JP2008201112A - Latent image forming and developing image forming method, and recording sheet or recording sheet set - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording method which can send confidential information to the third person under a state invisible to a third person and a recording method and a recording sheet which are suitable in visualizing confidential information in mass production and to provide a recording sheet. <P>SOLUTION: The latent image forming and developing image forming method is characterized as follows. A micro-capsule which contains an oxidation color developing type dyes precursor having a substituent disconnected by heating or light irradiation is formed on a first base material (1) after forming a latent image on the first base material by discharging the oxidation color developing type dyes precursor by pressurizing the micro-capsule or (2) the oxidation color developing type dyes precursor is discharged from the micro-capsule by pressurizing the micro-capsule, after forming the latent image on the second base material arranged opposed to a micro capsule containing layer, the forming latent image is color developed by heating or light irradiation of the formed latent image. In addition, the recording sheet or a recording sheet set are disclosed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a novel latent image formation and color image formation method that can be applied as a means for invisibility of secret information in place of a concealment label, and a recording sheet or a recording sheet set used therefor.

  Conventionally, when a postcard containing confidential information such as personal information is mailed, a concealment label (in order to conceal the part where the confidential information is described) in order to prevent the confidential information from being viewed by a third party. A concealment seal) has been put into practical use.

  Such a concealment label can be read by the sender attaching the concealment label to the confidential information portion of the postcard and mailing it, and the recipient peeling off the concealment layer of the concealment label and making the confidential information visible. It is what I did. For this reason, it is necessary to use a special adhesive that can be peeled off for the concealment label, or to make a complicated laminated structure, and it takes time and money to manufacture the concealment label, and a large amount of concealment label is applied. Or, there is a problem that it takes time to peel off.

  As a concealment label that eliminates the need for peeling off the concealment label, a concealment label (see Patent Document 1) in which the concealment layer of the concealment label is formed of a thermal decoloring ink that decolorizes at a predetermined temperature higher than normal temperature has been proposed. Yes. If such a concealment label is used, it is not necessary to peel off the concealment label, and the concealment layer becomes transparent by heating to a predetermined temperature or higher, and the secret information can be made visible. However, this concealment label also requires the use of a special eraser such as a steroidal compound in addition to the color former (leuco dye) and developer in the concealment layer, and requires label processing. There are difficulties such as.

  For this reason, confidential information written on postcards is not made known to third parties in the mailing process, and there is no need for label processing like concealment labels. Therefore, there is a demand for the development of a new recording method and recording sheet that does not bother users.

JP 2001-054992 A

  It is an object of the present invention to send confidential information invisible to a third party when delivering postcards or the like on which confidential information such as personal information is written by means such as mail. It is an object of the present invention to provide a recording method suitable for visualizing a large amount of postcards in which confidential information is written, and a recording sheet suitable for the purpose.

The present inventors can fill in confidential information as a latent image invisible to a third party, and the secret information is formed as a latent image even if a postcard or other document filled with the confidential information is delivered by mail or other means. Therefore, it was invisible to a third party, and a system for visualizing confidential information by visualizing a latent image on the side receiving such a document was studied repeatedly.
As a result, use a oxidative coloring dye precursor that has a substituent in the molecule that can be removed by heating, etc., and is colorless until the substituent is released, and becomes colored when the substituent is released. I found that the target system can be constructed.
The present invention has been completed by further studies based on such findings, and provides the following latent image formation and developer image formation method, and a recording sheet or recording sheet set.

[Item 1] On the first support, a layer containing microcapsules encapsulating an oxidative coloring dye precursor having in its molecule a substituent that is eliminated by heating or light irradiation is formed,
(1) Pressurizing the microcapsule to release the oxidative coloring dye precursor from the microcapsule to form a latent image on the first support, or
(2) Pressurizing the microcapsule to release the oxidation coloring dye precursor from the microcapsule and transferring it onto the second support disposed opposite the microcapsule-containing layer, After forming the latent image on the support,
A latent image forming method and a developed color image forming method characterized in that a formed latent image is heated or irradiated with light to release a substituent to develop a color.

[Item 2] The latent image formation and color image formation method according to Item 1, wherein the substituent that is released by heating or light irradiation is a tertiary alkyloxycarbonyl group.

[Item 3] The latent image formation and color development according to Item 1 or 2, wherein the oxidative coloring dye precursor is a compound represented by the following general formula (1) or a compound represented by the general formula (2): Image forming method.

[In General Formula (1), X represents an oxygen atom, a sulfur atom or NR ₁₀ , and R ₁ represents a tertiary alkyl group having 4 to 10 carbon atoms. R ₂ , R ₅ , R ₆ and R ₉ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an aryl group, a nitro group or an arylazo group. To express. R ₃ , R ₄ , R ₇ and R ₈ are independently of each other NR ₁₁ R ₁₂ , a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and an aryl group. Represents a nitro group or an arylazo group. R ₁₁ and R ₁₂ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an aryl group, or COOR ₁ . R ₁₀ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group, or COOR ₁ . R ₂ and R ₃ , R ₃ and R ₄ , R ₄ and R ₅ , R ₆ and R ₇ , R ₇ and R _8, and R ₈ and R ₉ are bonded to each other and bonded to each other. An aromatic ring may be formed. In the general formula (2), Y ₁ and Y ₂ each independently represent a sulfur atom or NR ₃₁ , but Y ₁ and Y ₂ may be bonded in the form of N—A—N. Here, R ₃₁ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, COR ₃₂ or COOR ₃₃ , A represents a saturated or unsaturated alkylene group having 1 to 10 carbon atoms, and R ₃₂ and R ₃₃ represent Independently of each other, it represents an alkyl group having 1 to 12 carbon atoms; a benzyl group; an aryl group optionally substituted by a halogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. R ₂₁ and R ₂₂ each independently represent a tertiary alkyl group having 4 to 12 carbon atoms. R _{23 to} R ₃₀ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a nitro group, NR ₃₄ R ₃₅ or SR ₃₆ . Here, R ₃₄ and R ₃₅ are each independently a hydrogen atom; an alkyl group having 1 to 12 carbon atoms; a cycloalkyl group having 4 to 12 carbon atoms; a halogen atom, an alkyl group having 1 to 6 carbon atoms; An aralkyl group which may be substituted with an alkoxy group having ˜6; a halogen atom, an alkyl group having 1 to 6 carbon atoms, an aryl group which may be substituted with an alkoxy group having 1 to 6 carbon atoms; ₃₄ and R ₃₅ may form a pyrrolidino group, piperidino group or hexamethyleneimino group together with the adjacent nitrogen atom. R ₃₆ represents an alkyl group having 1 to 10 carbon atoms. R ₂₃ and R ₂₄ , R ₂₄ and R ₂₅ , R ₂₅ and R ₂₆ , R ₂₇ and R ₂₈ , R ₂₈ and R _29, and R ₂₉ and R ₃₀ may form a benzene ring independently of each other. Good. ]

[Item 4] The oxidative coloring dye precursor is 3,7-bis (dimethylamino) -10- (tert-butoxycarbonyl) phenothiazine, 2-methyl-3-amino-7-diethylamino-10- (tert- Butoxycarbonyl) phenoxazine, 3,7-bis (dimethylamino) -4-nitro-10- (tert-butoxycarbonyl) phenothiazine, 3,7-bis (diethylamino) -10- (tert-butoxycarbonyl) phenoxazine, 3,7-bis (dimethylamino) -1,9-dimethyl-10- (tert-butoxycarbonyl) phenothiazine, 9-dimethylaminobenzo (a) -12- (tert-butoxycarbonyl) phenoxazine, 2,8- Dimethyl-3,7-bis (ethylamino) -10- (tert-but Cicarbonyl) phenothiazine, 3,7-bis (dimethylamino) -10- (tert-pentyloxycarbonyl) phenothiazine, 2-methyl-3-amino-7- (dimethylamino) -10- (tert-butoxycarbonyl) phenothiazine 3- (4-Dimethylaminophenylazo) -7-diethylamino-5-phenyl-10- (tert-butoxycarbonyl) phenazine, 5-amino-9-diethylaminobenzo (a) -12- (tert-butoxycarbonyl) Phenoxazine, 3,7-bis (phenylmethylamino) -10- (tert-butoxycarbonyl) phenothiazine, 3,7-bis (phenylethylamino) -10- (tert-butoxycarbonyl) phenothiazine, 3,7-bis (Diphenylamino) -1 0- (tert-butoxycarbonyl) phenothiazine, 3,7-bis (phenylmethylamino) -10- (tert-butoxycarbonyl) phenoxazine, 3,7-bis (phenylethylamino) -10- (tert-butoxycarbonyl) ) Phenoxazine and 3,7-bis (diphenylamino) -10- (tert-butoxycarbonyl) phenoxazine, O, O'-di (tert-butoxycarbonyl) indigo white, O, O'-di (tert-butoxy) Carbonyl) -5,5 ′, 7,7′-tetrabromoindigo white, O, O′-di (tert-butoxycarbonyl) thioindigo white, O, O′-di (tert-butoxycarbonyl) -4,4 '-Dimethyl-6,6'-dichlorothioindigo white, O, O' Di (tert-butoxycarbonyl) -4,4 ', 7,7'-tetramethyl-5,5'-dichlorothioindigo white, O, O', N, N'-tetra (tert-butoxycarbonyl) indigo white Item 4. The latent image formation and developer image formation method according to any one of Items 1 to 3, which is at least one selected from the group consisting of:

[Item 5] The oxidative coloring dye precursor is 3,7-bis (dimethylamino) -10- (tert-butoxycarbonyl) phenothiazine, O, O′-di (tert-butoxycarbonyl) indigo white, O, Item 5. The latent image formation and color image formation method according to Item 4, which is at least one selected from the group consisting of O ', N, N'-tetra (tert-butoxycarbonyl) indigo white.

[Item 6] The latent image formation and color image formation method according to any one of Items 1 to 5, wherein an acidic substance is allowed to act upon heating or light irradiation.

