JPH0280290A - Sublimable thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To obtain a uniform image quality which has no sudden decrease in transfer density due to an increase in the number of printings and also has no density irregularity by adding titanium dioxide to a dye feed layer. CONSTITUTION:As titanium dioxide used, the fine particle rutile type and anatase-type are pointed out which are generally used as white pigment. No particular limits exist in term of the size of particle and surface treatment procedures. The effective addition quantity of titanium dioxide is 5% by weight or more for pigment, especially within the range of 10 to 80% by weight. For the dye feed layer, the addition quantity is 20 parts for sublimable dye and 5 parts for titanium dioxide. For the transfer contribution layer, the addition quantity is 10 parts for sublimable dye. Their respective compositions are dispersed. Next, polyimide film is used as a base 1, and ink for the dye feed layer 4 is applied on the polyimide film. In addition, ink for the dye transfer contribution layer 5 is applied on the coat of ink for the dye feed layer. In this way, a sublimable thermal transfer recording medium is formed.

Description

[Detailed description of the invention] [Industrial application 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 the thermal transfer method is the most commonly used because of its ease of maintenance and low noise.

This thermal transfer consists of a solidified color ink sheet and an image-receiving paper, and the ink is thermally melted transferred or sublimated onto the image-receiving paper using thermal energy controlled by electrical signals such as a laser or a thermal head to form an image. It uses 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, and in the latter, in principle, the sublimation dye is sublimated in a monomolecular form in response to the thermal energy key from a thermal head, etc. Therefore, it has the advantage that intermediate tones 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 dye-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 shortcoming and are trying to improve this shortcoming 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 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, and proposed a sublimation-type heat-sensitive transfer recording medium in Japanese Patent Application No. 63-62866@). By making it a "contributing layer," the decrease in density during multiple recordings was improved.

By the way, the dye supply layer contains the dye pigment together with the binder.
An ink is prepared by dissolving it in a solvent or dispersing it in the form of fine particles, and the ink is applied onto a base film.
Then, it is necessary to create a transfer sheet by drying. However, since the dye supply layer is used multiple times, the dye concentration is set higher than before, so after the ink is applied and dried, the dye dissolved in the ink crystallizes in the layer, resulting in dye crystals. Even if a transfer contributing layer is provided thereon, if transfer recording is performed using a transfer sheet with dye crystals, density unevenness will occur in the transferred recorded image.
There is a problem in that it gives a grainy feel and makes it impossible to obtain uniform image quality.

[Problem to be Solved by the Invention 1] The present invention provides a sublimation type thermal transfer recording medium that does not cause a rapid decrease in transfer density even with an increase in the number of printing operations and can obtain uniform image quality without density unevenness. This is an issue that must be solved.

[Means for Solving the Problems] According to the present invention, a dye supply layer and a transfer contribution layer each comprising a sublimable dye dispersed in an organic binder are laminated on a substrate in order from the substrate side. The present invention provides a sublimation type thermal transfer recording medium characterized in that the dye supply layer contains titanium dioxide.

Patent application No. 63-6286, which the present inventors have already filed for invention
As a result of intensive study of the No. 6 recording medium, we found that, although the reason is not clear, by including titanium dioxide in the layer,
Not only good multi-time recording characteristics but also good uniform image quality could be obtained.

The titanium dioxide used in the present invention includes fine particulate rutile type and anatase type titanium dioxide, which are generally used as white pigments, and there are no particular restrictions on particle size, surface treatment method, etc. do not have. Furthermore, the amount of titanium dioxide to be added is effective at 5% by weight or more based on the pigment, particularly in the range of 10 to 80% by weight.

