JPH02231191A - Sublimable thermal transfer recording method - Google Patents

Abstract

PURPOSE:To prevent the occurrence of the delamination of an ink layer and the fusion bond of the ink layer with an image receiving sheet, to improve running properties, and to obtain a high-quality image by interposing a lubricating or releasable substance between an image receiving sheet and a sublimable thermal transfer recording medium having the ink layer functionally divided into a dye supply layer and a transfer contributing layer. CONSTITUTION:An image receiving sheet 3 is overlapped on a transfer contributing layer 5 of a sublimable thermal transfer recording medium formed by laminating a dye supply layer 4 and the transfer contributing layer 5, each of which is formed by dispersing a sublimable dye in a resin binder, on a substrate 1 in this order from the substrate side. The both are run in the condition of (image receiving sheet speed),(recording medium speed)>1 or (image receiving sheet feed amount)/(recording medium feed amount)>1. A lubricating or releasable substance 7 is interposed between the transfer contributing layer 5 and the image receiving sheet 3, and this is subjected to thermal printing from the side of the recording medium, whereby a dye in the transfer contributing layer 5 of the corresponding part is sublimated and transferred onto the image receiving sheet 3. In this manner, the reduction of a transfer image density is almost eliminated, and the delamination and fusion bond of the ink layer and a failure in running are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sublimation thermal transfer recording method that utilizes the sublimation phenomenon of sublimable dyes due to heat.

[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 often used because it is easy to maintain and is noiseless. This thermal transfer method is a thermal transfer recording medium (so-called color ink film), which is formed by providing an ink layer on a substrate, in which a coloring agent is dispersed in a heat-fusible substance or a sublimable dye is dispersed in a resin binder. An image-receiving sheet is placed on the ink layer surface of g), and thermal energy controlled by an electric signal from a laser or a thermal head is applied from the recording medium side to thermally melt transfer or sublimation transfer the ink in that area onto the image-receiving sheet. This is a recording method that forms an image using

This thermal transfer recording method is roughly divided into a heat-melting transfer type and a sublimation transfer type depending on the type of recording medium used, but the latter in particular has a principle in which dyes are transferred in response to heat energy from a thermal head, etc. Since it sublimates in a monomolecular form, it has the advantage of easily obtaining intermediate tones and being able to control the gradation at will, and is considered to be the most suitable method for full-color printers. However, this sublimation thermal transfer recording method uses one sheet each of yellow, magenta, cyan, and (black) ink sheets to obtain one full-color image, and selective thermal printing is performed on each ink sheet. The disadvantage is that the running cost is high because any unused parts are discarded after that.

In order to overcome this drawback, in recent years a method has been used in which the same ink sheet is repeatedly used to print and record many times. Specifically, the constant speed mode method involves printing repeatedly while the ink sheet and image-receiving sheet are running at a constant speed, and the method in which the speed of the image-receiving sheet is n times the speed of the ink sheet (n>
There are two methods: 1) and an n-fold mode method in which printing is performed repeatedly with both sheets running. The latter n-times mode method is a method in which printing is performed multiple times using a relative speed method in which the overlap between the previously used portion of the ink layer and the later used portion is shifted little by little. Note that in the n-fold mode method, it goes without saying that the larger the n value, the more advantageous it is in terms of cost.

In such a multi-time recording method using the n-times mode method, a part of the unused portion of the ink layer is always supplied each time printing is performed, so the multiple times recording method using the constant-velocity mode method, which is simply a repeated use of the used portion, is indispensable. Compared to the repeat recording method, it has the advantage of reducing variations in the amount of remaining ink due to recording history (IEICE Transactions CvoQ J70-C, No.
11, pp. 1537-1544, November 1987).

However, in the sublimation thermal transfer recording method, the sublimation and evaporation reactions are basically zero-order reactions, and even in the n-fold mode method, even though the ink layer contains a sufficient amount of dye to withstand multiple uses. , as the n value increases, that is, as the relative speed of the recording medium decreases, the transfer density, especially in high image density areas, decreases, making it difficult to perform satisfactory printing 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.

