JPH09207237A - Method for producing polycarbonate sheet - Google Patents

Abstract

(57) An object of the present invention is to provide a method for producing a polycarbonate sheet having a birefringence of 40 nm or less, which is used for a substrate for optical applications, in particular, an optical disk, and which simultaneously satisfies mechanical strength and durability. SOLUTION: When a polycarbonate resin is plasticized and extruded into a sheet form from a T die, and the polycarbonate resin is rolled and sheeted using a plurality of mirror-shaped shaping rolls, the sheet from which the final mirror-shaped shaping roll is peeled off is the final mirror-shaped shaping roll. The surface temperature on the roll side of the sheet immediately after traveling the radius of the shaped roll is the glass transition temperature of the resin −10 to +3.
A method for producing a polycarbonate sheet, which comprises forming at 0 ° C. and forming a final shaping mirror surface roll and a take-up roll at a speed ratio of 1: 0.95 to 1.05.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a polycarbonate sheet used for optical applications.

[0002]

2. Description of the Related Art Polycarbonate resins are widely used in the optical field because they are excellent in transparency, impact resistance, heat resistance, dimensional stability and workability. For example, there are discs and optical cards that use laser light. These polycarbonate substrates used for optical disks and the like are mainly produced by an injection molding method. Although this injection molding method is excellent in mass productivity, it is difficult to flow due to the fluidity of a general injection molding grade, so that optical distortion is caused. Easy to remain, birefringence is 1
Higher than 50 nm and not practical.

That is, since it is necessary to mold a resin having a low molecular weight at a high temperature as compared with a general injection molding grade, impact resistance, which is a characteristic of a polycarbonate resin, is significantly reduced, and further, an aluminum vapor-deposited film and other recording portions are deteriorated. There is a drawback that cracks are likely to occur due to the solvent during cleaning and coating in the protective film forming step. Further, as a substrate used for an optical disk or the like, birefringence is usually required to be 50 nm or less.

In order to improve the drawbacks of these injection-molded products, attention has been paid to the extruded sheet, and some studies have been made in the past, but there was a problem. For example, Japanese Patent Laid-Open No. 62-140817 describes that a sheet is formed by a mirror-finished roll and then heat-treated by being sandwiched between stainless steel plates.
This method requires significant improvement of the apparatus and tends to retain secondary strain due to being sandwiched between stainless steel plates. Further, the method described in JP-A-4-166319 uses a polycarbonate resin having a viscosity average molecular weight of 14,000 to 19,000, but has a low molecular weight and is inferior in impact resistance and solvent resistance.

Further, Japanese Patent Publication No. 5-71026 discloses that the surface temperature of a sheet at a point of traveling 300 mm after peeling the final mirror surface roll is specified as a heat deformation temperature of ± 6 ° C. and a take-up speed is set within a specific range. Although proposed, the surface temperature of the sheet at the time of traveling 300 mm after the final mirror surface peeling is not much different from the surface temperature immediately after peeling the final mirror surface roller in view of the speed described in the examples of the publication, While contacting with and applying a bending stress in the circumferential direction, the contact surface of the final mirror surface roll, which is the surface temperature measurement surface described in this publication, is cooled and solidified, and residual strain remains due to stress and birefringence increases. Also, since the condition included in the range of the specific take-up speed described in the publication includes the case where the final mirror surface roll speed is extremely high compared to the take-up roll speed, the final mirror surface roll is formed by this method. Sheet can not be molded sag occurs continuously in the sheet after.

Further, in Japanese Patent Laid-Open No. 7-276471, the temperature of the molten sheet is raised from the glass transition temperature to the glass transition temperature while sagging and sagging the molten sheet between the final mirror roll and the first transfer roll. , A method in which residual stress is not left by not applying an external force to the molten sheet is described, but with this method, a peeling mark is likely to be formed when the sheet is peeled off from the last mirror surface roll, and an excellent appearance is obtained. difficult.

[0007]

SUMMARY OF THE INVENTION The present invention solves the technical problems of impact resistance, solvent resistance, low birefringence index and no peeling marks at the same time, that is, it is used for optical disk substrates. The present invention provides a method for producing a polycarbonate sheet having a birefringence of 40 nm or less and excellent mechanical strength and durability.

