JPH0365386A - Thermosensitive transfer material and thermosensitive transfer recording method - Google Patents

Abstract

PURPOSE:To form a good recording image without generating background staining even in double-density recording by constituting the heat-meltable binder in a thermal transfer ink layer of at least an isocyanate polymer of ester of higher fatty acid and pentaerithritol, a lubricant and ester of higher fatty acid and polyhydric alcohol contained if necessary. CONSTITUTION:The heat-meltable binder of a thermosensitive transfer material is constituted of at least an isocyanate polymer of ester of higher fatty acid and pentaerithritol being a wax component, ester of higher fatty acid and polyhydric alcohol, if necessary, and a lubricant. The content of the wax component is 20-75% by wt. of the total binder and the content of the lubricant is set to 1-5% by wt. of the total binder. By this method, even in double-density recording, a recording image not generating background staining and the whisker-like part and tailing of the rear end part thereof and having good transfer properties and uniform density can be obtained. Further, the thermosensitive transfer material generating no curl and ink omission and extremely good in handling can be obtained.

Description

[Detailed Description of the Invention] - [Industrial Application Field] The present invention relates to a thermal transfer material used for thermal transfer recording, specifically,
The present invention relates to a thermal transfer material and a thermal transfer recording method that allow good recording to be obtained even if the amount of thermal transfer material used is reduced.

[Conventional technology]

In addition to the general features of thermal recording methods, such as the equipment used is lightweight, compact, noiseless, and has excellent operability and maintainability, the thermal transfer recording method does not require colored processed paper, and it also improves the quality of the recorded image. It has the feature of excellent durability and has been widely used recently.

This thermal transfer recording method uses a thermal transfer material in which a thermal transferable ink layer consisting of a colorant dispersed in a heat-melting binder is coated on a support, which is generally in the form of a sheet. By overlapping the thermally transferable ink layer so that it is in contact with the recording medium, and applying heat from the base material side using a thermal head to transfer the melted ink layer to the recording medium,
A transferred recorded image is formed on a recording medium according to a heat supply shape (pattern).

In conventional thermal transfer recording, the thermal transfer ink is almost completely transferred from the thermal transfer material to the recording medium by one heat application, so it is disposable, and running costs are high. There were also concerns that confidential information would be leaked from the material.

On the other hand, Japanese Patent Application Laid-open No. 57-83471, Japanese Patent Application Laid-open No. 5
Publication No. 8-201686 or Special Publication No. 62-5891
As in Japanese Patent No. 7, a recording method (hereinafter referred to as double-density recording) has been proposed in which the amount of thermal transfer material used is reduced by increasing the relative speed between the thermal transfer material and the recording medium.

[Problem that the invention is trying to solve]

However, this recording method has conventionally had the following problems.

The first problem is that background smudge (unnecessary ink transfer to a recording medium such as paper) occurs.

This occurs because in double-density recording, the thermal transfer material and the recording medium slide, so the ink layer of the thermal transfer material is scratched off the surface of the recording medium and transferred to the entire surface of the recording medium.

As a countermeasure against scumming, Japanese Patent Laid-Open No. 178088/1988 proposes a heat-sensitive transfer material in which an ohno layer containing no colorant is provided on an ink layer.

The second problem is that unnecessary whisker-like transfer occurs at the end of the transferred ink layer in the head running direction due to poor cutting performance.

This is due to the cohesive force of the thermally transferable ink layer after heat application.

As a countermeasure against whisker-like transfer, there is a description in Japanese Patent Application No. 1-25278 filed earlier by the present applicant.

In the above-mentioned publication, a thermal transfer ink made by dispersing a coloring material in a heat-melting binder made of ethylene vinyl acetate copolymer and wax is used, and by setting its breaking strength within a specific range, it can be used not only for whisker-like transfer. The first problem, scumming, is also prevented and solved.

The third problem is that the thermal transfer material curls and ink drops.

In particular, in thermal transfer materials used for double-density recording, most of the ink in the thermal transfer ink layer is not transferred to the recording medium by one heat application, but is gradually transferred to the recording medium by multiple heat applications. Must be photographed. Furthermore, it is necessary that the recorded image obtained has a certain density, for example, a reflection density of 1.0 or more.

As a result, the coating amount or coating thickness of the thermal transfer ink layer coated on the support must be increased compared to conventional thermal transfer materials, and the thickness of the support must be significantly increased. The thickness of the ink exceeds 100,000 yen, curling occurs, and even ink smearing occurs, which is inconvenient in handling the thermal transfer material.

The fourth problem is that in manufacturing a thermal transfer material, it is difficult to homogenize the thermal transfer ink layer.

Generally, the so-called hot-melt method and the solvent coating method, in which the ink is dissolved or dispersed in an organic solvent or water, coated, and dried, are used to form a thermally transferable ink layer coated on a support. .

