Pressure plate assemblies, pressure plates, microcapsules, dispersed fluids, methods for manufacturing pressure plate assemblies, and methods for manufacturing pressure plates.

Abstract

The invention relates to a plate set for pressure measurement capable of high temperature measurement, a plate for pressure measurement, microcapsules (13), a dispersion fluid, a method for producing a plate set for pressure measurement, and a method for producing a plate for pressure measurement. The plate set for pressure measurement under the invention consists of: a first plate (16) which includes a first layer of microcapsules which enclose the coloring agent; and a second plate (22) which includes a second layer (20) of the coloring agent which includes the compound represented by the formula (1), and the thermal decomposition temperature of the capsule walls of the microcapsules is 250°C or higher.

Description

Pressure measurement sheet set, pressure measurement sheet, microcapsules, dispersion liquid, method for manufacturing pressure measurement sheet set, method for manufacturing pressure measurement sheet

[0001] The present invention relates to a sheet set for pressure measurement, a sheet for pressure measurement, microcapsules, a dispersion liquid, a method for manufacturing a sheet set for pressure measurement, and a method for manufacturing a sheet for pressure measurement.

[0002] In recent years, the need to measure pressure distribution has increased due to the increasing functionality and precision of products. Pressure measurement sheet sets and pressure measurement sheets (hereinafter simply referred to as "pressure measurement sheet sets, etc.") are generally used as methods for measuring pressure distribution due to their convenience. For example, Patent Documents 1 to 3 disclose pressure measurement sheet sets, etc., that utilize microcapsules containing a color former.

[0003] International Publication No. WO 2004 / 024809 International Publication No. WO 2018 / 062017 International Publication No. WO 2020 / 149410

[0004] In recent years, accurate pressure measurement has been required even in applications such as high-temperature hot pressing, heat pressing, and bonding. Conventional pressure measurement sheet sets, etc., cannot withstand high-temperature pressures above 180°C, making it impossible to accurately measure pressure. Therefore, measures such as temporarily lowering the temperature to below 150°C are necessary. However, because the object being measured, such as a mold, expands due to heat in a high-temperature environment (especially above 180°C), the pressure distribution obtained when measured in a high-temperature environment (especially above 180°C) is strictly different from that obtained when measured in a low-temperature environment (especially below 150°C), making accurate measurement often impossible. In other words, pressure measurement data obtained at a lower temperature may not reflect the pressure distribution in a high-temperature environment. Therefore, there has been a demand for pressure measurement sheet sets, etc., that can accurately measure pressure in high-temperature environments above 180°C. The inventors have found that when measuring pressure distributions using conventional pressure measurement sheet sets, etc., in high-temperature environments above 180°C, coloring occurs in areas other than the pressurized area, making it difficult to easily recognize the shape of the colored area due to pressure, making it impossible to accurately measure the pressure distribution. It was also newly discovered that when pressure is measured in a high-temperature environment, the color of the colored region changes depending on the pressure duration. If the color of the colored region changes depending on the pressure duration even when the same pressure is applied, accurate pressure measurement becomes impossible, and therefore improvement was desired. Hereinafter, the ability to easily recognize the shape of the colored region under pressure and to suppress color change in the colored region depending on the pressure duration will also be referred to as excellent high-temperature suitability.

[0005] In the examples and the like described in Patent Document 1, conventional pressure measurement sheet sets and the like are used not in high-temperature environments (particularly 180° C. or higher) but at temperatures below 150° C. The present inventors also studied the pressure measurement sheet sets and the like described in Patent Documents 2 and 3 and found that when used in high-temperature environments (particularly 180° C. or higher), they are inferior in high-temperature suitability.

[0006] In view of the above circumstances, an object of the present invention is to provide a pressure measurement sheet set having excellent high-temperature suitability, a pressure measurement sheet having excellent high-temperature suitability, and a method for manufacturing a microcapsule, a dispersion, a pressure measurement sheet set, and a pressure measurement sheet.

[0007] As a result of extensive research into the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by the following configuration.

[0008] [1] A sheet set for pressure measurement comprising a first sheet having a first layer containing microcapsules encapsulating a color former, and a second sheet having a second layer containing a color developer, wherein the color former contains a compound represented by formula (1) described below, and the thermal decomposition temperature of the capsule walls of the microcapsules is 250° C. or higher. [2] The sheet set for pressure measurement according to [1], wherein, when the first sheet is heated at 220° C. for 10 minutes, the thermal shrinkage rate Sa1 in the longitudinal direction of the first sheet and the thermal shrinkage rate Sa2 in the width direction perpendicular to the longitudinal direction of the first sheet are both −0.5 to 3.0%. [3] The sheet set for pressure measurement according to [1] or [2], wherein the capsule walls of the microcapsules contain at least one material selected from the group consisting of polyurethane urea having a polymethylene polyphenylene structure and melamine resin. [4] The sheet set for pressure measurement according to any one of [1] to [3], wherein the capsule walls of the microcapsules contain a resin having Structure A or Structure B. Structure A: A structure obtained by reacting an aromatic or alicyclic diisocyanate with a compound having three or more active hydrogen groups in one molecule and polymethylene polyphenyl polyisocyanate. Structure B: A structure obtained by reacting melamine with formaldehyde. [5] The sheet set for pressure measurement according to any one of [1] to [4], wherein the capsule walls of the microcapsules have a thickness of 80 to 300 nm. [6] The sheet set for pressure measurement according to any one of [1] to [5], wherein the content of the compound represented by Formula (1) is 70 mass% or more relative to the total mass of the color former. [7] A pressure measurement sheet having a first layer containing microcapsules encapsulating a color former, and a second layer containing a color developer, wherein the color former contains a compound represented by formula (1) described below, and the thermal decomposition temperature of the capsule walls of the microcapsules is 250° C. or higher. [8] The pressure measurement sheet according to [7], wherein, when the pressure measurement sheet is heated at 220° C. for 10 minutes, the heat shrinkage rate Sb1 in the longitudinal direction of the pressure measurement sheet and the heat shrinkage rate Sb2 in the width direction perpendicular to the longitudinal direction of the pressure measurement sheet are both −0.5 to 3.0%.[9] The pressure measurement sheet according to [7] or [8], wherein the capsule walls of the microcapsules contain at least one selected from the group consisting of polyurethane urea having a polymethylene polyphenylene structure and melamine resin.

[10] The pressure measurement sheet according to any one of [7] to [9], wherein the capsule walls of the microcapsules contain a resin having Structure A or Structure B. Structure A: A structure obtained by reacting an aromatic or alicyclic diisocyanate, a compound having three or more active hydrogen groups in one molecule, and polymethylene polyphenyl polyisocyanate. Structure B: A structure obtained by reacting melamine with formaldehyde.

[11] The pressure measurement sheet according to any one of [7] to

[10] , wherein the capsule walls of the microcapsules have a thickness of 80 to 300 nm.

[12] The pressure measurement sheet according to any one of [7] to

[11] , wherein the content of the compound represented by Formula (1) is 70 mass% or more relative to the total mass of the color former.

[13] A microcapsule encapsulating a color former, wherein the color former comprises a compound represented by formula (1) described below, and wherein the thermal decomposition temperature of the microcapsule wall is 250°C or higher.

[14] The microcapsule according to

[13] , wherein the capsule wall comprises at least one selected from the group consisting of polyurethane urea having a polymethylene polyphenylene structure and melamine resin.

[15] The microcapsule according to

[13] or

[14] , wherein the capsule wall comprises a resin having structure A or structure B. Structure A: A structure obtained by reacting an aromatic or alicyclic diisocyanate, a compound having three or more active hydrogen groups in one molecule, and polymethylene polyphenyl polyisocyanate. Structure B: A structure obtained by reacting melamine with formaldehyde.

[16] The microcapsule according to any one of

[13] to

[15] , wherein the thickness of the microcapsule wall is 80 to 300 nm.

[17] The microcapsule according to any one of

[13] to

[16] , wherein the content of the compound represented by formula (1) is 70% by mass or more relative to the total mass of the color former.

[18] A dispersion containing the microcapsules according to any one of

[13] to

[17] .

[19] A method for manufacturing the sheet set for pressure measurement according to any one of [1] to [6], which includes a step of forming the first layer using the dispersion according to

[18] .

[20] A method for manufacturing the sheet for pressure measurement according to any one of [7] to

[12] , which includes a step of forming the first layer using the dispersion according to

[18] .

[0009] According to the present invention, it is possible to provide a sheet set for pressure measurement having excellent high-temperature suitability, a sheet for pressure measurement having excellent high-temperature suitability, and a method for manufacturing a microcapsule, a dispersion, a sheet set for pressure measurement, and a sheet for pressure measurement.

[0010] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments and is not to be construed as limiting the invention.

[0011] The present invention will be described in detail below. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​described before and after "to" as the upper and lower limits. Furthermore, in the numerical ranges described in stages in this specification, the upper or lower limit described in a certain numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in the numerical ranges described in this specification, the upper or lower limit described in a certain numerical range may be replaced with a value shown in the examples. In this specification, when simply referring to a substituent, examples of the substituent include the groups exemplified by the substituent T below.

[0012] (Substituent T) Examples of the substituent T include a halogen atom (such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom), an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an aryl group, a heterocyclic group, a cyano group, a hydroxy group, a nitro group, a carboxy group, an alkoxy group, an aryloxy group, a silyloxy group, a heterocyclic oxy group, an acyloxy group, a carbamoyloxy group, an amino group (including an alkylamino group and an anilino group), an acylamino group, an aminocarbonylamino group, an alkoxycarbonylamino group, an aryl ... Examples of the substituents include a carbonylamino group, a sulfamoylamino group, an alkyl or arylsulfonylamino group, a mercapto group, an alkylthio group, an arylthio group, a heterocyclic thio group, a sulfamoyl group, a sulfo group, an alkyl or arylsulfinyl group, an alkyl or arylsulfonyl group, an acyl group, an aryloxycarbonyl group, an alkoxycarbonyl group, a carbamoyl group, an aryl or heterocyclic azo group, an imido group, a phosphino group, a phosphinyl group, a phosphinyloxy group, a phosphinylamino group, a silyl group, and a group containing a polymerizable group. Among the above substituents, those having a hydrogen atom may further have the hydrogen atom portion in the substituent substituted with any of the above substituents.

[0013] A characteristic feature of the pressure measurement sheet set and pressure measurement sheet of the present invention is that the color former contains a compound represented by formula (1) (hereinafter also referred to as the "specific compound") and the capsule wall has a thermal decomposition temperature of 250°C or higher. The inventors have discovered that when the color former contains the specific compound and the capsule wall has a predetermined thermal decomposition temperature, the pressure measurement sheet set and the like have excellent high-temperature suitability. Specifically, the inventors speculate that the inclusion of the specific compound with excellent thermal stability suppresses color change in the colored region even when heated for a long period of time, and that the inclusion of capsule walls that are resistant to thermal decomposition suppresses color development in regions other than the pressurized portion at high temperatures (especially 180°C or higher), making it easy to identify the area where the color developed under pressure. Hereinafter, excellent high-temperature suitability of the pressure measurement sheet set and the like is also referred to as the excellent effects of the present invention.

