CN116209928A

CN116209928A - Cover member, base film for cover member, and display device provided with same

Info

Publication number: CN116209928A
Application number: CN202180063474.9A
Authority: CN
Inventors: 藤枝奈奈惠; 建部隆; 大久保康; 南条崇; 田坂公志
Original assignee: Konica Minolta Inc
Current assignee: Konica Minolta Inc
Priority date: 2020-09-17
Filing date: 2021-08-30
Publication date: 2023-06-02
Also published as: TWI814068B; WO2022059465A1; TW202234098A; KR20230041762A; JP2023133318A; JPWO2022059465A1; JP7315110B2

Abstract

The technical problems of the invention are as follows: provided are a cover member, a base film for the cover member, and a display device provided with the cover member, wherein the cover member has improved operability and does not cause crease on the base film provided with the cover member when repeatedly bent. The cover member of the present invention is a cover member having a base material film of 1 [ mu ] m or more and less than 15 [ mu ] m and a transparent base material of 5 [ mu ] m or more and less than 50 [ mu ] m, wherein a slope of a straight line connecting an origin and a breaking point in a stress-strain curve of the base material film is 1.1 to 25.0.

Description

Cover member, base film for cover member, and display device provided with same

Technical Field

The present invention relates to a cover member, a base film for the cover member, and a display device provided with the cover member and the base film. More specifically, the present invention relates to a cover member, a base film for the cover member, and a display device including the cover member, which improve operability of the cover member and prevent crease from occurring in the base film provided in the cover member.

Background

Recently, many foldable or rollable flexible displays have been developed. The display is composed of a cover glass unit (hereinafter, also referred to as a "cover member") for protecting the display and a display unit including a polarizing plate.

Here, as the transparent substrate used in the cover glass unit, for example, flexibility is required in the case of using a glass substrate, and thus, thinning of the glass substrate itself is required, and a method for manufacturing a thin glass or the like is disclosed in accordance with these requirements (for example, refer to patent document 1).

On the other hand, in order to protect the glass substrate, an invention is disclosed in which, when a polymer layer (protective film) is laminated on the glass substrate, the waviness of the surface of the polymer layer is controlled (for example, refer to patent document 2).

In the flexible display having the folding specification, by thinning each member, the bending radius of the cover member is made smaller when the display is folded. In this case, according to the studies by the present inventors, it is necessary for the protective film (also referred to as "base film" in the present invention) provided on the cover member to be: the protective function (press-in strength) of the cover member is improved to such an extent that cracking of the glass substrate does not occur during folding of the cover member, and the protective film does not have a characteristic of being creased when the cover member is repeatedly bent.

However, in the cover member formed of the laminate of the glass substrate and the protective film produced by the above disclosed technique, it is difficult to achieve both improvement of the protective function in further thinning and the characteristic that the protective film does not generate a crease in repeated bending.

Prior art literature

Patent literature

Patent document 1 International publication No. 2017/066924

Patent document 2 Japanese patent application laid-open No. 2002-534305

Disclosure of Invention

Technical problem to be solved by the invention

The present invention has been made in view of the above problems and conditions, and solves the technical problems: a cover member, a base film for the cover member, and a display device provided with the cover member, wherein operability of the cover member is improved, and crease is not generated on the base film provided with the cover member when the cover member is repeatedly bent.

Technical means for solving the problems

In order to solve the above-described problems, the present inventors have found that, in the course of studying the cause of the problems and the like: when the cover member includes a substrate film having a specific thickness and a transparent substrate, and the relationship between the stress of the substrate film and the strain corresponding thereto satisfies a specific relationship, it is possible to obtain: the cover member has the characteristics of improving the operability of the cover member and preventing crease on a base film provided in the cover member.

That is, the technical problem of the present invention is solved by the following means.

1. A cover member having a base film of 1 μm or more and less than 15 μm and a transparent base film of 5 μm or more and less than 50 μm, wherein,

The slope of a straight line connecting the origin and the breaking point in the stress-strain curve of the base material film is 1.1 to 25.0.

2. The cover member according to claim 1, wherein,

when the surface of the base material film bonded to the transparent base material is referred to as the A surface and the back surface of the base material film opposite to the A surface is referred to as the B surface,

film density of the A-plane (ρ) _A ) Less thanFilm density of the B-side (ρ) _B )。

3. The cover member according to

claim

1 or 2, wherein,

film density of the B-side (ρ) _B ) Film Density (ρ) relative to the A-plane _A ) Ratio (ρ) _A /ρ _B ) The value of (2) is in the range of 0.80 to 0.95.

4. The cover member according to any one of items 1 to 3, wherein,

the base film contains rubber particles in a range of 40 to 85 mass%.

5. The cover member according to any one of items 1 to 4, wherein,

the elastic modulus of the transparent substrate is in the range of 55-80 GPa, and the ratio of the elastic modulus of the transparent substrate to the elastic modulus of the substrate film (elastic modulus of the transparent substrate/elastic modulus of the substrate film) is 30 or more.

6. A base film for a cover member, wherein,

the substrate film is 1 μm or more and less than 15 μm,

7. The base material film for a cover member according to claim 6, wherein,

the substrate film is attached to the transparent substrate,

film density of the A-plane (ρ) _A ) Film density (ρ) less than the B-plane _B )。

8. The base material film for a cover member according to claim 6 or 7, wherein,

the substrate film is attached to the transparent substrate,

9. The base material film for a cover member according to any one of the items 6 to 8, wherein,

the base film contains rubber particles in a range of 40 to 85 mass%.

10. A display device is provided with:

The cover member according to any one of items 1 to 5 or the base film for a cover member according to any one of items 6 to 9.

ADVANTAGEOUS EFFECTS OF INVENTION

By the method of the invention, it is possible to provide: a cover member, a base film for the cover member, and a display device provided with the cover member and the base film are provided, wherein operability of the cover member is improved, and crease is not generated on the base film provided with the cover member when the cover member is repeatedly bent.

The expression mechanism or action mechanism of the effect of the present invention is not specifically defined, but it is assumed that the following is possible.

The cover member of the present invention is composed of a laminate of a base material film and a transparent base material having a specific thickness range, wherein the slope of a straight line connecting the origin and the breaking point in the stress-strain curve of the base material film is 1.1 to 25.0.

By such a feature, it is possible to obtain: the operability of the cover member is improved, and crease is not generated on a base film of the cover member when the cover member is repeatedly bent.

Here, "operability of the cover member" means that, in the present invention, when the cover member is folded and opened, the base material film provided in the cover member performs a protective function (press-in strength), and cracks or the like are not generated in the transparent base material. Further, the "crease" means that the base film whitens at the folded portion with the opening and closing operation by repeated folding, is observed as a crease, and is peeled off from the transparent base film to cause deterioration in visibility such as image distortion.

When the slope of a straight line connecting the origin and the breaking point in the stress-strain curve of the base film exceeds 25.0, that is, when the base film is hard and reaches the breaking point quickly, a rapid stress increase occurs in the stretched state of the base film, that is, in the state where the device is closed, particularly, in the outside of the base film, and therefore, in the repeated opening and closing operation, deterioration of the physical properties from the outside to the inside occurs, whitening of the folded portion or adhesion failure occurs, and the "crease" is visually recognized. In addition, it is presumed that stress is directly concentrated on the transparent substrate when the transparent substrate is pressed, and thus cracks of the transparent substrate are easily generated.

On the other hand, when the slope of the straight line is less than 1.1 and the substrate film is relatively soft, deterioration of the physical properties of the outside-inside is less likely to occur in the repeated opening and closing operation, but the substrate film is repeatedly stretched and contracted as a whole in a form in which the substrate film integrally follows the transparent substrate in accordance with the opening and closing operation, and therefore the substrate film floats up at the folded portion due to poor adhesion or the like, and visibility is lowered. Further, it is presumed that when the base material film is pressed together with the transparent base material, the base material film is too soft, and therefore the physical deformation amount of the transparent base material becomes too large, and cracks of the transparent base material are likely to occur.

Drawings

FIG. 1A is a cross-sectional view of a laminate of a substrate film and a transparent substrate

FIG. 1B is a cross-sectional view of a laminate of another embodiment of a substrate film and a transparent substrate

FIG. 1C is a schematic view of a folded laminate

FIG. 1D is a schematic view of a laminate according to another embodiment

FIG. 2 is a graph showing the slope of the stress-strain curve and the straight line connecting the origin and the breaking point of the base material film

FIG. 3 is a schematic view showing a method for producing a base film according to an embodiment of the present invention

FIG. 4 is a schematic view showing an example of a method for producing a glass substrate suitable for a transparent substrate

FIG. 5A is a schematic view showing the adhesion of a substrate film with a support to a transparent substrate

FIG. 5B is a schematic view showing the adhesion of another embodiment of the support-equipped substrate film to a transparent substrate

Fig. 6 is an application example of the cover member to the organic EL display as an example of the display device of the present invention

Detailed Description

The cover member of the present invention is a cover member having a base film having a thickness of 1 [ mu ] m or more and less than 15 [ mu ] m and a transparent base material having a thickness of 5 [ mu ] m or more and less than 50 [ mu ] m, wherein a slope of a straight line connecting an origin and a breaking point in a stress-strain curve of the base film is 1.1 to 25.0. This technical feature is common to or corresponding to the following embodiments.

In the present invention, from the viewpoint of the effect of the present invention, when the surface of the substrate film bonded to the transparent substrate is referred to as the a-surface, and the back surface of the substrate film opposite to the a-surface is referred to as the B-surface, the film density (ρ _A ) Film density (ρ) less than the B-plane _B ) Preferably, the film density (. Rho.) of the B-side _B ) Film Density (ρ) relative to the A-plane _A ) Ratio (ρ) _A /ρ _B ) The value of (2) is in the range of 0.80 to 0.95. This is because, when the cover member is folded toward the transparent base material side, a greater tensile stress is applied to the B-side of the base material film than to the a-side, and if the film density on the a-side is low, the tensile stress can be relaxed.

The base film preferably contains rubber particles in a range of 40 to 85 mass%. The impact resistance is improved by adding a large amount of rubber particles, and crease resistance during repeated bending is improved.

Preferably, the elastic modulus of the transparent substrate is in the range of 55 to 80GPa, and the ratio of the elastic modulus of the transparent substrate to the elastic modulus of the substrate film (elastic modulus of the transparent substrate/elastic modulus of the substrate film) is 30 or more. This is because, in order to provide a cover member that has improved press-in strength and does not cause creasing by using a transparent substrate having a low elastic modulus due to thinning, the protective function of the transparent substrate can be further improved by using a substrate film having a lower elastic modulus, that is, by setting the value of the ratio of elastic modulus (elastic modulus of the transparent substrate/elastic modulus of the substrate film) to 30 or more with respect to the transparent substrate.

In the present invention, the substrate film for a cover member has a thickness (also referred to as "film thickness") of 1 μm to 15 μm, and a slope of a straight line connecting an origin and a breaking point in a stress-strain curve of the substrate film is 1.1 to 25.0. By adjusting the slope of the straight line to be within the above range, the press-in strength and crease resistance of the base film are improved, and the operability of the base film when the base film is provided on the lid member is improved.

In the substrate film, when the surface of the substrate film bonded to the transparent substrate is referred to as a-side and the back surface of the substrate film opposite to the a-side is referred to as B-side, the film density (ρ _A ) Film density (ρ) less than the B-plane _B ) From the viewpoint of the above effects, the film density (ρ _B ) Film Density (ρ) relative to the A-plane _A ) Ratio (ρ) _A /ρ _B ) The value of (2) is in the range of 0.80 to 0.95.

In addition, it is also preferable that the base film contains rubber particles in a range of 40 to 85 mass%.

The display device of the present invention includes the cover member of the present invention or the base film for the cover member of the present invention. With this display device, a foldable display and a rollable display can be obtained, which are improved in operability by providing a cover member and which do not cause creases in a base film provided in the cover member when repeatedly bent.

The present invention and its constituent elements and specific embodiments and modes for carrying out the present invention will be described in detail below. In the present application, "to" means that the numerical values described before and after "are included as the lower limit value and the upper limit value.

Summary of the cover Member of the invention

The cover member of the present invention is a cover member having a base film having a thickness of 1 [ mu ] m or more and less than 15 [ mu ] m and a transparent base material having a thickness of 5 [ mu ] m or more and less than 50 [ mu ] m, wherein a slope of a straight line connecting an origin and a breaking point in a stress-strain curve of the base film is 1.1 to 25.0.

Fig. 1 is a cross-sectional view of a laminate of a base material film and a transparent base material in a cover member of the present invention and a schematic view when the cover member (laminate) is folded.

Fig. 1A shows a minimum structure of a cover member 10 of the present invention, and a base film 1 is bonded to a transparent base 3 via an adhesive layer 4 to form a laminate. When the base film 1 is bonded to the transparent base 3, the bonding surface of the base film 1 to the transparent base 3 is referred to as an a-surface, and the back surface of the base film opposite to the a-surface is referred to as a B-surface.

Fig. 1B shows another embodiment of the cover member 10 of the present invention. The substrate film 1 is bonded to the transparent substrate 3 via the adhesive layer 4, and the substrate film 2 is bonded to the transparent substrate 3 via the adhesive layer 4, thereby forming a laminate. The base film 2 may be a film having the same specification as the base film 1, or may be a film having another material and specification. For example, in order to increase the surface hardness, a functional film such as a hard coat film may be used.

Fig. 1C is a schematic view of the cover member 10 shown in fig. 1A folded toward the transparent base material 3. The bending radius at the time of folding here means a radius R of the inside of the folded portion at the time of folding the cover member 10 in fig. 1C or 1D.

As described above, when the cover member is folded toward the transparent base material 3, a tensile stress is applied to the B-side of the base material film more than to the a-side, and if the film density on the a-side is low, the tensile stress can be relaxed.

Fig. 1D is a schematic view of the cover member 10 shown in fig. 1B folded toward the transparent base material 3. In this case, the B-side surface of the base film 1 is subjected to a tensile stress greater than that of the a-side surface, and if the film density of the a-side surface is low, the tensile stress can be relaxed.

The stress-strain curve of the present invention shows the relationship between the tensile stress and the tensile elongation at break of the base film measured according to JIS K7127:1999.

The base film was cut into a size of 100mm (MD direction: longitudinal direction) ×10mm (TD direction: width direction), to obtain a sample film. The sample film was subjected to humidity control at 23℃and 55% RH for 24 hours, and the humidity-controlled sample film was subjected to stretching in the MD direction until fracture at a distance of 50mm according to JIS K7127:1999 using a universal tensile tester RTC-1225A manufactured by ORIENTEC Co. The vertical axis of the stress-strain curve is expressed as stress (MPa), and the horizontal axis is expressed as tensile elongation at break (%). The stress-strain curve was measured at 23℃and 55% RH at a tensile speed of 50 mm/min.

A method of determining the slope of a straight line according to the present invention from the stress-strain curve of the base material film obtained by the measurement will be described with reference to the drawings.

Fig. 2 is a graph showing the slope of a stress-strain curve of a base material film and a straight line connecting an origin and a breaking point.

