JP2013000899A - Mold release polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold release polyester film capable of realizing high-degree precision in executing the optical inspection of a polarizing plate by a crossed Nicol method.SOLUTION: The mold release polyester film which is a mold release film having a silicone mold release layer at least on one surface thereof and is characterized in that the internal transparency of the mold release film is 96.5% or above, the surface roughness (Ra) of the silicone mold release layer is 9.0 nm or above and the MOR value of the mold release film is 1.5-3.0.

Description

  The present invention relates to a release polyester film advantageous for optical inspection for optical applications.

  Polyester films represented by polyethylene terephthalate and polyethylene naphthalate have excellent mechanical strength, dimensional stability, flatness, heat resistance, chemical resistance, optical properties, etc. It is used in applications. However, as the application diversifies, the processing conditions and usage conditions of the polyester film diversify. When used as a release polyester film for polarizing plates, the particle component in the release film is a bright spot when inspecting foreign matter. Thus, problems such as a decrease in inspection accuracy occur.

  In recent years, with the rapid spread of mobile phones and personal computers, the demand for liquid crystal displays (LCDs) that are thinner, lighter, consume less power, and have higher image quality than the conventional display CRT is growing significantly. There is also a remarkable growth in the technology for increasing the screen size of LCDs. As an example of increasing the screen size of LCD, recently, LCD is used for large TV applications of 30 inches or more. An LCD with a large screen is often a bright LCD with a large screen by increasing the luminance of a backlight incorporated in the LCD or incorporating a film for improving the luminance into a liquid crystal unit.

  In such a so-called high-brightness type LCD, a small bright spot existing in the display is often a problem, and in a component such as a polarizing plate, a retardation plate or a retardation polarizing plate incorporated in the display, As a result, there is a problem of a foreign material having a minute size that has not been a problem in conventional low-brightness LCDs. For this reason, while preventing the entry of foreign matter in the manufacturing process, it is also important to improve the inspection accuracy so that even if foreign matter is mixed, it can be recognized as a defect.

  Conventionally, the particles in the polyester film are usually used to ensure the slipperiness and winding characteristics of the film, and if the appropriate particle size and blending amount are not satisfied, the desired slipperiness cannot be ensured. As a result, the winding characteristics deteriorate, and as a result, the productivity deteriorates. However, when the particle size and blending amount are within the normally used range, as described above, when used as a release film for polarizing plates, the particles become bright spots in the foreign substance inspection process, which hinders inspection. Is a problem.

  For example, as a defect inspection of a polarizing plate, a visual inspection by a crossed Nicols method is generally used. Further, for example, for a polarizing plate used for a large TV application of 40 inches or more, an inspection by an automatic particle inspection device using the crossed Nicols method is used. Is also being implemented. According to this crossed Nicol method, two polarizing plates are put in a quenching state with their orientation principal axes orthogonal to each other, and if there are foreign matters or defects, they appear as bright spots, so a visual defect inspection or a line sensor camera, etc. Automatic defect inspection can be performed. Here, the pressure-sensitive adhesive layer is usually provided on the polarizing plate, and a polyester film provided with a release layer is used as the release film for that purpose. When a product having such a configuration is inspected, a crossed Nicols inspection is performed in a state where a release polyester film is sandwiched between two polarizing plates. In general, when a release polyester film is used for this, foreign matter and defects are difficult to see in the crossed Nicols inspection, and it may be easy to miss them.

  Regarding these, when a polyester film is sandwiched between two polarizing plates, an inspection property is improved when the retardation value is within a certain range (see Patent Document 1). Even if these are used at a level where quality is required, accuracy may be insufficient when inspection is performed to find defects reliably.

  Further, when inspecting a defect such as distortion or unevenness of a polarizing plate, a reflection visual inspection under a fluorescent lamp may be performed. In this case, in order to inspect the polarizing plate provided thereunder through the release film, if the release film is extremely white, defects of the polarizing plate are difficult to see and it is easy to miss them. May occur. In this regard, in the release film to be used, the internal haze alone may leave a grainy feeling (see Patent Document 2), but the transparency of the film including the internal haze is important.

