Polycarbonate resin film, multilayer film, display device, polycarbonate resin film manufacturing method, and multilayer film manufacturing method

Abstract

Provided is a polycarbonate resin film comprising a constituent unit represented by formula (1), said polycarbonate resin film having uniformity of the principal axis orientation and low phase difference properties. Also provided are a multilayer film, a display device, a polycarbonate resin film manufacturing method, and a multilayer film manufacturing method. The polycarbonate resin film contains a polycarbonate resin and satisfies conditions 1-3. Condition 1: the principal constituent unit of the polycarbonate resin is the constituent unit represented by formula 1. Condition 2: deviation from the average value of the principal axis orientation angle of the film is within ±11°. Condition 3: the phase difference in the film is 5-50 nm.

Description

Polycarbonate resin film, multilayer film, display device, method for producing polycarbonate resin film, and method for producing multilayer film

[0001] The present invention relates to a polycarbonate resin film, a multilayer film, a display device, a method for producing a polycarbonate resin film, and a method for producing a multilayer film.

[0002] Polycarbonate resins (hereinafter sometimes referred to as "PC-A") obtained by reacting 2,2-bis(4-hydroxyphenyl)propane (hereinafter sometimes referred to as "bisphenol A") with a carbonate precursor have traditionally been widely used as engineering plastics in many fields due to their excellent transparency, heat resistance, mechanical properties, and dimensional stability. Furthermore, in recent years, their transparency has led to their widespread use as optical materials in fields such as optical disks, films, and lenses. However, polycarbonate resins (particularly PC-A) have a higher photoelastic coefficient than acrylic resins and cyclic olefin resins, and are prone to exhibiting phase retardation under stress. Therefore, when used as substrates for transparent conductive films or display front panels, they can exhibit rainbow irregularities when viewed through polarized sunglasses. Furthermore, head-up display devices, which have begun to be installed in automobiles in recent years, require dust covers to prevent dust and debris from entering through the projection port that projects an image from the device body onto a projection unit such as glass. When using a cover made of polycarbonate resin, if the cover itself has a high retardation or if the principal axis orientation varies greatly, distortion may occur in the projected image, so it is necessary to reduce the retardation and make the principal axis orientation uniform. Furthermore, if the surface hardness of the cover itself is low, there is a problem that the surface may be scratched when it comes into contact with sharp corners. Until now, it has been considered difficult to achieve a low retardation and a uniform principal axis orientation for polycarbonate resin films using PC-A, and the above problem has been addressed by changing the main skeleton of the polymer to a structure that is less likely to generate retardation, as in Patent Documents 1, 2, and 3.

[0003] Japanese Patent Application Laid-Open No. 2004-331688 Japanese Patent Application Laid-Open No. 08-134199 International Publication No. 2020 / 166408

[0004] However, reducing retardation by modifying the polymer skeleton has the problem of high development costs. That is, it would be extremely beneficial if a film with low retardation could be obtained using the conventionally commonly used PC-A. Furthermore, it would be even more beneficial if the main axis orientation could be made uniform for PC-A, where it is difficult to reduce retardation. The present invention aims to solve this problem by providing a polycarbonate resin film using PC-A as a raw material, which has low retardation and uniform main axis orientation, as well as a multilayer film, a display device, a method for producing a polycarbonate resin film, and a method for producing a multilayer film, all of which use the polycarbonate resin film.

[0005] In light of the above-mentioned problems, the present inventors have conducted research and have succeeded in achieving low retardation and uniformity of the principal axis orientation of a polycarbonate resin film by adjusting the manufacturing method of the polycarbonate resin film while using PC-A as a raw material. Specifically, the above-mentioned problems have been solved by the following means. <1> A polycarbonate resin film containing a polycarbonate resin and satisfying the following conditions 1 to 3: Condition 1: The polycarbonate resin has a main structural unit represented by the following formula (1); Condition 2: The deviation of the principal axis orientation angle of the film from the average value is within ±11°; Condition 3: The retardation of the film is 5 to 50 nm. Formula (1) <2> The polycarbonate resin film according to <1>, wherein the thickness of the polycarbonate resin film is 50 to 1500 μm. <3> A multilayer film comprising a polycarbonate resin film and at least one other layer, and satisfying the following conditions A to C: Condition A: The polycarbonate resin has a main structural unit represented by the following formula (1); Condition B: The deviation of the main axis azimuth angle of the multilayer film from the average value is within ±11°; Condition C: The retardation of the multilayer film is 5 to 50 nm. Formula (1) <4> The multilayer film according to <3>, wherein the pencil hardness measured from the other layer side of the multilayer film is HB or higher. <5> The multilayer film according to <3> or <4>, wherein the total thickness of the polycarbonate resin film and one other layer is 50 to 1500 μm. <6> The multilayer film according to any one of <3> to <5>, wherein the ratio of the thickness of the polycarbonate resin film to the thickness of the other layer is 2 / 1 to 10 / 1. <7> The multilayer film according to <5> or <6>, wherein the thickness of the other layer is 20 to 100 μm. <8> The multilayer film according to any one of <3> to <7>, wherein the other layer is a layer containing a (meth)acrylic resin. <9> A multilayer film having a hard coat layer on one or both sides of the polycarbonate resin film according to <1> or <2> or the multilayer film according to any one of <3> to <8>. <10> A multilayer film having a masking film on one or both sides of the polycarbonate resin film according to <1> or <2>, or the multilayer film according to any one of <3> to <9>. <11> A display device comprising the polycarbonate resin film according to <1> or <2> and / or the multilayer film according to any one of <3> to <10>. <12> A method for producing a polycarbonate resin film according to <1> or <2>, wherein the distance between the inter-roll points of the first cooling roll and the second cooling roll in a direction perpendicular to the rotation axis direction of the rolls is 160 to 450 mm. <13> A method for producing a polycarbonate resin film according to <12>, wherein the peripheral speed ratio between the first cooling roll and the take-up roll is 1:0.995 to 1:0.975. <14> The method for producing a polycarbonate resin film according to <12> or <13>, which includes extruding a resin composition for forming a polycarbonate resin film through a T-die, wherein the width of the T-die is 600 mm or more. <15> The method for producing a polycarbonate resin film according to any one of <12> to <14>, wherein the contact length between the second cooling roll and the semi-molten polycarbonate resin film in a direction perpendicular to the rotation axis direction of the roll is 2 to 400 mm.<16> The method for producing a multilayer film according to any one of <3> to <8>, wherein the distance between the inter-roll points of the first cooling roll and the second cooling roll in a direction perpendicular to the direction of the rotation axis of the rolls is 160 to 450 mm. <17> The method for producing a multilayer film according to <16>, wherein the peripheral speed ratio between the first cooling roll and the take-up roll is 1:0.995 to 1:0.975. <18> The method for producing a multilayer film according to <16> or <17>, comprising extruding a resin composition for forming a polycarbonate resin film and a resin composition for forming other layers through a T-die, wherein the width of the T-die is 600 mm or more. <19> The method for producing a multilayer film according to any one of <16> to <18>, wherein the contact length between the second cooling roll and the semi-molten multilayer film in a direction perpendicular to the direction of the rotation axis of the rolls is 2 to 400 mm. <20> The method for producing a multilayer film according to any one of <16> to <19>, wherein the other layer is a layer containing a (meth)acrylic resin.

[0006] The present invention makes it possible to provide a polycarbonate resin film using PC-A as a raw material, which has low retardation and uniformity of the principal axis orientation, as well as a multilayer film, a display device, a method for producing a polycarbonate resin film, and a method for producing a multilayer film.

[0007] Fig. 2 is a schematic diagram showing an example of a multilayer film of the present embodiment. Fig. 3 is a schematic diagram showing a method for producing the polycarbonate resin film of the present embodiment using rolls. Fig. 4 is a partial enlarged view of Fig. 2. Fig. 5 is a schematic diagram mainly for explaining the distance between roll contacts of a semi-molten polycarbonate resin film. Fig. 6 is a partial enlarged view of Fig. 2. Fig. 7 is a schematic diagram mainly for explaining the contact length between a second cooling roll and a semi-molten polycarbonate resin film in a direction perpendicular to the rotation axis direction of the rolls.

[0008] Hereinafter, a detailed description of an embodiment of the present invention (hereinafter simply referred to as "the present embodiment") will be given. The following present embodiment is merely an example for explaining the present invention, and the present invention is not limited to this embodiment. In this specification, the term "to" is used to mean that the numerical values ​​before and after the term are included as lower and upper limits. In this specification, various physical property values ​​and characteristic values ​​are those at 23°C, unless otherwise specified. In the description of a group (atomic group), a notation that does not specify whether it is substituted or unsubstituted encompasses both a group (atomic group) that has no substituent and a group (atomic group) that has a substituent. For example, the term "alkyl group" encompasses not only an alkyl group that has no substituent (unsubstituted alkyl group) but also an alkyl group that has a substituent (substituted alkyl group). In this specification, when a notation that does not specify whether it is substituted or unsubstituted is used, unsubstituted is preferred. In this specification, "(meth)acrylic" refers to both acrylic and methacrylic, or to either one of them. In this specification, weight average molecular weight and number average molecular weight are values ​​measured in terms of polystyrene using gel permeation chromatography (GPC) unless otherwise specified. The term "film" as used herein refers to a generally flat molded body that is thin relative to its length and width, and includes the term "sheet." The term "film" as used herein may be either single-layer or multi-layer, but single-layer film is preferred. If the measurement method or other aspects of the standards used in this specification differ depending on the fiscal year, they shall be based on the standards as of January 1, 2021, unless otherwise specified.

