JP2015068996A - Screen protection base film and screen protection sheet using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screen protection base film and a screen protection sheet using the same which achieve both of an excellent design having a uniform glossy feeling and visibility in addition to antistatic properties and dent resistance.SOLUTION: A screen protection base film provided with an easily adhesive layer at least on one surface of a laminate film satisfies the following conditions (1) to (4). (1) A lamination film has a layer made from a resin A (hereinafter, called an A layer) and a layer made from a resin B (hereinafter, called a B layer) alternately stacked with a total of 250 layers or more in a thickness direction, and includes three or more thick film layers having a thickness of at least 1 μm or more and 20 μm or less. (2) The easily adhesive layer is composed of a composition comprising an acrylic-urethane copolymer resin, cross-linking agents of two or more kinds, a chemical compound having a polythiophene structure, and the chemical compound having an anion structure. (3) An average reflectance in wavelength bands 400 to 700 nm of the screen protection base film is 10% or more and 35% or less, brightness L(SCI) in a catoptric light is 35.0 or more and 70.0 or less, and a color difference ΔE of a film width direction 1 m is 5.0 or less. (4) The easily adhesive layer side of the screen protection base film has specific surface resistivity of 1.0×10Ω/sq. or less.

Description

  The present invention relates to a screen protecting base film and a screen protective sheet using the same, having both excellent design and visibility with uniform glossiness, and further having antistatic properties and dent resistance.

  Generally, the screen protection sheet is a transparent sheet for protecting the surface of a screen such as a liquid crystal display mounted on a portable device from dirt and damage and maintaining visibility.

  In recent years, screen protection sheets have been used mainly for small displays such as mobile phones, smartphones, portable game machines, and portable audio players, as well as screen protection applications for various products such as flat-screen TVs, personal computers, and various touch panels. The functions required in response to this trend are also diversifying. For example, high gloss, design properties such as color and design, filter effect to prevent peeping, anti-fingerprint property to prevent smudges such as fingerprints, anti-reflective effect such as reflection and glare, etc. .

  Under such circumstances, in Patent Document 1, by providing a conductive layer containing a carbon nanotube and a polymer between the base material layer and the adhesive layer, it has high transparency and can withstand high electric resistance. A film has been proposed.

  Further, in Patent Document 2, a fine adhesive layer is formed on one side of a plastic base film, and a release layer formed by applying and solidifying a liquid resin agent is formed on the surface of the fine adhesive layer. In addition, even if dust adheres to the fine adhesion layer in the manufacturing process, a screen protection sheet has been proposed that can remove them easily and reliably and prevents deterioration of the display function and display quality of the image display device.

JP 2012-166252 A JP 2006-119186 A

  The antistatic film described in Patent Document 1 can obtain an antistatic function by a conductive layer having high conductivity. However, the screen protective sheet has a high haze and is not designed with sufficient consideration for visibility.

  The screen protective sheet described in Patent Document 2 can easily remove dust adhering to the fine adhesive layer by the peeling and removing operation of the peeling layer, but the electric protection property of the screen protective sheet itself is sufficiently considered. Was not. Further, visibility and design properties have not been sufficiently taken into consideration.

  Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art, achieve both excellent design and visibility with uniform gloss, and further have antistatic properties and dent resistance, and is a screen protection substrate. It is providing the material film and the screen protection sheet using the same.

The present invention employs the following means in order to solve such problems. That is, the base film for screen protection which satisfy | fills the conditions of the following (1)-(4) in which the easily bonding layer was provided in the at least one surface of the laminated | multilayer film.
(1) It has a layer made of resin A (hereinafter referred to as A layer) and a layer made of resin B (hereinafter referred to as B layer), and a total of 250 or more layers are alternately laminated in the thickness direction, and at least 1 μm or more and 20 μm or less A laminated film including three or more thick film layers having a certain thickness.
(2) The easy-adhesion layer is composed of an acrylic / urethane copolymer resin, two or more kinds of cross-linking agents, a compound having a polythiophene structure, and a composition having an anion structure.
(3) The average reflectance of the base film for screen protection in the wavelength band of 400 to 700 nm is 10% to 35%, the brightness L ^* (SCI) in reflected light is 35.0 to 70.0, and the film width direction is 1 m. The color difference [Delta] E is 5.0 or less.
(4) The surface specific resistance value on the easy adhesion layer side of the screen protecting base film is 1.0 × 10 ¹² Ω / □ or less.

  According to the present invention, there is obtained a base film for screen protection and a screen protection sheet using the same, having both excellent design and visibility with uniform glossiness, and further having antistatic properties and dent resistance. Can do.

The figure which shows the design layer thickness of Examples 1-5 and Comparative Examples 1-3 and 5 The figure which shows the design layer thickness of Example 6 The figure which shows the design layer thickness of Example 7 and Comparative Example 4

  In the base film for screen protection of the present invention, the laminated film constituting the base film for screen protection is a layer composed of a resin A in order to achieve both excellent design and visibility with uniform gloss ( Hereinafter referred to as A layer) and resin B layer (hereinafter referred to as B layer), and a total of 250 or more layers are alternately laminated in the thickness direction, and there are 3 thick film layers having a thickness of at least 1 μm and 20 μm. It is necessary to include more than one layer.

  The laminated film in the present invention needs to have a structure in which a total of 250 layers or more are alternately laminated in the thickness direction. More preferred is a structure in which a total of 400 or more layers are alternately laminated in the thickness direction, and still more preferred is a structure in which 800 or more layers are laminated. When the number of layers is less than 250, visible light cannot be uniformly reflected and a large colored film may be formed.

  The laminated film in the present invention needs to have a structure in which three or more thick film layers having a thickness of at least 1 μm to 20 μm are included. More preferably, they are 2 micrometers or more and 10 micrometers or less. When the thickness is less than 1 μm, it is not preferable because a mark is easily generated when a load is applied to the film surface. When the thickness exceeds 20 μm, the thickness of the thick film layer alone is at least 60 μm or more, which is not preferable because it is too strong and difficult to handle as a base film for screen protection.

  As an example of a preferred layer structure of the laminated film in the present invention, FIG. 1 showing the design layer thickness will be described. FIG. 1 shows a layer made of resin A (hereinafter referred to as “A layer”) and a layer made of resin B layer (hereinafter referred to as “layer A”), in which layers made of two types of resins (resin A and resin B) are alternately laminated in the thickness direction. It is the figure which plotted B for each layer order (henceforth a layer number). The layer thickness corresponds only to the integer layer number in the figure, the layer made of resin A corresponds to the odd number, and the layer made of resin B corresponds to the even number. The thick film layer is formed of a layer made of resin A. The same applies to FIGS. 2 and 3.

