JP4289042B2 - Thermal transfer sheet - Google Patents

Description

【００３２】
【表２】

【００３３】
【表３】

【００３４】
（２）評価
実施例１〜６、比較例１〜６の各熱転写シートを、UPC1010（ソニー（株）製、UP-1800用プリントメディア）のマゼンタ部に切貼りし、プリンター（ソニー（株）製、UP-1800）にてUPC1010の印画紙にステップ印画をした。印画直後の最高濃度（ベタ部）をマクベス濃度計TR-924(Greenフィルター)にて測定し、次の計算式により、結晶化防止剤を添加しない比較例１に対する濃度低下率を求めた。
【００３５】
【数１】

【００３６】
こうして求めた濃度低下率は、次の３段階に評価した。
【００３７】
○…濃度低下率５％以下
△…５％超１０％以下
×…１０％より大
【００３８】
また、実施例１〜６、比較例１〜６の各熱転写シートを６０℃、湿度５０％で１週間保持し、上述の印画直後の濃度低下率の測定の場合と同様に、UPC1010の印画紙にステップ印画をした。そして、得られた印画物を目視で観察し、染料結晶化による印画ムラの有無を調べ、次の２段階に評価した。
【００３９】
○…問題なし
×…結晶化発生
【００４０】
以上の評価結果を表２に示す。
【００４１】
表２の結果から、本発明の実施例１〜６の熱転写シートは結晶化が防止され、さらに濃度低下のない優れた特性を示すことが分かる。一方、結晶化防止剤を多く添加した比較例２では濃度低下が大きく、添加剤の少ない比較例３、ＩＯ値が大きい比較例４と比較例６、融点の低い比較例５においては、いずれも染料の結晶化により印画ムラが引き起こされ、満足な結果を得られなかった。
【００４２】
【発明の効果】
本発明によれば、基材シートの一方の面に熱転写染料層を有する熱転写シートにおいて、熱転写染料層が常温で固体かつＩＯ値０．３５以下の結晶化防止剤を含有し、その結晶化防止剤の熱転写染料層中の含有量を乾燥塗膜中０．２〜２０重量％とするので、染料の結晶化が起き難く、発色濃度も確保することができる。
【図面の簡単な説明】
【図１】 熱転写シートの模式的断面図である。
【図２】 熱転写シートの平面図である。
【図３】 熱転写シートの平面図である。
【図４】 熱転写シートの平面図である。
【図５】 熱転写シートの平面図である。
【図６】 熱転写シートの平面図である。
【符号の説明】
１…基材シート、 ２…熱転写染料層（Ｙ）、 ３…熱転写染料層（Ｍ）、
４…熱転写染料層（Ｃ）、 ５…熱転写染料層（Ｂ）、 ６…転写保護層、 ７…耐熱滑性層、 ８…センサーマーク、 ９…転写型染料受容層、
１００Ａ、１００Ｂ、１００Ｃ、１００Ｄ，１００Ｅ、１００Ｆ…熱転写シート[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermal transfer sheet having a thermal transfer dye layer, and more particularly, to a thermal transfer sheet excellent in preservability by preventing dye crystallization in the thermal transfer dye layer.
[0002]
[Prior art]
The thermal transfer method using sublimation dyes, which has been widely adopted in recent years, transfers a large number of color dots from a thermal transfer sheet to a transfer material by heating in an extremely short time, and reproduces a full color image of a document with multicolored color dots. To do.
[0003]
As a thermal transfer sheet used at this time, a sheet in which a thermal transfer dye layer composed of a sublimable dye and a binder resin is formed on one side of a base sheet is used (see Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent No. 2911462 [0005]
[Problems to be solved by the invention]
However, when the conventional thermal transfer sheet is stored in a high humidity environment, the dye in the thermal transfer dye layer tends to crystallize on the surface of the thermal transfer dye layer. This crystallization is particularly likely to occur when the same dyes are close to each other. The dye crystallization causes uneven printing.
[0006]
Therefore, conventionally, in order to prevent crystallization of the dye, the dye concentration in the thermal transfer dye layer is lowered, but when the dye concentration is lowered, the image density is also lowered and a high quality image can be obtained. Disappear.
[0007]
On the other hand, an object of the present invention is to prevent crystallization of the dye in the thermal transfer dye layer without reducing the dye concentration in the thermal transfer dye layer in the thermal transfer sheet having the thermal transfer dye layer.
[0008]
[Means for Solving the Problems]
In the thermal transfer sheet having the thermal transfer dye layer, the present inventors include a crystallization inhibitor that is solid at room temperature and has a specific IO value in the thermal transfer dye layer, and prevents the crystallization on the surface of the thermal transfer dye layer. It was found that a coating of the agent was formed, thereby preventing the dye from crystallizing on the surface of the thermal transfer dye layer.
[0009]
That is, the present invention is a thermal transfer sheet having a thermal transfer dye layer on one side of the base sheet, the thermal transfer dye layer contains a crystallization inhibitor having a melting point of 27 ° C. or more and an IO value of 0.35 or less. The content of the crystallization inhibitor is 0.2 to 20% by weight of the dry coating film of the thermal transfer dye layer, and the coating film of the crystallization inhibitor is formed on the surface of the thermal transfer dye layer. A thermal transfer sheet is provided.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. In each figure, the same numerals indicate the same or equivalent components.
