JP2010131886A - Sheet with protection film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet with a protection film capable of using the protection film of low adhesive force on an irregular-shaped face of a resin material, by providing a flat area formed with no irregular shape on a face formed with an irregular shape of the resin material, and capable of preventing the protection film from being separated when cut or transported. <P>SOLUTION: This sheet with the protection film includes the resin material having areas formed with the irregular shape and the flat areas formed with no irregular shape, on at least one face, and the protection film having a pressure-sensitive adhesive face. In the sheet with the protection film, the areas formed with the irregular shape and the flat areas are alternately provided repeatedly with a fixed interval along a fixed direction, and the protection film is bonded over astride the areas formed with the irregular shape and the flat areas, while directing the pressure-sensitive adhesive face to a resin base material side. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sheet with a protective film comprising a sheet having a concavo-convex shape formed on at least one surface of a resin substrate and a protective film bonded to the surface of the sheet having the concavo-convex shape.

  Liquid crystal display devices are used in various applications such as notebook computers and mobile phone devices, televisions, monitors, car navigation systems, and the like. The liquid crystal display device incorporates a backlight device serving as a light source, and is configured to display light by controlling light beams from the backlight device through a liquid crystal cell. The characteristic required for this backlight device is not only as a light source for emitting light, but also to make the entire screen shine brightly and uniformly.

  In recent years, colorization of liquid crystal display devices such as color liquid crystal televisions has progressed, and it has become impossible to ensure sufficient luminance with the surface light source means used in conventional monochromatic liquid crystal display devices. Therefore, a brightness enhancement sheet is generally used between the various backlight devices and the liquid crystal cell. In many cases, the brightness enhancement sheet has a specification in which a concave-convex shape is provided on the surface of the sheet and light is collected to improve the front brightness. As one of the methods for providing a concavo-convex shape on a sheet surface, a press molding method is known in which the concavo-convex shape provided on the surface of a mold is transferred to the surface of a sheet-like substrate such as a thin film (Patent Document 1, Patent). Document 2), a sheet prepared by this method is referred to as an uneven shape transfer sheet in the present invention.

In addition, since the brightness enhancement sheet becomes a product defect if the uneven surface is soiled or scratched, it is common to prevent contamination and scratches by attaching a protective film to the uneven surface during assembly, various processing, and transportation. Has been used. Generally, a protective film consists of a base material layer and an adhesive layer, and the adhesive layer is required to be easily adhesive and easily peelable from the uneven surface.
JP 2005-199455 A JP-A-2005-310286

It is often necessary to attach a protective film to the uneven transfer sheet to prevent dirt and scratches. As a general method, use a nip roll that can be easily incorporated into production equipment. In many cases, the side is directed to the concavo-convex shape transfer sheet, and pressure is applied to the joining portion.

  The protective film on the concave-convex surface side of the concave-convex transfer sheet should be a protective film having a low adhesive strength so that it can be peeled with as light a force as possible so as not to damage the film when peeling the protective film during use. Done. However, this may cause a problem of peeling during cutting or transportation.

  On the other hand, a protective film (hereinafter, sometimes referred to as a “back surface protective film” to be distinguished from a protective film having a concavo-convex shape) may be bonded to a surface on which the concavo-convex shape is not transferred. In order to prevent the deformation | transformation which generate | occur | produces when peeling a back surface protective film from the surface which has not transferred uneven | corrugated shape, the adhesive force of the protective film is adjusted. However, when the same protective film is bonded to the concavo-convex shape surface, the adhesion area between the resin base material and the protective film is reduced, so that there is a problem that the adhesion force is weakened and the concavo-convex shape surface is not adhered.

  For this reason, it is common to use a protective film with a different adhesive force on the uneven surface and the surface on which the uneven shape has not been transferred. However, when the protective film is bonded to the uneven transfer sheet, the surface to be bonded is mistaken. There was a problem such as.

The present invention employs the following means in order to solve such problems. That is, at least a resin base material having a region in which an uneven shape is formed on one side and a flat region in which the uneven shape is not formed,
A protective film having an adhesive surface, and a sheet with a protective film comprising:
The region where the uneven shape is formed and the flat region are alternately and repeatedly provided at a constant interval in one direction,
This protective film is a sheet | seat with a protective film bonded across the area | region in which this uneven | corrugated shape was formed, and this flat area | region, making this adhesive surface the said resin base material side.

