JP7792226B2 - Film, multilayer body, and transparent conductive film - Google Patents

Description

The present invention relates to a film, a multilayer body, and a transparent conductive film.

Transparent conductive films are used in touch panel film sensors, electronic paper, dye-sensitized solar cells, touch sensors, and the like. A known transparent conductive film 10, for example, as shown in FIG. 1, is composed of an electrode layer (transparent conductive film) 11, a substrate 12, an adhesive layer 13, and a protective film 14. A specific example of such a transparent conductive film is that described in Patent Document 1. Films primarily composed of polycarbonate resin are sometimes used as the substrate or protective film for such transparent conductive films. Furthermore, films primarily composed of polycarbonate resin described in Patent Documents 2 and 3 are also being considered.

Japanese Patent Application Laid-Open No. 2018-152187 International Publication No. 2016/060100 Japanese Patent Application Laid-Open No. 2019-002023

Here, when a film primarily composed of polycarbonate resin is used as a transparent conductive film, depending on the application, a small change in retardation before and after thermal shaping and flex resistance may be required. That is, when the film is used for a curved display, a large change in retardation during thermal shaping can cause rainbow unevenness (coloring due to birefringence). Furthermore, poor flex resistance can make it difficult to use the film in curved displays or foldable displays. Furthermore, since it is a display, it is naturally required that the film be transparent. Such performance is also required when a film primarily composed of polycarbonate resin is used as a shatterproof film for curved glass.
The present invention aims to solve such problems, and relates to a film that has a small change rate of retardation before and after thermal shaping, excellent bending resistance, and excellent transparency, as well as a multilayer body and a transparent conductive film that include the film.

In light of the above-mentioned problems, the inventors have conducted research and found that the above-mentioned problems can be solved by using an aromatic polycarbonate resin having a predetermined terminal structure and a predetermined molecular weight, and by adjusting the thickness and surface roughness of the film to fall within a predetermined range.
Specifically, the above problems were solved by the following means.
<1> A film containing an aromatic polycarbonate resin having a terminal structure represented by formula (1), wherein the viscosity average molecular weight of the aromatic polycarbonate resin is 17,000 to 40,000, the thickness of the film is 20 to 150 μm, and the surface roughness Ra of the film is less than 0.7 μm.

(In formula (1), ^R1 represents an alkyl group having 8 to 36 carbon atoms or an alkenyl group having 8 to 30 carbon atoms. Each ^R2 independently represents a halogen atom, an alkyl group having 1 to 20 carbon atoms, or an aryl group having 6 to 12 carbon atoms. n represents an integer of 0 to 4. * represents a bonding site to another site.)
<2> The film according to <1>, wherein the glass transition temperature of the film is 115 to 142°C.
<3> The film according to <1> or <2>, wherein the aromatic polycarbonate resin has a viscosity average molecular weight of 30,000 to 40,000.
<4> The film according to <1> or <2>, wherein the aromatic polycarbonate resin has a viscosity average molecular weight of 17,000 or more and less than 30,000.
<5> The film according to any one of <1> to <4>, wherein the surface roughness Ra of the film is 0.1 μm or less.
<6> The film according to any one of <1> to <5>, wherein the haze of the film is 10% or less.
<7> The film according to any one of <1> to <6>, wherein the retardation (Re) of the film at a wavelength of 543 nm is 25 nm or less.
<8> The film according to any one of <1> to <7>, which is a single-layer film.
<9> A multilayer body having the film according to any one of <1> to <8> and at least one other layer.
<10> The multilayer body according to <9>, wherein the other layer includes an adhesive layer.
<11> A transparent conductive film having a protective layer, an adhesive layer, a substrate, and an electrode layer in this order, wherein at least one of the substrate and the protective layer is the film according to any one of <1> to <8>.

The present invention makes it possible to provide a film that exhibits a small change in retardation before and after thermal shaping, has excellent flex resistance, and is highly transparent, as well as a multilayer body and a transparent conductive film that include the film.

FIG. 1 is a schematic cross-sectional view showing an example of the layer structure of a transparent conductive film. FIG. 2 is a diagram showing a mold for measuring the rate of increase in retardation before and after thermal shaping in the examples. FIG. 1 is a diagram showing how strain is applied to measure chemical resistance in an example.