The dye supply layer and the dye 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 is characterized by the following 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 and/or the 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 dye in the ink layer follows Fick's law, that is, the amount dn of dye passing through cross-sectional area q in time dt is expressed as D When is 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 dye transfer contribution layer, there are two ways to make it easier to diffuse and supply the sublimable dye from the dye supply layer to the dye transfer contribution layer. Regarding the diffusion coefficient in each layer, there is a means to establish the relationship of dye supply layer>dye transfer contributing layer. As for the specific method of manipulating the diffusion coefficient regarding the above (2), for example, Toyoko Sakai et al. No. 12 (1974)
``Dyeing Theory Chemistry'' by Nobuhiko Kuroki, published by Suikichiten, p. 503~
; Introduced in the 1st Non-Impact Printing Technology Symposium Proceedings 3-5, etc. With reference to these, concrete methods for realizing the above means (1) are as follows: (1) Since the diffusion coefficient is influenced by the energetic suppression effect on dye diffusion due to hydrogen bonding between the dye and the organic binder, etc. (2) A method of using an organic polymer material having many proton-donating groups or proton-accepting groups that easily form hydrogen bonds with sublimable dyes as a binder for the dye transfer contributing layer. The diffusion coefficient is dependent on the glass transition or softening temperature of the organic binder in the dye supply layer. A method of using a substance having a lower glass transition temperature or lower softening temperature than that of the dye transfer contributing layer as a binder, (
3) Containing in the dye supply layer a plasticizer that is compatible with at least one organic binder in the dye supply layer and incompatible with all organic binders in the dye transfer contributing layer. (4) A method of appropriately combining methods (1), (2), and (3) above, etc., but is not limited to these methods as long as the above relationship of diffusion coefficients is satisfied. That goes without saying.

In designing the material formulation of the dye supply layer and the dye transfer contributing layer in the present invention, the above steps and/or means (2) are useful, and it is confirmed whether or not the intended improvement is realized by these effects. A simple method is to form the dye supply layer and the dye transfer contributing layer with the same coating amount as individual layers on the substrate, overlap each with a separate image receiving layer, and apply a constant sublimation temperature. There is a method of selecting each layer such that the sublimation transfer layer has a relationship of dye supply layer>dye transfer contributing layer.

Next, the thickness of the dye transfer contributing layer is -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 0.5 to 5 μm.

Furthermore, known sublimable dyes, binders, etc. used in the dye transfer contribution 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 used in thermal transfer printing such as disperse dyes and oil-soluble dyes, such as C, 1, disperse yellow. 1.3.8.9.1641, 54.6
0.77, 116, etc., 1.4.6.11.15.17.55.59.60.
73.83 etc., C11, Tishasuf/L/-(7
)3.14.19,26,56606472.99.1
08 etc., C, 1, Rubent Yellow 77.116
etc., C,1, Solvent Red 23.25.27, etc., C,1,'/Lugento 7/L, -no 36.83.1
05, etc., and these dyes can be used alone or in combination.

Thermoplastic or thermosetting resins are used as binders for the dye transfer contributing layer and the dye supplying 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, polystyrene,
Examples include polypropylene, acrylic resin, phenolic resin, polyester, polyurethane, epoxy resin, silicone resin, fluororesin, butyral resin, melamine resin, 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 having a glass transition temperature of O'C or lower or a softening temperature of 60 °C or lower are preferred. Specifically, syndiotactic 1°2-polybutadiene (J
SRRB810°820, 830 manufactured by Japan Synthetic Rubber Co., Ltd.);
Olefin copolymers and terpolymers containing acids or non-acidic acids (commercially available as Dexon XEA-7, manufactured by Dexon Chemical Company); ethylene-vinyl acetate copolymers (
400 & 400A, 405, 430 as commercial products
, Allied Fibers &Plastics; P-33
07 (EV150), P-2807 (EV250)
, Mitsui"T'l (manufactured by Honpolychemical Co., Ltd.); low molecular weight polyolefin polyols and their derivatives (commercially available products include Polytail [1, HE manufactured by Mitsubishi Chemical Industries, Ltd.];
Brominated epoxy resin (YDB-340, 400, 500
, 600 made by Tokagaku Co., Ltd.); Novolac type epoxy resin (
YDCN-701, 702, 703 manufactured by Tobu Kagaku Co., Ltd.); thermoplastic acrylic trusion (Titanal [R107
5, 1080, 1081, 1082, 1063, 107
9 Mitsubishi Rayon Co., Ltd.); Thermoplastic acrylic emulsion (LX-400, LX-450 Mitsubishi Rayon Co., Ltd.); Polyethylene oxide (Alcox E-30, 45° Alcox R-150, 400, 1000 Meisei Chemical Industry Co., Ltd.) ); Caprolactone polyol (Plaxel H-
1, 4, 7, manufactured by Daicel Chemical Industries, Ltd.); and the like are preferred, and polyethylene oxide and polycaprolactone polyol are particularly useful for practical purposes. Or, it is preferable to use it in a mixed form with several kinds.

