JPH07195854A - Image forming method based on thermal transfer method - Google Patents

Abstract

PURPOSE: To reduce wear of a thermal head by a method wherein when an assembly of dye-donor element and image receiving element is heated to form an image, a heating element corresponding to an image pixel for which no density is required during image-wise heating is activated so that an amount of heat is generated according to a specific formula. CONSTITUTION: A dye-donor element, having on a support a dye layer containing a thermally transferable dye, is placed, with the dye layer in face-to-face relationship with an image receiving element to provide an assemblage. And the assemblage is image-wise heated by activating a number of heating elements of a thermal head being in contact with the dye donor element, each of the heating elements corresponding to an image pixel. Thereafter, the dye-donor element is separated from the image receiving element. In this case, during the image- wise heating, heating elements corresponding to an image pixel for which no density is required are activated so that they generate an amount of heat He in accordance with the following formula: 0.5 HD<He <HDO, wherein HD represents a minimum amount of heat required to cause visible dye transfer from the dye donor element to the image receiving element.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to a method of forming an image according to a thermal transfer method in which an assembly of a dye-donor element and an image-receiving element is heated by a thermal head to form the image. More particularly, the present invention relates to thermal transfer methods in which thermal head wear is reduced.

[0002]

BACKGROUND OF THE INVENTION Thermal dye transfer methods include thermal dye sublimation transfer, also referred to as thermal dye diffusion transfer. This latter is
A recording method in which the amount of dye transferred to the image receiving element can be controlled by controlling the amount of heat applied to the assemblage of the dye-donor element and the receiving element.

Image-wise heating can be provided by a thermal head having a plurality of heating elements or heat generating resistors. Generally, the dye-donor element and receiver element assembly is heated by a thermal head from the back side of the dye-donor element, i.e., from the support side of the dye-donor element opposite the side containing the dye layer. The back of such dye-donor elements is generally provided with a backing layer containing a heat-resistant binder and a number of additives such as particles and lubricants to provide a backing layer on the thermal head. It ensures a smooth transfer of the dye-donor element.

Image-wise heating of the assembly is generally carried out row by row, in which the image information is divided in many rows, which are fed continuously to the thermal head. The image value (ima
It consists of a number of pixels that display a ge value). By activating each of the heating elements, one column being arranged along the other, one column of image data can be reproduced according to the image value of the pixel to which they correspond. For example, if the image value of a pixel is 0, the heating element for the corresponding pixel is not activated, but when displaying a certain density of the image value of the pixel, the pixel is activated and the desired density is displayed on the image receiving element. obtain. This method is repeated for every row of the image to obtain its perfect reproduction.

The problem with the above method is that the heating elements of the thermal head wear out after many prints. as a result,
Their efficiency is reduced resulting in poor image quality. When the image needs to be printed on a resin support, such as an image-receiving element based on a polyester film, and especially on a transparent image-receiving element, the hardness of the resin support surface is greater than that of the paper support. This problem is particularly noticeable.

[0006]

SUMMARY OF THE INVENTION One object of the present invention is to provide a method of forming an image according to a thermal transfer method which uses a thermal head with reduced wear of the thermal head.

Another object of the present invention is to provide an improved method for forming images on resin-based image-receiving elements.

Further objects of the present invention will be apparent from the following description.

According to the present invention, a dye-donor element is provided having on its support a dye layer containing a heat transferable dye in opposed relation to the image-receiving element, and the resulting assembly is placed in a thermal head. Image-wise heating by activating a plurality of heating elements in contact with the dye-donor element such that each of the plurality of heating elements corresponds to a pixel, and separating the dye-donor element from the image-receiving element. in the method for forming an image comprising the step of, during the imagewise heating of the heating elements corresponding to the pixels that are not required concentration, they are the following _{formulas: 0.5H D <H e <H} D (I) Where H _D represents the minimum amount of heat required to cause visible dye transfer from the dye-donor element to the image-receiving element.
The method is characterized by activating to produce an amount of heat (H _e ) according to.

[0010]

DETAILED DESCRIPTION OF THE INVENTION In accordance with the present invention, it has been found that wear of the thermal head can be reduced by activating the heating elements of the thermal head which correspond to pixels where density is not required. Activation of these heating elements, the heating elements is carried out in such a way as to generate an amount of heat (H _e) in accordance with the above formula (I). Preferably, the activation of the heating elements corresponding to the pixels for displaying the concentration of 0 is such that the amount of heat between 0.7 H _D and H _D is generated.

