TWI607856B - Polyester film - Google Patents

Description

Polyester film

The present invention relates to an easily adhesive polyester film. More specifically, the polyester film which exhibits excellent adhesiveness in various laminated applications and printing applications, and a method for producing the same.

Biaxially stretched polyester film represented by polyethylene terephthalate (PET) film, due to its excellent transparency, dimensional stability, mechanical properties, electrical properties, chemical resistance, etc. It is used in a wide range of fields such as tapes, photo films, tracing films, packaging materials, electrical insulating materials, information recording materials, and various engineering papers. However, due to the highly crystalline alignment of the biaxially stretched polyester film, the surface of the film lacks adhesion to various adhesives, coatings, inks, sensitizers, magnetic coatings, matting agents, and the like. Therefore, in a simple method, for the film system, in addition to the annealing treatment at a high temperature, the high-temperature treatment is also performed by heat setting in the film forming step, thereby reducing the overall alignment of the film so that A method of easy adhesion, but in the prior art, there is a problem that the film is embrittled.

Therefore, in the conventional method, in actual use in various processes, it is often necessary to apply any easy adhesion treatment to the surface of the polyester film. The following examples: It is known that a material having a small amount of heat (for example, a polyalkylene glycol) is added by adding a raw material to a raw material, and the surface is easily melted, thereby increasing the ink adhesion and the strength of the laminate (for example, refer to the patent). Literature 1, etc.). However, this conventional technique improves the adhesion by lowering the degree of crystallization of the surface, but the adhesion of the surface on the substrate side is liable to lower at a high temperature, and there is a problem that it is easy to block.

Further, a technique of increasing the ink adhesion and the laminate strength by using a resin layer formed by laminating a coating layer which is easy to adhere to the surface by coating or off-line coating on a production line (see, for example, Patent Document 2). However, this prior art has a problem that the process composition is complicated and the surface layer component is mixed when the film end which cannot be used as a product is recovered.

On the other hand, in order to increase the adhesion between ink adhesion and laminate strength during printing or lamination, physical methods such as ultraviolet irradiation treatment, corona discharge treatment, plasma discharge treatment, and flame treatment, or alkali are known. Chemical treatment such as treatment, primer treatment, etc. For example, a technique of increasing ink adhesion and layering strength by a polar group formed on a surface layer is known (for example, see Patent Document 3). However, since the corona treatment also causes the degree of crystallization of the surface of the film to become high, there is a problem that easy adhesion becomes difficult.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Laid-Open Patent Publication No. 51-90346

[Patent Document 2] Japanese Patent Publication No. 41-8470

[Patent Document 3] Japanese Patent Publication No. Sho 58-25331

The present invention has been accomplished in the light of the above-described problems of the prior art. That is, an object of the present invention is to provide a biaxially stretched polyester film having both film strength and easy adhesion by a simple method such as easy adhesion treatment such as corona discharge treatment.

The inventors of the present invention have devoted themselves to the review in order to achieve the object, and have finally completed the present invention. That is, the present invention is:

A biaxially stretched polyester film characterized by a recrystallization temperature observed by DSC at a temperature of 40 ° C / min from a molten state and a rate of 20 ° C / min The resin having a recrystallization temperature of 0 to 15 ° C is composed of a polyester resin having a thickness of 3 to 50 μm and satisfying the following physical properties of the materials (1) to (4); (1) heat shrinkage in the MD direction The rate is 0.5~10%; (2) the spur strength is 5~20N; (3) the surface crystallization degree obtained by ATR-IR is 1.10~1.35 on the easy adhesion treatment side; (4) from the film The value of the surface crystallization degree on one side minus the surface crystallization degree on the other side of the film is in the range of -0.1 to 0.

2. The biaxially stretched polyester film according to 1, wherein the polyester resin has an isophthalic acid component.

3. The biaxially stretched polyester film according to the above 1, wherein the polyester resin contains a polyester resin polymerized from a glycol component derived from a plant.

According to the present invention, by making the respective surfaces of the biaxially stretched polyester film into a specific surface state, it is possible to reduce the crystallinity and alignment of the surface on one side while maintaining the strength of the film, and to improve the adhesion of the film. .

According to the present invention, in addition to the balance between the adhesion and the mechanical properties which are difficult to coexist in the past, it is possible to provide an easily-adhesive polyester film which is free from the incorporation of other materials and which is excellent in heat resistance of the surface layer.

[Formation of the Invention]

Hereinafter, the present invention will be described in detail.

The polyester resin used in the present invention is a polyester (A) obtained by using terephthalic acid (TPA) and ethylene glycol (EG) as main constituent components, and the content of TPA is preferably 60% by mass or more. It is preferably 70% by mass or more, particularly preferably 75% by mass or more, and most preferably 80% by mass or more. When it is less than 60% by mass, the crystallinity is lowered and the film properties are insufficient.

In the polyester (A) used as the main component, the TPA is preferably 90 mol% or more, more preferably 95 mol% or more, and still more preferably 98 mol% or more in terms of the dicarboxylic acid component. With respect to the diol component, EG is preferably 90 mol% or more, more preferably 95 mol% or more, still more preferably 97 mol% or more. In this case, it is preferred that impurities other than the by-products generated by the ether bond at the time of polymerization are not contained. Since such impurities are extremely small, the melting point of the polyester resin is drastically lowered.

