JPH0386595A - Thermal transfer ink sheet - Google Patents

Abstract

PURPOSE:To enhance heat resistance by incorporating a main agent being a compound of a carboxyl modified nitrocellulose resin with amino modified silicone oil, and an urethane resin in a back coat material and setting the compounding ratio of main agent/urethane resin to a specific range. CONSTITUTION:In a thermal transfer ink sheet wherein a thermal transfer ink layer is provided on a base film and a film of a back coat material is provided at the rear thereof, the back coat material contains a main agent being a compound of a carboxyl modified nitrocellulose resin with amino modified silicone oil and an urethane resin being a modifier and the compounding ratio of main agent/urethane resin is set to a range of 9/1 - 5/5 (wt. ratio). When the wt. ratio of main agent/urethane resin becomes larger than 9/1, the non-antistaining properties of a thermal head lowers and, when said wt. ratio is below 5/5, the heat resistance of the ink sheet is lowered. As the urethane resin, one whose solution viscosity of a methyl ethyl ketone solution with solid content of 35wt.% at 20 deg.C is 100 - 100,000cps is pref.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal transfer ink sheet and its material, and more particularly to a thermal transfer ink sheet whose heat resistance is improved by a back coat material.

[Problems to be solved by conventional techniques and inventions] Currently,
Thermal transfer printers are widely used as compact, lightweight, and inexpensive popular printers. Thermal transfer media include those consisting of a thermal transfer sheet in which a heat sublimable dye is provided on a support and a receiving sheet that receives a heat sublimable dye image by thermal printing from side A of the sheet, and media that are made of a heat fusible material and A combination of a transfer sheet and a receiving sheet is known, in which a transfer layer of pigments or dyes is provided on a support.Also, substances that react with each other to develop color due to heat are supported on separate supports, and this Thermal transfer media are also known in which thermal printing is performed by bringing layers into opposing contact.

As the field of application of thermal transfer printers has expanded in this way, new demands have arisen that have never existed before. The main ones are rough surface paper printing and high speed printing. In response to these demands, a wide range of improvements have been made not only to ink but also to printers themselves. Particularly significant improvements include (1) changing the shape of the thermal head to a protruding type, (2) increasing the platen pressure (the pressure used to press the thermal head), and (3) increasing the printing energy. . As a result, while printing conditions have become stricter and printing quality has made significant progress, a new important issue has arisen: how to improve the heat resistance of base films (mainly PET films) and thermal transfer ink sheets.

These problems have been addressed using silicone resins, epoxy resins, phenol resins, fluororesins, polyimide resins, nitrocellulose resins, etc., as seen in Japanese Patent Application Laid-Open No. 55-7467. These resins lack heat resistance and runnability. It was also found that the thermal head was significantly contaminated.

Furthermore, when using liquid oil such as silicone oil, mineral oil, vegetable oil, or synthetic oil as seen in JP-A-59-148697, the liquid oil migrates to the ink side over time, resulting in long-term problems. After storage, running properties deteriorate significantly.

Therefore, in JP-A-60-137693, a heat-resistant resin such as polyvinylidene chloride resin, polyvinyl butyral resin, or nitrocellulose resin is combined with silicone wax as a lubricating component, but the heat resistance and runnability are not sufficient. Moreover, the prevention of contamination of the thermal head is not sufficient.

That is, the current situation is that there is still no satisfactory heat-resistant film for thermal transfer ink sheets.

[Means to solve the problem]

In view of the above-mentioned problems, the inventors of the present invention have conducted extensive research and found that by applying a bank coat material containing a urethane resin and a base resin that is a combination of a specific resin and oil to one side of the film, the thermal transfer ink sheet can run smoothly. The present inventors have discovered that the properties, heat resistance, and thermal head non-contamination properties can be improved, and have completed the present invention.

That is, the present invention provides a thermal transfer ink sheet in which a thermal transfer ink layer is provided on a base film and a bank coating material film is provided on the back surface of the base film, and the back coating material is a mixture of a carboxyl-modified nitrocellulose resin and an amino-modified silicone oil. To provide a thermal transfer ink sheet, which contains a base resin and a urethane resin as a modifier, and has a base resin/urethane resin blending ratio in the range of 9/1 to 5/5 (weight ratio). It is something.

The carboxyl-modified nitrocellulose resin used in the present invention is, for example, a hydroxyl group (-o
It can be obtained by further oxidizing trocellulose resin) to a cellulose derivative obtained by substituting n) with a nitric acid group (-ONO□) to introduce a carboxyl group (-COOH).

