Coating film and mold

Abstract

To provide a coating film with high hardness and excellent release properties. [Solution] The coating film of the present disclosure contains polyimide and secondary particles of fluororesin, wherein the secondary particles of fluororesin are aggregates of two or more primary particles of fluororesin, and the average primary particle size of the primary particles is 0.25 μm or more and 1.00 μm or less.

Description

Technical Field

[0001] The present disclosure relates to a coating film and a mold.

Background Art

[0002] When molding a polymer material using a mold for rubber molding, a mold for resin molding, etc., a releasability between the material to be pressure-bonded such as rubber or resin to be molded and the mold is required. Therefore, in order to prevent the material to be pressure-bonded from adhering to the mold when performing mold molding, a resin-made release sheet is disposed between the mold and the material to be pressure-bonded. In the prior art, for the purpose of preventing the material to be pressure-bonded from adhering to the mold and reducing molding defects of a resin sheet (resin sheet contained in the material to be pressure-bonded) caused by gas generated from the material to be pressure-bonded, a heat-resistant release sheet having a base material layer, a porous resin layer, and a release layer has been proposed (see Patent Document 1). In this heat-resistant release sheet, the base material layer contains a metal and a resin having a melting temperature of 280°C or higher, the porous resin layer contains a resin selected from a polyimide resin, a polyamideimide resin, and a fluororesin, and the release layer contains a fluororesin.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The coating film of the present disclosure contains polyimide and secondary particles of a fluororesin, the secondary particles of the fluororesin are aggregates of two or more primary particles of the fluororesin, and the average primary particle diameter of the primary particles is 0.25 μm or more and 1.00 μm or less.

Brief Description of the Drawings

[0005] [Figure 1] FIG. 1 is a schematic partial cross-sectional view of a mold according to an embodiment of the present disclosure. [Modes for carrying out the invention]

[0006] [Issues this disclosure aims to address] Conventional heat-resistant release sheets possess both release properties and heat resistance, but the fluororesin release layer that comes into contact with the object being pressed is relatively soft, making it susceptible to damage from contact. Furthermore, conventional heat-resistant release sheets have a laminated structure, which increases the manufacturing process.

[0007] This disclosure aims to provide a coating film with high hardness and excellent mold release properties.

[0008] [Effects of this disclosure] The coating film of this disclosure has high hardness and excellent mold release properties.

[0009] [Description of Embodiments in this Disclosure] First, the embodiments of this disclosure will be listed and described.

[0010] (1) The coating film of the present disclosure contains polyimide and secondary particles of fluororesin, wherein the secondary particles of fluororesin are aggregates of two or more primary particles of fluororesin, and the average primary particle size of the primary particles is 0.25 μm or more and 1.00 μm or less.

[0011] The coating film contains polyimide and secondary particles of fluororesin, which improves the hardness and release properties of the coating film. Therefore, the scratch resistance of the coating film is improved, it has excellent durability, and when used as a coating film for molds, it allows for good peeling of the molded rubber, resin, etc. Furthermore, because the coating film is a single layer, manufacturing efficiency can be increased. In addition, the average primary particle size of the primary particles is between 0.25 μm and 1.00 μm, which improves the release properties of the coating film and maintains good hardness. Thus, the coating film has high hardness and excellent release properties.

[0012] The above "average particle size" refers to the median diameter (D50), which is the value at which the volume-based cumulative distribution calculated in accordance with JIS-Z-8819-2:2001 reaches 50%. Specifically, the median diameter (D50) can be measured by the following method: A laser diffraction particle size distribution analyzer is used as the measuring device. A scattering measurement mode is adopted, and laser light is irradiated onto a wet cell through which a dispersion liquid in which the particles of the sample to be measured are dispersed in a dispersion solvent circulates, and the scattered light distribution is obtained from the sample to be measured. The scattered light distribution is then approximated by a log-normal distribution, and the particle size corresponding to the cumulative degree of 50% (D50) is taken as the median diameter. "Primary particles" refer to particles that do not have grain boundaries visible when observed using a scanning electron microscope (SEM) or the like. "Secondary particles" refer to particles formed by the aggregation of multiple primary particles. In other words, secondary particles are aggregates of primary particles. The fact that the secondary particles of the fluororesin described above are aggregates of two or more primary particles of the fluororesin can be confirmed by scanning electron microscopy.