The polyester may also be a copolymer. Examples of the dicarboxylic acid component copolymerizable with the polyester include isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, biphenyl dicarboxylic acid, cyclohexane dicarboxylic acid, adipic acid, and hydrazine. Diacid, sebacic acid, etc. Examples of the diol component copolymerizable with the polyester include ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, neopentyl glycol, and 1,5-pentane. Alcohol, 1,6-hexanediol, diethylene glycol, cyclohexanediol, polyethylene glycol, polytetramethylene glycol, polycarbonate diol, and the like. Since the copolymerization of these components has an effect of lowering the crystallization ease of polyethylene terephthalate and the crystal melting point, the surface crystallization can be easily alleviated by the heat during the treatment such as corona discharge treatment. A very good method for the purposes of the present invention.

Further, the other constituent components of the polyester are not particularly limited, and examples thereof include polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), and polybutylene naphthalate. A polyester resin other than the polyester (A) such as (PBN) or polytrimethylene terephthalate (PPT). In addition, in order to improve the pinhole resistance at the time of bending, a polyester system and a polypene obtained by copolymerizing at least one of a soft polyether component, a polycarbonate component, and a polyester component may be added to the additive. An amine-based elastomer, a polyolefin-based elastomer, or the like. The lower limit of the amount of these additives is preferably 0% by weight, and the upper limit is preferably 20% by weight. When it exceeds 20% by weight, in addition to the effect of saturation, problems such as a decrease in transparency of the film may occur.

A slip agent may be contained in the polyester film. The type of the lubricant is preferably an inorganic slipper other than cerium oxide, calcium carbonate, alumina, or the like, and more preferably cerium oxide or calcium carbonate, and particularly preferably cerium oxide. . By adding the above-mentioned slip agent, the film can be given through Brightness and slipperiness.

The lower limit of the concentration (ppm) of the lubricant in the polyester film is preferably 10, more preferably 30, still more preferably 50. If it is less than the above, the practicality will become low in terms of slipperiness. The upper limit of the concentration of the lubricant (ppm) is preferably 10,000, more preferably 9000, still more preferably 8,000. If it exceeds the above, the transparency of the film is lowered.

Regarding the particle diameter of the lubricant, the lower limit of the primary particle diameter is 0.005 μm, preferably 0.010 μm, more preferably 0.015 μm. When it is 0.005 μm or less, it is not preferable to increase the viscosity at the time of melting. Regarding the particle diameter of the lubricant, the upper limit of the primary particle diameter is 50 μm, preferably 40 μm, more preferably 30 μm. When it is 50 μm or more, it is not preferable to reduce the transparency or fall off.

The polyester resin may contain a conventional additive such as a slip agent, a stabilizer, a colorant, an antioxidant, an antistatic agent, an ultraviolet absorber, or the like as needed.

These additives must be adjusted within a range that satisfies the impact strength or spur strength.

The polyester resin in the present invention is characterized by a recrystallization temperature (hereinafter referred to as Tc(A)) and a DSC observed by cooling from a molten state at a rate of 20 ° C/min obtained by DSC. The difference in recrystallization temperature (hereinafter referred to as Tc (B)) obtained at a rate of 40 ° C /min (hereinafter referred to as Tc (A) - Tc (B)) is characterized by a specific range.

The lower limit of Tc(A)-Tc(B) is preferably 0, more preferably 0.5, still more preferably 1. When the temperature is less than 0 ° C, the crystallization rate is too slow, which is not preferable for the present invention.

The upper limit of Tc(A)-Tc(B) is preferably 15, more preferably 14.5, further More preferably 14, the best is 13.5, and the best is 13.3. When it exceeds the above, since it is very stable to heat such as corona discharge treatment, it is not preferable to improve the effects of various adhesions. The reason for this is presumably because the crystallization rate is high, and strong surface crystals are formed at a lower temperature, and are not easily melted by heat such as corona discharge treatment.

It is known that Tc(A)-Tc(B) can be controlled by the kind of the slip agent in the polyester resin, the amount of impurities in the resin, the kind of the copolymerization component, or the addition of an additive having a crystallization delay effect.

The lower limit of Tc(A) is preferably 140, more preferably 141, still more preferably 143. When it is less than the above, the crystallization rate is too low, and the heat resistance of the film is lowered.

The upper limit of Tc(A) is preferably 175, more preferably 170, still more preferably 168. When it exceeds the above, the difference between the crystallization temperature and the melting temperature becomes too small, and the elongation is lowered.

The lower limit of Tc(B) is preferably 130, more preferably 131, still more preferably 133. When it is less than the above, the crystallization rate is too low, and the heat resistance of the film is lowered.

The upper limit of Tc(B) is preferably 165, more preferably 155, still more preferably 155. When it exceeds the above, adhesion will not be obtained.

In the film of the present invention, the upper limit of the amount of the crystal nucleating agent contained in the polyester resin is 100 ppm, preferably 10 ppm, in order to set the Tc(A)-Tc(B) of the polyester resin to the above range. It is 5 ppm or less.

In addition, impurities other than impurities contained in a raw material such as a nitrogen-based compound or a sulfur-based compound are also referred to as being mixed during polymerization or melt extrusion. The upper limit of the amount of the mixture is preferably 1 ppm or less, more preferably 0.5 ppm or less, and most preferably 0.1 ppm or less.

When the respective upper limits are exceeded, the change in the degree of crystallization due to the corona discharge treatment is small, and the effect of easy adhesion is reduced. Although the reason is not clear, it is presumed that the precursor will form a strong alignment crystal at a low temperature before the alignment crystallization in the heat setting, and as a result, the thermal stability of the crystal of the surface layer after the biaxial stretching becomes high, and it is difficult to cause the object of the present invention. The heat during the treatment causes melting of the crystals, and the effect of easy adhesion becomes small.

The polyester film of the present invention may be a polyester resin obtained by using a raw material derived from a plant in addition to a polyester resin obtained by using a raw material derived from a fossil fuel. From the viewpoint of recent reduction in environmental load, it is of course preferred to use raw materials derived from plants. Specific examples thereof include TPA, EG, BD, adipic acid, sebacic acid, dimer acid, hydrogenated dimer acid, isosorbide, and furan dicarboxylic acid derived from plants, but are not limited thereto. .

In particular, although the polyester resin obtained from the raw material of the plant has a problem of limited removal of impurities during the purification process, and there are problems such as residual nitrogen compounds, etc., the polyester resin obtained from the raw material of the plant will help Since the crystallization of the film is promoted to form a strong alignment crystal, the crystallization of the surface layer due to the heat during the treatment is reduced and the adhesiveness is lowered. Therefore, it is important to use a raw material having a high purity system.

The polyester film of the present invention can be obtained only from a new raw material, and a recycled raw material can also be used. In particular, it is possible to contribute to the recent reduction in environmental load by using a recycled PET resin obtained by recovering a PET bottle.

The lower limit of IV (inherent viscosity, unit [dL/g]) of the recycled PET resin must be 0.5, more preferably 0.55. When it is less than 0.5, in addition to a decrease in mechanical properties, it is not preferable because the molecular weight is lowered and the crystallization rate is increased, and the film forming property is lowered. The upper limit of IV must be in the range of 0.8, preferably 0.75. When the IV exceeds 0.8, the melt viscosity is too high, and the discharge amount of the extruder is lowered to deteriorate the productivity.

The amount of the raw material to be recycled such as the recycled PET resin is not particularly limited, but may be determined in consideration of the color tone or the IV of the film. Even if the total amount is a recycled PET resin, the Co-b value of the color tone is preferably in the range of 10 or less, specifically 0 to 95%.

When the recycled PET resin is used, the copolymerization amount is preferably from 0.5 to 2.5 mol%, more preferably from 1.0 to 2.5 mol%, based on the acid component of isophthalic acid in the polyester resin of the film.

Further, when a raw material for a PET bottle or a recycled PET resin is used, it is preferable to add an additive for adjusting the specific resistance of the melt in order to impart a fluid-tight electrostatic adhesion. As the additive, a well-known compound can be used, and specifically, a Mg-based compound, a P-based compound, a Na-based compound, a K-based compound, or the like can be used, and the amount of addition or the like can be determined from the viewpoints of melting specific resistance, color tone, and the like.

Hereinafter, the film forming method of the biaxially stretched film of the present invention will be specifically described, but is not limited thereto.

The stretched film of the present invention may be a uniaxially stretched film in the longitudinal direction (MD direction) or the transverse direction (TD direction), but is preferably a biaxially stretched film. In the case of biaxial stretching, it may be a sequential biaxial extension or a simultaneous biaxial extension, but preferably a sequential biaxial extension.

By forming the stretched film, it is possible to obtain a film which is unpredictable in the conventional polypropylene film and which has a low heat shrinkage rate even at 150 °C.

Hereinafter, a method of producing a longitudinally-transversely extending sequential biaxially stretched film of a preferred embodiment will be described.

First, a polyester resin is heated and melted in a single-axis or 2-axis extruder, and extruded on a cooling roll to obtain an unstretched film.

The lower limit of the resin melting temperature (°C) is preferably 220, more preferably 240, still more preferably 260. When it is less than the above, the melt viscosity is high and the discharge becomes difficult. The upper limit of the resin melting temperature (°C) is preferably 350, more preferably 340, still more preferably 330. When it exceeds the above, it is not preferable because molecular weight reduction or coloring due to thermal decomposition is observed.

The lower limit of the extrusion die temperature (°C) is preferably 220, more preferably 240, still more preferably 260. When it is less than the above, the melt viscosity is high and the discharge becomes difficult. The upper limit of the extrusion die temperature (°C) is preferably 350, more preferably 340, still more preferably 330. When it exceeds the above, it is not preferable because molecular weight reduction or coloring due to thermal decomposition is observed.

The lower limit of the chill roll temperature (°C) is preferably 0, more preferably 2, still more preferably 5. If the temperature of the chill roll is too low as described above, the chill roll will be dew condensation, which degrades the stability of the quality, which is not preferable. The upper limit of the chill roll temperature (°C) is preferably 80, more preferably 50, still more preferably 40. When it exceeds the above, the cooling will be insufficient, and the elongation will be lowered or the thickness will be poor.

The lower limit of the casting speed (m/min) is preferably 2, more preferably 5, still more preferably 10, and particularly preferably 20. When it is less than the above, productivity will become low.

The upper limit of the casting speed (m/min) is preferably 120, more preferably 110, further preferably 100. When it exceeds the above, the casting will be unstable. The lower limit of the casting thickness (μm) is preferably 10, more preferably 15, and still more preferably 20. When it is less than the above, the casting thickness is too thin, and the biaxial stretching becomes difficult.

The upper limit of the casting thickness (μm) is preferably 1,250, more preferably 1,000, still more preferably 800. When it exceeds the above, the cooling becomes insufficient, and it is difficult to obtain stable elongation.

As the MD extension method, it is preferable to have a plurality of extensions of two extensions and the like in addition to one extension. In particular, in order not to increase the surface alignment after the biaxial stretching or to reduce the skew after the biaxial stretching, it is preferable to extend the plurality of sections such as the two-stage extension. As the MD stretching method, a roll heating method or an infrared heating method is preferred.

The lower limit of the MD stretching ratio (times) is preferably 3, more preferably 3.1, still more preferably 3.2. When it is less than the above, the mechanical properties such as the spur strength are lowered. The upper limit of the MD stretching ratio (times) is preferably 4.5, more preferably 4.4, still more preferably 4.3. When it exceeds the above, the fracture is observed at the time of film formation, and productivity is lowered.

The lower limit of the MD preheating temperature (°C) is preferably 30, more preferably 35, still more preferably 40. When it is less than the above, the preheating system is insufficient, and the elongation becomes difficult. The upper limit of the MD preheating temperature (°C) is preferably 200, more preferably 180, still more preferably 150. When it exceeds the above, it will crystallize and it will become difficult to extend.

The lower limit of the MD extension temperature (°C) is preferably 50, more preferably 60, still more preferably 70, and particularly preferably 80. When it is less than the above, the resin does not soften and the elongation becomes difficult. The upper limit of the MD extension temperature (°C) is preferably 150, more preferably 145, still more preferably 140. Crystallization, extension Stretching will become difficult.

The stretching temperature in the infrared heating mode is appropriately adjusted depending on the film forming conditions, but the film temperature at the time of stretching is preferably in the above range.

The lower limit of the MD stretching speed (%/min) is preferably 100, more preferably 150, still more preferably 200. Below this, productivity will become low. The upper limit of the MD stretching speed (%/min) is preferably 100,000, more preferably 90,000, still more preferably 80,000. When the above is exceeded, the film formation stability is lowered.

The lower limit of the MD stretching ratio is preferably 2.5, more preferably 2.6, still more preferably 2.7. When it is less than the above, the degree of crystallization of the surface layer is low, and when the conditions of the extrusion build-up are changed, in addition to the change in the peeling force, the spur strength is also lowered. The upper limit of the MD stretching ratio is preferably 4.5, more preferably 4.4, still more preferably 4.35. When it exceeds the above, the productivity at the time of film formation will fall.

The lower limit of the thickness (μm) after the MD extension is preferably 5, more preferably 10, still more preferably 15. When it is less than the above, the lateral extension becomes difficult.

The upper limit of the thickness (μm) after the MD extension is preferably 250, more preferably 240, still more preferably 230. When the above is exceeded, the thickness after biaxial stretching is too thick and is not suitable for the purpose of the present invention.

The lower limit of the TD stretching ratio (times) is preferably 3.5, more preferably 3.6, still more preferably 3.7. When it is less than the above, the productivity in the film formation is lowered, and the uniformity of the thickness is lowered. The upper limit of the TD stretching ratio (times) is preferably 5, more preferably 4.8, still more preferably 4.5. When it exceeds the above, a fracture or the like is observed at the time of film formation, and productivity is lowered.

The lower limit of the TD preheating temperature (°C) is preferably 30, more preferably 40, still more preferably 50, and particularly preferably 60. When it is less than the above, the preheating system is insufficient, and the elongation becomes difficult. The upper limit of the TD preheating temperature (°C) is preferably 150, more preferably 145, still more preferably 140. When it exceeds the above, it will crystallize and it will become difficult to extend.

The lower limit of the TD extension temperature (°C) is preferably 50, more preferably 60, still more preferably 70, particularly preferably 80, most preferably 100. When it is less than the above, the resin does not soften and the elongation becomes difficult.

The upper limit of the TD extension temperature (°C) is preferably 180, more preferably 175, still more preferably 170, particularly preferably 165, most preferably 160. When it exceeds the above, it will crystallize and it will become difficult to extend.

The setting of heat setting conditions is the most important point in the present invention. In the present invention, in order to exhibit adhesion, it is necessary to set the heat setting conditions so that the crystal on the surface of the film is moderated by heat during the treatment such as corona discharge treatment. When the crystal is solidified on the surface before the corona discharge treatment, the relaxation of the structure such as melting of the crystal becomes difficult to occur, and the effect of improving the adhesion by the corona discharge treatment is small. Therefore, it is necessary to set the heat setting condition in accordance with the state before the heat setting immediately after the biaxial stretching.

