JP2014208734A - Surface protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface protective film which exhibits appropriate adhesion strength to an adherend and prevents blistering or peeling from an adherend even when the protective film is transported, stored or processed at a high temperature.SOLUTION: The surface protective film has an adhesive layer formed of an olefin copolymer (A) and a styrene elastomer (B). The olefin copolymer is a copolymer of propylene and at least one olefin selected from olefins having 4 to 20 carbon atoms, and shows a peak temperature of 5°C or higher for a tan δ value (loss tangent) in the measurement of dynamic viscoelasticity at 10 Hz.

Description

  The present invention relates to a surface protective film used for optical products, building materials, automobile parts, semiconductor wafers and the like. Specifically, the present invention relates to a surface protective film that exhibits an appropriate adhesive strength with respect to an adherend and does not float or peel from the adherend even when transported, stored or processed at high temperatures.

  The surface protective film is used by being attached to an adherend such as a resin product, a metal product, a glass product, a semiconductor wafer, etc. for optical use or building materials, and is damaged or damaged during transportation, storage or processing, or It plays the role of a support or the like in the next step while preventing foreign matters from being mixed in or with the surface protective film adhered. These surface protective films generally comprise a non-adhesive surface layer and an adhesive layer for adhering to the adherend. The surface layer is usually formed from a polyolefin such as polyethylene or polypropylene, a polyester such as polyethylene terephthalate, or a vinyl polymer such as polyvinyl chloride.

The properties required for the surface protective film are not only that the adhesive layer shows an appropriate adhesive strength to the adherend, and that the adhesive layer does not remain on the adherend when it is peeled off. It is required that there is no lifting or peeling. In particular, when the surface protective film attached to the adherend is placed under a high temperature condition before the surface protective film is peeled off, an even higher level is required.

  In recent years, a transition from a cathode ray tube display to a flat panel display such as a liquid crystal display or a plasma display and a portable information terminal represented by a multifunctional mobile phone, a so-called smart phone, have been popularized. In recent years, with the increase in functionality and performance of members used in these, the number of members having a large uneven surface shape or surface treatment has increased, and the contact area of the surface protective film with the adhesive layer is inevitable. Therefore, the surface protective film is partially deformed. In such a state, when it is placed under high temperature during transportation, storage or processing, the deformed part tries to recover to its original state, so the surface protective film may float or peel off from the adherend. .

Conventionally, the surface protective film generally used is a natural rubber in which an appropriate amount of a tackifier or the like is blended with natural rubber or modified natural rubber on a polyolefin such as polyethylene or polypropylene, or a polyester such as polyethylene terephthalate. There are some adhesives such as acrylic adhesives that are three-dimensionally cross-linked with isocyanate compounds or methylol compounds and acrylic rubbers or synthetic rubber adhesives such as polyisobutylene.
These adhesive-coated surface protective films have a relatively high degree of freedom in adjusting the adhesive strength of the adhesive layer, and it is possible to create an adhesive layer that does not float or peel off. There is a risk that the contamination of the body will deteriorate.

JP 2012-131978 A discloses a surface protective film obtained by coextrusion molding, wherein a resin composition comprising a composition of a styrene elastomer, a tackifier resin and a polyolefin resin is used as an adhesive layer. A surface protective film is disclosed. However, the method according to the publication shows moderate adhesive strength when applied at room temperature, but there is a risk that floating or peeling will occur at a high temperature particularly in a member having a large uneven surface shape or surface treatment. There is.

JP 2012-131978 A

The present invention is used for optical products, building materials, automobile parts, semiconductor wafers, etc., and exhibits an appropriate adhesive strength to the adherend, even when transported, stored or processed at high temperatures. The present invention relates to a surface protective film that does not float or peel off and does not contaminate the adherend. Specifically, as adherends (members) have increased in functionality and performance in recent years, they have an appropriate adhesive strength for adherend surfaces that have a large uneven surface shape or surface treatment. In addition, when exposed to high temperatures during transportation, storage, and processing, surface protection that prevents the adhesive layer from being lifted or peeled off by applying stress relaxation to the deformation recovery of the adhesive layer deformed by application To provide a film.

  As a result of intensive studies in view of the above problems, the present inventors have found that the above problems can be solved by a surface protective film having an adhesive layer made of a specific resin composition, and have completed the present invention.

That is, the present invention is a copolymer of propylene and at least one olefin selected from 4 to 20 carbon atoms, and the peak temperature of tan δ value (loss tangent) in dynamic viscoelasticity measurement at 10 Hz is 5 ° C. or higher. It is related with the surface protection film which has an adhesion layer which consists of 3-100 weight% of olefin-type copolymers (A) which are and styrene-type elastomer (B) 0-97 weight%.

