JPH0363180A - Thermal transfer material and thermal transfer recording method - Google Patents

Abstract

PURPOSE:To prevent background staining or whiskerlike transfer even in double- density recording and to also express an isolated dot by setting the storage modulus E' of an ink layer at definite temp. to a specific range and also setting temp. giving the definite value of the temp. differentiated value of a dynamic energy loss angle tan delta to specific temp. CONSTITUTION:A thermal transfer material 1 and a material 2 to be recorded such as paper are superposed one upon another to be heated by a recording head 3 such as a thermal head and the thermal transfer ink of the thermal transfer material is transferred to the material 2 to be recorded to obtain a recording image. Storage modulus (E') and the temp. differentiated value of a dynamic energy loss angle (tandelta) well correspond each other and, further, a thermal transfer ink layer has storage modulus (E') of 1X10<7=E'<=1X10<9>N/m<2> at 30 deg.C and has special heat sensitivity wherein temp. giving the temp. differentiated value (d) (tandelta) of a dynamic energy loss angle is between 40 and 60 deg.C. By this method, the transfer properties of an isolated dot are well and whiskerlike transfer can be prevented.

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).

[Problem that the invention is trying to solve]

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, JP-A-57-83471, JP-A-58-
As in No. 201686 or Japanese Patent Publication No. 62-58917, there is a recording method (hereinafter referred to as double-density recording) that reduces the amount of thermal transfer material used by providing a relative speed between the thermal transfer material and the recording medium. Proposed. However, this recording method has some problems like the conventional method.

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 Application Laid-Open No. 178088/1988 proposes a heat-sensitive transfer material in which an overlayer containing no colorant is provided on an ink layer.

The second problem is that, as shown in FIG.
0 occurs.

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 previously filed 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 in double-density recording, it is not possible to record by generating heat once from the isolated dot-expressing heating element.

This means that in double-density recording, the thickness of the thermal transfer ink layer of the thermal transfer material is compared to the thickness of the thermal transfer ink layer of conventional thermal transfer recording (in which the thermal transfer material and the recording material are conveyed without relative speed). However, since it has to increase in proportion to the double density (double density is the number of times the same area of the thermal transfer material is repeatedly used for double density recording), the thermal energy obtained from the thermal head is extremely disadvantageous. Furthermore, in double-density recording, which will be explained in detail later, when printing an isolated single dot, heat is applied to completely unused thermal transfer material, but the number of consecutive dots in the printing direction is When printing dots, i/N (f is the size of the heating element of the thermal head in the thermal transfer material feeding direction, N is the double density)
The ink is heated once, but f − (j!/N)
The portion has already been subjected to heat application once or more (maximum N-1 times) and has been used again, and the thermal transfer ink layer itself has accumulated heat. For this reason, printing of a continuous number of dots is extremely advantageous for transfer compared to printing of isolated dots. Furthermore, due to heat accumulation in the ink, excessive energy is likely to be applied to the ink in continuous N-dot printing, and it is necessary to suppress the applied energy compared to conventional thermal transfer recording. Therefore, when it comes to printing isolated dots, double-density recording is extremely disadvantageous compared to conventional thermal transfer recording.

Now, as is clear from the above explanation, when printing one isolated dot, the temperature reached by the ink during heat application is extremely low compared to when printing a number of consecutive dots. Therefore, the thermal transfer ink layer required for double-density recording has extremely high thermal sensitivity.

On the other hand, in double-density recording, when printing a number of consecutive dots, heat is applied to the same ink layer multiple times (up to N-1 times). Since the recording time for each dot is usually several msec, the thermal transfer ink that has been heated multiple times will receive the next heat application one after another before it is completely cooled down to room temperature, and the temperature reached by the ink will increase. (This is called ink heat storage.) Therefore, even if heat application is stopped after printing a number of consecutive dots, (1) it takes time for the ink to cool down to room temperature; (2) The thermal transferable ink layer and the recording medium slide even within this time. Unnecessary whisker-like transfer occurs at the head running end of the ink layer transferred from these two points.

As a countermeasure for this whisker-like transfer, there is a description in Japanese Patent Application No. 1-25278 filed earlier by the present application, but there is still room for improvement in the reproducibility of isolated dots.

