JP3604969B2 - Base paper for heat-sensitive stencil printing - Google Patents

Description

【００５５】
以上の如く、比較例１では印刷版の剥離が観察され、またカール、塗布液の安定性が不十分であった。これに対して、実施例１ではやや長時間塗布の性能に不満が見られたが、実施例２の水の粘度を高めたものは問題なかった。実施例３では顔料では顔料をシリカからタルクに変えたが、印刷濃度が少し低下する傾向がみられた。
【００５６】
【発明の効果】
本発明のマスタは印刷時の版の剥離が無く、排版時の剥離のない優れた画質、少ない裏移り特性を保持しつつ、液安定性に優れ、カールが小さく、コシが強いものである。
【図面の簡単な説明】
【図１】実施例１〜３の多孔膜の孔の部分に体質顔料が集合している状態を電子顕微鏡で観察した図。
【図２】多孔膜樹脂内に体質顔料が混練りされた状態を電子顕微膜で観察した図。
【図３】比較例１の多孔膜形状の孔部を電子顕微鏡で観察した図。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a heat-sensitive stencil sheet.
[0002]
[Prior art]
The heat-sensitive stencil sheet (hereinafter also referred to as "master") is made by bonding a porous thin paper or the like as an ink-permeable support to a thermoplastic resin film with an adhesive and, if necessary, applying a thermal head to the surface of the thermoplastic resin film. And a stick prevention layer for preventing stick. In practice, a master in which hemp fiber, synthetic fiber, wood fiber, or the like is mixed as a porous thin paper and a film is attached with an adhesive and a stick prevention layer is provided on the film surface is widely used.
[0003]
However, such a conventional master has the following problems.
(1) A large amount of adhesive accumulates in a “bird web” state at the portion where the thermoplastic resin film is in contact with the overlapping portion of the fibers, making it difficult for the thermal head to pierce that portion. In addition, that portion hinders the passage of ink, and printing unevenness occurs.
(2) The fibers themselves impede the passage of ink, causing printing unevenness.
(3) Porous thin paper or the like is expensive, and the loss due to lamination is large, and the master becomes expensive.
(4) When the printed papers overlap, the ink adheres to the back surface of the paper overlaid thereon (set-off occurs).
[0004]
Some masters have been proposed in consideration of these points, but none of them has yet been solved.
For example, JP-A-3-193445 discloses an ink-permeable support using ultrafine fibers having a fineness of 1 denier or less. According to this, the problems (2) and (4) are solved, but the problems (1) and (3) remain.
[0005]
JP-A-62-198459 discloses a method of forming a substantially closed heat-resistant resin pattern on a thermoplastic resin film by using a printing method such as gravure, offset, or flexo. However, it is difficult to print a pattern having a line width of 50 μm or less with the current printing technology, and even if it is possible, the productivity is low and the cost is high. Moreover, in general, when the line width is 30 μm or more, the heat-resistant resin hinders perforation by the thermal head, and printing unevenness occurs.
[0006]
Also, JP-A-4-7198 discloses that a master is manufactured by applying a mixture of a water-dispersible polymer and fine particles such as colloidal silica to the surface of a thermoplastic resin film and drying to form a porous layer. A method of making a master using a stencil printing machine (Print Gokko plate making machine) manufactured by Riso Kagaku Kogyo Co., Ltd., and printing using the obtained stencil printing plate and an ink jet recording ink (HG-4800 ink) manufactured by EPSON is disclosed. Have been. However, the porous layer obtained by this method has poor printing ink properties, and conventional thermal stencil printing inks are not practical because a sufficient density cannot be obtained during printing.
