JP2744759B2 - Thermal transfer media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer medium capable of forming a clear printed image on paper having poor surface smoothness.

[0002]

2. Description of the Related Art Conventionally, there has been known a thermal transfer medium for forming a printed image of good quality even on paper having poor surface smoothness (hereinafter referred to as rough paper).

In this type of thermal transfer medium, a cross-linking transferable ink layer (a high melt viscosity which is transferred only in the form of a bridge without adhering to the convex portions of the rough surface of the rough paper and adhering to the concave portions). Of the ink layer) is used.

[0004] However, such a bridge transfer ink having a high melt viscosity has poor permeability to paper. In particular, when the image is transferred to rough paper, it adheres only to the convex portion of the rough paper. Therefore, if the permeability is poor, the fixability of the printed image becomes extremely poor, and the friction resistance and the like become poor.

As a means for improving the fixing property, it is conceivable to increase the printing energy to improve the permeability, but it is difficult to perform high-speed printing and it is not preferable in terms of energy saving.

In order to suppress the printing energy, a material having good permeability must be contained in the ink layer. However, in this case, the melt viscosity of the ink layer is reduced, and the original cross-linking transferability is deteriorated.

If the printing energy is to be suppressed in this way, it is impossible to achieve both the cross-linking transfer property and the fixing property.

In view of the foregoing, the present invention improves the fixability while maintaining good cross-linking transferability, and therefore has a low printing energy, clear and robustness on rough paper without voids or chips. It is an object to provide a thermal transfer medium capable of forming a good printed image.

[0009]

According to the first aspect of the present invention,
A release layer containing a wax-like substance as a main component, a glass transition point of 50 ° C. or higher, and a melt viscosity of 1 × 10 ⁴ cps / 16.
A first heat transfer layer made of a heat-fusible material containing 20 to 100% by weight of a resin having a temperature of 0 ° C. or less, and a second heat transfer layer made of the heat-fusible material and having a melt viscosity of 1 × 10 ⁵ cps / 160 ° C. or more And a thermal transfer medium in which at least one of the first transfer layer and the second transfer layer contains a colorant.

According to a second aspect of the present invention, in the first aspect, the resin in the heat-fusible material of the first thermal transfer layer is a petroleum resin, a phenol resin, an acrylic resin, or a styrene resin. A styrene-acrylic copolymer resin, a rosin-based resin, a pinene-based resin, a cumarone-indene-based resin, and a thermal transfer medium of at least one selected from the group consisting of these copolymerized resins.

[0011] The invention according to claim 3 is the invention according to claim 1 or 2.
In the described invention, the heat-fusible material of the second thermal transfer layer is
The present invention relates to a thermal transfer medium containing 50 to 100% by weight of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 20% by weight or less.

[0012]

Operation and Examples The second thermal transfer layer according to the present invention comprises:
It is a cross-linkable ink layer having a high melt viscosity and shows a strong adhesive force immediately after softening, but has poor fixability due to poor permeability to paper.

On the other hand, the first thermal transfer layer is a layer having a low melt viscosity, has a good permeability to paper, and has a strong fixing property when solidified (a resin having a glass transition point of 50 ° C. or higher is hard at room temperature. For). This fixing property is not exhibited unless it is solidified.

When printing on rough paper using the heat transfer medium of the present invention having such a first heat transfer layer and a second transfer layer in this order from the substrate side, the first heat transfer layer at the heated portion is melted. As a result, a low-viscosity molten material permeates and penetrates the second thermal transfer layer and penetrates into the convex portion of the rough paper. When the thermal transfer medium is peeled off from the rough paper, the resin of the first thermal transfer layer that has penetrated into the rough paper is not solidified, but is transferred to the paper by the adhesive force of the second thermal transfer layer. The resin of the penetrated first thermal transfer layer is solidified, and the fixing strength of printing is improved. The mechanism by which the melted resin of the first thermal transfer layer penetrates and penetrates the second thermal transfer layer is not yet clear.

As described above, the thermal transfer medium of the present invention has excellent cross-linking properties and fixing properties for rough paper. Moreover, since the first thermal transfer layer is easily softened and melted, there is no need to increase the printing energy, and high-speed printing is possible.

Since it takes time for the first thermal transfer layer to solidify after melting, if the first thermal transfer layer is provided on the second thermal transfer layer, high-speed printing cannot be performed.

The second thermal transfer layer in the present invention has a high melt viscosity and is originally excellent in background stain resistance. However, if the second thermal transfer layer does not contain a coloring agent, the background thermal stain resistance is further improved. Be improved.

