JPS62299393A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To contrive higher preservability and heat sensitivity and make it possible to obtain high-density images with excellent gradation properties, by using a wax having a critical surface tension of at least a specified value as a heat-fusible substance in a heat-fusible ink component. CONSTITUTION:A heat-fusible ink component comprising a heat-fusible substance which is solid at normal temperature and a coloring agent as main constituent is contained in a microporous resin structure provided on a support base. A wax having a critical surface tension of at least 18dyn/cm is used as is used as the heat-fusible substance, whereby favorable images with a sufficiently high saturated image density can be obtained. Namely, when a wax having a critical surface tension approximate to that of the coloring agent is used, wetting of the coloring agent takes palce favorably, and the agent is favorably dispersed, so that the images recorded with such an ink have high density.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Technical Field The present invention relates to a thermal recording medium on which a recording image is transferred by heating with a thermal head laser or the like.

BACKGROUND ART Conventionally, as a thermal transfer recording medium, a transfer sheet in which a heat-sublimable dye layer is provided on a support, a transfer sheet in which a heat-fusible material and a face rat are provided on a support is known; It is used to form an image on a receiving sheet.

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; 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 having a structure containing a heat-melting ink component mainly composed of a heat-melting substance and a coloring agent, which are solid at room temperature, in a microporous structure made of resin formed on a support is proposed. compared to conventional heat-melting recording media.
Although the gradation improved, the saturated image temperature was still inferior.

Purpose The present invention improves the drawbacks of the above-mentioned conventional technique 1 (・i't!/υ, which has excellent image storage stability and thermal sensitivity, and particularly high-density images with excellent gradation by 2%). The purpose of the present invention is to provide a thermal transfer recording medium that can be used.

Structure The structure of the present invention to achieve the above-mentioned object is that a heat-melting material containing a heat-melting substance and a coloring agent, which are solid at room temperature as main components, is formed on a support and has a microporous structure made of a resin. In a thermal transfer recording medium having a structure containing a molten ink component,
In the heat-sensitive transfer recording medium, the heat-melting substance is a wax having a critical surface tension of 18 dl/ne/Cm or more.

In the present invention, a thermofusible ink containing a thermofusible substance and a colorant is held by a network structure made of a microporous structure of the resin. This ink is melted by heating with a thermal head or the like, oozes out from between the network structures of the microporous structure of the resin, and oozes little by little onto the receiving sheet. The amount of ink that oozes out varies depending on the amount of thermal energy applied by a thermal head, etc., and by controlling the applied thermal energy, the amount of ink transferred can be changed, allowing for a wide range of tones. It is possible to faithfully reproduce images over a wide range of areas, and to obtain fine-grained, clear images.

At this time, when natural wax is used as the heat-melting substance, its critical surface tension is 1, as shown in Figure 1.
When a wax of 8 dl/ne/Cm or more is used, a good image with sufficiently high saturated image density is obtained, and when a synthetic wax is used, its critical surface tension is 28 dyne/Cm or more as shown in Figure 2. It has been found that images with high saturated image density can be obtained when using this method.

This can be explained by the following reasons.

In other words, since the colorant is a powder, it was not possible to measure its critical surface tension, but the value is 30 dyne/c.
It is estimated that it is more than m. Therefore, it is presumed that if a wax having a critical surface tension close to that of the colorant is used, the colorant will wet well and be dispersed well, resulting in a higher density of the image drawn with the ink.

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.

Figures 1 and 2 show an oil-soluble copper phthalocyanine dye, Ne0Zal)On!, as a dye. 31tle80
7 (BASF ¥A) on synthetic paper in the same manner as in the examples. As shown in the examples, there is almost no difference in the gradation curves, but in terms of saturated image density, the higher the wax critical surface tension, the higher the density can be obtained. It has been found that the critical surface tension J of wax is preferably 18 dVne/C1n or more.

However, the critical surface tension was determined by measuring the contact angle using a standard reagent and using the Zisman plot method.