[0007]
However, Japanese Patent Application Laid-Open No. 54-33117 discloses a master which does not use an ink-permeable support and is substantially composed of only a film, and according to this, the above (1), (2), and (3) ) Will be resolved, but it will create new problems. One of the problems is that when the film has a thickness of 10 μm or less, its stiffness is weak and it becomes difficult to convey the film. As a solution to this problem, Japanese Patent Publication No. 5-70595 discloses that a film is wound around a peripheral wall of a stencil printing machine without being cut, and the entire film rotates with the rotation of the plate cylinder during printing. The idea to do is shown. However, in this method, since the film and the plate receiving / discharging unit rotate with the rotation of the plate cylinder during printing, the moment of rotation increases, and the deviation from the rotation axis of the center of gravity is large. , There is a problem that it must be enlarged. Another is that when the film has a thickness of 5 μm or more, its thermal sensitivity is reduced, and it is difficult to perform perforation by a thermal head.
[0008]
As a means for solving these problems, the present applicant disclosed in Japanese Patent Application Laid-Open No. Hei 10-24667 a liquid (mixture) containing a resin, a good solvent and a poor solvent, applied to a thermoplastic resin film, dried, and dried. A master with a resin film was proposed.
In the drying process, the resin is deposited due to the relative increase of the poor solvent due to the evaporation of the good solvent and the concentration of the liquid in the drying process, and the porous resin film composed of a three-dimensional network structure is dried to form a thermoplastic resin. Formed on film.
Masters manufactured in this way are certainly superior to previously known masters, and the aforementioned problems hardly occur. However, the solvent of the coating solution, the proportion of the poor solvent, the coating conditions, and the like must be accurately maintained, and it is difficult to apply for a long time, and it is possible to continuously form a porous resin film having desired characteristics. With caution.
[0009]
The present applicants have also proposed a master in which a fluid mainly composed of a W / O (water-in-oil) emulsion of a resin is coated on a thermoplastic resin film and dried to form a porous film. (Japanese Patent Application No. 9-350024). However, even with this master, the emulsion is unstable to mechanical stress and easily broken, and long-term production is accompanied by considerable difficulty.
[0010]
By the way, after the present inventor has performed a large amount of stencil printing using the above master, when the master is artificially jammed on the plate cylinder at a low temperature and peeled off from the plate cylinder in order to remove it, the heat of the master is In some cases, the plastic resin film and the porous film were separated and the porous film remained on the plate cylinder. This phenomenon was particularly noticeable when the printed master remained on the plate cylinder for a long time.
Further, when printing is performed using a printing paper having a particularly large thickness, for example, a postcard or an envelope, the porous film at a portion corresponding to the edge of the postcard or the envelope may be subjected to a particularly large impact and peeled off from the thermoplastic resin film.
Furthermore, it has been found that in a high-humidity environment, stiffness may decrease, and in a high-humidity or low-humidity environment, curling may occur, which may hinder conveyance.
[0011]
Investigations have been made to solve problems such as print peeling, stiffness, and curling of the thermoplastic resin film and the porous resin film, but no satisfactory results have been obtained yet.
[0012]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION The object of the present invention has been made in view of the above-mentioned circumstances of the prior art, and solves the above-mentioned problems (1), (2), (3) and (4) and provides a thermoplastic resin film. The heat-sensitive stencil printing material has a porous film that does not peel off even after a long time has elapsed after printing, and has a moderately large stiffness and low curl. Paper To provide.
[0013]
[Means for Solving the Problems]
The present inventor has conducted many researches and studies on heat-sensitive stencil printing base paper, and as a result, the coating solution for the porous resin film does not gel when applied to the thermoplastic resin film, and has a good film-forming property, It has been found that the above-mentioned problems can be achieved by forming a porous resin film having good adhesion to a plastic resin film and high rigidity. The present invention has been made based on this.
[0014]
According to the present invention, first, a porous resin film is laminated on a thermoplastic resin film. In the heat-sensitive stencil sheet thus obtained, the porous resin film was formed by dispersing the pigment in a continuous phase using a solution obtained by dissolving the resin in a solvent containing 50% by weight or more of a solvent having a boiling point of 130 ° C. or less under atmospheric pressure. A W / O (water-in-oil) emulsion resin liquid having a water phase as a discontinuous phase is formed by coating and drying the thermoplastic resin film, A heat-sensitive stencil sheet is characterized in that the extender pigment is concentrated at the pores of the porous resin film.
