Release sheet and method for producing the release sheet

Abstract

To provide: a release sheet which enables manufacture of a resin molding that has remarkable three-dimensional feeling of a pattern and shows diffraction glossiness; and a method for manufacturing the same.SOLUTION: A release sheet has a base material layer and a release layer on one surface side of the base material layer, wherein the release layer has a first uneven structure, composed of a plurality of first projections and recesses positioned among the first projections, on a surface opposite to the base material layer, each of the first projections has an apex, the apex is a region where a second uneven structure finer than the first uneven structure is formed, the second uneven structure is not formed in the recesses, the second uneven structure extends in a first direction when the release layer is viewed planarly and has a plurality of second projections that are arranged in a second direction that is approximately perpendicular to the first direction, the second uneven structure shows diffraction glossiness, and the surface of the release layer has kurtosis (Sku) specified by ISO 25178-2:2012 of less than 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a release sheet, a method for producing the same, and a resin molded product. [Background technology]

[0002] Resin molded products, such as synthetic leather products and decorative sheets used in furniture and automotive interior components, are sometimes provided with a patterned surface with unevenness. These patterns can, for example, create a texture similar to that of natural leather, or can be given geometric patterns to enhance the design. Optical design features, such as gloss, may also be imparted to the resin molded products. For example, resin molded products have been proposed that have fine unevenness on their surfaces, resulting in a multicolored luster (e.g., a rainbow-like luster) whose color changes depending on the viewing angle due to the diffraction of light.

[0003] The resin molded product having the above-mentioned design is produced by using a release sheet having a surface formed with irregularities such as a pattern, and transferring the irregularities on the surface of the release sheet. Patent Document 1 discloses a release paper in which a fine uneven structure exhibiting diffractive gloss is formed on the surface of the release layer. Patent Document 2 discloses a release sheet having a surface shape that combines large irregularities with fine irregularities that are sized to impart a multicolored gloss. The release sheet of Patent Document 2 is characterized in that the surface shape of the release layer has a first irregularity structure consisting of a convex structure having a top surface and inclined side surfaces and concave portions between the convex structures, and a fine second irregularity structure is provided on the top surface and the concave portions, while the second irregularity structure is not provided on the inclined side surfaces. A resin molded product produced using the release sheet of Patent Document 2 produces a difference in appearance due to the multicolored gloss between areas where the second irregularity structure is formed and areas where it is not formed, which can be recognized by an observer as a pattern corresponding to the first irregularity structure. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-55133 [Patent Document 2] Japanese Patent Application Publication No. 2018-164992 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0005] The release paper of Patent Document 1 only has a diffractive gloss design, and does not mention any pattern with three-dimensional unevenness. In Patent Document 2, the pattern is recognized by differences in gloss, so the formed pattern lacks a three-dimensional feel. In addition, the release sheet of Patent Document 2 has a problem in that the area where the fine uneven structure is provided is large, so the contrast of gloss tends to become unclear. Furthermore, it is difficult to design the dimensions of the inclined side surface where the second uneven structure is not formed, so the degree of freedom in pattern design is limited. In other words, the patterns that can be expressed using the release sheet of Patent Document 2 are limited.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a release sheet that enables the production of a resin molded product that has a prominent three-dimensional pattern and exhibits diffractive gloss, and a method for producing the release sheet. The present disclosure also aims to provide a resin molded product that is produced using the release sheet and that has a prominent three-dimensional pattern and exhibits diffractive gloss. [Means for solving the problem]

[0007] In order to solve the above problems, the present disclosure provides the following [1]-

[13] . [1] A release sheet comprising a base layer and a release layer on one side of the base layer, wherein the release layer has a first uneven structure on the surface opposite the base layer, the first uneven structure being composed of a plurality of first convex portions and concave portions located between the first convex portions, each of the first convex portions having an apex, and the apex being an area where a second uneven structure finer than the first uneven structure is formed, the second uneven structure not being formed in the concave portions, the second uneven structure extending in a first direction when the release layer is viewed in a plane and having a plurality of second convex portions arranged in a second direction substantially perpendicular to the first direction, the second uneven structure exhibiting diffractive gloss, and the surface of the release layer having a kurtosis (Sku) defined in ISO 25178-2:2012 of less than 3. [2] The release sheet according to [1], wherein each of the first convex portions has a side portion connecting the top portion and the concave portion, and the second uneven structure is not formed on the side portion. [3] The release sheet according to [1] or [2], wherein the surface of the release layer has a skewness (Ssk) defined in ISO 25178-2:2012 of less than 0. [4] The release sheet according to [1] or [2], wherein the surface of the release layer has a skewness (Ssk) of 0 or more as defined in ISO 25178-2:2012. [5] The release sheet according to any one of [1] to [4], wherein the 85-degree gloss value of the surface of the release layer measured in accordance with JIS Z 8741:1997 satisfies the following formula (1): G1>G2 …(1) G1: 85-degree gloss value obtained by irradiating the measurement light from the first direction G2: 85-degree gloss value obtained by irradiating the measurement light from the second direction [6] The release sheet according to any one of [1] to [5], wherein the substrate layer comprises a paper substrate. [7] The release sheet according to [6], wherein the paper substrate has a thickness of 25 μm or more and 200 μm or less. [8] The paper base material has a basis weight of 40 g / m 2 More than 400g / m 2 The release sheet according to [6] below. [9] The release sheet according to any one of [1] to [8], wherein the release layer contains a thermoplastic resin.

[10] The release sheet according to [9], wherein the thermoplastic resin comprises at least one selected from the group consisting of polypropylene-based resins, polymethylpentene-based resins, (meth)acrylic resins, and (meth)acrylic acid ester copolymers.

[11] The release sheet according to any one of [1] to

[10] , wherein the thickness of the release layer is 5 μm or more and 120 μm or less.

[0008]

[12] A method for producing a release sheet according to any one of [1] to

[11] , comprising: a step (1) of forming a precursor layer having the second uneven structure on the base material layer; and a step (2) of pressing an embossing roll having a surface shape corresponding to the first uneven structure against the surface of the precursor layer to form a release layer having the first uneven structure and the second uneven structure on the surface, wherein in the step (2), the embossing roll and the precursor layer are brought into contact with each other at positions corresponding to the recesses, and the embossing roll and the precursor layer are separated from each other at positions corresponding to the peaks.

[0009]

[13] A resin molded product comprising a support layer and a resin layer on one side of the support layer, the resin layer having a first uneven structure on the side opposite the support layer, the first uneven structure being composed of a plurality of recesses and first protrusions located between the recesses, each of the recesses having a bottom, the bottom being an area in which a second uneven structure finer than the first uneven structure is formed, the second uneven structure not being formed on the first protrusions, the second uneven structure extending in a first direction when the resin layer is viewed in a plane and having a plurality of second protrusions arranged in a second direction approximately perpendicular to the first direction, and the second uneven structure exhibiting diffractive gloss. [Effects of the Invention]

[0010] By using the release sheet of the present disclosure, it is possible to obtain a release sheet and a resin molded product that can be produced that have a prominent three-dimensional pattern and exhibits diffractive gloss. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing an example of a release sheet according to a first embodiment. [Figure 2] FIG. 3 is a cross-sectional view showing an example of a release sheet according to a second embodiment. [Figure 3] FIG. 10 is a schematic plan view for explaining a second concave-convex structure. [Figure 4] 4 is a schematic cross-sectional view of the second protrusions in FIG. 3 in the arrangement direction. FIG. [Figure 5] FIG. 3 is a cross-sectional view showing another example of the release sheet according to the first embodiment. [Figure 6] FIG. 4 is a cross-sectional view showing another example of the release sheet according to the second embodiment. [Figure 7] FIG. 10 is a schematic diagram illustrating how gloss values are measured by irradiating measurement light at a low angle. [Figure 8] FIG. 10 is a schematic diagram illustrating how gloss values are measured with the incident angle of the measurement light set to 85 degrees. [Figure 9] FIG. 2 is a schematic view illustrating a step of forming a first concave-convex structure in the method for producing a release sheet of the present disclosure. [Figure 10] 1 is a cross-sectional view showing an example of a resin molded product according to a first embodiment. [Figure 11] FIG. 3 is a cross-sectional view showing an example of a resin molded product according to a second embodiment. [Figure 12] 1 is a laser microscope photograph of the surface of the release layer in the release sheet of Example 1. [Figure 13] 1 is a laser microscope photograph of the surface of the release layer in the release sheet of Example 2. [Figure 14] 1 is a laser microscope photograph of the surface of the release layer in the release sheet of Example 3. [Figure 15] 1 is a laser microscope photograph of the surface of the release layer in the release sheet of Example 4. [Figure 16] 1 is a laser microscope photograph of the surface of the release layer in the release sheet of Example 5. [Figure 17]1 is a laser microscope photograph of the surface of the release layer in the release sheet of Example 6. [Figure 18] 1 is a laser microscope photograph of the surface of the release layer in the release sheet of Example 7. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Release sheet] The release sheet of the present disclosure has a base layer and a release layer on one side of the base layer, and the release layer has a first uneven structure on the surface opposite the base layer, the first uneven structure being composed of a plurality of first convex portions and concave portions located between the first convex portions, each of the first convex portions having an apex, and the apex being an area where a second uneven structure finer than the first uneven structure is formed, the second uneven structure is not formed in the concave portions, the second uneven structure extends in a first direction when the release layer is viewed in a plane, and has a plurality of second convex portions arranged in a second direction approximately perpendicular to the first direction, the second uneven structure exhibits diffractive gloss, and the surface of the release layer has a kurtosis (Sku) defined in ISO 25178-2:2012 of less than 3. In this disclosure, when simply referring to "kurtosis," it refers to kurtosis (Sku) as defined in ISO 25178-2:2012.

[0013] <Surface shape of release layer> First, the shape of the surface of the release layer opposite to the substrate layer (hereinafter, sometimes simply referred to as the "surface of the release layer") will be described. As described above, the surface of the release layer has an uneven surface composed of a first uneven structure and a second uneven structure. However, because the second uneven structure is finer than the first uneven structure, the surface roughness parameters measured in accordance with ISO 25178-2:2012 largely reflect the surface shape resulting from the first uneven structure.

