Silicone rubber roll for embossing, method and apparatus for producing plastic film using same, and surface protective film
阅读说明：本技术 压花成型用有机硅橡胶辊、使用其的塑料膜的制造方法及制造装置、以及表面保护膜 (Silicone rubber roll for embossing, method and apparatus for producing plastic film using same, and surface protective film ) 是由 长荣克和 富田优佳 松本忠 于 2019-09-13 设计创作，主要内容包括：本发明提供在表面没有微小的凹陷缺陷、进而在压花成型而得的塑料膜表面不产生突起的压花成型用有机硅橡胶辊。就本发明的压花成型用有机硅橡胶辊而言,表面的有机硅橡胶层包含球状固体粒子,在球状固体粒子中,粒径为0.8μm以下的球状固体粒子及粒径为30μm以上的球状固体粒子的体积含有率分别为球状固体粒子整体的体积的1％以下。(The invention provides a silicone rubber roller for embossing, which has no tiny dent defects on the surface and no protrusion on the surface of a plastic film obtained by embossing. In the silicone rubber roller for embossing of the present invention, the silicone rubber layer on the surface contains spherical solid particles, and the volume content of spherical solid particles having a particle size of 0.8 μm or less and spherical solid particles having a particle size of 30 μm or more among the spherical solid particles is 1% or less of the volume of the entire spherical solid particles.)
1. An organic silicon rubber roller for embossing, which is a rubber roller whose surface is coated with a rubber layer containing organic silicon as a main component,
the rubber layer contains spherical solid particles which are,
the volume content of the spherical solid particles having a particle diameter of 0.8 μm or less and the volume content of the spherical solid particles having a particle diameter of 30 μm or more are each 1% or less of the volume of the entire spherical solid particles.
2. The silicone rubber roller for embossing according to claim 1, wherein the spherical solid particles are made of a silicone resin.
3. A method for producing a plastic film, wherein a molten resin is discharged from a die, the discharged molten resin is cooled while being nipped between an emboss roller and a cooling roller or a cooling belt to solidify the molten resin, and a web-like plastic film is obtained,
the embossing roll is the silicone rubber roll for embossing molding described in claim 1 or 2.
4. A method for producing a plastic film, wherein after heating and softening a plastic film, the softened plastic film is cooled and solidified while being nipped between an emboss roller and a chill roller or a chill belt,
the embossing roll is the silicone rubber roll for embossing molding described in claim 1 or 2.
5. A plastic film manufacturing apparatus comprising a mold, an emboss roller, and a cooling roller or cooling belt,
a mold, an emboss roller, and a cooling roller or a cooling belt arranged so as to nip the molten resin discharged from the mold in a web shape with the emboss roller and the cooling roller or the cooling belt,
the embossing roll is the silicone rubber roll for embossing molding described in claim 1 or 2.
6. A plastic film manufacturing apparatus comprising a plastic film heating means, an emboss roller, and a cooling roller or cooling belt,
a heating unit, an emboss roller, and a cooling roller or a cooling belt are arranged so that the emboss roller and the cooling roller or the cooling belt nip the plastic film heated by the heating unit of the plastic film,
the embossing roll is the silicone rubber roll for embossing molding described in claim 1 or 2.
7. A surface protective film composed of a single layer or a plurality of layers,
at least one outermost surface is a pear peel surface with fine concave-convex,
the concave part of the fine concave-convex is approximately hemispherical, the convex part is made of a single material,
the material constituting the convex portion is the same as the material of the portion where the concave portion is formed.
Technical Field
The present invention relates to a silicone rubber roller for embossing, a method and an apparatus for manufacturing a plastic film using the same, and a surface protective film.
Background
Conventionally, as an emboss roller for forming a pearskin shape on a surface of a plastic film, for example, a rubber roller having a surface coated with a silicone rubber as described in patent document 1 has been proposed.
By using the silicone rubber roll as the emboss roll, the releasability between the resin in a molten state formed for embossing and molding and the surface of the emboss roll can be improved. This can prevent the molten resin from being wound around the emboss roller, and therefore, the molding speed can be increased. Further, the surface roughness of the pear skin pattern can be controlled by appropriately selecting the particle size of the solid particles added to the silicone rubber.
Further, patent document 1 discloses the following technique: the volume of solid particles having a particle diameter of more than 19 [ mu ] m among solid particles mixed as a filler in silicone rubber is 1% or less of the total volume of the solid particles, thereby preventing the generation of a particle size of 0.05mm on the surface of a plastic film subjected to embossing2The protrusions have a height of 5 μm or more. When the plastic film produced by this technique is used as a surface protective film for protecting a surface of a mesh-like product such as an optical film by being bonded thereto, the above-mentioned protrusions are not present, and therefore, the occurrence of indentations due to the protrusions can be prevented.
Documents of the prior art
Patent document
Patent document 1: international publication No. 2013/080925
Disclosure of Invention
Problems to be solved by the invention
However, in recent years, various optical films used in flat panel displays have been made thinner, and when these optical films are used as a target (hereinafter referred to as an adherend) to which a surface protective film is bonded, it is not sufficient to prevent the protrusion of the above size, and even a very small protrusion causes the occurrence of a dent.
The invention aims to: to solve the above problems, there are provided an organic silicone rubber roller for embossing having no depressions on the surface and no protrusions on the surface of an embossed plastic film, a method and an apparatus for producing a plastic film using the same, and a surface protective film having no protrusions on the surface and causing no indentations on an adherend.
Means for solving the problems
The silicone rubber roller for embossing of the present invention to solve the above problems is a rubber roller whose surface is coated with a rubber layer containing silicone as a main component,
the rubber layer contains spherical solid particles,
the volume content of the spherical solid particles having a particle diameter of 0.8 μm or less and the volume content of the spherical solid particles having a particle diameter of 30 μm or more are each 1% or less of the volume of the entire spherical solid particles.
In the silicone rubber roll for embossing of the present invention, the spherical solid particles are preferably made of a silicone resin.