The amount of heat supplied to the heating element can be easily adjusted by adjusting the magnitude of the current flowing through the heat generating resistor of the heating element and / or the time the current flows through the heating element. . The actual amount of heat H _D depends on a number of factors, such as the type of dye-donor element and the receiving element, the temperature of the heat sink of the thermal head and the heater array of the thermal head, ambient temperature, and the like. The value of H _{D for} a particular combination can be readily determined by simple experimentation, where the amount of heat supplied to the heating element is increased in steps until a detectable concentration is produced. This value is then stored in the printer and the exact value of H _D for the particular combination of dye-donor element and receiver element can be retrieved and used during printing, either manually or automatically.

[0012] It minimal amount of heat to cause a visible dye transfer (H _D) is reduced during printing as the result of increase of the heat sink (heatsink) temperature of the thermal head will be appreciated. Therefore, in order to maintain it according to formula (I), H
It is necessary to adjust _e . This can be done by continuous measurement of the temperature of the heat sink during printing, and the results of this measurement can be used to be maintained according to the invention during printing.

The force exerted by the thermal head on the back of the dye-donor element in length units of the heater array is preferably 150 g /
between cm and 400 g / cm, and more preferably 250
It is between g and 400 g / cm. When too low a force is used the thermal head is strongly contaminated due to the poor quality of the image,
On the other hand, too great a force causes the thermal head to wear rapidly and lead to the destruction of the glass bulb of the thermal head. Inorganic particles added to the optional backing layer of the dye-donor element to avoid thermal head contamination also increase thermal head wear at high pressure. It is a particular advantage of the present invention that forces of up to 400 g / cm can be used to reduce thermal head contamination without substantially increasing thermal head wear.

The dye-donor element for use in accordance with thermal dye sublimation transfer comprises a very thin support, such as a polyester support, one side of which is coated with a dye layer comprising a printing dye. Generally, an adhesive or subbing layer is provided between the support and the dye layer. Suitably, the opposite side is coated with a heat resistant layer. An adhesive layer may be provided between the support and the heat resistant layer.

The heat resistant layer may suitably comprise a lubricating material in a heat resistant polymeric binder, such as a surface active agent, a liquid lubricant, a solid lubricant or mixtures thereof.
Surfactants are known in the art, such as carboxylates, sulfonates, phosphates, aliphatic amine salts, aliphatic quaternary ammonium salts, polyoxyethylene alkyl ethers, polyethylene glycol fatty acid esters, fluoroalkyl. it can be a C ₂ -C ₂₀ fatty acids. Examples of liquid lubricants include silicone oils, synthetic oils, saturated hydrocarbons and glycols. Examples of solid lubricants include various higher alcohols such as stearyl alcohol, fatty acids and fatty acid esters. Suitable lubricants are polyethylene oxide, modified polydimethylsiloxane and zinc stearate. The refractory layer is preferably solid particles such as inorganic particles such as salts derived from silica such as talc, clay, kaolin, mica, hypochlorite, silica, or carbonates such as calcium carbonate, magnesium carbonate or carbonate. Magnesium calcium (dolomite) can be further added to the heat resistant layer.

European Patent Application Publication No. 9320164
It is highly preferred to add to the heat-resistant layer a mixture of particles having a Mohs hardness of less than 2.7 and particles having a Mohs hardness of greater than 2.7 as described in 2.1.
A mixture of talc and dolomite particles is preferred.

The binder for the heat resistant layer is a hardened binder or a polymeric thermoplastic. The cured binder can be obtained by the chemical reactions described, for example, in EP 153,880 and EP 194,106, or for example in EP 9120.
It can be prepared by the influence of water as described in 2098.9 or by irradiation of the radiation-curable composition described in for example EP 314,348 and EP 458,538. .

Due to the fact that the coating process of polymeric thermoplastics is very convenient, they are preferably used as binders for heat-resistant layers. Suitable polymeric thermoplastics are those having a glass transition temperature above 100 ° C. and these thermoplastics are dimensionally stable at elevated temperatures and are therefore suitable for use as binders in heat resistant layers. Polymers having a glass transition temperature above 170 ° C. are particularly preferred. Further preferred polymeric thermoplastics are those that are soluble in economically acceptable solvents such as ketones (eg ethyl methyl ketone and acetone) and alcohols (eg isopropanol).

Representative examples of polymeric thermoplastics suitable for use as binders in the heat resistant layer are, for example,
(Styrene-co-acrylonitrile), bisphenol A
Derived from, polyvinyl butyral, polyvinyl acetal, ethyl cellulose, cellulose acetate butyrate, cellulose acetate propionate, and polyparabanic acid.

