KR20160108445A - Method of manufacturing stretched film - Google Patents

Abstract

A film-forming process before stretching to form a film 100 before stretching by melt-extruding the thermoplastic resin from the molding die 220 and then cooling and solidifying the film, a process of smoothing both sides defining the thickness of the film 100 before stretching And a stretching step of forming a stretched film by heating and stretching the stretched film (100) obtained by smoothing the both sides of the stretched film (100) at least in the longitudinal direction.

Description

 METHOD OF MANUFACTURING STRETCHED FILM [0002]

The present invention relates to a method for producing an oriented film.

In order to produce a stretched film, a method of preparing a film to be a material and stretching the prepared film is used. As a method of stretching the film, both ends of the film are transported into a heating furnace while grasping with a clip, And a biaxial stretching method in which heating and stretching are performed simultaneously in the longitudinal direction and the width direction by a clip holding both ends of the biaxial stretching method.

In this simultaneous biaxial stretching method, the film is heated and stretched to a required stretching ratio by pulling the film in the longitudinal direction and the width direction in the heating furnace. When the film is stretched, a large stress is applied to both ends of the film, As a result, cracks are generated at both ends, and the entire film may be broken in this case.

On the other hand, for example, in Patent Document 1, in order to prevent the film from being broken at the time of heat stretching by simultaneous biaxial stretching, a technique of reinforcing the film before heat stretching by thickening both end portions gripped by the clip, .

Japanese Patent Application Laid-Open No. 11-105131

However, in the technique of Patent Document 1, since the film for heat elongation is formed by melt extrusion of the thermoplastic resin by the molding die, the film thickness of the both sides Even when both ends of the film are thickened, there is a problem that when the film is heated and stretched in the longitudinal direction by simultaneous biaxial stretching, stress is locally concentrated on the loose portions of both sides of the film, and the film tends to be broken.

The present invention takes this fact into consideration and provides a method for producing a stretched film which can prevent a film from being broken when a stretched film is produced by heat stretching the film to obtain a stretched film excellent in productivity and quality .

The inventors of the present invention have found that the above object can be achieved by smoothing both side surfaces of a film obtained by melt-extrusion from a molding die before heat elongation, and have completed the present invention.

That is, according to the present invention, there is provided a process for producing a film, comprising: a pre-stretching film forming step of forming a pre-stretching film by melt-extruding a thermoplastic resin from a molding die, A smoothing step of smoothing both sides defining the thickness of the film before stretching; And a stretching step of stretching the stretched film obtained by smoothing the both sides of the stretched film at least in the longitudinal direction to form a stretched film.

In the manufacturing method of the present invention, it is preferable that smoothing of the smoothing step is performed by removing regions located at both ends in the width direction of the film before stretching.

In the production method of the present invention, it is preferable to remove a range of 30 mm or less in width from both sides of the region located at both ends in the width direction of the film before stretching.

In the production method of the present invention, it is preferable to remove the region located at both ends in the width direction of the film before stretching.

In the manufacturing method of the present invention, it is preferable that the pre-stretching film of the stretching step is heat-stretched by simultaneous biaxial stretching which stretches also in the longitudinal direction of the film before stretching.

In the production method of the present invention, it is preferable that heating and stretching of the film before stretching in the stretching step is performed so that the thickness of the stretched film after heat stretching is in a range of 15 to 50 mu m.

Further, in the manufacturing method of the present invention, in the pre-stretching film forming step, the first thermoplastic resin and the second thermoplastic resin different from the first thermoplastic resin are used as the thermoplastic resin, and the first thermoplastic resin and the second thermoplastic resin 2 thermoplastic resin is molten co-extruded from a molding die, and then cooled and solidified to form a central portion made of the first thermoplastic resin and both end portions made of the second thermoplastic resin formed at both ends of the central portion in the width direction It is preferable to form the pre-stretched film.

In the manufacturing method of the present invention, when the pre-stretch film is formed by melt co-extrusion as the first thermoplastic resin and the second thermoplastic resin, the rupture elongation at both ends of the second thermoplastic resin at room temperature, It is preferable to use a thermoplastic resin that is larger than the elongation at break of the central portion of the first thermoplastic resin at room temperature.

As the production method of the present invention, it is preferable to use an acrylic resin as the first thermoplastic resin.

As the production method of the present invention, it is preferable to use a mixed resin obtained by blending polycarbonate (PC) as the second thermoplastic resin with a thermoplastic resin having a glass transition temperature lower than that of the acrylic resin.

Further, as the production method of the present invention, it is preferable that the first thermoplastic resin and the second thermoplastic resin are each a thermoplastic resin having a glass transition temperature difference of 10 占 폚 or less.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to prevent breakage when stretching, and to provide a method for producing a stretched film excellent in productivity and yield.

1 is a view for explaining an example of a method for producing a composite film in a composite film forming process.
2 is a view for explaining a method of stretching a composite film by a simultaneous biaxial stretching method in a stretching step.
3 is a view for explaining another example of a method for producing a composite film in the composite film forming process.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

The method for producing a stretched film according to the present embodiment is characterized in that a first thermoplastic resin and a second thermoplastic resin different from the first thermoplastic resin are melt co-extruded by a T die for molding to form a composite film, A composite film forming step of trimming both ends of the composite film, and a stretching step of heating and stretching the composite film in the longitudinal direction and the width direction.

