JPH0363151A - Heat sensitive transfer recording method and heat sensitive transfer material - Google Patents

Abstract

PURPOSE:To prevent scumming, whiskerlike transfer, adherence, solid print and to obtain a printing excellent in density uniformity by employing a heat sensitive transfer material which satisfies specific relationship between the melting point of a colored layer and the melting point of a top layer, and shortening a moving distance of the material to a recording head. CONSTITUTION:A heat sensitive transfer material 1 and a medium 2 to be recorded have a relative speed, a head 3 is not moved, the material 1 is moved slower than that of the medium 2, and the moving distance of the material 1 is shorter. The material 1 is heated by a heat generator 3a while sliding with the medium such as a sheet, etc., to form a recording image on the medium 2. Thus, a support has at least a colored layer and a top layer from the support side, and the material which satisfies relationship of mp1<=mp2 between the melting point mp1 of the colored layer and that mp2 of the top layer is employed. Thus, it can prevent scumming, provide satisfactory reproducibility of independent dots, no adherence and obtains a recording image having uniform density.

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 with a single application of heat, so it is disposable, has high running costs, and can be kept confidential from the used thermal transfer material. There was also concern that the information would be leaked.

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 providing a 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 unnecessary whisker-like powder copying, so-called trailing, occurs at the ends of the transferred ink layer in the head running direction. This is presumed to be due to excessive ink cohesive failure in the ink layer other than the ink layer subjected to 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.

The above publication uses a thermal transfer ink consisting of a colorant dispersed in a heat-melting binder consisting of an ethylene vinyl acetate copolymer and wax, and prevents whisker-like transfer by controlling its breaking strength within a specific range. There is.

The second 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 third problem is that background smear (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 Application Laid-Open No. 60-178088 proposes a heat-sensitive transfer material in which an overlayer containing no colorant is provided on an ink layer.

However, in double-density recording, when using a thermal transfer material with an overlayer of the above structure, when using a thermal transfer material with only a heat-melting first ink layer without an overlayer, It has become clear that when the same thermal energy is applied from the Kurabe thermal head, the transferability of the ink material to the recording medium, especially the transferability of minute dot-shaped ink, decreases. Furthermore, when printing fine print images, especially Chinese characters, more ink material than the desired shape is transferred, which tends to cause the so-called "collapse" phenomenon of the print.

The present invention has been made to solve the above problems, and not only reduces the amount of thermal transfer material used and reduces running costs, but also prevents background smudges and improves the reproducibility of isolated dots. An object of the present invention is to provide a thermal transfer recording method and a thermal transfer material that can obtain a recorded image having a uniform density without causing sticking.

[Means to solve the problem]

The thermal transfer recording method of the present invention has at least a colored layer and a top layer on a support from the support side, and the melting point mpl of the colored layer and the melting point mp2 of the top layer are m p 1≧
Using a thermal transfer material that satisfies the relationship mp2, it is confirmed that 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. This is a characteristic feature.

Further, the thermal transfer material of the present invention has at least a colored layer and a top layer on the support from the support side, and the melting point m p 1 of the colored layer and the melting point m p 2 of the top layer are such that mpl≧m p 2 The coloring layer and the top layer satisfy the following relationship, and the heat-melting binder contained in the colored layer and the top layer contains an isocyanate polymer of higher fatty acid pentaerythritol ester and, if necessary, higher fatty acid polyhydric alcohol ester It is.

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 driven by a motor 14, and the platen roller 12 is driven by a motor 15, respectively. The transported thermal transfer material l is
It is wound up by a winding roller lO 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 l moves and the distance that the recording medium moves within the same time, the moving distance of the thermal transfer material l is shorter. As a result, with this recording method, the third
Recording is performed as shown in FIGS.

As shown in FIG. 3, if the width of the heating element 3a of the recording head 3 in the direction of feeding the thermal transfer material (in the direction of the arrow) is l, then 1
The second heat application is applied to a completely unused thermal transfer material l with a magnitude of l (FIG. 3). Incidentally, the thermal transfer material 1 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 1/N with respect to the recording head 3 (N=5° in FIG. 3). The value of N depends on how many times the same part of the thermal transfer material l can be printed.Since only 1) moves, the part (f - 1/N)) of the thermal transfer material l is a part that has already been heated once. will be used again (Figure 4).