By performing a tensile test on the base material film, a breaking point X is taken after elongation, and when a straight line Y connecting the breaking point X and the origin (0 point) is drawn, the slope α of the straight line is defined as the so-called "slope of the straight line connecting the origin and the breaking point in the stress-strain curve of the base material film" in the present invention. As described above, since the slope α is required to be 1.1 to 25.0 from the viewpoint of obtaining the effect of the present invention, it is not excessively hard although it is elastic, and therefore, it is possible to obtain a cover member which can improve the operability of the cover member by improving the press-in strength of the base material film and which does not cause a crease in the base material film itself provided in the cover member even when repeatedly bent.

The constituent elements of the present invention will be described in detail below. However, in the following description, the present invention is not limited thereto.

[1] Substrate film

[1.1] outline of substrate film

In the following description, unless otherwise specified, the "base film" will be described as "base film 1" in fig. 1.

In the substrate film of the present invention, the slope of a straight line connecting the origin and the breaking point in the stress-strain curve of the substrate film is 1.1 to 25.0 in the range of 1 μm or more and less than 15 μm, and the substrate film has an effect of not causing a crease in the substrate film itself when the substrate film is repeatedly bent in addition to improving the operability such as the press-in strength when the substrate film is provided in the lid member.

As described above, when the slope of the straight line exceeds 25.0, a sharp increase in stress occurs particularly on the outside of the base film in the stretched state of the base film, i.e., in the closed state of the device, and therefore, deterioration of the physical properties from the outside to the inside occurs in the repeated opening and closing operations, and whitening or poor adhesion occurs in the folded portion, which is visually confirmed as a crease. In addition, when the transparent substrate is pressed, stress is directly concentrated on the transparent substrate, and thus cracks of the transparent substrate are easily generated.

On the other hand, when the slope of the straight line is less than 1.1 and the substrate film is soft, the substrate film is repeatedly stretched and contracted as the substrate film and the transparent substrate integrally follow each other in accordance with the opening and closing operation, and therefore, the substrate film floats up at the folded portion due to poor adhesion or the like, and visibility is lowered and visually confirmed as a crease. In addition, when the base material film is pressed together with the transparent base material, the base material film is too soft, and therefore the physical deformation amount of the transparent base material becomes too large, and cracks of the transparent base material are likely to occur.

When the film thickness is less than 1 μm, the waist becomes weak as a base film, and the press-in strength of the lid member is lowered. In addition, when 15 μm or more, the waist portion becomes strong as the base film, and the crease is likely to be generated with repeated opening and closing of the display, so that it is necessary to be within the above range.

Further, the surface of the base material film bonded to the transparent base material is referred to as the A surface, and the back surface of the base material film opposite to the A surfaceWhen the surface B is used, the film density (. Rho. _A ) Film density (ρ) less than the B-plane _B ) Preferably, the film density (. Rho.) of the B-side _B ) Film Density (ρ) relative to the A-plane _A ) Ratio (ρ) _A /ρ _B ) The value of (2) is in the range of 0.80 to 0.95. This is because, when the cover member is folded toward the transparent base material side, a greater tensile stress is applied to the B-side of the base material film than to the a-side, and if the film density on the a-side is low, the tensile stress can be relaxed.

< measurement of the densities of the A and B surfaces of the substrate film >

The density of the surface (a-side and B-side) of the substrate film was measured by an X-ray reflectance method (XRR method). When the angle of incidence of the X-rays is equal to or greater than the critical angle for total reflection, the X-rays enter the film and the reflectivity is reduced. The reflectance distribution measured by the XRR method can be analyzed by using a dedicated reflectance analysis software, and in the present invention, when the angle at which the reflectance starts to decrease is defined as θa, the density at which the fitting error between the measurement result and the calculation result is minimized is defined as the surface density in the range of 2θ from 2θ to 2θ+0.1°. At this time, the surface roughness was set to be in the range of 0nm to 1nm, and fitting was performed.

The substrate film was cut into 30mm by 30mm sizes, and the cut substrate film was fixed to a sample stage, and measured under the following measurement conditions.

(measurement conditions)

Device: film X-ray diffraction apparatus (ATX-G manufactured by RIGAKU Co., ltd.)

Sample size: 30mm by 30mm

Incident X-ray wavelength:

measurement range (θ): 0 to 6 DEG

Analysis software: reflectance analysis software GXRR (manufactured by RIGAKU Co., ltd.)

To set the film density (ρ) of the B-side _B ) Film Density (ρ) relative to the A-plane _A ) Ratio of (2)Example (ρ) _A /ρ _B ) The value of (2) is set to be in the range of 0.80 to 0.95, and in the process of producing a base film, the following findings can be used as an example.

(a) The amount of rubber particles, microparticles relative to the resin is varied. For example, when the amount of rubber particles or fine particles is increased, the diffusion of the solvent is promoted, and the density difference between the front surface and the back surface is less likely to occur.

(b) The concentration of the solid component in the dope was changed. For example, when the solid content is high, the solvent is relatively small, and thus a density difference is less likely to occur.

(c) The drying method was changed. For example, in addition to the slow drying, the density difference may be increased by performing spot drying (applying a heater to the surface) or the like.

By combining the technical means derived from the findings of (a) to (c), the density ratio (ρ) of the a-plane/B-plane can be reduced _A /ρ _B ) The value of (2) is adjusted to be in the range of 0.80 to 0.95.

[1.2] Material for substrate film

The resin used in the base film of the present invention is not particularly limited, and examples thereof include: the cellulose ester resin, cycloolefin resin, fumaric acid diester resin, polypropylene resin, (meth) acrylic resin, polyester resin, polyarylate resin, polyimide resin, and styrene resin or a composite resin thereof are preferable, and from the viewpoint of controlling physical properties such as bending resistance and improving optical properties by containing a linear polymer material having a carbonyl group in a side chain or a polymer material having a cyclic structure in a main chain, the resin may be (meth) acrylic resin, styrene- (meth) acrylate copolymer, cycloolefin resin, polyimide resin, or the like.

(meth) acrylic resin ]

The (meth) acrylic resin for the substrate film preferably contains at least: structural units (U1) derived from methyl methacrylate and structural units (U2) derived from phenylmaleimide. The (meth) acrylic resin containing the structural unit (U2) derived from phenylmaleimide has an advantage that the photoelastic coefficient of the base film is reduced, and unevenness is less likely to occur even if the film swells with moisture.

The (meth) acrylic resin may further contain other structural units than the above. Examples of such other building blocks include: alkyl (meth) acrylates such as adamantyl acrylate; and (meth) acrylic acid cycloalkanes such as 2-ethylhexyl acrylate. Among them, from the viewpoint of reducing the brittle deterioration caused by the inclusion of the structural unit (U2) derived from phenylmaleimide, the structural unit (U3) derived from an alkyl acrylate is preferably further included.

That is, the (meth) acrylic resin more preferably contains a structural unit (U1) derived from methyl methacrylate, a structural unit (U2) derived from phenylmaleimide, and a structural unit (U3) derived from alkyl acrylate.

The content of the structural unit (U1) derived from methyl methacrylate is preferably in the range of 50 to 95 mass%, more preferably in the range of 70 to 90 mass%, relative to the total structural units constituting the (meth) acrylic resin.

The structural unit (U2) derived from phenylmaleimide has a relatively rigid structure, and thus can improve the mechanical strength of the base film. Further, since the structural unit (U2) derived from phenylmaleimide has a structure with relatively large steric hindrance, it has minute voids in the resin matrix that can move the rubber particles, and therefore it is easy to bias the rubber particles to the surface layer portion existing in the base film.

The content of the structural unit (U2) derived from phenylmaleimide is preferably in the range of 1 to 25 mass% relative to the total structural units constituting the (meth) acrylic resin. When the content of the structural unit (U2) derived from phenylmaleimide is 1 mass% or more, the substrate film is excellent in storage stability under a high humidity environment. If the amount is 25% by mass or less, the brittleness of the base film is not easily impaired excessively. From the standpoint of the above, the content of the structural unit (U2) derived from phenylmaleimide is more preferably in the range of 7 to 15 mass%.

The structural unit (U3) derived from an alkyl acrylate can impart appropriate flexibility to the resin, and thus, for example, brittleness due to inclusion of the structural unit (U2) derived from phenylmaleimide can be improved.

The alkyl acrylate is preferably an alkyl acrylate having an alkyl moiety having 1 to 7 carbon atoms, preferably 1 to 5 carbon atoms. Examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, and the like.

The content of the structural unit (U3) derived from the alkyl acrylate is preferably in the range of 1 to 25 mass% relative to the total structural units constituting the (meth) acrylic resin. If the content of the structural unit (U3) derived from the alkyl acrylate is 1 mass% or more, the (meth) acrylic resin can be given appropriate flexibility, and therefore the base film does not become excessively brittle and is less likely to break. When the content of the structural unit (U3) derived from the alkyl acrylate is 25 mass% or less, tg of the base film does not become too low, and the base film is excellent in storage under a high humidity environment. From the standpoint of the above, the content of the structural unit (U3) derived from the alkyl acrylate is more preferably in the range of 5 to 15 mass%.

The ratio of the structural unit (U2) derived from phenylmaleimide to the total amount of the structural unit (U2) derived from phenylmaleimide and the structural unit (U3) derived from alkyl acrylate is preferably in the range of 20 to 70 mass%. When the ratio is 20% by mass or more, the elastic modulus of the base film is easily increased, and when the ratio is 70% by mass or less, the base film does not become excessively brittle.

The glass transition temperature (Tg) of the (meth) acrylic resin is preferably 100℃or higher, more preferably in the range of 120 to 150 ℃. When the Tg of the (meth) acrylic resin is within the above range, the heat resistance of the base film is easily improved. In order to adjust the Tg of the (meth) acrylic resin, it is preferable to adjust the content of, for example, a structural unit (U2) derived from phenylmaleimide and a structural unit (U3) derived from alkyl acrylate.

The weight average molecular weight (Mw) of the (meth) acrylic resin is not particularly limited and may be adjusted according to the purpose. The weight average molecular weight of the (meth) acrylic resin is preferably 10 ten thousand or more, more preferably 100 ten thousand or more, from the viewpoints of, for example, promoting entanglement of resin molecules with each other and improving toughness of the base film to prevent breakage, and appropriately increasing the coefficient of humidity expansion to easily adjust the curl amount to a preferable degree of adhesion. When the weight average molecular weight of the (meth) acrylic resin is 100 ten thousand or more, the toughness of the obtained base film can be improved. In this way, in the process of manufacturing, breakage of the base material film due to the conveyance tension can be suppressed when the laminate film is conveyed as a later-described laminate film, and the conveyance stability can be improved. From the same viewpoint, the weight average molecular weight of the (meth) acrylic resin is more preferably in the range of 150 to 300 tens of thousands. The method for measuring the weight average molecular weight is as follows.

< gel permeation chromatography >

Solvent: dichloromethane (dichloromethane)

Column: shodex K806, K805, K803G (3 pieces of Shodex K.K. manufactured by Showa Denko Co., ltd.)

Column temperature: 25 DEG C

Sample concentration: 0.1 mass%

A detector: RI Model 504 (GL SCIENCE company)

And (3) a pump: l6000 (Hitachi manufacturing Co., ltd.)

Flow rate: 1.0mL/min

Calibration curve: calibration curves based on 13 samples of standard polystyrene STK standard polystyrene (TOSOH (manufactured by TOSOH corporation)) in the range of mw=500 to 2800000 were used. The 13 samples are preferably used at substantially equal intervals.

Styrene- (meth) acrylate copolymer

Styrene- (meth) acrylate copolymers (hereinafter also referred to as styrene-acrylic resins) are excellent in transparency when used in a substrate film. Further, since the coefficient of hygroscopic expansion can be adjusted by the copolymerization ratio of the styrene moiety, by changing these ratios, curling as a laminate can be controlled.

The styrene-acrylic resin is formed by addition-polymerizing at least a styrene monomer and a (meth) acrylate monomer. Styrene monomer other than from CH ₂ ＝CH-C ₆ H ₅ In addition to styrene represented by the structural formula (I), the styrene derivative having a known side chain or functional group in the styrene structure is also included.

Furthermore, (meth) acrylate monomers, other than from CH (R) ₁ )＝CHCOOR ₂ (R ₁ Represents a hydrogen atom or a methyl group, R ₂ Alkyl group having 1 to 24 carbon atoms), and also includes acrylate derivatives and methacrylate derivatives having known side chains and functional groups in the structures of these esters.

Examples of styrene monomers include: styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, alpha-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2, 4-dimethylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene and p-n-dodecylstyrene.

Examples of (meth) acrylate monomers include: acrylic ester monomers such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate (2 EHA), stearyl acrylate, lauryl acrylate, and phenyl acrylate; methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate and other methacrylates.

In the present specification, "(meth) acrylate monomer" is a generic term for "acrylate monomer" and "methacrylate monomer" and means one or both of them. For example, "(meth) acrylic acid methyl ester" means one or both of "acrylic acid methyl ester" and "methacrylic acid methyl ester".

The number of the (meth) acrylate monomers may be 1 or more. For example, any one of the following may be used: the copolymer is formed by using a styrene monomer and more than 2 acrylate monomers, the copolymer is formed by using a styrene monomer and more than 2 methacrylate monomers, and the copolymer is formed by using a styrene monomer, an acrylate monomer and a methacrylate monomer in combination.

The weight average molecular weight (Mw) of the styrene-acrylic resin is preferably in the range of 5000 to 150000, more preferably in the range of 30000 to 120000, from the viewpoint of easy control of moldability.

The styrene-acrylic resin used in the present invention may be commercially available, and as an example, MS resin "TX320XL" manufactured by DENKA Co., ltd.

Rubber particle

In the substrate film of the present invention, particularly when a (meth) acrylic resin or a styrene- (meth) acrylate copolymer is used, rubber particles are preferably contained in a range of 40 to 85 mass% from the viewpoint of imparting toughness (flexibility) and improving crease resistance.

The rubber particles are particles containing a rubbery polymer. The rubbery polymer is a soft crosslinked polymer having a glass transition temperature of 20 ℃ or lower. Examples of such crosslinked polymers include: butadiene-based crosslinked polymers, (meth) acrylic crosslinked polymers, and organosiloxane-based crosslinked polymers. Among them, from the viewpoint of a small refractive index difference from the (meth) acrylic resin and less damage to the transparency of the substrate film, the (meth) acrylic crosslinked polymer is preferable, and the acrylic crosslinked polymer (acrylic rubbery polymer) is more preferable.

That is, the rubber particles are preferably particles containing the acrylic rubbery polymer (a).

Regarding the acrylic rubbery polymer (a):

the acrylic rubbery polymer (a) is a crosslinked polymer containing a structural unit derived from an acrylic acid ester as a main component. The inclusion thereof as a main component means that the content of structural units derived from acrylic esters is within a range described later. The acrylic rubbery polymer (a) is preferably a crosslinked polymer comprising structural units derived from an acrylic acid ester, structural units derived from other monomers copolymerizable therewith, and structural units derived from a polyfunctional monomer having 2 or more radical polymerizable groups (non-conjugated reactive double bonds) in 1 molecule.

The acrylic acid ester is preferably an alkyl acrylate having 1 to 12 carbon atoms such as methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, sec-butyl acrylate, isobutyl acrylate, benzyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate or the like. The number of acrylic acid esters may be 1 or 2 or more.

The content of the structural unit derived from the acrylic acid ester is preferably in the range of 40 to 80% by mass, more preferably in the range of 50 to 80% by mass, relative to the total structural units constituting the acrylic rubber-like polymer (a 1). When the content of the acrylic acid ester is within the above range, sufficient toughness is easily imparted to the protective film.