JP 2000-338327 A JP 2009-214360 A Japanese Patent Application No. 2011-2605

  This invention is made | formed in view of the said situation, Comprising: The solution subject is providing the release polyester film which can implement | achieve a high precision in the optical test | inspection by the cross Nicol method of a polarizing plate.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that the above problem can be easily solved by a polyester film having a specific configuration, and have completed the present invention.

  That is, the gist of the present invention is a release film having a silicone release layer on at least one side, the internal transparency of the release film is 96.5% or more, and the surface of the silicone release layer is rough. (Ra) is 9.0 nm or more, and the release film has a MOR value of 1.5 to 3.0.

  According to the present invention, a member such as polarized light in a state where a release film is bonded is excellent in a clear feeling, and is inspected when visual inspection by a cross Nicol method is performed for inspection of defects such as distortion and unevenness and the presence of foreign matter. Since the polyester film which is excellent in productivity and excellent in productivity can be provided, the industrial value of the present invention is high.

  The polyester film referred to in the present invention is a film which is melt-extruded from an extrusion die, and is subjected to stretching and heat treatment as necessary after cooling a molten polyester sheet extruded by a so-called extrusion method.

The polyester constituting the film of the present invention is obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Representative polyesters include polyethylene terephthalate (PET), polyethylene-2,6-naphthalenedicarboxylate (PEN), and the like. The polyester used may be a homopolyester or a copolyester. In the case of a copolyester, it may be a copolymer containing 30 mol% or less of the third component.
Examples of the dicarboxylic acid component of such a copolyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid (eg, P-oxybenzoic acid). 1 type or 2 types or more chosen from are mentioned. One glycol component includes one or more selected from ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like.

  In the polyester obtained by the present invention, a weathering agent, a light-proofing agent, an antistatic agent, a lubricant, a light-shielding agent, an antioxidant, a fluorescent whitening agent, a matting agent, and a heat-stabilizing agent as long as the gist of the present invention is not impaired. You may mix | blend an agent and coloring agents, such as dye and a pigment.

  Examples of the particles to be blended in the film include silicon oxide, alumina, calcium carbonate, kaolin, titanium oxide, and crosslinked polymer fine powder as described in JP-B-59-5216. These particles may be used alone or in combination of two or more components. The blending amount of these particles is usually 1% by weight or less, preferably 0.01 to 1% by weight, more preferably 0.02 to 0.6% by weight, based on the polyester constituting the film. When the content of the particles is small, the film surface cannot be appropriately roughened, and in the film production process, there is a tendency that the surface is easily scratched or the winding properties are inferior. Further, when the content of the particles exceeds 1% by weight, the degree of roughening of the film surface becomes too large, and the transparency may be impaired.

  The average particle size of the particles blended in the polyester film is not particularly limited, but is usually 0.02 μm to 5 μm, preferably 0.02 μm to 3.5 μm, more preferably 0.02 μm to 3.2 μm. Range. When particles having an average particle size of less than 0.02 μm are used, sufficient slipperiness cannot be imparted, so that the winding characteristics in the film production process tend to be inferior. On the other hand, when the average particle diameter exceeds 5 μm, the degree of roughening of the film surface becomes too large, and the cloudiness of the film may increase.

  On the other hand, in order to improve the transparency of the film, when a laminated film of two or more layers is used, a method of blending particles only in the surface layer is also preferably employed. The surface layer in this case is at least one of the front and back layers, and of course, particles can be blended in both the front and back layers. The blending amount of the particles in the case of such a laminated film is preferably 0.01 to 1% by weight, more preferably 0.02 to 0.6% by weight, based on the polyester constituting the surface layer.

