the color difference ⁇ E * (P) in observation in all directions with a polar angle of 20 to 70° and an azimuth angle of 0 to 360° is not particularly limited, but can be, for example, 60 or less, or 40 or less.
- the birefringent layer is a C plate and Re(A) 0 is a small value such as 30 nm or less
- the color difference ⁇ E * (P) is equal to or greater than the lower limit at one azimuth angle, it is usually , the color difference ⁇ E * (P) is equal to or greater than the lower limit.
- the color difference ⁇ E * (P) can take the maximum value at a certain angle within the polar angle range of 20 to 70°.
- the polar angle at which the color difference ⁇ E * (P) is maximized is more preferably 30 to 60°.
- the optical display medium can exhibit an identification function when observed with polarized light. , and such identification features are available by simple observation. Specifically, when an observer wearing polarized sunglasses observes the authenticity of an optical display medium attached to an article in normal use from different angles, the change in the color of the latent image. It is possible to make a judgment by simple observation such as examining the presence or absence of a ray and the difference in brightness from the surroundings.
- the authenticity of the optical display medium attached to the article in the state of normal use such as the state of being displayed as a product and the state of being held by a user other than the identifier in a normal use manner, It can be determined by a simple observation such as an unobstructed glance at the state of use.
- Examples of light incident on the optical display medium include non-polarized light and polarized light, and examples of polarized light include linearly polarized light, circularly polarized light, and elliptically polarized light.
- non-polarized light-polarized light observation can be performed by selectively observing the linearly polarized light component or the circularly polarized light component of the reflected light.
- incident light When the incident light is non-polarized, general ambient light such as sunlight and indoor lighting can be used as such non-polarized light.
- linearly polarized light obtained by transmitting non-polarized light through a linear polarizer can be used as such linearly polarized light.
- the apparatus for supplying linearly polarized light may be a dedicated item for use with the optical display medium of the present invention, or may be a combination of a general light source and a general linear polarizer used for other applications. good.
- a device in which a light source and a linear polarizer are combined, which is commonly used for other purposes, may be used.
- non-polarized light obtained by transmitting non-polarized light through a circular polarizer can be used as such circularly polarized light.
- the apparatus for supplying circularly polarized light may be a dedicated item for use with the optical display medium of the present invention, or may be a combination of a general light source and a general circular polarizer used for other applications. good.
- a device in which a light source and a circular polarizer are combined, which is commonly used for other purposes, may be used.
- elliptically polarized light obtained by transmitting unpolarized light through an appropriate optical element can be used as such elliptically polarized light.
- the device for supplying elliptically polarized light may be dedicated to the use of the optical display medium of the present invention, but may be a combination of a common light source and a common linear or circular polarizer used for other applications. may be used. Alternatively, a device in which a light source and a linear polarizer or a circular polarizer are combined, which is commonly used for other purposes, may be used.
- many electronic devices with display screens such as personal computers and smartphones with general liquid crystal display screens, emit linearly polarized light as emitted light from the display screen. It can be used as a device for providing polarized light. More specifically, by operating the electronic device close to the optical display medium, the environment where the incidence of unpolarized ambient light is small and the light emitted from the electronic device is relatively large.
- An optical display medium can be positioned to achieve linear polarization delivery.
- some electronic devices with display screens such as personal computers and smartphones with general liquid crystal display screens, emit circularly polarized light as emitted light from the display screen.
- the device can be used as a device for providing circularly polarized light. More specifically, by operating the electronic device close to the optical display medium, the environment where the incidence of unpolarized ambient light is small and the light emitted from the electronic device is relatively large.
- An optical display medium can be positioned to achieve the provision of circularly polarized light.
- a post-attached film may be attached for various purposes to the display screen of the electronic device that emits the above-mentioned linearly polarized light or circularly polarized light.
- post-attached films include those that are laminated for various purposes such as protection of the display screen, adjustment of the viewing angle of the display screen, and improvement of visibility when the display screen is observed through polarized sunglasses. is mentioned.
- Many of these films have some kind of retardation, and therefore can exhibit the function of converting linearly polarized light into circularly polarized light or elliptically polarized light, or converting circularly polarized light into linearly polarized light or elliptically polarized light.
- the provision of linear, circular, or other elliptically polarized light can also be achieved.
- the linear viewing polarizer and the circular viewing polarizer can usually be used in a state separated from the optical display medium.
- the lower limit of the separation distance can be appropriately adjusted according to the dimensions of the optical display medium and the linear polarizer for observation, and is usually 100 mm or more.
- the upper limit of the separation distance can be appropriately adjusted within the range in which the reflected light of the optical display medium can be observed, but it is usually 30 m or less.
- the observation linear polarizer used at a position spaced apart from the optical display medium may be a dedicated product for use with the optical display medium of the present invention, but a general linear polarizer used for other purposes may be used. It may be a polarizer.
- polarizer since many commercially available polarized sunglasses can function as linear polarizers, such commercially available polarized sunglasses may be used as linear viewing polarizers.
- viewing circular polarizers include circular polarizers constructed by combining a linear polarizer and a retardation film, and circular polarizers comprising a layer of cholesteric material (e.g., described in WO 2020/121791 that are used).
- the optical display medium 100 shown in FIGS. 1-2 wherein the reflective polarizer layer is a silver reflective circular polarizer (i.e., has a reflection band spanning the entire visible light range), and the substrate 101 is light absorbing.
- the reflective polarizer layer is a silver reflective circular polarizer (i.e., has a reflection band spanning the entire visible light range)
- the substrate 101 is light absorbing.
- the latent image is not observed either when the viewing direction is at a polar angle of 0° or when the polar angle is greater than 0°.
- the light passes through isotropic layer 112 and reaches reflective polarizer layer 102 .
- the reflective polarizer layer 102 is a reflective circular polarizer, it separates unpolarized light into right-handed circularly polarized light and left-handed circularly polarized light, reflecting one and transmitting the other.
- the transmitted circularly polarized light is absorbed by the substrate 101 .
- the reflected circularly polarized light is transmitted through the isotropic layer 112 again and emitted upward. Since the isotropic layer 112 is an isotropic layer, the phase difference of light passing through the isotropic layer 112 is It does not change, nor does the polarization state.
- the light passes through birefringent layer 111 and reaches reflective polarizer layer 102 .
- the reflective polarizer layer 102 is a reflective circular polarizer, it separates unpolarized light into right-handed circularly polarized light and left-handed circularly polarized light, reflecting one and transmitting the other.
- the transmitted circularly polarized light is absorbed by the substrate 101 .
- the reflected circularly polarized light is transmitted through the birefringent layer 111 again and emitted upward.
- the observation direction is a polar angle of 0°
- the observer observes the light emitted after the circularly polarized light passes through the birefringent layer 111 perpendicularly. Since the birefringent layer 111 is a C-plate, the phase difference of light passing through the birefringent layer 111 perpendicularly does not change before and after transmission, and the polarization state does not change either. Therefore, no latent image is observed between the area RA and the area RB , since the difference in appearance cannot be visually recognized.
- the birefringent layer 111 is a C plate, and functions as a layer having an oblique retardation with respect to obliquely transmitted light.
- the emitted light becomes elliptically polarized light or linearly polarized light, and the observer observes linearly polarized light particularly at a polar angle where the birefringent layer 111 functions as a ⁇ /4 wavelength plate.
- no difference in polarization state is visible.
- no latent image is observed between the area RA and the area RB , since the difference in appearance cannot be visually recognized.
- the latent image is not observed when the observation direction is at a polar angle of 0°, but is observed in a certain observation angle range with a polar angle greater than 0°.
- the light emitted from the optical display medium 100 is circularly polarized light as in the case of non-polarized observation.
- the linearly polarized light component along the transmission axis of the linear polarizer of the circularly polarized light is transmitted through the linear polarizer for observation and reaches the observer.
- the region RB is observed with a lower brightness compared to observation with non - polarized light.
- the isotropic layer 112 is an isotropic layer, and the phase difference of light passing through the isotropic layer 112 does not change before and after transmission, regardless of whether the observation direction has a polar angle of 0° or a polar angle of more than 0°. Since the polarization state also does not change, no significant change in appearance due to the change in polar angle is observed in the region RB . Further, even if the angular relation between the transmission axis direction of the observation linear polarizer and the optical display medium 100 changes, no significant change in appearance is observed.
- the light emitted from the optical display medium 100 has a polar angle of 0 as in the case of observation with unpolarized light.
- the angle is 0°
- the light becomes circularly polarized light
- the polar angle exceeds 0°
- the light becomes elliptically polarized light or linearly polarized light.
- the linearly polarized component of the emitted circularly polarized light along the transmission axis of the linear polarizer becomes the linearly polarized light for observation.
- the region RA is observed with a lower brightness compared to observation with non-polarized light.
- the polar angle is greater than 0°, the linearly polarized light component along the linear polarizer transmission axis of the emitted elliptically polarized light or linearly polarized light is transmitted through the linear polarizer for observation to the observer. reach.
- the appearance of the region RA greatly changes due to changes in the transmission axis direction of the observation linear polarizer and the angular relationship with the optical display medium 100 .
- the transmission axis of the observation linear polarizer and the apparent slow axis of the refraction layer are 45° or 135° from the observation direction.
- the brightness of the region RA is maximum or minimum. Due to such a change in appearance, the boundary between the refractive layer 111 and the isotropic layer 112 is clearly visible, and a latent image is observed.
- the latent image is not observed when the viewing direction is at a polar angle of 0°, but is observed in a certain viewing angle range with a polar angle greater than 0°.
- the circularly polarized light consists of only the right-handed circularly polarized light component or the left-handed circularly polarized light component. Since the isotropic layer 112 is an isotropic layer, the phase difference of light passing through the isotropic layer 112 is It does not change, nor does the polarization state.
- the viewing direction is greater than 0° in polar angle
- the light that is incident at a polar angle greater than 0° and is reflected by the reflective polarizer layer 102 and emitted is observed.
