Cured product, and method for manufacturing the cured product

Abstract

The present invention provides a cured product that exhibits iridescent colors, and a method for manufacturing the cured product. [Solution] In the second image, let x be the horizontal frequency with respect to the origin, and let y be the vertical frequency, f 2 =x 2 +y 2 The average power spectral intensity for a given spatial frequency f is calculated, and the common logarithm of this average is plotted to obtain a logarithmic spectrum in which the logarithmic spectrum has a peak PK in the average power spectral intensity at 0.2 < |f| < 1 (cycles / μm), and the difference I is obtained by subtracting the average value of the common logarithms of the average power spectral intensity at 0 < |f| ≤ 0.2 (cycles / μm) from the common logarithm of the average power spectral intensity at peak PK, and the difference I is 0.7 or greater.

Description

[Technical Field]

[0001] This disclosure relates to cured products and methods for manufacturing cured products. [Background technology]

[0002] An example of a decorative sheet comprises a resin substrate layer, a transparent resin layer, and a colored layer located between the resin substrate layer and the transparent substrate layer. In the decorative sheet, L is measured from the transparent resin layer side before and after the tensile test. * a * b * L in the SCE color system * The absolute value of the difference is 1.5 or less (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-28516 [Overview of the project] [Problems that the invention aims to solve]

[0004] For decorative sheets that can be used to decorate items, there is a demand for decorative sheets that exhibit rainbow colors. [Means for solving the problem]

[0005] A cured product for solving the above problem has a surface, and the surface includes wrinkle-like fine irregularities. Three-dimensional data obtained by measuring the fine irregularities using an optical interferometry method or a contact method is converted into first image data in which the height of the fine irregularities included in the three-dimensional data is used as the pixel value, the first image data is converted into a second image by a fast Fourier transform, and in the second image, the horizontal frequency with respect to the origin is set to x, the vertical frequency to y, and f 2 =x 2 +y 2The average value of the power spectral intensity with respect to a spatial frequency f is calculated, and in the logarithmic spectrum obtained by plotting the common logarithm of the average value, the logarithmic spectrum has a peak in the average value of the power spectral intensity at 0.2 < |f| < 1 (cycles / μm), and when the difference value I is obtained by subtracting the average value of the common logarithms of the power spectral intensity at 0 < |f| ≤ 0.2 (cycles / μm) from the common logarithm of the average value of the power spectral intensity at the peak, the difference value I is 0.7 or greater.

[0006] According to the cured material described above, since the difference value I is 0.7 or more, the cured material diffracts the reflected or transmitted light, causing interference between the diffracted light, and as a result the cured material 11 can exhibit vivid rainbow colors.

[0007] In the cured product described above, the average value of the power spectral intensity at the peak may be 10,000 or more. According to the above cured material, the difference value I tends to be large, so the cured material tends to exhibit more vivid rainbow colors.

[0008] In the cured product described above, the distance between the protrusions in the fine irregularities may be 1.0 μm or more and 5.0 μm or less. According to the above cured material, diffraction is likely to occur on the surface of the cured material.

[0009] In the cured product described above, the depth of the fine irregularities may be 0.3 μm or more and 1.5 μm or less. The above-described cured material makes it possible to increase the likelihood of diffraction occurring on the surface of the cured material.

[0010] A method for producing a cured product to solve the above problems includes forming a coating film by applying a coating solution containing a photopolymerizable compound and a polymer to at least one of the first and second surfaces of a substrate, and curing the coating film by irradiating it with an electron beam, thereby forming a cured product having a surface containing wrinkle-like fine irregularities.

[0011] According to the method for producing the cured product, by irradiating an electron beam onto a coating film containing a photopolymerizable compound and a polymer, a cured product having a surface with wrinkled fine irregularities can be formed, so that a cured product capable of exhibiting an iridescent color can be easily obtained.

[0012] In the method for producing the cured product, the polymer may contain at least one of a repeating unit derived from an acrylate ester and a repeating unit derived from a methacrylate ester, and the weight average molecular weight of the polymer may be 5000 or more and 1000000 or less.

[0013] In the method for producing the cured product, the polymer may contain a methyl methacrylate skeleton. According to the method for producing the cured product, the compatibility of the polymer with the photopolymerizable compound is enhanced.

[0014] In the method for producing the cured product, the photopolymerizable compound may contain at least one of a methacrylate containing two functional groups in one molecule and an acrylate containing two functional groups in one molecule. According to the method for producing the cured product, fine irregularities are likely to be uniformly formed on the surface of the cured product.

[0015] In the method for producing the cured product, the photopolymerizable compound may contain at least one of an acyclic acrylate and an acyclic methacrylate.

[0016] In the method for producing the cured product, the photopolymerizable compound may contain at least one of an alkyl acrylate and an alkyl methacrylate. According to the method for producing the cured product, since the photopolymerizable compound contains an acrylate having a linear shape, fine irregularities are likely to be formed on the surface of the cured product.

Advantages of the Invention

[0017] According to the cured product and the method for producing the cured product of the present disclosure, an iridescent color can be exhibited.