[0013] (2) In (1) above, the fluororesin may be polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, or tetrafluoroethylene-hexafluoropropylene copolymer. By using polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), or tetrafluoroethylene-hexafluoropropylene copolymer (FEP) as the fluororesin, the hardness can be improved while maintaining good release properties of the coating film.

[0014] (3) In (1) or (2) above, the coating film may further contain metal oxide particles, and the average particle size of the metal oxide particles may be 0.10 μm or more and 0.60 μm or less. By further containing metal oxide particles and having an average particle size of the metal oxide particles within the above range, the hardness can be maintained while improving the release properties of the coating film, even if the content of secondary particles of the fluororesin is increased.

[0015] (4) In (3) above, the metal oxide particles may be alumina, silica, or titanium oxide. The hardness of the coating film can be further improved by using alumina, silica, or titanium oxide as the metal oxide particles.

[0016] (5) In any of (1) to (4) above, the content of secondary particles of the fluororesin in the coating film may be 0.01% by volume or more and 5.0% by volume or less. When the content of secondary particles of the fluororesin in the coating film is 0.01% by volume or more and 5.0% by volume or less, the surface properties of the coating film are improved and the release properties can be further improved.

[0017] (6) In (3) or (4) above, the content of the metal oxide particles may be 1.0 volume% or more and 3.0 volume% or less. The heat resistance of the coating film can be further improved by having the content of the metal oxide particles in the coating film be 1.0 volume% or more and 3.0 volume% or less.

[0018] (7) In addition, coating films of other embodiments of the present disclosure contain polyimide and molybdenum disulfide, wherein the molybdenum disulfide content is 1% by volume or more and 20% by volume or less.

[0019] The coating film contains polyimide and molybdenum disulfide, which improves its hardness and release properties. Therefore, the coating film has improved scratch resistance and excellent durability, and when used as a coating for molds, it allows for easy removal of the molded rubber, resin, etc. Furthermore, because the coating film is a single layer, manufacturing efficiency can be increased. Additionally, by ensuring the molybdenum disulfide content in the coating film is within the specified range, the surface properties of the coating film are improved, further enhancing its hardness and release properties. Consequently, the coating film exhibits high hardness and excellent release properties.

[0020] (8) Further, the mold of the present disclosure includes a substrate and the coating film according to any one of (1) to (7) described above laminated on at least a part of the surface of the substrate. Since the mold includes the substrate and the coating film, it has excellent durability and good peelability of rubber, resin, etc. to be molded.

[0021] [Details of Embodiments of the Present Disclosure] Hereinafter, the coating film and the mold according to the embodiments of the present disclosure will be described in detail with reference to the drawings.

[0022] <Coating Film> [First Embodiment] The coating film of the first embodiment of the present disclosure contains polyimide and secondary particles of a fluororesin. Since the coating film has high hardness and excellent releasability, it can be suitably used as a coating film for coating a mold for molding a polymer material.

[0023] (Polyimide) By containing polyimide in the coating film, the hardness in the coating film can be increased and the scratch resistance can be improved.

[0024] The lower limit of the content of polyimide in the coating film of the first embodiment may be 90.00% by volume, may be 92.00% by volume, or may be 93.00% by volume. When the content of the polyimide is at least 90.00% by volume, the coating film can obtain sufficient hardness. On the other hand, the upper limit of the content of polyimide in the coating film may be 99.99% by volume, may be 99.95% by volume, or may be 99.90% by volume. When the content of the polyimide is 99.99% by volume or less, the content of the secondary particles of the fluororesin can be sufficient, and the coating film can obtain sufficient releasability.

