JPH0480090A - Thermal transfer sheet - Google Patents

Abstract

PURPOSE:To obtain the above thermal transfer sheet imparting long service life to a thermal head, having excellent antistatic properties and leakage-of- secret preventing properties and capable of imparting excellent mat-like printing by providing a transfer ink layer melted by heating to one surface of a base material film through a mat layer and forming the mat layer from a binder and a specific amount of carbon black. CONSTITUTION:A thermal transfer sheet is formed by providing a transfer ink layer melted by heating to one surface of a base material film through a mat layer and the mat layer consists of a binder and carbon black and 40 wt.% or more of the mat layer is occupied by carbon black. Since excellent antistatic effect is obtained by adding a large amount of carbon black to the mat layer without adding carbon black to a back surface layer, the abrasion of a thermal head is not generated. At the same time, since a large amount of carbon black is present in the mat layer, the surface of the mat layer becomes uneven to impart excellent mat-like printing. Further, the printing mark of missing dots is not generated in the thermal transfer sheet after printing and the leakage of a secret due to the used thermal transfer sheet is also prevented at the same time.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a thermal transfer sheet, and more specifically, it has a long service life for a thermal head, has excellent anti-static properties, and prevents leakage of secrets, and provides excellent matte signature characters. Regarding thermal transfer sheets.

(Prior art and its problems) Conventionally, when printing output prints from computers or word processors using a thermal transfer method, a thermal transfer sheet with a heat-melting ink layer provided on one side of a base film has been used. .

This conventional thermal transfer sheet has a thickness of 1 mm as a base film.
Using paper such as capacitor paper or paraffin paper with a thickness of 0 to 20 μm, or plastic film such as polyester or cellophane with a thickness of 3 to 20 μm, a layer of heat-melting ink made by mixing coloring agents such as pigments and dyes with wax is applied. It is manufactured by coating.

In the case of conventional thermal transfer sheets such as those mentioned above, when the base film is a thermoplastic resin film, there is a problem that the thermal head fuses to the film during printing, and these problems are solved by a heat fusion prevention layer on the back side. is solved by forming . Further, conventional thermal transfer sheets are charged with static electricity during use, resulting in a problem that the running properties of the thermal transfer sheets are poor.

Such a problem can be solved by adding carbon black as a conductive agent to the thermal fusion prevention layer, but in this case, the problem arises that the carbon black significantly accelerates the wear of the thermal head.

In addition, when printing with the thermal transfer sheet as described above, if a film with a smooth surface is used as the base film, the surface of the printed image will be smooth and glossy and beautiful, but on the other hand,
In the case of images such as characters, the characters are often difficult to see depending on the angle, causing eye strain.

These problems can be solved by adding minute irregularities to the surface of the base film and transferring these minute irregularities to the surface of the printed image.
This problem is solved by making the surface of the printed image matte.

The matte layer is conventionally formed by applying a coating solution containing a fine particle matting agent, but this matte layer is required to have good adhesion to the base film and sufficient heat resistance. Usually, it is formed using a highly heat-resistant thermoplastic resin as a binder.

However, when such heat-resistant resins are used, it has been difficult to form a thin matte layer industrially because there is no suitable solvent for dissolving these resins.

Further, in printing using a thermal transfer sheet as described above, there is a problem of leakage of information. In other words, when a thermal transfer sheet after printing is discarded, the printed part of the used thermal transfer sheet is blank, so the printed information remains on the discarded thermal transfer sheet. .

Therefore, an object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to provide a thermal transfer sheet that provides excellent matte signature printing while having a long service life for the thermal head, excellent antistatic properties, and anti-secret leakage properties. The aim is to provide this with good productivity.

(Means for solving problems) The above objects are achieved by the present invention as described below.

That is, the present invention provides a thermal transfer sheet having a transfer ink layer that is melted by heating via a matte layer on one side of a base film, wherein the matte layer is made of a binder and carbon black, and the carbon black is 4
The thermal transfer sheet is characterized in that it accounts for 0% by weight or more.

(Function) By incorporating a large amount of carbon black into the matte layer, an excellent antistatic effect can be obtained without adding carbon black to the back layer, so the problem of thermal head wear does not occur.

At the same time, since a large amount of carbon black exists in the matte layer, the surface becomes uneven, giving excellent matte printing. Furthermore, no white print marks are generated on the thermal transfer sheet after printing, and leakage of secrets due to the used thermal transfer sheet is also prevented.