≪ Composite Film Forming Step &

The composite film forming step is a step of melt-co-extruding the first thermoplastic resin and the second thermoplastic resin from a T die to form a composite film 100 and trimming both ends of the composite film 100 formed. Here, FIG. 1 is a view for explaining a composite film forming process. In this embodiment, as shown in Fig. 1, the composite film 100 includes a central portion 110 and both end portions 120 formed at both ends in the width direction of the central portion 110, 1 < / RTI > thermoplastic resin and both ends 120 are made of the second thermoplastic resin. On the other hand, the central portion 110 of the composite film 100 is a portion that becomes a stretched film by being stretched by heating in a stretching process to be described later. Both ends 120 of the composite film 100 are for reinforcing the central portion 110 when heating and stretching the composite film 100. After the composite film 100 is stretched by heating, can do. When cutting the composite film 100, it is preferable to completely remove both ends 120 by cutting a part of both ends of the central part 110. [ In this case, both ends of the central portion 110 are also removed, but it is preferable to remove all the portions held by the clip 310 described later.

In the composite film forming step, the first thermoplastic resin and the second thermoplastic resin are supplied to the T die 220 through the feed block 210 while being heated and melted.

In the present embodiment, the first melt-extruder (not shown) for melt-extruding the first thermoplastic resin and the second melt-extruder (not shown) for melt-extruding the second thermoplastic resin are connected to the feed block 210 . Such a melt extruder is not particularly limited, and both a single screw extruder and a twin screw extruder can be used. In this embodiment, the first thermoplastic resin and the second thermoplastic resin are melt-extruded by the respective melt extruders at a temperature equal to or higher than the melting point (melting) temperature, respectively, to be supplied to the feed block 210.

On the other hand, when feeding the first thermoplastic resin and the second thermoplastic resin from the feed block 210 to the T die 220, the composite film 100 obtained by the T die 220 has a The first thermoplastic resin and the second thermoplastic resin are supplied so that both ends of the second thermoplastic resin are formed at both ends of the center portion 110 made of one thermoplastic resin.

Specifically, the feed block 210 is provided on both sides in the width direction of the T die 220 with respect to the inlet for feeding the first thermoplastic resin and the inlet for feeding the first thermoplastic resin, An inlet for supplying the first thermoplastic resin to the first thermoplastic resin 210 and an inlet for supplying the second thermoplastic resin on both sides in the width direction of the T die 220 with respect to the inlet for feeding the first thermoplastic resin are provided have. In the present embodiment, the first thermoplastic resin and the second thermoplastic resin introduced from the inlet of the feed block 210 join together in the feed block 210, and the T die 220 at the exit of the feed block 210, The first thermoplastic resin flows in the central portion with respect to the width direction of the first thermoplastic resin and flows out to the both ends of the first thermoplastic resin in such a manner that the second thermoplastic resin flows to the T die 220.

In the T die 220, the first thermoplastic resin and the second thermoplastic resin supplied from the feed block 210 are fed in the width direction (the first thermoplastic resin and the second thermoplastic resin) by the manifold 221 provided in the T die 220 2 thermoplastic resin), and is thereby co-extruded from the die lip 222 into a sheet form.

Subsequently, the first thermoplastic resin and the second thermoplastic resin on the coextruded sheet are continuously drawn by the touch roll 230 and the cooling roll 240 as shown in Fig. 1, and are compressed and cooled and solidified, A composite film 100 having a central portion 110 made of a first thermoplastic resin and both end portions 120 formed at both ends of the central portion 110 and made of a second thermoplastic resin is manufactured.

In the present embodiment, the produced composite film 100 is subjected to continuous trimming by a cutter 250 to a predetermined width from both side surfaces of the both end portions 120, so that both side surfaces defining the thickness of the film The surface which becomes a side surface when melt-extruded by the extrusion molding machine) is smoothed. According to the present embodiment, when the composite film 100 is heated and stretched by pulling both ends 120 of the composite film 100 in a stretching step to be described later, It is possible to prevent the local concentration of stress and to prevent the occurrence of cracks at both ends 120 and to improve the productivity of the stretched film.

On the other hand, the smoothing of the side surfaces of the both ends 120 reduces the side surface irregularities of both ends 120 and may be performed to such an extent that no stress is concentrated on a part of both ends 120 when the composite film 100 is pulled in the longitudinal direction .

As the cutter 250, any material may be used as long as it can smoothly smoothen the side surface of the both ends 120 by trimming. For example, the cutter 250 may be a razor blade or a circular blade, It is possible to use a rotary shear cutter for performing cutting by a laser, a solid laser, a semiconductor laser, a liquid laser, a gas laser or the like. However, stress applied to the composite film 100 at the time of trimming can be reduced, A laser cutter is preferable from the viewpoint of preventing the occurrence of cracks in the composite film 100.