Particularly suitable polymeric thermoplastics have the general formula (II):

[0021]

[Chemical 1]

[Wherein R ¹ , R ² , R ³ and R ⁴ are each independently hydrogen, halogen, a C ₁ -C ₈ alkyl group, a substituted C ₁ -C ₈ alkyl group, C ₅ -C ₆ cycloalkyl group, a substituted C ₅ -C ₆ cycloalkyl group, C ₆ -C ₁₀
Aryl groups, substituted C ₆ -C ₁₀ aryl group, C ₇ -C
₁₂ aralkyl group or a substituted C ₇ -C ₁₂ aralkyl group, and X is alicyclic ring C ₁ -C ₆ alkyl may also be 5-～8- membered substituted with groups optionally, 5 −
Or a 6-membered cycloalkyl group or fused 5
Represents a necessary atom to complete a 6-membered cycloalkyl group] or a bis- (hydroxyphenyl) -cycloalkane derived polycarbonate. The heat-resistant layer produced in this way is about 0.0
It has a thickness of 1 to 3 μm, preferably 0.3 to 1.5 μm.

The dye layer of the dye-donor element may be a monochromatic dye layer, or it may be a dye in which it is colored differently, for example successive repeats of a dye having a shade of cyan, magenta, yellow and optionally black. It can also comprise parts. When a dye-donor element containing three or more primary color dyes is used, a multicolor image is obtained by successively performing the dye transfer process steps for each color.

The primary colored dye layer, eg the magenta or cyan or yellow dye layer, may also comprise only one primary colored dye (magenta, cyan or yellow dye respectively), or two or more thereof. It may also comprise a mixture of the above-mentioned primary dyes having the same color tone (two magenta dyes, two cyan dyes or two yellow dyes, respectively).

Any dye can be used in such dye layers provided it is readily transferable to the receiver sheet or element by the action of heat.

Typical individual examples of dyes for use in thermal dye sublimation transfer are eg EP 209,9.
90, European Patent 209,991, European Patent 216,483, European Patent 218,3.
97, European Patent 227,095, European Patent 227,096, European Patent 229,3.
74, European Patent 235,939, European Patent 247,737, European Patent 257,5.
77, European Patent 257,580, European Patent 258,856, European Patent 279,3.
30, European Patent 279,467, European Patent 285,665, US Patent 4,743,58.
2, U.S. Pat. No. 4,753,922, U.S. Pat. No. 4,
753,923, US Pat. No. 4,757,046, US Pat. No. 4,769,360, US Pat. No. 4,771,0.
35, U.S. Pat. No. 5,026,677.

The dye layer generally comprises a binder in which one or more dyes are dissolved or dispersed. The quantitative ratio of dye or dye mixture to binder is 9: 1 to 1: 3 by weight, preferably 3: 1 to 1: 2.
Is.

The following polymers can be used as polymeric binders: cellulose derivatives such as ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxycellulose, ethyl hydroxyethyl cellulose,
Hydroxypropyl cellulose, methyl cellulose, cellulose nitrate, cellulose acetate formate, cellulose acetate hydrogen phthalate, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate pentanate, cellulose acetate benzoate, cellulose triacetate; vinyl type resins and derivatives , For example polyvinyl alcohol,
Polyvinyl acetate, polyvinyl butyral, copolyvinyl butyral-vinyl acetal-vinyl alcohol, polyvinyl pyrrolidone, polyvinyl acetoacetal, polyacrylamide; polymers and copolymers derived from acrylates and acrylate derivatives, such as polyacrylic acid, polymethyl Methacrylate and styrene-acrylate copolymers; polyester resins; polycarbonates; copoly (styrene-co-acrylonitrile); polysulfones; polyphenylene oxides; organosilicones such as polysiloxanes; epoxy resins and natural resins such as gum arabic. Preferably, the binder for the dye layer of the present invention comprises poly (styrene-co-acrylonitrile) or a mixture of poly (styrene-co-acrylonitrile) and toluenesulfonamide condensation products.

The dye layer may also contain other additives such as thermal solvents,
Stabilizers, hardeners, preservatives, organic or inorganic fine particles,
It may also contain dispersants, antistatic agents, antifoaming agents, and viscosity modifiers, and these and other ingredients are described in EP 133,011, EP 133,
012, EP 111,004 and EP 279,467 are more fully described.

European Patent Application Publication No. 9220349
The addition of polyolefin wax or amide wax beads and / or polymethylsilylsesquioxane particles to the dye layer as described in 6.2 is particularly preferred, the beads and / or particles protruding from the surface of the layer. .

