CN117136320A - Method for producing optical laminate - Google Patents

Method for producing optical laminate Download PDF

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Publication number
CN117136320A
CN117136320A CN202180096963.4A CN202180096963A CN117136320A CN 117136320 A CN117136320 A CN 117136320A CN 202180096963 A CN202180096963 A CN 202180096963A CN 117136320 A CN117136320 A CN 117136320A
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CN
China
Prior art keywords
separator
roller
bonding
peeling
optical laminate
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202180096963.4A
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Chinese (zh)
Inventor
今泉飒矢
秦和也
出崎忍
岩本展明
白子未来
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Nitto Denko Corp
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Nitto Denko Corp
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Publication date
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Publication of CN117136320A publication Critical patent/CN117136320A/en
Pending legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/12—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by using adhesives
    • B32B37/1284—Application of adhesive
    • B32B37/1292—Application of adhesive selectively, e.g. in stripes, in patterns
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/0046—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by constructional aspects of the apparatus
    • B32B37/0053—Constructional details of laminating machines comprising rollers; Constructional features of the rollers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B41/00—Arrangements for controlling or monitoring lamination processes; Safety arrangements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/02—Physical, chemical or physicochemical properties
    • B32B7/023—Optical properties
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B41/00—Arrangements for controlling or monitoring lamination processes; Safety arrangements
    • B32B2041/04—Detecting wrong registration, misalignment, deviation, failure

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Polarising Elements (AREA)

Abstract

The invention provides a method for manufacturing an optical laminate capable of suppressing curling. The method for manufacturing an optical laminate (100) of the present invention comprises: a separator bonding step (ST 3) for bonding the separator to the long-strip-shaped polarizer (10) via an adhesive layer (3) formed on the long-strip-shaped separator (4); a surface protective film laminating step (ST 5) in which a long strip-shaped surface protective film (5) is laminated to the polarizing plate after the separator laminating step; and a 1 ST separator peeling/bonding step (ST 6) of peeling the long strip-shaped separator from the adhesive layer after the surface protective film bonding step, and bonding the long strip-shaped separator to the polarizing plate via the adhesive layer.

Description

Method for producing optical laminate
Technical Field
The present invention relates to a method for producing an optical laminate including at least a polarizing plate, a separator, and a surface protective film. In particular, the present invention relates to a method for manufacturing an optical laminate capable of suppressing curling.
Background
Conventionally, a polarizing plate has been used as a constituent material of a liquid crystal display device, an organic EL display device, or the like. The polarizing plate includes a retardation film or the like in addition to the polarizing film according to the application. The polarizing film is composed of, for example, a polarizer dyed with a dichroic material such as iodine, and a protective film for protecting the polarizer. The long-strip polarizing film can be produced by laminating a long-strip protective film on at least one surface of a long-strip polarizer. A long-strip polarizing plate can be produced by bonding a long-strip phase difference film or the like to one surface of the produced long-strip polarizing film. A long-strip-shaped diaphragm (release film) is bonded to one surface of the produced long-strip-shaped polarizing plate, and a long-strip-shaped surface protective film is bonded to the other surface thereof, whereby a long-strip-shaped optical laminate can be produced. The bonding of these long strip-shaped films is generally performed in a roll-to-roll manner or a roll-to-sheet manner. The optical laminate in the form of a long strip can be cut into a size and shape according to the application, and used in a liquid crystal display device or the like. In addition, when the optical laminate is used in a liquid crystal display device or the like, the separator is peeled off, and the remaining constituent elements of the optical laminate are bonded to the liquid crystal display device or the like.
Fig. 8 is a flowchart showing an outline process example of a conventional method for manufacturing an optical laminate. As shown in fig. 8, the conventional method for manufacturing an optical laminate includes: polarizing film manufacturing step ST1', phase difference film bonding step ST2', separator bonding step ST3', inspection step ST4', and surface protective film bonding step ST5'.
In the polarizing film manufacturing step ST1', a long strip-shaped resin film is formed into a roll, and the roll is immersed in various treatment baths while being transported in the longitudinal direction, and various treatments such as dyeing treatment and stretching treatment are performed to manufacture a long strip-shaped polarizing plate. Then, a long strip-shaped protective film is attached to at least one surface of the long strip-shaped polarizer, thereby producing a long strip-shaped polarizing film.
In the retardation film laminating step ST2', a long-strip-shaped polarizing plate is manufactured by laminating a long-strip-shaped retardation film (1/2 wave plate, 1/4 wave plate, etc.) on one surface of the long-strip-shaped polarizing film.
In the separator bonding step ST3', an adhesive is applied while the long strip-shaped separator is conveyed in the longitudinal direction, and the applied adhesive is heated and dried by an oven or the like, so that the adhesive is cured, thereby forming an adhesive layer. Then, an adhesive layer side of the long-strip-shaped separator (separator with an adhesive layer) was bonded to one surface of the long-strip-shaped polarizer, and a long-strip-shaped intermediate obtained by laminating the polarizer, the adhesive layer, and the separator was produced.
In the inspection step ST4', only the separator is peeled off in a state where the adhesive layer sandwiched between the separator and the polarizer is left on the polarizer side, and the polarizer is inspected. Examples of the method for inspecting the polarizing plate include a transmission inspection, a cross Nicol (cross Nicol) inspection, and a reflection inspection. In the inspection step ST4', after the polarizing plate is inspected, the peeled separator is bonded again to the polarizing plate, and the original intermediate state is recovered.
In the surface protective film laminating step ST5', a long strip-shaped surface protective film is laminated on the surface of the long strip-shaped polarizing plate on the opposite side to the side on which the separator is laminated.
The polarizing film manufacturing step ST1 'to the surface protective film bonding step ST5' described above can manufacture an optical laminate in the form of a long strip.
However, in the optical laminate manufactured as described above, curling (warping of the end portion) which is a problem in use may occur in the optical laminate after being cut into a product size.
For example, patent document 1 proposes a method of setting the material of a protective film for protecting a polarizer to a specific material as a method of suppressing curling of a polarizing film, but the material of the protective film is limited and therefore is not general-purpose. A method is desired which can suppress curling without particularly changing the material of the constituent elements of the optical laminate used in the past.
Prior art literature
Patent literature
Patent document 1: japanese patent laid-open No. 2007-256568
Disclosure of Invention
Problems to be solved by the invention
The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide a method for manufacturing an optical laminate capable of suppressing curling.
Means for solving the problems
As a result of intensive studies to solve the above-described problems, the present inventors have found that the formation of an adhesive layer on a separator in a separator lamination step (ST 3' in fig. 8) in the conventional method for producing an optical laminate may be one of the main causes of curling of the optical laminate. Specifically, when the adhesive applied to the separator is heated and dried, the separator is considered to shrink, and irregularities are generated in the thickness direction thereof. It is considered that, when the separator is bonded to the polarizing plate in the separator bonding step and when the separator is bonded to the polarizing plate again in the inspection step (ST 4' of fig. 8), the separator is bonded in a state in which irregularities generated in the separator by heating have been stretched, but after the lapse of time from the bonding, a force that is required to restore the contracted state of the separator acts, and therefore, curling occurs in the optical laminate.