[0014] [First Embodiment] Fig. 1 is a cross-sectional view of one embodiment of a sheet set for pressure measurement. The sheet set for pressure measurement 10 includes a first sheet 16 having a first support 12 and a first layer 14 containing microcapsules 13 disposed on the first support 12, and a second sheet 22 having a second support 18 and a second layer 20 containing a color developer disposed on the second support 18. When using the sheet set for pressure measurement 10, as shown in Fig. 2, the first sheet 16 and the second sheet 22 are laminated so that the first layer 14 in the first sheet 16 faces the second layer 20 in the second sheet 22. By applying pressure from at least one of the first support 12 side of the first sheet 16 and the second support 18 side of the second sheet 22 in the resulting laminate, the microcapsules 13 are broken in the pressurized areas, and the color former encapsulated in the microcapsules 13 is released from the microcapsules 13, causing a color-developing reaction between the color former and the color developer in the second layer 20. As a result, color development occurs in the pressure-applied area.

[0015] As described below, the first sheet 16 may have the first layer 14 but may not have the first support 12. The second sheet 22 may have the second layer 20 but may not have the second support 18. Although the first support 12 and the first layer 14 are directly laminated together in FIG. 1 , this is not a limitation, and as described below, another layer (e.g., an adhesive layer) may be disposed between the first support 12 and the first layer 14. Although the second support 18 and the second layer 20 are directly laminated together in FIG. 1 , this is not a limitation, and as described below, another layer (e.g., an adhesive layer) may be disposed between the second support 18 and the second layer 20.

[0016] The configurations of the first sheet 16 and the second sheet 22 that make up the pressure measurement sheet set 10 will be described in detail below.

[0017] <<First Sheet>> The first sheet 16 shown in FIG. 1 has a first support 12 and a first layer 14 including microcapsules 13 that encapsulate a color former.

[0018] When the first sheet is heated at 220°C for 10 minutes, the heat shrinkage rate Sa1 in the longitudinal direction of the first sheet and the heat shrinkage rate Sa2 in the width direction perpendicular to the longitudinal direction of the first sheet are preferably both -0.5 to 3.0%. The method for measuring the heat shrinkage rates Sa1 and Sa2 of the first sheet is as shown in the Examples section. There are no particular limitations on the method for adjusting the heat shrinkage rate of the first sheet to the above ranges, but it is preferable to use a film as the first support whose heat shrinkage rates in the longitudinal direction and width direction when heated at 220°C for 10 minutes are -0.5 to 3.0, and it is more preferable to use a polyethylene naphthalate film or a polyimide film.

[0019] The longitudinal direction of the first sheet refers to the long dimension of the first sheet. Specifically, if the first sheet 16 is rectangular, it refers to the direction along the long side. The width direction of the first sheet refers to the direction perpendicular to the longitudinal direction of the first sheet (short direction). For example, if the first sheet is rectangular, it refers to the direction along the short side. However, if the first sheet is square, the direction along one of the sides constituting the square is the long axis direction, and the direction along the side perpendicular to the long axis direction is the width direction. The first sheet may be a sheet (single sheet) or may be long. Each component will be described in detail below.

[0020] [First Support] The first support is a member for supporting the first layer. Note that if the first layer itself can be handled, the first sheet does not need to have a first support.

[0021] The first support may be in the form of a sheet or a plate. Examples of the first support include resin films and synthetic paper. Examples of resin films include polyester films such as polyethylene naphthalate and polyethylene terephthalate films; cellulose derivative films such as cellulose triacetate; polyolefin films such as polypropylene and polyethylene; and polystyrene films. Examples of synthetic paper include synthetic paper (e.g., Yupo) made by biaxially stretching polypropylene or polyethylene terephthalate to form a large number of microvoids; synthetic paper made using synthetic fibers such as polyethylene, polypropylene, polyethylene terephthalate, and polyamide; and synthetic paper in which these are laminated on a portion, one side, or both sides of the paper. Among these, resin films or synthetic paper are preferred as the first support, with resin films being more preferred, polyester films being even more preferred, and polyethylene naphthalate films being particularly preferred. Examples of commercially available polyethylene naphthalate films include Teonex (registered trademark) Q51, Q53, Q81, and Q83 (manufactured by Teijin Film Solutions Co., Ltd.). The first support is preferably transparent so that the color development can be visually confirmed even when viewed from the support side.

[0022] The thickness of the first support is preferably 10 to 200 μm.

[0023] [First Layer] The first layer contains microcapsules that encapsulate a specific compound and have capsule walls with a predetermined thermal decomposition temperature. First, the materials that make up the microcapsules will be described in detail below.

[0024] <Microcapsules> Microcapsules have a core portion and a capsule wall for encapsulating a core material (the substance to be encapsulated (hereinafter also referred to as "encapsulated component")) that forms the core portion. In the present invention, the microcapsules encapsulate a color former containing a specific compound as the core material (encapsulated component). Generally, since the color former is encapsulated in the microcapsules, the color former can remain in the microcapsules until the microcapsules are ruptured by pressure.

[0025] The microcapsules have a capsule wall encapsulating a core material. The thermal decomposition temperature of the microcapsule wall is 250°C or higher, preferably above 250°C, more preferably 255°C or higher, and even more preferably 260°C or higher. The upper limit is not particularly limited, but is often 500°C or lower. The thermal decomposition temperature of the capsule wall is measured as follows. 50 first layers (microcapsule layers) measuring 1 cm long x 1 cm wide are prepared, immersed in 10 mL of water, and allowed to stand for 24 hours to obtain an aqueous dispersion of microcapsules. When the first sheet includes a first support, 50 first sheets measuring 1 cm long x 1 cm wide may be prepared and immersed. The obtained aqueous dispersion of microcapsules is centrifuged at 15,000 rpm for 30 minutes to separate the microcapsules. Ethyl acetate (1000 times or more) is added to the separated microcapsules, and the mixture is further stirred at 25°C for 24 hours. The resulting solution is then filtered, and the resulting residue is vacuum-dried at 60°C for 48 hours to obtain microcapsules (hereinafter simply referred to as "measurement material") that contain nothing inside. In other words, the capsule wall material of the microcapsules, the thermal decomposition temperature of which is to be measured, is obtained. Next, the thermal decomposition temperature of the obtained measurement material is measured using a thermogravimetric differential thermal analyzer TG-DTA (device name: DTG-60, manufactured by Shimadzu Corporation). Note that the thermal decomposition temperature (°C) is the temperature at which the measurement material is heated from room temperature at a constant heating rate (10°C / min) in thermogravimetric analysis (TGA) in an atmospheric atmosphere, and the mass of the measurement material before heating is reduced by 5% by mass.

[0026] Examples of the material (wall material) for the capsule wall of the microcapsule include known resins that have traditionally been used as wall materials for microcapsules encapsulating color formers in the applications of pressure-sensitive copying paper and thermal recording paper. The capsule wall of the microcapsule is preferably substantially composed of a resin. "Substantially composed of a resin" means that the resin content is 90% by mass or more, preferably 100% by mass, of the total mass of the capsule wall of the microcapsule. In other words, the capsule wall of the microcapsule is preferably composed of a resin.

[0027] Examples of the resin include polyurethane, polyurea, polyurethane urea, melamine resin, acrylic resin, and gelatin. Among these, in terms of achieving superior effects of the present invention, the capsule wall of the microcapsule preferably contains at least one selected from the group consisting of polyurethane, polyurea, polyurethane urea, and melamine resin, more preferably contains at least one selected from the group consisting of polyurethane urea and melamine resin, and even more preferably contains polyurethane urea or melamine resin having a polymethylene polyphenylene structure. The polymethylene polyphenylene structure refers to a structure represented by formula (Y). In formula (Y), n represents an integer of 1 or more, preferably an integer of 1 to 10, and more preferably an integer of 1 to 5.

[0028]

[0029] The melamine resin is preferably a reaction product formed by polycondensation of melamine and formaldehyde. The polyisocyanate is a compound having two or more isocyanate groups. Examples of polyisocyanates include aromatic polyisocyanates and aliphatic polyisocyanates. Aromatic polyisocyanates are preferred because they can introduce aromatic ring groups into the capsule walls of the microcapsules. Examples of aromatic polyisocyanates include aromatic diisocyanates, such as m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, naphthalene-1,4-diisocyanate, diphenylmethane-4,4'-diisocyanate, 3,3'-dimethoxy-biphenyl diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, 4-chloroxylylene-1,3-diisocyanate, 2-methylxylylene-1,3-diisocyanate, 4,4'-diphenylpropane diisocyanate, and 4,4'-diphenylhexafluoropropane diisocyanate.

[0030] The aliphatic polyisocyanate includes aliphatic diisocyanates, such as trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,3-diisocyanate, cyclohexylene-1,4-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,4-bis(isocyanatemethyl)cyclohexane, 1,3-bis(isocyanatemethyl)cyclohexane, isophorone diisocyanate, lysine diisocyanate, and hydrogenated xylylene diisocyanate.

[0031] The polyisocyanate may also be a tri- or higher functional polyisocyanate (e.g., a trifunctional triisocyanate and a tetrafunctional tetraisocyanate). Specific examples of the polyisocyanate include biuret or isocyanurate trimers of the bifunctional polyisocyanates, adducts (addition products) of polyols such as trimethylolpropane with bifunctional polyisocyanates, formalin condensates of benzene isocyanate, polyisocyanates having a polymerizable group such as methacryloyloxyethyl isocyanate, and lysine triisocyanate. For information on polyisocyanates, see "Polyurethane Resin Handbook" (edited by Keiji Iwata, published by Nikkan Kogyo Shimbun, Ltd. (1987)).

[0032] Among these, a preferred embodiment of the polyisocyanate is a tri- or higher functional polyisocyanate. Examples of the tri- or higher functional polyisocyanate include tri- or higher functional aromatic polyisocyanates and tri- or higher functional aliphatic polyisocyanates. As the tri- or higher functional polyisocyanate, a tri- or higher functional polyisocyanate that is an adduct (addition product) of an aromatic or alicyclic diisocyanate and a compound having three or more active hydrogen groups in one molecule (for example, a tri- or higher functional polyol, polyamine, or polythiol, etc.) (adduct-type tri- or higher functional polyisocyanate), and a trimer (biuret type or isocyanurate type) of an aromatic or alicyclic diisocyanate are also preferred, and the above-mentioned tri- or higher functional polyisocyanate that is an adduct (addition product) are more preferred.