  The surface protective film of the present invention is not particularly lifted or peeled off from the adherend even when transported, stored or processed at high temperatures, not only for optical applications, but also for building materials, automotive parts, As a protective film for semiconductor wafer processing applications, the industrial utility value is extremely high.

The surface protective film of the present invention comprises at least one base layer in consideration of rigidity, dimensional stability, handleability and the like, and is composed of at least two layers.
The adhesive layer of the surface protective film of the present invention is a copolymer of propylene and at least one olefin selected from 4 to 20 carbon atoms, and has a tan δ value (loss tangent) in dynamic viscoelasticity measurement at 10 Hz. It consists of an olefin copolymer (A) having a peak temperature of 5 ° C. or higher and a styrene elastomer (B).

  Tan δ in the measurement of dynamic viscoelasticity at 10 Hz of the olefin copolymer (A), which is a copolymer of propylene and at least one olefin selected from 4 to 20 carbon atoms, which forms the adhesive layer of the present invention. The peak temperature of the value (loss tangent) is 5 ° C. or higher. When the peak temperature of the tan δ value (loss tangent) is less than 5 ° C., there is a risk of floating or peeling from the adherend when transported, stored or processed at a high temperature. Specific examples of the olefin having 4 to 20 carbon atoms forming the olefin copolymer (A) include 1-butene, 4-methylpentene-1, 1-hexene, 1-decene, 1-dodecene and the like. Can do. Examples of the olefin copolymer (A) include propylene / 4-methylpentene-1 copolymer, propylene / 1-butene / 4-methylpentene-1 copolymer, and propylene / 4-methylpentene-1 / 1. -Dodecene copolymer, propylene / 1-hexene copolymer, propylene / 1-butene / 1-hexene copolymer and the like. Preferred are propylene / 4-methylpentene-1 copolymer and propylene / 1-butene / 4-methylpentene-1 copolymer. The melt flow rate (MFR) measured at 230 ° C. of the olefin copolymer (A) is in the range of 0.1 to 100 g / 10 minutes, preferably 0.5 to 50 g / 10 minutes. The molecular weight distribution (Mw / Mn) measured by gel permeation chromatography is in the range of 1.5 to 4.0, preferably in the range of 1.8 to 3.0.

Generally, the peak temperature of tan δ (loss tangent) in dynamic viscoelasticity measurement at 10 Hz of a styrene elastomer (B) exhibiting adhesiveness is less than 5 ° C. When transported, stored, or processed by using this method, there is a risk of floating or peeling from the adherend.
As the styrene elastomer (B), a known styrene elastomer having a polystyrene phase as a hard segment can be used. Specifically, styrene / butadiene copolymer (SBR), styrene / isoprene / styrene copolymer (SIS), styrene / butadiene / styrene copolymer (SBS), styrene / ethylene / butadiene / styrene copolymer ( SEBS) and hydrides thereof, styrene / isobutylene / styrene triblock copolymer (SIBS), and styrene / isobutylene diblock copolymer (SIB). Preferably, a styrene / isobutylene / styrene triblock copolymer (SIBS), a styrene / isobutylene diblock copolymer (SIB), or a styrene / isobutylene / styrene triblock copolymer (SIBS) and a styrene / isobutylene diblock copolymer It is a blend of polymer (SIB).

The melt flow rate (MFR) measured at 230 ° C. of the styrene elastomer (B) is in the range of 0.1 to 100 g / 10 minutes, preferably 0.5 to 50 g / 10 minutes.
The pressure-sensitive adhesive layer of the surface protective film of the present invention is formed from the olefin copolymer (A) and the styrene elastomer (B). The content of the olefin copolymer (A) is 3 to 100% by weight, preferably 20 to 85% by weight, more preferably 40 to 65% by weight, and the content of the styrene elastomer (B) is 0. It is -97 weight%, Preferably it is 15-80 weight%, More preferably, it is 35-60 weight%. (The total of the olefin copolymer (A) and the styrene elastomer (B) is 100% by weight)

Furthermore, for the purpose of controlling the adhesive strength of the adhesive layer, a polyolefin modifier such as polyethylene or polypropylene, a resin modifier such as an acid-modified polyolefin, polyester or polyamide, or a petroleum resin, as long as the characteristics of the present invention are not impaired. Various additives such as tackifiers such as hydrogenated petroleum resins, styrene resins, chroman and indene resins, rosin derivatives, terpene resins, antistatic agents, crystal nucleating agents, and antioxidants may be added. .

