Pressure measurement sheet set

Abstract

The present invention provides a pressure measurement sheet set capable of measuring pressure distribution even when used in high-temperature environments. The pressure measurement sheet set comprises: a first sheet having a first layer containing microcapsules containing a coloring agent and a matrix component; and a second sheet having a second layer containing a coloring agent. The pressure measurement sheet set has a color density of 0.30 or less as determined by the following color density measurement 1. Color density measurement 1 involves laminating the first and second sheets so that the first layer of the first sheet and the second layer of the second sheet face each other to obtain a laminate. After pressurizing the laminate at 220°C and 4.5 MPa for 2 minutes, the optical density of the first sheet is measured as the color density.

Description

Technical Field

[0001] The invention relates to a sheet material set for pressure measurement. Background Art

[0002] In recent years, the need to measure pressure distribution has been increasing due to the advancement in product functionality and resolution.

[0003] For example, Patent Document 1 proposes a pressure measurement sheet using microcapsules containing an electron-donating leuco dye precursor.

[0004] Previous technical literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2009-019949 Summary of the Invention

[0007] Technical issues to be solved by the invention

[0008] On the other hand, in various high-temperature environments such as thermocompression bonding of integrated circuits and wiring on printed circuit boards, precise pressure distribution measurement is desired to improve profitability.

[0009] The present inventors measured pressure distribution in a high temperature environment (180° C. or higher) using the pressure measurement sheet described in Patent Document 1 and found that color development occurred in areas other than the pressurized area, making it impossible to measure precise pressure distribution.

[0010] In view of the above circumstances, an object of the present invention is to provide a pressure measurement sheet set capable of measuring pressure distribution even when used in a high-temperature environment.

[0011] Means for solving technical problems

[0012] As a result of intensive research on the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by the following configuration.

[0013] (1) A pressure measurement sheet set comprising:

[0014] a first sheet having a first layer including microcapsules containing a color-forming agent and a matrix component; and

[0015] a second sheet having a second layer containing a developer,

[0016] In the pressure measurement sheet set,

[0017] The color density determined by the following color density measurement 1 is 0.30 or less.

[0018] Color density measurement 1: The first sheet and the second sheet were stacked so that the first layer of the first sheet and the second layer of the second sheet faced each other to obtain a laminate. After the laminate was pressurized at 220°C and 4.5 MPa for 2 minutes, the optical density of the first sheet was measured and the result was taken as the color density.

[0019] (2) The pressure measurement sheet set according to (1), wherein the matrix component contains a polymer compound, and the polymer compound has a glass transition temperature of 100° C. or higher.

[0020] (3) The pressure measurement sheet set according to (2), wherein the polymer compound is selected from sodium carboxymethyl cellulose, sodium polyacrylate, and polyacrylamide.

[0021] (4) The pressure measurement sheet set according to any one of (2) to (3), wherein the content of the polymer compound is 40% by mass or more relative to the matrix component.

[0022] (5) The pressure measurement sheet set according to any one of (1) to (4), wherein the capsule wall of the microcapsule comprises at least one resin selected from polyurea, polyurethaneurea, and polyurethane.

[0023] The glass transition temperature of the capsule wall is 150° C. or higher, or the capsule wall does not exhibit a glass transition temperature.

[0024] (6) The pressure measurement sheet set according to (5), wherein the resin is a trifunctional or higher functional polyisocyanate A which is an adduct of an aromatic or alicyclic diisocyanate and a compound having three or more active hydrogen groups in one molecule, and

[0025] It is formed from a polyisocyanate B selected from aromatic diisocyanates and polymethylene polyphenyl polyisocyanates.

[0026] (7) The pressure measurement sheet set according to (6), wherein:

[0027] The mass ratio of the polyisocyanate A to the polyisocyanate B is 98 / 2 to 20 / 80.

[0028] (8) The pressure measurement sheet set according to any one of (1) to (7), wherein:

[0029] The molecular weight of the coloring agent is 550 or more.

[0030] (9) The pressure measurement sheet set according to any one of (1) to (8), wherein:

[0031] The microcapsules satisfy the relationship of formula (1).

[0032] Formula (1) δ / Dm>0.010

[0033] δ represents the number average wall thickness of the microcapsules (μm), and Dm represents the volume-based median diameter of the microcapsules (μm).

[0034] Effects of the Invention

[0035] According to the present invention, it is possible to provide a pressure measurement sheet set capable of measuring pressure distribution even when used in a high-temperature environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a cross-sectional view of one embodiment of a pressure measurement sheet set.

[0037] Figure 2 This is a diagram for explaining how to use the pressure measurement sheet set. DETAILED DESCRIPTION

[0038] Hereinafter, the present invention will be described in detail.

[0039] In addition, in this specification, the numerical range expressed using "to" means a range including the numerical values described before and after "to" as the lower limit and the upper limit.

[0040] Furthermore, in the numerical ranges described in this specification, the upper limit or lower limit described in one numerical range may be replaced by the upper limit or lower limit of the numerical range described in another stage. Furthermore, in the numerical ranges described in this specification, the upper limit or lower limit described in one numerical range may be replaced by the value shown in the Examples.

[0041] The various components described below may be used alone or in combination of two or more. For example, the polyisocyanate described below may be used alone or in combination of two or more.

[0042] A characteristic feature of the pressure measurement sheet set of the present invention is that the color density obtained by the predetermined color density measurement (color density measurement 1) described later is equal to or less than a predetermined value.

[0043] As described above, the present inventors conducted pressure distribution measurements in a high-temperature environment (e.g., 180°C or higher) using conventional pressure measurement sheets. They discovered for the first time that when a first sheet having a first layer containing microcapsules containing a coloring agent and a second sheet having a second layer containing a coloring agent are combined and pressurized, the sheets adhere to each other, causing the layers to separate when the sheets are peeled off. Furthermore, investigations into the cause of this problem revealed that in a high-temperature environment, the matrix component contained in the first layer melts at high temperatures, causing it to adhere to the second layer. To address this issue, the present inventors discovered that by using a pressure measurement sheet set in which the color density obtained by the color density difference measurement performed in the present invention is below a specified value, the sheets can be prevented from adhering to each other. As a result, even in a high-temperature environment, color unevenness is avoided, enabling accurate pressure distribution measurement.

[0044] <<First embodiment>>

[0045] Figure 1 This is a cross-sectional view of one embodiment of a pressure measurement sheet set.

[0046] The pressure measurement sheet set 10 includes a first sheet 16 and a second sheet 22 , wherein the first sheet 16 has a first support 12 and a first layer 14 including predetermined microcapsules 13 arranged on the first support 12 , and the second sheet 22 has a second support 18 and a second layer 20 including a color developer arranged on the second support 18 .

[0047] like Figure 2 As shown, when using the pressure measurement sheet set 10, the first sheet 16 and the second sheet 22 are stacked so that the first layer 14 of the first sheet 16 and the second layer 20 of the second sheet 22 face each other. 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 stack, the microcapsules 13 rupture in the pressurized areas, allowing the coloring agents contained in the microcapsules 13 to escape from the microcapsules and react with the coloring agents in the second layer 20. As a result, color development occurs in the pressurized areas.

[0048] As will be described later, the first sheet 16 only needs to have the first layer 14 and may not have the first support 12 . Furthermore, the second sheet 22 only needs to have the second layer 20 and may not have the second support 18 .

[0049] In addition, Figure 1 In the embodiment, the first support 12 and the first layer 14 are directly laminated, but the present invention is not limited to this embodiment. As described later, other layers (for example, an easy-adhesion layer) may be arranged between the first support 12 and the first layer 14. Figure 1In the embodiment, the second support 18 and the second layer 20 are directly laminated, but the present invention is not limited to this embodiment. As described later, another layer (for example, an easy-adhesion layer) may be arranged between the second support 18 and the second layer 20.

[0050] In the pressure measurement sheet set 10 , the color density determined by the following color density measurement 1 is 0.30 or less, preferably 0.25 or less, and more preferably 0.20 or less. The lower limit is not particularly limited, but is usually 0.1 or more.

[0051] Color density measurement 1: The first sheet and the second sheet were stacked so that the first layer of the first sheet and the second layer of the second sheet faced each other to obtain a laminate. The optical density of the laminate after heating the laminate at 220°C at 4.5 MPa for 2 minutes was taken as the color density.

[0052] In color density measurement 1, the laminate was heated under the prescribed conditions as described above. The measurement was performed at 4.5 MPa. Furthermore, when heating at 220°C, the laminate was heated from room temperature (approximately 23°C) to the prescribed temperature.

[0053] The optical density was measured using an X-rite eXact (manufactured by X-Rite) without a filter, at ISO T and D50 / 2°. The optical density was measured as OD (Optical Density). OD was measured in each of the CMYK (Cyan, M Magenta, Y Yellow, K Black) modes, and the optical density exhibiting the highest OD was selected.

