KR102036487B1 - Production device and production method for polarizing film, and polarizing film - Google Patents

Abstract

Provided are an apparatus and a method for producing a polarizing film that is less likely to generate bright spots (light leakage) when applied to a liquid crystal display device.
A manufacturing apparatus for manufacturing a polarizing film from a polyvinyl alcohol-based resin film, comprising: a plurality of rolls constituting a conveying path of the polyvinyl alcohol-based resin film and arranged to be in contact with the surface of the polyvinyl alcohol-based resin film; A wet treatment portion disposed in the wet treatment portion including at least one treatment tank containing a treatment liquid in which the polyvinyl alcohol resin film is immersed, and a drying treatment portion for drying the polyvinyl alcohol resin film after wet treatment disposed on a conveying path. The plurality of rolls are provided with a manufacturing apparatus including a low rotational resistance roll having a rolling resistance of 0.025 N or less, a manufacturing method using the same, and a polarizing film having a density of a specific uneven defect of 20 or less / m 2.

Description

Manufacturing apparatus and manufacturing method of a polarizing film, and a polarizing film TECHNICAL FIELD AND POLARIZING FILM

This invention relates to the manufacturing apparatus and manufacturing method of a polarizing film which can be used as a structural member of a polarizing plate, for example. Moreover, this invention relates to a polarizing film.

As a polarizing film, what adsorbed and oriented dichroic dyes, such as iodine and a dichroic dye, to the uniaxially stretched polyvinyl alcohol-type resin film is used conventionally. Generally, a polarizing film is manufactured by carrying out the dyeing process of dyeing a polyvinyl alcohol-type resin film with a dichroic dye, the crosslinking process of processing with a crosslinking agent, and a film drying process, and carrying out uniaxial stretching process between manufacturing processes [ For example, Japanese Patent Laid-Open No. 2001-141926 (Patent Document 1)].

The manufacturing apparatus of a polarizing film has a conveyance path | route of the polyvinyl alcohol-type resin film normally passing through processing tanks, such as a dyeing process tank and a crosslinking process tank, and a drying installation. The polyvinyl alcohol-type resin film conveyed along the path is supported by rolls, such as a guide roll and the nip roll which nips a film.

Japanese Patent Laid-Open No. 2001-141926

One of the main uses of a polarizing film is a polarizing plate use which is an essential member of a liquid crystal display device. A polarizing plate means the optical member which laminated | stacked and bonded a protective layer (protective film etc.) on one side or both surfaces of a polarizing film typically using an adhesive agent. In recent years, the improvement of visibility (brightness) is calculated | required by the liquid crystal display device, and the backlight which has higher luminance has been used for the liquid crystal display device according to this request | requirement.

Under these circumstances, the present inventors raise the luminance of the backlight to a certain degree or more, and when the luminance is lower than this, the dot-shaped bright spot (light leakage), which is not visible on the screen of the liquid crystal display device, is not a problem. I faced a new task to be done. For example, in the liquid crystal panel, when bubbles are mixed between the pressure-sensitive adhesive layer bonding the polarizing plate to the liquid crystal cell and the liquid crystal cell, it is known that this bubble causes a bright point (light leakage). Although some technique of suppressing is proposed, it has turned out that the said bright spot which this inventor faced newly is not caused by the bubble mixed between an adhesive layer and a liquid crystal cell. And it was clear by the inventor's examination that the factor of the said bright spot exists in the polarizing film which comprises a polarizing plate.

An object of the present invention is to provide an apparatus and a method for producing a polarizing film which is less likely to generate bright spots (light leakage) newly encountered by the present inventor as described above when applied to a liquid crystal display device. Moreover, another object of this invention is to provide the polarizing film which is hard to produce the said bright spot (light leakage).

MEANS TO SOLVE THE PROBLEM This inventor exists in the specific unevenness | corrugation defect (henceforth "a specific unevenness | corrugation defect") which arises in the surface of the polyvinyl alcohol-type resin film in the manufacturing process of a polarizing film mentioned above, and shows below, According to the manufacturing apparatus and manufacturing method of the polarizing film which concerns on this invention, it discovered that the specific uneven | corrugated defect of a polarizing film and also the bright spot (light leakage) can be suppressed effectively.

That is, this invention provides the manufacturing apparatus and manufacturing method of a polarizing film shown below, and a polarizing film.

[1] A manufacturing apparatus for producing a polarizing film from a polyvinyl alcohol-based resin film,

A plurality of rolls constituting a conveying path of the polyvinyl alcohol-based resin film and disposed to be in contact with the surface of the polyvinyl alcohol-based resin film;

A wet treatment part disposed on the conveying path and including one or more treatment tanks containing a treatment liquid in which the polyvinyl alcohol-based resin film is immersed;

It is arrange | positioned on the said conveyance path, and the drying process part for drying the polyvinyl alcohol-type resin film after a wet process

Including,

And the plurality of rolls comprises a low rolling resistance roll having a rolling resistance of 0.025 N or less.

[2] The production apparatus according to [1], wherein the low rotation resistance roll is disposed at any position in a conveyance path from the wet treatment portion to the dry treatment portion.

[3] The wet treatment part includes a dyeing treatment tank containing a dyeing treatment liquid containing a dichroic dye and a crosslinking treatment tank containing a crosslinking treatment liquid containing a crosslinking agent in this order,

The production apparatus according to [2], wherein the low rotation resistance roll is disposed after the crosslinking treatment tank.

[4] The production apparatus according to any one of [1] to [3], wherein the low rotation resistance roll has a surface whose contact angle with respect to water is 60 degrees or more.

[5] The production apparatus according to [4], wherein the surface is composed of a fluorine resin, a silicon atom-containing resin, carbon, or diamond-like carbon.

[6] The production apparatus according to any one of [1] to [5], wherein the low rotational resistance roll has a weight per unit volume of 1500 kg / m 3 or less.

[7] The production apparatus according to any one of [1] to [6], wherein the low rotation resistance roll is a guide roll.

[8] The production apparatus according to any one of [1] to [7], wherein the polyvinyl alcohol-based resin film in contact with the low rotation resistance roll has a thickness of 15 µm or less.

[9] A method for producing a polarizing film from a polyvinyl alcohol-based resin film,

A wet treatment step of immersing in one or more treatment liquids while conveying the polyvinyl alcohol-based resin film along a conveyance path constituted by a plurality of rolls disposed to contact the surface of the polyvinyl alcohol-based resin film;

Drying process process which dries the polyvinyl alcohol-type resin film after a wet process, conveying the said polyvinyl alcohol-type resin film along the said conveyance path | route.

Including,

And the plurality of rolls comprises a low rolling resistance roll having a rolling resistance of 0.025 N or less.

[10] The production method according to [9], wherein the low rotational resistance roll is disposed at any position in a conveyance path from the wet treatment step to the dry treatment step.

[11] The wet treatment step includes a step of dipping in a dyeing treatment liquid containing a dichroic dye;

Including the step of immersing in the crosslinking treatment liquid containing the crosslinking agent in this order,

The said low rotation resistance roll is a manufacturing method as described in [10] arrange | positioned at the conveyance path | route after the process immersed in the said crosslinking process liquid.

[12] The production method according to any one of [9] to [11], wherein the low rotation resistance roll has a surface whose contact angle with respect to water is 60 degrees or more.

[13] The production method according to [12], wherein the surface is composed of a fluorine resin, a silicon atom-containing resin, carbon, or diamond-like carbon.

[14] The production method according to any one of [9] to [13], wherein the low rotational resistance roll has a weight per unit volume of 1500 kg / m 3 or less.

[15] The production method according to any one of [9] to [14], wherein the low rotational resistance roll is a guide roll.

[16] The production method according to any one of [9] to [15], wherein the polyvinyl alcohol-based resin film in contact with the low rotation resistance roll has a thickness of 15 µm or less.

[17] A polarizing film having a dichroic dye adsorbed on a polyvinyl alcohol-based resin film,

The density of the uneven | corrugated defect in at least one surface is 20 pieces / m <2> or less,

The uneven defect is made up of a combination of one convex portion protruding from that relative to the surface of the polarizing film other than the uneven defect, and one concave portion adjacent to the convex portion while recessed from the reference, and has a long diameter of 0.5 to Polarizing film in the range of 5 mm.

According to this invention, even when it applies to the liquid crystal display device which used the backlight with high brightness | luminance, it can provide the polarizing film which is hard to produce the bright spot (light leakage) resulting from the specific uneven | corrugated defect on the film surface.

BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional schematic diagram which shows an example of the polarizing film manufacturing apparatus which concerns on this invention.
It is a cross-sectional schematic diagram which expands and shows the dry process part which the polarizing film manufacturing apparatus shown in FIG. 1 has.
3 is a flowchart showing an example of a method of manufacturing a polarizing film according to the present invention.

<The manufacturing apparatus and manufacturing method of a polarizing film>

This invention relates to the manufacturing apparatus and manufacturing method for manufacturing a polarizing film from a polyvinyl alcohol-type resin film (henceforth a "PVA-type resin film"). A polarizing film is manufactured by performing a series of processes including the immersion process (wet process), a drying process, etc. to a processing tank with respect to a PVA system resin film. The dichroic dye is adsorptively oriented to the stretched PVA system resin film.

