JP2011173415A - Method of manufacturing surface protective film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a surface protective film that is slightly adhesive on one surface, in which blocking hardly occurs and fish eyes can be reduced. <P>SOLUTION: This method of manufacturing the surface protective film includes a step of, when pinching a thermoplastic resin molten film by a metal cooling roll and an elastic roll, the metal cooling roll satisfying the conditions that (1) the surface roughness is 2.0 μm or more and (2) the surface temperature is between a temperature at which water vapor is condensed +1°C or more and a crystallization temperature of the thermoplastic resin -40°C or less, and the elastic roll satisfying the conditions that (3) the surface is made of metal and is a mirror surface, (4) the surface temperature is between a temperature at which water vapor is condensed +1°C or more and a crystallization temperature of the thermoplastic resin -50°C or less, and (5) the surface length is smaller than that of the metal cooling roll, adjusting the width of a portion of the thermoplastic resin molten film to be pinched to be smaller than the surface length of the metal cooling roll and larger than the surface length of the elastic roll and pinching the film. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention provides a method for producing a surface protective film that has slight adhesiveness on one side of a film, is difficult to block when the film is rolled up or stacked, and can reduce fish eyes of the film. It is about.

  If the film has many defects called so-called fish eyes, it may cause problems such as deterioration of appearance and printing omission at the time of printing. In particular, a resin film, a resin plate, a metal plate (hereinafter referred to as “attachment”) In order to protect the surface, the surface protection film bonded to these surfaces may have a dent on the adherend, or may be erroneously detected during foreign matter inspection of the adherend. Reduction was demanded.

  As a method for reducing such fish eyes, for example, Patent Document 1 discloses that when an amorphous thermoplastic resin film extruded in a sheet form from a die attached to an extruder is brought into close contact with a cooling roll, the surface roughness is reduced. A method for producing an optical film is described in which pressing is performed between an elastically deformable touch roll having a thickness Ry of 0.5 μm or less and a rigid cooling roll. Further, in Patent Document 2, a melted transparent resin is sandwiched between a first cooling roll made of a rubber roll or a metal elastic roll and a second cooling roll made of a metal roll having an uneven shape formed on the outer peripheral surface, thereby forming an uneven shape. Describes a method for producing a resin film having a formed thereon.

JP 2004-330651 A JP 2009-202382 A

However, the methods described in Patent Document 1 and Patent Document 2 described above are methods for producing a film suitable for optical applications, and the adhesiveness and antiblocking properties required as a surface protective film are not disclosed.
Under such circumstances, it is an object of the present invention to have slight adhesiveness on one side of a film, to prevent blocking when the film is rolled up or stacked, and to reduce fish eyes of the film. It is in providing the manufacturing method of the surface protection film which can do.

As a result of intensive studies, the inventor has found that the present invention can solve the above-described problems, and has completed the present invention.
That is, the present invention provides a step of obtaining one or more thermoplastic resin melt films by melting and extruding one or more crystalline or semi-crystalline thermoplastic resins from a T die (step 1), A thermoplastic resin melt film, a metal cooling roll that satisfies the following requirement (1) and the following requirement (2), and an elastic roll that satisfies the following requirement (3), the following requirement (4), and the following requirement (5): When sandwiching with, the width of the melted thermoplastic resin film of the portion to be sandwiched is adjusted to be smaller than the surface length of the metal cooling roll and larger than the surface length of the elastic roll and sandwiched. Thus, the present invention relates to a method for producing a surface protective film having a step of obtaining one or more films (step 2) and a step of winding up the film (step 3), wherein the film thickness is from 30 μm to 300 μm.
Requirement (1): The surface roughness of the surface of the metal cooling roll is 2.0 μm or more at the maximum height (Rmax). Requirement (2): The surface temperature of the metal cooling roll is water vapor in the air. The temperature at which dew condensation occurs on the surface of the cooling roll made from + 1 ° C. or higher and the crystallization temperature of the thermoplastic resin is −40 ° C. or lower. Requirement (3): The surface of the elastic roll is made of metal and has a mirror surface. The surface temperature of the elastic roll is a temperature at which water vapor in the air condenses on the surface of the elastic roll + 1 ° C. or higher and the crystallization temperature of the thermoplastic resin is −50 ° C. or lower Requirement (5): The surface length of the elastic roll is made of metal Less than the surface length of the cooling roll

  According to the present invention, it is possible to obtain a surface protective film that has slight adhesiveness on one side, is difficult to block when rolled up or stacked, and has reduced fish eyes.

