TW202204151A - Set of sheets for pressure measurement and method for manufacturing the same, and, sheet for pressure measurement, and, sheet - Google Patents

Abstract

The present invention addresses the problem of providing a pressure measurement sheet set exhibiting high coloring density, a method for manufacturing the same, and a pressure measurement sheet exhibiting high coloring density. The present invention also addresses the problem of providing a sheet used for the pressure measurement sheet set exhibiting the high coloring density. This pressure measurement sheet set comprises a first sheet having a first resin base material and a first layer, and a second sheet having a second resin base material and a second layer, wherein the first layer includes microcapsules containing a coloring agent and a solvent with a boiling point of at least 100 DEG C; the second layer includes a developer; and when a 5*5 cm region of the surface of the second layer on the side opposite to the second resin base material is observed with a laser microscope, a crack with a depth of at least 2 [mu]m, a width of 10 [mu]m or less, and a length of at least 10 [mu]m is observed in the observation region.

Description

Sheet kit for pressure measurement, method for producing the same, sheet for pressure measurement, and sheet

The present invention relates to a sheet kit for pressure measurement, a method for producing the same, a sheet for pressure measurement, and a sheet.

In recent years, the need to measure the distribution of pressure tends to increase due to the high-performance and high-definition products. For example, in Patent Document 1, a pressure measurement sheet using microcapsules containing a coloring agent and a solvent for dissolving the coloring agent is proposed.

[Patent Document 1] Japanese Patent Laid-Open No. 55-137992

The inventors of the present invention produced the sheet for pressure measurement described in Patent Document 1 and examined it, and found that there is a further improvement in the development of the pressure-producing area by the reaction of the color-forming agent and the color-developing agent. The space of the color concentration of the color part.

Therefore, the subject of this invention is to provide the sheet kit for pressure measurement which expresses a high color development density, its manufacturing method, and the sheet for pressure measurement which expresses a high color development density. Moreover, the subject of this invention is to provide the sheet|seat provided in the sheet|seat set for pressure measurement which expresses the high color density|concentration.

In order to solve the above-mentioned problem, the present inventors have found that the above-mentioned problem can be solved by the following structure, as a result of intensive research.

[1] A sheet kit for pressure measurement, comprising: a first sheet having a first resin base material and a first layer; and a second sheet having a second resin base material and a second layer, the pressure In the sheet kit for measurement, the first layer contains microcapsules, and the microcapsules contain a solvent with a boiling point of 100° C. or higher and a coloring agent, the second layer contains a coloring agent, and the first layer is observed by a laser microscope. In the area of 5 cm×5 cm on the surface of the two layers opposite to the second resin substrate, cracks with a depth of 2 μm or more, a width of 10 μm or less and a length of 10 μm or more were observed in the observation area. [2] The sheet set for pressure measurement according to [1], wherein there are 10 or more cracks in an arbitrary field of view of 500 μm×500 μm in the area of 5 cm×5 cm. [3] The sheet set for pressure measurement according to [1] or [2], wherein the solvent having a boiling point of 100° C. or higher contains an aromatic group-containing solvent. [4] The sheet set for pressure measurement according to any one of [1] to [3], wherein the solvent having a boiling point of 100° C. or higher contains two or more kinds of aromatic group-containing solvents. [5] The sheet set for pressure measurement according to any one of [1] to [4], wherein the solvent having a boiling point of 100° C. or higher includes a solvent containing two aromatic groups in a molecule. [6] The sheet kit for pressure measurement according to any one of [3] to [5], wherein the solvent having a boiling point of 100° C. or higher further comprises a solvent containing an aliphatic structure, and the solvent containing an aromatic group The content is 50.0 to 90.0 mass % with respect to the total mass of the above-mentioned aromatic group-containing solvent and the above-mentioned aliphatic structure-containing solvent. [7] The sheet set for pressure measurement according to any one of [3] to [6], wherein the oil absorption of the aromatic group-containing solvent with respect to the second sheet is 2.0 to 20.0 g/ m ² . [8] The sheet set for pressure measurement according to any one of [1] to [7], wherein the coloring agent contains two or more kinds of aromatic group-containing coloring agents. [9] The sheet set for pressure measurement according to any one of [1] to [8], wherein the arithmetic mean roughness Ra of the first sheet is 3.0 to 7.0 μm. [10] The sheet set for pressure measurement according to any one of [1] to [9], wherein the arithmetic mean roughness Ra of the second sheet is 1.2 μm or less. [11] The sheet set for pressure measurement according to any one of [1] to [10], wherein the haze of the second resin base material is 20% or less. [12] The sheet set for pressure measurement according to any one of [1] to [11], wherein the first layer contains inorganic particles. [13] A sheet for pressure measurement, comprising a resin base material, a second layer, and a first layer in this order, wherein the first layer of the sheet for pressure measurement includes microcapsules, and the microcapsules contain microcapsules with a boiling point of 100° C. In the above solvent and coloring agent, the second layer contains a coloring agent, and when a 5 cm x 5 cm area of the surface of the second layer on the first layer side is observed with a laser microscope, it is observed in the observation area. Cracks with a depth of 2 μm or more, a width of 10 μm or less, and a length of 10 μm or more. [14] A method for manufacturing a sheet set for pressure measurement, which is the method for manufacturing a sheet set for pressure measurement according to any one of [1] to [12], comprising the step of manufacturing the second sheet , the step of manufacturing the above-mentioned second sheet has the following steps: coating the second layer-forming composition comprising a color developer and a polymer binder on the second resin substrate so that the solid content coating amount becomes 14.0 g/m ² or less, the obtained coating film is subjected to hot air treatment at 60°C or higher to form a second layer, and the mass content ratio of the color developer relative to the polymer binder in the second layer forming composition is 2.0 above. [15] The method for producing a sheet kit for pressure measurement according to [14], further comprising the step of producing the first sheet, wherein the step of producing the first sheet comprises the steps of: The composition for forming the first layer of the microcapsules of the solvent at 100° C. or higher and the coloring agent is applied on the first resin substrate, and the obtained coating film is subjected to drying treatment to form the first layer. [16] A sheet including a second resin base material and a second layer, wherein the second layer contains a color developer, and when the second layer and the second resin are observed by a laser microscope In the area of 5 cm×5 cm on the surface opposite to the base material, cracks with a depth of 2 μm or more, a width of 10 μm or less, and a length of 10 μm or more were observed in the observation area. [Inventive effect]

According to the present invention, it is possible to provide a pressure measurement sheet kit that exhibits high color development density and a method for producing the same, and a pressure measurement sheet that exhibits high color development density. Moreover, according to this invention, the sheet provided in the sheet set for pressure measurement which expresses high color density can be provided.

[Sheet kit for pressure measurement and method for manufacturing the same, and sheet for pressure measurement and method for manufacturing the same] Hereinafter, the present invention will be described in detail. In addition, in this specification, the numerical range represented using "-" means the range which includes the numerical value described before and after "-" as a lower limit and an upper limit. Moreover, in the numerical range described in stages in the present invention, the upper limit value or the lower limit value described in a certain numerical range may be replaced by the upper limit value or the lower limit value of the numerical range described in another stage. In addition, in the numerical range described in this specification, the upper limit value or the lower limit value described in a certain numerical range can be replaced with the value shown in an Example. In addition, in this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid.

As a characteristic point of the sheet set for pressure measurement and the sheet for pressure measurement of the present invention, cracks having a predetermined size (hereinafter also referred to as "specific cracks") on the surface of the second layer containing the color developer can be mentioned. point. In addition, the surface of the second layer refers to the surface of the second layer opposite to the second resin substrate side in the sheet set for pressure measurement, and refers to the first layer side of the second layer in the sheet for pressure measurement s surface. In the pressure measurement sheet set and the pressure measurement sheet of the present invention having the above-described structure, the color density of the color-developing portion generated by the reaction of the color-forming agent and the color-developing agent in the pressurized region is high.

Although the mechanism of action of the above-mentioned constitution and effects is not clear, the present inventors presume as follows. In the sheet set for pressure measurement and the sheet for pressure measurement, there are specific cracks on the surface of the second layer containing the color developer, whereby the color development from the first layer to the second layer in the pressurized area is present The agent and the solvent easily penetrate into the inside of the second layer along the specific cracks, and the color-developing reaction between the color-forming agent and the color-developing agent easily proceeds. That is, by the above-mentioned mechanism, it can be estimated that the color development density in the color development part is excellent.

Furthermore, this time, the present inventors have confirmed that the above-mentioned microcapsules (hereinafter also referred to as "specific microcapsules") containing a solvent and a coloring agent with a boiling point of 100° C. or higher contained in the first layer When the solvent contains two or more kinds of aromatic group-containing solvents, the color development concentration in the color development part is more excellent. For the above reason, it is presumed that the color-forming agent moves to the second layer containing the color-developing agent in a state of being dissolved in a solvent (a state in which precipitation is more suppressed), so that the color-forming agent easily penetrates into the second layer, and it is easy to proceed. The chromogenic reaction of the chromogenic agent and the chromogenic agent.

Furthermore, when the boiling point of the solvent contained in the specific microcapsules is 100° C. or higher, at the time of manufacture and/or storage of the specific microcapsules, and/or at the time of manufacture of the sheet set for pressure measurement and the sheet for pressure measurement And/or the volatilization of the solvent during storage is suppressed and it is easy to maintain in the specific microcapsules. This point can also be assumed to be one of the reasons why the color-developing reaction between the color-forming agent and the color-developing agent in the pressurized region is more easily performed when the pressure-measuring sheet set and the pressure-measuring sheet are used.

Hereinafter, the structure of the sheet set for pressure measurement and the sheet for pressure measurement of the present invention will be described in detail. Moreover, these manufacturing methods are also demonstrated in detail at the same time.

[First Embodiment] FIG. 1 is a cross-sectional view of one embodiment of the sheet set for pressure measurement. The sheet kit 10 for pressure measurement includes a first sheet 16 and a second sheet 22. The first sheet 16 has a first resin base 12 and is disposed on the first resin base 12 and includes a solvent and a hair dryer. In the first layer 14 of the colorant microcapsules 13, the second sheet 22 has a second resin substrate 18 and a second layer 20 disposed on the second resin substrate 18 and containing a color developer. Specific cracks 24 are present on the surface 20A of the second layer 20 on the side opposite to the side having the second resin base 18 . Here, the specific crack 24 represents a crack whose depth is 2 μm or more, width is 10 μm or less, and length is 10 μm or more, measured from the observed image obtained by observing the surface 20A of the second layer 20 with a laser microscope. In addition, a crack shows the recessed part (opening part) which continues and extends. The specific crack 24 may or may not penetrate the second layer 20 . An example of the observation image of the specific crack 24 observed by a laser microscope is shown in FIG.

As shown in FIG. 5 , when the sheet set 10 for pressure measurement is used, the first sheet is laminated so that the first layer 14 of the first sheet 16 and the second layer 20 of the second sheet 22 face each other. 16 and the second sheet 22 are used. By applying pressure from at least one of the first resin base material 12 side of the first sheet 16 and the second resin base material 18 side of the second sheet 22 in the obtained laminate, In this area, the microcapsules 13 are ruptured, and the color-developing agent contained in the microcapsules 13 comes out of the microcapsules 13 and undergoes color-developing reaction with the color-developing agent in the second layer 20 . As a result, color develops in the pressurized area.

In addition, although the 1st resin base material 12 and the 1st layer 14 are laminated|stacked directly in FIG. 1, it is not limited to this aspect, As mentioned later, you may arrange|position between the 1st resin base material 12 and the 1st layer 14. There are other layers (eg, adhesive layers). In addition, in FIG. 1, the 2nd resin base material 18 and the 2nd layer 20 are laminated directly, but it is not limited to this aspect, As mentioned later, you may arrange|position between the 2nd resin base material 18 and the 2nd layer 20 There are other layers (eg, adhesive layers).

Hereinafter, the structure of the 1st sheet 16 and the 2nd sheet 22 which comprise the sheet set 10 for pressure measurement is demonstrated in detail.

＜＜＜1st sheet＞＞＞ The first sheet 16 shown in FIG. 1 has the first resin base material 12 and the first layer 14 including the microcapsules 13 . Hereinafter, each member will be described in detail.

<<First resin base material>> The first resin base material is a member for supporting the first layer.

