JPH0364318B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF APPLICATION IN INDUSTRY This invention relates to dye-donor elements for use in thermal dye transfer, and more particularly to subbing layers (hereinafter referred to as Dye blocking/undercoat layer”,
``blocking/subbing layer'' or simply ``subbing layer''). TECHNICAL FIELD In recent years, thermal transfer systems have been developed to obtain prints from images generated electronically from color video cameras. According to one method of obtaining such prints, the electronic image is first subjected to color separation by color filters. The images after each color separation are then converted into electronic signals. These signals are then manipulated to create cyan, magenta and yellow electronic signals. These signals are then transmitted to a thermal printer. To obtain a print, a cyan, magenta, or yellow dye-donor element is placed opposite a dye-receiver element. The two are then inserted between the thermal print head and the platen roller. Heat is applied from the back of the dye donor sheet using a linear thermal print head. The thermal printhead has many heating elements that are heated sequentially in response to cyan, magenta, and yellow signals. This process is then repeated for the other two colors. A color hardcopy is thus obtained, which corresponds to the original picture seen on the screen. Further details of this process and the apparatus for carrying it out are disclosed in U.S. Pat. JP-A-60-19138 discloses an image-receiving element for thermal dye transfer printing. In Example 3 of that publication, a dye-donor element is also described in which a 2 g/m ² gelatin subbing layer is located between the dye layer and the support. It would be desirable to increase the dye density obtainable with this type of device. In European Patent Application No. 109295, a "base coat" such as polycarbonate or polyester
A dye-donor sheet having the following properties is disclosed. These basecoats are said to be hydrophilic and melt when the sheet is heated. Since most dyes used in thermal printing are also hydrophilic, they easily diffuse into such layers, thus reducing the amount of dye available for transfer. Problems to be Solved by the Invention For dye layers that are applied directly onto a support for the dye-donor element of a thermal dye transfer print, such as poly(ethylene terephthalate), the dye is transferred to the support during the transfer process. The problem is that it is wasted due to uncontrolled and directionless diffusion into the interior. The dye-donor support has the inherent property of softening during heating and acting as a receiver for the dye. The dye lost through this wasteful diffusion results in less dye being transferred to the dye-receiving element. Since the background density in a thermal dye transfer system is essentially constant, any increase in the density of transferred dye in the image area results in improved color discrimination, which is highly desirable. Another problem with dye-donor elements used in thermal transfer is obtaining adequate adhesion between the dye layer and the support. A separate subbing layer is usually used. It is an object of the present invention to eliminate the need for a separate subbing layer in the dye-donor element. Another object of the present invention is to provide a method for increasing transferred dye density. Means for Solving the Problems These and other objects are achieved in accordance with the present invention, which comprises a support having a dye layer thereon, and a hydrophilic dye blocking/subbing layer comprising a dye dye layer. It consists of a dye-donor element for thermal dye transfer located between the layer and the support, the dye blocking/subbing layer being a (butyl acrylate/2-aminoethyl methacrylate/2-hydroxyethyl methacrylate) copolymer, (N -isopropylacrylamide/2-aminoethyl methacrylate/2-hydroxy methacrylate) copolymer, (2-chloroethylacrylamide/methacrylic acid) copolymer or gelatin nitrate. The weight ratios of the components in these acrylic polymers can vary widely and are not critical. In a preferred embodiment of the invention, the dye blocking/subbing layer is present in an amount up to 1.8 g/m ² . In another preferred embodiment of the invention, the dye blocking/subbing layer consists of gelatin nitrate. This material is a mixture of gelatin, cellulose nitrate, and salicylic acid (20:
5:2) obtained by applying a solution. Any dye may be used in the dye layer of the dye-donor element of this invention, so long as it is transferable to the dye-receiving layer by the action of heat. Particularly good results have been obtained with sublimable dyes, such as: or with any of the dyes disclosed in US Pat. No. 4,541,830. The above dyes may be used alone or in combination to obtain a single color. Dye is 0.05
It may be used at a coverage of ~1 g/m ² and is preferably hydrophobic. The dye in the dye-donor element of the invention is a cellulose derivative, such as cellulose acetate hydrogen phthalate, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose triacetate; polycarbonate; (styrene/acrylonitrile) copolymer, poly(sulfone) or dispersed in a polymeric binder such as poly(phenylene oxide). The binder may be used at a coverage of 0.1 to 5 g/m ² . The dye layer of the dye donor element may be coated onto the support or printed thereon by printing techniques such as gravure. Any material can be used as the support for the dye element of this invention, so long as it is dimensionally stable and capable of withstanding the heat of the thermal print head. Such materials include polyesters such as poly(ethylene terephthalate); polyamides; glassine paper; condenser paper; cellulose esters;
Fluorine polymer; polyether; polyacetal;
Includes polyolefins; and polyimides. The support generally has a thickness of 2 to 30 μm. The backside of the dye-donor element may be coated with a slipping layer to prevent the print head from sticking to the dye-donor element. Such a sliding layer may contain surfactants, surfactants, with or without a polymeric binder.