It is an example of the schematic which shows a part of apparatus concerning this invention.

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

The method for producing the surface protective film of the present invention is a step of obtaining one or more thermoplastic resin melt films by melt-extruding one or more crystalline or semi-crystalline thermoplastic resins from a T-die ( Hereinafter, the process may be referred to as “step 1”.), The thermoplastic resin melt film is made of a metal cooling roll that satisfies the following requirement (1) and the following requirement (2), the following requirement (3), and the following: When pinching with an elastic roll that satisfies the requirement (4) and the following requirement (5), the width of the molten thermoplastic resin film in the portion to be pinched is smaller than the surface length of the metal cooling roll, A step of obtaining a film of one or more layers by adjusting and pinching so as to be larger than the surface length of the elastic roll (hereinafter sometimes referred to as “step 2”), and a step of winding the film ( Hereinafter referred to as “Step 3”. Having a certain.) Is.
Requirement (1): The surface roughness of the surface of the metal cooling roll is 2.0 μm or more at the maximum height (Rmax). Requirement (2): The surface temperature of the metal cooling roll is water vapor in the air. The temperature at which dew condensation occurs on the surface of the cooling roll made from + 1 ° C. or higher and the crystallization temperature of the thermoplastic resin is −40 ° C. or lower. Requirement (3): The surface of the elastic roll is made of metal and has a mirror surface. The surface temperature of the elastic roll is a temperature at which water vapor in the air condenses on the surface of the elastic roll + 1 ° C. or higher and the crystallization temperature of the thermoplastic resin is −50 ° C. or lower Requirement (5): The surface length of the elastic roll is made of metal Less than the surface length of the cooling roll

  Step 1 is a step of obtaining one or more thermoplastic resin melt films by melting and extruding one or more crystalline or semi-crystalline thermoplastic resins from a T die.

  The crystalline or semi-crystalline thermoplastic resin used in Step 1 is one that can be crystallized 100% or partially by cooling the molten thermoplastic resin. Such a resin is preferably a polyolefin resin, more preferably a polyethylene resin or a polypropylene resin, and still more preferably a polyethylene resin.

  The polyethylene-based resin means a resin in which the content (% by weight) of a structural unit derived from ethylene is 50% by weight or more, for example, low density polyethylene, ultra low density polyethylene, high density polyethylene, medium density polyethylene, Homopolymer of ethylene, copolymer of ethylene and α-olefin having 4 to 12 carbon atoms, copolymer of ethylene and vinyl acetate, copolymer of ethylene and unsaturated carboxylic acid, ethylene and unsaturated carboxylic acid Examples thereof include a copolymer with an acid ester and a copolymer of ethylene and vinylcyclohexane. Examples of the α-olefin include 1-butene, 1-pentene, 1-hexene, 1-octene, and 4-methylpentene-1, and examples of the unsaturated carboxylic acid include acrylic acid and methacrylic acid. Examples of the unsaturated carboxylic acid ester include ethyl acrylate, methyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, glycidyl acrylate, methyl methacrylate, ethyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, glycidyl methacrylate, and the like. It is done. Examples of the copolymer of ethylene and an α-olefin having 4 to 12 carbon atoms include, for example, a copolymer of ethylene and 1-butene, a copolymer of ethylene and 1-hexene, and a copolymer of ethylene and 1-octene. A polymer etc. are mentioned. The content (% by weight) of the structural unit derived from ethylene is preferably 60% by weight or more, more preferably 70% by weight or more, and still more preferably 80% by weight or more.