[0009] <Polycarbonate Resin Film> The polycarbonate resin film of this embodiment contains a polycarbonate resin and satisfies the following conditions 1 to 3. Condition 1: The polycarbonate resin has a main structural unit represented by the following formula (1). Condition 2: The deviation of the principal axis azimuth angle of the film from the average value is within ±11°. Condition 3: The retardation of the film is 5 to 50 nm. Formula (1)

[0010] In this embodiment, by adjusting the production method, it is possible to provide a polycarbonate resin film having low retardation and uniform principal axis orientation while using a polycarbonate resin made from PC-A as a raw material. Furthermore, by providing another layer, for example, a high-hardness resin layer such as a (meth)acrylic resin layer on the surface (preferably the front surface) of the polycarbonate resin film of this embodiment, it is possible to obtain a high-hardness film (multilayer film).

[0011] The polycarbonate resin used in the polycarbonate resin film of this embodiment has a main structural unit represented by the following formula (1):

[0012] Here, "a structural unit whose main structural unit is represented by formula (1)" usually means that 85% by mass or more of the polycarbonate resin contained in the polycarbonate resin film is a structural unit represented by formula (1), preferably 90% by mass or more is a structural unit represented by formula (1), more preferably 95% by mass or more is a structural unit represented by formula (1), and even more preferably 99% by mass or more, excluding terminal structures, is a structural unit represented by formula (1). A typical example of such a polycarbonate resin is PC-A.

[0013] The polycarbonate resin used in this embodiment may also be a polycarbonate resin obtained by adding a monohydric phenol represented by the following formula (2) as a terminal terminator for the purpose of controlling the glass transition temperature. Specifically, an example is a polycarbonate resin containing the structural unit represented by the above formula (1) and produced using a monohydric phenol represented by formula (2) as a terminal terminator.

[0014] (In formula (2), R １ represents an alkyl group having 8 to 36 carbon atoms or an alkenyl group having 8 to 36 carbon atoms; R ２ ~R ５each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms which may have a substituent, or an aryl group having 6 to 12 carbon atoms which may have a substituent, and the substituent is a halogen atom, an alkyl group having 1 to 20 carbon atoms, or an aryl group having 6 to 12 carbon atoms.) The monohydric phenol represented by formula (2) is preferably a monohydric phenol represented by formula (3). (In formula (3), R １ represents an alkyl group having 8 to 36 carbon atoms or an alkenyl group having 8 to 36 carbon atoms.

[0015] R in formula (2) or formula (3) １ It is more preferable that the number of carbon atoms in R is within a specific numerical range. １ The upper limit of the number of carbon atoms in R is preferably 30 or less, more preferably 22 or less, and particularly preferably 18 or less. １ The lower limit of the number of carbon atoms in R in formula (2) or (3) is preferably 10 or more, more preferably 12 or more. １ When the number of carbon atoms in the formula (3) is within the above range, the productivity (economic efficiency) is excellent, the increase in the glass transition temperature of the polycarbonate resin is suppressed, and the thermoformability is excellent. Among the monohydric phenols represented by formula (2) or formula (3), it is particularly preferable to use either or both of parahydroxybenzoic acid hexadecyl ester and parahydroxybenzoic acid 2-hexyldecyl ester as the end terminator. For example, in formula (3), R １ When a monohydric phenol in which R is an alkyl group having 16 carbon atoms is used as the end terminator, it is particularly preferable because it is possible to obtain a polycarbonate resin excellent in glass transition temperature, melt fluidity, moldability, drawdown resistance, etc. An example of a polycarbonate resin using such a monohydric phenol as the end terminator is Iupizeta T-1380 (manufactured by Mitsubishi Gas Chemical Company, Ltd.).

[0016] From the viewpoints of impact resistance and thermal stability, the weight average molecular weight (Mw) of the polycarbonate resin used in this embodiment is preferably 15,000 or more, and more preferably 20,000 or more. The weight average molecular weight (Mw) of the polycarbonate resin is preferably 75,000 or less, and more preferably 65,000 or less. Preferred specific examples of polycarbonate resins that can be used in this embodiment include Iupilon S-2000, Iupilon S-1000, and Iupilon E-2000, manufactured by Mitsubishi Engineering-Plastics Corporation.

[0017] The polycarbonate resin content in the polycarbonate resin film of this embodiment is usually 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 98% by mass or more. The upper limit of the polycarbonate resin content in the polycarbonate resin film may be 100% by mass. The polycarbonate resin film of this embodiment may contain only one type of polycarbonate resin, or may contain two or more types. When two or more types are contained, the total amount is preferably within the above range.

[0018] The polycarbonate resin film of this embodiment may be formed solely from polycarbonate resin, or may be formed from a resin composition containing polycarbonate resin and additives. The additives may be those commonly used in resin sheets, such as antioxidants, anti-coloring agents, anti-static agents, release agents, lubricants, dyes, pigments, plasticizers, flame retardants, resin modifiers, compatibilizers, and reinforcing materials such as organic and inorganic fillers. These additives may be used alone or in combination. The method for mixing the additives and polycarbonate resin is not particularly limited, and methods such as total compounding, masterbatch dry blending, and total dry blending may be used. The amount of additive is preferably 0 to 10% by mass, more preferably 0 to 7% by mass, and particularly preferably 0 to 5% by mass, based on the total mass of the polycarbonate resin film (i.e., the resin composition for forming the polycarbonate resin composition).

[0019] The polycarbonate resin film of this embodiment satisfies the above-mentioned condition 1. That is, in the polycarbonate resin film of this embodiment, the deviation of the principal axis azimuth angle from the average value is within ±11°. The polycarbonate resin film of this embodiment is preferable in that, although there is some phase difference, the principal axis azimuth angle can be made close to 90°. The deviation of the principal axis azimuth angle from the average value is more preferably ±10° or less, even more preferably ±9° or less, even more preferably ±8° or less, still more preferably ±6° or less, particularly preferably ±4° or less, and even particularly preferably ±3° or less. The lower limit of the deviation of the principal axis azimuth angle from the average value is ideally 0°, but even ±0.1° or more satisfies the required performance, and ±1° or more is practical. In this embodiment, the deviation of the principal axis azimuth angle from the average value is achieved by producing a polycarbonate resin film by a predetermined method described below.

[0020] The average value of the principal axis azimuth angle in the polycarbonate resin film of this embodiment is preferably 88° or more, more preferably 89° or more, and even more preferably 90° or more, and is preferably 95° or less, more preferably 93° or less, and even more preferably 92° or less. From the viewpoint of stabilizing the principal axis azimuth angle and retardation, the thickness deviation of the polycarbonate resin film of this embodiment is preferably within the average value ±15%, more preferably within the average value ±10%, and even more preferably within the average value ±5%. By setting the deviation within this range, when the molten resin flowing out from the T-die is pressure-bonded between the touch roll and the first cooling roll to transfer the mirror surface of the touch roll and the first cooling roll, it is possible to effectively suppress a problem in which the mirror surface transfer is not carried out due to the thickness deviation, resulting in poor appearance.

[0021] The polycarbonate resin film of this embodiment has a low film retardation (maximum retardation). Specifically, the film retardation is 50 nm or less, preferably 48 nm or less, more preferably 40 nm or less, and even more preferably 38 nm or less. The lower limit of the film retardation is 5 nm or more. Polycarbonate resin films, particularly PC-A, tend to exhibit retardation more easily than acrylic resin films, but in this embodiment, deviation of the principal axis orientation can be effectively suppressed in polycarbonate resin films that exhibit such slight retardation.

[0022] The thickness of the polycarbonate resin film of this embodiment can be appropriately determined depending on the application, etc., but is preferably 50 μm or more, more preferably 70 μm or more, more preferably 100 μm or more, and may be 150 μm or more, or may be 200 μm or more. By setting the thickness at or above the lower limit, the film rigidity is increased, and when used as a resin cover, the film tends to be less deflected, making it easier to use as a large resin cover. Furthermore, the upper limit of the thickness of the polycarbonate resin film is preferably 1500 μm or less, more preferably 1000 μm or less, even more preferably 500 μm or less, even more preferably 490 μm or less, even more preferably 450 μm or less, and even more preferably 400 μm or less. By setting the thickness at or below the upper limit, it is easier to reduce the deviation of the principal axis azimuth angle, and when used as a resin cover for a head-up display, image distortion tends to be reduced.

[0023] The width of the polycarbonate resin film of this embodiment is preferably 800 mm or more, more preferably 1000 mm or more, and even more preferably 1200 mm or more. By making it equal to or greater than the above lower limit, it becomes possible to efficiently apply a hard coat or the like in a subsequent process. Furthermore, the upper limit of the width of the polycarbonate resin film of this embodiment is preferably 5000 mm or less, more preferably 3000 mm or less, even more preferably 2500 mm or less, even more preferably 2200 mm or less, and even more preferably 2000 mm or less.