When heat is applied continuously in the horizontal direction in this way, the heat-sensitive transfer material that receives heat from the second time onwards will be in an unused state by 1N, and the rest will have already been heat-applied several times by 1N. (Figures 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, when heat is applied for the second, third time, etc., the thermal transfer material l is applied with i! to the recording head 3, respectively. It is assumed that the thermal transfer material 1 is moved by /N, but the thermal transfer material 1 can be saved if the movement is less than 1 and more than l)/N. For the above N, 2
-10, more preferably 3-8.

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 1 moves relative to the recording head 3 is shorter.

As is clear from the above description, in the double-density recording method, heat is applied from the heating element 3a while sliding on the recording medium 2, such as paper, to form a recorded image on the recording medium 2. For this reason, the above-mentioned scumming and sticking occur easily, and furthermore, the reproducibility of minute dots is poor.

Now, the present inventors have determined that among the ink layers of the thermal transfer material, the melting point m p 1 of the colored layer and the melting point m p 2 of the top layer are m
Using a thermal transfer material with a relationship of p 1 layer m p 2,
It has been found that by performing double-density recording, minute dots can be more easily reproduced, and furthermore, "collapse" of recorded images can be reduced.

The above effects can be considered as follows.

FIG. 7 is a schematic cross-sectional view in the thickness direction of the heat-sensitive transfer material of the present invention used in the double-density recording method. Thermal transfer material 1 is support 1a
Colored layer lb on top! , and top layers 1b2 are sequentially laminated.

The colored layer 1b1 consists of a colorant and a heat-melting binder,
Further, the top layer lb2 is made of a heat-melting binder. As explained in FIGS. 3 to 6, the heat area of the heat-sensitive transfer material l at least after the second dot is partially subjected to two or more heat marks at the same location, and the first ink ib of the heat-sensitive transfer material l The second ink layer lb2 receives more thermal energy and progresses to a thermal softening or thermal melting state, that is, the melt viscosity decreases, and transfer to the recording medium is extremely advantageous. However, in the heat area of the first dot, since the thermal transfer material 1 is composed of two layers, the colored layer 1b and the top layer lb2, the colored layer containing the colored component is transferred to the recording medium to form an image. For this purpose, it is necessary to depend on the transferability of the top layer. Therefore, by setting mpl≧mp2, it is possible to maintain the transferability of minute dots, prevent background smearing, and prevent "bulge" in printing.

In addition, by containing an isocyanate polymer of higher fatty acid pentaerythritol ester and, if necessary, higher fatty acid polyhydric alcohol ester in the heat-melting binder contained in the colored layer and top layer, the reproducibility of minute dots can be improved. We found that it is effective in preventing crushing.

The thermal transfer material of the present invention will be explained in detail below.

As the support 2, conventionally known films can be used as they are, and for example, films of relatively heat-resistant plastics such as polyester, polycarbonate, triacetylcellulose, polyamide, polyimide, etc. can be suitably used.

In addition, when a thermal head is used as a means for applying heat to the thermal transfer material, the surface of the support that comes into contact with the thermal head is
By providing a heat-resistant protective layer made of silicone resin, fluororesin, polyimide resin, epoxy resin, phenol resin, melamine resin, nitrocellulose, etc., the heat resistance of the support can be improved, or it is possible to improve the heat resistance of the support. It is also possible to use other support materials.

The thickness of the support 2 is preferably 3 to 20 μm, more preferably 4 to 12 μm. As long as it has high strength and heat resistance, a thin one of 3 μm or less can also be used. Furthermore, an excessively thick support is undesirable since it has poor thermal conductivity.

The colored layer 1b consists of a colorant and a heat-melting binder. The colored layer herein refers to one in which the content of a coloring agent is 7 to 50% by weight based on the colored layer, and the thickness of the ink layer is in the range of 3 g/d to 30 g/d in terms of dry weight. If the content of the colorant is less than 7%, sufficient print density cannot be obtained, which is not preferable.

