JPS63276591A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To enable a transfer image which is high in saturated image density and efficient in gradation expression (wide in gradation reproduction) to be obtained on plain paper of low smoothness, by a method wherein plasticizer is contained in a thermal fusion ink layer of a thermal transfer recording medium on which the thermal fusion ink layer is established. CONSTITUTION:Plasticizer is contained in a thermal fusion ink layer of a thermal transfer recording medium to which a recording image is transferred by heating of a thermal head, laser, etc. Content of this plasticizer is preferably 20-50wt.%. For a method how the plasticizer is contained in the thermal fusion ink layer, it is preferable that, for instance, the plasticizer is dispersed in thermal fusion ink components, or otherwise the plasticizer is dissolved in suitable solvent and added into the thermal fusion ink components as an additive. As an oil which is an adjuvant for forming porous matter, if it is only noncompatible with thermoplastic resin and nonvolatile, either of liquid or semisolid may be used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a thermal transfer recording medium on which a recorded image is transferred by heating with a thermal head, laser, or the like.

[Prior Art] Conventionally, as thermal 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. , is used to form an image on a receiving sheet by thermal printing.

However, methods that use heat-sublimable dyes have excellent gradation expression in images, but have the drawbacks of low heat sensitivity and poor image storage stability, and also use heat-fusible substances and pigments. This method rarely had the disadvantage of being superior in heat sensitivity and storage stability, or being unable to express gradation.

Therefore, a heat-sensitive transfer recording medium has been proposed that has a structure in which a heat-melting ink component, which is mainly composed of a heat-melting substance and a colorant that are solid at room temperature, is contained in a microporous structure made of resin formed on a support. has been done.

This heat-melting substance is melted by heating with a thermal head, etc., and together with the coloring agent, it oozes out from between the network structures of the microporous structure of the resin and oozes out onto the receiving sheet little by little, reducing the amount of heating energy by 1. By controlling this, a recorded image with different gradations can be obtained. At this time, images recorded on paper with high smoothness such as synthetic paper or high-quality paper can obtain satisfactory gradation characteristics and saturated image density, but images recorded on rough paper with low smoothness, that is, 100 seconds or less, can be obtained. The images were unsatisfactory with respect to gradation characteristics (particularly dot formation in low density areas) and saturated image density. In other words, a defective recorded image was obtained in which ink adhered only to the convex portions of the rough surface of the paper, and almost no ink was transferred to the concave portions.

Therefore, the Olson-Pill formula for permeation of liquid when external pressure is applied to paper made of capillary tubes % formula % d - Depth into which liquid is pushed at the moment pressure is applied P - External pressure r - Radius of capillary tube One hour η - From the viscosity of the liquid, it is recognized that if p, r, and t are constant, the smaller the value of η, the greater the ink penetration depth dv, that is, the amount of transfer. Amount: 20-50% content ■ Surfactant: 20-50% content ■ Low viscosity oil: 300 CpS or less was proposed, and the above problems have been solved.

However, when simply creating black and white or monochrome sheets, coating methods such as wire bars and blades are used, so the concentration of the solid content of the ink including the solvent is 2.
Since it is low at 0 weight maximum % or less, there was no problem, 2 colors,
When creating a color sheet with three or more colors arranged in order, the above coating cannot be applied.
It is common knowledge that a gravure printing method is used to print three colors in a random pattern. When using this gravure printing method, the solid content is preferably 20% by weight or more; in this case, the amount of solvent is inevitably reduced, and the oil and the resin forming the porous structure do not mix well and gel. Unfortunately, a problem arose in that gravure printing was not possible.

[Purpose] The purpose of the present invention is to provide a heat-sensitive transfer recording medium that can produce high-density images with excellent gradation on plain paper with particularly low smoothness, and that can produce good color sheets by gravure printing. do.

[Structure] The structure of the present invention is that a heat-melting ink layer containing a heat-melting substance that is solid at room temperature and a coloring agent as main components is provided in a microporous structure made of a resin formed on a support. : A thermal transfer recording medium characterized in that the heat-melting ink layer contains a plasticizer.

In other words, the inventors of the present invention have made earnest efforts to improve the drawbacks of the above-mentioned prior art, and as a result of incorporating a plasticizer into the heat-melting ink layer as in the present invention, it is possible to create a grade even on rough paper with a smoothness of 100 seconds or less. It is possible to obtain recorded images with excellent tonality and saturated image density, and in addition, during gravure printing (solid content concentration 20%)
When the temperature was increased above 100%), good color sheets of two or more colors could be produced without gelation. The reason for preventing gelation is thought to be that plasticizers were originally used because they had relatively good compatibility with any resin, and in this respect, good results were obtained, unlike other oils.

