MATERIAL FOR PRESSURE MEASUREMENT

Abstract

A material for pressure measurement includes a first material having a color developer layer containing a microcapsule A encapsulating an electron-donating dye precursor disposed on a first base material and a second material having a developer layer containing an electron-accepting compound disposed on a second base material, the first base material contains an inorganic filler, and a proportion of the inorganic filler having a particle diameter of 0.1 m or more in all of the inorganic filler contained in the first base material is 5% by volume or less, and an arithmetic average roughness Ra of a surface of the developer layer satisfies 0.1 mRa1.1 m.

Claims

1. A material for pressure measurement comprising: a first material having a color developer layer containing a microcapsule A encapsulating an electron-donating dye precursor disposed on a first base material; and a second material having a developer layer containing an electron-accepting compound disposed on a second base material, wherein the first base material contains an inorganic filler, and a proportion of the inorganic filler having a particle diameter of 0.1 m or more in the inorganic filler contained in the first base material is 5% by volume or less, and an arithmetic average roughness Ra of a surface of the developer layer satisfies 0.1 mRa1.1

2. The material for pressure measurement according to claim 1, wherein the color developer layer is adjacent to the first base material.

3. The material for pressure measurement according to claim 1, wherein a coefficient of variation of a number-based particle size distribution of particles having a particle diameter of 2 m or larger contained in the color developer layer is 50% to 100%.

4. The material for pressure measurement according to claim 3, wherein the color developer layer is adjacent to the first base material.

5. The material for pressure measurement according to claim 1, wherein at least one of the color developer layer or the developer layer contains a microcapsule B not encapsulating the electron-donating dye precursor.

6. The material for pressure measurement according to claim 1, wherein the color developer layer contains a microcapsule B not encapsulating the electron-donating dye precursor.

7. The material for pressure measurement according to claim 4, wherein the color developer layer contains a microcapsule B not encapsulating the electron-donating dye precursor.

8. The material for pressure measurement according to claim 5, wherein a material of a capsule wall of the microcapsule B is a melamine formaldehyde resin.

9. The material for pressure measurement according to claim 1, wherein a material of a capsule wall of the microcapsule A is a melamine formaldehyde resin.

10. The material for pressure measurement according to claim 7, wherein a material of a capsule wall of each of the microcapsule A and the microcapsule B is a melamine formaldehyde resin.

11. The material for pressure measurement according to claim 1, wherein a color optical density difference D before and after pressurization at 0.03 MPa is 0.08 or more.

12. The material for pressure measurement according to claim 1, wherein the proportion of the inorganic filler having a particle diameter of 0.1 m or more in all of the inorganic filler contained in the first base material is 2% by volume or less.

13. The material for pressure measurement according to claim 12, wherein a color optical density difference D before and after pressurization at 0.03 MPa is 0.08 or more.

14. The material for pressure measurement according to claim 1, wherein the electron-accepting compound is a clay substance that is at least one selected from the group consisting of acid clay, activated clay, attapulgite, zeolite, bentonite and kaolin.

15. The material for pressure measurement according to claim 10, wherein the electron-accepting compound is a clay substance that is at least one selected from the group consisting of acid clay, activated clay, attapulgite, zeolite, bentonite and kaolin.

16. The material for pressure measurement according to claim 13, wherein the electron-accepting compound is a clay substance that is at least one selected from the group consisting of acid clay, activated clay, attapulgite, zeolite, bentonite and kaolin.

17. The material for pressure measurement according to claim 1, wherein a total content of the inorganic filler contained in the first base material is 0.005% by mass to 5% by mass of a total amount of the first base material.

18. The material for pressure measurement according to claim 10, wherein a total content of the inorganic filler contained in the first base material is 0.005% by mass to 5% by mass of a total amount of the first base material.

19. The material for pressure measurement according to claim 16, wherein a total content of the inorganic filler contained in the first base material is 0.005% by mass to 5% by mass of a total amount of the first base material.

Description

EXAMPLES

[0192] Hereinafter, the present invention will be specifically described using examples, but the present invention is not limited to the following examples within the scope of the gist of the present invention. In the following description, unless particularly otherwise described, % and parts are mass-based.

[0193] In the following description, the densities of color development regions were measured using a reflection densitometer RD-19I (manufactured by GretagMacbeth LLC).

Example 1

<Preparation of Microcapsule A1-Containing Liquid>

[0194] The following compound (A) (20 parts) that is an electron-donating dye precursor was dissolved in linear alkyl benzene (JXTG Nippon Oil & Energy Corporation, GRADE ALKENE L) (57 parts), thereby obtaining a solution A.

