JP4565058B2 - SURFACE PROTECTIVE FILM FOR PRISM SHEET, MANUFACTURING METHOD THEREOF, AND PRISM SHEET Attached To It - Google Patents

Description

  The present invention relates to a surface protective film for a prism sheet, a method for producing the same, and a prism sheet to which the film is attached.

  The prism sheet has a plurality of triangular prisms serving as lens surfaces on one side, and can improve the luminance of the liquid crystal display. In order not to damage the prism, a surface protection film is attached to the prism formed on the surface of the prism sheet for protection.

  Since the prism sheet with the surface protective film attached may be exposed to high temperatures during transportation or storage, the adhesive used for the surface protective film is a rubber-based adhesive that has a small increase in adhesive strength due to heating or passage of time. An adhesive is used.

  On the other hand, the surface protective film is handled as a scroll. The rubber-based pressure-sensitive adhesive generally has a large force (development force) required for unwinding from the scroll, and there is a problem that the deployment force gradually increases when stored as a scroll for a long period of time.

  A surface protective film with a large unfolding force is drawn out from the roll while the surface protective film is pulled. Therefore, when the surface protective film is affixed to the prism sheet, the surface protective film is lifted from the adhesive surface with the prism sheet. There is a problem that a so-called “float” is generated. For this reason, there has been a demand for a surface protective film having a small development force (so-called “light development”).

  When a release layer is provided on the surface protective film, the developing force can be reduced. However, when the release agent is peeled off from the base material layer and transferred to the adhesive layer, there is a problem that the adhesive strength of the surface protective film decreases. It was. When a surface protective film is applied to the lens surface of the prism sheet, the contact area between the irregularities of the lens surface and the adhesive layer of the surface protective film is small, so the release agent transferred to the adhesive layer is the adhesive layer and the lens. The contact area with the surface irregularities is reduced, and the adhesive strength of the surface protective film is greatly reduced. Patent Document 1 proposes a surface protective film in which a release layer is difficult to transfer to an adhesive layer.

JP 2003-41216 A

  However, the release layer of the surface protective film described in Patent Document 1 is formed by applying a release agent to the substrate. When a release agent is applied using an organic solvent, the load on the environment is large. Further, when an aqueous dispersion of a release agent is applied, a drying process is required. When an ultraviolet curable resin liquid as a release agent is applied, an ultraviolet irradiation device is required.

  An object of the present invention is to provide a surface protective film for a prism sheet that has a small developing force from a scroll and is less likely to have a reduced adhesive force even when a release layer adheres to the adhesive layer.

  Moreover, the other object of this invention is to provide the manufacturing method of the surface protection film for prism sheets of this invention.

The present invention provides a surface protective film of the following [1] to [6], a method for producing a surface protective film of the following [7], and a prism sheet to which the surface protective film of the following [8] is attached. To do.
[1]
Molding raw material A containing saturated fatty acid bisamide and polyolefin resin, and molding raw material B containing styrene elastomer
Manufactured by co-extrusion,
(A) A release layer mainly composed of saturated fatty acid bisamide and having a thickness of 1 to 100 nm. (B) A polyolefin resin layer as a base material layer, and (C) a styrene elastomer layer as an adhesive layer. Surface protection film for prism sheets.
[2]
The surface protection film for a prism sheet according to claim 1, wherein the molding raw material A contains 1 to 4 parts by weight of a saturated fatty acid bisamide with respect to 100 parts by weight of the polyolefin resin.
[3]
The surface protective film for a prism sheet according to [1] or [2], wherein the saturated fatty acid bisamide is ethylene bis stearamide, methylene bis stearamide, or hexamethylene bis stearamide.
[4]
The surface protective film for a prism sheet according to [1] or [2], wherein the saturated fatty acid bisamide is a saturated fatty acid aromatic bisamide.
[5]
The surface protective film for prism sheets according to any one of [1] to [4], wherein an intermediate layer is formed between the base material layer and the pressure-sensitive adhesive layer.
[6]
The surface protective film for a prism sheet according to [5], wherein the intermediate layer is a mixture of a polyolefin-based resin and a styrene-based elastomer containing a saturated fatty acid bisamide.
[7]
(A) a release layer having a thickness of 1 to 100 nm mainly composed of saturated fatty acid bisamide;
(B) a polyolefin resin layer which is a base material layer,
(C) A method for producing a surface protective film for a prism sheet in which a styrene-based elastomer layer as an adhesive layer is laminated in this order,
A method for producing a surface protection film for a prism sheet, comprising co-extruding a molding raw material A containing 1 to 4 parts by weight of a saturated fatty acid bisamide and a molding raw material B containing a styrene elastomer with respect to 100 parts by weight of a polyolefin resin.
[8]
A prism sheet having a plurality of triangular prisms on the lens surface, and a release layer having a thickness of 1 to 100 nm mainly composed of (A) a saturated fatty acid bisamide, and (B) base Including a surface protective film for a prism sheet in which a polyolefin resin layer as a material layer, and (C) a styrene elastomer layer as an adhesive layer are laminated,
A prism sheet having a surface protective film attached thereto, wherein a depth of penetration of the prism into the pressure-sensitive adhesive layer is 0.3 μm or more.

  ADVANTAGE OF THE INVENTION According to this invention, the surface protection film for prism sheets can be provided that the expansion force from a scroll is small, and even if a release layer adheres to an adhesive layer, an adhesive force does not fall easily.

  Furthermore, according to this invention, the manufacturing method which manufactures the surface protection film for prism sheets in which the very thin release layer was formed can be provided.

