JP5500846B2 - Protective film - Google Patents

Description

  The present invention relates to a protective film, and more specifically, for example, an optical application using glass as a main component of a display member such as a liquid crystal display (hereinafter abbreviated as LCD), a plasma display (hereinafter abbreviated as PDP), and the like. It relates to a protective film used for protecting the glass surface.

  The main part of the LCD is called a liquid crystal cell. The liquid crystal cell has a structure in which two glass plates are used, and a liquid crystal, an alignment film, a spacer, and the like are arranged in the gap between them. The surface in contact with the outside is a glass surface. A polarizing plate is installed on both sides of the liquid crystal cell via an adhesive to become a final product incorporated in the liquid crystal module. This is called a liquid crystal panel. Usually, the manufacturer of the liquid crystal cell and the manufacturer of the polarizing plate are different manufacturers, and the liquid crystal cell and the polarizing plate are bonded together by a liquid crystal module assembly manufacturer to form a liquid crystal panel.

  In recent years, LCD TVs have become larger in screen size, and liquid crystal cells have become larger accordingly. If the glass surface, which is the surface of the liquid crystal cell, is scratched, the liquid crystal cell cannot be used, greatly affecting the production yield. Conventionally, for transporting the liquid crystal cell, only a special box designed to prevent the glass surface of the liquid crystal cell from contacting is used, and no protective film or the like has been installed. However, as described above, since the loss of one liquid crystal cell has a great influence on the production yield, it has recently been studied to attach a protective film for protecting the glass surface of the liquid crystal cell. Yes.

  The protective film that protects the glass surface is typically polyethylene film with slight adhesiveness used for window glass, etc., but since these films are not produced for optical use, There is much mixing. If the foreign matter remains on the surface of the liquid crystal cell, it becomes a bright spot when the final product LCD is formed, and therefore, it is not preferable to use a polyethylene film or the like.

  The liquid crystal panel has a configuration in which polarizing plates are bonded to both surfaces of a liquid crystal cell. A polyester film coated with an adhesive is used as a protective film for protecting the surface of the polarizing plate. Polyester films represented by polyethylene terephthalate and polyethylene naphthalate have excellent mechanical strength, dimensional stability, flatness, heat resistance, chemical resistance, optical properties, etc., and excellent cost performance. The polyester film coated with the agent has a high unit price and is not suitable for use as a protective film that only serves as a process paper for protecting the surface of the liquid crystal cell.

  By the way, with regard to the mixing of foreign matter, the release film used to protect the adhesive of the polarizing plate to be bonded to the liquid crystal panel has a track record that there are few foreign matters at a level that does not pose a problem in the production yield of the liquid crystal panel. Have. The release film is often a film having a structure in which silicone is applied as a release layer on one side of a polyester film. In addition, since only silicone is applied, cost performance is superior to a protective film in which an adhesive is applied to a polyester film. However, since it is a release film, it has no adhesion to glass and cannot be used as a protective film for liquid crystal cells.

  As a film that protects the glass surface of the liquid crystal cell, there is little risk of contamination and less burden on the manufacturing cost of the liquid crystal panel. The Conventionally, such a protective film did not exist.

JP 2003-334911 A

  The present invention has been made in view of the above-mentioned circumstances, and the solution to the problem is that the production yield of the liquid crystal panel is not deteriorated with respect to the mixing of foreign matter, the load on the cost is small, and the glass surface of the liquid crystal cell. An object of the present invention is to provide a protective film that is in close contact with and easily peeled off.

  As a result of intensive studies in view of the above problems, the present inventor has found that the above problems can be easily solved by a film having a specific configuration, and has completed the present invention.

That is, the gist of the present invention is a polyester film having a coating layer containing a silane alkoxy oligomer on one side and a silicone coating layer having a coating amount of 0.1 to 0.5 g / m ^{2 on} the coating layer. In the glass surface protective film, the following formula is satisfied.

−Rmax ÷ 3 ≦ ds−Rmax ≦ 1.5 × Rmax
(In the above formula, Rmax means the maximum height of the polyester film surface (μm), ds means the thickness of the silicone coating layer (μm))

Hereinafter, the present invention will be described in detail.
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.