[0024] <Multilayer Film> The polycarbonate resin film of this embodiment may be used as a single layer or multilayer film consisting of only the polycarbonate resin film, or may be a multilayer film containing layers other than the polycarbonate resin film of this embodiment. That is, the multilayer film of this embodiment is a multilayer film having a polycarbonate resin film and at least one other layer. Another embodiment of the multilayer film of this embodiment is a multilayer film having a polycarbonate resin film and at least one other layer and satisfying the following conditions A to C. Condition A: The polycarbonate resin has a main structural unit represented by the following formula (1); Condition B: The deviation of the principal axis azimuth angle of the film from the average value is within ±11°; Condition C: The retardation of the film is 5 to 50 nm. Formula (1)

[0025] The polycarbonate resin used in the multilayer film of this embodiment has a main structural unit represented by the following formula (1). Details of these are the same as those in Condition 1 described for the polycarbonate resin film of this embodiment, and the preferred ranges are also the same. Furthermore, the preferred ranges of the polycarbonate resin film are also the same as those described above for the polycarbonate resin film of this embodiment.

[0026] 1 shows an example of the multilayer film of the present embodiment, in which 1 indicates a polycarbonate resin film and 2 indicates other layers. In the multilayer film of the present embodiment, the polycarbonate resin film may be a single layer or may be two or more layers, and is usually a single or two layer film.

[0027] The multilayer film of this embodiment satisfies condition B. That is, in the multilayer film of this embodiment, the deviation of the principal axis azimuth angle from the average value is within ±11°. The deviation of the principal axis azimuth angle from the average value is preferably ±10° or less, more preferably ±9° or less, even more preferably ±8° or less, still more preferably ±7° or less, particularly more preferably ±6° or less, and even particularly more preferably ±5° or less. The lower limit of the deviation of the principal axis azimuth angle from the average value is ideally 0°, but even ±0.1° or more satisfies the required performance, and ±1° or more is practical. It is preferable that the principal axis azimuth angle of the multilayer film, measured not from the polycarbonate resin film side but from the other layer side, satisfies the above range.

[0028] The multilayer film of this embodiment satisfies condition C. That is, the multilayer film of this embodiment preferably has a low retardation (maximum retardation) of the film. Specifically, the retardation of the film is 50 nm or less, preferably 45 nm or less, more preferably 40 nm or less, even more preferably 35 nm or less, even more preferably 30 nm or less, and even more preferably 25 nm or less. In addition, the lower limit of the retardation of the multilayer film is 5 nm or more. It is preferable that the retardation of the multilayer film, measured from the other layer side, satisfies the above range.

[0029] The average principal axis azimuth angle in the multilayer film of this embodiment is preferably 88° or more, more preferably 89° or more, and even more preferably 90° or more. It is also preferably 93° or less, more preferably 92° or less, and even more preferably 91° or less. The average principal axis azimuth angle in the multilayer film refers to the average principal axis azimuth angle in the raw film. When the multilayer film is incorporated into an actual display or the like, the average principal axis azimuth angle may deviate depending on the cutting direction. From the viewpoint of stabilizing the principal axis azimuth angle and retardation, the thickness deviation of the multilayer film of this embodiment is preferably within the average value ±15%, more preferably within the average value ±10%, and even more preferably within the average value ±5%. By setting the deviation within this range, when the molten resin flowing out from the T-die is pressure-bonded between the touch roll and the first cooling roll to transfer the mirror surface between the touch roll and the first cooling roll, it is possible to effectively prevent mirror surface transfer from being performed due to thickness deviation, resulting in poor appearance.

[0030] In the multilayer film of this embodiment, the total thickness of the polycarbonate resin film and the other layer (preferably the (meth)acrylic resin layer) is preferably 50 to 1500 μm. The lower limit of the total thickness is preferably 100 μm or more, more preferably 125 μm or more, even more preferably 130 μm or more, still more preferably 140 μm or more, and may be 180 μm or more. The upper limit of the total thickness is preferably 800 μm or less, more preferably 600 μm or less, even more preferably 550 μm or less, still more preferably 500 μm or less, and may be 450 μm or less, or even 400 μm or less. In the multilayer film of this embodiment, the total thickness (total thickness) of the multilayer film is preferably 100 to 3000 μm.

[0031] The width of the multilayer film of this embodiment is preferably 800 mm or more, more preferably 1000 mm or more, and even more preferably 1200 mm or more. The upper limit of the width of the multilayer film of this embodiment is preferably 5000 mm or less, more preferably 3000 mm or less, even more preferably 2500 mm or less, even more preferably 2200 mm or less, and even more preferably 2000 mm or less.

[0032] The multilayer film of this embodiment preferably has a pencil hardness of HB or higher, more preferably H or higher, measured from the other layer side (for example, the side of layer 2 in FIG. 1 ). There is no particular upper limit to the pencil hardness, but 3H or lower is practical. The pencil hardness is measured by the method described in the Examples below (the same applies to pencil hardness hereinafter). Furthermore, it is preferable that the side of the multilayer film of this embodiment with a higher pencil hardness satisfies the above-mentioned pencil hardness.

[0033] The haze of the multilayer film of this embodiment is preferably 2% or less, more preferably 1% or less, and even more preferably 0.5% or less, from the viewpoint of transparency. The haze (unit: %) can be measured using a haze meter under conditions of a D65 light source and a 10° field of view.

[0034] The other layers in the multilayer film of this embodiment are not particularly limited in type, but examples include a layer containing a high-hardness resin, a masking film, and a hard coat layer. Furthermore, the number of other layers may be one or two or more, and is typically one to seven, preferably one to five, and more preferably one to three. In this specification, the layer containing a high-hardness resin is sometimes referred to as a high-hardness resin layer.

[0035] The other layer is preferably a film having low retardation and uniformity of the principal axis orientation. In particular, when the other layer is a (meth)acrylic resin layer and / or a hard coat layer, these layers are also preferably films having low retardation and uniformity of the principal axis orientation. Specifically, the other layer (preferably a (meth)acrylic resin layer and / or a hard coat layer, more preferably a (meth)acrylic resin layer) preferably has a deviation of the principal axis azimuth angle of the film from the average value of ±11° or less, and a retardation of the film of 5 to 50 nm. By forming such a film into a multilayer structure with a polycarbonate resin film, a multilayer film having low retardation and uniformity of the principal axis orientation can be obtained. The retardation of the other layer is preferably 45 nm or less, more preferably 40 nm or less, even more preferably 35 nm or less, even more preferably 30 nm or less, and even more preferably 25 nm or less. The lower limit of the retardation of the other layer is 5 nm or more. Furthermore, the deviation of the principal axis azimuth angle in the other layer from the average value is preferably ±11° or less, more preferably ±10° or less, more preferably ±9° or less, even more preferably ±8° or less, even more preferably ±7° or less, particularly more preferably ±6° or less, and even more particularly preferably ±5° or less. The lower limit of the deviation of the principal axis azimuth angle from the average value is ideally 0°, but even ±0.1° or more satisfies the required performance, and ±1° or more is practical. On the other hand, when the other layer is a film that is peeled off during use, such as a masking film, the other layer does not necessarily have low retardation and uniform principal axis orientation.

[0036] The thickness of each of the other layers is preferably 1 μm or more, more preferably 3 μm or more, even more preferably 20 μm or more, even more preferably 25 μm or more, and even more preferably 30 μm or more. By making the thickness equal to or greater than the lower limit, the pencil hardness tends to be increased. Furthermore, the thickness of the other layer is preferably 100 μm or less, more preferably 85 μm or less, even more preferably 70 μm or less, even more preferably 50 μm or less, and even more preferably 40 μm or less. By making the thickness equal to or less than the upper limit, the toughness of the film increases, and problems such as cracking during handling tend to be less likely to occur. In particular, when the other layer is a (meth)acrylic resin layer, the thickness of the other layer is preferably 20 to 100 μm.

[0037] In the multilayer film of the present embodiment, the ratio of the polycarbonate resin film to one other layer (preferably a (meth)acrylic resin layer) is preferably 2 / 1 to 10 / 1, more preferably 2 / 1 to 8 / 1, and may be 2 / 1 to 7 / 1.

[0038] <<First Example of Multilayer Film>> A first example of the multilayer film of this embodiment is a multilayer film having a polycarbonate resin film and at least one other layer, wherein the at least one other layer is a resin layer containing a high-hardness resin (high-hardness resin layer), preferably a resin layer containing a high-hardness resin as a main component. Here, the term "main component" means that 50% by mass or more of the components of the other layer are the high-hardness resin, preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 99% by mass or more of the high-hardness resin.

[0039] An example of the high-hardness resin is a (meth)acrylic resin. That is, it is preferable that the other layer is a layer containing a (meth)acrylic resin (a (meth)acrylic resin layer). In this embodiment, the high-hardness resin is preferably a resin having a pencil hardness of HB or more, and more preferably a resin having a pencil hardness of H or more. The high-hardness resin contained in the high-hardness resin layer may be one type or two or more types. There is no particular upper limit for the pencil hardness of the high-hardness resin, but for example, 3H or less is practical.

