JP3131031B2 - Polycarbonate film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polycarbonate film, and more particularly, to a film made of an aromatic polycarbonate copolymer having a specific structural unit and composition, and having mechanical strength, heat resistance, and chemical durability. A film with excellent properties, especially high surface hardness, and excellent properties such as high transparency and high electrical insulation as required. It can be suitably used for various applications as a laminated film, a coated film (coating, etc.), for example, a film used for various electronic and electric equipment parts, an optical film, a heat resistant film, an electrically insulating film, etc. As a polycarbonate film useful as a

[0002]

2. Description of the Related Art Polycarbonate is known as an engineering resin having a well-balanced mechanical strength, heat resistance, chemical durability, transparency, electrical properties, etc., and is used as a variety of molded articles for various applications. Have been. Polycarbonates having various chemical structures and compositions are known, and among these, certain types are also formed into films and used. Such a polycarbonate film is considered to be useful, for example, as a film for electronic / electric equipment parts, an optical film, a heat-resistant film, an insulating film, and the like, and is expected to be used in a much wider range in the future.

However, although a wide variety of polycarbonates have been proposed in the past, few of them have been clarified for practical properties as a film, and the types of commercially available polycarbonates are limited. What is used as a film is extremely limited. Heretofore, the most common and widely marketed polycarbonates are bisphenol A-based polycarbonates made from 2,2-bis (4-hydroxyphenyl) propane and a carbonate-forming compound such as phosgene, and are thus the most commonly used polycarbonates. The polycarbonate film used is also obtained by molding this bisphenol A-based polycarbonate.

[0004] However, as the functions and performance of various products such as electronic and electric equipment components in recent years have increased, strict requirements have been placed on the characteristics of polycarbonate films. Polycarbonate films obtained by molding polycarbonate have not been able to adequately meet such demands.

[0005] In fact, it has been revealed that a film obtained by molding a commercially available polycarbonate such as the above-mentioned bisphenol A-based polycarbonate is not satisfactory in various points such as insufficient surface hardness depending on the use. In addition, among these conventional commercially available polycarbonates, there are many that are likely to cause gelation or crystallization due to the action of a solvent or the like,
It has often been a problem that the mechanical strength and transparency of the film are reduced.

Under such circumstances, it has become an important issue to examine polycarbonates other than the conventional commercially available polycarbonates and to find a specific polycarbonate from which a high-performance film free from the above-mentioned problems can be obtained. Was.

[0007] Under such circumstances, various kinds of polycarbonates having different chemical structures and copolymer compositions have been developed.

For example, by reacting 4,4'-dihydroxydiphenyl and 2,2-bis (4-hydroxyphenyl) alkane with diphenyl carbonate, a polycarbonate copolymer having excellent mechanical strength and thermal properties can be obtained. It is known that it can be obtained. However, since this polycarbonate is inferior in transparency, a film excellent in transparency cannot be obtained, and there is a problem that the application is narrowly limited.

Of course, other than this example, polycarbonates of various structures and compositions have been proposed. In practice, however, those having any chemical structure, composition and molecular weight characteristics described above have the above-mentioned transparency and surface hardness. It has not been clarified as to whether or not an excellent polycarbonate film satisfies strict requirements including the above.

That is, in order to develop a high-performance polycarbonate film free of the above-mentioned problems, various polycarbonates are actually formed into films, and the characteristics and performance of the films are examined in detail to obtain appropriate films. The type of polycarbonate must be specified.

[0011]

The present invention has been made in view of the above circumstances.

An object of the present invention is to provide a film formed by molding various aromatic polycarbonate copolymers having a specified structural unit, copolymer composition range, etc., and to provide mechanical strength, heat resistance, and chemical durability. Etc., in particular, has improved surface hardness, and also has excellent properties such as high transparency and high electrical insulation as required,
An object of the present invention is to provide a high-performance polycarbonate film which can sufficiently cope with the above strict requirements and can be advantageously applied to a wider range of applications.

