JP7722103B2 - Release sheet and method for producing the release sheet - Google Patents

Description

This disclosure relates to a release sheet, a method for producing the same, and a resin molded product.

Resin molded products such as synthetic leather products and decorative sheets used in furniture and automotive interior components may have a patterned, uneven surface. This pattern can, for example, express a texture similar to that of natural leather, or can be given geometric patterns to enhance the design. The above-mentioned resin molded products may also be given optical design features such as a glossy appearance. For example, resin molded products have been proposed that have fine irregularities formed on the surface, giving them a multicolored luster (e.g., a rainbow-like luster) whose color changes depending on the observation angle due to the diffraction of light.

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.

Japanese Patent Application Laid-Open No. 2020-55133 JP 2018-164992 A

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 the difference in gloss, so the three-dimensionality of the formed pattern is lacking. 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.

The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a release sheet that can be used to produce resin molded products that have a prominent three-dimensional pattern and exhibit diffractive gloss, as well as 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.

In order to solve the above problems, the present disclosure provides the following [1] to [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 a 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 being not 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) defined in ISO 25178-2:2012 of 0 or more.
[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 measurement light from the first direction G2: 85-degree gloss value obtained by irradiating measurement light from the second direction [6] The release sheet according to any one of [1] to [5], wherein the base material layer comprises a paper base material.
[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 release sheet according to [6], wherein the paper substrate has a basis weight of 40 g/m ² or more and 400 g/m ² or less.
[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.

[12] A method for producing a release sheet according to any one of [1] to [11], comprising: step (1) of forming a precursor layer having the second uneven structure on the substrate layer; and 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 step (2), the embossing roll and the precursor layer are brought into contact 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.

[13] A resin molded product comprising a support layer and a resin layer on one side of the support layer, the resin layer having, on the surface opposite the support layer, a first uneven structure consisting 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 substantially perpendicular to the first direction, and the second uneven structure exhibiting diffractive gloss.

By using the release sheet of the present disclosure, it is possible to obtain a release sheet and resin molded products that enhance the three-dimensionality of the pattern and that can be used to produce resin molded products that exhibit diffractive gloss.

1 is a cross-sectional schematic view showing an example of a release sheet according to a first embodiment. FIG. FIG. 2 is a cross-sectional view illustrating an example of a release sheet according to a second embodiment. FIG. 10 is a schematic plan view for explaining a second concave-convex structure. FIG. 4 is a schematic cross-sectional view of the second protrusions in FIG. 3 in the arrangement direction. FIG. 3 is a cross-sectional view showing another example of the release sheet according to the first embodiment. FIG. 10 is a cross-sectional schematic view showing another example of the release sheet according to the second embodiment. FIG. 10 is a schematic diagram illustrating how gloss values are measured by irradiating measurement light at a low angle. FIG. 10 is a schematic diagram illustrating how gloss values are measured when the incident angle of the measurement light is 85 degrees. FIG. 2 is a schematic diagram illustrating a step of forming a first concavo-convex structure in the method for producing a release sheet according to the present disclosure. 1 is a cross-sectional view showing an example of a resin molded product according to a first embodiment. FIG. FIG. 4 is a cross-sectional view showing an example of a resin molded product according to a second embodiment. 1 is a laser microscope photograph of the surface of the release layer in the release sheet of Example 1. 1 is a laser microscope photograph of the surface of the release layer in the release sheet of Example 2. 1 is a laser microscope photograph of the surface of the release layer in the release sheet of Example 3. 1 is a laser microscope photograph of the surface of the release layer in the release sheet of Example 4. 1 is a laser microscope photograph of the surface of the release layer in the release sheet of Example 5. 1 is a laser microscope photograph of the surface of the release layer in the release sheet of Example 6. 1 is a laser microscope photograph of the surface of the release layer in the release sheet of Example 7.

[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 substantially 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 referred to as "kurtosis," it refers to kurtosis (Sku) as defined in ISO 25178-2:2012.

<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 the first uneven structure and the second uneven structure. However, since the second uneven structure is finer than the first uneven structure, the surface roughness parameter measured in accordance with ISO 25178-2:2012 largely reflects the surface shape resulting from the first uneven structure.

