JP2015096916A - Manufacturing method for polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a polarizing plate, which prevents displacement (separation) between a polarizing film and a protective film during a polarizing plate manufacturing process and improves yield.SOLUTION: A method of manufacturing a polarizing plate comprising a polarizing film and a first protective film uses a polarizing plate manufacturing apparatus having a film conveying path that passes through a bonding section and ultraviolet irradiation section in the described order, and includes: a preliminary step, in which an elongate polarizing film and an elongate first lead film are continuously conveyed along the film conveying path to be bonded together via an adhesive layer made of an ultraviolet-curable adhesive in the bonding section, after which the adhesive layer is cured by being irradiated with an ultraviolet ray in the ultraviolet irradiation section; and a switching step, in which the first lead film being continuously conveyed along the film conveying path is replaced by an elongate first protective film. The first lead film has an ultraviolet transmittance of 10% or more over an entire range of a half width of an absorption wavelength band of the ultraviolet-curable adhesive.

Description

  The present invention relates to a method for producing a polarizing plate in which a protective film is bonded to a polarizing film via an adhesive layer.

  A polarizing plate is widely used as a constituent member of a liquid crystal display device. As a polarizing plate, the thing of the structure which bonded the protective film to the single side | surface or both surfaces of the polarizing film which consists of polyvinyl alcohol-type resin etc. using the adhesive agent is common. Various types of adhesives have been conventionally proposed as adhesives used for laminating a polarizing film and a protective film, and one representative example is an ultraviolet curable adhesive.

  For example, JP 2009-134190 A (Patent Document 1) discloses an adhesive coating apparatus for applying an ultraviolet curable adhesive to a protective film, and a nip roll for bonding a polarizing film and a protective film ( A long polarizing film and a long protective film continuously on a film transport path of a polarizing plate manufacturing apparatus comprising an ultraviolet irradiation device for curing an ultraviolet curable adhesive in this order. Through this, a method for continuously producing a polarizing plate is described by sequentially performing bonding of a polarizing film and a protective film via an ultraviolet curable adhesive and curing of an adhesive layer by ultraviolet irradiation. Yes.

JP 2009-134190 A

  In order to start the continuous production of a polarizing plate using a polarizing film production apparatus as described in Patent Document 1 and using a long film as a raw material film, it should generally be bonded to the polarizing film and this from the beginning of production. Rather than supplying both protective films to the film transport path of the polarizing plate manufacturing apparatus, it is called a “lead film” (that is, a film that passes through the film transport path prior to the film to be incorporated into the product) In this way, a cheaper film is used instead of the protective film, and the same process as the actual polarizing plate manufacturing process is performed as a preliminary process.

  Preliminary process using lead film is carried out because the film transport tends to become unstable at the beginning of the polarizing plate manufacturing apparatus, so if a protective film is used from the beginning of the manufacturing, the film transport is unstable. This is because various problems occur and a large amount of defective portions are generated in the obtained polarizing plate. In order to avoid this, a preliminary process using a lead film is performed first, and when the polarizing film and the lead film are stably conveyed, the lead film is switched to a protective film, Start manufacturing.

  Conventionally, a polyethylene terephthalate (PET) film has been used as the lead film from the viewpoints of handleability and low cost.

  However, in the continuous production of the conventional polarizing plate including the preliminary steps as described above, a bonding film obtained by bonding a polarizing film and a lead film through an uncured ultraviolet curable adhesive layer is used as a film transport path. If it is conveyed along, there is a possibility that the problem that the relative positional relationship between the lead film and the polarizing film is not fixed frequently occurs. Hereinafter, this defect is referred to as “deviation”.

  When this “deviation” is present, “floating” may occur as shown in FIGS. 2 and 3. 2 and 3 are schematic cross-sectional views illustrating an example of a state when a deviation starts to occur. The arrows in the figure indicate the film transport direction. For ease of viewing, the ultraviolet curable adhesive layer interposed between the polarizing film 11 and the lead films 12 and 13 is omitted.

  With reference to FIG. 2, when a deviation occurs, a bonding film 10 in which the polarizing film 11 and the lead film 12 are bonded via an ultraviolet curable adhesive layer is guided by a guide roll 20 or the like along the film conveyance path. When transporting while supporting, when the film on the side in contact with the guide roll 20 or the like (lead film 12 in the example of FIG. 2) passes through the guide roll 20 or the like, another film (polarizing film 11 in the example of FIG. 2). In this case, the film may be stagnated without being followed, and may be displaced from other films, resulting in a floating (air biting) 30. As shown in FIG. 3, when the bonding film 10 further has a lead film 13 bonded to the other surface of the polarizing film 11, when passing through the guide roll 20 or the like, Not only the film on the contact side (lead film 12 in the example of FIG. 3) but also the outer film (lead film 13 in the example of FIG. 3) may float.

  2 and 3 show the state of the moment when the deviation starts to occur. Actually, when the laminated film 10 is continuously conveyed, the float 30 is continuously generated along the film longitudinal direction. And once such a shift | offset | difference arises in the bonding film 10 using the lead film 12, even after switching the lead film 12 to a protective film, this shift | offset | difference (floating 30) will be succeeded.

  The continuous shift (floating 30) that occurs in the bonding film (which becomes the product polarizing plate) after switching to the protective film causes defective parts in the resulting long polarizing plate, reducing the product yield. Let That is, as can be understood from FIG. 2 and FIG. 3, even if the floating 30 once occurs, the floating 30 is then eliminated, and the polarizing film 11 and the lead films 12 and 13 come into close contact again, but the floating 30 once occurs. The part that has been brought into close contact again remains as a band-like mark that can be visually distinguished from the other parts in the obtained polarizing plate, and the polarizing plate part having such a mark becomes a defective product.

