TWI447022B - Substrate film - Google Patents

Description

Substrate film

The present invention relates to a substrate film for use in a protective film formed by laminating an adhesive on one side, and in detail, after laminating an adhesive layer to form a protective film, it is adhered to and adhered to the object after being wrapped (protected In the case of a film, a base film for a protective film which does not cause problems such as air bubbles is mixed, and is particularly suitable for a base film of a surface protective film of an optical member.

In the production of steel sheets, resin sheets, automobiles, optical parts, and the like, and during transportation and storage after the production, in order to protect the surface of the product from damage or dirt, a protective film is adhered to the surface of the product for protection. These protective films are usually composed of a substrate film and an adhesive layer laminated thereon.

In recent years, the demand for surface protective films for optical parts, particularly various parts in the field of liquid crystal related, is increasing. Since the optical parts are manufactured by combining a large number of parts, the surface of each part is required to have a very high degree of smoothness (refer to Japanese Laid-Open Patent Publication No. Hei 11-160505), and it is necessary to prevent foreign matter from being mixed or damaged on the surface of the parts. In the manufacture of such optical parts, in order to protect the parts from damage, dirt, etc., after the parts produced in the respective steps are sent to the next step, the surface protective film is directly adhered under clean conditions after production. Under the storage and transportation, the optical inspection of the part specifications is also carried out with the protective film attached. In order to properly perform optical inspection of optical parts, when a protective film is adhered to an attached body (optical part) via an adhesive layer, it is strictly required that air bubbles cannot be caught. Moreover, the surface protection film which is required to be temporarily adhered does not inadvertently peel off during storage and transportation of the parts, but on the other hand, upon reaching the next step, it is required to be quickly removed, and the optical parts after removal are required. No trace of adhesive remains on the surface.

In order not to be an obstacle to the above optical inspection, the protective film is required to have few fish eyes.

Moreover, it is convenient to store the protective film in a wound body wound into a roll shape. In the production of the wound body, if air bubbles are trapped between the adhesive layer and one of the lower film layers, the traces of the air bubbles remain in the adhesive layer, which is an obstacle to the optical inspection described above. The worst situation is that wrinkles occur during winding, and there are cases where it cannot be used as a product. Further, when the protective film is a wound body, it is required that the adhesive film layer and the base film of the underlying film layer do not have a bad strong adhesion, and the protective film is easily pulled out during use.

In this way, the adhesion of the adhesive layer of the protective film is required to conform to various properties of the scene and the object to be contacted, and fine adjustment is required. Conventionally, this adjustment is usually performed from the material surface of the adhesive and the winding conditions at the time of production of the wound body. However, it has been pointed out that according to this method, the balance between the performance required at the time of manufacture and use of the wound body and the performance as a protective film is extremely difficult, and the reproducibility cannot be obtained.

In this regard, JP-A-2007-160598 discloses a technique for roughening a single surface of a protective film relating to a protective film of a printed circuit board. However, the technique described in this publication relates to the formation of a rough surface for transferring unevenness on the surface of the photosensitive resist resin composition layer of the printed circuit board, and when the protective film for optical parts is a wound body, The effect of suppressing the adhesion of the adhesive film layer to the underlying film layer is weak, and the base film of the publication is a biaxially stretched film which is not suitable for the above optical component because of its polarizing characteristics. Optical inspection.

However, when the protective film is used for the purpose of protecting the surface of the optical component, not only the single surface of the optical component but also the protective film may be attached to both surfaces. In this case, in order to easily distinguish the front and back of the optical component, at least one of the two protective films is preferably colored.

As a method of coloring a film used for this purpose, for example, a method of applying a printing to the surface of a film is known. However, according to this method, in addition to the formation of the film, the step of applying the printing is additionally required, which is not only economically disadvantageous, but also it is difficult to uniformly print the film on the surface of the film, and the possibility of uneven printing is high, due to uneven printing. Optical inspection of optical components poses a problem. Further, in the colored film produced by the printing method, there is also a problem that the printing ink on the surface is eluted in the organic solvent used in the subsequent lamination step of the adhesive layer.

As another method of coloring a film, it is proposed to apply a coating liquid containing a colorant after longitudinally stretching a polypropylene film in the production of a biaxially oriented polypropylene film, remove the solvent, and then stretch in the transverse direction. In the first step, a method of producing a colored film having no uneven printing is disclosed (JP-A-2000-25108). However, the problem that the printing ink on the surface of the film is eluted into the organic solvent remains unresolved, and since the biaxially stretched film has a polarizing property, it is not suitable for optical inspection of the optical component at all.