However, in the above-mentioned recording medium, theoretically, the dye supply layer generally has a small content of binder resin in order to increase the dye concentration or increase the diffusion coefficient, as will be described later. If the recording conditions were changed (for example, when the applied voltage was increased or the receiving layer was changed), the entire ink layer would be transferred to the image receptor side (so-called ink layer peeling), which would impair image quality. .

Further, as described above, when recording is attempted many times using the N-times mode method, there is a risk that the dye transfer contributing layer and the surface of the image receptor will come into closer contact or friction, resulting in poor running. [Problems to be Solved by the Invention] An object of the present invention is to eliminate the above-mentioned drawbacks of the conventional n-time mode method, to achieve a method that hardly reduces the transferred image density even with an increase in the n value, and to provide It is an object of the present invention to provide a sublimation type thermal transfer recording method that does not cause layer peeling or fusion and prevents running defects.

[Structure and operation of the invention]

The sublimation thermal transfer recording method of the present invention is a sublimation thermal transfer recording medium in which a dye supply layer and a transfer contribution layer each having a sublimable dye dispersed in a resin binder are laminated on a substrate in order from the substrate side. Layer the image-receiving sheets on top of each other and run both under the conditions of [image-receiving sheet speed]/[recording medium speed]>1 or [image-receiving sheet feed amount]/[recording medium feed amount]>1. , a substance having lubricity or release properties is interposed between the transfer contributing layer of the recording medium and the image receiving sheet, and thermal printing is performed from the recording medium side to transfer the dye in the transfer contributing layer in that area onto the image receiving sheet. It is characterized by sublimation transfer. The recording method of the present invention has a configuration as shown in FIG. Here, 1 is a substrate, 2 is an ink layer consisting of a dye supply layer 4 and a dye transfer contributing layer 5, 6 is a thermal head, and 7
indicates a substance that has slipperiness or mold release properties. A substance having lubricity or release properties is applied to the dye transfer contributing layer or the image receiving sheet by coating with a roller or spraying, etc. before print recording, and is applied to the transfer contributing layer of the thermal transfer recording medium and the image receiving sheet. It is sufficient to intervene between the two.

Examples of substances having lubricity or mold release properties (lubricity substances) used in the recording method of the present invention include petroleum-based lubricating oils such as liquid paraffin, hydrogen halides, diester oils, silicone oils, and fluorine-containing oils. Synthetic lubricating oils such as silicone oil, various modified silicone oils (epoxy modified, amino modified,
(alkyl-modified, polyether-modified, etc.), silicone-based lubricating oil substances such as copolymers of silicone and organic compounds such as polyoxyalkylene glycol, various fluorine-based surfactants such as fluoroalkyl compounds, trifluorochloride ethylene low polymers Fluorinated lubricating oil substances such as fluororesins, waxes such as paraffin wax and polyethylene wax, higher fatty acids, higher fatty alcohols, higher fatty acid amides,
Examples include higher fatty acid esters, higher fatty acid salts, and the various particles mentioned above as particles having lubricity or heat releasability.

Next, the sublimation type thermal transfer recording medium used in the method of the present invention will be explained.

The thermal transfer recording medium of the present invention has a conventional homogeneous ink layer provided on a substrate, a transfer contributing layer as a surface layer having the function of sublimation-transferring a sublimable dye onto an image receiving sheet, and a dye in this surface layer. By adopting a multi-layer structure in which the dye supply layer has a function of diffusing and supplying the dye and the dye supply layer is separated, the reduction in transferred image density caused by multiple printing is improved.

In such a recording medium, during thermal printing, the sublimable dye is sublimated and transferred from the transfer supply layer onto the image receiving sheet via the free surface, but at the same time, the dye from the lower dye supply layer is transferred to this transfer supply layer. Supplied diffusely. In this case, in order to obtain a high-density transferred image, it is of course desirable that the amount of dye supplied to the transfer contributing layer be commensurate with the amount of dye consumed in the transfer contributing layer. To achieve this, it is necessary to facilitate the diffusion and supply of dye from the dye supply layer to the transfer supply layer during printing.
As a means for this, there is a method that utilizes the difference in concentration or the difference in diffusion coefficient of the dye between the two layers, as described below.