[0033] The trifunctional or higher polyisocyanate adduct is preferably a trifunctional or higher polyisocyanate adduct of an aromatic or alicyclic diisocyanate and a polyol having three or more hydroxy groups per molecule, and more preferably a trifunctional polyisocyanate adduct of an aromatic or alicyclic diisocyanate and a polyol having three hydroxy groups per molecule. The adduct is preferably an adduct obtained using an aromatic diisocyanate, as this provides better effects of the present invention. The polyol is preferably, for example, a trifunctional or higher low-molecular-weight polyol as described below, and more preferably trimethylolpropane.

[0034] Examples of tri- or higher functional adduct polyisocyanates include Takenate (registered trademark) D-102, D-103, D-103H, D-103M2, P49-75S, D-110N, D-120N, D-140N, D-160N (manufactured by Mitsui Chemicals, Inc.), Desmodur (registered trademark) L75, UL57SP (manufactured by Sumika Bayer Urethane Co., Ltd.), Coronate (registered trademark) HL, HX, L (manufactured by Nippon Polyurethane Co., Ltd.), P301-75E (manufactured by Asahi Kasei Corporation) and Burnock (registered trademark) D-750 (manufactured by DIC Corporation). Among these, as the adduct type tri- or higher functional polyisocyanate, Takenate (registered trademark) D-110N, D-120N, D-140N, D-160N (manufactured by Mitsui Chemicals, Inc.) or Burnock (registered trademark) D-750 manufactured by DIC Corporation is preferred, and Burnock (registered trademark) D-750 manufactured by DIC Corporation is more preferred.

[0035] Examples of isocyanurate-type trifunctional or higher polyisocyanates include Takenate (registered trademark) D-127N, D-170N, D-170HN, D-172N, D-177N, D-204 (manufactured by Mitsui Chemicals, Inc.), Sumidur N3300, Desmodur (registered trademark) N3600, N3900, Z4470BA (Sumika Bayer Urethane), Coronate (registered trademark) HX, HK (manufactured by Nippon Polyurethane Co., Ltd.), Duranate (registered trademark) TPA-100, TKA-100, TSA-100, TSS-100, TLA-100 and TSE-100 (manufactured by Asahi Kasei Corporation).

[0036] Examples of biuret-type tri- or higher functional polyisocyanates include Takenate (registered trademark) D-165N, NP1100 (manufactured by Mitsui Chemicals, Inc.), Desmodur (registered trademark) N3200 (manufactured by Sumika Bayer Urethane), and Duranate (registered trademark) 24A-100 (manufactured by Asahi Kasei Corporation).

[0037] Furthermore, polymethylene polyphenyl polyisocyanate is also preferred as the polyisocyanate. As the polymethylene polyphenyl polyisocyanate, a compound represented by formula (X) is preferred.

[0038]

[0039] In formula (X), n represents an integer of 1 or more. n is preferably an integer of 1 to 10, and more preferably an integer of 1 to 5, from the viewpoint of enabling better measurement of pressure distribution at high temperatures.

[0040] Examples of polyisocyanates containing polymethylene polyphenyl polyisocyanate include Millionate MR-100, Millionate MR-200, Millionate MR-400 (manufactured by Tosoh Corporation), WANNATE PM-200, WANNATE PM-400 (manufactured by Wanka Japan Co., Ltd.), Cosmonate M-50, Cosmonate M-100, Cosmonate M-200, Cosmonate M-300 (manufactured by Mitsui Chemicals, Inc.), and Boranate M-595 (manufactured by The Dow Chemical Company).

[0041] A polyol is a compound having two or more hydroxy groups. Examples of polyols include low molecular weight polyols (e.g., aliphatic polyols and aromatic polyols), polyvinyl alcohol, polyether polyols, polyester polyols, polylactone polyols, castor oil polyols, polyolefin polyols, and hydroxy group-containing amine compounds. The low molecular weight polyol refers to a polyol having a molecular weight of 400 or less, and examples thereof include bifunctional low molecular weight polyols such as ethylene glycol, diethylene glycol, and propylene glycol; and trifunctional or higher low molecular weight polyols such as glycerin, trimethylolpropane, hexanetriol, pentaerythritol, and sorbitol.

[0042] Examples of hydroxy group-containing amine compounds include oxyalkylated derivatives of amino compounds, with amino alcohols being preferred. Examples of amino alcohols include propylene oxide and ethylene oxide adducts of amino compounds such as ethylenediamine, specifically N,N,N',N'-tetrakis[2-hydroxypropyl]ethylenediamine and N,N,N',N'-tetrakis[2-hydroxyethyl]ethylenediamine.

[0043] Polyamines are compounds having two or more amino groups (primary amino groups or secondary amino groups). Examples of polyamines include aliphatic polyamines such as diethylenetriamine, triethylenetetramine, 1,3-propylenediamine, and hexamethylenediamine; epoxy compound adducts of aliphatic polyamines; alicyclic polyamines such as piperazine; and heterocyclic diamines such as 3,9-bis-aminopropyl-2,4,8,10-tetraoxaspiro-(5,5)undecane.

[0044] Suitable embodiments of the resin contained in the capsule wall of the microcapsule include those having Structure A or Structure B. Structure A or Structure B can improve rigidity while maintaining a high crosslink density, thereby further suppressing the migration of the encapsulated color former out of the capsule, thereby further improving the effects of the present invention. Structure A is a structure obtained by reacting an aromatic or alicyclic diisocyanate, a compound having three or more active hydrogen groups in one molecule, and polymethylene polyphenyl polyisocyanate (preferably a compound represented by Formula (X)). Structure B is a structure obtained by reacting melamine with formaldehyde.

[0045] Another preferred embodiment of the resin contained in the capsule wall of the microcapsule is formed using a polyisocyanate A (hereinafter simply referred to as "polyisocyanate A") having three or more functional groups, which is an adduct of an aromatic or alicyclic diisocyanate and a compound having three or more active hydrogen groups in one molecule, and a polyisocyanate B (hereinafter simply referred to as "polyisocyanate B") selected from the group consisting of aromatic diisocyanates and polymethylene polyphenyl polyisocyanates. In other words, the capsule wall of the microcapsule preferably contains a resin formed using the polyisocyanate A and polyisocyanate B, in view of the excellent effects of the present invention.

[0046] As the polyisocyanate B, an aromatic diisocyanate may be used alone, or a polymethylene polyphenyl polyisocyanate may be used alone, or both may be used in combination. Among these, a mixture of an aromatic diisocyanate and a polymethylene polyphenyl polyisocyanate is preferred as the polyisocyanate B. In the mixture, the mass ratio of the mass of the polymethylene polyphenyl polyisocyanate to the mass of the aromatic diisocyanate (mass of polymethylene polyphenyl polyisocyanate / mass of aromatic diisocyanate) is preferably 0.1 to 10, more preferably 0.5 to 2, and even more preferably 0.75 to 1.5.

[0047] The viscosity of the polyisocyanate B is preferably 100 to 1000 mPa·s, the viscosity being measured at 25°C.

[0048] When polyisocyanate A and polyisocyanate B are used in combination, the mass ratio of the mass of polyisocyanate A to the mass of polyisocyanate B (mass of polyisocyanate A / mass of polyisocyanate B) is preferably 20 / 80 to 98 / 2, more preferably 20 / 80 to 90 / 10, and even more preferably 20 / 80 to 70 / 30, in terms of excellent effects of the present invention.

[0049] The volume-based median diameter (D50) of the microcapsules is preferably 1 to 80 μm, more preferably 5 to 70 μm, and even more preferably 10 to 50 μm. The volume-based median diameter of the microcapsules can be controlled by adjusting the manufacturing conditions of the microcapsules. Here, the volume-based median diameter of the microcapsules refers to the diameter at which the total volume of the particles on the larger and smaller diameter sides is equal when the entire microcapsules are divided into two parts using a threshold particle diameter at which the cumulative volume is 50%. In other words, the median diameter corresponds to the so-called D50. The surface of the first layer of the first sheet having a first layer containing microcapsules is photographed at 1000x magnification using an optical microscope, and the size of all microcapsules within a 500 μm x 500 μm area is measured and calculated. The volume-based median diameter of the microcapsules contained in the dispersion may also be measured using a laser diffraction / scattering particle size distribution analyzer (LA-960 / manufactured by HORIBA).

[0050] The thickness of the capsule wall of the microcapsules (number average wall thickness) is often 0.01 to 2.0 μm, preferably 0.05 to 1.0 μm, more preferably 50 to 500 nm, and even more preferably 80 to 300 nm from the viewpoint of better effects of the present invention, and particularly preferably 80 to 250 nm and most preferably 100 to 200 nm from the viewpoint of better gradation at high temperatures. The thickness of the microcapsule refers to the thickness of the capsule wall that forms the capsule particle of the microcapsule, and the number average wall thickness refers to the average value obtained by averaging the individual capsule wall thicknesses of five microcapsules measured using a scanning electron microscope (SEM). More specifically, a cross-sectional slice of a first sheet having a first layer containing microcapsules is prepared, and the cross-section is observed at 200x magnification using an SEM. Five microcapsules having major diameters in the range of [(volume-based median diameter (D50) of microcapsules) x 0.9] to [(volume-based median diameter (D50) of microcapsules) x 1.1] are selected, and the cross-sections of the selected individual microcapsules are observed at 15,000x magnification to determine the thickness of the microcapsule walls and calculate the average value. Note that the major diameter means the longest diameter when observing the microcapsules.

[0051] The ratio (δ / Dm) of the number-average wall thickness δ of the microcapsules to the volume-based median diameter (D50) Dm of the microcapsules is not particularly limited, but is often 0.001 or greater. In particular, it is preferable to satisfy the relationship of formula (1) in order to obtain superior effects of the present invention. Formula (1) 0.100 > δ / Dm > 0.001 In other words, it is preferable that the ratio (δ / Dm) is greater than 0.001 and less than 0.100. When the relationship of formula (1) is satisfied, it is possible to achieve a range in which the color density gradation according to pressure is easily discernible.

[0052] The content of the microcapsules in the first layer is preferably 50 to 90% by mass, more preferably 55 to 80% by mass, based on the total mass of the first layer.

[0053] (Color former) The microcapsules encapsulate a color former containing a compound represented by formula (1). A color former is a compound that changes from a colorless state to a color upon contact with a color developer, which will be described later. As the color former, an electron-donating dye precursor (a precursor of a color-forming dye) is preferred. In other words, as the color former, an electron-donating colorless dye is preferred.

[0054] ((Compound represented by formula (1)))

[0055]

[0056] In formula (1), R １ represents an alkyl group which may have a substituent. ３ is -NR Ａ R Ｂ Represents R Ａ and R Ｂ R each independently represents an alkyl group which may have a substituent or an aryl group which may have a substituent. ２ and R ４ each independently represents a halogen atom; Q represents a benzene ring or a naphthalene ring; X represents —O— or —NR ５ - represents. ５represents an alkyl group which may have a substituent or an aryl group which may have a substituent. p and q each independently represent an integer of 0 to 4. r represents an integer of 1 to 3. s represents an integer of 0 to 3. However, p+q is an integer of 0 to 4, and r+s is an integer of 1 to 4.