  The dicarboxylic acid component of the copolymerized polyester is selected from isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid and oxycarboxylic acid (for example, P-oxybenzoic acid). The 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 content of the film layer to which these particles are added is usually 1% by weight or less, preferably 0.01 to 1% by weight, and more preferably 0.02 to 0.6% by weight. When the content of the particles is small, the film surface is flattened, and in the film production process, the surface is liable to be scratched or the winding properties tend to be 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 in the polyester film is usually 0.02 to 5 μm, preferably 0.1 to 3 μm, more preferably 0.2 to 1.8 μm. When the particle size is less than 0.2 μm, the film surface is flattened and the winding properties in the film production process tend to be inferior. When the particle diameter exceeds 5 μm, when used as a polarizing plate release film, it may become a bright spot and hinder foreign matter inspection.

  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.

  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 used in the present invention may be obtained by forming a chip after melt polymerization and subjecting it to further 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 preferably 0.40 to 0.90 dl / g.

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

  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 100 μm, preferably 9 to 50 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, this invention 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 transesterification of dimethyl terephthalate and ethylene glycol is carried out, the product is transferred to a polymerization tank, the temperature is increased while reducing the pressure, and finally vacuum is applied. Under heating to 280 ° C., the polymerization reaction proceeds to obtain a polyester.

  The intrinsic viscosity of the polyester used in the present invention is usually in the range of 0.40 to 0.90, preferably 0.45 to 0.80, more preferably 0.50 to 0.70. When the intrinsic viscosity is less than 0.40, the mechanical strength of the film tends to be weakened. When the intrinsic viscosity is more than 0.90, the melt viscosity becomes high, the load on the extruder is increased, and the production cost is increased. Problems may occur.

  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 a die and rapidly cooled and solidified on a rotary cooling drum so that the temperature is 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 and / or solvent-based for off-line coating, but is preferably water-based or water-dispersed for in-line coating.

  The protective film in the present invention may be coated with a silane alkoxy oligomer as a coating layer in order to improve the coating film adhesion between the silicone layer and the polyester film.

  The silane alkoxy oligomer is represented by the following average composition formula (1), and examples thereof include those described in JP-A No. 2002-88155 and JP-A No. 2005-8755.

_{^{R k R 1 m Si (OR}} 2) n O (4-k-m-n) / 2 ... (1)
(In the above formula, R is one or more groups selected from unsubstituted or substituted alkyl groups and aryl groups, R ¹ is an aliphatic unsaturated double bond-containing group, and R ² is a group having 1 to ² carbon atoms. Represents an alkyl group having 3 carbon atoms, an acyl group having 2 or 3 carbon atoms, or an alkoxyalkyl group having 3 to 5 carbon atoms, and k, m, and n are numbers that simultaneously satisfy the following relational expression: 0 ≦ k <1 .5, 0.01 ≦ m ≦ 1, 0.5 ≦ k + m ≦ 1.8, 0.01 ≦ n ≦ 2.5, 1 ≦ k + m + n ≦ 3)

  Specific examples of R include an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group and a decyl group, a cycloalkyl group such as a cyclohexyl group, an alkenyl group such as a vinyl group and an allyl group, An aryl group such as a phenyl group or a tolyl group, or a cyanoethyl group substituted with a cyano group, such as a chloromethyl group, a chloropropyl group, or a trifluoropropyl group, wherein some or all of the hydrogen atoms of these groups are substituted with halogen atoms, etc. Glycidoxypropyl group substituted with epoxy group, epoxycyclohexylethyl group, etc., methacryloxypropyl group substituted with (meth) acrylic group, acryloxypropyl group, etc., aminopropyl group substituted with amino group, aminoethylaminopropyl Examples include mercaptopropyl groups substituted with mercapto groups, etc.

Specific examples of R ¹ include an aliphatic group such as a vinyl group, an allyl group, an isopropenyl group, a 1-butenyl group, a 2-butenyl group, and a 3-butenyl group, a 2-cyclohexylenyl group, a 3-cyclohexylenyl group, Substituents such as alicyclic systems such as 2-vinylcyclohexenyl groups, aromatic systems such as 2-vinylphenyl groups, 3-vinylphenyl groups and 2-allylphenyl groups, and 3- (meth) acryloxypropyl groups It contains.

Specific examples of R ² include an alkyl group selected from a methyl group, an ethyl group, a propyl group, and an isopropyl group, an acyl group such as an acetyl group, a methoxyethyl group, an ethoxyethyl group, a propoxyethyl group, a methoxypropyl group, and an ethoxy group. Examples include alkoxyalkyl groups such as propyl group.