  According to the present invention, the surface of the resin substrate on which the concavo-convex shape is formed (hereinafter referred to as the concavo-convex shape surface) is adhered to the concavo-convex shape surface of the resin base material by providing a flat region on which the concavo-convex shape is not formed. A protective film with a low strength can be used, and a sheet with a protective film that does not peel off during cutting or transportation can be provided.

  The present invention is a sheet with a protective film comprising a resin base material having a region in which an uneven shape is formed on at least one surface and a flat region in which the uneven shape is not formed, and a protective film having an adhesive surface, The region where the uneven shape is formed and the flat region are alternately and repeatedly provided at a certain interval in one direction, and the protective film has the uneven surface with the adhesive surface facing the resin substrate. It is a sheet | seat with a protective film currently bonded across the area | region in which the shape was formed, and this flat area | region.

  Hereinafter, the sheet | seat with a protective film of this invention, the protective film concerning this invention, and the sheet | seat in which the uneven | corrugated shape was formed are demonstrated in detail. In the following description, a concavo-convex shape transfer sheet having a concavo-convex shape formed on the surface of a resin base material by transfer molding will be described as an example. However, the present invention is limited to a sheet having a concavo-convex shape formed by transfer molding. In short, the same effect can be obtained if the sheet has a concavo-convex shape formed on the surface of the resin substrate.

  The sheet with a protective film of the present invention has a protective film on the concave / convex shape transfer surface of a resin base material (hereinafter referred to as a concave / convex shape transfer sheet) to which the concave / convex shape is transferred, and the adhesive layer surface of the protective film has the concave / convex shape transfer sheet side. Paste with a pressing device to face. At that time, the back surface protective film may be bonded simultaneously or separately with a pressing device such that the back surface protective film faces the surface of the uneven shape transfer sheet and the back surface protective film faces the uneven shape transfer sheet side. As the back surface protective film, the same protective film as that of the concavo-convex shape transfer surface is used. Here, the “concavo-convex shape” in the present invention refers to a shape in which the distance from the top of the convex portion to the bottom of the concave portion is in the range of 1 μm to 200 μm. When the distance is smaller than 1 μm, sufficient luminance condensing ability cannot be obtained when the uneven shape transfer sheet is incorporated in the backlight. On the other hand, if the distance is larger than 200 μm, when the sheet is incorporated in the backlight, the shadow of the top of the convex portion or the bottom of the concave portion is reflected on the liquid crystal cell, and the screen cannot be illuminated uniformly. In addition, there are no particular restrictions on the pitch of the “concave shape” (distance between adjacent convex vertices of the concavo-convex shape) or the period, so that the ability to collect the luminance when the concavo-convex shape transfer sheet is incorporated in the backlight is obtained. Therefore, the pitch is substantially 400 μm or less. Moreover, the uneven | corrugated shape preferably uses the line shape which aligned in the longitudinal direction of the sheet | seat at the point that it can produce easily.

  In the present invention, the concavo-convex shape transfer sheet has a flat region on the concavo-convex shape surface on which the `` concavo-convex shape '' referred to in the present invention is not transferred, and the regions where the concavo-convex shape is formed and the flat regions are alternately arranged in one direction. It is necessary to exist repeatedly with a certain period. Usually, the longitudinal direction of the concavo-convex shape transfer sheet is set as a repeating direction. FIG. 1 is a view of the concavo-convex shape transfer sheet as viewed from the concavo-convex surface side. Here, the “flat region” in the present invention refers to a surface having a surface roughness level of a resin base that is usually used in an optical sheet. Specifically, the center line surface roughness Ra is 0.5 μm or less. Surface. The centerline surface roughness Ra here is a value measured based on JIS B0601 (1994). The “flat region” means a resin substrate surface that has been processed to be flat as well as a resin substrate surface that has not been subjected to processing such as concavo-convex transfer as long as the above surface roughness is satisfied. Is also included.