The present invention has been made in view of the above-mentioned circumstances, and aims to provide a thermal transfer material and a thermal transfer recording method that not only prevent background stains and whisker-like transfer even by double-density recording, but also make it possible to express isolated dots. purpose.

[Means to solve the problem]

The thermal transfer material of the present invention has a thermal transferable ink layer on a support, and the storage elastic modulus E' at 30°C of the ink layer is I i, and the temperature that gives the temperature differential value d(tanδ)/dT=IX10-'' of the mechanical energy loss angle tanδ is between 40°C and 60°C.

Further, the thermal transfer recording method of the present invention uses the thermal transfer material and moves the recording medium relative to the recording head within the same time (
5) The heat-sensitive transfer material according to claim (1) is characterized in that the distance that the heat-sensitive transfer material moves relative to the recording head is shorter than the distance that the heat-sensitive transfer material moves with respect to the recording head.

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 connected to a capstan roller 5, a pinch roller 9, and a platen roller 4.
As a result of the rotation, the recording medium 2 continuously moves toward the heat-sensitive transfer material from arrows A and B, respectively, and recording is performed on the recording medium 2 one after another. Capstan roller 5 and pinch roller 9
is driven by a motor 7, and the platen roller 4 is driven by a motor 6. Thermal transfer material transported
is wound up by a winding roller 10 driven by a motor 7.

A spring 8 presses the recording head 3 against the platen roller 4 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 toward the thermal transfer material rather than completely opposite.

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 case of 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. In other words, the distance that the thermal transfer material 1 moves within the same amount of time Comparing the moving distance of the recording medium, the moving distance of the thermal transfer material 1 is shorter than that of the thermal transfer material 1. As a result, in this recording method, the distance traveled by the thermal transfer material 1 is shorter than that of the thermal transfer material 1.
Recording is performed as shown in FIG.

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 the heat is applied for the second time, the recording medium 2 moves l in the direction of arrow B, while the thermal transfer material 1 moves l in the direction of arrow B, while the thermal transfer material 1 moves l in the direction of arrow B. /NC In FIG. 3, N=5° The value of N depends on how many times the same portion of the thermal transfer material 1 can be printed. ), the CI of thermal transfer material 1 - (i/N)
) is the part that has already been subjected to heat application once and will be used again (Fig. 4).

In this way, when heat is applied continuously in the lateral direction, the heat-sensitive transfer material that receives heat from the second time onwards has only 17N unused, and the rest has already been heated several times in l/N increments. The voltage is applied (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 l/N relative to the recording head 3 during the second, third, etc. heat application, but it is less than 1, more than It/N. , the amount of thermal transfer material can be saved. The above N is 2~
10. Furthermore, 3 to 8 are preferable.

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 1 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 of the thermal transfer material 1 is shorter than the distance that the thermal transfer material 1 moves relative to the recording head 3.

Now, as a result of an in-depth study of thermal transfer materials in order to solve the two contradictory problems of the above-mentioned requirement for high thermal sensitivity to print isolated dots and the requirement for low thermal sensitivity to prevent whisker-like transfer, It has been found that the storage modulus (E') and the temperature differential value of the mechanical energy loss angle (tan δ) in the measurement of dynamic viscoelasticity can correspond extremely well as physical properties that capture thermal sensitivity. Furthermore, the storage modulus (E') at 30°C is I X 1x107≦E'≦1xlO@N/rr? It is a thermally transferable ink layer of It has been found that a thermally transferable ink layer has good transferability of isolated dots and can also prevent whisker-like transfer.

The thermal sensitivity described above does not correspond to the melting point in differential scanning calorimetry (DSC) or the outflow start temperature in the flow tester (F, T,), but rather to the mechanical energy loss angle in the dynamic viscoelasticity measurement described above. The temperature differential values correspond extremely well.

If the storage modulus E' is larger than 1 x 10''N/- at 30°C, the initial elastic modulus of the thermal transferable ink layer is too large, giving d(tanδ)/dT=1 x 10''. Even if this happens, the desired softened state will not be achieved, which is not preferable. Furthermore, if E' is smaller than 1×1 O'N/rrr, the initial elastic modulus of the thermal transferable ink layer will be too small and scumming will occur even at 30° C., which is not preferable. E' at 30°C is I x 1×107≦E≦
Even if it is 1×1×107N/rrf, d (tan δ
) If the temperature that gives dT=l×10= is lower than 40°C, whisker-like transfer or, in some cases, scumming will occur, and if the temperature that gives d(tanδ)/dT=1×10-3 is lower than 40°C, If the temperature exceeds .degree. C., the transfer of isolated dots will be insufficient.