As described above, the base film which can be applied to the surface protective film of an optical component has not been proposed in the past.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a base film which can be used for producing a protective film which can be wound up quickly and easily without causing air bubbles to be wound into a wound body. The body is pulled out, and when it is adhered to the attached body, especially the optical component, no air bubbles are caught.

According to the present invention, the above objects and advantages of the present invention are achieved by a substrate film which is used for a protective film formed by laminating an adhesive layer on one side, the substrate film having each At least two laminated thin films made of a free polyolefin resin, each of which constitutes an outermost layer on the side of the laminated adhesive layer and an outermost layer on the side of the non-laminated adhesive layer, and the laminate of the base film The average roughness (Ra) of the surface on the side of the adhesive layer is 0.25 μm or less, and the average roughness (Ra) of the surface of the base film on the side where the adhesive layer is not laminated is 0.30 μm or more, and is used for optical parts. Protective film.

Best form for implementing the invention

The base film of the present invention has a laminate film of at least two layers each made of a polyolefin resin. Each of the two layers constitutes the outermost layer on the side of the laminated adhesive layer and the outermost layer on the side of the non-laminated adhesive layer. The base film of the present invention may have a multilayer structure of three or more layers having a layer other than the two layers as an intermediate layer (inner layer). Hereinafter, the characteristics of each layer constituting the base film of the present invention, the method for producing the base film of the present invention, and the base film of the present invention will be described in order.

<the outermost layer on the side of the laminated adhesive layer>

The polyolefin-based resin used for the outermost layer on the side of the layer of the adhesive layer is preferably a polypropylene-based resin from the viewpoint of ensuring the smoothness of the surface and suppressing the occurrence of fish eyes. Here, the polypropylene resin is preferably a crystalline polypropylene resin, and the melt flow rate (MFR) measured at 230 ° C in accordance with JIS K 7210 is preferably from 1 to 25 g/10 min, more preferably from 3 to 10 g/ 10 minutes. Further, the melting point of the crystalline polypropylene resin is preferably 125 ° C or higher, more preferably 125 to 165 ° C. Examples of the crystalline polypropylene resin include a homopolymer of propylene (homopolypropylene), a random copolymer of propylene and another α-olefin (random polypropylene), or a block copolymer (block polypropylene). Or such a mixture, etc. Examples of the other α-olefin copolymerizable with the above propylene include ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, and 1 - terpene, 4-methyl-1-pentene, and the like. From the viewpoint of maintaining the crystallinity of the polypropylene-based resin, the copolymerization ratio of propylene to the random copolymer of the other α-olefin or the other α-olefin in the block copolymer is preferably 10 mol% or less. Among them, the polypropylene homopolymer is most suitable in addition to the occurrence of fish eyes, high transparency, and easy to exhibit smoothness.

The thickness of the outermost layer on the side of the layered adhesive layer is preferably 2 μm or more, and more preferably 5 to 50 μm from the viewpoint of reducing the surface unevenness on the opposite side, that is, the surface unevenness on the side of the adhesive layer. It is particularly preferably 10 to 30 μm.

As will be described later, a coloring agent may be blended in the outermost layer on the side of the laminated adhesive layer.

<the outermost layer on the side where the adhesive layer is not laminated>

The polyolefin resin used for the outermost layer on the side where the pressure-sensitive adhesive layer is not laminated is preferably a blend of a polypropylene resin and a polyethylene resin. In other words, the polypropylene resin and the polyethylene resin are incompatible with each other, and since the blend forms an island structure, and appropriate irregularities are formed on the surface, the surface of the base film is not laminated on the side of the adhesive layer. The average roughness (Ra) is 0.30 μm or more.

The polypropylene resin is the same as the above-exemplified polypropylene resin which is preferably used as the outermost layer on the side of the layered adhesive layer. Among these, it is preferred to use homopolypropylene or block polypropylene from the viewpoint of less occurrence of fish eyes, high transparency, and exhibiting appropriate surface unevenness.

