JPH01238988A - thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To make it possible to print high-resolution images even on a receiving material low in smoothness by using a combination of a specified ethylene-ethyl acrylate copolymer with a high molecular weight substance difficultly compatible with the copolymer, as a heat-fusible constituent of a thermal transfer ink layer. CONSTITUTION:A thermally transferable ink layer 13 (heat-fusible ink layer) is provided on a heat-resistant base 11 by using a combination of an ethylene- ethyl acrylate copolymer having an ethyl acrylate content of at least 15wt.% with a high molecular weight substance being difficultly compatible with the copolymer and serving as a binder (heat-fusible constituent). The high molecular weight substance is a resin which separates out when being left to stand in mixture with the copolymer in a thermally melted state, and may be, for example, a ketone resin or a vinyl resin. By this method, a thermal transfer recording medium with high thermal sensitivity can be obtained which shows excellent clearness, fixation properties and blocking resistance, regardless of the smoothness of a receiving material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a thermal transfer recording medium, and more specifically, the present invention relates to a thermal transfer recording medium having excellent thermal transferability and high smoothness. Of course, the present invention relates to a thermal transfer recording method that provides a high-resolution printed image even to a transfer medium with low smoothness.

[Prior art] In recent years, thermal transfer recording methods using thermal heads have been developed (1).
It has become widely used due to its advantages such as being noiseless, (i) the device is relatively inexpensive and can be made compact, (i) easy to maintain, and (i) the printed image is stable. However, the problem with this thermal transfer recording method is that the print quality is easily affected by the smoothness of the surface of the transfer target, and it is difficult to make clear prints on paper with poor surface smoothness. have.

However, many attempts have been made to improve these problems. For example, heat treatment is performed after printing (Japanese Unexamined Patent Publication No. 58-7
6276), Magnetic force during transfer (Japanese Patent Application Laid-Open No. 52-9654)
9) or electrostatic distribution (Japanese Patent Laid-Open No. 55-65590), or by adding a large amount of oily substance to lower the melt viscosity during transfer (Japanese Patent Laid-Open No. 55-65590). 60
-25762), thermally decomposable substances (JP-A-6O-82389) or thermally expandable substances.1. Measures have been proposed, such as adding T (Japanese Patent Application Laid-Open No. 60-25762) to sense ring 2. In addition, there is also a known technology that attempts to improve printing quality by multilayering heat-melting ink layers. Adding pigments to one layer or both layers (Japanese Patent Application Laid-Open No. 59-2243
No. 92), a layer made of a heat-fusible substance containing no coloring agent is provided on the fusible ink layer (Japanese Unexamined Patent Publication No. 60-978).
Techniques such as Japanese Patent Publication No. 88) have been proposed. However, all of these conventional attempts involve recording by transferring ink that has been melted into a liquid state. The reality is that compared to materials with a high level of transfer, only inferior print quality can be obtained, and it cannot fundamentally solve the drawback that conventional print quality depends on the smoothness of the surface of the material to be transferred. It is.

On the other hand, by providing an ink layer whose main component is a resin that exhibits tackiness due to thermal energy applied during printing, but does not melt into a low-viscosity liquid and has a certain degree of mechanical strength. It is known that high-quality printing can be obtained even on objects with poor surface smoothness by applying ink to the convex portions of the surface of the object and transferring the ink to cover the concave portions. There is. The ink layer containing such a resin can firmly fix a printed image not only on paper but also on a transfer object such as a plastic film. However, if such an ink layer whose main component is resin has a thermal sensitivity that enables transfer using the thermal energy of a thermal head, an ink layer whose main component is wax that has the same thermal sensitivity It has the disadvantage that it has stronger adhesion at low temperatures than a layer, and is more likely to cause blocking during storage before use.

In order to eliminate these drawbacks, increasing the amount of pigment added, using resin with a higher melting point, adding wax, etc.
Alternatively, measures such as providing an anti-blocking layer on the opposite side of the ink layer have been taken. However, in such a case, new disadvantages such as deterioration of sensitivity, decrease in strength during heat softening, increase in the number of steps, and increase in cost are undesirable.

