JPH0361583A - Thermal transfer material - Google Patents

Abstract

PURPOSE:To obtain a recording image having good reproducibility by preventing the sticking of an ink layer and a recording material, in a thermal transfer material used in a double-density recording method, by setting the melt viscosity of the ink layer at a specific temp. in a specific range and setting a specific relation between the thickness and the double-density of the ink layer. CONSTITUTION:In a thermal transfer material used in a double-density recording method, the melt viscosity of an ink layer at 120 deg.C is within a range of 1X10<3>-3X10<4> centipoise and the relation between the thickness (tmum) and double- density (n) of the ink layer satisfies formula 3n+4>=t>=3n-4 (wherein n is 10>=n>=2). When the thickness of the ink layer is less than that defined by the formula and the melt viscosity is less than 1X10<3>, for example, the density of a solid image having extremely high black ratio is lowered. When the melt viscosity is larger than 3X10<4>, density irregularity and sticking may occur easily. When the thickness of the ink layer is larger than that defined by the formula and the melt viscosity is less than 1X10<3>, printing collapse and resolving power inferiority may occur and, when he melt viscosity is larger than 3X10<4>, sticking, density irregularity and missing printing may occur.

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 that allows good recording to be obtained even if the amount of thermal transfer material used is reduced.

[Prior Art] In addition to the general features of thermal recording methods, such as the equipment used is lightweight, compact, noiseless, and easy to operate and maintain, the thermal transfer recording method also eliminates the need for colored processed paper. , which also has the feature of excellent durability of recorded images, 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).

Furthermore, an electrically conductive thermal transfer recording method is also known as one of the thermal transfer recording methods. This method involves applying a voltage to a conductive support or ink layer and causing the conductive support or ink layer itself to generate heat using Joule heat (Japanese Patent Laid-Open No. 58-2207
No. 95, Japanese Unexamined Patent Publication No. 58-12790, etc.), by transferring molten ink onto a recording medium, a transferred recorded image corresponding to the shape of heat supply is formed on the recording medium.

[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, making it disposable, resulting in high running costs, and the risk of leaking confidential information from the used thermal transfer material. There were also concerns about leaks.

On the other hand, as in Japanese Patent Application Laid-Open No. 57-83471 or Japanese Patent Publication No. 62-58917, a recording method reduces the amount of thermal transfer material used by providing a relative speed between the thermal transfer material and the recording medium. (hereinafter referred to as double density recording) has been proposed. However, this recording orientation has hitherto had a problem in that a transferred recorded image having a uniform print density cannot be obtained.

As a measure to maintain and stabilize this printing density, JP-A No. 62-1
As seen in No. 04794, it is stated that the thicker the ink layer of a thermal transfer film that can be printed multiple times, the more times the ink can be printed completely without adhering to the printing area, but it is more specific. The printing elasticity and number of printing times are not described. Furthermore, there is no description regarding obtaining a uniform concentration.

Furthermore, in the double-density recording method, the thermal transfer material must always move at a constant relative speed to the recording medium, and for this reason, the recording medium and the thermal transfer material are glued together by heat application, and cannot move at a relative speed. A problem of “stickiness” arose.

In addition, thermal transfer material is generally wound into a roll (called an ink roll), and since this is installed in a recording device, it is necessary to prepare Even if the density is specified, strictly speaking, the double density changes gradually. This is because even if the thermal transfer material is always fed out and wound up at the same number of rotations, the outer diameter of the ink roll changes, so the feeding amount of the thermal transfer material changes. For this reason, in conventional double-density recording, it is difficult to obtain recorded images with uniform density.

The present invention was made to solve the above-mentioned drawbacks, and even if the double density changes within a certain range, a homogeneous image density can be obtained.
A further object of the present invention is to provide a heat-sensitive transfer material that does not stick to a recording medium.

[Means to solve the problem]

The thermal transfer material of the present invention is used in a double-density recording method in which 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. The melt viscosity of the ink layer at 120°C is in the range of 1 x 103 to 3 x 10' centipoise,
and the thickness (t microns) and double density (n) of the ink layer.
The relationship is expressed by the following formula % Formula %) The present invention will be described below with reference to the drawings.

In addition, in the following description, "%" and "
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 heat-melting ink of the thermal transfer material 1 is transferred to the recording medium 2, and a recorded image is obtained. The thermal transfer material 1 and the recording medium 2 are continuously moved in the directions of arrows A and H 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 the motor 1
4, and the platen roller 12 is driven by a motor 15, respectively. The transported thermal transfer material l is wound up by a winding roller 10 driven by a motor 14. The motor 14 is set at a constant rotation speed and winds up the thermal transfer material l around the winding roller 10. The outer diameter of the take-up roller 10 is small at the initial stage of ink roll use, and becomes thicker at the stage near the end of use.The motor 14 is set at a constant rotation speed, so the outer diameter of the thermal transfer material is small. The speed of movement in the A direction is different between the initial stage and the stage near the end, and as a result, the double density changes. 16 is a spring that records on the platen roller 11 via the thermal transfer material 1 and the recording medium 2. This is for pressing the head 3.

In FIG. 1, the thermal transfer material 1 and the recording medium 2 are moving in the same direction, but for example, by conveying the recording medium 2 in the direction opposite to the direction of arrow B, the thermal transfer material 1 and the recording medium There is no problem even if the body 2 moves in the completely opposite direction.

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. 2 to 5.

As shown in FIG. 2, 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, the first heat application is applied to the completely unused thermal transfer material 1 with a width of l. This is done in terms of size (Figure 2). The heat-sensitive transfer material 1 is formed by providing a heat-melting ink layer 1b on a support la.

However, when heat is applied for the second time, the recording medium 2 is moving l in the direction of arrow B, while the thermal transfer material l is A/n (n is double density) with respect to the recording head 3. Then, the value of n=5゜n depends on how many times the same part of the thermal transfer material 1 can be printed.), so the CI! of the thermal transfer material I!
-(I!/n)), which has already been heated once, will be used again (FIG. 3).

When heat is applied continuously in the lateral direction in this way, the heat-sensitive transfer material that receives heat from the second time onwards has only 1/n unused, and the remaining parts are 1/n each a number of times. Otherwise, heat has already been applied (FIGS. 3 to 5). 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, in the second, third, etc. heat application, the thermal transfer material l is l/n relative to the recording head 3, respectively.
Although it is assumed that the movement is less than 1 and more than 1/n, the thermal transfer material 1 can be saved. The above n is 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. 1 to 5. That is, in the thermal transfer recording method of the present invention, the distance that the thermal transfer material l moves relative to the recording head 3 is shorter than the distance that the recording medium 2 moves relative to the recording head 3 within the same time.

More specifically, when forming a continuous dot image, it is ideal that an amount of ink with an ink thickness of t/n (t is the ink thickness and n is the double density) is always supplied at a constant rate.

However, as is clear from FIGS. 3 to 5, the feeding length of the thermal transfer material having the initial thickness is l! /n.

To further explain using FIG. 4 as an example, in order to obtain the third dot transfer image, the corresponding ink material of the thermal transfer material is 1-
The area of 21/n has received heat twice in the past, and once again.
Also, ink material is consumed for forming the second dot transfer image. Another 21 remaining! /n, l/n is 1
Ink material is consumed in applying heat twice and forming a transferred image on the second dot. The area that has not undergone any thermal history and has an initial ink thickness results in only l/n.

As described above, 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, there is a situation in which ink that has been heated up to n times is transferred to the recording medium. Furthermore, there may be situations in which the number of times of heat application history is different.