Examples of the polyethylene-based resin include high-density polyethylene resin (HDPE), low-density polyethylene resin (LDPE), and linear low-density polyethylene resin (LLDPE). The polyethylene-based resin used for the outermost layer on the side where the pressure-sensitive adhesive layer is not laminated is preferably a polyethylene resin having a melt flow rate (MFR) measured at 190 ° C according to JIS K 7210 of 0.5 to 15 g/10 minutes. It is preferably a polyethylene resin of 1 to 10 g/10 minutes. The polyethylene-based resin is preferably a low-density polyethylene resin (LDPE) from the viewpoint of transparency of the obtained base film and visibility of surface unevenness on the side of the non-laminated adhesive layer.

In the polyolefin resin used for the outermost layer on the side of the non-laminated adhesive layer, the blend ratio of the polypropylene resin and the polyethylene resin is aggregated for the total of the polypropylene resin and the polyethylene resin. The content ratio of the vinyl resin is 5 to 50% by weight, and it is preferable from the viewpoint of appropriately exhibiting surface unevenness and suppressing the occurrence of fish eyes. In other words, when the content of the polyethylene-based resin in the blend is less than 5% by weight, the surface unevenness cannot be sufficiently exhibited, and the protective film obtained by applying the adhesive film to the base film can be easily wound. When the content of the polyethylene resin is more than 50% by weight, the surface unevenness is extremely large, and the fish eye from the polyethylene resin is likely to be generated, which is not suitable for use in optical parts and the like. Surface protection film. The content of the polyethylene-based resin in the blend is more preferably from 10 to 40% by weight.

The polyolefin-based resin used for the outermost layer on the side where the pressure-sensitive adhesive layer is not laminated is preferably a blend of a polypropylene-based resin and a polyethylene-based resin, which can be prepared by a known method. For example, the respective pellets may be introduced into a suitable kneader at a predetermined ratio, preferably at 200 to 300 ° C, preferably after mixing for 0.1 to 2 minutes, for the production of the base film used in the present invention. As a preferable kneading machine, an extruder is mentioned, for example, and it is especially preferable to use a uniaxial extruder. In the preparation of a blend of a polypropylene resin and a polyethylene resin, when an extruder is used, the die temperature is preferably the same as the resin temperature.

In the blend of the polypropylene resin and the polyethylene resin, the blend ratio of the polypropylene resin to the polyethylene resin and the kneading conditions (especially shear) of the kneader can be set. The surface roughness of the side surface of the obtained substrate film which is not laminated with the adhesive layer is arbitrarily controlled.

The thickness of the outermost layer on the side of the non-laminated adhesive layer is preferably 2 μm or more, more preferably 5 to 50 μm, from the viewpoint of exhibiting appropriate unevenness on the surface on the side where the pressure-sensitive adhesive layer is not laminated. It is 10 to 30 μm.

As will be described later, a coloring agent may be blended in the outermost layer on the side where the adhesive layer is not laminated.

<intermediate layer>

In the base film of the present invention, the surface unevenness of both surfaces of the outermost layer is very important. Therefore, in order to reduce the influence of the surface unevenness of the outermost layer on one side on the surface unevenness of the outermost layer on the opposite side, it is preferable to have the outermost layer on the side of the laminated adhesive layer and the outermost layer on the side of the laminated adhesive layer. The layer acts as an intermediate layer. In this case, the intermediate layer is preferably a polyolefin resin. Examples of the polyolefin-based resin include a polypropylene-based resin and a polyethylene-based resin.

The polypropylene-based resin in this case is the same as the above-exemplified example of the polypropylene-based resin which is preferably used as the outermost layer on the side of the layered adhesive layer. The polyethylene-based resin in this case is the same as the above-exemplified polyethylene resin which is preferably used as the outermost layer on the side of the non-laminated adhesive layer.

The polyolefin-based resin used as the intermediate layer is preferably a polypropylene-based resin from the viewpoint of occurrence of a small amount of fish eyes, and from the viewpoint of ensuring the flexibility of the obtained base film, it is particularly preferable. Atactic polypropylene or block polypropylene.

The intermediate layer may be composed of only one layer or two or more layers, and is preferably only one layer from the viewpoint of simplicity in film production.

The thickness of the intermediate layer is preferably from 2 to 96 μm, more preferably from 6 to 70 μm, particularly preferably from 10 to 50 μm.

As will be described later, a coloring agent can be blended in at least one layer in the intermediate layer.

