KR20210122188A - Cover film and manufacturing method thereof - Google Patents

Abstract

The present invention is a cover film for a curved display, comprising a transparent base layer and a transparent surface layer laminated on one side of the base layer, wherein the base layer contains a urethane-based (meth)acrylate; and a bifunctional or more (meth)acrylate, the surface layer contains a tetrafunctional or more (meth)acrylate, the base layer contains 50 parts by weight or more of the urethane-based (meth)acrylate, and the surface layer contains 65 parts by weight or more of the tetrafunctional or more (meth)acrylate, the thickness of the surface layer is 40 μm or more, and the thickness of the base layer is 45 μm or more and 85 μm or less. According to the present invention, both flexuosity resistance and high surface hardness can be ensured.

Description

Cover film and its manufacturing method

The present invention relates to a cover film and a method for manufacturing the same.

In recent years, various cover films for protecting the surface of a display such as a smartphone have been proposed. As such a cover film, the cover film which has a hard-coat layer and a transparent film is proposed by patent document 1, for example. This transparent film is produced as follows. For example, in patent document 1, after apply|coating an ultraviolet curable acrylic resin on a 1st base film, and laminating|stacking a 2nd base film on this ultraviolet curable acrylic resin, irradiating an ultraviolet-ray and a crosslinking rate is 40- It hardens so that it may become 60 %. In this way, a transparent film is formed from an ultraviolet curable acrylic resin. Next, after peeling two base films, the ultraviolet curable resin for hard-coat layers containing a fluorine is apply|coated on a transparent film, and an ultraviolet-ray is irradiated. In this way, ultraviolet curable resin is hardened|cured and a hard-coat layer is formed. Through the above process, the cover film provided with a transparent film and a hard-coat layer is formed.

Japanese Patent Laid-Open No. 2017-159506

In the cover film as described above, in addition to bending resistance, high surface hardness is calculated|required. However, as a cover film which makes bending resistance and high surface hardness compatible, what has sufficient performance was still not proposed, but there existed room for improvement. The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a cover film for a curved display that is compatible with bending resistance and high surface hardness, and a method for manufacturing the same.

Item 1. A cover film for a curved display, comprising:

a transparent base layer;

A transparent surface layer laminated on at least one surface of the base layer,

The base layer contains a urethane-based (meth)acrylate and a (meth)acrylate having a bifunctional or higher function,

The surface layer contains tetrafunctional or more (meth)acrylate,

The base layer contains 50 parts by weight or more of the urethane-based (meth)acrylate,

The surface layer contains 65 parts by weight or more of the tetrafunctional or higher (meth)acrylate,

The thickness of the surface layer is 40 μm or more,

The thickness of the said base material layer is 45 micrometers or more and 85 micrometers or less, The cover film.

Item 2. The cover film according to Item 1, wherein the surface layer further contains 10 parts by weight or more of trifunctional or less (meth)acrylate.

Item 3. The cover film according to Item 1 or 2, wherein the base layer contains 15 parts by weight or more of the low-viscosity bifunctional or higher (meth)acrylate.

Item 4. The cover film according to any one of Items 1 to 3, wherein the base layer further contains a trifunctional or higher (meth)acrylate.

Item 5. A step of laminating a resin composition for a substrate layer containing a urethane-based (meth)acrylate and a bifunctional or higher (meth)acrylate on a support film;

A step of crosslinking the resin composition for a base material layer so that the crosslinking rate is 90% or less;

A step of laminating a resin composition for a surface layer containing a tetrafunctional or higher (meth)acrylate on the resin composition for a base material layer;

curing the resin composition for a base layer and the resin composition for a surface layer to form a cover film having a base layer and a surface layer;

The thickness of the surface layer is 40 μm or more,

The thickness of the said base material layer is 45 micrometers or more and 85 micrometers or less, The manufacturing method of a cover film.

ADVANTAGE OF THE INVENTION According to the cover film which concerns on this invention, bending resistance and high surface hardness are compatible.

1 : is sectional drawing of a cover film.
Fig. 2 is a schematic diagram showing a bending test machine and a method for using the same.

