JP2003025744A - Heat transfer sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat transfer sheet, capable of obtaining a printed matter having a picture of high sensitivity and high quality while retaining a printing suitability on a rough paper and permitting the achievement of space saving in a printer or the like. SOLUTION: The heat transfer sheet 1 is provided with a heat resistant layer 6, arranged on one side of a film substrate 2, and a separating layer 3 having the principal constituent of at least wax, an ink layer 4 having the principal constituents of a coloring agent and a binding agent and a bonding layer 5 having the principal constituents of a thermoplastic resin and wax, which are arranged on the opposite side of the film substrate 2 sequentially. The coating amount of the heat resistant layer is specified so as to be 0.01-0.20 g/m<2> , the thickness of the film substrate is specified so as to be 1.0-3.0 μm, the coating amount of the separating layer is specified so as to be 0.1-0.7 g/m<2> , the total sum of coating amount of all coating layers is specified so as to be 0.51-1.8 g/m<2> and the containing amount of the coloring agent in the ink layer is specified so as to be 40-90 wt.% whereby a thinned heat transfer sheet is obtained and the purpose can be achieved.

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 thermal transfer printer or the like for transferring by heating a thermal head or the like, and more particularly to a thermal transfer sheet which is a thin film and can perform good transfer to rough paper. .

[0002]

2. Description of the Related Art Conventionally, a thermal transfer sheet has been used in which a colored ink layer in which a colorant such as a pigment or a dye is dispersed in a hot-melt wax or a binder such as a resin is carried on a base material sheet such as a plastic film. There is known a melt transfer method in which energy corresponding to image information is applied by a heating device such as a thermal head to transfer a colorant together with a binder onto an image receiving sheet such as paper or a plastic sheet.
The printed image formed by the melt transfer method has high density and excellent sharpness, and is suitable for recording binary images such as characters and line drawings. It is also possible to form multicolor or full-color images by subtractive mixing by using a thermal transfer sheet with colored ink layers of yellow, magenta, cyan, black, etc., and recording and recording each colored ink layer on the image receiving sheet. Is.

In recent years, due to improvements in thermal transfer printer technology, there has been an increasing demand for high-speed printing and high-quality printing, as well as a demand for recording media that have lower running costs and space saving. A heat-melt transfer type printer represented by a facsimile can record an excellent image even on a rough paper having a low surface smoothness, and thus has been widely accepted in the market. However, due to the recent rapid development of inkjet printer technology, a thermal transfer sheet having higher sensitivity, high image quality, low running cost, and space saving has been required for a recording medium for a thermal fusion transfer printer.

Conventionally, a thermal transfer sheet used for printing on rough paper having a low surface smoothness is provided with a heat-melting type colored ink layer of about 5 to 10 g / m ² to form a mesh on the paper surface (papermaking In the case of melt-penetration type that obtains an image without white spots by penetrating ink into the mesh left on the surface that contacts the plow net, or by forming a film-forming layer in the transfer layer A bridge transfer type has been devised to obtain an image without white spots by transferring in a bridged state on a mesh. However, in the former case, there is a problem that the transfer sensitivity cannot be increased and the ribbon capacity becomes large because the sufficient whiteout preventing effect cannot be obtained unless the ink layer is thickened. Further, in the latter case, compared with the former case, the thermal transfer sheet can be made thinner, but the functions such as high image quality and low running cost are not sufficient, which is a problem.

[0005]

SUMMARY OF THE INVENTION Therefore, in order to solve the above problems, the present invention provides a high-sensitivity and high-quality printed matter while maintaining printability on rough paper, and can be used in a printer or the like. An object is to provide a thermal transfer sheet that can achieve space saving.