[0011]
FIG. 1 is a schematic cross-sectional view of a thermal transfer sheet 100A of one embodiment of the present invention. This thermal transfer sheet 100 </ b> A has thermal transfer dye layers 2 to 4 on one side of the base sheet 1 and a heat-resistant slipping layer 7 on the other side.
[0012]
The thermal transfer dye layers 2 to 4 correspond to yellow (Y), magenta (M), and cyan (C) colors, but the order of yellow, magenta, and cyan does not necessarily have to be the same.
[0013]
In general, the thermal transfer dye layers 2, 3, and 4 are formed of a binder resin and a dye. In the present invention, the thermal transfer dye layers 2, 3, and 4 are solid at room temperature, and preferably have a melting point of 27 ° C or higher. Preferably, it contains a crystallization inhibitor having a melting point of 47 ° C. or higher and an IO value of 0.35 or lower. If the melting point of the crystallization inhibitor is low and it is liquid at room temperature, the degree of freedom of the dye in the thermal transfer dye layers 2, 3, and 4 increases, and on the contrary, the crystallization of the dye on the surface of the thermal transfer dye layers 2, 3, and 4 occurs. It tends to happen.
[0014]
The IO value is an index of hydrophilicity or hydrophobicity of the organic compound calculated from the structure of the organic compound itself. The larger the numerical value, the more hydrophilic, and the smaller the numerical value, the more hydrophobic. In the present invention, this IO value is set to 0.35 or less. As a result, the crystallization inhibitor bleeds on the surfaces of the thermal transfer dye layers 2, 3, and 4, so that a film can be easily formed. Therefore, the crystallization of the dye can be efficiently inhibited.
[0015]
Specific examples of the crystallization inhibitor having such a melting point and IO value include fatty acid esters of polyhydric alcohols such as glyceryl tristearate, decaglyceryl decastearate, cholesteryl stearate, POE (6) sorbitol hexastearate, etc. And fatty acid esters such as ethyl stearate and methyl stearate, and ethers such as diphenyl ether.
[0016]
The content of the anti-crystallization agent in the thermal transfer dye layers 2, 3, and 4 is preferably such that the concentration is 0.2 to 20% by weight in the dried coating film. If the concentration of the crystallization inhibitor is too low, there is no effect of addition, and if it is too high, the image density decreases.
[0017]
As the dye to be contained in the thermal transfer dye layers 2, 3, and 4, known heat transferable dyes conventionally used in thermal transfer dye layers can be used. For example, azo dyes, disazo dyes, methine dyes, styryl dyes, pyridone / azo dyes and mixed dyes as yellow dyes, and magenta dyes as azo dyes, anthraquinone dyes, styryl dyes, heterocyclic azo dyes and the like As the mixed dye and cyan dye, anthraquinone dyes, naphthoquinone dyes, heterocyclic azo dyes, indoaniline dyes, and the like and mixed systems thereof can be used.
[0018]
Moreover, in the thermal transfer dye layers 2, 3, and 4, as the binder resin for supporting the dye and the crystallization inhibitor, any of those conventionally used as the binder resin for the thermal transfer dye layer can be used. . Examples of preferred binder resins include cellulose resins such as ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxy cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate, cellulose butyrate, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinyl pyrrolidone, Examples thereof include vinyl resins such as polyacrylamide and polyester. Among these, cellulose-based, acetal-based, butyral-based, and polyester-based resins are particularly preferable.
[0019]
In addition to the thermal transfer dye layers 2, 3, and 4, various additives such as an antioxidant, an ultraviolet absorber, and a light stabilizer can be blended as necessary.
[0020]