Magnetic coating can be provided on one or both sides of the dye-donor element. The magnetic layer may be on the entire surface of the dye-donor element or along a dye-frame where a detection mark is generally provided on a particular portion, such as an intermediate region between the dye-frames in a three-color dye element, or the dye-donor element You can coat at the beginning or end of. This magnetic coating can be used to write information about the dyes used in the dye-donor element, the manufacturing data, the type of receiving element used in combination with the dye-donor element, and the like.

20 msec at temperatures up to 400 ° C.
Is dimensionally stable over a period of time and resistant to that temperature and the heat applied to one side is transmitted through the dye to the other side, typically for such a short period of 1-10 msec. Any material can be used as a support for the dye-donor element provided it is thin enough to allow transfer to the receiver sheet in-house. Such materials include polyesters such as polyethylene terephthalate, polyamides, polyacrylates, polycarbonates, cellulose esters, fluorinated polymers, polyethers, polyacetals, polyolefins, polyimides, glassine paper. And condenser paper. A support comprising polyethylene terephthalate is suitable. Generally, the support is 2
It has a thickness of 30 μm. The support may optionally be coated with a subbing layer adhesive. Examples of suitable subbing layers are eg EP 433,496, EP 311, 841 and EP 26.
8,179, U.S. Pat. No. 4,727,057 and U.S. Pat. No. 4,695,288.

The support for the receiver element used in combination with the dye-donor element is a transparent resin support such as polyethylene terephthalate, polyether sulfone, polyimide, cellulose ester, or polyvinyl alcohol-co-acetal. Can be The support is reflective, such as barita coated paper, polyethylene coated paper or an opaque resin support,
For example, white polyester, that is, white pigment colored polyester may be used. A blue colored polyethylene terephthalate film can also be used as a support.

In order to avoid the poor adsorption of the transferred dye to the support of the receiving element, this support is preferably coated with a special layer called the image-receiving layer in which the dye can readily diffuse. The image-receiving layer can comprise, for example, polycarbonate, polyurethane, polyester, polyamide, polyvinyl chloride, polystyrene-co-acrylonitrile, polycaprolactone, or mixtures thereof. The image-receiving layer can also comprise the heat-cured product of poly (vinyl chloride-co-vinyl acetate-co-vinyl alcohol) and polyisocyanate. Suitable image-receiving layers are, for example, EP 133,011,
European Patent No. 133,012, European Patent No. 144,247, European Patent No. 227,094,
And European Patent No. 228,066.

UV absorbers, singlet oxygen scavengers, such as HALS compounds (sterically hindered amine light stabilizers) and / or antioxidants, in order to improve the light fastness and other stability of the recorded images. Agents can be added to the image receiving layer.

The dye layer of the dye-donor element or the image-receiving layer of the receiver sheet can also contain a release agent that aids in separating the dye-donor element from the receiver sheet after transfer. The release agent can be applied to at least part of the dye layer or image receiving layer in a separate layer. Suitable release agents are solid waxes, fluorine- or phosphate-containing surfactants and silicone oils. Suitable release agents are, for example, EP 133,012, JP 85 / 19,138, and EP 227,
092.

A subbing layer can be provided between the receiving layer and the support. Suitable subbing layers are based on vinylidene chloride copolymers, aromatic copolyesters and polystyrene sulphonic acid. A hydrophilic layer can be applied between the subbing layer and the dye receiving layer to enhance the reusability of the support. The hydrophilic layer generally comprises a water-soluble binder such as gelatin, polyvinyl alcohol, hydroxypropyl cellulose, hydroxyethyl cellulose or polystyrene sulfonic acid (or sodium salt), or mixtures thereof, anionic, cationic, nonionic. It comprises with or without zwitterionic or zwitterionic surfactants. A mixture of hydroxyethyl cellulose and polystyrene sulfonic acid is particularly suitable.

The following examples illustrate the invention but do not limit it to them. All parts are by weight unless otherwise noted.

[0039]

【Example】

Example 1 Copolyester ethylmethyl comprising isophthalic acid units / terephthalic acid units / ethylene glycol units / neopentyl glycol units / adipic acid units / glycerol units on both sides of a polyethylene terephthalate film having a thickness of 5.7 μm. An undercoat layer was provided from a solution in ketone.

A solution comprising 9% by weight of dye A, 2% by weight of dye B, and 10% by weight of poly (styrene-co-acrylonitrile) in ethyl methyl ketone as binder was prepared.

From the resulting solution, a layer having a wet thickness of 10 μm was coated on a subbed polyethylene terephthalate film. The resulting dye layer was dried by evaporation of the solvent.