[0195] The obtained solution A was stirred, and synthetic isoparaffin (Idemitsu Kosan Co., Ltd., IP SOLVENT 1620) (15 parts) and N,N,N,N-tetrakis(2-hydroxypropyl)ethylene diamine (ADEKA Corporation, ADEKA POLYETHER EDP-300) dissolved in ethyl acetate (1.2 parts) (0.2 parts) were added thereto, thereby obtaining a solution B.

[0196] The obtained solution B was stirred, and a trimethylolpropane adduct of torylene diisocyanate (DIC Corporation, BURNOCK D-750) dissolved in ethyl acetate (3 parts) (1.4 parts) was added thereto, thereby obtaining a solution C.

[0197] Next, the solution C was added to a solution obtained by dissolving polyvinyl alcohol (PVA-205, Kuraray Co., Ltd.) (10 parts) in water (140 parts), emulsified, and dispersed. Water (340 parts) was added to the obtained emulsified liquid, heated up to 70 C. under stirring, stirred for one hour, and then cooled. Water was further added to the cooled liquid, thereby adjusting the concentration of the solid content.

[0198] A microcapsule A1-containing liquid containing a microcapsule A1 as the microcapsule A encapsulating an electron-donating dye precursor (concentration of solid content: 19.6%) was obtained in the above-described manner.

##STR00001##

[0199] For the microcapsule A1 that was contained in the microcapsule A1-containing liquid, the volume-based median size (hereinafter, also referred to as D50A) and the number-average wall thickness (hereinafter, also referred to as wall thickness) were values shown in Table 1.

[0200] In addition, a material of a capsule wall (hereinafter, also referred to as wall material) of the microcapsule A1 was, as shown in Table 1, a urethane-urea resin (hereinafter, also referred as PUR).

[0201] The D50A and wall thickness of the microcapsule A1 were computed as described below.

[0202] First, the microcapsule A1-containing liquid was applied and dried on a 75 m-thick polyethylene terephthalate (PET) sheet, thereby obtaining an applied film.

[0203] D50A of the microcapsule A1 was computed on the basis of a result obtained by capturing a surface of the applied film using an optical microscope at a magnification of 150 times and measuring the equivalent circle diameters of all of the microcapsule A1 present in a 2 cm2 cm range.

[0204] The wall thickness (that is, the number-average wall thickness) of the microcapsule A1 was computed by forming a cross section of the applied film, selecting five microcapsule A1 from the formed cross section, obtaining the thicknesses (m) of individual capsule walls using a scanning electron microscope (SEM), and simply averaging the obtained values.

<Preparation of Coating Fluid for Forming Color Developer Layer>

[0205] The microcapsule A1-containing liquid (18 parts), water (63 parts), colloidal silica (Nissan Chemical Corporation, SNOWTEX 30, content of solid content: 30%) (1.8 parts), a 10% aqueous solution of carboxymethylcellulose sodium (DKS Co., Ltd., CELLOGEN 5A) (1.8 parts), a 1% aqueous solution of carboxymethylcellulose sodium (DKS Co., Ltd., CELLOGEN EP) (30 parts), a 15% aqueous solution of sodium alkylbenzene sulfonate (DKS Co., Ltd., NEOGEN T) (0.3 parts), and a 1% aqueous solution of NOIGEN LP70 (DKS Co., Ltd.) (0.8 parts) were mixed together, thereby obtaining a coating fluid for forming a color developer layer.

<Production of First Base Material>

[0206] Polyester (polyethylene terephthalate in detail) and an inorganic filler (amorphous silica particles, volume-average particle diameter: 0.02 m) were melted and kneaded, thereby producing pellets containing the inorganic filler. The amount of the inorganic filler used was set to an amount at which the total content of inorganic filler with respect to all of the finally obtained first base material reached 2% by mass.

[0207] The obtained pellets were melted, extruded, and then biaxially stretched, thereby obtaining a 75 m-thick first base material.

[0208] In the obtained first base material, the proportion of the inorganic filler having a particle diameter of 0.1 pm or more in all of the inorganic filler contained was 0% by volume.

<Production of First Material>

[0209] The coating fluid forming a color developer layer was stirred for two hours, then, applied onto a first base material so that the mass after drying reached 2.8 g/m.sup.2, and dried, thereby forming a color developer layer.

[0210] A first material having the color developer layer containing the microcapsule A1 disposed on the first base material was obtained in the above-described manner.

<Preparation of Coating Fluid for Forming Developer Layer>

[0211] 3,5-Di--zinc methylbenzylsalicylate (hereinafter, also simply referred to as zinc salicylate) that is an electron-accepting compound (10 parts), calcium carbonate (100 parts), sodium hexametaphosphate (1 part), and water (200 parts) were dispersed using a sand grinder so that the average particle diameter of all particles reached 2 m, thereby preparing a dispersion liquid. Next, a polyvinyl alcohol (PVA-203, Kuraray Co., Ltd.) 10% aqueous solution (100 parts), styrene-butadiene latex (10 parts in terms of the solid content), and water (450 parts) were added to the prepared dispersion liquid, thereby obtaining a coating fluid for forming a developer layer containing the electron-accepting compound.

