JP5531440B2 - Adhesive film - Google Patents

Description

  The present invention relates to an adhesive film. The pressure-sensitive adhesive film of the present invention protects the surface of an article from undesirable effects such as dust adhesion and scratching by sticking it on the surface of an article such as a synthetic resin plate, a decorative plywood, a metal plate, and a coated steel plate. It can be particularly preferably used as a surface protective film for the purpose and as a surface protective film when the printed circuit board is immersed in solder. The term “adhesive film” in the present invention also means an adhesive sheet or an adhesive tape.

  Conventionally, adhesive films aimed at protecting the surface of coated materials have been used during processing, storage, and transportation of building materials, electrical, electronic products, automobiles, etc. Such adhesive films have good adhesive properties. In addition, after use, each surface must be able to be easily peeled off without being contaminated with an adhesive. In recent years, adhesive films based on polyolefin resins have been used instead of adhesive films based on plasticized vinyl chloride resins. However, these polyolefin resin-based adhesive films are mainly composed of a low-crystalline or amorphous adhesive layer such as EVA or low-density polyethylene, or an adhesive layer made of an elastomer such as SIS or SEBS as the base material layer. What is integrally formed by coextrusion is used. However, the above-mentioned adhesive film is easily affected by the environment in which the joined body is placed, particularly under a high temperature environment, causing an extreme change over time, and thus the adhesive force is increased and peeling from the adherend is difficult. There was a problem that the pressure sensitive adhesive remained.

For this problem, an amorphous olefin polymer and a specific ethylene-based polymer are used as a pressure-sensitive adhesive that maintains suitable tackiness under extreme low temperature and high temperature conditions regardless of the operating temperature range. A composition made of a polymer has been proposed (see, for example, Patent Documents 1, 2, and 3).
The above adhesive film also has a problem that blocking occurs upon storage.

Moreover, the film which provided the surface layer which has specific surface roughness on the opposite surface of the adhesion layer, and improved the blocking resistance is disclosed (for example, refer to Reference 4).
However, this film was not sufficient in terms of performance.

JP 2006-63123 A JP 2006-299060 A JP 2006-257191 A JP 2008-68564 A

  The problem to be solved by the present invention is that there is little blocking between the adhesive films, there is little change in adhesive force immediately after bonding to the adherend and after lapse of time, and further, when the adhesive film is stored in a roll state An object of the present invention is to provide an adhesive film that is not affected by storage conditions.

In view of the above problems, the present inventors have conducted extensive studies. As a result, when the pressure-sensitive adhesive films are overlapped, the surface of the pressure-sensitive adhesive layer is easily affected by the opposite surface, and the adhesive force is reduced or adhered to the adherend. The present inventors have found that the adhesive strength may change after combining and arrived at the present invention.
That is, the present invention relates to a stretched polypropylene system comprising a laminate formed by laminating a pressure-sensitive adhesive layer on one side of a base material layer made of a polypropylene resin and laminating a release layer containing a crystalline polypropylene resin and polymethyl methacrylate particles on the opposite side. A resin film having an average surface roughness SRa of the release layer surface of 0.200 μm or less, an average surface roughness SRa of the adhesive layer surface of 0.030 μm or less, and 50 The difference between the initial adhesive strength at 23 ° C. and the initial adhesive strength at 23 ° C. is 10 cN / 25 mm or less.

According to the present invention, it is possible to obtain an adhesive film with little change in adhesive strength over time without being affected by the storage state of the adhesive film.
Moreover, it is excellent in tackiness, has little change over time, and has excellent processability.

  In this case, the scratch resistance evaluation value of the film is preferably 350 cm or more.

  Furthermore, in this case, it is preferable that the adhesive layer of the film contains an amorphous polypropylene resin.

  Furthermore, in this case, it is preferable that the average surface roughness SRa of the release layer surface of the film is 0.100 μm or less.

  Furthermore, in this case, it is preferable that the average surface roughness SRa of the adhesive layer surface of the film is 0.020 μm or less.

  Furthermore, in this case, it is preferable that the base material layer, the adhesive layer, and the release layer are melt-extruded and laminated from a plurality of extruders by a coextrusion method.

  Furthermore, in this case, it is preferable that the adhesive film is in the form of a film roll having a width of 450 mm or more and a length of 300 m or more.

  The pressure-sensitive adhesive film according to the present invention has little blocking between pressure-sensitive adhesive films, and there is little change in pressure-sensitive adhesive force immediately after bonding to an adherend and after a lapse of time. Further, when the pressure-sensitive adhesive film is stored in a roll state, Has the advantage of not being affected.