[0014] In the present disclosure, the kurtosis, skewness, root mean square height, arithmetic mean height, and maximum height (which may be collectively referred to as "surface roughness parameters") are values measured using a laser microscope. The numerical values of the surface roughness parameters in the present disclosure are specifically obtained by the following procedure. First, 25 combined images (image area: approximately 26 mm) are taken using a 10x objective lens for 20 arbitrary locations in the release layer. 2 ) is obtained. The image is then processed to set a reference surface. Next, Gaussian filter processing is performed, and the cutoff wavelengths are set to S filter: 5 μm and L filter: 8 mm, and surface roughness analysis is performed. The average values of the measurements obtained at 20 locations are used as the numerical values of the above surface roughness parameters.

[0015] The surface of the release layer in the present disclosure has a kurtosis of less than 3 (Sku<3). Kurtosis is a parameter that represents the sharpness of the height distribution in surface roughness. A kurtosis of greater than 3 (Sku>3) indicates that the height distribution is sharp, representing a surface that tends to have sharp peaks or valleys. On the other hand, a kurtosis of less than 3 (Sku<3) indicates that the surface height distribution is flat, and a surface with a kurtosis of less than 3 represents a surface that tends to have gentle peaks or valleys. In other words, a kurtosis of less than 3 on the surface of the release layer means that the first uneven structure is an uneven surface that tends to have a relatively gentle slope.

[0016] In the present disclosure, the surface of the release layer preferably has a skewness (Ssk) as defined in ISO 25178-2:2012 of less than 0. Alternatively, the surface of the release layer preferably has a skewness (Ssk) as defined in ISO 25178-2:2012 of 0 or greater. In the present disclosure, when simply referring to "skewness," it refers to the skewness (Ssk) as defined in ISO 25178-2:2012.

[0017] Skewness is a parameter that represents the symmetry (degree of bias) of the height distribution in surface roughness. A skewness of less than 0 (Ssk<0) indicates that the height distribution is biased upward relative to the average plane. In other words, a skewness of the surface of the release layer of less than 0 means that the first uneven structure has a surface shape in which the proportion of convex portions is higher than that of concave portions. A skewness of greater than 0 (Ssk>0) indicates that the height distribution is biased downward relative to the average plane. In other words, a skewness of the surface of the release layer of greater than 0 means that the first uneven structure has a surface shape in which the proportion of concave portions is higher than that of convex portions. A skewness of 0 (Ssk=0) indicates that the height distribution is symmetrical relative to the average plane. In other words, a skewness of 0 on the surface of the release layer means that the first uneven structure has a shape in which the proportion of convex portions to concave portions is equal.

[0018] In the present disclosure, the surface of the release layer preferably has a maximum height (Sz) of 60 μm or more as defined in ISO 25178-2: 2012. In the present disclosure, when simply referring to "maximum height," it refers to the maximum height (Sz) as defined in ISO 25178-2: 2012. The maximum height can be said to reflect the maximum height of the first uneven structure. As will be described later, the first uneven structure corresponds to the pattern of the release sheet and imparts a pattern to the resin molded product. Therefore, when the maximum height (Sz) is 30 μm or more, the visibility of the pattern is improved. The maximum height of the surface of the release layer is more preferably 50 μm or more. On the other hand, in consideration of the ease of forming the release layer, the ease of shaping into a resin molded product, and the aesthetic appearance of the obtained resin molded product, the maximum height of the surface of the release layer is preferably 300 μm or less, and more preferably 280 μm or less.

[0019] In the present disclosure, the surface of the release layer preferably has a root mean square height (Sq) of 6.0 μm or more as defined in ISO 25178-2:2012. The surface of the release layer preferably has an arithmetic mean height (Sa) of 8.0 μm or more as defined in ISO 25178-2:2012. In the present disclosure, when simply referring to "root mean square height" or "arithmetic mean height," these refer to the root mean square height (Sq) and arithmetic mean height (Sa) as defined in ISO 25178-2:2012, respectively.

[0020] Kurtosis represents the fourth-square mean of the height in a reference length that is made dimensionless by the fourth power of the root mean square height. Skewness represents the third-square mean of the height in a reference length that is made dimensionless by the cube of the root mean square height. By having the root mean square height in the above range, the surface of the release layer can easily satisfy the above ranges of kurtosis and skewness.

[0021] The cross-sectional structure of the release sheet according to the present disclosure will be described with reference to the drawings. Fig. 1 is a cross-sectional schematic diagram showing an example of a release sheet according to a first embodiment, in which the surface of the release layer satisfies Sku<3 and Ssk<0. Fig. 2 is a cross-sectional schematic diagram showing an example of a release sheet according to a second embodiment, in which the surface of the release layer satisfies Sku<3 and Ssk≧0.

[0022] In both the release sheet 10 of the first embodiment and the release sheet 20 of the second embodiment, a release layer 12, 22 is formed on one surface of a base layer 11, 21. The release layer 12, 22 is integrally formed with a shaping portion 12a, 22a, which is a thickness portion having an uneven surface, and a base portion 12b, 22b, which is a thickness portion supporting the shaping portion 12a, 22a. In the case of the release sheet of the second embodiment, the shaping portion 22a corresponds to the first convex portion described later. First concave-convex structures 13, 23 and second concave-convex structures 18, 28 are formed on the release layers 12, 22. The second concave-convex structures 18, 28 have finer concave-convex structures than the first concave-convex structures 13, 23.

[0023] <<First uneven structure>> 1 and 2 are schematic representations for explaining the form of the first uneven structure below. The actual first uneven structure is not limited to the cross-sectional shapes of FIGS. 1 and 2. It should be noted that the actual first uneven structure may differ in shape from those of FIGS. 1 and 2 depending on the pattern applied to the release sheet and the cut location within the release layer surface, in terms of the shapes of the convex and concave portions.

[0024] The first uneven structures 13, 23 serve to impart a pattern to the resin molded product. In other words, the first uneven structures 13, 23 are visible to the naked eye. The pattern is selected depending on the design required for the resin molded product. Even if the pattern has the same name, some first uneven structures are classified as the first type and some are classified as the second type.

[0025] The first uneven structure 13, 23 has a plurality of first protrusions 14, 24 and recesses 15, 25 between the first protrusions 14, 24. Each of the first protrusions 14, 24 is composed of a peak 16, 26 and a side surface 17, 27. The peaks 16, 26 are regions where the second uneven structure 18, 28 is formed. In the present disclosure, the recesses 15, 25 do not have the second uneven structure formed therein.

[0026] The shape of the first protrusions 14, 24 is not particularly limited and can be various shapes depending on the handle. For example, the height of the first protrusions 14, 24 may be approximately constant. That is, the tops 16, 26 may be approximately flat surfaces when the second concave-convex structure is not considered. Alternatively, the tops 16, 26 may be curved surfaces that are convex in the +Z direction or the -Z direction. The side surfaces 17, 27 may be flat, convex surfaces that bulge outward from the first protrusions 14, 24, or concave surfaces that curve inward from the first protrusions 14, 24. The side surfaces 17, 27 may be inclined surfaces as illustrated in FIGS. 1 and 2, or may be surfaces that extend approximately parallel to the thickness direction. The first protrusions 14, 24 may be symmetrical or asymmetrical about the Z axis as illustrated in FIGS. 1 and 2.

[0027] As shown in Figures 1 and 2, the first convex portions 14, 24 may have side portions 17, 27, which are surfaces connecting the peaks 16, 26 and the recesses 15, 25. When the release sheets 10, 20 are viewed in a plan view from the +Z direction, the side portions 17, 27 are located on the periphery of the peaks 16, 26. When the side portions 17, 27 are provided, the second uneven structure is not formed on the side portions 17, 27. By configuring the side portions 17, 27, the contrast of the diffractive gloss, which will be described later, can be improved. Note that when the first convex portions do not have side portions, the second uneven structure is formed over the entire first convex portions.

[0028] The recesses 15, 25 and the side surfaces 17, 27 may have minute irregularities formed thereon that originate from the outermost surface of an embossing roll used in the method for producing a release sheet, which will be described later.

[0029] In the first embodiment, the kurtosis of the surface of the release layer is less than 3, and the skewness is less than 0. If the second uneven structure is not taken into consideration, the first uneven structure 13 in the first embodiment can be schematically expressed as a form in which shallow depressions are formed on a substantially flat surface, and the bottoms of the depressions correspond to the recesses 15. In the second embodiment, the kurtosis of the surface of the release layer is less than 3, and the skewness is 0 or greater. If the second uneven structure is not taken into consideration, the first uneven structure 23 in the second embodiment can be schematically expressed as a form in which gentle mountain-like first projections 24 protrude from recesses 25, which are a substantially flat surface.

[0030] The sizes of the first protrusions 14, 24 and the spacing between adjacent first protrusions 14, 24 are designed according to the pattern. The dimensions of the first uneven structures 13, 23 are set so that the pattern is visible when the resin molded product is made.

[0031] In both the first and second embodiments, in order for the surface of the release layer to easily satisfy Sku<3, the height of the first protrusions 14, 24 (the length in the thickness direction between the top and the bottom of each first protrusion, shown by the symbol H in Figures 1 and 2) is preferably 300 μm or less, more preferably 280 μm or less. Considering the visibility of the pattern due to the first uneven structure and the ease of forming the pattern, the height H is preferably 30 μm or more, more preferably 50 μm or more. The height H of the first convex portions 14, 24 can be obtained by analyzing the connected image used for the analysis of kurtosis and the like.

[0032] When the release sheets 10, 20 are viewed in cross section, the width of the first convex portions 14, 24 (the width of the bottom of the first convex portion, indicated by the symbol W in Figures 1 and 2) can be set in the range of 5 μm to 20 mm, depending on the pattern.

[0033] When the release layers 12, 22 are viewed in a plane from the +Z direction, the area ratio of the region where the first convex portions 14, 24 are formed depends on the pattern, but can be set in the range of 10% to 95% in order to obtain a diffractive gloss effect and a three-dimensional effect of the pattern. The area ratio of the region where the first convex portions 14, 24 are formed can be obtained using the connected image used in the analysis of kurtosis or the like.

[0034] The recesses 15 and 25 may be substantially flat surfaces, or may be concave curved surfaces recessed toward the base layer side (-Z direction in FIGS. 1 and 2).

[0035] <<Second uneven structure>> The second uneven structures 18, 28 of the release sheet exhibit diffractive gloss. The second uneven structures 18, 28 play a role in imparting unevenness that exhibits diffractive gloss to the resin molded product.