As a general guideline:

‧When using a material with a high crystallization rate or a high alignment after biaxial stretching, it will become a crystal sturdy on the surface. It must be heat set at a high temperature as the temperature reached by the film surface, but if it is exposed to high temperature for a long time. Underneath, the mechanical properties of the film will be reduced. Therefore, it is necessary to make the temperature reached by the film high and to make the processing time at a high temperature short.

‧ When using a raw material with a slow crystallization rate or a low alignment after biaxial stretching, it is difficult to cause crystallization of the film due to heat during heat setting, and the film may be melted during heat setting at a high temperature. The mechanical properties of the film are reduced. Therefore, it is necessary to carry out heat setting at a low temperature for a long period of time, but when it is too low temperature and treated for a long period of time, there is no improvement in mechanical properties of the film or melting of crystals on the surface, and corona discharge treatment is not caused. The improvement in adhesion. Therefore, after confirming the physical properties of the film, it is necessary to reduce the heat setting time at a high temperature while increasing the suitable heat setting temperature.

When reviewing these points, it was found that the film forming conditions (stretching ratio) and the heat setting conditions were adjusted so as to be in the range of the surface crystallization degree to be described later, and the surface before and after the corona discharge treatment was adjusted. , the improvement of adhesion can be obtained. Based on these points, the conditions must be appropriately adjusted, as exemplified below, but are not limited by such methods or conditions.

The following description assumes that the heat setting zone is one or more (the first half is zone 1 and the second half is zone 2).

The lower limit of the heat setting temperature (°C) of each zone is preferably 150, more preferably 160, still more preferably 170. When it is less than the above, the heat shrinkage rate becomes too large, and the dimensional stability of various processing steps becomes poor. The upper limit of the heat setting temperature (°C) of each zone is preferably 280, more preferably 270, still more preferably 260. When it exceeds the above, not only the crystallization of the surface layer but also the alignment of the entire film is disintegrated, and the mechanical properties are lowered.

The lower limit of the heat setting time (second) is preferably 0.5, more preferably 1, still more preferably 1.2, particularly preferably 1.5, and most preferably 2.5. Less than the above At the time, productivity will decrease. The upper limit of the heat setting time (seconds) is preferably 50, more preferably 15, more preferably 10, particularly preferably 7, and most preferably 5. When it exceeds the above, productivity will decrease.

The lower limit of the TD relaxation rate (%) is preferably 0, more preferably 0.5, still more preferably 0.8. When it is less than the above, it will be easily broken and the productivity will be lowered. The upper limit of the TD relaxation rate (%) is preferably 20, more preferably 15, and still more preferably 10. When it exceeds the above, sagging occurs, and the thickness accuracy in the width direction is lowered.

The lower limit of the film forming speed (m/min) of the TD outlet is preferably 3, more preferably 5, still more preferably 10, and particularly preferably 20. When it is less than the above, the productivity is low and it is not suitable from the industrial point of view. The upper limit of the film forming speed (m/min) of the TD outlet is preferably 500, more preferably 400, still more preferably 300. When it exceeds the above, the skew will become larger.

The lower limit of the thickness (μm) after biaxial stretching is preferably 3, more preferably 4, still more preferably 5. When it is less than the above, it is too thin and the workability is lowered. The upper limit of the thickness (μm) after the biaxial stretching is preferably 50, more preferably 45, still more preferably 40. When it exceeds the above, the workability is lowered in addition to being too thick, and the flexibility is lowered when used as a packaging material.

(film properties)

The lower limit of the heat shrinkage ratio (%) in the MD direction at 150 ° C for 15 minutes of the present invention is preferably 0.5, more preferably 0.6, still more preferably 0.7. When it is less than the above, the practical effect due to an increase in dimensional stability is saturation. The upper limit of the heat shrinkage ratio (%) in the MD direction at 150 ° C for 15 minutes is preferably 10, more preferably 8, more preferably 5. When more than the above, various kinds of addition occur The pitch of the steps of the work is offset, and the appearance is low.

The lower limit of the degree of surface crystallization of the easy-adhesive treated surface of the present invention is preferably 1.1, more preferably 1.15, still more preferably 1.2, most preferably 1.25. When it is less than the above, the change in the degree of crystallization of the surface layer of the film due to heat is large, and various adhesiveness changes due to the heat treatment after the treatment. The upper limit of the degree of surface crystallization of the easy-adhesive treated surface is preferably 1.35, more preferably 1.34, still more preferably 1.33, particularly preferably 1.3, most preferably 1.28. When it exceeds the above, the degree of crystallization of the surface layer of the film is too high, and the adhesion is lowered.

The lower limit of the degree of surface crystallization of the non-treated surface of the present invention is preferably 1.1, more preferably 1.15, still more preferably 1.2, most preferably 1.25. The degree of surface crystallization of the non-treated surface is the same as that before the treatment such as corona discharge treatment. However, if it is less than the above, the degree of crystallization of the surface layer of the film is too low, and various adhesion properties are changed. The upper limit of the degree of surface crystallization of the non-treated surface is preferably 1.5, more preferably 1.45, still more preferably 1.4. As described above, the non-treated surface is substantially the same as the treatment surface before the various treatments. However, if the degree of crystallization of the surface layer of the film is too high, the adhesion of the surface of the film to the side of the easy-to-adhere treatment surface is not preferable.

