Material for measuring pressure and method for manufacturing the material for measuring pressure

Abstract

To provide a material for pressure measurement with which color development is obtained that exhibits superior gradation in a high pressure region.SOLUTION: Provided is a material for pressure measurement that includes a substrate and a pressure sensitive layer, the pressure sensitive layer containing a polymer matrix including a high molecular compound of 1000 or greater in molecular weight, and a microcapsule enclosing an electron donative dye precursor and a solvent and an electron acceptor compound, the pressure sensitive layer further including a color-revelation layer having an electron acceptor compound and a polymer matrix and a color-developing layer having a microcapsule. The substrate, the color-revelation layer, and the color-developing layer are included in the order stated, the thickness of the color-developing layer being half the thickness of the color-revelation layer or less, the color-revelation layer having a recess, with part of the microcapsule penetrating into the recess. The arithmetic mean roughness on the outermost surface of the color-developing layer that is on the side opposite the substrate is 1.5 μm or greater, the particle size d2 of the microcapsule is 1 μm to 50 μm, and a concentration difference (ΔD2) derived by subtracting a concentration after color development by applying pressure at 100 MPa from a concentration after color development by applying pressure at 500 MPa is 0.1 or greater.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to a pressure measuring material and a method for manufacturing a pressure measuring material. [Background technology]

[0002] Pressure measuring materials (i.e., materials used to measure pressure) are used in applications such as the bonding process of liquid crystal glass, solder printing on printed circuit boards, and pressure adjustment between rollers. An example of a material used for pressure measuring is pressure measuring film, such as Prescale (product name; registered trademark) provided by Fujifilm Corporation.

[0003] Various pressure measuring materials have been investigated for measuring minute pressures. For example, Japanese Patent Publication No. 2009-19949 proposes a pressure measuring material in which the difference in color density ΔD before and after pressurization at 0.05 MPa is 0.02 or more, in order to obtain a density that can be seen or read at minute pressures. [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] As seen in the aforementioned Japanese Patent Publication No. 2009-19949, various pressure measuring materials for measuring minute pressures have been investigated. On the other hand, there is a demand for pressure measuring materials for measuring pressures in the high-pressure range (preferably in the range of 100 MPa to 10,000 MPa) in applications such as compression process control in various manufacturing processes. However, the upper limit of the measurable pressure range that commercially available pressure measuring films can handle, that is, the upper limit of the pressure range in which color development can be obtained by pressurization, is practically around 300 MPa. Therefore, conventional pressure measuring materials may not be able to handle pressure measurements, especially those exceeding 300 MPa. Thus, there is a demand for pressure measurement in the high-pressure range, and while conventional pressure measurement materials can address this to some extent, further improvements are desired.

[0005] An embodiment of the present disclosure aims to provide a pressure measurement material that can obtain excellent gradation coloring in a high-pressure region (preferably in the range of 100 MPa to 10,000 MPa).

Means for Solving the Problems

[0006] The present disclosure includes the following aspects. <1> A pressure measurement material having a base material and a pressure-sensitive layer, wherein the pressure-sensitive layer contains a polymer matrix containing a polymer compound having a molecular weight of 1000 or more, microcapsules encapsulating an electron-donating dye precursor and a solvent, and an electron-accepting compound. <2> The pressure measurement material according to <1>, which is in the form of a sheet. <3> The pressure measurement material according to <1> or <2>, wherein the arithmetic mean roughness Ra on the outermost surface opposite to the base material is 10.0 μm or less. <4> The pressure measurement material according to any one of <1> to <3>, wherein the microcapsules and the electron-accepting compound are contained in the polymer matrix. <5> The pressure measurement material according to <4>, wherein the arithmetic mean roughness Ra on the outermost surface opposite to the base material is less than 2.0 μm. <6> The pressure measurement material according to <4> or <5>, wherein the electron-accepting compound contains a metal salt of salicylic acid. <7> The pressure 2 measurement material according to any one of <4> to <6>, wherein the void fraction is 5 mL / m or less. <8> The pressure measurement material according to any one of <4> to <7>, wherein the content of the microcapsules is 10% to 80% by volume based on the pressure-sensitive layer. <9> The pressure measurement material according to <3>, wherein the pressure-sensitive layer has a color-developing layer having the electron-accepting compound and the polymer matrix and a color-forming layer having the microcapsules, the base material, the color-developing layer, and the color-forming layer are provided in this order, and the thickness of the color-forming layer is half or less of the thickness of the color-developing layer. The pressure measurement material according to <9>, wherein the arithmetic mean roughness Ra on the outermost surface on the side opposite to the base material is 2.0 to 10.0 μm. The pressure measurement material according to <9> or <10>, wherein the electron-accepting compound contains acid clay or activated clay. The pressure measurement material according to <11>, wherein the pressure-sensitive layer has inorganic particles other than the electron-accepting compound. <13> The void fraction is 5 mL / m 2 ~20 mL / m 2 The pressure measurement material according to any one of <9> to <12>. <14> The ratio T / p of the thickness T of the layer obtained by subtracting the thickness of the base material from the thickness of the pressure measurement material to the inner diameter p of the microcapsule is 1.2 or more. The pressure measurement material according to any one of <1> to <13>. <15> The ratio T / p of the thickness T of the layer obtained by subtracting the thickness of the base material from the thickness of the pressure measurement material to the inner diameter p of the microcapsule is 1.2 to 5.0. The pressure measurement material according to <14>. <16> The pressure measurement material according to any one of <1> to <15>, wherein the polymer compound having a molecular weight of 1000 or more is contained in an amount of 10% by mass or more based on the total mass of the pressure-sensitive layer. <17> The pressure measurement material according to any one of <1> to <16>, wherein the base material is a polyethylene terephthalate base material or a polyethylene naphthalate base material. <18> The pressure measurement material according to any one of <1> to <17>, which has an easy adhesion layer between the base material and the pressure-sensitive layer. <19> The pressure measurement material according to any one of <1> to <18>, wherein the wall material of the microcapsule contains at least one selected from polyurethane urea and polyurethane. <20> A method for producing a pressure measurement material, comprising the step of disposing a pressure-sensitive layer forming composition containing a polymer matrix containing a polymer compound having a molecular weight of 1000 or more, a microcapsule encapsulating an electron-donating dye precursor and a solvent, and an electron-accepting compound on a base material. The method according to any one of <4> to <8> and <14> to <19>. <21> The process includes the steps of: obtaining a color-developing layer-forming composition containing an electron-donating dye precursor and a solvent in microcapsules and a solvent; obtaining a color-developing layer-forming composition containing an electron-accepting compound and a polymer compound with a molecular weight of 1000 or more; arranging the color-developing layer-forming composition on a substrate to form a color-developing layer; and arranging the color-developing layer-forming composition on the color-developing layer to form a color-developing layer. <9> ~ <19> A method for manufacturing a pressure measuring material as described in any one of the following. [Effects of the Invention]

[0007] According to one embodiment of the present disclosure, a pressure measuring material can be provided that can produce excellent color gradation in the high-pressure region (preferably the region of 100 MPa to 10000 MPa). [Brief explanation of the drawing]

[0008] [Figure 1] This graph shows the relationship between pressure and color intensity in the evaluation of color development characteristics in the examples. [Figure 2] This is a schematic cross-sectional view showing an example of a pressure measuring material in this disclosure. [Figure 3] This is a schematic cross-sectional view showing an example of a pressure measuring material in this disclosure. [Modes for carrying out the invention]

[0009] The pressure measuring material described herein, including its manufacturing method, will be described in detail below. The pressure measuring material and its manufacturing method described herein are not limited in any way to the embodiments described below, and can be implemented with appropriate modifications within the scope of the purpose of this disclosure.

[0010] In this disclosure, a numerical range represented by "~" means a range that includes the numbers written before and after "~" as the lower and upper limits, respectively. In numerical ranges described in stages within this disclosure, an upper or lower limit stated in one numerical range may be replaced with an upper or lower limit in another numerical range described in stages. Furthermore, in numerical ranges described within this disclosure, an upper or lower limit stated in one numerical range may be replaced with a value shown in an example. In this disclosure, the amount of each component in the composition means the total amount of any multiple substances present in the composition, unless otherwise specified, if there are multiple substances corresponding to each component in the composition. In this disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In this disclosure, an electron-donating dye precursor is also referred to as a "chromogen," and an electron-accepting compound that causes an electron-donating dye precursor to develop color is also referred to as a "chromogen."

[0011] <Materials for measuring pressure and methods for manufacturing the same> The pressure measuring material of this disclosure is a pressure measuring material having a substrate and a pressure-sensitive layer, wherein the pressure-sensitive layer contains a polymer matrix containing a polymer compound with a molecular weight of 1000 or more (hereinafter also simply referred to as "polymer matrix"), microcapsules containing an electron-donating dye precursor and a solvent, and an electron-accepting compound. In addition to the substrate and the pressure-sensitive layer, the pressure measuring material of this disclosure may optionally have other layers (e.g., a white layer, a protective layer, an easy-adhesion layer, etc.).

[0012] Pressure measuring materials have been proposed and widely used for some time. However, conventional pressure measuring materials focus on obtaining a concentration that is visible or readable even when minute pressures are applied. For example, the pressure measuring material described in Japanese Patent Publication No. 2009-19949 is intended for measurement at minute pressures of less than 0.1 MPa.

[0013] However, even with effective means to obtain a wide range of density gradations in pressure measuring materials for measurements at minute pressures (for example, controlling the particle size, wall thickness, and constituent materials of microcapsules), it can be difficult to design such materials to produce a wide range of density gradations when measuring pressure in the high-pressure range using only these means.

[0014] In view of the above, the pressure measuring material of this disclosure comprises a substrate and a pressure-sensitive layer, the pressure-sensitive layer being a layer containing a polymer matrix, microcapsules containing an electron-donating dye precursor and a solvent, and an electron-accepting compound. As a result, the pressure measuring material of this disclosure can produce a color with excellent gradation in the high-pressure range (preferably the range of 100 MPa to 10,000 MPa, more preferably the range of 300 MPa to 3,000 MPa).

[0015] Although the reason why the pressure measuring material of this disclosure exhibits the above-mentioned effects is not entirely clear, the inventors speculate that the pressure-sensitive layer, by containing a polymer matrix, microcapsules encapsulating an electron-donating dye precursor and solvent, and an electron-accepting compound, relieves the pressure on the microcapsules even when high pressure is applied, enabling pressure measurement with excellent color gradation. However, this speculation is not intended to limit the interpretation of the effects of the pressure measuring material of this disclosure.

[0016] In this disclosure, "gradation of color development" means the property that the color intensity increases as the pressure applied to the pressure measuring material increases.

[0017] The pressure measuring material of this disclosure develops color in the pressure-sensitive layer when an electron-donating dye precursor encapsulated in microcapsules comes into contact with an electron-accepting compound, which is a color developer. This color development exhibits a density corresponding to the intensity of the external force (pressure applied from the outside, hereinafter the same) applied to the pressure measuring material, i.e., a gradation of color development. For example, when surface pressure is applied to the pressure measuring material, if the applied surface pressure is not uniform across the entire surface, the material develops color to a density corresponding to the pressure, resulting in an image with a density gradation.

[0018] Furthermore, the pressure measuring material of this disclosure may be capable of achieving color gradation in the range of 100 MPa to 10,000 MPa, and may also be capable of achieving color gradation when pressures below 100 MPa and / or above 10,000 MPa are applied.