The surface protective film for a prism sheet of the present invention is
(A) A release layer mainly composed of saturated fatty acid bisamide and having a thickness of 1 to 100 nm, (B) a polyolefin resin layer serving as a base material layer, and (C) a styrene elastomer layer serving as an adhesive layer in this order. Are stacked.
The thickness of the surface protective film for a prism sheet of the present invention is not particularly limited, but the lower limit is usually 12 μm, preferably 20 μm, and the upper limit is usually 100 μm, preferably 60 μm, more preferably 50 μm, still more preferably. 45 μm.

(A) Release layer The release layer is mainly composed of saturated fatty acid bisamide. Here, “consisting mainly of” means that the release layer is formed of saturated fatty acid bisamide bleeded out from the olefin resin layer. More specifically, it means that the content of saturated fatty acid bisamide is 90% by weight or more of the entire release layer.

Saturated fatty acid bisamides include, for example, saturated fatty acid aliphatic bisamides such as ethylene bis stearamide, methylene bis stearamide, and hexamethylene bis stearamide; and m-xylylene bis stearamide, and NN ′ -Saturated fatty acid aromatic bisamides such as distearyl isophthalic acid amide are preferred. Among the saturated fatty acid aliphatic bisamides, ethylene bis stearamide is more preferable. Of the saturated fatty acid aromatic bisamides, m-xylylene bisstearic acid amide is more preferred.
These saturated fatty acid bisamides may be used alone or in combination of two or more.
Moreover, you may use another mold release agent together.

The thickness of the release layer is 1 to 100 nm.
The lower limit of the thickness is preferably 5 nm, more preferably 7 nm, and still more preferably 9 nm. On the other hand, the upper limit of the thickness is preferably 80 nm, more preferably 60 nm, and still more preferably 40 nm.

  When the surface protection film for a prism sheet of the present invention is in the form of a scroll, the release layer is in contact with the pressure-sensitive adhesive layer and transferred to the surface of the pressure-sensitive adhesive layer. Therefore, if the ridgeline of the prism on the surface of the prism sheet breaks through the release layer and the depth of penetration of the prism into the adhesive is 0.3 μm or more, there is no occurrence of floating, which is a practical problem. No adhesive force can be secured.

  When the release layer has a thickness of 100 nm or less, it adheres to the pressure-sensitive adhesive layer when the surface protection film is rewound from the roll by the ridgeline of the prismatic prism of the prism sheet when the prism sheet is attached ( That is, the transferred release layer is broken through, and the prism sheet and the pressure-sensitive adhesive layer come into contact with each other. Thereby, a practically sufficient adhesive strength can be obtained.

  On the other hand, when the thickness of the release layer is 1 nm or more, the developing force from the scroll can be sufficiently reduced.

  The thickness of the release layer is determined by the following method. The prism sheet surface protective film of the present invention is dyed with ruthenium tetroxide, and the release layer and the base material layer are dyed separately using the difference in dyeability. A plurality of thin film pieces are prepared by repeatedly thinning a resin sample in which a surface protective film is sealed using an ultramicrotome (REICHERT ULTRACUT S, manufactured by Leica) having a section thickness set to 70 nm. An observation thin film piece capable of observing the cross section of the release layer and the base material layer is selected from a plurality of thin film pieces using a transmission electron microscope. The observation thin film piece was observed using a transmission electron microscope, and the thickness of the release layer was measured at three locations. The average value of the measured values is taken as the thickness of the release layer.

(B) Base material layer A base material layer consists of polyolefin resin.

  The release layer of the surface protective film for a prism sheet of the present invention is formed by bleeding out the release agent from the base material layer. In the base material layer, the saturated fatty acid bisamide added to the polyolefin-based resin for forming the release layer remains.

  Examples of polyolefin resins include low density polyethylene resin, medium density polyethylene resin, high density polyethylene resin, linear low density polyethylene resin, ethylene-α-olefin copolymer resin, ethylene-ethyl acrylate copolymer resin, ethylene-acetic acid. Examples include vinyl copolymer resins, ethylene-methyl acrylate copolymer resins, ethylene-n-butyl acrylate copolymer resins, and polypropylene resins, and mixtures thereof.

  Such a resin may contain an additive usually added to the resin. Examples of the additive include an antioxidant, an ultraviolet absorber, and an antiaging agent. The amount of the additive is usually 5% by weight or less, preferably 3% by weight or less, based on the entire resin.

  The thickness of the base material layer can be appropriately adjusted according to the material of the prism sheet and the shape of the prism, and is generally set to 4 to 80 μm, preferably 20 to 50 μm.

(C) Pressure-sensitive adhesive layer The pressure-sensitive adhesive layer contains a styrene-based elastomer.

  The pressure-sensitive adhesive layer mainly contains a styrene-based elastomer and preferably further contains a tackifier. Here, the main component means that it occupies the most weight among all components of the pressure-sensitive adhesive layer, and preferably means that it is contained by 50% by weight or more.

The styrene elastomer used in the present invention is preferably the following polymer (i), the following polymer (ii), or a mixture thereof.
“Polymer (i)” includes the following polymer block A and the following polymer block B, and is represented by the general formula [AB] n (wherein A represents the polymer block A and B represents the polymer block B). , N represents an integer of 1 to 3.) (I) or a hydrogenated product thereof. As “n” represents an integer of 1 to 3, as is clear, examples of the “structure represented by the formula [A-B] n” include AB, ABAB, And a structure represented by A-B-A-B-A-B. In these block copolymers, A and B may be the same or different in repetition.
The “polymer (ii)” includes the following polymer block A and the following polymer block B, and is represented by the general formula A-B-A (the symbols in the formula are as defined above) or the general formula (A- B) x-Y (wherein x represents an integer of 2 or more, Y represents a coupling agent residue, and other symbols are as defined above).
Or a hydrogenated product thereof.
The styrenic elastomer is a mixture of the polymer (i) and the polymer (ii), and the total amount and weight of the polymer block A contained in the polymer (i) and the polymer (ii). A mixture having a weight ratio with the total amount of the combined block B in the range of 5:95 to 25:75 is preferable.
“Polymer block A” is a polymer block in which aromatic alkenyl compound units are continuous and mainly composed of aromatic alkenyl compound units.
The “polymer block B” is an aromatic alkenyl-conjugated diene copolymer block in which a conjugated diene compound unit and an aromatic alkenyl compound unit are randomly included.