[0040] As mentioned above, high-hardness resins include (meth)acrylic resins, but are not limited thereto, and a wide variety of known high-hardness resins can be used. High-hardness resins are typically thermoplastic resins. As the (meth)acrylic resin, a polymer of a (meth)acrylic compound monomer can be used. Examples of (meth)acrylic compound monomers include acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, and (meth)acrylic acid esters. Examples of (meth)acrylic acid esters include methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, and 2-ethylhexyl methacrylate. Among these, methyl methacrylate (MMA) is preferred. Two or more of these (meth)acrylic compound monomers may be mixed. Furthermore, other monomers such as vinyl compounds (e.g., styrene) may be copolymerized within the scope of the present invention. In the (meth)acrylic resin used in this embodiment, the proportion of (meth)acrylic compound monomer units is preferably 80% by mass or more, and more preferably 90% by mass or more, of the total.

[0041] The high-hardness resin layer may be formed solely from a high-hardness resin (preferably a (meth)acrylic resin) or from a resin composition containing a high-hardness resin (preferably a (meth)acrylic resin) and an additive. The additives may be those commonly used in resin sheets, such as antioxidants, anti-colorants, anti-static agents, release agents, lubricants, dyes, pigments, plasticizers, flame retardants, resin modifiers, compatibilizers, and reinforcing materials such as organic and inorganic fillers. The method for mixing the additives and resin is not particularly limited, and methods such as compounding the entire amount, dry blending a masterbatch, and dry blending the entire amount can be used. The amount of additive is preferably 0 to 10% by weight, more preferably 0 to 7% by weight, and particularly preferably 0 to 5% by weight, relative to the total weight of the high-hardness resin layer (i.e., the resin composition for forming the other layers).

[0042] The thickness of the high-hardness resin layer (preferably a (meth)acrylic resin layer) is preferably 20 μm or more, more preferably 25 μm or more, and even more preferably 30 μm or more. By making the thickness equal to or greater than the lower limit, the pencil hardness tends to be high. Furthermore, the thickness of the high-hardness resin layer is preferably 100 μm or less, more preferably 85 μm or less, even more preferably 70 μm or less, even more preferably 50 μm or less, and even more preferably 40 μm or less. By making the thickness equal to or less than the upper limit, the toughness of the film increases, and defects such as cracking during handling tend to be less likely to occur.

[0043] In the first example of the multilayer film, the thickness ratio of the polycarbonate resin film to the high-hardness resin layer (preferably the (meth)acrylic resin layer) is preferably 2 / 1 to 10 / 1, more preferably 2 / 1 to 8 / 1, and may be 2 / 1 to 7 / 1.

[0044] The first example of a multilayer film includes at least one polycarbonate resin film and at least one high-hardness resin layer (preferably a (meth)acrylic resin layer), and the total thickness of the polycarbonate resin film and the high-hardness resin layer is preferably 50 to 1500 μm. The lower limit of the total thickness is preferably 100 μm or more, more preferably 130 μm or more, even more preferably 140 μm or more, and may be 180 μm or more. The upper limit of the total thickness is preferably 1000 μm or less, more preferably 800 μm or less, even more preferably 550 μm or less, even more preferably 500 μm or less, and may be 450 μm or less, or even 400 μm or less.

[0045] The multilayer film of the first example preferably has a pencil hardness of HB or more, more preferably H or more, measured from the high-hardness resin layer side. There is no particular upper limit to the pencil hardness, but a practical upper limit is 3H or less.

[0046] <<Second Example of Multilayer Film>> A second example of the multilayer film of the present embodiment is a multilayer film having a masking film on one or both surfaces of the polycarbonate resin film of the present embodiment or the multilayer film of the present embodiment (particularly the multilayer film of the first example above and the multilayer film of the third example described below). The masking film may be provided on the surface of the polycarbonate resin film, the surface of the high-hardness resin layer, the surface of the hard coat layer, or the surface of any other layer.

[0047] It is preferable that the masking film has an adhesive surface that has a suitable adhesive strength with the adjacent layer. The masking film may be a single layer consisting of only an adhesive layer, but it is preferable that it has a two-layer structure consisting of a substrate and an adhesive layer. The masking film may also have a multilayer structure that further includes layers other than the substrate and adhesive layer.

[0048] The substrate of the masking film is preferably a thermoplastic resin film, and more preferably a polyolefin resin film. Examples of polyolefin resins that can be used include polyethylene and polypropylene, and they may be homopolymers or copolymers. Among polyolefin resins, polyethylene is preferred. Examples of polyethylene that can be used include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), very low-density polyethylene (VLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE), with low-density polyethylene being preferred. Furthermore, examples of polyolefin copolymers include copolymers of ethylene and / or propylene with monomers copolymerizable therewith. Examples of monomers copolymerizable with ethylene and / or propylene include α-olefins, styrenes, dienes, cyclic compounds, and oxygen-containing compounds. The polyolefin resin may also contain a modified polyolefin resin modified with a small amount of a carboxyl-containing monomer, such as acrylic acid, maleic acid, methacrylic acid, maleic anhydride, fumaric acid, or itaconic acid. Modification is typically achieved by copolymerization or graft modification.

[0049] The polyolefin resin film that is the substrate of the masking film preferably contains 80 mass % or more of polyolefin resin, more preferably 90 mass % or more of polyolefin resin, and even more preferably 95 mass % or more of polyolefin resin, based on the total mass of the substrate.

[0050] The adhesive layer of the masking film is preferably formed from a thermoplastic resin containing an elastomer. Examples of the thermoplastic resin contained in the adhesive layer include polyolefin resins such as polypropylene and modified polyolefin. Examples of the polyolefin resin contained in the masking film include polyethylene and polypropylene, and may be either a homopolymer or a copolymer. Among polyolefin resins, polyethylene is preferred.

[0051] The adhesive layer of the masking film preferably contains 80% by mass or more of thermoplastic resin, more preferably 90% by mass or more of thermoplastic resin, and even more preferably 95% by mass or more of thermoplastic resin, based on the total mass of the adhesive layer.

[0052] The adhesive strength value of the adhesive surface of the masking film is preferably 5 (mN / 25 mm) or more and 5000 (mN / 25 mm) or less, and more preferably 9 (mN / 25 mm) or more and 3000 (mN / 25 mm) or less, relative to the surface of the PMMA (polymethyl methacrylate resin layer).

[0053] The thickness of the masking film is preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more, and is preferably 100 μm or less, more preferably 90 μm or less, and even more preferably 80 μm or less.

[0054] In addition to the above, for details of the masking film, please refer to JP 2021-123079 A, ​​the descriptions in paragraphs 0013 to 0025 of WO 2020 / 031968, and the descriptions in paragraphs 0089 to 0094 of JP 2017-185772 A, the contents of which are incorporated herein by reference.

[0055] <<Third Example of Multilayer Film>> A third example of the multilayer film of the present embodiment is a multilayer film having a hard coat layer on one or both surfaces of the polycarbonate resin film of the present embodiment or the multilayer film of the present embodiment (particularly the multilayer film of the first example and the multilayer film of the second example). The hard coat layer may be provided on the surface of the polycarbonate resin film, on the surface of the high-hardness resin layer, or on the surface of any other layer.

[0056] The hard coat layer can be formed using known crosslinked film-forming compounds such as (meth)acrylic, silicone, melamine, urethane, and epoxy compounds. In terms of thermal formability, (meth)acrylic and (meth)urethane acrylate compounds are preferred. Furthermore, known curing methods such as ultraviolet curing, heat curing, and electron beam curing can be used. Of these, the surface side is preferably one with a pencil hardness of HB or higher, and more preferably one with a pencil hardness of H or higher. A practical pencil hardness rating of 3H or lower is 3H or lower. The method for applying the hard coat liquid is not particularly limited, and known methods can be used. Examples include spin coating, dipping, spraying, slide coating, bar coating, roll coating, gravure coating, meniscus coating, flexographic printing, screen printing, beat coating, and brushing. The hard coat layer may be further modified. For example, one or more of anti-reflection treatment, antifouling treatment, antistatic treatment, weather resistance treatment, infrared blocking treatment, and anti-glare treatment can be applied. These treatment methods are not particularly limited, and known methods can be used. For example, methods include applying a reflection-reducing coating, vapor-depositing a dielectric thin film, and applying an antistatic coating. The thickness of the hard coat layer is preferably 1 μm or more, more preferably 2 μm or more, and preferably 40 μm or less, more preferably 10 μm or less. A thickness of 1 μm or more can provide sufficient hardness. Furthermore, a film thickness of 40 μm or less can suppress the occurrence of cracks during bending.

[0057] As the hard coat layer, in addition to the above, 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.