Naturally, the thermal transfer medium of the present invention can form a good printed image even on smooth paper because of its excellent fixability.

Next, the present invention will be described specifically.

The second thermal transfer layer in the present invention is a conventionally known cross-linkable ink layer having a heat-fusible material and a colorant, and having a melt viscosity of 1 × 10 ⁵ cps / 1.
More than 60 ° C.

The melt viscosity of the second thermal transfer layer is 1 × 10 ⁵ cps /
When the temperature is lower than 160 ° C., the cross-linking transferability becomes poor, and when transferred to rough paper, voids and chips are likely to be generated in the printed image. Although the upper limit of the melt viscosity of the second thermal transfer layer is not particularly limited, it is preferably about 1 × 10 ⁹ cps / 160 ° C. or less from the viewpoint of transfer sensitivity.

The heat-fusible material of the second thermal transfer layer is mainly composed of a heat-fusible resin (including an elastomer, the same applies hereinafter), and a small amount of a wax-like substance may be blended if necessary.

Examples of the resin include ethylene-vinyl acetate copolymer, ethylene-vinyl butyrate copolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid alkyl ester copolymer (alkyl Examples of the group include those having about 1 to 16 carbon atoms such as methyl, ethyl, propyl, butyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, dodecyl and hexadecyl), ethylene-acrylonitrile copolymer, ethylene- Acrylamide copolymer, ethylene-
Ethylene copolymers such as N-methylol acrylamide copolymer and ethylene-styrene copolymer; poly (meth) acrylates such as polylauryl methacrylate and polyhexyl acrylate; polyvinyl chloride, vinyl chloride-vinyl acetate Polymers, vinyl chloride (co) polymers such as vinyl chloride-vinyl alcohol copolymers; other polyester resins, polyamide resins, cellulose resins, natural rubber, styrene-butadiene copolymers, isoprene polymers, chloroprene polymers Etc. can be used alone or in combination. The polyester resin is obtained by polycondensation of an acid and a diol, and as an acid component, a saturated dibasic acid such as phthalic acid, phthalic anhydride, sebacic acid, azelaic acid, maleic anhydride, fumaric acid, etc. One or more kinds of saturated dibasic acids, dimer acids and the like can be used, and as the diol component, ethylene glycol, propylene glycol, decanediol, dodecanediol, hexadecanediol, bisphenol compounds and ethylene oxide or propylene oxide adducts thereof One or more of these can be used.
Ethylene-vinyl acetate copolymer is particularly preferred because of its high melt viscosity and excellent adhesiveness.

Examples of the waxy substance include natural waxes such as wood wax, beeswax, carnauba wax, candelilla wax, montan wax and ceresin wax; petroleum waxes such as paraffin wax and microcrystalline wax; oxidized waxes and esters Synthetic waxes such as wax, polyethylene wax, Fischer-Tropsch wax, α-olefin-maleic anhydride copolymerized wax; higher fatty acids such as myristic acid, palmitic acid, stearic acid and behenic acid; higher aliphatic alcohols such as stearyl alcohol and docosanol Esters of higher fatty acid monoglyceride, fatty acid ester of sucrose, fatty acid ester of sorbitan and the like; amides such as stearamide, oleylamide and bisamide Etc. can be used alone or as a mixture.

Preferred as the heat-fusible material of the second thermal transfer layer is a vinyl acetate content of 20% (% by weight, hereinafter the same).
It contains 50 to 100% of the following ethylene-vinyl acetate copolymer.

An ethylene-vinyl acetate copolymer having a vinyl acetate content of 20% or less has a higher softening point than an ethylene-vinyl acetate copolymer having a vinyl acetate content of more than 20%,
It usually has a softening point in the range of 70 to 100 ° C.

Therefore, the softening point of the second thermal transfer layer should be increased by including 50 to 100% of such an ethylene-vinyl acetate copolymer in the vehicle, for example, in the range of 60 to 100 ° C. Becomes possible.

If the vinyl acetate content is too low, the softening point becomes too high, and the transfer sensitivity is lowered. Therefore, the vinyl acetate content is preferably 10% or more.

When the softening point of the second thermal transfer layer is high as described above, there is an advantage that background contamination of the receiving paper does not occur even during continuous printing.

