JP2904544B2 - Image receiving sheet for thermal transfer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image receiving sheet for receiving a thermal transfer image of a sublimation dye. More specifically, the present invention transfers a full-color image using a sublimable disperse dye.
The present invention relates to an image receiving sheet for a thermal transfer printer to be dyed.

The image receiving sheet of the present invention has a high-density, clear image,
The transfer is performed with high sensitivity, the suitability for use in a thermal printer is good, and the storage stability such as heat resistance is excellent.

[Problems to be solved by conventional technologies and inventions]

In recent years, the development of a high-quality color hard copy of a thermal transfer system, particularly a dye transfer printer has been rapidly progressing.
In a dye transfer printer, three primary colors (yellow,
The ink containing a sublimable dye of magenta and cyan) is heated while continuously controlling the heating energy applied to the thermal head, and the dye of each color is transferred to the image receiving sheet while changing the transfer amount. This makes it possible to transfer a full-color image of a density gradation.

An image receiving sheet for thermal transfer of a dye has a dyeing image receiving layer containing, as a main component, a polymer which easily dyes the dye transferred from the ink sheet.

High-quality images are formed on the image receiving sheet at high speed, so the dye transfer speed and dyeing amount are large, there is little fusing by heat, there is little resublimation after printing, and dyeing with good storability is possible. Image-receiving layers have been studied, but have not been satisfactory yet.

Conventionally, various polyester resins have been used as such a polymer for dyeing. For example, it has been proposed to lower the glass transition point in order to obtain a polymer having a high transfer rate and / or a large amount of dyeing. That is,
Using ethylene glycol as a diol component, and a polycondensation product obtained using terephthalic acid as a dicarboxylic acid component, that is, polyethylene terephthalate,
To lower the glass transition point, various diols,
A method of copolymerizing a dicarboxylic acid is known. In this case, it is considered that when the glass transition point is lowered, the transfer start temperature is lowered, so that the transfer speed is increased. However, in order to increase the density of the image receiving layer, it is necessary to increase the heat transfer rate and increase the heating temperature. Polymers with a low glass transition point reduce the film strength of the image-receiving layer at high temperatures, which in turn causes fusing during the printing process and reduces runnability, which in turn reduces the sensitivity of the thermal transfer system. I was
Further, there is little evidence that the dyeing concentration in the original meaning can be increased by lowering the glass transition point of the polymer.

A dye-dyeing polymer having reduced fusion and excellent preservability can be obtained by increasing the glass transition point, but the transfer start temperature is increased, and the sensitivity is still increased under the same heating conditions. There is a disadvantage that it will be reduced.

An object of the present invention is to solve the above-mentioned disadvantages of the prior art, to provide an image receiving sheet for thermal transfer, which has high print sensitivity and density of an image, has less fusion in a printing process, and has excellent heat and light preservability. It is.

[Means for solving the problem]

The image receiving sheet for thermal transfer of the present invention has a sheet-like support and an image receiving layer formed on at least one surface thereof and containing a polymer capable of dyeing and fixing the thermally transferred dye image as a main component. And the main component polymer in the image receiving layer has a melt viscosity of 10 ⁶ Pa · S or more at 140 ° C. and a melt viscosity of 10 ⁵ Pa · S or more at 160 ° C.
It is characterized by comprising at least one member selected from a polymer containing an ester bond unit in the molecule and a crosslinked product thereof.

The dye-dyeing polymer used in the present invention preferably has a number average molecular weight of 10,000 or more, and preferably has a glass transition point of 50 ° C. or more.

When the dye-dyeing polymer is a crosslinked polymer, it contains 1 mol equivalent or more, preferably 3 mol equivalent to 20 mol equivalent of a crosslinkable functional group per 1 mol of the uncrosslinked polymer molecule.