[0057] R １ represents an alkyl group which may have a substituent. The alkyl group may be linear, branched, or cyclic, and is preferably linear or branched. The number of carbon atoms in the alkyl group is preferably 1 to 10, more preferably 1 to 5. Examples of the substituent that the alkyl group may have include the groups exemplified above for the substituent T. When a plurality of R １ may be the same or different.

[0058] R ３ is -NR Ａ R Ｂ Represents R Ａ and R Ｂ each independently represents an alkyl group which may have a substituent or an aryl group which may have a substituent. The alkyl group may be linear, branched, or cyclic, and is preferably linear or branched. The alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms. The aryl group preferably has 6 to 20 carbon atoms, more preferably 6 to 10 carbon atoms. The aryl group may be either monocyclic or polycyclic. Examples of the substituent that the alkyl group and the aryl group may have include the groups exemplified above for the substituent T. Among these, R Ａ and R Ｂ At least one of R preferably represents an alkyl group which may have a substituent, and more preferably represents an unsubstituted alkyl group. ３ may be the same or different.

[0059] R ２ and R ４each independently represents a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. A chlorine atom or a bromine atom is preferred, and a bromine atom is more preferred.

[0060] X is —O— or —NR ５ Among them, X is preferably —O—. ５ represents an alkyl group which may have a substituent or an aryl group which may have a substituent. The alkyl group may be linear, branched, or cyclic, and is preferably linear or branched. The alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms. The aryl group preferably has 6 to 20 carbon atoms, more preferably 6 to 10 carbon atoms. The aryl group may be either monocyclic or polycyclic. Among these, R ５ is preferably an alkyl group which may have a substituent or an aryl group which may have a substituent, more preferably an aryl group which may have a substituent. Examples of the substituent which the alkyl group and the aryl group may have include the groups exemplified above for the substituent T, and is preferably at least one selected from the group consisting of a halogen atom, a cyano group, a nitro group and a carboxy group, more preferably a nitro group.

[0061] p and q each independently represent an integer of 0 to 4. r represents an integer of 1 to 3. s represents an integer of 0 to 3. However, p + q is an integer of 0 to 4, and r + s is an integer of 1 to 4. p is preferably an integer of 0 to 2. q is preferably an integer of 0 to 1. r is preferably an integer of 1 to 2, and 1 is more preferred. s is preferably an integer of 0 to 1, and 0 is more preferred. Furthermore, when Q represents a naphthalene ring, p and q are preferably 0. p + q is preferably an integer of 0 to 3, and 0 to 2 is more preferred. r + s is preferably an integer of 1 to 3, and 1 or 2 is more preferred, and 1 is even more preferred.

[0062] ((Compound Represented by Formula (2))) As the compound represented by formula (1), a compound represented by formula (2) is preferred.

[0063]

[0064] In formula (2), R ６ represents an alkyl group which may have a substituent. ７ represents a halogen atom. Ａ and R Ｂ each independently represents an alkyl group which may have a substituent or an aryl group which may have a substituent. Q represents a benzene ring or a naphthalene ring. t and u each independently represent an integer of 0 to 4, provided that t + u is an integer of 0 to 4.

[0065] R ６ represents an alkyl group which may have a substituent. The alkyl group includes R １ The same definition and preferred range are also the same.

[0066] R ７ represents a halogen atom. ７ is R in formula (1). ２ The same definition and preferred range are also the same.

[0067] R Ａ and R Ｂ each independently represents an alkyl group which may have a substituent or an aryl group which may have a substituent. Q represents a benzene ring or a naphthalene ring. Ａ , R Ｂ and Q are R in the above formula (1), respectively. Ａ , R Ｂ and Q have the same meanings and preferred ranges.

[0068] t and u each independently represent an integer of 0 to 4. However, t + u is an integer of 0 to 4. t is preferably an integer of 0 to 2. u is preferably an integer of 0 to 1. Furthermore, when Q represents a naphthalene ring, t and u are preferably 0. t + u is preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0069] The specific compounds include the following compounds.

[0070]

[0071] The microcapsules may contain other color formers in addition to the specific compound. The other color formers are not particularly limited as long as they are color formers other than the specific compound, and include color formers known for use in pressure-sensitive copying paper or thermal recording paper.

[0072] As the other color former, the compound represented by formula (D) is preferred in terms of excellent visibility.

[0073]

[0074] In formula (D), R Ｄ１ and R Ｄ３ R each independently represents a hydrogen atom, an alkyl group which may have a substituent, or an aryl group which may have a substituent. Ｄ１ and R Ｄ３ The number of carbon atoms in the alkyl group represented by the formula (I) is preferably 1 to 10, more preferably 1 to 5. The number of carbon atoms in the aryl group is preferably 6 to 20, more preferably 6 to 10. Examples of the substituent that the alkyl group and the aryl group may have include the groups exemplified above for the substituent T, and R Ｄ１ and R Ｄ３ are each independently preferably an alkyl group which may have a substituent or an aryl group which may have a substituent, more preferably an alkyl group which may have a substituent, and still more preferably an unsubstituted alkyl group.

[0075] R Ｄ２ and R Ｄ４ R each independently represents an alkyl group which may have a substituent, or an aryl group which may have a substituent. Ｄ２ and R Ｄ４ The number of carbon atoms in the alkyl group represented by R is preferably 1 to 10, and more preferably 1 to 5. Ｄ２ and R Ｄ４The aryl group represented by the formula (I) may be either monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 20, more preferably 6 to 10. Examples of the substituent that the alkyl group and the aryl group may have include the groups exemplified above for the substituent T. Among these, R Ｄ２ and R Ｄ４ Each of the alkyl groups is preferably an alkyl group which may have a substituent, and more preferably an unsubstituted alkyl group.

[0076] Among them, R Ｄ１ ~R Ｄ４ are preferably all unsubstituted alkyl groups, and more preferably the same unsubstituted alkyl groups.

[0077] R Ｄ５ is —O— or —NR Ｄ６ Among them, -NR Ｄ６ - is preferred. Ｄ６ represents an alkyl group which may have a substituent, or an aryl group which may have a substituent. Ｄ６ The number of carbon atoms in the alkyl group represented by R is preferably 1 to 10, more preferably 1 to 5. The number of carbon atoms in the aryl group is preferably 6 to 20, more preferably 6 to 10. Ｄ６ The aryl group represented by the formula (I) may have a monocyclic structure or a polycyclic structure. Examples of the substituent that the alkyl group and the aryl group may have include the groups exemplified above as the substituent T. Among them, R Ｄ６ As the alkyl group, an aryl group which may have a substituent is preferable, an aryl group substituted with a group selected from the group consisting of a halogen atom, a cyano group, a nitro group, and a carboxyl group is more preferable, and an aryl group substituted with a nitro group is even more preferable.

[0078] The molecular weight of the compound represented by formula (D) is not particularly limited, but is preferably 300 or more, more preferably 500 or more. The upper limit is not particularly limited, but is preferably 2000 or less, more preferably 1000 or less.

[0079] Other color formers include, for example, triphenylmethane phthalide compounds, fluoran compounds, phenothiazine compounds, indolylphthalide compounds, azaindolylphthalide compounds, leucoauramine compounds, rhodamine lactam compounds, triphenylmethane compounds, diphenylmethane compounds, triazene compounds, spiropyran compounds, and fluorene compounds. Other color formers include, for example, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-n-octyl-2-methylindol-3-yl)phthalide, 3-[2,2-bis(1-ethyl-2-methylindol-3-yl)vinyl]-3-(4-diethylaminophenyl)-phthalide, 2-anilino-6-dibutylamine Examples of the compounds include 2-(2-chloroanilino)-6-dibutylaminofluoran, 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide, 2-anilino-6-diethylamino-3-methylfluoran, and 3',6'-bis(diethylamino)-2-(4-nitrophenyl)spiro[isoindole-1,9'-xanthene]-3-one. For details of the above compounds, reference can be made to the description in JP-A-5-257272.

[0080] The molecular weight of the color former is often not less than 300. The upper limit is often not more than 1000, and is preferably not more than 600 in terms of achieving better effects of the present invention.

[0081] The color former may be used alone or in combination of two or more. The content of the color former in the first layer is 0.1 to 10 g / m ２ is preferred, and 0.1 to 4 g / m ２ The content of the specific compound is preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 50% by mass or more, based on the total mass of the color former, and particularly preferably 70% by mass or more in terms of excellent light resistance after color development. The upper limit is preferably 100% by mass or less, based on the total mass of the color former.

[0082] (Other Components) The microcapsules may contain other components in addition to the color former described above. Examples of other components include solvents and additives such as ultraviolet absorbers, light stabilizers, antioxidants, waxes, and odor suppressants, with solvents being preferred. The ultraviolet absorber is preferably a compound having a benzotriazole structure. From the perspective of improving the solubility of the color former, the solvent preferably contains an aromatic solvent. Examples of solvents include aromatic hydrocarbons such as alkylnaphthalene compounds such as diisopropylnaphthalene, diarylalkane compounds such as 1-phenyl-1-xylylethane, alkylbiphenyl compounds such as isopropylbiphenyl, triarylmethane compounds, alkylbenzene compounds, benzylnaphthalene compounds, diarylalkylene compounds, and arylindane compounds; aliphatic hydrocarbons such as dibutyl phthalate and isoparaffin; natural animal and vegetable oils such as soybean oil, corn oil, cottonseed oil, rapeseed oil, olive oil, palm oil, castor oil, and fish oil, and high-boiling fractions of natural products such as mineral oils.

[0083] The solvent may be used alone or in combination of two or more. When a solvent is encapsulated in the microcapsules, the mass ratio of the mass of the color former to the mass of the solvent (mass of solvent / mass of color former) is preferably 98 / 2 to 30 / 70, more preferably 97 / 3 to 40 / 60, from the viewpoint of color development.

[0084] <Method for producing microcapsules> The method for producing microcapsules containing a color former is not particularly limited, and includes known methods such as interfacial polymerization, internal polymerization, phase separation, external polymerization and coacervation, among others.Preferably, the interfacial polymerization method is a preferred interfacial polymerization method.Preferably, the interfacial polymerization method includes the following steps: dispersing an oil phase containing a color former and a capsule wall material (e.g., a raw material containing polyisocyanate and at least one selected from the group consisting of polyol and polyamine. Note that, when polyamine is produced in the system by reacting polyisocyanate with water, polyol and polyamine may not be used) into an aqueous phase containing an emulsifier to prepare an emulsion (emulsification step); and polymerizing the capsule wall material at the interface between the oil phase and the aqueous phase to form a capsule wall, thereby forming a microcapsule containing a color former (encapsulation step). The mass ratio of the total amount of polyol and polyamine to the amount of polyisocyanate in the raw materials (total amount of polyol and polyamine / amount of polyisocyanate) is not particularly limited, but is preferably 0.1 / 99.9 to 30 / 70, and more preferably 1 / 99 to 25 / 75. As mentioned above, the polyisocyanate may be a combination of the polyisocyanate A and polyisocyanate B. When both are used in combination, the preferred range of the mixing ratio between them is as mentioned above.

