Resin molding mold

Abstract

A resin molding mold (10) for use in molding a resin molded product with an embossing, having the following features: a molding die (12) and a buffer layer (16) formed on an entire surface of a molding surface (12a) of the molding die (12), wherein the buffer layer (16) is formed from a mixture of a thermosetting resin and fine particles (18) having spherical shapes, wherein the fine particles (18) have a relative bulk density in a range of 0.4 g / ml or more to 0.9 g / ml or less, wherein the particle size of the fine particles (18), measured under magnified observations, is randomly set in a range of 1.0 µm or more to 15 µm or less, wherein the fine particles (18) comprise fine particles of urethane or acrylic resin having an elastic property, on a surface of the buffer layer (16), a plurality of gloss adjustment convex portions (20) having spherical shapes derived from the fine particles (18) are formed, some of the plurality of spherically shaped gloss adjustment convex portions (20) being formed by allowing the fine particles (18) to be exposed from the surface of the buffer layer (16), and wherein the buffer layer (16) has a thickness in a range of 1.0 µm or more to 20 µm or less and is larger than the particle size of the fine particles (18).

Description

Field of the invention

[0001] This invention relates to a resin molding mold, and more particularly, to a resin molding mold for molding a resin molded product in which defects in external appearance on the surface thereof on which an embossing is formed are prevented from occurring. Background of the invention

[0002] For example, conventionally, resin-molded products used as interior parts for vehicles, particularly instrument panels, ornaments, etc., arranged around windows, require a high-quality feel, and resin-molded products with reduced gloss to prevent window reflection are in demand. Regarding such resin-molded products, a surface finishing process called embossing is performed on a mold, and by using this mold, these resin-molded products are manufactured. Thus, a very small pattern of concave-convex portions, called embossing, is formed on the surface of each of these resin-molded products.Then, the surface with an embossed pattern formed thereon has a reduced gloss (that is, a reduced gloss value), so that the surface thereof is given fine shadows and a fine touch feeling.

[0003] In order to obtain the above-mentioned embossing, a satin embossing is formed by an etching process, or the inner surface of the forming mold subjected to the embossing process is further roughened by a sandblasting process to perform the gloss value reduction treatment (for example, see Patent Document 1). Prior art documentsPatent document

[0004] Patent Document 1: JPH 11-320627 A Non-patent document

[0005] Non-Patent Document 1: “Analysis of Transfer Irregularity Generation Mechanism on Embossed Surface” (Speech Proceedings of the 23rd Plastic Molding Processing Society, pages 131-132, 2012), written by Hidetoshi Yokoi and Norimichi Masuda

[0006] DE 11 2012 001 024 T5 discloses a mold in which gloss control granules adhere at intervals to a mold surface to form gloss control protrusions. The gloss control granules are added such that a surface of a molded product cast on the mold surface to which the gloss control granules adhere forms a surface with low specular reflection or diffuse reflection. Brief description of the inventionProblems to be solved by the invention

[0007] However, in the case where the inner surface of the molding die subjected to the embossing process is roughened by sandblasting, irregularities sometimes occur in a portion irradiated with glass beads, or the inner surface of the molding die is sometimes brought into a state of deep grooves. For this reason, when the resin molded product is cooled and contracted, scratches (hereinafter referred to as "fretting wear") caused by protrusions on the inner surface of the molding die relative to a drawing direction at the time of drawing a resin molded product from the molding die, or scratches caused by stress or friction applied to the resin molded product, tend to occur, making it difficult to completely reduce gloss in a stable manner on the surface of the resin molded product.

[0008] Furthermore, in recent years, it has been recognized that some resin-molded products with the above-mentioned embossing formed thereon sometimes cause a defective appearance, that is, a so-called "white blur" (or "transfer irregularity"), in which the surface with an embossing appears white blurred when viewed from a relative direction (for example, see Non-Patent Document 1). It is said that this "white blur" is caused, for example, by the fact that the transferred embossing mold is partially tilted, resulting in a higher luminance when irradiated with light from the tilt direction; however, at present, no means for suppressing this "white blur" have been clearly established.

[0009] Therefore, it is an object of the present invention to provide a resin molding mold which, in a resin-molded product having an embossing, improves the texture of the resin-molded product by controlling a gloss appearance and can prevent whitening from occurring on the surface of the resin-molded product having the shaped embossing formed thereon. Facilities to solve the problem

[0010] The present invention provides a resin molding mold according to claim 1.

