JPH0263793A - Sublimable thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To make possible the prevention of a sudden decrease in transfer density even with an increase in the number of printings by allowing a filler to be added as a main body to a dye supply layer. CONSTITUTION:The subject medium consists of a dye supply layer 4 with sublimable dye dispersed in filler and organic binder and a dye transfer contribution layer 5 with sublimable dye dispersed in the organic binder, laminated sequentially from a base 1 on the base 1. Under this constitution, dye is stably supplied continuously from the dye supply layer to the dye transfer contribution layer by the capillary action between filler particles as the main body of the dye supply layer. Consequently, the printing density does not substantially reduce, if printing is performed many times, and thus superior high-frequency printing characteristic is ensured.

Description

[Detailed description of the invention] For land use 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, 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 1 constant velocity mode, even though the ink layer contains enough 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 Special 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" to improve the density drop during multiple recordings. However, this sublimation type thermal transfer recording Regarding the medium, there were also some problems in terms of stable and continuous supply of dye from the dye supply layer to the dye transfer contributing layer. It is an object of the present invention to provide a sublimation type thermal transfer recording medium for multiple printing that does not cause blemishes.

Enoki-Isso The present invention provides (i) on a substrate in order from the substrate side.
A sublimation type comprising a layered layer including a dye supply layer in which a sublimable dye is dispersed in a filler and an organic binder, and (ii) a dye transfer contributing layer in which a sublimable dye is dispersed in an organic binder. It consists of a thermal transfer recording medium substrate.

Although it is not clear why the stable and continuous supply of dye from the dye supply layer to the dye transfer contributing layer can be ensured by containing a filler as a matrix in the dye supply layer of the dye sublimation type thermal transfer recording medium of the present invention, This seems to be due to the capillary function between the filler particles as the matrix of the supply layer.

The surface dye supply layer and the transfer contribution layer are each formed as a single layer on the substrate with the same amount of adhesion according to each formulation, and each of them is overlapped with a separate image receiving layer, and the same thermal energy is applied to both. In this case, the amount of dye transferred to each image-receiving layer has a relationship of dye supply layer>dye transfer contributing layer.

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

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, that is, the amount of dye dn that has passed through the cross-sectional area q for the waiting time of dt is expressed as dc/dx, where the concentration gradient of the dye in the diffusion direction is dc/dx. When the average diffusion coefficient of each part in the ink layer is taken as the average diffusion coefficient of each part in the ink layer when heat is applied, the relationship dn == -D (dc/dx)qdt is applied.

Therefore, as a means to facilitate the diffusion and supply of the sublimable dye from the dye supply layer to the transfer contribution layer, there are the following: (1) In terms of dye concentration, the relationship is "dye supply layer > transfer contribution layer"; and/or (2) respectively. Regarding the diffusion coefficients in the layers, there is a means to establish the relationship of dye supply layer>transfer contribution layer.

The present invention is a method devised with particular attention to the above point I.

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 0.5 to 30 μm, preferably 1 to 10 μm.
It is μm.

Examples of fillers forming the matrix constituting the dye supply layer include fine powders of metal oxides such as zinc oxide, tin oxide, and aluminum oxide, fine powders of metals such as aluminum, copper, and cobalt (in some cases). (in some cases in the form of metal foil), diatomaceous earth, molecular sieves, organic fine powders such as phenolic resins and epoxy resins, carbon blank fine powders, combinations of two or more of these, and others. Although all such fine powders have excellent cohesiveness, carbon black, which has particularly high cohesiveness, is most suitable as a fine powder.

Although carbon black is normally used as a black pigment, in the present invention, it does not play the role of a pigment, but rather a medium for exuding the ink composition whose viscosity has been reduced by heat. It is not transferred onto the image-receiving sheet together with the ink composition and remains as it is on the substrate.

In the present invention, the particle size of the fine powder as described above is 0.01
Advantageously, it is ˜200 μm.

