JP2006175635A - Method for manufacturing thermal recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a thermal recording medium, with high whiteness, which has excellent quality in terms of color developing sensitivity and plasticizer resistance. <P>SOLUTION: A thermal recording layer is formed by applying a coating material containing a colorless or pale-color electron-donative leuco dye and a coating material containing an electron-receptive developer discretely to the surface of a support. Thus it is possible to manufacture the thermal recording medium with high whiteness which has excellent quality in terms of color developing sensitivity and plasticizer resistance by using this manufacturing method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a high-whiteness thermal recording material excellent in color development sensitivity and plasticizer resistance.

  Thermosensitive recording media have come to be used for various purposes such as facsimiles, terminal printers for computers, automatic ticket vending machines, measuring recorders, and cash vouchers represented by car betting paper. In addition, diversification and high performance of recording apparatuses have been promoted, and the required quality for thermal recording media has become higher. For example, writing ability, printing ability, head residue, chemical resistance, etc., and color images for natural environment such as heat, water, humidity, light, sebum when handled by hand, oil, plasticizer, solvent, etc. Storage stability is required. Further, there can be mentioned, for example, a significant decrease in image density or decoloration due to contact with a sebum component or a plasticizer (DOP / DOA etc.) contained in a wrap film such as a vinyl chloride film. In particular, further improvements are required for recording characteristics (coloring sensitivity) and storage stability (plasticizer resistance).

A thermal recording medium is a support for paper, synthetic paper, film, plastic, etc., to obtain a recorded image by color development by an instantaneous chemical reaction by heating such as a thermal head, hot stamp, thermal pen, laser light, etc. Are provided with a thermosensitive recording layer. This heat-sensitive recording layer comprises a colorless or light-colored electron-donating leuco dye and an electron-accepting developer that are ground and dispersed in fine particles as essential components, and optionally includes binders, fillers, sensitizers, lubricants, and the like. It is formed by applying and drying paint mixed with other auxiliaries. In particular, the heat-sensitive recording layer has a great influence on the recording characteristics (color development sensitivity, high definition, etc.), whiteness, and storage stability (plasticizer resistance, light resistance, etc.) of the heat-sensitive recording medium. Therefore, the electron-donating dye and the electron-accepting developer, which are essential components of the heat-sensitive recording layer, are: 1) the electron-donating leuco dye and the electron-accepting developer are mixed from the viewpoint of the whiteness of the heat-sensitive recording material. It is selected by paying attention to the fact that it is not colored at the time, 2) it exhibits high color developability even at low applied energy, and 3) it is difficult to be colored or faded by oil or light.
Conventionally, in order to improve the storage stability of an image or the whiteness of a heat-sensitive recording material, a recording material combining a specific developer and a dye has been proposed (Patent Document 1). However, although the color development sensitivity and the plasticizer resistance are improved, there is a problem that the whiteness of the thermal recording resistance is lowered.
JP 2002-211141 A

  In view of the circumstances as described above, an object of the present invention is to provide a method for producing a high-whiteness thermal recording material having quality excellent in color development sensitivity and plasticizer resistance.

  As a result of diligent study of the above problems, the present inventors have provided a thermosensitive recording layer provided with a thermosensitive recording layer containing an electron-donating leuco dye and an electron-accepting developer that are colored when mixed and dispersed on the support. In the production method of the present invention, the present invention has been achieved by separately applying a coating containing a colorless or light-colored electron-donating leuco dye and a coating containing an electron-accepting developer to form a heat-sensitive recording layer. .

  By using the production method of the present invention, it is possible to produce a high whiteness thermal recording material having excellent color development sensitivity and plasticizer resistance.

Hereinafter, specific details of the present invention will be described.
The present invention relates to a method for producing a heat-sensitive recording material provided with a heat-sensitive recording layer comprising an electron-donating leuco dye that is colored when mixed and dispersed on a support and an electron-accepting developer. This is a method for producing a heat-sensitive recording material, in which a paint containing a donating leuco dye and a paint containing an electron-accepting developer are separately applied to form a heat-sensitive recording layer.
The electron-donating leuco dye and electron-accepting developer that can be used in the present invention are an electron-accepting developer dispersion (6.0 parts developer, 18.8 parts polyvinyl alcohol (10% aqueous solution)), 11.2 parts of water mixed and dispersed) and electron-donating leuco dye dispersion (2.0 parts of dye, 4.6 parts of polyvinyl alcohol (10% aqueous solution), 2.6 parts of water mixed and dispersed) for 30 minutes (23 C.) Any combination of an electron-donating leuco dye and an electron-accepting color developer that combine to give a Hunter whiteness of 60% or less after mixing and stirring is not particularly limited.