On the other hand, when trimming both ends 120 of the composite film 100, it is preferable to trim both ends 120 while heating them. This makes it possible to make the side surfaces of both ends 120 more smooth, and to more appropriately prevent the composite film 100 from being broken when the composite film 100 is heated and stretched.

On the other hand, in the case of trimming both ends 120 of the composite film 100, the width of trimming is preferably 30 mm or less in width, more preferably 30 mm or less in width from the most protruding portions on both side surfaces of the both end portions 120 toward the central portion 110 Is 10 mm or less in width, and more preferably 5 mm or less in width. Thus, the amount of the second thermoplastic resin for forming the both ends 120 can be reduced since the amount of the both ends 120, which are trimmed and removed while smoothing the side surfaces of the both end portions 120, can be reduced, It is cost effective.

In the present embodiment, the composite film 100 in which the both ends 120 are trimmed in this way is wound by a composite film winding roll (not shown), whereby the composite film 100 can be continuously obtained.

<Stretching Step>

The drawing step is a step of heating and stretching the composite film 100 obtained by the composite film forming step in the machine direction and the width direction. Here, FIG. 2 is a view for explaining a drawing process. In the present embodiment, in the stretching process, the composite film 100 is fed from the above-described multiple film winding roll, and as shown in Fig. 2, while both ends 120 of the composite film 100 are gripped by the clip 310, Direction and the width direction of the composite film 100 by the simultaneous biaxial stretching method.

Concretely, in the stretching step, the composite film 100 is continuously fed from the multiple film winding roll, and both ends 120 of the composite film 100 are held at regular intervals by using a plurality of clips, The composite film 100 is conveyed into the stretching furnace 320 and the composite film 100 is stretched in the longitudinal direction and the width direction by the respective clips 310 in the stretching furnace 320 to be stretched. At this time, the composite film 100 is conveyed in a state gripped by the clip 310 to pass through the stretching furnace 320, and in the preheating zone in the stretching furnace 320, the composite film 100 constitutes Heated to a temperature higher by about 10 ° C to 30 ° C than the glass transition temperature of the second thermoplastic resin at the both ends 120 and then transferred to the clip 310 in the drawing zone in the stretching zone in the stretching furnace 320 In the longitudinal direction and in the width direction and stretched in the longitudinal direction and the width direction. Then, the stretched film can be obtained by cooling and solidifying in the succeeding cooling heat fixing zone. Then, the clip 310 is opened and wound on a roll, whereby a stretched film can be continuously obtained.

On the other hand, in the present embodiment, a stretched film can be obtained by using a continuous process (continuous process) for the stretching process and the complex film forming process.

In this embodiment, a pair of guide rails for allowing the clip 310 to move through the inside of the stretching furnace 320 are provided. The pair of guide rails are respectively provided at the positions of the clip 310 holding the upper ends 120 of the upper side of the composite film 100 shown in Fig. 2 and the clip 310 holding the lower ends 120 thereof And are parallel to each other in the preheating zone in the stretching furnace 320, and are mutually spaced apart in the width direction of the composite film 100 in the stretching zone, and are mutually parallel in the cooling heat fixing zone. Alternatively, in the cooling heat fixing zone, the distance between the pair of guide rails in the cooling heat fixing zone is set so that the distance between the pair of guide rails at the exit side of the stretching zone, in consideration of the shrinkage at the time of solidification of the stretched film heat- The width direction may be approached by several percent in the width direction. In the present embodiment, the clip 310 holding both ends 120 of the composite film 100 moves along these guide rails so that the composite film 100 can be transported and stretched.

In this embodiment, the composite film 100 is stretched in the stretching zone in the stretching furnace 320 by using the clip 310 which moves along the guide rails. That is, in the stretching zone in the stretching furnace 320, the clips 310 holding the both ends 120 of the composite film 100 are moved so as to be wider in the width direction along the guide rails, The both ends 120 of the composite film 100 are pulled in the longitudinal direction and the width direction as shown by the arrows in Fig. Thus, the central portion 110 and both end portions 120 of the composite film 100 are stretched by heating until they become necessary stretching magnifications in the longitudinal and transverse directions, respectively. The heat-stretched composite film 100 is cooled and solidified in a cooling heat fixing zone in the stretching furnace 320 and wound by a roll provided outside the stretching furnace 320, whereby a stretched film can be continuously obtained .

On the other hand, in the present embodiment, the thickness of the central portion 110 of the composite film 100 after heat stretching is preferably 15 to 50 占 퐉, more preferably 20 to 40 占 퐉. By controlling the thickness of the central portion 110 of the composite film 100 after heat stretching in the above range, breakage of the composite film 100 during heat stretching can be prevented and the composite film 100 can be appropriately heated and stretched.

In the present embodiment, the stretched film obtained by heating and stretching the composite film 100 may be cut at both ends 120 as necessary. Thus, the stretched film can be made into a film consisting of only the central portion 110.

As described above, in this embodiment, the composite film 100 having the central portion 110 made of the first thermoplastic resin and the both end portions 120 made of the second thermoplastic resin is formed by the composite film forming step, The central portion 110 and the both end portions 120 of the composite film 100 are heat-stretched by smoothing both side surfaces of the both ends 120 of the formed composite film 100 and then the stretched film can be obtained. Thus, according to the present embodiment, it is possible to prevent the composite film 100 from being broken when heat-stretching the composite film 100, and to improve the productivity of the stretched film.