The first resin base material may be in either a sheet shape or a plate shape. Examples of the first resin substrate include polyester films such as polyethylene terephthalate films, cellulose derivative films such as cellulose triacetate, polyolefin films such as polypropylene and polyethylene, and resins such as polystyrene films. film.

The thickness of the first resin base material is not particularly limited, but is preferably 10 to 200 μm.

＜＜1st floor＞＞ ＜Microcapsules＞ The first layer contains microcapsules containing a solvent and a color-forming agent. The above-mentioned microcapsules include microcapsules (hereinafter also referred to as "specific microcapsules") containing a solvent and a coloring agent having a boiling point of 100° C. or higher. In addition, the above-mentioned first layer may also contain other microcapsules other than the specific microcapsules (for example, microcapsules containing a solvent with a boiling point of less than 100° C. and a coloring agent (wherein, no solvent with a boiling point of 100° C. or higher is contained) microcapsules. ).

(specific microcapsules) Hereinafter, the material constituting the specific microcapsule will be described in detail first. Certain microcapsules typically have a core and a capsule wall for containing the core material (the inclusions (also referred to as inclusions)) that make up the core. Specific microcapsules contain a solvent and a color-forming agent with a boiling point of 100°C or higher as a core material (components contained therein). Since the coloring agent is contained in the microcapsules, the coloring agent can exist stably until the microcapsules are ruptured by applying pressure.

"Capsule Wall" Certain microcapsules have a capsule wall containing a core material. Examples of the material (wall material) of the capsule wall of the specific microcapsules include known resins conventionally used as wall materials for color-forming agent-containing microcapsules in applications of pressure sensitive carbon paper or thermal recording paper. As said resin, a polyurethane, a polyurea, a polyurethane urea, a melamine-formaldehyde resin, and gelatin are mentioned specifically,.

It is preferable that the capsule wall of a specific microcapsule consists substantially of resin. Substantially composed of 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. That is, it is preferable that the capsule wall of a specific microcapsule is made of resin. In addition, the polyurethane refers to a polymer having a plurality of urethane bonds, and a reaction product formed from a raw material containing a polyol and a polyisocyanate is preferable. In addition, the polyurea is a polymer having a plurality of urea bonds, and a reaction product formed from a raw material containing a polyamine and a polyisocyanate is preferable. In addition, it is possible to synthesize a polyurea using a polyisocyanate without using a polyamine by reacting a part of the polyisocyanate with water to form a polyamine. In addition, the urethane urea refers to a polymer having a urethane bond and a urea bond, and a reaction product formed from a raw material comprising a polyol, a polyamine and a polyisocyanate is preferable. Moreover, when a polyol and polyisocyanate are made to react, a part of polyisocyanate reacts with water and becomes a polyamine, as a result, a polyurethane urea can be obtained. In addition, the melamine-formaldehyde resin is preferably the reaction product formed by the polycondensation of melamine and formaldehyde.

In addition, the said polyisocyanate means the compound which has two or more isocyanate groups, and aromatic polyisocyanate and aliphatic polyisocyanate are mentioned. The polyisocyanate may be, for example, an adduct (adduct) of a polyhydric alcohol such as trimethylolpropane and a bifunctional polyisocyanate. In addition, the above-mentioned polyol is a compound having two or more hydroxyl groups, for example, low-molecular-weight polyols (eg, aliphatic polyols, aromatic polyols). In addition, "low-molecular-weight polyols" mean molecular weights of 400 or less ), polyvinyl alcohol, polyether polyols, polyester polyols, polylactone polyols, castor oil polyols, polyolefin polyols and hydroxyl-containing amine compounds (such as Examples of amino alcohols include N,N,N',N'-tetrakis[2-hydroxyl groups of propylene oxide or ethylene oxide adducts of amino compounds such as ethylenediamine, for example. propyl]ethylenediamine, etc.). Moreover, the said polyamine is a compound which has two or more amine groups (a first-order amine group or a second-order amine group), for example, diethylenetriamine, triethylenetetramine, and 1,3-propane are mentioned. Aliphatic polyamines such as diamine and hexamethylenediamine; epoxy compound adducts of aliphatic polyamines; alicyclic polyamines such as piperidine; 3,9-bis-aminopropyl-2,4 ,8,10-Tetraoxaspiro-(5,5) Undecane and other heterocyclic diamines.

"Colorant" Certain microcapsules contain coloring agents. Here, the "color-forming agent" refers to a compound that develops color from a colorless state by contacting with a color-developing agent to be described later. As the coloring agent, an electron-donating dye precursor (precursor of a coloring dye) is preferable. That is, as a color-forming agent, an electron-donating leuco dye is preferable.

From the viewpoint of further increasing the color density of the color-developing portion, it is preferable that the color-forming agent contained in the specific microcapsules is an aromatic group-containing coloring agent (hereinafter also referred to as "specific color-forming agent"). In other words, it is preferable that the specific microcapsules contain an aromatic group-containing coloring agent as a coloring agent. In the specific microcapsules, it is more preferable to contain two or more kinds of aromatic group-containing coloring agents. When two or more kinds of color formers are contained, the state of being dissolved in the solvent is easily maintained, so that the color development density is further excellent. Here, "containing an aromatic group" means containing a monocyclic aromatic ring group and/or a condensed polycyclic aromatic ring group in the molecule.

As an aromatic ring contained in the said aromatic group, an aromatic hydrocarbon ring and an aromatic heterocyclic ring are mentioned. As the above-mentioned aromatic hydrocarbon ring, any of a monocyclic ring and a condensed polycyclic ring may be used as described above. Moreover, the said aromatic hydrocarbon ring may have a substituent. In addition, when the above-mentioned aromatic hydrocarbon ring has a plurality of substituents, the substituents may be bonded to each other to form an alicyclic ring. In other words, the above-mentioned aromatic hydrocarbon ring may contain an alicyclic structure (for example, a benzolactone ring or the like). The number of carbon atoms in the aromatic hydrocarbon ring is not particularly limited, but is preferably 6 to 30, more preferably 6 to 18, and even more preferably 6 to 10. As a monocyclic aromatic hydrocarbon ring, a benzene ring is mentioned, for example. As a condensed polycyclic aromatic hydrocarbon ring, a naphthalene ring is mentioned, for example.

As the above-mentioned aromatic heterocyclic ring, any of a monocyclic ring and a condensed polycyclic ring may be used as described above. Moreover, the said aromatic heterocyclic ring may have a substituent. In addition, when the said aromatic heterocyclic ring has a plurality of substituents, the substituents may be mutually bonded to form an alicyclic ring. In other words, the above-mentioned aromatic heterocycle may contain an alicyclic structure. As a hetero atom contained in the said aromatic heterocyclic ring, a nitrogen atom, an oxygen atom, and a sulfur atom are mentioned, for example. The number of ring members of the aromatic heterocycle is not particularly limited, but 5 to 18 are preferred. Examples of the above-mentioned aromatic heterocyclic ring include a pyridine ring, a pyridine ring, a pyrimidine ring, a pyridine ring, a trisium ring, a thiophene ring, a thiazole ring, an imidazole ring, a koushankou ring, and a benzoshankou ring.

The number of the aromatic groups in the specific coloring agent is not particularly limited, and may be one or two or more. In addition, when the specific coloring agent contains two or more aromatic groups, the two aromatic groups may be bonded to each other by a substituent that can exist on each aromatic group to form a polycyclic structure (which does not include condensed polycyclic structures).

As the specific coloring agent, as long as it contains an aromatic group, a well-known one can be used for applications of pressure-sensitive carbon paper or thermal recording paper. As the specific coloring agent, for example, triphenylmethanephthalide-based compounds, fluorescent yellow parent-based compounds, phenothiazine-based compounds, indolylphthalide-based compounds, and azaindolylphthalide-lactone-based compounds can be mentioned. compounds, white gold amine compounds, rhodamine lactamide compounds, triphenylmethane compounds, diphenylmethane compounds, triazene compounds, spiropyran compounds and perylene compounds. For details of the above-mentioned compounds, reference can be made to the descriptions in Japanese Patent Laid-Open No. 5-257272 and WO2009/8248 [0029] to [0034]. As the specific coloring agent, from the viewpoint of more excellent coloring concentration, a coloring agent containing the Kouyamakou star ring in the molecule is preferable.

The molecular weight of the specific coloring agent is not particularly limited, and is preferably 300 or more. The upper limit is not particularly limited, but preferably 1000 or less.

As a specific coloring agent, 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)-phthalolactone, 2-aniline Base-6-dibutylamino-3-methyl fluorescein precursor, 6-diethylamino-3-methyl-2-(2,6-stubamino)-fluorescein precursor, 2 -(2-Chloroanilino)-6-dibutylamino fluorescent yellow precursor, 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide, 2 - Anilino-6-diethylamino-3-methyl fluorescein yellow parent, 9-[ethyl (3-methylbutyl) amino] spiro[12H-benzo[a] mouth Yamaguchi star- 12,1'(3'H)Isobenzofuran]-3'-one, 2'-methyl-6'-(N-p-tolyl-Nethylamino)spiro[isobenzofuran-1 (3H),9'-[9H]kouyamaguchi-shin]-3-one, 3',6'-bis(diethylamino)-2-(4-nitrophenyl)spiro[isoindole- 1,9'-Kouyamaguchi star]-3-one, 6'-(diethylamino)-1',3'-dimethylfluorescein precursor and 3,3-bis(2-methyl- 1-Octyl-3-indolyl) phthalolactone, etc. Moreover, as a specific color former, Pink-DCF and Orange-DCF (both are manufactured by Hodogaya Chemical Co., Ltd.) can also be used.

The content of the specific color former is preferably 50 to 100% by mass, more preferably 80 to 100% by mass, and even more preferably 90 to 100% by mass relative to the total amount of the color former.

"Solvents with a boiling point of 100°C or higher" A solvent having a boiling point of 100° C. or higher is contained in the specific microcapsules. In addition, the so-called "boiling point" refers to the boiling point under standard atmospheric pressure. The boiling point of the solvent contained in the specific microcapsules is preferably 120°C or higher, more preferably 150°C or higher, and even more preferably 200°C or higher. Moreover, although it does not specifically limit as an upper limit of a boiling point, For example, it is 400 degrees C or less.

As a solvent with a boiling point of 100° C. or higher contained in the specific microcapsules, it is preferable to contain an aromatic group-containing solvent. In other words, it is preferable that the specific microcapsules contain a solvent having a boiling point of 100° C. or higher and an aromatic group-containing solvent (hereinafter, also referred to as a “specific solvent”). Here, "containing an aromatic group" means containing a monocyclic aromatic ring group and/or a condensed polycyclic aromatic ring group in the molecule.

As an aromatic ring contained in the said aromatic ring group, an aromatic hydrocarbon ring and an aromatic heterocyclic ring are mentioned. As the above-mentioned aromatic hydrocarbon ring, any of a monocyclic ring and a condensed polycyclic ring may be used as described above. Moreover, the said aromatic hydrocarbon ring may have a substituent. In addition, when the above-mentioned aromatic hydrocarbon ring has a plurality of substituents, the substituents may be bonded to each other to form an alicyclic ring. In other words, the above-mentioned aromatic hydrocarbon ring may have an alicyclic structure. The number of carbon atoms in the aromatic hydrocarbon ring is not particularly limited, but is preferably 6 to 30, more preferably 6 to 18, and even more preferably 6 to 10. As a monocyclic aromatic hydrocarbon ring, a benzene ring is mentioned, for example. As a condensed polycyclic aromatic hydrocarbon ring, a naphthalene ring is mentioned, for example.

As the above-mentioned aromatic heterocyclic ring, any of a monocyclic ring and a condensed polycyclic ring may be used as described above. Moreover, the said aromatic heterocyclic ring may have a substituent. In addition, when the said aromatic heterocyclic ring has a plurality of substituents, the substituents may be mutually bonded to form an alicyclic ring. In other words, the above-mentioned aromatic heterocycle may contain an alicyclic structure. As a hetero atom contained in the said aromatic heterocyclic ring, a nitrogen atom, an oxygen atom, and a sulfur atom are mentioned, for example. The number of ring members of the aromatic heterocycle is not particularly limited, but 5 to 18 are preferred. As said aromatic heterocyclic ring, a pyridine ring, a pyridine ring, a pyrimidine ring, a pyridine ring, a tris ring, a thiophene ring, a thiazole ring, an imidazole ring, and a Koyamaguchi star ring are mentioned, for example.