According to the findings of the present inventors, the diffusion of dye in the ink layer follows Fick's law, that is, the amount of dye dn passing through the cross-sectional area q in time dt is the concentration gradient of the dye in the diffusion direction as dc/dx, When (2) is the average diffusion coefficient of each part in the ink layer when heat is applied, the following relationship is applied: dn=-U(dc/dx)qdt.

Therefore, as a means for making it easier for the sublimable dye to be constantly diffused and supplied from the dye supply layer to the transfer contribution layer, there are the following: (1). With regard to dye concentration, the relationship of dye supply layer>transfer contributing layer should be established; and/or (1). Regarding the diffusion coefficients in each layer, it is possible to establish a relationship of dye supply layer>transfer contribution layer.

Furthermore, as a specific method for manipulating the diffusion coefficient with respect to the above H, for example, Toyoko Sakai et al., Journal of the Japanese Society of Textile Technology Vol. 30,
Nα1.2 (1974); “Dyeing Theory Chemistry” by Nobuhiko Kuroki, published by Maki Shoten, p. 503; introduced in the 1st Non-Impact Blinting Technology Symposium Proceedings 3-5, etc.

Referring 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 binder, etc. 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 for the transfer contributing layer; (2) The diffusion coefficient is determined by dispersing the dye. The binder is dependent on the glass transition or softening temperature, and the diffusion coefficient is higher when the glass transition or softening temperature is lower than the temperature rise characteristics of the layer during printing in this process. (3) A method using a substance having a lower glass transition temperature or lower softening temperature than that of the transfer contributing layer; A method of incorporating a plasticizer that is incompatible with the binder in the dye supply layer, (4) the above (1). Examples include a method in which methods (2) and (3) are appropriately combined, but it goes without saying that the method is not limited to these methods as long as the above-mentioned relationship of diffusion coefficients is satisfied.

In designing the material formulation of the dye supply layer and the transfer contributing layer in the recording medium of the present invention, the above means I and/or (2) are useful. In addition, as a simple method to confirm whether the intended improvement has been achieved through these effects, the dye supply layer and transfer contribution layer are each formulated as a single layer with the same amount of adhesion on the substrate, and each is coated separately. There is a method of checking whether the amount of sublimation transfer of dye is in the relationship of dye supply layer>transfer contributing layer when a separate image receiving sheet is overlapped and a constant sublimation temperature is applied.

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 0.5 μm.
~8μ■.

The sublimable dye, binder, etc. used in the transfer contribution layer and dye supply layer as described above may be known ones.

Sublimable dyes may be dyes that sublimate or vaporize at 60° C. or higher, and are mainly used in the field of thermal transfer recording, such as disperse dyes and oil-soluble dyes, such as C.I. I. Disperse yellow 1, 3, 8, 9, 16, 41, 5
4, 60, 77, 116, etc., C. I. Dispersed thread 1, 4, 6, 11, 15, 17, 55, 5
9, 60, 73, 83, etc., C. I. Disperse blue 3.14, 19, 26, 56, 60, 64, 72
, 99, 108, etc., C. I. Solvent Yellow 7
7,116 etc., C. I. Solvent Red 23.2
5.27 etc.C. I. Solvent blue 36.83,
105 and the like. These dyes may be used alone or in combination.

Thermoplastic or thermosetting resins are used as the binders used in the transfer contribution layer and the dye supply layer, and examples of resins with relatively high glass transition points or high softening properties include vinyl chloride resins and acetic acid resins. Vinyl resin, polyamide, polyethylene, polycarbonate, polystyrene, polypropylene, acrylic resin, phenolic resin, polyester, polyurethane, epoxy resin, silicone resin, fluororesin, butyral resin, melamine resin, natural rubber, synthetic rubber, polyvinyl alcohol, various celluloses , and copolymers thereof. These resins may be used alone or in combination.