[0058] The layer structure of the multilayer film of this embodiment may be as follows: It goes without saying that the multilayer film of this embodiment is not limited to these. (1) (meth)acrylic resin layer / polycarbonate resin layer (2) Masking film / (meth)acrylic resin layer / polycarbonate resin layer / masking film (3) Hard coat layer / (meth)acrylic resin layer / polycarbonate resin layer (4) Masking film / hard coat layer / (meth)acrylic resin layer / polycarbonate resin layer / masking film (5) Hard coat layer / (meth)acrylic resin layer / polycarbonate resin layer / hard coat layer (6) Masking film / hard coat layer / (meth)acrylic resin layer / polycarbonate resin layer / hard coat layer / masking film (7) (meth)acrylic resin layer / polycarbonate resin layer / hard coat layer (8) Masking film / (meth)acrylic resin layer / polycarbonate resin layer / hard coat layer / masking film (9) (meth)acrylic resin layer / polycarbonate resin layer / (meth)acrylic resin layer (10) Masking film / (meth)acrylic resin layer / polycarbonate resin layer / (meth)acrylic resin layer / masking film (11) Hard coat layer / (meth)acrylic resin layer / polycarbonate resin layer / (meth)acrylic resin layer (12) Masking film / hard coat layer / (meth)acrylic resin layer / polycarbonate resin layer / (meth)acrylic resin layer / masking film (13) Hard coat layer / (meth)acrylic resin layer / polycarbonate resin layer / (meth)acrylic resin layer / hard coat layer (14) Masking film / hard coat layer / (meth)acrylic resin layer / polycarbonate resin layer / (meth)acrylic resin layer / hard coat layer / masking film

[0059] <Applications> The applications of the polycarbonate resin film and / or the multilayer film of the present embodiment are not particularly limited, and the film can be used for various applications such as electronic and electrical devices. The film is preferably used in a display device, and more preferably in a liquid crystal display device, an organic EL display device, or a head-up display device.

[0060] <Method for Producing Polycarbonate Resin Film> The polycarbonate resin film of this embodiment is not particularly limited as long as it can be produced so as to satisfy the above conditions 1 to 3. For example, extrusion molding and cast molding are preferred. An example of extrusion molding is a method in which the resulting semi-molten polycarbonate resin film is cooled and solidified while passing through rolls to form a finished product. More specifically, a method in which a resin composition for forming a polycarbonate resin film consisting solely of polycarbonate resin, or a resin composition for forming a polycarbonate resin film containing polycarbonate resin and additives, is extruded through a T-die or the like, and the resulting semi-molten polycarbonate resin film is cooled and solidified while passing through rolls to form a finished product is exemplified. Here, the resin composition for forming a polycarbonate resin film is prepared by melting and kneading pellets, flakes, or powder in an extruder, and then extruding it through a T-die or the like. The extruder may be single-screw or twin-screw, and either a vented or non-vented extruder may be used. The temperature of the resin composition when extruding the resin composition for forming a polycarbonate resin film from a T-die is preferably 200°C or higher, more preferably 240°C or higher, even more preferably 260°C or lower, and preferably 320°C or lower, more preferably 300°C or lower, and even more preferably 280°C or lower.

[0061] In the polycarbonate resin film of this embodiment, it is preferable to precisely set the distance between the first cooling roll and the second cooling roll while transporting the semi-molten polycarbonate resin film. Specifically, the method for producing a polycarbonate resin film of this embodiment includes a method in which the distance between the inter-roll points of the first cooling roll and the second cooling roll in a direction perpendicular to the direction of the rotation axis of the rolls is 160 to 450 mm. The direction perpendicular to the direction of the rotation axis usually refers to the direction in which the rolls rotate and transport the film. FIG. 2 is a schematic diagram showing the production of the polycarbonate resin film of this embodiment using rolls, in which 21 indicates a T-die, 22 a touch roll, 23 a first cooling roll, 24 a polycarbonate resin film (semi-molten polycarbonate resin film) in the process of production, 25 a second cooling roll, and 26 a third roll (take-up roll). Here, the polycarbonate resin film 24 during the production process includes, for example, a polycarbonate resin film in a molten state after being extruded from a T-die and before being completely cooled. In FIG. 2 , a semi-molten resin composition for forming a polycarbonate resin film is extruded into a film form from a T-die 21, passes through a touch roll 22 and a first cooling roll 23, and then passes through a second cooling roll 25. In this embodiment, the distance between the inter-roll points between the first cooling roll 23 and the second cooling roll 25 in a direction perpendicular to the rotational axis direction of the rolls is set to 160 to 450 mm. This configuration allows precise adjustment of the time during which tension is applied to the film 24, allows the second cooling roll 25 to uniformly apply tension to the film 24, and makes it easier to straighten the main axis of the film. Here, the distance between the inter-roll points between the first cooling roll and the second cooling roll in a direction perpendicular to the rotational axis direction of the rolls is explained using FIG. 3 . FIG. 3 is a partial enlarged view of FIG. 2 , and the reference numerals are the same as those in FIG. 1 . First, the rotation axis direction of the roll is the direction perpendicular to the direction in which the roll rotates, that is, the direction perpendicular to the direction in which the film (usually a semi-molten polycarbonate resin film) is transported.Therefore, in relation to the first cooling roll 23, the direction perpendicular to the direction of the rotation axis of the roll refers to the direction of a line connecting the center (23a) of the rotation axis of the first cooling roll 23 and the point (23b) where the first cooling roll 23 and the film 24 contact each other. The point (23b) where the first cooling roll 23 and the film 24 contact each other is the point of contact with the first cooling roll 23. Similarly, in relation to the second cooling roll 25, the direction perpendicular to the direction of the rotation axis of the roll refers to the direction of a line connecting the center (25a) of the rotation axis of the second cooling roll 25 and the point (25b) where the second cooling roll 25 and the film 24 contact each other. The point (25b) where the second cooling roll 25 and the film 24 contact each other is the point of contact with the second cooling roll 25. In this embodiment, the distance between the contact point 23b between the first cooling roll 23 and the film 24 and the contact point 25b between the second cooling roll 25 and the film 24 (the inter-roll distance) is 160 to 450 mm. The contact point 23b between the first cooling roll 23 and the film 24 may not be fixed at a single point like a geometric contact point. In this case, the point at which the film 24 finally peels off from the first cooling roll 23 is defined as the contact point 23b between the first roll 23 and the film 24. Similarly, the point at which the film 24 first comes into contact with the second cooling roll 25 is defined as the contact point 25b between the film 24 and the second cooling roll 25. The lower limit of the inter-roll distance is preferably 200 mm or more, more preferably 225 mm or more, even more preferably 250 mm or more, even more preferably 280 mm or more, and even more preferably 300 mm or more. By setting the distance equal to or greater than the lower limit, the uniformity of the principal axis azimuth angles tends to be higher. The upper limit of the distance between the inter-roller points is preferably 420 mm or less, more preferably 400 mm or less, even more preferably 350 mm or less, even more preferably 330 mm or less, and still more preferably 315 mm or less. By setting the distance to the upper limit or less, the uniformity of the main axis azimuth angle tends to be improved.

[0062] The diameter of the first cooling roll is preferably 100 mm or more, more preferably 150 mm or more, even more preferably 200 mm or more, even more preferably 250 mm or more, and even more preferably 280 mm or more. By setting the diameter at or above the lower limit, the time the film is in contact with the roll at a constant molding speed is extended, which makes it easier for the film temperature to be constant across the entire width of the film when the resin is peeled from the roll, and as a result, the major axis azimuth angle tends to be more uniform. Furthermore, the diameter of the first cooling roll is preferably 1000 mm or less, more preferably 900 mm or less, even more preferably 800 mm or less, even more preferably 700 mm or less, and even more preferably 650 mm or less. By setting the diameter at or below the upper limit, it is possible to bring the T-die lip portion closer to the bonding point when the semi-molten resin is bonded between the touch roll 22 and the first cooling roll 23, which tends to make it easier to improve appearance defects such as poor film transfer and die lines. The diameter of the second cooling roll is preferably 100 mm or more, more preferably 150 mm or more, even more preferably 200 mm or more, even more preferably 250 mm or more, and even more preferably 280 mm or more. By setting the diameter at or above the lower limit, the contact length between the first cooling roll 23 and the film 24 can be easily changed by changing the position of the second cooling roll 25 or the position of the guide roll, and the main axis azimuth angle tends to be easily uniform. Furthermore, the diameter of the first cooling roll is preferably 1000 mm or less, more preferably 900 mm or less, even more preferably 800 mm or less, even more preferably 700 mm or less, and even more preferably 650 mm or less. By setting the diameter at or below the upper limit, the mass of the roll can be reduced, and the position of the second cooling roll 25 tends to be easily changed.