That is, when the softening point of the heat-meltable ink layer is low, the entire head is heated by the heat storage of the thermal head during continuous printing, so that the ink layer corresponding to the non-heat-generating dots is also softened. Although the receiving paper is liable to be stained, if the softening point of the second thermal transfer layer in contact with the receiving paper is high as described above, even if heat is accumulated in the thermal head due to continuous printing, it will not be softened. Dirty soil is prevented.

The content of the specific ethylene-vinyl acetate copolymer in the vehicle of the second thermal transfer layer is preferably 50% or more. If it is less than 50%, the characteristics of the copolymer will not be sufficiently utilized.

The softening point of the second thermal transfer layer is suitably from about 40 to 90 ° C. from the viewpoints of thermal stability, transfer sensitivity and the like, and 60 to 90 ° C. in consideration of stain resistance in continuous printing. C is preferred. The coating amount of the second thermal transfer layer (the coating amount after drying, the same applies hereinafter) is suitably about 0.5 to ² g / m ² .

The first thermal transfer layer of the present invention contains 20 to 100% of a resin having a glass transition point of 50 ° C. or higher and a melt viscosity of 1 × 10 ⁴ cps / 160 ° C. or lower (hereinafter referred to as a glassy resin). It consists of a heat-fusible material.

The melt viscosity of the glassy resin is 1 × 10 ⁴ cp
When the temperature is higher than s / 160 ° C., it becomes difficult to penetrate and penetrate the second thermal transfer layer at the time of printing, and the fixing property is deteriorated. If the melt viscosity is too low, it will penetrate the paper too much.
0 ° C. or higher is preferred. If the glass transition point is lower than 50 ° C., the fixing strength of the printed image is low, and the fixability to paper becomes poor. If the glass transition point is too high, the transfer sensitivity deteriorates.
The glass transition point is preferably 130 ° C. or lower.

Examples of the glassy resin include petroleum resins (C ₅ -based aliphatic or alicyclic hydrocarbons or polymers of their derivatives, C ₉ -based aromatic or alicyclic hydrocarbons and their derivatives). Derivative polymer, etc.), phenolic resin, acrylic resin, styrene resin, styrene-acrylic copolymer resin, rosin resin, pinene resin, cumarone-indene resin and the like, and copolymer resins thereof Etc. can be used alone or in combination. The softening point of the glassy resin is suitably about 60 to 140 ° C.

The content of the glassy resin in the heat-fusible material is preferably 20 to 100%. When the content of the glassy resin is less than the above range, the fixing property is deteriorated.

As a component other than the glassy resin in the heat-fusible material of the first thermal transfer layer, the resin for the second thermal transfer layer can be used, and a small amount of a wax-like substance may be blended.

The coating amount of the first thermal transfer layer is 0.5 to ² g / m ^2.
The degree is appropriate.

In the present invention, the coloring agent may be blended in both the first and second thermal transfer layers, or may be blended in either one.

When a colorant is incorporated into both thermal transfer layers,
It is easy to obtain images with high print density.

When the coloring agent is blended in the first thermal transfer layer and not blended in the second thermal transfer layer, the ground fouling resistance is excellent, and the background fouling does not particularly occur during continuous printing.

When the coloring layer is not blended with the first thermal transfer layer, but is blended with the second thermal transfer layer, there is an advantage that the obtained printed image is not rubbed.

As the colorant, any of those conventionally used as colorants for this type of hot-melt ink can be used.
Various organic pigments and dyes can be used as appropriate.

The content of the colorant is 10 to 40 in the first thermal transfer layer.
%, And about 10 to 50% in the second thermal transfer layer.

The release layer in the present invention is a heat-meltable release layer containing a wax-like substance as a main component.

As the wax-like substance of the release layer, those exemplified for the second thermal transfer layer can be used without particular limitation.

A small amount of resin may be added to the release layer for the purpose of adjusting the adhesiveness between the substrate and the first thermal transfer layer, if necessary. As such a resin, the same resin as the resin for the first thermal transfer layer or the resin for the second thermal transfer layer can be used.

The melting point of the release layer is preferably about 60 to 120 ° C., and the coating amount is preferably about 0.5 to ² g / m ² .

The substrate in the present invention is generally used as a polyester film such as a polyethylene terephthalate film, a polyethylene naphthalate film, a polyarylate film, a polycarbonate film, a polyamide film, an aramid film, and other types of substrate films for this type of ink ribbon. Various plastic films used can be used. Also, high-density thin paper such as condenser paper may be used. The thickness of the substrate is preferably about 1 to 10 μm, particularly preferably about 2 to 7 μm, from the viewpoint of improving heat conduction.