[0011] The present invention provides a resin molding mold used for molding a resin-molded product with an embossing, and the resin molding mold is provided with a molding die and a buffer layer formed on an entire surface of a molding surface of the molding die, and the buffer layer is formed by a mixture of a thermosetting resin and fine particles having spherical shapes, wherein the fine particles have a relative bulk density in a range of 0.4 g / ml or more to 0.9 g / ml or less, wherein the particle size of the fine particles, measured under magnified observations, is randomly set in a range of 1.0 µm or more to 15 µm or less, wherein the fine particles comprise fine particles of urethane or acrylic resin having an elastic property, wherein a plurality of gloss-adjusting convex portions having spherical shapes are formed on a surface of the buffer layer,which are derived from the fine particles, wherein some of the plurality of spherically shaped gloss adjustment convex portions are formed by allowing the fine particles to be exposed from the surface of the buffer layer, and wherein the buffer layer has a thickness in a range of 1.0 µm or more to 20 µm or less and is larger than the particle size of the fine particles. According to the resin molding mold of the present invention, since gloss adjustment convex portions having substantially spherical shapes are formed on the surface of the buffer layer of the resin molding mold, the molding surface of the molding mold is prevented from having a deep groove state. Therefore, by molding a resin molded product by performing an injection molding process using this resin molding mold, concave portions to be formed on an embossing formation surface of the resin molded product areformed with substantially spherical shapes; therefore, even if the resin molded product contracts at the time of cooling, since it is possible to prevent scratches on the surface of the resin molded product due to stress applied to the resin molded product or friction caused by fretting wear at the time of pulling the resin molded product out of the resin molding die, a resin molded product with a reduced gloss can be obtained, and a resin molded product that can prevent whitening from occurring on the embossing formation surface thereof can also be obtained.

[0012] Moreover, when light is incident on the surface of the resin molded product formed using the resin molding mold, the incident light is reflected by the inner surfaces of the concave portions with substantially spherical shapes of the resin molded product to form diffused light rays that are reflected in numerous directions. Since the incident light is randomly reflected, the reflected light rays reaching the eyes of an observer become fewer. Since a large number of concave portions with substantially spherical shapes of different depths are formed on the surface of the resin molded product, the gloss of the entire resin molded product (gloss value) is lowered.

[0013] In this way, since the surface of the resin molded product molded using the resin molding mold according to the present invention has a glossless surface characteristic, it is not necessary to further apply a coating process to the corresponding resin molded product, and it becomes possible to obtain a desired resin molded product whose texture is improved by reducing gloss.

[0014] In addition, since the concave portions to be formed by an embossing process are not buried, in the case where the particle size of fine particles contained in the buffer layer is set in a range of 1.0 μm or more to 15 μm or less, it is possible to prevent occurrence of fretting wear or the like while maintaining the shape of the embossed pattern of the resin molded product.

[0015] Further, in the case where the thickness of the buffer layer is set in a range of 1.0 μm or more to 20 μm or less and is also larger than the particle size of the fine particles, it is possible to positively ensure the shape of a plurality of gloss adjustment convex portions having substantially spherical shapes derived from the fine particles on the surface of the buffer layer. Effects of the invention

[0016] According to the present invention, it is possible to provide a resin molding mold that can improve the texture of a resin-molded product having an embossing by controlling a gloss appearance, and can prevent the resin-molded product from having whitening on the surface thereof on which the molded embossing is formed.

[0017] These and other objects, features and advantages of the present invention will become apparent upon consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings. Short description of the drawings Fig. 1 is a cross-sectional view showing an example of a resin molding die according to the present invention. Fig. 2 is an enlarged cross-sectional view in which a portion corresponding to a buffer layer of the Fig. 1 shown resin molding mold. Fig. 3 is a cross-sectional view showing a state in which a resin molded product injection-molded using the resin molding mold according to the invention is drawn therefrom. Fig. 4(a) and Fig.4(b) shows an external appearance of a test plate of a resin-molded product used in an experiment; Fig. 4(a) is a front view, and Fig. 4(b) is a side view. Fig. 5 is a schematic view showing a state of an experiment carried out to confirm the presence / absence of occurrence of white smearing in a resin-molded product used in the experiment. Fig. 6 is a cross-sectional view showing a state in which a resin molded product injection-molded using a molding die designed to suppress gloss by irradiating it with balls is pulled out therefrom. Detailed Description of the Invention 1. Resin molding mold

[0018] Fig.1 is a cross-sectional view showing an example of a resin molding die according to the present invention, and Fig. 2 is an enlarged cross-sectional view in which a portion corresponding to a buffer layer of the Fig. 1 shown resin molding mold. Fig. 3 is a cross-sectional view showing a state in which a resin molded product injection-molded using the resin molding mold according to the invention is drawn therefrom.

