JP2019066502A - Polarizing plate and method for manufacturing the same, and display - Google Patents

Abstract

To provide a polarizing plate that can make streak-like unevenness inconspicuous regardless of a change in hue.SOLUTION: A polarizing plate 1 comprises a polarizer 2, and protective films 3, 4 arranged on at least one face of the polarizer 2 with an adhesive layer therebetween, wherein the visibility correction single transmittance (Ty) measured in an initial state is 44% or more, and the orthogonal hue measured in the initial state and after an endurance test does not change in sign across an a coordinate axis and a b coordinate axis in the ab chromaticity coordinates.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polarizing plate, a method of manufacturing the same, and a display.

  For example, in Patent Document 1 below, since streak-like unevenness is observed which is confirmed by shading of the reflected light originating from streaks on the surface of the polarizer, the height of the surface asperity of the polarizer should be 280 nm or less It has been proposed to suppress streak-like unevenness caused by shading of reflected light.

Patent No. 6166431

  In recent years, for the purpose of reduction of power consumption and the like, high transmission of a polarizing plate has been advanced. On the other hand, when the polarizing plate becomes highly transparent, as described in Patent Document 1, even if the surface unevenness of the polarizer is 280 nm or less, the polarizer is obtained in the cross nicol state due to the surface unevenness of the polarizer. It was found that streaky unevenness was caused by the transmitted light.

  Furthermore, with regard to a high transmission polarizing plate, while using the polarizing plate, even if the streak-like unevenness visually recognized by transmitting the polarizer in the cross nicol state is controlled by controlling the hue in the initial state, When the hue (color tone) of this polarizing plate changes, streak-like unevenness may be noticeable.

  The present invention has been proposed in view of such conventional circumstances, and a polarizing plate and its manufacturing method, which make it possible to make streak-like unevenness inconspicuous regardless of changes in hue, and It aims at providing a display provided with such a polarizing plate.

  According to an aspect of the present invention, there is provided a polarizing plate including a polarizer and a protective film disposed on at least one surface of the polarizer via an adhesive layer, as means for solving the above problems. The visibility corrected single transmittance (Ty) measured in the initial state is 44% or more, and the orthogonal hue measured in the initial state and after the endurance test sandwiches the a coordinate axis and the b coordinate axis in the ab chromaticity coordinates There is provided a polarizing plate characterized in that the sign does not change.

  In the polarizing plate, after the endurance test, it may be after being subjected to heating at 105 ° C. for 30 minutes in a dry atmosphere at least from the initial state.

  In the polarizing plate, the polarizer may be a polarizing film in which a dichroic dye is adsorbed and oriented to a uniaxially stretched polyvinyl alcohol-based resin film.

  In the polarizing plate, the thickness of the polarizer may be 3 to 15 μm.

  Moreover, in the polarizing plate, when the protective film is removed, an unevenness having a height difference of 80 to 250 nm may be present on the surface of the polarizer to which the adhesive is attached.

  In the polarizing plate, the polarizer may be an iodine-based polarizer.

  Further, according to an aspect of the present invention, there is provided a display device comprising a display panel and any one of the polarizing plates.

  Further, according to an aspect of the present invention, there is provided a method of manufacturing a polarizing plate including a polarizer and a protective film disposed on at least one surface of the polarizer via an adhesive layer, wherein the polarizing plate is in an initial state and durable. A method of manufacturing a polarizing plate is provided, which includes a hue adjustment step of adjusting orthogonal hues measured after the test so that the sign does not change across the a coordinate axis and the b coordinate axis in the ab chromaticity coordinates. .

  In the method of manufacturing the polarizing plate, the hue adjustment step may be a method of adjusting at least the hue of the polarizer.

  In the method of manufacturing the polarizing plate, the protective film disposed on at least one side or both sides of the polarizing plate may be selected as the hue adjusting step.

  As described above, according to the aspect of the present invention, it is possible to provide a polarizing plate which makes it possible to make streak-like unevenness inconspicuous regardless of a change in hue, and to be bendable including such a polarizing plate. It is possible to provide a display device.

It is sectional drawing which shows the structure of the polarizing plate which concerns on one Embodiment of this invention. It is sectional drawing which shows the structure of the polarizing plate which concerns on another embodiment of this invention. It is sectional drawing which shows the structure of the polarizing plate which concerns on another embodiment of this invention. It is sectional drawing which shows the structure of the display apparatus provided with the polarizing plate shown in FIG. It is an ab chromaticity coordinate figure for demonstrating the change of the orthogonal hue measured before and behind the endurance test of a polarizing plate. It is a schematic diagram which shows the structure of the manufacturing apparatus of a polarizing film. It is an ab chromaticity coordinate figure which shows the change of the orthogonal hue measured before and behind the endurance test in Example 1, 2. It is an ab chromaticity coordinate figure which shows the change of the orthogonal hue measured before and behind the endurance test in Examples 3 and 4 and Comparative Examples 1 and 2. FIG. 6 is an ab chromaticity coordinate diagram showing changes in orthogonal hues measured before and after the endurance test in Reference Example 1;

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In the drawings used in the following description, in order to make each component easy to see, the component may be schematically shown, and depending on the component, the scale of the dimensions may be different. In addition, the materials, numerical values, and the like exemplified in the following description are merely examples, and the present invention is not necessarily limited to them, and various modifications can be made without departing from the scope of the present invention. .

(Polarizer)
First, for example, a polarizing plate 1 shown in FIG. 1 will be described as an embodiment of the present invention.
FIG. 1 is a cross-sectional view showing a schematic configuration of the polarizing plate 1.

  The polarizing plate 1 of the present embodiment includes a polarizer 2 and protective films 3 and 4 disposed on at least one surface (both surfaces in the present embodiment) of the polarizer 2 as shown in FIG. The protective films 3 and 4 have a structure in which both surfaces of the polarizer 2 are bonded (laminated through an adhesive layer) by an adhesive (not shown).

  The polarizer 2 has a function of converting light such as natural light into linearly polarized light, and has a transmission axis and an absorption axis. The transmission axis of the polarizer 2 is the vibration direction of the transmitted light when natural light is transmitted through the polarizer 2. On the other hand, the absorption axis of the polarizer 2 is in the direction orthogonal to the transmission axis of the polarizer 2.

  The polarizer 2 is generally made of a polarizing film in which a dichroic dye such as iodine or a dichroic dye is adsorbed and oriented to a uniaxially stretched polyvinyl alcohol (PVA) -based resin film. Therefore, the absorption axis direction of the polarizer 2 coincides with the stretching direction (MD), and the transmission axis direction of the polarizer 2 coincides with the width direction (TD).

  The PVA-based resin film is usually obtained by saponifying a polyvinyl acetate-based resin. The degree of saponification is usually about 85 mol% or more, preferably about 90 mol% or more, more preferably about 99 mol% or more.