On the other hand, conventionally, in order to prevent the film obtained by melt extrusion of the thermoplastic resin by molding dies when the film is heated and stretched by simultaneous biaxial stretching, both ends of the film before heat elongation are formed thicker than the central portion Is known. However, in this method, since the shapes of both side surfaces of the film become uneven and coarse due to the uneven extrusion due to the molding dies, stress is concentrated on the roughened portions on both sides of the film when the film is stretched by the clip 310 Thus, there is a problem that the film tends to break. At this time, as a method of smoothing both sides of the film, a method of adjusting the extrusion amount by the molding dies and adjusting the position and the conveying speed of the touch roll 230 and the cooling roll 240 may be considered. However, It is difficult to sufficiently smooth both sides of the film by the method alone. Further, in the method of increasing the thickness of both ends of such a film, the amount of the thermoplastic resin required for obtaining the stretched film increases, which is also disadvantageous in terms of cost.

On the contrary, the inventors of the present invention have found that the properties of the thermoplastic resin used in the production of a stretched film are such that when the film is heated to the glass transition temperature or higher, the breaking elongation (value indicating the elongation to the dimension before stretching when the film is stretched) In the meantime, when the film made of the thermoplastic resin is heated and stretched in an actual manufacturing process as shown in Figs. 1 and 2, the film is broken at a stretching ratio lower than the breaking elongation percentage As a result of the examination, it was found that the breakage of the film at the time of heat elongation was caused by the unevenness of both sides of the film. Based on this finding, the inventors of the present invention can prevent the composite film 100 from being broken at the time of heat stretching by smoothing the side surface of the both ends 120 with respect to the composite film 100 before heat stretching .

Particularly, according to the present embodiment, as a method for smoothing both side surfaces of the both end portions 120 of the composite film 100, by using the method of trimming the both end portions 120 as described above, the composite film 100 is heat- It is possible to prevent the composite film 100 from being broken due to the roughness of both sides of the both ends 120 and to prevent cracks in the portions where the thickness of the boundary between the central part 110 and the both ends 120 becomes thin Can be prevented.

That is, in the composite film 100 melt-extruded from the T die 220, a phenomenon called neck-in which is stretched in the longitudinal direction and contracts in the width direction by being pulled by the cooling roll 240 immediately after melt- Lt; / RTI &gt; Here, when the composite film 100 is stretched in the longitudinal direction by the cooling roll 240, contiguous thermoplastic resin exists in the central portion 110 located at the center of the composite film 100, And a force for contracting only in the thickness direction acts. That is, since the center portion 110 is constituted by arranging the first thermoplastic resin in the width direction, it is considered that contraction in the width direction of the central portion 110 is suppressed by pulling the adjacent resins together. On the other hand, in the both end portions 120, one end portion is adjacent to the central portion 110, and since the adjacent resin does not exist at the other end portion, a force contracting in the width direction in addition to the thickness direction acts . As a result, the thermoplastic resin tends to be pulled toward the both end portions 120 at the boundary portion between the other central portion 110 and the opposite end portions 120 where the stress is applied when the neckline occurs, so that the thickness of the boundary portion tends to be thinned. In this case, when the thickness of the both end portions 120 is too thick with respect to the thickness of the boundary portion between the center portion 110 and the both end portions 120, stress is exerted on the thin-walled boundary portion when the composite film 100 is heated and stretched in the stretching process So that cracks tend to be generated in the boundary portion.

In contrast, according to the trimming of both end portions 120 of the composite film 100, since the thickened portions of the both end portions 120 can be removed by trimming, the difference in thickness between the both end portions 120 and the boundary portion And it is possible to effectively prevent the occurrence of cracks at the boundary portion by suppressing concentration of stress at the boundary portion when the composite film 100 is stretched by heating.

Conventionally, rubber elastic particles are added to both end portions 120 of the composite film 100 to soften the both end portions 120 (breaking at room temperature) in order to prevent breakage of the composite film 100 during heat elongation A method of increasing elongation is known. However, in this method, the rubber elastic particles in the both end portions 120 are easily deteriorated by heat, resulting in the following problems. That is, when the composite film 100 is melt-co-extruded from the T die 220, rubber elastic particles deteriorated by heat are deposited on the dies 222 of the T die 220 to form sediments, There is a possibility that a pressing mark is formed on the composite film 100 or sediments are mixed at the time of winding the product of the stretched film to deteriorate the quality of the stretched film. 2, when the composite film 100 is heated and stretched by using the clip 310, a deposit is formed between the composite film 100 and the clip 310 There is a possibility that the composite film 100 is easily broken.

On the other hand, according to the present embodiment, it is not necessary to add the rubber elastic particles to the both end portions 120 of the composite film 100, or the amount of the rubber elastic particles to be added to the both end portions 120 can be made small , Precipitation of the rubber elastic particles when the composite film 100 is melt co-extruded can be suppressed, and a stretched film excellent in quality can be obtained.