Hereinafter, an embodiment of the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. Note that the present embodiment is an example for explaining the present invention, and the present invention is not limited to only this embodiment.
In this specification, the word "to" is used to mean that the numerical values before and after it are included as the lower limit and upper limit.
In this specification, various physical properties and characteristic values are those at 23° C. unless otherwise specified.
In the description of groups (atomic groups) in this specification, when a notation does not specify whether they are substituted or unsubstituted, it includes both groups (atomic groups) that have no substituents and groups (atomic groups) that have substituents. For example, the term "alkyl group" includes not only alkyl groups that have no substituents (unsubstituted alkyl groups) but also alkyl groups that have substituents (substituted alkyl groups). In this specification, when a notation does not specify whether they are substituted or unsubstituted, it is preferable to use unsubstituted.
The term "multilayer body" as used herein includes bodies in the form of a film or a sheet. The terms "film" and "sheet" refer to generally flat bodies that are thin relative to their length and width, respectively. The term "film" as used herein may be either a single layer or a multilayer body.
In this specification, "parts by mass" indicates the relative amount of a component, and "% by mass" indicates the absolute amount of a component.

The film of the present embodiment is a film containing an aromatic polycarbonate resin having a terminal structure represented by formula (1), characterized in that the viscosity average molecular weight of the aromatic polycarbonate resin is 17,000 to 40,000, the thickness of the film is 20 to 150 μm, and the surface roughness Ra of the film is less than 0.7 μm.

(In formula (1), ^R1 represents an alkyl group having 8 to 36 carbon atoms or an alkenyl group having 8 to 30 carbon atoms. Each ^R2 independently represents a halogen atom, an alkyl group having 1 to 20 carbon atoms, or an aryl group having 6 to 12 carbon atoms. n represents an integer of 0 to 4. * represents a bonding site to another site.)

By adopting the above-mentioned constitution, a film having a small change rate of retardation before and after thermal shaping, excellent bending resistance, and excellent transparency can be obtained. Furthermore, a film having excellent chemical resistance can be obtained. When an adhesive layer or a hard coat layer is applied, the occurrence of cracks due to a solvent can be effectively suppressed.
That is, by making the terminal of the aromatic polycarbonate resin have a structure represented by formula (1), the glass transition temperature of the aromatic polycarbonate resin is lowered, and further, by reducing the thickness of the film, the thermal resistance of the film is reduced, and the film is shaped in a softened state, which is presumably why an increase in retardation (Re) during thermal shaping can be suppressed. Suppressing the increase in Re during thermal shaping reduces birefringence, effectively suppressing rainbow unevenness (coloration due to birefringence) on displays. Furthermore, by setting the molecular weight of the aromatic polycarbonate resin within a predetermined range and reducing the film thickness, it is possible to increase resistance to bending, and it is presumed that a film with excellent flex resistance was obtained. Furthermore, by using an aromatic polycarbonate resin and reducing the surface roughness of the film, it is presumed that a film with excellent transparency was obtained. Furthermore, it is presumed that setting the molecular weight of the aromatic polycarbonate resin within a predetermined range can result in a film with excellent chemical resistance.
The details of this embodiment will be described below.

The film of the present embodiment contains an aromatic polycarbonate resin having a terminal structure represented by formula (1). By using such an aromatic polycarbonate resin, the glass transition temperature of the aromatic polycarbonate resin is lowered, and an increase in retardation (Re) during thermal shaping can be suppressed.

(In formula (1), ^R1 represents an alkyl group having 8 to 36 carbon atoms or an alkenyl group having 8 to 30 carbon atoms. Each ^R2 independently represents a halogen atom, an alkyl group having 1 to 20 carbon atoms, or an aryl group having 6 to 12 carbon atoms. n represents an integer of 0 to 4. * represents a bonding site to another site.)

^R1 represents an alkyl group having 8 to 36 carbon atoms or an alkenyl group having 8 to 30 carbon atoms, preferably an alkyl group or alkenyl group having 12 or more carbon atoms, and more preferably an alkyl group or alkenyl group having 14 or more carbon atoms. ^R1 is also preferably an alkyl group or alkenyl group having 22 or less carbon atoms, and more preferably an alkyl group or alkenyl group having 18 or less carbon atoms. ^R1 is preferably an alkyl group. The alkyl group and alkenyl group are preferably linear or branched alkyl groups or alkenyl groups, and more preferably linear alkyl groups or alkenyl groups.
In this embodiment, R ¹ is particularly preferably a hexadecyl group.
Furthermore, R ¹ may be located at any of the meta, para, and ortho positions, but is preferably located at the meta or para position, and more preferably at the para position.

