JPH02227295A - Dye sublimation thermal transfer recording media - Google Patents

Abstract

PURPOSE:To obtain a thermal transfer recording medium which prevents a transferred image density from becoming reduced due to an increase in printing frequency without dropout of recorded data or irregularities by laminating antistatic layers of resin containing an antistatic agent on the rear of a base. CONSTITUTION:A thermally transferable recording medium consists of an ink layer 2 which is composed of a dye supply layer 4 and a dye transfer contributing layer 5 and an antistatic layer 3 formed on a base 1. The antistatic layer is formed with a mixture of an antistatic agent kneaded into resin as a binder. This antistatic layer is dispersed in an organic solvent in which resin as a binder is dissolved. The antistatic layer is 0.1 to 5mum, but the mixture ratio of the binder and the antistatic agent is determined so that the surface resistivity after application and drying is 1X10<10>OMEGAcm or less. In addition, the dye supply layer and the dye transfer contributing layer are formed on the base as independent layers by using the same amount of the mixture for both layers, then these layers are placed together with another image-receiving layer respectively and the same amount of thermal energy is applied to them. In this case, the amount of dye transferred to the image-receiving layer should be in the relationship of the dye supply layer the dye transfer contributing layer. Consequently, an image is obtained which does not decrease its printing density however much frequently data is printed and is free from any dropout of recorded data or irregularities.

Description

[Detailed description of the invention] Transfer of delivery The present invention relates to a sublimation type thermal transfer recording medium.

]q (4) In recent years, the demand for full-color printers has increased year by year, and the recording methods for these full-color printers include electrophotography,
There are inkjet methods, thermal transfer methods, etc., but among these, the thermal transfer method is often used because it is easy to maintain and is noiseless.

This thermal transfer consists of a solidified color ink sheet and an image receiving paper, and images are formed by thermally melting transferring or sublimating the ink onto the receiving paper using thermal energy controlled by electrical signals from a laser or thermal head. This is a recording method that allows

This thermal transfer recording method can be roughly divided into the above-mentioned heat-melting transfer type and sublimation transfer type. In the latter, in principle, the sublimation dye is sublimated in a monomolecular form in response to thermal energy from a thermal head, etc. This method has the advantage that halftones can be easily obtained and the gradation can be controlled at will, and is considered to be the most suitable method for full-color printers.

However, this sublimation transfer recording method uses a color ink sheet as a recording supply and selectively performs heating recording based on image signals. This method has the drawback that running costs are high because one ink sheet is used, and even if there is an unused portion, it is discarded.

Therefore, we are currently focusing on this drawback, and in an attempt to improve this drawback by using the ink sheet many times, we have developed a constant velocity mode method in which the ink sheet and image receptor are moved at a constant speed and used repeatedly, and the traveling speed of the ink sheet. An N-fold mode method has been proposed in which the overlapping portions of the first and second used portions of the coloring material layer are slightly shifted at a slower rate than that of the image receptor.

However, in the sublimation thermal transfer recording method, sublimation and evaporation reactions are basically zero-order reactions, and in constant velocity mode, even though the ink layer contains a sufficient amount of dye to withstand multiple uses, As the number of printing increases, the transfer density, especially in high image density areas, rapidly decreases, making it virtually impossible to print multiple times.

Therefore, the present inventors proposed a sublimation type heat-sensitive transfer recording medium with a laminated structure in Japanese Patent Application No. 63-62866.
Between the dye supply layer and the dye transfer contributing layer, the dye release ability is changed to "dye supply layer>dye transfer contributing layer'', thereby improving the density loss caused by multiple recordings.

On the other hand, as the quality of multiple recordings improves, the drawbacks caused by static electricity have become more noticeable. for example.

Dust is attracted by the electrostatic attraction generated by the running and friction of the sheet, and dust adheres between the thermal transfer sheet and the receiving paper, or between the thermal head and the thermal transfer sheet, resulting in missing records (partial recording loss). There are problems such as failure of recording), damage to the elements of the thermal head, sagging of each sheet, poor running, etc., and these problems are particularly serious in a multiple-time system such as the present invention.