EMBODIMENT OF THE INVENTION Hereinafter, one Embodiment of the cover film which concerns on this invention is demonstrated, referring drawings. 1 : is sectional drawing of this cover film. As shown in FIG. 1, the cover film which concerns on this invention is laminated|stacked on the at least one surface of the transparent base material layer 1 and this base material layer 1, The surface layer which is harder and transparent than the base material layer 1 (2) is provided. Hereinafter, each layer will be described in detail. In addition, in the specification, the numerical value connected with "-" means the numerical range which includes the numerical value before and after "-" as a lower limit and an upper limit. In addition, when a plurality of lower limit values and a plurality of upper limits are separately described, arbitrary lower limits and upper limits are selected and can be connected with "-".

<1. Base layer>

The base material layer (1) which concerns on this invention is an ionizing-radiation-curable resin containing the compound which has the radical polymerization property which polymerizes or cross-links by an ionizing radiation (ultraviolet ray or an electron beam). Specifically, it can be set as the resin material containing a urethane type (meth)acrylate and the (meth)acrylate more than bifunctional. In addition, with this base material layer 1, the (meth)acrylate more than trifunctional which are mentioned later, a polymerization initiator, and an additive can also be mix|blended as needed. In addition, "bifunctional or more" means that at least 2 or more of ethylenic unsaturated bonds are included in a structural unit, for example. This point is the same also in the surface layer 2 mentioned later.

<1-1. Urethane-based (meth)acrylate>

As urethane type (meth)acrylate, For example, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urethane Prepolymer, dipentaerythritol pentaacrylate toluene diisocyanate urethane prepolymer, pentaerythritol triacrylate isophorone diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate isophorone diisocyanate urethane prepolymer, etc. can be used.

1000-10000 are preferable, and, as for the weight average molecular weight of a urethane type (meth)acrylate, 2000-5000 are more preferable, for example. Moreover, as a measuring method of molecular weight, GPC method can be used.

<1-2. (meth)acrylates having more than bifunctional function>

As a bifunctional compound containing two unsaturated bonds, for example, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, hexanediol di(meth)acrylate ) acrylate, nonanediol di (meth) acrylate, ethoxylated hexanediol di (meth) acrylate, propoxylated hexanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di ( Meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, ethoxylated neopentyl glycol di (meth) acrylate, tripropylene glycol Di(meth)acrylates, such as di(meth)acrylate and hydroxypivalate neopentyl glycol di(meth)acrylate, etc. are mentioned. Such a bifunctional or higher (meth)acrylate has a relatively low viscosity, for example, preferably 300 mPa·s (25° C.) or less, more preferably 100 mPa·s (25° C.) or less, and 50 It is more preferable that it is mPa·s (25°C) or less.

<1-3. (Meth) acrylate more than trifunctional>

Examples of the polyfunctional compound containing three or more unsaturated bonds include trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth) Tri(meth)acrylates, such as acrylate, tris 2-hydroxyethyl isocyanurate tri(meth)acrylate, and glycerol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol Trifunctional (meth)acrylate compounds such as tri(meth)acrylate and ditrimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and ditrimethylolpropane tetra(meth)acrylate , dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, ditrimethylol propane penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ditrimethylol propane hexa Trifunctional or more trifunctional (meth)acrylate compounds such as (meth)acrylate, and polyfunctional (meth)acrylate compounds in which a part of these (meth)acrylates are substituted with an alkyl group or ε-caprolactone (meth) ) acrylate compounds. The viscosity of such trifunctional or more than trifunctional (meth)acrylate is higher than the viscosity of the bifunctional or more than bifunctional (meth)acrylate described in the item <1-2>, for example, the viscosity is 1000 to 9000 mPa·s (25 deg.

<1-4. Content>

It is preferable that it is 50-90 weight part with respect to 100 weight part of base material layers, and, as for urethane-type (meth)acrylate, it is more preferable that it is 70-80 weight part. When urethane-type (meth)acrylate is more than 90 weight part, since it is high viscosity, it becomes difficult to manufacture the base material layer (1). Moreover, bending resistance falls that urethane type (meth)acrylate is less than 50 weight part. On the other hand, it is preferable that it is 15-50 weight part with respect to 100 weight part of base material layers, and, as for the (meth)acrylate more than bifunctional, it is more preferable that it is 20-30 weight part. Moreover, multiple types of (meth)acrylates can also be contained. For example, bifunctional (meth)acrylate and the trifunctional or more than trifunctional (meth)acrylate described in the section <1-3> can be contained. In this case, it is preferable that the trifunctional or more than trifunctional (meth)acrylate described in the item <1-3> is 15-35 weight part with respect to 100 weight part of base material layers. In addition, as a combination of bifunctional or more functional low-viscosity (meth)acrylate and trifunctional or more than trifunctional (meth)acrylate, for example, bifunctional low-viscosity (meth)acrylate and tetrafunctional (meth)acryl Although it can be set as a low-viscosity (meth)acrylate of trifunctional rate or a hexafunctional (meth)acrylate, it is not limited to this.

<1-5. Photoinitiator>

Examples of the polymerization initiator include benzyl methyl ketals such as 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxycyclohexylphenyl ketone, and 2-hydroxy-2-methyl-1-one. α-hydroxyketones such as phenylpropan-1-one, 2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1 α-aminoketones such as -(4-morpholinophenyl)butanone-1, and bisacylphosphine oxides such as bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide , 2,2'-bis(o-chlorophenyl)-4,4',5,5'-tetraphenyl-1,1'-biimidazole, bis(2,4,5-triphenyl)imidazole, etc. of bisimidazoles, N-arylglycines such as N-phenylglycine, organic azides such as 4,4'-diazidechalcone, 3,3',4,4'-tetra(tert-butylperoxycarin) Including organic peroxides such as carboxyl) benzophenone, J. Photochem. Sci. Technol. 2, 283 (1987). compounds described in .

Specific examples thereof include iron arene complexes, trihalogenomethyl-substituted S-triazine, sulfonium salts, diazonium salts, phosphonium salts, selenonium salts, arsonium salts, and iodonium salts. Moreover, as an iodonium salt, Macromolecules, 10, 1307 (1977). compounds described in, for example, diphenyliodonium, ditolyliodonium, phenyl(p-anisyl)iodonium, bis(m-nitrophenyl)iodonium, bis(p-tert-butylphenyl)iodonium, Chloride, bromide, or borofluoride salt of iodonium such as bis(p-chlorophenyl)iodonium, hexafluorophosphate salt, hexafluoroarsenate salt, aromatic sulfonate salt, diphenylphenacylsulfonium (n- Sulfonium organic boron complexes, such as butyl) triphenyl borate, are mentioned.

<1-6. Additives>

The following additives can be blended as needed. For example, silicone type and fluorine type additives (for example, leveling agent) which provide leveling, surface slip property, low water contact angle, etc. are mentioned. By mix|blending such an additive, the abrasion resistance of the surface of the base material layer 1 can be improved. The compounding quantity of these additives can be made into 0.01-0.5 weight part with respect to 100 weight part of base material layers, for example.

<1-7. Thickness of base layer>

It is preferable that they are 45 micrometers or more and 85 micrometers or less, for example, and, as for the thickness of the base material layer 1, it is more preferable that they are 50 micrometers or more and 80 micrometers or less.

<2. surface layer>

Next, the surface layer 2 is demonstrated. The surface layer 2 is also an ionizing-radiation-curable resin containing the compound which has radical polymerizability which polymerizes or cross-links by an ionizing radiation (ultraviolet-ray or electron beam) similarly to the base material layer 1. Specifically, it can be set as the resin material containing tetrafunctional or more than (meth)acrylate. In addition to this, you may further contain trifunctional or less than trifunctional (meth)acrylate. Like the base material layer 1, you can mix|blend the polymerization initiator and additive mentioned later with this surface layer 2 as needed. In addition, "tetrafunctional or more" means that at least 4 or more ethylenic unsaturated bonds are included in a structural unit, for example. Moreover, the viscosity of trifunctional or less than trifunctional (meth)acrylate is higher than the viscosity of the bifunctional or more than bifunctional (meth)acrylate described in the <1-2> term of the base material layer (1), For example, 300-7000 It is preferable that it is mPa*s (25 degreeC), It is more preferable that it is 400-6000 mPa*s (25 degreeC), It is still more preferable that it is 500-5000 mPa*s (25 degreeC).

For the (meth)acrylate of tetrafunctional or higher, the same material as the (meth)acrylate of trifunctional or higher in the base layer (1) can be used. In addition, the same material as the base material layer 1 can be used also about a polymerization initiator and an additive.