The number of the aromatic groups in the specific solvent is not particularly limited, and may be one or two or more. In addition, when the specific solvent contains two or more aromatic groups, the two aromatic groups may be bonded to each other by a substituent that can exist on each aromatic group to form a polycyclic structure (which does not include condensed polycyclic groups). ring structure).

Among the specific solvents, a solvent containing two aromatic groups in the molecule is preferable from the viewpoint of further increasing the color concentration of the color-developing portion. The lower limit of the content of the specific solvent containing two aromatic groups in the molecule is, for example, 5% by mass or more, preferably 50% by mass or more, and more preferably 70% by mass or more, based on the total mass of the specific solvent. . As an upper limit of content of the specific solvent containing two aromatic groups in a molecule|numerator, it is 100 mass % or less, for example.

The molecular weight of the specific solvent is not particularly limited, but is often 100 or more. Among them, 150 or more is preferable. The upper limit is not particularly limited, and is preferably 1000 or less, more preferably 500 or less, and even more preferably 300 or less.

Examples of the specific solvent include compounds represented by the following general formula (1), and compounds represented by the following general formulae (1A) to (1C) are preferred, and among them, the color development of the color-developing portion is further improved. From the viewpoint of concentration, the compound represented by the following general formula (1A) is more preferable.

[Chemical formula 1]

In the general formula (1), m ¹ represents 0 or 1. As m ¹ , 1 is preferable from the viewpoint of further increasing the color density of the color-developing portion.

When m ¹ represents 0: When m ¹ represents 0, Ar ¹ represents an aromatic ring having ^a substituent represented by -LA -RA (hereinafter, also referred to as "substituent ^W ".). Examples of the aromatic ring represented by Ar ¹ include an aromatic hydrocarbon ring and an aromatic heterocyclic ring. The aromatic hydrocarbon ring and the aromatic heterocyclic ring are as described above.

In the substituent W, L ^A represents a single bond, an oxysulfonyl group (* ¹ -SO ₂ -O-* ² ) or a sulfonyloxy group (* ¹ -O-SO ₂ -* ² ). In addition, * ¹ represents the bonding position with Ar ¹ , and * ² represents the bonding position with ^RA .

In the substituent W, R ^A represents a monovalent aliphatic hydrocarbon group. The monovalent aliphatic hydrocarbon group represented by R ^A may be any of a monovalent saturated aliphatic hydrocarbon group and a monovalent unsaturated aliphatic hydrocarbon group. Moreover, any of linear, branched chain and cyclic may be sufficient. The number of carbon atoms in the monovalent aliphatic hydrocarbon group is not particularly limited, but is, for example, 1 to 15, preferably 1 to 10, more preferably 1 to 6, and even more preferably 1 to 4. As said monovalent aliphatic hydrocarbon group, an alkyl group, an alkenyl group, and an alkynyl group are mentioned, An alkyl group is preferable. In addition, the above-mentioned monovalent aliphatic hydrocarbon group may have a substituent.

^The aromatic ring represented by Ar ¹ may have one substituent represented by -LA ^-RA , or may have two or more.

- When m ¹ represents 1: When m ¹ represents 1, Ar ¹ and Ar ² each independently represent a monovalent aromatic group which may have a substituent. The monovalent aromatic group represented by Ar ¹ and Ar ² includes a monovalent aromatic hydrocarbon group and a monovalent aromatic heterocyclic group. The aromatic hydrocarbon ring contained in the monovalent aromatic hydrocarbon group and the aromatic heterocyclic ring contained in the monovalent aromatic heterocyclic group are as described above. In addition, the monovalent aromatic hydrocarbon group and the monovalent aromatic heterocyclic group can be formed by removing one hydrogen atom from the above-mentioned aromatic hydrocarbon ring and the above-mentioned aromatic heterocyclic ring. Among the monovalent aromatic groups represented by Ar ¹ and Ar ² , a monovalent aromatic hydrocarbon group is preferable, and a phenyl group is more preferable.

The monovalent aromatic group represented by Ar ¹ and Ar ² may have a substituent. Although it does not specifically limit as a substituent, Non-aromatic substituents are preferable, for example, the above-mentioned substituent W etc. are mentioned.

L ¹ represents a single bond, a divalent aliphatic hydrocarbon group, or a divalent linking group represented by the following general formula (L ^A ).

[Chemical formula 2]

In the above-mentioned general formula (LA ), R ¹ represents ^a monovalent aromatic group which may have a substituent. In the general formula (1), R ¹ has the same meaning as that of Ar ¹ and Ar ² (that is, a monovalent aromatic group which may have a substituent) when m ¹ represents 1, and the preferred aspects are also the same. .

The divalent aliphatic hydrocarbon group represented by L ¹ may be any of a divalent saturated aliphatic hydrocarbon group and a divalent unsaturated aliphatic hydrocarbon group. Moreover, any of linear, branched chain and cyclic may be sufficient. The number of carbon atoms in the divalent aliphatic hydrocarbon group is not particularly limited, but is, for example, 1 to 10, preferably 1 to 6, more preferably 1 to 4, and even more preferably 1 or 2. Examples of the divalent aliphatic hydrocarbon group include an alkylene group, an alkenylene group, and an alkynylene group, and an alkylene group is preferred. In addition, in the above-mentioned divalent aliphatic hydrocarbon group, a carbon atom may be substituted with a divalent group represented by >C=CH ₂ .

Among them, a single bond or a divalent aliphatic hydrocarbon group is preferable as L ¹ .

[Chemical formula 3]

In the general formula (1A), L ¹¹ represents a single bond or a divalent aliphatic hydrocarbon group. The divalent aliphatic hydrocarbon group represented by L ¹¹ has the same meaning as the divalent aliphatic hydrocarbon group represented by L ¹ in the general formula (1), and the preferred aspects are also the same. R ¹¹ and R ¹² each independently represent a non-aromatic substituent. The non-aromatic substituent represented by R ¹¹ and R ¹² is not particularly limited, but a monovalent aliphatic hydrocarbon group is preferable, and specifically, those represented by R ^A in the above-mentioned substituent W can be mentioned. The monovalent aliphatic hydrocarbon group is the same. Among them, the monovalent aliphatic hydrocarbon group is preferably an alkyl group having 1 to 4 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms. n ¹¹ and n ¹² each independently represent an integer of 0 to 5. Preferably, n ¹¹ and n ¹² represent an integer of 0 to 2. Wherein, it is preferable that any one of n ¹¹ and n ¹² represents 1 or 2 and the other represents 0 or 1. In addition, when n ¹¹ and n ¹² represent an integer of 2 or more, the plural R ^11s and the plural R ^12s may be the same or different from each other.

Specific examples of the solvent represented by the general formula (1A) include 1,2-dimethyl-4-(1-phenylethyl)benzene, 1,3-dimethyl-4-(1). -Phenylethyl)benzene, 1,4-dimethyl-2-(1-phenylethyl)benzene, 1-(ethylphenyl)-1-phenylethane, isopropylbiphenyl ( For example, 4-isopropyl biphenyl), diisopropyl biphenyl (for example, 4,4'-isopropyl biphenyl) and α-methylstyrene dimer and the like.

[Chemical formula 4]

In general formula (1B), L ²¹ represents a single bond, an oxysulfonyl group (* ¹ -SO ₂ -O-* ² ) or a sulfonyloxy group (* ¹ -O-SO ₂ -* ² ). In addition, * ¹ represents the bonding position to the phenyl group shown in general formula (1B), and * ² represents the bonding position to R ²² . R ²¹ represents a non-aromatic substituent. The meaning of the non-aromatic substituent represented by R ²¹ is the same as that of the non-aromatic substituent represented by R ¹¹ in the general formula (1A), and the preferred aspects are also the same. n ²¹ represents an integer of 0-5. n ²¹ preferably represents an integer of 0 to 2. In addition, when n ²¹ represents an integer of 2 or more, the plural R ^21s present may be the same or different from each other. R ²² represents a monovalent aliphatic hydrocarbon group. Examples of the monovalent aliphatic hydrocarbon group represented by R ²² include the same ones as the monovalent aliphatic hydrocarbon group represented by R ^A in the above-mentioned substituent W.

Specific examples of the solvent represented by the general formula (1B) include a benzenesulfonic acid methyl group, a p-toluenesulfonic acid methyl group, and a linear alkylbenzene having 1 to 15 carbon atoms.

[Chemical formula 5]

In the general formula (1C), R ³¹ , R ³² and R ³³ each independently represent a non-aromatic substituent. The meanings of the non-aromatic substituents represented by R ³¹ , R ³² and R ³³ are the same as those of the non-aromatic substituent represented by R ¹¹ in the general formula (1A), and the preferred aspects are also the same. n ³¹ , n ³² and n ³³ each independently represent an integer of 0 to 5. Preferably, n ³¹ , n ³² and n ³³ each independently represent an integer of 0 to 2. In addition, when n ³¹ , n ³² and n ³³ represent an integer of 2 or more, plural R ^31s , plural R ^32s , and plural R ^33s may be the same or different from each other.

Specific examples of the solvent represented by the general formula (1C) include tricresyl phosphate, tricresyl phosphate, and the like.

From the viewpoint of further increasing the color concentration of the color-developing portion, any one of the specific solvents contained in the aromatic group-containing solvent is preferably selected from the solvents represented by the general formula (1A) described above.

From the viewpoint of further increasing the color density of the color-developing portion, the specific solvent contained in the specific microcapsules is preferably two or more, more preferably three or more, and even more preferably four or more. 1,2-dimethyl-4-(1-phenylethyl)benzene, 1,3-dimethyl benzene, 1,3-dimethyl benzene, -Combination of 4-(1-phenylethyl)benzene, 1,4-dimethyl-2-(1-phenylethyl)benzene and 1-(ethylphenyl)-1-phenylethane Wait.

It is preferable that the specific microcapsules further contain a solvent containing an aliphatic structure as a solvent having a boiling point of 100° C. or higher. The solvent containing an aliphatic structure can contribute to the formation of the capsule wall as described later. Here, "containing an aliphatic structure" means containing a non-aromatic hydrocarbon group in the molecule. In addition, in the above-mentioned non-aromatic hydrocarbon group, the carbon atoms in the hydrocarbon group may be substituted with a hetero atom, carbonyl carbon, or the like. Moreover, the said hydrocarbon group may have a substituent. In addition, the solvent containing an aliphatic structure does not contain an aromatic group. In other words, the solvent containing an aliphatic structure does not contain an aromatic ring in the molecule. Therefore, a solvent containing an aromatic group and an aliphatic structure is classified as an aromatic group-containing solvent. The solvent containing an aliphatic structure is not particularly limited, and examples thereof include aliphatic hydrocarbons such as diethyl succinate, methyl laurate, and isoalkanes (for example, isoalkanes having 10 or more carbon atoms); soybean oil, corn oil , natural animal and vegetable oils such as cottonseed oil, rapeseed oil, olive oil, coconut oil, castor oil and fish oil, as well as high-boiling fractions of natural products such as mineral oil. The solvent containing an aliphatic structure may be used individually by 1 type, or may be used in mixture of 2 or more types.

The specific microcapsule preferably contains at least a specific solvent, and more preferably contains a specific solvent and a solvent containing an aliphatic structure. When the specific microcapsules contain a specific solvent and a solvent containing an aliphatic structure as a solvent having a boiling point of 100°C or higher, the content of the specific solvent relative to the solvent containing an aliphatic structure is considered to further increase the color concentration of the color-developing portion. The total mass of the solvent and the specific solvent is preferably 50.0 to 90.0 mass %, and more preferably 75.0 to 90.0 mass % from the viewpoint of further excellent color development concentration.

In the specific microcapsules, as the mass ratio of the solvent with a boiling point of 100°C or higher and the color-forming agent (mass of the solvent with a boiling point of 100°C or higher/mass of the color-forming agent), from the viewpoint of more excellent color concentration, 98/ The range of 2-30/70 is preferable, and the range of 97/3-40/60 is more preferable.

"Other Ingredients" The specific microcapsules may contain, in addition to the above-mentioned components, one or more additives such as light stabilizers, antioxidants, paraffins, ultraviolet absorbers, and deodorants, as required. In addition, the specific microcapsules may contain solvents having a boiling point of less than 100° C. (for example, ketones such as methyl ethyl ketone, esters such as ethyl acetate, and alcohols such as isopropyl alcohol) within the range that does not hinder the effects of the present invention. Wait).