[0019] [Base material] The pressure measuring material of this disclosure has a base material. The shape of the substrate may be any shape, such as sheet or plate. The shape of the substrate is preferably sheet-like. That is, the pressure measuring material of this disclosure is preferably a sheet-like pressure measuring material having a sheet-like substrate and a pressure-sensitive layer. In this disclosure, "sheet-like" means having two main planes, a thickness of 1 mm or less (preferably 1 μm to 1 mm), and being flexible. In this disclosure, "sheet-like" includes "film-like," and the two terms are used as synonyms. "Plate-like" means having two main planes and a thickness of more than 1 mm (preferably more than 1 mm and 10 mm or less). The substrate is not particularly limited, and specific examples include paper, synthetic paper, plastic substrates, metal substrates, etc., and composite substrates thereof may also be used. From the viewpoint of ease of handling, plastic substrates are preferred.

[0020] Specific examples of paper include fine paper, medium-quality paper, newsprint, neutral paper, acidic paper, recycled paper, coated paper, machine-coated paper, art paper, cast-coated paper, lightly coated paper, tracing paper, and the like. Specific examples of plastics used to form plastic substrates include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), cellulose derivatives such as cellulose triacetate, polyolefins such as polypropylene and polyethylene, and polystyrene.

[0021] Specific examples of synthetic paper include synthetic paper (such as Yupo) produced by biaxially stretching polypropylene or polyethylene terephthalate to form numerous microvoids, synthetic paper made using synthetic fibers such as polyethylene fibers, polypropylene fibers, polyethylene terephthalate fibers, and polyamide fibers, and laminates formed by laminating these onto one, one, or both sides of another synthetic paper.

[0022] The substrate may also preferably be a substrate containing metal. Examples of substrates in this embodiment include metal substrates and composite substrates of metal and plastic. While there are no particular restrictions on the metal used, stainless steel (SUS) or similar metals are preferred because they are less prone to deformation under measurement pressure.

[0023] As for the plastic substrate, polyethylene terephthalate or polyethylene naphthalate is preferable because it can be formed as a substrate with high hardness and flatness, and can better balance measurement in the high-pressure range with color development density.

[0024] From the viewpoint of reproducibility of color intensity in response to pressure, it is preferable to use a substrate that exhibits less deformation due to pressure application, is unaffected by the object being measured, and suppresses pressure dispersion, which is a factor that reduces measurement accuracy. Suitable substrates for this purpose include polyethylene naphthalate substrates or substrates containing metals.

[0025] Since visibility can be further improved by increasing the contrast between the colored and uncolored areas, it is also preferable for the base material to be white. As a white base material, a plastic base material is preferred, and a white polyethylene terephthalate base material is preferred. As a white polyethylene terephthalate base material, a base material containing a known white coloring agent (for example, a white pigment) can be used.

[0026] The thickness of the substrate is not particularly limited, but 10 μm to 500 μm is preferred, and 10 μm to 200 μm is more preferred, for reasons of ease of handling and the ability to supply in roll form.

[0027] [Pressure-sensitive layer] The pressure measuring material of this disclosure has a pressure-sensitive layer on a substrate. The pressure-sensitive layer is a layer containing a polymer matrix, microcapsules encapsulating electron-donating dye precursors and solvents, and electron-accepting compounds.

[0028] (Polymer matrix) In this disclosure, the term "polymer matrix" is used to refer to a matrix that is a component of a pressure-sensitive layer and is formed by including a polymer compound with a molecular weight of 1000 or more (hereinafter also referred to as a specific polymer compound). The specific polymer compound preferably functions as a binder in the pressure-sensitive layer. Compounds constituting the microcapsules (including the contents of the microcapsules, the wall material, and the dispersant used when forming the microcapsules) and electron-accepting compounds are not included in the specific polymer compound. The fact that the polymer matrix is ​​a component of the pressure-sensitive layer relating to the pressure measuring material of this disclosure is confirmed by the inclusion of a specific polymer compound in the pressure-sensitive layer.

[0029] To further improve gradation in the high-pressure region, it is preferable that the specific polymer compound be present in 10% by mass or more, and more preferably 20% by mass or more, relative to the total mass of the pressure-sensitive layer. When the amount of the specific polymer compound is 10% by mass or more, it is easier to retain components such as microcapsules and electron-accepting compounds in the pressure-sensitive layer by easing the external force (pressure) applied to the pressure measuring material. From the viewpoint of color intensity, the content of the specific polymer compound that forms the polymer matrix is ​​preferably 10% to 70% by mass, and more preferably 20% to 50% by mass, relative to the total mass of the pressure-sensitive layer.

[0030] There are no particular restrictions on the specific polymer compound; it can be appropriately selected according to the desired properties for the pressure-sensitive layer, which is resistant to deformation under measurement pressure. The specific polymer compound may be used alone or in combination of two or more types.

[0031] Examples of specific polymer compounds include polyvinyl alcohol, polyurethane-based urethane polymers, vinyl chloride polymers, vinyl acetate polymers, acrylic polymers, styrene-butadiene rubber (SBR), or copolymers thereof. Here, urethane polymers, vinyl chloride polymers, vinyl acetate polymers, and acrylic polymers are defined as constituent units having urethane bonds and vinyl chloride, respectively. This refers to a polymer containing constituent units derived from vinyl acetate and constituent units derived from (meth)acrylic acid. The specific polymer compound may be contained in the pressure-sensitive layer in the form of a dispersion.

[0032] One suitable embodiment for the specific polymer compound is polyvinyl alcohol, from the viewpoint of applicability in microcapsule preparation and productivity in aqueous coating. There are no particular restrictions on the polyvinyl alcohol used; it can be appropriately selected according to the desired properties for the pressure-sensitive layer. The degree of polymerization of polyvinyl alcohol is preferably 100 to 10,000, and preferably 100 to 3,000, in that it retains microcapsules and further improves the gradation in the high-pressure range.

[0033] In order to further improve gradation in the high-pressure region by holding microcapsules, etc., the molecular weight of the specific polymer compound is 1,000 or more, preferably 2,000 or more, more preferably 5,000 or more, and even more preferably 10,000 or more. There is no particular upper limit to the molecular weight, but for example, 1,000,000 can be cited. From the viewpoint of ease of manufacture, the molecular weight is preferably 2,000 to 100,000, more preferably 5,000 to 100,000, and even more preferably 10,000 to 100,000. Here, the molecular weight of the specific polymer compound represents the number average molecular weight measured by gel permeation chromatography (GPC). Specifically, the molecular weights mentioned above were determined using a gel permeation chromatography (GPC) analyzer with TSKgel GMHxL, TSKgel G4000HxL, and TSKgel G2000HxL columns (all product names manufactured by Tosoh Corporation), detected with THF (tetrahydrofuran) as the solvent using a differential refractometer, and converted using polystyrene as the standard substance.

[0034] Commercially available products can also be used as specific polymer compounds. Examples of commercially available products include: PVA-105 (polyvinyl alcohol) and PVA-205 (polyvinyl alcohol) from Kuraray Co., Ltd.; Superflex 170 (urethane polymer), Superflex 820 (urethane polymer), Superflex 830HS (urethane polymer), and Superflex 870 (urethane polymer) from Daiichi Kogyo Seiyaku Co., Ltd.; and Vinibran 287 (vinyl chloride / acrylic polymer), Vinibran 900 (vinyl chloride / acrylic polymer), Vinibran 2684 (acrylic polymer), and Vinibran 2 from Nisshin Chemical Co., Ltd. 685 (acrylic polymer), Vinibran 2687 (acrylic polymer), Vinibran 715S (vinyl chloride polymer); Sumikaflex 752HQ (ethylene-vinyl acetate copolymer emulsion), Sumikaflex 808HQ (ethylene-vinyl acetate-vinyl chloride copolymer emulsion), Sumikaflex 850HQ (ethylene-vinyl acetate-vinyl chloride copolymer emulsion), Sumikaflex 830 (ethylene-vinyl acetate-vinyl chloride copolymer emulsion) manufactured by Sumika Chemtex Co., Ltd.; Nipol manufactured by Nippon Zeon Co., Ltd. LX433C (styrene-butadiene rubber), Nipol LX2507H (styrene-butadiene rubber), Nipol LX416 (styrene-butadiene rubber), Nipol LX814 (acrylic polymer), Nipol LX855EX1 (acrylic polymer); Movinyl 742A (acrylic polymer), Movinyl 1711 (acrylic polymer), Movinyl 6520 (acrylic polymer), Movinyl 7980 (acrylic polymer), Movinyl 081F (vinyl acetate-ethylene polymer) manufactured by Nippon Synthetic Chemical Co., Ltd. Copolymer), Movinyl 082 (vinyl acetate-ethylene copolymer); Nippon A&L Co., Ltd. Examples include the company's own Smartex SN-307R (styrene-butadiene latex).

[0035] Martens hardness is one of the suitable physical properties used as an indicator for specific polymer compounds that form a polymer matrix. The polymer matrix according to this disclosure achieves a balance between pressure measurement in the high-pressure range (preferably 100 MPa to 10000 MPa, more preferably 300 MPa to 3000 MPa) and color density, resulting in a Martens hardness of 100 N / mm². 2 It is preferable that the above polymer compounds are included. The polymer matrix has a Martens hardness of 100 N / mm². 2 The inclusion of the above polymer compounds is preferable because it suppresses deformation of the pressure-sensitive layer even when measuring pressure in the high-pressure region of the pressure-sensitive layer, resulting in highly accurate color gradation. The Martens hardness of polymer compounds is 140 N / mm². 2 It is more preferable that the above conditions are met. There is no particular upper limit to the Martens hardness of polymer compounds, but 300 N / mm² is generally considered a good limit. 2 The following is possible:

[0036] Martens hardness can be determined using the nanoindentation method in accordance with ISO 14577-1 (instrumented indentation hardness), as the value obtained by dividing the maximum test load by the indenter surface area at the maximum indentation depth. Measurement can be performed using a microhardness tester such as the "HM2000" manufactured by Fischer Instruments Co., Ltd. The specific measurement method will be shown in the examples described below.

[0037] (Microcapsules) The pressure-sensitive layer contains microcapsules encapsulating an electron-donating dye precursor and a solvent. A microcapsule typically has a core and a capsule wall for enclosing the core material (also called the encapsulated substance or encapsulated component) that makes up the core. The microcapsules contain an electron-donating dye precursor and a solvent as core materials (encapsulated components). Because the electron-donating dye precursor is encapsulated within the microcapsule, it can remain stable until it is pressurized and the microcapsule is destroyed.

[0038] -Microcapsule wall material- As the wall material for the microcapsule, any water-insoluble or oil-insoluble polymer that has been conventionally used as the wall material for microcapsules containing electron-donating dye precursors for pressure-sensitive recording materials can be used without particular limitation. Among these, polyurethane urea, polyurethane, polyurea, melamine formaldehyde resin, and gelatin are preferred as wall materials, and from the viewpoint of obtaining good color development, polyurethane urea, polyurethane, polyurea, and melamine formaldehyde resin are more preferred, and polyurethane urea containing urethane bonds and polyurethane are particularly preferred.

[0039] The capsule walls of microcapsules are preferably composed substantially of resin. "Substantially composed of resin" means that the resin content is 90% or more by mass relative to the total mass of the capsule wall, and 100% by mass is preferable. In other words, the capsule walls of microcapsules are preferably composed of resin. Furthermore, polyurethane is a polymer having multiple urethane bonds, and is preferably a reaction product formed from raw materials containing polyol and polyisocyanate. Furthermore, polyurea is a polymer having multiple urea bonds, and is preferably a reaction product formed from raw materials containing polyamine and polyisocyanate. It is also possible to synthesize polyurea using polyisocyanate without using polyamine, by utilizing the fact that a portion of the polyisocyanate reacts with water to form polyamine. Furthermore, polyurethane urea is a polymer having urethane and urea bonds, and is preferably a reaction product formed from raw materials containing a polyol, a polyamine, and a polyisocyanate. Note that when the polyol and polyisocyanate react, some of the polyisocyanate may react with water to form a polyamine, resulting in the acquisition of polyurethane urea. Furthermore, melamine-formaldehyde resin is a product of polycondensation between melamine and formaldehyde. It is preferable that the reaction product is formed from these.