By lowering the melt viscosity of the dye-dyeable polymer, the method of trying to increase the sensitivity and the amount of dyeing involves running problems such as fusing to the obtained image-receiving layer, and a decrease in storage stability. Produces undesirable results. According to the study of the present inventors, the sensitivity and the dyeing of the image receiving layer are not improved as the melt viscosity of the dye-dyeable polymer is lower, and the dye-dyeing property is independent of the viscosity. Dye diffusibility and dye solubility of the polymer are important. Based on such findings, the present inventors have determined that a polymer having high dye solubility and high melt viscosity is suitable as a dyeing polymer, and has developed such a polymer. That is, as a polymer containing an ester group in the molecule, a polyester resin,
By using a vinyl acetate copolymer or an acrylic copolymer, it is possible to obtain an image receiving sheet having a large dyeing capacity, a large melt viscosity, no trouble such as fusion, and a good storage stability. Was.

The dye-dyeing polymer useful in the present invention is obtained, for example, by polycondensation of an aromatic dicarboxylic acid such as terephthalic acid and an aromatic diol such as an ethylene oxide adduct of bisphenol A [general formula (I)]. There is a polyester resin. In this case, the diol component includes aliphatic glycols such as propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, and the like. An alicyclic glycol such as 1,4-cyclohexanedimethanol can be used in combination with the aromatic diol.

As the dicarboxylic acid component of the dye-dyeing polyester resin, aromatic dicarboxylic acids such as terephthalic acid, orthophthalic acid, and 2,6-naphthalenedicarboxylic acid are used. As dicarboxylic acids other than aromatic dicarboxylic acids, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecandionic acid, aliphatic dicarboxylic acids such as dimer acid, and alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid. An acid may be used in combination with the aromatic dicarboxylic acid.

Generally, the melt viscosity of a dye-dyeable polymer depends on the molecular weight of the same composition. The molecular weight is
It depends on the ratio of diol to dicarboxylic acid, purity, side reaction, progress of condensation reaction depending on reaction conditions, and the like. The easiest way to control the molecular weight is to change the temperature and time of the dehydration condensation reaction.

The image-receiving layer is formed by blending another resin such as a polyester resin, a polycarbonate resin, an acrylic resin, and a solvent-soluble synthetic resin such as a vinyl acetate resin with the dye-dyeing polymer useful in the present invention. You can also. It is preferable that the image receiving layer of the present invention contains a polymer having the above characteristics as a main component in an amount of 70% by weight or more.

The crosslinking agent added to the dyeing layer of the present invention undergoes a crosslinking reaction with a resin such as polyester to make the resin three-dimensional and improve the heat resistance of the dyeable coating. For example, a 2- to 3-functional isocyanate compound such as tolylene diisocyanate is preferably used. In general, if the amount of the crosslinking agent is too large, the resin is excessively cured, the crosslinking property is reduced, and the sensitivity is reduced. Therefore, the added amount is preferably per one polymer chain of the uncrosslinked polymer, that is, per mole. Has one or more crosslinkable functional groups, that is, 1
It is at least molar equivalent, more preferably at least 3 molar equivalents, still more preferably from 3 molar equivalents to 20 molar equivalents. If the content of the crosslinkable functional group is less than 1 molar equivalent, the crosslinking effect is generally not sufficient. One crosslinkable functional group per one molecular chain means that one mole equivalent of a crosslinkable functional group is added per one mole of a polymer molecule obtained from a number average molecular weight. When molar equivalents are added and 100% of the reaction is performed, the number of crosslinking points per polymer chain of the polymer becomes one.

The dye-dyeing polymer used in the present invention has a melt viscosity of 10 ⁶ Pa · S or more at 140 ° C. and 10 ⁵ P
When the melt viscosity of the polymer for dye dyeing is less than the above value, having a melt viscosity of aS or more, the obtained image receiving layer may be easily fused to the ink ribbon during the printing operation. Or the disadvantage that the dye in the image tends to be retransferred during storage of the print.

The image receiving layer of the present invention preferably contains 0.1 to 10% by weight of a release agent such as silicone for the purpose of preventing fusion with the ink ribbon during printing. If the release agent content exceeds 10%, the adhesion between the image receiving layer and the sheet-like support may be impaired. On the other hand, if the content is less than 0.1%, the effect of preventing heat fusion is not sufficiently exhibited.

The image receiving layer of the present invention may contain a low molecular organic compound such as a substituted phenol or terpene for the purpose of preventing oxidation, absorbing ultraviolet light, sensitizing or the like. Further, a white pigment for improving whiteness and opacity, a fluorescent dye for adjusting color tone, and other coloring pigments and dyes may be added to the image receiving layer.

The white pigment, and additives such as an ultraviolet absorber,
It is convenient to apply the mixture by mixing with the dyeing polymer which is the main component of the image receiving layer, but it is also possible to provide the ultraviolet absorber layer as an independent coating layer above or below the image receiving layer. Good.

Generally, the thickness of the image receiving layer is generally 1 to 20 μm, preferably 2 to 8 μm. If the thickness is too low, the density of the image decreases, and the image becomes non-uniform due to restrictions on coating accuracy. On the other hand, if it is too thick, the effect will be saturated and uneconomical, and the film strength of the image receiving layer may be reduced.

During traveling of the image receiving sheet of the present invention in a printer, static electricity is generated, and in order to prevent troubles such as double feeding and jamming, at least one surface of the sheet may be subjected to an antistatic treatment. Normal. An antistatic agent may be included in the image receiving layer or coated as a separate coating layer on the image receiving layer. As the antistatic agent, a cationic hydrophilic polymer is often used.

As the sheet-like support used in the present invention, various plastic films such as high-quality paper, coated paper, mono- or biaxially-stretched film containing polyolefin and inorganic pigment as main components, or synthetic paper composed of the same, or composites thereof, depending on the application. A laminated sheet or the like can be used. As an example of the composite sheet, the polyethylene layer is made of high quality paper,
Alternatively, there is a laminated sheet laminated on both sides of coated paper. The thickness of the sheet-like support used in the present invention is generally 20 to 250 μm, and its basis weight is preferably ²⁰ to 250 g / m ² .

〔Example〕

 The present invention will be further described by way of examples.

Synthesis Example 1 Synthesis of polyester resin- (1) Dicarboxylic acid component composition Terephthalic acid 60 mol% (99.7 g) Isophthalic acid 40 mol% (66.5 g) Diol component composition Ethylene glycol 20 mol% (12.4 g) Heopentyl glycol 10 mol % (11.6g) Aromatic diol (4% ethylene oxide based on bisphenol A)
0 mol added, Trade mark: Uniol, DA400 manufactured by NOF Corporation 70 mol% (280.0 g) The above carboxylic acid component and diol component are added together with a catalyst composed of trace amounts of calcium acetate and antimony trioxide together with a nitrogen atmosphere. After heating in and heating up to 150 ° C,
This temperature was maintained for 1 hour to cause a reaction, and a polycondensation reaction was further performed at 260 ° C. for 4 hours while maintaining a vacuum of 0.1 mmHg or less. Unreacted ethylene glycol was removed from the obtained polymerization product to obtain a polyester resin- (1). The number average molecular weight (by GPC) of this resin was 23,000.

Synthesis Example 2 Synthesis of Polyester Resin- (2) Dicarboxylic Acid Component Composition Same as Synthesis Example 1 Diol Component Composition Ethylene glycol 40 mol% (24.8 g) Neopentyl glycol 20 mol% (23.1 g) Diol; (Same as Synthesis Example 1) 40 mol% (160.0 g) The above dicarboxylic acid component and diol component were heated in a nitrogen atmosphere together with a trace amount of a catalyst of calcium acetate and antimony trioxide and heated to 150 ° C., and then the temperature was raised for 1 hour. The polycondensation reaction was carried out at 240 ° C. for 2 hours while maintaining a vacuum at 0.1 mmHg or less. Unreacted ethylene glycol was removed from the obtained polymerization product to obtain a polyester resin- (2). The number average molecular weight (by GPC) of this resin was 16,000.

Polyester resin- (3): Commercial product Trade name: Byron 290 Number average molecular weight: 24,000 Polyester resin- (4) manufactured by Toyobo Co., Ltd. Trade name: 1051 Number average molecular weight: 15,000 Resin- (1) manufactured by Arakawa Chemical Co., Ltd. ), (2), (3) and (4) were measured for melt viscosity using a melt flow tester. Table 1 shows the results.