On the other hand, in the present embodiment, it can be selected according to the use of the stretched film required as the first thermoplastic resin for forming the central portion 110, and examples thereof include acrylic resin (PMMA), cyclic olefin copolymer (COC ) Can be used.

The second thermoplastic resin is not particularly limited as long as it is capable of appropriately smoothing the side surface after the both ends 120 of the composite film 100 are formed. For example, in the composite film 100, It is preferable to use a thermoplastic resin having a high ductility. Specifically, as the second thermoplastic resin, it is preferable to use a thermoplastic resin in which the both end portions 120 of the composite film 100 before heat elongation have a higher breaking elongation at room temperature than the central portion 110. On the other hand, the elongation at break at room temperature is a value indicating the elongation to the dimension before stretching when stretched until the center portion 110 or the both ends 120 are broken under a room temperature environment of about 10 to 30 占 폚. As a result, the stress applied to the composite film 100 when trimming both ends 120 of the composite film 100 can be relaxed, and the occurrence of cracks in the composite film 100 at the time of trimming can be effectively prevented have.

Particularly when the both ends 120 of the composite film 100 are trimmed, if the elongation at break of the central part 110 at room temperature is as low as 10% or less, by the stress applied to the composite film 100 at the time of trimming, There is a fear that cracks may be generated in the heat sink 110. On the other hand, as described above, by using the thermoplastic resin as the second thermoplastic resin so that the both end portions 120 of the second thermoplastic resin have a higher breaking elongation at room temperature, the stress at the time of trimming can be relaxed, It is possible to effectively prevent the occurrence of cracks.

The difference between the glass transition temperature (Tg ₁ ) of the first thermoplastic resin and the glass transition temperature (Tg ₂ ) of the second thermoplastic resin (| Tg ₁ -Tg ₂ |) of the thermoplastic resin Is preferably used. Thus, in the present embodiment, when the both ends 120 of the composite film 100 are gripped by the clip 310 by the stretching process and heat elongation is performed, the both ends 120 held by the clip 310 are stretched It is possible to appropriately soften by heating by the furnace 320 to prevent clipping during heating and stretching, breakage of the composite film 100, and the like, so that the productivity of the stretched film can be improved.

At this time, the difference (Tg ₁ -Tg ₂ |) between the glass transition temperatures of the first thermoplastic resin and the second thermoplastic resin is preferably 10 ° C or lower, more preferably 5 ° C or lower, still more preferably 3 ° C Or less.

In the present embodiment, as the second thermoplastic resin, the following thermoplastic resins can be specifically used based on the above-described viewpoints. For example, when an acrylic resin is used for the first thermoplastic resin, one kind of polyethylene naphthalate (PEN), a cyclic olefin polymer (COP), or the like may be used alone as the second thermoplastic resin, Mixed resins can be used.

As the second thermoplastic resin, a resin to which a small amount of rubber elastic particles are added may be used for the first thermoplastic resin as long as the productivity of the stretched film is not impaired.

Alternatively, as the second thermoplastic resin, a thermoplastic resin (heat-resistant thermoplastic resin) having a glass transition temperature higher than that of the first thermoplastic resin and a difference of more than 10 ° C is used as the thermoplastic resin having a glass transition temperature lower than that of the first thermoplastic resin A molten thermoplastic resin) may be used. At this time, by adjusting the blending ratio of the heat-resistant thermoplastic resin and the low-temperature-melting thermoplastic resin, the glass transition temperature of the obtained mixed resin is set so that the difference (| Tg ₁ -Tg ₂ |) between the glass transition temperature with the first thermoplastic resin is It is preferable to adjust it to the above range.

For example, when an acrylic resin having a glass transition temperature (Tg ₁ ) of about 120 ° C. is used as the first thermoplastic resin, a polycarbonate (PC) having a glass transition temperature as high as about 150 ° C. is used as the second thermoplastic resin 70 blended with lower polyethylene terephthalate (PET) and so ℃, it is possible to use a mixed resin glass transition the glass transition temperature (Tg ₁₎ with the same amount of adjustment at about 120 ℃ temperature.

On the other hand, when such a mixed resin is used as the second thermoplastic resin, polycarbonate (PC), cyclic olefin polymer (COP) and the like can be used as the heat-resistant thermoplastic resin. Examples of the low temperature meltable thermoplastic resin include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), acrylonitrile, butadiene, styrene (ABS), polyethylene (PE) Low temperature acrylic resin, polyester (PEs), polybutylene terephthalate (PBT), or the like can be used. In the present embodiment, it is preferable to use polycarbonate (PC) as the heat resistant thermoplastic resin and polyethylene terephthalate (PET) as the low temperature melting thermoplastic resin from the viewpoint of easily adjusting the glass transition temperature of the obtained mixed resin Do.

