JP2010208078A - Method for manufacturing acrylic resin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a film of fine appearance with no flaw while reducing the occurrence of thickness unevenness in the width direction of the film in a longitudinal stretching process to solve problems wherein the thickness of both ends of a longitudinally stretched film is thicker than the center part by neck-in in a roll longitudinal stretching process regarding a method for manufacturing a successive biaxially-oriented film for optical use, and the film is liable to break from a chuck portion in a following lateral stretching process to make stable production difficult in a brittle resin film such as an acrylic resin film in particular regarding such a longitudinally stretched film. <P>SOLUTION: In the process for carrying out roll longitudinal stretching of an unstretched molten extruded acrylic resin film, a distance between film holding parts is set large, and roll longitudinal stretching is carried out while giving a temperature gradient in the width direction of the film to be Te>Tc when setting the temperature of both ends of the film in conveyance to Te and the temperature of the center part to Tc between a low peripheral speed roll and a high peripheral speed roll. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  In recent years, along with the downsizing, thinning, and weight reduction of notebook computers, word processors, mobile phones, personal digital assistants, etc., liquid crystal display devices that take advantage of the light weight and compactness of these electronic devices have come to be widely used. It is coming. In the liquid crystal display device, various films such as a polarizing film are used in order to maintain the display quality. In order to further reduce the weight of liquid crystal display devices for portable information terminals and mobile phones, liquid crystal display devices using resin films instead of glass substrates have been put into practical use.

  Plastic films used in devices that handle polarized light such as liquid crystal display devices are required to have appropriate mechanical characteristics and highly controlled in-plane and birefringence in the film thickness direction. Biaxial stretching is required to improve the mechanical properties of the plastic film and to impart birefringence in the film plane and in the film thickness direction with high control. In this case, the biaxial stretching is generally sequential biaxial stretching composed of longitudinal and lateral sequential stretching. Here, a zone longitudinal stretching method or a roll longitudinal stretching method is used as the first longitudinal stretching method in sequential biaxial stretching.

  The zone longitudinal stretching method is a method of stretching a film while conveying it in a heating zone provided between a low peripheral speed roll and a high peripheral speed roll. According to this method, since the interval between the stretching rolls can be made sufficiently long, the force that prevents the shrinkage in the film width direction can be reduced, and the shrinkage rate in the film width direction can be sufficiently obtained. This makes it easy to obtain optical homogeneity, but it is difficult to increase the production speed due to the high cost and large area of the equipment.

  Roll longitudinal stretching is a method in which a film is stretched in the traveling direction while being heated to a predetermined temperature by a low peripheral speed roll and a high peripheral speed roll which are close to each other.

  In roll longitudinal stretching, as described in Patent Document 1, as a longitudinal stretching method of an optical film, a method for easily producing a film having a beautiful appearance without scratching the film has been reported.

  However, in Patent Document 1, neck-in occurs at the time of longitudinal stretching, so that the thickness of both end portions of the longitudinally stretched film becomes thicker than the central portion. With respect to such a longitudinally stretched film, particularly a brittle resin film such as an acrylic resin film, the film tends to break from the chuck portion in the subsequent lateral stretching process, and stable production becomes difficult. Further improvement is necessary for the above reasons.

  On the other hand, regarding roll longitudinal stretching, as described in Patent Document 2, a method of longitudinal stretching of a film in which an infrared heater is installed between stretching rolls has been reported. However, Patent Document 2 reports improvement in thickness variation in the film longitudinal direction during stretching due to thickness variation in the unstretched film width direction, but when stretching an unstretched film with little thickness variation in the first place. There is no thickness variation in the film longitudinal direction. Further, the longitudinal stretching method of Patent Document 2 is intended for a method for producing a rigid PET resin film or the like for applications such as a magnetic recording medium. Unlike a brittle acrylic resin film, the variation in the longitudinally stretched film width direction is a lateral stretching step. Will not lead to instability.

Japanese Patent Laid-Open No. 2006-130884 JP 2007-268971 A

  In order to solve the above-described problems, an object of the present invention is to provide a method for producing an acrylic resin film by eliminating thickness unevenness in the film width direction that occurs during longitudinal stretching.