[0025] (Secondary Particles of Fluororesin) The coating film contains secondary particles of fluororesin. These secondary particles are aggregates of two or more primary particles of fluororesin. The inclusion of these secondary particles improves the hardness of the coating film. The fluororesin may be polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkoxyethylene copolymer, or tetrafluoroethylene-hexafluoropropylene copolymer. Among these, polytetrafluoroethylene may be preferred for its ability to further enhance the hardness of the coating film.

[0026] The lower limit of the average primary particle size of the fluororesin is 0.25 μm, but it may also be 0.30 μm or 0.35 μm. Having an average primary particle size of 0.25 μm or more improves the surface properties of the coating film and further enhances its release properties. On the other hand, the upper limit of the average primary particle size of the fluororesin is 1.00 μm, but it may also be 0.70 μm or 0.60 μm. Having an average primary particle size of 1.00 μm or less maintains good hardness of the coating film.

[0027] The lower limit of the content of secondary fluororesin particles in the coating film may be 0.01% by volume, 0.05% by volume, 0.10% by volume, or 0.50% by volume. A content of 0.01% by volume or more of secondary fluororesin particles reduces the surface free energy of the coating film, further improving its release properties. On the other hand, the upper limit of the content of secondary fluororesin particles may be 5.0% by volume or 3% by volume. A content of 5.0% by volume or less of secondary fluororesin particles improves the surface properties of the coating film, further improving its release properties.

[0028] (metal oxide particles) The coating film may further contain metal oxide particles. The inclusion of metal oxide particles in the coating film can improve its heat resistance. Examples of metal oxide particles include alumina, silica, titanium oxide, and magnesium oxide.

[0029] The lower limit of the average particle size of the metal oxide particles may be 0.10 μm or 0.15 μm. A particle size of 0.10 μm or more allows for further improvement of the hardness of the coating film. On the other hand, the upper limit of the average particle size of the metal oxide particles may be 0.60 μm or 0.55 μm. A particle size of 0.60 μm or less allows for sufficient maintenance of the number of metal oxide particles, thereby further improving the hardness of the coating film. Therefore, by keeping the average particle size of the metal oxide particles within the above range, even if the content of secondary particles of fluororesin is increased, the hardness of the coating film can be maintained well while improving its release properties.

[0030] The lower limit of the content of metal oxide particles in the coating film may be 1.0 volume% or 1.5 volume%. A content of 1.0 volume% or more of metal oxide particles improves the heat resistance of the coating film. On the other hand, the upper limit of the content of metal oxide particles may be 3.0 volume% or 2.5 volume%. A content of 3.0 volume% or less of metal oxide particles improves the surface properties of the coating film, further enhancing its hardness and release properties.

[0031] The coating film may contain other additive components besides those mentioned above, as needed. Examples of additives include anti-settling agents, dispersants, defoaming agents, coloring pigments, antioxidants, UV absorbers, antistatic agents, surfactants, leveling agents, and rheology control agents.

[0032] [Second Embodiment] The coating film of the second embodiment of this disclosure contains polyimide and molybdenum disulfide. The configuration of the coating film according to the second embodiment is the same as that of the coating film according to the first embodiment, except for the fluororesin secondary particles and metal oxide particles of the coating film according to the first embodiment, so the description of the overlapping components will be omitted.

[0033] The lower limit of the polyimide content in the coating film of the second embodiment may be 79.5% by volume, 80.0% by volume, 82.0% by volume, or 83.0% by volume. A polyimide content of 79.5% by volume or more allows the coating film to achieve sufficient hardness. On the other hand, the upper limit of the polyimide content in the coating film may be 99.0% by volume, 98.0% by volume, or 97.0% by volume. A polyimide content of 99.0% by volume or less allows for a sufficient molybdenum disulfide content, improving the hardness and release properties of the coating film.

[0034] (Molybdenum disulfide) The coating film of the second embodiment contains molybdenum disulfide.

[0035] The shape of molybdenum disulfide is not particularly limited, but it may be in the form of flakes. The inclusion of flake-shaped molybdenum disulfide in the coating film can improve the hardness and release properties of the coating film. "Flake-shaped" refers to shapes that also include thin flakes and plates.

[0036] The lower limit of the average particle size of the molybdenum disulfide mentioned above may be 0.20 μm or 0.30 μm. Having an average particle size of 0.20 μm or more improves the hardness and release properties of the coating film. On the other hand, the upper limit of the average particle size of the molybdenum disulfide may be 2.20 μm, 1.00 μm, 0.80 μm, or 0.60 μm. Having an average particle size of 2.20 μm or less improves the surface properties of the coating film, further enhancing its hardness and release properties.

[0037] The lower limit of the molybdenum disulfide content in the coating film may be 1 volume% or 3 volume%. A molybdenum disulfide content of 1 volume% or more improves the surface properties of the coating film, further enhancing its hardness and release properties. On the other hand, the upper limit of the molybdenum disulfide content may be 20 volume% or 15 volume%. A molybdenum disulfide content of 20 volume% or less improves the surface properties of the coating film, further enhancing its hardness and release properties.

[0038] This coating film exhibits high hardness and excellent release properties.

[0039] <Mold> [First Embodiment] A mold according to the first embodiment of this disclosure comprises a substrate and a coating film laminated on at least a portion of the surface of the substrate. In the mold according to the first embodiment, the coating film is the coating film according to the first embodiment described above. Specifically, the coating film contains polyimide and secondary particles of fluororesin.

[0040] Figure 1 is a schematic partial cross-sectional view showing a mold 1 according to one embodiment of the present disclosure. The mold 1 comprises a substrate 2 and a coating film 3 laminated on at least a portion of the surface of the substrate 2.

[0041] [Base] The main component of substrate 2 is not particularly limited and includes, for example, metals, super engineering plastics, ceramics, and carbon materials. Examples of metals include iron alloys such as stainless steel, nickel, aluminum, aluminum alloys, copper, and copper alloys. Among these, stainless steel or nickel may be used because they have excellent malleability and heat resistance. The metals may be used individually or in combination of two or more. Examples of super engineering plastics include polyimide, polyamide-imide, polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, liquid crystal polymer, polysulfone, and polyethersulfone. Examples of ceramics include alumina, aluminum nitride, silicon nitride, boron nitride, silicon carbide, zirconia, cordierite, sialon, steatite, sapphire, and cermet. Examples of carbon materials include diamond, graphite, C / C composite, and C / SiC composite. The term "main component" refers to the component with the highest mass content, for example, a component with a content of 60% by mass or more.

[0042] The shape of the base 2 is not particularly limited and can be changed as appropriate depending on the application. For example, it is not limited to plate-shaped, cylindrical, conical, elliptical conical, pyramidal, gourd-shaped, elliptical prism-shaped, or prismatic shape, and various mold shapes such as rotors can be adopted.

[0043] The average thickness of the base 2 is not particularly limited and can be changed as appropriate depending on the application. Furthermore, the sliding surface of the base 2 does not need to be flat; it may have patterns such as grooves or dimples (indentations) formed on its surface. The base 2 may also have through holes.

[0044] [Coating film] The coating film 3 according to the first embodiment does not need to be laminated over the entire surface of the substrate 2, but only needs to be laminated over at least a portion of the surface of the substrate 2, that is, at least the surface of the substrate that is in contact with the object to be pressed. The coating film 3 contains polyimide and secondary particles of fluororesin. Because the coating film 3 contains polyimide and secondary particles of fluororesin, it has high hardness and excellent release properties.

[0045] The lower limit of the average thickness of the coating film 3 may be 5 μm or 10 μm. On the other hand, the upper limit of the average thickness may be 70.0 μm or 50.0 μm. Having an average thickness of 5 μm or more and 70.0 μm or less allows for good durability and elasticity.

[0046] The coating film 3 may be a coating layer or formed from a film. Forming the coating film 3 from a coating layer or a film makes it easier to control the surface roughness of the coating film 3 and the accuracy of the average thickness of the coating film 3.

[0047] The coating film 3 according to the first embodiment may further contain metal oxide particles. By further containing metal oxide particles in the coating film 3, the heat resistance of the coating film 3 can be improved.

[0048] Details of the metal oxide particles are as described above for the metal oxide particles in the coating film according to the first embodiment.

[0049] The coating film 3 may contain other additive components besides those mentioned above, as needed. Examples of additives include anti-settling agents, dispersants, defoaming agents, coloring pigments, antioxidants, UV absorbers, antistatic agents, surfactants, leveling agents, and rheology control agents.

[0050] [Second Embodiment] The mold according to the second embodiment of this disclosure comprises a substrate and a coating film laminated on at least a portion of the surface of the substrate. In the mold according to the second embodiment, the coating film is the coating film according to the second embodiment described above. The configuration of the mold according to the second embodiment is the same as that of the mold according to the first embodiment, except for the coating film, so the configuration other than the coating film will not be described. Specifically, the coating film contains polyimide and molybdenum disulfide. The mold according to the second embodiment also has the coating film of the second embodiment, so it has high hardness and excellent release properties.

[0051] In the second embodiment, the lower limit of the average thickness of the mold coating film may be 5 μm or 10 μm. On the other hand, the upper limit of the average thickness may be 70.0 μm or 50.0 μm. Having an average thickness of 5 μm or more and 70.0 μm or less allows for good durability and elasticity.

[0052] The average particle size range for the molybdenum disulfide described above is as stated above.

[0053] [Mold manufacturing method] A manufacturing method according to one embodiment of the mold comprises a step of laminating coating layers formed from a coating film composition.

[0054] (Lamination process) In this process, a coating layer formed from a coating film composition containing a polyimide precursor and secondary particles of fluororesin is laminated onto at least a portion of the surface of a substrate. The coating film composition may contain a solvent.

[0055] As the solvent, individual amide solvents such as N-methylpyrrolidone, 2-pyrrolidone, dimethylacetamide, N,N-dimethylformamide, and N,N-diethylformamide can be used, or mixtures of the above amide solvents with other solvents such as water, alcohols, ketones, ethers, esters, amines, or combinations thereof can be used. The coating film composition can be prepared by preparing the above-mentioned predetermined amounts of each component contained in the coating film, using an appropriate organic solvent as the solvent, and uniformly stirring and mixing it using mechanical force.

[0056] The lower limit of the solid content concentration of the coating film composition may be 5% by mass, 25% by mass, or 40% by mass. On the other hand, the upper limit of the solid content concentration of the coating film composition may be 60% by mass, 50% by mass, or 45% by mass. By setting the solid content concentration of the coating film composition within the above ranges, the applicability can be improved, and as a result, a coating film with fewer coating defects can be easily and reliably formed.

[0057] Polyimide precursors refer to resins that are converted to polyimide through heat treatment or chemical treatment with acids or bases. Polyimide precursors are reaction products obtained by the polymerization condensation reaction of aromatic tetracarboxylic dianhydrides and aromatic diamines. Polyimide precursors are also known as polyamic acids. Polyimide precursors form cyclic imides through polymerization condensation reactions.

[0058] Known methods can be used for the polymerization condensation reaction described above. A specific method for this polymerization condensation reaction is, for example, mixing an aromatic tetracarboxylic dianhydride and an aromatic diamine in a solvent consisting of an organic solvent. This method allows the aromatic tetracarboxylic dianhydride and the aromatic diamine to polymerize, yielding a solution in which the polyimide precursor is dissolved in the solvent. Furthermore, the degree of polymerization (weight-average molecular weight) can be controlled by carrying out the polymerization condensation reaction in the presence of a reaction control agent.

[0059] The lower limit of the polyimide precursor content in the coating film composition may be 10% by mass or 20% by mass. The upper limit of the above content may be 50% by mass or 40% by mass. By setting the above content to be above the lower limit, the amount of coating film composition required throughout the entire manufacturing process to obtain a coating film of the desired thickness when forming the coating film using the coating film composition can be reduced, and the number of steps for applying and heating the coating film composition can be reduced. By setting the polyimide precursor content to be below the above upper limit, the viscosity of the coating film composition can be appropriately adjusted while maintaining good properties of the coating film, thereby improving the coatability.

[0060] Examples of the lamination methods include dipping paint, electrostatic painting, air spray painting, inkjet painting, dispenser painting, electrodeposition painting, screen printing, spin coating, die coating, roll coating, wire bar coating, blade coating, gravure coating, and thermocompression bonding of a film containing the coating composition to the substrate.

[0061] Examples of the above-mentioned coatings include coatings obtained by dispersing or dissolving a coating film composition in a solvent. In the above-mentioned lamination process, the coating is applied to at least a portion of the surface of the substrate. The solvent used is the same as the solvent used for the coating film composition described above.

[0062] When the above film is heat-pressed onto the substrate, the upper limit of the pressing pressure may be 100 MPa, 80 MPa, or 50 MPa. A pressure of 100 MPa or less prevents damage to the substrate or the pressing jig. On the other hand, the lower limit of the pressure may be 10 kPa or 20 kPa. A pressure of 10 MPa or more ensures good adhesion between the film and the substrate.

[0063] When the above film is heat-pressed onto a substrate, the heating and pressing time can be, for example, 5 minutes to 2 hours. Furthermore, by using a high-frequency welding machine and applying high-frequency heat while pressing, the pressing time can be shortened.

[0064] After performing electrostatic coating, dipping coating, air spray coating, inkjet coating, dispenser coating, electrodeposition coating, screen printing, spin coating, die coating, roll coating, wire bar coating, blade coating, gravure coating, or heat-compression bonding of film, the substrate is placed in a heating furnace and heated to bake the laminated film. This heating allows the solvent in the coating to evaporate. The heating temperature when baking the laminated film can be, for example, 350°C to 450°C. The heating time when baking the laminated film can be, for example, 10 minutes to 60 minutes. By setting the heating temperature and heating time within the above range, a film with excellent density can be formed while reducing the decomposition of polyimide. After that, the film is cooled to laminate the coating film onto the surface of the substrate.

[0065] According to this mold, since it comprises a base body and the aforementioned coating film, it offers excellent durability and good peelability of the molded rubber, resin, etc.

[0066] [Other embodiments] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is not limited to the configurations of the embodiments described above, but is indicated by the claims, and all modifications within the meaning and scope equivalent to the claims are intended to be included.

[0067] In the above embodiment, the coating film was directly laminated on the surface of the substrate, but an intermediate layer may be provided between the substrate and the coating film. [Examples]

[0068] The present disclosure will be further described below with reference to examples, but the present disclosure is not limited to the following examples.

[0069] <Coating film No.3 to No.11> A coating film composition was prepared by adding PTFE particles and alumina particles to a polyimide precursor solution, stirring with a magnetic stirrer, and dispersing the composition in an organic solvent. Next, the coating was applied to an aluminum plate with an average thickness of 3 mm, which served as the substrate, using the bar coating method. After drying the solvent at 100°C for 10 minutes, the coating film containing polyimide was obtained by baking at 380°C for 20 minutes. The average thickness of the coating film was 30 μm. Table 1 shows the content of each component in coating films No. 3 to No. 11.

[0070] <Coating film No. 1> Coating film No. 1 was obtained in the same manner as coating film No. 3, except that PTFE particles and alumina particles were not added to the polyimide precursor solution. The component content in coating film No. 1 is shown in Table 1.

[0071] <Coating film No. 2> Coating film No. 2 was obtained in the same manner as coating film No. 3, except that PTFE particles were dispersed in pure water as the solvent to prepare the coating. The component content in coating film No. 2 is shown in Table 1.

[0072] <Coating film No. 12~No. 16> Coating films No. 12 to No. 16 were obtained in the same manner as coating film No. 3, except that molybdenum disulfide having a layered structure of overlapping flakes was added to a polyimide precursor solution (Unitika's "U-imide varnish") instead of PTFE particles and alumina particles. The average thickness of the coating films was 30 μm. Table 2 shows the content of each component in coating films No. 12 to No. 16.

