JP3752864B2 - Thermosensitive stencil printing film and thermal stencil printing master - Google Patents

Description

【００７５】
【発明の効果】
ポリ乳酸を主体とするポリマーからなる二軸延伸フィルムであって、該フィルムを８０℃で１０分間処理したときの少なくとも一方向の熱収縮率が３０〜９０％であるフィルムとすることにより、低エネルギーでの穿孔性に優れた感熱孔版印刷用フィルムを得ることができる。すなわち、印刷機のサーマルヘッドに供給するエネルギーを小さくでき、サーマルヘッドの寿命延長や製版に要する時間短縮、印刷物の高精細化につながるものである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermal head or a heat-sensitive stencil printing film and a heat-sensitive stencil printing master that are perforated by a halogen lamp, a xenon lamp, a flash lamp, a laser beam, etc., and more particularly, excellent in perforation sensitivity. The present invention relates to a film and a master excellent in perforation by energy.
[0002]
[Prior art]
Conventionally, as a heat-sensitive stencil printing master, a porous film composed of a thermoplastic resin film such as a vinylidene chloride film, a polyester film, or a polypropylene film, a natural fiber, a chemical fiber, a synthetic fiber, or a thin paper, a nonwoven fabric, a cocoon, etc. mixed with these. A structure in which an adhesive support is bonded with an adhesive is known (for example, Japanese Patent Laid-Open Nos. 51-2513 and 57-182495).
[0003]
However, recently, high resolution is required for printed materials. For example, in the case of punching with a thermal head, in order to obtain high resolution, each head is made smaller and the head heating cycle is shortened to increase the number of punches per unit area. Attempts have been made. In such a case, it is necessary to reduce the energy supplied to the individual heads in order to obtain perforations of an appropriate size in a short period of time, and to suppress the load on the thermal head and extend the life. However, it is desired to perforate with low energy, that is, to increase the sensitivity of the film.
[0004]
However, for the purpose of increasing the sensitivity of the film, a film in which the composition of the polymer used in the film is defined (Japanese Patent Laid-Open Nos. 2-158391, 7-276839, 10-119453), heat shrinkage Films having specified characteristics (Japanese Patent Laid-Open Nos. 62-282893 and 63-160895) have been proposed, but they are insufficient in terms of sensitivity, and further enhancement of sensitivity has been desired. .
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a high-sensitivity heat-sensitive stencil printing film excellent in punchability at low energy, which could not be realized by such a conventional technique, and a heat-sensitive stencil printing master using the film.
[0006]
[Means for Solving the Problems]
As a result of diligent research paying attention to the functions of the heat-sensitive stencil printing film and the master and the mechanism of perforating plate-making and printing, the present inventors have found that the heat-shrinkage characteristics of the polylactic acid film in addition to the previously filed film made of L-lactic acid polymer The present invention has been completed by finding that a film having a higher sensitivity can be obtained by setting the value in a specific range.
[0007]
That is, this invention consists of the following structures.
[0008]
[Means for Solving the Problems]
[1] A biaxially stretched film composed of a polymer mainly composed of polylactic acid, wherein the film has a thermal shrinkage rate in at least one direction when the film is treated at 80 ° C. for 10 minutes. 30 A film for heat-sensitive stencil printing, characterized by being -90%.
[0009]
[2] The heat-sensitive stencil printing film as described in [1] above, wherein a heat shrinkage rate in at least one direction when the film is treated at 60 ° C. for 10 minutes is less than 3%.
[0010]
[3] The film for heat-sensitive stencil printing according to [1] or [2] above, wherein the film has a thickness of 0.2 to 8 μm.
[0011]
[4] A heat-sensitive stencil printing master comprising the film according to any one of [1] to [3] and a porous support bonded to each other.
[0012]
[5] The heat-sensitive stencil printing master as described in [4] above, wherein the film and the porous support are bonded without using an adhesive.