[0040] The polyisocyanates mentioned above are compounds having two or more isocyanate groups, and include aromatic polyisocyanates and aliphatic polyisocyanates. For example, the polyisocyanate may be an adduct (compound) of a polyol such as trimethylolpropane and a bifunctional polyisocyanate. Furthermore, the polyols mentioned above are compounds having two or more hydroxyl groups, and include, for example, low molecular weight polyols (e.g., aliphatic polyols, aromatic polyols; "low molecular weight polyols" refers to polyols with a molecular weight of 400 or less), polyvinyl alcohol, polyether polyols, polyester polyols, polylactone polyols, castor oil polyols, polyolefin polyols, and hydroxyl group-containing amine compounds (for example, amino alcohols. Examples of amino alcohols include N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine, which is a propylene oxide or ethylene oxide adduct of an amino compound such as ethylenediamine). Furthermore, the polyamines mentioned above are compounds having two or more amino groups (primary or secondary amino groups), and examples include aliphatic polyhydric amines such as diethylenetriamine, triethylenetetramine, 1,3-propylenediamine, and hexamethylenediamine; epoxy compound adducts of aliphatic polyhydric amines; alicyclic polyhydric amines such as piperazine; and heterocyclic diamines such as 3,9-bis-aminopropyl-2,4,8,10-tetraoxaspiro-(5,5)undecane.

[0041] The number-average wall thickness δ of microcapsules depends on various conditions such as the type of capsule wall material and capsule diameter, but from the viewpoint of color development in the high-pressure region (preferably 100 MPa to 10000 MPa, more preferably 300 MPa to 3000 MPa), it is preferably 0.02 μm to 3 μm, and more preferably 0.05 μm to 2 μm.

[0042] Microcapsule wall thickness refers to the thickness (μm) of the resin film (so-called capsule wall) that forms the capsule particles of the microcapsule. Number-average wall thickness refers to the average value obtained by measuring the thickness (μm) of the individual capsule walls of five microcapsules using a scanning electron microscope (SEM). Specifically, first, the microcapsule liquid is coated onto a suitable support and dried to form a coating film. A cross-sectional section of the obtained coating film is prepared, and the cross-section is observed using an SEM. Five microcapsules are selected, and the cross-section of each selected microcapsule is observed to determine the capsule wall thickness and calculate the average value. Cross-sectional sections can also be prepared from pressure measurement materials.

[0043] -Electron-donating dye precursor- Electron-donating dye precursors include those that donate electrons, or protons (hydrogen ions; H) such as acids. + There are no particular restrictions as long as it has the property of receiving a chromogenic agent and developing color, but it is preferable that it be colorless. The electron-donating dye precursor can function as a color developer. In particular, as the electron-donating dye precursor, a colorless compound having a partial skeleton such as lactone, lactam, sultone, spirobipyran, ester, amide, etc., and when contacted with the electron-accepting compound described later, these partial skeletons are ring-opened or cleaved is preferred.

[0044] As the electron-donating dye precursor, those known in the applications of pressure-sensitive copying paper or thermal recording paper can be used. Examples of the electron-donating dye precursor include triphenylmethane phthalide-based compounds, fluoran-based compounds, phenothiazine-based compounds, indolyl phthalide-based compounds, leucoauramine-based compounds, rhodamine lactam-based compounds, triphenylmethane-based compounds, diphenylmethane-based compounds, triazene-based compounds, spirobipyran-based compounds, fluorene-based compounds, and various other compounds. For details of the above compounds, reference can be made to the descriptions in JP-A-5-257272 and paragraphs

[0029] to

[0034] of WO 2009 / 8248. The electron-donating dye precursor may be used alone or in combination of two or more.

[0045] In one aspect of the present disclosure, from the viewpoint of visibility, the electron-donating dye precursor preferably has a high molar absorption coefficient (ε). The molar absorption coefficient (ε) of the electron-donating dye precursor is 10000 mol -1 ·cm -1 ·L or more, preferably 15000 mol -1 ·cm -1 ·L or more, more preferably 25000 mol -1 ·cm -1 ·L or more.

[0046] The molar absorption coefficient (ε) can be calculated from the absorbance when the electron-donating colorless dye is dissolved in a 95% by mass acetic acid aqueous solution. Specifically, in a 95% by mass acetic acid aqueous solution of the electron-donating colorless dye whose concentration is adjusted so that the absorbance is 1.0 or less, when the length of the measurement cell is A cm, the concentration of the electron-donating colorless dye is B mol / L, and the absorbance is C, it can be calculated by the following formula. Molar extinction coefficient (ε) = C / (A×B)

[0047] The content (e.g., coating amount) of the electron-donating dye precursor in the pressure-sensitive layer is preferably 0.1 g / m² in mass after drying, from the viewpoint of enhancing color development in the pressure range of 100 MPa to 10000 MPa (more preferably 300 MPa to 3000 MPa). 2 ~5g / m 2 Preferably, 0.1 g / m 2 ~4g / m 2 More preferably, 0.2 g / m 2 ~3g / m 2 That is even more preferable.

[0048] -solvent- The microcapsules contain at least one solvent. The solvent can function as an oil component that dissolves the electron-donating dye precursor. As a solvent, those known for use in pressure-sensitive copying paper applications can be used. The solvent preferably contains 50% to 100% by mass of a solvent with a boiling point above 130°C, more preferably 70% to 100% by mass, and even more preferably 90% to 100% by mass, in order to stably dissolve the electron-donating dye precursor without precipitating it. There is no particular upper limit to the boiling point, but for example, 500°C is one example, and it is preferably between 130°C and 500°C. Examples of solvents include alkylnaphthalene compounds such as diisopropylnaphthalene; diarylalkane compounds such as 1-phenyl-1-xylethane; alkylbiphenyl compounds such as isopropylbiphenyl; triarylmethane compounds; alkylbenzene compounds; benzylnaphthalene compounds; diarylalkylene compounds; aromatic hydrocarbons such as arylindan compounds; ester compounds such as dibutyl phthalate; aliphatic hydrocarbons such as isoparaffins; natural animal and vegetable oils such as soybean oil, corn oil, cottonseed oil, rapeseed oil, olive oil, coconut oil, castor oil, and fish oil; and natural high-boiling fractions such as mineral oils.

[0049] The solvent may be used alone or in a mixture of two or more types.

[0050] The mass ratio (solvent:precursor) of the solvent to the electron-donating dye precursor encapsulated in the microcapsules is preferably in the range of 98:2 to 30:70, more preferably in the range of 97:3 to 40:60, and even more preferably in the range of 95:5 to 50:50, in terms of color development.

[0051] -Other ingredients- In addition to the electron-donating dye precursor, solvent, and auxiliary solvent described above, the microcapsules may contain additives as needed. Examples of additives include UV absorbers, light stabilizers, antioxidants, waxes, and odor suppressants. Furthermore, the manufacturing of the microcapsules... The solvent used in this process may have a boiling point of 130°C or lower (for example, ketone compounds such as methyl ethyl ketone, ester compounds such as ethyl acetate, and alcohol compounds such as isopropyl alcohol).

[0052] The content of microcapsules in the pressure-sensitive layer (or the amount applied if applied by coating) is preferably 10% to 80% by mass, more preferably 10% to 60% by mass, and more preferably 10% to 50% by mass, relative to the total solid content mass of the pressure-sensitive layer.

[0053] -Method for producing microcapsules- Microcapsules can be manufactured by any known method, such as interfacial polymerization, internal polymerization, phase separation, external polymerization, or coacervation. Examples of microcapsule fabrication using polyurethane urea, polyurethane, and polyurea as capsule wall materials can be found in paragraphs

[0040] to

[0044] of Japanese Patent Publication No. 2009-19949. Specifically, one method involves mixing a compound for forming the microcapsule wall material with a microcapsule core material and reacting the compound for forming the microcapsule wall material to form the microcapsule. It is preferable to use a dispersant such as polyvinyl alcohol when forming microcapsules.

[0054] (Electron-accepting compounds) The pressure-sensitive layer contains at least one electron-accepting compound. The electron-accepting compound can function as a color developer.

[0055] Examples of electron-accepting compounds include inorganic compounds and organic compounds. Specific examples of inorganic compounds include clay materials such as acid clay, activated clay, attapulgite, zeolite, bentonite, and kaolin. Specific examples of organic compounds include metal salts of aromatic carboxylic acids (preferably metal salicylates), phenol-formaldehyde resins, and metal salts of carboxylated terpene phenol resins. In particular, preferred electron-accepting compounds include acid clay, activated clay, zeolite, kaolin, metal salts of aromatic carboxylic acids, or metal salts of carboxylated terpene phenol resins, with acid clay, activated clay, kaolin, or metal salts of aromatic carboxylic acids being more preferred.

[0056] Preferred specific examples of aromatic carboxylic acids in metal salts of aromatic carboxylic acids include 3,5-di-t-butylsalicylic acid, 3,5-di-t-octylsalicylic acid, 3,5-di-t-nonylsalicylic acid, 3,5-di-t-dodecylsalicylic acid, 3-methyl-5-t-dodecylsalicylic acid, 3-t-dodecylsalicylic acid, 5-t-dodecylsalicylic acid, 5-cyclohexylsalicylic acid, and 3,5-bis(α,α-dimethylbenzyl Examples include salicylic acid, 3-methyl-5-(α-methylbenzyl)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, and 3-phenyl-5-(α,α-dimethylbenzyl)salicylic acid. In addition, carboxylated terpene phenol resins and salicylic acid resins, which are reaction products of 3,5-bis(α-methylbenzyl)salicylic acid and benzyl chloride, can also be used as aromatic carboxylic acids. Specific examples of metal salts in the metal salts of aromatic carboxylic acids include zinc salts, nickel salts, aluminum salts, and calcium salts.

[0057] The content of electron-accepting compounds in the pressure-sensitive layer (or the amount applied if applied by coating) is given by dry mass. 0.1g / m 2 ~30g / m 2 This is preferable. When the electron-accepting compound is an inorganic compound, the content is more preferably 3 g / m² by dry mass. 2 ~20g / m 2 And more preferably, 5 g / m 2 ~15g / m 2 The content of the electron-accepting compound when it is an organic compound is more preferably 0.1 g / m³ by dry mass. 2 ~15g / m 2 And more preferably, 0.2 g / m 2 ~10g / m 2 That is the case.

[0058] (Oil-absorbing particles) The pressure-sensitive layer preferably contains at least one type of oil-absorbing particle on the outside of the microcapsule.

[0059] Because high pressure is applied to the pressure measuring material of this disclosure, the solvent (oil component) encapsulated in the microcapsules tends to leach out to the outside of the pressure-sensitive layer. Leakage of the oil component is undesirable as it causes oil staining. In contrast, by including oil-absorbing particles outside the microcapsules in the pressure-sensitive layer, the leachage of the oil component to the outside of the pressure-sensitive layer can be effectively suppressed.

[0060] In this disclosure, "oil-absorbing particles" means particles that absorb linseed oil at 25°C in an amount of 50% or more of their own weight. The method for measuring oil absorption shall be in accordance with JIS-K5101-13-1:2004. Examples of particle shapes include spheres, ellipses, rods, etc., but other shapes are also acceptable.