[0008]

[Means for Solving the Problems] The present inventors have specified the surface temperature of a sheet at the time of molding a polycarbonate sheet,
Further, it has been found that the above technical problems can be solved by setting the final mirror surface shaping roll (hereinafter abbreviated as mirror surface roll) and the take-up speed to specific conditions, and has completed the present invention.

That is, according to the present invention, when rolling and sheeting a polycarbonate resin using a plurality of mirror-finished rolls, the sheet from which the final mirror-finished roll has been peeled runs right after the sheet runs the radius of the final mirror-finished roll. Has a glass transition temperature of −10 to + 30 ° C., and the speed ratio of the final mirror surface roll to the take-up roll is 1:
It is a method for producing a polycarbonate sheet, characterized in that it is formed in a range of 0.95 to 1.05.

Hereinafter, the present invention will be described in detail. The polycarbonate resin used in the present invention is a polymer derived from a divalent phenolic compound represented by bisphenol A, and may be produced by any of the phosgene method, the transesterification method, and the solid phase polymerization method. . In addition to these conventional polycarbonate resins, a special polycarbonate resin polymerized by the transesterification method of an aromatic dihydroxy compound and a carbonic acid diester can also be used. The aromatic dihydroxy compound is HO-A.
In the formula, Ar represents a divalent aromatic group, for example, an organic group represented by the following general formula.

[0011]

Embedded image (In the formula, R ¹ and R ² are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 ring-constituting carbon atoms, or A phenyl group, m and n are integers of 1 to 4, and when m is 2 to 4, each R ¹ may be the same or different, and when n is 2 to 4 Is each R
² may be the same or different).

The aromatic group Ar is, for example, --Ar ^1-
A divalent aromatic group represented by Y—Ar ² — (in the formula,
Ar ¹ and Ar ² each independently have 5 to 7 carbon atoms.
Represents a divalent carbocyclic or heterocyclic aromatic group having 0,
Y represents a divalent alkane group having 1 to 30 carbon atoms). In the divalent aromatic groups Ar ¹ and Ar ² , one or more hydrogen atoms are other substituents that do not adversely affect the reaction, for example, a halogen atom, an alkyl group having 1 to 10 carbon atoms, and 1 to 10 carbon atoms. It may be substituted with 10 alkoxy groups, phenyl groups, phenoxy groups, vinyl groups, cyano groups, ester groups, amide groups, nitro groups and the like.

Preferred specific examples of the heterocyclic aromatic group include aromatic groups having one to a plurality of ring-forming nitrogen atoms, oxygen atoms or sulfur atoms. The divalent aromatic groups Ar ¹ and Ar ² represent groups such as substituted or unsubstituted phenylene, substituted or unsubstituted biphenylene, and substituted or unsubstituted pyridylene. The substituent here is as described above. The divalent alkane group Y is, for example,
An organic group represented by the following general formula.

[0014]

Embedded image (In the formula, R ³ , R ⁴ , R ⁵ , and R ⁶ are each independently hydrogen,
An alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 ring carbon atoms, a carbocyclic aromatic group having 5 to 10 ring carbon atoms, and 6 to 1 carbon atoms
Represents a carbocyclic aralkyl group of 0. k represents an integer of 3 to 11, R ⁷ and R ⁸ are individually selected for each X, and independently of each other represent hydrogen or an alkyl group having 1 to 6 carbon atoms, and X represents a carbon number. In addition, R ³ , R ⁴ ,
In R ⁵ , R ⁶ , R ⁷ , and R ⁸ , other substituents such as a halogen atom, an alkyl group having 1 to 10 carbon atoms, and a carbon number of 1 are included as long as one or more hydrogen atoms do not adversely affect the reaction.
-10 may be substituted with an alkoxy group, a phenyl group, a phenoxy group, a vinyl group, a cyano group, an ester group, an amide group, a nitro group or the like. Examples of such a divalent aromatic group Ar include those represented by the following general formula.

[0015]

Embedded image (In the formula, R ¹ , R ² , m and n are as described above.) Further, the divalent aromatic group Ar is -Ar ¹ -Z-Ar ^2.
-May be indicated. (Wherein, Ar ¹ , A
r ^{2 is} as described above, Z is a single bond or —O—, —CO.
-, - S -, - SO 2 -, - SO -, - COO -, - C
Represents a divalent group such as ON (R ¹ ) —. However, R ¹ is as described above. Examples of such a divalent aromatic group Ar include those represented by the following general formula.