"Manufacturing method of specific microcapsules" The manufacturing method of a specific microcapsule is not specifically limited, For example, well-known methods, such as an interfacial polymerization method, an internal polymerization method, a phase separation method, an external polymerization method, and a coacervation method, are mentioned. Among them, the interfacial polymerization method is preferable. Hereinafter, the interfacial polymerization method will be described by taking the production method of specific microcapsules whose capsule walls are polyurea or polyurethane urea as an example. The interfacial polymerization method includes mixing a color former, a solvent with a boiling point of 100° C. or higher, and a capsule wall material (for example, a raw material containing at least one selected from the group consisting of polyisocyanate, polyol, and polyamine. In addition, When a polyisocyanate is reacted with water to produce a polyamine in the reaction system, the oil phase of the polyol and polyamine may not be used.) The oil phase is dispersed in the water phase containing an emulsifier to prepare an emulsion (emulsification). step) and the interfacial polymerization method of polymerizing the capsule wall material at the interface of the oil phase and the water phase to form the capsule wall and forming the microcapsules containing the color-forming agent (encapsulation step) is preferable. In addition, the mass ratio of the total amount of polyol and polyamine to the amount of polyisocyanate (the total amount of polyol and polyamine/the amount of polyisocyanate) in the above-mentioned raw materials is not particularly limited, and 0.1/99.9 to 30/70 is Preferably, 1/99～25/75 is more preferable. Moreover, in an emulsification process, it is preferable that the solvent whose boiling point is 100 degreeC or more contains a specific solvent and a solvent containing an aliphatic structure. In addition, the solvent containing an aliphatic structure tends to precipitate polyisocyanate, which is a raw material of the capsule wall, and can contribute to the formation of the capsule wall.

Moreover, the kind of the emulsifier used in the said emulsification process is not specifically limited, For example, a dispersing agent and a surfactant are mentioned. As a dispersing agent, polyvinyl alcohol is mentioned, for example.

(other microcapsules) The first layer may also contain other microcapsules than the specific microcapsules as described above. Examples of other microcapsules include microcapsules containing a solvent and a color-forming agent having a boiling point of less than 100° C. (however, a solvent having a boiling point of 100° C. or higher is not contained). In the microcapsules contained in the first layer, the content of the specific microcapsules is preferably 80% by mass or more, more preferably 90% by mass or more, and more preferably 95% by mass or more with respect to the total mass of the microcapsules , 98% by mass or more is particularly good. Moreover, as an upper limit, it is 100 mass % or less.

(physical properties of microcapsules) Hereinafter, the physical properties of the microcapsules (specific microcapsules and other microcapsules optionally included) contained in the first layer will be described. The average particle size of the microcapsules contained in the first layer is not particularly limited, and is preferably 1 to 80 μm, more preferably 5 to 70 μm, and even more preferably 10 to 50 μm in terms of the volume-based median diameter (D50). Preferably, 15 to 40 μm is particularly preferred. The average particle diameter is appropriately designed according to the pressure region to be measured, but is preferably 20 to 40 μm in a low pressure region of 1 MPa or less, and preferably 25 to 40 μm in a slight pressure region of 0.1 MPa or less. The volume-based median diameter of the microcapsules can be controlled by adjusting the production conditions of the microcapsules and the like. Here, the volume-based median diameter of the microcapsules refers to the difference between the large-diameter side and the small-diameter side particles when the entire microcapsule is divided into two with the particle size at which the cumulative volume becomes 50% as a threshold value. The sum of the volumes becomes the diameter of the equivalent. That is, the median diameter corresponds to so-called D50. It is calculated by measuring the size of all the microcapsules in the range of 500 μm×500 μm by photographing the surface of the 1st layer of the 1st sheet with the 1st layer containing the 1st layer of microcapsules by an optical microscope at 1000 times. value.

The number average wall thickness of the capsule wall of the microcapsules is not particularly limited, but is preferably 0.01 to 2.0 μm, more preferably 0.02 to 1.0 μm, from the viewpoint of excellent pressure responsiveness. In addition, the wall thickness of the microcapsule 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 thickness of each capsule wall of five microcapsules obtained by scanning electron microscopy (SEM). The average value of the thickness (μm) was averaged. More specifically, a cross-sectional section of the first sheet having the first layer containing microcapsules was prepared, and the cross section was observed at 200 magnifications by SEM. (The value of the average particle size of the microcapsules) On the basis of any 5 microcapsules with a particle size in the range of 1.1, the cross section of each selected microcapsule was observed at 15,000 times, and the thickness of the capsule wall was obtained to calculate the average. value. In addition, the long diameter refers to the longest diameter when the microcapsules are observed.

The ratio (δ/Dm) of the number-average wall thickness δ of the microcapsules to the average particle diameter of the microcapsules (δ/Dm) is not particularly limited, and is often 0.001 or more. Among them, it is preferable to satisfy the relationship of the formula (1) from the viewpoint of being excellent in the color development density according to the pressure. Formula (1) δ/Dm＞0.001 That is, it is preferable that the above-mentioned ratio (δ/Dm) is larger than 0.001. Moreover, it is preferable that the said ratio (delta/Dm) is 0.002 or more. The upper limit is not particularly limited, but preferably 0.2 or less.

(Content of Microcapsules in the First Layer) The content of the microcapsules in the first layer is not particularly limited, but is preferably 60 to 98% by mass, more preferably 75 to 95% by mass relative to the total mass of the first layer . In addition, the content of the coloring agent in the first layer is not particularly limited, but is preferably 0.1 to 2.0 g/m ² , more preferably 0.2 to 1.0 g/m ² .

<Other components that can be contained in the first layer> The first layer may contain other components other than the above-mentioned microcapsules. Examples of other components include polymer binders, mold release agents (eg, inorganic particles), optical brighteners, antifoaming agents, penetrants, ultraviolet absorbers, surfactants, and antiseptics. The mass per unit area (solid content coating amount) (g/m ² ) of the first layer is not particularly limited, but is, for example, 0.5 to 20.0 g/m ² , more preferably 0.5 to 10.0 g/m ² .

When the sheet set for pressure measurement is bonded and used under high humidity and high pressure (for example, 1 MPa or more, humidity 70%), the first sheet and the second sheet may stick together without peeling off. Therefore, it is preferable that the 1st layer contains an inorganic particle as a mold release agent for the purpose of improving easy peelability. Examples of the inorganic particles include silica particles (eg, colloidal silica), alumina particles, and the like, and silica particles are preferred. In addition, the inorganic particles referred to here are distinguished from the color developer contained in the second layer in the second sheet described later, and are not electron acceptor compounds. The particle diameter 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 the volume-based median diameter. The particle diameter of the inorganic particles can be measured by the same method as the average particle diameter of the microcapsules described above. As content of an inorganic particle, 1-20 mass % is preferable with respect to the total mass of a 1st layer, 5-20 mass % is more preferable.

Examples of the polymer binder contained in the first layer include styrene-butadiene copolymer, polyvinyl acetate, polyacrylate, polyvinyl alcohol, polyacrylic acid, maleic anhydride-styrene Copolymers, (meth)acrylic acid-styrene copolymers, olefin resins, modified acrylate copolymers, starch, casein, gum arabic, gelatin, carboxymethyl cellulose or its salts, and methyl cellulose, etc. Molecules and natural polymers. As a polymer binder, which is selected from the group consisting of styrene-butadiene copolymer, (meth)acrylic acid-styrene copolymer, olefin resin, modified acrylate copolymer and carboxymethyl cellulose or its salt One or more of the group is preferred. The polymer binder may be used alone or in combination of two or more. As content of a polymer binder, 0.1-10 mass % is preferable with respect to the total mass of a 1st layer, and 0.5-5 mass % is more preferable.

As the surfactant contained in the first layer, any one or more of an anionic surfactant, a cationic surfactant, and a nonionic surfactant is preferably contained, and an anionic surfactant and a nonionic surfactant are contained. Any one or more of the surfactants are more preferable. Surfactant may be used individually by 1 type, or may be used in mixture of 2 or more types. As content of a surfactant, 0.1-10 mass % is preferable with respect to the total mass of a 1st layer, and 0.5-5 mass % is more preferable.

<<Method for forming the first layer>> The formation method of the said 1st layer is not specifically limited, A well-known method is mentioned. For example, the method of apply|coating the composition for 1st layer formation containing specific microcapsules and a solvent whose boiling point is 100 degreeC or more on a 1st resin base material, and drying a coating film as needed is mentioned. It is preferable that the composition for forming a first layer contains at least specific microcapsules and a solvent having a boiling point of 100°C or higher. Moreover, the microcapsule dispersion liquid obtained by the above-mentioned interfacial polymerization method can also be used as the composition for 1st layer formation. The composition for forming a 1st layer may contain other components which may be contained in the above-mentioned 1st layer.

The method of coating the composition for forming the first layer is not particularly limited, and examples of the coating machine used for coating include an air knife coater, a rod coater, a bar coater, and a curtain coater. Cloth coaters, gravure coaters, extrusion coaters, die coaters, slide bead coaters and knife coaters. The method of coating may be a method of coating the composition for forming the first layer in a single layer, a step of dividing the coating into a plurality of times, or a method of dividing the material contained in the composition for forming the first layer into separate layers. The step of coating each composition. Specifically, for example, a method of applying a plurality of layers of the composition A for forming the first layer containing the binder and not containing the microcapsules, and the composition B for forming the first layer containing the binder and the microcapsules can be mentioned.

After apply|coating the composition for 1st layer formation on a 1st resin base material, you may give a drying process to a coating film as needed. As a drying process, a heat process is mentioned.

＜＜Other components＞＞ The first sheet may have other members than the above-mentioned first resin base material and first layer. For example, the first sheet may have an adhesive layer between the first resin base material and the first layer for improving the adhesiveness of both. The thickness of the adhesive layer is not particularly limited, and is preferably 0.005 to 5.0 μm, more preferably 0.01 to 2.0 μm, and even more preferably 0.05 to 1.0 μm.

The arithmetic mean roughness Ra of the first sheet is preferably 3.0 to 7.0 μm from the viewpoint of further improving the color density and from the viewpoint of being more excellent in image quality (resolution). In addition, the arithmetic mean roughness Ra of the first sheet means the arithmetic mean roughness of the surface of the first sheet facing the second sheet (the side in contact with) when the pressure measurement sheet set is used Degree Ra. When the first layer is located on the outermost surface of the first sheet on the side facing the second sheet, the arithmetic mean roughness Ra corresponds to the side opposite to the first resin substrate side of the first layer The arithmetic mean roughness Ra of the surface. In addition, the arithmetic mean roughness Ra of the 1st sheet in this specification means the arithmetic mean roughness Ra prescribed|regulated by JIS B 0681-6:2014. In addition, as a measurement device, a scanning white light interferometer using an optical interference method (specifically, NewView5020 manufactured by Zygo: Stich mode; objective lens×50 times; intermediate lens×0.5 times) was used.

When the arithmetic mean roughness Ra of the first sheet is 3.0 μm or more, since the amount of the color former is often sufficient, a higher color density tends to occur. 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 properly absorb the disintegration of the microcapsules in the pressurized region. The solvent that flows out together with the color-forming agent can obtain a good image quality with little penetration. In addition, the arithmetic mean roughness Ra of the first sheet can be controlled by adjusting the solid content coating amount of the composition for forming a first layer and adjusting the amount of microcapsules in the first layer of the first sheet.

＜＜＜Second sheet＞＞＞ The second sheet 22 shown in FIG. 1 has the second layer 20 including the second resin base material 18 and the color developer arranged on the second resin base material 18 . Specific cracks 24 are present on the surface 20A of the second layer 20 on the side opposite to the side having the second resin base 18 . Hereinafter, each member will be described in detail.

<<Second resin base material>> The second resin base material is a member for supporting the second layer. The aspect of the second resin substrate is the same as the aspect of the first resin substrate described above. From the viewpoint of being able to visually recognize the color development state after the pressure measurement through the second resin base material, it is preferable that the second resin base material is transparent. The haze of the second resin base material is preferably 20% or less, more preferably 0 to 20%, and even more preferably 0 to 10%. The above-mentioned haze value is the total light haze value, and the total light haze of the second resin base material was measured according to JIS-K-7361 using a haze meter (HGM-2DP, manufactured by Suga Test Instruments Co., Ltd.) ( %). The first resin base material and the second resin base material may be the same or different.