[Item 7] The latent image formation and color image formation method according to Item 6, wherein the acidic substance is at least one selected from the group consisting of a salicylic acid derivative and a polyvalent metal salt thereof.

[Item 8] The latent image formation and color image formation method according to Item 7, wherein the acidic substance is a zinc salt of 3,5-bis (α-methylbenzyl) salicylic acid.

[Item 9] A recording sheet or recording sheet set for forming information as a latent image, wherein the recording sheet or recording sheet set has at least a substituent in the molecule that is eliminated by heating or light irradiation. A recording sheet or a recording sheet set, comprising a sheet provided with a layer containing microcapsules encapsulating a mold dye precursor on a first support.

[Item 10] A recording sheet or recording sheet set for recording information as a latent image and then developing the latent image into visible information, wherein the recording sheet or recording sheet set is at least heated or irradiated with light. A recording sheet or a recording sheet set comprising a sheet provided with a layer containing a microcapsule encapsulating an oxidative coloring dye precursor having in its molecule a substituent that can be eliminated by the above-described method .

[Item 11] The recording sheet or recording sheet set according to item 9 or 10, wherein the substituent that is released by heating or light irradiation is a tertiary alkyloxycarbonyl group.

[Item 12] The recording according to any one of Items 9 to 11, wherein the oxidative coloring dye precursor is a compound represented by the following general formula (1) or a compound represented by the general formula (2): Sheet or recording sheet set.

[In General Formula (1), X represents an oxygen atom, a sulfur atom or NR ₁₀ , and R ₁ represents a tertiary alkyl group having 4 to 10 carbon atoms. R ₂ , R ₅ , R ₆ and R ₉ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an aryl group, a nitro group or an arylazo group. To express. R ₃ , R ₄ , R ₇ and R ₈ are independently of each other NR ₁₁ R ₁₂ , a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and an aryl group. Represents a nitro group or an arylazo group. R ₁₁ and R ₁₂ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an aryl group, or COOR ₁ . R ₁₀ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group, or COOR ₁ . R ₂ and R ₃ , R ₃ and R ₄ , R ₄ and R ₅ , R ₆ and R ₇ , R ₇ and R _8, and R ₈ and R ₉ are bonded to each other and bonded to each other. An aromatic ring may be formed. In the general formula (2), Y ₁ and Y ₂ each independently represent a sulfur atom or NR ₃₁ , but Y ₁ and Y ₂ may be bonded in the form of N—A—N. Here, R ₃₁ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, COR ₃₂ or COOR ₃₃ , A represents a saturated or unsaturated alkylene group having 1 to 10 carbon atoms, and R ₃₂ and R ₃₃ represent Independently of each other, it represents an alkyl group having 1 to 12 carbon atoms; a benzyl group; an aryl group optionally substituted by a halogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. R ₂₁ and R ₂₂ each independently represent a tertiary alkyl group having 4 to 12 carbon atoms. R _{23 to} R ₃₀ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a nitro group, NR ₃₄ R ₃₅ or SR ₃₆ . Here, R ₃₄ and R ₃₅ are each independently a hydrogen atom; an alkyl group having 1 to 12 carbon atoms; a cycloalkyl group having 4 to 12 carbon atoms; a halogen atom, an alkyl group having 1 to 6 carbon atoms; An aralkyl group which may be substituted with an alkoxy group having ˜6; a halogen atom, an alkyl group having 1 to 6 carbon atoms, an aryl group which may be substituted with an alkoxy group having 1 to 6 carbon atoms; ₃₄ and R ₃₅ may form a pyrrolidino group, piperidino group or hexamethyleneimino group together with the adjacent nitrogen atom. R ₃₆ represents an alkyl group having 1 to 10 carbon atoms. R ₂₃ and R ₂₄ , R ₂₄ and R ₂₅ , R ₂₅ and R ₂₆ , R ₂₇ and R ₂₈ , R ₂₈ and R _29, and R ₂₉ and R ₃₀ may form a benzene ring independently of each other. Good. ]

[Item 13] The oxidative coloring dye precursor is 3,7-bis (dimethylamino) -10- (tert-butoxycarbonyl) phenothiazine, 2-methyl-3-amino-7-diethylamino-10- (tert- Butoxycarbonyl) phenoxazine, 3,7-bis (dimethylamino) -4-nitro-10- (tert-butoxycarbonyl) phenothiazine, 3,7-bis (diethylamino) -10- (tert-butoxycarbonyl) phenoxazine, 3,7-bis (dimethylamino) -1,9-dimethyl-10- (tert-butoxycarbonyl) phenothiazine, 9-dimethylaminobenzo (a) -12- (tert-butoxycarbonyl) phenoxazine, 2,8- Dimethyl-3,7-bis (ethylamino) -10- (tert-butyl Xycarbonyl) phenothiazine, 3,7-bis (dimethylamino) -10- (tert-pentyloxycarbonyl) phenothiazine, 2-methyl-3-amino-7- (dimethylamino) -10- (tert-butoxycarbonyl) phenothiazine 3- (4-Dimethylaminophenylazo) -7-diethylamino-5-phenyl-10- (tert-butoxycarbonyl) phenazine, 5-amino-9-diethylaminobenzo (a) -12- (tert-butoxycarbonyl) Phenoxazine, 3,7-bis (phenylmethylamino) -10- (tert-butoxycarbonyl) phenothiazine, 3,7-bis (phenylethylamino) -10- (tert-butoxycarbonyl) phenothiazine, 3,7-bis (Diphenylamino)- 10- (tert-butoxycarbonyl) phenothiazine, 3,7-bis (phenylmethylamino) -10- (tert-butoxycarbonyl) phenoxazine, 3,7-bis (phenylethylamino) -10- (tert-butoxycarbonyl) ) Phenoxazine and 3,7-bis (diphenylamino) -10- (tert-butoxycarbonyl) phenoxazine, O, O'-di (tert-butoxycarbonyl) indigo white, O, O'-di (tert-butoxy) Carbonyl) -5,5 ′, 7,7′-tetrabromoindigo white, O, O′-di (tert-butoxycarbonyl) thioindigo white, O, O′-di (tert-butoxycarbonyl) -4,4 '-Dimethyl-6,6'-dichlorothioindigo white, O, O -Di (tert-butoxycarbonyl) -4,4 ', 7,7'-tetramethyl-5,5'-dichlorothioindigo white, O, O', N, N'-tetra (tert-butoxycarbonyl) indigo Item 13. The recording sheet or recording sheet set according to any one of Items 9 to 12, which is at least one selected from the group consisting of white.

[Item 14] The oxidative coloring dye precursor is 3,7-bis (dimethylamino) -10- (tert-butoxycarbonyl) phenothiazine, O, O′-di (tert-butoxycarbonyl) indigo white, O, Item 14. The recording sheet according to Item 13, which is at least one selected from the group consisting of O ′, N, N′-tetra (tert-butoxycarbonyl) indigo white.

[Item 15] The recording sheet is a sheet in which a single layer containing the microcapsules and an acidic substance is provided on the same surface of the first support, or contains a layer containing the mylocapsule and an acidic substance. Item 15. The recording sheet according to any one of Items 9 to 14, which is a sheet provided by laminating layers.

[Item 16] A recording sheet set comprising at least a sheet provided with a layer containing the microcapsule on the back surface of the first support and a sheet containing an acidic substance on the surface of the second support. Item 15. The recording sheet set according to any one of Items 9 to 14, comprising:

[Item 17] The recording sheet or recording sheet set according to item 15 or 16, wherein the acidic substance is at least one selected from the group consisting of a salicylic acid derivative and a polyvalent metal salt thereof.

[Item 18] The recording sheet or recording sheet set according to item 17, wherein the acidic substance is a zinc salt of 3,5-bis (α-methylbenzyl) salicylic acid.

  The latent image forming method and the developed color image forming method, and the recording sheet or the recording sheet set according to the present invention, when delivering postcards or the like on which confidential information such as personal information is written by means of mail or the like, Can be sent to a third party in an invisible state, and it does not take time to invisible the confidential information, and it is also a simple method for visualizing the invisible confidential information entered on a postcard etc. Can be processed in large quantities, and there is an advantage that the visualized information is excellent in robustness.

As described above, the method for forming a latent image and a developed color image according to the present invention includes a layer containing a microcapsule containing an oxidative coloring dye precursor having in its molecule a substituent that is eliminated by heating or light irradiation. On the first support,
(1) Pressurizing the microcapsule to release the oxidative coloring dye precursor from the microcapsule to form a latent image on the first support, or
(2) Pressurizing the microcapsule to release the oxidation coloring dye precursor from the microcapsule and transferring it onto the second support disposed opposite the microcapsule-containing layer, After forming the latent image on the support,
The formed latent image is heated or irradiated with light to release a substituent and develop a color.

  The “oxidative coloring dye precursor” in the present invention is a compound having a substituent in the molecule that is released by heating or light irradiation. In the state having this substituent, it is oxidized by oxygen in the air. It is a compound that can maintain a colorless state without being heated, and is a compound that becomes a colored dye by being oxidized by oxygen in the air when a substituent is removed upon heating or light irradiation. .

  In the present invention, a tertiary alkyloxycarbonyl group is preferable as a substituent that is released by heating or light irradiation because it is easily released by heating or light irradiation treatment.

  Specific examples of such a preferred oxidative coloring dye precursor include a compound represented by the following general formula (1) or a compound represented by the general formula (2).

