JP2006051681A - Mold release film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold release film improved in the adhesion of a coating film to a base material, having proper releasability and capable of corresponding to the protection of a pressure-sensitive adhesive layer used at the time of printing of LCD, a green sheet used at the time of production of a ceramic electronic part, the dielectric layer of PDP and the molding of a sheet such as a partition wall or the like. <P>SOLUTION: The mold release film is constituted by providing a mold release layer, which contains a solventless type silicone resin (A) containing an SiO<SB>3/2</SB>structure and a solventless type silicone resin (B) containing no SiO<SB>3/2</SB>structure, on one side of a biaxially stretched polyester film and local sagging is not present substantially. This mold release film simultaneously satisfies the formulae: F300/F30≤2.0 (1) and F<100 (2) [wherein F300, F30 and F are peel strengths (mN/cm) of the surface of the mold release layer and an acrylic pressure-sensitive adhesive tape at peeling speeds of 300, 30 and 0.3 m/min]. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a release film, and more specifically, for protecting a pressure-sensitive adhesive layer or a ceramic multilayer capacitor used in manufacturing a liquid crystal display such as a liquid crystal polarizing plate and a retardation plate (hereinafter sometimes abbreviated as LCD). Mold release suitable for green sheet molding used for manufacturing ceramic electronic parts such as ceramic substrates, and sheet molding for plasma display panel (hereinafter, abbreviated as PDP) dielectric layer or partition wall member molding It relates to film.

  Conventionally, a release film based on a polyester film is used for protecting a pressure-sensitive adhesive layer used in LCD production such as a liquid crystal polarizing plate and a retardation plate, or for ceramic release such as a ceramic multilayer capacitor and a ceramic substrate, and a PDP dielectric. Used for forming layers or partition walls. With respect to the release layer constituting the release film, when a release layer containing a solventless silicone resin is provided on the polyester film, for example, in offline coating, the solventless silicone resin is included in the organic solvent. When the coating liquid is applied onto the polyester film, the solventless silicone resin itself has a low viscosity, so that the wettability with respect to the polyester film is poor and repelling may occur. In addition, the adhesiveness to the base material tends to be poor immediately after processing, and it is difficult to deal with applications that particularly require the adhesiveness. With regard to improvement studies from the release agent side, adhesive agent improvement studies on polyester films have been earnestly studied by release agent manufacturers, and various improvement methods have been proposed, but depending on the application in which the release film is used, It does not reach the required characteristics.

  In PDP, LCD applications, etc., as plasma TVs or liquid crystal TVs become larger, the area of the release film to be used is increased in order to further improve product collection efficiency for the purpose of improving productivity in the manufacturing process. In some cases, a mold release film having a wider film width is required in production. For example, when a release film having a film width of 2 m or more is to be manufactured, it may be difficult to cope with offline coating due to restrictions such as equipment specifications. Also, with the aim of improving productivity at the manufacturing site, with the increase in speed in the manufacturing process, for example, a release film having good peelability (light release) in a high-speed peeling region of 30 m / min or more also in the peeling process. May be required. Therefore, even if a solventless silicone resin is used, there is a need for a release film having good coating film adhesion and moderate release properties, particularly in a high-speed release region of 30 m / min or more. .

  On the other hand, as an example of the sheet forming application, there is a green sheet forming used for a ceramic multilayer capacitor or the like. In this application, as the ceramic multilayer capacitor has been downsized and increased in capacity in recent years, the thickness of the green sheet tends to become thinner and thinner. When a ceramic slurry is applied using a release film having local tarmi, uneven density of the slurry is generated, and a green sheet with a large thickness fluctuation may be obtained after a drying process. Furthermore, when a ceramic multilayer capacitor is manufactured using the green sheet having a large thickness, it is difficult to obtain a high-performance ceramic multilayer capacitor due to a large variation in capacitance in terms of performance. The above-mentioned defects tend to appear more prominently as the green sheet is further thinned. Therefore, even when a solventless silicone resin is used, a release film having good coating film adhesion and moderate release properties, particularly in a high-speed release region of 30 m / min or more, has good release properties and good flatness. is needed.