[0019] A resin molding mold 10 includes a molding mold 12.

[0020] The molding die 12 may be made of a material that can be heated to at least 150°C, and is formed, for example, using a metal material such as iron steel, aluminum, ZAS, or the like, or a synthetic resin material. The molding surface 12a of the molding die 12 is subjected to an embossing process, for example, by etching, resulting in the formation of an embossing convex portion 14a and an embossing concave portion 14b. The maximum height T between the embossing convex portion 14a and the embossing concave portion 14b obtained by the embossing process is preferably set to 10 µm or more. If it is less than 10 µm, a portion of the embossing concave portion 14b is undesirably buried by a buffer layer 16, which will be described later.

[0021] Furthermore, a drawing gradient for use in injection molding is formed in the molding die 12. This drawing gradient is specified with respect to the maximum height T between the embossing-forming convex portion 14a and the embossing-forming concave portion 14b formed by the embossing process, and is set to approximately 1 degree, for example, when the maximum height T between the embossing-forming convex portion 14a and the embossing-forming concave portion 14b is 10 μm.

[0022] The embossing method is a method for forming a concave-convex pattern, such as leather embossing, geometric embossing, satin embossing, or the like. The embossing pattern includes a leather embossing pattern, a skin texture pattern, a wood grain pattern, a satin pattern, a leaf vein pattern, a scale pattern, a marble pattern, a hairline pattern, a geometric pattern, a polishing pattern, a coating pattern, or the like.

[0023] In addition, the embossing process may form a concavo-convex pattern using a method other than etching, and the pattern may be formed, for example, by carving, a machining process, or polishing lines. Furthermore, in the embossing process, a concavo-convex pattern may be partially formed by the molding surface 12a of the molding die 12. In this case, the molding surface 12a of the molding die 12 is formed into a mirror surface without an embossing formed thereon.

[0024] The resin molding mold 10 includes the buffer layer 16 formed on the entire surface of the molding surface 12a of the molding mold 12. In addition, the buffer layer 16 may be formed only on a portion of the molding surface 12a of the molding mold 12.

[0025] The buffer layer 16 includes at least a thermosetting resin and fine particles 18. The buffer layer 16 is preferably formed to have a thickness in a range of 1.0 μm or more to 20 μm or less. Moreover, the thickness of the buffer layer 16 is preferably greater than the particle size of the fine particles 18. Further, the thickness of the buffer layer 16 is at least smaller than the maximum height T between the embossing-forming convex portion 14a and the embossing-forming concave portion 14b formed by the embossing process. When the thickness of the buffer layer 16 is greater than the maximum height T between the embossing-forming convex portion 14a and the embossing-forming concave portion 14b formed by the embossing process, the embossing process is no longer performed on the resin-molded product.This buffer layer 16 may be formed on both the core mold and the hollow mold, or a buffer layer 16 may be formed only on the hollow mold.

[0026] In addition, the thickness of the buffer layer 16 can be measured, for example, by an electromagnetic eddy current film thickness gauge (manufactured by Sanko Electronic Laboratory Co., Ltd., Model No.: SWT-9100).

[0027] Regarding the thermosetting resin to be used for the buffer layer 16, heat resistance, mold release property, adhesiveness to the molding surface 12a of the molding die 12, wear resistance, etc. are necessary. In terms of heat resistance, those that do not melt at a temperature lower than 100°C are preferably used, and the curing temperature of the thermosetting resin is adjusted according to the heat resistance temperature of the molding die 12. For example, in the case where the buffer layer 16 is formed on a molding die 12 made of a material with a low melting point such as aluminum, ZAS, or the like, a thermosetting resin that cures at a temperature range of 100°C or more to 150°C or less is used according to the heat resistance temperature of the molding material.In terms of wear resistance, those that have sufficient wear resistance to the flow of molten substances of the resin at the time of injection molding are preferably used. For example, in the case of a molding process using a synthetic resin, for example, at the time of injection molding, those materials that are resistant to molding processes of 1,000 injections or more are preferably used. This is because, in the molding of resin-molded products, a large number of resin-molded products are molded using the same molding die 12.

[0028] Furthermore, to meet the above requirements for the buffer layer 16, materials having high thermal insulation properties are used as the thermosetting resin to be used for the buffer layer 16. For example, a thermosetting resin with a thermal conductivity in a range of 0.10 W / (mK) or more to 0.99 W / (mK) or less is used as the thermosetting resin to be used for the buffer layer 16.