Dye A

[0043]

[Chemical 2]

Dye B

[0045]

[Chemical 3]

A heat-resistant layer having a wet thickness of 10 μm was provided on the primed back of a polyethylene terephthalate film with a polycarbonate binder (13% by weight) having the structure shown below and 0.5% by weight of microdol. -Coated from a solution in ethyl methyl ketone containing Microdol Super (Norwegian talc).

Polycarbonate for heat resistant layer:

[0048]

[Chemical 4]

Here, n has a value which gives a polycarbonate having a relative viscosity of 1.295 (measured in a 0.5% by weight solution in dichloromethane).

The side of the donor element showing the heat resistant layer was coated with a topcoat making solution which was a 0.5 wt% solution of Tegoglide 410 (commercially available from Goldschmidt) in isopropanol.

Preparation of the receiving element: Polyethylene terephthalate with a thickness of 175 μm was added with 3.6 g / m ² of poly
(Vinyl chloride / co-vinyl acetate / co-vinyl alcohol)
(Vinylite (V supplied by Union Carbide
inylite) VAGD), 0.336 g / m ² diisocyanate (Desmodur supplied by Bayer AG
modur N 75) and 0.2 g / m ² of hydroxy-modified polydimethylsiloxane (Tegomer H SI 2111 supplied by Goldschmidt).
Receptor elements were prepared by coating a dye-image-receptive layer from a solution of ## STR3 ## in ethyl methyl ketone.

Printing step: 20 with the dye layer in face-to-face relationship with the image-receiving layer of the image-receiving element as described above.
0 meters of the above dye-donor element is a blank image, ie 0
It was printed with an image containing only the density. Behind the dye-donor element is a thermal head (Kyocera type KGT-219-12MP with a resistor length of 20 cm (8 inches).
4-12-SPM) and a force of 160 g / cm was applied to the dye-donor element-receiving element assembly. According to printing step A, the heating elements of the thermal head were not activated, whereas according to step B they were activated with an amount of heat corresponding to 85% of H _D.

Results: Thermal head wear was measured using an optical profilometer (Rodenstock). In the case of printing process A, 1.7μ at the center of the heating element
m was worn, but in the case of printing step B this is 0.1
It was less than μm.

Example 2 A dye-donor element was prepared similar to the dye-donor element described in Example 1, but with the addition of 0.5% zinc stearate in the heat-resistant layer. .

2200 meters of the dye-donor element so produced were used, followed by the printing process B described in Example 1 on the receiving element described in Example 1, but with a thermal head. Printed on the dye-donor element with a force of 350 g / cm.

It was found that the center of the heating element was worn less than 0.1 μm.

The main features and aspects of the present invention are as follows.

1. A dye-donor element having a dye layer containing a thermally transferable dye in opposing relationship with an image-receiving element is placed on a support, and the resulting assembly is provided with each of the plurality of heating elements of the thermal head forming a pixel. Image-wise heating by activating a plurality of heating elements in contact with the dye-donor element so as to correspond to, and separating the dye-donor element from the image-receiving element. in the method for forming, during heating of said image as the heating elements corresponding to pixels which are not required concentration, they are the following _{formulas: 0.5H D <H e <H} D (I) [ wherein, H _D is Represents the minimum amount of heat required to cause visible dye transfer from the dye-donor element to the image-receiving element]
Activating to produce an amount of heat (H _e ) according to.

2. A method according to claim 1 wherein the thermal head is in contact with the side of the support of the dye-donor element opposite the side bearing the dye layer and the thermal head exerts a force of 400 g / cm or less.

3. A process according to claim 1 or 2 wherein the dye-donor element comprises a heat-resistant layer comprising inorganic particles dispersed in a heat-resistant binder on the side of the support opposite the side carrying the dye layer.

4. A method according to any of the preceding clauses wherein said image-receiving element comprises an image-receiving layer on a support, said image-receiving layer being in face-to-face relationship with said dye layer during image-wise heating.

5. The method according to claim 4, wherein the support of the image receiving material is a resin support.

6. The method according to 4 or 5 above, wherein the image receiving material is transparent.

Claims (1)

[Claims] 1. A dye-donor element having a dye layer containing a thermally transferable dye in opposing relationship with an image-receiving element on a support, and the resulting assembly is provided with a plurality of heating heads. Image-wise heating by activating the plurality of heating elements in contact with the dye-donor element so that each of the elements corresponds to a pixel, and separating the dye-donor element from the image-receiving element. in the method for forming an image comprising, during the heating of said image as the heating elements corresponding to pixels which are not required concentration, they are the following _{formulas: 0.5H D <H e <H} D (I) [ Where H _D represents the minimum amount of heat required to cause visible dye transfer from the dye-donor element to the image-receiving element.
Activating to produce an amount of heat (H _e ) according to.