Brief Description of the Drawings

[0018] [Figure 1] FIG. 1 is a cross-sectional view showing the structure of a decorative film including a cured product of one embodiment. [Figure 2] FIG. 2 is a plan view schematically showing a first image obtained from the surface of the cured product. [Figure 3] FIG. 3 is an example of a second image obtained by performing a fast Fourier transform on the first image. [Figure 4] FIG. 4 is a logarithmic spectrum plotting the common logarithm of the average value of the power spectrum intensity in the second image shown in FIG. 3. [Figure 5] FIG. 5 is a process diagram showing one step included in the method for manufacturing the cured product. [Figure 6] FIG. 6 is a process diagram showing one step included in the method for manufacturing the cured product. [Figure 7] FIG. 7 is a process diagram showing one step included in the method for manufacturing the cured product. [Figure 8] FIG. 8 is a table showing the composition of the coating liquid, the Nv value of the coating liquid, the film thickness of the cured product, and the active energy ray used for irradiation in each example and each comparative example. [Figure 9] FIG. 9 is a table showing the evaluation results of each example and each comparative example. [Figure 10] FIG. 10 is an example of a first image obtained by converting three-dimensional data acquired using a laser microscope. [Figure 11] FIG. 11 is a graph plotting the chromaticity coordinates (x, y) obtained by converting the spectral spectra obtained for Example 1, Example 7, and Comparative Example 1 into the XYZ colorimetric system.

Embodiments for Carrying Out the Invention

[0019] Referring to FIGS. 1 to 11, one embodiment of a cured product and a method for manufacturing the cured product will be described. [Decorative Film] The decorative film 10 shown in Figure 1 comprises a cured product 11 of the present disclosure and a substrate 12 that supports the cured product 11. In the example shown in Figure 1, the decorative film 10 has the cured product 11 on only the first surface 12S1 of the two opposing surfaces 12S1 and 12S2 of the substrate 12. The surface 11S is the surface of the cured product 11 that is opposite to the surface in contact with the substrate 12. The decorative film 10 may also have the cured product 11 on both the first surface 12S1 and the second surface 12S2 of the substrate 12.

[0020] The decorative film 10 may include, for example, the following layers in addition to the cured product 11 and the substrate 12. The decorative film 10 may include at least one of a hard coat layer, a primer layer, a printing layer, a vapor deposition layer, and an adhesive layer. The decorative film 10 may include only one of the hard coat layer, primer layer, printing layer, vapor deposition layer, and adhesive layer, or two or more of which are optionally selected.

[0021] If the decorative film 10 includes a hard coat layer, the hard coat layer may cover the second surface 12S2 of the substrate 12, or it may cover the surface 11S of the cured product 11. If the hard coat layer covers the surface 11S of the cured product 11, the hard coat layer must have optical properties that do not hinder the diffraction of light that occurs on the surface 11S of the cured product 11. The hard coat layer can increase the hardness of the outer surface of the decorative film 10.

[0022] If the decorative film 10 includes a primer layer, the primer layer may be located, for example, between the cured product 11 and the substrate 12. The primer layer enhances the adhesion between the two opposing layers via the primer layer.

[0023] If the decorative film 10 includes a printed layer, the printed layer may be located, for example, between the cured product 11 and the substrate 12, or on the second surface 12S2 of the substrate 12. Alternatively, the printed layer may be located on the surface 11S of the cured product 11, to the extent that diffraction on the surface of the cured product 11 is not hindered. The printed layer allows any design to be added to the decorative film 10, thereby enhancing the aesthetic appeal of the decorative film 10.

[0024] If the decorative film 10 includes a vapor-deposited layer, the vapor-deposited layer may be located, for example, on the second surface 12S2 of the substrate 12, or on the surface 11S of the cured product 11. If the vapor-deposited layer is located on the surface 11S of the cured product 11, it is necessary that the vapor-deposited layer has optical properties that do not hinder the diffraction of light that occurs on the surface 11S of the cured product 11. The reflectance of the vapor-deposited layer may be higher than the reflectance of the substrate 12 and the reflectance of the cured product 11. In this case, the reflectance of the second surface 12S2 of the substrate 12, or the surface 11S of the cured product 11, can be increased.

[0025] If the decorative film 10 includes an adhesive layer, the adhesive layer may be located, for example, on the second surface 12S2 of the substrate 12. In this case, the decorative film 10 may include a release sheet located on the opposite side of the substrate 12 from the adhesive layer. This allows the cured product 11 to be attached to the object by the adhesive layer by peeling the release sheet of the decorative film 10 from the adhesive layer. Since it is easy to attach the cured product 11 to the object, the applications of the decorative film 10 can be expanded.

[0026] [Cured product] The cured product 11 will be explained with reference to Figures 2 to 4. As described above, the cured product 11 of this disclosure has a surface 11S. The surface 11S contains wrinkle-like fine irregularities. When the fine irregularities are analyzed by the method described below, the conditions 1 and 2 described later are satisfied.

[0027] When analyzing microscopic surface irregularities, three-dimensional data is first obtained by measuring the irregularities using optical interferometry or contact methods. The obtained three-dimensional data includes the position within the two-dimensional measurement surface and the height of the microscopic irregularities. For example, three-dimensional data of microscopic irregularities can be obtained using optical interferometry by using a laser microscope. Next, the three-dimensional data is converted into first image data, in which the height of the microscopic irregularities contained in the three-dimensional data is used as the pixel value.

[0028] Figure 2 shows an example of the first image. In the first image, tonal values ​​are applied such that the higher parts of the surface 11S become brighter, and the lower parts become darker. That is, in the first image, the convex parts of the micro-irregularities are bright, while the concave parts of the micro-irregularities are dark. However, in Figure 2, for illustrative purposes, the convex parts of the micro-irregularities are shown with black medials.

[0029] As shown in Figure 2, in the first image, the protrusions 11SA included in the surface 11S have a wrinkled appearance. The protrusions 11SA extend in a 360° direction with respect to any point within the measurement surface. In other words, the protrusions 11SA do not have a predetermined directionality within the measurement surface.