- linearly polarized light incident at a polar angle of more than 0° obliquely passes through the birefringent layer 111 and is converted into elliptically polarized light or circularly polarized light and reaches the reflective polarizer layer 102 .
- the reflective polarizer layer 102 further reflects only the right-handed circularly polarized light component or the left-handed circularly polarized light component.
- the amount of reflected circularly polarized light component will vary depending on the polarization state of the light reaching the reflective polarizer layer 102 , which is the direction of polarization of the incident linearly polarized light and the apparent slow axis of the birefringent layer 111 . Varies by relationship. Due to such a change in appearance, the boundary between the refractive layer 111 and the isotropic layer 112 is clearly visible, and a latent image is observed.
- the optical display medium can be determined to be authentic when the difference between the observation with non-polarized light and the observation with polarized light and the difference due to the polar angle in the observation with polarized light are visually recognized.
- the clarity of the latent image when viewed varies depending on the polar angle of the observation direction, and the position of the polarization direction of the incident polarized light or the transmission axis direction of the linear polarizer for observation and the optical display medium. It also changes when relationships change. When such a change is visually recognized, it can be determined that the optical display medium is authentic.
- a reflective circular polarizer was used as the reflective polarizer layer, and linearly polarized light was used for observation with polarized light (i.e., a linearly polarized light source or a linear polarizer for observation was used).
- the optical display medium of the invention and the method of using the same are not limited to this. and when linearly polarized light is used for observation with polarized light, and when a reflective linear polarizer is used as the reflective polarizer layer and circularly polarized light is used for observation with polarized light, the polarizer layer is a C plate. Based on a certain fact, a latent image is observed when the polar angle exceeds 0° in observation with polarized light, so it can be used in a similar manner.
- reflective polarizer layer A material constituting the reflective polarizer layer and a method for forming the reflective polarizer layer will be specifically described.
- reflective polarizer layers include reflective circular polarizers, exemplified as reflective polarizer layer 102 above, and reflective linear polarizers.
- the reflective polarizer layer may exhibit such a function by a single layer, or may exhibit such a function by combining a plurality of layers.
- the reflective polarizer layer is preferably an ink layer containing flaky reflective materials.
- An ink layer is a layer of a cured product of ink, and is usually formed by applying and curing ink. Inks typically contain a solvent and solids, and some or all of the solvent volatilizes during curing. Therefore, the ink layer is a layer containing ink solids. Therefore, an ink for forming a reflective polarizer layer may contain flaky reflective material as a solid content.
- a flake-shaped reflective material is flakes, that is, particles having a flake-shaped shape, and each particle has a function as a reflective polarizer. More specifically, a film capable of functioning as a reflective polarizer layer is prepared as a raw material for flakes, and the raw material film is crushed into flakes, which can be used as a flake-shaped reflective material.
- the average particle size of the flakes is not particularly limited, and can be a particle size suitable for forming an ink layer.
- the average particle diameter is preferably 10 ⁇ m or more, more preferably 20 ⁇ m or more, and is preferably 300 ⁇ m or less, more preferably 100 ⁇ m or less.
- the average particle size can be the D50 average particle size that can be obtained by measuring the particle size distribution with a laser diffraction/scattering particle size distribution analyzer (for example, product name “LA-960” manufactured by Horiba Ltd.).
- the ratio l/d of the average particle size l of the flakes to the thickness d of the flakes is preferably 2 or more, more preferably 4 or more, while it is preferably 100 or less, more preferably 50 or less.
- Components other than flakes in the ink are not particularly limited, and substances such as commercially available ink media and diluents can be used.
- the degree of freedom in manufacturing is high. For example, it is possible to easily form a reflective polarizer layer even on the surface of a base material that does not have alignment control force, and there is no need to perform treatments such as alignment treatment and band broadening treatment in the production of each optical display element. Advantages can be obtained, such as the ability to easily adjust the planar shape and thickness of the reflective polarizer layer on the display surface of the optical display medium, which can be performed collectively at the time of film preparation.
- films that can be used as a reflective circular polarizer layer include layers of materials having cholesteric regularity.
- Cholesteric regularity means that the molecular axes are lined up in a certain direction on one plane inside the material, but the direction of the molecular axes on the next plane that overlaps with it is slightly deviated, and the next plane has a further angle. It is a structure in which the angles of the molecular axes in the planes are shifted (twisted) as they pass through the planes that are arranged to overlap one another, such that the planes are shifted.
- the molecules when molecules inside a layer of a certain material have cholesteric regularity, the molecules are aligned such that their molecular axes are oriented in a certain direction on a certain first plane inside the layer.
- the direction of the molecular axis In the next second plane within the layer, which overlaps the first plane, the direction of the molecular axis deviates at a small angle from the direction of the molecular axis in the first plane.
- the direction of the molecular axis In the next third plane, which further overlaps the second plane, the direction of the molecular axis is angularly offset from the direction of the molecular axis in the second plane. In this way, the angles of the molecular axes in the planes that are arranged to overlap each other gradually shift (twist).
- Such a structure in which the direction of the molecular axis is twisted is usually a helical structure and an optically chiral structure.
- a more specific example of a material having cholesteric regularity is a cholesteric resin layer.
- the cholesteric resin layer is a layer obtained by curing a curable liquid crystal compound exhibiting a cholesteric liquid crystal phase.
- the cholesteric resin layer can be obtained, for example, by polymerizing a polymerizable liquid crystalline compound while exhibiting a cholesteric liquid crystal phase.
- a liquid crystal composition containing a polymerizable liquid crystalline compound is formed into a layer state by, for example, coating it on an appropriate base material, aligned in a cholesteric liquid crystal phase, and cured to form a cholesteric resin layer. can get
- a photopolymerizable liquid crystal compound is preferable as the polymerizable liquid crystal compound.
- a photopolymerizable liquid crystal compound that can be polymerized by irradiation with an active energy ray can be used.
- an energy ray that can promote the polymerization reaction of the photopolymerizable liquid crystal compound can be used from among a wide range of energy rays such as visible light, ultraviolet rays, and infrared rays, and ionizing radiation such as ultraviolet rays is particularly preferred. is preferred.
- the photopolymerizable liquid crystal compound preferably used in the cholesteric liquid crystal composition is preferably a rod-like liquid crystal compound having two or more reactive groups in one molecule, and particularly preferably a compound represented by formula (1). .
- R 3 and R 4 are reactive groups, each independently a (meth)acryl group, (thio)epoxy group, oxetane group, thietanyl group, aziridinyl group, pyrrole group, vinyl group , allyl group, fumarate group, cinnamoyl group, oxazoline group, mercapto group, iso(thio)cyanate group, amino group, hydroxyl group, carboxyl group and alkoxysilyl group.
- D 3 and D 4 are each independently a single bond, a linear or branched alkyl group having 1 to 20 carbon atoms, and represents a group selected from the group consisting of linear or branched alkylene oxide groups.
- M represents a mesogenic group.
- R 5 and R 7 represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms.
- R 5 and R 7 are alkyl groups
- R 6 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.
- substituents in the "alkyl group having 1 to 10 carbon atoms which may have a substituent" include a halogen atom, a hydroxyl group, a carboxyl group, a cyano group, an amino group, and 1 to 10 carbon atoms. 6 alkoxy groups, alkoxyalkoxy groups having 2 to 8 carbon atoms, alkoxyalkoxyalkoxy groups having 3 to 15 carbon atoms, alkoxycarbonyl groups having 2 to 7 carbon atoms, 2 carbon atoms 1 to 7 alkylcarbonyloxy groups, alkoxycarbonyloxy groups having 2 to 7 carbon atoms, and the like.
- the rod-like liquid crystal compound preferably has an asymmetric structure.
- the asymmetric structure refers to R 3 -C 3 -D 3 -C 5 -M- and -M-C 6 -D 4 -C 4 -R 4 with the mesogenic group M in the formula (1) as the center. , they refer to different structures. Alignment uniformity can be further enhanced by using a rod-like liquid crystal compound having an asymmetric structure.
- rod-like liquid crystalline compound examples include the following compounds (B1) to (B10).
- the rod-like liquid crystalline compound is not limited to the following compounds.
- the liquid crystal composition preferably contains a compound represented by Formula (2) as an alignment aid in combination with the rod-shaped liquid crystal compound.
- Formula (2) a compound represented by Formula (2) as an alignment aid in combination with the rod-shaped liquid crystal compound.
- R 1 and R 2 are each independently a linear or branched alkyl group having 1 to 20 carbon atoms, a linear or a branched alkylene oxide group, a hydrogen atom, a halogen atom, a hydroxyl group, a carboxyl group, a (meth)acrylic group optionally interposed with a bonding group, an epoxy group, a mercapto group, an isocyanate group, an amino group, and a cyano group.
- the alkyl group and alkylene oxide group may be unsubstituted or substituted with one or more halogen atoms.
- the halogen atom, hydroxyl group, carboxyl group, (meth)acrylic group, epoxy group, mercapto group, isocyanate group, amino group, and cyano group are alkyl groups having 1 to 2 carbon atoms, and alkylene oxides. It may be bonded to a group.
- R 1 and R 2 include halogen atoms, hydroxyl groups, carboxyl groups, (meth)acryl groups, epoxy groups, mercapto groups, isocyanate groups, amino groups and cyano groups.
- At least one of R 1 and R 2 is preferably a reactive group.
- the compound represented by the formula (2) is fixed in the liquid crystal composition cured layer during curing, and a stronger layer can be formed.
- the reactive group includes, for example, a carboxyl group, (meth)acryl group, epoxy group, mercapto group, isocyanate group, and amino group.
- a 1 and A 2 are each independently a 1,4-phenylene group, a 1,4-cyclohexylene group, a cyclohexene-1,4-ylene group, a 4,4′-biphenylene group, a 4 ,4'-bicyclohexylene group and 2,6-naphthylene group.
