JP2018016000A - Method for producing color developing composition for heat-sensitive recording, color developing composition for heat-sensitive recording, and heat-sensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-sensitive recording material capable of forming an image part which causes little ground fogging and has good color developing properties and excellent preservability (especially alcohol resistance and water resistance), and to provide a color developing composition for heat-sensitive recording which achieves the same and a method for producing the same.SOLUTION: There is provide a method for producing a color developing composition for heat-sensitive recording, which comprises a step of reacting 4,4'-dihydroxydiphenylsulfone with an aralkyl halide compound in an aqueous solvent having a water content of 96 mass% or more. Further, the color developing composition for heat-sensitive recording comprises 100 pts.mass of 4-aralkyloxy-4'-hydroxydiphenylsulfone and 0.2 to 10 pts.mass of a compound represented by the following general formula (I). [where, Rrepresents an aralkyl group which may have a substituent, Rand Reach represent an aralkyl group which may have a substituent, and one of n and m is 1 and the other is 0].SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a thermal recording developer composition, a thermal recording developer composition, and a thermal recording material.

  In general, a heat-sensitive recording material is provided with a heat-sensitive coloring layer mainly composed of an electron-donating colorless or light leuco dye and an electron-accepting developer on a support. By heating the thermosensitive coloring layer with a thermal head, a thermal pen, laser light, or the like, the leuco dye and the developer react instantaneously to form an image portion, and recording occurs. Such heat-sensitive recording materials have advantages such that recording can be obtained with a relatively simple device, maintenance is easy, noise generation is low, thermal printers such as various portable terminals, ultrasonic echoes, etc. It is used for medical image printers, thermopen recorders such as electrocardiograms and analytical instruments, air tickets, boarding tickets, and POS labels for products.

  The characteristics required for the heat-sensitive recording material include low background fogging, color development at a low density and high density, excellent storage stability of image areas, and whiteness of uncolored areas. When the heat-sensitive recording material is used for a microwave processed food label, a parking ticket, a delivery label, a ticket or the like, the storability of the image portion is particularly important. In these applications, the recorded image may be exposed to water, alcohol, alcohol for disinfection, a plasticizer contained in a wallet or packaging wrap film, or exposed to high temperature and humidity due to climatic conditions. Therefore, it is required for a heat-sensitive recording material that a recording image having excellent storage stability such as alcohol resistance, water resistance, plasticizer resistance, heat and moisture resistance, and heat resistance can be formed.

  Studies have been made so far to improve the performance of heat-sensitive recording materials by using a developer. For example, Patent Documents 1 and 2 listed below propose heat-sensitive recording color developers mainly composed of 4-allyloxy-4'-hydroxydiphenylsulfone or 4-isopropoxy-4'-hydroxydiphenylsulfone.

JP 2005-305812 A JP 60-13852 A

  However, even a heat-sensitive recording material blended with the above-described color developer for heat-sensitive recording is not yet sufficient in alcohol resistance and water resistance, and the market requirements are sufficiently satisfied for the storage stability of the image area. I cannot say that.

  The present invention is a heat-sensitive recording material that can form an image portion with little background fogging, good color development, and excellent storage stability (especially alcohol resistance and water resistance), and heat sensitivity that can be realized. It is an object of the present invention to provide a recording developer composition and a method for producing the same.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have obtained 4-aralkyloxy-4'-hydroxydiphenylsulfone obtained by reacting 4,4'-dihydroxydiphenylsulfone and aralkylhalide in water. And a specific compound in a specific ratio as a developer, a heat-sensitive recording material has little background fog, good color development, and preserves image areas such as alcohol resistance and water resistance. The present inventors have found that an image portion having excellent properties can be formed, and have completed the present invention based on this finding.

  That is, the present invention comprises a step of reacting 4,4′-dihydroxydiphenylsulfone and aralkyl halide in an aqueous solvent having a water content of 96% by mass or more, and a developer composition for thermal recording. A manufacturing method is provided.

  According to the developer composition for heat-sensitive recording obtained by the production method of the present invention, the image area having less background fogging, good color development, and excellent storage stability (particularly alcohol resistance and water resistance). It is possible to realize a heat-sensitive recording material capable of forming the film.

［式（Ｉ）中、Ｒ^１は置換基を有していてもよいアラルキル基を示し、Ｒ^２及びＲ^３は置換基を有していてもよいアラルキル基を示し、ｎ及びｍは、一方が１であり、他方が０（即ち、無置換）である。］ The present invention also provides a color for thermal recording, comprising 100 parts by mass of 4-aralkyloxy-4′-hydroxydiphenylsulfone and 0.2 to 10 parts by mass of a compound represented by the following general formula (I). An agent composition is provided.

[In formula (I), R ¹ represents an aralkyl group which may have a substituent, R ² and R ³ represent an aralkyl group which may have a substituent, and n and m are Is 1 and the other is 0 (ie, unsubstituted). ]

  By blending the developer composition for heat-sensitive recording of the present invention in the heat-sensitive color-developing layer of the heat-sensitive recording material, the heat-sensitive color-developing layer has less background fogging and good color developability, and has good storage stability ( In particular, an image portion excellent in alcohol resistance and water resistance) can be formed.

  The present invention also provides a heat-sensitive recording material comprising a support and a heat-sensitive color-developing layer containing the leuco dye and the developer composition for heat-sensitive recording according to the present invention provided on the support.

  According to the present invention, there is little background fogging, color developability is good, and a heat-sensitive recording material capable of forming an image area with excellent storage stability (particularly alcohol resistance and water resistance), and its realization can be realized. It is possible to provide a developer composition for thermal recording and a method for producing the same.

