Coating liquid composition, substrate with coating film, separator, secondary battery, and electrode material

Abstract

[Problem] To provide a coating liquid composition which is less likely to be deformed even when heat is applied, in a coating liquid for a paint mainly including a polymer, an ink, an adhesive, and a positive electrode, a negative electrode, and a separator of a lithium ion battery. [Solution] A coating liquid composition is characterized by including a filler, a solvent, a dispersant, and a thickener, wherein a coating film having a thickness of 0.5-20 μm is formed by coating a substrate, and the shrinkage rate of the coating film at 200 °C at 15 minutes is 20.0% or less.

Description

[Technical Field]

[0001] The present invention relates to a coating liquid composition containing a filler, a solvent, a dispersant, and a thickener, and to a substrate with a coating film containing the coating liquid composition of the present invention. The present invention relates to a coating liquid composition that can form a coating film that is resistant to deformation even when heat is applied, mainly in coating liquids containing polymers, such as paints, inks, adhesives, positive electrodes, negative electrodes, and separators of lithium ion batteries. [Background technology]

[0002] Coating and printing techniques using compositions are widely used in the industrial field in general from the viewpoints of environment, safety, and efficiency. However, the factors that contribute to the heat resistance and shape retention of a coating film that maintains a certain porosity in the substrate have not been understood.

[0003] In Patent Document 1, the dispersibility and ease of application of a battery separator coating liquid are improved by adjusting the thixotropy index (TI) of a suspension obtained by diluting fibrous cellulose with ion-exchanged water to a specific value. However, the TI value of a liquid containing components other than fibrous cellulose and ion-exchanged water is not disclosed, and factors that contribute to heat resistance are not described or suggested.

[0004] Patent Document 2 discloses a coating liquid that has excellent coatability and can form a uniform coating film, but the content of water-soluble components in the coating liquid is 5 mass % or less, meaning that the solid content is high relative to the water-soluble components.

[0005] None of these patent documents necessarily suggests anything in terms of heat resistance or deformability. In particular, when lithium-ion secondary batteries or the like are installed in electric vehicles or the like, if the temperature exceeds the crystalline melting point of the polypropylene in the porous polyolefin film contained in the coating film in the event of abnormal heat generation, the pore size generally shrinks, blocking the passage of lithium ions and suppressing further heat generation. However, if the temperature rises further, the temperature at which the separator film melts and breaks is called the meltdown temperature, and it is known that if this meltdown temperature is exceeded, the polyolefin film shrinks, causing a short circuit between the positive electrode and the negative electrode, which can cause a fire. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2018 / 070473 [Patent Document 2] Patent No. 5829557 Summary of the Invention [Problem to be solved by the invention]

[0007] Since it is possible to prevent the above problems if the shape of the substrate can be maintained when heated, the inventors thought that the above problems could be solved by limiting the properties of the coating film, but it was not at all clear what properties the coating film or coating liquid should have. [Means for solving the problem]

[0008] Under these circumstances, the inventors conducted extensive research and found that when a coating film is formed from a coating liquid under specified conditions, by setting the shrinkage rate of the coating film within a specified range, it is possible to form a coating film that has excellent heat deformation resistance and a smooth surface, and that can be fully used for the above-mentioned applications, and thus completed the present invention.

[0009] That is, the present invention is configured as follows. [1] Contains fillers, solvents, dispersants, thickeners, and binders. A coating liquid composition, which when applied to a substrate to form a coating film having a thickness of 0.5 to 20 μm, has a shrinkage rate of 20.0% or less at 200° C. for 15 minutes. [2] The coating composition according to [1], wherein the filler accounts for 20% by mass or more of the coating composition. [3] The coating liquid composition according to [1] or [2], wherein the thickener is poly(N-vinylcarboxylic acid amide). [4] The coating liquid composition according to any one of [1] to [3], wherein the thickener is poly-N-vinylacetamide. [5] The coating liquid composition according to any one of [1] to [4], wherein the solvent is water. [6] The coating liquid composition according to any one of [1] to [5], wherein the binder is an emulsion selected from the group consisting of an acrylic emulsion and a styrene-butadiene polymer emulsion. [7] The coating liquid composition according to any one of [1] to [6], wherein the substrate is a polyolefin film. [8] The coating liquid composition according to [7], wherein the polyolefin film is at least one selected from polyethylene and polypropylene. [9] The coating liquid composition according to [7] or [8], wherein the polyolefin film is a three-layer laminate film of polypropylene, polyethylene, and polypropylene.