  Hereinafter, embodiments of the pressure-sensitive adhesive film of the present invention will be described.

(Base material layer)
The adhesive film of the present invention requires a base material layer made of a polypropylene resin, and the polypropylene resin used here includes crystalline polypropylene, random copolymer or block copolymer of propylene and a small amount of α-olefin, and the like. More specifically, as a crystalline polypropylene resin, an n-heptane-insoluble isotactic propylene homopolymer used in ordinary extrusion molding or the like containing polypropylene and 60% by weight or more of propylene A copolymer with an α-olefin can be mentioned, and this propylene homopolymer or a copolymer of propylene and another α-olefin can be used alone or in combination.
Here, n-heptane insolubility is an index of polypropylene crystallinity and at the same time indicates safety. In the present invention, n-heptane insolubility (25 ° C.) according to Ministry of Health and Welfare Notification No. 20 in February 1982 is used. It is a preferred embodiment to use one that is compatible with an elution amount of 150 pPm or less when extracted for 60 minutes (30 PPm or less when the operating temperature exceeds 100 ° C.).

As the α-olefin copolymerization component of the copolymer of propylene and other α-olefin, α-olefin having 2 to 8 carbon atoms such as ethylene, 1-butene, 1-pentene, 1-hexene, 4 C4 or higher α-olefins such as -methyl-1-pentene are preferred.
Here, the copolymer is preferably a random or block copolymer obtained by polymerizing one or more α-olefins exemplified above with propylene.
Moreover, a melt flow rate (MFR) is 0.1-100 g / 10min, Preferably it is 0.5-20 g / 10min, More preferably, the thing of the range of 1.0-10 g / 10min can be illustrated. The range of 2.0 to 5.0 g / 10 min is particularly preferable.
Two or more types of copolymers of propylene and other α-olefins may be mixed and used. When a 1-butene copolymerized polypropylene copolymer is used, the film becomes soft and tackiness is improved.
As a preferable example of the polypropylene resin constituting the base material layer of the present invention, for example, FS2011DG3 (crystalline polypropylene resin having an ethylene content of 0.6% by mass) manufactured by Sumitomo Chemical Co., Ltd. can be mentioned.

(Adhesive layer)
In addition, as a resin used for the adhesive layer, which is a requirement of the present invention, it is preferable to use an olefin polymer in order to increase the interlayer strength or to cover the film after peeling because the adhesive layer is laminated on the layer made of polypropylene resin. This is desirable in terms of preventing the adhesive layer from remaining on the adherend.

Furthermore, in order to achieve a difference of 10 cN / 25 mm or less between the initial adhesive force at 50 ° C. and the initial adhesive force at 23 ° C., which is a requirement of the present invention, It is preferable to use an amorphous polypropylene resin having a crystallization heat amount of 40 J / g or less in order to obtain sufficient adhesive force.
At this time, it is preferable to use a polypropylene resin having a heat of crystal fusion and a heat of crystallization of 10 J / g or more in order to suppress blocking resistance, smoothness and surface deformability.
Examples of the amorphous polypropylene resin here include “Tough Selenium H3522A” manufactured by Sumitomo Chemical Co., Ltd., “Notio PN3560” manufactured by Mitsui Chemicals, Inc., and the like.
“Tough selenium H3522A” manufactured by Sumitomo Chemical Co., Ltd. is a mixture of a completely amorphous polypropylene resin and a crystalline polypropylene resin, and the completely amorphous polypropylene resin is preferably contained in the adhesive layer in an amount of 50% by weight or more.
Further, the olefin polymer to be mixed with the amorphous polypropylene resin is not particularly limited, and ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, Ethylene-1-octene copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene-propylene-1-butene copolymer, ethylene-propylene-1-hexene copolymer, ethylene-1-butene- 1-hexene copolymer, propylene-1-butene copolymer, propylene-1-hexene copolymer, propylene-1-octene copolymer, propylene-4-methyl-1-pentene copolymer, propylene-1 -Butene-1-hexene copolymer, propylene-1-butene-4-methyl-1-pentene copolymer and the like.
The melt flow rate is preferably in the range of 1 to 10 g / 10 minutes, and more preferably in the range of 2 to 5 g / 10 minutes.

The average roughness SRa of the surface of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film of the present invention needs to be 0.030 μm or less. Preferably, it is 0.025 μm or less, more preferably 0.020 μm or less, and particularly preferably 0.015 μm or less. Here, when the average roughness SRa of the surface of the pressure-sensitive adhesive layer exceeds 0.030 μm, the contact area is reduced at the time of bonding to the adherend, which is not preferable because it causes a decrease in the adhesive force. One of the factors that determine the adhesive strength is the force that attracts materials, that is, the van der Waals force, on each surface of the laminated film that is in contact. Yes. Here, the fact that the contact area is small means that the attractive force between the bonded film surface and the adherend surface is reduced, and the adhesive force is lowered, which is not preferable.
In order to achieve this requirement, it is necessary to make the surface of the pressure-sensitive adhesive layer as flat as possible, and it is preferable not to add additives that form surface irregularities as much as possible. Furthermore, in the present invention, since the surface crystals are preferably aligned by using a stretched film, the surface roughness of the surface is smoothed and the flatness is further improved.
On the other hand, it can be said that it is practically difficult to make the average roughness SRa of the surface of the adhesive layer less than 0.010 μm even in a stretched film without additives.

Furthermore, the dynamic hardness of the pressure-sensitive adhesive layer surface of the pressure-sensitive adhesive film of the present invention is preferably 0.15 gf / μm ² or more and 1.4 gf / μm ² or less.

Here, as described in Shimadzu review, 50, 3, 321 (1993), the dynamic hardness represents the hardness in the ultrafine region. In this process, the indentation depth and pressure, and the deformation resistance of the sample are measured continuously to obtain the hardness. It is expressed by 1).
DH = αP / D * D (1)
DH: Dynamic hardness α: Constant depending on indenter shape,
P: test load, D: indentation depth (μm)
This dynamic hardness is a hardness obtained from a load and an indentation depth in the process of indenting the indenter, and is a characteristic value in a state where the plastic deformation and elastic deformation of the sample are combined.

  The dynamic hardness in the present invention is the hardness of the film surface, which indicates the hardness at a certain depth from the outermost surface of the film, and the hardness at a part having a depth of 1 μm was used as an index.

Here, the dynamic hardness of the preferred adhesive layer surface, 0.20gf / μm ² or more, more preferably 1.2gf / μm ² or less, particularly preferably, 0.25gf / μm ² or more, 1.0 gf / [mu] m ² or less Most preferably, it is 0.50 gf / μm ² or more and 0.8 gf / μm ² or less.
When the dynamic hardness of the adhesive layer surface is less than 0.15 gf / μm ² , since the surface is soft and easily deformed, it is easily affected by the surface condition of the adherend after being bonded to the adherend. When the body surface is smooth, the adhesive layer surface deforms according to its smoothness, and fine irregularities formed on the adhesive layer surface gradually disappear over time, resulting in an increase in contact area with the adherend. Therefore, since the adhesive force is improved from the set value, it may be difficult to peel off, or adhesive residue may be generated.
Moreover, when the dynamic hardness of the adhesive layer surface exceeds 1.4 gf / μm ² , it is not preferable because viscoelasticity, which is another factor that determines the adhesive strength, is low and the desired adhesive strength is not obtained. In addition to the van der Waals force that acts on the adhesive surface, the viscoelasticity of the adhesive film surface layer is greatly involved in the force when peeling the adhesive film from the adherend. The stress acting in the direction opposite to the direction increases, and the adhesive strength increases. The increase in the dynamic hardness of the surface of the pressure-sensitive adhesive layer here means that the film surface layer is hardened, which means that the viscoelasticity is lowered and the pressure-sensitive adhesive force is hardly produced.

  In the film of the present invention, the difference between the initial adhesive strength at 50 ° C. and the initial adhesive strength at 23 ° C. of the adhesive layer surface is preferably 10 cN / 25 mm or less, particularly preferably less than 5 cN / 25 mm. Thus, when the adhesive force at high temperature is small compared to the case at normal temperature, the change in adhesive force with time is small. Moreover, it is preferable that adhesive force becomes large at high temperature.

  The pressure-sensitive adhesive strength of the pressure-sensitive adhesive film of the present application is preferably in the range of 3 to 50 cN / 25 cm at 23 ° C. from the viewpoint of protective performance and peelability of the adherend. The adhesive strength can be appropriately set by controlling the amorphousness of the resin of the adhesive layer.

  The pressure-sensitive adhesive film of the present invention preferably has a thickness variation rate in the transverse direction, which is a direction perpendicular to the winding direction during film production, in the range of 2.0% to 7.5%, preferably 7.0% or less, and more preferably 6.5% or less. When the thickness variation rate exceeds 7.5%, when the pressure-sensitive adhesive film is pressure-applied to the adherend, pressure unevenness occurs depending on the location, which causes a decrease in the adhesive strength. On the other hand, it can be said that it is difficult in terms of film forming technology to suppress the thickness variation rate to less than 2.0%.