The copolymerizable other monomer is a monomer other than the polyfunctional monomer among the monomers copolymerizable with the acrylic acid ester. That is, the copolymerizable monomer does not have 2 or more radical polymerizable groups. Examples of copolymerizable monomers include: methacrylate esters such as methyl methacrylate; styrenes such as styrene and methylstyrene; (meth) acrylonitriles; (meth) acrylamides; (meth) acrylic acid. Among them, the other copolymerizable monomer preferably contains styrenes. The other copolymerizable monomer may be 1 or 2 or more.

The content of the structural unit derived from the other copolymerizable monomer is preferably in the range of 5 to 55 mass%, more preferably in the range of 10 to 45 mass%, relative to the total structural units constituting the acrylic rubbery polymer (a).

Examples of the polyfunctional monomer include allyl (meth) acrylate, triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl malate, divinyl adipate, divinylbenzene, ethylene glycol di (meth) acrylate, diethylene glycol (meth) acrylate, triethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, dipropylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate.

The content of the structural unit derived from the polyfunctional monomer is preferably in the range of 0.05 to 10 mass%, more preferably in the range of 0.1 to 5 mass%, relative to the total structural units constituting the acrylic rubbery polymer (a). If the content of the polyfunctional monomer is 0.05 mass% or more, the crosslinking degree of the obtained acrylic rubbery polymer (a) is easily increased, and therefore the hardness and rigidity of the obtained base film are not excessively impaired, and if it is 10 mass% or less, the toughness of the base film is less likely to be impaired.

The monomer composition constituting the acrylic rubbery polymer (a) can be measured, for example, by the peak area ratio detected by pyrolysis GC-MS.

The glass transition temperature (Tg) of the rubbery polymer is preferably 0℃or lower, more preferably-10℃or lower. When the glass transition temperature (Tg) of the rubbery polymer is 0℃or lower, the film can be given appropriate toughness. The glass transition temperature (Tg) of the rubbery polymer was measured in the same manner as described above.

The glass transition temperature (Tg) of the rubbery polymer can be adjusted depending on the composition of the rubbery polymer. For example, in order to lower the glass transition temperature (Tg) of the acrylic rubber-like polymer (a), it is preferable to increase the mass ratio of the acrylic ester having an alkyl group with a carbon number of 4 or more to the copolymerizable other monomer in the acrylic rubber-like polymer (a) (for example, 3 or more, preferably in the range of 4 to 10).

The particles containing the acrylic rubbery polymer (a) may be particles composed of the acrylic rubbery polymer (a) or particles having a hard layer composed of the hard crosslinked polymer (c) having a glass transition temperature of 20 ℃ or higher and a soft layer composed of the acrylic rubbery polymer (a) disposed around the hard layer (these are also referred to as "elastomers"); the acrylic graft copolymer particles may be obtained by polymerizing a mixture of monomers such as methacrylate in the presence of the acrylic rubbery polymer (a) for at least 1 stage. The particles composed of the acrylic graft copolymer may be core-shell type particles having a core portion containing the acrylic rubbery polymer (a) and a shell portion covering the same.

Regarding the core-shell rubber particles containing the acrylic rubbery polymer:

(core)

The core contains the acrylic rubbery polymer (a) and, if necessary, the hard crosslinked polymer (c). That is, the core may have a soft layer made of an acrylic rubber-like polymer and a hard layer made of a hard crosslinked polymer (c) disposed inside thereof.

The crosslinked polymer (c) may be a crosslinked polymer containing methacrylate as a main component. That is, the crosslinked polymer (c) is preferably a crosslinked polymer containing a structural unit derived from an alkyl methacrylate, a structural unit derived from another monomer copolymerizable therewith, and a structural unit derived from a polyfunctional monomer.

The alkyl methacrylate may be the alkyl methacrylate; other copolymerizable monomers may be the styrenes, acrylates, etc.; the polyfunctional monomer may be the same as the monomer mentioned as the polyfunctional monomer.

The content of the structural unit derived from the alkyl methacrylate may be in the range of 40 to 100 mass% with respect to the entire structural units constituting the crosslinked polymer (c). The content of the structural unit derived from the other copolymerizable monomer may be in the range of 60 to 0 mass% with respect to the total structural units constituting the other crosslinked polymer (c). The content of the structural unit derived from the polyfunctional monomer may be in the range of 0.01 to 10 mass% with respect to the total structural units constituting the other crosslinked polymer.

(Shell portion)

The shell portion comprises a methacrylic polymer (b) (other polymer) comprising a structural unit derived from methacrylate as a main component, grafted to the acrylic rubbery polymer (a). The inclusion thereof as a main component means that the content of structural units derived from methacrylate esters is within a range described later.

The methacrylate ester constituting the methacrylic polymer (b) is preferably an alkyl methacrylate having 1 to 12 carbon atoms in the alkyl group such as methyl methacrylate. The number of the methacrylates may be 1 or 2 or more.

The content of the methacrylate ester is preferably 50 mass% or more with respect to the entire structural units constituting the methacrylic polymer (b). When the content of the methacrylic acid ester is 50 mass% or more, compatibility with a methacrylic resin containing a structural unit derived from methyl methacrylate as a main component is easily obtained. From the above viewpoint, the content of the methacrylate ester is more preferably 70 mass% or more with respect to the entire structural units constituting the methacrylic polymer (b).

The methacrylic polymer (b) may further contain structural units derived from other monomers copolymerizable with the methacrylate ester. Examples of other copolymerizable monomers include: acrylic esters such as methyl acrylate, ethyl acrylate, and n-butyl acrylate; benzyl (meth) acrylate, dicyclopentanyl (meth) acrylate, phenoxyethyl (meth) acrylate, and the like, (meth) acrylic monomers having an alicyclic, heterocyclic, or aromatic ring (ring-containing (meth) acrylic monomers).

The content of the structural unit derived from the copolymerizable monomer is preferably 50% by mass or less, more preferably 30% by mass or less, relative to the total structural units constituting the methacrylic polymer (b).

In the present embodiment, when the base film is not stretched, the shape of the rubber particles may be a shape close to a spherical shape. That is, the aspect ratio of the rubber particles may be about 1 to 2 when the cross section or surface of the base film is observed.

The average particle diameter of the rubber particles is preferably in the range of 100 to 400 nm. When the average particle diameter of the rubber particles is 100nm or more, sufficient toughness and stress relaxation property are easily imparted to the base film, and when the average particle diameter is 400nm or less, the transparency of the base film is less likely to be impaired. From the same viewpoint, the average particle diameter of the rubber particles is more preferably in the range of 150 to 300 nm.

The average particle diameter of the rubber particles can be calculated by the following method.

The average particle diameter of the rubber particles can be measured as an average value of the circle equivalent diameters of 100 particles obtained by SEM photography or TEM photography of the surface or slice of the base film. The circle equivalent diameter can be obtained by converting the projected area of the particles obtained by imaging into a diameter of a circle having the same area. At this time, rubber particles observed by SEM observation and/or TEM observation at a magnification of 5000 times were used for calculation of the average particle diameter.

The content of the rubber particles is not particularly limited, but is preferably in the range of 40 to 85 mass% with respect to the base film, and more preferably in the range of 45 to 75 mass%.

< cycloolefin resin >

The cycloolefin resin used for the base film is preferably a polymer of cycloolefin monomer or a copolymer of cycloolefin monomer and a copolymerizable monomer other than the cycloolefin monomer.

The cycloolefin monomer is preferably a cycloolefin monomer having a norbornene skeleton, and more preferably a cycloolefin monomer having a structure represented by the following general formula (A-1) or (A-2).

[ chemical formula 1]

General formula (A-1)

In the general formula (A-1), R ¹ ～R ⁴ Each independently represents a hydrogen atom, a hydrocarbon group having 1 to 30 carbon atoms, or a polar group. p represents an integer of 0 to 2. Wherein R is ¹ ～R ⁴ Not all of them simultaneously represent hydrogen atoms, R ¹ And R is ² Not simultaneously representing hydrogen atoms, R ³ And R is ⁴ Not simultaneously representing hydrogen atoms.

As R in the general formula (A-1) ¹ ～R ⁴ The hydrocarbyl group having 1 to 30 carbon atoms represented is, for example, preferably a hydrocarbyl group having 1 to 10 carbon atoms, and more preferably a hydrocarbyl group having 1 to 5 carbon atoms. Carbon sourceThe hydrocarbon group having a number of 1 to 30 may also have a linking group containing, for example, a halogen atom, an oxygen atom, a nitrogen atom, a sulfur atom or a silicon atom. Examples of such a linking group include a polar group having a valence of 2 such as a carbonyl group, an imino group, an ether bond, a silyl ether bond, a thioether bond, or the like. Examples of the hydrocarbon group having 1 to 30 carbon atoms include methyl, ethyl, propyl, butyl and the like.

R in the general formula (A-1) ¹ ～R ⁴ Examples of the polar group represented include carboxyl group, hydroxyl group, alkoxy group, alkoxycarbonyl group, aryloxycarbonyl group, amino group, amide group, and cyano group. Among them, carboxyl group, hydroxyl group, alkoxycarbonyl group and aryloxycarbonyl group are preferable, and alkoxycarbonyl group and aryloxycarbonyl group are preferable from the viewpoint of securing solubility at the time of solution film formation.

From the viewpoint of improving the heat resistance of the optical film, p in the general formula (a-1) is preferably 1 or 2. This is because when p is 1 or 2, the steric hindrance of the resulting polymer becomes high, and the glass transition temperature tends to be high. In addition, the laminate has an advantage that it can react slightly to humidity and can easily control the curl balance as a laminate.

[ chemical formula 2]

General formula (A-2)

In the general formula (A-2), R ⁵ Represents a hydrogen atom, a hydrocarbon group having 1 to 5 carbon atoms, or an alkylsilyl group having an alkyl group having 1 to 5 carbon atoms. R is R ⁶ Represents a carboxyl group, a hydroxyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amide group, a cyano group or a halogen atom (fluorine atom, chlorine atom, bromine atom or iodine atom). p represents an integer of 0 to 2.

R in the general formula (A-2) ⁵ Preferably a hydrocarbon group having 1 to 5 carbon atoms, more preferably a hydrocarbon group having 1 to 3 carbon atoms.

R in the general formula (A-2) ⁶ Preferably represents a carboxyl group, a hydroxyl group, an alkoxycarbonyl group or an aryloxycarbonyl group, and more preferably from the viewpoint of securing solubility in solution film formationAlkoxycarbonyl and aryloxycarbonyl.

From the viewpoint of improving the heat resistance of the optical film, p in the general formula (a-2) preferably represents 1 or 2. This is because when p represents 1 or 2, the steric hindrance of the resulting polymer becomes high, and the glass transition temperature tends to be high.

From the viewpoint of improving the solubility in an organic solvent, cycloolefin monomers having a structure represented by the general formula (A-2) are preferable. In general, an organic compound has reduced crystallinity by breaking symmetry, and thus has improved solubility in an organic solvent. R in the general formula (A-2) ⁵ And R is ⁶ Since the substitution is performed only on the ring constituting carbon atom on the side of the symmetry axis of the molecule, the symmetry of the molecule is low, that is, the solubility of the cycloolefin monomer having the structure represented by the general formula (A-2) is high, and thus the method is suitable for producing an optical film by solution casting.

The content of the cycloolefin monomer having the structure represented by the general formula (A-2) in the polymer of the cycloolefin monomer may be, for example, 70 mol% or more, preferably 80 mol% or more, and more preferably 100 mol% based on the total of all cycloolefin monomers constituting the cycloolefin resin. When the cycloolefin monomer having a structure represented by the general formula (A-2) is contained at least in a certain amount, the orientation of the resin is improved, and thus the value of the retardation (phase retardation) is liable to rise.

Specific examples of cycloolefin monomers having a structure represented by the general formula (A-1) are shown in example compounds 1 to 14, and specific examples of cycloolefin monomers having a structure represented by the general formula (A-2) are shown in example compounds 15 to 34.

[ chemical formula 3]

Examples of copolymerizable monomers copolymerizable with cycloolefin monomers include: a copolymerizable monomer ring-opening copolymerizable with a cycloolefin monomer, a copolymerizable monomer addition-copolymerizable with a cycloolefin monomer, and the like.

Examples of the ring-opening copolymerizable monomer include: cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, dicyclopentadiene, and the like.

Examples of addition copolymerizable comonomers include: compounds containing an unsaturated double bond, vinyl cyclic hydrocarbon monomers, and (meth) acrylic esters. Examples of the compound containing an unsaturated double bond include olefin compounds having 2 to 12 carbon atoms (preferably 2 to 8), and examples thereof include ethylene, propylene, butene and the like. Examples of vinyl-based cyclic hydrocarbon monomers include: vinyl cyclopentene monomers such as 4-vinyl cyclopentene and 2-methyl-4-isopropenyl cyclopentene. Examples of (meth) acrylates include: alkyl (meth) acrylates having 1 to 20 carbon atoms such as methyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and cyclohexyl (meth) acrylate.

The content of the cycloolefin monomer in the copolymer of the cycloolefin monomer and the copolymerizable monomer may be, for example, 20 to 80mol%, and preferably 30 to 70mol% based on the total of all the monomers constituting the copolymer.

As described above, the cycloolefin resin is a polymer obtained by polymerizing or copolymerizing a cycloolefin monomer having a norbornene skeleton, preferably a cycloolefin monomer having a structure represented by the general formula (A-1) or (A-2), and examples thereof include the following.

1) Ring-opened polymers of cycloolefin monomers

2) Ring-opened copolymer of cycloolefin monomer and copolymerizable monomer ring-opened copolymerizable therewith

3) The hydrogenated compound of the ring-opened (co) polymer of 1) or 2)

4) Cyclizing the ring-opened (co) polymer of 1) or 2) by Friedel Crafts reaction, and then hydrogenating to obtain (co) polymer

5) Saturated copolymers of cycloolefin monomers with compounds containing unsaturated double bonds

6) Addition copolymer of cycloolefin monomer and vinyl cyclic hydrocarbon monomer and hydrogenated product thereof

7) Alternating copolymers of cycloolefin monomers with (meth) acrylic esters

The polymers of 1) to 7) can be obtained by a known method, for example, the method described in Japanese patent application laid-open No. 2008-107534, and Japanese patent application laid-open No. 2005-227606. For example, the catalyst or solvent used in the ring-opening copolymerization of the above 2) may be any one described in paragraphs 0019 to 0024 of Japanese patent application laid-open No. 2008-107534. The catalysts used in the hydrogenation of 3) and 6) may be, for example, those described in paragraphs 0025 to 0028 of Japanese patent application laid-open No. 2008-107534. The acidic compound used in the Friedel Crafts reaction of 4) may be, for example, one described in paragraph 0029 of Japanese patent application laid-open No. 2008-107534. The catalysts used in the addition polymerization of 5) to 7) may be those described in paragraphs 0058 to 0063 of JP 2005-227606A. The alternating copolymerization of 7) can be carried out, for example, by the methods described in paragraphs 0071 and 0072 of Japanese patent application laid-open No. 2005-227606.

