JPH02299887A - Preparation of heat-sensitive stencil paper - Google Patents

Abstract

PURPOSE:To obtain excellent printing durability by increasing bonding strength by using an adhesive based on an active hydrogen-containing resin having a specific range of a wt. average MW and containing a hydroxyl group and mixing polyisocyanate with said adhesive at the time of lamination so that the ratio of an NCO group and an OH group becomes a specific range to lami nate a film to a perforated support. CONSTITUTION:A thermoplastic resin film and an ink previous perforated support not changed substantially at the melt-shrinking temp. of said film are bonded by pref. applying an active hydrogen-containing resin solution to the surface of the film and coating the perforated support with a polyisocyanate solution to superpose both of them one upon another in an undried state and drying the same. The active hydrogen-containing resin used at this time is a thermoplastic resin mainly containing a hydroxyl group and having characteristic values such that a wt. average MW is 10,000 - 1,500,000, a hydroxyl value is 7 or less and glass transition temp. is 70 deg.C or lower. The addition rate of polyisocyanate to the active hydrogen-containing resin is set to 2.0 - 3.5 as an NCO/OH equivalent ratio.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing a heat-sensitive stencil paper having a structure in which a thermoplastic resin film and a porous support such as porous thin paper or a mesh-like sheet are bonded together. .

C. Prior Art] The structure of conventionally used heat-sensitive stencil paper consists of a heat-melting shrinkable resin film and a porous support that is permeable to stencil printing ink, which does not melt and shrink at the temperature at which the film melts and shrinks. The film is bonded with an adhesive, and a coating is provided on the surface of the film to prevent fusion with the original or the heating element.

That is, the basic components of the heat-sensitive stencil paper are the two members, the heat-melt shrinkable film and the porous support, and it is essential that these are laminated and bonded tightly to each other.

The reason for this is that the heat melt shrinkable film used is extremely thin with a thickness of less than 10 mm, so it is not only weak and inconvenient to handle, but also prone to deformation and distortion during plate-making heating, or the perforations falling off. This is because it cannot be used because it occurs and has no purpose.

Therefore, it is necessary to adopt a laminated structure of a film and a porous support, and since it is a laminated structure, an adhesive is essential. This is an important factor that affects the quality of stencil paper.

Therefore, many techniques have been proposed in this regard.

For example, bonding methods include stacking a film and porous paper, impregnating the porous paper with a synthetic resin solution, drying and bonding (Japanese Patent Publication No. 55-47997), and applying adhesive to the porous paper using a gravure roll. A method of coating and bonding with a film (Japanese Unexamined Patent Publication No. 147398/1983)
, a method in which adhesive is gravure coated on either the film or porous paper and then adhered with a pressure roll (
JP-A-58-188698), a method in which hot-melt adhesive is applied to a film in advance, porous paper is stacked on top of the film, and the film is bonded by pressing with a heating roll (JP-A-59-1679).
0), a method of applying an adhesive solution with a viscosity of 100 cps or less to the film surface, overlapping porous paper in an undried state, and drying and bonding (Japanese Patent Application Laid-Open No. 59-2279 [!), Film There is a method of applying an adhesive to a porous paper, impregnating a porous paper with a solvent, overlapping the two in an undried state, and drying and adhering them (Japanese Patent Laid-Open No. 81-2597).