[0013]
It is.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The polymer mainly composed of polylactic acid in the heat-sensitive stencil printing film of the present invention is a lactic acid homopolymer, a copolymer of lactic acid and other hydroxycarboxylic acid, or a mixture thereof. As the lactic acid component constituting the polymer, L-lactic acid, D-lactic acid, or a mixture thereof can be used. Examples of hydroxycarboxylic acids that can be used in combination with the lactic acid component include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid, and 6-hydroxycaproic acid. Furthermore, dicarboxylic acids and glycols can be used as long as the effects of the invention are not impaired. The mixture of the lactic acid component and the other components is preferably used in various combinations so that the content of the lactic acid component in the polymer is 50 mol% or more.
[0015]
The heat-sensitive stencil printing film of the present invention needs to be a biaxially stretched film. An unstretched film has a small thermal shrinkage and melts at the time of punching, but the hole does not easily expand, resulting in poor perforation sensitivity. The film strength is low, and the film may be broken when printing a large number of copies.
[0016]
The heat-sensitive stencil printing film of the present invention has a heat shrinkage rate in at least one direction when treated at 80 ° C. for 10 minutes. 30 It must be -90%. Preferably 30 -80%, more preferably 30-75%. It is more preferable that each is in the above range in both the longitudinal direction and the width direction of the film. Thermal shrinkage after treatment for 10 minutes at 80 ° C in at least one direction 30 If it is less than%, a hole of an appropriate size cannot be obtained in the low energy region, and if it exceeds 90%, the variation in the diameter of the hole increases, for example, the holes are connected at the time of drilling.
[0017]
Further, the heat shrinkage rate of the film of the present invention is preferably less than 5%, more preferably less than 3%, and still more preferably less than 1% in at least one direction when treated at 60 ° C. for 10 minutes. It is particularly preferable that the shrinkage rate is the same in both the longitudinal direction and the width direction of the film. If the heat shrinkage ratio after treatment at 60 ° C. for 10 minutes in at least one direction exceeds 5%, the film and the base paper may be deformed or the sensitivity may be lowered due to a change in temperature and humidity during long-term storage.
[0018]
The thickness of the film of the present invention is determined by the sensitivity required for the base paper, the method of perforation used, the handleability of the film, etc., but is preferably 0.2-8 μm, more preferably 0.3- It is 7 μm, more preferably 0.5 to 5 μm.
[0019]
The heat-sensitive stencil printing film of the present invention is preferable because the effects of the present invention are more remarkably exhibited when the surface characteristics of the film, that is, the center line average roughness and the maximum roughness are set in the ranges described below.
[0020]
That is, the central average roughness [Ra] of the film of the present invention is preferably in the range of 0.01 to 0.5 [mu] m, and is preferably from the viewpoint of stable productivity, punchability and printability from the film formation to the master preparation process. More preferably, it is 05 to 0.4 μm.
[0021]
The maximum roughness [Rt] of the film of the present invention is preferably in the range of 0.3 to 5 [mu] m, and more preferably 0.5 to 4 [mu] m from the viewpoints of film handling properties, productivity, and perforation sensitivity variations.
[0022]
Further, the crystal melting energy [ΔHu] of the film of the present invention is preferably 20 to 60 J / g from the viewpoint that the dimensional change due to a change in temperature and humidity is small, and the handleability and low energy perforation properties are good. More preferably, it is 30-50 J / g. The crystal melting temperature [Tm] of the film of the present invention is preferably 200 ° C. or lower, more preferably 190 ° C. or lower, and further preferably 170 ° C. or lower. It is preferable to set the crystal melting temperature to 200 ° C. or less because a melted portion that becomes a starting point for punching is easily formed and the punching sensitivity is improved. Further, when the shoulder is present due to the composition of the film or the like, or when there are a plurality of peaks, it is preferable that at least the shoulder or peak at the lowest temperature is in the above range, More preferably, the peak satisfies the above range.
[0023]
The glass transition temperature [Tg] of the film of the present invention is preferably 50 to 85 ° C, more preferably 55 to 80 ° C. A glass transition temperature of 50 to 85 ° C. is preferable because dimensional stability and perforation sensitivity are improved.
[0024]
The heat-sensitive stencil printing master of the present invention is formed by bonding a film and a porous support. The porous support is a porous material made of natural fibers, synthetic fibers, etc., which can transmit printing ink and do not substantially undergo thermal deformation under heating conditions in which the film is perforated. Nonwoven fabrics, woven fabrics, folds or other porous materials.
[0025]
The basis weight of the porous support bonded to the film of the present invention is 1 to 20 g / m from the viewpoint of printability. ² Is preferred. More preferably 2 to 16 g / m ² And more preferably 2 to 14 g / m ² It is. The basis weight is 20 g / m ² If it is below, the ink permeability is good, and even if the printing speed is increased, the printed image does not fade. The basis weight is 1 g / m ² If it is above, it can be set as the outstanding master from which the holding | maintenance of ink is favorable and a clear image is obtained.
[0026]
The average diameter of the fibers constituting the porous support is preferably 0.5 to 20 μm, more preferably 1 to 15 μm, still more preferably 1 to 10 μm, and particularly preferably 1 to 5 μm. If an average diameter is 20 micrometers or less, it can be set as a master with uniform ink permeability. In addition, if the average diameter is 0.5 μm or more, sufficient strength as a support can be obtained, so that the transportability is good.
[0027]
Furthermore, the fibers constituting the porous support may all have the same diameter, or may be a mixture of fibers having different fiber diameters.
[0028]
The film and master of the present invention can be produced, for example, by the following method.
[0029]
The polymer mainly composed of polylactic acid in the present invention can be obtained by the following method. As a raw material, hydroxycarboxylic acids such as glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, and hydroxycaproic acid can be used in combination mainly with a lactic acid component of L-lactic acid or D-lactic acid. Moreover, the cyclic ester intermediate of these hydroxycarboxylic acids, for example, lactide, glycolide, etc. can also be used as a raw material. Furthermore, dicarboxylic acids and glycols can also be used.
[0030]
A polymer mainly composed of polylactic acid can be obtained by a method of directly dehydrating and condensing the raw materials or a method of ring-opening polymerization of the cyclic ester intermediate. For example, in the case of producing by direct dehydration condensation, lactic acid or lactic acid and hydroxycarboxylic acid are preferably subjected to azeotropic dehydration condensation in the presence of an organic solvent, particularly a phenyl ether solvent, and particularly preferably a solvent distilled by azeotropic distillation. Polymerization is carried out by a method in which water is removed from the solvent and the solvent is brought into a substantially anhydrous state and returned to the reaction system, whereby a high molecular weight polymer suitable for the present invention is obtained.
[0031]
A high molecular weight polymer can also be obtained by subjecting a cyclic ester intermediate such as lactide produced when a low molecular weight polymer is depolymerized under high temperature and reduced pressure to ring-opening polymerization under reduced pressure using a catalyst such as tin octylate. It is known that The molecular weight of the polymer is preferably in the range of a weight average molecular weight of 10,000 to 1,000,000 from the viewpoint of moldability as a film. More preferably, it is 100,000 to 500,000.
[0032]
In addition, in the polymer mainly composed of polylactic acid of the present invention, polyglycolic acid, polybutyric acid, polyhydroxybutyrate having a hydroxycarboxylic acid component as a constituent component, as long as the amount of lactic acid component is within a range of 50 mol% or more. Polyethylene terephthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, polyhexamethylene terephthalate, polyethylene isophthalate, polycyclohexanedimethylene terephthalate, polybutylene succinate, etc. containing dicarboxylic acid component and glycol component as constituents Polyesters of these, or blends with copolymers mainly composed of these polyesters may also be used. In the case of a copolymer, it may be a random copolymer or a block copolymer.