In the present disclosure, the kurtosis, skewness, root mean square height, arithmetic mean height, and maximum height (sometimes 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 ² ) are acquired using a 10x objective lens for 20 arbitrary locations in the release layer. A reference surface setting process is then performed on the images. Gaussian filter processing is then performed, and surface roughness analysis is performed with the cutoff wavelengths set to 5 μm for the S filter and 8 mm for the L filter. The average values of the measurements obtained at the 20 locations are used as the numerical values of the surface roughness parameters.

The surface of the release layer in this 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 a pointed height distribution, representing a surface that tends to have sharp peaks or valleys. On the other hand, a kurtosis of less than 3 (Sku<3) indicates a flattened surface height distribution, 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.

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

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 the proportion 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 the proportion 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.

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.
It can be said that the maximum height reflects 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.

In this disclosure, the surface of the release layer preferably has a root mean square height (Sq) of 6.0 μm or more as specified 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 specified in ISO 25178-2:2012. In this 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 specified in ISO 25178-2:2012, respectively.

Kurtosis represents the fourth-squared mean of the height over a reference length that has been made dimensionless by the fourth power of the root-mean-square height. Skewness represents the third-squared mean of the height over a reference length that has been made dimensionless by the cube of the root-mean-square height. By having the root-mean-square height within the above range, the surface of the release layer can more easily satisfy the above ranges of kurtosis and skewness.

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

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 shape-imparting 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 shape-imparting portion 12a, 22a. In the case of the release sheet of the second embodiment, the shape-imparting portion 22a corresponds to the first convex portion described later.
First uneven structures 13, 23 and second uneven structures 18, 28 are formed on the release layers 12, 22. The second uneven structures 18, 28 have finer unevenness than the first uneven structures 13, 23.

<<First concave-convex 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 Figures 1 and 2. It should be noted that the actual first uneven structure may differ in shape from Figures 1 and 2 in terms of the convex and concave portions, etc., depending on the pattern imparted to the release sheet and the cut location within the release layer surface.

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 others as the second type.

The first uneven structure 13, 23 has a plurality of first convex portions 14, 24 and concave portions 15, 25 between the first convex portions 14, 24. Each of the first convex portions 14, 24 is composed of a peak 16, 26 and a side portion 17, 27. The peaks 16, 26 are areas where the second uneven structure 18, 28 is formed. In this disclosure, the concave portions 15, 25 do not have a second uneven structure formed therein.

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

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, it is possible to improve the contrast of the diffractive gloss, which will be described later. Note that when the first convex portions do not have side portions, the second uneven structure is formed over the entire first convex portion.

The recesses 15, 25 and side surfaces 17, 27 may have minute irregularities formed on the outermost surface of the embossing roll used in the method for producing the release sheet described below.

In the first embodiment, the surface of the release layer has a kurtosis of less than 3 and a skewness of less than 0. The first uneven structure 13 in the first embodiment, ignoring the second uneven structure, can be schematically represented as a structure in which shallow depressions are formed on a substantially flat surface, with the bottoms of the depressions corresponding to the recesses 15. In the second embodiment, the surface of the release layer has a kurtosis of less than 3 and a skewness of 0 or greater. The first uneven structure 23 in the second embodiment, ignoring the second uneven structure, can be schematically represented as a structure in which gently sloping first protrusions 24 protrude from recesses 25, which are a substantially flat surface.

The various 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.

In both the first and second aspects, in order for the surface of the release layer to easily satisfy Sku<3, the height of the first convex portions 14, 24 (the length in the thickness direction between the top and the bottom of each of the first convex portions, indicated by the symbol H in Figures 1 and 2) is preferably 300 μm or less, and more preferably 280 μm or less. In consideration of the visibility of the pattern due to the first uneven structure, the ease of forming the pattern, and the like, the height H is preferably 30 μm or more, and 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.

When the release sheets 10, 20 are viewed in cross section, the width of the first convex portions 14, 24 (the width of the base 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.

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.

The recesses 15, 25 may be substantially flat surfaces, or may be concave curved surfaces recessed toward the substrate layer (-Z direction in Figures 1 and 2).

<<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.

Figure 3 is a schematic plan view illustrating the second uneven structure. The second uneven structure 38 is composed of a plurality of second convex portions 39. The second uneven structure 38 has linear structures arranged at approximately equal intervals. Each of the second convex portions 39 extends in a first direction (the Y-axis direction in Figure 3) when the release sheet is viewed in a plan view (when viewed from the +Z direction in Figure 3). The multiple second convex portions 39 are arranged at approximately equal intervals in a second direction (the X-axis direction in Figure 3). This allows for the creation of a multicolored diffractive luster. "Multicolored" means that reflected light in two or more wavelength ranges (particularly reflected light from a resin molded product) is visible to the naked eye. "Multicolored" 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.