If it exceeds 50%, the melt viscosity of the colored layer increases, resulting in a decrease in transferability, which is not preferable. If the ink layer thickness is less than 3 g/rd, sufficient print density cannot be obtained, which is undesirable. If it exceeds 30 g/+yr, problems such as an increase in recording energy occur, which is undesirable.

The top layer 1b2 is basically made of a heat-melting binder and preferably does not contain a colorant, but may contain a colorless or white filler depending on the case, and may contain 5% by weight of a colorant. The following may be included.

Also, the thickness of the top layer is 0.5 to 10 g/rrr dry weight.
is preferable, and more preferably l~5g/rr? is desirable. If the content of the top layer is less than 0.5 g/rrr, scumming tends to occur, and if it exceeds 10 g/rrr, the transferability of ink corresponding to fine shapes tends to deteriorate, which is not preferable.

In the thermal transfer material of the present invention, a layer that does not affect the effects of the present invention may be interposed between the colored layer and the top layer or between the colored layer and the support.

Examples of coloring agents used in the colored layer include carbon black, nigrosine dye, lamp black, and Sudan black S.
M, First Yellow, Benzine Yellow, Pigment Yellow, India First Orange, Irgazine Red, Paranitroaniline ◆Red, Toluidine Red, Carmine FB, Permanent Bordeaux FR
R, 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 First Yellow CGG, Kaya Set Y963
, Kayaset YG, Sumiplast Yellow GG, Zapon First Orange RR, Oil Scarlet, Sumiplast Orange G1 Orazole Brown G1 Pomelo First Scarlet CG, Eisen Subiron Red BEH, Oil Pink OP1 Victoria Blue F
One or more known dyes and pigments such as 4R, Fast Dan Blue 500F, Sudan Blue, and Oil Peacock Blue can be used.

The thermal transfer material of the present invention uses thermofusible resins and waxes as the thermofusible binder.

Examples of resin components include polyolefin resins, polyamide resins, polyester resins, epoxy resins,
Polyurethane resin, polyacrylic resin, polyvinyl chloride resin, cellulose resin, polyvinyl alcohol resin, petroleum resin, phenolic resin, polystyrene resin, vinyl acetate resin, natural rubber, styrene-butadiene rubber, isoprene Rubber, elastomers such as chloroprene rubber, polyisobutylene, bolybdenum, etc. can be used, but ethylene-vinyl acetate copolymer, or ethylene-vinyl acetate copolymer, which has film properties and softens/melts well when heat is applied, can be used. Ethylene-ethyl acrylate copolymer is preferred, and its content is 25 to 80% by weight, more preferably 35 to 70% by weight based on the total binder amount, and if it is less than 25% by weight, whisker-like transfer (tailing) may occur. ,
Background smearing is likely to occur, and if it exceeds 80% by weight, it is undesirable because transferability deteriorates, sticking occurs, energy increases, and cutting performance deteriorates.

In addition, its melt flow rate is 150 to 800g/
10min, even 150~400g
/10 min is suitable. If the melt flow rate is less than 150 g/10 m1n, the melt viscosity will increase, 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 /10m1n, background stains and whisker-like transfer (tailing) are likely to occur.

Among these, ethylene-vinyl acetate copolymer is preferred, and the most suitable is one with a vinyl acetate content of 15 to 33% by weight; if it is less than 15% by weight, the solubility in organic solvents decreases and the viscosity of the coating ink increases. If it is more than 33% by weight, scumming and whisker-like transfer (tailing) are likely to occur, which is not preferable.

In the above, melt flow rate (hereinafter abbreviated as MFR)
and vinyl acetate content (hereinafter abbreviated as VA) according to JIS
It is defined in accordance with K6730.

Examples of waxes include natural waxes such as carnauba wax, candelilla wax, rice wax, vegetable waxes such as wood wax, ceresin wax,
Mineral waxes such as montan wax and derivatives thereof, such as acid wax, ester wax, partially saponified ester wax, etc., are examples of montan wax derivatives. 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 may be contained in the binder.