The content of plasticizer is preferably 20 to 50% by weight.

If it is less than 20% by weight, excellent recording will not be obtained, and if it exceeds 50% by weight, the resolution of the recorded image will decrease and the occurrence of scumming will become noticeable. Therefore, preferable results are obtained with a content of 20 to 50% by weight, more preferably 20 to 40% by weight.

The plasticizer used in the present invention is a relatively non-volatile solvent that is added to a polymeric substance to improve its processability or change its physical properties.

It can also be said to be a substance that reduces the melt viscosity, secondary transition point, and elastic modulus of the polymer substance, such as Dimethyl Phthalate,
Dietyl Phthalate, Dibut
yl Phthalate, Diheptyl Ph
thalate, Dioctyl Phthalate
, Diisononyl Phthalate, D
iisodecyl Phthalate, Buty
l Benzyl PhthalateSDilaury
l Phthalate, Dicyclohexyl
Phthalate, TricresylPhosp
Hate, Triethyl Phosphate
.

Tributyl Phosphate, Trioc
tyl Phosphate.

Tris (β-chloroethyl) Phos
Phate.

Tributoxyethyl Phosphate
, Dingris (dichloropropyl) P
phosphate, Tris (β-chlorop
rol)yl) Phosphate, Triph
enylPhosphate, 0ctyl Dip
henyl Phosphate.

TriS(isOpropVlpheny+) pho
Spate.

Dioctyl Adipate, Diisono
nyl Adipate, Diisodecyl Ad
ipate, Dialkyl Adipate, Di
(butyl dj glycol) Adipate,
Di-2-ethy+hexyIAzelate,
Dibutyl 5ebacate.

Dioctyl 5ebacate, Acetyl
TriethylCitrate, Acetyl
Tributyl C1trate, Dibuty
l 1laleate, Di-2-ethylhe
xylMaleate, Dibutyl Fum
arate, Butyl 01eat.

Butyl 5tearate, other trimellitic acid plasticizers, polyester plasticizers, epoxy plasticizers,
Examples include stearic acid plasticizers, rubber plasticizers, chlorinated paraffin, and castor oil.

These may be used alone or in combination of two or more.

The plasticizer of the present invention can be incorporated into the hot melt ink layer using any method.
Alternatively, it may be dissolved in a suitable solvent and added as an additive to the hot-melt ink component.

The oil used as an auxiliary agent for forming porosity may be either liquid or semi-solid as long as it is incompatible with the above-mentioned thermoplastic resin and is non-volatile.

Examples of liquid oils include animal and vegetable oils such as cottonseed oil, rapeseed oil, whale oil; motor oil, spindle oil,
Mineral oils such as dynamo oil are used, and examples of semi-solid oils include lanolin, lanolin derivatives, vaseline, and lard.

Regarding this oil, preferably it is a lanolin derivative oil of the same type as the above-mentioned lanolin derivative wax,
More preferably, it is an oil of lanolin fatty acid or lanolin fatty acid ester, and specific examples thereof include Neocoat 0ES-181, 0ES-183, LFC-50M, and LFC-50M.
Examples include S-3102MB (all manufactured by Yoshikawa Oil Co., Ltd.).

As the support used in the present invention, conventionally known films and papers can be used as they are, such as films of relatively heat-resistant plastics such as polyester, polycarbonate, triacetylcellulose, nylon, and polyimide, cellophane, or Parchment paper or the like 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 for thermal transfer, but it is preferable to use a heat source that can selectively heat the thermal transfer ink layer, such as a laser beam. 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, phenol 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.

There are no particular restrictions on the method for producing the heat-melting ink layer having the structure described above, but the following method is generally used. That is, a heat-melting substance and a coloring agent;
An ink dispersion (or a solution) is obtained by mixing and dispersing the oil, which serves to form the porosity of the resin, with a suitable organic solvent using a dispersion device such as an attritor or a ball mill. 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 resulting dispersion is applied onto a support and dried to obtain a hot-melt ink layer having the above-mentioned fine structure.

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 acetate, 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.

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, sacil wax, microcrystalline wax, etc. Waxes such as castor wax; stearic acid, palmitic acid, lauric acid, aluminum stearate, lead stearate, barium stearate, zinc stearate, zinc palmitate, methyl hydroxy stearate, glycerol monohydroxy stearate, etc. higher fatty acids or their derivatives such as metal salts and esters; polyethylene, polypropylene, polyisobutylene, polyethylene wax, polyethylene oxide, polytetrafluoroethylene, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer , thermoplastic resins made of single or copolymers of olefins such as ethylene-vinyl acetate copolymers, or derivatives thereof. 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 colorants include the following.

