JP4882982B2 - Thermal transfer sheet - Google Patents

Description

The present invention relates to a thermal transfer sheet.

In general, a thermal transfer printer uses a line-shaped thermal head in which heating elements are arranged in a row, and scans with the thermal transfer sheet and the transfer material overlapped in a direction perpendicular to the length direction of the thermal head. An image is formed by applying heat.

In this thermal transfer sheet, when printing is performed by directly contacting a thermal head with a plastic film substrate, sticking (chattering) occurs during scanning due to the frictional force generated between the substrate and the thermal head, resulting in poor printing. It may become. Further, the base material is fused to the thermal head by heat at the time of printing, which prevents the thermal transfer sheet from running and causes sticking, and in some cases, may cause sheet breakage. In order to prevent these problems, a heat-resistant slipping layer is conventionally provided on the surface of the thermal transfer sheet in contact with the thermal head of the substrate for the purpose of improving heat resistance and running stability by imparting slipperiness.

Various methods for forming the heat resistant slipping layer are known.
For example, a method for forming a heat-resistant layer made of a thermosetting resin having high heat resistance (Patent Document 1) has been proposed, but although this method improves heat resistance, it does not improve the lubricity of the thermal head. Moreover, since it is necessary to use a curing agent such as a cross-linking agent, the coating liquid becomes a two-liquid type, which causes problems such as pot life. Furthermore, since the base material is a plastic thin film that cannot be processed at high temperature, heat treatment (aging) for a long time at low temperature is required after coating in order to obtain a sufficient cured film. This not only complicates the manufacturing process but also tends to cause problems such as wrinkling and blocking. Thus, from the viewpoint of production efficiency, a non-curing resin has been desired as a component for forming the heat-resistant slipping layer.

In Patent Document 2, a mixture of a specific amount of a polyamideimide resin and a polyamideimide silicone resin is used as a binder, and further a resin composition in which a polyvalent metal salt of an alkyl phosphate ester and a filler are mixed. A heat-resistant slip layer having excellent properties is disclosed. However, the heat resistant slipping layer disclosed here does not cause the above-mentioned problems specific to the curing system, but is inferior in heat resistance as compared with the curing heat resistant slipping layer.

Patent Document 3 is characterized by comprising at least two types of waxes, a branched α-olefin polymer, and at least one other type of wax in order to improve running stability and heat resistance by providing lubricity. Although a heat resistant slipping layer is disclosed, the heat resistant slipping layer disclosed here is also inferior in heat resistance as compared with the above-mentioned curable heat resistant slipping layer.

In recent years, it has been strongly desired to shorten the printing time. In order to perform printing at high speed, it is necessary to increase the applied energy per unit time. Even if this applied energy is increased, higher heat resistance and slipperiness are required to enable good printing, but these are still insufficient with conventionally known thermal transfer sheets. For this reason, development of the thermal transfer sheet which has the further outstanding heat resistance and lubricity was desired.
JP-A 61-14983 JP 2001-334760 A Special table 2007-516104 gazette

An object of the present invention is to provide a thermal transfer sheet that has excellent heat resistance and high slipperiness, and is capable of suitable printing even when high energy is applied.

The present invention is a thermal transfer sheet having a color material layer on one surface of a substrate and a heat-resistant slipping layer on the other surface of the substrate, wherein the heat-resistant slipping layer has a number average molecular weight of 1000 or more. A thermal transfer sheet comprising a linear polyethylene wax and a binder resin.
The linear polyethylene wax having a number average molecular weight of 1000 or more is preferably contained in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the binder resin.
The heat resistant slipping layer preferably contains a metal soap.
The binder resin is preferably a polyamideimide resin and a polyamideimide silicone resin.
Hereinafter, the present invention will be described in detail.