The lower limit of the value after the surface crystallization degree of one side of the film of the present invention minus the crystallization degree of the other side of the film is preferably -0.1, more preferably -0.08, still more preferably -0.05. When it is less than the above, the effect of improving the adhesion is saturated. The upper limit of the value after the surface crystallization degree of one side of the film minus the crystallization degree of the other side of the film is preferably 0, more preferably -0.001, still more preferably -0.004, most preferably -0.008. When it exceeds the above, the degree of crystallization of the surface is increased by the adhesion treatment such as corona discharge treatment, and the adhesion cannot be improved.

In the case of further limiting, the value obtained by subtracting the degree of crystallization of the non-treated surface from the degree of crystallization of the easy-adhesion treated surface of the film may be within the above range.

The lower limit of the spur strength (N) of the film of the present invention is preferably 5, more preferably 6, still more preferably 7. When it is less than the above, it is easy to cause breakage during processing or the like. The upper limit of the spur strength (N) is preferably 20, more preferably 18, still more preferably 17. When the above is exceeded, the effect will be saturated.

In the present specification, the term "easy adhesion treatment surface" means a surface to which the adhesion treatment is as follows. In the adhesion processing method of the present invention, in addition to the physical methods such as ultraviolet irradiation treatment, corona discharge treatment, plasma discharge treatment, flame treatment, etc., chemical treatment such as alkali treatment, primer treatment, or the like can be used. Wait. Preferably, it is a physical method capable of dry treatment, more preferably ultraviolet irradiation treatment, corona discharge treatment, plasma discharge treatment, flame treatment, and further preferably ultraviolet irradiation treatment, corona discharge treatment, plasma discharge treatment, The best is corona discharge treatment.

For the corona discharge treatment, a well-known method can be used (for example, refer to JP-A-62-106934). The lower limit of the preferable discharge amount (W‧min/m ² ) is 1, more preferably 5, still more preferably 10. When it is less than the above, the effect of the treatment is small, and the effect of improving the adhesion is not observed. The upper limit of the preferable discharge amount (W‧min/m ² ) is 200, more preferably 180, still more preferably 150. When it exceeds the above, the oxidation of the surface is excessive, and the effect of improving the adhesion is not observed.

In the present invention, by making each characteristic of the film into the range of the present invention, it is possible to impart a very high adhesiveness during lamination processing (strong laminate) degree).

The lower limit of the buildup strength is preferably 3, more preferably 3.5, still more preferably 4. When it is less than the above, when a strong punch is applied as a bag or a cover material, there is a problem that it is easy to break a bag or the like. The upper limit of the buildup strength is preferably 15, more preferably 13, and even more preferably 10. When the above is exceeded, the effect is saturated.

This case is based on Japanese Patent Application No. 2012-172815 filed on August 3, 2002, and claims priority. The entire contents of the specification of Japanese Patent Application No. 2012-172815, filed on Jan. 3, 2008, the entire disclosure of which is incorporated herein by reference.

[Examples]

Next, the present invention will be described in more detail by way of examples, but the invention is not limited by the following examples. Further, the evaluation of the film was carried out by the following measurement method.

[Intrinsic viscosity of polyester]

0.1 g of the polyester was dissolved in 25 mL of a mixed solvent of phenol/tetrachloroethane (volume ratio: 3/2), and measured at 30 ° C using an Oswald viscometer.

[melting point of polyester]

The measurement was carried out using a SU-based differential scanning calorimeter (DSC) at a sample rate of 10 mg and a temperature increase rate of 20 ° C /min. The melting endothermic peak temperature detected here was taken as the melting point.

[thickness]

It was measured by the method according to JIS-Z-1702.

[Surface crystallinity]

The FT-IR ATR measurement was performed under the following conditions on both the easy-adhesive treated surface and the non-treated surface of the sample.

FT-IR device: FTS-60A/896 made by Bio Rad DIGILAB

1st reflection ATR accessory: golden gate MKII (made by SPECAC)

Internal reflective element: diamond

Angle of incidence: 45°

Decomposition energy: 4cm ^-1

Cumulative number: 128 times

The degree of crystallinity was calculated from the intensity of the absorption lines of the absorption occurring in the vicinity of 1340cm ^-1 and 1410cm ^-1 appear in the vicinity of ratio (1340cm ^-1 / ^{1410cm -1).} Here, absorption by the deformation vibration of CH ₂ (trans structure) of 1340 cm ^-1 ethylene glycol, and absorption of 1410 cm ^-1 irrespective of crystallization and alignment.

In addition, as "the value obtained by subtracting the surface crystallization degree of the other side of the film from the surface crystallization degree of one side of the film", "the surface crystallization degree of the easy-adhesion treated surface of the film is subtracted from the non-treatment. The value after the surface crystallization degree of the surface".

[breaking strength, elongation at break]

According to JIS K 7113. A sample having a width of 10 mm and a length of 100 mm was cut out in the longitudinal direction and the width direction of the film using a razor as a sample. After being allowed to stand in an environment of 23 ° C and 35% RH for 12 hours, the measurement was carried out under the conditions of a cross-clamp distance of 40 mm and a tensile speed of 200 mm/min in an environment of 23 ° C and 35% RH. The average of the measurement results of the second time. As the measuring device, Autograph AG5000A manufactured by Shimadzu Corporation was used.

[spur strength]

It is measured according to the "2. Strength and other test methods" of "Standards for Foods and Additives, No. 3: Apparatus and Container Packaging" (Showing No. 20 of the Ministry of Health and Welfare in the Showa 57). The needle having a tip end portion of 0.7 mm was spurted at a spur speed of 50 mm/min, and the strength at which the needle penetrated the film was measured to obtain the spur strength. The measurement was carried out at room temperature (23 ° C) in units of [N].

[heat shrinkage rate]

The measurement was carried out by a dimensional change test method described in JIS-C-2318 except for a test temperature of 150 ° C and a heating time of 10 minutes.

[layer strength]

A laminate having a width of 15 mm and a length of 200 mm was formed by a laminate of a polyolefin film having a thickness of 40 μm, and was used as a test piece by "Tensilon UMT-II-500" manufactured by TOYO BALDWIN Co., Ltd. at a temperature of 23 ° C and 65%. The peeling strength of the joint surface of the untreated surface of the polyester film 1 and the polyolefin resin layer was measured under the conditions of relative humidity. Further, the stretching speed was 10 cm/min, and the peeling angle was 180 degrees.

[Ink Adhesion]

According to the checkerboard evaluation described in JIS-K5400, after printing the ink on the easy-adhesive surface of the film, the cross-cut guide was used to make 100 1 mm squares by the blade, and the adhesive tape (NICHIBAN company's celluloid tape) was used. ), evaluate the closeness of the square part.

As the ink to be used, a solvent type ink (900 series Tetron ink manufactured by Shikoku Co., Ltd.) was used, and screen printing of #250 was carried out on the coating layer of the film (the coating layer A of the present invention), and then the dryer was placed for 24 hours.

[Production Example of Polyester Resin 1]

In a mixture of terephthalic acid and ethylene glycol, magnesium acetate tetrahydrate was added in such a manner that the Mg atom in the polyester was 60 ppm, and the esterification reaction was carried out at a temperature of 255 ° C under normal pressure. Then, antimony trioxide in an amount of 150 ppm of the Sb atom in the polyester and trimethyl phosphate in an amount of 40 ppm in the polyester were added, and the reaction was further carried out at a temperature of 260 °C.

Next, the reaction product was transferred to a polycondensation reaction layer, and an ethylene glycol slurry of cerium oxide particles having an average particle diameter of 2.3 μm was added so that cerium oxide became 1000 ppm in the polyester, and then the temperature was raised while heating. The reaction system was slowly depressurized, and polycondensed at 280 ° C under a reduced pressure of 133 Pa (1 mmHg) by a usual method to obtain a polyester scrap of IV = 0.62. Further, the obtained polyester resin was obtained by DSC and the recrystallization temperature [Tc(A)] observed by cooling from a molten state at a rate of 20 ° C /min was 161 ° C at 40 ° C / min. The recrystallization temperature of the speed [Tc(B)] was 157 ° C, and Tc (A) - Tc (B) was 4 °C.

[Example 1]

The polyester resin 1 was dried under reduced pressure (1.3 hPa) at 120 ° C for 24 hours, and after melting at 280 ° C using a uniaxial extruder, it was cast from a 30 cm wide T die (280 ° C) to a cooling roll (surface). At a temperature of 10 ° C), a voltage of 7.2 kV was applied from a tungsten wire electrode having a diameter of 30 μm disposed opposite to the circumferential surface of the cooling roll, and a current of 0.2 mA was passed to make electrostatic adhesion, and the thickness of the central portion was obtained. It is an unextended sheet of 170 μm.

The unstretched sheet was preheated at a roll temperature of 95 ° C, extended 3.5 times in the length direction at an elongation temperature of 100 ° C, and then extended 4.0 times in the transverse direction at 100 ° C, followed by a relaxation rate of 3.0% at 230 ° C. The heat setting treatment was carried out to obtain a polyester film having a thickness of 12 μm. The speed of the TD outlet is 50 m/min, and the residence time in the heat setting zone is 2 seconds. Then, after preheating to 40 ° C, one side of the film was subjected to corona discharge treatment. The corona discharge treatment was carried out at 90 W ‧ min/m ² . Then, it is wound on a paper tube to form a polyester film 1. The properties of the resulting film are shown in Table 1.

[Embodiment 2]

A film was obtained according to the conditions described in Table 1. Table 1 shows the film forming conditions, physical properties, and evaluation results of the obtained film.

[Example 3]

After washing the PET bottle as a raw material, the recycled PET resin (IV: 0.68, Co-b: 8, isophthalic acid copolymerization amount: 2.0 mol%) obtained by regranulation was mixed with an average particle of 60%. A polyester resin having a diameter of 1.3 μm and a condensed cerium oxide of 40% was used, and when the concentration of cerium oxide was 700 ppm, a film was obtained according to the conditions described in Table 1. Table 1 shows the film forming conditions, physical properties, and evaluation results of the obtained film. Further, in the above raw material formulation, the recrystallization temperature [Tc(A)] observed by DSC at a rate of 20 ° C /min from the molten state was 151 ° C at 40 ° C / min. The recrystallization temperature [Tc (B)] of the speed was 144 ° C, and Tc (A) - Tc (B) was 7 ° C.