[0063] The surface temperature of the first cooling roll is preferably 80°C or higher, more preferably 90°C or higher, and even more preferably 95°C or higher. By setting the surface temperature at or above the lower limit, there is a tendency for poor appearance, such as poor film transfer and die lines, to be improved. Furthermore, the surface temperature of the first cooling roll is preferably 140°C or lower, more preferably 120°C or lower, even more preferably 110°C or lower, and even more preferably 105°C or lower. By setting the surface temperature at or below the upper limit, there is a tendency for the film 24 to be easily peeled from the first cooling roll 23. The surface temperature of the second cooling roll is preferably 110°C or higher, more preferably 120°C or higher, and even more preferably 130°C or higher. By setting the surface temperature at or above the lower limit, there is a tendency for the adhesion between the second cooling roll 25 and the film 24 to be improved, thereby stabilizing the peeling of the first cooling roll 23 and the film 24. Furthermore, the surface temperature of the first cooling roll is preferably 160°C or lower, more preferably 150°C or lower, and even more preferably 145°C or lower. By setting the temperature to the upper limit or less, it tends to be possible to effectively prevent excessive adhesion between the second cooling roll 25 and the film 24, resulting in adhesion between the second cooling roll 25 and the film 24 and resulting in poor appearance. The difference in surface temperature between the second cooling roll and the first cooling roll is preferably 10°C or more, more preferably 20°C or more, and even more preferably 30°C or more. By setting the temperature to the lower limit or more, it tends to be possible to reduce warpage of the film by alleviating warpage of the film generated by the first cooling roll with the second cooling roll. Furthermore, the difference in surface temperature between the second cooling roll and the first cooling roll is preferably 60°C or less, more preferably 50°C or less, and even more preferably 45°C or less. By setting the temperature to the upper limit or less, it is possible to effectively prevent excessive warpage on the second cooling roll.

[0064] The surface temperature of the touch roll is preferably 80°C or higher, more preferably 90°C or higher, and even more preferably 95°C or higher. By setting the surface temperature at or above the lower limit, there is a tendency for appearance defects such as poor transfer of the film and die lines to be easily improved. Furthermore, the surface temperature of the touch roll is preferably 140°C or lower, more preferably 110°C or lower, and even more preferably 105°C or lower. By setting the surface temperature at or below the upper limit, there is a tendency for the film to stick to the touch roll, resulting in poor appearance, to be effectively prevented.

[0065] On the other hand, the surface materials of the touch roll 22, the first cooling roll 23, and the second cooling roll 25 are not particularly limited, but are preferably metal and mirror-finished. By using rolls made of such materials, a polycarbonate resin film with less variation in the main axis orientation can be obtained.

[0066] In the method for producing a polycarbonate resin film, the number of cooling rolls does not need to be two, and may be three or more. In this embodiment, the first and second cooling rolls through which the polycarbonate resin extruded from the T-die passes are preferably the first cooling roll and the second cooling roll, respectively.

[0067] In this embodiment, the peripheral speed ratio between the first cooling roll and the take-up roll is preferably 1:0.995 to 1:0.975. By setting the peripheral speed ratio to 0.975 or more, the tension between the second cooling roll 25 and the take-up roll tends to be an appropriate value, and the principal axis azimuth angle tends to be more uniform. Furthermore, by setting the peripheral speed ratio to 0.995 or less, the phase difference tends to be more easily adjusted to a range of 5 to 50 nm. Here, the take-up roll corresponds to, for example, the third roll 26 in FIG. 2 . That is, it is a roll that acts to take up the film. The peripheral speed ratio between the first cooling roll and the take-up roll is more preferably 0.980 or more relative to the peripheral speed of the first cooling roll (1). Furthermore, the peripheral speed ratio between the first cooling roll and the take-up roll is more preferably 0.993 or less relative to the peripheral speed of the first cooling roll (1), even more preferably 0.990 or less, and even more preferably 0.987 or less.

[0068] In the method for producing a polycarbonate resin film according to this embodiment, a resin composition for forming a polycarbonate resin film is typically extruded through a T-die 21, as shown in FIG. 2 . The width of the T-die is preferably 600 mm or more. By setting the width at or above the lower limit, the moldability and handleability of the resulting polycarbonate resin film tend to be further improved. The width of the T-die is preferably 800 mm or more, more preferably 1000 mm or more, and even more preferably 1200 mm or more. The upper limit of the width of the T-die is preferably 5000 mm or less, more preferably 3000 mm or less, even more preferably 2500 mm or less, even more preferably 2200 mm or less, and even more preferably 2000 mm or less.

[0069] In the polycarbonate resin film manufacturing method of this embodiment, the contact length between the second cooling roll and the semi-molten polycarbonate resin film in a direction perpendicular to the rotation axis direction of the roll is preferably 2 to 400 mm. Setting the contact length at or above the lower limit tends to further improve the uniformity of the principal axis orientation. Setting the contact length at or below the upper limit relaxes the principal axis orientation angle, which is uniform between the first cooling roll and the second cooling roll, on the second cooling roll, thereby preventing the principal axis orientation from becoming more variable and reducing the variation in the principal axis orientation. Here, the contact length in the perpendicular direction refers to the length of the arc where the second cooling roll and the film are in contact. For example, as shown in FIG. 4 (the symbols in FIG. 4 are the same as those in FIG. 2), this refers to the length 30 where the polycarbonate resin film 24 in the process of being manufactured is in contact with the second cooling roll 25. Here, the length refers to the length of contact with the second cooling roll 25 in the direction perpendicular to the rotation axis of the second cooling roll 25, i.e., in the transport direction of the polycarbonate resin film. The polycarbonate resin film 24 in contact with the second cooling roll 25 is a film in a molten state, and therefore is in contact with the second cooling roll at a constant distance. The contact length is more preferably 10 mm or more, even more preferably 15 mm or more, even more preferably 20 mm or more, even more preferably 30 mm or more, and even more preferably 35 mm or more. The contact length is also more preferably 350 mm or less, even more preferably 300 mm or less, even more preferably 200 mm or less, even more preferably 150 mm or less, even more preferably 100 mm or less, and may be 80 mm or less. By setting the contact length to the upper limit or less, uniformity of the major axis orientation tends to be further improved.

[0070] <Method for producing multilayer film> The multilayer film of the present embodiment is not particularly limited, and any known method can be used as long as it satisfies the above conditions A to C and allows the production of a multilayer film having a polycarbonate resin film and other layers.

[0071] A first example of the method for producing a multilayer film of this embodiment includes a distance between the inter-roll points of the first cooling roll and the second cooling roll in a direction perpendicular to the rotation axis direction of the rolls of 160 to 450 mm. Furthermore, in the method for producing a multilayer film of this embodiment, the peripheral speed ratio between the first cooling roll and the take-up roll is preferably 1:0.995 to 1:0.975. Furthermore, in the method for producing a multilayer film of this embodiment, the resin composition for forming the polycarbonate resin film and the resin compositions for forming the other layers are extruded through a T-die, and the width of the T-die is preferably 600 mm or more. That is, the polycarbonate resin film and the other layers are typically co-extruded and produced using rolls similar to the method for producing a polycarbonate resin film described above. Furthermore, in the method for producing a multilayer film of this embodiment, the contact length between the second cooling roll and the semi-molten multilayer film in a direction perpendicular to the rotation axis direction of the rolls is preferably 2 to 400 mm. In the method for producing a multilayer film of this embodiment, the second cooling roll may be in contact with the polycarbonate resin film or with another layer. In the first example of the multilayer film, the other layer is preferably a (meth)acrylic resin layer. Furthermore, after producing a multilayer film by the method described in the first example, a hard coat layer and / or a masking film may be provided thereon. In addition to the above, the details of the first example of the method for producing a multilayer film of this embodiment are the same as those of the method for producing a polycarbonate resin film described above, and the preferred ranges are also the same. Furthermore, the resulting multilayer film is the same as that of the multilayer film of this embodiment described above, and the preferred ranges are also the same.

[0072] A second example of the method for producing a multilayer film according to the present embodiment is a method in which a polycarbonate resin film is formed and then another layer is provided. Specifically, a polycarbonate resin and a high-hardness resin layer are laminated together. Alternatively, a hard coat layer and / or a masking film may be provided on the polycarbonate resin film or on a multilayer film of a polycarbonate resin and a high-hardness resin layer.

[0073] In addition to the above, for the production of multilayer films, the descriptions in JP 2018-103518 A and JP 2016-060786 A can be taken into consideration within the scope of the present invention, and the contents of these publications are incorporated herein by reference.

[0074] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be changed as appropriate 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.

[0075] Various physical properties were measured according to the following methods.

[0076] <Pencil Hardness> The pencil hardness of the film was measured under a load of 500 g±10 g in accordance with JIS K5600-5-4, except for the load. For multilayer films, the measurement was performed from the side with higher hardness. For the multilayer film shown in this example, the measurement was performed from the high-hardness resin layer ((meth)acrylic resin layer) side.

[0077] <Major Axis Azimuth Angle> The major axis azimuth angle of the polycarbonate resin film and the multilayer film was the azimuth angle of the slow axis, which represents the direction in which the refractive index is greatest. Furthermore, since the value of the major axis azimuth angle varies depending on the measurement location, in this example, the average value of the major axis azimuth angle was measured. A PA-300 manufactured by Photonic Lattice, Inc. was used to measure the major axis azimuth angle. The film was installed so that the direction perpendicular to the longitudinal direction faced from the front to the back of the device. The measurement point of the device was the center connecting the diagonal corners of the film, and the major axis azimuth angles were measured at 50 mm intervals toward both ends in the longitudinal direction. For the measurement, the film was cut so that the width direction and the film flow direction were 1300 mm and 300 mm, respectively, and the center point of a 300 x 200 mm area was used as the measurement point. The deviation (°) of the principal axis azimuth angle from the average value was calculated by subtracting the principal axis azimuth angle at each measurement point from the average value of the measured principal axis azimuth angles, and the value with the largest absolute value was taken as the deviation from the average value of the principal axis azimuth angle. For multilayer films, the principal axis azimuth angle was measured from the high-hardness resin layer ((meth)acrylic resin layer) side.