[0013]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, have found that a repeating unit having a specific structure of a 4,4'-dihydroxydiphenyl carbonate structure type and a bisphenol carbonate are used. It consists of repeating units of a specific structure of the structural type, and the proportion of these units is in a specific range, and the reduced viscosity [η _sp / c] of the polymer solution measured under certain predetermined conditions is in a specific range. When formed into a film using various polycarbonates having the specified chemical structure, copolymer composition and molecular weight characteristics as raw materials, it has excellent mechanical strength, heat resistance, chemical durability, etc. In particular, it has been found that an excellent film having particularly improved surface hardness can be easily obtained. In addition, this polycarbonate film can be made into a film having extremely high transparency or a film having high electric insulation by utilizing the excellent properties such as high transparency and electric insulation of the raw material polycarbonate itself. I knew I could do it. The present inventors have clarified that by using a specific polycarbonate as a molding raw material in this way, it is possible to easily realize a high-performance polycarbonate film that sufficiently satisfies the above objects, and to complete the present invention. Reached.

That is, the present invention provides the following general formula [I]

[0015]

Embedded image Wherein R ¹ and R ² in the formula [I] each independently represent an alkyl group having 1 to 6 carbon atoms, and a and b each independently represent an integer of 0 to 4. And a repeating unit [I] represented by the following general formula [II]:

[0016]

Embedded image Wherein R ³ and R ⁴ in the formula [II] are each independently:
Represents an alkyl group having 1 to 6 carbon atoms, c and d each independently represent an integer of 0 to 4, and Q represents the following general formula [II
I]

[0017]

Embedded image (However, R ⁵ and R ⁶ in the formula [III] each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.)
Or a cyclohexylene group. {II}, and the ratio of these units is 0.0 in a molar ratio {[I] / ([I] + [II])}.
The reduced viscosity [η _sp / c] at 20 ° C. of a solution having a concentration of 0.5 g / dl using methylene chloride as a solvent is in a range of 0.5 to 2.5 dl / g. The present invention provides a polycarbonate film obtained by molding the polycarbonate copolymer described in (1).

The polycarbonate copolymer used as a raw material for forming the polycarbonate film of the present invention comprises at least a repeating unit represented by the general formula [I], that is, a repeating unit [I] and a general formula [II]. And repeating units [II], and the proportion of these repeating units is within the above-mentioned specific range.

In the general formula [I], R ¹ and R ²
Each independently represents an alkyl group having 1 to 6 carbon atoms,
Specific examples of the alkyl group include, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, isobutyl group, n-pentyl group, isopentyl group , Sec-pentyl, tert-pentyl, n-hexyl, isohexyl, sec-hexyl, tert-hexyl, neohexyl, cyclopentylmethyl and the like. As R ¹ and R ² , a particularly preferred example is a methyl group.

In the general formula [I], a and b are
Each independently represents an integer of 0 to 4, and among them, a and b are each preferably 0 to 2, and particularly preferably, a and b are both 0 or 1. In the case where a = 0, the substituent R
¹ has no substituent R, and b = 0 does not have the substituent R ² , and particularly, a = b = 0 has the substituent R
Those that do not have a ¹ and R ^2.

Of the repeating unit [I], specific examples of particularly preferred repeating units include the following structural units.

[0022]

Embedded image

In the above general formula [II], R ³ and R
⁴ each independently represents an alkyl having 1 to 6 carbons,
Specific examples of the alkyl group include, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, isobutyl group, n-pentyl group, isopentyl group , Sec-pentyl, tert-pentyl, n-hexyl, isohexyl, sec-hexyl, tert-hexyl, neohexyl, cyclopentylmethyl and the like. Particularly preferred examples of R ³ and R ⁴ include, for example, a methyl group.

In the general formula [II], c and d
Each independently represents an integer of 0 to 4, and among them, those in which both c and d are 0 to 2 are preferable, and those in which both c and d are 0 or 1 are particularly preferable. Those with c = 0 have no substituent R ³ , and those with d = 0 have substituent R ³
Those having no ⁴ and particularly those having c = d = 0 have no substituents R ³ and R ⁴ .