[0030] The distance P between the protrusions 11SA in the fine irregularities may be, for example, 1.0 μm or more and 5.0 μm or less. In this case, diffraction is likely to occur on the surface 11S of the cured product 11. The distance P between the protrusions 11SA may be, for example, the distance between the protrusions 11SA that extend along a predetermined direction. The depth of the fine irregularities may be, for example, 0.3 μm or more and 1.5 μm or less. In this case, the likelihood of diffraction occurring on the surface 11S of the cured product 11 can be increased. The depth of the fine irregularities is the distance along the height direction between the highest and lowest positions of adjacent protrusions and recesses, respectively.

[0031] Thus, since the fine irregularities have a wrinkled shape that spreads in random directions and the distance between the convex portions 11SA is within a predetermined range, the reflected light on the surface 11S of the cured product 11 includes scattered light and diffracted light. Therefore, the cured product 11 exhibits cloudiness due to the scattered light and can exhibit different colors as the observation direction of the observer changes.

[0032] Next, the first image data is converted into a second image P2 (see FIG. 3) by fast Fourier transform. FIG. 3 is an example of the second image P2. As shown in FIG. 3, since the wrinkled fine irregularities included in the cured product 11 have no directivity, in the second image P2, an annular ring centered on the center of the second image P2 and having a high luminance is recognized. In the second image P2, let the horizontal frequency with respect to the origin be x, the vertical frequency be y, and f 2 =x 2 +y 2 Calculate the average value of the power spectrum intensity for the spatial frequency f. A logarithmic spectrum is obtained by plotting the common logarithm of the average value.

[0033] In other words, the distance from the DC component in the second image P2 is converted into the spatial frequency f, and then, for the spatial frequency f, the logarithm of the circumferential average value of the true number in the power spectrum intensity is taken, thereby obtaining a logarithmic spectrum.

[0034] The obtained logarithmic spectrum satisfies the following conditions 1 and 2. (Condition 1) The logarithmic spectrum has a peak PK (see FIG. 4) in the average value of the power spectrum intensity at 0.2 < |f| < 1 (cycles / μm).

[0035] (Condition 2) When the difference value I is obtained by subtracting the average value of the common logarithm of the power spectrum intensity in the range of 0 < |f| ≤ 0.2 (cycles / μm) from the common logarithm of the average value of the power spectrum intensity at the peak PK, the difference value I is 0.7 or more. <0000​​Figure 4 shows the logarithmic spectrum obtained from the second image P2 shown in Figure 3. Hereafter, the average value of the power spectral intensity with respect to spatial frequency f will be referred to as the first mean value, and the value obtained by averaging the first mean values ​​in the range where spatial frequency f is greater than 0 and less than or equal to 0.2 will be referred to as the second mean value.

[0037] As shown in Figure 4, the logarithmic spectrum has a peak PK in the range 0.2 < |f| < 1 (cycles / μm). In the example shown in Figure 4, the logarithmic spectrum has a peak PK in the range greater than 0.2 and less than or equal to 0.4. Also, the second mean, which is the average of the first mean values ​​in the range 0 < |f| ≤ 0.2, is less than 4. Therefore, the difference value I, obtained by subtracting the second mean from the common logarithm of the first mean at the peak PK, is greater than 2.

[0038] In the fine irregularities of the cured product 11, the larger the difference value I, the higher the regularity as a diffraction grating, which in turn causes the cured product to exhibit a more vivid color. In the cured product 11 of this disclosure, the difference value I is 0.7 or greater, so the cured product 11 diffracts reflected or transmitted light, causing interference between the diffracted light, and as a result the cured product 11 can exhibit a vivid rainbow color.

[0039] As described above, it is preferable that the distance between the protrusions 11SA in the fine irregularities is 1.0 μm or more and 5.0 μm or less, and the depth of the fine irregularities is 0.3 μm or more and 1.5 μm or less, satisfying at least one of these conditions. That is, only the distance between the protrusions 11SA may be included in the above range, only the depth of the fine irregularities may be included in the above range, or both the distance between the protrusions 11SA and the depth of the fine irregularities may be included in the above range. This makes it possible to obtain sufficient effects due to diffraction and interference in the reflected or transmitted light of the cured product 11.

[0040] In the logarithmic spectrum, the average power spectral intensity at peak PK may be 10,000 or more. In this case, the difference value I tends to be larger, so the cured product 11 is more likely to exhibit a vivid rainbow color.

[0041] [Method for manufacturing hardened products] The method for manufacturing the cured product will be explained with reference to Figures 5 to 7. The method for producing the cured product 11 in this disclosure includes forming a coating film and forming the cured product 11. Forming a coating film is performed by applying a coating solution containing a photopolymerizable compound and a polymer to at least one of the first surface 12S1 and the second surface 12S2 of the substrate 12. Forming the cured product 11 is performed by curing the coating film by irradiating it with an electron beam, thereby forming a cured product 11 having a surface containing wrinkle-like fine irregularities.

[0042] According to the method for manufacturing the cured product 11 of this disclosure, a cured product 11 having a surface containing fine irregularities can be formed by irradiating the coating film with an electron beam, making it possible to easily manufacture a cured product 11 that exhibits iridescence. The method for manufacturing the cured product 11 will be described in more detail below with reference to the drawings.

[0043] As shown in Figure 5, when manufacturing the cured product 11, first a base material 12 is prepared. The base material 12 may be a resin film made of various resins. For example, the base material 12 may be a polyethylene terephthalate (PET) film. The base material 12 includes a first surface 12S1 and a second surface 12S2 opposite to the first surface 12S1.

[0044] As shown in Figure 6, a coating film 21 is formed on the first surface 12S1 of the substrate 12 by applying the coating liquid to the first surface 12S1. The coating liquid contains a photopolymerizable compound and a polymer. The thickness of the coating film 21 may be thicker or thinner than the thickness of the substrate 12. The surface 21S of the coating film 21 is the surface opposite to the surface in contact with the substrate 12. The surface 21S of the coating film 21 is substantially flat.