[10] The coating liquid composition according to any one of [1] to [9], wherein the coating liquid composition has a filler / thickener mass ratio of 0.1 to 200.

[11] The coating liquid composition according to any one of [1] to

[10] , wherein the viscosity of the thickener is 30 mPa·s or more and 10,000 mPa·s or less in terms of the actual viscosity.

[12] A substrate with a coating film, comprising a substrate and a coating film formed from the coating liquid composition according to any one of [1] to

[11] .

[13]

[12] A separator made of a substrate with a coating film.

[14]

[13] A secondary battery using the separator.

[15]

[13] Lithium-ion secondary battery using the separator.

[16] An electrode material comprising a substrate surface provided with a coating film formed from the coating liquid composition according to any one of [1] to

[11] . [Effects of the Invention]

[0010] The coating liquid composition of the present invention exhibits little thermal deformation of the coating film, making it possible to suppress deformation of the substrate and, for example, to be used as an electrode material that is resistant to change even in high-temperature environments such as those of automobiles. If such a technology is adopted for coating films such as electrodes and separators of secondary batteries, particularly lithium-ion secondary batteries, it can improve the safety of the secondary batteries when they heat up. [Brief explanation of the drawings]

[0011] [Figure 1] 1 shows optical photographs of the coating films of Example 7 and Comparative Examples 7 and 8 before the heat resistance test. [Figure 2] 1 shows optical photographs of the coating films of Example 7 and Comparative Examples 7 and 8 after the heat resistance test. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described. [Coating liquid composition] The coating liquid composition of the present embodiment contains a filler, a thickener, a solvent, a dispersant, and a binder.

[0013] When such a coating liquid composition is applied to a substrate and dried to form a coating film having a thickness of 0.5 to 20 μm, the coating film has a shrinkage rate of 20.0% or less at 200° C. for 15 minutes.

[0014] The shrinkage percentage of the coating film at 200°C for 15 minutes is 20.0% or less, preferably 15.0% or less, and more preferably 7.0% or less. The shrinkage percentage of the coating film at 200°C for 15 minutes is preferably 0.01% or more, more preferably 2.0% or more, and even more preferably 5.0% or more. The shrinkage percentage is measured by the method described in the Examples. A shrinkage percentage within the above range is preferred as it provides excellent heat resistance.

[0015] The substrate is preferably a polyolefin film, and more preferably at least one selected from polyethylene and polypropylene. The substrate is also preferably a three-layer laminate film of polypropylene, polyethylene, and polypropylene. The size and thickness of the film are not particularly limited. [Filler] The filler may be an inorganic filler or an organic filler, but is preferably an inorganic filler such as alumina, boehmite, talc, kaolin calcium carbonate, calcium phosphate, magnesium oxide, amorphous silica, crystalline glass filler, titanium dioxide, silica-alumina composite oxide particles, barium sulfate, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide, mica, etc. Of these, alumina and boehmite are more preferred.

[0016] The shape of the filler is not particularly limited, and may be spherical, polyhedral, plate-like, scale-like, columnar, tubular, or fibrous. When the filler has a shape other than a sphere or a regular polyhedron, the aspect ratio of the filler is preferably 2 or more, more preferably 5 or more, and even more preferably 10 or more. When the aspect ratio of the filler is 2 or more, the lamination effect of the filler is such that when lithium dendrites grow, they are less likely to penetrate the separator. The aspect ratio of the filler is preferably 100 or less.

[0017] The major axis of the filler is preferably in the range of 0.1 to 1000 μm, more preferably 1 to 100 μm. The minor axis of the filler is preferably in the range of 0.01 to 100 μm, more preferably 0.1 to 10 μm.