Hereinafter, each layer constituting the thermal transfer sheet of the present invention will be described in detail.
(Heat resistant slipping layer)
The present invention is a thermal transfer sheet having a color material layer on one surface of a substrate and a heat-resistant slipping layer on the other surface of the substrate, wherein the heat-resistant slipping layer has a number average molecular weight of 1000 or more. The linear polyethylene wax and a binder resin are included.
A polyethylene wax having a number average molecular weight of 1000 or more and a linear type is characterized by high melting point and hardness and low polarity. Therefore, it is difficult to interact with the binder resin, and it is difficult to cause softening of the resin even when high energy is applied. Therefore, the thermal transfer sheet having a heat-resistant slipping layer containing a linear polyethylene wax having a number average molecular weight of 1000 or more is excellent in heat resistance.
The number average molecular weight is preferably 2000 or more, and preferably 5000 or less. The number average molecular weight is a value obtained in terms of polystyrene by gel permeation chromatography (GPC).

Examples of commercially available linear polyethylene wax having a number average molecular weight of 1000 or more include, for example, “Polywax 1000”, “Polywax 2000”, and “Polywax 3000” (all trade names, manufactured by Toyo Petrolite) Etc.

The linear polyethylene wax having a number average molecular weight of 1000 or more is preferably contained in the heat resistant slipping layer in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the binder resin. If it is less than 1 part by mass, the desired performance is not exhibited, and there is a risk of causing the thermal head and the heat-resistant slipping layer to be fused due to insufficient heat resistance. If it exceeds 50 parts by mass, the film strength of the heat resistant slipping layer may be lowered. The linear polyethylene wax is more preferably contained in an amount of 2 to 30 parts by mass.

The heat resistant slipping layer preferably contains a metal soap.
When the metal soap is added, the friction coefficient at the time of application of intermediate energy to high energy can be lowered. Therefore, the thermal transfer sheet having the heat-resistant slip layer containing the metal soap can exhibit excellent slipperiness. Further, by using in combination with the above-described linear polyethylene wax, excellent lubricity can be imparted in addition to heat resistance.
Examples of the metal soap include polyvalent metal salts of alkyl phosphates and metal salts of alkyl carboxylic acids.

The polyvalent metal salt of an alkyl phosphate ester in the present invention is, for example, the following structural formula 1

Or the following structural formula 2

(In each formula, R ¹ is an alkyl group having 12 or more carbon atoms, M ¹ represents an alkaline earth metal, zinc or aluminum, and n ¹ represents the valence of M ¹ ). Is preferred.
R ¹ is preferably an alkyl group having 12 to 18 carbon atoms. Examples of R ¹ include a cetyl group, a lauryl group, and a stearyl group. Among them, a stearyl group is preferable in terms of avoiding contamination problems such as cost and bleed out.
Examples of the alkaline earth metal represented as M ¹ include barium, calcium, and magnesium.

Examples of the metal salt of the alkylcarboxylic acid include the following structural formula 3

(Wherein R ² represents an alkyl group having 11 or more carbon atoms, M ² represents an alkaline earth metal, zinc, aluminum, or lithium, and n ² represents the valence of M ² ). Is mentioned.
R ² is preferably an alkyl group having 11 to 18 carbon atoms. Examples of R ² include a dodecyl group, a hexadecyl group, a heptadecyl group, a stearyl group, and the like. , A stearyl group is preferable, and a stearyl group is more preferable.
Examples of the alkaline earth metal represented by M ² include barium, calcium, and magnesium.

The metal soap can exhibit lubricity when intermediate energy to high energy is applied, and is preferably a magnesium-based, zinc-based or aluminum-based compound, and is a zinc-based compound in terms of heat resistance. It is more preferable. The metal soap is more preferably zinc stearate.

The metal soap preferably has an average particle size of 3 to 20 μm, more preferably 3 to 15 μm.
If the average particle size is too large, printing stains are likely to occur, and if the average particle size is too small, sufficient heat resistance cannot be obtained in the heat-resistant slip layer, which may cause problems such as printing wrinkles.
The average particle diameter is a value measured by a laser diffraction method.

It is preferable that content of the said metal soap is 1-50 mass parts with respect to 100 mass parts of binder resin. If it is less than 1 part by mass, the desired performance cannot be exhibited, and there is a possibility of causing fusion due to insufficient lubricity with the thermal head during heat application and insufficient releasability. If it exceeds 50 parts by mass, the film strength of the heat resistant slipping layer may be lowered. The content is more preferably 2 to 30 parts by mass.