[0045] For example, the material contained in the coating 21 may satisfy at least one of the following conditions 3 to 7. That is, the material contained in the coating 21 may satisfy only one of conditions 3 to 7, or it may satisfy two or more selected from conditions 3 to 7. It is preferable that the material contained in the coating 21 satisfies all of conditions 3 to 7.

[0046] (Condition 3) The polymer contains at least one of repeating units derived from acrylic acid ester and repeating units derived from methacrylic acid ester, and the weight-average molecular weight of the polymer is 5,000 or more and 1,000,000 or less.

[0047] (Condition 4) The polymer contains a methyl methacrylate skeleton. (Condition 5) The photopolymerizable compound comprises at least one of a methacrylate containing two functional groups in one molecule and an acrylate containing two functional groups in one molecule.

[0048] (Condition 6) The photopolymerizable compound comprises at least one of an acyclic acrylate and an acyclic methacrylate. (Condition 7) The photopolymerizable compound comprises at least one of an alkyl acrylate and an alkyl methacrylate.

[0049] In condition 3, the polymer may contain only one of either repeating units derived from acrylic acid esters or repeating units derived from methacrylic acid esters, or both. In condition 5, the photopolymerizable compound may contain only one of either a methacrylate containing two functional groups in one molecule or an acrylate containing two functional groups in one molecule, or both. In condition 6, the photopolymerizable compound may contain only one of either an acyclic acrylate or an acyclic methacrylate, or both. In condition 7, the photopolymerizable compound may contain only one of either an alkyl acrylate or an acrylic methacrylate, or both.

[0050] From the viewpoint of uniformly forming fine irregularities on the surface 11S of the cured product 11, the photopolymerizable compound preferably contains a linear compound, and preferably contains at least one of a methacrylate containing two functional groups in one molecule and an acrylate containing two functional groups in one molecule. Furthermore, if the photopolymerizable compound contains an alkyl methacrylate that is linear and contains two functional groups in one molecule, or an alkyl acrylate that is linear and contains two functional groups in one molecule, fine irregularities are easily formed on the surface of the cured product 11. From the viewpoint of improving compatibility with the photopolymerizable compound, the polymer is preferably a synthetic resin containing repeating units derived from methyl methacrylate or the like. The mass ratio (MA / MB) of the photopolymerizable compound (A) to the polymer (B) may be, for example, 8 / 2 or more and 9 / 1 or less.

[0051] As shown in Figure 7, the coating 21 is irradiated with an electron beam (EB). In this case, the coating 21 is directly irradiated with the electron beam (EB) without going through the substrate 12. The dose of the electron beam (EB) may be, for example, 10 kGy or more and 60 kGy or less.

[0052] The fine irregularities on the surface 11S of the cured product 11 are thought to be formed by the following mechanism. Specifically, buckling occurs on the surface 21S of the coating film 21 due to differences in the degree of curing or curing speed resulting from phase separation between the photopolymerizable compound and the polymer within the coating film 21, and this is thought to cause the formation of fine irregularities on the surface 11S of the cured product 11. Photopolymerizable compounds are compounds that harden when irradiated with active energy rays such as ultraviolet light or electron beams EB. In photopolymerizable compounds, the distance between newly bonded atoms decreases due to the bonding of molecules that occurs during the curing of the photopolymerizable compound, and this causes the photopolymerizable compound to shrink. In the manufacturing method of this disclosure, electron beams EB, which have approximately 1000 times more energy than ultraviolet light, are irradiated onto the coating film 21, so hardening and shrinkage occur instantaneously within the coating film 21. Therefore, the effect of the difference in curing speed between the photopolymerizable compound and the polymer is large, and it is thought that wrinkle-like fine irregularities are easily formed on the surface 11S of the cured product 11. Alternatively, in the manufacturing method of the present disclosure, the high-energy electron beam EB may generate heat on the surface 21S of the coating film 21, causing the surface 21S to expand thermally, which may result in the formation of fine irregularities on the surface 11S of the cured product 11.

[0053] The thickness of the cured material 11 allows for adjustment of the distance between the protrusions 11SA in the fine irregularities, the depth of the fine irregularities, and the appearance of the cured material 11 as seen by the naked eye. The thickness of the cured material 11 may be, for example, 0.3 μm or more and 2.0 μm or less.

[0054] Thus, in the method for manufacturing the cured product 11, a cured product 11 having a surface 11S with wrinkle-like fine irregularities can be formed by irradiating a coating film containing a photopolymerizable compound and a polymer with an electron beam EB, making it easy to obtain a cured product 11 capable of exhibiting iridescence. In the manufacturing of the cured product 11, it is not necessary to use a mold corresponding to the fine irregularities of the surface 11S of the cured product 11. Therefore, the cost of forming the mold can be reduced. Furthermore, when the cured product 11 is formed using a mold, if defects or scratches occur in the mold, these defects or scratches are transferred to the surface 11S of the cured product 11. In contrast, according to the method for manufacturing the cured product 11 in this disclosure, since a mold corresponding to the fine irregularities of the surface 11S is not used, defects or scratches are not transferred. In addition, since the distance between the protrusions 11SA in the fine irregularities and the depth of the fine irregularities can be changed depending on the material used to form the cured product 11 and the conditions when irradiating with an electron beam, it is not necessary to prepare a mold for each shape of fine irregularities.

[0055] Since the fine irregularities are formed by spontaneous buckling that occurs on the surface 21S of the coating film 21, it is difficult to form a cured product 11 with exactly the same shape of fine irregularities on its surface 11S. Therefore, in addition to the decorative properties due to the color exhibited by the cured product 11, it also has the effect of preventing counterfeiting.