JP 2003-192987 A JP-A-10-323944

  The present invention has been made in view of the above circumstances, and the problem to be solved is that even when a release layer containing a solvent-free silicone resin is provided on a polyester film, the coating film adhesion to the substrate is good and appropriate. It has excellent releasability, and can be lightly releasable especially in a high-speed releasable area of 30 m / min or more, has good flatness, and is used for protecting the adhesive layer used when manufacturing LCDs such as liquid crystal polarizing plates and retardation plates. Another object of the present invention is to provide an inexpensive release film that can be used for forming a green sheet, a dielectric layer of PDP, or a sheet for forming a partition, such as a ceramic multilayer capacitor or a ceramic substrate.

  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 release film having a specific configuration, and have completed the present invention.

That is, the gist of the present invention, on one side of the biaxially oriented polyester _film, a solvent-free type silicone resin (A), solventless silicone resin not containing _{SiO 3/2} structure including a _{SiO 3/2} structural (B) The release layer containing a release film provided in the production process of the film is substantially free from local tarmi and satisfies the following formulas (1) and (2) simultaneously: It exists in a release film.
F300 / F30 ≦ 2.0 (1)
F ≦ 100 (2)
(In the above formula, F300, F30 and F represent the peeling force (mN / cm) between the release layer surface and the acrylic adhesive tape at peeling rates of 300 m / min, 30 m / min and 0.3 m / min, respectively. )

Hereinafter, the present invention will be described in more detail.
The polyester film constituting the release film in the present invention may have a single-layer structure or a laminated structure. For example, the polyester film may have a four-layer or a three-layer structure as long as the gist of the present invention is not exceeded other than the two-layer or three-layer structure. It may be a multilayer having more than that, and is not particularly limited.

  The polyester used for the polyester film in the present invention may be a homopolyester or a copolyester. In the case of a homopolyester, those obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol are preferred. 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 polyester includes polyethylene terephthalate (PET) and the like. On the other hand, examples of the dicarboxylic acid component of the 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 are mentioned, As a glycol component, 1 type or 2 types or more, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1, 4- cyclohexane dimethanol, neopentyl glycol, is mentioned. In any case, the polyester referred to in the present invention refers to a polyester that is usually 60 mol% or more, preferably 80 mol% or more of polyethylene terephthalate or the like which is an ethylene terephthalate unit.

  In the present invention, it is preferable to blend particles in the polyester layer mainly for the purpose of imparting slipperiness. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and magnesium phosphate. , Particles of kaolin, aluminum oxide, titanium oxide and the like. Further, the heat-resistant organic particles described in JP-B-59-5216, JP-A-59-217755 and the like may be used. Examples of other heat-resistant organic particles include thermosetting urea resins, thermosetting phenol resins, thermosetting epoxy resins, benzoguanamine resins, and the like. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

  On the other hand, the shape of the particles to be used is not particularly limited, and any of a spherical shape, a block shape, a rod shape, a flat shape, and the like may be used. Moreover, there is no restriction | limiting in particular about the hardness, specific gravity, a color, etc. These series of particles may be used in combination of two or more as required.

  Moreover, the average particle diameter of the particle | grains to be used is 0.01-3 micrometers normally, Preferably it is the range of 0.01-1 micrometer. When the average particle diameter is less than 0.01 μm, the particles are likely to aggregate and dispersibility may be insufficient. On the other hand, when the average particle diameter exceeds 3 μm, the surface roughness of the film becomes too rough and There may be a problem when a release layer is applied in the process.

  Furthermore, the particle content in the polyester layer is usually in the range of 0.001 to 5% by weight, preferably 0.005 to 3% by weight. When the particle content is less than 0.001% by weight, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 5% by weight, the transparency of the film is insufficient. There is.

  The method for adding particles to the polyester layer is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage for producing the polyester constituting each layer, but the polycondensation reaction may proceed preferably after the esterification stage or after the transesterification reaction.