Q in the general formula [II] represents a group represented by the general formula [III] or a cyclohexylene group, wherein R ⁵ and R ⁶ in the general formula [III] are
Each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Here, specific examples of R ⁵ and R ⁶ include, for example, a hydrogen atom, a methyl group, an ethyl group,
n-propyl group, isopropyl group, n-butyl group, se
c-butyl group, tert-butyl group, isobutyl group, n
-Pentyl group, isopentyl group, sec-pentyl group,
Examples include a tert-pentyl group, an n-hexyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, a neohexyl group, a cyclopentylmethyl group, a cyclohexyl group, and a methylcyclohexyl group. Particularly preferred examples of each of R ⁵ and R ⁶ include, for example, a hydrogen atom, a methyl group and an ethyl group. Note that R ⁵ and R ⁶ may be the same or different from each other.

When Q is a cyclohexylene group, specific examples of the cyclohexylene include a 1,1-cyclohexylene group and a 1,4-cyclohexylene group. , 1-cyclohexylene groups are preferred.

Examples of some of the preferable groups for Q include, for example, the following groups.

[0028]

Embedded image Some particularly preferable examples of the repeating unit [II] include the following structural units.

[0029]

Embedded image

The polycarbonate copolymer used as a raw material for forming the polycarbonate film of the present invention comprises:
A polymer comprising at least one kind of the repeating unit [I] and at least one kind of the repeating unit [II], and at the same time, the proportion of these units [I] and [II] is
The molar ratio {[I] / ([I] + [II])} is 0.05 to
It is important to be in the range of 0.4.

Here, if this molar ratio, that is, the content of the repeating unit [I] with respect to the total content of the repeating unit [I] and the repeating unit [II] is 0.
When it is less than 0.05, when formed into a film, the surface hardness and heat resistance become insufficient.
If it is larger than 4, the transparency of the film will be reduced, and the object of the present invention cannot be sufficiently achieved in any of these cases.

In particular, the molar ratio ｛[I] /
([I] + [II])} is preferably a copolymer composition having a range of 0.1 to 0.25.

In the polycarbonate copolymer, there is no particular limitation on the arrangement of the repeating unit [I] and the repeating unit [II], and various types such as a random type, an alternating type, a block type, or a combination thereof are used. Can be used as a copolymer of the type Among them, the random type is generally more preferably used because it has advantages such as easy production.

Further, these polycarbonate copolymers are not limited to those comprising one kind of repeating unit [I] and one kind of repeating unit [II].
It may have one or more kinds of repeating units [I],
It may have two or more kinds of repeating units [II].
Further, these polycarbonate copolymers may be copolymers having a repeating unit other than the repeating unit [I] and the repeating unit [II] as long as the object of the present invention is not impaired. And a copolymer having a branched structure, such as a graft copolymer or a copolymer having a cross-linked structure, into which an appropriate branched-type repeating unit is introduced.

The polycarbonate copolymer used as a raw material for forming the polycarbonate film of the present invention comprises:
A polymer containing the repeating unit [I] and the repeating unit [II] in the proportions described above,
A concentration of 0.5 g /
It is also important that the reduced viscosity [η _sp / c] of the dl solution at 20 ° C. is in the range of 0.5 to 2.5 dl / g.

If the reduced viscosity [η _sp / c] of the polymer measured under the above conditions is less than 0.5 dl / g, the properties such as mechanical strength and heat resistance of the film become insufficient.
On the other hand, if it is more than 2.5 dl / g, the moldability into a film is reduced, and troubles such as difficulty in molding into a uniform film are liable to occur. Can not be achieved.

Among them, usually, the above-mentioned reduced viscosity [η _sp
/ C] is in the range of 0.5 to 1.2 dl / g.

The polycarbonate copolymer used as a raw material for forming the polycarbonate film of the present invention comprises:
The production method is not particularly limited, and known methods, for example, a phosgene method using a dihydric phenol as a starting monomer component (an interfacial polycondensation method, a pyridine method, etc.), a transesterification method (a melting method, a solid-phase polymerization method) And the like). At that time, the repeating unit [I]
And, in addition to the respective raw material monomer components (for example, corresponding dihydric phenols and the like) giving the repeating unit [II], a range in which the properties of the target film are not impaired,
For example, it may be produced by adding an appropriate amount of other various dihydric phenols such as catechol, resorcin, hydroquinone and the like and copolymerizing them. Further, in addition to these dihydric phenols, for example, a branching agent such as a polyhydroxy compound may be added to obtain a polycarbonate copolymer having an appropriate degree of branching and a branched structure. For example, such a branching agent is added in an amount of 0.05 to 2.0 mol% based on the dihydric phenol.
A method in which polymerization is carried out by adding a certain amount is also suitably employed.