[Purpose] The present invention is capable of forming high-quality printed images with excellent clarity and fixation properties even when paper with a low surface smoothness or plastic film with a high surface smoothness is used as a transfer material. , and even more.

The object of the present invention is to provide a transfer type thermal recording medium (thermal transfer recording medium) with high thermal sensitivity that has excellent blocking resistance and is easy to manufacture.

[Structure] The present invention provides a thermal transfer recording medium having a thermal transfer ink layer (heat-melting ink layer) on a heat-resistant support, in which ethyl acrylate monomer accounts for 15% by weight or more as a thermal melting component of the thermal transfer ink layer. It is characterized in that it uses a combination of an ethyl acrylate copolymer and a polymeric substance that is hardly compatible with the copolymer.

Incidentally, as a result of various studies conducted by the present inventors on thermal transfer recording media that can obtain high-quality printed images regardless of the surface smoothness of the transfer target, two types of heat-melting components were identified as heat-melting components of the thermal transfer ink layer. It has been confirmed that the above objectives can be fully achieved by using a combination of compounds. The present invention has been made based on this.

In the following, the invention will be explained in more detail with reference to the accompanying drawings.

Figures 1 (a), (b) and (c) show three representative thermal transfer recording media according to the present invention, in which 11 is a heat-resistant support;
2 represents a release layer, 13 represents a hot-melt ink layer, and 14 represents an anti-sticking layer.

As the heat-resistant support 11, a film made of polyester, polyimide, polycarbonate, polysulfone, polyethersulfone, polyphonylin sulfide, polyether/ether ketone, etc., which has a heat resistance temperature of 150° C. or higher, or a material such as condenser paper or glassine paper is used. The thickness is preferably in the range of about 3 to 20 μm.

If necessary, as shown in FIG. An anti-sticking layer 14 made of resin is provided.

Thermal transferable ink layer 13 formed on the heat-resistant support 11
(heat-melting ink layer) contains coloring material and binder (heat-melting ink layer).
The main component is molten component). This layer 13
may be m layers or a laminate of multiple layers, and in the case of a single layer, the only layer is the layer farthest from the heat-resistant support 11, that is, the top layer, surface layer, or overlay. Each layer called a coating layer exhibits stickiness when thermal energy is applied, but it does not melt into a low-viscosity liquid and is adjusted to have a certain degree of mechanical strength.

However, the reality is that such adjustment cannot be achieved by using wax as the heat-melting component. Polyamide resins, polyester resins, polyvinyl acetate resins, and ethylene-ethyl acrylate copolymers are examples of resins that exhibit tackiness when heat energy is applied but have a certain degree of mechanical strength without melting into a low-viscosity liquid. resin, ethylene-vinyl acetate copolymer resin, etc., but as a result of intensive research by the present inventors, the main components of the layer closest to the transfer object are sensitivity, fixing power, flexibility, and pigment dispersibility. It has been found that ethylene-ethyl acrylate copolymer is most suitable from these viewpoints. In addition, the properties of the ethylene-ethyl acrylate copolymer vary greatly depending on the ratio of ethylene to ethyl acrylate. % of ethylene-ethyl acrylate copolymer (hereinafter sometimes referred to as "compound (a)") is the most effective.

However, relying only on the compound (a) as the heat-melting component of the thermal transfer ink layer 13 has some drawbacks in image storage stability and blocking resistance.

The present invention solves this problem by using a binder (heat-melting component).
This problem has been overcome by using a combination of the compound (a) and a polymer substance that is difficult to miscible with the compound (a) (hereinafter sometimes referred to as "compound (b)"). In addition, by using compound (b) in combination, the melt viscosity is increased compared to conventional heat-melt ink layers, and the cohesive force of the heat-melt ink itself at the transfer stage is increased, which is a convex function. .

Here, "'polymer substance that is difficult to be miscible with compound (a)"
[That is, compound (b)] means compound (a) in a heated molten state.
) refers to resins that are in a relationship such that they will split when left to stand even if mixed with other resins, such as resins with large species properties such as ketone resins (including acetone furfural resin and cyclic ketone resin), hydrogenated petroleum Examples include hydrocarbon resins, cellulose resins, polyamide resins, and vinyl resins. Specific examples include polystyrene, polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, various commercially available ketone resins, and hydrogenated petroleum-based hydrocarbon resins, but especially cellulose resins, polyamide resins, and ketone resins. , the use of hydrogenated petroleum-based hydrocarbon resin is effective.