- the 1,4-phenylene group, 1,4-cyclohexylene group, cyclohexen-1,4-ylene group, 4,4'-biphenylene group, 4,4'-bicyclohexylene group and 2,6-naphthylene group is unsubstituted or substituted with one or more substituents such as halogen atoms, hydroxyl groups, carboxyl groups, cyano groups, amino groups, alkyl groups having 1 to 10 carbon atoms, halogenated alkyl groups, etc. may be When two or more substituents are present in each of A 1 and A 2 , they may be the same or different.
- a 1 and A 2 include groups selected from the group consisting of 1,4-phenylene groups, 4,4'-biphenylene groups and 2,6-naphthylene groups. These aromatic ring skeletons are relatively rigid compared to alicyclic skeletons, and have high affinity with mesogens of rod-like liquid crystal compounds, resulting in higher alignment uniformity.
- Specific preferred examples of the compound represented by formula (2) include the following compounds (A1) to (A10). One of these may be used alone, or two or more of them may be used in combination at any ratio.
- the weight ratio represented by (total weight of compounds represented by formula (2))/(total weight of rod-like liquid crystal compounds) is preferably 0.001 or more, more preferably 0.01 or more, and still more preferably 0.01 or more. 05 or more, preferably 1 or less, more preferably 0.65 or less.
- the refractive index anisotropy ⁇ n of the liquid crystal composition can be increased, it is possible to stably obtain a liquid crystal composition cured layer having desired optical performance such as selective reflection performance for circularly polarized light.
- the total weight of the compound represented by the formula (2) is the weight when only one type of the compound represented by the formula (2) is used, and when two or more types are used Indicates total weight.
- the total weight of the rod-like liquid crystal compounds indicates the weight when only one type of rod-like liquid crystal compound is used, and indicates the total weight when two or more types of rod-like liquid crystal compounds are used.
- the compound represented by the formula (2) preferably has a molecular weight of less than 600, and the rod-like liquid crystal compound has a molecular weight of 600 or more. is preferably As a result, the compound represented by Formula (2) can enter the gaps of the rod-like liquid crystal compound having a higher molecular weight than that, so that the alignment uniformity can be improved.
- the liquid crystal composition for forming the cholesteric resin layer may further contain optional components constituting the cholesteric resin layer and a solvent for facilitating handling of the liquid crystal composition.
- optional ingredients include chiral agents, polymerization initiators, and surfactants.
- Specific examples of optional components and solvents include those described in JP-A-2019-188740.
- a film that can be used as a reflective circular polarizer layer can be obtained by coating the liquid crystal composition on the surface of a support having an alignment regulating force to form a layer of the liquid crystal composition, aligning the composition to a cholesteric liquid crystal phase, and curing the composition.
- a support having alignment control power a film whose surface is rubbed, a film whose surface is given alignment control power by stretching, and the like can be used.
- the liquid crystal composition aligns to a cholesteric liquid crystal phase immediately after coating, but the alignment can be achieved by subjecting the composition to a treatment such as heating as necessary so as to exhibit a cholesteric liquid crystal phase.
- a method can be selected according to the components contained in the cholesteric liquid crystal composition.
- a layer of the cholesteric liquid crystal composition is cured by polymerizing a polymerizable component such as a polymerizable liquid crystal compound that is usually contained in the cholesteric liquid crystal composition.
- the polymerization method include a method of irradiating an active energy ray and a thermal polymerization method. Among them, the method of irradiating with active energy rays is preferable because the polymerization reaction can proceed at room temperature.
- the active energy rays to be irradiated may include light such as visible rays, ultraviolet rays, and infrared rays, and arbitrary energy rays such as electron beams.
- the active energy rays to be irradiated may include light such as visible rays, ultraviolet rays, and infrared rays, and arbitrary energy rays such as electron beams.
- the preferred intensity of the irradiated active energy rays varies depending on the liquid crystal composition used. can be two .
- the layer of the cholesteric liquid crystal composition may be subjected to a band broadening treatment.
- a band widening treatment can be performed, for example, by a combination of one or more active energy ray irradiation treatments and heating treatments.
- the energy of the irradiated light varies depending on the liquid crystal composition used, but can be, for example, 0.01 mJ/cm 2 to 50 mJ/cm 2 .
- the heat treatment can be performed, for example, by heating to a temperature of preferably 40° C. or higher, more preferably 50° C. or higher, preferably 200° C. or lower, and more preferably 140° C. or lower.
- Examples of reflective linear polarizers include films in which multilayer thin films are laminated (for example, the product name "DBEF", manufactured by 3M) and wire grid polarizers.
- the maximum reflectance of the non-polarized light incident on the reflective polarizer layer is 50%.
- the reflective polarizer layer visually exhibits different colors.
- a reflective polarizer layer is observed as a silver layer when the reflectance by the reflective polarizer layer of unpolarized light incident on the reflective polarizer layer is 35-50% at all wavelengths in the wavelength region 420 nm-650 nm. . If the band of 35-50% reflection is narrower than this, the reflective polarizer layer may exhibit different colors depending on the band.
- the center wavelength of the reflection band when the center wavelength of the reflection band is near 450 nm, 550 nm, and 650 nm, respectively, colors such as blue, green, and red can be exhibited.
- the center wavelength of the reflection band can be adjusted by the type of material constituting the film, the ratio of its components, and the film manufacturing conditions.
- the pitch of the cholesteric regularity helix can be adjusted by changing the type of liquid crystalline compound and chiral agent and the content of the chiral agent. By doing so, slight pitch adjustments can be easily achieved. Such adjustment makes it possible to easily adjust the center wavelength of the reflection band to a desired value.
- the optical display medium of the present invention may have only one layer as the reflective polarizer layer, or may have multiple layers.
- the optical display medium may also have only one type of layer as the reflective polarizer layer, or may have a plurality of types of layers with different polarization states of reflected light.
- the reflective polarizer layer a plurality of pieces of reflective polarizers exhibiting a plurality of colors such as red, green, blue, and silver are laid out in the horizontal direction. can have
- the reflective polarizer layer is preferably a reflective circular polarizer from the viewpoint of not needing to align the directions.
- the reflective polarizer layer is preferably silver or a combination of silver and other colors.
- birefringent layer A material forming the birefringent layer and a method of forming the birefringent layer will be specifically described.
- the birefringent layer may exhibit a function by a single layer, or may exhibit a function by combining a plurality of layers.
- the birefringent layer is a layer containing flaky birefringent material, preferably an ink layer containing flaky birefringent material.
- the ink for forming the birefringent layer may contain flaky birefringent material as a solid content.
- the birefringent layer is a flaky ink layer, the advantage of a high degree of freedom in manufacturing can be enjoyed particularly advantageously.
- a birefringent layer can be easily formed on the surface of a base material that does not have alignment control force, a birefringent layer can be easily formed on the already formed reflective polarizer layer by a process such as printing. can be formed.
- the planar shape of the birefringent layer on the display surface of the optical display medium can be easily adjusted, the degree of freedom in designing the shape of the latent image can be increased.
- the thickness of the birefringent layer can be easily adjusted, it is possible to easily adjust the thickness-dependent optical characteristics of the C plate.
- films that can be used as birefringent layers include layers of materials having cholesteric regularity.
- the material, the liquid crystal composition that can be used to make the film, the components thereof, and the method of making the film are the same as for the film that can be used as the reflective circular polarizer layer.
- the birefringent layer is made of a material having cholesteric regularity, part or all of its reflection band must be outside the visible region.
- the central wavelength of the reflection band may be in the ultraviolet region of 380 nm or less, or in the infrared region of 780 nm or more.
- the reflectance can be a small value of 20% or less at any wavelength in the visible region of 400 nm to 680 nm.
- the film exhibits a transparent appearance similar to that of a general transparent resin film in non-polarized light observation, while functioning as a C plate due to the orientation of the liquid crystalline compound. It can have optical anisotropy that can be used.
- Such a film can be adjusted according to the types of materials constituting the film, the proportions of the components thereof, and the conditions for producing the film.
- the pitch of the cholesteric regular helix can be adjusted by the type of liquid crystalline compound and chiral agent, and the content of the chiral agent.
- a material forming the isotropic layer and a method of forming the isotropic layer will be specifically described. Any material that is optically isotropic can be used for the isotropic layer.
- a particularly preferable example of the material constituting the isotropic layer is a material having a small color difference with the birefringent layer. Examples of such materials include a film obtained by curing a liquid crystal composition containing the same liquid crystalline compound as the polymerizable liquid crystalline compound used for forming the birefringent layer while being oriented in an isotropic phase. .
- the same liquid crystal composition as the liquid crystal composition used for forming the birefringent layer is used except that the amount of the chiral agent is reduced or the chiral agent is not used, and this is aligned in an isotropic phase.
- a transparent film with very little color difference from the birefringent layer can be obtained.
- An isotropic layer having a very small color difference from the birefringent layer can be easily obtained by making this film into flakes and forming an ink layer in the same procedure as the formation of the birefringent layer.
- the birefringent layer and the isotropic layer which are ink layers, can be formed using ink by applying ink to the surface of the reflective polarizer layer and curing the ink. Specifically, formation of such an ink layer can be performed by a known printing method. From the viewpoint of efficient production, a printing method such as a screen printing method or an inkjet printing method is preferable.
- one of the birefringent layer and the isotropic layer is formed as a first layer so as to exhibit a desired surface shape by applying and curing ink by a printing method, and then the birefringent layer and the isotropic layer are formed. is formed as a second layer at a position in contact with or separated from the first layer by a short distance by applying and curing ink by a printing method, thereby forming these layers by such a tweezers printing method can be achieved.
- optical display media goods
- an article having an identification function By mounting the optical display medium of the present invention on other components, an article having an identification function can be constructed.
- the optical display medium of the present invention itself can be used as an article having an identification function.
- articles include various articles such as clothing, shoes, hats, accessories, jewelry, and daily necessities.