The present inventors have made intensive studies with an eye on the cause of the occurrence of the above-described problem, and as a result, have found that it is effective to perform a step of bonding a separator after peeling the separator as in the conventional inspection step after the surface protective film bonding step (ST 5' of fig. 8) in order to suppress the occurrence of curling. That is, it has been found that the laminate having the surface protective film laminated thereon has higher rigidity than the laminate before the surface protective film is laminated thereon, and therefore, if the separator in a state where the irregularities are stretched is laminated on the laminate having high rigidity, curling is less likely to occur even if a force for restoring the contracted state of the separator acts.
The present invention has been completed based on the above-described findings of the present inventors.
That is, in order to solve the above-described problems, the present invention provides a method for manufacturing an optical laminate, the method comprising: a separator bonding step of bonding the separator to a long-strip-shaped polarizing plate via an adhesive layer formed on the long-strip-shaped separator; a surface protective film laminating step of laminating a long strip-shaped surface protective film to the polarizing plate after the separator laminating step; and a 1 st separator peeling/bonding step of peeling the long-strip-shaped separator from the adhesive layer after the surface protective film bonding step, and bonding the long-strip-shaped separator to the polarizing plate via the adhesive layer.
In the separator peeling/bonding step 1 of the present invention, the peeled separator and the separator to be bonded may be the same separator or may be different separators. That is, the 1 st separator peeling/bonding step of the present invention includes a case where the same separator is bonded again to the polarizing plate via the adhesive layer after the separator is peeled off from the adhesive layer (only the separator is peeled off in a state where the adhesive layer remains on the polarizing plate). In addition, the 1 st separator peeling/bonding step includes a case where a new separator (i.e., a separator which is not heated to form an adhesive layer and is less likely to have irregularities) different from the peeled separator is bonded (alternatively bonded) to the polarizer via the adhesive layer.
According to the present invention, the separation of the separator and the lamination of the separator can be performed by including the 1 st separator separation/lamination step. In other words, even if the bonded separator is the same as the peeled separator, bonding with the polarizing plate can be performed in a state where the irregularities of the separator are stretched. Further, since the 1 st separator peeling/bonding step is performed after the surface protective film bonding step, the separator in which the irregularities are stretched is bonded to the laminate having high rigidity, and curling can be suppressed even if a force for restoring the contracted state of the separator acts.
The separator bonding step includes, for example: and an adhesive layer forming step of applying an adhesive to the long strip-shaped separator, and heating the applied adhesive to cure the adhesive to form the adhesive layer.
Preferably the invention comprises: and a 2 nd separator peeling/bonding step of peeling the long-strip-shaped separator from the adhesive layer before the surface protective film bonding step, and bonding the long-strip-shaped separator to the polarizing plate via the adhesive layer.
In the separator peeling/bonding step 2, the separator after peeling and the separator to be bonded may be the same separator or may be different from each other, as in the separator peeling/bonding step 1.
According to the preferred method described above, the separation of the separator and the lamination of the separator can be performed not only after the surface protective film lamination step but also before the surface protective film lamination step. In other words, even if the bonded separator is the same as the peeled separator, the bonding with the polarizing plate is performed in a state where the irregularities of the separator are stretched, and therefore curling can be further suppressed.
The separator peeling/bonding step 2 preferably serves as an inspection step for inspecting the polarizing plate after peeling the long strip-shaped separator.
According to the preferred method described above, since the 2 nd separator peeling/bonding step serves as the inspection step of the polarizing plate, there is an advantage that the manufacturing step is simplified as compared with the case where the 2 nd separator peeling/bonding step and the inspection step are provided separately.
In the separator peeling/bonding step 1, the time from peeling the long strip-shaped separator to bonding the long strip-shaped separator is preferably 1 minute or less.
According to the above preferred method, the time from peeling the long strip-shaped separator to bonding the long strip-shaped separator, in other words, the time for exposing the adhesive layer is short. Therefore, even if the humidity in the 1 st separator peeling/bonding step changes due to, for example, the influence of seasons, the influence of the daytime or nighttime, the deviation of curl of the polarizing plate due to swelling of moisture in the gas atmosphere absorbed from the pressure-sensitive adhesive layer side can be suppressed.
In the case where the present invention includes the 2 nd separator peeling/bonding step, the time from peeling the long strip-shaped separator to bonding the long strip-shaped separator is preferably 1 minute or less in the 2 nd separator peeling/bonding step.
In the separator peeling/bonding step 1, the long-strip-shaped separator is bonded to the polarizing plate by a bonding roller, the entrance angle of the separator to the bonding roller is preferably smaller than 90 °, and the entrance angle of the polarizing plate to the bonding roller is preferably smaller than 90 °.
In the above-described preferred method, the "separator-to-bonding roller entry angle" refers to an angle formed by a vector which is orthogonal to a straight line passing through the centers of rotation of the pair of opposing rollers constituting the bonding roller and directed to the exit side of the bonding roller, and a vector indicating the traveling direction of the separator before contact with the bonding roller. Similarly, the "entry angle of the polarizer to the laminating roller" means an angle formed by a vector which is orthogonal to a straight line passing through the rotation centers of the pair of rollers constituting the laminating roller and directed to the exit side of the laminating roller, and a vector indicating the traveling direction before the polarizer contacts the laminating roller.
According to the findings of the present inventors, when the entrance angle of the separator to the laminating roller is large (90 ° or more), the curl in the TD direction (the direction orthogonal to the conveyance direction (MD direction) of the long strip-shaped optical laminate) increases and the negative curl (the curl in which the separator is concave) increases, and when the entrance angle of the polarizer to the laminating roller is large (90 ° or more), the curl in the TD direction increases and the positive curl (the curl in which the separator is convex) increases.
According to the above preferred method, by setting both the entrance angles of the separator and the polarizing plate to the laminating roller to be less than 90 °, curling can be suppressed even further.
In the case where the present invention includes the 2 nd separator peeling/bonding step, it is also preferable that the 2 nd separator peeling/bonding step is performed by bonding the long strip-shaped separator to the polarizing plate by a bonding roller, the angle of entry of the separator to the bonding roller is smaller than 90 °, and the angle of entry of the polarizing plate to the bonding roller is smaller than 90 °.
The laminating roller is preferably composed of a 1 st roller in contact with the separator and a 2 nd roller in contact with the polarizing plate, and one of the 1 st roller and the 2 nd roller is preferably composed of a resin and the other is preferably composed of a metal.
When the surface of the 1 st roll and the surface of the 2 nd roll are both made of metal, there is a possibility that bubbles are generated at the interface between the separator and the polarizer (interface between the separator and the adhesive layer) when the separator and the polarizer are bonded. When both the surface of the 1 st roll and the surface of the 2 nd roll are formed of resin, there is a risk that the separator may wrinkle.
According to the above preferred method, in the 1 st roll and the 2 nd roll, the surface of one is formed of resin, and the surface of the other is formed of metal, whereby the occurrence of the hidden trouble of bubbles and wrinkles can be suppressed.