  Examples of the polypropylene resin include a propylene homopolymer, a copolymer of propylene and one or more of ethylene and one or more α-olefins having 4 to 12 carbon atoms, and a polymer obtained by polymerizing monomers mainly composed of propylene. A polypropylene copolymer obtained by producing a copolymer component and a copolymer component obtained by copolymerizing propylene and ethylene and / or a monomer comprising an α-olefin having 4 to 12 carbon atoms in at least two or more stages. A polymer etc. are mentioned. The content (% by weight) of the structural unit derived from propylene contained in the polypropylene resin is preferably 60% by weight or more, more preferably 70% by weight or more, and still more preferably 80% by weight or more. (However, the total weight of the polypropylene resin is 100% by weight).

  The thermoplastic resin used in the present invention is crystalline or semi-crystalline. When the thermoplastic resin melt film is sandwiched between the metal cooling roll and the elastic roll in Step 2, the surface temperature of the metal cooling roll and the elastic roll is determined to be crystalline or semi-crystalline. When the temperature is lower than the crystallization temperature, the viscosity of the thermoplastic resin increases due to the crystallization of the thermoplastic resin, and film breakage hardly occurs.

  The glass transition temperature (Tg) of the crystalline or semi-crystalline thermoplastic resin is preferably 0 ° C. or lower, more preferably −10 ° C. or lower. In step 2, the temperature of the roll is usually set to a temperature higher than the temperature at which moisture condenses on the roll surface, that is, 15 ° C. or higher, so that the molten thermoplastic resin film is sandwiched between the metal cooling roll and the elastic roll. If the Tg of the crystalline or semicrystalline thermoplastic resin is 0 ° C. or lower when the molten thermoplastic resin film is cooled, troubles such as film breakage occur because the thermoplastic resin is not easily brittle. It is less likely to occur and is preferable.

  The crystalline or semi-crystalline thermoplastic resin may be used alone or in combination of two or more. One kind of resin constituting one layer may be used alone, or a mixture of two or more kinds may be used. Two or more types of mixture are prepared by mixing pellets to a predetermined mixing ratio using a normal mixing operation, for example, a tumbler blender method, a Henschel mixer method, a Banbury mixer method, an extrusion granulation method, or a metering mixer. The method etc. are mentioned and the mixture obtained by these methods should just be thrown into an extruder.

  Further, the film of the present invention may be a single layer or may be a laminate of a plurality of layers. When a plurality of layers are laminated, a molten film of two or more crystalline or semicrystalline thermoplastic resins can be obtained by, for example, a coextrusion method.

  The crystalline or semi-crystalline thermoplastic resin used in step 1 may be used by mixing additives as necessary, as long as the effects of the present invention are not impaired. Examples of the additive include an antioxidant, a heat stabilizer, an ultraviolet absorber, an antistatic agent, and a metal deactivator. From the viewpoint of reducing the amount of deposits remaining on the adherend, the concentration of the additive to the crystalline or semicrystalline thermoplastic resin is preferably 500 ppm or less, and more preferably 250 ppm or less. Lubricants and anti-blocking agents may be added, but if the surface protective film is bonded to the adherend, the adherend may be contaminated or scratched. preferable.

  These additives may be in the form of a masterbatch previously kneaded in a resin such as low density polyethylene, linear low density polyethylene, or polypropylene, and the base resin of the masterbatch unless the effects of the present invention are impaired. There is no particular restriction on the type of the.

  In step 1, when the melt resin temperature in the lip of the T die or the melt resin temperature immediately after being extruded from the T die is 200 ° C. or higher, the surface of the elastic roll used in step 2 is smoothed. Is easily transferred to the thermoplastic resin melt, and the resulting film surface is likely to be smooth, so that the adhesion when the obtained film is bonded to an adherend is preferably increased, more preferably at 240 ° C. or higher. Yes, and more preferably 270 ° C or higher. As for the upper limit of the temperature, if the temperature is too high, it becomes easy for the molten film of the thermoplastic resin to be wound around the mirror-like elastic roll having a metal surface or the metal cooling roll having a large hugging angle, or the thermoplastic resin is severely deteriorated by heat. Therefore, the temperature is preferably 300 ° C. or lower, more preferably 290 ° C. or lower.

