WO2012026377A1 - Method and apparatus for manufacturing stretched film - Google Patents

Abstract

A method for manufacturing a stretched film, the method comprising: imparting tension to a film; and raising the temperature of part of the tensioned film from a temperature at which there is no change in film width to a temperature at which necking occurs, whereby the film is caused to undergo necking/stretching.

Description

Method and apparatus for producing stretched film

The present invention relates to a stretched film manufacturing method and a stretched film manufacturing apparatus.

Conventionally, as a method for producing a stretched film, tension is applied to the film through a film between a low-speed roll and a high-speed roll, and if necessary, the heater is installed between the low-speed roll and the high-speed roll. A manufacturing method is known in which the film is stretched in the longitudinal direction by heating the film (for example, Patent Document 1 to Patent Document 3). Moreover, the manufacturing method which extends | stretches also to a horizontal direction following the extending | stretching of the vertical direction is known (for example, patent document 4).

And in the stretched film production method, there is a stretching method called necking stretching. The necking stretching is a stretching method in which necking (necking) occurs in a narrow range of the film and the film is stretched. The advantage of carrying out the necking stretching in the method for producing the stretched film is a process performed in blow stretching or the like, and a process for increasing the thickness of the film end for preventing excessive shrinkage in the width direction. Therefore, it is possible to reduce the ends that are cut off and become waste, and to increase productivity.

However, in the necking stretching, it is difficult to control the position and stability of the necking.
In the necking stretching, usually, the position of the necking cannot be controlled, and the position of the necking is moved to a site where the film is in contact with the roll. Cannot be manufactured. Therefore, it is desired that the position of the necking can be controlled.
Further, if the stability of the necking cannot be controlled, a plurality of stretching start points appear from weak or non-uniform portions, and a stretched film with little stretching unevenness cannot be produced. Therefore, it is desired that the stability of the necking can be controlled.
Further, when the necking is stretched, a change in the width due to the necking (neck-in) occurs (for example, Non-Patent Document 1), which affects the productivity of the stretched film obtained when the neck-in is large. It is desired that the necking-in ratio (NR) of the necking can be reduced.

As a technique related to the necking stretching, a hot plate is used, and a temperature gradient is provided from the low temperature portion on the film inlet side stretched to the hot plate to the high temperature portion on the film delivery side, and the necking generated in the film along with stretching. A technique has been proposed in which stretching is performed at the low temperature portion of the hot plate and stretching is completed at the high temperature portion of the hot plate (for example, Patent Document 5).
However, in this proposal, since the temperature of the film that causes the necking is not examined, the position of the necking cannot be controlled, and as a result of the movement of the position of the necking, the film is cut. Moreover, the stability of the necking cannot be sufficiently controlled, and there is a problem that it is difficult to obtain a stretched film with little stretch unevenness. Furthermore, since the range of the necking is relatively wide, there is a problem that it is difficult to reduce the neck-in ratio.

Moreover, in the manufacturing method of a stretched film, when manufacturing a stretched film by biaxial stretching, the manufacturing method of the stretched film which performs necking extending | stretching by the 1st step | stretch is proposed (for example, patent document 6). In this proposal, it is proposed that the first-stage stretching is performed at a temperature lower than the glass transition temperature of the film.
However, in this proposal, since the temperature of the film that causes the necking is not examined, the position of the necking cannot be controlled, and as a result of the movement of the position of the necking, the film is cut. Moreover, the stability of the necking cannot be sufficiently controlled, and there is a problem that it is difficult to obtain a stretched film with little stretch unevenness.

Therefore, a method for producing a stretched film that can perform necking stretching by controlling the position of necking, can obtain a stretched film with little stretching unevenness by controlling the stability of necking, and can further reduce the neck-in ratio. In addition, the present situation is that provision of an apparatus for producing a stretched film is required.

Japanese Patent Laid-Open No. 1-195020 JP 2007-216658 A JP 2009-39983 A JP 2009-173309 A JP-A-5-104619 JP-A-9-295344

This invention makes it a subject to solve the said various problems in the past and to achieve the following objectives. That is, the present invention can perform necking stretching by controlling the position of necking, and can achieve a stretched film with less stretching unevenness by controlling the stability of necking, and further can reduce the neck-in ratio. It aims at providing the manufacturing method of a film, and the manufacturing apparatus of a stretched film.

Means for solving the problems are as follows. That is,
<1> Necking and stretching the film by applying a tension to the film and raising a part of the film to which the tension is applied from a temperature at which the width of the film does not change to a temperature at which necking occurs. It is the manufacturing method of the stretched film characterized.
<2> By applying tension to the film, and heating a part of the film to which the tension is applied to a temperature at which the width of the film does not change by the cooling means, and then raising the temperature to a temperature at which necking occurs by the heating means. The method for producing a stretched film according to <1>, wherein the film is necked and stretched.
<3> The cooling means is a coolable member, the heating means is a heatable member,
It is a manufacturing method of the stretched film as described in said <2> in which tension | tensile_strength is provided in the state which the film contacted the said cooling means and the said heating means.
<4> The method for producing a stretched film according to any one of <2> to <3>, wherein the cooling temperature by the cooling means is a temperature lower by 5 ° C. or more than the glass transition point of the film.
<5> The method for producing a stretched film according to any one of <1> to <4>, wherein the film has a half width of a crystalline peak in X-ray diffraction of less than 9 ° as 2θ.
<6> The method for producing a stretched film according to any one of <1> to <5>, wherein the average thickness of the film is 1.5 μm to 200 μm.
<7> The obtained stretched film has cavities oriented in the stretching direction inside, the average length of the cavities is L (μm), and the cavities in the direction orthogonal to the orientation direction of the cavities The method for producing a stretched film according to any one of <1> to <6>, wherein the L / r ratio when the average diameter is r (μm) is 10 or more.
<8> The method for producing a stretched film according to any one of <1> to <7>, wherein the obtained stretched film is composed of only a crystalline polymer.
<9> The method for producing a stretched film according to any one of <1> to <8>, wherein the obtained stretched film has a reflectance of 50% or more.
<10> Necking is caused in a film heated to a temperature at which necking occurs, the film is necked and stretched, and the position of the necking is moved to the vicinity of the film maintained at a temperature at which the width of the film does not change, It is a manufacturing method of the stretched film in any one of said <1> to <9> to fix.
<11> Necking is caused in the film heated to a temperature at which necking occurs by the heating means, the film is necked and stretched, and the position of the necking is maintained at a temperature at which the width of the film does not change by the cooling means. It is the manufacturing method of the stretched film in any one of said <1> to <10> which moves to the film vicinity and fixes.
<12> tension applying means for applying tension to the film;
An apparatus for producing a stretched film, comprising: a necking generating unit that raises a part of the film to which tension is applied by the tension applying unit to a temperature at which necking occurs from a temperature at which the width of the film does not change. .
<13> The above-mentioned <12>, wherein the necking generating means includes a cooling means for cooling a part of the film to which tension is applied to a temperature at which the width of the film does not change, and a heating means for raising the temperature to a temperature at which necking occurs. It is a manufacturing apparatus of the stretched film as described in.
<14> The stretched film manufacturing apparatus according to <13>, wherein the cooling unit is a coolable member, and the heating unit is a heatable member.

According to the present invention, the conventional problems can be solved, necking can be controlled by controlling the position of necking, and the stability of necking can be controlled to obtain a stretched film with less stretching unevenness. It is possible to provide a stretched film manufacturing method and a stretched film manufacturing apparatus capable of reducing the neck-in ratio.

FIG. 1 is a diagram showing an outline of necking. FIG. 2A is a diagram for specifically explaining the aspect ratio, and is a perspective view of a stretched film having a cavity. FIG. 2B is a diagram for specifically explaining the aspect ratio, and is a cross-sectional view taken along line A-A ′ of the stretched film having a cavity in FIG. 2A. FIG. 2C is a diagram for specifically explaining the aspect ratio, and is a B-B ′ sectional view of a stretched film having a cavity in FIG. 2A. FIG. 3 is a schematic view of one embodiment of the stretched film production apparatus of the present invention. FIG. 4 is a schematic view of one embodiment of the stretched film production apparatus of the present invention. FIG. 5 is a schematic view of one embodiment of the stretched film production apparatus of the present invention. FIG. 6 is a schematic view of one embodiment of the stretched film production apparatus of the present invention. FIG. 7 is a schematic view of one embodiment of the stretched film production apparatus of the present invention. FIG. 8 is a schematic view of a stretched film manufacturing apparatus used in the reference example. FIG. 9 is a schematic view of a stretched film manufacturing apparatus used in the reference example.