1-The present invention does not cause a rapid decrease in transfer density even with an increase in the number of printings, eliminates the above-mentioned drawbacks due to electrostatic attraction, and has smooth running with less recording omissions and unevenness. The purpose is to provide a sublimation type thermal transfer recording medium.

(2) The present invention provides a sublimation thermal transfer medium in which a dye supply layer and a dye transfer contributing layer each comprising a sublimable dye dispersed in an organic binder are laminated on a substrate in order from the substrate side, The sublimation type thermal transfer recording medium is characterized in that an antistatic layer made of a resin containing an antistatic agent is thinly laminated on the back surface of the substrate.

The sublimation type thermal transfer recording medium of the present invention has a structure as shown in FIG. Here, 1 indicates the base of the recording medium, and 2
3 indicates an ink layer consisting of a dye supply layer 4 and a dye transfer contributing layer 5, and 3 indicates an antistatic layer.The image receiver consists of a substrate 8 and an image receiving layer 7.

The antistatic layer is provided to facilitate the release of charges generated on the thermal transfer sheet due to charging during handling of the thermal transfer sheet, and may be formed using any electrically conductive material. However, it is usually formed using a mixture of a so-called antistatic agent kneaded into a resin.

As an antistatic agent, a cationic surfactant (for example, a quaternary surfactant) is used.
ammonium salts, polyamine derivatives, etc.), anionic surfactants (e.g., alkyl phosphates, etc.),
Amphoteric ionic surfactants (for example, betaine type surfactants) or nonionic surfactants (for example, fatty acid esters) can be used, and polysiloxane surfactants can also be used. In relation to the above-mentioned antistatic agents, amphoteric ionic surfactants, cationic water-soluble acrylic resins, water-soluble polystyrene resins, etc. can be used alone as a paint without a binder.

An antistatic layer can be obtained by forming a coating film with a dry coating weight of about 0.1 to 2 g/rf.

Such a water-soluble resin is preferable because it does not affect the coloring material layer of the thermal transfer layer (which comes into contact with the antistatic layer when stacked or rolled) and dissolves the dye even at high temperatures.

On the other hand, there are also inorganic fine powders that have excellent electronic conductivity.1 For example, doping fine powders such as titanium oxide or zinc oxide (mixing impurities with titanium oxide or zinc oxide and baking it to form a crystal lattice of titanium oxide or zinc oxide) A fine powder of tin oxide or the like can be used.

The above-mentioned antistatic agent is used by being dissolved or dispersed in an organic solvent in which a resin to be a binder is dissolved.

The resin to be the binder is (a) a thermosetting resin, such as a thermosetting polyacrylic acid ester resin or a polyurethane resin, or (b) a thermoplastic resin, such as a polyvinyl chloride resin, a polyvinyl butyral resin, or a polyester resin. Resins selected from , etc. are preferable.

The prepared conductive paint is generally coated using a conventional coating method, such as a blade coater or a gravure coater, or may be spray coated.

The thickness of the antistatic layer is 0.1 to 5 μm, preferably 0.1
~3μm, and the surface resistivity of the antistatic layer after coating and drying (after curing in some cases) is 1×101′′ΩcI
The ratio of binder and antistatic agent is determined so that it is 11 or less. Note that the amphoteric ion type or cation type water-soluble acrylic resin can also be made into an alcohol solution, added as an antistatic agent to the binder in an amount of 5 to 30% by weight as a solid content, and used as a paint.

The antistatic layer may contain a release agent or filler, if necessary.

The dye supply layer and the dye transfer contribution layer were each formed as a single layer on the substrate with the same amount of adhesion according to each formulation, and each of them was overlapped with a separate image receiving layer, and the same thermal energy was applied to both. At this time, the amount of dye transferred to each image-receiving layer is in the relationship: dye supply layer>dye transfer contributing layer.