The reason for this is not clear; (1) The state of the ink layer that causes the whisker-like transfer is in an extremely slightly softened state (not a sufficiently softened state, but an initial state in which it begins to soften).

■ The ink is transferred to the recording medium by applying heat,
In double-density recording, unlike normal thermal transfer recording, the recording medium and the thermal transfer ink layer are sliding when heat is applied, so that transfer starts in a unique softened state.

There are two special points mentioned above, and this unique softening state cannot be captured by the melting point of DSC, the melt viscosity by a flow tester, or the outflow start temperature, but by the storage modulus E', which corresponds to the elasticity of the ink, and the viscosity. It has been found that this can be correctly captured by the slope of tan δ = E'/E', which is the ratio to the corresponding loss modulus E'. Further d (ta
The unique softening state giving nδ)/dT=1×10−” is a minute softening state that causes this whisker-like transfer, and a softening state that sufficiently transfers the ink as a print (an isolated dot can be expressed in this softening state. It is assumed that the softening states of the two are relatively close to each other. Therefore, within the temperature range that provides this value, both prevention of whisker-like transfer and reproduction of isolated dots can be satisfied.

A method for measuring the temperature differential values of storage modulus E', loss modulus E', and mechanical energy loss angle (tan δ) in the present invention will be explained.

[Preparation of measurement sample] A sample for performing dynamic viscoelasticity measurement is prepared as follows. That is, the same ink material as the ink layer used for the thermal transfer material is applied onto release paper using an applicator or wire bar, and the thickness after drying is 60 to 200 mm.
Make it so that it is μm. After the ink layer dries, the release paper is removed to form an ink film.

Alternatively, it may be created as follows. In other words, a mold of a predetermined shape (for example, vertical 6 mm x horizontal 3
The molten thermal transfer ink is poured into a mold (0 mm x height 0.2 mrn), cooled, and then removed from the mold.

Furthermore, the following samples may be used. That is, the measurement is performed using a heat-sensitive transfer material obtained by coating a support with a heat-transferable ink layer as it is. However, in that case, the dynamic viscoelastic behavior of the two-layer system of the support itself and the thermal transfer ink layer itself is measured, so the dynamic viscoelastic behavior of the support itself can be calculated from the theoretical formula shown below. The subtracted value is the dynamic viscoelastic behavior of the thermal transfer ink layer itself.

E1=(Et E2t2)/ll E: Elastic modulus of thermal transfer material t: Thickness of thermal transfer material El: Elastic modulus of thermal transfer ink tl: Thickness of thermal transfer ink layer E2: Elastic modulus of support t2: Support [Measuring device] In the present invention, the storage modulus E′ and the loss modulus E are measured using a dynamic viscoelasticity measuring device (Rheolograph Solid, manufactured by Toyo Seiki Seisakusho Co., Ltd.) under the following conditions. ' and the mechanical energy loss angle (tan δ=E'/E) was measured. Also, the temperature differential value of the mechanical energy loss angle tan δ is t
Calculated from the temperature change of anδ.

Straight line and forced vibration frequency: 9.8 Hz Static tension: 20 g Temperature increase rate: 2° C./min Next, the structure and each constituent material of the thermal transfer material used in the present invention will be explained. FIG. 8 is a schematic cross-sectional view in the thickness direction showing one embodiment of the thermal transfer material used in the present invention. support la
The thermal transfer ink layer 1b coated thereon is formed by mixing a coloring material into a heat-melting binder.

As the support 1a, conventionally known plastic films, paper, etc. can be used, but since heat is applied many times to the same location on the base material in double-density recording, for example, aromatic polyamide film, polyphenylene sulfide film, Preferably, materials with high heat resistance such as polyetheretherketone and condenser paper are used. In addition, when using polyester film (especially polyethylene terephthalate film, abbreviated as PET film), which has been suitably used in conventional heat-sensitive transfer materials, it is necessary to provide a heat-resistant and slippery material on the surface opposite to the ink surface as a backside treatment. is preferred. The thickness of the base material is preferably 3 to 20 μm, more preferably 4 to 12 μm.
m is desirable. 3μm if it has high strength and heat resistance
The thinner ones below can also be used. Further, excessively thick materials are not preferable because they have poor thermal conductivity.