  The polyvinyl acetate-based resin can be, for example, polyvinyl acetate which is a homopolymer of vinyl acetate, or a copolymer of vinyl acetate and another monomer copolymerizable therewith, or the like. As another monomer which can be copolymerized, unsaturated carboxylic acids, olefins, vinyl ether, unsaturated sulfonic acids etc. can be mentioned, for example. The polymerization degree of the polyvinyl alcohol-based resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000. These polyvinyl alcohol resins may be modified, and for example, polyvinyl formal modified with aldehydes, polyvinyl acetal, polyvinyl butyral and the like can also be used.

  The thickness of the polarizer 2 is preferably thin from the viewpoint of thinning of the polarizing plate 1, but is appropriately set according to the application of the polarizing plate 1 and the like. The thickness of the polarizer 2 may be, for example, 25 μm or less, preferably 20 μm or less, more preferably 15 μm or less, and for example, 1 μm or more, preferably 3 μm or more. When the thickness of the polarizer 2 is 15 μm or less, wrinkles are easily generated during conveyance of the PVA-based resin film during processing, and unevenness is easily generated in the polarizer 2, so the effect of the present invention is increased. The thickness of the polarizer 2 in the polarizing plate 1 may be considered to be substantially equal to the thickness of the polarizer 2 after bonding and curing the protective films 3 and 4 with an adhesive.

  As the protective films 3 and 4, for example, a film composed of an acetylcellulose-based resin such as triacetylcellulose or diacetylcellulose; a film composed of a polyester-based resin such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; polycarbonate-based resin Film; cycloolefin resin film; acrylic resin film; film made of linear olefin resin of polypropylene resin.

  When the protective films 3 and 4 are disposed on both sides of the polarizer 2, the protective films 3 and 4 made of the same kind of resin may be used, or the protective films 3 and 4 made of different kinds of resin may be used. .

  The thickness of the protective films 3 and 4 is preferably thin from the viewpoint of thinning of the polarizing plate 1, but is appropriately set according to the application of the polarizing plate 1 and the like. The thickness of the protective films 3 and 4 may be, for example, 85 μm or less, preferably 50 μm or less, and more preferably 30 μm or less.

  On the other hand, the thickness of the protective films 3 and 4 is preferably a thickness that can ensure a certain degree of strength from the viewpoint of processability, and may be, for example, 5 μm or more, preferably 10 μm or more.

  The adhesive may be a water-based adhesive or an active energy ray-curable adhesive. Examples of the aqueous adhesive include aqueous solutions of polyvinyl alcohol resins, or aqueous solutions in which a crosslinking agent is blended, and aqueous adhesives such as urethane emulsion adhesives.

  The active energy ray-curable adhesive means an adhesive which is cured by irradiation with active energy rays such as ultraviolet rays and electron beams. As an active energy ray-curable adhesive, when classified according to the curing mode, a cationically polymerizable adhesive containing a cationically polymerizable compound as a curable compound, a radically polymerizable adhesive containing a radically polymerizable compound as a curable compound, a cationic The curable adhesive etc. which contain both a polymeric compound and a radically polymerizable compound are mentioned. An epoxy compound, an oxetane compound etc. are mentioned as a cationically polymerizable compound. As a radically polymerizable compound, the (meth) acrylic-type compound etc. which have one or more (meth) acryloyl groups in a molecule | numerator are mentioned.

  The thickness of the adhesive layer formed by the aqueous adhesive may be, for example, 20 nm or more, preferably 40 nm or more. On the other hand, the thickness of the adhesive may be such that it is not excessively large from the viewpoint of production cost and the like, and may be, for example, 1000 nm or less, preferably 500 nm or less, more preferably 300 nm or less.

  The thickness of the adhesive layer formed by the active energy ray-curable adhesive is preferably 0.1 μm or more, preferably 10 μm or less, more preferably 5 μm or less, and further preferably 3 μm or less. preferable.

  As another embodiment of the present invention, for example, the configuration of the polarizing plate 1A shown in FIG. 2 or the polarizing plate 1B shown in FIG. 3 may be used. FIG. 2 is a cross-sectional view showing a schematic configuration of the polarizing plate 1A. FIG. 2 is a cross-sectional view showing a schematic configuration of the polarizing plate 1B.

  Specifically, in addition to the configuration of the polarizing plate 1, the polarizing plate 1A shown in FIG. 2 is disposed on the surface of the at least one protective film (the protective film 4 in the present embodiment) opposite to the polarizer 2. And a pressure-sensitive adhesive (PSA) layer 5. On the other hand, the polarizing plate 1B shown in FIG. 3 includes the polarizer 2, the protective film 3 disposed on one side of the polarizer 2, and the pressure-sensitive adhesive layer 5 disposed on the other side of the polarizer 2. It is a structure.

  The pressure-sensitive adhesive layer 5 can be bonded to the polarizer 2 and the protective films 3 and 4 due to its own adhesiveness. The pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer 5 may be appropriately selected from conventionally known ones, and has adhesiveness to such an extent that peeling does not occur in an environment where the polarizing plates 1A and 1B can be exposed. I hope there is. Specifically, acrylic pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives and the like can be mentioned, and acrylic pressure-sensitive adhesives are particularly preferable in terms of transparency, weather resistance, heat resistance and processability. The thickness of the pressure-sensitive adhesive layer 5 is usually about 3 to 100 μm, preferably 5 to 50 μm.

  Further, the adhesive may be, if necessary, a filler comprising a tackifier, a plasticizer, glass fiber, glass beads, metal powder, other inorganic powder, etc., a pigment, a colorant, a filler, an antioxidant, Various additives such as an ultraviolet absorber, an antistatic agent, and a silane coupling agent may be appropriately blended.

  The pressure-sensitive adhesive layer 5 is used to bond the polarizing plates 1A and 1B to other members. A release film (not shown) may be provided on the surface of the pressure-sensitive adhesive layer 5 in advance. When a release film is present on the surface of the pressure-sensitive adhesive layer 5, the release film may be peeled off from one of the surfaces, and the pressure-sensitive adhesive layer 5 may be bonded (laminated) to the polarizer 2 or the protective films 3 and 4. it can. Further, after peeling the release film from the other side, it can be pasted to another member via the pressure-sensitive adhesive layer 5.

  In addition, about the structure of the polarizing plate to which this invention is applied, it is not necessarily limited to the structure of polarizing plate 1, 1A, 1B shown to the said FIGS. 1-3. That is, the polarizing plate to which the present invention is applied has only to be a configuration including a polarizer and a protective film disposed on at least one surface or both surfaces of the polarizer, and the other configuration is appropriately modified. It is possible.

  For example, in the polarizing plates 1 and 1A, in place of the protective film 4, for example, another functional layer such as a retardation film or a brightness enhancement film may be applied.