[0033]
In the polymer mainly comprising polylactic acid in the present invention, if necessary, a flame retardant, a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, a crystal nucleating agent, a pigment, a plasticizer, a terminal blocking agent, Organic lubricants such as fatty acid esters and waxes or antifoaming agents such as polysiloxane can be blended.
[0034]
Furthermore, easy slipperiness can be imparted according to the purpose. The method for imparting slipperiness is not particularly limited. For example, inorganic particles such as clay, mica, titanium oxide, calcium carbonate, calcium phosphate, kaolin, talc, alumina, zirconia, spinel, wet or dry silica, acrylic acid There are a method of blending organic particles, etc. containing a polymer or polystyrene as a constituent, a method of applying a surfactant, and the like. The amount of particles to be blended is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 3 parts by weight with respect to 100 parts by weight of the polymer. Moreover, as an average diameter of the particle | grains mix | blended, 0.01-3 micrometers is preferable, More preferably, it is 0.1-2 micrometers. Such particles may be used in combination of a plurality of different types and average diameters.
[0035]
The film of the present invention can be obtained by biaxial stretching using the above-described polymer. The stretching method is biaxially stretched by any of the inflation simultaneous biaxial stretching method, the stenter simultaneous biaxial stretching method, and the stenter sequential biaxial stretching method. In that respect, a film formed by a stenter sequential biaxial stretching method is preferred.
[0036]
The film of the present invention can be produced by the following method using the above-described polymer. After fully drying the polymer, the polymer is supplied to an extruder, melted at 150 to 250 ° C., and extruded onto a casting drum by a T-die extrusion method to obtain an unstretched film.
[0037]
As an adhesion method to the casting drum, any method of an electrostatic application method, an adhesion method using surface tension such as water, an air knife method, a press roll method, etc. may be used, but the flatness is good. As a technique for obtaining a film having few surface defects, it is particularly preferable to use a contact casting method utilizing surface tension such as water or an electrostatic application method. At this time, an unstretched film having a desired thickness can be produced by adjusting the slit width of the die, the discharge amount of the polymer used for the film, and the rotation speed of the casting drum. Subsequently, a biaxially stretched film can be produced by biaxially stretching the unstretched film simultaneously or sequentially. In the case of sequential biaxial stretching, the stretching order may be the order of the film in the longitudinal direction and the width direction, or vice versa. Further, in the sequential biaxial stretching, the stretching in the longitudinal direction or the width direction can be performed twice or more. The stretching conditions of the film can be appropriately adjusted according to the heat shrink characteristics and orientation degree, strength, elastic modulus and the like of the target film, and can be performed by an arbitrary method. The stretching temperature of the film is preferably lower than the glass transition temperature of the polymer used and not more than the crystallization temperature, more preferably the glass transition temperature of the polymer + 20 ° C. or less. Moreover, it is preferable to perform preheating before extending | stretching at the lower temperature below the extending | stretching temperature of a film. The draw ratio in the longitudinal direction and the width direction of the film can be arbitrarily set in the range of 1.2 to 5.0 times that can set the stretching temperature lower, and preferably 1.5 times or more. . Either the stretching ratio in the longitudinal direction or the width direction may be increased or the stretching ratio may be the same.
[0038]
Furthermore, after the film is biaxially stretched, heat treatment may be performed for the purpose of improving strength, stability over time, and shrinkage characteristics. This heat treatment can be performed by any method such as in an oven or on a heated roll. The heat treatment temperature is preferably a lower temperature in the range of 30 ° C. or more and the melting point or less, and more preferably 100 ° C. or less. The heat treatment time can be arbitrary, but it is preferably performed in a shorter time in the range of 1 to 60 seconds, more preferably 30 seconds or less. The heat treatment may be performed while relaxing the film in the longitudinal direction and / or the width direction. The heat-treated film may be rapidly cooled to the glass transition temperature or lower after the heat treatment, or may be cooled stepwise.