Consists of lubricating substances such as liquid lubricants, solid lubricants or mixtures thereof. The dye-receiving element used with the dye-donor element of this invention usually consists of a support having a dye image-receiving layer thereon. For example, the support may be a transparent film, such as poly(ethylene terephthalate), or it may be reflective, such as baryta-coated paper or white polyester (polyester with white pigments incorporated therein). The dye image-receiving layer may be made of, for example, polycarbonate,
polyurethane, polyester, polyvinyl chloride,
(styrene/acrylonitrile) copolymers, poly(caprolactam) or mixtures thereof. As noted above, the dye-donor elements of the present invention are used to form dye transfer images. Such a process involves imagewise heating of the dye-donor element as described above;
It consists of transferring a dye image to a dye-receiving element to form a dye-transfer image. The dye-donor elements of the invention may be used in sheet form or as a continuous roll or ribbon.
If continuous rolls or ribbons are used,
It may carry only one dye on it,
Alternatively, it may have different regions of different dyes such as sublimable cyan, magenta, yellow, black, etc., as described in US Pat. No. 4,541,830. In a preferred embodiment of the invention, the dye-donor element comprises a poly(ethylene terephthalate) support coated with sequentially repeating regions of cyan, magenta and yellow dyes as described above, and the process steps described above are performed in order for each of the dyes. It is performed in color to obtain a three-color dye transfer image. Of course, when the process is only carried out for a single color, a monochromatic dye transfer image is obtained. Thermal print heads that can be used to transfer dye from the dye-donor elements of this invention are commercially available. For example, Fujitsu thermal head (FTP-
040MCS001), TDK thermal head F415HH7−
1089 or ROHM Thermal Head KE2008
−F3 can be used. A thermal dye transfer assembly employing the present invention comprises (a) a dye-donor element as described above, and (b) a dye-receiving element as described above, the dye-receiving element being in superimposed relationship with the dye-donor element. The dye layer of the donor element is then in contact with the dye image-receiving layer of the receiver element. The assembly of these two elements may be preassembled as an integral unit when it is desired to obtain a monochromatic image. This may be done by temporarily gluing the two elements together at their edges. After transfer, the dye-receiving element is then peeled away to create a dye-transferred image. When it is desired to obtain a three-color image, the above assemblage is changed to three while the heat is applied by the thermal print head.
times are formed. After the first dye has been transferred, the element is peeled off. A second dye-donor element (or another area of the donor element with a different dye area) is then aligned with the dye-receiver element and the process repeated. A third color is obtained in a similar manner. The following examples are provided to illustrate the invention. Example 1 (A) A dye-donor element according to the invention was made by coating the following layers in the order listed on a 6 μm poly(ethylene terephthalate) support. (1) Dye blocking/priming layer of gelatin nitrate (gelatin, cellulose nitrate, and salicylic acid in a weight ratio of approximately 20:5:2 in acetone, methanol, and water solvents) with coverage as shown in Table 1 ( 2) Applied from tetrahydrofuran, 0.15
g/m ² of 2-ethyl-2-hydroxymethyl-1,3-propanediol and 0.54 g/m ² of high viscosity cellulose acetate in a binder of magenta dye (0.15 g/m ² ). Contains a dye layer. (B) A control element was made identical to (A), but without the dye blocking/subbing layer. (C) Another dye-donor element was made as in (A) except that the dye layer was 8% in 2-butanone.