  Since the heat-sensitive recording material of the present invention has less background fogging and good color development, it can cope with small currents and high-speed printing of a portable terminal. Furthermore, since the heat-sensitive recording material of the present invention has good storage stability of the image area, particularly alcohol resistance and water resistance, sufficient image quality can be maintained for a long time after printing even in a harsh environment. it can.

  First, a preferred embodiment of a method for producing a heat-sensitive recording developer composition will be described.

  The method for producing a developer composition for heat-sensitive recording of the present embodiment comprises a step of reacting 4,4′-dihydroxydiphenylsulfone and aralkyl halide in an aqueous solvent having a water content of 96% by mass or more. Prepare. In addition, the aralkyl group of aralkyl halide may have a substituent.

  An aqueous solvent having a water content of 96% by mass or more has a content of 4% by mass or less, an alcohol having 1 to 4 carbon atoms such as methanol, ethanol, 1-propanol, 2-propanol, monoethylene glycol monobutyl ether, An organic solvent such as a monoalkyl ether having 1 to 4 carbon atoms of (mono, di, or tri) glycol such as diethylene glycol monobutyl ether, monopropylene glycol monomethyl ether, or dipropylene glycol monomethyl ether can be included. From the viewpoint of removability of the by-product alkyl metal halide, the water content in the aqueous solvent is preferably 98% by mass or more, and more preferably 100% by mass. From the viewpoint of removability of the by-product alkyl metal halide, the content of the organic solvent in the aqueous solvent is preferably 2% by mass or less, more preferably 0% by mass, that is, no organic solvent is contained. .

  The above step is, for example, in the presence of an alkali catalyst, 0.9 to 1.4 mol, preferably 0.95 to 1.2 mol, more preferably aralkyl halide to 1 mol of 4,4′-dihydroxydiphenylsulfone. Can react 1.0-1.1 mol.

  As the alkali catalyst, an alkali metal hydroxide or a salt thereof can be used, and specific examples include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate and the like.

  As the aralkyl halide, benzyl chloride, benzyl iodide, benzyl bromide, methyl benzyl chloride, phenethyl chloride, methyl phenethyl chloride, and the like can be used, and the color development and storability of the resulting heat-sensitive recording material (especially alcohol resistance and water resistance). Benzyl chloride or methyl benzyl chloride is preferable, and benzyl chloride is more preferable.

  The concentration of 4,4′-dihydroxydiphenyl sulfone at the time of reaction (at the time of raw material charging) can be 5 to 50% by mass based on the mass of the aqueous solvent, and the solubility in the reaction solvent and the production efficiency can be improved. From a viewpoint, 7-40 mass% is preferable and 10-35 mass% is more preferable.

  The pH of the aqueous solvent at the start of the reaction can be 8 to 13, and 9 to 12 is preferable and 10 to 11 is more preferable from the viewpoint of suppression of aralkyl halide decomposition and reaction efficiency.

  The reaction temperature can be 50 to 80 ° C., and 55 to 70 ° C. is preferable and 60 to 65 ° C. is more preferable from the viewpoint of suppressing generation of by-products and impurities.

  Although reaction time is not specifically limited, From a viewpoint of manufacturing efficiency, 4 to 12 hours are preferable and 6 to 8 hours are more preferable.

  In the present embodiment, a purification step for purifying the reaction product obtained in the above step can be further provided. By providing the purification step, impurities and coloring can be reduced.

  The reaction product is preferably separated from the reaction solution after completion of the reaction by filtration.

  The method for purification is not particularly limited, and examples thereof include salting out, aciding out, recrystallization, reprecipitation, and the like. Recrystallization and reprecipitation are preferable from the viewpoint of solvent reuse and waste disposal costs.

  The solvent used for the purification is not particularly limited, but a water-alcohol mixed solvent is preferable, and the alcohol used is preferably an alcohol having 1 to 4 carbon atoms, specifically, methanol, ethanol, 1-propanol, 2-propanol or the like. Can be mentioned. From the viewpoint of efficiently obtaining the developer composition according to this embodiment, a water-methanol mixed solvent is preferable. The methanol content (concentration) in the water-methanol mixed solvent is preferably 50 to 95% by mass, and more preferably 60 to 90% by mass with respect to water.

［式（Ｉ）中、Ｒ^１は置換基を有していてもよいアラルキル基を示し、Ｒ^２及びＲ^３は置換基を有していてもよいアラルキル基を示し、ｎ及びｍは、一方が１であり、他方が０（即ち、無置換）である。］ According to the method for producing a developer composition for thermal recording of the present embodiment, 4-aralkyloxy-4′-hydroxydiphenylsulfone and a compound represented by the following general formula (I) (hereinafter referred to as Compound I) In some cases, a developer composition for thermal recording can be obtained. In addition, the aralkyl group of 4-aralkyloxy-4′-hydroxydiphenylsulfone may have a substituent.

[In formula (I), R ¹ represents an aralkyl group which may have a substituent, R ² and R ³ represent an aralkyl group which may have a substituent, and n and m are Is 1 and the other is 0 (ie, unsubstituted). ]

［式（Ｉ−ａ）中、Ｒ^４及びＲ^５はベンジル基を示し、ｓ及びｔは、一方が１であり、他方が０（即ち、無置換）である。］ According to the method for producing a developer composition for heat-sensitive recording of the present embodiment, for example, when benzyl halide is used as aralkyl halide, 4-benzyloxy-4′-hydroxydiphenylsulfone and compound I are represented by the following general formula ( A developer composition for thermal recording containing a compound represented by Ia) (hereinafter sometimes referred to as Compound Ia) can be obtained.