[0054] Hereinafter, the structures of the first sheet 16 and the second sheet 22 constituting the pressure measurement sheet set 10 will be described in detail.

[0055] <1st Sheet>

[0056] Figure 1 The first sheet 16 described in has a first support 12 and a first layer 14 including microcapsules 13 containing a coloring agent and a matrix component.

[0057] Hereinafter, each component will be described in detail.

[0058] (First Support)

[0059] The first support is a member for supporting the first layer. In addition, when the first layer itself can be handled, the first sheet may not have the first support.

[0060] The first support may be in any of sheet, film, and plate shapes.

[0061] Examples of the first support include paper, plastic film, and synthetic paper.

[0062] Examples of the paper include premium paper, mid-grade paper, straw paper, neutral paper, acid paper, recycled paper, coated paper, on-machine coated paper, art paper, cast-coated paper, micro-coated paper, tracing paper, and recycled paper.

[0063] Examples of the plastic film include polyester films such as polyethylene terephthalate films, cellulose derivative films such as cellulose triacetate, polyolefin films such as polypropylene and polyethylene, and polystyrene films.

[0064] Examples of synthetic paper include synthetic paper (Yupo, etc.) obtained by biaxially stretching polypropylene or polyethylene terephthalate to form multiple micropores, synthetic paper made from synthetic fibers such as polyethylene, polypropylene, polyethylene terephthalate, and polyamide, and synthetic paper obtained by layering these on part of the paper, one side, or both sides.

[0065] Among these, from the viewpoint of further increasing the color development density due to pressure, a plastic film or synthetic paper is preferred, and a plastic film is more preferred.

[0066] The thickness of the first support is not particularly limited, but is preferably 10 to 200 μm.

[0067] (Layer 1)

[0068] The first layer contains microcapsules containing chromogenic agents and a matrix component.

[0069] Hereinafter, the materials constituting the microcapsules will first be described in detail.

[0070] [Microcapsules]

[0071] Microcapsules generally have a core and a capsule wall. The capsule wall is used to contain a core material (a substance contained therein (also referred to as an internal component)) constituting the core.

[0072] In the present invention, the microcapsules contain a coloring agent as a core material (inner component). Since the coloring agent is contained in the microcapsules, the coloring agent can exist stably until the microcapsules are ruptured by applying pressure.

[0073] Microcapsules have a capsule wall containing a core material.

[0074] The capsule wall in the microcapsule is not particularly limited, but preferably comprises at least one resin selected from polyurea, polyurethaneurea, polyurethane, melamine resin, and acrylic resin, and more preferably comprises at least one resin selected from polyurea, polyurethaneurea, and polyurethane.

[0075] The capsule wall of the microcapsule is preferably substantially composed of a resin. Substantially composed of a resin means that the content of the resin relative to the total mass of the capsule wall is 90% by mass or more, preferably 100% by mass. In other words, the capsule wall of the microcapsule is preferably composed of a resin.

[0076] In addition, polyurethane is a polymer having a plurality of urethane bonds, and is preferably a reaction product formed from raw materials containing polyol and polyisocyanate.

[0077] Furthermore, polyurea is a polymer having multiple urea bonds, and is preferably a reaction product formed from raw materials including polyamines and polyisocyanates. In addition, polyurea can be synthesized using polyisocyanates instead of polyamines by reacting a portion of the polyisocyanates with water to form polyamines.

[0078] Polyurethane urea is a polymer having urethane bonds and urea bonds, and is preferably a reaction product formed from raw materials including polyols, polyamines, and polyisocyanates. In addition, when polyols and polyisocyanates are reacted, a portion of the polyisocyanate reacts with water to form polyamines, resulting in polyurethane urea.

[0079] Polyisocyanate refers to a compound having two or more isocyanate groups, and examples thereof include aromatic polyisocyanates and aliphatic polyisocyanates. From the viewpoint of being able to introduce aromatic ring groups into the capsule wall of the microcapsule, aromatic polyisocyanates are preferred.

[0080] Examples of the aromatic polyisocyanate include aromatic diisocyanates, such as m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-toluene diisocyanate, 2,4-toluene 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.

[0081] Examples of the aliphatic polyisocyanate include 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.

[0082] In addition, although bifunctional aromatic polyisocyanates and aliphatic polyisocyanates are exemplified above, trifunctional or higher-functional polyisocyanates (for example, trifunctional triisocyanates and tetrafunctional tetraisocyanates) may also be mentioned as polyisocyanates.

[0083] More specifically, examples of the polyisocyanate include biuret forms or isocyanurate forms which are trimers of the above-mentioned bifunctional polyisocyanates, adducts (adducts) of polyols such as trimethylolpropane and bifunctional polyisocyanates, formalin condensates of phenylisocyanate, polyisocyanates having polymerizable groups such as isocyanoethyl methacrylate, and lysine triisocyanate.

[0084] Polyisocyanate is described in “Polyurethane Resin Handbook” (edited by Keiji Iwata, published by NIKKAN KOG YOSHIMBUN, Ltd. (1987)).

[0085] Among them, as one of the preferred aspects of the polyisocyanate, trifunctional or higher-functional polyisocyanates are preferred.

[0086] Examples of trifunctional or higher-functional polyisocyanates include trifunctional or higher-functional aromatic polyisocyanates and trifunctional or higher-functional aliphatic polyisocyanates.

[0087] Preferred trifunctional or higher-functional polyisocyanates include adducts (adducts) of aromatic or alicyclic diisocyanates and compounds having three or more active hydrogen groups in one molecule (for example, trifunctional or higher-functional polyols, polyamines, or polythiols), i.e., trifunctional or higher-functional polyisocyanates (adduct-type trifunctional or higher-functional polyisocyanates), and trimers (biuret-type or isocyanurate-type) of aromatic or alicyclic diisocyanates. More preferred are trifunctional or higher-functional polyisocyanates as the above-mentioned adducts (adducts).

[0088] Regarding the trifunctional or higher polyisocyanate as the above-mentioned adduct, a trifunctional or higher polyisocyanate which is an adduct of an aromatic or alicyclic diisocyanate and a polyol having three or more hydroxyl groups in one molecule is preferred, and a trifunctional polyisocyanate which is an adduct of an aromatic or alicyclic diisocyanate and a polyol having three or more hydroxyl groups in one molecule is more preferred.

[0089] As the adduct, an adduct obtained using an aromatic diisocyanate is preferably used from the viewpoint of achieving more excellent effects of the present invention.

[0090] As the polyol, for example, a trifunctional or higher-functional low-molecular-weight polyol described below is preferred, and trimethylolpropane is more preferred.

[0091] Examples of the adduct-type trifunctional or higher-functional polyisocyanates include TAKENATE (registered trademark) D-102, D-103, D-103H, D-103M2, P49-75S, D-110N, D-120N, D-140N, and D-160N (manufactured by Mitsui Chemicals, Inc.), DESMODULE (registered trademark) L75 and UL57SP (manufactured by Sumika Bayer Urethane Co., Ltd.), CORONATE (registered trademark) HL, HX, and L (manufactured by Nippon Polyurethane Industry Co., Ltd.), P301-75E (manufactured by Asahi Kasei Corporation), and BURNOCK (registered trademark) D-750 (manufactured by DIC Corporation).

[0092] Among them, as the addition-type trifunctional 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.

[0093] Examples of the isocyanurate-type trifunctional or higher-functional polyisocyanates include TAKENATE (registered trademark) D-127N, D-170N, D-170HN, D-172N, D-177N, and D-204 (manufactured by Mitsui Chemicals, Inc.), SUMIDURN 3300, DESMODULE (registered trademark) N3600, N3900, and Z4470BA (manufactured by Sumika Bayer Urethane Co., Ltd.), CORONATE (registered trademark) HX and HK (manufactured by Nippon Polyurethane Industry Co., Ltd.), and Duranate (registered trademark) TPA-100, TKA-100, TSA-100, TSS-100, TLA-100, and TSE-100 (manufactured by Asahi Kasei Corporation).

[0094] Examples of biuret-type trifunctional or higher-functional polyisocyanates include TAKENATE (registered trademark) D-165N and NP1100 (manufactured by Mitsui Chemicals, Inc.), DESMODULE (registered trademark) N3200 (manufactured by Sumika Bayer Urethane Co., Ltd.), and Duranate (registered trademark) 24A-100 (manufactured by Asahi Kasei Corporation).

[0095] Furthermore, as the polyisocyanate, polymethylene polyphenyl polyisocyanate is also preferable.

[0096] As the polymethylene polyphenyl polyisocyanate, a compound represented by formula (X) is preferred.