Other higher fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid; higher alcohols such as stearyl alcohol and behenyl alcohol;
It is also possible to use esters such as sucrose fatty acid ester and sorbitan fatty acid ester, and amides such as oleylamide.

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

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,
One type or a mixture of two or more types selected from hydrogenated rosin triethylene glycol ester, hydrogenated rosin pentaerythritol ester, polymerized rosin ester, aliphatic petroleum resin, alicyclic petroleum resin, synthetic polyterpene, pentagene resin, etc. .

Furthermore, as the heat-melting binder used in the present invention, it is particularly preferable to use isocyanate polymers of higher fatty acid pentaerythritol esters and higher fatty acid polyhydric alcohol esters mixed as necessary.

The polymer will be explained 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, palmitic 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, aragidonic acid, sardine acid, nisic acid, propiolic acid , unsaturated fatty acids such as stearic acid, branched fatty acids such as invaleric acid, cycloaliphatic fatty acids such as malvalic acid, stearic acid, hydronocarbic acid, Schollmoubleic acid, golulic acid, sabinic acid, ibrolic acid, and serapinolic acid. Oxygen-containing fatty acids such as , uniberic acid, ricinoleic acid, feronic acid, and cerebronic acid can be used. In particular, fatty acids having a melting point of 20° C. or higher and a carbon number of 10 to 30 can be preferably 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.

If the fatty acid used does not have a carboxyl group,
The ester is converted into a monoester, diester, or triester and subjected to reaction with an isocyanate compound. Monoesters, diesters, and triesters can be used alone or as a mixture of two or three types.

Examples of isocyanate compounds include methyl isocyanate, ethyl isocyanate, n-propylisocyanate, n-butyl isocyanate, octadecyl isocyanate, polymethylene polyphenylisocyanate, etc.
．． 4-) lylene diisocyanate, 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.
6-diisocyanate methyl caproate, etc., triphenylmethane triisocyanate, tris(4-phenylisocyanate thiophosphate)) 4.4', 4'
-trimethyl3.3',3'-triisocyanate)
-2,4,6-triphenyl cyanurate and the like are used. Diisocyanates and triisocyanates are particularly preferred, and aromatic ones are more preferred.

The reaction between the ester and the isocyanate can be carried out using a heating and stirring operation according to a conventional method. If the heating temperature is too high, the coloring of the obtained product will be significant, and if it is too low, the reaction time will become long.
It is desirable to select a temperature in the range of 0 to 150°C. The above reaction can also be carried out using metal salt catalysts such as stannic chloride, ferric chloride,
The use of potassium oleate, dibutyltin dilaurate, etc. allows the process to proceed relatively quickly at lower temperatures. 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 the ester. 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., and it is possible to improve workability during the production of thermal transfer materials, that is, to reduce volatile solvents by heating the coating ink. Further, since there is no precipitation of waxes, a homogeneous thermal transferable ink layer can be formed extremely efficiently.

Furthermore, when the above-mentioned waxes are used, the number of rolls of thermal transfer material is extremely small, making it easy to handle the thermal transfer material. 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, it is effective to simultaneously use higher fatty acid polyhydric alcohol ester if necessary.

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

The higher fatty acid pentaerythritol ester used in combination with the above-mentioned isocyanate polymer is effective in finely adjusting the melting point or melt viscosity of the entire wax component, thereby making it possible to vary the properties of the thermal transfer ink. .

The mixing amount of the ester is preferably 50% or less, more preferably 40% or less, and even more preferably 35% or less based on the total amount of the heat-melting binder.

If it exceeds 50%, the solubility of the wax component in the solvent will be poor, and workability will be lowered and curling will likely 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, preferably 30 to 6% by weight based on the total binder amount.
Contains 5% by weight.

If it 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 the applied thermal energy, which tends to damage the thermal head, which is the heat source. Alternatively, if the supplied thermal energy is insufficient, the thermal transfer material and the recording medium will stick together, resulting in unstable running properties, resulting in blurred recorded images, insufficient density, and insufficient uniformity of density. If it exceeds 75% by weight, whisker-like transfer (tailing) and scumming 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 the temperature 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.