[0056] In the method for manufacturing the cured product 11 in this disclosure, the coating film 21 is cured by electron beam irradiation, so the coating film 21 does not need to contain a photopolymerization initiator, as in the case where the coating film is cured by ultraviolet irradiation. Therefore, the environmental impact of the cured product 11 can be reduced. Furthermore, if the cured product 11 does not contain metal, the environmental impact of the cured product 11 can be reduced, and since the cured product 11 does not interfere with radio waves, the cured product 11 can be added to electronic devices for decoration.

[0057] [Examples] Examples and comparative examples will be described with reference to Figures 8 to 11. In each example and comparative example, the composition of the coating solution, the type of active energy ray, and the thickness of the cured film were set as shown in Figure 8. The materials described below were used to prepare the coating solution.

[0058] CHA: Cyclohexyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) NDDA: 1,9-nonanediol diacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) HDDA: 1,6-Hexanediol diacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) DCPA: Dimethylol-tricyclodecanediaacrylate (manufactured by Kyoeisha Chemical Co., Ltd.) PMMA: Methyl methacrylate polymer (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight approximately 800,000) Omnirad 819: Photopolymerization initiator (manufactured by IGM Resins BV) PGMEA: Propylene glycol monomethyl ether acetate

[0059] Furthermore, one of the following was used for the activation energy rays. EB:Electron beam UV: Ultraviolet light

[0060] Furthermore, polymer resin 1 was manufactured by the following method. 2.4 g of 1,2,2,6,6-pentamethyl-4-piperidyl methacrylic acid (FA-711MM, manufactured by Showa Denko Materials Co., Ltd.), 5.6 g of methyl methacrylate (manufactured by Kanto Chemical Co., Ltd.), 31 g of cyclohexanone (manufactured by Kanto Chemical Co., Ltd.), and 0.11 g of 2,2'-azobis(isobutyronitrile) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were placed in a reaction vessel. The contents of the reaction vessel were then heated and stirred under a nitrogen gas atmosphere at 70°C for 8 hours.

[0061] Subsequently, the contents of the reaction vessel were further heated and stirred at 100°C for 1 hour to obtain a polymer solution. This polymer solution was poured into 400 mL of methanol (manufactured by Kanto Chemical Co., Ltd.), and the resulting precipitate was filtered and then dried. This yielded resin 1, in which 1,2,2,6,-pentamethyl-4-piperidyl methacrylic acid and methyl methacrylate were copolymerized in a ratio of 15:85 (mol%). The weight-average molecular weight of the copolymer was 120,000.

[0062] [Example 1] In Example 1, a photopolymerizable compound was prepared by mixing cyclohexyl acrylate and 1,9-nonanediol diacrylate in a mass ratio of 30:70. A polymer, resin 1, was prepared by dissolving resin 1 in cyclohexanone to have a solid content of 51.0%. Propylene glycol monomethyl ether acetate was prepared as the solvent.

[0063] Then, a coating solution was obtained by mixing the photopolymerizable compound, polymer, and solvent such that the amount of photopolymerizable compound added was 25.5% by mass, the amount of polymer added was 14.7% by mass, and the amount of solvent added was 59.8% by mass. In Example 1, the Nv (Non-Volatile matter content) value of the coating solution was 33.0%.

[0064] A PET film with a thickness of 38 μm was prepared as the substrate 12. A coating film was formed on the first surface of the PET film by applying a coating solution using a bar coater (No. 4). After drying the coating film at 90°C for 1 minute, the coating film was irradiated with an electron beam in a nitrogen atmosphere with an oxygen concentration of 1 ppm to 10 ppm. A large substrate compatible electron beam irradiation device (manufactured by I-Electron Beam Co., Ltd.) was used for this. The conditions for electron beam irradiation were set to a voltage of 120 kV, a current of 2.3 mA, a conveyor speed of 6.0 m / min, a dose of 30 kGy, and one irradiation. As a result, a cured product 11 with a thickness of 1.2 μm was obtained. The thickness of the cured product 11 was measured using a contact film thickness gauge.

[0065] [Example 2] In Example 1, the amount of photopolymerizable compound added was changed to 15.5% by mass, the amount of polymer added was changed to 8.9% by mass, and the amount of solvent added was changed to 75.6% by mass. Otherwise, the cured product 11 of Example 2, having a thickness of 0.5 μm, was obtained by the same method as in Example 1. In Example 2, the Nv value of the coating solution was 20.0%.

[0066] [Example 3] In Example 1, the amount of photopolymerizable compound added was changed to 30.9% by mass, the amount of polymer added was changed to 17.8% by mass, and the amount of solvent added was changed to 51.3% by mass. Otherwise, the cured product 11 of Example 3, having a thickness of 1.6 μm, was obtained by the same method as in Example 1. In Example 3, the Nv value of the coating solution was 40.0%.

[0067] [Example 4] In Example 4, a methyl methacrylate polymer dissolved in acetone was prepared as the polymer, with a solid content of 5.0%. In Example 4, the photopolymerizable compound, polymer, and solvent were mixed to obtain a coating solution, with the photopolymerizable compound added at a rate of 23.4% by mass, the polymer added at a rate of 60.0% by mass, and the solvent added at a rate of 16.6% by mass. Otherwise, the cured product 11 of Example 4, having a thickness of 1.1 μm, was obtained by the same method as in Example 1. In Example 4, the Nv value of the coating solution was 26.4%.

[0068] [Example 5] In Example 1, the amount of photopolymerizable compound added was changed to 23.5% by mass, the amount of solvent added was changed to 59.8% by mass, and the amount of photopolymerization initiator added was 2.0% by mass, with the photopolymerization initiator added to the coating solution. Otherwise, the cured product 11 of Example 5, having a thickness of 1.3 μm, was obtained by the same method as in Example 1. In Example 5, the Nv value of the coating solution was 33.0%.