The dye a degree of the dye transfer contribution layer is usually about 5 to 80% by weight, preferably about 10 to 60% by weight.

Regarding the dye concentration in the dye supply layer, a dye concentration of 5 to 80% by weight is preferable, 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
~3 times is desirable.

Films such as capacitor paper, polyester film, polyethylene film, polystyrene film, polysulfone film, polyimide film, and polyamide film are used as the base sheet, and conventionally used films are used between the base sheet and the dye supply layer as necessary. An adhesive layer or the like may be provided, and a conventional heat-resistant lubricant layer may be provided on the back surface of the base sheet as required.

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 an 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, "Plastic Compounds" by Sakura Yamada (published by Taiseisha, D, 17-) and "9887 Chemical Products" (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.

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 dye transfer contributing layer. 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 thermal transfer recording medium of the present invention can be applied to a recording method in which recording thermal energy is applied by a method other than a thermal head, such as a thermal printing plate, a laser beam, or a recording method using a thermal head. It can also be used for methods using Joule heat generated in a medium such as a substrate. Among these, the most well-known is the so-called electric thermal transfer method, which uses Joule heat generated in the medium.
SP4.103.066, JP 57-14060, JP 57-110801 or JP 59-9096
It is described in many documents such as

When used in this current transfer method, aluminum, copper, iron, tin, zinc, nickel, molybdenum is used as a substrate for resins with relatively good heat resistance such as polyester, polycarbonate, triacetyl cellulose, nylon, polyimide, aromatic polyamide, etc. , a substrate in which a metal powder such as silver and/or a conductive powder such as carbon black is dispersed to adjust the resistance value to an intermediate value between an insulator and a good conductor, and a conductive metal as described above is deposited or A sputtered substrate may be used. The thickness of these substrates is preferably about 2 to 15 μm in consideration of Joule heat conduction efficiency.

Furthermore, when used in a laser beam transfer method, a material that absorbs laser beams and generates heat may be selected as the substrate. 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 the substrate is used.

[Example] Next, the present invention will be explained with reference to Examples. Please note that the division is based on the 5th grade standard.

Example 1 Polyvinyl butyral resin Bχ-110 parts (manufactured by Tansui Kagaku Kogyo ■) Sublimation dye KAYASE'r BLUEγ14 (manufactured by Nippon Koyaku ■) Solvent Toluene 100 parts Methyl ethyl ketone 100 parts In the above formulation, the above-mentioned sublimation dye supply layer formulation 20 parts of color dye and titanium dioxide JA-1 (manufactured by Teikoku Kako ■)
5 parts, and 10 parts of the above sublimable dye in the transfer-contributing footwear formulation, and each composition was dispersed in a ball mill for 24 hours.

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) was used as the substrate 1, and after coating the ink for the dye supply layer 4 to a thickness of 2.40 μm using a wire bar, the dye transfer layer was roughly applied onto it. The ink for layer 5 was applied to a thickness of 0.61 μm to form a sublimation type thermal transfer recording medium. Almost no crystallization of the dye was observed on the surface of the ink layer, and a transfer medium with uniform coating was obtained.