[0006]

In order to achieve the above object, the thermal transfer sheet of the present invention is provided with a heat resistant layer on one surface of a film base material, and has at least a wax as a main component on the opposite surface of the film base material. The heat-resistant layer is applied in an amount of 0.0
1 to 0.20 g / m ² and a film substrate thickness of 1.0 to
3.0 μm, the amount of release layer applied is 0.1 to 0.7 g / m ²
And the coating amount of the ink layer is 0.3 to 0.8 g / m ² , the coating amount of the adhesive layer is 0.1 to 0.7 g / m ² , and the total coating amount of all coating layers is 0.51 to 0.51. At 1.8 g / m ² , the content of the colorant in the ink layer is 40 to 90% by weight to form a thin thermal transfer sheet, which has high sensitivity while maintaining printability on rough paper. , You can get high quality prints,
Space saving was achieved inside the printer. In the dynamic viscoelasticity measurement of the ink layer, the storage elastic modulus G'at 50 ° C is preferably 10 ⁶ to 10 ⁹ and the storage elastic modulus G'at 120 ° C is preferably 10 ⁵ to 10 ^7. As a result, the change in the elastic modulus of the ink layer with respect to the temperature change during printing is small, and the ink layer becomes a cross-linked state on the transfer target and is transferred, resulting in a print with no blank areas on the transfer target of rough paper. I can do it.

Further, it is desirable that the binder for the ink layer contains at least one thermoplastic resin selected from the group consisting of acrylic resin, polyester resin and vinyl chloride-vinyl acetate copolymer resin. The reflection density measured from the surface side of the thermal transfer sheet provided with the ink layer is 1.5.
The above is preferable, and even if the thickness of the ink layer becomes thin due to the thinning of the thermal transfer sheet, the density of the ink layer can be maintained at a certain level or more, and the reduction of the image density on the printed matter is prevented. be able to.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below with reference to preferred embodiments. FIG. 1 is a vertical cross-sectional view showing one embodiment of the thermal transfer sheet of the present invention. In the thermal transfer sheet 1 shown in the figure, a heat-resistant layer 6 is provided on the back side of a film base material 2, and a release layer 3, an ink layer 4, and an adhesive layer 5 are provided in this order on the front surface side of the film base material 2. It is the configuration provided.

(Film base material) As the film base material 2 used in the thermal transfer sheet of the present invention, the same film base material as that used in the conventional thermal transfer sheet can be used as it is, and other materials can also be used. Can be used. Specific examples of the preferable film substrate include, for example, polyester such as polyethylene terephthalate,
Polypropylene, cellophane, polycarbonate, cellulose acetate, triacetyl cellulose, polyethylene, polyvinyl chloride, polystyrene, nylon, polyimide,
There are relatively heat-resistant plastics such as polyvinylidene chloride, polyvinyl alcohol, fluororesins, chlorinated rubber, and ionomers, papers such as condenser paper and paraffin paper, and non-woven fabrics, etc., and film substrates that combine these. May be However, the thickness of the film substrate in the present invention can be appropriately changed depending on the material so that the strength and thermal conductivity thereof are appropriate, but is 1.0 to 3.0 μm. It is the thinnest range of thickness that can be stably supplied by the current film substrate manufacturing technology.

(Heat-Resistant Layer) In the present invention, it is preferable to provide a heat-resistant layer 6 on the surface of the base material film which is in contact with the thermal head so as to improve the slipperiness of the thermal head and prevent sticking. The heat-resistant layer contains a heat-resistant resin and a substance acting as a thermal release agent or a lubricant as basic constituent components. By providing such a heat-resistant layer, thermal printing can be performed without sticking on a thermal transfer sheet based on a heat-sensitive plastic film, and the plastic film has a difficulty in cutting and easy processing. You can take advantage of such advantages.

This heat-resistant layer comprises a binder resin, a slip agent, and
It is formed by suitably using a material to which a surfactant, inorganic particles, organic particles, a pigment, etc. are added. The binder resin used in the heat-resistant layer is, for example, cellulose-based resin such as ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate, cellulose acetate butyrate, nitrified cotton, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal. , Vinylpyrrolidone, acrylic resin, polyacrylamide, vinyl resin such as acrylonitrile-styrene copolymer, polyester resin, polyurethane resin, silicone-modified or fluorine-modified urethane resin, and the like.