The surface protective film of the present invention can be provided with a base material layer in consideration of rigidity, dimensional stability, handleability, and the like on the adhesive layer. As a base material layer, well-known polyolefin resin, such as a polypropylene and polyethylene, can be mentioned. Examples of polypropylene include homopolypropylene, random polypropylene, block polypropylene, and polyethylene. High pressure method low density polyethylene, linear low density polyethylene, and high density polyethylene can be exemplified. Among these, a resin mainly composed of polypropylene which has high rigidity and does not generate fish eyes (crosslinked gel) is preferably used.
In the composition for forming the base material layer, various additions such as an antistatic agent, a release agent, an antioxidant, a weathering agent, a crystal nucleating agent, etc., within a range not impairing the characteristics as the surface protective film of the present invention. It is also possible to add an agent or a resin modifier such as polyolefin or elastomer.

  Furthermore, the base material layer is composed of at least two types of layers, that is, an intermediate layer that is in contact with the adhesive layer and a surface layer that is located on the opposite side of the adhesive layer. You can also.

  Although there is no restriction | limiting in particular as an intermediate | middle layer, Generally, well-known polyolefin resin, such as a polypropylene and polyethylene, can be mentioned. Examples of polypropylene include homopolypropylene, random polypropylene, block polypropylene, and polyethylene. High pressure method low density polyethylene, linear low density polyethylene, and high density polyethylene can be exemplified. In addition, depending on the application, various olefin elastomers, modified polyolefins such as maleic acid modified, styrene elastomers and polyester elastomers may be mentioned. These may be used alone or by blending components having different compositions, and if necessary, as long as they do not impair the properties of the surface protective film of the present invention, antistatic agents, antioxidants, and weather resistance. It is also possible to add various additives such as an agent and a crystal nucleating agent, and various resin modifiers. Among these, it is preferable to use a polypropylene resin as the intermediate layer from the viewpoint of rigidity and productivity.

  The surface layer is not particularly limited, but a known release material may be added to the resin component of the intermediate layer for the purpose of improving the unwinding property when the surface protective film of the present invention is unwound from a roll. .

Although there is no restriction | limiting in particular about the method of laminating | stacking an adhesion layer and a base material layer, By the well-known laminating methods, such as extrusion lamination and extrusion coating, on the base material layer film previously obtained by T-die shaping | molding or inflation molding. Examples include a method of laminating and a method of laminating each film by dry lamination after independently forming the base material layer and the adhesive layer into a film. From the viewpoint of productivity, the adhesive layer and the base material layer are multilayered. The co-extrusion molding is preferably performed using the above-mentioned extruder. As a method of coextrusion molding, T-die molding is more preferable in terms of thickness accuracy.

As thickness of the adhesion layer in the surface protection film of this invention, it is 5-100 micrometers, Preferably it is 5-80 micrometers, More preferably, it is 5-60 micrometers, More preferably, it is 6-40 micrometers.
The minimum value of the thickness of the surface protective film of the present invention is preferably 5 μm. A preferred maximum thickness is 300 μm, preferably 200 μm, more preferably 100 μm.

  By using the pressure-sensitive adhesive layer in the above preferred form, it shows an appropriate pressure-sensitive adhesive strength to the adherend, and there is no lifting or peeling from the adherend even when transported, stored or processed at high temperatures. Furthermore, there is no contamination of the adherend, and it can be suitably used not only for optical applications but also for building material applications, automotive parts applications, semiconductor wafer processing applications, and the like.

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.
[Example]
[Evaluation method]
(Acrylic board adhesive strength):
The acrylic plate was cut into a width of 50 mm and a length of 125 mm, and a surface protective film was attached to the test plate using a 2 kg rubber roller. Next, under the conditions of room temperature 23 ° C. and humidity 50% RH, the peeling force when peeling (180 degree peeling) at a rate of 300 mm / min was measured using an orientec Tensilon universal testing machine RTC-1225A. The peel strength per 50 mm width was defined as the adhesive strength (N / 50 mm).

(Adherent adhesion strength (initial)):
As an adherend, a prism sheet was prepared in which the lens part was made of an acrylic resin, and the dimensions of the triangular prism-shaped lens part were 26 μm high and 50 μm wide. The prism sheet was cut into a width of 50 mm and a length of 125 mm, and a surface protective film was attached to the test plate using a 2 kg rubber roller. Next, under the conditions of room temperature 23 ° C. and humidity 50% RH, the peeling force when peeling (180 degree peeling) at a rate of 300 mm / min was measured using an orientec Tensilon universal testing machine RTC-1225A. The peel strength per 50 mm width was defined as the adhesive strength (N / 50 mm).