  When the polarizing plates 1, 1A and 1B are used as circularly polarizing plates, a quarter wavelength (λ / 4) plate may be included in addition to the above configuration. The λ / 4 plate has a function of converting linearly polarized light of a specific wavelength into circularly polarized light (or circularly polarized light into linearly polarized light). The λ / 4 plate is disposed on the surface of the protective film 4 opposite to the polarizer 2 via the pressure-sensitive adhesive layer 5.

  When the polarizing plates 1, 1A and 1B are used as circularly polarizing plates, a positive C plate may be included in addition to the λ / 4 plate. The positive C plate can reduce the change in the reflected hue (color tone) of the polarizing plates 1, 1A, 1B. When the positive C plate is included, the λ / 4 plate is preferably a reverse wavelength dispersive λ / 4 plate. The positive C plate is disposed on the surface (other surface) of the λ / 4 plate opposite to the polarizer 2 through the adhesive layer or the pressure-sensitive adhesive layer. Therefore, for example, in the case of the polarizing plate 1, it has a laminated structure of the polarizing plate 1, the pressure-sensitive adhesive layer 5, the λ / 4 plate, the pressure-sensitive adhesive layer or the adhesive layer, and the positive C plate.

  Moreover, when using said polarizing plate 1, 1A, 1B as a circularly-polarizing plate, it is good also as a structure containing 1/2 wavelength ((lambda) / 2) board other than (lambda) / 4 board. The λ / 2 plate gives a phase difference of π (= λ / 2) to the electric field vibration direction (polarization plane) of incident light, and has a function of changing the direction (polarization direction) of linear polarization. In addition, when circularly polarized light is made incident, the rotational direction of circularly polarized light can be reversed. The λ / 2 plate is disposed on the surface (other surface) of the λ / 4 plate opposite to the polarizer 2 through the adhesive layer or the pressure-sensitive adhesive layer. Therefore, for example, in the case of the polarizing plate 1, it has a laminated structure of the polarizing plate 1, the pressure-sensitive adhesive layer 5, the λ / 4 plate, the pressure-sensitive adhesive layer or the adhesive layer, and the λ / 2 plate.

(Display device)
Next, the display device of the present embodiment will be described with reference to FIG.
4 is a cross-sectional view showing the configuration of a display device 10 provided with the polarizing plate 1A shown in FIG.

  As shown in FIG. 4, the display device 10 of the present embodiment includes a display panel 11 and a polarizing plate 1 </ b> A disposed on the viewing side of the display panel 11. The polarizing plate 1 </ b> A is bonded to the display panel 11 via the adhesive layer 5.

  The display panel 11 is not particularly limited, and may be, for example, a liquid crystal display element or an organic electroluminescence (EL) display element. When a liquid crystal display panel is used as the display panel 11, the display device 10 is called a liquid crystal display device. On the other hand, when an organic EL display element is used as the display panel 11, the display device 10 is referred to as an organic EL display device.

  The configuration of the display device to which the present invention is applied is not necessarily limited to the configuration of the display device 10 shown in FIG. That is, as long as the display device to which the present invention is applied includes the polarizing plate to which the present invention described above is applied, the configuration of the display panel can be appropriately modified. On the other hand, the application of the polarizing plate to which the present invention is applied is not limited to the display described above, and can be used for various optical applications.

  By the way, in the polarizing plate 1 of the present embodiment, the orthogonal hue measured in the initial state and after the endurance test is adjusted so that the sign does not change across the a coordinate axis and the b coordinate axis in the ab chromaticity coordinates. It features. That is, the change of the orthogonal hue measured before and after the endurance test of the polarizing plate 1 is set to a value that does not straddle the a coordinate axis and the b coordinate axis. As a result, even if the orthogonal hue of the polarizing plate 1 changes before and after the endurance test, it is possible to make the streak-like unevenness generated in the polarizing plate 1 inconspicuous regardless of the change in the hue.

  Specifically, the change in orthogonal hue measured before and after the endurance test of the polarizing plate 1 will be described with reference to FIG. FIG. 5 is an ab chromaticity coordinate diagram for explaining changes in orthogonal hues measured before and after the endurance test of the polarizing plate 1.

  The change in orthogonal hue measured before and after the endurance test of the polarizing plate 1 can be measured using a spectrophotometer or the like.

  Moreover, in the present embodiment, the transmission hue is measured by a spectrophotometer. Then, after being subjected to heating at 105 ° C. for 30 minutes in a dry atmosphere, the transmission hue is again measured by the spectrophotometer. Then, it was confirmed that the transmission hues measured in the initial state of the polarizing plate 1 and after the endurance test did not change in sign across the a coordinate axis and the b coordinate axis.

  Moreover, the streak-like unevenness which generate | occur | produced in the polarizing plate 1 can be observed by the cross nicol transmitted light on a backlight. Specifically, a polarizing plate is attached to the illumination surface of the white backlight, and the polarizing plate 1 is placed on the polarizing plate so that the absorption axes are orthogonal to each other, and the intensity of unevenness can be observed visually.

  Also in the case where the protective films 3 and 4 of the polarizing plate 1 include retardation plates such as λ / 4 plate, positive C plate, λ / 2 plate, etc., these retardation plates are on the opposite side of the backlight (viewing side) It should be installed on the back light and observed. Moreover, when both of the protective films 3 and 4 of the polarizing plate 1 have a configuration of a retardation plate, a retardation plate is placed on the backlight in which the polarizing plate is attached to the illumination surface, and Can be placed and observed so that it becomes cross nicol.

  In the present embodiment, the orthogonal hue measured before and after the endurance test of the polarizing plate 1 does not change with respect to the a coordinate axis and the b coordinate axis, for example, in the ab color coordinate diagram shown in FIG. And b are synonymous with not crossing the quadrant across the coordinate axis. In this case, even if the orthogonal hue of the polarizing plate 1 changes before and after the endurance test, it is possible to make the streak-like unevenness generated in the polarizing plate 1 inconspicuous regardless of the change in the hue. On the other hand, when straddling a quadrant sandwiching the a coordinate axis and the b coordinate axis, it is easy to see streak-like unevenness generated in the polarizing plate 1 due to a change in orthogonal hue.

About the streak-like unevenness generated in the polarizing plate 1, it is preferable that the height difference ΔH of the streak-like unevenness on the surface of the polarizing plate 1 is 80 to 250 nm. When the protective films 3 and 4 are removed, the height difference ΔH of the streak-like unevenness is the surface of the polarizer 2 to which the adhesive is attached, the surface of the polarizing plate 1 in the direction orthogonal to the extension direction of the streaks. While scanning, measure the line surface roughness. And from this measurement result, as shown in the following formula (1), the height (H1) at the top of the highest convex with respect to the average line of the surface and the two concaves respectively adjacent to the highest convex And the sum of the depth and the depth (H2) at the bottom of the deeper recess. In addition, the extension direction of the streaks is usually a direction coinciding with the stretching direction (MD).
80 nm ≦ ΔH = H1 + H2 ≦ 250 nm (1)

  In the polarizing plate 1 of the present embodiment, such an orthogonal hue measured in the initial state and after the endurance test is adjusted so that the sign does not change across the a coordinate axis and the b coordinate axis in the ab chromaticity coordinates. It is possible to make the streak-like unevenness generated in the polarizing plate 1 inconspicuous regardless of the change in hue.

