JP7336190B2 - Method for producing polycarbonate resin film - Google Patents

Description

The present invention relates to a method for producing a polycarbonate resin film.

Conventionally, polycarbonate resin has excellent heat resistance, impact resistance, and dimensional stability. Used for film.

Here, this film is formed by molding a polycarbonate resin, which is a film-forming material, into a film by a method such as an injection method, a melt extrusion method, or a compression method. is widely used.

This melt extrusion method includes a heating step of heating a polycarbonate resin and an extrusion step of extruding the heated polycarbonate resin into a film. More specifically, first, a polycarbonate resin is extruded by an extruder heated to a predetermined temperature, and then pressed between rolls to form a film. manufactured (see, for example, Patent Document 1).

JP 2017-95605 A

Here, since the general-purpose polycarbonate resin has a large photoelastic coefficient (50×10 ⁻¹² Pa ⁻¹ to 100×10 ⁻¹² Pa ⁻¹ ), when it is made into a film, the phase difference changes due to external stress. In addition, since the value of the intrinsic birefringence is large (0.1 to 0.2), the refractive index in the stretching direction increases when the polycarbonate resin is molded into a film.

Therefore, in the conventional melt extrusion method, it is difficult to reduce the birefringence of the polycarbonate resin film (in-plane birefringence Re, thickness direction birefringence Rth). It was difficult to apply it to the base film and the like that require birefringence.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a method for producing a polycarbonate resin film that can be used for the above-described base film or the like that requires low birefringence. .

In order to achieve the above object, the method for producing a polycarbonate resin film of the present invention comprises a step of extruding a polycarbonate resin heated and melted in an extruder into a film form from an outlet of the extruder; At least a step of pinching the extruded film-like polycarbonate resin with a touch roll and a chill roll that are provided and arranged so as to be in contact with each other, and the glass transition temperature of the polycarbonate resin is Tg. The melting temperature of the polycarbonate resin is (Tg + 120) ° C. or higher and (Tg + 150) ° C. or lower, the temperature of the chill roll is (Tg - 5) ° C. or higher and (Tg + 5) ° C. or lower, and the polycarbonate resin is extruded from the exit of the extruder, The time taken to reach the contact point between the touch roll and the chill roll is 0.29 seconds or more and 0.40 seconds or less, and the pressure of the touch roll against the polycarbonate resin film sandwiched between the touch roll and the chill roll is 1.5 kg/cm. It is characterized by being more than or equal to 4.0 kg/cm or less.

According to the present invention, a polycarbonate resin film having low birefringence can be provided.

1 is a schematic diagram showing an apparatus for manufacturing a polycarbonate resin film according to an embodiment of the invention; FIG.

Preferred embodiments of the present invention are described below.

<Polycarbonate resin>
The type of polycarbonate resin that constitutes the polycarbonate resin film of the present invention is not particularly limited, and is, for example, a thermoplastic resin obtained by reacting a dihydroxy compound with phosgene or diphenyl carbonate.

As the dihydroxy compound, for example, 2,2-bis(4-hydroxyphenyl)propane (“bisphenol A”), hydroquinone, tetramethylbisphenol A, resorcinol, and 4,4-dihydroxydiphenyl can be used. can. In addition, N-phenylphenolphthalein (melting point: 293° C.) represented by the following formula (1), bisphenol TMC (melting point: 208° C.) represented by the following formula (2), and biscresol fluorene (melting point: 208° C.) represented by the following formula (3) melting point 218-219° C.) can be used.

In addition, these can be used individually or in combination of 2 or more types.

Further examples include polycarbonate resins described in JP-A-2005-290378, JP-A-2017-19944, and International Publication No. 2011/7744.

Moreover, the method for producing the polycarbonate resin is not particularly limited, and for example, a phosgene method (interfacial polymerization method), a melt polymerization method (transesterification method), or the like can be used. In addition, a polycarbonate resin that has been subjected to a treatment for adjusting the amount of terminal OH groups may be used with respect to a polycarbonate resin raw material produced by a melt polymerization method.

Moreover, the glass transition temperature (Tg) of the polycarbonate resin is preferably 140° C. or higher and 210° C. or lower. When the Tg is 140°C or higher, the dimensional change of the film itself is favorable, and when the Tg of the polycarbonate resin is 210°C or lower, the processing suitability of the film itself is favorable, which is preferable.