Thermal transfer may be performed by a thermal head, or may be performed by electrical transfer by adjusting the support layer and/or ink layer to generate Joule heat by applying electricity.

Furthermore, it is also possible to utilize a laser transfer method by selecting a material that absorbs laser light and generates heat as the support.

According to the knowledge of the present invention, the diffusion of the dye in the ink layer is based on Fick's law. When it is taken as the average diffusion coefficient of each part in the ink layer when heat is applied.

The relationship dn = -75(dc/dx)qdt applies.

Therefore, as a means for facilitating the diffusion and supply of the sublimable dye from the dye supply layer to the transfer contributing layer.

1. Concerning the dye concentration, there is a means to establish the relationship of dye supply layer>transfer contribution layer, and/or 2. Concerning the diffusion coefficient in each layer, there is a means to establish the relationship of dye supply layer>transfer contribution layer. Furthermore, regarding the above-mentioned (2), as a specific method for manipulating the diffusion coefficient, for example, Toyoko Sakai et al. Na12 (1974); Nobuhiko Kuroki, [Dyeing Theoretical Chemistry], published by Maki Shoten, p. 503-: Introduced in the 1st Non-Impact Printing Technology Symposium Proceedings 3-5, etc. Referring to these,
Specific methods for realizing the above means (1) include: (1) Since the diffusion coefficient is influenced by the energetic suppression effect on dye diffusion due to hydrogen bonds between the dye and the organic binder, A method of using an organic polymer material having a large number of proton-donating groups or proton-accepting groups that easily form hydrogen bonds with sublimable dyes as a binder; (2) the diffusion coefficient is
The diffusion coefficient is dependent on the glass transition or softening temperature of the organic binder in which the dye is dispersed, and the diffusion coefficient is higher when the glass transition or softening temperature is lower than the temperature rise characteristic of the layer during printing in this process. As an organic binder in the supply layer,
(3) A method using a substance having a lower glass transition temperature or lower softening temperature than that of the transfer contributing layer; (3) a substance that is compatible with at least one organic binder in the dye supply layer and that Examples include a method in which a plasticizer that is incompatible with the organic binder is contained in the dye supply layer, and (4) a method in which the above methods (1), (2), and (3) are appropriately combined. However, as long as the above diffusion coefficient relationship is satisfied, the method is not limited to these methods.
Needless to say.

In designing the material formulation of the dye supply layer and the transfer contributing layer in the present invention, the above measures 1 and/or 2 are useful, and it is easy to confirm whether or not the intended improvement is realized by these effects. As a method, when the dye supply layer and the transfer contribution layer are each formed in the same amount as a single layer on the substrate, each layer is overlapped with a separate image receiving layer, and a certain sublimation temperature is applied, sublimation occurs. There is a method of selecting each layer such that the transfer amount satisfies the following relationship: dye supply layer>transfer contribution layer.

Next, the thickness of the transfer contributing layer is generally 0.05 to 5 μm, preferably 0.1 to 2 μm. The thickness of the dye supply layer is generally 0.1 to 20 μm, preferably 0.1 μm to 20 μm.
It is a 5-10μ grave.

Further, known sublimable dyes, binders, etc. used in the transfer contributing layer and dye supply layer of the present invention can be used.

Sublimable dyes are dyes that sublimate or vaporize at temperatures above 60°C, and are mainly disperse dyes, oil-soluble dyes, and other dyes used in thermal transfer printing.For example, C, 1, disperse yellow 1.3 ,8゜9.16,41,54,
60, 77.116, etc., C, 1, Dispersed thread 1.4, 6, 11, 15, 17, 55, 59, 60,
73.83 etc., C, 1, Disperse Blue 3.1
4,19,26,56,60゜64.72,99,10
8 etc., C, 1, Solvent Yellow 77.116
C,1, solvent red 23.25.27, C,1, solvent blue 36.83,105, etc., and these dyes can be used as a type of dye.
It is also possible to use a mixture of several types.