Among these, those having several reactive groups, for example, those having a hydroxyl group, are used as a cross-linking agent.
It is preferable to use a crosslinked resin in combination with polyisocyanate or the like. The means for forming the heat-resistant layer is a coating liquid prepared by dissolving or dispersing a material obtained by adding a lubricant, a surfactant, inorganic particles, organic particles, a pigment, etc. to the binder resin as described above in a suitable solvent. Was prepared, and the coating solution was applied to a coating solution having a thickness of 0.01 to 0.01 by a conventional coating means such as a gravure coater, a roll coater, and a wire bar.
A heat resistant layer of 0.20 g / m ² is formed.

(Release Layer) In the present invention, the release layer 3 is formed between the film substrate and the ink layer. The release layer is a layer provided adjacent to the film base material, and is mainly composed of wax having a melting point or a softening point of 70 ° C to 120 ° C. This layer is a layer provided to improve the releasability between the film base material and the ink layer when heat is applied, and therefore is composed of a component that melts into a low-viscosity liquid when heat is applied by a thermal head. Desirably, it is preferable to adjust the layer components so that the layer is easily cut near the interface between the heated portion and the non-heated portion.

Specific examples of the wax used in the release layer include natural waxes such as beeswax, spermaceti wax, wood wax, rice bran wax, carnauba wax, candelilla wax and montan wax; paraffin wax, microcrystalline wax, oxidized wax. , Ozokelite, ceresin,
Synthetic waxes such as ester wax and polyethylene wax; higher saturated fatty acids such as margaric acid, lauric acid, myristic acid, palmitic acid, stearic acid, furoic acid and behenic acid; higher saturated monohydric alcohols such as stearyl alcohol and behenyl alcohol; sorbitan Higher esters such as fatty acid esters; higher fatty acid amides such as stearic acid amide and oleic acid amide.
It is also possible to impart elasticity to the release layer to improve the adhesion between the thermal transfer sheet and the transfer target. To achieve this object, the release layer is made of rubber such as isoprene rubber, butyl rubber or nitrile rubber. Is added. In addition, in order to prevent the release layer from falling off, it is possible to add a resin having a strong adhesive property to the layer. The resin added for this purpose is an ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate. There are copolymers and the like.

To form the release layer, a release layer-forming coating liquid is used.
It is provided by a conventionally known method such as hot melt coating, hot lacquer coating, gravure direct coating, gravure reverse coating, knife coating, air coating, and roll coating at a thickness of 0.1 to 0.7 g / m ² in a dry state. is there. When the thickness of the dry coating film is less than 0.1 g / m ² , the adhesiveness between the film base material and the ink layer is improved and a good peeling effect cannot be obtained. Also, the thickness is 0.7 g / m
^When it exceeds ² , the transfer sensitivity at the time of printing is lowered, which is not preferable.

(Ink Layer) The ink layer 4 containing the colorant and the binder as the main components of the thermal transfer sheet of the present invention may contain various additives such as a dispersant and an antistatic agent, if necessary. Good. The colorant is preferably an organic or inorganic pigment or dye having good characteristics as a recording material, for example, a pigment having a sufficient coloring density and not fading due to light, heat, temperature or the like. . Further, as the colorant, an appropriate one can be selected and used from carbon black, organic pigments, inorganic pigments, or various dyes depending on the required color tone.

Binder used for the ink layer
Is preferably composed mainly of resin, and specifically, as the resin, acrylic resin, cellulose resin,
Melamine resin, polyester resin, polyamide resin, polyolefin resin, acrylic resin, styrene resin, polyamide, ethylene-vinyl acetate copolymer,
Examples thereof include thermoplastic elastomers such as vinyl chloride-vinyl acetate copolymer and styrene-butadiene rubber. Particularly, those having a relatively low softening point, which has been conventionally used as a heat-sensitive adhesive, for example, a softening point of 50 to 150 ° C. are preferable.