As the heat-melting binder used in the heat-transferable ink layer 1b, wax and heat-melting resin are used. Natural waxes include carnauba wax, candelilla wax, rice wax, vegetable waxes such as genuine wax, ceresin wax, montan wax,
Examples of mineral waxes such as montan waxes and derivatives thereof include acid waxes, ester waxes, and partially saponified ester waxes.

Animal waxes such as beeswax, spermaceti, and lanolin and their derivatives; and petroleum waxes such as paraffin wax and microcrystalline wax. Synthetic waxes include polyethylene wax and Fischer-Tropsch wax.

Other higher fatty acids such as lauric acid, myristic acid, balmitic acid, stearic acid, 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, a compound obtained by addition polymerization with an isocyanate-containing compound using the residual hydroxyl group of an ester compound obtained from a saturated fatty acid, an unsaturated fatty acid, and a polyhydric alcohol as specifically shown below is preferably used as the wax. More preferably, the compound has a melting point of 55°C to 80°C.
℃, and the melt viscosity at 100℃ is preferably 500 cps or less.

The saturated fatty acids include capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecyl acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, heptacanoic acid, and montanic acid. acid, melisic acid,
Rafuselic acid and the like are used.

In addition, the unsaturated fatty acids include acrylic acid, crotonic acid, isocrotonic acid, caproleic acid, undecylic acid, oleic acid, elaidic acid, cetoleic acid, erucic acid, brassic acid, sorbic acid, linoleic acid, lylunic acid,
arachidonic acid, propiolic acid, sardine acid, nisic acid,
Stearolic acid and the like are used.

Further, the polyhydric alcohols 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, glycerin, trimethylolpropane, pentaerythritol, dipentaerythritol, l,3-butylene glycol, monoallyl glycerin, (4-(hydroxyethoxy)phenol)propane, sorbitol, sorbitol, neopentyl glycol, trishydroxyethyl Isocyanurates, bisphenols, hydrogenated bisphenols, bisphenol glycol ethers, various epoxies (for example, triglycidyl isocyanurate), and the like are used.

In addition, examples of the incyanate-containing compound 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-tolylene diisocyanate. '-Diphenylmethane diisocyanate, dianisidine diisocyanate, metaxylylene diisocyanate, l,5-naphthalene diisocyanate, transvinylene diisocyanate, N,N'
(4゜4'-dimethyl-3,3'-diphenyl diisocyanate) uredione, diisocyanates such as 2,6-diisocyanate methyl caproate, triphenylmethane triisocyanate, tris(4-phenylisocyanate thiophosphate) -)) 4.4'4'-trimethyl-3,3',3'-)reincyanate-2,4,6-)riphenyl cyanurate, etc. are used.

In order to satisfy the melting point and melt viscosity, in some cases, the esterified product of the saturated fatty acid and unsaturated fatty acid and polyhydric alcohol, and the isocyanate addition polymerized compound of the esterified product may be appropriately mixed and used. .

Heat-melting resins include polyolefin resins, polyamide resins, polyester resins, epoxy resins, polyurethane resins, polyacrylic resins, polyvinyl chloride resins, cellulose resins, polyvinyl alcohol resins, and petroleum resins. , phenolic resin, polystyrene resin, vinyl acetate resin, natural rubber, elastomers such as styrene-butadiene rubber, inbrene rubber, chloroprene rubber, polyisobutylene, polypden, etc. can be used, especially ethylene-vinyl acetate copolymer. , vinyl acetate-ethylene copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-
Acrylic acid aster copolymers, polyamides, polyesters, etc. can be suitably used.

Examples of colorants include carbon black, nigrosine dye, lamp black, Sudan Black SM, Fast Yellow G1 Benzine Yellow Pigment Yellow,
Indofast Orange, Irgazine Red, Paranitroaniline Red, Toluidine Red, Carmine F
B1 permanent Bordeaux FRR, pigment orange R1 litho point 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 01 Orazur Brown G1 Zabon Fast Scarlet CG, Eisen Subiron Red F4R,
Conventionally known colorants such as Fastgen Blue 5007, Sudan Blue, and Oil Peacock Blue are used alone or in combination of two or more.