^R2 's each independently represent a halogen atom, an alkyl group having 1 to 20 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and are preferably a fluorine atom, a chlorine atom, a methyl group, an ethyl group, or a phenyl group, and more preferably a fluorine atom, a chlorine atom, or a methyl group.
n represents an integer of 0 to 4, preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0.

The terminal structure represented by formula (1) can be added to polycarbonate by using a terminal blocking agent such as parahydroxybenzoic acid hexadecyl ester. For details, see paragraphs 0022 to 0030 of JP 2019-002023 A, the contents of which are incorporated herein by reference.
In the aromatic polycarbonate resin having a terminal structure represented by formula (1) used in this embodiment, the terminal structure represented by formula (1) may be of one type or of two or more types.

In this embodiment, the aromatic polycarbonate resin having the terminal structure represented by formula (1) is preferably a bisphenol polycarbonate resin, and more preferably a bisphenol A polycarbonate resin.

The bisphenol A polycarbonate resin may also have other structural units in addition to the carbonate structural units derived from bisphenol A and its derivatives. Examples of dihydroxy compounds constituting such other structural units include the aromatic dihydroxy compounds described in paragraph 0014 of JP-A-2018-154819, the contents of which are incorporated herein by reference.
In the bisphenol polycarbonate resin of the present embodiment, carbonate structural units derived from bisphenol A and its derivatives preferably account for 90% by mass or more of all structural units excluding terminal structures, more preferably 95% by mass or more, and even more preferably 97% by mass or more.

There are no particular limitations on the method for producing bisphenol A polycarbonate resin, and any method can be used. Examples include interfacial polymerization, melt transesterification, pyridine, ring-opening polymerization of cyclic carbonate compounds, and solid-phase transesterification of prepolymers.

The aromatic polycarbonate resin used in this embodiment has a viscosity-average molecular weight of 17,000 to 40,000. A viscosity-average molecular weight of 17,000 or more makes it possible to improve resistance to bending, resulting in a film with excellent flex resistance. Furthermore, a viscosity-average molecular weight of 40,000 or less tends to effectively lower the glass transition temperature of the film, effectively suppressing an increase in Re during thermal shaping.
The viscosity average molecular weight of the aromatic polycarbonate resin is preferably 20,000 or more, more preferably 22,000 or more, even more preferably 24,000 or more, and may even be 30,000 or more. In particular, a viscosity average molecular weight of 30,000 or more tends to further improve flex resistance. Furthermore, the viscosity average molecular weight of the aromatic polycarbonate resin is preferably 38,000 or less, even 35,000 or less, particularly less than 30,000, and more particularly 28,000 or less. In particular, by adjusting the viscosity average molecular weight to less than 30,000, or even 28,000 or less, the viscosity of the aromatic polycarbonate resin decreases, and filter permeability tends to improve. Improved filter permeability can reduce foreign matter in the film.
When the film of the present embodiment contains an aromatic polycarbonate resin having a terminal structure represented by formula (1) and another aromatic polycarbonate resin, it is preferable that the viscosity average molecular weight of the polycarbonate resin that is the blend satisfies the above range.

The Q value of the aromatic polycarbonate resin used in this embodiment is preferably 30× ¹⁰ cc/sec or less, more preferably 20× ¹⁰ cc/sec or less, even more preferably 10× ¹⁰ cc/sec or less, still more preferably 8× ¹⁰ cc/sec or less, and even more preferably 4.0× ¹⁰ cc/sec or less. By making the Q value equal to or less than the upper limit, the bending resistance and chemical resistance of the film tend to be improved. The lower limit of the Q value is preferably 0.1×10 ⁻² cc/sec or more, more preferably 0.5×10 ⁻² cc/sec or more, even more preferably 1.0×10 ⁻² cc/sec or more, still more preferably 3.0×10 ⁻² cc/sec or more, and may be 5.0×10 ⁻² cc/sec or more. By setting the Q value at or above the lower limit, the fluidity tends to be increased and the filter permeability tends to be improved. Improved filter permeability allows for a reduction in foreign matter in the film.
When the film of the present embodiment contains an aromatic polycarbonate resin having a terminal structure represented by formula (1) and another aromatic polycarbonate resin, it is preferable that the Q value of the polycarbonate resin that is the blend satisfies the above range.