[0016]

Embedded image (In the formula, R ¹ , R ² , m and n are as described above.) The aromatic dihydroxy compound used in the present invention is a single
It does not matter if there are two or more types. A typical example of the aromatic dihydroxy compound is bisphenol A. In addition, these aromatic dihydroxy compounds are
It is preferable that the content of chlorine atoms and alkali or alkaline earth metal is small, and if possible, it is preferable that they are substantially not contained.

The diaryl carbonate used in the present invention is represented by the following general formula.

[0018]

Embedded image (Wherein, Ar ^3, Ar ⁴ represents a monovalent aromatic group, respectively.) Ar ³ and Ar ⁴ represent a monovalent carbocyclic or heterocyclic aromatic group, this Ar ^3, Ar ^{In 4} , one or more hydrogen atoms are other substituents that do not adversely affect the reaction,
For example, a halogen atom, an alkyl group having 1 to 10 carbon atoms,
It may be substituted by an alkoxy group having 1 to 10 carbon atoms, a phenyl group, a phenoxy group, a vinyl group, a cyano group, an ester group, an amide group, a nitro group, or the like. A
r ³ and Ar ⁴ may be the same or different. Typical examples of the monovalent aromatic groups Ar ³ and Ar ⁴ include a phenyl group, a naphthyl group, a biphenyl group and a pyridine group. These may be substituted with one or more types of the above-mentioned substituents. Preferred Ar ³ and Ar ⁴ include, for example, the following general formulas.

[0019]

[Chemical 6] Representative examples of the diaryl carbonate include substituted or unsubstituted diphenyl carbonates represented by the following general formula.

[0020]

Embedded image (In the formula, R ⁹ and R ¹⁰ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 ring carbon atoms, or phenyl. Represents a group, p and q are integers of 1 to 5, and when p is 2 or more, each R ⁹ may be different, and when q is 2 or more, each R ¹⁰ is It may be different.)

Among these diphenyl carbonates,
Symmetrical diaryl carbonates such as unsubstituted diphenyl carbonate and lower alkyl-substituted diphenyl carbonates such as ditolyl carbonate and di-t-butylphenyl carbonate are preferred, but diphenyl carbonate having a particularly simple structure is used. Is preferred. These diaryl carbonates may be used alone or in combination of two or more. In addition, these diaryl carbonates,
It is preferable that the content of chlorine atoms and alkali or alkaline earth metal is small, and if possible, it is preferable that they are substantially not contained.

The use ratio (charge ratio) of the aromatic dihydroxy compound and the diaryl carbonate is the kind of the aromatic dihydroxy compound and the diaryl carbonate used, the polymerization temperature and other polymerization conditions, and the molecular weight and terminal ratio of the polycarbonate to be obtained. Depending on the amount of diaryl carbonate, the amount of diaryl carbonate is usually 0.9 to 2.5 mol, preferably 0.
95 to 2.0 moles, more preferably 0.98 to 1.
Used in a proportion of 5 mol. These polycarbonate resins may be used alone or in combination of two or more, and may be a copolymer or a mixture.

In addition, these polycarbonate resins may contain ultraviolet absorbers, antioxidants, antistatic agents, heat stabilizers, light stabilizers, flame retardants, mold release agents, surfactants, dispersants, if necessary.
Additives such as a lubricant, an anti-blocking agent, a light diffusing agent, a colorant, an inorganic feeler, a glass fiber, a cross-linking agent, a foaming agent, a plasticizer and an organic cross-linking agent may be contained.

The apparatus used in the present invention is an apparatus for plasticizing a polycarbonate resin and extruding it into a sheet form from a T-die, and a mirror surface roll having a plurality of highly smooth surfaces.
It consists of a take-up roll that takes in the sheet shaped by the mirror-finished roll, and an example thereof is shown in FIG. In FIG. 1, 1 is an extruder, 2 is a T-die, 3 (lower roll), 4 (middle roll), 5 (upper roll) is a mirror surface roll (5 is a final mirror surface roll), 6 is a heater, and 7 is a transfer roller. , 8 are take-up rolls.