  Further, in the polarizing plate 1 of the present embodiment, the hue of the polarizer 2 is adjusted, or the protective films 4 and 5 disposed on at least one surface or both surfaces of the polarizing plate 1 are selected to be orthogonal to each other. It is possible to adjust the hue.

  In the polarizing plate 1 of the present embodiment, the luminous transmittance correction single transmittance (Ty) is preferably 44.0% or more, more preferably 44.3% or more, and still more preferably 44.5% or more. . Moreover, in the polarizing plate 1 of the present embodiment, the visibility correction polarization degree (Py) is 95% or more, preferably 98% or more, and more preferably 99% or more. Ty and Py can be measured, for example, using a spectrophotometer or the like.

  In addition to the polarizing plate 1 described above, the present invention is also in an initial state for polarizing plates including the above-described polarizing plates 1A and 1B, or a retardation film such as a λ / 4 plate, a positive C plate, or a λ / 2 plate. And the orthogonal hue measured after the endurance test is adjusted so that the sign does not change across the a coordinate axis and the b coordinate axis in the ab color coordinate, thereby transmitting the polarizer 2 in the cross nicol state generated in the polarizing plate It is possible to make the streak-like unevenness caused by the light not noticeable as a result of the change in hue.

(Method of manufacturing polarizing plate)
Next, a method of manufacturing the polarizing plate of the present embodiment will be described with reference to FIG.
In addition, FIG. 6 is a schematic diagram which shows the manufacturing apparatus 100 of the polarizing film used as the said polarizer 2. As shown in FIG. Moreover, the arrow shown in FIG. 6 has shown the conveyance direction of the film F used as a polarizing film.

  In the present embodiment, first, a polarizing film to be the polarizer 2 of the polarizing plate 1 is manufactured using the manufacturing apparatus 100 shown in FIG. Specifically, with a long unstretched PVA-based resin film (raw film) F as a starting material, a predetermined processing step is carried out while continuously conveying the film F along the film conveyance path of the manufacturing apparatus 100. To produce a continuous long polarizing film.

  As a predetermined treatment step, a swelling treatment step of immersing the film F in the swelling bath 102, a dyeing treatment step of immersing the film F after the swelling treatment step in the dyeing bath 103, and a crosslinking bath of the film F after the dyeing treatment step A cross-linking treatment step of immersing in 104, a washing treatment step of immersing the cross-linked film F in the washing bath 105, a stretching treatment step of uniaxially stretching the film F being conveyed, and a film F after the washing treatment step And drying in a drying oven 106. Furthermore, other processing steps may be added as needed.

  The apparatus 100 for producing a polarizing film shown in FIG. 6 includes a swelling bath 102 provided on the film conveyance path while conveying the film F along the film conveyance path while continuously unwinding the film F from the raw film roll 101. The film F is sequentially passed through the dyeing bath 103, the crosslinking bath 104, and the washing bath 105, and finally the film F is passed through the drying furnace 106. The obtained polarizing film can be conveyed as it is, for example, to the next production step of the polarizing plate 1 (step of bonding a protective film to one side or both sides of the polarizing film).

  In the manufacturing apparatus 100 shown in FIG. 6, one swelling bath 102, one dyeing bath 103, one crosslinking bath 104 and one washing bath 105 are provided as treatment baths containing treatment liquid for treating the film F. Although the illustrated case is illustrated, as necessary, two or more treatment baths may be provided.

  The manufacturing apparatus 100 shown in FIG. 6 supports the film F to be conveyed in addition to the processing baths 102 to 105 described above on the film conveyance path, and changes the conveyance direction of the film F to be conveyed as necessary. The guide rolls 30 to 41 and the film F to be conveyed are pressed and held, and the drive force by the rotation is applied to the film F, and the nip rolls 50 to 55 to change the conveyance direction of the film F conveyed as needed. And are appropriately arranged.

  The guide rolls 30 to 41 and the nip rolls 50 to 55 can be disposed before and after the processing baths 102 to 105 or in the processing baths 102 to 105. Thereby, introduction and immersion of the film F to each processing bath 102-105 and extraction from the processing bath 102-105 can be performed. For example, one or more guide rolls 30 to 41 are provided in each of the processing baths 102 to 105, and the film F is transported to each of the processing baths 102 to 105 along the guide rolls 30 to 41. It can be soaked.

  In the manufacturing apparatus 100 shown in FIG. 6, nip rolls 50 to 55 are disposed before and after each of the processing baths 102 to 105. As a result, in any one or more of the processing baths 102 to 105, a circumferential speed difference is provided between the nip rolls 50 to 55 disposed in front of and behind the inter-roll stretching for longitudinally uniaxially stretching the film F. It is possible to carry out.

Hereinafter, each processing process given to the film F when producing a polarizing film is demonstrated.
<Swelling step>
The swelling treatment step is carried out for the purpose of removal of foreign matter present on the surface of the film F to be a raw film, removal of a plasticizer present in the film F, imparting of easy-to-stain properties, plasticization of the film F, etc. . Processing conditions are determined in the range which does not produce problems, such as extreme melt | dissolution of the film F, and devitrification, in the range which can achieve the said objective.

  As a raw film, an unstretched PVA-based resin film having a thickness of 65 μm or less, preferably about 10 to 50 μm, more preferably about 10 to 35 μm can be used. The raw film is usually prepared as a roll (rolled product) of a long unstretched PVA-based resin film. However, the raw film may be a stretched film which has been uniaxially stretched in gas in advance before the swelling process.

  In the swelling treatment step, the treatment contained in the swelling bath 102 while passing the film (raw film) continuously unwound from the raw fabric roll 101 in the order of the nip roll 50 and the guide rolls 30 to 32. Immerse in liquid for a predetermined time. Thereby, the film F is subjected to a swelling process. In addition, the film F can also be uniaxially stretched in the swelling bath 102 using the circumferential speed difference between the nip roll 50 and the nip roll 51 as a stretching step.

  In addition to pure water, boric acid (see JP-A 10-153709), chloride (see JP-A 06-281816), inorganic acid, inorganic salt, and pure water in the treatment liquid of the swelling bath 102. An aqueous solution to which a water-soluble organic solvent, an alcohol and the like are added in a range of about 0.01 to 10% by weight can be used.