  In addition, a sharp particle size distribution is preferably used. Specifically, those having a particle size distribution value of 1.0 to 2.0, which is an index representing the sharpness of the particle size distribution, are preferable. Here, the particle size distribution value is the particle size distribution value d25 / d75 (d25 and d75 are calculated by calculating the accumulated accumulation of the particle group from the large particle side, and the particle size (μm corresponding to 25% and 75% of the total volume, respectively) Is a value defined by When the particle size distribution value exceeds 2.0, transparency may be insufficient.

  In the present invention, the method of blending the particles with the polyester is not particularly limited, and a known method can be adopted. For example, it can be added at any stage for producing the polyester, but it is preferably added as a slurry dispersed in ethylene glycol or the like at the stage of esterification or before the start of the polycondensation reaction after completion of the transesterification reaction. The condensation reaction may proceed. Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a method of blending dried particles and a polyester raw material using a kneading extruder Etc.

  The polyester may be converted into chips after melt polymerization, and further subjected to solid phase polymerization as necessary under heating under reduced pressure or in an inert gas stream such as nitrogen. The intrinsic viscosity of the obtained polyester is preferably 0.40 dL / g or more, and more preferably 0.40 to 0.90 dL / g.

  The total thickness of the film of the present invention is not particularly limited as long as it can be formed as a film, but is usually in the range of 4 to 300 μm, preferably 25 to 188 μm.

  Next, although the manufacturing method of the film of this invention is demonstrated concretely, as long as the summary of this invention is satisfied, it is not specifically limited to the following illustrations.

  First, the preferable example of the manufacturing method of polyester used by this invention is demonstrated. Here, an example in which polyethylene terephthalate is used as the polyester is shown, but the production conditions differ depending on the polyester used. According to a conventional method, esterification from terephthalic acid and ethylene glycol, or dimethyl terephthalate and ethylene glycol are transesterified, the product is transferred to a polymerization tank, and the temperature is increased while reducing the pressure. The polymerization reaction proceeds by heating to 280 ° C. under vacuum to obtain polyethylene terephthalate.

Next, for example, the polyester chip obtained as described above and dried by a known method is supplied to a melt-extrusion apparatus and heated to a temperature equal to or higher than the melting point of each polymer and melted. Next, the molten polymer is extruded from the die, and rapidly cooled and solidified on the rotary cooling drum so as to have a temperature equal to or lower than the glass transition temperature to obtain a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum. In the present invention, an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed. In the present invention, the sheet thus obtained is stretched biaxially to form a film.
Specifically describing the stretching conditions, the unstretched sheet is preferably stretched 2 to 6 times at 70 to 145 ° C. in the longitudinal direction to form a longitudinal uniaxially stretched film, and then 2 to 90 to 160 ° C. in the lateral direction. It is preferable to perform ~ 6 times stretching and heat treatment at 150 to 240 ° C for 1 to 600 seconds. Further, at this time, a method of relaxing 0.1 to 20% in the longitudinal direction and / or the transverse direction in the maximum temperature zone of the heat treatment and / or the cooling zone at the heat treatment outlet is preferable. Further, it is possible to add re-longitudinal stretching and re-lateral stretching as necessary. Furthermore, it is also possible to perform simultaneous biaxial stretching of the unstretched sheet so that the area magnification is 10 to 40 times.

  The polyester film of the present invention can be subjected to so-called in-line coating for treating the film surface during the stretching step as long as the effects of the present invention are not impaired. Although it is not limited to the following, for example, after the first stage of stretching is completed, before the second stage of stretching, improvement of antistatic property, slipperiness, adhesion, etc., secondary workability improvement, weather resistance, etc. In order to improve the property and surface hardness, a coating treatment with an aqueous solution, an aqueous emulsion, an aqueous slurry, or the like can be performed. Various coatings may be performed by offline coating after film production. Such a coat may be either single-sided or double-sided. The coating material may be either water-based or solvent-based for offline coating, but is preferably water-based for in-line coating.