[0039]
In the film of the present invention, as a method of setting a specific range of heat shrinkage rate in at least one direction when treated at 80 ° C. for 10 minutes, for example, a method of adjusting the composition and mixing ratio of the raw material polymer, mixing conditions, There are methods to change the extrusion temperature, residence time, preheating temperature, stretching temperature, speed, magnification, heat treatment temperature, time, etc. during film molding, especially lower preheating temperature, stretching temperature, heat treatment temperature and more heat treatment time. It is preferable to adjust to a short time and maintain a high orientation in the film because it is effective for improving the heat shrinkage properties and the effects of the present invention are more remarkably exhibited.
[0040]
The heat-sensitive stencil printing master of the present invention can be prepared by joining the above film and a porous support.
[0041]
Bonding of the film and the porous support may be performed using an adhesive or the like as long as it does not hinder the perforation suitability of the film, but it is bonded using conditions such as thermocompression bonding without using the adhesive. The method is more preferable because the permeation of ink is not hindered by an adhesive or the like. More preferably, it is a method of obtaining a non-oriented nonwoven fabric composed of a thermoplastic resin on a film by thermocompression bonding and co-stretching in the film production process. The unstretched film and unstretched nonwoven fabric are stretched together in the thermocompression bonded state, so that the nonwoven fabric serves as a reinforcing body, curling resistance and printing durability are improved, and the film is not easily torn during manufacturing. It is preferable because it is extremely excellent in film formation stability. The co-stretching method is not particularly limited, and is preferably the same as the film stretching method such as a stenter sequential biaxial stretching method.
[0042]
The film and master of the present invention are subjected to an aging treatment for the purpose of reducing deformations such as dimensional changes and curls due to changes in temperature and humidity during long-term storage, as long as the effects of the present invention are not impaired. Also good. As processing conditions, it is preferable to apply at a processing temperature of 30 to 80 ° C. for about 1 to 100 hours.
[0043]
The fiber constituting the porous support may be subjected to chemical treatment such as acid or alkali, corona treatment, low-temperature plasma treatment or the like on the surface of the fiber as necessary in order to impart affinity with the ink.
[0044]
In the master of the present invention, it is preferable to apply a release agent to the film surface in order to prevent fusion with a thermal head or the like. As the release agent, silicone oil, silicone resin, fluorine resin, surfactant, wax release agent and the like can be used. In these release agents, various additives can be used in combination as long as the effects of the present invention are not impaired. For example, antistatic agents, heat-resistant agents, antioxidants, organic particles, inorganic particles, pigments and the like can be mentioned. The release agent may be applied at any stage before or after stretching the film.
[0045]
The application method is not particularly limited, but it is preferable to apply using a roll coater, a gravure coater, a reverse coater, a bar coater or the like. Moreover, you may perform a corona discharge process in air | atmosphere and various other atmospheres as needed before apply | coating a mold release agent.
[0046]
[Characteristic measurement method]
(1) Film thickness
Ten film samples were arbitrarily selected and cut out in the cross-sectional direction, photographed with an electron microscope at a magnification of 2000 times, and the thickness of the film was measured. This was performed for 10 photographs and expressed as an average value.
[0047]
(2) Thermal contraction rate of film
The film sample was heat-treated in an oven kept at a temperature of 80 ° C. in a tensionless state for 10 minutes, the length of the sample before and after that was measured, and calculated according to the following formula.
[0048]
Thermal shrinkage rate (%) = 100 × {(sample length before heat treatment) − (sample length after heat treatment)} / (sample length before heat treatment)
Five points were measured in the longitudinal direction and the width direction of the film, and the average value was obtained.
[0049]
The same method was used to measure the heat shrinkage rate at 60 ° C.
[0050]
(3) Perforation sensitivity
The prepared master was supplied to RISOGRAPH “GR377” manufactured by Riso Kagaku Kogyo Co., Ltd., and a 5 mm square black solid was made in a grid by a thermal head type plate making method (600 dpi). At this time, the energy supplied to the thermal head was 17 μJ per dot. In this state, punching was performed, and 100 punched portions of the film were observed with a scanning microscope at a magnification of 200 times, and the area of the punched portion of the film was measured. The average perforation area per dot was determined and the perforation sensitivity was evaluated. ◎ and ○ are practically usable.
[0051]
A: Average perforation area is 450 μm ² More than that.
[0052]
○: Average perforation area is 300 μm ² 450 μm or more ² Less than.
[0053]
Δ: Average perforation area is 150 μm ² 300 μm or more ² Less than.
[0054]
×: Average perforation area is 150 μm ² Less than.
[0055]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples.
[0056]
Example 1
Twin screw extrusion with different rotation directions after adding 0.5 parts by weight of calcium carbonate particles having an average particle size of 1.5 μm to 100 parts by weight of L-lactic acid polymer synthesized from 80 parts by weight of L-lactic acid and 20 parts by weight of hydroxycaproic acid It was fed to a machine and extruded at 200 ° C. to form pellets. The obtained pellets were treated at 50 ° C. under reduced pressure for crystallization and drying. Next, the pellets were supplied to an extruder having a screw diameter of 45 mm, extruded at a T die die temperature of 200 ° C., and cast onto a drum cooled to 25 ° C. having a diameter of 300 mm to produce an unstretched film having a thickness of 13 μm. Next, the film is stretched 2.5 times in the longitudinal direction between 60 ° C. heated rolls, then sent to a tenter type stretching machine, stretched 2.5 times in the width direction at 65 ° C., and further heat treated at 70 ° C. for 10 seconds in the tenter. Thus, a biaxially stretched film having a thickness of 2.0 μm was produced. When the film was treated at 80 ° C. for 10 minutes, the thermal shrinkage rate was 38% and 46% in the longitudinal direction and the width direction, respectively. The heat shrinkage at 60 ° C. was 2.0% and 2.5%.
[0057]
Next, a basis weight of 10 g / m based on Manila hemp using vinyl acetate adhesive on one side of the obtained film ² Pasted with Japanese paper and a silicone release agent on the other side of the film using a bar coater. ² A heat-sensitive stencil printing master was prepared by coating. The evaluation results are shown in Table 1.
[0058]
Comparative Example 1
After adding 0.5 parts by weight of calcium carbonate particles having an average particle size of 1.5 μm to 100 parts by weight of L-lactic acid polymer synthesized from 80 parts by weight of L-lactic acid and 20 parts by weight of hydroxycaproic acid, two axes having different rotation directions are mixed. The product was supplied to an extruder and extruded at 200 ° C. to form pellets. The obtained pellets were treated at 50 ° C. under reduced pressure for crystallization and drying. Next, the pellets were supplied to an extruder and melted at 200 ° C. to obtain a film having a thickness of 13 μm from a T die at the tip of the extruder. The obtained film was stretched 2.5 times in the longitudinal direction and the width direction at 80 ° C. with a film stretcher, and further heat treated at 120 ° C. for 60 seconds to obtain a biaxially stretched film.
[0059]
The thickness of the obtained film was 2.0 μm, and the heat shrinkage rate when the film was treated at 80 ° C. for 10 minutes was 7.0% and 6.0% in the longitudinal direction and the width direction, respectively. Moreover, the thermal contraction rate in 60 degreeC was 0.1% and 0.2%.
[0060]
A basis weight of 10 g / m based on Manila hemp using vinyl acetate adhesive on one side of the obtained film ² Pasted with Japanese paper and a silicone release agent on the other side of the film using a bar coater. ² A heat-sensitive stencil printing master was prepared by coating. The evaluation results are shown in Table 1.
[0061]
Example 2
A biaxial shaft having a thickness of 2.0 μm as in Example 1 except that an L-lactic acid polymer synthesized using 100 parts by weight of L-lactic acid instead of 80 parts by weight of L-lactic acid and 20 parts by weight of hydroxycaproic acid is used. A stretched film was prepared. When the film was treated at 80 ° C. for 10 minutes, the thermal shrinkage rate was 45% and 62% in the longitudinal direction and the width direction, respectively. Moreover, the thermal contraction rate in 60 degreeC was 0.5% and 1.0%.
[0062]
A basis weight of 10 g / m based on Manila hemp using vinyl acetate adhesive on one side of the obtained film ² Pasted with Japanese paper and a silicone release agent on the other side of the film using a bar coater. ² A heat-sensitive stencil printing master was prepared by coating. The evaluation results are shown in Table 1.
[0063]
Comparative Example 2
A film having a thickness of 2.0 μm was produced in the same manner as in Example 2 except that the stretching temperature in the longitudinal direction and the width direction were 80 ° C. and 85 ° C., respectively, and the heat treatment temperature was 140 ° C. When the film was treated at 80 ° C. for 10 minutes, the thermal shrinkage rate was 1.5% and 1.0% in the longitudinal direction and the width direction, respectively. Moreover, the thermal contraction rate in 60 degreeC was 0.3% and 0.3%.
[0064]
A basis weight of 10 g / m based on Manila hemp using vinyl acetate adhesive on one side of the obtained film ² Pasted with Japanese paper and a silicone release agent on the other side of the film using a bar coater. ² A heat-sensitive stencil printing master was prepared by coating. The evaluation results are shown in Table 1.
[0065]
Comparative Example 3
A copolymerized polyester of ethylene terephthalate and ethylene adipate (copolymerization molar ratio 80/20) containing 0.5 parts by weight of calcium carbonate particles having an average particle diameter of 1.5 μm is crystallized and then reduced pressure at 110 ° C. for 3 hours. After drying, it was extruded at a T die die temperature of 270 ° C. using an extruder with a screw diameter of 45 mm, and cast on a cooling drum with a diameter of 300 mm to produce an unstretched film. Next, the film is stretched 3.5 times in the longitudinal direction between 65 ° C. heated rolls, then sent to a tenter type stretching machine, stretched 3.5 times in the width direction at 72 ° C., and further heat treated at 80 ° C. in the tenter, A film having a thickness of 2.0 μm was produced. When the film was treated at 80 ° C. for 10 minutes, the thermal shrinkage was 38% and 42% in the longitudinal direction and the width direction, respectively. Moreover, the thermal contraction rate in 60 degreeC was 4.5% and 5.0%.
[0066]
A basis weight of 10 g / m based on Manila hemp using vinyl acetate adhesive on one side of the obtained film ² Pasted with Japanese paper and a silicone release agent on the other side of the film using a bar coater. ² A heat-sensitive stencil printing master was prepared by coating. The evaluation results are shown in Table 1.
[0067]
Example 3
A film having a thickness of 3.0 μm in the same manner as in Example 1 except that 100 parts by weight of the L-lactic acid polymer used in Example 2 is used, and the stretching temperatures in the longitudinal direction and the width direction are 65 ° C. and 70 ° C., respectively. Was made. When the film was treated at 80 ° C. for 10 minutes, the thermal shrinkage rate was 52% and 66% in the longitudinal direction and the width direction, respectively. The heat shrinkage at 60 ° C. was 1.0% and 1.5%.
[0068]
A basis weight of 10 g / m based on Manila hemp using vinyl acetate adhesive on one side of the obtained film ² Pasted with Japanese paper and a silicone release agent on the other side of the film using a bar coater. ² A heat-sensitive stencil printing master was prepared by coating. The evaluation results are shown in Table 1.