[0097] [Chemical Formula 1]

[0098]

[0099] In formula (1), n represents the number of repeating units. As the number of repeating units, it represents an integer greater than 1. From the perspective of being able to better measure pressure distribution in a high temperature environment (hereinafter also referred to as "the perspective of the present invention having a more excellent effect"), n is preferably an integer of 1 to 10, and more preferably an integer of 1 to 5.

[0100] Examples of the polyisocyanate containing polymethylene polyphenyl polyisocyanate include MILLIONATE TEMR-100, MILLIONATE MR-200, and MILLIONATE MR-400 (manufactured by TOSOH Corporation), WANNATE PM-200 and WANNATE PM-400 (manufactured by Wanhua Chemical Japan Co., Ltd.), COSMONATE M-50, COSMONATE M-100, COSMONATEM-200, and COSMONATE M-300 (manufactured by Mitsui Chemicals, Inc.), and VORANATE M-595 (manufactured by Dow Chemical Japan Limited).

[0101] Polyol refers to a compound having two or more hydroxyl groups, and examples thereof include low molecular weight polyols (e.g., aliphatic polyols, aromatic polyols), polyvinyl alcohol, polyether polyols, polyester polyols, polylactone polyols, castor oil polyols, polyolefin polyols, and hydroxyl-containing amine compounds.

[0102] 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 glycerol, trimethylolpropane, hexanetriol, pentaerythritol, and sorbitol.

[0103] Examples of hydroxyl-containing amine compounds include amino alcohols, such as alkoxylated derivatives of amino compounds. Examples of amino alcohols include N,N,N',N'-tetrakis[2-hydroxypropyl]ethylenediamine and N,N,N',N'-tetrakis[2-hydroxyethyl]ethylenediamine, which are propylene oxide or ethylene oxide adducts of amino compounds such as ethylenediamine.

[0104] Polyamine refers to a compound having two or more amino groups (primary or secondary amino groups), and examples thereof include aliphatic polyamines such as diethylenetriamine, triethylenetetramine, 1,3-propylenediamine and hexamethylenediamine; epoxy 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.

[0105] Among them, the resin contained in the capsule wall is preferably formed using an adduct of an aromatic or alicyclic diisocyanate and a compound having three or more active hydrogen groups in one molecule, that is, a trifunctional or higher-functional polyisocyanate A (hereinafter also referred to as "polyisocyanate A") and a polyisocyanate B selected from aromatic diisocyanates and polymethylene polyphenyl polyisocyanates (hereinafter also referred to as "polyisocyanate B").

[0106] That is, the capsule wall is preferably a capsule wall composed of the resin (at least one resin selected from polyurea, polyurethaneurea, and polyurethane) formed using the polyisocyanate A and the polyisocyanate B.

[0107] The use of polyisocyanate A and polyisocyanate B achieves even greater advantages in the present invention. Furthermore, the temperature dependence of color development is minimal. Temperature dependence of color development refers to the characteristic indicating the difference in the degree of color development caused by the temperature at which pressure is applied to the pressure measurement sheet set (or the pressure measurement sheet described below). More specifically, when the pressure measurement sheet set (or the pressure measurement sheet described below) is used and the degree of color development is observed while varying the heating temperature within a high temperature range (180°C or higher), the temperature dependence of the color development is considered to be significant.

[0108] In addition, aromatic diisocyanate may be used alone, polymethylene polyphenyl polyisocyanate may be used alone, or both may be used in combination as polyisocyanate B. Among them, polyisocyanate B is preferably a mixture of aromatic diisocyanate and polymethylene polyphenyl polyisocyanate.

[0109] In the mixture, the mass ratio of polymethylene polyphenyl polyisocyanate to aromatic diisocyanate (mass of polymethylene polyphenyl polyisocyanate / mass of aromatic diisocyanate) is not particularly limited, but is preferably 0.1 to 10, more preferably 0.5 to 2, and even more preferably 0.75 to 1.5.

[0110] The viscosity of the polyisocyanate B is not particularly limited, but is preferably 100 to 1000 mPa·s from the viewpoint of achieving more excellent effects of the present invention.

[0111] In addition, the above-mentioned viscosity is the viscosity at 25°C.

[0112] When polyisocyanate A and polyisocyanate B are used simultaneously, the mass ratio of polyisocyanate A to polyisocyanate B (mass of polyisocyanate A / mass of polyisocyanate B) is not particularly limited, but is preferably 98 / 2 to 20 / 80, more preferably 80 / 20 to 20 / 80, and even more preferably 80 / 20 to 45 / 55.

[0113] When the mass ratio is within the above range, the effects of the present invention are more excellent and the temperature dependence of color development is also small.

[0114] From the perspective of achieving even greater effects of the present invention, the glass transition temperature of the microcapsule wall is preferably 150°C or higher, or the capsule wall preferably does not exhibit a glass transition temperature. Specifically, the glass transition temperature of the material constituting the microcapsule wall is preferably 150°C or higher, or the material constituting the microcapsule wall preferably does not exhibit a glass transition temperature.

[0115] When the capsule wall of the microcapsule exhibits a glass transition temperature, the temperature is preferably 160°C or higher, more preferably 180°C or higher, and even more preferably 200°C or higher, from the viewpoint of further improving the effects of the present invention. When the capsule wall of the microcapsule exhibits a glass transition temperature, the upper limit of the temperature is not particularly limited. The capsule wall of the microcapsule is often below the thermal decomposition temperature, usually 250°C or lower.

[0116] Among them, from the viewpoint of achieving more excellent effects of the present invention, it is preferred that the capsule wall of the microcapsule does not exhibit a glass transition temperature.

[0117] The phrase "the capsule wall of the microcapsule does not exhibit a glass transition temperature" means that the capsule wall of the microcapsule (the material constituting the capsule wall of the microcapsule) does not exhibit a glass transition temperature between 25°C and a temperature (thermal decomposition temperature - 5°C) minus 5°C from the thermal decomposition temperature of the capsule wall described below. Specifically, the phrase means that the capsule wall does not exhibit a glass transition temperature within the range of "25°C" to "(thermal decomposition temperature (°C) - 5°C)."

[0118] There are no particular limitations on the method for achieving a glass transition temperature of 150°C or higher in the microcapsule wall, or for achieving a glass transition temperature in the capsule wall. This temperature can be adjusted by appropriately selecting the raw materials used to produce the microcapsules. For example, polyurea exhibits a high glass transition temperature, so a method of forming the capsule wall from polyurea is possible. Alternatively, a method of increasing the crosslink density of the material forming the capsule wall is also possible. Furthermore, a method of introducing an aromatic ring group (e.g., a benzene ring group) into the material forming the capsule wall is also possible.

[0119] The glass transition temperature of the capsule wall is measured as follows.

[0120] Prepare 50 sheets of the first layer (microcapsule layer) measuring 1 cm in length by 1 cm in width, immerse all of them in 10 ml of water and let them stand for 24 hours to obtain an aqueous dispersion of microcapsules. Alternatively, if the first sheet includes the first support, prepare 50 sheets of the first sheet measuring 1 cm in length by 1 cm in width and immerse them.

[0121] The resulting aqueous dispersion of microcapsules was centrifuged at 15,000 rpm for 30 minutes to separate the microcapsules. Ethyl acetate was added to the separated microcapsules, and the mixture was further stirred at 25°C for 24 hours. The resulting solution was then filtered, and the resulting residue was vacuum-dried at 60°C for 48 hours to obtain microcapsules free of any inclusions (hereinafter referred to as "measurement material"). This yielded the capsule wall material for the microcapsules to be measured for the glass transition temperature.

[0122] Next, the thermal decomposition temperature of the obtained test material was measured using a thermogravimetric differential thermal analyzer TG-DTA (device name: DTG-60, Shimadzu Corporation). The thermal decomposition temperature (°C) refers to the temperature at which the test material is heated from room temperature at a constant heating rate (10°C / min) in atmospheric thermogravimetric analysis (TGA) and the weight of the test material decreases by 5% by mass relative to the weight before heating.

[0123] Next, the glass transition temperature of the material was measured using a differential scanning calorimeter (DSC) (DSC-60a Plus, Shimadzu Corporation) in a sealed pan at a heating rate of 5°C / min within a range of 25°C to (thermal decomposition temperature (°C) - 5°C). The glass transition temperature of the microcapsule wall was the value obtained during the second heating cycle.

[0124] The particle size of the microcapsules is not particularly limited, but is preferably 1 to 80 μm, more preferably 5 to 70 μm, and even more preferably 10 to 50 μm in terms of volume-based median diameter (D50).

[0125] The volume-based median diameter of the microcapsules can be controlled by adjusting the production conditions of the microcapsules, for example.