The pressure-sensitive adhesive film of the present invention can contain known additives as necessary. For example, a lubricant, an antiblocking agent, a heat stabilizer, an antioxidant, an antistatic agent, a light resistance agent, an impact resistance improvement agent and the like may be contained.
In this case, the low molecular weight substance on the surface of the adhesive layer is preferably less than 1 mg / m ² . Here, the measurement of the low molecular weight substance on the surface of the adhesive layer was carried out by the following procedure. After the surface of the adhesive layer is washed with an organic solvent that does not erode the resin constituting the adhesive layer such as ethanol, the organic solvent is removed from the cleaning solution with an evaporator, and the residue obtained by weighing the residue is washed. It was obtained by dividing by the surface area of the layer surface. Here, if the residue is present in an amount of 1 mg / m ² or more, foreign matter exists between the surface of the adhesive layer and the adherend surface, which reduces the contact area and decreases the van der Waals force. It is lowered and not preferable. In the case of adding an additive, it is preferable not to transfer or transfer to the adhesive layer by selecting an additive such as a polymer type or examining an addition method.

(Release layer)
In the pressure-sensitive adhesive film of the present invention, it is necessary to form a release layer on the opposite surface of the pressure-sensitive adhesive layer, so that even if the pressure-sensitive adhesive films are stacked, blocking resistance can be obtained and used as a product.
The surface unevenness of the release layer is preferably a surface having an average surface roughness SRa of 0.200 μm or less. When the average surface roughness SRa exceeds 0.200 μm, when the adhesive films are stacked or stored in roll form, the surface irregularities of the release layer are transferred to the adhesive layer, reducing the contact area during adhesion. In particular, there are difficulties in applications in which the initial adhesive strength is lowered, the adhesive strength is greatly changed over time, transparency is lowered, and high transparency is required.
By setting the average surface roughness SRa to 0.200 μm or less, for example, there is no significant change in the adhesive force immediately after being bonded to the adherend by the method described in Examples and the adhesive force after 24 hours.
The film of the present invention preferably has an average surface roughness SRa of the release layer surface of 0.020 μm or more.
The surface irregularity of the release layer is preferably a surface having an average surface roughness SRa of 0.150 μm or less, more preferably 0.020 μm or more and 0.100 μm or less, 0.030 μm or more, 0.080 μm. The following are most preferred.
In order to form the surface irregularities, for example, it is preferable to form protrusions by containing inorganic or organic fine particles in a crystalline polypropylene resin.
Examples of the crystalline polypropylene resin used here include Sumitomo Chemical “FS2011DG3”.
In addition, inorganic particles such as silica or organic particles such as polymethyl methacrylate (PMMA) are used as the particles used here.
A rough surface can be formed by mixing a polypropylene polymer or a propylene ethylene block copolymer and polyethylene, or a propylene ethylene block copolymer alone. Further, it is easy to control the height of the surface protrusion.
At this time, the particles to be used are preferably spherical PMMA particles or spherical silica in terms of blocking resistance and transparency and little influence on the adhesive layer, the particle size is 2.5 to 5.0 μm, and the addition amount is 0.5 to The range of 1.5% by weight is preferable, and these are also preferable in that uniform projections can be formed with a small particle size distribution.

(Adhesive film)
The scratch resistance evaluation value of the adhesive film of the present invention is preferably 350 cm or more from the viewpoint of the protective performance of the adherend when the adhesive film is bonded to the adherend.
The haze value of the pressure-sensitive adhesive film of the present invention is preferably in the range of 30% or less, particularly when used for an optical adherend. More preferably, it is 20% or less, particularly preferably 15% or less, and the self-adhesive film is excellent in transparency if it is about 5%.

  The production method of the pressure-sensitive adhesive film of the present invention is not particularly limited, but after forming the base material layer and the pressure-sensitive adhesive layer using an inflation film production apparatus or a T-die film production apparatus, they can be bonded together by an extrusion laminating method. A multilayer film may be formed by coextrusion from the beginning. Here, in order to obtain a preferable range of the thickness variation rate, it is preferable to perform monoaxial stretching or biaxial stretching after the multilayer film is formed by a coextrusion method. By using the stretched film, crystal orientation of the base layer and the adhesive layer resin occurs as compared with the unstretched film, and the stability of the adhesive force and the excellent pinhole resistance at the time of bending and bending can be obtained.