<Production of Second Material>

[0212] The coating fluid for forming a developer layer was applied onto a 75 m-thick polyethylene terephthalate (PET) sheet (second base material) so that the dried film thickness reached 12 m and dried, thereby forming a developer layer.

[0213] A second material having the developer layer containing the electron-accepting compound (zinc salicylate) disposed on the second base material was obtained in the above-described manner.

[0214] A two-sheet type material for pressure measurement including the first material and the second material was obtained in the above-described manner.

<Measurement and Evaluation>

[0215] The following measurement and evaluation were carried out using the obtained material for pressure measurement.

[0216] The results are shown in Table 1.

(CV Value of Particle Size Distribution)

[0217] The coefficient of variation of the number-based particle size distribution of particles having a particle diameter of 2 m or more contained in the color developer layer in the first material (in the present embodiment, referred to as the CV value of the particle size distribution) was measured using the above-described method.

(Arithmetic Average Roughness Ra of Surface of Developer Layer)

[0218] The arithmetic average roughness Ra of the surface of the developer layer in the second material was measured using a scanning-type white interferometer using optical interferometry (in detail, NewView5020: Micro mode manufactured by Zygo Corporation).

(Color Optical Density Difference D Before and After Pressurization in Condition of 0.03 MPa)

[0219] The first material and the second material were respectively cut to a 5 cm5 cm size.

[0220] The cut first material and the cut second material were superimposed so that a surface of the color developer layer in the first material and a surface of the developer layer in the second material came into contact with each other.

[0221] The superimposed first material and second material were placed on a desk in a state of being sandwiched between two glass plates having a flat surface, and then a weight was placed on these two glass plates, thereby pressurizing the first material and the second material sandwiched between the two glass plates at a pressure of 0.03 MPa for 120 seconds.

[0222] After pressurization, the first material and the second material were peeled off from each other.

[0223] Next, the density after 20 minutes from the end of the pressurization (hereinafter, regarded as color optical density DA) in a color development region formed in the developer layer in the second material was measured.

[0224] Separately from the above-described density, the density of the developer layer in an unused second material (hereinafter, regarded as initial density DB) was measured.

[0225] The initial density DB was subtracted from the color optical density DA, and the obtained result was regarded as the color optical density difference D before and after pressurization at 0.03 MPa.

(Color Optical Density Uevenness in Condition of 0.05 MPa)

[0226] A color development region was formed in the developer layer in the second material in the same manner as in the measurement of the color optical density DA except for the fact that the pressure was changed from 0.03 MPa to 0.05 MPa. The pressure was changed by changing the weight of the weight.

[0227] The color development region formed in the developer layer in the second material was visually observed, and the color optical density unevenness in a condition of 0.05 MPa was evaluated according to the following evaluation standards.

[0228] In the following evaluation standards, the color optical density unevenness is further suppressed as the numerical values of evaluation ranks increases. The evaluation rank at which the color optical density unevenness is most suppressed is 5.

Evaluation Standards of Color Optical Density Unevenness in Condition of 0.05 MPa

[0229] 5: There was no color optical density unevenness.

[0230] 4: There was slight color optical density unevenness which was on a level of no practical problem.

[0231] 3: There was color optical density unevenness which was on a level of no practical problem.

[0232] 2: There was clear color optical density unevenness which might cause a practical difficulty.

[0233] 1: There was severe color optical density unevenness, which was practically unavailable.

(Color Development by Rubbing)

[0234] The first material and the second material were respectively cut to a 10 cm15 cm size.

[0235] The cut first material and the cut second material were superimposed so that a surface of the color developer layer in the first material and a surface of the developer layer in the second material came into contact with each other.

[0236] The color developer layer and the developer layer were rubbed against each other by reciprocally moving the first material against the second material 20 times in the above-described state.

[0237] The developer layer in the second material after rubbing was visually observed, and color development by rubbing was evaluated according to the following evaluation standards.

[0238] In the following evaluation standards, color development by rubbing (that is, unintended color development) is further suppressed as the numerical values of evaluation ranks increases. The evaluation rank at which color development by rubbing is most suppressed is 5.

Evaluation Standards of Color Development by Rubbing

[0239] 5: Color development in the developer layer in the second material was not recognized.

[0240] 4: Color development in the developer layer in the second material was extremely slightly recognized, which was on a level of no practical problem.

[0241] 3: Color development was observed in some of the developer layer in the second material, which was on a level of no practical problem.

[0242] 2: Color development was observed in the majority of the developer layer in the second material, which was on a level with a practical problem.