[0126] The volume-based median diameter of microcapsules refers to the diameter at which the combined volume of the larger and smaller diameter particles is equal, when the particle size at which the cumulative volume of the entire microcapsule is 50% is divided into two thresholds. In other words, the median diameter corresponds to the so-called D50.

[0127] The value is calculated by photographing the surface of the first layer of the first sheet having the first layer containing microcapsules at 1000 times magnification using an optical microscope, and measuring the sizes of all microcapsules within a range of 500 μm×500 μm.

[0128] The number average wall thickness of the capsule wall of the microcapsule is not particularly limited, but is preferably 0.01 to 2 μm, more preferably 0.05 to 1 μm.

[0129] The term "microcapsule wall thickness" refers to the thickness (μm) of the capsule wall of the capsule particles forming the microcapsule, and the number-average wall thickness refers to the average of the individual capsule wall thicknesses (μm) of 20 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 observed using an SEM at 15,000x magnification. Twenty microcapsules having a particle size ranging from (the volume-based median diameter of the microcapsules) × 0.9 to (the volume-based median diameter of the microcapsules) × 1.1 are randomly selected. The capsule wall thickness is then determined and the average value is calculated by observing the cross-sections of each selected microcapsule.

[0130] The ratio (δ / Dm) of the number average wall thickness δ of the microcapsules to the volume-based median diameter (Dm) of the microcapsules is not particularly limited and is often 0.005 or greater. From the viewpoint of achieving even better effects of the present invention, it is preferred that the relationship of formula (1) be satisfied.

[0131] Formula (1) δ / Dm>0.010

[0132] That is, the ratio (δ / Dm) is preferably greater than 0.010. Furthermore, the ratio (δ / Dm) is preferably 0.015 or greater. The upper limit is not particularly limited, but is preferably 0.050 or less.

[0133] When the microcapsules satisfy the relationship of the above formula (1), the balance between the size of the capsule and the thickness of the capsule wall is good, and there is less concern about leakage of the contents of the microcapsules in a high-temperature environment.

[0134] The colorant is contained in microcapsules.

[0135] The coloring agent refers to a compound that develops color from a colorless state by contact with a coloring agent described later. As the coloring agent, an electron-donating dye precursor (a precursor of a color-developing dye) is preferred. That is, as the coloring agent, an electron-donating leuco dye is preferred.

[0136] The coloring agent can be a coloring agent known for use in pressure-sensitive copying paper or thermal recording paper. Examples of the coloring agent include triphenylmethanephthalide compounds, fluoran compounds, phenothiazine compounds, indolylphthalide compounds, azaindolylphthalide compounds, colorless auramine compounds, rhodamine lactam compounds, triphenylmethane compounds, diphenylmethane compounds, triazene compounds, spiropyran compounds, and fluorene compounds.

[0137] For details of the above compounds, reference can be made to the description in Japanese Patent Application Laid-Open No. 5-257272.

[0138] The coloring agents may be used alone or in combination of two or more.

[0139] The molecular weight of the coloring agent is not particularly limited, but is generally 300 or greater. From the perspective of achieving more excellent effects of the present invention, it is preferably 420 or greater, and more preferably 550 or greater. The upper limit is not particularly limited, but is preferably 1000 or less.

[0140] The molar absorption coefficient (ε) of the pigment (corresponding to the pigment that develops color) (hereinafter also referred to as "specific pigment") obtained by contacting the coloring agent with the coloring agent described later is not particularly limited, but is preferably 10,000 mol -1 cm -1 L or more, more preferably 15000 mol -1 cm -1 L or more, more preferably 25000 mol -1 cm -1 The upper limit of the molar absorption coefficient (ε) is not particularly limited, but is usually 50,000 mol -1 cm -1 L or less.

[0141] Examples of the coloring agent include 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide (ε=61000), 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-n-octyl-2-methylindol-3-yl)phthalide (ε=40000), 3-[2,2-bis(1-ethyl-2-methylindol-3-yl)vinyl]-3-(4-diethylaminophenyl)phthalide (ε=40000), 9-[ethyl(3-methylbutyl)amino]spiro[12H-benzo[a]oxy]phthalide, Anthracene-12,1'(3'H)isobenzofuran]-3'-one (ε=34000), 2-phenylamino-3-methyl-6-dibutylaminofluoran (ε=22000), 6-diethylamino-3-methyl-2-(2,6-dimethylanilino)-fluoran (ε=19000), 2-(2-chloroanilino)-6-dibutylaminofluoran (ε=21000), 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide (ε=16000) and 2-phenylamino-3-methyl-6-diethylaminofluoran (ε=16000), etc.

[0142] In addition, the above-mentioned ε represents the molar absorption coefficient of each compound after color development.

[0143] The molar absorptivity (ε) can be calculated from the absorbance when a specific pigment is dissolved in a 95% by mass acetic acid aqueous solution. Specifically, in a 95% by mass acetic acid aqueous solution containing a specific pigment whose concentration is adjusted so that the absorbance is 1.0 or less, the molar absorptivity (ε) can be calculated using the following formula, assuming the length of the measurement cell is A cm, the concentration of the specific pigment is B mol / L, and the absorbance is C.

[0144] Molar absorptivity (ε) = C / (A×B)

[0145] The microcapsules may contain other ingredients besides the above-mentioned coloring agents.

[0146] For example, the microcapsules preferably contain a solvent.

[0147] The solvent is not particularly limited, and examples thereof include 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 arylindan compounds; aliphatic hydrocarbons such as dibutyl phthalate and isoparaffins; natural animal and plant oils such as soybean oil, corn oil, cottonseed oil, rapeseed oil, olive oil, coconut oil, castor oil and fish oil; and high-boiling-point fractions of natural products such as mineral oils.

[0148] The solvent may be used alone or in combination of two or more.

[0149] When the solvent is contained in the microcapsules, the mass ratio of the solvent to the colorant (mass of solvent / mass of colorant) is preferably in the range of 98 / 2 to 30 / 70, more preferably in the range of 97 / 3 to 40 / 60, from the viewpoint of color development.

[0150] The microcapsules may contain, in addition to the above-mentioned components, one or more additives such as ultraviolet absorbers, light stabilizers, antioxidants, paraffin wax, and odor inhibitors as needed.

[0151] [Microcapsule Manufacturing Method]

[0152] The method for producing microcapsules containing a coloring agent is not particularly limited, and examples thereof include known methods such as interfacial polymerization, internal polymerization, phase separation, external polymerization, and coacervation. Among them, interfacial polymerization is preferred.

[0153] As an interfacial polymerization method, an interfacial polymerization method is preferably one that includes a step of dispersing an oil phase containing a colorant and a capsule wall material (for example, a raw material containing at least one selected from polyisocyanate, polyol and polyamine. In addition, when polyamine is produced in the system by reacting polyisocyanate with water, polyol and polyamine can also be omitted) in an aqueous phase containing an emulsifier to prepare an emulsion (emulsification step); and a step of polymerizing the capsule wall material at the interface between the oil phase and the aqueous phase to form a capsule wall and form microcapsules containing the colorant (encapsulation step).

[0154] 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, more preferably 1 / 99 to 25 / 75.

[0155] Furthermore, as described above, the polyisocyanate A and the polyisocyanate B may be used together as the polyisocyanate. When both are used together, the preferred range of the mixing ratio of the both is as described above.

[0156] Furthermore, the type of the emulsifier used in the emulsification step is not particularly limited, and examples thereof include dispersants and surfactants.

[0157] Examples of the dispersant include polyvinyl alcohol. In the present invention, when the emulsifier is separated from the capsule, the emulsifier also serves as the polymer compound described below.

[0158] The first layer comprises the above-mentioned microcapsules.

[0159] The content of the microcapsules in the first layer is not particularly limited, but is preferably 50 to 90% by mass, more preferably 55 to 80% by mass, based on the total mass of the first layer, from the viewpoint of achieving more excellent effects of the present invention.

[0160] The content of the coloring agent in the first layer is not particularly limited, but is preferably 0.1 to 10 g / m2 from the viewpoint of achieving a more excellent effect of the present invention. 2 , more preferably 0.1 to 4 g / m 2 .

[0161] [Matrix components]

[0162] Layer 1 contains the matrix components.

[0163] The matrix component refers to a component comprising solid components other than the aforementioned microcapsules. Specifically, it includes a polymer compound, an inorganic filler, a fluorescent whitening agent, a defoaming agent, a penetrant, a UV absorber, a surfactant, and a preservative. From the perspective of maintaining the microcapsules and ensuring close adhesion to the substrate, the matrix component preferably contains a polymer compound, and more preferably contains a water-soluble polymer compound.