It is preferable that it is, for example, 10-35 weight part with respect to 100 weight part of surface layers, and, as for the trifunctional or less-functional (meth)acrylate, it is more preferable that it is 15-30 weight part. Moreover, it is preferable that it is, for example, 65-90 weight part with respect to 100 weight part of surface layers, and, as for the (meth)acrylate more than tetrafunctional, it is more preferable that it is 70-85 weight part. In addition, as a combination of trifunctional or less than trifunctional (meth)acrylate and tetrafunctional or more than tetrafunctional (meth)acrylate, for example, trifunctional (meth)acrylate and tetrafunctional (meth)acrylate, or bifunctional Although it can be set as (meth)acrylate of and 6 functional (meth)acrylate, it is not limited to this.

The thickness of the surface layer 2 is preferably 40 µm or more and 90 µm or less, more preferably 50 µm or more and 80 µm or less, and still more preferably 60 µm or more and 75 µm or less. Since the surface layer 2 is a hard layer, in order to raise the surface hardness measured by pencil hardness etc., it is required that thickness is 40 micrometers or more. On the other hand, since bending|flexion performance will fall when it is too thick, it is unpreferable.

Moreover, it is preferable that it is 5H or more, It is preferable that it is 6H or more, and, as for the surface layer 2, it is more preferable that it is 7H or more in the surface pencil hardness test prescribed|regulated by JIS-K5600-5-4 (1999).

<3. Manufacturing method of cover film>

Although the manufacturing method in particular of the cover film which concerns on this invention is not limited, For example, it can manufacture as follows. First, a 1st base film is conveyed by a roll-to-roll, and after apply|coating the resin composition for base material layers prepared with the material mentioned above on it, it is made to dry. This 1st base film is polyethylene terephthalate, for example; polyamide; polycarbonate; acrylic resin; polyolefin resins such as polypropylene and polyethylene; Cellulose-type resin, such as a diacetyl cellulose and a triacetyl cellulose; It can form with polyvinylidene chloride etc.

As a coating method of the resin composition for base material layers, well-known methods, such as a roll coater, a reverse roll coater, a gravure coater, a knife coater, and a bar coater, are employable, for example.

The method of drying the applied resin composition for a base material layer is not specifically limited. For example, the method of passing the 1st base film to which the resin composition for base material layers was apply|coated in the dryer is mentioned. It is preferable that the drying temperature at this time is 40-100 degreeC, for example. The above application|coating method and drying method are the same also in the resin composition for surface layers mentioned later.

Next, ionizing radiation is irradiated to the resin composition for base material layers, and it bridge|crosslinks. It is preferable that it is 90 % or less, and, as for the crosslinking ratio at this time, it is more preferable that it is 50 % or less. When the crosslinking rate of the resin composition for a base material layer is more than 90 %, since the bond between a base layer and a surface layer becomes weak, bending resistance falls. In addition, it is preferable to use an ultraviolet-ray as an ionizing radiation source, and light sources, such as a high-pressure mercury-vapor lamp, a low-pressure mercury-vapor lamp, an ultra-high-pressure mercury-vapor lamp, a metal halide lamp, a carbon arc, a xenon arc, can be used. This point is the same also in irradiation of the ionizing radiation with respect to the resin composition for surface layers.

Then, on this resin composition for base material layers, the resin composition for surface layers prepared with the above-mentioned material is apply|coated, and it is made to dry. Further, a second base film containing fluorine is laminated on the resin composition for the surface layer. This 2nd base film is a film which has a coating layer containing a fluorine-type additive on a base film. This base film can be formed from the same material as a 1st base film. Moreover, a 2nd base film is laminated|stacked so that a coating layer may contact|connect the resin composition for surface layers. For this reason, when a fluorine-type additive is added to the resin composition for surface layers, a fluorine-type additive can segregate in the outermost surface (surface opposite to a base material layer) of a surface layer.

Subsequently, ionizing radiation is irradiated to bridge|crosslink and harden the resin composition for surface layers and the resin composition for base material layers. Finally, when a 1st base film and a 2nd base film are peeled, the cover film which concerns on this invention is completed.

<4. Features>

According to the cover film which concerns on this embodiment, the following effects can be acquired.