As the binder resin in the heat-resistant slip layer, a resin having high heat resistance is preferable, and among them, a mixture of a polyamide-imide resin and a polyamide-imide silicone resin is preferable from the viewpoint of excellent heat resistance and slipperiness.

Examples of the polyamide-imide resin and the polyamide-imide silicone resin include those described in JP-A-8-244369 and JP-A-8-113647.
The polyamideimide resin is preferably soluble in an alcohol solvent.
The polyamide-imide silicone resin is preferably a polyamide-imide resin copolymerized or modified with a polyfunctional silicone compound.
As the polyfunctional silicone compound, those having a molecular weight of 1000 to 6000 and a copolymerization or modification amount of 0.01 to 1 with respect to the polyamideimide resin 1 are particularly preferred. If the amount of copolymerization or modification is outside the above range, sufficient lubricity cannot be obtained, and sticking may occur, or heat resistance and film strength may be reduced.
The polyfunctional silicone compound is preferably a silicone compound having any one of a hydroxyl group, a carboxyl group, an epoxy group, an amino group, an acid anhydride group, and an unsaturated group.

When the binder resin is a mixture of a polyamideimide resin and a polyamideimide silicone resin, the mixing ratio (polyamideimide resin / polyamideimide silicone resin) is preferably 1/5 to 5/1. If the mixing ratio is less than 1/5, heat resistance may be insufficient and head residue may easily occur. If it exceeds 5/1, the slipperiness may be insufficient and sticking may occur. The mixing ratio is more preferably 1/3 to 3/1 in terms of mass ratio.

The heat resistant slipping layer may contain a filler.
By including the filler, it is possible to suitably adjust the cleaning property, slipperiness, blocking prevention, and the like of the residue attached to the thermal head.
Examples of the filler include talc, kaolin, mica, graphite, calcium carbonate, molybdenum disulfide, silicone rubber filler, benzoguanamine resin, melamine / formaldehyde condensate, among others, talc, silicone rubber filler, calcium carbonate. Is preferable, and talc is more preferable.

It is preferable that content of the said filler is 1-30 mass parts with respect to 100 mass parts of binder resin. If it is less than 1 part by mass, performance such as cleaning properties may not be exhibited. If it exceeds 30 parts by mass, the flexibility and film strength of the heat resistant slipping layer may be reduced. The content is more preferably 1 to 20 parts by mass.

The heat resistant slipping layer may contain a polyester resin. By including the polyester resin, it is possible to enhance the adhesion to the substrate.
It is preferable that content of the said polyester resin is 0.5-10 mass parts with respect to 100 mass parts of binder resin. If it is less than 0.5 parts by mass, the heat-resistant slipping layer may have insufficient adhesion to the substrate and may cause peeling. If it exceeds 10 parts by mass, the heat resistance may decrease. The content is more preferably 1 to 10 parts by mass.

In addition to the components described above, the heat resistant slipping layer may contain other components as long as the effects of the present invention are not affected. Examples of the other components include waxes other than the linear polyethylene wax, higher fatty acid amides, surfactants, silicone oils, thermal release agents such as other resins, and lubricants. These can be known ones.

The heat-resistant slip layer is formed by dissolving or dispersing the linear polyethylene wax having a number average molecular weight of 1000 or more, the binder resin, and other components used as necessary in a solvent. A layer forming coating solution is prepared, and the resulting heat resistant slipping layer forming coating solution is applied by a conventional coating method such as a gravure coater, a roll coater, or a wire bar and dried.

The heat resistant slipping layer can have sufficient desired performance of the present invention as long as the coating amount is generally 2.0 g / m ² or less based on dry solids.
The coating amount is preferably 0.1 to 1.5 g / m ² on a dry solid basis, and more preferably 0.2 to 1.0 g / m ² .
If the heat-resistant slipping layer is too thin, the function of the heat-resistant slipping layer may not be sufficiently exerted, and if it is too thick, the sensitivity during printing may be lowered.