The thermal transfer material used for this double-density recording has a higher resin content than conventional thermal transfer materials because the breaking strength of the thermal transfer ink layer is set within a specific range. The melt viscosity is too high, making it difficult to apply. Furthermore, even in the latter solvent coating method, when the heat-melting binder is dispersed in an organic solvent or water, the breaking strength must be delicately controlled under drying conditions, resulting in extremely low production efficiency.

From the above, it is most suitable to employ a solvent coating method using a coating ink in which a heat-melting binder is dissolved in an organic solvent.

However, the waxes contained in the heat-melting binder have poor solubility in organic solvents, and the coating ink must be heated to a relatively high temperature, which poses a problem in workability. In addition, when heating is not performed, waxes precipitate, making it difficult to form a homogeneous thermal transfer ink layer having a predetermined breaking strength.

The fifth problem is that so-called sticking occurs because the thermally transferable ink layer transferred to the recording medium does not undergo cohesive failure within the ink layer.

As a result, the conveyance of the thermal transfer material or the conveyance of the recording medium becomes irregular, and the ink transferred to the recording medium becomes uneven, resulting in a decrease in the sharpness, density, and uniformity of the density of the recorded image.

Furthermore, in the worst case, the thermal transfer material may break.

The sixth problem is that it is difficult to obtain a recorded image corresponding to the shape of fine dots, that is, so-called poor dot reproducibility and poor transferability.

The seventh problem is unnecessary ink transfer that occurs at the ends of the recorded image in the head running direction, which is called trailing.

This is presumed to be due to excessive ink cohesive failure in the ink layer other than the ink layer subjected to heat application.

The eighth problem is that when a nearly solid recorded image is formed, a so-called white stripe occurs near the leading edge of the recorded image, making it impossible to obtain a recorded image having a desired uniform density.

In particular, in thermal transfer materials used for double-density recording, most of the ink in the thermal transfer ink layer is not transferred to the recording medium with one heat application, but is gradually transferred to the recording medium with multiple heat applications. Must. Furthermore, uniformity is desired for any recorded image obtained.

The present invention has been made in view of the above circumstances, and even with double-density recording, there is no background smearing, trailing at the trailing edge of the recorded image, or sticking. It is an object of the present invention to provide a thermal transfer material and a thermal transfer recording method which can obtain a recorded image having a uniform density even in such a recorded image, and which are free from curling and ink smearing.

[Means to solve the problem]

The heat-sensitive transfer material of the present invention has a heat-transfer raw ink layer containing a coloring material in a heat-fusible binder on a support, wherein the heat-fusible binder is formed by at least isocyanate polymerization of higher fatty acid pentaerythritol ester. The binder is characterized in that the content of the isocyanate polymer and the high grade agent is 1 to 5% by weight based on the total binder.

Further, in the thermal transfer recording method of the present invention, the thermal transfer material described above is used, and the distance that the thermal transfer material moves relative to the recording head is longer than the distance that the recording object moves relative to the recording head within the same time. It is characterized by a shorter ′.

The present invention will be described below with reference to the drawings.

In addition, in the following description, "%" and "%" representing quantitative ratios are used.
Parts are by weight unless otherwise specified.

The thermal transfer recording method (double-density recording method) using the thermal transfer material of the present invention is, as shown in FIG. By heating with a recording head 3 such as a head, the thermal transferable ink of the thermal transfer material 1 is transferred to the recording medium 2 to obtain a recorded image. The thermal transfer material 1 and the recording medium 2 are continuously moved in the directions of arrows A and B by the rotation of the capstan roller 12, the pinch roller 13, and the platen roller 11, respectively, and are transferred onto the recording medium 2 one after another. A recording is made. The capstan roller 12 and the pinch roller 13 are operated by a motor 14, and the platen roller 12 is operated by a motor 1.
5, respectively. Conveyed thermal transfer material 1
is wound up by a winding roller 10 driven by a motor 14. A spring 16 presses the recording head 3 against the platen roller 11 via the thermal transfer material 1 and the recording medium 2.

In FIG. 1, the thermal transfer material 1 and the recording medium 2 are moving in the same direction, but as shown in FIG. The material 1 and the recording medium 2 may be moved in completely opposite directions.

Now, in this thermal transfer recording method, there is a relative speed between the thermal transfer material 1 and the recording medium 2. In the example shown in FIG. 1, the head 3 does not move, and the thermal transfer material 1 moves slower than the recording medium 2. That is, when comparing the distance that the thermal transfer material 1 moves and the distance that the recording medium moves within the same time, the distance that the thermal transfer material 1 moves is shorter. As a result, in this recording method, recording is performed as shown in FIGS. 3 to 6.

