JP2000301752A - Thermal head and its surface modifying method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent adhesion of a thermally molten product to a thermal head by lowering the surface tension of a protection layer while maintaining the heat conductivity from a heat generating resistor of the thermal head to the surface, and the smoothness of the protection layer. SOLUTION: This thermal head comprises a heat generating resistor 2 provided on an insulated substrate 1, a conductive layer 3 for supplying the electric power thereto, and a protection layer 4 provided thereon. The protection layer is applied with the surface treatment by an organic silicone-containing compound 6 with the water and oil-repellent properties and the heat resistance so as to provide a 95 degrees or more contact angle with respect to water. The organic silicone-containing compound is preferably a fluoroalkylsiliane with 6 to 10 carbon fluorides having a hydrolyzable reactive group at the ends. By applying a heat treatment at 50 deg.C or more, the compound is bonded firmly with the protection group via a silanol group. The protection layer surface is preferably applied with a pretreatment with an organic silicone compound 5 having a isocyanate group bonded with a silicon atom.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head whose surface has been modified to a low surface tension state without impairing the heat transfer property, and more particularly to a thermal stencil sheet for stencil printing.
The present invention relates to a thermal head capable of maintaining excellent piercing properties for a long time.

[0002]

2. Description of the Related Art Conventionally, a plate making method using a thermal head has been known as one of the plate making methods for heat-sensitive stencil paper.
In this plate making method, the surface of the thermoplastic resin film of the heat-sensitive stencil sheet is brought into contact with the thermal head, and the portion of the thermoplastic resin film corresponding to the image portion of the original is melt-punched by the heat of the thermal head.

However, when plate making is performed continuously by this method, the hot melt of the film adheres to the surface of the thermal head, so that there is a problem that the thermal piercing property of the thermal head gradually decreases.

[0004] Generally, thermal heads are classified into thin-film type, thick-film type, semiconductor type, and the like according to their structures. As shown in FIG. 1, the structure of the thin-film thermal head includes a heating resistor 2 provided on an insulating substrate 1 and a heating resistor 2 provided on the insulating substrate 1.
And a protective layer 4 covering the heating resistor 2 and the conductive layer 3 and having a layered structure. As shown in FIG. 2, the structure of the thick-film type thermal head is a conductive member 3 provided on an insulating substrate 1, a heating resistor 2, the conductive layer 3, and the heating resistor.
It has a layered structure, which is roughly divided into a protective layer 4 covering the layer 2. Therefore, the surface of the thermal head generally means the surface of the protective layer 4.

The material of the protective layer 4 is Ta ₂ O ₅ , Si
Inorganic materials having relatively good thermal conductivity, such as O ₂ , SiON, and Si ₃ N _3, are used. However, such an inorganic material has a high surface free energy and thus a high surface tension, and has a property that a hot melt of the film easily adheres to the surface of the thermal head.

In order to solve this drawback, a water-repellent, oil-repellent and heat-resistant resin layer is further provided on the surface of the thermal head, that is, on the protective layer 4, so that the heat of the film on the surface is reduced. It has been proposed to prevent the adhesion of the melt (see Japanese Utility Model Publication No. 4-7967, Japanese Unexamined Patent Publication No. Sho 60-2382, Japanese Unexamined Patent Publication No. Sho 60-178068, Japanese Unexamined Patent Publication No. Sho 62-48569, etc.). ). Such a resin layer is typically formed of a fluororesin such as Teflon (trade name of DuPont: polytetrafluoroethylene). In order to coat such a fluororesin on the surface of the thermal head, usually 50-60%
It is necessary to prepare a dispersion containing the solid of polytetrafluoroethylene, apply the liquid to the surface of the thermal head, pre-dry it, and then heat it to about 350 ° C.

Although this fluororesin layer is excellent for lowering the surface tension of the surface of the thermal head, its processing step (heating step) imposes a large thermal load on electronic components attached to the thermal head. It is not a simple and appropriate processing method. In addition, the fluororesin has a problem in that the binding strength with the vitreous material of the protective layer is not sufficient.

The resin layer is a resin coating layer.
Since the thickness is about μm, it hinders efficient heat conduction from the heating resistor to the surface. Further, there is a limit in increasing the surface smoothness by making the thickness of the resin layer uniform. Actually, the units of the obtained thickness and surface roughness are on the order of microns.