[0015]
Secondly, the first heat-sensitive stencil sheet is provided, wherein the porous resin film itself has an adhesive ability.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in more detail.
As described above, the master according to the present invention is completely different from a master suitable for an ink having a very low viscosity used for ink jet recording as disclosed in JP-A-3-240596 and a master known so far. They have different structures and functions.
[0018]
The master of the present invention has, on one surface of the thermoplastic resin film, a porous film mainly composed of a resin formed of the porous resin film of the present invention, and pigments are aggregated in pore portions of the porous film. (FIG. 1).
The master in which the porous film is provided on such a thermoplastic resin film has a high stiffness, and the rigidity is further improved due to the concentration of the extender pigment in the pores of the porous film. It is preferable that the porous membrane itself has an adhesive ability, so that a master having high adhesive strength can be obtained. In particular, for stiffness, it is more effective to consider the thickness of the porous membrane, and for perforation sensitivity and adhesive strength, it is more effective to appropriately select the material of the porous membrane.
[0019]
In the present invention, the porous film and the thermoplastic resin film may be in direct contact with each other, or a thin resin layer may be formed at the interface between the porous film and the thermoplastic resin film. The thin layer may be formed of a resin contained in the W / O emulsion resin liquid at the time of production of the master, or may be newly provided on a thermoplastic resin film. Both of them have adhesiveness and stiffness (Stiffness). ), Which contributes to improvement in curling.
[0020]
The porous film of the present invention in which the extender pigment is aggregated in the porous portion has a continuous phase of a solution obtained by dissolving the resin in a solvent containing a solvent having a boiling point at atmospheric pressure of 130 ° C. or lower and 50% by weight or more. A W / O (water-in-oil) emulsion resin liquid having a dispersed aqueous phase as a discontinuous phase is coated on a thermoplastic resin film and dried to form an extender pigment dispersed and blended in an aqueous phase component. After evaporating and drying the solvent of the liquid, the aqueous phase region becomes pores of the porous film, and is observed in a state in which the extender is aggregated on the adjacent interface with the thermoplastic resin film.
[0021]
The aggregate of the extender is not always present in all the pores of the porous membrane, but is relatively determined by the concentration of the extender added to the aqueous phase. The porous film formed by the porous resin film of the present invention is obtained by pulverizing and dispersing a general extender in an aqueous phase with a water-soluble resin or the like, and in some cases, there is a problem in that a surfactant having a dispersing effect is used in combination therewith. It can be used without. Next, although it is an oil phase component, pigments can be used depending on the purpose. In the emulsification method of the present invention, when added to the oil phase component, it is observed in a state of being kneaded inside the resin in an internally added state. You. FIG. 2 shows this state observed with an electron microscope.
[0022]
As described above, the porous membrane shape in which the pores of the porous membrane shape are spaces is known, but the thermosensitive stencil using the porous membrane of the present invention having the structure in which the extender is aggregated in the pore portions. The printing base paper is completely new.
[0023]
The porous resin film when used as the heat-sensitive stencil printing base paper of the present invention is not necessarily a film having holes continuous in the thickness direction from its surface to a thermoplastic resin film or a thin layer of resin. Alternatively, a thin film partially formed of a resin contained in the application emulsion at the time of the application and drying may be formed at the boundary with the thermoplastic resin film. It is unknown what mechanism this thin film is formed from, but as the solvent and water of the resin evaporate from the surface during drying, from a resin solution that forms a continuous phase that uniformly wets the thermoplastic resin film surface It is presumed that the solvent gradually decreases to form a resin thin film as it is. This thin film has little effect on thermal sensitivity.
As described above, the pigment may be present in the continuous phase mainly composed of resin other than the pores of the porous membrane, but this does not deny the effectiveness of the present invention.
[0024]
The master of the present invention exhibits a printing peeling improving effect between the thermoplastic resin film and the porous film, a strong stiffness and a small curl that could not be predicted, and exhibits high image quality and stable coating suitability.