As shown in FIG. 3, when the width of the heating element 3a of the recording head 3 in the thermal transfer material feeding direction (arrow A direction) is l, 1
The second heat application is applied to a completely unused thermal transfer material 1 with a magnitude of 1 (FIG. 3). In addition, the thermal transfer material l is a support l.
A thermally transferable ink layer 1b is provided on a.

However, when heat is applied for the second time, the recording medium 2 moves l in the direction of arrow B, while the thermal transfer material l moves l/n with respect to the recording head 3 (N=5° in FIG. 3). The value of N depends on how many times the same portion of the thermal transfer material 1 can be printed.

) of the thermal transfer material l, the CI −(1/
The part N)) which has already been subjected to heat application once will be used again (FIG. 4).

When heat is applied continuously in the lateral direction in this way, the heat-sensitive transfer material subjected to the second and subsequent heat application has a It/N
1 is in an unused state, and the rest has already been heated several times by 11N (FIGS. 4 to 6). In other words, the thermal transfer material is in the same state as if the same location had been used N times, and moreover, it is moving while rubbing the surface of the recording medium.

In the above example, it is assumed that the thermal transfer material l moves by 1N with respect to the recording head 3 during the second, third, etc. heat application, but the movement is less than 1 or more than 1/N. If so, the thermal transfer material 1 can be saved. The above N is 2~l
O1 is further preferably 3 to 8.

In the above explanation, an example was shown in which the recording head 3 does not move. However, even when the thermal head 3 moves, the moving distance of each of the thermal transfer material l and the recording medium 2 is determined by the recording head 3.
If the distance from the recording head 3 is taken as a reference, it can be considered in the same way as the example explained in FIGS. 3 to 6. In other words, in the thermal transfer recording method of the present invention, the distance that the recording medium 2 moves relative to the recording head 3 within the same time is
The distance that the thermal transfer material l moves relative to the recording head 3 is shorter.

As is clear from the above description, the thermal transfer material 1 of the present invention
While sliding on a recording medium such as paper, heat is applied from the heating element 3a, and the ink must be gradually consumed from the surface of the thermal transferable ink layer to form a recorded image on the recording medium 2. . However, when obtaining a recorded image that is close to a completely solid image,
White streaks in the main scanning direction with extremely different densities are likely to occur near the leading edge of the recorded image that is often obtained.

Although the cause is not clear, it is speculated as follows.

That is, in the double-density recording method, compared to the conventional method, that is, a method in which the thermal transfer material and the recording medium do not have a relative velocity, a situation is assumed in which ink that has been heated up to n times is transferred to the recording medium. In the case of a full solid image, almost all of the transferred ink is subjected to n times of heat application. However, in the vicinity of the leading edge of the recorded image, the ink that receives only 1 to (n-1) heat applications forms a transferred image. Therefore, when the number of times of heat application is small, for example, the surface of the ink layer and the recording medium are sufficiently bonded by the first heat application, but the convergence force within the ink layer is sufficiently reduced to the point of condensation failure. It is assumed that there is no such case. As a result, repeated fractures within the ink layer occur near the support, resulting in insufficient ink being supplied to the recording medium during the next heat application, for example during the second heat application. This results in white streaks.

In the heat-sensitive transfer material of the present invention, the heat-melting binder contains an isocyanate polymer of higher fatty acid pentaerythritol ester as a wax component and, if necessary, higher fatty acid polyhydric alcohol ester (the above materials are collectively referred to as the wax main component). and a lubricant,
The content of wax main component is 20~20% of the total binder.
75% by weight, and the lubricant content is 1 based on the total binder.
~5% by weight.

The isocyanate polymer of higher fatty acid pentaerythritol ester will be described in detail below.

The polymer is obtained by reacting higher fatty acid pentaerythritol ester with an isocyanate compound.

The higher fatty acids constituting the ester include capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, valmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, and serotin. acids, saturated fatty acids such as heptacanoic acid, montanic acid, melisic acid, lafcelic acid,
Acrylic acid, crotonic acid, isocrotonic acid, caproleic acid, undecylic acid, oleic acid, elaidic acid, cetoleic acid, erucic acid, brassic acid, sorbic acid, linoleic acid, linuric acid, arachidonic acid, sardine acid, nisic acid, propiolic acid , unsaturated fatty acids such as stialolic acid, branched fatty acids such as invaleric acid, malvalic acid,
Cycloaliphatic fatty acids such as stearic acid, hydronocarbic acid, schorumubric acid, and golulic acid; oxygenated fatty acids such as sabinic acid, ibrolic acid, yarabinolic acid, unipelic acid, ricinoleic acid, feronic acid, and cerebronic acid may be used. In particular, the melting point is 20℃ or higher and the number of carbon atoms is 1.
0 to 30 fatty acids can be suitably used.

Pentaerythritol is used as the alcohol.