Furthermore, when a difference is made in the glass transition or softening temperature between the transfer contribution layer and the dye supply layer, the glass transition temperature is 0.
℃ or less, or a resin or natural or synthetic rubber with a softening temperature of 60℃ or less, specifically syndiotactic 1.2
-Polybutadiene (JSR RB810 as a commercial product,
820, 830, Japan Synthetic Rubber); Olefin copolymers and turborimers containing acids or non-acidic acids (Dexon XEA-7, Dexon Chemical as commercial products); Ethylene-vinyl acetate copolymers (400 & 400 as commercial products)
A, 405, 430, Allied Fibers &Plastics; P-3307 (EV150), P-2
807 (EV250), Mitsui DuPont Polychemical)
:Low molecular weight polyolefin polyol and its derivatives (Polytail H. HE Mitsubishi Chemical Industries, Ltd. as a commercial product):
Brominated epoxy resin (YDB-340, 400, 5
00, 600 Tobu Kagaku); Novolak type epoxy resin (YDCN-701, 702, 703, Tobu Kagaku);
Thermoplastic acrylic resin solution (Dianal LR1075
,1080, 1081, 10g2, 1063,1
079, Mitsubishi Rayon) = thermoplastic acrylic resin emulsion E (LX-400, LX-450, Mitsubishi Rayon); polyethylene oxide (Alcox E-3
0.45, Alcox R-150, 400,
1000, Meisei Chemical Industry); caprolactone polyol (Plaxel H-1.4,7, Daicel Chemical Industry);
Among them, polyethylene oxide and polybrolactone polyol are particularly useful for practical use, and it is also preferable to use them in a mixture with the above-mentioned thermoplastic or thermosetting resin and one or more of the above-mentioned resins. The dye concentration (content) of the transfer contributing layer is usually about 5 to 80% (by weight, hereinafter the same), preferably about 10 to 60%. On the other hand, the dye concentration in the dye supply layer is usually 5 to 8.
However, when creating a dye concentration gradient between the transfer contribution layer and the dye supply layer, the dye concentration in the dye supply layer is 1.1 to 5 times the dye concentration in the transfer contribution layer, preferably 1. .5
~3 times is appropriate. Substrates include capacitor paper, polyester film, polystyrene film, polysulfone film,
Films such as polyimide film and polyamide film are used. If necessary, a conventional adhesive layer may be provided between the substrate and the dye supply layer, and a conventional heat-resistant adhesive layer may be provided on the back side of the substrate (the surface opposite to the ink layer), if necessary. A lubricating layer may also be provided. The plasticizer used in the method (3) above may be any known plasticizer, but one with excellent heat resistance and volatility is preferred. Examples of such plasticizers include tricresyl phosphate, tri-2-ethylhexyl phosphate, triphenyl phosphate, di-2-ethylhexyl phthalate, diisodecyl phthalate, ditridecyl phthalate, and the like. Examples of compatible and incompatible resins for binding that can be combined with these plasticizers are listed in the table below. Literature on plasticizers includes, for example, Sakura Yamada,
"Plastic compounding agent" (Published by Taiseisha, p.l7-)
9887 Chemical Products” (published by Kagaku Kogyo Nippo, p.
．． 745-''), etc. In any case, the blending ratio of the plasticizer to the resin is usually 10 to 100%, preferably 10 to 50%.

The above thermal transfer recording medium has been described as an example in which the ink layer is divided into two layers, but if the recording medium of the present invention has an effect of improving the reduction in transferred image density during multiple printing due to the functional separation intended, three or more layers can be formed. It is also possible to have multiple layers.

In addition to thermal heads, thermal printing means include thermal printing plates,
Laser light (in this case, a substrate that generates heat by absorption of laser light is used) or a method that utilizes Joule heat generated by making the substrate and/or ink layer conductive can be used. Among these, the so-called electric thermal transfer method, which uses Joule heat generated in the medium, is the most well-known.
It is described in many documents such as JP-A No. 7-14060, JP-A No. 57-11080, and JP-A No. 59-9096.
When using the current transfer method, the base material is a relatively heat-resistant resin such as polyester, polycarbonate, triacetylcellulose, polyamide, polyimide, aromatic polyamide, etc., and aluminum, copper, iron, tin, zinc, or nickel. , metal powders such as molybdenum, silver, and/or conductive powders such as carbon black are dispersed, and the resistance value is adjusted to be between that of an insulator and a good conductor. It is sufficient to use vapor-deposited or sputtered material. The thickness of these substrates is preferably about 2 to 15 microns 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 such a light absorption layer is formed on the front or back surface 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.
Furthermore, between the dye supply layer and the dye transfer contribution layer, there is an intermediate layer to prevent unnecessary movement of the dye from the dye supply layer to the dye transfer contribution layer during non-recording (during storage). may be provided.

