JP3078374B2 - Drawing protection film and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface protection film which can be peelably adhered to a plate-like article such as a metal plate or a synthetic resin plate.

More specifically, the present invention relates to a protective film having a drawing property in which characters or designs can be written on a surface of a surface protective film bonded to a plate-like article with a pencil.

[0003]

2. Description of the Related Art Conventionally, in the case of plate-like articles such as metal plates, synthetic resin plates, glass plates, etc., in order to prevent dust from adhering to the surface of the articles or to prevent surface damage due to damage during the storage period before use, or A surface protection material is used for the purpose of preventing damage in a processing step such as bending or drawing after cutting these plate-like articles into a predetermined shape.

[0004] As surface protective materials, paper-based protective papers and film-based protective films are known. Protective paper is inexpensive and has the advantage that characters and designs can be written on its surface.However, once pasted together, the inner base material cannot be seen, so check for defects after bonding with the base material or There is a drawback that it is difficult to confirm the type of the object. Compared to this, the protective film based on film has transparency, so there is an advantage that the inner substrate can be seen well after pasting with the substrate, but characters and designs can not be written on the film with a pencil For this reason, when cutting into a certain shape, it must be cut with a guide, and the sample NO and the name could not be written.

[0005] On the other hand, as a known example of the drawing property of an olefin film, as shown in JP-A-53-31741, a small amount of a filler is added to an olefin resin and then stretched uniaxially or biaxially. Is known. However, a surface protective film having good drawing properties and transparency has not been known as an unstretched polyolefin film. This is because it was considered difficult to achieve these objects in view of the softness of the unstretched olefin resin and the opacity due to the addition of filler. In addition, it is desired that a drawing-protective film processed under heating has a small change in adhesive force depending on the processing temperature.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface protective film having a drawing property in which the above-mentioned drawbacks are eliminated without losing the function as the surface protective film.

[0007]

The problem to be solved by the present invention is solved by the following means (1) to (5).

(1) An unstretched laminated polyolefin film having an A layer on one surface and a B layer on the other surface and having a total light transmittance of 70% or more, wherein the A layer comprises an olefin resin and inorganic particles. Vickers hardness (H) and surface roughness (Ra) are 1.4 ≦ H ≦ 5.5 0.4 μ ≦ Ra ≦ 1.5 μ, and the B layer is composed of linear low-density polyethylene and An image-forming protective film comprising an adhesive layer having a surface roughness (Ra) of 0.03 μ ≦ Ra ≦ 0.18 μ, comprising a tackifier.

[2] The aspect ratio of the inorganic particles is 5 or less, the refractive index (D) and the average particle diameter (R) are 1.48 ≦ D ≦ 1.72 2 μ ≦ R ≦ 10 μ, and the addition amount is 2. The drawing-protective film according to the above item 1, wherein the content is 15 to 50% by weight.

[3] The drawable protective film according to [1] or [2], wherein the olefin resin having a polar group is mixed in the A layer at 2 to 15% by weight.

[4] The above 1 wherein the polystyrene resin and the polymethyl methacrylic resin are mixed in the A layer at 2 to 15% by weight.
4. The drawing-protective film according to any one of items 1 to 3.

[5] A resin obtained by mixing inorganic particles (A)
5. The method for producing a drawing-protective film according to any one of the above 1 to 4, wherein the layer (A) and the pressure-sensitive adhesive resin (B) are each melted, and then extruded on a cooling drum and cast. A method for producing a drawing-protective film, characterized in that the layer surface is on the drum side.

In the present invention, the olefin resin used for the layer A may be a simple substance of medium-density polyethylene, high-density polyethylene, poly (4-methylpentene-1), polypropylene, or low-density polyethylene, medium-density polyethylene,
It is a mixture of two or more kinds selected from high-density polyethylene, poly-4-methylpentene-1, polypropylene, polystyrene, and polymethylmethacrylic resin. These resins may be copolymerized with copolymerizable monomers as long as the basic properties are not impaired, or may be blended with various additives.