(Stretched film manufacturing method and stretched film manufacturing apparatus)
The method for producing a stretched film of the present invention includes at least a stretching step, and further includes other steps as necessary.
The stretching step is a step of stretching the film, and includes at least a tension applying process and a necking generating process, and further includes other processes as necessary.
The stretched film production apparatus of the present invention has at least a stretching machine, and further includes other equipment as necessary.
The stretching machine has at least a tension applying unit and a necking generating unit, and further includes other units as necessary.
In the method for producing a stretched film of the present invention, the stretching step can be performed by the stretching machine. The tension applying process can be performed by the tension applying means. The necking generation process can be performed by the necking generating means.

In necking stretching, since stretching occurs at once in a very narrow range, it is important to heat uniformly in the width direction of the film at the necking position. This is because uniform heating in the width direction of the film can suppress wrinkling of the film during necking stretching, and it is also difficult for uneven thickness of the film to occur. Therefore, it is preferable to heat uniformly in the width direction of the film.
If the heating in the width direction of the film is not uniform, the necking position may not be constant, and the film may wave. Moreover, the film may be distorted by the undulation of the film, and the film may be broken. In normal heating and stretching, since the entire stretching zone is heated and the film is sufficiently soft, the occurrence of unevenness of the film is less than that of necking stretching, and the film is less broken.

<Film>
There is no restriction | limiting in particular as a material of the said film, According to the objective, it can select suitably, For example, a thermoplastic resin etc. are mentioned.
The film may contain a heat stabilizer, an antioxidant, an organic lubricant, a nucleating agent, a dye, a pigment, a dispersant, a coupling agent, and the like. Moreover, after extending | stretching, you may contain cavity formation agents, such as an inorganic fine particle and resin which is not compatible, for producing a cavity in a stretched film.
There is no restriction | limiting in particular as said thermoplastic resin, According to the objective, it can select suitably, For example, a crystalline polymer and an amorphous polymer are mentioned. Among these, the crystalline polymer is preferable in that a stretched film having a cavity can be obtained without using a cavity forming agent such as inorganic fine particles or incompatible resin.

-Crystalline polymer-
In general, polymers are classified into crystalline polymers and amorphous (amorphous) polymers, but even crystalline polymers are not 100% crystalline, and long chain molecules are regularly formed in the molecular structure. It includes aligned crystalline regions and non-regularly arranged amorphous (amorphous) regions.
Therefore, the crystalline polymer only needs to include at least the crystalline region in the molecular structure, and the crystalline region and the amorphous region may be mixed.

There is no restriction | limiting in particular as said crystalline polymer, According to the objective, it can select suitably, For example, polyolefin (for example, low density polyethylene, high density polyethylene, polypropylene, etc.), polyamides (PA) (for example, Nylon-6, etc.), polyacetals (POM), polyesters (eg, PET, PEN, PTT, PBT, PPT, PHT, PBN, PES, PBS, etc.), syndiotactic polystyrene (SPS), polyphenylene sulfide ( PPS), polyether ether ketones (PEEK), liquid crystal polymers (LCP), fluororesin, isotactic polypropylene (isoPP) and the like. Among these, polyolefins, polyesters, syndiotactic polystyrene (SPS), and liquid crystal polymers (LCP) are preferable, and polyolefins and polyesters are more preferable from the viewpoints of durability, mechanical strength, production, and cost. Two or more kinds of these polymers may be blended or copolymerized.

The melt viscosity of the crystalline polymer is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 50 Pa · s to 700 Pa · s, more preferably 70 Pa · s to 500 Pa · s, and more preferably 80 Pa · s. Particularly preferred is s to 300 Pa · s. When the melt viscosity is within the preferred range, the shape of the melt film discharged from the die head during melt film formation is stable, and it is easy to form a uniform film, and the viscosity during melt film formation is appropriate. It is advantageous in that it is easy to extrude, and the melted film at the time of film formation can be leveled to reduce unevenness, and if it is in the particularly preferred range, it is advantageous in that the effect becomes remarkable.
Here, the melt viscosity can be measured by a plate type rheometer or a capillary rheometer.

The intrinsic viscosity (IV) of the crystalline polymer is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.4 to 1.2, more preferably 0.6 to 1.0. 0.7 to 0.9 is particularly preferable. When the IV is in the preferred range, it is advantageous in that the strength of the film formed becomes high and the film can be efficiently stretched, and when the particularly preferred range, the effect becomes remarkable. Is advantageous.
Here, the IV can be measured by an Ubbelohde viscometer.

The melting point (Tm) of the crystalline polymer is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 40 ° C to 350 ° C, more preferably 100 ° C to 300 ° C, and more preferably 100 ° C to 260 ° C. ° C is particularly preferred. When the melting point is in the preferred range, it is easy to keep the shape in the temperature range expected for normal use, and even without special techniques required for processing at high temperatures, it is uniform. It is advantageous in that a stable film can be formed, and if it is in the particularly preferable range, it is advantageous in that the above-described effect becomes remarkable.
Here, the melting point can be measured by a differential thermal analyzer (DSC).

--- Polyester resin--
The polyesters (hereinafter referred to as “polyester resins”) mean a general term for polymer compounds having an ester bond as a main bond chain. Therefore, as the polyester resin suitable as the crystalline polymer, the exemplified PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PTT (polytrimethylene terephthalate), PBT (polybutylene terephthalate), PPT (polypenta). Methylene terephthalate), PHT (polyhexamethylene terephthalate), PBN (polybutylene naphthalate), PES (polyethylene succinate), PBS (polybutylene succinate), as well as by polycondensation reaction of dicarboxylic acid component and diol component All the resulting polymers are included.

The dicarboxylic acid component is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, oxycarboxylic acids, and polyfunctional acids. Can be mentioned.

Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, diphenylsulfone dicarboxylic acid, naphthalenedicarboxylic acid, diphenoxyethanedicarboxylic acid, and 5-sodium sulfoisophthalic acid. Among these, terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, and naphthalenedicarboxylic acid are preferable, and terephthalic acid, diphenyldicarboxylic acid, and naphthalenedicarboxylic acid are more preferable.

Examples of the aliphatic dicarboxylic acid include oxalic acid, succinic acid, eicoic acid, adipic acid, sebacic acid, dimer acid, dodecanedioic acid, maleic acid, and fumaric acid. Examples of the alicyclic dicarboxylic acid include cyclohexane dicarboxylic acid. Examples of the oxycarboxylic acid include p-oxybenzoic acid. Examples of the polyfunctional acid include trimellitic acid and pyromellitic acid. Among the aliphatic dicarboxylic acids and alicyclic dicarboxylic acids, succinic acid, adipic acid, and cyclohexanedicarboxylic acid are preferable, and succinic acid and adipic acid are more preferable.

The diol component is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include aliphatic diols, alicyclic diols, aromatic diols, diethylene glycol, and polyalkylene glycols. Of these, aliphatic diols are preferred.

Examples of the aliphatic diol include ethylene glycol, propane diol, butane diol, pentane diol, hexane diol, neopentyl glycol, and triethylene glycol. Among these, propanediol, butanediol, pentanediol, and hexanediol are particularly preferable.
Examples of the alicyclic diol include cyclohexanedimethanol.
Examples of the aromatic diol include bisphenol A and bisphenol S.

The melt viscosity of the polyester resin is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 50 Pa · s to 700 Pa · s, more preferably 70 Pa · s to 500 Pa · s, and more preferably 80 Pa · s. ˜300 Pa · s is particularly preferred. The higher the melt viscosity, the easier to express cavities during stretching, but if the melt viscosity is within the above preferred range, it will be easier to extrude during film formation or the resin flow will be more stable and less likely to stay. The point that the quality is stabilized, the stretching tension is properly maintained at the time of stretching, it is easy to stretch uniformly, it is difficult to break, and the form of the molten film discharged from the die head at the time of film formation is It is advantageous in terms of improving physical properties such as being easy to maintain, being able to be stably molded, and being less likely to break the product, and is advantageous in that the above-described effects become significant if it is in the particularly preferred range. is there.