  Even if it is possible to correct the deviation that occurred in the bonding film after switching to the protective film, a certain amount of work time is required for that purpose, and the bonding film continues to be conveyed during that time. The polarizing plate produced in this way becomes a defective product, and the yield of the product is greatly reduced.

  Therefore, an object of the present invention is to provide a method for producing a polarizing plate that can suppress the above-described “deviation” and thereby improve the yield.

The present invention provides the following method for producing a polarizing plate.
[1] A polarizing plate including a polarizing film and a first protective film disposed on one surface thereof is manufactured using a polarizing plate manufacturing apparatus including a film transport path that passes through a bonding unit and an ultraviolet irradiation unit in this order. A way to
While continuously transporting the long polarizing film and the long first lead film along the film transport path, the pasting portion is pasted via an adhesive layer made of an ultraviolet curable adhesive. After combining, a preliminary step of curing the adhesive layer by irradiating with ultraviolet rays in the ultraviolet irradiation portion,
A switching step of switching the film to be continuously conveyed along the film conveyance path from the first lead film to the long first protective film;
Including
The said 1st lead film is a manufacturing method of a polarizing plate whose transmittance | permeability of an ultraviolet-ray is 10% or more in the whole range of the range of the half value width of absorption wavelength of the said ultraviolet curable adhesive.

  [2] The method for producing a polarizing plate according to [1], wherein the first lead film has an expansion / contraction rate in at least one of a longitudinal direction and a width direction of the film of 0.75% or less.

  [3] The method for producing a polarizing plate according to [1] or [2], wherein the first lead film is a chain olefin resin film.

  [4] The method for producing a polarizing plate according to [3], wherein the first lead film is a stretched polypropylene resin film.

  [5] The method for producing a polarizing plate according to any one of [1] to [4], wherein the first protective film is an amorphous polyolefin resin film.

  [6] In any one of [1] to [5], a transport speed of the polarizing film, the first lead film, and the first protective film transported along the film transport path is 10 m / min or more. The manufacturing method of the polarizing plate of description.

  [7] The polarized light according to any one of [1] to [6], wherein the film conveyance path has a path portion in which the film conveyance direction changes by 60 ° or more by a guide roll in a path after the ultraviolet irradiation unit. A manufacturing method of a board.

  [8] After the switching step, the polarizing film and the first protective film are bonded to each other through the adhesive layer made of an ultraviolet curable adhesive at the bonding unit, and then the ultraviolet irradiation unit. The manufacturing method of the polarizing plate in any one of [1]-[7] which further includes the protective film lamination process of irradiating an ultraviolet-ray and hardening this adhesive bond layer.

[9] In the preliminary step, while continuously transporting the long first lead film, the long polarizing film, and the long second lead film along the film transport path, After the first lead film is bonded to one surface of the polarizing film and the second lead film is bonded to the other surface through an adhesive layer made of an ultraviolet curable adhesive at the bonding portion, the ultraviolet light is then bonded. The adhesive layer is cured by irradiating with ultraviolet rays at the irradiation part,
In the switching step, the film that is continuously conveyed along the film conveyance path is switched from the first lead film to the long first protective film, and from the second lead film to the long second protection. The manufacturing method of the polarizing plate in any one of [1]-[7] switched to a film.

  [10] After the switching step, the first protective film is disposed on one surface of the polarizing film and the second surface is disposed on the other surface via an adhesive layer made of an ultraviolet curable adhesive at the bonding portion. After bonding a protective film, the manufacturing method of the polarizing plate as described in [9] which further includes the protective film lamination process which irradiates an ultraviolet-ray in the said ultraviolet irradiation part, and hardens this adhesive bond layer.

  According to the method of the present invention, since the problem of “displacement” as described above can be solved, the yield of the obtained polarizing plate can be improved.

It is a side view which shows typically an example of the manufacturing method of the polarizing plate which concerns on this invention, and a polarizing plate manufacturing apparatus used for it. It is a schematic sectional drawing which shows an example of a mode when a shift | offset | difference begins to arise. It is a schematic sectional drawing which shows another example of a mode when a shift | offset | difference begins to arise. It is a side view which shows typically another example of the manufacturing method of the polarizing plate which concerns on this invention, and the polarizing plate manufacturing apparatus used for it.

  The present invention relates to a method for continuously producing a long polarizing plate in which a long protective film is bonded to a long polarizing film via an adhesive layer. The protective film may be bonded only to one surface of the polarizing film via an adhesive layer (a first protective film described later), or may be bonded to both surfaces via an adhesive layer ( First and second protective films described later). In the present invention, an ultraviolet curable adhesive is used as the adhesive forming the adhesive layer.

  In the manufacturing method of the present invention, the preliminary process using the lead film as described above is performed, and then the lead film is switched to the protective film that is a constituent element of the polarizing plate (switching step), and the manufacturing of the polarizing plate is performed. Is started (protective film lamination step).

In one embodiment, the method for producing a polarizing plate according to the present invention includes the following steps:
After laminating a long polarizing film and a long first lead film through an adhesive layer made of an ultraviolet curable adhesive while continuously conveying along the film conveying path of the polarizing plate production apparatus A preliminary film for curing the adhesive layer by irradiating the obtained bonding film (hereinafter, a laminated film obtained by bonding a polarizing film and a lead film is also referred to as a “first bonding film”) with ultraviolet rays. Process,
A switching step of switching the film to be continuously conveyed along the film conveyance path from the first lead film to the long first protective film;
After bonding a polarizing film and a 1st protective film through the adhesive bond layer which consists of an ultraviolet curable adhesive, the laminated film which bonded the obtained bonding film (henceforth, a polarizing film and a protective film " It is also a method including a protective film laminating step in this order in which the adhesive layer is cured by irradiating the adhesive layer with ultraviolet rays.

  Hereafter, each process is demonstrated in detail, referring FIG.1 and FIG.4. FIG.1 and FIG.4 is a side view which shows typically the example of the manufacturing method of the polarizing plate which concerns on this invention, and the polarizing plate manufacturing apparatus used for it. The arrow in FIG.1 and FIG.4 shows the conveyance direction of a film, or the rotation direction of various rolls.

  FIG. 1 shows an example in which a polarizing plate is manufactured by laminating the first lead film 2a (preliminary process) or the first protective film 2b (protective film laminating process) on one surface of the polarizing film 1. As shown in FIG. 4, the second lead film 2c (preliminary process) or the second protective film 2d (protective film laminating process) is bonded to the other surface of the polarizing film 1 so that one of the polarizing films 1 is bonded. It is also possible to produce a polarizing plate in which the first protective film 2b is laminated on the other surface and the second protective film 2d is laminated on the other surface. In this case, as shown in FIG. 4, a transport path for the second lead film 2c and the second protective film 2d is further provided above the polarizing film 1 with respect to the polarizing plate manufacturing apparatus of FIG.

  The polarizing plate manufacturing apparatus shown in FIG. 1 (the same applies to the polarizing plate manufacturing apparatus shown in FIG. 4 except that a transport path for the second lead film 2c and the second protective film 2d is further provided). Is provided with an adhesive coating device 3 for applying an ultraviolet curable adhesive to the bonding surface of the first lead film 2a or the first protective film 2b to form an adhesive layer (not shown). Process part 3A; 4A of bonding parts provided with a pair of bonding rolls 4 and 4 for bonding the polarizing film 1 and the 1st lead film 2a or the 1st protective film 2b through an adhesive bond layer; An ultraviolet irradiation unit 5A including an ultraviolet irradiation device 5 for irradiating ultraviolet rays from the first lead film 2a or the first protective film 2b side is included with respect to the first or second bonding film. The transport path of each film is constructed so as to pass through the coating part 3A (only for the first lead film 2a and the first protective film 2b), the bonding part 4A, and the ultraviolet irradiation part 5A in this order. In constructing the film transport path, guide rolls 6 and 7 for supporting the traveling film are provided at appropriate positions.

<Preliminary process>
In this step, first, a roll (rolled product) of a long polarizing film 1 and a roll of a long first lead film 2a are prepared, and polarized while being unwound continuously using an unshown unwinding device. It introduces into each film conveyance path | route of a plate manufacturing apparatus, and starts the continuous conveyance of a film. Each film is conveyed so that the longitudinal direction thereof is the conveyance direction.

  The conveyance path | route of the 1st lead film 2a is arrange | positioned at the bonding surface side (lower side in FIG. 1) of the polarizing film 1 with which the 1st lead film 2a is bonded. Usually, the conveyance direction (film longitudinal direction) of the polarizing film 1 and the conveyance direction (film longitudinal direction) of the first lead film 2a are parallel (first protective film 2b, second lead film 2c, and second protective film 2d). The same applies to.)

  Then, the continuous conveyance of each film along each film conveyance path | route is continued, and the application (adhesive layer) of the ultraviolet curable adhesive to the bonding surface of the 1st lead film 2a in the coating part 3A Of the polarizing film 1 and the first lead film 2a at the bonding part 4A; UV irradiation to the obtained first bonding film at the ultraviolet irradiation part 5A In order. Normally, in the preliminary process, the polarizing film 1 and the first lead film 2a are continuously conveyed, and each treatment in the coating unit 3A, the bonding unit 4A, and the ultraviolet irradiation unit 5A is performed on the polarizing film 1, It continues until it will be in the state by which the 1st bonding film formed by bonding the 1st lead film 2a and these was stably conveyed. The state of being stably conveyed refers to a state in which “displacement” with the polarizing film 1 generated on the first lead film 2a side is eliminated.

  As shown in FIG. 1, in the case where the first lead film 2a is bonded to one surface of the polarizing film 1 and the second lead film 2c is not bonded to the other surface, for example, ultraviolet rays in the ultraviolet irradiation unit 5A Irradiation is performed from the first lead film 2a side.

(1) Application of UV curable adhesive Application of the UV curable adhesive (formation of an adhesive layer) at the coating portion 3 </ b> A is performed using the adhesive application device 3. In the example of FIGS. 1 and 4, the adhesive is applied to the first lead film 2 a and the second lead film 2 c side, but may be applied to the bonding surface of the polarizing film 1. The means for applying the ultraviolet curable adhesive to the bonding surface is not particularly limited, and various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used.

  When the second lead film 2c is bonded to the other surface of the polarizing film 1, an ultraviolet curable adhesive for bonding this, and an ultraviolet curable adhesive for bonding the first lead film 2a, May be the same or different, but are preferably the same from the viewpoint of production efficiency. For the same reason, the ultraviolet curable adhesive for bonding the polarizing film 1 and the lead film is the same type as the ultraviolet curable adhesive for bonding the polarizing film 1 and the protective film. Is preferred.

  The thickness (after curing) of the adhesive layer is usually about 0.001 to 10 μm, preferably about 0.01 to 5 μm, more preferably about 0.01 to 2 μm.

  In order to improve the adhesiveness with the polarizing film 1, a surface activation treatment may be performed on the bonding surface of the first lead film 2a or the second lead film 2c prior to the application of the ultraviolet curable adhesive. Specific examples of the surface activation treatment include plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, and saponification treatment (immersion in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide). You may perform a surface activation process on the bonding surface of the polarizing film 1 instead of the bonding surface of the 1st lead film 2a or the 2nd lead film 2c, or the said bonding surface. The description regarding the surface activation treatment described here is also cited for the first protective film 2b and the second protective film 2d in the protective film laminating step.

(2) UV curable adhesive As the UV curable adhesive, an adhesive containing an epoxy compound that is cured by cationic polymerization as a curable component can be preferably used. The epoxy compound means a compound having an average of 1 or more, preferably 2 or more epoxy groups in the molecule. As an epoxy compound, a hydrogenated epoxy compound (having an alicyclic ring) obtained by reacting an epicyclohydrin with an alicyclic polyol obtained by hydrogenating an aromatic ring of an aromatic polyol. A glycidyl ether of a polyol); an aliphatic epoxy compound such as an aliphatic polyhydric alcohol or a polyglycidyl ether of an alkylene oxide adduct thereof; an epoxy compound having at least one epoxy group bonded to an alicyclic ring in the molecule The alicyclic epoxy-type compound which is can be mentioned.

  The ultraviolet curable adhesive may further contain a (meth) acrylic compound that is radically polymerizable as a curable component. The (meth) acrylic compound is a (meth) acrylate monomer having at least one (meth) acryloyloxy group in the molecule; obtained by reacting two or more functional group-containing compounds, and at least two in the molecule. And (meth) acryloyloxy group-containing compounds such as (meth) acrylate oligomers having (meth) acryloyloxy groups.

  When the ultraviolet curable adhesive contains, as a curable component, an epoxy compound that is cured by cationic polymerization, it preferably contains a photocationic polymerization initiator. Examples of the photocationic polymerization initiator include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; iron-allene complexes. Further, when the ultraviolet curable adhesive contains a radical polymerizable curable component such as a (meth) acrylic compound, it is preferable to contain a photo radical polymerization initiator. Examples of the photo radical polymerization initiator include acetophenone initiator, benzophenone initiator, benzoin ether initiator, thioxanthone initiator, xanthone, fluorenone, camphorquinone, benzaldehyde, anthraquinone and the like.

  UV curable adhesives, if necessary, cationic polymerization accelerators such as oxetanes and polyols, photosensitizers, ion trapping agents, antioxidants, chain transfer agents, tackifiers, thermoplastic resins, filling An additive such as an agent, a flow modifier, a plasticizer, an antifoaming agent, an antistatic agent, a leveling agent, and a solvent can be contained.

(3) Polarizing film As the polarizing film 1, a film obtained by adsorbing and orienting a dichroic dye on a uniaxially stretched polyvinyl alcohol resin can be suitably used. As the dichroic dye, iodine or a dichroic dye can be used. As a polyvinyl alcohol-type resin which comprises the polarizing film 1, what saponified the polyvinyl acetate-type resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids and acrylamides having ammonium groups.

  The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, and for example, polyvinyl formal and polyvinyl acetal modified with aldehydes may be used. The degree of polymerization of the polyvinyl alcohol resin is usually about 1000 to 10000, preferably about 1500 to 5000.

  The polarizing film 1 includes a step of uniaxially stretching a raw film made of the polyvinyl alcohol resin, a step of dyeing a polyvinyl alcohol resin film with a dichroic dye and adsorbing the dichroic dye, It can be manufactured through a process of treating the adsorbed polyvinyl alcohol-based resin film with a boric acid aqueous solution and a step of washing with water after the treatment with the boric acid aqueous solution. You may provide the swelling process which performs the immersion process to water before a dyeing | staining process.

  Uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before, simultaneously with, or after dyeing the dichroic dye. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Moreover, you may uniaxially stretch in these several steps. The draw ratio is usually about 3 to 8 times.

  After the washing step, the polarizing film 1 is obtained by performing a drying process. The thickness of the polarizing film 1 is about 1-80 micrometers normally, Preferably it is about 5-40 micrometers. In this invention, the elongate polarizing film 1 obtained by making it above is prepared as a roll which is a wound product of a elongate film.

(4) First Lead Film In the present invention, as the first lead film 2a, a film having an ultraviolet transmittance of 10% or more in the entire range of the absorption wavelength half width of the ultraviolet curable adhesive is used, preferably A thermoplastic resin film that satisfies the transmittance is used. The transmittance is preferably 30% or more, more preferably 50% or more, and further preferably 60% or more. By using the first lead film 2a having the transmittance of 10% or more, the ultraviolet rays irradiated from the first lead film 2a side in the ultraviolet irradiation section 5A can pass through the first lead film 2a with sufficient transmittance. Since it can permeate | transmit, the ultraviolet curable adhesive bond layer interposed between the 1st lead film 2a and the polarizing film 1 can be hardened. Thereby, in the film conveyance path | route after the ultraviolet irradiation part 5A, the above "deviation (floating)" arises in the 1st bonding film formed by bonding the polarizing film 1 and the 1st lead film 2a. It can be effectively suppressed.

  Therefore, even when the first lead film 2a is switched to the first protective film 2b in the switching step after the preliminary step, the polarizing film 1 and the first protective film 2b do not cause “shift” from the beginning of the switching. Can be bonded and bonded, and the yield of the polarizing plate can be improved.

  On the other hand, in the conventional manufacturing method of a polarizing plate including a preliminary process using a lead film such as a PET film, the lead film hardly transmits ultraviolet rays. Even when irradiated, the adhesive layer was difficult to cure, and this caused frequent misalignment. And as mentioned above, when this lead film was switched to the protective film, this displacement was a problem that it was taken over by the protective film.

  In general, the displacement (floating) in the bonding film formed by bonding the polarizing film and the lead film is such that the transport direction of the film transported in the film transport path is a guide roll (for example, the ultraviolet irradiation unit 5A in FIGS. 1 and 4). It tends to occur in a path portion that is changed (bent) by a guide roll 7) installed in a later transport path. Further, this deviation (floating) is likely to occur in the film on the side in contact with the guide roll. According to the present invention, even if the guide roll 7 for changing the film transport direction is installed in the film transport path after the ultraviolet irradiation unit 5A, the adhesive layer is formed by the ultraviolet light that passes through the first lead film 2a. Since it is cured and the adhesiveness between the polarizing film 1 and the first lead film 2a is high, the effect of misalignment when passing through the guide roll 7 (the misalignment of the first lead film 2a in the examples of FIGS. 1 and 4) is effective. Can be suppressed. For example, even when the film transport direction is changed by 60 ° or more, further 70 ° or more, and even 75 ° or more by the guide roll 7, the displacement when passing through the guide roll 7 is effectively suppressed. Can do. Moreover, in the example of FIG. 4, the shift | offset | difference of the 2nd lead film 2c at the time of passing the guide roll 7 can also be suppressed effectively for the same reason.

  1 and FIG. 4, the angle is determined by the guide roll 7 before the film transport direction is changed (the transport direction immediately before passing through the guide roll 7), and the guide roll 7 is used for film transport. It means an angle θ formed by the transport direction (the transport direction immediately after passing through the guide roll 7) after the direction is changed.

  Moreover, although the shift | offset | difference at the time of the bonding film formed by bonding a polarizing film and a lead film passing through the guide roll 7 tends to arise so that the diameter of the guide roll 7 is large, according to this invention, it is a guide. Even when the diameter (diameter) of the roll 7 is 100 mm or more, and even 150 mm or more, the deviation at the time of passing through the guide roll 7 can be effectively suppressed.

  The conveyance speed of the film (each film such as the polarizing film 1, the first lead film 2a, and the first protective film 2b) conveyed along the film conveyance path of the polarizing plate manufacturing apparatus is usually 10 m / min or more. Although the deviation tends to occur as the conveyance speed increases, the deviation can be effectively suppressed according to the present invention, so the film conveyance speed needs to be reduced (and thus the production efficiency is reduced) in consideration of the problem of deviation. There is no. According to the present invention, even when the film conveyance speed is set to, for example, 15 m / min or more, or even 25 m / min or more, the deviation can be effectively suppressed, and the production efficiency is improved by increasing the film conveyance speed. Can do.

  On the other hand, in the conventional method for manufacturing a polarizing plate including a preliminary process using a lead film such as a PET film, when the film conveyance speed is increased, not only is the shift more likely to occur, but the shift is corrected. More polarizing plate portions (defective products) having the band-like traces generated between them are generated.

  The first lead film 2a preferably has an expansion / contraction rate in TD (direction perpendicular to the machine flow direction (MD) of the film) of 0.75% or less, and more preferably 0.3% or less. If the expansion / contraction rate in TD is 0.75% or less, it prevents the adhesive from sticking out when the polarizing film 1 and the first lead film 2a are bonded, resulting in line contamination. There is an effect to suppress. Moreover, although the film in a polarizing plate manufacturing apparatus is conveyed in the state which applied predetermined | prescribed tension | tensile_strength, if the expansion / contraction rate is in the said range, this tension | tensile_strength can be maintained stably. When the tension becomes unstable, the conveyed film may meander. For the same reason, the expansion / contraction ratio in the MD of the first lead film 2a is also preferably 0.75% or less, and more preferably 0.6% or less. The above-mentioned description about the 1st lead film 2a is referred also about the expansion-contraction rate in TD and MD of the 2nd lead film 2c.

The expansion ratio in TD of the first lead film 2a is the TD dimension W _TD01 immediately after _unwinding of the first lead film 2a and the TD just before bonding the first lead film 2a to the polarizing film 1 in the polarizing plate manufacturing apparatus. From the dimension W _TD1 , the following formula:

Is required.
In the polarizing plate manufacturing apparatus, the MD ratio W _MD01 immediately after _unwinding the first lead film 2a and the MD just before bonding the first lead film 2a to the polarizing film 1 in the MD of the first lead film 2a. From the dimension W _MD1 , the following formula:

Is required.
The expansion ratio in TD of the second lead film 2c is the TD dimension _WTD02 immediately after _unwinding of the second lead film 2c and the TD just before bonding the second lead film 2c to the polarizing film 1 in the polarizing plate manufacturing apparatus. From the dimension W _TD2 , the following formula:

Is required.
The MD expansion ratio of the second lead film 2c is the MD dimension W _MD02 immediately after _unwinding the second lead film 2c and the MD just before bonding the second lead film 2c to the polarizing film 1 in the polarizing plate manufacturing apparatus. From the dimension W _MD2 , the following formula:

Is required.
The first lead film 2a suitably used in the present invention (the same applies to the second lead film 2c) is a chain olefin resin film, and a specific example of the chain olefin resin constituting the first lead film 2a is propylene. Polypropylene resins such as homopolymers, copolymers of propylene and other α-olefins; polyethylene resins such as homopolymers of ethylene and copolymers of ethylene and other α-olefins. Polypropylene resin films and polyethylene resin films are excellent in ultraviolet transparency. Moreover, since it is inexpensive and excellent in handleability, it is suitable as a lead film.

  Among them, the stretched polypropylene resin film is not only excellent in handleability and inexpensiveness, but also advantageous in terms of the stretch rate in the above-described TD and MD. Examples of the stretching treatment include uniaxial stretching and biaxial stretching. Examples of the stretching direction include MD of an unstretched film, a direction TD orthogonal to the MD, a direction oblique to the MD, and the like. Biaxial stretching may be simultaneous biaxial stretching in which stretching is performed simultaneously in two stretching directions, or sequential biaxial stretching in which stretching is performed in a predetermined direction and then stretching in another direction. Among them, the stretched polypropylene resin film is preferably a biaxially stretched polypropylene resin film. Examples of the biaxially stretched polypropylene resin film include those manufactured by Toray Industries, Inc. and those manufactured by Phutamura Chemical Co., Ltd.

  In the stretched polypropylene resin film, the transmittance of ultraviolet rays in the entire range of the absorption wavelength half-value width of the ultraviolet curable adhesive is usually in the range of 10 to 90%.

  The thickness of the first lead film 2a (the same applies to the second lead film 2c) is not particularly limited, but is usually 10 to 200 μm, preferably 60 μm or more, preferably 150 μm or less, more preferably 100 μm or less. is there. When the thickness is less than 60 μm, it may be difficult to achieve the preferable stretch rate.

  In the present invention, the first lead film 2a as described above (the same applies to the second lead film 2c) is prepared as a roll which is a wound product of a long film.

  Here, in the preliminary step, when the second lead film 2c is further bonded to the other surface of the polarizing film 1 via an adhesive layer, the ultraviolet transmittance of the second lead film 2c is not particularly limited, and is described above. The transmittance may be less than 10%. Since ultraviolet rays are irradiated from the first lead film 2a side in the ultraviolet irradiation unit 5A, the ultraviolet rays of the second lead film 2c are used to cure the adhesive layer interposed between the polarizing film 1 and the second lead film 2c. This is because the permeability is not particularly relevant.

  Therefore, as the second lead film 2c, not only the film exemplified above but also a film that hardly transmits ultraviolet rays, such as a PET film, can be used.

(5) Bonding of Polarizing Film and First Lead Film As shown in FIG. 1, bonding between the polarizing film 1 and the first lead film 2 a (the same applies to the second lead film 2 c) in the bonding portion 4 </ b> A. In the bonding through the agent layer, the polarizing film 1 and the first lead film 2a which are continuously conveyed along the respective conveying paths are overlapped so that their longitudinal directions (conveying directions) are parallel to each other. It can carry out by pressing the laminated | stacked film from the upper and lower sides with the bonding rolls 4 and 4 by letting them pass between the bonding rolls 4 and 4. The pressure applied to the film by the bonding rolls 4 and 4 is, for example, about 0.5 to 4 MPa.

(6) Ultraviolet irradiation to the 1st bonding film The ultraviolet irradiation to the 1st bonding film in the ultraviolet irradiation part 5A is performed using the ultraviolet irradiation device 5. By this ultraviolet irradiation, the adhesive layer interposed between the first lead film 2a and the polarizing film 1 can be cured. The effect of curing the adhesive layer is as described above. The ultraviolet irradiation is performed from the first lead film 2a side.

  The light source of the ultraviolet irradiation unit 5A is not particularly limited, but has a light emission distribution at a wavelength of 400 nm or less. A lamp or the like can be preferably used.

The irradiation intensity of ultraviolet rays is determined for each composition of the ultraviolet curable adhesive and is not particularly limited. However, the irradiation intensity in the wavelength region effective for activating the polymerization initiator is 0.1 to 100 mW / cm ^2. It is preferable that When the light irradiation intensity is 0.1 mW / cm ² or more, the reaction time does not become too long, and when the light irradiation intensity is 100 mW / cm ² or less, the adhesive radiates heat from the light source and heat generated when the adhesive is cured. There is little possibility of causing yellowing of light and deterioration of the polarizing film 1. The irradiation time of the ultraviolet rays is also controlled for each composition of the adhesive and is not particularly limited. However, the integrated light amount expressed as the product of the irradiation intensity and the irradiation time is 10 to 5000 mJ / m ^2. It is preferable to set to. By integrated light quantity is 10 mJ / m ² or more, the curing reaction can be more surely to proceed, also by at 5000 mJ / m ² or less, the irradiation time not too long, a good productivity Can be maintained.

  A plurality of ultraviolet irradiation devices 5 may be installed, and ultraviolet irradiation may be performed in a plurality of times.

  When curing the adhesive layer by irradiating ultraviolet rays, irradiating the ultraviolet rays in a state where the first bonding film is in close contact with the convex curved surface may cause wrinkles and curls that may occur in the obtained first bonding film after curing. This is advantageous in that it can be suppressed. As the convex curved surface, an outer peripheral surface of a roll such as a guide roll or a cooling roll can be suitably used. In particular, when ultraviolet rays are irradiated while being wound around the outer peripheral surface of a cooling roll that has been appropriately cooled, the effect of suppressing wrinkles and curls is great. The temperature of a cooling roll is 10-30 degreeC, for example, Preferably it is 15-25 degreeC.

<Switching process>
In this step, in order to start the main production of the polarizing plate, the film that is continuously conveyed along the film conveyance path of the polarizing plate manufacturing apparatus is switched from the first lead film 2a to the long first protective film 2b. It is a process. The film is switched by preparing a roll which is a wound product of the long first protective film 2b, and connecting the longitudinal end of the first lead film 2a and the longitudinal start of the first protective film 2b. What is necessary is just to continue conveyance. Such film switching can also be performed using a turret. The same applies to the switching from the second lead film 2c to the second protective film 2d.

  The connection between the first lead film 2a and the first protective film 2b can be a connection using a connection tape (for example, a single-sided adhesive tape), a connection by heat sealing, or the like.

<Protective film lamination process>
In this step, after switching the film by connecting the first lead film 2a and the first protective film 2b, the first protective film 2b is continuously conveyed along the conveyance path, and the polarizing film 1 is The application of the first protective film 2b in the coating part 3A is carried out in the same manner as in the preliminary step except that the first protective film 2b is used instead of the first lead film 2a by being conveyed along the conveyance path. Application of an ultraviolet curable adhesive to the bonding surface (which may be the bonding surface of the polarizing film 1) (formation of an adhesive layer); the polarizing film 1 and the first protective film at the bonding portion 4A Bonding through the adhesive layer with 2b; Curing of the adhesive layer by ultraviolet irradiation to the obtained second bonding film in the ultraviolet irradiation unit 5A is sequentially performed. Thereby, the elongate polarizing plate with which the 1st protective film 2b was laminated | stacked on the single side | surface of the polarizing film 1 is manufactured continuously.

  In the preliminary step, when the second lead film 2c is further bonded to the other surface of the polarizing film 1 via an adhesive layer, switching from the first lead film 2a to the first protective film 2b in the switching step. At the same time, the second lead film 2c is switched to the second protective film 2d, and in this step, the first protective film 2b is laminated on one surface of the polarizing film 1, and the second protective film 2d is formed on the other surface. Is obtained.

  When laminating protective films on both surfaces of the polarizing film 1, it is not easy to correct the misalignment, and even if it can be corrected, the correction operation is extremely complicated. Even in the case of producing a polarizing plate having a protective film laminated thereon, the deviation can be effectively suppressed.

  The first protective film 2b and the second protective film 2d (hereinafter also collectively referred to as “protective film”) are stacked on the polarizing film 1 and play at least the role of protecting the polarizing film 1. The protective film is not particularly limited as long as it has translucency (preferably transparency), and can be a film made of a thermoplastic resin film or a glass material. Examples of the film made of a glass material include glass films described in JP 2012-247785 A, International Publication No. 12/090693, JP 08-283041 A, and the like.

  Specific examples of the thermoplastic resin constituting the protective film are, for example, cyclic polyolefin resin (norbornene resin); polyester resin such as polyethylene terephthalate; (meth) acrylic resin such as methyl methacrylate resin; cellulose Cellulosic resins such as triacetate and cellulose diacetate; polycarbonate resins; polyvinyl alcohol resins; polyvinyl acetate resins; polyarylate resins; polystyrene resins; polyethersulfone resins; A polyimide resin; and a mixture or copolymer thereof. The protective film may have a multilayer structure of resin layers made of a thermoplastic resin. In addition, (meth) acryl means methacryl and / or acryl.

  The cyclic polyolefin resin is an amorphous resin having a unit of a monomer composed of a cyclic olefin such as norbornene or a polycyclic norbornene monomer. For example, a hydrogenated product of the ring-opening polymer of the cyclic olefin, two or more types Of hydrogenated ring-opening copolymers using cyclic olefins, aromatic compounds having cyclic olefins and chain olefins (ethylene, propylene, etc.) and / or vinyl groups (styrene, α-methylstyrene, nuclear alkyl substitution) Addition polymers with styrene and the like).

  The protective film can contain various additives as required. Specific examples of additives include fluorescent brighteners, dispersants, surfactants, heat stabilizers, light stabilizers, ultraviolet absorbers, infrared absorbers, antistatic agents, antioxidants, lubricants, organic dyes, pigments And inorganic pigments.

  The thickness of the protective film is usually about 2 to 300 μm, preferably 10 μm or more, preferably 200 μm or less, more preferably 150 μm or less, and still more preferably 100 μm or less.

  The protective film may be obtained by subjecting the thermoplastic resin film to a stretching treatment. Arbitrary retardation value can be provided by extending | stretching. A protective film having a predetermined retardation characteristic is also referred to as an optical compensation film or a retardation film. Examples of the stretching treatment include uniaxial stretching and biaxial stretching. Examples of the stretching direction include a machine flow direction (MD) of an unstretched film, a direction perpendicular to the machine flow direction (TD), and a direction oblique to the machine flow direction (MD). Biaxial stretching may be simultaneous biaxial stretching in which stretching is performed simultaneously in two stretching directions, or sequential biaxial stretching in which stretching is performed in a predetermined direction and then stretching in another direction.

  Even if the protective film has a surface treatment layer such as a hard coat layer, an antiglare layer, an antistatic layer, an antireflection layer, and an antifouling layer on the surface opposite to the bonding surface with the polarizing film 1. Good.

  When laminating the second protective film 2d on the other surface of the polarizing film 1, the first protective film 2b and the second protective film 2d may be the same type of film or different types of films. Good.

  The long polarizing plate obtained as described above is usually wound up sequentially by a winding device not shown in FIGS. 1 and 4 to form a film roll.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further more concretely, this invention is not limited by these examples.

<Example 1>
A preparatory process, a switching process, and a protective film laminating process are sequentially performed using the polarizing plate manufacturing apparatus shown in FIG. 4, and the first protective film 2 b is laminated on one surface of the polarizing film 1 via an adhesive layer. Then, continuous production of a polarizing plate in which the second protective film 2d was laminated on the other surface of the polarizing film 1 was performed. The raw material film used, production conditions, etc. are as follows.

Roll-shaped polarizing film 1: A polarizing film (thickness of about 30 μm) in which iodine is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol resin.
Roll-shaped first lead film 2a and second lead film 2c: biaxially stretched polypropylene resin film “Trephan” manufactured by Toray Industries, Inc. [thickness 60 μm, absorption wavelength half-width range of UV curable adhesive shown below: 250 to The transmittance of ultraviolet rays in the entire 330 nm region is 75% or more. ],
Roll-shaped first protective film 2b: Amorphous polyolefin-based resin film “ZEONOR” [thickness 50 μm] manufactured by Nippon Zeon Co., Ltd.
-Roll-shaped second protective film 2d: Triacetyl cellulose (TAC) film "KC6UAW" [thickness 60 μm] manufactured by Konica Minolta,
UV curable adhesive: UV curable adhesive having an epoxy compound as a curable component (absorption wavelength half-width range 250 to 330 nm),
・ Conveying speed of each film: 25 m / min,
The angle θ in the film transport direction that changes with the guide roll 7: 75 °.

By continuously unwinding the respective films from the rolls of the polarizing film 1, the first lead film 2a and the second lead film 2c, and continuously transporting them along their transport paths, in the coating unit 3A, Application of ultraviolet curable adhesive to the bonding surfaces of the first lead film 2a and the second lead film 2c using the adhesive coating device 3 (gravure coater); the polarizing film 1 in the bonding portion 4A Bonding with the first lead film 2a and the second lead film 2c through an adhesive layer; UV irradiation unit 5 (D bulb manufactured by Fusion UV Systems, integrated light quantity 1500 mJ / cm ² ) in the UV irradiation unit 5A UV irradiation (irradiation from the first lead film 2a side) to the obtained first laminated film was performed in order.

  After the polarizing film 1, the first lead film 2a, and the second lead film 2c are conveyed (preliminary process) for 5 minutes, the first lead film 2a is used as the first protective film 2b, and the second lead film 2c is used as the second protective film. It switched to the film 2d (switching process). No deviation was observed during the preliminary process.

  Subsequent to the switching step, the first protective film 2b, the second protective film 2d, and the polarizing film 1 are transported along the transport path to thereby apply the ultraviolet curable adhesive, the polarizing film 1 and the first protective film 2b. And the polarizing plate was continuously manufactured by implementing bonding and ultraviolet irradiation through the adhesive bond layer with the 2nd protective film 2d in order (protective film lamination process). No deviation was observed in the protective film laminating process.

<Comparative Example 1>
Except for using a polyethylene terephthalate film (thickness 38 μm) as the first lead film 2 a and the second lead film 2 c, a preliminary process was performed in the same manner as in Example 1; Occurred. The switching step was carried out in this state, and immediately after starting the protective film laminating step, the shift correction work was started. As a result of taking 3 minutes for this correction work, the polarizing plate portion of about 80 m became defective.

  DESCRIPTION OF SYMBOLS 1,11 Polarizing film, 2a 1st lead film, 2b 1st protective film, 2c 2nd lead film, 2d 2nd protective film, 3 adhesive coating apparatus, 3A coating part, 4 bonding roll, 4A bonding Part, 5 UV irradiation device, 5A UV irradiation part, 6, 7 guide roll, 10 bonding film, 12, 13 lead film, 20 guide roll, 30 float.

Claims (10)

A method for producing a polarizing plate comprising a polarizing film and a first protective film disposed on one surface of the polarizing plate using a polarizing plate production apparatus including a film transport path that passes through the bonding part and the ultraviolet irradiation part in this order. There,
While continuously transporting the long polarizing film and the long first lead film along the film transport path, the pasting portion is pasted via an adhesive layer made of an ultraviolet curable adhesive. After combining, a preliminary step of curing the adhesive layer by irradiating with ultraviolet rays in the ultraviolet irradiation portion,
A switching step of switching the film to be continuously conveyed along the film conveyance path from the first lead film to the long first protective film;
Including
The said 1st lead film is a manufacturing method of a polarizing plate whose transmittance | permeability of an ultraviolet-ray is 10% or more in the whole range of the range of the half value width of absorption wavelength of the said ultraviolet curable adhesive.   The said 1st lead film is a manufacturing method of the polarizing plate of Claim 1 whose expansion-contraction rate in at least one of the longitudinal direction and the width direction of a film is 0.75% or less.   The method for producing a polarizing plate according to claim 1, wherein the first lead film is a chain olefin resin film.   The method for producing a polarizing plate according to claim 3, wherein the first lead film is a stretched polypropylene resin film.   The said 1st protective film is a manufacturing method of the polarizing plate of any one of Claims 1-4 which is an amorphous polyolefin resin film.   The polarized light according to any one of claims 1 to 5, wherein a transport speed of the polarizing film, the first lead film, and the first protective film transported along the film transport path is 10 m / min or more. A manufacturing method of a board.   The said film conveyance path | route has a path | route part in which a film conveyance direction changes 60 degrees or more with a guide roll in the path | route after the said ultraviolet irradiation part, Manufacture of the polarizing plate of any one of Claims 1-6. Method.   After the switching step, the polarizing film and the first protective film are bonded via an adhesive layer made of an ultraviolet curable adhesive at the bonding portion, and then the ultraviolet rays are irradiated at the ultraviolet irradiation portion. The manufacturing method of the polarizing plate of any one of Claims 1-7 which further includes the protective film lamination process which irradiates and hardens this adhesive bond layer. In the preliminary step, the laminating portion while continuously conveying the long first lead film, the long polarizing film, and the long second lead film along the film conveying path. After bonding the first lead film on one surface of the polarizing film and the second lead film on the other surface through an adhesive layer made of an ultraviolet curable adhesive, To cure the adhesive layer by irradiating with ultraviolet rays,
In the switching step, the film that is continuously conveyed along the film conveyance path is switched from the first lead film to the long first protective film, and from the second lead film to the long second protection. The manufacturing method of the polarizing plate of any one of Claims 1-7 switched to a film.   After the switching step, the first protective film is provided on one surface of the polarizing film and the second protective film is provided on the other surface via an adhesive layer made of an ultraviolet curable adhesive at the bonding portion. The method for producing a polarizing plate according to claim 9, further comprising a protective film laminating step in which the adhesive layer is cured by irradiating ultraviolet rays at the ultraviolet irradiation unit after pasting.

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