The blending ratio of compound (a) and compound (b) is
A suitable amount of compound (b) is 20 to 70 parts by weight, preferably 30 to 60 parts by weight, per 100 parts by weight of a).

As mentioned above, the heat-melting ink layer 13 is mainly composed of a coloring material and a specific heat-melting component [a binder consisting of a combination of compound (a) and compound (b)]. As colorants, inorganic and organic pigments such as carbon black, lake red, alkali blue, and ultramarine blue, as well as oil-soluble or basic dyes that are highly soluble in fatty acids such as nigrosine, oil black, and methyl violet, are used. . Dyes are effective when added as an adjunct to create colors that cannot be achieved with materials alone, or to adjust the color tone.

The ratio of the colorant to the heat-melting component [binder consisting of a combination of compound (a) and compound (b)] is 5 to 4.
0% by weight, preferably 10-20% by weight, and 60-95% by weight, preferably 80-90% by weight of the hot melt component.

Furthermore, in the present invention, paraffin wax, microcrystalline wax, oxidized paraffin wax, candelilla wax, carnauba wax having a melting point of 40 to 100° C. is used in consideration of the melting point and melt viscosity of the heat-melting ink layer l3. , montan wax, ceresin wax, polyethylene wax, oxidized polyethylene wax, castor wax, hardened tallow oil, lanolin, wood wax,
In addition to spiral substances such as sorbitan stearate, sorbitan palmitate, stearyl alcohol, polyamide wax, oleylamide, stearacryamide, hydroxystearic acid, synthetic ester wax, and synthetic metal-containing wax, polyvinyl butyral, vinyl chloride-vinyl acetate, etc. Polymer resins, nitrocellulose, epoxy resins, ethylene-α-olefin copolymer resins, α-olefin-maleic anhydride copolymer resins, ethylene-methacrylic acid copolymer resins, ethyl cellulose, etc., one or two or more resins are mixed together. good.

The amount of wax or the like having a melting point of 40 to 100° C. added to the heat-melting ink layer 13 is determined by the binder component [compound (a)
and a binder consisting of compound (b)] is 30% by weight or less, preferably in the range of 1 to 10% by weight.

The peeling layer 12 has a low melt viscosity and the heat-melting ink layer 13
It is made of wax that has poor affinity with ink. Such waxes include beeswax, whale wax,
Natural waxes such as candelilla wax, carnauba wax, rice bran wax, montan wax, and osikelite; petroleum waxes such as paraffin wax, polyethylene wax, and microcrystalline wax;
Examples include various modified waxes, hydrogen waxes, long chain fatty acids, and the like. Note that wax alone may be used as the release layer 12, but fillers such as bentonite, kaolin, and talc may be added to meet various requirements for the ink ribbon. Viscosity etc. can be changed in a preferable direction.

The thickness of each of these layers constituting the thermal transfer recording medium of the present invention depends somewhat on the materials used therein, but the thickness of the heat-melting ink layer 13 is 1 to 10 μm, preferably 2 to 6 μm,
The peeling layer 12 has a thickness of 0.5 to 4 μm, preferably 1 to 2 μm, and the anti-sticking layer 14 has a thickness of 0.05 to 1 μm, preferably 0.01 to 0.1 μm.

Here, the outline of the means for forming each layer in the thermal transfer recording medium of the type shown in FIG. 1(c) is as follows.

(1) Formation of release layer 12: A wax emulsion is diluted with water to form a coating liquid. Also,
When adding a filler, it is dispersed in the coating liquid using ultrasonic waves. This coating liquid is applied onto a heat-resistant support (film-like support) 11 using an appropriate coating device. Dry it at 80-100°C.