[0164] From the perspective of achieving even greater effects of the present invention, the glass transition temperature of the polymer compound contained in the matrix component is preferably 100°C or higher, more preferably 105°C or higher, even more preferably 110°C or higher, and particularly preferably 115°C or higher. The upper limit is not particularly limited, but is generally 180°C or lower. In this application, polymer compounds having a glass transition temperature of 100°C or higher are also referred to as specific polymer compounds.

[0165] The glass transition temperature of a polymer compound can be measured as follows.

[0166] The thermal decomposition temperature of the polymer compound was measured using a thermogravimetric differential thermal analyzer TG-DTA (DTA: DTG-60, Shimadzu Corporation). The thermal decomposition temperature (°C) refers to the temperature at which the material being measured decreases by 5% by mass relative to the mass of the material before heating when the temperature is increased from room temperature at a constant heating rate (10°C / min) in atmospheric thermogravimetric analysis (TGA).

[0167] Next, the glass transition temperature of the polymer compound was measured using a differential scanning calorimeter (DSC) (DSC-60a Plus, Shimadzu Corporation) in a sealed pan at a temperature increase rate of 5°C / min within a range of 25°C to (thermal decomposition temperature (°C) - 5°C). The glass transition temperature was the value obtained during the second cycle of temperature increase.

[0168] Specific examples of the specific polymer compound are not particularly limited, but include carboxymethylcellulose sodium, polyacrylic acid sodium and its derivatives, polymethacrylic acid sodium and its derivatives, polyacrylamide and its derivatives, aromatic polyacrylates, aromatic polymethacrylates, aromatic polyesters, aromatic polyurethanes, polyimides, and emulsions and latexes thereof. From the viewpoint of dissolving the coating liquid and achieving a better effect, a water-soluble polymer compound is preferred, and more preferably, one selected from the group consisting of carboxymethylcellulose sodium and polyacrylic acid sodium polyacrylamide.

[0169] From the viewpoint of maintaining the microcapsules and adhering closely to the substrate, the specific polymer compound is more preferably a water-soluble polymer compound.

[0170] The specific polymer compound can be used alone or in combination of two or more.

[0171] From the perspective of achieving a more superior effect of the present invention, the content of the specific polymer compound relative to the matrix component is preferably 40% by mass or greater, more preferably 45% by mass or greater. The upper limit may be, for example, 100% by mass, but from the perspective of achieving a more superior effect of the present invention, it is preferably 80% by mass or less, more preferably 75% by mass or less. If the specific polymer compound is 40% by mass or greater relative to the matrix component, the peelability when the first and second sheets are peeled off after being pressurized at high temperature is more excellent.

[0172] From the viewpoint of further improving the releasability when peeling the first sheet and the second sheet after being pressed, the matrix component preferably contains a release agent as inorganic particles.

[0173] As inorganic particles, silica particles (e.g., colloidal silica) and alumina particles can be cited, preferably silica particles. In addition, the inorganic particles mentioned here are different from the developer contained in the second layer of the second sheet described later and are not electron-accepting compounds.

[0174] The particle size of the inorganic particles is preferably 1 to 100 nm, more preferably 1 to 50 nm, and even more preferably 5 to 30 nm in terms of volume-based median diameter. The particle size of the inorganic particles can be measured by the same method as the average particle size of the microcapsules described above.

[0175] The content of the inorganic particles is preferably 1 to 20% by mass, more preferably 5 to 20% by mass, relative to the total solid content of the first layer, and preferably 1 to 60% by mass, more preferably 10 to 50% by mass, relative to the matrix component.

[0176] Furthermore, 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 .

[0177] [Method for forming the first layer]

[0178] The method for forming the first layer is not particularly limited, and a known method may be used.

[0179] For example, there can be mentioned a method in which a first layer-forming composition containing microcapsules and a matrix is applied onto a first support and then dried as needed.

[0180] The first layer-forming composition preferably contains at least microcapsules and a solvent. Alternatively, a microcapsule dispersion obtained by the above-mentioned interfacial polymerization method may be used as the first layer-forming composition.

[0181] The first layer-forming composition may contain other components that can be contained in the above-mentioned first layer.

[0182] The method for applying the first layer-forming composition is not particularly limited. Examples of the coater used for coating include an air knife coater, a rod coater, a bar coater, a curtain coater, a gravure coater, an extrusion coater, a die coater, a bead coater, and a knife coater.

[0183] After the first layer-forming composition is applied onto the first support, the coating film may be dried as needed. Examples of the drying treatment include heating.

[0184] Furthermore, although the method of forming the first layer on the first support has been described above, the method is not limited thereto. For example, the first sheet composed of the first layer may be formed by forming the first layer on a temporary support and then peeling the temporary support.

[0185] The temporary support is not particularly limited as long as it is a releasable support.

[0186] (Other parts)

[0187] The first sheet may include other members in addition to the above-mentioned first support and first layer.

[0188] For example, the first sheet may include an easily adhesive layer between the first support and the first layer for improving the adhesion between the two.

[0189] The easily adhesive layer is preferably a resin layer containing a resin. If the easily adhesive layer is a resin layer, the microcapsules contained in the first layer interact with the easily adhesive layer, so that the microcapsules can be stably present.

[0190] The material constituting the adhesion layer is not particularly limited, but examples thereof include styrene-butadiene resin, styrene (meth)acrylic resin, (meth)acrylic resin, olefin resin, polyurethane resin, polyester resin, and polyvinyl alcohol resin. Among them, styrene-butadiene resin, styrene (meth)acrylic resin, or (meth)acrylic resin is more preferred from the viewpoint of achieving better adhesion between the resin substrate and the first layer.

[0191] The thickness of the easily adhesive layer is not particularly limited, but is preferably 0.005 to 3 μm, more preferably 0.01 to 2 μm.

[0192] To further enhance color density and achieve superior image quality (resolution), the arithmetic mean roughness Ra of the first sheet is preferably 3.0 to 7.0 μm. The arithmetic mean roughness Ra of the first sheet refers to the arithmetic mean roughness Ra of the surface of the first sheet that faces (contacts) the second sheet when the pressure measurement sheet set is used. When the first layer is located on the outermost surface of the first sheet facing the second sheet, the arithmetic mean roughness Ra corresponds to the arithmetic mean roughness Ra of the surface of the first layer opposite the first resin substrate side.

[0193] The arithmetic mean roughness Ra of the first sheet in this specification refers to the arithmetic mean roughness Ra specified in JIS B 0681-6: 2014. A scanning white interferometer utilizing optical interference (specifically, NewView5020 manufactured by Zygo Corporation: Stich type; objective lens ×50; intermediate lens ×0.5) was used as the measuring device.

[0194] When the arithmetic mean roughness Ra of the first sheet is 3.0 μm or greater, the colorant is present in sufficient quantities, resulting in a higher color density. On the other hand, when the arithmetic mean roughness Ra of the first sheet is 7.0 μm or less, the second layer of the second sheet can appropriately absorb the solvent that escapes along with the colorant upon rupturing the microcapsules in the pressurized area, thereby achieving excellent image quality with minimal bleeding.

[0195] The arithmetic mean roughness Ra of the first sheet can be controlled by adjusting the solid content of the first layer-forming composition applied and adjusting the amount of microcapsules in the first layer of the first sheet.

[0196] <Second Sheet>

[0197] Figure 1 The second sheet 22 described in has a second support 18 and a second layer 20 including a developer disposed on the second support 18 .

[0198] Hereinafter, each component will be described in detail.

[0199] (Second support)

[0200] The second support is a member for supporting the second layer. In addition, when the second layer itself can be processed, the second sheet may not have a second support.

[0201] The configuration of the second support is the same as that of the first support described above, and therefore description thereof will be omitted.

[0202] (Layer 2)

[0203] The second layer is a layer containing a color developer.

[0204] The coloring agent is a compound that has no coloring function itself but has the property of causing the coloring agent to develop color when in contact with the coloring agent. As the coloring agent, an electron-accepting compound is preferred.

[0205] Examples of the color developer include inorganic compounds and organic compounds.

[0206] Examples of the inorganic compound include clay substances such as acidic clay, activated clay, attapulgite, zeolite, bentonite, and kaolin.

[0207] Examples of the organic compound include metal salts of aromatic carboxylic acids, metal salts of phenol formaldehyde resins and carboxylated terpene phenol resins, and the like.

[0208] Among them, the color developer is preferably acidic clay, activated clay, zeolite, kaolin, metal salts of aromatic carboxylic acids, or metal salts of carboxylated terpene-phenol resins, and more preferably acidic clay, activated clay, kaolin, or metal salts of aromatic carboxylic acids.