The term "glass transition temperature" used herein refers to the midpoint glass transition temperature measured according to JIS-K-7121 (1987).

<Polycarbonate resin film>
As a method for producing the polycarbonate resin film of the present embodiment, a melt extrusion method is used, which includes a heating step of heating the polycarbonate resin that is the film-forming material, and an extrusion step of extruding the heated polycarbonate resin into a film. ing.

FIG. 1 is a schematic diagram showing an apparatus for producing a polycarbonate resin film according to this embodiment.

As shown in FIG. 1, a polycarbonate resin heated and melted in an extruder 1 is extruded into a film form from an exit 1a of the extruder 1, and a touch roll 2, a chill roll 3, and a cast roll 4 are used to form an extruded film. After compressing the polycarbonate resin, the film is slowly cooled on a plurality of transfer rolls 9 arranged linearly. Then, the unstretched polycarbonate resin film F can be obtained by taking off the film with the take-off roll 5 .

For the die of the extruder 1, for example, a T die or a coat hanger die can be used.

Further, as shown in FIG. 1, the touch roll 2 and the chill roll 3 are provided in the extrusion direction of the polycarbonate resin (the direction of the arrow X in the drawing), and are arranged so as to face and contact each other.

As the touch roll 2, chill roll 3, cast roll 4, and take-up roll 5, metal rolls or rubber rolls can be used.

Here, in the conventional melt extrusion method, as described above, it is difficult to reduce the birefringence of the polycarbonate resin film (in-plane birefringence Re, thickness direction birefringence Rth). There is a problem that it is difficult to apply a polycarbonate resin film to the base film or the like that requires low birefringence.

Therefore, the present inventors focused on this point and manufactured a polycarbonate resin film that can be used as a base film used in liquid crystal display devices and organic EL display devices that require low birefringence. I found the conditions for

More specifically, in the method for producing a polycarbonate resin film of the present invention, the melting temperature of the polycarbonate resin in the extruder 1 (the temperature of the polycarbonate resin during melt extrusion) is determined in consideration of the glass transition temperature (Tg) described above. is set at (Tg+120)° C. or more and (Tg+150)° C. or less. This is because the higher the melting temperature of the resin, the longer the state of temperature above Tg, so that the birefringence of the film can be reduced. This is because degraded resin (burnt or carbonized matter) is likely to occur.

From the viewpoint of preventing the occurrence of degraded resin and reliably reducing the birefringence of the film, the melting temperature of the polycarbonate resin is preferably 265° C. or higher and 295° C. or lower, and more preferably 275° C. or higher and 285° C. preferable.

In addition, the time T represented by the following formula (1) (the time until the polycarbonate resin is extruded from the outlet 1a of the extruder 1 and reaches the contact point C between the touch roll 2 and the chill roll 3) is 0.29 seconds or more. .40 seconds or less.

[Number 1]
Time T [seconds] = (distance D [cm] from exit 1a to contact C)/(velocity from exit 1a of polycarbonate resin to contact C [cm/s] (1)

This is because when the time T is less than 0.29 seconds, the stress acting in the film's mechanical axis (longitudinal) direction (hereinafter referred to as "MD direction") increases, and the refractive index difference with the thickness direction increases. As a result, the birefringence Rth in the thickness direction increases, and when it exceeds 0.40 seconds, the stress acting in the MD direction decreases, and the (width) direction perpendicular to the MD direction (hereinafter referred to as "TD direction") ), the in-plane birefringence Re increases. This is because it must be set within

The time T is preferably 0.29 seconds or more and 0.40 seconds or less, and more preferably 0.29 seconds or more and 0.33 seconds or less when the in-plane birefringence index Re is decreased. Further, when the birefringence index Rth in the thickness direction is to be decreased, the time is more preferably 0.33 seconds or more and 0.40 seconds or less.

The temperature of the chill roll 3 is set to (Tg-5)° C. or higher and (Tg+5)° C. or lower in consideration of the glass transition temperature (Tg) described above. This is because when the temperature of the chill roll 3 is less than (Tg−5)° C., the film temperature cannot be maintained above Tg, so the birefringence is less likely to decrease. This is because although the birefringence index can be lowered, the film may become difficult to separate from the chill roll 3, resulting in a decrease in productivity.

The temperature of the chill roll 3 is preferably 140° C. or higher and 150° C. or lower, more preferably 145° C. or higher and 150° C. or lower, from the viewpoint of preventing a decrease in productivity and reliably reducing the birefringence of the film.