[0061] The particle size of the oil-absorbing particles is preferably 0.5 μm to 20 μm, preferably 1 μm to 10 μm, and more preferably 2 μm to 8 μm. The particle size of oil-absorbing particles can be measured using the Microtrac MT3300EXII (manufactured by Nikkiso Co., Ltd.).

[0062] Examples of oil-absorbing particles include inorganic particles such as porous silica particles, calcium carbonate, kaolin, aluminum silicate, colloidal silica, alumina, and aluminum hydroxide, and polymer particles such as polyolefins, acrylics, polystyrenes, and polyesters. At least one inorganic particle selected from porous silica particles, calcium carbonate, and kaolin is preferred. The oil-absorbing particles may be electron-accepting compounds that are used as color developers and also possess oil-absorbing properties. As oil-absorbing particles, commercially available products may be used, such as the "Brilliant Series" manufactured by Shiraishi Industries Co., Ltd.

[0063] The amount of oil-absorbing particles in the pressure-sensitive layer can be set appropriately according to the desired oil absorption level.

[0064] (Inorganic particles) The pressure-sensitive layer preferably contains at least one inorganic particle that is not an electron-accepting compound on the outside of the microcapsule.

[0065] Examples of inorganic particles include porous silica particles, calcium carbonate, kaolin, aluminum silicate, colloidal silica, alumina, and aluminum hydroxide, with silica being preferred. The inorganic particles may also be the inorganic particles described above for oil-absorbing particles. As inorganic particles, commercially available products may be used, such as the "Mizukasil series" manufactured by Mizusawa Chemical Industries, Ltd. The particle size of the inorganic particles is preferably 1 μm to 30 μm, and more preferably 5 μm to 20 μm.

[0066] (Other ingredients) Other components that the pressure-sensitive layer may contain include, for example, surfactants, fluorescent whitening agents, defoaming agents, penetrating agents, ultraviolet absorbers, and preservatives.

[0067] (Thickness t of the pressure-sensitive layer) There are no particular restrictions on the thickness t of the pressure-sensitive layer, and it can be selected according to the purpose, etc. The thickness t of the pressure-sensitive layer is preferably 1 μm to 250 μm, more preferably 3 μm to 200 μm, even more preferably 5 μm to 150 μm, and particularly preferably 5 μm to 50 μm. Furthermore, as described in the second embodiment later, if the pressure-sensitive layer has a color-developing layer and a color-developing layer, the total thickness of the pressure-sensitive layer is the sum of the thickness of the color-developing layer and the thickness of the color-developing layer.

[0068] The thickness t of the pressure-sensitive layer can be measured by microscopic observation. Specifically, the pressure-measuring material to be measured is cut vertically to create a cross-sectional section, and this section is observed using a scanning electron microscope (SEM). From the resulting image, the thickness of the pressure-sensitive layer can be determined. An example of a scanning electron microscope is the desktop microscope "Miniscope TM3030Plus" (manufactured by Hitachi High-Technologies Corporation). In this disclosure, the thickness of the pressure-sensitive layer is the arithmetic mean of the thicknesses of 10 randomly selected locations.

[0069] The coefficient of variation (CV value; hereinafter also referred to as the CV value) of the particle size distribution of all particles contained in the pressure-sensitive layer is preferably between 20% and 150%. When the CV value is within the above range, the particle distribution within the pressure-sensitive layer, especially the relative variation of microcapsules, is small, resulting in excellent color development. A CV value of 20% to 110% is preferred, and 25% to 80% is more preferred.

[0070] The CV value represents the relative variation of particles contained in the pressure-sensitive layer and is a value that can be calculated from the following. CV value (%) = Standard deviation / Arithmetic mean particle size × 100 The arithmetic mean particle size and standard deviation are calculated by photographing the surface of the pressure-sensitive layer with an optical microscope at 150x magnification and measuring the size of all microcapsules within a randomly set 2cm x 2cm area.

[0071] (Layer structure of the pressure-sensitive layer) The pressure-sensitive layer configuration of the present disclosure may be a single-layer configuration or a multi-layer configuration. One configuration of the pressure-sensitive layer is one in which microcapsules and electron-accepting compounds are contained within a polymer matrix. A pressure-sensitive layer adopting this configuration will be described in detail later, using the first configuration of the pressure-sensitive layer as an example. Another embodiment of the pressure-sensitive layer of this disclosure may have a color-developing layer having an electron-accepting compound and a polymer matrix, and a color-developing layer having microcapsules. A pressure-sensitive layer adopting this embodiment will be described in detail later, using the second embodiment of the pressure-sensitive layer as an example.

[0072] <First aspect> A first aspect of the pressure-sensitive layer of this disclosure is a pressure-sensitive layer containing microcapsules and an electron-accepting compound in a polymer matrix.

[0073] Details of each component (specific polymer compound, microcapsule, electron-accepting compound, etc.) applied to the pressure-sensitive layer according to the first embodiment are the same as described above, and the preferred embodiment is also It is the same.

[0074] In this disclosure, "a component is contained in a polymer matrix" means that at least a portion of that component is contained in the pressure-sensitive layer in contact with a specific polymer compound. The containment state may be either dispersed or dissolved, and if it is a solid, a portion of it may be exposed on the surface of the pressure-sensitive layer. Specifically, in the case of microcapsules, both states in this disclosure, where the entire microcapsule is located inside the pressure-sensitive layer and where a portion of the microcapsule wall is exposed on the surface of the pressure-sensitive layer, are included in the description of the microcapsule being contained within a polymer matrix. Here, the state in which the entire microcapsule is in contact with a specific polymer compound includes both states in which the microcapsule itself, consisting of the encapsulant and wall material, is in direct contact with the specific polymer compound, and states in which the microcapsule is in contact with the specific polymer compound via a dispersant.

[0075] An example of a pressure measuring material having a pressure-sensitive layer according to the first embodiment will be described with reference to Figure 2 as appropriate. Figure 2 is a schematic cross-sectional view showing an example of a pressure measuring material having a pressure-sensitive layer according to the first embodiment. Note that Figure 2 is used to explain the first embodiment, and the components shown do not correspond to the actual size and proportions.

[0076] In the pressure measuring material 10 shown in Figure 2, the pressure-sensitive layer 14 is provided on the substrate 12. The pressure-sensitive layer 14 has microcapsules 18 and an electron-accepting compound 15. 18a represents the capsule wall of the microcapsule, and 18b represents the contents of the microcapsule (i.e., the core material). 16 represents a polymer matrix containing a specific polymer compound (not shown).

[0077] The pressure measuring material having a pressure-sensitive layer according to the first embodiment is particularly suitable for use in a pressure range of 500 MPa or higher.

[0078] From the viewpoint of excellent gradation in the high-pressure region of 500 MPa or higher, the arithmetic mean roughness Ra of the pressure measuring material according to the first embodiment is preferably less than 2.0 μm. In other words, it is preferable that the majority of the microcapsules and electron-accepting compounds are located within the polymer matrix without being exposed on the surface of the pressure-sensitive layer.

[0079] In this disclosure, the arithmetic mean roughness Ra of the pressure measurement material refers to the arithmetic mean roughness Ra as defined in JIS B 0681-6:2014. The measuring device used is a scanning white light interferometer using the optical interferometry method (specifically, a NewView5020 from Zygo: Stitch mode; objective lens ×50x; intermediate lens ×0.5x).

[0080] The above arithmetic mean roughness Ra corresponds to the arithmetic mean roughness Ra of the surface opposite to the substrate side. The arithmetic mean roughness Ra of the pressure measuring material according to the first embodiment is preferably 0 μm or more and less than 2.0 μm, more preferably 0 μm to 1.0 μm, and even more preferably 0 μm to 0.5 μm.

[0081] Methods to achieve an arithmetic mean roughness Ra of less than 2.0 μm include increasing the amount of specific polymer compound in the pressure-sensitive layer, and it is preferable that the specific polymer compound is 20% by mass or more relative to the total solid content constituting the pressure-sensitive layer.

[0082] From the viewpoint of excellent gradation in the high-pressure range of 500 MPa or higher, the pressure measuring material having a pressure-sensitive layer according to the first embodiment has a void volume of 5 mL / m 2 The following is preferable: If the amount of void is low The microcapsules are less likely to break and are more resistant to pressure exceeding 500 MPa. is 0 mL / m 2 ~5 mL / m² 2 Preferably, 0 mL / m² 2 ~3 mL / m² 2 More preferably, 0 mL / m 2 ~1 mL / m² 2 That is even more preferable. Here, the amount of void is a value that can be calculated using the following formula. The mass (m1) of a 10cm x 10cm piece of pressure-measuring material is measured. Next, diethylene glycol is allowed to penetrate the surface of the pressure-sensitive layer of the pressure-measuring material. After wiping off the remaining diethylene glycol from the surface, the mass (m2) is measured. Then, assuming X = m2 - m1, the amount of void can be calculated from the following formula. Note that the density of diethylene glycol is 1.118. Void volume (m l / m²) = 100 × X ÷ 1.118

[0083] In order to reduce the amount of voids, the electron-accepting compound contained in the pressure-sensitive layer of the first embodiment preferably contains an organic compound, more preferably contains it as a main component, and more preferably contains it in an amount of 50% to 100% by mass. Preferred electron-accepting compounds include those similar to those described above, preferably contain a metal salt of an aromatic carboxylic acid, and among these, contain a metal salt of salicylic acid is particularly preferred. In this specification, "contained as a main component" means the component with the highest content among the electron-accepting compounds.

[0084] The microcapsule content (volume fraction) is preferably 10% to 80% relative to the pressure-sensitive layer, more preferably 20% to 60% relative to the pressure-sensitive layer, and even more preferably 30% to 60% relative to the pressure-sensitive layer, in terms of superior gradation in the high-pressure range.

[0085] The content (volume fraction) of microcapsules in the pressure-sensitive layer can be measured by the following method. Refer to Figure 2 for details. Cross-sectional sections of the pressure measurement material 10 are prepared, and the cross-sections are observed at 1000x magnification using a scanning electron microscope (SEM). From the SEM image of the cross-section, the interior of the microcapsule 18 (inclusions 18b) and the matrix portion containing the capsule wall 18a, a polymer matrix 16 containing a specific polymer compound (not shown), and an electron-accepting compound 15 are observed separately. For all microcapsules 18 present in the observed field of view, the interior of the microcapsule 18 (inclusions 18b) and the matrix portion containing the capsule wall 18a, a polymer matrix 16 containing a specific polymer compound, and an electron-accepting compound 15 are separated by image analysis, and the area of ​​the microcapsule interior and the area of ​​the matrix portion are calculated, respectively, and the content A (area %) inside the microcapsule is determined from their ratio. Next, another cross-sectional section is prepared in a direction perpendicular to the above cross-sectional section and perpendicular to the substrate, and the microcapsule content B (area %) is determined in the same manner. The average value of content A (area %) inside the microcapsule and content B (area %) inside the microcapsule is calculated. This operation is performed at two randomly selected locations, and the average of the average values ​​obtained at the two locations is taken as the microcapsule content (volume %).

[0086] -Microcapsule particle size d1- In the first embodiment, “microcapsule particle size d1” means the median diameter of the volume standard. The median diameter of the microcapsule volume standard refers to the diameter (D50) at which, when the total volume of microcapsules contained in the pressure-sensitive layer is divided into two parts based on a particle diameter threshold where the cumulative volume is 50%, the sum of the volumes of the particles on the larger diameter side and the smaller diameter side is equal. The median diameter of the volume standard of the microcapsules is a value calculated by applying a microcapsule liquid to a support, photographing the surface of the coating film formed after drying with an optical microscope at 150 times magnification, and measuring the sizes of all the microcapsules within a range of 2 cm × 2 cm. From the viewpoint of color development properties in a high-pressure region (preferably 100 MPa to 10,000 MPa, more preferably 300 MPa to 3,000 MPa), the particle diameter d of the microcapsules is preferably 1 μm to 5

[0087] From the viewpoint of achieving both the height of the measurement pressure and the color density, the ratio of the thickness t of the pressure-sensitive layer to the particle diameter d1 of the microcapsules contained in the pressure-sensitive layer preferably satisfies the relationship shown in the following formula 1. 1 < t / d1 < 5 ··· Formula 1 When t / d1 < 5, better color development properties can be obtained, and when 1 < t / d1, it becomes easier to suppress fogging.

[0088] - Inner diameter p1 of the microcapsule - From the viewpoint of better gradation properties in the high-pressure region and the color development properties in the high-pressure region, the inner diameter p1 of the microcapsules is preferably 0.5 μm to 50 μm, more preferably 1 μm to 30 μm, and still more preferably 2 μm to 20 μm.

[0089] In the first aspect, the "inner diameter p1 of the microcapsules" is a value obtained by the following method. This will be described with reference to Figure 2. Cross-sectional sections of the pressure measurement material 10 are prepared, and these sections are observed at 1000x magnification using a scanning electron microscope (SEM). From the SEM image of the section, the interior of the microcapsule 18 (inclusions 18b), the capsule wall 18a, and the polymer matrix 16 containing a specific polymer compound and the matrix portion containing an electron-accepting compound 15 can be observed separately. The major axis (inner diameter) of the 10 microcapsules present in the observed field of view is measured in order from the largest microcapsule, and the arithmetic mean of these is calculated to obtain the average value. This operation is performed in 5 fields of view, and the average of the average values ​​obtained at each location is calculated to obtain the average inner diameter of the microcapsules. Note that the major axis refers to the longest inner diameter when observing the microcapsule.

[0090] <Second aspect> A second aspect of the pressure-sensitive layer of the present disclosure is a pressure-sensitive layer having a color-developing layer having an electron-accepting compound and a polymer matrix and a color-developing layer having microcapsules, wherein the substrate, the color-developing layer and the color-developing layer are arranged in this order, and the thickness of the color-developing layer is half or less of the thickness of the color-developing layer.

[0091] Details of each component (specific polymer compound, microcapsule, electron-accepting compound, etc.) applied to the pressure-sensitive layer according to the second embodiment are the same as those described above, and the preferred embodiment is also the same.

[0092] An example of a pressure measuring material having a pressure-sensitive layer according to the second embodiment will be described with reference to the drawings. Figure 3 is a schematic cross-sectional view showing an example of a pressure measuring material having a pressure-sensitive layer according to the second embodiment. Note that Figure 3 is used to explain the second embodiment, and the components shown do not correspond to the actual size and proportions.

[0093] In the pressure measuring material 20 shown in Figure 3, the pressure-sensitive layer 24 is provided on the substrate 22. It is formed from a color-developing layer 24a and a color-developing layer 24b. The color-developing layer 24a has microcapsules 28, and the color-developing layer 24b has an electron-accepting compound 25 and a polymer matrix 26 containing a specific polymer compound. 28a represents the capsule wall of the microcapsule, and 28b represents the contents of the microcapsule (i.e., the core material). It is preferable that the color-developing layer 24a contains a specific polymer compound.

[0094] From the viewpoint of achieving superior gradation in the high-pressure range of 100 MPa or higher, the thickness of the color-developing layer is preferably half or less of the thickness of the color-developing layer, and more preferably one-third or less. There is no particular lower limit. In one aspect of this disclosure, the thickness of the color-developing layer is 0.001 of the thickness of the color-developing layer. It is preferably between 0.5 times and 0.001 times, more preferably between 0.001 times and 0.4 times, and even more preferably between 0.001 times and 0.33 times.

[0095] The thickness of the color-developing layer and the color-developing layer can be measured by microscopic observation. Specifically, the pressure measurement material to be measured is cut vertically to create a cross-sectional section. A scanning electron microscope (SEM) is used to observe an 800 μm × 600 μm field of view of this cross-sectional section. From this image, the thickness of the chromogenic and chromogenic layers is measured at 10 locations at 50 μm intervals, and the arithmetic mean of these measurements is calculated to determine the thickness of the chromogenic and chromogenic layers. An example of a scanning electron microscope is the desktop microscope "Miniscope TM3030Plus" (manufactured by Hitachi High-Technologies Corporation). As shown in Figure 3, if there are areas in the color development layer where microcapsules are not present, the color development layer is counted as 0 μm.

[0096] The second embodiment is one that can be preferably used in a pressure range of 100 MPa to 500 MPa. From the viewpoint of excellent gradation in the high-pressure range of 100 MPa to 500 MPa, the pressure measuring material having a pressure-sensitive layer according to the second embodiment has a void amount of 5 mL / m 2 ~20 mL / m² 2 Preferably, it is 8 mL / m² 2 Super 15mL / m 2 The following is more preferable. The amount of void is the value obtained by the formula described above.

[0097] In order to set the amount of voids within a specific range, the electron-accepting compound in the second embodiment preferably contains inorganic particles, more preferably contains them as the main component, and more preferably contains them in an amount of 50% to 100% by mass. Preferred electron-accepting compounds include those similar to those described above, and it is preferable that they contain acid clay or activated clay. The electron-accepting compound in the second embodiment may be mainly inorganic particles, or it may contain other electron-accepting compounds. From the viewpoint of excellent gradation in the high-pressure range of 100 MPa to 500 MPa, the pressure-sensitive layer in the second embodiment preferably contains inorganic particles other than electron-accepting compounds. Examples of inorganic particles other than electron-accepting compounds are the same as those described above, and silica is preferred. From the viewpoint of achieving superior gradation in the high-pressure range of 100 MPa to 500 MPa, it is preferable that the pressure-sensitive layer (preferably the color-developing layer) in the second embodiment contains inorganic particles that are electron-accepting compounds, and also has inorganic particles that are not electron-accepting compounds. By having both inorganic particles as electron-accepting compounds and inorganic particles that are not electron-accepting compounds, the probability of electron-donating dye precursors leaking from microcapsules coming into contact with electron-accepting compounds can be suppressed while maintaining the amount of voids within a specific range, thus making it possible to create a material suitable for gradation in the high-pressure range of 100 MPa to 500 MPa.

[0098] From the viewpoint of having excellent gradation in the high-pressure range of 100 MPa to 500 MPa, the arithmetic mean roughness Ra of the pressure measuring material according to the second embodiment is preferably 2.0 μm to 10.0 μm. The above arithmetic mean roughness Ra corresponds to the arithmetic mean roughness Ra of the surface opposite to the substrate side. The arithmetic mean roughness Ra of the pressure measuring material according to the second embodiment is preferably 2.0 μm to 8.0 μm, and more preferably 2.0 μm to 5.0 μm.

[0099] Methods for adjusting the arithmetic mean roughness Ra to 2.0 μm to 10.0 μm include, for example, the methods shown in (1) and (2) below, as well as methods combining these. (1) Method of making the color-developing layer a thin layer (2) A method to increase the amount of inorganic particles in the color-developing layer. This method adjusts the surface roughness of the color-developing layer by utilizing the difference between areas where inorganic particles are present and areas where they are not.

[0100] In particular, if the amount of inorganic particles (the total amount of electron-accepting inorganic particles and non-electron-accepting inorganic particles) is greater than the total amount of specific polymer compounds present in the color-developing layer, particles will appear on the surface of the color-developing layer, making the surface of the color-developing layer prone to becoming rough. Furthermore, if microcapsules and specific polymer compounds are thinly arranged on top of this, the microcapsules will fill the depressions in the roughened color-developing layer, resulting in the arithmetic mean roughness Ra of the pressure-measuring material tending to be between 2.0 μm and 10.0 μm. In the above state where the arithmetic mean roughness Ra is 2.0 μm to 10.0 μm, there are microcapsules that penetrate into the depressions of the color-developing layer and do not break even under high-pressure conditions, and there are also regions on the surface where microcapsules are not present. Therefore, the pressure measuring material of the second embodiment can be made suitable for high-pressure regions of 100 MPa to 500 MPa.

[0101] Furthermore, in the second embodiment, it is preferable that the microcapsules are not present on the entire surface of the pressure-sensitive layer opposite to the substrate side, and the proportion of microcapsules is preferably 95% or less, and preferably 90% or less. The method for measuring the proportion of microcapsules described above involves first observing the surface of the color-developing layer from an arbitrary position using a laser microscope (KEYENCE VK-8510, field of view size: 100 μm × 150 μm), measuring the total number of microcapsules observed within the field of view, and then calculating the area of ​​the number of microcapsules observed within the field of view through image analysis and dividing it by the field of view area. From the viewpoint of allowing microcapsules to easily penetrate the recesses of the color development layer and providing excellent gradation in the high-pressure range of 100 MPa to 500 MPa, it is preferable that the total solid content of the color development layer forming composition is less than the total solid content of the color development layer forming composition. Preferably, the total solid content of the color development layer forming composition is 0.001 to 0.45 times, and more preferably 0.005 to 0.25 times, the total solid content of the color development layer forming composition.

[0102] -Microcapsule particle size d2- In the second embodiment, "microcapsule particle size d2" refers to the average particle size. The average particle size of microcapsules is measured by performing image analysis on images taken from the surface of the chromogenic layer containing the microcapsules using an optical microscope (OLYMPUS BX60, field of view: 320 μm × 450 μm). The major axis (particle size) of the 30 microcapsules, starting with the largest one, is measured, and the arithmetic mean of these is calculated to obtain the average value. This operation is performed at five arbitrary locations (five fields of view) in the first layer, and the average of the average values ​​obtained at each location is calculated to obtain the average particle size of the microcapsules. Note that the major axis refers to the longest diameter when observing the microcapsules. From the viewpoint of color development in the high-pressure range (preferably 100 MPa to 10000 MPa, more preferably 300 MPa to 3000 MPa), the particle size d2 of the microcapsules is preferably 1 μm to 50 μm, and more preferably 5 μm to 30 μm.

[0103] -Inner diameter of microcapsule p2- The inner diameter p2 of the microcapsule is preferably 1 μm to 50 μm, more preferably 2 μm to 20 μm, and even more preferably 2 μm to 15 μm, from the viewpoint of superior gradation in the high-pressure range of 100 MPa to 500 MPa, and from the viewpoint of color development in the high-pressure range.

[0104] In the second embodiment, the "inner diameter p2 of the microcapsule" is a value determined by the following method. First, we determine the wall thickness of the microcapsules. The wall thickness of a microcapsule refers to the thickness (μm) of the capsule wall that forms the capsule particles of the microcapsule, and the number-average wall thickness is the thickness of 5 particles. This refers to the average value obtained by determining the thickness (μm) of the individual capsule walls of microcapsules using a scanning electron microscope (SEM). More specifically, cross-sectional sections of microcapsules present in a pressure measurement material are prepared, and these cross-sections are observed at 15,000x magnification using an SEM. Five arbitrary microcapsules with major diameters in the range of (average particle size) × 0.9 to (average particle size) × 1.1 are selected, and the cross-sections of each selected microcapsule are observed to determine the capsule wall thickness and calculate the average value. The major diameter refers to the longest diameter observed when the microcapsule is observed. Furthermore, the inner diameter of the microcapsule is calculated by dividing the average particle diameter by twice the wall thickness of the microcapsule.

[0105] <Formation of a pressure-sensitive layer> The formation of the pressure-sensitive layer is not particularly limited as long as it involves a process of forming a pressure-sensitive layer containing a polymer matrix containing a polymer compound with a molecular weight of 1000 or more (specific polymer compound), microcapsules containing an electron-donating dye precursor and a solvent, and an electron-accepting compound.

[0106] In the first embodiment, the pressure-sensitive layer can be formed by preparing a pressure-sensitive layer-forming composition, applying it (e.g., coating) onto a substrate, and drying it.

[0107] In other words, a pressure measuring material having a pressure-sensitive layer according to the first embodiment is, It is preferable to obtain the pressure-sensitive layer-forming composition by a manufacturing method that includes the step of placing a pressure-sensitive layer-forming composition containing a polymer matrix containing a specific polymer compound, microcapsules containing an electron-donating dye precursor and a solvent, and an electron-accepting compound onto a substrate.

[0108] The pressure-sensitive layer-forming composition used for forming the pressure-sensitive layer in the first embodiment can be prepared, for example, by preparing a dispersion of microcapsules and mixing the obtained dispersion with a solution (or emulsion) of a specific polymer compound (a polymer compound that forms a polymer matrix), an electron-accepting compound, and other optional components (for example, oil-absorbing particles).

[0109] In a second embodiment, the pressure-sensitive layer can be formed, for example, by preparing two compositions consisting of a color-developing layer composition and a color-developing layer composition as a pressure-sensitive layer-forming composition, applying (e.g., coating) the color-developing layer composition onto a substrate, applying (e.g., coating) the color-developing layer composition thereon, and drying it. The color-developing layer-forming composition can be prepared, for example, by preparing a dispersion of microcapsules and mixing the obtained dispersion, a solution (or emulsion) of a specific polymer compound, and other optional components (e.g., surfactants). The color-developing layer-forming composition can be prepared, for example, by mixing an electron-accepting compound, a solution (or emulsion) of a specific polymer compound, and other optional components (e.g., inorganic particles).

[0110] In other words, the pressure measuring material having a pressure-sensitive layer according to the second embodiment is Preferably, the product can be obtained by a manufacturing method comprising the steps of: obtaining a color-developing layer-forming composition containing microcapsules encapsulating an electron-donating dye precursor and a solvent (preferably a solvent with a boiling point of 130°C or higher) and a solvent (preferably a solvent with a boiling point of 130°C or lower); obtaining a color-developing layer-forming composition containing an electron-accepting compound and a polymer compound (specific polymer compound) with a molecular weight of 1000 or higher; arranging the color-developing layer-forming composition on a substrate to form a color-developing layer; and arranging the color-developing layer-forming composition on the color-developing layer to form a color-developing layer. Furthermore, the color-forming layer composition preferably contains a polymer compound (specific polymer compound) with a molecular weight of 1000 or more. The specific polymer compounds contained in the color-developing layer-forming composition and the specific polymer compounds preferably contained in the color-developing layer-forming composition may be one type each, or two or more types may be combined. The specific polymer compounds included may be the same polymer compound or different polymer compounds.

[0111] The specific preparation method, application amount, drying conditions, etc., of the pressure-sensitive layer forming composition should be determined as appropriate, depending on the type of components to be included in the pressure-sensitive layer forming composition, the specific form of the material to be used for pressure measurement, etc.

[0112] When a pressure-sensitive layer is formed by applying a pressure-sensitive layer-forming composition onto a substrate, the application can be carried out by known application methods. Examples of application methods include those using an air knife coater, rod coater, bar coater, curtain coater, gravure coater, extrusion coater, die coater, slide bead coater, blade coater, etc.

[0113] [Other layers] The pressure measuring material of this disclosure may have layers other than the pressure-sensitive layer on the substrate. Other layers include a protective layer, a white layer, and an easy-adhesion layer.

[0114] -Protective layer- The pressure measuring material of this disclosure may further have a protective layer on the side opposite to the side having the pressure-sensitive layer substrate. The pressure measuring material of this disclosure may have a protective layer as the outermost layer, but is not limited to this embodiment. Because high pressure is applied to the pressure measuring material of this disclosure, the solvent (oil component) encapsulated in the microcapsules tends to leach out to the outside of the pressure-sensitive layer. Leakage of the oil component is undesirable as it causes oil staining. In contrast, by having a protective layer in the pressure measuring material, the leachage of the oil component to the outside of the pressure-sensitive layer can be effectively suppressed. Therefore, the protective layer is preferably a layer with low permeability to oil components.

[0115] The protective layer can be provided by attaching a protective layer-forming sheet or film onto the pressure-sensitive layer.

[0116] If a protective layer is to be provided by attaching a protective layer-forming sheet or film, the desired protective layer-forming sheet or film should be prepared and attached to the pressure-sensitive layer by a known method (for example, by adhesive).

[0117] There are no particular restrictions on the thickness of the protective layer; it can be selected according to the purpose and other factors. The thickness of the protective layer is preferably 0.1 μm to 50 μm, and more preferably 0.5 μm to 10 μm.

[0118] -White layer- The pressure measuring material of this disclosure may further have a white layer between the substrate and the pressure-sensitive layer. The presence of a white layer enhances the contrast between the colored and uncolored areas, thereby improving visibility.

[0119] The white layer may be a coated layer formed between the substrate and the pressure-sensitive layer using a white layer-forming composition, or it may be a layer formed by attaching a white layer-forming sheet or film to the substrate prior to providing the pressure-sensitive layer.

[0120] The white layer can be provided as a layer containing, for example, a known white coloring agent (e.g., white pigment), a resin component, etc. Specifically, white pigments such as titanium dioxide, zinc oxide, and calcium carbonate are used as white colorants. It can be listed. The white layer is a layer that does not contain the above-mentioned microcapsules and / or electron-accepting compounds.

[0121] If a white layer is to be formed by applying a white layer-forming composition, for example, the white layer-forming composition can be prepared, applied (e.g., coated) onto the substrate, and dried. In this case, the same method as that used for the pressure-sensitive layer described above can be used for application.

[0122] If a white layer is to be provided by attaching a white layer-forming sheet or film, the desired white layer-forming sheet or film should be prepared and attached to the substrate by a known method (for example, by adhesive).

[0123] -Easy adhesion layer- The easy-adhesion layer is preferably provided to improve the adhesion between the substrate and the pressure-sensitive layer.

[0124] When an easy-adhesion layer is present, the pressure measuring material of this disclosure preferably comprises, at least, a substrate, an easy-adhesion layer, and a pressure-sensitive layer, in this order. When an easy-adhesion layer and a white layer are present, it is preferable that the substrate, the easy-adhesion layer, the white layer, and the pressure-sensitive layer are arranged in this order. The easy-adhesion layer is a layer that does not contain the above-mentioned microcapsules and / or electron-accepting compounds. From the viewpoint of improving the adhesion between the substrate and the polymer matrix of the pressure-sensitive layer, it is preferable that the easy-adhesion layer contains a resin. Examples of resins include acrylate resins, urethane resins, styrene resins, and vinyl resins.

[0125] The easy-adhesion layer may be a layer containing a urethane polymer, blocked isocyanate, or the like.

[0126] An easy-to-adhere layer can be formed by laminating a substrate with an easily-adhere sheet or film, applying an easy-to-adhere layer-forming composition onto the substrate, or by other means.

[0127] There are no particular restrictions on the thickness of the easy-adhesion layer; it can be selected according to the purpose and other factors. The thickness of the easy-adhesion layer is preferably 0.005 μm to 1.0 μm, more preferably 0.005 μm to 0.5 μm, even more preferably 0.005 μm to 0.2 μm, and most preferably 0.01 μm to 0.1 μm.

[0128] (Thickness of the material used for pressure measurement) The thickness of the pressure measuring material of this disclosure is not particularly limited, but is preferably 10 μm to 800 μm, and more preferably 10 μm to 500 μm.

[0129] -Thickness T- The thickness T of the layer, obtained by subtracting the thickness of the substrate from the thickness of the pressure measuring material, is preferably 1 μm to 250 μm, more preferably 3 μm to 200 μm, and even more preferably 5 μm to 150 μm. The thickness T can be measured in the same way as the thickness t of the pressure-sensitive layer described above. Specifically, the thickness of the pressure measurement material and the thickness of the base material are measured at 10 randomly selected locations, and the value can be calculated by taking the arithmetic mean of the difference between the thickness of the pressure measurement material and the thickness of the base material.

[0130] (Arithmetic mean roughness Ra of pressure-measuring material) The arithmetic mean roughness Ra of the pressure measurement material is preferably 10.0 μm or less. The preferred ranges for the arithmetic mean roughness Ra when the pressure-sensitive layer is in the first and second embodiments are as previously described. The arithmetic mean roughness Ra mentioned above corresponds to the arithmetic mean roughness Ra of the surface opposite to the substrate side. The method for measuring the arithmetic mean roughness Ra is as previously described.

[0131] (Ratio of thickness T to inner diameter p of microcapsule) The ratio T / p of the thickness T to the inner diameter p of the microcapsule in the pressure measuring material is preferably 1.2 or greater, and more preferably 1.3 or greater. When T / p is 1.2 or greater, the gradation in the high-pressure region of 100 MPa or higher is superior. A ratio of 1.2 to 5 is more preferable. In the case of having a pressure-sensitive layer according to the first embodiment, the ratio T / p1 of the thickness T to the inner diameter p1 of the microcapsule is preferably 5 or less, more preferably 1.2 to 5, and even more preferably 1.2 to 3. In the case of having a pressure-sensitive layer according to the second embodiment, the ratio T / p2 of the thickness T to the inner diameter p2 of the microcapsule is preferably 5 or less, more preferably 1.2 to 5, and even more preferably 1.3 to 5.

[0132] <Matters concerning pressure measurement> Pressure measurement using the pressure measuring material of this disclosure can be performed by placing the pressure measuring material at a site where pressure or pressure distribution is to be measured, and then applying pressure to the pressure measuring material in this state. The pressure may be point pressure, line pressure, or surface pressure.

[0133] In the pressure measuring material of this disclosure, it is preferable that the concentration difference (ΔD) obtained by subtracting the concentration after applying pressure at 2000 MPa from the concentration after applying pressure at 1000 MPa to develop color is 0.6 or more. By having a ΔD greater than 0.6, the pressure measuring material of this disclosure can be made into a pressure measuring material with superior reproduction of visible or readable density and density gradation when pressure is applied and color is produced.

[0134] In the pressure measuring material having the pressure-sensitive layer according to the first embodiment described above, when color is developed, the difference in concentration (ΔD1) obtained by subtracting the concentration after color development by applying pressure at 1000 MPa from the concentration after color development by applying pressure at 2000 MPa is preferably 0.1 or more, and more preferably 0.4 or more. By having ΔD1 of 0.1 or greater (preferably 0.4 or greater), the pressure measuring material of this embodiment can be made into a pressure measuring material with superior reproduction of density and density gradation that is visible or readable when a pressure of 500 MPa or more is applied and color is produced.

[0135] In the pressure measuring material having the pressure-sensitive layer according to the second embodiment described above, when color is developed, the difference in concentration (ΔD2) obtained by subtracting the concentration after color development by applying pressure at 100 MPa from the concentration after color development by applying pressure at 500 MPa is preferably 0.1 or more, and more preferably 0.4 or more. By having ΔD2 of 0.1 or greater (preferably 0.4 or greater), the pressure measuring material of this embodiment can be made into a pressure measuring material with superior reproduction of visible or readable density and density gradation when a pressure of 100 MPa to 500 MPa is applied and color is produced.