The Vickers hardness (H) of the layer A of the present invention is 1.4 ≦ H ≦ 5.5, preferably 1.7 ≦ H ≦ 5.0. If the Vickers hardness of the layer A is less than 1.4, the drawing property does not appear even if inorganic particles are blended. Also,
When the Vickers hardness exceeds 5.5, the layer A becomes too hard, so that the adhesiveness between the layer B and the base material is reduced due to the lowering of the adhesion between the base material and the synthetic resin plate or the metal plate. Occur.

The amount of the inorganic particles added to the layer A is 15
It is good to be 50% by weight, preferably 20-45% by weight. If the addition amount is less than 15% by weight, the expression of the drawing property is poor, and if it exceeds 50% by weight, the composite film-forming property with the B layer is deteriorated.

The aspect ratio of the inorganic particles blended in the layer A is preferably 5 or less, more preferably 3 or less, and the refractive index (D) is preferably 1.48 ≦ D ≦ 1.70, more preferably 1.50. ≦ D ≦ 1.65, average particle size (R) is preferably 2μ ≦ R ≦ 10μ, more preferably 2.0μ ≦
R ≦ 8μ. Addition of inorganic particles having an aspect ratio of more than 5 does not improve drawing performance, and the refractive index is 1.4.
When inorganic particles smaller than 8 or more than 1.70 are added, the transparency of the layer A deteriorates, so that it is difficult to check the defects in the lamination with the substrate and the defects after the lamination. The addition of inorganic particles having an average particle diameter of less than 2μ does not improve the drawability. When inorganic particles exceeding 10μ are added, the surface roughness of the surface of the layer B becomes too large, so that the adhesion to the base material is increased. Floating occurs when combined. This phenomenon is presumed to be due to the fact that the surface roughness of the layer A affects the surface roughness of the layer B.

In the present invention, the surface roughness Ra of the layer A to which the inorganic particles are added is 0.4 μ ≦ Ra ≦ 1.5 μ, preferably 0.45 μ ≦ Ra ≦ 1.4 μ. If the surface roughness of the A layer is smaller than 0.4 μ, the drawing property does not appear,
If it exceeds 1.5 μm, the surface roughness of the B layer becomes too large. The surface roughness Ra of the B layer is 0.03 μ ≦ Ra ≦
0.18 μ, preferably 0.04 ≦ Ra ≦ 0.16. It is practically difficult to reduce the surface roughness of the layer B to less than 0.03 μm, and if it exceeds 0.18 μm, floating occurs during bonding with the substrate.

That is, it is advantageous to make the layer A hard and increase its surface roughness in order to make the surface protective film exhibit drawing properties, but it is advantageous to make the layer A too hard or
If the surface roughness of the layer is made too large, defects such as the surface roughness of the layer B become too large, so that the function as a protective film is lost.

The inorganic particles added to the layer A of the present invention include calcium carbonate, magnesium hydroxide, dolomite, silica, clay and the like. These inorganic particles have a certain shape and a certain refractive index. These non-flat shapes favor drawing properties, and a constant refractive index favors transparency. However, even if these inorganic particles are used, the stretched film becomes opaque due to generation of voids. By forming an unstretched film using these inorganic particles, a surface protective film having drawing properties and transparency can be obtained.

The layer B, which is an adhesive layer, comprises a linear low-density polyethylene and a tackifier. As the linear low-density polyethylene, a linear low-density polyethylene having a density of 0.905 to 0.925 (g / cm ³ ) from the viewpoint of the adhesive effect and the surface contamination of the adherend is used. MI from the point of film properties
(Melt Index) 2 to 10 linear low-density polyethylenes are preferred.

Examples of the tackifier include rosin, modified rosin, terpene resin, cyclopentadiene resin, aliphatic and aromatic petroleum resin, coumarone indene resin, alkylphenol resin, and styrene resin.