(Preferred Embodiments) Next, the present invention will be explained in more detail with reference to preferred embodiments.

As the base film used in the present invention, the same base film used in conventional thermal transfer sheets can be used as is, and other films can also be used, and there are no particular limitations.

Specific examples of preferred base films include polyester, polypropylene, cellophane, polycarbonate, cellulose acetate, polyethylene, polyvinyl chloride,
Polystyrene, nylon, polyimide, polyvinylidene chloride, polyvinyl alcohol, fluororesin, chlorinated rubber,
Examples include plastic films such as ionomers, papers such as condenser paper and paraffin paper, nonwoven fabrics, and base films made of composites of these materials.

The thickness of this base film can be changed as appropriate depending on the material so that its strength and thermal conductivity are appropriate; the thickness is 0.5 to 50 μm, preferably 3 to 10 μm.
It is m.

The matte layer that mainly characterizes the present invention is formed on one side of the above-mentioned base film from a binder and a large amount of carbon black.

The binder used may be any conventionally known thermoplastic or thermosetting resin, but particularly preferred binders are cellulose resins or styrene/acrylonitrile copolymers (hereinafter referred to as SAN).

Cellulose resins used as binders include:
Examples include cellulose resins such as ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate, and cellulose acetate butyrate,
Particularly preferred are cellulose acetate propionate resin (hereinafter referred to as CAP), cellulose acetate butyrate resin (hereinafter referred to as CBA), and nitrified cotton. These binders are suitable for the present invention because they have excellent heat resistance and are soluble in general-purpose solvents.

Further, SAN is obtained by copolymerizing styrene and acrylonitrile, such as Sebian AD,
Various grades of Sevian LD and Sevian NA (manufactured by Daicel Chemical Company) are readily available on the market, and any of them can be used in the present invention, and can be easily produced according to conventional methods.

Among various grades, particularly suitable SAN has a molecular weight of 100,000 to 200,000, preferably 150,000 to 190,000, and an acrylonitrile content of 20 to 40 mol%, preferably 25 to 200,000.
30 mol % and a softening temperature of 400° C. or higher as determined by differential thermal analysis is preferred from the viewpoint of dissolution stability in organic solvents and heat resistance.

Furthermore, in order to impart sufficient heat resistance to the binder and adhesion to the base film, it is preferable to use polyisocyanate in combination when forming the matte layer. As the polyisocyanate compound used in the present invention, general polyisocyanate compounds can be used, but preferred are polyurethane polyisocyanates having a relatively high molecular weight and reacted with polyisocyanate dimers, trimers, or polyol compounds. be. Specifically, for example, a cyclic trimer of 2,4-tolylene diisocyanate, a cyclic trimer of 2,6-tolylene diisocyanate, a trimer of diphenylmethane-44'-diisocyanate, and 3 moles of diisocyanate. Reaction product of phenylmethane-44'-diisocyanate and 1 mol of trimethylolpropane, 3 mol of 2.4-1-lylene diisocyanate and 1 mol of trimethylolpropane, 3 mol of 2
, Reaction product of 6-tolylene diisocyanate and 1 mole of trimethylolpropane, Reaction product of 3 moles of 2,4-tolylene diisocyanate and 1 mole of trimethylolethane, 3 moles of 2,6-trimethylolethane reaction product of diisocyanate and 1 mole of trimethylolethane,
A reaction product of a mixture of 3 moles of 2,4- and 2,6-tolylene diisocyanate and 1 mole of trimethylolpropane, a cyclic trimer of a mixture of 2,4- and 2,6-tolylene diisocyanate, etc. Stabilized polyisocyanates blocked with phenol or cresol can be mentioned.

These polyisocyanate compounds are available under trade names such as Takenate (manufactured by Takeda Pharmaceutical Co., Ltd.), Parnock (manufactured by Inu Nippon Ink Chemical Co., Ltd.), Coronate (manufactured by Nippon Polyurethane Co., Ltd.), Duranate (manufactured by Asahi Kasei Industries, Ltd.), and Dismodur (manufactured by Bayer Co., Ltd.). It can be obtained and used in the present invention.

The above polyisocyanate compound is the binder 1
It is preferable to use it at a ratio of 0.5 to 50 parts by weight per 00 parts by weight. If the amount used is too small, the matte layer formed will be soft (or scratched when applying an ink layer later). In addition, the adhesion to the base film is poor, and there is a risk that the ink layer will be transferred at the same time during thermal transfer.On the other hand, if the amount is too large, the formed film will be hard and lack flexibility, and cracks will occur, so this is not preferred. do not have.