[0136] The color density is a value measured using a reflectance densitometer (for example, the RD-19I manufactured by Greda Macbeth).

[0137] Furthermore, the pressure measuring material of this disclosure is preferably 100 MPa to 10000 MPa (more Preferably, when a pressure of 100 MPa to 3000 MPa is applied, the color intensity increases with increasing pressure, i.e., it exhibits color gradation. In the pressure measuring material of this disclosure, a preferred color gradation is a property in which the color density increases linearly with increasing pressure (i.e., pressure and color density are proportional).

[0138] The pressure measuring material of this disclosure can be configured to measure a range of pressure, including the range described above, depending on the measurement application. For example, one embodiment of the pressure measuring material of this disclosure can be used for measuring pressures in a range above 1000 MPa (e.g., 1000 MPa to 3000 MPa, preferably 1000 MPa to 2000 MPa). Another embodiment of the pressure measuring material of this disclosure can be used for measuring pressures in a range below 1000 MPa (e.g., 100 MPa to 500 MPa).

[0139] The applications of the pressure measuring materials disclosed herein include, but are not limited to, the following examples of use in various fields. Note that the following examples may overlap. Examples of applications include the manufacture of automobiles and other vehicles or aircraft (for example, confirmation of pressure distribution in the molding of various components, bodies, etc., or in the assembly of components), construction (for example, confirmation of pressure distribution in the assembly of building materials), the manufacture of electronic products (for example, confirmation of pressure distribution in curved surface processing (lamination of curved displays, etc.)), transportation (for example, confirmation of impact force applied to cargo during transportation), metalworking (for example, confirmation of pressure per mold in the manufacture of various metal products), molding of resin products (for example, confirmation of pressure per mold during the molding of resin products), molding of pharmaceuticals (for example, confirmation of pressure distribution in tablet compression), furniture (for example, confirmation of pressure distribution on furniture surfaces (chairs, sofa seats, etc.)), stationery (for example, confirmation of grip force applied to writing instruments, etc.), and sporting goods (for example, confirmation of impact force applied to articles made of elastic materials (balls, etc.)). [Examples]

[0140] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples unless it exceeds the spirit of the invention. Unless otherwise specified, "%" and "parts" are based on mass.

[0141] (Example 1) <Preparation of microcapsule solution (A) containing electron-donating dye precursor> Solution A was obtained by dissolving 10 parts of the following compound (A), which is an electron-donating dye precursor, in 53 parts of linear alkylbenzene (JX Energy Corporation, Grade Alkene L, boiling point 130°C or higher). Next, 0.4 parts of N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine (ADEKA Corporation, ADEKA Polyether EDP-300), dissolved in 14 parts of synthetic isoparaffin (Idemitsu Kosan Co., Ltd., IP Solvent 1620, boiling point 130°C or higher) and 1.2 parts of ethyl acetate, were added to the stirred solution A to obtain solution B. Furthermore, 18 parts of trimethylolpropane adduct of tolylene diisocyanate dissolved in 3 parts of ethyl acetate (DIC Corporation, Barnock D-750) were added to the stirred solution B to obtain solution C. Then, solution C was added to a solution prepared by dissolving 8 parts of polyvinyl alcohol (PVA-205, Kuraray Co., Ltd., number average molecular weight 25,000, dispersant) in 110 parts of water, and the mixture was emulsified and dispersed. 340 parts of water were added to the emulsion after dispersion, and the mixture was heated to 70°C while stirring. After stirring for 1 hour, the mixture was cooled. After cooling, water was added to the liquid to adjust the concentration, and an electron-donating dye precursor-encapsulated microcapsule solution (A) with a solid content of 25% was obtained.

[0142] [ka]

[0143] The volume-based median diameter (D50) of the obtained microcapsules was 11 μm. The volume-based median diameter was measured using a Microtrac MT3300EXII (manufactured by Nikkiso Co., Ltd.).

[0144] <Preparation of pressure measurement sheet (A)> To 20 parts of the microcapsule solution (A) obtained above, 11 parts of a 40% dispersion of zinc 3,5-bis(α-methylbenzyl)salicylate, an electron-accepting compound, as a color developer, and 20 parts of a 20% aqueous solution of polyvinyl alcohol (PVA-105, Kuraray Co., Ltd., number average molecular weight 22,000) as a specific polymer compound for forming a polymer matrix were mixed to obtain a pressure-sensitive layer-forming composition (A). The obtained pressure-sensitive layer-forming composition (A) was applied to a 75 μm thick PET substrate (A4300: manufactured by Toyobo) using a bar coater to a dry film thickness of 15 μm, and dried at 80°C to obtain a pressure measuring sheet (A) (pressure measuring material) having a pressure-sensitive layer on the PET substrate.

[0145] The thickness (film thickness) of the pressure-sensitive layer was determined by using a desktop microscope "Miniscope TM3030Plus" (manufactured by Hitachi High-Technologies Corporation) to observe the cross-section of the pressure-measuring sheet (A) at 10 arbitrary locations by vertically cutting the sheet. The thickness of the pressure-measuring sheet (A) and the thickness of the PET substrate were measured, and the difference between the thickness of the pressure-measuring sheet (A) and the thickness of the PET substrate was calculated and the arithmetic mean was taken to determine the thickness (film thickness) of the pressure-sensitive layer. It was confirmed that the thickness (film thickness) of the pressure-sensitive layer was 15 μm. The ratio (t / d) of the thickness t of the pressure-sensitive layer to the particle size d of the microcapsule is 1.36.

[0146] The Martens hardness of polyvinyl alcohol (PVA-105, Kuraray Co., Ltd.), which forms the polymer matrix, was measured using a Fischer Instruments HM2000 microhardness tester. The measurement was performed using a diamond indenter (Belkovich indenter) in a laboratory environment of 23°C and 50% RH. First, a load from 0 mN to the maximum test load was applied for 10 seconds, then the load was held at the maximum test load for 5 seconds, and finally, the load was removed from the maximum test load to 0 mN for 10 seconds. The Martens hardness (N / mm²) was calculated by dividing the maximum test load by the indenter surface area at the maximum indentation depth. 2 ) was sought.

[0147] For a 5 μm thick polymer matrix (PVA105) film deposited on a glass substrate, the Martens hardness measured at the maximum test load resulting in a maximum indentation depth of 0.5 μm was 165 N / mm². 2 That is the case.

[0148] <Color development evaluation A> The pressure measurement sheet (A) obtained in Example 1 above was cut into four samples measuring 9 cm to 11 cm. Each sample was pressurized using one of the pressures shown in the pressure column of Table 1 below, and it was confirmed that the sample changed color upon pressurization. Pressurization was performed using a press machine (DSF-C1 -A (manufactured by Aida Engineering Co., Ltd.) The color intensity of the colored samples was measured using a spectrophotometer (X-Rite 504, manufactured by X-Rite Corporation). The measurement results are shown in the color intensity column of Table 1. Furthermore, Figure 1 shows a graph illustrating the relationship between pressure and color intensity.

[0149] [Table 1]

[0150] As shown in Table 1 and Figure 1, the pressure measurement sheet of Example 1 was confirmed to produce excellent color gradation in the high-pressure range exceeding 1000 MPa.

[0151] (Example 2) The pressure measuring sheet (pressure measuring material) of Example 2 was prepared in the same manner as in Example 1, except that a portion of the PVA-105 in the preparation of the pressure measuring sheet (A) was replaced with a polyol polyalkylene alkyl ether surfactant (Neugen LP-90, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).

[0152] (Examples 3-8) Pressure measurement sheets for Examples 3 to 8 were prepared in the same manner as in Example 2, except that the composition of each material was changed as shown in Table 2. The microcapsule solution (B) was prepared as follows.

[0153] <Preparation of microcapsule solution (B) containing electron-donating dye precursor> Solution A2 was obtained by dissolving 70 parts of Hyzol SAS-296 (an oil component (solvent) manufactured by Nippon Oil Corporation; a mixture of 1-phenyl-1-xylylethane and 1-phenyl-1-ethylphenylethane) in 6 parts of 3',6'-bis(diethylamino)-2-(4-nitrophenyl)spiro[isoindole-1,9'-xanthene]-3-one (manufactured by Hodogaya Chemical Co., Ltd., Pink-DCF) and 8 parts of 6'-(diethylamino)-1',3'-dimethylfluorane (manufactured by Hodogaya Chemical Co., Ltd., Orange-DCF) as electron-donating dye precursors. Next, 19 parts of synthetic isoparaffin (Idemitsu Kosan Co., Ltd., IP Solvent 1620) and 0.7 parts of N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine (Adeka Corporation, Adeka Polyether EDP-300) dissolved in 2.5 parts of methyl ethyl ketone were added to the stirred solution A2 to obtain solution B2. Furthermore, 77 parts of trimethylolpropane adduct of tolylene diisocyanate dissolved in 6 parts of ethyl acetate (DIC Corporation, Barnock D-750, containing 25% ethyl acetate) were added to the stirred solution B to obtain solution C. Then, solution C2 was added to a solution prepared by dissolving 10 parts of polyvinyl alcohol (KL-318, Kuraray Co., Ltd.) in 140 parts of water and emulsified / dispersed. 200 parts of water were added to the emulsion after dispersion, and the mixture was heated to 70°C while stirring, stirred for 1 hour, and then cooled. Water was added to adjust the concentration, and a solution of electron-donating dye precursor encapsulated in microcapsules (B) with a solid content concentration of 20% by mass was prepared. The median diameter of the microcapsules was 8 μm.

[0154] (Comparative Example 1) According to Example 1 of Japanese Patent Application Publication No. 2009-19949, an electron-donating colorless dye sheet and a color developer are provided. A two-sheet type pressure measuring sheet was fabricated.

[0155] 〔evaluation〕 The "void volume measurement" was performed on the pressure-sensitive layer of each pressure measuring sheet in Examples 1 to 8. Furthermore, the following evaluations, "Density Gradation Evaluation A" and "Color Development Evaluation B," were performed on each pressure measurement sheet in Examples 2-8 and Comparative Example 1.

[0156] [Measurement of void volume] The pressure measuring sheets (PET film with a pressure-sensitive layer formed on it) of Examples 1 to 8 were cut into 10cm x 10cm pieces, and their mass (m) was measured. l The mass (m²) was measured. Next, diethylene glycol was placed on the surface of the side with the pressure-sensitive layer and allowed to penetrate. After wiping off the diethylene glycol remaining on the surface, the mass (m²) was measured. Then, X = m² - m1 was calculated, and the amount of void was determined from the following formula. The density of diethylene glycol is 1.118. Void volume (m l / m²) = 100 × X ÷ 1.118

[0157] The void volume of each pressure measuring sheet obtained in Examples 1 to 8 was 1 mL / m². 2 The following Ta.

[0158] [Density gradation evaluation A (1000MPa~2000MPa)] For the pressure measurement sheets of Examples 1 to 8 and Comparative Example 1, the color density at 1000 MPa and the color density at 2000 MPa were measured. The difference ΔD1, obtained by subtracting the color density at 1000 MPa from the color density at 2000 MPa, was calculated and evaluated according to the evaluation criteria below. The pressurization method and measuring device were the same as those used for color development evaluation A described above. Furthermore, both "A" and "B" are within the acceptable range for practical use, with "A" being the best. The results are shown in Table 2. <Evaluation Criteria> "A": ΔD1 is 0.4 or greater. "B": ΔD1 is between 0.1 and less than 0.4. "C": ΔD1 is less than 0.1.