  The coating solution used in the present invention is usually preferably adjusted with water as the main medium from the viewpoint of safety and hygiene. As long as water is the main medium, a small amount of an organic solvent may be contained for the purpose of improving the dispersion in water or improving the film forming performance. The organic solvent is preferably used as long as it dissolves in water when mixed with water, which is the main medium. Alternatively, it may be used in a state where it does not dissolve in water. The organic solvent may be used alone or in combination of two or more as necessary.

  The release layer in the present invention is not particularly limited as long as it contains a material having releasability. Among them, the one containing a curable silicone resin is preferable because the releasability is improved. A type having a curable silicone resin as a main component may be used, or a modified silicone type by graft polymerization with an organic resin such as a urethane resin, an epoxy resin, or an alkyd resin may be used.

  As the type of the curable silicone resin, any of the curing reaction types such as an addition type, a condensation type, an ultraviolet ray curable type, an electron beam curable type, and a solventless type can be used.

  Specific examples of the curable silicone resin include KS-774, KS-775, KS-778, KS-779H, KS-847H, KS-856, X-62-2422, X-manufactured by Shin-Etsu Chemical Co., Ltd. 62-2461, DKQ3-202, DKQ3-203, DKQ3-204, DKQ3-205, DKQ3-210 manufactured by Dow Corning Asia Co., Ltd. YSR-3022, TPR-6700, TPR-6720 manufactured by Toshiba Silicone Co., Ltd. , TPR-6721, SD 7220, SD 7226, SD 7229 manufactured by Toray Dow Corning Co., Ltd., and the like. Further, a release control agent may be used in combination to adjust the release property of the release layer. Further, as described above, a silane compound having an amino group may be added to the release layer.

In the present invention, as a method for providing a release layer on the polyester film, a conventionally known coating method such as reverse roll coating, gravure coating, bar coating, doctor blade coating, or the like can be used. The application amount of the release layer in the present invention is usually in the range of 0.01 to 1 g / m ² .

  In the present invention, a coating layer such as an adhesive layer, an antistatic layer and an oligomer precipitation preventing layer may be provided on the surface where the release layer is not provided, and the polyester film may be subjected to corona treatment, plasma treatment, etc. A surface treatment may be applied.

  Moreover, drying and / or curing (thermal curing, ionizing radiation curing, etc.) of the coating film of the pressure-sensitive adhesive layer or the release layer can be performed individually or simultaneously. When performing simultaneously, it is preferable to carry out at the temperature of 80 degreeC or more. The drying and curing conditions are preferably 80 ° C. or higher and 10 seconds or longer. If the drying temperature is less than 80 ° C. or the curing time is less than 10 seconds, the coating film is incompletely cured and the coating film tends to fall off.

  In order to make the coated layer of the polyester film of the present invention clean and strong, a transition metal catalyst is used. The content of the transition metal catalyst in the coating layer is 0.5 to 5.0% by weight, preferably 1.5 to 4.0% by weight. When the content of the transition metal catalyst in the coating layer is lower than 0.5% by weight, there may be a problem such as deterioration of the surface condition due to insufficient peeling force or insufficient curing reaction in the coating layer. On the other hand, if the content of the transition metal catalyst in the coating layer exceeds 5.0% by weight, the cost is increased, the reactivity is increased, and process defects such as generation of gel foreign matter are caused. End up.

  In the present invention, it may be a film having a structure in which a polyester having a low oligomer content is coextruded and laminated on at least one surface of a layer made of a polyester having a normal oligomer content. In the polyester film for release film obtained by the invention, the effect of preventing bright spots due to the precipitated oligomer is obtained, which is particularly preferable.

  In the present invention, the internal transparency of the film in the measurement method described later needs to be 96.5% or more, preferably 97% or more. When the transparency of the film is less than 96.5%, the transparency of the film is lowered. In order to set the internal transparency of the film within the above range, for example, the type of particles to be used, the particle size, the amount added, the strengthening of the filter in the production line, the film production conditions (film stretching temperature, draw ratio), used in the film production line This can be achieved by appropriately combining various conditions such as smoothing the rolls to be rolled.