[0243] 1: Color development was observed on the entire surface of the developer layer in the second material, which was on a level with a practical problem.

(Gradation Property of Color Development)

[0244] Color optical densities in the cases of applying individual pressures of 0.02 MPa, 0.03 MPa, 0.04 MPa, 0.05 MPa, and 0.06 MPa by changing the weight of the weight placed on the two glass plates in the above-described measurement of the color optical density DA were measured respectively.

[0245] On the basis of the measurement results, the gradation property of color development was evaluated according to the following evaluation standards.

[0246] In the following evaluation standards, the gradation property of color development becomes more favorable as the numerical values of evaluation ranks increases. The evaluation rank at which the gradation property of color development is most favorable is 5.

Evaluation Standards of Gradation Property of Color Development

[0247] 5: A high color optical density was shown in a condition of 0.06 MPa, and an increase in the color optical density with an increase in the pressure was linear.

[0248] 4: A high color optical density was shown in a condition of 0.06 MPa, and there were a small number of folding points in the increase in the color optical density with the increase in the pressure, which was on a level of no practical problem.

[0249] 3: The density at 0.06 Mpa was low or the increase in the color optical density with the increase in the pressure in a pressure range of 0.04 MPa or lower was saturated, which was on a level of no practical problem.

[0250] 2: The density at 0.06 Mpa was low or the increase in the color optical density with the increase in the pressure in a pressure range of 0.03 MPa or lower was saturated, which was on a level with a practical problem.

[0251] 1: The density at 0.06 Mpa was near zero or the increase in the color optical density with the increase in the pressure was not shown, which was on a level with a practical problem.

(Color Development Rate)

[0252] In the above-described measurement of the color optical density DA, the density of the color development region was measured every 30 seconds from the end of pressurization.

[0253] In a case where the above-described color optical density DA (that is, the color optical density 20 minutes after the end of pressurization) was set to 100%, a time taken to obtain a color optical density of 80% or more (that is, a time taken from the end of pressurization to the measurement of the density) was confirmed.

[0254] The color development rate becomes faster as the time taken to obtain the color optical density of 80% or more becomes shorter.

(Color Optical Density After Storage (Relative Value))

[0255] The first material was stored for ten days in an environment of 45 C. and 70%RH. The same operation as that in a condition of 0.06 MPa regarding the above-described gradation property of color development was carried out using the first material after storage, and the density in the color development region of the developer layer (hereinafter, referred to as color optical density DC) was measured.

[0256] Regarding the color optical density DC, a relative value (%) of a case where the color optical density in a condition of 0.06 MPa regarding the above-described gradation property of color development was set to 100% was computed and regarded as the color optical density after storage (relative value).

Example 2

[0257] The same operation as in Example 1 was carried out except for the fact that Ra of the surface of the developer layer was changed as shown in Table 1.

[0258] The results are shown in Table 1.

[0259] Ra of the surface of the developer layer was changed by changing the dispersion condition using the homogenizer (stirring rotating speed per unit time) in the preparation of the coating fluid for forming the developer layer.

[0260] Specifically, Ra of the surface of the developer layer increases as the stirring rotating speed per unit time becomes slower.

Examples 3 and 4

[0261] In Examples 3 and 4 each, the same operation as in Examples 1 and 2 was carried out except for the fact that the proportion of the inorganic filler having a particle diameter of 0.1 m or more in all of the inorganic filler in the first base material was changed as shown in Table 1 without changing the total content of the inorganic filler in the first base material.

[0262] The results are shown in Table 1.

[0263] Here, the proportion of the inorganic filler having a particle diameter of 0.1 m or more in all of the inorganic filler in the first base material was adjusted by adjusting the ratio between the amounts of an inorganic filler A (amorphous silica particles, volume-average particle diameter: 0.02 m) and an inorganic filler B (amorphous silica particles including amorphous silica particles having a particle diameter of 0.1 m or more, volume-average particle diameter: 0.08 m) used in the production of the first base material using the inorganic filler A and the inorganic filler B.

Example 5

[0264] The same operation as in Example 2 was carried out except for the fact that the kind of the electron-accepting compound was changed as shown in Table 1.

[0265] The results are shown in Table 1.

[0266] The kind of the electron-accepting compound was changed by changing the coating fluid for forming the developer layer to the following coating fluid for forming the developer layer (Example 5).

<Preparation of Coating Fluid for Forming Developer Layer (Example 5)>

[0267] A 40% sodium hydroxide aqueous solution (5 parts) and water (300 parts) were added to activated clay (100 parts) as a clay substance that is an electron-accepting compound, and the obtained liquid was dispersed using a homogenizer, thereby obtaining a dispersion liquid. A 10% aqueous solution of a sodium salt of casein (50 parts) and styrene-butadiene latex (30 parts as the solid content amount) were added to the obtained dispersion liquid, thereby obtaining a coating fluid for forming a developer layer containing the clay substance.