[0018] 50% particle size D in the volume-based cumulative particle size distribution of the filler 50 It is desirable that the thickness is preferably in the range of 0.01 to 1000 μm, more preferably 0.1 to 100 μm. [Thickener] Preferred thickeners include poly-N-vinylcarboxylic acid amides, poly-N-vinylpyrrolidone, sodium salts of carboxymethylcellulose, polyacrylamides, polyvinyl alcohols, polysaccharides such as carrageenan, xanthan gum, guar gum, and pectin, cellulose-based polymers such as carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, methylethylhydroxycellulose, methylcellulose, and hydroxypropylcellulose, and ammonium salts and alkali metal salts of these cellulose-based polymers.

[0019] The thickener is preferably poly(N-vinyl carboxylic acid amide), more preferably poly(N-vinyl acetamide). Use of such a thickener enables the formation of a coating film with little thermal deformation, resulting in a coating film with excellent surface appearance.

[0020] Specific examples of monomers constituting poly N-vinylcarboxylic acid amide include N-vinylformamide, N-vinylacetamide, N-vinylpropionamide, N-vinylbenzamide, N-vinyl-N-methylformamide, N-vinyl-N-ethylformamide, N-vinyl-N-methylacetamide, N-vinyl-N-ethylacetamide, N-vinylpyrrolidone, etc. Among these, N-vinylacetamide is particularly preferred in view of its coatability and affinity with solvents including water.

[0021] The poly(N-vinylcarboxylic acid amide) may be a homopolymer or a copolymer. When copolymerized, in addition to the N-vinylcarboxylic acid amide, acrylonitrile, vinyl acetate, acrylic acid, methacrylic acid, and salts of acrylic acid, methacrylic acid, itaconic acid, maleic acid, crotonic acid, etc. may also be copolymerized, but there is no particular limitation. The content of N-vinylacetamide-derived components in the poly(N-vinylcarboxylic acid amide) is preferably 60 mol % or more.

[0022] The viscosity of the thickener is preferably in the range of 30 mPa·s to 10,000 mPa·s in terms of the actual viscosity (without adjusting the solution concentration). This range is preferable because it makes coating easier. [binder] Suitable binders include emulsions of styrene-butadiene resins or acrylic resins dispersed in water, and various rubber-based latexes. Of these, acrylic emulsions and styrene-butadiene resin emulsions (styrene-butadiene polymer emulsions) are preferred, and cross-linked acrylic emulsions are even more preferred. The acrylic binder may be either a homopolymer or a copolymer. The emulsion may be used as is, or may be solidified before use.

[0023] The binder is preferably 1 part by mass or more, more preferably 2 parts by mass or more, per 100 parts by mass of the filler. The binder is preferably 30 parts by mass or less, more preferably 7 parts by mass or less, per 100 parts by mass of the filler. [solvent] The solvent is not particularly limited as long as it disperses or dissolves the above-mentioned components and does not react with them, but a highly volatile solvent is used in consideration of drying properties. Specifically, water or a polar solvent compatible with water is used, but a solvent containing 50 mass% or more of water is preferred, and water alone is more preferred. Ion-exchanged water is particularly preferred as the water. Examples of solvents other than water include alcohols such as methanol, ethanol, and isopropanol. Water is preferred because of its ease of handling, in addition to the drying properties and ability to disperse or dissolve the components. [Dispersant] The coating liquid composition of this embodiment may contain a dispersant as needed. The dispersant is not particularly limited as long as it can disperse the filler in the solvent, but dodecylbenzenesulfonic acid, polyvinyl alcohol, polyacrylamide, polymethacrylic acid, higher alcohol ethylene oxide adducts, polypropylene glycol ethylene oxide adducts, sorbitol, and sorbitan fatty acid esters are preferred. The salt is not particularly limited, but metal-free ammonium salts are preferred.

[0024] When a dispersant is contained, the amount thereof is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, per 100 parts by mass of the filler. The amount of the dispersant is preferably 5 parts by mass or less, more preferably 2 parts by mass or less, per 100 parts by mass of the filler. When the dispersant is contained in this range, the dispersibility of the filler can be improved. [Composition and preparation method of coating liquid composition] In the coating liquid composition of this embodiment, the mass of the filler in the coating liquid composition is preferably in the range of 20 to 70 mass%, more preferably 25 to 60 mass%, and even more preferably 40 to 50 mass%. By including the filler in such an amount, it is possible to form a coating film with little thermal deformation.