Further, the carbon black used in the present invention may be general carbon black that has been conventionally used as an antistatic agent, a conductive agent, a filler, a coloring agent, etc. (although not particularly limited).
The particle size of carbon black is also important in order to provide appropriate matte printing, and the preferable particle size is about 0.1 to
The range is 0.5 μm. By using carbon black having these particle sizes, a matte layer having an average matte depth (depth of irregularities) of 0.15 to 2.0 μm can be formed. If the average matte depth is less than 0.15 μm, the matte effect of the printed image will be insufficient, while if the average matte depth exceeds 2 μm, the transferability of the ink layer will be insufficient, resulting in poor resolution of the printed image. This is not preferable because it lowers the temperature. By setting the average matte depth as described above, the glossiness of the printed image can be brought to a preferable level of approximately 30 or less.

Such carbon black is used in the matte layer in an amount of 40% by weight or more, preferably 50 to 70% by weight. If the amount of carbon black used is less than 40% by weight, it is difficult to simultaneously achieve excellent antistatic effects, matte signature printing, and secret leakage prevention effects. On the other hand, if the amount used exceeds 70% by weight, even if polyisocyanate is used as a binder, the binding properties of carbon black will be insufficient, and there is a risk that the matte layer will be transferred together with the ink layer during printing. In addition, in order to obtain a sufficient effect of preventing secret leakage, the carbon black concentration should be such that the light transmittance of the ink layer transfer trace is 10% or less, preferably 5% or less.

In addition, if the adhesion of the binder resin to the base film is insufficient, when forming the layer with pine, it is possible to use other adhesive resins together, or to form a primer layer on the base film using these adhesive resins in advance. It is preferable to do so.

As the adhesive resin, various known adhesive resins such as chlorinated polymethylpentene, high molecular weight acrylic resin, and cyclized rubber can be used. However, when the base film is a polyester film, especially linear saturated polyester resin is used. is suitable. Particularly preferred polyester resins are amorphous linear polyester resins with a glass transition point of 50°C or higher, such as Vylon (manufactured by Toyobo), Elitere (manufactured by Unitika), Polyester (products of Nippon Gosei Kagaku L!RI, etc.). Various grades are available on the market, and any of them can be used in the present invention.

In addition, when forming a primer layer using the above-mentioned adhesive resin, it is preferable to form a layer with a thickness of about 0.05 to 1.0 μm; if it is too thin, the adhesiveness will be insufficient;
If it is too thick, the sensitivity and heat resistance of the thermal head will decrease, which is not preferable.

In addition, when used by mixing with the binder resin,
It is preferable to use it in a proportion of 5 to 200 parts by weight per 100 parts by weight of the binder resin. If the amount used is too small, the adhesion will be insufficient, while if it is too large, the heat resistance of the matte layer will decrease, which is not preferable. .

In the present invention, since the carbon black is also used as a matting agent, it is not necessary to use a so-called conventionally known matting agent, but in some cases, it may be used as long as it does not hinder the achievement of the objectives of the present invention. Various such matting agents are known per se, such as silica powder, silane-treated silica powder, talc powder, calcium carbonate powder, precipitated barium sulfate powder, alumina powder, acid clay powder, clay powder, and magnesium carbonate powder. , potassium titanate powder, carbon black, tin oxide powder, titanium white powder, synthetic nitrogen mica powder, silicone, acrylic resin crosslinked powder, styrene acrylic resin crosslinked powder, epoxy resin crosslinked powder, porous polyurethane resin crosslinked powder, melamine resin Crosslinked powder, benzoguanamine resin crosslinked powder, urea resin crosslinked powder, silanized starch,
Examples include aminoblast crosslinked starch, epichlorohydrin crosslinked starch, phosphoric acid crosslinked starch, acrolein crosslinked starch, and the like.

In addition, in the present invention, when forming a matte layer from the above-mentioned materials, it is preferable to include a heat release agent or a lubricant in the matte layer for the purpose of improving the releasability of the matte layer and the ink layer during thermal transfer. .

