JP7407694B2 - Film manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a film.

BACKGROUND ART Conventionally, a film manufacturing method is known that includes a step of melt-extruding a resin to form a film and a step of stretching the formed resin film (see, for example, Patent Document 1).

Japanese Patent Application Publication No. 2020-023170

In the method described in Patent Document 1 mentioned above, if the formed resin film is made of resin that is easily broken (brittle resin), the resin film may break during stretching.

The present invention provides a method for producing a film that can suppress expansion of the fractured portion when a portion of the base material is fractured during stretching of the base material.

The present invention [1] includes an attaching step of attaching an adhesive tape to a base material made of brittle resin and conveyed in the flow direction in a width direction perpendicular to the flow direction, and the base material to which the adhesive tape is attached. and a stretching step of stretching a material together with the adhesive tape.

According to such a method, the base material is stretched together with the adhesive tape while the adhesive tape is attached to the base material.

Therefore, when a part of the base material breaks during stretching, the adhesive tape can suppress the spread of the broken part.

The present invention [2] includes the method for manufacturing a film according to the above [1], wherein in the pasting step, a plurality of the adhesive tapes are pasted on the base material at regular intervals in the flow direction of the base material.

According to such a method, when a part of the base material is broken during stretching, expansion of the broken part can be suppressed at regular intervals.

The present invention [3] provides the above-mentioned [1] or [1], further comprising a cutting step of cutting the base material at a location where the adhesive tape is pasted after the pasting step and before the stretching step. 2].

According to this method, the base material is cut at the point where the adhesive tape is pasted, so the adhesive tape is stuck to the edge of the cut base material (the edge created by cutting). It remains.

Therefore, when the cut base material is stretched in the stretching process, the adhesive tape can prevent the base material from breaking from the edges caused by cutting.

In the present invention [4], the base material is made of acrylic resin, and the adhesive tape has an adhesive tape base material made of polyolefin resin, and an adhesive layer disposed on one side of the adhesive tape base material. , including the method for producing a film according to any one of [1] to [3] above.

In the present invention [5], the adhesive tape has an adhesive tape base material and an adhesive layer disposed on one side of the adhesive tape base material, and the elongation rate of the adhesive tape base material is 21°C. includes the method for producing a film according to any one of [1] to [3] above, wherein the film is 200% or more and 800% or less.

The present invention [6] provides the film according to any one of [1] to [5] above, wherein the adhesive strength of the adhesive tape to the base material is 5 N/18 mm or more and 20 N/18 mm or less at 25°C. Including manufacturing method.

According to the film manufacturing method of the present invention, when a part of the base material is broken during stretching of the base material, expansion of the broken part can be suppressed.

FIG. 1 is a cross-sectional view of a film manufactured by a film manufacturing system. FIG. 2 is a schematic diagram of a film manufacturing system. FIG. 3A is an explanatory diagram illustrating a method for manufacturing a film as an embodiment of the present invention, and shows a pasting process. FIG. 3B is an explanatory diagram for explaining the film manufacturing method together with FIG. 3A, and shows the first stretching step. FIG. 3C is an explanatory diagram for explaining the film manufacturing method together with FIGS. 3A and 3B, and shows a second stretching step. FIG. 4 is a cross-sectional view of the adhesive tape shown in FIG. 3A. FIG. 5 is an explanatory diagram for explaining a modification, and shows a cutting process.

1. Film Manufacturing System A manufacturing system 1 for film F will be described.

As shown in FIG. 1, the film F includes a base material S and a coating C. The base material S has a first surface S1 and a second surface S2 in the thickness direction of the base material S. The coating C is arranged on the first surface S1 of the substrate S. The coating C covers the first surface S1 of the base material S. The coating C may be an easily adhesive layer. When coating C is an easily adhesive layer, film F is an easily adhesive film. Easily adhesive films are used, for example, in polarizing plates of image display devices such as mobile devices, car navigation devices, personal computer monitors, and televisions. Specifically, the easily adhesive film is used as a protective film that protects the polarizer of a polarizing plate. The easily adhesive film is bonded to a polarizer via an adhesive layer. The easily adhesive film is bonded to the polarizer using the easily adhesive layer.

As shown in FIG. 2, the film F manufacturing system 1 includes an extrusion molding device 2, a first stretching device 4A as an example of a stretching device, a coating device 3, a second stretching device 4B, and a slitting device. 5, a knurling device 6, and a winding device 7.

(1) Extrusion molding device The extrusion molding device 2 extrudes the base material S (extrusion molding process). The base material S extruded from the extrusion molding device 2 has a sheet shape. The base material S is conveyed in the machine direction MD.

The base material S is made of thermoplastic resin. Examples of thermoplastic resins include acrylic resins, polyolefin resins, cyclic polyolefin resins, polyester resins (polyethylene terephthalate, etc.), polycarbonate resins, polystyrene resins, polyamide resins, polyimide resins, acetate resins (diacetyl cellulose, triacetyl cellulose, etc.), and the like. can be mentioned.

When producing an easily adhesive film used as a protective film for a polarizer, the material for the base material S is preferably an acrylic resin.

Furthermore, when producing an easily adhesive film used as a protective film for a polarizer, the acrylic resin may be an acrylic resin having a glutaric anhydride structure or an acrylic resin having a lactone ring structure. Acrylic resins with a glutaric anhydride structure and acrylic resins with a lactone ring structure have high heat resistance, high transparency, and high mechanical strength, so they are suitable for polarizing plates with a high degree of polarization and excellent durability. Suitable for manufacturing. Acrylic resins having a glutaric anhydride structure are described in JP-A No. 2006-283013, JP-A No. 2006-335902, and JP-A No. 2006-274118. Acrylic resins having a lactone ring structure are described in JP 2000-230016, JP 2001-151814, JP 2002-120326, JP 2002-254544, and JP 2005-146084. has been done.

Moreover, in addition to the acrylic resin, the base material S may contain a thermoplastic resin other than the acrylic resin. By containing another thermoplastic resin, the birefringence of the acrylic resin can be canceled out, and an easily adhesive film with excellent optical isotropy can be obtained. Moreover, the mechanical strength of the easily adhesive film can also be improved.

Note that the base material S may contain additives such as antioxidants, stabilizers, reinforcing materials, ultraviolet absorbers, flame retardants, antistatic agents, colorants, fillers, plasticizers, lubricants, and fillers. .

In this embodiment, the base material S is made of brittle resin. The term "brittle resin" refers to a resin among the above-mentioned thermoplastic resins that can withstand less than 50 folds in a folding strength test according to JIS P 8115:2001.

The folding strength test is conducted under the following conditions using BE-202 (manufactured by Tester Sangyo) as a testing machine.

<Bending strength test conditions>
Test piece size: width 15mm, length 110mm
Test speed: 175cpm
Bending angle: 135°
Load: 200g heavy Bending clamp radius of curvature R: 0.38mm
Bending clamp opening: 0.25mm
When the base material S is made of a brittle resin, the base material S is easily broken when the base material S is stretched by the first stretching device 4A and the second stretching device 4B.

Specifically, in this embodiment, the base material S is made of a brittle resin in an unstretched state. The unstretched state is a state after the extrusion molding process but before the extruded base material S is stretched in the machine direction MD or the width direction TD. The width direction TD is orthogonal to the flow direction MD.

This embodiment is preferable for brittle resins that can be folded less than 10 times, and more preferably for brittle resins that can be folded less than 5 times.

Specifically, the brittle resin includes acrylic resin.

(2) First stretching device The first stretching device 4A heats the base material S extruded in the extrusion molding process, and then stretches it in the machine direction MD of the base material S (first stretching process).

(3) Coating device The coating device 3 applies a coating liquid to the first surface S1 of the base material S (coating process). Examples of the coating device include a bar coater, a gravure coater, and a kiss coater. Note that the first surface S1 of the base material S may be subjected to surface treatment such as corona treatment or plasma treatment after the extrusion molding process and before the coating process.

When producing an easily adhesive film, the coating liquid is an easily adhesive composition for forming an easily adhesive layer.

The easily adhesive layer contains a binder resin and fine particles.

Examples of the binder resin include thermosetting resins such as urethane resin and epoxy resin, and thermoplastic resins such as acrylic resin and polyester resin. When the easily adhesive film is used as a protective film for a polarizer, the binder resin is preferably a thermosetting resin. Multiple types of binder resins can be used in combination.

Examples of fine particles include oxides such as silicon oxide (silica), titanium oxide (titania), aluminum oxide (alumina), and zirconium oxide (zirconia); carbonates such as calcium carbonate; Examples include silicates such as aluminum acids and magnesium silicate, silicate minerals such as talc and kaolin, and phosphates such as calcium phosphate. When the easily adhesive film is used as a protective film for a polarizer, the fine particles are preferably an oxide, more preferably silicon oxide. Multiple types of fine particles can be used in combination.

The coating liquid (adhesive composition) contains a resin component, the above-mentioned fine particles, and a dispersion medium.

The resin component forms the above-mentioned binder resin film (easily adhesive layer) through a stretching process described later. When the binder resin is a urethane resin, examples of the resin component include water-based urethane resins. Examples of water-based urethane resins include non-reactive water-based urethane resins that are emulsions of urethane resins, and reactive water-based urethane resins that are emulsions of urethane resins whose isocyanate groups are protected with blocking agents. When the binder resin is a urethane resin, the coating liquid may contain a urethane curing catalyst (such as triethylamine) and an isocyanate monomer.

Examples of the dispersion medium include water, alcohols such as methanol and ethanol, and ketones such as acetone and methyl ethyl ketone.

(4) Second stretching device The second stretching device 4B dries the coating liquid applied in the coating process. As a result, the coating liquid becomes the coating C described above. Further, the second stretching device 4B heats the base material S on which the coating film C is formed, and then stretches it in the width direction TD of the base material S (second stretching step). In the second stretching step, the base material S on which the coating C is formed is stretched in the width direction TD, and the film F described above is obtained.

(5) Slitting device The slitting device 5 cuts the film F stretched in the second stretching step into a predetermined width (slitting step).

(6) Knurling device The knurling device 6 forms knurls at both ends in the width direction of the film F cut into a predetermined width by the slitting process (knurling process). Knarls are formed by laser. The knurls may be formed by heated embossing rolls.

(7) Winding device The winding device 7 winds up the film F in which knurls have been formed in the knurling process (winding process). By completing the winding process, a roll of film F can be obtained.

2. Method for Manufacturing Film As shown in FIGS. 3A to 3C, the method for manufacturing film F includes a pasting process (see FIG. 3A) and a stretching process (see FIGS. 3B and 3C).

(1) Attaching step In the attaching step, the operator attaches the adhesive tape 100 to the base material S extruded in the extrusion molding step, as shown in FIG. 3A, before the first stretching step. The adhesive tape 100 is attached to the second surface S2 of the base material S. In a state where the adhesive tape 100 is attached to the base material S, the adhesive tape 100 extends in the width direction TD. Adhesive tape 100 has a linear shape. Preferably, the adhesive tape 100 is pasted from one end of the base material S in the width direction TD to the other end of the base material S in the width direction TD.

Preferably, in the pasting process, an operator pastes a plurality of adhesive tapes 100 onto the base material S at regular intervals in the machine direction MD. Thereby, when a part of the base material is broken during stretching, expansion of the broken part can be suppressed at regular intervals. Note that the constant interval is 0.5 times or more and 1.5 times or less the width of the base material S.

The adhesive tape 100 attached to the base material S can be stretched together with the base material S in the first stretching process and the second stretching process. Specifically, as shown in FIG. 4, the adhesive tape 100 includes an adhesive tape base material 101 and an adhesive layer 102 disposed on one side of the adhesive tape base material 101.

The elongation rate of the adhesive tape base material 101 is, for example, 200% or more, preferably 300% or more at 21°C. When the elongation rate of the adhesive tape base material 101 is equal to or higher than the above lower limit value, the adhesive tape 100 can be stretched together with the base material S in the first stretching process and the second stretching process. The upper limit of the elongation rate of the adhesive tape base material 101 is not limited. The elongation rate of the adhesive tape base material 101 is, for example, 800% or less, preferably 600% or less. The elongation rate of the adhesive tape base material 101 is measured by a tensile test specified in JIS K7161-1:2014 at a test speed of 50 mm/min and a test temperature of 21±2°C.

Examples of the material for the adhesive tape base material 101 include polyolefin resin and amorphous polyethylene terephthalate. The material of the adhesive tape base material 101 is preferably polyolefin resin.

The adhesive strength of the adhesive tape 100 to the base material S is, for example, 5 N/18 mm or more, preferably 6 N/18 mm or more at 25°C. When the adhesive strength of the adhesive tape 100 is equal to or higher than the above lower limit value, peeling of the adhesive tape 100 from the base material S can be suppressed in the first stretching process and the second stretching process. The adhesive force of the adhesive tape 100 to the base material S is, for example, 20 N/18 mm or less, preferably 10 N/18 mm or less at 25°C. The adhesive strength of the adhesive tape 100 to the base material S is measured by the 180° peel adhesive strength measuring method specified in JIS Z0237:2000.

The adhesive layer 102 may be made of, for example, an acrylic adhesive.

(2) Stretching process Next, in the stretching process, the base material S to which the adhesive tape 100 is attached is stretched together with the adhesive tape 100 in the machine direction MD (see FIG. 3B) in the first stretching process described above. In the second stretching step, the film is stretched in the width direction TD (see FIG. 3C). Thereby, even if a part of the base material S is broken during stretching, the adhesive tape 100 can suppress the spread of the broken part.

When the base material S is an acrylic resin (softening temperature: 120°C), in the first stretching step and the second stretching step, the base material S is, for example, 100°C or higher, preferably 120°C or higher, for example, 140°C. Hereinafter, it is preferably heated to 130° C. or lower.

In the first stretching step, the base material S is stretched in the machine direction MD by, for example, 1.5 times or more, preferably 2.0 times or more, and for example, 3.0 times or less.

In the second stretching step, the base material S is stretched in the width direction TD by, for example, 1.5 times or more, preferably 2.0 times or more, and for example, 3.0 times or less.

Note that the operator may peel off the adhesive tape 100 from the base material S after the second stretching process and before the slitting process.

3. Modifications (1) As shown in FIG. 5, the method for manufacturing film F may further include a cutting step. In the cutting process, the operator cuts the base material S at the location where the adhesive tape 100 is pasted after the pasting process (see FIG. 3A) and before the stretching process (see FIG. 3B). Specifically, the operator cuts the area to which the adhesive tape 100 is pasted along the adhesive tape 100 in the width direction TD.

In this case, since the base material S is cut at the location where the adhesive tape 100 is pasted, the adhesive tape 100 is pasted on the edge E of the cut base material S (edge E generated by cutting). remain in the state.

Therefore, when the cut base material S is stretched in the stretching process, the adhesive tape 100 can prevent the base material S from breaking from the edge E generated by cutting.

(2) The film F production system 1 may further include a pre-stretch slitting device. The pre-stretch slitting device cuts the base material S into a predetermined width after the extrusion molding process and before the first stretching process (pre-stretch slitting process). In this case, in the pasting step, the adhesive tape 100 is pasted at the location to be cut in the pre-stretch slitting step, and in the pre-stretch slitting step, the base material S is cut at the location where the adhesive tape 100 is pasted. Good too.

(3) The film F manufacturing system 1 does not need to include the extrusion molding device 2. In this case, in the pasting step, the base material S may be unrolled from a roll of the base material S, and the adhesive tape 100 may be pasted on the unrolled base material S.

(4) The production system 1 for the film F does not need to include the first stretching device 4A. The base material S coated with the coating liquid may be stretched in the flow direction MD and the width direction TD (biaxial simultaneous stretching) by the second stretching device 4B.

(5) Instead of the knurling device 6, the film F manufacturing system 1 may include a masking film feeding device that feeds out a masking film, and a bonding device that bonds the fed masking film to the film F.

100 Adhesive tape 101 Adhesive tape base material 102 Adhesive layer F Film S Base material

Claims (7)

an attaching step of attaching an adhesive tape to a base material made of brittle resin and conveyed in the flow direction in a width direction perpendicular to the flow direction;
a stretching step of stretching the base material to which the adhesive tape is attached together with the adhesive tape ,
In the pasting step, a plurality of the adhesive tapes are pasted onto the base material at regular intervals in the flow direction . an attaching step of attaching an adhesive tape to a base material made of brittle resin and conveyed in the flow direction in a width direction perpendicular to the flow direction;
After the pasting step, a cutting step of cutting the base material at the location where the adhesive tape is pasted;
After the cutting step, a stretching step of stretching the base material to which the adhesive tape is attached together with the adhesive tape;
A method of manufacturing a film, including: an attaching step of attaching an adhesive tape to a base material made of brittle resin and conveyed in the flow direction in a width direction perpendicular to the flow direction;
a stretching step of stretching the base material to which the adhesive tape is attached together with the adhesive tape;
including;
The adhesive tape has an adhesive tape base material and an adhesive layer disposed on one side of the adhesive tape base material,
The method for producing a film, wherein the adhesive tape base material has an elongation rate of 200% or more and 800% or less at 21°C. The method for manufacturing a film according to claim 2 or 3, wherein in the pasting step, a plurality of the adhesive tapes are pasted to the base material at regular intervals in the flow direction. The method for manufacturing a film according to claim 3 , further comprising a cutting step of cutting the base material at a location where the adhesive tape is pasted after the pasting step and before the stretching step. The base material is made of acrylic resin,
Production of the film according to any one of claims 1 to 5 , wherein the adhesive tape has an adhesive tape base material made of a polyolefin resin and an adhesive layer disposed on one side of the adhesive tape base material. Method. The method for producing a film according to any one of claims 1 to 6 , wherein the adhesive force of the adhesive tape to the base material is 5 N/18 mm or more and 20 N/18 mm or less at 25°C.

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