Figure 4 is a schematic cross-sectional view of the second convex portions in Figure 3 in the arrangement direction (X-axis direction). The second convex portions 39 shown in Figure 4 have a cross-sectional shape that is approximately an isosceles triangle. The cross-sectional shape is not limited to that shown in Figure 4 as long as it 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 diffractive gloss and the ease of forming the second uneven structure, it is preferable that the cross-section of the second convex portions be approximately an isosceles triangle or approximately equilateral triangle.

The pitch of the second uneven structure (the length of the repeating unit of the shape in the cross section in FIG. 4, indicated by symbol P in FIG. 4) preferably has a lower limit of 0.5 μm or more, more preferably 0.8 μm or more, and an upper limit of 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) preferably has an upper limit of 0.05 μm or more, more preferably 0.1 μm or more, and a lower limit of 3.0 μm or more, more preferably 2.0 μm or less.
In order 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% or more and +50% or less, and more preferably varies within a range of -40% or more and +40% or less.
The various dimensions of the second uneven structure can be determined by obtaining cross-sectional and surface observation images using a scanning electron microscope and analyzing the images. The pitch P of the second uneven structure can be determined by analyzing images obtained using a laser microscope with a 100x objective lens.

Note that, in the release sheet shown in Figures 1 and 2, an example is shown 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 to this. For example, as shown in Figures 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.

<Optical characteristics of the surface of the release layer>
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 measurement light from a first direction G2: 85-degree gloss value obtained by irradiating measurement light from a second direction The first direction is the direction in which the second convex portions of the second uneven structure extend. The second direction is the direction in which the multiple second convex portions are arranged.

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 uneven structure and the second uneven 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. FIG. 7 is a schematic diagram illustrating how gloss values are measured by irradiating measurement light at a low angle (e.g., 20 degrees). FIG. 7( a) illustrates 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). FIG. 7( b) illustrates 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 FIGS. 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 measurements at low angles, 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. That is, in measurements at low angles, the difference in gloss value derived from the second uneven structure due to 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) illustrates 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) illustrates 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 at an incident angle of 85 degrees, as shown in FIG. 8( a), the measurement light incident from the first direction can also penetrate into the valleys of the second uneven structure, and the reflected light reflected inside 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 in which 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 due to the second uneven structure occurs in the gloss value.

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 path of the incident light and reflected light, acting as a barrier. This can result in anisotropy in the gloss value due to the first uneven structure. However, because the first and second directions are directions derived from the second uneven structure, there is little correlation with the pattern of the first uneven structure. For this reason, 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.

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 greater, and more preferably 5.0 or greater. The G1 value is preferably 40.0 or less, and more preferably 35.0 or less. The G2 value is preferably 0.3 or greater, and more preferably 0.8 or greater. The G2 value is preferably 20.0 or less, and more preferably 17.0 or less.

The average value of G1 and G2 ((G1 + G2)/2) is preferably 1.0 or greater, and more preferably 3.0 or greater. The average value of G1 and G2 is preferably 25.0 or less, and 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 perceived even when the release sheet is viewed from various directions.

The greater the difference between G1 and G2 (ΔG = G1 - G2), the better the diffractive gloss can be. The difference between G1 and G2 is preferably 1.0 or greater. However, if the difference between G1 and G2 is too large, the diffractive gloss may vary depending on the observation angle, which may result in poor design. For this reason, it is preferable that the difference between G1 and G2 be 30.0 or less.

Furthermore, the greater the ratio of G1 to G2 (G1/G2), and the greater 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 gloss can be obtained. G1/G2 is preferably 1.1 or greater, and (G1-G2)/(G1+G2) is preferably 0.05 or greater. Furthermore, to minimize differences in diffractive gloss due to different observation angles, G1/G2 is preferably 8.0 or less, and (G1-G2)/(G1+G2) is preferably 0.8 or less.

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 described below, 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 area where the second uneven structure has been deformed has a different optical path of reflected light than the other areas. Therefore, the area where the second uneven structure has been deformed has a diffractive gloss that is different from the other areas, allowing the above-mentioned design to be expressed.

<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 an undercoat layer, in order to improve adhesion to the release layer.

The thickness of the substrate 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. A substrate layer thickness within this range provides adequate rigidity, improving workability when forming the release layer or shaping the resin molded product. It also prevents the release sheet from becoming too thick and resulting in an excessively large winding diameter.

