JPH01133785A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To make it possible to obtain high-density images with excellent gradation qualities, by providing in a laminate form a plurality of heat-fusible ink layers differing in the contents of a coloring agent and a heat-fusible substance therein. CONSTITUTION:An ink layer 2 on a base 1 has a laminate structure comprising an ink layer 3 having a higher ink content and an ink layer 4 having a lower ink content. The lower ink content and the higher ink content mean that the total amount of a coloring agent and a heat-fusible substance is respectively 1-5 parts and 5-50 parts per 10 parts of a porous structure forming resin, the mixing ratio of the coloring agent to the heat-fusible substance being 3:1-1:10. When a thermal transfer recording medium with such a structure is used, the amount of the coloring agent caused to exude is varied depending on the quantity of thermal energy applied by a thermal head 5 or the like, so that the amount of the coloring agent transferred can be varied. Thus, it is possible to obtain images with a wide range of gradations faithful to the original and to obtain delicate and clear images.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a thermal recording medium to which a recorded image is transferred by heating.

Prior Art Conventionally, as transfer recording media, there have been known transfer sheets in which a heat-sublimable dye layer is provided on a support, and transfer sheets in which a heat-fusible substance and pigment are provided on a support. It is used to form an image on top.

However, although methods using heat-sublimable dyes have excellent gradation expression in images, they have the drawbacks of low heat sensitivity and poor image storage stability; Although this method has excellent thermal sensitivity and storage stability, it has the drawback of not being able to express gradation.

Therefore, a heat-sensitive transfer recording medium has been proposed in which a structure containing a heat-melting ink component mainly composed of a heat-melting substance and a colorant, which are solid at room temperature, is formed on a support in a microporous structure made of resin. Although gradation has been improved, the reproducibility of dots in saturated image density and low image density regions is still insufficient compared to images transferred using heat-sublimable dyes.

Purpose The present invention aims to improve the drawbacks of the above-mentioned prior art.
An object of the present invention is to provide a transfer recording medium from which high-density images with excellent gradation can be obtained.

In addition, the present invention has a plurality of layers having a structure in which a heat-melting ink component containing a heat-melting substance that is solid at room temperature, a coloring agent, and an oil as main components is contained in a microporous structure made of a resin. A heat-sensitive transfer recording medium provided on a support, characterized in that it is formed by laminating a plurality of ink layers containing different concentrations of colorants and heat-melting substances in the heat-melting ink layer. It is a medium.

In the present invention, a hot-melt ink component consisting of a hot-melt substance, a colorant, and an oil is retained by the network structure of the microporous structure of the resin. This heat-melting substance is melted by heating with a thermal head or the like, and oozes out from between the network structures of the microporous structure of the resin together with the coloring agent and oil, and gradually oozes out into the second half of the receiving sheet.

As shown in FIG. 1, the thermal transfer recording medium of the present invention has an ink layer 2 on a support 1 having a laminated structure of an ink layer 3 with a high ink concentration and an ink layer 4 with a low ink concentration. ing.

Although a two-layer structure is illustrated in FIG. 1, it may be three or more layers.

In the present invention, low ink content concentration and high ink content concentration mean that the mixing amount of the colorant and the heat-fusible substance is 1 to 5, and the latter is 5 to 5 with respect to the porous structure forming resin 10. 50
and preferably the former is 1 to 3 and the latter is 10 to 30
It is.

The mixing ratio of the colorant and the heat-melting substance is 3:1 to 1:10.
The ratio is preferably 1:1 to 1:5.

By using a thermal transfer recording medium with such a structure, the amount of colorant that oozes out varies depending on the amount of thermal energy applied by the thermal head 5 etc., and by controlling the applied thermal energy, the transferred color can be adjusted. The amount of the agent can be changed, and when compared with conventional single-layer ink layers, it is possible to obtain images that faithfully and broadly represent gradations, as well as fine-grained and clear images.

