JPH04219294A - Thermal transfer method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer method, and more specifically, it is an object of the present invention to provide a thermal transfer method that has excellent dye migration properties during thermal transfer and can provide excellent image density.

0002

[Prior Art] In place of conventional general printing methods, inkjet methods and thermal transfer methods have been developed as methods for providing excellent monochrome or full-color images easily and quickly. The most excellent method is the so-called sublimation thermal transfer method, which uses sublimable dyes, as it has excellent continuous gradation properties and provides full-color images comparable to color photographs. The thermal transfer sheet used in the above-mentioned sublimation type thermal transfer method has a dye layer consisting of a sublimable dye and a binder formed on one side of a base film such as polyester film, and a dye layer consisting of a sublimable dye and a binder on the other side to prevent the thermal head from sticking. A base film with a heat-resistant layer provided on the other side is generally used. The dye layer surface of such a thermal transfer sheet is placed on a transfer material having an image-receiving layer made of polyester resin, etc., and the dye in the dye layer is transferred to the transfer material by heating it in an imagewise manner from the back side of the thermal transfer sheet with a thermal head. The desired image is formed.

0003

Problems to be Solved by the Invention In the thermal transfer method as described above, only the dye in the dye layer is transferred to the transfer material, and the binder remains on the base film side. On this occasion,
The better the transferability of the dye, the clearer and higher density the image will be formed. As a method to improve dye migration,
The simplest method is to increase the printing energy, but high printing energy is undesirable as it increases the printing cost.Also, when using a plastic film as the base film, there is a limit to the amount of energy that can be added. There is. Another known method is to include a low melting point sensitizer in the dye layer, but in this case, the relationship between the sensitizer and the dye and the resin binder forming the dye layer are There is a problem in that the compatibility of dyes and resin binders that can be used is limited. In other words, the presence of a sensitizer promotes the crystallization of the dye, resulting in a decrease in sensitivity, and as a result of the requirement for compatibility with the binder, it is not possible to use a binder with excellent heat resistance, and the fusion with the image-receiving sheet occurs during thermal transfer. There are problems such as abnormal transfer occurring due to adhesion. Therefore, an object of the present invention is to provide a thermal transfer method that can form images of satisfactory density with lower printing energy than conventional techniques, and that can form images of even higher density with the same printing energy as conventional techniques. It is to be.

0004

[Problems to be Solved] The above objects are achieved by the present invention as described below. That is, in the present invention, a thermal transfer sheet in which a dye layer consisting of a dye and a binder is provided on a base film, and a thermal transfer image-receiving sheet having a dye-receiving layer are stacked on top of each other, and the dye-receiving layer is formed by heating image-wise from the back side of the thermal transfer sheet. This thermal transfer method is characterized in that, before image formation, a dye transfer accelerator that is melted by the heat during thermal transfer is applied to the dye layer and/or the dye-receiving layer.

[0005]

[Operation] A dye transfer accelerator is applied to the dye layer surface of the thermal transfer sheet and/or the dye receiving surface of the thermal transfer image receiving sheet before or during thermal transfer, and when the dye is transferred from the dye layer after that, there is a gap between the dye layer and the dye receiving layer. The space is eliminated, and the heat applied from the thermal head is quickly propagated to the dye-receiving layer, thereby efficiently heating the dye-receiving layer. Furthermore, the molten dye transfer accelerator also acts as a solvent for the dye, further promoting dye transfer.

[0006]

[Preferred Embodiments] Next, the present invention will be explained in more detail by citing preferred embodiments. The thermal transfer sheet used in the present invention is one in which a dye layer consisting of a sublimable dye and a resin binder is provided on the surface of a suitable base film such as a polyester film, which itself is well known in the technical field. . The thermal transfer image-receiving sheet used in the present invention is a resin film that can be dyed with a sublimable dye, or a dye-receiving layer made of such a dyeable resin is provided on a suitable base sheet such as paper. and are likewise well known in the art. Furthermore, thermal transfer methods using these thermal transfer sheets and image-receiving sheets are also well known. In the thermal transfer method of the present invention, for example, as shown in Figures 1 to 3, a thermal transfer sheet 1 and a thermal transfer image-receiving sheet 2 are transferred to a platen 3 in the conventional thermal transfer method described above.
When forming an image on the dye-receiving layer of the image-receiving sheet by heating image-wise from the back side of the thermal transfer sheet with the thermal head 4, the dye layer and/or the dye-receiving layer of the thermal transfer sheet are heated by the heat during the thermal transfer. It is characterized by the addition of a dye transfer accelerator that melts.

