JPH0794628B2 - Thermal transfer ink - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-sensitive transfer ink used for a heat-sensitive transfer ink sheet.

(Prior Art) Thermal transfer recording is one type of non-impact recording and is noiseless. It is a recording method that is increasingly used in recent years because it has features such as a simple device and low cost. The thermal recording method is a recording method in which an ink layer on an ink sheet is heated and melted and transferred onto a recording material (paper, plastic sheet, etc.), and the ink layer is usually a natural or synthetic wax. In the composition, a colorant such as carbon black is dispersed, and necessary additives are further added. Generally, carbon black (hereinafter referred to as CB) is a pigment that is difficult to disperse finely and uniformly in the binder of inks and paints, but it is not possible to disperse it uniformly in wax, which is the most widely used binder component of thermal transfer inks. It is known to be particularly difficult. In order to improve this point, a method of preparing a masterbatch in which CB is dispersed in a vinyl polymer and mixing this with a wax has been proposed, but the effect is insufficient, and In order to improve the dispersibility, for example, a method of grafting a vinyl monomer such as styrene to CB is also known, but this also has a sufficient effect of improving the dispersibility because of a low grafting ratio of the vinyl monomer to CB. However, a better method for improving the dispersibility of CB was required. Further, the heat-sensitive transfer ink using wax as a binder has insufficient scratch resistance on the recording surface and has a problem in image durability.

(Problems to be improved by the present invention) An object of the present invention is to develop a thermal transfer ink which does not have the above-mentioned drawbacks, that is, a thermal transfer ink having good dispersibility of CB, high image quality and excellent image durability. To do.

(Means and Actions for Solving Problems) As a result of earnest studies on the dispersibility of CB and the durability of a recorded image, the present inventors have found that a polymer having reactivity between CB and CB under specific conditions. The present invention has been accomplished by finding that the object can be achieved by using a carbon black graft polymer (hereinafter referred to as a CB graft polymer) obtained by reacting below.

That is, the present invention comprises a CB graft polymer obtained by reacting CB with a polymer having reactivity with CB (hereinafter referred to as polymer (A)) under the condition of 0 to 350 ° C. The present invention relates to a characteristic heat-sensitive transfer ink.

In the present invention, in order to obtain a CB graft polymer, CB
Utilizing surface functional groups (-OH, -COOH, C = O, etc.). As the polymer (A) in the present invention, any polymer having a reactive group capable of easily reacting with a functional group existing on the CB surface can be used without particular limitation. Examples of the reactive group capable of easily reacting with the functional group present on the CB surface include aziridine group, oxazoline group, N-hydroxyalkylamide group, epoxy group, thioepoxy group, isocyanate group, vinyl group, silicon-based hydrolyzable group. Groups, amino groups and the like, and examples of the polymer (A) include vinyl polymers having one or more of the above reactive groups in the molecule, polyesters, polyurethanes and polyethers. In order to obtain such a polymer (A), for example, a method of polymerizing the above-mentioned polymerizable monomer having a reactive group in the molecule with other polymerizable monomer according to a known procedure or the above-mentioned reaction A method of reacting a compound having a functional group in the molecule with a polymer having a group capable of reacting with the compound can be appropriately adopted. In the present invention, one or two selected from an aziridine group, an oxazoline group, an N-hydroxyalkylamide group, an epoxy group, a thioepoxy group, and an isocyanate group, particularly in terms of reactivity with a functional group existing on the surface of CB. It is preferable to use a polymer having at least one species as a reactive group, and more preferably a polymer having at least one species selected from an aziridine group, an oxazoline group and an N-hydroxyalkylamide group as a reactive group (A ).

In the present invention, the type of the polymer (A) is the property to be imparted to the CB graft polymer, namely, the adhesiveness with the binder component of the thermal transfer ink, the affinity with the binder component and the solvent, and the recording material. It is appropriately selected in consideration of adhesiveness.

The molecular weight of the polymer (A) is not particularly limited,
In terms of remarkable treatment effect on CB, workability during reaction with CB, and performance as a thermal ink, the average molecular weight is
It is preferably in the range of 200 to 1,000,000, and more preferably in the range of 300 to 100,000.

Further, the polymer (A) has an average of reactive groups of 1 in 1 molecule.
It is necessary to have 1 or more, but in order to make the reactivity with CB and the properties of the obtained CB graft polymer within a good range, it is preferable to have 1 to 5 in one molecule on average, More preferably, it is 1-2.

In the production method of the present invention, the CB graft polymer is CB
And the above polymer (A) at 0 to 350 ° C, preferably 70 ° C to 3
It is obtained by stirring and mixing under a temperature condition of 00 ° C. to react. When the temperature condition during the reaction exceeds 350 ° C., the polymer component is deteriorated, which is not preferable.

The type of CB used in the present invention is not particularly limited, but when the reactive group of the polymer (A) is a relatively low reactive group such as an epoxy group or a thioepoxy group, CB having a pH of 7 or less, especially the surface thereof. The amount of carboxyl groups is 0.05 mg equivalent
It is preferable to use CB of / g or more. When the reactive group is a relatively high reactive group such as an aziridine group, an oxazoline group, an N-hydroxyalkylamide group, or an isocyanate group, it is not necessary to limit the type of CB and various CBs can be preferably used. it can.

The ratio of CB to the polymer (A) used is not particularly limited, but is preferably 1 to 1,000 parts by weight, particularly preferably 5 to 500 parts by weight, of the polymer (A) per 100 parts by weight of CB.

The reaction between CB and the polymer (A) may be a method in which only these two components are reacted, and the polymer component and the polymerizable monomer which do not correspond to the polymer (A) include organic solvents, water, etc. The reaction may be carried out in the presence of other substances.

The CB graft polymer thus obtained is extremely easily dissolved and dispersed in the binder component of the ink, so that a thermal transfer ink in which CB is uniformly micro-dispersed can be obtained. The binder component of the thermal transfer ink is a known natural or synthetic wax such as carnauba wax, montan wax, paraffin wax, microcrystalline wax, oxidation wax, low molecular weight polyethylene wax and low molecular weight polypropylene wax; polysulfone ether, polycarbonate, polystyrene, silicone. resin,
Examples include synthetic resins such as acrylic resins.

It is extremely easy to disperse the surface-treated CB in the binder component, and it is not necessary to knead it under high shearing force using a kneading machine such as a ball mill or a roll mill. It suffices to use a stirrer such as a melt mixer for mixing under low shearing force. There is also a method in which the reaction between CB and the polymer (A) is carried out in the presence of a binder component for the ink. By this method, a thermal transfer ink can be obtained all at once. Further, by selecting a polymer (A) suitable for the binder of the ink, the treated CB can be used as it is as a thermal transfer ink without adding other binder components. The amount of CB in the thermal transfer ink is not particularly limited, but is usually 5 to 30.
It is preferably in the range of% by weight. In addition to the above ingredients,
Known additives may be added if necessary.

The thermal transfer ink of the present invention may be applied to a support typified by PET film, polyimide film, condenser paper, silk fabric, aluminum foil, etc. by a known method such as hot melt coater, reverse roll coater, gravure roll coater. It is possible to obtain a heat-sensitive transfer ink sheet having excellent quality.

(Effect of the Invention) The thermal transfer ink of the present invention contains a CB graft polymer in which the polymer (A) having reactivity with CB is grafted on the surface of CB. The polymer (A) has a much higher grafting ratio to CB than conventionally known grafting methods, the polymer is firmly bonded to the CB surface, and various polymers are selected as the skeleton of the polymer. As a result, the surface properties of CB can be modified freely, effectively and economically so as to match the binder component of the ink used. Therefore, the CB graft polymer of the present invention is extremely uniformly microdispersed in the thermal transfer ink, and CB and the binder component of the ink have a high affinity through the polymer (A). Therefore, an image recorded using the heat-sensitive transfer ink of the present invention has extremely high quality and is excellent in durability.

(Examples) Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples. still,
Parts in the examples are parts by weight and% is% by weight.

Reference Example 1 A flask equipped with a stirrer, an inert gas introducing tube, a reflux condenser and a thermometer was charged with 400 parts of deionized water in which 0.2 part of polyvinyl alcohol was dissolved. 196 parts of styrene and isopropenyloxazoline 4 which had been adjusted in advance
Benzoyl Peroxide 16
A mixture in which parts were dissolved was charged and stirred at high speed to obtain a uniform suspension. Then, the mixture was heated to 80 ° C. while blowing nitrogen gas, the mixture was continuously stirred at this temperature for 5 hours to carry out a polymerization reaction, and then cooled to obtain a polymer suspension. The polymer suspension was filtered, washed and dried to obtain a polymer having an oxazoline group as a reactive group. The molecular weight of this polymer was Mn = 5,800 as measured by GPC.

20 parts of a polymer having an oxazoline group as a reactive group and CB
20 parts of MA-600 (manufactured by Mitsubishi Kasei Co., Ltd.) is mixed with a Labo Plastomill (manufactured by Toyo Seiki Co., Ltd.) under the conditions of 160 ° C. and 100 rpm to react, then cooled, crushed and CB Graft polymer (1) was obtained.

Reference Example 2 The same flask used in Reference Example 1 was charged with 100 parts of toluene and 100 parts of methyl isobutyl ketone and heated to 80 ° C. while blowing nitrogen gas. 100 parts of styrene, 90 parts of butyl acrylate and 2-
A mixture prepared by dissolving 4 parts of benzoyl peroxide in a polymerizable monomer consisting of 10 parts of (1-aziridinyl) ethyl methacrylate was added dropwise from a dropping funnel over 2 hours, and stirring was continued for 5 hours to carry out a polymerization reaction. After cooling, a polymer solution was obtained. The molecular weight of this polymer is Mn measured by GPC.
= 3,000.

40 parts of a solution of a polymer having an aziridine group as a reactive group and 20 parts of CB MA-600 were reacted at 160 ° C. using a pressure kneader to obtain a dispersion liquid of CB graft polymer (2).

Reference Example 3 Instead of the polymerizable monomer in Reference Example 1, styrene 120 was used.
Parts, 76 parts of stearyl acrylate and 4 parts of N-hydroxyethylmethacrylamide were repeated to obtain a polymer having an N-hydroxyalkylamide group as a reactive group of Mn = 4,000 by repeating the same operation as in Reference Example 1. 10 parts of the polymer, carnauba wax which is a component of the heat-sensitive transfer ink
The same operation as in Reference Example 1 was repeated using 70 parts of CB MA-600 and 20 parts of CB MA-600 to obtain a CB graft polymer (3).

Reference Example 4 206 parts of toluene was charged into the same flask as used in Reference Example 1 and heated to 90 ° C. while blowing nitrogen gas. A mixture prepared by dissolving 5.44 parts of mercaptoethanol and 1.32 parts of azobisisobutyronitrile in a polymer monomer composed of 200 parts of behenyl acrylate prepared in advance was added thereto.
The mixture was added dropwise from the dropping funnel over a period of time, and stirring was continued for 5 hours to carry out a polymerization reaction. The molecular weight of this polymer is GPC
According to the measurement, Mn = 2,500.

Then, to 200 parts of this reaction product (a solution containing a prepolymer having a carboxyl group at the end), 6 parts of toluene diisocyanate was added and reacted at 80 ° C. for 2 hours to obtain a polymer having an isocyanate group as a reactive group at the end. A solution (nonvolatile content 50%) was obtained.

40 parts of a solution of a polymer having an isocyanate group at the end (nonvolatile content 50%) and poly (behenyl acrylate) (molecular weight about 30
60 parts of a 50% solution of 00) and 20 parts of CB MA-100R were subjected to a kneading reaction using a pressure kneader at 160 ° C. to obtain a dispersion liquid of CB graft polymer (4).

Reference Example 5 In the same flask as used in Reference Example 1, linear saturated polyester Alloplatz OB-63 containing a terminal carboxyl group (manufactured by Nippon Shokubai Chemical Co., Ltd., molecular weight Mn = 6,000, non-volatile content 50)
%) 200 parts and 2-p-phenylene-bis-2-oxazoline (3.60 parts) were added and reacted at 110 ° C. for 2 hours to give a solution of a polymer having an oxazoline group as a reactive group at the end (nonvolatile content 50.9%). Got 40 parts of a solution of a polymer having an oxazoline group at the end (nonvolatile matter 50.9%) and CB MA-100R 2
0 part was kneaded under the same conditions as in Reference Example 4 to obtain a dispersion liquid of CB graft polymer (5).

Reference Example 6 In Reference Example 1, the polymerizable monomer used was styrene 100
Parts, stearyl methacrylate 95 parts and glycidyl methacrylate 5 parts were repeated in the same manner as in Reference Example 1 to obtain a polymer having an epoxy group as a reactive group.

40 parts of a polymer having an epoxy group as a reactive group and CB MA
20 parts of -100R (manufactured by Mitsubishi Kasei Co., Ltd.) was kneaded using a Labo Plastomill under the conditions of 220 ° C. and 100 rpm, reacted, cooled and pulverized to obtain a CB graft polymer (6).

Reference Example 7 In Reference Example 2, the same method as in Reference Example 2 was repeated except that the polymerizable monomers used were 195 parts of stearyl acrylate and 5 parts of 2,3-epithiopropyl methacrylate, and thioepoxy was used as the reactive group. A polymer having groups was obtained.

Using a pressure kneader, 32 parts of a solution of a polymer having a thioepoxy group as a reactive group (nonvolatile content 50%) and 24 parts of CB MA-100R (manufactured by Mitsubishi Kasei Co., Ltd.) were used at 220 ° C. and 100 rp.
A kneading reaction was carried out under the condition of m to obtain a dispersion liquid of CB graft polymer (7).

Comparative Reference Example 1 Styron-66, which is polystyrene having no reactive group
6 (Asahi Kasei Kogyo Co., Ltd., Mn = 40,000) 20 parts and CB MA-60
After reacting 20 parts with the same manner as in Reference Example 1, the mixture was cooled and pulverized to obtain a CB graft polymer (1) for comparison.

Comparative Reference Example 2 Xylene 200 was added to a flask similar to that used in Reference Example 1.
Parts, 25 parts of stearyl methacrylate, 0.2 parts of azobisisobutyronitrile and 100 parts of carbon black MA-600 are charged, while blowing nitrogen gas, heated to 80 ° C., and stirred at this temperature for 10 hours to continue the polymerization reaction. After that, it was cooled.
After the reaction, the product was reprecipitated in 7,000 parts of methanol and compared with C
B graft polymer (2) was obtained.

Example 1 CB graft polymers (1) to (2) and (5) to (7) obtained in Reference Examples 1 to 2 and 5 to 7 and Comparative Reference Example 1 to
Comparative CB graft polymer (1) obtained in 2
(2) In addition, thermal transfer inks each containing untreated CB MA-100R were prepared with the formulations shown in Table 1.

The inks of Nos. [1], [2], [5], [6], [7] and comparative [1], [2] were prepared by stirring and mixing the respective components at 100 ° C. for 30 minutes, The ink for comparison [3] was prepared by stirring and mixing the components at 100 ° C. for 30 minutes and then kneading with a three-roll mill. Also, obtained in Reference Examples 3 to 4.
The CB graft polymers (3) to (4) were directly used as thermal transfer ink Nos. [3] to [4]. Each of the obtained inks was thinly coated on a glass plate, the dispersed state of CB was observed with a microscope, and the quality of dispersibility was evaluated by ◯ to ×. The results are shown in Table 2.

Example 2 Each of the thermal transfer inks obtained in Example 1 was used in a thickness of 6 μm.
An axially stretched PET film was coated such that the dry film thickness of the ink layer was 4 μm. The coating was performed using a wire bar by heating the ink to a temperature suitable for each ink to bring the ink into a fluid state. The obtained thermal transfer sheet was mounted on a thermal printer and printed on plain paper. The image quality was evaluated by combining the resolution and the presence or absence of white spots, and a 5-point evaluation of 5 points (good) to 1 point (bad) was performed. In addition, the scratch strength of the image is 1 for a hemispherical stainless rod with a diameter of 1.5 mm at one end.
Apply a load of 00g and rub the image surface to remove scratches.
It evaluated by x. The results are shown in Table 3.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kiyoshi Kawamura 5-8 Nishimitabicho, Suita City, Osaka Prefecture Central Research Institute of Nippon Shokubai Kagaku Kogyo Co., Ltd. (72) Tadanori Sano 5th Nishimitabicho, Suita City, Osaka Prefecture No. 8 Youko Nakajima, Examiner, Central Research Laboratory, Nippon Shokubai Chemical Co., Ltd.

Claims (2)

[Claims] 1. A heat-sensitive transfer ink comprising a carbon black graft polymer obtained by reacting carbon black and a polymer having reactivity with carbon black under conditions of 0 to 350 ° C. 2. A polymer having reactivity with carbon black is one or more selected from aziridine group, oxazoline group, N-hydroxyalkylamide group, epoxy group, thioepoxy group and isocyanate group in the molecule. The heat-sensitive transfer ink according to claim 1, which is a polymer having the reactive group of.