  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 blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  In addition to the above-mentioned particles, conventionally known antioxidants, antistatic agents, thermal stabilizers, lubricants, dyes, pigments, and the like can be added to the polyester film in the present invention as necessary.

Although the thickness of the polyester film which comprises the release film of this invention will not be specifically limited if it is a range which can be formed into a film, Usually, 5-250 micrometers, Preferably it is the range of 5-188 micrometers.

Next, although the manufacture example of the polyester film in this invention is demonstrated concretely, it is not limited to the following manufacture examples at all.
First, a method of using the polyester raw material described above and cooling and solidifying a molten sheet extruded from a die with a cooling roll to obtain an unstretched sheet is preferable. In this case, in order to improve the flatness of the sheet, it is necessary to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method and / or a liquid application adhesion method are preferably employed. Next, the obtained unstretched sheet is stretched in the biaxial direction. In that case, first, the unstretched sheet is stretched in one direction by a roll or a tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Subsequently, the extending | stretching temperature orthogonal to the 1st step | paragraph extending | stretching direction is 70-170 degreeC normally, and a draw ratio is 3.0-7 times normally, Preferably it is 3.5-6 times. Subsequently, heat treatment is performed at a temperature of 180 to 270 ° C. under tension or under relaxation within 30% to obtain a biaxially oriented film. In the above-described stretching, a method in which stretching in one direction is performed in two or more stages can be employed. In that case, it is preferable to carry out so that the draw ratios in the two directions finally fall within the above ranges.

  The simultaneous biaxial stretching method can also be adopted for the production of the polyester film in the present invention. The simultaneous biaxial stretching method is a method in which the unstretched sheet is usually stretched and oriented in the machine direction and the width direction at 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is as follows: The area magnification is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times. Subsequently, heat treatment is performed at a temperature of 170 to 250 ° C. under tension or under relaxation within 30% to obtain a stretched oriented film. With respect to the simultaneous biaxial stretching apparatus that employs the above-described stretching method, a conventionally known stretching method such as a screw method, a pantograph method, or a linear driving method can be employed.

  Furthermore, a so-called coating stretching method (in-line coating) in which the film surface is treated during the above-described polyester film stretching step can be applied. When a coating layer is provided on a polyester film by a coating stretching method, coating can be performed simultaneously with stretching and the thickness of the coating layer can be reduced according to the stretching ratio, producing a film suitable as a polyester film. it can.

  In order to improve the film flatness, the release film in the present invention needs to be substantially free from local tarmi. The “local tarmi” in the present invention is synonymous with those specifically described in, for example, Japanese Patent Application Laid-Open Nos. 2004-196856 and 2004-202703, and the depression angle is 45 to 45 under a fluorescent lamp. Talmi whose presence is confirmed locally when the sample film surface is visually observed within the range of 90 degrees is a target (except for hygroscopic tarmi, which will be described later). Or the existence of local tarmi itself becomes a problem rather than the size of the interval between tarmi and tarmi. Among them, the presence of row-like local tarmi is regarded as the most problematic for the use of the present invention. In addition, “substantially free of local tarmi” in the present invention means that the local tarmi is continuously generated from the film end to the center of the film, mainly generated by moisture absorption (hereinafter referred to as moisture absorption). (Sometimes abbreviated as "tarmi"), which does not fall under "local tarmi" and means that it is clearly distinguished.

This is because, in a ceramic release film for forming a green sheet, it is common not to apply ceramic slurry to the end of the film, and therefore, moisture absorption tarmi is not particularly problematic. On the other hand, when the ceramic slurry is applied using a release film in which local tarmi exists, unevenness of the density of the slurry is generated, and after passing through the drying process, a green sheet having a large thickness fluctuation is obtained. Furthermore, when a ceramic multilayer capacitor is manufactured using the green sheet having a large thickness, it is difficult to obtain a high-performance ceramic multilayer capacitor due to a large variation in capacitance in terms of performance. The above-mentioned defects tend to appear more prominently as the green sheet is further thinned. Furthermore, as a specific method for preventing local tarmi from being substantially present in the polyester film itself, in the polyester film manufacturing process, a technique such as increasing the film transverse stretching ratio in the transverse stretching process to 4.8 times or more is exemplified. Is done.