An example of the structure of nitrocellulose is shown below.

(2) Although the structure of H carboxyl-modified nitrocellulose is not certain, it is presumed that a carboxyl group is introduced at the end of the nitrocellulose.

Even when carboxyl-modified nitrocellulose is used alone as a back coating material for a thermal transfer ink sheet, the lubricity is insufficient.

The amino-modified silicone oil used in the present invention may be any silicone oil in which an amino group or a compound having an amino group is introduced into the molecule.
For example, there is a silicone oil in which an amino group or an organic group having an amino group is introduced into a part of the methyl group of dimethylpolysiloxane, and an example of its structure is shown below.

(In the formula, R represents a CH1 group or a 0CHa group, and n and Akebono represent an integer of 1 or more.) In addition, the amino-modified silicone oil according to the present invention includes alcohol-modified silicone oil, carboxyl-modified silicone oil, and epoxy-modified silicone oil. It also includes amino group-containing silicone oils in which amino groups are secondarily introduced using the functional groups of modified silicone oils other than amino-modified oils. An example of a possible method for preparing an amino group-containing silicone oil is shown below.

(Epoxy-modified silicone oil) [TyoITrueH]-0H+ (Alcohol-modified silicone oil) OCN-R-NGO (In the above formula, R represents an alkylene group or an arylene group) Carboxyl-modified nitrocellulose as a main ingredient in the present invention The blending ratio of the resin and amino-modified silicone oil is preferably within the range of the following formula (1).

(Note) Car: Functional group equivalent is the average molecular weight with I equivalent functional groups.

In the present invention, the blending ratio of carboxyl-modified nitrocellulose resin and amino-modified silicone oil is expressed by formula (1)
However, for boat fishing, a mixture in which 1 to 50 parts by weight of amino-modified silicone oil is added to 100 parts by weight of carboxyl-modified nitrocellulose resin can be used as the main ingredient. If the amount of amino-modified silicone oil added is less than 1 part by weight, the lubricity, which is the main function of silicone oil, cannot be fully demonstrated. This is not preferable because the subsequent coated surface becomes sticky and contamination of the ink surface increases.

The functional group equivalent (carboxyl equivalent f) of the carboxyl-modified nitrocellulose resin used in the present invention is 2000 to 200.
The range of 00 is preferable, and less than 2000 is not preferable because the heat resistance is insufficient or the coating film strength is insufficient.
If it exceeds 000, the amount of modified silicone oil to be added must be reduced, resulting in insufficient lubricity as a back coat material, which is not preferable.

The functional group equivalent (amino equivalent) of the amino-modified silicone oil used in the present invention is preferably in the range of 300 to 20,000; if it is less than 300, the amount of the amino-modified silicone oil added is too small and the lubricity as a back coat material is insufficient. If it exceeds 20,000, the coated surface of the back coat material becomes sticky and contamination of the ink surface increases, which is not preferable.

When only the above-mentioned main agent is used as a back coating agent, sufficient performance is exhibited in terms of lubricity and heat resistance, but contamination of the thermal head is unavoidable when printing for a long time. Therefore, we searched for a modifier that could be used in combination with the base resin and had excellent non-contaminating properties for thermal heads without reducing lubricity or heat resistance, and as a result we found a urethane resin.

In the present invention, the blending ratio of the base resin and the urethane resin is as follows:
The weight ratio of main resin/urethane resin is 9/1 to 5/5.

If the weight ratio of the base resin/urethane resin is greater than 9/1, the non-contamination property of the thermal head will decrease, and if the weight ratio of the base resin/urethane resin is less than 5/5, the heat resistance of the ink sheet will decrease, which is undesirable. .

The urethane resin used in the present invention is used as a solution (solvents such as methyl ethyl ketone, ethyl acetate, tetrahydrofuran, toluene, etc. can be used alone or in combination), and the urethane resin is used as a solution in methyl ethyl ketone with a solid content of 35% by weight at 25°C. Teno solution viscosity is 100-10000
0 cps (7) range is preferred, solution viscosity is 1
If it is less than 100,000 cps, the resin strength will be low and the non-contamination property of the thermal head will be poor, which is undesirable. If it exceeds 100,000 cps, the compatibility with the base resin will be poor, which is not preferred.

The urethane resin used in the present invention is synthesized from a polyhydric alcohol, a polyhydric isocyanate, and, if necessary, a polyhydric amino by a commonly known method.

Examples of polyhydric alcohols include ethylene glycol,
Propylene glycol, butanediol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, heptamethylene glycol, octamethylene glycol, nonamethylene glycol, decamethylene glycol, undecamethylene glycol, dodecamethylene glycol, tridecamethylene glycol, tetradeca Low molecule polyvalents such as methylene glycol, octadecamethylene glycol, eicosamerethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, hexaethylene glycol, dihydroxymethylbenzene, quinitol, hexahydroresorcinol, resorcinol, glycerol, pentaerythritol Examples include alcohols, polyether polyols such as polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol, and polyester polyols obtained by reacting the above-mentioned low-molecular polyhydric alcohols with polyhydric acids.

Examples of the polyacid constituting the polyester polyol mentioned here include oxalic acid, malonic acid, succinic acid, geltar acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid, decanedicarboxylic acid, and undecanedicarboxylic acid. , dodecanedicarboxylic acid, maleic acid, phthalic acid, terephthalic acid, isophthalic acid, n-butenylsuccinic acid, n-butylsuccinic acid, isobutenylsuccinic acid, isobutylsuccinic acid, n-octenylsuccinic acid, n-octylsuccinic acid, inoctenylsuccinic acid acid, isooctylsuccinic acid, n-dodecenylsuccinic acid, n-dodecylsuccinic acid, isododecenylsuccinic acid, isododecylsuccinic acid, hexahydroterephthalic acid, and the like.

The polyvalent incyanate used in the synthesis of the urethane resin of the present invention is a compound having two or more isocyanate groups, such as paraphenylene diisocyanate,
．． 4-toluene diisocyanate), 2.64 toluene diisocyanate, dichloro-2,4-phenyl diisocyanate, 2-chloro-1,4-phenyl diisocyanate, 4,4'-diphenylmethane diisocyanate, dianisidine diisocyanate, meta-xylene Diisocyanate, hexamethylene diisocyanate, 1.5
- diisocyanates such as naphthalene diisocyanate, isophorone diisocyanate, triisocyanates such as triphenylmethane triisocyanate, the reaction product of 1 mol of trimethylolpropane and 3 mol of tolylene diisocyanate, urethane prepolymers such as polytetramethylene ether glycol, 4.4 Examples include prepolymers obtained from equivalent reactants of '-diphenylmethane diisocyanate.

Polyvalent amines used in the base of the urethane resin of the present invention include ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, isophoronediamine, piperazine, 2-hydroxyethylethylenediamine, 2-hydroxyethylethylenediamine,
．． Examples include 4°diaminodicyclohexylmethane, xylylene diamine, and p-phenylenecyamine.

In addition, the coating amount of the back coat material in the present invention is 0.0
5 to 2.0 g/rd (dry) is suitable.

If the amount is less than this range, the function of the above-mentioned compound as a back coat material will be insufficient, and if it is more than this range, the conduction of heat from the thermal head will be inhibited, which may cause poor ink transfer.

In the present invention, other heat-resistant components (for example, silicone resin, epoxy resin, polyimide resin, salt-vinyl acetate resin, etc.) are added to the mixture of the above-mentioned carboxyl-modified nitrocellulose resin and amino-modified silicone oil, and urethane resin.
Alternatively, other lubrication imparting components (for example, silicone oil, fine silica powder, alkyl phosphate, fluorine compounds, etc.) can be added depending on the purpose. It is also possible to add a pigment such as carbon black to the back coat material to prevent static charge or leakage of secrets.

The base film used in the present invention is desirably a film that has heat resistance strength, high dimensional stability, and surface smoothness. In addition to (PET), resin films made of polycarbonate, polyethylene, polystyrene, polypropylene, polyimide, etc. and having a thickness of 2 to 20 μm are preferably used.

The thermal transfer ink used in the present invention is not particularly limited, and any ink used in ordinary thermal transfer ink sheets can be used.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples and its advantages will be shown, but the present invention is of course not limited to these Examples.

In addition, "parts" and "%" in the examples are based on weight unless otherwise specified.

Example 1 Carboxyl-modified nitrocellulose resin Seltsuba BTKI/8 (carboxyl weight: 112,500) manufactured by Asahi Kasei Co., Ltd.
Amino-modified silicone oil 5F manufactured by Toray Silicone ■
8417 (amino equivalent 3500) and 100:
Mixture blended at a weight ratio of 20 (back coat main ingredient)
was made into a 10% by weight methyl ethyl ketone solution, and urethane resin Nipporan N-230 manufactured by Nippon Polyurethane was added to this.
1 (melt viscosity of 35% by weight methyl ethyl ketone solution at 25°C: 10,600 cps) was blended in the proportions shown in Table 1 to obtain a back coat material solution. This is 3.5μ
A heat-resistant film was obtained by coating one side of a PUT film with a coating amount of 0.4 g/rrr (dry).

Using this heat-resistant film, a running test was conducted using a commercially available personal word processor (Banaward UIPRO501 manufactured by Matsushita Electric). That is, by applying ordinary thermal transfer ink to the opposite side of the heat-resistant film to which the back coat material was applied,
Printing was performed using a thermal head at the highest energy level from the surface coated with the back coat material, and heat resistance (film damage), runnability, and non-staining properties of the thermal head were evaluated by the following methods.

The results are shown in Table 1. Heat resistance (film damage), runnability, and non-contamination of the thermal head are extremely good when the blending ratio of base resin/urethane resin is in the range of 9/1 to 5/5 (weight ratio). It has been found that a back coat material can be formed.

Evaluation method〉 Runability: Run the ink sheet for 2000 m in a word processor.

O: The vehicle traveled 2,000 meters without any problems.

x: The thermal head was fused to the film and did not run.

Film damage: After solid printing was performed 10 times at the same position on the ink sheet, film damage was observed and evaluated using a microscope.

○: Film is in perfect condition.

Δ: Pinholes occur in the film.

×; Film has holes.

Thermal head non-contamination: Ink sheet with word processor 2
After running for 000 m, the head was observed and evaluated using a microscope.

○: The head is not dirty at all.

Δ: There was dirt on the head.

×: Large hand stain.

Comparative Example 1 As described in JP-A-60-137693, 175 parts of Nipporan N-230 manufactured by Nippon Polyurethane ■ and 22-80025 parts of Silicone Wax X manufactured by Shin-Etsu Chemical were combined to obtain a 5% methyl ethyl ketone/toluene-1/1 solution. . An ink sheet was prepared using this back coat material in the same manner as in Example 1, and when this sample was printed under the same conditions as in Example 1, holes appeared in the film and contamination of the thermal head was observed.

Example 2 A long-term storage stability test was conducted on the ink sheets of sample numbers 1, 3, 4, and 5 of Example 1 and the ink sheet obtained in Comparative Example 1 by the following method.

The results are shown in Table 2.

<Test conditions> Ink sheets were placed so that the ink surface and the back coating material applied surface overlapped at 50°C, 180% humidity, and 1 kg.
/ cd pressure and left for 30 days. Thereafter, running properties, film damage, and thermal head non-contamination properties were evaluated in the same manner as in Example 1.

Table 2 Results of long-term storage stability test As is clear from the results of the long-term storage stability test shown in Table 2, the ink sheets of the present invention with sample numbers 3, 4, and 5 showed no problems in runnability, film damage, and thermal stability. Head non-contamination properties were good. However, the ink sheet of Comparative Example 1 had poor runnability and fused to the thermal head during long-term storage.

Claims (1)

[Claims] 1. A thermal transfer ink sheet in which a thermal transfer ink layer is provided on a base film and a back coat material film is provided on the back surface of the base film, the back coat material comprising a carboxyl-modified nitrocellulose resin and an amino-modified silicone oil. Contains a main ingredient that is a blend of and a urethane resin,
A thermal transfer ink sheet characterized in that the blending ratio of main ingredient/urethane resin is in the range of 9/1 to 5/5 (weight ratio). 2. The thermal transfer ink sheet according to claim 1, wherein the main ingredient of the back coating material is a mixture of 1 to 50 parts by weight of amino-modified silicone oil to 100 parts by weight of carboxyl-modified nitrocellulose resin. 3. The thermal transfer ink sheet according to claim 1, wherein the carboxyl-modified nitrocellulose resin has a carboxyl equivalent in the range of 2,000 to 20,000. 4. The amino equivalent of the amino-modified silicone oil is 300
The thermal transfer ink sheet according to claim 1, wherein the ink sheet has a molecular weight of 20,000 to 20,000. 5. The urethane resin has a melt viscosity of 100 to 1 at 25°C of a methyl ethyl ketone solution with a solid content of 35% by weight.
The thermal transfer ink sheet according to claim 1, wherein the thermal transfer ink sheet is in the range of 00,000 cps.