JP2008087331A - Thermal transfer recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal transfer recording medium which is proof to thermal fusion-bonding with an object to which an image is transferred during thermal transfer, and can realize the formation of a high-density image. <P>SOLUTION: This thermal transfer recording medium has a thermal transfer ink layer containing a dye and a binder resin, formed on one surface of a base. The binder resin is composed of a reaction product of a resin with an OH group and an oligomer of tetraalkoxysilane represented by formula: R<SB>1</SB>O(Si(OR<SB>2</SB>)<SB>2</SB>O)<SB>n</SB>R<SB>3</SB>, wherein R<SB>1</SB>, R<SB>2</SB>and R<SB>3</SB>are independently a methyl group, an ethyl group, a propyl group or a butyl group, any two or more of them may be the same or all of them are entirely different from each other, and n is an integer of 1 to 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a thermal transfer recording medium, and more particularly to a thermal transfer recording medium that can prevent thermal fusion with a transfer medium during thermal transfer and can form a sharp and high-quality image with a clear density difference.

  In recent years, a so-called sublimation type thermal transfer recording system has attracted attention as a kind of full-color printing system because of its characteristics such as fidelity of color tone reproduction and high image quality. This method uses a sublimation transfer sheet containing a sublimation dye on a base material and a sublimation transfer layer provided with a layer (hereinafter referred to as “receptive layer”) having a dyeing property to the dye on another base material. An image receiving sheet (hereinafter referred to as “image receiving sheet”) is pressed against the sheet, and thermal energy is applied by a thermal head having a heating element that selectively applies a voltage in accordance with a recording signal. This is a recording method in which a desired recording image is obtained by transferring and fixing (transferring) the receptor layer by adhesion, adsorption, dyeing or the like.

  A thermal transfer recording medium used in such a sublimation type thermal transfer recording system is generally one in which a thermal transfer ink layer is formed on a substrate made of a polyethylene terephthalate film or the like. The thermal transfer ink layer is usually formed by dispersing a sublimable dye in a binder resin. As the binder resin, polyvinyl acetal resins such as polyvinyl butyral resin and polyvinyl acetoacetal resin are widely used in consideration of compatibility with sublimation dyes, recording density, heat resistance and the like.

  By the way, when recording is performed using such a thermal transfer recording medium, the heat transfer ink layer of the thermal transfer recording medium and the image receiving layer of the image receiving sheet are fused by heat at the time of recording, causing a so-called blocking phenomenon. there were.

  In order to solve such problems, a thermal transfer ink layer of a thermal transfer recording medium is made to contain a release component such as silicone oil or silicone resin (for example, Patent Document 1 and Patent Document 2).

  However, in order to prevent blocking with the image receiving sheet, a large amount of silicone oil or silicone resin must be added. When a large amount of silicone oil is added, the receiving layer surface of the image receiving sheet is soiled by the silicone oil bleed from the thermal transfer ink layer, or the protective layer that is transferred after printing to protect the transferred image is transferred from the thermal transfer ink layer to the receiving layer surface. There was a problem that the adhesion was hindered by the silicone oil transferred to. In the case of a silicone resin, a similar problem occurs due to bleeding of unreacted silicone contained in the silicone resin.

  By the way, in order to improve the image quality, the high density portion printed by applying high energy by the printer has a high density, and the density of the low density portion printed by applying low energy by the printer has to be low. However, when the silicone oil or the like bleeds, the density is increased due to the influence of bleed even in the portion where the concentration is not desired in the low concentration portion. This makes it impossible to perform so-called “footstep” that keeps the density of the low density portion low, and the sharpness of the image is impaired.

On the other hand, when applying the coating liquid for forming the thermal transfer ink layer on the substrate with a gravure coater or the like, when silicone oil is added as described above, air is easily involved and bubbles are generated in the coating liquid, There was a problem that so-called omission and streaks occur on the coated surface due to the bubbles. If there are such omissions and streaks, the appearance of the product will deteriorate. In addition, since there is no ink layer or only a thin layer in the omission or streak portion, if printing is performed in this state, the image quality of the printed material is deteriorated, and the dye is not transferred to the printed material. Phenomena such as missing state, lack of color, or light color occur. For this reason, it is necessary to suppress the occurrence of missing or streaks on the coated surface.
JP-A-8-310136 Japanese Patent No. 3150691

  The present invention has been made to solve the above problems, and does not cause blocking even if silicone oil or silicone resin is not blended in the thermal transfer ink layer, and forms a sharp image with a clear density difference. It is an object of the present invention to provide a thermal transfer recording medium that can be used.