Further, the pressure (pressing line pressure) P of the touch roll 2 against the polycarbonate resin film sandwiched between the touch roll 2 and the chill roll 3 shown in FIG. 1 is set to 1.5 kg/cm or more and 4.0 kg/cm or less. be. This is because if the pressure of the touch roll 2 is less than 1.5 kg/cm, the force that presses the film is weak, making it impossible to perform transfer on the surface of the touch roll 2, and uneven transfer may occur. /cm, the stress in the thickness direction of the film increases, and the birefringence index Rth in the thickness direction increases.

From the viewpoint of preventing the occurrence of transfer unevenness and surely reducing the birefringence Rth in the thickness direction, the pressure (pressing line pressure) P of the touch roll 2 is set to 1.5 kg/cm or more and 4.0 kg. /cm or less is preferable, and 2.5 kg/cm or more and 3.5 kg/cm or less is more preferable.

Thus, in the method for producing a polycarbonate resin film of the present invention, (1) the pressing line pressure P is set to 1.5 kg/cm or more and 4.0 kg/cm or less, and (2) the melting temperature of the polycarbonate resin is set to ( (3) set the temperature of the chill roll 3 to (Tg-5) ° C. or higher and (Tg+5) ° C. or lower; and (4) set the time T until reaching the contact point C. It is configured to be set to 0.29 seconds or more and 0.40 seconds or less.

Therefore, from the viewpoint of avoiding image distortion and occurrence of polarized spots, the conditions for low birefringence (in-plane birefringence Re <10 [nm] and birefringence in the thickness direction Rth [mm]×1000/film thickness [μm] <1.0).

Although the thickness T of the polycarbonate resin film is not particularly limited, it is preferably 100 μm or more and 130 μm or less.

The polycarbonate resin film of the present embodiment is used for optical films such as diffusion sheets, light guide plates, polarizing films, etc., as well as base films used in liquid crystal display devices, organic EL display devices, and the like.

The present invention will be described below based on examples. The present invention is not limited to these examples, and these examples can be modified and changed based on the spirit of the present invention, and they are excluded from the scope of the present invention. isn't it.

(Example 1)
<Measurement of glass transition temperature>
The glass transition temperature of a polycarbonate resin (manufactured by Sumika Polycarbonate Co., Ltd., trade name: SD Polyca 301-15) was measured according to JIS K7121. More specifically, using a differential scanning calorimeter (manufactured by Rigaku Co., Ltd., trade name: TMA8310), the temperature was raised to 200 ° C. and then cooled to room temperature, and then from room temperature to 200 ° C. at 5 ° C./ A DSC curve was measured at a heating rate of 1 minute. Then, the midpoint glass transition temperature obtained from the DSC curve measured during the second heating was taken as the glass transition temperature of the polycarbonate resin. Table 1 shows the above results.

<Method for producing polycarbonate resin film>
Next, using the apparatus shown in FIG. 1, a polycarbonate resin film was produced. More specifically, first, the pellet-shaped product of the polycarbonate resin described above is extruded at a discharge rate of 200 kg / hour from the extruder 1 set at 285 ° C. (that is, the melting temperature of the polycarbonate resin is 285 ° C.). With the time T to reach 0.4 seconds, the temperature of the chill roll 3 set to 150° C., and the presser line pressure P set to 1.5 kg/cm, after being pressed by the touch roll 2 and the chill roll 3, a plurality of transfer The film was slowly cooled on roll 9. Then, this film was taken off by a take-off roll 5 to obtain a polycarbonate resin film having a thickness of 100 μm.

<Measurement of birefringence>
Next, the film evaluation was performed by measuring the birefringence of the produced polycarbonate resin film. More specifically, a polycarbonate resin film sample (length: 35 mm, width: 35 mm, thickness: 100 μm) was prepared, and an automatic birefringence meter (manufactured by Oji Scientific Instruments Co., Ltd., trade name: KOBRA-21ADH) was used. Measure the in-plane birefringence Re [nm] of the sample at a temperature of 23 ± 2 ° C., a humidity of 50 ± 5%, a wavelength of 590 nm, and an incident angle of 0 °. The birefringence index Rth [mm] in the thickness direction of the sample was measured under conditions of a humidity of 50±5%, a wavelength of 590 nm and an incident angle of 0° and 40°.