Furthermore, the melt viscosity of the wax main component is 10 at 100°C.
~103c ps, preferably 10-500c
p s , more preferably 1O to 200 cps.

This is because when heated, the main wax component acts like a solvent for the resin component, so 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. It is presumed that cohesive failure becomes easier and sticking is reduced. the result,
It is presumed that the sharpness of the recorded image increases and density deficiency or density uniformity is achieved.

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 adhesion but also transferability.

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

The melting point mpl of the colored layer 1b is preferably 50°C to 150°C, more preferably 60°C to 130°C. Melting point m of top layer lb2
p2 is 40℃~130℃, furthermore 50℃~110℃
is preferred. When the melting point of the top layer is lower than 40° C., it is possible to reduce the heating energy required for ink transfer, but this is not preferable because it causes problems in the storage stability of the heat-sensitive transfer material, such as sagging of the ink material due to blocking. On the other hand, if the temperature exceeds 130° C., it becomes necessary to increase the applied heating energy, which is not preferable because the durability of the thermal head and the recording speed decrease. The ranges of the melting point mpl of the colored layer and the melting point m p 2 of the top layer are as described above, but furthermore, the range mp 1 - mp 2, that is, the difference in melting point between the colored layer and the top layer is 0 to 40°C, furthermore 0 ~20°C is preferred.

In the above description, the melting point of the resin, the melting point of the wax, and the difference in melting end and melting start temperatures were measured as follows.

〔measuring device〕

Differential scanning calorimetry analyzer fiDsc-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 determined as follows. . - As an example, Fig. 8 shows Rannox 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 defined as the melting point.

△T is the intersection point of the peak slope and the baseline, point B (melting start temperature) and point 0 (melting end temperature), respectively, Ti and T.
It is defined as e and the runner-up.

ΔT=Te-Ti When the colored layer and the top layer have a single heat-melting binder, the melting point of the binder is the melting point of the ink layer.

In addition, when the ink layer is composed of two or more types of heat-melting binders, the melting point of the ink layer is an average value defined by the following formula.

mpaV: mpXl: mpX2: mpxn: Mixing ratio x2: 2nd
Weight blending ratio of the heat-melting binder x, : Weight blending ratio of the n-th heat-melting binder In producing the heat-sensitive transfer material of the present invention, the above-mentioned binder material may be mixed with, for example, toluene, methyl ethyl ketone, isopropyl alcohol, or methanol. , dissolved in an organic solvent such as xylene,
The most suitable method is a solvent coating method, in which a colorant is mixed and sufficiently dispersed using a dispersing machine such as a sand mill, and then applied onto a 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.

〔Example〕

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

The coating liquid described below was 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 nozzle and dried with hot air. , coating amount after drying is colored layer 12g/rr
A heat-sensitive transfer material was obtained by forming a heat-transferable ink layer of 3 g/rrr on the top layer of f.

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. Comparative examples Coating liquid 1> Coating liquid 2><Coating liquid 3> Coating liquid 4><Coating liquid 7> Coating liquid A><Coating liquid 5> Coating liquid 6> Coating liquid B> Coating liquid C> Coating liquid D> Coating liquid F> Coating liquid E> Coating liquid G> Length, 1L721 The above coating liquids 1 to 6 and Thermal transfer materials shown in Table 1 were obtained by the method described above using coating solutions A to F.

Table 1 Thermal transfer materials (2) shown in Table 2 were obtained in the same manner as in Examples using Coating Liquid 7 and Coating Liquid G.

Table 2 On the other hand, by partially modifying Fukushimari manufactured by Canon Co., Ltd. (trade name: Canofax 630), the recording medium and the thermal transfer material were modified so that the thermal transfer material and the recording medium had a relative speed as shown in FIG. The evaluation machine was modified so that the conveyance length of the thermal transfer material was 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-head with 8 pel/mm, and the heater size is 100 μm in the main scanning direction and 60 μm in the sub-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.
It is 2 mm/sec.