In the above example, as shown in Fig. 1, a method for producing a composite film 100 using the first thermoplastic resin and the second thermoplastic resin is a method in which a composite film The touch roll 230 and the cooling roll 240 may be used to pull out the touch panel 100 by using the touch roll 230 and the cooling roll 240. In this embodiment, A method of pulling the composite film 100 only by the film 240 can be used. As a result, the distance between the T die 220 and the cooling roll 240 can be reduced, and the first thermoplastic resin and the second thermoplastic resin extruded from the T die 220 are attracted to the cooling roll 240 It is possible to suppress the occurrence of the neck-up (the phenomenon of stretching in the longitudinal direction and narrowing of the width due to being pulled by the cooling roll 240) to be produced by the neck roll, By suppressing the shrinkage, variation in thickness can be suppressed.

In the above example, the side surfaces of the both end portions 120 are smoothed by trimming the both end portions 120 with respect to the composite film 100 before heat-stretching. In the present embodiment, however, the side surfaces of the both end portions 120 are smoothed A method of polishing the end portions of the both end portions 120 and heating and pressing the end portions of the both end portions 120 can be used.

In the above-mentioned example, as a method of heating and stretching the composite film 100, there is a method of heating and stretching the composite film 100 in both longitudinal and transverse directions as shown in Fig. 2 However, in the present embodiment, a method of uniaxially stretching the composite film 100 only in the longitudinal direction may be used.

At this time, heating and stretching in the longitudinal direction of the composite film 100 can be performed in the same manner as the simultaneous biaxial stretching method shown in Fig. That is, both ends 120 of the composite film 100 are transported into the stretching furnace 320 while being gripped by the clips 310, and then both ends 120 of the multiple films 100 are transported in the stretching furnace 320 It is possible to use a method of heating and stretching only in the longitudinal direction by widening the interval between the clips 310 without moving each of the holding clips 310 in the width direction.

In the present embodiment, both end portions 120 of the composite film 100 are attached to the clips 310 (as shown in Fig. 2) in the case of simultaneous biaxial stretching in the longitudinal direction and in the width direction, ), The productivity of the stretched film can be improved as compared with the sequential biaxial stretching method which has been conventionally used, and a stretched film with higher quality can be obtained.

On the other hand, in the conventional sequential biaxial stretching method, the composite film 100 produced by the method shown in Fig. 1 is first heat-stretched in the longitudinal direction, and then heated and stretched in the transverse direction. In the sequential biaxial stretching method, after the composite film 100 is heated and stretched in the longitudinal direction by being conveyed by a plurality of rolls, the both ends 120 of the composite film 100 are wound around the clip 310 as shown in Fig. While heating and stretching in the width direction.

Here, the longitudinal direction stretching of the composite film 100 in the sequential biaxial stretching method is specifically carried out as follows. That is, according to the sequential biaxial stretching method, the composite film 100 is preliminarily heated to the glass transition temperature of both ends 120 while being conveyed by a plurality of preheated preheating rolls, and the preheated composite film 100 And is continuously conveyed by the cooling roll while being heated again to a temperature higher by about 10 ° C to 30 ° C than the glass transition temperature of the both end portions 120 by an infrared heater or the like. At this time, by making the conveying speed by the cooling roll faster than the conveying speed by the preheating zone roll, tensile force is generated between the preheating zone roll and the cooling roll, and by using this tensile force, .

In the sequential biaxial stretching method, since the surface of the composite film 100 comes into contact with the preheating roll and the cooling roll when the composite film 100 is stretched in the longitudinal direction, scratches are generated on the surface of the composite film 100 There is a possibility that the appearance quality of the resulting stretched film is lowered. In the sequential biaxial stretching method, when the composite film 100 is heated and elongated in the longitudinal direction, the positions of both ends 120 of the composite film 100 in the width direction are not fixed, There is a possibility that the film is shrunk in the transverse direction by heat and the productivity of the stretched film is lowered.

On the other hand, according to this embodiment, by performing the stretching in the longitudinal direction of the composite film 100 using the above-described simultaneous biaxial stretching method or the above-described method of uniaxially stretching only in the longitudinal direction As shown in Fig. 2, since the contact with the roll can be avoided by performing the stretching in the longitudinal direction while grasping the both ends 120 of the composite film 100 with the clip 310) It is possible to reduce the scratches on the surface of the composite film 100 after it. As a result, it is possible to improve the appearance quality of the stretched film obtained by cutting the both ends 120 of the heat-stretched composite film 100, and can be particularly preferably used for an optical film having a demand for an excellent appearance quality. According to the present embodiment, since both ends 120 of the composite film 100 are held by the clip 310 when the composite film 100 is stretched in the longitudinal direction, Shrinkage in the width direction can be prevented, and the productivity of the stretched film can be improved.

In the above example, the composite film 100 is formed of two kinds of resins, that is, the first thermoplastic resin and the second thermoplastic resin. However, in the present embodiment, the composite film 100 is made of only the first thermoplastic resin . That is, the central portion 110 and the both end portions 120 may be all formed of a first thermoplastic resin and the composite film 100 may be a film made of only the first thermoplastic resin with respect to the composite film 100.

In this case, since the first thermoplastic resin is a resin determined according to the required stretched film, when the both ends are trimmed after being formed as a film by the T die 220, both end portions 120 of the second thermoplastic resin In contrast, when the film made of such a first thermoplastic resin is trimmed, the side of the film is adjusted to a degree that locally stress is not concentrated during heat stretching by adjusting the trimming conditions It may be smoothed.

