JP2911909B2 - Sublimation type thermal transfer recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a sublimation type thermal transfer recording medium for multiple recordings.

(Prior art)

Conventionally, two ink layers are formed, the outermost ink layer dye concentration <the support side ink layer dye concentration, the outermost ink layer dye diffusion coefficient <the support side ink layer dye diffusion coefficient, thereby increasing the sensitivity and maintaining the storage stability. A thermal transfer sheet has been proposed (see JP-A-63-47193).

A thermal transfer paper is also known in which a dye is dyed on the base film in an amount of 2 to 20 times the amount of the ink layer, and the dye is supplied from the base film to the ink layer each time, and the thermal transfer paper is used many times (Japanese Patent Application Laid-Open No.
63-176186).

However, these conventional devices still have insufficient printing ability for many times. In addition, in the latter case, since a large amount of dye is present in the base film itself, the strength of the film is reduced, and there is a disadvantage that it is difficult to be used as a ribbon.

In view of this, the present inventors have disclosed in Japanese Patent Application No. 63-268204 that the functions of a dye supply layer and a dye transfer contributing layer are separated into two ink layers and that a particulate dye is present in the dye supply layer. Improved printing ability many times.

However, due to the presence of the particulate dye, unevenness occurs on the surface of the lower layer (dye supply layer) due to aggregation of the dye particles.

Due to the unevenness, the large portion of the convex portion is not covered with the upper layer (dye transfer contributing layer) and is exposed, and the dye is transferred directly from the lower layer (supply layer) to the image receiving member during recording, and density unevenness occurs. As a result, the image uniformity tends to deteriorate, leaving room for improvement. The present invention is a further improvement of this prior invention.

〔Purpose〕

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sublimation type thermal transfer recording medium which overcomes the conventional disadvantages, has improved printing characteristics for a number of times, and has improved image quality.

〔Constitution〕

The present inventors have conducted intensive studies to achieve the above object, and as a result, on the substrate, in order from the substrate side, a dye supply layer containing at least an undissolved particulate sublimable dye and an organic binder, and at least In a sublimation type thermal transfer recording medium provided with an ink layer because a dye transfer contributing layer containing a molecularly dispersed sublimable dye and an organic binder is laminated, the surface roughness of the ink layer surface is JIS B0601. According to the measurement, it is determined that (i) when the average roughness of the center line is Ra ≦ 1.0 μm, or (ii) when the average roughness of the center line is Ra> 1.0 μm, the average interval between the irregularities is Sm ≦ 10 μm. It has been found that the object can be achieved by providing a sublimation type thermal transfer recording medium which is a feature.

That is, if the particulate dye is present in the dye supply layer, unevenness occurs on the surface of the ink layer, and as a result, uneven adhesion may occur between the ink layer and the image receiving layer.

Further, in the portion where the adhesion is insufficient, the dye diffusion is hindered (intervened by air), and normal dye diffusion transfer becomes impossible. (The recording density decreases.) As a result, it is considered that there is a sensitivity difference between n = 1 and n ≧ 2. However, in the measurement according to JIS B0601, the surface roughness of the ink layer is determined to be the center line average roughness. It has been found that, when having a smoothness of Ra ≦ 1.0 μm, good multi-time printing characteristics having no sensitivity difference between n = 1 and n ≧ 2 can be obtained.

Also, in the two-layer ink layer having a surface roughness of Ra> 1.0 μm, n = 1 and n ≧ 2 only when the average interval Sm of irregularities (irregularities) is Sm ≦ 10 μm, as in the case of Ra ≦ 1.0 μm.
It has been found that good multi-time printing characteristics having no sensitivity difference between them can be obtained.

Here, it is particularly problematic to eliminate the difference in sensitivity between n = 1 and n ≦ 2, and when n ≧ 2, n = 1
The surface of the ink layer is smoothed to soften (due to the heat from the thermal head, the pressure from the platen roller, the thermal head, etc.). As a result, normal dye diffusion transfer (normal recording density) is obtained when n ≧ 2.