<Coordination of colorants>

At least one of the outermost layer on the side of the layered adhesive layer of the base film of the present invention and the outermost layer on the side of the non-laminated adhesive layer and any intermediate layer present may be blended with a coloring agent. Floor. The base film of the present invention having at least one layer of a colorant-doped layer is suitable as a colored film for producing a problem of no coloring unevenness and no problem of dissolution of an organic solvent by a printing ink (or a coloring agent). Substrate film.

As the coloring agent, any of a dye and a pigment can be used, and from the viewpoint of more reliably preventing elution of an organic solvent and having less weathering deterioration, a pigment is preferably used. The pigment to be used is not particularly limited, and organic pigments and inorganic pigments generally used as pigments for plastics can be suitably used.

Examples of the above-mentioned organic pigments include an azo pigment, a phthalocyanine pigment, an aniline pigment, and a quinacridone pigment. Examples of the inorganic pigment include titanium oxide and iron oxide red. Ultramarine, carbon black, cobalt blue, etc. These pigments may be used alone or in combination of two or more. Among them, the occurrence of defects such as fish eyes due to secondary aggregates of the pigment itself is small, and the dispersibility in the polyolefin-based resin used as the material constituting each layer of the base film of the present invention is good. It is preferably an organic pigment.

The mixing ratio of the colorant to the polyolefin resin is appropriately determined depending on the thickness of the base film, the thickness of the outermost layer on the side of the laminated adhesive layer, and the like, and considering the transparency (transparency) of the final protective film, 100 parts by weight of the polyolefin-based resin is preferably 0.01 parts by weight to 5 parts by weight. If the mixing ratio is less than 0.01 parts by weight, the hue is unclear, and there is a case where it is impossible to recognize whether or not a colored protective film is attached. On the other hand, when the mixing ratio is more than 5 parts by weight, not only the transparency (transparency) of the protective film is insufficient, but also the occurrence of defects such as fish eyes due to secondary aggregates of the pigment itself becomes remarkable, and coloring The cost burden of the agent also becomes large, so it is not practical.

The method of blending the coloring agent in the polyolefin-based resin is not particularly limited, and for example, a method of directly blending a coloring agent into the pellet of the polyolefin-based resin may be employed, and once the polyolefin-based resin and the coloring agent are mixed in advance, the product is produced. A masterbatch (colorant masterbatch) of a high concentration of a coloring agent, a method of mixing the coloring agent masterbatch and a pellet of a polyolefin resin, and the like, in consideration of the dispersion state of the coloring agent, and avoiding adhesion of the coloring agent to the molding machine, etc. Preferably, a method of using a colorant masterbatch is used.

When a coloring film is blended in at least one layer constituting the layer of the base film of the present invention to form a colored film, the base film is the outermost layer on the side of the laminated adhesive layer and the most non-laminated adhesive layer side. The intermediate layer having at least one layer other than the outer layer, preferably the layer to which the coloring agent is blended is at least one layer in the intermediate layer. By blending the coloring agent only in at least one layer in the intermediate layer, it is possible to more reliably prevent the problem of the dissolution of the coloring agent to the organic solvent used in the laminating step of the subsequent adhesive layer, and prevent the coloring agent from being formed. The machine, especially the problem of adhesion inside the die, is particularly good.

<Method for Producing Substrate Film>

Examples of the method for producing the base film of the present invention include an inflation method, a casting method, and a method of monoaxial stretching. The stretching of the two or more axes is not suitable as a protective film for optical parts because the obtained base film has polarizing characteristics. Therefore, it is preferable to mold without stretching, and in particular, if it is a non-stretched film of a casting method, it can become a base film which is small heat-shrinkage. Therefore, the dimensional change from the step of laminating the adhesive layer is small, and the protective film finally obtained is preferably excellent in the followability of the surface unevenness of the attached body.

In the case of the base film of the present invention, it is preferred that all of the layers constituting the film are unstretched films.

As a method of making the base film into a multilayer structure, for example, a well-known method such as a co-extrusion method or an in-line layer method represented by a multi-manifold method or a feed block method can be employed. Further, each layer may be laminated via an adhesive layer by dry lamination or the like.

<Substrate film>

The thickness (total thickness) of the base film of the present invention thus obtained can be appropriately set in accordance with the area, shape, and the like of the attached body, and is preferably 10 to 100 μm, more preferably 20 to 80 μm, and particularly preferably 40 to 40. 60 μm. Here, if the thickness of the base film is too thin, heating in the step of laminating the adhesive layer thereon may introduce a "hot rash" wrinkle into the film, and it cannot be used as a product. On the other hand, if the thickness of the base film is too large, the flexibility is insufficient, and when it is adhered to the attached body having irregularities on the surface, the surface shape of the attached body cannot be followed, wrinkles are generated, and the bubble is caught. Happening.