When the release layer contains a resin curable with ionizing radiation such as ultraviolet light or electron beams, it is preferable that the substrate layer be transparent to ionizing radiation.

For example, the paper substrate can be a strong sizing bleached or unbleached paper substrate, or pure white roll paper, kraft paper, paperboard, coated paper, cast-coated paper, processed base paper, fine paper, lightly coated printing paper, coated printing paper, resin-coated paper, release base paper, double-sided coated release base paper, etc. Furthermore, the paper substrate can also have an intermediate layer such as a sealing layer or a resin layer formed in advance. If necessary, the paper substrate can also be used in combination with various resin films, etc.

The paper substrate preferably has a basis weight of 40 g/m2 or ^more and 400 g/ ^m2 or less, and more preferably a basis weight of 100 g/ ^m2 or more and 250 g/ ^m2 or less. If the paper substrate has a basis weight within the above range, various problems during the production of the release sheet, such as curling and waviness, are unlikely to occur. 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.

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.

To provide the release sheet with sufficient heat resistance, the paper substrate is preferably neutral paper. Among these, neutral paper sized using alkyl ketene dimer as a sizing agent is more preferred.

Examples of the resin film 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.

(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.

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

When using a material with a relatively rough surface, such as kraft paper or fine paper, as the paper substrate, providing a smoothing layer containing a polyolefin resin makes it easy to improve the smoothness of the paper substrate.

There are no particular limitations on the clay that can be used. Examples of clay that can be used include kaolin, talc, bentonite, smectite, vermiculite, mica, chlorite, kibushi clay, gairome clay, halloysite, and mica. Talc has a low hardness (Mohs hardness of 1) and excellent heat resistance, which can improve heat resistance and dimensional stability during embossing.

The clay preferably contains pigments such as calcium carbonate, titanium dioxide, amorphous silica, expandable barium sulfate, and satin white. Using calcium carbonate or titanium dioxide as a pigment can increase the smoothness of the clay coating layer's surface. Furthermore, calcium carbonate is preferred because it is inexpensive.

The coating solution for applying the clay-containing smoothing layer contains the above-mentioned clay in a solvent, a binder, and, as necessary, other pigments and additives. The solvent typically used is water, alcohol, or the like. The binder typically used is a latex-based binder (e.g., styrene-butadiene latex, acrylic latex, vinyl acetate latex), or a water-soluble binder (e.g., starch (modified starch, oxidized starch, hydroxyethyl etherified starch, starch phosphate), polyvinyl alcohol, casein, etc.). Additives typically used include pigment dispersants, antifoaming agents, anti-foaming agents, viscosity modifiers, lubricants, water-resistant agents, and water-retaining agents.

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

The thickness of the clay-containing smoothing layer is not particularly limited, but the dry basis weight is preferably ⁵ g/m to 40 g/ ^m , and ^more preferably 10 g/m to 40 g/m ^. By having the dry basis weight within the above range, it is possible to impart appropriate smoothness to the base layer and also to improve adhesion to the base layer.

The smoothing layer made of polyolefin resin may be formed by extrusion coating onto the base layer.

(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.

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

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 ester latex and polyvinylidene chloride latex; and carboxyl-modified versions of these latexes. Water-soluble anchor coating agents 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.

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.

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 preferably 0.1 g/m2 or ^more and 5 g/m2 or ^less when dried, and the thickness after drying is preferably 0.1 μm or more and 5 μm or less.

<<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.

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 one or more resins selected from the group consisting of polypropylene resins, polymethylpentene resins, (meth)acrylic resins, and (meth)acrylic acid ester copolymers. The copolymers may be random copolymers or block copolymers. 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-based resins, and 160°C or higher and 190°C or lower for polymethylpentene-based resins.

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

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

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.

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 and inorganic fillers, plasticizers, stabilizers, and colorants, provided the additives do not impair the objectives of the present disclosure.

The color of the release layer is not particularly limited, and can be any desired color such as red or black using a colorant. If you want to reduce the reflectance over the entire wavelength range of visible light, it is preferable to color the resin layer black.

The colorant may be a pigment or a dye. There are no particular restrictions on the type of pigment, but in order to color the second uneven structure all the way to the tip, it is preferable to use a dye rather than a pigment with a large particle size.