  The “aromatic alkenyl compound unit” is a repeating unit derived from an aromatic alkenyl compound. Examples of the “aromatic alkenyl compound” include styrene, tert-butylstyrene, α-methylstyrene, p-methylstyrene, p-ethylstyrene, divinylbenzene, 1,1-diphenylethylene, vinylnaphthalene, vinylanthracene, N , N-diethyl-p-aminoethylstyrene, vinylpyridine and the like.

  Examples of the “conjugated diene compound” include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-octadiene, 1,3- Examples include hexadiene, 1,3-cyclohexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, myrcene, and chloroprene.

  Although the thickness in particular of an adhesive layer is not restrict | limited, It is 2-20 micrometers, Preferably it is 3-15 micrometers.

  The pressure-sensitive adhesive layer of the present invention usually contains a tackifier.

  Examples of the tackifier include petroleum-based resins such as aliphatic copolymers, aromatic copolymers, aliphatic / aromatic copolymers and alicyclic copolymers, and coumarone-indene resins. , Terpene resins, terpene phenolic resins, rosin resins such as polymerized rosin, (alkyl) phenolic resins, xylene resins or hydrogenated products such as those generally used for pressure-sensitive adhesives are used without particular limitation can do. It is more preferable to use a tackifier having a softening point of 90 to 140 ° C. These tackifiers may be used alone or in combination of two or more. In addition, in order to improve peelability and weather resistance, it is more preferable to use a hydrogenated resin as a tackifier. Moreover, you may use the tackifier marketed as a mixture with an olefin resin.

  The tackifier is preferably compatible with the polymer block B having a conjugated diene compound unit or a hydrogenated conjugated diene compound unit.

  The tackifier is used in an amount capable of preventing adhesive residue when the surface protective film is peeled off from the adherend. For example, the blending ratio of the tackifier is preferably 5 to 50 parts by weight, more preferably 20 to 40 parts by weight with respect to 100 parts by weight of the styrene elastomer. The blending ratio varies depending on the type of tackifier. For example, in the case of a tackifier having a softening point of 90 to 140 ° C., 15 to 40 weights is preferable, more preferably 20 to 20 parts by weight with respect to 100 parts by weight of the styrenic elastomer. 30 parts by weight. If the amount of the tackifier is within this range, even if the surface protective film is pasted on the prism sheet for a long time, the adhesive force is hardly lowered, and the surface protective film bonded to the prism sheet is not easily lifted.

  For the purpose of controlling the adhesive force, the pressure-sensitive adhesive layer may contain known additives such as a softening agent, an antioxidant, and an adhesion progressing prevention agent as necessary.

  Examples of the softener include low molecular weight diene polymer, polyisobutylene hydrogenated polyisoprene, hydrogenated polybutadiene, paraffin process oil, naphthene process oil, aromatic process oil, castor oil, tall oil, natural oil, liquid Examples thereof include polyisobutylene resin, polybutene, and hydrogenated products thereof. These softeners may be used alone or in combination of two or more.

  The antioxidant is not particularly limited. For example, a phenol-based antioxidant (eg, monophenol-based antioxidant, bisphenol-based antioxidant, polymer-type phenol-based antioxidant), sulfur-based antioxidant, Examples thereof include phosphorus-based antioxidants.

Adhesion progress inhibitors include fatty acid amides, polyethyleneimine long-chain alkyl grafts, soybean oil-modified alkyd resin (Arakawa Chemical Co., trade name “Arachid 251”), tall oil-modified alkyd resin (Arakawa Chemical Co., Ltd., product) Name "Arachid 6300").
(D) Intermediate layer The surface protective film for a prism sheet of the present invention may further include an intermediate layer between the base material layer and the pressure-sensitive adhesive layer.

  The release layer is formed by bleeding out on the surface in the process in which the surface of the base material layer (opposite side of the adhesive layer) melted immediately after coextrusion comes into contact with the cooling roll and solidifies. At this time, saturated fatty acid bisamide bleeds out also on the surface of the base material layer opposite to the release layer. When the saturated fatty acid bisamide layer is in contact with the pressure-sensitive adhesive layer, the bonding force between the base material layer and the pressure-sensitive adhesive layer may be reduced. The intermediate layer has a function of preventing a decrease in the bonding force.

  The intermediate layer may be a resin that can be bonded to the base material layer and the adhesive layer, but a layer made of a polyolefin-based resin is preferable.

  Preferably, the polyolefin resin in the intermediate layer contains a saturated fatty acid bisamide and a styrene elastomer. Such an intermediate layer may be manufactured using the end material of the surface protective film for prism sheet.

<Manufacturing method>
The surface protective film for a prism sheet of the present invention is produced by coextrusion of a molding raw material A made of a polyolefin resin containing a saturated fatty acid bisamide and a molding raw material B containing a styrene elastomer.
The saturated fatty acid bisamide is usually synthesized by a dehydration condensation reaction between a diamine and a saturated fatty acid. For this reason, saturated fatty acid bisamide may contain diamine and saturated fatty acid as impurities. According to the study by the present inventors, the diamine and saturated fatty acid described above are related to the characteristics of the method for producing a surface protective film for a prism sheet according to the present invention in which a release layer is formed by bleed out. It was found that the production apparatus was contaminated during the production of the prism sheet surface protective film. Therefore, the saturated fatty acid bisamide used in the present invention preferably has a low content of diamine and saturated fatty acid.