[0036] FIG. 3 is a schematic plan view illustrating the second uneven structure. The second uneven structure 38 is composed of a plurality of second protrusions 39. The second uneven structure 38 has linear structures arranged at approximately equal intervals. Each of the second protrusions 39 extends in a first direction (the Y-axis direction in FIG. 3) when the release sheet is viewed in plan (when viewed from the +Z direction in FIG. 3). The plurality of second protrusions 39 are arranged at approximately equal intervals in a second direction (the X-axis direction in FIG. 3). This allows for the presentation of a multicolored diffractive luster. "Multicolor" means that reflected light in two or more wavelength ranges (particularly, reflected light from a resin molded product) is visible to the naked eye. "Multicolor" can also be expressed as "rainbow color," and it is preferable that reflected light in five or more wavelength ranges is visible to the naked eye.

[0037] Fig. 4 is a cross-sectional schematic diagram of the arrangement direction (X-axis direction) of the second convex portions in Fig. 3. The second convex portions 39 shown in Fig. 4 have a cross-sectional shape of a substantially isosceles triangle. The cross-sectional shape is not limited to that of Fig. 4 as long as it has a shape that exhibits diffractive gloss, and may be, for example, an equilateral triangle, a right triangle, a rectangle, a trapezoid, a sinusoidal wave, or the like. In particular, when considering the sense of diffractive gloss and the ease of forming the second uneven structure, it is preferable that the cross section of the second convex portions be a substantially isosceles triangle or a substantially equilateral triangle.

[0038] The pitch of the second uneven structure (the length of the repeating unit of the shape in the cross section of FIG. 4, indicated by symbol P in FIG. 4) has a lower limit of preferably 0.5 μm or more, more preferably 0.8 μm or more, and an upper limit of preferably 3.0 μm or less, more preferably 2.5 μm or less. The height of the second convex portion (the length in the thickness direction between the top and bottom of the second convex portion, indicated by symbol D in FIG. 4) has an upper limit of preferably 0.05 μm or more, more preferably 0.1 μm or more, and a lower limit of preferably 3.0 μm or more, more preferably 2.0 μm or less. To obtain a "gentle diffractive gloss" (described later), the height of the second convex portions may vary within the apex. In this case, the height D of the second convex portions preferably varies within a range of -50% to +50%, and more preferably within a range of -40% to +40%. The dimensions of the second uneven structure can be determined by analyzing cross-sectional and surface images obtained using a scanning electron microscope. The pitch P of the second uneven structure can be determined by analyzing images obtained using a laser microscope with a 100x objective lens.

[0039] 1 and 2 show an example in which the first uneven structure and the second uneven structure are not formed on the surface of the base layer opposite the release layer, but the present disclosure is not limited thereto. For example, as shown in FIGS. 5 and 6, unevenness reflecting the first uneven structure may be formed on the surface of the base layer 11, 21 opposite the release layer 12, 22. Alternatively, unevenness reflecting the first uneven structure and the second uneven structure may be formed on the surface of the base layer opposite the release layer.

[0040] <Optical characteristics of the release layer surface> In the present disclosure, it is preferable that the 85 degree gloss value of the surface of the release layer measured in accordance with JIS Z 8741:1997 satisfies the following formula (1). G1>G2 …(1) G1: 85-degree gloss value obtained by irradiating the measurement light from the first direction G2: 85-degree gloss value obtained by irradiating the measurement light from the second direction The first direction is the direction in which the second convex portions of the second concavo-convex structure extend, and the second direction is the direction in which the second convex portions are arranged.

[0041] When gloss measurement is performed on the surface of the release layer of the release sheet of the present disclosure, the obtained gloss value reflects the influence of light reflected by each of the first concave-convex structure and the second concave-convex structure. As described above, the second uneven structure has a regular linear structure, with a pitch and height of the second convex portions approximating the wavelength of visible light. Figure 7 is a schematic diagram illustrating how gloss values are measured by irradiating measurement light at a low angle (e.g., 20 degrees). Figure 7(a) shows the case where measurement light is incident from a first direction (the direction in which the second convex portions extend, the Y direction in the figure). Figure 7(b) shows the case where measurement light is incident from a second direction (the direction in which the second convex portions are arranged, the X direction in the figure). When measuring gloss at a low angle, the measurement light can penetrate into the valleys of the second uneven structure whether incident from the first direction or the second direction. Furthermore, as shown in Figures 7(a) and 7(b), the second convex portions are rarely present in the optical path of the reflected light reflected inside the valleys, and the reflected light is less affected by the second convex portions. For this reason, in low-angle measurements, there is little difference in gloss value between when the measurement light is incident from the first direction and when the measurement light is incident from the second direction. In other words, in low-angle measurements, the difference in gloss value derived from the second uneven structure depending on the direction of incident light is small. FIG. 8 is a schematic diagram illustrating how to measure gloss values with a measurement light incident angle of 85 degrees. FIG. 8(a) shows the case where the measurement light is incident from a first direction (the direction in which the second convex portions extend, the Y direction in the figure). FIG. 8(b) shows the case where the measurement light is incident from a second direction (the direction in which the second convex portions are arranged, the X direction in the figure). In measurements with an incident angle of 85 degrees, as shown in FIG. 8(a), the measurement light incident from the first direction can penetrate into the valleys of the second uneven structure, and the reflected light reflected from the valleys is detected without being affected by the second convex portions. On the other hand, when the measurement light is incident from the second direction, as shown in FIG. 8(b), near the tops of the second convex portions, the measurement light A hits the second convex portions, and the reflected light is detected without being obstructed by the second convex portions. However, as shown by "measurement light B," the measurement light traveling toward point P located inside the valley is blocked by the adjacent second convex portion and cannot penetrate into the valley. Furthermore, the reflected light of measurement light B that strikes the adjacent second convex portion is reflected in a direction different from the direction of the detector and is therefore not detected. Thus, in measurements where measurement light is incident from the second direction at an incident angle of 85 degrees, the obtained gloss value is affected by the second convex portion. Therefore, the gloss value obtained when measurement light is incident from the second direction is smaller than the gloss value obtained when measurement light is incident from the first direction. In other words, in measurements at an incident angle of 85 degrees, anisotropy occurs in the gloss value due to the second unevenness structure.

[0042] Regarding the first uneven structure, when measuring at a high angle of 85 degrees, depending on the pattern, the first convex portions may be present in the optical paths of the incident and reflected light and may act as a barrier. This may result in anisotropy of the gloss value due to the first uneven structure. However, since the first and second directions are directions derived from the second uneven structure, they have little correlation with the pattern of the first uneven structure. Therefore, measurements from the first and second directions have little effect on the gloss value due to the first uneven structure. Therefore, it can be said that the anisotropy of gloss in the first and second directions is largely influenced by the second uneven structure.

[0043] Therefore, when the 85-degree gloss value of the release layer surface satisfies formula (1), the release sheet has an excellent diffractive gloss and also has excellent pattern visibility. The G1 value is preferably 3.0 or more, and more preferably 5.0 or more. The G1 value is preferably 40.0 or less, and more preferably 35.0 or less. Furthermore, the G2 value is preferably 0.3 or more, and more preferably 0.8 or more. The G2 value is preferably 20.0 or less, and more preferably 17.0 or less.

[0044] Furthermore, the average value of G1 and G2 ((G1+G2) / 2) is preferably 1.0 or more, more preferably 3.0 or more. Furthermore, the average value of G1 and G2 is preferably 25.0 or less, more preferably 20.0 or less. When the average values of G1 and G2 are within the above ranges, an excellent sense of diffractive gloss can be felt even when the release sheet is viewed from various directions.

[0045] The greater the difference between G1 and G2 (ΔG=G1-G2), the better the diffractive glossiness can be obtained. The difference between G1 and G2 is preferably 1.0 or more. If the difference between G1 and G2 is too large, the diffractive glossiness may vary depending on the observation angle, which may result in poor design. For this reason, the difference between G1 and G2 is preferably 30.0 or less.

[0046] Furthermore, the larger the ratio of G1 to G2 (G1 / G2) and the larger the ratio of the difference between G1 and G2 to the sum of G1 and G2 ((G1-G2) / (G1+G2)), the more excellent the diffractive glossiness can be obtained. G1 / G2 is preferably 1.1 or more, and (G1-G2) / (G1+G2) is preferably 0.05 or more. In order to reduce the difference in diffractive glossiness depending on the observation angle, G1 / G2 is preferably 8.0 or less, and (G1-G2) / (G1+G2) is preferably 0.8 or less.

[0047] The release sheet of the present disclosure may give the impression of a gentle diffractive gloss. The term "gentle diffractive gloss" refers to a design in which, when observing the release sheet and a resin molded product made from the release sheet, the gloss is relatively weak and the impression of sparkle is weak, but when the observation angle is changed, the diffraction intensity changes repeatedly and continuously from "strong to weak to strong to weak," and at the same time, the color changes gently and continuously. By imparting such diffractive gloss, the impression of a subdued, multicolored gloss can be given to the resin molded product. The design with a gentle diffractive gloss as described above is obtained depending on the state of the second uneven structure. During the manufacturing process of the release sheet, which will be described later, deformation of the second uneven structure may occur, such as when the height of the second convex portions is partially reduced, when the pitch of the second convex portions is partially widened or narrowed, or when the second convex portions are no longer continuous linearly but are partially missing. In this way, the optical path of reflected light in the area where the second uneven structure has been deformed is different from that in other areas. Therefore, the area where the second uneven structure has been deformed has a diffractive gloss that is different from that in other areas, allowing the above-mentioned design to be expressed.

[0048] <Layer structure of release sheet> The layer structure of the release sheets according to the first and second embodiments will be described. <<Base material layer>> In the present disclosure, the substrate layer serves to provide shapeability, flex resistance, rigidity, etc. The substrate layer can be made of a known material generally used for release sheets and process papers. Specific examples of the material for the substrate layer include various paper substrates, resin films, metal foils, woven fabrics, and nonwoven fabrics. One or a combination of two or more selected from these can be used for the substrate layer. In consideration of shapeability, it is particularly preferable to use a paper substrate. The surface of the substrate layer may be subjected to various treatments, such as corona discharge treatment, ozone treatment, or other adhesion-improving treatments, or surface treatments such as a smoothing layer or undercoat layer, in order to improve adhesion to the release layer.