The outermost layer on the side of the pressure-sensitive adhesive layer of the base film of the present invention is composed of a polyolefin resin, preferably composed of a polypropylene resin, and has an outer surface having an average roughness (Ra) of 0.25 μm or less. This value is preferably from 0.05 to 0.25 μm, more preferably from 0.1 to 0.20 μm. In the base film of the present invention, since the surface on the side of the laminated adhesive layer is very smooth as described above, the surface of the adhesive layer laminated thereon is also smooth, so that when it is adhered to the attached body, , will not get involved in the bubble.

On the other hand, the outermost layer on the side of the non-laminated adhesive layer of the base film of the present invention is composed of a polyolefin resin, and is preferably composed of a blend of a polypropylene resin and a polyethylene resin. The average roughness (Ra) of the outer surface is 0.30 μm or more. This value is preferably from 0.30 to 1.5 μm, more preferably from 0.30 to 1.0 μm, particularly preferably from 0.35 to 0.8 μm. In the base film of the present invention, since the surface on the side where the pressure-sensitive adhesive layer is not laminated is the above-mentioned moderately rough surface, the base film is adhered to the protective film and then wound into a wound body, which is effective. Since the air is released, the air bubbles are not caught, and since the contact area between the adhesive layer in the wound body and the surface of the lower film substrate is small, the drawing from the wound body can be quickly and easily performed. The above surface roughness can be measured in accordance with JIS B 0601.

The base film of the present invention produced as described above is very few fish eyes. The size and number of fish eyes are important in the substrate film used for the protective film. In other words, when a fish eye having a large size is present in the base film, it is a major factor of visual disturbance when it is optically inspected by adhering it to the object (optical part), even if the optical part is Good products will also be judged as bad products. Even if the number of fish eyes is small, if it is large, it will become a major factor of visual disturbance. The number of fish eyes having a long diameter of less than 1.0 mm in the base film of the present invention may be 5 pieces/m ² or less, and may be 3 pieces/m ² or less. Further, the number of fish eyes having a long diameter of 1.0 mm or more may be 1/m ² or less, and may be 0/m ² . Therefore, even when the base film of the present invention is used for a protective film of an optical component, the main cause of visual disturbance due to fish eyes is extremely small, and appropriate and correct results can be obtained in optical inspection of optical components.

The base film of the present invention is high in transparency. The base film of the present invention may have a haze of 80% or less, more preferably 50% or less, measured in accordance with JIS K 7105. Since the base film of the present invention has extremely high transparency as described above, it does not become an obstacle to optical inspection when it is adhered to the attached body after being used as a protective film.

The base film of the present invention has moderate strength. The base film of the present invention preferably has a tensile modulus of elasticity of from 400 to 1,100 MPa, more preferably from 600 to 900 MPa, particularly preferably from 650 to 850 MPa. The tensile elastic modulus of the base film is preferably in the above range in both the MD direction (machine direction) and the TD direction (lateral direction) of the film. The protective film produced from the base film of the present invention having such a tensile modulus is excellent in handleability when it is adhered to the attached body and peeled off from the attached body. This tensile elastic modulus can be measured in accordance with JIS K 7127 using a JIS-5 test piece.

When a coloring agent is blended in at least one layer constituting the layer of the base film of the present invention to form a colored film, since the colored film is not unevenly colored, appropriate correct results are obtained even in optical inspection of optical parts. Moreover, problems such as dissolution of the colorant to the organic solvent at the time of lamination of the adhesive layer can be avoided.

In the base film of the present invention, from the viewpoint of further improving the adhesion to the adhesive layer laminated thereon, it is preferred to apply the surface treatment in an in-line or off-line manner on the surface on the side of the laminated adhesive layer. Thereafter, the adhesive layer is laminated. Examples of the surface treatment include corona discharge treatment, flame treatment, and the like.

Example

The invention is illustrated by the following examples and comparative examples, but the invention is not limited by the examples.

The following evaluation procedures were adopted for each evaluation system in the following examples and comparative examples.

(1) Haze

As an index of transparency, a haze meter (model: HGM-2DP) manufactured by a Suga tester (manufactured by a stock) was used, and the haze was measured in accordance with JIS K 7105.