Below, preferred physical properties of the ethylene-vinyl acetate copolymer and wax will be explained using an example of creating the thermal transfer material of the present invention using the ethylene-vinyl acetate copolymer, wax, and colorant. do.

(a) Preferred conditions for ethylene-vinyl acetate copolymer (EVA) ■ Preferred conditions for wax (WAX) ■ Preferred blending ratio, that is, MFR of ethylene-vinyl acetate copolymer is 1
If it is smaller than 50, d (tan δ) /dT= l
If the temperature that gives ``
The temperature that gives (tan δ)/dT=1xlo-1 is 4
This is not preferable since the temperature is less than 0°C. VA conte
When nt is less than 15%, the applied temperature increases and the VA
If the content exceeds 33%, the temperature given will be 4.
This is not preferable since the temperature is less than 0°C. Incidentally, the melt flow rate can naturally be adjusted by mixing two or more types.

On the other hand, if the wax has a melting point of less than 55°C, the temperature applied will be less than 40°C, which is undesirable, and if the melting point exceeds 80°C, the applied temperature will exceed 60°C, which is not preferable. do not have.

If ΔT exceeds 20℃, the temperature applied should be 40℃~
This is not preferable because it becomes difficult to maintain the temperature at 60°C.

The melt flow rate and vinyl acetate content of the ethylene-vinyl acetate copolymer are determined by the measurement method shown below.

Melt flow rate (MFR): JIS K673
Vinyl acetate content (VA content) according to 0:
In accordance with JIS K6730, the differential scanning calorimetry measurement melting point (D
SC measurement melting point) and melting behavior ΔT were measured using the following measuring device.

[Measurement device] Differential scanning calorimetry analyzer DSC-7 (manufactured by PerkinElmer) Normal heating rate: 5° C./min The melting point and ΔT are determined as follows. -For example, the seventh
The figure shows the measurement results of Rannox FPS-7 manufactured by Yoshikawa Oil Co., Ltd.

Point A in FIG. 7, that is, the peak value of absorption, is taken as the melting point.

ΔT is defined by the intersection points B and C of the peak slope and the baseline, with absorption start temperature Ti1 and absorption end temperature Te, and the next point.

△T=Te-Ti Also, the blending ratio of EVA and WAX "t'(EVA)/(WA
C
When EVA)/(WAX)>4.7, the film strength of the entire ink layer increases, which is disadvantageous for reproduction of isolated dots, which is not preferable.

In addition, the wax has a penetration rate at room temperature, melt viscosity,
It is preferable that the temperature dependence of the melt viscosity satisfies the following conditions.

Penetration: 5 or less (at 25℃) Melt viscosity
500cps or less (at 100℃) η1wc: 100
Melt viscosity at °C (cps) rII″c, 150 °C
Melt viscosity (cps) The above melt viscosity is a value measured using the following measuring equipment.

B-type viscometer (Rotovisco TK-I-0.3 manufactured by Haake)
If the penetration exceeds 5, the hardness of the entire ink layer decreases, and the temperature at which d (tan δ)/dT=1×10 − ” is likely to be less than 40° C., which is not preferable.

When the melt viscosity exceeds 500 cps, the melt viscosity of the entire ink layer becomes high and d (tan δ)/dT=1×
This is not preferable because the temperature at which a value of 10-'' is given tends to exceed 60°C.

When the temperature dependence of melt viscosity is large, d (tan
This is equivalent to an increase in the temperature that gives δ)/dT=1×10 − ”, which is not preferable.

The wax used is preferably one that has good compatibility with the ethylene-vinyl acetate copolymer and exhibits a single softening and melting behavior as a thermally transferable ink layer.

The amount of coloring material 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 the coloring material is less than 1% by weight, the density of the print will decrease, which is undesirable, and if it exceeds 50% by weight, the elasticity of the entire ink layer will decrease, which is not preferred.