When the above-mentioned plastic film is used as the base material, the back surface (the surface on the side in contact with the heating head) of which is a silicone resin, a fluororesin, a nitrocellulose resin, or a silicone-modified urethane resin modified by these, for example. For example, a conventionally known stick prevention layer made of various heat resistant resins or a mixture of these heat resistant resins with a lubricant may be provided.

Next, the present invention will be described with reference to Examples and Comparative Examples.

Examples 1-3 and Comparative Examples 1-3 A toluene solution of paraffin wax was applied to the surface of a 6 μm thick polyethylene terephthalate film having a 0.1 μm thick silicone-modified urethane resin layer formed on the back surface, and dried. A release layer having a melting point of 70 ° C. and a coating amount of 1.0 g / m ² was formed.

Next, a coating solution obtained by dissolving and dispersing the composition for the first thermal transfer layer shown in Table 1 in a mixed solvent of toluene and methyl ethyl ketone was applied on the release layer, and dried to obtain a coating amount of 1.
A first thermal transfer layer of 5 g / m ² was formed. In Comparative Example 1, the first thermal transfer layer was not provided.

Next, a coating solution obtained by dissolving and dispersing the composition for the second thermal transfer layer having the following formulation in a mixed solvent of toluene and methyl ethyl ketone was applied onto the first thermal transfer layer and dried.
Softening point 50 ° C, melt viscosity 1 × 10 ⁶ cps / 160 ° C, coating amount 1.
A second thermal transfer layer of 0 g / m ² was formed to obtain a thermal transfer medium.

(Second Thermal Transfer Layer) Component Part Ethylene-vinyl acetate copolymer 70 (vinyl acetate content 28%, softening point 46 ° C., melt viscosity 1 × 10 ⁵ cps / 160 ° C.) carbon black 30

[0056]

[Table 1]

Example 4 A thermal transfer medium was manufactured in the same manner as in Example 1 except that the second thermal transfer layer was changed to the following.

That is, a coating solution obtained by dissolving and dispersing the composition for the second thermal transfer layer having the following formulation in a mixed solvent of toluene and methyl ethyl ketone was applied on the first thermal transfer layer, dried and melted at a softening point of 75 ° C. A second thermal transfer layer having a viscosity of 1 × 10 ⁶ cps / 160 ° C. and a coating amount of 1.0 g / m ² was formed.

(Second Thermal Transfer Layer) Component Part Ethylene-vinyl acetate copolymer 70 (vinyl acetate content 19%, softening point 75 ° C., melt viscosity 1 × 10 ⁵ cps / 160 ° C.) carbon black 30 Example 5 A thermal transfer medium was manufactured in the same manner as in Example 1 except that carbon black was not used in the second thermal transfer layer.

Using each of the thermal transfer media obtained above, a thermal transfer printer (PC-PR150V manufactured by NEC Corporation)
A printing test was performed under the following printing conditions to evaluate the cross-linking transferability, fixability, and ground stain resistance. Table 2 shows the results.

Printing conditions Printing energy: 0.1 mJ / dot Printing speed: 100 cps Receiving paper: rough paper with a Beck smoothness of 28 seconds (1) Cross-linking transferability Reflection density (OD value) of the solid printed portion obtained on the receiving paper ) Was measured and evaluated according to the following criteria.

3 ... 1.5 or more 2 ... 1 or more and less than 1.5 1 ... less than 1 (2) Fixability The print obtained on the receiving paper is applied to a plastic eraser by 50
The sample was rubbed 20 times with a load of 0 g, and evaluated according to the following criteria.

3: No change 2: Readable 1: Unreadable (3) Ground stain resistance The printing was performed in an environment of 40 ° C., and the background stain near the print was evaluated according to the following criteria.

3: No background stains 2: Background stains exist, but characters can be read. 1 ... Background stains are severe, and characters cannot be read.

[0065]

[Table 2]

With respect to the thermal transfer media obtained in Examples 1, 4 and 5, the soil resistance was checked under more severe conditions (the environmental temperature during printing was changed to 50 ° C.) than in the stain resistance test. Was. Table 3 shows the results.

[0067]

[Table 3]

As is evident from Table 3, as the vehicle of the second thermal transfer layer, ethylene-vinyl acetate content of 20% or less was used.
In Example 4 using a vinyl acetate copolymer, the soil resistance at a high temperature was superior to that in Example 1 using an ethylene-vinyl acetate copolymer having a vinyl acetate content of more than 20%. It can be seen that this is equivalent to Example 5 containing no coloring agent.