[0209] Preferred metal salts of aromatic carboxylic acids include 3,5-di-tert-butylsalicylic acid, 3,5-di-tert-octylsalicylic acid, 3,5-di-tert-nonylsalicylic acid, 3,5-di-tert-dodecanoic acid, 3-methyl-5-tert-dodecanoic acid, 3-tert-dodecanoic acid, 5-tert-dodecanoic acid, 5-cyclohexylsalicylic acid, 3,5-bis(α,α-dimethylbenzyl)salicylic acid, 3-methyl-5-(α-methylbenzyl)salicylic acid, 3-(α,α-dimethylbenzyl)salicylic acid, and 3-(α,α-dimethylbenzyl)salicylic acid. salicylic acid resin, a reaction product of 3,5-bis(α-methylbenzyl)salicylic acid and benzyl chloride, i.e., a zinc salt, a nickel salt, an aluminum salt or a calcium salt, etc.

[0210] The content of the color developer in the second layer is not particularly limited, but is preferably 20 to 95% by mass, more preferably 30 to 90% by mass, based on the total mass of the second layer, from the viewpoint of achieving more excellent effects of the present invention.

[0211] The color developer may be used alone or in combination of two or more.

[0212] The content of the color developer in the second layer is not particularly limited, but is preferably 0.1 to 30 g / m 2 When the developer is an inorganic compound, the content of the developer is preferably 3 to 20 g / m 2, more preferably 5 to 15 g / m 2 When the developer is an organic compound, the content of the developer is preferably 0.1 to 5 g / m 2 , more preferably 0.2 to 3 g / m 2 .

[0213] The second layer may contain other components in addition to the above-mentioned developer.

[0214] Examples of other components include a base, a pigment, a fluorescent whitening agent, a defoaming agent, a penetrant, an ultraviolet absorber, a surfactant, and a preservative.

[0215] Examples of the matrix include synthetic polymers and natural polymers such as styrene-butadiene copolymers, polyvinyl acetate, polyacrylates, polyvinyl alcohol, polyacrylic acid, maleic anhydride-styrene copolymers, starch, casein, gum arabic, gelatin, carboxymethyl cellulose, and methyl cellulose.

[0216] Examples of the pigment include heavy calcium carbonate, light calcium carbonate, talc, and titanium dioxide.

[0217] The thickness of the second layer is not particularly limited, but is preferably 1 to 50 μm, more preferably 2 to 30 μm, from the viewpoint of achieving more excellent effects of the present invention.

[0218] Furthermore, the mass per unit area of the second layer (g / m 2 ) is not particularly limited, but is preferably 0.5 to 30 g / m 2 .

[0219] [Method for forming the second layer]

[0220] The method for forming the second layer is not particularly limited, and a known method may be used.

[0221] For example, there can be mentioned a method in which a second layer-forming composition containing a color developer is applied onto the second support and then dried as needed.

[0222] The second layer-forming composition may be a dispersion obtained by dispersing a developer in water or the like. When the developer is an inorganic compound, the developer-dispersed dispersion can be prepared by mechanically dispersing the inorganic compound in water. Furthermore, when the developer is an organic compound, the developer can be prepared by mechanically dispersing the organic compound in water or dissolving it in an organic solvent.

[0223] The second layer-forming composition may contain other components that can be contained in the above-mentioned second layer.

[0224] The method of applying the second layer forming composition is not particularly limited, and examples thereof include a method using the same coater used when applying the above-mentioned first layer forming composition.

[0225] After the second layer-forming composition is applied onto the second support, the coating film may be dried as needed. Examples of the drying treatment include heating.

[0226] In addition, the method of forming the second layer on the second support is described above, but it is not limited to the above method. For example, the second layer may be formed on a temporary support and then the temporary support may be peeled off to form a second sheet composed of the second layer.

[0227] The temporary support is not particularly limited as long as it is a releasable support.

[0228] (Other parts)

[0229] The second sheet may include other members in addition to the above-mentioned second support and second layer.

[0230] For example, the second sheet may include an easily adhesive layer between the second support and the second layer for improving the adhesion between the two.

[0231] As the aspect of the easily adhesive layer, the aspect of the easily adhesive layer which the above-mentioned 1st sheet|seat may have is mentioned.

[0232] The pressure sheet set of the present invention can be used by laminating the first sheet and the second sheet so that the first layer of the first sheet and the second layer of the second sheet face each other to obtain a laminate, and then pressurizing the laminate.

[0233] Example

[0234] The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to the following Examples unless it deviates from the gist of the present invention.

[0235] <Example 1>

[0236] (Preparation of Microcapsules)

[0237] The following compound (A) (molecular weight: 623) (11.3 parts by mass) as a coloring agent was dissolved in linear alkylbenzene (ENEOS Corporation, Grade Olefin L) (86 parts by mass) to obtain Solution A. Next, synthetic isoparaffin (Tdemitsu Kosan Co., Ltd., IP Solvent 1620) (14 parts by mass) was added to the stirred Solution A to obtain Solution B. Separately, trimethylolpropane adduct of toluene diisocyanate (DICCORPORATION, BURNOCK D-750) (13.8 parts by mass) dissolved in 2-butanone (23 parts by mass) was added to the stirred Solution B to obtain Solution C. Note that BURNOCK D-750 is a solution having a solids concentration of 75% by mass.

[0238] Furthermore, the above-mentioned solution C was added to a solution of polyvinyl alcohol (JP-45, Japan VAM & Poval Co., Ltd., glass transition temperature less than 100°C) (4.0 parts by mass) dissolved in water (100 parts by mass) to form an emulsified dispersion. Water (130 parts by mass) was added to the emulsified dispersion, and the mixture was heated to 70°C while stirring for 1 hour, then cooled. Water was then added to adjust the concentration, yielding a microcapsule solution containing a coloring agent with a solids concentration of 25% by mass.

[0239] Furthermore, as shown in the following structural formula, the BURNOCK D-750 corresponds to an adduct of an aromatic diisocyanate and trimethylolpropane, that is, a trifunctional polyisocyanate.

[0240] [Chemical Formula 2]

[0241]

[0242] [Chemical Formula 3]

[0243]

[0244] The volume-based median diameter of the microcapsules containing the colorant was 20 μm. The number-average wall thickness was 0.44 μm. Furthermore, δ / Dm was 0.022. Furthermore, the glass transition temperature of the capsule wall of the microcapsules was 150°C.

[0245] As described below, after preparing a first sheet having a first layer containing microcapsules, the surface of the first layer was photographed at 1000x magnification using an optical microscope, and the sizes of all microcapsules within a range of 500 μm×500 μm were measured to calculate the median diameter (Dm).

[0246] Regarding the number average wall thickness, as described later, after preparing a first sheet having a first layer containing microcapsules, a cross-sectional slice of the first sheet having the first layer containing microcapsules is prepared, and the cross-section is observed at 15,000 times by SEM. Based on the selection of 20 arbitrary microcapsules having a particle size in the range of (the value of the median particle size based on the volume of the microcapsules) × 0.9 to (the value of the median particle size based on the volume of the microcapsules) × 1.1, the cross-sections of the selected microcapsules are observed, the thickness of the capsule wall is determined, and the average value is calculated.

[0247] In addition, the glass transition temperature of the capsule wall of the microcapsule was measured by the following method.

[0248] First, as described below, a first sheet having a first layer containing microcapsules was prepared. The sheet was then cut into 50 pieces, each measuring 1 cm in length and 1 cm in width. All of the pieces were immersed in 10 ml of water and allowed to stand for 24 hours. Specifically, 50 pieces of the first sheet, each measuring 1 cm in length and 1 cm in width, having a first layer, were prepared and immersed in 10 ml of water for 24 hours to obtain an aqueous dispersion of microcapsules. The resulting aqueous dispersion of microcapsules was centrifuged at 15,000 rpm for 30 minutes to separate the microcapsules. Ethyl acetate was added to the separated microcapsules, and the mixture was further stirred at 25°C for 24 hours. The resulting solution was then filtered, and the resulting residue was vacuum-dried at 60°C for 48 hours to obtain microcapsules free of any internal components (hereinafter referred to as the "test material"). The thermal decomposition temperature of the test material was then measured using a thermogravimetric differential thermal analyzer (TG-DTA) (DTG-60, manufactured by Shimadzu Corporation). The thermal decomposition temperature (°C) was determined by thermogravimetric analysis (TGA) in an atmospheric environment. The temperature at which the material was heated from room temperature at a constant heating rate (10°C / min) and reduced by 5% by mass relative to the mass of the material before heating was used as the thermal decomposition temperature. Next, the glass transition temperature (Tg) of the material was measured using a differential scanning calorimeter (DSC) (DSC-60a Plus, Shimadzu Corporation) in a sealed pan at a heating rate of 5°C / min within a range of 25°C to (thermal decomposition temperature - 5°C). The value obtained during the second heating cycle was used as the glass transition temperature of the microcapsule wall.

