JPS63137891A - Thermal transfer ink sheet - Google Patents

Abstract

PURPOSE:To improve the thermal sensibility, thus forming a high quality image and to improve the ink transfer efficiency and the repeating life characteristic, by partially heating a thermally fusible ink by means of a heating print and liquefying said ink then pushing out through a through-hole and transferring onto a transfer sheet. CONSTITUTION:A portion of thermally fusible ink 5-1 filled in a thermally fusible ink layer 3 and a porous film 4 heated by means of a heating print is liquefied uniformly then flows through a hole 4-1 while being pressurized. Since the thermally fusible ink is held sufficiently on a base material 2, sufficient quantity 5-1t of thermally fusible ink is transferred onto a transfer sheet 9, thus providing a high reflection density. Since a smaller quantity of thermally fusible ink is held on a basic material 2 at a portion 5-2 when compared with the portion 5-1, the quantity 5-2t of ink layer to be transferred onto the transfer sheet 9 reduces as repeating times of print increases, thus reducing the reflection density. Furthermore, most of ink is consumed at a portion 5-3 where repeating time has increased, whereby the ink can be utilized efficiently without loss.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a thermal transfer ink sheet for use in a thermal printer or a thermal typewriter, and more particularly to a thermal transfer ink sheet that can be used many times.

[Prior art and its problems]

Conventional thermal transfer sheets have the following drawbacks because they have a structure in which a heat-melt ink layer consisting of a heat-melt binder and a coloring material is provided on a base film. That is, 1
It was a so-called one-time type thermal transfer sheet, in which almost no ink layer of the recording medium remained on the base film after two transfers, and only prints with uneven density were obtained after the second use. Therefore, the cost of obtaining records has increased. In addition, since printing marks are clearly left on the thermal transfer sheet side after only - times of printing, there is also a problem in terms of information maintenance. Against this background, studies are underway on heat transfer sheets that can be used repeatedly.

Conventional thermal transfer sheets that can be used repeatedly have a heat-sensitive transfer material structure in which a heat-resistant resin layer with a fine porous network structure is provided on a base film, and hot-melt ink is contained in the pores of the heat-resistant resin layer. (Japanese Unexamined Patent Publication No. 55-105579). The transfer material is attracting attention as a means for controlling the amount of ink transferred according to the magnitude of the energy applied to the heating element of the thermal head.

However, since there is a limit to the pore void ratio due to the durability of the porous layer that is the ink retainer, there is also a limit to the amount of ink that can be filled into the voids. For this reason, when the same amount of ink is held in a porous body, the ink sheet becomes bulkier than when it is not held, which is disadvantageous in terms of thermal sensitivity. Even if a high-density transferred image was obtained by applying high energy, a good print quality could not be obtained. Furthermore, the heat-melting ink heated by the thermal head did not completely transfer to the transfer object, leaving a problem in terms of efficient use of the ink.

On the other hand, as an improvement for efficient use of ink, a heat-melting ink layer is provided on the base film, and on the ink layer,
Furthermore, there is a proposal for a thermal transfer sheet provided with a porous film (Japanese Patent Application Laid-open No. 135294/1983).

In this transfer sheet, the thickness of the porous film is set to be thinner than the heat-melting ink layer, so after printing with the thermal head, the amount of ink retained in the porous body and remaining is small, and the ink is It is effective for efficient use. However, since the porous body is not filled with ink in advance,
Since unnecessary energy is consumed until the ink passes through the film, it is disadvantageous in terms of thermal response. In addition, since the thermal transfer sheet simply laminates media with different shrinkage stresses, it tends to curl and cause poor running during transportation.Furthermore, the adhesion between the ink surface and the porous material is insufficient, so printing In this case, destruction of the porous body may occur. In addition, increasing the amount of ink applied to improve the number of repetitions has the disadvantage that the ink layer easily peels off from the substrate.For this reason, in the case of a transfer sheet that can be used repeatedly, It has been confirmed that there are no.

[Problem that the invention seeks to solve]

In view of the above circumstances, the present invention aims to improve the conventional technology of the thermal transfer sheet as described above, and improves the thermal intensity of the thermal transfer sheet that can be used many times, and provides a thermal transfer sheet that can form high-quality images. It is an object of the present invention to provide an ink sheet, and also to provide a heat-sensitive transfer ink sheet that can be used many times and has improved characteristics regarding ink transfer efficiency and repetition life.