The thermal transfer recording medium of the present invention is a thermal transfer recording medium having a thermal transfer ink layer containing a dye and a binder resin on one side of a substrate, wherein the binder resin has a resin having an OH group, and the following general formula (1 ):
R ₁ O (Si (OR ₂ ) ₂ O) _n R ₃ (1)
(In the formula, R ₁ , R ₂ and R ₃ are each independently a methyl group, an ethyl group, a propyl group or a butyl group, and even if any two or more are the same, all are different. Or n represents an integer of 2 to 10), and is characterized by comprising a reaction product with an oligomer of tetraalkoxysilane.

  According to the thermal transfer recording medium of the present invention, blocking is prevented without adding a silicone resin or silicone oil which has been conventionally used to prevent thermal fusion (blocking) with a transfer target during thermal transfer. be able to.

  In addition, since it is not necessary to use silicone oil, it is possible to keep the print density of the low density areas where the density is not desired low, and to increase the density in the high density area. An image can be formed.

  Furthermore, since the occurrence of missing or streaks on the coated surface is suppressed, a thermal transfer recording medium having an excellent appearance as a product can be obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in the schematic cross-sectional view in the thickness direction of FIG. 1, the thermal transfer recording medium 1 according to the present invention is provided with a thermal transfer ink layer 3 containing a dye and a binder resin on one surface of a substrate 2. Become.

  As a base material used for the thermal transfer recording medium of the present invention, a known material conventionally used as a base material can be used as it is. For example, polyester film such as polyethylene terephthalate film, polyethylene naphthalate film, polycarbonate film, polyvinyl chloride film, polyvinylidene chloride film, cellulose acetate film, polyvinyl alcohol film, nylon film, fluororesin film, aramid film, polyamide film, polyethylene Film, polysulfone film, polystyrene film, polyimide film, polypropylene film, cellophane film, ionomer film and other synthetic resin films, chlorinated rubber film and other rubber films, condenser paper, glassine paper, thin paper such as tracing paper, non-woven fabric, and Although these composites etc. are mentioned, it is not limited to these. Among them, a film having heat resistance is preferable, and a polyethylene terephthalate film is particularly preferable from the viewpoint of price, mechanical strength, dimensional stability, heat resistance, and the like. The thickness of the substrate is preferably 0.5 to 20 μm, and more preferably 3 to 10 μm.

  Note that the surface of the substrate 2 opposite to the surface on which the thermal transfer ink layer 3 is formed (the back surface), that is, the surface to which heat is directly applied during transfer, protects the substrate from heat and fuses with the thermal head. It is desirable to provide a heat resistant slipping layer for the purpose of preventing adhesion, improving running performance, and preventing blocking between the back surface of the substrate and the thermal transfer ink layer. The heat resistant slipping layer can be formed of a fluororesin, a silicone resin, a reaction product of a polyvinyl butyral resin and an isocyanate resin, a curable silicone oil, a curable silicone wax, or the like. Further, it is possible to further improve the lubricity by adding a filler such as a phosphate ester-based surfactant, talc, and mica to the heat-resistant slip layer.

  The dye blended in the thermal transfer ink layer coating liquid in the thermal transfer recording medium of the present invention is a dye that melts, diffuses, or sublimates by heat, and any of the dyes used in conventionally known thermal transfer recording media. It can be used.

  For example, methine series such as diarylmethane series, thiazole series, indoaniline, acetophenone azomethine, imidazole azomethine, azomethine series represented by pyridone azomethine, xanthene series, oxazine series, cyanomethylene series represented by dicyanostyrene, azine series, Examples include thiazines, benzeneazos, pyridoneazos, isothiazoleazos, imidazoleazos, pyrroloazos, disazos, triazoleazos, and other azos, naphthoquinones, anthraquinones, quinophthalones, rhodamine lactams, and the like.