[0069] [Example 6] In Example 1, the photopolymerizable compound was changed to 1,6-hexanediol diacrylate. Otherwise, the cured product 11 of Example 6, having a thickness of 1.6 μm, was obtained by the same method as in Example 1. In Example 6, the Nv value of the coating solution was 33.0%.

[0070] [Example 7] In Example 1, the photopolymerizable compound was changed to 1,9-nonanediol diacrylate. Otherwise, the cured product 11 of Example 7, having a thickness of 1.7 μm, was obtained by the same method as in Example 1. In Example 7, the Nv value of the coating solution was 33.0%.

[0071] [Comparative Example 1] In Example 1, the amount of photopolymerizable compound added was changed to 23.5% by mass, and the amount of photopolymerization initiator added to the coating solution was 2.0% by mass. Also in Example 1, the large substrate compatible electron beam irradiation device was changed to a high-pressure mercury ultraviolet conveyor irradiation device, and the coating film was irradiated with ultraviolet light using this device. At this time, the conditions for ultraviolet irradiation were set to an integrated irradiation dose of 195 mJ / cm². 2 The number of irradiations was set to one for each case. As a result, a cured product 11 of Comparative Example 1 with a thickness of 1.0 μm was obtained.

[0072] [Comparative Example 2] In Comparative Example 2, a cured product 11 with a thickness of 1.1 μm was obtained by the same method as in Example 1, except that the amount of photopolymerizable compound added was changed to 33.0% by mass, no polymer was added, and the amount of solvent added was changed to 67.0% by mass. In Comparative Example 2, the Nv value of the coating solution was 33.0%.

[0073] [Comparative Example 3] In Comparative Example 3, cured product 11 was obtained by the same method as in Example 1, except that 1,9-nonanediol diacrylate was replaced with dimethylol-tricyclodecane diacrylate. In Comparative Example 3, the Nv value of the coating solution was 33.0%.

[0074] [Evaluation Method] [Surface shape] [Measurement of 3D data] The surface 11S of the cured product 11 of each example and comparative example was observed using a laser microscope (VK-X3000 Series, manufactured by Keyence Corporation). Three-dimensional data was measured using optical interferometry for the surface 11S of cured products 11 containing fine irregularities. The measurement conditions were set as follows.

[0075] Measurement size: Standard Measurement mode: Surface shape Scan mode: Laser confocal Lens magnification: 150 Measurement range: 94.80 μm × 71.31 μm (1024 pixels x 768 pixels)

[0076] The shape of the surface 11S of the cured product 11 of each example and each comparative example was evaluated at the following two levels. A: Fine, wrinkle-like irregularities were observed. B: No wrinkle-like fine irregularities were observed.

[0077] From the obtained 3D data, the distance between the protrusions 11SA and the depth were measured at 10 arbitrary points in the fine surface irregularities. At this time, arbitrary points were selected that were included in the irregularities extending along a predetermined direction. Subsequently, the average values ​​for the distance between the protrusions 11SA and the depth were calculated. These average values ​​were set as the distance between the protrusions 11SA and the depth in each example and comparative example.

[0078] [Fast Fourier Transform (FFT) Analysis] Using the free software "ImageJ 1.53h" in a Windows (registered trademark) 10 environment, FFT analysis was performed on 3D data of surface 11S containing wrinkle-like fine irregularities using the following procedure.

[0079] Step 1: Perform FFT processing by referring to the height measurements contained in the 3D data. Step 2: The second image P2 obtained by the FFT process is subjected to a process to reconstruct the measured power spectral intensity.

[0080] Step 3: Output the power spectral intensity as a function of distance from the origin in the second image P2 after the restoration process. Step 4: Convert the X-coordinate of the output power spectrum intensity to a spatial frequency f (cycles / μm) based on the pixel size of the 3D data.

[0081] Step 5: Plot the common logarithm of the average power spectral intensity against spatial frequency f on a two-dimensional coordinate system with the common logarithm of the average power spectral intensity against spatial frequency f on the vertical axis and spatial frequency (cycles / μm) on the horizontal axis, thereby obtaining the logarithmic spectrum.

[0082] In the obtained logarithmic spectrum, the spatial frequency of peak PK, the intensity of peak PK, the second mean value at 0 < |f| ≤ 0.2 (cycles / μm), and the difference value I were confirmed.

[0083] [Chromaticity's dependence on viewing angle] A black polyethylene terephthalate film was attached to the second surface 12S2 of the substrate 12 of the decorative film 10 in each example and comparative example. Then, the reflected light on the surface 11S of the cured product 11 was measured by irradiating it with light emitted from a halogen lamp. In this process, the incident angle θs, which is the angle formed by the plane containing the direction of light irradiation and the second surface 12S2 of the substrate 12, was changed in 10° increments within the range of 0° to 60°. Furthermore, by setting the light receiving angle θd of the measuring device to the same angle as the incident angle θs, the specular reflected light of the cured product 11 was measured. A spectroscopic variable-angle colorimeter (Nippon Denshoku Industries Ltd., GC 5000) was used as the measuring device.

[0084] After obtaining a spectral spectrum in the visible light region between 400 nm and 700 nm from the measured specular reflection, the obtained spectral spectrum is converted to the XYZ color system (JIS Z 8701:1999 "Method of representing colors - XYZ color system and X10 Y 10 Z 10 The values ​​were converted to a color system. Next, for each of the obtained x and y values, the maximum value of the change was calculated as the difference value obtained by subtracting the minimum value from the maximum value, and the maximum value of the color coordinate distance was calculated from the x and y values.