For example, if n = 5 and heat is applied for 4 consecutive dots, then 2 dots are applied without heat, and then 2 consecutive dots are applied for heat, the 1st dot of the last 2 consecutive dots is the ink of the 1st dot shown in Figure 2. The situation should be clearly different from that of . In other words, a different heat application history means a different melting state.

In addition, if the double density changes, the number of heat cycles and the area of newly supplied ink material (12/n in Figures 3 to 5) will also change, so it is necessary to always use the ink material during transfer. It is virtually impossible to control the thermal melting state to a constant state.

In particular, in this method, the ink material must be divided in the thickness direction in a thermally molten state, and "sticking" will occur if the ink material is not properly divided.

Although this recording method has been explained in detail above, in practice it cannot necessarily be understood as simply as the above explanation.

However, it will be understood that the thickness, double density, and melt viscosity of the ink layer are extremely closely related to print density, uniformity of print image density, and poor runnability due to sticking.

Now, as is clear from the above explanation, the ink layer of the thermal transfer material 1 of the present invention has a melt viscosity of IX at 120°C.
103~3 X 10'cPoise, 1.5
More preferably Xlo3 to 2X10'cPoise.

Furthermore, the relationship between the thickness (t microns) of the ink layer and the double density (n) satisfies the following equation.

3n+4≧t≧3n-4 (however, 10≧n≧2) In this relational expression, for example, when n=2, the thickness of the ink layer is 2 to 1
Oμ, 11~19μ when n=5, 26~ when n=10
It becomes 34μ.

1. When the thickness of the ink layer is thinner than the above relational expression, 1.
-a) When the melt viscosity is less than 1xlo', a large amount of ink is transferred with one heat application, and only a small amount of ink is transferred with the second and subsequent heat applications, for example, a solid image with an extremely high black ratio. concentration will decrease.

1-b) When the melt viscosity is in the range of 1XIO3 to 3X10', the situation of 1-a) above is less likely to occur, but
Overall reflection density is insufficient.

1-c) When the melt viscosity is greater than 3×10', density unevenness occurs, probably because it becomes difficult to control the amount of ink transferred. Furthermore, sticking becomes more likely to occur.

2. When the thickness of the ink layer satisfies the above relational expression, 2.
-a) When the melt viscosity is less than lXl0'', 1-a
), the concentration tends to decrease as well.

2-b) When the melt viscosity is in the range of 1.times.IO3 to 3.times.10', density, density unevenness, sticking, crushing, etc. do not occur, and an overall preferable recorded image can be obtained.

2-c) When the melt viscosity is greater than 3×10 4 , not only density occurs, but also sticking tends to occur, resulting in missing prints due to poor feeding of the thermal transfer material.

3. When the thickness of the ink layer is thicker than the above relational expression, 3.
-a) When the melt viscosity is less than 1×1O3, printing density and density unevenness are unlikely to occur, but a single application of heat transfers an extremely large amount of ink, making it impossible to express fine patterns, so-called “printing”. This results in "blurring" and "poor resolution," resulting in extremely poor print or image quality.

3-b) When the melt viscosity is in the range of 1xlO3 to 3xlO', the image quality deteriorates as in 3-a) above, and a large amount of ink remains on the support, resulting in a large amount of ink material being wasted. c) When the melt viscosity is greater than 3 x 10', sticking occurs significantly, resulting in not only density unevenness but also missing prints due to poor feeding of the thermal transfer material, and ribbon breakage or sheet breakage due to inability to feed.

Increasing the applied thermal energy may be considered as a solution to the above-mentioned feeding failure phenomenon, but this increases damage to the support, which is undesirable because image quality is likely to deteriorate or a sticking phenomenon occurs.

Regarding the relationship between double density and melt viscosity, if the double density is low, it can be used up to the area where the melt viscosity is relatively high in the above range, and when the double density is high, it can be used in the area where the melt viscosity is relatively low in the above range. It can be used up to

Next, if you plot the relational expression between double density and ink layer thickness on a graph, it will look like Figure 6, where the diagonal line range is 30 + 4.
The range satisfies ≧t≧3n-4.

In the above, the melt viscosity is a value measured using an E-type viscometer (Harke Roto Visco RV-12-Nobuta Roku PK-D0.3).

In the thermal transfer material of the present invention, the ink layer is a mixture of a binder and a coloring material. Materials used for the binder include ethylene-vinyl acetate copolymer, which has film properties and softens/melts well when heat is applied.
Alternatively, ethylene-ethyl acrylate copolymer is preferred. Among these, ethylene-vinyl acetate copolymer is preferred. The copolymerization ratio of ethylene and vinyl acetate is 90, 10
~50: 50 is good, softening point (ring and ball method) is 70-1
Ethylene-vinyl acetate copolymers in the range of 30°C, more preferably 50-too°C are preferred. The copolymerization ratio of ethylene and ethyl acrylate of the ethylene-ethyl acrylate copolymer is preferably 90:10 to 65.35, and the softening point (ring and ball method) is 70 to 130°C, more preferably 85 to
A temperature range of 100°C is preferred.

If most of the binder is composed of ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer, the melt viscosity will be increased and the breaking strength of the ink layer will also be increased. Therefore, carnauba wax and montan wax are used to adjust the melting viscosity of the ink layer and the breaking strength of the ink layer.

Natural waxes such as linole wax, synthetic waxes such as paraffin wax, microcrystalline wax, castor wax, polyethylene wax, Sasol wax, and their derived waxes.

One or two types of waxes selected from ester wax, polyethylene wax, polypropylene wax, etc.
It is preferable to mix a mixture of waxes with the binder.

The content of ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer in the binder is
40 to 70% by weight, more preferably 45 to 6% by weight based on the binder
5% by weight is preferred. In addition, the wax content is 30
-60% by weight, more preferably 35-50% by weight.

Further, the binder may contain a tackifier so that the ink layer firmly adheres to the 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, hydrogenated rosin triethylene glycol ester, hydrogenated rosin pentaerythritol ester, polymerized rosin ester, aliphatic petroleum resin, alicyclic One type or a mixture of two or more types selected from group petroleum resins, synthetic polyterpenes, pentadiene resins, etc. are used.

When the binder contains tackifier, the content of tackifier is preferably 5 to 15% by weight, more preferably 7 to 12% by weight, based on the binder.

Examples of colorants include carbon black, nigrosine dye, lamp black, Sudan Black SM, Fast Yellow 61 Benzine Yellow Pigment Yellow,
Indofast Orange, Irgazine Red, Varanitroaniline Red, Toluidine Red, Carmine F
B, Permanent Bordeaux FRR, Pigment Orange R1 Resole 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.

Conventional coloring agents such as Kayaset Y963, Sumiplast Yellow GG, Zapon Fast Orange RR, Oil Scarlet, Sumiplast Orange G1 Orazole Brown G1 Pomelo Fast Scarlet CG, Fastgen Blue 5007, Sudan Blue, Oil Peacock Blue, etc. Use seeds or a mixture of two or more.

The amount of colorant contained in the ink layer is preferably 5 to 40% by weight, more preferably 10 to 35% by weight based on the entire ink layer.
is desirable. If the amount of coloring material is less than 5% by weight, the density of the recorded image will be extremely low, and if it exceeds 35% by weight, the recording energy will increase, the breaking strength of the ink layer will decrease, or the transferability to the recording medium will decrease. This is undesirable because problems such as a decrease in

Furthermore, in the present invention, it is well known that depending on the type of binder, the amount of coloring material may be relatively small to make the ink layer slightly thicker, or conversely, the amount of coloring material may be relatively increased to make the ink layer slightly thinner. The amount of the material is preferably 0 to 35% by weight.

Conventionally known plastic films and paper can be used as the base material, but in double-density recording, heat is applied many times to the same location on the base material, so for example, aromatic polyamide film, polyphenylene sulfide film, polyamide Preferably, materials with high heat resistance such as ether ether ketone 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. 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.