  Further, in the present invention, for the sake of convenience, the layer thickness configuration of FIG. 1 is referred to as a four-step inclined structure, the layer thickness configuration of FIG. 2 is referred to as a three-step inclined structure, and the layer thickness configuration of FIG. . The four-step inclined structure refers to a structure that can be approximated by four monotone increasing curves and / or monotonic decreasing curves.

  In this invention, the thick film layer which consists of resin A is located in the change point of the layer of the outermost surface of both sides of a film, and a monotone increase curve and / or a monotone decrease curve. Moreover, it is preferable that the composition of resin A has a polyethylene terephthalate or a polyethylene naphthalate as a main component from a viewpoint of impression resistance (dentation resistance). Furthermore, since the structure having a larger number of thick intermediate layers improves the stamping resistance (scratch resistance), it is preferably a three-stage or more inclined structure, and a four-stage or more inclined structure. And more preferred. If the slope is 3 steps or more, even if a stacking fault occurs in a small part and deviates from the design layer thickness, the same layer thickness exists in other parts, so coloring can be minimized. it can.

  In the laminated film of the present invention, from the viewpoint of suppressing coloring, the number of layers having a layer pair thickness of 10 nm or more and less than 220 nm is preferably larger than the number of layers having a layer pair thickness of 220 nm or more and 350 nm or less. Here, the “layer-to-thickness” referred to in the present invention is a thickness obtained by adding the respective layer thicknesses of the adjacent A layer and B layer. The layer-to-layer thickness should be the sum of the thickness of the mth A layer counted from one film surface for the A layer only and the mth B layer counted from the same surface for only the adjacent B layer. I must. Here, m represents an integer. For example, when the A1 layer / B1 layer / A2 layer / B2 layer / A3 layer / B3 layer... Are arranged on the opposite surface from one film surface, the A1 layer and the B1 layer are the first layer. The A2 layer and the B2 layer are the second layer pair, and the A3 layer and the B3 layer are the third layer pair. When the number of layers having a layer pair thickness of 10 nm or more and less than 220 nm is the same as or less than the number of layers having a layer pair thickness of 220 nm or more and 350 nm or less, the reflectance decreases with decreasing wavelength in the reflection band of the wavelength band 400 nm to 1100 nm. Since it may have a tinged appearance, it is not preferable. This occurs because the density of the layer pair that causes reflection on the low wavelength side is reduced. Therefore, as the layer pair thickness order of the layers constituting the laminated film, the layer pair thickness does not increase and decrease monotonically in a monotonic sequence, but the layer pair thickness increases and decreases in a geometric sequence while satisfying the above conditions. Is preferred. More preferably, the number of layers having a layer pair thickness of 120 nm or more and less than 220 nm is preferably 1.05 or more and 2.5 or less of a layer pair thickness of 220 nm or more and 350 nm or less.

  The two types of resins A and B may be either a thermoplastic resin or a thermosetting resin, or a copolymer or a mixture of two or more types of resins. Among them, it is preferable to use a thermoplastic resin, and it is particularly preferable to use a polyester resin from the viewpoints of strength, heat resistance, transparency, and versatility.

  As the polyester resin, a polyester obtained by polymerization from a monomer mainly composed of an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol is preferable. Here, as the aromatic dicarboxylic acid, for example, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4′- Examples thereof include diphenyl dicarboxylic acid, 4,4′-diphenyl ether dicarboxylic acid, 4,4′-diphenyl sulfone dicarboxylic acid, and the like. Examples of the aliphatic dicarboxylic acid include adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, cyclohexanedicarboxylic acid and ester derivatives thereof. Among them, terephthalic acid and 2,6-naphthalenedicarboxylic acid having a high refractive index are preferable. Only one kind of these acid components may be used, or two or more kinds may be used in combination, and further, an oxyacid such as hydroxybenzoic acid may be partially copolymerized. Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, and 1,5-pentanediol. 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-hexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2-bis (4- Hydroxyethoxyphenyl) propane, isosorbate, spiroglycol and the like. Of these, ethylene glycol is preferably used. These diol components may use only 1 type and may use 2 or more types together.

  Among the above polyesters, polyethylene terephthalate and copolymers thereof, polyethylene naphthalate and copolymers thereof, polybutylene terephthalate and copolymers thereof, polybutylene naphthalate and copolymers thereof, and polyhexamethylene terephthalate and copolymers thereof. It is preferable to use a polymer, rihexamethylene naphthalate, a copolymer thereof, and the like.

  As a preferable combination of the resin A and the resin B selected from the thermoplastic resins, it is preferable to use a resin including the same basic skeleton as one of the resins. Here, the “basic skeleton” referred to in the present invention is a repeating unit constituting the resin. For example, when one resin is polyethylene terephthalate, ethylene terephthalate is the basic skeleton. Examples of the polymer include a polymer (copolymer) composed of an ethylene terephthalate unit and a cyclohexane 1,4-dimethylene terephthalate unit. As another example, when one resin is polyethylene, ethylene is a basic skeleton. When the resin having the same basic skeleton is used, problems such as stacking faults such as flow marks and peeling between layers are less likely to occur in the formation of a laminated film.

  The substrate film for screen protection of the present invention needs to have an average reflectance of 10% or more and 35% or less in a wavelength band of 400 to 700 nm. More preferably, it is 12% or more and 32% or less. An average reflectance of less than 10% is not preferable because the reflection is low, so that there is no difference from a general transparent film and the design as a highly reflective film may be inferior. When the average reflectance exceeds 35%, the transmittance is lowered and the visibility of the liquid crystal display may be lowered.

The base film for screen protection of the present invention needs to have a lightness L ^* (SCI) in reflected light of 35.0 or more and 70.0 or less. More preferably, it is 40.0 or more and 65.0 or less. When the lightness L ^* (SCI) is less than 35.0, it is not preferable because sufficient gloss may not be obtained. If the lightness L ^* (SCI) exceeds 70.0, the gloss is too high and the visibility of the liquid crystal display may be lowered, which is not preferable. Here, SCI is a lightness measurement method for reflected light, and there is no light trap on the detection side, and the color is measured without removing regular reflection.