Next, formation of the release layer in the present invention will be described.
The release layer constituting the release film in the present invention needs to be provided on the polyester film in the film production process such as the above-described coating stretching method (in-line coating). Preferably, a coating stretching method (in-line coating) is preferable, but the coating stretching method is not limited to the following, but for example, in the sequential biaxial stretching, the first stage stretching is completed, and the second stage A coating treatment can be performed before stretching. When a release layer is provided on a polyester film by a coating and stretching method, the film can be applied simultaneously with stretching, and the thickness of the release layer can be reduced according to the stretching ratio. Can be manufactured.

As the kind of the solventless silicone resin, any of the curing reaction types such as an addition type, an ultraviolet curing type, and an electron beam curing type can be used.
As specific examples, X-62-1387, KNS-3051, X-62-1496, KNS320A, KNS316, X-62-1574A / B, X-62-7052, X-62-7028A, manufactured by Shin-Etsu Chemical Co., Ltd. / B, X-62-7619, X-62-7213, Toray Dow Corning Silicone (manufactured) SP7259, BY24-468C, SP7248S, BY24-452, SP7268S, SP7265S, LTC1000M, LTC1050L, GE Toshiba Silicone (made) ) TPR6500, TPR6501, UV9300, UV9425, XS56-A2775, XS56-A2982, UV9430, TPR6600, TPR6604, TPR6605 and the like.

  Regarding the viscosity (25 ° C.) of the solventless silicone resin to be used, for example, when considering coating properties by a coating stretching method (in-line coating), 100 to 2000 (cps), preferably 100 to 1000 ( cps) is preferred. When the viscosity of the solventless silicone resin is less than 100 (cps), there may be a problem such as repellency when the polyester film is applied. On the other hand, when the viscosity exceeds 2000 (cps), curability and the like. May become insufficient.

Further, in the release layer, a crosslinking agent may be used in combination as long as the gist of the present invention is not impaired, and specific examples include methylolated or alkylolated urea, melamine, guanamine, acrylamide, Polyamide compounds, epoxy compounds, aziridine compounds,
A block polyisocyanate, a silane coupling agent, a titanium coupling agent, a zirco-aluminate coupling agent, etc. are mentioned. These crosslinking components may be previously bonded to the binder polymer.

  Further, inorganic particles may be contained for the purpose of improving the fixing property and slipperiness of the release layer, and specific examples include silica, alumina, kaolin, calcium carbonate, titanium oxide, barium salt and the like.

Further, an antifoaming agent, a coating property improver, a thickener, an organic lubricant, organic polymer particles, an antioxidant, an ultraviolet absorber, a foaming agent, a dye and the like may be contained as necessary.
In the case of the coating stretching method (in-line coating), a coating solution in which the above-mentioned series of compounds is used as a solvent-free or organic solvent dispersion and the solid content concentration is adjusted to about 1 wt% to 100 wt% as a guide is applied to the polyester film. It is preferable to produce a release film in the manner of application.

  In the range not exceeding the gist of the present invention, the coating solution may contain a small amount of an organic solvent for the purpose of improving the dispersibility of the coating solution and improving the film forming property. Only one type of organic solvent may be used, or two or more types may be used as appropriate.

  In the present invention, conventionally known coating methods such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating and the like can be used as a method for providing a release layer on the polyester film. Regarding the coating method, there is a description example in “Coating method” published by Yasuharu Harasaki in 1979.