(Base material)
The thermal transfer sheet of the present invention has the above-mentioned heat-resistant slip layer on one surface of the substrate.
The base material may be any material as long as it has a conventionally known heat resistance and strength. For example, a polyethylene terephthalate film, a 1,4-polycyclohexylenedimethylene terephthalate film, a polyethylene naphthalate film, Polyphenylene sulfide film, polystyrene film, polypropylene film, polysulfone film, aramid film, polycarbonate film, polyvinyl alcohol film, cellophane, cellulose derivatives such as cellulose acetate, polyethylene film, polyvinyl chloride film, nylon film, polyimide film, ionomer film, etc. Resin film; paper such as condenser paper, paraffin paper, synthetic paper; non-woven fabric; composite of paper or non-woven fabric and resin; It is.
The substrate generally has a thickness of about 0.5 to 50 μm, preferably about 1.5 to 10 μm.
The base material may be subjected to a surface treatment in order to improve adhesion with an adjacent layer. As the surface treatment, known resin surface modification techniques such as corona discharge treatment, flame treatment, ozone treatment, ultraviolet treatment, radiation treatment, surface roughening treatment, chemical treatment, plasma treatment, grafting treatment, etc. should be applied. Can do. Only one type of surface treatment may be performed, or two or more types may be performed.
In the present invention, among the surface treatments described above, corona treatment or plasma treatment is preferable because of its low cost. Moreover, you may form an undercoat layer (primer layer) in the one surface or both surfaces as needed.

(Color material layer)
The thermal transfer sheet of the present invention has a color material layer on one surface of the substrate. That is, a color material layer is provided on the other surface different from the surface of the substrate having the heat-resistant slip layer.
When the desired image is monochromatic, the thermal transfer sheet of the present invention may be formed of only one color layer appropriately selected as the color material layer, or when the desired image is a full color image, As the color material layer, cyan, magenta, and yellow (and black as necessary) can be selected and formed.
When the thermal transfer sheet of the present invention is a sublimation type thermal transfer sheet, a layer containing a sublimable dye is formed as a color material layer, and when it is a heat melting type thermal transfer sheet, a pigment or the like is used as a color material layer. A hot-melt ink layer colored with is formed.
Hereinafter, although the case of a sublimation type thermal transfer sheet is demonstrated, this invention is not limited only to a sublimation type thermal transfer sheet.

The sublimation dye used in the sublimation dye layer is not particularly limited, and conventionally known dyes can be used.
Examples of the sublimable dye include diarylmethane dyes; triarylmethane dyes; thiazole dyes; merocyanine dyes; pyrazolone dyes; methine dyes; indoaniline dyes; Azomethine dyes such as imidazoazomethine and pyridone azomethine; xanthene dyes; oxazine dyes; cyanostyrene dyes such as dicyanostyrene and tricyanostyrene; thiazine dyes; azine dyes; acridine dyes; benzeneazo dyes; , Thiophenazo, isothiazole azo, pyrrole azo, pyrazole azo, imidazole azo, thiadiazole azo, triazole azo, disazo and other azo dyes; spiropyran dyes; Dyes; fluorane dyes; rhodamine lactam dyes; naphthoquinone dyes; anthraquinone dyes; quinophthalone dyes; and the like. .
In the dye layer, the sublimable dye is 5 to 90% by weight, preferably 10 to 70% by weight, based on the total solid content of the dye layer.
When the amount of the sublimable dye used is less than the above range, the print density may be lowered, and when it exceeds the above range, the storage stability may be lowered.

As the binder resin for supporting the dye, generally, a resin having heat resistance and appropriate affinity with the dye can be used.
Examples of the binder resin include cellulose resins such as ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxy cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate, and cellulose butyrate; polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetoacetal, polyvinyl pyrrolidone Vinyl resins such as poly (meth) acrylates, poly (meth) acrylamides and the like; polyurethane resins; polyamide resins; polyester resins;
As the binder resin, among them, heat resistance, dye transferability and the like, cellulose resin, vinyl resin, acrylic resin, urethane resin, polyester resin, etc. are preferable, vinyl resin is more preferable, More preferred are polyvinyl butyral, polyvinyl acetoacetal, and the like.

The dye layer may use additives such as a release agent, inorganic fine particles, and organic fine particles as desired.
Examples of the mold release agent include silicone oil and phosphate ester.
Examples of the inorganic fine particles include carbon black, aluminum, and molybdenum disulfide.
Examples of the organic fine particles include polyethylene wax.