[0159] [Color development rating B] Each pressure measurement sheet from Examples 1-8 and Comparative Example 1 was evaluated according to the following evaluation criteria based on the color density measurement results at 1000 MPa obtained in the above density gradation evaluation A. The results are shown in Table 2. <Evaluation Criteria> "A": The color intensity is 0.5 or higher. "B": The color intensity is less than 0.5.

[0160] [Table 2]

[0161] In Table 2, T represents the layer thickness obtained by subtracting the substrate thickness from the thickness of the pressure measurement material, T / p1 represents the ratio of the thickness T to the inner diameter p1 of the microcapsule, T / d1 represents the ratio of the thickness T to the particle diameter d1 (median diameter) of the microcapsule, and Ra represents the arithmetic mean roughness at the outermost surface (pressure-sensitive layer surface) opposite the substrate. All of these values ​​were obtained by the method described above. In Table 2, "-" indicates that the corresponding ingredient is not contained or that the corresponding item has not been measured.

[0162] (Example 9) -Preparation of the color-developing layer- 100 parts of activated clay, Silton F-242 (Mizusawa Chemical Industries, Ltd.), an electron-accepting compound; 100 parts of amorphous silica (Mizusawa Chemical Industries, Ltd., Mizukasil P-78A, inorganic particles that are not electron-accepting compounds); 10 parts of a 10% by mass sodium hydroxide aqueous solution; 750 parts of water; and 1 part of sodium hexametaphosphate (Nippon Chemical Industrial Co., Ltd.) were added and dispersed in a homogenizer. Further, a modified acrylic acid ester copolymer (Nippon Zeon Corporation, Nipol) was added. A color-developing layer-forming composition containing an electron-accepting compound was prepared by mixing 140 parts of LX814 (solids content 47%, specific polymer compound), 28 parts of anionic olefin resin (Arakawa Chemical Industries, Polymaron 482, solids content 25%, specific polymer compound), 5 parts of a 15% aqueous solution of side-chain alkylbenzene sulfonate amine salt (Daiichi Kogyo Seiyaku, Neogen T), 35 parts of a 1% aqueous solution of polyoxyethylene polyoxypropylene lauryl ether (Daiichi Kogyo Seiyaku, Neogen LP-70), and 35 parts of a 1% aqueous solution of sodium-bis(3,3,4,4,5,5,6,6,6-nonafluorohexyl)-2-sulfinatooxysuccinate (Fujifilm, W-AHE).

[0163] -Preparation of color-forming composition- To 70 parts of the 20% solution (B) of electron-donating dye precursor-encapsulated microcapsules obtained above, 0.8 parts of anionic olefin resin (Arakawa Chemical Industries, Polymaron 482, solids content 25%, specific polymer compound), 3.1 parts of polymer (Rohm & Haas, Orotan 165A, solids content 21%, specific polymer compound), 0.5 parts of a 15% aqueous solution of side-chain alkylbenzene sulfonate amine salt (Daiichi Kogyo Seiyaku, Neogen T), 5 parts of a 1% aqueous solution of polyoxyethylene polyoxypropylene lauryl ether (Daiichi Kogyo Seiyaku, Neogen LP-70), and 5 parts of a 1% aqueous solution of sodium-bis(3,3,4,4,5,5,6,6,6-nonafluorohexyl)-2-sulfinatooxysuccinate (Fujifilm, W-AHE) were mixed to prepare a color-forming layer composition.

[0164] -Preparation of materials for pressure measurement- The resulting color-developing layer-forming composition was applied to a 75 μm thick polyethylene terephthalate (PET) film (A4300: manufactured by Toyobo) at a solid content application rate of 20 g / m². 2 The material was then applied using a bar coater to form a color development layer. Next, the color development layer-forming composition was applied on top of the applied color development layer, with a solid content application amount of 3.5 g / m². 2 The colorant layer was formed by applying it using a bar coater. In this way, a monosheet type pressure measuring material was fabricated having a pressure-sensitive layer in which two layers, a color developer layer and a colorant layer, were sequentially laminated on a PET film base material.

[0165] (Examples 10-15) A pressure measurement sheet was prepared in the same manner as in Example 9, except that the composition of each material was changed as shown in Table 3.

[0166] (Comparative Example 2) The same pressure measuring sheet used in Comparative Example 1 described above was used.

[0167] 〔evaluation〕 For each of the pressure measuring sheets in Examples 9 to 15, the "void volume measurement" was performed. Furthermore, for each pressure measurement sheet in Examples 9-15 and Comparative Example 2, the following "concentration level" is described below. We performed evaluations for "Tone Evaluation B" and "Color Development Evaluation C".

[0168] [Measurement of void volume] The void size of each pressure measuring sheet in Examples 9 to 15 was measured in the same manner as the pressure measuring sheets in Examples 1 to 8 above. The void volume of each pressure measuring sheet obtained in Examples 9-15 was 5 mL / m². 2 ~20m L / m 2 It was within the range.

[0169] [Density gradation evaluation B (100MPa~500MPa)] For the pressure measurement sheets of Examples 9-15 and Comparative Example 2, the color intensity at 100 MPa and the color intensity at 500 MPa were measured. The difference ΔD2 obtained by subtracting the color intensity at 100 MPa from the color intensity at 500 MPa was calculated and evaluated according to the evaluation criteria below. The pressurization method and measuring device were the same as those used for color development evaluation A described above. Furthermore, both "A" and "B" are within the acceptable range for practical use, with "A" being the best. The results are shown in Table 3.

[0170] <Evaluation Criteria> "A": ΔD2 is 0.4 or greater. "B": ΔD2 is between 0.1 and less than 0.4. "C": ΔD2 is less than 0.1.

[0171] [Color development rating C] For each pressure measuring sheet in Examples 9-15 and Comparative Example 2, the color intensity at 300 MPa was measured. The pressurization method and measuring apparatus were the same as those used in color evaluation A above. Based on the obtained measurement results, the evaluation was performed according to the following evaluation criteria. The results are shown in Table 3.

[0172] <Evaluation Criteria> "A": The color intensity is 0.5 or higher. "B": The color intensity is less than 0.5.

[0173] [Table 3]

[0174] In Table 3, T represents the layer thickness obtained by subtracting the substrate thickness from the thickness of the pressure measurement material, T / p2 represents the ratio of the thickness T to the inner diameter p2 of the microcapsule, T / d2 represents the ratio of the thickness T to the particle diameter d2 (average particle size) of the microcapsule, and Ra represents the arithmetic mean roughness at the outermost surface (pressure-sensitive layer surface) opposite to the substrate. All of these values ​​were obtained by the method described above. In Table 3, "-" indicates that the corresponding ingredient is not contained or that the corresponding item was not measured.

[0175] (Explanation of symbols) 10, 20 Pressure measuring materials 12, 22 Base material 14, 24 pressure-sensitive layer 24a Color-developing layer 24b Developing layer 15, 25 Electron-accepting compounds 16, 26 Polymer matrix 18, 28 microcapsules 18a, 28a Capsule wall 18b, 28b Microcapsule encapsulated material (core material)

[0176] The disclosure of Japanese Patent Application No. 2019-006244, filed on 17 January 2019, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted to be incorporated by reference.

Claims

1. A pressure measuring material having a base material and a pressure-sensitive layer, The pressure-sensitive layer contains a polymer matrix containing a polymer compound with a molecular weight of 1000 or more, microcapsules containing an electron-donating dye precursor and a solvent, and an electron-accepting compound. The pressure-sensitive layer has a color-developing layer having the electron-accepting compound and the polymer matrix, and a color-developing layer having the microcapsules, and the substrate, the color-developing layer and the color-developing layer are arranged in this order, and the thickness of the color-developing layer is half or less the thickness of the color-developing layer. The polymer compound with a molecular weight of 1000 or more includes polyvinyl alcohol, vinyl chloride polymer, vinyl acetate polymer, acrylic polymer, styrene-butadiene rubber (SBR), or copolymers thereof. The color-developing layer has a recess, and a portion of the microcapsule is embedded in the recess. The arithmetic mean roughness Ra of the outermost surface of the color-developing layer opposite to the substrate side is 1.5 μm or more and 5.0 μm or less. Particle size d of the microcapsule ２ The size is 5 μm to 11 μm. The capsule wall of the aforementioned microcapsule is substantially composed of resin, The difference in concentration (ΔD2) obtained by subtracting the concentration obtained by applying pressure at 100 MPa from the concentration obtained by applying pressure at 500 MPa is 0.1 or greater. Materials for pressure measurement.

2. The pressure measuring material according to claim 1, wherein the arithmetic mean roughness Ra of the outermost surface of the color-developing layer opposite to the substrate side is 2.0 μm or more and 5.0 μm or less.

3. The pressure measuring material according to claim 1 or claim 2, wherein the electron-accepting compound comprises acid clay or activated clay.

4. The void volume is 5 mL / m². ２ ~20 mL / m² ２ A pressure measuring material according to any one of claims 1 to 3.

5. The pressure measuring material according to any one of claims 1 to 4, wherein the ratio T / p of the thickness of the layer obtained by subtracting the thickness of the substrate from the thickness of the pressure measuring material to the inner diameter p of the microcapsule is 1.2 or more.

6. The pressure measuring material according to claim 5, wherein the ratio T / p of the thickness of the layer obtained by subtracting the thickness of the substrate from the thickness of the pressure measuring material to the inner diameter p of the microcapsule is 1.2 to 5.

0.

7. A pressure measuring material according to any one of claims 1 to 6, wherein the material contains 10% by mass or more of the polymer compound with a molecular weight of 1000 or more, relative to the total mass of the pressure-sensitive layer.

8. The pressure measuring material according to any one of claims 1 to 7, wherein the base material is a polyethylene terephthalate base material or a polyethylene naphthalate base material.

9. A pressure measuring material according to any one of claims 1 to 8, comprising an easy-adhesion layer between the substrate and the pressure-sensitive layer.

10. The pressure measuring material according to any one of claims 1 to 9, wherein the wall material of the microcapsule comprises at least one selected from polyurethane urea and polyurethane.

11. A pressure measuring material according to any one of claims 1 to 10, which is in the form of a sheet.

12. A pressure measuring material according to any one of claims 1 to 11, used for measuring pressures of 100 MPa to 500 MPa.

13. A step to obtain a color-forming composition comprising a microcapsule containing an electron-donating dye precursor and a solvent, and a solvent. A step to obtain a color-developing layer-forming composition containing an electron-accepting compound and a polymer compound with a molecular weight of 1000 or more. A step of forming a color-developing layer by placing the color-developing layer-forming composition on a substrate, and The process includes placing the color-developing layer-forming composition on the color-developing layer to form a color-developing layer, The polymer compound with a molecular weight of 1000 or more includes polyvinyl alcohol, vinyl chloride polymer, vinyl acetate polymer, acrylic polymer, styrene-butadiene rubber (SBR), or copolymers thereof. The arithmetic mean roughness Ra of the outermost surface of the color-developing layer opposite to the substrate side is 1.5 μm or more and 5.0 μm or less. The color-developing layer has a recess, and a portion of the microcapsule is embedded in the recess. Particle size d of the microcapsule ２ The size is 5 μm to 11 μm. The capsule wall of the aforementioned microcapsule is substantially composed of resin, To obtain a pressure measuring material in which the concentration difference (ΔD2), obtained by subtracting the concentration after applying pressure at 100 MPa from the concentration after applying pressure at 500 MPa to produce color, is 0.1 or greater. A method for manufacturing a pressure measuring material according to claim 1.

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