It is not clear what mechanism the thermoplastic resin film and porous film of the master do not peel off after a long time after printing, but it is presumed that the pigment in the holes reduces the tack force of the ink on the master. You. Surprisingly, the pigments that have collected in the pores of the master of the present invention do not fall off and do not hinder the passage of the ink unless the porous membrane is destroyed.
[0025]
The resin to be dissolved in the continuous layer of the solvent of the W / O emulsion used in the present invention is not particularly limited, but a copolymer having a hydrophilic group as a resin component is preferably used.
As the hydrophilic group, -SO ₃ H, -SO ₃ M, -OSO ₃ H, -OSO ₃ M, -COOM, -NR ₃ X, -COOH, -NH ₂ , -CN, -OH, -NHCONH ₂ ,-(OCH ₂ CH ₂ ), -CH ₂ OCH ₃ , -OCH ₃ , -COOCH ₃ , -CS, a phosphate group, and various groups generated by condensation of these groups (R: alkyl group, M: alkali metal or -NH ₄ , X: halogen).
[0026]
As specific polymers, for example, acrylic, ester, urethane, olefin, vinylidene chloride, epoxy, amide, styrene, vinyl, cellulose derivatives and modified products thereof, copolymers are preferred. Particularly, vinyl butyral-based, urethane-based, and polyvinyl acetate-based polymers are preferably used. It goes without saying that it is also used as a mixture.
[0027]
In the present invention, a desirable porous membrane is not formed unless a solvent containing 50% by weight or more of a solvent having a boiling point of 130 ° C. or less is used.
Specific examples of preferably used solvents include methylene chloride, chloroform, ethyl acetate, methyl acetate, diethyl ether, carbon tetrachloride, cyclohexane, hexane, pentane, benzene, MEK, toluene and the like.
[0028]
Examples of the extender filled in the pores of the porous film include talc, kaolin, silica, silica gel, colloidal silica, calcium carbonate, magnesium carbonate, calcium hydroxide, zinc oxide, titanium dioxide, barium sulfate, magnesium hydroxide, and water. Inorganic pigments such as aluminum oxide, zinc sulfide, zinc carbonate, zeolite, alumina, alumina sol, carbon black, etc .: Mineral needle pigments such as zeolite, potassium titanate, wollastonite, zonolite, gypsum fiber: Other powdered organic pigments .
[0029]
Next, as a thin resin material provided as necessary on the interface between the thermoplastic resin film and the porous film of the present invention, for example, polyvinyl acetate, polyvinyl butyral, vinyl chloride-vinyl acetate copolymer, vinyl chloride- Vinyl resins such as vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, styrene-acrylonitrile copolymer, polyamides such as polybutylene and nylon, polyphenylene oxide, (meth) acrylic acid ester, polycarbonate, copolymers, mixtures, and modifications thereof. A body or the like is used. Further, various fillers, antistatic agents, anti-stick agents, surfactants, preservatives, defoamers, modifiers, and the like can be used within a range that does not impair the effects of the present invention.
[0030]
The thickness of the thin layer after drying is preferably 0.1% or more and 50% or less, more preferably 1% or more and 20% or less of the thickness of the thermoplastic resin film. If it is less than 0.1% of the thermoplastic resin film, the effect of improving the adhesiveness, stiffness and curl is small, and if it exceeds 50%, the heat perforation sensitivity is adversely affected.
The material of the thin layer, the thickness after drying, is actually determined by several experiments.
[0031]
When biaxially stretched polyester is used as the thermoplastic resin film and butyral resin is used as the porous film, polyester, a reaction product of polyol and isocyanate, isocyanate polymer, etc. are preferably used as the thin layer.
[0032]
When a thin film is present at the interface between the thermoplastic resin film and the porous film, there is a concern that the thermal head may adversely affect perforation heat sensitivity, but in practice it has been found that there is almost no effect. This is presumed to be mainly because the thickness of the thin layer is smaller than the thickness of the thermoplastic resin film.
[0033]
In the porous film of the present invention, an antistatic agent, an anti-stick agent, a surfactant, a preservative, an antifoaming agent, and the like can be used in combination as long as the effects of the present invention are not impaired.
[0034]
Next, a method of manufacturing the master will be described. First, the resin is dissolved in a solvent containing 50% by weight or more of a solvent having a boiling point of 130 ° C. or less. The amount of the resin is determined by experiment to form a good porous film, but is generally 5 to 20% by weight. In order to form a stable emulsion, a surfactant having an HLB (Hydrophilic-Lyophilic Balance) of 8 to 20, preferably 4 to 6 is added.
On the other hand, the extender is dispersed in water using a ball mill, a high-speed rotating dispersing device, or the like. If the extender is dispersed in the solvent phase instead of the aqueous phase, the extender will not fill the pores. The weight ratio of water / extender pigment is from 0.5 to 10, particularly preferably from 1 to 5. If the amount of the extender is less than this, the printing peel strength between the thermoplastic resin film and the porous film becomes worse, and if it is more, the formation of the emulsion becomes unstable.
[0035]
It was found that when the water phase was thickened more than pure water, the emulsion became stable and hard to break. The preferred viscosity is 10 to 500 centipoise at the liquid temperature at the time of coating. If it is less than 10 centipoise, the effect of stabilizing the emulsion will be small, and if it exceeds 500 centipoise, drying will be slow and production efficiency will be poor.
As a means therefor, addition of a water-soluble compound is suitably used. For example, polyvinyl alcohol, carboxymethyl cellulose, polyacrylic acid, polyethylene glycol, polyvinyl pyrrolidone and the like are used.
[0036]
While stirring the solution in which the resin is dissolved, an aqueous phase in which the extender is dispersed is added.
The fluid mainly composed of the W / O emulsion prepared as described above is directly applied to a thermoplastic resin film or a thin resin layer and dried to form a porous film.
The coating is performed by a general roll, slot die, gravure, wire bar, blade or other type of coating machine.
The pigments mainly gather in the aqueous phase of the porous film to form pores through which the ink passes after drying, and the resin in the solvent (which may contain additives such as fillers and emulsifiers) forms a structure.
[0037]
The amount of adhesion of the porous membrane itself after drying is 1 to 20 g / m2. ² It is. 1g / m ² If it is smaller, the ink adhesion amount is not controlled, and the set-off of the printed matter becomes worse, and the stiffness of the master itself also becomes smaller. 20g / m ² Exceeding the limit impedes the passage of ink and deteriorates the image.
[0038]
By providing this porous resin film, it can be used as a master for thermosensitive stencil printing. In this case, the size of the voids in the porous resin film is an important factor. When this porous resin film is observed at an arbitrary cross section or surface, the pore diameter is distributed between 1 μm and 50 μm in terms of a perfect circle. When the pore diameter is less than 1 μm, the ink permeability is deteriorated, the aerobic effect is further reduced, and the heat insulating effect of the porous resin film is suppressed, which undesirably impairs the perforation sensitivity of the thermoplastic film. As a countermeasure, if a low-viscosity ink is used, image bleeding may occur in a printed image, or ink may bleed from the side of the printing drum or the rear end of the wound master for heat-sensitive stencil printing. On the other hand, if the pore diameter is 50 μm or more, the passage of the ink becomes too easy, so that excess ink adheres to the printing location, causing set-off and causing a problem.
Since the pore size of the porous resin film is 1 to 50 μm, the size of the volume pigment is appropriately smaller than the above pore size and 0.05 to 20 μm.
[0039]
Examples of the thermoplastic resin film used in the present invention include vinyl chloride, vinyl chloride-vinylidene chloride copolymer, polypropylene, polyester, and other films conventionally used for heat-sensitive stencil printing masters, particularly those obtained by biaxially stretching polyester. Can be suitably used.
The thickness of the thermoplastic resin film is 0.5 to 10 µm, more preferably 1.0 to 5.0 µm. If it is less than 0.5 μm, it is too thin to apply the resin solution, and if it exceeds 10 μm, it becomes difficult to perforate with a thermal head.
[0040]
When a thin layer of resin is present at the interface between the film and the porous film, there is a concern that the thermal head may adversely affect perforation heat sensitivity, but it has been found that it has practically no effect. This is presumed to be mainly because the thickness of the thin layer is smaller than the thickness of the film.
[0041]
Also in the master of the present invention, a stick prevention layer for preventing stick with the thermal head can be provided on the opposite surface of the film on which the porous film is formed. In this case, as the stick prevention agent to be used, a silicone-based release agent, a fluorine-based release agent, a phosphate ester-based surfactant and the like generally used in conventional heat-sensitive stencil printing base paper can be used. An antistatic agent for preventing generation of static electricity may be added.
[0042]
【Example】
Next, the present invention will be described specifically with reference to examples.
[0043]
Example 1
(Preparation of solution A)
2.0 parts by weight of polyvinyl butyral (Sekisui Chemical Co., Ltd., BHS)
Ethyl acetate 30.0 parts by weight
Sorbitan monooleate (Toho Chemical Co., 0.1 parts by weight
Sorbon S80)
Solution A was prepared by mixing the above compositions.
(Adjustment of aqueous phase liquid)
Silica (special grade reagent, precipitation method, amorphous) 5.0 parts by weight
15.0 parts by weight of water
Polyoxyethylene glycol fatty acid ester 0.05 parts by weight
The above composition was well dispersed in a ball mill to prepare an aqueous phase liquid.
[0044]
The aqueous phase solution was added to the solution A and further dispersed using a high-speed homomixer to prepare a W / O emulsion.
This was dried in a liquid temperature atmosphere of 20 ° C. and 50% RH on a biaxially stretched polyester film having a thickness of 2.0 μm with a gravure roll, and the adhesion amount was 6.1 g / m 2. ² To form a porous film. The coating speed was 10 m / min and the drying temperature was 60 ° C.
After 50 minutes had passed, streaks began to appear on the coated surface, making it impossible to continue coating.
A mixture of silicon and a cationic antistatic agent was applied to the polyester film surface on the opposite side of the side where the porous film was formed, with an adhesion amount after drying of 0.05 g / m 2. ² To obtain a master.
[0045]
Example 2
Polyacrylic acid was added to the aqueous phase of Example 1 to adjust the viscosity at 20 ° C. of the aqueous phase liquid to 80 centipoise.
Otherwise, a W / O emulsion was applied in the same manner as in Example 1. This liquid could be applied without any abnormality even after 90 minutes.
7.2 g / m after drying ² Met. A mixture of silicon and a cationic antistatic agent was applied to the polyester film surface on the opposite side of the side where the porous film was formed, with an adhesion amount after drying of 0.05 g / m 2. ² To obtain a master.
[0046]
Example 3
The pigment of Example 2 was changed to talc instead of silica. Otherwise, a W / O emulsion was applied in the same manner as in Example 2 to obtain a master. This liquid could be applied without any trouble even after 90 minutes.
[0047]
Comparative Example 1
(Preparation liquid of W / O emulsion)
2.0 parts by weight of polyvinyl butyral (Sekisui Chemical Co., Ltd., BHS)
Ethyl acetate 30.0 parts by weight
Sorbitan monooleate (Toho Chemical Co., 0.15 parts by weight
Sorbon S80)
Talc 0.5 parts by weight
Dissolve and disperse the above composition,
15.0 parts by weight of water
Was slowly added with stirring to obtain a cloudy emulsion coating solution.
[0048]
This was dried on a biaxially stretched polyester film having a thickness of 2.0 μm with the same gravure roll as in Comparative Example 1 in an atmosphere of 20 ° C. and 50% RH, and the adhesion amount was 6.1 g / m 2. ² To form a porous film. The coating speed was 10 m / min and the drying temperature was 60 ° C. After the elapse of 40 minutes, streaks began to appear on the coated surface.