  As the stretching conditions at that time, it is desirable to obtain an appropriate temperature within the range where the film does not melt in the preheating and stretching temperature in the stretching step, in order to obtain the stability of the adhesive strength, Insufficient heat increases the film surface hardness due to crystal orientation and may reduce the adhesive strength, which is not preferable. If the temperature is high, the crystal part of the adhesive layer is melted and becomes amorphous, increasing the amorphous part. For this reason, the dynamic hardness of the pressure-sensitive adhesive layer surface is lowered, and the change in the pressure-sensitive adhesive force with time may increase, which is not preferable.

Taking the case of the longitudinal stretching temperature at the time of sequential biaxial stretching as an example, a preferable temperature range can be exemplified by 100 to 135 ° C. as the preheating temperature at the longitudinal stretching and 100 to 125 ° C. as the stretching temperature. Here, when the preheating temperature is less than 100 ° C. and the stretching temperature is less than 100 ° C., stretching spots are generated and the average surface roughness SRa of the adhesive layer varies, which is not preferable. Preheating is 135 ° C. and stretching is 125 ° C. If it exceeds 1, stretching becomes difficult.
In the longitudinal stretching, the roll temperature on the pressure-sensitive adhesive layer side is preferably set to be several degrees lower than the temperature of the roll on the release layer side.
At this time, the temperature is set mainly with reference to the softening temperature of the adhesive layer.
Further, regarding the draw ratio, it is preferable to take an appropriate range. If the ratio is low, a preferable thickness fluctuation rate may not be obtained, and if the ratio is high, the target adhesive force may not be obtained, so it is preferable. Absent. Preferable stretching ratios for sequential biaxial stretching include 3 to 6 times in the longitudinal direction and 6 to 10 times in the transverse direction. More preferably, it is 4 to 5 times in the vertical direction and 8 to 10 times in the horizontal direction.

  Moreover, in order to make the average roughness SRa of the adhesive layer 0.030 μm or less, it is preferable not to make the transverse stretching preheating temperature during stretching too low, and when the preheating temperature during stretching is lowered, the unevenness formed is Since it will form excessively, it is not preferable. As a preheating temperature at the preferred transverse stretching, 150 ° C. or more can be exemplified.

The thickness of the pressure-sensitive adhesive layer of the present invention is preferably 1 μm or more and less than 15 μm.
When the thickness of the pressure-sensitive adhesive film is less than 1 μm, the pressure-sensitive adhesive force may be insufficient, and when it is 15 μm or more, there is a problem that the pressure-sensitive adhesive force on the surface of the pressure-sensitive adhesive layer is too strong.
The thickness of the adhesive layer is preferably 2 μm or more and less than 10 μm. When increasing the adhesive force, the viscosity can be taken into consideration, for example, 5 μm or more and 10 μm.

The thickness of the base material layer of the present invention is preferably 5 μm or more and less than 50 μm, and more preferably 15 μm or more and less than 25 μm.
When the thickness of the adhesive film is less than 5 μm, there is a problem that the lumbar feeling becomes weak and wrinkles or adhesive force cannot be obtained sufficiently, and when it is 50 μm or more, the tack property is not sufficient. is there.
The tackiness means instantaneous adhesive force and is an index of ease of adhesion at the initial bonding time.

The upper limit of the width and the winding length of the film roll is not particularly limited, but from the viewpoint of ease of handling, the width is generally 1.5 m or less, and the winding length is preferably 6000 m or less when the film thickness is 45 μm. Moreover, as a winding core, a plastic core and metal cores, such as 3 inches, 6 inches, and 8 inches, can usually be used.
Moreover, it is preferable that it is the film roll wound up by the dimension of length 300m or more and width 450mm or more from the suitability of a process.

  The adhesive film of the present invention particularly protects the surface of a synthetic resin plate, a stainless steel plate (for example, for building materials), an aluminum plate, a decorative plywood, a steel plate, a glass plate, a home appliance, a precision machine, and an automobile body at the time of manufacture. Therefore, in order to prevent damage from stacking, storing, and transporting articles, and from scratching during secondary processing (for example, bending and pressing) of articles. Can be preferably used.

  The following examples further illustrate the invention. However, the present invention is not limited to the following examples without departing from the gist thereof. In addition, the evaluation method of the physical property in a following example and a comparative example is as follows.

<Crystal melting heat and crystallization heat amount>
About 5 mg of polyolefin resin was weighed, and the temperature was raised from room temperature to 200 ° C. at a temperature rising rate of 10 ° C./min using a differential scanning calorimeter (DSC-60) manufactured by Shimadzu Corporation, and at 200 ° C. for 5 minutes. After holding, after cooling to 0 ° C. at a temperature drop rate of 10 ° C./min, the heat of crystal melting and the amount of crystallization are obtained from the chart when the temperature is raised again to 200 ° C. at 10 ° C./min.