- An article can have an identification function by being provided with the optical display medium of the present invention. By having such an identification function, it is possible to identify whether the article is genuine and not forged. Additionally, the optical display medium can impart a design effect to the article.
- the optical display medium can be provided on an article as a tag, charm, emblem, sticker, or the like, as an accessory, part, or attachment of the article.
- the article of the present invention may further comprise a polarizer viewer in addition to the optical display medium of the present invention.
- the polarizer viewer is equipped with an observation polarizer such as the above-described observation linear polarizer or observation circular polarizer, and is provided in the article so that the optical display medium can be observed through the observation polarizer.
- the polarizer viewer may be in the form of a tag, for example, and attached to the article body via a string or the like. In this way, by further providing a polarizer viewer in addition to the optical display medium, general article users can easily identify the optical display medium.
- the transparent adhesive tape "LUCIACS CS9621T” manufactured by Nitto Denko Corporation (thickness 25 ⁇ m, visible light transmittance 90% or more, in-plane retardation 3 nm or less) is used. board.
- the oblique 45° phase difference Re 45 is obtained by setting the polar angle (the angle formed by the observation direction and the normal direction of the surface of the object to be measured) to 45° and the azimuth angle (the in-plane direction of the object to be measured and the observation direction to be tilted). The angle formed with the direction) was measured over the entire circumference at intervals of azimuth angle of 5° in the range of 0° or more and less than 360°, and the arithmetic mean was obtained.
- the angles of measurement were appropriately set to the angles required to obtain measurement data.
- the measurement was performed with a linear polarizer interposed between the detection unit of the measuring device and the object to be measured.
- the linear polarizer is arranged so that its surface is perpendicular to the observation direction, the azimuth angle of the absorption axis in the plane is rotated 360 ° in each observation, and the value of ⁇ E * at the azimuth angle at which ⁇ E * is maximized is , was taken as the measured value in that observation.
- the measurement was performed without interposing a linear polarizer between the photometer and the measurement target.
- the optical display media thus obtained were subjected to the following various visual evaluations.
- linearly polarized light As the linearly polarized light, a commercially available smartphone (manufactured by Samsung, trade name "GalaxyA41”) or a commercially available personal computer (manufactured by Panasonic Corporation, trade name “Let's note CF-SZ6”) from a liquid crystal display device provided Output light was used. In all examples, the determination results were the same when either polarization was used.
- Liquid crystalline compound (X1) A photopolymerizable liquid crystalline compound represented by the formula (B5).
- Liquid crystalline compound LC242 trade name “Paliocolor LC242” manufactured by BASF.
- Chiral agent trade name “Paliocolor LC756” manufactured by BASF.
- Alignment aid (X2) A photopolymerizable non-liquid crystal compound represented by the formula (A10).
- Example 1 (1-1. Film for birefringent layer) A support film (a long polyethylene terephthalate film, "PET film A4100" manufactured by Toyobo Co., Ltd., thickness: 100 ⁇ m, same below) was prepared, and its surface was rubbed. The coating liquid 1B obtained in Production Example 1 was applied to the rubbed surface with a bar coater to form a film of the coating liquid in an uncured state.
- a support film a long polyethylene terephthalate film, "PET film A4100” manufactured by Toyobo Co., Ltd., thickness: 100 ⁇ m, same below
- the coating liquid 1B obtained in Production Example 1 was applied to the rubbed surface with a bar coater to form a film of the coating liquid in an uncured state.
- the film of the coating liquid was heated in an oven at 140° C. for 2 minutes to orient the liquid crystalline compound in the coating liquid, and the film was dried. Then, after cooling at room temperature for 1 minute, the film was cured by irradiating ultraviolet rays. Irradiation is performed in a nitrogen atmosphere (oxygen concentration of 400 ppm or less), a high-pressure mercury lamp is used as a radiation source, the illuminance at 365 nm (i-line) is 280 mW/cm, and the exposure at 365 nm (i-line) is 400 mJ/cm. 2 . Thus, a birefringent layer film 1B was formed on the support film. The thickness of the birefringent layer film was 3.1 ⁇ m.
- a roller having an uneven shape is pressed against the birefringent layer film 1B formed on the support film to form cracks, and then air is blown to separate the birefringent layer film from the support film, leaving a peeled piece. Obtained.
- the peeled pieces were pulverized with a cutter mill ("Micro Powder MPW-G008" manufactured by West Co., hereinafter the same) and classified using a 51 ⁇ m sieve. Only the particles that passed through the sieve were recovered to obtain the birefringent layer flakes 1B. When the particle size distribution of the birefringent layer flakes 1B was measured to find the average particle size, it was 30 ⁇ m.
- the coating liquid 1D obtained in Production Example 1 was applied to one surface of a new support film with a bar coater to form a film of the coating liquid in an uncured state.
- the film of the coating liquid was heated in an oven at 210° C. for 5 minutes to dry the film. After that, the film was cured by irradiating it with ultraviolet rays. Irradiation is carried out in a nitrogen atmosphere (oxygen concentration of 400 ppm or less), at a temperature of 210 ° C. during heating, using a high-pressure mercury lamp as a radiation source, illuminance at 365 nm (i-line) at 280 mW / cm 2 , and 365 nm. The exposure dose for (i-line) was set to 400 mJ/cm 2 . Thus, an isotropic layer film 1D was formed on the support film. The thickness of the isotropic layer film was 3.1 ⁇ m.
- Isotropic layer flakes and ink In place of the birefringent layer film 1B on the support film, the isotropic layer film 1D on the support film was used, but the same operations as (1-2) to (1-3) were performed to obtain the isotropic layer film. Flakes 1D and isotropic layer ink 1D were obtained. The average particle diameter of the isotropic layer flakes 1D was 30 ⁇ m.
- the film of the coating liquid was heated in an oven at 120° C. for 4 minutes to orient the liquid crystalline compound in the coating liquid, and the film was dried. After that, the film was subjected to a band broadening treatment. In this band broadening treatment, irradiation of weak ultraviolet rays of 5 mJ/cm 2 to 30 mJ/cm 2 and heating treatment of 100° C. to 120° C. are alternately repeated multiple times, thereby increasing the wavelength range in which the circularly polarized light separation function can be exhibited. It was controlled to have a desired wavelength width. After that, the film was cured by irradiating the film with curing ultraviolet rays of 800 mJ/cm 2 . This formed the film 2S for reflective polarizer layers on the support film. The thickness of the film for reflective polarizer layer was 5.2 ⁇ m. When the film 2S for a reflective polarizer layer was visually observed under natural light, it was silver.
- the reflective polarizer layer flakes 2S were obtained in the same manner as in (1-2) except that the reflective polarizer layer film 2S on the support film was used instead of the birefringent layer film 1B on the support film. rice field.
- the average particle size of the reflective polarizer layer flakes 2S was 30 ⁇ m.
- Ink 2S for reflective polarizer layer was obtained in the same manner as in (1-3) except that flakes 2S for reflective polarizer layer were used instead of flakes 1B for birefringent layer.
- a substrate polyethylene terephthalate film colored black
- a film of the ink 2S for the reflective polarizer layer obtained in (1-7) was formed on the corona-treated surface by screen printing (using a screen plate with a line number of 120 per inch; the same shall apply hereinafter).
- the film was dried to form a reflective polarizer layer, yielding a multilayer comprising a reflective polarizer layer and a substrate.
- the resulting reflective polarizer layer was visually observed under natural light, it had a silver appearance.
- a film of the birefringent layer ink 1B obtained in (1-3) is applied to a rectangular region of a part of the surface of the multilayer product on the reflective polarizer layer side obtained in (1-8) by screen printing. formed. The film was dried to form a birefringent layer.
- a birefringent layer is formed on the support film by the same method as the formation method described above, and this is transferred to glass via a commercially available adhesive to form a birefringent layer for phase difference measurement. formed.
- the in-plane retardation Re 0 and oblique 45° retardation Re 45 were measured. Table 3 shows the measurement results. When the obtained birefringent layer was visually observed under natural light, it had the appearance of a transparent layer similar to that of a general transparent film.
- isotropic layer optical display medium
- a film of the isotropic layer ink 1D obtained in (1-5) was applied to a rectangular region adjacent to the birefringent layer on the surface of the multilayer product obtained in (1-9) on the reflective polarizer layer side, It was formed by screen printing.
- the membrane was dried to form an isotropic layer.
- the amount of ink applied was adjusted so that the thickness of the isotropic layer was the same as that of the adjacent birefringent layer. This yielded an optical display medium having the shape shown schematically in FIG.
- an isotropic layer for phase difference measurement was formed on the glass plate by the same method as the formation method described above, and the in-plane phase difference Re 0 and oblique 45° phase difference Re 45 were measured. Table 3 shows the measurement results. When the resulting isotropic layer was visually observed under natural light, it had the appearance of a transparent layer similar to that of a general transparent film.
- Example 2 An optical display medium and other structures were obtained and evaluated by the same operations as in Example 1 except for the following changes. Both the birefringent and isotropic layers obtained had the appearance of transparent layers similar to common transparent films.
- the coating liquid 1A was used instead of the coating liquid 1B.
- the coating liquid 1C was used instead of the coating liquid 1D.
- the coating thickness of the ink for the birefringent layer was changed. The thickness, in-plane retardation Re 0 and oblique 45° retardation Re 45 of the obtained birefringent layer were as shown in Table 3.
- Examples 3 and 4 An optical display medium and other structures were obtained and evaluated by the same operations as in Example 1 except for the following changes. - In the formation of the birefringent layer in (1-9), the coating thickness of the ink for the birefringent layer was changed. The in-plane retardation Re 0 and oblique 45° retardation Re 45 of the obtained birefringent layer were as shown in Table 3. The resulting birefringent layer had the appearance of a transparent layer similar to a common transparent film.