The forming raw material A and the forming raw material B can be prepared by mixing each component by a known method. For example, in the case of the forming raw material A, specifically, it can be prepared by pelletizing a polyolefin-based resin containing a saturated fatty acid amide with a twin screw extruder.

By adjusting the amount of saturated fatty acid bisamide contained in the forming raw material A, the thickness of the release layer formed on the surface of the base material layer can be adjusted. The lower limit of the amount of the saturated fatty acid bisamide contained in the forming raw material A is preferably 1 part by weight, more preferably 1.5 parts by weight with respect to 100 parts by weight of the polyolefin-based resin in order to form a release layer by bleed out. Part. On the other hand, the upper limit of the amount of the saturated fatty acid bisamide contained in the forming raw material A is to obtain sufficient adhesive force with the prism sheet by forming a release layer having an appropriate thickness, and the peeled release layer is formed on the forming roll. From the viewpoint of suppressing adhesion, the amount is preferably 4 parts by weight, more preferably 2-3 parts by weight with respect to 100 parts by weight of the polyolefin resin.

A molding raw material A made of a polyolefin resin containing saturated fatty acid bisamide and a molding raw material B containing a styrene elastomer are coextruded by a T-die method using two or more multilayer extruders, for example. Thereafter, the resin side from which the forming raw material A is extruded is rapidly cooled by a cooling roll. Thereby, a multilayer film is obtained.

  The extrusion temperature is preferably 160 to 230 ° C.

  First, a base material layer and an adhesive layer are formed by coextrusion.

Next, the base layer immediately after coextrusion comes into contact with the cooling roll, and the saturated fatty acid bisamide contained in the forming raw material A bleeds out to the surface of the base layer due to its own properties, thereby forming a release layer. Is done.

  When 1 to 4 parts by weight of saturated fatty acid bisamide is contained in the polyolefin resin, a release layer of 1 to 100 nm is formed on the surface of the base material layer.

  The surface protective film of the present invention thus formed is usually cooled by a cast roll, wound by a take-up roll, and stored as a roll.

  As for the thickness of the release layer, the cast roll temperature is set to 20 to 90 ° C. The release layer of the present invention is a layer formed on the surface of the base material layer opposite to the pressure-sensitive adhesive layer.

<Surface protection film>
As described above, the surface protective film for a prism sheet of the present invention is usually wound up and stored as a scroll. At this time, the release layer contacts the pressure-sensitive adhesive surface of the wound pressure-sensitive adhesive layer. When this roll is developed and attached to the prism sheet, a part of the release layer is transferred to the surface of the adhesive surface. Usually, the adhesive force of the surface protective film is significantly reduced by the transfer of the release layer. However, in the surface protective film of the present invention, the ridge line of the prism of the prism sheet breaks through the transferred release layer. Thereby, even if the release layer is transferred, the adhesive force of the adhesive layer is exhibited.

(Depth of penetration)
In the surface protective film of the present invention, the prism biting depth of the prism sheet into the pressure-sensitive adhesive layer is preferably 0.3 μm or more. Thereby, an appropriate adhesive strength is exhibited. The upper limit of the bite depth is not particularly limited, but is usually 2 μm or less.

  The biting depth was affixed at a speed of 300 mm / min using a 2 kg pressure rubber roller in an environment of a room temperature of 23 ° C. and a relative humidity of 50%, and left in that state for 30 minutes, and then a surface protective film was applied. This is a numerical value measured by freezing the prism sheet using a freezing microtome and observing the cut section using a scanning electron microscope.

  The biting depth is adjusted by adjusting the shear modulus and thickness of the pressure-sensitive adhesive layer of the surface protective film of the present invention according to the size of the prism ridge of the triangular prism of the prism sheet to which the surface protective film of the present invention is applied. Can be adjusted.

From this viewpoint, the shear modulus (23 ° C.) of the pressure-sensitive adhesive layer is preferably 5 × 10 ⁶ or less. However, from the viewpoint of preventing the occurrence of adhesive residue, the shear elastic modulus is preferably 5 × 10 ⁴ or more.

  From this viewpoint, the thickness of the pressure-sensitive adhesive layer is preferably 4 μm or more. However, from the viewpoint of cost, the thickness is preferably 15 μm or less.

(Development power)
The roll of the surface protective film of the present invention can be easily rewound. The deploying force at a speed of 20 m / min with a 50 mm width scroll is preferably 3.5 N or less, more preferably 2 N or less. By using such a deployment force, for example, even when the width of the scroll exceeds 1000 mm, it is possible to reduce the sound generated during deployment and prevent the occurrence of floating after being attached to the prism sheet.

(Adhesive strength over time)
The surface protective film of the present invention preferably has a pasting adhesive strength at 23 ° C. measured under the following conditions of 0.05 to 0.50 N / 25 mm.
[conditions]
Within 3 days from the creation of the surface protective film, a 25 mm wide surface protective film is applied so as to cover the lens surface of the prism sheet. A prism sheet made of acrylic resin having a thickness of 130 μm and having a prism pitch of 50 μm and a height of 25 μm is used. A surface protective film is attached at a speed of 300 mm / min using a 2 kg pressure-bonded rubber roller in an environment of room temperature 23 ° C. and relative humidity 50%. After being left for 2 weeks in an environment of room temperature 23 ° C. and relative humidity 50%, the surface protective film is peeled off at a speed of 300 mm / min in accordance with JIS Z0237, and the 180 ° peel strength is measured. The direction in which the surface protective film is peeled off is the ridge line direction of the prism. The 180 degree peel strength measured in this way is defined as the adhesive strength with time at 23 ° C.