[0049] The thickness of the base layer is not particularly limited, but is preferably 25 μm or more and 200 μm or less, and more preferably 50 μm or more and 150 μm or less. When the thickness of the base layer is within the above range, it has appropriate rigidity, which improves workability when forming a release layer or shaping a resin molded product. In addition, it is possible to prevent the release sheet from becoming too thick and the winding diameter from becoming too large.

[0050] When the release layer contains a resin curable with ionizing radiation such as ultraviolet light or electron beams, the substrate layer preferably has ionizing radiation transparency.

[0051] Examples of paper substrates that can be used include strong sizing bleached or unbleached paper substrates, pure white roll paper, kraft paper, paperboard, coated paper, cast-coated paper, processed base paper, wood-free paper, lightly coated printing paper, coated printing paper, resin-coated paper, release base paper, and double-coated release base paper. Furthermore, the paper substrate may have an intermediate layer such as a sealing layer or a resin layer formed thereon in advance. If necessary, the paper substrate can also be used in combination with various resin films.

[0052] The paper base material has a basis weight of 40 g / m 2 More than 400g / m 2 It is preferable that the basis weight is 100 g / m or less. 2 More than 250g / m 2 It is more preferable that the paper substrate has a basis weight within the above range. When the paper substrate has a basis weight within the above range, various problems such as curling and waviness are unlikely to occur during the production of the release sheet. In addition, it is possible to prevent the release sheet from becoming too thick and the winding diameter from becoming too large, and to prevent a decrease in work efficiency. Furthermore, the formability into a resin molded product is also good.

[0053] The thickness of the paper substrate is not particularly limited, but considering the rigidity and ease of production of the release sheet, it is preferably 25 μm or more and 200 μm or less, and more preferably 50 μm or more and 150 μm or less. The raw material pulp for the paper base material is preferably a mixture of softwood pulp (N-wood) and hardwood pulp (L-wood). This makes it easier to obtain strength and smoothness that can withstand the manufacturing process and transfer process of the release sheet. Furthermore, if the mixing ratio of hardwood pulp (L-wood) is in the range of 50% to 90%, the smoothness of the paper base material is improved, which is more preferable.

[0054] In order to provide the release sheet with sufficient heat resistance, the paper substrate is preferably neutral paper, and among these, neutral paper sized using alkyl ketene dimer as a sizing agent is more preferred.

[0055] Examples of resin films include polyester substrates such as polyethylene terephthalate and polyethylene naphthalate, polyamides such as various nylons, polypropylene, etc. In the present disclosure, polyester-based resins are preferred, and highly adhesive PET is particularly preferred. A paper substrate is preferred because it is less susceptible to thermal degradation and has high adhesion to the release layer. On the other hand, when heat resistance and smoothness are required, a polyester substrate such as polyethylene terephthalate or polyethylene naphthalate is preferred.

[0056] (smoothing layer) In order to improve the smoothness of the surface of the base layer, increase the hardness of the base layer, improve the formability of the above-mentioned uneven structure, and further improve the moldability of the transfer product, a smoothing layer made of clay and / or polyolefin resin can be provided on the surface of the base layer on the release layer side.

[0057] The thickness of the smoothing layer is not particularly limited, but is preferably in the range of 0.1 μm to 60 μm.

[0058] When a material with a relatively rough surface, such as kraft paper or fine paper, is used as the paper substrate, the smoothness of the paper substrate can be easily improved by providing a smoothing layer containing a polyolefin resin.

[0059] The clay can be used without any particular limitation. Examples of clay that can be used include kaolin, talc, bentonite, smectite, vermiculite, mica, chlorite, kibushi clay, gairome clay, halloysite, and mica. Talc has low hardness (Mohs hardness 1) and excellent heat resistance, and therefore can improve heat resistance and dimensional stability during embossing.

[0060] The clay preferably contains a pigment such as calcium carbonate, titanium dioxide, amorphous silica, expandable barium sulfate, or satin white. By using calcium carbonate or titanium dioxide as a pigment, the smoothness of the clay coating layer can be increased. Furthermore, calcium carbonate is preferably used because it is inexpensive.

[0061] The coating liquid for applying the clay-containing smoothing layer contains the above-mentioned clay in a solvent, a binder, and, if necessary, other pigments and additives. Typically, water, alcohol, or the like is used as the solvent. Typically, a latex-based binder (e.g., styrene-butadiene latex, acrylic latex, vinyl acetate latex), a water-soluble binder (e.g., starch (modified starch, oxidized starch, hydroxyethyl etherified starch, phosphated starch), polyvinyl alcohol, casein, or the like) is used as the binder. Typically, a pigment dispersant, an antifoaming agent, an antifoaming agent, a viscosity modifier, a lubricant, a water-resistant agent, a water-retaining agent, or the like is used as the additive.

[0062] The method for applying the clay-containing coating solution is not particularly limited, but coating methods such as air knife coating, blade coating, short dwell coating, and cast coating can be used.

[0063] The thickness of the clay-containing smoothing layer is not particularly limited, but the dry basis weight is preferably 5 g / m 2 More than 40g / m 2 Preferably, it is 10 g / m or less. 2 More than 40g / m 2When the basis weight after drying is within the above range, it is possible to impart appropriate smoothness to the base layer and also to improve the adhesion to the base layer.

[0064] The smoothing layer made of a polyolefin resin may be formed on the substrate layer by extrusion coating.

[0065] (Anchor coat layer) In the present disclosure, if necessary, an anchor coat layer may be provided on the substrate layer or the smoothing layer to improve adhesion between the release layer and the smoothing layer, or between the release layer and the substrate layer. For example, when a clay-containing smoothing layer is provided on a substrate layer, the surface of the smoothing layer has good lubricity, so adhesion to the release layer tends to be poor. By forming an anchor coat layer, this adhesion can be improved.

[0066] The anchor coat layer can be formed, for example, by applying a water-soluble or water-dispersible emulsion or dispersion anchor coat agent.

[0067] Examples of anchor coating agents include emulsions or dispersions of polypropylene, modified polyolefin, ethylene-vinyl acetate copolymer, polyethyleneimine, polybutadiene, polyurethane, and polyester resins; polyvinyl chloride emulsion, urethane acrylic resin emulsion, silicone acrylic resin emulsion, vinyl acetate acrylic resin emulsion, and acrylic resin emulsion; rubber latexes such as styrene-butadiene copolymer latex, acrylonitrile-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, chloroprene latex, and polybutadiene latex; polyacrylic acid ester latex and polyvinylidene chloride latex; and carboxyl-modified products of these latexes. Examples of water-soluble anchor coating agents that can be used include aqueous solutions of polyvinyl alcohol, water-soluble ethylene-vinyl acetate copolymer, polyethylene oxide, water-soluble acrylic resin, water-soluble epoxy resin, water-soluble cellulose derivative, water-soluble polyester, water-soluble isocyanate, and water-soluble lignin derivative.

[0068] Among these, emulsions or dispersions of polypropylene-based or modified polyolefin-based resins are preferred because they can further increase the lamination strength of the polypropylene-based resin layer to the paper and also have excellent heat resistance.

[0069] The anchor coating agent can be applied by, for example, gravure coating, reverse roll coating, knife coating, kiss coating, etc. The amount of coating is 0.1 g / m when dried. 2 More than 5g / m 2 Or, the thickness after drying is preferably 0.1 μm or more and 5 μm or less.

[0070] <<Release layer>> The resin component contained in the release layer is not particularly limited as long as it can function as a release layer. Examples of the resin component of the release layer include various thermoplastic resins, thermosetting resins, and ionizing radiation curable resins such as ultraviolet rays or electron beams, and one or more of these resins can be selected and used. In consideration of formability, it is particularly preferable that the release layer contains a thermoplastic resin. As the resin for the release layer, it is preferable to use only a thermoplastic resin, but it may contain a resin other than a thermoplastic resin as a main component.

[0071] Examples of thermoplastic resins include (meth)acrylic resins such as polyacrylate and polymethyl methacrylate; polyolefin resins such as polyethylene resins, polypropylene resins, polymethylpentene resins, ethylene-propylene copolymers, propylene-1-butene copolymers, propylene-1-hexene copolymers, propylene-4-methyl-1-pentene copolymers, propylene-1-octene copolymers, and propylene-1-decene copolymers; polyester resins such as melamine alkyd resins, polyethylene terephthalate, and polybutylene terephthalate; vinyl resins such as polyvinyl chloride; styrene resins such as polystyrene; polycarbonate resins; polyamide resins (nylon); and polyvinyl alcohol. Among these, it is preferable to use at least one selected from the group consisting of polypropylene resins, polymethylpentene resins, (meth)acrylic resins, and (meth)acrylic acid ester copolymers. The copolymer may be a random copolymer or a block copolymer. Considering transferability by heat and pressure, the softening point of the thermoplastic resin is preferably 90° C. or higher and 135° C. or lower for polypropylene resin, and 160° C. or higher and 190° C. or lower for polymethylpentene resin.

[0072] Examples of thermosetting resins include unsaturated polyesters; melamine-based resins such as melamine alkyd resins, methylol melamine resins, and methoxymethylol melamine resins; epoxy resins; (meth)acrylic resins such as polyester (meth)acrylates, urethane (meth)acrylates, epoxy (meth)acrylates, polyether (meth)acrylates, polyol (meth)acrylates, melamine (meth)acrylates, and triazine-based acrylates; and silicone resins.

[0073] Examples of the resin curable by ionizing radiation such as ultraviolet light or electron beams include urethane resins, epoxy resins, ester resins, (meth)acrylic resins, and acrylic acid ester copolymers.

[0074] For general purposes, polypropylene-based resins are preferred, and when heat resistance is required for the release sheet, polymethylpentene-based resins are preferred. Furthermore, when high precision in forming the second uneven structure is required, it is preferable to use an ultraviolet curable resin, and a (meth)acrylic resin or an acrylic acid ester copolymer is particularly preferable.

[0075] The release layer may further contain optional additives such as antioxidants, weathering agents, lubricants, antistatic agents, antifogging agents, chlorine scavengers, nucleating agents, antiblocking agents, organic or inorganic fillers, plasticizers, stabilizers, and colorants, provided that the purpose of the present disclosure is not impaired.

[0076] The color of the release layer is not particularly limited, and can be a desired color such as red, black, etc., using a colorant. When it is desired to reduce the reflectance over the entire wavelength range of visible light, it is preferable to color the resin layer black.