[In General Formula (1), X represents an oxygen atom, a sulfur atom or NR ₁₀ , and R ₁ represents a tertiary alkyl group having 4 to 10 carbon atoms. R ₂ , R ₅ , R ₆ and R ₉ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an aryl group, a nitro group or an arylazo group. To express. R ₃ , R ₄ , R ₇ and R ₈ are independently of each other NR ₁₁ R ₁₂ , a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and an aryl group. Represents a nitro group or an arylazo group. R ₁₁ and R ₁₂ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an aryl group, or COOR ₁ . R ₁₀ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group, or COOR ₁ . R ₂ and R ₃ , R ₃ and R ₄ , R ₄ and R ₅ , R ₆ and R ₇ , R ₇ and R _8, and R ₈ and R ₉ are bonded to each other and bonded to each other. An aromatic ring may be formed. In the general formula (2), Y ₁ and Y ₂ each independently represent a sulfur atom or NR ₃₁ , but Y ₁ and Y ₂ may be bonded in the form of N—A—N. Here, R ₃₁ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, COR ₃₂ or COOR ₃₃ , A represents a saturated or unsaturated alkylene group having 1 to 10 carbon atoms, and R ₃₂ and R ₃₃ represent Independently of each other, it represents an alkyl group having 1 to 12 carbon atoms; a benzyl group; an aryl group optionally substituted by a halogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. R ₂₁ and R ₂₂ each independently represent a tertiary alkyl group having 4 to 12 carbon atoms. R _{23 to} R ₃₀ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a nitro group, NR ₃₄ R ₃₅ or SR ₃₆ . Here, R ₃₄ and R ₃₅ are each independently a hydrogen atom; an alkyl group having 1 to 12 carbon atoms; a cycloalkyl group having 4 to 12 carbon atoms; a halogen atom, an alkyl group having 1 to 6 carbon atoms; An aralkyl group which may be substituted with an alkoxy group having ˜6; a halogen atom, an alkyl group having 1 to 6 carbon atoms, an aryl group which may be substituted with an alkoxy group having 1 to 6 carbon atoms; ₃₄ and R ₃₅ may form a pyrrolidino group, piperidino group or hexamethyleneimino group together with the adjacent nitrogen atom. R ₃₆ represents an alkyl group having 1 to 10 carbon atoms. R ₂₃ and R ₂₄ , R ₂₄ and R ₂₅ , R ₂₅ and R ₂₆ , R ₂₇ and R ₂₈ , R ₂₈ and R _29, and R ₂₉ and R ₃₀ may form a benzene ring independently of each other. Good. ]

  Specific examples of the compound represented by the general formula (1) include 3,7-bis (dimethylamino) -10- (tert-butoxycarbonyl) phenothiazine, 2-methyl-3-amino-7-diethylamino. -10- (tert-butoxycarbonyl) phenoxazine, 3,7-bis (dimethylamino) -4-nitro-10- (tert-butoxycarbonyl) phenothiazine, 3,7-bis (diethylamino) -10- (tert- Butoxycarbonyl) phenoxazine, 3,7-bis (dimethylamino) -1,9-dimethyl-10- (tert-butoxycarbonyl) phenothiazine, 9-dimethylaminobenzo (a) -12- (tert-butoxycarbonyl) phenoxy Sajin, 2,8-dimethyl-3,7-bis (ethylamino) -1 -(Tert-butoxycarbonyl) phenothiazine, 3,7-bis (dimethylamino) -10- (tert-pentyloxycarbonyl) phenothiazine, 2-methyl-3-amino-7- (dimethylamino) -10- (tert- Butoxycarbonyl) phenothiazine, 3- (4-dimethylaminophenylazo) -7-diethylamino-5-phenyl-10- (tert-butoxycarbonyl) phenazine, 5-amino-9-diethylaminobenzo (a) -12- (tert -Butoxycarbonyl) phenoxazine, 3,7-bis (phenylmethylamino) -10- (tert-butoxycarbonyl) phenothiazine, 3,7-bis (phenylethylamino) -10- (tert-butoxycarbonyl) phenothiazine, 3, , 7-bis ( Phenylamino) -10- (tert-butoxycarbonyl) phenothiazine, 3,7-bis (phenylmethylamino) -10- (tert-butoxycarbonyl) phenoxazine, 3,7-bis (phenylethylamino) -10- ( Examples thereof include, but are not limited to, tert-butoxycarbonyl) phenoxazine and 3,7-bis (diphenylamino) -10- (tert-butoxycarbonyl) phenoxazine. Moreover, 2 or more types of compounds can also be used together as needed.

  Among the compounds represented by the general formula (1), 3,7-bis (dimethylamino) -10- (tert-butoxycarbonyl) phenothiazine is particularly preferable because of its high color density when developed. .

  Specific examples of the compound represented by the general formula (2) include, for example, O, O′-di (tert-butoxycarbonyl) indigo white, O, O′-di (tert-butoxycarbonyl) -5. -Bromoindigo white, O, O'-di (tert-butoxycarbonyl) -5,5'-dibromoindigo white, O, O'-di (tert-butoxycarbonyl) -5,5 ', 7-tribromoindigo White, O, O′-di (tert-butoxycarbonyl) -5,5 ′, 7,7′-tetrabromoindigo white, O, O′-di (tert-butoxycarbonyl) -4,4 ′, 5 5 ′, 7,7′-hexabromoindigo white, O, O′-di (tert-butoxycarbonyl) -4,4′-dichloroindigo white, O, O′-di tert-butoxycarbonyl) -4,4 ', 5,5'-tetrachloroindigo white, O, O'-di (tert-butoxycarbonyl) -5,5'-dimethylindigo white, O, O'-di ( tert-butoxycarbonyl) -5,5'-difluoroindigo white, O, O'-di (tert-butoxycarbonyl) -4,4'-dichloro-5,5'-dibromoindigo white, O, O'-di (Tert-butoxycarbonyl) -7,7'-dimethylindigowhite, O, O'-di (tert-butoxycarbonyl) -5,5'-dimethyl-7,7'-dichloroindigowhite, O, O'- Di (tert-butoxycarbonyl) -7,7'-diethylindigo white, O, O'-di (tert-butoxycarbonyl) -6 6'-diethoxyindigo white, O, O'-di (tert-butoxycarbonyl) -6,6'-dimethoxyindigo white, O, O'-di (tert-butoxycarbonyl) -6,6'-diethylmercapto Indigo white, O, O'-di (tert-butoxycarbonyl) thioindigo white, O, O'-di (tert-butoxycarbonyl) -6,6'-dichlorothioindigo white, O, O'-di (tert -Butoxycarbonyl) -7,7'-dichlorothioindigo white, O, O'-di (tert-butoxycarbonyl) -7,7'-diaminothioindigo white, O, O'-di (tert-butoxycarbonyl) -5,5'-dichloro-7,7'-diaminothioindigo white, O, O'-di (tert- Toxicarbonyl) -5,5'-dibromo-6,6'-diaminothioindigo white, O, O'-di (tert-butoxycarbonyl) -5,5'-dibromothioindigo white, O, O'-di (Tert-butoxycarbonyl) -6,6'-diethoxythioindigo white, O, O'-di (tert-butoxycarbonyl) -5,5'-dibromo-6,6'-diethoxythioindigo white, O , O'-di (tert-butoxycarbonyl) -6,6'-diethylmercaptothioindigo white, O, O'-di (tert-butoxycarbonyl) -4-methyl-6,6'-dichlorothioindigo white, O, O'-di (tert-butoxycarbonyl) -4-methyl-6-chloro-6'-methoxythioindigo white, O, '-Di (tert-butoxycarbonyl) -4,4'-dimethyl-6,6'-dichlorothioindigo white, O, O'-di (tert-butoxycarbonyl) -4,4', 7,7'- Tetramethyl-5,5′-dichlorothioindigo white, O, O ′, N, N′-tetra (tert-butoxycarbonyl) indigo white, O, O ′, N, N′-tetra (tert-butoxycarbonyl) -5-bromoindigo white, O, O ', N, N'-tetra (tert-butoxycarbonyl) -5,5'-dibromoindigo white, O, O', N, N'-tetra (tert-butoxycarbonyl) ) -5,5 ', 7-tribromoindigo white, O, O', N, N'-tetra (tert-butoxycarbonyl) -5,5 ', 7,7'-te Labromoindigo white, O, O ′, N, N′-tetra (tert-butoxycarbonyl) -4,4 ′, 5,5 ′, 7,7′-hexabromoindigo white, O, O ′, N, N'-tetra (tert-butoxycarbonyl) -4,4'-dichloroindigo white, O, O ', N, N'-tetra (tert-butoxycarbonyl) -4,4', 5,5'-tetrachloro Indigo white, O, O ′, N, N′-tetra (tert-butoxycarbonyl) -5,5′-dimethylindigo white, O, O ′, N, N′-tetra (tert-butoxycarbonyl) -5 5'-difluoroindigo white, O, O ', N, N'-tetra (tert-butoxycarbonyl) -4,4'-dichloro-5,5'-dibromoindigo white, O, O ', N, N'-tetra (tert-butoxycarbonyl) -7,7'-dimethylindigo white, O, O', N, N'-tetra (tert-butoxycarbonyl) -5,5'-dimethyl- 7,7'-dichloroindigo white, O, O ', N, N'-tetra (tert-butoxycarbonyl) -7,7'-diethylindigo white, O, O', N, N'-tetra (tert- Butoxycarbonyl) -6,6'-diethoxyindigo white, O, O ', N, N'-tetra (tert-butoxycarbonyl) -6,6'-dimethoxyindigo white, O, O', N, N ' -Tetra (tert-butoxycarbonyl) -6,6'-diethylmercaptoindigo white and the like are exemplified, but not limited thereto. Moreover, 2 or more types of compounds can also be used together as needed.

  Among the compounds represented by the general formula (2), O, O′-di (tert-butoxycarbonyl) indigo white and O, O ′, N, N′-tetra (tert-butoxycarbonyl) indigo white, O, O ′, N, N′-tetra (tert-butoxycarbonyl) indigo white is preferably used because of its high color density after color development.

  In the latent image formation and color image formation method according to the present invention, the oxidation coloring dye precursor is encapsulated in a microcapsule and a layer containing the microcapsule is formed on a support (first support). And (1) forming a latent image of the oxidative coloring dye precursor on the first support by pressurizing the microcapsule to release the oxidative coloring dye precursor from the microcapsule, or ( 2) Pressurizing the microcapsule to release the oxidation coloring dye precursor from the microcapsule, and transferring the oxidation coloring dye precursor onto the second support disposed facing the layer containing the microcapsule. By doing so, a latent image is formed. In order to develop the formed latent image, the first support or the second support on which the latent image is formed is heated or irradiated with light to remove the substituent, and the air This is achieved by making it oxidizable with oxygen therein.