[0029] As the thermosetting resin to be used for the buffer layer 16, a phenol resin, an alkyd resin, a melamine urea resin, an epoxy resin, a polyurethane resin, a silicone resin, a chloride rubber-based resin, a vinyl acetate resin, an acrylic resin, a vinyl chloride resin, a fluororesin, cellulose, a polystyrene resin, or the like can be used, and either a single substance or a copolymer can be used.

[0030] With regard to the fine particles 18 contained in the buffer layer 16, fine particles made of urethane or acrylic resin with flexibility are used. The fine particles 18 are concentrated near the surface layer of the buffer layer 16. As the fine particles 18, those particles are used that have a low relative density relative to the thermosetting resin contained in the buffer layer 16. The fine particles 18 have a relative bulk density in a range of 0.4 g / ml or more to 0.9 g / ml or less. If the relative bulk density is less than 0.4 g / ml, handling thereof becomes difficult. If the relative bulk density is greater than 0.9 g / ml, it becomes difficult to arrange the fine particles 18 near the surface layer of the buffer layer 16. In addition, the fine particles 18 can have a true relative density in a range of 1.0 g / cm 3 or more up to 1.3 g / cm3 or less. If the true relative density is less than 1.0 g / cm 3 handling becomes difficult. If the true relative density is greater than 1.3 g / cm 3 it becomes difficult to arrange the fine particles 18 near the surface layer of the buffer layer 16.

[0031] Furthermore, the material of the fine particles 18 has higher heat resistance than that of the thermosetting resin used for the buffer layer 16. Furthermore, the material of the fine particles 18 has solvent resistance properties with respect to the thermosetting resin used for the buffer layer 16.

[0032] In this case, the fine particles 18 have a substantially spherical shape, and the particle size thereof is set in a range of 1.0 μm or more to 15 μm or less. This is because the thickness of the buffer layer 16 must be set to 1.0 μm or more. Moreover, the particle size of the fine particles 18 does not need to be uniform but may be random. Further, the fine particles 18 preferably have an elastic property. In addition, since the particle size of the fine particles 18 is smaller than the maximum height T between the embossing-forming convex portion 14a and the embossing-forming concave portion 14b derived from the embossing process, no influences are exerted on the shape of the embossing process performed on the resin-molded product.

[0033] Since the fine particles 18 are concentrated near the surface (upper layer side) of the buffer layer 16, in the case where such fine particles 18 are used, a plurality of gloss adjustment convex portions 20 having substantially spherical shapes derived from the fine particles 18 are formed on the surface of the buffer layer 16, as shown in Fig.2. The protrusion height t1 from the surface of the buffer layer 16 at each of the plurality of gloss adjustment convex portions 20 has a size that differs depending on the respective gloss adjustment convex portions 20. Moreover, some of the plurality of substantially spherically shaped gloss adjustment convex portions 20 can be formed by allowing the fine particles 18 to be exposed from the surface of the buffer layer 16. Further, a flat surface maintaining part 22 is formed on the surface of the buffer layer 16 in a region where no gloss adjustment convex portions 20 are formed. The flat surface maintaining part 22 forms a substantially flat surface on the molded surface of the resin molded product. On the other hand, on the lower layer side of the buffer layer 16, a smaller number of the fine particles 18 is present.

[0034] In addition, the particle size of the fine particles 18 can be measured, for example, using a microscope for magnified observations. 2. Manufacturing process of a resin mold

[0035] The following description discusses a manufacturing method of a resin molding mold according to the present invention.

[0036] First, a molding die 12 subjected to an embossing process is prepared. Through this embossing process, an embossing-forming convex portion 14a and an embossing-forming concave portion 14b are formed on a molding surface 12a of the molding die 12. As a base material of the molding die 12, a material that can be heated to at least 150°C can be used, and for example, a metal material such as iron steel, aluminum, ZAS, or the like, and a synthetic resin material can be used.

[0037] Furthermore, an embossing process for forming a concave-convex pattern, such as leather embossing, geometric embossing, satin embossing, or the like, is optionally performed on the molding surface 12a of the molding die 12. The embossing pattern is selected from the group consisting of a leather embossing pattern, a skin texture pattern, a wood grain pattern, a satin pattern, a leaf vein pattern, a scale pattern, a marble pattern, a hairline pattern, a geometric pattern, a polishing pattern, a coating pattern, or the like.

[0038] Further, the molding surface 12a of the molding mold 12 is degreased and washed to form a buffer layer 16 in a process to be performed later.

[0039] Next, the buffer layer 16 is formed on the molding surface 12a of the molding die 12.

[0040] To form the buffer layer 16, a thermosetting resin and fine particles 18 are first prepared. Then, a mixed solution formed by dispersing the thus prepared thermosetting resin and fine particles 18 in a solvent is prepared.