The polycarbonate copolymer produced by various methods as described above can be used as a molding material of the present invention.

The polycarbonate film of the present invention can be produced by using at least one or more of the above-mentioned polycarbonate copolymers as a forming raw material or a forming raw material component, and forming this into a film having desired properties. .

That is, in the polycarbonate film of the present invention, only one of the above-mentioned specific polycarbonate copolymers may be used, or two or more of them may be used. Accordingly, in addition to the polycarbonate copolymer, various polymer components (for example, various thermoplastic resins exemplified below) and various additives such as known additives may be used as long as the properties of the target film are not impaired. May be added in an appropriate amount. These additional components may be added to the polycarbonate copolymer in advance, may be added at the time of molding into a film, or may be added at any time. When two or more polymers are used, they may be mixed in advance and used as a composition, or may be mixed at the time of molding into a film, or may be used in combination as a multilayer film or the like. May be.

Examples of the thermoplastic resin include, but are not limited to, polyalkylene terephthalate, polyolefin, other polycarbonate, polyether sulfone, polyarylate, polysulfone, polyphenylene sulfide, and the like. .

Examples of the additives include a flame retardant, an antioxidant, an antistatic agent, an ultraviolet absorber, an infrared absorber,
A wide variety of substances such as a visible light absorber, a filler, a plasticizer, an impact modifier, a hydrolysis stabilizer, a pigment, a dye, a coloring agent, a coloring stabilizer, and an inorganic fine powder can be appropriately added.

The polycarbonate film of the present invention can be produced by molding the above polycarbonate copolymer or a film thereof together with other components, but the method of forming the film is not particularly limited. However, various methods such as known film forming methods exemplified below can be appropriately employed.

That is, for forming into a film, for example, press forming such as hot press forming, rolling method using a hot roll, various extrusion methods (cast roll method, inflation method, tuber method, etc.), a polymer solution to a belt, etc. Casting or coating on the surface of a substrate, and removing the solvent by evaporation to form a film into a thin film or thick film, or a coating method in which a polymer solution is directly applied to a predetermined article and then the solvent is removed A wide variety of methods can be used.

In the film-forming method using a solvent, various solvents can be used for preparing the polycarbonate copolymer-containing solution and the polymer-containing coating solution. Specific examples of the solvent include, for example, benzene , Aromatic solvents such as toluene, xylene and chlorobenzene, ketones such as acetone, methyl ethyl ketone and cyclohexanone, alcohols such as methanol, ethanol and isopropanol, esters such as ethyl acetate and ethyl cellosolve,
Examples include halogenated hydrocarbons such as carbon tetrachloride, chloroform, methylene chloride, and tetrachloroethane; ethers such as tetrahydrofuran and dioxane; dimethylformamide, diethylformamide, and dimethylsulfoxide. These can be used alone or in combination of two or more.
Furthermore, if necessary, various additives can be added and used.

The film formed as described above may be further subjected to a conventional stretching method (eg, a tender method, a tuber method, a multi-stage stretching method, a uniaxial stretching method, a biaxial stretching method, etc.), if necessary. ) And the like, and may be stretched to a desired stretching ratio, or may be subjected to post-treatment such as heat treatment as needed to finish the product.

The thickness of the polycarbonate film of the present invention is not particularly limited and may be any desired thickness, but is usually selected in the range of 0.1 to 1000 μm, preferably 1 to 500 μm. Is preferred.

As described above, the polycarbonate film of the present invention obtained as described above has a specific structural unit and a copolymer composition and a specific reduced viscosity [η _sp
/ C], which is excellent in mechanical strength, heat resistance, chemical durability and the like, and particularly has high surface hardness and, if necessary, high transparency. It is a high-performance resin film having excellent properties such as high electrical insulation. Therefore, the polycarbonate film of the present invention can be advantageously used as a film of various properties such as a single film, a laminated film, and a coated film (coating, etc.) utilizing such characteristics. For example, various electronic and electric equipment parts It can be suitably used for a wide range of applications such as films, optical films, heat-resistant films, and electrically-insulating films.