＜＜2nd floor＞＞ The second layer is a layer containing a developer. The color-developing agent refers to a compound that has no color-developing function but has the property of making the color-developing agent color by contacting with the color-developing agent. As the developer, an electron-accepting compound is preferable. As a color developer, an inorganic compound and an organic compound are mentioned.

Examples of the inorganic compound include clay substances such as acid clay, activated clay, attapulgite, zeolite, bentonite, and kaolin.

Examples of the organic compound include metal salts of aromatic carboxylic acids, metal salts of phenol formaldehyde resins, and carboxyl group-modified terpene phenol resins. Specific examples of the above-mentioned organic compounds include, for example, 3,5-di-tertiary butylsalicylic acid, 3,5-di-tertiary octyl salicylic acid, 3,5-di-tri- nonylsalicylic acid -Tertiary dodecylsalicylic acid, 5-cyclohexylsalicylic acid, 3,5-bis(α,α-dimethylbenzyl)salicylic acid, 3-methyl-5-(α-methyl) benzyl) salicylic acid, 3-(α,α-dimethylbenzyl)-5-methylsalicylic 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, carboxyl modified terpene phenol resin and 3,5-bis(α-methylbenzyl) salicylic acid and benzyl Metal salts (eg, zinc salts, nickel salts, aluminum salts, calcium salts, etc.) of compounds in the group of salicylic acid resins that are the reaction products of chlorides. As a color developer, among them, acid clay, activated clay, zeolite, kaolin, metal salt of aromatic carboxylic acid or metal salt of carboxyl modified terpene phenol resin are preferred, acid clay, activated clay, kaolin or aromatic carboxylic acid Metal salts of acids are more preferable, and metal salts of acidic clays, activated clays, or aromatic carboxylic acids are more preferable from the viewpoints of more excellent color concentration in the color-developing portion and from the viewpoint of more excellent image quality after color development. , acid clay or activated clay is particularly good.

The content of the color developer in the second layer is not particularly limited, but is preferably 50 to 95% by mass, more preferably 70 to 90% by mass relative to the total mass of the second layer. A color developer may be used individually by 1 type, and may be used in mixture of 2 or more types.

The content of the color developer in the second layer is not particularly limited, but is preferably 1.0 to 40 g/m ² . When the color developer is an inorganic compound, the content of the color developer is preferably 2.0 to 30 g/m ² , more preferably 3.0 to 20 g/m ² .

The second layer may contain other components than the above-mentioned developer. Examples of other components include polymer binders, pigments, optical brighteners, antifoaming agents, penetrants, ultraviolet absorbers, surfactants, pH adjusters, dispersants, and preservatives. As a surfactant, the thing similar to the surfactant which the said 1st layer has can be mentioned, and the preferable aspect is also the same. Preferably, the second layer contains a pH adjuster. When the second layer contains the pH adjuster, the color developer becomes easy to be uniformly arranged without aggregation, and thus the image quality after color development becomes more favorable. When the color developer exhibits acidity, it is preferable that the pH adjuster is an alkaline pH adjuster. Alkaline pH adjusters refer to compounds exhibiting basicity capable of adjusting the degree of pH.

Although it does not specifically limit as an alkaline pH adjuster, For example, sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, and potassium carbonate are mentioned. As the pH adjuster, either an organic base or an inorganic base may be used, but an inorganic base is preferable from the viewpoint of improving the image quality. A pH adjuster may be used individually by 1 type, and may mix and use 2 or more types. The content of the pH adjuster is preferably 0.1 to 5.0 mass %, more preferably 0.5 to 2.0 mass %, relative to the total mass of the color developer.

For the purpose of disposing the color developer uniformly without agglomeration, it is preferable to use a color developer and a dispersant together. The dispersant may be either a low molecular weight dispersant or a high molecular weight dispersant, but from the viewpoint of uniformly dispersing the color developer, a low molecular weight dispersant is preferred. Here, low molecular weight means a molecular weight of 1,000 or less, and preferably a molecular weight of 500 or less. The lower limit of the molecular weight is not particularly limited, but is, for example, 20. When the color developer exhibits acidity, it is preferable that the dispersant used together is an anionic dispersant.

As a polymer binder, the thing similar to the polymer binder which the above-mentioned 1st layer has can be mentioned, and the preferable aspect is also the same. As content of a polymer binder, 0.1-30 mass % is preferable with respect to the total mass of a 2nd layer, 5-25 mass % is more preferable.

From the viewpoint of more excellent color density in the color-developing portion and from the viewpoint of more excellent image quality after color development, the mass content ratio of the color-developing agent to the polymer binder in the second layer (color-developing agent/high Molecular adhesive) is preferably 2.0 or more, more preferably 2.0 to 10.0. When the color developer is an inorganic compound, the mass content ratio of the color developer relative to the polymer binder (color developer/polymer binder) is preferably 2.0 to 8.0, more preferably 3.3 to 6.0, and 3.3 -5.0 is more preferable. As the amount of the color developer increases, cracks are more likely to occur, and the color density of the color-developing portion becomes good. On the other hand, the more the polymer binder, the better the film strength, and the film does not break and fall off when the sheet for pressure measurement is cut.

The second layer has specific cracks on the surface on the side opposite to the second resin base material side. However, the fact that the second layer has a specific crack on the surface opposite to the second resin base means that the surface of the second layer opposite to the second resin base is observed with a laser microscope 5 cm× In the area of 5 cm, cracks (specific cracks) having a depth of 2 μm or more, a width of 10 μm or less, and a length of 10 μm or more were observed in the observation area. A crack represents a concave portion (opening portion) that continues and extends.

The shape of a specific crack may be a curved line or a straight line, for example, and may have a curved part. Here, the length of the crack refers to the length connecting the two farthest points of the crack (in other words, the length of the distance between one end connecting the crack and the other end farthest from the above-mentioned end). That is, as shown in Fig. 3, when the crack is linear, the length of the crack refers to the length L1 of the farthest point connecting the two cracks, and the width of the crack refers to the direction in which the crack extends (the propagation of the crack). direction) the maximum length W1 of the crack in the direction orthogonal to T1. Also, as shown in FIG. 4, when the crack has a curved portion, the length of the crack is the length L2 along the distance between one end of the crack and the other end farthest from the one end along the bend, and the width of the crack is the same as the length of the crack. The maximum length W2 of the crack in the direction perpendicular to the direction of extension (the propagation direction of the crack) T2. In addition, the depth of a crack means the length of the film thickness direction of the 2nd layer of a crack. The specific crack may or may not penetrate through the second layer, but it is preferable not to penetrate through the second layer. The shape of the specific crack is not limited as long as the depth is 2 μm or more, the width is 10 μm or less, and the length is 10 μm or more. For example, the shape may have the same length and width. The lower limit of the width of the specific crack is, for example, 0.1 μm or more in many cases, and from the viewpoint of more excellent color density in the color-developing portion, 0.5 μm or more is preferable, and 1.0 μm or more is more preferable. As an upper limit of the length of a specific crack, for example, it is 500 micrometers or less in many cases, and 100 micrometers or less is preferable from a viewpoint of being more excellent in image quality (resolution). As an upper limit of the depth of a specific crack, for example, it is often 40 micrometers or less, and 30 micrometers or less is preferable from a viewpoint of being more excellent in image quality (resolution).

From the viewpoint that the color density of the color-developing portion is more excellent, the number of specific cracks observed when a 5 cm×5 cm area on the surface of the second layer is observed with a laser microscope is preferably 100 or more, and preferably 1000 or more. More preferably, 100,000 or more are further more preferable, and 200,000 or more are particularly preferable. In addition, although there is no restriction|limiting in particular as an upper limit, For example, it is 10 million or less. The measurement of the number of specific cracks was implemented based on the observation image obtained by observing the area|region of 5 cm x 5 cm of the surface of the 2nd layer using a laser microscope. As shown in FIGS. 1 to 5 , among the cracks observed in the observation images, the cracks having a depth of 2 μm or more, a width of 10 μm or less, and a length of 10 μm or more correspond to the specific cracks 24 .

In addition, from the viewpoint that the color density of the color-developing portion is more excellent, when the area of 5 cm x 5 cm on the surface of the second layer is observed with a laser microscope, an arbitrary field of view of 500 μm x 500 μm in the area of 5 cm x 5 cm is observed. It is preferable to have one or more specific cracks inside, and from the viewpoint of more excellent image quality (resolution), 10 or more are more preferable, 20 or more are further more preferable, and 30 or more are particularly preferable. The upper limit is not particularly limited. For example, it is often 1000 or less, and 500 or less is preferable from the viewpoint of better image quality (resolution).

The thickness of the second layer is not particularly limited, but is preferably 0.5 to 30 μm, more preferably 3.5 to 30 μm. In addition, the mass per unit area (solid content coating amount) (g/m ² ) of the second layer is not particularly limited, but is, for example, 0.5 to 30.0 g/m ² . From the viewpoint that specific cracks are more likely to be formed on the surface of the second layer, the upper limit is preferably 14.0 g/m ² or less, and more preferably 10.0 g/m ² or less. In addition, from the viewpoint of more excellent image quality (resolution), the lower limit value is preferably 3.5 g/m ² or more. The mass per unit area of the second layer (solid content coating amount) (g/m ² ) is 3.5 to 14.0 from the viewpoint of easily forming specific cracks and from the viewpoint of being more excellent in image quality (resolution). g/m ² is preferable, and 3.5 to 10.0 g/m ² is more preferable.

<<Method for forming the second layer>> As a method of forming the second layer, a method of applying a second layer-forming composition containing a color developer and a polymer binder to a second resin substrate and subjecting the obtained coating film to a predetermined treatment can be mentioned. method. As a method of forming specific cracks in the second layer, when the above-mentioned composition for forming a second layer is used, the mixing ratio of the color developer and the polymer binder in the composition for forming a second layer can be mentioned. A method of adjusting to a predetermined mixing ratio, a method of subjecting the coating film of the composition for forming the second layer to drying treatments by heating, air drying, and hot air drying, etc., and a method of applying the coating film of the composition for forming the second layer to A method of adjusting the mass per unit area (solid content coating amount) to a predetermined amount and a method of combining these. In addition, the method of forming specific cracks in the second layer can select the optimum conditions according to the material and amount of the polymer binder used.

When the coating film of the second layer-forming composition with a small amount of the binder to the developer is subjected to quick-drying treatment (rapid-drying treatment) to form the second layer, specific cracks are particularly likely to be formed. As a specific method of the quick-drying treatment, a method of reducing the mass per unit area (solid content coating amount) of the coating film of the second layer-forming composition (that is, reducing the solid content of the second-layer-forming composition) can be mentioned. method of coating amount of ingredients) and method of drying the coating film with heating, etc. As a specific method of the drying treatment accompanied by heating, a method of heating the coating film while blowing air (hereinafter sometimes referred to as "heating and air drying"), heating the coating film, and then applying heat treatment to the coating film. The method of blowing air to the film, and the method of performing heat treatment after blowing air to the coating film, etc. Moreover, the wind speed at the time of air supply is preferably 0.1 to 30 m/sec, more preferably 0.1 to 20 m/sec, and even more preferably 0.1 to 5 m/sec.

In the case of performing the drying treatment accompanied by heating (for example, it is also equivalent to the case of performing the hot air treatment described later.), as the heating temperature condition, the optimum temperature is selected according to the material and amount of the polymer binder to be used, but from From the viewpoint of easier formation of specific cracks on the surface of the second layer, 60°C or higher is preferable, and 70°C or higher is more preferable. Although the upper limit is not particularly limited, it is often 180°C or lower, and from the viewpoint of easier formation of specific cracks on the surface of the second layer, 140°C or lower is preferable, and 120°C or lower is more preferable. In addition, the heating time is not particularly limited, but from the viewpoint of easier formation of specific cracks on the surface of the second layer and the viewpoint of productivity, 1.0 to 20 minutes is preferable, and 3.0 to 10 minutes is more preferable.

<An example of a method for forming the second layer> As a specific example of the method for forming the second layer, as will be described later, a composition for forming a second layer containing a color developer and a polymer binder in a predetermined blend ratio is applied in a solid content below a predetermined amount. A method of applying on a second resin base material and subjecting the obtained coating film to drying treatment with heating.