The above dye layer is prepared by dissolving or dispersing the above-mentioned dye and binder resin in an appropriate organic solvent or water together with additives to be added as necessary. Further, a gravure printing method, screen It can be formed by applying the coating solution on one surface of the substrate and drying it by a known means such as a printing method or a reverse roll coating printing method using a gravure plate.
Examples of the organic solvent include toluene, methyl ethyl ketone, ethanol, isopropyl alcohol, cyclohexanone, dimethylformamide [DMF] and the like.
The coating amount of the dye layer, dried 0.2~6.0g / ^{m 2} in solid standard, preferably 0.2 to 3.0 g / ^{m 2} approximately.

(Other)
If the thermal transfer sheet of the present invention is provided with a color material layer on one surface of a substrate and a heat-resistant slipping layer on the other surface of the substrate, an adhesive layer, a release layer as a transfer protective layer Further, other layers such as a release layer or an undercoat layer may be provided.
When the transfer protective layer is formed in the surface order with the color material layer described above, the protective layer protecting the image surface can be transferred after image formation.
The configuration and preparation of the transfer protective layer are not particularly limited, and can be selected from conventionally known techniques according to the characteristics of the base material sheet, the color material layer, and the like to be used.
The undercoat layer is not particularly limited, and a composition that improves the adhesion between the base material and the color material layer and the transfer efficiency of the dye can be appropriately selected and provided.

(Print)
The thermal transfer sheet of the present invention can be printed by heating and pressurizing a portion corresponding to the printing portion from the heat-resistant slipping layer side of the above-mentioned substrate using a thermal head or the like, and transferring the color material to the transfer material. it can.
When the thermal transfer sheet of the present invention is a thermal sublimation thermal transfer sheet, a thermal transfer image receiving sheet or the like can be used as the transfer material.
The thermal transfer image-receiving sheet is not particularly limited as long as the recording surface has dye acceptability. For example, a dye-receiving layer is formed on at least one surface of a substrate such as paper, metal, glass, or synthetic resin. Things can be mentioned. The thermal transfer image-receiving sheet does not need to be provided with a receiving layer as long as the substrate itself has dye-receptive properties.
When the thermal transfer sheet is a heat-melting type thermal transfer sheet, ordinary paper, plastic film, or the like can be used as a material to be transferred.
The printer used for performing the thermal transfer is not particularly limited, and a known thermal transfer printer can be used.

Since the thermal transfer sheet of the present invention has the above-described configuration, it is excellent in heat resistance and slipperiness. For this reason, even during high-speed printing where high energy is applied, printing defects such as printing wrinkles and sticking do not occur and good printing is possible, so the thermal transfer sheet of the present invention is suitable as a thermal transfer sheet for high-speed printing. Can be used.

Hereinafter, the present invention will be described in more detail with reference to examples. In the text, “part” or “%” is based on mass unless otherwise specified.

Examples 1-4, Comparative Examples 1-3
(Color material layer formation)
A polyethylene terephthalate (PET) film having a thickness of 4.5 μm is used as a base sheet, and a color material layer coating liquid having the following composition is applied to one surface thereof by a gravure coating to a dry coating amount of 0.7 g / m. ^It was applied and dried to form a color material layer.
<Coloring material layer coating solution>
C. I. Solvent Blue 63 6.0 parts Polyvinyl butyral resin (ESREC BX-1, manufactured by Sekisui Chemical Co., Ltd.) 3.0 parts Methyl ethyl ketone 45.5 parts Toluene 45.5 parts