In producing the thermal transfer material of the present invention, the 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, for example, by sand milling, etc. 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.

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.

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

After mixing the above materials in a ball mill, the thickness is 6 μm.
A heat-sensitive transfer material was obtained by coating a PET film with a width of 260 mm using a Meyer bar so that the dry coating weights were as shown in Table 1 for each of the Examples and Comparative Examples.

In addition, the surface opposite to the ink-coated surface of the polyester film is coated with a silicone-acrylic-9127 tertiary copolymer back treatment agent in advance so that the dry coating type fi is 0.3 g/rrr. It was used.

The melt viscosity of the ink layer was also measured and the results are shown in Table 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 mechanical and physical conditions of this device are as follows.

(1) Equipped with a full multi-thermal head of 8 pel/mm and 1 kg/c against the platen roller.
rr? is fixed with pressure.

(2) The feeding amount of the thermal transfer material can be varied from 1/l to 1/10 compared to 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 energy of the thermal head is 22mJ
/m-.

A heat-sensitive transfer material was prepared using the above material in the same manner as in Example 1, and the melt viscosity of the ink layer was measured. The results are shown in Table 1.

(Salt 1 lower margin) Tsuji "L Inverted 2-1" A heat-sensitive transfer material was prepared in the same manner as in Example 1 using the above materials, and the melt viscosity of the ink layer was measured. The results are shown in Table 1.

A heat-sensitive transfer material was prepared in the same manner as in Example 1 using the above materials, and the melt viscosity of the ink layer was measured. The results are shown in Table 1.

5/-〉, l \ (Hereinafter 'margin → 1E Example'-11 Using the above materials, a heat-sensitive transfer material was prepared in the same manner as in Example 1, and the melt viscosity of the ink layer was measured. Results first
Shown in the table.

Using the above thermal transfer material, the image of the Institute of Image Electronics Engineers facsimile test chart No. 12 is transferred to plain paper (10, TRW-IA manufactured by Jo Paper Co., Ltd., Beck smoothness 220 seconds).
It was output to .

The evaluation items are as follows.

Print density: The reflection density of the part 1 of the test chart with no density unevenness was measured using a Macbeth densitometer RD-100.

○: 1.0 or higher

○: The image is homogeneous with almost no streaks. ×: There are streaks and the image cannot be said to be homogeneous. Stickiness: Is there a white streak in the main scanning direction in the country part of the test chart? .

○: No white streaks. Shown in the table.

Table 1 [Effects of the Invention] As explained above, according to the thermal transfer material of the present invention, the ink layer and the recording medium are easy to separate without sticking at any double density, and the print density is uniform. A clear recorded image with good reproducibility of fine lines can be obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of an apparatus using the thermal transfer material of the present invention, and FIGS. 2 to 5 are partial side views showing an example of using the thermal transfer material of the present invention for double-density recording. FIG. 6 is a plan view showing the relationship between the double density (n) and the thickness (microns) of the ink layer according to the present invention. 1...Thermal transfer material 2...Recorded object 3...Recording head 3a...Mature body

Claims (3)

[Claims] (1) When a thermal transfer material having a thermally transferable ink layer and a recording medium are overlapped, 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 material used in a double-density recording method in which the distance traveled by the ink layer is shorter than that of the ink layer; A thermal transfer material characterized in that the relationship between thickness (t microns) and double density (n) satisfies the following formula. 3n+4≧t≧3n-4 (however, 10≧n≧2) (2) The ink layer has a binder and a colorant, and the binder contains 40% of ethylene-vinyl acetate copolymer.
The thermal transfer material according to claim 1, which contains wax in an amount of 30 to 60% by weight. (3) Add 5 to 1 tatsuki fire in the binder.
The thermal transfer material according to claim (2), containing 5% by weight.