  Examples of commercially available products include KR-401N, X-40-9227, X-40-9247, KR-510, KR-9218, KR-213, KR-217, X-41-1053, manufactured by Shin-Etsu Chemical Co., Ltd. -40-1056, X-41-1805, X-41-1810, X-40-2651, X-40-2652B, X-40-2655A, X-40-2761, X-40-2672, and the like. .

  The organic solvent used in forming the coating layer in the present invention is not particularly limited, and a conventionally known organic solvent such as toluene, methyl ethyl ketone, ethyl acetate, hexane, methyl isobutyl ketone, 2-propanol, etc. is used. be able to. Only one type of organic solvent may be used, or two or more types may be used as appropriate.

  In the coating layer, a crosslinking agent (C) may be used in combination as long as the gist of the present invention is not impaired. Specific examples include methylolated or alkylolated urea, melamine, guanamine, and acrylamide. System, polyamide compound, epoxy compound, aziridine compound, block polyisocyanate, silane coupling agent, titanium coupling agent, zirco-aluminate coupling agent and the like.

  Further, inorganic particles (D) may be contained for the purpose of improving the adhesion and slipperiness of the coating layer, and specific examples include silica, alumina, kaolin, calcium carbonate, titanium oxide, barium salt and the like.

  Moreover, an antifoamer, a coating property improving agent, a thickener, an organic lubricant, organic polymer particles, an antioxidant, a UV absorber foaming agent, a dye, and the like may be contained as necessary.

The coating amount of the polyester film on the coating layer provided for forming the protective film of the present invention (after drying) is generally 0.005~1g / ^{m 2,} preferably in the range of 0.005 to 0.5 / ^{m 2} is there. When the coating amount is less than 0.005 g / m ² , the uniformity of the coating thickness may be insufficient, and the adhesion of the release layer may not be sufficient. On the other hand, when the coating is applied in excess of 1 g / m ² , problems such as a decrease in slipperiness may occur.

  In the present invention, the curing conditions for forming the coating layer on the polyester film are not particularly limited. For example, when the coating layer is provided by off-line coating, usually at 80 to 200 ° C. for 3 to 40 seconds, The heat treatment is preferably performed at 120 to 180 ° C. for 3 to 40 seconds as a guide.

  Moreover, you may use together heat processing and active energy ray irradiation, such as ultraviolet irradiation, as needed.

Next, formation of the silicone layer in the present invention will be described.
The silicone layer constituting the protective film in the present invention preferably employs a so-called off-line coating that is applied outside the system on a once produced film.

  Moreover, it is preferable that the silicone layer which comprises the protective film in this invention contains a curable silicone resin. 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 curable type, an electron beam curable type, and a solventless type can be used. Specific examples include KS-774, KS-775, KS-778, KS-779H, KS-847H, KS-856, X-62-2422, X-62-2461, X manufactured by Shin-Etsu Chemical Co., Ltd. -62-1387, KNS-3051, X-62-1496, KNS320A, KNS316, X-62-1574A / B, X-62-7052, X-62-7028A / B, X-62-7619, X-62 -7213, GE Toshiba Silicones Co., Ltd. YSR-3022, TPR-6700, TPR-6720, TPR-6721, TPR6500, TPR6501, UV9300, UV9425, XS56-A2775, XS56-A2982, UV9430, TPR6600, TPR6604, TPR6605, SM3200, SM3030, Toray Da DKQ3-202, DKQ3-203, DKQ3-204, DKQ3-205, DKQ3-210, SRX357, SRX211, SD7220, LTC750A, LTC760A, SP7259, BY24-468C, SP7248S, BY24-452, SP7265S, SP7265S , LTC1000M, LTC1050L, SYLOFF7900, SYLOFF7198, SYLOFF22A, and the like. Further, a release control agent may be used in combination to adjust the peelability of the silicone layer.

  In the present invention, the curing conditions for forming the silicone layer on the polyester film are not particularly limited. For example, when the silicone layer is provided by off-line coating, usually at 80 to 200 ° C. for 3 to 40 seconds, The heat treatment is preferably performed at 100 to 180 ° C. for 3 to 40 seconds as a guide. 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 energy source can be used as an energy source for hardening by active energy ray irradiation.