  The base film for screen protection of the present invention needs to have a color difference ΔE of 1 m in the film width direction of 5.0 or less. When the color difference ΔE exceeds 5.0, the color difference increases to such an extent that the color difference on the liquid crystal display can be visually recognized, which is not preferable because design quality may deteriorate in addition to deterioration of the quality of the film itself.

The base film for screen protection of the present invention is provided with an easy adhesion layer on at least one surface of the laminated film, and the surface specific resistance value on the easy adhesion layer side is 1.0 × 10 ¹² Ω / □ or less. It is necessary. Preferably, it is 1.0 × 10 ¹¹ Ω / □ or less, and particularly preferably 1.0 × 10 ¹⁰ Ω / □ or less. When exceeding 1.0 × 10 ¹² Ω / □, for example, a silicone-based adhesive is applied as an adhesive layer to the screen protective base film, and then applied to a liquid crystal display as a screen protective sheet. Etc. are not preferable because high appearance may not be realized.

  The screen protective substrate film of the present invention preferably has a haze of 3.0 or less. More preferably, it is 2.0 or less, and particularly preferably 1.5 or less. When the haze exceeds 3.0, the visibility of the display (screen) may be lowered when a screen protective sheet using the screen protective substrate film is attached to the liquid crystal display, which is not preferable.

In the screen protecting base film of the present invention, the difference between the in-plane average refractive index of the A layer of the laminated film and the in-plane average refractive index of the B layer is preferably 0.030 or more and 0.055 or less. More preferably, it is 0.032 or more and 0.050 or less. When the difference in the in-plane average refractive index is less than 0.030, it is not preferable because sufficient reflectance and lightness L ^* may not be obtained. When the difference in the in-plane average refractive index exceeds 0.055, the transmittance becomes too low and the visibility of the liquid crystal display may be lowered, which is not preferable.

  The screen protective substrate film of the present invention is pressed when the surface of the film is weighted at 0.9 kgf (11.1 MPa) with a terminal having a hemispherical tip with a diameter of 1 mm using a hardness meter and held for 5 seconds. It is preferable that the amount of deformation due to the trace is 250 nm or less. When the deformation amount exceeds 250 nm, it is not preferable because the screen protection sheet is greatly deformed when foreign matter such as dust enters between the liquid crystal display and the screen protection sheet, which may impair the appearance and the visibility of the screen. In addition, to reduce the deformation amount of the laminated film, it can be achieved by increasing the thickness of the thick film layer of the surface layer, but in that case, the entire thickness of the laminated film is simultaneously increased, which is disadvantageous in terms of cost, The thickness of the thick film layer is preferably 10 μm or less.

  In the present invention, the easy-adhesion layer provided on at least one surface of the laminated film is an acrylic layer for preventing the adhesion of foreign matters such as dust due to charging during the manufacturing process of the screen protection sheet and the use of the screen protection sheet. -It needs to be comprised with the composition which consists of a urethane copolymer resin, two or more types of crosslinking agents, the compound which has a polythiophene structure, and the compound which has an anion structure.

  For the acrylic / urethane copolymer resin of the easy-adhesion layer used in the present invention, examples of the acrylic monomer include alkyl acrylate (the alkyl group is methyl, ethyl, n-propyl, n-butyl, isobutyl, t-butyl, 2- Ethyl hexyl, cyclohexyl etc.), 2-hydroxylethyl acrylate, 2-hydroxylethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate and other hydroxy group-containing monomers, acrylamide, methacrylamide, N-methyl methacrylamide, N-methyl Amino such as acrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N, N-diethylaminoethyl acrylate, N, N-diethylaminoethyl methacrylate A monomer containing a carboxyl group of a glycidyl group such as a monomer containing glycidyl acrylate or glycidyl methacrylate, acrylic acid, methacrylic acid or a salt thereof (sodium salt, potassium salt, ammonium salt, or the like) or a salt thereof. it can.

  For the crosslinking agent of the easy-adhesion layer used in the present invention, it is preferable to copolymerize a crosslinkable functional group. For example, melamine-based crosslinking agent, isocyanate-based crosslinking agent, aziridine-based crosslinking agent, epoxy-based crosslinking agent, methylolation or alkylation. Rolled urea crosslinking agents, acrylamide crosslinking agents, polyamide crosslinking agents, oxazoline crosslinking agents, carbodiimide crosslinking agents, various silane coupling agents, various titanate coupling agents, and the like can be used. Further, from the viewpoint of heat-and-moisture resistance to the hard coat layer and the silicone-based adhesive layer, it is preferable to use two or more types of crosslinking agents. Specifically, at least one of the crosslinking agents is an oxazoline-based crosslinking agent or a carbodiimide. It is preferable to use a system crosslinking agent.

  In the easy-adhesion layer used in the present invention, it contains a conductive polymer made of polythiophene from the viewpoint of imparting an antistatic function in order to prevent foreign matter from being mixed between the liquid crystal display and the screen protection sheet. It is preferable. As polythiophene, for example, a compound in which an oxygen atom is bonded to the 3rd and 4th carbon atoms of the thiophene ring can be suitably used. In the case where a hydrogen atom or a carbon atom is bonded directly to the carbon atom, it may be difficult to make the coating solution water-based.

  Regarding the compound having an anion structure of the easy-adhesion layer used in the present invention, the compound having an anion structure is an acidic polymer in a free acid state, for example, a polymer carboxylic acid, a polymer sulfonic acid, or a polyvinyl sulfonic acid. Etc. Examples of the polymer carboxylic acid include polyacrylic acid, polymethacrylic acid, polymaleic acid and the like, and it is particularly preferable to use polystyrene sulfonic acid in terms of antistatic properties. The free acid may be in the form of a partially neutralized salt. In addition, the compound having an anion structure can be used in a form copolymerized with other copolymerizable monomers such as acrylic acid ester, methacrylic acid ester, styrene and the like. In that case, it is preferable from a viewpoint of antistatic property that the ratio of the other monomer in the compound which has an anion structure is 20 weight% or less. The molecular weight of the polymer carboxylic acid or polymer sulfonic acid used as the compound having an anion structure is not particularly limited, but the weight average molecular weight is 1,000 or more and 1,000 from the viewpoint of coating stability and antistatic properties. Is preferably 5,000 or less, more preferably 5,000 or more and 150,000 or less. Moreover, you may contain alkali salts and ammonium salts, such as lithium salt and sodium salt, in the range which does not inhibit the effect of this invention. In the case of a salt in which a polyanion is neutralized, it is considered to act as a dopant. This is because polystyrene sulfonic acid and ammonium salt, which function as very strong acids, are out of equilibrium on the acidic side due to the equilibrium reaction after neutralization. By adding these compounds having an anion structure at the time of polymerization of the compound having a thiophene structure, the compound having a polythiophene structure that is originally insoluble in water can be easily dispersed in water or made aqueous. Furthermore, the function of an anion as an acid also functions as a polythiophene doping agent, leading to an improvement in antistatic properties. Therefore, it is preferable to use a composition comprising a compound having a polythiophene structure and a compound having an anion structure for the easy adhesion layer in the present invention from the viewpoint of imparting an antistatic function.