The method for producing a plastic film of the present invention for solving the above problems comprises: discharging the molten resin from the die, cooling the discharged molten resin while nipping the molten resin with an emboss roller and a chill roller or a chill belt to solidify the molten resin to obtain a web-like plastic film,
the embossing roll is the silicone rubber roll for embossing molding of the present invention.
Another embodiment of the method for manufacturing a plastic film of the present invention for solving the above problems is: heating and softening the plastic film, cooling the softened plastic film while nipping the plastic film with an emboss roller and a cooling roller or a cooling belt to solidify the plastic film,
the embossing roll is the silicone rubber roll for embossing molding of the present invention.
The apparatus for manufacturing a plastic film according to the present invention for solving the above problems includes a die, an emboss roller, and a cooling roller or a cooling belt, the die, the emboss roller, and the cooling roller or the cooling belt being arranged so that the emboss roller and the cooling roller or the cooling belt nip the molten resin discharged from the die in a web form,
the embossing roll is the silicone rubber roll for embossing molding of the present invention.
Another embodiment of the plastic film manufacturing apparatus according to the present invention for solving the above problems includes a heating unit for a plastic film, an emboss roller, and a cooling roller or cooling belt, the heating unit, the emboss roller, and the cooling roller or cooling belt being arranged such that the plastic film heated by the heating unit for the plastic film is nipped by the emboss roller and the cooling roller or cooling belt,
the embossing roll is the silicone rubber roll for embossing molding of the present invention.
The surface protective film of the present invention for solving the above problems is a surface protective film composed of a single layer or a plurality of layers,
at least one outermost surface is a pear peel surface with fine concave-convex,
the concave part of the fine unevenness is substantially hemispherical, the convex part is made of a single material,
the material constituting the convex portion is the same as the material of the portion where the concave portion is formed.
The terms in the present invention are defined as follows.
The "rubber containing silicone as a main component" is the same as a rubber generally called silicone rubber, and means a synthetic rubber containing a linear polymer having a main chain composed of siloxane bonds and having organic substituents such as methyl groups, phenyl groups, and vinyl groups in side chains as a main component. The main component herein means that 51 mass% or more is contained in the rubber component.
The "spherical solid particles" are particles made of a material which is solid at normal temperature, for example, a metal, a mineral, a ceramic, a synthetic resin, a glass, or a mixture thereof, and each of the particles has a substantially spherical shape.
The "silicone resin" refers to a silicone resin that is solid at room temperature and does not exhibit rubber-like elasticity, and examples thereof include a polyorganosilsesquioxane cured product having a structure in which siloxane bonds are crosslinked into a three-dimensional network.
The "emboss roller" is a roller having a pearskin-shaped surface and intended to transfer the pearskin shape to the surface of a plastic film.
The "cooling roll" is a roll for the purpose of solidifying a molten resin by cooling the molten resin while contacting the molten resin.
The "cooling belt" is a belt for the purpose of solidifying a molten resin by cooling the belt while contacting the molten resin.
The "carrier roller" is a roller disposed opposite to the emboss roller and used for nipping a plastic film together with the emboss roller, and is defined as being different from the above-mentioned "cooling roller" that cools and solidifies a completely melted resin.
The "transfer belt" is a belt disposed opposite to the emboss roller and used for nipping a plastic film together with the emboss roller, and is defined as being different from the above-mentioned "cooling belt" that cools and solidifies a completely molten resin.
The "heating unit for a plastic film" means a unit for heating the plastic film from at least one surface of the plastic film being conveyed in the longitudinal direction to raise the temperature, and means, for example, an infrared heater, a hot air generator, an induction heating roller, or the like.
The "surface protective film" refers to a plastic film used for the following purposes: the adhesive sheet is bonded to a sheet-like or web-like adherend such as an optical plastic film such as a retardation film or a brightness enhancement film, a metal foil, a glass plate, or a resin plate, thereby protecting the surface of the adherend from damage such as scratches or dirt during the production process or during transportation.
Effects of the invention
According to the present invention, there can be provided a silicone rubber roll for embossing which has no depressions on the surface and no protrusions on the surface of an embossed plastic film, and a method and an apparatus for producing a plastic film using the same. Further, according to the present invention, there can be provided a surface protective film which has no protrusion on the surface and does not cause an indentation on an adherend.
Drawings
Fig. 1 is a schematic cross-sectional view showing one embodiment of the silicone rubber roller for embossing of the present invention.
Fig. 2 is a schematic side view showing one embodiment of the apparatus for manufacturing a plastic film of the present invention.
Fig. 3 is a schematic side view showing another embodiment of the apparatus for manufacturing a plastic film of the present invention.
Fig. 4 is a schematic side view showing another embodiment of the apparatus for manufacturing a plastic film of the present invention.
Fig. 5 is a schematic side view showing another embodiment of the apparatus for manufacturing a plastic film of the present invention.
Detailed Description
Hereinafter, examples of preferred embodiments of the present invention will be described with reference to the drawings.
As shown in fig. 1, a silicone rubber roller for embossing (hereinafter, sometimes referred to as a silicone rubber roller) 100 of the present invention has a roller core 12 coated with a rubber layer 11 containing silicone as a main component.
The structure of the roll core 12 is not particularly limited, but is preferably a structure in which the surface temperature of the silicone rubber roll 100 can be controlled, as shown in fig. 1, by providing a flow path 13 or the like inside for circulating a heat medium such as water. When the silicone rubber roller 100 is used as the emboss roller 3 in the apparatus for producing a plastic film as shown in fig. 2 to 5, the surface temperature of the silicone rubber roller is lowered, so that the releasability from the molten resin can be easily improved to prevent the resin from being wound around the emboss roller 3, and the speed of curing the molten resin can be easily increased to improve the speed of embossing. The material of the roll core 12 is not particularly limited, and may be appropriately selected from general structural materials such as metal, plastic, and fiber-reinforced resin, but a metal material having low thermal conductivity may be preferably used from the viewpoint of controlling the temperature, as described above. As the metal material, for example, carbon steel, stainless steel, aluminum alloy, or the like can be preferably used.
The rubber layer 11 for coating the surface of the roller core 12 is not particularly limited as long as it is a rubber containing silicone as a main component (hereinafter, may be referred to as silicone rubber), and it is usually preferable to use RTV (Room Temperature Vulcanization) silicone rubber, or a silicone rubber in which a state before it becomes a rubber-like elastic body by crosslinking, which is referred to as liquid silicone rubber, is liquid. Since the liquid rubber is coated on the core 12 before crosslinking and crosslinked, a seamless surface can be easily obtained, and therefore, when the silicone rubber roller 100 is used as the emboss roller 3, a seam is not transferred to the embossed surface of the plastic film.
As a method for coating the rubber layer 11 on the surface of the roller core 12, the method includes, as in the case of manufacturing various rubber rollers: a method of winding a sheet-like uncrosslinked rubber and crosslinking the same; a method of coating or blowing liquid uncrosslinked rubber or filling it in a mold and then crosslinking; and a method of inserting and bonding the roll core 12 to the crosslinked rubber hose.
The silicone rubber layer 11 contains spherical solid particles, and the volume content of each of the spherical solid particles having a particle diameter of 0.8 μm or less and the spherical solid particles having a particle diameter of 30 μm or more is 1% or less of the volume of the entire spherical solid particles. In addition, it is preferable that: the volume content of spherical solid particles having a particle diameter of 8 μm or more among the spherical solid particles is 1% or less of the volume of the entire spherical solid particles. In addition, it is further preferable that: the volume content of the spherical solid particles having a particle diameter of 0.8 μm or less and the volume content of the spherical solid particles having a particle diameter of 8 μm or more are 0.1% or less of the volume of the entire spherical solid particles, respectively.
The inventors of the present application found that: the reason why the surface protection film is indented on the surface of an adherend such as an optical film, for example, a cycloolefin resin (COP) film having a thickness of 50 μm or less, is that: protrusions with a size of 30 μm or more are positioned on the embossing molding surface of the surface protective film. The protrusions are formed by flowing molten resin into fine recesses having a size of 30 μm or more on the surface of the silicone rubber roll for embossing, and the reason for this is found to be the detachment of particles having a particle size of 0.8 μm or less and coarse particles having a size of 30 μm or more among particles contained in the silicone rubber in many cases. Here, the size of the protrusions on the film surface and the micro-depressions on the silicone rubber roller surface means the length in the direction having the longest length in the surface direction of each defect, so-called the major axis length. Further, it was found that: when the shape of the particles is a random shape such as a crushed shape, the particles are likely to aggregate by the shape regardless of the particle diameter.
Based on these findings, the following findings were made: the particles contained in the rubber are spherical solid particles, and the volume content of each of the spherical solid particles having a particle diameter of 0.8 μm or less and the spherical solid particles having a particle diameter of 30 μm or more is 1% or less of the volume of the entire spherical solid particles, whereby most of the fine recesses having a size of 30 μm or more, which are problematic in embossing a film, can be eliminated. Further, by setting the volume content of the spherical solid particles having a particle diameter of 8 μm or more to 1% or less of the volume of the entire spherical solid particles, the surface can be easily formed into a more dense and uniform rind shape, and the rind shape of the embossed surface can be easily prevented from being transferred to the surface of the adherend when the surface protection film is adhered to the adherend and wound up. In addition, since the chips become fine when the surface of the rubber layer 11 is polished, scratches during polishing can be easily prevented. Further, by setting the volume content of the spherical solid particles having a particle diameter of 0.8 μm or less and the volume content of the spherical solid particles having a particle diameter of 8 μm or more to 0.1% or less of the volume of the entire spherical solid particles, even in the case of a large-sized roller having a larger surface area such as a surface length of more than 3m, for example, it becomes easy to more reliably prevent fine depressions and scratches due to aggregation of the particles.
As the spherical solid particles, there can be used: inorganic particles such as alumina, silica, and glass; fluororesin, acrylic resin, and the like. Further, spherical solid particles obtained by subjecting them to surface treatment such as silane coupling treatment may be used. Among them, particles made of a silicone resin are particularly preferably used. The inventors of the present application found that: in the case of particles made of a silicone resin, when the particles are mixed with a silicone rubber, the increase in viscosity and the deterioration in thixotropy can be suppressed more than in the case of other particles. This can suppress the generation of bubbles during mixing and facilitate defoaming, and therefore, the generation of depressions in the surface of the silicone rubber roller due to bubbles can be easily suppressed.
The average particle diameter of the spherical solid particles can be appropriately selected according to the roughness of the intended surface of the pear skin, and when the pear skin of the plastic film used as the surface protective film is intended to be embossed, particles having an average particle diameter of 2 to 5 μm are preferably used. If it is within this range, releasability and slidability are easily imparted by embossing the pearskin surface formed on the film surface, and transfer of the pearskin surface to an adherend is easily prevented. In the measurement of the particle size of the solid particles, a particle size distribution measuring instrument using a laser diffraction/scattering method (for example, LMS-30 manufactured by SEISHIN corporation)
The amount of the spherical solid particles added to the silicone rubber is appropriately selected depending on the roughness of the embossed pear skin surface to be obtained and the rubber hardness, and about 20 to 70% by volume of the rubber and the particles as a whole is a generally acceptable range.
The silicone rubber layer 11 containing the spherical solid particles may be coated on the outermost surface layer of the silicone rubber roller 100 for embossing. For example, another rubber layer or an adhesive layer for adhering the rubber layer 11 and the roller core 12 may be provided between the silicone rubber layer 11 containing the spherical particles and the roller core 12. As the other rubber layer, for example, a layer in which HTV silicone rubber having high thermal conductivity of alumina particles, a layer of rubber softer than the rubber of the silicone rubber layer containing the spherical solid particles, and the like are mixed can be preferably provided. If a rubber layer having high thermal conductivity is provided, the temperature control of the surface of the silicone rubber roller 100 becomes easy. If a soft rubber layer is provided, the width of contact with the embossed surface of the molten resin 2 or film 46 becomes wide, so that the molten resin 2 or film 46 is easily cooled, and the speed of embossing is easily increased.
The rubber hardness of the silicone rubber layer 11 is not particularly limited, but is preferably within the range of 40 to 90Hs JIS A (JIS K6301-1995). In the structure in which the rubber layer is laminated with another rubber layer as exemplified above, it is preferable that the whole of the laminated rubber is within the above range. If the rubber hardness is in the above range, unevenness of contact pressure due to unevenness of processing accuracy of the silicone rubber roller and the opposing roller and thickness in the width direction of the film is easily alleviated at the time of embossing molding, and embossing is easily performed uniformly.
The thickness of the silicone rubber layer 11 is not particularly limited, but is preferably a rubber layer coated with about 1 to 15 mm. In the structure in which the rubber layer is laminated with another rubber layer as exemplified above, it is preferable that the whole of the laminated rubber is within the above range. Within this range, unevenness in contact pressure due to unevenness in processing accuracy of the silicone rubber roller and the opposing roller and thickness in the film width direction can be easily alleviated during embossing, and uniform embossing can be easily performed. In addition, when the temperature of the surface of the silicone rubber roller 100 is controlled by a structure such as circulating a heat medium inside the roller core 12, the temperature control becomes easy.
The silicone rubber roller 100 may be formed in a so-called crown shape in which the outer diameter gradually decreases from the center portion toward the end portions. By setting an appropriate crown shape in accordance with the length, rigidity (flexibility difficulty), and pressure at the time of embossing of the silicone rubber roller 100, a uniform pressure distribution is exhibited in the width direction, and as a result, a film having a uniform embossed pear skin surface in the width direction is easily obtained. In addition, the same effect can be obtained by forming the roll core 11 in a crown shape instead of forming the silicone rubber layer 11 in a crown shape and forming the silicone rubber layer 11 to have a constant outer diameter. In this case, it is preferable that the surface has a constant outer diameter so that abrasion due to a circumferential speed difference in the axial direction does not occur.
The method of removing the surface of the silicone rubber layer 11 and the method of removing the surface are not particularly limited, and it is preferable to perform surface polishing by a rotary grindstone as the removal process of the final processing. In the case of the surface polishing by the rotary grindstone, streaked (japanese: ベスジ -shaped) polishing marks and scratches are less likely to be generated than in the case of cutting and polishing by a cutter (bite) or sandpaper, and the change in the surface shape due to initial wear when the silicone rubber roller 100 is used as the emboss roller is more easily suppressed than in the case of not removing the surface.
Fig. 2 shows an example of a first embodiment of the plastic film manufacturing apparatus according to the present invention. In the first embodiment of the plastic film manufacturing apparatus of the present invention, the molten resin 2 discharged from the T-die 1 is nipped and cooled by the cooling roll 4 and the emboss roll 3, thereby obtaining the plastic film 6. Subsequently, if necessary, the cutting step 21 cuts or trims the edge 23, and the winding step 22 winds the cut or trimmed edge into a roll shape to form the film roll 10. Then, the product is rolled up again through a slitting step and other processing steps as necessary. The mold is not limited to the T-die, but a T-die is preferably used.
The T-die 1 continuously discharges the molten resin 2, which is melted and kneaded by an extruder not shown and conveyed, from a slit provided in a depth direction with respect to the drawing, and thereby extrudes the molten resin 2 into a sheet shape. It is preferable to provide a filter device called a polymer filter between the extruder and the T-die 1 because foreign matter called fish eyes and mixing of deteriorated resin are easily reduced. The width of the slit of the T-die 1 is preferably adjustable for each fixed interval in the width direction of the film 6 to control the thickness variation in the width direction of the film 6. The thickness of the film 6 to be formed can be adjusted by the ratio of the discharge speed of the molten resin 2 to the rotation speed of the cooling roll 4. When the film 6 to be formed has a multilayer structure, a multilayer film can be obtained by providing a stacking device of molten resin called a feed block (feed block) upstream of the T-die 1, or by co-extruding the T-die 1 in a structure having a plurality of manifolds called a multi-manifold structure. Further, the width of the film 6 to be formed may be changed by limiting the width of the flow path of the molten resin 2 in the film width direction.
The T-die 1 is preferably configured to be adjustable in positional relationship with the chill roll 2 and the emboss roll 3. In general, in order to transfer the surface shape of the emboss roller 3 to the molten resin 2 with good accuracy, it is preferable to nip the molten resin 2 in a molten state before cooling, and therefore, as shown in fig. 2, it is preferable to adjust the positions of the T-die 1 or the chill roller 4 so that the molten resin 2 directly enters the nip point, but for the purpose of adjusting the transfer states of the chill roller 4 and the emboss roller 3 on the respective surfaces of the film 6, the positional relationship between the T-die 1 and the chill roller 4 and the emboss roller 3 can be appropriately adjusted.
The temperature of the molten resin 2 may be appropriately set according to the kind of the resin used and the speed of embossing, and may be selected from a range of about 130 to 300 ℃ in the case of a normal polyethylene resin, for example.
As the cooling roller 4, for example, a cooling roller having a flow path for flowing a heat medium therein and capable of controlling the surface temperature can be used. The surface temperature of the cooling roll 4 may be appropriately set depending on the type of the molten resin 2, the contact time between the molten resin 2 and the cooling roll 4, and the room temperature and humidity, but is preferably 10 to 60 ℃ from the viewpoints of the film forming speed and the surface quality of the film. If the surface temperature of the cooling roll 4 is within the above range, the molten resin 2 is easily cooled and solidified within a practical film forming speed range, and the surface quality of the film 6 is easily prevented from deteriorating due to dew condensation occurring on the surface of the cooling roll 4 during film formation.