The intrinsic viscosity (IV) of the polyester resin is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.4 to 1.2, more preferably 0.6 to 1.0, 0.7 to 0.9 is particularly preferable. When the IV is larger, cavities are more likely to be generated during stretching. However, when the IV is within the preferred range, extrusion is easy during film formation, and the resin flow is stable and stagnation is difficult to occur. Is advantageous in that it is stable, and if it is in the particularly preferred range, it is advantageous in that the above-described effect becomes remarkable. Furthermore, when the IV is within the preferable range, the stretching tension is appropriately maintained at the time of stretching, so that it is easy to stretch uniformly, and it is advantageous in that the load is not easily applied to the apparatus. If it exists, it is advantageous at the point from which the said effect becomes remarkable. In addition, when the IV is in the preferred range, it is advantageous in that the product is less likely to be damaged and the physical properties are increased, and in the particularly preferred range, it is advantageous in that the effect is remarkable. .

The melting point of the polyester resin is not particularly limited and may be appropriately selected depending on the intended purpose. However, from the viewpoint of heat resistance and film forming property, 70 ° C. to 300 ° C. is preferable, and 90 ° C. to 270 ° C. More preferred.

In addition, as said polyester resin, the said dicarboxylic acid component and the said diol component may respectively superpose | polymerize with 1 type, and may form the polymer, and the said dicarboxylic acid component and / or the said diol component are 2 or more types. A polymer may be formed by copolymerization. Further, as the polyester resin, two or more kinds of polymers may be blended and used.

In the blend of two or more polymers, the polymer added to the main polymer has a melt viscosity and an intrinsic viscosity that are close to those of the main polymer, and the addition amount is smaller when the film is formed or melted. It is preferable in that the physical properties are enhanced during extrusion and the extrusion becomes easy.

In addition, for the purpose of improving the flow characteristics of the polyester resin, controlling light transmittance, and improving the adhesion with the coating solution, a resin other than polyester may be added to the polyester resin.

It is preferable that the film can confirm the half width of the crystalline peak in X-ray diffraction. As a half value width, 2θ is preferably less than 9 °, more preferably 7 ° or less, and particularly preferably 5 ° or less. If the half width is 9 ° or more, it is difficult to obtain a stretched film having a cavity. When the half width is in a particularly preferable range, it is advantageous in that a stretched film having a cavity having an appearance with excellent glitter can be produced with stable quality.

The half width can be measured by, for example, an X-ray diffractometer (for example, RINT TTR III, manufactured by Rigaku Corporation).

The average thickness of the film is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 1.5 μm to 200 μm, more preferably 5 μm to 150 μm, and more preferably 20 μm to 100 μm. It is particularly preferred. If the average thickness is less than 1.5 μm, uniform stretching may not be possible, and if it exceeds 200 μm, the manufacturing machine may be burdened and may not be suitable for production (manufacturing may be difficult). When the average thickness is within the particularly preferable range, it is advantageous in that uniform necking stretching is possible and in terms of production suitability.

The average thickness of the film is an average value when the thickness of the film is measured at 10 points using, for example, Long Range Contact Displacement Meter AF030 (measurement unit) and AF350 (instruction unit) manufactured by Keyence Corporation.

<Tension applying treatment and tension applying means>
The tension applying process can be performed by the tension applying means.

-Tensioning means-
The tension applying means is not particularly limited as long as it is a means for applying tension to the film, and can be appropriately selected according to the purpose. For example, a tension applying means having a low speed roll and a high speed roll, Examples include tension applying means using gripping members that grip both ends of the film. Among these, a tension applying means having a low speed roll and a high speed roll is preferable in that a tension can be continuously applied to the film.

For example, in the conveyance of the film using the low-speed roll and the high-speed roll, the low-speed roll is arranged on the upstream side in the conveyance direction of the film. Then, the high-speed roll is arranged on the downstream side, the film is conveyed so as to be in contact with these rolls, and the difference between the peripheral speeds of these rolls is used.

There is no restriction | limiting in particular as the conveyance speed of the said film, According to the objective, it can select suitably.
The transport speed of the film at the position in contact with the low-speed roll is not particularly limited as long as it is lower than the transport speed of the film at the position in contact with the high-speed roll, and can be appropriately selected according to the purpose. 1 mm / min to 500,000 mm / min is preferable, 10 mm / min to 100,000 mm / min is more preferable, and 40 mm / min to 50,000 mm / min is particularly preferable. If the conveying speed is less than 1 mm / min, mechanical control may be difficult, and if it exceeds 500,000 mm / min, the production load may be increased. When the conveyance speed is in the particularly preferred range, it is advantageous in that necking stretching can be performed stably.
The transport speed of the film at the position in contact with the high-speed roll is not particularly limited as long as it is higher than the transport speed of the film at the position in contact with the low-speed roll, and can be appropriately selected according to the purpose. 10 mm / min to 1,000,000 mm / min is preferable, 100 mm / min to 500,000 mm / min is more preferable, and 400 mm / min to 200,000 mm / min is particularly preferable. If the conveying speed is less than 10 mm / min, mechanical control may be difficult, and if it exceeds 1,000,000 mm / min, the production load may be increased. When the conveyance speed is in the particularly preferred range, it is advantageous in that necking stretching can be performed stably.

Here, the conveyance speed of the film at the position in contact with the low-speed roll can be obtained from the peripheral speed of the low-speed roll because it is the same speed as the peripheral speed of the low-speed roll. Moreover, since the conveyance speed of the film in the position in contact with the high-speed roll is the same as the peripheral speed of the high-speed roll, it can be obtained from the peripheral speed of the high-speed roll.

The ratio (h / l) of the film conveyance speed (l) at the position in contact with the low-speed roll and the film conveyance speed (h) at the position in contact with the high-speed roll is particularly limited as long as it exceeds 1. However, (h / l) = 1.1 to 10 is preferable, 2 to 8 is more preferable, and 3 to 6 is particularly preferable. If the ratio is less than 1.1, stretching may not be possible, and if it exceeds 10, the film may be broken during stretching. If the ratio is within the particularly preferable range, it is advantageous in that necking stretching can be performed stably.

The tension applying means having the low speed roll and the high speed roll preferably further has a nip roll. By niping the film with the nip roll and any of the low-speed roll and the high-speed roll, tension can be stably applied to the film.

There is no restriction | limiting in particular as a structure and a magnitude | size of the said low speed roll, the said high speed roll, and the said nip roll, According to the objective, it can select suitably.
There is no restriction | limiting in particular as a shape of the said low speed roll, the said high speed roll, and the said nip roll, According to the objective, it can select suitably, For example, a column shape is mentioned.
There is no restriction | limiting in particular as a material of the said low speed roll, the said high speed roll, and the said nip roll, According to the objective, it can select suitably, For example, a metal, silicon rubber, etc. are mentioned.

The tension applying means having the low speed roll and the high speed roll preferably further has an auxiliary roll. By having the auxiliary roll, tension can be uniformly applied to the film.

The tension applied to the film by the tension application treatment is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 5 MPa to 40 MPa, more preferably 10 MPa to 30 MPa, and particularly preferably 10 MPa to 20 MPa. preferable. When the tension is less than 5 MPa, stretching unevenness is likely to occur, and when it exceeds 40 MPa, the film may be easily cut. When the tension is within the particularly preferable range, it is advantageous in that stretching can be performed stably even at a high speed.
Here, the said tension | tensile_strength shows the tension | tensile_strength with respect to a film (film before extending | stretching).

<Necking generation processing and necking generation means>
The necking generation process can be performed by the necking generation means.

Here, necking is a constriction that occurs in a narrow area of a film during stretching. An outline of necking is shown in FIG. In FIG. 1, W ₀ indicates the width of the film (film before stretching), W indicates the width of the stretched film, and L ₀ is the length of the range of the film in which necking occurs. Usually, in necking stretching, the length of L ₀ is 0.05 mm to 5 mm.