  In addition, it is preferable to set a filter such as a wire mesh filter or a metal fiber sintered filter on the breaker plate and remove fish eyes or foreign matters to some extent in advance, so that the fish eyes can be easily crushed during pinching. It is desirable to remove large fish eyes as much as possible. Furthermore, it is preferable to arrange a leaf disk filter between the extruder and the die to remove fish eyes and foreign matters to some extent in advance.

Step 2 includes one or more thermoplastic resin melt films obtained in Step 1, a metal cooling roll that satisfies the following requirement (1) and the following requirement (2), the following requirement (3), and the following requirement ( 4) and the elastic roll satisfying the following requirement (5), the width of the molten thermoplastic resin film in the portion to be pinched is smaller than the surface length of the metal cooling roll, and the elastic roll It is the process of obtaining the film of one or more layers by adjusting and pinching so that it may become larger than this surface length. In step 2, at least one layer or more of the thermoplastic resin molten film obtained in step 1 is cooled and solidified to obtain one or more layers of film.
Requirement (1): The surface roughness of the surface of the metal cooling roll is 2.0 μm or more at the maximum height (Rmax). Requirement (2): The surface temperature of the metal cooling roll is water vapor in the air. The temperature at which dew condensation occurs on the surface of the cooling roll made from + 1 ° C. or higher and the crystallization temperature of the thermoplastic resin is −40 ° C. or lower. Requirement (3): The surface of the elastic roll is made of metal and has a mirror surface. The surface temperature of the elastic roll is a temperature at which water vapor in the air condenses on the surface of the elastic roll + 1 ° C. or higher and the crystallization temperature of the thermoplastic resin is −50 ° C. or lower Requirement (5): The surface length of the elastic roll is made of metal Less than the surface length of the cooling roll

  Moreover, after the process 2 performs the process 2, it is preferable to perform the process 2 continuously.

  The metal cooling roll used in step 2 has a surface roughness of 2.0 μm or more, preferably 2.5 μm or more, and more preferably 4.5 μm or more, at the maximum height (Rmax). is there. When a metal cooling roll having a surface roughness of 2.0 μm or more at the maximum height (Rmax) is used, the surface roughness of the metal cooling roll is transferred to one surface of the thermoplastic resin melt film, and the metal When the surface of the thermoplastic resin molten film on the side in contact with the cooling roll is appropriately placed, the film to be manufactured is difficult to block. Such metal cooling rolls include what are generally called satin rolls, semi-matt rolls, and mat rolls. When the obtained film is wound up in step 3, the films overlap, but if the surface of the metal cooling roll is too large on the surface of the transferred film, the opposite surface of the film is easily damaged. Or when used as a surface protective film used to protect the surface of a film-like object such as an optical film, it is wound on or stacked after being attached to an optical film, etc. Since the surface of the film to which the surface roughness is transferred comes into contact with the surface on which the surface protective film is not bonded, such as an optical film that is an adherend, the surface of the optical film or the like may be easily damaged. Therefore, the surface roughness of the metal cooling roll surface is preferably 10 μm or less as the maximum height (Rmax), and more Mashiku is at 8μm or less, still more preferably 6μm or less. The maximum height (Rmax) is defined in JIS B0601-1982.

  The metal material of the metal cooling roll used in step 2 is not particularly limited as long as it is generally used for a cooling roll of a film processing machine, and examples thereof include carbon steel and stainless steel. Those subjected to hard chrome plating treatment are preferable. From the viewpoint of cooling efficiency, the surface material of the cooling roll is preferably made of metal.