<Prism sheet with surface protective film>
The surface protective film for a prism sheet of the present invention is attached to the lens surface of the prism sheet.

Prism sheet with a surface protective film to which the surface protective film for a prism sheet of the present invention is attached, that is,
A prism sheet having a plurality of triangular prisms on the lens surface, and a release layer having a thickness of 1 to 100 nm mainly composed of (A) a saturated fatty acid bisamide, and (B) base Including a surface protective film for a prism sheet in which a polyolefin resin layer as a material layer, and (C) a styrene elastomer layer as an adhesive layer are laminated,
A prism sheet with a surface protective film, wherein a depth of biting of the prism into the pressure-sensitive adhesive layer is 0.3 μm or more, is also an embodiment of the present invention.

  As a prism sheet to which the surface protective film for a prism sheet of the present invention is attached, for example, in a plurality of triangular prisms having apex angles of about 90 ° on the ridge line on the lens surface, between the vertices of adjacent prisms. The thing whose distance is about 10-1000 micrometers is mentioned.

As a prism sheet to which such a surface protective film is attached,
A prism sheet having a plurality of triangular prisms on the lens surface, and the prism sheet according to any one of [1] to [6] attached to the lens surface of the prism sheet,
A prism sheet on which a surface protective film is attached, in which a depth of biting of the prism into the pressure-sensitive adhesive layer is 0.3 μm or more, is preferable.

  Below, the surface protection film of this invention is demonstrated in detail based on an Example and a comparative example. The present invention is not limited to the following examples.

Example 1
As a forming raw material A, a mixture of 100 parts by weight of polypropylene “Y900GV (manufactured by Prime Polymer)” and 1 part by weight of ethylene bis-stearic acid amide “Alflow H50F (manufactured by NOF Corporation)” which is a saturated fatty acid bisamide, and a forming raw material B As a styrene elastomer “Dynalon 1320P (manufactured by JSR)” 100 parts by weight, tackifier “Alcon P100 (manufactured by Arakawa Chemical)” 20 parts by weight, and antioxidant “Irganox 1010 (manufactured by Ciba Specialty Chemicals)” The mixture consisting of 1 part by weight was coextruded by the T-die method under the following conditions to prepare a surface protective film. The surface protective film had a substrate layer thickness of 34 μm and an adhesive layer thickness of 6 μm.
The thickness of the release layer of the surface protective film was 6 nm.
<Conditions>
Extrusion temperature: 200 ° C
Cast roll temperature: 25 ° C
<Method for measuring thickness of release layer>
The thickness of the release layer was determined by the following method. The prism sheet surface protective film was dyed with ruthenium tetroxide, and the release layer and the base material layer were dyed separately using the difference in ease of dyeing. A resin sample encapsulating the surface protective film was repeatedly thinned using an ultramicrotome (Leica Corporation, REICHERT ULTRACUT S) with a section thickness set to 70 nm to create a plurality of thin film pieces. The thin film piece for observation which can observe the cross section of a mold release layer and a base material layer was selected from the some thin film piece using the transmission electron microscope (the JEOL company make, JEM-2100). The thin film piece for observation was observed using the transmission electron microscope (the product made by JEOL, JEM-2100), and the thickness of the mold release layer was measured at three places. The average value of the measured values was taken as the thickness of the release layer.

(Example 2)
A surface protective film was prepared in the same manner as in Example 1 except that the amount of ethylenebisstearic acid amide was 1.5 parts by weight. The surface protective film had a substrate layer thickness of 34 μm, an adhesive layer thickness of 6 μm, and a release layer thickness of 9 nm.

(Example 3)
A surface protective film was prepared in the same manner as in Example 1 except that the amount of ethylenebisstearic acid amide was 3 parts by weight. The surface protective film had a substrate layer thickness of 34 μm and an adhesive layer thickness of 6 μm. Moreover, the thickness of the release layer of the surface protective film was 80 nm.

Example 4
The end material produced when both ends of the surface protective film of the present invention were trimmed was molded into pellets using a twin screw extruder.
As a forming raw material A, a mixture composed of 100 parts by weight of polypropylene “Y900GV (manufactured by Prime Polymer)” and 1 part by weight of ethylene bis-stearic acid amide “Alflow H50F (manufactured by NOF Corporation)” which is a saturated fatty acid bisamide, and an intermediate layer As a raw material to be formed, a mixture composed of 70 parts by weight of polypropylene “Y900GV (manufactured by Prime Polymer)” and 30 parts by weight of the above pellets, and 100 parts by weight of a styrene elastomer “Dynalon 1320P (manufactured by JSR)” as a forming raw material B The mixture of 20 parts by weight of the tackifier “Alcon P100 (Arakawa Chemical Co., Ltd.)” and 1 part by weight of the antioxidant “Irganox 1010 (Ciba Specialty Chemicals)” was used under the same conditions as in Example 1. Then, co-extrusion by T-die method to create a surface protection film .
The surface protective film had a base material layer thickness of 28 μm, an intermediate layer thickness of 6 μm, and an adhesive layer thickness of 6 μm. Moreover, the thickness of the release layer of the surface protective film was 65 nm.

(Example 5)
A surface protective film was prepared in the same manner as in Example 1 except that 3 parts by weight of methylene bis stearamide “Bisamide LA (manufactured by Nippon Kasei Co., Ltd.)” was used as the saturated fatty acid bisamide. The surface protective film had a substrate layer thickness of 34 μm and an adhesive layer thickness of 6 μm. Moreover, the thickness of the release layer of the surface protective film was 40 nm.