[0085] Furthermore, the appearance of the cured product 11 was visually observed and evaluated at the following three levels. A: When the viewing angle of the cured material 11 was changed, it was observed that the color of the cured material 11 changed clearly, that is, the cured material 11 exhibited a vivid iridescent luster.

[0086] B: When the viewing angle of the cured material 11 was changed, the change in the color of the cured material 11 was small, but it was observed that the cured material exhibited an iridescent sheen. C: Even if the viewing angle of the hardened material 11 is changed, the color of the hardened material 11 does not change.

[0087] [Evaluation Results] The evaluation results for the cured products of each example and comparative example are shown in Figures 9 to 11.

[0088] As shown in Figure 9, when the surface 11S of the cured product 11 was observed with a laser microscope, it was found that the surface 11S of the cured products 11 of Examples 1 to 7 had wrinkle-like fine irregularities. In contrast, it was found that the surface 11S of the cured products 11 of Comparative Examples 1 to 3 did not have wrinkle-like fine irregularities. The first image P1 based on the three-dimensional data obtained for Example 1 is shown in Figure 10.

[0089] The spatial frequency f of the peak PK in the logarithmic spectrum was found to be 0.31 cycles / μm in Example 1, 0.52 cycles / μm in Example 2, and 0.26 cycles / μm in Example 3. The spatial frequency f of the peak PK in the logarithmic spectrum was found to be 0.34 cycles / μm in Example 4, 0.24 cycles / μm in Example 5, and 0.22 cycles / μm in Examples 6 and 7.

[0090] The average power spectral intensity at peak PK was 1.7 × 10⁻⁶ in Example 1. 6 In Example 2, 3.6 × 10 5 Therefore, in Example 3, 3.2 × 10 6 In Example 4, the result was 1.9 × 10 6 It was confirmed that the average power spectral intensity at peak PK was 2.6 × 10⁻⁶ in Example 5. 6 In Example 6, 7.4 × 10 6 In Example 7, 2.3 × 10 6 It was confirmed that this was the case.

[0091] The difference value I was found to be 2.07 in Example 1, 1.68 in Example 2, 1.62 in Example 3, 1.65 in Examples 4 and 5, 0.73 in Example 6, and 0.59 in Example 7.

[0092] The distance between the protrusions 11SA was found to be 2.6 μm in Example 1, 1.9 μm in Example 2, and 2.9 μm in Examples 3 and 6. The distance between the protrusions 11SA was found to be 2.4 μm in Example 4, 1.9 μm in Example 5, and 3.0 μm in Example 7.

[0093] The depth of the fine irregularities was found to be 0.58 μm in Example 1, 0.34 μm in Example 2, and 0.61 μm in Example 3. The depth of the fine irregularities was found to be 0.64 μm in Example 4, 0.37 μm in Example 5, 0.62 μm in Example 6, and 0.76 μm in Example 7.

[0094] The maximum change in x-value was 0.14 in Example 1, 0.12 in Examples 2 and 3, and 0.17 in Example 4. The maximum change in x-value was 0.13 in Example 5, 0.10 in Example 6, and 0.03 in Example 7. The maximum change in x-value was 0.01 in Comparative Examples 1 to 3.

[0095] The maximum change in the y-value was found to be 0.09 in Examples 1 and 3, 0.10 in Examples 2 and 5, 0.15 in Example 4, 0.05 in Example 6, and 0.04 in Example 7. The maximum change in the y-value was found to be 0.00 in Comparative Examples 1 to 3.

[0096] The maximum color coordinate distance was found to be 0.23 in Example 1, 0.20 in Example 2, 0.15 in Example 3, and 0.22 in Example 4. The maximum color coordinate distance was found to be 0.23 in Example 5, 0.11 in Example 6, and 0.04 in Example 7. The maximum color coordinate distance was found to be 0.01 in Comparative Examples 1 to 3. The x and y values ​​obtained for the cured products 11 of Example 1, Example 7, and Comparative Example 1 are shown in Figure 11.

[0097] Visual inspection of the cured product 11 revealed that it was grade A in Examples 1 to 6, grade B in Example 7, and grade C in Comparative Examples 1 to 3. From the evaluation results of Examples 1 to 3, it can be said that the film thickness of the cured product 11 can be varied by varying the Nv value of the coating liquid. Furthermore, the smaller the film thickness of the cured product 11, the larger the spatial frequency f at the peak PK and the smaller the distance between the protrusions 11SA. Therefore, it can be said that the shape of the fine irregularities can be adjusted by changing the film thickness of the cured product 11.

[0098] From the evaluation results of Examples 1 and 4, and Comparative Example 2, it can be said that while it is possible to form a cured product 11 with fine irregularities even when the type of polymer is changed, it is not possible to form a cured product 11 with fine irregularities when the coating liquid does not contain a polymer. Furthermore, from the evaluation results of Example 5 and Comparative Example 1, it can be said that it is not possible to form a cured product 11 with fine irregularities unless electron beam EB is used to cure the coating film 21. From the evaluation results of Examples 1 and 5, and Comparative Example 1, it can be said that it is not essential for the coating liquid to contain a photopolymerization initiator in order to form a cured product 11 with fine irregularities.

[0099] From the evaluation results of Examples 1 and 6 and Comparative Example 3, it can be said that the type of photopolymerization compound can be changed, and the distance and depth between protrusions in the fine irregularities can be adjusted by the composition of the coating film. From the evaluation results of Comparative Example 4, it can be said that when a photopolymerization compound containing an alicyclic skeleton is used, the surface 11S of the cured product 11 does not have wrinkle-like fine irregularities.