  In the sheet with a protective film of the present invention, the protective film is bonded to the uneven surface of the uneven transfer sheet, but separate protective films are bonded to the region where the uneven shape is formed and the flat region. Instead, one protective film is bonded so as to straddle the region where the irregular shape is formed and the flat region. Therefore, even a protective film having a weak adhesion force that cannot be brought into intimate contact with the uneven surface can be bonded due to the presence of the flat region. In that case, the repetition direction period of the flat region is preferably 200 mm to 1200 mm. If the period is longer than 1200 mm, the ratio of the contact area of the protective film to the uneven surface of the uneven transfer sheet may decrease, and the contact surface may not adhere to the uneven surface. When the period for providing the flat region is shorter than 200 mm, the efficiency is deteriorated when cutting in a subsequent process.

  The length of the flat region in the repeating direction is preferably 10 mm or more. If the area is smaller than 10 mm, the contact area of the protective film is reduced, and may not adhere to the uneven surface. The length of the flat region in the repeating direction is not particularly limited as long as it is 10 mm or more. However, since the flat region is a region that cannot be used as a concavo-convex shape transfer sheet, it is preferable to make the region as small as possible. Moreover, it is preferable that the repeating direction length of the flat region is 1/5 or less of the repeating direction period of the flat region. There is no particular problem if the length of the flat region in the repeat direction is greater than 1/5 of the cycle in the repeat direction of the flat region, but the flat region is a region that cannot be used as a concavo-convex shape transfer sheet, and is therefore as small as possible. It is preferable to make it an area.

  The protective film according to the present invention preferably has a pressure-sensitive adhesive surface in the range of 0.001 to 0.5 N / 25 mm for the adhesion to the flat region of the resin base material, 0.001 to 0.01 N / A range of 25 mm is more preferable. If the adhesive strength is less than 0.001 N / 25 mm, it will be easier to peel off the optical sheet in various post-processes. In addition, when the adhesive strength is greater than 0.5 N / 25 mm, problems such as deformation of the concavo-convex shape transfer sheet are likely to occur when the protective film is peeled from the concavo-convex shape transfer sheet.

  Conventionally known devices and methods can be used as the pressing device and pressing method for bonding the protective film and the concavo-convex shape transfer sheet, but a nip roll that can be easily incorporated into a production device is used to join the protective film and the concavo-convex shape transfer sheet. A method of applying the pressure together is preferably used. The pressure of the nip roll is not particularly limited, but is preferably 10 to 50 N / cm. When the nip roll pressure is larger than 50 N / cm, there may be a problem that the concavo-convex shape transfer sheet is deformed when the protective film is peeled from the concavo-convex shape transfer sheet. On the other hand, if it is less than 10 N / cm, it is easy to peel off from the concavo-convex shape transfer sheet in each subsequent step. The material of the nip roll is not particularly defined, but silicon rubber or the like is preferably used in consideration of scratches on the protective film and the uneven shape transfer sheet and use at high temperatures.

  The protective film according to the present invention is a film characterized in that a special adhesive process is applied to a thermoplastic film and has heat resistance, adhesiveness, and removability. Films used as foil stamping, protection during coating and as a support can be used.

  Although a general plastic film can be used for the base material layer of a protective film, it is preferable that the plastic film which has high transparency is used so that an external appearance test | inspection can be performed with an adhesive film affixed. For example, a polyester film, a polypropylene film, a polyethylene film, a polycarbonate film, a polystyrene film, a triacetate film, etc. can be mentioned. Of these, polyester films, polypropylene films, and polyethylene films that are excellent in productivity and processability can be preferably used.

  The thickness of the plastic film is preferably 5 to 200 μm, particularly preferably 10 to 60 μm. If the thickness is less than 5 μm, the film strength is insufficient, sufficient protection performance cannot be obtained, and problems such as breakage of the protective film during peeling tend to occur. On the other hand, when the thickness is larger than 200 μm, the transparency of the film is deteriorated or the protective film itself tends to be expensive.

  The pressure-sensitive adhesive used for the protective film pressure-sensitive adhesive layer is not particularly defined, but is preferably a rubbery polymer or copolymer of a diene monomer such as an acrylic copolymer, isoprene, isobutylene, or butadiene, silicone rubber, natural rubber, or the like. used. These adhesives preferably have a glass transition point of -20 ° C or lower. Although there is no restriction | limiting in particular about the minimum of the glass transition point of an adhesive, Generally it is -80 degreeC from manufacturing possibility.