In particular, when making a thermal stencil sheet with such a thermal head, the unevenness of the resin layer formed on the surface of the thermal head hinders the close contact between the thermal head and the thermal stencil sheet, and reduces the thermal conductivity. However, there has been a problem that uniform perforation of the heat-sensitive stencil sheet cannot be ensured.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to maintain the thermal conductivity from the heating resistor of the thermal head to the surface and the smoothness of the protective layer. An object of the present invention is to prevent the hot melt from adhering to the thermal head by reducing the surface tension of the protective layer.

[0011]

According to the present invention, there is provided a heat generating resistor provided on an insulating substrate, a conductive layer connected to the heat generating resistor to supply electric power, A thermal head comprising a body and a protective layer provided on the conductive layer, wherein the protective layer is surface-treated with a water-repellent, oil-repellent, and heat-resistant organic silicon-containing compound. Achieved.

The protective layer of the thermal head is usually made of Ta
_Since it is made of glass containing ₂ O ₅ , SiO ₂ , SiON, Si ₃ N _{3 and the} like, as the water-repellent, oil-repellent and heat-resistant compound, for example, an organic silicon-containing compound such as a silane compound is surface-treated. When used as an agent, the surface of the protective layer can be chemically modified. Such an organosilicon-containing compound is hydrolyzed in the presence of a hydrolysis catalyst by water in an aqueous solution or air, or water adsorbed on the surface of an inorganic material to form a highly reactive silanol group (Si-OH). However, since this silanol group is a reactive group capable of adsorbing or chemically bonding to the surface of the inorganic material, by using this organosilicon compound for the surface treatment of the protective layer of a thermal head made of glass, The surface of the protective layer can be chemically modified. According to the present invention, it has been confirmed that this surface treatment can improve the contact angle of the surface of the protective layer with water to 95 degrees or more. Since the silanol groups are bonded to the OH groups present on the surface of the solid, any protective layer made of any material can be treated with water and oil repellency as long as the protective layer is made of a material capable of providing such OH groups. It is possible to

Therefore, according to another aspect of the present invention,
A surface treatment method for a thermal head, comprising applying a water-repellent, oil-repellent, and heat-resistant organic silicon-containing compound having a hydrolyzable reactive group to a protective layer of a thermal head in the presence of a hydrolysis catalyst. Is done.

Thus, according to the present invention, the water-, oil-repellent, and heat-resistant organosilicon-containing compound is bonded to the surface of the protective layer of the thermal head to form a film at a molecular level. In order to improve water and oil repellency
It has no effect on the thermal conductivity of the thermal head.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The water-repellent, oil-repellent and heat-resistant organosilicon-containing compound used for the surface treatment of the protective layer of the thermal head in the present invention is one which imparts water-repellent and oil-repellent properties to the surface of the thermal head. It is not particularly limited. Such compounds have recently been used as a water / oil repellent treatment agent with glass.
Although provided in the form of various compositions, typical examples of the compound include a fluoroalkylsilane having a hydrolyzable reactive group at a terminal represented by the following general formula (1).

CF ₃ (CF ₂ ) _m (CH ₂ ) _n SiR _p X _3-p (1)

(Wherein R represents a substituted or unsubstituted monovalent hydrocarbon group, X represents a hydrolyzable group, m is an integer of 5-10, n is an integer of 2-10, p is 0 Represents an integer from 2 to 2)

Specific examples of the substituted or unsubstituted monovalent hydrocarbon group (R) include, for example, an alkyl group such as a methyl group, an ethyl group, a propyl group and a hexyl group, a vinyl group and an allyl group. Alkenyl group, cyclopentyl group,
A cycloalkyl group such as a cyclohexyl group, a phenyl group,
An aryl group such as a tolyl group, and a group in which a part of these groups are substituted with a halogen atom, an amino group, a hydroxyl group, an alkoxy group, or the like can be given.

Specific examples of the hydrolyzable group (X) include, for example, alkoxy groups such as methoxy group, ethoxy group, isopropoxy group, n-propoxy group, n-butoxy group, aminoxy group, ketoxime group, and acetoxy group. Examples thereof include a group, an amide group, and an alkenyloxy group. Among them, an alkoxy group-based methoxy group or an ethoxy group is preferable because good pot life, reactivity, and good water and oil repellency are obtained.