[0069]
Example 4
85 parts by weight of L-lactic acid polymer used in Example 2 and 15 parts by weight of a copolymer of poly-3-hydroxybutyric acid and poly-3-hydroxyvaleric acid (copolymerization molar ratio 92/8) have an average particle size of 1.0 μm. After adding 0.3 parts by weight of calcium carbonate particles and mixing, the mixture was supplied to a twin screw extruder and extruded at 210 ° C. to obtain pellets. Using the obtained pellets, a 2.0 μm thick film was produced in the same manner as in Example 1. When the film was treated at 80 ° C. for 10 minutes, the thermal shrinkage was 40% and 52% in the longitudinal direction and the width direction, respectively. Moreover, the thermal contraction rate in 60 degreeC was 3.0% and 3.3%.
[0070]
Next, a basis weight of 10 g / m based on Manila hemp using vinyl acetate adhesive for the obtained film. ² Pasted with Japanese paper and a silicone release agent on the other side of the film using a bar coater. ² A heat-sensitive stencil printing master was prepared by coating. The evaluation results are shown in Table 1.
[0071]
Example 5
Using a rectangular spinneret with a hole diameter of 0.35 mm and a hole number of 100, a copolymer polyester of ethylene terephthalate and ethylene isophthalate (copolymerization molar ratio 80/20) is melt blown at a base temperature of 290 ° C. and a discharge rate of 35 g / min. Spinning by the method, collecting the fibers on the conveyor, and calendering between metal rolls heated to 70 ° C., the basis weight of the fiber is 100 g / m ² An unstretched nonwoven fabric was prepared.
[0072]
Separately, the L-lactic acid polymer used in Example 2 was dried at 120 ° C. under reduced pressure for 3 hours, then extruded at a T die die temperature of 225 ° C. using an extruder with a screw diameter of 45 mm, and cast onto a cooling drum with a diameter of 300 mm. Thus, an unstretched film was produced.
[0073]
An unstretched non-woven fabric was layered on the unstretched film obtained, supplied to a heated roll, and thermocompression bonded at a roll temperature of 100 ° C. The laminate thus obtained was stretched 2.5 times in the length direction between 83 ° C. heated rolls, then fed into a tenter type stretching machine and stretched 3.0 times in the width direction at 86 ° C. A heat-sensitive stencil master having a thickness of 70 μm was prepared by heat treatment at 70 ° C. On the film surface of the master, at the entrance of the tenter, the wax-based release agent is 0.1 g / m in weight after drying using a gravure coater. ² Applied. The fiber basis weight of the obtained master is 12 g / m ² The average fiber diameter was 6 μm. The thickness of the film alone was 1.5 μm, and the heat shrinkage rate when treated at 80 ° C. for 10 minutes was 30% and 35% in the longitudinal direction and the width direction, respectively. The heat shrinkage at 60 ° C. was 1.0% and 1.6%. The evaluation results are shown in Table 1.
[0074]
[Table 1]

[0075]
【The invention's effect】
A biaxially stretched film composed of a polymer mainly composed of polylactic acid, wherein the film has a heat shrinkage ratio in at least one direction when the film is treated at 80 ° C. for 10 minutes. 30 By setting the film to ˜90%, it is possible to obtain a heat-sensitive stencil printing film excellent in perforation property at low energy. That is, the energy supplied to the thermal head of the printing press can be reduced, leading to the extension of the life of the thermal head, the time required for plate making, and the high definition of the printed matter.

Claims (5)

A heat-sensitive stencil characterized in that it is a biaxially stretched film composed of a polymer mainly composed of polylactic acid, and has a thermal shrinkage of 30 to 90% in at least one direction when the film is treated at 80 ° C. for 10 minutes. Film for printing. The heat-sensitive stencil printing film according to claim 1, wherein the film has a heat shrinkage rate of less than 5% in at least one direction when the film is treated at 60 ° C for 10 minutes. The film for heat-sensitive stencil printing according to claim 1 or 2, wherein the film has a thickness of 0.2 to 8 µm. A heat-sensitive stencil printing master comprising the film according to any one of claims 1 to 3 and a porous support. The heat-sensitive stencil printing master according to claim 4, wherein the film and the porous support are bonded substantially without using an adhesive.