  Although the thickness of the adhesive layer of the protective film in the present invention is not particularly defined, it is preferably thinner than the height of the concavo-convex shape of the concavo-convex shape transfer sheet to be bonded. If the thickness of the pressure-sensitive adhesive layer is larger than the height of the concavo-convex shape, the pressure-sensitive adhesive layer is easily filled into the concavo-convex shape recess, and the nip roll stop mark tends to remain.

  The resin base material in the present invention may be a thin plate-like material mainly composed of a thermoplastic resin, and is a single layer body formed of a thermoplastic resin for molding (hereinafter referred to as a thermoplastic resin for molding) to be described later, one side of the support. A two-layer laminate in which a thermoplastic resin for molding is laminated on, a three-layer laminate in which a thermoplastic resin for molding is laminated on one surface of the support and a resin different from the thermoplastic resin for molding on the other surface, and a support There are three-layer laminates in which molding thermoplastic resins are laminated on both sides. A monolayer is preferable from the viewpoint of excellent handling on the film. In addition, a single layer body made of a molded thermoplastic resin, a layer made of a thermoplastic resin for molding on the molding surface of a two-layer laminate or a three-layer laminate, has a molding thermoplastic as long as the effect of the present invention is not impaired. Components other than the resin may be included. The thickness of the resin substrate is preferably in the range of 0.01 to 3 mm, more preferably in the range of 0.01 to 1 mm. If it is less than 0.01 mm, the thickness may not be sufficient for molding, and if it exceeds 3 mm, it may be difficult to convey due to the rigidity of the substrate.

  The thermoplastic resin for molding according to the present invention is a thermoplastic resin having a glass transition temperature Tg of preferably 40 to 180 ° C, more preferably 50 to 160 ° C, and most preferably 50 to 120 ° C. When the glass transition temperature Tg is less than 40 ° C., the heat resistance of the molded product is lowered and the shape may change with time. In addition, if the temperature exceeds 180 ° C., the molding temperature must be increased, resulting in inefficiency in energy, and the volume fluctuation during heating / cooling of the film increases, so that the film can be bitten into the mold and released. Even if it disappears or can be released from the mold, the transfer accuracy of the pattern may be lowered, or the pattern may be partially lost, which may be a defect. The thermoplastic resin for molding is preferably a polyester resin such as polyethylene terephthalate, polyethylene-2, 6-naphthalate, polypropylene terephthalate or polybutylene terephthalate, or a polyolefin resin such as polyethylene, polystyrene, polypropylene, polyisobutylene, polybutene or polymethylpentene. From thermoplastic resins such as resins, polyamide resins, polyimide resins, polyether resins, polyesteramide resins, polyetherester resins, acrylic resins, polyurethane resins, polycarbonate resins, or polyvinyl chloride resins It will be. Among these, there are various types of monomers to be copolymerized, and it is easy to adjust the physical properties of the materials, so that polyester resins, polyolefin resins, polyamide resins, acrylic resins or these are particularly preferable. It is preferable that it is mainly formed from a thermoplastic resin selected from the above mixture, and it is more preferable that the above-mentioned thermoplastic resin is composed of 50% by weight or more.

Below, the measuring method and evaluation method of each Example and a comparative example are demonstrated.
(Measurement and evaluation method)
A. Adhesion confirmation In order to confirm the adhesion force between the concavo-convex shape surface of the concavo-convex shape transfer sheet and the protective film, the protective film and the concavo-convex shape transfer sheet are manufactured by MC Co., Ltd., using a laminator MRK-600 type. The adhesive layer surface of the protective film and the concavo-convex shape surface of the concavo-convex shape transfer sheet were faced to each other for bonding. Lamination conditions are as follows.
・ Pressing pressure: 3.3 to 4.8 kg / cm ²
・ Conveying speed: 500mm / min
・ Pressing temperature: Normal temperature (no temperature rise)
The laminated product thus bonded was cut out to a width of 520 mm and a length of 2000 mm, placed on a desk with the protective film side facing the ground, and the concavo-convex shape transfer sheet was held and lifted to confirm the adhesion of the protective film.