(2) Formation of heat-fusible ink layer 13: There are three methods for dissolving or dispersing the coloring material and the binder agent (heat-fusible components mainly composed of compounds (a) and (b)) in a solvent. A commonly used dispersing machine such as a roll mill, a sentry mill, a sand mill, or a ball mill is used. This solution or dispersion liquid is used as an ink coating liquid. This coating liquid is applied onto the release layer 12 using an appropriate coating device. Dry it at 80-100°C.

(3) Formation of anti-sticking layer 14: Using a silicone resin solution as a coating liquid, it is applied using an appropriate coating device and dried.

The process of transferring heat-melting ink when printing on a transfer target with low smoothness using this type of thermal transfer recording medium 1 will be described.

The thermal head 2 moves the thermal transfer recording medium 1 onto the platen (
When the thermal head 2 generates heat, the heat passes through the film-like support 11 to the release layer 12 and the heat-fusible ink layer 13 (FIG. 2). is conducted, the release layer 12 and the heat-fusible ink Jii 13 are melted, and the heat-fusible ink that is in contact with the convex portions of the printing paper 3 adheres to (partially penetrates) the convex portions.
Then, when the thermal head 2 stops generating heat, the heat-melting ink layer 13 is cooled and fixed to the printing paper 3. At this time, the heated portion of the release layer 12 still remains liquid, and the heat-melting ink layer 13 corresponding to this portion is
Although its internal cohesive force is strong, its adhesion with the release layer 12 is extremely poor (it is significantly smaller than the adhesion between the heat-melting ink layer 13 and the release layer 12 in the non-heated portion).

Therefore, the heat-melting ink layer 13 in the heated portion, that is, the printed image portion, is easily transferred to the printing paper 3 side, including the portions (concave portions) that are not in contact with the printing paper 3, as shown in FIG. . At this time, the following relationship holds true.

F4>Fl>F2>F3 Fl: Adhesive force of the heat-fusible ink layer 13 to the printing paper 3 F2: Cohesive force of the heat-fusible ink layer 13 at the boundary between the heated portion and the non-heated portion F3: Hot-fusible ink What is the adhesion or peeling between the layer 13 and the release layer 12? 12 and the film-like support 11 F4: Cohesive force of the heat-melting ink layer 13 in the heated portion. In addition, by utilizing the fact that wax, etc. in the release layer 12 has a low melt viscosity and poor affinity with heat-melting ink, it is possible to achieve high print quality without scratches even on printing paper 3 with low smoothness. Printing will be available.

Note that not only the thermal transfer recording medium shown in FIG. 1(c),
It goes without saying that high-quality printed images can be formed on the thermal transfer recording media shown in FIGS. 1(a) and 1(b).

Next, examples will be shown. Both parts and percentages herein are based on weight.

Example 1 Carbon black 1.5
20 parts toluene
An ink layer coating solution was prepared by cross-dispersing a mixture consisting of 1.0 and 1.0 parts in a ball mill for 24 hours.

This coating liquid was applied to a polyimide film (about 7 μl thick11) using a wire bar, and dried to form a heat-melting ink layer about 5 μl thick. ] was created.

Comparative Example 1 12.5 parts of a 20% toluene solution of ethyl cellulose was removed from the ink layer coating solution, and 1 part of carbon black was added to that amount.
．． A thermal transfer recording medium was produced in exactly the same manner as in Example 1 except that parts were changed from 5 parts to 14 parts. Example 2 A mixture consisting of 1.5 parts of carbon black and 20 parts of toluene was treated in the same manner as in Example 1 to form an ink. A layer coating solution was prepared.

This coating liquid was applied to a polyimide film (about 7 μl thick) using a wire bar, and dried to form a heat-melting ink layer about 5 μl thick, which was used to form a thermal transfer recording medium [of the type shown in Figure 1 (a)]. ] was created.