<Definition of average interval Sm> As shown in Fig. 2, two peak count levels parallel to the center line of the roughness curve according to JIS B0601 are provided, and the lower peak count level and curve When there is one or more points where the upper peak count level and the curve cross one or more times between two points where.

However, when the peak count level is Ra ≦ 1.0 μm, the peak count level is set to 1.0 μm because the sensitivity difference is small and good multi-time recording characteristics are provided.

Next, when the distance between the peaks between the reference lengths is Smi, Or , And this Sm is defined as an average interval of unevenness (concavities and convexities).

In order to form an ink layer having desirable surface characteristics according to the present invention, it is necessary to control the particle diameter of the dye, or to apply and transfer the ink layer onto a substrate after forming the ink layer on the above-mentioned smooth member, or to transfer the dye onto the substrate. After applying and forming only the supply layer or both layers, it is easily formed by applying a load (using heat as needed) using a member having a smoothness higher than the above (metal roller or the like) and smoothing. it can.

Hereinafter, the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is an explanatory view showing the structure of a sublimation type thermal transfer recording medium of the present invention, wherein 1 indicates a support, and 2 indicates a dye supply layer 4.
And an ink layer composed of a dye transfer contributing layer 5 and
Reference numeral 3 denotes an image receiving body such as paper, and reference numeral 6 denotes a thermal head.

By mixing undissolved particulate dyes in the dye supply layer and providing an appropriate dye supply layer and concentration gradient and diffusion coefficient gradient between the dye transfer contributing layers, it is possible to perform good multiple recordings while maintaining the initial gradient each time. .

Here, the undissolved particulate dye refers to a dye which cannot be completely dissolved in the organic binder after the ink (organic binder + sublimable dye + solvent) is applied and dried at the time of forming the ink layer, and which precipitates as particles. This means that the same binder and dye have different undissolved particulate dyes depending on the solvent. The presence or absence of the undissolved particulate dye can be easily identified by an electron microscope after forming the dye supply layer. The particle size of the undissolved particulate dye varies depending on the thickness of the dye supply layer, but is preferably 0.01 μm to 20 μm, preferably
1.0 μm to 5 μm.

Further, the dye state in the dye transfer contributing layer is that it is dispersed in a monomolecular state which actually contributes to the transfer, preventing the occurrence of uneven transfer density, and the dye between the dye supply layer and the dye transfer contributing layer. It is desirable to keep the concentration gradient stable.

Next, the thickness of the dye transfer contributing layer is generally 0.05 to 5 μm.
m, preferably 0.5 to 1.5 μm, particularly preferably 0.6 to 1.5 μm.
1.2 μm. The thickness of the dye supply layer is generally
It is 0.1 to 20 μm, preferably 0.5 to 10 μm.

Here, if the thickness of the dye transfer contributing layer is too thin (for example, 0.
When the thickness is less than 5 μm), the dye supply layer containing particulate dyes and having surface irregularities cannot be completely covered, and the dye supply layer is exposed, and abnormal transfer of the dye at the exposed portion (dye transfer amount is large) As a result, the density unevenness tends to increase, and the image quality tends to decrease. On the other hand, if the thickness of the dye transfer contributing layer is too thick (for example, more than 1.5 μm), the diffusion distance of the dye in one recording is not infinite but finite. Cannot reach the vicinity of the surface of the dye transfer contributing layer, and as a result, the printing characteristic tends to decrease many times.

Known sublimable dyes, binders and the like used in the transfer contributing layer and the dye supply layer of the present invention can be used.