The release layer is formed from a resin composition containing the above-mentioned raw materials. The resin composition used to form the release layer may or may not contain a solvent.

The release layer may consist of a single layer, or two or more layers of the same or different resin types.

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. Having a release layer thickness within the above range improves the dimensional accuracy of the first uneven structure and the second uneven structure. Furthermore, in the process of producing the release sheet and the process of producing the resin molded product, curling of the release sheet can be suppressed and flexibility is improved, resulting in improved workability.

[Method of manufacturing the release sheet]
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 portion.

<Step (1)>
Step (1) is a step of forming a precursor layer, which will be 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 on the entire surface of the precursor layer. The precursor layer may be provided on 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.

In step (1), a master plate is used that has a surface configuration that can transfer the second uneven structure of the release layer of the release sheet. The surface of the master plate has unevenness that is a roughly inverse of the second uneven structure. That is, the master plate has a surface configuration in which recesses of the same shape as the second protrusions are formed at positions corresponding to the second protrusions. The master plate may be made of any material, such as metal, resin, or rubber. The master plate may also be in the form of a roll, cylinder, plate, sheet, or the like.

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.

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 "matte 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.

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 improve shaping properties. The pressure and heating temperature during pressing are set taking into consideration the type of resin used, the hardness during pressing, the thickness of the precursor layer, etc., so that the surface morphology of the master plate is well 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.

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.

The method for applying the resin composition is not particularly limited, and any known method can be used. For example, die coating, extrusion coating, roll coating, reverse roll coating, microbar coating, bar coating, knife coating, gravure coating, etc. can be used.

Once the master plate has been brought into contact with the substrate layer, it is preferable to fix the shape of the precursor layer by a curing method appropriate to the resin components of the resin composition, such as heating and drying, exposure to ionizing radiation such as ultraviolet rays or electron beams, or cooling. When attaching the precursor layer to the substrate layer, an adhesive may be inserted between the precursor layer and the substrate layer, if necessary.

<Step (2)>
Step (2) is a step of forming a first uneven structure by embossing. Step (2) will be described below with reference to Fig. 9. Fig. 9 shows a method for producing a release sheet of the first embodiment exemplified in Fig. 1, but a similar method is also used in a method for producing a release sheet of the second embodiment exemplified in Fig. 2.
In step (2), an embossing master plate is used, which 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. 9A , the surface of the embossing roll 40 is formed with irregularities that are roughly the inverse of the first convex portions and concave portions of the first uneven structure. The embossing roll 40 has concave portions 42 at positions corresponding to the first convex portions of the first uneven structure. Furthermore, the positions corresponding to the concave portions of the first uneven structure are convex portions 41 of the embossing roll. The concave portions 42 have openings that are roughly the same shape as the bottoms of the first convex portions of the first uneven structure, and have side surfaces 44 that have portions that are roughly 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 located 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. By designing the roll in this way, the embossing roll and the precursor layer are separated during pressing, as described below, and the second uneven structure can be left in the areas corresponding to the first convex portions.

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

Next, as shown in Figure 9(b), the sheet 50 is passed between the embossing roll 40 and the back roll (not shown) while being pressed. If the resin for the release layer contains a thermoplastic resin, it is preferable to heat it 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 other factors. The heating temperature in step (2) can be in the range of 90°C or higher and 140°C or lower.

As shown in Figure 9(b) , when the sheet 50 is pressed by the embossing roll 40 in this step, the convex portions 41 of the embossing roll 40 come into contact with the precursor layer 52. At the locations corresponding to the concave portions 42 of the embossing roll 40, the precursor layer 52 enters the concave portions 42. At this time, at the bottoms 43 of the concave portions 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 concave-convex 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 concave-convex structure remains.
Thereafter, when the sheet 50 is peeled 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 regions 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.

As shown in Figure 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 are formed on the first protrusions 14, as shown in Figure 9(b), where the second uneven structure is not formed.

In the release sheet of the present disclosure, the areas that come into contact with the embossing roll (the recesses and side surfaces of the first uneven structure) may have irregularities resulting from the fine irregularities on the surface of the embossing roll. For example, as described above, if the outermost surface of the embossing roll has minute irregularities resulting from plating particles, the recesses and side surfaces of the first uneven structure may have irregularities that are approximately the inverse of the minute irregularities described above.