The present invention will be explained below in more detail with reference to Examples. All parts are by weight.

Example 1 Composition for dye supply layer: Toluene Methyl ethyl ketone Composition for transfer contribution layer: Polyvinyl butyral resin BX-1 Sublimation dye KAYASET BLUE714 Toluene 100 parts 100 parts 10 parts 10 parts 100 parts Methyl ethyl ketone 100 parts The mixture was dispersed in a ball mill for a time, and a sublimation type thermal transfer recording medium having the structure shown in FIG. 1 was prepared using these dispersions in the following manner.

First, a polyimide film with a thickness of 8.5μI (
The dispersion for the dye supply layer 4 was coated and dried using a wire bar (manufactured by DuPont Toray Co., Ltd.) to form a dye supply layer with a thickness of 2.40 μm, and then the dispersion for the transfer contribution layer 5 was applied on top of the dispersion for the transfer contribution layer 5. A sublimation thermal transfer recording medium was prepared by coating and drying to form a transfer contribution layer with a thickness of 0.61 μm. Next, the ink M2 surface of this recording medium is coated with silicone oil as a substance having lubricity or release properties using a roll (Hitachi Video Printer VY-50
Supplies for VY-5100) 3 are overlapped and the thermal head 6 is used from the recording medium side to obtain the highest printing energy 2.
21 mj/dot and speed ratio n of image receiving paper and recording medium =
Printing was performed under conditions of 1 to 15 (V in the figure is speed).

Example 2 The same procedure as in Example 1 was repeated except that image receiving paper coated with Teflon particles (manufactured by Daikin Industries, Ltd., having an average particle size of about 5 μm) was used as a substance having lubricity or mold release properties.

The above results are shown in FIG. The maximum transferred image density (optical density) is 1 degree, and the Macbeth densitometer RD-51
Measured at 4. As can be seen from this figure, Examples 1 and 2
In the case of , almost no decrease in image density was observed up to a speed ratio of 15, and on the other hand, no ink layer peeling or fusion between the ink layer and the image-receiving sheet occurred, resulting in good running performance and high-quality images. Understood.

[Function and effect of the invention]

The method of the present invention combines a sublimation thermal transfer recording medium, in which the ink layer is functionally separated into a dye supply layer and a transfer contribution layer, with an n-fold mode method by interposing a substance having lubricity or release properties. Therefore, even with an increase in the n value, there is almost no decrease in the transferred image density, and neither ink layer peeling nor fusion between the ink layer and the image-receiving sheet occur, resulting in good running properties and high-quality images.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an example of the method of the present invention, and FIG. 2 is a graph showing the relationship between the speed ratio of the image receiving sheet/thermal transfer recording medium and the transferred image density in Examples 1 and 2. DESCRIPTION OF SYMBOLS 1...Substrate 2...Ink layer 3...Image receiving sheet 4...Dye supply layer 5...Transfer contributing layer 6...Thermal head 7...Lubricity or mold release property substance that has

Claims (1)

[Scope of Claims] 1. Dye transfer of a sublimation type thermal transfer recording medium comprising a dye supply layer and a dye transfer contributing layer each having a sublimable dye dispersed in a resin binder laminated on a substrate in order from the substrate side. An image-receiving sheet is stacked on the contributing layer, and both are run under the conditions of [image-receiving sheet speed]/[recording medium speed]>1 or [image-receiving sheet feed amount]/[recording medium feed amount]>1. In a sublimation thermal transfer recording method in which thermal printing is performed from the recording medium side and the dye in the transfer contributing layer in that part is sublimated and transferred onto the image receiving sheet, between the dye transfer contributing layer of the recording medium and the image receiving sheet, A sublimation thermal transfer recording method characterized by intervening a substance having lubricity or releasability.