  The surface temperature of the metal cooling roll used in step 2 is the temperature at which water vapor in the air condenses on the surface of the metal cooling roll (hereinafter sometimes referred to as “dew point temperature”) + 1 ° C. or more of the thermoplastic resin The crystallization temperature is −40 ° C. or lower. If the surface temperature of the metal cooling roll is a dew point temperature of + 1 ° C. or higher, the surface of the metal cooling roll will not condense, so that the resulting film will not be contaminated with moisture or poor appearance. Further, by setting the surface temperature of the metallic cooling roll to the crystallization temperature of the thermoplastic resin of −40 ° C. or lower, the thermoplastic resin is melted when the thermoplastic resin melt film is sandwiched between the metallic cooling roll and the elastic roll. Since the film is cooled to such an extent that its elasticity is sufficiently large, the film is hardly cut.

  The dew point temperature is the temperature at which condensation starts when air containing water vapor is cooled, either measured directly with a dew point thermometer, or the water vapor pressure is determined from the temperature and relative humidity, and the water vapor pressure is taken as the saturated water vapor pressure. Is obtained from seeking

  The crystallization temperature can be obtained, for example, from a temperature showing an exothermic peak when the temperature is lowered to the melting point of the resin or higher using a differential scanning calorimeter.

The elastic roll used in step 2 has a metal surface and a mirror surface. Here, “the surface of the elastic roll is a mirror surface” means that the surface roughness of the surface of the elastic roll is 0.5 μm or less at the maximum height (Rmax). It is 3 μm or less, more preferably 0.2 μm or less. When an elastic roll having a mirror surface is used, the surface of the elastic roll is smooth, and this is transferred to one surface of the thermoplastic resin melt film, thereby increasing the smoothness of the surface of the film to be manufactured and the adherend as a film. When sticking together, it becomes easy to adhere, that is, the effect of slight adhesiveness is obtained.
When the surface roughness of the surface of the elastic roll exceeds 0.5 μm at the maximum height (Rmax), the smoothness of the surface to which the adherend is attached is poor and the adhesiveness is lowered, so that the adherence to the adherend is reduced. It tends to be insufficient. The maximum height (Rmax) is preferably 0.01 to 0.5 μm.

  The surface of the elastic roll used in step 2 is a metal material. The inner surface may be affixed with an elastic material, or in a thin sleeve, which is a metal surface, not in contact with the entire circumference of the inner surface of the sleeve, but only in the vicinity of the clamping part The rubber roll may be present in a state in which the metal is thin, and cooling water or the like may be present in the gap between the thin metal sleeve and the rubber roll. Examples of the metal material include nickel plated with hard chrome. Examples of the material of the elastic body include rubber. Further, water or oil for cooling or heating may be present in the space between the metal surface and the shaft portion of the elastic roll. Examples of the elastic roll used in step 2 include a flex roll (trade name: manufactured by Sumitomo Heavy Industries Modern Co., Ltd.), a TES roll (trade name: manufactured by Toshiba Machine Co., Ltd.), and a UF roll (trade name: manufactured by Hitachi Zosen Corporation). ) And the like. In particular, if the structure part for sandwiching the resin of the elastic roll can be elastically deformed in all directions including both ends, it can be elastically deformed in all the width directions of the roll. Since it can be pinched in a planar shape, the fish eye is more easily crushed, which is preferable.

  When a roll whose surface is not made of metal and whose surface is an elastic body such as rubber is used, the elastic force of the elastic body is specific to the material used, so the surface pressure on the molten thermoplastic resin film is changed. In some cases, it is necessary to exchange the elastic bodies of other materials having different surface pressures each time. On the other hand, when a roll whose surface is made of a metal material is used, the thermoplastic resin melt film is simply changed by changing the supply pressure of a cooling fluid such as water existing inside the metal outer cylinder on the roll surface. It may be possible to change the surface pressure. Also, the metal is easier to crush the fish eye than the rubber.

  As a method of processing the surface roughness of the metal cooling roll and elastic roll used in step 2 to a predetermined roughness, for example, a known surface finishing method such as buffing can be used.