[0249] (Preparation of the first sheet)

[0250] The coloring agent was prepared by adding a microcapsule solution (43 parts by mass), water (15 parts by mass), colloidal silica (Nissan Chemical Corporation, SNOWTEX (registered trademark) 30, solid content 30%) (5.7 parts by mass), Polymaron 482 (Arakawa Chemical Industries, Ltd., glass transition temperature less than 100°C) 10% by mass aqueous solution (1.8 parts by mass), carboxymethyl cellulose sodium (DKS Co., Ltd., CELLOGEN 5A, glass transition temperature 135°C) 10% by mass aqueous solution (22 parts by mass), carboxymethyl cellulose sodium (DKS Co., Ltd., CELLOGEN EP, glass transition temperature 135°C) 1% by mass aqueous solution (14 parts by mass), sodium alkylbenzenesulfonate (DKS Co., Ltd., NEOGEN T) 2% by mass aqueous solution (3.4 parts by mass), RAPISOL A-90 (NOF A 1 mass % aqueous solution (0.7 mass part) of NAROACTY CL-95 (Sanyo Chemical Industries, Ltd., a polyoxyalkylene alkyl ether surfactant) and a 1 mass % aqueous solution (0.7 mass part) of NAROACTY CL-95 were mixed and stirred for 2 hours to obtain a composition for forming the first layer.

[0251] The obtained first layer forming composition was applied to a 75 μm thick polyethylene terephthalate sheet with an easily adhesive layer (TOYOBO CO., LTD., COSMOSHINE (registered trademark) A4300) using a bar coater so that the mass after drying would be 5.3 g / m 2 , and dried to form the first layer, thereby producing the first sheet.

[0252] The pressure measurement sheet sets produced in Examples and Comparative Examples were subjected to color density measurement 1, and the color density was determined as follows.

[0253] The first and second sheets prepared in Example were cut into 5 cm x 5 cm sizes, and the first and second sheets were stacked in contact with the first layer surface of the first sheet and the second layer surface of the second sheet to obtain a laminate.

[0254] Next, a hot press equipped with two upper and lower heated stages was prepared. The stages were separated, and a 5mm-wide ring-shaped SUS substrate was placed on the lower stage. The laminate was then placed so that it covered the SUS substrate. The laminate was then sandwiched between the two heated stages heated to 220°C and pressed at 4.5 MPa for two minutes. After the pressurization was completed, the optical density A of the pressed area of the peeled first sheet was measured at nine points to determine the color density.

[0255] The optical density was measured using an X-rite eXact (manufactured by X-Rite) without a filter, at ISO T and D50 / 2°. The optical density was measured using the OD value. The OD was measured in each of the CMYK (Cyan, M Magenta, Y Yellow, K Black) modes, and the optical density with the highest OD was selected.

[0256] (Preparation of the Second Sheet)

[0257] A dispersion was prepared by dispersing sulfuric acid-treated activated clay (200 parts by mass) as a developer, sodium hexametaphosphate (0.7 parts by mass), a 10% by mass aqueous solution of sodium hydroxide (10 parts by mass), and water (135 parts by mass) using a sand mill so that the average particle size of the total particles became 2 μm.

[0258] Next, to the prepared dispersion, a 29% by mass aqueous dispersion of NIPOL LX-814 (Zeon Corporation) (163 parts by mass), a 3.3% by mass aqueous solution of POLYMARON 482 (ARAKAWA CHEMICAL INDUSTRIES, LTD.) (170 parts by mass), a 1% by mass aqueous solution of carboxymethylcellulose sodium (DKS Co. Ltd., CELLOGEN EP) (123 parts by mass), a 2% by mass aqueous solution of sodium alkylbenzenesulfonate (DKS Co. Ltd., NEOGENT) (28 parts by mass), and a 1% by mass aqueous solution of NOIGEN LP70 (DKS Co. Ltd.) (66 parts by mass) were mixed to prepare a coating solution containing a developer.

[0259] The coating liquid containing the developer was applied on a polyethylene terephthalate sheet having a thickness of 75 μm so that the solid content coating amount became 13.0 g / m 2 , and dried to form a second layer, thereby obtaining a second sheet.

[0260] <Example 2>

[0261] A first sheet and a second sheet were prepared by the same procedure as in Example 1, except that the amount of a 10 mass % aqueous solution of carboxymethylcellulose Na (DKS Co. Ltd., CELLOGEN 5A) was changed from 22 mass parts to 17 mass parts.

[0262] <Examples 3 to 5>

[0263] The first and second sheets were prepared by the same procedure as in Example 2 except that the amount of CELLOGEN 5A was adjusted to the total amount of carboxymethylcellulose Na, that is, the total amount of CELLOGEN 5A and CELLOGEN EP was as shown in Table 1.

[0264] <Examples 6 to 9>

[0265] The first and second sheets were prepared in the same procedure as in Example 1, except that carboxymethyl cellulose Na (DKS Co. Ltd., CELLOGEN 5A) was replaced with CELLOGEN 7A (carboxymethyl cellulose Na, DKS Co. Ltd., glass transition temperature 136°C), CELLOGEN F-5A (carboxymethyl cellulose Na, DKS Co. Ltd., glass transition temperature 134°C), Aron A-20L (polyacrylic acid Na, Toagosei Company, Limited, glass transition temperature 250°C), and polyacrylamide (Wako Pure Chemical Industries, Ltd., glass transition temperature 160°C), respectively.

[0266] <Example 10>

[0267] The first and second sheets were prepared in the same procedure as in Example 1, except that a trimethylolpropane adduct of toluene diisocyanate (DIC CORPORATION, BURNOCK D-750) (13.2 parts by mass) (solid content mass: 9.9 parts by mass) and polyisocyanate B (T0SOH Corporation, MILLIONATE MR-200) (0.5 parts by mass) were used instead of the trimethylolpropane adduct of toluene diisocyanate (DIC CORPORATION, BURNOCK D-750) (13.8 parts by mass).

[0268] In Example 10, the total mass of the solid content of the trimethylolpropane adduct of tolylene diisocyanate and polymethylene polyphenyl polyisocyanate was 10.4 parts by mass.

[0269] Furthermore, MILLIONATE MR-200 used as the polyisocyanate B corresponds to a mixture of diphenylmethane diisocyanate and polymethylene polyphenyl polyisocyanate (corresponding to the compound represented by formula (X)).

[0270] <Examples 11 to 13>

[0271] The first and second sheets were prepared in the same procedure as in Example 10, except that the total amount of the trimethylolpropane adduct of toluene diisocyanate and polyisocyanate B was the same as in Example 10 (10.4 parts by mass) and the mixing mass ratio thereof was as shown in Table 1.

[0272] <Example 14>

[0273] As shown in Table 1, a trimethylolpropane adduct of 1,3-bis(isocyanatemethyl)cyclohexane (Mitsui Chemicals, Inc., TAKENATE D-120N) was used instead of a trimethylolpropane adduct of toluene diisocyanate (DIC CORPORATION, BURNOCK D-750), and the mixing mass ratio with polyisocyanate B was adjusted to that shown in Table 1. A first sheet and a second sheet were produced in the same procedure as in Example 12, except that the mixing mass ratio with polyisocyanate B was adjusted to that shown in Table 1.

[0274] As shown in the following structural formula, TAKENATE D-120N corresponds to an adduct of an alicyclic diisocyanate and trimethylolpropane, that is, a trifunctional polyisocyanate.

[0275] [Chemical Formula 4]

[0276]

[0277] <Examples 15-16>

[0278] A first sheet and a second sheet were produced according to the same procedure as in Example 12, except that MILLIONATE MR-100 or MILLIONATE MR-400 was used instead of MILLIONATE MR-200.

[0279] The above-mentioned MILLIONATE MR-100 and MILLIONATE MR-400 correspond to a mixture of diphenylmethane diisocyanate and polymethylene polyphenyl polyisocyanate (corresponding to the compound represented by formula (X)).

[0280] <Implementation, 17-20>

[0281] As shown in Table 1, the first and second sheets were produced according to the same procedure as in Example 12, except that compounds (B) to (E) were used instead of compound (A).

[0282] In addition, compounds (B) to (E) are shown below.

[0283] [Chemical Formula 5]

[0284]

[0285] <Examples 21 to 24>

[0286] A first sheet and a second sheet were produced by the same procedure as in Example 12, except that the amount of the polyisocyanate solid content used was changed to that described in "Polyisocyanate solid content (parts by mass)" in Table 1.

[0287] The solid content used refers to the total mass of the solid content of the trimethylolpropane adduct of tolylene diisocyanate and the polyisocyanate B.

[0288] <Comparative Example 1>

[0289] According to the procedure described in Example 1 of Patent Document 1, a first sheet (electron-donating leuco dye sheet) and a second sheet (developer sheet) were produced.