(2) Tensile modulus of elasticity

Using the Autograph (Model: AG-500D) manufactured by Shimadzu Corporation, the JIS-5 test piece was used in accordance with JIS K 7127, and each of the MD and TD directions was stretched at a tensile speed of 50 mm/min. Determination of the modulus.

(3) Surface roughness

(Unit) Mitutoyo contact surface roughness measuring device (Model: SJ-401), according to JIS B 0601, stylus tip radius 2μm (60°), measuring speed 0.5mm/s, cutoff value (λc) 0.8mm, The cutoff value (λs) was 25 μm, the measurement length was 0.8 mm, and the number of measurements in one direction was five times, and the measurement of the average roughness (Ra) of the surface was performed. The average roughness (Ra) is an average value of five measurements of the MD direction of the base film and five measurements (10 times of measurement times) in the TD direction.

(4) Fisheye

The base film was cut into a size of 500 mm × 500 mm (0.25 m ² ) to serve as a test piece. The fish eyes present on the test piece were visually observed, and the long diameter was measured for each fish eye found with a magnifying glass with a minimum unit of 0.1 mm. The same measurement was performed on eight test pieces (0.25 m ² × 8 pieces = 2 m ² ), and the number of fish eyes found was converted into the number per 1 m ² and evaluated.

(5) Bubble entrapment

(5-1) Bubble entrapment during winding after processing

The adhesive layer was laminated on the side of the layered adhesive layer of the base film by a method described later so that the layer thickness was about 5 μm, and the film was continuously wound by a winder. The state of entrapment of the bubble in this case was visually confirmed.

(5-2) Bubbles caught when attached to the body

When the base film laminated with the adhesive layer was adhered to the attached body (acrylic plate), the state of entrapment of the air bubbles was visually confirmed.

The respective bubble entrapment states described above are determined by the following.

Good: No seeing of the entrapment of bubbles.

Poor: A state in which the appearance of a bubble is impaired and the appearance is poor.

Example 1

(Formation of substrate film)

Using homopolypropylene A (manufactured by Sumitomo Chemical Co., Ltd., product number: FLX80E4, melting point = 163 ° C, MFR = 7 g/10 min; 230 ° C) and low-density polyethylene A (Ube Maru-good polyethylene) The product number: F120N, density = 0.920 g/cm ³ , melting point = 109 ° C, MFR = 1.2 g/10 min; at 190 ° C), the film was produced by the following method.

A three-layer extruder consisting of a single-axis extruder with a screw diameter of 75 mm for the intermediate layer and a single-axis extruder with a screw diameter of 50 nm for two outer layers, and a total of three extruders of two. a T-die type film forming apparatus comprising a homopolypropylene A for an intermediate layer extruder and a homopolypropylene A for an outer layer (lamination of the adhesive layer side = cooling roll side), and An extruder for the outer layer (on the side of the non-laminated adhesive layer) was supplied by mixing 90 parts by weight of homopolypropylene A with 10 parts by weight of low-density polyethylene A at a resin temperature of 250 ° C for a residence time of 1 minute. The T die was extruded at a temperature of 250 ° C, and extruded through a T die, and passed through a 25 ° C cooling roll to obtain an outer layer having a thickness of 12 μm (on the side of the laminated adhesive layer), an intermediate layer having a thickness of 16 μm, and a thickness of 12 μm. A three-layer unstretched polypropylene film having a total thickness of 40 μm composed of an outer layer (on the side of the non-laminated adhesive layer). Next, a corona discharge treatment was applied so that the wetting index of the surface of the film on the side of the layer of the adhesive layer was 42 mN/m, and the substrate film was obtained by aging at 40 ° C for 24 hours.

The evaluation of the above (1) to (4) was carried out using this base film. The evaluation results are shown in Table 2.

(Lamination of the adhesive layer to the substrate film)

The surface of the corona-treated surface of the base film obtained above was coated with an acrylic adhesive and dried to laminate an adhesive layer having a thickness of 10 μm.

The film of the above (5) was evaluated by using the film laminated with this adhesive layer. The evaluation results are shown in Table 2.