  The surface temperature of the elastic roll used in step 2 can be adjusted by flowing a cooling medium such as water or oil in the roll. The surface temperature of the elastic roll is a temperature at which water vapor in the air is condensed on the surface of the elastic roll + 1 ° C or more and a crystallization temperature of the thermoplastic resin -50 ° C or less. If the temperature is too low, condensation occurs. If the temperature is too high, the molten resin tends to be wound around the roll, or the fine tackiness is hardly exhibited. The upper limit temperature is more preferably a crystallization temperature of −60 ° C. or less, and further preferably a crystallization temperature of −70 ° C. or less.

  If the surface length of the metallic cooling roll used in step 2 is not larger than the width of the thermoplastic molten resin, the molten resin film will sneak around the side surface of the metallic cooling roll, making film formation difficult. If the surface length of the elastic roll is wider than the width of the thermoplastic molten resin film, both ends of the elastic roll come into direct contact with the metal cooling roll, and the roll is damaged. Therefore, it is necessary to adjust the neck-in width of the thermoplastic resin molten film so that the width of the thermoplastic resin molten film is larger than the width of the elastic roll. Neck-in adjustment may be performed by appropriately selecting the temperature of the molten resin, the take-up speed of the molten film, the air gap, and the like. From these facts, the surface length of the elastic roll needs to be smaller than the surface length of the metal cooling roll. Here, the surface length is the length of the width of the roll surface designed as a portion of the roll structure where the molten resin extruded from the die contacts. In order to stably form a film, it is preferable to make the thickness distribution in the width direction and the flow direction of the thermoplastic resin melt film as small as possible. Further, it is desirable that the elastic roll is not in contact with the edge bead portions having increased thickness at both ends of the thermoplastic resin melt film as much as possible.

  The pinching pressure in step 2 is to sandwich the molten thermoplastic resin film extruded from the T die passing between these rolls by pressing the elastic roll against the metal cooling roll.

  As a method of sandwiching at least one layer of the thermoplastic resin molten film obtained in Step 1 between the metal cooling roll and the elastic roll, for example, the position of the metal cooling roll is fixed, and the elastic Examples include a method of moving and pressing the roll, a method of fixing the position of the elastic roll, and pressing the metal cooling roll. Preferably, the position of the metal cooling roll is fixed and the elastic roll is moved. It is a method to press. The pressure at the time of pressing may be higher than the pressure at which the thermoplastic resin melt film is completely adhered to the metal cooling roll, and is appropriately adjusted depending on the melt viscosity of the thermoplastic resin melt film, the thickness of the thermoplastic resin melt film, etc. do it.

  By sandwiching one or more layers of the thermoplastic resin molten film obtained in Step 1 with the metal cooling roll and the elastic roll in Step 2, the thermoplastic resin molten film is cooled and solidified, and one or more layers are formed. Film is obtained. At this time, one surface of the thermoplastic resin melt film in contact with the elastic roll becomes smooth, and one surface of the resulting film develops slight adhesion. In addition, since one surface of the thermoplastic resin molten film in contact with the metal cooling roll is transferred, the surface of the obtained film is less likely to cause blocking, and the film becomes slippery even during processing of the film. It becomes easy to wind up neatly. Further, since the blocking between the films is reduced when the film is fed out, the film is easily fed out. Furthermore, the fish eye is crushed by the pinching pressure, and the film surface of the fish eye existing portion is smoothed without swelling, so that even when pasted on the adherend, the dent on the swelled portion of the fish eye portion is transferred to the adherend. There is nothing.

  Step 3 is a step of winding up one or more layers of film obtained in Step 2. As a winding method, a normal method such as winding with a winder may be used.

  The film obtained by the production method of the present invention is used as a surface protective film. Examples of the surface protective film include resin plates, metal plates; liquid crystal display base glass, liquid crystal display polarizing films, retardation films, light diffusion sheets and other flat panel display (FPD) members; Blu-ray discs, DVDs, etc. It is suitably used as a film for protecting the surface of a film constituting an optical disk;

  Hereinafter, the present invention will be described based on examples.