The glass transition temperature of the aromatic polycarbonate resin having a terminal structure represented by formula (1) used in this embodiment is preferably 145°C or lower, more preferably 142°C or lower, even more preferably 140°C or lower, even more preferably 135°C or lower, and even more preferably 132°C or lower. Setting the glass transition temperature at or below the upper limit tends to more effectively suppress an increase in Re during thermal shaping. Furthermore, the glass transition temperature of the aromatic polycarbonate resin having a terminal structure represented by formula (1) used in this embodiment is preferably 115°C or higher, more preferably 120°C or higher, and even more preferably 123°C or higher. Setting the glass transition temperature at or above the lower limit tends to further improve flex resistance. Furthermore, when the film of this embodiment contains an aromatic polycarbonate resin having a terminal structure represented by formula (1) and another aromatic polycarbonate resin, it is preferable that the glass transition temperature of the blended polycarbonate resins satisfy the above range.

The proportion of the aromatic polycarbonate resin (preferably an aromatic polycarbonate resin having a terminal structure represented by formula (1)) in the film of this embodiment is preferably 90% by mass or more of the film, more preferably 95% by mass or more, and even more preferably 97% by mass or more. By making it equal to or greater than the above-mentioned lower limit, a film with better transparency can be obtained. The upper limit of the proportion of the aromatic polycarbonate resin in the film of the embodiment may be 100% by mass.
The film of the present embodiment may contain only one type of aromatic polycarbonate resin, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

<Other ingredients>
In addition to the aromatic polycarbonate resin having the terminal structure represented by Formula (1), the film of this embodiment may contain other components within the scope of the present invention. Specifically, the film may contain polycarbonate resins other than the above-mentioned aromatic polycarbonate resins, thermoplastic resins other than polycarbonate resins, antioxidants, transesterification inhibitors, release agents, heat stabilizers, flame retardants, flame retardant assistants, ultraviolet absorbers, colorants, antistatic agents, fluorescent brighteners, antifogging agents, flow improvers, plasticizers, dispersants, antibacterial agents, antiblocking agents, impact improvers, sliding improvers, hue improvers, acid trapping agents, etc. These components may be used alone or in combination of two or more. For details, please refer to the descriptions in JP 2017-031313 A, WO 2015/190162 A, JP 2019-002023 A, and JP 2018-199745 A, the contents of which are incorporated herein by reference.

<Film properties and characteristics>
The thickness of the film of this embodiment is 20 to 150 μm. By making the thickness 20 μm or more, breakage of the film is suppressed, and a film with excellent strength is obtained. Furthermore, by making the thickness 150 μm or less, an increase in Re during thermal shaping can be suppressed and flex resistance can be improved. The thickness of the film is preferably 25 μm or more, more preferably 25 μm or more, and even more preferably 30 μm or more. Furthermore, the thickness of the film is preferably 140 μm or less, more preferably 100 μm or less, even more preferably 70 μm or less, and even more preferably 60 μm or less.

The film of this embodiment has a surface roughness Ra of less than 0.7 μm. This configuration allows for the production of a film with excellent transparency. The surface roughness is preferably 0.5 μm or less, more preferably 0.1 μm or less, even more preferably 0.08 μm or less, even more preferably 0.05 μm or less, and even more preferably 0.02 μm or less. The lower limit of the film's surface roughness Ra is ideally 0 μm, but a practical value is 0.0001 μm or more, and even a value of 0.001 μm or more will fully satisfy the required performance.
The glass transition temperature of the film of this embodiment is preferably 115 to 142°C. By setting the glass transition temperature to be equal to or greater than the lower limit, flex resistance tends to be further improved. Furthermore, by setting the glass transition temperature to be equal to or less than the upper limit, an increase in Re during thermal shaping tends to be more effectively suppressed. The glass transition temperature of the film is preferably 140°C or less, more preferably 135°C or less, and even more preferably 132°C or less. Furthermore, the glass transition temperature of the film is preferably 115°C or more, more preferably 120°C or more, and even more preferably 123°C or more.