[0290] Table 1 summarizes the median particle size, δ / Dm, and glass transition temperature of the capsule wall of the microcapsules in each of the Examples and Comparative Examples.

[0291] In addition, the thermal decomposition temperature of the capsule wall of the microcapsules produced in each example was approximately 250°C.

[0292] Then, the color density was determined according to the procedure of the color density measurement 1. The results are summarized in Table 1.

[0293] <Evaluation>

[0294] (Measurement of uneven hair color density)

[0295] The first and second sheets prepared in each example and comparative example were cut into a size of 5 cm×5 cm, and the first and second sheets were placed in contact with and overlapped with the surface of the first layer of the first sheet and the surface of the second layer of the second sheet to obtain a laminate.

[0296] Next, a hot press equipped with two upper and lower heated stages was prepared. The stages were separated, and a 5mm-wide ring-shaped SUS substrate was placed on the lower stage. The laminate was then arranged so that it covered the SUS substrate. The laminate was then sandwiched between the two heated stages heated to 200°C and pressed at 2.0 MPa for two minutes. After the pressing, the optical density A of the colored areas of the laminate was measured at nine points, and the difference between the maximum and minimum values was used as the color density unevenness.

[0297] The optical density was measured using an X-rite eXact (manufactured by X-Rite) without a filter, at ISO T and D50 / 2°. The optical density was measured using the OD value. The OD was measured in each of the CMYK (Cyan, M Magenta, Y Yellow, K Black) modes, and the optical density with the highest OD was selected.

[0298] (Pressure distribution measurement)

[0299] The first and second sheets prepared in each example and comparative example were cut into a size of 5 cm×5 cm, and the first and second sheets were placed in contact with and overlapped with the surface of the first layer of the first sheet and the surface of the second layer of the second sheet to obtain a laminate.

[0300] Next, a hot press equipped with two upper and lower heated stages was prepared. The stages were separated, and a 5mm-wide ring-shaped SUS substrate was placed on the lower stage. The laminate was then arranged so that it covered the SUS substrate. The SUS substrate and the laminate were then sandwiched between the two heated stages heated to 220°C, and pressurized at 2.0 MPa for 2 minutes. After the pressurization was completed, the shape of the color-developed regions of the resulting laminate was observed and evaluated according to the following criteria.

[0301] “5”: There is no sparseness or density in the color development, and the shape of the color development area is very well recognized as being the same ring shape as that of the SUS substrate.

[0302] "4": The density of the color development is very small, but the shape of the color development area is well recognized as a ring shape similar to that of the SUS substrate.

[0303] "3": There are sparse and dense areas of color development, but the shape of the color development area is sufficiently recognizable as a ring.

[0304] "2": Due to the density of the color development, there is a ring-shaped portion where the color development area cannot be identified.

[0305] "1": The density of the color is very large, and the shape of the color area is almost unrecognizable as a ring.

[0306] (Evaluation of color development temperature dependence)

[0307] According to the same procedure as described above (pressure distribution measurement), two laminated bodies composed of the first sheet and the second sheet produced in each of the examples and comparative examples were prepared.

[0308] Next, a heat press equipped with two upper and lower heating stages was prepared. The stages were separated, and the laminate was placed on the lower stage. The laminate was then sandwiched between the two heated stages heated to 200°C and pressed at 2.0 MPa for 2 minutes. After heating, the optical density (B) of the color-emitting region of the laminate was measured.

[0309] The laminate was then pressed in the same manner as above except that the temperature of the heating stage was changed to 180° C. After heating was completed, the optical density C of the color-emitting region of the laminate was measured.

[0310] Next, the difference between the optical density B and the optical density C (optical density B - optical density C) was determined and evaluated according to the following criteria: The smaller the difference, the smaller the difference in the degree of color development due to temperature.

[0311] "4": The above difference is 0.3 or less.

[0312] “3”: The difference is greater than 0.3 and less than 0.4.

[0313] "2": The difference is greater than 0.4 and less than 0.5.

[0314] "1": The above difference is greater than 0.5.

[0315] The optical density was measured using an X-rite eXact (manufactured by X-Rite) without a filter, at ISO T and D50 / 2°. The optical density was measured using the OD value. The OD was measured in each of the CMYK (Cyan, M Magenta, Y Yellow, K Black) modes, and the optical density with the highest OD was selected.

[0316] In Table 1, "specific polymer compound" indicates a polymer compound having a glass transition temperature of 100° C. or higher, and "content" indicates the content ratio of the specific polymer compound in the matrix component.

[0317] In Table 1, "polyisocyanate A" represents an adduct of an aromatic or alicyclic diisocyanate and a compound having three or more active hydrogen groups in one molecule, i.e., a trifunctional or higher-functional polyisocyanate, and "polyisocyanate B" represents a mixture of diphenylmethane diisocyanate and polymethylene polyphenyl polyisocyanate (equivalent to the compound represented by formula (X)).

[0318] In Table 1, “mass ratio (A / B)” represents the mass ratio of the mass of polyisocyanate A to the mass of polyisocyanate B.

[0319] In Table 1, "polyisocyanate solid content (parts by mass)" indicates the total amount of the solid content mass of polyisocyanate A and the solid content mass of polyisocyanate B.

[0320] In Table 1, the "Type" column in the "Coloring Agent" column shows the above-mentioned compounds (A) to (E), respectively, and the "Molecular Weight" column shows the molecular weight of each compound.

[0321] In Table 1, the column "Particle size (μm)" shows the volume-based median size (μm) of the microcapsules.

[0322] In Table 1, "δ / Dm" represents "δ / Dm" in the above formula (1), δ represents the number average wall thickness (μm) of the microcapsules, and Dm represents the volume-based median diameter (μm) of the microcapsules.

[0323] The column "Glass transition temperature of capsule wall (° C.)" shows the glass transition temperature of the capsule wall in the microcapsule.

[0324] In Table 1, "None" in the "Capsule Wall Glass Transition Temperature" column indicates that the microcapsule exhibited no glass transition temperature during the above measurement. In other words, this means that the microcapsule wall exhibited no glass transition temperature within the range of "25°C" to "(thermal decomposition temperature (°C) - 5°C)."

[0325] In Table 1, the column “Color Density” shows the color density obtained by the above-mentioned Color Density Measurement 1.

[0326] [Table 1]

[0327]

[0328] 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.

[0329] Explanation of symbols

[0330] 10 - Pressure measurement sheet set, 12 - First support, 13 - Microcapsule, 14 - First layer, 16 - First sheet, 18 - Second support, 20 - Second layer, 22 - Second sheet.

Claims

1. A pressure measurement sheet set comprising: a first sheet having a first layer including microcapsules containing a color-forming agent and a matrix component; and a second sheet having a second layer containing a developer, The matrix component contains a polymer compound, the polymer compound has a glass transition temperature of 100° C. or higher, and the content of the polymer compound is 40% by mass or higher relative to the matrix component. In the pressure measurement sheet set, The color density obtained by the following color density measurement 1 is 0.30 or less, Color density measurement 1: The first sheet and the second sheet are stacked so that the first layer of the first sheet and the second layer of the second sheet are opposite each other to obtain a laminate. The optical density of the first sheet after pressurizing the laminate at 220°C and 4.5 MPa for 2 minutes is measured and used as the color density.

2. The pressure measurement sheet set according to claim 1, wherein: The polymer compound is selected from sodium carboxymethyl cellulose, sodium polyacrylate and polyacrylamide.

3. The pressure measurement sheet set according to claim 1 or 2, wherein: The capsule wall of the microcapsule comprises at least one resin selected from polyurea, polyurethaneurea and polyurethane, The glass transition temperature of the capsule wall is 150° C. or higher, or the capsule wall does not exhibit a glass transition temperature.

4. The pressure measurement sheet set according to claim 3, wherein: The resin uses a trifunctional or higher functional polyisocyanate A which is an adduct of an aromatic or alicyclic diisocyanate and a compound having three or more active hydrogen groups in one molecule, and It is formed from a polyisocyanate B selected from aromatic diisocyanates and polymethylene polyphenyl polyisocyanates.

5. The pressure measurement sheet set according to claim 4, wherein: The mass ratio of the polyisocyanate A to the polyisocyanate B is 98 / 2 to 20 / 80.

6. The pressure measurement sheet set according to claim 1 or 2, wherein: The molecular weight of the coloring agent is 550 or more.

7. The pressure measurement sheet set according to claim 1 or 2, wherein: The microcapsules satisfy the relationship of formula (1), Formula (1) δ / Dm>0.010 δ represents the number average wall thickness of the microcapsules, in μm, and Dm represents the volume-based median diameter of the microcapsules, in μm.

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