JP2670539B2 - Thermal transfer sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a sublimable dye in a thermal transfer layer when a thermal transfer sheet containing a sublimable dye or the like in a thermal transfer layer is stacked or wound and stored. And the like relate to an improved thermal transfer sheet which is prevented from migrating and dyeing on the back side of the thermal transfer sheet with which the thermal transfer layer is in contact. [Prior Art] A thermal transfer sheet in which a thermal transfer layer containing a sublimable dye typified by a sublimable disperse dye in a synthetic resin binder is laminated on a base material of paper is known as "sublimation transfer paper". ing. For example, for dyes on polyester fiber cloth,
A dry sublimation printing method using "sublimation transfer paper" is performed. Recently, in addition to the above-mentioned application to cloth, since a high-speed point heating means such as a thermal head has been developed, a heat transfer sheet is used to apply heat according to image information to print a white background. Attempts have been made to form images on paper. In such an image forming method, a pattern is already formed on “sublimation transfer paper” in a sublimation printing method on a cloth, whereas a heat transfer sheet may have a uniform heat transfer layer. Not only is there a difference in the structure of the thermal transfer sheet, but there is also a difference in the applied heat, so there is a new problem not found in the sublimation printing method for fabrics. For example, in the sublimation printing method for fabrics, at 200 ℃ for 1 minute,
Heating is performed in a static state with "sublimation transfer paper" and fabric overlaid, but in the image forming method that uses a thermal head, the temperature of the thermal head when it generates heat is not clear, but it is estimated to be about 300 ° C. Heating time is 2-20m
sec, and the thermal transfer sheet usually runs together with the photographic paper. In addition, from the viewpoint of running strength, it is common to change the substrate sheet from sublimation transfer paper for fabric to a plastic film such as a polyester film,
Since the resin film travels while contacting the thermal head, the plastic film may melt and wear, so that a slag may adhere to the thermal head, or the thermal transfer sheet may weld to the thermal head and break. In order to prevent these troubles in the image forming method using a thermal head, a slip layer is formed on the back surface of the thermal transfer sheet (the surface on the side without the thermal transfer layer) using a highly heat-resistant material having slip properties. However, such a slip layer often uses a plastic having a lower degree of polymerization and a glass transition point as a binder than the plastic constituting the substrate, and the plastic as the binder is a thermal transfer sheet. Overlap,
When the film is wound up and stored, the transfer and dyeing of the dye in the heat transfer layer in contact with the film occur, which not only impairs the appearance of the heat transfer sheet but also leads to loss of the dye. [Problems to be Solved by the Invention] Therefore, in the present invention, the back surface of the thermal transfer sheet used in the image forming method using a high temperature spot heating means such as a thermal head is dyed with the dye transferred from the thermal transfer layer. The purpose is to prevent wearing. [Means for Solving the Problems] In order to solve the above problems, as a result of research by the present inventor, the material applied to the back surface is composed of a material having low dyeability of a sublimation dye. It was found that the problem of was solved. The present invention provides a "side having a thermal transfer layer containing a dye which is melted or sublimated to be transferred by heating in a resin binder on one side of a base sheet, and which is provided with the thermal transfer layer of the base sheet. On the other side, the dye migration prevention consisting of the reaction product of an acrylic polyol resin and an isocyanate compound having an average number of OH groups per molecule in the range of 1 to 36.5 and a glass transition point of 60 ° C or higher, and an additive A thermal transfer sheet having a layer. ] As its gist. Substrate sheet As the substrate sheet 2, condenser paper, polyester film, polyethylene naphthalate film,
A plastic film such as a polystyrene film, a polysulfone film, a polyimide film, a polyvinyl alcohol film, a cellophane, or an aramid (aromatic polyamide) film is used.