[0041] With respect to the thermosetting resin to be used for the formation of the buffer layer 16, a phenol resin, an alkyd resin, a melamine urea resin, an epoxy resin, a polyurethane resin, a silicone resin, a chloride rubber-based resin, a vinyl acetate resin, an acrylic resin, a vinyl chloride resin, a fluororesin, cellulose, a polystyrene resin, or the like can be used, and either a single substance or a copolymer can be used.

[0042] As the fine particles 18 to be incorporated into the buffer layer 16, fine particles of urethane or acrylic resin having flexibility can be used. Particles having a low relative density relative to the thermosetting resin contained in the buffer layer 16 are used as the fine particles 18. The fine particles 18 have a relative bulk density in a range of 0.4 g / ml or more to 0.9 g / ml or less. In addition, the fine particles 18 can have a true relative density in a range of 1.0 g / cm 3 or more up to 1.3 g / cm 3 or less. Furthermore, the material of the fine particles 18 has a heat resistance higher than that of the thermosetting resin used for the buffer layer 16. Furthermore, the material of the fine particles 18 has a solvent-resistant property relative to the thermosetting resin used for the buffer layer 16.

[0043] The particle size of the fine particles 18 is set in a range from 1.0 μm or more to 15 μm or less, and those fine particles 18 having a particle size smaller than the maximum height between the embossing-forming convex portion 14a and the embossing-forming concave portion 14b derived from the embossing process and formed on the forming die 12 are selected. Furthermore, the fine particles 18 have a substantially spherical shape, and their particle size does not need to be uniform but may be random. Furthermore, the fine particles 18 preferably have an elastic property.

[0044] As a solvent to be used for forming the buffer layer 16, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, n-butyl acetate, n-butyl alcohol, methyl alcohol, and ethylene glycol monomethyl ether acetate can be used.

[0045] Thereafter, in order to form the buffer layer 16, the thus prepared mixture is applied to the molding surface 12a of the molding mold 12 using, for example, a spraying method to have a thickness in a range of 1.0 µm or more to 20 µm or less.

[0046] The spraying conditions of the mixed solution for forming the buffer layer 16 are set such that, for example, a coating pressure (pneumatic pressure) is 0.25 MPa, the diameter of a spray gun is 0.8 mm, and a coating distance is in a range of 15 cm or more to 40 cm or less. Furthermore, the spraying process is performed in a direction as vertical as possible relative to the mold surface 12a of the molding die 12 to be coated. This arrangement is selected to enable the buffer layer 16 to be uniformly applied to the mold surface 12a of the molding die 12. The location where the coating is performed is, for example, a coating room.

[0047] In addition, the buffer layer 16 may be formed not only on the entire surface of the molding surface 12a of the molding mold 12, but also on a partial portion thereof.

[0048] Thereafter, the molding mold 12 coated with the mixed solution is baked at a baking temperature of 100°C or more to 150°C or less for 2 hours or more to 5 hours or less, so that the buffer layer 16 is formed on the molding surface 12a of the molding mold 12; thus, a resin molding mold 10 is obtained. 3. Resin molded product

[0049] Using this resin molding mold 10, an injection molding process is performed using a heated and melted thermosetting resin. The materials of the thermoplastic resin to be molded using the present resin molding mold 10 include, for example, polypropylene, ABS resin, which is a synthetic copolymer resin of acrylonitrile, butadiene, and styrene, polyvinyl chloride (PVC), and so on. Furthermore, with respect to the thickness of the resin-molded product, which is not specifically limited, molded products with a desired thickness can be manufactured.

[0050] As in Fig.3, a plurality of concave portions 110 having substantially spherical shapes are formed on the surface of the resin molded product 100 molded using the resin molding mold 10. The depths on the inner surface of the plurality of concave portions 110 having substantially spherical shapes differ depending on the concave portions 110 having substantially spherical shapes.

[0051] After forming a resin molded product on which an embossing is formed using a conventional resin molding mold 1, in order to reduce a gloss on the surface of the resin molded product, a molding process was carried out using a resin molding mold 1 having fine concave-convex surfaces 3 formed on the surface of the molding mold by irradiating the molding surface of the molding mold 2 with glass beads, sand, or the like, as shown in Fig.6. In this case, irregularities sometimes occur in a portion irradiated with glass beads, sand, or the like, or the molding surface of the molding die 2 sometimes tends to have deep grooves. In the case where a resin molded product 4 is formed using the molding die 2 having such a surface, scratches tend to be easily caused on the resin molded product 4 due to galling, stress, or friction at the time of pulling the resin molded product 4 out of the molding die 1, and contraction at the time of cooling the resin molded product 4. For this reason, these scratches make it difficult to completely reduce gloss in a stable manner on the surface of the resin molded product 4, and also cause whitening.

[0052] According to the resin molding mold 10, it becomes possible to prevent the occurrence of scratches due to abrasion, stress, or friction on the resin molded product 100 having an embossing at the time of pulling the resin molded product 100 out of the resin molding mold 10, and thus to obtain the resin molded product 100 that can prevent the occurrence of whitening on a surface on which the embossing is formed. That is, as shown in Fig. 3, since gloss adjustment convex portions 20 having substantially spherical shapes are formed on the surface of the buffer layer 16, a deep groove state is hardly caused on the molding surface 12a of the molding die 12.

[0053] Therefore, in the case where a resin molded product 100 is molded by performing an injection molding process using the resin molding mold 10, since the concave portions 110 formed on the embossing formation surface of the resin molded product 100 have substantially spherical shapes, it is possible to prevent occurrence of scratches on the surface of the resin molded product 100 due to stress or friction caused by fretting wear at the time of pulling the resin molded product 100 out of the resin molding mold 10, even if the resin molded product 100 contracts at the time of cooling, and thus to obtain the resin molded product 100 with a reduced gloss; therefore, it becomes possible to obtain the resin molded product 100 that can prevent occurrence of whitening on the embossing formation surface.

[0054] Moreover, when light is incident on the surface of the resin molded product 100 formed using the resin molding mold 10, the incident light is reflected by inner surfaces of the concave portions 110 having substantially spherical shapes of the resin molded product 100 to form diffused light rays reflected in numerous directions. Since the incident light is randomly reflected, reflected light rays reaching the eyes of an observer become fewer. Since a large number of concave portions 110 having substantially spherical shapes with different depths are formed on the surface of the resin molded product 100, the gloss (gloss value) of the entire resin molded product 100 is lowered.

[0055] In this way, since the surface of the resin molded product 100 molded using the resin molding mold 10 according to the present embodiment has a glossless surface characteristic, it is not necessary to further perform a coating process on the corresponding resin molded product, and it becomes possible to obtain a desired resin molded product 100 whose texture is improved by reducing gloss.

[0056] Moreover, according to the resin molding mold 10, since the particle size of the fine particles 18 contained in the buffer layer 16 is set in a range from 1.0 μm or more to 15 μm or less, the embossing forming concave portion 14b to be formed by an embossing process is not buried; therefore, it is possible to prevent generation of fretting wear or the like while maintaining the shape of the embossed pattern of the resin molded product 100.

[0057] Further, according to the resin molding mold 10, since the thickness of the buffer layer 16 is set in a range of 1.0 μm or more to 20 μm or less and is larger than the particle size of the fine particles 18, it is possible to maintain the shape of the plurality of gloss adjustment convex portions having substantially spherical shapes derived from the fine particles 18 on the surface of the buffer layer 16. (Experimental example)

[0058] Experiments were conducted in which a test plate of a resin molding mold in which a buffer layer 16 was formed on a molding mold 12, serving as an example, and a test plate of a resin molding mold in which no buffer layer is formed on the molding mold, serving as a comparative example, were prepared, and the respective test plates of the resin molding molds and the test plates of the resin molded products molded by the resin molding molds were evaluated. The evaluation was conducted by measuring the gloss value of the molding surface of each of the test plates of the resin molding molds and the embossed surface of each of the test plates of the resin molded products. In addition, the evaluation was further conducted by confirming the presence / absence of whitening on the embossed surface of the test plate of the resin molded product. 1. Resin molding mold (practical examples)

[0059] All raw materials of the mold test plates from Practical Example 1 to Practical Example 7 were made of carbon steel for mechanical engineering (S50C). Furthermore, the size of each resin mold test plate from Practical Example 1 to Practical Example 7 was set to 220 mm in the longitudinal direction, 320 mm in the transverse direction, and 10 mm thick.

[0060] Furthermore, in Practical Example 1 to Practical Example 7, embossing processes were carried out for each different pattern using the conventional method. In addition, in Practical Example 1 to Practical Example 7, the maximum height T between embossing formation convex portions and embossing formation concave portions was set to 50 μm or more by the embossing process. A buffer layer was formed on the molding surface of the test plate of each of the molding dies of Practical Example 1 to Practical Example 7. An acrylic resin was used as a resin contained in these buffer layers, and fine urethane particles with a relative bulk density in a range of 0.4 g / ml or more to 0.9 g / ml or less were used as the fine particles. In addition, the particle size of the fine particles was set in a range of 1.0 μm or more to 12 μm or less.Further, the thickness of the buffer layer formed on the molding surface of the test plate of each of the molding dies of Practical Example 1 to Practical Example 7 was set in a range of 1.0 μm or more to 20 μm or less.