In the state where the ratio of the maximum thickness Dmax and the minimum thickness Dmin with respect to the thickness in the width direction is Dmax / Dmin <1.20, and the unstretched melt-extruded acrylic resin film is transported and the film being transported is heated. In the method for producing an acrylic resin film comprising a step of longitudinally stretching the roll in the traveling direction,
When the distance between the film sandwiching portions is L, and the radii of the low circumferential speed roll and the high circumferential speed roll are R1 and R2, respectively, the distance satisfying L> (R1 + R2) × 1.1 with respect to the distance L between the film sandwiching portions. Set to
A temperature gradient is provided between the low peripheral speed roll and the high peripheral speed roll in the film width direction so that Te> Tc when Te is the temperature at both ends of the film being transported and Tc is the temperature at the center. A method for producing an acrylic resin film, characterized in that the film is longitudinally stretched while being rolled, is provided. That is, the present invention relates to the following.

(I) Concerning the thickness in the width direction, the ratio of the maximum thickness Dmax to the minimum thickness Dmin is Dmax / Dmin <1.20, and the unstretched melt-extruded acrylic resin film is transported and the film being transported is heated. In the method for producing an acrylic resin film comprising a step of longitudinally stretching the roll in the direction of travel in a state where the film is held, the film does not contact each roll between the film sandwiching portions by the low peripheral speed roll and the high peripheral speed roll. When the distance between the clamping parts is L, and the radii of the low peripheral speed roll and the high peripheral speed roll are R1 and R2, respectively,
L> (R1 + R2) × 1.1
Between the low peripheral speed roll and the high peripheral speed roll, the temperature in the film width direction is such that Te> Tc, where Te is the temperature at both ends of the film being transported and Tc is the temperature at the center. A method for producing an acrylic resin film, wherein the roll is longitudinally stretched with a gradient.

  (II) The method for producing an acrylic resin film according to (I), wherein the temperature gradient is performed by further locally heating both ends of the film.

  (III) The method for locally heating both ends of the film is to selectively heat both ends in the film width direction by means of heaters installed at both ends in the film width direction. Manufacturing method.

  (IV) The acrylic according to (III), wherein the film width direction whole area is heated by a heater installed in the entire film width direction separately from the heating by the heaters installed at both ends in the film width direction. Of a resin-based resin film.

  (V) The rotation direction of the said low peripheral speed roll and the said high peripheral speed roll is the same as the conveyance direction of the said film, The manufacture of the acrylic resin film as described in (I)-(IV) characterized by the above-mentioned. Method.

  (VI) The acrylic resin film according to any one of (I) to (V), wherein the acrylic resin is a glutarimide resin, a glutaric anhydride resin, or a resin having a lactone ring structure. Law.

  (VII) The glutarimide resin has the following general formula (1):

(Wherein R1 and R2 are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, and R3 is an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or This is a substituent containing an aromatic ring having 5 to 15 carbon atoms.)
And the following general formula (2)

(Wherein R4 and R5 are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, and R6 is an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or And a unit represented by an aromatic ring having 5 to 15 carbon atoms). The method for producing an acrylic resin film according to any one of (I) to (VI).

  (VIII) The glutarimide resin has the following general formula (3)

(In the formula, R7 is hydrogen or an alkyl group having 1 to 8 carbon atoms, and R8 is an aryl group having 6 to 10 carbon atoms.)
The method for producing an acrylic resin film according to any one of (I) to (VII), further comprising a unit represented by:

  By improving the thickness variation of the longitudinally stretched film, it becomes possible to stably produce the next laterally stretched film, and the variation in physical properties in the film width direction is reduced. It leads to increase.

It is the schematic which shows an example of the roll longitudinal stretch method. It is the schematic which shows an example of the roll longitudinal stretch method. It shows an example of an embodiment of the present invention and is a schematic diagram showing a roll longitudinal stretching method. It shows an example of an embodiment of the present invention and is a schematic diagram showing a relationship between a heater and a film as seen from the film width direction.