[In the formula (Ia), R ⁴ and R ^{5 each} represent a benzyl group, and one of s and t is 1 and the other is 0 (ie, unsubstituted). ]

  The developer composition for heat-sensitive recording obtained by the method of the present embodiment is a 4-aralkyloxy compound from the viewpoint of obtaining a heat-sensitive recording material capable of forming an image part having excellent storage stability (particularly alcohol resistance and water resistance). It contains 100 parts by mass of -4'-hydroxydiphenylsulfone and 0.2 to 10 parts by mass of compound I, preferably 0.3 to 5 parts by mass, more preferably 0.4 to 2 parts by mass. preferable.

  Compound I includes 3-aralkyl-4-aralkyloxy-4'-hydroxydiphenylsulfone and 4-aralkyloxy-3'-aralkyl-4'-hydroxydiphenylsulfone. One or both of these may be contained in the developer composition for thermal recording. Examples of the compound Ia include 3-benzyl-4-benzyloxy-4'-hydroxydiphenylsulfone and 4-benzyloxy-3'-benzyl-4'-hydroxydiphenylsulfone.

  In this embodiment, the production amount of Compound I can be controlled by selecting the reaction conditions such as the type and amount of the reaction solvent, the reaction temperature, and the reaction time. For example, if the amount of aralkyl halide added is small, the reaction temperature is low, and the dropping rate is slow, the production of Compound I can be reduced, while the amount of aralkyl halide is increased, the reaction temperature is high, and the dropping rate is increased. Promptly, the production of compound I can be increased.

  Moreover, it becomes easy to ensure sufficiently content of the said compound in a composition by using said water-alcohol mixed solvent in a refinement | purification process.

  From the viewpoint of improving the color developability of the resulting thermal recording material, the developer composition for thermal recording obtained by the method of the present embodiment is based on 100 parts by mass of 4-aralkyloxy-4′-hydroxydiphenylsulfone. Bis (4-aralkyloxyphenyl) sulfone (hereinafter sometimes referred to as Compound II) in an amount of 0.1 to 10 parts by mass, preferably 0.2 to 5 parts by mass, more preferably 0.3 to 3 parts by mass. It is preferable to do.

  Further, the developer composition for thermal recording obtained by the method of the present embodiment has a content of 4,4′-dihydroxydiphenylsulfone as a raw material of 4 from the viewpoint of obtaining a thermal recording material excellent in color developability. -It is preferable that it is 5 mass parts or less with respect to 100 mass parts of aralkyloxy-4'-hydroxy diphenyl sulfone, and it is more preferable that it is 3 mass parts or less.

  The content ratio of 4-aralkyloxy-4′-hydroxydiphenylsulfone, compound I, compound II, and 4,4′-dihydroxydiphenylsulfone contained in the developer composition for thermal recording obtained by the method of the present embodiment. Can be calculated from the peak area ratio in the chart by high performance liquid chromatography (HPLC).

  According to the method of the present embodiment, alkali metal halides generated from aralkyl halides and alkali catalysts can be reduced. By reducing the halide of the alkali metal, it is possible to reduce the wear of the printer head of the thermal recording material printing machine (thermal printer).

  According to the method of this embodiment, for example, when aralkyl chloride and sodium hydroxide are used, the content of sodium chloride contained in the developer composition for thermal recording can be reduced to 1000 ppm or less. From the viewpoint, it is preferably 300 ppm or less, and more preferably 150 ppm or less.

  The alkali metal halide contained in the developer composition for thermal recording can be quantified by ICP emission analysis.

  The reason why the production method of the present embodiment can reduce the content of alkali metal halides (such as sodium chloride) in the developer composition for thermal recording is that the water content is 96% by mass or more. The present inventors consider that the reaction is performed in a solvent.

  In this embodiment, by combining the purification steps described above, the compound I and the compound are sufficiently increased while sufficiently increasing the content (purity) of 4-aralkyloxy-4′-hydroxydiphenylsulfone in the developer composition for thermal recording. It is possible to achieve both a high level of reducing the content of II within the above-described preferable range and reducing the content of alkali metal halide.

  Next, preferred embodiments of the developer composition for thermal recording according to the present invention will be described.

  The developer composition for heat-sensitive recording of this embodiment contains 4-aralkyloxy-4'-hydroxydiphenyl sulfone and the compound represented by the general formula (I). In addition, the aralkyl group of 4-aralkyloxy-4'-hydroxydiphenylsulfone may have a substituent.

In formula (I), R ¹ represents an aralkyl group which may have a substituent, R ² and R ³ represent an aralkyl group which may have a substituent, and n and m are One is 1 and the other is 0 (ie, unsubstituted).

R ¹ in the formula (I) has a substituent from the viewpoint of obtaining a heat-sensitive recording material that is excellent in color developability and can form an image portion excellent in storage stability (particularly alcohol resistance and water resistance). An aralkyl group having 7 to 13 carbon atoms which may be present is preferable, an aralkyl group having 7 to 10 carbon atoms which may have a substituent is more preferable, and an alkyl group having 7 to 8 carbon atoms which may have a substituent. More preferred is an aralkyl group.

  When the aralkyl group has a substituent, the substituent is preferably an alkyl group having 1 to 4 carbon atoms, more preferably a methyl group or an ethyl group, and further preferably a methyl group. Examples of the alkyl group having 1 to 4 carbon atoms include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, and tert-butyl group.