The above-mentioned higher fatty acids can be used alone or in combination of two or more.

The ester must be reactive with the isocyanate compound. That is, it must have a carboxyl group derived from a fatty acid or a hydroxyl group derived from pentaerythritol as an active hydrogen. When the fatty acid used does not have a carboxyl group, the ester is reacted with an isocyanate compound in the form of a mononiser, diester or triester. Monoester, diester, triester may be used alone or in combination
It is also possible to use species and mixtures of the three species.

Examples of isocyanate compounds include monoisocyanates such as methyl isocyanate, ethyl isocyanate, n-propylisocyanate, n-butyl isocyanate, octadecyl isocyanate, and polymethylene polyphenylisocyanate, 2.4-tolylene diisocyanate, and 4.4'-diphenylmethane. Diisocyanate, dianisidine diisocyanate, metaxylylene diisocyanate, 1゜5-naphthalene diisocyanate, transvinylene diisocyanate, N, N' (4
, 4'-dimethyl-3,3'-diphenyl diisocyanate) uredione, 2. ' Diisocyanates such as 6-diisocyanate methylcabroate, triphenylmethane triisocyanate, tris(4-phenylisocyanate thiophosphate)4. 4', 4'-
) Dimethyl-3,3', 3'-triisocyanate-2°4.6-) Various isocyanates of triisocyanate such as liphenyl cyanurate can be used. Particularly preferred are diisocyanates and triisocyanates, and more preferred are aromatic ones.

The reaction between the ester and the isocyanate can be carried out according to a conventional method using heating and stirring.

If the heating temperature is too high, the resulting product will be markedly colored, and if it is too low, the reaction time will be prolonged, so it is usually desirable to select a temperature in the range of about 70 to 150°C. Furthermore, the above reaction can be carried out relatively quickly at lower temperatures by using metal salt catalysts such as stannic chloride, ferric chloride, potassium oleate, dibutyltin dilaurate, and the like. It is appropriate that the reaction time is usually about 0.5 to 5 hours.

The amount of isocyanate used in the above reaction is appropriately selected depending on the type of each raw material used, reaction conditions, etc., but is usually about 0.1 to 40% by weight, preferably about 0.1 to 30% by weight based on Nisel. The desired polymerization reaction can proceed within this range, and the wax can be produced.

The wax obtained as described above shows good solubility in organic solvents, especially toluene, xylene, benzene, etc.
Workability during the production of thermal transfer materials, i.e., by heating the coating ink, it is possible to reduce volatile solvents generated during work, and furthermore, because there is no precipitation of waxes, the formation of a homogeneous thermal transfer ink layer is extremely efficient. can.

Furthermore, when the above-mentioned waxes are used, curling of the heat-sensitive transfer material is extremely small, and the heat-sensitive transfer material is easy to handle. This is presumed to be because the volume shrinkage rate of the waxes from the molten state to the solidified state is relatively small.

In the heat-melting binder of the present invention, in addition to the above-mentioned isocyanate polymer of higher fatty acid pentaerythritol ester as a wax component, it is effective to simultaneously use higher fatty acid polyhydric alcohol ester, if necessary.

The polyhydric alcohols of the higher fatty acid polyhydric alcohol Nisel include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol,
dipropylene glycol, polypropylene glycol,
trimethylene glycol, butanediol, bentanediol, hexylene diol, octylene glycol,
Glyceride, trimethylolpropane, pentaerythritol, dipentaerythritol, 1,3-butylene glycol, monoallyl glycerin, (4-(hydroxyethoxy)phenol)propane, nrubitol, sorbitol, neopentyl glycol, trishydroxyethyl isocyanurate, bisphenol , hydrogenated bisphenol, bisphenol glycol ether, various epoxies (eg, triglycidyl isocyanurate), etc. are used.

The higher fatty acid polyhydric alcohol ester used in combination with the isocyanate polymer is effective in finely adjusting the melting point or melt viscosity of all the wax components, thereby making it possible to variously change the characteristics of the thermal transfer ink. Become. 7 The mixing amount of the above ester is preferably 50% or less based on the total amount of the heat-melting binder, more preferably 40% or less, and if it exceeds 50%, the solvent solubility of the wax component becomes poor, and more preferably 35% or less. % or less is better. Workability is reduced and curling is more likely to occur.

The amount of the isocyanate polymer or the mixture of the isocyanate polymer and higher fatty acid polyhydric alcohol ester (collectively referred to as the wax main component) is 20 to 75% by weight, more preferably 30 to 75% by weight based on the total binder amount.
Contains 65% by weight. If the amount is less than 20% by weight, the tensile strength of the thermal transferable ink layer becomes too large, and the viscosity when melted increases, resulting in an increase in applied thermal energy, which tends to damage the thermal head, which is a heat source. Alternatively, if the supplied thermal energy is insufficient, the running performance becomes unstable due to sticking between the thermal transfer material and the recording medium.
The recorded image may become blurred, or the density may be insufficient or uniform. If it exceeds 76% by weight, trailing and scumming will occur, which is undesirable.