[0077] The colorant may be a pigment or a dye. The type of pigment is not particularly limited, but in order to color the second uneven structure to the tip, it is preferable to use a dye rather than a pigment with a large particle size.

[0078] The release layer is formed from a resin composition containing the above-mentioned raw materials. The resin composition for forming the release layer may or may not contain a solvent.

[0079] The release layer may be composed of one layer or two or more layers made of the same or different resin types.

[0080] The thickness of the release layer is not particularly limited, but the lower limit is preferably 4 μm or more, more preferably 10 μm or more, and the upper limit is preferably 120 μm or less, more preferably 80 μm or less. When the thickness of the release layer is within the above range, the dimensional accuracy of the first uneven structure and the second uneven structure is improved. Furthermore, in the manufacturing process of the release sheet and the manufacturing process of the resin molded product, curling of the release sheet can be suppressed and flexibility is improved, thereby improving workability.

[0081] [Release sheet manufacturing method] The method for producing a release sheet according to the present disclosure includes the steps of: (1) forming a precursor layer having the second uneven structure on the surface opposite to the base layer; and (2) pressing an embossing roll having a surface shape corresponding to the first uneven structure against the surface of the precursor layer to form a release layer having the first uneven structure and the second uneven structure on the surface, wherein in the step (2), the embossing roll and the precursor layer are brought into contact with each other at positions corresponding to the recesses, and the embossing roll and the precursor layer are separated from each other at a position corresponding to the top surface.

[0082] <Process (1)> Step (1) is a step of forming a precursor layer, which serves as a precursor of the release layer, on a substrate layer. The precursor layer has the second uneven structure described above on the surface opposite to the base layer, but does not have the first uneven structure. The second uneven structure is preferably provided over the entire surface of the precursor layer. The precursor layer may be provided over the entire surface of the base layer, or may be provided partially on the base layer, for example, in an area other than the end of the base layer.

[0083] In step (1), an original plate having a surface configuration capable of transferring the second uneven structure of the release layer of the release sheet is used. The surface of the original plate has an unevenness that is a roughly inverted version of the second uneven structure. That is, the original plate has a surface configuration in which recesses having the same shape as the second protrusions are formed at positions corresponding to the second protrusions. The original plate may be made of any material, such as metal, resin, or rubber. The shape of the original plate may be any shape, such as a roll, cylinder, plate, or sheet.

[0084] There are two methods for forming the precursor layer: The first formation method is a method in which a layer of a resin composition for the release layer (a precursor layer before shaping) is formed on a substrate layer, and then the second uneven structure is shaped into this precursor layer using the master plate. The substrate layer may be a continuous sheet (roll form) or a discrete sheet.

[0085] The method for forming the precursor layer is not particularly limited, and known methods can be applied. For example, die coating, extrusion coating lamination, roll coating, reverse roll coating, microbar coating, bar coating, knife coating, gravure coating, etc. can be applied. After forming the precursor layer, the sheet may be passed between a chill roll and a pressure roll so that the precursor layer comes into contact with the surface-treated chill roll, thereby improving the surface smoothness of the precursor layer. As the chill roll, either a chill roll with a mirror-finished surface (also called a "mirror chill roll") or a chill roll with a matte-finished surface (also called a "matt chill roll") can be used. In particular, extrusion coating lamination is preferred because it can simplify the process by simultaneously forming the precursor layer and mirror-finishing the surface, and can also provide a release layer of appropriate thickness. In extrusion coating lamination, the precursor layer can be formed, for example, under conditions of an extrusion temperature of 280°C or higher and 320°C or lower, and a line speed of 50 m / min or higher and 100 m / min or lower.

[0086] Next, the precursor layer surface of the sheet and the surface of the master plate having the surface morphology are placed face-to-face and pressed together to transfer the surface morphology of the master plate to the precursor layer. When the resin for the release layer contains a thermoplastic resin, it is preferable to heat the sheet simultaneously with pressing to enhance shaping properties. The pressure and heating temperature during pressing are set, taking into consideration the type of resin used, its hardness during pressing, and the thickness of the precursor layer, so that the surface morphology of the master plate is successfully transferred to the precursor layer. For example, transfer can be performed under conditions of a heating temperature of 90°C to 140°C, a pressure of 2 MPa to 14 MPa, and a line speed of 3 m / min to 30 m / min. The heating temperature in step (1) is preferably in the range of 65% to 125%, and more preferably 75% to 95%, of the heating temperature in step (2) taken as 100%. Thereafter, the sheet is cooled and then peeled off from the master to obtain a sheet on which a precursor layer having a second relief structure is formed.

[0087] The second formation method is a method in which a resin composition for a release layer is applied to the surface of an original plate having the above-mentioned surface morphology to form a coating film, the original plate is brought into contact with a base layer to attach the coating film to the base layer, and then the base layer and coating film are released. The substrate layer may be a continuous sheet (roll form) or a discrete sheet.

[0088] The method for applying the resin composition is not particularly limited, and known methods can be used, such as die coating, extrusion coating, roll coating, reverse roll coating, microbar coating, bar coating, knife coating, and gravure coating.

[0089] At the stage where the master plate is brought into contact with the base layer, it is preferable to fix the shape of the precursor layer by a curing method appropriate for the resin components of the resin composition, such as heating and drying, irradiation with ionizing radiation such as ultraviolet rays or electron beams, cooling, etc. When attaching the precursor layer to the base layer, an adhesive may be inserted between the precursor layer and the base layer, if necessary.

[0090] <Process (2)> Step (2) is a step of forming a first uneven structure by embossing. Step (2) will be described below with reference to Figure 9. Figure 9 shows a method for producing a release sheet of the first embodiment exemplified in Figure 1, but a similar method is also used for producing a release sheet of the second embodiment exemplified in Figure 2. In step (2), an embossing master plate is used that has a surface configuration capable of transferring the first uneven structure of the release layer of the release sheet. The shape of the embossing master plate may be any shape, such as a roll, a cylinder, a plate, or a sheet. The embossing master plate may be made of any material, such as metal, resin, or rubber. When the embossing master plate is made of metal, minute unevenness derived from plating particles may be formed on the outermost surface of the embossing master plate. Figure 9 shows an example in which an embossing roll is used as the embossing master plate. As shown in FIG. 9( a), the surface of the embossing roll 40 has a surface profile that is a substantially inverse of the first convex portions and concave portions of the first concave-convex structure. The embossing roll 40 has concave portions 42 at positions corresponding to the first convex portions of the first concave-convex structure. Furthermore, the positions corresponding to the concave portions of the first concave-convex structure are convex portions 41 of the embossing roll. The concave portions 42 have openings with substantially the same shape as the bottoms of the first convex portions of the first concave-convex structure, and have side surfaces 44 with portions with substantially the same shape as the side surfaces of the first convex portions. However, the bottoms 43 of the concave portions 42 are shaped so as to be deeper than the height of the first convex portions on the extension of the side surfaces 44. The length corresponding to the depth of the concave portions 42 is longer than the length corresponding to the height of the first convex portions, including the second convex portions. This design allows the embossing roll and the precursor layer to separate during pressing, as described below, leaving the second concave-convex structure in the areas corresponding to the first convex portions.

[0091] In step (2), as shown in FIG. 9(a), a sheet 50 having a precursor layer 52 formed on a base layer 51 is placed so that the precursor layer 52 faces the embossing roll 40.

[0092] Next, as shown in FIG. 9(b), the sheet 50 is passed between an embossing roll 40 and a back roll (not shown) while being pressed. When the resin for the release layer contains a thermoplastic resin, it is preferable to heat the sheet simultaneously with pressing in order to improve its shaping properties. The heating temperature is set taking into consideration the material of the precursor layer, the transferability of the surface morphology of the master, and the like. The heating temperature in step (2) can be set within a range of 90°C or higher and 140°C or lower.

[0093] As shown in FIG. 9(b), when the sheet 50 is pressed by the embossing roll 40 in this step, the protrusions 41 of the embossing roll 40 come into contact with the precursor layer 52. At the locations corresponding to the recesses 42 of the embossing roll 40, the precursor layer 52 enters the recesses 42. At this time, at the bottoms 43 of the recesses 42, the precursor layer 52 and the embossing roll 40 are separated and do not come into contact with each other. At the locations that come into contact with the embossing roll 40, the second uneven structure disappears due to the pressing. On the other hand, at the locations that do not come into contact with the embossing roll 40, the second uneven structure remains. Thereafter, when the sheet 50 is peeled off from the embossing roll 40, the unevenness formed by the contact between the precursor layer 52 and the embossing roll 40 remains, as shown in FIG. 9(c). This forms a release layer 12 having a first uneven structure. The depressions 15 of the first uneven structure are areas where the second uneven structure is not formed because they came into contact with the embossing roll 40. On the other hand, the areas where the second uneven structure 18 remains without coming into contact with the embossing roll 40 form the peaks 16 of the first peaks 14. That is, in step (2), the embossing roll and the precursor layer are brought into contact at positions corresponding to the depressions of the release layer, and the embossing roll and the precursor layer are separated at positions corresponding to the peaks, thereby forming a release layer having a first uneven structure and a second uneven structure.

[0094] 9(b), when the side surfaces 44 of the recesses 42 of the embossing roll 40 come into contact with the precursor layer 52, the second uneven structure similarly disappears at the contact points. When the sheet is then peeled off from the embossing roll, side surfaces 17 on which the second uneven structure is not formed are formed on the first protrusions 14, as shown in FIG.

[0095] In the release sheet of the present disclosure, the portions that come into contact with the embossing roll (the recesses and side surfaces of the first recessed / protruding structure) may have irregularities resulting from the fine irregularities on the surface of the embossing roll. For example, as described above, when fine irregularities resulting from plating particles are formed on the outermost surface of the embossing roll, the recesses and side surfaces of the first recessed / protruding structure may have irregularities that are approximately the inverse of the fine irregularities described above.

[0096] The pressing pressure in step (2) is set within a range that allows the precursor layer to penetrate into the recesses of the embossing roll, but does not contact the bottom of the recesses. The pressure is set taking into consideration the material of the resin component of the precursor layer (release layer), the material and thickness of the base layer, the temperature during pressing, the dimensions of the recesses of the embossing roll, etc. For example, the higher the pressure, the higher the first convex portions in the first concave-convex structure tend to become, and the higher the kurtosis (Sku) of the surface of the resulting release layer tends to be. To keep the kurtosis of the surface of the release layer in the resulting release sheet less than 3, it is preferable to adjust the pressure so as not to press the embossing roll (embossing master) too hard. Furthermore, when the second uneven structure is formed by shaping in step (1) (using the first forming method), the base layer is crushed and its thickness is reduced by the pressure applied in step (1). This also increases the hardness of the sheet on which the precursor layer is formed. For this reason, the pressure applied in step (2) is preferably higher than the pressure applied in step (1).