Then, the film was evaluated according to the following evaluation criteria. Table 1 shows the above results.

In-plane birefringence Re < 10 [nm] and thickness direction birefringence Rth [mm] × 1000 / film thickness [μm] < 1.0: ○
In-plane birefringence Re≧10 [nm], or thickness direction birefringence Rth [mm]×1000/film thickness [μm]≧1.0: ×

(Examples 2-4, Comparative Examples 1-2)
A polycarbonate resin film was produced in the same manner as in Example 1, except that the pressing wire pressure P was changed to the value shown in Table 1, and the birefringence index was measured. Table 1 shows the above results.

In Comparative Example 1, since the pressing line pressure P was low (1.0 kg/cm), the film could not be pressed with a roll, and a polycarbonate resin film could not be obtained.

(Examples 5-7, Comparative Examples 3-4)
A polycarbonate resin film was produced in the same manner as in Example 3, except that the melting temperature of the polycarbonate resin was changed to the value shown in Table 2, and the birefringence index was measured. Table 2 shows the above results.

In Comparative Example 4, since the melting temperature of the polycarbonate resin was high (305° C.), deterioration of the resin occurred, and a polycarbonate resin film could not be obtained.

(Examples 8-9, Comparative Examples 5-6)
A polycarbonate resin film was produced in the same manner as in Example 3, except that the temperature of the chill roll was changed to the value shown in Table 3, and the birefringence index was measured. Table 3 shows the above results.

In Comparative Example 6, since the temperature of the chill roll 3 was high (155° C.), the film was difficult to separate from the chill roll 3, and a polycarbonate resin film could not be obtained.

(Examples 10-13, Comparative Examples 7-8)
A polycarbonate resin film was produced and the birefringence index was measured in the same manner as in Example 3, except that the time T until reaching the contact point C was changed to the value shown in Table 4. Table 4 shows the above results.

As shown in Tables 1 to 4, the pressing line pressure P is set to 1.5 kg / cm or more and 4.0 kg / cm or less, and the melting temperature of the polycarbonate resin is set to (Tg + 120) ° C. or more (Tg + 150) ° C. or less (that is, 265 ° C. or higher and 295 ° C. or lower), the temperature of the chill roll 3 is set to (Tg-5) ° C. or higher and (Tg + 5) ° C. or lower (that is, 140 ° C. or higher and 150 ° C. or lower), and the time T to reach the contact point C was set to 0.29 seconds or more and 0.40 seconds or less. It can be seen that it is possible to obtain a polycarbonate resin film that can be used as the base film or the like that requires refractive properties.

INDUSTRIAL APPLICABILITY As described above, the present invention is particularly useful in a method for producing a polycarbonate resin film that can be used as a substrate film that requires low birefringence.

1 extruder 2 touch roll 3 chill roll 4 cast roll 5 take-up roll 9 transfer roll

Claims (4)

A step of extruding a polycarbonate resin heated and melted in an extruder into a film form from the exit of the extruder;
Manufacture of a polycarbonate resin film comprising at least a step of pinching the extruded film-like polycarbonate resin with a touch roll and a chill roll which are provided in the extrusion direction of the polycarbonate resin and are arranged so as to face and contact each other. a method,
When the glass transition temperature of the polycarbonate resin is Tg, the melting temperature of the polycarbonate resin is (Tg + 120) ° C. or higher and (Tg + 150) ° C. or lower,
The temperature of the chill roll is (Tg-5) ° C. or more and (Tg+5) ° C. or less,
The polycarbonate resin is extruded from the exit of the extruder, and the time until it reaches the contact point between the touch roll and the chill roll is 0.33 seconds or more and 0.40 seconds or less,
A method for producing a polycarbonate resin, wherein the pressure of the touch roll against the polycarbonate resin film sandwiched between the touch roll and the chill roll is 1.5 kg/cm or more and 4.0 kg/cm or less. The method for producing a polycarbonate resin according to claim 1, wherein the melting temperature of the polycarbonate resin is 265°C or higher and 295°C or lower. 2. The method for producing a polycarbonate resin according to claim 1, wherein the chill roll has a temperature of 140[deg.] C. or more and 150[deg.] C. or less. 2. The method for producing a polycarbonate resin according to claim 1, wherein the pressure of the touch roll is 2.5 kg/cm or more and 3.5 kg/cm or less.

Images