The pressing pressure in step (2) is set within a range in which the precursor layer can penetrate into the recesses of the embossing roll, but does not contact the bottom of the recesses of the embossing roll. The pressure is set to a value taking into consideration the material of the resin component of the precursor layer (release layer), the material and thickness of the substrate 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 uneven structure tend to become, and the higher the kurtosis (Sku) of the surface of the resulting release layer tends to be. In order to make 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 formation method), the base layer is crushed and its thickness is reduced by pressing in step (1). As a result, the hardness of the sheet itself on which the precursor layer is formed also increases. For this reason, it is preferable that the pressure in step (2) be higher than the pressure in step (1).

In the method for producing a release sheet of the present disclosure, the first uneven structure and the second uneven structure are formed in the order of step (1) and step (2), making 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 sufficient pressure is not applied 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, if the first uneven structure is formed on a sheet that does not have a second uneven structure formed, such as by reversing the order of steps (1) and (2), the sheet is likely to deform. 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.

The design with the aforementioned "gentle diffractive gloss" 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 occur more easily by applying a relatively high pressure during pressing.

[Resin molded product]
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.

The resin molded product according to the present disclosure comprises a support layer and a resin layer on one side of the support layer, the resin layer having, on the surface opposite the support layer, a first uneven structure composed of a plurality of recesses and first protrusions 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 not being formed on the 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 substantially perpendicular to the first direction, and the second uneven structure exhibiting diffractive gloss.

Figure 10 is a cross-sectional schematic diagram showing an example of a resin molded product according to the first aspect. Figure 11 is a cross-sectional schematic diagram showing an example of a resin molded product according to the second aspect. The resin molded product according to the first aspect is manufactured using the release sheet according to the first aspect. The resin molded product according to the second aspect is manufactured using the release sheet according to the second aspect.

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.

Support layers 101, 111 may be selected as appropriate depending on the type and application of the resin molded product, and may include, for example, woven fabric, nonwoven fabric, mesh fabric, paper, resin films such as polyester and polyolefin, metal plates, glass plates, etc. Fibers used for woven and nonwoven fabrics 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. There are no particular limitations on the thickness of support layers 101, 111, as long as they are thick enough to support resin layers 102, 112.

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 resin materials 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 can be set appropriately depending on the intended use of the resin molded product.

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, with the first uneven structure 103 having a structure that is a roughly inverted version of the first uneven structure of the release layer, and the second uneven structure 108 having 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.

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 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, with the first uneven structure 113 having a structure that is a roughly inverted version of the first uneven structure of the release layer, and the second uneven structure 118 having 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.

The first uneven structure 103, 113 has a plurality of recesses 104, 114 and first convex portions 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 convex portions of the release layer of the release sheet. The first convex portions 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 portion 106, 116 and a side portion 107, 117 connecting the bottom portion 106, 116 and the recesses 104, 114. A second uneven structure 108, 118 is formed on the bottom portion 106, 116.

In the resin molded articles of the first and second aspects, it is preferable that the size of each of the first uneven structure and the second uneven structure is approximately the same as the size of the corresponding structure of the release sheet.
For the surface of the resin layer in the resin molded product of the first and second aspects, the value of kurtosis (Sku) specified in ISO 25178-2:2012 is not particularly limited. That is, the surface of the resin layer in the resin molded product may have a kurtosis (Sku) of less than 3 or may be 3 or greater, but is preferably less than 3. In the present disclosure, a resin molded product is produced using a release sheet whose release layer surface has a kurtosis (Sku) of less than 3. Therefore, even if the kurtosis (Sku) of the resin layer surface is 3 or greater, the kurtosis (Sku) does not become too high. As a result, the resin molded product can have a prominent three-dimensional pattern and exhibit diffractive gloss.
In addition, it is preferable that the surface of the resin layer in the resin molded product of the first aspect 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 aspect has a skewness (Ssk) defined in ISO 25178-2:2012 that satisfies Ssk ≦ 0.

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 of 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 of the present disclosure has good visibility of both the pattern and the diffractive gloss, and a noticeable contrast can be seen between areas that exhibit diffractive gloss and areas that do not, resulting in an aesthetically pleasing resin molded product.

[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.

The support layer can be selected appropriately depending on the type and application of the laminate, and can include, for example, woven fabric, nonwoven fabric, mesh fabric, paper, resin films such as polyester and polyolefin, metal plates, glass plates, etc. Fibers used in woven and nonwoven fabrics 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 can be set appropriately depending on the application.

The release sheet and the support layer are preferably bonded via an adhesive layer. Any known adhesive can be used, and the adhesive can be selected depending on the support layer and the base layer of the release sheet.