Although the above describes an example of the heat-sensitive transfer material of the present invention in which ethylene-vinyl acetate copolymer and wax are selected as the heat-melt binder, the present invention is not limited thereto, and the heat-melt binder described above is not limited thereto. is used as appropriate, and E' at 30°C is I x 107≦E≦I x 10''
The design may be such that the temperature giving d (tan δ)/dT=1×10 − ” is in the range of 40° C. to 60° C.

Although the thickness of the ink layer varies depending on the double density, it is generally preferably 6 to 30 g/rrr in dry weight coating amount, and more preferably 6 to 20 g/d. If it is less than 6 g/rrf, sufficient recording density cannot be obtained in double-density recording, and if it is less than 30 g/ITr
Exceeding this is not preferable because problems such as an increase in recording energy will occur.

Further, in the above description, the thermal transferable ink layer provided on the support has been explained as having a single layer structure, but it may have a layer structure of two or more layers. However, in this case as well, the ink layer as a whole is d (
The temperature that gives tan δ)/dT = 1 x 10-' needs to be in the range of 40°C to 60°C.

In producing the thermal transfer material of the present invention, a binder material selected from the above-mentioned viewpoints is dissolved in an organic solvent such as toluene, methyl ethyl ketone, isopropyl alcohol, methanol, xylene, etc., and a coloring material is mixed therein, and then the binder material is mixed with a coloring material and then processed using a sand mill or the like. It can be sufficiently dispersed using a dispersing machine, and then applied onto a substrate using a coating method such as a bar code or gravure coating. Alternatively, the resin may be heated to a temperature above its softening point to disperse the coloring material, and then applied using a so-called hot melt coating. Furthermore, the resin or colorant may be applied as an aqueous emulsion by adding a dispersant such as a surfactant.

EXAMPLES The present invention will be explained in more detail with reference to Examples below.

Example 1 The above materials were dissolved and dispersed using a sand mill to create a thermal transfer ink. A thermal transfer material comprising a thermal transfer ink layer using the ink, coated using a wire bar on a polyester film with a thickness of 6 μm that has been subjected to back treatment, and dried, with a coating weight of 16 g/nf after drying. (1) was obtained.

Separately, the thermal transfer ink was applied to a release paper using a wire bar, dried, and then the thermal transfer ink was peeled off from the release paper to prepare a sample for dynamic elasticity measurement.

Example 2 Example 3 Example 4 Example 5 Example 6 Example 9 Example 7 Example 8 Comparative Example 1 Comparative Example 2 Comparative Example 4 Comparative Example 3 Said Examples 2 to 9, Comparative Example 1 to Comparison A thermal transfer material was obtained using the formulation material of Example 4 in the same manner as in Example 1. In addition, a dynamic viscoelasticity measurement sample was also obtained in the same manner as in Example 1.

On the other hand, a facsimile manufactured by Canon Co., Ltd. (trade name: Canofax 630) was partially modified and used for evaluation as a double-density recording facsimile device.

The physical conditions of this device are as follows.

(1) Equipped with an 8 pel/mm full multi-thermal head.

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

(3) The thermal transfer material and the recording medium are fed in opposite directions.

(4) Printing speed on recording medium is 25 mm/
It is sec. Further, the relative speed between the recording medium and the thermal transfer material at this time was 31.2 mm/sec.

(5) The surface heat generation energy of the thermal head is 22 m
J/m resistance.

Next, the above-mentioned thermal transfer material is inserted into this device and the received image is transferred to the Image Electronics Engineers of Japan facsimile test chart No.
The image of No. 2 was output on plain paper (TRW-IA Beck smoothness: 220 seconds, manufactured by Jujo Paper Industries). In the test chart, the presence or absence of scumming and whisker-like transfer was mainly evaluated. Next, a person image (Canon GENESIS) is used as the received image.
The image of the evaluation chart) was output on plain paper in halftone mode. The right eye portion of the chip was enlarged to evaluate the transfer status of isolated dots.

By the way, Comparative Example 1 is a typical example of a thermal transfer material used in conventional thermal transfer recording (in which the thermal transfer material and the recording medium are conveyed without having a relative speed). The thermal transfer material of Comparative Example 1 was also evaluated using a thermal transfer recording facsimile machine (trade name: Canfux 630). As a result, the thermal transfer material of Comparative Example 1 produced clear prints with no stains or whisker-like transfers and good reproduction of isolated dots in the conventional thermal transfer recording.