[Failure to solve the problem]

The heat-sensitive transfer ink sheet of the present invention has a heat-meltable ink layer that is solid at room temperature provided on at least a substrate via an adhesive layer, and is further provided with a polymeric ink layer having a porous structure filled with nuclear heat-meltable ink. This is a heat-sensitive transfer ink sheet having at least four layers, characterized in that it is formed by laminating holding layers. After placing the transfer paper facing the porous ink retaining layer filled with the heat-melting ink of the heat-sensitive transfer ink sheet, the heat-sensitive transfer ink is pressed from both the substrate and the back of the transfer paper using a pressing medium. A heating printing body that has means for generating thermal energy in response to an arbitrary image signal from the sheet base surface side partially heats the hot-melt ink to fluidize it, and prints the hot-melt ink through the through-holes. Push out the ink and transfer it to the paper to be transferred.

[Detailed description of the invention]

Hereinafter, in order to make the present invention more clear, the present invention will be described in detail with reference to the drawings.

FIGS. 1 and 2 are schematic cross-sectional views of an example of the structure of a thermal transfer ink sheet applied in the present invention. In FIGS. 1 and 2, 1 and IB are a heat-fusible ink layer 3 containing a coloring material 7 and a heat-fusible ink layer 3 containing a coloring material 7 on a substrate 2 via an adhesive layer 15, and a heat-fusible ink 5 in porous films 4 and 4B, respectively. 1 shows a thermal transfer ink sheet formed by laminating a porous membrane ink holding layer 6.6B filled with .5B. The cross-sectional shapes of the porous membranes 4 and 4B each have independent holes that penetrate to the heat-sensitive ink layer 3 and communicating holes that penetrate in a three-dimensional network.

The substrate 2 is a dense, thin, and smooth medium with high thermal conductivity.
A conventionally known substrate is used to prevent the hot-melt ink 3 from leaking from the substrate back surface 8-1 and to prevent contamination of the heated printed material and the like. - Examples include polymer films such as polyethylene, polypropylene, polyethylene terephthalate, and polyimide, or thin paper-like materials such as condenser paper, laminated paper, and coated paper. Considering the strength,
A thickness of 3 to 15 (μ) is suitable, but is not limited thereto. Furthermore, a heat-resistant treatment may be applied to the back surface 8 of the base 2, which faces the heat-meltable ink layer 3 and comes into contact with a heated printed body or the like.

An adhesive layer 15 is provided between the base 2 and the hot-melt ink layer 3, and this has the effect of preventing the hot-melt ink 3 from peeling off from the base 2. The thickness of the adhesive layer is 0.1~
Although it is possible to set it in the range of 5 (μm), when considering thermal sensitivity and adhesive strength, it is preferable to use it in the range of 0.3 to 2 (μm). Specific materials used for the adhesive layer 15 include polyethylene, crosslinked polyethylene, chlorinated polyethylene, ethylene-vinyl acetate copolymer, polyethylene terephthalate, polypropylene, polyisobutylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyvinyl alcohol, polyvinyl acecool,
Fluororesin, acrylic resin, polyacrylonitrile, polystyrene, acetal resin, polyamide, polycarbonate, cellulose plastic, styrene-acrylonitrile copolymer, acrylonitrile-butadiene
Styrene terpolymer, phenolic resin, urea resin,
Evoxy resin, unsaturated polyester resin, acrylic ester resin, alkyd resin, melamine resin, silicone resin, polyurethane, diallyl phthalate resin, polyphenylene oxide, polyimide, polysulfone, chlorinated rubber, hydrochloric acid rubber, cyclized rubber, polyisoprene, polybutadiene , styrene-butadiene copolymer, polychloroprene, nitrile rubber, butyl rubber, acrylic rubber, ethylene-propylene rubber, etc., and one or more of these may be used in combination. The adhesive layer 15 described above can be formed using a coating method such as true melt coating or solvent coating.