[0085] The type of emulsifier used in the emulsification step is not particularly limited, but examples thereof include dispersants and surfactants. Examples of dispersants include polyvinyl alcohol.

[0086] The first layer may contain other components in addition to the microcapsules described above. Examples of other components include polymer binders, inorganic fillers (e.g., colloidal silica), fluorescent brighteners, antifoaming agents, penetrants, UV absorbers, surfactants, and preservatives. Examples of polymer binders include synthetic and natural polymers such as styrene-butadiene copolymers, polyvinyl acetate, polyacrylic acid esters, polyvinyl alcohol, polyacrylic acid, maleic anhydride-styrene copolymers, starch, casein, gum arabic, gelatin, carboxymethyl cellulose or its salts, and methyl cellulose. The content of the polymer binder is not particularly limited, but is preferably 0 to 50% by mass relative to the total mass of the first layer. From the viewpoint of suitability for low-pressure regions of 20 MPa or less, a content of 0.1 to 20% by mass is preferred, and 0.2 to 10% by mass is more preferred. Examples of surfactants include anionic surfactants, nonionic surfactants, and cationic surfactants. Anionic or nonionic surfactants are preferred from the viewpoint of maintaining the dispersibility of the microcapsules. Examples of surfactants include fluorine-based surfactants, silicone-based surfactants, and hydrocarbon-based surfactants, with hydrocarbon-based surfactants being preferred in terms of maintaining coatability and dispersibility of the microcapsules. The content of the surfactant is not particularly limited, but is preferably 0.01 to 10% by mass, and more preferably 0.1 to 5% by mass, relative to the total mass of the first layer.

[0087] The inorganic filler is preferably incorporated to facilitate peeling of the first and second sheets after the sheets are stacked and the heating and pressure measurement is performed. Silica particles or alumina particles are preferred as the inorganic filler in order to facilitate peeling of the first and second sheets. The median diameter of the inorganic filler is preferably 0.001 to 1 μm, more preferably 0.005 to 0.1 μm, and even more preferably 0.005 to 0.05 μm. The content of the inorganic filler is preferably 1 to 50% by mass, more preferably 3 to 30% by mass, and more preferably 5 to 20% by mass, relative to the total mass of the first layer.

[0088] The thickness of the first layer is not particularly limited, but is preferably 0.01 to 5 μm, and more preferably 0.02 to 3 μm. Here, the thickness of the first layer means the thickness excluding the microcapsules exposed from the layer surface when the average particle size of the microcapsules is larger than the layer thickness. If the thickness of the first layer is within the above range, aggregation of the microcapsules can be suppressed when the first layer-forming composition containing the microcapsules is applied and then dried, and the thickness can be adjusted so that the capsules break at a desired pressure. The thickness of the first layer is preferably 50% or less, and more preferably 25% or less, of the average particle size of the microcapsules. The thinner the thickness of the first layer is compared to the microcapsules, the more easily the microcapsules break, so the thickness can be adjusted according to the pressure range to be measured. In addition, the mass per unit area of ​​the first layer (g / m ２ ) is not particularly limited, but is preferably 0.5 to 20 g / m ２ is preferred.

[0089] [Method for Forming First Layer] The method for forming the first layer is not particularly limited, and known methods can be used. For example, a method can be used in which a composition for forming a first layer containing microcapsules is applied to a first support and, if necessary, dried. The composition for forming the first layer can be a dispersion in which microcapsules are dispersed in water or the like. A dispersion in which microcapsules are dispersed can be prepared by mechanically dispersing the microcapsules in water or the like. The composition for forming the first layer preferably contains at least microcapsules and a solvent. Note that the microcapsule dispersion obtained by the interfacial polymerization method described above can also be used as the composition for forming the first layer. The composition for forming the first layer can also contain other components that can be contained in the first layer described above.

[0090] The method for applying the composition for forming the first layer is not particularly limited, but examples of coating machines used for application include an air knife coater, a rod coater, a bar coater, a curtain coater, a gravure coater, an extrusion coater, a die coater, a slide bead coater, and a blade coater.

[0091] After the first layer-forming composition is applied to the first support, the coating may be subjected to a drying treatment, such as a heating treatment, if necessary.

[0092] Although the method of forming the first layer on the first support has been described above, the present invention is not limited to the above embodiment. For example, the first layer may be formed on the temporary support, and then the temporary support may be peeled off to form a first sheet made of the first layer. The temporary support is not particularly limited as long as it is a peelable support.

[0093] <Other Members> The first sheet may include other members in addition to the members described above. For example, the first sheet may include an adhesion layer between the first support and the first layer to enhance adhesion between them. The adhesion layer is not particularly limited, but is preferably a layer containing a resin. The thickness of the adhesion layer is preferably 0.005 to 5 μm, more preferably 0.01 to 1 μm.

[0094] 1 has a second support 18 and a second layer 20 containing a developer disposed on the second support 18. The preferred ranges of the heat shrinkage rates Sc1 and Sc2 of the second sheet are the same as the preferred ranges of the heat shrinkage rates Sa1 and Sa2 of the first sheet, respectively.

[0095] The method for measuring the thermal shrinkage rates Sc1 and Sc2 of the second sheet is the same as the method for measuring the thermal shrinkage rates Sa1 and Sa2 of the first sheet, except that the second sheet is used instead of the first sheet. The definitions of the longitudinal direction and width direction of the second sheet are the same as those of the first sheet, except that the first sheet is read as the second sheet. The second sheet may be a single sheet (single sheet) or may be long. Each component will be described in detail below.

[0096] [Second Support] The second support is a member for supporting the second layer. The configuration of the second support is the same as the configuration of the first support described above, and therefore a description thereof will be omitted.

[0097] [Second Layer] The second layer is a layer containing a color developer. A color developer is a compound that does not have a color-forming function by itself but has the property of causing a color former to develop color upon contact with the color former. An electron-accepting compound is preferred as the color developer. Examples of the color developer include inorganic and organic compounds. Examples of inorganic compounds include clay substances such as acid clay, activated clay, attapulgite, zeolite, bentonite, and kaolin. Examples of organic compounds include metal salts of aromatic carboxylic acids, phenol-formaldehyde resins, and metal salts of carboxylated terpene phenol resins.

[0098] Examples of metal salts of aromatic carboxylic acids include 3,5-di-t-butylsalicylic acid, 3,5-di-t-octylsalicylic acid, 3,5-di-t-nonylsalicylic acid, 3,5-di-t-dodecylsalicylic acid, 3-methyl-5-t-dodecylsalicylic acid, 3-t-dodecylsalicylic acid, 5-t-dodecylsalicylic acid, 5-cyclohexylsalicylic acid, 3,5-bis(α,α-dimethylbenzyl)salicylic acid, 3-methyl-5-(α-methylbenzyl)salicylic acid, and 3-(α,α-dimethylbenzyl)-5-methylsalicylic acid.

[0039] Preferred are zinc, nickel, aluminum, or calcium salts of salicylic acid, 3-(α,α-dimethylbenzyl)-6-methylsalicylic acid, 3-(α-methylbenzyl)-5-(α,α-dimethylbenzyl)salicylic acid, 3-(α,α-dimethylbenzyl)-6-ethylsalicylic acid, 3-phenyl-5-(α,α-dimethylbenzyl)salicylic acid, a carboxy-modified terpene phenol resin, or a salicylic acid resin which is a reaction product of 3,5-bis(α-methylbenzyl)salicylic acid with benzyl chloride.

[0099] Among these, as the color developer, clay substances, metal salts of aromatic carboxylic acids, or metal salts of carboxylated terpene phenol resins are preferred, clay substances or metal salts of aromatic carboxylic acids are more preferred, and clay substances are even more preferred in terms of the excellent effects of the present invention, with acid clay, activated clay, or kaolin being particularly preferred.

[0100] The content of the color developer in the second layer is preferably 20 to 95% by mass, more preferably 30 to 90% by mass, based on the total mass of the second layer, in terms of achieving excellent effects of the present invention.

[0101] The content of the developer in the second layer is 0.1 to 30 g / m ２ When the color developer is an inorganic compound, the content of the color developer in the second layer is preferably 3 to 20 g / m ２ is preferred, and 5 to 15 g / m ２ When the color developer is an organic compound, the content of the color developer in the second layer is preferably 0.1 to 5 g / m ２ is preferred, and 0.2 to 3 g / m ２ is more preferred.

[0102] The second layer may contain other components in addition to the above-mentioned color developer. Examples of such other components include polymer binders, pigments, fluorescent brighteners, antifoaming agents, penetrants, UV absorbers, surfactants, and preservatives. Examples of polymer binders include synthetic polymers and natural polymers such as styrene-butadiene copolymers, polyvinyl acetate, polyacrylic acid esters, polyvinyl alcohol, polyacrylic acid, maleic anhydride-styrene copolymers, starch, casein, gum arabic, gelatin, carboxymethyl cellulose, and methyl cellulose. Examples of pigments include heavy calcium carbonate, light calcium carbonate, talc, and titanium dioxide.

[0103] The thickness of the second layer is preferably 1 to 50 μm, more preferably 2 to 30 μm, in terms of excellent effects of the present invention. ２ ) is 0.5 to 20 g / m ２ is preferred.

[0104] [Method for Forming Second Layer] The method for forming the second layer is not particularly limited, and known methods can be used. For example, a method can be used in which a second layer-forming composition containing a developer is applied to the second support and, if necessary, dried. The second layer-forming composition can be a dispersion in which the developer is dispersed in water or the like. If the developer is an inorganic compound, the dispersion in which the developer is dispersed can be prepared by mechanically dispersing the inorganic compound in water. If the developer is an organic compound, the dispersion can be prepared by mechanically dispersing the organic compound in water or dissolving it in an organic solvent. The second layer-forming composition can also contain other components that can be contained in the second layer described above.

[0105] The method for applying the second layer forming composition is not particularly limited, but examples include a method using the coater used when applying the first layer forming composition described above.

[0106] After the second layer-forming composition is applied to the second support, the coating may be subjected to a drying treatment, such as a heating treatment, if necessary.

[0107] Although the method of forming the second layer on the second support has been described above, the present invention is not limited to the above embodiment. For example, after forming the second layer on the temporary support, the temporary support may be peeled off to form a second sheet made of the second layer. The temporary support is not particularly limited as long as it is a peelable support.