According to measurements made by the inventor, natural waxes having a critical surface tension of 18 dyne/cm or more include the following:

Montan Wax S (manufactured by Hoechst) 18,7 dyne/cm Montan Wax LP (manufactured by Hoechst) 19,0 dyne/cm tt SW (n) 19.3 dyne/cm/
/OP (//) 21.5dyne/cmn
X-55(//) 18.3dyne/cm//
OM (//) 19.2dyn
e/cm11 BJ(tt)26.1dyne/
cm lanolin wax HtlC-82 (manufactured by Yoshikawa Oil Co., Ltd.) 1
9.2 dyne/Cm // Y-223, 1 dyne/cm Carnauba wax 20.0 dyne/cm The synthetic waxes having a critical surface tension of 28 dyne/Cm or more include, for example, the following.

Polyethylene wax old - Wax 4252 E (Mitsui Petrochemical!> 31.4 dyne/cm Polyester resin Plaxel 350 (Daicel Chemical) 31.9 dyne/cm As the support used in the present invention, conventionally known films and Paper can be used as it is, and for example, films of relatively heat-resistant plastics such as polyester, polycarbonate, triacetic acid cellulose, nylon, and polyimide, cellophane, or parchment paper can be suitably used.The thickness of the support is When considering a thermal head as a heat source for thermal transfer, it is desirable that the diameter be about 2 to 15 microns, but there are no particular restrictions when using a heat source such as a laser beam that can selectively heat the thermal transferable ink layer. 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. is applied to the surface of the support that comes into contact with the thermal head. By providing this, the heat resistance of the support can be improved, or a support material that could not be used conventionally can be used.

Although there are no particular limitations on the method for producing the heat-melting ink layer having the above-described structure, the following method is generally used. That is, a heat-melting substance and a coloring agent;
Oil, which serves to form the porosity of the resin, is mixed and dispersed with a suitable organic solvent using a dispersion device such as an attritor or a ball mill to obtain 1 q of an ink dispersion (which may also be a solution). Separately, a solution of a thermoplastic resin dissolved in an organic solvent is prepared, 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 form a heat-melting ink layer with the above-mentioned fine structure.
given. A humectant, a dispersant, 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 resin constituting the microporous resin structure is selected from vinyl chloride, vinyl acetate, vinylidene chloride, acrylic acid, methacrylic acid, acrylic ester, and methacrylic ester in relation to oil as described below. It is preferable to use thermoplastic resins such as single or copolymers of - and thermosetting resins such as phenol, furan, formaldehyde, urea, melamine, alkyd, unsaturated polyester, 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 then applied to the support to form a resin layer. A transfer layer having the above-described structure can also be obtained by dissolving the substance in the above-mentioned solvent to form a porous resin structure, and then filling the porous structure with thermal transfer ink.

Specific examples of the coloring agent include the following.

@ Color dyes and colored pigments may be used, but dyes provide images with more preferable gradation.

Such dyes that do not sublimate include the following direct dyes, acid dyes, basic dyes, tR dyes, dye dyes, sulfur dyes, vat dyes, azoic dyes, oil dyes, etc.

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

2) Acid dye: Tartrazine, Acid Violet 6
B, Antono 7 Stretched 3G, etc.

3> Basic dyes: safranin, Δ-lamin, 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: 1 Norfabrilliant Green 4G, etc.

6) Vat dyes: Indanstremble, etc.

7) Azoic dyes: 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.

Specific colored fine particle pigments used as colorants are shown below. All of them are made by Hekiss 1~, and the color index number is in parentheses.

shows.

Permanent Yellow GG, 2 (Pigment Yellow 17), Permanent Yellow D to IG Transformer 02
(Pigment Yellow 12), Novopalm Yellow 1RO3 (Pigment Yellow 83), Hansa Brilliant Yellow 5GXO2 (Pigment Yellow 74), Permanent Orange RLO1 (Pigment Orange 34), Novopalm Red HFG (Pigment Orange 38), Novopalm Red IFT ( Pigment Red 175), Permanent Lake Red LCLLO2 (Pigment Red 53:1), Novopalm Red HF4B (Pigment Red 187)
, Permanent Carmine FBBO2 (Pigment Red 146), Permanent Lupinshi 6B (Pigment Red 57:1), Hostapalm Pink Hytrans (Pigment Red 122), Reflex Blue R50 (Pigment Blue 61), etc.