Example 3 A release layer (approximately 2 μl thick) was formed by hot-ment coating a polyester film approximately 6 μm thick with microcrystalline wax (manufactured by Nippon Oil Co., Ltd.) heated to 155° F. Subsequently, an ink layer coating solution consisting of the following mixture was further applied onto the release layer using a wire bar, and dried to form a heat-melting ink layer with a thickness of about 5 μI to form a thermal transfer recording medium [shown in Figure 1 (b). I made a type of one.

carbon black 1.2
Part toluene/MEK=80/20 mixed solvent
20 parts Comparative Example 2 9 parts of the 20% MEK solution of vinyl chloride-vinyl acetate copolymer was removed from the ink layer coating solution, and 20 parts of ethylene-dityl acrylate copolymer with an ethyl acrylate content of 35% was removed. A thermal transfer recording medium was prepared in exactly the same manner as in Example 3 except that the amount of the toluene solution was changed from 35 parts to 44 parts.

Example 4 Ho IJ ethylene wax emulsion (Polylon #393 manufactured by Chusha Yushi Co., Ltd.) 92.5% and bentonite 7.5%
A release layer coating solution was prepared by diluting 100 parts of the release layer component consisting of 100 parts of water with 100 parts of water.

On the other hand, an ink layer coating liquid having the following composition was prepared.

Ethylene-ethyl acrylate copolymer same as that used in Example 1 25 parts Carbon black (MA-7 manufactured by Mitsubishi Chemical Industries, Ltd.) 15 parts Methyl isobutyl ketone 300 parts Subsequently, on a polyester film having a base thickness of about 3.5 μm The above-mentioned release layer coating liquid was applied and dried to form a release layer with a thickness of about 1 μm.Furthermore, the above-mentioned ink layer coating liquid was applied on this release layer to a thickness of 80 to 10 μm.
It was dried at 0 DEG C. to form a heat-fusible ink layer having a thickness of about 4 to 6 .mu.m, thereby producing a thermal transfer recording medium (of the type shown in FIG. 1(b)).

Example 5 A release layer coating solution was prepared by diluting 100 parts of polyethylene wax emulsion (Polylon A manufactured by Chusha Yushi Co., Ltd.) with 100 parts of water.

On the other hand, an ink layer coating liquid having the following composition was prepared.

Ketone′! I! JUJIU8 carbon black (manufactured by Mitsubishi Chemical Industries, Ltd. H)
A-7) 20 parts methyl isobutyl ketone
A thermal transfer recording medium was prepared in exactly the same manner as in Example 4 using 240 parts of these release layer coating liquid and ink layer coating liquid.

Example 6 While preparing the same release layer coating solution as in Example 5, an ink layer coating solution having the following composition was prepared! ! I made it.

Carbon black (HA-7 manufactured by Mitsubishi Chemical Industries, Ltd.)
20 parts methyl isobutyl ketone
240 parts A thermal transfer recording medium was prepared using these release layer coating liquid and ink layer coating liquid in exactly the same manner as in Example 4. Comparative Example 3 Hydrogenated rosin (Hyperel manufactured by Arayo Kagaku Kogyo Co., Ltd.) 40 parts Carbon black (Mitsubishi MA-100 manufactured by Kasei Kogyo Co., Ltd.)
20 parts toluene
A thermal transfer recording medium was prepared in the same manner as in Example 4 using an ink layer coating liquid having a composition of 400 parts. In addition, here, polyethylene wax emulsion (
Chukyo Yushisha 39ME-10) was used.

Comparative Example 4 Carbon black (HA-100 manufactured by Mitsubishi Chemical Industries, Ltd.)
20 parts toluene
A thermal transfer recording medium was prepared in the same manner as in Example 4 using an ink layer coating liquid having a composition of 400 parts. Here, a polyethylene wax emulsion (ME-10, manufactured by Chuguruma Yushi Co., Ltd.) was used as a component of the release layer.

Comparative Example 5 Ketone resin (Ketone resin manufactured by Arayo Kagaku Kogyo Co., Ltd. -90)
40 parts carbon black (MA-10 manufactured by Mitsubishi Chemical Industries, Ltd.)
0) 20 parts isopropyl alcohol
A thermal transfer recording medium was prepared in the same manner as in Example 4 using an ink layer coating liquid having a composition of 400 parts. Here, a polyethylene wax emulsion (ME-10 manufactured by Nakasei Yushi Co., Ltd.) was used as a component of the release layer.

EXAMPLE A thermal transfer recording medium [of the type shown in FIG. 1(B)] was prepared in exactly the same manner as in Example 4, except that the coating liquid for the ink layer was replaced with the one shown below.

Carbon black (MA-7 manufactured by Mitsubishi Chemical Industries, Ltd.)
15 parts methyl isobutyl ketone
300 parts Example 8 Carbon black (MA-7 manufactured by Mitsubishi Chemical Industries, Ltd.)
20 parts methyl isobutyl ketone 2
A thermal transfer recording medium was prepared in the same manner as in Example 4 using an ink layer coating liquid having a composition of 40 parts. Here, a polyethylene wax emulsion (Polyron A manufactured by Chukyo Yushi Co., Ltd.) was used as a component of the release layer.

Example 9 Carbon black (MA-7 manufactured by Mitsubishi Chemical Industries, Ltd.)
20 parts methyl isobutyl ketone
A thermal transfer recording medium was prepared in the same manner as in Example 4 using an ink layer coating liquid having a composition of 240 parts. Here, a polyethylene wax emulsion (Polyron A manufactured by Chukyo Yushi Co., Ltd.) was used as a component of the release layer.

Comparative Example 6 Boryamide (Sanmide #615A manufactured by Sansho Kagaku Kogyo Co., Ltd.)
50 parts hydrogenated petroleum hydrocarbon resin
25 parts carbon black (MA-1 manufactured by Mitsubishi Chemical Industries, Ltd.)
00) 20 parts methyl isobutyl ketone
A thermal transfer recording medium was prepared in the same manner as in Example 4 using an ink layer coating liquid having a composition of 400 parts. Here, a polyethylene wax emulsion (ME-10 manufactured by Chukyo Yushi Co., Ltd.) was used as a component of the release layer.

These inventive products (Examples 1 to 9) and comparative products (Comparative Examples 1 to 9)
6) was tested for printing quality and storage stability, and the results are summarized in Table 1.

(1) Print quality test 2 using a line head type printing tester with 8 dots/mm
．． Bond paper (
It was printed with a smoothness of about 40 seconds).

(2) Preservability test The thermal transfer recording media were stacked so that the heat-melting ink layer surface and the back surface (film-like support surface) were in contact with each other, and a load of 1 kg was applied to the media and left at 50°C for 72 hours to check for blocking. I looked at the situation.

Table 1 As is clear from the test results, the products of the present invention had clear printing and did not cause blocking during storage, which was satisfactory. It was also confirmed that the print fixability was also good.

On the other hand, in the case of a comparative amount, all properties were inferior to the product of the present invention, and especially in the storage test, blocking was severe and the ink layer was partially or completely peeled off.

In particular, the thermal transfer recording medium of Comparative Example 2 tended to stick when the ink layer surfaces came into contact with each other and was difficult to handle.

Although the above results are for bond paper with a relatively rough surface as a transfer medium, the product of the present invention also produced clear prints with good fixing properties when printed on a polyester sheet with a smooth surface.

〔effect〕

According to the thermal transfer recording medium of the present invention, good printing can always be obtained regardless of the surface condition and quality of the transfer target,
Blocking during storage, ink layer (heat-melting ink layer)
In addition, the uninvented thermal transfer recording medium does not cause damage to the ink layer due to the adhesion of the ink layer, and is also industrially easy to manufacture, as is clear from the description of the examples.

[Brief explanation of the drawing]

FIG. 1 shows three cross-sectional views of a thermal transfer recording medium according to the present invention. FIGS. 2 and 3 are diagrams for explaining the process of printing on a transfer target using the thermal transfer recording medium shown in FIG. 1(c). 1... Thermal transfer recording medium 2... Thermal head 3... Printing paper (transferred object) 11... Heat-resistant support 12... Peeling layer 13
...Thermofusible ink layer

Claims (1)

[Claims] 1. In a thermal transfer recording medium having a thermal transfer ink layer on a heat-resistant support, an ethylene-ethyl acrylate copolymer in which the ethyl acrylate monomer accounts for 15% by weight or more as a heat-melting component of the thermal transfer ink layer, and a copolymer and the copolymer thereof. A thermal transfer recording medium characterized by using a combination of polymeric substances that are difficult to dissolve.