The sublimable dye is a dye that sublimates or vaporizes at 60 ° C. or higher, and may be any of those mainly used in thermal transfer printing such as disperse dyes and oil-soluble dyes.For example, CI Disperse Yellow 1,3,8, CI Disperse Blue 3,14,19, such as 9,16,41,54,60,77,116, CI Disperse Red 1,4,6,11,15,17,55,59,60,73,83 , 26,56,60,64,7
2,99,108, CI Solvent Yellow 77,116, etc.
CI Solvent Blue 23, 25, 27 and CI Solvent Blue 36, 83, 105 and the like can be mentioned. One of these dyes can be used, but a mixture of several dyes can be used.

Thermoplastic or thermosetting resin is used for the binder used for the dye transfer contributing layer and the dye supply layer. Among the resins having a relatively high glass transition point or high softening property, for example, vinyl chloride resin , Vinyl acetate resin, polyamide, polyethylene, polycarbonate, polystyrene, polypropylene, acrylic resin, phenol resin,
Polyester, polyurethane, epoxy resin, silicone resin, fluorine resin, butyral resin, melamine resin,
Examples include natural rubber, synthetic rubber, polyvinyl alcohol, and cellulose resin. These resins can be used singly, but a mixture of several resins or a copolymer may be used.

Further, when making a difference in glass transition or softening transition between the dye transfer contributing layer and the dye supply layer, a resin or natural, synthetic rubber, waxes having a glass transition temperature of 0 ° C or less, or a softening temperature of 60 ° C or less are preferable. , Syndiotactic 1,2-polybutadiene (commercially available as JSR RB810,82
0,830 Nippon Synthetic Rubber); Olefin copolymers and terpolymers containing acid or non-acidic acid (Dexon as a commercial product)
XEA-7, Dexon Chemical); ethylene-vinyl acetate copolymer (400 & 400A, 405,430 as commercial products, Allied Fibers &Plastics; P-3307 (EV150), P-280
7 (EV250), DuPont Mitsui Polychemical); low molecular weight polyolefin polyol and its derivatives (Polytail H, HE Mitsubishi Kasei Kogyo as commercial products); brominated epoxy resin (YDB-340,400,500,600 Toto Kagaku); novolak epoxy resin ( YDCN-701,702,703 Toto Chemical); Thermoplastic acrylic solution (Tynalnal LR1075,1080,10)
81,1082,1063,1079 Mitsubishi Rayon); Thermoplastic acrylic emulsion (LX-400, LX-450, Mitsubishi Rayon); Polyethylene oxide (Alcox E-30,45, Alcox R-150,400,1000 Meisei Chemical) Preferred are caprolactone polyols (Placcel H-1,4,7, Daicel Chemical Industries), and particularly, polyethylene oxide and polycaprolactone polyols are practically useful, and the thermoplastic or thermosetting resins described above. And above 1
It is preferably used in the form of a mixture with several or several species.

The dye concentration of the transfer contributing layer is usually 5 to 80%, preferably,
It is about 10-60%.

The dye concentration of the dye supply layer is preferably from 5 to 80%. However, when a dye concentration gradient is provided between the dye transfer contribution layer and the dye supply layer, the dye concentration is 1.1 to 1.1%. It is desirably from 10 to 10 times, preferably from 1.5 to 3 times.

As the base sheet, a film such as a condenser paper, a polyester film, a polystyrene film, a polysulfone film, a polyimide film, or a polyamide film is used. If necessary, a conventional adhesive layer may be interposed between the base sheet and the dye supply layer. A conventional heat-resistant lubricating layer may be provided on the back surface of the base sheet, if necessary.

So far, an example in which the dye layer is divided into two layers has been described. However, if an appropriate difference in dye transfer amount is generated and the function separation intended by the present invention can be achieved, the dye layer may be formed into a multilayer of two or more layers. It is possible.

The above description has been made with reference to a recording method using a thermal head, or the transfer medium of the present invention is a recording method in which recording heat energy is applied by a method other than the thermal head, for example, a hot printing plate, a laser beam, or a support. It can also be used for a method utilizing Joule heat generated by energization in a medium such as a body and / or an ink layer. Of these, the so-called energetic thermal transfer method using Joule heat generated in a medium is the best known, for example, USP 4,103,066, JP-A-57-1.
4060, JP-A-57-11080, or JP-A-59-9906.