The surface material of the cooling roll 4 is not particularly limited, and a metal, a ceramic, a composite film of a resin and a metal, or a carbon-based coating such as diamond-like carbon can be used. Further, rubber may be used as the surface material of the cooling roll 4. As the metal, iron, steel, stainless steel, aluminum, titanium, chromium, nickel, or the like can be preferably used. As the ceramic, a sintered body of alumina, silicon carbide, silicon nitride, or the like can be preferably used. Since the surface shape of the chill roll 4 is transferred to the molten resin to become a surface shape opposite to the surface of the film 6 in contact with the emboss roll 3, industrial chromium plating or ceramics having excellent durability and rust prevention are also preferably used from the viewpoint of preventing the appearance quality of the film 6 from being deteriorated and the occurrence of the convex defect. In order to form the surface of the cooling roll 4 into metal, a known surface treatment technique such as electroplating or electroless plating may be used as appropriate, in addition to ordinary machining using a metal material. In addition, in the same manner, in order to obtain a ceramic surface, a known surface treatment technique such as melt blowing or coating may be appropriately used in addition to ordinary mechanical processing using a ceramic material.
The surface shape of the cooling roll 4 is transferred to the molten resin 2, and determines the shape of the surface of the film 6 opposite to the surface in contact with the emboss roll 3. Therefore, the surface shape of the cooling roll 4 is appropriately designed according to the film 6 produced using the apparatus for producing a plastic film of the present invention, and in the case of producing a surface protective film, the arithmetic average roughness Ra (JIS B0601: 2013) of the cooling roll 4 is preferably 0.2 μm or less, and more preferably Ra is 0.1 μm or less. In the case of producing the surface protective film, the above-mentioned opposite surface is a surface to be bonded to a surface of an adherend (hereinafter referred to as a bonding surface), and the larger the arithmetic average roughness Ra of the bonding surface is, the smaller the bonding force is, and the more difficult the bonding to the adherend is, so that the above-mentioned range is preferable. Although the adhesive strength can also be enhanced by mixing an additive such as a tackifier with the resin, the additive may remain on the adherend when the surface protective film is peeled off from the adherend or the recycling of the resin may be difficult due to the additive, and therefore it is preferable in terms of quality and cost that the surface roughness be in the above range and the resin alone exhibit sufficient adhesive strength as a surface protective film. It should be noted that it is very difficult and costly to manufacture the arithmetic average roughness Ra to be less than 0.001 μm, and therefore the arithmetic average roughness Ra is preferably 0.001 μm or more, but the effect of the present invention is not lost even if it is less than 0.001 μm. The arithmetic mean roughness Ra of the chill roll 4 can be made 0.2 μm or less by normal mirror polishing such as buffing.
The emboss roller 3 is the silicone rubber roller 100 for emboss molding of the present invention. As described above, the silicone rubber roller 100 for embossing of the present invention suppressed surface depressions having a size of 30 μm or more. Since the protrusion defect is generated by the molten resin flowing into the depressions of the surface of the emboss roller and solidifying, by using the silicone rubber roller of the present invention as the emboss roller 3, it is possible to suppress the generation of the protrusion defect on the surface of the film 6 on the emboss roller 3 side. When the produced film 6 is a surface protective film, as described above, it was found that a projection defect having a size of 30 μm or more may cause an indentation in an adherend, and according to the present invention, the indentation can be greatly reduced.
As means for pressing the emboss roller 3 against the chill roller 4 and nipping the molten resin 2, a method of controlling a gap between the chill roller 2 and the emboss roller 3, or a press-in amount of the emboss roller 3, that is, a relative position of the emboss roller 3 and the chill roller 4 by a method of sandwiching a tapered block or the like may be used, or a method of controlling a force of pressing the emboss roller 3 by an air cylinder or the like may be used. However, in the case of forming a film such that the thickness of the molten resin 2 at the nip point (nip point) is 100 μm or less, or in the case of forming an elastic body coated on the emboss roller 3 having a rubber hardness of 90Hs JIS a or more, the pressure unevenness may become excessive in the control based on the press-in amount, and therefore, a method of controlling the pressing force is preferable. The pressing pressure may be set as appropriate, but is preferably in the range of about 0.1 to 5 kN/m. If the pressing pressure is in the above range, transfer of the surface of the emboss roller 3 onto the molten resin 2 is easily performed well.
As shown in fig. 3, the molten resin 2 is sandwiched between the cooling roll 4 and the cooling belt 34, whereby the film 6 can be similarly obtained.
The cooling belt 34 is conveyed by a pressing roller 35 and a cooling conveyance roller 36. The pressing roller 35 may be a rubber roller coated with rubber on the surface thereof, but the pressing roller 35 need not be a rubber roller in view of the fact that the opposing emboss roller 3 is coated with rubber. When the surface of the squeeze roll 35 is not rubber, the surface thereof can be subjected to a general surface treatment such as industrial chromium plating. The squeeze roller 35 and the cooling conveyance roller 36 are preferably configured to cool the cooling belt 34 while having a temperature control function such as a configuration in which a heat medium is circulated inside. By cooling the cooling belt 34, the releasability from the molten resin is improved, and a film can be easily formed at a high speed. The pressing roll 35 nips the molten resin 2 with the emboss roll 3 via the cooling belt 34. The cooling conveyance roller 36 may be similarly pressed against the emboss roller 3, or may be merely brought close to it without being pressed against it. If the cooling conveyor roller 36 is formed in a crown shape, the cooling belt 34 is less likely to run in a curved manner, which is preferable. In this case, it is preferable that each cooling conveyor roller has a temperature adjusting function for controlling the temperature of the cooling belt 34 or a function of preventing the cooling belt 34 from moving in a curved manner. As a function of preventing the cooling belt 34 from meandering, in addition to the crown shape described above, a so-called Edge Position Controller (EPC) may be used which monitors the widthwise position of the conveyor belt 54 with an optical sensor or the like, and automatically adjusts the angle of the cooling conveyor roller 36 with respect to the belt conveying direction to correct meandering when meandering occurs.