  As a combination of the electron donating leuco dye and the electron accepting developer, 3-diethyl-amino-6-methyl-7-anilinofluorane, 4,4′-dihydroxydiphenylsulfone, 3-dibutylamino-6 -Methyl-7-anilinofluorane and 4,4'-dihydroxydiphenylsulfone, 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluorane and 4,4'-dihydroxydiphenyl Examples include sulfone, 3-dibutylamino-6-methyl-7-anilinofluorane and urea urethane.

  In the conventional method for producing a thermal recording material, a thermal recording layer is formed by applying a paint in which a dispersion containing an electron-donating leuco dye and a dispersion containing an electron-accepting developer are mixed to form a thermal recording layer. When the coating material of the layer is colored, there is a problem that the whiteness of the produced thermal recording material is greatly reduced.

  On the other hand, in the production method of the present invention, a coating containing an electron-donating leuco dye and a coating containing an electron-accepting developer are separately applied to form a heat-sensitive recording material. In other words, a combination of a highly reactive electron-donating leuco dye and an electron-accepting developer can also be used, and has a high whiteness that is superior in color development and plasticizer resistance compared to conventional ones. A heat-sensitive recording material can be produced.

  The coloring mechanism of the mixed dispersion of the electron-donating leuco dye and the electron-accepting developer is because the hydrophilic functional groups of the electron-donating leuco dye and the electron-accepting developer ionize and react in water. For example, when 4, -4′-dihydroxydiphenylsulfone is used as the electron-accepting developer and 3-dibutylamino-6-methyl-7-anilinofluorane is used as the polarity of the electron-donating leuco dye, an ionized hydroxy group Colored to react with the butylamino group to form a chromophore.

  For this reason, if the hydrophilic functional groups of the electron-donating leuco dye and the electron-accepting developer are not ionized, that is, in the dried coating layer, they are not colored. Further, even when the hydrophilic functional groups of the electron-donating leuco dye and the electron-accepting developer are ionized, they hardly react in a short contact. Therefore, the present invention can produce a high whiteness thermal recording material excellent in color development sensitivity and plasticizer resistance.

  In the method for producing a heat-sensitive recording material of the present invention, the order of application of the paint containing an electron-donating leuco dye and the paint containing an electron-accepting developer and the presence or absence of a drying step are particularly limited. It can be selected as appropriate. The coating method is not particularly limited, and can be applied according to well-known conventional techniques. For example, air knife coating, varibar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating Etc. can be appropriately selected.

  However, in the case of so-called wet-on-wet where there is no drying process between coatings, air knife coating, varivar blade coating, pure blade coating, rod for coating of the layer away from the support (the upper layer of the thermal recording layer) A coating method such as blade coating, short dwell coating, or the like, which is scraped off and set to a desired coating amount is not preferable. In such an application method, even the paint applied in the first application part is scraped off, and therefore, curtain coating and spray coating without such influence are preferable. The curtain coating method is a method in which the paint is allowed to flow down and fall freely and is applied to the support in a non-contact manner, and a known method such as a slide curtain method, a slit curtain method, a slot curtain method, etc. can be adopted. Not limited. Various conditions such as coating concentration, coating speed, curtain film width, drop angle and the like are appropriately adjusted.

  Next, various materials used in the present invention are exemplified, but each coating layer provided as necessary, such as an under layer, an intermediate layer, a heat-sensitive recording layer, and an overcoat layer provided on the heat-sensitive recording layer. Can also be used.