Further, the melting point of the wax main component is preferably in the range of 50°C to 90°C, more preferably in the range of 60°C to 85°C. If it is lower than 50°C, the storage stability of the thermal transfer material will be poor and blocking will easily occur, and if it exceeds 90°C, the transferability will be poor, which is disadvantageous. In addition, the melt viscosity of the wax main component is 10~lo"cps at 100°C.
, preferably 10 to 500 cps.

More preferably, it is 10 to 200 cps.

This is because when heated, the main wax component acts like a solvent for the resin component, and as a result, the viscosity of the thermal transfer ink decreases, which lowers the tensile strength and cohesive force of the ink layer, making the ink layer as a whole more likely to break, and the inside of the ink layer. It is presumed that this makes cohesive failure easier and reduces sticking. As a result, the sharpness of the recorded image increases, and it is presumed that insufficient density or density uniformity will be resolved.

Further, it is preferable that the difference between the melting end temperature and the melting start temperature of the wax main component is 5 to 20°C, more preferably 5 to 20°C.
~15°C is good.

That is, due to the sharp melting behavior, the viscosity of the thermal transfer ink described above decreases more steeply, making it possible to improve not only stickiness but also transferability.

In the above, the melt viscosity is measured using an E-type viscometer (Roto Visco RV-12 manufactured by Haake Co., Ltd., rotor used, PK-1-0, 3).
This is the value measured using

Further, in the present invention, the melting point and the difference between melting end and melting start temperatures were measured as follows.

[Measurement device: Differential scanning calorimeter DSC-7 (manufactured by PerkinElmer) [Measurement conditions] Heating rate = 5°C/min The difference between the melting end temperature and the melting start temperature (expressed as △T) is as follows Ask like this. - As an example, Fig. 7 shows Lanox FPS.
-7 (manufactured by Yoshikawa Oil Co., Ltd.) measurement results are shown.

Point A in the figure, that is, the peak value of absorption, is taken as the melting point. ΔT
The intersection point B (melting start temperature) and 0 point (melting end temperature) of the peak slope and the baseline are Ti and Te, respectively.
It is defined by the following equation.

ΔT=Te-Ti The heat-sensitive transfer material of the present invention contains a resin component in addition to the wax main component as a heat-melting binder constituent material. Examples of resin components include polyolefin resins, polyamide resins, polyester resins, epoxy resins, polyurethane resins, polyacrylic resins, polyvinyl chloride resins, cellulose resins, polyvinyl alcohol resins,
petroleum resin, phenolic resin, polystyrene resin,
Vinyl acetate resin, natural rubber, styrene-butadiene rubber, isoprene rubber, chloroprene rubber, and other elastomers, polyisobutylene, polybutene, etc. can be used, but they especially have film properties and soften well when heat is applied. / Ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer is preferable as the material that melts, and the content thereof is 25 to 8% based on the total binder amount.
0% by weight, more preferably 35-70% by weight, and 2
If it is less than 5% by weight, trailing and background smudges tend to occur, and if it exceeds 80% by weight, it is undesirable because transferability deteriorates, sticking occurs, energy increases, and hairs appear at the trailing edge of the recorded image.

In addition, its melt flow rate (MFR) is 150 to 8
00 g/l Omin, and even 15
0 to 400 g/10 m1n is suitable. If the melt flow rate is less than 150 g/10 m1n, the melt viscosity increases, making it difficult to cause cohesive failure, resulting in a decrease in transferability or an increase in applied heating energy.
If it is larger than g/l 0 min, trailing and scumming are likely to occur. It is of course possible to adjust the melt flow rate by mixing two or more types. Among these, ethylene-vinyl acetate copolymer is preferred, and those with a vinyl acetate content (VA) of 15 to 33% by weight are most suitable; if it is less than 15% by weight, the solubility in organic solvents decreases and the coating ink is 33% by weight, which increases the viscosity of
If it is larger, tailing tends to occur, which is not preferable.

In the above, the melt flow rate and vinyl acetate content are defined in accordance with JIS K6730.