(1) After applying the resin composition for the base layer, the crosslinking rate after application of the resin composition is set to 90% or less, and then the resin composition for the surface layer is applied and the entirety is crosslinked, so that the bond between the base layer 1 and the surface layer 2 is strong. , can improve the bending performance.

(2) Surface hardness becomes strong by containing 65 weight part or more of (meth)acrylates more than tetrafunctional in surface layer (2). In addition to this, when trifunctional or less than trifunctional (meth)acrylate is contained, hardness will not become high too much. Thereby, it can suppress that a crack generate|occur|produces at the time of bending|flexion.

(3) Pencil hardness can be made into 5H or more by making the thickness of the surface layer 2 into 40 micrometers or more.

(4) By having a base material layer containing a urethane-type (meth)acrylate, the stress at the time of bending can be relieved and the breakage of the cover film resulting from generation|occurrence|production of a crack in the surface layer 2 can be suppressed.

(5) Bending resistance can be improved by making the thickness of the base material layer 1 into 45 micrometers or more and 85 micrometers or less.

From the above, the cover film which concerns on this invention can be used suitably as a cover film for curved displays.

Example

Next, an embodiment of the present invention will be described. However, the present invention is not limited to the following examples.

<1. Preparation of Examples and Comparative Examples>

Below, preparation of the cover film which concerns on Examples 1-7 and Comparative Examples 1-5 is demonstrated.

First, for the base layer, a trifunctional urethane-based acrylate (UV-7510B manufactured by Mitsubishi Chemical Corporation) having a viscosity of 800 to 1800 mPa·s (60° C.) (10000 mPa·s (25° C.) or more), a viscosity of 10 mPa·s ( A resin composition for a base material layer containing a bifunctional (meth)acrylate (light acrylate 1.9ND-A manufactured by Kyoeisha Chemical Co., Ltd.) and a polymerization initiator (Omnirad1173 manufactured by IGM Resins BV) of 25°C) was prepared. Moreover, about Example 3 and Comparative Example 1, the hexafunctional (meth)acrylate (Kyoeisha Chemical Co., Ltd. light acrylate DPE-6A) of a viscosity 4000-7000 mPa*s (25 degreeC) is contained further. did.

On the other hand, for the surface layer, a hexafunctional (meth)acrylate having a viscosity of 4000 to 7000 mPa·s (25°C) (light acrylate DPE-6A manufactured by Kyoeisha Chemical Co., Ltd.), a viscosity of 700 to 900 mPa·s (25°C) ) of a bifunctional (meth)acrylate (light acrylate BP-4EAL manufactured by Kyoeisha Chemical Co., Ltd.), a polymerization initiator (Omnirad1173 manufactured by IGM Resins BV), and a fluorine additive (KY-1211 manufactured by Shin-Etsu Chemical Co., Ltd.) A resin composition for a surface layer was prepared. The composition and thickness of the base layer and the surface layer are as shown in Table 1.

Next, as the first base film, a PET film (U48 manufactured by Toray Corporation) having a thickness of 100 µm was prepared. Next, the resin composition for a base material layer was coated on this PET film using the wire bar coater. Then, after drying the dilution solvent by heat treatment for 2 to 5 minutes at 80 degreeC, this resin composition for base material layers was hardened by the accumulated light quantity of 200 mJ/cm<2> using UV irradiation apparatus (made by Heraeus Corporation). . The crosslinking ratio at this time is as showing in Table 1.

Then, the resin composition for surface layers was coated using the wire bar coater on the resin composition for base material layers which bridge|crosslinked a part. Then, on this resin composition for surface layers, the 2nd base film mentioned above is laminated|stacked. A 2nd base film is a film which has on the surface the hard-coat layer used as the film thickness of 2 micrometers after hardening the ultraviolet curable resin containing a fluorine additive on the same base film as a 1st base film.

Then, the same ultraviolet-ray as above was irradiated from on the 2nd base film, and the resin composition for surface layers and the resin composition for base material layers were hardened. Finally, both base films were peeled off, and the cover film which concerns on an Example and a comparative example was obtained.