  As the binder used in the present invention, fully saponified polyvinyl alcohol having a polymerization degree of 200 to 1900, partially saponified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, Butyral modified polyvinyl alcohol, olefin modified polyvinyl alcohol, nitrile modified polyvinyl alcohol, pyrrolidone modified polyvinyl alcohol, silicone modified polyvinyl alcohol, other modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, styrene-maleic anhydride copolymer, Styrene-butadiene copolymer, ethyl cellulose, acetyl Cellulose derivatives such as cellulose, casein, arabic gum, oxidized starch, etherified starch, dialdehyde starch, esterified starch, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylate, polyvinyl butyral, polystyrose and their Examples thereof include copolymers, polyamide resins, silicone resins, petroleum resins, terpene resins, ketone resins, and coumaro resins. These polymer substances are used by dissolving in water, alcohol, ketones, esters, hydrocarbons and other solvents, and are used in the form of emulsification or paste dispersion in water or other media. It can also be used in combination.

  Examples of the crosslinking agent used in the present invention include glyoxal, methylol melamine, melamine formaldehyde resin, polyamidoamine epichlorohydrin, potassium persulfate, ammonium persulfate, sodium persulfate, ferric chloride, magnesium chloride, borax, boric acid. And alum, ammonium chloride and the like.

The amount of the binder and the crosslinking agent used in the overcoat layer of the present invention is determined according to the required performance and recording suitability, and is not particularly limited, but 1 to 100 parts is usually sufficient with respect to 100 parts of the binder. It demonstrates its performance. Further, the coating amount of the coating solution for forming the overcoat layer is not particularly limited, but if it is less than 0.1 g / m ² , the desired effect of the present invention cannot be sufficiently obtained, and 10 g / m. ^If it exceeds ² , the recording sensitivity of the heat-sensitive recording material may be remarkably lowered. Therefore, the dry weight is generally adjusted in the range of 0.1 to 10 g / m ² , preferably about 0.5 to 10 g / m ^2. . The coating solution for forming the overcoat layer is generally prepared as an aqueous coating solution, and after being sufficiently mixed and dispersed by a mixing stirrer such as a mixer, attritor, ball mill, roll mill, etc., if necessary, on the heat-sensitive recording layer. Applied.

  Moreover, in this invention, a conventionally well-known sensitizer can be used in the range which does not inhibit the desired effect with respect to the said subject. Such sensitizers include ethylene bis fatty acid amide, fatty acid monoamide, montanic acid wax, polyethylene wax, 1,2-di- (3-methylphenoxy) ethane, p-benzylbiphenyl, β-benzyloxynaphthalene, 4-biphenyl. -P-tolyl ether, m-terphenyl, 1,2-diphenoxyethane, 4,4'-ethylenedioxy-bis-benzoic acid dibenzyl ester, dibenzoyloxymethane, 1,2-di (3-methyl Phenoxy) ethylene, 1,2-diphenoxyethylene, bis [2- (4-methoxy-phenoxy) ethyl] ether, methyl p-nitrobenzoate, dibenzyl oxalate, di (p-chlorobenzyl) oxalate, oxalic acid Di (p-methylbenzyl), dibenzyl terephthalate, p-benzyloxybenzoate Acid benzyl, di-p-tolyl carbonate, phenyl-α-naphthyl carbonate, 1,4-diethoxynaphthalene, 1-hydroxy-2-naphthoic acid phenyl ester, 4- (m-methylphenoxymethyl) biphenyl, orthotoluenesulfone Amides and paratoluenesulfonamides can be exemplified, but are not particularly limited thereto. These sensitizers may be used alone or in combination of two or more.

  Examples of the filler used in the present invention include inorganic or organic fillers such as silica, calcium carbonate, kaolin, calcined kaolin, diatomaceous earth, talc, titanium oxide, and aluminum hydroxide. In addition, lubricants such as waxes, benzophenone and triazole ultraviolet absorbers, dispersants, antifoaming agents, antioxidants, fluorescent dyes, and the like can be used.

  In the present invention, 4,4′-butylidene (6-tert-butyl-3-methylphenol) is used as a stabilizer for imparting oil resistance and the like of recorded images within a range that does not impair the desired effect on the above-described problems. 2,2'-di-t-butyl-5,5'-dimethyl-4,4'-sulfonyldiphenol, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenylbutane, 4-benzyloxy-4 '-(2,3-epoxy-2-methylpropoxy) diphenylsulfone, epoxy resin Etc. can also be added.