  The screen protective substrate film of the present invention is a screen protective sheet provided with a hard coat layer on the surface of the easily protective layer side of the screen protective substrate film and an adhesive layer on the other surface, for example, a mobile phone, It can be suitably used for screen protection applications such as various touch panels, mainly small devices such as smartphones, portable game machines, and portable audio players.

  In the screen protection sheet using the screen protection substrate film of the present invention, the screen protection sheet is provided by providing a hard coat layer on the surface opposite to the surface (adhesive layer side) on which the screen protection sheet is attached to the liquid crystal display. The sheet can be prevented from being damaged, and higher appearance can be realized. However, for applications that do not require a hard coat layer in terms of cost, it is not always necessary to provide a hard coat layer.

  As the hard coat layer, for example, acrylic resins, urethane resins, melamine resins, organic silicate resins, silicone resins, and the like can be used. Among these, from the viewpoints of hardness, durability, and productivity, silicone resins and acrylic resins are preferable, and acrylic resins, particularly active ray curable acrylic resins are more preferable.

  In the composition of the hard coat layer, various additives can be blended as necessary within a range not impairing the effects of the present invention. For example, stabilizers such as antioxidants, light stabilizers, ultraviolet absorbers, surfactants, leveling agents, antistatic agents, and the like can be used. Although the thickness of a hard-coat layer is decided according to a use, Usually, 0.1 micrometer or more and 30 micrometers or less are preferable, More preferably, they are 1 micrometer or more and 15 micrometers or less. When the thickness of the hard coat layer is less than 0.1 μm, even if the composition of the hard coat layer is sufficiently cured, the film thickness is too thin, so that the surface hardness is low and the surface may be easily damaged. When the thickness of the hard coat layer exceeds 30 μm, the cured film may easily crack due to stress such as bending.

  In the screen protective sheet using the screen protective base film of the present invention, an adhesive layer can be provided on the screen protective base film surface on the side where the screen protective sheet is attached to the liquid crystal display. It does not specifically limit as an adhesive layer, A well-known adhesive, a curable adhesive, a hot-melt-adhesive etc. can be used. Moreover, the formation method of an adhesive layer can use a well-known means, and although it does not specifically limit, For example, it can form by apply | coating the coating agent containing an adhesive agent. The thickness of the adhesive layer is not particularly limited, but is preferably 0.05 to 30 μm, and more preferably 0.1 to 10 μm. By setting it as such a range, favorable adhesiveness is obtained.

  The screen protective sheet using the screen protective substrate film in the present invention can be further provided with a release layer such as an isolation separator on the surface side on which the adhesive layer is provided.

  Next, the preferable manufacturing method of the screen protection base film of this invention is demonstrated below. Two types of resins A and B are prepared in the form of pellets. The pellets are dried in hot air or under vacuum as necessary, and then supplied to a separate extruder. In the extruder, the resin melted by heating to a temperature equal to or higher than the melting point is made uniform by a gear pump or the like, and the foreign matter or modified resin is removed through a filter or the like.

  Resins A and B sent out from different flow paths using these two or more extruders are then fed into the multilayer laminating apparatus. As the multi-layer laminating apparatus, a multi-manifold die, a feed block, a static mixer, etc. can be used. In particular, in order to efficiently obtain the configuration of the present invention, at least two members having a large number of fine slits are separately provided. It is desirable to use a feed block including the above.

  When such a feed block is used, the apparatus does not become extremely large, so that foreign matter due to thermal deterioration is small, and even when the number of layers is extremely large, it is possible to stack with high accuracy. Also, the stacking accuracy in the width direction is significantly improved as compared with the prior art. It is also possible to form an arbitrary layer thickness configuration. In this apparatus, since the thickness of each layer can be adjusted by the slit shape (length, width, gap), an arbitrary layer thickness can be achieved. For this reason, the layer structure which is the feature of the present application can be easily achieved. On the other hand, in the conventional apparatus, in order to achieve lamination of 300 layers or more, it was common to use a square mixer together. However, in such a method, the lamination flow is deformed and laminated in a similar system. In addition, it has been difficult to achieve an arbitrary layer thickness.

  In the present invention, since the inclined structure has two or more steps, the change from the thin layer to the thick layer or the change in the layer thickness from the thick layer to the thin layer becomes very steep. In the present invention, a feed block including at least two members having a large number of fine slits is used. However, the layer thickness distribution changed immediately after merging at the location where the resins fed from the separate feed blocks merged, which was a major factor in varying the color tone in the width direction. Furthermore, since the resin velocity near the pipe decreases due to the influence of the wall surface of the pipe in the path from the feed block to the base, the color tone uniformity in the film width direction is further deteriorated due to the flow velocity difference between the pipe wall surface and the pipe center. . Therefore, it is possible to obtain a film that expresses a uniform color tone in the width direction without losing the lamination ratio by replacing a certain distance between the film resurfacing portion and the resin merging portion of separate feed blocks with the same polymer. . At this time, since the thick film layer of the film outermost layer becomes the resin A, the resin A corresponds to the surface thick film layer. For this reason, it is preferable that the resin A is a higher crystalline resin than the resin B in order to improve the anti-scratch resistance. In addition, the resin used as the middle thick film layer is not limited to the resin A or the resin B, but it is preferable to use the resin A used as a highly crystalline resin in order to improve the dent resistance. In adjusting the thickness of the thick film layer, it is particularly preferable to adjust the flow rate corresponding to the thickness of the corresponding layer with the gap between the slits. In this case, the gap accuracy of each slit gap is preferably ± 10 μm or less. By using such a special feed block, it is possible to form an inclined structure with high accuracy and two or more stages.