Colored dyes and colored pigments may be used, but dyes 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: Direct Sky Blue, Direct Black W, etc.

2) Acid dye: Tartrazine, Acid Violet 6
B, Acid Fast Red 3G, etc.

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

4) Mordant dyes: Sunchromine Fast Blue-MB, Elio from Azurol B1 Alizarin Yellow B, etc.

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

6) Vat dyes: indanthremble, etc.

7) Azoic dye: naphthol A3 etc.

8) Oil dye: Nigrosine, 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 the appetizer pigment include colored fine particle pigments and monoazo pigments.

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

Permanent Yellow GG, 2 (Pigment Yellow 17), Permanent Yellow DHG Transformer 02
(Pigment Yellow 12), Novo Palm Yellow HRO3 (Pigment Yellow 83), Hansa Brilliant Yellow 5GXO2 (Pigment Yellow 74), Permanent Orange RLOI (Pigment Orange 34), Novo Palm Red HFG (Pigment Orange 38), Novo Palm Red HFT (Pigment Red) 175), Permanent Lake Red LCLLO2 (Pigment Red 53:1), Novo Palm Red HF4B (Pigment Red 187),
Permanent Carmine FBBO2 (Pigment Red 14B), Permanent Lupine L6B (Pigment Red 57:1), Hostapalm Pink F Trans (Pigment Red 122), Reflex Blue R50 (Pigment Blue 61) Monoazo pigments are represented by the structural formula below. Compounds that can be mentioned include:

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

(1) 5ico Fast Yellow D 13
55 (made by BASF) (2) 5ico Fast
Yellow D 1250 (made by BASF F) (3)
The structural formula of Lake Red LC (manufactured by Hoechst) is (4) Lake Red C405 (manufactured by Jinnisseika) (
5) Fast Red 1547 (manufactured by Dainichiseika Chemical Co., Ltd.) has the following structural formula: In order to roughly improve the gradation obtained in the present invention, it is also possible to add a gradation control agent to be described later.

In other words, the gradation control agent has better wettability 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. This is done by delicately controlling the pore size of the tissue 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.

1) Acicular crystal pigment (Japanese Patent Application No. 60-38868) 2) Azo pigment (Japanese Patent Application No. 60-192098) 3) Phthalocyanine pigment (Japanese Patent Application No. 60-168562) Addition of the above gradation control agent The amount is 0.5 per part by weight of 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.

Above, we have described the effect on paper with particularly low smoothness.
On the other hand, even on paper with high smoothness, such as coated paper or coated synthetic paper, it was found that the reproduction of low-density areas was better, making it possible to express gradations close to those of photographs.

Next, an example will be described.

Example 1 and Comparative Example 1 Table 1 The above hot melt ink components were quantum dispersed for about 24 hours using a ball mill at about 85°C.

Next, 45 parts of a 20% by weight vinyl chloride-vinyl acetate copolymer resin solution (9 parts by weight of resin, 18 parts of toluene, 18 parts of methyl ethyl ketone) was added to each of the above ink dispersions, and dispersed in a ball mill for about 1 hour to form a thermal transfer composition. I created a paint for things.

This paint 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 to form a heat-melting ink with a thickness of approximately 5 μm. formed a layer.

The ink layer of the transfer medium obtained in this way is used as a receiver on plain paper (XerOX Real Paper 402) with a smoothness of 37 seconds.
4) were stacked so as to face each other, and images were recorded from the back side of the transfer medium using a thermal head with a recording output of 0.26 W and a recording density of 6 dots/nun by changing the heating energy key, as shown in Figure 1 and Table 2. Got the results.

Table 2 Image quality uniformity and background smear When the content is 20% by weight or more, the saturated image density also exceeds 1.0, and the image quality uniformity is good, but when it exceeds 50% by weight, background smear occurs, and the result is 20 to 50% by weight. It has been found that good images can be obtained within a range of % by weight.

In addition, even when the amount of solvent was reduced to 25% by weight, no gelation occurred at all, and when tested with a simple gravure printing tester, the screen line count was 155.
Line/inch, plate depth 30. czm, 40μm, 50
A good ink layer was formed in fim.

Example 2 and Comparative Example 2 Table 3 Table 3 (Continued) Each of the above hot melt ink components was dispersed in a ball mill at about 85° C. for about 24 hours.