  Specifically, C.I. I. (Color Index) Disperse Yellow 3, 7, 23, 51, 54, 60, 79, 141 etc., C.I. I. (Color Index) Disperse Blue 14, 19, 24, 26, 56, 287, 301, 354, C.I. I. (Color Index) Disper Thread 1, 59, 60, 73, 135, 167, etc., C.I. I. (Color Index) Disperse Violet 4, 13, 26, 31, 36, 56, etc., C.I. I. (Color Index) Disperse Orange 149, C.I. I. (Color Index) Solvent Yellow 14, 16, 29, 56, 201 etc., C.I. I. (Color Index) Solvent Blue 11, 35, 36, 49, 50, 63, 97, 105 etc., C.I. I. (Color Index) Solvent Red 18, 19, 23, 24, 25, 81, 143, 182, etc., C.I. I. (Color Index) Solvent Violet 13, etc., C.I. I. (Color Index) Solvent Green 3 etc., C.I. I. (Color Index) Solvent Black 3 etc. can be mentioned.

  The dye in the thermal transfer ink layer coating liquid is preferably blended in an amount of 5 to 90% by weight, more preferably 10 to 70% by weight, based on all components constituting the thermal transfer ink layer.

  The binder resin in the present invention for supporting the dye as described above comprises a reaction product of a resin having an OH group and a tetraalkoxysilane oligomer represented by a specific general formula.

  Any resin having an OH group may be used as long as it has an OH group for reacting with an oligomer of tetraalkoxysilane described later, and a known resin can be used. Specifically, cellulose resins such as ethyl cellulose, methyl cellulose, ethyl hydroxy cellulose and cellulose acetate, vinyl resins such as polyvinyl butyral, polyvinyl alcohol, polyvinyl acetal and polyvinyl acetate, acrylic resins such as poly (meth) acrylate, polyurethane Examples thereof include resins, polyamide resins, and polyester resins. These can be used alone or in combination.

An oligomer of tetraalkoxysilane (hereinafter referred to as “silicate”) to be reacted with a resin having an OH group has the following general formula:
R ₁ O (Si (OR ₂ ) ₂ O) _n R ₃ (1)
(In the formula, R ₁ , R ₂ and R ₃ are each independently a methyl group, an ethyl group, a propyl group or a butyl group, and even if any two or more are the same, all are different. And n represents an integer of 2 to 10.

  Here, n represents the degree of oligomerization of the oligomer. Since usually available silicates may be a mixture of oligomers with different n, the degree of multimerization is represented by average n. Preferred n is 2 to 10, particularly 2 to 8. If n exceeds 10, the viscosity is high and it may be difficult to adjust the coating solution. On the other hand, n is 1, that is, a monomer cannot be used because it is harmful to the eyes. Therefore, it is necessary to make the monomer content less than about 0.2%, and this can be carried out by adding a step of removing the monomer in the silicate production step.

  In the present specification, the structural formula is expressed as having a linear structure, but it is actually considered to be a mixture of those having a branched, cyclic, or network structure. However, since it is difficult to specify the structure, in the present specification, a linear product is expressed as a representative of these mixtures.

  Of the silicates, methoxysilicate is preferred from the viewpoint of reactivity and film-forming property. As such silicates, MS51, MS56, MS56S, MS57 (above, tetramethoxysilane, manufactured by Mitsubishi Chemical), MS58B15, MS58B30 (the methoxy group of the tetramethoxysilane partially modified to a butoxy group, manufactured by Mitsubishi Chemical) , BTS (tetrabutoxysilane, manufactured by Mitsubishi Chemical), and the like, which can be easily obtained from the market.

  The mixing ratio of the OH group-containing resin and silicate is preferably 1 to 20 parts by weight with respect to 100 parts by weight of the OH group-containing resin. If the amount is less than 1 part by weight, the effect of the addition cannot be obtained. On the other hand, even if added over 20 parts by weight, not only the effect can not be obtained, but also after the coating, the stickiness of the coated surface until heating, drying and reacting becomes stronger, so There is a risk of blocking.

  The reaction product of the resin having an OH group and the tetraalkoxysilane oligomer represented by the general formula (1) has a temperature in the range of 30 to 80 ° C. and a reaction time in the range of 12 to 72 hours, for example. It can be obtained by reacting.

  The thermal transfer recording medium of the present invention can be produced as follows. An optional component such as a dye, a resin having an OH group, a silicate, a stabilizer, a dispersant, and fine particles is added to an appropriate solvent, and dissolved or dispersed to prepare a coating solution for forming a thermal transfer ink layer. This is applied and dried on a base material such as polyethylene terephthalate so that the thickness of the layer is 0.1 to 5.0 μm, preferably 0.3 to 2.0 μm. Thereafter, for example, by heating at 60 ° C. for about 24 hours, a resin having an OH group and silicate are reacted to form a thermal transfer ink layer, and the thermal transfer recording medium according to the present invention can be manufactured.

  If necessary, a heat-resistant slipping layer as described above may be provided on the substrate opposite to the side on which the thermal transfer ink layer is provided. Furthermore, an intermediate layer may be provided between the base material and the thermal transfer ink layer for the purpose of improving adhesiveness and cushioning.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, these Examples are illustrations and this invention is not limited to these Examples.

(Compatibility evaluation and production of thermal transfer media)
[Example 1]
On the other surface of a 5 μm thick polyethylene terephthalate film that has been heat-treated on one surface as a substrate, a coating solution for forming a thermal transfer ink layer having the following composition has a thickness of 1. It apply | coated with the gravure coater so that it might be set to 0 micrometer, and was dried. Thereafter, it was allowed to stand at 60 ° C. for 24 hours to produce a thermal transfer medium of the present invention having a thermal transfer ink layer.

<Composition of coating liquid for thermal transfer ink layer>
Butyral resin 10.0 parts by weight (Denka Butyral 3000-1, manufactured by Denki Kagaku Kogyo, hydroxyl value 20)
Kayaset Blue 714 (Nippon Kayaku sublimation dye) 9.0 parts by weight Silicate 1.0 parts by weight (MS56S, manufactured by Mitsubishi Chemical Corporation)
Toluene 40.0 parts by weight Methyl ethyl ketone (MEK) 40.0 parts by weight Total 100.0 parts by weight

[Examples 2 to 5]
A thermal transfer medium was produced in the same manner as in Example 1 except that the composition of the thermal transfer ink layer coating solution in Example 1 was changed as shown in Table 1.

ＢＸ−１：積水化学製ポリビニルブチラール樹脂
ＫＳ−１：積水化学製ポリビニルアセタール樹脂
ＭＳ５６Ｓ：三菱化学製テトラメトキシシラン
ＭＳ５８Ｂ３０：三菱化学製変性テトラメトキシシラン
ＫＦ９６：信越シリコーン製ジメチルシリコーンオイル
ダイアロマーＳＰ３０２３：大日精化製シリコーン変性塩化ビニル樹脂
サイマックＵＳ３８０：東亜合成化学製シリコーン変性アクリル樹脂

BX-1: Polyvinyl butyral resin manufactured by Sekisui Chemical KS-1: Polyvinyl acetal resin manufactured by Sekisui Chemical MS56S: Tetramethoxysilane manufactured by Mitsubishi Chemical MS58B30: Modified tetramethoxysilane manufactured by Mitsubishi Chemical KF96: Dimethylsilicone oil manufactured by Shin-Etsu Silicone Dialomer SP3023: Dainichi Silicone Modified Vinyl Chloride Resin Cymac US380: Toa Gosei Chemical's Silicone Modified Acrylic Resin

[Comparative Examples 1-3]
A thermal transfer medium was produced in the same manner as in Example 1 except that the composition of the thermal transfer ink layer coating solution in Example 1 was changed as shown in Table 2.

(Surface quality evaluation of thermal transfer ink layer)
Each thermal transfer medium of the above Examples and Comparative Examples was continuously produced for 1500 m, and the coated surface of the formed thermal transfer ink layer was visually observed. The evaluation criteria are as follows, and the results are shown in Table 3.
○: No bubbles or streaks were observed. ×: Bubbles or streaks were observed.

(Preparation of image receiving sheet for evaluation)
An unstretched polypropylene film (Toyobo's Pyrene Film-CT is applied on a Mitsubishi paper A-2 coat (thickness: 165 μm) as a base material so that the applied amount of urethane adhesive is 5 g / m ^2. P1128, thickness 30 μm) was laminated by dry lamination.

Further, on the unstretched polypropylene film, a receiving layer coating solution having the following composition was applied so as to have a coating amount of 4.0 g / m ² and dried at 100 ° C. for 60 minutes to obtain an image receiving sheet used for evaluation. It was.

<Composition of coating liquid for receiving layer>
Polyester resin (Byron 290, manufactured by Toyobo) 100 parts by weight Toluene / methyl ethyl ketone (1: 1) 500 parts by weight

(Evaluation of printing density)
Each thermal transfer recording medium obtained in the above examples and comparative examples was set in a Sony sublimation thermal transfer printer CVP-G7. The image receiving sheet was used by cutting the image receiving sheet prepared above into a size of 100 × 140 mm. Using the printer, gradation printing of 32 gradations was performed on the image receiving sheet, and the reflection densities of the low density part and the high density part were measured with Macbeth RD-918 manufactured by Gretag Macbeth. The evaluation is performed by printing all examples and comparative examples under the same conditions, measuring the same gradation portion, and using the measurement results of Example 1 (high density range 2.4, low density range 0.25) as a reference. It was as follows. The results are shown in Table 3.

(High concentration range)
A: Same as Example 1, or high print density (Example 1: A).
○: Inferior to Example 1, but the decrease rate is less than 10%.
X: It is inferior to Example 1, and a fall rate is 10% or more.

(Low concentration range)
A: The printing density is the same as in Example 1 (Example 1 is A).
○: Concentration increase is less than 10% with respect to Examples.
X: Concentration increase is 10% or more with respect to Example 1.

(Evaluation of blocking)
The thermal transfer recording media produced in the above examples and comparative examples were set in a Sony sublimation thermal transfer printer CVP-G7. The image receiving sheet was used by cutting the image receiving sheet prepared above into a size of 100 × 140 mm. Using the printer, a gradation printing of 32 gradations was performed on the image receiving sheet in an environment of 50 ° C. and 80% RH, and the blocking state at that time was confirmed. The evaluation criteria are as follows, and the results are shown in Table 3.
A: There is almost no peeling sound.
○: When printing, the peeling sound when the thermal transfer recording medium is peeled off from the image receiving sheet is small enough not to bother.
X: The sound of peeling when the thermal transfer recording medium is peeled off from the image receiving sheet during printing is large.

  From the above results, the thermal transfer recording medium of each example has suppressed the generation of bubbles at the time of manufacture, but the thermal transfer recording medium of each comparative example generated bubbles, and as a result, the surface quality of the coated surface was inferior. You can see that In addition, the reflection density is increased in the low density region of the comparative example, but this is an apparent increase due to the bleeding of the silicone, and the so-called print density of the part where the density is not desired to be low in the low density part is suppressed. It can be seen that the image cannot be sharp enough and the image is not sharp. On the other hand, in each embodiment, since the footing in the low density region is surely made, the sharpness of the image in combination with the low density in the low density region and the high density in the high density region. It can be seen that is formed.

1 is a schematic cross-sectional view in the thickness direction showing the structure of an example of a thermal transfer recording medium according to the present invention.

Explanation of symbols

1: Thermal transfer recording medium 2: Base material 3: Thermal transfer ink layer

Claims (2)

In a thermal transfer recording medium having a thermal transfer ink layer containing a dye and a binder resin on one surface of a substrate, the binder resin has a resin having an OH group, and the following general formula (1):
R ₁ O (Si (OR ₂ ) ₂ O) _n R ₃ (1)
(In the formula, R ₁ , R ₂ and R ₃ are each independently a methyl group, an ethyl group, a propyl group or a butyl group, and even if any two or more are the same, all are different. And n represents an integer of 2 to 10). A thermal transfer recording medium comprising a reaction product with an oligomer of tetraalkoxysilane represented by: 2. The thermal transfer recording medium according to claim 1, wherein the tetraalkoxysilane oligomer is selected from tetramethoxysilane, partially modified tetramethoxysilane in which a methoxy group of tetramethoxysilane is partially modified to a butoxy group, or tetrabutoxysilane.

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