[0050]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples of the present invention and Comparative Examples thereof, but the present invention is not limited to these Examples.

Example 1 Synthesis Example of Polycarbonate Copolymer 2,2-bis (4-hydroxyphenyl) propane 74
g of 650 ml of a phosgene gas in a solution of 950 ml / s under cooling with stirring while mixing a solution obtained by dissolving g in 550 ml of a 6% aqueous sodium hydroxide solution and 250 ml of methylene chloride.
ec was blown for 15 minutes. Then, the reaction solution was allowed to stand and separated to obtain a methylene chloride solution of an oligomer having a degree of polymerization of 2 to 4 in the organic layer and having a chloroformate group at a molecular end. After adding methylene chloride to a methylene chloride solution of the obtained oligomer to make the total amount 450 ml,
A solution prepared by dissolving 24 g of 4,4'-dihydroxybiphenyl in 150 ml of an 8% aqueous sodium hydroxide solution was mixed, and 3.0 g of p-tert-butylphenol as a molecular weight regulator was added thereto. Next, 2 ml of a 7% aqueous solution of triethylamine was added as a catalyst while vigorously stirring this mixed solution, and the mixture was reacted at 28 ° C. with stirring for 1.5 hours. At the end of the reaction, the reaction product is diluted with 1 l of methylene chloride and then twice with 1.5 l of water.
The mixture was washed twice with 1 liter of 0.01N hydrochloric acid and 1 liter of water in this order, and the organic layer was poured into methanol for reprecipitation purification.

The polymer thus obtained was prepared by adding a 0.5 g / dl solution of methylene chloride as a solvent at 20 ° C.
The reduced viscosity [η _sp / c] was 0.82 dl / g. Further, ¹ H-NMR spectrum analysis confirmed that this polymer was a polycarbonate copolymer having the following repeating units and copolymer composition.

[0053]

Embedded image

A 10% by weight solution of this copolymer in tetrahydrofuran was prepared, left at ordinary temperature for one month, and the solution viscosity was measured. Even after leaving for one month, turbidity and gel generation did not occur,
No change in viscosity was observed.

Film Production Examples and Evaluation Examples 1 part by weight of the copolymer obtained above was dissolved in 50 parts by weight of chloroform to prepare a polymer solution. This polymer solution was cast on a glass substrate using a doctor knife and dried under reduced pressure at 120 ° C. for 24 hours to give a wall thickness of 20 μm.
m of the desired film were obtained.

Next, the film obtained above was subjected to a tensile test using an autograph. Furthermore, JIS-K
A pencil hardness test was performed according to -5400 to measure the surface hardness. In order to check the transparency of this film, a haze computer manufactured by Suga Test Instruments Co., Ltd.
The haze was measured according to 7105. Table 1 shows these results.
Shown in

Example 2 The same operation as in Example 1 was carried out except that 74 g of 2,2, -bis (4-hydroxyphenyl) propane was changed to 87 g of 1,1-bis (4-hydroxyphenyl) cyclohexane in Example 1. And a polycarbonate copolymer having the following composition and copolymer composition ([η _sp /c]=0.89)
dl / g).

[0058]

Embedded image Using this copolymer, the same operation as that for forming the film of Example 1 was performed to obtain a desired film. Table 1 shows the results of each test.

Example 3 In Example 1, 24 g of 4,4'-dihydroxybiphenyl was replaced by 12 g of 4,4'-dihydroxybiphenyl.
2,2-bis (4-hydroxyphenyl) propane 15
Except for changing to g, a polycarbonate copolymer ([η _sp /c]=0.75 dl / g) comprising the following structural units and copolymer composition was obtained in the same manner as in Example 1.

[0060]

Embedded image Using this copolymer, the same operation as that for forming the film of Example 1 was performed to obtain a desired film. Table 1 shows the results of each test.