Next, 45 parts of a 20 M% vinyl chloride-vinyl acetate copolymer resin solution (9 parts by weight of resin, 18 parts of toluene, 18 parts of methyl ethyl ketone) was added to each of the above ink dispersions, and dispersed in a ball mill for about 1 hour to form a thermal transfer composition. I created a paint for things.

This paint 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 to form a heat-melting ink with a thickness of approximately 5 μm. formed a layer.

The ink layer of the transfer medium thus obtained passes through the receiver on plain paper (XerOX Bond Paper 402) with a smoothness of 37 seconds.
4) were stacked so as to face each other, and an image was recorded from the back side of the transfer medium using a thermal head while changing the heating energy, and the results shown in FIG. 2 and Table 4 were obtained.

Table 4 As a comparative example of image quality uniformity and background smudge, when the plasticizer in Table 3 was replaced with linseed oil and soybean oil, results similar to those in Table 4 were obtained regarding image quality uniformity and background smear, but the hardness The gelation state with a mold content of 25% by weight is as shown in Table 5 below.

Table 5 Example 3 and Comparative Example 3 The sheet created in Example 1-2 was referred to as Example 3, and the sheet created with the formulation of Example 1-2 except for the plasticizer n-butyl oleate was referred to as Comparative Example 3. shall be. On the other hand, the liquid with the formulation shown in Table 6 below was mixed and dispersed for about 1 hour using an attritor, and then placed on a commercially available synthetic paper (YUPO FPG-95, made by Tamago Yuka Synthetic Paper, about 95μ thick). , coated with a wire bar and provided a coating layer with a thickness of about 10 μm, l0k
g/Cm' calender, Oken type smoothness 350
A reception medium of 0 seconds was obtained.

Table 6 The sheets of Example 3 and Comparative Example 3 were stacked so as to face the coated synthetic paper used as the receiving medium, and images were recorded in the same manner as in Example 1. The results shown in FIG. 3 were obtained. Ta.

As a result, it was found that Example 3 was also superior in terms of saturated image density and sensitivity.

When the reproduction of the part (roughly low) was observed using an optical microscope (200x magnification), it was found that in Example 3, there was almost no missing dot transition than in Comparative Example 3, and the shape was well-reproduced. It was recognized that

Example 4 and Comparative Example 4 27 Among the ink components listed in Table 1 described in the section of Example 1 and Comparative Example 1, purified castor oil (manufactured by Ito Oil Co., Ltd.) was used instead of the plasticizer 1ln-butyl olein. A thermal transfer recording medium was made under the same conditions as in Example 1 and Comparative Example 1, except that 100% was used, and images were recorded under the same conditions. All other results were as in Example 1 and Comparative Example 1.

However, Example 1-1 to Comparative Example 1-3 in Tables 1 and 2 above correspond to Example 4-1 to Comparative Example 4-3 in FIG. 4, respectively.

Example 5 Among the ink components of Example 2, dehydrated castor oil DCO (manufactured by Ito Oil Co., Ltd.) was used instead of dioctyl adipate, which is a plasticizer.
A thermal transfer medium was prepared under the same conditions as in Example 2, except that the image was recorded under the same conditions, and the test results regarding image density were as shown in Figure 5. It was the same as Example 2.

Example 6 The sheet created in Example 4-2 was layered so as to face the coated synthetic paper (receiving paper medium) created and used in Example 3, and image recording was performed under the same conditions as Example 1. The saturated image density and sensitivity were as shown in FIG.

[Effect] As is clear from the above explanation, in the transfer recording medium of the present invention, depending on the magnitude of heating energy, ink with low viscosity oozes out from between the porous resin structure and transfers to the surface of the receiving sheet. By controlling the heating energy during transfer, it is possible to obtain a transferred image with high saturated image density and excellent gradation expression (wide gradation reproduction) on plain paper with low smoothness. Furthermore, even on G1 coated paper with high smoothness, low density areas can be reproduced well, making it possible to express gradation close to that of a photograph. Full color images can also be obtained by selecting various dyes.

[Brief explanation of drawings]

1 to 6 are graphs showing the sensitivity and saturated image density of thermal transfer recording media of Examples and Comparative Examples of the present invention.

Claims (2)

[Claims] (1) A heat-sensitive transfer recording medium in which a heat-melting ink layer containing a heat-melting substance and a colorant as main components, which are solid at room temperature, is provided in a microporous structure made of a resin formed on a support, A heat-sensitive transfer recording medium characterized in that the heat-melting ink layer contains a plasticizer. (2) The thermal transfer recording medium according to claim (1), wherein the content of the plasticizer is 20 to 50% by weight.