Specific examples of R ¹ include benzyl, phenethyl, methylbenzyl, dimethylbenzyl, trimethylbenzyl, methylphenethyl, dimethylphenethyl, and trimethylphenethyl groups.

R ² or R ^{3 in} formula (I) is a substituent from the viewpoint of obtaining a heat-sensitive recording material that is excellent in color developability and can form an image portion excellent in storage stability (particularly alcohol resistance and water resistance). An aralkyl group having 7 to 13 carbon atoms which may have is preferable, an aralkyl group having 7 to 10 carbon atoms which may have a substituent is more preferable, and a carbon number 7 which may have a substituent Even more preferred are -8 aralkyl groups.

  When the aralkyl group has a substituent, the substituent is preferably an alkyl group having 1 to 4 carbon atoms, more preferably a methyl group or an ethyl group, and further preferably a methyl group. Examples of the alkyl group having 1 to 4 carbon atoms include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, and tert-butyl group.

Specific examples of R ² or R ³ include benzyl, phenethyl, methylbenzyl, dimethylbenzyl, trimethylbenzyl, methylphenethyl, dimethylphenethyl, and trimethylphenethyl groups.

  Specific examples of compound I include 3-benzyl-4-benzyloxy-4′-hydroxydiphenylsulfone, 3-phenethyl-4-phenethyloxy-4′-hydroxydiphenylsulfone, and 3-methylbenzyl-4-methylbenzyl. 3-aralkyl-4-aralkyloxy-4'-hydroxydiphenylsulfone such as oxy-4'-hydroxydiphenylsulfone, and 4-benzyloxy-3'-benzyl-4'-hydroxydiphenylsulfone, 4-phenethyloxy- 4-aralkyloxy-3′-aralkyl-4′-hydroxydiphenylsulfone such as 3′-phenethyl-4′-hydroxydiphenylsulfone and 4-methylbenzyloxy-3′-methylbenzyl-4′-hydroxydiphenylsulfone To mention Can. These can be contained in the composition singly or in combination of two or more.

  From the viewpoint of obtaining a heat-sensitive recording material that is excellent in color developability and can form an image portion excellent in storage stability (particularly alcohol resistance and water resistance), the developer composition for heat-sensitive recording is 3-aralkyl-4- It preferably contains aralkyloxy-4′-hydroxydiphenylsulfone and / or 4-aralkyloxy-3′-aralkyl-4′-hydroxydiphenylsulfone, and 3-aralkyl-4-aralkyloxy-4′-hydroxydiphenylsulfone And 4-aralkyloxy-3′-aralkyl-4′-hydroxydiphenylsulfone is more preferable.

  The developer composition for thermal recording of the present embodiment is a 4-aralkyloxy-4′- from the viewpoint of obtaining a thermal recording material capable of forming an image portion having excellent storage stability (particularly alcohol resistance and water resistance). It is preferable to contain 0.2-10 mass parts of Compound I with respect to 100 mass parts of hydroxydiphenyl sulfone, more preferably 0.3-5 mass parts, and 0.4-2 mass parts. Is more preferable. By setting it as such a range, it becomes easy to express said characteristic, fully reducing the background fog of a heat-sensitive recording material.

  Further, the compound I having good compatibility with 4-aralkyloxy-4′-hydroxydiphenylsulfone is a ratio of 10 parts by mass or less with respect to 100 parts by mass of 4-aralkyloxy-4′-hydroxydiphenylsulfone. In the thermosensitive recording developer composition, a uniform solid solution can be formed in the thermosensitive coloring layer, and excellent thermochromic properties can be expressed.

  From the viewpoint of obtaining a heat-sensitive recording material excellent in color developability, in particular, color development sensitivity, the developer composition for heat-sensitive recording of the present embodiment is bis ((a) in addition to 4-aralkyloxy-4′-hydroxydiphenylsulfone and compound I. It is preferable that 4-aralkyloxyphenyl) sulfone (compound II) is further contained. In this case, the content of bis (4-aralkyloxyphenyl) sulfone is preferably 0.2 to 10 parts by mass with respect to 100 parts by mass of 4-aralkyloxy-4′-hydroxydiphenyl sulfone. It is more preferably 3 to 5 parts by mass, and still more preferably 0.4 to 2 parts by mass. By setting it as such a range, it becomes easy to express said characteristic, fully reducing the background fog of a heat-sensitive recording material.

  In addition, from the viewpoint of obtaining a heat-sensitive recording material excellent in color developability, the developer composition for heat-sensitive recording of the present embodiment has a 4,4′-dihydroxydiphenylsulfone content of 4-aralkyloxy-4′-. The amount is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, based on 100 parts by mass of hydroxydiphenylsulfone.

  The content ratio of 4-aralkyloxy-4′-hydroxydiphenylsulfone, compound I, compound II, 4,4′-dihydroxydiphenylsulfone contained in the developer composition for thermal recording of this embodiment is a high-speed liquid. The value calculated from the peak area ratio in the chart by the chromatography method (HPLC) is pointed out.

  The developer composition for thermal recording of the present embodiment has an alkali metal halide content of 1000 ppm or less from the viewpoint of reducing the wear of the printer head of a thermal recording material printing machine (thermal printer). It is preferably 300 ppm or less, and more preferably 150 ppm or less. Examples of the alkali metal halide include sodium chloride and potassium chloride.

  Such a heat-sensitive recording developer composition can be obtained by the above-described method for producing a heat-sensitive recording developer composition of the present embodiment. For example, when aralkyl chloride and sodium hydroxide are used, The content of sodium chloride contained in the developer composition for thermal recording can be adjusted to the above range.