In the case where the present invention includes the 2 nd separator peeling/bonding step, it is also preferable that the bonding roller is composed of the 1 st roller in contact with the separator and the 2 nd roller in contact with the polarizing plate, and one of the 1 st roller and the 2 nd roller is formed of a resin and the other is formed of a metal.
Preferably, the surface of the 1 st roll is formed of metal, and the surface of the 2 nd roll is formed of resin.
According to the preferred method described above, in addition to the potential for the generation of bubbles and wrinkles, the surface of the 2 nd roller in contact with the polarizing plate is formed of resin (not formed of metal), and thus occurrence of defects in appearance such as scratches and scratches in the polarizing plate can be suppressed.
In the case where the present invention includes the 2 nd separator peeling/bonding step, it is also preferable that the surface of the 1 st roll is formed of a metal and the surface of the 2 nd roll is formed of a resin in the 2 nd separator peeling/bonding step.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, curling can be effectively suppressed without particularly changing the material of the constituent elements of the optical laminate used conventionally.
Drawings
Fig. 1 is a cross-sectional view schematically showing a schematic configuration of an optical laminate manufactured by the manufacturing method according to one embodiment of the present invention.
Fig. 2 is a flowchart showing an outline of a method for manufacturing an optical laminate according to an embodiment of the present invention.
Fig. 3 is a side view schematically showing an outline configuration example of an apparatus for carrying out the inspection step ST4 shown in fig. 2 (a view seen from a horizontal direction orthogonal to the transport direction of each film).
Fig. 4 is a side view schematically showing an outline configuration example of an apparatus for performing the 1 ST separator peeling/bonding step ST6 shown in fig. 2 (a view seen from a horizontal direction orthogonal to the transport direction of each film).
Fig. 5 is an explanatory view for explaining the bonding of the 3 rd intermediate M3 and the separator 4b by the bonding roller R7 shown in fig. 4.
Fig. 6 is a side view schematically showing an outline configuration example of an apparatus for carrying out the modification of the 1 ST separator peeling/bonding step ST6 shown in fig. 2 (a view seen from a horizontal direction orthogonal to the transport direction of each film).
Fig. 7 is an explanatory diagram for explaining a curl evaluation method.
Fig. 8 is a flowchart showing an outline process example of a conventional method for manufacturing an optical laminate.
Symbol description
1- & gtpolarizing film
10. Polarizer
11 polarizer
12. 13. Protective film
2.phase difference film
3. Adhesive layer
4. Separator
5 surface protective film
100. 100S optical laminate
ST 1. Polarization film production Process
ST2 & gtphase difference film laminating step
ST3 separator bonding step
ST 4. Inspection step (separator peeling and bonding step 2)
ST5 surface protective film laminating step
ST 6. 1 ST separator peeling/bonding step
Detailed Description
Hereinafter, a method for manufacturing an optical laminate according to an embodiment of the present invention will be described with reference to the drawings. Note that, each of the drawings is shown by way of reference, and the dimensions, scale, and shape of the constituent elements of the optical layered body and the device shown in each of the drawings may be different from actual ones.
Structure of optical laminate
First, the structure of the optical laminate manufactured by the manufacturing method of the present embodiment will be described.
Fig. 1 is a cross-sectional view schematically showing the schematic configuration of an optical laminate manufactured by the manufacturing method of the present embodiment.
As shown in fig. 1, an optical laminate 100 of the present embodiment includes a polarizing film 1, a retardation film 2, an adhesive layer 3, a separator 4, and a surface protective film 5. The laminate of the polarizing film 1 and the phase difference film 2 constitutes a polarizing plate 10. The laminated body of the polarizing plate 10 and the adhesive layer 3 constitutes the 1 st intermediate M1. The laminated body of the 1 st intermediate M1 and the separator 4 constitutes the 2 nd intermediate M2. The laminated body of the 1 st intermediate M1 and the surface protective film 5 constitutes the 3 rd intermediate M3. The constituent elements of the optical laminate 100 will be described below.
[ polarizing film 1]
The polarizing film 1 is composed of a polarizer 11 and protective films 12 and 13 for protecting the polarizer 11. In the present embodiment, the protective films 12 and 13 are bonded to both surfaces of the polarizer 11, but the present invention is not limited to this, and the protective films may be bonded to at least one surface of the polarizer 11.
(polarizer 11)
Typically, the polarizer 11 is composed of a resin film containing a dichroic substance.
As the resin film, any suitable resin film that can be used as a polarizer can be used. Typically, the resin film is a polyvinyl alcohol resin (hereinafter referred to as "PVA-based resin") film. The resin film may be a single-layer resin film or a laminate of two or more layers.
As the PVA-based resin forming the PVA-based resin film, any suitable resin may be used. Examples thereof include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. The polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer can be obtained by saponifying an ethylene-vinyl acetate copolymer.
The average polymerization degree of the PVA-based resin may be appropriately selected according to the purpose. The average polymerization degree is usually 1000 to 10000, preferably 1200 to 4500, more preferably 1500 to 4300. The average polymerization degree can be determined in accordance with JIS K6726-1994.
Examples of the dichroic substance contained in the resin film include: iodine, organic dyes, and the like. They may be used alone or in combination of two or more. Iodine is preferably used.
The resin film may be a single-layer resin film or a laminate of two or more layers.
As a specific example of a polarizer composed of a single-layer resin film, a polarizer obtained by subjecting a PVA-based resin film to a dyeing treatment with iodine and a stretching treatment (typically, a unidirectional stretching treatment) is cited. The dyeing treatment with iodine can be performed, for example, by immersing the PVA-based film in an aqueous iodine solution. The stretching ratio of the unidirectional stretching is preferably 3 to 7 times. Stretching may be performed after dyeing or while dyeing. In addition, dyeing may be performed after stretching. The PVA-based resin film may be subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, and the like as needed.
Specific examples of the polarizer formed of the laminate include: a polarizer comprising a laminate of a resin base material and a PVA-based resin layer (PVA-based resin film) laminated on the resin base material, or a laminate of a resin base material and a PVA-based resin layer formed on the resin base material by coating. A polarizer composed of a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate by coating can be produced by: for example, a PVA-based resin solution is applied to a resin substrate, dried to form a PVA-based resin layer on the resin substrate, a laminate of the resin substrate and the PVA-based resin layer is obtained, and then the laminate is stretched and dyed to form a polarizer from the PVA-based resin layer. In the present embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution to perform stretching. Further, the stretching may include stretching the laminate in a gas atmosphere at a high temperature (for example, 95 ℃ or higher) before stretching in an aqueous boric acid solution, as needed. The resulting laminate of the resin substrate and the polarizer may be used as it is (that is, the resin substrate may be used as a protective layer for the polarizer), or the resin substrate may be peeled off from the laminate of the resin substrate and the polarizer, and any appropriate protective layer according to the purpose may be laminated on the peeled surface. Details of such a method for manufacturing a polarizer are described in, for example, japanese patent application laid-open No. 2012-73580. The entire disclosure of this publication is incorporated by reference into this specification.