The olefin resin having a desirable polar group when mixed in the layer A includes ethylene-acrylic acid copolymer resin, ethylene-methacrylic acid copolymer resin, ethylene-methyl acrylate copolymer resin, ethylene-methyl acrylate copolymer resin.・ Ethyl acrylate copolymer resin, ethylene / vinyl acetate copolymer resin,
And maleic acid-grafted polypropylene resin. The mixing amount of the olefin resin having a polar group is preferably 2 to 25% by weight, more preferably 5 to 20% by weight. Mixing these resins has the effect of making letters written on the layer A with a pencil more readable. This is considered to be a phenomenon that occurs because the glossiness of the surface of the layer A is further reduced. When the mixing amount of these resins is less than 2% by weight, the effect is small, and when the mixing amount exceeds 25%, there arises a problem of expression of drawing properties or floating in bonding with a substrate. Further, the layer A is preferably mixed with 2 to 15% by weight, preferably 5 to 12% by weight of polystyrene and polymethyl methacrylate resin. When these hard resins are appropriately dispersed in the surface layer, the drawing performance with a pencil is improved. However, if the mixing amount is less than 2%, the effect is small, and if the mixing amount is more than 15% by weight, floating occurs in bonding with the substrate.

The total light transmittance of the composite film of the present invention is 7
0% or more, preferably 75% or more. When the total light transmittance of the composite film is less than 70%, it is difficult to check for defects in the lamination with the substrate and to check for defects in the substrate.

As the composite co-extrusion method in the present invention, a known composite extrusion method can be adopted. In the composite extrusion, the film is a layer B surface cast. In the A-side layer cast, the surface roughness of the B layer is too large at the same time as the casting is unstable. Producing the drawing-protective film by the composite co-extrusion method can produce at a higher speed without concern about the organic solvent as compared with the method of coating using a solvent.

The total thickness and the composition ratio in the two-layer film of the A layer / B layer are not particularly limited, but the total thickness is in the range of 30 μm to 100 μm, and the total thickness is A / B. Is preferably in the range of 4/1 to 1/4.

Next, the method for producing the drawing-protective film of the present invention will be described, but the method is not limited to this. That is, the resin component of the pressure-sensitive adhesive layer and the resin component of the A layer, which are the B layer, are charged from separate inlets by a melt co-extrusion apparatus,
They are combined by a die or a short tube to form a composite fluid and extruded. By casting and winding so that the layer B surface of the molten film discharged from the die is in contact with the drum, a two-layer composite unstretched film of layer B and layer A can be obtained.

The drawable protective film of the present invention can be widely used as a protective film for various articles such as a synthetic resin plate or a metal plate, or for a protective film utilizing its aesthetic appearance.

[0028]

The effects of the present invention are listed below.

(1) The film obtained by the present invention has a pencil drawing property and can check the defects of the substrate even after being bonded to the substrate.

(2) Even if it is heat-processed after being bonded to the base material, it can be easily peeled off because the change in adhesive strength is small.

(3) Since the surface of the layer A is made uneven, there is no shininess and the appearance is excellent.

(4) Since it is manufactured by a co-extrusion method, it is safer and less expensive than a method using a solvent.

[0033]

[Characteristic measurement method and evaluation criteria]

(1) Vickers hardness Using a Shimadzu micro hardness tester type 2 manufactured by Shimadzu Corporation, J
It measured according to IS standard B7734.

(2) Refractive Index of Inorganic Particles Liquids having different refractive indices were placed in a test tube, inorganic particles were added thereto, and the mixture was shaken sufficiently to indicate the refractive index of the transparent liquid.

(3) Aspect Ratio of Inorganic Particles The ratio of the major axis / minor axis of ten particles was determined using a scanning electron microscope, and the average value was defined as the aspect ratio.

(4) Average particle diameter of inorganic particles The average particle diameter was measured by a centrifugal sedimentation method using CAPA5000 manufactured by HORIBA, Ltd.

(5) Surface Roughness (Ra) Ra was measured at a cutoff of 0.25 mm according to JIS B0601.

(6) Total light transmittance (Tt) Measured according to ASTM-D-1003-52.