-Necking generation means-
The necking generating means is not particularly limited as long as it is a means for raising a part of the film to which tension is applied from a temperature at which the width of the film does not change to a temperature at which necking occurs. You can choose.

--Temperature at which film width does not change--
The temperature at which the width of the film does not change is a temperature at which the width of the film does not change in the state where the tension is applied, for example, a temperature that is 5 ° C. or more lower than the glass transition point (Tg) of the film.
The width of the film refers to the length in the direction perpendicular to the direction in which the tension is applied in the film. The change usually means shortening.
Here, the glass transition point (Tg) can be measured by a differential thermal analyzer (DSC).
There is no restriction | limiting in particular as the method of making it the temperature which does not change the width | variety of the said film, According to the objective, it can select suitably, For example, the method of making it the temperature which does not change the width | variety of a film with a cooling means, etc. are mentioned.
By cooling to a temperature at which the width of the film does not change by the cooling means, the position of necking can be moved and fixed in the vicinity of the film maintained at a temperature at which the width of the film does not change.

--- Cooling means ---
The cooling means is not particularly limited as long as it can cool the tensioned film to a temperature at which the width of the film does not change, and can be appropriately selected according to the purpose. Examples thereof include setting a member, a cold air generator, and a room in which the stretched film manufacturing apparatus is installed to a cooling temperature. Among these, a coolable member is preferable.

The member that can be cooled is not particularly limited as long as the member itself can be cooled to cool the film, and can be appropriately selected according to the purpose. Examples include a metal member that circulates and a metal member that is attached with a cooling element using electronic cooling.
There is no restriction | limiting in particular as said refrigerant | coolant, According to the objective, it can select suitably, For example, the cooled gas, liquid, etc. are mentioned. An example of the cooled gas is cooled air. Examples of the cooled liquid include cooled water and antifreeze.

There is no restriction | limiting in particular as a magnitude | size of the said member which can be cooled, a structure, and a material, According to the objective, it can select suitably.
The shape of the coolable member is not particularly limited and may be appropriately selected depending on the purpose. However, the coolable member having a substantially arcuate convex surface is easy to contact the film. It is preferable in that it can easily control the temperature.

The coolable member having the substantially arcuate convex surface is not particularly limited and may be appropriately selected depending on the purpose. However, as shown in FIGS. 4 and 6, the end of the substantially arcuate convex surface However, a coolable member having a structure that does not contact the film is preferable in that it can prevent the film from coming into contact with the end portion.

When using the member that can be cooled, it is preferable that the film is in contact with the member that can be cooled in terms of easy control of the temperature of the film.

The cold air generator is not particularly limited as long as it can apply cold air to the film, and can be appropriately selected according to the purpose.
The cold air generator preferably has a dustproof filter. By providing the dustproof filter, dust, dust and the like contained in the cold air can be removed, and a clean stretched film free from adhesion of dust and dust can be produced.

The cooling temperature of the film cooled by the cooling means is not particularly limited as long as the width of the film does not change, and can be appropriately selected according to the purpose, but is 5 from the glass transition point of the film. Preferred is a temperature lower by 50 ° C. or more, more preferred is a temperature lower by 50 ° C. than the glass transition point of the film, and particularly preferred is a temperature in the range of 60 ° C. lower than the glass transition point of the film to 100 ° C. lower than the glass transition point of the film. . If the cooling temperature is higher than a temperature that is 5 ° C. or more lower than the glass transition point of the film, the stretching position may deviate from the heatable member, or stretching unevenness may occur. When the cooling temperature is in the particularly preferable range, it is advantageous in that necking stretching can be stably performed on a heatable member.

--Temperature at which necking occurs--
The temperature at which necking occurs is a temperature at which necking occurs in the film in a state where the tension is applied, and is, for example, a temperature of 5 ° C. lower than the glass transition point (Tg) of the film.
There is no restriction | limiting in particular as the method of making the said necking temperature, It can select suitably according to the objective, For example, the method of making it the temperature which necking with a heating means is mentioned.

--- Heating means ---
The heating means is not particularly limited as long as it can heat the film to which tension is applied to a temperature at which necking occurs, and can be appropriately selected according to the purpose. And laser. Among these, the heatable member is preferable.

The heatable member is not particularly limited as long as the member can be heated by heating the member itself, and can be appropriately selected according to the purpose. The metal member with which a heat medium circulates is mentioned.
There is no restriction | limiting in particular as said heat medium, According to the objective, it can select suitably, For example, the heated gas, liquid, etc. are mentioned. Examples of the heated gas include heated air. Examples of the heated liquid include heated water and heat transfer oil.

There is no restriction | limiting in particular as a magnitude | size of the said member which can be heated, a structure, and a material, According to the objective, it can select suitably.
Further, the shape of the heatable member is not particularly limited and may be appropriately selected according to the purpose. However, the heatable member having a substantially arc-shaped convex surface is easily contacted with the film. It is preferable in that it can easily control the temperature.

The heatable member having the substantially arc-shaped convex surface is not particularly limited and can be appropriately selected according to the purpose. However, as shown in FIGS. 3 and 4, the end of the substantially arc-shaped convex surface. However, a heatable member having a structure that does not come into contact with the film is preferable in that it can prevent the film from coming out of contact with the end portion.

When using the heatable member, it is preferable that the film is in contact with the heatable member in terms of easy control of the temperature of the film.

The heating unit is not particularly limited as long as it has a space capable of heating the film, and can be appropriately selected according to the purpose. Examples thereof include a hot air furnace and a far infrared furnace.

The heating temperature of the film heated by the heating means is not particularly limited as long as it is a temperature at which necking occurs, and can be appropriately selected according to the purpose, but it is 5 from the glass transition point (Tg) of the film. A temperature equal to or higher than the lower temperature is preferable, a temperature equal to or higher than the glass transition point of the film is more preferable, and a temperature in the range of 10 ° C. higher than the glass transition point (Tg) of the film is particularly preferable. . When the heating temperature exceeds a temperature 10 ° C. higher than the glass transition point (Tg) of the film, the neck-in ratio increases and the productivity may be inferior. When the heating temperature is within the particularly preferred range, it is advantageous in that necking stretching is stabilized and productivity is improved.

--- Temperature difference--
In the necking generation process, the temperature difference (BA) between the temperature (A) at which the width of the film does not change and the temperature (B) at which the necking occurs is not particularly limited and is appropriately selected depending on the purpose. However, it is preferably 1 ° C to 100 ° C, more preferably 5 ° C to 80 ° C, and particularly preferably 10 ° C to 50 ° C. If the temperature difference is less than 1 ° C, necking may be difficult to occur, and if it exceeds 100 ° C, the film may be easily cut. If the temperature difference is within the particularly preferred range, it is advantageous in that the film can be stably produced without being cut.
When the film material is a polyester resin, the temperature difference is preferably 5 ° C. to 80 ° C., more preferably 8 ° C. to 50 ° C., and particularly preferably 10 ° C. to 20 ° C. If the temperature difference exceeds 80 ° C., necking may not occur. If the temperature difference is within the particularly preferred range, it is advantageous in that the film can be stably produced without being cut.

In the necking generation process, the film that has been heated to a temperature at which necking occurs is necked, the film is necked and stretched, and the position of the necking is maintained at a temperature at which the width of the film does not change It is preferable to move it to the vicinity and fix it from the viewpoint of easily controlling the position of necking.
As a method of moving and fixing the position of necking in the vicinity of the film maintained at a temperature at which the width of the film does not change, for example, after necking is generated on the downstream side in the film transport direction, the position of necking is set. Is gradually moved to the vicinity of the film, which is upstream of the film conveyance direction from the position where the necking occurs and is maintained at a temperature at which the film width does not change, and the position of the necking is moved to that position. The method of fixing is mentioned.

Here, an example of a method for moving and fixing the position of necking in the vicinity of the film maintained at a temperature at which the width of the film does not change will be described using the manufacturing apparatus of FIG.
The stretched film manufacturing apparatus in FIG. 4 includes a low-speed roll 3, a high-speed roll 4, a coolable member (cooling means) 5, a heatable member (heating means) 6 a, a nip roll 7, and an auxiliary roll 8. The coolable member 5 is a metal member having a substantially arc-shaped convex surface through which a coolant circulates, and the substantially arc-shaped convex surface is in contact with the film 2, but the end of the substantially arc-shaped convex surface. The part has a structure that does not contact the film 2. The heatable member 6a is a metal member having a substantially arc-shaped convex surface, in which a heat medium circulates. The substantially arc-shaped convex surface is in contact with the film 2, but the substantially arc-shaped convex surface The end has a structure that does not contact the film 2.

As a method of moving and fixing the position of the necking in the vicinity of the film maintained at a temperature at which the width of the film does not change, first, the film 2 is transported between the low-speed roll 3 and the high-speed roll 4. . At this time, the film 2 is conveyed from the low-speed roll 3 side to the high-speed roll 4 side by making the peripheral speed of the high-speed roll 4 faster than the low-speed roll 3. Further, tension is applied to the film 2 by the difference in peripheral speed between the low-speed roll 3 and the high-speed roll 4. The film 2 is nipped by the low-speed roll 3 and the nip roll 7, and the film 2 is nipped by the high-speed roll 4 and the nip roll 7, whereby a tension is stably applied to the film 2.
Subsequently, a part of the film 2 being conveyed is brought into contact with the member 5 that can be cooled to cool the film 2 to a temperature at which the width of the film does not change. Subsequently, a part of the film 2 cooled to a temperature at which the width of the film does not change is moved by conveying the film 2 and brought into contact with the heatable member 6a to raise the temperature to a temperature at which necking occurs. . By this temperature increase, necking occurs in the film 2, and the film is necked and stretched.
At this time, necking occurs on the downstream side (position b in FIG. 4) in the transport direction of the film 2, and necking stretching starts. When the necking stretching is continued, the necking position is upstream in the transport direction of the film 2, and the vicinity of the film 2 maintained at a temperature at which the width of the film does not change by the coolable member 5 (see FIG. The position of necking is fixed at the position (position a in FIG. 4).
4 denote the same components in FIGS. 3 to 8. FIG.

<Stretched film>
There is no restriction | limiting in particular as a material of the said stretched film, According to the objective, it can select suitably, For example, it may consist only of crystalline polymers and contains other components other than crystalline polymers. It may be a thing. Among these, it is preferable that the stretched film is composed only of the crystalline polymer in that the stretched film obtained is a stretched film having cavities, and the stretched film having the cavities can be produced with stable quality.

Here, the stretched film made of only the crystalline polymer may contain other components other than the crystalline polymer as necessary as long as it does not contribute to the development of the cavity. Examples of the other components include a heat resistance stabilizer, an antioxidant, an organic lubricant, a nucleating agent, a dye, a pigment, a dispersant, and a coupling agent. Whether or not the other component contributes to the development of the cavity can be determined by whether or not a component other than the crystalline polymer is detected in the cavity or at the interface portion of the cavity.

-Stretched film with cavities-
The stretched film having a cavity is a stretched film having a cavity therein.

The term “cavity” means a vacuum domain or a gas phase domain present inside a stretched film having the cavity. The cavity can be confirmed by a photograph taken with an optical microscope or a scanning electron microscope.

The stretched film having the cavities preferably has the cavities oriented in the stretching direction, and the aspect ratio of the cavities is preferably in a specific range.

The aspect ratio is an L / r ratio when the average length of the cavities is L (μm) and the average diameter of the cavities in the direction orthogonal to the orientation direction of the cavities is r (μm) (hereinafter, “ It may be abbreviated as “aspect ratio”.)
There is no restriction | limiting in particular as said aspect-ratio, Although it can select suitably according to the objective, 10 or more are preferable, 15 or more are more preferable, and 20 or more are especially preferable.

2A to 2C are diagrams for specifically explaining the aspect ratio, FIG. 2A is a perspective view of a stretched film having a cavity, and FIG. 2B is an A view of the stretched film having a cavity in FIG. 2A. FIG. 2C is a cross-sectional view taken along the line −A ′, and FIG. 2C is a cross-sectional view taken along the line BB ′ of the stretched film having a cavity in FIG. 2A.

In the manufacturing process of the stretched film having the cavities, the cavities are usually oriented along the first stretching direction. Accordingly, the “average length of the cavities (L (μm))” is a cross section perpendicular to the surface 1a of the stretched film 1 having independent cavities and parallel to the first stretching direction (B in FIG. 2A). This corresponds to the average length L (see FIG. 2C) of the cavity 100 in (−B ′ cross section). The “average diameter of cavities (r (μm))” is a cross section perpendicular to the surface 1a of the stretched film 1 having independent cavities and perpendicular to the first stretching direction (AA in FIG. 2A). This corresponds to the average thickness r (see FIG. 2B) of the cavity 100 in the “cross section”.

In addition, said 1st extending | stretching direction shows the extending direction of 1 axis | shaft, when extending | stretching is only 1 axis | shaft. In the present invention, since the necking stretching is performed along the transport direction of the film during the production of the stretched film, the necking stretching direction corresponds to the first stretching direction.
Moreover, when extending | stretching is biaxial or more, at least 1 direction is shown among the extending directions aiming at cavity formation. Usually, even in biaxial or more stretching, the necking stretching direction corresponds to the first stretching direction.

Here, the average length (L (μm)) of the cavity can be measured by an image of an optical microscope or an electron microscope. Similarly, the average diameter (r (μm)) of the cavities can be measured by an image of an optical microscope or an electron microscope.

The average number P of the cavities in the direction orthogonal to the orientation direction of the cavities (the thickness direction of the stretched film having the cavities) is not particularly limited and may be appropriately selected depending on the purpose, but may be 5 or more. 10 or more is more preferable, and 15 or more is particularly preferable.

In the manufacturing process of the stretched film having the cavities, the cavities are usually oriented along the first stretching direction. Therefore, the “number of the cavities in the direction orthogonal to the orientation direction of the cavities” is a cross section perpendicular to the surface 1a of the stretched film 1 having the cavities and perpendicular to the first stretch direction (A− in FIG. 2A). In the A ′ cross section), this corresponds to the number of cavities 100 included in the film thickness direction.
Here, the average number P of the cavities in the direction orthogonal to the orientation direction of the cavities can be measured by an image of an optical microscope or an electron microscope.

The average thickness of the stretched film is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 1.5 μm to 200 μm, more preferably 5 μm to 150 μm, and more preferably 20 μm to 100 μm. It is particularly preferred that If the average thickness is less than 1.5 μm, uniform stretching may not be possible, and if it exceeds 200 μm, the manufacturing machine may be burdened and may not be suitable for production (manufacturing may be difficult). When the average thickness is within the particularly preferable range, it is advantageous in that uniform necking stretching is possible and in terms of production suitability.

The average thickness of the stretched film is, for example, an average value when the thickness of the stretched film is measured at 10 points using a long range contact displacement meter AF030 (measurement unit) and AF350 (instruction unit) manufactured by Keyence Corporation. is there.

There is no restriction | limiting in particular as a reflectance of the said stretched film, Although it can select suitably according to the objective, It is preferable that it is 50% or more, It is more preferable that it is 80% or more, It is 85% or more. It is particularly preferred. When the reflectance is within the particularly preferable range, it is advantageous in that the obtained stretched film can be applied to an aluminum reflective film.

The reflectance of the stretched film is the wavelength when the integrating sphere is attached to a spectrophotometer (“V-570”; manufactured by JASCO Corporation), and the reflectance is measured for each wavelength of 200 nm to 2,500 nm. The reflectance at 550 nm. Here, as a reference value, the reflectance of the standard white board attached to the apparatus is set to 100%.

The width of the stretched film is preferably little changed with respect to the width of the film after stretching. The change in the width (W) of the stretched film with respect to the width (W ₀ ) of the film (film before stretching) is represented by an index called a neck-in ratio (NR). The neck-in ratio is expressed by the following equation.
Formula NR = (W ₀ −W) / W ₀
The smaller the numerical value, the smaller the value of the neck-in ratio, and the smaller the change in the width of the film before and after stretching, the better.
The neck-in ratio is preferably 0.05 to 0.5, more preferably 0.05 to 0.3, and particularly preferably 0.05 to 0.15. When the neck-in ratio is in the particularly preferable range, it is advantageous in that necking stretching can be performed stably.