In the present invention, the curing conditions for forming the release layer on the polyester film are not particularly limited. For example, when the release layer is provided by a coating stretching method (in-line coating), usually, 170 to The heat treatment may be performed at 280 ° C. for 3 to 40 seconds, preferably 200 to 280 ° C. for 3 to 40 seconds. Moreover, you may use together heat processing and active energy ray irradiation, such as ultraviolet irradiation, as needed. In addition, a conventionally well-known apparatus and an energy source can be used as an energy source for hardening by active energy ray irradiation. The coating amount of the release layer from the viewpoint of coating property, usually 0.01-5 g / ^{m 2,} preferably in the range of 0.01 to 2 g / ^{m 2.} If the coating amount is less than 0.01 g / m ² , the coating property may be less stable and it may be difficult to obtain a uniform coating film. On the other hand, when the coating is thicker than 5 g / m ² , the coating layer adhesion and curability of the release layer itself may be lowered.

  Regarding the release film 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, as long as the gist of the present invention is not exceeded. .

  Further, the polyester film constituting the release film may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

  In the present invention, it is based on the knowledge that it is important to lightly release the peeling force at a high peeling speed of 30 m / min or more in designing a release film. Therefore, in the release film in the present invention, the ratio (F300 / F30) of the peeling force at two different peeling speeds (300 m / min and 30 m / min) is 2.0 or less under a high-speed peeling area of 30 m / min or more. Must be present, preferably 1.5 or less. When F300 / F30 exceeds 2.0, for example, it is difficult to achieve light peeling in a high-speed peeling region of 30 m / min or more.

As a specific method for satisfying the above-mentioned range for the release force of the release film in the present invention, a solvent-free silicone containing a SiO _3/2 structure (hereinafter sometimes abbreviated as T unit) in the release layer. It is necessary to contain a resin (A) and a solventless silicone resin (B) that does not contain a SiO _3/2 structure. The proportion of the solventless silicone resin (A) containing the T unit structure in the release layer is preferably 30% by weight or more, and preferably 50% by weight or more for the purpose of the present invention. When the said range is less than 30 weight%, especially in the high-speed peeling area | region of 30 m / min or more, light peeling may become inadequate and it may become difficult to obtain desired peeling force.

In the release layer constituting the release film in the present invention, by using a solventless silicone resin (A) containing a SiO _3/2 structure, the cross-linking point in the cross-linking reaction at the time of forming the release layer is compared with usual. Therefore, it is possible to further increase the crosslinking density of the obtained release layer itself. As a result, it is possible to achieve light release particularly in a high-speed release region of 30 m / min or more, and it is possible to cope with, for example, an increase in productivity associated with productivity improvement for sheet molding or adhesive layer protection. Further, as an incidental effect of using the solventless silicone resin (A) containing the T unit structure, the coating film adhesion to the polyester film often tends to be good.

  Regarding the release film in the present invention, the release force (F) between the release layer surface and the acrylic adhesive tape at a release rate of 0.3 / min needs to be 100 mN / cm or less, preferably 50 mN / cm or less. Good. When F exceeds 100 mN / cm, for example, in sheet forming applications such as a green sheet, it becomes difficult to peel off the sheet.

  The release film in the present invention can be peeled with an appropriate peelability even in a low speed region near 0.3 m / min by satisfying the additional requirement of F at the same time.

  Furthermore, regarding the release film in the present invention, the peel force (F300) between the release layer surface and the acrylic pressure-sensitive adhesive tape at a peel speed of 300 m / min is preferably 200 mN / cm or less, more preferably 150 mN / cm or less. Good. When F300 exceeds 200 mN / cm, for example, in sheet forming applications such as a green sheet, it may be difficult to remove at the time of sheet peeling.

  The release film according to the present invention satisfies the additional requirement of the above-mentioned peeling force F300 at the same time, and at the manufacturing site, by speeding up with productivity improvement, especially in a high-speed peeling area of 30 m / min or more, further light peeling. Is possible.

  Regarding the release film in the present invention, the residual adhesion rate of the release layer is preferably 90% or more, more preferably 95% or more, in order to suppress the migration or transfer of the release component to the surface of the mating base material to be bonded. Good. When the residual adhesive rate is less than 90%, the amount of the release component transferred to the surface of the counterpart substrate that comes into contact with the release surface of the release film increases. For example, the adhesive strength between sheets decreases when the green sheets are laminated, or the pressure-sensitive adhesive. In layer protection applications, problems such as a decrease in adhesive strength may occur.