The film of this embodiment preferably has a retardation (Re) at a wavelength of 543 nm of 25 nm or less, more preferably 15 nm or less, even more preferably 10 nm or less, even more preferably 8 nm or less, even more preferably 5 nm or less, and even more preferably 3 nm or less. By setting the retardation at or below the upper limit, rainbow unevenness tends to be more effectively suppressed. The lower limit of the retardation (Re) is ideally 0 nm, but practically 0.01 nm or more is preferred.

The film of this embodiment preferably has a haze of 10% or less, more preferably 5% or less, even more preferably 1% or less, even more preferably 0.5% or less, and even more preferably 0.2% or less. By setting the haze at or below the upper limit, the transparency of the film tends to be further improved. The lower limit of the haze of the film is ideally 0%, but practically 0.001% or more.
The Ra, glass transition temperature, Re and haze are measured according to the description in the examples below.

<Film manufacturing method>
The film of this embodiment can be produced by a known method, and for example, extrusion molding or cast molding is preferred. Examples of extrusion molding include a method in which pellets, flakes, or powder of an aromatic polycarbonate resin, or a resin composition containing additives as needed, is melted and kneaded in an extruder, and then extruded through a T-die or the like, and the resulting semi-molten sheet is cooled and solidified while being sandwiched and pressed between polishing rolls or the like to form a product. The extruder may be single-screw or twin-screw, and either vented or non-vented may be used.

When the film of this embodiment is a multilayer body, it can be produced by known methods. For example, during melt extrusion using a T-die, the materials can be laminated inside the die and formed into a film, or the materials can be formed into a film and then laminated to form a multilayer film.

<Application>
The film of this embodiment can be used as a single layer film. Furthermore, as described above, the film of this embodiment can also be used as a multilayer body having the film of this embodiment and at least one other layer. The other layer can be a known layer, such as an adhesive layer or a hard coat layer, and preferably includes an adhesive layer. Of course, the film may have both an adhesive layer and a hard coat layer.
The adhesive layer may be, for example, a polyolefin resin layer.
For the hard coat layer, the descriptions in paragraphs 0045 to 0055 of JP-A-2013-020130, the descriptions in paragraphs 0073 to 0076 of JP-A-2018-103518, and the descriptions in paragraphs 0062 to 0082 of JP-A-2017-213771 can be referred to, and the contents of these can be incorporated into this specification.
The film of the present embodiment is preferably used as a protective film or substrate for a transparent conductive film, particularly as a transparent conductive film having a protective layer, an adhesive layer, a substrate, and an electrode layer in this order, in which at least one of the substrate and the protective layer (preferably at least the protective layer) is the film of the present embodiment.
The transparent conductive film is also preferably used as a transparent conductive film for use in film sensors of touch panels, electronic paper, dye-sensitized solar cells, touch sensors, and the like.
Furthermore, the film of the present embodiment is also preferably used for applications other than those mentioned above, which require a small change in retardation before and after thermal shaping, excellent bending resistance, and high transparency. For example, it is used as a shatterproof film.

The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.
If the measuring instruments used in the examples are difficult to obtain due to discontinuation or the like, measurements can be made using other instruments with equivalent performance.