Example

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

&Lt; Example 1 &gt;

An acrylic resin (glass transition temperature (Tg ₁ ): 123 캜, breaking elongation at room temperature: 5%) was prepared as a first thermoplastic resin for forming the central portion 110 of the composite film 100, (Glass transition temperature (Tg ₂ ): 125 캜, breaking elongation at room temperature: 18%) to which a small amount of rubber elastic particles were added as a second thermoplastic resin for forming both ends

Here, the glass transition temperature of the first thermoplastic resin and the second thermoplastic resin was measured by differential scanning calorimetry (DSC), and the breaking elongation at room temperature was measured by a tensile tester (product number: RTC-1210A ). The same was applied to the following Examples 2 to 4 and Comparative Examples 1 and 2.

Subsequently, the prepared first thermoplastic resin and second thermoplastic resin were fed to the feed block 210 by a twin-screw extruder, respectively, and the composite film 100 was produced by the method shown in Fig. 1 under the following conditions. Here, the composite film 100 has a total width of about 315 mm, and both end portions 120 have a width of about 50 mm from the ends of both ends of the composite film 100, and the central region 110 has the other central region. In the manufactured composite film 100, the thickness of the central portion 110 was about 150 to 170 mu m, and the maximum thickness of the both end portions 120 was about 400 mu m. On the other hand, in the present embodiment, an acrylic resin to which rubber elastic particles are added is used as the second thermoplastic resin. However, since the amount of the rubber elastic particles added is small, the amount of the rubber elastic particles Precipitation can be suppressed.

T Dice (220) Outlet width: 380mm

Air gap length: 60 mm

Rotation speed of the cooling roll 240: 6mpm

Feed amount of the first thermoplastic resin to the feed block 210: 15 kg / hr

Feed rate of the second thermoplastic resin to the feed block 210: 5 kg / hr

On the other hand, the above-described air gap length is determined by the position of the cooling roll 240 and the touch roll 230 from the outlet of the thermoplastic resin in the dies lip 222 (that is, the contact position between the cooling roll 240 and the thermoplastic resin Position).

Subsequently, the obtained composite film 100 was conveyed by a cooling roll 240, and then both end portions 120 were successively trimmed with a razor blade. On the other hand, the trimming was performed by cutting the both end portions 120 from both sides by 10 mm in width.

Next, with respect to the composite film 100 obtained by trimming both ends 120, the both ends 120 are held by a clip 310 and, as shown in Fig. 2, are stretched by the simultaneous biaxial stretching method in the longitudinal direction And heat-stretched in the width direction.

Speed when entering before heat elongation: 1mpm

Speed at exit after heat elongation: 2mpm

Drawing magnification: 100% in the longitudinal direction x 100% in the width direction (2 times in the longitudinal direction x 2 times in the width direction)

Clip 310: grip position: 15 mm from the end of composite film 100

Preheat zone temperature, distance: 140 ℃, 350mm

Elongation zone temperature, distance: 140 DEG C, 500 mm

Cooling heat fixing zone temperature, distance: 90 ℃, 700mm

On the other hand, in this embodiment, when the composite film 100 is subjected to continuous heat stretching over a length sufficient to confirm the productivity of the stretched film (good or bad), the breakage of the composite film 100 No stretching film with good quality could be continuously produced.

&Lt; Example 2 &gt;

3, the first thermoplastic resin melt-co-extruded from the T-die 220 and the second thermoplastic resin are melt-kneaded without using the touch roll 230, The distance between the T die 220 and the cooling roll 240 is made close to the length of the air gap length (the cooling roll 240 from the outlet of the thermoplastic resin in the dice lip 222) And the position where the thermoplastic resin contacts the thermoplastic resin) was 25 mm, a stretched film was obtained in the same manner as in Example 1.

In the second embodiment, the composite film 100 before trimming has a thickness of about 140 to about 180 占 퐉 in the central part 110, a maximum thickness of about 170 占 퐉 in the both end parts 120, It is confirmed that the neckline is suppressed and the both end portions 120 are thinned as compared with the above-described Embodiment 1, and the entire composite film 100 is flattened.

Also in Example 2, as in Example 1, precipitation of rubber elastic particles can be suppressed when melt-co-extruding the composite film 100, and while the composite film 100 is again stretched by heating, It was possible to continuously produce a stretched film excellent in quality without causing breakage of the substrate 100.

&Lt; Example 3 &gt;

A mixed resin comprising 25% by weight of polyethylene terephthalate (PET) blended with 75% by weight of polycarbonate (PC) (glass transition temperature (Tg ₂ ): 125 캜, elongation at break at room temperature: 20%).

On the other hand, in Example 3, as in Example 1, while the composite film 100 was heated and stretched, no breakage of the composite film 100 occurred, and a stretched film excellent in quality could be continuously produced.