Specific examples of the above fluoroalkylsilane include, for example, CF ₃ (CF ₂ ) ₅ CH ₂ CH ₂ Si (OCH ₃ ) ₃ , CF ₃ (CF ₂ ) ₇
CH ₂ CH ₂ Si (OCH ₃ ) ₃ , CF ₃ (CF ₂ ) ₉ CH ₂ CH ₂ Si (OCH ₃ ) ₃ , CF ₃ (C
F ₂ ) ₇ CH ₂ CH ₂ Si (OC ₂ H ₅ ) ₃ , CF ₃ (CF ₂ ) ₇ CH ₂ CH ₂ Si (CH ₃ ) (OC
H ₃ ) _{2 and the} like, and those having a fluoroalkyl group having 6 to 10 carbon atoms are preferable. These compounds may be used alone or in combination of two or more.

The organosilicon-containing compound having a hydrolyzable reactive group at the terminal such as a fluoroalkylsilane can be prepared as a surface treating agent by mixing and dispersing it in an organic solvent together with a suitable hydrolysis catalyst.

As the above-mentioned hydrolysis catalyst, for example, a silane containing an aminoalkyl group can be used in addition to a strong acid or strong alkali catalyst, a fatty acid metal salt and a metal alkoxide. These catalysts may be used alone or in combination of two or more.

The strong acid or strong alkali catalyst includes:
Specifically, inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid; organic acids such as formic acid, acetic acid, oxalic acid, sulfonic acid, acetic anhydride, and benzoic acid; and inorganic bases such as ammonia, sodium hydroxide, and potassium hydroxide. And organic bases such as ethylenediamine and triethanolamine. Of these, inorganic acids and organic acids are preferable, and hydrochloric acid and nitric acid are particularly preferable, since good pot life and water repellency can be obtained.

Some thermal head materials are not suitable for strong acids and strong bases. In such cases, it is convenient to use the above-mentioned fatty acid metal salts, metal alkoxides or aminoalkyl group-containing silanes as hydrolysis catalysts. It is.

As the above fatty acid metal salt, specifically,
Metal soap, fatty acid organic metal salts and the like, among which fatty acid organic tin salts are preferred . Examples of the fatty acid organic tin salt include, for example, dialkyltin dialkanoate, alkyltin trialkanoate, and the like,
Among them, dialkyltin dialkanoates are preferred. Examples of the dialkyltin dialkanoate include dibutyltin dilaurate, dibutyltin diacetate,
Examples include dioctyltin dilaurate, dioctyltin diacetate, dimethyltin dilaurate, dimethyltin diacetate, and dibutyltin dilaurate is particularly preferred.

Specific examples of the metal alkoxide include titanium alkoxide, iron alkoxide, and organotin alkoxide, and among them, titanium alkoxide is preferable. As the titanium alkoxide, for example,
Examples thereof include tetraethyl titanate, tetrabutyl titanate, and tetraisopropyl titanate, with tetraisopropyl titanate being particularly preferred. Examples of the iron alkoxide include iron octylate. Examples of the organotin alkoxide include dibutyltin dioctylate, methyltin trioctylate,
And dioctyltin dioctylate.

The aminoalkyl group-containing silane is a compound represented by the following general formula (2).

R ¹ SiR ² _q Y _3-q (2)

Wherein R ² is a monovalent hydrocarbon group, Y is an alkoxy group, R ¹ is an aminoalkyl group, and q is an integer of 0 to 2.

In the aminoalkyl group-containing silane of the above general formula (2), the monovalent hydrocarbon group represented by R ² is specifically the same group as R in the above general formula (1). And a methyl group is particularly preferable. Examples of the alkoxy group represented by Y include the same groups as those in X in the general formula (1). Among them, a methoxy group and an ethoxy group are preferable, and a methoxy group is particularly preferable. Examples of the aminoalkyl group represented by R ¹ include a β-aminoethyl group, γ
-Aminopropyl group, δ-aminobutyl group, N- (β-
Aminoethyl) aminomethyl group, N- (β-aminoethyl) -γ-aminopropyl group and the like. Also,
q is preferably 0 or 1 because the resulting coating has good water repellency.