As the heat-melting ink N3 provided on the adhesive layer 15, a conventionally known heat-melting ink is used as is, and is composed of colorants, waxes, resins, oils, and the like. As a coloring agent, for example, in the case of pigment-based black, carbon black, oil black, etc. can be used, and in the case of color, Henjin Yellow, Rhodamine Lake B, etc. can be used.
Ordinary materials such as , fucrocyanine blue, etc. can be used. Of course, there is no particular restriction on the use of dyes depending on the purpose. Examples of waxes that can be used include paraffin wax, microcrystalline wax, carnauba wax, montan wax, Japanese wax, beeswax, low molecular weight polyethylene wax, and synthetic wax. As the resin, ethylene-vinyl acetate copolymer, polyamide resin, rosin derivative, petroleum resin, acrylic resin, polyester resin, etc. are used. Mineral oil, vegetable oil, etc. are used as the oil.

The heat-melting ink layer 3 is made by adding a colorant to the binder as appropriate.
It is mixed and dispersed to form a hot-melt, solvent-based, or water-based ink, and is formed using a gravure method, a roll rotor method, or a flexographic printing method.

On the other hand, on the heat-fusible ink layer 3 is a porous membrane ink retaining layer 6.6B in which a porous membrane 4.4B is filled with this ink 5.5B.
is laminated, but this porous membrane ink retention J! 16.
It is desirable that the thickness of ink 6B be set as thin as possible than the thickness of hot-melt ink N3 within a range that can maintain mechanical strength. This is because the porous membrane 4.4B has a mechanical durability, so there is a limit to the volume of the pores, and as a result, there is a limit to the amount of ink that can be filled into the pores. Therefore, if you try to fill the porous membrane 4.4B with more heat-melting ink, a bulkier porous membrane ink retaining layer 6.6B will be required, which will be disadvantageous in terms of thermal sensitivity, and high-speed recording will be required. Not only is it difficult to
This is because there are many disadvantages such as poor conveyance due to the thick film and a decrease in recording capacity due to a shortened recording length when wound around a ribbon core.

In order to improve the sensitivity, as mentioned above, 5.5B of heat-melting ink is held in the minimum necessary thin porous film 4.4B, and the amount of ink required for multiple transfers is reduced by the heat-melting ink in the underlying layer. It is more convenient to adopt a configuration in which ink is replenished from the ink layer 3. In this case, the thickness of the porous membrane ink retaining layer 6.6B is 0.
．． The effect of the present invention is exhibited within the range of 3 to 5 (μm). The thickness of the porous membrane ink holding N6.6B is 0.3 (μ
l11) If it is below, the mechanical strength is insufficient, so
The porous membrane will be damaged and will no longer function as an ink sheet that can be used many times.On the other hand, if the porous membrane is more than 5 (μm), the thermal sensitivity will decrease, making it difficult to obtain high-quality, high-density images. However, after being printed by the leisurely head, a large amount of ink remains retained by the porous membranes 4, 4B (there is also a problem in the efficient use of ink).

In addition, the porous membrane 4 constituting the porous membrane ink retaining layer 6.6B
．． The diameter range of the independent holes and the communicating holes of 4B depends on the minimum particle diameter of the heat-melting ink 3 and 5.5B and the size of the unit recording pixel of the thermal transfer printer. The minimum diameter of the pores is 0.5 (μ
m), the maximum diameter is preferably 160 (μm) or less, assuming that six heating elements are provided per cylinder. In addition, the void ratio of the porous membrane 4.4B when it is not filled with ink is 30 to 97% due to the balance between the mechanical strength of the porous membrane, the pixel density of the heating element, and the thermal sensitivity of the thermal transfer ink sheet. Set to range.

Furthermore, a limit is also placed on the volumetric filling rate of the heat-melting ink 5.5B held in the voids of the porous membrane 4.4B.

A state B in which no thermofusible ink 5.5B is held in the voids of the porous film 4.4B, that is, a state B in which the porous body is simply laminated on the thermofusible ink layer 3 (ink volume filling) 0%), curling is likely to occur because materials with different shrinkage stresses are simply laminated together, and the adhesion between the hot-melt ink layer 3 and the porous film 4.4B is not sufficient, so during printing, It has been recognized that the porous film is easily destroyed and cannot be put to practical use in the case of a heat-sensitive transfer ink sheet that can be used repeatedly.