Next, the present disclosure will be explained in more detail using examples, but the present disclosure is not limited to these examples in any way.

1. Evaluation of Release Sheets 1-1. Appearance Evaluation (1) Evaluation of Pattern Visibility The release layer surfaces of the release sheets of the Examples and Comparative Examples were visually observed, and the visibility of the patterns 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 a three-dimensional effect is felt. 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 confirmed to be present, but is difficult to see and has poor three-dimensional effect. D: The pattern is not visible. (2) Evaluation of Diffraction Gloss The release layer surfaces of the release sheets of the Examples and Comparative Examples were visually observed, and the diffraction gloss was evaluated according to the following criteria.
A: Diffractive gloss (multi-color gloss) is clearly visible when observed from all angles. B: Diffractive gloss is present, but the intensity of the diffractive gloss varies depending on the observation angle. C: Diffractive gloss is difficult to see. D: No diffractive gloss is present. (3) Overall Evaluation The overall evaluation of 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.

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, a 3D image of the surface of the release layer was obtained using an objective lens with a magnification of 50 (image area of 0.06 mm ² ). 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.

1-3. Surface Roughness Parameters For 20 locations on the surface of the above sample, 25 combined images (image area: approximately 26 mm ² ) were acquired using a shape analysis laser microscope (Keyence Corporation, VK-X150) with a 10x objective lens. The acquired images were subjected to a reference plane setting process, followed by Gaussian filter processing. Surface roughness analysis was performed with the cutoff wavelengths set to 5 μm for the S filter and 8 mm for the L filter. 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 parameters 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.

1-4. Gloss Value A4 size (210 mm x 297 mm) samples were cut out from the release sheets of the Examples and Comparative Examples. At this time, markings were made on the samples 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.

2. Preparation of release sheet [preparation of base sheet]
(1) Unformed original fabric 1, original fabric 1
An 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) in this order was formed on high-quality paper (basis weight 125 g/m ² ). The blend resin layer and the 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 heat-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 FIG. 3 Cross-sectional shape of convex portion: Approximately triangular as shown in FIG. 4 Pitch of convex portion: 2 μm
Height of convex portion: 650 nm

(2) Unshaped original fabric 2
An unshaped base roll 2 was prepared, which had a clay layer (thickness 15 μm) and a melamine alkyd resin layer (coating amount 7 g/m ² ) in this order on fine paper (basis weight 164 g/m ² ). The melamine alkyd resin layer was formed by cast coating. During the formation of the melamine alkyd resin layer, the surface of the resin was mirror-finished with a mirror chill roll.

(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.
A second uneven structure identical to that of raw material roll 1 was formed on unshaped raw material roll 3 under the same conditions as raw material roll 1, to obtain raw material roll 3 (shaped raw material roll).

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

[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 (first convex portion is mesh-like, concave portion is scale-like)
Average height of first convex portion (cross-sectional view): 80 μm

[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 portion has a mesh shape)
Average height of first convex portion (cross-sectional view): 80 μm

[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 pattern)
Average height of first convex portion (cross-sectional view): 90 μm

[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. A plurality of first convex portions are formed within the cells. The first convex portions within the cells extend randomly in directions perpendicular, parallel, and oblique to the cell arrangement direction. The width and circumference of the embossing roll are the minimum repeating units.)
Average height of first convex portion (cross-sectional view): 42 μm

[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 hot-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-colored areas correspond to the first convex portions, and the light-colored 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 portion (cross-sectional view): 60 μm

[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 both the major and minor 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 portion (cross-sectional view): 149 μm

[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 approximately 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 portion (cross-sectional view): 117 μm

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

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

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

[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, and a release sheet of Comparative Example 4 was obtained.

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

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

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

[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 convex portions extending in one direction are arranged in a direction substantially perpendicular to the extending direction. A plurality of second convex portions extend in the arrangement direction of the first convex portions and are arranged in the extension 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 are substantially perpendicular to each other.)
Average height of first convex portion (cross-sectional view): 44 μm

[Comparative Example 9]
A release sheet of Comparative Example 9 was obtained in the same manner as in 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 portion (cross-sectional view): 38 μm

[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 a position corresponding to the apex of the first convex portion in the same manner as in Comparative Example 8, to obtain a release sheet of Comparative Example 10.
(First concave-convex structure)
Pattern: A pattern in which a plurality of substantially diamond-shaped first protrusions are periodically arranged in the direction of each symmetry axis. The spaces between the substantially diamond-shaped first protrusions correspond to recesses.
Average height of first convex portion (cross-sectional view): 32 μm

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

3. Results The evaluation results of the release sheets of the Examples and Comparative Examples are shown in Tables 1 and 2.