Example 2 Prescription of dye supply layer> Polyvinyl butyral resin BX-11 parts (manufactured by Shimizu Chemical Co., Ltd., glass transition temperature: 83°C) Polyethylene oquinide Alcox R400 (manufactured by Meisei Chemical Co., Ltd., glass transition temperature: 83°C)
Glass transition temperature -60℃) 9 parts sublimable dye KAYASET BLIJE 714
10 parts titanium dioxide) IT-1003 (Teikoku Kako ■
) 3 parts solvent toluene ioo
After dispersing the composition of the above formulation in a ball mill for 24 hours, 8 parts medemethyl ethyl ketone 100 parts
．． After applying the above dye supply tube ink composition to a 5 μm polyimide film (manufactured by DuPont Azuma Co., Ltd.) using a wire bar to a film thickness of 2.40 μm, a dye having the same formulation as in Example 1 was roughly applied thereon. A transfer contributing ink composition was applied to a film thickness of 0.61 μm to form a sublimation type thermal transfer recording medium.

As in Example 1, almost no crystallization of the dye was observed on the surface of the ink layer, and a transfer medium coated uniformly was obtained.

Example 3 <Formulation of dye supply layer> Polyvinyl butyral resin BX-11 parts (manufactured by Katsuzu Kagaku Kogyo Co., Ltd., glass transition temperature: 83°C) Polycaprolactone Plecel H-7 (manufactured by Daicel Chemical Industries, Ltd., glass transition temperature: -60°C) 'C) 9 parts sublimable dye KAYA
SET BLυE714 10 parts (Nippon Kajimi Co., Ltd.) Titanium dioxide Thai Bake R-6805 parts (Ishihara Sangyo ■
) Solvent: 100 parts of toluene 100 parts of methyl ethyl ketone After dispersing the composition of the above formulation in a whole mill for 24 hours,
．． Using a wire bar, the above ink composition for the dye supply layer was applied to a 5 μm polyimide film (manufactured by DuPont) so that the film thickness was 2.40 μm. An ink composition contributing to dye transfer was applied to a film thickness of 0.61 μm to form a sublimation type thermal transfer recording medium. As in Example 1, almost no crystallization of the dye was observed on the surface of the ink layer, and a transfer medium coated uniformly was obtained.

In Comparative Example, a sublimation thermal transfer recording medium was prepared in the same manner as in Example 1 without adding titanium oxide. However,
Needle-shaped pigment crystals were observed on the surface of the ink layer.

Comparative Example 2 A sublimation thermal transfer recording medium was prepared in the same manner as in Example 1 except that silica Aerosil 130 (manufactured by Nippon Aerosil@J) was contained in place of the titanium dioxide used in Example 1. However, needle-like crystals of the dye were observed on the surface of the ink layer.

Comparative Example 3 A sublimation thermal transfer recording medium was prepared in the same manner as in Example 1 except that calcium carbonate (reagent manufactured by Kanto Kagaku ■) was contained in place of titanium dioxide. However, needle-like crystals of the dye were observed on the surface of the ink layer.

Next, thermal transfer was performed in the following manner. As the image receptor 3, an image receiving paper supplied by Hitachi Video Printer VY-50, VY-3100, which is an image receiving paper for sublimation type thermal transfer recording, was used.

For the sublimation thermal transfer recording media of Examples 1, 2.3 and Comparative Example 1.2.3, as shown in FIG. 442 mW/dot, maximum applied energy 2.21 m
As a result of printing multiple times at the same location using J/dot, the multiple-time recording characteristics were good in all cases, and there was almost no decrease in image density up to 7 times.

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

However, regarding the uniformity of image quality, density unevenness occurred in the comparative example, and the results were visually evaluated as shown in Table 1.

Table 1

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the state of printing and recording using the sublimation type thermal transfer recording medium of the present invention. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Ink layer, 3... Image receptor, 4
...Dye supply layer, 5...Dye transfer contributing layer, 6...
goomall head

Claims (1)

[Claims] In a sublimation type thermal transfer recording medium in which a dye supply layer and a transfer contribution layer each having a sublimable dye dispersed in an organic binder are laminated on a substrate in order from the substrate side, titanium dioxide is added to the dye supply layer. A sublimation type thermal transfer recording medium characterized by comprising: