JPH02239973A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance flexibility, slip properties, releasability and non-stickiness by using a specific polyester resin in the formation of a back layer. CONSTITUTION:A thermal recording material consists of a base sheet, the thermal recording layer provided to one surface of said base sheet and the back layer provided to the other surface of the base sheet and the back layer is formed from a siloxane modified polyester resin consisting of a siloxane compound having an active hydrogen group and a lactone compound. The reaction of the siloxane compound and the lactone compound is performed by mixing both compounds to react the same at 150-200 deg.C for several hr-ten several hr pref. using a catalyst under a nitrogen stream and a desired siloxane modified polyester copolymer is obtained. At this time, said compounds are pref. reacted in such a ratio that a slioxane segment occupies 10-80wt.% in the copolymer. The back layer may be formed according to a conventional known method pref. in a thickness of about 0.1-10mum.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material useful in a thermal transfer method or a sublimation transfer method.

(Prior art) Conventionally, dyes or pigments are supported by binder resin on one side of a base sheet such as a polyester film to form a heat-sensitive recording layer, and the ink is applied to the transfer material by heating from the back side in a pattern. Further, a method in which a heat-sublimable dye is used as the above-mentioned dye and similarly sublimation transfers only the dye onto a transfer material is well known.

Since this method applies thermal energy from the back side of the base sheet, the back side of the base sheet has sufficient slip properties, peelability, non-adhesive properties, etc., and the thermal head does not stick to the back side. It is required not to do so.

For this reason, in the prior art, a layer having relatively good heat resistance, such as a polyurethane resin, an acrylic resin, a modified cellulose resin, or a mixture thereof, is formed on the back side of a base sheet of a heat-sensitive recording material.

(Problems to be Solved by the Invention) The heat-sensitive recording materials of the prior art as described in Section 7 have a back layer made of the above-mentioned resins formed on the back side, but these resins are thermoplastic and have sufficient Since it does not have heat resistance, it tends to stick to the thermal head, and has the drawback of insufficient running performance of the thermal head and insufficient separation from the heat-sensitive recording material.

In order to solve these drawbacks, attempts have been made to add inorganic fillers such as talc, fluororesin powder, etc. to the back layer as described above, but the back layer containing such additives also causes problems on its surface. The presence of these powders has the disadvantage of significantly contaminating and wearing out the thermal head, significantly shortening the life of the expensive thermal head.

These various drawbacks can be solved to some extent by using resins with very high softening points, but conventionally known so-called heat-resistant resins do not have suitable solvents, making it difficult to apply them to base sheets. Moreover, even if they could be applied, these conventional layers made of heat-resistant resins have insufficient adhesion to the base sheet and are hard and brittle, so it is necessary to have a back surface with sufficient flexibility. No layer could be formed.

Therefore, in order to solve these problems, we have developed excellent flexibility,
There is a demand for the development of resins that have slip properties, peel properties, non-adhesive properties, etc. at the same time.

The inventor of the present invention has solved the above-mentioned drawbacks of the prior art and, as a result of intensive research in order to meet the above-mentioned needs, has found that the object of the present invention can be achieved by using a specific polyester resin for forming the back layer. I found out.

(Means for Solving the Problems) That is, the present invention comprises a base sheet, a heat-sensitive recording layer provided on one side of the base sheet, and a back layer provided on the other side of the base sheet, The heat-sensitive recording material is characterized in that the back layer is formed from a siloxane-modified polyester resin comprising a siloxane compound having an active hydrogen group and a lactone compound.

(Function) By using a polyester resin having a specific segment to form the back layer, a heat-sensitive recording material having excellent slip properties, peelability, non-adhesive properties, etc. and to which the thermal head does not stick can be provided.

(Preferred Embodiments) Next, the present invention will be described in more detail by citing preferred embodiments.

The polyester resin used in the present invention is obtained by copolymerizing a siloxane compound having an active hydrogen group and a lactone compound.

Preferred examples of the active hydrogen group-containing siloxane compound used in the present invention include the following compounds.

(1) Amino-modified siloxane oil (m-1 to 10, n=2 to 10, R=1. or OC
H3, R' = aliphatic divalent group or aliphatic ether group)
(m=0 to 200) (n・2 to 1(1) (m=1 to 10, n=2 to 10, R=GH3 or D
C}13) (branch point = 2 to 3, R/lower alkyl group,
1-2 to 200, m=2 to 200. n=
2 to 200) (n-1 to 200.1=lower alkyl group) (2) Epoxy-modified siloxane oil (Rho 1 to 10) (nl to 200) (m=1 to 10, n=2 to 10) Above The epoxy compound can be used by reacting with polyol, polyamine, polycarboxylic acid, etc. so that it has an active hydrogen (m=1 to 10, n=2 to 10) group at the end.

Alcohol-modified siloxane oil (n = 1 to 200) (Rho 1 to 200) (branch point -2 to 3, R = lower alkyl group, 1-2 to 200, m = 2 to 200, n = 2 to 200) ( m = 1 to 10, n = 2 to 1O, R = aliphatic divalent group or aliphatic ether group) (n = 0 to 200) (4) Mercabuto-modified siloxane oil (1-1 to 1
0, m-10 to 200, n=1 to 5) (m=1 to 10, n=2 to 10) (n=1 to 200, R=lower alkyl) (n-2 to 10) R R R R゜(R=lower alkyl group, R' hydrogen atom, aJre(branch point=2 to 3, R-lower alkyl group, kyl group, K=1 to 250, l=o to 5, m=0 to 1 =2 to 200, t2 to 200, n=2 to 200) 50, n=1 to 5) R R R RSIO (510) ks1 (C}lz) + (
OCH20H2) ,. , (0[J+2CIICH2)
. (n = 1 to 200, R - lower alkyl group) R R R 0H (5) Carboxyl-modified siloxane oil (R = lower alkyl group, R' monohydrogen atom, anolekyl group, k = 1 to 250, 1-0 〜5, m=o〜50, n
= 2 to 5) (m-1 to 10, n = 2 to 10) (n = 1 to 200) (branch point = 2 to 3, R-lower alkyl group, 1 = 2 to 200, m = 2 to 200 , n=2 to 200
) (n=1 to 200, R=lower alkyl group) The siloxane compounds having an active hydrogen group as described above are preferred examples of siloxane compounds in the present invention, and the present invention is not limited to these examples. However, the above-mentioned exemplified compounds and other siloxane compounds are currently commercially available and can be easily obtained from the market,
Any of these can be used in the present invention.

In the present invention, the lactone compound reacted with the siloxane compound having an active hydrogen group includes ε-caprolactone,
Lactone compounds that can form polyesters by conventional lactone ring-opening polymerization, such as δ-valerolactone, and mono- or di-substituted derivatives thereof such as alkyl, halogen, haloalkyl, alkoxy, alkoxyalkyl, etc. can also be used. I can do it. Particularly suitable lactone compounds are C-cabrolactone and derivatives thereof.

The reaction between the siloxane compound and the lactone compound is carried out by mixing the two and reacting them at a temperature of 150 to 200° C. for several hours to several hours, preferably using a suitable catalyst under a nitrogen stream. , a desired siloxane-modified polyester copolymer is obtained.

Although both can be reacted at any reaction ratio, for the purpose of the present invention, it is preferable to react at a ratio such that the siloxane segment occupies 10 to 80% by weight in the resulting copolymer. If the amount of the siloxane compound used is too small, the slip properties, runnability, peelability, non-adhesiveness, etc. of the siloxane-modified polyester resin ultimately obtained will be insufficient; on the other hand, if the amount is too large, the siloxane-modified polyester resin obtained This is not preferable because it reduces the film-forming properties and film strength of the resin.

The above polyester resins have excellent slip properties,
Although it has runnability and non-adhesiveness, it is easily soluble in various organic solvents and can form an excellent flexible back layer.

However, the above copolymer still contains the non-reactive siloxane compound contained in the siloxane compound used, and although it varies depending on the siloxane compound used and the copolymerization ratio, usually about Since it is contained as an impurity at a proportion of 1.0 to 10% by weight, it is preferable to remove these impurities. Although the purpose of the present invention can be achieved even if these impurities exist,
These impurities may bleed out onto the film surface after forming the back layer, causing problems.Also, even if a crosslinking agent is used during film formation, the impurities are non-reactive and will not react with the crosslinking agent. Even with a cross-linked film, the problem of bleed-out cannot be solved.

Although the above impurities are difficult to separate at the raw material stage, in the present invention, the copolymerization is performed at a temperature of about 100 to 250°C, preferably under an inert atmosphere such as nitrogen gas, at a pressure of 10 mmHg, preferably after the copolymerization. is 5 mm
It can be easily removed by vacuum treatment under conditions of Hg or less, and a polyester resin containing substantially no unreacted siloxane compound can be obtained. In the present invention, the term "substantially free" refers to one in which the content of unreacted siloxane compounds is less than 1.0%.

The polyester resin used in the present invention as described above may have any molecular weight, but in consideration of usability, it is about 1.0
Those with a molecular weight of about 00 to 30,000 are preferable,
Molecular weight may be adjusted using known techniques as they are.

In addition, the polyester resin has a reactive hydroxyl group at the end, and can be crosslinked (cured) with various crosslinking agents (curing agents).
It is possible to do so.

Furthermore, when forming the back layer, it is possible to obtain a back layer with even better physical properties by crosslinking with various crosslinking agents.

As the crosslinking agent, a compound containing two or more functional groups that can react with the terminal hydroxyl group of the polyester resin, for example,
Any polyisocyanate compound or polyepoxy compound can be used, and if the terminal hydroxyl group is further modified with another functional group, crosslinking can also be achieved with a crosslinking agent having a hydroxyl group, an amino group, an aldehyde group, etc. Particularly preferred crosslinking agents are polyisocyanate compounds.

As the polyisocyanate, any conventionally known polyisocyanate can be used, but for example, 4,4'-diphenylmethane diisocyanate (MD
I), hydrogenated MDI, inphorone diisocyanate, 1,3-xylylene diisocyanate, 1.4-xylylene diisocyanate, 2.4-tolylene diisocyanate, 2.6-1 lylene diisocyanate, 1,5-naphthalene diisocyanate , m-phenylene diisocyanate, p-phenylene diisocyanate, etc., or urethane prepolymers obtained by reacting these polyisocyanates with low molecular weight polyols or polyamines to form terminal incyanates may also be used. I can do it.

The back layer cross-linked with the above-mentioned cross-linking agent has slip properties,
In addition to running properties and non-adhesive properties, it has excellent migration resistance and bleed resistance, making it a strong back layer.

Next, the formation of the back layer of the heat-sensitive recording material of the present invention, such as a heat-sensitive transfer film, will be explained.

A thermal recording material is a material in which a transfer ink layer or a sublimation transfer dye layer is provided on one surface of a base sheet such as a polyester film, and the ink layer or dye is transferred to the transfer material by heating from the back side in an imagewise manner with a thermal head. A monochrome or multicolor image is formed by using a thermal head, and when a thermal head is used for transfer, the thermal head sticks to the back surface, causing various troubles.

The polyester resin used in the present invention has excellent flexibility as well as excellent slip properties, peelability, and non-adhesive properties, especially under elevated temperatures, making it ideal for such purposes. .

In forming the back layer, the polyester resin can be used alone or in combination with conventional general resins.

The above-mentioned general resins include various conventionally known film-forming resins, and any of these conventionally known resins can be used.
For example, vinyl chloride resin, vinylidene chloride resin, vinyl chloride/vinyl acetate/vinyl alcohol copolymer resin, alkyd resin, epoxy resin, acrylonitrile-butadiene resin, polyurethane resin, polyurea resin, nitrocellulose resin. Examples include resins, polybutyral resins, polyester resins, fluorine resins, melamine resins, urea resins, acrylic resins, polyamide resins, etc., and particularly preferred ones have urea bonds, urethane bonds, etc. in their structures. It is a resin that has

For forming the back layer, it is preferable to use a paint formed by dissolving or dispersing the above-mentioned polyester resin (or a mixture with other resins) in a suitable organic solvent. The concentration of the polyester resin in the paint is preferably about 10 to 55% by weight.

Preferred organic solvents include methyl ethyl ketone, methyl-n-propyl ketone, methyl isobutyl ketone, diethyl ketone, methyl formate, ethyl formate,
Probyl formate, methyl acetate, ethyl acetate, butyl acetate, etc. Also, acetone, cyclohexane, tetrahydrofuran, dioxane, methanol, ethanol, isopropyl alcohol, butanol, toluene, xylene,
Dimethylformamide, dimethyl sulfoxide, perchlorethylene, trichlorethylene, methyl cellosolve, butyl cellosolve, cellosolve acetate, etc. can also be used.

As long as the above-mentioned components are essential components, the paint for forming the back layer may contain other subcomponents other than the above, such as pigments, extender pigments,
Optional additives such as plasticizers, antistatic agents, surfactants, lubricants, crosslinking agents, anti-aging agents, stabilizers, foaming agents, and antifoaming agents may be included.

The method for forming the back layer itself may be the same as any conventionally known method, and it is preferably formed to a thickness of about 0.1 to 10 μm.

In addition, any conventionally known base sheet can be used, such as polyester film, polypropylene film, cellulose triacetate film, cellulose diacetate film, polycarbonate film, etc. with a thickness of 5 to 50 μm. Can be used arbitrarily.

The heat-sensitive recording material may be prepared by any known method, except for the use of polyester resin as described above to form the back layer.
For example, the heat-sensitive recording layer can be formed using conventionally known binder resins, dyes or pigments, organic solvents, and various necessary additives according to conventionally known methods.

For example, as the binder resin, a resin such as the above-mentioned film-forming resin can be used, as the organic solvent, the above-mentioned organic solvent can be used, as the additive, the above-mentioned additive can be used, and as the dye or pigment, for example, , organic pigments such as azo, cyanine, quinacridone, and polycyclic pigments, and inorganic pigments such as carbon black, iron oxide, yellow lead, and cadmium sulfide, and various conventionally known dyes. Also, sublimable dyes, disperse dyes, etc. can be used.

(Effects) The heat-sensitive recording material of the present invention obtained as described above has a back layer having various properties such as flexibility, strength, electrical properties,
While maintaining its chemical and physical properties, it has high slip properties, runnability, and non-adhesion properties that cannot be achieved with conventional technology.

Therefore, the heat-sensitive recording material of the present invention does not cause the back layer to become sticky due to the heat of the thermal head, compared to the heat-sensitive recording materials of the prior art, and can be used extremely stably, thus solving the drawbacks of the prior art. be.

Furthermore, since the back layer of the heat-sensitive recording material of the present invention is formed from the above-mentioned polyester resin, the silicone component bleeds over time to the surface of the back layer as in the prior art, contaminating the thermal head. This shortcoming has been resolved.

(Example) Next, the present invention will be explained in more detail by giving reference examples, examples, and comparative examples. Note that parts and percentages in the text are based on weight.

Reference Example 1 (m and n are values that give an amine equivalent of 3,800) In a reactor equipped with a stirrer, a thermometer, a nitrogen gas introduction tube, and a reflux condenser, 240 parts of ε-cabrolactone and the above structure (
100 parts of an amino-modified siloxane oil containing 1) and 0.05 part of tetrabutyl titanate were charged, and the mixture was reacted at a temperature of 180° C. for 10 hours under a nitrogen stream. As the reaction progresses, the viscosity of the reactant increases.

Thereafter, the reaction was continued for 1 hour at 180° C. under a reduced pressure of 5 mmHg to complete the reaction and completely remove the non-reactive siloxane compound and unreacted substances contained in the raw material siloxane compound. The amount of unreacted siloxane compound removed was 15 parts. The obtained product is a waxy polysiloxane-polyester copolymer with a hydroxyl value of 16 and a melting point of 72°C. The copolymer was dissolved in methyl ethyl ketone to make a 30% solution.

Reference Example 2 (m and n are values that give an amine equivalent of 3,500) In the same manner as in Reference Example 1, 160 parts of ε-cabrolactone,
140 parts of amino-modified siloxane oil having the above structure (2) and 0.04 part of tetrabutyl titanate were charged and reacted at a temperature of 180° C. for 10 hours under a nitrogen stream. As the reaction progresses, the viscosity of the reactant increases.

Thereafter, the reaction was continued for 1 hour at 180° C. under a reduced pressure of 5 mmHg to complete the reaction and completely remove the non-reactive siloxane compound and unreacted substances contained in the raw material siloxane compound. The amount of unreacted siloxane compound removed was 18 parts. The resulting product is a waxy polysiloxane-polyester copolymer with a hydroxyl value of 18 and a melting point of 76°C. The copolymer was dissolved in methyl ethyl ketone to make a 30% solution.

Reference Example 3 In the same manner as in Reference Example 1, 200 parts of ε-cabrolactone,
160 parts of alcohol-modified siloxane oil having the above structure (3) and 0.05 part of tetrabutyl titanate were charged and reacted at a temperature of 180° C. for 10 hours under a nitrogen stream. As the reaction progresses, the viscosity of the reactant increases.

Thereafter, the reaction was continued for 1 hour at 180° C. under a reduced pressure of 4 mmHg to complete the reaction and completely remove the non-reactive siloxane compound and unreacted substances contained in the raw material siloxane compound. The amount of unreacted siloxane compound removed was 18 parts. The resulting product is a waxy polysiloxane-polyester copolymer with a hydroxyl value of 12 and a melting point of 78°C. The copolymer was dissolved in methyl ethyl ketone to make a 30% solution.

Reference Example 4 (m and n are values that give a hydroxyl value of 25) (m and n are values that give a hydroxyl value of 32) In the same manner as in Reference Example 1, 180 parts of C-cabrolactone and the above structure ( 4) and 0.04 part of tetrabutyl titanate were charged and reacted at a temperature of 180° C. for 10 hours under a nitrogen stream. As the reaction progresses, the viscosity of the reactant increases.

Thereafter, the reaction was continued for 1 hour at 180° C. under a reduced pressure of 3 mmHg to complete the reaction and completely remove the non-reactive siloxane compound and unreacted substances contained in the raw material siloxane compound. The amount of unreacted siloxane compound removed was 16 parts. The obtained product is a waxy polysiloxane-polyester copolymer with a hydroxyl value of 14 and a melting point of 75°C. The copolymer was dissolved in methyl ethyl ketone to make a 30% solution.

Reference Example 5 An adduct of 1 mol of trimethylolpropane and 3 mol of tolylene diisocyanate (Coronate L, manufactured by Nippon Polyurethane, NGO% 13.5) was added to 100 parts of each copolymer solution obtained in Reference Examples 1 to 4. ) was added in an amount such that NCO/OH=1 to prepare a paint for forming a back layer.

Reference Example 6 30 parts of each modified siloxane used in Reference Examples 1 to 4 was added to 7
An adduct of 1 mol of trimethylolpropane and 3 mol of tolylene diisocyanate (coronated, made by Nippon Polyurethane, NCO%=13.5) was dissolved in 0 parts of methyl ethyl ketone, and NCO/OH= 1
This amount was added to form a back layer forming paint for a comparative example.

Reference example 7 Silicone resin (KS841) 10 manufactured by Shin-Etsu Chemical Co., Ltd.
0 part and 1 part of the catalyst (PL-7) were dissolved in 1,000 parts of toluene to prepare a paint for forming a back layer for a comparative example.

Examples 1 to 4 and Comparative Examples 1 to 5 The paints prepared in Reference Examples 5 to 7 were applied to the back side of a 6.0 μm thick polyester film on which a heat-sensitive recording layer had been formed in advance, so that the dry thickness was 0. It was coated with a gravure coater to a thickness of .5 μm, and the solvent was dried in a drier to form a back layer. This was cut to a predetermined width to prepare a heat-sensitive recording material of the present invention and a heat-sensitive recording material for comparison, respectively, and recording was carried out using a thermal printer to obtain the results shown in Table 1 below.

~-, 1 Example 1 Example 2 Example 3 Example 4 Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Comparative example 5 0. +57 0.125 0.175 0.166 0. +46 0.110 0.138 0.113 0.141 The coefficient of friction in Table 1 above is the measured value of the coefficient of friction between the untreated surface of polyethylene terephthalate and the back layer formed in the present invention or in the comparative example. shows.

Sticking property is determined by subjecting it to a heat-sensitive recording mounting test and visually evaluating the detachability of the heat-sensitive recording material from the thermal head during pressing operation between the thermal head and the heat-sensitive recording material on a five-grade scale, and selecting the best one. I gave it a 5.

To check for dirt on the head, subject it to a thermal recording mounting test, observe the dirt status of the thermal head, and select the one with the least dirt as 5.
It was evaluated on a five-point scale.

The back migration property is a value measured at 50° C. for 3 days, and the smaller the value, the less the migration is, indicating that it is better.

From the above results, it is clear that in the heat-sensitive recording material using the siloxane-modified polyester resin of the present invention, although the friction coefficient of the back layer is somewhat higher, head contamination and back migration are significantly improved. be.

Claims (3)

[Claims] (1) Consists of a base sheet, a heat-sensitive recording layer provided on one side of the base sheet, and a back layer provided on the other side of the base sheet, and the back layer is made of a siloxane compound having an active hydrogen group. A heat-sensitive recording material characterized in that it is formed from a siloxane-modified polyester resin comprising a lactone compound. (2) Claim 1 in which the siloxane segment accounts for 10 to 80% by weight in the siloxane-modified polyester resin.
The heat-sensitive recording material described in . (3) The heat-sensitive recording material according to claim 1, wherein the siloxane-modified polyester resin does not substantially contain unreacted siloxane compounds.