[0025] The mass ratio of the thickener to the filler (filler / thickener) is preferably 0.1 or more and 200 or less, more preferably 30 or more and 150 or less, and even more preferably 60 or more and 100 or less. This ratio makes it possible to form a coating film having a predetermined heat distortion resistance.

[0026] The solvent such as water corresponds to the remainder of the above-mentioned components in the coating liquid composition, and typically, the amount of filler is preferably 0.1 to 200 parts by mass, more preferably 40 to 100 parts by mass, per 100 parts by mass of the solvent. Within this range, the coating liquid composition has good fluidity, high coatability, and the resulting coating film has improved smoothness.

[0027] The method for mixing the components of the coating liquid composition is not particularly limited, but to achieve a more uniform mixture, it is preferable to disperse at least the binder, thickener, and dispersant in a solvent and then add and mix the filler. More preferably, the filler is added sequentially while continuing to stir a solution in which at least the binder, thickener, and dispersant have been dissolved, and the mixture is stirred and mixed to achieve uniformity. This makes it possible to achieve an ideal mixture. In another embodiment, it is also preferable to first add a dispersant to the filler and solvent under stirring, break up secondary aggregation, and then add the binder and thickener to uniformly mix the components while suppressing re-aggregation. [Application] The coating composition of the present invention can be used in various coating liquids such as paints, inks, adhesives, positive electrodes, negative electrodes, and separators of lithium ion batteries, depending on the type of filler to be blended.

[0028] The coating liquid composition can be used as a coating liquid as it is, but if necessary, the concentration and viscosity can be adjusted appropriately with a solvent or the like before use as a coating liquid. For example, the coating composition is applied to the surface of a substrate and dried to produce a coating film. Alternatively, a coating film made of the coating composition may be provided on the surface of a substrate (referred to as a substrate with a coating film) to be used as an electrode material.

[0029] Furthermore, if the coating liquid composition contains a thickener, it is possible to provide a coating and drying method in which the drying time is significantly shortened. The method for applying the coating liquid composition to the substrate is not particularly limited, and in addition to spray coating, roll coating, bar coating, gravure coating, die coating, knife coating, inkjet coating, brush coating, and dip coating, continuous coating using a roll-to-roll pattern coating device is also possible.

[0030] Furthermore, the coating liquid composition may contain known materials that are added to paints other than those described above, such as a thixotropic agent, a surface conditioner, an antifoaming agent, a leveling agent, a pigment, a dye, an adhesive component, an adhesive component, a tackifier, etc.

[0031] As the substrate, films, nonwoven fabrics, porous bodies, plates, etc. can be used without any particular limitation. Examples of materials constituting the substrate include organic resin materials such as ethylene copolymers with other α-olefins, homopolypropylene, copolymers of propylene with other olefins, polyethylene terephthalate, polyethylene naphthalate, polyamide ether ketone, polyimide, polyamide, polyphenylene sulfone, polyphenylene ether, polyethylene, polyether sulfone, polyether ether ketone, polybenzimidazole, polyetherimide, polyamide imide, poly(p-phenylene-2,6-benzobisoxazole), fluororesin, and epoxy resin; metal materials such as aluminum, copper, silver, and iron; and inorganic materials such as glass (silicon oxide), alumina, magnesia, aluminum nitride, aluminum carbide, silicon nitride, and barium titanate. The substrate may be used alone or in combination of two or more. Among these, polyolefins are preferred, more preferably at least one selected from polyethylene and polypropylene, and most preferably a three-layer laminate consisting of polypropylene / polyethylene / polypropylene. Porous substrates made of such materials can be used as separators for secondary batteries. When the porous substrate is a polyolefin film, it is not particularly limited to those produced by a wet method or a dry method. In addition, when the porous substrate is a three-layer laminate, it is preferable that all three layers are produced by a dry method. Those having such a structure do not curl and have good heat resistance, mechanical strength, etc.

[0032] The dry method is a dry process that does not use a solvent during production, and examples include melt molding of molten resin using a T-die or injection molding. The outer and inner layers may be formed by either a dry method or a wet method, and the wet method is a method in which a film is formed using a resin to which additives have been added and mixed, and then the additives are extracted with a solvent.