As a method of encapsulating the oxidation coloring dye precursor in a microcapsule, a microencapsulation technique applied to a pressure-sensitive recording medium or the like can be used.
In order to form a latent image, the microcapsules can be destroyed under pressure. When forming a latent image on the first support, use an iron brush or a spare sheet such as fine paper. A normal writing instrument such as a ballpoint pen or an impact printer may be used. When a latent image is formed on the second support, an ordinary writing instrument or an impact printer may be used via the first support. That's fine. The information entered on the spare sheet or on the first support can be used as a record.

When the above oxidative coloring dye precursor is heated or irradiated with light and the substituent is released, it is oxidized and visualized (visualized) by oxygen in the air, but the detachment of the substituent is promoted. For this purpose, it is preferable to let an acidic substance act.
Examples of acidic substances include phenolic compounds, novolac-type phenol resins and their polyvalent metal salts, salicylic acid derivatives, and their derivatives that are known as substances that develop electron-donating leuco dyes in heat-sensitive recording bodies and pressure-sensitive recording bodies. Polyvalent metal salts, silicon oxide, active clay minerals containing silicon oxide, and the like can be used.

  Among the above acidic substances, it is desirable to use at least one selected from salicylic acid derivatives and polyvalent metal salts thereof, particularly zinc salt of 3,5-bis (α-methylbenzyl) salicylic acid.

A recording sheet or recording sheet set for use in the latent image forming and developer image forming method according to the present invention will be described below.
The recording sheet or recording sheet set according to the present invention includes at least a sheet provided with a layer containing a microcapsule encapsulating an oxidative coloring dye precursor on a first support.

  Such a recording sheet or recording sheet set can be used as a recording sheet or recording sheet set for forming information as a latent image, or after recording information as a latent image, the latent image is developed to be visible information. It can also be used as a recording sheet or a recording sheet set.

  In the present invention, a layer containing a microcapsule encapsulating an oxidative coloring dye precursor is formed on the first support, and the oxidative coloring dye precursor released by breaking the microcapsule under pressure is released. A sheet used to form a latent image on the first support is referred to as a “recording sheet”. In addition, a layer containing microcapsules encapsulating the oxidative coloring dye precursor is formed on the back surface of the first support, and the oxidative coloring dye precursor released by pressure destruction of the microcapsules A set of at least two sheets that are transferred onto the support and configured to form a latent image on the second support is referred to as a “recording sheet set”.

  As described above, the oxidative coloring dye precursor used in the recording sheet or recording sheet set according to the present invention has a substituent in the molecule which is released by heating or light irradiation, and has this substituent. A compound that can maintain a colorless state without being oxidized by oxygen in the air in a state, and is oxidized by oxygen in the air to become a colored dye when the substituent is removed by heating or light irradiation It is.

  The oxidative coloring dye precursor preferably used in the present invention is a compound that prevents the oxidative coloring mechanism of the oxidative coloring dye by introducing a tertiary alkyloxycarbonyl group as a substituent.

  Specific examples of such preferred oxidative coloring dye precursors include compounds represented by the general formula (1) and compounds represented by the general formula (2), and the general formula (1) and the general formula (1). Specific compounds included in the formula (2) and particularly preferable compounds are also as described above.

  The oxidative coloring dye precursor is applied to a high-boiling hydrophobic medium for the purpose of easily releasing the oxidative coloring dye precursor from the microcapsule when the microcapsule is broken under pressure. Dissolved and encapsulated in microcapsules.

  Examples of the hydrophobic medium include dibasic acid esters such as cottonseed oil, hydrogenated terphenyl, hydrogenated terphenyl derivatives, alkylbiphenyl, alkylnaphthalene, diarylalkane, phenylxylylethane, paraffin, naphthenic oil, and phthalic acid ester. Natural or synthetic hydrophobic media such as, and at least one of these is used.

  The ratio of the oxidative coloring dye precursor and the hydrophobic medium encapsulated in the microcapsule is usually about 100 to 5000 parts by weight of the hydrophobic medium with respect to 100 parts by weight of the oxidative coloring dye precursor. preferable.

  In the present invention, the type of the wall material of the microcapsule is not particularly limited. For example, any of synthetic polymer materials such as aminoaldehyde resin, polyurea resin, polyurethane resin, and polyamide resin, and natural materials such as gelatin can be used. It can also be used.

The aminoaldehyde resin wall membrane capsule is composed of at least one amine such as urea, thiourea, alkylurea, ethyleneurea, acetoguanamine, benzoguanamine, melamine, guanidine, biuret, cyanamide, formaldehyde, acetaldehyde, paraformaldehyde, hexahexa It is produced by an in-situ polymerization method using at least one aldehyde such as methylenetetramine, glutaraldehyde, glyoxal or furfural, or an initial condensate obtained by condensing them.
In this case, an oily liquid obtained by dissolving an oxidative coloring dye precursor in a hydrophobic medium is emulsified and dispersed in an aqueous medium in which a water-soluble polymer such as an ethylene-maleic anhydride copolymer salt is dissolved. After adding a wall film agent to the dispersion and adjusting the pH, the polymerization is carried out by heating under stirring.

Polyurethane resin and polyurea resin wall membrane capsules, for example, interfacial polymerization using polyisocyanate and water, polyisocyanate and polyol, isothiocyanate and water, isothiocyanate and polyol, polyisocyanate and polyamine, isothiocyanate and polyamine, etc. Manufactured by. The polyamide resin wall membrane capsule is manufactured by an interfacial polymerization method such as acid chloride and amine.
In this case, isocyanates and acid chlorides are dissolved in an oily liquid containing an oxidative coloring dye precursor and a hydrophobic medium, and the oily liquid containing these is dissolved in an aqueous medium in which a water-soluble polymer such as polyvinyl alcohol is dissolved. The mixture is emulsified and dispersed, and if necessary, amines are added and heated under stirring to proceed the polymerization.

The gelatin capsule is manufactured by a coacervation method using an amphoteric polymer gelatin and an anionic polymer such as gum arabic or carboxymethylcellulose.
In this case, an oily liquid containing an oxidative coloring dye precursor and a hydrophobic medium is emulsified and dispersed in an aqueous gelatin solution, an anionic polymer such as gum arabic is mixed in the emulsified dispersion, diluted with warm water, pH The coacervation is advanced by adjusting, and after cooling, after curing with formalin or the like, the pH is adjusted to produce microcapsules.

  There is no restriction | limiting in particular about the average particle diameter of a microcapsule, Generally, what is necessary is just to adjust in the range of about 1-30 micrometers.

  In the microcapsules, various known ultraviolet absorbers, antioxidants, and other auxiliaries can be included as required.

The microcapsules encapsulating the specific oxidative coloring dye precursor thus prepared include adhesives such as polyvinyl alcohols, starches, carboxymethylcellulose, and latexes, as well as tilting agents such as pulp powder and raw starch powder. Various auxiliary agents are appropriately blended to prepare a coating liquid for forming a microcapsule-containing layer.
The adhesive is generally blended at a ratio of about 5 to 100 parts by mass with respect to 100 parts by mass of the microcapsules, and the tilting agent is blended at a ratio of about 5 to 150 parts by mass with respect to 100 parts by mass of the microcapsules. .

The recording sheet or recording sheet set according to the present invention includes at least a sheet on which a microcapsule-containing layer is formed by applying and drying the above-described coating liquid for forming a microcapsule-containing layer on a support.
The coating amount of the microcapsule-containing layer forming coating solution in such a sheet is desirably adjusted so that the coating amount of the specific oxidation coloring dye precursor is about 0.02 to 1 g / m ² .

The support used in the recording sheet or recording sheet set of the present invention is not particularly limited, and paper, synthetic paper, film, etc. can be used, but paper is generally used. As such paper, paper produced by blending waste paper pulp as necessary, acid paper making or neutral paper making, and paper having a pigment coating layer formed on the surface of these papers should be used. Can do.
The basis weight of the support is also not particularly limited, and generally about 40 to 400 g / m ² is used.

The coating method of the microcapsule-containing layer-forming coating liquid is not particularly limited, and it is an on-board equipped with a known coating apparatus such as an air knife coater, roll coater, blade coater, rod blade coater, curtain coater, lip coater, etc. A machine or an off-machine coater can be selected as appropriate.
In addition, the microcapsule is separated from the microcapsule dispersion, and a microcapsule ink is prepared by adding a vehicle, an adhesive, an auxiliary agent, and the like. Can also be formed.

As described above, the specific oxidative coloring dye precursor used in the present invention is oxidized by oxygen in the air to develop a visible color (visualized image) when the substituent is removed upon heating or light irradiation treatment. )
However, in order to promote elimination of substituents, it is preferable to configure the recording sheet or recording sheet set so that the oxidative coloring dye precursor released from the microcapsules can come into contact with the acidic substance.

  As such a configuration, a single layer containing microcapsules and an acidic substance is formed on the same surface of a support (first support), a layer containing microcapsules and a layer containing an acidic substance. In addition to the structure in which the support (first support) is laminated on the same surface, a layer containing microcapsules is formed on the back surface of the first support, and the surface of the second support contains an acidic substance. There is a configuration in which layers are formed so that the microcapsule-containing layer and the acidic substance-containing layer are opposed to each other.

Examples of the acidic substance include phenolic compounds, novolak type phenol resins and their polyvalent metal salts, salicylic acid derivatives and their polyvalent metal salts, silicon oxide and active clay minerals containing silicon oxide.
Specific examples of the phenolic compound include, for example, bisphenol A, 4-hydroxy-4'-isopropoxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfone, bis (3-allyl- 4-hydroxyphenyl) sulfone and the like can be exemplified.

  As the novolak-type phenol resin, phenolic raw materials for phenol resin include, for example, unsubstituted phenol, alkyl group-substituted phenol (eg, cresol, ethylphenol, butylphenol, octylphenol, nonylphenol, etc., mainly para-substituted products), aralkyl group-substituted phenol (Examples: para-benzylphenol, para-cumylphenol, etc.), those using aryl group-substituted phenols (example: para-phenylphenol) and the like.