Among them, the polymers of 1) to 3) and 5) are preferable, and the polymers of 3) and 5) are more preferable. That is, the cycloolefin resin preferably contains at least one of the structural unit represented by the following general formula (B-1) and the structural unit represented by the following general formula (B-2), more preferably contains only the structural unit represented by the general formula (B-2), or contains both the structural unit represented by the general formula (B-1) and the structural unit represented by the general formula (B-2), from the viewpoint of being capable of increasing the glass transition temperature of the resulting cycloolefin resin and improving the light transmittance. The structural unit represented by the general formula (B-1) is a structural unit derived from the cycloolefin monomer represented by the general formula (A-1), and the structural unit represented by the general formula (B-2) is a structural unit derived from the cycloolefin monomer represented by the general formula (A-2).

[ chemical formula 4]

General formula (B-1)

In the general formula (B-1), X represents-CH=CH-or-CH =CH- ₂ CH ₂ -。R ¹ ～R ⁴ And p is independently R of the formula (A-1) ¹ ～R ⁴ And p is synonymous.

[ chemical formula 5]

General formula (B-2)

In the general formula (B-2), X represents-CH=CH-or-CH =CH- ₂ CH ₂ -。R ⁵ ～R ⁶ And p is independently R of the formula (A-2) ⁵ ～R ⁶ And p is synonymous.

The cycloolefin resin used in the present invention may be commercially available. Examples of commercial products of cycloolefin resins include ARTON (ARTON) G (e.g., G7810, etc.), ARTONF, ARTONR (e.g., R4500, R4900, R5000, etc.), and ARTONRX (e.g., RX4500, etc.), manufactured by JSR (co.).

Intrinsic viscosity [ eta ] of cycloolefin resin]inh is preferably 0.2 to 5cm in a measurement at 30 DEG C ³ In the range of/g, more preferably 0.3 to 3cm ³ In the range of/g, it is more preferably 0.4 to 1.5cm ³ In the range of/g.

The number average molecular weight (Mn) of the cycloolefin resin is preferably 8000 to 100000, more preferably 10000 to 80000, and even more preferably 12000 to 50000. The weight average molecular weight (Mw) of the cycloolefin resin is preferably in the range of 20000 to 300000, more preferably in the range of 30000 to 250000, and even more preferably in the range of 40000 to 200000. The number average molecular weight and the weight average molecular weight of the cycloolefin resin can be measured by converting the cycloolefin resin into polystyrene by Gel Permeation Chromatography (GPC).

When the intrinsic viscosity [ eta ] inh, the number average molecular weight and the weight average molecular weight are within the above-mentioned ranges, the cycloolefin resin is excellent in heat resistance, water resistance, chemical resistance, mechanical properties and moldability as a base film.

The cycloolefin resin has a glass transition temperature (Tg) of usually 110℃or higher, preferably 110 to 350℃and more preferably 120 to 250℃and still more preferably 120 to 220 ℃. When Tg is 110℃or higher, deformation under high-temperature conditions is easily suppressed. On the other hand, when Tg is 350 ℃ or lower, molding processing becomes easy, and deterioration of the resin due to heat during molding processing is easily suppressed.

The content of the cycloolefin resin is preferably 70% by mass or more, more preferably 80% by mass or more, relative to the base film.

Microparticle

When cycloolefin resin is used as the base film of the present invention, fine particles are preferably contained.

As the fine particles used in the present invention, examples of the inorganic compound include: silica, titania, alumina, zirconia, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. In addition, fine particles of an organic compound can be preferably used. As examples of the organic compound, there may be mentioned: polytetrafluoroethylene, cellulose acetate, polystyrene, polymethyl methacrylate, polypropylene, polymethyl acrylate, polyethylene carbonate, styrene-based acrylic resin, polysiloxane-based resin, polycarbonate resin, benzoguanamine-based resin, melamine-based resin, polyolefin-based powder, polyester-based resin, polyamide-based resin, polyimide-based resin, fluorinated ethylene-based resin, crushed fractions of organic polymer compounds such as starch, and polymer compounds synthesized by suspension polymerization.

From the viewpoint of reducing turbidity, the fine particles preferably contain silicon, and particularly preferably silicon dioxide, and for example, trade names commercially available as AEROSIL R972, R972V, R974, R812, 200V, 300, R202, OX50, TT600 (manufactured by japan AEROSIL (ltd) above) can be used.

< polyimide resin >

The polyimide-based resin may be a polymerization reactant of tetracarboxylic dianhydride and diamine.

The tetracarboxylic dianhydride may be any of aromatic tetracarboxylic dianhydride, aliphatic tetracarboxylic dianhydride, and alicyclic tetracarboxylic dianhydride, and is preferably aromatic tetracarboxylic dianhydride. The diamine may be any of aromatic diamine, aliphatic diamine, and alicyclic diamine, and is preferably aromatic diamine.

The weight average molecular weight Mw of the polyimide resin is not particularly limited, but is preferably in the range of 10 to 30 tens of thousands, more preferably 13 to 25 tens of thousands, from the viewpoint of improving the toughness of the base film and preventing breakage due to the transport tension. The method for measuring the weight average molecular weight Mw of the polyimide-based resin is the same as described above.

The content of the polyimide-based resin is preferably 60 mass% or more, more preferably 70 mass% or more, relative to the base film.

[1.3] physical Properties

Phase differences Ro and Rt

The base film of the present invention may be laminated on the surface of a polarizer and function as an optical film such as a retardation film.

The substrate film is preferably used as a retardation film for the IPS mode, and the retardation Ro in the in-plane direction measured in an environment of a measurement wavelength of 590nm, 23 ℃ and 55% rh is preferably in the range of 0 to 10nm, more preferably in the range of 0 to 5 nm. The retardation Rt of the base film in the thickness direction is preferably in the range of-40 to 40nm, more preferably in the range of-25 to 25 nm.

Ro and Rt are defined by the following formulas, respectively.

Formula (a): ro= (n) _x -n _y )×d

Formula (b): rt= ((n) _x +n _y )/2-n _z )×d

(in the formula (I),

n _x refractive index in the in-plane slow axis direction (direction of maximum refractive index) of the base material film

n _y Refractive index in a direction perpendicular to the in-plane slow axis of the base film

n _z Indicating the refractive index of the base film in the thickness direction

d represents the film thickness (nm) of the base material film. )

The in-plane slow axis of the substrate film was confirmed by an automatic birefringence meter Axo scan (Axo Scan MuellerMatrix Polarimeter: manufactured by AXOMETRICS Co.).

Ro and Rt can be determined by the following method.

1) The substrate film was conditioned at 23℃and 55% RH for 24 hours. The average refractive index of the film was measured by an Abbe refractometer, and the film thickness d was measured by a commercially available micrometer.

2) An automatic birefringence meter Axo scan (Axo Scan Mueller Matrix Polarimeter: AXOMETRICS Co.) was used to measure the phase retardation Ro and Rt of the humidity-controlled film at a measurement wavelength of 590 nm.

The retardation Ro and Rt of the base film can be adjusted according to, for example, the type of resin, stretching conditions, and drying conditions. For example, rt can be reduced by increasing the drying temperature.

[1.4] Process for producing substrate film

The form of the base film of the present invention is not particularly limited, and may be, for example, a tape-like form. That is, the base film of the present invention is preferably wound in a roll shape in a direction perpendicular to the width direction thereof to form a roll.

[ method of production ]

The method for producing a base film of the present invention comprises: 1) A step of obtaining a solution for a base material film; 2) A step of applying the obtained substrate film solution to the surface of a support; 3) And removing the solvent from the solution for the substrate film to form the substrate film.

1) Step of obtaining a solution for a base film

A solution (also referred to as a "dope") for a substrate film including the resin and a solvent is prepared.

The solvent used for the solution for a base film is not particularly limited as long as it can satisfactorily disperse or dissolve the resin. For example, examples of the organic solvent used in the present invention include: alcohols (methanol, ethanol, diols, triols, tetrafluoropropanol, etc.), glycols, cellosolves, ketones (acetone, methyl ethyl ketone, etc.), carboxylic acids (formic acid, acetic acid, etc.), carbonates (ethylene carbonate, propylene carbonate, etc.), esters (ethyl acetate, propyl acetate, etc.), ethers (isopropyl ether, THF, etc.), amides (dimethyl sulfoxide, etc.), hydrocarbons (heptane, etc.), nitriles (acetonitrile, etc.), aromatics (cyclohexylbenzene, toluene, xylene, chlorobenzene, etc.), haloalkyl (dichloromethane (also called "methylene chloride", etc.), amines (1, 4-diazabicyclo [2.2.2] octane, diazabicycloundecene, etc.), lactones, etc.

Among them, a solvent for a base film having a boiling point of 100 ℃ or less at atmospheric pressure is preferable as a chlorine-based solvent, more specifically, dichloromethane (also referred to as "methylene chloride") from the viewpoint of easy handling, and when a dope for a base film is prepared and a film is formed. This is preferable in terms of high solubility and high drying speed when preparing a dope for a base film and forming a film, and thus, the film quality of a coating film can be adjusted. In addition, a hydrophilic solvent may be added. Examples of the hydrophilic solvent include ketones and alcohols, and alcohols are preferable. More preferably isopropanol, ethanol, methanol, etc., most preferably methanol. The amount to be added is preferably in the range of 1 to 20% by mass, more preferably in the range of 3 to 10% by mass.

The resin concentration of the solution for a base film is preferably in the range of 1.0 to 20 mass%, for example, from the viewpoint of easy adjustment of the viscosity to the range described later. In addition, from the viewpoint of reducing the shrinkage amount at the time of drying of the coating film, the resin concentration of the solution for a base film is preferably high, more preferably more than 5% by mass and 20% by mass or less, and still more preferably more than 5% by mass and 15% by mass or less. Further, by adjusting the concentration of the solution, the time until the film is formed can be shortened, and the drying time thereof can also be a means for controlling the surface state of the base film. For the purpose of increasing the concentration, a mixed solvent may be suitably used.

The viscosity of the solution for a base film is not particularly limited as long as it can form a base film having a desired film thickness, and is preferably in the range of 5 to 5000mpa·s, for example. If the viscosity of the solution for a base film is 5mpa·s or more, a base film having a suitable film thickness is easily formed, and if it is 5000mpa·s or less, occurrence of film thickness unevenness due to an increase in the viscosity of the solution can be suppressed. From the same viewpoint, the viscosity of the solution for a base film is more preferably in the range of 100 to 1000mpa·s. The viscosity of the solution for a substrate film can be measured at 25℃with an E-type viscometer.

2) Step of applying solution for substrate film

Next, the obtained solution for a substrate film is applied to the surface of the support. Specifically, the obtained solution for a substrate film is applied to the surface of a support. The laminate of the support and the base film is also referred to as a "laminate film".

Support body

The support is an object that supports the substrate film when it is formed, and generally includes a resin film. The film thickness of the support is preferably 50 μm or less. The film thickness of the support is a thin film, but the support needs a certain degree of strength (waist and rigidity), and therefore is preferably in the range of 15 to 45 μm, and more preferably in the range of 20 to 40 μm.

Examples of the resin used include cellulose ester resins, cycloolefin resins, polypropylene resins, acrylic resins, polyester resins, polyarylate resins, and styrene resins or composite resins thereof, and among these, polyester resins are preferable as resins excellent in storage stability under a high humidity environment.

Examples of the resin film include: among them, a polyester resin film containing polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) is preferable from the viewpoint of easy handling.

The resin film may be a film after heat treatment (heat relaxation) or a film after stretching treatment.

The heat treatment is not particularly limited, and may be performed in the range of (tg+60) to (tg+180) degrees celsius when the glass transition temperature of the resin constituting the resin film is Tg, in order to reduce the residual stress of the resin film (for example, residual stress accompanying stretching).

The stretching treatment is preferably performed in the biaxial direction of the resin film, for example, in order to increase the residual stress of the resin film. The stretching treatment may be performed under any conditions, and may be performed at a stretching ratio of about 120 to 900%, for example. Whether the resin film is stretched or not can be confirmed by, for example, whether or not there is an in-plane slow axis (axis extending in the direction of the refractive index maximum). The stretching treatment may be performed before laminating the base film, or may be performed after laminating, and stretching is preferably performed before laminating.

As the polyester resin film (also simply referred to as a polyester film), commercially available ones can be used, and for example, polyethylene terephthalate film TN100 (manufactured by Toyobo Co., ltd.), MELINEX ST504 (manufactured by TEIJIN DUP ONT FILMS Co.) and the like can be preferably used.

The support may also have a release layer provided on the surface of the resin film. The release layer can easily peel the support from the base film at the time of preparing the cover member.

The release layer may contain a known release agent, and is not particularly limited. Examples of the release agent contained in the release layer include silicone-based release agents and non-silicone-based release agents.

Examples of the silicone-based release agent include known silicone-based resins. Examples of non-silicone based release agents include: long-chain alkyl suspension polymers obtained by reacting long-chain alkyl isocyanates with polyvinyl alcohol or ethylene-vinyl alcohol copolymers, olefin resins (e.g., copolymerized polyethylene, cyclic polyolefin, polymethylpentene), polyarylate resins (e.g., polycondensates of aromatic dicarboxylic acid components and dihydric phenol components), fluorine resins (e.g., polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), PF a (copolymer of tetrafluoroethylene and perfluoroalkoxyethylene), FEP (copolymer of tetrafluoroethylene and hexafluoropropylene), ETFE (copolymer of tetrafluoroethylene and ethylene), and the like.

The thickness of the release layer is not particularly limited as long as it can exhibit a desired peelability, and is, for example, in the range of 0.1 to 1.0 μm.

The support may contain a plasticizer as an additive. The plasticizer is not particularly limited, and is preferably selected from a polyol ester plasticizer, a phthalate plasticizer, a citric acid plasticizer, a fatty acid ester plasticizer, a phosphate plasticizer, a polycarboxylic acid ester plasticizer, a polyester plasticizer, and the like.

The support may contain an ultraviolet absorber. Examples of the ultraviolet absorber used include: and an absorber of benzotriazole, 2-hydroxybenzophenone or salicylic acid phenyl ester. For example, there may be mentioned: triazoles such as 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [ 2-hydroxy-3, 5-bis (. Alpha.,. Alpha. -dimethylbenzyl) phenyl ] -2H-benzotriazole, 2- (3, 5-di-t-butyl-2-hydroxyphenyl) benzotriazole, and benzophenones such as 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, and 2,2' -dihydroxy-4-methoxybenzophenone.

In addition, the support used in the present invention preferably contains fine particles in order to improve the transport property.

As the fine particles, as examples of the inorganic compound, there are given: silica, titania, alumina, zirconia, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. In addition, fine particles of an organic compound can be preferably used. As examples of the organic compound, use may be made of: polytetrafluoroethylene, cellulose acetate, polystyrene, polymethyl methacrylate, polypropylene, polymethyl acrylate, polyethylene carbonate, styrene-based acrylic resin, polysiloxane-based resin, polycarbonate resin, benzoguanamine-based resin, melamine-based resin, polyolefin-based powder, polyester-based resin, polyamide-based resin, polyimide-based resin, fluorinated ethylene-based resin, crushed fractions of an organic polymer compound such as starch, and a polymer compound synthesized by a suspension polymerization method.

As a method for producing the support used in the present invention, a usual production method such as a blow molding method, a T-die method, a rolling method, a cutting method, a casting method, an emulsion method, a hot pressing method, or the like can be used, and from the viewpoint of suppressing coloration, suppressing defects of foreign matter, suppressing optical defects such as a die line, or the like, the film production method is preferably a solution casting method or a melt casting method. In addition, since the temperature in the processing step is low in the case of the solution casting method, it is possible to impart high functionality by using various additives.