[0073] The materials used are as follows: (1) Polyimide (polyimide precursor solution) Unitika's "U-Imido Varnish" (2) Fluororesin particles Kitamura Co., Ltd. "KTL-500F" (3) Alumina Admatex "AO-502" (4) Molybdenum disulfide (MoS2) Daizo's "M-5 Powder"

[0074] [Table 1]

[0075] [Table 2]

[0076] <Rating> Next, the surface hardness of coating films No. 1 to No. 16 was evaluated using the pencil hardness scale, and the release properties were evaluated using the tape peeling force scale.

[0077] (Tape peeling strength) The tape peeling force was measured by a tape peeling test in accordance with JIS-Z0237:2009. Specifically, NITTO mending tape (19 mm wide) was applied to the surfaces of coating films No. 1 to No. 16, and the peeling force was measured when peeled off at a speed of 5 cm / min at a 180° angle.

[0078] [Pencil hardness] Pencil hardness was measured using a pencil hardness tester under conditions of a 45° angle and a load of 1000g, in accordance with JIS-K-5600-5-4 (1999). A rating of 6H or higher indicates that the surface is resistant to scratches and of good quality.

[0079] Tables 1 and 2 show the evaluation results for tape peeling force and pencil hardness for coating films No. 1 to No. 16.

[0080] As shown in Table 1, coating films No. 3 to No. 11, which contain polyimide and secondary particles of fluororesin, where the secondary particles of fluororesin are aggregates of two or more primary particles of fluororesin, and the average primary particle size of the primary particles is between 0.25 μm and 1.00 μm, exhibited high pencil hardness of 6H or higher and low tape peeling force, demonstrating good performance. Furthermore, the results for coating films No. 4 to No. 5 and No. 7 to No. 8 show that by including alumina, a metal oxide particle, it is possible to maintain low tape peeling force while improving pencil hardness, even when increasing the content of secondary particles of fluororesin. On the other hand, coating film No. 1, which contains only polyimide and no secondary particles of fluororesin, showed high pencil hardness but also high tape peeling force, indicating reduced release properties. In addition, coating film No. 2, which does not contain polyimide, showed very low tape peeling force and excellent release properties, but also very low pencil hardness.

[0081] As shown in Table 2, coating films No. 12 to No. 16, which contain polyimide and molybdenum disulfide, with a molybdenum disulfide content of 1% to 20% by volume, showed better results compared to coating film No. 1, which contains only polyimide, with a higher pencil hardness of 7H or higher and a lower tape peeling force.

[0082] From the above, it was demonstrated that the coating film has high hardness and excellent release properties. [Explanation of symbols]

[0083] 1. Mold 2 Base 3. Coating film

Claims

1. Polyimide and Fluororesin secondary particles and It contains, The secondary particles of the above-mentioned fluororesin are aggregates of two or more primary particles of the fluororesin. A coating film having an average primary particle size of 0.25 μm or more and 1.00 μm or less.

2. The coating film according to claim 1, wherein the fluororesin is polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, or tetrafluoroethylene-hexafluoropropylene copolymer.

3. It further contains metal oxide particles, The coating film according to claim 1, wherein the average particle size of the metal oxide particles is 0.10 μm or more and 0.60 μm or less.

4. The coating film according to claim 3, wherein the metal oxide particles are alumina, silica, or titanium oxide.

5. The coating film according to claim 1, wherein the content of secondary particles of the fluororesin is 0.01% by volume or more and 5.0% by volume or less.

6. The coating film according to claim 3, wherein the content of the above-mentioned metal oxide particles is 1.0 volume% or more and 3.0 volume% or less.

7. Polyimide and Molybdenum disulfide and It contains, A coating film having a molybdenum disulfide content of 1% by volume or more and 20% by volume or less.

8. Substrate and, A coating film according to any one of claims 1 to 7 is laminated on at least a portion of the surface of the above substrate. A mold equipped with the following features.

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