<Average particle size>
In a 25 mL glass bottle, 0.1 g of a sample, 0.3 g of a surfactant (Emulgen 109P, manufactured by Kao Corporation) and 20 g of water were weighed, stoppered and shaken for 5 minutes to prepare an aqueous dispersion of the sample. Using Coulter Counter Multisizer II (manufactured by Beckman Coulter, Inc.), the volume median diameter of the sample was measured under the conditions of a measurement range of 1.760 to 61.20 μm, and the average particle diameter was obtained.

<Film haze>
It measured using Nippon Denshoku Industries Co., Ltd. haze meter NDH-2000 based on the optical characteristic test method of JIS-K-7105 plastics.

(3) Measurement of average surface roughness Using a contact type three-dimensional center plane surface roughness meter (model ET-30HK) and a three-dimensional roughness analyzer (SPA-11) manufactured by Kosaka Laboratory Ltd., release The center surface average roughness (SRa) of the surfaces of the surface and the adhesive surface was measured by the stylus method under the following conditions.
The conditions were as follows, and the average value of 20 measurements was taken as the value.
Stitch tip radius: 0.5 μm
Stylus pressure: 20mg
Cut-off value: 80 μm
Measurement length: 1000 μm
Longitudinal magnification: 5000 times Measurement speed: 100 μm / s
Measurement interval: 2 μm

<Adhesive strength>
It measured by the following method based on the JIS-Z-0237 (2000) adhesive tape * adhesive sheet test method.
As an adherend, an acrylic plate (Mitsubishi Rayon Co., Ltd .: Acrylite 3 mm thick) 50 mm × 150 mm is prepared, and a test piece is 25 mm in the winding direction at the time of film production and 180 mm in the direction perpendicular thereto. A piece was cut out, and using a rubber roll having a mass of 2000 g (with a spring hardness of 80 Hs on the roller surface and a width of 45 mm and a diameter (including the rubber layer) of 95 mm, covered with a rubber layer having a thickness of 6 mm), The test piece was reciprocated once at a speed of 5 mm / sec. Made by Toyo Seiki Co., Ltd. after being pressed and left for 30 minutes in an environment of a temperature of 23 ° C. and a relative humidity of 65%, initially for 24 hours, and for 7 or 30 days. Using “Tensilon” (UTM-IIIL), the resistance value when peeled 180 ° at a speed of 300 mm / min was defined as the adhesive strength [cN / 25 mm].
180 degree peeling means holding the peeling angle between the acrylic plate and the film at the time of measuring the resistance value at the time of peeling at 180 degrees.
At the time of measurement, a polyester sheet having a thickness of 190 μm and a size of 25 mm × 170 mm is prepared as a grip for the measurement sample, and the cellophane with a width of 15 mm is provided at the adhesive film side end of the measurement sample obtained by pressure-bonding the adhesive film and the acrylic plate. Affixed with tape and used as a grip for measurement. A schematic diagram of the measurement sample is shown in FIG. The measurement was performed three times for one sample, and the average value was defined as the adhesive strength of the sample.
Further, after crimping, the one that was allowed to stand for 30 minutes in an environment with a temperature of 50 ° C. and a relative humidity of 65% was set to a high temperature, and “Tensilon” (UTM-IIIL) manufactured by Toyo Seiki Co., Ltd. was used at 180 ° at a speed of 300 mm / min. The resistance value at the time of peeling was defined as adhesive strength [cN / 25 mm].

<Dynamic hardness>
Using a Shimadzu Dynamic Ultra Micro Hardness Tester DUH-201, measurement was performed under the following conditions in an environment of a room temperature of 23 ° C. and a humidity of 65%.
Test mode Soft material test (MODE3)
Indenter Triangular pan indenter 115 °
Test load 0.20gf
Load speed 10 (0.0145 gf / sec)
Holding time 1 second Displacement full scale 10μ
After five measurements, the dynamic hardness of the indentation depth of 1 μm was picked up from the analysis data, the average value was obtained, and the dynamic hardness of the sample was taken. This dynamic hardness (DH) is a hardness obtained from the load and the indentation depth in the process of indenting the indenter, and is defined by the following equation (1).
DH = αP / D * D (1)
DH: Dynamic hardness α: Constant depending on indenter shape P: Test load, D: Depth of indentation (μm)

<Scratch resistance>
Using a fastness tester manufactured by Toyo Seiki Co., Ltd., rubbing against the corrugated cardboard surface with a load of 37 g, measuring the friction travel distance when pinholes are generated, and the value is 100 cm or more Was marked with ○ and the others were marked with ×.