The developer composition for thermal recording of the present embodiment includes a compound I in which R ¹ in formula (I) is a benzyl group and R ² or R ³ is a benzyl group (ie, compound Ia) as compound I. In this case, the developer composition for heat-sensitive recording can be obtained by the method for producing a developer composition for heat-sensitive recording of this embodiment using benzyl chloride as aralkyl chloride. It can adjust similarly about the compounding ratio of each component.

  Further, the developer composition for thermal recording of the present embodiment may be prepared by blending 4-aralkyloxy-4′-hydroxydiphenylsulfone, compound I, and each component described above as necessary. Good. In this case, Compound I is produced, for example, by Friedel-Crafts reaction between a compound in which an aralkyl group which may have a substituent is bonded to one hydroxyl group of 4,4′-dihydroxydiphenylsulfone and aralkyl halide. Can be blended. Also in the developer composition for heat-sensitive recording obtained by the method for producing a developer composition for heat-sensitive recording of this embodiment using benzyl chloride as aralkyl chloride, the total content of compound I including compound Ia is Compound I can be blended so as to be within the preferred range described above.

  Next, the heat-sensitive recording material according to the present invention will be described.

  The heat-sensitive recording material of the present embodiment includes a support and a heat-sensitive coloring layer that is provided on the support and contains a developer and a coloring substance. As the developer, the developer composition for thermal recording obtained by the production method of the present embodiment described above or the developer composition for thermal recording of the present embodiment described above can be used.

  The support used for the heat-sensitive recording material is not particularly limited. For example, paper such as neutral paper or acid paper, recycled paper using waste paper pulp, synthetic paper, film, nonwoven fabric, woven fabric, or the like may be used. it can.

  As the coloring substance, a colorless or light leuco dye can be used. Examples of leuco dyes include fluorane derivatives, quinazoline derivatives, phthalide derivatives, triphenylmethane derivatives, phenothiazine derivatives, and the like. These leuco dyes can be used singly or in combination of two or more.

  Among these, leuco dyes having a fluoran structure can be particularly preferably used because of good color developability. Examples of the leuco dye having a fluorane structure include 3-isoamylethylamino-6-methyl-7-anilinofluorane, 3- (N- (4-methylphenyl) -N-ethyl) amino-6-methyl- 7-anilinofluorane, 3-diamylamino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilino Fluorane, 3-cyclohexylmethylamino-6-methyl-7-anilinofluorane and the like can be mentioned.

  The content of the coloring substance in the thermosensitive coloring layer can be appropriately selected according to the characteristics of the target recording material.

  The content of the developer composition for heat-sensitive recording according to the present invention in the heat-sensitive coloring layer can be appropriately selected according to the properties of the target recording material. For example, for 100 parts by weight of the leuco dye, The proportion of 4-aralkyloxy-4′-hydroxydiphenylsulfone is preferably 50 to 300 parts by mass.

  The heat-sensitive coloring layer can further contain a developer other than the heat-sensitive recording developer composition according to this embodiment. Examples of the developer used in combination include 4,4′-dihydroxydiphenylsulfone, 2,4′-dihydroxydiphenylsulfone, 3,3′-diallyl-4,4′-dihydroxydiphenylsulfone, and 4-hydroxybenzenesulfonic acid. Examples thereof include phenylsulfone such as phenyl ester and derivatives of benzenesulfonic acid. By using another developer together, it is possible to develop the coloring substance to a higher degree or to improve the storage stability.

  When 4,4′-dihydroxydiphenylsulfone is contained in the thermosensitive coloring layer for the purpose of improving color developability, the content of 4,4′-dihydroxydiphenylsulfone in the thermosensitive coloring layer is such that 4-aralkyloxy-4 ′. -It is preferable that it is 5 mass parts or less with respect to 100 mass parts of hydroxy diphenyl sulfone, and it is more preferable that it is 3 mass parts or less.

  Further, Tomirax 244 (trade name, manufactured by API Corporation, alkylphenol formalin condensate), diphenylsulfone cross-linked compound represented by the following formula (III) described in JP-A-10-29969, or JP-A-2008-303225 The image storage stability of the resulting heat-sensitive recording material can also be improved by using in combination with a high storage color developer such as a diphenylsulfone cross-linking compound represented by the following formula (IV) described in Japanese Patent Publication No. JP-A.

［式中、Ｘ及びＹはそれぞれ独立に直鎖若しくは分枝を有してもよい炭素数１〜１２の飽和、不飽和若しくはエーテル結合を有してもよい炭化水素基、

（Ｒはメチレン基又はエチレン基を表し、Ｔは水素原子又は炭素数１〜４のアルキル基を表す）を示し、Ｒ^１０〜Ｒ^１５はそれぞれ独立にハロゲン原子、炭素数１〜６のアルキル基、又はアルケニル基を示し、ａ、ｂ、ｃ、ｄ、ｅ、ｆは０〜４の整数を表し、ｇは１〜１０の整数を表す。なお、ａ、ｂ、ｃ、ｄ、ｅ、ｆが２以上のときは、Ｒ^１０〜Ｒ^１５はそれぞれ異なっていてもよい。］

[Wherein, X and Y are each independently a hydrocarbon group optionally having a straight chain or branched chain and having a C 1-12 saturated, unsaturated or ether bond,

(R represents a methylene group or an ethylene group, T represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms), and R ^{10 to} R ¹⁵ are each independently a halogen atom or an alkyl group having 1 to 6 carbon atoms. Or an alkenyl group, a, b, c, d, e, f represent an integer of 0 to 4, and g represents an integer of 1 to 10. In addition, when a, b, c, d, e, and f are 2 or more, R ^{10 to} R ¹⁵ may be different from each other. ]

［式中、ｊは１〜１０の整数を表す。］

[Wherein j represents an integer of 1 to 10. ]

  The total content of the developer in the thermosensitive coloring layer is preferably 100 to 500 parts by mass with respect to 100 parts by mass of the coloring substance.