Regarding adhesive selection, acrylic resin should be 1.5 to 1
Method of applying 0g/go (Special Publication No. 1187/1987)
, 2 to 10 g of adhesive whose main component is vinyl acetate resin
/rrr coating method (Special Publication No. 1188/1988)
, a method of dissolving and using vinyl acetate resin in a mixed solvent of methanol and other alcoholic solvents (Japanese Patent Publication No. 1973-
17338), a method using an adhesive made by adding polyvinyl alcohol to polyvinylidene chloride latex (Japanese Patent Publication No. 48-29730), a method of applying 0.5 to 2 g/rd of an adhesive whose main component is an acrylic resin. (Japanese Patent Publication No. 51-33004), method using vinyl acetate resin added with rosin resin (Japanese Patent Publication No. 59-33004),
871! B), a method in which a vinyl acetate-based or acrylic adhesive is applied to a film and dried, this surface is impregnated with a water-dispersed vinyl acetate resin, and porous paper is layered in an undried state, dried, and bonded. (Japanese Unexamined Patent Publication No. 59-1 [1795]), a method using methoxymethylated polyamide (Japanese Unexamined Patent Publication No. 59-115899), adhesive containing vinyl chloride copolymer as the main component, 0.1 to 5 g/ rrr coating method (Japanese Unexamined Patent Publication No. 59-215894), a method of applying OJ to 2.5 g/g of incyanate prepolymer on the film surface and pressing at 2 kg/d or more (Japanese Unexamined Patent Publication No. 6111)
8595), diisocyanate and average molecular weight 40
NC010H with polyether diol from 0 to 2000
A method using an adhesive whose main component is a reacted prepolymer with an equivalent ratio of 1.5 to 2.0 and whose flow initiation temperature after curing is 150 to 260° C.

Publication No. 181374, etc.).

[Problems to be Solved by the Invention] With the heat-sensitive stencil paper having the above structure, it is necessary to achieve stronger and more uniform adhesion using as little adhesive as possible.

That is, if the amount of adhesive is large, the thermal perforation sensitivity of the film will be reduced and the perforations will be blocked, preventing ink from passing through, making it impossible to produce clear printed matter. This defect is more pronounced as the adhesive has higher heat resistance and melt viscosity, and the harder and stronger the adhesive film is, the more this tendency is exhibited.

On the other hand, if the amount of adhesive is small, the adhesive force will be weak and serious defects such as film lifting and wrinkles will easily occur during the bonding process, and the printing ink will penetrate into the porous support during printing. Since a tensile force is applied between the film and the film, the two easily separate, causing the film to break and making it impossible to print. The weaker and poorer the heat resistance of the adhesive, the more this tendency occurs.

However, since the above requirements are mutually contradictory with many other requirements required for heat-sensitive stencil paper, they have not been satisfactorily resolved by conventional techniques.

For example, an attempt was made to improve resolution by impregnating porous paper with a synthetic resin and overlapping it with a film, without intervening an adhesive layer between the film and the porous paper. In the first place, adhesion between a film and porous paper is nothing but adhesion at the interface between the two, so if the amount of resin impregnated is small, most of the resin will be adsorbed to the porous paper, and the amount that contributes to adhesion at the interface will be reduced. The amount of adhesive strength decreases and the required adhesive strength cannot be achieved. If the amount of resin is increased to increase adhesive strength, it will fill the pores in the porous paper and prevent ink from passing through, making it impossible to produce clear prints.

Therefore, a method was proposed in which an adhesive is applied to a film, the film is overlapped with a porous paper in an undried state, and the film is dried and bonded so that the adhesive is effectively present at the interface between the film and the porous paper.

Although this method allows the amount of adhesive to be reduced compared to the above method, the adhesive solution permeates into the porous paper from the time the adhesive is stacked until the adhesive dries. When the viscosity is low, penetration is significant, the amount of adhesive at the interface is reduced, and the adhesive strength is reduced. On the other hand, if the viscosity of the adhesive solution is high, penetration will be reduced, but it will be difficult to uniformly apply a small amount of adhesive to the film, resulting in variations in quality.

Furthermore, in an attempt to make a small amount of adhesive exist only at the interface between the film and porous paper, a solvent-free adhesive that had been heated to a low viscosity was applied to the film, and then porous paper was layered on top of it. A method of applying heat and pressure has been proposed. However, with this method, it is difficult to adjust the tack when heating to lower the viscosity, and the adhesive does not wet and dig into the porous paper simply by stacking, so heating and pressure after stacking is required, which requires a considerable amount of work. Due to the high temperature, it cannot be used in porous paper made of synthetic resin fibers such as polyester and polypropylene.

Regarding the adhesive itself, if vinyl acetate resin, acrylic resin, vinyl chloride resin, polyester resin, etc. are used, the solid resin content at the time of bonding is 1 g/r.
If the porous paper is not more than f, the film will lift and wrinkle, and these resins will be softened, swollen, and dissolved by the printing ink, so if the porous paper is made of synthetic resin fibers, there will be no particular problem. If the item is made of natural fibers such as honeycomb, manila hemp, etc., the printing ink will penetrate into the fibers, so if the amount of adhesive is small, it will peel off easily. /d or more, which lowers the printing clarity.Furthermore, vinyl chloride resin has the disadvantage that it releases chlorine, which is harmful to the thermal head during plate making.

Furthermore, when using a moisture-curing urethane adhesive that is a reaction prepolymer of diisocyanate and polyether diol, this resin has good ink resistance, so even a small amount can be replaced with one that has high printing durability. It is difficult to manage pot life and adjust humidity.
It tends to cause uneven curing.

The present invention solves the problems of these conventional techniques, and enables adhesive strength with a small amount, no generation of harmful substances, and is less affected by humidity and with less unevenness, resulting in clear printing durability. The purpose is to produce heat-sensitive stencil paper with excellent strength.

[Means for Solving the Problems] In the present invention, when manufacturing a heat-sensitive stencil paper by bonding a thermoplastic resin film and a porous support with an adhesive, the adhesive has a weight average molecular weight of 10,000 to 10,000. 1,500,000, using an active hydrogen-containing resin containing mainly hydroxyl groups as the active hydrogen-containing group as the main component, and adding polyisocyanate to it before or during the bonding process.
The ratio of CO group and O)[ group is NCOloH-2,0 to 3
．． 5 (molar ratio), and the thermoplastic resin film and the porous support are bonded together.

[Function and Examples] Although the urethane adhesive based on incyanate is so widely used that it is said to be a universal adhesive, and is particularly known for film lamination, it is not heat-sensitive. As a result of various studies, we discovered an extremely effective adhesive formulation for stencil paper, which had not been adopted because it had a high heat softening point, was difficult to make, and did not produce clear prints. .

That is, by using a high molecular weight active hydrogen-containing resin as the main component and mixing a predetermined amount of polyisocyanate immediately before or at the time of bonding, the thermoplastic resin film and the porous support can be bonded together with a small amount of adhesive. The inventors have discovered that it is possible to use a heat-sensitive stencil paper that can be bonded relatively easily and has strong adhesion after curing, thereby producing a stencil with high printing durability, and has thus arrived at the present invention.

The present invention comprises a thermoplastic resin film and an ink-permeable porous support that does not substantially change at the melting and shrinking temperature of the film, preferably by applying an active hydrogen-containing resin solution to the film surface, and applying a polyisocyanate solution to the film surface. It is characterized in that it is applied to a porous support, the two are overlapped in an undried state, and then dried and bonded.

The active hydrogen-containing resin used in the present invention is a thermoplastic resin that mainly contains hydroxyl groups as active hydrogen groups, and has a weight average molecular weight of 10,000 to 1,500,000, preferably 2.
1,200,000 to 1,200,000, and preferably has a hydroxyl value of 7
Below, the glass transition temperature is preferably 3 to 5, more preferably 70°C or lower, preferably 0 to 50°C, and vinyl acetate resin, acrylic resin, polyester resin, etc. are used. can.

If the molecular weight is less than 10,000, the tack force will be insufficient and the film will lift and wrinkle when bonded. Molecular weight is 150
If it exceeds 10,000, the fluidity will be insufficient and uniform coating will not be possible, resulting in wrinkles and curls. When the hydroxyl value exceeds 7, thermal softening properties decrease due to reaction hardening with polyisocyanate, the flow start temperature becomes higher than 250° C., and plate-making perforability tends to be inhibited. When the glass transition temperature exceeds 70° C., the wettability of the resin is insufficient, wrinkles due to film displacement during bonding, and local temperature unevenness of the resin occur, which tends to cause variations in plate-making perforability.

The active hydrogen-containing resin of the present invention mainly contains hydroxyl groups as active hydrogen groups, but may also contain small amounts of other active hydrogen groups such as carboxyl groups, epoxy groups, and amide groups.

When the active hydrogen-containing resin is an addition polymer of acrylic resin, vinyl acetate resin, etc., the following active hydrogen-containing monomers may be used.

Examples of hydroxyl group-containing monomers include hydroxymethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxymethyl vinyl ether, 5-hydroxyhexyl vinyl ether, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monoacrylate, and polyethylene glycol monoacrylate. Examples include brobylene gelicol monomethacrylate. Examples of carboxyl group-containing monomers include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Examples of the epoxy group-containing monomer include glycidyl acrylate and glycidyl methacrylate. Examples of the amide group-containing monomer include acrylamide, methacrylamide, and N-methylolacrylamide.

As the active hydrogen-containing acrylic resin, the active hydrogen-containing monomer may be combined with an acrylic monomer (for example, (meth)acrylic acid lower alkyl ester (here, the alkyl group includes, for example, one having 1 to 18 carbon atoms), acrylonitrile, etc. Examples include those copolymerized with

Examples of the active hydrogen-containing vinyl acetate resin include those obtained by copolymerizing the above-mentioned active hydrogen-containing monomer with vinyl acetate.

Examples of active hydrogen-containing polyester resins include linear saturated polyesters obtained by condensation polymerization of a dicarboxylic acid component and a diol component and having hydroxyl groups at the molecular ends.

Examples of the dicarboxylic acid component include aromatic dicarboxylic acids such as terephthalic acid and inphthalic acid, aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and examples of the diol component include ethylene glycol, 1,4-butanediol, and diethylene glycol. , neopentyl glycol, etc.

The obtained linear saturated polyester can be subjected to a transesterification reaction to contain a hydroxyl group at the end of the molecule.

Moreover, if the hydroxyl group is etherified with epichlorohydrin, it can be converted into an epoxy group.

As the polyisocyanate to be mixed with the active hydrogen-containing resin, those having a molecular weight of 1001) or less are preferably used, such as tolylene diisocyanate (TDI).
, 3.3'-tolylene-4,4'-diisocyanate,
Diphenylmethane-p, p', p''-triisocyanate (TM), 2,4-tolylene dimer (TT), naphthalene-1,5-diisocyanate, tris(4-phenylisocyanate) thiophosphate, polymeric diphenylmethane-4, 4°-diisocyanate, hexamethylene diisocyanate trimer, dicyclohexylmethane-4,4-diisocyanate (1!MDI),
Hydrogenated TD1 (HTDI), metaxylylene diisocyanate (XDI), hexahydrometaxylylene diisocyanate (IXDI), hexamethylene diisocyanate (HMDI), trimethylolpropane-1-methyl-2-isocyanato-4-cababamate, trimethylolpropane -isocyanatohexamethylene-cababamate, polymethylene polyphenylisocyanate, 3
, 3'-dimethoxy-4,4°-diphenyldiisocyanate), 2,4-diisocyanato-1-methylcyclohexane, 2,6-diisocyanato-l-methylcyclohexane, diisocyanatosifurobucane, tetramethylene diisocyanate , cyclohexylmethadiisocyanate, dimethyldicyclohexylmethane diisocyanate, lysine diisocyanate alkyl ester, 3-methyldiphenyl-4,4°-diisocyanate, naphthalene-1,5-diisocyanate, diphenyl-4,4
'-diisocyanate-3,3'-dimethylphenyl,
Examples include 1.3.5-triisopropylbenzene-2,4-diisocyanate, mixtures of two or more thereof, and low polymers thereof.

Particularly desirable are those having three or more NCO groups.

When the molecular weight of the polyisocyanate exceeds 1000, the reactivity and solubility are poor, making handling inconvenient.

The addition ratio of polyisocyanate to the active hydrogen-containing resin is 2.0 to 2.0 to 0.011 NCO/011 equivalent ratio (mole ratio).
3.5, preferably 2.5 to 3.0.

If the N 2 CO/OH equivalent ratio is smaller than the above range, the reaction rate is slow and reaction unevenness tends to occur, resulting in insufficient water resistance effect on the porous support (this will be described later) and strength of the cured product. If it is larger than the above range, not only no further improvement in adhesive strength can be expected, but also unreacted isocyanate remains and distortion occurs.

The amount of the active hydrogen-containing resin used as the main component of the adhesive used in the present invention depends on the type and density of the fibers of the porous support, but the dry coating amount is preferably 0.2 to 5 g/d. is 0
．． 3-1. Or/go, more preferably 0.3-0.5g
It is 1st.

The amount of polyisocyanate to be used is in the equivalent ratio as described above to the amount of active hydrogen-containing resin used.

In the present invention, a large adhesive strength can be obtained with a small amount of adhesive, so that a high perforation clarity and a large printing durability can be obtained without impairing ink permeability.

The reaction between the active hydrogen-containing resin and the polyisocyanate progresses after the film and porous support are adhered, and reaches high printing strength in 24 to 48 hours at room temperature after adhesion, and usually lasts for 5 to 7 days at room temperature. It is completed with.

However, the dry hardening of the active hydrogen-containing resin itself provides sufficient adhesive strength for winding operations, and the adhesive does not block or flow down. Note that the curing time may be shortened by heating to about 50°C.

In the present invention, from the point of view of plate-making perforation, the hydroxyl group value, N, C010H equivalent ratio, etc. are adjusted within the above-mentioned ranges to obtain a reaction cured product with an appropriate crosslinking density, and the flow initiation temperature of the reaction cured product is below 250℃, <150
It is preferable to adjust the temperature to 230°C.

As the thermoplastic resin film used in the present invention, a highly oriented or stretched heat-melt shrinkable film having a melting point of 180 to 270°C and a thickness of 1 to 10 mm is preferably used, such as polyvinylidene chloride, vinylidene chloride- Examples include films made of vinyl chloride copolymer, polyester, polypropylene, etc. Particularly preferred is a polyester film having a thickness of 1.5-3.

Porous supports include Kozo, Mitsumata, Manila hemp,
A non-woven fabric with a basis weight of 5 to 15 C/g consisting of natural fibers such as jute, semi-synthetic fibers such as rayon, synthetic fibers such as polyester, vinylon, nylon, polypropylene, etc., alone or in a mixture of 2fiJi or more, the semi-synthetic fibers or synthetic fibers mentioned above. 50-2 consisting of one type or a mixture of two or more of
00 mesh screen gauze is preferably used.

In the present invention, the reaction product of the active hydrogen-containing resin and the polyisocyanate is present at a higher density at the bonding interface between the thermoplastic resin film and the porous support. preferable. By doing so, the adhesive strength can be improved without compromising the perforation clarity.

In order to achieve the above conditions, the active hydrogen-containing resin may be applied to the thermoplastic resin film, the polyisocyanate may be applied to the porous support, and the two may be bonded together.

To describe this bonding method more specifically, the active hydrogen-containing resin is diluted with a solvent to a concentration of 2 to 15% (by weight, hereinafter the same), and the viscosity (25°C) is 500 cps or less.
It is desirably adjusted to 5 to 200 cps, and a predetermined amount is applied to the film surface. Polyisocyanate has a concentration of 0.05~
The solution is diluted to 3% with a solvent and applied to a porous support in a predetermined equivalent amount to the active hydrogen-containing resin. Lay them together and glue them together in an undried state.

If the porous support is made of natural fibers, the fibers are hydrophilic and absorbent, so they are easily affected by humidity, causing expansion and shrinkage, and absorb ink during printing, causing film and porosity. The adhesive expands at the interface with the support, making it easier to peel off.

For these reasons, natural fibers are usually unusable unless they are treated to make them waterproof, so conventionally the fibers have been treated to become viscose or the porous support has been overcoated with a synthetic resin.

However, the viscose-forming process requires special equipment, resulting in poor efficiency and high cost.Furthermore, clumping tends to occur in areas where the fibers are tightly intertwined, resulting in poor ink permeability. In addition, in the resin coating treatment, the resin tends to form a film in the voids between the fibers, reducing the porosity or porosity of the porous support and reducing the print clarity.

On the other hand, the polyisocyanate used in the present invention has a small molecular weight, excellent solubility, does not have self-forming properties, and has extremely high affinity with fibers, so it penetrates sufficiently between the fibers, but does not fill the voids between the fibers. It does not block the fibers and form a film, but instead makes the surface of the fibers hydrophobic through a chemical reaction with the fibers or a self-polymerization reaction, so a high water resistance effect can be easily achieved by applying with a general coater.

Furthermore, since the porous support is impregnated with a solvent and then laminated, the active hydrogen-containing resin solution applied to the film surface does not penetrate excessively into the porous support, and even a small amount of adhesive can be applied to the film. It acts effectively at the contact interface between the active hydrogen-containing resin and the porous support, and the urethanization reaction between the active hydrogen-containing resin and the polyisocyanate proceeds more densely at the contact interface, resulting in strong adhesion.

Furthermore, the active hydrogen-containing resin and polyisocyanate are prepared separately, and the polyisocyanate is used as a low-concentration solvent solution, so pot life management is unnecessary.
Moreover, tack adjustment is easy.

In addition, since the curing reaction is mainly a reaction between the polyisocyanate and the active hydrogen-containing resin and the active hydrogen of the fiber,
Humidity adjustment as in moisture curing is not necessary.

In the present invention, a thermoplastic resin film and a porous support may be laminated using a mixture of an active hydrogen-containing resin and a polyisocyanate in advance.

In this case, as long as hot life is taken care of, there is an advantage that the adhesion work is simpler than the above-mentioned method of applying them separately. Furthermore, the ink resistance of the active hydrogen-containing resin is greatly improved by isocyanate crosslinking, so the amount of resin does not need to be extremely small.Therefore, even when premixed, the mixed liquid has a low concentration and low viscosity, resulting in a long pot life. Become. Moreover, during lamination, the adhesive liquid easily penetrates into the porous support, and although the amount of adhesive at the interface between the film and the porous support is reduced compared to the amount applied, it still maintains sufficient strength and the penetrating liquid does not clog the porous support and acts effectively to improve the wet strength of the porous support.

In this bonding method, preferably the active hydrogen-containing resin and the polyisocyanate are dissolved in a solvent such that the concentration of the active hydrogen-containing resin is 2 to 10% and the polyisocyanate satisfies the above-mentioned equivalent ratio, and the viscosity is 200
cps or less, preferably 5 to 5 Qcps: A predetermined amount of the adjusted solution is applied to the film surface, and the porous support is laminated and bonded in an undried state.

A conventionally known anti-stick layer may be provided on the film surface of the base paper of the present invention in order to prevent fusion with the original or the heating element during plate making.

Next, the present invention will be explained with reference to Examples and Comparative Examples.

Example 1 A biaxially stretched polyester film with a thickness of 2ρ was used as a thermoplastic resin film, and a weight of 111 g was used as a porous support.
/rrf Manila linen thin paper was used for lamination.

An acrylic copolymer with a weight average molecular weight of 900,000, a glass transition temperature of 11"C, and a hydroxyl value of 4.3 obtained by copolymerizing hydroxymethyl methacrylate with ethyl acrylate, methyl methacrylate, and acrylonitrile as active hydrogen-containing resins. A polymer resin was used.The polyisocyanate was trimethylolpropane-1-methyl-2-isocyanato-4-cababamate (NCO
Group content=12-13%) was used.