B. Adhesive strength with resin base material A resin base material before forming an uneven shape was prepared. The protective film and the resin base material were bonded so that the adhesive layer side of the protective film faced the resin base material side in the laminating apparatus and the laminating conditions described above.
Cut the laminated body into a strip with a width of 25 mm and a length of 120 mm, affix the resin substrate part of the laminated body to a smooth acrylic board with a thickness of 2 mm with double-sided tape, and use the acrylic board as the upper chuck. The sample was fixed and hung on a load cell of a Tensilon tensile tester (UTMIII manufactured by Toyo Sokki Co., Ltd.). Next, with the protective film portion of the laminated body fixed to the lower chuck, it is pulled downward (180 °) at a crosshead speed of 300 mm / min, and the maximum adhesion (N / 25 mm) between the resin substrate and the protective film is measured. did. Measurement was performed three times on one sample, and the average value of the obtained values was evaluated.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, this invention is not necessarily limited to these.

(Uneven shape transfer sheet)
First, a concavo-convex shape transfer sheet was prepared by the methods described in (1) to (8) below based on the apparatus and method described in International Publication No. 2008-047540.
(1) Mold size: 450 mm (film width direction) × 760 mm (film running direction) × 20 mm (thickness).
(2) Mold material: copper.
(3) Concave and convex shape: a pitch of 10 μm, a convex part width of 10 μm, a distance from the top of the convex part to the bottom of the concave part was 5 μm, and the cross section when viewed from the film running direction was triangular.
(4) Press device: It can pressurize up to 3000 kN, and pressurization is performed by a hydraulic pump. Two temperature control plates made of an aluminum alloy and having a size of 700 mm (film width direction) × 1000 mm (film running direction) are attached in the upper and lower sides in the press device, and are connected to a heating device and a cooling device, respectively. The mold is attached to the lower temperature control plate. The heating device is a heat medium circulation device, and the heat medium is Barrel Therm # 400 (manufactured by Matsumura Oil Co., Ltd.), which is heated to 150 ° C. and flows at a flow rate of 100 L / min. Moreover, a cooling device is a cooling water circulation device, and flows the water cooled at 20 degreeC with the flow volume of 150 L / min.
(5) Intermediate substrate: Between the upper temperature control plate and the substrate (PET film), the thickness is 0.2 mm, and the surface is coated with diamond-like carbon, so that the static friction coefficient with the PET film is 0.20. A silicone rubber sheet (thermal conductivity: 0.2 W / m · K) is pasted.
(6) Mold release apparatus: An apparatus having a mechanism that includes a peeling roll and an auxiliary roll and peels the film from the mold while rotating the peeling roll on the upper part of the film pressed against the mold.
(7) Resin base material: made of polyethylene terephthalate (Toray Lumirror (registered trademark) T60), having a thickness of 100 μm (thickness variation: ± 10 μm), a width of 520 mm, and a centerline surface roughness Ra of 0.037 μm . The film is fed out and wound up by an unwinding / winding device installed opposite to the pressing device.
(8) Operation method: Using the above-mentioned apparatus, molding was performed intermittently as follows. In advance, the film is passed from the unwinding device to the winding device via a press device. Next, after the temperature control plate is heated to 110 ° C. both in the upper and lower directions, the upper plate is lowered and the film pressing is started. The press was performed at 5 MPa on the mold surface for 30 seconds. Thereafter, the temperature control plate is cooled both top and bottom while the press is continued. Cooling is stopped when each temperature control plate reaches 60 ° C. When the cooling is completed for both the upper and lower sides, the press is released. The upper plate is raised to the upper limit and the release device is driven to release the film from the mold.
(9) The following uneven | corrugated shaped transfer sheet was created by said operation | movement.
Uneven shape transfer sheet 1: The distance from the top of the uneven convex portion to the bottom of the concave portion is 5 μm. It has a flat region where the uneven shape has not been transferred, the flat region has a repetition direction length of 10 mm, and the flat region has a repetition direction period of 770 mm.
Convex / concave transfer sheet 2: The distance from the apex of the concave / convex convex portion to the bottom of the concave portion is 5 μm. There is no flat area where the uneven shape is not transferred.