The surface of the mirror rolls 3, 4, and 5 is important in determining the appearance of the sheet. Surface roughness of 0.1
A smoothness of 0.005 μm is required. A heat medium such as water or oil can be circulated inside the roll so that the temperature of the roll can be adjusted. 6 is a heater to prevent overcooling of the sheet during molding.
Is a metal roll that guides the running of the sheet. 8 is a roll made of rubber for pulling a sheet.

The plasticized and melted polycarbonate resin is 2
Mirror-like rolls 3, 4, and 5 extruded in sheet form from the T-die
Is rolled, shaped, and runs while being in close contact with the rolls. The sheet from which the final mirror surface roll 5 has been peeled off is guided by the transfer roll 7 and taken by the take-up roll 8. The sheet thus taken is cut into a desired size or wound as it is. The sheet thickness is 0.1 to 3.0 mm for the optical use.

According to the present invention, after the sheet is peeled from the final mirror-finished roll of a plurality of mirror-finished rolls, the surface temperature of the sheet on the roll-peeling surface is measured immediately after the running sheet has traveled the radius of the roll. Transition temperature-10
~ +30 ℃, and by further controlling the final mirror surface roll and take-up roll speed ratio in the range of 1: 0.95 to 1.05 in order to suppress the orientation applied to the sheet as much as possible, practical use with excellent birefringence It was found that an optical sheet having no problem above can be obtained.

According to the present invention, after the sheet is peeled off from the final mirror-finished roll, the temperature immediately after the peeled surface of the sheet passes through the radial length of the roll, that is, the sheet surface which is substantially the closest to the peeling point which can be measured. It measures temperature. Specifically, when the roll diameter is 200 mmφ, the sheet runs 100 mm away from the roll, and the length added with 40 mm which is a length that can be measured by setting a measuring machine, that is, the sheet peels from the roll and runs 140 mm. The points are the surface temperature measurement points of the sheet. 1 if the roll diameter is 300 mmφ
90 mm corresponds to the measurement point.

The sheet surface measurement point described in Japanese Patent Publication No. 5-71026 is a point where the sheet has run 300 mm after the final mirror roll peeling, but a roll diameter of 250 mm of a general size.
When calculated in the range of about φ to 400, the sheet surface measurement point of the present invention is closer to the roll peeling point of the sheet as compared with the method described in Japanese Patent Publication No. 5-71026, and when the traveling speed is slow, it strictly travels. It is a measurement point that can measure the high temperature of the sheet.

The surface temperature of the polycarbonate resin sheet running at the measuring point is defined as the glass transition temperature of the resin -10 to +
It is necessary to adjust to 30 ° C. The glass transition temperature of the polycarbonate resin is preferably −5 to + 20 ° C. In the method described in Japanese Patent Publication No. 5-71026, the surface temperature of the sheet after leaving the final mirror surface roll is set to a thermal deformation temperature of ± 6 ° C., but the heat described in Japanese Patent Publication No. 5-71026 is used. The deformation temperature is about 20 ° C. lower than the glass transition temperature and indicates the temperature at which the polycarbonate resin is solidified. Birefringence is related to the strain remaining in the molded product, and the greater the strain, the greater the birefringence. The temperature at which the distortion remains in the molded product depends on whether any stress is applied at the stage where the polycarbonate is solidified from the molten state. Considering the temperature of the sheet for sheet forming, it is important to maintain the molten state when the sheet exits the final mirror roll and is released from deformation, that is, to maintain the glass transition temperature or higher.

The preferred range of the sheet surface temperature in the present invention is the glass transition temperature of -10 ° C to + 30 ° C, and the range below the glass transition temperature is included in the range, which is the temperature measurement of the sheet exiting the final mirror roll. The surface is running while contacting the final mirror surface roll, and it shows the lowest temperature when considering the thickness direction of the sheet, but the sheet shows the lowest temperature while running past the measurement point. Since the sheet temperature measurement surface is affected by the heat capacity of the resin and rises to the glass transition temperature or higher, it is a range in which substantially excellent birefringence is maintained. Glass transition temperature-1
If the temperature is less than 0 ° C, the birefringence in the width direction of the sheet greatly varies, and if it exceeds the glass transition temperature + 30 ° C, peeling between the final mirror surface roll and the sheet becomes uneven, and a proper appearance cannot be obtained.