  When the film F is an unstretched film, the temperature of the swelling bath 102 is, for example, about 10 to 50 ° C., preferably about 10 to 40 ° C., and more preferably about 15 to 30 ° C. The immersion time of the film F is preferably about 10 to 300 seconds, and more preferably about 20 to 200 seconds. On the other hand, when the film F is a stretched film, the temperature of the swelling bath 102 is, for example, about 20 to 70 ° C., preferably about 30 to 60 ° C. The immersion time of the film F is preferably about 30 to 300 seconds, and more preferably about 60 to 240 seconds.

  In the swelling process, the film F is likely to swell in the width direction and wrinkles may occur in the film F. As one means for conveying the film F while removing the wrinkles, a roll having a widening function such as an expander roll, a spiral roll, or a crown roll may be used for the guide rolls 30, 31 and / or the guide roll 32. Other widening devices such as cross guiders, bend bars and tenter clips can be used. On the other hand, as another means for suppressing the occurrence of wrinkles, stretching can be performed.

  In the swelling process, the film F swells and expands in the transport direction of the film F. Therefore, when the film F is not positively stretched, for example, the swelling bath 102 is removed to eliminate the slack of the film F in the transport direction. It is preferable to take measures such as controlling the speed of the nip rolls 50 and 51 arranged in the front and back. In addition, in order to stabilize transport of the film F in the swelling bath 102, the water flow in the swelling bath 102 is controlled by a shower in water, or an EPC device (Edge Position Control device: film edge detected, film It is also useful to use a device that prevents the meandering of

  The film F pulled out of the swelling bath 102 passes the guide roll 32 and the nip roll 51 in order and is conveyed to the dyeing bath 103 side.

<Staining process>
The dyeing process is performed for the purpose of adsorbing and orienting the dichroic dye on the film F after the swelling process. Processing conditions are determined in the range which does not produce problems, such as extreme melt | dissolution of the film F, and devitrification, in the range which can achieve the said objective.

  In the dyeing process, while passing the film F after the swelling process in the order of the nip roll 51 and the guide rolls 33 to 35, the film F is immersed in the treatment liquid contained in the dyeing bath 103 for a predetermined time. Thus, the film F is subjected to a dyeing process. In addition, the film F can also be uniaxially stretched in the dyeing bath 103 by using the circumferential speed difference between the nip roll 51 and the nip roll 52 as a stretching step.

  The film F to be subjected to the dyeing treatment step is preferably a film F subjected to at least a certain degree of uniaxial stretching treatment in order to enhance the dyeability of the dichroic dye, and the uniaxial stretching treatment is added before the dyeing treatment. Alternatively, it is preferable to perform uniaxial stretching at the time of dyeing in addition to uniaxial stretching before dyeing.

  When iodine is used as the dichroic dye, for example, the concentration of the treatment liquid of the dyeing bath 103 is iodine / potassium iodide / water = about 0.003 to 0.3 / about 0.1 to 10/100 in weight ratio. The aqueous solution which is can be used. Instead of potassium iodide, other iodides such as zinc iodide may be used, and potassium iodide and other iodides may be used in combination. In addition, compounds other than iodide, for example, boric acid, zinc chloride, cobalt chloride and the like may coexist. When boric acid is added, it is distinguished from the crosslinking treatment described later in that it contains iodine, and if the aqueous solution contains about 0.003 parts by weight or more of iodine with respect to 100 parts by weight of water, the dyeing bath 103 It can be regarded as

  The temperature of the dyeing bath 103 in this case is usually about 10 to 45 ° C., preferably 10 to 40 ° C., and more preferably 20 to 35 ° C. The immersion time of the film F in this case is usually about 30 to 600 seconds, preferably 60 to 300 seconds.

  On the other hand, when using a water-soluble dichromatic dye as the dichromatic dye, the treatment liquid of the dyeing bath 103 is, for example, a dichromatic dye / water concentration of about 0.001 to 0.1 / 100 by weight ratio. Preferably, an aqueous solution of about 0.003 to 0.03 / about 0.1 to 10/100 can be used In this case, the processing solution of the dyeing bath 103 may be allowed to coexist with a dyeing assistant and the like. For example, it may contain an inorganic salt such as sodium sulfate, a surfactant, etc. Only one dichroic dye may be used alone, or two or more dichroic dyes may be used in combination. You may

  The temperature of the dyeing bath 103 in this case is, for example, about 20 to 80 ° C., preferably 30 to 70 ° C. The immersion time of the film F in this case is usually about 30 to 600 seconds, preferably about 60 to 300 seconds It is.

  In the dyeing process, as in the case of the swelling process described above, as one means for transporting the film F while removing the wrinkles of the film F, the guide rolls 33, 34 and / or the guide roll 35 are expander rolls, spirals It is possible to use rolls having a widening function such as rolls or crown rolls, or to use other widening devices such as cross guiders, bend bars, or tenter clips. On the other hand, as another means for suppressing the occurrence of wrinkles, stretching treatment can be performed as in the case of the above-mentioned swelling treatment.

  The film F drawn from the dyeing bath 103 passes through the guide roll 35 and the nip roll 52 in order and is introduced to the cross-linking bath 104 side.

<Crosslinking treatment process>
The crosslinking treatment step is a treatment performed for the purpose of water resistance and hue adjustment by crosslinking. In the crosslinking treatment step, while passing the film F after the dyeing treatment step in the order of the nip roll 52 and the guide rolls 36 to 38, the film F is immersed in the treatment liquid contained in the crosslinking bath 104 for a predetermined time. Thereby, the film F is cross-linked. The film F can also be uniaxially stretched in the cross-linking bath 104 by using the circumferential speed difference between the nip roll 52 and the nip roll 53 as a stretching step.

  An aqueous solution containing, for example, about 1 to 10 parts by weight of boric acid with respect to 100 parts by weight of water can be used as the treatment liquid of the crosslinking bath 104. When the dichroic dye used in the dyeing process is iodine, the treatment liquid of the crosslinking bath 104 preferably contains an iodide in addition to boric acid, and the amount thereof is, for example, 1 per 100 parts by weight of water. To 30 parts by weight. Examples of the iodide include potassium iodide and zinc iodide. In addition, compounds other than iodide, for example, zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate and the like may coexist.

  In the crosslinking treatment, depending on the purpose, the concentration of the crosslinking agent (such as boric acid) and iodide and the temperature of the crosslinking bath can be appropriately changed. For example, in the case where the purpose of the crosslinking treatment is to make water resistant by crosslinking and the unstretched polyvinyl alcohol resin film is subjected to swelling treatment, dyeing treatment and crosslinking treatment in this order, the concentration of the crosslinking agent-containing liquid in the crosslinking bath is It can be an aqueous solution of boric acid / iodide / water = 3-10 / 1-20 / 100 by weight. Further, if necessary, in place of boric acid, another crosslinking agent such as glyoxal or glutaraldehyde may be used, or boric acid and another crosslinking agent may be used in combination.