[0108] As described above, the first sheet and the second sheet are used by laminating the first sheet and the second sheet so that the first layer of the first sheet faces the second layer of the second sheet to obtain a laminate, and then applying pressure to the laminate. In other words, the first sheet corresponds to a sheet used to measure pressure together with the second sheet. The L of the colored portion when coloring is caused by applying pressure to the laminate is ＊ a ＊ b ＊ The chromaticity in the color system is not particularly limited, but from the viewpoint of ease of visual recognition of the color development, chromaticity a ＊ is preferably more than 30 and not more than 80, and the chromaticity b ＊is preferably greater than -50 and equal to or less than 50. When measuring the chromaticity, the first sheet and the second sheet of the laminate are peeled off after pressure is applied, and the chromaticity of the color-developing portion of the second sheet is measured using a densitometer RD-19 (manufactured by GretagMacbeth). When the second sheet includes a transparent second support and the chromaticity of the color-developing portion can be measured from the second support side, the chromaticity of the color-developing portion may be measured from the second support side.

[0109] <Other Components> The second sheet may include other components in addition to the components described above. For example, the second sheet may include an adhesion layer between the second support and the second layer to enhance adhesion between them. Examples of the adhesion layer include the adhesion layer that may be included in the first sheet described above.

[0110] [Second embodiment] Figure 3 is a cross-sectional view of one embodiment of a pressure measurement sheet. The pressure measurement sheet 30 has, in this order, a support 32, a second layer 20 containing a color developer, and a first layer 14 containing predetermined microcapsules 13. When using the pressure measurement sheet 30, pressure is applied from at least one of the support 32 side and the first layer 14 side, causing the microcapsules 13 to break in the pressurized areas, releasing the color former encapsulated in the microcapsules 13 and causing a color-developing reaction between the microcapsules 13 and the color developer in the second layer 20. As a result, color is developed in the pressurized areas.

[0111] As will be described later, the pressure measurement sheet 30 may have the first layer 14 and the second layer 20, and may not have the support 32. Furthermore, in FIG. 3, the support 32 and the second layer 20 are directly laminated together, but this is not a limitation. As will be described later, another layer (e.g., an adhesive layer) may be disposed between the support 32 and the second layer 20. Furthermore, in FIG. 3, the pressure measurement sheet 30 is shown having the support 32, the second layer 20, and the first layer 14 in this order, but this is not a limitation. The pressure measurement sheet may also have the support 32, the first layer 14, and the second layer 20 in this order.

[0112] When the pressure measurement sheet is heated at 220° C. for 10 minutes, it is preferable that the heat shrinkage rate Sb1 in the longitudinal direction of the pressure measurement sheet and the heat shrinkage rate Sb2 in the width direction perpendicular to the longitudinal direction of the pressure measurement sheet 22 are both −0.5 to 3.0%. The methods for measuring the heat shrinkage rates Sb1 and Sb2 of the pressure measurement sheet are the same as the methods for measuring the heat shrinkage rates Sa1 and Sa2 of the first sheet described above, except that the measurement object is changed to a pressure measurement sheet.

[0113] The first layer 14 and the second layer 20 in the pressure measurement sheet 30 are the same materials as the first layer 14 and the second layer 20 described in the first embodiment, and therefore a description thereof will be omitted. The following mainly describes the support 32 in detail.

[0114] [Support] The support is a member for supporting the first layer and the second layer. Note that if the laminate of the first layer and the second layer itself can be handled, the pressure measurement sheet does not need to have a support. The preferred embodiment of the support is the same as the preferred embodiment of the first support described above, and therefore, description thereof will be omitted.

[0115] [Method for manufacturing pressure measurement sheet] The method for manufacturing the pressure measurement sheet is not particularly limited, and known methods can be used. For example, a method can be used in which a second layer-forming composition containing a color developer is applied to a support, and if necessary, a drying treatment is performed to form a second layer on the support, and then a first layer-forming composition containing predetermined microcapsules is applied to the second layer, and if necessary, a drying treatment is performed to form a first layer. The method for forming the microcapsules is as described above. The method for forming the first layer using the first layer-forming composition is as described in the first embodiment. The method for forming the second layer using the second layer-forming composition is also as described in the first embodiment.

[0116] <Other Components> The pressure measurement sheet may include other components in addition to the components described above. For example, the pressure measurement sheet may have an adhesive layer between the support and the second layer to enhance adhesion between them. Examples of the adhesive layer include the adhesive layer that may be included in the first sheet described above.

[0117] [Uses] The pressure measurement sheet set of the present invention can be used for various purposes, for example, to verify or manage various manufacturing processes that include high-temperature pressing. More specifically, it can be used to check the pressure distribution in the lamination process in the field of batteries (lithium ion batteries, fuel cells), the lamination process in the field of printed wiring boards (FPC, BWB), the pressure distribution in thermocompression bonding processes such as ACF bonding and lamination of wiring extraction parts, and the pressure distribution in mold clamping parts.

[0118] [Third embodiment] The third embodiment includes a dispersion liquid (hereinafter also simply referred to as "first dispersion liquid") containing microcapsules encapsulating a color former, which is used to form a layer to be used in combination with a layer containing a color developer (dispersion liquid for forming a pressure measurement layer).

[0119] [First Dispersion] The first dispersion is a dispersion of microcapsules containing microcapsules encapsulating a color former containing a specific compound, and the thermal decomposition temperature of the capsule walls of the microcapsules is 250°C or higher. The components contained in the first dispersion are synonymous with the components contained in the first layer described above, and the preferred ranges are also the same. Examples of the first dispersion include the first layer-forming composition described above. The first dispersion preferably contains a solvent. Examples of solvents contained in the first dispersion include water and organic solvents. The first dispersion, like the first layer-forming composition, is used to form a layer used for pressure measurement (corresponding to the first layer described above).

[0120] [Second Dispersion] The first dispersion may be used in combination with a dispersion used to form a layer containing a developer (hereinafter simply referred to as "second dispersion"). In other words, the first dispersion and the second dispersion may be used as a set (dispersion set). The second dispersion is a dispersion containing a developer. The components contained in the second dispersion are synonymous with the components contained in the second layer described above, and the preferred ranges are also the same. Examples of the second dispersion include the second layer-forming composition described above. The second dispersion preferably contains a solvent. Examples of the solvent contained in the second dispersion include water and organic solvents.

[0121] From the viewpoint of preventing clogging when the first dispersion is applied by spraying or the like, it is preferable that the first dispersion does not contain coarse particles. From the above viewpoint, the volume-based median diameter (D50) of the microcapsules is preferably 1 to 80 μm, more preferably 5 to 70 μm, and even more preferably 10 to 50 μm. From the above viewpoint, it is preferable that the second dispersion does not contain coarse particles. From the above viewpoint, the color developer contained in the second dispersion is preferably an organic compound. As the organic compound, a metal salt of an aromatic carboxylic acid is preferable, a metal salicylate is more preferable, and a zinc salicylate is even more preferable.

[0122] The first dispersion can be applied to objects for which pressure measurement is difficult using a pressure measurement sheet set or the like. More specifically, pressure measurement is made possible by applying only the required amount of the first dispersion to the area of ​​the pressure measurement object where pressure measurement is required, and forming a layer containing the microcapsules in that area, regardless of the surface shape of the pressure measurement object. This is particularly suitable for measuring pressure on curved surfaces.

[0123] [Fourth Embodiment] An example of a fourth embodiment is a dispersion (hereinafter also referred to simply as "third dispersion") (pressure measurement layer-forming dispersion) containing microcapsules encapsulating a color former and a color developer, which is used to form a layer for pressure measurement. The components contained in the third dispersion are synonymous with the components contained in the first or second layer described above, and the preferred ranges are also the same. Examples of the microcapsules contained in the third dispersion include those contained in the first layer-forming composition. Examples of the color developer contained in the third dispersion include those contained in the second layer-forming composition. The third dispersion preferably contains a solvent. Examples of the solvent contained in the third dispersion include water and an organic solvent. Examples of the third dispersion include a dispersion in which the color developer is mixed with the first layer-forming composition described above, and a dispersion in which the second layer-forming composition described above is mixed with the first layer-forming composition described above.

[0124] From the viewpoint of preventing clogging when the first dispersion is applied by spraying or the like, it is preferable that the third dispersion does not contain coarse particles. From the viewpoint mentioned above, the volume-based median diameter (D50) of the microcapsules is preferably 1 to 50 μm. From the viewpoint mentioned above, the color developer contained in the third dispersion is preferably an organic compound. As the organic compound, a metal salt of an aromatic carboxylic acid is preferable, a metal salicylate is more preferable, and a zinc salicylate is even more preferable.

[0125] Because the third dispersion contains microcapsules encapsulating a color former and a developer, pressure measurement becomes possible using only the layer formed by applying the third dispersion. In other words, the third dispersion can be applied to objects for which pressure measurement is difficult using sheets such as pressure measurement sheet sets and pressure measurement sheets, as with the first and second dispersions. More specifically, pressure measurement becomes possible by applying only the required amount of the third dispersion to an area of ​​the pressure measurement object where pressure measurement is required and forming a layer in that area, regardless of the surface shape of the pressure measurement object.

[0126] The first, second, and third dispersions described above are primarily used for pressure measurement during automobile manufacturing, high-temperature heat pressing, heat pressing, bonding, and the like, but can also be used for a variety of other applications, including confirmation of pressure distribution during molding or assembly of various components, bodies, and the like, in the manufacture of vehicles such as automobiles or aircraft, confirmation of pressure distribution during assembly of building materials, confirmation of pressure distribution during curved surface processing of electronic products, confirmation of impact force applied to cargo during transportation, confirmation of mold contact in the manufacture of metal products, confirmation of mold contact during molding of resin products, confirmation of pressure distribution during tablet compression of pharmaceuticals, confirmation of pressure distribution on furniture surfaces such as sofa seats, confirmation of pressure in stationery such as checking the grip force applied to writing implements, confirmation of impact force applied to sports goods such as balls made of elastic material, and confirmation of gaps (clearance) between upper and lower teeth in dental products.

[0127] The present invention will be described in more detail below based on examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the examples shown below. In the following, "parts" and "%" are based on mass unless otherwise specified.