On the other hand, the base material sheet 1 can use conventionally well-known various base material sheets. For example, a polyester film, a polystyrene film, a polypropylene film, a polysulfone film, a polycarbonate film, a polyimide film, an aramid film, and the like can be given. As thickness of the base material sheet 1, 1-30 micrometers is preferable and 2-10 micrometers is more preferable.
[0021]
The heat-resistant slip layer 7 on the back surface of the base sheet 1 is provided to prevent the thermal transfer sheet 100A and the thermal head from sticking during thermal transfer and to ensure good running properties of the thermal transfer sheet 100A.
[0022]
The heat-resistant slip layer 7 is formed from a resin and a filler, and various additives such as a curing agent are added as necessary. The resin used for the heat-resistant active layer 7 is preferably a resin having a relatively high glass transition temperature, and examples thereof include polyvinyl acetal, polyvinyl butyral, phenoxy resin, and acetopropyl cellulose.
[0023]
Examples of the filler include inorganic fillers such as silica, talc, clay, zeolite, titanium oxide, zinc oxide, and carbon, and organic fillers such as silicone resin, polytetrafluoroethylene resin, and benzoguanamine resin. .
[0024]
Preferable examples of the curing agent added to the heat-resistant active layer 7 include polyisocyanate compounds having two or more isocyanate groups in the molecule. Specifically, tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-xylene diisocyanate, hexamethylene diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), methylcyclohexane-2,4 (or 2, 6) -Diisocyanate, 1,3-di (isocyanatemethyl) cyclohexane, isophorone diisocyanate, trimethyl-hexamethylene diisocyanate and the like, and polyisocyanate adducts (polyisocyanate prepolymer) in which diisocyanate and polyol are partially added and reacted. For example, an adduct body obtained by reacting tolylene diisocyanate and trimethylolpropane can be used.
[0025]
The thermal transfer sheet 100A having the above-described layers is coated with a heat-resistant slip layer forming coating on one side of the base sheet 1 and dried, and the thermal transfer dye layer forming coating is applied to the other side of the base sheet 1 by a conventional method. It can be produced by drying. In this case, a primer layer that improves the adhesion between the thermal transfer dye layers 2, 3, 4 and the base sheet 1 is provided between the base sheet 1 and the thermal transfer dye layers 2, 3, 4 as necessary. It may be formed. The primer layer can be formed from, for example, a polyester resin, an acrylic resin, a methacrylic acid resin, or the like.
[0026]
The thermal transfer sheet of the present invention can take various modes as long as the thermal transfer dye layer contains the above-described crystallization inhibitor.
[0027]
For example, a sensor mark 8 for detecting the sheet position may be provided as in the thermal transfer sheet 100B shown in FIG.
[0028]
Further, only a single color such as black may be formed as the thermal transfer dye layer 5 as in the thermal transfer sheet 100C shown in FIG. 3, and further, yellow as the thermal transfer dye layer as in the thermal transfer sheet 100D shown in FIG. , Magenta, cyan, and black may be formed.
[0029]
Further, as in the thermal transfer sheet 100E shown in FIG. 5, in addition to the thermal transfer dye layers 2, 3, and 4, a transparent transfer protective layer 6 may be provided for protecting the print screen by transferring it to the print screen after printing. good. Furthermore, a transfer type dye receiving layer 9 for transferring to plain paper may be provided as in the thermal transfer sheet 100F shown in FIG.
[0030]
【Example】
Examples 1-6 and Comparative Examples 1-6
(1) Preparation of thermal transfer sheet A polyester film having a thickness of 6 μm (manufactured by Toray Industries, Inc., Lumirror) is used as a base sheet, and the ink composition shown in Table 1 is applied on one side of the base sheet so as to have a dry thickness of 1 μm. did. Moreover, the heat-resistant slipping layer forming composition shown in Table 3 was applied to the other surface of the base sheet so as to have a dry thickness of 0.5 μm, thereby obtaining a thermal transfer sheet for evaluation.
[0031]
[Table 1]

[0032]
[Table 2]

[0033]
[Table 3]

[0034]
(2) The thermal transfer sheets of Evaluation Examples 1 to 6 and Comparative Examples 1 to 6 were cut and pasted on the magenta part of UPC1010 (manufactured by Sony Corporation, UP-1800 print media), and the printer (Sony Corporation) Made a UPC1010 photographic paper with a step print. The maximum density (solid part) immediately after printing was measured with a Macbeth densitometer TR-924 (Green filter), and the density reduction rate relative to Comparative Example 1 in which no crystallization inhibitor was added was determined by the following calculation formula.
[0035]
[Expression 1]

[0036]
The concentration reduction rate thus determined was evaluated in the following three stages.
[0037]
○: Density reduction rate 5% or less △… More than 5%, 10% or less ×… More than 10%
In addition, each of the thermal transfer sheets of Examples 1 to 6 and Comparative Examples 1 to 6 is held at 60 ° C. and a humidity of 50% for one week. Step printed. And the obtained printed matter was observed visually, the presence or absence of the printing nonuniformity by dye crystallization was investigated, and it evaluated in the following two steps.
[0039]
○: No problem ×: Crystallization occurred [0040]
The above evaluation results are shown in Table 2.
[0041]
From the results in Table 2, it can be seen that the thermal transfer sheets of Examples 1 to 6 of the present invention show excellent characteristics in which crystallization is prevented and there is no decrease in density. On the other hand, in Comparative Example 2 in which a large amount of the crystallization inhibitor was added, the decrease in concentration was large, Comparative Example 3 with few additives, Comparative Example 4 and Comparative Example 6 with a large IO value, and Comparative Example 5 with a low melting point were all. Printing unevenness was caused by crystallization of the dye, and satisfactory results could not be obtained.
[0042]
【The invention's effect】
According to the present invention, in the thermal transfer sheet having the thermal transfer dye layer on one surface of the base sheet, the thermal transfer dye layer contains an anti-crystallization agent that is solid at room temperature and has an IO value of 0.35 or less. Since the content of the agent in the thermal transfer dye layer is 0.2 to 20% by weight in the dry coating film, crystallization of the dye hardly occurs and the color density can be secured.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a thermal transfer sheet.
FIG. 2 is a plan view of a thermal transfer sheet.
FIG. 3 is a plan view of a thermal transfer sheet.
FIG. 4 is a plan view of a thermal transfer sheet.
FIG. 5 is a plan view of a thermal transfer sheet.
FIG. 6 is a plan view of a thermal transfer sheet.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Base material sheet, 2 ... Thermal transfer dye layer (Y), 3 ... Thermal transfer dye layer (M),
4 ... Thermal transfer dye layer (C), 5 ... Thermal transfer dye layer (B), 6 ... Transfer protective layer, 7 ... Heat-resistant slip layer, 8 ... Sensor mark, 9 ... Transfer dye receiving layer,
100A, 100B, 100C, 100D, 100E, 100F ... thermal transfer sheet

Claims (2)

In the thermal transfer sheet having a thermal transfer dye layer on one side of the base sheet,
The thermal transfer dye layer contains a crystallization inhibitor having a melting point of 27 ° C. or more and an IO value of 0.35 or less, and the content of the crystallization inhibitor is 0.2 to 20 of the dry coating film of the thermal transfer dye layer. A thermal transfer sheet having a weight percent, wherein a film of an anti-crystallization agent is formed on the surface of the thermal transfer dye layer.   The thermal transfer sheet according to claim 1, wherein the crystallization inhibitor comprises a fatty acid ester.

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