- Example 5 (5-1. Reflective polarizer layer film 2B and flakes 2B) Reflective polarizer layer film 2B and reflective polarizer layer flakes 2B were obtained in the same manner as in (1-6) of Example 1, except for the following changes. - The coating liquid 2B was used instead of the coating liquid 2SG. ⁇ Bandwidth processing was not performed. That is, the dried film was subjected to UV irradiation for curing without undergoing a band-broadening treatment. When the obtained film 2B for a reflective polarizer layer was visually observed under natural light, it had a blue appearance.
- a reflective polarizer layer ink 2B was obtained in the same manner as in (1-3) of Example 1, except that the reflective polarizer layer flakes 2B were used instead of the birefringent layer flakes 1B.
- Example 6 (6-1. Reflective polarizer layer film 2G and flakes 2G) A reflective polarizer layer film 2G and reflective polarizer layer flakes 2G were obtained by the same operation as in Example 1 (1-6) except for the following changes. ⁇ Bandwidth processing was not performed. That is, the dried film was subjected to UV irradiation for curing without undergoing a band-broadening treatment. When the obtained film 2B for a reflective polarizer layer was visually observed under natural light, it had a green appearance.
- Ink 2G for reflective polarizer layer was obtained in the same manner as in Example 1 (1-3) except that flakes 2G for reflective polarizer layer were used instead of flakes 1B for birefringent layer.
- Example 7 (7-1. Reflective polarizer layer film 2R and flakes 2R) A reflective polarizer layer film 2R and reflective polarizer layer flakes 2R were obtained by the same operation as in Example 1 (1-6) except for the following changes. - The coating liquid 2R was used instead of the coating liquid 2SG. ⁇ Bandwidth processing was not performed. That is, the dried film was subjected to UV irradiation for curing without undergoing a band-broadening treatment. When the obtained film 2R for a reflective polarizer layer was visually observed under natural light, it had a red appearance.
- Ink 2R for reflective polarizer layer was obtained in the same manner as in (1-3) of Example 1, except that flakes 2R for reflective polarizer layer were used instead of flakes 1B for birefringent layer.
- Example 8 (8-1. Ink 2RGB for reflective polarizer layer) Instead of 15 parts of the birefringent layer flakes 1B, 5 parts of the reflective polarizer layer flakes 2B obtained in (5-1), 5 parts of the reflective polarizer layer flakes 2G obtained in (6-1), and ( Ink 2RGB for a reflective polarizer layer was obtained in the same manner as in (1-3) of Example 1, except that 5 parts of the reflective polarizer layer flakes 2R obtained in 7-1) were used in combination.
- the ink 2RGB for the reflective polarizer layer obtained in (8-1) was used instead of the ink 2S for the reflective polarizer layer.
- Optical display media and other structures were obtained and evaluated by the same operations as (1-1) to (1-5) and (1-8) to (1-10). When the reflective polarizer layer was visually observed under natural light when the reflective polarizer layer was obtained, it had a silver appearance.
- Example 9 An optical display medium and other structures were obtained and evaluated by the same operations as in Example 1 except for the following changes. - In the formation of the isotropic layer film of (1-4), the coating liquid 1E was used instead of the coating liquid 1D. The isotropic layer had the appearance of a transparent layer similar to a common transparent film.
- C1-2. Ink for isotropic layer 100 parts of a screen ink ("No. 2500 medium” manufactured by Jujo Chemical Co., Ltd.) and 10 parts of a diluent exclusively for the screen ink (Tetoron standard solvent) were mixed to obtain an isotropic layer ink 1G.
- the particle size distribution of the birefringent layer flakes 1H was measured, and the average particle size was found to be 40 ⁇ m.
- a birefringent layer for phase difference measurement is formed on the support film by the same method as the formation method described above, and this is transferred to glass via a commercially available adhesive, and phase difference measurement is performed.
- a birefringent layer for was formed.
- the in-plane retardation Re 0 and oblique 45° retardation Re 45 were measured. The measurement results were as shown in Table 3.
- the latent image was not visually recognized at a polar angle of 0° in observation with various polarized light, while the polar It can be seen that the peculiar property that the contrast of the latent image is maximized at an angle exceeding 0° is shown, and the effectiveness as an identification medium is high.
- Example 9 using a liquid crystalline compound different from the liquid crystalline compound composing the birefringent layer as the liquid crystalline compound composing the isotropic layer, the region RA of the birefringent layer and the isotropic The color difference from the region RB of the layer was slightly large, and a latent image was slightly visible even when observed with non - polarized light.