[0128] [Example 1] [Preparation of color former-encapsulating microcapsules] 1,1-diphenylethane (JXTG Energy Corporation, SAS-296) (50 parts by mass) was dissolved in 3',6'-bis(diethylamino)-2-(4-nitrophenyl)spiro[isoindole-1,9'-xanthene]-3-one (Hodogaya Chemical Co., Ltd., Pink-DCF) (3 parts by mass) as a color former, 6'-(diethylamino)-1',3'-dimethylfluoran (Hodogaya Chemical Co., Ltd., Orange-DCF) (4 parts by mass) and 2-(2'-hydroxy-5'-methylphenyl)benzotriazole (Johoku Chemical Co., Ltd., JF-77-P) (3 parts by mass) as an ultraviolet absorber to obtain solution A. Next, synthetic isoparaffin (Idemitsu Kosan Co., Ltd., IP Solvent 1620) (13 parts by mass) was added to the stirred solution A to obtain solution B. Furthermore, a trimethylolpropane adduct of tolylene diisocyanate (DIC Corporation, Burnock D-750, solids concentration 75% by mass) (1.6 parts by mass) dissolved in ethyl acetate (6 parts by mass) and Millionate MR-200 (Tosoh Corporation) (3.7 parts by mass) were added to the stirred solution B to obtain solution C. Millionate MR-200 is a mixture of diphenylmethane diisocyanate and polymethylene polyphenyl polyisocyanate. Then, the above solution C was added to a solution obtained by dissolving polyvinyl alcohol (JP-45, Japan Acetate & Poval Co., Ltd.) (4 parts by mass) in water (140 parts by mass), and emulsified and dispersed. Water (200 parts by mass) was added to the emulsion after emulsification and dispersion, heated to 70 ° C. with stirring, stirred for 1 hour, and then cooled. Further, water was added to adjust the concentration, and a color former-encapsulated microcapsule solution with a solids concentration of 25% was obtained. The volume-based median diameter (D50) of the obtained color former-encapsulating microcapsules was 20 μm. The volume-based median diameter (D50) was measured using an optical microscope by the method described above.

[0129] [Preparation of pressure measurement sheet set] <Preparation of first sheet> A color former-encapsulating microcapsule liquid (solid content concentration 25%) (43 parts by mass), water (15 parts by mass), colloidal silica (Nissan Chemical Industries, Ltd., Snowtex (registered trademark) 30, solid content concentration 30%) (5.7 parts by mass), a 10% by mass aqueous solution of Polymaron 482 (Arakawa Chemical Industries, Ltd.) (1.8 parts by mass), a 10% by mass aqueous solution of carboxymethylcellulose Na (Dai-ichi Kogyo Seiyaku Co., Ltd., Cellogen EP) (24 parts by mass), a 1% by mass aqueous solution of Rapisol A-90 (NOF Corporation) (0.7 parts by mass), and a 1% by mass aqueous solution of Noigen LP-70 (Dai-ichi Kogyo Seiyaku Co., Ltd., polyoxyalkylene alkyl ether surfactant) (0.7 parts by mass) were mixed and stirred for 2 hours to obtain a first layer-forming composition.

[0130] Furthermore, an adhesion layer-forming composition containing styrene butadiene latex was applied and dried on a 75 μm-thick polyethylene naphthalate sheet (Teonex (registered trademark) Q53, manufactured by Teijin Film Solutions Co., Ltd.) serving as a first support, forming an adhesion layer having a thickness of 100 nm on the first support, thereby obtaining a first support having an adhesion layer. The above-mentioned first layer-forming composition was applied on the adhesion layer of the obtained first support having an adhesion layer using a bar coater, and dried to form a first layer of approximately 500 nm, thereby producing a first sheet.

[0131] <Preparation of second sheet> A dispersion liquid was prepared by dispersing, using a sand grinder, sulfuric acid-treated activated clay (200 parts by mass) as a color developer, sodium hexametaphosphate (1 part by mass), a 10% by mass aqueous solution of sodium hydroxide (30 parts by mass), and water (290 parts by mass) so that the average particle size of all particles was 2 μm. Next, the resulting dispersion was mixed with 180 parts by mass of a 19% by mass aqueous dispersion of Nippol LX-814 (manufactured by Zeon Corporation), 220 parts by mass of a 3.3% by mass aqueous solution of Polymaron 482 (manufactured by Arakawa Chemical Industries, Ltd.), 80 parts by mass of a 1% by mass aqueous solution of carboxymethylcellulose Na (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., Cellogen EP), 4.7 parts by mass of a 15% by mass aqueous solution of sodium alkylbenzene sulfonate (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., Neogen T), and 70 parts by mass of a 1% by mass aqueous solution of Noigen LP70 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., polyoxyalkylene alkyl ether surfactant), to obtain a composition for forming a second layer. The composition for forming the second layer was applied to a 75 μm-thick polyethylene naphthalate sheet (manufactured by Teijin Film Solutions Co., Ltd., Teonex (registered trademark) Q53) as a second support in a solids amount of 12.0 g / m. ２ and dried to form a second layer, thereby obtaining a second sheet.

[0132] [Examples 2 to 24, Comparative Examples 1 and 2, Reference Examples 1 and 2] The first and second sheets of each of the Examples, Comparative Examples, and Reference Examples were produced according to the same procedure as in Example 1, except that various conditions such as the materials and the amounts of each material were changed as shown in Table 1. Comparative Example 1 was produced with reference to Comparative Example 1 described in Patent Document 2. Comparative Example 2 was produced with reference to Example 13 described in Patent Document 3.

[0133] Comparative Example 3 As in the example described in Patent Document 1, Prescale LLW (manufactured by Fujifilm Corporation) was used as the pressure measurement sheet set.

[0134] [Measurement and Evaluation] [High-Temperature Suitability] The first sheet obtained in the above (Preparation of the First Sheet) and the second sheet obtained in the above (Preparation of the Second Sheet) cut to a size of 5 cm x 5 cm were overlapped with the surface of the color-forming layer of the first sheet facing the surface of the color-developing layer of the second sheet to obtain a laminate. The obtained laminate was placed on a hot plate at 200°C, and a 5 mm wide ring-shaped SUS mold was placed on top of the laminate. Measurement was performed at a pressure of 2.5 MPa for a pressure measurement time of 5 seconds. The obtained laminate was removed from the hot plate, and the overlapping first and second sheets were peeled off. The shape of the color-developing region of the second sheet was visually confirmed and evaluated according to the following evaluation criteria. The same procedure as above was used, except that the pressure measurement time was changed to 2 minutes. The shape of the color-developing region of the second sheet was visually confirmed and evaluated according to the following evaluation criteria. (Evaluation criteria) A: In both cases where the pressure measurement time was 5 seconds and 2 minutes, the shape of the colored region was clearly recognizable as a ring shape similar to that of the SUS mold, and no change was observed between the color of the colored region when the pressure measurement time was 5 seconds and the color of the colored region when the pressure measurement time was 2 minutes. B: In both cases where the pressure measurement time was 5 seconds and 2 minutes, the outline of the colored region when pressurized was slightly unclear, but it was recognizable as a ring shape similar to that of the SUS mold, and no change was observed between the color of the colored region when the pressure measurement time was 5 seconds and the color of the colored region when the pressure measurement time was 2 minutes. C: In both cases where the pressure measurement time was 5 seconds and 2 minutes, the outline of the colored region when pressurized was unclear, and although there were some areas where the shape of the colored region was not recognizable as a ring shape similar to that of the SUS mold, it was recognizable as a link shape similar to that of the SUS mold in most areas, and no change was observed between the color of the colored region when the pressure measurement time was 5 seconds and the color of the colored region when the pressure measurement time was 2 minutes. D: In both cases where the pressure measurement time was 5 seconds and 2 minutes, it was not possible to recognize that the colored area had the same link shape as the SUS mold, and a change was observed between the color of the colored area when the pressure measurement time was 5 seconds and the color of the colored area when the pressure measurement time was 2 minutes.

[0135] [Gradation at high temperatures] The first sheet obtained in the above (Preparation of the first sheet) and a second sheet obtained by cutting the second sheet obtained in the above (Preparation of the second sheet) to a size of 5 cm x 5 cm were overlapped with each other so that the surface of the color-forming layer of the first sheet faced the surface of the color-developing layer of the second sheet, and the obtained sheets were pressed using a hot press at a temperature of 200°C and a pressure of 0.5 MPa, 1.5 MPa, or 2.5 MPa to develop color. Next, the overlapping first and second sheets were peeled off, and the density (DA) of the colored portion of the obtained second sheet was measured at each pressure using a densitometer RD-19 (manufactured by GretagMacbeth).

[0136] Separately, the initial density (DB) of an unused second sheet was measured in the same manner as above. The initial density (DB) was then subtracted from the density (DA) of the colored portion at each pressure to determine the color density ΔD, which was then evaluated according to the following evaluation criteria. "B" indicates a practically acceptable range. (Evaluation Criteria) A: ΔD is 0.4 or more at pressures of 0.5 MPa, 1.5 MPa, and 2.5 MPa. B: ΔD is 0.1 or more and less than 0.4 at two of the pressures of 0.5 MPa, 1.5 MPa, and 2.5 MPa. C: ΔD is less than 0.1 at two of the pressures of 0.5 MPa, 1.5 MPa, and 2.5 MPa.

[0137] [Lightfastness after Color Development] The first sheet obtained in the above (Preparation of the First Sheet) and the second sheet obtained in the above (Preparation of the Second Sheet) cut to a size of 5 cm x 5 cm were overlapped with the surface of the color-forming layer of the first sheet facing the surface of the color-developing layer of the second sheet. The resulting sheets were pressed using a hot press at a temperature of 200°C and a pressure of 1.0 MPa to develop color. Next, the overlapping first and second sheets were removed from the hot plate, peeled off, and the image of the colored portion of the second sheet was scanned using an image analysis system FPD-8010J manufactured by FUJIFILM Corporation. The resulting second sheet was then stored at room temperature for one week. The image of the colored portion of the second sheet after storage was then scanned in the same manner, and the image data before and after one week were compared and evaluated according to the following evaluation criteria. (Evaluation Criteria) A: No change in color or density. B: At least one of the color and density changed.

[0138] [Thermal Decomposition Temperature] The thermal decomposition temperature of the capsule wall of the microcapsule was measured by the method described above.

[0139] [Thermal Shrinkage Measurement] Three samples were prepared by cutting the first sheets produced in each Example, Comparative Example, and Reference Example to a length of 150 mm along the longitudinal direction of the first sheet and a length of 20 mm along the transverse direction. Marked lines were marked at position A, approximately 25 mm from the center (starting point) of one short side of the sample toward the center of the other short side, in a direction parallel to the long side. Marked lines were also marked at position B, approximately 25 mm from the center (starting point) of the other short side toward the center of the one short side, in a direction parallel to the long side. The distance between positions A and B (the distance between the marked lines) was 100 mm ± 2 mm. These samples were used to measure the thermal shrinkage Sa1 of the first sheet in the longitudinal direction. The obtained measurement samples were heated at 220°C for 10 minutes, and then returned to room temperature (23°C). The distance between the gauge lines of the measurement samples was measured, and the heat shrinkage rate Sa3 was calculated according to the following formula: Heat shrinkage rate Sa3 [%] = 100 x {(distance between the gauge lines on the measurement sample before heating) - (distance between the gauge lines on the measurement sample after heating)} / (distance between the gauge lines on the measurement sample before heating). The arithmetic average of the heat shrinkage rates Sa3 of the three measurement samples was calculated, and this was designated as the heat shrinkage rate Sa1. The distance between the gauge lines was measured to the nearest 0.1 mm.