[0100] From the evaluation results of Examples 1 to 7, it can be said that the larger the difference value I, the greater the likelihood of a larger maximum color coordinate distance. Furthermore, from a comparison of the evaluation results of Examples 1 to 6 with the evaluation result of Example 7, it can be said that a difference value I of 0.7 or higher makes it possible for the cured product 11 to exhibit a more vivid rainbow color. In addition, it can be said that for both the x and y values, a maximum change of 0.05 or higher, or a maximum color coordinate distance of 0.1 or higher, makes it possible for the cured product 11 to exhibit a more vivid rainbow color.

[0101] As described above, according to one embodiment of the cured product and the method for manufacturing the cured product, the following effects can be obtained. (1) Since the difference value I is 0.7 or more, the cured product 11 diffracts the reflected or transmitted light, causing interference between the diffracted light, and as a result the cured product 11 can exhibit vivid rainbow colors.

[0102] (2) When the average value of the power spectral intensity at peak PK is 10,000 or more, the difference value I tends to be large, so the cured product 11 tends to exhibit a more vivid rainbow color. (3) When the distance between the protrusions 11SA of the fine irregularities is 1.0 μm or more and 5.0 μm or less, diffraction is likely to occur on the surface 11S of the cured product 11.

[0103] (4) When the depth of the fine irregularities is 0.3 μm or more and 1.5 μm or less, the probability of diffraction occurring on the surface 11S of the cured product 11 can be increased. (5) By irradiating a coating film containing a photopolymerizable compound and a polymer with an electron beam EB, a cured product 11 having a surface 11S with wrinkle-like fine irregularities can be formed, making it easy to obtain a cured product 11 that exhibits iridescence.

[0104] (6) When the polymer contains a methyl methacrylate skeleton, the compatibility of the polymer with photopolymerizable compounds is enhanced. (7) When the photopolymerizable compound contains at least one of a methacrylate containing two functional groups in one molecule and an acrylate containing two functional groups in one molecule, fine irregularities are easily formed uniformly on the surface 11S of the cured product 11.

[0105] (8) When the photopolymerizable compound contains at least one of alkyl acrylate and alkyl methacrylate, since the photopolymerizable compound contains linear acrylate, fine irregularities are easily formed on the surface 11S of the cured product 11.

[0106] The above-described embodiment can be implemented with the following modifications. [Method for manufacturing hardened products] The coating liquid for forming the cured product 11 may be applied to a portion of the first surface 12S1 or the second surface 12S2 of the substrate 12 in any shape. In this case, the coating liquid may be applied to the substrate 12 by an inkjet method, or the coating liquid may be applied to only a portion of the substrate 12 by masking. This makes it possible to form a cured product 11 exhibiting iridescence with any shape on the substrate 12.

[0107] The solvent contained in the coating solution is not limited to propylene glycol monomethyl ether acetate; any solvent with high compatibility with photopolymerizable compounds and polymers may be used. Examples of such solvents include methyl ethyl ketone and cyclohexanone.

[0108] [Base material] At least one of the first surface 12S1 and the second surface 12S2 of the substrate 12 may be an uneven surface. The uneven surface may include, for example, microlenses. This allows the decorative film 10 to exhibit an appearance that combines the optical effect of the uneven surface of the substrate 12 with the iridescent color exhibited by the cured product 11. [Explanation of symbols]

[0109] 10… Decorative film 11…Cured product 11S…Surface 12...Base material 12S1...Side 1 12S2…Second side

Claims

1. Equipped with a surface, The aforementioned surface includes wrinkle-like fine irregularities, The three-dimensional data obtained by measuring the aforementioned fine irregularities using an optical interference method or a contact method is converted into first image data in which the height of the fine irregularities included in the three-dimensional data is used as the pixel value. The first image data is converted into a second image by the Fast Fourier Transform, In the second image above, let x be the horizontal frequency with respect to the origin, and let y be the vertical frequency, and f ２ = x ２ +y ２ The average power spectral intensity for a given spatial frequency f is calculated, and in the logarithmic spectrum obtained by plotting the common logarithm of the average value, The logarithmic spectrum has a peak in the average value of the power spectral intensity at 0.2 < |f| < 1 (cycles / μm), When the difference I is obtained by subtracting the average of the common logarithms of the average power spectral intensity at the peak from the common logarithm of the average power spectral intensity at 0 < |f| ≤ 0.2 (cycles / μm), the difference I is 0.7 or greater. cured product.

2. The average value of the power spectral intensity at the peak is 10,000 or more. The cured product according to claim 1.

3. The distance between the protrusions in the aforementioned fine irregularities is 1.0 μm or more and 5.0 μm or less. The cured product according to claim 1 or 2.

4. The depth of the aforementioned fine irregularities is 0.3 μm or more and 1.5 μm or less. The cured product according to claim 1 or 2.

5. A coating solution containing a photopolymerizable compound and a polymer is applied to at least one of the first and second surfaces of a substrate to form a coating film, and The process includes curing the coating film by irradiating it with an electron beam, thereby forming a cured product having a surface containing wrinkle-like fine irregularities. A method for manufacturing a cured product.

6. The polymer comprises at least one of repeating units derived from an acrylic acid ester and repeating units derived from a methacrylic acid ester. The weight-average molecular weight of the polymer is 5,000 or more and 1,000,000 or less. A method for producing a cured product according to claim 5.

7. The polymer contains a methyl methacrylate skeleton. A method for producing a cured product according to claim 5 or 6.

8. The photopolymerizable compound comprises at least one of a methacrylate containing two functional groups in one molecule and an acrylate containing two functional groups in one molecule. A method for producing a cured product according to claim 5 or 6.

9. The photopolymerizable compound comprises at least one of an acyclic acrylate and an acyclic methacrylate. A method for producing a cured product according to claim 5 or 6.

10. The photopolymerizable compound comprises at least one of an alkyl acrylate and an alkyl methacrylate. A method for producing a cured product according to claim 5 or 6.

Images