  Moreover, the surface roughness (Ra) of the release layer is 9.0 nm or more, and preferably 12 nm or more. When Ra of the film is less than 9.0 nm, the film surface becomes extremely flat, and the winding characteristics in the film manufacturing process are inferior. Moreover, when Ra of the film exceeds 22 nm, the planarity of the surface may be impaired, and the film may become whitish. Therefore, the upper limit of Ra is preferably 22 nm.

  The above-mentioned means for satisfying the roughness range of the polyester film is to optimally adjust the blending amount using appropriate organic particles having an arbitrary particle size distribution range.

  In the release polyester film of the present invention, the optimization of the MOR_C value obtained by measuring the release film with a microwave molecular orientation meter is very important in order to reduce the occurrence of foreign matter and light interference colors in the optical inspection of the process. It is.

  The MOR_C value of the release film of the present invention is 1.5 to 3.0, preferably 1.8 to 2.7, more preferably 2.1 to 2.4. When the MOR_C value is larger than 3.0, the release layer is not uniform, and in optical inspection, the light interference color is easily visible. When the MOR_C value is smaller than 1.5, there is a problem that the production yield of the release film itself is deteriorated.

  A means for satisfying the range of the MOR_C value of the release film of the present invention is to ingenuate stretching conditions for a desired film thickness during film formation.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. The measurement method and evaluation method used in the present invention are as follows.

(1) Measurement of intrinsic viscosity of polyester 1 g of polyester from which other polymer components and pigments incompatible with polyester have been removed are precisely weighed, and 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) is added. It was dissolved and measured at 30 ° C.

(2) Measurement of average particle size (d50: μm) 50% integrated (weight basis) in equivalent spherical distribution measured using centrifugal sedimentation type particle size distribution measuring device (SA-CP3 type manufactured by Shimadzu Corporation) The value was defined as the average particle size.

(3) Measurement of transmittance of polyester film According to JIS-K7105, the total light transmittance of the polyester film was measured with an integrating sphere turbidimeter NDH-300A manufactured by Nippon Denshoku Industries Co., Ltd. Judgment is based on the following criteria.

(4) Measurement of Heat Shrinkage Ratio of Polyester Film A polyester film is sampled at an arbitrary length L (cm) in a longitudinal direction (hereinafter abbreviated as MD) and a lateral width direction (hereinafter abbreviated as TD). To do. Subsequently, the sample is heated in an oven at 160 ° C. for 5 minutes, and the sample is taken out of the oven and the length l (cm) is measured. This operation is performed three times, and the average value is adopted as the value of the heat shrinkage rate. The heat shrinkage rate can be calculated by the following formula.
Heat shrinkage (%) = {(L−l) / L} × 100

(5) Evaluation of release film peeling force (F) After attaching one side of a double-sided adhesive tape (Nitto Denko “No. 502”) to the surface of the release layer of the sample film, cut into a size of 50 mm × 300 mm After that, the peel strength after standing for 1 hour at room temperature is measured. For the peeling force, a tensile tester (“Intesco model 2001 type” manufactured by Intesco Co., Ltd.) was used, and 180 ° peeling was performed under the condition of a tensile speed of 300 mm / min.

(6) Measurement of transparency inside the film The transparency inside the film was measured in ethanol using a transparency measuring instrument (TM-1D two decimal place type: light source wavelength 546 ± 5 nm) manufactured by Murakami Color Research Laboratory. The internal transparency is defined by the following formula.
Internal transparency (%) = (light quantity when film is in ethanol solution / light quantity when film is not in ethanol solution) × 100

(7) Measurement of two-dimensional surface roughness (Ra) of polyester film Ra was measured according to JIS B0601-1994 using a surface roughness measuring machine (SE3500 type) manufactured by Kosaka Laboratory. The measurement length was 2.5 mm.