  More preferably, the thermosensitive coloring layer further contains a sensitizer. Although there is no restriction | limiting in particular in the sensitizer to contain, It is preferable that it is a sensitizer with melting | fusing point 90-140 degreeC. Examples of such a sensitizer include fatty acid amides such as stearic acid amide, ethers such as 1,2-bisphenoxyethane, 1,2-bis (m-tolyloxy) ethane, and 2-benzyloxynaphthalene, Esters such as di (4-methylbenzyl) oxalate, sulfonamides such as N-phenylsulfonamide, sulfonic acid esters such as toluenesulfonic acid naphthyl ester, aromatics such as m-terphenyl and p-benzylbiphenyl Hydrocarbon compounds, various waxes, condensates of aromatic carboxylic acids and amines, higher linear glycols, higher ketones, diphenyl sulfone, bisphenol S derivatives, bisphenol A derivatives, p-hydroxybenzoic acid esters, phthalic acid Examples include diesters. These sensitizers can be used alone or in combination of two or more.

  The content of the sensitizer in the thermosensitive coloring layer is preferably 40 to 400 parts by mass with respect to 100 parts by mass in total of the developer, and in particular, 4-aralkyloxy-4′- contained in the thermosensitive coloring layer. It is preferable that it is 50-300 mass parts with respect to 100 mass parts of hydroxy diphenyl sulfone.

  The heat-sensitive color forming layer may further contain an image stabilizer. The image stabilizer to be contained is not particularly limited, and examples thereof include 4-benzyloxy-4 ′-(2-methylglycidyloxy) diphenylsulfone, 1,1,3-tris (2-methyl-4-hydroxy-5- Examples include cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, and a substance having a urethane structure. These image stabilizing materials can be used alone or in combination of two or more.

  In the heat-sensitive recording material of the present embodiment, a filler can be contained in the heat-sensitive coloring layer as necessary. Examples of the filler include inorganic fillers and organic fillers. Furthermore, if necessary, other additives can be contained in the thermosensitive coloring layer. Examples of other additives include lubricants, ultraviolet absorbers, water resistance agents, dispersants, antifoaming agents, antioxidants, and fluorescent dyes.

  There is no particular limitation on the method for producing the heat-sensitive recording material of the present invention. The other components to be added are dispersed in a medium such as an aqueous medium together with an appropriate binder to prepare a coating solution for the thermosensitive coloring layer, and this coating solution is applied on a support and dried. Can be manufactured.

  A dispersion containing a color former, developer and sensitizer is prepared separately for a dispersion containing a color former, a dispersion containing a developer, and a dispersion containing a sensitizer. Then, it can prepare by mixing these dispersion liquids. In each dispersion liquid, it is desirable that the color developing substance, the developer, and the sensitizer are finely divided and dispersed. A sand mill, a ball mill, etc. can be used for preparation of such a dispersion.

  The binder is not particularly limited, and examples thereof include cellulose derivatives such as hydroxyethyl cellulose and carboxymethyl cellulose, polyvinyl alcohols such as polyvinyl alcohol and modified polyvinyl alcohol, gelatin, casein, starch, polyacrylic acid, polyacrylate, poly Examples thereof include vinyl acetate, polyacrylamide, styrene-maleic acid copolymer, styrene-butadiene copolymer, polyamide resin, petroleum resin, and terpene resin. These binders can be used alone or in combination of two or more.

  In the heat-sensitive recording material of the present embodiment, an undercoat layer containing an inorganic filler or an organic filler can be provided as necessary. Furthermore, if necessary, a water-soluble resin such as a cellulose derivative or polyvinyl alcohol, a water-soluble emulsion resin such as a styrene-butadiene copolymer, a water-insoluble resin, or a resin thereof on the thermosensitive coloring layer. An overcoat layer formed from a material added with a filler, an isocyanate, a monomer such as an unsaturated compound, an oligomer, or a crosslinking agent can be provided.

  The heat-sensitive recording material of the present embodiment can be a heat-sensitive multicolor recording material in which a color forming layer containing color developing substances having different color tones is formed in multiple layers.

  EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited to these examples.

<Production of developer composition>
The content of each component in the obtained developer composition was calculated from the peak area ratio in the chart by high performance liquid chromatography (HPLC). HPLC measurement was performed under the following conditions.

[HPLC measurement conditions]
Column: Shim-pack HRC-ODS (inner diameter 4.6 mm × length 250 mm, manufactured by Shimadzu LLC)
Mobile phase: 70% acetonitrile water Column temperature: 40 ° C
Flow rate: 1.0 mL / min
Detector: SPD-10Avp (manufactured by Shimadzu Corporation)
Detection wavelength: UV (254 nm)
Sample concentration: reaction product / mobile phase = 20 mg / 50 mL

Example 1
A reaction vessel equipped with a stirrer and a condenser is charged with 2,000 parts by weight of purified water, 250 parts by weight of 4,4′-dihydroxydiphenylsulfone and 42 parts by weight of sodium hydroxide, and 126.5 parts by weight of benzyl chloride at about 65 ° C. The portion was added dropwise over 4 hours. After completion of dropping, the reaction was carried out at 60 to 65 ° C. for 4 hours. After completion of the reaction, the pH was adjusted to 8.5 using sodium hydroxide, the mixture was heated to 80 ° C., and the product was separated by filtration.