[Margin below] The above active hydrogen-containing resin was diluted with toluene/ethyl acetate, and a solution adjusted to a solid content concentration of 5% and a viscosity of 50 cps/25°C was applied to the film surface at 6 g/nf (0.0 g/nf as dry resin content).
42 g/rr? ) was applied. The polyisocyanate was diluted with toluene and a solution adjusted to a solid content concentration of 0.2% was applied to porous tissue paper at a rate of 15 g/rd.
10f (equivalence ratio was 2.8). The flow start temperature of the reaction cured product of this active hydrogen-containing resin and polyisocyanate was 180°C.

The lamination process is carried out by laminating the coated film and porous thin paper in an undried state, and heating at 50°C.
The film was dried for 60 seconds, and then a fatty acid ester of polyhydric alcohol was applied to the film surface at a rate of 0.5 g/rrr, and the film was wound up onto a roll. There was no lifting, wrinkles, or curling of the film during the bonding process, and there was no blocking or bleeding after winding, and the film was good in that small roll processing and single-wafer processing could be performed immediately after bonding and winding.

Plate making tests and printing tests were conducted on the obtained heat-sensitive stencil paper.

The plate-making test was carried out by perforation plate-making using Galaken ODX (Teiken ■ sheet-fed thermal plate making machine, thermal head: IG dot/■, 3 pis/line, 0.15 s+joulc/dot). As a result, the resolution is 8
The resolution was as high as the book/discussion level.

Note that the facsimile test chart No. 2 of the Institute of Image Electronics Engineers of Japan was used as the manuscript.

The printing test was carried out by perforation plate making and rotary printing using a Gestellatner CD 550 (integrated printing press manufactured by Gestellatner).

As a result, extremely clear printed matter was obtained, and the number of prints was more than 5,000 at 28 prints after lamination. Note that the number of printing sheets is the number of sheets printed until a 0.1511-width horizontal line becomes 0.3 foot-width.

Example 2 The same thermoplastic resin film and porous support as in Example 1 were used.

Linear saturated polyester resin as active hydrogen-containing resin,
The material used had a weight average molecular weight of 130,000, a glass transition temperature of 35° C., and a hydroxyl value of 4.0.

Trimethylolpropane-isocyanatohexamethylene-cababamate (NCO group content = 12 to 13%), which is an aromatic triisocyanate, was used as the polyisocyanate.

The active hydrogen-containing resin was diluted with toluene/ethyl acetate to give a solid content concentration of 8% and a viscosity of 25 cps/25°C.
One part by weight of the prepared solution was mixed with 11 parts by weight of a solution of the polyisocyanate diluted with toluene to give a solid content concentration of 5%. The viscosity of the resulting adhesive liquid was 24 cps.
/25°C. Also in this case NCO/OI
The I equivalent ratio was 2.9. Further, the pot life of the mixed liquid was 48 hours or more (no change in viscosity). Further, the flow initiation temperature of the reaction cured product of the mixture was 220°C.

Apply the above mixed solution to the film surface at 6g/d<dry applicationffl
Example 1
Similarly, a fatty acid ester of polyhydric alcohol was applied to the film surface at a rate of 0.05 g/d, and the film was wound onto a roll.

There was no lifting, wrinkles, or curling of the film during the bonding process, and there was no blocking or bleeding after winding, and the film was good in that small roll processing and single-wafer processing could be performed immediately after bonding and winding.

When the obtained heat-sensitive stencil paper was subjected to the same plate-making test and printing test as in Example 1, the resolution was 8.
The resolution was higher than that of a book. Furthermore, the number of printing sheets was 5,000 or more on the second day after the bonding process.

Example 3 The thermoplastic resin film, porous support, active hydrogen-containing resin, and polyisocyanate were the same as in Example 1, and the processing conditions for applying the release agent on the film surface were the same as in Example 1, and lamination processing was carried out. was carried out in the same manner as in Example 2.

However, the adhesive liquid was prepared as follows.

Solution 10 of active hydrogen-containing resin diluted with toluene/ethyl acetate to give a solid content concentration of 5% and a viscosity of 18 cps/25°C.
(To 1 part by weight, 867 parts by weight of a solution of polyisocyanate diluted with toluene to give a solid content concentration of 5% was added and mixed. The viscosity of the resulting adhesive liquid was 18 cps/25°C.
Met. Also, the NC010H equivalent ratio in this case is 2.
It was 8. In addition, the flow start temperature of the reaction cured product is 1110
It was ℃. As with Example 2, good results were obtained in terms of lamination workability, print clarity, and printability.

Comparative Examples 1 to 4 In Examples 2 and 3, the amount of polyisocyanate solution added was changed as shown in Table 1. The results are shown in Table 2.

Comparative Example 5 Using the same thermoplastic resin film and porous support as in Example 1, applying the release agent on the film surface under the same conditions, and using a polyurethane adhesive for film lamination to bond the film and the porous support. The body was glued together.

The adhesive is Takenate A-280 manufactured by Takeda Pharmaceutical Company Limited.
(Terminated incyanate prepolymer with average molecular ffi 2000 (viscosity at 25°C: 350000 cps)
A liquid moisture curing adhesive] was used.

The adhesive was diluted with toluene/ethyl acetate, and a solution adjusted to a solid concentration of 50% and a viscosity of 80 cps/25°C was applied to the film surface at 1.4 g/r& (0.7 as dry resin content).
g, /r&) and bonded to a porous support.

The pot life of the adhesive solution was about 12 hours, which is the time until a skin formed on the surface during storage, but a gelled substance was generated in the solution during the lamination process, causing lumpy granular protrusions on the surface of the laminated film. This resulted in a high defective rate. Adhesion was generally good, but curing time varied depending on temperature and humidity. Further, the printing durability did not reach 5,000 sheets or more until 7 days or more had passed at room temperature. Moreover, the print clarity was poor, with many missing small letters and white spots in midtones.

The reason why the printing clarity is poor is that although the flow start temperature of this cured product is 200 to 220°C, the molecular weight of the prepolymer is small, so the urethane bond density of the cured product is high and the whole becomes a rubber-like elastic body. Does not have a clear melting point,
It is speculated that this is due to poor liquidity.

``Effect of the invention'' By using an adhesive containing a high molecular weight active hydrogen-containing resin as the main component and adding polyisocyanate to it as an adhesive for bonding a thermoplastic resin film and a porous support, it is possible to achieve a large amount with a small amount. The adhesive strength is changed, and therefore the heat-sensitive stencil paper with high perforation clarity and long printing durability can be changed.

Claims (1)

[Scope of Claims] 1. When producing a heat-sensitive stencil paper by bonding a thermoplastic resin film and a porous support with an adhesive, the adhesive has a weight average molecular weight of 10,000 to 1,500,000 and contains active hydrogen. An active hydrogen-containing resin containing hydroxyl groups as the main component is used, and before or during bonding, polyisocyanate is added to this resin so that the ratio of NCO groups to OH groups is NCO/OH=2. 1. A method for producing a heat-sensitive stencil paper, which comprises mixing the thermoplastic resin film and a porous support in a molar ratio of 0 to 3.5. 2. The method according to claim 1, wherein the reaction product of the active hydrogen-containing resin and polyisocyanate is made to exist at a higher density at the bonding contact interface between the thermoplastic resin film and the porous support. 3. The method according to claim 2, wherein the thermoplastic resin film is coated with the active hydrogen-containing resin, the porous support is coated with the polyisocyanate, and the two are bonded together. 4. The method according to claim 1, wherein the active hydrogen-containing resin and the polyisocyanate are mixed before use, and the mixture is applied to the thermoplastic resin film, and then the porous support is laminated and bonded to the coated surface. Method. 5 Hydroxyl group value (mgK) of the active hydrogen-containing resin
5. The method according to claim 1, 2, 3 or 4, wherein the glass transition temperature is 70° C. or less and the glass transition temperature is 70° C. or less.