Further, the amount of the fine powder used is 10 to 80% by weight, preferably 30% by weight, based on the total amount of the ink composition.
Advantageously, it is 60% by weight.

The amount used can be arbitrarily selected within the above range depending on various factors such as transfer recording conditions, desired results, and other factors, as in the case of the low melting point compound mentioned above. It is possible.

This fine powder forms a stone wall structure when applied to a support, but no special means are required for the application method.

Acicular crystal pigments are also mentioned, and specific examples thereof include ocher, yellow lead G, phthalocyanine blue, Lysole red, Bonmartone light, white clay, acicular zinc oxide, 2,7-bis[2 -Hydroxy-3-(2-chlorophenylcarbamoyl)naphthalen-1-ylazogo9-fluorenone, 4',4"-bis[2-hydroxy-3-(2,4-dimethylphenyl)carbamoylnaphthalen-1-ylazo) Examples include -1,4-distyrylbenzene, but any material can be used as long as the crystals are acicular and are arranged in a network structure in the transfer layer.

The length of this needle-like crystal is about 0.3 to 3μ, and the width and thickness are 0.5μ or less.

The amount of the needle-like crystal pigment added is 0 per part by weight of the dye.
．． 5 to IO parts by weight, preferably 1 to 5 parts by weight.

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/L/-(7
)3,14,19,26,56,60゜64.72,9
9,108 etc., C, 1, Solvent Yellow 77.
116 etc., C, I, Solvent Red 23.25.
27 etc. C, 1, Solvent Blue 36.83, 10
5, etc., and these dyes can be used alone or in combination of several kinds.

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, phenolic resin.

Polyester, polyurethane, epoxy resin, silicone resin, fluorine resin, butyral resin, melamine resin,
Examples include natural rubber, synthetic rubber, polyvinyl alcohol, and cellulose resin.

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 for.

Syndiotactic 1,2-polybutadiene (JSRRB810, 820, 830 Japan Synthetic Rubber as a commercial product)
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 (EV15
0), P-2807 (EV250), Mitsui DuPont Polychemical): Low molecular weight polyolefin polyol and its derivatives (Polytail 11.11 as a commercial product)
E Mitsubishi Chemical Industries); Brominated epoxy resin (YDB-34
0, 400, 500, 600 Tobu Kagaku); Novolak type epoxy resin (YDCN-701, 702, 703 Tobu Kagaku); Thermoplastic acrylic trusion (Tya Knurshi R) 075, 1080.1081.1082.106
3.1079 Mitsubishi Rayon); Thermoplastic acrylic emulsion (LX-400, LX-450, Mitsubishi Rayon)
; Polyethylene oxide (Alcox E-30,4
5, Alcox R150, 400, 1000 Meisei Chemical Industry); Caprolactone polyol (Plaxel H-1
．． 4,7. Daicel Chemical Industries); etc. are preferred, and polyethylene oxide and polycaprolactone polyols are particularly useful for practical purposes. is preferred.

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 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.

The dye supply layer may contain a plasticizer that is effective for promoting the diffusion of the dye, and the plasticizer here refers to the fan, which enters between the molecules of the resin and causes the hard network structure of the resin. It is a substance that weakens the Der Waals bond and, as a result, lowers the secondary transition point of the resin. Also, compatibility means that the resin and plasticizer have an affinity for each other, the gelation rate is fast, and the resin remains stable even after molding. Defined as one in which the plasticizer does not separate.

In addition, specifically, books, literature, catalogs, etc. that mention plasticizers, taking into account the compatibility between plasticizers and resins,
For example, you can freely select from those listed in "Plastic compounding agents" (published by Taiseisha, p. 17-) and "R9887 chemical products" (published by Kagaku Kogyo Nippo, p. 17-) written by Sakura Yamada. can.

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
Creates an appropriate difference in dye transfer amount.

If the functional separation intended by the present invention can be achieved, it is also possible to have a multilayer dye layer 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 be applied to a recording method 1 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.

