JPH02229080A - Dye sublimation thermal transfer recording media - Google Patents

Abstract

PURPOSE:To eliminate the rapid reduction of a printing density even in a multi- time printing and to enhance the shelf stability of an ink sheet by providing an intermediate layer lower than a transfer contributing layer in dye diffusion properties between a dye supply layer and the transfer contributing layer. CONSTITUTION:On a substrate, a dye supply layer 4 and a transfer contributing layer 6 are provided in this order from the side of the substrate. A sublimable dye is adjusted so as to be easily diffused and supplied from the dye supply layer 4 to the transfer contributing layer 6 by the amount to be consumed from the transfer contributing layer 6 through a free surface by a sublimable transfer method. In addition, an intermediate layer 5 lower than the transfer contributing layer 6 in dye diffusion properties is provided between the dye supply layer 4 and the transfer contributing layer 6 to improve the shelf stability of an ink sheet.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to a sublimation type thermal transfer recording medium.

[Prior art]

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, in this sublimation transfer recording method, color ink sheet 1 is used as a recording supply, and thermal recording is performed selectively according to image signals. This method has the drawback that the running cost is high because one ink sheet (black) is used, and even if there is an unused portion, it is discarded.

Therefore, we are currently focusing on this drawback and are trying to improve this drawback by using Inksee I- many times.We are using the 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 is An N-fold mode method has been proposed in which the coloring material layer is used at a slower rate than that of the image receptor, and the overlapping portions of the first and second used portions of the coloring material layer are shifted little by little.

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 contribution layer, the dye release ability is changed to the dye supply layer>the dye transfer contribution layer, thereby improving the density loss caused by multiple recordings.

As a result, although the ability to print multiple times has certainly improved,
If Inksee 1- is stored for a long period of time, dye will move from the supply layer (high dye concentration) to the transfer contributing layer (low dye concentration), causing the initially set density of each layer to change, causing printing problems before and after storage. There is a problem that the characteristics change, and there is still room for improvement, and the present invention is a further improvement on this prior invention.

〔the purpose〕

SUMMARY OF THE INVENTION An object of the present invention is to overcome the conventional drawbacks and provide a sublimation type thermal transfer recording medium that has multiple printing characteristics and has excellent long-term storage stability.

〔composition〕

The present invention replaces the conventional homogeneous ink layer provided on the substrate with
It has a multi-layer structure in which the functions are separated into a relatively thin surface layer (transfer contribution layer) that has the function of sublimation transfer and a layer (dye supply M) that has the function of diffusing and supplying the sublimation dye to the surface layer. By providing an intermediate layer between the supply layer and the transfer contribution layer, which has lower dye diffusivity than the transfer contribution layer, the print density does not decrease rapidly even after printing many times.
Moreover, the present invention provides a sublimation transfer medium in which the ink sheet has high storage stability.

That is, in the present invention, a dye supply layer and a transfer contributing layer are provided on a substrate in order from the substrate side, and the amount of dye consumed by sublimation transfer from the transfer contributing layer via the free surface (unit: weight/time) - By adjusting the sublimation dye on the surface vL) to be easily diffused and supplied from the dye supply layer to the transfer contribution layer, printing can be performed multiple times,
Furthermore, an intermediate layer having lower dye diffusivity than the transfer contributing layer is provided between the dye supplying layer and the transfer contributing layer to improve the storage stability of the ink sheet.

Preservability is closely related to dye movement during storage, and if the dye concentrations in the supply layer and transfer contribution layer change during storage,
Changes occur in printing characteristics such as multiplicity and image density.

Therefore, it is desirable that the dye concentration in each layer does not change during storage, but in ink sheets for multiple recording consisting of a dye supply layer and a transfer contribution layer, the dye concentration is in the relationship of supply layer > transfer contribution layer. Because of this, the dye easily migrates from the supply layer to the transfer contributing layer during storage.

Therefore, in order to prevent dye migration during storage, this problem was solved by providing an intermediate layer with lower dye diffusivity than the transfer contributing layer between the dye supply layer and the transfer contributing layer.