Hereinafter, the specific procedure of the formation method of a 2nd layer is demonstrated. The composition for forming the second layer may be a dispersion liquid in which a color developer is dispersed in water or the like. In the case where the color developer is an inorganic compound, a dispersion liquid in which the color developer is dispersed can be prepared by mechanically dispersing the inorganic compound in water. Moreover, in the case of a color developer-type organic compound, it can be prepared by mechanically dispersing an organic compound in water or dissolving it in an organic solvent. In addition, the specific aspects of the color developer and the polymer binder are as described above. The composition for forming a second layer may contain other components that may be contained in the above-mentioned second layer.

The method in particular of apply|coating the composition for 2nd layer formation is not restrict|limited, The method similar to the method of apply|coating the composition for 1st layer formation mentioned above is mentioned. However, the microcapsules in the composition for forming the first layer are replaced with a color developer in the composition for forming the second layer.

From the viewpoint of easier formation of specific cracks on the surface of the second layer, the mass content ratio of the color developer to the polymer binder in the composition for forming the second layer (color developer/polymer binder) is: 2.0 or more is preferable, and 2.0 to 10.0 is more preferable. When the color developer is an inorganic compound, the mass content ratio of the color developer to the polymer binder (color developer/polymer binder) is considered to be more likely to form specific cracks on the surface of the second layer. It is preferably 2.0 to 8.0, more preferably 3.3 to 6.0, and even more preferably 3.3 to 5.0.

The upper limit of the solid content coating amount (g/m ² ) of the composition for forming the second layer is not particularly limited, but it is, for example, 30.0 g/m ² or less, and from the viewpoint of easier formation of specific cracks, 14.0 g/m ² or less is preferable, and 10.0 g/m ² or less is more preferable. Further, the lower limit is not particularly limited, but it is, for example, 0.5 g/m ² or more, and is preferably 3.5 g/m ² or more from the viewpoint of more excellent image quality (resolution).

The method of drying treatment with heating is as described above. Among the above-mentioned steps, from the viewpoint that specific cracks are easily formed, a method of performing heat treatment (heating and blowing drying) while blowing air to the coating film is preferable. As a specific method of heating and air drying, it can be a method of heating the coating film by heating means such as a heater while blowing air to the coating film, or a method of blowing hot air to the coating film (hereinafter also referred to as "" hot air treatment").

From the viewpoint of easier formation of specific cracks on the surface of the second layer, the method for producing a pressure measurement sheet kit of the present invention preferably includes the following steps: coating a color developer and a polymer binder with a relatively high The mass content ratio of the color developer of the molecular binder (color developer/polymeric binder) is 2.0 or more. The composition for forming the second layer, so that the solid content coating amount is 14.0g/ ^m2 or less, for all The obtained coating film is subjected to hot air treatment at 60° C. or higher to form the second layer.

In addition, it is preferable to produce a second sheet including the second layer in the above-mentioned steps, and to combine the obtained second sheet and the first sheet produced by the above-mentioned procedure to produce a pressure-measuring sheet set. As the size of the second layer of the second sheet, it is preferable to include at least a size of a square of 5 cm×5 cm.

＜＜Other components＞＞ The second sheet may have other members than the above-mentioned second resin base material and second layer. For example, the second sheet may have an adhesive layer between the second resin base material and the second layer for improving the adhesiveness of both. In particular, in forming the second sheet, when the composition for forming the second layer is applied and then quick-drying is performed, it is preferable to have an adhesive layer from the viewpoint of preventing the color developer from drying and coagulating. As an aspect of an adhesive layer, the aspect which can have the adhesive layer of the said 1st sheet is mentioned.

As described above, the first sheet and the second sheet are laminated so that the first layer of the first sheet and the second layer of the second sheet are opposed to each other to obtain a laminate, And the laminated body is pressurized and used.

From the viewpoint of more excellent color development concentration, the specific solvent for the second sheet (the specific solvent refers to a solvent with a boiling point of 100°C or higher and containing an aromatic group that can be contained in the specific microcapsules as described above.) The oil absorption is preferably 2.0 to 20.0 g/m ² . When the oil absorption of the specific solvent relative to the second sheet is 2.0 g/m ² or more, in the pressurized region, the solution containing the coloring agent and the specific solvent flows out due to the disintegration of the specific microcapsules It is easily absorbed by the 2nd layer of the 2nd sheet, and a higher density of color development tends to occur. On the other hand, when the oil absorption of the specific solvent with respect to the second sheet is 20.0 g/m ² or less, in the pressurized region, the coloring agent and the The solution of the specific solvent cannot reach the deep part of the second layer of the second sheet, and as a result, the amount of the coloring agent present in the surface region of the second layer is large, and a higher color development density is likely to occur.

In addition, regarding the oil absorption amount of the specific solvent with respect to the second sheet, the difference between the weight of the second sheet before absorbing the specific solvent and the weight of the second sheet after absorbing the specific solvent was obtained, and the difference per unit area was calculated. Converted.

The arithmetic mean roughness Ra of the second sheet is preferably 1.2 μm or less from the viewpoints of more excellent color density and more excellent image quality (resolution). In addition, the arithmetic mean roughness Ra of the second sheet refers to the arithmetic mean roughness of the surface of the second sheet facing the first sheet (the side in contact with the first sheet) when the pressure measurement sheet set is used Degree Ra. When the second layer is located on the outermost surface of the second sheet on the side facing the first sheet, the arithmetic mean roughness Ra corresponds to the side opposite to the second resin substrate side of the second layer The arithmetic mean roughness Ra of the surface. In addition, the arithmetic mean roughness Ra of the 2nd sheet in this specification means the arithmetic mean roughness Ra prescribed|regulated by JIS B 0681-6:2014. In addition, as a measurement device, a scanning white light interferometer using an optical interference method (specifically, NewView5020 manufactured by Zygo: Micro mode; objective lens×50 times; intermediate lens×0.5 times) was used.

<<<Manufacturing method of sheet set for pressure measurement>>> As a method of manufacturing the sheet set for pressure measurement, it has a step of manufacturing a second sheet, a step of manufacturing the second sheet, and a process of manufacturing the first sheet. steps are better. In addition, the manufacturing method of the 1st sheet material and the 2nd sheet material provided as the sheet set for pressure measurement is as described above. As the step of manufacturing the second sheet, from the viewpoint of making it easier to form specific cracks in the second layer, it is preferable to include a step of developing a color with respect to the polymer binder including a color developer and a polymer binder. The mass content ratio of the agent (color developer/polymer binder) is 2.0 or more The composition for forming a second layer is coated on the second resin substrate so that the solid content coating amount is 14.0g/ ^m2 or less , the obtained coating film is subjected to hot air treatment at a temperature of 60°C or higher to form the second layer. As the step of producing the first sheet, it is preferable to have the step of applying, on the first resin base material, a composition for forming a first layer containing microcapsules containing a solvent having a boiling point of 100° C. or higher and a coloring agent. On the above, the obtained coating film is subjected to a drying process to form a first layer. Moreover, the formation method of the 1st layer using the composition for 1st layer formation, and the formation method of the 2nd layer using the composition for 2nd layer formation are as mentioned above.

[Second Embodiment] Fig. 6 is a cross-sectional view of one embodiment of the pressure measurement sheet. The sheet 30 for pressure measurement includes a resin substrate 32, a second layer 20 containing a color developer, and a first layer 14 containing microcapsules 13 containing a solvent and a color developer in this order. Specific cracks 24 are present on the surface 20A of the second layer 20 on the side of the first layer 14 . Here, the specific crack 24 represents a crack whose depth is 2 μm or more, width is 10 μm or less, and length is 10 μm or more, measured from the observed image obtained by observing the surface 20A of the second layer 20 with a laser microscope. In addition, a crack shows the recessed part (opening part) which continues and extends. The specific crack 24 may or may not penetrate the second layer 20 . An example of the observation image of the specific crack 24 observed by a laser microscope is shown in FIG. When the sheet 30 for pressure measurement is used, by applying pressure from at least one of the resin base material 32 side and the first layer 14 side, the microcapsules 13 are ruptured in the pressed area, and the inside of the microcapsules 13 is broken. The contained color-forming agent comes out of the microcapsules 13 and undergoes a color-developing reaction with the color-developing agent in the second layer 20 . As a result, color develops in the pressurized area.

In FIG. 6 , the resin substrate 32 and the second layer 20 are directly laminated, but the present invention is not limited to this, and as will be described later, other layers (for example, adhesive layer). 6 discloses the pressure measurement sheet 30 having the resin base 32, the second layer 20, and the first layer 14 in this order, but it is not limited to this aspect, and may have a resin base in this order Sheets for pressure measurement of the material 32 , the first layer 14 and the second layer 20 .

The first layer 14 and the second layer 20 in the pressure measurement sheet 30 are the same members as the first layer 14 and the second layer 20 described in the above-mentioned first embodiment, and therefore their description is omitted. Hereinafter, the resin base material 32 will be mainly described in detail.

＜＜＜Resin substrate＞＞＞ The resin substrate is a member for supporting the first layer and the second layer. The preferable aspect of the resin base material is the same as the preferable aspect of the above-mentioned first resin base material, and therefore the description is omitted.

<<<Manufacturing method of the sheet for pressure measurement >>> The manufacturing method of the sheet for pressure measurement is not particularly limited, and a known method can be mentioned. From the viewpoint that specific cracks are more likely to be formed on the surface of the second layer, it is preferable as a method for producing a pressure measurement sheet to have the following steps: coating a color developer and a polymer binder, which is relatively The mass content ratio of the color developer (color developer/polymer binder) is 2.0 or more, so that the solid content coating amount is 14.0g/ ^m2 or less, and the obtained coating composition is used. The film is subjected to hot air treatment at 60° C. or higher to form the second layer. Further, as a method for producing a sheet for pressure measurement, it is more preferable to include the steps of applying a composition for forming a first layer containing microcapsules containing a solvent having a boiling point of 100° C. or higher and a coloring agent, The obtained coating film is subjected to drying treatment to form the first layer. The method for forming the first layer using the composition for forming the first layer and the method for forming the second layer using the composition for forming the second layer are as described in the first embodiment, respectively.

＜＜＜Other components＞＞＞ The sheet for pressure measurement may contain other members other than the resin base material, the second layer, and the first layer. For example, the sheet for pressure measurement may have an adhesive layer between the resin substrate and the second layer for improving the adhesiveness of both. As an aspect of an adhesive layer, the aspect which can have the adhesive layer of the said 1st sheet is mentioned.

As described above, the sheet for pressure measurement is used by pressing the surface thereof.

From the viewpoint of more excellent color density, the oil absorbs oil with respect to the specific solvent of the second layer (the specific solvent is, as described above, the solvent having a boiling point of 100°C or more and containing an aromatic group that can be contained in the specific microcapsules.) The amount is preferably 2.0 to 20.0 g/m ² . When the oil absorption of the specific solvent of the second layer is 2.0 g/m ² or more, the solution containing the coloring agent and the specific solvent that flows out due to the disintegration of the specific microcapsules in the pressurized area is easily Absorbed by layer 2 and prone to higher chromophore density. On the other hand, when the oil absorption with respect to the specific solvent of the second layer is 20.0 g/m ² or less, in the pressurized region, the coloring agent and the specific microcapsule flow out due to the disintegration of the specific microcapsules. The solution of the solvent cannot reach the deep part of the second layer, and as a result, the amount of the coloring agent existing in the surface region of the second layer is large, and a higher color concentration is likely to occur.

The size of the sheet for pressure measurement is preferably a size that can include at least a square of 5 cm×5 cm.

[Sheet] The present invention also relates to a sheet. The sheet of the present invention is the same as the second sheet in the above-mentioned pressure measurement sheet set. [Example]

Hereinafter, the present invention will be described in further detail based on examples. The materials, usage amounts, ratios, processing contents, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention should not be limitedly construed by the examples shown below. In addition, unless otherwise specified, the following "parts" and "%" are based on mass.

[Production of Sheet Kit for Pressure Measurement] [Example 1] <Preparation of microcapsules containing color-forming agent> In 1,2-dimethyl-4-(1-phenylethyl)benzene, 1,3-dimethyl-4-(1-phenylethyl)benzene, 1,4-dimethyl-2 A mixture of -(1-phenylethyl)benzene and 1-(ethylphenyl)-1-phenylethane (manufactured by Yantai Jinzheng Fine Chemical Co., Ltd., SRS-101) was dissolved in 50 parts as a developer. ',6'-Bis(diethylamino)-2-(4-nitrophenyl)spiro[isoindole-1,9'-kouyamaguchi]-3-one (Hodogaya Chemical Co., Ltd .Manufactured, Pink-DCF) 3 parts, 6'-(diethylamino)-1',3'-dimethyl fluorescent yellow precursor (Hodogaya Chemical Co., Ltd. manufacture, Orange-DCF) 4 parts , to obtain solution A. Next, N,N,N',N'-tetrakis(2-hydroxypropyl) was dissolved in 13 parts of synthetic isoalkane (Idemitsu Kosan Co., Ltd., IP Solvent 1620) and 2.5 parts of methyl ethyl ketone 0.3 part of ethylenediamine (ADEKA CORPORATION, ADEKA POLYETHER EDP-300) was added to the stirred solution A, whereby a solution B was obtained. Furthermore, 2.5 parts of trimethylolpropane adducts of toluene diisocyanate (DIC CORPORATION, BURNOCKD-750) dissolved in 6 parts of ethyl acetate were added to the stirred solution B, and a solution C was obtained. And the said solution C was added to the solution which melt|dissolved 7 parts of polyvinyl alcohol (PVA-217E, Kuraray Co., Ltd.) in 140 parts of water, and it emulsified and dispersed. 200 parts of water were added to the emulsified liquid after emulsification and dispersion, and the mixture was heated to 70° C. with stirring, and was cooled after stirring for 1 hour. Furthermore, water was added to adjust the concentration, thereby obtaining a color-forming agent-containing microcapsule liquid with a solid content concentration of 20%. The obtained microcapsules containing the color-forming agent had an average particle diameter of 20 μm. The average particle size was measured by means of an optical microscope and by the method described above.

<Preparation of sheet set for pressure measurement> (Production of the first sheet) Mix 18 parts of the obtained microcapsule liquid containing color-forming agent, 10 parts of water, 1.8 parts of colloidal silica (Nissan Chemical Industries, LTD., SNOWTEX 30, particle size 10nm, solid content 30%), carboxymethyl 2 parts of a 1% aqueous solution of sodium carboxymethylcellulose (DKS Co.Ltd., SEROGEN 5A), 4.5 parts of a 1% aqueous solution of sodium carboxymethylcellulose (DKS Co.Ltd., SEROGEN EP), side chain alkylbenzenesulfonic acid 1 part of 15% aqueous solution of acid amine salt (DKS Co. Ltd., NEOGEN T), 0.2 part of 1% aqueous solution of polyoxyethylene polyoxypropylene lauryl ether (DKS Co. Ltd., NOIGEN LP-70), sodium- 0.2 part of a 1% aqueous solution of bis(3,3,4,4,5,5,6,6,6-nonafluorohexyl)-2-sulfooxyoctanoic acid (FUJIFILM Corporation, W-AHE) to obtain the first A composition for forming one layer.

The obtained composition for forming a first layer was applied on a polyethylene terephthalate (PET) sheet having a thickness of 75 μm by a bar coater so that the mass after drying would be 6.0 g/m ² . Next, the obtained coating film was dried at 80 degreeC, the 1st layer was formed, and the 1st sheet was produced.

(Production of the second sheet) 100 parts of activated clay (Mizusawa Industrial Chemicals, Ltd., Shilton F-242), 0.5 part of Na hexametaphosphate (Nippon Chemical Industry Co., Ltd., sodium hexametaphosphate), and 10% hydroxide were added as color developer 15 parts of sodium aqueous solution, 240 parts of water, 15 parts of olefin resin (ARAKAWA CHEMICAL INDUSTRIES, LTD., Polymaron 482, solid content concentration 25 mass %), modified acrylate copolymer (Zeon Corporation, Nippon) were mixed with the obtained dispersion liquid LX814, 36 parts of solid content concentration 47 mass %, 100 parts of 1% aqueous solution of sodium carboxymethylcellulose (DKS Co. Ltd., SEROGEN EP), Na alkylbenzene sulfonate (DKS Co. Ltd., NEOGEN T ) 18 parts of a 15% aqueous solution, 20 parts of a 1% aqueous solution of polyoxyethylene polyoxypropylene lauryl ether (DKS Co. Ltd., NOIGEN LP-70), sodium-bis(3,3,4,4,5, 20 parts of a 1% aqueous solution of 5,6,6,6-nonafluorohexyl)-2-sulfonyloxyoctanoic acid (FUJIFILM Corporation, W-AHE) to prepare a coating liquid containing a developer.

The coating liquid containing the developer was applied on a polyethylene terephthalate (PET) sheet (TOYOBO CO., LTD., COMOSHINE A4300) with an adhesive layer with a thickness of 75 μm to coat the solid content. The amount was 7.0 g/m ² . Next, the obtained coating film was dried with hot air at 80° C. for 5 minutes using a dryer to form a second layer, thereby obtaining a second sheet. In addition, the mass content ratio (color developer/polymer binder) of the color developer to the polymer binder (olefin resin, modified acrylate copolymer, and sodium carboxymethyl cellulose) was 4.6. In addition, the haze of the above-mentioned 75-micrometer-thick PET sheet with an adhesive layer was 0.9%. In addition, the measurement method of the haze is as described above.

[Examples 2 to 12, Comparative Examples 1 to 3] The pressure measurement sheet sets of Examples 2 to 13 and Comparative Examples 1 to 3 were produced in the same procedure as in Example 1, except that various requirements shown in Table 1 to be described later were changed.

[Example 13] In the above (preparation of the second sheet), the olefin resin, modified acrylate copolymer and sodium carboxymethyl cellulose as the polymer binder were changed to styrene acrylic copolymer (AS-563A, DAICEL FINECHEM LTD. A coating liquid containing a color developer was prepared according to the same procedure as in Example 1, except for the production and solid content of 27.5% by mass). Next, the sheet set for pressure measurement of Example 13 was produced according to the same procedure as Example 1 except that the coating liquid containing the obtained color developer was used. In addition, in the coating liquid containing the developer in Example 13, the solid content of the styrene acrylic copolymer (AS-563A, manufactured by DAICEL FINECHEM LTD., solid content 27.5% by mass) was adjusted to be the same as that in Example 1. The total amount of each solid content of the olefin resin, modified acrylate copolymer and sodium carboxymethyl cellulose in the coating liquid containing the color developer is the same.

[Measurement and Evaluation] [Measurement of oil absorption (g/m ² ) of the aromatic group-containing solvent with respect to the second sheet] The aromatic group-containing solvent (for example, in Example 1, "SRS- 101") penetrated into the entire second sheet, and wiped off the overflowing aromatic group-containing solvent that was not absorbed into the sheet. Next, a value obtained by subtracting the weight of the second sheet before permeation with the aromatic group-containing solvent from the weight of the second sheet after permeation with the aromatic group-containing solvent was calculated, and calculated per 1 m of the second sheet. ² oil absorption.

[Evaluation of Cracks on the Surface of the Second Layer in the Second Sheet] (Crack Evaluation 1) Using a laser microscope (VK-8700 manufactured by KEYENCE Corporation), one site in an arbitrary 5 cm×5 cm square region of the surface of the second layer opposite to the PET sheet side was observed. Based on the obtained observation image, the presence or absence of specific cracks was confirmed. In addition, as mentioned above, a specific crack means the crack of 2 micrometers or more in depth, 10 micrometers or less in width, and 10 micrometers or more in length. (Crack Evaluation 2) Next, using a laser microscope (VK-8700 manufactured by KEYENCE Corporation), any 1 of a square of 500 μm × 500 μm in the above-mentioned area of a square of 5 cm × 5 cm on the surface of the second layer opposite to the PET sheet side was measured. The number of specific cracks in the field of view at each site was classified according to the following criteria. <Benchmark> "A": 30 or more "B": 10 or more and less than 30 "C": less than 10

[Measurement of each arithmetic mean roughness Ra of the first sheet and the second sheet] The arithmetic mean roughness Ra of the first sheet (equivalent to the arithmetic mean roughness Ra of the surface opposite to the PET sheet side of the first layer) and the arithmetic mean roughness Ra of the second sheet (corresponding to the The method for measuring the arithmetic mean roughness Ra) of the surface on the opposite side to the PET sheet side of the second layer is as described above.

[Evaluation of Color Density] <Measurement of Density (DA) of Color-Developed Parts Formed in the Second Sheet> The evaluation of the sheet set for pressure measurement was implemented using the 1st sheet and the 2nd sheet produced in each Example and the comparative example. Specifically, the first sheet and the second sheet having a size of 5 cm×5 cm were stacked so that the surface of the first layer of the first sheet and the surface of the second layer of the second sheet were in contact, thereby obtaining Laminated body. Next, the laminated body was pressurized under a pressure of 1 Mpa by a pressurizing press (DSF-C1-A, manufactured by AIDA ENGINEERING, LTD.) to develop color. Then, the first sheet and the second sheet constituting the layered product were peeled off, and a densitometer RD-19 (manufactured by X-Rite Inc.) was used to measure the surface of the resin substrate (PET sheet) through the resin substrate. Density (DA) of the colored portion of the second sheet.

<Calculation of Color Development Density ΔD1> In addition, using a concentration meter RD-19 (manufactured by X-Rite Inc.), the initial concentration ( DB). Then, the initial density DB was subtracted from the density DA to obtain the color development density ΔD1, and the evaluation was performed according to the following evaluation criteria. In addition, "B" is the range which can be actually used. The results are shown in Table 1.

<Evaluation Criteria> "A": ΔD1 was 0.9 or more (high concentration and color development were observed). "B": ΔD1 is 0.4 or more and less than 0.9 (color development is observed). "C": ΔD1 was less than 0.4 (color development was not observed).

[Image quality (resolution) evaluation] The surface of the first layer of the unused first sheet was observed with an optical microscope, and the average particle diameter of the microcapsules (microcapsule diameter D (μm)) was determined. The method for measuring the average particle diameter of the microcapsules is as described above. In addition, the surface of the second layer of the second sheet after color development was observed with an optical microscope, and the average spot diameter of the color spots (color spot diameter D' (μm)) was determined. The color point diameter D' (μm) with respect to the microcapsule diameter D (μm) was obtained from the obtained value, and the evaluation was performed according to the following evaluation criteria. In addition, the specific measurement method of the color point diameter D' (μm) is as follows. About color development point diameter D' (μm): The surface of the second layer of the second sheet after color development was photographed from the surface of the second layer with an optical microscope (OLYMPUS BX60, size of field of view: 320 μm×450 μm) The image was subjected to image analysis, the major diameters of 30 color development points were sequentially measured from the largest color development point, and the average value was obtained by arithmetically averaging these. This operation was carried out at any 5 locations (5 fields of view) of the first layer, the average of the average values obtained at each location was calculated, and the obtained value was defined as the average dot diameter of the color dots (color dot diameter). D' (μm)). In addition, the long diameter refers to the longest diameter when the color point is observed. The results are shown in Table 1.

<Evaluation Criteria> "A": D'/D is less than 50 (high quality). "B": D'/D is 50 or more and less than 300 (medium image quality). "C": D'/D is 300 or more (low quality).