[0061] In Practical Example 1 to Practical Example 7, spraying conditions of the mixed solution for forming the buffer layer were set as follows. • Coating pressure (pneumatic pressure): 0.25 MPa • Diameter of a spray gun: 0.8 mm • Coating distance: 30 mm or more to 40 mm or less • Coating direction: as vertical as possible to a mold surface of a mold • Coating location: Coating room • Coating thickness: 18 µm (Comparison example)

[0062] A test plate of a molding die according to Comparative Example 1 is subjected to a series of embossing processes including surface treatment by sandblasting and glass beads in the same manner as the embossing processes performed on the molding die of Practical Example 1, and also corresponds to a test plate on which no buffer layer is formed. In the following description, test plates of molding dies according to Comparative Example 2 to Comparative Example 7 are subjected to a series of embossing processes including surface treatment by sandblasting and glass beads in the same manner as the embossing processes performed on Practical Example 2 to Practical Example 7, respectively, and also correspond to test plates on which no buffer layer is formed.Furthermore, all raw materials of molds from Comparative Example 1 to Comparative Example 7 were made of carbon steel for mechanical engineering (S50C). The size of each test plate from Comparative Example 1 to Comparative Example 7 was also set to the same size as the test plates from Practical Example 1 to Practical Example 7. 2. Resin molded product

[0063] Fig. 4 shows an external appearance of a test plate of a resin molded product used for experiments, and Fig. 4(a) is a front view, and Fig. 4(b) is a side view.

[0064] Injection molding processes for molding resin-molded products of Practical Example 1 to Practical Example 7 and Comparative Example 1 to Comparative Example 7 were performed using a conventional injection molding method. Furthermore, polypropylene (PP) was used as the material for all resin-molded products of Practical Example 1 to Practical Example 7 and Comparative Example 1 to Comparative Example 7. Furthermore, the size of the resin-molded products of Practical Example 1 to Practical Example 7 and Comparative Example 1 to Comparative Example 7 was set to 200 mm in the longitudinal direction, 300 mm in the transverse direction, and approximately 3 mm in thickness. (measurement method)

[0065] The gloss value (gloss level of Gs (60°)) of the mold surface 12a of the test plate of the molding mold 12 was measured using a gloss meter manufactured by KONIKA MINOLTA, Inc. (trade name: UNI GLOSS GM-60). Gs (60°) refers to a mirror surface gloss (degree) at a measurement angle of 60°.

[0066] The mirror surface gloss level was measured by the following method according to a measurement method specified by JIS Z8741-1997 "Mirror Surface Gloss Degree-Measuring Method." That is, using a mirror surface gloss level meter in accordance with the above-mentioned standard, the surface reflectance was measured under a condition of an incident angle of 60°. Next, the measured value was converted to a percentage value when the gloss level on the reference surface is defined as 100 and represented as the mirror surface gloss level.With reference to the reference surface, a black glass reference surface was used in which a refractive index was set to a constant value of 1.567 over the entire visible wavelength range as specified by the above-mentioned standard, and when the angle of incidence = 60°, a mirror surface reflectance of 10% was defined as a gloss level of 100. By using the gloss meter manufactured by KONIKA MINOLTA Inc. (trade name: UNI GLOSS GM-60), which is equivalent to a mirror surface gloss meter that, when measurements are taken, automatically performs the above-mentioned conversion and outputs a mirror surface gloss level, the respective sections of the test plate surface were measured at N = 5 under the condition of an angle of incidence = 60°, and the average value was defined as the mirror surface gloss level of each of the test plate surfaces.In addition, when the gloss value (gloss level) becomes lower, the corresponding condition represents a reduced gloss condition.

[0067] The gloss value (gloss level of Gs (60°)) of the surface of the test plate relating to a resin molded product was measured using the same method as the measurement method of the gloss value of the mold surface of the test plate of the molding mold, and measurements were carried out using the gloss meter manufactured by KONIKA MINOLTA, Inc. (trade name: UNI GLOSS GM-60) in accordance with JIS Z 8741.