(Example 6)
A surface protective film was prepared in the same manner as in Example 1 except that 2.5 parts by weight of hexamethylene bis-stearic acid “Sripacs ZHS (manufactured by Nippon Kasei Co., Ltd.)” was used as the saturated fatty acid bisamide. The surface protective film had a substrate layer thickness of 34 μm and an adhesive layer thickness of 6 μm. Moreover, the thickness of the release layer of the surface protective film was 15 nm.

(Example 7)
A surface protective film was prepared in the same manner as in Example 1 except that 2.5 parts by weight of m-xylylene bis stearamide “Sripacs PXS (manufactured by Nippon Kasei Co., Ltd.)” was used as the saturated fatty acid bisamide. The surface protective film had a substrate layer thickness of 34 μm and an adhesive layer thickness of 6 μm. Moreover, the thickness of the release layer of the surface protective film was 30 nm.
(Comparative Example 1)
A surface protective film was obtained in the same manner as in Example 1 except that the saturated fatty acid bisamide was not used.

(Comparative Example 2)
A surface protective film was prepared in the same manner as in Example 1 except that the amount of ethylenebisstearic acid amide was changed to 0.5 parts by weight. An attempt was made to measure the thickness of the release layer, but the release agent layer could not be observed.

(Comparative Example 3)
A surface protective film was prepared in the same manner as in Example 1 except that the amount of ethylenebisstearic acid amide was changed to 5 parts by weight. The thickness of the release layer of the surface protective film was 200 nm.

(Comparative Example 4)
A surface protective film was prepared in the same manner as in Example 1 except that 3 parts by weight of stearic acid amide “Alflow S-10 (manufactured by NOF Corporation)” was used as the saturated fatty acid amide. A surface protective film was prepared. An attempt was made to measure the thickness of the release layer, but the release agent layer could not be observed.

(Comparative Example 5)
The same as Example 1 except that 3 parts by weight of oleic acid amide “Alflow E-10 (manufactured by NOF Corporation)” which is an unsaturated fatty acid amide was used instead of ethylene bisstearic acid amide which is a saturated fatty acid bisamide. The surface protection film was created by the method. An attempt was made to measure the thickness of the release layer, but the release agent layer could not be observed.

(Comparative Example 6)
The same as Example 1 except that 3 parts by weight of erucic acid amide “Alflow P-10 (manufactured by NOF Corporation)” which is an unsaturated fatty acid amide was used instead of ethylene bisstearic acid amide which is a saturated fatty acid bisamide. The surface protection film was created by the method. A surface protective film was prepared. An attempt was made to measure the thickness of the release layer, but the release agent layer could not be observed.

(Comparative Example 7)
Example 1 except that 3 parts by weight of ethylene bisoleic acid amide “Alflow AD-281 (manufactured by NOF Corporation)” which is an unsaturated fatty acid bisamide is used instead of ethylene bisstearic acid amide which is a saturated fatty acid bisamide. A surface protective film was prepared in the same manner. The thickness of the release layer of the surface protective film was 20 nm.

(Evaluation)
The following items were evaluated for the obtained surface protective films of Examples 1 to 7 and Comparative Examples 1 to 7.
The results are shown in Table 1.

(1) Unfolding force Each surface protective film was wound around a paper core having an inner diameter of 3 inches to create a 50 mm wide scroll. Based on JIS Z0237, the surface protection film was rewound from the roll at a rewinding speed of 20 m / min, and the high-speed rewinding force was measured. The measured value obtained is the deployment force.
Excellent when the deployment force is 2 N / 50 mm or less (◎), better than 2 N / 50 mm, good when it is 3.5 N / 50 mm or less (◯), poor when the deployment force exceeds 3.5 N / 50 mm ( X).
(Evaluation of stability of deployment force over time)
Moreover, after rolling the scroll whose evaluation of the unfolding force was excellent or good for one week in a constant temperature bath at 40 ° C., the unfolding force was measured, and the unfolding force was evaluated according to the same criteria. Note that Comparative Example 3 in which the initial adhesive strength was poor was not evaluated.

(2) Presence or absence of floating, initial adhesive strength and depth of penetration into the adhesive layer The prism is made of an acrylic resin with a thickness of 130 μm, and the prism pitch is 50 μm and the height is 25 μm. A test piece was prepared by attaching a surface protective film having a width of 25 mm so as to cover the lens surface of the sheet. The surface protective film was attached to the prism sheet at a rate of 300 mm / min using a 2 kg pressure-bonded rubber roller at a room temperature of 23 ° C. and a relative humidity of 50%. After leaving the test piece in that state for 30 minutes, the presence or absence of floating was evaluated. Those in which no floating occurred were evaluated as good (◯), and those in which floating occurred were evaluated as poor (×).

Subsequently, the initial adhesive force of the test piece in which no lifting occurred was measured. In accordance with JIS Z0237, the surface protective film was peeled off at a speed of 300 mm / min, and the 180-degree peel strength was measured. The direction in which the surface protective film was peeled was the ridge line direction of the prism. The obtained 180 degree peel strength is the initial adhesive strength.
Moreover, as a result of observing the depth at which the apex of the prism ridge line of the prism sheet penetrated into the adhesive with a scanning electron microscope (SEM), the depth of penetration into the adhesive was 0.6 μm.

  A case where the peel strength (initial adhesive strength) was 0.5 N / 25 mm or less was evaluated as good (◯), and a case where the peel strength exceeded 0.5 N / 25 mm was evaluated as defective (×).