To form the matte layer, mix the above materials with acetone,
Prepare a coating solution by dissolving or dispersing it in an appropriate solvent such as methyl ethyl ketone, toluene, xylene, etc., apply this coating solution using a conventional coating method such as a gravure coater, a roll coater, a wire bar, etc., and dry it. formed by

The coating amount, that is, the thickness of the matte layer is also important, and in the present invention, it is preferably 0.2 to 2.0 g/rr on a solid content basis.
A matte layer having sufficient performance can be formed with a thickness of 1'. If it is less than 0.2 g/rrl', it is difficult to obtain the above-mentioned average matte depth (and if the matte layer is too thick, the sensitivity during transfer will decrease, which is not preferable).

In the present invention, a heat-melting ink layer is further formed on the matte layer using an ink containing necessary materials.

The ink for forming the fusible ink layer used in the present invention comprises a colorant and a vehicle, and may further contain various additives as necessary.

Among organic or inorganic pigments or dyes, the colorant is preferably one that has good properties as a recording material, such as one that has sufficient color density and does not discolor due to light, heat, temperature, etc. .

In addition to colorants forming cyan, magenta, yellow, and black hues, colorants of various other colors can also be used.

The vehicle used includes wax as a main component, and mixtures of wax with drying oil, resin, mineral oil, cellulose, rubber derivatives, and the like.

Typical examples of wax include microcrystanone wax, carnauba wax, and paraffin wax. In addition, various waxes such as Fischer-Tropsch wax, various low molecular weight polyethylenes, wood wax, beeswax, spermaceti wax, privet wax, wool wax, shellac wax, candelilla wax, petrolatum, assorted waxes, fatty acid esters, fatty acid amides, etc. are used. It will be done.

Further, in order to provide the hot-melt ink layer with good thermal conductivity and melt transferability, a thermally conductive substance can be blended into the hot-melt ink. Examples of this substance include carbonaceous substances such as carbon black, aluminum, copper, tin oxide, and molybdenum disulfide.

In addition to hot melt coating, methods for forming a hot melt ink layer directly or indirectly on a base film include:
Examples include hot lacquer coating, gravure coating, gravure reverse coating, and roll coating. It should be determined so that it can be taken, and is in the range of 0.1 to 30 tLm, preferably in the range of 1 to 201.Lm.

In the present invention, a surface layer can be further formed on the ink layer. The surface layer forms part of the transfer film, forms the surface that comes into contact with the transfer paper, seals the printed area of the transfer paper during transfer, prevents scumming, and protects the ink layer from being transferred. It has the function of improving adhesion to paper.

In addition, a heat fusion prevention layer is formed on the back side of the base film,
It is possible to prevent the thermal head from fusing during printing and improve the running performance of the thermal head. At this time, carbon black was conventionally added to the thermal adhesion prevention layer for the purpose of imparting antistatic properties, but in the present invention, the addition of such carbon black is unnecessary, and therefore the thermal head caused by the presence of carbon black No wear problems occur.

(Example) Next, the present invention will be explained in more detail by giving examples and comparative examples. In the text, parts or percentages are based on weight unless otherwise specified.

Example 1 Mud ink A SAN (Sevian AD, manufactured by Daicel Chemical) 5.0 parts Polyester resin (Vylon 200, Tg = 40-80
℃, manufactured by Toyobo ■) 3.75 parts carbon black (average particle size 23 mμ, manufactured by Mitsubishi Kasei ■)
12.0 parts Polyisocyanate (XDI) 1.0 parts ""' (MEK
/toluene=1/1) 80. 0 total
100.0 parts of the above composition was dispersed for 200 hours using a ball mill to obtain a coating liquid.

Example 2 Mud ink B CAP (482-05, manufactured by Kodak) 5.6
Part polyester resin (UE3200.7g 65°C, manufactured by Unitika) 4.0 parts Colored carbon (Geast S, 66mμ, manufactured by Tokai Electrode)
10.0 parts soybean lecithin (lecithin, manufactured by Ajinomoto) 0.4 parts MEK/toluene =
1/11 80.0 total i
Parts oo and o The above composition was subjected to a dispersion treatment for 4 hours using an attritor to prepare a coating liquid.

Example 3 Mad ink C 3AN (Sevian AD, manufactured by Daicel Chemical) 5.0 parts Polyester resin (Vylon 200, Tg = 40-80
℃, manufactured by Toyobo @) 4.75 parts carbon black (average particle size 23 mμ, manufactured by Mitsubishi Kasei ■)
12.0 copies” MEK/
Toluene = 1/1) 80.0 parts total
100.0 parts of the above composition was dispersed for 200 hours using a ball mill to obtain a coating solution.