  The temperature of the crosslinking bath 104 is usually about 50 to 70 ° C., preferably 53 to 65 ° C. The immersion time of the film F is usually about 10 to 600 seconds, preferably 20 to 300 seconds, and more preferably 20 to 200 seconds. On the other hand, the temperature of the crosslinking bath 104 in the case of subjecting the film F, which has been stretched in advance, to a dyeing process and a crosslinking process in this order is usually about 50 to 85 ° C, preferably 55 to 80 ° C.

  In the crosslinking treatment for the purpose of color adjustment, for example, when iodine is used as a dichroic dye, a crosslinking bath containing boric acid / iodide / water = 1 to 5/3 to 30/100 at a weight ratio is used. It can be used. The temperature of the crosslinking bath 104 when the film F is immersed is usually about 10 to 45 ° C. The immersion time of the film F is usually about 1 to 300 seconds, preferably 2 to 100 seconds.

  The crosslinking treatment may be performed multiple times, and is usually performed 2 to 5 times. In this case, the composition and temperature of each crosslinking bath 104 may be the same or different within the above range. The crosslinking treatment for waterproofing by crosslinking and the crosslinking treatment for hue adjustment may be performed in a plurality of steps.

  In the cross-linking treatment, as in the case of the swelling treatment described above, as one means for conveying the film F while removing the wrinkles of the film F, the guide rolls 36, 37 and / or the guide roll 38 include expander rolls, spirals It is possible to use rolls having a widening function such as rolls or crown rolls, or to use other widening devices such as cross guiders, bend bars, or tenter clips. On the other hand, as another means for suppressing the occurrence of wrinkles, stretching treatment can be performed as in the case of the above-mentioned swelling treatment.

  The film F drawn from the crosslinking bath 104 passes through the guide roll 38 and the nip roll 53 in order and is introduced to the cleaning bath 105 side.

Cleaning process
The cleaning treatment step is performed for the purpose of removing an extra chemical such as boric acid or iodine adhering to the film F. In the cleaning process, for example, while passing the film F after the crosslinking process in the order of the nip roll 53 and the guide rolls 39 to 41, the film F is immersed in the cleaning liquid (water) contained in the cleaning bath 105 for a predetermined time. Alternatively, water is sprayed as a shower on the film F after the crosslinking treatment step. Or it can carry out by using these washing processes together.

  In the manufacturing apparatus 100 shown in FIG. 6, the case where the film F is immersed in the cleaning bath 105 to perform the cleaning process is illustrated. The temperature of the washing bath 105 is usually about 2 to 40 ° C. The immersion time of the film F is usually about 2 to 120 seconds.

  In the washing process, as in the case of the swelling process described above, as one means for transporting the film F while removing the wrinkles of the film F, the guide rolls 39, 40 and / or the guide roll 41 can be expanded by an expander roll, a spiral It is possible to use rolls having a widening function such as rolls or crown rolls, or to use other widening devices such as cross guiders, bend bars, or tenter clips. On the other hand, as another means for suppressing the occurrence of wrinkles, stretching treatment can be performed as in the case of the above-mentioned swelling treatment.

  The film F pulled out of the cleaning bath 105 passes through the guide roll 41 and the nip roll 54 in order and is introduced to the drying furnace 106 side.

<Dry treatment process>
In the drying process, the film F after the cleaning process is subjected to a drying process. The drying process of the film F is not particularly limited, and can be performed using the drying furnace 106 in the manufacturing apparatus 100 shown in FIG. More specifically, for example, the film F can be dried using a hot air dryer, a far infrared heater, or the like.

  The drying temperature of the film F is, for example, 20 to 100 ° C., preferably 20 to 80 ° C. The drying time of the film F is, for example, 10 to 600 seconds, preferably 30 to 300 seconds.

<Stretching process>
The stretching treatment process is carried out on the film F wet or dry between the series of treatment processes described above (that is, before or after any one or more treatment processes and / or during any one or more treatment processes). And uniaxially stretch.

  As a specific method of uniaxial stretching processing, for example, longitudinal uniaxial stretching is performed by providing a circumferential speed difference between two nip rolls (for example, two nip rolls disposed before and after the processing bath) constituting a film conveyance path. Stretching between rolls, hot roll stretching as described in Japanese Patent No. 2731813, tenter stretching, etc. can be used, and preferably, stretching between rolls.

  The stretching process can be performed a plurality of times between the film F and the polarizing film. Further, the stretching treatment is also advantageous for the suppression of the wrinkles generated in the film F described above.

  The final cumulative stretching ratio of the polarizing film is usually about 4.5 to 7 times, preferably 5 to 6.5 times, based on the unstretched film F.

<Other processing steps>
In the preparation process of a polarizing film, it is also possible to add treatment processes other than the above-mentioned treatment process. As an example of the treatment process to be added, for example, a treatment process of immersion in a boric acid-free iodide aqueous solution (complementary color treatment process) performed after the crosslinking treatment process, a zinc chloride etc. containing no boric acid, etc. And the immersion treatment step (zinc treatment step) in an aqueous solution.

  The polarizer 2 can be obtained by appropriately cutting the produced polarizing film. In addition, the polarizer 2 may have a rectangular shape or a long film. As mentioned above, although the preparation process of the polarizing film used as the polarizer 2 was demonstrated, it is also possible to produce the polarizing film used as the polarizer 2 using another method.

  Next, after producing the above-mentioned light polarizer 2, a pretreatment process which pre-treats on a bonding side of light polarizer 2 and / or protection films 3 and 4, protective films 3 and 4 on both sides of light polarizer 2 The polarizing plate 1 can be manufactured by passing through a bonding treatment step of bonding with an adhesive and a curing treatment step of curing the polarizer 2 to which the protective films 3 and 4 are bonded.

<Pretreatment process>
In the preliminary treatment step, prior to the bonding treatment step, corona treatment is performed on the bonding surface of the polarizer 2 and / or the protective films 3 and 4 in order to improve the adhesion between the polarizer 2 and the protective films 3 and 4. Surface treatment such as flame treatment, plasma treatment, ultraviolet irradiation, primer coating treatment, saponification treatment, etc.

<Paste treatment process>
In the bonding treatment step, the protective films 3 and 4 are bonded to both sides of the polarizer 2 with an adhesive. The adhesive may be a water-based adhesive or an active energy ray-curable adhesive. The bonding conditions are set such that the amount of adhesive applied to the surface of the polarizer 2 is relatively large.