[0033] The overall thickness of the substrate is appropriately selected from the viewpoints of mechanical strength, performance, miniaturization, etc. according to the purpose, and is preferably 7.0 μm or more, with the upper limit being preferably 50 μm or less. A thickness within this range can achieve high strength and high ionic conductivity.

[0034] In the case of a porous substrate, the air permeability is preferably 80 s / 100 cc or more, with the upper limit being preferably 700 s / 100 cc or less. With an air permeability in this range, short circuits are less likely to occur and ion mobility is high.

[0035] The porosity of the porous substrate is preferably 30% or more, with the upper limit being preferably 70% or less. A porosity within this range provides high mechanical strength, prevents short circuits, and increases ion mobility.

[0036] The maximum pore size of the porous substrate is preferably 0.05 μm or more, and the upper limit is preferably 2 μm or less. When the size is within this range, the ion mobility is high and the resistance is low and large when the substrate is used as a separator.

[0037] The method for drying the coating film is not particularly limited, and examples thereof include spin drying, vacuum drying, hot air drying, infrared drying, etc. The drying time is also not particularly limited. When a separator is formed, it can be formed by a method of applying the coating liquid composition to the surface of the substrate.

[0038] When constructing an electrode, the coating liquid composition is mixed with a positive electrode active material or a negative electrode active material and the mixture is applied to the surface of the substrate or the surface of a current collector. Alternatively, a mixture of a positive electrode active material, a negative electrode active material, or both is applied to an electrode foil, or the coating liquid composition is formed into a thin film and inserted onto the surface of a positive electrode or a negative electrode or both current collectors, thereby forming a battery electrode.

[0039] The components that make up a lithium-ion secondary battery can be broadly divided into a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode and the negative electrode each contain an active material that undergoes an oxidation / reduction reaction in which electrons are sent and received. The positive electrode and the negative electrode can be used in the form of an electrode group having a laminated structure in which they are stacked with a battery separator in between, or in the form of an electrode group having a wound structure in which they are further wound.

[0040] There are no particular limitations on the positive electrode, as long as it is a positive electrode used in conventionally known lithium ion secondary batteries. + It contains an active material capable of absorbing and releasing ions. The negative electrode is not particularly limited as long as it is a negative electrode used in conventionally known lithium ion secondary batteries. + It contains an active material capable of absorbing and releasing ions.

[0041] The positive electrode and the negative electrode can be stacked with a separator between them to form a stacked electrode group, or further wound together to form a wound electrode group. The electrolyte solution is a solution in which a lithium salt is dissolved in an organic solvent. The lithium salt dissociates in the solvent to form Li + There are no particular limitations on the organic solvent as long as it forms ions and does not cause side reactions such as decomposition within the voltage range used in the battery. The organic solvent is not particularly limited as long as it dissolves the lithium salt and does not cause side reactions such as decomposition within the voltage range used in the battery.

[0042] Each member prepared using the coating liquid composition of the present invention is used as appropriate for each member of the battery. Lithium-ion batteries are used as power sources for a variety of devices, including mobile phones, notebook personal computers, electric vehicles, hybrid vehicles, electric motorcycles, electrically assisted bicycles, power tools, and shavers, as well as for a variety of other conventionally known applications. [Example]

[0043] The present invention will be described below with reference to examples, but the present invention is not limited to these examples in any way. [Materials used] Filler Alumina: Showa Denko AL160SG-3 D50:0.52μm Scaly boehmite: Cerasure (Kawai Lime Industry Co., Ltd.) Aspect ratio: 20-40 Scaly alumina: Cerasure α (Kawai Lime Industry Co., Ltd.) Aspect ratio: 20-40 ·binder Acrylic emulsion: Polysol (registered trademark) LB-350 (manufactured by Showa Denko K.K.) SBR (styrene butadiene rubber): BM400B (manufactured by Zeon Corporation) Thickener Poly-N-vinylacetamide PNVA (registered trademark)-1: GE191-043 (Showa Denko K.K.), viscosity of 5000 mPa·s, solid content of 4 mass% Poly-N-vinylacetamide PNVA (registered trademark)-2: GE191-104 (Showa Denko K.K.), as-is viscosity 18,000 mPa·s, solid content 10% by mass Poly-N-vinylacetamide PNVA (registered trademark)-3: GE191-107 (Showa Denko K.K.), viscosity of 50 mPa·s, solid content of 10% by mass Poly-N-vinylacetamide PNVA (registered trademark)-4 (copolymer of N-vinylacetamide and sodium acrylate (copolymerization ratio = 90:10 (molar ratio))): GE167-103 (manufactured by Showa Denko K.K.), viscosity of 5000 mPa·s, solid content of 10 mass% Carboxymethyl cellulose CMC-Na:MAC350HC (Nippon Paper Industries Co., Ltd.) Polyvinylpyrrolidone: PVP K-90 (Tokyo Chemical Industry Co., Ltd.) Dispersant Ammonium polyacrylate: Aron (registered trademark) A-30SL (manufactured by Toagosei Co., Ltd.) Sodium dodecylbenzenesulfonate: Neopelex (registered trademark) G-65 (Kao Corporation) [Examples 1 - 10, Comparative Examples 1 - 10] Weigh the specified amounts of ion-exchanged water, dispersant, binder, thickener, and filler in a 200 ml resin container in this order, and put them into a planetary mixer (ARE-250 manufactured by Shinki Co., Ltd.). Seal it and mix under the conditions of mixing (MIXING) for 60 seconds and defoaming (Deforming) for 60 seconds to obtain a uniform coating liquid composition.

[0044] Note that the dispersant, binder, and thickener are in parts by mass of the solid content.

[0045] [Table 1] The following evaluations were performed on the obtained coating liquid composition. <Coating Test Method> Fix 3.5 g of the obtained coating liquid composition to a 16 μm thick polypropylene sheet, which is the substrate, with a curing tape, and further fix the polypropylene sheet to the coating table of the coating machine with double-sided tape (15 cm × 30 cm: thickness 0.1 μm), place it on a bar coater (width: 50 mm × thickness: 5 μm manufactured by Yoshimitsu Seiki Co., Ltd.), and coat it at a speed of 200 mm / second with an automatic coating machine (Pi-1210 manufactured by Tester Sangyo Co., Ltd.).

[0046] After that, dry the coated polypropylene sheet in a hot air dryer at a temperature of 40 °C for 1 hour to produce a coating film. <Rotational Viscosity> Using a Brookfield DV2T type viscometer, spindle SC4-28, and a small sample adapter with a water jacket, put 20 g of the coating liquid composition into the sample holder and measure the shear viscosity at shear rates of 0.3 rpm and 100 rpm. <Solution Viscosity> Evaluate the viscosity of the coating liquid composition at 23 °C with a Brookfield DV2T type viscometer, spindle SC4-28, and a small sample adapter with a water jacket at 50 rpm. <TI Value> The TI value (thixotropy index) is calculated by the following formula.

[0047] TI value = viscosity at a low shear rate of 0.01 / s (Pa s) ÷ viscosity at a high shear rate of 10,000 / s (Pa s) The viscosity was measured using a rotational viscometer (rheometer) manufactured by Anton Parr. Specifically, the viscosity at 23°C was measured at a shear rate of 0.01 sec -1 From 10,000 seconds -1 The speed was increased over 400 seconds, and then the measurement was continued for 10,000 seconds. -1 to 0.01 seconds -1 The viscosity was measured while decreasing the shear rate over 400 seconds. The measured values ​​obtained while decreasing the shear rate were regarded as the viscosity at each shear rate, and the viscosity ratios at the shear rates shown in Table 2 were calculated. <Coating film thickness> Using a constant pressure thickness measuring instrument PF-11J manufactured by Teclock, measurements were taken at three points in accordance with JIS K6400-1-2004: the center of the coating film and two points 10 cm above and below the center, and the weighted average was calculated. <Appearance> The surface appearance of the coating film was evaluated according to the following criteria. ◯: No voids were observed on the coating surface. △: Up to 10 voids were found on the coating surface. ×: More than 10 voids were found on the coating surface. <Surface roughness ratio> Using a skid-type Surtronic Duo surface roughness meter (manufactured by Taylor Hobson) in accordance with JIS B0601-2013, the surface roughness Ra was measured at three points: the center and two points 10 cm above and below the center, and the average was calculated. The surface roughness ratio was calculated by dividing Ra by the coating film thickness. <Peeling> A cellophane tape peeling test was performed on the printed surface of the coating film (the surface opposite the substrate) using 15 mm wide cellophane tape made by Nichiban, and the adhesion between the coating film and the polypropylene sheet was evaluated using the following three levels. ○: The coated part did not peel off. △: The coated part peels off. ×: The coated portion had peeled off before the test. <Shrinkage rate> The coating direction of the coating film was defined as the M direction, and the direction perpendicular to this as the T direction. Square samples of 1 cm on each side were cut out so that each side coincided with the M direction and the T direction, and then placed in air ovens with internal temperatures adjusted to 150°C and 200°C, respectively, and heated in air for 15 minutes.The shrinkage rate of the length (l) after heat treatment relative to the length (L) before heat treatment was expressed as a percentage for each of the M direction (coating direction) and T direction (direction perpendicular to the coating direction).

[0048] Shrinkage rate in each direction (%) = (Ll) / L x 100 The arithmetic average of the shrinkage rates in the M and T directions was taken as the shrinkage rate.

[0049] [Table 2] The items indicated by the shaded areas could not be calculated for Example 6 and Comparative Example 9. Furthermore, the shaded areas were not measured for Example 10. "Over" indicates values ​​above the measurement limit.

[0050] As can be seen from Table 2, the coating films of the Examples all had a surface roughness ratio of 0.178 or less, and thus had a smooth surface, whereas the coating films of the Comparative Examples all had a surface roughness ratio of 0.200 or more, and thus had an unsmooth surface.

[0051] As can be seen from Table 2, the shrinkage of the coating films of the Examples was 18.58% or less at 200°C. On the other hand, the shrinkage of the Comparative Examples was 20.60% or more at 200°C, and as shown in Figure 2, the shape of the coating film was distorted, making it impossible to measure the dimensions, and the coating films were unsuitable for use at high temperatures.

[0052] As can be seen from Table 2, no voids were observed in the surface appearance of the coating films of the Examples, whereas voids were observed in all of the coating films of the Comparative Examples. For Example 4 and Comparative Examples 7 and 8, the state of the coating film was observed before the heat resistance test.

[0053] The condition of the coated sheet before the heat resistance test is shown in Figure 1, and the condition of the coated sheet after heating to 200°C is shown in Figure 2. In Comparative Examples 7 and 8, cracks and peeling occurred in the coating film on the sheets, but in Example 4, there was no change.

Claims

1. Contains fillers, solvents, dispersants, thickeners, and binders. when the composition is applied to a substrate to form a coating film having a thickness of 0.5 to 20 μm, the coating film has a shrinkage rate of 20.0% or less at 200°C for 15 minutes; the filler is alumina, the thickener is poly(N-vinylcarboxylic acid amide); A coating liquid composition, characterized in that the viscosity of the thickener is 5,000 mPa·s or more and 10,000 mPa·s or less in terms of actual viscosity.

2. The coating composition according to claim 1 , wherein the filler accounts for 20% by mass or more and 70% by mass or less of the coating composition.

3. The coating liquid composition according to claim 1, wherein the thickener is poly(N-vinylcarboxylic acid amide).

4. The coating liquid composition according to claim 1 , wherein the solvent is water.

5. 2. The coating liquid composition according to claim 1, wherein the binder is an emulsion selected from the group consisting of an acrylic emulsion and a styrene-butadiene polymer emulsion.

6. The coating liquid composition according to claim 1 , wherein the substrate is a polyolefin film.

7. The coating liquid composition according to claim 6, wherein the polyolefin film is at least one selected from polyethylene and polypropylene.

8. The coating liquid composition according to claim 6, wherein the polyolefin film is a three-layer laminate film of polypropylene, polyethylene, and polypropylene.

9. The coating liquid composition according to claim 1 , wherein the mass ratio of the filler to the thickener in the coating liquid composition is 0.1 or more and 200 or less.

10. A substrate with a coating film, comprising a substrate and a coating film formed from the coating liquid composition according to any one of claims 1 to 9.

11. A separator comprising the substrate with the coating film according to claim 10.

12. A secondary battery using the separator according to claim 11.

13. A lithium ion secondary battery using the separator according to claim 11.

14. An electrode material comprising a substrate surface having a coating film formed from the coating liquid composition according to any one of claims 1 to 9.

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