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

In all of Examples 1 to 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 furthermore, it was felt that the contrast between glossy and non-glossy areas was 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 multicolor gloss was observed. In Comparative Example 11, an excellent multicolor gloss was observed, but no pattern was observed.

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-described 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 deformation due to pressing was more likely to be large compared to the Examples.

The surface of the release layer in Examples 1-4 corresponds to the first aspect, and the surface of the release layer in Examples 5-7 corresponds to the second aspect. In Examples 1-4, the diffractive gloss was particularly clear. In contrast, in Examples 5-7, the gloss seemed to be weaker than in Examples 1-4, but the design had a "gentle diffractive gloss." When the surface of the release layer in Example 6 was observed in detail, the second uneven structure was partially missing or somewhat unclear in the central part of the top of the first convex portion. On the other hand, the second uneven structure could be clearly observed at the edge of the top. In this way, the presence or absence of deformation in the second uneven structure could provide variation in the diffractive gloss.

4. Production of resin molded product [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)
Example 8: Polyurethane (Rezamin NE-8811, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.) 5 parts by mass Colorant (Seika Seven NET-5794 (PM) Black, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.) 1 part by mass Solvent A fabric (wet base, manufactured by Kinki Vinyl Co., Ltd.) was bonded to the resin layer using an adhesive (product name: Rezamin NE-8811, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.). The adhesive was then dried and aged, and the release sheet was peeled off to obtain a resin molded product (synthetic leather) of Example 8.

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

5. Evaluation of Appearance of Resin Molded Articles The resin molded articles of Examples 8 to 14 and Comparative Examples 12 to 22 were visually observed and evaluated for appearance (pattern visibility and diffractive gloss).
In all of Examples 8 to 14, the pattern corresponding to the release sheet was visible. The pattern in Examples 8 to 14 was clear and had a three-dimensional feel. In addition, in Examples 8 to 14, a multicolored glossy feel was felt.
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 gloss was felt, it was weaker than in the Examples, and the contrast of the gloss 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 patterns were 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 gloss, and no gloss contrast was felt.
In the resin molded products of Comparative Examples 12 to 18 produced using the release sheets of Comparative Examples 1 to 7, the patterns corresponding to Examples 8 to 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.

DESCRIPTION OF SYMBOLS 10, 20: Release sheet 11, 21: Base material layer 12, 22, 52: Release layer 13, 23: First uneven layer 14, 24, 54: First convex portion 15, 25, 55: Concave portion 16, 26, 56: Top portion 17, 27, 57: Side portion 18, 28, 38, 58: Second uneven structure 39: Second convex portion 40: Embossing roll 41: Convex portion of embossing roll 42: Concave portion of embossing roll 43: Bottom portion 44: Side portion 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: Concave portion 105, 115: First convex portion 106, 116: Bottom portion 107, 117: Side portion 108, 118: Second uneven structure

Claims (12)

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. The release sheet of claim 1, wherein each of the first protrusions has a side surface connecting the peak and the recess, and the second uneven structure is not formed on the side surface. The release sheet according to claim 1 or claim 2, wherein the surface of the release layer has a skewness (Ssk) of less than 0 as defined in ISO 25178-2:2012. The release sheet according to claim 1 or 2, wherein the surface of the release layer has a skewness (Ssk) of 0 or greater as defined in ISO 25178-2:2012. 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 The release sheet according to any one of claims 1 to 5, wherein the substrate layer comprises a paper substrate. The release sheet according to claim 6, wherein the paper substrate has a thickness of 25 μm or more and 200 μm or less. The release sheet according to claim 6, wherein the paper substrate has a basis weight of 40 g/m ² or more and 400 g/m ² or less. The release sheet according to any one of claims 1 to 8, wherein the release layer contains a thermoplastic resin. The release sheet according to claim 9, wherein the thermoplastic resin comprises one or more selected from the group consisting of polypropylene-based resins, polymethylpentene-based resins, (meth)acrylic resins, and (meth)acrylic acid ester copolymers. The release sheet according to any one of claims 1 to 10, wherein the thickness of the release layer is 5 μm or more and 120 μm or less. 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.