0.22 g/m ² magenta dye and 0.39 g/m ² applied from cyclohexanone and 11% acetone
of cellulose acetate and hydrogen phthalate (18-21% acetyl, 32-36% phthalyl). (D) Another control element was made identical to (C), but without the dye blocking/subbing layer. Dye-Receiving Element For Donor Elements A and B, the dye-receiving element consists of a reflective paper support with a water-resistant poly(ethylene) titanium dioxide overcoat, which is coated with Urarak P-2504 (GCA Chemical Corporation) hydroxylated polymer. branched polyester resin
It was coated with a dye image-receiving layer consisting of 4.8 g/m ² . For donor elements (C) and (D), 2.9 g/m ² of Macrolon 5705 (Bayer AG) polycarbonate resin was coated onto an IC Melinex 990 white polyester support from a solvent mixture of dichloromethane and trichloroethylene. The dye side of a 0.75 inch (19 mm) wide strip of dye-donor element was placed in contact with the dye image-receiving layer of a dye-receiver element of the same width. Stepper this assembly.
It was secured with the jaws of a motor-driven tensioner. Place the assembly on top of a 0.55 (14 mm) diameter rubber roller;
A Fujitsu thermal head was spring-loaded with 3.5 pounds (1.6 Kg) force toward the dye-donor side of the assembly, forcing the assembly toward the rubber roller. The imaging electronics were activated and the pulling device pulled the assembly between the print head and the roller at 0.123 inches/second (3.1 mm/second).
At the same time, the resistive element in the thermal print head is
milliseconds, heating in 4.5 millisecond increments from 0 to create a step density test pattern. The voltage supplied to the print head was approximately 19 volts, representing approximately 1.75 watts/dot. Estimated head temperature is 250-400
It was warm at ℃. Separate the assembly, discard the dye-donor element, and transfer the dye to the dye-receiver element using an X-Lite 338 color reflection densitometer with a Status A filter.
It was measured with The following results were obtained.

TABLE The results show that the gelatin nitrate dye blocking/subbing layer of the present invention is effective in significantly increasing D-max compared to the control without dye blocking/subbing layer. Example 2 (A) A dye-donor element according to the invention was coated with 6 μm poly(ethylene terephthalate) with the following layers in the order listed:
It was prepared by coating it on a support. (1) A dye blocking/subbing layer of (butyl acrylate/2-aminoethyl methacrylate/2-hydroxyethyl methacrylate) copolymer (30:10:60 weight ratio) with coverage as shown in Tables 2 and 3, and ( 2) Cellulose acetate propionate binder (2.5% acetyl,
45% propionyl) (0.34g/m ² ),
Dye layer containing the following magenta dye (0.17 g/m ² ). On the back side of this element, tetrahydrofuran:
(styrene/acrylonitrile) applied from a cyclopentanone (90:10) solvent mixture
Copolymer (weight ratio 70:30) binder (0.58
Gafatsuku RA600 in g/ ^m2 )
(GAF), complex phosphate mono- and di-
Ester nonionic surfactant, (0.032g/
m ² ), a slip layer was applied. (B) The dye donor element was made in the same manner as in (A), but
However, the barrier/undercoat layer had a weight ratio of 30:20:50. (C) The dye donor element was made in the same manner as in (A), but
The barrier/subbing layer had a weight ratio of 48:12:42. (D) The dye donor element was made in the same manner as in (A), but
However, the barrier/undercoat layer was a (N-isopropylacrylamide/2-aminoethyl methacrylate/2-hydroxy methacrylate) copolymer in a weight ratio of 50:5:45. (E) The dye donor element was made in the same way as (D), but
However, the barrier/undercoat layer had a weight ratio of 70:5:25. (F) The dye donor element was made in the same manner as in (A), but
However, the barrier/priming layer was a (2-chloroethyl acrylamide/methacrylic acid) copolymer (95:5 weight ratio). (G) The dye donor element was made in the same manner as (F), but
However, the barrier/subbing layer had a weight ratio of 98:2. (H) The dye donor element was made in the same manner as in (A), but