On the other hand, using the dynamic elasticity measurement sample, E', E'
The temperature dispersion of tan δ was measured. - Example 1 as an example
The measurement results are shown in FIGS. 9 and 10. FIG. 11 is a plot of differential values at each temperature based on the temperature dispersion of tan δ in FIG. 10. Using Figure 11, g
The temperature that gives (tan/δ)dt=1×10 − ” is determined. Examples 2 to 9 and Comparative Examples 1 to 4 were also determined by the same method.

The reproducibility of background stains, whisker-like transfers, and isolated dots is based on the following evaluation criteria.

Background stain ○ Almost no background stain △ There is background stain, but it can be used in practical use × There is a lot of background stain, and it is not practical × Beard-like transfer [Effects of the Invention] As is clear from the above results, according to the present invention, even in the double-density recording method, background stains and whisker-like transfer can be prevented, and the reproducibility of isolated dots is good. Print is obtained.

Dot reproducibility Good reproducibility of isolated dots There are some imperfections, but it can withstand practical use. Not practical Part 1 table

[Brief explanation of drawings]

FIGS. 1 and 2 are perspective views showing an example of a device using the thermal transfer material of the present invention, and FIGS. 3 to 6 are portions showing an example of using the thermal transfer material of the present invention for double-density recording. A side view, FIG. 7 is a diagram showing an example of DSC measurement results, FIG. 8 is a schematic sectional view showing an example of the thermal transfer material of the present invention, and FIGS. 9, 10, and 11 are diagrams showing dynamic viscoelasticity. FIG. 12, a graph showing an example of the measurement results, is an explanatory diagram of whisker-like transfer. ■・・・・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・Thermal transfer material 1a・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・Support ■ lb・ ・・・ ・・・・・・・・・・・・・・・・・・
......Thermal transferable ink layer 2...
・・・・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・
・・Recording medium 3・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・ Thermal head 4・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・
...Platen roller 5 ...
・・・・・・・・・・・・・・・Capstan roller 6
．． 7 ・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・
・・・・Motor 8 ・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・ Spring 10,・ ・・・・・・・・・・・・・・・
・・・・・・・・・ ・・・・・・・・・・・・ Winding reroller working hard Diagram of blind man

Claims (1)

[Scope of Claims] (1) In a thermal transfer material having a thermal transferable ink layer on a support, the storage elastic modulus E' at 30°C of the thermal transferable ink layer is 1×10^7≦E′≦1 ×10^9N/m^2,
and the temperature differential value d(
The temperature that gives tanδ)/dT=1×10^-^2 is 4
A thermal transfer material characterized by a temperature between 0°C and 60°C. (2) Claim (1) wherein the temperature giving the temperature differential value d(tanδ)/dT=1×10^-^2 of the mechanical energy loss angle tanδ is between 45°C and 55°C.
Thermal transfer material. (3) In a thermal transfer material having a thermal transferable ink layer on a support, the thermal transferable ink contains at least an ethylene-vinyl acetate copolymer, a wax, and a colorant, and the ethylene-vinyl acetate and the wax each contain A thermal transfer material characterized by satisfying the following conditions (a) and (b). (a) Ethylene-vinyl acetate copolymer melt flow rate (MFR) = 150 to 800 Vinyl acetate content = 15 to 33% (b) Wax DSC measurement melting point = 55°C to 80°C Melting behavior ΔT = 20°C or less ( 4) The thermal transfer material according to claim 3, wherein a weight mixing ratio of the ethylene-vinyl acetate copolymer and the wax in the thermal transfer ink layer satisfies the following formula. 0.3≦(ethylene-vinyl acetate copolymer)/(wax)≦4.7 (5) When the thermal transfer material according to claim (1) is used, the recording medium is moved against the recording head within the same time. 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 thermal transfer material moves relative to the recording head. (6) Using the thermal transfer material according to claim (2), the distance that the thermal transfer material moves relative to the recording head is greater than the distance that the recording medium moves relative to the recording head within the same time. A thermal transfer recording method characterized by a shorter length. (7) Using the thermal transfer material according to claim (3), the distance that the thermal transfer material moves relative to the recording head is longer than the distance that the recording medium moves relative to the recording head within the same time. A thermal transfer recording method characterized by a shorter length.