The ink layer has a storage elastic modulus G'at 50 ° C. of 10 ⁶ to 10 ⁹ and a storage elastic modulus G'at 120 ° C. of 10 ⁵ to 10 ⁷ in the dynamic viscoelasticity measurement. It is preferable to use a plastic resin, the change in the elastic modulus of the ink layer is small with respect to the temperature change during printing, the ink layer is in a crosslinked state on the transfer target, and is transferred and transferred on the transfer target of rough paper. You can print without white spots. Examples of the thermoplastic resin that imparts such dynamic viscoelastic behavior to the ink layer include acrylic resin, polyester resin, vinyl chloride-
Examples thereof include vinyl acetate copolymer resin. The ink layer preferably contains a colorant and a binder as main components, and the content of the colorant in the ink layer is preferably 40 to 90% by weight with respect to the ink layer. In this way, by relatively increasing the content ratio of the colorant in the ink layer, the density of the ink layer can be maintained at a certain level or more even if the ink layer is thinly formed on the thermal transfer sheet. The image density transferred by can be maintained high. Also, since the elastic modulus of the ink layer can be kept high even when the temperature changes during printing,
High-resolution printing is possible because the ink layer can be transferred in a bridged state and the ink layer is well cut.

The ink layer is formed by using the above-mentioned coloring agent component and binder component, and further an ink layer-forming coating liquid in which a solvent component such as water or an organic solvent is adjusted if necessary. With a conventionally known method such as gravure direct coating, gravure reverse coating, knife coating, air coating, or roll coating, the thickness is 0.3 to
It forms an ink layer of 0.8 g / m ² . If the thickness of the dry coating film is too small, it will be difficult to obtain a sufficient concentration. Further, if the thickness is too large, high energy is required at the time of printing transfer, and printing can be performed only by a special thermal transfer printer, or printing sensitivity is insufficient. The ink layer thus formed preferably has a reflection density of 1.5 or more as measured from the surface side of the thermal transfer sheet on which the ink layer is provided. Is thin,
It is possible to secure the density of the ink layer to a certain level or higher, and it is possible to prevent the image density on the printed matter from lowering.

(Adhesive Layer) In the thermal transfer sheet of the present invention, the adhesive layer 5 can be provided on the ink layer. The adhesive layer is
It is possible to improve the adhesiveness between the transferred material (image-receiving sheet) and the transferred ink layer. This adhesive layer is mainly composed of a thermoplastic resin that softens and exhibits adhesiveness by heating with a thermal head, a laser or the like, and a wax for adjusting the melt permeation viscosity to the transfer paper. In addition, in order to prevent blocking when the resulting thermal transfer sheet is wound into a roll, an antiblocking agent such as waxes, amides, esters and salts of higher fatty acids, fluororesins and powders of inorganic substances are added. be able to.

As the thermoplastic resin, for example, ethylene-
Vinyl acetate copolymer (EVA), ethylene-acrylic acid ester copolymer (EEA), polyester resin, polyethylene, polystyrene, polypropylene, polybutene, petroleum resin, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, polyvinyl alcohol , Vinylidene chloride resin, methacrylic resin, polyamide, polycarbonate,
Polyvinyl formal, polyvinyl butyral, acetyl cellulose, nitrocellulose, polyvinyl acetate,
Examples thereof include polyisobutylene, ethyl cellulose, polyacetal and the like, and those having a relatively low softening point conventionally used as a heat-sensitive adhesive, for example, a softening point of 50 to 150 ° C. are preferable. The mixing ratio of the thermoplastic resin and the wax of the adhesive layer is 4/1 to 1/2, preferably 3/1 to 1/1 as the thermoplastic resin / wax weight ratio.
Is.

To form the adhesive layer, the above-mentioned thermoplastic resin and additives are hot-melt coated or a coating liquid for forming an adhesive layer, which is dissolved or dispersed in a suitable organic solvent or water, is used in a conventionally known hot-melt coating or hot-melt coating. By lacquer coat, gravure direct coat, gravure reverse coat, knife coat, air coat, roll coat, etc.,
A thickness of 0.1 to 0.7 g / m ² is provided in a dry state. When the thickness of the dry coating film is less than 0.1 g / m ² ,
Adhesion between the transfer target and the ink layer is poor, and transfer failure occurs during printing. On the other hand, if the thickness exceeds 0.7 g / m ² , the transfer sensitivity at the time of printing is lowered and satisfactory printing quality cannot be obtained.