An example of the polarizing film manufacturing apparatus which concerns on this invention is shown in FIG. It is a cross-sectional schematic diagram which expands and shows the dry process part which the polarizing film manufacturing apparatus shown in FIG. 1 has. The polarizing film manufacturing apparatus shown in FIG. 1 and FIG. 2 is an apparatus for manufacturing the long polarizing film 25 continuously from the long PVA system resin film 10 which is a raw material film. The arrow in FIG. 1 and FIG. 2 shows the conveyance direction of a film. In the manufacture of the polarizing film 25 using the manufacturing apparatus shown in FIG. 1 and FIG. 2, the swelling treatment tank 13 and the dyeing process are carried out continuously, unwinding the PVA system resin film 10 from the unwinding roll 11. It is immersed in the tank 15, the crosslinking process tank 17, and the washing process tank 19 one by one, and finally, it passes through the drying furnace 21, and a drying process is performed and the polarizing film 25 is obtained. The polarizing film 25 manufactured as a long object may be wound up by the winding roll 27 one by one.

Polarizing film manufacturing apparatus WHEREIN: The 1 or more processing tank which accommodates the processing liquid in which the film is immersed, such as the swelling processing tank 13, the dyeing processing tank 15, the crosslinking processing tank 17, and the washing processing tank 19. In the present specification, the zone to be subjected to the wet treatment using the &quot; wet treatment portion &quot; In addition, the zone which performs a drying process with respect to the film after a wet process like the drying furnace 21 is called "dry processing part" (dry processing part 22 shown to FIG. 1 and FIG. 2) in this specification. The polarizing film manufacturing apparatus which concerns on this invention has the conveyance path | route of the PVA system resin film 10 containing a wet process part and a dry process part. A series of processes are performed by conveying the PVA system resin film 10 along this conveyance path, and the polarizing film 25 is obtained. The conveyance speed of the PVA system resin film 10 conveyed along a conveyance path is 10-50 m / min normally, From a viewpoint of a production efficiency, Preferably it is 15 m / min or more.

As shown in FIG. 1, the said conveyance path supports and guides the film (PVA system resin film 10 and polarizing film 25) in running so that it may pass through the wet process part 20 and the dry process part 22. As shown in FIG. Is built by a roll of. The plurality of rolls may include a guide roll which is a free roll supporting one side of the film and / or a pair of rolls (usually driving rolls), and may include a nipe roll which presses or presses the film from both sides. In the example shown to FIG. 1 and FIG. 2, the manufacturing apparatus contains guide rolls 1a-1s and nip rolls 2a-2f. The some roll which prescribes a conveyance path | route may also include the suction roll (suction roll) which is 1 type of a drive roll. Usually, all these rolls contact the surface (main surface) of one or both of the films in a conveyance path | route, and support the film. These rolls can be arrange | positioned at appropriate positions, such as before and after each treatment tank and a drying means (drying furnace), and inside a treatment tank and a drying means (drying furnace).

In addition, a drive roll means the roll which can provide the driving force for film conveyance with respect to the film which contacts it, and can be a roll etc. which roll drive sources, such as a motor, were connected directly or indirectly. A free roll means the roll which plays the role which simply supports the film which runs, and cannot provide the driving force for film conveyance.

The flowchart of an example of the manufacturing method of the polarizing film which concerns on this invention is shown in FIG. Referring to Figure 3, the method for producing a polarizing film according to the present invention, the following process:

Wet processing process (S101) which is immersed in one or more process liquids, conveying a PVA system resin film along the conveyance path comprised by the some roll arrange | positioned so that it may contact the surface of a PVA system resin film, and

Drying process process (S102) which dries the PVA system resin film after a wet process, conveying a PVA system resin film along the said conveyance path | route.

It includes. The wet process step S101 is a process performed by the above-described wet process unit 20, and the dry process step S102 is a process performed by the above-described dry process unit 22.

* The polarizing film 25 obtained is an extending | stretching process (usually uniaxial stretching process). For this reason, the manufacturing apparatus of the polarizing film which concerns on this invention can contain the extending | stretching means (wet extending | stretching means) of the PVA-type resin film 10, The manufacturing method of the polarizing film which concerns on this invention is a PVA-type resin film The stretching treatment process (wet stretching treatment process) of (10) may be included.

(1) PVA system resin film

The PVA-based resin film 10 (provided in the wet processing step S101) introduced into the wet processing unit 20 is a film composed of polyvinyl alcohol-based resin. As polyvinyl alcohol-type resin, what saponified polyvinyl acetate type resin can be used. As polyvinyl acetate type resin, the copolymer of vinyl acetate and the other monomer copolymerizable with this besides the polyvinyl acetate which is a homopolymer of vinyl acetate is illustrated. As another monomer copolymerizable with vinyl acetate, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, (meth) acrylamide which has an ammonium group, etc. are mentioned, for example. In addition, "(meth) acryl" represents at least 1 sort (s) chosen from the group which consists of an acryl and methacryl. The same applies to other terms in which "(meta)" is added.

Although the degree of saponification of the polyvinyl alcohol-based resin may be in the range of 80.0 to 100.0 mol%, preferably in the range of 90.0 to 100.0 mol%, more preferably in the range of 94.0 to 100.0 mol%, still more preferably It is the range of 98.0-100.0 mol%. When saponification degree is less than 80.0 mol%, the water resistance and moisture heat resistance of the polarizing plate containing the polarizing film 25 obtained can fall.

Saponification Doran, acetate group contained in the polyvinyl material is polyvinyl acetate-based resin of the alcohol-based resin (acetoxy group: -OCOCH ₃₎ would have shown a ratio change to hydroxyl group by a saponification process in the unit ratio (mol%) , The following formula:

Saponification degree (mol%) = 100 * (number of hydroxyl groups) / (number of hydroxyl groups + number of acetate groups)

Is defined as Saponification degree can be calculated | required based on JISK6726 (1994).

The average polymerization degree of polyvinyl alcohol-type resin becomes like this. Preferably it is 100-10000, More preferably, it is 1500-8000, More preferably, it is 2000-5000. The average degree of polymerization of polyvinyl alcohol-based resin can also be obtained in accordance with JIS K 6726 (1994). If the average degree of polymerization is less than 100, it is difficult to obtain a polarizing film 25 having desirable polarization performance. If the average degree of polymerization exceeds 10000, solubility in a solvent may deteriorate, and formation of the PVA-based resin film 10 may be difficult. .

One example of the PVA-based resin film 10 is an unstretched film formed by film production of the polyvinyl alcohol-based resin. A film manufacturing method is not specifically limited, Well-known methods, such as a melt extrusion method and the solvent casting method, can be employ | adopted. Another example of the PVA system resin film 10 is a stretched film formed by stretching the above unstretched film. This stretching is usually uniaxial stretching, preferably longitudinal uniaxial stretching. Longitudinal stretching means extending | stretching to the mechanical flow direction MD of a film, ie, the longitudinal direction of a film. This stretching is preferably dry stretching. Dry stretching means extending | stretching performed in the air and usually becomes longitudinal uniaxial stretching. As dry stretching, heat roll extending | stretching which makes a film pass through the heat roll with which the surface was heated, and the guide roll (or the heat roll may be different) from a circumferential speed different from this heat roll, and performs longitudinal stretch under heating using a heat roll; Roll-to-roll stretching which longitudinally stretches by the circumferential speed difference between these two nip rolls, passing some heating means (oven etc.) between two nip rolls provided at a distance; Tenter stretching; Compression stretching and the like. Stretching temperature (surface temperature of a heat roll, temperature in oven, etc.) is 80-150 degreeC, for example, Preferably it is 100-135 degreeC.

Although the draw ratio of the said draw depends on whether or not wet drawing is performed in the wet process process (S101) mentioned later, and the draw ratio in the wet drawing is normally 1.1 to 8 times, Preferably it is 2.5 to 5 times. .

The PVA system resin film 10 may contain additives, such as a plasticizer. Preferred examples of the plasticizer are polyhydric alcohols, and specific examples thereof include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerine, triethylene glycol, triglycerine, tetraethylene glycol, trimethylolpropane, polyethylene glycol and the like. . The PVA-based resin film 10 may contain one kind or two or more kinds of plasticizers. Content of a plasticizer is 5-20 weight part normally with respect to 100 weight part of polyvinyl alcohol-type resin which comprises the PVA-type resin film 10, Preferably it is 7-15 weight part.

The thickness of the PVA-based resin film 10 (provided in the wet processing step S101) introduced into the wet processing unit 20 depends on whether or not the PVA-based resin film 10 is stretched. It is 150 micrometers, From a viewpoint of thinning of the polarizing film 25 obtained, Preferably it is 100 micrometers or less, More preferably, it is 65 micrometers or less, More preferably, it is 50 micrometers or less, Especially preferably, it is 35 micrometers or less (for example, 30 micrometers). 20 micrometers or less). The smaller the thickness of the PVA-based resin film 10, and therefore the smaller the thickness of the polarizing film 25, the more tends to cause specific irregularities. Therefore, when using a small PVA system resin film 10 (for example, 65 micrometers or less thick, 50 micrometers or less, and further 35 micrometers or less), or the small polarizing film 25 (for example, 20 micrometers or less in thickness), , 15 μm or less, and further 10 μm or less) is particularly advantageous.

(2) wet treatment unit and wet treatment process (S101)

The wet processing part 20 is a zone arrange | positioned on the conveyance path | route of the PVA system resin film 10, and contains the 1 or more process tank which accommodates the process liquid in which the PVA system resin film 10 is immersed. In this wet process part 20, the wet process process (S101) which is immersed in the said 1 or more process liquid, conveying the PVA system resin film 10 is performed. As mentioned above, the conveyance path is constructed by a plurality of rolls that support and guide the film during travel, and a part of the plurality of rolls is usually disposed in the wet processing unit 20.

The wet processing part 20 generally includes a dyeing treatment tank 15 and a crosslinking treatment tank 17 as the treatment tank. Preferably, the swelling treatment tank 13 and the washing treatment tank 19 are further provided. Include. These treatment tanks are normally arranged in the order of the swelling treatment tank 13, the dyeing treatment tank 15, the crosslinking treatment tank 17, and the washing treatment tank 19 in order from the upstream side of the conveyance path (see FIG. 1). ). In addition, although the example which provided one swelling processing tank 13, the dyeing processing tank 15, the crosslinking processing tank 17, and the washing processing tank 19 was shown in FIG. 1, respectively, the dyeing processing tank 15 is shown as needed. 2 or more sets may be provided, and 2 or more sets may be provided for the crosslinking process tank 17. FIG. The same applies to the swelling treatment tank 13 and the washing treatment tank 19.

The treatment liquid contained in the swelling treatment tank 13 may be, for example, water (pure water) or an aqueous solution to which a water-soluble organic solvent such as alcohols is added. This treatment liquid (swelling bath) may also contain boric acid, chlorides, inorganic acids, inorganic salts, and the like. A swelling process is performed by immersing the PVA system resin film 10 in a swelling bath. A swelling process is a process performed as needed for the purpose of foreign material removal of a PVA-type resin film 10, plasticizer removal, provision of dichroism, plasticization of a film, etc. During the swelling treatment, the wet stretching treatment (usually uniaxial stretching treatment) may be performed on the PVA-based resin film 10. The draw ratio in that case is 1.2 to 3 times normally, Preferably it is 1.3 to 2.5 times. The temperature of the swelling bath is usually 10 to 70 ° C, preferably 15 to 50 ° C. Immersion time (retention time in a swelling bath) of the PVA system resin film 10 is 10 to 600 second normally, Preferably it is 20 to 300 second.

The treatment liquid contained in the dyeing treatment tank 15 is a dyeing treatment liquid containing a dichroic dye. A dyeing process is performed by immersing the PVA system resin film 10 in this dyeing process liquid. Thereby, a dichroic dye is adsorb | sucked to the PVA-type resin film 10. FIG. The dichroic dye may be iodine or a dichroic organic dye, preferably iodine. Dichroic dye may be used individually by 1 type, and may use 2 or more types together.

When iodine is used as the dichroic dye, an aqueous solution containing iodine and potassium iodide can be used for the dyeing treatment liquid. Instead of potassium iodide, other iodides such as zinc iodide may be used, or potassium iodide and other iodide may be used in combination. In addition, compounds other than iodide, such as boric acid, zinc chloride, cobalt chloride, etc. may coexist. When boric acid is added, it differs from the crosslinking process liquid mentioned later by the point containing iodine. The content of iodine in the dyeing treatment liquid is usually 0.003 to 1 part by weight per 100 parts by weight of water. Content of iodide, such as potassium iodide, in a dyeing process liquid is 0.1-20 weight part normally per 100 weight part of water. The temperature of a dyeing process liquid is 10-45 degreeC normally, Preferably it is 10-40 degreeC, More preferably, it is 20-35 degreeC. Immersion time (retention time in a dyeing process liquid) of the PVA system resin film 10 is 20 to 600 second normally, Preferably it is 30 to 300 second.

When using a dichroic organic dye as a dichroic dye, the aqueous solution containing a dichroic organic dye can be used for a dyeing process liquid. The content of the dichroic organic dye in the dyeing treatment liquid is usually 1 × 10 ^-4 to 10 parts by weight, and preferably 1 × 10 ^{-3 to} 1 part by weight per 100 parts by weight of water. This dyeing treatment liquid may coexist with a dyeing aid, for example, and may contain inorganic salts, surfactants, etc., such as sodium sulfate. Dichroic organic dye may be used individually by 1 type, or may use 2 or more types together. The temperature of the dyeing process liquid containing a dichroic organic dye is 20-80 degreeC, for example, Preferably it is 30-70 degreeC. Immersion time of the PVA system resin film 10 is 30 to 600 second normally, Preferably it is 60 to 300 second.

In order to improve the dyeability of a dichroic dye, it is preferable that the PVA system resin film 10 provided for a dyeing process is given at least some extending | stretching process (usually uniaxial stretching process). Instead of the stretching treatment before the dyeing treatment or in addition to the stretching treatment before the dyeing treatment, the stretching treatment may be performed while the dyeing treatment is performed. The draw ratio of the integration up to the dyeing treatment (the stretching ratio in the dyeing treatment when there is no stretching step until the dyeing treatment) is usually 1.6 to 4.5 times, preferably 1.8 to 4 times.

The treatment liquid contained in the crosslinking treatment tank 17 is a crosslinking treatment liquid containing a crosslinking agent. A crosslinking process is performed by immersing the PVA system resin film 10 after dyeing process in this crosslinking process liquid. Thereby, water resistance, color adjustment, etc. of the PVA system resin film 10 by crosslinking are performed. You may perform an extending | stretching process (usually uniaxial stretching process), performing crosslinking process.

Examples of the crosslinking agent include boric acid, glyoxal, glutaraldehyde, and the like. Boric acid is preferably used. You may use together 2 or more types of crosslinking agents. The content of the crosslinking agent in the crosslinking treatment liquid is usually 0.1 to 15 parts by weight, preferably 1 to 12 parts by weight, per 100 parts by weight of water. When a dichroic dye is iodine, it is preferable that a crosslinking process liquid contains an iodide in addition to a crosslinking agent. The content of the iodide in the crosslinking treatment liquid is usually 0.1 to 20 parts by weight, and preferably 5 to 15 parts by weight per 100 parts by weight of water. Examples of iodide include potassium iodide, zinc iodide, and the like. The crosslinking treatment liquid may also contain compounds other than iodide such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate and the like. The temperature of the crosslinking treatment liquid is usually 50 to 85 ° C, preferably 50 to 70 ° C. Immersion time (retention time in a crosslinking process liquid) of the PVA system resin film 10 is 10 to 600 second normally, Preferably it is 20 to 300 second.

The treatment liquid contained in the washing treatment tank 19 may be, for example, water (pure water) or an aqueous solution to which a water-soluble organic solvent such as alcohol is added. The washing treatment is performed by immersing the PVA-based resin film 10 after the crosslinking treatment in this treatment liquid (washing bath). A washing process is a process performed as needed for the purpose of removing the chemical | medical agent, such as the excess crosslinking agent and dichroic dye which were affixed on the PVA system resin film 10. The temperature of a washing bath is 2-40 degreeC, for example. You may perform an extending | stretching process (usually uniaxial stretching process), performing a washing process.

The washing treatment may be a treatment in which the washing liquid is sprayed onto the PVA resin film 10 after the crosslinking treatment as a shower, or the immersion in the washing bath may be combined with the spray of the washing liquid. In FIG. 1, the example in the case of performing a washing process by immersing the PVA system resin film 10 in the water in the washing process tank 19 is shown.

As mentioned above, you may perform wet extending | stretching with respect to the PVA-type resin film 10 in a wet process process (S101). Wet stretching is usually uniaxial stretching, and can be carried out while performing any one of swelling treatment, dyeing treatment, crosslinking treatment, washing treatment, or two or more treatments selected from these. Wet stretching is preferably drawn in one or two or more steps prior to or in the crosslinking process. As mentioned above, in order to raise the dyeing property of a dichroic dye, and to obtain the polarizing film 25 which has favorable polarization characteristic, the PVA system resin film 10 provided for dyeing process is given the extending | stretching process of at least some degree. It is more preferable. From the viewpoint of the polarization characteristics of the polarizing film 25 obtained, the draw ratio of wet stretching is preferably the final cumulative stretching ratio of the polarizing film 25 (the PVA system resin film 10 provided for the wet treatment is stretched). When it is, the cumulative stretching ratio including this stretching is adjusted to be 3 to 8 times.

When performing a wet extending | stretching process, the polarizing film manufacturing apparatus contains the wet extending | stretching means of the PVA system resin film 10. As shown in FIG. The wet stretching means is preferably stretching means for performing inter-roll stretching. For example, the stretching means for performing roll-to-roll stretching during the cross-linking treatment in a wet manner is two nipple rolls 2c and 2d arranged before and after the crosslinking treatment tank 17. Also in the case of extending | stretching during another wet process, the two nip rolls spaced apart can be used as a wet extending | stretching means.

(3) Drying treatment part and drying treatment step (S102)

The drying process part 22 is a zone for drying the PVA system resin film 10 after the wet process process S101 arrange | positioned downstream of the wet process part 20 on the conveyance path | route of the PVA system resin film 10. FIG. . While continuing conveying the PVA system resin film 10 after a wet process process (S101), a drying process can be performed by introducing the film into the dry process part 22, and the polarizing film 25 is obtained by this.

The drying process part 22 contains the drying means (heating means) of a film. One suitable example of drying means is a drying furnace. The drying furnace is preferably one capable of controlling the temperature in the furnace. A drying furnace is a hot air oven which can raise a furnace temperature, for example by supply of hot air. In addition, the drying process by a drying means is the process which adhere | attaches the PVA system resin film 10 after a wet process process (S101) to 1 or 2 or more heating bodies which have a convex curved surface, or the process which heats the film using a heater. You may.

As said heating body, the roll (for example, the guide roll which doubles as a heat roll) which has a heat source (for example, heating mediums, such as hot water, and an infrared heater) inside, and can raise surface temperature is mentioned. As said heater, an infrared heater, a halogen heater, a panel heater etc. are mentioned. 1 and 2, an example in which the PVA-based resin film 10 after the wet treatment step (S101) is introduced into the drying furnace 21 and dried while conveying the film along the guide rolls (1 m to 1 s) in the furnace. Indicates. Thus, a part (1 or 2 or more) of some roll which builds up the conveyance path | route of the PVA system resin film 10 which a polarizing film manufacturing apparatus has can be arrange | positioned in the drying process part 22 (drying means).

The temperature of a drying process (for example, the furnace temperature of the drying furnace 21, the surface temperature of a heat roll, etc.) is 30-100 degreeC normally, and it is preferable that it is 50-90 degreeC. The drying time is not particularly limited but is, for example, 30 to 600 seconds.

The moisture content of a film is reduced by a drying process. The moisture content of the polarizing film 25 obtained through a drying process is 5-20 weight% normally, Preferably it is 8-15 weight%. If the moisture content is less than 5% by weight, the flexibility of the polarizing film 25 may be excessively lowered, and the polarizing film 25 may be damaged or broken at the time of subsequent conveyance or handling. Moreover, when the moisture content of the polarizing film 25 is higher than 20 weight%, the thermal stability of the polarizing film 25 will fall easily. The moisture content here is measured by the dry weight method.

The dichroic pigment | dye is adsorption-oriented to the PVA system resin film extended | stretched (usually uniaxially stretched) of the polarizing film 25. As shown in FIG. The thickness of the polarizing film 25 is 2-40 micrometers normally. From the viewpoint of thinning the polarizing plate including the polarizing film 25, the thickness of the polarizing film 25 is preferably 20 μm or less, more preferably 15 μm or less, and still more preferably 10 μm or less. As described above, the present invention is particularly advantageous in the case of producing a small thickness polarizing film 25 (for example, 20 µm or less in thickness, 15 µm or less in thickness, and even 10 µm or less).

The visibility correction single transmittance Ty of the obtained polarizing film 25 is preferably 40 to 47%, more preferably 41 to 45% in consideration of the balance with the visibility correction polarization degree Py. It is preferable that it is 99.9% or more, and, as for visibility correction polarization degree Py, it is more preferable that it is 99.95% or more. The larger the visibility correction single transmittance Ty of the polarizing film 25, the easier it is to see the bright point (light leakage) when applied to the liquid crystal display device. Therefore, this invention is especially advantageous when manufacturing the polarizing film 25 whose visibility correction single transmittance Ty is 41% or more, 42% or more, and 43% or more. Ty and Py are measured according to description of the term of the Example mentioned later.

The obtained polarizing film 25 may be wound up in the winding roll 27 one by one, and may be in roll form, and a protective layer (protective film, etc.) may be carried out as it is on a single side or both sides of the polarizing plate production process without winding up. To a step of laminating].

(4) low rolling resistance roll

The plurality of rolls described above, which are arranged to contact the surface of the PVA-based resin film 10 to be conveyed by establishing and defining a conveying path of the polarizing film manufacturing apparatus, have at least one low rotational resistance roll having a rotational resistance of 0.025 N or less. Include. Thereby, the specific unevenness | corrugation defect which may arise in the surface of the polarizing film 25 can be suppressed. It is preferable that the rotational resistance of a low rotational resistance roll is 0.01 N or less from a viewpoint which suppresses a specific unevenness | corrugation defect more effectively. The rolling resistance of the roll is usually 0.001 N or more.

The rolling resistance of a roll here means the rolling resistance value measured as follows. That is, after winding a thin film on a roll, it is a load applied only to the spring when the edge part of the wound film is fixed only to a spring, and only the spring is pulled out at a constant speed so that the rotation speed of a roll may be 100 rpm.

By using a low rotational resistance roll, the specific uneven | corrugated defect can be suppressed, the tension | tensile_strength of the PVA-type resin film 10 in conveyance at the time of contact with the low rotational resistance roll is reduced, The adhesion between the PVA-based resin films 10 is lowered, and as a result, the PVA-based resin film 10, which may occur when the PVA-based resin film 10 falls from the low-rotational resistance roll, continues to the low-rotational resistance roll. It is assumed that the deformation of the PVA-based resin film 10 according to the drag force based on the adhesion force to be adhered to is suppressed.

The kind of the low rotational resistance roll is not particularly limited, and may be a free roll such as a guide roll or a drive roll such as a nip roll or a suction roll. When applying a low rotational resistance roll to a nip roll, only one of the pair of rolls which comprise a nip roll may be a low rotational resistance roll, and both may be a low rotational resistance roll. The low rotational resistance roll is preferably a guide roll because the effect of suppressing specific irregularities defects can be enhanced as long as it is a free roll having no driving force for film conveyance.

For example, the rolling resistance of a roll can be made small by reducing the weight per unit volume of a roll, or using the bearing with a small friction moment. Among these, reducing the weight per unit volume of a roll is effective in reducing the rolling resistance of a roll. In order to make the rotational resistance of a roll into the above-mentioned range, the weight per unit volume of a low rotational resistance roll becomes like this. Preferably it is 1500 kg / m <3> or less, More preferably, it is 1000 kg / m <3> or less, More preferably, 700 Kg / m 3 or less. It is possible to reduce the weight per unit volume of a roll by using lightweight materials, such as carbon and aluminum, or using a hollow roll as core material (or material of the whole roll) of a roll. The weight per unit volume of the roll is usually 200 kg / m 3 or more.

By examination of the present inventors, it has been found that the low wettability of the surface of the low rotational resistance roll (the surface in contact with the PVA-based resin film 10 during conveyance) acts advantageously to suppress specific irregularities. This is estimated in order to contribute to the fall of the above-mentioned adhesive force between the low rotational resistance roll and the PVA system resin film 10 which contacts this. Therefore, it is preferable that the low rotational resistance roll has a low wettability surface (the surface in contact with the PVA-based resin film 10 during transport), and specifically, the low rotational resistance roll has a contact angle (water contact angle) with respect to water. It has a surface which is preferably at least 60 degrees, more preferably at least 80 degrees, even more preferably at least 100 degrees. The maximum value of the contact angle with respect to water is about 120 degrees normally. The contact angle with respect to the water of the low rolling resistance roll surface is measured according to description of the term of the Example mentioned later.

The roll having a large logarithmic contact angle as described above may be provided with a surface layer (coating layer) made of a material having a large logarithmic contact angle on the roll surface. Specific examples of the material having a large logarithmic contact angle include fluorine-based resins such as polytetrafluoroethylene; Silicone atom-containing resins such as siloxane resins; Carbon materials, such as carbon and diamond like carbon (DLC), are included.

* The number of arrangements of the low rotational resistance rolls is not particularly limited, and the low rotational resistance rolls may be disposed at any position in the conveyance path that the polarizing film production apparatus has. Therefore, although the low rotation resistance roll may arrange | position two or more low rotation resistance rolls to the conveyance path | route, or all the rolls which contact the surface of the PVA system resin film 10 conveyed, in order to acquire the suppression effect of a specific uneven | corrugated defect, at least, It is preferable to arrange | position the low rotational resistance roll in any position of the conveyance path | route from the wet process part 20 (wet process process S101) to the dry process part 22 (dry process process S102). "From the wet processing part 20 (wet processing process S101)" means the upstream end (PVA system resin film 10) of the swelling processing tank 13 to the swelling bath, for example, when the first wet processing is a swelling process. Point of immersion]. "Over the drying process part 22 (dry processing process S102)" refers to the downstream end (dry processing end time point) of the drying process part 22 (drying means).

Especially, it is more preferable to select the arrangement position of a low rotational resistance roll in consideration of the following point.

* [A] Rather than before the crosslinking treatment, the present inventors have confirmed a tendency to cause a specific irregularity defect when the PVA-based resin film 10 after the crosslinking treatment comes into contact with the roll. Therefore, it is preferable to arrange | position at least 1 low rotational resistance roll in the conveyance path | route after the crosslinking process tank 17 (crosslinking process tank 17 or downstream side), and to the conveyance path | route after the crosslinking process tank 17 When a some roll exists, it is preferable to make all of these rolls into a low rotational resistance roll.

[B] Rather than during the wet treatment, the present inventors have confirmed a tendency to cause specific irregularities when the PVA-based resin film 10 after the wet treatment is in contact with the roll. Therefore, it is preferable to arrange | position at least 1 low rotational resistance roll in the conveyance path | route downstream of the bridge | crosslinking process tank 17, and when several roll exists in the conveyance path | route downstream of the bridge | crosslinking process tank 17, It is preferable to make all of these rolls a low rotational resistance roll. In the case of performing the wet treatment such as the washing treatment after the crosslinking treatment, it is preferable to arrange at least one low-rotational resistance roll in the conveyance path downstream of the wet treatment portion 20, and to convey the downstream side of the wet treatment portion 20. When several roll exists in a path | route, it is preferable to make all these rolls into a low rotational resistance roll.