Next, in order to set the relative reflectance in the wavelength band of 400 nm to 700 nm, which is a feature of the present invention, to 10% or more and 35% or less, it is necessary to design the layer thickness of each layer based on the following formula 1. The laminated film in the present invention can reflect / transmit light, but the reflectance is controlled by the difference in refractive index between the layer made of resin A and the layer made of resin B and the number of layers.
2 × (na · da + nb · db) = λ Equation 1
na: In-plane average refractive index of the layer made of resin A nb: In-plane average refractive index of the layer made of resin B da: Layer thickness (nm) of the layer made of resin A
db: Layer thickness of the layer made of resin B (nm)
λ: main reflection wavelength (primary reflection wavelength)
The molten laminate formed in the desired layer configuration in this way is then formed into a desired shape by a die and then discharged. And the sheet | seat laminated | stacked in the multilayer discharged | emitted from die | dye is extruded on cooling bodies, such as a casting drum, and is cooled and solidified, and a casting film is obtained. At this time, it is preferable to use a wire-like, tape-like, wire-like, or knife-like electrode to be brought into close contact with a cooling body such as a casting drum by an electrostatic force and rapidly solidify. Also preferred is a method in which air is blown out from a slit-like, spot-like, or planar device to be brought into close contact with a cooling body such as a casting drum and rapidly cooled and solidified, or a cooling body is brought into close contact with a nip roll to rapidly cool and solidify.

  The casting film thus obtained is preferably biaxially stretched as necessary. Biaxial stretching refers to stretching in the longitudinal direction and the width direction. Stretching may be performed sequentially in biaxial directions or simultaneously in two directions. Further, re-stretching may be performed in the longitudinal direction and / or the width direction. In particular, in the present invention, it is preferable to use simultaneous biaxial stretching from the viewpoint of suppressing in-plane orientation difference and suppressing surface scratches.

  First, the case of sequential biaxial stretching will be described. Here, stretching in the longitudinal direction refers to stretching for imparting molecular orientation in the longitudinal direction to the film, and is usually performed by a difference in peripheral speed of the roll, and this stretching may be performed in one step, It may be performed in multiple stages using book roll pairs. The stretching ratio varies depending on the type of resin, but usually 2 to 15 times is preferable, and 2 to 7 times is particularly preferable when polyethylene terephthalate is used for any of the resins constituting the screen protective base film. Used. Moreover, as extending | stretching temperature, the glass transition temperature-glass transition temperature +100 degreeC of resin which comprises a laminated | multilayer film are preferable.

  In order to give an easy-adhesion layer to a laminated film, a method of coating and laminating a coating material is preferable. As a method of coating the coating material, it is easy to adhere by applying the coating process during the manufacturing process of the screen protection base film and the so-called off-line coating method, which is a coating process separate from the manufacturing process of the screen protection base film. There is a so-called in-line coating method in which the layers are laminated at once. It is preferable to adopt an in-line coating method from the viewpoint of cost and uniformity of coating thickness, and the solvent of the coating liquid used in that case is preferably an aqueous system from the viewpoint of environmental pollution and explosion-proof property, and water is used. It is the most preferred embodiment to use.

  When laminating an easy-adhesion layer by in-line coating, a coating material constituting the easy-adhesion layer is continuously applied to a uniaxially stretched film. As a coating method of a coating material (water-based coating material) using water as a solvent, for example, a reverse coating method, a spray coating method, a bar coating method, a gravure coating method, a rod coating method, a die coating method, or the like can be used.

  Before applying the water-based coating material, it is preferable to perform corona discharge treatment or the like on the surface of the screen protection substrate film as the substrate. This is because the adhesion between the screen protective substrate film and the coating material is improved and the coating property is also improved.

  The easy-adhesive layer has a crosslinking agent, antioxidant, heat-resistant stabilizer, anti-glare stabilizer, ultraviolet absorber, organic easy-to-lubricant, pigment, dye, organic or inorganic as long as the effect of the invention is not impaired. You may mix | blend particle | grains, a filler, and surfactant.

  Subsequent stretching in the width direction refers to stretching to give orientation in the width direction of the film, usually using a tenter, transporting the film while holding both ends with clips, and applying heat to the film. After preheating, the film is stretched in the width direction. The aqueous coating material applied immediately before the tenter is dried during this preheating. The stretching ratio varies depending on the type of resin, but usually 2 to 15 times is preferable, and 2 to 7 times is particularly preferable when polyethylene terephthalate is used for any of the resins constituting the screen protective base film. Used. Moreover, as extending | stretching temperature, the glass transition temperature-glass transition temperature +120 degreeC of resin which comprises a screen protection base film is preferable.

  The film thus biaxially stretched is preferably subjected to a heat treatment not less than the stretching temperature and not more than the melting point in the tenter in order to impart flatness and dimensional stability. After being heat-treated in this way, it is gradually cooled and then cooled to room temperature and wound up. Moreover, you may use a relaxation process etc. together in the case of annealing from heat processing as needed.

  Next, the case of simultaneous biaxial stretching will be described. In simultaneous biaxial stretching, the coating material which comprises an easily bonding layer is apply | coated continuously to the obtained cast film. As a coating method of a coating material (water-based coating material) using water as a solvent, for example, a reverse coating method, a spray coating method, a bar coating method, a gravure coating method, a rod coating method, a die coating method, or the like can be used.

  Before applying the water-based coating material, it is preferable to perform corona discharge treatment or the like on the surface of the screen protection substrate film as the substrate. This is because the adhesion between the screen protective substrate film and the coating material is improved and the coating property is also improved.

  The easy-adhesive layer has a crosslinking agent, antioxidant, heat-resistant stabilizer, anti-glare stabilizer, ultraviolet absorber, organic easy-to-lubricant, pigment, dye, organic or inorganic as long as the effect of the invention is not impaired. You may mix | blend particle | grains, a filler, and surfactant.

  Next, the cast film coated with the coating material is guided to a simultaneous biaxial tenter, and conveyed while holding both ends of the film with clips, and stretched simultaneously and / or stepwise in the longitudinal direction and the width direction. As simultaneous biaxial stretching machines, there are pantograph method, screw method, drive motor method, linear motor method, but it is possible to change the stretching ratio arbitrarily and drive motor method that can perform relaxation treatment at any place or A linear motor system is preferred. Although the stretching magnification varies depending on the type of resin, it is usually preferably 6 to 50 times as the area magnification. When polyethylene terephthalate is used as one of the resins constituting the laminated film, the area magnification is 8 to 30 times. Is particularly preferably used. In particular, in the case of simultaneous biaxial stretching, it is preferable to make the stretching ratios in the longitudinal direction and the width direction the same and to make the stretching speeds substantially equal in order to suppress the in-plane orientation difference. Moreover, as extending | stretching temperature, the glass transition temperature-glass transition temperature +120 degreeC of resin which comprises a laminated | multilayer film are preferable.