  The types and amounts of the basic leuco dye, developer, and other various components used in the heat-sensitive recording material of the present invention are determined according to required performance and recording suitability, and are not particularly limited. A developer of 0.5 to 10 parts and a sensitizer of about 0.5 to 10 parts are used with respect to 1 part of the functional leuco dye.

  The desired thermosensitive recording sheet can be obtained by coating the coating liquid having the above composition on an arbitrary support such as paper, recycled paper, synthetic paper, film, plastic film, foamed plastic film, and nonwoven fabric. Moreover, you may use the composite sheet which combined these as a support body.

Basic leuco dye, color developer, and materials to be added as necessary are finely pulverized to a particle size of several microns or less with a pulverizer such as a ball mill, attritor, or sand glider, or an appropriate emulsifying device. Add various additive materials to make a coating solution. With respect to the coating layer other than the overcoat layer, the means for applying is not particularly limited and can be applied according to well-known conventional techniques, such as air knife coating, varibar blade coating, pure blade coating, rod blade coating, An off-machine coating machine or an on-machine coating machine equipped with various coaters such as short dwell coating, curtain coating, and die coating is appropriately selected and used. The coating amount of the heat-sensitive recording layer is not particularly limited and is usually in the range of ² to 12 g / m ^{2 by} dry weight.

  The heat-sensitive recording material of the present invention may further be provided with an undercoat layer or an intermediate layer such as a polymer material containing a filler under the heat-sensitive recording layer for the purpose of increasing the color development sensitivity. It is also possible to correct the curl by providing a backcoat layer on the opposite side of the support from the thermosensitive recording layer. Also, various known techniques in the heat-sensitive recording material field can be added as appropriate, such as applying a smoothing process such as supercalendering after coating each layer.

The method for producing a heat-sensitive recording material of the present invention will be described below with reference to examples. In the description, parts and% represent parts by weight and% by weight, respectively, unless otherwise specified.
Example 1
A composition comprising the following composition was stirred and dispersed to prepare an undercoat layer coating solution.
Baked kaolin (trade name: Ensilex 90, manufactured by Engelhard)
<Oil absorption 90cc / 100g>)
100 parts Styrene-butadiene copolymer latex (solid content 48%) 40 parts Polyvinyl alcohol 10% aqueous solution 30 parts Water 146 parts Next, after coating the undercoat onto one side of the support (50 g / m ² base paper) Then, drying was performed to obtain an undercoat layer-coated paper having a dry coating amount of 10.0 g / m ² .

Developer liquid dispersion (A liquid), leuco dye dispersion liquid (B liquid), and sensitizer dispersion liquid (C liquid) of the following composition are each separately separately with a sand grinder until the average particle diameter becomes 0.5 microns. Wet grinding was performed.
Liquid A (developer dispersion)
4,4′-Dihydroxydiphenylsulfone (4-4′-BPS)
6.0 parts polyvinyl alcohol 10% aqueous solution 18.8 parts water 11.2 parts Liquid B (leuco dye dispersion)
3-Dibutylamino-6-methyl-7-anilinofluorane (ODB-2)
2.0 parts polyvinyl alcohol 10% aqueous solution 4.6 parts water 2.6 parts C liquid (sensitizer dispersion)
Dibenzyl oxalate 6.0 parts Polyvinyl alcohol 10% aqueous solution 18.8 parts Water 11.2 parts Then, the dispersion was mixed at the following ratio to obtain a coating solution for the thermosensitive recording layer.
Liquid X Liquid B (leuco dye dispersion) 13.8 parts Liquid C (sensitizer dispersion) 10.0 parts Polyvinyl alcohol 10% aqueous solution 7 parts Liquid Y Liquid A (developer dispersion) 36.0 parts C Liquid (sensitizer dispersion) 26.0 parts Polyvinyl alcohol 10% aqueous solution 18 parts Next, each heat-sensitive recording layer coating liquid is applied by dry coating of X liquid onto the undercoat layer of the undercoat layer coated paper by blade coating. 1.7 g / m ² , Y liquid is applied in a wet-on-wet state by curtain coating so that the dry coating amount is 4.3 g / m ^2, and then dried. A heat-sensitive recording material was obtained by processing for 1000 to 2000 seconds.