In the case of producing a film by solution casting, the method for producing a support preferably includes: a step of preparing a dope by dissolving and dispersing an additive such as a thermoplastic resin and the fine particles in a solvent (dissolution step; dope preparation step); a step of casting the dope onto an endless metal support (casting step); a step of drying the cast dope as a web (solvent evaporation step); a step of peeling from the metal support (peeling step); drying, stretching, and maintaining the width (stretching-maintaining the width-drying step); and a step (winding step) of winding the completed film into a roll.

The substrate film of the present invention is preferably formed by the following method using the support manufactured as described above.

The method of applying the solution for a base film is not particularly limited, and for example, a known method such as a back coating method, a gravure coating method, a spin coating method, a wire rod coating method, or a roll coating method can be used. Among them, back coating (Back coat method) is preferable in that a thin and uniform film thickness of the coating film can be formed.

3) Step of Forming base film

Next, the solvent is removed from the solution for a substrate film applied to the support, thereby forming a substrate film.

Specifically, the solution for the substrate film applied to the support is dried. Drying may be performed by, for example, blowing or heating. Among them, from the viewpoint of easily suppressing curling of the base material film, it is preferable to dry the base material film by blowing air, and from the viewpoint of controlling the film thickness deviation described below, it is preferable to form a difference in air velocity between the initial drying stage and the latter half of drying. Specifically, the higher the initial wind speed, the larger the film thickness deviation tends to become, and the lower the initial wind speed, the smaller the film thickness deviation tends to become.

Therefore, by adjusting the drying conditions (for example, the drying temperature, the drying air volume, the drying time, and the like), the density of the base material film can be controlled, and the film thickness of the base material film can be adjusted so as to satisfy the following formula 1.

Formula 1: average value (B) -average film thickness value (A) |/average film thickness value (A) ×100 < 20 (%)

Here, the average film thickness value (a) is an average value of film thickness values of 10 points randomly selected from the film.

When the value represented by the formula 1 is set to be more than 5%, the surface is provided with appropriate irregularities, and the effect of improving the adhesion to the upper layer can be obtained, and when the value is set to be less than 20%, the irregularities on the surface are not excessively large, and the coating property and smoothness of the upper layer are not affected.

As a film thickness measurement, a commercially available film thickness-keeping measuring apparatus can be used, and for example, F20-UV (manufactured by FILMETRICS Co.) can be used as a film thickness measuring system.

The variation in film thickness of the base film is preferably adjusted to be within the range of 0.5.+ -. 0.2. Mu.m. From the viewpoint of improving adhesion to the upper layer, the film quality is preferably adjusted in a direction of thinning, specifically, the drying rate is preferably increased, and it is preferably 0.0015 to 0.05 kg/hr.m ² More preferably 0.002 to 0.05 kg/hr.m ² Within a range of (2).

The drying speed is expressed as: mass of solvent evaporated per unit time per unit area. The drying speed can generally be adjusted by the drying temperature. The drying temperature depends on the kind of the solvent used, and may be, for example, in the range of 50 to 200 ℃ (Tb-50 to Tb+50) DEG C with respect to the boiling point Tb of the solvent used). The temperature control may be performed in multiple stages. The drying rate and the film quality can be controlled by drying at a higher temperature after drying to a certain extent.

As described above, the base film of the present embodiment may be in a band shape. Therefore, the method for producing a laminated film according to the present embodiment preferably further includes: 4) And winding the strip-shaped laminated film into a roll shape to form a roll.

4) Winding a base film to obtain a roll

The obtained band-shaped base material film was wound into a roll shape in a direction perpendicular to the width direction thereof, and a roll was produced.

The length of the band-shaped base film is not particularly limited, and may be, for example, about 100 to 10000 m. The width of the strip-shaped laminated film is preferably 1m or more, and more preferably in the range of 1.1 to 4 m. From the viewpoint of improving the uniformity of the film, the range of 1.3 to 2.5m is more preferable.

[ manufacturing apparatus ]

The method for producing a base film used in the present invention can be carried out by, for example, a production apparatus shown in fig. 3.

Fig. 3 is a schematic diagram of a manufacturing apparatus B200 for performing the method for manufacturing a base film according to the present embodiment. The manufacturing apparatus B200 includes a supply unit B210, an application unit B220, a drying unit B230, a cooling unit B240, and a winding unit B250.Ba to Bd denote conveying rollers that convey the support B110.

The supply unit B210 includes a feeding device (not shown) for feeding the roll B201 of the band-shaped support B110 wound around the winding core.

The coating unit B220 is a coating apparatus, and includes: a support roller B221 for holding the support body B110, a coating head B222 for coating the support body B110 held by the support roller B221 with a solution for a substrate film, and a decompression chamber B223 provided on the upstream side of the coating head B222.

The flow rate of the solution for the substrate film discharged from the coating head B222 can be adjusted by a pump not shown. The flow rate of the base material film solution discharged from the coating head B222 is set to an amount that can stably form a coating layer of a predetermined film thickness when continuously coated under the conditions of the coating head B222 adjusted in advance.

The decompression chamber B223 is a mechanism for stabilizing beads (accumulation of coating liquid) formed between the substrate film solution from the coating head B222 and the support B110 at the time of coating, and can adjust the degree of decompression. The decompression chamber B223 is connected to a decompression blower (not shown), and the inside is decompressed. The decompression chamber B223 is in a state of no air leakage, and the gap with the support roller is also adjusted to be narrow, so that stable beads of the coating liquid can be formed.

The drying unit B230 is a drying device for drying a coating film applied on the surface of the support B110, and includes a drying chamber B231, an inlet B232 for a drying gas, and an outlet B233. The temperature and the air volume of the drying air are appropriately determined according to the type of the coating film and the type of the support B110. The amount of residual solvent in the dried coating film can be adjusted by setting the temperature of the drying air, the air volume, the drying time, and other conditions in the drying unit B230. The residual solvent content of the dried coating film can be measured by comparing the unit mass of the dried coating film with the mass of the coating film after sufficient drying.

(residual solvent amount)

Since the base film is obtained by coating a solution for the base film, a solvent derived from the solution may remain. The amount of the residual solvent can be controlled by using the solvent/coating liquid concentration, the air speed during drying of the substrate film, the drying temperature/time, the conditions of the drying chamber (external air, internal air circulation), the heating temperature of the back roller at the time of coating, and the like.

As described above, when dried at a high speed, the film becomes sparse, and the surface state can be controlled.

From the viewpoint of the curl balance of the base film, the residual solvent amount of the base film is S ₁ When the compound satisfies the following formula 2.

Formula 2:10<S ₁ <1000(ppm)

Specifically, the residual solvent amount of the base film is more preferably less than 800ppm, and in view of the curl balance of the base film, it is more preferably less than 500 to 700ppm. In addition, by selecting a solvent-coating process in which a solvent remains in the support, adhesion between the support and the substrate film can be improved. The residual solvent amount of the support is preferably in the range of 10 to 100 ppm.

The residual solvent amounts of the support and substrate film can be determined by headspace gas chromatography. In headspace gas chromatography, a sample is sealed in a container, heated, and the gas in the container is rapidly injected into a gas chromatograph with the container filled with volatile components, and mass spectrometry is performed to determine the volatile components while determining the compounds. In the headspace method, the full peak of the volatile component can be observed by a gas chromatograph, and the volatile substance, the monomer, and the like can be simultaneously quantified with high accuracy by using an analysis method using electromagnetic interaction.

The cooling unit B240 cools the temperature of the support B110 having the coating film (base film) obtained by drying in the drying unit B230 to an appropriate temperature. The cooling unit B240 includes a cooling chamber B241, a cooling air inlet B242, and a cooling air outlet B243. The temperature and the air volume of the cooling air can be appropriately determined according to the type of the coating film and the type of the support B110. In addition, in the case where an appropriate cooling temperature can be achieved even if the cooling unit B240 is not provided, the cooling unit B240 may not be provided.

The winding unit B250 is a winding device (not shown) for winding the support B110 on which the base film is formed to obtain a roll B251.

[2] Transparent substrate

The term "transparent" as used herein means that the total light transmittance measured after humidity is adjusted at 23℃and 55% RH is 80% or more, preferably 85% or more, more preferably 90% or more, and particularly preferably 95% or more. The total light transmittance can be measured according to JIS 7573 (determination of plastic-total light transmittance and total light reflectance).

The transparent substrate of the present invention is a transparent substrate having flexibility (flexi ability) with a thickness of 5 μm or more and less than 50 μm. If the thickness is less than 5 μm, the strength cannot be maintained, so that the breakage rate during processing is high, the yield is rapidly deteriorated, and the durability such as breakage with repeated opening and closing of the display is poor. When the thickness is 50 μm or more, the overall thickness of the lid member becomes too thick, and flexibility (occurrence of cracks and the like), weight and the like are poor, so that it is necessary to fall within the above-mentioned range. More preferably, the thickness is 10 μm or more and less than 30 μm.

In the transparent substrate of the present invention, the elastic modulus is preferably in the range of 55 to 80GPa, and the ratio of the elastic modulus of the transparent substrate to the elastic modulus of the substrate film (elastic modulus of the transparent substrate/elastic modulus of the substrate film) is preferably 30 or more. This is because, in order to use a transparent substrate having a low elastic modulus due to the thinning, a cover member having an improved press-in strength and no crease is provided, and by using a substrate film having a lower elastic modulus, that is, by setting the value of the ratio of elastic modulus (elastic modulus of the transparent substrate/elastic modulus of the substrate film) to 30 or more with respect to the transparent substrate, the protective function of the transparent substrate can be further improved.

< determination of modulus of elasticity >

The elastic modulus (also referred to as tensile elastic modulus) of the substrate film and the transparent substrate was determined by linear regression with a strain of 0.05 to 0.25%, as follows.

Regarding the MD direction, the tensile elastic modulus was measured according to JIS K7127 (1999) by the following method.

1) The substrate film or the transparent substrate was cut into a size of 100mm (MD direction). Times.10 mm (TD direction) as a test piece.

2) The test piece was stretched at a stretching speed of 50mm/min in the longitudinal direction (MD direction) of the test piece by using a universal tensile tester RTC-1225A manufactured by ORIENTEC, the distance between chucks was set to 50mm, and the tensile elastic modulus in the MD direction was measured. The measurement was performed at 23℃and 55% RH.

[2.1] glass substrate

The transparent substrate of the present invention is preferably a thin glass substrate from the viewpoint of excellent durability, flatness, etc., and examples thereof include soda lime glass, silicate glass, etc., preferably silicate glass, more preferably silica glass or borosilicate glass, specifically.

The glass constituting the glass substrate is alkali-free glass substantially free of alkali components, and specifically, glass having an alkali component content of 1000ppm or less is preferable. The content of the alkali component in the glass substrate is preferably 500ppm or less, more preferably 300ppm or less. The glass substrate containing the alkali component is likely to undergo a sodium blow phenomenon by cation substitution on the film surface. Thus, the density of the film surface layer is easily reduced, and the glass substrate is easily broken.

The glass substrate may be formed by a generally known method, such as a float process, a downdraw process, an overflow downdraw process, and the like. Among them, the overflow downdraw method is preferable from the viewpoint that the surface of the glass substrate is not in contact with the molding member during molding and the surface of the obtained glass substrate is less likely to be damaged.

The glass substrate used in the present invention can be obtained by grinding a thick glass such as borosilicate glass to a desired thickness, for example, but it is difficult to obtain a glass substrate of less than 200 μm by grinding and polishing a thick glass sheet.

Therefore, in order to obtain the glass substrate of the present invention having a thickness of 5 μm or more and less than 50 μm, a special float method is preferably used.

The thinner the thickness, the more difficult it is to handle and process the extremely thin glass sheet, and the lower the strength of the glass, the higher the probability of breakage. In order to facilitate handling and processing of a thin glass substrate, a method has been proposed in which a thin glass substrate is processed while being temporarily bonded to a thicker support substrate (hereinafter also referred to as a "carrier substrate"), and the support substrate is peeled off as a step after the processing to obtain the thin glass substrate.

For example, according to the international publication No. 2017/066924, soda lime glass having a thickness of less than 100 μm can be produced by the following process.

(step 1) a step of forming the 1 st surface of the glass base material 22 so that the 1 st surface of the glass base material 22 is in contact with the glass carrier substrate having the joint surface, and adhering a contact film (also referred to as "contact film") having an adhesive force to the 2 nd surface on the opposite side of the 1 st surface.

That is, the method for producing a glass substrate includes, as shown in fig. 4 (step 1): and a step of forming the 1 st surface of the glass base material 22 by injecting a material for forming the glass base material to a desired thickness on the carrier substrate 21 having a sufficient strength and a thickness that is easy to process, and then attaching the contact film 23 to the 2 nd surface on the opposite side of the glass base material 22 so as to contact the carrier substrate 21.

(step 2) next, a step of peeling the glass substrate 22 from the carrier substrate 21 by the contact film 23 having high adhesion (fig. 4 (step 2)).

(step 3) the step of removing the contact film 23 from the 2 nd surface of the glass substrate 22 peeled off from the carrier substrate by the weakening treatment (electromagnetic radiation irradiation 24) for weakening the adhesion of the contact film (fig. 4 (step 3)).

That is, by using the contact film 23 for safely holding the glass substrate, the glass substrate 22 can be protected, and thus, for example, the exposed surface of the glass substrate 22 can be protected from mechanical damage that may occur, for example, and the glass substrate can be safely and easily handled.

The contact film may contain a hard or soft material according to specific requirements, and polyethylene terephthalate (PET), polyethylene (PE), or Polyolefin (PO) may be used as a preferable material.

The contact film is typically bonded to the glass substrate by an adhesive layer composed of an adhesive provided on one side of the substrate. However, it is not excluded that the substrate of the contact film itself has adhesiveness.

In order to eliminate the bonding force between the carrier substrate and the glass substrate at the time of press bonding, the bonding force between the contact film and the 2 nd surface of the glass substrate is selected so that a sufficient force can be transmitted to the glass substrate at the time of peeling by the peeling means.

The contact film may be provided as a foil or tape, which may be wound from a roll or provided as a sheet, for example. The thickness of the contact film is preferably 50 μm or more, more preferably 80 μm or more, still more preferably 125 μm or more, particularly preferably 150 μm or more.

As mentioned above, the glass substrate is preferably made from an alkali-containing glass composition. Preferred glass materials are, for example, lithium aluminosilicate glass, soda lime glass, borosilicate glass, alkali aluminosilicate glass and aluminosilicate glass having a low alkali content. Alkali-free compositions are also preferred. Such glass is preferably produced by, for example, the downdraw method, overflow downdraw method, float method, or the like.

The carrier substrate preferably has a thickness of at least 100 μm or more, preferably 300 μm or more, more preferably 500 μm or more, and a maximum dimension of at least 3 inches (1 inch is 2.54 cm) or more, preferably 6 inches or more, more preferably 8 inches or more, particularly preferably 12 inches or more. In particular, the carrier substrate may have a substrate size of 1×1m to 3×3m, for example, of a first generation size of glass substrate or more, for example, second generation to eighth generation, or more. The carrier substrate may have various shapes, such as rectangular, quadratic or elliptical, or circular.