  Moreover, regarding the release film in the present invention, the peel force (F) between the release layer surface and the acrylic pressure-sensitive adhesive tape under a peel speed of 0.3 m / min needs to be 100 mN / cm or less, preferably 80 mN. / Cm or less is preferable. When F exceeds 100 mN / cm, for example, in a green sheet forming application, it becomes difficult to peel off when the green sheet is peeled off.

  According to the release film of the present invention, the coating film adhesion to the substrate is good and has an appropriate release property, and in particular, a light release can be achieved in a high-speed release region of 30 m / min or more, and the release surface is flat. Green sheets used for protecting adhesive layers such as liquid crystal polarizing plates and retardation plates, or ceramic electronic components such as ceramic multilayer capacitors and ceramic substrates, dielectric layers for plasma display panels, and sheets for forming partition walls A release film that can be used for molding can be provided at low cost, and the industrial value of the present invention is high.

  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 measuring method used in the present invention is 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 diameter (d ₅₀ : μm) Integration (weight basis) 50% in equivalent spherical distribution measured using centrifugal sedimentation type particle size distribution measuring device (SA-CP3 type manufactured by Shimadzu Corporation) Was the average particle size.

(3) Evaluation of release film release force (F) After applying 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 Then, the peel strength after standing at room temperature for 1 hour 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 a tensile speed of 300 mm / min.

(4) Evaluation of release film release force (F30, F300) After sticking an adhesive tape (“No. 31B” manufactured by Nitto Denko) on the surface of the release layer of the sample film, it was cut into a size of 50 mm × 300 mm, The peel force after standing for 1 hour at room temperature was measured. The peeling force was measured using a tester industry (manufactured by) high-speed peeling tester “TE-702 type”, fixed so that the release surface of the sample film became the upper surface, and bonded to the other party No. In the method of peeling the 31B adhesive tape side, 180 ° peeling was performed under the conditions of peeling speeds of 30 m / min and 300 m / min, respectively.

(5) Application amount measurement of mold release layer Mold release under the following measurement conditions by FP (Fundamental Parameter Method) method using a fluorescent X-ray measurement apparatus (Shimadzu Corporation, model “XRF-1500”). The amount of silicon element on the surface provided with the release layer and the surface without the release layer of the film was measured, and the difference was taken as the amount of silicon element in the release layer.
Next, the coating amount (Si) (g / m ² ) as a unit of —SiO (CH ₃ ) ₂ was calculated using the obtained amount of silicon element.
"Measurement condition"
Spectral crystal: PET (pentaerythritol)
2θ: 108.88 °
Tube current: 95 mA
Tube voltage: 40 kv

(6) Practical property substitution evaluation The sample film was bonded to a polarizing plate with a pressure-sensitive adhesive layer (thickness 25 μm) (“NPF-F1205DU” manufactured by Nitto Denko), then left at room temperature for 1 hour, and then slowly peeled off (0.3 m). / Min) and high-speed peeling (30 m / min) were evaluated for peelability, and the following judgment criteria were used.
<Criteria>
○… Peelable (practically no problem)
×: Difficult to peel off (Practical problem level)

(7) Local tarmi evaluation in release film (film flatness evaluation)
A sample film cut in advance to a width of 200 mm and a length of 1 m from a release film roll having a width of 1000 mm is placed on a cutting mat made of an olefin resin (in the case of a single-side coated product, the coated surface is the upper surface), and the sample film surface Handle the film until local tarmi is virtually unnoticeable with a rubber roller. After standing in this state for 5 minutes, the flatness of the sample film is visually observed under a fluorescent lamp, and appears as a result of occurrence of local talmi in the sample film. The presence or absence of a portion (local tarmi portion) was determined according to the following criteria. In this evaluation, a film in which talmi is continuously generated from the film end toward the center of the film is defined as “hygroscopic talmi” and excluded from local talmi.
<Criteria>
○: Local tarmi is substantially absent and flatness is good. ×: Local tarmi is clearly observed and flatness is poor. Also, “the absence of local tarmi is substantially absent” means that the depression angle is 45 to 90 degrees. When the sample film surface is visually observed within the range, the clear local tarmi is not observed.