[0268] As the activated clay, FURACOLOR SR that is sulfate-treated activated clay manufactured by BYK Additives & Instruments was used.

Example 6

[0269] The same operation as in Example 5 was carried out except for the fact that, in the preparation of the coating fluid for forming the color developer layer, two kinds of microcapsule A-containing liquids (specifically, a microcapsule A1-containing liquid and a microcapsule A2-containing liquid) were used.

[0270] The results are shown in Table 1.

[0271] The amount of the microcapsule A1-containing liquid added and the amount of the microcapsule A2-containing liquid added were set to an amount at which the mass ratio of a microcapsule A1 to a microcapsule A2 in the color developer layer (hereinafter, regarded as A1/A2 mass ratio) reached a value shown in Table 1.

[0272] The total amount of the amount of the microcapsule A1-containing liquid added and the amount of the microcapsule A2-containing liquid added in Example 6 was set to be the same as the amount of the microcapsule A1-containing liquid added in Example 1.

[0273] In Example 6, the microcapsule A1-containing liquid included the microcapsule A1 having DSOA and a wall thickness shown in Table 1, and the microcapsule A2-containing liquid included the microcapsule A2 having D50A and a wall thickness shown in Table 1.

[0274] The microcapsule A1-containing liquid and the microcapsule A2-containing liquid were both prepared in the same manner as the microcapsule A1-containing liquid included the microcapsule A having D50A and a wall in Example 5. The D50A and wall thickness of the microcapsule A were changed as shown in Table 1 by changing the stirring rotating speed per unit time during the emulsification and dispersion in the preparation of the microcapsule A1-containing liquid in Example 5.

[0275] Specifically, as the stirring rotating speed per unit time decreases, D50A of the microcapsule A increases, and the wall thickness of the microcapsule A becomes thicker.

Examples 7 and 8

[0276] The same operation as in Example 5 was carried out except for the fact that the CV value of the particle size distribution of the color developer layer was changed as shown in Table 1.

[0277] The results are shown in Table 1.

[0278] The CV value of the particle size distribution of the color developer layer was changed by changing the stirring time during the emulsification and dispersion.

[0279] Specifically, the CV value of the particle size distribution of the color developer layer increases as the stirring time becomes shorter.

Example 9

[0280] The same operation as in Example 6 was carried out except for the fact that, in the preparation of the coating fluid for fonning the color developer layer, furthermore, the following microcapsule B1-containing liquid containing the microcapsule B1 as the microcapsule B not encapsulating an electron-donating dye precursor was added thereto.

[0281] The results are shown in Table 1.

[0282] The amount of the microcapsule B1-containing liquid added was set to an amount at which the mass ratio of the microcapsule B1 to the total of the microcapsule A1 and the microcapsule A2 in the color developer layer (hereinafter, also referred to as B1/(A1+A2) mass ratio) reached a value shown in Table 1.

Preparation of Microcapsule B1-Containing Liquid

[0283] Synthetic isoparaffin (Idemitsu Kosan Co., Ltd., IP SOLVENT 1620) (15 parts) and N,N,N,N-tetrakis(2-hydroxypropyl)ethylene diamine (ADEKA Corporation, ADEKA POLYETHER EDP-300) dissolved in ethyl acetate (3 parts) (0.4 parts) were added to 1-phenyl-1-xylyl ethane (manufactured by Nippon Oil Corporation, HISOL SAS296) (78 parts) under stirring, thereby obtaining a solution X.

[0284] The obtained solution X was stirred, and a trimethylolpropane adduct of torylene diisocyanate (DIC Corporation, BURNOCK D-750) dissolved in ethyl acetate (7 parts) (3 parts) was added thereto, thereby obtaining a solution Y.

[0285] Next, the solution Y was added to a solution obtained by dissolving polyvinyl alcohol (PVA-205, Kuraray Co., Ltd.) (9 parts) in water (140 parts), emulsified, and dispersed. Water (340 parts) was added to the obtained emulsified liquid, heated up to 70 C. under stirring, stirred for one hour, and then cooled. Water was further added to the cooled liquid, thereby adjusting the concentration of the solid content.

[0286] A microcapsule B1-containing liquid containing a microcapsule B1 as the microcapsule B not encapsulating an electron-donating dye precursor (concentration of solid content: 19.6%) was obtained in the above-described manner.

[0287] For the microcapsule B1 that was contained in the microcapsule B 1-containing liquid, the volume-based median size (hereinafter, also referred to as D50B) and the wall thickness were values shown in Table 1.

[0288] Methods for measuring the D50B and wall thickness of the microcapsule B1 were respectively set to be the same as the methods for measuring the D50A and wall thickness of the microcapsule A1.