m, preferably 2 to 12 μm. These plastic films are preferable because they have a smooth surface and high mechanical strength. Among them, polyester films and aramid films are preferable. In the present invention, from the point of the invention, the base sheet is mainly made of a plastic film.In addition, when importance is placed on the price of the sheet itself and the heat resistance of the sheet itself, paper such as condenser paper is used. it can. Thermal Transfer Layer The thermal transfer layer is composed of a dye and a binder which are melted or sublimated by heating to be transferred. The dye is preferably a sublimable disperse dye, a sublimable oil-soluble dye, or a sublimable basic dye, and has a molecular weight of
It is 150-800, preferably 350-700. These dyes are selected in consideration of the sublimation temperature, hue, weather resistance, solubility in the ink or the binder resin, and the like. CI (abbreviation of chemical index, the same applies below) Yellow 51, Same 3, Same 54, Same 79, Same 60, Same 23, Same 7, Same 141, CI Disperse Blue 24, Same 56, Same 14, 14, Same 301 , Same 3
34, 165, 19, 19, 72, 87, 287, 154, 26, CI Disperse Red 135, 146, 59, 1, 1
73, 60, 167, CI Disperse Violet 4, 13, 13, 36, 5
6, the same 31, CI solvent violet 13, CI solvent black 3, CI solvent green 3, CI solvent yellow 56, the same 14, 16, 16, 29, CI solvent blue 70, the same 63, the same 36, the same 50 ,
49, 111, 105, 97, 11, CI Solvent Red 135, 81, 18, 18, 25, 1
9, 23, 24, 143, 146, 182. As the binder of the thermal transfer layer, ethyl cellulose,
Cellulosic resins such as hydroxyethyl cellulose, ethyl hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate, and cellulose acetate butyrate, and vinyl resins such as polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, polyester, polyvinyl acetate, and polyacrylamide can be used. . As an example of a more preferred binder, instead of the normal vinyl butyral resin described above, the molecular weight is 60,000 to 200,
000, the weight% of the vinyl alcohol portion is 10 to 40% in the polyvinyl butyral resin, preferably 15 to 30%, a special polyvinyl butyral resin having a glass transition point of 60 ° C to 110 ° C, preferably 70 ° C to 110 ° C. To be Molecular weight 60,000
If it is less than 20, the binding force as a binder is insufficient, and
If it exceeds 0,000, the viscosity at the time of application becomes too high, which hinders application. When the vinyl alcohol portion is less than 10%, the thermal transfer layer has insufficient stability over time.
Dye aggregation, precipitation, and bleeding on the surface cannot be avoided.
Conversely, if it exceeds 40%, the sublimation of the dye is hindered due to the affinity of the polyvinyl alcohol portion for the dye, and the print density decreases. The weight ratio of the dye to the binder in the thermal transfer layer is preferably such that the ratio of the dye to the binder is 0.3 or more. If it is less than 0.3, the print density and the thermal sensitivity are insufficient. On the other hand, if the dye / binder exceeds 2.3, the retention of the dye in the binder becomes insufficient and the storability of the thermal transfer sheet deteriorates. Accordingly, the dye / binder content is preferably 0.3 to 2.3, more preferably 0.55 to 1.5. It is desirable that the dye is dissolved in the binder of the thermal transfer layer. In conventional sublimation transfer papers for textiles, the dye is dispersed in the binder, so in order to sublimate the dye, energy is exerted to overcome the interaction between the dye molecules and the interaction between the dye molecule and the binder. As a result of needing and inevitably high energy,
Thermal sensitivity decreases. In this regard, the fact that the dye is dissolved in the binder is advantageous in terms of heat sensitivity. The thermal transfer layer may be formed by selecting a dye and transferring two or more thermal transfer layers having different dyes to one thermal transfer sheet, if necessary, so that a desired hue can be transferred when printed. For example, when the printing of each color is repeated according to the color separation signal to form an image such as a natural color photograph, it is desirable that the hue when printing is cyan, magenta, and yellow. Line up the three thermal transfer layers containing the dye that gives the dye. Alternatively, a thermal transfer layer containing a dye giving a black hue in addition to cyan, magenta and yellow may be added. It is preferable to provide a mark for position detection at the same time when any one of the thermal transfer layers is formed during the formation of these thermal transfer layers, because an ink and a printing step different from the thermal transfer layer formation are not required. Dye transfer prevention layer The dye transfer prevention layer can be used to stack thermal transfer sheets,
This is a layer that prevents the dye in the thermal transfer layer from migrating to the back surface of the adjacent thermal transfer sheet and being dyed when wound up. The dye transfer prevention layer may be basically composed of a resin having a low dye-dyeing property, preferably one having a small number of dye-dyeing functional groups, one having a high glass transition point, one having a high degree of polymerization, etc. . Since the dye transfer prevention layer also occupies the outermost layer on the back side of the thermal transfer sheet, it is necessary to play a role of ensuring smooth traveling when traveling in contact with the thermal head,
In this sense, a material having excellent heat resistance and excellent sliding performance even under heating is desired. Considering the above points, the average number of OH groups per molecule is 1