The polyester used in the examples and comparative examples was prepared as follows.
<Manufacture of polyester>
Production Example 1 (Polyethylene terephthalate A1)
100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate are placed in a reactor, the temperature is raised by heating, methanol is distilled off, transesterification is performed, and 4 hours are required from the start of the reaction. The temperature was raised to 230 ° C. to substantially complete the transesterification reaction. Next, 0.04 part of ethylene glycol slurry ethyl acid phosphate, 0.03 part of antimony trioxide and 0.05 part of silica particles having an average particle size of 1.5 μm were added, and then the temperature was 280 ° C. and the pressure was increased in 100 minutes. The pressure reached 15 mmHg, and the pressure was gradually reduced thereafter to finally reach 0.3 mmHg. After 4 hours, the system was returned to atmospheric pressure to obtain polyethylene terephthalate A1 having an intrinsic viscosity of 0.61.

The polyethylene terephthalate A1 produced in Production Example 1 was dried at 180 ° C. for 4 hours in an inert gas atmosphere, melted at 290 ° C. by a melt extruder, extruded from a die, and the surface temperature was adjusted to 40 using an electrostatic application adhesion method. The sheet was cooled and solidified on a cooling roll set to ° C. to obtain an unstretched sheet. First, the unstretched sheet obtained was stretched 3.6 times in the MD direction at 95 ° C., and the following release agent was applied by a reverse gravure coating method, then guided to a tenter and 5.0 times in the TD direction. Were sequentially biaxially stretched. Thereafter, it was heat-set at 230 ° C. for 3 seconds to obtain a PET film having a thickness of 38 μm provided with a release layer having a coating amount (after drying) of 0.2 g / m ² .

Examples of compounds constituting the release layer are as follows.
(Compound example)
Solvent-free silicone resin containing SiO _3/2 structure (A): X-62-1387: manufactured by Shin-Etsu Chemical Solvent-free silicone resin not containing SiO _3/2 structure (B): KNS320A: manufactured by Shin-Etsu Chemical Curing agent ( C): PL-56: manufactured by Shin-Etsu Chemical

<Releasing agent composition>
Solvent-free silicone resin containing SiO _3/2 structure (A): 50% by weight
Solvent-free silicone resin (B) containing no SiO _3/2 structure: 49% by weight
Curing agent (C): 1% by weight

(Example 2 to Example 3) and (Comparative Example 1 to Comparative Example 2)
In Example 1, a release film was obtained in the same manner as in Example 1 except that the release agent composition was changed to the release agent composition shown in Table 1 below.

(Comparative Example 3)
In Example 1, a release film was obtained in the same manner as in Example 1 except that the stretch ratio in the TD direction was changed to 3.4 times when the polyester film was produced.
Table 1 shows the properties of the release films obtained in the above Examples and Comparative Examples.

  The film of the present invention is a green sheet, a PDP dielectric layer or a PDP for protecting an adhesive layer used at the time of manufacturing an LCD such as a liquid crystal polarizing plate and a retardation plate, or at the time of manufacturing a ceramic electronic component such as a ceramic multilayer capacitor and a ceramic substrate. It can be suitably used as a release film that can be used for sheet molding such as partition wall molding.

Claims (1)

On one side of the biaxially oriented polyester film, a solventless type silicone resin (A) and release layer containing a solventless type silicone resin containing no SiO _3/2 structure (B) is the containing SiO _3/2 structure A release film provided in the film production process, which is substantially free of local tarmi and satisfies the following formulas (1) and (2) simultaneously.
F300 / F30 ≦ 2.0 (1)
F ≦ 100 (2)
(In the above formula, F300, F30 and F represent the peeling force (mN / cm) between the release layer surface and the acrylic adhesive tape at peeling rates of 300 m / min, 30 m / min and 0.3 m / min, respectively. )