Although the reason for this is not certain, the following can be predicted. In the low recording energy area, the low density ink in the second layer is transferred, resulting in a small amount of ink transfer, resulting in good reproducibility in the low density area, and in the high recording energy area, the high content in the lower layer is transferred. It is thought that since a large amount of ink transfers, a large amount of ink transfer occurs, and the saturated image density suddenly increases, resulting in a gradation recorded image with a wide dynamic range in terms of gradation characteristics.

Here, the level of heating energy varies depending on the type of each material and the thickness of the ink layer, and is a relative value.

As the support used in the present invention, conventionally known films and papers can be used as they are, such as polyester, polycarbonate, 1-lyacetylcellulose,
Plastic films with relatively good heat resistance such as nylon or polyimide 1, cellophane or parchment paper can be suitably used. The thickness of the support is preferably about 2 to 15 microns when considering a thermal head as a heat source during thermal transfer, but it is preferable to use a heat source that can selectively heat the thermal transferable ink layer, such as a laser beam, for example. There are no particular restrictions in this case. In addition, when using a thermal head, a heat-resistant protective layer made of silicone resin, fluororesin, polyimide resin, epoxy resin, phenolic resin, melamine resin, nitrocellulose, etc. should be provided on the surface of the support that comes into contact with the thermal head. This makes it possible to improve the heat resistance of the support, or to use a support material that could not be used conventionally.

Further, it can also be used for electrical transfer in which the support is made conductive and a current is applied to the support to generate Joule heat and melt and transfer the ink components.

Although there are no particular limitations on the method for producing the heat-melting ink layer having the structure described in 1., the following method is generally used. That is, a heat-fusible substance, a colorant, and an oil or the like are mixed and dispersed together with a suitable organic solvent using a dispersion device such as an attritor or a ball mill to obtain an ink dispersion (which may also be a solution). Separately, a solution of a thermoplastic resin dissolved in an organic solvent is obtained, mixed with the ink dispersion, and uniformly dispersed using a mixer such as a ball mill. Next, the obtained dispersion is applied onto a support and dried to form the first particle with the above-mentioned fine structure.
A hot-melt ink layer of 100% is obtained. Then, in the same manner, it is coated on the first heat-melt ink layer to obtain a second heat-melt ink layer. The preferred thickness range of each of the first and second heat-melting ink layers is 1 to 10 μm.

A wetting agent, a dispersing agent, etc. may be added to the dispersion liquid in order to improve the dispersion of the above-mentioned heat-melting substance, colorant, and oil. Also, if necessary, fillers commonly used in resin coatings of this type can be added.

The resins constituting the microporous resin structure include vinyl chloride, vinyl acetate, vinylidene chloride, nitrocellulose, cellulose butyrate, cellulose acetate, acrylic acid, methacrylic acid, acrylic ester and It is preferable to use thermoplastic resins such as single or copolymers of monomers selected from methacrylic acid esters, and thermosetting resins such as phenol, furan, formaldehyde, urea, melamine, alkyds, unsaturated polyesters, and epoxy.

Alternatively, a substance that is incompatible with the resin that forms the porous structure and soluble in a solvent that does not dissolve the resin is kneaded with the resin, and is coated on the support to form a resin layer. A transfer layer having the above-described structure can also be obtained by dissolving a substance in the above-mentioned solvent to form a porous resin structure, and then filling the porous structure with a thermally transferable ink.

The generally preferred pore diameter range of the microporous structure obtained in this way is 1 to 20 μm, and the preferred pore density range is 2,000 to 300,000 pores/mm2.