[0097] In the method for producing a release sheet according to the present disclosure, the first uneven structure and the second uneven structure are formed in the order of step (1) and step (2), which makes it easier to adjust the kurtosis (Sku) of the release layer surface to less than 3. In particular, as described above, forming the second uneven structure by shaping in step (1) increases the hardness of the sheet. Therefore, although it is difficult to form the first uneven structure if the pressing force is not sufficient in step (2), it can be said that it is easier to adjust the kurtosis (Sku) of the resulting release layer surface to less than 3. In other words, when the first uneven structure is formed on a sheet without a second uneven structure, such as by reversing the order of steps (1) and (2), deformation of the sheet is likely to occur. As a result, the surface of the resulting release layer is likely to have a kurtosis (Sku) of 3 or more, making it difficult to adjust the surface roughness.

[0098] The design with the "gentle diffractive gloss" described above can be achieved by adjusting the shape of the top of the first uneven structure in step (2). For example, by using an embossing roll with narrow recess openings, pressure tends to concentrate near the center of the top when the precursor layer penetrates the recess, making it easier for the second uneven structure to become distorted at the top. This makes it possible to vary the height of the second uneven structure within the top. A similar phenomenon can also be easily achieved by applying a relatively high pressure during pressing.

[0099] [Resin molded products] The resin molded product of the present disclosure is produced by transferring the surface shape of the release layer of the release sheet described above onto the surface of an object to be transferred. Specific examples of the resin molded product include resin leather such as synthetic leather and artificial leather, decorative sheets, wallpaper, and woven fabrics for clothing.

[0100] The resin molded product of the present disclosure has a support layer and a resin layer on one side of the support layer, and the resin layer has a first uneven structure on the side opposite the support layer, the first uneven structure being composed of a plurality of recesses and first convex portions located between the recesses, each of the first recesses having a bottom, the bottom being an area in which a second uneven structure finer than the first uneven structure is formed, the second uneven structure is not formed on the convex portions, the second uneven structure extends in a first direction when the resin layer is viewed in a plane, and has a plurality of second convex portions arranged in a second direction approximately perpendicular to the first direction, and the second uneven structure exhibits diffractive gloss.

[0101] Fig. 10 is a cross-sectional view showing an example of a resin molded product according to the first embodiment. Fig. 11 is a cross-sectional view showing an example of a resin molded product according to the second embodiment. The resin molded product according to the first embodiment is produced using the release sheet according to the first embodiment. The resin molded product according to the second embodiment is produced using the release sheet according to the second embodiment.

[0102] In both the resin molded product 100 of the first embodiment and the resin molded product 110 of the second embodiment, a resin layer 102, 112 is formed on one surface of the support layer 101, 111.

[0103] The support layers 101, 111 may be selected as appropriate depending on the type and application of the resin molded product, for example, woven fabric, nonwoven fabric, mesh fabric, paper, resin film such as polyester or polyolefin, metal plate, glass plate, etc. Examples of fibers used for the woven fabric and nonwoven fabric include natural fibers such as cotton, linen, and wool; regenerated or semi-synthetic fibers such as rayon and acetate; and synthetic fibers such as polyamide, polyester, polyacrylonitrile, polyvinyl alcohol, and polyolefin. The thickness of the support layers 101, 111 is not particularly limited as long as it is thick enough to support the resin layers 102, 112.

[0104] The resin material constituting the resin layers 102, 112 is selected depending on the intended use of the resin molded product. For example, the resin material may be a thermoplastic resin or a thermosetting resin. Specific examples of the resin material include polyurethane resin, nylon resin, and polyvinyl chloride resin. The resin layers 102, 112 may contain additives such as plasticizers, stabilizers, and colorants. The thickness of the resin layers 102, 112 may be any thickness that allows the first and second uneven structures to be formed, and may be appropriately set depending on the intended use of the resin molded product.

[0105] The resin layer 102 of the first embodiment has a shape complementary to the release layer of the release sheet of the first embodiment on the surface opposite the support layer 101. Specifically, a first uneven structure 103 and a second uneven structure 108 are formed on the surface of the resin molded product 100 of the first embodiment, and the first uneven structure 103 has a structure that is a roughly inverted version of the first uneven structure of the release layer, and the second uneven structure 108 has a structure that is a roughly inverted version of the second uneven structure of the release layer. Therefore, the second uneven structure 108 has finer unevenness than the first uneven structure 103.

[0106] The resin layer 112 of the second embodiment has a shape complementary to the release layer of the release sheet of the second embodiment on the surface opposite to the support layer 111. Specifically, a first uneven structure 113 and a second uneven structure 118 are formed on the surface of the resin molded product 110 of the second embodiment, and the first uneven structure 113 has a structure that is a roughly inverted version of the first uneven structure of the release layer, and the second uneven structure 118 has a structure that is a roughly inverted version of the second uneven structure of the release layer. Therefore, even in the resin molded product of the second embodiment, the second uneven structure 118 has finer unevenness than the first uneven structure 113.

[0107] The first uneven structure 103, 113 has a plurality of recesses 104, 114 and first protrusions 105, 115 located between the plurality of recesses 104, 114. The recesses 104, 114 in the first uneven structure 103, 113 correspond to the first protrusions of the release layer of the release sheet. The first protrusions 105, 115 in the first uneven structure 103, 113 correspond to the recesses of the release layer of the release sheet. Each of the recesses 104, 114 is composed of a bottom 106, 116 and a side surface 107, 117 connecting the bottom 106, 116 and the recesses 104, 114. A second uneven structure 108, 118 is formed on the bottom 106, 116.

[0108] In the resin molded articles of the first and second aspects, it is preferable that the size of each of the first concave-convex structure and the second concave-convex structure is approximately the same as the size of the corresponding structure of the release sheet. The surface of the resin layer in the resin molded product of the first and second embodiments is not particularly limited to a kurtosis (Sku) value as defined in ISO 25178-2:2012. That is, the surface of the resin layer in the resin molded product may have a kurtosis (Sku) of less than 3 or greater than 3, but preferably less than 3. In the present disclosure, the resin molded product is manufactured using a release sheet having a release layer surface with a kurtosis (Sku) of less than 3. Therefore, even if the kurtosis (Sku) of the surface of the resin layer is greater than 3, the kurtosis (Sku) is prevented from becoming too high. As a result, the resin molded product can have a prominent three-dimensional pattern and exhibit diffractive luster. In addition, it is preferable that the surface of the resin layer in the resin molded product of the first embodiment has a skewness (Ssk) defined in ISO 25178-2:2012 that satisfies Ssk > 0. It is preferable that the surface of the resin layer in the resin molded product of the second embodiment has a skewness (Ssk) defined in ISO 25178-2:2012 that satisfies Ssk ≦ 0.

[0109] The first uneven structure 103, 113 corresponds to the pattern of the resin molded product. This pattern is visible to the naked eye. The second uneven structure 108 exhibits diffractive gloss. Therefore, when an observer views the resin molded product according to the present disclosure from the resin layer side, the surface of the three-dimensional pattern has a matte finish, and multicolored diffractive gloss can be recognized in the recesses of the pattern. The resin molded product according to the present disclosure has good visibility of both the pattern and the diffractive gloss, and a noticeable contrast can be seen between areas exhibiting diffractive gloss and areas without diffractive gloss, resulting in a resin molded product with excellent aesthetics.

[0110] [Laminate] The laminate in the present disclosure comprises a support layer and the release sheet described above laminated on one side of the support layer. The resin molded article has a surface with an inverted uneven shape to the release layer of the release sheet, whereas the laminate has a surface with an uneven shape that matches the release layer of the release sheet. Specific applications of the laminate include decorative sheets, wallpaper, and the like.

[0111] The support layer may be selected as appropriate depending on the type and application of the laminate, for example, woven fabric, nonwoven fabric, mesh fabric, paper, resin film such as polyester or polyolefin, metal plate, glass plate, etc. Fibers used for woven fabric and nonwoven fabric include natural fibers such as cotton, linen, and wool; regenerated or semi-synthetic fibers such as rayon and acetate; and synthetic fibers such as polyamide, polyester, polyacrylonitrile, polyvinyl alcohol, and polyolefin. The thickness of the support layer may be set as appropriate depending on the application.

[0112] The release sheet and the support layer are preferably bonded via an adhesive layer. Known adhesives can be used, and the adhesive can be selected depending on the support layer and the base layer of the release sheet. [Example]

[0113] Next, the present disclosure will be described in more detail by way of examples, but the present disclosure is not limited to these examples in any way.

[0114] 1. Evaluation of release sheets 1-1.Appearance evaluation (1) Evaluation of pattern visibility The surfaces of the release layers of the release sheets of the Examples and Comparative Examples were visually observed, and the visibility of the pattern was evaluated according to the following criteria. A + : The uneven pattern is clearly visible and the three-dimensional effect is particularly excellent. A: The uneven pattern is clearly visible and gives a sense of three-dimensionality. B: The uneven pattern is visible, but the three-dimensional effect and clarity of the pattern are inferior to those of an A rating. C: The pattern is visible, but it is difficult to see and lacks a three-dimensional effect. D: The pattern cannot be seen (2) Evaluation of diffractive gloss The release layer surfaces of the release sheets of the Examples and Comparative Examples were visually observed, and the diffractive gloss was evaluated according to the following criteria. A: Diffraction gloss (multicolored gloss) is clearly visible from all angles. B: There is a diffractive gloss, but the intensity of the diffractive gloss changes depending on the observation angle. C: Diffraction gloss is hard to see D: No diffraction gloss (3) Overall evaluation The overall evaluation of the appearance was made according to the following criteria. A: Both pattern visibility and diffractive gloss are rated A. B: Either pattern visibility or diffractive gloss is rated B C: Either pattern visibility or diffractive gloss is rated C D: Either pattern visibility or diffractive gloss is rated D

[0115] 1-2. Microscopic observation A4 size (210 mm × 297 mm) samples were cut out from the release sheets of the examples and comparative examples. For each sample, a shape analysis laser microscope (Keyence Corporation, VK-X150) was used to observe the surface at a magnification of 10 times using an objective lens. In addition, the objective lens is set to 50x (image area 0.06mm 2) A 3D image of the release layer surface was obtained. The convex portions of the first uneven structure were identified in the 3D image, and the presence or absence of linear fine unevenness and the formation position of the fine unevenness were confirmed in the convex portions.