The above-mentioned thermal transfer sheet preferably has a winding hardness of 15 to 200 N when wound around the core.
If the winding hardness is less than this range, winding deviation is likely to occur and the outer diameter of the ribbon becomes large, so that the number of windings m becomes short. When the winding hardness is larger than the above range, the number of winding m can be increased, but blocking is likely to occur. By winding the thinned thermal transfer sheet onto the core with a winding hardness within the above range, it becomes possible to attach a long winding of the thermal transfer sheet to the storage space of the thermal transfer sheet in the printer.

[0024]

EXAMPLES Next, the present invention will be described more specifically with reference to examples. In the text, “part” or “%” is based on weight unless otherwise specified. Example 1 A polyethylene terephthalate film having a thickness of 2.5 μm was used as a film substrate. To one surface of this support, the release layer coating liquid described below was applied in order so that the solid coating amount was 0.30 g / m ² , and dried to form a release layer. The coating liquid was applied so that the coating amount of solid content was 0.40 g / m ² , and dried to form an ink layer. The following adhesive layer coating liquid was applied onto the ink layer so that the solid content coating amount was 0.20 g / m ² .
It was dried to prepare a thermal transfer sheet of Example 1. However, a heat-resistant layer coating solution having the following composition was applied to the other surface of the film substrate so that the solid content was 0.10 g / m ² and dried to form a heat-resistant layer in advance. deep.

[0025] (Coating liquid for release layer)   Paraffin wax 15 parts   Water / IPA (weight ratio 1/1) 85 parts

(Coating Liquid for Ink Layer) Carbon black 10 parts Acrylic resin * 1 10 parts Methyl ethyl ketone / toluene (weight ratio 1/1) 80 parts * 1: Storage elastic modulus G at 50 ° C. in dynamic viscoelasticity measurement ′ Is 5 × 10 ⁸ Pa and the storage elastic modulus G ′ at 120 ° C. is 3 × 10 ⁵ Pa. Therefore, the storage elastic modulus G ′ at 50 ° C. is 10 ⁶ to 10 ⁹ and the storage elastic modulus G ′ at 120 ° C. is 10 ⁵ to 10 ⁷ in the dynamic viscoelasticity measurement as the ink layer. This storage elastic modulus is measured by a dynamic viscoelasticity measuring device ARES (measurement frequency: manufactured by Rheometric Scientific Co., Ltd.).
It was measured at 1 Hz). The ink layer has a reflection density of 2.0 measured from the surface side of the thermal transfer sheet provided with the ink layer. Macbeth reflection density measuring instrument RD
It was measured at 914.

[0027] (Coating liquid for adhesive layer)   Polyester resin 10 parts   Carnauba wax 5 parts   Water / IPA (weight ratio 1/1) 85 parts

[0028] (Heat-resistant layer coating liquid)   20 parts of silicone-acrylic copolymer (Toa Gosei Chemical Co., Ltd., Cymac US350)   Toluene 50 parts   Methyl ethyl ketone 50 parts

(Example 2) In the thermal transfer sheet prepared in Example 1, the ink layer was changed to the following ink layer coating liquid, and the solid content coating amount was 0.60 g / m ² and dried. To form an ink layer. Otherwise in the same manner as in Example 1, a thermal transfer sheet of Example 2 was produced. (Ink layer coating liquid) Carbon black 10 parts Polyester resin * 2 10 parts Methyl ethyl ketone / toluene (weight ratio 1/1) 80 parts

* 2: Storage elastic modulus G'at 50 ° C. in dynamic viscoelasticity measurement is 7 × 10 ⁸ Pa and 120 ° C.
Has a storage elastic modulus G ′ of 2 × 10 ⁶ Pa. Therefore, in the dynamic viscoelasticity measurement as the ink layer, 50 ° C
Has a storage elastic modulus G'of 10 ⁶ to 10 ⁹ and 120 ° C.
Has a storage elastic modulus G'of 10 ⁵ to 10 ⁷ . The ink layer has a reflection density of 2.0 measured from the surface side of the thermal transfer sheet provided with the ink layer.