As the heat-melting substance that is solid at room temperature, heat-melting binders that constitute heat-melting ink in ordinary heat-sensitive transfer recording media can be used, such as carnauba wax, paraffin wax, Sasol wax, and microcrystalline. Waxes such as wax and castor wax; stearic acid, palmitic acid, lauric acid, aluminum stearate, lead stearate, barium stearate, zinc stearate, zinc palmitate, methyl monoheloxystearate-1-, glycerol monohydroxystearate higher fatty acids such as esters, or derivatives such as their metal salts and esters; polyethylene, polypropylene, polyisobutylene, polyethylene wax, polyethylene oxide, polytetrafluoroethylene, ethylene-acrylic acid copolymer, ethylene-acrylic acid Thermoplastic resins made of olefins alone or copolymers such as ethyl copolymer, ethylene-vinyl acetate copolymer, or derivatives thereof are used. These holding materials are used alone or in a mixture of two or more at a ratio of 50 to 200 parts per 100 parts of the thermoplastic resin constituting the thermal transfer layer.

Specific examples of the coloring agent include the following.

Coloring dyes and color pigments may be used, but dyes can provide images with more preferable gradation.

Examples of such dyes that do not sublimate include the following direct dyes, acid dyes, basic dyes, mordant dyes, sulfur dyes, vat dyes,
There are azoic dyes, oil-based dyes, etc.

1) Direct dyes: Dairef 1-Sky Blue, Dairef 1-Black W, etc.

2) Acid dye: Tartrazine, Acid Violet 6
B, Acidophus 1 to Red 3G, etc.

3) Basic dyes: safranin, auramine, crystal violet, methylene blue, rhodamine B, Victoria blue B, etc.

4) Mordant dye: Sunchromine Firth 1-Blue MB,
Erio from Azurol B, Alizarin Yellow B, etc.

5) Sulfur dye: Sulfur Brilliant Green 4G, etc.

6) Vat dyes: indanthremble, etc.

7) Azoic dye: naphthol AS, etc.

8) Oil-based dye Nigrosin, Spirit Black EB,
Varifast Orange 3206, Oil Black 215
, Butter Yellow, Sudan Blue ■, Oil Red B
, Rhodamine B et al.

These dyes are preferably in a dissolved state.

Examples of colored pigments include colored fine particle pigments and monoazo pigments.

Specific colored fine particle pigments are shown below. All are made by Hoechst, and the color index numbers are shown in parentheses.

Permanent Yellow GG, 2 (Pigment Yellow 1
7), Permanent Yellow DHG Trans 02 (Pigment Yellow 12), Novopalm Yellow HRO
3 (Pigment 1 to Yellow 83), Hansa Brilliant Yellow 5GXO2 (Pigment Yellow 74), Permanent Orange RLOI (Pigment Orange 34)
), Novopalm Red HFG (Pigment Orange 3
8), Novo Palm Red HFT (Pigment Red 175), Lake Red LCLL to Permanen 1
O2 (Pigment Red 53:1), Novopalm Red HF4B (Pigment Red 187), Permanent Carmine FBBO2 (Pigment Red 146)
, Permanent Lupine L6B (Pigment Red 57
:1), Hostapalm Pink E-Trans (Pigmen 1)
~ Red 122), Reflex Blue R50 (Pigment Blue 61).

Examples of monoazo pigments include compounds represented by the following structural formula.

X-N=N-Y however, Particularly specific examples of product names include the following.

(1) 5ico Fast Yellow D 13
55 (made by BASF) (2) 5ico Fas
t Yellow D 1250 (manufactured by BASF) (3) Lake Red LC (manufactured by Hoechst) (4) Lake Red C405 (manufactured by Dainichiseika)
(5) The structural formula of Fast Red 1547 (manufactured by Dainichiseika Chemical Co., Ltd.) is as follows: The above-mentioned microporous formation aid oil may be incompatible with the above-mentioned thermoplastic resin and non-volatile. For example, either liquid or semi-solid can be used. Examples of liquid oils include animal and vegetable oils such as cottonseed oil, rapeseed oil, and whale oil; mineral oils such as motor oil, spindle oil, and dynamo oil; examples of semisolid oils include lanolin, lanolin derivatives, vaseline, and lard.