  Examples of the salicylic acid derivative include 3-phenylsalicylic acid, 5-phenylsalicylic acid, 3-benzylsalicylic acid, 5-benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 5- (α-methylbenzyl) salicylic acid, 3- ( α, α-dimethylbenzyl) salicylic acid, 5- (α, α-dimethylbenzyl) salicylic acid, 3,5-diphenylsalicylic acid, 3,5-dibenzylsalicylic acid, 3,5-di (α-methylbenzyl) salicylic acid, 3 , 5-di (α, α-dimethylbenzyl) salicylic acid, 3,5-di (4-methylbenzyl) salicylic acid, benzylated styrenated salicylic acid, pinenated salicylic acid and the like.

  Specific examples of polyvalent metals that form salts with novolac-type phenolic resins and salicylic acid derivatives include magnesium, calcium, zinc, aluminum, iron, cobalt, nickel, etc. Among these, color development reaction Zinc is most preferably used because of the vividness of the color developed in (1).

  Examples of the active clay mineral containing silicon oxide include clay minerals such as activated clay, attapulgite, zeolite and bentonite. Here, the activated clay indicates acid clay activated by acid treatment.

Among the above acidic substances, the salicylic acid derivative and the polyvalent metal salt thereof stably maintain the latent image as the latent image until the color development processing is performed even if it is in contact with the formed latent image. It is preferably used because it is excellent in light resistance of the latent image.
Among salicylic acid derivatives and polyvalent metal salts thereof, 3,5-bis (α-methylbenzyl) salicylic acid zinc salt is more preferably used because it is particularly excellent in the above properties.
The salicylic acid derivative and its polyvalent metal salt can be used by solidifying the solid into fine particles by means such as wet pulverization, or by heating and melting or dissolving in an organic solvent in advance in the form of a fine emulsion in an aqueous medium. You can also

  The coating liquid containing the acidic substance is usually prepared by a method of dispersing the acidic substance and the adhesive in water. Examples of the adhesive include starch, casein, gum arabic, carboxymethyl cellulose, polyvinyl alcohol, styrene / butadiene copolymer latex, vinyl acetate latex and the like. In addition, the coating liquid contains inorganic pigments such as kaolin, zinc oxide, magnesium sulfate, titanium oxide, aluminum hydroxide, calcium carbonate, magnesium sulfate, magnesium oxide, and calcium sulfate, antifoaming agents, and UV absorption as necessary. Various auxiliary agents such as an agent, an antioxidant, a fluidity modifier, and a water retention agent can be added as appropriate.

  The usage-amount of an adhesive agent is mix | blended in the ratio of about 10-300 mass parts with respect to 100 mass parts of acidic substances. Moreover, it is preferable that the usage-amount in the case of mix | blending a pigment shall be about 1000 mass parts or less with respect to 100 mass parts of acidic substances.

The dry coating amount of the coating liquid containing an acidic substance is desirably adjusted so that the acidic substance is about 0.2 to 20 g / m ² .

  Among the sheets constituting the recording sheet set of the present invention, as a support (second support) for forming a layer containing an acidic substance, a microcapsule containing a specific oxidation coloring dye precursor is included. It can be used by appropriately selecting from those exemplified as the support (first support) for forming the layer to be contained. In this case, a support different from the first support can be used, or a support having a different basis weight can be used.

As a coating method for forming a layer containing an acidic substance, the same method as the coating method for forming a layer containing a microcapsule can be adopted, and it may be selected appropriately from these methods.
In addition, an ink layer containing an acidic substance can be formed on the entire surface or a part of the second support by a printing method using an ink containing an acidic substance and a vehicle, an adhesive, an auxiliary agent, and the like.

  The sheet on which the layer containing the acidic substance is formed may be subjected to a smoothing treatment with a super calendar or the like, if necessary.

  The recording sheet set according to the present invention includes at least a first sheet in which a layer containing a microcapsule encapsulating an oxidative coloring dye precursor is formed on the back surface, and an oxidative coloring type released by pressure destruction of the microcapsule. A second sheet for receiving the dye precursor is required. Further, the second sheet having a layer containing microcapsules encapsulating the oxidative coloring dye precursor on the back surface between the first sheet and the second sheet. Three sheets can be added to form a recording sheet set. Further, the third sheet may be a plurality of two or more sheets. And it is as above-mentioned that it is preferable that the layer containing an acidic substance is formed in the surface of these 2nd, 3rd sheets.

  Further, when the recording sheet set of the present invention is configured as a set of three or more sheets as described above, the specific oxidation color development so that a latent image can be formed between any two sheets of the sheet set. A type dye precursor is used, and a normal dye precursor (electron-donating leuco dye) can be used between other sheets so that a visible image can be obtained.

  Various character information, designs, advertisements, and the like can be printed on the recording sheet and the recording sheet set of the present invention. If necessary, a tint block print can be applied to a portion where a latent image of secret information is formed.

  In the present invention, when a latent image is formed on a recording sheet consisting of a single sheet, an iron writing brush is used, or a normal writing instrument such as a ballpoint pen or an impact printer through a spare sheet such as fine paper. Can be used to form a latent image by pressure-breaking the microcapsule and releasing the oxidized coloring dye precursor from the microcapsule. In addition, when forming a latent image on a recording sheet set composed of two or more sheets, a normal writing instrument such as a ballpoint pen or an impact printer is used from above the sheet set to break the microcapsule under pressure, A latent image can be formed by transferring the oxidative coloring dye precursor to the second sheet. Information written with a writing instrument or the like on the spare sheet or the top sheet of the recording sheet set can be used as a record.

In the latent image forming method and the developed color image forming method, and the recording sheet or the recording sheet set according to the present invention, in order to develop the latent image formed (visualize), the latent image is formed as described above. It is necessary to heat or irradiate the formed sheet.
Such heat treatment may be performed at a temperature range of 80 to 300 ° C. for about 1 to 100 seconds. As a heat treatment method, a latent image is formed by using a device in which a nip is constituted by a metal roll and an elastic roll heated to a surface temperature of about 100 to 200 ° C., and at least one of the rolls is motor-driven. There is a method of drawing a sheet between nips, and this method is suitable when a large amount of latent image development processing is performed.

Moreover, what is necessary is just to process about 1 to 100 second as a light irradiation process with the lamp | ramp which emits an ultraviolet-ray (output: 1-10000 watts). As a light irradiation treatment method, one or more such lamps are disposed, and an apparatus having means for conveying a sheet on which a latent image is formed is used. There is a method of processing. Such a device can be provided with a hood so that light does not leak outside.
Of the color development methods, color development by heat treatment is preferable in terms of energy efficiency.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Further, “parts” and “%” in the examples represent parts by mass and mass%, respectively, unless otherwise specified.
Further, in the following examples and comparative examples, a sheet having a layer containing a microcapsule enclosing a dye precursor on the back is indicated as “upper sheet”, and a sheet having a layer containing an acidic substance on the surface is provided. “Lower sheet” is displayed.

Example 1
(Preparation of coating solution for acidic substance layer)
20 parts of zinc salt of 3,5-bis (α-methylbenzyl) salicylic acid, 80 parts of kaolin, 20 parts of carboxy-modified styrene-butadiene copolymer latex (solid content), 1 part of sodium carboxymethylcellulose and 200 parts of water were mixed. Then, an acidic substance layer coating solution was prepared.

[Manufacture of lower sheet]
The acidic substance layer coating solution obtained above was coated on an 157 g / m ² high-quality paper with an air knife coater so that the dry weight was 5 g / m ^2, and a supercalender treatment was performed to prepare a lower sheet. .

[Preparation of microcapsule dispersion A]
In a stirring and mixing container equipped with a heating device, 150 parts of a 3% aqueous solution of polyvinyl alcohol (trade name: PVA-217EE, manufactured by Kuraray Co., Ltd.) was added to obtain an aqueous medium for capsule production.
Separately, 100 parts of a hydrophobic medium mainly composed of phenylxylylethane (trade name: Nisseki Hysol SAS 296, manufactured by Shin Nippon Oil Co., Ltd.) and 3,7-bis (dimethylamino)- 10 parts of 10- (tert-butoxycarbonyl) phenothiazine and 2 parts of 2- (2'-hydroxy-5'-methylphenyl) benzotriazole as UV absorber are dissolved in polymer MDI (trade name: 44V-20, Sumika) An oily liquid obtained by dissolving 3 parts of Bayer Urethane Co., Ltd. and 5 parts of hexamethylene diisocyanate trimer having a burette bond (trade name: N-3200, manufactured by Sumika Bayer Urethane Co., Ltd.) The mixture was dispersed in an aqueous medium at 7000 rpm for 1 minute using a homomixer to obtain an emulsified dispersion.
After adding 1 part of diethylenetriamine to this emulsified dispersion and stirring for 30 minutes at room temperature, the temperature of the system was raised to 70 ° C. and allowed to react for 3 hours while continuing stirring, then the temperature was lowered to room temperature and the average particle size was reduced. Was prepared. A microcapsule dispersion A comprising a polyurea resin / polyurethane resin wall membrane having an average film thickness of 0.15 μm was prepared.

[Preparation of microcapsule-containing layer coating solution A]
To 100 parts (solid content) of the microcapsule dispersion A obtained above, 70 parts of wheat starch powder and 20 parts of oxidized starch aqueous solution (solid content) were added to prepare a coating liquid A for a microcapsule-containing layer.

[Manufacture of upper sheet]
The microcapsule-containing layer-forming coating solution A obtained above was applied onto a fine paper of 40 g / m ² and dried with an air knife coater so that the dry weight was 4 g / m ² to obtain an upper sheet.

[Preparation of recording sheet set]
On the lower sheet obtained above, the upper sheet obtained above was overlapped so that the acidic substance-containing layer and the microcapsule-containing layer faced to obtain a recording sheet set.