In the present invention, materials suitable as dye transfer accelerators are compounds that melt due to the heat during thermal transfer, such as low molecular weight substances having a melting point of 50 to 150°C, preferably 60 to 130°C. The melting point may be lower than 50°C, but in this case, handling is not good due to adhesion, blocking, etc. On the other hand, if the melting point exceeds 150°C, the accelerating effect decreases rapidly, which is not preferable. Further, the low melting point compound used in the present invention preferably has a molecular weight in the range of 100 to 1,500, and if the molecular weight is less than 100, the melting point is lower than 50°C.
On the other hand, when the molecular weight is 1,
If it exceeds 500, the sharpness of the melting of the low melting point compound during thermal transfer will be lost and the accelerating effect will be insufficient, which is not preferable. The above low melting point compound may be any known low molecular weight substance, but preferred low melting point compounds in the present invention include thermoplastic resin oligomers, such as polyurethane oligomers, polystyrene oligomers, polyester oligomers, polyacrylic oligomers,
polyethylene oligomer, polyvinyl chloride oligomer,
Various oligomers such as polyvinyl acetate oligomer, ethylene/vinyl acetate copolymer oligomer, ethylene acrylic copolymer oligomer, polyoxyethylene oligomer, polyoxypropylene oligomer, polyoxyethylene propylene oligomer; myristic acid, palmitic acid,
Fatty acid amides such as margaric acid, stearic acid, arachic acid, montanic acid, caproic acid amide, caprylic acid amide, lauric acid amide, stearic acid amide, oleic acid amide, eicosenoic acid amide, methyl behenate, methyl lignocerate , methyl montanate, pentadecyl palmitate, hexacosyl stearate, carbamic acid [1,4-phenylenebis(methylene)]bisdimethyl ester, etc., fatty acid ester, etc., etc., 1
, 4-dicyclohexylbenzene, benzoic acid, aminobenzophenone, dimethyl terephthalate, fluoranthene, phenols, naphthalenes, phenoxy compounds and other aromatic compounds, and various waxes.

A particularly preferred low melting point compound in the present invention is a compound represented by the following general formula (I).

[Chemical formula 3] A-[B-X-Y-Z]2 (I)
(However, A in the above formula is the following structural formula

[Image Omitted] represents any of the groups represented by [Image Omitted], n is an integer of 1 or more, B represents either -NHCOO-, -NHCONR-, -CONH- or -NHCO-, and R has a substituent. is a C1 to C6 straight or branched alkyl group which may have a substituent, X is a straight or branched alkylene group which may have a substituent, and Y is a single bond, -O-, - S-, -COO
-, -OOC-, -NHCOO-, -OOCHN-, -
CONH-, -NHCO-, -SO2NH-, -NHS
A bonding group such as O2-, -SO2-, -O2S-, etc., and Z
is a hydrogen atom, a straight chain or branched alkyl group which may have a substituent and/or an unsaturated group, or a phenyl group. ) The compound represented by the above general formula (I) can be obtained by reacting a diisocyanate compound with an alcohol of the general formula HO-X-Y-Z or an N-substituted amine of the general formula HN(R)-X-Y-Z, or The dicarboxylic acid compound has the general formula H2N-X-Y-
Either by reacting the amine of Z or by adding the general formula H to the diamine compound.
It is a compound obtained by reacting OOC-X-Y-Z carboxylic acid. R, X, Y and Z in the above formula are as defined above. Among them, particularly preferred specific examples are as follows.

[C5]

[C6]

[C7]

[Chemical formula 8]

[0009] The method of applying the dye transfer accelerator as described above is not particularly limited, but preferred methods include the following methods. (1) As shown in Figure 1, as a thermal transfer sheet,
As shown in the figure, a method using a thermal transfer sheet in which layers consisting of a dye layer 20 and an accelerator 30 are sequentially provided. In the thermal transfer sheet used in this method, a dye layer 20 is formed on a base film 10 in the same manner as in the prior art, as shown in FIG.
0 is provided in sequential order. In the illustrated example, three colors of yellow (Y), cyan (C), and magenta (M) are provided as dye layers, and dye migration accelerator layers 31, 32, and 33 are provided in front of each color. The layer is not limited to three colors, but may be one color, two colors, or even four colors including black, and the dye transfer accelerator layer 30 may be provided before or after each color, Alternatively, only one area may be provided for each of three to four colors. For example, as shown in FIG. 5, the accelerator layer 31, Y, M,
When provided in the order C, the accelerator layer 31 may first be transferred over the entire surface to the required area of the image-receiving sheet.

[0010] In the above, the base film and the dye layer are the same as those in the prior art, and the dye migration accelerator layer is formed by applying a low concentration organic solvent solution or dispersion of the low melting point compound onto the base film using various coating methods. The layer is formed by coating the film with a solvent and evaporating the solvent. The promoter layer does not need to form a complete film, and may exist discontinuously in the form of particles as long as it melts and forms a liquid phase depending on the temperature during thermal transfer. The thickness of such a dye transfer accelerator layer is preferably 0.01 to 1.0 g/m<2> when expressed in terms of coating amount. If the coating amount is less than the above range, the effect of promoting dye transfer will be insufficient, while if it exceeds the above range, the effect of promoting dye transfer will be reduced. Further, when forming the dye transfer accelerator layer, various binders and various mold release agents can be used in combination with the low melting point compound within a range that does not impede achievement of the object of the present invention. Furthermore, various additives such as ultraviolet absorbers and antioxidants can also be used in combination.

An image forming method using the above thermal transfer sheet will be explained with reference to FIGS. 1 and 4. First, the dye transfer accelerator layer 31 of the thermal transfer sheet 1 is placed on the dye-receiving layer surface of the thermal transfer image-receiving sheet 2 placed on the platen 3, and the accelerator layer 31 is transferred onto the dye-receiving layer using a thermal head, a hot roll, or the like. The yellow (Y) dye layer of the thermal transfer sheet is then superimposed on the transferred accelerator layer 31 to form a desired yellow image. Accelerator layer 32 is then transferred and the magenta image is transferred. Similarly, the accelerator layer 33
A full color image is formed by transferring the cyan image and the cyan image. (2) A method of transferring an accelerator to the dye-receiving layer of the thermal transfer image-receiving sheet 2 using an accelerator transfer sheet 5 as shown in FIG. The accelerator transfer sheet 5 used in this method is the thermal transfer sheet used in (1) above, in which an accelerator layer is formed on the entire surface of the base film. An image forming method using the accelerator transfer sheet 5 will be explained with reference to FIG. 2. First of all,
The accelerator layer of the accelerator transfer sheet 5 is overlaid on the dye-receiving layer surface of the thermal transfer image-receiving sheet 2 placed on the platen 3, and the accelerator layer is transferred onto the dye-receiving layer using a thermal head, a thermal roll 6, etc. Then, the yellow dye layer of the thermal transfer sheet 1 is overlaid on the transferred accelerator layer to form a desired yellow image. The magenta and cyan images are then transferred to form a full color image. (3) A method of transferring the accelerator to the dye layer of the thermal transfer sheet 1 using the accelerator transfer sheet 5 as shown in FIG. In this method, the accelerator is transferred from the accelerator transfer sheet 5 similar to that in (2) above to the dye layer surface of the thermal transfer sheet, and then the dye is transferred to the dye-receiving layer of the image-receiving sheet to form a full-color image in the same way. .