<Example 4>

An acrylic resin (glass transition temperature (Tg ₁ ): 123 캜, breaking elongation at room temperature: 5%) identical to that of the first thermoplastic resin was used as the second thermoplastic resin for forming the both ends 120 of the composite film 100 , A stretched film was obtained in the same manner as in Example 1 except that a single film composed of only the acrylic resin was formed as the composite film 100.

On the other hand, in Example 4, in the single film before trimming, the thickness of the portion corresponding to the central portion 110 is about 140 to 175 占 퐉, the maximum thickness of the portion corresponding to the both end portions 120 is about 310 占 퐉, The end portions 120 are thicker than the central portion 110 in the same manner as in Embodiment 1. [

In Example 4, since the acrylic resin constituting the single film had a low breaking elongation at room temperature of 5% and a low ductility, when the single film was trimmed, the side surface of the single film was the same as that of Examples 1 to 3 As a result, the single film ruptured once when the single film was continuously stretched by heating. However, in Example 4, the frequency of occurrence of breakage of a single film at the time of heat stretching was remarkably low, and the productivity of the stretched film was not deteriorated. As a result, a stretched film excellent in quality could be continuously produced.

&Lt; Comparative Example 1 &

After the composite film 100 was produced, a stretched film was obtained in the same manner as in Example 1 except that trimming of the both end portions 120 was not performed.

On the other hand, in Comparative Example 1, since both sides of the both ends 120 were in a state of being rough without trimming the both ends 120 after the composite film 100 was produced, when the composite film 100 was heated and stretched, The film 100 was broken frequently, and the productivity of the stretched film deteriorated.

&Lt; Comparative Example 2 &

After the composite film 100 was produced, a stretched film was obtained in the same manner as in Example 2 except that trimming of both end portions 120 was not performed.

On the other hand, in Comparative Example 2, since both sides of the both ends 120 were in a state of being rough without trimming the both ends 120 after the composite film 100 was produced, when the composite film 100 was heated and stretched, The film 100 was broken frequently, and the productivity of the stretched film deteriorated.

As described above, in Examples 1 to 4, in which the sides were smoothed with respect to the composite film 100 before heat elongation or a single film, when the composite film 100 was heat-elongated, breakage of the composite film 100 was suppressed It was possible to obtain a stretched film excellent in quality, and the productivity of the stretched film could be improved.

On the other hand, as described above, in Comparative Example 1 and Comparative Example 2 in which the side face was not smoothed with respect to the composite film 100 before heat elongation, when the composite film 100 was heated and stretched, The productivity of the stretched film deteriorated.

100 ... Composite film 110 ... Central part
120 ... Both ends 210 ... Feed block
220 ... T Dice 230 ... Touch roll
240 ... Cooling roll 250 ... cutter
310 ... Clip 320 ... Stretching furnace

Claims (11)

An unstretched film forming step of melt-extruding a thermoplastic resin from a molding die, and then cooling and solidifying to form a stretched film;
A smoothing step of smoothing both sides defining the thickness of the film before stretching; And
And a stretching step of stretching the stretched film obtained by smoothing the both sides of the stretched film at least in the longitudinal direction to form a stretched film. The method according to claim 1,
Wherein the smoothing step of smoothing is performed by removing a region located at both ends in the width direction of the film before stretching. 3. The method of claim 2,
Wherein a range of a width of 30 mm or less is removed from both sides of the region located at both ends in the width direction of the stretched film. The method according to claim 2 or 3,
Stretching film is removed by cutting a region located at both ends in the width direction of the stretched film. 5. The method according to any one of claims 1 to 4,
Wherein the stretching process is characterized in that the stretching process of the film before stretching is performed by simultaneous biaxial stretching which stretches also in the longitudinal direction of the film before stretching. 6. The method according to any one of claims 1 to 5,
Wherein the stretching film is heated and stretched so that the thickness of the stretched film after heat stretching is in the range of 15 to 50 占 퐉. 7. The method according to any one of claims 1 to 6,
In the pre-stretching film forming step, a first thermoplastic resin and a second thermoplastic resin different from the first thermoplastic resin are used as the thermoplastic resin, and the first thermoplastic resin and the second thermoplastic resin are melted Extruded and then solidified by cooling to form the stretched film having a central portion made of the first thermoplastic resin and both end portions made of the second thermoplastic resin and formed at both ends of the central portion in the width direction By weight based on the total weight of the film. 8. The method of claim 7,
Wherein when the pre-stretch film is formed by melt co-extrusion as the first thermoplastic resin and the second thermoplastic resin, the elongation at break of the both ends of the second thermoplastic resin at room temperature is higher than that of the first thermoplastic resin Wherein the thermoplastic resin is a thermoplastic resin which has a larger elongation at break than the center at the room temperature. 9. The method according to claim 7 or 8,
Wherein the first thermoplastic resin is an acrylic resin. 10. The method of claim 9,
Wherein a mixed resin obtained by blending polycarbonate (PC) as said second thermoplastic resin with a thermoplastic resin having a lower glass transition temperature than said acrylic resin is used as said second thermoplastic resin. 11. The method according to any one of claims 7 to 10,
Wherein the first thermoplastic resin and the second thermoplastic resin are each a thermoplastic resin having a glass transition temperature difference of 10 占 폚 or less.

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