Regarding this oil, it is preferably a lanolin derivative oil of the same type as the above-mentioned lanolin derivative wax,
More preferred are oils of lanolin fatty acids or lanolin fatty acid esters, specific examples of which include Neocor 1
-OES481.0ES-183, LFC-50M, L
Examples include S-3102MB (all manufactured by Yoshikawa Oil Co., Ltd.).

The above oil may be contained in an amount of 20 parts by weight or more, but in order to lower the viscosity of the ink component, a low viscosity oil having a viscosity of 300 cps or less as shown below can be added.

■Higher alcohol ester former 5ORATE = 4 Ricinoleic acid 53
．． 6! ! =5 isooctanoic acid 8.8n
='l persatic acid 12.7:1
0 isostearic acid 24.3n = ll stearic acid 20. OII = 10] Cupric acid 22.2JT = 105 Isooctanoic acid 24.2JT = 107 Parsateic acid 36.8II = 108 Dimer acid 36. OJr = 110 isostearic acid 56. OII = 111 stearic acid 36.8〃 = 417 oleic acid
80■Hydroxy fatty acid ester Co-FA methyl methyl lysyllate 40Co-F
A Butyl Butyl lysyllate 40 Other soybean oil 120 Bean nut oil 150 Liquid paraffin 250 All of the above have a volatile content (120°C) of 1.0% or less. In consideration of stability over time, ■ is preferable.

The total oil content is 10 to 50% of the total amount of ink components.
Weight percent is preferred.

Furthermore, in order to further improve the gradation obtained by the present invention, it is also possible to add a gradation control agent, which will be described later.

In other words, the gradation control agent has better wetting and compatibility with the resin than low-melting substances such as oil and wax, which are the main components of hot-melt ink, and is firmly held in the sponge resin structure. It seems that the pore size is delicately controlled to make it even smaller. Therefore, even when thermal energy is applied, it is not transferred out, but is retained in the porous structure, and acts as a good gradation control agent by controlling the amount of colorant and ink existing in the surrounding area that transfers. it is conceivable that. In addition, by adding a gradation control agent, the unevenness of the surface increases, the contact point with the receptor becomes smaller, and the effect of preventing background smearing can be cited.

As the gradation control agent, the following are shown as specific examples.

=16- 1) Acicular crystal pigment (Patent Application No. 60-38868) 2)
Azo pigment (Japanese Patent Application No. 60-192098) 3) Phthalocyanine pigment (Japanese Patent Application No. 60-168562) The amount of the gradation control agent added is 0.5 per part by weight of the dye.
~10 parts by weight, preferably 1 to 5 parts by weight.

In order to maintain the porous resin structure more strongly,
It is also possible to provide an intermediate adhesive layer on the support in advance.

Examples of the intermediate adhesive layer include so-called plastic resins and plastic resins to which fillers are added.

The receiving sheet may basically be plain paper or synthetic paper, but if necessary, it may be made of the above resins, TiO□, silica, ZnO.
It is also possible to apply a filler containing fillers such as the like on plain paper to facilitate the transfer of the colorant.

Next, an example will be described. All parts are parts by weight.

Example 1 Colorant: Neozapon Blue 807 (
(manufactured by BASF) 10 parts Heat-melting substance: Carnauba wax No. 1 (manufactured by Noda Wax) 20 parts Auxiliary agent for forming fine pores: Lanolin fatty acid oil (OE
S-183, manufactured by Yoshikawa Oil Co., Ltd.) 6 parts Low viscosity oil: Oleic acid ester oil (Hisorate
#117 Ito Oil Co., Ltd.) 10 parts powder
0.5 part liquid paraffin
3 parts of the above heat-melting ink components are dispersed in a ball mill for about 48 hours at about 90° C. with a mixed solution of 60 parts of methyl ethyl ketone and 150 parts of toluene.

Then 10% by weight of cellulose acetate butyrate (
Kanto Kagaku Nibutyl group 17%, melting point 230-240°C
) solution (15 parts of resin, 67.5 parts of 1Helene, 67.5 parts of methyl ethyl ketone) was added to the above ink dispersion and dispersed in a ball mill for about 1 hour to prepare a coating of the first thermal transfer composition. did.