An evaluation test was conducted on the thermal transfer sheets of the above-obtained examples by the following method. Printing conditions Printer: Alps MD-5000 Printing pattern: Character, solid

The evaluated items are as follows. 1. Printing quality The printed product obtained under the above printing conditions is visually observed to evaluate the printing quality. ⊚: The image is clear with no voids or scratches. ◯: Almost no void or scraping. Δ: Some voids and scratches. X: Voids and scratches are conspicuous and unclear.

2. Print Density The reflection density of the printed portion of the printed matter obtained under the above printing conditions was measured with a Macbeth reflection density measuring instrument RD914.

(Evaluation Result) The evaluation result of the above-mentioned embodiment is
It is shown in Table 1 below.

[0035]

[Table 1]

Further, the total thickness of the thermal transfer sheets obtained in Examples 1 and 2 is less than half the thickness for conventional printers used, and the thermal transfer sheet storage space inside the printer has been the same as before. Compared with winding a thermal transfer sheet,
A long take-up roll having a length more than twice the length can be attached, the frequency of take-up exchanges is reduced, and as a result the running cost is reduced and a space-saving thermal transfer sheet is obtained. Further, as shown in Table 1, with the thermal transfer sheets of Examples 1 and 2, high-sensitivity and high-quality printed matter was obtained while maintaining printability on rough paper.

[0037]

As described above, the thermal transfer sheet of the present invention is
A heat-resistant layer is provided on one side of the film substrate, and a release layer containing a wax as a main component, an ink layer containing a coloring agent and a binder as a main component, a thermoplastic resin and a wax are mainly provided on the opposite side of the film substrate. With a structure in which adhesive layers as components are sequentially provided,
The heat-resistant layer coating amount is 0.01 to 0.20 g / m ² , the film substrate thickness is 1.0 to 3.0 μm, and the release layer coating amount is 0.1 to 0.7 g / m ² . Layer coating amount is 0.3-
At 0.8 g / m ² , the adhesive layer coating amount is 0.1 to 0.7 g /
m ^{2, and} the total coating amount of Zen'nuriko layer 0.51~1.8g
/ M ² , the content of the colorant in the ink layer is 40 to 90
The heat transfer sheet was thinned to have a weight percentage of 50%, and high-sensitivity and high-quality printed matter was obtained while maintaining printability on rough paper, and space saving was achieved in the printer.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing one embodiment of a thermal transfer sheet of the present invention.

[Explanation of symbols]

1 Thermal transfer sheet 2 Film substrate 3 Release layer 4 ink layer 5 Adhesive layer 6 Heat-resistant layer

Claims (4)

[Claims] 1. A heat-resistant layer is provided on one surface of a film substrate, and a release layer containing at least a wax as a main component, an ink layer containing a colorant and a binder as a main component is provided on the opposite surface of the film substrate.
In a thermal transfer sheet in which an adhesive layer composed mainly of a thermoplastic resin and a wax is sequentially provided, the heat-resistant layer coating amount is 0.0
1 to 0.20 g / m ² and a film substrate thickness of 1.0 to
3.0 μm, the amount of release layer applied is 0.1 to 0.7 g / m ²
And the coating amount of the ink layer is 0.3 to 0.8 g / m ² , the coating amount of the adhesive layer is 0.1 to 0.7 g / m ² , and the total coating amount of all coating layers is 0.51 to 0.51. A thermal transfer sheet having a colorant content of 40 to 90% by weight at 1.8 g / m ² . 2. The storage elastic modulus G ′ at 50 ° C. in the dynamic viscoelasticity measurement of the ink layer is 10 ⁶ to 10 ⁹ and the storage elastic modulus G ′ at 120 ° C. is 10 ⁵ to 10 ⁷ . The thermal transfer sheet according to claim 1, wherein: 3. The binder of the ink layer is acrylic resin,
The thermal transfer sheet according to claim 1 or 2, which contains at least one thermoplastic resin selected from the group consisting of a polyester resin and a vinyl chloride-vinyl acetate copolymer resin. 4. The thermal transfer sheet according to claim 1, wherein a reflection density measured from the surface side of the thermal transfer sheet provided with the ink layer is 1.5 or more. .