(Protective film)
As protective films, protective film 1: “Toretec” # 100 7721 manufactured by Toray Film Processing Co., Ltd. and protective film 2: Hitachilex (registered trademark) L-7320 manufactured by Hitachi Chemical Co., Ltd. were prepared.

Example 1
The protective film 1 is laminated with a laminator (manufactured by MC Co., Ltd., laminating device MRK-600 type) so that the adhesive surface faces the uneven surface of the uneven transfer sheet 1. A shape transfer sheet was prepared. The evaluation results are shown in Table 1.
This concavo-convex shape transfer sheet with a protective film adhered to the concavo-convex shape surface, and it was confirmed that the concavo-convex shape transfer sheet was not deformed even when peeled from the concavo-convex shape surface.

(Example 2)
In Example 1, a fine shape transfer sheet with a protective film was prepared in the same manner as in Example 1 except that the protective film 2 was used instead of the protective film 1. The evaluation results are shown in Table 1.
This concavo-convex shape transfer sheet with a protective film adhered to the concavo-convex shape surface, and it was confirmed that the concavo-convex shape transfer sheet was not deformed even when peeled from the concavo-convex shape surface.

(Comparative Example 1)
In Example 1, an uneven shape transfer sheet with a protective film was prepared in the same manner as in Example 1 except that the uneven shape transfer sheet 2 was used instead of the uneven shape transfer sheet 1. The evaluation results are shown in Table 1.
Since this uneven | corrugated shaped transfer sheet | seat with a protective film did not have the flat area | region where the uneven | corrugated shape was not transferred in the uneven | corrugated shaped surface, it was not able to contact | adhere to the uneven | corrugated shaped surface.

(Comparative Example 2)
In Example 1, an uneven shape transfer sheet with a protective film was prepared in the same manner as in Example 1 except that the uneven shape transfer sheet 2 was used instead of the uneven shape transfer sheet 1 and the protective film 2 was used instead of the protective film 1. did. The evaluation results are shown in Table 1.
Since this uneven | corrugated shaped transfer sheet | seat with a protective film did not have the flat area | region which the uneven | corrugated shape was not transferred in the uneven | corrugated shaped transfer surface, it was not able to contact | adhere to the uneven | corrugated shaped surface.

  According to the present invention, by providing a flat region in which a concavo-convex shape is not formed on a surface on which a concavo-convex shape of a resin base material is formed (hereinafter referred to as a concavo-convex shape surface), adhesive force is applied to the concavo-convex shape surface of the resin base material. A low protective film can be used, and a sheet with a protective film can be provided in which the protective film does not peel off during cutting or transportation.

It is the schematic which looked at the sheet | seat in which the uneven | corrugated shape in this invention was formed from the uneven | corrugated shaped surface side. It is sectional drawing of the state by which the uneven | corrugated shaped transfer sheet and the protective film are bonded together.

Explanation of symbols

1: Sheet with concavo-convex shape 2: Area with concavo-convex shape 3: Flat area without concavo-convex shape 4: Ear 5: Repeat cycle 6: Repeat direction 20: Convex-concave shape transfer sheet and protective film Schematic diagram 21 in the state of bonding: protective film substrate layer 22: protective film adhesive layer 23: concavo-convex shape transfer sheet 24: concavo-convex shape transfer sheet and air layer between adhesive layers

Claims (4)

A resin base material having a region in which an uneven shape is formed on at least one surface and a flat region in which the uneven shape is not formed,
A protective film having an adhesive surface, and a sheet with a protective film comprising:
The region where the uneven shape is formed and the flat region are alternately and repeatedly provided at a constant interval in one direction,
The protective film is a sheet with a protective film, which is bonded across the region where the uneven shape is formed and the flat region, with the adhesive surface facing the resin base.   The sheet | seat with a protective film of Claim 1 whose repetition direction length of the said flat area | region is 10 mm or more and 1/5 or less of this repetition direction period of this flat area | region.   The sheet | seat with a protective film of Claim 1 or 2 whose repetition direction period of the said flat area | region is 200 mm-1200 mm.   The sheet | seat with a protective film in any one of Claims 1-3 in which the said protective film has the adhesive surface of 0.001-0.5N / 25mm of adhesive force with the said flat area | region of the said resin base material. .

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