Example 1 A sheet-like support made of a high-quality paper having a basis weight of 64 g / m ² and a polyethylene film having a thickness of 30 µm laminated on both surfaces thereof was used as a sheet-like support. On one surface of this support, coating material-1 having the following composition was applied so that the coating amount of the solid content was 5 g / m ² , and dried to form an image receiving layer, thereby producing an image receiving sheet for dye thermal transfer. .

Paint-1 Component Weight Polyester resin-(1) 100 g Crosslinker (trifunctional isocyanate, trademark: Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) 2 g Silicone resin (trademark: SH3476, manufactured by Toray Silicone Co., Ltd.) 10 g Toluene 200 g Methyl ethyl ketone (molar ratio of crosslinkable group / polyester = 4.2) 200 g The image receiving sheet for thermal transfer of the dye thus obtained was transferred to a commercially available sublimation transfer video printer (Sony Corporation).
And UP-5000) to print a color test pattern. The maximum density of the obtained print, heat-resistant fusing with the ink ribbon during printing, and
Time was tested for discoloration after storage.

The maximum density of the printed image was measured with a Macbeth densitometer. Further, the heat-resistant fusing property of the image receiving sheet was evaluated by a sensory test for the presence or absence of fusing between the ink ribbon and the image receiving sheet when a gradation pattern was printed by a video printer. The heat-resistant storage stability of the printed image was evaluated by observing the fading of the image after storage at 60 ° C. for 48 hours. The result is
It is shown in the table.

Example 2 The same operation as in Example 1 was performed. However, Paint-2 having the following composition was used instead of Paint-1.

Paint-2 Component weight polyester resin-(3) 100 g Crosslinker (bifunctional isocyanate, tolylene diisocyanate) 10 g Toluene 200 g Methyl ethyl ketone 200 g The test results are shown in Table 2.

Example 3 The same operation as in Example 1 was performed. However, Paint-3 having the following composition was used instead of Paint-1.

Paint-3 Component Weight Polyester resin (1) 100 g Crosslinking agent (trifunctional isocyanate, trademark: Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) 2 g Silicone resin (trademark: SH3476, manufactured by Toray Silicone Co., Ltd.) 3 g Table 2 shows the test results.

Comparative Example 1 Paint-4 having the following composition on the same support as in Example 1
A coating so that the solid content coating amount is 5 g / m ^2, and dried,
An image receiving layer was formed to obtain a receiving sheet.

Paint-4 Component weight polyester resin- (2) 100 g Silicone resin (trade name: SH3476, manufactured by Toray Silicone Co., Ltd.) 3 g Toluene 200 g Methyl ethyl ketone 200 g The test results are shown in Table 2.

Comparative Example 2 On the same substrate as in Example 1, a coating material 5 having the following composition was applied so as to have a solid content of 5 g / m ² , and dried to form an image receiving layer. I got a sheet.

Paint-5 Component Weight Polyester resin (4) 100 g Crosslinker (trifunctional isocyanate, trademark: Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) 5 g Silicone resin (trademark: SH3476, manufactured by Toray Silicone Co., Ltd.) 3 g Table 2 shows the test results.

[Effects of the Invention] The image receiving sheet for thermal transfer of the present invention has an image receiving layer containing a specific polymer having a specific melt viscosity, whereby the sensitivity and color density of an image formed by the transferred dye are high and vivid. In addition, it has the advantage of excellent storage stability and is highly practical.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-105689 (JP, A) JP-A-58-215398 (JP, A) JP-A-2-34392 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) B41M 5/38-5/40

Claims (1)

(57) [Claims] 1. An image receiving apparatus comprising: a sheet-like support; and an image receiving layer formed on at least one surface of the support and containing a polymer capable of dyeing and fixing a thermally transferred dye image as a main component. The main polymer in the layer is 10 ^{6 at} 140 ° C.
Shows a melt viscosity of Pa · S or more and at 160 ° C, 10 ⁵
An image-receiving sheet for thermal transfer, comprising a polymer having a melt viscosity of Pa · S or higher and having at least one member selected from a polymer containing an ester bond unit in its molecule and a crosslinked product thereof.