  The film thus biaxially stretched is preferably subsequently subjected to a heat treatment not less than the stretching temperature and not more than the melting point in the tenter in order to impart flatness and dimensional stability. In order to suppress the distribution of the main orientation axis in the width direction during this heat treatment, it is preferable to perform a relaxation treatment in the longitudinal direction immediately before and / or immediately after entering the heat treatment zone. After being heat-treated in this way, it is gradually cooled down uniformly, then cooled to room temperature and wound up. Moreover, you may perform a relaxation | loosening process in a longitudinal direction and / or the width direction at the time of annealing from heat processing as needed. Immediately before and / or immediately after entering the heat treatment zone, relaxation treatment is performed in the longitudinal direction.

  EXAMPLES Hereinafter, although this invention is demonstrated along an Example, this invention is not restrict | limited by these Examples. Various characteristics were measured by the following methods.

(1) Layer structure and layer thickness of film A sample obtained by cutting a cross section using a microtome was obtained by electron microscope observation. That is, using a transmission electron microscope (H-7100FA, manufactured by Hitachi, Ltd.), the cross section of the film was magnified 40,000 times with an acceleration voltage of 75 kV, and the cross-section of the film was photographed to obtain a layer structure. The thickness of each layer was measured. The total thickness of each layer was defined as the total thickness of the laminated film. In this example, RuO ₄ was used for staining in order to obtain high contrast.

A specific method for obtaining the film laminate structure will be described. About 40,000 times TEM photographs were captured with CanonScan D123U at an image size of 729 dpi. The image was saved in JPEG format, and then the JPEG file was opened and image analysis was performed using image processing software (sales company Planetron Co., Ltd., Imagc-Pro Plus ver. 4). In the image analysis process, the relationship between the thickness in the thickness direction and the average brightness of the area sandwiched between the two lines in the width direction was read as numerical data in the vertical thick profile mode. Using spreadsheet software (Excel2000), the data of position (nm) and brightness were sampled at sampling step 6 (decimation 6) and subjected to numerical processing of 3-point moving average. Furthermore, the data obtained by periodically changing the brightness is differentiated, and the maximum and minimum values of the differential curve are read by a VBA (Visual Basic For Applications) program. Calculated as the layer thickness. This operation was performed for each photograph, and the layer thicknesses of all layers were calculated. Of the obtained layer thickness, the thin film layer was a layer having a thickness of 500 nm or less. For the thin film layer, the average values of the adjacent A layer and B layer were sequentially obtained for all groups. Therefore, the number of sets of average layer thickness is half of the total number of thin film layers. The inclined structure is obtained by determining the average layer thickness of each group from the thicknesses of the respective A layer and B layer, and the group number in which the difference in the average thickness of adjacent groups is continuously increased or decreased in a range of 50 nm or less. And a group consisting of layer thickness distributions of layer A and layer B having an average layer thickness distribution having a positive or negative slope in which the square of R is 0.5 or more. It was defined as an inclined structure, and the relationship between the number and inclination was examined. (See Figures 1-3)
(2) In-plane average refractive index For each of the A layer and the B layer, cut into a 0.5 mm thick film, cut out a test piece having a width of 5 mm and a length of 20 mm, and an Abbe refractometer (manufactured by Atago, The refractive index at 23 ° C. and a wavelength of 589 nm was measured by DR-M2), and an average value of n number 5 was calculated.

(3) Average reflectance A 5 cm square sample was cut out from the central part of the film width direction of the base film for screen protection. Subsequently, the relative reflectance in incident angle (PHI) = 10 degree | times was measured using the spectrophotometer (The Hitachi, Ltd. make, U-4100 Spectrophotometer). The inner wall of the attached integrating sphere is barium sulfate, and the standard plate is aluminum oxide. The measurement wavelength was 250 nm to 1200 nm, the slit was 2 nm (visible) / automatic control (infrared), the gain was set to 2, and the scanning speed was measured at 600 nm / min. The back of the sample was painted black with oil-based ink. Next, the average reflectance in the wavelength band of 400 to 700 nm was calculated. The average reflectance is calculated by calculating the area enclosed by the reflection curve and the wavelength band based on the Simpson method formula using absolute reflectance data for each wavelength of 1 nm, and dividing by 300, which is the width of the wavelength band. Thus, the average reflectance was obtained. A detailed explanation of the Simpson method is described in “Numerical calculation method I for electronic computers” (Baifukan) (1965) by Jiro Yamauchi et al.

(4) Lightness L ^* , color difference ΔE
Using a spectrocolorimeter (manufactured by Konica Minolta Sensing Co., Ltd., CM-3600d), the lightness L ^* and a ^* , b ^* at each point were measured at an interval of 10 cm in the width direction for 1 m in the film width direction. The average value of n number 5 was calculated.

In addition, as a means of measurement, after performing zero configuration of reflectance in the zero configuration box attached to the spectrocolorimeter, then performing 100% calibration using the attached white calibration plate, the film was subjected to the following conditions. The brightness L ^* and a ^* b ^* were measured.
Mode: Reflection, SCI / SCE simultaneous calibration Measurement diameter: 8mm
Sample: Black ink is applied to the non-measurement side Light source: D65
Next, the color difference ΔE was determined from the lightness L ^* and a ^* , b ^* . The definition of the color difference ΔE is as follows. The color difference ΔE was set to the maximum combination value at each point measured at a distance of 10 cm in the width direction for a film having a width direction of 1 m.
ΔE = ((ΔL ^* ) ² + (a ^* ) ² + (b ^* ) ² ) ^1/2
The lightness L ^*, a ^* , and b ^* used in the calculation of the color difference ΔE were SCI values.

(5) Haze Measured using a fully automatic direct reading haze computer (HGM-2DP, manufactured by Suga Test Instruments Co., Ltd.) after leaving the screen protecting substrate film for 2 hours under the conditions of 23 ° C. and relative humidity 65%. The average value of n number 3 was calculated.