Examples 2-13
In the preparation of the microcapsule dispersion A of Example 1, the following compound was used as the oxidative coloring dye precursor instead of 3,7-bis (dimethylamino) -10- (tert-butoxycarbonyl) phenothiazine. Except for the above, 12 types of microcapsule dispersions were prepared in the same manner as in Example 1, and an upper sheet was produced in the same manner as in Example 1 except that these microcapsule dispersions were used. Got a set.
In addition, each average particle diameter and average film thickness of each prepared microcapsule were the range of 5.2-5.9 micrometers and 0.15-0.20 micrometer, respectively.

Example 2: 2-methyl-3-amino-7-diethylamino-10- (tert-butoxycarbonyl) phenoxazine Example 3: 3,7-bis (dimethylamino) -4-nitro-10- (tert -Butoxycarbonyl) phenothiazine. Example 4: 3,7-bis (diethylamino) -10- (tert-butoxycarbonyl) phenoxazine. Example 5: 3,7-bis (dimethylamino) -1,9-dimethyl- 10- (tert-butoxycarbonyl) phenothiazine, Example 6: 9-dimethylaminobenzo (a) -12- (tert-butoxycarbonyl) phenoxazine, Example 7: 2,8-dimethyl-3,7-bis ( Ethylamino) -10- (tert-butoxycarbonyl) phenothiazine. Example 8: 3,7-bis (dimethyl) Amino) -10- (tert-pentyloxycarbonyl) phenothiazine, Example 9: 2-Methyl-3-amino-7- (dimethylamino) -10- (tert-butoxycarbonyl) phenothiazine, Example 10: 3- ( 4-Dimethylaminophenylazo) -7-diethylamino-5-phenyl-10- (tert-butoxycarbonyl) phenazine, Example 11: 3,7- (bisphenylmethylamino) -10- (tert-butoxycarbonyl) phenothiazine Example 12: 3,7-bis (diphenylamino) -10- (tert-butoxycarbonyl) phenothiazine Example 13: 3,7-bis (phenylethylamino) -10- (tert-butoxycarbonyl) phenoxazine

Example 14
In the production of the upper sheet of Example 1, the upper sheet was produced in the same manner as in Example 1 except that the microcapsule dispersion B prepared by the following method was used to obtain a recording sheet set.
[Preparation of microcapsule dispersion B]
In a stirring and mixing vessel equipped with a heating apparatus, 200 parts of a 3% aqueous solution of an ethylene-maleic anhydride copolymer (trade name: EMA31, manufactured by Monsanto) was charged, and then a 20% aqueous sodium hydroxide solution was added dropwise to adjust the pH to 6 Was adjusted to 0.0 to obtain an aqueous medium for capsule production.
Separately, a hydrophobic medium mainly composed of phenylxylylethane (trade name: Nisseki Hysol SAS 296, manufactured by Shin Nippon Oil Co., Ltd.) and 3,7-bis (dimethylamino) -10- as an oxidative coloring dye precursor. An oily liquid was obtained by dissolving 10 parts of (tert-butoxycarbonyl) phenothiazine and 2 parts of 2- (2'-hydroxy-5'-methylphenyl) benzotriazole as an ultraviolet absorber.
Next, this oily liquid was charged into the above-mentioned capsule-producing aqueous medium, and emulsified and dispersed for 1 minute at 10,000 rotations per minute using a homomixer, and then heated to 55 ° C.
A prepolymer aqueous solution obtained by adding 15 parts of melamine to 45 parts of an aqueous 37% formaldehyde solution and reacting at 60 ° C. for 15 minutes is added dropwise to the emulsion and further stirred, and then the pH is adjusted to 5 with 0.1 N hydrochloric acid. After the temperature was raised to 80 ° C., the temperature was kept at that temperature for 1 hour, the pH was lowered to 3.5 with 0.2N hydrochloric acid, and the temperature was further kept for 3 hours. A microcapsule dispersion B comprising an aminoaldehyde resin film having an average film thickness of 3 μm and an average film thickness of 0.15 μm was prepared.

Example 15
In the production of the upper sheet of Example 1, the upper sheet was produced in the same manner as in Example 1 except that the microcapsule dispersion C prepared by the following method was used to obtain a recording sheet set.
[Preparation of microcapsule dispersion C]
100 parts of a hydrophobic medium mainly composed of phenylxylylethane (trade name: Nisseki Hysol SAS 296, manufactured by Nippon Oil Corporation) and 3,7-bis (dimethylamino) -10- as an oxidative coloring dye precursor An oily liquid was obtained by dissolving 10 parts of (tert-butoxycarbonyl) phenothiazine and 2 parts of 2- (2'-hydroxy-5'-methylphenyl) benzotriazole as an ultraviolet absorber.
Separately, 25 parts of pigskin gelatin having an isoelectric point of 8 and 25 parts of gum arabic as an encapsulating agent were dissolved in 300 parts of warm water (50 ° C.). The oily liquid obtained above was added to this gelatin-gum arabic mixed solution with stirring and emulsified and dispersed.
The emulsion is further diluted with 1000 parts of warm water, acetic acid is gradually added to adjust the pH of the solution to 4 to 4.3, and a sol formed by depositing an encapsulating agent around the oil droplets. Obtained capsules. The capsule was cooled to about 10 ° C. and 10 parts of a 25% aqueous solution of glutaraldehyde was added to harden the capsule. Gelatin-based wall microcapsules having an average particle diameter of 6.2 μm and an average film thickness of 0.37 μm Dispersion C was prepared.

Example 16
In the preparation of the coating solution for the acidic substance layer of Example 1, instead of 20 parts of zinc salt of 3,5-bis (α-methylbenzyl) salicylic acid and 80 parts of kaolin, activated clay (silicon oxide content 72%) 100 A coating solution for an acidic substance layer was prepared in the same manner as in Example 1 except that the coating part was used, and a lower sheet was produced in the same manner as in Example 1 except that this coating solution was used. Obtained.

Comparative Example 1
In the preparation of the microcapsule dispersion A of Example 1, 3,3-bis (p-dimethylamino) was used as a dye precursor instead of 3,7-bis (dimethylamino) -10- (tert-butoxycarbonyl) phenothiazine. A dispersion A of microcapsules having an average particle diameter of 5.7 μm and an average film thickness of 0.17 μm was prepared in the same manner as in Example 1 except that 10 parts of (phenyl) -6-dimethylaminophthalide was used. An upper sheet was produced in the same manner as in Example 1 except that this microcapsule dispersion A was used to obtain a recording sheet set.

Comparative Example 2
In the preparation of the microcapsule dispersion A of Example 1, 10 parts of benzoylleucomethylene blue was used as the dye precursor instead of 3,7-bis (dimethylamino) -10- (tert-butoxycarbonyl) phenothiazine. As in Example 1, a microcapsule dispersion A having an average particle size of 5.5 μm and an average film thickness of 0.16 μm was prepared, and this microcapsule dispersion A was used. Thus, an upper sheet was produced to obtain a recording sheet set.

Example 17
In the production of the upper sheet of Example 1, the upper sheet was produced in the same manner as in Example 1 except that the microcapsule dispersion D prepared by the following method was used to obtain a recording sheet set.
[Preparation of microcapsule dispersion D]
In a stirring and mixing container equipped with a heating device, 150 parts of a 3% aqueous solution of polyvinyl alcohol (trade name: PVA-217EE, manufactured by Kuraray Co., Ltd.) was added to obtain an aqueous medium for capsule production.
Separately, 100 parts of a hydrophobic medium mainly composed of phenylxylylethane (trade name: Nisseki Hyzol SAS296, manufactured by Nippon Oil Corporation) and O, O'-di (tert-butoxycarbonyl) indigo as a dye precursor 5 parts of white, 2 parts of 2- (2'-hydroxy-5'-methylphenyl) benzotriazole as UV absorber, 3 parts of polymeric MDI (trade name: 44V-20, manufactured by Sumitomo Bayer Urethane Co., Ltd.) and burette Using a homomixer, an oily liquid obtained by dissolving 5 parts of a hexamethylene diisocyanate trimer (trade name: N-3200, manufactured by Sumitomo Bayer Urethane Co., Ltd.) having a bond in the aqueous medium for capsule production was used. An emulsified dispersion was obtained by dispersing for 1 minute at 7000 rpm.
After adding 1 part of diethylenetriamine to this emulsified dispersion and stirring for 30 minutes at room temperature, the temperature of the system was raised to 70 ° C. and allowed to react for 3 hours while continuing stirring, then the temperature was lowered to room temperature and the average particle size was reduced. Was prepared. A microcapsule dispersion D comprising a polyurea resin / polyurethane resin wall film having a thickness of 5.5 μm and an average film thickness of 0.15 μm was prepared.

Examples 18-22
In the preparation of the microcapsule dispersion D of Example 17, Example 17 was used except that the following compound was used in place of O, O′-di (tert-butoxycarbonyl) indigo white as the oxidative coloring dye precursor. Five types of microcapsule dispersions were prepared in the same manner as described above, and an upper sheet was produced in the same manner as in Example 17 except that these microcapsule dispersions were used to obtain five types of recording sheet sets.
In addition, each average particle diameter and average film thickness of each prepared microcapsule were the range of 5.2-5.9 micrometers and 0.15-0.20 micrometer, respectively.