(7) Floating A two-layer film of A layer / B layer was pressed with a small press roll at room temperature (linear pressure: 2 kg / 20 mm) so that the B layer surface and the resin plate were fitted. The adhesiveness (floating) between the film of the obtained laminate and the resin plate was visually determined. ○: No lifting between resin plate and film ×: White lifting due to lifting between resin plate and film

(8) Drawability Characters were written from the upper surface (A layer) of the film bonded to the resin plate with a free hand using an HB pencil, and the drawability was visually evaluated. ◎: Able to write letters on the surface of layer A and easy to read written letters ○: Able to write letters on the surface of layer A ×: A letter which cannot be written on the surface of layer A

(9) Defect Check A circle with a diameter of about 1 mm is painted in advance on a resin plate with yellow magic, and a film is pasted on the surface in the same manner as in (7). It was visually determined from above the film surface of the bonded plate to determine whether or not a defect check was possible. ○: Magic mark is visible visually ×: Magic mark is not visible visually

(10) Change in Adhesive Force During Heating A drawable protective film is adhered to each resin plate heated to room temperature (23 ° C.) and 70 ° C., and the adhesive force is increased by a 300 mm / min tensile speed. Measure. The adhesive force at room temperature (23 ° C.) is P ₁ , the adhesive force at 70 ° C. is P ₂ ,
It was determined by the value of P ₂ / P _1. ：: (P ₂ / P ₁ ) <5: Small change in adhesive force during heating and good peeling resistance. Δ: 5 ≦ (P ₂ / P ₁ ) ≦ 10 A change in the adhesive force during the heating process is moderate and the film can be peeled off. ×: (P ₂ / P ₁ )> 10: A change in adhesive force during heating is large, and peeling is difficult.

[0043]

Next, the present invention will be described with reference to examples.

Examples 1 to 6, Comparative Examples 1 to 8 Commercially available low density polyethylene (melt index: 2 g)
/ 10 min), high-density polyethylene (met index: 6 g / 10 min), polypropylene (melt index: 15 g / 10 min), and polystyrene (melt index: 7.5 g / 10 min).
These powdered resins were mixed with calcium carbonate, talc, mica, titanium oxide, and clay having various particle diameters in the proportions shown in Table 1, and pelletized with a biaxial pelletizer to obtain a layer A resin composition.

These resins are supplied from the 40 mmφ side of a composite extruder (40 mmφ, 30 mmφ) having a T die.
On the other hand, from the 30 mmφ extruder side, linear low density polyethylene (FZ202: Sumitomo Chemical Co., Ltd.) / Alcon P-100
(98/2). Extruder set temperature 200-2
20 ° C., cast and solidified so that layer B is in contact with a cooling drum having a surface temperature of 35 ° C., and solidified to 60 μm (layer A / B
A two-layer composite unstretched film having a layer thickness ratio of 2/1) was obtained.

The obtained composite film and a 1 mm-thick polycarbonate resin plate (hereinafter referred to as PC plate) are bonded together at room temperature using a small roll laminator (linear pressure: 2 kg / 20 cm). evaluated.

As can be seen from Table 2, Examples 1 to 6
The film was free from floating when bonded to the C plate, had drawing properties on the surface of the A layer, and was capable of checking for defects on the PC plate even after being bonded to the PC plate.

On the other hand, low density polyethylene (LDP)
Comparative Example 1 using E) and Comparative Examples 3 and 4 using talc and mica having a large aspect ratio as inorganic particles did not exhibit drawing properties. Polystyrene (PS) is A
Comparative Example 2, which was used for the layer, had a drawing property with a single-layer film, but could not be formed into a composite film with the layer B.

Comparative Example 5, in which titanium oxide was used as the inorganic particles, was opaque because it lacked drawability and could not be checked for defects.

Further, Comparative Example 6 in which the average particle diameter of calcium carbonate was 1.8 μm and Comparative Example 8 in which the addition amount of calcium carbonate was 10% by weight did not exhibit drawability, and the average particle diameter was 11 μm. Comparative Example 7 using calcium carbonate had drawing properties, but floating occurred during bonding with a PC board.