The mud ink compositions of Examples 1 to 3 were each coated on a polyester base film at a rate of 0.5 g/I during drying using a bar coater.
I) was coated at a rate of 5 g/rd to form a thermal transfer sheet of the present invention.

Example 4 Prior to coating a mud ink composition on a polyester base film, a brimer paint with the following composition was prepared, and after forming a coating film of 0.3 g/rrf when dried with bar caulk, Add 0.5g of the following mud ink C composition to
/rr? It was applied at a ratio of

Next, hot-melt ink composition (II) was applied at a rate of 5 g/ni'' to obtain a thermal transfer sheet of the present invention.

1.1.5 Polyester resin (Byron RV 290, manufactured by Toyobo)
5.0 parts (h!EK/l-luene=2/l) 95.
0 parts total 100.0 parts Mad ink D SAN (Sevian AD, manufactured by Daicel Chemical) 7.0 parts Carbon (Geast 50143mm μm, manufactured by Tokai Electrode)
12.0 parts soybean lecithin (
lecithin, manufactured by Ajinomoto) 0.4 parts polyisocyanate (X
DI) 0.6 parts MEK/l-luene=1/
1) 80. 0 total 10
0.0 parts of the above composition was dispersed for 3 hours using a paint shaker to obtain a coating liquid.

Comparative Examples 1 and 2 Heat-melt ink compositions (I) and (II) were prepared in Example 1 without providing a matte layer on the polyester base film.
They were coated in the same manner as above to obtain a thermal transfer sheet as a comparative example.

(Margin below) Fever insect ink.

A hot-melt ink was prepared by kneading the above composition at 100° C. for 6 hours using a blade kneader.

Pressure Value The thermal transfer sheets obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were printed and evaluated under the following conditions. The results are shown in Table 1 below.

Thermal head: Thin film type thermal head Applied energy: 0.4 mJ/dot transfer Paper 2 Mitsubishi Paper "Tokukobishi" 46 size/72K
G Takumi - Ichiro Hatake
Measurement was performed using DP at a measurement angle of 75°.

(2) Average matte depth: The coated surface of the matte ink composition was measured using a surface roughness meter (Sokoita Research Institute rSEF-10AJ).

(3) Surface electrical resistance: Measure the surface resistance of the coated surface using a super insulation resistance meter YHP432.
9A-16008A was used. The antistatic effect is ○, 101 if the surface resistance value when the printer is running is 109Ω or less.
If it is 0Ω or more, problems are likely to occur, so it was set as X.

Printing sound during transfer The thermal transfer sheet has the structure shown in Figure 1. During printing, the matte layer surface and the heat-fusible ink layer surface separate at the interface, and only the heat-fusible ink layer is printed on the transfer paper.

In this case, the releasability differs depending on the degree of affinity between the matte layer surface and the heat-fusible ink layer surface under the applied heat of the thermal head. The heavier the releasability, the greater the transfer noise during printing, which poses a problem. Those with low printing noise were rated ○, those with large printing noise were rated X, and the intermediate grade (practically usable range) was rated △.

Confidentiality: The security effect was determined by observing the sheet after printing, and rated as "x" if the part (printed part) where the heat-melting ink layer was removed was easily readable, and "○" if it was difficult to read.

(6) Light transmittance: The light transmittance of the printed trace was measured using Macbeth TD914.

(Seat configuration and performance ) (Margin below) (effect)

Claims (1)

[Scope of Claims] (1) A thermal transfer sheet having a transfer ink layer that is melted by heating via a matte layer on one side of a base film, wherein the matte layer is composed of a binder and carbon black, and the matte layer is composed of a binder and carbon black. A thermal transfer sheet comprising 40% by weight or more of the matte layer. (2) The thermal transfer sheet according to claim 1, wherein the binder comprises a cellulose resin, a styrene/acrylonitrile copolymer, and a polyisocyanate compound. (3) The thermal transfer sheet according to claim 1, wherein the binder contains a linear saturated polyester resin. (4) The average depth of the unevenness of the mat layer is 0.15 to 2.0μ
The thermal transfer sheet according to claim 1, wherein the thermal transfer sheet has a particle size of m. (5) The thermal transfer sheet according to claim 1, wherein a heat fusion prevention layer is formed on the other surface of the base film, and the heat fusion prevention layer does not substantially contain carbon black.