Example 4 The procedure of Example 1 was repeated, except that 24 g of 4,4'-dihydroxybiphenyl was changed to 27.6 g of 4,4'-dihydroxy-2,2'-dimethylbiphenyl. , A polycarbonate copolymer comprising the following structural units and a copolymer composition ([η _sp /c]=0.90 dl /
g) was obtained.

[0062]

Embedded image Using this copolymer, the same operation as that for forming the film of Example 1 was performed to obtain a desired film. Table 1 shows the results of each test.

Comparative Example 1 Tetrahydrofuran 10 of a commercially available polycarbonate (Idemitsu Petrochemical Co., Ltd .: Idemitsu Polycarbonate A2500)
When the weight% solution was prepared and left at room temperature for one month, cloudiness and generation of gel occurred.

Using this commercially available polycarbonate, a film was formed in the same manner as in Example 1 to obtain a film as a comparative example. Table 1 shows the test results of the film.

[0065]

[Table 1]

Comparative Example 2 A solution of 4
A solution in which 23.4 g of 4'-dihydroxybiphenyl and 3.5 g of 2,2-bis (4-hydroxyphenyl) propane were dissolved, and 250 ml of methylene chloride were introduced into a 1-liter flask. The reaction solution was stirred vigorously while maintaining the liquid temperature around 10 ° C. by external cooling, and phosgene was added to the solution for 34 hours.
Blowing was performed at a rate of 0 ml / min for 30 minutes.

Thereafter, stirring was continued for 1 hour to complete the polymerization. After completion of the reaction, the organic layer was diluted by adding 500 ml of methylene chloride, washed with water, dilute hydrochloric acid and water in that order, and then poured into methanol to obtain a polycarbonate copolymer as a comparative example having the following structure and copolymer composition ( [Η _sp / c] =
0.73 dl / g).

[0068]

Embedded image Using this copolymer, the same operation as that for forming the film of Example 1 was performed to obtain a film as a comparative example. However, the film was immediately clouded and a transparent film was not obtained.

[0069]

The polycarbonate film of the present invention has
As described above, since it is a film made of an aromatic polycarbonate copolymer having a specific structural unit and a copolymer composition, and having a specific reduced viscosity [η _sp / c],
Excellent in mechanical strength, heat resistance, chemical durability, etc., compared with conventional polycarbonate film, especially the surface hardness is improved and sufficiently high, and if necessary, high transparency, high electrical insulation It is a high-performance resin film having excellent properties such as having Therefore, the polycarbonate film of the present invention can be advantageously used in a wide range of application fields as a film having various properties such as a single film, a laminated film, and a coated film (coating or the like) utilizing such characteristics.

That is, according to the present invention, there can be provided various high-performance polycarbonate films having such excellent properties and which can be suitably used in a wide range of fields.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomohiro Nagao 1280 Kamiizumi, Sodegaura-shi, Chiba Idemitsu Kosan Co., Ltd. (56) References JP-A-56-104934 (JP, A) JP-A-1-201328 (JP, A) JP-A-1-201329 (JP, A) JP-A-1-156323 (JP, A) JP-A-61-264026 (JP, A) (58) Fields investigated (Int. Cl. ⁷⁾ , DB name) C08J 5/18 C08G 64/06

Claims (1)

(57) [Claims] [Claim 1] The following general formula [I] Wherein R ¹ and R ² in the formula [I] each independently represent an alkyl group having 1 to 6 carbon atoms, and a and b each independently represent an integer of 0 to 4. And a repeating unit [I] represented by the following general formula [II]: Wherein R ³ and R ⁴ in the formula [II] are each independently:
Represents an alkyl group having 1 to 6 carbon atoms, c and d each independently represent an integer of 0 to 4, and Q represents the following general formula [II
I] embedded image (However, R ⁵ and R ⁶ in the formula [III] each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.)
Or a cyclohexylene group. {II}, and the ratio of these units is 0.0 in a molar ratio {[I] / ([I] + [II])}.
The reduced viscosity [η _sp / c] at 20 ° C. of a solution having a concentration of 0.5 g / dl using methylene chloride as a solvent is in a range of 0.5 to 2.5 dl / g. A polycarbonate film obtained by molding the polycarbonate copolymer according to any one of claims 1 to 3.