(3) Adhesion over time A surface protective film having a width of 25 mm was attached so as to cover the lens surface of the prism sheet. A prism sheet made of acrylic resin having a thickness of 130 μm and a prism pitch of 50 μm and a height of 25 μm was used. A surface protective film was attached at a speed of 300 mm / min using a 2 kg pressure-bonded rubber roller in an environment of room temperature of 23 ° C. and relative humidity of 50%. After being left for 2 weeks in an environment of room temperature 23 ° C. and relative humidity 50%, the surface protective film was peeled off at a speed of 300 mm / min in accordance with JIS Z0237, and the 180 ° peel strength was measured. The direction in which the surface protective film was peeled was the ridge line direction of the prism. The 180 degree peel strength measured in this way was defined as the adhesive strength with time at 23 ° C.

  The case where the peel strength was 0.7 N / 25 mm or less was evaluated as good (◯), and the case where the peel strength exceeded 0.7 N / 25 mm was evaluated as defective (×).

[result]

(Example 8)
As a forming raw material A, a mixture of 100 parts by weight of polypropylene “Y900GV (manufactured by Prime Polymer)” and 3 parts by weight of ethylene bis stearic acid amide “Alflow H50F (manufactured by NOF Corporation)” which is a saturated fatty acid bisamide, and a forming raw material B As 100 parts by weight of a styrene elastomer “Dynalon 1320P (manufactured by JSR)”, 15 parts by weight of a tackifier “Alcon P100 (manufactured by Arakawa Chemical)” as a tackifier, and “Irganox 1010 as an antioxidant” (Ciba Specialty Chemicals Co., Ltd.) "A mixture consisting of 1 part by weight was coextruded by the T-die method under the following conditions to produce a surface protective film. The surface protective film had a thickness of 40 μm, a base material layer thickness of 34 μm, and an adhesive layer thickness of 6 μm.
Moreover, the thickness of the release layer of the surface protective film was 49 nm.
<Conditions>
Extrusion temperature: 200 ° C
Cast roll temperature: 25 ° C

Example 9
A surface protective film was obtained in the same manner as in Example 8, except that the amount of the tackifier “Alcon P100 (Arakawa Chemical Co., Ltd.)” was 20 parts by weight.
Moreover, the thickness of the release layer of the surface protective film was 50 nm.

(Example 10)
A surface protective film was obtained in the same manner as in Example 8 except that the amount of the tackifier “Alcon P100 (Arakawa Chemical Co., Ltd.)” was 25 parts by weight.
Moreover, the thickness of the release layer of the surface protective film was 48 nm.

(Example 11)
A surface protective film was obtained in the same manner as in Example 8, except that the amount of the tackifier “Alcon P100 (manufactured by Arakawa Chemical Co.)” was 30 parts by weight.
Moreover, the thickness of the release layer of the surface protective film was 53 nm.

(Example 12)
A surface protective film was obtained in the same manner as in Example 8, except that the amount of the tackifier “Alcon P100 (manufactured by Arakawa Chemical Co.)” was 35 parts by weight.
Moreover, the thickness of the release layer of the surface protective film was 55 nm.

(Example 13)
A surface protective film was obtained in the same manner as in Example 8 except that the amount of the tackifier “Alcon P100 (Arakawa Chemical Co., Ltd.)” was 40 parts by weight.
Moreover, the thickness of the release layer of the surface protective film was 48 nm.

(Example 14)
A surface protective film was obtained in the same manner as in Example 8, except that the amount of the tackifier “Alcon P100 (Arakawa Chemical Co., Ltd.)” was 45 parts by weight.
Moreover, the thickness of the release layer of the surface protective film was 52 nm.

(Comparative Example 8)
A surface protective film was obtained in the same manner as in Example 8 except that no saturated fatty acid bisamide was used.
(Comparative Example 9)
A surface protective film was obtained in the same manner as in Example 8 except that the saturated fatty acid bisamide was not used and the tackifier “Alcon P100 (Arakawa Chemical Co., Ltd.)” was changed to 30 parts by weight.

(Evaluation)
The following items were evaluated for the surface protective films of Examples 8 to 14 and Comparative Examples 8 to 9 obtained.
The results are shown in Table 2.

(1) Unfolding force Each surface protective film was wound around a paper core having an inner diameter of 3 inches to prepare a 50 mm wide scroll. Based on JIS Z0237, the surface protection film was rewound from the roll at a rewinding speed of 20 m / min, and the high-speed rewinding force was measured. The measured value obtained is the deployment force.
Excellent when the deployment force is 2 N / 50 mm or less (◎), better than 2 N / 50 mm, good when it is 3.5 N / 50 mm or less (◯), poor when the deployment force exceeds 3.5 N / 50 mm ( X).

(2) Initial adhesive strength Within 3 days after creating the surface protective film, it was affixed to cover the lens surface of the prism sheet. A prism sheet made of acrylic resin having a thickness of 130 μm and having a prism pitch of 50 μm and a height of 25 μm was prepared. Affixing conditions are a room temperature of 23 ° C. and a relative humidity of 50%, using a 2 kg pressure rubber roller, affixing at a speed of 300 mm / min, leaving in that state for 30 minutes, in accordance with JIS Z0237, The 180 degree peel strength at 25 mm width was measured at a speed of 300 mm / min. The peeling direction at this time was the ridge line direction of the prism. The peel strength measured in this way was used as the initial adhesive strength.

(3) Adhesive strength at 23 ° C pasting time Adhesive strength measured by the same method as the initial adhesive strength except that the surface protective film was left to stand for 1 week in a 23 ° C environment was defined as 23 ° C pasting adhesive strength at 23 ° C.
[result]

  As is apparent from Table 2, the surface protective film not using the saturated fatty acid bisamide has an appropriate adhesive force, but is inferior in the developing force despite the amount of the tackifier being suppressed. On the other hand, the surface protective film of the present invention using ethylene bis stearic acid amide which is a saturated fatty acid bisamide can obtain an appropriate developing force and an appropriate initial adhesive force.