Examples of lubricants include metal soaps such as barium stearate, calcium stearate, aluminum stearate, and magnesium stearate, cetyl alcohol, margaryl alcohol, stearyl alcohol, nonadecyl alcohol, eicosyl alcohol, ceryl alcohol, and mericyl alcohol. higher alcohols, capric acid amide, undecanoic acid amide, lauric acid amide, trizocanic acid amide, myristic acid amide, pentadecanoic acid amide, valmitic acid amide, pentadecanoic acid amide, stearic acid amide, elaidic acid amide, oleic acid amide, erucic acid Simple fatty acid amides such as amides, N
-Hydroxyethyl 12-hydroxystearylamide, N,N' -Ethylene bisoleylamide, N,N'
-Ethylenebislycylylamide, N,N' -Ethylenebisoctadecagenylamide, N,N' -Ethylenebis12-hydroxystearylamide, N,N'
-Ethylenebisstearylamide, N,N' -Hexamethylenebislycylylamide, N,N' -Hexamethylene 12-hydroxystearylamide, N,N'
- Derivatives of fatty acid amide such as xylylene bis-12-hydroxystearylamide can be used alone or in combination of two or more.

The lubricant preferably has 10 to 30 carbon atoms,
Further, it is preferable that the melting point is 50°C to 120°C. Among those listed above, fatty acid amides are most preferred. In particular, oleic acid amide and erucic acid amide have excellent solubility in organic solvents, and are extremely suitable for the thermal transfer material of the present invention.

The reason why these lubricants suppress the occurrence of white streaks at the leading edge of all solid recorded images is not necessarily clear, but it is presumed as follows. That is, when a coating ink prepared by dissolving and dispersing a thermally transferable ink in an organic solvent is coated on a support and dried to form a thermally transferable ink layer, the lubricant is added to the thermally transferable ink layer formation stage during drying. This is presumed to be because it has the property of being deposited on the surface of the ink layer, which improves the slipperiness of the surface layer and suppresses the adhesion to the recording medium caused by the first heat application.

The content of the lubricant is 1% based on the total amount of the heat-melting binder.
-5% by weight, preferably 1-3% by weight. 1
If it is less than % by weight, the above-mentioned white streaks are likely to occur,
If it exceeds 5% by weight, powdery tailing will occur, which is undesirable.

Furthermore, although it was an unexpected effect, it was observed that it was effective not only against white streaks at the leading edge of the recorded image described above, but also against sticking, and was particularly effective against sticking, which tends to occur when the binder component contains a large amount of resin component. be.

This is presumed to have an advantageous effect on cohesive failure within the ink layer since the ink fluidity is improved when the thermal transferable ink is melted.

In addition to those detailed above, the constituent materials of the heat-melting binder include, if necessary, conventionally known waxes, such as natural waxes such as carnauba wax, candelilla wax, rice wax, tree wax, and other vegetable waxes; Mineral waxes such as ceresin wax and montan wax, and derivatives thereof; examples of derivatives of montan wax include acid wax, ester wax,
Partially saponified ester wax etc. Animal waxes such as beeswax, spermaceti, and lanolin and their derivatives; and petroleum waxes such as paraffin wax and microcrystalline wax. Synthetic waxes such as polyethylene wax and Fischer-Tropsch wax can also be used together.

In particular, it is generally effective to add tackifier as a resin component in order to firmly adhere a recorded image to a recording medium.

Tackifiers include coumaron indene resin, phenol/formaldehyde resin, polyterpene resin, xylene/formaldehyde resin, polybutene, rosin pentaerythritol ester, rosin glycerin ester, hydrogenated rosin, hydrogenated rosin methyl ester, and hydrogenated rosin triester. One type or a mixture of two or more types selected from ethylene glycol ester, hydrogenated rosin pentaerythritol ester, polymerized rosin ester, aliphatic petroleum resin, alicyclic petroleum resin, synthetic polyterpene, pentagene resin, etc. is used.

The heat-melting binder described above is contained in the heat transferable ink layer in an amount of 50 to 99% by weight, preferably 65 to 95% by weight.

Conventionally known plastic films, paper, etc. can be used as the base material for the thermal transfer material of the present invention, but since heat is applied many times to the same location on the base material in double-density recording, for example, aromatic polyamide Preferably, materials with high heat resistance such as film, polyphenylene sulfide film, polyether ether ketone, and condenser paper are used. In addition, polyester film (
Especially polyethylene terephthalate film, abbreviated as PET.
When using a film), it is preferable to provide a heat-resistant and slippery material on the opposite side to the ink side as a backside treatment. The thickness of the base material is preferably 3 to 20 μm, more preferably 4 to 12 μm. As long as the material has high strength and heat resistance, it is also possible to use a material as thin as 3 μm or less. Further, excessively thick materials are not preferable because they have poor thermal conductivity.

Examples of colorants include carbon black, nigrosine dye, lamp black, Sudan Black 3M1 Fast Yellow 61 Benzine Yellow Pigment Yellow,
Indofast Orange, Irgazine Red, Paranitroaniline Red, Toluidine Red, Carmine F
B, Permanent Bordeaux FRR, Pigment Orange R1 Linole Red 2G, Lake Red C10
- Damin FB.