As the aminoalkyl group-containing silane, specifically, H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ , H ₂ N (CH ₂ ) ₂ NH (CH
_{2) 3 Si (OC 2 H} 5) 3, H 2 N (CH 2) 3 Si (CH 3) (OC 2 H 5) 2, H 2 N (CH 2) 3
_{Si (OC 2 H 5) 3} , H 2 N (CH 2) 2 NH (CH 2) 3 Si (CH 3) (OC 2 H 5) 2 and the like.

The organic solvent is not particularly limited as long as it can dissolve or disperse the organic silicon-containing compound and the hydrolysis catalyst, but is preferably an anhydrous solvent containing an alcohol as a main component. Specifically, for example, alcohols such as methanol, ethanol, isopropyl alcohol, n-propyl alcohol, and n-butyl alcohol; ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, tetrahydrofuran, and dioxane Alcohols and ethers, acetone, ketones such as methyl ethyl ketone,
Methyl acetate, esters such as ethyl acetate, n-hexane, gasoline, aliphatic hydrocarbons such as mineral spirits, benzene, toluene, aromatic hydrocarbons such as xylene, octamethylcyclotetrasiloxane,
Hexamethyldisiloxane, volatile silicones such as octamethyltrisiloxane, and among them, ether alcohols and alcohols are preferable, and ethanol and isopropyl alcohol are particularly preferable from the viewpoint of pot life of the surface treatment agent and good coating properties. preferable. The above solvents may be used alone or in combination of two or more.

The method for preparing the composition of the surface treating agent used in the present invention is not particularly limited, and it can be obtained by mixing the above components at room temperature to obtain a uniform composition. Preferably, the composition is prepared by the last addition procedure.

In order to surface-treat the protective layer of the thermal head according to the present invention, the surface treating agent may be applied to the thermal head and dried.

The method of applying the surface treatment agent to the surface of the protective layer of the thermal head is not particularly limited. For example, the treatment agent can be applied by hand by immersing it in a cloth. Coating can also be performed using dipping, a coating roller, brush coating, a blade, or the like.

The degree of surface modification of the surface treatment agent, that is, the binding or abrasion resistance of the surface treatment agent to the thermal head, depends on the drying temperature after application and the treatment time. Preferred drying conditions are a drying temperature of 50 ° C. or more and a processing time of 30 minutes or more, and the drying temperature is particularly preferably 60 ° C. or more. Needless to say, the upper limit of the drying temperature is limited by the heat resistance of the thermal head and the thermal decomposition temperature of the surface treating agent.

When the surface is treated with the water-, oil-repellent and heat-resistant organic silicon-containing compound, the protective layer is preferably pretreated with a pretreatment agent.
As the pretreatment agent, an organic silicon compound having an isocyanate group directly bonded to a silicon atom, particularly one that cures at room temperature can be used. In this case, the durability of the modified protective layer surface is improved.

This pretreatment step can be carried out, for example, by applying a coating liquid containing an organic silicon compound having an isocyanate group directly bonded to a silicon atom as a main component on the protective layer and drying it at normal temperature. Thus, since the silica base layer (underlayer) having high surface activity is formed on the protective layer, the adhesion between the lower protective layer surface and the upper water-repellent and oil-repellent layer is further increased. be able to. In this case, high-temperature baking is not necessarily required, and a film having sufficient hardness can be obtained by baking at room temperature or relatively low temperature, and the film thickness to be formed can be appropriately selected by adjusting the coating solution. The desired silica base layer (underlayer) can be formed easily and efficiently.

Examples of the organosilicon compound having an isocyanate group directly bonded to a silicon atom include an organosilicon compound represented by the following general formula (3).

R _4-m Si (NCO) _m (3)

M is an integer of 3-4. R is a monovalent hydrocarbon group.

As the compound represented by the general formula (3), for example, tetraisocyanate silane [Si (NC
O) ₄ ], monomethyl triisocyanate silane [CH ₃ Si (N
CO) ₃ ], but tetraisocyanate silane is preferred because good structure can be obtained.

It is preferable that the organic silicon compound having an isocyanate group directly bonded to a silicon atom is prepared as a coating solution by mixing with an appropriate organic solvent. The organic solvent is not particularly limited as long as it can stably dissolve the organosilicon compound represented by the general formula (3), but is preferably an anhydrous solvent containing esters as a main component. Specific examples include ethyl acetate, esters such as butyl acetate, acetone, ketones such as methyl isobutyl ketone, toluene, and aromatic hydrocarbons such as xylene. Depending on the thickness and the manufacturing conditions of the target product, an appropriate organic solvent is appropriately selected and used.