[Example 1]
[resin]
F723-P, which is a low density polyethylene manufactured by Sumitomo Chemical Co., Ltd., was used. The crystallization temperature was 93.5 ° C. The crystallization temperature was set at 24 ° C. using a differential scanning calorimeter (Perkin Elmer PYRIS Diamond DSC), heated to 150 ° C. at 200 ° C./min, and held at 150 ° C. for 5 minutes. The temperature showed an exothermic peak when the temperature was lowered to 20 ° C. at 5 ° C./min. The crystallization temperature −40 ° C. is 53.5 ° C., and the crystallization temperature −50 ° C. is 43.5 ° C.

[Create film]
Using Sumitomo Heavy Industries Modern Co., Ltd. φ40mm Extruder, Sumikasen F723-P, a low density polyethylene made by Sumitomo Chemical Co., Ltd. The extruded molten resin is a chilled steel roll having a surface of 650 mm and a surface roughness of Rmax of 4.5 μm and a hard chrome plated surface, and a surface length of 430 mm. And a roll-like elastic roll having a surface roughness of 0.2 S and having a rubber portion inside the roll, and having a hard chrome-plated nickel surface. The width of the molten film is larger than that of the cooling roll. The molten resin is cooled by pinching it so that it is smaller and larger than the elastic roll, and then wound around the cooling roll, and the resulting film is taken up. A single-layer film having a thickness of 50 μm was obtained by taking up with a take-up machine at a take-up speed of 17 m / min and taking up with a winder. The elastic roll used was elastically deformable over the entire length including both ends. The surface temperature of the cooling roll was 30 ° C., and the surface temperature of the elastic roll was 30 ° C. The die was in a clean room, and the molten resin was extruded and wound up in the clean room. The extruder is installed outside the clean room, and the feed pipe connecting the extruder and the die penetrates the wall of the clean room. The temperature in the clean room was 22 ° C., the relative humidity was 50%, and the outdoor temperature was 11 ° C. A wire mesh filter was arranged on the breaker plate in the order of 80 mesh, 120 mesh, and 80 mesh from the upstream side to the downstream side.

[Physical property measurement method]
The physical properties in the examples were measured by the following methods.

(1) Blocking strength It was carried out by the upper and lower blocking method as follows. The film obtained by the above method was cut into a size of 225 mm × 100 mm, and prepared by laminating the elastic roll surfaces so that the elastic roll surfaces and the metal cooling roll surface were in contact with each other at 23 ° C. and 3 kg. after 30 minute hold while applying a load, the Toyo Seiki Seisakusho Ltd. tester vertical blocking meter, so as to peel in the direction perpendicular to the film plane (vertical direction), and two films superimposed is 100 cm ² It attached so that it might contact, and it peeled at the fixed peeling speed | rate from the contact | adherence state at 20 g / min, the load when the upper and lower jigs opened was read, and it was set as blocking strength. The results are shown in Tables 1 and 2.

(2) Coefficient of friction The coefficient of friction was measured as follows according to JIS K7125-1987. The friction coefficient between the cooling roll surfaces is measured by attaching a film of 250 mm length and 100 mm width on an acrylic base plate so that the elastic roll surface side is in contact with a slip piece of 63 g square and weighing 200 g. A film of × 70 mm was stuck so that the elastic roll surface was in contact, and was placed on the film stuck on the base plate. Using a tensile tester AB-401 manufactured by Tester Sangyo, the sliding piece was pulled at a speed of 100 mm / min, the static friction force was measured with a load cell, and the static friction coefficient was calculated. Moreover, about the friction coefficient between an elastic roll surface and a cooling roll surface, it affixed on a base plate so that a cooling roll surface might contact, and measured. The results are shown in Tables 1 and 2.

The shape of the fish eye in the film in the examples was confirmed as follows.
Using a Keyence ultra-deep shape measurement microscope VK-8500, the shape observation of the fish eye part and the height of the bulge of the fish eye part film surface were measured. The results are shown in Tables 1 and 2.