The thickness of the polarizer 11 is preferably 15 μm or less, more preferably 1 μm to 12 μm, still more preferably 3 μm to 10 μm, particularly preferably 3 μm to 8 μm.
The polarizer 11 preferably exhibits absorption dichroism at any wavelength in the range of 380nm to 780 nm. The transmittance of the polarizer 11 is preferably 40.0% to 45.0%, more preferably 41.5% to 43.5%. The polarization degree of the polarizer 11 is preferably 97.0% or more, more preferably 99.0% or more, and still more preferably 99.9% or more.
(protective film 12, 13)
As the protective films 12, 13, any suitable resin film may be used. Examples of the material for forming the resin film include: and (meth) acrylic resins, cellulose resins such as diacetyl cellulose and triacetyl cellulose, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, ester resins such as polyethylene terephthalate resins, polyamide resins, polycarbonate resins, copolymer resins thereof, and the like. The "(meth) acrylic resin" refers to an acrylic resin and/or a methacrylic resin. The protective films 12 and 13 may be formed of the same material or different materials.
The thickness of the protective films 12, 13 is typically 10 μm to 100 μm, preferably 20 μm to 40 μm. The thicknesses of the protective films 12, 13 may be the same or different.
The surfaces of the protective films 12 and 13 on the side opposite to the polarizer 11 may be subjected to surface treatments such as hard coat treatment, antireflection treatment, anti-blocking treatment, and antiglare treatment, as necessary. Further, if necessary, a process (typically, a process of imparting (elliptical) polarization function or a process of imparting an ultra-high phase difference) to the surface of the protective films 12, 13 on the side opposite to the polarizer 11 may be performed to improve visibility when viewing through polarized sunglasses. In the case of forming the surface-treated layer by performing the surface treatment, the thickness of the protective films 12 and 13 is the thickness including the surface-treated layer.
The protective films 12 and 13 are laminated on the polarizer 11 via any appropriate adhesive layers (not shown). As the adhesive constituting the adhesive layer, PVA-based adhesives and active energy ray-curable adhesives are typically used.
[ phase film 2]
The retardation film 2 may be, for example, a compensation plate for imparting a wide viewing angle, or a retardation plate (circularly polarizing plate) such as a 1/2 wave plate or a 1/4 wave plate for generating circularly polarized light when used together with a polarizing film. The thickness of the retardation film 2 is, for example, 1 to 200. Mu.m.
The retardation film 2 is formed of, for example, a layer or a resin formed by polymerizing a polymerizable liquid crystal. The polymerizable liquid crystal is a compound having a polymerizable group and having liquid crystallinity. The polymerizable group means a group participating in polymerization reaction, and is preferably a photopolymerizable group. Here, the photopolymerizable group means a group that can participate in polymerization reaction by a living radical, an acid, or the like generated by a photopolymerization initiator. Examples of the polymerizable group include vinyl, vinyloxy, 1-chlorovinyl, isopropenyl, 4-vinylphenyl, acryloyloxy, methacryloyloxy, oxiranyl, and oxetanyl groups. Among them, acryloyloxy, methacryloyloxy, ethyleneoxy, ethyleneoxide, and oxetanyl groups are preferable, and acryloyloxy is more preferable. The liquid crystallinity of the polymerizable liquid crystal may be thermotropic liquid crystal or lyotropic liquid crystal, and if the thermotropic liquid crystal is classified according to order, it may be nematic liquid crystal or smectic (smetic) liquid crystal.
Examples of the resin for forming the retardation film 2 include: polyarylates, polyamides, polyimides, polyesters, polyaryletherketones, polyamideimides, polyesterimides, polyvinyl alcohols, polyfumarates, polyethersulfones, polysulfones, norbornene resins, polycarbonate resins, cellulose resins, and polyurethanes. These resins may be used alone or in combination.
The retardation film 2 is laminated to the polarizing film 1 (protective film 13) via any appropriate adhesive layer or pressure-sensitive adhesive layer (not shown). As the adhesive constituting the adhesive layer, PVA-based adhesives and active energy ray-curable adhesives are typically used.
[ adhesive layer 3]
The adhesive is applied to one surface of the separator 4, and the applied adhesive is heated and dried by an oven or the like, thereby curing the adhesive to form the adhesive layer 3.
The heating temperature of the adhesive is preferably set in the range of 100 to 160 ℃, more preferably in the range of 140 to 160 ℃. At this heating temperature, heating is preferably performed for 20 seconds to 3 minutes, and more preferably for 1 minute to 3 minutes.
Specific examples of the adhesive for forming the adhesive layer 3 include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the kind, amount, combination and blending ratio of the monomers forming the base resin of the adhesive, and the blending amount, reaction temperature, reaction time, and the like of the crosslinking agent, an adhesive having desired characteristics according to the purpose can be produced. The base resin of the adhesive may be used alone or in combination of two or more. From the viewpoints of transparency, processability, durability, and the like, an acrylic adhesive is preferable. Details of the adhesive constituting the adhesive layer are described in, for example, japanese patent application laid-open No. 2014-115468, the description of which is incorporated by reference into the present specification. The thickness of the pressure-sensitive adhesive layer may be, for example, 10 μm to 100 μm.
[ diaphragm 4]
As the separator 4, any suitable separator may be used. Specific examples thereof include plastic films, nonwoven fabrics, and papers having their surfaces coated with a release agent. Specific examples of the release agent include silicone release agents, fluorine release agents, and long-chain alkyl acrylate release agents. Specific examples of the plastic film include polyethylene terephthalate (PET) film, polyethylene film, and polypropylene film. The thickness of the separator 4 may be, for example, 10 μm to 100 μm.
[ surface protective film 5]
The surface protective film 5 typically has a base material and an adhesive layer. In the present embodiment, the thickness of the surface protective film 5 is, for example, 30 μm or more. The upper limit of the thickness of the surface protective film 5 is, for example, 150 μm. In the present specification, the "thickness of the surface protective film" refers to the total thickness of the base material and the adhesive layer.
The substrate may be composed of any suitable resin film. Examples of the material for forming the resin film include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof. Ester resins (particularly polyethylene terephthalate resins) are preferred.
As the adhesive for forming the adhesive layer, any suitable adhesive may be used. Examples of the base resin of the binder include: acrylic resins, styrene resins, silicone resins, urethane resins, and rubber resins.
< manufacturing method of the present embodiment >
Hereinafter, a method for manufacturing the optical laminate 100 according to the present embodiment is described, and the method is used to manufacture the optical laminate 100 having the above-described configuration.
Fig. 2 is a flowchart showing an outline of a method for manufacturing the optical layered body 100 according to the present embodiment.
As shown in fig. 2, the manufacturing method of the present embodiment includes: a polarizing film manufacturing step ST1; a phase difference film laminating step ST2; a separator bonding step ST3; an inspection step (also referred to as a 2 nd separator peeling/bonding step) ST4; a surface protective film laminating step ST5; and a 1 ST separator peeling/bonding step ST6. The following describes each step ST1 to ST6.