(6) Glossiness Using a digital variable glossiness meter (manufactured by Suga Test Instruments, UGV-5D), the glossiness was measured according to JIS Z8741 (1997). The number of measurements was n = 5, and the average value of the three measured values excluding the maximum and minimum values was calculated.

(7) Surface specific resistance value The substrate film for screen protection was allowed to stand for 24 hours under the conditions of 23 ° C. and 65% relative humidity, and then used with a digital ultrahigh resistance / microammeter (manufactured by Advantest Corporation, R8340A). The surface specific resistance value after application for 10 seconds at an applied voltage of 100 V was determined. The measurement surface is the coating surface side of the easy adhesion layer.

(8) Surface Deformation Depth Using a hardness meter (manufactured by Shimadzu Corporation, HARDNESS TESTER No13881), the film surface is weighted under the following conditions, and the maximum deformation depth of the sample is measured by a surface shape measuring device (Co., Ltd.). It was measured by Ryoka System, VertScan 2.0).
Load: 0.9kgf (11.1MPa)
Weighting time: 5 seconds Hardness tip diameter: Φ1mm
Sample size: 100mm x 100mm
Surface shape measuring device: Ryoka System Co., Ltd., VertScan 2.0
Measurement environment: 23 ° C, humidity 65% RH
(9) Glossiness (6) From the measurement results of glossiness, evaluation was made according to the following criteria.
Over 500: x (because the gloss is too strong and visibility decreases)
250 or more and 500 or less: ○
Less than 250: x (because gloss is too low to achieve high designability)
(10) Color tone unevenness (4) From the measurement result of the color tone ΔE, the following criteria were evaluated.
5.0 or less: ○
More than 5.0: ×
(11) Visibility of the screen When the brightness setting of “iPhone” made by Apple is darkened under the screen protective base film and viewed through the base film for screen protection, the size is 3 mm × 3 mm. Were visually observed at a distance of 50 cm and evaluated according to the following criteria.
Characters can be clearly recognized: ○
Characters are not clear but can be recognized:
Characters can be recognized only at a certain angle: ×
(12) Antistatic property (7) From the measurement result of the surface specific resistance value, evaluation was made according to the following criteria.
1.0 × 10 ¹² Ω / □ or less: ○
More than 1.0 × 10 ¹² Ω / □: ×
(13) Scratch resistance (8) From the measurement result of the surface deformation depth, the following criteria were evaluated.
<200 nm: ○
200 nm to 250 nm: △
Over 250 nm: ×
(material)
(Resin A-1)
To a mixture of 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, 0.09 parts by weight of magnesium acetate and 0.03 parts by weight of antimony trioxide are added with respect to the amount of dimethyl terephthalate, and the temperature is raised by a conventional method. Then, a transesterification reaction is performed. Subsequently, 0.020 part by weight of 85% aqueous solution of phosphoric acid is added to the transesterification product with respect to the amount of dimethyl terephthalate, and then the polycondensation reaction tank is transferred. Furthermore, the reaction system was gradually depressurized while being heated and heated, and a polycondensation reaction was carried out by a conventional method at 290 ° C. under a reduced pressure of 1 mmHg. Polyethylene terephthalate (hereinafter referred to as PET) having an intrinsic viscosity (IV) of 0.63. Got).

(Resin A-2)
Polymerization was carried out in the same manner as Resin A-1, except that a mixture of 100 parts by weight of dimethyl 2,6-naphthalenedicarboxylate and 60 parts by weight of ethylene glycol was used. , Sometimes referred to as PEN).

(Resin B-1)
Polyethylene terephthalate copolymerized with 30 mol% of cyclohexanedimethanol (CHDM) having an intrinsic viscosity (IV) of 0.72.

(Resin B-2)
Copolymer polyethylene terephthalate obtained by mixing Resin A-1 and Resin B-1 at 1: 3.

(Resin B-3)
Copolymer polyethylene terephthalate in which resin A-1 and resin B-1 are mixed at a ratio of 1: 1.

(Resin B-4)
Copolymer polyethylene terephthalate in which resin A-1 and resin B-1 are mixed at a ratio of 3: 1.

(Resin B-5)
Copolymer polyethylene naphthalate in which resin A-1 and resin A-2 are mixed at 1: 1.

(Composition 1 of an easily bonding layer)
-Aqueous dispersion of acrylic / urethane copolymer resin (a): Sannaron WG658 (solid content concentration 30% by weight), manufactured by Sannan Synthetic Chemical Co., Ltd.
-Aqueous dispersion of isocyanate compound (b): Elastron E-37 (solid content concentration: 28% by weight) manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
-Aqueous dispersion of epoxy compound (c): manufactured by DIC Corporation, CR-5L (solid content concentration: 100% by weight)
-An aqueous dispersion of the composition (d) comprising a compound having a polythiophene structure and a compound having an anion structure (solid content concentration 1.3% by weight)
-Aqueous dispersion of oxazoline compound (e): Nippon Shokubai Co., Ltd., Epocross WS-500 (solid content concentration 40% by weight)
-Aqueous dispersion of carbodiimide compound (f): Nisshinbo Co., Ltd., Carbodilite V-04 (solid content concentration 40%)
-Silica particles (g): JGC Catalysts & Chemicals, Spherica slurry 140 (solid content 40%)
-Acetylene diol-based surfactant (h): manufactured by Nissin Chemical Co., Ltd., Olfine EXP4051 (solid content concentration 50%)
-Aqueous solvent (i): pure water The above-mentioned (a) to (h) in terms of solid weight ratio (a) / (b) / (c) / (d) / (e) / (f) / ( g) / (h) = 100/100/75/25/60/60/10/15 and (i) is mixed so that the solid content concentration of the aqueous coating material is 3% by weight, The concentration was adjusted.

(Composition 2 of an easily bonding layer)
(A) / (b) / (c) / (e) / (f) / (g) / (h) (a) to (c) and (e) to (h) described above in terms of solid content weight ratio. ) = 100/100/75/60/60/10/15, and (i) was mixed and the concentration was adjusted so that the solid content concentration of the aqueous coating material was 3% by weight.

Example 1
Resin A-1 and Resin B-2 are each melted at 280 ° C. with separate vented twin-screw extruders, and then have three separate members having 301 slits via a gear pump and a filter. They were merged in a 901-layer feed block. In addition, the surface layer portions on both sides that become the thick film layer are made of resin A, and the resin A and the resin B are alternately laminated, and the layer thickness of the layer made of the adjacent resin A and the layer made of the resin B is substantially the same. I made it. Next, after being led to a T-die and formed into a sheet, it was brought into close contact with a casting drum maintained at a surface temperature of 25 ° C. by applying electrostatic force, and rapidly solidified to obtain a cast film.