[0116] 1-3. Surface roughness parameters A shape analysis laser microscope (Keyence Corporation, VK-X150) was used to capture 25 connected images (image area: approximately 26 mm) of 20 locations within the surface of the sample, with the objective lens set at 10x magnification. 2 ) were acquired. The obtained images were subjected to a reference plane setting process, and then Gaussian filter processing was performed, with the cutoff wavelengths set to 5 μm for the S filter and 8 mm for the L filter, and surface roughness analysis was performed. As a result, the kurtosis (Sku), skewness (Ssk), arithmetic mean height (Sa), root mean square height (Sq), and maximum height (Sz) at each measurement point were obtained. The average values of the obtained values of each parameter were used as the kurtosis (Sku), skewness (Ssk), arithmetic mean height (Sa), root mean square height (Sq), and maximum height (Sz) for each example and comparative example.

[0117] 1-4.Gross value A4 size (210 mm × 297 mm) samples were cut out from the release sheets of the examples and comparative examples. At this time, the samples were marked so that the extension direction (first direction) and arrangement direction (second direction) of the second uneven structure could be identified. The gloss values in the first direction and the second direction were measured at five locations on the surface of the sample in accordance with JIS Z 8741:1997. A gloss meter (PG-1M, manufactured by Nippon Denshoku Industries Co., Ltd.) was used for the measurements.

[0118] 2. Preparation of release sheet [Preparation of raw material] (1) 1 unformed original roll, 1 original roll High-quality paper (basis weight 125g / m 2An unshaped raw roll 1 was prepared, in which a resin layer having a blend resin layer (thickness 15 μm) and a homopropylene layer (thickness 15 μm) formed in this order on a base roll. The blend resin layer and homopropylene layer were formed by extrusion molding (temperature: 310°C, raw roll conveying speed: 80 m / min). The resin for the blend resin layer was a mixed resin of polypropylene and polyethylene manufactured by SunAllomer Co., Ltd. (polypropylene / polyethylene = 80 / 20 (mass ratio), obtained by dry blending and then melt mixing). The homopropylene layer was formed using a homopropylene polymer manufactured by SunAllomer Co., Ltd. Note that when forming each layer, the surface of the resin was mirror-finished with a mirror chill roll. The unshaped raw roll 1 was placed so that the resin layer of the unshaped raw roll 1 faced the rubber master roll, and the unshaped raw roll 1 was heated and pressed with the master roll and the counter roll while being transported. By this embossing, a raw roll 1 (shaped raw roll) having a precursor layer on which the second uneven structure described below was formed was obtained. (Second uneven structure) Shape: Linear structure as shown in Figure 3 Cross-sectional shape of the convex part: Approximately triangular as shown in Figure 4 Convex pitch: 2μm Height of convex part: 650nm

[0119] (2) Unshaped original fabric 2 High-quality paper (basis weight 164 g / m 2 ), a clay layer (thickness 15 μm) and a melamine alkyd resin layer (coating amount 7 g / m 2 An unshaped raw material 2 having the above-mentioned components in this order was prepared. The melamine alkyd resin layer was formed by cast coating. When the melamine alkyd resin layer was formed, the surface of the resin was mirror-finished with a mirror chill roll.

[0120] (3) Unformed original fabric 3, original fabric 3 Unshaped base roll 3 having a precursor layer was prepared in the same manner as unshaped base roll 1, except that an unshaped base roll in which a clay layer (thickness 15 μm) was formed between the high-quality paper and the blend resin layer was used. The same second uneven structure as that of raw roll 1 was formed on unshaped raw roll 3 under the same conditions as those for raw roll 1, to obtain raw roll 3 (shaped raw roll).

[0121] (4) Unshaped original fabric 4 Unshaped base material 4 was obtained in the same manner as in the production of unshaped base material 1, except that a matt chill roll (a roll whose surface was roughened by sandblasting) was used when forming each layer.

[0122] [Example 1] The raw web 1 was placed so that the precursor layer faced the embossing roll, and while the raw web 1 was being transported, it was heat-pressed between the embossing roll and the back roll. This embossing process yielded a release sheet having a release layer on which the following first uneven structure was formed. A laser microscope photograph of the release layer in the release sheet of Example 1 is shown in Figure 12. In the photograph in Figure 12, the dark areas correspond to the recesses, and the light areas correspond to the first protrusions. Pattern: Random scale-like structure (the first convex part is mesh-like, and the concave part is scale-like) Average height of first convex part (cross-sectional view): 80 μm

[0123] [Example 2] A release sheet of Example 2 was obtained in the same manner as in Example 1, except that the following first uneven structure was formed. A laser microscope photograph of the release layer in the release sheet of Example 2 is shown in Figure 13. In the photograph of Figure 13, the dark colored areas correspond to the recesses, and the light colored areas correspond to the first protrusions. Pattern: Random mesh structure (first convex part is mesh-shaped) Average height of first convex part (cross-sectional view): 80 μm

[0124] [Example 3] A release sheet of Example 3 was obtained in the same manner as in Example 1, except that the following first uneven structure was formed. A laser microscope photograph of the release layer in the release sheet of Example 3 is shown in Figure 14. In the photograph of Figure 14, the dark colored areas correspond to the first convex portions, and the light colored areas correspond to the concave portions. Pattern: Japanese paper pattern (first convex part is random radial) Average height of first convex part (cross-sectional view): 90 μm

[0125] [Example 4] A release sheet of Example 4 was obtained in the same manner as in Example 1, except that the following first uneven structure was formed. A laser microscope photograph of the release layer in the release sheet of Example 4 is shown in Figure 15. In the photograph of Figure 15, the dark colored areas correspond to the first convex portions, and the light colored areas correspond to the concave portions. Pattern: Random shape (Cells of different widths are arranged in one direction. Multiple first convex portions are formed within the cells. The first convex portions within the cells extend randomly in directions perpendicular, parallel, and diagonal to the cell arrangement direction. The width and circumference of the embossing roll are the minimum repeating units.) Average height of first convex part (cross-sectional view): 42 μm

[0126] [Example 5] The raw web 1 was placed so that the precursor layer faced the embossing roll, and while the raw web 1 was being transported, it was heat-pressed between the embossing roll and the back roll. This embossing process yielded a release sheet having a release layer on which the following first uneven structure was formed. A laser microscope photograph of the release layer in the release sheet of Example 5 is shown in Figure 16. In the photograph in Figure 16, the dark areas correspond to the first convex portions, and the light areas correspond to the concave portions. Pattern: Line shape arranged in one direction (the width and height of the lines are not uniform and are arranged randomly) Average height of first convex part (cross-sectional view): 60 μm

[0127] [Example 6] A release sheet of Example 6 was obtained in the same manner as in Example 5, except that the following first uneven structure was formed. A laser microscope photograph of the release layer in the release sheet of Example 6 is shown in Figure 17. In the photograph of Figure 17, the dark colored areas correspond to the recesses, and the light colored areas correspond to the first protrusions. Pattern: A pattern in which multiple large ellipses are periodically arranged in the long and short axis directions. The large ellipses are the first convex portions. In the areas between the ellipses, first convex portions with a scale-like structure smaller than the ellipses are formed. The areas between the ellipses and the scale-like shapes correspond to the concave portions. Average height of first convex part (cross-sectional view): 149 μm

[0128] [Example 7] A release sheet of Example 7 was obtained in the same manner as in Example 5, except that the following first uneven structure was formed. A laser microscope photograph of the release layer in the release sheet of Example 7 is shown in Figure 18. In Figure 18, the dark colored areas correspond to the first convex portions, and the light colored areas correspond to the concave portions. Pattern: Lizard leather look (Multiple blocks are arranged in two directions that are roughly perpendicular to each other. First convex portions with rib shapes of different sizes are arranged within each block. The overall pattern is random.) Average height of first convex part (cross-sectional view): 117 μm

[0129] [Comparative Example 1] Using the unshaped raw sheet 1 described above, the same first uneven structure as in Example 1 was formed on the resin layer, to obtain a release sheet of Comparative Example 1.

[0130] Comparative Example 2 The above unshaped raw sheet 1 was used, and the same first uneven structure as in Example 2 was formed on the resin layer to obtain a release sheet of Comparative Example 2.

[0131] Comparative Example 3 Using the unshaped raw sheet 1 described above, the same first uneven structure as in Example 3 was formed on the resin layer, to obtain a release sheet of Comparative Example 3.

[0132] Comparative Example 4 Using the unshaped raw sheet 2 described above, the same first uneven structure as in Example 4 was formed on the resin layer, to obtain a release sheet of Comparative Example 4.

[0133] Comparative Example 5 Using the unshaped raw sheet 1 described above, the same first uneven structure as in Example 5 was formed on the resin layer, to obtain a release sheet of Comparative Example 5.

[0134] Comparative Example 6 The above unshaped raw sheet 1 was used, and the same first uneven structure as in Example 6 was formed on the resin layer, to obtain a release sheet of Comparative Example 6.

[0135] Comparative Example 7 The above unshaped raw sheet 1 was used, and the same first uneven structure as in Example 7 was formed on the resin layer to obtain a release sheet of Comparative Example 7.