[ polarizing film production Process ST1]
In the polarizing film production step ST1, a long strip-shaped resin film is formed into a roll, and the roll is immersed in various treatment baths while being transported in the longitudinal direction (MD direction), and various treatments such as dyeing treatment and stretching treatment are performed to produce the long strip-shaped polarizing plate 11. Then, the long-strip-shaped protective films 12 and 13 are bonded to the long-strip-shaped polarizer 11, whereby the long-strip-shaped polarizing film 1 is manufactured.
[ phase-contrast film laminating Process ST2]
In the retardation film laminating step ST2, the long-strip-shaped retardation film 2 is laminated on one surface (the protective film 13) of the long-strip-shaped polarizing film 1, thereby manufacturing the long-strip-shaped polarizing plate 10.
In the case where the optical laminate 100 does not include the retardation film 2 (the polarizing plate 10 does not include the retardation film 2), the retardation film attaching step ST2 is not required.
[ separator bonding Process ST3]
In the separator bonding step ST3, an adhesive layer forming step is performed in which an adhesive is applied while the long strip-shaped separator 4 is conveyed in the longitudinal direction (MD direction), and the applied adhesive is heated and dried by an oven or the like, thereby curing the adhesive to form the adhesive layer 3. Then, the separator 4 is bonded to the long band-shaped polarizing plate 10 via the adhesive layer 3 formed on the long band-shaped separator 4. Specifically, the adhesive layer 3 side of the long band-shaped separator 4 (separator 4 with adhesive layer 3) is bonded to one surface (retardation film 2) of the long band-shaped polarizing plate 10. Thus, a 2 nd intermediate M2 in which the polarizer 10, the adhesive layer 3, and the separator 4 are laminated was produced.
[ inspection step (separator peeling/bonding step 2) ST4]
The inspection step ST4 of the present embodiment is performed before the surface protective film bonding step ST 5. In the inspection step ST4, the long band-shaped separator 4 is peeled off from the adhesive layer 3 (only the separator 4 is peeled off in a state where the adhesive layer 3 sandwiched between the separator 4 and the polarizer 10 is left on the polarizer 10 side), and then the polarizer 10 is inspected. After the inspection of the polarizing plate 10, the peeled separator 4 is again bonded to the polarizing plate 10, and the original state of the 2 nd intermediate M2 is restored.
Fig. 3 is a side view schematically showing an outline configuration example of an apparatus for carrying out the inspection step ST4 (a view seen from a horizontal direction orthogonal to the transport direction of each film). The arrows shown in fig. 3 indicate the transport direction of each film.
In the inspection step ST4, the 2 nd intermediate M2 manufactured in the separator bonding step ST3 as described above is wound around the delivery roller R1 shown in fig. 3 and disposed on the most upstream side of the apparatus (the most upstream side in the conveyance direction of the 2 nd intermediate M2). Then, the 2 nd intermediate M2 fed from the feed roller R1 is conveyed toward the peeling roller R2. In the peeling roller R2, the separator 4 is peeled from the 2 nd intermediate M2, and the peeled separator 4 is conveyed to the laminating roller R3.
On the other hand, the 1 st intermediate M1 is inspected by the inspection device 20, and the 1 st intermediate M1 is a laminate of the polarizing plate 10 and the adhesive layer 3 obtained by peeling the separator 4 from the 2 nd intermediate M2 by the peeling roller R2.
The inspection apparatus 20 shown in fig. 3 is an apparatus for performing transmission inspection, and includes a light source 20a, an imaging means 20b, and a calculation means (not shown). The imaging means 20b of the inspection device 20 receives the light emitted from the light source 20a and transmitted through the 1 st intermediate M1, images the light, and outputs an electric signal corresponding to the amount of the light as an imaging signal to the arithmetic means. The arithmetic means generates a transmission image based on the input imaging signal. Then, the arithmetic means detects a defect in the 1 st intermediate M1 (polarizing plate 10) by applying a known image processing such as 2-valued processing to extract a pixel region having a luminance value (pixel value) different from that of the other pixel regions to the generated transmission image.
The inspection performed in the inspection step ST4 is not limited to the above-described transmission inspection. An orthogonal nicol inspection may be employed in which an orthogonal nicol image is generated by an inspection polarization filter disposed so as to be orthogonal to the polarization axis of the polarizer 11 included in the polarizer 10 and light transmitted through the 1 st intermediate M1, and a defect in the 1 st intermediate M1 (polarizer 10) may be detected based on the orthogonal nicol image. In addition, a reflection inspection may be employed, which generates a reflection image from light reflected by the 1 st intermediate M1, and detects a defect existing in the 1 st intermediate M1 (polarizing plate 10) based on the reflection image. Further, any combination of transmission inspection, orthogonal nicol inspection, and reflection inspection may be performed.
The 1 st intermediate M1 after inspection by the inspection device 20 is conveyed to the bonding roller R3. Then, the separator 4 is again bonded to the 1 st intermediate M1 by the bonding roller R3. That is, the separator 4 is bonded to the polarizer 10 constituting the 1 st intermediate M1 via the adhesive layer 3 constituting the 1 st intermediate M1. Thereby, the 2 nd intermediate M2 is produced, and is wound by the winding roller R4. The separator 4 of the 2 nd intermediate M2 fed from the feeding roller R1 and the separator 4 of the 2 nd intermediate M2 wound by the winding roller R4 are the same separator 4.
[ surface protective film laminating Process ST5]
The surface protective film laminating step ST5 is performed before the 1 ST separator peeling/laminating step ST 6. In the surface protective film laminating step ST5, the long strip-shaped surface protective film 5 is laminated on the long strip-shaped 2 nd intermediate M2. Specifically, a long strip-shaped surface protective film 5 is bonded to the surface of the polarizer 10 constituting the 2 nd intermediate M2 opposite to the side to which the separator 4 is bonded. Thereby manufacturing an optical laminate 100 in the form of a long strip.
[ 1 ST separator peeling/bonding Process ST6]
In the 1 ST separator peeling/bonding step ST6, the long-strip-shaped separator 4 is peeled from the adhesive layer 3 (only the separator 4 is peeled in a state where the adhesive layer 3 sandwiched between the separator 4 and the polarizing plate 10 is left on the polarizing plate 10 side) with respect to the long-strip-shaped optical laminate 100, and then the long-strip-shaped separator 4 is bonded to the polarizing plate 10 via the adhesive layer 3, whereby the state of the original optical laminate 100 is restored.
Fig. 4 is a side view schematically showing an outline configuration example of an apparatus for carrying out the 1 ST separator peeling/bonding step ST6 (a view seen from a horizontal direction orthogonal to the transport direction of each film). The arrows shown in fig. 4 indicate the transport direction of each film.
In the 1 ST separator peeling/bonding step ST6, the optical laminate 100 manufactured in the surface protective film bonding step ST5 described above is wound around the feed roller R5 shown in fig. 4 and disposed on the most upstream side of the apparatus (the most upstream side in the conveyance direction of the optical laminate 100). Then, the optical laminate 100 fed out from the feed-out roller R5 is conveyed toward the peeling roller R6. At the peeling roller R6, the separator 4 is peeled from the optical laminate 100, and the peeled separator 4 is conveyed to the laminating roller R7.
On the other hand, the 3 rd intermediate M3 is also conveyed to the laminating roller R7, and the 3 rd intermediate M3 is a laminate of the surface protective film 5, the polarizing plate 10, and the adhesive layer 3 obtained by peeling the separator 4 from the optical laminate 100 by the peeling roller R6. Then, the separator 4 is again bonded to the 3 rd intermediate M3 by the bonding roller R7. That is, the separator 4 is bonded to the polarizer 10 constituting the 3 rd intermediate M3 via the adhesive layer 3 constituting the 3 rd intermediate M3. The optical laminate 100 is thus manufactured, and wound by the winding roller R8. The separator 4 of the optical laminate 100 fed from the feeding roller R5 and the separator 4 of the optical laminate 100 wound by the winding roller R8 are the same separator 4.
The manufacturing method of the present embodiment includes the 1 ST separator peeling/bonding step ST6, thereby peeling the separator 4 and bonding the separator 4. In other words, even if the bonded separator 4 is the same as the peeled separator 4, bonding with the polarizing plate 10 can be performed in a state where the irregularities of the separator 4 are stretched. Then, since the 1 ST separator peeling/bonding step ST6 is performed after the surface protective film bonding step ST5, by bonding the separator 4 in a state where the irregularities are stretched to the laminate (3 rd intermediate M3) having high rigidity, curling can be suppressed even if a force for restoring the contracted state of the separator 4 acts.
In addition, the manufacturing method of the present embodiment includes the inspection step ST4 as the 2 nd separator peeling/bonding step, and thus the separation of the separator 4 and the bonding of the separator 4 can be performed not only after the surface protective film bonding step ST5 but also before the surface protective film bonding step ST 5. Therefore, curling can be further suppressed.
In the present embodiment, in the 1 ST separator peeling/bonding step ST6, the time from peeling the long strip-shaped separator 4 to bonding the long strip-shaped separator 4 is 1 minute or less, preferably 45 seconds or less, and more preferably 30 seconds or less. Specifically, as shown in fig. 4, when the length of the conveyance path of the optical laminate 100 from the peeling roller R6 to the bonding roller R7 is L and the conveyance speed is V, the length L of the conveyance path and the conveyance speed V are set so as to be L/V1 minute or less (preferably 45 seconds, more preferably 30 seconds).
As described above, in the present embodiment, since the time from peeling the separator 4 to bonding the separator 4, in other words, the time to expose the pressure-sensitive adhesive layer 3 is short, even if the humidity in the 1 ST separator peeling/bonding step ST6 changes due to, for example, the influence of seasons, the influence of the daytime or nighttime, the deviation of curl caused by swelling of the polarizer 10 due to absorption of moisture in the gas atmosphere from the pressure-sensitive adhesive layer 3 side can be suppressed.
The following describes more specifically the bonding of the 3 rd intermediate M3 to the separator 4 by the bonding roller R7.
Fig. 5 is an explanatory view for explaining the lamination of the 3 rd intermediate M3 and the separator 4 by the lamination roller R7. As shown in fig. 5, the laminating roller R7 is constituted by a pair of 1 st and 2 nd rollers R71 and R72 facing each other. The 1 st roller R71 is a roller that contacts the separator 4 and conveys the separator 4 between the 1 st roller R71 and the 2 nd roller R72. The surface of the 1 st roller R71 is formed of metal (e.g., iron). The 2 nd roller R72 is a roller that contacts the 3 rd intermediate M3 and conveys the 3 rd intermediate M3 to between the 1 st roller R71 and the 2 nd roller R72. The surface of the 2 nd roller R72 is formed of a resin (e.g., rubber).
As shown in fig. 5, a straight line (virtual straight line) passing through the rotation centers C1 and C2 of the 1 st and 2 nd rollers R71 and R72 is set as a straight line CL. A vector (virtual vector) orthogonal to the straight line CL and directed to the exit side (right side in fig. 5) of the bonding roller R7 is set as a vector VC. At this time, the entry angle α of the separator 4 to the laminating roller R7 is an angle formed by the pointing amount VC and a vector indicating the traveling direction before the separator 4 contacts the laminating roller R7. The entry angle β of the 3 rd intermediate M3 to the laminating roller R7 (corresponding to the entry angle of the polarizing plate 10 to the laminating roller R7) is an angle formed by the pointing amount VC and a vector indicating the traveling direction (corresponding to the traveling direction of the polarizing plate 10) before the 3 rd intermediate M3 contacts the laminating roller R7.
In the present embodiment, both the entry angle α and the entry angle β are set to be smaller than 90 °. In fig. 4, for convenience, it is illustrated with α=90°, β=0°, but in practice, α < 90 °, β < 90 °, preferably 10 ° < α < 80 °, more preferably 20 ° < α < 50 °. Further, it is preferably 0 ° < β < 80 °, more preferably 0 ° < β < 75 °. By increasing the entrance angle α, the transportability of the 3 rd intermediate M3 (polarizing plate 10) is improved.
According to the findings of the present inventors, when the entrance angle α of the separator 4 to the bonding roller R7 is large (90 ° or more), the curl in the TD direction increases with negative curl (the curl in which the side of the separator 4 is concave), and when the entrance angle β of the 3 rd intermediate M3 (polarizing plate 10) to the bonding roller R7 is large (90 ° or more), the curl in the TD direction increases with positive curl (the curl in which the side of the separator 4 is convex).
Therefore, as described above, by setting α < 90 °, β < 90 °, curling can be suppressed even further.
In the present embodiment, the case where the separator 4 peeled off in the 1 ST separator peeling/bonding step ST6 is the same separator 4 as the separator 4 to be bonded was described as an example, but the present invention is not limited to this. In the 1 ST separator peeling/bonding step ST6, the separator 4 after peeling and the separator 4 to be bonded may be different from each other. A modification of the 1 ST separator peeling/bonding step ST6 in which the peeled separator 4 is different from the separator 4 to be bonded will be described below.
In the modification of the 1 ST separator peeling/bonding step ST6, a new separator 4 different from the peeled separator 4 is bonded to the polarizing plate 10 via the adhesive layer 3. Hereinafter, the peeled separator 4 (the separator 4 bonded in the inspection step ST 4) is appropriately referred to as "separator 4a", and the new separator 4 bonded in the modification of the 1 ST separator peeling/bonding step ST6 is referred to as "separator 4b", so that both are distinguished.
Fig. 6 is a side view schematically showing a schematic configuration example of an apparatus for carrying out the modification of the 1 ST separator peeling/bonding step ST6 (a view seen from a horizontal direction orthogonal to the transport direction of each film). The arrows shown in fig. 6 indicate the transport direction of each film.
In the modification of the 1 ST separator peeling/bonding step ST6, the optical laminate 100 manufactured in the surface protective film bonding step ST5 described above is wound around the feed roller R9 shown in fig. 6 and disposed on the most upstream side of the apparatus (the most upstream side in the conveyance direction of the optical laminate 100). Then, the optical laminate 100 fed out from the feed-out roller R9 is conveyed toward the peeling roller R10. In the peeling roller R10, the separator 4a is peeled from the optical laminate 100, and the peeled separator 4a is wound by the winding roller R11.
On the other hand, the 3 rd intermediate M3 is conveyed to the laminating roller R12, and the 3 rd intermediate M3 is a laminate of the surface protective film 5, the polarizing plate 10, and the adhesive layer 3 obtained by peeling the separator 4a from the optical laminate 100 by the peeling roller R10. A new separator 4b wound around the feed roller R13 (that is, a separator that is less likely to have irregularities due to the non-application of heat for forming the adhesive layer 3) is prepared, and the separator 4b is fed from the feed roller R13 to the laminating roller R12. Then, the separator 4b is bonded to the 3 rd intermediate M3 by the bonding roller R12. That is, the separator 4b is bonded to the polarizer 10 constituting the 3 rd intermediate M3 via the adhesive layer 3 constituting the 3 rd intermediate M3. The optical laminate 100 is thus manufactured, and wound by the winding roller R14. The separator 4 of the optical laminate 100 fed from the feeding roller R9 is a separator 4a, and the separator 4 of the optical laminate 100 wound by the winding roller R14 is a separator 4b.
According to the modification of the 1 ST separator peeling/bonding step ST6, the new separator 4b different from the peeled separator 4a is bonded, and therefore curling can be further suppressed.
In the present modification, the elastic modulus (elastic modulus in the TD direction) of the new separator 4b bonded to the polarizing plate 10 in the modification of the 1 ST separator peeling/bonding step ST6 is 6000[ n/mm ], for example 2 ]On the other hand, the elastic modulus (elastic modulus in the TD direction) of the separator 4a after the adhesive layer forming step (i.e., after heating) in the separator bonding step ST3 is, for example, less than 6000[ N/mm ] 2 ]The elastic modulus of the diaphragm 4b is higher than that of the diaphragm 4 a. When the elastic modulus of the separator 4b is higher than that of the separator 4a, the new separator 4b bonded (replacement bonded) in the modification of the 1 ST separator peeling/bonding step ST6 is less likely to shrink, and therefore, curling can be further suppressed. The upper limit of the elastic modulus (elastic modulus in TD direction) of the separator 4b is not particularly limited, and is 7000[ N/mm 2 ]Hereinafter, 6500[ N/mm ] is preferable 2 ]The following is given. The lower limit of the elastic modulus (elastic modulus in TD direction) of the separator 4a is not particularly limited, and is, for example, 5000[ N/mm 2 ]Above, preferably 5500[ N/mm ] 2 ]The above.
The elastic modulus can be measured, for example, using a tensile tester "Autograph" manufactured by Shimadzu corporation. Specifically, samples having a width (dimension in the MD direction) of 10mm and a length (dimension in the TD direction) of 100mm were cut out from the separator 4a and 4b monomers, and the samples were set in an Autograph, and were stretched in the TD direction at a speed of 50mm/min, and the elastic modulus was calculated based on the force [ N ] applied to stretch the samples by a predetermined amount.
In the modification of the 1 ST separator peeling/bonding step ST6, as in the 1 ST separator peeling/bonding step ST6 described with reference to fig. 4 and 5, the time from peeling of the separator 4a by the peeling roller R10 to bonding of the separator 4b by the bonding roller R12 is 1 minute or less, preferably 45 seconds or less, and more preferably 30 seconds or less. In the modification of the 1 ST separator peeling/bonding step ST6, the surfaces of the pair of opposing rollers constituting the bonding roller R12, which are in contact with the separator 4b and convey the separator 4b between the pair of rollers, are also formed of metal (for example, iron). The surface of the roller that contacts the 3 rd intermediate M3 and conveys the 3 rd intermediate M3 to between the pair of rollers is formed of resin (e.g., rubber). In the modification of the 1 ST separator peeling/bonding step ST6, both the entrance angle α of the separator 4b to the bonding roller R12 and the entrance angle β of the 3 rd intermediate M3 (polarizing plate 10) to the bonding roller R12 are set to be smaller than 90 °. Accordingly, in the modification of the separator peeling/bonding step ST6 of the 1 ST embodiment, curling can be further suppressed. The entry angle α of the separator 4b to the laminating roller R12 and the entry angle β of the 3 rd intermediate M3 (polarizing plate 10) to the laminating roller R12 are preferably 10 ° < α < 80 °, more preferably 20 ° < α < 50 °, further preferably 0 ° < β < 80 °, more preferably 0 ° < β < 75 °. By increasing the entrance angle α, the transportability of the 3 rd intermediate M3 (polarizing plate 10) is improved.
In the inspection step ST4 described with reference to fig. 3, the time from the separation of the separator 4 by the separation roller R2 to the bonding of the separator 4 by the bonding roller R3 is 1 minute or less, preferably 45 seconds or less, and more preferably 30 seconds or less, as in the 1 ST separator separation/bonding step ST6 described with reference to fig. 4 and 5. In the inspection step ST4, as in the 1 ST separator peeling/bonding step ST6, the surfaces of the rollers which are in contact with the separator 4 and convey the separator 4 between the pair of rollers among the pair of opposing rollers constituting the bonding roller R3 are formed of metal (for example, iron). The surface of the roller that contacts the 1 st intermediate M1 and conveys the 1 st intermediate M1 to between the pair of rollers is formed of resin (e.g., rubber). In the inspection step ST4, as in the 1 ST separator peeling/bonding step ST6, both the entrance angle α of the separator 4 to the bonding roller R3 and the entrance angle β of the 1 ST intermediate M1 (polarizing plate 10) to the bonding roller R3 are set to be smaller than 90 °. This can further suppress curling in the inspection step ST 4. In the inspection step ST4, a new separator 4 different from the separator 4 after separation may be bonded to the polarizing plate 10 after inspection, as in the modification of the 1 ST separator separation/bonding step ST6 described with reference to fig. 6. The entry angle α of the separator 4 to the laminating roller R3 and the entry angle β of the 1 st intermediate M1 (polarizing plate 10) to the laminating roller R3 are preferably 10 ° < α < 80 °, more preferably 20 ° < α < 50 °, further preferably 0 ° < β < 80 °, more preferably 0 ° < β < 75 °. By increasing the entrance angle α, the transportability of the 1 st intermediate M1 (polarizing plate 10) is improved.
According to the manufacturing method of the present embodiment described above, curling can be effectively suppressed without particularly changing the material of the constituent elements of the optical laminate 100 that has been conventionally used.
In the present embodiment, the mode in which the inspection step ST4 serves as the 2 nd separator peeling/bonding step has been described, but the present invention is not limited to this, and the inspection step ST4 and the 2 nd separator peeling/bonding step may be performed separately. Alternatively, the inspection step ST4 may be performed without performing the inspection (that is, the 2 nd separator peeling/bonding step in which only the separation and bonding of the separator 4 are performed). Alternatively, the inspection step ST4 itself may not be performed (that is, the separation and attachment of the separator 4 is performed only in the 1 ST separator separation/attachment step ST 6).
In the present embodiment, the polarizing plate 10 is described as a laminate of the polarizing film 1 and the phase difference film 2, but the present invention is not limited thereto. The polarizing plate 10 may be a laminate of the polarizing film 1, the phase difference film 2, and other components, a laminate of the polarizing film 1 and other components without the phase difference film 2, or a laminate of the polarizing film 10 and the other components, or a laminate in which only the polarizing film 1 is present in the polarizing plate 10.
An example of the result of evaluating the curl of the optical laminate 100 manufactured by the manufacturing method (example) of the present embodiment shown in fig. 2 and an example of the result of evaluating the curl of the optical laminate manufactured by the conventional manufacturing method (comparative example) shown in fig. 8 will be described below.
The optical layered bodies 100 produced in the examples and comparative examples each have a structure in which they are layered in the following order.
( 1) The surface protective film 5 (base material: PET/thickness 38 μm, adhesive layer: acrylic adhesive/thickness 10 μm )
(2) Cycloolefin protective film 12 (total thickness 32 μm) with hard coat layer (thickness 7 μm)
(3) Adhesive agent
(4) Polyvinyl alcohol polarizer 11 (thickness 12 μm)
(5) Adhesive agent
(6) Cellulose triacetate protective film 13 (thickness 25 μm)
(7) Adhesive agent
(8) Polymerizable liquid crystal 1/2 wave plate 2 (thickness: 2.5 μm)
(9) Acrylic pressure-sensitive adhesive layer 3 (thickness 20 μm)
(10) Diaphragm 4 (PET/thickness 38 μm)
In the optical laminate 100 manufactured in the example, the same separator 4 as the separator 4 after separation was bonded to the polarizing plate 10 after inspection in the 1 ST separator separation/bonding step ST6 and the inspection step ST4 (the replacement bonding of the separator 4 was not performed in the 1 ST separator separation/bonding step ST6 and the inspection step ST 4).
Fig. 7 is an explanatory diagram for explaining a curl evaluation method.
As shown in fig. 7 (a), in the embodiment, a rectangular optical laminate 100S of a multi-sheet product size (longitudinal 148mm×transverse 70 mm) is cut along the TD direction of the long optical laminate 100. In fig. 7 (a), 3 sheets of the optical laminate 100S are illustrated for convenience, but in practice, 10 sheets of the optical laminate 100S are cut out along the TD direction of 1 optical laminate 100. The above operation was performed on the plurality of optical laminates 100, and a total of 500 sheets of optical laminates 100S were obtained. Then, curl was evaluated for 100 sheets randomly selected from 500 sheets of the optical laminate 100S. As shown in fig. 7 (b), when the optical laminate 100S is cut, the cut is made obliquely so that the MD direction of the optical laminate 100 (the direction corresponding to the absorption axis of the polarizer 11) becomes 45 ° with respect to the long side and the short side of the optical laminate 100S.
As shown in fig. 7 (c), when evaluating curl, the optical laminate 100S was placed on the flat placement table 30 such that the lower side of the optical laminate 100S was convex (such that the warpage of the 4 corners of the optical laminate 100S was directed upward in the vertical direction), and the distances H from the upper surface of the placement table 30 to the vertical direction of the corners were measured for the 4 corners of the optical laminate 100S, respectively. The distance H is measured by erecting a scale extending in the vertical direction near the corner of the optical laminate 100S and reading the scale of the scale by visual observation.
When the optical laminate 100S is placed on the placement table 30 so that the lower side thereof is convex, the case where the side of the separator 4 of the optical laminate 100S is downward (the side of the surface protective film 5 is upward) is set to a positive curl, and the measured distance H is calculated as the curl value. On the other hand, when the optical laminate 100S is placed on the placement table 30 so that the lower side thereof is convex, the curl is negative when the side of the optical laminate 100S on which the separator 4 is located is upward (the side of the surface protective film 5 is downward), and a value obtained by multiplying the measured distance H by-1 is calculated as the curl value.
Next, the separator 4 is peeled off from the optical laminate 100S to be in the state of the 3 rd intermediate M3. Then, the curl values of the 4 corners were also calculated for the 3 rd intermediate M3 in the same manner as described above.
Then, the case where the curl values of the 4 corners of the optical laminate 100S and the curl values of the 4 corners of the 3 rd intermediate M3 all satisfy the condition that-5 mm. Ltoreq.curl value. Ltoreq.5 mm was regarded as pass, and the case where they did not satisfy was regarded as fail.
In the comparative example, the curl value was calculated in the same manner as in the above-described example, and whether the curl value was acceptable or unacceptable was determined.
Table 1 shows the evaluation results of the curl of examples and comparative examples.
TABLE 1
As shown in table 1, in the comparative example, 44 sheets out of the 100 sheets of optical laminate were acceptable (pass rate 44%), whereas in the example, 95 sheets out of the 100 sheets of optical laminate were acceptable (pass rate 95%), and it was found that curl was suppressed.

Claims (8)

1. A method of manufacturing an optical laminate, the method comprising:
a separator bonding step of bonding a separator to a long-strip-shaped polarizing plate via an adhesive layer formed on the long-strip-shaped separator;
a surface protective film laminating step of laminating a long strip-shaped surface protective film to the polarizing plate after the separator laminating step; and
and a 1 st separator peeling/bonding step of peeling the long-strip-shaped separator from the adhesive layer after the surface protective film bonding step, and bonding the long-strip-shaped separator to the polarizing plate via the adhesive layer.
2. The method for producing an optical laminate according to claim 1, wherein,
the separator laminating process comprises the following steps: and an adhesive layer forming step of applying an adhesive to the long strip-shaped separator, and heating the applied adhesive to cure the adhesive to form the adhesive layer.
3. The method of manufacturing an optical laminate according to claim 1 or 2, comprising: and a 2 nd separator peeling/bonding step of peeling the long-strip separator from the adhesive layer before the surface protective film bonding step, and bonding the long-strip separator to the polarizing plate via the adhesive layer.
4. The method for producing an optical laminate according to claim 3, wherein,
the 2 nd separator peeling/bonding step serves as an inspection step for inspecting the polarizing plate after peeling the long band-shaped separator.
5. The method for producing an optical laminate according to any one of claims 1 to 4, wherein,
in the 1 st separator peeling/bonding step, the time from peeling the long strip-shaped separator to bonding the long strip-shaped separator is 1 minute or less.
6. The method for producing an optical laminate according to any one of claims 1 to 5, wherein,
in the 1 st separator peeling/bonding step, a long strip-shaped separator is bonded to the polarizing plate by a bonding roller,
the entrance angle of the diaphragm to the laminating roller is smaller than 90 degrees, and the entrance angle of the polaroid to the laminating roller is smaller than 90 degrees.
7. The method for producing an optical laminate according to claim 6, wherein,
the laminating roller is composed of a 1 st roller contacted with the diaphragm and a 2 nd roller contacted with the polaroid,
in the 1 st roller and the 2 nd roller, one surface is formed of a resin, and the other surface is formed of a metal.
8. The method for producing an optical laminate according to claim 7, wherein,
the surface of the 1 st roller is formed of metal,
the surface of the 2 nd roller is formed of resin.
CN202180096963.4A 2021-04-16 2021-11-24 Method for producing optical laminate Pending CN117136320A (en)

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