[0051]

[Table 1]

[0052]

[Table 2]

Example 7 and Comparative Example 9 The pelletizing raw material used in Example 1 was mixed with a composite extruder 4
Two-layer composite film formation was performed by supplying from the 0 mmφ side and supplying linear low density polyethylene (FZ202: Sumitomo Chemical Co., Ltd.) / Escolets 5320 (Exxon Chemical Co., Ltd.) = 97/4 from the 30 mmφ side. The casting surface of the film (the surface in contact with the cooling drum) was performed under the conditions shown in Table 3 to obtain a composite unstretched film having a thickness of 80 μm (A layer / B layer = １ ／). The obtained film was bonded to a 1 mm thick PMMA plate (polymethyl methacryl plate) in the same manner as in Examples 1 to 6, and evaluated.

Example 7 was a protective film which had good composite film-forming properties, did not float when bonded to a resin plate, had drawing properties, and could be checked for defects. By comparison,
Comparative Example 9 in which layer A was cast so as to be in contact with the cooling drum
In addition, the film formation was unstable, and floating occurred during lamination with the resin plate.

[0055]

[Table 3]

Examples 8 to 9 and Comparative Examples 10 to 11 The pelletizing raw material used in Example 1 was mixed with
It is supplied from the 0 mmφ side, and linear low density polyethylene (FZ202: Sumitomo Chemical Co., Ltd.), ethylene / vinyl acetate copolymer resin (Mitsui Polychemical Co., Ltd .: Evaflex P0803), Escolets 5320 (Exxon Chemical ( And a pelletized product obtained by mixing the same in Table 4 to obtain a two-layer composite unstretched film in the same manner as in Example 1.

The obtained composite film and a 1 mm thick PC board were compacted at room temperature and 70 ° C. (the PC board was sufficiently kept warm).
Evaluation was carried out by lamination using a lula luminator (linear pressure: 2 kg / 20 cm).

Examples 8 and 9 were good protective films which had a small P ₂ / P ₁ value and could be easily peeled off even when bonded at a high temperature. However, in Comparative Examples 10 to 11, P ₂ / P ₁
Since the value was large, a large peeling force was required, and the film was difficult to peel.

[0059]

[Table 4]

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoichi Matsuura 1-5 Sakuramachi, Takatsuki City, Osaka Prefecture Toray Gosei Film Co., Ltd. (56) References JP-A-6-71821 (JP, A) JP-A-6 −91829 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (5)

(57) [Claims] A first layer having an A layer and a second layer having a B layer;
An unstretched laminated polyolefin film having a total light transmittance of 70% or more, wherein the A layer is obtained by mixing inorganic particles with an olefin resin and has a Vickers hardness (H) and a surface roughness (R).
a) is 1.4 ≦ H ≦ 5.5 0.4 μ ≦ Ra ≦ 1.5 μ, the B layer is composed of a linear low-density polyethylene and a tackifier, and has a surface roughness (Ra) of 0. A drawing-protective film, characterized in that it is an adhesive layer satisfying 03 μ ≦ Ra ≦ 0.18 μ. 2. The inorganic particles have an aspect ratio of 5 or less, a refractive index (D) and an average particle size (R) of 1.48 ≦ D ≦ 1.702μ ≦ R ≦ 10μ, and an addition amount of 15 or less. 2. The drawing-protective film according to claim 1, wherein the content of the film is 50 to 50% by weight. 3. The drawing-protective film according to claim 1, wherein the layer A contains 2 to 25% by weight of an olefin resin having a polar group. 4. The drawing-protective film according to claim 1, wherein a polystyrene resin and / or a polymethyl methacrylic resin are mixed in the A layer in an amount of 2 to 15% by weight. 5. A resin obtained by mixing inorganic particles (layer A) and a pressure-sensitive resin (layer B) comprising a linear low-density polyethylene and a tackifier are respectively melted and then extruded on a cooling drum. A method for producing a drawing-protective film according to any one of claims 1 to 4, wherein the casting is performed by setting the B layer surface to the drum surface side.