Among these, the so-called electrical thermal transfer method, which uses Joule heat generated in the medium, is the most well-known.For example, USP4,
103, 066, JP-A-57-14060, JP-A-5
It is described in many documents such as 7-11080 and JP-A-59-9096.

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.

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 The following dye supply layer formulation was prepared, and parts by weight of carbon black fine powder, 20 parts by weight, and 20 parts by weight of solvent were added.
Toluene lOO methyl ethyl ketone
100 Furthermore, the following dye transfer contributing wear formulation was prepared and weighed in parts by weight.

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

An 8.5 μm polyimide film (manufactured by DuPont Toshi) is used as the support 1, and the ink for the dye supply layer 4 in the ink layer 2 is applied onto this using a wire bar to a film thickness of 5.6 μm.
After coating the ink in a thickness of 0.8 μm, the ink for the dye transfer contribution layer 5 in the ink layer 2 was further applied thereon to a thickness of 0.8 μm to form a sublimation type thermal transfer medium.

Example 2 [Prescription of ink composition for dye supply layer] Solvent: 100 methyl ethyl ketone 100 Disperse each composition in a ball mill for 24 hours Sublimable dye KAYASET BLUE 714 Carbon Black Fine powder Solvent: Toluene methyl ethyl ketone Above After dispersing the prescribed composition in a ball mill for 24 hours,
．． After applying the above dye supply layer ink composition to a 5 μm polyimide film (manufactured by DuPont Toshi) using a wire bar to a film thickness of 5.0 μm, a dye transfer layer having the same formulation as in Example 1 was further applied thereon. The layer ink composition has a film thickness of 0.
．． It was applied to a thickness of 7 μm to form a sublimation type thermal transfer medium.

Example 3 [Formulation 3 of ink composition for dye supply layer After applying the ink composition for parts by weight to a film thickness of 4.8 μm,
Furthermore, an ink composition for a dye transfer contribution layer having the same formulation as in Example 1 was applied thereon to a thickness of 0.6 μm to form a sublimation type thermal transfer medium.

(Left below) Sublimation dye KAYASET BLLIE 714
10 Solvent: Toluene
50 Methyl ethyl ketone 50 After dispersing the composition of the above formulation in a ball mill for 24 hours, 8.5
Using a wire bar on a μm polyimide film (manufactured by DuPont Toshi), the dye supply layer was then subjected to sublimation thermal transfer recording in the following manner. The image receptor 3 is Hitachi Video Printer VY-50, which is image receptor paper for sublimation type thermal transfer recording.
Image receiving paper supplied by VY-3100 was used.

For the sublimation transfer recording media of Examples 1.2 and 3, the first
As shown in the figure, a thermal head 6 is placed on the image receptor 3.
The printing conditions were an applied power of 442 mW/dot,
As a result of printing multiple times at the same location with a maximum applied energy of 2.21 mJ/dot, the results shown in FIGS. 2, 3, and 4 were obtained.

However, the print density (optical density) is Macbeth Densitometer RD-
514 was used for evaluation.

2, 3 and 4 show the relationship between the print reflection density and the applied energy of the sublimation transfer recording media of Examples 1, 2 and 3 of the present invention, respectively, and the number of printings (n
) was increased from 5 to 7 times, there was virtually no difference in image density from the first printing.

Effects As described above, the sublimation type thermal transfer material of the present invention with an improved ink layer structure does not substantially reduce print density even after multiple printings, and has good multiple printing characteristics. There is.

[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, FIG. 3, and FIG. 4 are graphs showing the relationship between print reflection density and applied energy of the sublimation type thermal transfer material of the present invention.

Claims (1)

[Claims] 1. On the substrate, in order from the substrate side, (i) a dye supply layer in which a sublimable dye is dispersed in a filler and an organic binder, and (ii) a sublimable dye in an organic binder. A sublimation type thermal transfer recording medium comprising a layer of dispersed dye transfer contributing layers.