  In the present invention, when the silicone layer is provided on the coating layer, the silicone layer may be continuously provided on the coating layer after the coating layer is provided. Providing the coating layer and the silicone layer sequentially and continuously is preferable because the production amount per unit time increases.

  In the present invention, there are conventionally known coating methods such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, etc. as a method for providing a coating layer and a silicone layer on a polyester film. An appropriate coating method may be used.

The relationship between the surface roughness of the base film on the silicone-coated surface of the protective film of the present invention and the thickness of the silicone coat needs to satisfy the following formula (1), and preferably satisfies the following formula (2).
−Rmax ÷ 2 ≦ ds−Rmax ≦ 2 × Rmax (1)
−Rmax / 3 ≦ ds−Rmax ≦ 1.5 × Rmax (2)
(In the above formula, Rmax means the maximum height of the polyester film surface (μm), ds means the thickness of the silicone coating layer (μm))

  If the value obtained by subtracting the maximum height (Rmax) of the surface roughness of the base film from the thickness (ds) of the silicone coating layer is a negative value, and the absolute value is larger than half of the maximum height (Rmax), the peelability However, there is a problem that the adhesion to the glass is lost. On the other hand, when the value obtained by subtracting the maximum height (Rmax) of the surface roughness of the base film from the thickness (ds) of the silicone coating layer is a plus value, and is twice the maximum height (Rmax), the peelability Although there is no problem in adhesion, blocking occurs when the protective film is stored in a roll, which causes a problem.

The coating amount of the silicone coating layer of the present invention is usually in the range of 0.05 to 1 g / m ² , preferably 0.1 to 0.5 g / m ² . When the coating amount is less than 0.05 g / m ² , a special polyester film must be used to bring the relationship between the surface roughness of the silicone coat surface and the thickness of the silicone coat into the required range. Is not preferable. On the other hand, when thick coating is performed exceeding 1 g / m ² , coating film adhesion, curability and the like of the silicone layer itself may be lowered.

  Regarding the protective 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 silicone layer is not provided as long as the gist of the present invention is not impaired.

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

  According to the present invention, the production yield of the liquid crystal panel is not deteriorated from the current state with respect to the mixing of foreign matters, the load on the cost is small, and the liquid crystal cell can be easily peeled in close contact with the glass surface. A protective film can be provided, and the industrial value is much higher.

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 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) Application amount of silicone layer Using a fluorescent X-ray measurement apparatus (Shimadzu Corporation model “XRF-1500”) by the FP (Fundamental Parameter Method) method under the following measurement conditions, The amount of silicon element on the surface provided with the release layer and the surface without the release layer was measured, and the difference was taken as the amount of silicon element in the release layer.

Next, using the amount of silicon element obtained, the coating amount (Si) (g / m ² ) as a unit of —SiO (CH ₃ ) ² was calculated and divided by the specific gravity (0.95) of silicone rubber. The coat thickness (nm) was determined.

"Measurement condition"
Spectral crystal: PET (pentaerythritol)
2θ: 108.88 °
Tube current: 95 mA
Tube voltage: 40 kv

(4) Adhesiveness of protective film to glass The silicone coated surface of the protective film is placed on the glass surface used for the LCD panel, and a test piece is collected with a rubber roller. The test piece is set up vertically and allowed to stand in a room controlled at constant temperature and humidity for 24 hours to observe whether the protective film is peeled off from the glass surface. When peeling is recognized, it is considered as defective.

  Next, in a sample having good adhesion, it is observed whether or not the protective film is peeled off by lightly tapping 10 times by hand from the glass surface side. When it does not peel off, the adhesion is very good.

(5) Measurement of the number of foreign objects The protective film is halogen-light-projected in a blackout room installed in a clean room with a clean degree of 100 class, and a visual inspection is performed for 10 m ^2. Is measured using an optical microscope, and the number of foreign matters is counted visually. A case where the number of foreign matters having a major axis of 100 μm or more is 10 or less is judged as ◯, and a case where the number exceeds 10 is judged as ×.

(6) Adhesion between silicone and PET After coating the protective film with silicone, the coated surface is rubbed with a finger. The case where the coating layer does not fall off even after rubbing 10 times is marked as ○, and the case where the coating layer does not fall off even after rubbing is marked as ◎.