This coating was applied to the surface of a 6 μm thick polyester film with a silicone resin heat-resistant layer on the back side using a wire bar, and dried at a drying temperature of 100°C for 1 minute. A hot melt ink layer was formed.

Next, the following formulations were used as hot-melt ink components: Colorant: Neozapon B], ue 807 (
(manufactured by BASF) 2-part dispersant
0.5 part liquid paraffin
A second heat-sensitive transfer composition coating was prepared in exactly the same manner as in the preparation of the first heat-sensitive transfer composition coating except that 3 parts were used. A coating agent of this second heat-sensitive transfer composition was similarly applied onto the first heat-melt ink layer to form a second heat-melt ink layer having a thickness of about 2 μm.

The ink layer of the transfer medium obtained in this way was stacked so as to face the coated synthetic paper (YUPO PFK-90 manufactured by Tamago Yuka Synthetic Paper Co., Ltd.) serving as a receptor, and the heating energy was varied using a thermal head from the back side of the transfer medium. When image recording was performed, the results shown in Table 1 and FIG. 2 below were obtained. The recording density of the thermal head is 6 dots/■, and the recording output is 0.
It was 25W/dot.

Example 2 Colorant: Neozapon Blue 807 (B
Made by ASF) 10 parts castor oil
12 part dispersant 0.
5 parts liquid paraffin 3 parts The above heat-melting ink components were mixed with 60 parts methyl ethyl ketone at about 90°C.
and 150 parts of toluene in a ball mill for about 48 hours.

Next, a 20% by weight vinyl chloride vinyl acetate copolymer resin solution (20 parts resin, 40 parts toluene, 40 parts methyl ethyl ketone)
100 parts of the ink dispersion was added to the above ink dispersion and dispersed in a ball mill for about 1 hour to prepare a coating of the first thermal transfer composition.

This coating was applied to the surface of a 6 μm thick polyester film with a silicone resin heat-resistant layer on the back side using a wire bar, and dried at a drying temperature of 100°C for 1 minute. A hot melt ink layer was formed.

Next, the following formulation as a hot-melt ink component, colorant: Neozapon Blue 807 (B
(manufactured by ASF) 2 parts Heat-melting substance: Montan wax S (manufactured by Hoechst) 6 parts lanolin fatty acid oil (OES-183, manufactured by Yoshikawa Oil) 3 parts castor oil 6 parts powder 0.5 parts liquid paraffin Except for the use of 3 parts A second heat-sensitive transfer composition coating was prepared in exactly the same manner as in the preparation of the first heat-sensitive transfer composition coating. The coating agent of this second thermal transfer composition was applied to the coating agent of the first thermal transfer composition in the same manner.
A second heat-melt ink layer having a thickness of about 2 μm was formed by coating the heat-melt ink layer on the heat-melt ink layer.

When images were recorded on the thermal transfer recording medium thus prepared in the same manner as in Example 1, the results shown in Table 1 and FIG. 2 below were obtained.

Example 3 Colorant: SOT Pink 1 (manufactured by Hodugaya Chemical)
10 parts Dispersant 0.5 parts Liquid paraffin 3 parts The above heat-melting ink stand was heated to about 90°C with a mixed solution of 60 parts of methyl ethyl ketone and 150 parts of toluene in a ball mill for about 4.
Spread over time.

Next, 75 parts of a 20% by weight vinyl chloride-vinyl acetate copolymer resin solution (15 parts of resin, 30 parts of 1 to 1, 30 parts of methyl ethyl ketone) was added to the above ink dispersion, and dispersed in a ball mill for about 1 hour. A coating of the heat-sensitive transfer composition No. 1 was prepared.

This coating was applied to the surface of a 6 μm thick polyester film with a silicone resin heat-resistant layer on the back side using a wire bar, dried for 1 minute at a drying temperature of 100°C, and then heated to a thickness of approximately 3 μm. A molten ink layer was formed.