- the color difference between the region RA of the birefringent layer and the region RB of the isotropic layer was very small, and the secrecy of the portion having the identification function was particularly high.
- Optical display medium 101 Substrate 101U: Upper surface of substrate 102: Reflective polarizer layer 102U: Upper surface of reflective polarizer layer 111: Birefringent layer 112: Isotropic layer 119: Boundary R L : Reflective Area R A : Area R B : Area
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Abstract
Description
すなわち、本発明は、下記のものを含む。
前記表示面の一部又は全部の領域である反射領域RLに設けられる反射偏光子層と、
前記反射偏光子層より視認側に設けられ、前記反射領域RLの一部を占める領域RAに設けられる複屈折層とを備え、
前記反射偏光子層は、入射光を、円偏光または直線偏光として反射する層であり、
前記複屈折層は、フレーク状複屈折素材を含み、Cプレートとしての光学特性を示す層である、光学表示媒体。
〔2〕 前記反射偏光子層が、コレステリック規則性を有する材料の層である、〔1〕に記載の光学表示媒体。
〔3〕 前記反射偏光子層が、フレーク状反射素材を含むインキ層である、〔1〕又は〔2〕に記載の光学表示媒体。
〔4〕 前記光学表示媒体を非偏光で観察した際の、前記領域RAと、前記反射領域RLのうちの前記領域RA以外の領域RBとの色差ΔE*(N)が、極角0°方向の観察において1以下である、〔1〕~〔3〕のいずれか1項に記載の光学表示媒体。
〔5〕 前記色差ΔE*(N)が、極角20~70°且つ方位角0~360°の全方向の観察の全てにおいて1以下である、〔4〕に記載の光学表示媒体。
〔6〕 前記光学表示媒体を偏光で観察した際の、前記領域RAと、前記反射領域RLのうちの前記領域RA以外の領域RBとの色差ΔE*(P)が、極角20~70°且つ方位角0~360°の全方向の観察うちのどれか1において3以上である、〔1〕~〔5〕のいずれか1項に記載の光学表示媒体。
〔7〕 前記色差ΔE*(P)が、極角0°方向の観察において1以下である、〔6〕に記載の光学表示媒体。
〔8〕 極角0°方向から測定した前記複屈折層の面内位相差Re(A)0が、Re(A)0≦30nmを満たし、
極角45°のいずれかの方位角から測定した前記複屈折層の斜め位相差Re(A)45が、下記式(e1):
70nm≦Re(A)45≦700nm 式(e1)
を満たす、〔1〕~〔7〕のいずれか1項に記載の光学表示媒体。
〔9〕 前記反射偏光子層より視認側に設けられ、前記反射領域RLのうちの前記領域RA以外の領域RBの一部又は全部を占める等方層をさらに備え、
極角0°方向から測定した前記等方層の面内位相差Re(B)0が、Re(B)0≦30nmを満たし、
前記等方層の斜め位相差Re(B)45が、0≦Re(B)45≦30を満たす、
〔1〕~〔8〕のいずれか1項に記載の光学表示媒体。
具体的には、極角φにおける斜め位相差Reφは、式Reφ=|ny-nx’|・dφにより求められる。
ここでdφは斜め方向の層内の光路長であり、式dφ=d/cosφにより求められる。
nx’は、下記式(e2)により求められる。
・光学表示媒体に非偏光を入射させ、光学表示媒体からの反射光を通常の態様(特段の偏光成分の選択を伴わない態様)で観察する。
・光学表示媒体に非偏光を入射させ、光学表示媒体からの反射光のうちの偏光成分を選択的に観察する。
・光学表示媒体に偏光を入射させ、光学表示媒体からの反射光を通常の態様で観察する。
といった観察態様で観察しうる。説明の便宜のため、以下の説明においては、前記3つの態様のうちの第1のものを「非偏光での観察」、第2のものを「非偏光-偏光観察」、第3のものを「偏光-非偏光観察」という場合がある。第2のものと第3のものの総称として、これらを「偏光での観察」という場合がある。
本発明の光学表示媒体は、表示面を有し、表示面の一部又は全部の領域である反射領域RLに設けられる反射偏光子層と、反射偏光子層より視認側に設けられ、反射領域RLの一部を占める領域RAに設けられる複屈折層とを備える。
反射偏光子層は、入射光を、円偏光または直線偏光として反射する層である。反射偏光子層は、入射光のうちのある波長における偏光成分の一部または全部を透過させ、他の偏光成分の一部または全部を反射させる。反射偏光子層としては、反射型円偏光子または反射型直線偏光子を用いうる。
反射型円偏光子とは、ある波長の入射光の、右円偏光成分及び左円偏光成分のうちの一方を透過させ、他の一方を反射する光学素子である。反射型直線偏光子とは、ある波長の入射光の、ある直線偏光成分及び当該成分と垂直な直線偏光成分のうちの一方を透過させ、他の一方を反射する光学素子である。
光学表示媒体の、識別媒体としての使用に際しての容易さの観点から、反射偏光子層は、好ましくは反射型円偏光子である。光学表示媒体の使用に際しては、利用の容易さの観点から直線偏光子又は直線偏光光源を利用することが好ましいところ、反射偏光子層が反射型円偏光子であることにより、かかる直線偏光子等を利用した光学表示媒体の使用に際して、直線偏光子の透過軸の向きへの依存が少ない識別機能の発現が期待される。
本願において、複屈折層は、Cプレートとしての光学特性を示す層である。
Cプレートは、ポジティブCプレート又はネガティブCプレートである。ポジティブCプレートは、主屈折率nx、ny及びnzが、nx=nyであるか又はそれに近い関係であり、且つnx<nzである、板状の形状を有する光学部材である。ネガティブCプレートは、主屈折率nx、ny及びnzが、nx=nyであるか又はそれに近い関係であり、且つny>nzである、板状の形状を有する光学部材である。
本発明の光学表示媒体は、複屈折層及び反射偏光子層のみからなっていてもよいが、それらに加えて、任意の構成要素を備えうる。任意の構成要素の例として、等方層が挙げられる。等方層は、光学的に等方な層であり、即ちその面内位相差及び厚み方向位相差が、無いか、又は十分に小さい層である。具体的には、極角0°方向から測定した等方層の面内位相差Re(B)0は、好ましくは30nm以下、より好ましくは15nm以下であり、理想的には0nmである。また、等方層の厚み方向位相差Rth(B)は、好ましくは-30nm以上、より好ましくは-15nm以上であり、一方好ましくは30nm以下、より好ましくは15nm以下である。等方層の斜め45°位相差Re(B)45は、好ましくは30nm以下、より好ましくは15nm以下であり、理想的には0nmである。
その他の任意の構成要素の例としては、光吸収層、基材層、装飾部材、及び装着部材が挙げられる。
光学表示媒体は、非偏光での観察において、領域RAと領域RBとの色差ΔE*(N)が小さいことが好ましい。具体的には、非偏光での観察における色差ΔE*(N)は、極角0°方向の観察において、好ましくは1以下、より好ましくは0.7以下であり、理想的には0である。加えて、極角20~70°且つ方位角0~360°の全方向の観察の全てにおいて、ΔE*(N)は好ましくは1以下、より好ましくは0.7以下であることが好ましい。より好ましくは、極角20~70°且つ方位角0~360°の全方向の観察の全てにおいて、ΔE*(N)は、前記数値範囲の要件を満たす。このような小さいΔE*(N)を有することにより、非偏光での通常の観察における、光学表示媒体の識別機能の秘匿性を高めることができる。
本発明の光学表示媒体の使用に際しては、入射光をその表示面に入射させ、反射偏光子層において反射させ反射光とし、反射光を観察する。その具体的な例としては、
・非偏光での観察(識別媒体に非偏光を入射させ、識別媒体からの反射光を通常の態様即ち特段の偏光成分の選択を伴わない態様で観察する)、及び
偏光での観察
が挙げられ、偏光での観察の具体的な例としては、
・非偏光-偏光観察(識別媒体に非偏光を入射させ、識別媒体からの反射光のうちの偏光成分を選択的に観察する)、及び
・偏光-非偏光観察(識別媒体に偏光を入射させ、識別媒体からの反射光を通常の態様で観察する)
が挙げられる。
図1~図2に示した光学表示媒体100であって、反射偏光子層が銀色の(即ち可視光領域全体に亘る反射帯域を有する)反射型円偏光子であり、基材101が光吸収層として機能するものを例にとり、本発明の光学表示媒体の識別媒体としての使用方法及びそれによる識別機能発現の例を、より具体的に説明する。
等方層112は等方な層であるため、観察方向が極角0°である場合も、極角0°超である場合も、等方層112を透過する光の位相差は透過前後で変化せず、偏光状態も変化しない。
ここで、観察方向が極角0°である場合は、観察者は、円偏光が複屈折層111を垂直に透過した後に出射する光を観察することになる。複屈折層111はCプレートであるため、複屈折層111を垂直に透過する光の位相差は透過前後で変化せず、偏光状態も変化しない。したがって、領域RAと領域RBでは、その外観の相違が視認できないので、潜像は観察されない。
観察方向が極角0°超である場合は、観察者は、円偏光が複屈折層111を斜めに透過した後に出射する光を観察することになる。複屈折層111はCプレートであり、斜めに透過する光に対しては、斜め位相差を有する層として機能する。その結果、出射する光は楕円偏光又は直線偏光となり、特に複屈折層111がλ/4波長板として機能する極角においては、観察者は直線偏光を観察することになる。しかしながら、目視による観察では、偏光状態での相違は視認されない。そのため結局、領域RAと領域RBでは、その外観の相違が視認できないので、潜像は観察されない。
観察方向が極角0°超であると、極角0°超で入射し反射偏光子層102で反射され出射する光を観察することになる。この場合、極角0°超で入射した直線偏光は、複屈折層111を斜めに透過して楕円偏光又は円偏光に変換され反射偏光子層102に到達する。反射偏光子層102では、さらにその右円偏光成分又は左円偏光成分のみが反射される。反射される円偏光成分の多少は、反射偏光子層102に到達する光の偏光状態によって変化することになり、それは、入射直線偏光の偏光方向と複屈折層111の見掛けの遅相軸との関係により変化する。このような外観の変化により、屈折層111と、等方層112との境界が明確に視認され、潜像が観察される。
反射偏光子層を構成する材料及び反射偏光子層を形成する方法について具体的に説明する。反射偏光子層の例としては、上に述べた反射偏光子層102として例示される反射型円偏光子、及び反射型直線偏光子が挙げられる。また、反射偏光子層は、1層のみの層によりかかる機能を発現するものであってもよく、複数の層の組み合わせによりかかる機能を発現するものであってもよい。
R3-C3-D3-C5-M-C6-D4-C4-R4 式(1)
R1-A1-B-A2-R2 (2)
Bとして特に好ましいものとしては、単結合、-O-(C=O)-及び-CH=N-N=CH-が挙げられる。
潜像の視認を明確にするという観点からは、反射偏光子層は、銀色のもの、又は銀色のものとその他の色のものとの組み合わせであることが好ましい。
複屈折層を構成する材料及び複屈折層を形成する方法について具体的に説明する。複屈折層は、1層のみの層により機能を発現するものであってもよく、複数の層の組み合わせにより機能を発現するものであってもよい。