When the voids in the porous membrane 4.4B are completely filled with the heat-fusible ink 5.5B (ink volume filling rate 100χ), the voids in the porous membrane are smaller than when the ink volume filling rate is 0%. Since no energy is required for the heat-fusible ink to penetrate, the thermal response is improved, and furthermore, the adhesive force between the heat-fusible ink layer 3 and the porous membrane 4゜4B is strengthened.
It becomes possible to obtain strength that can withstand many repetitions. Furthermore, the problem of poor conveyance due to curling is also improved.

The higher the volume filling rate of the thermofusible ink 5.5B into the voids of the pores #4.4B, the better, but the practical volume filling rate is set in the range of 3 to 100χ.

The amount of coating of the heat-fusible ink layer 3 that supplies the amount of ink necessary for performing multiple transfers depends on the number of repetitions required, but from the standpoint of practical energy sensitivity, it should be 0.
It is possible to set the coating amount in the range of 4 to 20 g/rrf, but when repeating 3 or more times and expecting high resolution and high density images, a coating amount of 2 to Log/rrr is preferable. , in this case, the heat-melting ink 5,5 to be laminated
When the thickness of the porous membrane ink holding layer 6.6B filled with B is thinner than the thickness of the heat-melting ink layer 3, the function of the heat-sensitive transfer ink sheet that can be used many times according to the present invention is maximized. becomes possible.

The polymer used for the porous membranes 4, 4B, which are the constituent components of the porous membrane ink retaining layer 6.6B, preferably has a heat-resistant temperature, that is, a softening temperature or melting temperature of 100'C or higher, and polyacetic acid Vinyl heptachloride-vinyl acetate copolymer, polyvinyl butyral, acrylic resin, polyamide, acrylonitrile-vinyl chloride copolymer, cellulose plastic, polyester, polyurethane, synthetic rubber, and mixtures thereof can be used. In order to improve suitability for printing or coating and improve apparent heat resistance, pigment particles such as calcium carbonate, titanium oxide, silicon oxide, zinc oxide, and carbon may be included as constituent components.
By selecting an appropriate solvent, non-solvent or anti-solvent, it is possible to use a composition exhibiting a slurry state.

The heat-sensitive transfer ink sheet of the present invention, which can be used many times, is produced by coating the polymer slurry on the heat-melting ink layer 3, and then using the difference in evaporation rate between a good solvent and a poor solvent to create a void that penetrates the sheet. It is obtained by obtaining a microporous structure having a crack, and then subjecting it to heat treatment and filling the porous membrane 4.4B with a heat-fusible ink 5.5B.

An embodiment of the thermal transfer recording method of the present invention will be described with reference to the drawings using the thus obtained thermal transfer ink sheet having at least four layers.

First, in FIG. 3, after placing the transfer paper 9 facing the porous ink retaining layer 6 of the thermal transfer ink sheet 1 as exemplified above, a heated printing body 10 and a rubber-like elastic material are formed on at least the surface thereof. Pressure roller 1 comprising 12-a
The pressure roller 12 inserted between the two and kept in a pressurized state may be one in which a rubber-like elastic body 12-a is provided on a support body 12-b, or it may be an integrally molded product.
The signal generated by
-a becomes fluidized by the heat propagated through the substrate 2, deforms under strong pressure, is pushed out through the pores 4-a of the porous membrane 4, and reaches the transfer paper 9. After that, the thermal transfer ink sheet 1 and the transfer paper 9 are conveyed by a portion of the conveying roller 13-.
Transfer image 5-b when peeled off at a and 13-b
can be obtained. In the above, continuous transfer is possible by rotating the pressure roller 12 in the direction of the arrow 14 while the heated print body 10 is generating heat.

Next, the principle of multiple use will be explained with reference to FIG.

In FIG. 4, the heated printed body and the pressure roller are omitted, but their positional relationship is as shown in FIG. 3.

In Fig. 4, 5-1.5-2.5-3 are schematic diagrams of the transfer form achieved when the same position on the thermal transfer ink sheet is printed with the same energy and the number of repetitions increases. This is an explanation.

First, the heat-melting ink layer 3 heated by the heated printing body
and 5-1 of the hot melt ink 5 filled in the porous membrane 4
The portion uniformly becomes a fluid state, and while being pressurized, the hole 4-a
It begins to flow. Since a sufficient amount of hot-melt ink is retained on the substrate 2, the transfer 1 to the transfer paper 9 is not possible.
5-It is also abundant, and high reflection density can be obtained.