[C] The present inventors have a tendency to easily cause specific irregularities when the PVA-based resin film 10 having a moisture content lower than the moisture content immediately after the end of the wet treatment (immediately after the last wet treatment tank) is in contact with the roll. It is confirmed by. Therefore, also in this point, it is preferable to arrange | position at least 1 low rotational resistance roll in the conveyance path | route downstream of the wet process part 20, and there exists a some roll in the conveyance path | route downstream of the wet process part 20. In that case, it is preferable to make all of these rolls into a low rotational resistance roll. In particular, when the PVA-based resin film 10 is in contact with the rolls immediately after the wet treatment is completed, and the polarizing film 25 having the desired moisture content is completed by the completion of the drying treatment, specific irregularities are likely to occur. Therefore, it is preferable to arrange | position at least one low rotational resistance roll in the conveyance path | route which connects the wet process part 20 and the drying process part 22, or the conveyance path | route of the first half of the drying process part 22, and the wet process part 20 When a plurality of rolls exist in the conveyance path | route which connects and the drying process part 22, and the conveyance path | route of the first half of the drying process part 22, it is preferable to make all these rolls into a low rotational resistance roll. The moisture content of the above-mentioned "PVA-based resin film 10 having a moisture content lower than that of water immediately after the end of the wet treatment (right after the last wet treatment tank)" is, for example, 8 to 30% by weight, and further 10 to 25% by weight. %to be. The meaning (measurement method) of moisture content is the same as that of the above.

[D] The smaller the thickness of the PVA-based resin film 10 in contact with the roll, the easier it is to generate specific irregularities. Therefore, the roll which contact | connects the PVA-type resin film 10 whose thickness is smaller by a wet extending | stretching process than the thickness of the PVA-type resin film 10 at the time provided to a wet process process S101 is made into a low rotational resistance roll. In the case where a plurality of such rolls are present, it is preferable to make all of these rolls a low rotational resistance roll. Specifically, after the dyeing treatment tank 15 (the dyeing treatment tank 15 or the downstream side) or the crosslinking treatment tank 17 (the crosslinking treatment tank 17 or the downstream side) after which the wet drawing is often performed. It is preferable to arrange | position at least 1 low rotational resistance roll in the conveyance path | route, and when a some roll exists in the conveyance path | route, it is preferable to make all these rolls into a low rotational resistance roll. The thickness of the above-mentioned "PVA system resin film 10 whose thickness is smaller by the wet extending | stretching process than the thickness of the PVA system resin film 10 at the time provided to a wet process process S101" is 15, for example. It is micrometer or less, Furthermore, it is 12 micrometers or less, and is further 10 micrometers or less.

(E) There exists a tendency which tends to produce a specific uneven | corrugated defect when it changes rather than when the conveyance direction of the PVA system resin film 10 does not change before and after contacting a roll. Therefore, it is preferable to make the roll which changes the conveyance direction of the PVA system resin film 10 which contact | connects it the low rotation resistance roll. PVA system immediately before contacting a roll is made into A and the conveyance direction vector of the PVA system resin film 10 immediately after it fell away from the roll as A, and the conveyance direction vector of the PVA system resin film 10 just before contacting a roll. The angle (conveying direction change angle) which the vectors A and B make when the conveyance direction of the resin film 10 and the conveyance direction of the PVA system resin film 10 immediately after it removed from the roll are the same direction without a change (alpha) ((alpha) Is 0 °, and the vector when the conveying direction of the PVA-based resin film 10 immediately before contacting the roll and the conveying direction of the PVA-based resin film 10 immediately after being separated from the roll is completely opposite. When the angle α formed by and B) is 180 degrees, the present invention is particularly advantageous when the angle α satisfies 30 to 180 degrees, and further 45 to 180 degrees.

(5) specific irregularities and defects

The specific uneven | corrugated defect which may arise on the surface of a polarizing film produces a bright point (light leakage) when this polarizing film is applied to a liquid crystal display device. This bright point is a defect which is visually recognized for the first time when the brightness of a backlight is raised to a certain degree or more, and this point is a new subject first discovered by the present inventors. The above-mentioned "when the brightness of a backlight is raised to some extent or more" is when the brightness of the backlight measured with the luminance meter is about 10,000 mW / m <2> or more. The brightness of this backlight is the brightness of the light emitted from the liquid crystal display device including the backlight and the liquid crystal panel disposed thereon (the liquid crystal panel includes a liquid crystal cell and polarizing plates disposed on both surfaces thereof). In other words, it corresponds to approximately 500 mW / m 2 or more.

Specific uneven | corrugated defect typically consists of the combination of one convex part which protrudes more than that with respect to the polarizing film surface other than the uneven | corrugated defect, and one concave part which is recessed than the said reference | standard and adjoins the convex part. . Usually, a convex part exists in the upstream of a film conveyance direction, and a recessed part exists in the downstream side. In the conventional polarizing film, a plurality of such concave and convex portions consisting of convex portions and concave portions were randomly formed in a dot shape over substantially the entire surface of the polarizing film. When the shape of the uneven portion is viewed from above (when viewed from the direction perpendicular to the film surface), for example, a circular shape, an elliptic shape, or the like, it may be irregular. The specific unevenness | corrugation defect is about 0.5-5 mm (for example, 1-3 mm) in the long diameter (maximum diameter) when a polarizing film is seen from the top (when viewed from the direction perpendicular | vertical with respect to a film surface). Specific uneven | corrugated defect is typically about 0.05-0.5 micrometer in height of the convex part and the depth of a recessed part with respect to the said reference | standard. The height difference (film thickness direction distance from the top part of a convex part to the bottom part of a concave part) in a specific unevenness | defective defect is about 0.1-1 micrometer. When the long diameter and the height difference of a specific uneven | corrugated defect are out of the said range, the uneven | corrugated defect does not produce a bright point, and it tends to become difficult to become a problem. The presence of a certain uneven | corrugated defect can be confirmed by a loupe etc., for example. The long diameter and elevation difference of a specific uneven | corrugated defect are measured in accordance with the method as described in the term of the Example mentioned later.

According to this invention, generation | occurrence | production of the above-mentioned specific uneven | corrugated defect in the surface of a polarizing film can be suppressed or prevented. Thereby, even when a polarizing film is applied to the liquid crystal display device using the backlight with high brightness | luminance, bright spot (light leakage) can be suppressed or prevented effectively.

It is preferable that the density of the specific uneven | corrugated defect in the at least one surface of the polarizing film which concerns on this invention is 20 pieces / m <2> or less, It is more preferable that it is 15 pieces / m <2> or less, It is more preferable that it is 10 pieces / m <2> or less. . Although it can be said that the density of the specific uneven | corrugated defect in the at least one surface of a polarizing film is 0 piece / m <2>, the bright point at the time of seeing the screen of a liquid crystal display device will be that screen if it is 20 pieces / m <2> or less. Regardless of the size, it has little effect on the visibility of the screen. On the other hand, when the density of specific uneven | corrugated defects exceeds 20 pieces / m <2>, visibility may be impaired depending on the size of a screen. The density of a specific uneven | corrugated defect is measured in accordance with the method as described in the term of the Example mentioned later. Moreover, when a specific uneven | corrugated defect is recognized by one surface of a polarizing film, the specific uneven | corrugated defect which the convex part and the recessed part reversed is formed in the same position also on the other surface normally.

<Polarizing plate>

A polarizing plate can be obtained by forming a protective layer on one side or both sides of the polarizing film 25. The protective layer may be a protective film made of a thermoplastic resin and may be a cured product layer of an active energy ray curable resin composition. When using a protective film, a polarizing plate can be obtained by bonding a protective film to the single side | surface or both surfaces of the polarizing film 25 through an adhesive bond layer. When the protective film is bonded to both surfaces of the polarizing film 25, the thermoplastic resin constituting these protective films may be the same kind or different kinds.

The thermoplastic resin constituting the protective film is a thermoplastic resin having light transparency, preferably an optically transparent thermoplastic resin. Thermoplastic resins include, for example, polyolefin resins such as chain polyolefin resins (polypropylene resins and the like) and cyclic polyolefin resins (norbornene resins and the like); Cellulose resins such as triacetyl cellulose and diacetyl cellulose; Polyester resins such as polyethylene terephthalate and polybutylene terephthalate; Polycarbonate resins; (Meth) acrylic resins such as methyl methacrylate resin; Polystyrene resin; Polyvinyl chloride resins; Acrylonitrile butadiene styrene resin; Acrylonitrile-styrene resins; Polyvinyl acetate type resin; Polyvinylidene chloride-based resins; Polyamide-based resins; Polyacetal resins; Modified polyphenylene ether resins; Polysulfone resins; Polyether sulfone resin; Polyarylate resins; Polyamideimide resin; Polyimide resin and the like.