It is preferable to form the dye transfer preventing layer using an acrylic polyol resin having a glass transition point of 60 ° C. or higher in the range of 3 to 36.5. It is preferable that the acrylic polyol resin be a reaction product of an acrylic polyol resin and an isocyanate compound by adding an isocyanate compound for the purpose of further improving heat resistance and adhesion to a base sheet. It is advisable to add an additive for the purpose of producing slip properties. As the isocyanate compound, diisocyanate,
Polyisocyanates such as triisocyanate may be used alone or as a mixture. For example, paraphenylene diisocyanate, 1-chloro-2,4-phenyldiisocyanate, 2-chloro-1,4
-Phenyl diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, hecisamethylene diisocyanate, 4,4'-biphenylene diisocyanate, triphenylmethane triisocyanate,
Triphenylmethane triisocyanate, 4,4 ', 4 "-
Trimethyl-3,3 ', 2'-triisocyanate-2,4,6-
Specific examples of the isocyanate compound include triphenyl cyanurate, and further an adduct (adduct) of trimethylolpropane and tolylene diisocyanate. As the additive, an alkali metal salt of a phosphoric acid ester, an alkaline earth metal salt of a phosphoric acid ester, a phosphoric acid ester not in a salt form, or a filler can be appropriately used alone or in combination of two or more kinds. The alkali metal salt or alkaline earth metal salt of phosphoric acid ester has a function of giving lubricity to the heat-resistant protective layer,
Gaffac RD720 manufactured by Toho Kagaku is used. The alkali metal salt or alkaline earth metal salt of the phosphoric ester is used in an amount of 1 to 50% by weight, preferably 10 to 40% by weight, based on the acrylic polyol. Since the alkali metal salt or alkaline earth metal salt of the phosphate ester is added as a lubricant in a state of being dissolved in a binder in a molecular state, it may be added when a solid lubricant such as mica or talc is added. Compared with this, there is an advantage that no roughness occurs in the printing portion. As the alkali metal salt or alkaline earth metal salt of the phosphoric acid ester, a sodium salt of the phosphoric acid ester is particularly preferable, and one example thereof is represented by the following general formula. (Wherein, R is an alkyl group or alkylphenyl group having 8 to 30 carbon atoms, and n is the average number of moles of ethylene oxide added.) The alkali metal salt or alkaline earth metal salt of a phosphoric acid ester is thermally protected. When used as a slip agent in the layer, even if the thermal transfer layer and the heat-resistant protective layer are in close contact, the alkali metal salt or alkaline earth metal salt of phosphate does not migrate to the thermal transfer layer at all, and contamination of the thermal transfer layer is also recognized. There is an advantage that can not be. As the filler, clay, talc, zeolite, aluminosilicate, calcium carbonate, Teflon powder,
Inorganic or heat-resistant organic fillers such as zinc oxide, titanium oxide, magnesium oxide, silica, carbon, and condensates of benzoguanamine and formaldehyde are used. The filler has an average particle size of 3 μm or less, preferably 0.1 μm or less.
It is preferable that the thickness be 2 μm. Further, the filler is 0.1 to 25% by weight with respect to the acrylic polyol, preferably 1.0
Used in an amount of 〜10% by weight. By using such a filler in the dye transfer preventing layer, the fusion between the thermal head and the thermal transfer sheet is reduced, and the so-called sticking phenomenon is not recognized at all. To provide a dye transfer prevention layer on a base sheet, the above components are dissolved in an appropriate solvent to form a dye transfer prevention layer forming ink, which is formed on the base sheet by an appropriate printing method and coating method. Then, by heating to a temperature of 30 to 80 ° C., the dye transfer prevention layer may be formed by drying and reacting the acrylic polyol with the isocyanate compound. When the filler is used in combination, it is preferable to knead the filler in advance with an alkali metal salt or an alkaline earth metal salt of a phosphoric acid ester to prepare a filler kneading dispersion composition. The dye transfer prevention layer is 1 to 4 g / m ² , and preferably 1 to ² g / m ² .
It is preferable to have a coating amount (when dried) of m ² . If the coating amount is 1 g / m ² less than, not sufficient effect as the dye migration preventive layer, and if more than 4g / m ^2, the heat transfer becomes poor print density from a thermal head to the thermal transfer layer Is disadvantageously reduced. As described above, the dye transfer prevention layer should have an average OH per molecule.
Formed with a reaction product of an acrylic polyol resin having a number of groups of 1 to 36.5 and a glass transition point of 60 ° C or higher and an isocyanate compound, an alkali metal salt of phosphoric acid ester, an alkaline earth metal salt, or a filler. Thereby, a dye transfer preventing layer having sufficiently excellent performance can be obtained, but in some cases, when a thermal transfer sheet having such a dye transfer preventing layer is transferred inside a print transfer device or the like, it is added to the thermal transfer sheet. Depending on the tension or the printing pressure of the thermal head, a problem may occur in the transportability of the thermal transfer sheet. In such a case, it is preferable to add a phosphoric acid ester which is not in a salt form to the dye transfer preventing layer, in addition to the above components. As the phosphoric acid ester not in the salt form, those not in the salt form of the phosphoric acid ester represented by the above-mentioned alkali metal salt or alkaline earth metal salt of the phosphoric acid ester are used. Pharmaceutical PRYSURF A208S, Toho Chemical's GAFAC RS710, etc. may be used. The phosphate ester not in such a salt form is 1 to 50% by weight, preferably 1 to 30% by weight, based on the acrylic polyol.
It is used in amounts by weight. If it exceeds 50% by weight,
When it is stored in the case where it is stacked or wound up, the dye is transferred to the dye transfer preventing layer in the dye or pigment in the thermal transfer layer, which is not preferable. The dye transfer prevention layer is mainly composed of the above components, but in order to prevent blocking in a wound state,
A small amount of particulate matter such as talc, silica, calcium carbonate, and Teflon powder may be added. The order of providing the thermal transfer layer and the dye transfer prevention layer on the substrate sheet is preferably heating in order to accelerate the reaction between the acrylic polyol and the isocyanate compound, and the thermal transfer layer is not affected by heat during this heating. In order to do so, it is preferable to provide the dye transfer prevention layer on the substrate sheet and then provide the thermal transfer layer. The thermal transfer sheet according to the present invention basically has the above configuration, but may be subjected to the following additional processing. First, a primer layer may be provided between the thermal transfer layer and the substrate sheet or between the dye transfer preventing layer and the substrate sheet in order to improve the adhesive strength of each layer. Known primer layers can be used. For example, when a primer layer of acrylic resin, polyester resin, polyol and diisocyanate, etc. is used, the adhesiveness of both layers is particularly improved when polyester is used as the base sheet 2. Be improved. It is also possible to add about 1% by weight of silicone oil to the dye transfer prevention layer. Instead of the formation of the primer layer, a corona discharge treatment may be performed on one or both of the side of the base sheet where the thermal transfer layer is provided and the side where the dye transfer prevention layer is provided. Further, the primer layer may be formed after the corona treatment. [Operation / Effect of the Invention] According to the present invention, the dye transfer prevention layer has an average per molecule.
Formed by a reaction product of an acrylic polyol resin having an OH group number in the range of 1 to 36.5 and a glass transition point of 60 ° C. or higher and an isocyanate compound, an alkali metal salt of phosphoric acid ester, an alkaline earth metal salt, or a filler. As a result, dyeing due to migration of the dye to the back surface of the thermal transfer sheet is prevented, the appearance of the thermal transfer sheet is not impaired during storage, and the print density is not reduced. Example A polyethylene terephthalate film having a thickness of 6 μm was used as a base sheet, and a thermal transfer layer-forming composition having the following composition was used on one surface of the film, and a thermal transfer of 1.2 g / m ² (when dry) was applied by a gravure printing method. Layers were formed. Composition for forming thermal transfer layer Cyan dye (Kayaset Blue 714, Hodogaya Chemical Co., Ltd.)
5.0 parts by weight polyvinyl butyral resin (Sekisui Chemical Co., Ltd.
92 parts by weight Methyl ethyl ketone 22.54 parts by weight Toluene 50.18 parts by weight Methyl isobutyl ketone 13.0 parts by weight Xylene 5.0 parts by weight Next, a coating amount of 2 g / m on the surface of the base sheet opposite to the side on which the thermal transfer layer is provided by the gravure printing method. ³ to form a dye migration preventive layer of the following composition (dry). Dye transfer prevention layer composition Acrylic polyol resin 100 parts by weight Isocyanate compound 30 parts by weight Slip agent (phosphate ester Na salt, manufactured by Dai-ichi Kogyo Seiyaku Co., Plysurf A208S) 25 parts by weight However, as an acrylic polyol resin,
Each of these was used and after coating, it was aged at a temperature of 40 ° C. for 3 days. When thermal transfer was performed using the obtained thermal transfer sheet, there was no hindrance to the running performance of the thermal head. In order to see the effect of the dye transfer prevention layer of the obtained thermal transfer sheet, a polyethylene terephthalate film provided with only the dye transfer prevention layer was prepared, and the dye transfer prevention layer had 20 g of the thermal transfer layer of the heat transfer sheet. The following table shows the results of measuring the reflection density of the cyan dye transferred to the dye transfer prevention layer after leaving them in contact with each other at a pressure of / cm ² for 7 days at a temperature of 50 ° C. as they are. However, in the above table, T represents toluene, E represents ethyl acetate, M represents methyl ethyl ketone, and B represents n-butyl acetate.

Claims (1)

(57) [Claims] The base sheet has a thermal transfer layer containing a dye which is melted or sublimated by heating and transferred in a resin binder, and the surface of the base sheet opposite to the side on which the thermal transfer layer is provided. In addition, the average number of OH groups per molecule is 1 to
A reaction product of an acrylic polyol resin and an isocyanate compound having a glass transition point of 60 ° C. or higher in the range of 36.5,
A thermal transfer sheet comprising a dye transfer prevention layer comprising: and an additive. 2. The thermal transfer sheet according to claim 1, wherein the additive is either a phosphate ester surfactant or talc, or a mixture of both.