The glass substrate is peeled off from the carrier substrate together with the contact film by the adhesive force of the contact film, and then the contact film is peeled off, whereby the glass substrate 22 alone serving as the transparent substrate 3 shown in fig. 1 is obtained.

In a preferred embodiment, the contact film is preferably subjected to a weakening treatment of the adhesion force before the contact film is removed from the glass substrate, whereby the adhesion force between the contact film and the extremely thin substrate is reduced. The embrittlement treatment is preferably chosen in such a way that the adhesion can be reduced below 0.5N/25 mm.

The embrittlement treatment may be selected so as to be within a specific wavelength range of the electromagnetic radiation selected, for example, infrared rays, ultraviolet rays, or visible light. The electromagnetic radiation selected may be of a narrow band, or may cover a wider band, or may be laser radiation, depending on the adhesive material used.

Preferably, the outside of the visible spectrum is chosen such that the adhesion force does not deteriorate in case of exposure to visible light. There are various adhesive materials commercially available that can be at least partially deactivated by electromagnetic radiation irradiation, and the preferred choice depends on the particular requirements.

Alternatively, when the adhesiveness of the contact film can be reduced by increasing or decreasing the temperature, it is also advantageous to perform the heat treatment as a embrittlement treatment.

The electromagnetic radiation irradiation is preferably performed from the outside of the contact film, i.e., from the side not adhered to the glass substrate.

The preferred adhesive materials are widely available, for example, commercially available under the trade name "NDS4150-20", and the corresponding embrittlement treatment involves irradiation with ultraviolet light at a wavelength of 365 nm.

Specific examples of the production of the glass substrate are described in the examples. The glass substrate described above may be a thin glass made of SCHOTT or japan electric nitrate.

[2.2] thermoplastic resin substrate

The transparent substrate of the present invention may use a thermoplastic resin film, and the thermoplastic resin is not particularly limited, and may use a cellulose ester resin, a cycloolefin resin, a fumaric acid diester resin, a polypropylene resin, a (meth) acrylic resin, a polyester resin, a polyarylate resin, a polyimide resin, a styrene resin, or a composite resin thereof. Among them, from the viewpoints of optical characteristics and physical characteristics, a thermoplastic resin film using a polyimide resin is preferably used as the transparent substrate 3 shown in fig. 1.

Polyimide resin

Polyimide-based resins are obtained, for example, by synthesizing a polyamic acid (polyimide precursor) from an acid anhydride and a diamine compound, and imidizing the polyamic acid with heat and a catalyst.

The acid anhydride used for the synthesis of polyimide is not particularly limited, and examples thereof include: and aromatic tetracarboxylic dianhydrides such as diphenyl tetracarboxylic dianhydride (BPDA), terphenyl tetracarboxylic dianhydride, benzophenone tetracarboxylic dianhydride, pyromellitic dianhydride (PMDA), oxy diphthalic dianhydride, diphenyl sulfone tetracarboxylic dianhydride, hexafluoroisopropylidene diphthalic dianhydride, and cyclobutane tetracarboxylic dianhydride.

The diamine compound used for the synthesis of polyimide is not particularly limited, examples thereof include p-Phenylenediamine (PDA), m-phenylenediamine, 2, 4-diaminotoluene, 4' -diaminodiphenylmethane, 4' -diaminodiphenyl ether (ODA), 3,4' -diaminodiphenyl ether, 3' -dimethyl-4, 4' -diaminobiphenyl, 2' -bis (trifluoromethyl) -4,4' -diaminobiphenyl, and aromatic diamines such as 3, 7-diamino-dimethyldibenzothiophene-5, 5' -dioxide, 4' -diaminobenzophenone, 4' -bis (4-aminophenyl) sulfide, 4' -diaminobenzanilide, and 1, 4-bis (4-aminophenoxy) benzene.

Further, as commercial products, polyimide varnishes containing a polyimide precursor as a main component, for example, U-VARNISHS (manufactured by Yu Zu Xingxing Co., ltd.), ECRIOS (manufactured by Sanchi chemical Co., ltd.), and the like can be used.

In the case of using a polyimide having ultraviolet transmittance according to purposes, for example, a polyimide containing a polyimide precursor (polyamic acid) as a main component is commercially available: TORMED-S, X (product of IST Co., ltd.), SPIXARA HR003, GR003 (product of SOM AR Co., ltd.), FLUPI (product of NTT Co., ltd.), type HM (product of Toyo-yo Co., ltd.), type-C (product of Sanjing chemical Co., ltd.), PI-100 (product of Wash chemical Co., ltd.), HDN-20D (product of New Japanese physicochemical Co., ltd.), CBDA-6FDAC (product of CENTRAL GLASS Co., ltd.), Q-VR-X-1655 (product of PI R & D), and the like.

[3] Method for manufacturing cover member

[3.1] structural example of cover Member

The substrate film (substrate film 1) of the present invention is disposed on at least one surface of the transparent substrate in the structure shown in fig. 1A. As described later, when the display device is a display unit having a polarizing plate, the base film 1 side of the cover member of the present invention is preferably bonded to the polarizing plate via an adhesive layer.

As the arrangement of the substrate film with respect to the transparent substrate, it is preferable that the substrate film be arranged on the surface (B surface) which is the back surface of the surface (a surface) opposite to the one side of the substrate film so that the film density (ρ) _B ) Film Density (ρ) relative to the A-plane _A ) Ratio (ρ) _A /ρ _B ) The a-side of the substrate film adjusted so that the value of (a) is in the range of 0.80 to 0.95 is set as the transparent substrate side.

On the surface of the transparent substrate opposite to the substrate film 1, a substrate film 2 (fig. 1B) described later is preferably disposed.

The base film 1 or the base film 2 is bonded to the transparent base 3 via an adhesive layer or an adhesive layer.

Fig. 5 is a schematic view showing the adhesion of the substrate film with the support to the transparent substrate.

Fig. 5A shows a laminate of the substrate film 1 formed on the support 5, and the surface of the substrate film 1 in contact with the support 5 corresponds to the B-surface.

Next, as shown in fig. 5B, the a-side of the substrate film 1 is bonded to the transparent substrate 3 via the adhesive layer 4, and then the support 5 is peeled off.

[3.2] adhesive layer

The adhesive layer is preferably formed by drying and partially crosslinking an adhesive composition comprising a base polymer, a prepolymer and/or a crosslinkable monomer, a crosslinking agent and a solvent. That is, at least a part of the adhesive composition may be crosslinked.

Examples of adhesive compositions include: acrylic adhesive composition based on (meth) acrylic polymer, silicone adhesive composition based on silicone polymer, and rubber adhesive composition based on rubber. Among them, the acrylic pressure-sensitive adhesive composition is preferable from the viewpoints of transparency, weather resistance, heat resistance and processability.

The (meth) acrylic polymer contained in the acrylic adhesive composition may be a copolymer of an alkyl (meth) acrylate and a monomer containing a functional group crosslinkable with a crosslinking agent.

The alkyl (meth) acrylate is preferably an alkyl acrylate having an alkyl group with 2 to 14 carbon atoms.

Examples of monomers containing functional groups crosslinkable with the crosslinking agent include: amide group-containing monomers, carboxyl group-containing monomers (acrylic acid, etc.), hydroxyl group-containing monomers (hydroxyethyl acrylate, etc.).

Examples of the crosslinking agent contained in the acrylic pressure-sensitive adhesive composition include: epoxy-based crosslinking agents, isocyanate-based crosslinking agents, peroxide-based crosslinking agents, and the like. The content of the crosslinking agent in the adhesive composition is usually, for example, 0.01 to 10 parts by weight relative to 100 parts by weight of the base polymer (solid component).

The adhesive composition may further comprise, as needed: various additives such as tackifiers, plasticizers, glass fibers, glass beads, metal powders, other fillers, pigments, colorants, fillers, antioxidants, ultraviolet absorbers, and silane coupling agents.

The thickness of the pressure-sensitive adhesive layer is usually about 3 to 100. Mu.m, preferably 5 to 50. Mu.m.

The surface of the adhesive layer is protected by a release film subjected to a release treatment. Examples of the release film include plastic films such as acrylic films, polycarbonate films, polyester films, and fluororesin films.

[3.3] adhesive layer

Instead of the adhesive layer, an adhesive layer may be used, and the adhesive layer 4 shown in fig. 1 may be an adhesive layer.

The adhesive layers are disposed between the substrate film and the transparent substrate, respectively. It is preferable that the polarizing plate be disposed between the polarizing plate and a polarizing plate described later to form a display device. The types of the adhesives contained in the adhesive layer may be the same or different.

The adhesive layer may be a layer made of a water-soluble polymer or a cured product of an active energy ray-curable adhesive. In the case of the water-soluble polymer, the water-soluble polymer may be an adhesive made of a vinyl alcohol polymer, or an adhesive containing at least a water-soluble crosslinking agent of a vinyl alcohol polymer such as boric acid, borax, glutaraldehyde, melamine, oxalic acid, or the like. The adhesive layer is formed as a coating dry layer of an aqueous solution, and other additives, acid, and other catalysts may be blended as necessary in the preparation of the aqueous solution.

The active energy ray-curable adhesive may be a photo radical-polymerizable composition or a photo cation-polymerizable composition. Among them, a photo cation polymerizable composition is preferable.

The photo cation polymerizable composition contains an epoxy compound and a photo cation polymerization initiator.

The epoxy compound is a compound having 1 or more, preferably 2 or more epoxy groups in the molecule. Examples of the epoxy compound include: hydrogenated epoxy compounds (glycidyl ethers of alicyclic polyols) obtained by reacting epichlorohydrin with alicyclic polyols; aliphatic epoxy compounds such as polyglycidyl ethers of aliphatic polyols or alkylene oxide adducts thereof; alicyclic epoxy compounds having 1 or more epoxy groups bonded to an alicyclic ring in the molecule. The epoxy compound may be used in an amount of 1 or 2 or more.

The photo-cationic polymerization initiator includes, for example, an aromatic diazonium salt; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; iron-arene complexes, and the like.

The photo cation polymerization initiator may further comprise, as needed: additives such as cationic polymerization accelerators such as oxetanes and polyols, photosensitizers, ion traps, antioxidants, chain transfer agents, tackifiers, thermoplastic resins, fillers, flow regulators, plasticizers, antifoaming agents, antistatic agents, leveling agents, solvents, and the like.

The thickness of the adhesive layer is not particularly limited, but is preferably in the range of 0.01 to 10. Mu.m, more preferably in the range of 0.01 to 5. Mu.m.

[3.4] substrate film 2

As the opposed film of the base film 1, the base film 1 may be used, or another resin film may be used, and examples thereof include: cycloolefin resin, polypropylene resin, acrylic resin, polyester resin, polyarylate resin, cellulose ester resin, styrene resin, composite resin thereof, and the like. Among them, a resin film containing a polyester resin is preferably used as a resin excellent in storage stability under a high humidity environment.

Examples of the resin film include: among them, a polyester resin film containing polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) is preferable from the viewpoint of easy handling.

The resin film may be a film subjected to heat treatment (heat relaxation), or may be a film subjected to stretching treatment.

The heat treatment is not particularly limited in order to reduce the residual stress of the resin film (for example, residual stress accompanying stretching), and may be performed in the range of (tg+60) to (tg+180) c when the glass transition temperature of the resin constituting the resin film is Tg.

As the polyester resin film (also referred to simply as a polyester film), commercially available ones can be used, and for example, polyethylene terephthalate film TN100 (manufactured by eastern spinning corporation), MELINEX ST504 (manufactured by TEIJIND UPONT FILMS corporation) and the like can be preferably used.

The thickness of the base film 2 may be appropriately selected, and is preferably in the range of 10 to 100 μm, more preferably in the range of 10 to 50 μm, from the viewpoint of thinning the cover member.

Further, a functional layer such as a hard coat layer may be provided on the base film 2.

(hard coat)

The polyester film located on the surface of the folding display to protect the display preferably has a hard coating layer on its surface. The hard coat layer is preferably used in a display on the display surface side of the polyester film. The resin for forming the hard coat layer may be, but not particularly limited to, acrylic, silicone, inorganic hybrid, urethane acrylate, polyester acrylate, epoxy, and the like. In addition, 2 or more kinds of materials may be mixed and used, and particles such as an inorganic filler and an organic filler may be added.

The film thickness of the hard coat layer is preferably in the range of 1 to 50. Mu.m. When the thickness is 1 μm or more, the cured product is sufficiently cured, and a good pencil hardness can be obtained. Further, when the thickness is 50 μm or less, curling caused by curing shrinkage of the hard coat layer can be suppressed, and the film handleability can be improved.

The method of applying the hard coat layer may be, without particular limitation, a wire bar, a gravure coater, a die coater, a knife coater, or the like, and may be appropriately selected according to the viscosity and film thickness.

As a curing method of the hard coat layer, energy rays such as ultraviolet rays and electron rays, a curing method using heat, and the like can be used, and in order to reduce damage to the film, a curing method using ultraviolet rays, electron rays, and the like is preferable.

The pencil hardness of the hard coat layer is preferably B or more, more preferably H or more, and particularly preferably 2H or more. If the pencil hardness is greater than B, the pencil is less likely to be injured, and the visibility is not lowered. Generally, the pencil hardness of the hard coat layer is preferably high, and may be 9H or less, or 8H or less, and even 6H or less may be practically used without any problem.

The hard coat layer used in the present invention can be used to improve the pencil hardness of the surface to protect the display, as described above, and preferably has high transmittance. The transmittance of the hard coat film is preferably 87% or more, and more preferably 88% or more. If the transmittance is 87% or more, sufficient visibility can be obtained. The total light transmittance of the hard coat film is generally as high as 99% or less, or 97% or less. The haze of the hard coat film is generally preferably low, preferably 3% or less. The haze of the hard coat film is more preferably 2% or less, and most preferably 1% or less. If the haze is 3% or less, the visibility of the image can be improved.

The hard coat layer may also be added with other functions. For example, in the present invention, a hard coat layer having a specific pencil hardness, such as an antiglare layer, an antiglare antireflection layer, an antireflection layer, a low reflection layer, and an antistatic layer, to which a functionality is added, is preferably used.

[4] Display device

The display device of the present invention is characterized by comprising the cover member of the present invention or a base film for the cover member. The display device of the present invention can be obtained by bonding the cover member of the present invention to the surface of the display device preferably via a polarizing plate, for example, through an adhesive layer or an adhesive layer. The display device is a device having a display mechanism, and includes a light emitting element or a light emitting device as a light emitting source. As a display device, there may be mentioned: in particular, as the display device of the present invention, an organic EL display device and a touch panel display device are preferable, and an organic EL display device is particularly preferable, and the display device is a display device.

Further, the folding display is preferably a structure in which a continuous 1-sided display can be folded in half when carried, thereby reducing the size by half and improving portability. In addition, it is preferable to realize both of a thin shape and a light weight. Therefore, the bending radius of the folding display is preferably 5mm or less, more preferably 3mm or less. If the bending radius is 5mm or less, thinning can be achieved in the folded state. The smaller the bending radius, the better, but may be 0.1mm or more, or 0.5mm or more. Even if it is 1mm or more, the usability is sufficiently good as compared with a conventional display having no folding structure. Here, the bending radius at the time of folding refers to a radius R inside a folded portion at the time of folding the cover member 10 in fig. 1C or 1D.

Fig. 6 shows an application example in which the cover member is applied to an organic EL display as an example of a display device of the present invention.