(High temperature float / peeling evaluation):
As an adherend, a prism sheet was prepared in which the lens part was made of an acrylic resin, and the dimensions of the prismatic lens part were 26 μm in height and 50 μm in width. The prism sheet was cut into a width of 50 mm and a length of 125 mm, and a surface protective film was attached to the test plate using a 2 kg rubber roller. Next, after standing for 3 days under conditions of 50 ° C. and 75% RH, the state of the surface protective film floating or peeling off from the adherend was visually confirmed. The case where there was no lifting or peeling was marked with ○, and the case where lifting or peeling was confirmed was marked with ×.

(Adherent adhesion strength (after storage)):
As an adherend, a prism sheet was prepared in which the lens portion was made of an acrylic resin, and the prismatic lens portion had a height of 23 μm and a width of 50 μm. The prism sheet was cut into a width of 50 mm and a length of 125 mm, and a surface protective film was attached to the test plate using a 2 kg rubber roller. Next, it was left for 3 days under conditions of 50 ° C. and 75% RH, and then left for 1 hour under conditions of room temperature of 23 ° C. and humidity of 50% RH, and 300 mm using an orientec Tensilon universal tester RTC-1225A. The peel force when peeled at a speed of / min (180 degree peel) was measured, and the peel force per 50 mm width was defined as the adhesive strength (N / 50 mm).

(Melting point):
Based on JIS K7121, the temperature at the peak of the melting peak measured at a heating rate of 10 ° C. per minute was determined as the melting point using a differential scanning calorimeter (DSC). When there were a plurality of melting peaks, the highest temperature was taken as the melting point.

(Melt flow rate (MFR)):
In accordance with ASTM D1238, the load was 2.16 kg and measurement was performed at a predetermined temperature.

(Measurement of tan δ value (loss tangent)):
Using a rotational rheometer AR2000ex manufactured by TA Instruments, the target resin was subjected to a temperature change of −50 ° C. to 150 ° C. at a heating rate of 4 ° C./min, a frequency of 10 Hz, and a strain of 0.05%, and 8 mm The melt viscoelasticity was measured in a shear mode using a parallel plate.
The tan δ peak temperature is a temperature at which the tan δ value reaches a maximum value at a temperature below the melting point.

[Raw materials]
(PP-1): Block polypropylene
(Melting point 160 ° C., ethylene component 12 wt%, Rockwell hardness 80,
MFR (230 ° C) 6g / 10min)
(PP-2): Homopolypropylene
(Melting point 160 ° C., MFR (230 ° C.) 7 g / 10 min)
(X-1): Styrene-isobutylene-styrene triblock copolymer and styrene
-Mixtures with isobutylene-styrene diblock copolymers
(MFR (230 ° C.) 30 g / 10 min, A hardness = 14,
tan δ peak temperature −27 ° C., tan δ peak value 1.4)
(X-2): Propylene / 4-methylpentene-1 / 1-butene copolymer
(MFR (230 ° C.) 10 g / 10 min, tan δ peak temperature 34 ° C.,
tan δ peak value 2.3)
(X-3): Propylene / 4-methylpentene-1 / 1-butene copolymer
(MFR (230 ° C.) 6 g / 10 min, tan δ peak temperature 11 ° C.,
tan δ peak value 0.98)
(X-4): Propylene / ethylene copolymer (manufactured with metallocene catalyst)
(Melting point 115 ° C., MFR (230 ° C.) 7 g / 10 minutes,
tan δ peak temperature -2 ° C, tan δ peak value 0.18)

(Example 1)
The above resin is added to a three-type three-layer T-die molding machine having a die width of 400 mm, which has a single screw extruder of 40 mmφ for the surface layer, the intermediate layer, and the adhesive layer. Thus, a surface protective film having a total thickness of 35 μm was obtained. The evaluation results of the obtained film are shown in Table 1.

(Examples 2 to 4) and (Comparative Examples 1 to 3)
The surface protection film having a total thickness of 35 μm was obtained in the same manner as in Example 1 with the resin composition and layer thickness ratio of the various layers set to the resin composition and layer thickness ratio shown in Table 1. The evaluation results of the obtained film are shown in Table 1. As shown in Table 1, the surface protective films of Examples 1 to 4 did not float or peel off at high temperatures, and appropriate adhesive strengths were obtained.

Even when transported, stored, or processed at high temperatures, it exhibits moderate adhesion strength to the adherend, so there is no lifting or peeling from the adherend, so optical products, building materials, automotive parts, semiconductor wafers, etc. Used for.

Claims (1)

An olefin copolymer which is a copolymer of propylene and at least one olefin selected from 4 to 20 carbon atoms, and has a peak temperature of tan δ value (loss tangent) in a dynamic viscoelasticity measurement at 10 Hz of 5 ° C. or higher. A surface protective film having an adhesive layer comprising 3 to 100% by weight of a polymer (A) and 0 to 97% by weight of a styrene-based elastomer (B).