[0078] <Retardation> The retardation of the polycarbonate resin film and the multilayer film was measured as the maximum value of the in-plane retardation at a measurement wavelength of 520 nm. The unit is expressed in nm. A PA-300 manufactured by Photonic Lattice was used to measure the retardation. The film was placed with the direction perpendicular to the longitudinal direction facing from the front to the back of the device. The measurement points of the device were set at the center connecting the diagonal corners of the film, and the retardation was measured at 50 mm intervals toward both ends in the longitudinal direction. The highest retardation among these was defined as the retardation in the present invention. For the multilayer film, the retardation was measured from the high-hardness resin layer ((meth)acrylic resin layer) side.

[0079] <Thickness of Multilayer Film> The thickness of the multilayer film was measured in accordance with Method A of JIS K 7130.

[0080] Example 1 A multilayer film was molded using a multilayer extrusion device having a single-screw extruder with a 50 mm shaft diameter, a single-screw extruder with a 100 mm shaft diameter, a feed block connected to all extruders, and a 1500 mm wide T-die connected to the feed block. A (meth)acrylic resin (manufactured by Arkema Inc., trade name: Altuglas V020, composition: polymethyl methacrylate) was continuously introduced as a high-hardness resin into the single-screw extruder with a 50 mm shaft diameter and extruded at a cylinder temperature of 240°C. A polycarbonate resin (manufactured by Mitsubishi Engineering-Plastics Corporation, trade name: Iupilon S-1000, bisphenol A polycarbonate resin, weight average molecular weight: 59,000) was continuously introduced into the single-screw extruder with a 100 mm shaft diameter and extruded at a cylinder temperature of 280°C. The single-screw extruder with a 50 mm shaft diameter and the single-screw extruder with a 100 mm shaft diameter were set to have a discharge rate ratio of 35 / 90. A feed block connected to all extruders was equipped with two-type, two-layer distributor pins, and the high-hardness resin and polycarbonate resin were introduced and laminated at a temperature of 270°C. The film was extruded onto a T-die connected to the end of the die, which was also heated to 270°C. In a film production apparatus using rolls such as that shown in FIG. 2, the surface temperature of the touch roll 22 was 100°C, the surface temperature of the first cooling roll 23 was 100°C, and the surface temperature of the second cooling roll 25 was 140°C. The film was cooled while transferring a mirror finish using three mirror-finishing rolls. The distance between the contact points of the first cooling roll 23 and the second cooling roll 25 was 305 mm, the contact length between the multilayer film and the second cooling roll 25 was 40 mm, the peripheral speed ratio of the take-up roll (third roll) 26 to the first cooling roll was 0.991, and the line speed was set so that the total thickness of the polycarbonate resin and (meth)acrylic resin layers (hereinafter referred to as the total thickness) was 125 μm, resulting in a multilayer film. The thickness of the (meth)acrylic resin layer of the obtained multilayer film was 35 μm near the center. The polycarbonate resin layer side was in contact with the second cooling roll. The pencil hardness, average principal axis azimuth angle, deviation from the average principal axis azimuth angle, and retardation of the obtained multilayer film were measured and calculated.

[0081] Example 2 A multilayer film was obtained in the same manner as in Example 1, except that the output ratio of the single-screw extruder with a shaft diameter of 50 mm to the single-screw extruder with a shaft diameter of 100 mm was set to 40 / 140, the peripheral speed ratio of the take-up roll 26 to the first cooling roll 23 was set to 0.985, and the total thickness of the multilayer film was set to 180 μm. The thickness of the (meth)acrylic resin layer was 40 μm near the center. The pencil hardness, average principal axis azimuth angle, deviation from the average principal axis azimuth angle, and phase difference of the obtained multilayer film were measured and calculated.

[0082] Example 3 A multilayer film was obtained in the same manner as in Example 1, except that the output ratio of the single-screw extruder with a shaft diameter of 50 mm to the single-screw extruder with a shaft diameter of 100 mm was set to 55 / 199, the peripheral speed ratio of the take-up roll 26 to the first cooling roll 23 was set to 0.985, and the total thickness of the multilayer film was set to 254 μm. The thickness of the (meth)acrylic resin layer was 55 μm near the center. The pencil hardness, average principal axis azimuth angle, deviation from the average principal axis azimuth angle, and phase difference of the obtained multilayer film were measured and calculated.

[0083] Example 4 A multilayer film was obtained in the same manner as in Example 1, except that the output ratio of the single-screw extruder with a shaft diameter of 50 mm to the single-screw extruder with a shaft diameter of 100 mm was set to 55 / 320, the peripheral speed ratio of the take-up roll 26 to the first cooling roll 23 was set to 0.985, and the total thickness of the multilayer film was set to 375 μm. The thickness of the (meth)acrylic resin layer was 55 μm near the center. The pencil hardness, average principal axis azimuth angle, deviation from the average principal axis azimuth angle, and phase difference of the obtained multilayer film were measured and calculated.

[0084] Example 5 A multilayer film was obtained in the same manner as in Example 4, except that the contact distance between the first cooling roll 23 and the second cooling roll 25 was set to 320 mm and the contact length between the multilayer film and the second cooling roll was set to 310 mm. The pencil hardness, average principal axis azimuth angle, deviation from the average principal axis azimuth angle, and phase difference of the obtained multilayer film were measured and calculated.

[0085] Example 6 A multilayer film was obtained in the same manner as in Example 4, except that the contact distance between the first cooling roll 23 and the second cooling roll 25 was set to 205 mm and the contact length between the multilayer film and the second cooling roll 25 was set to 60 mm. The pencil hardness, average value of principal axis azimuth angle, deviation from the average value of the principal axis azimuth angle, and phase difference of the obtained multilayer film were measured and calculated.

[0086] Example 7 A multilayer film was obtained in the same manner as in Example 1, except that the output ratio of the single-screw extruder with a shaft diameter of 50 mm to the single-screw extruder with a shaft diameter of 100 mm was set to 55 / 445, the peripheral speed ratio of the take-up roll 26 to the first cooling roll 23 was set to 0.985, and the total thickness of the multilayer film was set to 500 μm. The thickness of the (meth)acrylic resin layer was 55 μm near the center. The pencil hardness, average principal axis azimuth angle, deviation from the average principal axis azimuth angle, and phase difference of the obtained multilayer film were measured and calculated.

[0087] Example 8 A multilayer film was obtained by applying a 5 μm thick UV-curable urethane acrylate hard coat (UV-curable urethane acrylate manufactured by Mitsubishi Chemical, product name UV-7650B) by roll coating to the surface of the (meth)acrylic resin layer of the multilayer film (total thickness 180 μm, (meth)acrylic resin layer thickness 40 μm) produced in Example 2. The pencil hardness, average value of principal axis azimuth angle, deviation from the average value of principal axis azimuth angle, and phase difference of the obtained multilayer film were measured and calculated.

[0088] Example 9 A multilayer film was obtained by applying a 5 μm thick UV-curable urethane acrylate hard coat (UV-curable urethane acrylate manufactured by Mitsubishi Chemical Corporation, product name UV-7650B) by roll coating to the surface of the (meth)acrylic resin layer of the multilayer film (total thickness 375 μm, (meth)acrylic resin layer thickness 55 μm) produced in Example 4. With respect to the obtained multilayer film, the pencil hardness, average value of principal axis azimuth angle, deviation from the average value of principal axis azimuth angle, and phase difference were measured and calculated.

[0089] Comparative Example 1 A multilayer film was obtained in the same manner as in Example 1, except that the contact distance between the first cooling roll 23 and the second cooling roll 25 was 41 mm and the contact length between the multilayer film and the second cooling roll 25 was 190 mm. The total thickness of the multilayer film was 125 μm, and the thickness of the (meth)acrylic resin layer near the center was 35 μm. The pencil hardness, average value of the principal axis azimuth angle, deviation from the average value of the principal axis azimuth angle, and phase difference of the obtained multilayer film were measured and calculated.

[0090] Comparative Example 2 A multilayer film was obtained in the same manner as in Example 3, except that the contact distance between the first cooling roll 23 and the second cooling roll 25 was 41 mm and the contact length between the multilayer film and the second cooling roll 25 was 190 mm. The total thickness of the multilayer film was 254 μm, and the thickness of the (meth)acrylic resin layer near the center was 55 μm. The pencil hardness, average value of the principal axis azimuth angle, deviation from the average value of the principal axis azimuth angle, and phase difference of the obtained multilayer film were measured and calculated.

[0091] Comparative Example 3 A multilayer film was obtained in the same manner as in Example 4, except that the contact distance between the first cooling roll 23 and the second cooling roll 25 was 41 mm and the contact length between the multilayer film and the second cooling roll 25 was 190 mm. The total thickness of the multilayer film was 375 μm, and the thickness of the (meth)acrylic resin layer near the center was 55 μm. The pencil hardness, average value of the principal axis azimuth angle, deviation from the average value of the principal axis azimuth angle, and phase difference of the obtained multilayer film were measured and calculated.