A general structure of an organic EL display is a display unit including an organic EL layer 101 and a polarizing plate 102, wherein the organic EL layer 101 is composed of an electrode, an electron transport layer, a light emitting layer, a hole transport layer, and a transparent electrode, and the polarizing plate 102 is provided with a retardation plate (λ/4 plate) for improving image quality. The display device 100 of the present invention is a preferred embodiment, in which the base film 1 side of the cover member 10 of the present invention is bonded to the polarizing plate 102 via the adhesive layer 4.

According to this embodiment, the display device of the present invention is a display device in which operability of the cover member is improved and no crease is generated in the base film provided in the cover member, and in particular, as a cover member of a folding display, the display device is excellent in visibility after repeated folding while maintaining mass productivity, and no disturbance of an image is generated in a folded portion of the display. For example, a portable terminal device mounted with the folding display provides a beautiful image, has a rich functionality, and is excellent in convenience such as portability.

Examples

The present invention will be specifically described below by way of examples, but the present invention is not limited thereto. In the examples, "part" or "%" is used, but unless otherwise specified, "part by mass" or "% by mass" is indicated.

Preparation of substrate film

< preparation of substrate film 101 >

(support)

As the support, a polyethylene terephthalate film (PET film) was used: (TN 100 manufactured by Toyobo Co., ltd., a release layer containing a non-silicone release agent, and a film thickness of 38 μm).

(preparation of solution for substrate film 101)

The following components were mixed to obtain a solution for the base film 101.

800 parts by mass of methylene chloride (boiling point 41 ℃ C.)

Acrylic 1:MMA/PMI/MADA copolymer (60/20/20 mass ratio), mw:150 ten thousand, tg:137 ℃ (hereinafter abbreviated as "MMA: methyl methacrylate, PMI: phenylmaleimide, MADA: adamantyl acrylate) 20 parts by mass

80 parts by mass of rubber particles R1

The dispersant (polyoxyethylene lauryl ether sodium phosphate: molecular weight 332) was added to the base film in an amount of 0.006% by mass

(preparation of substrate film 101)

After a solution for the base material film 101 was coated on the release layer of the support by a back coating method using a die, the base material film was dried by the following drying step, thereby forming a base material film having a film thickness of 5 μm, and the base material film 101 was obtained.

(initial drying)

Step 1: at 40℃for 1 minute

Step 2: at 70℃for 1 minute

Step 3: at 100℃for 1 minute

Step 4: at 130℃for 2 minutes

(post-drying)

Step 5: at 110℃for 15 minutes

< preparation of rubber particle R1 >

Rubber particles prepared by the following method were used.

The following materials were charged into an 8L polymerization apparatus equipped with a stirrer.

180 parts by mass of deionized water

Polyoxyethylene lauryl ether phosphate 0.002 parts by mass

Boric acid 0.473 parts by mass

Sodium carbonate 0.473 mass parts

Sodium hydroxide 0.008 mass portion

After the inside of the polymerization machine was sufficiently replaced with nitrogen gas, the internal temperature was set to 80℃and 0.021 parts by mass of potassium persulfate was charged as a 2% by mass aqueous solution. Next, a mixed solution obtained by adding 0.07 part by mass of polyoxyethylene lauryl ether phosphate to 21 parts by mass of a monomer mixture (c') composed of 84.6% by mass of methyl methacrylate, 5.9% by mass of butyl acrylate, 7.9% by mass of styrene, 0.5% by mass of allyl methacrylate, and 1.1% by mass of n-octyl mercaptan was continuously added to the above solution over 63 minutes. Further, by allowing the polymerization reaction to continue for 60 minutes, the innermost hard polymer (c) was obtained.

Then, 0.021 parts by mass of sodium hydroxide was used as a 2% by mass aqueous solution, and 0.062 parts by mass of potassium persulfate was added as a 2% by mass aqueous solution. Then, a mixed solution obtained by adding 0.25 part by mass of polyoxyethylene lauryl ether phosphate to 39 parts by mass of a monomer mixture (a') composed of 80.0% by mass of butyl acrylate, 18.5% by mass of styrene and 1.5% by mass of allyl methacrylate was continuously added over 117 minutes. After completion of the addition, 0.012 parts by mass of potassium persulfate was added to the 2% by mass aqueous solution, and the polymerization was continued for 120 minutes to obtain a soft layer (layer composed of the acrylic rubbery polymer (a)). The glass transition temperature (Tg) of the soft layer was-30 ℃. The glass transition temperature of the soft layer is calculated by averaging the glass transition temperatures of homopolymers of the monomers constituting the acrylic rubbery polymer (a) from the composition ratio.

Then, 0.04 part by mass of potassium persulfate was added to the 2% by mass aqueous solution, and 26.1 parts by mass of a monomer mixture (b') composed of 97.5% by mass of methyl methacrylate and 2.5% by mass of butyl acrylate was continuously added thereto over 78 minutes. The polymerization was continued for 30 minutes to obtain a polymer (b).

The polymer (b) thus obtained was put into a 3 mass% aqueous sodium sulfate solution and salted out and coagulated. Subsequently, the acrylic graft copolymer particles (rubber particles R1) having a 3-layer structure were obtained by repeating dehydration and washing and then drying. The average particle diameter of the obtained rubber particles R1 was 200nm.

The average particle diameter of the rubber particles was measured by the following method.

(average particle diameter)

The dispersion particle diameter of the rubber particles in the obtained dispersion was measured by a ZETA potential and particle diameter measuring system (ELS Z-2000ZS, manufactured by OTSUKA ELECTRONICS Co., ltd.).

< preparation of substrate films 102 to 104 >

Base films 102 to 104 were produced in the same manner except that the content of the rubber particles R1 was changed to 65, 45, and 20 mass% in the production of the base film 101, respectively.

< preparation of substrate film 105 >

(support)

(preparation of solution for substrate film 105)

The following components were mixed to obtain a solution for the base film 105.

Dichloromethane (boiling point 41 ℃): 860 parts by mass

Methanol (boiling point 65 ℃): 40 parts by mass

100 parts by mass of COP1 (G7810: ARTON G7810, mw:14 ten thousand cycloolefin resin having a carboxylic acid group, manufactured by JSR (Co., ltd.)

Antioxidant (Irganox 1076: molecular weight 531 from BASF corporation)

An amount of 0.002 mass% was added to the base film

(preparation of substrate film 105)

After a solution for the base material film 105 was coated on the release layer of the support by a back coating method using a die, the base material film was dried by the following drying step, thereby forming a base material film having a film thickness of 5 μm, and the base material film 105 was obtained.

Step 1: at 40℃for 1 minute

Step 2: at 70℃for 1 minute

Step 3: at 100℃for 1 minute

Step 4: at 130℃for 2 minutes

< preparation of substrate film 106 >

(support)

(preparation of polyimide powder)

Into a 4-necked flask equipped with a dry nitrogen inlet tube, a cooler, a Dean-Stark condenser filled with toluene, and a stirrer, 5.146g (20 mmol) of MeO-DABA represented by the following formula was charged, 20 ml of gamma-butyrolactone (GBL) and 10 ml of toluene were added, and the mixture was stirred at room temperature under a nitrogen flow.

[ chemical formula 6]

MeO-DABA

To this was added 4.483g (20 mmol) of cis, cis-1, 2,4, 5-cyclohexane tetracarboxylic dianhydride (H-PMDA) powder, and the mixture was heated and stirred at 80℃for 6 hours. Then, the external temperature was heated to 190℃to remove water produced by imidization by azeotropic distillation together with toluene. After continuing heating, refluxing and stirring for 6 hours, no more water generation was observed. Toluene was distilled off continuously and heated for 7 hours, and after toluene was distilled off again, methanol was added to reprecipitate to obtain 6.4g (yield: 72%) of polyimide powder.

(preparation of solution for substrate film 106)

The following components were mixed to obtain a solution for the base film 106.

900 parts by mass of methylene chloride (boiling point 41 ℃)

100 parts by mass of polyimide 1 (the polyimide powder)

(preparation of substrate film 106)

After a solution for the base material film 106 was coated on the release layer of the support by a back coating method using a die, the base material film was dried by the following drying step, and the base material film 106 having a film thickness of 5 μm was obtained.

(initial drying)

Step 1: at 40℃for 1 minute

Step 2: at 70℃for 1 minute

Step 3: at 100℃for 1 minute

Step 4: at 130℃for 2 minutes

(post-drying)

Step 5: 15 minutes at 110 DEG C

< preparation of substrate films 107, 108 >

In the production of the base film 101, base films 107 and 108 were produced in the same manner except that the film thicknesses were set to 10 μm and 14 μm, respectively.

< preparation of substrate film 109 >

In the production of the base film 105, the base film 109 was produced in the same manner except that the solid content concentration of COP1 (G7810) in the dope was produced to 20 mass%.

< preparation of substrate film 110 >

The substrate film 110 was prepared in the same manner as in the preparation of the substrate film 105, except that the following dopant in which silica fine particles were added to the dopant was used.

(preparation of microparticle additive solution)

4 parts by mass of silica particles (AEROSIL R812: manufactured by AEROSIL Co., ltd., primary average particle diameter: 7nm, apparent specific gravity 50 g/L)

48 parts by mass of methylene chloride

48 parts by mass of ethanol

After mixing the above with a dissolver for 50 minutes, dispersion was performed by Manton Gorlin. Further, the secondary particles are dispersed by a mill so that the particle size of the secondary particles becomes a predetermined size. This was filtered through FINEMET NF made by Japanese Kogyo Co., ltd to prepare a fine particle additive solution.

(preparation of solution for substrate film 110)

The following composition of the dopant was prepared. First, methylene chloride and ethanol were added to a pressurized dissolution tank. Cycloolefin resin (DOP): G7810 was added to a pressurized dissolution tank containing a mixed solution of methylene chloride and ethanol with stirring. Further, 15 minutes after the start of solvent addition, the prepared microparticle additive solution was added and heated to 80℃to be completely dissolved while stirring. At this time, the temperature was raised from room temperature to 5℃per minute, and after dissolution for 30 minutes, the temperature was lowered at 3℃per minute. The resulting solution was filtered using an deposition filter paper No.244 made by deposition filter paper (Co., ltd.) to prepare a dope.

(composition of dopant)

COP1 (G7810) 100 parts by mass

Dichloromethane 200 parts by mass

Ethanol 10 parts by mass

1 part by mass of a microparticle additive solution

< preparation of substrate film 111 >

In the production of the base film 102, the base film 111 is produced in the same manner as in the production process except that the PET film as a support is peeled off, the B surface is dried, and then the PET film is stuck again on the B surface and wound.

< preparation of substrate film 112 >

In the production of the base film 105, the base film 112 was produced in the same manner except that the rubber particles R1 were added to the dope so as to be 65 mass%.

< preparation of substrate film 113 >

(support)

As a support, KAPTON film 200H/V (manufactured by TORAY/DUPONT Co., ltd.) was used, and the film thickness was 50. Mu.m.

(preparation of substrate film 113)

In dehydrated dimethylacetamide (DMAc, manufactured by tokyo chemical industry Co., ltd., boiling point 165 ℃) as diamine, 2' -bistrifluoromethyl-4, 4' -diaminobiphenyl (TFMB, manufactured by TORAY. FINE CHEMICAL Co.) and 4,4' -diaminodiphenyl ether (DPE, manufactured by tokyo chemical industry Co., ltd.) were dissolved in an amount of 90 mol% relative to the total amount of diamine as diamine under a nitrogen stream, and the liquid temperature was cooled to 5℃with an ice water bath. Then, while maintaining the system under a nitrogen stream in an ice-water bath, 2-chloro terephthaloyl chloride (CTPC, manufactured by japan light metals corporation) was added in an amount of 99 mol% relative to the total amount of diamine for 30 minutes, and after the total amount was added, the aromatic polyamide (polymer a) was polymerized by stirring for about 2 hours. To the obtained solution, allyl glycidyl ether (neutralizing agent E) was added in an amount corresponding to 100 mol% based on the amount of hydrogen chloride (i.e., the amount of amide groups of the aromatic polyamide) generated in the above-mentioned reaction, and the mixture was stirred for about 1 hour to obtain an aromatic polyamide solution composed of polymer a (polyamide 1).

The obtained aromatic polyamide solution was cast in a film form on the support at room temperature using an applicator, at 115℃for 30 minutes and at 265℃for 5 minutes, and dried in a hot air oven, whereby a base film 113 composed of polymer A (polyamide 1) was obtained having a film thickness of 5. Mu.m. The hot air oven was used as a safety oven SPH100 (ESPEC corporation) and was used after a temperature of 50% of the opening/closing damper was shown to reach the set temperature for 1 hour.

< preparation of substrate film 114 >

(support)

(preparation of substrate film 114)

In a 300mL 5-necked round-bottomed flask having a stainless steel half-moon shaped stirring blade, a nitrogen gas introduction tube, a Dienstak (Dean-Stark) equipped with a condenser, a thermometer, and a glass end cap, as a diamine component, 9.76g (0.028 mol) of 9, 9-bis (4-aminophenyl) fluorene (manufactured by Santa Clara chemical Co., ltd.) and 8.62g (0.021 mol) of 2, 2-bis [4- (4-aminophenoxy) phenyl ] propane (manufactured by Kagaku Co., ltd.), 6.72g (0.021 mol) of 4,4 '-diamino-2, 2' -bis (trifluoromethyl) biphenyl (manufactured by Kagaku Co., ltd.), 46.86g of gamma-butyrolactone (manufactured by MITSUBISHI CHEMICAL Co., ltd.), the mixture was stirred at a temperature of 70℃in the system under a nitrogen atmosphere at a rotation speed of 200rpm to obtain a solution.

To this solution, 16.47g (0.07 mol) of 1,2,4, 5-cyclohexane tetracarboxylic dianhydride (manufactured by MI TSUBISHI GAS CHEMICAL corporation) and 11.72g of γ -butyrolactone (manufactured by MITS UBISHI CHEMICAL corporation) were added together as tetracarboxylic acid components, and 3.54g of triethylamine (manufactured by kato chemical corporation) was added as an imidization catalyst, and the mixture was heated by a mantle heater, and the temperature in the reaction system was raised to 190℃for about 20 minutes. The distilled components were collected, and the temperature in the reaction system was kept at 190℃for 5 hours under reflux while the rotation speed was adjusted according to the increase in viscosity.

Then, 97.62g of gamma-butyrolactone (manufactured by MITSUBISHI CHEMICAL Co., ltd.) was added, the temperature in the reaction system was cooled to 120℃and then stirred for about 3 hours to homogenize the mixture, thereby obtaining a polyimide 2 solution having a solid content concentration of 20% by mass. Next, the obtained polyimide 2 solution was coated on the support by a die using a back coating method in the same manner as the preparation of the substrate film 101, and then the substrate film was dried by the following drying step, thereby forming a substrate film having a film thickness of 5 μm, and obtaining a substrate film 114.

(initial drying)

Step 1: at 40℃for 10 minutes

Step 2: at 70℃for 10 minutes

Step 3: 30 minutes at 100 DEG C

Step 4: 30 minutes at 130 DEG C

(post-drying)

Step 5: 30 minutes at 250 DEG C

< preparation of substrate film 115 >

(support)

As the support, a polyethylene terephthalate film (PET film) was used: (TN 100 manufactured by Toyo-yo) and a release layer containing a non-silicone release agent, the film thickness was 38. Mu.m.