Since the surface of the cooling belt 34 may be transferred to the surface of the film 6 if a seam is present, the cooling belt 34 is preferably a seamless endless belt, and the material is not particularly limited, but a cooling belt made of metal such as stainless steel or nickel may be used.
The thickness of the cooling belt 34 is not particularly limited, and a cooling belt having a thickness of 30 μm to 500 μm can be preferably used. When the amount is within this range, a cooling zone which is easy to manufacture and has sufficient strength and bendability can be easily obtained.
Fig. 4 shows another embodiment of the plastic film manufacturing apparatus according to the present invention. In this embodiment, the film 46 is heated by a heating means 41 for a plastic film (hereinafter simply referred to as heating means) to soften at least the surface of the side on which embossing is performed to a state in which embossing is possible, and then is nipped by the embossing roll 3 and the carrier roller 42 to perform embossing.
The surface temperature of the film 46 before embossing may be appropriately set depending on the kind of resin used and the speed of embossing, and for example, in the case of a normal polyethylene resin, the surface temperature may be selected from the range of about 130 ℃ to 300 ℃.
The production process of the film 46 before the embossing is not particularly limited, and a film obtained by a so-called T-die method, which is a process of forming a film by discharging a resin melted and kneaded by an extruder in a web form from a T-die, and cooling and solidifying the resin on a cooling roll, may be used as it is, or a film produced by another film production apparatus may be temporarily wound up as shown in fig. 4 to produce a film roll 40, and the film roll 40 may be unwound from an unwinding apparatus. Further, a film produced by a general method for producing a plastic film such as inflation may be used, or a film obtained by subjecting the surface opposite to the surface subjected to embossing of the film 46 to various surface treatments such as plasma treatment, coating, and vapor deposition, or a film cut into an arbitrary width may be used.
As the heating unit 41, a heating unit generally used in a film production process, for example, an infrared heater, a hot air generator, an induction heating roller, or the like can be used. The film 6 may be heated at once to a temperature at which embossing is possible, or may be heated in stages by a plurality of heating units. When the film 6 is heated to a temperature at which embossing is possible, it may stick to a metal surface or the like, and therefore the following method is preferably used: the sheet is heated to a temperature at which the sheet does not adhere to the sheet by a contact heating means such as an induction heating roller, and then heated to a temperature at which embossing is possible by a non-contact heating means such as an infrared heater. By heating in stages in this manner, wrinkles and deformation of the film 6 during heating can be easily prevented.
The emboss roller 3 is the silicone rubber roller 100 for emboss molding of the present invention. By using the silicone rubber roller of the present invention as the emboss roller 3, it is possible to suppress the occurrence of the projection defect on the surface of the film 46 on the emboss roller 3 side, as in the other embodiments described above.
The carrier roller 42 may be made of the same material and structure as those of a film transport roller used in a general film production apparatus and a processing apparatus, and preferably has a temperature adjusting function by allowing a heat medium to flow therein or by providing a heater or the like. By having the temperature adjusting function, the temperature of the film 46 is easily kept constant, and unevenness of embossing processing is easily prevented.
The surface material and shape of the backup roll 42 can be appropriately selected according to the film to be produced, similarly to the cooling roll 4. For example, in the case of manufacturing a surface protective film, since the surface of the film 46 opposite to the surface in contact with the emboss roller 3 is preferably smoothed for obtaining adhesion, the Ra of the surface of the backup roller 42 is preferably 0.2 μm or less, more preferably 0.1 μm or less, as in the case of the cooling roller 4. On the other hand, in the case of producing a film having a pearskin surface on both sides, the surface of the carrier roller 42 may be formed into a pearskin shape and simultaneously embossed with the surface in contact with the emboss roller 3.
The means for pressing the emboss roller 3 against the backup roller 42 and nipping the film 46 may be any of various means as in the case of pressing against the chill roller 4, but it is preferable to press by an air cylinder.
In another embodiment of the plastic film manufacturing apparatus of the present invention, as shown in fig. 5, a conveyor belt 54 may be used instead of the carrier roller 42.
The conveyor belt 54 is preferably an endless belt having no seam on the surface, as in the cooling belt 34, and the material is not particularly limited, and for example, a conveyor belt made of metal such as stainless steel or nickel may be used.
The thickness of the conveyor belt 54 is not particularly limited, and a conveyor belt having a thickness of 30 μm to 500 μm can be preferably used. Within this range, a conveyor belt which can be easily produced and has sufficient strength and flexibility can be easily obtained.
As shown in fig. 5, in the case of using the conveyor belt 54, the film 46 may be heated on the conveyor belt using the heating unit 41. Since the rigidity of the film 46 is lowered when the film 46 is heated for embossing, for example, a film having a thickness of 100 μm or less, or a film made of only a resin having low rigidity, for example, low-density polyethylene, may be stretched or broken between rollers in a so-called free span. When the conveyor belt 54 is heated, the conveyor belt 54 supports the film 46, and therefore, even the above-described film is unlikely to cause such problems.
The conveying belt 54 is conveyed by a belt conveying roller 55 and the pressing roller 52. The press roll 52 may be a rubber roll as in the press roll 35, or may be a metal roll subjected to a normal surface treatment. The tape conveying roller 52 may be plural, and it is preferable that each tape conveying roller has a temperature adjusting function for controlling, for example, the temperature of the conveying tape 54 or a function of preventing the conveying tape 54 from meandering. As the temperature adjusting function, a heat medium may be circulated inside the roller, or various heaters may be provided. As a function of preventing the meandering of the transport belt 54, a method of gradually reducing the outer diameter of the belt transport roller 55 from the widthwise central portion to the end portion may be used as the simplest method, and a so-called Edge Position Controller (EPC) that monitors the widthwise position of the transport belt 54 with an optical sensor or the like and automatically adjusts the angle of the belt transport roller 55 with respect to the belt transport direction to correct the meandering when the meandering occurs may be used.
The surface protective film of the present invention can be produced by the silicone rubber roll for embossing of the present invention, the method and the apparatus for producing a plastic film using the silicone rubber roll, and as described above, the silicone rubber roll for embossing of the present invention can suppress the protrusion of the embossed surface, and therefore, even when the adherend is a thin optical film such as a COP film of 30 μm or less, the indentation can be suppressed.