(Example 15)
As a forming raw material A, a mixture of 100 parts by weight of polypropylene “Y900GV (manufactured by Prime Polymer)” and 3 parts by weight of ethylene bis stearic acid amide “Alflow H50F (manufactured by NOF Corporation)” which is a saturated fatty acid bisamide, and a forming raw material B As 100 parts by weight of a styrene elastomer “Dynalon 1320P (manufactured by JSR)”, 20 parts by weight of a tackifier “Alcon P100 (manufactured by Arakawa Chemical)” as a tackifier, and “Irganox 1010 as an antioxidant” (Ciba Specialty Chemicals Co., Ltd.) "A mixture of 1 part by weight was coextruded by the T-die method under the following conditions to prepare a surface protective film. The surface protective film had a thickness of 40 μm, a base material layer thickness of 34 μm, and an adhesive layer thickness of 6 μm.
Moreover, the thickness of the release layer of the surface protective film was 50 nm.

<Conditions>
Extrusion temperature: 200 ° C
Cast roll temperature: 25 ° C

(Comparative Example 10)
A surface protective film roll was obtained in the same manner as in Example 15 except that the saturated fatty acid bisamide was not used.

(Evaluation)
The following items were evaluated for each surface protective film obtained as described above. The results are shown in Table 3.

(1) Unfolding force A 50 mm-wide roll of each surface protective film of Examples and Comparative Examples was measured according to JIS Z0237, and a high-speed unwinding force was measured at a unwinding speed of 20 m / min.

  Excellent when the deployment force is 2 N / 50 mm or less (◎), better than 2 N / 50 mm, good when it is 3.5 N / 50 mm or less (◯), poor when the deployment force exceeds 3.5 N / 50 mm ( X).

(2) Adhesive strength (room temperature)
A surface protection film roll was prepared and then cured for one week in a constant temperature layer at 23 ° C., and then adhered to the lens surface of the prism sheet and the acrylic plate. Pasting conditions were as follows: JIS Z0237 was a product that was pasted at a speed of 300 mm / min using a 2 kg pressure rubber roller in an environment of room temperature 23 ° C. and relative humidity 50%, and then left in a 23 ° C. environment for 1 day. The 180 degree peel strength at 25 mm width was measured at a speed of 300 mm / min. Thus, the measured adhesive force was made into lens surface adhesive force (normal temperature) and flat surface adhesive force (normal temperature), respectively.

(3) Adhesive strength (40 ° C)
The adhesive strength measured by the same method as the adhesive strength (room temperature) except that the curing condition of the roll of the surface protective film was 40 ° C., respectively, the lens surface adhesive strength (40 ° C.) and the flat surface adhesive strength (40 ° C.). It was.

(4) Temperature stability The value obtained by dividing the adhesive strength (40 ° C.) of each lens surface and flat surface by the adhesive strength (room temperature) was taken as the adhesive strength reduction ratio. The case where the reduction ratio was 70% or more was evaluated as good stability (◯), and the case where it was less than 70% was evaluated as poor stability (x).

[result]

  As is clear from Table 3, the surface protective film not using saturated fatty acid bisamide is excellent in temperature stability of adhesive force but inferior in developing force. On the other hand, the surface protective film of the present invention using ethylene bis-stearic acid amide which is a saturated fatty acid bisamide, when applied to the lens surface of the prism sheet, has both the temperature stability of the adhesive force and the development force. Also excellent.

  The surface protective film of the present invention can be used for protecting the lens surface of a prism sheet.

Claims (8)

Molding raw material A containing saturated fatty acid bisamide and polyolefin resin, and molding raw material B containing styrene elastomer
Manufactured by co-extrusion,
(A) a release layer mainly composed of saturated fatty acid bisamide and having a thickness of 1 to 100 nm,
(B) A surface protective film for a prism sheet in which a polyolefin resin layer as a base material layer and (C) a styrene elastomer layer as an adhesive layer are laminated. The surface protection film for prism sheets of Claim 1 in which the said shaping | molding raw material A contains 1-4 weight part of saturated fatty acid bisamide with respect to 100 weight part of polyolefin resin. The surface protection film for prism sheets according to claim 1 or 2, wherein the saturated fatty acid bisamide is ethylene bis stearamide, methylene bis stearamide, or hexamethylene bis stearamide. The surface protective film for a prism sheet according to claim 1 or 2, wherein the saturated fatty acid bisamide is a saturated fatty acid aromatic bisamide. The surface protection film for prism sheets of any one of Claims 1-4 which has an intermediate | middle layer between the said base material layer and the said adhesive layer. The surface protective film for a prism sheet according to claim 5, wherein the intermediate layer is a mixture of a polyolefin-based resin and a styrene-based elastomer containing a saturated fatty acid bisamide. (A) a release layer having a thickness of 1 to 100 nm mainly composed of saturated fatty acid bisamide;
(B) a polyolefin resin layer to be a base material layer,
(C) A method for producing a surface protective film for a prism sheet in which a styrene elastomer layer to be an adhesive layer is laminated in this order,
A method for producing a surface protective film for a prism sheet, comprising coextruding a molding raw material A containing 1 to 4 parts by weight of a saturated fatty acid bisamide and a molding raw material B containing a styrene elastomer with respect to 100 parts by weight of a polyolefin resin. A prism sheet having a plurality of triangular prisms on the lens surface, and a release layer having a thickness of 1 to 100 nm mainly composed of (A) a saturated fatty acid bisamide, and (B) base Including a surface protective film for a prism sheet in which a polyolefin resin layer as a material layer, and (C) a styrene elastomer layer as an adhesive layer are laminated,
A prism sheet to which a surface protective film having a biting depth of 0.3 μm or more into the pressure-sensitive adhesive layer of the prism is attached.