Thermoplastic or thermosetting resins are used as binders for the dye transfer contributing layer and the dye supplying layer, and among them, resins with relatively high glass transition points or high softening properties include:
For example, vinyl chloride resin, vinyl acetate resin, polyamide, polyethylene, polycarbonate, polystyrene, polypropylene, acrylic resin, phenol resin, polyester, polyurethane, epoxy resin, silicone resin, fluorine resin, butyral resin, melamine resin, natural rubber, synthetic rubber. , polyvinyl alcohol, cellulose resin, etc.

These resins can be used alone, but several types may be mixed or a copolymer may be used.

Furthermore, when creating a difference in glass transition or softening temperature between the dye transfer contribution layer and the dye supply layer, resins or natural or synthetic rubbers with a glass transition temperature of 0°C or less or a softening temperature of 60°C or less are preferred, and specific Syndiotactic 1,2-polybutadiene (commercially available JSRRB810, 820, 830 Japan Synthetic Rubber)
; olefin copolymers and terpolymers containing acids or non-acidic acids (commercially available as Dexon XEA-7, Dexon Chemical); ethylene-acid picopolymers (commercially available as 400 & 400A, 405.430, Allied Fibers &Plastics; P-3307 (EV150
), P-2807 (IliV250), DuPont Polychemicals); low molecular weight polyolefin polyols and their derivatives (Polynal H1HE Mitsubishi Chemical Industries, Ltd. as commercial products); brominated epoxy resins (YDB-340,
400, 500, 600 Tsukuto Kagaku); Novolac type epoxy resin (YDCN-701, 702, 703 Tobu Kagaku);
1075, 1080, 1081, 1082, 1063,
1079 Mitsubishi Rayon); Thermoplastic acrylic emulsion (LX-400, LX-450, Mitsubishi Rayon): Polyethylene oxide (Alcox E-30, 45,
Alcox R-150, 400, 1000 Meisei Chemical Industry); Caprolactone Boriol (Plaxel) l-1
, 4, 7, Daicel Chemical Industries); and the like are preferred, and polyethylene oxide and polycaprolactone polyols are particularly useful for practical purposes, and the above-mentioned thermoplastic or thermosetting resins are mixed with one or more of the above. It is preferable to use it in this form.

The dye concentration of the transfer contributing layer is usually 5 to 80%, preferably
It is about 10 to 60%.

Further, the dye concentration in the dye supply layer is preferably 5 to 80%, but when creating a dye concentration gradient between the dye transfer contribution layer and the dye supply layer, the dye concentration in the dye transfer contribution layer is 1%. .1 to 5 times.

Preferably, it is 1.5 to 3 times.

In order to continue supplying the dye stably for a long time and maintain good printing characteristics, it is preferable that the dye supply layer contains at least undissolved particulate sublimable dye. When forming the ink layer, the ink (organic binder + sublimable dye and solvent) was applied and dried, but it was not completely dissolved in the organic binder.

It refers to dyes that precipitate in the form of particles, and even if the binder and dye are the same, the presence of undissolved particulate dyes differs depending on the solvent. The presence or absence of undissolved particulate dye can be easily identified by electron microscopy after the dye supply layer is formed. The particle size of the undissolved particulate dye varies depending on the layer thickness of the dye supply layer, but is 0.
The range is from 01μ to 20μ, preferably from 1.0μ to 5μ.

In addition, the state of the dye in the dye transfer contribution layer is dispersed in a monomolecular form that actually contributes to transfer, which prevents uneven transfer density and prevents the dye from forming between the dye supply layer and the dye transfer contribution layer. This is desirable because it keeps the concentration gradient stable.

Further, as the base sheet, films such as condenser paper, polyester film, polystyrene film, polysulfone film, polyimide film, polyamide film, etc. are used, and a conventional adhesive layer is provided between the base sheet and the dye supply layer as necessary. Furthermore, a conventional heat-resistant lubricant layer may be provided on the back surface of the base sheet, if necessary.