The surface protective film of the present invention may have a single-layer structure or a multilayer structure including 2 or more layers. For example, in the case of a single-layer structure, equipment cost and maintenance cost can be suppressed in order to simplify the device configuration, and in the case of a 3-layer structure and using a recycled material for the intermediate layer, material cost can be suppressed. Even when the resin is formed into a single-layer structure or a multi-layer structure, the raw material can be easily reused as long as the resins of the respective layers are made of the same material.
The outermost surface of at least one surface of the surface protective film of the present invention is a pearskin surface having fine irregularities. Since the surface protection film has adhesive force on one surface, the other surface is made to be a pearskin surface in order to prevent the surface and the back surface of the film from sticking to each other and becoming unable to peel off or becoming wrinkles when wound in a roll. However, when the uneven shape of the pearskin surface is rough, the following problems may occur: when the film is rolled up into a roll shape, the shape of the unevenness is transferred to the adhesive surface to reduce the adhesive force; or the shape of the unevenness is transferred to the surface of the adherend when the adhesive sheet is wound into a roll after being attached to the adherend; and the like. It is preferable that the RzJIS (JIS B0601: 2013) of the pear peel surface is 1 to 5 μm and the average length RSm (JIS B0601: 2013) of the roughness curve elements is 5 to 40 μm, because these problems are less likely to occur. Further, if the RzJIS is 1 to 3 μm and the RSm is 5 to 15 μm, these problems are less likely to occur even when the adherend is a material to which unevenness is highly likely to be transferred, for example, a cycloolefin film having a thickness of 20 μm or less, and therefore, the RzJIS is more preferable. In the measurement of RzJIS and RSm, a stylus-type surface roughness meter is generally used, but when the stylus-type surface roughness meter is a compact and fine shape in the above range and is made of a soft material such as polyethylene resin, the stylus cannot be accurately measured because the diameter of the stylus tip is large, and the stylus may have different values depending on mechanical errors such as the shape of the tip of the stylus and the contact pressure. Therefore, for the measurement of RzJIS and RSm, a high-precision and non-contact measurement means such as a laser microscope and a white interferometer is preferably used.
Since the peel surface of the surface protective film of the present invention is obtained by embossing the surface shape of the silicone rubber roll for embossing of the present invention, the concave and convex portions of the peel surface have a substantially hemispherical shape. In addition, since the projections and recesses are formed by embossing, the projections are formed of a single material and are formed of the same material as the portions where the recesses are formed.
On the other hand, as a method for obtaining a pearskin surface without using embossing, for example, a method of mixing a different material such as solid particles with a resin constituting a layer of the pearskin surface is included. In this case, if spherical particles or the like are mixed as a different material, the convex portions of the concave and convex portions of the pear peel surface may be formed into a substantially hemispherical shape, but the concave portions cannot be formed into a substantially hemispherical shape, and the material of the convex portions is composed of 2 or more kinds of materials and includes a material different from the portion where the concave portions are formed.
The resin constituting the surface protective film of the present invention is not particularly limited, and may be suitably selected from polyesters represented by polyethylene terephthalate, polyethylene-2, 6-naphthalate and the like, polyolefins represented by polyethylene, polypropylene and the like, polyethylene represented by polyvinyl chloride, polyvinylidene chloride and the like, polyamides, aromatic polyamides, polyphenylene sulfides and the like, depending on the required characteristics, and polyolefins may be preferably used. Among them, it is particularly preferable to use Low Density Polyethylene (LDPE) and Linear Low Density Polyethylene (LLDPE) for the layer forming the pearskin surface and the layer forming the adhesive surface. When the unevenness of the pearskin surface is formed of a hard resin, the following problem may occur: when the film is wound in a roll, the shape of the irregularities is transferred to the adhesive surface to reduce the adhesive force, or when the film is wound in a roll after being attached to an adherend, the shape of the irregularities is transferred to the surface of the adherend. LDPE and LLDPE are soft, and therefore these problems are not likely to occur. In addition, these resins can exhibit adhesive force to a smooth adherend without adding an additive such as a pressure-sensitive adhesive by setting the arithmetic average roughness Ra (JIS B6010: 2013) of the surface to 0.1 μm or less. This is preferable because the adhesive can be prevented from remaining on the surface of the adherend when the surface protective film is peeled off due to bleeding of the adhesive. On the other hand, other resins may be used for the layers other than the pearskin surface-forming layer and the adhesive surface-forming layer. For example, when the film is composed of only LDPE or LLDPE, the rigidity is insufficient, and the rigidity can be improved by using high-density polyethylene or polypropylene. In some cases, a surface protective film having a high rigidity to some extent is less likely to cause a process problem such as wrinkles or curling, and is more easily used.
Examples
The present invention will be described more specifically with reference to examples below, but the present invention is not limited to these examples. Various evaluation and measurement methods are shown below.
[ number of depressions on the surface of the roll ]
The surface of the produced roller was sampled at 3 places in a size of a square having a side of 3cm (hereinafter referred to as 3cm square), and observed with a laser microscope. Counting the number of pits with a long side of 30 μm or more for each sample, and forming 3 pits for each sampleThe number of traps was counted up to 27cm2The number of depressions in (a).
[ number of indentations ]
A retardation film having a smooth surface and a thickness of 40 μm and formed of a cycloolefin resin was used as an adherend. The surface protective films of examples 3 to 5 and comparative example 2 after being stored at a temperature of 23 ℃ and a humidity of 50% RH for 24 hours were attached to an adherend using a roll press (a special pressure-bonding roll manufactured by Antian Seiko Co., Ltd.) at a bonding pressure of 9,100N/m and a bonding speed of 300 cm/min. Then, both sides were held by a smooth polycarbonate plate (plate thickness 2mm), and 1.3kg/cm was applied2The load of (2) was stored in a hot air oven at 60 ℃ for 3 days. Then, the temperature was returned to room temperature, and the surface protective film was peeled off from the adherend. The adherend was sampled at 3 places in a 3cm square, and whether or not indentations were generated in the adherend was visually checked, and the total number of indentations at 3 was counted.