[0068] Table 1 shows evaluation results from Practical Example 1 to Practical Example 7. In addition, Table 2 shows evaluation results from Comparative Example 1 to Comparative Example 7. [Table 1] Mold surface with embossing of a mold Embossing surface of a resin molded product Average value (N = 5) of a gloss value Average value (N = 5) of a gloss value Practical example 1 1,4 1,6 Practical example 2 1,5 1,4 Practical example 3 1,4 2,0 Practical example 4 1,7 1,9 Practical example 5 1,2 1,6 Practical example 6 1,5 1,6 Practical example 7 1,4 1,4 [Table 2] Mold surface with embossing of a mold Embossing surface of a resin molded product Average value (N = 5) of a gloss value Average value (N = 5) of a gloss value Comparison example 1 5,0 2,6 Comparison example 2 8,7 2,3 Comparison example 3 6,0 3,3 Comparison example 4 11,0 4,3 Comparison example 5 6,1 2,6 Comparison example 6 10,3 4,1 Comparison example 7 8,0 3,2

[0069] When considering the average value of gloss values on the mold surface with embossing of the molding die, it is in a range of 1.4 to 1.7 in Practical Example 1 to Practical Example 7 and is in a range of 5.0 to 11.0 in Comparative Example 1 to Comparative Example 7; therefore, it is confirmed that the gloss is greatly lowered by forming a buffer layer on the mold surface of the molding die.

[0070] Furthermore, when considering the average value of gloss values on the embossing formation surface of a resin-molded product, it is in a range of 1.4 to 2.0 in Practical Example 1 to Practical Example 7 and in a range of 2.3 to 4.3 in Comparative Example 1 to Comparative Example 7; therefore, it is confirmed that in the case of a resin-molded product injection-molded using a resin molding die having a buffer layer formed on the molding surface of the die, the gloss is greatly lowered.

[0071] Next, the presence / absence of white smearing on the embossing formation surface of the test plate of a resin-molded product was confirmed.

[0072] Confirmation of the presence / absence of white smearing was performed by photographing each of the test plates of resin-molded products with a camera under predetermined conditions, and the resulting images were visually confirmed. The photography process of the embossed formation surface of the test plates of the resin-molded products was carried out under conditions specified in Fig. 5 are shown. Fig.5 is a schematic view showing a state of an experiment conducted to confirm the presence / absence of white smearing on the resin-molded product used for the experiment. That is, first, a test plate 200 was tilted 30° from the reference surface. Then, the test plate 200 was photographed by a camera C in a direction parallel to the reference surface with sunlight L directed onto the surface for use in measuring the gloss value of the test plate 200.

[0073] As a result of confirming the presence / absence of white smearing on any of the embossed formation surfaces of the test sheets of resin-molded products from Practical Example 1 to Practical Example 7, no white smearing occurred. On the other hand, on any of the embossed formation surfaces of the test sheets of resin-molded products from Comparative Example 1 to Comparative Example 7, it was confirmed that white smearing occurred in broad areas.

[0074] Based on the above-mentioned evaluation results, it is confirmed that by allowing the buffer layer formed on the molding surface of the molding die to contain fine particles having a relative bulk density in a range of 0.4 g / ml or more to 0.9 g / ml or less, and by forming a plurality of convex portions having substantially spherical shapes derived from the fine particles on the surface of the buffer layer, a resin molded product in which a gloss on the embossing formation surface of the resin molded product is lowered and the occurrence of whitening is prevented can be obtained. List of reference symbols 10 Resin molding mold 12 Forming mold 12a mold surface 14a Embossing formation convex section 14b Imprint formation concave section 16 Buffer layer 18 fine particles 20 Gloss adjustment convex section 22 Flat surface retention part 100 resin molded product 110 Concave section T Maximum height between embossing convex section and embossing concave section t1 protrusion height of surface of buffer layer 16 on gloss adjustment convex section L Sunlight C Camera

Claims

[1] A resin molding mold (10) for use in molding a resin molded product with an embossing, having the following features: a molding die (12) and a buffer layer (16) formed on an entire surface of a molding surface (12a) of the molding die (12), wherein the buffer layer (16) is formed from a mixture of a thermosetting resin and fine particles (18) having spherical shapes, wherein the fine particles (18) have a relative bulk density in a range of 0.4 g / ml or more to 0.9 g / ml or less, wherein the particle size of the fine particles (18), measured under magnified observations, is randomly set in a range of 1.0 µm or more to 15 µm or less, wherein the fine particles (18) comprise fine particles of urethane or acrylic resin having an elastic property, on a surface of the buffer layer (16), a plurality of gloss adjustment convex portions (20) having spherical shapes derived from the fine particles (18) are formed, some of the plurality of spherically shaped gloss adjustment convex portions (20) being formed by allowing the fine particles (18) to be exposed from the surface of the buffer layer (16), and wherein the buffer layer (16) has a thickness in a range of 1.0 µm or more to 20 µm or less and is larger than the particle size of the fine particles (18).

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