(Formation of heat-resistant slip layer)
Next, each material was mixed according to the composition shown in Table 1, and the resulting mixture was adjusted to ethanol / toluene = 1/1 so that the solid content was 20%, stirred, and then dispersed for 1 hour with a paint shaker The treatment was performed to obtain a coating solution for forming a heat resistant slipping layer. The obtained coating solution for forming a heat resistant slipping layer was subjected to gravure coating on the surface of the color material layer-coated film opposite to the surface on which the color material layer was formed. It was applied and dried to 4 g / m ² to form a heat-resistant slip layer, and a thermal transfer sheet was produced.
In addition, what was used about each component is shown below.
Polyamideimide resin (HR-15ET, manufactured by Toyobo Co., Ltd.)
Polyamideimide silicone resin (HR-14ET, manufactured by Toyobo Co., Ltd.)
Polyester resin (Byron 220, manufactured by Toyobo Co., Ltd.)
Filler (Microace P-3, Talc, Nippon Talc Co., Ltd.)
Metal soap (SZ-PF, zinc stearate, manufactured by Sakai Chemical Industry Co., Ltd.)
Linear polyethylene wax: Number average molecular weight 3000 (polywax 3000, manufactured by Toyo Petrolite Co., Ltd.)
Linear polyethylene wax: Number average molecular weight 2000 (Polywax 2000, manufactured by Toyo Petrolite Co., Ltd.)
Linear polyethylene wax: Number average molecular weight 1000 (polywax 1000, manufactured by Toyo Petrolite Co., Ltd.)
Linear polyethylene wax: Number average molecular weight 850 (polywax 850, manufactured by Toyo Petrolite Co., Ltd.)
Branched polyethylene wax: number average molecular weight 1100 (Petrolite EP-1100, manufactured by Toyo Petrolite Co., Ltd.)

The above thermal transfer sheets were combined with a thermal transfer image-receiving sheet for a sublimation printer CP9000D manufactured by Mitsubishi Electric Corporation, and the dynamic friction coefficient was measured while printing under the following conditions, and the following evaluations were performed. In addition, the thermal transfer printer with a frictional force measurement function described in Unexamined-Japanese-Patent No. 2003-300388 was used for the measurement of a printing and a dynamic friction coefficient.
Thermal head: Toshiba Hokuto Electronics Co., Ltd. thermal head, head resistance 6549Ω
Line speed: 1ms / Line
Pulse duty: 90%
Applied voltage: 29.00V
Printing pressure: 40N

<Maximum print gradation value>
Under the above conditions, the gradation value is changed in increments of 5, and a solid pattern is printed. The highest printing gradation is one weaker energy than the occurrence of defects such as wrinkles, sticking, and scratching of the heat-resistant slip layer. The printing performance of each thermal transfer sheet was evaluated as a value.
It is assumed that the gradation value of the print data corresponds to 100% solid of 255 gradation, and the ratio of the gradation value at the time of printing divided by 255 is the applied energy of the pattern with respect to the maximum applied energy (for example, If the gradation value at the time of printing is 210 gradations, 210/255 = 0.823, that is, 82% solid). Therefore, it can be said that the higher the maximum print gradation value, the higher the applied energy can be withstood. The results are shown in Table 2.

<Dynamic friction coefficient>
Also, when the solid print of the above-mentioned maximum printing gradation value and the solid pattern printing of 128/255 gradation (gray) are performed and the dynamic friction coefficient is less than 0.4, ◎, 0.4 or more and less than 0.5 The thing was made into (circle) and the thing 0.5 or more was made into x.
In Table 2, “high density portion” represents a solid pattern printed with the highest printing gradation value, and “intermediate density portion” represents a solid pattern printed with 128/255 gradation.
The results are shown in Table 2.

From Table 2, the thermal transfer sheet of the present invention was excellent in heat resistance and lubricity, and good printing was possible even when high energy was applied. On the other hand, the thermal transfer sheet of the comparative example had a low maximum printing gradation value and was inferior in heat resistance.

The thermal transfer sheet of the present invention can be suitably used as a thermal transfer sheet for high-speed printing.

Claims (4)

A thermal transfer sheet having a color material layer on one side of the substrate and a heat-resistant slipping layer on the other side of the substrate,
The heat-resistant slip layer comprises a linear polyethylene wax having a number average molecular weight of 1000 or more and a binder resin. The thermal transfer sheet according to claim 1, wherein the linear polyethylene wax having a number average molecular weight of 1000 or more is contained in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the binder resin. The thermal transfer sheet according to claim 1 or 2, wherein the heat-resistant slip layer contains a metal soap. The thermal transfer sheet according to claim 1, wherein the binder resin is a polyamideimide resin and a polyamideimide silicone resin.