Examples of the present invention will be described below, but the present invention is not limited to the following examples.

(Production Example 1)
<Manufacture of film>
PBT (polybutylene terephthalate 100% resin) having an intrinsic viscosity (IV) = 0.71 was extruded from a T-die at 245 ° C. using a melt extruder and solidified by a casting drum to have a width of 100 mm and an average thickness of 158 μm. A polymer molded body (film A) was obtained.
The glass transition point of the obtained film A was 36 ° C.
It was confirmed that the half width of the crystalline peak in X-ray diffraction of the obtained film A was less than 9 ° as 2θ.

<Measurement>
The glass transition point and crystallite size were measured by the following methods.
<< 1 >> Glass transition point (Tg)
The glass transition point (Tg) of the film was measured with a differential thermal analyzer (DSC).

<< 2 >> Measurement of half-width of crystalline peak The obtained film was made to have a width of 25 mm and pasted on a glass sample holder, and the following measurement conditions were used using an X-ray diffractometer (RINT TTR III, manufactured by Rigaku Corporation). After the measurement, the peak separation of the crystalline peak and the amorphous peak (2θ = 20 °) was performed, and the half width of each peak was measured.
-Measurement condition-
X-ray intensity: 50 kV-300 mA
Divergent slit: Open Divergent longitudinal slit: 10mm
Scattering slit: 0.05 mm
Light receiving slit: 0.15 mm
Scanning speed: 4 ° / min
Scan range: 2θ = 5-60 °

(Production Example 2)
<Manufacture of film>
PET (polyethylene terephthalate) having an intrinsic viscosity (IV) = 0.66 is extruded from a T die using a melt extruder at 300 ° C. and solidified by a casting drum, and a polymer molded body having a width of 100 mm and an average thickness of 80 μm ( Film B) was obtained.
The glass transition point of the obtained film B was 75 ° C.
It was confirmed that the half width of the crystalline peak in X-ray diffraction of the obtained film B was less than 9 ° as 2θ.

(Production Example 3)
<Manufacture of film>
PET (polyethylene terephthalate) with intrinsic viscosity (IV) = 0.66 and PEN (polyethylene naphthalate) with intrinsic viscosity (IV) = 0.64 are mixed at 60/40 (mass ratio), and melt extrusion is performed. A polymer molded body (film C) having a width of 100 mm and an average thickness of 90 μm was obtained by extrusion from a T die at 260 ° C. using a machine and solidifying with a casting drum.
The glass transition point of the obtained film C was 90 ° C.
It was confirmed that the half width of the crystalline peak in X-ray diffraction of the obtained film C was 11 ° as 2θ.

Example 1
<Stretching of film>
The film A was necked and stretched using the stretched film manufacturing apparatus shown in FIG.
First, the transport speed of the film A at a position in contact with the low speed roll 3 is 200 mm / min, the transport speed of the film A at a position in contact with the high speed roll 4 is 1,100 mm / min, and the film A is removed from the low speed roll 3. It was conveyed toward the high-speed roll 4. At this time, a tension of 10 MPa was applied to the film A. The film A was conveyed so as to be in contact with the heatable member 6a.
While transporting the film A, a part of the film A was set to 25 ° C. (temperature at which the width of the film does not change) on the upstream side in the transport direction of the film A from the heatable member 6a. A part of the film A at 25 ° C. was moved to the downstream side in the conveyance direction by conveyance of the film A, brought into contact with the heatable member 6a, and heated to 43 ° C. (temperature at which necking occurred).
Necking occurred in the film A by these treatments. The position of necking was the position of b in FIG. 3 immediately after starting the necking stretching, but when the necking stretching was continued, the position of FIG. 3 a (the film maintained at a temperature at which the film width did not change). It moved back to the vicinity of A), fixed at that position, and then stopped moving.
During the necking stretching, the film A was not cut and a stretched film could be produced stably.
The following evaluation was performed about the obtained stretched film. The evaluation results are shown in Table 1.
In addition, although the external appearance of the film A was transparent, the external appearance of the stretched film which has the cavity obtained by extending | stretching was silver. Therefore, the position of necking was easily confirmed by visually observing the appearance of the film being stretched.

<Evaluation>
<< 1 >> Average thickness of (stretched) film Using a long-range contact displacement meter AF030 (measurement unit) and AF350 (indicating unit) manufactured by Keyence Corporation, the thickness of the (stretched) film was measured at 10 points. The average value was defined as the average thickness.

<< 2 >> Stretching Unevenness The stretched film was visually observed, and the stretching unevenness was evaluated according to the following evaluation criteria.
No stretching unevenness: Streaks are not visible in the width direction of the film.
Small stretch unevenness: Streaks appear in the width direction of the film.
Uneven stretching: streaks appear in the width direction of the film, and there are still undrawn portions that are not stretched.
Here, the undrawn portion refers to a portion having a thickness that is twice or more the average thickness of the stretched film. The thickness was measured using a long range contact displacement meter AF030 (measurement unit) and AF350 (instruction unit) manufactured by Keyence Corporation.

<< 3 >> Neck-in ratio (NR)
The neck-in ratio (NR) was measured. The neck-in ratio (NR) is an index showing the relationship between the width (W ₀ ) of the film before stretching and the width (W) of the stretched film in FIG.
Formula NR = (W ₀ −W) / W ₀
The smaller the numerical value, the smaller the value of the neck-in ratio, and the smaller the change in the width of the film before and after stretching, the better.

<< 4 >> Presence / absence of voids Photographs taken with an optical microscope or a scanning electron microscope were observed to confirm the presence / absence of voids.

<< 5 >> Aspect Ratio A section (see FIG. 2B) perpendicular to the surface of the stretched film and perpendicular to the longitudinal stretching direction (necking stretching direction), and perpendicular to the surface of the stretched film and the longitudinal stretching A cross section parallel to the direction (see FIG. 2C) was examined using a scanning electron microscope at an appropriate magnification of 300 to 3000 times, and a measurement frame was set in each of the cross-sectional photographs. This measurement frame was set so that 50 to 100 cavities were included in the measurement frame.
Next, the number of cavities included in the measurement frame is measured, and the number of cavities included in the measurement frame having a cross section perpendicular to the longitudinal stretching direction (see FIG. 2B) is m and the cross section parallel to the longitudinal stretching direction. The number of cavities included in the measurement frame (see FIG. 2C) was n.
Then, the longitudinal stretching direction perpendicular cross section of the measurement frame measured one by one in the thickness of the cavity (r _i) included in (see FIG. 2B), and the thickness of the average and the average diameter r. Further, the length (L _i ) of each cavity included in the measurement frame (see FIG. 2C) having a cross section parallel to the longitudinal stretching direction was measured, and the average length was defined as L.
That is, r and L can be represented by the following formulas (1) and (2), respectively.
r = (Σr _i ) / m (1)
L = (ΣL _i ) / n (2)
Then, L / r was calculated as an aspect ratio.

<< 6 >> Reflectance An integrating sphere was attached to a spectrophotometer (“V-570”; manufactured by JASCO Corp.), and the reflectance was measured for each wavelength of 200 nm to 2,500 nm. Of these, the reflectance at a wavelength of 550 nm was taken as the reflectance in this measurement. Here, as a reference value, the reflectance of the standard white board attached to the apparatus was set to 100%.

(Example 2)
<Stretching of film>
The film A was necked and stretched using the stretched film manufacturing apparatus shown in FIG.
First, the transport speed of the film A at a position in contact with the low speed roll 3 is 110 mm / min, the transport speed of the film A at a position in contact with the high speed roll 4 is 510 mm / min, and the film A is moved from the low speed roll 3 to the high speed. It was conveyed toward the roll 4. At this time, a tension of 10 MPa was applied to the film A. Further, the film A was conveyed so as to come into contact with the coolable member 5 and the heatable member 6a.
While transporting the film A, a part of the film A was brought into contact with the coolable member 5 and cooled to 10 ° C. (temperature at which the width of the film did not change). A part of the cooled film A was moved to the downstream side in the transport direction by transport of the film A, brought into contact with the heatable member 6a, and heated to 38 ° C. (temperature at which necking occurred).
Necking occurred in the film A by these treatments. The position of necking was the position of b in FIG. 4 immediately after starting the necking stretching, but when the necking stretching was continued, the position of FIG. 4 a (the film maintained at a temperature at which the film width did not change). It moved back to the vicinity of A), fixed at that position, and then stopped moving.
During the necking stretching, the film A was not cut and a stretched film could be produced stably.
Evaluation similar to Example 1 was performed about the obtained stretched film. The evaluation results are shown in Table 1.

(Example 3)
<Stretching of film>
The film A was necked and stretched using the stretched film manufacturing apparatus shown in FIG. In the stretched film manufacturing apparatus shown in FIG. 5, the interval between the low speed roll 3 and the high speed roll 4 was set to 20 cm. Moreover, the heating part 6b was installed so that the edge part might be installed in the position 5 cm away from the said low speed roll 3, and the said high speed roll 4 may be covered. The high speed roll 4 may be outside the heating unit 6b.
First, the conveyance speed of the film A at a position in contact with the low-speed roll 3 is 110 mm / min, the conveyance speed of the film A at a position in contact with the high-speed roll 4 is 510 mm / min, and the film A is removed from the low-speed roll 3. It was conveyed toward the high-speed roll 4. At this time, a tension of 10 MPa was applied to the film A.
While transporting the film A, a part of the film A is placed at 25 ° C. (the width of the film is outside the heating unit 6b and upstream of the heating unit 6b in the transport direction of the film A). Temperature). A part of the film A at 25 ° C. was moved downstream in the transport direction by transport of the film A, and the temperature was raised to 40 ° C. (temperature at which necking occurred) in the heating unit 6b.
Necking occurred in the film A by these treatments. Necking occurred in the heating unit 6b, and the position of necking was fixed at a position near 6 cm from the low speed roll 3 in the heating unit 6b.
During the necking stretching, the film A was not cut and a stretched film could be produced stably.
Evaluation similar to Example 1 was performed about the obtained stretched film. The evaluation results are shown in Table 1.

Example 4
<Stretching of film>
The film A was necked and stretched using the stretched film manufacturing apparatus shown in FIG. In the stretched film manufacturing apparatus shown in FIG. 6, the distance between the low speed roll 3 and the high speed roll 4 was set to 20 cm. Moreover, the heating part 6b was installed so that the edge part might be installed in the position 5 cm away from the said low speed roll 3, and the said high speed roll 4 may be covered. The high speed roll 4 may be outside the heating unit 6b.
First, the conveyance speed of the film A at a position in contact with the low-speed roll 3 is 100 mm / min, the conveyance speed of the film A at a position in contact with the high-speed roll 4 is 520 mm / min, and the film A is removed from the low-speed roll 3. It was conveyed toward the high-speed roll 4. At this time, a tension of 10 MPa was applied to the film A.
While transporting the film A, a part of the film A was brought into contact with the coolable member 5 and cooled to 10 ° C. (temperature at which the width of the film did not change). A part of the cooled film A was moved downstream in the transport direction by transport of the film A, and the temperature was raised to 37 ° C. (temperature at which necking occurred) in the heating unit 6b.
Necking occurred in the film A by these treatments. Necking occurred in the heating unit 6b, and the position of necking was fixed at a position near 6 cm from the low speed roll 3 in the heating unit 6b.
During the necking stretching, the film A was not cut and a stretched film could be produced stably.
Evaluation similar to Example 1 was performed about the obtained stretched film. The evaluation results are shown in Table 1.

(Example 5)
<Stretching of film>
The film A was necked and stretched using the stretched film manufacturing apparatus shown in FIG. In the stretched film manufacturing apparatus shown in FIG. 7, the distance between the low speed roll 3 and the high speed roll 4 was set to 20 cm. Moreover, the heating part 6b was installed so that the edge part might be installed in the position 5 cm away from the said low speed roll 3, and the member 5 which can be cooled, and the said high speed roll 4 may be covered. The high speed roll 4 may be outside the heating unit 6b.
First, the transport speed of the film A at a position in contact with the low speed roll 3 is 150 mm / min, the transport speed of the film A at a position in contact with the high speed roll 4 is 810 mm / min, and the film A is moved from the low speed roll 3. It was conveyed toward the high-speed roll 4. At this time, a tension of 10 MPa was applied to the film A.
While transporting the film A, a part of the film A was brought into contact with the coolable member 5 and cooled to 15 ° C. (a temperature at which the width of the film did not change). A part of the cooled film A was moved downstream in the transport direction by transport of the film A, and the temperature was raised to 41 ° C. (temperature at which necking occurred) in the heating unit 6b.
Necking occurred in the film A by these treatments. Necking occurred in the heating unit 6b, and the position of necking was fixed at a position 1 to 2 cm away from the coolable member 5 in the heating unit 6b on the downstream side in the transport direction.
During the necking stretching, the film A was not cut and a stretched film could be produced stably.
Evaluation similar to Example 1 was performed about the obtained stretched film. The evaluation results are shown in Table 1.

(Example 6)
<Stretching of film>
In Example 2, the film A was cooled at 15 ° C. by the coolable member 5 and the film A was heated at 39 ° C. by the heatable member 6a. A was necked and stretched.
The position of necking was the position of b in FIG. 4 immediately after starting the necking stretching, but when the necking stretching was continued, the position of FIG. 4 a (the film maintained at a temperature at which the film width did not change). It moved back to the vicinity of A), fixed at that position, and then stopped moving.
During the necking stretching, the film A was not cut and a stretched film could be produced stably.
Evaluation similar to Example 1 was performed about the obtained stretched film. The evaluation results are shown in Table 1.

(Example 7)
<Stretching of film>
In Example 4, the transport speed of the film A at the position in contact with the low-speed roll 3 is 110 mm / min, the transport speed of the film A at the position in contact with the high-speed roll 4 is 510 mm / min, and the film by the coolable member 5 The film A was necked and stretched in the same manner as in Example 4 except that the cooling temperature of A was 15 ° C. and the heating temperature of the film A in the heating unit 6b was 40 ° C.
Necking occurred in the heating unit 6b, and the position of necking was fixed at a desired position in the heating unit 6b.
During the necking stretching, the film A was not cut and a stretched film could be produced stably.
Evaluation similar to Example 1 was performed about the obtained stretched film. The evaluation results are shown in Table 1.

(Example 8)
<Stretching of film>
In Example 2, the film B was necked and stretched by the same stretching method as in Example 2 except that the film type, cooling temperature, and heating temperature were the conditions shown in Table 1.
The position of necking was the position of b in FIG. 4 immediately after starting the necking stretching, but when the necking stretching was continued, the position of FIG. 4 a (the film maintained at a temperature at which the film width did not change). It moved back to the vicinity of B), fixed at that position, and then stopped moving.
During the necking stretching, the film B was not cut, and a stretched film could be produced stably.
Evaluation similar to Example 1 was performed about the obtained stretched film. The evaluation results are shown in Table 1.

Example 9
<Stretching of film>
In Example 4, the transport speed of the film A at the position in contact with the low speed roll 3 is 110 mm / min, the transport speed of the film A at the position in contact with the high speed roll 4 is 510 mm / min, and the type of film and the cooling temperature The film B was necked and stretched by the same stretching method as in Example 4 except that the heating temperature was changed to the conditions shown in Table 1.
Necking occurred in the heating unit 6b, and the position of necking was fixed at a desired position in the heating unit 6b.
During the necking stretching, the film B was not cut, and a stretched film could be produced stably.
Evaluation similar to Example 1 was performed about the obtained stretched film. The evaluation results are shown in Table 1.

(Example 10)
<Stretching of film>
In Example 2, the film C was necked and stretched in the same manner as in Example 2 except that the film type, cooling temperature, and heating temperature were the conditions shown in Table 1.
The position of necking was the position of b in FIG. 4 immediately after starting the necking stretching, but when the necking stretching was continued, the position of FIG. 4 a (the film maintained at a temperature at which the film width did not change). It moved back to the vicinity of C), fixed at that position, and then stopped moving.
During the necking stretching, the film C was not cut, and a stretched film could be produced stably.
Evaluation similar to Example 1 was performed about the obtained stretched film. The evaluation results are shown in Table 1.