As a method to differentiate the dye diffusivity, that is, to make the diffusion coefficient of the two layers into a relationship between the transfer contributing layer and the intermediate layer, for example: (1) The diffusion coefficient is determined by the hydrogen bond between the dye and the organic binder, etc. A method of using an organic polymeric material having a large number of proton-donating groups or proton-accepting groups that easily form hydrogen bonds with sublimable dyes as a binder in the intermediate layer, since this is influenced by the energetic suppression effect on dye diffusion by (2) The diffusion coefficient has a property that depends on the glass transition or softening temperature of the organic binder in which the dye is dispersed, and the glass transition or softening temperature is lower than the temperature rise characteristic of the layer during printing in this process. (3) At least one type of organic binder in the two layers contributing to transfer is used as the organic binder in the transfer contributing layer, which has a lower glass transition temperature or lower softening temperature than that in the intermediate layer. There is a method in which the transfer contributing layer contains a plasticizer that is compatible with the binder and incompatible with all the organic binders in the intermediate layer.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is an explanatory diagram showing the structure of the sublimation type thermal transfer recording medium of the present invention, in which 1 represents a support, 2 represents a dye supply layer 4, and 2 represents a dye supply layer 4.
, an ink layer composed of an intermediate layer 5 and a dye transfer contribution layer 6, 3 is an image receptor such as paper, and 7 is a thermal head.

In the present invention, preferably, undissolved particulate dye is mixed in the dye supply layer 4, and an appropriate concentration gradient or/further diffusion coefficient gradient may be created between the dye supply layer 4 and the dye transfer contributing layer 6. This makes it possible to record multiple times in good condition while maintaining the initial slope each time.

However, here, undissolved particulate dye refers to undissolved particulate dye that cannot be completely dissolved in the organic binder and precipitates in the form of particles after the ink (organic binder + sublimable dye + solvent) is applied and dried during the formation of the ink layer. It refers to a dye, and even if the binder and dye are the same, the presence of undissolved particulate dye 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 0.01 μm to 20 μm, preferably 1.0 μm to 5 μm.

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.

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

Sublimable dyes are dyes that sublimate or vaporize at temperatures above 60°C, and are mainly used in thermal transfer printing such as disperse dyes and oil-soluble dyes, such as 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, such as 77.116, C,1, Solvent Red, 2:L25,27, C,1, Solvent Blue, 36.83,105, etc.2 types of these dyes However, it is also possible to use a mixture of several types.

Thermoplastic or thermosetting resins are used as binders for the dye supply layer, intermediate layer, and dye transfer contribution layer, and examples of resins having relatively high glass transition points or high softening properties include, for example, Vinyl chloride resin, vinyl acetate resin, polyamide, polyethylene, polycarbonate-1-, polystyrene, polypropylene, acrylic resin, phenol resin, polyester, polyurethane, epoxy resin, silicone resin, fluorine resin, butyral resin, melamine resin, natural rubber, synthetic Examples include rubber, polyvinyl alcohol, cellulose resin, and the like. These resins can be used alone, but several types may be mixed or a copolymer may be used.

Examples of materials that may be mixed in to create a difference in glass transition point or softening temperature between the dye transfer contribution layer, dye supply layer, and intermediate layer include resins with a glass transition temperature of 0°C or lower or a softening temperature of 60°C or lower. , wax, natural and synthetic rubber, etc. Specific examples include syndiotactic 1,2-
Volibutadiene (JSRRB810,82 as a commercial product)
Olefin copolymers and terpolymers containing acids or non-acidic acids (Lanolin XEA-7, Lanolin Chemical as commercial products); Ethylene-acid picopolymers (400 & 400A, 405 as commercial products)
, 430, Allied Fibers &Plastics;
P-3307 (EV150), P-2807 (EV2
50), Mitsui DuPont Polychemicals); low molecular weight polyolefin polyols and their derivatives (commercially available products include Polytail H1l (E Mitsubishi Chemical Industries); brominated epoxy resins (YDB-340, 400, 500, 600 Tobu Kagaku); Novolac Type epoxy resin (YDCN-701,
702゜703 Tobu Kagaku); ・Thermoplastic acrylic trusion (Titanal LR1075, 1080, 108
1,1'082.1063, 1079 Mitsubishi Rayon);
Thermoplastic acrylic emulsion: L (LX-400, L
X-450, Mitsubishi Rayon); Polyethylene oxide (Alcox E-30, 45° Alcox R-15
0,400,1000 Meisei Chemical Industries); caprolactone polyol (Plaxel H-1,4,7° Daicel Chemical Industries); and the like.

Among them, paraffin wax, polyethylene wax,
Waxes such as carnauba wax and lanolin wax,
Higher fatty acids, higher fatty acid amides, higher fatty acid esters,
low molecular weight polyolefin polyols and derivatives thereof,
Polyethylene oxide, polycaprolactone polyol, etc. are preferred, and polyethylene oxide, waxes, etc. are particularly useful for practical purposes.

At least one of these materials can be used in a mixed form with the thermoplastic or thermosetting resin described above.