<Handability>
The one with a small resistance when the film was unwound from the roll film was rated as “◯”.

<Thickness variation rate>
Measurement was carried out by the following method using Anritsu FILM THICKNESS TESTER KG601A and K306C.
Measurement speed 0.01 seconds Feed speed 1.5m / min HIGH CUT OFF
Thinning off
A sample having a length of 40 mm with respect to the winding direction during film production and a length of 500 mm with respect to the direction orthogonal to the winding direction was cut out, and the continuous thickness in the direction orthogonal to the winding direction was measured under the above conditions. Based on the result obtained by the measurement, the thickness variation rate was determined by the following equation (2). The measurement was performed 5 times for one sample, and the average value was defined as the thickness variation rate of the sample.
Thickness variation rate (%) = [(maximum thickness−minimum thickness) / average thickness] × 100 (2)

<Amount of film surface additive>
A sample of 1 m square was cut out from the test film and cut into about 5 cm square to prepare a test piece. Subsequently, the entire surface was strongly washed one by one with ethanol with a washing bottle against the adhesive surface of the test piece, and the washing solution was collected. At this time, the film is picked with tweezers, the lower part from the part first gripped, and after the ethanol is contained, the lower part is gripped and turned over to clean the upper part of the first pinched part. Since ethanol always remains on the film after washing, in order not to miss the extract, ethanol was reciprocated several times to ensure that the extract was collected.
Subsequently, after removing ethanol from the collected washing solution with an evaporator, redissolved with chloroform and passed through filter paper to remove dust and the like mixed during work, and chloroform was completely removed with an evaporator and the remaining weight was measured. did. This weight was defined as the amount of surface additive per square meter.

<Example 1>
(Create base layer)
As a base layer, 100% by weight of FS2011DG3 (manufactured by Sumitomo Chemical Co., Ltd., crystalline polypropylene resin having an ethylene content of 0.6% by mass, melt flow rate of 2.5 g / 10 min) is applied to a 60 mmφ single screw extruder (L / D; 22). And 4) were melt extruded to form a base layer.
(Creation of adhesive layer)
As an adhesive layer, 100% by weight of Tough selenium H3522A (manufactured by Sumitomo Chemical Co., Ltd., melt flow rate 3 g / 10 min, heat of crystal fusion: 29 J / g, heat of crystallization 28 J / g) is 45φ twin screw extruder (L / D; In 19), it was melt-extruded to obtain an adhesive layer.
(Release layer)
As the release layer, FS2011DG3 (manufactured by Sumitomo Chemical Co., Ltd., crystalline polypropylene resin having an ethylene content of 0.6% by mass, melt flow rate of 2.5 g / 10 min) and PMMA particles having an average particle size of 4 μm (Nippon Shokubai Co., Ltd.) The product No. E poster MA1004) was mixed at a ratio of 99/1% by weight, and melt-mixed and extruded with a 65 mmφ single screw extruder (L / D; 25) to form a release layer.
(Create film)
While the adhesive layer, base layer, and release layer were melted in each extruder, lamination extrusion was performed in a three-layer T die (multi-manifold type, lip width 250 mm, lip gap 1.2 mm) at 260 ° C. . The extruded resin was sprayed onto a 20 ° C. casting roll with an air knife, closely adhered, taken at a speed of 3 m / min, and cooled and solidified to obtain an unstretched sheet. After preheating with a roll heated to 120 ° C, 4.5% longitudinal stretching is performed by setting a difference in speed between the rolls heated to 118 ° C, 3 m / min and 13.5 m / min. After cooling once with a roll heated to 50 ° C., preheating at a rate of 13.45 m / min in an oven heated to 172 ° C., and then at a deformation rate of 0.2 m / min at 155 ° C. The film was then stretched 9.0 times, and further relaxed for 7 seconds in an environment of 160 ° C. for 22 seconds, and the adhesive layer was 8 μm, the base layer was 20 μm, and the release layer was 2 μm. A seed 3 layer biaxially stretched film was obtained.
The obtained film was made into a roll state having a width of 500 mm, a width of 500 m, and a winding hardness of 80 (manufactured by Shimadzu Corporation, a thread winding hardness meter No. K66846). Table 1 shows the physical properties of the obtained film.
The film sample was rewound from the film roll obtained in the example, and a sample having a length of 250 mm and a width of 350 mm centered at a distance of 10 m from the end of the film roll surface and 1/2 of the film width from both ends of the film was long. Three pieces are cut out continuously in the scale direction and measured as described above, and the average is obtained.