However, the barrier/subbing layer was gelatin nitrate. (I) A control dye-donor element was made as in (A) but without the blocking/subbing layer. (J) A control dye-donor element was made as in (A) except that the blocking/subbing layer was gelatin. (K) A control dye-donor element was prepared by applying a subbing layer of (acrylonitrile/vinylidene chloride/acrylic acid) copolymer (14:80:6 weight ratio). The dye-receiving element was prepared using a solution of Macrolon/5707 (Bayer AG) polycarbonate resin (2.9 g/m ² ) and mold release agent FC-431 (3M) (40 mg/m ² ) on an ICI Melinex 990 white polyester support. The above was prepared by coating from a solvent mixture of methylene chloride and trichloroethylene. The dye side of a 1 inch (25 mm) wide dye-donor element was placed in contact with the dye image-receiving layer of a dye-receiving element of the same width. This assembly was secured in the jaws of a Stepper motor-driven tensioner. Place the assembly on top of a 0.55 (14 mm) diameter rubber roller;
8 TDK thermal head L-133 (No.C6-0242)
A force of pounds was applied by the spring to force the assembly toward the dye-donor element, forcing the assembly toward the rubber roller. The imaging electronics were activated and the pulling device pulled the assembly between the printhead and rollers at a speed of 0.123 inches/second (3.1 mm/second). At the same time, the resistive elements within the thermal print head were pulsed for approximately 8 milliseconds to produce a full density image. The voltage supplied to the print head was approximately 22 volts, and the maximum power was approximately 1.5 watts/
dot (12 joules/dot). Each dye acceptor was separated from the dye donor element and the maximum green Status A reflection density was read. Each dye-donor element was also subjected to tape adhesion testing. Press a small area (approximately 1/2 inch x 2 inches) of 3M Highland 6200 Permanent Mending Tape firmly by hand onto the top dye layer of the dye-donor element, enough to serve as a handle for pulling the tape. A free area remains. When pulling the tape by hand, none of the dye layers in contact with the adjacent/subbing layer came off under ideal conditions. When the dye layer peeled off, this indicated a weak bond between the support and the coating layer. Effective subbing layers consistently have stronger bonds between other layers, thus preventing such dye layers from peeling onto the tape. The following categories were confirmed: E-Excellent (no peeling of the dye layer) G-Good (the amount and area of the peeling of the dye layer are negligible) F-Very good (the amount of peeling of the dye layer is small and the area is small) P - Not good (dye layer peels off over a considerable area) U - Unacceptable (dye layer peels off completely) The following results were obtained.

【table】

【table】

TABLE The results show that the dye blocking/subbing layers of the present invention are generally effective in obtaining good transferred dye density and at least adequate adhesion. Gelatin and acrylonitrile copolymer controls showed undesirable adhesion and dye transfer when used alone. Effects of the Invention The above-mentioned hydrophilic polymer used in the present invention has a hydrophilic property or solubility in a hydrophilic substance because most of the dyes used in thermal dye transfer printing are hydrophobic as described above. is negligible, so it functions as a dye blocking layer. Thus, the barrier layer prevents the transfer of dye into the donor element support in an inappropriate manner, resulting in an increased increase in transferred dye density. The hydrophilic polymers described above for use in the present invention also have adequate adhesion to the support and dye layer, thus eliminating the need for a separate subbing layer. The particular hydrophilic polymers mentioned above for use as the sole layer in the donor element thus serve a dual function and are therefore referred to as dye blocking/subbing layers.

Claims (1)

[Scope of Claims] 1. A dye-donor element for thermal dye transfer consisting of a support having a dye layer on the upper surface, wherein a hydrophilic subbing layer having dye-blocking properties is between the dye layer and the support. The undercoat layer is (butyl acrylate/2-
(aminoethyl methacrylate/2-hydroxyethyl methacrylate) copolymer, (N-isopropylacrylamide/2-aminoethyl methacrylate/2-hydroxymethacrylate) copolymer, (2-chloroethyl acrylamide/methacrylic acid) copolymer or gelatin nitrate; A dye donor element characterized by: