JP2021018301A - Method for manufacturing polarization film and apparatus for manufacturing polarization film - Google Patents

Abstract

To provide a method and the like for manufacturing a polarization film, in which excellent adhesiveness between a polarizer and other films can be maintained.SOLUTION: A method for manufacturing a polarization film comprises: an adhesive coating step of coating an active energy beam curable adhesive on at least one of the polarizer and other films by an adhesives coating apparatus 54 in a conveyance process of conveying a polarizer 11 and the other films 12 and 13; and a polarization film preparation step of preparing a polarization film 1 by sticking the polarizer and the other films together through the adhesive and curing the adhesive. The adhesive coating apparatus 54 includes a viscometer 54e continuously measuring the viscosity of the adhesives to be coated, and in the adhesive coating step, a control device 58 controls the temperature (the temperature of the heat carrier of a heat exchanger 54f) of the adhesive in such a manner that a change in the viscosity of the adhesive measured by the viscometer falls within a fixed range.SELECTED DRAWING: Figure 4

Description

The present invention relates to a method for producing a polarizing film by bonding a polarizing element and another film via an adhesive, and an apparatus for producing the polarizing film. In particular, the present invention relates to a method and an apparatus for producing a polarizing film, which can maintain good adhesion between a polarizer and another film in the polarizing film.

Conventionally, a polarizing film containing a polarizing element has been used as a constituent material for a liquid crystal display device, polarized sunglasses, and the like. The polarizing film is composed of, for example, a polarizing element dyed with a dichroic substance such as iodine and a protective film that protects the polarizing element.
For the polarizing film, for example, as described in Patent Document 1, an active energy ray-curable adhesive such as a photocurable adhesive is applied to a protective film to form an adhesive layer, and the adhesive layer is formed. It is obtained by adhering the polarizer and the protective film through the film.
Patent Document 1 describes that a solvent-free adhesive having a low viscosity is used in order to improve the adhesiveness between the polarizer and the protective film.

Japanese Unexamined Patent Publication No. 2010-02627

If the viscosity of the adhesive is too high, the adhesiveness between the polarizer and another film such as a protective film deteriorates. Therefore, the adhesiveness is improved by using a low-viscosity adhesive as in Patent Document 1. You may be able to.
However, it has been found that even if the viscosity of the adhesive is too low, the adhesiveness may deteriorate.
Therefore, in order to obtain good adhesion between the polarizer and other films, it is important to adjust the viscosity of the adhesive within a certain range.

On the other hand, when the adhesive is continuously applied to a polarizer or another film with an adhesive coating device using a gravure roll or the like, even if the adhesive has the same composition, the adhesive has moisture in the atmosphere. The viscosity of the adhesive may change (mainly decrease) with time due to absorption of the adhesive.
Therefore, even if the viscosity of the adhesive is adjusted to be within a certain range where good adhesiveness can be obtained at the start of coating, the viscosity of the adhesive may change over time and deviate from the above-mentioned certain range. There is.
Since the polarizing film is required to have stable optical characteristics, it is required to maintain good adhesion between the polarizing element and another film.

Therefore, it is an object of the present invention to provide a method and an apparatus for producing a polarizing film capable of maintaining good adhesion between a polarizer and another film.

In order to solve the above-mentioned problems, the present inventors have made extensive studies focusing on controlling the temperature which has a great influence on the viscosity. As a result, the adhesive coating device adopts a configuration equipped with a viscometer that continuously measures the viscosity of the adhesive to be applied, so that the change in the viscosity of the adhesive measured by this viscometer is within a certain range. In addition, he found that the temperature of the adhesive to be coated should be controlled, and completed the present invention.

That is, in order to solve the above-mentioned problems, in the present invention, the polarizer and the other film are each conveyed, and in the transfer process, at least one of the polarizer and the other film is subjected to an adhesive coating device. A polarizing film is produced by an adhesive coating step of applying an active energy ray-curable adhesive, the polarizer and the other film are bonded together via the adhesive, and the adhesive is cured. The adhesive coating apparatus includes a polarizing film manufacturing step of continuously measuring the viscosity of the adhesive to be coated, and in the adhesive coating step, the adhesive meter is provided. Provided is a method for producing a polarizing film in which the temperature of the adhesive is controlled so that the change in the viscosity of the adhesive measured in 1) is within a certain range.

According to the present invention, since the temperature of the adhesive is controlled so that the change in the viscosity of the adhesive measured by the viscometer is within a certain range, good adhesiveness can be obtained at the initial stage of coating. It is possible to maintain good adhesiveness over time as long as it is adjusted so that it can be used.

Preferably, the adhesive coating apparatus comprises a heat exchanger that exchanges heat between the adhesive and the heat medium, and the adhesive measured by the viscometer in the adhesive coating step. The temperature of the heat medium is controlled so that the change in viscosity is within a certain range.

Preferably, in the adhesive coating step, the viscosity of the adhesive at 25 ° C. at the start of coating is 1 mPa · s to 100 mPa · s, and the absolute value of the change in the viscosity of the adhesive is 1 mPa · s. The temperature of the adhesive is controlled so as to be within the range.

Preferably, in the adhesive coating step, the coating thickness of the adhesive is 0.1 μm to 5 μm.

Preferably, in the adhesive coating step, the transport speed of the polarizer and the other film is 15 m / min to 40 m / min.

The present invention is particularly effective when the adhesive is a solvent-free type that does not substantially contain an organic solvent. In general, solvent-free adhesives are more likely to absorb moisture than adhesives containing organic solvents. For this reason, the solvent-free adhesive absorbs moisture in the atmosphere, so that the viscosity tends to decrease with time, which may deteriorate the adhesiveness with time. Therefore, in order to maintain good adhesiveness, it is effective to control the change in the viscosity of the adhesive so as to be within a certain range.
The adhesive to which the present invention can be applied is not limited to the solvent-free type, and can also be applied to an adhesive containing an organic solvent. In the case of an adhesive containing an organic solvent, the viscosity may change due to the volatilization of the solvent. Therefore, by applying the present invention, it is possible to maintain good adhesiveness.

Further, in order to solve the above-mentioned problems, in the present invention, an active energy ray-curable adhesive is applied to at least one of a transport device for transporting a polarizer and another film and the polarizer and the other film. An adhesive coating device to be coated, an active energy ray irradiating device for irradiating and curing the adhesive between the polarizer and the other film bonded via the adhesive, and the above. The adhesive coating device includes a control device for controlling the adhesive coating device, and the adhesive coating device includes a viscometer for continuously measuring the viscosity of the adhesive to be coated, and the control device is said to be said. It is also provided as a polarizing film manufacturing apparatus that controls the temperature of the adhesive so that the change in the viscosity of the adhesive measured by a viscometer is within a certain range.

According to the present invention, it is possible to maintain good adhesion between the polarizer and other films.

It is sectional drawing which shows the structural example of the polarizing film obtained by the manufacturing method which concerns on this invention. It is sectional drawing which shows the other structural example of the polarizing film obtained by the manufacturing method which concerns on this invention. It is a figure which shows typically the structural example of the polarizing film manufacturing apparatus which concerns on one Embodiment of this invention. It is a figure which shows typically the specific structural example of the adhesive coating apparatus and a control apparatus shown in FIG.

Hereinafter, a method for producing a polarizing film and an apparatus for producing a polarizing film according to an embodiment of the present invention will be described with reference to the accompanying drawings.
In this specification, the numerical range represented by "lower limit value X to upper limit value Y" means a lower limit value X or more and an upper limit value Y or less. When a plurality of the numerical values are described separately, it is possible to select an arbitrary lower limit value and an arbitrary upper limit value and set "arbitrary lower limit value to arbitrary upper limit value".
Also, please note that each figure is for reference only, and the dimensions, scale, and shape of the members shown in each figure may differ from the actual ones.

[Polarizing film]
First, a configuration example of the polarizing film obtained by the production method according to the present invention will be described.
1 and 2 are cross-sectional views showing a configuration example of the polarizing film 1 obtained by the production method according to the present invention.
In the polarizing film 1 of the configuration example shown in FIG. 1, the second film 12, the adhesive layer 31, the polarizer 11, the adhesive layer 32, and the third film 13 are laminated in this order.
In the polarizing film 1 of the configuration example shown in FIG. 2, the polarizing element 11, the adhesive layer 31, and the second film 12 are laminated in this order.
However, the polarizing film obtained by the production method according to the present invention is not limited to the configuration examples of FIGS. 1 and 2, and can be appropriately changed.
For example, one or more arbitrary other films may be laminated on the polarizing film of each of the above-mentioned constitution examples.

<Polarizer>
The polarizer 11 refers to an optical element having a property of transmitting light (polarized light) that vibrates in only one specific direction and blocking light that vibrates in the other direction. The polarizer 11 of the present invention is in the form of a flexible film.
Specifically, examples of the polarizer 11 include a hydrophilic polymer film dyed with a dichroic substance (for example, a polyvinyl alcohol-based film dyed with a dichroic substance) and the like.

<2nd film, 3rd film, etc.>
Other films (films other than the polarizer 11) such as the second film 12 and the third film 13 are films that do not contain a polarizer. Other films such as the second film 12 and the third film 13 are films having lower hydrophilicity (having hydrophobicity) than the polarizer 11.
The second film 12 is adhered to one side of the polarizer 11 via an adhesive layer 31 (see FIGS. 1 and 2).
The third film 13 is adhered to the other side of the polarizer 11 via the adhesive layer 32, if necessary (see FIG. 1).

Any optical film can be used as the other film such as the second film 12 and the third film.
As the optical film, conventionally known ones can be used, and examples thereof include a protective film, a retardation film, an antiglare film, a brightness improving film, a viewing angle improving film, and a transparent conductive film.
Other films such as the second film 12 and the third film 13 are independently selected from a protective film, a retardation film, an antiglare film, a brightness improving film, a viewing angle improving film, a transparent conductive film, and the like. Can be used.
Above all, it is preferable to use a protective film such as a TAC film as the second film 12. When the third film 13 is adhered to one side of the polarizer 11, it is preferable to use a protective film as the third film 13.

<Adhesive layer>
The adhesive layer is a solidifying layer of an adhesive, which is a layer interposed between two films and adhering the two films.
The adhesive layer between the polarizer and the second film is composed of an active energy ray-curable adhesive.
The adhesive layer between the layers of the film other than the layer between the polarizer and the second film may be composed of an active energy ray-curable adhesive, or may be composed of another adhesive. Of the adhesive layers, at least the adhesive layer between the polarizer and the other film is preferably composed of an active energy ray-curable adhesive, and all the adhesive layers are active energy ray-curable adhesives. More preferably, it is composed of an agent.
Specifically, in the case of the polarizing film 1 shown in FIG. 1, the adhesive layer 31 is composed of an active energy ray-curable adhesive, and the adhesive layer 32 is composed of an active energy ray-curable adhesive. Is preferable.
Details of the active energy ray-curable adhesive and the adhesive layer will be described later.

[Polarizing film manufacturing equipment]
Next, the polarizing film manufacturing apparatus according to the present invention will be described.
In the polarizing film manufacturing apparatus according to the present invention, an active energy ray-curable adhesive is applied to at least one of a conveying device that conveys a polarizer and another film, and the polarizer and the other film. The adhesive coating device, the active energy ray irradiating device for irradiating the adhesive between the polarizing element and the other film bonded via the adhesive to cure the adhesive, and the adhesive. A control device for controlling the coating device is provided. In the present invention, the adhesive coating device includes a viscometer that continuously measures the viscosity of the adhesive to be coated, and the control device has a viscosity of the adhesive measured by the viscometer. It is characterized in that the temperature of the adhesive is controlled so that the change of the adhesive is within a certain range.

The polarizing film manufacturing apparatus according to the present invention may be in the form of continuously adhering another film to the polarizing element after manufacturing the polarizing element, or a polarizing element may be prepared separately and used as the polarizing element. It may be in the form of adhering another film. The former form is a form in which a series of steps from the production of a polarizing element to the bonding of another film to obtain a polarizing film is performed on one production line, and the latter form is a form in which the production of a polarizer is performed in one. This is a form in which the process of obtaining a polarizing film by adhering another film to the polarizer on a production line is performed on another production line.
The manufacturing apparatus according to the present invention is preferably of a roll-to-roll type in which a series of steps from the manufacture of the polarizer to the adhesion of at least the second film to obtain the polarizing film is performed on one production line.

FIG. 3 is a diagram schematically showing a configuration example of a polarizing film manufacturing apparatus according to the present embodiment. The manufacturing apparatus shown in FIG. 3 is an apparatus for manufacturing the polarizing film 1 of the configuration example shown in FIG. That is, it is an apparatus for producing a polarizing film having a layer structure of a second film 12 / an adhesive layer 31 / a polarizing element 11 / an adhesive layer 32 / a third film 13.
As shown in FIG. 3, the manufacturing apparatus 9 according to the present embodiment has a polarizer producing zone 4 for producing the polarizer 11, and a film lamination zone for adhering the second film 12 and the third film 13 to the polarizer 11. 5 and at least.
The polarizer manufacturing zone 4 includes a first roll portion 41 around which the untreated film raw fabric 1a is wound, a conveying device 42 for conveying the film raw fabric 1a, a processing portion, and a drying device 43. The processing unit is a portion that processes the untreated film raw fabric 1a and changes the film raw fabric 1a into a polarizer 11. The processing unit includes, for example, a swelling treatment tank 4A, a dyeing treatment tank 4B, a cross-linking treatment tank 4C, a stretching treatment tank 4D, and a cleaning treatment tank 4E in order from the upstream side in the film transport direction.
In the film lamination zone 5, a transport device 51 for transporting the polarizer 11, the second film 12, and the third film 13, a second roll portion 52 around which the second film 12 is wound, and a third film 13 are wound. A third roll portion 53, an adhesive coating device 54 having a gravure roll 61 and the like, a control device 58 for controlling the adhesive coating device 54 (not shown in FIG. 3, see FIG. 4 described later), and A bonding portion 55 having a nip roll 7, an active energy ray irradiating device 56 that irradiates an adhesive between the polarizing element 11 and another film with an active energy ray to cure the adhesive, and a winding roll for winding the manufactured polarizing film. It has a part 57 and.

(1) Polarizer production zone <Untreated film raw fabric and transport device>
An untreated film raw fabric 1a is wound around the first roll portion 41. The original film 1a is transported to the processing unit by a transport device 42 provided with a guide roller or the like. The white arrow shown in FIG. 3 indicates the transport direction (traveling direction) of the film to be transported.

The original film 1a has a long strip shape. In the present specification, the long strip shape means a rectangular shape whose length in the longitudinal direction is sufficiently larger than the length in the lateral direction (direction orthogonal to the longitudinal direction). The length of the long strip in the longitudinal direction is, for example, 10 m or more, preferably 50 m or more.
The original film 1a is not particularly limited, but a film containing a hydrophilic polymer film (for example, a polyvinyl alcohol-based film) is preferably used because it is excellent in dyeability with a bicolor substance. Preferably, a hydrophilic polymer film is used. Examples of the film containing the hydrophilic polymer film include a film in which a hydrophilic polymer film and a non-hydrophilic polymer film are laminated. In this case, it is preferable that the hydrophilic polymer film is laminated on the front surface and / or the back surface of the non-hydrophilic polymer film. In this case, the hydrophilic polymer film laminated on the front surface and / or the back surface of the non-hydrophilic polymer film may be in the form of a thin film having a thickness of about several μm.

The hydrophilic polymer film is not particularly limited, and conventionally known films can be used. Specifically, examples of the hydrophilic polymer film include polyvinyl alcohol (PVA) -based film, partially formalized PVA-based film, polyethylene terephthalate (PET) film, ethylene / vinyl acetate copolymer film, and partial saponification of these. Examples include film. In addition to these, a polyene-oriented film such as a dehydrated product of PVA or a dehydrochlorinated product of polyvinyl chloride, a stretch-oriented polyvinylene-based film, or the like can also be used. Among these, a PVA-based polymer film is particularly preferable because it is excellent in dyeability with a dichroic substance.
As the raw material polymer of the PVA-based polymer film, for example, a polymer obtained by polymerizing vinyl acetate and then saponified, or a small amount of a copolymerizable monomer such as unsaturated carboxylic acid or unsaturated sulfonic acid is copolymerized with vinyl acetate. Polymers, etc. may be mentioned. The degree of polymerization of the PVA-based polymer is not particularly limited, but is preferably 500 to 10000, more preferably 1000 to 6000, from the viewpoint of solubility in water and the like. The degree of saponification of the PVA-based polymer is preferably 75 mol% or more, more preferably 98 mol% to 100 mol%.
The thickness of the untreated film raw fabric 1a is not particularly limited, but is, for example, 15 μm to 110 μm.

<Swelling treatment tank>
The swelling treatment tank 4A is a treatment tank containing a swelling treatment liquid. The swelling treatment liquid swells the film raw fabric 1a. As the swelling treatment liquid, for example, water can be used. Further, water obtained by adding an appropriate amount of an iodine compound such as glycerin or potassium iodide to water may be used as the swelling treatment liquid. When glycerin is added, the concentration is preferably 5% by weight or less, and when an iodine compound such as potassium iodide is added, the concentration is preferably 10% by weight or less.

<Dyeing tank>
The dyeing treatment tank 4B is a treatment tank containing a dyeing treatment liquid. The dyeing solution dyes the original film 1a. Examples of the dyeing solution include a solution containing a dichroic substance as an active ingredient. Examples of the dichroic substance include iodine and organic dyes. Preferably, a solution in which iodine is dissolved in a solvent can be used as the dyeing solution. Water is generally used as the solvent, but an organic solvent compatible with water may be further added. The concentration of iodine in the dyeing solution is not particularly limited, but is preferably 0.01% by weight to 10% by weight, more preferably 0.02% by weight to 7% by weight, and 0.025% by weight. It is more preferably% to 5% by weight. If necessary, an iodine compound may be added to the dyeing solution in order to further improve the dyeing efficiency. The iodine compound is a compound containing iodine and an element other than iodine in the molecule. For example, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, etc. Examples thereof include barium iodide, calcium iodide, tin iodide, and titanium iodide.

<Crosslink processing tank>
The cross-linking treatment tank 4C is a treatment tank containing a cross-linking treatment liquid. The cross-linking treatment liquid cross-links the dyed film raw fabric 1a. As the cross-linking treatment liquid, a solution containing a boron compound as an active ingredient can be used. For example, as the cross-linking treatment liquid, a solution in which a boron compound is dissolved in a solvent can be used. Water is generally used as the solvent, but an organic solvent compatible with water may be further added. Examples of the boron compound include boric acid and borax. The concentration of the boron compound in the cross-linking treatment liquid is not particularly limited, but is preferably 1% by weight to 10% by weight, more preferably 2% by weight to 7% by weight, and 2% by weight to 6% by weight. Is even more preferable. Further, since a polarizer having uniform optical characteristics can be obtained, an iodine compound may be added to the cross-linking treatment liquid, if necessary.

<Stretching tank>
The stretching treatment tank 4D is a treatment tank containing the stretching treatment liquid.
The stretching treatment liquid is not particularly limited, but for example, a solution containing a boron compound as an active ingredient can be used. As the stretching treatment liquid, for example, a solution in which a boron compound and, if necessary, various metal salts, zinc compounds and the like are dissolved in a solvent can be used. Water is generally used as the solvent, but an organic solvent compatible with water may be further added. The concentration of the boron compound in the stretching treatment liquid is not particularly limited, but is preferably 1% by weight to 10% by weight, more preferably 2% by weight to 7% by weight. From the viewpoint of suppressing the elution of iodine adsorbed on the film, an iodine compound may be added to the stretching treatment liquid, if necessary.

<Washing tank>
The cleaning treatment tank 4E is a treatment tank in which the cleaning treatment liquid is stored. The cleaning treatment liquid cleans the film raw fabric 1a after stretching. The cleaning treatment liquid is a treatment liquid for cleaning the treatment liquid such as the dyeing treatment liquid and the cross-linking treatment liquid adhering to the original film 1a. As the cleaning treatment liquid, water such as ion-exchanged water, distilled water, and pure water is typically used.

<Drying device>
The drying device 43 is provided on the downstream side of the cleaning treatment tank 4E. The drying device 43 is provided for drying the treated film.
In the example shown in FIG. 3, the treatment unit includes a swelling treatment tank 4A, a dyeing treatment tank 4B, a cross-linking treatment tank 4C, a stretching treatment tank 4D, and a cleaning treatment tank 4E, and one or two of them are treated. The tank may be omitted. On the other hand, the processing unit may further have an adjustment processing tank (not shown). The adjustment treatment tank is a treatment tank in which the adjustment treatment liquid is stored. This adjustment treatment tank is provided between the cross-linking treatment tank 4C and the stretching treatment tank 4D, or between the stretching treatment tank 4D and the cleaning treatment tank 4E. The adjusting treatment solution is a solution for adjusting the hue of the film, and a solution containing an iodine compound as an active ingredient can be used.
The film obtained by drying the washed film raw fabric 1a with the drying device 43 is the polarizer 11.

(2) Film lamination zone <Conveyor>
The transport device 51 in the film lamination zone 5 includes a guide roller and the like. The transport device 51 transports the long strip-shaped polarizer 11 to the downstream side such as the bonding portion 55. Further, the transport device 51 transports the long strip-shaped second film 12 and the third film 13 laminated on the polarizer 11 to the downstream side such as the bonding portion 55.

The manufacturing apparatus 9 according to the present embodiment has a second roll portion 52 around which the long strip-shaped second film 12 is wound, and a third roll portion 53 around which the long strip-shaped third film 13 is wound. .. The second film 12 of the second roll portion 52 and the third film 13 of the third roll portion 53 are independently transported from the roll portions 52 and 53 to the downstream side such as the bonding portion 55 by the transport device 51, respectively. Will be done.

<Adhesive coating device and control device>
The adhesive coating device 54 applies the adhesive to the film by the gravure roll 61. The adhesive coating device 54 is arranged on the upstream side of the bonding portion 55.
In the manufacturing apparatus 9 shown in FIG. 3, the adhesive coating apparatus 54 includes one side of the polarizer 11, the other one side of the polarizer 11, one side of the second film 12, and one side of the third film 13. They are placed on each side.
An adhesive is applied to one side of the polarizing element 11 and an adhesive is applied to one side of the second film 12 by the adhesive coating device 54 so that both adhesive layers face each other with the polarizer 11 and the first By bonding the two films 12 together, it is possible to effectively prevent the formation of air bubbles between the polarizer 11 and the second film 12.
Similarly, the adhesive coating device 54 applies an adhesive to one side of the polarizing element 11 and an adhesive to one side of the third film 13, so that both adhesive layers face each other. By adhering the 11 and the third film 13, it is possible to effectively prevent the formation of air bubbles between the polarizer 11 and the third film 13.

However, since the polarizer 11 and the second film 12 can be adhered to each other by applying an adhesive to at least one of the polarizer 11 and the second film 12, they are arranged on one side of the polarizer 11. Either one of the adhesive coating device 54 and the adhesive coating device 54 arranged on one side of the second film 12 may be omitted. Similarly, if an adhesive is applied to at least one side of the polarizer 11 and the third film 13, the polarizer 11 and the third film 13 can be adhered to each other, so that they are arranged on one side of the polarizer 11. One of the adhesive coating device 54 and the adhesive coating device 54 arranged on one side of the third film 13 may be omitted.

FIG. 4 is a diagram schematically showing a specific configuration example of the adhesive coating device 54 and the control device 58. FIG. 4 shows a state in which the inside of each component is appropriately seen through.
As shown in FIGS. 3 and 4, the adhesive coating device 54 includes a gravure roll 61, a backup roll 62 arranged to face the gravure roll 61, a container 63 in which the adhesive is stored, and a doctor blade 64. , Equipped with. Note that backup rolls are omitted for the adhesive coating devices 54 and 54 arranged on one side and the other side of the polarizer 11, and the gravure rolls 61 and 61 are arranged so as to face each other with the polarizer 11 in between. Has been done.
The surface of the gravure roll 61 is formed with a plurality of cells (recesses into which an adhesive enters). The surface of the gravure roll 61 rotates about an axis so that its surface contacts the adhesive stored in the container 63 (the direction of rotation of the gravure roll 61 is indicated by an arrow). As the rotation proceeds, the adhesive adheres to the surface of the gravure roll 61 including the cells, and the excess adhesive is scraped off into the container 63 by the doctor blade 64. When the gravure roll 61 containing the adhesive in the cell comes into contact with the polarizer 11 or the like, the adhesive in the cell is transferred to one side of the polarizer 11 or the like. In this way, the adhesive is applied to one side of each film such as the gravure roll 61 to the polarizer 11 in a solid shape.

Further, as shown in FIG. 4, the adhesive coating device 54 has a structure in which the adhesive A is circulated and supplied into the container 63. Specifically, the adhesive coating device 54 includes a storage tank 54a in which the adhesive A is stored, a supply pipe 54b for supplying the adhesive A stored in the storage tank 54a into the container 63, and the like. A discharge pipe 54c for discharging the adhesive A stored in the container 63 to the storage tank 54a is provided. As a result, the adhesive A circulates by moving in the direction indicated by the white arrow in FIG. 4 in the circulation path composed of the storage tank 54a, the supply pipe 54b, the container 63, and the discharge pipe 54c.
The adhesive coating device 54 includes a pump 54d attached to a supply pipe 54b. By this pump 54d, the adhesive A is sucked up from the storage tank 54a and moves into the container 63 through the supply pipe 54b.

The adhesive coating device 54 is attached near the container 63 of the supply pipe 54b, and includes a viscometer 54e that continuously measures the viscosity of the adhesive A to be coated. As the viscometer 54e, for example, a so-called vibration type continuous viscometer can be used. As the vibration type continuous viscometer, for example, "Twist vibration type viscometer" FEM-1000V-ST manufactured by SEKONIC Corporation can be used.
Further, the adhesive coating device 54 includes a heat exchanger 54f which is attached to the supply pipe 54b and exchanges heat between the adhesive A and the heat medium. The heat exchanger 54f is located upstream of the viscometer 54e in the moving direction of the adhesive A. Therefore, the viscometer 54e measures the viscosity of the adhesive A after heat exchange (cooling or heating) with the heat exchanger 54f. Although not particularly limited, as the heat exchanger 54f, a chiller whose heat medium is water is preferably used.

The control device 58 is electrically connected to the viscometer 54e and the heat exchanger 54f included in the adhesive coating device 54.
The control device 58 controls the temperature of the adhesive A so that the change in the viscosity of the adhesive A measured by the viscometer 54e is within a certain range. Specifically, the viscosity of the adhesive A measured by the viscometer 54e is continuously input to the control device 58, and the change in the viscosity of the adhesive A measured by the viscometer 54e is constant in the control device 58. The temperature of the heat medium used in the heat exchanger 54f is controlled so as to be within the range. For example, when the viscosity of the adhesive A decreases with time with respect to the viscosity at the initial stage of coating, the control device 58 increases the temperature of the heat medium so that the viscosity of the adhesive A increases. Become. On the contrary, when the viscosity of the adhesive A increases with time, the control device 58 lowers the temperature of the heat medium so that the viscosity of the adhesive A decreases. As a result, the change in the viscosity of the adhesive A can be kept within a certain range. Preferably, the control device 58 controls the temperature of the heat medium so that the absolute value of the change in the viscosity of the adhesive is within 1 mPa · s.

<Adhesive>
As the adhesive to be coated by the adhesive coating device 54, an active energy ray-curable adhesive is used. That is, the uncured active energy ray-curable adhesive is contained in the container 63 of the adhesive coating device 54.
As the active energy ray-curable adhesive, conventionally known ones can be used. The active energy ray-curable adhesive generally contains an active energy ray-curable component and a polymerization initiator, and if necessary, contains various additives.
The active energy ray-curable component can be roughly classified into electron beam curability, ultraviolet curability, and visible light curability. Further, the active energy ray-curable component can be roughly classified into a radical-polymerizable compound and a cationically polymerizable compound from the viewpoint of the curing mechanism.

Examples of the radically polymerizable compound include compounds having a radically polymerizable functional group of a carbon-carbon double bond such as a (meth) acryloyl group and a vinyl group. Moreover, either a monofunctional radical polymerizable compound or a bifunctional or higher functional radical polymerizable compound can be used. Further, these radically polymerizable compounds may be used alone or in combination of two or more. The radically polymerizable compound is preferably a compound having a (meth) acryloyl group, and examples thereof include a (meth) acrylamide derivative having a (meth) acrylamide group and a (meth) acrylate having a (meth) acryloyloxy group.
When a radically polymerizable compound is used as the active energy ray-curable adhesive, the polymerization initiator is appropriately selected according to the active energy ray. When the adhesive is cured by ultraviolet rays or visible light, an ultraviolet cleaving or visible light cleaving polymerization initiator is used. Examples of such a polymerization initiator include benzophenone compounds, aromatic ketone compounds, acetophenone compounds, aromatic ketal compounds, aromatic sulfonyl chloride compounds, and thioxanthone compounds.

Examples of the cationically polymerizable compound include a monofunctional cationically polymerizable compound having one cationically polymerizable functional group in the molecule, a polyfunctional cationically polymerizable compound having two or more cationically polymerizable functional groups in the molecule, and the like. Examples of the cationically polymerizable functional group include an epoxy group, an oxetanyl group, and a vinyl ether group. Examples of the cationically polymerizable compound having an epoxy group include an aliphatic epoxy compound, an alicyclic epoxy compound, and an aromatic epoxy compound. Examples of the cationically polymerizable compound having an oxetanyl group include 3-ethyl-3-hydroxymethyloxetane, 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene, and 3-ethyl-3- (phenoxymethyl). ) Oxetane and the like. Examples of the cationically polymerizable compound having a vinyl ether group include 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, and 4-hydroxybutyl vinyl ether.
When a cationically polymerizable compound is used as the active energy ray-curable adhesive, a cationic polymerization initiator is blended. This cationic polymerization initiator generates a cationic species or Lewis acid by irradiation with active energy rays such as visible light, ultraviolet rays, and electron beams, and initiates a polymerization reaction with an epoxy group of a cationically polymerizable compound. As the cationic polymerization initiator, a photoacid generator and a photobase generator can be used.

In the present invention, an active energy ray-curable adhesive that cures with light containing visible light of 380 nm to 450 nm can also be used. In this case, it is preferable to use an active energy ray-curable adhesive containing a radically polymerizable compound and a polymerization initiator.
Such an active energy ray-curable adhesive is disclosed in, for example, Japanese Patent Application Laid-Open No. 2018-092186, and as the active energy ray-curable adhesive of the present invention, the active energy ray-curable adhesive described in the above publication. Agents can be used. In the present specification, the description of the above publication is omitted due to space limitations, but the description of the adhesive of the above publication can be incorporated into the present specification as it is.

<Lasting part>
The bonding portion 55 is provided with a pair of nip rolls 7 and 7.
The laminated film composed of the polarizing element 11 and the second film 12 and the third film 13 bonded to each other via the adhesive layer is inserted between the nip rolls 7 and 7 and pressed.

<Active energy ray irradiation device>
The active energy ray irradiating device 56 is a device that irradiates the laminated film pressed by the nip rolls 7 and 7 with the active energy ray. The active energy ray is appropriately selected depending on the curability of the active energy ray-curable adhesive. Examples of the active energy ray include an electron beam, ultraviolet rays, and visible light. As described in the above-mentioned publication, an active energy ray irradiating device 56 capable of irradiating visible light of 380 nm to 450 nm can also be used.
Further, as shown in FIG. 3, it is preferable that the active energy ray irradiating device 56 is arranged on both side surfaces of the laminated film so that the active energy rays can be irradiated from both side surfaces of the laminated film.

[Manufacturing method of polarizing film]
Next, a method for producing a polarizing film according to the present invention will be described.
<Manufacturing process of polarizer>
As shown in FIG. 3, the untreated film raw fabric 1a is pulled out from the first roll portion 41, and the film raw fabric 1a is conveyed to the swelling treatment tank 4A by the conveying device 42. The film raw fabric 1a is swelled by immersing the film raw fabric 1a in the swelling treatment liquid while transporting the film raw fabric 1a by the guide roller 42 in the swelling treatment tank 4A. The temperature of the swelling treatment liquid is not particularly limited, but is, for example, 20 ° C to 45 ° C. The time for immersing the film raw fabric 1a in the swelling treatment liquid is not particularly limited, but is, for example, 5 seconds to 300 seconds. Next, by immersing the swelled film raw fabric 1a in the dyeing treatment liquid in the dyeing treatment tank 4B, the film raw fabric 1a is dyed with a dichroic substance. The temperature of the dyeing solution is not particularly limited, but is, for example, 20 ° C to 50 ° C. The time for immersing the film raw fabric 1a in the dyeing treatment liquid is not particularly limited, but is, for example, 5 seconds to 300 seconds. By immersing the dyed film raw fabric 1a in the cross-linking treatment liquid in the cross-linking treatment tank 4C, the dichroic substance of the film raw fabric 1a is crosslinked. The temperature of the cross-linking treatment liquid is not particularly limited, but is, for example, 25 ° C. or higher, preferably 40 ° C. to 70 ° C. The time for immersing the film raw fabric 1a in the cross-linking treatment liquid is not particularly limited, but is, for example, 5 seconds to 800 seconds.

The original film 1a after cross-linking is stretched while being conveyed by a guide roller in the stretching treatment liquid of the stretching treatment tank 4D. The temperature of the stretching treatment liquid is not particularly limited, but is, for example, 40 ° C. to 90 ° C. The draw ratio can be appropriately set depending on the intended purpose, but the total draw ratio is, for example, 2 to 7 times, preferably 4.5 to 6.8 times. The total draw ratio means the final draw ratio of the film raw fabric 1a. The film raw fabric 1a is washed by immersing the stretched film raw fabric 1a in the cleaning treatment liquid in the cleaning treatment tank 4E. The temperature of the cleaning treatment liquid is, for example, 5 ° C to 50 ° C. The cleaning time is, for example, 1 second to 300 seconds.
The polarizer 11 is obtained by drying the washed film raw fabric 1a in the drying apparatus 43. The obtained polarizer 11 is continuously conveyed to the film lamination zone 5.

<Adhesive coating process>
The long strip-shaped polarizer 11 is conveyed to the bonding portion 55 by the conveying device 51. In the transport process, the active energy ray-curable adhesive is applied to both surfaces of the polarizer 11 by the adhesive coating device 54. By applying the active energy ray-curable adhesive with the adhesive coating device 54, an adhesive layer made of the active energy ray-curable adhesive is formed on both sides of the polarizer 11.
On the other hand, the long strip-shaped second film 12 is pulled out from the second roll portion 52 and is conveyed to the bonding portion 55 by the conveying device 51. Similarly, the long strip-shaped third film 13 is pulled out from the third roll portion 53 and conveyed to the bonding portion 55 by the conveying device 51. In each transfer process, the active energy ray-curable adhesive is applied to one side of the second film 12 and one side of the third film 13 by the adhesive coating device 54, respectively. By applying the active energy ray-curable adhesive with the adhesive coating device 54, an adhesive layer made of the active energy ray-curable adhesive is applied to one side of the second film 12 and one side of the third film 13, respectively. Is formed.

The coating thickness of the adhesive layer is not particularly limited, but if it is too small, the adhesive strength of the film decreases, and if it is too large, the thickness of the polarizing film becomes relatively large. From this point of view, the coating thickness of the adhesive layer formed on the polarizer 11, the second film 12, and the third film 13 is preferably 0.1 μm to 5 μm, respectively.

The viscosity of the active energy ray-curable adhesive at the start of coating is not particularly limited, but if it is too small or too large, the adhesiveness of the adhesive will decrease from the start of coating. From this point of view, the active energy ray-curable adhesive preferably has a viscosity at 25 ° C. at the start of coating adjusted to 1 mPa · s to 100 mPa · s, and a viscosity at 25 ° C. at the start of coating. Is more preferably adjusted to 10 mPa · s to 50 mPa · s, and particularly preferably adjusted to 15 mPa · s to 45 mPa · s. The active energy ray-curable adhesive used in the present embodiment is a solvent-free type that substantially does not contain an organic solvent, and such a solvent-free active energy ray-curable adhesive is a thickener. By adjusting the viscosity modifier such as, the viscosity can be adjusted to the above-mentioned preferable range.
Then, after the start of coating, the control device 58 controls the temperature of the adhesive (the temperature of the heat medium of the heat exchanger 54f) so that the change in the viscosity of the adhesive measured by the viscometer 54e is within a certain range. To do.

Further, the surface tension of the active energy ray-curable adhesive at the time of coating is preferably 50 mN / m or less, and more preferably 5 mN / m to 45 mN / m or less. By using the active energy ray-curable adhesive having such surface tension, the adhesive is satisfactorily transferred from the cell of the gravure roll 61 to the polarizer 11 or the like (so that the adhesive is satisfactorily transferred). become).
The above surface tension can be measured by the so-called suspension method (pendant drop method).

Further, the transport speeds (line speeds) of the polarizer 11, the second film 12, and the third film 13 at the time of coating are not particularly limited, but if they are too fast, bubbles may be generated, and if they are too slow, polarization may occur. Film production efficiency is reduced. From this point of view, the transport speeds of the polarizer 11, the second film 12, and the third film 13 at the time of coating are preferably 15 m / min to 40 m / min, and more preferably 20 m / min to 35 m / min.

<Polarizing film manufacturing process>
The polarizer 11, the second film 12, and the third film 13 on which the adhesive layer (uncured active energy ray-curable adhesive) is formed are independently conveyed to the bonding portion 55. The adhesive layer formed on the polarizer 11 and the adhesive layer formed on the second film 12 face each other, and the adhesive layer formed on the polarizer 11 and the adhesive formed on the third film 13 face each other. These films are inserted between the nip rolls 7 and 7 while facing the layers. By passing through the nip roll 7, the polarizer 11, the second film 12, and the third film 13 are bonded together from the second film / uncured adhesive layer / polarizer / uncured adhesive layer / third film. A laminated film is obtained.
By irradiating the laminated film with the active energy ray by the active energy ray irradiating device 56, the active energy ray-curable adhesive is cured, and the second film 12 / the cured adhesive layer / the polarizer 11 / A polarizing film 1 composed of the cured adhesive layer / third film 13 is obtained. The thickness of the adhesive layer made of the active energy ray-curable adhesive is substantially the same before curing (at the time of coating) and after curing.
The obtained polarizing film is wound around the winding roll portion 57.

<Modification example>
In the above manufacturing method, a case where a polarizing film (polarizing film 1 shown in FIG. 1) composed of a second film 12 / an adhesive layer after curing / a polarizer 11 / an adhesive layer after curing / a third film 13 is produced. However, the present invention is not limited to this. For example, by omitting the bonding of the third film 13 to the polarizing element 11 in the above manufacturing method, a polarizing film 1 in which no other film is laminated on one side of the polarizing element 11 as shown in FIG. 2 can be obtained. Can be done.
Further, in the above manufacturing method, the active energy ray-curable adhesive is applied to both sides of the polarizer 11, and the active energy ray-curable adhesive is also applied to each side of the second film 12 and the third film 13. Then, the adhesive layers are bonded so as to face each other, but the present invention is not limited to this. For example, an active energy ray-curable adhesive is applied to only one side of the polarizing element 11 or one side of the second film 12 to form an adhesive layer, and the polarizing element 11 is formed through the adhesive layer. And the second film 12 may be bonded together. Similarly, an active energy ray-curable adhesive is applied to only one side of the polarizing element 11 or one side of the third film 13 to form an adhesive layer, and the polarizer is formed through the adhesive layer. 11 and the third film 13 may be bonded together.

[Use of polarizing film, etc.]
The polarizing film obtained by the production method according to the present invention is typically used as an optical film for a display such as a liquid crystal display device or an organic display device.
Further, the polarizing film obtained by the production method according to the present invention is not limited to the case where it is used for the above-mentioned display, and can be used for applications other than the display. Applications other than displays include optical equipment, buildings, medical / food fields, and the like. When a polarizing film is used in an optical instrument, the polarizing film is processed into, for example, a polarizing lens or a transparent radio wave blocking film. When a polarizing film is used in an electronic device, the polarizing film is processed into, for example, a dimming window film. When the polarizing film is used in the medical / food field, the polarizing film is processed into, for example, a photodegradation prevention film.

Hereinafter, Examples and Comparative Examples will be described, and the present invention will be described in more detail. However, the present invention is not limited to the following examples.

[Material used]
<Active energy ray-curable adhesive A>
As the radically polymerizable compound, hydroxyethylacrylamide (HEAA) manufactured by Kojin Co., Ltd., which has an SP value (solubility parameter) of 29.6 and a homopolymer glass transition temperature (Tg) of 123 ° C., was used. As another radically polymerizable compound, a tripropylene glycol diacrylate "ARONIX M-220" (M-220) manufactured by Toagosei Co., Ltd., which has an SP value of 19.0 and a homopolymer Tg of 69 ° C., was used. .. As still another radically polymerizable compound, acryloyl morpholine (ACMO) manufactured by Kojin Co., Ltd., which has an SP value of 22.9 and a homopolymer Tg of 150 ° C., was used. Further, as an acrylic oligomer obtained by polymerizing a (meth) acrylic monomer, "ARUFON UP-1190" (UP-1190) manufactured by Toagosei Co., Ltd. was used. Further, 2-acetoacetoxyethyl methacrylate (AAEM) manufactured by Nippon Synthetic Chemistry Co., Ltd., which has an SP value of 20.23 (MJ / M ³ ) ^1/2 and a homopolymer Tg of 9 ° C., was used. Further, as the polymerization initiator, "KAYACURE DETX-S" (DETX-S), which is diethyl thioxanthone manufactured by Nippon Kayaku Co., Ltd., was used. Further, as the polymerization initiator, "IRGACURE907" (IRG907), which is 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one manufactured by BASF, was used.
And the above-mentioned HEAA / M-220 / ACMO / UP-1190 / AAEM / IRG907 / DETX-S = 16.4 / 32.8 / 32.8 / 8.2 / 5.7 / 2.5 / 1. 6 (value is the weight% when the total amount of the composition is 100% by weight) was mixed, and the mixture was stirred at 50 ° C. for 1 hour to obtain an active energy ray-curable adhesive A.
The viscosity of this active energy ray-curable adhesive A at 25 ° C. at the start of coating was 40 mPa · s.

<Active energy ray-curable adhesive B>
63.48% by weight of 1,9-nonanediol diacrylate, 10% by weight of hydroxyethylacrylamide and 30% by weight of acryloylmorpholin (active energy ray-curable component), and BYK's "BYK-UV3570" 0 Active energy ray-curable adhesion by mixing .52% by weight (bubble inhibitor), 3% by weight IRGACURE 907 and 2% by weight KAYACURE DETX-S (polymerization initiator) and stirring for 3 hours. Agent B was obtained.
The viscosity of this active energy ray-curable adhesive B at 25 ° C. at the start of coating was 20 mPa · s.
The viscosities of the active energy ray-curable adhesives A and B at 25 ° C. at the start of coating were measured using an E-type viscometer.

<Polarizer>
A polyvinyl alcohol film having an average degree of polymerization of 2400 and a saponification degree of 99.9 mol% and a thickness of 45 μm was immersed in warm water at 30 ° C. for 60 seconds to swell. Then, the film was dyed by immersing it in an aqueous solution having a concentration of iodine / potassium iodide (weight ratio = 0.5 / 8) at a concentration of 0.3% and stretching it up to 3.5 times. Then, stretching was carried out in a boric acid ester aqueous solution at 65 ° C. so that the total stretching ratio was 6 times. After stretching, it was dried in a drying device at 40 ° C. for 3 minutes to obtain a long strip-shaped polyvinyl alcohol-based polarizer (thickness 18 μm).

<2nd film and 3rd film>
A twin-screw kneader containing 100 parts by weight of the imidized MS resin and 0.62 parts by weight of a triazine-based ultraviolet absorber (trade name: T-712) described in Production Example 1 of JP-A-2010-284840. The mixture was mixed at 220 ° C. to prepare resin pellets. The obtained resin pellets were dried at 100.5 kPa at 100 ° C. for 12 hours and extruded from a T-die at a die temperature of 270 ° C. using a single-screw extruder to form a film (thickness 160 μm). Further, the film is stretched in an atmosphere of 150 ° C. in the transport direction (thickness 80 μm), then an easy-adhesive containing an aqueous urethane resin is applied, and then in an atmosphere of 150 ° C. in a direction orthogonal to the film transport direction. A transparent acrylic film having a thickness of 40 μm (water permeability 58 g / m ² / 24h) was obtained. This transparent acrylic film was used as the second film.
As the third film, a cyclic polyolefin film (manufactured by Zeon Corporation) having a thickness of 52 μm was used.

[Example 1]
The active energy ray-curable adhesive A was stored in the storage tank 54a and the container 63 of the adhesive coating device 54 shown in FIG. While the above-mentioned polarizer, the second film and the third film are each conveyed at a speed of 25 m / min by the conveying device 51, both sides of the polarizer, one side of the second film and the third film are conveyed by the adhesive coating device 54. One side of the film was coated with a solid active energy ray-curable adhesive. At this time, the temperature of the heat medium of the heat exchanger 54f was controlled by the control device 58 so that the absolute value of the change in the viscosity of the adhesive continuously measured by the viscometer 54e was within 1 mPa · s. As a result, an adhesive layer having a coating thickness of about 0.7 μm is formed, and then inserted between the nip rolls 7 and 7 to form a second film / uncured adhesive layer / polarizer / uncured adhesive layer. / A laminated film of the third film was obtained. A polarizing film was continuously produced by irradiating the active energy rays (light having a wavelength of 380 nm to 450 nm) emitted from the active energy irradiation device 56 from both sides of the laminated film to cure the adhesive layer. The adhesive coating device 54 was continuously operated for about 12 hours to prepare a long strip-shaped polarizing film.

[Example 2]
A polarizing film was continuously produced in the same manner as in Example 1 except that the active energy ray-curable adhesive B was used.

[Comparative Example 1]
The polarizing film was continuously applied in the same manner as in Example 1 except that the control device 58 did not control (the temperature of the heat medium of the heat exchanger 54f was not changed for about 12 hours from the start of coating). Made.

[Comparative Example 2]
The polarizing film was continuously applied in the same manner as in Example 2 except that the control device 58 did not control (the temperature of the heat medium of the heat exchanger 54f was not changed for about 12 hours from the start of coating). Made.

なお、剥離強度の測定及び剥離界面の評価は、長尺帯状の偏光フィルムの先端部（初期に製造される部分）と後端部（約１２時間の稼働後に製造される部分）とを切断して、それぞれ試験片を作製し、各試験片について行った。表１に示す「剥離強度（初期）」は、偏光フィルムの先端部を切断して得られた試験片について測定した剥離強度を意味し、「剥離界面評価（初期）」は、偏光フィルムの先端部を切断して得られた試験片について剥離界面を評価した結果を意味する。表１に示す「剥離強度（１２時間連続稼働後）」は、偏光フィルムの後端部を切断して得られた試験片について測定した剥離強度を意味し、「剥離界面評価（１２時間連続稼働後）」は、偏光フィルムの後端部を切断して得られた試験片について剥離界面を評価した結果を意味する。 [Measurement of peel strength and evaluation of peel interface]
The peel strength of the polarizing films obtained in Examples 1 and 2 and Comparative Examples 1 and 2 was measured, and the peeling interface was evaluated. The results are shown in Table 1.

For the measurement of peel strength and the evaluation of the peel interface, the front end (the part manufactured at the beginning) and the rear end (the part manufactured after about 12 hours of operation) of the long strip-shaped polarizing film are cut off. Each test piece was prepared and carried out for each test piece. The "peeling strength (initial)" shown in Table 1 means the peeling strength measured for the test piece obtained by cutting the tip of the polarizing film, and the "peeling interface evaluation (initial)" is the tip of the polarizing film. It means the result of evaluating the peeling interface of the test piece obtained by cutting the portion. “Peeling strength (after continuous operation for 12 hours)” shown in Table 1 means the peeling strength measured for the test piece obtained by cutting the rear end portion of the polarizing film, and “evaluation of peeling interface (continuous operation for 12 hours)”. After) ”means the result of evaluating the peeling interface of the test piece obtained by cutting the rear end portion of the polarizing film.

Specifically, the above-mentioned test piece was cut into a size of 200 mm in a direction parallel to the stretching direction of the polarizer and 15 mm in a direction orthogonal to the stretching direction, and the test piece was attached to a glass plate. Make a notch between the second film of the test piece and the polarizer with a cutter knife, and use Tencilon to peel the second film and the polarizer in the 90 ° direction at a peeling speed of 500 mm / min to determine the peeling strength. It was measured.
In addition, the infrared absorption spectrum of the peeled surface after peeling was measured by the ATR method, and the peeling interface was evaluated based on the following criteria.
〇: Cohesive destruction of the second film or polarizer ×: Interfacial peeling between the adhesive layer / polarizer In the above criteria, “〇” indicates adhesiveness because the adhesive force of the adhesive layer is greater than or equal to the cohesive force of the film. Means very good. On the other hand, "x" means that the adhesive force at the interface between the adhesive layer / the polarizer is insufficient (adhesiveness is inferior).

As shown in Table 1, according to Examples 1 and 2, the absolute value of the change in viscosity of the adhesives A and B is within 1 mPa · s during continuous operation of the manufacturing apparatus for about 12 hours (Example 1). Was reduced by 0.2 mPa · s, and Example 2 was reduced by 0.1 mPa · s). Specifically, it was possible to suppress a decrease in viscosity by gradually increasing the temperature of the heat medium of the heat exchanger 54f. As a result, the peel strength hardly changed even after the lapse of about 12 hours, the peel interface was also agglomerated fracture of the second film or the polarizer, and the adhesiveness was excellent.
On the other hand, according to Comparative Examples 1 and 2, the absolute value of the change in viscosity of the adhesives A and B exceeded 1 mPa · s (Example 1 decreased by 5 mPa · s, Example 2 decreased by 3 mPa · s). ). As a result, the peel strength was significantly reduced after about 12 hours from the initial stage of operation, and the peel interface was also the interface peel between the adhesive layer / the polarizer, and the adhesiveness was inferior. In Comparative Examples 1 and 2, the interfacial peeling between the adhesive layer and the polarizer occurred because the coated adhesive became more hydrophilic than the polarizer as the viscosity of the adhesive decreased with time. It is presumed that the cause is that it easily penetrates into the lower second film side, and as a result, the adhesive strength of the adhesive layer is reduced.

1 ... Polarizing film 11 ... Polarizer 12 ... Other film (second film)
13 ... Other film (third film)
4 ... Polarizer manufacturing zone 5 ... Film lamination zone 9 ... Polarizing film manufacturing equipment 54 ... Adhesive coating equipment 54e ... Viscometer 54f ... Heat exchanger 58 ... Control device

Claims (7)

An adhesive that transports a polarizer and another film, respectively, and coats at least one of the polarizer and the other film with an active energy ray-curable adhesive by an adhesive coating device in the transfer process. The coating process and
A polarizing film manufacturing step of manufacturing a polarizing film by bonding the polarizer and the other film via the adhesive and curing the adhesive is included.
The adhesive coating apparatus includes a viscometer that continuously measures the viscosity of the adhesive to be coated.
In the adhesive coating step, the temperature of the adhesive is controlled so that the change in the viscosity of the adhesive measured by the viscometer is within a certain range.
Method for manufacturing polarizing film. The adhesive coating apparatus includes a heat exchanger that exchanges heat between the adhesive and a heat medium.
In the adhesive coating step, the temperature of the heat medium is controlled so that the change in the viscosity of the adhesive measured by the viscometer is within a certain range.
The method for producing a polarizing film according to claim 1. In the adhesive coating step, the viscosity of the adhesive at 25 ° C. at the start of coating is 1 mPa · s to 100 mPa · s, and the absolute value of the change in the viscosity of the adhesive is within 1 mPa · s. To control the temperature of the adhesive,
The method for producing a polarizing film according to claim 1 or 2. In the adhesive coating step, the coating thickness of the adhesive is 0.1 μm to 5 μm.
The method for producing a polarizing film according to any one of claims 1 to 3. In the adhesive coating step, the transport speed of the polarizer and the other film is 15 m / min to 40 m / min.
The method for producing a polarizing film according to any one of claims 1 to 4. The adhesive is a solvent-free type that is substantially free of organic solvents.
The method for producing a polarizing film according to any one of claims 1 to 5. A transport device that transports the polarizer and other films, respectively.
An adhesive coating device that coats at least one of the polarizer and the other film with an active energy ray-curable adhesive.
An active energy ray irradiating device that irradiates and cures the adhesive between the polarizing element and the other film bonded via the adhesive.
A control device for controlling the adhesive coating device is provided.
The adhesive coating apparatus includes a viscometer that continuously measures the viscosity of the adhesive to be coated.
The control device controls the temperature of the adhesive so that the change in the viscosity of the adhesive measured by the viscometer is within a certain range.
Polarizing film manufacturing equipment.

Images