Table 1 is shown below. In Table 1, in the "type" of the "aromatic group-containing solvent" column, the numerical value in parentheses that is also described in the solvent type indicates the mixing ratio (mass basis). For example, in the case of Example 6, it means that 4-isopropylbiphenyl and 4,4'-diisopropylbiphenyl are contained in a mass ratio of 50/50 as the aromatic group-containing solvent. In Table 1, "SRS-101" in the column "Aromatic group-containing solvent" is 1,2-dimethyl-4-(1-phenylethyl)benzene, 1,3-dimethyl-4- A mixture of (1-phenylethyl)benzene, 1,4-dimethyl-2-(1-phenylethyl)benzene and 1-(ethylphenyl)-1-phenylethane (Yantai Jinzheng Manufactured by Fine Chemicals Co., Ltd.). That is, four kinds of solvents containing two aromatic groups are contained in the molecule. In Table 1, "Hysol 100" in the column of "Aromatic group-containing solvent" is 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, 1,2,3-trimethylbenzene A mixture of benzene, cumene and xylene (manufactured by ENEOS Corporation). That is, three types of solvents containing one aromatic group are contained in the molecule. In Table 1, "content (%) of the aromatic group-containing solvent" means the content (%) of the aromatic group-containing solvent with respect to the total mass of the aromatic group-containing solvent and the aliphatic structure-containing solvent. In Table 1, "content (%) of the solvent containing two aromatic groups in the molecule" refers to the total mass of the solvent containing two aromatic groups in the molecule of the solvent containing two aromatic groups in the molecule. content(%). In Table 1, the column of "adhesive" shows the type of polymer adhesive constituting the second layer. In addition, resin A, resin B, resin C, and resin D refer to the following resins. Resin A: Olefin resin Resin B: Modified Acrylate Copolymer Resin C: Sodium carboxymethyl cellulose Resin D: Styrene acrylic copolymer

[Table 1] Main features of the first layer (main composition of the core material contained in the microcapsules) Key Features of Tier 2 Solid content coating amount [g/m ² ] physical property evaluate Solvents with a boiling point of 100°C or higher Content of solvent containing aromatic group (%) Content of solvent containing 2 aromatic groups (%) Color developer type adhesive Drying temperature [℃] Oil absorption of aromatic group-containing solvent relative to the second sheet [g/m ² ] Cracks in layer 2 Developer/binder ratio in layer 2 Arithmetic mean roughness Ra of the first sheet Arithmetic mean roughness Ra of the second sheet Color density Image quality (resolution) Aromatic solvents Solvents containing aliphatic structures Tier 1 Tier 2 type boiling point type presence or absence of cracks number of cracks Example 1 SRS-101 290-305℃ IP Solvent 79.4 100 activated clay Resin A/B/C 80 6.0 7.0 4.0 have A 4.6 5.0 1.0 A A Example 2 SRS-101 290-305℃ IP Solvent 79.4 100 activated clay Resin A/B/C 80 6.0 7.0 4.2 have A 5.5 5.0 1.0 A A Example 3 SRS-101 290-305℃ IP Solvent 79.4 100 activated clay Resin A/B/C 80 6.0 70 3.8 have B 3.1 5.0 1.0 B A Example 4 SRS-101 290-305℃ IP Solvent 79.4 100 activated clay Resin A/B/C 80 6.0 7.0 3.8 have C 2.3 5.0 1.0 B A Example 5 Hysol 100 150-185℃ IP Solvent 79.4 0 activated clay Resin A/B/C 80 6.0 7.0 4.0 have A 4.6 5.0 1.0 B A Example 6 4-Isopropylbiphenyl (50) 4,4'-Diisopropylbiphenyl (50) 291℃ 335℃ IP Solvent 79.4 100 activated clay Resin A/B/C 80 6.0 7.0 4.0 have A 4.6 5.0 1.0 A A Example 7 Toluene (70) 4,4'-Diisopropylbiphenyl (30) 110℃ 335℃ IP Solvent 79.4 30 activated clay Resin A/B/C 80 6.0 7.0 4.0 have A 4.6 5.0 1.0 B A Example 8 Toluene (30) 4-isopropylbiphenyl (35) 4,4'-diisopropylbiphenyl (35) 110℃ 291℃ 335℃ IP Solvent 79.4 70 activated clay Resin A/B/C 80 6.0 7.0 4.0 have A 4.6 5.0 1.0 A A Example 9 Tricresyl Phosphate (90) 4,4'-Diisopropylbiphenyl (10) 241-255℃ 335℃ IP Solvent 79.4 10 activated clay Resin A/B/C 80 6.0 7.0 4.0 have A 4.6 5.0 1.0 B A Example 10 SRS-101 290-305℃ IP Solvent 79.4 100 activated clay Resin A/B/C 80 12.0 7.0 4.0 have A 4.6 8.0 1.0 A B Example 11 SRS-101 290-305℃ IP Solvent 79.4 100 activated clay Resin A/B/C 80 6.0 3.5 2.0 have A 4.6 5.0 1.0 A A Example 12 SRS-101 290-305℃ IP Solvent 79.4 100 activated clay Resin A/B/C 80 6.0 1.8 1.0 have A 4.6 5.0 1.0 A B Example 13 SRS-101 290-305℃ IP Solvent 79.4 100 activated clay Resin D 80 6.0 7.0 4.0 have A 4.6 5.0 1.0 A A Comparative Example 1 SRS-101 290-305℃ IP Solvent 79.4 100 activated clay Resin A/B/C 80 6.0 7.0 3.7 without - 1.9 5.0 1.0 C A Comparative Example 2 SRS-101 290-305℃ IP Solvent 79.4 100 activated clay Resin A/B/C 40 6.0 7.0 3.8 without - 3.1 5.0 1.0 C A Comparative Example 3 SRS-101 290-305℃ IP Solvent 79.4 100 activated clay Resin A/B/C 80 6.0 15.0 8.2 without - 4.6 5.0 1.1 C A

From the results in Table 1, it can be seen that the color density of the sheet set for pressure measurement of Examples is high.

From the results of Example 1, Example 3, and Example 4, when the surface of the second layer opposite to the PET sheet side was observed with a laser microscope, it was confirmed that a specific crack in the field of view of 500 μm×500 μm When the number is 10 or more, the color density is further improved. Moreover, it was confirmed from the comparison of Example 1 and Example 5 that when the solvent containing an aromatic group contains the solvent containing two aromatic groups in a molecule|numerator, the color development density|concentration is more improved. In addition, from the comparison of Example 1 and Examples 5 to 9, it was confirmed that the solvent having a boiling point of 100° C. or higher includes a solvent containing two aromatic groups in a molecule and a solvent containing two aromatic groups in the molecule. When the content of the solvent is 50 mass % or more with respect to the total mass of the aromatic group-containing solvent, the color density is further increased. In addition, from the comparison between Example 1 and Example 10, it was confirmed that the mass per unit area (g/m ² ) of the first layer of the first sheet (see “Solid content coating amount g/m 2 ” in Table 1 m ² "column) is adjusted to 10.0 g/m ² or less, and when the arithmetic mean roughness Ra of the first sheet is 3.0 to 7.0 μm, the image quality of the color-developing portion formed in the second sheet (analysis degree) is more excellent. In addition, from the comparison of Example 1, Example 11 and Example 12, it was confirmed that the mass per unit area (g/m ² ) of the second layer of the second sheet (see "Solid Content Coating" in Table 1 The cloth amount (g/m ² ” column) is adjusted to 3.5 g/m ² or more, and the oil absorption (g/m ² ) of the aromatic group-containing solvent relative to the second sheet is 2.0 to 20.0 g/m ² In the above case, the image quality (resolution) of the color-developing portion formed on the second sheet is more excellent.

As can be seen from the results in Table 1, the sheet set for pressure measurement of the comparative example does not satisfy the desired requirements.

In addition, in the above, the state of using the sheet set for pressure measurement having the first sheet and the second sheet is shown, but the pressure measurement is made by laminating the second layer and the first layer on the resin substrate in this order. Using the sheet, the same test as above was carried out, and the same results as those of the respective Examples were obtained. For example, the second layer and the first layer produced in the above Example 1 are sequentially arranged on a polyethylene terephthalate sheet to produce a pressure measurement with the resin substrate, the second layer and the first layer in sequence. Using the sheet, the results of the above evaluations (color development density evaluation and image quality (resolution) evaluation) were carried out, and the same results as in Example 1 were obtained.

10: Sheet kit for pressure measurement 12: The first resin base material 13: Microcapsules 14: Tier 1 16: 1st sheet 18: Second resin base material 20: Tier 2 20A: Surface of layer 2 22: 2nd sheet 24: Specific cracks 30: Sheet for pressure measurement 32: Resin base L1, L2: length T1, T2: direction W1, W2: length

FIG. 1 is a cross-sectional view of one embodiment of the sheet set for pressure measurement. FIG. 2 is an example of an observation image of the specific crack 24 observed with a laser microscope. FIG. 3 is a schematic diagram for explaining a specific crack 24 . FIG. 4 is a schematic diagram for explaining a specific crack 24 . FIG. 5 is a diagram for explaining the usage form of the sheet set for pressure measurement. Fig. 6 is a cross-sectional view of one embodiment of the pressure measurement sheet.

10: Sheet kit for pressure measurement

12: The first resin base material

13: Microcapsules

14: Tier 1

16: 1st sheet

18: Second resin base material

20: Tier 2

20A: Surface of layer 2

22: 2nd sheet

24: Specific cracks

Claims (16)

A sheet kit for pressure measurement, comprising: a first sheet having a first resin substrate and a first layer; and A second sheet having a second resin base material and a second layer, in the aforementioned pressure measurement sheet set, The first layer contains microcapsules, and the microcapsules contain a solvent with a boiling point of 100° C. or higher and a color-forming agent, The aforementioned second layer contains a developer, When an area of 5 cm×5 cm on the surface of the second layer opposite to the second resin substrate was observed with a laser microscope, a depth of 2 μm or more, a width of 10 μm or less, and a length of 10 μm or more were observed in the observation area. of cracks. The sheet kit for pressure measurement according to claim 1, wherein In an arbitrary field of view of 500 μm×500 μm in the aforementioned region of 5 cm×5 cm, there are 10 or more of the aforementioned cracks. The sheet kit for pressure measurement as claimed in claim 1 or claim 2, wherein The solvent having a boiling point of 100° C. or higher includes an aromatic group-containing solvent. The sheet kit for pressure measurement as claimed in claim 1 or claim 2, wherein The solvent having a boiling point of 100° C. or higher includes two or more kinds of aromatic group-containing solvents. The sheet kit for pressure measurement as claimed in claim 1 or claim 2, wherein The above-mentioned solvent having a boiling point of 100° C. or higher includes a solvent containing two aromatic groups in the molecule. The sheet kit for pressure measurement according to claim 3, wherein The aforementioned solvent with a boiling point of 100°C or higher also includes a solvent containing an aliphatic structure, Content of the said aromatic group containing solvent is 50.0 mass % - 90.0 mass % with respect to the total mass of the said aromatic group containing solvent and the said aliphatic structure containing solvent. The sheet kit for pressure measurement according to claim 3, wherein the oil absorption of the aromatic group-containing solvent with respect to the second sheet is 2.0 g/m ² to 20.0 g/m ² . The sheet kit for pressure measurement as claimed in claim 1 or claim 2, wherein The aforementioned coloring agent includes two or more kinds of aromatic group-containing coloring agents. The sheet kit for pressure measurement as claimed in claim 1 or claim 2, wherein The arithmetic mean roughness Ra of the first sheet is 3.0 μm to 7.0 μm. The sheet kit for pressure measurement as claimed in claim 1 or claim 2, wherein The arithmetic mean roughness Ra of the second sheet is 1.2 μm or less. The sheet kit for pressure measurement as claimed in claim 1 or claim 2, wherein The haze of the second resin base material is 20% or less. The sheet kit for pressure measurement as claimed in claim 1 or claim 2, wherein The aforementioned first layer contains inorganic particles. A sheet for pressure measurement comprising a resin base material, a second layer and a first layer in this order, wherein the sheet for pressure measurement, The first layer contains microcapsules, and the microcapsules contain a solvent with a boiling point of 100° C. or higher and a color-forming agent, The aforementioned second layer contains a developer, When a 5 cm×5 cm area of the surface of the second layer on the first layer side was observed with a laser microscope, cracks with a depth of 2 μm or more, a width of 10 μm or less, and a length of 10 μm or more were observed in the observation area. A method for manufacturing a sheet set for pressure measurement, which is the method for manufacturing a sheet set for pressure measurement as described in any one of claim 1 to claim 12, comprising the step of manufacturing the second sheet, and manufacturing The above-mentioned step of the second sheet includes the steps of: coating the second layer-forming composition containing the color developer and the polymer binder on the second resin substrate so that the solid content coating amount becomes 14.0 g/ m ² or less, the obtained coating film is subjected to hot air treatment at 60°C or higher to form a second layer, and the mass content ratio of the color developer to the polymer binder in the second layer forming composition is 2.0 or more. The method for manufacturing a sheet kit for pressure measurement according to claim 14, further comprising the step of manufacturing the first sheet, The step of manufacturing the aforementioned first sheet includes the steps of: coating the first layer-forming composition containing microcapsules containing a solvent having a boiling point of 100° C. or higher and a coloring agent on a first resin substrate, and applying the composition to the first resin substrate. The obtained coating film is subjected to drying treatment to form the first layer. A sheet having a second resin base material and a second layer, wherein the sheet, The aforementioned second layer contains a developer, When an area of 5 cm×5 cm on the surface of the second layer opposite to the second resin substrate was observed with a laser microscope, a depth of 2 μm or more, a width of 10 μm or less, and a length of 10 μm or more were observed in the observation area. of cracks.

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