Another factor that constitutes the present invention is the take-up speed. The final mirror roll to take-up roll speed ratio should be adjusted to 1: 0.95 to 1.05, preferably 1: 0.94 to 1.04. The resin temperature of the sheet drops significantly while traveling to the take-up roll where the sheet comes out from the final mirror surface roll and becomes close to room temperature.When considering the sheet traveling direction, the resin undergoes heat shrinkage, and the take-up speed is higher than the final mirror surface roll speed. Even if it is late, the slack phenomenon of the sheet does not occur.

When the take-up speed is faster than the final mirror surface roll, tension is generally applied in the take-up direction to leave internal strain in the sheet, but in the case of the present invention, the sheet temperature running out of the final mirror surface roll should be kept above the glass transition temperature. To suppress the residual strain. When the speed ratio exceeds 1.05, residual strain is likely to remain in the sheet and birefringence increases. or,
If it is less than 0.95, the take-up balance between the mirror-finished roll and the take-up machine cannot be obtained, and unevenness occurs when the sheet is peeled off from the final mirror-finished roll, resulting in poor appearance.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to Examples and Comparative Examples. The evaluation and test methods used in each example and comparative example are as follows. (1) Sheet surface temperature Immediately after the running sheet peels the final mirror surface roll and the peeling surface of the sheet runs the radius of the roll, 5 points in the width direction are obtained using a non-contact type radiation thermometer 505 of Minolta Co., Ltd. It measured and calculated | required the average value. (2) Glass transition temperature It was measured using a differential scanning calorimeter DSC-7 manufactured by Perkin Elmer Inc. under the conditions of a sample weight of 5 mg and a heating rate of 10 ° C./min.

(3) Birefringence Birefringence measuring device BHS-323 (wavelength 78) of Olympus Optical Co.
0 nm) and the average value is shown. (4) Impact Strength Using a DuPont type impact tester, a weight of 1 kg was set on a shooting die having a tip R of 1/4 inch and dropped from a height of 1 m to check for cracks. (5) Solvent resistance In order to see the cracking resistance as one index of durability, a silicone hard coat liquid was applied as a cracking promoting liquid and changes in the surface condition were observed.

[0036]

【Example】

Examples 1 to 3 and Comparative Examples 1 to 4 Carried out using a sheet forming apparatus with three mirror surface rolls as shown in FIG. 1, the extruder used was Toshiba SE-90 DVB and a T-die having a lip width of 1,200 mm. The die temperature distribution was almost uniform, the extrusion rate was set to 240 Kg / h, and the sheet thickness, die temperature, mirror surface roll temperature, and speed are shown in Table 1. As the polycarbonate resin, a resin obtained by polymerizing bisphenol A and having a viscosity average molecular weight of 24,500 and a glass transition temperature of 153 ° C. was used. Form a sheet under the above conditions,
Birefringence, impact strength and solvent resistance were measured. The results are shown in Table 1.

Reference Example 1 Viscosity-Averaged Molecular Weight of Polymerized Bisphenol A 15,000
Diameter 1 by injection molding using 0 polycarbonate resin
Table 1 also shows the physical property table obtained by molding a 20 mmφ disc at 300 ° C.

[0038]

[Table 1]

[0039]

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to mold a polycarbonate sheet having a birefringence of 40 nm or less and excellent mechanical strength and durability for optical use.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a sheet suitable for carrying out the present invention.

[Explanation of symbols] 1 Extruder 2 T die 3 Mirror surface roll (lower roll) 4 Mirror surface roll (middle roll) 5 Mirror surface roll (upper roll) 6 Heating heater 7 Transfer roll 8 Take-up roll

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area // B29K 69:00

Claims (1)

[Claims] 1. When rolling and sheeting a polycarbonate resin using a plurality of mirror surface shaping rolls, the sheet from which the final mirror surface shaping roll has been peeled is immediately after running the radius of the final mirror surface shaping roll. The surface temperature on the roll side of the resin is a glass transition temperature of the resin of −10 to + 30 ° C., and the speed ratio of the final shaping mirror surface roll to the take-up roll is 1: 0.95 to 1.05. A method for producing a characteristic polycarbonate sheet.