Since there is less heat-melting ink held on the substrate 2 in the portion 5-2 than in the portion 5-1, as the number of printing repetitions increases, the amount of ink 5- transferred to the transfer paper 9 decreases. 2t decreases, indicating that the reflection density tends to decrease.

Furthermore, in the 5-3 section where the number of repetitions has increased, even the ink 5 that had been filled in the porous membrane ink retaining layer is transferred to the subject paper 9, and the ink in the 5-3 section of the thermal transfer ink sheet 1 is almost consumed. This shows that ink can be used efficiently and without waste.

〔Effect of the invention〕

Since the thermal transfer ink sheet according to the present invention has the above-mentioned structure, compared to the conventional one-time type transfer sheet,
It can be used many times and has improved mechanical resistance compared to conventional multi-use transfer sheet proposals, resulting in a stable repeated life. Due to its configuration, it has become possible to obtain high-quality, high-resolution images by applying low energy. As a result, we can expect a significant reduction in running costs as an added value.

〔Example〕

Examples and comparative examples of the present invention will be described below. Note that the present invention is not limited to these embodiments, and various modifications can be made without departing from the technical idea of the present invention.

<Example 1> On a polyethylene terephthalate film with a thickness of 6.0 (μm), a coating liquid for an adhesive layer shown in Treatment A was solvent coated using a gravure roll coater, and the dry film thickness was 1.0 (μm).
m) adhesive layer was provided.

(Treatment A) Ethylene-vinyl acetate copolymer: 5 parts by weight (manufactured by Diabond Kogyo Co., Ltd.) Toluene: 9si parts In addition, paraffin wax shown in Treatment B is mainly added. The roll surface temperature of the hot-melt ink material composition as an ingredient is 11
A hot melt ink was prepared by kneading it under heating in a three-roll mill heated to 0 ('C), and it was coated on the above adhesive layer using a flexographic printing method and heated to a temperature of 8 (μm). A meltable ink layer was provided.

(Decision B) Paraffin wax...60 weight 1 part (
Melting point 67℃) 1 Nippon Seiro Co., Ltd.) Carnauba wax...10 parts by weight (
Melting point 80 ('C), Nippon Seirosha) oxidized wax
...10 parts by weight (melting point 75 ('C)
), Nippon Tll Ro Co., Ltd.) Ethylene-vinyl acetate copolymer...5 parts by weight (Nippon Unicar Co., Ltd.) Carbon black...15 parts by weight (
(manufactured by Nippon Kayaku Co., Ltd.) Next, a coating liquid for a porous membrane protective layer was prepared using the material composition shown in Treatment C. This was coated on the hot-melt ink layer using a gravure roll coater to form a porous membrane protective layer having a thickness of 0.4 (μm).

Further heat treatment was performed to fill approximately 100% of the voids in the porous membrane with the heat-melting ink shown in Process B to form a porous membrane ink retaining layer to obtain a heat-sensitive transfer ink sheet of the present invention.

(Treatment C) Nitrocellulose (manufactured by Daicel Chemical Industries, Ltd.)
...10 parts by weight methyl ethyl ketone ...80 parts by weight water
...An electron microscope observation of the sheet obtained by 10 parts by weight revealed that the porous membrane pore diameter was 5 to 8 (μ
m) was distributed almost uniformly, and it was confirmed that the structure was such that a porous membrane ink retaining layer filled with the ink was laminated on top of the hot-melt ink.

The Hl % thermal transfer ink sheet was repeatedly printed on the same location using a commercially available handheld word processor for evaluation. As a word processor, NEC Bungo m1ni3B was used, the printing speed was set to standard mode, and the printing voltage was set to medium mode. Printed solidly on thermal transfer paper manufactured by Honshu Paper Co., Ltd., and measured the reflection density using Sakura Density System PDA-65 (
(manufactured by Konishiroku Photo Industry Co., Ltd.). As a result, as shown in Table 1, printing could be performed six times with no film peeling and little loss of density.