The plasticizer contained in the dye transfer contribution layer in the above method (3) enters between the molecules of the resin, weakens the van der Wals bonds that are the cause of the hard network structure of the resin, and as a result, the plasticizer It is a substance that lowers the secondary transition point, and ``compatibility'' is defined as a resin and a plasticizer having an affinity for each other, a gelation rate is fast, and 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, Sakura Yamada, "Plastic compounding agent" (published by Taiseisha, p. 17-') and "R9887 chemical products" (published by Kagaku Kogyo Nippo, p. 17-').

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 that is incompatible with the plasticizer is used for the intermediate layer, and the resin that is compatible with the plasticizer is used for 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 I, preferably 10 to 50%.

Next, the thickness of the transfer contribution layer and the intermediate layer is 0.0
5 to 5 μm, preferably 0°1 to 2 μm. The thickness of the dye supply layer is generally 0.1 to 20 μm, preferably 0.5 to 5 μm.

The dye concentration of the transfer contributing layer and the intermediate layer is usually about 5 to 80%, preferably 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 1.5 to 3 times.

Furthermore, as the base sheet, films such as capacitor 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. etc. may be provided,
Furthermore, a conventional heat-resistant lubricating layer may be provided on the back surface of the base sheet, if necessary.

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 utilizing Joule heat generated by electrical current in a medium such as a thermal printing plate, a laser beam, or a support and/or an ink layer. Among these, the so-called electrical thermal transfer method, which uses Joule heat generated in the medium, is the most well-known. It is described in many documents such as -9096.

When used in this current transfer method, aluminum, copper, iron, tin, zinc, nickel, Supports in which metal powders such as molybdenum, silver, etc. and/or conductive powders such as carbon black are dispersed to adjust the resistance value to an intermediate value between insulators and good conductors, and conductive metals such as those described above are used in these supports. A support on which is vapor-deposited or sputtered may be used. The thickness of these supports is desirably about 2 to 15 microns in consideration of Joule heat conduction efficiency.

Further, when used in a laser beam transfer method, a material that absorbs laser beams and generates heat may be selected as the support. For example, a conventional thermal transfer film containing a light absorption heat conversion material such as carbon, or a film in which an absorbing layer is formed on the front and back surfaces of a support is used.

Note that, if necessary, a release thin layer made of a substance having lubricity and heat resistance may be provided on the dye transfer contributing layer.

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 Each composition shown in Table 1 below was dispersed in a ball mill for 24 hours. Each layer was then laminated onto an 8.5 μI 11 polyimide film (manufactured by DuPont Toshi) support.

Dye supply layer: 2.40 μm thick Intermediate layer: 0.1 μm Transfer contribution layer: 0.61 μm (blank below) On the other hand, the image receiving medium is a solvent of toluene (part by weight), 40 methyl ethyl ketone (40 parts), and the above mixture is synthesized to a thickness of about 150 μm using a wire bar. Paper (YUPO FPG-150
, egg oil-treated synthetic paper) and dried at a drying temperature of 75°C.
It was dried for a minute to form a dyed layer (image-receiving layer) with a thickness of about 5 μm, and an image-receiving body was prepared.

The ink layer of the transfer medium thus obtained was superimposed so as to face the dyed layer of the image receiving medium, and an image was recorded from the back side of the transfer medium using a thermal head while changing heating energy. The recording density of the thermal head was 6 dots/h/mm, and the recording output was 0.42 W/dot.

Each ink sheet was placed in an open oven at 60° C. for 300 hours, and the recording characteristics were compared many times before and after that.

FIG.

1...Support 3...Image receiver 5...Intermediate layer 7...Thermal layer 2 -Ink layer 4...Dye supply layer 6...1 layer near dye transfer ×...Scattered [ Effects] As mentioned above, even if the number of printing increases, the print density does not decrease especially in high density areas, and good gradation is possible, and the intermediate layer has a lower dye diffusion coefficient than the dye transfer contributing layer. By providing this between the dye supply layer and the dye transfer contributing layer, a sublimation thermal transfer recording medium with good storage stability can be provided.

[Brief explanation of the drawing]

Claims (1)

[Claims] 1. A sublimation thermal transfer recording medium provided with an ink layer formed by laminating a dye supply layer and a dye transfer contributing layer in which a sublimable dye is dispersed in an organic binder, respectively, on a substrate in order from the substrate side. A sublimation type thermal transfer recording medium, characterized in that an intermediate layer having lower dye diffusivity than the dye transfer contributing layer is provided between the dye supplying layer and the dye transfer contributing layer.