Example 2
A thermosensitive recording material was prepared in the same manner as in Example 1 except that the X solution ODB-2 of Example 1 was changed to 3-diethylamino-6-methyl-7-anilinofluorane (ODB).
Example 3
The same as in Example 1 except that ODB-2 of the X liquid in Example 1 was changed to 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluorane (S-205). A thermal recording material was prepared.

Example 4
As in Example 1, except that ODB-2 of the X liquid in Example 1 was changed to 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-anilinofluorane (PSD-150). A thermal recording material was prepared.
Example 5
A heat-sensitive recording material was prepared in the same manner as in Example 1 except that 4-4′-BPS of the Y liquid in Example 1 was changed to urea urethane (UU).

Example 6
A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the coating method of the Y liquid in Example 1 was changed from curtain coating to spray coating.
Example 7
A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the coating method of the X liquid in Example 1 was changed from blade coating to curtain coating.

Example 8
On the undercoat layer of the undercoat layer coated paper used in Example 1, the Y solution was dried by blade coating with a dry coating amount of 4.3 g / m ² , and the X solution was dried by curtain coating with a dry coating amount of 1.7 g / m ² . Thus, a heat-sensitive recording material was prepared in the same manner as in Example 1 except that it was applied in a wet-on-wet state.
Example 9
The solution X of Example 1 was coated and dried by blade coating so that the dry coating amount was 1.7 g / m ^2, and then the Y solution of Example 1 was dried by curtain coating to 4.3 g. A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the density was set to / m ² .
Example 10
A heat-sensitive recording material was prepared in the same manner as in Example 9 except that the coating method of the Y liquid in Example 9 was changed to blade coating.

Comparative Example 1
Using a mixed solution of the X liquid (paint mainly composed of electron-sympathetic leuco dye) and Y liquid (paint mainly composed of electron-accepting color developer) of Example 1 and dry coating amount by blade coating A heat-sensitive recording material was prepared by coating to 0 g / m ² .
Comparative Example 2
A thermal recording material was prepared in the same manner as in Comparative Example 1 except that ODB-2 in Comparative Example 1 was changed to BK-305.

The coating conditions described above are shown in Table 1, and the color sensitivity, plasticizer resistance, and whiteness of each of the obtained thermal recording materials were measured. The measurement method is as follows, and the measurement results are shown in Table 2.
[Color development sensitivity]
Using TH-PMD manufactured by Okura Electric Co., Ltd., printing was performed on the produced thermal recording medium with an applied energy of 0.34 mJ / dot. The image density after printing was measured with a Macbeth densitometer (using an amber filter).
[Plasticizer resistance]
Using a TH-PMD manufactured by Okura Electric Co., Ltd., with a sample printed at an applied energy of 0.34 mJ / dot, a vinyl wrap (High Wrap KMA made by Mitsui Chemicals) was wrapped once around the paper tube, and the sample was attached. Further, a vinyl chloride wrap wrapped in three layers was allowed to stand in an environment at 23 ° C. for 24 hours, and then the Macbeth density (using an amber filter) of the printed portion was measured.
[Whiteness]
Using a Hunter whiteness meter manufactured by Company A, the whiteness (using an amber filter) of the produced thermal recording material was measured.

  In the production method of the present invention, a coating containing an electron-donating leuco dye and a coating containing an electron-accepting developer are separately applied to form a heat-sensitive recording material, and thus colored when the dispersion is mixed. In other words, a combination of a highly reactive electron-donating leuco dye and an electron-accepting developer can be used, and a high whiteness thermosensitive recording that is superior in color development and plasticizer resistance compared to conventional ones. The body can be manufactured.

Claims (2)

A colorless or light-colored electron-donating leuco dye in a method for producing a heat-sensitive recording material comprising a thermosensitive recording layer containing an electron-donating leuco dye and an electron-accepting developer that are colored when mixed and dispersed on a support. A method for producing a heat-sensitive recording material, comprising separately coating a paint containing an electron and a paint containing an electron-accepting developer to form a heat-sensitive recording layer. The electron donating leuco dye is 3-diethylamino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isoamylamino)- 6-methyl-7-anilinofluorane or 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-anilinofluorane, the electron-accepting developer is 4,4′-dihydroxydiphenylsulfone 2. The method for producing a heat-sensitive recording material according to claim 1, wherein the method is urea urethane.