[0092] Comparative Example 4 A multilayer film was obtained in the same manner as in Example 7, except that the contact distance between the first cooling roll 23 and the second cooling roll 25 was 41 mm and the contact length between the multilayer film and the second cooling roll 25 was 190 mm. The total thickness of the multilayer film was 500 μm, and the thickness of the (meth)acrylic resin layer near the center was 55 μm. The pencil hardness, average value of the principal axis azimuth angle, deviation from the average value of the principal axis azimuth angle, and phase difference of the obtained multilayer film were measured and calculated.

[0093]

[0094] Example 10 A polycarbonate resin film was molded using an extrusion device having a single-screw extruder with a shaft diameter of 100 mm and a 1,500 mm wide T-die connected to the extruder. A polycarbonate resin (manufactured by Mitsubishi Engineering Plastics Corporation, product name: Iupilon S-1000, bisphenol A polycarbonate resin, weight average molecular weight: 59,000) was continuously introduced as thermoplastic resin A into the single-screw extruder with a shaft diameter of 100 mm and extruded at a cylinder temperature of 280 ° C. The single-screw extruder with a shaft diameter of 100 mm was set to a discharge rate of 200 kg / h, and extruded onto a film using a T-die at a temperature of 270 ° C. The roll temperature of the touch roll 22 was 100 ° C., the roll temperature of the first cooling roll 23 was 100 ° C., and the roll temperature of the second cooling roll 25 was 140 ° C. The film was cooled while transferring a mirror surface using three mirror-finishing rolls. At that time, the distance between the contact points of the first cooling roll 23 and the second cooling roll 25 was set to 305 mm, the contact length between the polycarbonate resin film and the second cooling roll 25 was set to 40 mm, the peripheral speed ratio of the take-up roll 26 to the first cooling roll 23 was set to 0.985, and the line speed was set so that the thickness of the polycarbonate resin film would be 100 μm, thereby obtaining a polycarbonate resin film. With respect to the obtained polycarbonate resin film, the pencil hardness, the average value of the principal axis azimuth angle, the deviation from the average value of the principal axis azimuth angle, and the phase difference were measured and calculated.

[0095] Example 11 A polycarbonate resin film was obtained in the same manner as in Example 10, except that the extrusion rate of a single-screw extruder having a shaft diameter of 100 mm was set to 300 kg / h and the line speed was set so that the polycarbonate resin film thickness would be 254 μm. With respect to the obtained polycarbonate resin film, the pencil hardness, the average value of the principal axis azimuth angle, the deviation from the average value of the principal axis azimuth angle, and the phase difference were measured and calculated.

[0096] Example 12 A polycarbonate resin film was obtained in the same manner as in Example 10, except that the extrusion rate of a single-screw extruder having a shaft diameter of 100 mm was set to 300 kg / h and the line speed was set so that the polycarbonate resin film thickness would be 375 μm. With respect to the obtained polycarbonate resin film, the pencil hardness, the average value of the principal axis azimuth angle, the deviation from the average value of the principal axis azimuth angle, and the phase difference were measured and calculated.

[0097] Example 13 A polycarbonate resin film was obtained in the same manner as in Example 10, except that the extrusion rate of a single-screw extruder having a shaft diameter of 100 mm was set to 300 kg / h and the line speed was set so that the polycarbonate resin film thickness would be 500 μm. With respect to the obtained polycarbonate resin film, the pencil hardness, the average value of the principal axis azimuth angle, the deviation from the average value of the principal axis azimuth angle, and the phase difference were measured and calculated.

[0098] Comparative Example 5 A polycarbonate resin film was obtained in the same manner as in Example 10, except that the distance between the contact points of the first cooling roll 23 and the second cooling roll 25 was 41 mm and the contact length between the polycarbonate resin film and the second cooling roll 25 was 190 mm. With respect to the obtained polycarbonate resin film, the pencil hardness, the average value of the principal axis azimuth angle, the deviation from the average value of the principal axis azimuth angle, and the phase difference were measured and calculated.

[0099] Comparative Example 6 A polycarbonate resin film was obtained in the same manner as in Example 11, except that the distance between the contact points of the first cooling roll 23 and the second cooling roll 25 was 41 mm and the contact length between the polycarbonate resin film and the second cooling roll 25 was 190 mm. With respect to the obtained polycarbonate resin film, the pencil hardness, the average value of the principal axis azimuth angle, the deviation from the average value of the principal axis azimuth angle, and the phase difference were measured and calculated.

[0100] Comparative Example 7 A polycarbonate resin film was obtained in the same manner as in Example 12, except that the distance between the contact points of the first cooling roll 23 and the second cooling roll 25 was 41 mm and the contact length between the polycarbonate resin film and the second cooling roll 25 was 190 mm. With respect to the obtained polycarbonate resin film, the pencil hardness, the average value of the principal axis azimuth angle, the deviation from the average value of the principal axis azimuth angle, and the phase difference were measured and calculated.

[0101] Comparative Example 8 A polycarbonate resin film was obtained in the same manner as in Example 13, except that the contact distance between the first cooling roll 23 and the second cooling roll 25 was 41 mm and the contact length between the polycarbonate resin film and the second cooling roll 25 was 190 mm.

[0102]

[0103] As is clear from the above results, the multilayer film of the present invention had low retardation and uniformity of the principal axis orientation, despite having a polycarbonate resin film using PC-A as a raw material. Furthermore, the polycarbonate resin film of the present invention had low retardation and uniformity of the principal axis orientation, despite having PC-A as a raw material.

[0104] REFERENCE SIGNS LIST 1 Polycarbonate resin film 2 Other layers 21 T-die 22 Touch roll 23 First cooling roll 24 Polycarbonate resin film in the process of being produced 25 Second cooling roll 26 Third roll 30 Contact length

Claims

1. A polycarbonate resin film containing a polycarbonate resin and satisfying the following conditions 1 to 3: Condition 1: The polycarbonate resin has a main structural unit represented by the following formula (1): Condition 2: The deviation of the principal axis azimuth angle of the film from the average value is within ±11°; Condition 3: The retardation of the film is 5 to 50 nm. Formula (1) 【Chemical 1】

2. The polycarbonate resin film according to claim 1, wherein the thickness of the polycarbonate resin film is 50 to 1500 μm.

3. A film having a polycarbonate resin film and at least one other layer, A multilayer film that satisfies the following conditions A to C: Condition A: The polycarbonate resin has a main structural unit represented by the following formula (1): Condition B: The deviation of the principal axis azimuth angle of the film from the average value is within ±11°; Condition C: The retardation of the film is 5 to 50 nm. Formula (1) 【Chemistry 2】

4. The multilayer film according to claim 3, wherein the pencil hardness of the multilayer film measured from the other layer side is HB or higher.

5. 5. The multilayer film according to claim 3, wherein the total thickness of the polycarbonate resin film and one of the other layers is 50 to 1500 μm.

6. 5. The multilayer film according to claim 3, wherein the thickness ratio of the polycarbonate resin film to the other layer is 2 / 1 to 10 / 1.

7. The multilayer film according to claim 5, wherein the thickness of the other layer is 20 to 100 μm.

8. The multilayer film according to claim 3 or 4, wherein the other layer is a layer containing a (meth)acrylic resin.

9. A multilayer film having a hard coat layer on one or both sides of the polycarbonate resin film according to any one of claims 1 to 4.

10. A multilayer film having a masking film on one or both sides of the polycarbonate resin film according to any one of claims 1 to 4.

11. A display device comprising the polycarbonate resin film according to any one of claims 1 to 4.

12. 3. The method for producing a polycarbonate resin film according to claim 1 or 2, wherein the distance between the inter-roll points of the first cooling roll and the second cooling roll in a direction perpendicular to the rotation axis direction of the rolls is 160 to 450 mm.

13. The method for producing a polycarbonate resin film according to claim 12, wherein the peripheral speed ratio of the first cooling roll to the take-up roll is 1:0.995 to 1:0.

975.

14. 13. The method for producing a polycarbonate resin film according to claim 12, comprising extruding a resin composition for forming a polycarbonate resin film through a T-die, wherein the width of the T-die is 600 mm or more.

15. 13. The method for producing a polycarbonate resin film according to claim 12, wherein a contact length between the second cooling roll and the semi-molten polycarbonate resin film in a direction perpendicular to the rotation axis direction of the roll is 2 to 400 mm.

16. 5. The method for producing a multilayer film according to claim 3, wherein the distance between the inter-roll points of the first cooling roll and the second cooling roll in a direction perpendicular to the rotation axis direction of the rolls is 160 to 450 mm.

17. The method for producing a multilayer film according to claim 16, wherein the peripheral speed ratio of the first cooling roll to the take-up roll is 1:0.995 to 1:0.

975.

18. 17. The method for producing a multilayer film according to claim 16, comprising extruding a resin composition for forming a polycarbonate resin film and a resin composition for forming another layer through a T-die, wherein the width of the T-die is 600 mm or more.

19. The method for producing a multilayer film according to claim 16, wherein the contact length between the second cooling roll and the semi-molten multilayer film in a direction perpendicular to the rotation axis direction of the roll is 2 to 400 mm.

20. The method for producing a multilayer film according to claim 16 , wherein the other layer is a layer containing a (meth)acrylic resin.

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