[0012] The above examples are preferred examples, and other methods include preparing a dilute solution of the accelerator in a volatile solvent such as alcohol;
It is also possible to apply this to a thermal transfer sheet and/or an image-receiving sheet by coating or spraying. Any conventionally known means for applying thermal energy can be used to apply thermal energy when performing thermal transfer using the above-mentioned thermal transfer sheet and the above-mentioned thermal transfer image-receiving sheet. , 5 to 100 mJ/mm by controlling the recording time using a recording device such as a video printer VY-100).
A desired image is formed by applying thermal energy of about 2 degrees.

[0013]

[Examples] Next, the present invention will be explained in more detail by referring to reference examples, working examples, and comparative examples. In the text, parts or percentages are based on weight unless otherwise specified. Reference example 1~
28 A 5% ethyl alcohol solution of the low melting point compound shown in Table 1 below was applied to the surface of a 6 μm thick polyethylene terephthalate film as a base film at the solid content coating amount (
g/m2) using a gravure coater and drying to prepare a continuous film-like promoter transfer sheet of the present invention.

[Table 1] Table 1 1. CH2-[NHCOO-(CH2)2-CH3]2
2. (CH2)2-[NHCOO-(CH2)3-CH
3] 23. (CH2)3-[NHCOO-(CH2)2
-CH3]24. CH2-[NHCOO-(CH2)3
-CH3]2

[0014] The following ink composition for forming a dye layer was applied to the surface of a 6 μm thick polyethylene terephthalate film, which had been heat-resistant treated on the back side of the surface on which the dye layer was to be formed, as a base film to a dry thickness of 1.0 g/m2. A thermal transfer sheet was formed by coating and drying by gravure printing so as to have the following properties. Kayaset Blue 714 (Nippon Kayaku, C.I. Solvent Blue 63)

5.50 parts Polyvinyl butyral resin (S-LEC BX-1)
3.00 parts methyl ethyl ketone
22.5
Part 4 Toluene

68.18 parts Next, using synthetic paper (Oji Yuka Co., Ltd., Yupo FPG150) as a base film, a coating liquid with the following composition was applied to one side of the paper at a rate of 4.5 g/m2 when dry. , and dried at 100° C. for 30 minutes to obtain a thermal transfer image-receiving sheet. Polyester resin (manufactured by Toyobo, Vylon200)
11.5 parts Vinyl chloride-vinyl acetate copolymer (UCC, V
YHH) 5.0 parts Amino-modified silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., KF39
3) 1.2 parts epoxy modified silicone oil (manufactured by Shin-Etsu Chemical, X-22-343)
1.2 parts methyl ethyl ketone

40.8 parts toluene

40.8 copies
cyclohexanone

20.4 parts

Examples 1 to 5 The accelerator transfer sheets, the thermal transfer sheets, and the thermal transfer image receiving sheets of Reference Examples 1 to 5 in Table 1 were installed in a printer as shown in FIG. Place the receptor layer facing each other, and apply 12 sheets from the back side of the accelerator transfer sheet.
The accelerator was transferred to the entire surface using a heated roll at 0°C, and then a thermal head (KMT-85-6, MPD2) was used to apply a head voltage of 12.0 V and an applied pulse width of 16.0 m.
sec. 1msec from /line. step pattern, 6 lines/mm in the sub-scanning direction (
33.3msec. /line), thermal head recording was performed from the dye layer of the thermal transfer sheet, and the results shown in Table 2 below were obtained. In Comparative Example 1, the dye was directly transferred without transferring the dye transfer accelerator layer.