[0289] In addition, a wall material of the microcapsule B1 was, as shown in Table 1, PUR (that is, a urethane-urea resin).

Examples 10 and 11

[0290] The same operation as in Example 9 was carried out except for the fact that Ra of the surface of the developer layer was changed as shown in Table 1.

[0291] The results are shown in Table 1.

[0292] Ra of the surface of the developer layer was changed by changing the dispersion condition (stirring rotating speed per unit time) using a homogenizer in the preparation of the coating fluid for forming the developer layer.

[0293] Specifically, Ra of the surface of the developer layer increases as the stirring rotating speed per unit time becomes slower.

Example 12

[0294] The same operation as in Example 9 was carried out except for the fact that the proportion of the inorganic filler having a particle diameter of 0.1 m or more in all of the inorganic filler in the first base material was changed as shown in Table 1 without changing the total content of the inorganic filler in the first base material.

[0295] The results are shown in Table 1.

[0296] The proportion of the inorganic filler having a particle diameter of 0.1 m or more in all of the inorganic filler in the first base material was adjusted in the same manner as in Example 3.

Example 13

[0297] The same operation as in Example 5 was carried out except for the fact that the microcapsule A1-containing liquid was changed to the following microcapsule A1-containing liquid (Example 13).

[0298] The results are shown in Table 1.

<Preparation of Microcapsule A1-Containing Liquid (Example 13)

[0299] A partial sodium salt of polyvinyl sulfonic acid (average molecular weight: 500,000) (10 parts) was added to and dissolved in hot water (80 C., 140 parts) under stirring, and then cooled, thereby obtaining an aqueous solution M1. The pH of this aqueous solution M1 was two to three. A 20% by mass sodium hydroxide aqueous solution was added to the aqueous solution M1, and the pH was adjusted to 4.0, thereby obtaining an aqueous solution M2.

[0300] Separately, a solution B2 (that is, a solution including the compound (A) that is an electron-donating dye precursor) was prepared in the same manner as the solution B in the preparation of the microcapsule A1-containing liquid in Example 1. Here, the amount of the solution B2 prepared was also set to be the same as the amount of the solution B prepared in Example 1.

[0301] The solution B2 was added to the aqueous solution M2, emulsified, and dispersed, thereby obtaining an emulsified liquid M3.

[0302] Separately, melamine (6 parts) and a 37% by mass formaldehyde aqueous solution (11 parts) were heated to 60 C. and stirred at this temperature for 30 minutes, thereby obtaining a mixed aqueous solution M4 (pH 6 to 8) including melamine, formaldehyde, and a melamine-formaldehyde initial condensate.

[0303] Next, the emulsified liquid M3 and the mixed aqueous solution M4 were mixed together, the pH of a liquid was adjusted to 6.0 using a 3.6% by mass hydrochloric acid solution while stirring the obtained liquid, subsequently, the liquid temperature was increased to 65 C., and the liquid was continuously stirred at this temperature for 360 minutes. The stirred liquid was cooled, and then the pH of the liquid was adjusted to 9.0 using a sodium hydroxide aqueous solution.

[0304] A microcapsule A1-containing liquid (Example 13) which contained a microcapsule A1 as the microcapsule A encapsulating an electron-donating dye precursor (pH: 9.0, concentration of solid content: 19.6%) was obtained in the above-described manner.

[0305] For the microcapsule A1 that was contained in the microcapsule A1-containing liquid of Example 13, D50A and the wall thickness were values shown in Table 1.

[0306] Methods for measuring the D50A and wall thickness of the microcapsule A1 were as described above.

[0307] In addition, a wall material of the microcapsule A1 of Example 13 was, as shown in Table 1, a melamine formaldehyde resin (hereinafter, also referred to as MF).

Example 14

[0308] The same operation as in Example 13 was carried out except for the fact that, in the preparation of the coating fluid for forming the color developer layer, two kinds of microcapsule A-containing liquids (specifically, a microcapsule A1-containing liquid and a microcapsule A2-containing liquid) were used.

[0309] The results are shown in Table 1.

[0310] The amount of the microcapsule A1-containing liquid added and the amount of the microcapsule A2-containing liquid added were set to an amount at which the mass ratio of a microcapsule A1 to a microcapsule A2 in the color developer layer (hereinafter, regarded as A1/A2 mass ratio) reached a value shown in Table 1.

[0311] The total amount of the amount of the microcapsule A1-containing liquid added and the amount of the microcapsule A2-containing liquid added in Example 14 was set to be the same as the amount of the microcapsule A1-containing liquid added in Example 13.

[0312] In Example 14, the microcapsule A2-containing liquid included the microcapsule A1 having D50A and a wall thickness shown in Table 1, and the microcapsule A2-containing liquid included the microcapsule A2 having D50A and a wall thickness shown in Table 1.