(8) Observation of clear feeling of polyester film under three-wavelength fluorescent lamp The three-wavelength fluorescent lamp light was transmitted through the film, and the clearness of the film was visually observed. The clearness (transparency, clarity, graininess, etc.) of the film was evaluated according to the following criteria.
<Criteria for observation of particle feeling under a three-wavelength fluorescent lamp>
(Clear feeling high) ○ ＞ △ ＞ × (Clear feeling low)
Of the above criteria, those above Δ are levels that can be used without any problem in actual use.

(9) Evaluation of scratch resistance of polyester film The number of scratches on the film surface was counted, and the scratch resistance was evaluated in three stages. Evaluation was performed with an A4 size film.
<Criteria for scratch resistance>
(It is hard to be scratched) ○ ＞ △ ＞ × (It is easy to be scratched)
In the above criteria, only ○ is a level that can be used without any problem in actual use.
The film performance was comprehensively evaluated based on the evaluation results of (3), (5), (6), and (7).

(10) MOR_C value measurement by microwave molecular orientation meter of polyester film Using a microwave molecular orientation meter manufactured by Oji Scientific Instruments Co., Ltd., the MOR_C value was determined from the transmission microwave intensity pattern.

(11) MOR_C value measurement by microwave molecular orientation meter of polyester film Using a microwave molecular orientation meter manufactured by Oji Scientific Instruments Co., Ltd., the MOR_C value was determined from the transmission microwave intensity pattern. Judgment is based on the following criteria.
○: 2.0 to 2.5
Δ: 1.5 to 1.9, or 2.6 to 3.0
X: Lower than 1.5% or higher than 3.0

(12) Practical characteristics <Visual inspection under reflected light>
Taking the polarizing plate inspection into consideration, the width direction of the release film obtained by applying a release agent on the film and having a dryer temperature of 120 ° C. and a line speed of 30 m / min is parallel to the alignment axis of the polarizing film. As described above, the release film was closely adhered to the polarizing film through an adhesive to form a polarizing plate. The polarizing plate was visually observed under reflection of a fluorescent lamp, and the visual inspection property under reflected light was evaluated according to the following criteria. In the measurement, an A4 size sample was cut out.
"Criteria"
○: Good testability △: Can be inspected almost without problems ×: Poor testability ○ and △ are at a level where there is no problem in actual use

<Visual inspection under crossed Nicols>
Taking the polarizing plate inspection into consideration, the width direction of the release film obtained by applying a release agent on the film and having a dryer temperature of 120 ° C. and a line speed of 30 m / min is parallel to the alignment axis of the polarizing film. As described above, the release film was adhered to the polarizing film through the pressure-sensitive adhesive to obtain a polarizing plate. Here, when the polarizing plate was prepared, black metal powder (foreign matter) having a size of 50 μm or more was mixed between the pressure-sensitive adhesive and the polarizing film so as to be 50 / m ² . A polarizing plate for inspection is superimposed on the polarizing plate release film mixed with the foreign matter thus obtained so that the orientation axis is orthogonal to the width direction of the release film, and white light is irradiated from the polarizing plate side. Then, it was visually observed from a polarizing plate for inspection, and whether or not a foreign matter mixed between the adhesive and the polarizing film was found under crossed Nicols was evaluated according to the following criteria. In the measurement, A4 size samples were cut out from a total of three locations in the center and both ends in the width direction of the obtained film.
"Criteria"
○: Good foreign object recognition △: Recognize foreign objects with relatively no problem ×: Poor foreign substance recognition ○ ○ and △ are at a level where there is no problem in actual use. It is a level that can be used without any problems.
<Release properties>
The release characteristics were evaluated from the situation when the release film was peeled off from the laminated film having the adhesive layer.
○: The release film is peeled off cleanly, and the phenomenon that the adhesive adheres to the release layer is not observed. Δ: The release film peels off, but the adhesive adheres to the release layer when peeled off at a high speed. : Adhesive adheres to the release film

(13) Comprehensive evaluation An evaluation that takes all of film forming properties, productivity, inspection characteristics and the like into consideration is performed. Judgment is based on the following criteria.
○: Even if it is produced, it can be sufficiently supplied as a product. Δ: Productivity is good and the frequency of defects in optical inspection is low. ×: Productivity is poor. There are many problems with optical inspection.