Example 2

The resin of the extruder supplied to the intermediate layer was block polypropylene A (manufactured by Japan Polypropylene Co., Ltd., product number: BC3HF, propylene-ethylene block copolymer type, melting point = 162 ° C, MFR = 7 g/10 Minute; at 230 ° C), and the resin supplied to the extruder for the outer layer (the side of the non-laminated adhesive layer) is mixed with 70 parts by weight of the block polypropylene A and 30 parts by weight of the low density polyethylene A. A base film was obtained in the same manner as in Example 1 except the above. The substrate film was evaluated for the above (1) to (4), and a film in which an adhesive layer was laminated on a base film in the same manner as in Example 1 was evaluated, and the evaluation of the above (5) was carried out. The evaluation results are shown in Table 2.

Example 3

The base film was obtained in the same manner as in Example 2 except that the resin supplied to the extruder for the outer layer (the side of the layer of the adhesive layer) was block polypropylene A. The base film was evaluated for the above (1) to (4), and a film in which an adhesive layer was laminated on the base film in the same manner as in Example 1 was evaluated, and the evaluation of the above (5) was carried out. The evaluation results are shown in Table 2.

Example 4

The mixing ratio of the resin-based block polypropylene A and the low-density polyethylene A to the extruder for the outer layer (the side of the non-laminated adhesive layer) was as described in Table 1, and was carried out in the same manner as in the above-described Example 2. A substrate film was obtained. The substrate film was evaluated for the above (1) to (4), and a film in which an adhesive layer was laminated on a base film in the same manner as in Example 1 was evaluated, and the evaluation of the above (5) was carried out. The evaluation results are shown in Table 2.

Example 5

The resin supplied to the extruder for the intermediate layer was a random polypropylene A (manufactured by PRIMEPOLYMER, product number: F327BV, propylene-ethylene-butene random copolymer type, melting point = 138 ° C, MFR = 7 g /10 minutes; 230 ° C), and the resin supplied to the extruder for the outer layer (on the side of the non-laminated adhesive layer) is 70 parts by weight of random polypropylene A and 30 parts by weight of low density polyethylene B (Formed by Ube Maruzen Polyethylene Co., Ltd., product number: F522N, density = 0.922 g/cm ³ , melting point = 110 ° C, MFR = 5.0 g/10 min; at 190 ° C), and the above Example 1 The substrate film was obtained in the same manner. The substrate film was evaluated for the above (1) to (4), and a film in which an adhesive layer was laminated on a base film in the same manner as in Example 1 was evaluated, and the evaluation of the above (5) was carried out. The evaluation results are shown in Table 2.

Example 6

The same procedure as in the above-described Example 2 was carried out except that the thickness of the outer layer (the side of the layer of the adhesive layer) was 25 μm, the intermediate layer was 25 μm, and the outer layer (the side of the non-laminated adhesive layer) was 25 μm, and the total thickness was 75 μm. A substrate film was obtained. The substrate film was evaluated for the above (1) to (4), and a film in which an adhesive layer was laminated on a base film in the same manner as in Example 1 was evaluated, and the evaluation of the above (5) was carried out. The evaluation results are shown in Table 2.

Example 7

The thickness of the outer layer (the side of the layer of the adhesive layer) was 20 μm and the outer layer (the side of the layer on which the adhesive layer was not laminated) was 20 μm, and the supply of the raw material from the extruder of the intermediate layer was stopped to form a two-layer structure having a total thickness of 40 μm. A base film was obtained in the same manner as in Example 1 except that it was carried out. The substrate film was evaluated for the above (1) to (4), and a film in which an adhesive layer was laminated on a base film in the same manner as in Example 1 was evaluated, and the evaluation of the above (5) was carried out. The evaluation results are shown in Table 2.

Example 8

In addition to the resin as an extruder for the intermediate layer, 100 parts by weight of block polypropylene A (manufactured by Japan Polypropylene Co., Ltd., product number: BC3HF, propylene-ethylene block copolymer type, melting point = 162) was used. °C, MFR=7g/10min; 230°C), with 5 parts by weight of color masterbatch (DIC), product number: PEONY HP BLUE L-83285M, random polypropylene (propylene ethylene random) A base film was obtained in the same manner as in Example 2 except that the coloring resin of the copolymerization type, MFR = 8 g/10 min; and a masterbatch containing about 5% by weight of phthalocyanine blue at 230 ° C) was used. The substrate film was evaluated for the above (1) to (4), and a film in which an adhesive layer was laminated on a base film in the same manner as in Example 1 was evaluated, and the evaluation of the above (5) was carried out. The evaluation results are shown in Table 2. Further, in the base film of the present embodiment, it was confirmed that the elution of the colorant to the organic solvent did not occur at all when the adhesive layer was laminated.