[Example 4]

As a raw material, ethylene glycol of the polyester resin 1 was used as a plant-derived ethylene glycol, and an average particle diameter of 3500 ppm was mixed in a polyester resin (IV: 0.65) obtained by adding no condensed cerium oxide (80%). 20% of the PET resin of the condensed cerium oxide of μm was used, and when the concentration of cerium oxide was 700 ppm, a film was obtained according to the conditions described in Table 1. The thinness shown in Table 1 Film forming conditions, physical properties and evaluation results of the film. Further, in the above raw material formulation, the recrystallization temperature [Tc(A)] observed by DSC at a rate of 20 ° C/min from the molten state was 168 ° C at 40 ° C / min. The recrystallization temperature [Tc(B)] of the speed was 155 ° C, and Tc (A) - Tc (B) was 13 °C. Further, the amount of the nitrogen compound obtained by the oxygen cycle chemiluminescence method in the ethylene glycol derived from the plant is in the range of 0 to 1 ppm.

[Comparative Examples 1 to 4]

A film was obtained according to the conditions described in Table 1. Table 1 shows the film forming conditions, physical properties, and evaluation results of the obtained film.

[Comparative Examples 5 to 7]

In the polyester resin (IV: 0.65) obtained in the same manner as in Example 4, 80% of the polyester resin (IV: 0.65) obtained in the same manner as in Example 4 was mixed with an average particle diameter of 1.3 μm, except that a plant-derived ethylene glycol containing 10 ppm of a nitrogen-based compound as an impurity was used. 20% of the PET resin in which cerium oxide was condensed, and when the concentration of cerium oxide was 1000 ppm, a film was obtained according to the conditions described in Table 1. Table 1 shows the film forming conditions, physical properties, and evaluation results of the obtained film. Further, in the above raw material formulation, the recrystallization temperature [Tc(A)] observed by DSC at a rate of 20 ° C /min from the molten state was 175 ° C at 40 ° C / min. The recrystallization temperature [Tc(B)] of the speed was 155 ° C, and Tc (A) - Tc (B) was 20 °C.

[Comparative Example 8]

A film obtained by adding a 1% by weight of a crystal nucleating agent (Adekastab NA-05 manufactured by ADKEA) to the polyester resin 1 was used to obtain a film in accordance with the conditions described in Table 1. Table 1 shows the film forming conditions, physical properties and properties of the obtained film. Evaluation results. Further, in the above raw material formulation, the crystallization temperature [Tc(A)] observed by DSC at a rate of 20 ° C /min from the molten state was 185 ° C, at 40 ° C / min. The recrystallization temperature of the speed [Tc(B)] was 153 ° C, and Tc (A) - Tc (B) was 32 °C.

The above results are shown in Table 1.

[Industrial availability]

The polyester film of the invention can be widely used in a wide range of fields such as magnetic tapes, insulating tapes, photo films, tracing films, packaging materials, electrical insulating materials, information recording materials, various step papers, etc., especially because of heat resistance and dimensional stability. Excellent, and suitable for printing.

Moreover, since it is high in heat resistance, it can be dried at a high temperature during drying of coating or printing, and productivity can be improved, and a coating agent or ink which has been difficult to use in the past, a laminated adhesive, etc. can be used.

Further, it is also suitable for an insulating film such as a capacitor or a motor, a back sheet of a solar cell, a barrier film of an inorganic oxide, or a base film of a transparent conductive film such as ITO.

Claims (3)

A biaxially stretched polyester film characterized in that the recrystallization temperature (Tc(A)) observed by DSC from a molten state at a rate of 40 ° C/min is 140 ° C. Recrystallization temperature (Tc(B)) at 175 ° C at a rate of 20 ° C / min is 130 ° C ~ 165 ° C, the difference between Tc (A) and Tc (B) (Tc (A) - Tc (B)) It is composed of a polyester resin of 0 to 15 ° C. The polyester resin is a polyester (A) obtained by using terephthalic acid (TPA) and ethylene glycol (EG) as main components, and the content of terephthalic acid. It is 60% by mass or more, has a thickness of 3 to 50 μm, and satisfies the physical properties of the film of the following requirements (1) to (4); (1) the thermal shrinkage in the MD direction is 0.5 to 10%; and (2) the spur strength is 5~20N; (3) on the surface of the easy-adhesive treatment surface, the surface crystallization degree obtained by ATR-IR is 1.10~1.35; (4) the film is subtracted from the surface crystallization degree of the easy adhesion treatment surface of the film. The value of the surface crystallization degree of the non-treated surface is in the range of -0.1 to 0. The biaxially stretched polyester film of claim 1, wherein the polyester resin has an isophthalic acid component. The biaxially stretched polyester film of claim 1, wherein the polyester resin contains a polyester resin polymerized from a glycol component derived from a plant.