When used in this energization transfer method, relatively heat-resistant polyester, polycarbonate, triacetyl cellulose, nylon, polyimide, aromatic polyamide and other resins as a support, aluminum, copper, iron, tin, zinc,
Metal powders such as nickel, molybdenum, silver and / or conductive powders such as carbon black are dispersed to adjust the resistance to an intermediate value between the insulator and the good conductor. A support on which a conductive metal is deposited or sputtered may be used. The thickness of these supports is preferably about 2 to 15 microns in consideration of the efficiency of Joule heat conduction.

In the case of using a laser beam transfer method, a material that absorbs laser light and generates heat may be selected as a support.
For example, a conventional heat transfer film containing a light-absorbing heat conversion material such as carbon, or an absorption layer formed on the front and back surfaces of a support is used.

If necessary, a release thin layer made of a substance having lubricity and heat resistance may be provided on the dye transfer contributing layer, and a non-contact layer is provided between the dye supply layer and the dye transfer contributing layer. An intermediate layer may be provided to prevent unnecessary transfer of the sublimable dye from the dye supply layer to the dye transfer contributing layer during recording (during storage).

Hereinafter, the present invention will be described more specifically based on the following examples, but the present invention is not limited thereto.

Example 1 Two kinds of dye supply layers having the following compositions and inks for a dye transfer contributing layer were prepared, and on a 8.0 μm polyimide film support,
The dye supply layer was coated and dried to a thickness of 4.5 μm and a dye transfer contributing layer to a thickness of 0.8 μm to form a sublimation type thermal transfer recording medium.

The thermal transfer sheet thus formed was passed four times with a load of 10 kg / cm ² using a super calender to obtain a sheet having a center line average roughness of Ra = 0.534 μm.

Example 2 Two kinds of inks for a dye supply layer and a dye transfer contributing layer having the following compositions were prepared and coated on a 8.0 μm polyimide film support so that the dye supply layer was 4.5 μm thick and the dye transfer contributing layer was 0.8 μm thick. After drying, a sublimation type thermal transfer recording medium was formed.

The thermal transfer sheet thus formed was passed four times with a load of 10 kg / cm ² using a super calender to obtain a sheet having a center line average roughness of Ra = 0.543 μm.

Example 3 Two kinds of inks for a dye supply layer and a dye transfer contributing layer having the following compositions were prepared, and dried on a 8.0 μm polyimide film support so that the dye supply layer had a thickness of 5.0 μm and the dye transfer contributing layer had a thickness of 0.8 μm. Thus, a sublimation type thermal transfer recording medium was formed.

The thermal transfer sheet thus formed was passed four times using a super calender under a load of 10 kg / cm ² to obtain a sheet having a center line average roughness of Ra = 0.742 μm.

Example 4 Two kinds of inks for a dye supply layer and a dye transfer contributing layer having the following compositions were prepared, and gravure was carried out on a 8.0 μm polyimide film support so that the dye supply layer was 4.5 μm thick and the dye transfer contributing layer was 0.8 μm thick. Sublimation type thermal transfer recording medium was formed by coating and drying with a coater.

As a result of measuring the surface characteristics of the thus formed thermal transfer sheet, it was found that the center line average roughness, Ra = 1.844 μm, the average interval of irregularities (irregularities), and Sm = 7.149 μm.

Example 5 Two kinds of inks for a dye supply layer and a dye transfer contributing layer having the following compositions were prepared, and a gravure coater was prepared so that a dye supply layer was 4.5 μm thick and a dye transfer contributing layer was 0.8 μm thick on a 8.0 μm polyimide film support. To form a sublimation type thermal transfer recording medium.

As a result of measuring the surface characteristics of the thus formed thermal transfer sheet, it was found that the center line average roughness, Ra = 1.646 μm, the average interval of irregularities (irregularities), and Sm = 8.04 μm.

Example 6 Two types of inks for a dye supply layer and a dye transfer contributing layer having the following compositions were prepared, and a gravure coater was used so that a dye supply layer of 5.0 μm thick and a dye transfer contributing layer of 0.8 μm were formed on an 8.0 μm polyimide film support. To form a sublimation type thermal transfer recording medium.

As a result of measuring the surface characteristics of the thermal transfer sheet thus formed, the center line average roughness, Ra = 1.484 μm, the average interval of irregularities (irregularities), and Sm = 8.14 μm.

In Example 1, after forming the dye supply layer, the sample was observed at a magnification of 2,000 with a scanning electron microscope S-310A (manufactured by Hitachi, Ltd.). It was confirmed that dye particles in the form of needles having a uniform particle size of about 7.0 μm were present in a state of lying closely on one surface.

 This was the same in Examples 2 to 6.

As shown in FIG. 1, the sublimation-type thermal transfer recording media of Examples 1 to 6 were used as the image receiving member 3 to receive an image of a supply VY-S100 for a Hitachi video printer VY-50, which is an image-receiving paper for sublimation-type thermal transfer recording. As a result of performing printing many times at the same location on paper using the thermal head 6 at an applied power of 455 mW / dot as a printing condition, the results shown in Table 1 were obtained.

However, printing density (optical density) is Macbeth densitometer RD-
The density unevenness was visually evaluated using 914.

However, only a high recording density portion where a sensitivity difference easily occurs is shown.

As can be seen from the results shown in Table 1, even when the number of times of printing is increased, the printing density has no sensitivity difference from the first printing to the fifth printing, and a good gradation expression is obtained. Good image quality was obtained.

〔effect〕

As described above, in the sublimation type thermal transfer recording medium of the present invention, by specifying the surface characteristics of the ink layer, the density unevenness was improved, the image quality was improved, and a good multiple-time printing characteristic was obtained. .

[Brief description of the drawings]

FIG. 1 is an explanatory view showing the structure of a sublimation type thermal transfer body of the present invention. FIG. 2 is an explanatory diagram of the definition of the average interval Sm. DESCRIPTION OF SYMBOLS 1 ... Support, 2 ... Ink layer 3 ... Image receiving body 4, ... Dye supply layer 5 ... Dye transfer contributing layer 6 ... Thermal head

Continuation of front page (72) Inventor Hiroyuki Uemura 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd. (56) References JP-A-63-47193 (JP, A) JP-A-58-193192 (JP, A) JP-A-61-137783 (JP, A) JP-A-2-16795 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41M 5/38-5 / 40

Claims (3)

(57) [Claims] 1. A dye supply layer containing at least an undissolved particulate sublimable dye and an organic binder, and at least a molecularly dispersed sublimable dye and an organic binder on a substrate in this order from the substrate side. In a sublimation type thermal transfer recording medium provided with an ink layer formed by laminating a dye transfer contributing layer containing, the surface roughness of the ink layer surface is measured according to JIS B0601, and the center line average roughness Ra is Ra. ≦ 1.0 μm, a sublimation type thermal transfer recording medium. 2. A dye supply layer comprising at least an undissolved particulate sublimable dye and an organic binder, and at least a molecularly dispersed sublimable dye and an organic binder on the substrate in this order from the substrate side. In a sublimation type thermal transfer recording medium provided with an ink layer formed by laminating a dye transfer contributing layer containing, the surface roughness of the ink layer surface is measured according to JIS B0601, and the center line average roughness Ra is Ra. > 1.0 μm, and the average interval Sm of irregularities is Sm ≧ 10 μm. 3. The sublimation type thermal transfer recording medium according to claim 1, wherein the thickness of the dye transfer contributing layer is 0.5 to 1.5 μm.