[ volume content of solid particles (particle size distribution) ]
The particle size distribution was measured on a volume basis using a laser diffraction/scattering particle size distribution measuring instrument (LMS-30, manufactured by SEISHIN corporation), and the volume content of solid particles having an arbitrary particle size or less and above was measured by integral distribution.
[ example 1]
Spherical alumina particles having a volume average particle diameter of 3.5 μm were classified so as not to contain particles having a particle diameter of 0.8 μm or less and particles having a particle diameter of 30 μm or more, and then added to an RTV silicone rubber raw material containing no solid particles. The particle size distribution of the classified alumina spherical particles was measured, and as a result, the particles having a particle diameter of more than 8 μm and less than 30 μm were contained in an amount of 2.5% by volume. A mixture of the RTV silicone rubber raw material and the alumina spherical particles was stirred and defoamed, and a roll core having a structure shown in fig. 1 was lined. Then, the surface of the silicone rubber was polished with a rotating grindstone to obtain an embossing silicone rubber roller coated with a silicone rubber having a thickness of 10 mm. The rubber hardness of the silicone rubber layer thus obtained was 80Hs JIS A (JIS K6301-1995).
[ example 2]
Spherical silicone resin particles having a volume average particle diameter of 3.5 μm, which do not contain solid particles having a particle diameter of 0.8 μm or less and particles having a particle diameter of 8 μm or more, are added to an RTV silicone rubber raw material containing no solid particles. A mixture of the RTV silicone rubber raw material and the silicone resin spherical particles was stirred and defoamed, and a roll core having a structure shown in fig. 1 was lined. Then, the surface of the silicone rubber was polished with a rotating grindstone to obtain an embossing silicone rubber roller coated with a silicone rubber having a thickness of 10 mm. The rubber hardness of the silicone rubber layer obtained was 81Hs JIS A (JIS K6301-.
Comparative example 1
Spherical alumina particles having a volume average particle diameter of 3 μm and a cut point (cut point) of 11 μm were directly added to an RTV silicone rubber raw material containing no solid particles without being subjected to classification treatment. A mixture of the RTV silicone rubber raw material and the alumina spherical particles was stirred and defoamed, and the roll core having the structure shown in fig. 1 was lined. Then, the surface of the silicone rubber was polished with a rotating grindstone to obtain an embossing silicone rubber roller coated with a silicone rubber having a thickness of 10 mm. The rubber hardness of the silicone rubber layer thus obtained was Hs80JIS a. The alumina spherical particles before addition contain particles having a particle diameter of 0.8 μm or less in an amount of 2 to 3% by volume of the whole.
The production results of examples 1 and 2 and comparative example 1 are shown in table 1. In comparative example 1, the number of depressions having a size of 300 μm or more was 0, but the number of depressions having a size of 100 μm or more and less than 300 μm was 1, and the number of depressions having a size of 30 μm or more and less than 100 μm was 200 or more. On the other hand, in example 1, only 2 depressions of 30 μm or more and less than 100 μm were formed, and in example 2, 0 depression was formed. In addition, when the surface is scratched, the surface polishing is performed until no scratch is generated. The number of times of polishing was performed until a surface free from scratches was obtained was 15 times in comparative example 1. On the other hand, this was completed 5 times in example 1. Further, in example 2, the polishing was carried out 1 time, i.e., without further polishing.
[ Table 1]
[ example 3]
The apparatus for manufacturing a plastic film shown in fig. 2 was used. The discharge density was 0.93g/cm in 1-monolayer formation from a T-die having a slit width adjusted to 0.9mm at 220 deg.C3The low-density polyethylene (LDPE) of (2) was nipped and cooled by a chill roll and an emboss roll to obtain a surface protective film having a thickness of 30 μm. The embossing roll used the silicone rubber roll produced in example 1.
[ example 4]
A surface protective film was obtained by the same production apparatus and production method as in example 3, except that the silicone rubber roll produced in example 2 was used as an emboss roll.
[ example 5]
Prepared by using a T-die method in advance and coiled, and the density of the coiled material is 0.93g/cm31 monolayer film of Low Density Polyethylene (LDPE). Using the apparatus for producing a plastic film shown in fig. 5, the film was unwound, heated by an infrared heater serving as a heating means so that the surface of the film became 180 °, and subjected to nip pressing and cooling by a conveyor belt and an emboss roller, thereby obtaining a surface protective film having a thickness of 30 μm. The embossing roll used the silicone rubber roll produced in example 1.
Comparative example 2
A surface protective film was obtained by the same production apparatus and production method as in example 3, except that the silicone rubber roll produced in comparative example 1 was used as the emboss roller.
The surface protective films obtained in examples 3 to 5 and comparative example 2 were treated as described in [ number of indentations ] above, and the number of indentations of the adherend was measured. More than 200 indentations were observed in comparative example 2. On the other hand, only 1 indentation was observed in examples 3 and 5, and no indentation was observed in example 4.
Industrial applicability
The present invention is not limited to the apparatus and the method for producing the surface protective film, and may be applied to an apparatus and a method for producing a plastic film having at least one embossed pear skin surface, but the scope of application is not limited thereto.
Description of the reference numerals
1T type mould
2 melting the resin
3 embossing roller
4 Cooling roll
5 peeling roller
6 film
7 cutting machine
8 edge suction tube
9 near roller
10 film roll
11 Silicone rubber layer
12 roller core
13 flow path for heat medium
14 bearing
21 cutting process
22 coiling step
23 film edge
34 cooling zone
35 squeeze roll
36 cooling conveying roller
40 film roll before embossing
41 heating unit for plastic film
42 idler
46 film before embossing
52 squeeze roll
54 conveyor belt
55-belt conveying roller
Silicone rubber roller for 100 embossing
A direction of film advance