<Example 2>
In Example 1, the resin constituting the pressure-sensitive adhesive layer is H3522A (manufactured by Sumitomo Chemical Co., Ltd., melt flow rate 3 g / 10 min), 80% by weight, and FS2011DG3 (manufactured by Sumitomo Chemical Co., Ltd., ethylene content 0.6% by mass). A three-kind three-layer biaxially stretched film was obtained in the same manner as in Example 1 except that the polypropylene resin, melt flow rate 2.5 g / 10 min) was changed to 20% by weight.
FS of H3522A (Sumitomo Chemical Co., Ltd., melt flow rate 3 g / 10 min) is 80% by weight
The heat of crystal fusion of a resin in which 20% by weight of 2011DG3 (manufactured by Sumitomo Chemical Co., Ltd., crystalline polypropylene resin having an ethylene content of 0.6% by mass, melt flow rate of 2.5 g / 10 min) is 39.8 J / g, crystals The amount of heat of conversion was 39.8 J / g.

<Example 3>
In Example 1, the resin used for the release layer was FS2011DG3 (manufactured by Sumitomo Chemical Co., Ltd., crystalline polypropylene resin having an ethylene content of 0.6% by mass, melt flow rate of 2.5 g / 10 min) and PMMA having an average particle size of 4 μm. The same procedure as in Example 1 was performed except that particles (manufactured by Nippon Shokubai Co., Ltd., product number Eposter MA1004) were mixed at a ratio of 98.5 / 1.5% by weight.

<Comparative Example 1>
In Example 1, except that the resin constituting the release layer was changed to PC 523A (crystalline polypropylene resin manufactured by Sun Allomer Co., Ltd., melt flow rate 5 g / 10 min) at 100% by weight, the same as in Example 1, A film was obtained.

<Comparative example 2>
In Example 2, the take-off speed was 9 m / min, the discharge amount of each extruder was adjusted, and a total of 40 μm, three types of three-layer unstretched films laminated in the order of 5 μm adhesive layer, 30 μm base layer, and 5 μm release layer Got.

<Comparative Example 3>
In Example 2, the resin constituting the release layer was changed to PC 523A (crystalline polypropylene resin manufactured by Sun Allomer, melt flow rate 5 g / 10 min) to 100 wt%, the take-up speed was 9 m / min, and each extrusion was performed. By adjusting the discharge amount of the machine, a three-layer three-layer unstretched film having a total of 40 μm laminated in the order of 5 μm of adhesive layer, 30 μm of base layer and 5 μm of release layer was obtained.

  The results are shown in Table 1.

  The adhesive film of the present invention has little change in adhesive force immediately after being bonded to an adherend and after a lapse of time, and since it is less susceptible to storage conditions when storing the adhesive film in a roll state, It can be used in a wide range of application fields such as synthetic resin plates, decorative plywood, metal plates, and coated steel plates, as well as automobile baking and printed circuit boards, and contributes greatly to the industry.

It is a schematic diagram of a measurement sample.

Claims (6)

A stretched polypropylene resin film comprising a laminate formed by laminating an adhesive layer on one side of a base material layer made of polypropylene resin and a release layer containing crystalline polypropylene resin and polymethyl methacrylate particles on the opposite side. The adhesive layer contains an amorphous polypropylene resin, and the average surface roughness SRa of the release layer surface is 0.200 μm or less, and the average surface roughness SRa of the adhesive layer surface is 0.030 μm. The pressure-sensitive adhesive film is characterized in that the difference between the initial adhesive strength at 50 ° C. and the initial adhesive strength at 23 ° C. of the adhesive layer is 10 cN / 25 mm or less.   The adhesive film according to claim 1, wherein the scratch resistance evaluation value of the film is 350 cm or more.   The pressure-sensitive adhesive film according to claim 1, wherein the average surface roughness SRa of the surface of the release layer is 0.100 µm or less.   The pressure-sensitive adhesive film according to claim 1, wherein the surface roughness SRa of the pressure-sensitive adhesive layer surface is 0.020 µm or less.   The pressure-sensitive adhesive film according to claim 1, wherein the base material layer, the pressure-sensitive adhesive layer, and the release layer are melt-extruded and laminated from a plurality of extruders by a co-extrusion method.   The pressure-sensitive adhesive film according to claim 1, wherein the pressure-sensitive adhesive film is in the form of a film roll having a width of 450 mm or more and a length of 300 m or more.

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