[0313] The microcapsule A1-containing liquid and the microcapsule A2-containing liquid were both prepared in the same manner as the microcapsule A1-containing liquid in Example 13. The D50A and wall thickness of the microcapsule A were changed as shown in Table 1 by changing the stirring rotating speed per unit time during the emulsification and dispersion in the preparation of the microcapsule A1-containing liquid in Example 13.

[0314] Specifically, as the stirring rotating speed per unit time decreases, D50A of the microcapsule A increases, and the wall thickness of the microcapsule A becomes thicker.

Example 15

[0315] The same operation as in Example 14 was carried out except for the fact that, in the preparation of the coating fluid for forming the color developer layer, furthermore, the following microcapsule B1-containing liquid in Example 15 which contained a microcapsule B1 as the microcapsule B not encapsulating an electron-donating dye precursor was added thereto.

[0316] The results are shown in Table 1.

[0317] The amount of the microcapsule B1-containing liquid in Example 15 added was set to an amount at which the B1/(A1+A2) mass ratio in the color developer layer reached a value shown in Table 1.

<Preparation of Microcapsule B1-Containing Liquid in Example 15

[0318] The microcapsule B1-containing liquid in Example 15 which contained a microcapsule B1 as the microcapsule B not encapsulating an electron-donating dye precursor was prepared in the same manner as in the preparation of the microcapsule A1-containing liquid in Example 13 except for the fact that the solution B2 (that is, a solution including the compound (A) that is an electron-donating dye precursor) was changed to a solution X2 (that is, a solution not including an electron-donating dye precursor) which is the same solution as the solution X in Example 9. Here, the amount of the solution X2 used was set to be the same as the amount of the solution X prepared in Example 9.

[0319] For the microcapsule B1 that was contained in the microcapsule B1-containing liquid of Example 15, D50B and the wall thickness were values shown in Table 1.

[0320] Methods for measuring the D50B and wall thickness of the microcapsule B1 were respectively set to be the same as the methods for measuring the D50A and wall thickness of the microcapsule A1.

[0321] In addition, a wall material of the microcapsule B1 was, as shown in Table 1, a melamine formaldehyde resin (hereinafter, also referred as MF).

Comparative Examples 1 and 2

[0322] The same operation as in Examples 2 and 5 was carried out except for the fact that the proportion of the inorganic filler having a particle diameter of 0.1 m or more in all of the inorganic filler in the first base material was changed as shown in Table 1 without changing the total content of the inorganic filler in the first base material.

[0323] The results are shown in Table 1.

[0324] The proportion of the inorganic filler having a particle diameter of 0.1 m or more in all of the inorganic filler in the first base material was adjusted by adjusting the ratio between the amounts of the inorganic filler A (amorphous silica particles, volume-average particle diameter: 0.02 m) and the inorganic filler B (amorphous silica particles including amorphous silica particles having a particle diameter of 0.1 m or more, volume-average particle diameter: 0.08 m) used in the production of the first base material using the inorganic filler A and the inorganic filler B.

Comparative Example 3

[0325] The same operation as in Example 5 was carried out except for the fact that Ra of the surface of the developer layer was changed as shown in Table 1.

[0326] The results are shown in Table 1.

[0327] Ra of the surface of the developer layer was changed by changing the dispersion condition of activated clay by a homogenizer in the preparation of the coating fluid for forming the developer layer.