1. Raw materials <Production example of PC-1>
Based on the description in Organic Chemistry Handbook, pp. 143-150, esterification was carried out by dehydration using 4-hydroxybenzoic acid manufactured by Tokyo Chemical Industry Co., Ltd. and 1-hexadecanol manufactured by Tokyo Chemical Industry Co., Ltd. to obtain hexadecyl parahydroxybenzoate (CEPB).
7.1 kg (31.14 mol) of bisphenol A (BPA) manufactured by Nippon Steel & Sumikin Chemical Co., Ltd. and 30 g of hydrosulfite were dissolved in 57.2 kg of a 9% by mass aqueous solution of sodium hydroxide. 40 kg of dichloromethane was added thereto, and while stirring, 4.33 kg of phosgene was blown in over 30 minutes while maintaining the solution temperature in the range of 15 to 25°C.
After the completion of the phosgene blowing, 6 kg of a 9% by mass aqueous solution of sodium hydroxide, 11 kg of dichloromethane, and a solution in which 443 g (1.22 mol) of CEPB obtained above was dissolved in 10 kg of dichloromethane were added, and the mixture was emulsified by vigorously stirring. Then, 10 mL of triethylamine was added as a polymerization catalyst, and polymerization was carried out for about 40 minutes.
The polymerization solution was separated into an aqueous phase and an organic phase, the organic phase was neutralized with phosphoric acid, and the organic phase was repeatedly washed with pure water until the pH of the washings became neutral. The organic solvent was evaporated and distilled off from this purified aromatic polycarbonate resin solution to obtain an aromatic polycarbonate resin powder (PC-1).
To 100 parts by mass of the resulting aromatic polycarbonate resin powder, 0.0075 parts by mass of Adekastab 2112 (manufactured by ADEKA Corporation, tris(2,4-di-tert-butylphenyl)phosphite) as an antioxidant and 0.0045 parts by mass of Rikemal S-100A (manufactured by Riken Vitamin Co., Ltd., glycerin monostearate) as a mold release agent were added, and the mixture was mixed in a tumbler for 15 minutes. After that, the mixture was melt-kneaded at a cylinder temperature of 280°C in a vented twin-screw extruder with a screw diameter of 32 mm ("TEX30α" manufactured by The Japan Steel Works, Ltd.), and pellets were obtained by strand cutting. The viscosity average molecular weight (Mv) and glass transition temperature (Tg) of the resulting aromatic polycarbonate resin pellets were measured.

<Production Example of PC-2>
The same procedure was carried out as in the above <Production Example of PC-1>, except that the amount of CEPB was changed to 348 g (0.96 mol).

<Production Example of PC-3>
The same procedure was carried out as in the above <Production Example of PC-1>, except that the amount of CEPB was changed to 266 g (0.73 mol).

<Production Example of PC-4>
The same procedure was carried out as in the above <Production Example of PC-1>, except that the amount of CEPB was changed to 940 g (2.59 mol).

<Production Example of PC-5>
In the above <Production Example of PC-1>, the aromatic polycarbonate resin powder used in preparing the pellets was a mixture of a bisphenol A polycarbonate resin having a terminal structure of a p-t-butylphenyl group (manufactured by Mitsubishi Engineering-Plastics Corporation, E-2000F, viscosity average molecular weight: 28,000, Tg: 150°C) and a bisphenol A polycarbonate resin having a terminal structure of a p-t-butylphenyl group (manufactured by Mitsubishi Engineering-Plastics Corporation, S-3000F, viscosity average molecular weight: 21,000, Tg: 146°C) in a mass ratio of 1:1, and the rest was the same.

<Filter filtration>
When producing the pellets, a polymer filter with a 20 μm opening was attached to a vented twin-screw extruder, and if the pressure during extrusion exceeded the upper limit and extrusion was not possible, it was rated B, and if extrusion was possible, it was rated A.

<Measurement of viscosity average molecular weight (Mv)>
The viscosity average molecular weight of the aromatic polycarbonate resin was measured by the following method.
Using methylene chloride as a solvent, the intrinsic viscosity [η] (unit: dL/g) at 25°C was determined using an Ubbelohde viscometer, and calculated from Schnell's viscosity formula, i.e., η = 1.23 × 10 ^-4 Mv ^0.83 . The intrinsic viscosity [η] is a value calculated from the specific viscosity [ηsp] measured at each solution concentration [C] (g/dL) using the following formula:

<Q value>
The Q value of the aromatic polycarbonate resin was measured using a high-speed flow tester under a load of 160 kgf/cm ² , an orifice diameter of 1 mm, length of 10 mm, and 280° C. after drying the obtained pellets in a hot air circulation dryer at 110° C. for 5 hours. The Q value is expressed in units of 0.01 cc/sec.
The high-speed flow tester used was a CFT-500D manufactured by Shimadzu Corporation.

<Measurement of Glass Transition Temperature (Tg)>
The glass transition temperatures of the film and aromatic polycarbonate resin pellets were measured as follows.
Approximately 10 mg of the film or aromatic polycarbonate resin pellets was subjected to two heating and cooling cycles under the following DSC (differential scanning calorimeter) measurement conditions, and the glass transition temperature during the second heating cycle was measured. The initial glass transition temperature was determined as the point at which a line extending the low-temperature baseline toward the high-temperature side intersects with a tangent to the inflection point, and the final glass transition temperature was determined as the point at which a line extending the high-temperature baseline toward the low-temperature side intersects with a tangent to the inflection point. The midpoint between the initial and final glass transition temperatures was determined as the glass transition temperature (Tg, unit: ° C.) in the present invention.
Measurement start temperature: 30℃
Temperature rise rate: 10°C/min. Final temperature: 250°C
Temperature decreasing rate: 20° C./min. The measurement device used was a differential scanning calorimeter (DSC, manufactured by Hitachi High-Tech Science Corporation, "DSC7020").