Example 18: O, O′-di (tert-butoxycarbonyl) -5,5 ′, 7,7′-tetrabromoindigo white Example 19: O, O′-di (tert-butoxycarbonyl) thio Indigo white Example 20: O, O'-di (tert-butoxycarbonyl) -4,4'-dimethyl-6,6'-dichlorothioindigo whiteExample 21: O, O'-di (tert- Butoxycarbonyl) -4,4 ′, 7,7′-tetramethyl-5,5′-dichlorothioindigo white Example 22: O, O ′, N, N′-tetra (tert-butoxycarbonyl) indigo white

Example 23
In the production of the upper sheet of Example 17, the upper sheet was produced in the same manner as in Example 17 except that the microcapsule dispersion E prepared by the following method was used to obtain a recording sheet set.
[Preparation of microcapsule dispersion E]
In a stirring and mixing vessel equipped with a heating apparatus, 200 parts of a 3% aqueous solution of an ethylene-maleic anhydride copolymer (trade name: EMA31, manufactured by Monsanto) was charged, and then a 20% aqueous sodium hydroxide solution was added dropwise to adjust the pH to 6 Was adjusted to 0.0 to obtain an aqueous medium for capsule production.
Separately, a hydrophobic medium mainly composed of phenylxylylethane (trade name: Nisseki Hysol SAS 296, manufactured by Nippon Oil Corporation) and O, O'-di (tert-butoxycarbonyl) indigo white 5 as a dye precursor Part of 2- (2′-hydroxy-5′-methylphenyl) benzotriazole as an ultraviolet absorber was dissolved to obtain an oily liquid.
Next, this oily liquid was charged into the above-mentioned capsule-producing aqueous medium, and emulsified and dispersed for 1 minute at 10,000 rotations per minute using a homomixer, and then heated to 55 ° C.
A prepolymer aqueous solution obtained by adding 15 parts of melamine to 45 parts of a 37% formaldehyde aqueous solution and reacting at 60 ° C. for 15 minutes is dropped into the emulsion and further stirred, and then the pH is adjusted to 5. with 0.1N hydrochloric acid. 3 and then heated to 80 ° C., kept at that temperature for 1 hour, then lowered to pH 3.5 with 0.2N hydrochloric acid, further kept for 3 hours, and then allowed to cool to an average particle size of 5 A dispersion E of microcapsules composed of an aminoaldehyde resin film having a thickness of 0.4 μm and an average film thickness of 0.15 μm was prepared.

Example 24
In the production of the upper sheet of Example 17, the upper sheet was produced in the same manner as in Example 17 except that the microcapsule dispersion F prepared by the following method was used to obtain a recording sheet set.
[Preparation of microcapsule dispersion F]
100 parts of a hydrophobic medium mainly composed of phenylxylylethane (trade name: Nisseki Hysol SAS 296, manufactured by Nippon Oil Corporation) and O, O'-di (tert-butoxycarbonyl) indigo white 5 as a dye precursor Part of 2- (2′-hydroxy-5′-methylphenyl) benzotriazole as an ultraviolet absorber was dissolved to obtain an oily liquid.
Separately, 25 parts of pigskin gelatin having an isoelectric point of 8 and 25 parts of gum arabic as an encapsulating agent were dissolved in 300 parts of warm water (50 ° C.). The oily liquid obtained above was added to this gelatin-gum arabic mixed solution with stirring and emulsified and dispersed.
The emulsion is further diluted with 1000 parts of warm water, acetic acid is gradually added to adjust the pH of the solution to 4 to 4.3, and a sol formed by depositing an encapsulating agent around the oil droplets. Obtained capsules. The capsule was cooled to about 10 ° C. and 10 parts of a 25% aqueous solution of glutaraldehyde was added to harden the capsule. The gelatin-based wall membrane capsule having an average particle size of 6.2 μm and an average film thickness of 0.37 μm Dispersion F was prepared.

Example 25
In the recording sheet set of Example 17, the recording sheet set was obtained in the same manner as in Example 17 except that the lower sheet manufactured in the same manner as in Example 16 was used.

Comparative Example 3
In the preparation of the microcapsule dispersion D of Example 17, 3,3-bis (p-dimethylaminophenyl) -6 was used as a dye precursor instead of O, O'-di (tert-butoxycarbonyl) indigo white. -A microcapsule dispersion having an average particle size of 5.7 µm and an average film thickness of 0.16 µm was prepared in the same manner as in Example 17 except that 5 parts of dimethylaminophthalide was used. An upper sheet was produced in the same manner as in Example 17 except that the liquid was used to obtain a recording sheet set.

Comparative Example 4
In the preparation of the microcapsule dispersion D of Example 17, Example 17 was used except that 5 parts of benzoylleucomethylene blue was used as the dye precursor instead of O, O′-di (tert-butoxycarbonyl) indigo white. In the same manner as in Example 17, except that a microcapsule dispersion having an average particle diameter of 5.5 μm and an average film thickness of 0.16 μm was prepared and this microcapsule dispersion was used. A sheet was manufactured to obtain a recording sheet set.

The recording sheet set thus obtained was subjected to the following performance comparison test, and the results are shown in Table 1.
[Concealment test]
After printing each recording sheet set with a typewriter, the density of the image (latent image) formed on the lower sheet is measured with a Macbeth densitometer (Macbeth RD-914) using a visual filter. The degree of concealment was evaluated.

[Light resistance of latent image]
The lower sheet on which the latent image obtained above was formed was exposed to direct sunlight for 2 hours with the acidic substance-containing layer as the front, and then the density of the latent image was measured with a Macbeth densitometer. Evaluated.

[Color density after color development]
After printing each recording sheet set with a typewriter, each lower sheet is heat-treated at a temperature of 170 ° C. for 1 second to develop a latent image, and the color density of the obtained developed image is stored in a Macbeth densitometer. The color density after the color development treatment was evaluated.

[Light resistance of developed images]
After the above-described sheet for color development after exposure was exposed to direct sunlight for 8 hours with the acidic substance-containing layer as the front, the color density was measured with a Macbeth densitometer to evaluate the light fastness of the developed image. did.

[Plasticizer resistance of developed images]
Overlay the vinyl chloride film so that the acidic substance-containing layer and the vinyl chloride film are in contact with the lower sheet after the color development treatment obtained above, and let stand at 25 ° C for 7 days, then measure the color density with a Macbeth densitometer. The plasticizer resistance of the developed image was evaluated.

  As is apparent from the results in Table 1, the recording sheet set of the present invention in which a specific oxidation coloring dye precursor is encapsulated in a microcapsule has an extremely low latent image density and has a sufficient concealing property. In addition, those using a salicylic acid derivative as an acidic substance are excellent in light resistance of latent images, and in addition, the developed image after color development is excellent in color density and fastness, and it is a secret method by a simple method. Information can be made invisible and visible, and can be applied as a system to replace concealment labels.

Claims (18)

Forming a layer containing a microcapsule encapsulating an oxidative coloring dye precursor having in its molecule a substituent capable of leaving by heating or light irradiation on the first support;
(1) Pressurizing the microcapsule to release the oxidative coloring dye precursor from the microcapsule to form a latent image on the first support, or
(2) Pressurizing the microcapsule to release the oxidation coloring dye precursor from the microcapsule and transferring it onto the second support disposed opposite the microcapsule-containing layer, After forming the latent image on the support,
A latent image forming method and a developed color image forming method characterized in that a formed latent image is heated or irradiated with light to release a substituent to develop a color.   The latent image formation and color image formation method according to claim 1, wherein the substituent that is released by heating or light irradiation is a tertiary alkyloxycarbonyl group. The method for forming a latent image and a color image according to claim 1 or 2, wherein the oxidative coloring dye precursor is a compound represented by the following general formula (1) or a compound represented by the general formula (2). .