[0136] [Comparative Example 8] A release sheet of Comparative Example 8 was obtained in the same manner as in Example 1, except that raw sheet 3 was used and the first uneven structure described below was formed. Pattern: Striped pattern (a plurality of first protrusions extending in one direction are arranged in a direction substantially perpendicular to the extending direction. A plurality of second protrusions extend in the arrangement direction of the first protrusions and are arranged in the extension direction of the first protrusions. In other words, the arrangement direction of the first protrusions and the arrangement direction of the second protrusions are substantially perpendicular to each other.) Average height of first convex part (cross-sectional view): 44 μm

[0137] Comparative Example 9 A release sheet of Comparative Example 9 was obtained in the same manner as Comparative Example 8, except that the pattern of the first uneven structure was different. Pattern: Striped pattern (a pattern in which the arrangement direction of the second convex portions is different from that of Comparative Example 8. A plurality of first convex portions extending in one direction are arranged in a direction approximately perpendicular to the extending direction. A plurality of second convex portions extend in the extending direction of the first convex portions and are arranged in the arrangement direction of the first convex portions. In other words, the arrangement direction of the first convex portions and the arrangement direction of the second convex portions approximately coincide with each other.) Average height of first convex part (cross-sectional view): 38 μm

[0138] [Comparative Example 10] Using unshaped base material 4, the following first uneven structure was formed on the precursor layer (shaped base material 4). Next, a second uneven structure was formed on shaped base material 4 at positions corresponding to the apexes of the first convex portions in the same manner as in Comparative Example 8, to obtain a release sheet of Comparative Example 10. (First uneven structure) Pattern: A pattern in which a plurality of substantially diamond-shaped first protrusions are periodically arranged in the direction of each symmetrical axis. The spaces between the substantially diamond-shaped first protrusions correspond to recesses. Average height of first convex part (cross-sectional view): 32 μm

[0139] [Comparative Example 11] Raw roll 1 was used as Comparative Example 11.

[0140] 3.Results The evaluation results of the release sheets of the examples and comparative examples are shown in Tables 1 and 2.

[0141] [Table 1]

[0142] [Table 2]

[0143] In all of the release sheets of the examples, microscopic observation confirmed that a second uneven structure, which is a fine unevenness, was present on the tops of the convex portions of the first uneven structure, and that there were no fine unevenness in other areas (concave portions and side surfaces). In the release sheets of Comparative Examples 1-7, the convex portions of the first uneven structure were confirmed, but no fine unevenness was observed throughout. In Comparative Examples 8-9, it was confirmed that the second uneven structure, which is a fine unevenness, was present throughout the convex portions of the first uneven structure (i.e., the convex portions and side surfaces), and that there were no fine unevenness in the concave portions. In Comparative Example 10, the first uneven structure was confirmed, but it was confirmed that there were fine unevenness throughout (i.e., even in areas corresponding to the concave portions).

[0144] In all of Examples 1-7, a clear, three-dimensional pattern was visible, and a multicolored glossiness was felt. In contrast, in Comparative Examples 8 and 9, although a multicolored glossiness was felt, it was weaker than in the Examples, and the contrast between glossy and non-glossy areas was felt to be small. In Comparative Examples 8 and 9, the pattern was visible but not clear, and it was felt that the three-dimensional effect was poor. In Comparative Example 10, a multicolored glossiness was seen throughout the release layer, but the glossiness was weaker than in the Examples. Furthermore, in Comparative Example 10, the pattern was visible but not clear, and it was felt that the three-dimensional effect was poor. In Comparative Example 1-7, the pattern corresponding to Example 1-7 was visible, but no multicolored gloss was observed.In Comparative Example 11, an excellent multicolored gloss was observed, but no pattern was observed.

[0145] In all of Examples 1 to 7, the kurtosis was less than 3. On the other hand, in Comparative Examples 8 to 10, it exceeded 3. When combined with the above-mentioned appearance evaluation, it can be said that, among the surface roughness parameters of the release layer, kurtosis has an effect on the sensory evaluation of the appearance. In other words, because the first uneven structure has a relatively gently sloping uneven surface with a kurtosis of less than 3, the three-dimensional feel of the pattern can be felt, and a release sheet with excellent diffractive gloss can be obtained. In particular, in Comparative Examples 3, 4, and 7, the kurtosis was large, exceeding 3, compared to Examples 3, 4, and 7, in which the first uneven structure of the same pattern was formed under the same conditions. This was presumed to be because the Comparative Examples formed the first uneven structure on an unshaped base roll, and therefore were more likely to undergo large deformation due to pressing than the Examples.

[0146] The surface of the release layer of Examples 1-4 corresponds to the first aspect, and the surface of the release layer of Examples 5-7 corresponds to the second aspect. Examples 1-4 had a particularly clear diffractive gloss. In contrast, Examples 5-7 appeared to have a weaker gloss than Examples 1-4, but still had a design with a "gentle diffractive gloss." Detailed observation of the release layer surface of Example 6 revealed that the second uneven structure was partially missing or somewhat unclear in the central portion of the apex of the first convex portion. Meanwhile, the second uneven structure could be clearly observed at the edge of the apex. Thus, the presence or absence of deformation of the second uneven structure allowed for variation in the diffractive gloss.

[0147] 4. Manufacturing of resin molded products [Example 8] A resin layer-forming composition having the following composition was applied by bar coating onto the release layer of the release sheet of Example 1. Then, the composition was heated at 80° C. for 3 minutes to form a resin layer. (Composition for forming resin layer) Polyurethane (Rezamin NE-8811, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.) 5 parts by weight Colorant (Seika Seven NET-5794 (PM) Black, manufactured by Dainichi Seika Color & Chemicals Mfg. Co., Ltd.) 1 part by weight ·solvent A fabric (wet base, manufactured by Kinki Vinyl Co., Ltd.) was attached to the resin layer using an adhesive (product name: Lezamin NE-8811, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.). After drying and aging the adhesive, the release sheet was peeled off to obtain the resin molded product (synthetic leather) of Example 8.

[0148] [Examples 9-14, Comparative Examples 12-22] Using the release sheets of Examples 2-7 and Comparative Examples 1-11, resin molded products (synthetic leathers) of Examples 9-14 and Comparative Examples 12-22 were obtained in the same process as in Example 1, respectively.

[0149] 5. Appearance evaluation of resin molded products The resin molded articles of Examples 8-14 and Comparative Examples 12-22 were visually observed for appearance (pattern visibility and diffractive glossiness) and evaluated. In all of Examples 8 to 14, the pattern corresponding to the release sheet was visible. The patterns of Examples 8 to 14 were clear and had a three-dimensional feel. Furthermore, Examples 8 to 14 had a multicolored glossy feel. In contrast, in the resin molded products of Comparative Examples 19 and 20 produced using the release sheets of Comparative Examples 8 and 9, the patterns were visible but not clear, and it was felt that there was little three-dimensionality. Furthermore, in Comparative Examples 19 and 20, although a multicolored glossiness was felt, it was weaker than in the Examples, and the contrast of the glossiness was also felt to be small. In the resin molded product of Comparative Example 21 produced using the release sheet of Comparative Example 10, the pattern was visible but not clear, and it was felt that there was little three-dimensionality. Furthermore, in Comparative Example 21, the entire resin layer had a weak multicolored glossiness, and the gloss contrast was not felt. In the resin molded products of Comparative Examples 12-18 produced using the release sheets of Comparative Examples 1-7, the patterns corresponding to Examples 8-14 were visible, but no multicolored glossiness was observed. The resin molded product of Comparative Example 22 produced using the release sheet of Comparative Example 21 exhibited an excellent multicolored glossiness, but no pattern was visible, giving the impression of a monotonous design. [Explanation of symbols]

[0150] 10, 20: Release sheet 11,21: Base material layer 12,22,52: Release layer 13, 23: First uneven layer 14, 24, 54: First convex part 15, 25, 55: recess 16,26,56:Top 17,27,57: Side part 18, 28, 38, 58: Second uneven structure 39: Second convex part 40: Embossing roll 41: Embossing roll convex part 42: Embossing roll recess 43: Bottom 44: Side 50: Sheet 51: Base material layer 52: Precursor layer 100,110: Resin molded product 101,111: Support layer 102, 112: Resin layer 103, 113: First uneven structure 104,114: Recess 105,115: First convex part 106,116: Bottom 107,117: Side part 108,118: Second uneven structure

Claims

1. A substrate layer and a release layer on one surface of the substrate layer, the release layer has a first uneven structure on a surface opposite to the base layer, the first uneven structure being composed of a plurality of first convex portions and concave portions located between the first convex portions; each of the first convex portions has a top portion, and the top portion is a region where a second concave-convex structure that is finer than the first concave-convex structure is formed; the second uneven structure is not formed in the recess, the second uneven structure extends in a first direction when the release layer is viewed in a plane, and has a plurality of second convex portions arranged in a second direction substantially perpendicular to the first direction, and the second uneven structure exhibits diffractive gloss; The surface of the release layer has a kurtosis (Sku) defined in ISO 25178-2:2012 of less than 3.

2. 2. The release sheet according to claim 1, wherein each of the first convex portions has a side surface connecting the top surface and the concave portion, and the second uneven structure is not formed on the side surface.

3. The release sheet according to claim 1 or 2, wherein the surface of the release layer has a skewness (Ssk) defined in ISO 25178-2:2012 of less than 0.

4. The release sheet according to claim 1 or 2, wherein the surface of the release layer has a skewness (Ssk) defined in ISO 25178-2:2012 of 0 or more.

5. 5. The release sheet according to claim 1, wherein the 85-degree gloss value of the surface of the release layer measured in accordance with JIS Z 8741:1997 satisfies the following formula (1): G1>G2 ... (1) G1: 85-degree gloss value obtained by irradiating the measurement light from the first direction G2: 85-degree gloss value obtained by irradiating the measurement light from the second direction

6. The release sheet according to claim 1 , wherein the substrate layer comprises a paper substrate.

7. The release sheet according to claim 6, wherein the paper substrate has a thickness of 25 μm or more and 200 μm or less.

8. The paper substrate has a basis weight of 40 g / m ２ More than 400g / m ２ The release sheet according to claim 6, wherein:

9. The release sheet according to claim 1 , wherein the release layer comprises a thermoplastic resin.

10. 10. The release sheet according to claim 9, wherein the thermoplastic resin comprises at least one selected from the group consisting of polypropylene-based resins, polymethylpentene-based resins, (meth)acrylic resins, and (meth)acrylic acid ester copolymers.

11. 11. The release sheet according to claim 1, wherein the thickness of the release layer is 5 μm or more and 120 μm or less.

12. A method for producing the release sheet according to any one of claims 1 to 11, comprising: a step (1) of forming a precursor layer having the second uneven structure on the base layer; and (2) pressing an embossing roll having a surface shape corresponding to the first uneven structure against the surface of the precursor layer to form a release layer having the first uneven structure and the second uneven structure on the surface, In the step (2), the embossing roll and the precursor layer are brought into contact with each other at positions corresponding to the recesses, and the embossing roll and the precursor layer are separated from each other at positions corresponding to the peaks.

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