2. Examples 1 to 5 and Comparative Examples 1 to 4
<Film production>
The pellets obtained above were used to produce a film in the following manner.
The pellets obtained above were extruded into a molten state using a T-die melt extruder consisting of a vented twin-screw extruder (manufactured by The Japan Steel Works, Ltd., "TEX30α") with a barrel diameter of 32 mm and a screw L/D ratio of 31.5 at a discharge rate of 10 kg/h and a screw rotation speed of 150 rpm. The pellets were pressed between a first roll and a second roll, and then cooled and solidified to produce a film. The cylinder and T-die temperatures were 280°C.
The thickness (unit: μm) of the final film was adjusted by changing the roll speeds of the first roll and the second roll so as to obtain the value shown in Table 1 or Table 2.
Details of the first roll and second roll used are as follows.
First roll: Silicone rubber roll (IT68S-MCG) manufactured by Mochida Shoko Co., Ltd.
Dimensions: outer diameter 260mm x width 600mm
Roll temperature: 50°C
・Second roll: mirror-finished rigid metal roll (surface: hard chrome treated)
Core dimensions: outer diameter 250 mm x width 600 mm
Roll temperature: 120°C

The obtained film was evaluated as follows.
However, since Comparative Example 2 broke during the production of the film, the items marked with "-" in Table 2 were not evaluated.

<Surface roughness (Ra)>
The arithmetic mean surface roughness Ra of the film obtained above was measured using a contact surface roughness meter. Specifically, in accordance with JIS B0601:2001, measurements were taken at three points in the width direction on the surface of the film that was in contact with the second roll, and the average value was calculated. The unit is μm.
The measurement device used was "Surftest SJ-210" manufactured by Mitutoyo Corporation.

<Retardation (Re)>
The film obtained above was cut into a size of 50 x 150 mm, and the retardation was measured at a wavelength of 543 nm. The unit is nm.
The retardation was measured using a WPA-100 manufactured by Photonic Lattice.

<Retardation increase rate (ΔRe) before and after thermal shaping>
The film obtained above was cut into a size of 50 × 150 mm, and the retardation was measured at a wavelength of 543 nm. The measurement results were analyzed by line analysis over a 100 mm length in the longitudinal direction from positions 25 mm from the short edge of the film and 25 mm from the long edge of the film, and the maximum value was taken as the maximum retardation before thermal shaping. The upper mold 21 and lower mold 22 shown in Figure 2 were attached to a hydraulic jack press. The mold was heated to 130 °C, and the film after retardation measurement was placed on the mold and held for 1 minute with a gap of 1 mm between the upper and lower molds. Thermal shaping was performed under conditions of a pressure of 0.5 MPa and a pressure time of 1 minute. The film was removed and allowed to cool to 23 °C, after which the retardation was measured in the same manner as before thermal shaping to determine the maximum retardation after thermal shaping. The retardation increase rate (unit: %) before and after thermal shaping was calculated using the following formula:
Retardation increase rate = [(maximum retardation after thermal shaping - maximum retardation before thermal shaping) / maximum retardation before thermal shaping] x 100
The retardation was measured using a WPA-100 manufactured by Photonic Lattice.
The calculated increase in retardation was evaluated according to the following criteria.
A: 50% or less B: More than 50% and 120% or less C: More than 120%