A mixture of silicon and a cationic antistatic agent was applied to the polyester film surface on the opposite side of the side where the porous film was formed, with an adhesion amount after drying of 0.05 g / m 2. ² To obtain a master.
[0049]
The masters obtained in Examples 1 to 3 and Comparative Example 1 were evaluated as follows. Table 1 shows the results.
[0050]
[Printing peel strength test method between porous film and thermoplastic resin film]
Using a stencil printing machine (PRIPORT VT 3820) manufactured by Tohoku Ricoh Co., Ltd., 2,000 solid black images of A4 size are printed. After 45 days, hold one end of the master on the plate cylinder that has been intentionally broken on the plate cylinder in an atmosphere of 5 ° C. with both hands, and peel off vigorously from the plate cylinder.
When the thermoplastic resin film and the porous film were not peeled off at all, ○ indicates that the thermoplastic resin film and the porous film were peeled off at least half of the area, and Δ indicates the middle.
[0051]
(Curl test method)
A 10 cm × 10 cm sample is left on a flat table in an atmosphere of 20 ° C. 90% RH and 20 ° C. 10% RH for 10 minutes.
The curls on the four sides were measured, and those having an average value of 10 mm or less in any atmosphere were evaluated as ○, those having a low humidity, high humidity, or those rounded in a cylindrical shape in both atmospheres as x, and the others as Δ.
[0052]
[Perforation sensitivity, print density, set-off]
Printing was tested using the PRIPORT VT 3820 system.
Perforation sensitivity: も の indicates that the film portion of the master was perfectly perforated by the thermal head, Δ indicates that the perforation was performed but the perforation diameter was partially reduced, and x indicates that the perforation was not partially perforated.
Print density: The 20th print image was measured by Macbeth.
Set-off: The printed matter is observed with the naked eye, and a mark superior to the current master (manufactured by Ricoh Company, VT-2 master) is indicated by 、, a mark equivalent to the current master is indicated by Δ, and a sign inferior to the current master is indicated by ×.
[0053]
(Stability of coating liquid)
Using a gravure coater, the solution was continuously applied onto a 2 μm-thick biaxially stretched polyester film at a liquid temperature of 20 ° C. at an application speed of 10 m / min. ◎ indicates that no coating unevenness or streaking occurred for 90 minutes or more, ○ indicates that no coating unevenness occurred for 45 minutes or more, and x indicates that occurred by 45 minutes.
[0054]
[Table 1]

[0055]
As described above, in Comparative Example 1, peeling of the printing plate was observed, and curling and the stability of the coating solution were insufficient. On the other hand, in Example 1, some dissatisfaction was observed with respect to the performance of the coating for a long time. In Example 3, although the pigment was changed from silica to talc, the print density tended to slightly decrease.
[0056]
【The invention's effect】
The master of the present invention has excellent liquid stability, small curl, and strong stiffness while maintaining excellent image quality and little set-off property without peeling of the plate during printing and without peeling during plate discharging.
[Brief description of the drawings]
FIG. 1 is a view obtained by observing, with an electron microscope, a state in which an extender is aggregated in pore portions of porous membranes of Examples 1 to 3.
FIG. 2 is a view of a state in which an extender is kneaded in a resin of a porous membrane, which is observed by an electron microscope.
FIG. 3 is a view of a porous membrane-shaped hole of Comparative Example 1 observed with an electron microscope.

Claims (2)

In heat- sensitive stencil printing base paper in which a porous resin film is laminated on a thermoplastic resin film ,
The porous resin membrane has a continuous phase formed by dissolving the resin in a solvent containing 50% by weight or more of a solvent having a boiling point of 130 ° C. or lower at atmospheric pressure, and a discontinuous phase formed by dispersing the extender pigment. A W / O (water-in-oil) emulsion is formed by coating and drying the thermoplastic resin film,
A base paper for heat-sensitive stencil printing, characterized in that an extender is aggregated in the pores of the porous resin film. The heat-sensitive stencil sheet according to claim 1, wherein the porous resin film itself has an adhesive ability.

Images