Rhodamine B Lake, Methyl Violet B Lake, Phthalocyanine Blue, Pigment Blue Brilliant Green B1 Phthalocyanine Green, Oil Yellow GG, Zapon Fast Yellow GG.

Kayaset Y963, Sumiplast Yellow GG, Zapon Fast Orange RR, Oil Scarlet, Sumiblast Orange G1 Orazur Brown G1 Zabonfas Toscarlet CG, Eisen Subiron Red F4R
, Fast Dan Blue 500F, Sudan Blue, Oil Peacock Blue and the like may be used singly or in combination of two or more.

The amount of colorant contained in the ink layer is preferably 1 to 50% by weight, more preferably 5 to 35% by weight, based on the entire ink layer. If the amount of coloring material is less than 1% by weight, the density of the recorded image will be extremely low, and if it exceeds 50% by weight, problems such as an increase in recording energy, a decrease in transferability to the recording medium, and background stains may occur. occurs, which is undesirable.

In producing the thermal transfer material of the present invention, the above-mentioned binder material is dissolved in an organic solvent such as toluene, methyl ethyl ketone, isopropyl alcohol, methanol, xylene, etc., a colorant is mixed therein, and a dispersion machine such as a sand mill is used. The most suitable method is a solvent coating method in which the material is sufficiently dispersed and applied onto the substrate using a coating method such as a bar code or gravure coating. However, after heating the resin above its softening point and dispersing the coloring material, it may be applied using a so-called hot melt coating, or the resin and coloring material may be coated as an aqueous emulsion by adding a dispersant such as a surfactant. It is also possible.

When applying ink to the substrate, apply a single color (e.g. black) to the entire surface.
If colored ink is applied, a single color thermal transfer can be obtained. In addition, multiple color ink layers (for example, cyan ink, magenta ink, yellow ink, blue ink, green ink Alternatively, a thermal transfer material capable of multi-color recording can be obtained by repeatedly applying different colors (such as red ink) and recording so that the colors are overlapped during printing.

The thickness of the ink layer varies depending on the double density, but for example, when n = 3 to 8, the dry coating weight is preferably 15 to 30 g/d, and more preferably 16 to 25 g/n. If it is less than 15 g/rrr, sufficient recording density cannot be obtained in double-density recording, and if it exceeds 30 g/%, problems such as an increase in the recording energy of the thermal transfer material occur, which is not preferable.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples.

The following materials were dissolved and dispersed using a sand mill to obtain a coating ink, and the coating ink was coated on a back-treated polyester film with a thickness of 6 μm using a wire bar.
A heat-sensitive transfer material was obtained by drying with hot air using a commercially available dryer to form a heat-transferable ink layer having a coating weight of 16 g/rrr after drying.

In the following, Ranox (wax manufactured by Yoshikawa Oil Co., Ltd.) is a compound obtained by addition polymerizing tolylene diisocyanate to a mixture of higher fatty acids mixed with behenic acid and stearic acid esterified with pentaerythritol, and a compound obtained by adding tolylene diisocyanate, and a mixture of behenic acid and stearic acid. It is a mixture of esterified pentaerythritol.

Example 1 (Thermal transfer material I) \child.

Example 2 (Thermal transfer material ■) Example 3 (Thermal transfer material ■) (Hereafter the margin) ・14/ (Hereafter the margin) Knee Example 4 (Thermal transfer material ■) Example 6 (Thermal transfer material ■) Example 5 (Thermal transfer material ■) Example 7 (Thermal transfer material ■) ・'' \ Comparative example 1 (Thermal transfer material ■) Comparative example 3 (Thermal transfer material X) Comparative example 4 (Thermal transfer material XI) Comparative example 2 ( Thermal transfer material ■) On the other hand, a facsimile manufactured by Canon Co., Ltd. (trade name: Canofax 630) was partially modified so that the thermal transfer material and the recording material had relative speeds, as shown in Figure 2. The evaluation machine was modified to convey the thermal transfer material and to make the conveyance length of the thermal transfer material less than the conveyance length of the recording medium.The physical conditions of this evaluation machine are as follows.

(1) The thermal head is a thick film type full multi-layer of 8 p e 1 / mm, and the RAD and heater sizes are 100 μm in the main scanning direction and 60 μm in the KJ scanning direction.

(2) The feeding amount of the thermal transfer material is 115 times the feeding amount of the recording medium.

(3) The feeding directions of the thermal transfer material and the recording medium are opposite.

(4) The recording speed is 25 mm/sec, and the relative speed between the recording medium and the thermal transfer material is 31 mm/sec.
, 2 mm/sec.

(5) The surface heat energy of the thermal head during recording is 22 mj/mbo.

Images of the Institute of Image Electronics Engineers facsimile test charts No. 2 and Nα8 were sent as received images on plain paper (T
RW-IA Beck smoothness 220 seconds).