(preparation of solution for substrate film 115)

Methyl Ethyl Ketone (MEK) 90 parts by mass

Rubber particle R1 10 parts by mass

The resultant solution was stirred with a magnetic stirrer to obtain a solution for the base material film 115.

(preparation of substrate film 115)

After a solution for the base material film 115 was coated on the release layer of the support by a back coating method using a die, the base material film was dried by the following drying step to form a base material film having a film thickness of 5 μm, thereby obtaining the base material film 115.

(initial drying)

Step 1: at 40℃for 1 minute

Step 2: at 70℃for 1 minute

Step 3: at 100℃for 1 minute

Step 4: at 130℃for 2 minutes

(post-drying)

Step 5: 15 minutes at 110 DEG C

< preparation of substrate film 116 >

In the production of the base film 102, the base film 116 was produced similarly after the film thickness was adjusted to 25 μm.

Evaluation (evaluation)

The following evaluation was performed using the obtained base film.

< stress-strain curve >

The base film was cut into a size of 100mm (MD direction: longitudinal direction) ×10mm (TD direction: width direction), to obtain a sample film. The sample film was subjected to humidity control at 23℃and 55% RH for 24 hours, and the humidity-controlled sample film was subjected to stretching in the MD direction until fracture according to JIS K7127:1999, using a universal tensile tester RTC-1225A manufactured by ORIENTEC, inc., with a distance between chucks of 50mm, to obtain a stress-strain curve. The vertical axis of the stress-strain curve is expressed as stress (MPa), and the horizontal axis is expressed as tensile elongation at break (%). The stress-strain curve was measured at 23℃and 55% RH at a tensile speed of 50 mm/min.

The slope of the straight line of the present invention was obtained from the stress-strain curve of the base material film obtained by the measurement.

As shown in fig. 2, the substrate film was subjected to a tensile test, and after elongation, a breaking point X was taken, and when a straight line Y connecting the breaking point X and the origin (0 point) was drawn, the slope α of the straight line was referred to as "the slope of the straight line connecting the origin and the breaking point in the stress-strain curve of the substrate film" in the present invention.

< measurement of the densities of the A and B surfaces of the substrate film >

The density of the surface (a-side and B-side) of the substrate film was measured by an X-ray reflectance method (XRR method). When the angle of incidence of the X-rays is equal to or greater than the critical angle for total reflection, the X-rays enter the film and the reflectivity is reduced. The reflectance distribution measured by the XRR method can be analyzed by using a dedicated reflectance analysis software, and in the present invention, when the angle at which the reflectance starts to decrease is defined as θa, 2θ is in the range from 2θa to 2θa+0.1°, and the density at which the fitting error between the measurement result and the calculation result is minimized is defined as the surface density. At this time, fitting was performed with the surface roughness set in the range of 0 to 1 nm.

(measurement conditions)

Sample size: 30mm by 30mm

Incident X-ray wavelength:

measurement range (θ): 0 to 6 DEG

< measurement of elastic modulus of substrate film >

The measurement conditions of the elastic modulus (also referred to as tensile elastic modulus) were set as follows, and the elastic modulus was obtained by linear regression between strain 0.05 to 0.25%.

1) The base film was cut into a size of 100mm (MD direction). Times.10 mm (TD direction) as a test piece.

2) The test piece was stretched at a stretching speed of 50mm/min in the longitudinal direction (MD direction) of the test piece by using a universal tensile tester RTC-1225A manufactured by ORIENTEC, the distance between chucks was set to 50mm, and the tensile elastic modulus in the MD direction was measured. The measurement was performed at 23℃and 55% RH. The elastic modulus of the transparent substrate to be described later was also measured by the same method.

< push Strength >

The a-side and B-side of the base film were measured according to the procedure of the press-in test specified in ISO 14577. An ultra-micro hardness tester (manufactured by FISCHER INSTRU MENTS under the trade name "fisharscap 100C") was used as a tester at 23 ℃ under the environment of 55% rh, and a pyramidal diamond compact having a square base and a face-to-face angle of 136 ° was used as a compact.

In the measurement, the presser was pressed against the base film at a constant speed, and a load of 10mN was applied. The mahalanobis hardness was calculated by applying a load (10 mN) to the film and dividing the load by the surface area of the immersed press beyond the contact zero point.

The press-in strength of the base material film of the present invention was measured by the above method, and the surface hardness (mahalanobis hardness) was evaluated on the average of the a-plane and the B-plane according to the following criteria.

And (3) the following materials: hardness of 200N/mm ² Above mentioned

O: hardness of 50N/mm ² Above and below 200N/mm ²

Delta: hardness of 25N/mm ² Above and below 50N/mm ²

X: hardness of less than 25N/mm ²

If the evaluation level of the mahalanobis hardness is Δ or more, the press-in strength of the base material film is improved, and when the base material film is provided on the lid member, cracking of the transparent base material is prevented, so that the operability of the lid member is improved. Preferably, the range is from o to o.

The structure of the base film and the evaluation results are shown in table I below.

< preparation of transparent substrate 1: the table is described as glass >

A glass substrate having a size of 12 inches was prepared according to the following procedure (see fig. 4).

(step 1) a step of forming the 1 st surface of the glass substrate surface so that the 1 st surface of the glass substrate surface is brought into contact with the glass carrier substrate having the joint surface, and adhering a contact film (also referred to as a "contact film") having an adhesive force to the 2 nd surface on the opposite side of the 1 st surface.

(step 2) next, a step of peeling the glass substrate from the carrier substrate by using the contact film having high adhesion.

(step 3) removing the contact film from the 2 nd surface of the glass substrate peeled off from the carrier substrate by a weakening treatment (electromagnetic radiation irradiation) for weakening the adhesion of the contact film.

According to step 1, a glass base material 1 is formed so as to be in contact with a carrier substrate having a thickness of 500 μm, and after a predetermined thickness, the following contact film is attached. Then, the glass base material was peeled off from the carrier substrate together with the contact film within 30 seconds, and the carrier substrate was removed (step 2). The contact film comprises Polyolefin (PO) as a base material having a thickness of 150 μm and an adhesive layer of 10 μm, and is commercially available under the trade name "ND S4150-20".

Then, the exposed contact film is subjected to a embrittlement treatment to reduce the adhesion. In the embrittlement treatment, the contact film was irradiated with ultraviolet rays of 365nm for 10 seconds. The irradiation power of the ultraviolet light was about 500mW/cm ² Total irradiation energy of 500mJ/cm ² . At this time, the adhesion before the embrittlement treatment was about 11N/25mm, and after the embrittlement treatment, the adhesion was reduced to 0.4N/25mm. Thus, the contact film was easily peeled off from the glass substrate, and a glass substrate single body having a thickness of 28 μm was obtained (step 3).

The thickness of the transparent substrate was adjusted to 8 μm, 28 μm, 45 μm and 54 μm, and the elastic modulus based on the measurement was as described in Table II.

< preparation of transparent substrate 2: the table is described as polyimide >

In the preparation of the base film 114, the obtained polyimide 2 solution was coated on a glass plate, and the solvent was volatilized by holding at 100 ℃ for 60 minutes with a heating plate, thereby obtaining a colorless and transparent primary dried film having self-supporting properties. The film was fixed on a stainless steel frame, and heated at 250℃for 2 hours in a hot air dryer to evaporate the solvent, thereby obtaining a transparent substrate 2 having a thickness of 28. Mu.m. The elastic modulus based on the assay was 10GPa.

< preparation of substrate film 2 >

(preparation of polyethylene terephthalate particles (a))

As an esterification reaction apparatus, a continuous esterification reaction apparatus comprising a 3-stage complete mixing tank having a stirring apparatus, a separator, a raw material inlet and a product outlet was used, wherein terephthalic acid (TPA) was set to 2 tons/hr, ethylene Glycol (EG) was set to 2 moles relative to 1 mole of TPA, antimony trioxide was set to 160ppm relative to the amount of antimony (Sb) atoms produced in PET, and these slurries were continuously fed to the 1 st esterification reaction tank of the esterification reaction apparatus and reacted at 255℃with an average residence time of 4 hours under normal pressure.

Then, the reaction product in the 1 st esterification reaction vessel was continuously taken out of the system, supplied to the 2 nd esterification reaction vessel, 8 mass% of EG distilled off from the 1 st esterification reaction vessel with respect to the polymer produced (PET produced), and further added with an EG solution containing magnesium acetate in an amount of 65ppm of magnesium (Mg) atoms with respect to the PET produced and an EG solution containing tetramethyl phthalic acid (TMPA) in an amount of 20ppm of P atoms with respect to the PE T produced, and reacted at 260℃at an average residence time of 1.5 hours under normal pressure. Then, the reaction product in the 2 nd esterification reaction vessel was continuously taken out of the system, supplied to the 3 rd esterification reaction vessel, and EG solution containing TMPA in an amount of 20ppm of P atoms relative to the amount of PET produced was added thereto, and reacted at 260℃under normal pressure with an average residence time of 0.5 hours. The esterification reaction product produced in the 3 rd esterification reaction tank was continuously fed to a 3 rd stage continuous polycondensation reaction apparatus to be polycondensed, and further filtered through a filter medium (nominal filtration accuracy 5 μm particle 90% cut) of a stainless steel sintered body to obtain polyethylene terephthalate particles (a) having an limiting viscosity of 0.580 dl/g.

(preparation of polyethylene terephthalate film)

The pellets (a) of polyethylene terephthalate were fed to an extruder and melted at 285 ℃. The polymer was filtered through a stainless steel sintered filter medium (nominal filtration accuracy, 10 μm particles, 95% cut-off), pressed into a sheet form through a metal port, and then, the sheet was brought into contact with a casting drum having a surface temperature of 30℃by an electrostatic casting method, cooled and solidified to prepare an unstretched film. The unstretched film was uniformly heated to 75℃using a heated roll, heated to 100℃using a non-contact heater, and subjected to roll stretching (longitudinal stretching) by 1.5 times. The obtained uniaxially stretched film was fed into a tenter, heated to 125℃and stretched transversely to 5.5 times, and the width was fixed, and heat treatment was performed at 190℃for 5 seconds, and further, the film was relaxed at 100℃in the width direction by 4%, whereby a base film 2 (described as PET in the table) was obtained as a polyethylene terephthalate film having a film thickness of 50. Mu.m.

< preparation of cover Member >

< preparation of cover Member 201 >

The base film 101 prepared in example 1, the transparent base 1 prepared as described above, and the base film 2 were bonded via the following adhesive layers to prepare the lid member 201 shown in table II.

< Material of adhesive layer >

(preparation of acrylic Polymer)

A4-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube, and a cooler was charged with a monomer mixture containing 100 parts of n-butyl acrylate and 5 parts of acrylic acid. Further, 0.1 part of 2,2' -azobisisobutyronitrile as a polymerization initiator was added to 100 parts of the above-mentioned monomer mixture (solid content) together with 100 parts of ethyl acetate, and after nitrogen substitution by introducing nitrogen gas while stirring slowly, the liquid temperature in the flask was kept at about 55℃and polymerization was carried out for 8 hours to prepare a solution of an acrylic polymer having a weight average molecular weight (Mw) of 160 ten thousand.

(preparation of adhesive composition solution)

An acrylic pressure-sensitive adhesive composition was prepared by blending 0.45 part of an isocyanate-based crosslinking agent (CORONATEL, trimethylol propane toluene diisocyanate, manufactured by TOSOH corporation) with 100 parts of the solid content of the obtained acrylic polymer solution.

(formation of adhesive layer and preparation of cover Member)

Next, on the a-side of the base film 101, corona discharge treatment was performed at a corona output intensity of 2.0kW and a linear velocity of 18m/min, and on the corona discharge treated surface, the prepared adhesive composition solution was applied by a wire bar coater so that the film thickness after drying was about 3 μm, and then dried sequentially at 50 ℃, 60 ℃ and 70 ℃ for 60 seconds to form an adhesive layer, and after bonding, the support of the base film 101 was peeled off to obtain a lid member 201 (see fig. 5B).

< preparation of cover members 202 to 222 >

In the production of the lid member 201, the lid members 202 to 222 were produced in the same manner except that the combinations of the types of the base material film 1, the transparent base material and the base material film 2 were changed as described in table II.

The cover member 214 also uses the prepared base film 102 on the base film 2 in the preparation of the cover member 202. The substrate film 2 was bonded so that the a-plane side of the substrate film 102 was also disposed on the glass substrate side. In addition, the lid member 215 is not attached to the substrate film 2 side in the preparation of the lid member 202.

Evaluation (evaluation)

< evaluation of crease >

A cover member sample having dimensions of 20mm in the TD direction and 110mm in the MD direction was prepared. A non-load U-shaped expansion and contraction tester (manufactured by Yuasaa-SYSTEM Co., ltd., DLDMLH-FS) was used, and the bending radius was set to 1mm and the bending was performed 100 times at a speed of 1 time/second. At this time, the sample was fixed at a position of 10mm at both ends on the MD side, and the bent portion was set to 20 mm. Times.90 mm. After the bending treatment was completed, the bent portion of the sample was placed on ase:Sub>A flat surface with the inside facing downward, and the bent portion was measured by ase:Sub>A commercially available haze meter, and when the haze value before evaluation was ase:Sub>A and the haze value after evaluation was B, the difference (B-ase:Sub>A) between the values was obtained, and the following classification was performed.

And (3) the following materials: below 0.2

O: is 0.2 or more and less than 0.5

Delta: is 0.5 or more and less than 1.0

X: is more than 1.1

Preferably delta or more.

The constitution of the cover member and the evaluation results are shown in Table II below.

From the results shown in tables I and II, the lid members 201 to 217 using the base material films 101 to 112 of the present invention gave excellent results in evaluation of the press-in strength of the base material film and the crease of the lid member, as compared with the lid members 218 to 221 using the base material films 113 to 116 of the comparative example and the lid member 222 in which the transparent base material was thick film.

Industrial applicability

The cover member of the present invention has a feature that it does not cause a crease in a base film provided in the cover member when repeatedly bent, in addition to improving operability, and therefore, is suitable for a display device with the cover member, which does not cause disorder of an image at a folded portion of a display, and which is excellent in visibility, and which is suitable for a folding display using an organic electroluminescent element.

Symbol description

1 substrate film 1

2 substrate film 2

3 transparent substrate

4 adhesive layer

5 support body

10 cover member

21 carrier substrate

22 glass substrate

23 contact film

24 electromagnetic radiation

100 display device

101 organic EL layer

102 polarizer

B110 support body

B120 substrate film

B200 manufacturing apparatus

B210 supply part

B220 coating part

B230 dryer section

B240 cooling part

B250 winding part

R radius of curvature

Claims

2. The cover member of claim 1, wherein,

3. The cover member according to claim 1 or 2, wherein,

4. The cover member according to any one of claims 1 to 3, wherein,

the base film contains rubber particles in a range of 40 to 85 mass%.

5. The cover member according to any one of claims 1 to 4, wherein,

6. A base film for a cover member, wherein,

the substrate film is 1 μm or more and less than 15 μm,

7. The base material film for a cover member according to claim 6, wherein,

the substrate film is attached to the transparent substrate,

9. The base material film for a cover member according to any one of claims 6 to 8, wherein,

the base film contains rubber particles in a range of 40 to 85 mass%.

10. A display device is provided with:

the cover member according to any one of claims 1 to 5 or the base film for a cover member according to any one of claims 6 to 9.