(7) Blocking of protective film Two protective films are superposed on the silicone-coated surface of the protective film so that the PET surface of the protective film is in contact with the film, and it is used for 2 hours at 60 ° C. and 1 MPa using a hydraulic hot press. After pressing, it is left at room temperature for 1 hour to obtain a test piece. When peeling off the protective film of the obtained test piece by hand, especially when it is peeled without feeling abnormal noise or abnormality, ◎ when peeling off even while generating abnormal noise, the film will adhere When the film is peeled off, an abnormal sound is generated and the film cannot be peeled off stably.

The polyester used in the examples and comparative examples was prepared as follows.
<Manufacture of polyester (A)>
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 0.63 due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure to obtain a polyester chip (A). The intrinsic viscosity of this polyester was 0.63.

<Manufacture of polyester (B)>
In the method for producing polyester (A), after adding ethyl acid phosphate, an ethylene glycol slurry of synthetic calcium carbonate particles having an average particle diameter of 0.7 μm was added so that the content of the particles with respect to polyester was 1% by weight. Obtained polyester (B) using the method similar to the manufacturing method of polyester (A). The obtained polyester (B) had an intrinsic viscosity of 0.63.

<Manufacture of polyester (C)>
In the method for producing polyester (A), after adding ethyl acid phosphate, an ethylene glycol slurry of synthetic calcium carbonate particles having an average particle size of 1.5 μm was added so that the content of the particles with respect to polyester was 1% by weight. Obtained polyester (C) using the method similar to the manufacturing method of polyester (A). The obtained polyester (C) had an intrinsic viscosity of 0.63.

<Manufacture of base film (I)>
The mixed raw materials obtained by mixing the polyester (A) chips and the polyester (B) chips in the proportions shown in Table 1 are used as raw materials for the outermost layer (surface layer) and the intermediate layer, and are respectively supplied to two extruders. After melt extrusion at 290 ° C., an unstretched sheet was obtained by cooling and solidifying on a cooling roll having a surface temperature set to 40 ° C. using an electrostatic application adhesion method. Next, the film was stretched 2.8 times in the longitudinal direction at 100 ° C., then subjected to a preheating step in the tenter and subjected to transverse stretching of 4.9 times at 120 ° C., followed by heat treatment at 190 ° C. for 10 seconds, A polyester film was obtained by applying 10% relaxation in the width direction at 180 ° C. The total thickness of the obtained film was 40 μm, and the thickness of each layer was 4 μm / 32 μm / 4 μm.

<Manufacture of base film (II)>
A mixed raw material obtained by mixing the polyester (A) chip and the polyester (C) chip at a ratio shown in Table 1 is used as a raw material for the outermost layer (surface layer) and the intermediate layer, and is supplied to two extruders. Otherwise, a polyester film was obtained in the same manner as in the production method of the base film (I).
<Manufacture of base film (III)>
A polyester film was obtained in the same manner as in the production method of the base film (I) except that the above-mentioned polyester (A) chip was used as a raw material for the outermost layer (surface layer) and the intermediate layer and supplied to two extruders.

Comparative Example 1 :
A silicone liquid having the following composition is applied to the base film (I) by a rod coater method so that the coating amount (after drying) is 260 nm, and dried and cured under the conditions of 120 ° C. and 50 m / min to obtain a protective film. It was.
<< Silicone liquid composition >>
Curable silicone resin (KS-847H: manufactured by Shin-Etsu Chemical): 99% by weight
Curing agent (PL-50T: manufactured by Shin-Etsu Chemical): 1% by weight
The release agent was diluted with a MEK / toluene mixed solvent (mixing ratio was 1: 1) to prepare a coating solution having a concentration of 4% by weight.

Comparative Example 2 :
A protective film was obtained in the same manner as in Comparative Example 1 except that the silicone liquid was applied to the base film (II).

Comparative Example 3 :
A silicone liquid having the following composition was applied to the base film (III) by a rod coater so that the coating amount (after drying) was 130 nm, and dried and cured at 120 ° C. and 50 m / min to obtain a protective film. .
<< Silicone liquid composition >>
Curable silicone resin (KS-847H: manufactured by Shin-Etsu Chemical): 99% by weight
Curing agent (PL-50T: manufactured by Shin-Etsu Chemical): 1% by weight
The release agent was diluted with a MEK / toluene mixed solvent (mixing ratio was 1: 1) to prepare a coating solution having a concentration of 2% by weight.