等方層を構成する材料及び等方層を形成する方法について具体的に説明する。
等方層を構成する材料は、光学的に等方な、どのような材料をも使用しうる。等方層を構成する材料の特に好ましい例としては、複屈折層との色差が少ない材料が挙げられる。そのような材料の例としては、複屈折層の形成に用いる重合性の液晶性化合物と同じ液晶性化合物を含む液晶組成物を、等方相に配向した状態で硬化させてなるフィルムが挙げられる。より具体的には、カイラル剤の量を少なくするか又はカイラル剤を用いない他は、複屈折層の形成に用いる液晶組成物と同じ液晶組成物を用い、これを等方相に配向した状態で硬化させることにより、複屈折層との色差が非常に少ない、透明なフィルムを得うる。このフィルムを、複屈折層の形成と同じ手順でフレークとし、インキ層を形成することにより、複屈折層との色差が非常に少ない等方層を、容易に得ることができる。
インキを用いた、インキ層である複屈折層及び等方層の形成は、反射偏光子層の表面に、インキを塗布し、インキを硬化させることにより行いうる。かかるインキ層の形成は、具体的には、既知の印刷方法により行いうる。効率的な製造を行う観点からは、スクリーン印刷法、インクジェット印刷法等の印刷法が好ましい。特に、複屈折層の縁の側面が等方層の縁の側面と互いに接する配置、又は複屈折層と等方層との離隔距離が200μm以下といった短い距離である配置を達成する観点から、これらを毛抜き印刷法と呼ばれる手法により形成することが好ましい。具体的には、複屈折層及び等方層の一方を、第一の層として、印刷法によるインクの塗布及び硬化により所望の表面形状を呈するよう形成し、その後、複屈折層及び等方層のもう一方を、第二の層として、第一の層と接するか短い距離で離隔する位置に、印刷法によるインクの塗布及び硬化により形成することにより、かかる毛抜き印刷法によるこれらの層の形成を達成しうる。
本発明の光学表示媒体を、他の構成要素に備え付けることにより、識別機能を有する物品を構成しうる。又は本発明の光学表示媒体そのものを、識別機能を有する物品として用いうる。
物品の例としては、衣類、靴、帽子、装身具、宝飾品、日用品等の様々な物品が挙げられる。物品は、本発明の光学表示媒体を備えることにより、識別機能を有するものとしうる。かかる識別機能を有することにより、物品が、偽造品でない真正なものであることの識別を行いうる。加えて、光学表示媒体が、物品に意匠的効果を付与することができる。光学表示媒体は、タグ、チャーム、ワッペン、ステッカー等の、物品の装飾品、部品又は付属物として、物品に設けうる。
本発明の物品は、前記本発明の光学表示媒体に加えて、偏光子ビュワーをさらに備えうる。偏光子ビュワーとしては、上に述べた観察用直線偏光子又は観察用円偏光子等の観察用偏光子を備え、かかる観察用偏光子を介して光学表示媒体を観察しうるよう物品に備えられたものが挙げられる。偏光子ビュワーは、例えばタグの形状とし、紐等を介して物品本体に備え付けられた態様としうる。このように、光学表示媒体に加えて偏光子ビュワーをさらに備えることにより、一般の物品使用者が、簡単に光学表示媒体の識別を行うことができる。
(1.フレークの粒度分布及び平均粒径)
レーザー回折・散乱式粒子径分布測定装置(堀場製作所製、製品名「LA-960」)にて粒度分布を測定し、D50平均粒径を求めた。
Axometrics Axoscan Mueller Matrix Polarimeter(OPTO SCIENCE, INC.)により測定した。測定波長は550nmとした。斜め45°位相差Re45は、極角(観察方向と、測定対象の表面の法線方向とがなす角)を45°とし、方位角(測定対象のある面内方向と、観察方向を傾ける方向とがなす角)0°以上360°未満において、方位角5°の間隔で全周に亘り測定を行い、それらの算術平均を求めた。
光学表示媒体の、領域RA(表示媒体の上面の、複屈折層で占められる領域)及び領域RB(表示媒体の上面の、等方層で占められる領域)のそれぞれを測定対象とし、反射スペクトルを測定した。測定装置としては、平行照明ユニットを備え付けたディスプレイ測定システム(コニカミノルタ製、製品名「DMS803」)を用いた。
非偏光での観察による色差ΔE*(N)の取得を行う場合、光度計と測定対象との間に、直線偏光子を介在させない状態で測定を行った。
(3.1)非偏光での観察(ΔE*(N)):極角0°方向。
(3.2)偏光での観察(ΔE*(P)):極角0°方向。
(3.3)偏光での観察(ΔE*(P)):極角20~70°且つ方位角0~360°の全方向。測定の最大値と、かかる最大値を与えた極角とを記録した。
得られた光学表示媒体について、下記の各種の目視評価を行った。
(4.1)非偏光での目視評価。光学表示媒体の表示面を、自然光照射下において、様々な角度から、偏光子等を介さずに直接目視で観察し、領域RA及び領域RBの境界部が視認されるか否か、及び色の相違が視認されるか否かを、それぞれ判定した。
(4.2)直線偏光子を用いた、偏光での目視評価。光学表示媒体の表示面を、自然光照射下において、極角0°方向において、直線偏光子を介して観察し、コントラストの相違が視認されるか否かを判定した。併せて、極角を変更し0°超の様々な極角及び様々な方位角から観察し、コントラストの相違が視認されるか否かを判定し、全ての角度から視認できない場合は「見えない」と評価し、視認される場合はどの極角から最も大きな相違が視認されたかを記録した。
(4.3)偏光サングラスを用いた、偏光での目視評価。直線偏光子を用いず、その代わりに、観察者が直線偏光レンズを備えた偏光サングラスを装着した他は、上記(4.2)と同じ評価を行った。
(4.4)偏光光源を用いた、偏光での目視評価。直線偏光子を用いず、且つ、自然光に代えて直線偏光を用いた他は、上記(4.2)と同じ評価を行った。直線偏光としては、市販のスマートフォン(Samsung製、商品名「GalaxyA41」)又は市販のパーソナルコンピューター(パナソニック株式会社製、商品名「Let’s note CF-SZ6」)に設けられた液晶表示装置からの出射光を使用した。全ての例において、どちらの偏光を用いた場合も判定結果は同じであった。
表1に示す各成分を、表1に示す割合で混合し、塗布液A~Eを得た。
液晶性化合物(X1):前記式(B5)で表される光重合性の液晶性化合物。
液晶性化合物LC242:BASF社製、商品名「Paliocolor LC242」。
カイラル剤:BASF社製、商品名「Paliocolor LC756」。
配向助剤(X2):前記式(A10)で表される光重合性の非液晶性化合物。
光重合開始剤(OXE02):チバ・ジャパン社製、商品名「Irgacure OXE02」
光重合開始剤(907):チバ・ジャパン社製、商品名「Irgacure 907」
界面活性剤:AGCセイミケミカル社製、商品名「S-420」
MEK:メチルエチルケトン
CPN:シクロペンタノン
表2に示す各成分を、表2に示す割合で混合し、塗布液2SG、2G及び2Bを得た。
(1-1.複屈折層用フィルム)
支持フィルム(長尺のポリエチレンテレフタレートフィルム、東洋紡社製「PETフィルムA4100」、厚み100μm、以下において同じ)を用意し、その表面にラビング処理を施した。ラビング処理された面に、製造例1で得た塗布液1Bをバーコーターにて塗布し、未硬化状態の塗布液の膜を形成した。
支持フィルム上に形成された複屈折層用フィルム1Bに、凹凸形状を有するローラーを押し当てて亀裂を形成し、その後空気を吹き付けて、複屈折層用フィルムを支持フィルムから剥離し、剥離片を得た。剥離片をカッターミル(ウエスト社製「ミクロ・パウダーMPW-G008」、以下において同じ)で粉砕し、51μmの篩を用いて分級した。篩を通過した粒子のみを回収して、複屈折層用フレーク1Bを得た。複屈折層用フレーク1Bの粒度分布を測定し平均粒径を求めたところ、30μmであった。
スクリーンインキ(十条ケミカル社製「No.2500メジウム」)100部、当該スクリーンインキの専用希釈剤(テトロン標準溶剤)10部、及び複屈折層用フレーク1B 15部を混合し、複屈折層用インキ1Bを得た。
新たな支持フィルムの一方の表面に、製造例1で得た塗布液1Dをバーコーターにて塗布し、未硬化状態の塗布液の膜を形成した。塗布液の膜に、オーブンにて210℃で5分間加熱する処理を施して、膜を乾燥させた。その後、膜に紫外線を照射し硬化させた。照射は窒素雰囲気下(酸素濃度400ppm以下)で、加熱時の温度210℃の状態のまま行い、線源としては高圧水銀ランプを用い、365nm(i線)における照度を280mW/cm2とし、365nm(i線)における露光量を400mJ/cm2とした。これにより、支持フィルム上に、等方層用フィルム1Dを形成した。等方層用フィルムの厚みは、3.1μmであった。
支持フィルム上の複屈折層用フィルム1Bに代えて、支持フィルム上の等方層用フィルム1Dを用いた他は、(1-2)~(1-3)と同じ操作により、等方層用フレーク1D及び等方層用インキ1Dを得た。等方層用フレーク1Dの平均粒径は30μmであった。
支持フィルムを用意し、その表面にラビング処理を施した。ラビング処理された面に、製造例2で得た塗布液2SGをバーコーターにて塗布し、未硬化状態の塗布液の膜を形成した。
複屈折層用フレーク1Bに代えて反射偏光子層用フレーク2Sを用いた他は、(1-3)と同じ操作により、反射偏光子層用インキ2Sを得た。
基材(黒色に着色されたポリエチレンテレフタレートフィルム)を用意し、その表面にコロナ処理を施した。コロナ処理された面に、(1-7)で得た反射偏光子層用インキ2Sの膜を、スクリーン印刷(1インチ当たり線数120のスクリーン版を使用。以下において同じ。)により形成した。膜を乾燥させて、反射偏光子層を形成し、反射偏光子層及び基材を備える複層物を得た。得られた反射偏光子層を自然光の下で目視にて観察したところ、銀色の外観を有していた。
(1-8)で得た複層物の反射偏光子層側の表面の一部の、矩形の領域に、(1-3)で得た複屈折層用インキ1Bの膜を、スクリーン印刷により形成した。膜を乾燥させて、複屈折層を形成した。
(1-9)で得た複層物の反射偏光子層側の表面の、複屈折層に隣接する矩形の領域に、(1-5)で得た等方層用インキ1Dの膜を、スクリーン印刷により形成した。膜を乾燥させて、等方層を形成した。インキの塗布量は、等方層の厚みが隣接する複屈折層と同じ厚みとなるよう調整した。これにより、基材及び反射偏光子層、並びに反射偏光子層の表面上に設けられた複屈折層及び等方層を備える、図1に概略的に示す形状を有する光学表示媒体を得た。
下記の変更点以外は、実施例1と同じ操作により、光学表示媒体及びその他の構造物を得て評価した。得られた複屈折層及び等方層はいずれも、一般的な透明フィルムと同様の透明な層の外観を有していた。
・(1-1)の複屈折層用フィルムの形成において、塗布液1Bに代えて塗布液1Aを用いた。
・(1-4)の等方層用フィルムの形成において、塗布液1Dに代えて塗布液1Cを用いた。
・(1-9)の複屈折層の形成において、複屈折層用インキの塗布厚みを変更した。得られた複屈折層の厚み、面内位相差Re0及び斜め45°位相差Re45は表3に示す通りであった。
下記の変更点以外は、実施例1と同じ操作により、光学表示媒体及びその他の構造物を得て評価した。
・(1-9)の複屈折層の形成において、複屈折層用インキの塗布厚みを変更した。得られた複屈折層の面内位相差Re0及び斜め45°位相差Re45は表3に示す通りであった。得られた複屈折層は、一般的な透明フィルムと同様の透明な層の外観を有していた。
(5-1.反射偏光子層用フィルム2B及びフレーク2B)
下記の変更点以外は、実施例1の(1-6)と同じ操作により、反射偏光子層用フィルム2B及び反射偏光子層用フレーク2Bを得た。
・塗布液2SGに代えて塗布液2Bを用いた。