  The obtained cast film was heated in a roll group set at 75 ° C., and then stretched 3.3 times in the longitudinal direction while rapidly heating from both sides of the film with a radiation heater between 100 mm in the stretch section length, and then temporarily Cooled down. Next, corona discharge treatment was performed on both surfaces of this uniaxially stretched film in air, the coating tension of the film was 55 mN / m, and composition-1 of the easy adhesion layer was applied to both surfaces of the film with a # 4 metabar.

  This uniaxially stretched film was guided to a tenter, and after preheating with 100 ° C. hot air, it was stretched 3.5 times in the transverse direction at a temperature of 110 ° C. The stretched film was directly heat-treated in a tenter with hot air of 240 ° C., then subjected to a relaxation treatment of 7% in the width direction at the same temperature, and then cooled to room temperature and wound up. The film thickness obtained was 122 μm. The layer design of this laminated film is as shown in FIG. 1, and the layer thickness of each layer was controlled by adjusting the slit gap. A cross section in the thickness direction of the obtained film was observed with a TEM, and a layer thickness distribution was determined by image processing. The layer thickness of layer number 676, which is the outermost layer, was 4 μm. Table 1 shows the characteristics and evaluation results of the screen protecting substrate film.

(Example 2)
A base film for screen protection was obtained in the same manner as in Example 1 except that the resin B-2 was changed to the resin B-3.

(Example 3)
A screen protecting substrate film was obtained in the same manner as in Example 1 except that the slit gap of the feed block was changed. A cross section in the thickness direction of the obtained film was observed with a TEM, and a layer thickness distribution was determined by image processing. The layer thicknesses of layer number 1 and layer number 901 that are the outermost layers were all 10 μm, and the layer thicknesses of layer number 226, layer number 451, and layer number 676 were 4 μm.

Example 4
A base film for screen protection was obtained in the same manner as in Example 1 except that the slit shape of the feed block was changed so that the number of layers was 801 and the thickness was adjusted. The layer thicknesses of the layer number 1 and the layer number 801 that are the outermost layers were all 10 μm, and the layer thicknesses of the layer number 201, the layer number 401, and the layer number 601 were 4 μm.

(Example 5)
A base film for screen protection was obtained in the same manner as in Example 1 except that the resin A-1 was changed to the resin A-2 and the resin B-2 was changed to the resin B-5.

(Example 6)
A substrate film for screen protection was obtained in the same manner as in Example 1 except that the slit shape of the feed block was changed and the thickness was adjusted so that the layer design of the film was as shown in FIG. The layer thicknesses of layer number 1 and layer number 901 that are the outermost layers were both 10 μm, and the layer thicknesses of layer number 301 and layer number 601 were 4 μm.

(Example 7)
A base film for screen protection was obtained in the same manner as in Example 1 except that the slit shape of the feed block was changed so that the layer design of the film was as shown in FIG. The layer thicknesses of the layer number 1 and the layer number 901 that are the outermost layers were both 10 μm, and the layer thickness of the layer number 451 was 4 μm.

(Comparative Example 1)
A screen protecting substrate film was obtained in the same manner as in Example 1 except that the resin B-2 was changed to the resin B-1.

(Comparative Example 2)
A base film for screen protection was obtained in the same manner as in Example 1 except that the resin B-2 was changed to the resin B-4.

(Comparative Example 3)
A base film for screen protection was obtained in the same manner as in Example 1 except that the thickness of the film was designed by changing the slit shape of the feed block so that the intermediate thick film layer of FIG. 1 was not formed. The layer thicknesses of layer number 1 and layer number 901, which are the outermost layers, were both 10 μm, and there were no other layers of 1 μm or more.

(Comparative Example 4)
A base film for screen protection was obtained in the same manner as in Example 1 except that the slit shape of the feed block was changed so that the number of laminated layers was 199 and the thickness was adjusted from Example 7. The layer thicknesses of the layer number 1 and the layer number 199 that are the outermost layers were both 10 μm, and the layer thickness of the layer number 100 was 4 μm.

(Comparative Example 5)
A base film for screen protection was obtained in the same manner as in Example 1 except that the composition-1 of the easy adhesion layer was changed to the composition-2 of the easy adhesion layer.

The substrate film for screen protection of the present invention has both excellent design and visibility with uniform glossiness, and further has antistatic properties and dent resistance, so as a screen protection sheet using it, For example,
It can be suitably used for screen protection applications such as various touch panels, mainly small devices such as mobile phones, smartphones, portable game machines, and portable audio players.

1: Layer order 2: Layer thickness 3: Thick film layer 4: Layer thickness distribution of layer A 5: Layer thickness distribution of layer B

Claims (4)

A base film for screen protection that satisfies the following conditions (1) to (4), wherein an easy-adhesion layer is provided on at least one surface of the laminated film.
(1) It has a layer made of resin A (hereinafter referred to as A layer) and a layer made of resin B (hereinafter referred to as B layer), and a total of 250 or more layers are alternately laminated in the thickness direction, and at least 1 μm or more and 20 μm or less A laminated film including three or more thick film layers having a certain thickness.
(2) The easy-adhesion layer is composed of an acrylic / urethane copolymer resin, two or more kinds of cross-linking agents, a compound having a polythiophene structure, and a composition having an anion structure.
(3) The average reflectance of the base film for screen protection in the wavelength band of 400 to 700 nm is 10% to 35%, the brightness L ^* (SCI) in reflected light is 35.0 to 70.0, and the film width direction is 1 m. The color difference [Delta] E is 5.0 or less.
(4) The surface specific resistance value on the easy adhesion layer side of the screen protecting base film is 1.0 × 10 ¹² Ω / □ or less. The base film for screen protection according to claim 1, wherein a difference between the in-plane average refractive index of the A layer and the in-plane average refractive index of the B layer is 0.030 or more and 0.055 or less. Use of the screen protective base film provided with the easy adhesion layer on at least one surface according to claim 1 or 2, and providing an adhesive layer on the surface of the screen protection base film on the easy adhesive layer side. Screen protection sheet. The said screen protection base film in which the said easily bonding layer was provided in both the surfaces of Claim 1 or 2 was used, and a hard-coat layer was formed in one side of this screen protection base film, and the other surface Screen protective sheet provided with an adhesive layer.

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