<Hardening treatment process>
In the curing treatment step, the polarizer 2 to which the protective films 3 and 4 are bonded is cured. In the case of using a water-based adhesive, after bonding of the protective films 3 and 4, the adhesive layer is cured by drying treatment. The drying temperature is, for example, 30 to 100 ° C, preferably 40 to 90 ° C. The drying time is, for example, 30 to 1200 seconds, preferably 60 to 900 seconds. After drying, it may be cured at room temperature or a slightly higher temperature, for example, a temperature of about 20 to 45 ° C.

When an active energy ray-curable adhesive is used, the polarizer 2 and the protective films 3 and 4 are bonded and then cured by irradiation with active energy rays (ultraviolet rays, electron beams, X-rays, etc.). The light irradiation time is controlled for each active energy ray-curable adhesive and is not particularly limited, but the integrated light quantity represented as the product of the irradiation intensity and the irradiation time is 10 to 2,500 mJ / cm ² It is preferable to set as follows.

  The polarizing plate 1 may be rectangular as in the case of the polarizer 2 or may be a long film. The rectangular polarizing plate 1 may be obtained, for example, by cutting a long polarizing plate 1. Further, the long polarizing plate 1 may be a roll (wound product) of the polarizing plate 1.

  The method of manufacturing the polarizing plate 1 of the present embodiment adjusts the orthogonal hues measured in the initial state and after the endurance test so that the sign does not change across the a coordinate axis and the b coordinate axis in the ab chromaticity coordinates It is characterized by including.

  As a specific hue adjustment step, it is possible to adjust the orthogonal hue measured after the initial state of the polarizing plate 1 and after the endurance test by adjusting the hue of the polarizer 2. Further, the hue of the polarizer 2 is the concentration of the above-mentioned treatment solution (for example, the concentration of potassium iodide or dye in the dyeing bath 103, the concentration of boric acid in the crosslinking bath 104, the concentration of potassium iodide, etc.), and the treatment. The temperature of the solution, the strength of washing with water (time and temperature), the thickness of the film F, and the draw ratio of the film F can be used. Among them, it is useful to control the intensity of washing in order to adjust the orthogonal hue.

  In the hue adjustment step, by selecting the protective films 3 and 4 disposed on at least one surface or both surfaces of the polarizer 2, orthogonal hues measured in the initial state of the polarizing plate 1 and after the endurance test can be obtained. It is possible to adjust. That is, it is possible to adjust the orthogonal hue measured after the initial state of the polarizing plate 1 and the endurance test also by the types of the protective films 3 and 4 to be selected.

  The protective films 3 and 4 are preferably films formed of a cycloolefin resin, a cellulose resin, a polyester resin, and an acrylic resin from the viewpoint of adjustment of orthogonal hue change. Moreover, the hard coat layer may be provided to the protective film 3 which comes to the outermost surface.

  In the hue adjustment step, it is preferable to adjust the orthogonal hue measured in the initial state of the polarizing plate 1 and after the endurance test so as to be away from the a coordinate axis and the b coordinate axis in the ab chromaticity coordinates. . As a result, even if the orthogonal hue of the polarizing plate 1 changes before and after the endurance test, it does not cross the a coordinate axis and the b coordinate axis in the ab chromaticity coordinates, so the streak unevenness generated in the polarizing plate 1 changes in hue. It can be made inconspicuous regardless of.

  In the present invention, in addition to the case of manufacturing the polarizing plate 1 described above, also in the case of manufacturing a polarizing plate including polarizing plates 1A and 1B, λ / 4 plate, positive C plate, λ / 2 plate, etc. The orthogonal hue measured in the initial state and after the endurance test is generated in the manufactured polarizing plate by providing the hue adjustment step of adjusting so that the sign does not change across the a coordinate axis and the b coordinate axis in the ab chromaticity coordinates. It is possible to make the streak-like unevenness inconspicuous regardless of the change in hue.

  Hereinafter, the effects of the present invention will be made more apparent by examples. The present invention is not limited to the following examples, and can be appropriately modified and implemented without changing the gist of the invention.

Example 1
In Example 1, in the apparatus 100 for producing a polarizing film shown in FIG. 6, two crosslinking baths 104 (one is used as the crosslinking bath 104a and the second as the crosslinking bath 104b) are used. A polarizing film was manufactured using the same manufacturing apparatus as the above manufacturing apparatus 100, and a polarizing plate in which protective films were bonded to both sides of the obtained polarizing film was manufactured.

(1) Swelling Step First, a polyvinyl alcohol film (raw film) having a thickness of 30 μm (trade name “Klare Poval film VF-PE # 3000” manufactured by Kuraray Co., Ltd., average polymerization degree 2400, saponification degree 99.9 mol %) Was conveyed while being unrolled continuously from the raw film roll, and immersed in a swelling bath containing pure water at 20 ° C. for 30 seconds. In this swelling process, a circumferential speed difference is provided between the nip rolls 50 and 51 to perform inter-roll stretching (longitudinal uniaxial stretching). The draw ratio based on the raw film was 2.5 times.

(2) Dyeing step Next, the film which has passed through the nip roll 51 is made of pure water / potassium iodide / iodine / boric acid / (mass ratio) is 100/2 / 0.01 / 0.3 at 30 ° C. It was immersed in the dyeing bath for 120 seconds. Also in this dyeing process, a circumferential speed difference is provided between the nip rolls 51 and 52 to perform inter-roll stretching (longitudinal uniaxial stretching). The draw ratio based on the film after the swelling treatment step was 1.1.

(3) Crosslinking treatment step Next, the film having passed through the nip roll 52 was immersed for 70 seconds in a 56 ° C. crosslinking bath 104 a having a pure water / potassium iodide / boric acid / (mass ratio) of 100/12/4. . Between the nip rolls and nip rolls 52 and 53 disposed between the first crosslinking bath 104a and the second crosslinking bath 104b, a circumferential speed difference is made to perform inter-roll stretching (longitudinal uniaxial stretching). The draw ratio based on the film after the dyeing treatment step was 1.9.

(4) Complementary color treatment step Next, the film after the first crosslinking treatment is added to the crosslinking bath 104b at 40 ° C. in which potassium iodide / boric acid / pure water (mass ratio) is 9 / 2.9 / 100 for 10 seconds. Soaked.

(5) Cleaning Process Next, the film after the second crosslinking process was immersed in the cleaning bath 105 containing pure water at 5 ° C. for 5 seconds.

(6) Drying Treatment Step Next, the film after the washing treatment step was passed through a drying furnace and dried by heating at 80 ° C. for 190 seconds to produce a polarizing film. The thickness of the obtained polarizing film was about 12 μm.

(7) Bonding process process Next, the water-based adhesive which contains 5 mass parts of polyvinyl alcohols with respect to 100 mass parts of water as an adhesive agent was prepared. The protective films shown in Table 1 below were laminated on both sides of the polarizing film produced above using the prepared aqueous adhesive. The resulting laminate was dried by heating, and the adhesive was dried to prepare a polarizing plate. The thickness of the adhesive layer in the obtained polarizing plate was about 50 nm.