(5) The surface heat energy of the thermal head during recording is 22 m j /m rd.

A facsimile test chart No. 2 of the Institute of Image Electronics Engineers was used as a received image, and the image of the chart was output on plain paper (TRW-IA manufactured by Jujo Paper Industries, Beck smoothness: 220 seconds).

In the above-mentioned test chart, evaluations were made for scumming, whisker-like transfer, crushed print, reproducibility of minute dots, adhesion, and uniformity of density.

The evaluation criteria are based on the following:

Background smear ○ Almost no background smudge △ There is some background smudge, but it can be used in practical use × There is a lot of background smudge, and it is not practical. Beard-like transfer (tailing) ○ There is no whisker-like transfer △ There is some whisker-like transfer, but it can be used in practical use × There is a lot of whisker-like transfer, and the printing is not practical. ○ The thin lines are not crushed, and the characters are easy to read. △ The thin lines are slightly crushed, but the characters are legible and are not suitable for practical use. Obtained × Thin line parts are crushed, characters are difficult to read, and the density is not uniform enough to be used for practical purposes (uneven streaks in the main scanning direction in the part 1 of test chart No. 2 []) ○ Most of the streaks are uneven The image is homogeneous.

△ Slight unevenness is observed, but it can be used in practical use × There is some unevenness in the streaks, and it cannot be said that the image is homogeneous, and the image cannot be used in practical use. ○ No white streaks are observed △ Small white streaks are observed, but it can withstand practical use × White streaks are noticeable and curls are not suitable for practical use ○ Curls are extremely small and there is no inconvenience in handling △ Table 3 shows the evaluation results: Curling is somewhat large, but it can be used in practical use × Curling is severe and it cannot be used in practical use.

Table 3 also shows the first ink layer and second ink layer of this example and comparative example.
The melting point of the ink layer is also noted.

〔Effect of the invention〕

As is clear from the above results, according to the present invention, even in double-density recording, background smear, whisker-like transfer (tailing), sticking, and blurring of print can be prevented, and prints with excellent density uniformity can be obtained.

[Brief explanation of drawings]

FIGS. 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 schematic diagrams showing the principle of thermal transfer recording of the present invention, and FIG. FIG. 8, which is a cross-sectional view in the thickness direction of the thermal transfer material of the present invention, is a graph showing an example of DSC measurement results. I: Thermal transfer material la: Support 1b: Thermal transfer ink layer lb, : First ink layer lb2: Second ink layer 2: Recorded body 3: Recording head 10: Winding roller ll; Platen roller 12: Cab stun Roller 13: Pinch roller 14.15: Motor 16: Spring h revolving

Claims (5)

[Claims] (1) Using a thermal transfer material that has at least a colored layer and a top layer on a support from the support side, and in which the melting point mp1 of the colored layer and the melting point mp2 of the top layer satisfy the relationship mp1≧mp2, A thermal transfer recording method, characterized in that 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 a period of time. (2) The thermal transfer recording method according to claim 1, wherein the colored layer and the top layer contain an isocyanate polymer of a higher fatty acid pentaerythritol ester and, if necessary, a higher fatty acid polyhydric alcohol ester. (3) The content of the isocyanate polymer or the combined content of the isocyanate polymer and the higher fatty acid polyhydric alcohol ester is contained in each of the colored layer and the top layer. 3. The thermal transfer recording method according to claim 2, wherein the thermal transfer material is used in an amount of 20 to 75% by weight based on the binder. (4) In a thermal transfer material having at least a colored layer and a top layer on a support from the support side, the melting point mp1 of the colored layer and the melting point mp2 of the top layer satisfy mp1≧mp.
A heat-sensitive transfer material that satisfies the following relationship and contains an isocyanate polymer of a higher fatty acid pentaerythritol ester and, if necessary, a higher fatty acid polyhydric alcohol ester in the colored layer and the top layer. (5) The content of the isocyanate polymer or the combined content of the isocyanate polymer and the higher fatty acid polyhydric alcohol ester is the same as that of the binder contained in each of the colored layers and the top layer. Claim 4: 20 to 75% by weight of the
Thermal transfer material.