The polyester used in the examples and comparative examples was prepared as follows.
(Production of polyester (A))
Starting from 100% by weight of dimethyl terephthalate and 60% by weight of ethylene glycol, magnesium acetate tetrahydrate is added as a catalyst to the reactor, the reaction start temperature is 150 ° C., and the reaction temperature is gradually increased as methanol is distilled off. The temperature was raised to 230 ° C. after 3 hours.
After 4 hours, the transesterification reaction was substantially terminated. Ethyl acid phosphate was added to the reaction mixture, which was then transferred to a polycondensation tank, and 0.04 part of antimony trioxide was added to carry out a polycondensation reaction for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C.
On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.64 dL / g due to a change in the stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure to obtain a polyester chip (A). The intrinsic viscosity of this polyester was 0.64 dL / g.

(Manufacture of polyester (B))
Starting from 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, magnesium acetate tetrahydrate is added as a catalyst to the reactor, the reaction start temperature is 150 ° C., and the reaction temperature is gradually increased as methanol is distilled off. The temperature was raised to 230 ° C. after 3 hours.
After 4 hours, the transesterification reaction was substantially terminated. Ethyl acid phosphate was added to the reaction mixture, which was then transferred to a polycondensation tank, and 0.04 part of antimony trioxide was added to carry out a polycondensation reaction for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C.
On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.45 due to a change in stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure to obtain a polyester chip (B). The intrinsic viscosity of this polyester was 0.45.

(Manufacture of polyester (C))
The intrinsic viscosity of this polyester chip was increased by a solid phase polycondensation method. After treatment in a preliminary crystallization tank at 170 ° C. in a nitrogen atmosphere for 0.5 hours, the moisture content becomes 0.005% at a temperature of 200 ° C. using a tower dryer that flows an inert gas. Until dried. Thereafter, it was sent to a solid phase polymerization tank and subjected to solid phase polymerization at 240 ° C. for 3 hours to obtain polyester (C) having an intrinsic viscosity of 0.70.

(Production of polyester (D))
When producing the polyester (C), solid phase polymerization was performed in a solid phase polymerization tank for 5 hours to obtain a polyester (D) having an intrinsic viscosity of 0.80.

(Manufacture of polyester (E))
In the method for producing polyester (A), after adding ethyl acid phosphate, the content of ethylene glycol slurry of divinylbenzene / methyl methacrylate copolymer crosslinked particles having an average particle size of 1.4 μm is 0.5% by weight with respect to polyester. The polyester (E) was obtained using the same method as the production method of the polyester (A) except that the addition was made so as to be%. The obtained polyester (E) had an intrinsic viscosity of 0.62 dL / g.

(Manufacture of polyester (F))
In the method for producing polyester (E), the same method as the method for producing polyester (E), except that the additive particles are silica particles having an average particle diameter of 2.7 μm and the content with respect to the polyester is 0.3 wt%. Was used to obtain a polyester (F). The obtained polyester (F) had an intrinsic viscosity of 0.61 dL / g.
Met.

(Manufacture of polyester (G))
In the method for producing polyester (E), the additive particles are the same as in the method for producing polyester (E) except that silica particles having an average particle diameter of 3.2 μm are contained in the polyester in an amount of 0.6% by weight. Polyester (G) was obtained using the method. The average particle size was determined by a laser method. The obtained polyester (G) had an intrinsic viscosity of 0.62 dL / g.