Next, the following formulation was used as a hot-melt ink component: Colorant: SOT Pink 1 (manufactured by Hodugaya Chemical Co., Ltd.)
2-part dispersant 0.5
A second heat-sensitive transfer composition coating was prepared in exactly the same manner as in the preparation of the first heat-sensitive transfer composition coating, except that 3 parts of liquid paraffin were used. A coating agent of this second heat-sensitive transfer composition was similarly applied onto the first heat-melting ink layer to a thickness of about 2.
A second hot-melt ink layer of .mu.m was formed.

=23- When images were recorded on the thermal transfer recording medium thus prepared in the same manner as in Example 1, results as shown in Table 1 and FIG. 2 below were obtained.

Comparative Example 1 Example except that the second heat-melt ink layer was not provided as an ink layer, and the same first heat-melt ink layer forming liquid as in Example 1 was provided as a single layer with a thickness of about 5 μm. A thermal transfer recording medium was prepared in the same manner as in Example 1, and image recording was performed under the same conditions as in Example 1.

Comparative Example 2 As an ink layer, the first heat-melt ink layer was not provided, and the same liquid as the second heat-melt ink layer forming liquid of Example 1 was used for about 5μ+1
A heat-sensitive transfer recording medium was prepared in the same manner as in Example 1, except that it was provided as a single layer with a thickness of , and image recording was performed under the same conditions as in Example 1.

Comparative Example 3 Example 3 except that a second heat-melt ink layer was provided as the ink layer, and the same first heat-melt ink layer forming liquid as in Example 3 was provided as a single layer with a thickness of about 5 μm. A thermal transfer recording medium was prepared in the same manner as in Example 1, and image recording was performed under the same conditions as in Example 1.

Comparative Example 4 Example 3 except that the first heat-melting ink layer was not provided as the ink layer, and the same second heat-melting ink layer forming liquid as in Example 3 was provided as a single layer with a thickness of about 5 μm. A thermal transfer recording medium was prepared in the same manner as in Example 1, and image recording was performed under the same conditions as in Example 1.

The results of the above Examples and Comparative Examples are shown in Table 1 and FIG. 2 below.

Table 1 Earth 2-re U! L Niwajimaru Example 1 None ○ Example 2 None ○ Example 3 None ○ Comparative Example 1 Present × Comparative Example 2 None ○ Comparative Example 3 Present △ Comparative Example 4 None ○ As shown in Table 1 and Figure 2 above From the results, Examples 1 to 3
It can be seen that it is possible to obtain a fine-grained and clear image with wide gradation reproducibility and no background smudge.

As is clear from the above explanation, in the transfer recording medium of the present invention, ink oozes out from between the porous resin structures with small pore diameters and is transferred to the receiving sheet surface, depending on the magnitude of heating energy. Therefore, by controlling the heating energy during transfer, there is no background smudge and good reproducibility in low density areas.
In addition, a transferred image with high saturated image density and excellent gradation expression (wide gradation reproduction) can be obtained. Also, the ink is 1
Since it is not consumed at all by one recording, it can be used for many recordings. Full color images can also be obtained by selecting various dyes.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the thermal transfer recording medium of the present invention. FIG. 2 shows the relationship between the heating energy of the thermal head and the image density for the thermal transfer recording media of Examples and Comparative Examples. 111. Support, 2. ,, ink layer 301. First thermofusible ink layer 401. Second thermofusible ink layer 501. Thermal head patent applicant Rico Co., Ltd. −

Claims (1)

[Claims] 1. In a heat-sensitive transfer recording medium having a plurality of heat-melt ink layers containing heat-melt ink in a microporous structure made of resin on a support, the colorant in the heat-melt ink layer and the heat-melt 1. A thermal transfer recording medium characterized in that it is formed by laminating a plurality of ink layers containing different concentrations of sexual substances.