(Example 11)
<Stretching of film>
In Example 4, the transport speed of the film A at the position in contact with the low speed roll 3 is 110 mm / min, the transport speed of the film A at the position in contact with the high speed roll 4 is 510 mm / min, and the type of film and the cooling temperature The film C was necked and stretched in the same manner as in Example 4 except that the heating temperature was changed to the conditions shown in Table 1.
Necking occurred in the heating unit 6b, and the position of necking was fixed at a desired position in the heating unit 6b.
During the necking stretching, the film C was not cut, and a stretched film could be produced stably.
Evaluation similar to Example 1 was performed about the obtained stretched film. The evaluation results are shown in Table 1.

(Reference Example 1)
<Stretching of film>
The film A was necked and stretched using the stretched film manufacturing apparatus shown in FIG.
First, the transport speed of the film A at a position in contact with the low speed roll 3 is 110 mm / min, the transport speed of the film A at a position in contact with the high speed roll 4 is 510 mm / min, and the film A is moved from the low speed roll 3 to the high speed. It was conveyed toward the roll 4. At this time, a tension of 10 MPa was applied to the film A.
While transporting the film A, a part of the film A was heated to 40 ° C. (temperature at which necking occurs) by the preheating roll 9. A part of the heated film A was moved to the downstream side in the conveyance direction by conveyance of the film A, and contacted with the heatable member 6a and maintained at 40 ° C. (temperature at which necking occurred).
Necking occurred in the film A by these treatments.
While necking is being stretched, the state of necking is unstable and the position of necking moves to a part that contacts the low-speed roll. As a result, film A often breaks, producing a stretched film stably. could not.
Evaluation similar to Example 1 was performed about the obtained stretched film. The evaluation results are shown in Table 1.

(Reference Example 2)
<Stretching of film>
The film A was necked and stretched using the stretched film manufacturing apparatus shown in FIG. In the manufacturing apparatus, the distance between the low speed roll 3 and the high speed roll 4 was 20 cm. Moreover, the heating part 6b was installed so that the said low speed roll 3 and the said high speed roll 4 might be covered.
First, the conveyance speed of the film A at a position in contact with the low-speed roll 3 is 110 mm / min, the conveyance speed of the film A at a position in contact with the high-speed roll 4 is 510 mm / min, and the film A is removed from the low-speed roll 3. It was conveyed toward the high-speed roll 4. At this time, a tension of 10 MPa was applied to the film A.
While transporting the film A, a part of the film A was heated to 40 ° C. (temperature at which necking occurs) in the heating unit 6b.
Necking occurred in the film A by these treatments.
While necking is being stretched, the state of necking is unstable and the position of necking moves to a part that contacts the low-speed roll. As a result, film A often breaks, producing a stretched film stably. could not.
Evaluation similar to Example 1 was performed about the obtained stretched film. The evaluation results are shown in Table 1.

(Reference Example 3)
<Stretching of film>
In Reference Example 1, film B was necked and stretched in the same manner as in Reference Example 1 except that the film type and the heating temperature were changed to the conditions shown in Table 1.
While necking is being stretched, the state of necking is unstable and the position of necking moves to a part that contacts the low-speed roll. As a result, film B often breaks, producing a stretched film stably. could not.
Evaluation similar to Example 1 was performed about the obtained stretched film. The evaluation results are shown in Table 1.

(Reference Example 4)
<Stretching of film>
In Reference Example 1, the film C was necked and stretched in the same manner as in Reference Example 1 except that the type of film and the heating temperature were changed to the conditions shown in Table 1.
While necking is being stretched, the state of necking is unstable and the position of necking moves to the part that contacts the low-speed roll. As a result, film C often breaks, producing a stretched film stably. could not.
Evaluation similar to Example 1 was performed about the obtained stretched film. The evaluation results are shown in Table 1.

Nine crystalline peaks were observed in the X-ray diffraction of film A, and their half-widths were in the range of 0.4 ° to 4.1 °.
In the X-ray diffraction of film B, five crystalline peaks were observed, and their half widths were in the range of 4 ° to 7 °.
Since the stretched films obtained in Examples 10 and 11 and Reference Example 4 did not have independent cavities, the aspect ratio could not be obtained.

In the stretching methods of Examples 1 to 11, the state of necking was stable, and a stretched film with little or no stretching unevenness could be produced. During necking stretching, the film was not cut and a stretched film having an excellent neck-in ratio could be produced. In the stretching methods of Examples 2 to 9, a stretched film having no stretching unevenness and particularly excellent could be produced.
On the other hand, in the stretching methods of Reference Examples 1 to 4, the state of necking was unstable, and the obtained stretched film had large stretching unevenness. During necking stretching, the film was sometimes cut and the neck-in ratio was inferior to that of the examples.

The stretched film manufacturing method and stretched film manufacturing apparatus of the present invention can be suitably used for manufacturing a stretched film having a cavity, for example.

DESCRIPTION OF SYMBOLS 1 Stretched film which has a cavity 1a Surface 2 Film 3 Low speed roll 4 High speed roll 5 Coolable member (cooling means)
6a Heatable member (heating means)
6b Heating part (heating means)
7 Nip roll 8 Auxiliary roll 9 Preheating roll 100 Cavity L Cavity length in cavity orientation direction r Cavity thickness in thickness direction perpendicular to cavity orientation direction

Claims (14)

1. The film is necked and stretched by applying a tension to the film and raising a part of the film to which the tension is applied from a temperature at which the width of the film does not change to a temperature at which necking occurs. A method for producing a stretched film.
2. Applying tension to the film, and heating the part of the film to which tension is applied to a temperature at which the width of the film does not change by the cooling means, and then raising the temperature to a temperature at which necking occurs by the heating means. The manufacturing method of the stretched film of Claim 1 which carries out necking extending | stretching.
3. The cooling means is a coolable member, the heating means is a heatable member,
   The manufacturing method of the stretched film of Claim 2 in which tension | tensile_strength is provided in the state which the film contacted the said cooling means and the said heating means.
4. The method for producing a stretched film according to any one of claims 2 to 3, wherein the cooling temperature by the cooling means is a temperature lower by 5 ° C or more than the glass transition point of the film.
5. The method for producing a stretched film according to any one of claims 1 to 4, wherein the film has a half width of a crystallinity peak in X-ray diffraction of less than 9 ° as 2θ.
6. 6. The method for producing a stretched film according to claim 1, wherein the average thickness of the film is 1.5 μm to 200 μm.
7. The obtained stretched film has cavities oriented in the stretching direction inside, the average length of the cavities is L (μm), and the average diameter of the cavities in the direction orthogonal to the orientation direction of the cavities is The method for producing a stretched film according to claim 1, wherein an L / r ratio when r (μm) is 10 or more.
8. The method for producing a stretched film according to any one of claims 1 to 7, wherein the stretched film obtained is composed of only a crystalline polymer.
9. The method for producing a stretched film according to any one of claims 1 to 8, wherein the obtained stretched film has a reflectance of 50% or more.
10. Necking is caused in a film that has been heated to a temperature at which necking occurs, the film is necked and stretched, and the position of the necking is moved to the vicinity of the film maintained at a temperature at which the width of the film does not change, and fixed. Item 10. A method for producing a stretched film according to any one of Items 1 to 9.
11. Necking occurs in the film heated to a temperature at which necking occurs by heating means, the film is necked and stretched, and the position of the necking is maintained in the vicinity of the film maintained at a temperature at which the width of the film does not change by the cooling means. The method for producing a stretched film according to claim 1, wherein the stretched film is moved and fixed.
12. Tension applying means for applying tension to the film;
    An apparatus for producing a stretched film, comprising: a necking generating unit that raises a part of the film to which tension is applied by the tension applying unit from a temperature at which the width of the film does not change to a temperature at which necking occurs.
13. The stretching according to claim 12, wherein the necking generating means includes a cooling means for cooling a part of the tensioned film to a temperature at which the width of the film does not change, and a heating means for raising the temperature to a temperature at which necking occurs. Film production equipment.
14. The apparatus for producing a stretched film according to claim 13, wherein the cooling means is a coolable member, and the heating means is a heatable member.

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