Example 1:
(Manufacture of polyester film)
A mixed raw material obtained by mixing the polyester (A), (D) chip and the polyester (E), (F), (G) chip at a ratio as shown in Tables 1 and 2 below, is the outermost layer (surface layer) and The raw material for the intermediate layer is supplied to two extruders, melt-extruded at 280 ° C., and then cooled and solidified on a cooling roll set at a surface temperature of 40 ° C. using an electrostatic application adhesion method. A sheet was obtained. Next, the film was stretched 2.8 times in the longitudinal direction at 100 ° C., then subjected to a preheating step in a tenter and subjected to a transverse stretching of 5.1 times at 120 ° C., followed by heat treatment at 220 ° C. for 10 seconds, 4% relaxation was added in the width direction at 180 ° C. to obtain a master roll having a width of 4000 mm. A slit was made from a position of 1400 mm from the end of the master roll, and the core roll was wound up 1000 m to obtain a polyester film. The total thickness of the obtained film was 50 μm (layer structure: surface layer 2.5 μm / intermediate layer 45 μm / surface layer 2.5 μm).

A release agent composed of release agent composition-A shown below was applied to the obtained polyester film by a reverse gravure coating method so that the coating amount (after drying) was 0.1 g / m ² , and the dryer temperature was 120. A release polyester film having a roll peel strength of 21 mN / cm, internal transparency of 96.9%, Ra of 9.5 nm, and MOR_C value of 2.5 was obtained under the conditions of ° C and a line speed of 30 m / min.
<Releasing agent composition-A>
Curable silicone resin (KS-847H: manufactured by Shin-Etsu Chemical) 20 parts Catalyst (PL-50T: manufactured by Shin-Etsu Chemical) 0.3 parts (1.5% by weight)
MEK / toluene mixed solvent (mixing ratio is 1: 1)

  The index of internal transparency newly introduced in the evaluation of the film this time shows a higher correlation with clearness by visual inspection than the internal haze which is a conventional index of transparency.

  For the obtained polyester film, a deflector plate was prepared by the following method, and optical property inspection and peeling properties were evaluated. The obtained release film had good inspection by reflection and good recognition of foreign matter, and the polarizing plate was peeled off cleanly, and the phenomenon that the adhesive adhered to the release layer was not observed.

<Manufacture of polarizing plate with release film>
The acrylic adhesive shown below is applied to the polarizing plate so that the thickness after drying is 25 μm, and after passing through a 130 ° C. drying oven in 30 seconds, the release film is bonded, and the adhesive is interposed. Thus, a polarizing plate with a release film in which the release film and the polarizing film were adhered to each other was prepared. The laminating direction of the film was performed so that the width direction of the release film was parallel to the orientation axis of the polarizing film.
Acrylic adhesive coating solution Acrylic adhesive (Olivein BPS429-4: manufactured by Toyo Ink) 100 parts Curing agent (BPS8515: manufactured by Toyo Ink) 3 parts MEK / toluene mixed solvent (mixing ratio is 1: 1) 50 parts

Examples 2-4:
In Example 1, the polyester film was produced in the same manner as in Example 1 except that the draw ratio at the time of production of the polyester film, the film thickness, the particle-containing polyester type of the surface layer, and the compounding amount of the particle-containing polyester of the surface layer were changed. A film was obtained. The obtained results are summarized in Table 1 below.

Comparative Examples 1-6:
In Example 1, the polyester film was produced in the same manner as in Example 1 except that the draw ratio at the time of production of the polyester film, the film thickness, the particle-containing polyester type of the surface layer, and the compounding amount of the particle-containing polyester of the surface layer were changed. A film was obtained. The results obtained are summarized in Table 2 below.

  The film of the present invention can be suitably used as a release polyether film capable of realizing a high degree of accuracy in an optical inspection method necessary for polarizing plate substrate applications and the like.

Claims (1)

A release film having a silicone release layer on at least one surface, the release film has an internal transparency of 96.5% or more, and the surface roughness (Ra) of the silicone release layer is 9.0 nm. It is above, The MOR value of the said release film is 1.5-3.0, The release polyester film characterized by the above-mentioned.