A 2.0 x 9.0 cm sample piece was cut out from the Example and the comparative example produced as mentioned above using the laser cutting apparatus (The SpiritGX laser output by GCC company: 15 W, speed: 200 mm/sec). At this time, the protective film was affixed on both surfaces of the cover film, the laser was irradiated on it, and it cut|disconnected. The protective film was a PET film with a thickness of 100 µm in which an adhesion layer having a thickness of 5 µm was laminated, and the adhesion layer was affixed to the cover film.

<2. Evaluation test>

The surface pencil hardness test prescribed|regulated by JIS-K5600-5-4 (1999) was implemented. In addition, with respect to the sample piece of each cover film prepared as described above, using the no-load U-shaped tester shown in FIG. 2, the test speed was 0.85 sec/time, the bending diameter of φ 1.5 mm, and the surface layer was placed inside when bent. , the number of repeated bending was measured. More specifically, this testing machine has two movable plates that can be turned, and the rotation shafts of the movable plates are arranged adjacent to each other so that the rotation shafts of the movable plates become parallel. And on the movable plate of the horizontal state shown in Fig.2 (a), in the state which arrange|positioned the sample piece of a cover film, as shown in Fig.2(b), by turning both movable plates 90 degrees, the cover film The sample piece was bent in a U shape. And the number of times of repeated bending until the sample piece of a cover film fracture|ruptures was confirmed. The results are as shown in Table 2 below.

Since the comparative example 1 has little content rate of a urethane type (meth)acrylate, the base material layer is hardened. Therefore, it is thought that the flexibility is falling. In Comparative Example 2, since the thickness of the base layer is thin and the strength of the base layer is low, when the cover film is bent, the stress of the surface layer cannot be absorbed, and it is considered that the flexibility is lowered. In Comparative Example 3, since the thickness of the base layer is thick, when the cover film is bent, the stress applied to the surface layer becomes large, and it is considered that the flexibility is lowered. In Comparative Example 4, since the film thickness of the surface layer was thin, pencil hardness was low. And in Comparative Example 5, since there is little hexafunctional (meth)acrylate contained in a surface layer, it is thought that pencil hardness is falling.

On the other hand, Examples 1-7 did not generate|occur|produce the same problem as Comparative Examples 1-5, but it turned out that bending resistance and high surface hardness are compatible.

1: base layer
2: surface layer

Claims (5)

A cover film for a curved display, comprising:
a transparent base layer;
A transparent surface layer laminated on at least one surface of the base layer,
The base layer contains a urethane-based (meth)acrylate and a (meth)acrylate having a bifunctional or higher function,
The surface layer contains a tetrafunctional or higher (meth)acrylate,
The base layer contains 50 parts by weight or more and 90 parts by weight or less of the urethane-based (meth)acrylate with respect to 100 parts by weight of the base layer,
The surface layer contains 65 parts by weight or more of the tetrafunctional or higher (meth)acrylate with respect to 100 parts by weight of the surface layer,
The thickness of the surface layer is 40 μm or more,
The thickness of the said base material layer is 45 micrometers or more and 85 micrometers or less, The cover film. The method of claim 1,
The said surface layer further contains 10 weight part or more of trifunctional or less (meth)acrylates with respect to 100 weight part of said surface layers, The cover film. 3. The method according to claim 1 or 2,
The said base material layer, The cover film which contains 15 weight part or more of the said bifunctional or more than (meth)acrylates with respect to 100 weight part of said base material layers. 4. The method according to any one of claims 1 to 3,
The said base material layer, the cover film which further contains trifunctional or more than trifunctional (meth)acrylate. The step of laminating|stacking the resin composition for base material layers containing a urethane type (meth)acrylate and a bifunctional or more than bifunctional (meth)acrylate on a base film;
A step of crosslinking the resin composition for a base material layer so that the crosslinking ratio is 90% or less;
A step of laminating a resin composition for a surface layer containing a tetrafunctional or higher (meth)acrylate on the resin composition for a base material layer;
curing the resin composition for a base layer and the resin composition for a surface layer to form a cover film having a base layer and a surface layer;
The thickness of the surface layer is 40 μm or more,
The thickness of the base layer is 45 μm or more and 85 μm or less,
The method for producing a cover film, wherein the base layer contains 50 parts by weight or more and 90 parts by weight or less of the urethane-based (meth)acrylate with respect to 100 parts by weight of the base layer.

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