The coating solution is prepared by mixing the silicon compound represented by the general formula (3) and an organic solvent in a ratio of 1: 4 to 1: 999 (weight ratio).
It is preferable to adjust the blending ratio according to the film forming method or film thickness and the production conditions of the target product.

In order to reduce the surface tension of the thermal head surface by the surface treatment method of the present invention including this pretreatment step, an agent mainly containing an organosilicon compound having an isocyanate group directly bonded to a silicon atom is used. A certain coating liquid A is prepared as a pretreatment agent, and a coating liquid B, which is a chemical mainly composed of a water-repellent, oil-repellent, and heat-resistant organosilicon compound having a fluoroalkyl group, is prepared. The coating liquid A may be applied to the surface of the substrate and dried at room temperature to form a film, and the coating liquid B may be applied on the film and dried.

The method for sequentially applying the coating solution A and the coating solution B on the surface of the protective layer of the thermal head is not particularly limited. For example, the coating solution can be soaked and applied manually. It can also be applied using a dipping coating roller, brush coating or a blade.

The bondability or abrasion resistance of the underlayer to the protective layer due to the treatment of the coating solution A depends on the drying temperature after the application and the treatment time. A film of sufficient hardness can be obtained by baking at room temperature or at a relatively low temperature without the necessity, and actually reaches a practical hardness in about 6 hours at room temperature.

The degree of surface modification obtained with the coating liquid B, that is, the bonding property or abrasion resistance of the surface modified layer to the underlayer depends on the drying temperature and the treatment time after the application. The preferable drying conditions are the same as when the underlayer is not formed.

[0049]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the following examples, “parts” means “parts by weight”.

Example 1 To 97 parts of isopropyl alcohol, 2 parts of heptadecafluorodecyltrimethoxysilane [CF ₃ (CF ₂ ) ₇ CH ₂ CH ₂ Si (OCH ₃ ) ₃ ] as a fluoroalkylsilane was added and mixed. Then, 1 part of nitric acid (61% concentration) was further added as a hydrolysis catalyst and mixed uniformly to prepare a surface treating agent.

A thermal head having a protective layer composed of a Ta—SiO ₂ sputtered layer was prepared, and the surface of the protective layer was washed with alcohol. Then, the surface treating agent obtained above was coated with the treating agent. After coating with an impregnated cloth and air-drying at room temperature for 10 minutes, the thermal head was placed in a constant-temperature bath at 70 ° C. and heat-treated for 30 minutes to produce a thermal head having a modified protective layer. .

The thermal head thus surface-treated was subjected to the following performance tests. Table 1 shows the results.

Example 2 As a fluoroalkylsilane, heptadecafluorodecyltrimethoxysilane [CF ₃ (CF ₂ ) ₇ CH ₂ CH ₂ Si (OC
H ₃ ) ₃ ], and the surface treatment was performed in the same manner as in Example 1 except that heneicosafluorododecasyltrimethoxysilane [CF ₃ (CF ₂ ) ₉ CH ₂ CH ₂ Si (OCH ₃ ) ₃ ] was used. An agent was prepared to prepare a thermal head having a modified protective layer.

The surface-treated thermal head was subjected to the following performance tests. Table 1 shows the results.

Example 3 As a fluoroalkylsilane, heptadecafluorodecyltrimethoxysilane [CF ₃ (CF ₂ ) ₇ CH ₂ CH ₂ Si (OC
H ₃ ) ₃ ] was replaced with tridecafluorooctyltrimethoxysilane [CF ₃ (CF ₂ ) ₅ CH ₂ CH ₂ Si (OCH ₃ ) ₃ ] in the same manner as in Example 1, except that A prepared thermal head having a modified protective layer was prepared.

The surface-treated thermal head was subjected to the following performance tests. Table 1 shows the results.

Example 4 Same as Example 1 except that 0.1 part of γ-aminopropyltrimethoxysilane [H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ ] was used instead of nitric acid of Example 1. A surface treatment agent was prepared to prepare a thermal head having a modified protective layer.

The surface-treated thermal head was subjected to the following performance tests. Table 1 shows the results.

Example 5 A surface treating agent was prepared in the same manner as in Example 1 except that 0.5 parts of dibutyltin laurate was used in place of nitric acid in Example 1, and a thermal head having a modified protective layer was produced. .

The surface-treated thermal head was subjected to the following performance tests. Table 1 shows the results.

Example 6 Example 1 was repeated except that the heat treatment temperature in the thermostat was changed to 50 ° C.
In the same manner as in the above, a thermal head having a modified protective layer was produced.

The surface-treated thermal head was subjected to the following performance tests. Table 1 shows the results.

Example 7 Example 1 was repeated except that the heat treatment temperature in the thermostat was changed to 100 ° C.
In the same manner as in the above, a thermal head having a modified protective layer was produced.

The surface-treated thermal head was subjected to the following test. Table 1 shows the results.

Example 8 To 49 parts of ethyl acetate [CH ₃ COOC ₂ H ₅ ], 1 part of tetraisocyanate silane [Si (NCO) ₄ ] was added and mixed.
(Pretreatment agent) was prepared.

To 97 parts of isopropyl alcohol, 2 parts of heptadecafluorodecyltrimethoxysilane as a fluoroalkylsilane were added and mixed, and 1 part of nitric acid (61% concentration) was further added as a hydrolysis catalyst to obtain a uniform mixture. To prepare a coating solution B (surface treatment agent).

A thermal head provided with a protective layer composed of a Ta—SiO ₂ sputtered layer was prepared, and the surface of the protective layer was washed with alcohol, and then the coating solution A obtained above was applied to the surface. It was applied with an impregnated cloth and dried at room temperature for about 6 hours to form a silica-based underlayer. An abrasion resistance test was performed on this underlayer by a pencil hardness test. As a result, it was found that when the ratio of the coating liquid A was 1:49, a hard film having a pencil hardness of about H7 was obtained.

The coating solution B obtained above was applied to the surface of the silica-based base layer formed by the coating solution A with a cloth impregnated with the coating solution B, and air-dried at room temperature for 10 minutes. The thermal head was placed in a constant temperature bath at 70 ° C. and heat-treated for 30 minutes to produce a thermal head having a modified surface.

The thermal head thus surface-treated was subjected to the following performance tests. Table 1 shows the results.

Example 9 An underlayer similar to that of Example 8 was formed on a thermal head similar to that of Example 8.

The same evaluation as in Example 8 gave a hard film similar to that in Example 8.

Subsequently, a coating solution B was prepared in the same manner as in Example 1 except that henedecosafluorododecyltrimethoxysilane was used instead of heptadecafluorodecyltrimethoxysilane as the fluoroalkylsilane, and the surface was modified. A quality thermal head was manufactured.

The surface-treated thermal head was subjected to the following performance tests. Table 1 shows the results.

Example 10 The same underlayer as in Example 8 was formed on the same thermal head as in Example 8.

The same evaluation as in Example 8 gave a hard film similar to that in Example 8.

Subsequently, a coating solution B was prepared in the same manner as in Example 8 except that tridecafluorooctyltrimethoxysilane was used instead of heptadecafluorodecyltrimethoxysilane as the fluoroalkylsilane, and the surface was modified. A thermal head was manufactured.

The surface-treated thermal head was subjected to the following performance tests. Table 1 shows the results.

Example 11 An underlayer similar to that of Example 8 was formed on a thermal head similar to that of Example 8.

The same evaluation as in Example 8 showed a hard film similar to that in Example 8.

A coating liquid B was prepared in the same manner as in Example 8 except that 0.1 part of γ-aminopropyltrimethoxysilane was used in place of nitric acid in Example 8, and a thermal head having a modified surface was prepared. .

The surface-treated thermal head was subjected to the following performance tests. Table 1 shows the results.

Example 12 An underlayer similar to that of Example 8 was formed on a thermal head similar to that of Example 8.

The same evaluation as in Example 8 gave a hard film similar to that in Example 8.

A coating liquid B was prepared in the same manner as in Example 8 except that 0.5 parts of dibutyltin laurate was used in place of nitric acid in Example 8, and a thermal head having a modified surface was prepared.

The surface-treated thermal head was subjected to the following performance tests. Table 1 shows the results.

Example 13 The same underlayer as in Example 8 was formed on the same thermal head as in Example 8.

The same evaluation as in Example 8 gave a hard film similar to that in Example 8.

A thermal head having a modified surface was produced in the same manner as in Example 8, except that the heat treatment temperature in the thermostat was changed to 50 ° C.

The surface-treated thermal head was subjected to the following performance tests. Table 1 shows the results.

Example 14 An underlayer similar to that of Example 8 was formed on a thermal head similar to that of Example 8.

The same evaluation as in Example 8 gave a hard film similar to that in Example 8.

A thermal head having a modified surface was produced in the same manner as in Example 8, except that the heat treatment temperature in the thermostat was changed to 100 ° C.

The surface-treated thermal head was subjected to the following performance tests. Table 1 shows the results.

Comparative Example 1 An untreated thermal head similar to that in Example 1 was subjected to the following performance test without surface treatment. Table 1 shows the results.
Shown in

Comparative Example 2 An electronic component having low heat resistance was removed from the same thermal head as in Example 1, and a dispersion containing a solid of polytetrafluoroethylene was applied to the surface of the protective layer of the thermal head. After preliminary drying at room temperature, a heat treatment was performed at about 350 ° C. to obtain a thermal head in which the protective layer was covered with a resin layer made of polytetrafluoroethylene.

Performance Test Each of the thermal heads obtained in Examples 1 to 14 and Comparative Examples 1 and 2 was mounted on a rotary printing machine “Risograf (registered trademark)” TR-153 manufactured by Riso Kagaku Kogyo Co., Ltd. The performance of the thermal head was evaluated by the following items.

Evaluation items (1) Film piercing property
The number of defective perforations in the number of perforated units was measured, the occurrence rate of the number of defective perforations was calculated, and the film perforability was evaluated according to the following evaluation criteria.

[0098]

(2) Dirt of thermal head
After continuous plate making of about 000 m or 3000 m, the state of contamination on the surface of the thermal head was visually observed, and the adhesion prevention property of the hot melt was evaluated according to the following evaluation criteria.

[0100]

(3) Contact Angle The contact angle of the thermal head surface to purified water was measured immediately after the surface treatment (initial stage) and after continuous thermal stencil printing of about 1000 m or 3000 m. Of the surface treatment agent and the abrasion resistance of the surface treating agent.

[0102]

[Table 1] As is clear from Table 1, the thermal head treated in accordance with the present invention (Examples 1 to 7) has less stain on the thermal head after continuous plate making than the untreated thermal head (Comparative Example 1). It is shown that the melt of the thermoplastic resin film is not easily adhered, and furthermore, the film is more excellent in perforation property than the thermal head having the conventional polytetrafluoroethylene resin layer (Comparative Example 2), and the surface treatment of the present invention. Does not inhibit thermal conductivity from the pyrogenic low antibody to the surface. Further, from the comparison between Examples 1 and 2 and Example 3, it was found that the fluoroalkylsilane had 8 carbon atoms.
It is particularly preferable to use one having the above fluoroalkyl group, and a comparison between Examples 1 and 7 and Example 6 shows that the heat treatment temperature is particularly preferably 70 ° C. or higher. .

Further, the thermal head (Examples 8 to 14) in which the undercoat layer is formed with the coating liquid A and then the coating liquid B is applied to modify the water- and oil-repellent surface (Examples 8 to 14) Compared to the thermal head (Example 1) in which the coating solution B was applied directly on the surface of the protective layer, the thermal head after the long-term continuous plate making was less contaminated and the adhesion of the melt of the thermoplastic resin film was prevented. It was shown that the durability related to was excellent.

[0104]

According to the thermal head of the present invention, the surface of the protective layer of the thermal head is modified with a water- and oil-repellent and heat-resistant compound such as fluoroalkylsilane so that the surface free energy is low. Further, it is possible to effectively prevent the adhesion of the hot melt of the thermoplastic resin film which occurs during the process of making the heat-sensitive stencil sheet. Since the surface of the modified protective layer is only covered with an extremely thin film at the molecular level of the above compound, the heat conduction efficiency from the heating resistor of the thermal head to the surface of the protective layer is not reduced. Since the adhesiveness between the thermoplastic resin film to be perforated and the thermal head is not hindered, it is suitable for plate making of heat-sensitive stencil paper, and can be applied to a thermal transfer printer and a heat-sensitive printer. Furthermore, the surface treatment method of the present invention can firmly bond the film to the surface of the protective layer only by heat treatment at a relatively low temperature, so that there is little possibility of damaging electronic components of the thermal head, Can be easily implemented.