There is no way to prevent the sublimable dye from being supplied from the dye supply layer of the thermal transfer body to the dye transfer contribution layer during recording, and from the dye supply layer of the thermal transfer body during non-recording (during storage) to the dye transfer contribution layer or its surface. An intermediate layer may be provided between the dye supply layer and the dye transfer contributing layer in order to prevent migration of the sublimable dye.

Furthermore, in order to prevent background smearing, a layer such as the above-mentioned intermediate layer or a layer for preventing fusion with the image-receiving layer may be formed on the dye transfer contributing layer to an extent that does not cause a decrease in sensitivity.

The plasticizer contained in the dye supply layer in the above method (3) enters between the molecules of the resin, weakens the van der Waals bond that is the cause of the hard network structure of the resin, and as a result, the plasticizer that is contained in the dye supply layer It is a substance that lowers the transition point, and compatibility is defined as that the resin and plasticizer have affinity for each other, that the gelation rate is fast, and that the plasticizer does not separate even after molding.

In addition, specifically, books, literature, catalogs, etc. that mention plasticizers, taking into account the compatibility between plasticizers and resins,
For example, Yamada Adhesive, ``Plastic compounding agent'' (published by Taiseisha, p. 17-) and ``Chemical products of R9887'' (published by Kagaku Kogyo Nippo, p.).

745-) etc. can be freely selected from those described in .

Examples of these include the combinations shown in the table below.

(Left below) In these combinations, the resin compatible with the plasticizer is used in the dye supply layer, and the resin incompatible with the plasticizer is used in the transfer contribution layer. or,
Preferred plasticizers are those listed in the above table that have excellent heat resistance and volatility, and the blending ratio of the plasticizer to the resin is 10 to 100%, preferably 10 to 50%.

Up until now, we have described an example in which the dye layer is divided into two layers, but
If an appropriate difference in the amount of dye transfer is created and the functional separation as intended by the present invention can be achieved, it is possible to form the dye layer into a multilayer of two or more layers.

Although the above description has been made with reference to a recording method using a thermal head, the transfer medium of the present invention can also be applied to a recording method in which recording thermal energy is applied by a method other than a thermal head, for example.
It can also be used for methods using Joule heat generated in a medium such as a thermal printing plate, laser light, or a support.

Of these, Joule heat generated in the medium is used. The so-called electric heat-sensitive transfer method is the most well-known, for example, USP 4,1
03,066, Japanese Patent Publication No. 57-14060. Japanese Unexamined Patent Publication 1987-
11080, or Japanese Patent Application Laid-Open No. 59-9096.

When used in this current transfer method, polyester, polycarbonate, triacetyl cellulose, and nylon, which have relatively good heat resistance, are used as a support.

Metal powders such as aluminum, copper, iron, tin, zinc, nickel, molybdenum, silver, and/or conductive powders such as carbon black are dispersed in resins such as polyimide and aromatic polyamide to change the resistance value to an insulator and a good conductor. The thickness of these supports should be adjusted in consideration of the Joule heat conduction efficiency. Then, it is desirable that the thickness is about 2 to 15 microns.

In addition, when using the laser beam transfer method, it is only necessary to select a material that absorbs laser light and generates heat as the support. For example, a conventional thermal transfer film may contain a light absorption heat conversion material such as carbon, or A support with absorbent layers formed on the front and back surfaces is used.

EXAMPLES Hereinafter, the present invention will be explained in more detail based on the following examples, but the present invention is not limited thereto.

Example 1 An 8.5 μι polyimide film (manufactured by Toshi Dubon) was used as the substrate 1, and a mixed solution of the following formulation was applied as an antistatic layer onto this using a wire bar to a thickness of 0°5μ layer. It was dried at 100° C. for 1 minute to form an antistatic layer 3.

Weight part water ethanol Next.