・広帯域化処理を行わなかった。即ち、乾燥させた膜を、広帯域化処理を経ること無く硬化用紫外線照射に供した。得られた反射偏光子層用フィルム2Bは、自然光の下で目視で観察したところ、青色の外観を有していた。
複屈折層用フレーク1Bに代えて反射偏光子層用フレーク2Bを用いた他は、実施例1の(1-3)と同じ操作により、反射偏光子層用インキ2Bを得た。
(1-8)の反射偏光子層の形成において、反射偏光子層用インキ2Sに代えて、(5-2)で得た反射偏光子層用インキ2Bを用いた他は、実施例1の(1-1)~(1-5)及び(1-8)~(1-10)と同じ操作により、光学表示媒体及びその他の構造物を得て評価した。
(6-1.反射偏光子層用フィルム2G及びフレーク2G)
下記の変更点以外は、実施例1の(1-6)と同じ操作により、反射偏光子層用フィルム2G及び反射偏光子層用フレーク2Gを得た。
・広帯域化処理を行わなかった。即ち、乾燥させた膜を、広帯域化処理を経ること無く硬化用紫外線照射に供した。得られた反射偏光子層用フィルム2Bは、自然光の下で目視で観察したところ、緑色の外観を有していた。
複屈折層用フレーク1Bに代えて反射偏光子層用フレーク2Gを用いた他は、実施例1の(1-3)と同じ操作により、反射偏光子層用インキ2Gを得た。
(1-8)の反射偏光子層の形成において、反射偏光子層用インキ2Sに代えて、(6-2)で得た反射偏光子層用インキ2Gを用いた他は、実施例1の(1-1)~(1-5)及び(1-8)~(1-10)と同じ操作により、光学表示媒体及びその他の構造物を得て評価した。
(7-1.反射偏光子層用フィルム2R及びフレーク2R)
下記の変更点以外は、実施例1の(1-6)と同じ操作により、反射偏光子層用フィルム2R及び反射偏光子層用フレーク2Rを得た。
・塗布液2SGに代えて塗布液2Rを用いた。
・広帯域化処理を行わなかった。即ち、乾燥させた膜を、広帯域化処理を経ること無く硬化用紫外線照射に供した。得られた反射偏光子層用フィルム2Rは、自然光の下で目視で観察したところ、赤色の外観を有していた。
複屈折層用フレーク1Bに代えて反射偏光子層用フレーク2Rを用いた他は、実施例1の(1-3)と同じ操作により、反射偏光子層用インキ2Rを得た。
(1-8)の反射偏光子層の形成において、反射偏光子層用インキ2Sに代えて、(7-2)で得た反射偏光子層用インキ2Rを用いた他は、実施例1の(1-1)~(1-5)及び(1-8)~(1-10)と同じ操作により、光学表示媒体及びその他の構造物を得て評価した。
(8-1.反射偏光子層用インキ2RGB)
複屈折層用フレーク1B 15部に代えて、(5-1)で得た反射偏光子層用フレーク2B 5部、(6-1)で得た反射偏光子層用フレーク2G 5部、及び(7-1)で得た反射偏光子層用フレーク2R 5部を組み合わせて用いた他は、実施例1の(1-3)と同じ操作により、反射偏光子層用インキ2RGBを得た。
(1-8)の反射偏光子層の形成において、反射偏光子層用インキ2Sに代えて、(8-1)で得た反射偏光子層用インキ2RGBを用いた他は、実施例1の(1-1)~(1-5)及び(1-8)~(1-10)と同じ操作により、光学表示媒体及びその他の構造物を得て評価した。反射偏光子層が得られた時点で、反射偏光子層を自然光の下で目視にて観察したところ、銀色の外観を有していた。
下記の変更点以外は、実施例1と同じ操作により、光学表示媒体及びその他の構造物を得て評価した。
・(1-4)の等方層用フィルムの形成において、塗布液1Dに代えて塗布液1Eを用いた。等方層は、一般的な透明フィルムと同様の透明な層の外観を有していた。
(C1-1.複屈折層用フレーク)
市販のλ/4波長板フィルム(日本ゼオン製、商品名「ゼオノアフィルム」、厚み13μm、以下において同じ)を裁断して切片を得た。切片をカッターミルで粉砕し、51μmの篩を用いて分級した。篩を通過した粒子のみを回収して、複屈折層用フレーク1Fを得た。
スクリーンインキ(十条ケミカル社製「No.2500メジウム」)100部、及び当該スクリーンインキの専用希釈剤(テトロン標準溶剤)10部を混合し、等方層用インキ1Gを得た。
下記の変更点以外は、実施例1の(1-3)及び(1-6)~(1-10)と同じ操作により、光学表示媒体及びその他の構造物を得て評価した。
・(1-3)の複屈折層用インキの調製において、複屈折層用フレーク1Bに代えて、(C1-1)で得た複屈折層用フレーク1Fを用いた。
・(1-10)の等方層の形成において、等方層用インキ1Dに代えて、(C1-2)で得た等方層用インキ1Gを用いた。
(C2-1.複屈折層用フレーク)
市販のλ/2波長板フィルム(日本ゼオン製、商品名「ゼオノアフィルム」、厚み26μm、以下において同じ)を裁断して切片を得た。切片をカッターミルで粉砕し、51μmの篩を用いて分級した。篩を通過した粒子のみを回収して、複屈折層用フレーク1Hを得た。
下記の変更点以外は、実施例1の(1-3)及び(1-6)~(1-10)と同じ操作により、光学表示媒体及びその他の構造物を得て評価した。
・(1-3)の複屈折層用インキの調製において、複屈折層用フレーク1Bに代えて、(C2-1)で得た複屈折層用フレーク1Hを用いた。
・(1-10)の等方層の形成において、等方層用インキ1Dに代えて、比較例1の(C1-2)で得た等方層用インキ1Gを用いた。
下記の変更点以外は、実施例1の(1-6)~(1-10)と同じ操作により、光学表示媒体及びその他の構造物を得て評価した。
・(1-9)の複屈折層の形成において、複屈折層用インキの印刷による塗布及び乾燥を行うことに代えて、市販のλ/2波長板フィルム(日本ゼオン製、商品名「ゼオノアフィルム」)を反射偏光子層の表面に貼合し、それにより複屈折層を形成した。貼合は、波長板フィルムを、(1-9)において形成した複屈折層と同じ形状に裁断し、一方の表面に接着剤層を設け、当該接着剤層を介して反射偏光子層と波長板フィルムとを接着することにより行った。加えて、上記λ/2波長板フィルムの面内位相差Re0及び斜め45°位相差Re45を測定した。測定結果は表3に示す通りであった。
・(1-10)の等方層の形成において、等方層用インキ1Dに代えて、比較例1の(C1-2)で得た等方層用インキ1Gを用いた。
(C4-1.ポジティブA複屈折層用フィルム)
塗布液1Bに代えて塗布液1Dを用い、且つ塗布厚みを2通りに変更した他は、実施例1の(1-1)と同じ操作により、支持フィルム上に、複屈折層用フィルム1D-1を形成した。複屈折層用フィルム1D-1の厚みは1.2μmであった。
下記の変更点以外は、実施例1の(1-4)~(1-10)と同じ操作により、光学表示媒体及びその他の構造物を得て評価した。
・(1-9)の複屈折層の形成において、複屈折層用インキの印刷による塗布及び乾燥を行うことに代えて、(C4-1)で得た複屈折層用フィルム1D-1を反射偏光子層の表面に貼合し、それにより複屈折層を形成した。貼合は、複屈折層用フィルムを、(1-9)において形成した複屈折層と同じ形状に裁断し、一方の表面に接着剤層を設け、当該接着剤層を介して反射偏光子層と複屈折層用フィルムを接着し、その後支持フィルムを剥離することにより行った。加えて、支持フィルム上に、上に述べた形成方法と同じ方法で、位相差測定用の複屈折層を形成し、これを、市販の接着剤を介して、ガラスに転写し、位相差測定用の複屈折層を形成した。その面内位相差Re0及び斜め45°位相差Re45を測定した。測定結果は表3に示す通りであった。
下記の変更点以外は、実施例1の(1-3)~(1-10)と同じ操作により、光学表示媒体及びその他の構造物を得て評価した。
・(1-3)の複屈折層用インキの調製において、複屈折層用フレーク1Bに代えて、(C2-1)で得た複屈折層用フレーク1Hを用いた。
101:基材
101U:基材の上側の面
102:反射偏光子層
102U:反射偏光子層の上側の面
111:複屈折層
112:等方層
119:境界
RL:反射領域
RA:領域
RB:領域
Claims (9)
- 表示面を有する光学表示媒体であって、
前記表示面の一部又は全部の領域である反射領域RLに設けられる反射偏光子層と、
前記反射偏光子層より視認側に設けられ、前記反射領域RLの一部を占める領域RAに設けられる複屈折層とを備え、
前記反射偏光子層は、入射光を、円偏光または直線偏光として反射する層であり、
前記複屈折層は、フレーク状複屈折素材を含み、Cプレートとしての光学特性を示す層である、光学表示媒体。 - 前記反射偏光子層が、コレステリック規則性を有する材料の層である、請求項1に記載の光学表示媒体。
- 前記反射偏光子層が、フレーク状反射素材を含むインキ層である、請求項1又は2に記載の光学表示媒体。
- 前記光学表示媒体を非偏光で観察した際の、前記領域RAと、前記反射領域RLのうちの前記領域RA以外の領域RBとの色差ΔE*(N)が、極角0°方向の観察において1以下である、請求項1又は2に記載の光学表示媒体。
- 前記色差ΔE*(N)が、極角20~70°且つ方位角0~360°の全方向の観察の全てにおいて1以下である、請求項4に記載の光学表示媒体。
- 前記光学表示媒体を偏光で観察した際の、前記領域RAと、前記反射領域RLのうちの前記領域RA以外の領域RBとの色差ΔE*(P)が、極角20~70°且つ方位角0~360°の全方向の観察うちのどれか1において3以上である、請求項1又は2に記載の光学表示媒体。
- 前記色差ΔE*(P)が、極角0°方向の観察において1以下である、請求項6に記載の光学表示媒体。
- 極角0°方向から測定した前記複屈折層の面内位相差Re(A)0が、Re(A)0≦30nmを満たし、
極角45°のいずれかの方位角から測定した前記複屈折層の斜め位相差Re(A)45が、下記式(e1):
70nm≦Re(A)45≦700nm 式(e1)
を満たす、請求項1又は2に記載の光学表示媒体。 - 前記反射偏光子層より視認側に設けられ、前記反射領域RLのうちの前記領域RA以外の領域RBの一部又は全部を占める等方層をさらに備え、
極角0°方向から測定した前記等方層の面内位相差Re(B)0が、Re(B)0≦30nmを満たし、
前記等方層の斜め位相差Re(B)45が、0≦Re(B)45≦30を満たす、
請求項1又は2に記載の光学表示媒体。
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WO2020261923A1 (ja) * | 2019-06-26 | 2020-12-30 | 日本ゼオン株式会社 | 表示媒体、真正性判定方法、及び表示媒体を含む物品 |
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2022
- 2022-06-22 CN CN202280043650.7A patent/CN117546062A/zh active Pending
- 2022-06-22 JP JP2023533520A patent/JPWO2023282063A1/ja active Pending
- 2022-06-22 EP EP22837480.7A patent/EP4369064A1/en active Pending
- 2022-06-22 WO PCT/JP2022/024956 patent/WO2023282063A1/ja active Application Filing
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WO2020121791A1 (ja) | 2018-12-11 | 2020-06-18 | 日本ゼオン株式会社 | 真正性判定用のビュワー及びその製造方法、識別媒体の真正性の判定方法、並びに、真正性判定用セット |
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