  Next, as a purification step, 290 parts by mass of the product, 92 parts by mass of purified water and 680 parts by mass of methanol are charged into a container equipped with a stirrer and a cooling tube, and after heating and dissolving, 146 parts by mass of purified water is added. The product was cooled to room temperature, and the purified product was filtered off and dried. In this way, 245 parts by mass of the developer composition was obtained.

  The resulting developer composition was obtained by using 3-benzyl-4-benzyloxy-4′-hydroxydiphenylsulfone and 4-benzyloxy-3 with respect to 100 parts by mass of 4-benzyloxy-4′-hydroxydiphenylsulfone. It contained 0.6 parts by mass of '-benzyl-4'-hydroxydiphenylsulfone and 0.6 parts by mass of bis (4-benzyloxyphenyl) sulfone.

(Example 2)
A reaction vessel equipped with a stirrer and a condenser is charged with 2,000 parts by weight of water, 250 parts by weight of 4,4′-dihydroxydiphenylsulfone and 47 parts by weight of sodium hydroxide, and 4 parts of 139 parts by weight of benzyl chloride at about 65 ° C. It was added dropwise over time. After completion of dropping, the reaction was carried out at 60 to 65 ° C. for 5 hours. After completion of the reaction, the same operation as in Example 1 was performed to obtain 290 parts by mass of a developer composition.

  The resulting developer composition was obtained by using 3-benzyl-4-benzyloxy-4′-hydroxydiphenylsulfone and 4-benzyloxy-3 with respect to 100 parts by mass of 4-benzyloxy-4′-hydroxydiphenylsulfone. It contained 0.9 parts by mass of '-benzyl-4'-hydroxydiphenylsulfone and 0.7 parts by mass of bis (4-benzyloxyphenyl) sulfone.

(Example 3)
Except that the purification step after completion of the reaction was repeated twice, the same operation as in Example 1 was carried out to obtain 220 parts by mass of the developer composition.

  The resulting developer composition was obtained by using 3-benzyl-4-benzyloxy-4′-hydroxydiphenylsulfone and 4-benzyloxy-3 with respect to 100 parts by mass of 4-benzyloxy-4′-hydroxydiphenylsulfone. It contained 0.2 parts by mass of '-benzyl-4'-hydroxydiphenylsulfone and 0.3 parts by mass of bis (4-benzyloxyphenyl) sulfone.

Example 4
In a reaction vessel equipped with a stirrer and a condenser, 2,000 parts by weight of purified water, 250 parts by weight of 4,4′-dihydroxydiphenylsulfone and 40 parts by weight of sodium hydroxide were charged, and 177 parts by weight of benzyl chloride was added at about 65 ° C. The reaction was carried out at 60-80 ° C. for 4 hours. After completion of the reaction, the pH was adjusted to 8.5 using sodium hydroxide, the mixture was heated to 80 ° C., and the product was filtered off.

  Next, as a purification step, a product equipped with a stirrer and a cooling tube is charged with 820 mass of the above product and purified water, heated to 100 ° C., cooled to room temperature, the purified product is filtered and dried. The operation was performed. Thus, 258 mass of the developer composition was obtained.

  The resulting developer composition was obtained by using 3-benzyl-4-benzyloxy-4′-hydroxydiphenylsulfone and 4-benzyloxy-3 with respect to 100 parts by mass of 4-benzyloxy-4′-hydroxydiphenylsulfone. It contained 10 parts by mass of '-benzyl-4'-hydroxydiphenylsulfone and 3.4 parts by mass of bis (4-benzyloxyphenyl) sulfone.

  Table 1 shows the compositions (parts by mass) of the developer compositions obtained in Examples 1 to 4.

<Evaluation of thermal recording material>
The thermal recording materials produced in the examples and comparative examples were evaluated by the following method.

(1) Background fog The color density of the test paper before the color development test was measured using a Macbeth densitometer. The smaller the value, the whiter the surface is, and the better, and the larger the value, the more fog is seen and the worse.

(2) Color developability Using a thermal printer [Okura Electric Co., Ltd.], with a pulse width of 3 ms, color is developed by increasing the print energy every 0.07 mJ / dot, and the color density of the resulting image is the Macbeth density. Measured using a meter. The smaller the value, the thinner the image, and the larger the value, the darker the image.

(3) Alcohol resistance Using the above-mentioned thermal printing apparatus, an image developed with a printing voltage of 20 V and a pulse width of 3 ms and a white paper part are mixed with 25 parts by volume of ethanol at room temperature (20 ° C.) and 75 parts by volume of purified water. It was immersed in the liquid and left for 3 hours. Thereafter, the heat-sensitive recording material was pulled up, the surface was pressed with filter paper, and naturally dried, and then the color density of the image area and the color density of the white paper area before and after the test were measured using a Macbeth densitometer. The smaller the numerical value, the lighter the image is, and the larger the numerical value, the darker the image is.

(4) Water resistance Using the above-described thermal printing apparatus, an image developed at a printing voltage of 20 V and a pulse width of 3 ms and a white paper portion were immersed in purified water at room temperature (20 ° C.) and left for 24 hours. Thereafter, the heat-sensitive recording material was pulled up, the surface was pressed with filter paper, and naturally dried, and then the color density of the image area and the color density of the white paper area before and after the test were measured using a Macbeth densitometer. The smaller the numerical value, the lighter the image is, and the larger the numerical value, the darker the image is.