The oil may be either liquid or semi-solid as long as it is incompatible with the above-mentioned thermoplastic resin and is non-volatile.

Liquid oils include, for example, animal and vegetable oils such as cottonseed oil, rapeseed oil, and whale oil; or motor oil, spindle oil,
Mineral oils such as dynamo oil are used, and as semi-solid oils, for example, lanolin, lanolin derivatives, petrolatum, lard, etc. are used.

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

Further, in order to further improve the gradation obtained by the present invention, it is also possible to add a gradation control agent as described later.

In order to maintain the porous resin structure more strongly,
It is also possible to provide an intermediate stone 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 be plain paper or synthetic paper, but if necessary, it may be made of the above resins, TlO2, 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.

The gradation control agent used in the present invention 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. It seems that the pore size of the porous structure is finely controlled by the method. Therefore, it is not transferred even when thermal energy is applied, is retained in the porous structure, and is a good gradation control agent that controls the amount of colorant and ink existing around it that transfers. considered to be a thing.

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

Needle crystal face: Unmodified and organic materials can be used. Specific examples include ocher, yellow lead G, phthalocyanine blue, lithore red, honmartone light, and white clay. , nail-shaped zinc oxide, 2,7-bis[2-hydroxy-3-(2-chlorophenylcarbamoylen-1-ylazo]-9-fluorenone, 4',4''-bis[hydroxy-3-(2. 4-dimethylphenyl)carbamoylnaphthalen-1-ylazo) 1.4-distyrylbenzene, etc. are prohibited, but if the crystals are acicular and the crystals are arranged in a net-like structure in the transfer layer, substances such as You can use any.

Azo pigment: For example, one having the following chemical formula 1M3ti can be used.

X-+N=N-Y)n where, Derivatives thereof, metal phthalocyanine and derivatives thereof can be used, and specific examples thereof include the following.

hu, Na Addition q of the above gradation control agent is 0.5 to 1 part by weight of dye.
~10 hand-view parts, preferably 1-5 hand-view parts.

Hereinafter, the present invention will be specifically explained with reference to Examples. In addition, L~ (parts) of each component described in the examples are all parts by weight.

Example 1 Ink composition Colorant (Neozapon Blue 807, BAS
F) 10 parts Heat-melting substance (Montan Wax S, Hoechst > 30 parts Lanolin fatty acid oil (OES-183, Yoshikawa Oil)
15 parts dispersant 0.5 parts liquid paraffin 3 parts
Quantum dispersion was carried out for about 48 hours in a ball mill with a mixed solution of 100 parts of methyl ethyl ketone and 130 parts of toluene at °C.

Next, a 20% by weight vinyl chloride vinyl acetate copolymer resin solution (10 parts resin, 20 parts toluene, 20 parts methyl ethyl ketone)
300 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 a heat-sensitive 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 YA7-bar, and dried for 1 minute at a drying temperature of ioo'c.
A heat-melting ink layer having a thickness of about 5 μm was formed.

The ink layer of the transfer medium thus obtained was stacked so as to face the synthetic paper receiver, and an image was recorded from the back side of the transfer medium using a thermal head with varying heating energy, as shown in Figure 3. , cyan tone characteristic curve 3-a was recorded.

Example 2 A transfer medium was prepared in exactly the same manner as in Example 1, except that among the ink components of Example 1, Montan wax S, which is a heat-melting substance, was replaced with lanolin wax HHC-82 (manufactured by Yoshikawa Oil Co., Ltd.). When an image was recorded, a cyan tone characteristic curve 3-b was recorded as shown in FIG.

Example 3 A product was prepared in exactly the same manner as in Example 1 except that Montan Wax S, the heat-melting substance in Example 1, was replaced with Montan Wax OP' (manufactured by Hoechst), and an image was recorded as shown in Fig. 3. As shown, cyan tone characteristic curve 3-c
was recorded.

Comparative Example 1 Ink composition Colorant (Neozapon 131ue 807)
10 parts Hot melting substance (paraffin IINP-3) 30
Partial lanolin fatty acid oil 0ES-18315 Partial dispersion
0.5 part liquid paraffin
3 copies A thermal transfer recording medium was prepared under the same conditions as in Example 1, and images were recorded under the same conditions as in Example 1. The results were as shown by the gradation characteristic curve 3-x in FIG.

Comparative Example 2 Ink composition Colorant (Neozapon Blue 807)'
10 parts Heat-melting substance (paraffin HNP-10) 30 parts
1 part lanolin fatty acid oil (0ES-183) 15 parts dispersant 0.5 part liquid paraffin
3 copies A thermal transfer recording medium was prepared under the same conditions as in Example 1, and images were recorded under the same conditions as in Example 1. The result is the gradation characteristic curve 3-y in Figure 3.
It was indicated by .

Example 4 The colorant of Example 1 was added to 5pilon Red GRLTS.
A transfer medium was prepared in exactly the same manner as in Example 1, except that the medium was replaced with ``Special'' (manufactured by Hodogaya), and an image was recorded under the same conditions. As a result, a magenta tone characteristic curve 4-a as shown in Fig. 4 was obtained. was recorded.

Comparative Example 3 5pilOn Red GRLTS of the colorant of Comparative Example 1
A transfer medium was prepared in exactly the same manner as in Comparative Example 1, and an image was recorded under the same conditions. The gradation characteristic curve was curve 4 in Fig. 4.
The result shown in x must be Iko.

Example 5 Among the ink components of Example 1, the heat-melting substance was polyethylene wax (tli-Wax 4252 E).

The same hot-melt ink components as in Example 1, except that the ink composition was replaced with Mitsui Petrochemical (Mitsui Petrochemical), were sufficiently dispersed in a ball mill for about 48 hours with a mixed solution of 75 parts of methyl ethyl ketone and 120 parts of toluene at 90°C. Ta.

Using this ink solution, a thermal transfer medium was prepared under the same conditions as in Example 1, and tested under the same conditions as in Example 1.

As a result, as shown in FIG. 5, 1q of recordings were made as shown in the cyan gradation characteristic curve 5-a.

Example 6 A thermal transfer medium was prepared in the same manner as in Example 5, except that the heat-melting substance in the ink components of Example 5 was replaced with a polyester resin (Plaxel 350, manufactured by Daicel), and the same tests were conducted. .

As a result, a cyan tone characteristic curve 5-b as shown in FIG. 5 was obtained.

Example 7 The colored dye of Example 5 was added to 5pilon Red GRLT.
It was produced in exactly the same manner as in Example 5 except that Special (manufactured by Odogaya) was used, and when image recording was performed, the 6th
As shown in the figure, a mapped pink gradation characteristic curve 6-a was recorded.

[Effect] As is clear from the above explanation, in the thermal transfer medium of the present invention, ink oozes out from between the porous resin structures and transfers to the receiving sheet depending on the magnitude of heating energy, so that transfer is improved. By controlling the heating energy during BQ, transfer images with excellent gradation expression and wide gradation reproduction (
In addition, the image density is high, the image has good storage stability, and full-color images can be obtained by selecting various dyes.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between critical surface tension of natural wax and saturated image density. Figure 2 is a graph showing the relationship between critical surface tension of synthetic wax and saturation side @ density. Figure 3 is Examples 1 to 3. and a graph showing the gradation characteristic curves of the thermal transfer recording media of Comparative Examples 1 and 2, FIG. 4 is a graph showing the gradation characteristic curves of the thermal transfer recording media of Example 4 and Comparative Example 1, and FIG. FIG. 6 is a graph showing the gradation characteristic curve of the thermal transfer recording medium of Example 7. FIG. Patent applicant Rico Co., Ltd. - Agent Patent attorney Takeshi Komatsu Agent Patent attorney Hiroshi Asahi Figure 1 Critical surface tension γ (dsney cm) No. 2121 Critical surface tension γ (ζ)ne7cm) ll! I Tsubasa Kumoshima [ugly a drunkenness]

Claims (1)

[Claims] In a heat-sensitive transfer recording medium having a structure in which a heat-melting ink component containing a heat-melting ink component which is solid at room temperature and a coloring agent as main components is contained in a microporous structure made of a resin formed on a support, the above-mentioned 1. A heat-sensitive transfer recording medium, wherein the heat-melting substance is a wax having a critical surface tension of 18 dyne/cm or more.