Further, on the surface of the protective layer of the thermal head,
After forming a silica base film (underlying layer), if the surface of the silica base film is treated with a water-repellent, oil-repellent, and heat-resistant compound, the modified layer formed on the protective layer of the thermal head becomes repellent with the underlying layer. Although it has a two-layer structure consisting of a layer having water and oil repellency and heat resistance, both are only covered with an extremely thin film, which lowers the heat transfer efficiency from the low antibody of the thermal head to the surface of the modified layer. In addition, the above two layers can be firmly bonded to the surface of the protective layer only by heat treatment at a relatively low temperature. it can.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a general thin-film thermal head.

FIG. 2 is a cross-sectional view of a general thick film type thermal head.

FIG. 3 is a sectional view of a thermal head showing a preferred embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Insulating substrate, 2 ... Heating resistor, 3 ... Conductive layer, 4 ... Protective layer, 5 ... Underlayer, 6 ... Water / oil repellent layer

Claims (18)

[Claims] 1. A heating resistor provided on an insulating substrate, a conductive layer connected to the heating resistor and supplying electric power, and a protection layer provided on the heating resistor and the conductive layer. A thermal head according to claim 1, wherein the protective layer is surface-treated with a water-repellent, oil-repellent, and heat-resistant organic silicon-containing compound. 2. The thermal head according to claim 1, wherein a contact angle of the surface of the surface-treated protective layer with water is 95 degrees or more. 3. The thermal head according to claim 1, wherein the water- and oil-repellent and heat-resistant organosilicon-containing compound is a fluoroalkylsilane having a hydrolyzable reactive group at a terminal. 4. The thermal head according to claim 3, wherein the fluoroalkyl silane has a fluorocarbon length of 6 to 10. 5. The thermal head according to claim 3, wherein the fluoroalkylsilane has a fluorocarbon length of 8 to 10. 6. The thermal head according to claim 1, wherein the surface of the protective layer is pre-treated with a pre-treatment agent, and the surface treatment is performed on the pre-treated surface. 7. The thermal head according to claim 6, wherein the pretreatment agent is a chemical mainly composed of an organic silicon compound having an isocyanate group directly bonded to a silicon atom. 8. The organic silicon compound having an isocyanate group directly bonded to a silicon atom is represented by the following general formula: R _4-m Si (NCO) _m (where m is an integer of 3 to 4. , A monovalent hydrocarbon group). 9. The organic silicon compound having an isocyanate group directly bonded to a silicon atom is a tetraisocyanate silane represented by the following general formula Si (NCO) _4.
The thermal head according to 1. 10. The thermal head according to claim 1, wherein the thermal head is used for making a heat-sensitive stencil sheet. 11. A thermal head comprising applying a water-repellent, oil-repellent and heat-resistant organosilicon-containing compound having a hydrolyzable reactive group to a protective layer of a thermal head in the presence of a hydrolysis catalyst. Surface treatment method. 12. The surface treatment method according to claim 11, further comprising heating to 50 ° C. or higher. 13. The surface treatment method according to claim 11, wherein the organosilicon-containing compound is a fluoroalkylsilane. 14. The surface treatment method according to claim 11, wherein the protective layer has been pretreated with a pretreatment agent, and the organosilicon-containing compound is applied to the pretreated surface. 15. The surface treatment method according to claim 14, wherein the pretreatment agent is a medicine mainly composed of an organosilicon compound having an isocyanate group directly bonded to a silicon atom. 16. An organosilicon compound having an isocyanate group directly bonded to a silicon atom is represented by the following general formula: R _4-m Si (NCO) _m (where m is an integer of 3 to 4; R is , A monovalent hydrocarbon group). 17. The organic silicon compound having an isocyanate group directly bonded to a silicon atom is a tetraisocyanate silane represented by the following general formula Si (NCO) _4.
7. The surface treatment method according to 6. 18. The surface treatment method according to claim 11, wherein the thermal head is used for making a heat-sensitive stencil sheet.