[0140] Three samples were prepared by cutting the first sheet produced in each example to a length of 150 mm along the width direction of the first sheet and a length of 20 mm along the longitudinal direction. Then, a marking line was marked on the surface of each sample in the same manner as for the sample for measuring the thermal shrinkage rate Sa1. These samples were used as samples for measuring the thermal shrinkage rate Sa2 in the width direction of the first sheet. The obtained measurement samples were heated at 220°C for 10 minutes, then returned to room temperature (23°C). The distance between the marking lines on the measurement samples was measured, and the thermal shrinkage rate Sa4 was calculated according to the following formula: Thermal shrinkage rate Sa4 [%] = 100 × {(distance between the marking lines on the measurement sample before heating) - (distance between the marking lines on the measurement sample after heating)} / (distance between the marking lines on the measurement sample before heating). The arithmetic average of the thermal shrinkage rates Sa4 of the three measurement samples was calculated, and this was designated as the thermal shrinkage rate Sa2. The distance between the marking lines was measured to the nearest 0.1 mm. In all examples, when the first sheet was heated at 220°C for 10 minutes, the heat shrinkage rate Sa1 in the longitudinal direction of the first sheet and the heat shrinkage rate Sa2 in the width direction of the first sheet perpendicular to the longitudinal direction were both in the range of -0.5 to 3.0.

[0141] In Table 1, each material is as follows: [Various materials] [Resin] Polyurethane urea Melamine resin

[0142] <Wall Material A> D-750: Trimethylolpropane adduct of tolylene diisocyanate (manufactured by DIC Corporation, Burnock D-750, solid content concentration 75% by mass), corresponding to Polyisocyanate A. Melamine

[0143] <Wall Material B> MR-200: Millionate MR-200 (manufactured by Tosoh Corporation), which corresponds to Polyisocyanate B. Formaldehyde

[0144] [Color former] <Specific compounds> Orange-DCF: the following compound (6'-(diethylamino)-1',3'-dimethylfluoran, manufactured by Hodogaya Chemical Co., Ltd.) RED500: the following compound RED520: the following compound RED550: the following compound

[0145]

[0146] <Other color formers> Pink-DCF: the following compound (3',6'-bis(diethylamino)-2-(4-nitrophenyl)spiro[isoindole-1,9'-xanthene]-3-one, manufactured by Hodogaya Chemical Co., Ltd.) Color former A: 3,3-bis(2-methyl-1-octyl-3-indolyl)phthalide Color former B: the following compound

[0147]

[0148] In Table 1, the column "Mass ratio (A) / (B)" indicates the mass ratio of the mass of wall material A to the mass of wall material B (mass of wall material A / mass of wall material B). The compounds listed in the column "Specific compound (a)" indicate compounds that fall under the compound represented by formula (1). The compounds listed in the column "Other color former (b)" indicate color formers that do not fall under the compound represented by formula (1). The column "Mass ratio (a) / (b)" indicates the mass ratio of the mass of specific compound (a) to the mass of other color formers (b) (mass of specific compound (a) / mass of other color formers (b)).

[0149]

[0150] As shown in Table 1, it was confirmed that the desired effects were obtained when the pressure measurement sheet set of the present invention was used. A comparison of Examples 1 to 6 confirmed that the effects of the present invention were superior when the thermal decomposition temperature of the capsule wall was above 250°C, and even superior when the thermal decomposition temperature of the capsule wall was 260°C or higher. A comparison of Examples 6 to 10 confirmed that when the content of the specific compound was 70% by mass or more relative to the total mass of the color former, light resistance after color development was excellent. A comparison of Examples 6 and 12 to 16 confirmed that the effects of the present invention were superior when the capsule wall thickness of the microcapsules was 80 to 300 nm. Furthermore, a similar comparison confirmed that when the capsule wall thickness of the microcapsules was 80 to 250 nm, gradation at high temperatures was excellent, and when it was 100 to 200 nm, gradation at high temperatures was even better.

[0151] REFERENCE SIGNS LIST 10 Pressure measurement sheet set 12 First support 14 First layer 16 First sheet 18 Second support 20 Second layer 22 Second sheet 30 Pressure measurement sheet 32 ​​Support 20 Second layer 22 Second sheet 30 Pressure measurement sheet 32 ​​Support

Claims

1. A pressure measurement sheet set comprising a first sheet having a first layer containing microcapsules encapsulating a color former, and a second sheet having a second layer containing a developer, wherein the color former contains a compound represented by formula (1), and a pressure measurement sheet set in which a thermal decomposition temperature of a capsule wall of the microcapsules is 250° C. or higher. In formula (1), R １ represents an alkyl group which may have a substituent. R ３ is —NR Ａ R Ｂ represents. R Ａ and R Ｂ each independently represent an alkyl group which may have a substituent or an aryl group which may have a substituent. R ２ and R ４ each independently represent a halogen atom. Q represents a benzene ring or a naphthalene ring. X represents —O— or —NR ５ — represents. R ５ represents an alkyl group which may have a substituent or an aryl group which may have a substituent. p and q each independently represent an integer from 0 to 4. r represents an integer from 1 to 3. s represents an integer from 0 to 3. However, p + q is an integer from 0 to 4, and r + s is an integer from 1 to 4.

2. The pressure measurement sheet set according to claim 1, wherein when the first sheet is heated at 220° C. for 10 minutes, a thermal shrinkage rate Sa1 in the longitudinal direction of the first sheet and a thermal shrinkage rate Sa2 in the width direction orthogonal to the longitudinal direction of the first sheet are both -0.5 to 3.0%.

3. The pressure measurement sheet set according to claim 1 or 2, wherein the capsule wall of the microcapsules contains at least one selected from the group consisting of a polyurethane urea having a polymethylene polyphenylene structure and a melamine resin.

4. The pressure measurement sheet set according to any one of claims 1 to 3, wherein the capsule wall of the microcapsules contains a resin having structure A or structure B. Structure A: A structure formed by reacting an aromatic or alicyclic diisocyanate, a compound having three or more active hydrogen groups in one molecule, and a polymethylene polyphenyl polyisocyanate. Structure B: A structure formed by reacting melamine and formaldehyde.

5. The pressure measurement sheet set according to any one of claims 1 to 4, wherein the thickness of the capsule wall of the microcapsule is 80 to 300 nm.

6. The pressure measurement sheet set according to any one of claims 1 to 5, wherein the content of the compound represented by the formula (1) is 70% by mass or more based on the total mass of the color former.

7. A pressure measurement sheet having a first layer containing microcapsules encapsulating a color former and a second layer containing a developer, wherein the color former contains a compound represented by the formula (1), and the thermal decomposition temperature of the capsule wall of the microcapsule is 250 °C or higher. In the formula (1), R １ represents an alkyl group which may have a substituent. R ３ is -NR Ａ R Ｂ represents. R Ａ and R Ｂ each independently represent an alkyl group which may have a substituent or an aryl group which may have a substituent. R ２ and R ４ each independently represent a halogen atom. Q represents a benzene ring or a naphthalene ring. X represents -O- or -NR ５ -. R ５ represents an alkyl group which may have a substituent or an aryl group which may have a substituent. p and q each independently represent an integer of 0 to 4. r represents an integer of 1 to 3. s represents an integer of 0 to 3. However, p + q is an integer of 0 to 4, and r + s is an integer of 1 to 4.

8. When the pressure measurement sheet is heated at 220 °C for 10 minutes, the thermal shrinkage rate Sb1 in the longitudinal direction of the pressure measurement sheet and the thermal shrinkage rate Sb2 in the width direction orthogonal to the longitudinal direction of the pressure measurement sheet are both -0.5 to 3.0%. The pressure measurement sheet according to claim 7.

9. The pressure measurement sheet according to claim 7 or 8, wherein the capsule wall of the microcapsule contains at least one selected from the group consisting of polyurethane urea having a polymethylene polyphenylene structure and melamine resin.

10. The pressure measurement sheet according to any one of claims 7 to 9, wherein the capsule wall of the microcapsule contains a resin having Structure A or Structure B. Structure A: A structure formed by reacting an aromatic or alicyclic diisocyanate, a compound having three or more active hydrogen groups in one molecule, and a polymethylene polyphenyl polyisocyanate. Structure B: A structure formed by reacting melamine and formaldehyde.

11. The pressure measurement sheet according to any one of claims 7 to 10, wherein the thickness of the capsule wall of the microcapsule is 80 to 300 nm.

12. The pressure measurement sheet according to any one of claims 7 to 11, wherein the content of the compound represented by the formula (1) is 70% by mass or more based on the total mass of the color former.

13. A microcapsule encapsulating a color former, wherein the color former contains a compound represented by the formula (1), and the thermal decomposition temperature of the capsule wall of the microcapsule is 250 °C or higher. In the formula (1), R １ represents an alkyl group which may have a substituent. R ３ is -NR Ａ R Ｂ represents. R Ａ and R Ｂ each independently represent an alkyl group which may have a substituent or an aryl group which may have a substituent. R ２ and R ４ each independently represent a halogen atom. Q represents a benzene ring or a naphthalene ring. X represents -O- or -NR ５ -. R ５ represents an alkyl group which may have a substituent or an aryl group which may have a substituent. p and q each independently represent an integer of 0 to 4. r represents an integer of 1 to 3. s represents an integer of 0 to 3. However, p + q is an integer of 0 to 4, and r + s is an integer of 1 to 4.

14. The microcapsule according to claim 13, wherein the capsule wall of the microcapsule contains at least one selected from the group consisting of polyurethane urea having a polymethylene polyphenylene structure and melamine resin.

15. The microcapsule according to claim 13 or 14, wherein the capsule wall of the microcapsule contains a resin having Structure A or Structure B. Structure A: A structure formed by reacting an aromatic or alicyclic diisocyanate, a compound having three or more active hydrogen groups in one molecule, and a polymethylene polyphenyl polyisocyanate. Structure B: A structure formed by reacting melamine and formaldehyde.

16. The microcapsule according to any one of claims 13 to 15, wherein the thickness of the capsule wall of the microcapsule is 80 to 300 nm.

17. The microcapsule according to any one of claims 13 to 16, wherein the content of the compound represented by the formula (1) is 70% by mass or more based on the total mass of the color former.

18. A dispersion liquid comprising the microcapsule according to any one of claims 13 to 17.

19. A method for manufacturing a pressure measurement sheet set according to any one of claims 1 to 6, comprising a step of forming the first layer using the dispersion liquid according to claim 18.

20. A method for manufacturing a pressure measurement sheet according to any one of claims 7 to 12, comprising a step of forming the first layer using the dispersion liquid according to claim 18.

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