    The method for producing an acrylic resin film of the present invention transports an unstretched melt-extruded acrylic resin film in which the ratio of the maximum thickness Dmax to the minimum thickness Dmin in the thickness in the width direction is as small as Dmax / Dmin <1.20. In addition, in the method for producing an acrylic resin film containing a step of longitudinally stretching the roll in the traveling direction while the film being transported is heated, the film is sandwiched between the film sandwiching portions by the low peripheral speed roll and the high peripheral speed roll. Without contact with each roll, when the distance between the film sandwiching portions is L, and the radii of the low circumferential speed roll and the high circumferential speed roll are R1 and R2, respectively, with respect to the distance L between the film sandwiching portions, L> (R1 + R2 ) × 1.1 is set to a distance satisfying, between the low peripheral speed roll and the high peripheral speed roll, the temperature of both ends of the film being transported When the temperature of Te and the central portion is Tc, the roll is longitudinally stretched with a temperature gradient in the film width direction so that Te> Tc.

  The present invention will be described below.

First, an unstretched melt-extruded acrylic resin film will be described. The acrylic resin is not particularly limited, and examples thereof include a glutaric anhydride resin, a resin having a lactone ring structure, and a glutarimide resin. Although it does not restrict | limit especially as glutaric anhydride resin, It can manufacture according to the method of Unexamined-Japanese-Patent No. 2007-254703, etc. The resin having a lactone ring structure can be produced according to the method described in JP-A-2008-9378.
The glutarimide resin will be described in detail below. Specific examples of the glutarimide resin include the following general formula (1).

(Wherein R1 and R2 are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, and R3 is an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or This is a substituent containing an aromatic ring having 5 to 15 carbon atoms.)
(Hereinafter also referred to as “glutarimide unit”),
The following general formula (2)

(Wherein R4 and R5 are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, and R6 is an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or This is a substituent containing an aromatic ring having 5 to 15 carbon atoms.)
A glutarimide resin containing a unit represented by (hereinafter also referred to as “(meth) acrylic acid ester unit”) can be suitably used.

  Moreover, the said glutarimide resin is the following general formula (3) as needed.

(In the formula, R7 is hydrogen or an alkyl group having 1 to 8 carbon atoms, and R8 is an aryl group having 6 to 10 carbon atoms.)
(Hereinafter also referred to as “aromatic vinyl unit”).

  In the general formula (1), R1 and R2 are each independently hydrogen or a methyl group, R3 is preferably hydrogen, a methyl group, a butyl group, or a cyclohexyl group, and R1 is a methyl group R2 is more preferably hydrogen and R3 is more preferably a methyl group.

  The glutarimide resin may include only a single type as a glutarimide unit, or may include a plurality of types in which R1, R2, and R3 in the general formula (1) are different.

  The glutarimide unit can be formed by imidizing the (meth) acrylic acid ester unit represented by the general formula (2).

  In addition, acid anhydrides such as maleic anhydride, or half esters of such acid anhydrides and linear or branched alcohols having 1 to 20 carbon atoms; acrylic acid, methacrylic acid, maleic acid, maleic anhydride, The glutarimide unit can also be formed by imidizing an α, β-ethylenically unsaturated carboxylic acid such as itaconic acid, itaconic anhydride, crotonic acid, fumaric acid or citraconic acid.

  In the general formula (2), R4 and R5 are each independently hydrogen or a methyl group, R6 is preferably hydrogen or a methyl group, R4 is hydrogen, R5 is a methyl group, R6 is more preferably a methyl group.

  The glutarimide resin may contain only a single type as a (meth) acrylic acid ester unit, or a plurality of types in which R4, R5, and R6 in the general formula (2) are different. Also good.

  The glutarimide resin preferably contains styrene, α-methylstyrene or the like, more preferably styrene, as the aromatic vinyl structural unit represented by the general formula (3).

  Moreover, the said glutarimide resin may contain only the single kind as an aromatic vinyl structural unit, and may contain the several kind from which R7 and R8 differ.

  In the glutarimide resin, the content of the glutarimide unit represented by the general formula (1) is not particularly limited, and is preferably changed depending on, for example, the structure of R3.

  Generally, the content of the glutarimide unit is preferably 1% by weight or more of the glutarimide resin, more preferably 1% to 95% by weight, and 2% to 90% by weight. More preferably, it is more preferably 3 to 80% by weight.

  If the content of the glutarimide unit is within the above range, the heat resistance and transparency of the resulting glutarimide resin may decrease, or the moldability and mechanical strength when processed into a film may decrease. There is no.

  On the other hand, when the content of the glutarimide unit is less than the above range, the resulting glutarimide resin tends to be insufficient in heat resistance or impaired in transparency. On the other hand, if the amount is larger than the above range, the heat resistance and melt viscosity are unnecessarily increased, the molding processability is deteriorated, the mechanical strength during film processing becomes extremely brittle, or the transparency is impaired. Tend.

  In the glutarimide resin, the content of the aromatic vinyl unit represented by the general formula (3) is not particularly limited, and can be appropriately set according to required physical properties. Depending on the application used, the content of the aromatic vinyl unit represented by the general formula (3) may be zero. When the aromatic vinyl unit represented by the general formula (3) is included, it is preferably 10% by weight or more, preferably 10% by weight to 40% by weight, based on the total repeating unit of the glutarimide resin. More preferably, it is more preferably 15 to 30% by weight, and particularly preferably 15 to 25% by weight.

  If the content of the aromatic vinyl unit is within the above range, the resulting glutarimide resin will not have insufficient heat resistance, and the mechanical strength during film processing will not decrease.

  On the other hand, when there is more content of an aromatic vinyl unit than the said range, there exists a tendency for the heat resistance of the glutarimide resin obtained to be insufficient.

  The glutarimide resin may be further copolymerized with other units other than the glutarimide unit, the (meth) acrylic acid ester unit, and the aromatic vinyl unit, if necessary.

  As other units, for example, nitrile monomers such as acrylonitrile and methacrylonitrile, and maleimide monomers such as maleimide, N-methylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide are copolymerized. A structural unit can be mentioned.

  These other units may be directly copolymerized or graft copolymerized in the glutarimide resin.

The weight average molecular weight of the glutarimide resin is not particularly limited, but is preferably 1 × 10 ^{4 to} 5 × 10 ⁵ . If it is in the said range, moldability will not fall or the mechanical strength at the time of film processing will not be insufficient.

    On the other hand, when the weight average molecular weight is smaller than the above range, the mechanical strength when formed into a film tends to be insufficient. Moreover, when larger than the said range, the viscosity at the time of melt-extrusion is high, there exists a tendency for the moldability to fall and for the productivity of a molded article to fall.

  The glass transition temperature of the glutarimide resin is not particularly limited, but is preferably 110 ° C. or higher, and more preferably 120 ° C. or higher. When the glass transition temperature is within the above range, the applicable range of the obtained thermoplastic resin composition can be expanded.

  Although the manufacturing method in particular of the said glutarimide resin is not restrict | limited, For example, the method etc. which are described in Unexamined-Japanese-Patent No. 2008-273140 are mention | raise | lifted.

  Next, an unstretched acrylic resin film is demonstrated. Although there is no restriction | limiting in particular regarding the manufacturing method of an unstretched acrylic resin film, It is preferable to use the method described in Unexamined-Japanese-Patent No. 2002-221312.

  By using the above method, by melt extrusion, unstretched with a small thickness variation such that Dmax / Dmin <1.20, where Dmax is the maximum thickness in the film width direction and Dmin is the minimum value. It is possible to produce acrylic resin films.

  The method for measuring the film thickness is not particularly limited, but is performed by a continuous thickness gauge (KB601B manufactured by Anritsu). The film can be calculated by cutting a sample having a length of 50 mm in the longitudinal direction and a full width of the film in the width direction, measuring the thickness in the film width direction at a pitch of 1 mm, and calculating the thickness variation.

  Next, roll longitudinal stretching will be described. Roll longitudinal stretching is a method in which a film is stretched in the traveling direction while being heated to a predetermined temperature by a low peripheral speed roll and a high peripheral speed roll which are close to each other. The method of roll longitudinal stretching is not particularly limited, and examples thereof include single-stage stretching in which stretching is performed with a pair of rolls having different circumferential speed differences, and multi-stage stretching in which stretching is performed with two or more pairs of stretching rolls. The stretching is preferably performed by one-stage stretching.

  For example, as shown in FIG. 1, when the film 5 is sandwiched by the nip roll 3 and the nip roll 4 that are close to the stretching roll 1 and the stretching roll 2, respectively, as shown in FIG. There are a method in which the film is in contact with each roll between the sandwiching portions and a method in which the film is not in contact with each roll between the sandwiching portions as shown in FIG. 2, but in the present invention, as shown in the latter A method in which the film does not come into contact with each roll between the holding parts, that is, a method in which the film is stretched in the longitudinal direction without coming into contact with each roll between the film holding parts by the low peripheral speed roll and the high peripheral speed roll. . Among them, as specified in Patent Document 1, as shown in FIG. 3, the drawing roll 1 and the drawing roll 1 are drawn so that the plane including the rotation axis of the drawing roll 1 and the drawing roll 2 is parallel to the film conveyance surface. It is preferable to use a stretching method in which the rotation direction of the roll 2 is the same direction.

  Even if it is multistage stretching, it is within the scope of the present invention as long as a set of stretching rolls is configured such that the film does not contact each roll between the sandwiching portions as described above.

  By using the method specified in Patent Document 1, it is possible to produce a longitudinally stretched film having a beautiful appearance without scratching the film.

  The draw ratio is represented by the ratio of the high peripheral speed roll and the low peripheral speed roll. The preferred stretching ratio depends on the stretching temperature, but is preferably selected in the range of about 1.1 times to about 3.0 times, more preferably about 1.3 times to about 2.5 times, About 1.5 times or more and about 2.0 times or less are particularly preferable. For example, when the draw ratio is about 1.1 times or less, the film is not substantially stretched in the stretching step, and thus the mechanical properties of the film cannot be sufficiently improved. Thereby, the stretched film is easily broken. Moreover, when a draw ratio is about 3.0 times or more, the film before extending | stretching will become too thick, and will fracture | rupture at the time of unstretched film manufacture.

Next, the definition of the distance L between clamping parts is demonstrated using FIG. In the present invention, the film is conveyed and longitudinally stretched by sandwiching the film by both stretching rolls arranged at regular intervals and the nip rolls respectively close to the stretching rolls. At this time, the distance between the both sandwiching portions is L. Here, since the stretching roll and the nip roll are arranged so that the film transport path is parallel to the plane including the rotation axis of both stretching rolls, the following relationship is established.
(Distance between nipping parts) = (Distance between roll stretching)
That is, the distance between the sandwiching portions can be directly changed by changing the distance between the rolls.

  Regarding the distance between the stretching rolls, it is preferable to increase the distance L between the sandwiching portions because the thickness unevenness can be improved by increasing the contraction rate in the width direction.

When the heating source of the film is only heated by a roll at the time of stretching, when the following formula is satisfied with respect to the distance L between the sandwiching portions,
L> 1.1 × (R1 + R2)
(In the above formula, R1 and R2 respectively represent the radii of two stretching rolls.) That is, when the above formula is satisfied with respect to the distance L between the sandwiching portions, the force that prevents the shrinkage in the film width direction is reduced, and the film width direction This is preferable because a sufficient shrinkage rate can be obtained. L is L> 2.0 × (R1 + R2)
It is further preferable to satisfy

  Next, the temperature gradient of the film during longitudinal stretching will be described. The present invention is characterized in that roll longitudinal stretching is performed while applying a temperature gradient such that both end portions> center portion with respect to the temperature in the film width direction. The definition of the temperature Te at both ends of the film and the temperature Tc at the center of the film will be described with reference to FIGS. FIG. 3 is a view of the film as viewed from the side with respect to the conveying direction, and FIG. 4 is a view of the positional relationship among the infrared thermometer, the infrared heater, and the film in FIG. The temperature Te at both ends of the film is a temperature calculated as an average value of the temperatures Te1 and Te2 measured by two thermometers 8 installed at positions 50 mm from the left end or the right end of the film. The temperature Tc at the center of the film is a temperature measured by a thermometer 9 installed at the center in the film width direction.

  Although the measuring method of the said film temperature is not specifically limited, It is preferable to carry out with the infrared thermometer installed and fixed between the extending | stretching rolls.

  Although the said infrared thermometer is not restrict | limited in particular, It is preferable to install in the film upper surface which is 100 mm away from the film conveyance surface, or the film lower surface. In addition, when the film surface is heated from the outside in order to create a temperature gradient, the thermometer is preferably installed at a position that is not affected by external heat, and installed at a position opposite to the external heating source. Particularly preferred.

  The relationship between Te and Tc is not particularly limited as long as Te> Tc, but is preferably Te> Tc + 5 ° C., more preferably Te> Tc + 10 ° C., and particularly preferably Te> Tc + 15 ° C. If Te is (Tc + 5 ° C.) or less, the thickness variation becomes large. The upper limit of Te depends on the glass transition temperature of the film, but is preferably Tc + 50 ° C. or less, particularly preferably Te + 30 ° C. or less. If the difference is too large, it is not preferable because the film sticks to the roll.

  As a method of providing a temperature gradient in the film width direction, a method of locally heating both ends of the film can be mentioned.

  By increasing the temperature at both ends of the film by local heating at both ends of the film and increasing the plasticity, the increase in thickness at both ends during stretching can be mitigated.

  Examples of the local heating method include non-contact heating from the outside and contact heating with a roll. The method is not particularly limited, but a non-contact heating method using an infrared heater is preferable.

  The installation location of the infrared heater that heats both ends of the film will be described with reference to FIGS. Although the infrared heater 10 is not particularly limited, it is preferable that one infrared heater 10 is installed at a position of 50 mm from both ends (left end and right end) of the film.

  The installation location of the infrared heater 10 in the vertical direction is not particularly limited, but is preferably 10 mm or more away from the film transport surface, more preferably 10 mm or more and 80 mm or less, particularly preferably 40 mm or more, 60 mm. The position is within. If it is 10 mm or less, there is a possibility of contact with the transport film, which is not preferable. Moreover, since control of a temperature gradient is difficult for it to be 80 mm or more, it is unpreferable.

  In addition to local heating at both ends of the film, heating across the entire width direction of the film being transported between stretching rolls is preferable because the film can be prevented from cooling and breaking during stretching.

  Examples of the heating method in the entire film width direction include non-contact heating from the outside and contact heating with a roll, and are not particularly limited, but non-contact heating using an infrared heater is preferable.

  It is more preferable to perform non-contact heating between the rolls because the film can be prevented from being broken due to sticking of the film.

  The installation location of the infrared heater will be described with reference to FIGS. The infrared heater 11 is preferably installed at the center of the film.

  The installation location of the infrared heater in the vertical direction is not particularly limited, but is a position that is 10 mm or more away from the film conveyance surface, preferably within 950 mm, and particularly preferably within 40 mm or more and 200 mm or less. If it is within 10 mm, there is a possibility of contact with the transport film, which is not preferable, and if it is 950 mm or more, it is not preferable from the viewpoint of the heating length limit.

  The longitudinally stretched film thus obtained is improved in thickness variation in the film width direction, so that breakage is less likely to occur in the subsequent transverse stretching, and stable production becomes possible. Moreover, the variation in the physical property of a film width direction also decreases, and it leads to the increase in a product yield by suppressing the slit amount of both ends of a film.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by this.
(Production Example 1)
An imidized resin was produced using methyl methacrylate-styrene copolymer (styrene content 11 mol%) as a raw material resin and monomethylamine as an imidizing agent.

  The extruder used was a meshing type co-rotating twin screw extruder having a diameter of 15 mm. The set temperature of each temperature control zone of the extruder was 230 to 250 ° C., and the screw rotation speed was 150 rpm. A methyl methacrylate-styrene copolymer (hereinafter also referred to as “MS resin”) was supplied at 2 kg / hr, and the resin was melted and filled with a kneading block, and then 16 parts by weight of monomethyl from the nozzle to the resin. Amine (Mitsubishi Gas Chemical Co., Ltd.) was injected. A reverse flight was placed at the end of the reaction zone to fill the resin. By-products and excess methylamine after the reaction were removed by reducing the pressure at the vent port to -0.092 MPa. The resin that emerged as a strand from the die provided at the exit of the extruder was cooled in a water tank and then pelletized with a pelletizer to obtain an imidized MS resin (1).

  Next, in a meshing type co-rotating twin screw extruder with a diameter of 15 mm, the set temperature of each temperature control zone of the extruder was 230 ° C. and the screw rotation speed was 150 rpm. The imidized MS resin (1) obtained from the hopper was supplied at 1 kg / hr, and the resin was melted and filled with a kneading block, and then 0.8 parts by weight of dimethyl carbonate and 0. A mixed solution of 2 parts by weight of triethylamine was injected to reduce carboxyl groups in the resin. A reverse flight was placed at the end of the reaction zone to fill the resin. The by-product after reaction and excess dimethyl carbonate were removed by reducing the pressure at the vent port to -0.092 MPa. The resin coming out as a strand from the die provided at the exit of the extruder was cooled in a water tank and then pelletized with a pelletizer to obtain an imidized MS resin (2) having a reduced acid value.

  Further, the imidized MS resin (2) is applied to a meshing type co-rotating twin screw extruder having a diameter of 15 mm, the set temperature of each temperature control zone of the extruder is 230 ° C., the screw rotation speed is 150 rpm, and the supply amount is 1 kg / hr. It was put in the condition of. The vent port pressure was reduced to -0.095 MPa, and volatile components such as unreacted auxiliary materials were removed again. The devolatilized imide resin that emerged as a strand from the die provided at the exit of the extruder was cooled in a water tank and then pelletized with a pelletizer to obtain an imidized MS resin (3).

The imidized MS resin (3) includes a glutamylimide unit represented by the general formula (1) described in the above embodiment, and a (meth) acrylic acid ester unit represented by the general formula (2). It corresponds to a glutarimide resin copolymerized with an aromatic vinyl unit represented by the general formula (3). The weight ratio of general formula (1): general formula (2): general formula (3) in the imidized MS resin (3) was 73: 19: 8. The glass transition temperature was 140 ° C. The obtained imidized resin was formed into pellets with an extruder, and the obtained pellets were dried at 100 ° C. for 5 hours, and then extruded at 240 ° C. using a 40 mm single screw extruder and a 400 mm wide T-die to obtain an average thickness. An unstretched acrylic resin film having a thickness of 130 μm and a width of 300 mm was obtained. This unstretched acrylic resin film is a film with little thickness variation in the width direction where the maximum thickness Dmax = 134 μm, the minimum thickness Dmin = 126 μm, and Dmax / Dmin = 1.06. After forming an unstretched film, the film may be temporarily stored or moved as necessary, and then the film may be stretched.
(Examples 1-5) and (Comparative Example 1)
The obtained film was subjected to roll longitudinal stretching in the longitudinal stretching step of the present invention while applying a temperature gradient in the film width direction. The low peripheral speed roll, the high peripheral speed roll, and the nip roll in the longitudinal stretching step in this example were in the positional relationship described in FIG. The film width is 300 mm. The radius R1 of the drawing roll 1 and the radius R2 of the drawing roll are both 70 mm. As shown in FIG. 3, a stretching roll and a nip roll having a smaller radius than the stretching roll are arranged so that the film transport path is parallel to the plane including the rotation axis of both stretching rolls. The film was sandwiched by nip rolls close to the rolls, respectively, so that the film was transported and longitudinally stretched. And both extending | stretching rolls were the conveyance directions of a film, and were mutually rotated in the same direction. Further, the holding portion interval L was set to 400 mm. In order to create a temperature gradient in the film width direction, a pair of infrared heaters for heating both ends were installed on the top surface of the film and at a position of 50 mm from the film both ends toward the center. In order to prevent the film from cooling and breaking, an infrared heater for heating the entire region in the film width direction was installed on the upper surface of the film and in the center of the film. In order to measure the temperature gradient in the film width direction, a total of three infrared thermometers were installed at the center of the lower surface of the film and at a position of 50 mm from both ends to the center.

  And according to the conditions of Examples 1 to 5 in the table shown in Table 1, the film obtained in Production Example 1 is longitudinally stretched, the temperature distribution in the film width direction during longitudinal stretching, and the width direction in the obtained longitudinally stretched film The thickness variation was evaluated. Further, Comparative Example 1 in which longitudinal stretching was performed without applying a temperature gradient also performed the above evaluation.

In Table 1, “stretch ratio” is defined by the peripheral speed ratio of both the low peripheral speed roll and the high peripheral speed roll. That is, it is defined by the following formula.
Drawing ratio = (peripheral speed of high peripheral speed roll) / (peripheral speed of low peripheral speed roll)
In Table 1, the film temperature “center” is the temperature at one point in the film center, and the film temperature “both ends” is the average value of the temperatures at two points at both ends. The installation position of the infrared thermometer is the lower surface of the film (105 mm below the film surface), and both end portions are positions of 50 mm from both end portions toward the central portion.

  In Table 1, “temperature gradient” is a numerical value calculated by (Te−Tc) where Te is the temperature at both ends of the film and Tc is the temperature at the center.

  In Table 1, “thickness variation” is performed by a continuous thickness meter (KB601B manufactured by Anritsu). A sample having a length of 50 mm in the longitudinal direction and a full film width (300 mm) in the width direction was cut out, and the thickness in the film width direction was measured at a pitch of 1 mm. It is a numerical value represented by Dmax / Dmin, where Dmax is the maximum thickness of the measured value and Dmin is the minimum thickness.

  From Table 1, the evaluation results in Examples 1 to 5 and Comparative Example 1 are verified. First, in Examples 1 to 3 having a draw ratio of 1.5, it can be seen that the thickness variation decreases as the temperature gradient is increased by controlling the end heating by the heater and increasing the temperature at both ends of the film. This can be seen more conspicuously in comparison with Comparative Example 1 in which end heating is not performed. That is, it can be seen that the thickness unevenness in the width direction of the longitudinally stretched film can be improved by increasing the temperature gradient.

  In Examples 4 to 5 having a draw ratio of 2.0 times, it can be seen that the thickness variation is reduced by the temperature gradient as in Examples 1 to 3. That is, it can be seen that the thickness unevenness in the width direction of the longitudinally stretched film due to the temperature gradient can be improved in the range of the stretch ratio of 1.5 times to 2.0 times.

1. Stretching roll Stretch roll 2. Nip roll 4. 4. Nip roll Film 6. 6. Clamping part Nipping part 8. Infrared thermometer (both ends)
9. Infrared thermometer (central part)
10. Infrared heater (both ends)
11. Infrared heater (central part)

Claims (8)

In the state where the ratio of the maximum thickness Dmax and the minimum thickness Dmin with respect to the thickness in the width direction is Dmax / Dmin <1.20, and the unstretched melt-extruded acrylic resin film is transported and the film being transported is heated. In the method for producing an acrylic resin film comprising a step of longitudinally stretching the roll in the traveling direction, the film is not in contact with each roll between the film sandwiching portions between the film sandwiching portions by the low peripheral speed roll and the high peripheral speed roll. When the distance of L is L, the radius of the low peripheral speed roll and the high peripheral speed roll are R1 and R2, respectively,
L> (R1 + R2) × 1.1
Between the low peripheral speed roll and the high peripheral speed roll, the temperature in the film width direction is such that Te> Tc, where Te is the temperature at both ends of the film being transported and Tc is the temperature at the center. A method for producing an acrylic resin film, wherein the roll is longitudinally stretched with a gradient.   The method for producing an acrylic resin film according to claim 1, wherein the temperature gradient is performed by further locally heating both ends of the film.   3. The method for producing an acrylic resin film according to claim 2, wherein the local heating method at both ends of the film selectively heats the both ends in the film width direction by heaters installed at both ends in the film width direction. .   4. The acrylic resin film according to claim 3, wherein the film width direction whole area is heated by a heater installed in the entire film width direction separately from the heating by the heaters installed at both ends in the film width direction. Manufacturing method.   The method for producing an acrylic resin film according to claim 1, wherein the rotation direction of the low peripheral speed roll and the high peripheral speed roll is the same as the transport direction of the film.   6. The method for producing an acrylic resin film according to claim 1, wherein the acrylic resin is a glutarimide resin, a glutaric anhydride resin, or a resin having a lactone ring structure. The glutarimide resin has the following general formula (1)

(Wherein R1 and R2 are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, and R3 is an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or This is a substituent containing an aromatic ring having 5 to 15 carbon atoms.)
And the following general formula (2)

(Wherein R4 and R5 are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, and R6 is an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or The unit represented by this is a substituent containing a C5-C15 aromatic ring.) The manufacturing method of the acrylic resin film of Claims 1-6 characterized by the above-mentioned. The glutarimide resin has the following general formula (3)

(In the formula, R7 is hydrogen or an alkyl group having 1 to 8 carbon atoms, and R8 is an aryl group having 6 to 10 carbon atoms.)
The unit represented by these is further included, The manufacturing method of the acrylic resin film of Claims 1-7 characterized by the above-mentioned.

Images