TABLE-US-00001 TABLE 1 First material Color developer layer Microcapsule A Microcapsule B A1 A2 B1 CV value Wall Wall Wall of particle D50A thickness Wall D50A thickness Wall D50A thickness Wall A1/A2 B1/(A1 + A2) size (m) (nm) material (m) (nm) material (m) (nm) material mass ratio mass ratio distribution Example 1 25 58 PUR 65% Example 2 25 58 PUR 65% Example 3 25 58 PUR 65% Example 4 25 58 PUR 65% Example 5 25 58 PUR 65% Example 6 30 70 PUR 15 35 PUR 60/40 70% Example 7 25 58 PUR 53% Example 8 25 58 PUR 90% Example 9 30 70 PUR 15 35 PUR 60 125 PUR 60/40 20/100 75% Example 10 30 70 PUR 15 35 PUR 60 125 PUR 60/40 20/100 75% Example 11 30 70 PUR 15 35 PUR 60 125 PUR 60/40 20/100 75% Example 12 30 70 PUR 15 35 PUR 60 125 PUR 60/40 20/100 75% Example 13 25 58 MF 65% Example 14 30 70 MF 15 35 MF 60/40 70% Example 15 30 70 MF 15 35 MF 60 125 MF 60/40 20/100 75% Comparative 25 58 PUR 65% Example 1 Comparative 25 58 PUR 65% Example 2 Comparative 25 58 PUR 65% Example 3 First material First base material Evaluation Proportion of Color filler having optical Color particle density optical diameter of unevenness density 0.1 m or Second material D in in Gradation after more in all Developer layer condition condition Color property of Color storage filler (% by Electron-accepting Ra of 0.03 of 0.05 development color development (absolute volume) compound (m) MPa MPa by rubbing development rate value) Example 1 0 Zinc salicylate 0.4 0.08 5 4 4 2 minutes 80% Example 2 0 Zinc salicylate 0.7 0.10 5 4 4 2 minutes 80% Example 3 3 Zinc salicylate 0.4 0.10 4 4 4 2 minutes 80% Example 4 3 Zinc salicylate 0.7 0.12 4 4 4 2 minutes 80% Example 5 0 Activated clay 0.7 0.12 5 4 4 30 seconds 80% Example 6 0 Activated clay 0.7 0.12 5 4 5 30 seconds 80% Example 7 0 Activated clay 0.7 0.14 5 4 3 30 seconds 80% Example 8 0 Activated clay 0.7 0.08 5 4 3 30 seconds 80% Example 9 0 Activated clay 0.7 0.16 5 5 5 30 seconds 80% Example 10 0 Activated clay 0.4 0.14 5 5 5 30 seconds 80% Example 11 0 Activated clay 1.0 0.18 4 4 5 30 seconds 80% Example 12 3 Activated clay 0.7 0.18 4 5 5 30 seconds 80% Example 13 0 Activated clay 0.7 0.12 4 4 4 30 seconds 90% Example 14 0 Activated clay 0.7 0.12 4 4 5 30 seconds 90% Example 15 0 Activated clay 0.7 0.16 4 5 5 30 seconds 90% Comparative 8 Zinc salicylate 0.7 0.14 2 5 2 2 minutes 80% Example 1 Comparative 8 Activated clay 0.7 0.14 2 5 2 30 seconds 80% Example 2 Comparative 0 Activated clay 1.3 0.20 2 4 3 30 seconds 80% Example 3

[0328] As shown in Table 1, in Examples 1 to 15 for which the material for pressure measurement including the first material having the color developer layer containing the microcapsule A encapsulating an electron-donating dye precursor disposed on the first base material and the second material having the developer layer containing an electron-accepting compound disposed on the second base material, in which the first base material contains the inorganic filler, the proportion of the inorganic filler having a particle diameter of 0.1 in or more in all of the inorganic filler contained in the first base material is 5% by volume or less, and the arithmetic average roughness Ra of the surface of the developer layer satisfies 0.1 mRa1.1 m, was used, the color optical density difference D before and after pressurization at 0.03 MPa was large to a certain extent (that is, a color optical density that could be read at a pressure of 0.05 MPa or lower could be obtained), and color optical density unevenness in a condition of 0.05 MPa was suppressed.

[0329] In Examples 1 to 15 and Comparative Examples 1 to 3, Ra's of the surfaces of the color developer layers were measured in the same manner as Ra's of the surfaces of the developer layers and found out to be in a range of 1.5 m to 2.8 m in Examples 1 to 15 and Comparative Example 3 and be more than 3.0 m in Comparative Examples 1 and 2.

[0330] In contrast to Examples 1 to 15, in Comparative Examples 1 and 2 in which the proportion of an inorganic filler having a particle diameter of 0.1 m or more in all of the inorganic filler contained in the first base material was more than 5% by volume and Comparative Example 3 in which the arithmetic average roughness Ra of the surface of the developer layer was more than 1.1 m, the color optical density unevenness in a condition of 0.05 MPa deteriorated.

[0331] From the comparison between Examples 7 and 8 and other examples, it is found that, in a case where the CV value of the particle size distribution of the color developer layer (that is, the coefficient of variation of the volume-based particle size distribution of particles having a particle diameter of 2 m or more contained in the color developer layer) is 60% to 80%, the gradation property of color development further improves.

[0332] From the comparison between Examples 9, 10, 12, and 15 and other examples, it is found that, in a case where the color developer layer contains the microcapsule B not encapsulating an electron-donating dye precursor, color development by rubbing is further suppressed.

[0333] In addition, from the comparison between Examples 13 to 15 and other examples, it is found that, in a case where the wall materials of the microcapsule A and/or the microcapsule B (that is, the material of the capsule wall) is MF (that is, a melamine formaldehyde resin), the color optical density after storage is maintained on a high level.

[0334] The disclosure of Japanese Patent Application No. 2017-108377 filed on May 31, 2017 is all incorporated into the present specification by reference.

[0335] All of documents, patent applications, and technical standards described in the present specification are incorporated into the present specification by reference to approximately the same extent as a case where it is specifically and respectively described that the respective documents, patent applications, and technical standards are incorporated by reference.