Comparative example 1

A base film was obtained in the same manner as in Example 1 except that the resin of the extruder supplied to all the layers was only the block polypropylene A. The substrate film was evaluated for the above (1) to (4), and a film in which an adhesive layer was laminated on a base film in the same manner as in Example 1 was evaluated, and the evaluation of the above (5) was carried out. The evaluation results are shown in Table 2.

In addition, the abbreviation of the raw material in Table 1 has the following meaning.

H-PP-A: homopolypropylene A (manufactured by Sumitomo Chemical Co., Ltd., article number: FLX80E4, melting point = 163 ° C, MFR = 7 g / 10 min; 230 ° C)

B-PP-A: Block Polypropylene A (manufactured by Japan Polypropylene Co., Ltd., article number: BC3HF, propylene-ethylene block copolymer type, melting point = 162 ° C, MFR = 7 g / 10 min; 230 ° C)

R-PP-A: atactic polypropylene A (manufactured by PRIMEPOLYMER, article number: F327BV, propylene-ethylene-butene random copolymer type, melting point = 138 ° C, MFR = 7 g / 10 min; 230 ° C )

LDPE-A: low density polyethylene A (made by Ube Maruzen Polyethylene Co., Ltd., article number: F120N, density = 0.920 g/cm ³ , melting point = 109 ° C, MFR = 1.2 g/10 min; 190 ° C)

LDPE-B: low density polyethylene B (made by Ube Maruzen Polyethylene Co., Ltd., article number: F522N, density = 9.922g/cm ³ , melting point = 110 ° C, MFR = 5.0 g/10 min; 190 ° C)

PhB-MB: phthalocyanine blue masterbatch (DIC), article number: PEONY HP BLUE L-83285M, in atactic polypropylene (propylene-ethylene random copolymerization type, MFR = 8g/10 minutes; 230 Containing about 5% by weight of the masterbatch of phthalocyanine blue at °C)

Effect of the invention

In the base film of the present invention, since the surface on the side of the laminated adhesive layer is smooth and the adhesive layer laminated thereon is similarly smooth, the protective film produced by the film of the present invention is When it is adhered to the attached body, the entrapment of air bubbles does not occur. Since the substrate film of the present invention has a moderate surface roughness on the surface on the side where the adhesive layer is not laminated, the air can be efficiently discharged during the winding after the adhesion processing, so that the wound body is not manufactured at the time of manufacture. The entrapment of bubbles occurs. Further, since the base film of the present invention can be produced by a simple method with a short process time, the fisheye system mainly caused by the thermally deteriorated material during processing is extremely small.

Therefore, the base film of the present invention is particularly suitable for use as a protective film for optical parts of optical parts.

Claims (5)

A base film which is a base film for a protective film formed by laminating an adhesive layer on one side, characterized in that the base film has at least two layers of a laminate of a polyolefin-based resin. Each of the two layers constitutes an outermost layer on the side of the laminated adhesive layer and an outermost layer on the side of the non-laminated adhesive layer, and the average roughness (Ra) of the surface of the base film on the side of the adhesive layer is 0.25 μm or less, the surface of the base film on the side of the non-laminated adhesive layer has an average roughness (Ra) of 0.30 μm or more, and is used for a protective film for optical parts having a thickness of 10 to 100 μm, and each layer is Stretch the film. The substrate film of claim 1, wherein the outermost layer on the side of the adhesive layer of the base film is made of a polypropylene resin, and the base film is not laminated on the side of the adhesive layer. The outer layer is composed of a blend of a polypropylene resin and a polyethylene resin in a total content of the polyethylene resin in a ratio of 5 to 50% by weight based on the total of the polypropylene resin and the polyethylene resin. The base film of claim 1 or 2, wherein the fisheye of the long diameter of less than 1.0 mm is 5/m ² or less, and the fisheye of the long diameter of 1.0 mm or more is 0/m ² . The substrate film of claim 1 or 2, wherein at least one of the layers constituting the substrate film is a layer to which a colorant is blended. The substrate film of claim 4, wherein the substrate is thin The film system has at least one intermediate layer in addition to the outermost layer on the side of the laminated adhesive layer and the outermost layer on the side of the non-laminated adhesive layer, and the layer of the coloring agent is at least one of the intermediate layers. Floor.