(5) Heat resistance After using the above thermal printing apparatus and leaving the image and white paper portion developed at a printing voltage of 20 V and a pulse width of 3 ms at 60 ° C. or 100 ° C. for 24 hours, the color density of the image portion before and after the test. The color density of the white paper portion was measured using a Macbeth densitometer. The smaller the numerical value, the lighter the image is, and the larger the numerical value, the darker the image is.

(Example 5)
By dispersing 40 parts by weight of 3-dibutylamino-6-methyl-7-anilinofluorane, 80 parts by weight of a 10% by weight aqueous polyvinyl alcohol solution and 40 parts by weight of water using a sand mill for 4 hours, A coloring substance dispersion (liquid A) was prepared. The developer was obtained by finely pulverizing and dispersing 28 parts by weight of the developer composition obtained in Example 1 and 120 parts by weight of a 10% by weight polyvinyl alcohol aqueous solution and 52 parts by weight of water using a sand mill for 3 hours. A dispersion (liquid B) was prepared. A sensitizing substance dispersion liquid is obtained by finely pulverizing and dispersing 28 parts by mass of 1,2-bis (phenoxymethyl) benzene, 120 parts by mass of a 10% by mass polyvinyl alcohol aqueous solution and 52 parts by mass of water using a sand mill for 4 hours. (C solution) was prepared.

  Next, 60 parts by mass of B liquid, 60 parts by mass of C liquid, 16 parts by mass of a 10% by mass aqueous polyvinyl alcohol solution and 12.2 parts by mass of kaolin were stirred and mixed using a disper to prepare D liquid.

Next, 11.3 parts by mass of A solution and 100 parts by mass of D solution were mixed to prepare a coating solution for forming a thermosensitive coloring layer. This coating solution was applied to high-quality paper having a basis weight of 65 g / m ² so that the dry coating amount was about 6 g / m ² , air-dried, and subjected to calendar treatment to produce a heat-sensitive recording material, which was evaluated. .

(Example 6)
Example 5 except that the developer dispersion (liquid B) was prepared using the developer composition obtained in Example 2 instead of the developer composition obtained in Example 1. In the same manner as above, a heat-sensitive recording material was produced and evaluated.

(Example 7)
Example 5 except that the developer dispersion (liquid B) was prepared using the developer composition obtained in Example 3 instead of the developer composition obtained in Example 1. In the same manner as above, a heat-sensitive recording material was produced and evaluated.

(Example 8)
Example 5 except that the developer dispersion (liquid B) was prepared using the developer composition obtained in Example 4 instead of the developer composition obtained in Example 1. In the same manner as above, a heat-sensitive recording material was produced and evaluated.

(Comparative Example 1)
Instead of the developer composition obtained in Example 1, BPS-MAE (trade name, manufactured by Nikka Chemical Co., Ltd., 4-allyloxy-4′-hydroxydiphenylsulfone) was used as a developer dispersion ( A heat-sensitive recording material was produced and evaluated in the same manner as in Example 5 except that (Liquid B) was adjusted.

(Comparative Example 2)
Instead of the developer composition obtained in Example 1, 4-isopropoxy-4′-hydroxydiphenyl sulfone was used to prepare a developer dispersion (liquid B), which was the same as in Example 5. A thermosensitive recording material was prepared and evaluated.

  The evaluation results in Examples 5 to 8, Comparative Example 1 and Comparative Example 2 are shown in Tables 2 to 5.

  The heat-sensitive recording materials of Examples 5 to 8 were compared in terms of color developability, including the heat-sensitive recording material of Comparative Example 1 containing 4-allyloxy-4′-hydroxydiphenylsulfone and 4-isopropoxy-4′-hydroxydiphenylsulfone. The performance was the same as that of the heat-sensitive recording material of Example 2, which was a sufficiently practical level.

  In addition, the heat-sensitive recording materials of Examples 5 to 8 are superior to the heat-sensitive recording material of Comparative Example 1 and the heat-sensitive recording material of Comparative Example 2 in terms of the alcohol resistance and water resistance of the image portion of the image storage stability. The heat resistance of the image area was equal to or superior to that of the heat-sensitive recording material of Comparative Example 1, and the heat resistance of the blank paper area was superior to that of the heat-sensitive recording material of Comparative Example 2.

  Since the heat-sensitive recording material of the present invention has less background fogging and good color development, it can cope with small currents and high-speed printing of a portable terminal. Furthermore, since the heat-sensitive recording material of the present invention has good storage stability of the image area, particularly alcohol resistance and water resistance, sufficient image quality can be maintained for a long time after printing even in a harsh environment. it can.

Claims (3)

  A process for producing a developer composition for thermal recording, comprising a step of reacting 4,4'-dihydroxydiphenylsulfone and aralkyl halide in an aqueous solvent having a water content of 96% by mass or more. A developer composition for thermal recording, comprising 100 parts by mass of 4-aralkyloxy-4′-hydroxydiphenylsulfone and 0.2 to 10 parts by mass of a compound represented by the following general formula (I). .

[In formula (I), R ¹ represents an aralkyl group which may have a substituent, R ² and R ³ represent an aralkyl group which may have a substituent, and n and m are Is 1 and the other is 0. ] A thermosensitive recording material comprising: a support; and a thermosensitive color-developing layer containing the leuco dye and the developer composition for thermosensitive recording according to claim 2 provided on the support.