[0069]

According to the first aspect of the present invention, the bridging property and the fixing property for rough paper are both excellent, and a clear printed image without voids or chips can be formed on rough paper. Moreover, since the first thermal transfer layer is easily softened and melted, there is no need to increase the printing energy, and high-speed printing is possible. Further, since the second thermal transfer layer has a high melt viscosity, even if the transfer layer and the receiving paper are rubbed during printing, the receiving paper is hardly stained, and the ground stain resistance is good.

According to the second aspect of the invention, in addition to the above-mentioned functions and effects of the first aspect of the present invention, the use of a specific resin as the resin in the first thermal transfer layer further improves the fixability.

According to the third aspect of the present invention, in addition to the effects of the first or second aspect, the heat-fusible material of the second thermal transfer layer may be an ethylene-vinyl acetate copolymer having a vinyl acetate content of 20% by weight or less. By containing the polymer in an amount of 50 to 100% by weight, the softening point of the second thermal transfer layer is increased, and the background of the receiving paper is not stained during continuous printing.

Next, preferred embodiments of the present invention will be described.

(1) In the first aspect of the present invention, a release layer containing a wax-like substance as a main component, a glass transition point of 50 ° C. or more and a melt viscosity of 1 × 10 ⁴ cps / A first thermal transfer layer comprising a heat-fusible material and a colorant containing 20 to 100% by weight of a resin having a temperature of 160 ° C. or lower, and a melt viscosity of 1 × 10 ⁵ cps / 160 ° C. or more comprising the heat-fusible material and the colorant And a second thermal transfer layer provided in this order.

(2) In the invention described in the above item (1), the first
The resin in the heat-fusible material of the thermal transfer layer is a petroleum resin, a phenolic resin, an acrylic resin, a styrene resin, a styrene-acrylic copolymer resin, a rosin resin, a pinene resin, a cumarone-indene resin. At least one selected from the group consisting of resins and copolymer resins thereof
The thermal transfer medium that is the seed.

(3) In the invention described in the item (2), the second
A thermal transfer medium wherein the heat-fusible material of the thermal transfer layer contains 50 to 100% by weight of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 20% by weight or less.

(4) In the first aspect of the present invention, a release layer containing a wax-like substance as a main component, a glass transition point of 50 ° C. or more and a melt viscosity of 1 × 10 ⁴ cps / A first thermal transfer layer comprising a heat-fusible material and a colorant containing 20 to 100% by weight of a resin having a temperature of 160 ° C. or less, and a first heat transfer layer comprising a heat-fusible material and having a melt viscosity of 1 × 10 ⁵ cps / 160 ° C. or more. (2) A thermal transfer medium in which a thermal transfer layer is provided in this order.

(5) In the invention described in the above item (4), the first
The resin in the heat-fusible material of the thermal transfer layer is a petroleum resin, a phenolic resin, an acrylic resin, a styrene resin, a styrene-acrylic copolymer resin, a rosin resin, a pinene resin, a cumarone-indene resin. At least one selected from the group consisting of resins and copolymer resins thereof
The thermal transfer medium that is the seed.

(6) In the invention described in the above item (5), the second
A thermal transfer medium wherein the heat-fusible material of the thermal transfer layer contains 50 to 100% by weight of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 20% by weight or less.

Claims (3)

(57) [Claims] 1. A mold release layer comprising a wax-like substance as a main component, a glass transition point of 50 ° C. or higher and a melt viscosity of 1 on a substrate.
A first thermal transfer layer made of a heat-fusible material containing 20 to 100% by weight of a resin of × 10 ⁴ cps / 160 ° C. or less, and a melt-viscosity of 1 × 10 ⁵ cps / 160 ° C. or more And a second thermal transfer layer in this order, and at least one of the first transfer layer and the second transfer layer contains a coloring agent. 2. The resin in the heat-fusible material of the first thermal transfer layer is a petroleum resin, a phenolic resin, an acrylic resin, a styrene resin, a styrene-acrylic copolymer resin, a rosin resin, a pinene. The thermal transfer medium according to claim 1, wherein the thermal transfer medium is at least one selected from the group consisting of a resin based on a resin, a coumarone-indene resin, and a copolymer resin thereof. 3. The heat-fusible material of the second thermal transfer layer contains 50 to 100% by weight of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 20% by weight or less.
The thermal transfer medium according to any one of the preceding claims.