[In General Formula (1), X represents an oxygen atom, a sulfur atom or NR ₁₀ , and R ₁ represents a tertiary alkyl group having 4 to 10 carbon atoms. R ₂ , R ₅ , R ₆ and R ₉ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an aryl group, a nitro group or an arylazo group. To express. R ₃ , R ₄ , R ₇ and R ₈ are independently of each other NR ₁₁ R ₁₂ , a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and an aryl group. Represents a nitro group or an arylazo group. R ₁₁ and R ₁₂ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an aryl group, or COOR ₁ . R ₁₀ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group, or COOR ₁ . R ₂ and R ₃ , R ₃ and R ₄ , R ₄ and R ₅ , R ₆ and R ₇ , R ₇ and R _8, and R ₈ and R ₉ are bonded to each other and bonded to each other. An aromatic ring may be formed. In the general formula (2), Y ₁ and Y ₂ each independently represent a sulfur atom or NR ₃₁ , but Y ₁ and Y ₂ may be bonded in the form of N—A—N. Here, R ₃₁ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, COR ₃₂ or COOR ₃₃ , A represents a saturated or unsaturated alkylene group having 1 to 10 carbon atoms, and R ₃₂ and R ₃₃ represent Independently of each other, it represents an alkyl group having 1 to 12 carbon atoms; a benzyl group; an aryl group optionally substituted by a halogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. R ₂₁ and R ₂₂ each independently represent a tertiary alkyl group having 4 to 12 carbon atoms. R _{23 to} R ₃₀ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a nitro group, NR ₃₄ R ₃₅ or SR ₃₆ . Here, R ₃₄ and R ₃₅ are each independently a hydrogen atom; an alkyl group having 1 to 12 carbon atoms; a cycloalkyl group having 4 to 12 carbon atoms; a halogen atom, an alkyl group having 1 to 6 carbon atoms; An aralkyl group which may be substituted with an alkoxy group having ˜6; a halogen atom, an alkyl group having 1 to 6 carbon atoms, an aryl group which may be substituted with an alkoxy group having 1 to 6 carbon atoms; ₃₄ and R ₃₅ may form a pyrrolidino group, piperidino group or hexamethyleneimino group together with the adjacent nitrogen atom. R ₃₆ represents an alkyl group having 1 to 10 carbon atoms. R ₂₃ and R ₂₄ , R ₂₄ and R ₂₅ , R ₂₅ and R ₂₆ , R ₂₇ and R ₂₈ , R ₂₈ and R _29, and R ₂₉ and R ₃₀ may form a benzene ring independently of each other. Good. ]   The oxidative coloring dye precursor is 3,7-bis (dimethylamino) -10- (tert-butoxycarbonyl) phenothiazine, 2-methyl-3-amino-7-diethylamino-10- (tert-butoxycarbonyl) phenoxy. Sazine, 3,7-bis (dimethylamino) -4-nitro-10- (tert-butoxycarbonyl) phenothiazine, 3,7-bis (diethylamino) -10- (tert-butoxycarbonyl) phenoxazine, 3,7- Bis (dimethylamino) -1,9-dimethyl-10- (tert-butoxycarbonyl) phenothiazine, 9-dimethylaminobenzo (a) -12- (tert-butoxycarbonyl) phenoxazine, 2,8-dimethyl-3, 7-bis (ethylamino) -10- (tert-butoxycarbo Phenothiazine, 3,7-bis (dimethylamino) -10- (tert-pentyloxycarbonyl) phenothiazine, 2-methyl-3-amino-7- (dimethylamino) -10- (tert-butoxycarbonyl) phenothiazine, 3- (4-Dimethylaminophenylazo) -7-diethylamino-5-phenyl-10- (tert-butoxycarbonyl) phenazine, 5-amino-9-diethylaminobenzo (a) -12- (tert-butoxycarbonyl) phenoxy Sazine, 3,7-bis (phenylmethylamino) -10- (tert-butoxycarbonyl) phenothiazine, 3,7-bis (phenylethylamino) -10- (tert-butoxycarbonyl) phenothiazine, 3,7-bis ( Diphenylamino) -10- (t rt-butoxycarbonyl) phenothiazine, 3,7-bis (phenylmethylamino) -10- (tert-butoxycarbonyl) phenoxazine, 3,7-bis (phenylethylamino) -10- (tert-butoxycarbonyl) phenoxazine And 3,7-bis (diphenylamino) -10- (tert-butoxycarbonyl) phenoxazine, O, O'-di (tert-butoxycarbonyl) indigo white, O, O'-di (tert-butoxycarbonyl)- 5,5 ′, 7,7′-tetrabromoindigo white, O, O′-di (tert-butoxycarbonyl) thioindigo white, O, O′-di (tert-butoxycarbonyl) -4,4′-dimethyl -6,6'-dichlorothioindigo white, O, O'-di (te rt-butoxycarbonyl) -4,4 ', 7,7'-tetramethyl-5,5'-dichlorothioindigo white, O, O', N, N'-tetra (tert-butoxycarbonyl) indigo white The latent image formation and developed image formation method according to any one of claims 1 to 3, wherein the latent image formation method and the developed color image formation method are at least one selected from the group.   The oxidative coloring dye precursor is 3,7-bis (dimethylamino) -10- (tert-butoxycarbonyl) phenothiazine, O, O′-di (tert-butoxycarbonyl) indigo white, O, O ′, N 5. The latent image formation and color image formation method according to claim 4, which is at least one selected from the group consisting of N, N′-tetra (tert-butoxycarbonyl) indigo white.   6. The latent image formation and color image formation method according to claim 1, wherein an acidic substance is allowed to act upon heating or light irradiation.   The latent image formation and color image formation method according to claim 6, wherein the acidic substance is at least one selected from the group consisting of a salicylic acid derivative and a polyvalent metal salt thereof.   The latent image formation and color image formation method according to claim 7, wherein the acidic substance is a zinc salt of 3,5-bis (α-methylbenzyl) salicylic acid.   A recording sheet or recording sheet set for forming information as a latent image, wherein the recording sheet or recording sheet set has at least a substituent in the molecule that is eliminated by heating or light irradiation. A recording sheet or a recording sheet set, comprising a sheet provided with a layer containing microcapsules encapsulating the first support on a first support.   A recording sheet or recording sheet set for recording information as a latent image and then developing the latent image into visible information, wherein the recording sheet or recording sheet set is detached at least by heating or light irradiation. A recording sheet or a recording sheet set comprising a sheet provided on a first support with a layer containing a microcapsule encapsulating an oxidative coloring dye precursor having a substituent in the molecule.   The recording sheet or recording sheet set according to claim 9 or 10, wherein the substituent that is released by heating or light irradiation is a tertiary alkyloxycarbonyl group. The recording sheet or recording according to any one of claims 9 to 11, wherein the oxidative coloring dye precursor is a compound represented by the following general formula (1) or a compound represented by the general formula (2). Sheet set.

[In General Formula (1), X represents an oxygen atom, a sulfur atom or NR ₁₀ , and R ₁ represents a tertiary alkyl group having 4 to 10 carbon atoms. R ₂ , R ₅ , R ₆ and R ₉ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an aryl group, a nitro group or an arylazo group. To express. R ₃ , R ₄ , R ₇ and R ₈ are independently of each other NR ₁₁ R ₁₂ , a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and an aryl group. Represents a nitro group or an arylazo group. R ₁₁ and R ₁₂ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an aryl group, or COOR ₁ . R ₁₀ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group, or COOR ₁ . R ₂ and R ₃ , R ₃ and R ₄ , R ₄ and R ₅ , R ₆ and R ₇ , R ₇ and R _8, and R ₈ and R ₉ are bonded to each other and bonded to each other. An aromatic ring may be formed. In the general formula (2), Y ₁ and Y ₂ each independently represent a sulfur atom or NR ₃₁ , but Y ₁ and Y ₂ may be bonded in the form of N—A—N. Here, R ₃₁ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, COR ₃₂ or COOR ₃₃ , A represents a saturated or unsaturated alkylene group having 1 to 10 carbon atoms, and R ₃₂ and R ₃₃ represent Independently of each other, it represents an alkyl group having 1 to 12 carbon atoms; a benzyl group; an aryl group optionally substituted by a halogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. R ₂₁ and R ₂₂ each independently represent a tertiary alkyl group having 4 to 12 carbon atoms. R _{23 to} R ₃₀ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a nitro group, NR ₃₄ R ₃₅ or SR ₃₆ . Here, R ₃₄ and R ₃₅ are each independently a hydrogen atom; an alkyl group having 1 to 12 carbon atoms; a cycloalkyl group having 4 to 12 carbon atoms; a halogen atom, an alkyl group having 1 to 6 carbon atoms; An aralkyl group which may be substituted with an alkoxy group having ˜6; a halogen atom, an alkyl group having 1 to 6 carbon atoms, an aryl group which may be substituted with an alkoxy group having 1 to 6 carbon atoms; ₃₄ and R ₃₅ may form a pyrrolidino group, piperidino group or hexamethyleneimino group together with the adjacent nitrogen atom. R ₃₆ represents an alkyl group having 1 to 10 carbon atoms. R ₂₃ and R ₂₄ , R ₂₄ and R ₂₅ , R ₂₅ and R ₂₆ , R ₂₇ and R ₂₈ , R ₂₈ and R _29, and R ₂₉ and R ₃₀ may form a benzene ring independently of each other. Good. ]   The oxidative coloring dye precursor is 3,7-bis (dimethylamino) -10- (tert-butoxycarbonyl) phenothiazine, 2-methyl-3-amino-7-diethylamino-10- (tert-butoxycarbonyl) phenoxy. Sazine, 3,7-bis (dimethylamino) -4-nitro-10- (tert-butoxycarbonyl) phenothiazine, 3,7-bis (diethylamino) -10- (tert-butoxycarbonyl) phenoxazine, 3,7- Bis (dimethylamino) -1,9-dimethyl-10- (tert-butoxycarbonyl) phenothiazine, 9-dimethylaminobenzo (a) -12- (tert-butoxycarbonyl) phenoxazine, 2,8-dimethyl-3, 7-bis (ethylamino) -10- (tert-butoxycarbo Phenothiazine, 3,7-bis (dimethylamino) -10- (tert-pentyloxycarbonyl) phenothiazine, 2-methyl-3-amino-7- (dimethylamino) -10- (tert-butoxycarbonyl) phenothiazine, 3- (4-Dimethylaminophenylazo) -7-diethylamino-5-phenyl-10- (tert-butoxycarbonyl) phenazine, 5-amino-9-diethylaminobenzo (a) -12- (tert-butoxycarbonyl) phenoxy Sazine, 3,7-bis (phenylmethylamino) -10- (tert-butoxycarbonyl) phenothiazine, 3,7-bis (phenylethylamino) -10- (tert-butoxycarbonyl) phenothiazine, 3,7-bis ( Diphenylamino) -10- (t rt-butoxycarbonyl) phenothiazine, 3,7-bis (phenylmethylamino) -10- (tert-butoxycarbonyl) phenoxazine, 3,7-bis (phenylethylamino) -10- (tert-butoxycarbonyl) phenoxazine And 3,7-bis (diphenylamino) -10- (tert-butoxycarbonyl) phenoxazine, O, O'-di (tert-butoxycarbonyl) indigo white, O, O'-di (tert-butoxycarbonyl)- 5,5 ′, 7,7′-tetrabromoindigo white, O, O′-di (tert-butoxycarbonyl) thioindigo white, O, O′-di (tert-butoxycarbonyl) -4,4′-dimethyl -6,6'-dichlorothioindigo white, O, O'-di (te rt-butoxycarbonyl) -4,4 ', 7,7'-tetramethyl-5,5'-dichlorothioindigo white, O, O', N, N'-tetra (tert-butoxycarbonyl) indigo white The recording sheet or recording sheet set according to any one of claims 9 to 12, which is at least one selected from the group.   The oxidative coloring dye precursor is 3,7-bis (dimethylamino) -10- (tert-butoxycarbonyl) phenothiazine, O, O′-di (tert-butoxycarbonyl) indigo white, O, O ′, N The recording sheet according to claim 13, wherein the recording sheet is at least one selected from the group consisting of N, N′-tetra (tert-butoxycarbonyl) indigo white.   The recording sheet is a sheet provided with a single layer containing the microcapsule and an acidic substance on the same surface of the first support, or a layer containing the mylocapsule and a layer containing an acidic substance are laminated. The recording sheet according to claim 9, wherein the recording sheet is provided.   The recording sheet set is composed of at least a sheet provided with a layer containing the microcapsules on the back surface of the first support, and a sheet provided with a layer containing an acidic substance on the surface of the second support. The recording sheet set according to any one of claims 9 to 14.   The recording sheet or recording sheet set according to claim 15 or 16, wherein the acidic substance is at least one selected from the group consisting of a salicylic acid derivative and a polyvalent metal salt thereof.   The recording sheet or recording sheet set according to claim 17, wherein the acidic substance is a zinc salt of 3,5-bis (α-methylbenzyl) salicylic acid.