Part by Weight Solvent: Toluene Methyl Ethyl Ketone In the above formulation, the dye supply layer formulation uses 20 parts by weight of the above sublimable dye, and the dye transfer contributing layer formulation uses 10 parts by weight, and the respective compositions are ball milled for 24 hours. It was dispersed at

Next, a sublimation type heat-sensitive transfer medium having the structure shown in FIG. 1 was prepared as follows.

After coating the ink for the dye supply layer 4 in the ink layer 2 to a thickness of 2.40 μm using a wire bar on the opposite side of the polyimide film on which the antistatic layer was provided, the ink layer 2 was further applied on top of it. The ink for the dye transfer contribution layer 5 inside is 0.
．． 61μ! 1 coating and drying to produce a sublimation type thermal transfer recording medium.

(The following is a blank space) Example 2 A sublimation type thermal transfer medium was formed in the same manner as in Example 1, except that an antistatic layer forming liquid having the following formulation was used.

Part by weight Polyvinyl alcohol 2 Water
100 Example 3 As the substrate 1, a slippery heat-resistant layer made of a thermosetting acrylic resin containing fine silica powder was provided with a thickness of about 0.8 μl.
Dye-sublimation thermal transfer was carried out in exactly the same manner as in Example 1, except that μm aromatic polyamide film TX-I (manufactured by Toshi) was used and an antistatic layer similar to that in Example 1 was formed on the slippery heat-resistant layer side. formed the medium.

For the above-mentioned sublimation transfer recording medium, as an image receiving medium,
A mixed solution having the following formulation was applied onto a 150 μm thick synthetic paper 8 using a wire bar, and a receiving layer 7 having a thickness of about 5 μm was provided.

Parts by weight Toluene 50 Methyl ethyl ketone 50 As shown in Figure 1,
FIG. 2 shows the results of printing multiple times on the same spot on the above-mentioned receptor layer 7 using the thermal head 6 under the printing conditions of an applied power of 442++ W/dot and a maximum applied energy of 2.21 mJ/dot. However, the print density (optical density) was evaluated using a Macbeth densitometer RD-514. FIG. 2 shows the relationship between the number of printings and the saturated image density. In the thermal transfer recording media of Examples 1 to 3, even when the number of printings was increased to 7, the image density remained substantially the same as that of the first printing. No difference was observed. As described above, it was found that the thermal transfer recording medium of the present invention has good multi-time printing characteristics without a decrease in print density even when printing is performed multiple times.

The above is a macroscopic result of one image in terms of image density, but from a more microscopic perspective, beautiful gradation images with no missing images were obtained in Examples 1 to 3.

Further, in the sheets of Examples 1 to 3, almost no wrinkles were generated, and no dust was observed.

Effects As described above, the sublimation thermal transfer material of the present invention with an improved ink layer structure does not substantially reduce print density even after multiple printings, has good multiple printing characteristics, and is further free from static electricity. It eliminates troubles caused by target attraction, provides smooth running, and provides images with fewer recording gaps and unevenness.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the structure of the sublimation type heat-sensitive transfer material of the present invention. FIG. 2 is a graph showing the relationship between the saturated print density and the number of prints of the sublimation type thermal transfer material of the present invention. 1.8...Substrate 2...Ink layer 3...Antistatic layer 4...Dye supply layer 5...Transfer contributing layer 6...Thermal head 7...Receiving layer Patent applicant stock

Claims (1)

[Scope of Claims] 1. A sublimation type thermal transfer recording medium comprising a dye supply layer and a dye transfer contribution layer, each of which has a sublimable dye dispersed in an organic binder, laminated on a substrate in order from the substrate side. A sublimation type thermal transfer recording medium, characterized in that an antistatic layer is laminated on the back surface of the substrate. 2. The sublimation type thermal transfer recording medium according to claim 1, wherein the dye supply layer contains at least an undissolved particulate sublimable dye, and the dye transfer contributing layer contains at least a molecularly dispersed sublimable dye.