[Example 2]
The same operation as in Example 1 was performed except that the surface temperature of the cooling roll was 40 ° C. and the surface temperature of the elastic roll was 15 ° C.

[Example 3]
The same procedure as in Example 2 was performed except that the screw rotation speed was 190 rotations per minute, the take-up speed was 38 m / min, and the film thickness was 30 μm.

[Example 4]
The same operation as in Example 1 was performed except that the temperature of the die was 210 ° C.

[Example 5]
The same operation as in Example 4 was performed except that the surface temperature of the cooling roll was 50 ° C.

[Comparative Example 1]
The cooling roll was carried out in the same manner as in Example 2 except that the surface roughness was a mirror surface having a surface roughness of 0.1 μm.

[Comparative Example 2]
The same procedure as in Example 2 was performed except that an elastic chamber was not used, an air chamber was used, and the take-up speed was 14.5 m / min. The film thickness was 50 μm.

[Comparative Example 3]
It implemented like Example 4 except the surface temperature of the cooling roll having been 60 degreeC. The film was easy to stick to the cooling roll, and the phenomenon that the film was slightly separated from the cooling roll was observed.

[Comparative Example 4]
It implemented like Example 1 except the surface temperature of the cooling roll having been 10 degreeC. The test was stopped because the surface temperature of the cooling roll was lower than the dew point temperature and condensation was observed on the cooling roll.

[Comparative Example 5]
It implemented similarly to Example 1 except the surface temperature of the elastic roll having been 50 degreeC.

[Comparative Example 6]
It implemented similarly to Example 1 except the surface temperature of the elastic roll having been 10 degreeC. The test was stopped because the surface temperature of the elastic roll was lower than the dew point temperature and condensation was observed on the cooling roll.

[Comparative Example 7]
When implemented in the same manner as in Example 1 except that the width of the molten film is smaller than that of the cooling roll and smaller than that of the elastic roll, both ends of the elastic roll are in direct contact with the cooling roll and the elastic roll may be damaged. The test was stopped immediately.

1 Die 2 Metal cooling roll 3 Elastic roll 4 Film

Claims (3)

A step of obtaining one or more thermoplastic resin melt films by melting and extruding one or more crystalline or semi-crystalline thermoplastic resins from a T die (Step 1), When sandwiching between a metal cooling roll that satisfies the following requirement (1) and the following requirement (2), and an elastic roll that satisfies the following requirement (3), the following requirement (4), and the following requirement (5): One or more layers are formed by adjusting the width of the molten thermoplastic resin film in the portion to be pinched so as to be smaller than the surface length of the metal cooling roll and larger than the surface length of the elastic roll. A method for producing a surface protective film, comprising a step of obtaining a film (step 2) and a step of winding up the film (step 3), wherein the film thickness is from 30 μm to 300 μm.
Requirement (1): The surface roughness of the surface of the metal cooling roll is 2.0 μm or more at the maximum height (Rmax). Requirement (2): The surface temperature of the metal cooling roll is water vapor in the air. The temperature at which dew condensation occurs on the surface of the cooling roll made from + 1 ° C. or higher and the crystallization temperature of the thermoplastic resin is −40 ° C. or lower. Requirement (3): The surface of the elastic roll is made of metal and has a mirror surface. The surface temperature of the elastic roll is a temperature at which water vapor in the air condenses on the surface of the elastic roll + 1 ° C. or higher and the crystallization temperature of the thermoplastic resin is −50 ° C. or lower Requirement (5): The surface length of the elastic roll is made of metal Less than the surface length of the cooling roll   2. The process of claim 1, wherein the thermoplastic resin melt film is sandwiched between the metal cooling roll and the elastic roll immediately after the thermoplastic resin melt film is first brought into contact with the elastic roll in step 2. Method for producing the surface protective film of the present invention.   The method for producing a surface protective film according to claim 1 or 2, wherein the crystalline or semi-crystalline thermoplastic resin is a polyethylene resin.

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