Comparative Example 4 :
A protective film was obtained in the same manner as in Comparative Example 3 except that a silicone liquid having the following composition was applied to the base film (III) by a rod coater method so that the coating amount (after drying) was 180 nm.

Comparative Example 5 :
The following coating agent is applied to the base film (I) by a rod coater method so that the coating amount (after drying) is 0.05 g / m ² , and then dried and cured at 100 ° C. and a line speed of 50 m / min. It was.

Examples of compounds constituting the coating layer are as follows.
(Example compounds)
Zirconium chelate compound (A1): zirconium tris (acetylacetonate)
Silane alkoxy oligomer (B1): X-41-1056 (manufactured by Shin-Etsu Chemical)
<< Coating composition >>
Zirconium chelate compound (A1): 2% by weight
Silane alkoxy oligomer (B1): 98% by weight
The coating agent was diluted with a toluene / MEK mixed solvent (mixing ratio was 1: 1) to prepare a coating solution having a concentration of 1% by weight.

Next, a silicone liquid having the following composition is applied on the coating layer by a rod coater method so that the coating amount (after drying) is 260 nm, and dried and cured under the conditions of 120 ° C. and 50 m / min. Obtained.
<Releasing agent composition>
Curable silicone resin (KS-847H: manufactured by Shin-Etsu Chemical): 99% by weight
Curing agent (PL-50T: manufactured by Shin-Etsu Chemical): 1% by weight
The release agent was diluted with a MEK / toluene mixed solvent (mixing ratio was 1: 1) to prepare a coating solution having a concentration of 4% by weight.

Example 1 :
The following coating agent is applied to the base film (III) by a rod coater method so that the coating amount (after drying) is 0.05 g / m ² , and then dried and cured at 100 ° C. and a line speed of 50 m / min. It was.

Examples of compounds constituting the coating layer are as follows.
(Example compounds)
Zirconium chelate compound (A1): zirconium tris (acetylacetonate)
Silane alkoxy oligomer (B1): X-41-1056 (manufactured by Shin-Etsu Chemical)
<< Coating composition >>
Zirconium chelate compound (A1): 2% by weight
Silane alkoxy oligomer (B1): 98% by weight
The coating agent was diluted with a toluene / MEK mixed solvent (mixing ratio was 1: 1) to prepare a coating solution having a concentration of 1% by weight.

Next, a silicone liquid having the following composition is applied onto the coating layer by a rod coater method so that the coating amount (after drying) is 130 nm, and dried and cured under the conditions of 120 ° C. and 50 m / min. Obtained.
<Releasing agent composition>
Curable silicone resin (KS-847H: manufactured by Shin-Etsu Chemical): 99% by weight
Curing agent (PL-50T: manufactured by Shin-Etsu Chemical): 1% by weight
The release agent was diluted with a MEK / toluene mixed solvent (mixing ratio was 1: 1) to prepare a coating solution having a concentration of 2% by weight.

Comparative Example 6 :
A protective film was obtained in the same manner as in Comparative Example 1 except that the coating layer was provided so that the coating amount (after drying) of the silicone liquid in Comparative Example 1 was 130 nm.

Comparative Example 7 :
A protective film was obtained in the same manner as in Comparative Example 1 except that the base film was changed to the base film (III) in Comparative Example 1.

Comparative Example 8 :
A commercially available polyethylene slightly adhesive protective film was used. The number of foreign objects was large, and it was judged inappropriate for this application.

  The characteristics of the release films obtained in the above examples and comparative examples are summarized in Tables 2 and 3 below.

  The protective film of the present invention can be suitably used as, for example, a protective film that can be easily peeled while being in close contact with the glass surface of a liquid crystal cell.

Claims (1)

A polyester film having a coating layer containing a silane alkoxy oligomer on one side and a silicone coating layer having a coating amount of 0.1 to 0.5 g / m ^{2 on} the coating layer, and satisfying the following formula: A glass surface protective film characterized by that.
−Rmax ÷ 3 ≦ ds−Rmax ≦ 1.5 × Rmax
(In the above formula, Rmax means the maximum height of the polyester film surface (μm), ds means the thickness of the silicone coating layer (μm))