<Example 2> On a polyethylene terephthalate film with a thickness of 6.0 (μm), a gravure roll coater was used to apply a solvent coating solution for the adhesive layer shown in the procedure, and the dry film thickness was 1.0 (μm).
An adhesive layer of .mu.m) was provided.

(Decision D) Urethane resin (manufactured by Dainippon Ink Co., Ltd.)...5 parts by weight Toluene...95 parts by weight,
The heat-fusible ink material composition shown in Process E was heated and kneaded in the same manner as in Example 1, and coated on the adhesive layer by flexographic printing to form a heat-fusible ink layer of 8 (μII). has been established.

(Decision E) Ester wax...70 parts by weight (
Melting point 70 ("C), manufactured by Nippon Seirosha) Paraffin wax...10 parts by weight (melting point 67 ("C)
, Japan in Rousha) carbon black
...20 parts by weight (manufactured by Nippon Kayaku Co., Ltd.) Next, a coating liquid for a porous membrane protective layer was prepared using the material composition shown in Treatment F. This was applied on the hot-melt ink layer in the same manner as in Example 1 to form a porous membrane protective layer having a thickness of 0.4 (μm).

Further heat treatment was performed to form a porous ink retaining layer (volume filling rate of ink into the voids was approximately 100x) to obtain a thermal transfer ink sheet of the present invention.

(Decision F) Polyvinyl butyral...10 parts by weight (
(manufactured by Miki Kagaku Co., Ltd.) Methyl ethyl ketone...70 parts by weight Ethanol...10 parts by weight Water
...10 parts by weight This was repeatedly printed in the same manner as in Example 1 at standard mode speed and medium voltage. As a result, as shown in Table 1, printing with no film peeling and little loss of density was obtained six times.

(Comparative example) <Comparative example 1> Same as Example 2 except that the adhesive layer was not provided,
A heat-melting ink layer shown in Process E is provided on a 6 (μll) thick polyethylene terephthalate film as a substrate, and a coating liquid for a porous film protective layer shown in Process F is further applied to give a 0.4 (μll) thick polyethylene terephthalate film.
) A comparative sample was obtained by forming a porous membrane ink retaining layer having a thickness of . This was repeated in the same manner as in Example 1 at standard mode speed and medium voltage. As a result, after the fifth printing, film peeling occurred between the substrate and the heat-fusible ink layer, and a rapid decrease in density was observed. From the results of Example 2 and Comparative Example 1, in order to obtain a heat-sensitive transfer ink sheet with a more stable repeated life, it is necessary to provide an adhesive layer between the substrate and the heat-melting ink layer as shown in Example 2. is preferable (see Table 1) <Comparative Example 2> In the same manner as in Example 1 except that the porous ink retaining layer was not provided, a 6 (μm) thick polyethylene terephthalate film as a substrate was coated with the adhesive layer coating shown in Treatment A. The base adhesive layer is coated with a liquid and is further provided with a heat-melting ink layer as shown in the process.
A comparative sample with a three-layer structure consisting of a hot-melt ink layer was obtained.

This was repeated in the same manner as in Example 1 at standard mode speed and medium voltage. As a result, peeling occurs between the adhesive layer and the hot-melt ink layer, and all the ink is transferred in the first printing, making it a one-time product. It was found that the amount of ink printed on the transfer paper could not be fully controlled by simply providing this.

[Brief explanation of the drawing]

The drawings show examples of the present invention, and FIG. 1 is an explanatory diagram showing a cross section of the present thermal transfer ink sheet, and FIG. 2 is an explanatory diagram showing a cross section of the present thermal transfer ink sheet of another example. figure,
FIG. 3 is an explanatory cross-sectional view showing a recording method of a recording sheet using this sheet, and FIG. 4 is an explanatory cross-sectional view showing the recording principle when using this sheet shown in FIG. 1. 1. IB...Thermal transfer ink sheet 2...Base 3......Thermofusible ink layer 4.4B...
・Porous film 5.5B...Thermofusible ink 6.6B...Porous film ink retaining layer 7...Coloring material patent applicant Toppan Printing Co., Ltd. Representative Kazuo Suzuki Figure 2

Claims (1)

[Claims] 1) A heat-melting ink layer is provided on the substrate via an adhesive layer,
A heat-sensitive transfer ink sheet further comprising a porous ink-retaining layer filled with the heat-melting ink.