Examples 6 to 10 Using the printer shown in FIG. 3 and the accelerator transfer sheets of Reference Examples 6 to 10, the accelerator was transferred to the dye layer surface of the thermal transfer sheet, and the following procedure was carried out in the same manner as in Examples 1 to 5. The results shown in Table 2 below were obtained. Reference Examples 11 to 14 The following ink composition for forming a dye layer was applied to the surface of a 6 μm thick polyethylene terephthalate film, which had been heat-resistant treated on the back side of the surface on which the dye layer was to be formed, as a base film to a dry thickness of 1.0 g. /m2 width 3 by gravure printing
A dye layer was formed by coating and drying to a thickness of 0 cm. Kayaset Blue 714 (Nippon Kayaku, C.I. Solvent Blue 63)

5.50 parts Polyvinyl butyral resin (S-LEC BX-1)
3.00 parts methyl ethyl ketone
22.5
Part 4 Toluene

68.18 parts

Next, a 5% solution of the low melting point compound in Table 1 in ethyl alcohol was placed adjacent to the dye layer, and the solid content coating amount (g/
m2) using a gravure coater and drying to prepare a continuous film-like thermal transfer sheet. Examples 11-28 The thermal transfer sheets of Reference Examples 11-28 and the thermal transfer image-receiving sheet were overlapped with the dye transfer promoting layer and the dye-receiving layer facing each other, and a thermal head (K
Head applied voltage 1 using MT-85-6, MPD2)
2.0V, applied pulse width 16.0msec. /line
1msec. step pattern, 6 lines/mm in the sub-scanning direction (33.3 msec
．． /line) Perform thermal head recording under the conditions of
Next, a dye layer was layered on the transfer promoting layer under the same conditions, and thermal head recording was performed under the same conditions to obtain the results shown in Table 2 below.

[Table 2] Table 2 The relative sensitivity was determined by measuring the printed image density, and relative comparison was made with the printing density of Comparative Example 1 as 1.0.

[0018]

[Effects] As described above, according to the present invention, by applying a dye transfer accelerator to the dye layer and/or the dye receiving layer, an effect of improving density by 50% or more was obtained with the same printing energy.

[0019]

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically explaining the thermal transfer method of the present invention.

FIG. 2 is a diagram schematically explaining the thermal transfer method of the present invention.

FIG. 3 is a diagram schematically explaining the thermal transfer method of the present invention.

FIG. 4 is a diagram illustrating a thermal transfer sheet used in the present invention.

FIG. 5 is a diagram illustrating a thermal transfer sheet used in the present invention.

[Explanation of symbols]

1: Thermal transfer sheet 2: Image receiving sheet 3: Platen 4: Thermal head 5: Accelerator transfer sheet 6: Heat roll 10: Base film 20: Dye layer 30: Dye migration accelerator layer

Claims (5)

[Claims] Claim 1: A thermal transfer sheet in which a dye layer consisting of a dye and a binder is provided on a base film, and a thermal transfer image-receiving sheet having a dye-receiving layer are layered, and the thermal transfer sheet is heated in an imagewise manner from the back side to form the dye-receiving layer. 1. A thermal transfer method for forming an image, which comprises applying a dye transfer accelerator to a dye layer and/or a dye-receiving layer before image formation, which is melted by heat during thermal transfer. 2. The thermal transfer method according to claim 1, wherein the dye transfer accelerator comprises a compound represented by the following general formula (I). [Chemical formula 1] A-[B-X-Y-Z]2 (I)
(However, in the above formula, A represents any of the groups of the following structural formula [Chemical formula 2], n is an integer of 1 or more, and B is -NHCOO-, -NHCONR-, -CONH- or -NHCO- , R is a C1 to C6 straight chain or branched alkyl group which may have a substituent, and X is a straight chain or branched alkylene group which may have a substituent. Yes, Y is a single bond, -O-, -S-, -COO
-, -OOC-, -NHCOO-, -OOCHN-, -
CONH-, -NHCO-, -SO2NH-, -NHS
A bonding group such as O2-, -SO2-, -O2S-, etc., and Z
is a hydrogen atom, a straight chain or branched alkyl group which may have a substituent and/or an unsaturated group, or a phenyl group. ) Claim 3: The amount of dye transfer accelerator applied is 0.01
The thermal transfer method according to claim 1, wherein the amount is 1.0 g/m2. 4. The thermal transfer method according to claim 1, wherein the dye transfer accelerator is applied by a thermal transfer method. 5. An accelerator transfer sheet, characterized in that a transfer layer made of a compound that is melted by heat during thermal transfer is provided on a base film.