<Chemical resistance>
The resulting pellets were dried in a hot air circulation dryer at 110° C. for 5 hours, and then molded into 3 mm ISO multipurpose test specimens (JIS-K7139 Type A1 thickness changed from 4 mm to 3 mm) using an injection molding machine under conditions of a cylinder temperature of 280° C., a mold temperature of 80° C., and a molding cycle of 45 seconds.
The injection molding machine used was a "PE-100" (trade name) manufactured by Sodick Corporation. The obtained test specimens were annealed in an oven at 110°C for 2 hours. As shown in Figure 3, the annealed test specimens were coated with 2,2-bis(4-glycidyloxyphenyl)propane as the test substance while being subjected to a strain of 0.45%, and then held in an oven at 75°C for 3 hours, and then cooled to 23°C. In Figure 3, 31 indicates the test specimen, and L indicates the distance between supports.
The strain [ε] (%) was calculated from the following formula using the deflection [s] (mm) of the test piece, the thickness [h] (mm) of the test piece, and the distance between supports [L] (mm).
ε=600sh/L ²
The deflection [s] (mm) of the test piece was calculated from the following formula using I ₀ (mm) and I (mm) shown in FIG.
s = I ₀ - I
The test samples were visually inspected and evaluated according to the following criteria. The evaluation was carried out by five experts and judged by majority vote.
A: Chemical damage occurs on the coated surface, but the test piece does not break.
B: The test piece broke.

<Bending resistance>
The film obtained above was cut into a size of 75 x 25 mm and subjected to a bending resistance test at a bending radius of 4.0 mm using an FPC (flexible printed circuit board) bending tester in accordance with JIS C5016:1994. In this bending resistance test, the test sample after 2000 bending cycles was visually evaluated according to the following criteria. The evaluation was performed by five experts using a majority vote.
The FPC bending tester used was "No. 306 FPC bending tester" (product name) manufactured by Yasuda Seiki Seisakusho Co., Ltd.
S: Neither deformation nor cracking of the film occurs.
A: The film is slightly deformed into an arc shape, but no cracks occur.
B: The film is deformed into an arc shape, but no cracks occur.
C: Other than A and B above, for example, the film was deformed into an arc shape and cracks occurred.

<HAZE>
The haze (unit: %) of the film obtained above was measured using a haze meter under the conditions of a D65 light source and a 10° field of view.
The haze meter used was "HM-150" manufactured by Murakami Color Research Laboratory.

Comparative Example 5
The film was produced in the same manner as in Example 1, with the following changes:
Second roll: Embossed roll with arithmetic mean roughness of 2.4 μm Core dimensions: outer diameter 250 mm x width 600 mm
Roll temperature: 120°C
In Comparative Example 5, the use of an embossing roll resulted in a high film haze, making it unusable as an optical film. Therefore, evaluations of retardation, the rate of increase in retardation before and after thermal shaping, chemical resistance, and flex resistance were not performed.

10 Transparent conductive film 11 Electrode layer (transparent conductive film)
12 Substrate 13 Adhesive layer 14 Protective film 21 Upper mold 22 Lower mold 31 Test piece

Claims (11)

A film comprising an aromatic polycarbonate resin having a terminal structure represented by formula (1),
The aromatic polycarbonate resin has a viscosity average molecular weight of 17,000 to 40,000;
The thickness of the film is 20 to 150 μm,
The film has a surface roughness Ra of less than 0.7 μm.

(In formula (1), ^R1 represents an alkyl group having 8 to 36 carbon atoms or an alkenyl group having 8 to 30 carbon atoms. Each ^R2 independently represents a halogen atom, an alkyl group having 1 to 20 carbon atoms, or an aryl group having 6 to 12 carbon atoms. n represents an integer of 0 to 4. * represents a bonding site to another site.) The film according to claim 1, wherein the glass transition temperature of the film is 115 to 142°C. The film according to claim 1 or 2, wherein the aromatic polycarbonate resin has a viscosity average molecular weight of 30,000 to 40,000. The film described in claim 1 or 2, wherein the aromatic polycarbonate resin has a viscosity average molecular weight of 17,000 or more and less than 30,000. The film described in any one of claims 1 to 4, wherein the surface roughness Ra of the film is 0.1 μm or less. The film described in any one of claims 1 to 5, wherein the haze of the film is 10% or less. The film described in any one of claims 1 to 6, wherein the retardation (Re) of the film at a wavelength of 543 nm is 25 nm or less. The film described in any one of claims 1 to 7 is a single-layer film. A multilayer body having the film according to any one of claims 1 to 8 and at least one other layer. The multilayer body according to claim 9, wherein the other layer includes an adhesive layer. A protective layer;
An adhesive layer;
A substrate;
a transparent conductive film having, in this order, a first electrode layer and a second electrode layer,
A transparent conductive film, wherein at least one of the substrate and the protective layer is the film according to any one of claims 1 to 8.