For Test Char No. 2, evaluations were mainly made of background smear, whiskers and trailing at the trailing edge of recording, sticking, density uniformity, and trailing edge staining. Also, test chart N018
Then, we evaluated the white streaks near the edges of all solid images.

The evaluation criteria are based on the following:

Background stain ○ Almost no background stain △ There is background stain, but it can be used for practical purposes × A lot of whisker-like transfer, not practical Trailing O No trailing △ Slight amount, but can withstand practical use × Trailing is noticeable, not practical Density uniformity (test chart) No. 2 Line unevenness in the main scanning direction in the 1° section) ○ Almost no line unevenness is observed, and the image is homogeneous.

△ Slightly uneven streaks are observed and the image is strong enough to withstand practical use.
Adhesion that cannot be used in practical use (white streaks in the main scanning direction in the part of test chart No. 18 []) ○ Occurrence of white streaks is not observed) Δ Walls with minute white streaks, cannot be used in practical use × White streaks Transferability (Test chart NO, missing number in 2n part) ○ No chipping △ Slight chipping is observed, but it can be used in practical use × Chips are noticeable and it cannot be used in practical use Edge stain △ Slight powdery stain occurs at the rear edge of the image.

○ There is no dirt on the rear end.

curl ○ The curl is extremely small, so it is not inconvenient to handle. × The curl is so bad that it cannot be used for practical purposes. The evaluation results are shown in Table 1.

White stripes (test chart No., white stripes at the beginning of 8-peta image) ○ Hardly any white stripes are observed △ Some white stripes are observed × White stripes are noticeable and there is noticeable ink drop ○ Remove the sheet. The ink does not come off when the sheet is rubbed by hand.The ink does not come off when the sheet is rubbed by hand. [Effects of the Invention] As explained above, the heat-sensitive transfer material of the present invention has a heat-melting binder containing a large amount of ink relative to the total amount of binder. By containing 20 to 75% by weight of an isocyanate polymer of higher fatty acid pentaerythritol ester and optionally included higher fatty acid polyhydric alcohol ester as a wax component, background stains and the trailing edge of the recorded image can be prevented even when used for double-density recording. Beard and tail 1. Furthermore, it becomes possible to obtain a recorded image with good transferability and uniform density.

Furthermore, it is possible to obtain a heat-sensitive transfer material that is free from curling and ink smearing and is extremely easy to handle.

Furthermore, by containing a lubricant, it is possible to reduce the occurrence of white streaks and sticking at the leading edge, which tend to occur in recorded images that are close to full solid images.

[Brief explanation of drawings]

1 and 2 are perspective views showing an example of an apparatus using the thermal transfer material of the present invention. FIGS. 3 to 6 are partial side views showing examples in which the thermal transfer material of the present invention is used for double-density recording. FIG. 7 is a graph showing an example of DSC measurement results.

Claims (5)

[Claims] (1) A heat-sensitive transfer material having on a support a heat-transfer raw ink layer containing a coloring material in a heat-melt binder, in which the heat-melt binder includes at least an isocyanate polymer of higher fatty acid pentaerythritol ester, a lubricant and It is composed of a higher fatty acid polyhydric alcohol ester contained as necessary, and the content of the isocyanate polymer and the higher fatty acid polyhydric alcohol ester combined is 20 to 75% by weight based on the total binder, and the lubricant is contained. A thermal transfer material characterized in that the ratio of binder to the total binder is 1 to 5% by weight. (2) In a heat-sensitive transfer material having a heat-transferable ink layer formed of a heat-melting binder containing a coloring material on a support,
The heat-melting binder is at least one selected from ethylene vinyl acetate copolymer and ethylene ethyl acrylate copolymer, an isocyanate polymer of higher fatty acid pentaerythritol ester, and higher fatty polyhydric alcohol containing as necessary. Composed of esters,
The content of one selected from the ethylene vinyl acetate copolymer and the ethylene ethyl acrylate copolymer is 25 to 80% by weight based on the total binder, the isocyanate polymer and the higher fatty polyhydric alcohol ester. The content of the lubricant is 20 to 75% by weight based on the total binder, the content of the lubricant is 20 to 75% by weight based on the total binder, and the content of the lubricant is 1 to 5% by weight based on the total binder. % by weight. (3) The thermal transfer material according to claim 1 or 2, wherein the lubricant is a fatty acid amide. (4) Using the thermal transfer material according to claim 1, the distance that the thermal transfer material moves relative to the recording head is shorter than the distance that the recording medium moves relative to the recording head within the same time. A thermal transfer recording method characterized by the following. (5) When using the thermal transfer material according to claim 2, the distance that the thermal transfer material moves relative to the recording head is shorter than the distance that the recording object moves relative to the recording head within the same time. A thermal transfer recording method characterized by: