JP2003039837A - Thermal transfer sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal transfer sheet which is excellent in image reproducibility even after being stored for a long period and can form a quality image. SOLUTION: The thermal transfer sheet has a base material sheet and a dye layer formed from dye and a binder resin on one side of the base material sheet. The dye sheet contains at least two dyes having the same basic skeleton, and at least one of the dyes has a melting point which is different by at least 10 deg.C from the melting points of the other dyes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer sheet used in a sublimation type thermal transfer recording system, and more particularly, it has excellent long-term storage stability, excellent image reproducibility even after long-term storage, and gives a high-quality image. It relates to a thermal transfer sheet.

[0002]

2. Description of the Related Art Conventionally, a sublimation type thermal transfer recording system is widely known as a system for easily obtaining a full color image. In this recording method, three colors of thermal transfer are formed by forming dye layers of respective hues on one surface of a base material film such as a polyester film by using sublimable dyes of yellow, cyan and magenta colors and an appropriate binder resin. The basis is to use sheets. For image formation, these three color heat transfer sheets (adding black color if necessary) are sequentially laminated on a heat transfer image-receiving sheet having a dye-dyeing property, and the dye is transferred to the dye-receiving layer of the image receiving sheet by a thermal head each time. Sublimation is transferred to reproduce the full-color image of the original.

[0003]

With the spread of the sublimation type thermal transfer recording system as described above, it becomes possible to easily obtain a more photographic-like image by a dry process, and as a result, the required performance for media and images is also increased. It is rising. Among them, if the thermal transfer sheet is prepared and stored for a long period of time, the presence state of the dye in the dye layer changes and the dye becomes rich on the surface of the dye layer, depending on the storage environment. There is.

Therefore, when an image is formed using such a thermal transfer sheet, the dye easily transfers to the image receiving paper even with a low applied energy. Therefore, if the thermal transfer sheet so far is stored for a long period of time, a density higher than the desired density is developed particularly in the highlight portion of the image, and a good quality image cannot be obtained, or the image receiving paper is printed only by the platen pressure at the time of printing. There was an inconvenience that the dye migrated to.
Further, the dye is transferred to the image receiving paper by preheating the thermal head, and the image receiving paper is contaminated.
Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art,
An object of the present invention is to provide a thermal transfer sheet which has good image reproducibility even after long-term storage and is capable of forming a high-quality image.

[0005]

The above object can be achieved by the present invention described below. That is, the present invention is a thermal transfer sheet having a base material sheet and a dye layer formed from a dye and a binder resin on one surface of the base material sheet, the dye layer having at least the same basic skeleton. There is provided a thermal transfer sheet comprising two kinds of dyes, and at least one kind of the dyes has a melting point difference of 10 ° C. or more with other dyes.

According to the above invention, the dye layer contains at least two kinds of dyes having the same basic skeleton, and at least one of the dyes has a melting point difference of 10 ° C. or more with other dyes. By using a dye mixture having
It has been found that the above problems can be solved when the thermal transfer sheet is stored for a long period of time. Although the reason why the problem is solved is unknown, the difference in melting point is 10 ° C. or more, that is,
Since the crystallinity of one type becomes higher, the dye collected on the surface of the dye layer causes agglomeration, and when a predetermined energy is applied, a part of the energy is used to disperse the dye agglomerates, and apparently a predetermined amount. The following energy is applied. Therefore, it is the same as applying a thermal transfer sheet whose density has increased due to long-term storage with energy of a predetermined level or less, and has the same image reproducibility as when the thermal transfer sheet is manufactured, and a high-quality image can be formed. It is estimated.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to the following preferred embodiments. The dye used in the present invention is a dye that is transferred by heat and contains at least two kinds of dyes having the same basic skeleton, and at least one of the dyes has a melting point of 10 ° C. or more with other dyes. Any dye may be used as long as it is a dye having a difference of, and is not particularly limited.

Preferred yellow dyes in the present invention are:
A yellow dye having a basic skeleton selected from quinophthalone dyes represented by the following general formula 1 or dicyanostyryl dyes represented by the following general formula 2. (In the formula, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ can be independently selected, and each is a hydrogen atom, a halogen atom, a C1 to C8 alkyl group, a cycloalkyl group, an alkoxy group, an alkoxyalkoxy group, Represents an alkoxycarbonyl group, a thioalkoxy group, an alkylsulfonyl group, an amino group, a substituted or unsubstituted phenoxy group, or a substituted or unsubstituted thiophenoxy group, wherein R ₆ and R ₇ can be independently selected and each is a hydrogen atom. , An alkyl group, an alkoxyalkyl group, a cycloalkyl group, an allyl group, an aryl group which may have a substituent, an aralkyl group, a furfuryl group,
It represents a tetrahydrofurfuryl group or a hydroxyalkyl group. )

Among the dyes represented by the above general formula 1, particularly preferable dyes are shown in the following Table 1 by the substituents, but the present invention is not limited to the dyes exemplified below.

[0010] (R ₁ in the formula represents an allyl group or an alkyl group,
R ₂ represents a substituted or unsubstituted alkyl group or aryl group, A represents —CH ₂ —, —CH ₂ CH ₂ —, —CH ₂ CH ₂ O—, —
Represents CH ₂ CH ₂ OCH ₂ — or —CH ₂ CH ₂ OCH ₂ CH ₂ —, and R ₃ represents an alkyl group. )

Among the dyes represented by the above general formula 2, particularly preferable dyes are shown in the following Table 2 by the substituents, but the present invention is not limited to the dyes exemplified below.

The preferred magenta dye in the present invention is
It is a magenta dye having a basic skeleton selected from imidazole azo dyes represented by the following general formula 3 or anthraquinone dyes represented by the following general formula 4. (In the formula, R represents an alkyl group, an alkenyl group, an aryl group, a cyanoalkyl group, a substituted or unsubstituted alkoxycarbonylalkyl group, and R ₁ and R ₂ are an alkenyl group, an aralkyl group, or a substituted or unsubstituted group. X represents a hydrogen atom, a methyl group, a methoxy group, a formylamino group, an alkylcarbonylamino group, an alkylsulfonylamino group, or an alkoxycarbonylamino group, and Y represents a hydrogen atom, a methyl group, or a methoxy group. Represents a group or halogen atom.)

Among the dyes represented by the above general formula 3, particularly preferable dyes are shown in the following Table 3 by their substituents, but the present invention is not limited to the dyes exemplified below. (R in the formula represents a hydrogen atom, a hydroxyl group, a substituted or unsubstituted alkyl group or a substituted or unsubstituted alkoxy group, and X and Y represent an amino group or a hydroxyl group. N represents 1 or 2. .)

Among the dyes represented by the above general formula 4, particularly preferable dyes are shown in the following Table 4 by their substituents, but the present invention is not limited to the dyes exemplified below.

The preferred cyan dye in the present invention is a cyan dye having a basic skeleton selected from an indoaniline dye represented by the following general formula 5 or an anthraquinone dye represented by the following general formula 6. (In the formula, R ₁ represents an alkyl group optionally substituted by a hydrogen atom or a fluorine atom, an alkoxy group, a formylamino group, an alkylcarbonylamino group optionally substituted by a fluorine atom or a halogen atom, and R ₂ is ,
Represents an alkyl group optionally substituted by a hydrogen atom or a fluorine atom, an alkoxy group, or a halogen atom,
R ₃ and R ₄ represent a hydrogen atom, an alkyl group which may be substituted with a fluorine atom, an alkoxy group or a halogen atom, and R, R ₅ and R ₆ represent a hydrogen atom, C 1 to C ₆
Represents a substituted or unsubstituted alkyl group, aryl group or alkoxy group. )

Among the dyes represented by the above general formula 5, particularly preferable dyes are shown in the following Table 5 by the substituents, but the present invention is not limited to the dyes exemplified below.

[0017] (R ₁ and R ₂ in the formula each represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted allyl group or a substituted or unsubstituted aralkyl group.)

Among the dyes represented by the above general formula 6, particularly preferable dyes are shown in the following Table 6 by their substituents, but the present invention is not limited to the dyes exemplified below.

When using the dyes of the above-mentioned general formulas 1 to 6, at least two kinds of dyes having the same basic skeleton are used, and at least one of the dyes is 10 ° C. or more with another dye. Used so that they have different melting points. The number of dyes is at least 2 or more. For example, when 2 to 4 types of dyes are used, the dye having a higher melting point is A and the dyes having a lower melting point are B, C and D. The melting point of A is 1 than any of the melting points of dyes B, C and D.
Use a dye that is higher than 0 ° C. The usage ratio (weight ratio) of the dye A to another dye having the same basic structure is [A]: [B and / or C and / or D] = 20 to 90:80 to
It is preferably 10. If the amount of either one of the dyes is too much or too little, the object of the present invention is not sufficiently achieved.

The dyes having the same basic skeleton are used as the dyes having the same hue. If the basic skeletons are not the same, the difference in crystallinity is so large that the dyes are less likely to aggregate in the dye layer. On the other hand, the same basic skeleton increases the tendency of aggregation. Further, since there is a difference in melting point of 10 ° C. or more, sufficient effects are exhibited as in the present invention.

The substrate sheet used for the thermal transfer sheet of the present invention may be any one as long as it has a conventionally known degree of heat resistance and strength. For example, preferably paper having a thickness of about 0.5 to 50 μm, more preferably about 2 to 10 μm, various processed papers, polyester film, polystyrene film, polypropylene film, polysulfone film, polycarbonate film, aramid film, polyvinyl alcohol film, cellophane. The polyester film is particularly preferable.

The dye layer provided on the surface of the substrate sheet as described above contains at least two kinds of dyes having the same basic skeleton, and at least one of the dyes has a melting point of 10 ° C. or more with other dyes. It is a layer in which a dye mixture having a difference of is supported by an arbitrary binder resin. Any conventionally known binder resin can be used as the binder resin for supporting the dye mixture. Examples of preferred binder resins include ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxycellulose, hydroxypropyl cellulose, ethyl hydroxyethyl cellulose, methyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cellulose derivatives such as cellulose nitrate, polyvinyl alcohol, poly. Vinyl-based resins such as vinyl acetate, polyvinyl butyral, polyvinyl acetoacetal, polyvinyl pyrrolidone, polystyrene, polyvinyl chloride, acrylic resins such as polyacrylonitrile and polyacrylic acid ester, polyamide resins, polyester resins, polycarbonate resins, phenoxy resins, phenol resins ,Epoxy resin,
Examples thereof include elastomers, which may be mixed or copolymerized for use, or may be used as a crosslinked product with various crosslinking agents. In particular, polyvinyl butyral and polyvinyl acetoacetal are preferable from the viewpoint of heat resistance and dye transferability. The dye layer of the thermal transfer sheet of the present invention is basically formed of the above-mentioned materials, but may also include an organic filler such as polyethylene powder and various additives similar to conventionally known ones as necessary. it can.

For such a dye layer, the above-mentioned dye mixture, binder resin and other optional components are added to a suitable solvent to dissolve or disperse each component to prepare a dye layer forming coating liquid or ink. It is preferable to form this by coating and drying it on the above-mentioned substrate sheet. The dye layer thus formed is preferably 0.2 to 5.0 μm.
m, more preferably about 0.4 to 2.0 μm. Further, the above-mentioned dye mixture in the dye layer is preferably 5 to 70% by weight, more preferably 10 to 70% by weight based on the weight of the dye layer.
It is preferably present in an amount of 60% by weight.

The thermal transfer sheet of the present invention formed as described above may have a dye layer of only one color formed on the substrate film, or may have a plurality of colors, for example, dyes of three colors of yellow, magenta and cyan. The layers may be, for example, a multicolor thermal transfer sheet in which the layers are separately applied in the size of A4 or B5. 1 for multicolor thermal transfer sheet
This is convenient because a full-color image is formed by the thermal transfer sheet of the kind. Further, a black dye layer may be added in addition to the three color dye layers.

Further, the thermal transfer sheet of the present invention comprises a dye layer provided in a frame-sequential manner, and a transferable protective layer in which a transferable protective layer is further formed in a frame-sequential manner, and a protective layer for protecting an image surface after image formation can be transferred. Can be provided. In such a transferable protective layer, when the base film is not releasable, a release layer or a release layer is provided between the base film and the protective layer to improve the transferability of the protective layer. Is desirable. The structures of such a release layer, a release layer and a transferable protective layer are already known, and in the present invention, the transferable protective layer can be provided according to a known method.

The thermal transfer sheet of the present invention as described above is sufficiently useful as it is for thermal transfer, but an anti-adhesion layer, that is, a releasing layer may be further provided on the surface of the dye layer. By providing such a layer, it is possible to prevent the thermal transfer sheet and the image receiving sheet from sticking to each other during thermal transfer, use a higher thermal transfer temperature, and form an image with a more excellent density.

As the release layer, a considerable effect can be obtained by simply adhering the inorganic powder having anti-adhesion property. Further, for example, it can be formed by providing a release layer of preferably 0.01 to 5 μm, more preferably 0.05 to 2 μm from a resin having excellent release properties such as silicone polymer, acrylic polymer, and fluorinated polymer. it can. It should be noted that the inorganic powder or the releasing polymer as described above has a sufficient effect even when incorporated in the dye layer. Further, a heat-resistant layer may be provided on the back surface of such a thermal transfer sheet in order to prevent adverse effects due to the heat of the thermal head.

The image-receiving sheet used to form an image using the above-mentioned thermal transfer sheet may be any one as long as its recording surface has a dye-accepting property to the above-mentioned dye, and In the case of paper, metal, glass, synthetic resin or the like having no dye-accepting property, the dye-accepting layer may be formed on at least one surface thereof.

Particularly preferred is a sheet or film made of polyester or a processed paper provided with a polyester layer. Further, even if it is a non-dyeing image-receiving sheet of paper, metal, glass or the like, a solution or dispersion liquid of the dyeing resin as described above is applied to the recording surface and dried, or a resin film thereof. It is possible to obtain an image receiving sheet by laminating.

Further, even in the above-mentioned dye-receiving image-receiving sheet, a dye-receiving layer may be formed on the surface of the image-receiving sheet, as in the case of the above-mentioned paper, from a resin having a better dyeing property.
The dye-receptive layer thus formed may be made of a single material or a plurality of materials, and may further contain various additives as long as the intended purpose is not impaired.

As the means for applying the thermal energy used when performing thermal transfer using the thermal transfer sheet of the present invention as described above and the image receiving sheet as described above, any conventionally known applying means can be used. By controlling the recording time with a recording device such as a printer (for example, a video printer VY-100 manufactured by Hitachi), thermal energy of about 5 to 100 mJ / mm ² is applied to achieve the intended purpose sufficiently. can do.

[0032]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. In the following text, "part" or "%" is based on weight unless otherwise specified. Examples 1 to 5 and Comparative Examples 1 to 3 Ink compositions for forming a dye layer having the following compositions were prepared, and a 6 μm thick polyethylene terephthalate film (trade name Lumirror, manufactured by Toray Industries, Inc.) having a heat-treated back surface was prepared. The surface was coated with a wire bar coating method so that the dry coating amount was 1.0 g / m ² , followed by drying at 80 ° C. for 1 minute and the thermal transfer sheets (D1 to D5) of Examples 1 to 5 and Comparative Examples. 1-3 thermal transfer sheets (D6 to D8) were obtained. <Ink composition for forming dye layer> 3 parts of polyvinyl acetoacetal resin (Sekisui Chemical Co., Ltd., trade name KS-5) Dye mixtures D1 to D8 described in Table 7 below (the usage amounts are shown in Table 7). Methyl ethyl ketone / toluene (weight mixing ratio 1/1) 90 parts

[0033]

<Use Example> Next, a synthetic paper (trade name: YUPO FPG # 150, thickness 150 μm, manufactured by Oji Yuka Co., Ltd.) was used as a base sheet, and one surface of the synthetic paper was coated with the following composition for an intermediate layer. The coating solution and the coating solution for receiving layer were applied and dried by a wire bar so that the dried amounts were 1.0 g / m ² and 2.5 g / m ² , respectively, to obtain an image receiving sheet. <Coating liquid composition for intermediate layer> Polyester resin (Vylon200, manufactured by Toyobo) 10 parts Titanium oxide (trade name TCA-888, manufactured by Tochem Products) 20 parts Methyl ethyl ketone / toluene (weight ratio 1/1) 120 parts

[0035] <Receptor layer coating liquid composition R-1>   Cellulose acetate butyrate   (Product name: CAB551-0.2, manufactured by Eastman Chemical) 35 parts   Cellulose acetate butyrate   (Brand name CAB551-0.1, manufactured by Eastman Chemical) 65 parts   Polycaprolactone (Brand name Praxel H-5, manufactured by Daicel Chemical) 10 parts   Polyether-modified silicone (KF-6012, Shin-Etsu Chemical Co., Ltd.) 0.5 part   Methyl ethyl ketone / toluene (weight ratio 1/1) 440 parts

[0036] <Receptor layer coating liquid composition R-2>   Vinyl chloride / vinyl acetate copolymer   (Product name Denka Vinyl # 1000A, manufactured by Denki Kagaku Kogyo) 70 parts   Epoxy modified silicone (X-22-3000T, manufactured by Shin-Etsu Chemical Co., Ltd.) 10 parts   Methyl ethyl ketone / toluene (weight ratio 1/1) 400 parts

<Evaluation Method and Results> 60 ° C. free8
Thermal transfer sheet stored under accelerated conditions of time, thermal transfer sheet not stored and image receiving sheets R-1 and R-2
With the trade name CAMEDIA manufactured by Olympus Optical Co., Ltd.
P-330 is used to print a step pattern for sequentially decreasing the gradation value, and the OD of the printed matter on the untransferred thermal transfer sheet is measured at each step OD≈0.3. Concentration change after storage (ΔO
D _preservation ) was obtained and evaluated according to the following criteria. ΔOD _storage = (OD in stored thermal transfer sheet) − (OD in non-stored thermal transfer sheet) ◯: ΔOD _storage is less than 0.08, and the density change is small. Δ: When the ΔOD _storage is 0.08 or more and less than 0.15, a slight change in concentration is observed. X: ΔOD _storage is 0.15 or more, and the change in concentration is large.

[0038]

[0039]

According to the above evaluation results, the density difference after storage is large in the comparative example, whereas the density difference is small in the present invention. Therefore, according to the present invention, there is provided a thermal transfer sheet capable of obtaining the same density as that immediately after production, even if the thermal transfer sheet is stored for a long period of time.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09B 25/00 C09B 29/09 B 29/09 53/02 53/02 B41M 5/26 101K 101L 101B 101Z F Terms (reference) 2H111 AA01 AA27 AA52 BA11 BA14 BA39 BA42 BA43 BA44 BA47 BA48 BA49 BA53 BA71 BA74 4H056 AA01 AA02 AD09B AD24B AD28B CA02 CC02 CC04 CD08 CE02

Claims (7)

[Claims] 1. A thermal transfer sheet having a base sheet and a dye layer formed from a dye and a binder resin on one surface of the base sheet, wherein the dye layer has at least 2 having the same basic skeleton. A thermal transfer sheet comprising a dye of at least one type, and at least one of the dyes has a melting point difference of 10 ° C. or more with another dye. 2. The thermal transfer sheet according to claim 1, wherein the dye is a yellow dye having a basic skeleton selected from quinophthalone dyes represented by the following general formula 1 or dicyanostyryl dyes represented by the following general formula 2. (In the formula, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ can be independently selected, and each is a hydrogen atom, a halogen atom, a C1 to C8 alkyl group, a cycloalkyl group, an alkoxy group, an alkoxyalkoxy group, Represents an alkoxycarbonyl group, a thioalkoxy group, an alkylsulfonyl group, an amino group, a substituted or unsubstituted phenoxy group, or a substituted or unsubstituted thiophenoxy group, wherein R ₆ and R ₇ can be independently selected and each is a hydrogen atom. , An alkyl group, an alkoxyalkyl group, a cycloalkyl group, an allyl group, an aryl group which may have a substituent, an aralkyl group, a furfuryl group,
It represents a tetrahydrofurfuryl group or a hydroxyalkyl group. ) (R ₁ in the formula represents an allyl group or an alkyl group,
R ₂ represents a substituted or unsubstituted alkyl group or aryl group, A represents —CH ₂ —, —CH ₂ CH ₂ —, —CH ₂ CH ₂ O—, —C
H ₂ CH ₂ OCH ₂ — or —CH ₂ CH ₂ OCH ₂ CH ₂ — and R ₃ represents an alkyl group. ) 3. The thermal transfer sheet according to claim 1, wherein the dye is a magenta dye having a basic skeleton selected from imidazole azo dyes represented by the following general formula 3 or anthraquinone dyes represented by the following general formula 4. (In the formula, R represents an alkyl group, an alkenyl group, an aryl group, a cyanoalkyl group, a substituted or unsubstituted alkoxycarbonylalkyl group, and R ₁ and R ₂ are an alkenyl group, an aralkyl group, or a substituted or unsubstituted group. X represents a hydrogen atom, a methyl group, a methoxy group, a formylamino group, an alkylcarbonylamino group, an alkylsulfonylamino group, or an alkoxycarbonylamino group, and Y represents a hydrogen atom, a methyl group, or a methoxy group. Represents a group or halogen atom.) (R in the formula represents a hydrogen atom, a hydroxyl group, a substituted or unsubstituted alkyl group or a substituted or unsubstituted alkoxy group, and X and Y represent an amino group or a hydroxyl group. N represents 1 or 2. .) 4. The thermal transfer sheet according to claim 1, wherein the dye is a cyan dye having a basic skeleton selected from an indoaniline dye represented by the following general formula 5 or an anthraquinone dye represented by the following general formula 6. (In the formula, R ₁ represents an alkyl group optionally substituted by a hydrogen atom or a fluorine atom, an alkoxy group, a formylamino group, an alkylcarbonylamino group optionally substituted by a fluorine atom or a halogen atom, and R ₂ is ,
Represents an alkyl group optionally substituted by a hydrogen atom or a fluorine atom, an alkoxy group, or a halogen atom,
R ₃ and R ₄ represent a hydrogen atom, an alkyl group which may be substituted with a fluorine atom, an alkoxy group or a halogen atom, and R, R ₅ and R ₆ represent a hydrogen atom, C 1 to C ₆
Represents a substituted or unsubstituted alkyl group, aryl group or alkoxy group. ) (R ₁ and R ₂ in the formula each represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted allyl group or a substituted or unsubstituted aralkyl group.) 5. The thermal transfer sheet according to claim 1, wherein the binder resin is a polyvinyl acetoacetal resin or a polyvinyl butyral resin. 6. A yellow dye layer, a magenta dye layer,
A cyan dye layer and a base sheet are provided in a frame-sequential manner,
The dye in the yellow dye layer is the dye according to claim 2,
The dye of the magenta dye layer is the dye according to claim 3,
The thermal transfer sheet according to claim 1, wherein the dye of the cyan dye layer is the dye according to claim 4. 7. The thermal transfer sheet according to claim 1, wherein a transferable protective layer is repeatedly provided on the same surface as the surface on which the dye layer is formed in a frame-sequential manner.