As chain | strand polyolefin resin, the copolymer which consists of 2 or more types of chain | strand olefins besides the homopolymer of chain | strand olefins, such as a polyethylene resin and a polypropylene resin, is mentioned. More specific examples include polypropylene resin (polypropylene resin which is a homopolymer of propylene or a copolymer mainly composed of propylene) and polyethylene resin (polyethylene resin which is a homopolymer of ethylene and copolymer mainly composed of ethylene). It includes.

Cyclic polyolefin resin is a general term for resin superposed | polymerized using a cyclic olefin as a polymerization unit. Specific examples of the cyclic polyolefin resins include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins with chain olefins such as ethylene and propylene (typically random copolymers), and their unsaturated Graft polymers modified with carboxylic acid and derivatives thereof, and hydrides thereof. Especially, norbornene-type resin using norbornene-type monomers, such as a norbornene and a polycyclic norbornene-type monomer, is used suitably as cyclic olefin.

With cellulose resin, one part or all of the hydrogen atoms in the hydroxyl group of the cellulose obtained from raw material cellulose, such as cotton linter and wood pulp (leafwood pulp, coniferous pulp), are substituted by acetyl group, propionyl group, and / or butyryl group Cellulose organic acid ester or cellulose mixed organic acid ester. For example, what consists of acetic acid ester of cellulose, a propionic acid ester, butyric acid ester, these mixed ester, etc. are mentioned. Especially, triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate are preferable.

Polyester-based resin is resin other than the said cellulose resin which has an ester bond, and what consists of polycondensates of polyhydric carboxylic acid or its derivative (s), and a polyhydric alcohol is common. Divalent dicarboxylic acid or its derivative can be used as polyhydric carboxylic acid or its derivative, For example, terephthalic acid, isophthalic acid, dimethyl terephthalate, dimethyl naphthalene dicarboxylic acid, etc. are mentioned. Divalent diol can be used as a polyhydric alcohol, For example, ethylene glycol, a propanediol, butanediol, neopentyl glycol, cyclohexane dimethanol, etc. are mentioned. Examples of suitable polyester-based resins include polyethylene terephthalate.

Polycarbonate resin is an engineering plastic which consists of a polymer which the monomeric unit couple | bonded with the carbonate group, and is resin which has high impact resistance, heat resistance, flame retardance, and transparency. The polycarbonate-based resin may be a resin called modified polycarbonate, such as a modified polymer skeleton in order to lower the photoelastic coefficient, or a copolymerized polycarbonate having improved wavelength dependence.

(Meth) acrylic-type resin is a polymer containing the structural unit derived from a (meth) acrylic-type monomer. The polymer is typically a polymer containing methacrylic acid esters. Preferably, the ratio of the structural unit derived from methacrylic acid ester is a polymer containing 50 weight% or more with respect to all the structural units. The homopolymer of methacrylic acid ester may be sufficient as (meth) acrylic-type resin, and the copolymer containing the structural unit derived from another polymerizable monomer may be sufficient as it. In this case, the ratio of the structural unit derived from another polymerizable monomer becomes like this. Preferably it is 50 weight% or less with respect to all the structural units.

As methacrylic acid ester which can comprise (meth) acrylic-type resin, a methacrylic acid alkyl ester is preferable. As methacrylic acid alkyl ester, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, And methacrylic acid alkyl esters having 1 to 8 carbon atoms of alkyl groups such as 2-ethylhexyl methacrylate, cyclohexyl methacrylate and 2-hydroxyethyl methacrylate. Carbon number of the alkyl group contained in the alkyl methacrylate becomes like this. Preferably it is 1-4. In (meth) acrylic-type resin, methacrylic acid ester may be used individually by 1 type, or may use 2 or more types together.

As said other polymerizable monomer which can comprise (meth) acrylic-type resin, the compound which has a polymerizable carbon-carbon double bond in acrylate ester and another molecule | numerator is mentioned. Another polymerizable monomer may be used individually by 1 type, and may use 2 or more types together. As acrylate ester, an alkyl acrylate ester is preferable. As alkyl acrylate, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, 2-hydroxyethyl acrylate And alkyl acrylates having 1 to 8 carbon atoms of the same alkyl group. Carbon number of the alkyl group contained in the alkyl acrylate ester becomes like this. Preferably it is 1-4. In (meth) acrylic-type resin, acrylic ester may be used individually by 1 type, or may use 2 or more types together.

As a compound which has a polymerizable carbon-carbon double bond in another molecule | numerator, vinyl-type compounds, such as ethylene, propylene, and styrene, and vinyl cyan compounds, such as acrylonitrile, are mentioned. The compound which has a polymerizable carbon-carbon double bond in another molecule may be used individually by 1 type, or may use 2 or more types together.

The protective film may be a film having optical functions such as a retardation film and a brightness enhancing film. For example, it can be set as the retardation film in which arbitrary phase difference values were provided by extending | stretching (uniaxial stretching or biaxial stretching etc.) of the said thermoplastic resin, or forming a liquid crystal layer etc. on this film. The protective film may have a surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer, laminated on the surface thereof.

Although the thickness of a protective film is 1-100 micrometers normally, it is preferable that it is 5-60 micrometers from a viewpoint of intensity | strength, handleability, thinning of a polarizing plate, etc., and it is more preferable that it is 5-50 micrometers.

As an adhesive agent used for bonding the polarizing film 25 and a protective film, an aqueous adhesive agent, an active energy ray curable adhesive agent, or a thermosetting adhesive agent can be used, Preferably it is an aqueous adhesive agent and an active energy ray curable adhesive agent. When the protective film is bonded to both surfaces of the polarizing film 25, the adhesive for bonding these protective films may be the same kind of adhesive, or a heterogeneous adhesive may be sufficient as it.

The water-based adhesive is one in which the adhesive component is dissolved in water or dispersed in water. The aqueous adhesive used preferably is an adhesive composition using polyvinyl alcohol-type resin or urethane resin as a main component, for example.

When polyvinyl alcohol-based resin is used as the main component of the adhesive, the polyvinyl alcohol-based resin may be a polyvinyl alcohol resin such as partially saponified polyvinyl alcohol or fully saponified polyvinyl alcohol, and carboxyl group-modified polyvinyl alcohol and aceto. Modified polyvinyl alcohol-based resins such as acetyl group-modified polyvinyl alcohol, methylol group-modified polyvinyl alcohol and amino group-modified polyvinyl alcohol may be used. Polyvinyl alcohol-type resin is a polyvinyl alcohol-type copolymer obtained by saponifying the copolymer of vinyl acetate and the other monomer copolymerizable with this besides the vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate which is a homopolymer of vinyl acetate. You may.

The aqueous adhesive which uses polyvinyl alcohol-type resin as an adhesive component is usually an aqueous solution of polyvinyl alcohol-type resin. The concentration of the polyvinyl alcohol-based resin in the adhesive is usually 1 to 10 parts by weight, preferably 1 to 5 parts by weight with respect to 100 parts by weight of water.

The adhesive which consists of aqueous solution of polyvinyl alcohol-type resin contains curable components and crosslinking agents, such as a polyhydric aldehyde, a melamine type compound, a zirconia compound, a zinc compound, glyoxal, a glyoxal derivative, and a water-soluble epoxy resin, in order to improve adhesiveness. It is desirable to. Examples of the water-soluble epoxy resin include polyalkyl obtained by reacting epichlorohydrin with a polyamide amine obtained by a reaction of polyalkylene polyamines such as diethylenetriamine and triethylenetetramine with dicarboxylic acids such as adipic acid. Amide polyamine epoxy resin can be used suitably. As a commercial item of such a polyamide polyamine epoxy resin, "Sumirezu resin 650" (made by Takaokagaku Kogyo Co., Ltd.), "Sumirezu resin 675" (manufactured by Takaokagaku Kogyo Co., Ltd.), "WS-525" ( Nippon PMC Co., Ltd.) etc. are mentioned. The addition amount of these curable components and a crosslinking agent (when added together as a curable component and a crosslinking agent) is 1-100 weight part normally with respect to 100 weight part of polyvinyl alcohol-type resins, Preferably it is 1-50 weight part. . When the addition amount of the curable component or the crosslinking agent is less than 1 part by weight with respect to 100 parts by weight of the polyvinyl alcohol-based resin, the effect of improving the adhesion tends to be small, and the addition amount is 100 parts by weight of the polyvinyl alcohol-based resin. When it exceeds 100 parts by weight, the adhesive layer tends to be brittle.

Moreover, as a suitable example in the case of using a urethane resin as a main component of an adhesive agent, the mixture of the polyester-type ionomer type urethane resin and the compound which has glycidyloxy group is mentioned. The polyester ionomer-type urethane resin is a urethane resin which has a polyester frame | skeleton, and a small amount of ionic component (hydrophilic component) is introduce | transduced in it. Since such an ionomer-type urethane resin emulsifies in water directly without using an emulsifier, and becomes an emulsion, it is suitable as an aqueous adhesive agent.

An active energy ray curable adhesive agent is an adhesive which hardens by irradiation of active energy rays, such as an ultraviolet-ray, a visible light, an electron beam, and X-rays. When using an active energy ray curable adhesive agent, the adhesive bond layer which a polarizing plate has is a hardened | cured material layer of this adhesive agent.

The active energy ray curable adhesive may be an adhesive containing an epoxy compound that is cured by cationic polymerization as a curable component, and is preferably an ultraviolet curable adhesive containing such an epoxy compound as a curable component. The epoxy compound here means the compound which has an average of 1 or more, preferably 2 or more epoxy groups in a molecule | numerator. An epoxy compound may use only 1 type and may use 2 or more types together.

Specific examples of the epoxy compound that can be suitably used include a hydrogenated epoxy compound obtained by reacting epichlorohydrin with an alicyclic polyol obtained by performing a hydrogenation reaction on an aromatic ring of an aromatic polyol (glycol of a polyol having an alicyclic ring). Cyl ether); Aliphatic epoxy compounds such as polyglycidyl ethers of aliphatic polyhydric alcohols or their alkylene oxide adducts; An alicyclic epoxy compound which is an epoxy compound which has one or more epoxy groups couple | bonded with an alicyclic ring in a molecule | numerator is included.

An active energy ray curable adhesive agent may contain the (meth) acrylic-type compound which is radically polymerizable instead of or with this epoxy-type compound as a curable component. As a (meth) acrylic-type compound, (meth) acrylate monomer which has at least 1 (meth) acryloyloxy group in a molecule | numerator; It is obtained by making 2 or more types of functional group containing compounds react, and (meth) acryloyloxy-group containing compounds, such as (meth) acrylate oligomer which has at least 2 (meth) acryloyloxy group in a molecule | numerator, are mentioned.

When an active energy ray curable adhesive agent contains the epoxy-type compound hardened | cured by cationic polymerization as a curable component, it is preferable to contain a photocationic polymerization initiator. As a photocationic polymerization initiator, For example, Aromatic diazonium salt; Onium salts such as aromatic iodonium salts and aromatic sulfonium salts; Iron-Allene complex etc. are mentioned. Moreover, when an active energy ray curable adhesive contains radically polymerizable curable components like a (meth) acrylic-type compound, it is preferable to contain a radical photopolymerization initiator. As an optical radical polymerization initiator, an acetophenone type initiator, a benzophenone type initiator, a benzoin ether type initiator, a thioxanthone type initiator, a xanthone, a fluorenone, camphor quinone, benzaldehyde, anthraquinone, etc. are mentioned, for example.

Before bonding a protective film to a polarizing film, you may perform surface activation processing, such as a plasma process, a corona treatment, an ultraviolet irradiation process, a flame (flame) process, and a saponification process, to the bonding surface of a polarizing film and / or a protective film. . By this surface activation process, the adhesiveness of a polarizing film and a protective film can be improved.

Example

Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. Measurement or evaluation followed the following method.

(1) measurement of film thickness

It measured using the digital micrometer "MH-15M" by Nikon Corporation.

(2) Measurement of moisture content of film

Using a plurality of polyvinyl alcohol film samples having different moisture ratios, a calibration curve (converted equation) showing the correlation between the moisture content according to the dry weight method and the measured value of the infrared absorption moisture meter ("IRMA1100" manufactured by Chino Co., Ltd.) was used. Created. The measured value was obtained using the said moisture meter, and it substituted into the said analytical curve (conversion formula), and converted into the moisture content [weight%] according to the dry weight method, and made this the moisture content of a film. The moisture content according to the dry weight method is given by the weight of the polyvinyl alcohol film sample when heat-processed at 105 degreeC for 120 minutes as W1, and the weight of the polyvinyl alcohol film sample before heat processing as W0, The following formula:

Moisture content according to the dry weight method [% by weight] = (W0-W1) ÷ W0 x 100

Obtained according to. The said calibration curve was created whenever the thickness of the film of a measurement object differs.

(3) identification and evaluation of specific irregularities

One side of the obtained polarizing film (when a specific uneven | corrugated defect was recognized in one surface, the specific uneven | corrugated defect was normally formed in the same position also in the other surface) was observed with the loupe, and the presence or absence of the specific uneven | corrugated defect was confirmed. . As mentioned above, the specific unevenness | corrugation defect of one convex part which protrudes more than that with respect to the polarizing film surface other than the uneven | corrugated defect and the said recessed part adjacent to the convex part is recessed than the said reference | standard. In combination. If specific irregularities are present, the average length (average length) of the average specific irregularities and average heights (average height difference; convex portions) of the average specific irregularities and defects are obtained using the white interferometer "Vert Scan" manufactured by Ryoka Systems Co., Ltd. Film thickness direction average distance from the top to the bottom of the recess) was measured (see (4) below). Moreover, three pieces of samples of the transmission axis direction 200 mm x absorption axis direction 300 mm were cut out from a random area | region from the obtained polarizing film, observed with a loupe about each, and the number of a specific uneven | corrugated defect was measured, The density (number of specific uneven | corrugated defects per unit area of a polarizing film, unit: piece / m <2>) was calculated | required. Specifically, the calculation of the density of specific irregularities is as follows.

Density (piece / m²) of specific irregularities defect = (the total number of specific irregularities defect in three pieces of samples) / (total area of three samples)

Followed. The results are shown in Table 1. In addition, although the above-mentioned specific uneven | corrugated defect was confirmed only about the single side | surface of the obtained polarizing film, between the following Example and a comparative example, confirmation of the specific uneven | corrugated defect was performed about the same surface of a polarizing film.

(4) Measurement of average long diameter and average height difference of specific irregularities defect

The white interferometer "Vert Scan" by the Ryoka system make was used for the measurement. A long diameter (maximum diameter) means the longest distance from the outer end of a convex part to the outer end of a concave part when a specific uneven | corrugated defect is seen from the top (when viewed from the direction perpendicular | vertical with respect to a film surface). Ten specific uneven | corrugated defects were selected arbitrarily, and the average value of these long diameter was made into "average long diameter." Moreover, the elevation difference was measured about the said 10 specific unevenness | corrugation defects, and these average values were made into "average elevation difference." The results are shown in Table 1. In addition, in the Example and the comparative example, the long diameter of each specific uneven | corrugated defect measured was in the range of 0.5-5 mm, and the height difference was in the range of 0.1-1 micrometer.

(5) Confirmation and evaluation of bright spot (light leakage)

Three samples of the transmission axis direction 200 mm x absorption axis direction 300 mm were cut out from the random area | region from the obtained polarizing film, and bright spot (light leakage) was evaluated about each. Specifically, in a dark room, a polarizing plate for inspection is disposed on a backlight having a luminance of 20,000 mW / m 2 (measured using a luminance meter "BM-5A" manufactured by Topcon Techno House Co., Ltd.). The polarizing film sample was placed thereon. At this time, the polarizing plate and the polarizing film sample for inspection were arrange | positioned so that the transmission axis of the polarizing film contained in the polarizing plate for inspection and the transmission axis of a polarizing film sample may orthogonally cross. Then, the backlight was turned on and the presence or absence of the dot type bright spot (light leakage) in the surface of the sample was visually confirmed from the polarizing film sample side. When a bright point was recognized, the number was measured and the density (number of bright points per unit area, unit: piece / m <2>) was calculated | required. Specifically, the calculation of the density of the bright spot is the following formula:

Density (piece / m2) of bright spot = (the total number of bright spots in three samples) / (total area of three samples)

Followed. The results are shown in Table 1.

In addition, when brightness was recognized on the said conditions, the density of a bright spot was calculated | required as mentioned above except adding any one of the following conditions (A) or (B). The results are shown in Table 1.

(A) An ND filter having an average transmittance of 50% is further disposed between the backlight and the polarizing plate for inspection (in this case, the substantial luminance of the backlight is 10,000 mW / m 2).

(B) An ND filter having an average transmittance of 3% is further disposed between the backlight and the polarizing plate for inspection (in this case, the luminance of the backlight becomes 600 mW / m 2).

(6) Measurement of visibility correction single transmittance Ty and visibility correction polarization degree Py

Visibility correction was performed by the 2-degree field of view (C light source) of JIS Z 8701 with respect to the obtained transmittance and polarization degree using an absorbance photometer having an integrating sphere ("V7100" manufactured by Nihon Bunco Co., Ltd.) (Ty) and visibility correction polarization degree (Py) were measured.

(7) Measurement of Rotational Resistance of Guide Roll

After winding a thin film (polyethylene terephthalate film having a thickness of 25 μm) on the roll, the outer end of the wrapped film is fixed only to the spring, and only the spring is applied to the spring when the spring is pulled out at a constant speed so that the rotational speed of the roll is 100 rpm. The losing load was measured and this was made into the rotational resistance of a guide roll.

(8) Measurement of contact angle (logistic contact angle) with respect to water on guide roll surface

It measured on the conditions of the temperature of 23 degreeC, and 50% of the relative humidity according to the droplet method using the contact angle meter (automatic contact angle meter "DM-701" by Kyowa Chemical Co., Ltd.).

<Example 1>

Except for including a guide roll (pre-roll) having a total of 15 drying treatment parts (all in contact with the film surface), it is long from the long PVA-based resin film 10 using the same polarizing film manufacturing apparatus as in FIGS. 1 and 2. Polarizing film 25 was continuously manufactured. Then, the polarizing plate was produced using the obtained polarizing film 25. Specifically, it is as follows.

(1) Preparation of PVA-Based Resin Film 10

The following PVA resin film (a) was prepared as the PVA resin film 10. The PVA-based resin film (a) is a uniaxially stretched 4.1-fold polyvinyl alcohol film having a thickness of 30 µm, the saponification degree of the polyvinyl alcohol constituting the film is 99.9 mol% or more, and the average degree of polymerization is 2400, It contains 10 weight part plasticizer with respect to 100 weight part of polyvinyl alcohol which comprises a film.

(2) wet treatment process (S101)

While releasing the PVA-based resin film (a) from the unwinding roll (11), it is continuously conveyed while applying tension to maintain the tension state, and the residence time is 60 seconds in the swelling treatment tank (13) containing 40 ° C of pure water. It immersed and fully swells a PVA-type resin film (a) (swelling process process). While the film taken out from the swelling treatment tank 13 was immersed in the dyeing treatment tank 15 containing a dyeing treatment solution at 30 ° C. in which iodine / potassium iodide / water is 0.1 / 6/100 by weight, In the meantime, uniaxial stretching (inter-roll stretching in a bath) was performed (dyeing process). The film taken out from the dyeing treatment tank 15 was immersed in a crosslinking treatment tank 17 containing a 68 ° C crosslinking treatment liquid having potassium iodide / boric acid / water in a weight ratio of 15 / 5.5 / 100, with a residence time of 130 seconds, In the meantime, uniaxial stretching (roll-to-roll stretching in a bath) was performed (crosslinking process process). The film taken out from the crosslinking treatment tank 17 was immersed in the washing treatment tank 19 containing 20 degreeC pure water for 3 second residence time, and it wash | cleaned (washing process process). The cumulative draw ratio based on the PVA-based resin film (a) was 4.5 times.

(3) drying treatment step (S102)

Subsequently, while conveying the film drawn out from the washing process tank 19 continuously, it introduces into the drying furnace 21 which is a hot air oven, performs the drying process of 90 degreeC of residence time, and the temperature of 60 degreeC, and the polarizing film 25 Got. As for the thickness of the obtained polarizing film 25, 42.5%, visibility correction polarization degree (Py) of 12 micrometers and visibility correction | amendment single transmittance (Ty) were 99.993%, and moisture content was 10 weight%. Specific uneven | corrugated defect was confirmed about the obtained polarizing film 25. The results are shown in Table 1. In addition, the thickness of the film at the time of contacting the first low rotational resistance roll is substantially the same as the thickness of the polarizing film 25.

In Example 1, the guide roll (8 of the upstream side among 15 guide rolls) which builds up the conveyance path | route of the first half of the drying furnace 21 among the guide rolls which build up the conveyance path | route of the film which a polarizing film manufacturing apparatus has. Pieces) were made into all low rotational resistance rolls. The following low rotation resistance roll I was used for these low rotation resistance rolls. Next guide roll (II) was used for guide rolls (7 downstream) other than the guide roll which has built the conveyance path | route of the first half of the drying furnace 21. The next guide roll (II) was used for all the guide rolls of a wet process part.

[Low rotation resistance roll (I)]

Composition: A guide roll coated with a fluorine resin layer on the surface by using carbon as a core material,

Rotational resistance: 0.008 N

Weight per unit volume: 640 kg / m 3

Logarithmic contact angle of surface: 95 degrees,

Angle (alpha) (conveying direction change angle) of the film in each low rotation resistance roll: 90 degrees or 180 degrees (common to each Example and a comparative example).

(Guide Roll (II))

Composition: Guide roll with chromium plating on the surface by using SUS304 as core material

Rotational resistance: 0.03 N

Weight per unit volume: 1600 kg / m 3

Logarithmic contact angle of surface: 75 degrees.

About the obtained polarizing film 25, specific uneven | corrugated defect and bright spot (light leakage) were evaluated in accordance with the method mentioned above. The results are shown in Table 1.

(4) Preparation of the polarizing plate

The obtained polarizing film 25 is conveyed continuously, and the 1st protective film [TAC film "KC2UAW" made by Konica Minolta Opto Co., Ltd., thickness: 25 micrometers] and the 2nd protective film [cyclic olefin made by JSR Corporation] Brand name "FEKB015D3" which is a system resin film, thickness: 15 micrometers] is conveyed continuously, and inject | pouring an aqueous adhesive between the polarizing film 25 and a 1st protective film, and between a polarizing film 25 and a 2nd protective film, It was made to pass through between bonding rolls, and it was set as the laminated film which consists of a 1st protective film / water-based adhesive bond layer / polarizing film 25 / water-based adhesive bond layer / 2nd protective film.

The aqueous adhesive is a crosslinking agent in a polyvinyl alcohol solution having a concentration of 3% by weight in polyvinyl alcohol powder [Nihon Kosei Chemical Co., Ltd. product name "Gocefimer", average polymerization degree 1100] dissolved in hot water at 95 ℃. The aqueous solution which mixed [sodium glyoxylate by Nihon Kosei Chemical Co., Ltd. product] in 1 weight part with respect to 10 weight part of polyvinyl alcohol powder was used.

Subsequently, the obtained laminated | multilayer film was conveyed, it was made to pass through a hot air dryer, and 80 degreeC and 300 second heat processing were dried and the water-based adhesive bond layer was obtained, and the polarizing plate was obtained.

<Example 2>

Except having used the following low rotational resistance roll (III), it carried out similarly to Example 1, the polarizing film 25 (thickness 12 micrometers) was produced, and the polarizing plate was produced continuously. Table 1 shows the evaluation results of the specific uneven defects and bright spots (light leakage).

[Low rotation resistance roll (III)]

Composition: Guide roll coated with diamond-like carbon layer on the surface by using carbon as core material,

Rotational resistance: 0.008 N

Weight per unit volume: 640 kg / m 3

Logarithmic contact angle of surface: 105 degrees.

<Example 3>

In addition to all the guide rolls which form the conveyance path | route of the first half of the drying furnace 21, all the guide rolls which construct the conveyance path | route which connects the washing process tank 19 and the drying furnace 21 are made into the low rotational resistance roll ( Except having set it as I), it carried out similarly to Example 1, the polarizing film 25 (thickness 12 micrometers) was produced, and the polarizing plate was produced continuously. Table 1 shows the evaluation results of the specific uneven defects and bright spots (light leakage).

<Examples 4 to 6>

As the PVA-based resin film 10, a polarizing film was prepared in the same manner as in Examples 1 to 3, except that a PVA-based resin film (b) formed by uniaxially stretching a polyvinyl alcohol film having a thickness of 20 µm to 4.1 times in a dry manner was used. 25) (thickness 7 micrometers) was produced, and the polarizing plate was produced continuously. Table 1 shows the evaluation results of the specific uneven defects and bright spots (light leakage).

Comparative Example 1

The polarizing film was carried out similarly to Example 1 except having used the guide roll (II) mentioned above all the guide rolls which build the conveyance path | route of the film which a polarizing film manufacturing apparatus has without using the low rotational resistance roll (I). (25) (thickness 12 micrometers) was produced, and the polarizing plate was produced continuously. Table 1 shows the evaluation results of the specific uneven defects and bright spots (light leakage).

Comparative Example 2

As the PVA-based resin film 10, the polarizing film 25 was formed in the same manner as in Comparative Example 1 except that a PVA-based resin film (b) formed by uniaxially stretching a polyvinyl alcohol film having a thickness of 20 µm to 4.1 times in a dry manner was used. 7 micrometers thick) was produced, and the polarizing plate was produced continuously. Table 1 shows the evaluation results of the specific uneven defects and bright spots (light leakage).

1a, 1b, 1c, 1d, 1e, 1f, 1g, 1h, 1i, 1j, 1k, 1l, 1m, 1n, 1o, 1p, 1q, 1r, 1s guide roll, 2a, 2b, 2c, 2d, 2e, 2f nip roll, 10 polyvinyl alcohol resin film (PVA resin film), 11 unwinding roll, 13 swelling treatment tank, 15 dyeing treatment tank, 17 crosslinking treatment tank, 19 cleaning treatment tank, 20 wet treatment part, 21 drying furnace , 22 drying treatments, 25 polarizing films, 27 winding rolls.

Claims (17)

As a polarizing film in which a dichroic dye is adsorbed and oriented to a polyvinyl alcohol-based resin film,
The density of the uneven | corrugated defect in at least one surface is 20 pieces / m <2> or less,
The unevenness | corrugation defect consists of the combination of the one convex part which protrudes more than that with respect to the polarizing film surfaces other than the said unevenness | corrugation defect, and the one concave part adjacent to the said convex part while recessing than the said reference, and has a long diameter of 0.5- In the range of 5 mm,
When the said uneven | corrugated defect is recognized in one surface of the said polarizing film, the said uneven | corrugated defect by which the convex part and the recessed part were reversed in the same position in the other surface is formed,
Polarizing film whose thickness is 15 micrometers or less. The said uneven | corrugated defect is a polarizing film of Claim 1 whose height of a convex part and the depth of a concave part are 0.05-0.5 micrometer with respect to the said reference | standard. The polarizing film according to claim 1, wherein the unevenness is an elevation difference of 0.1 to 1 µm, which is a film thickness direction distance from the top of the convex portion to the bottom of the concave portion. The said uneven | corrugated defect generate | occur | produces the bright point visually recognized when the said polarizing film is apply | coated to a liquid crystal display device, and the brightness | luminance of the backlight measured with the luminance meter is 10,000 cd / m <^{2> or} more. Polarizing film. delete delete delete delete delete delete delete delete delete delete delete delete delete

Images