<Measurement of visibility corrected single transmittance>
The visibility-corrected single transmittance (Ty) of the obtained polarizing plate was measured according to "JIS Z 8729" using a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation). The measurement results are shown in Table 1 below.

<Measurement of surface asperity of polarizer>
The obtained polarizing plate is cut into small pieces of 10 cm × 5 cm, immersed in 600 mL of methylene dichloride, subjected to ultrasonic treatment for 30 minutes at room temperature, and the first and second protective films bonded are dissolved. Removed.

  About the polarizing film from which these protective films were removed, it is the surface of the front side (the side to which the 1st protective film was pasted), Comprising: The surface of the polarizer to which the adhesive adhered is perpendicular to the extending direction. By scanning in the direction, the surface asperity of the polarizer to which the adhesive was attached was line-measured. Then, from the measurement results, the size of unevenness (roughness difference) and the unevenness interval were calculated. The calculation results are shown in Table 1 below.

Here, the unevenness height difference and the unevenness interval are values calculated by the following.
Concave-convex height difference: The height (H1) at the top of the highest protrusion and the depth at the bottom of the deeper one of the two recesses adjacent to the highest protrusion with respect to the average line of the surface Sum with (H2).
Concave-convex distance: The distance in the direction parallel to the surface mean line between the top of the highest protrusion and the bottom of the deeper one of the two recesses adjacent to the highest protrusion.

In addition, the measurement of surface asperity was performed on condition of the following.
Measuring device: VertScan (registered trademark) (manufactured by Ryoka System Co., Ltd. Model R5500G)
Objective lens (magnification): 2.5 times
Measurement range: 3700 × 2800 μm
Resolution: 640 x 480 pixels
Measurement mode: Wave mode
Surface correction: fourth-order processing

<Measurement of hue>
The orthogonal a value and the orthogonal b value of the manufactured polarizing plate were measured using a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation). The measurement results are shown in Table 1 below.

  Thereafter, the manufactured polarizing plate was subjected to heating at 105 ° C. for 30 minutes in a dry atmosphere. The orthogonal a value and the orthogonal b value of the polarizing plate after heating were measured using a spectrophotometer equipped with an integrating sphere ("V7100" manufactured by JASCO Corporation). The measurement results are shown in Table 1 below.

<Measurement of streaky unevenness>
A polarizing plate A with a visibility correction single transmittance (Ty) of 41.6% and a visibility correction polarization degree (Py) of 99.997 is attached to the illumination surface of a white backlight module with a brightness of 20000 cd / m ² , The polarizing plate was placed on it.

At this time, the first protective film of the polarizing plate shown in the following Table 1 was placed on top, and the transmission axis of the polarizing plate A and the transmission axis of the polarizing plate were orthogonal to each other (crossed Nicol state). In this state, streak-like unevenness was visually confirmed from the first protective film side of the polarizing plate. The uneven streaks were evaluated in the following four stages. The evaluation results are shown in Table 1 below.
0: No streak unevenness is visible.
1: streak-like unevenness is hardly recognized.
2: streaky unevenness can be visually recognized thin.
3: streaky unevenness is clearly visible.

  Thereafter, the manufactured polarizing plate was subjected to heating at 105 ° C. for 30 minutes in a dry atmosphere. The polarizing plate after heating was subjected to the same method as described above to confirm streak-like unevenness and was evaluated in the same manner as described above. The evaluation results are shown in Table 1 below. Further, FIG. 7 shows the hue changes before and after the endurance test in the ab chromaticity coordinate diagram in Example 1.

Example 2
In Example 2, in order to adjust the hue of the polarizing film, the polarizing plate 2 is the same as in Example 1 except that only the cleaning conditions for the polarizing film are changed (specifically, the immersion time is 3 seconds). Was produced. Then, the same method as in Example 1 was applied to the visual sensitivity correction single transmittance (Ty) of the obtained polarizing plate, the surface unevenness of the polarizer, the hue change before and after the endurance test, and the change of streaky unevenness before and after the endurance test. It measured by. The measurement results are shown in Table 1 below. Further, in Example 2, the hue change before and after the endurance test is illustrated in the ab chromaticity coordinate diagram in FIG.

Example 3
(1) Swelling Step First, a polyvinyl alcohol film (raw film) having a thickness of 30 μm (trade name “Klare Poval film VF-PE # 3000” manufactured by Kuraray Co., Ltd., average polymerization degree 2400, saponification degree 99.9 mol %) Was conveyed while being unrolled continuously from the raw film roll, and immersed in a swelling bath containing pure water at 20 ° C. for 30 seconds. In this swelling process, a circumferential speed difference is provided between the nip rolls 50 and 51 to perform inter-roll stretching (longitudinal uniaxial stretching). The draw ratio based on the raw film was 2.2 times.

(2) Dyeing step Next, the film which has passed through the nip roll 51 is a pure water / potassium iodide / iodine / boric acid / (mass ratio) 30 which is 100 / 1.4 / 0.01 / 0.3. It was immersed in a 120 ° C. dyeing bath for 120 seconds. Also in this dyeing process, a circumferential speed difference is provided between the nip rolls 51 and 52 to perform inter-roll stretching (longitudinal uniaxial stretching). The draw ratio based on the film after the swelling treatment step was 1.2.

(3) Crosslinking treatment step Next, the film having passed through the nip roll 52 was immersed for 70 seconds in the 53 ° C. crosslinking bath 104 a having a pure water / potassium iodide / boric acid / (mass ratio) of 100/9/4. . Between the nip rolls and nip rolls 52 and 53 disposed between the first crosslinking bath 104a and the second crosslinking bath 104b, a circumferential speed difference is made to perform inter-roll stretching (longitudinal uniaxial stretching). The draw ratio based on the film after the dyeing treatment step was 2.1.

(4) Step of Complementing Color Next, the film after the first crosslinking treatment is added to the 50 ° C. crosslinking bath 104 b having a pure water / potassium iodide / boric acid / (mass ratio) of 100/9 / 3.9. Soaked for a second.

(5) Cleaning Process Next, the film after the second crosslinking process was immersed in the cleaning bath 105 containing pure water at 13 ° C. for 5 seconds.

(6) Drying Treatment Step Next, the film after the washing treatment step was passed through a drying furnace and dried by heating at 80 ° C. for 190 seconds to produce a polarizing film. The thickness of the obtained polarizing film was about 12 μm.

(7) Bonding process process Next, the protective film shown in the following Table 1 was laminated on the both sides of the manufactured polarizing film using the water-based adhesive which contains 5 mass parts of polyvinyl alcohols with respect to 100 mass parts of water. . The resulting laminate was dried by heating, and the adhesive was dried to prepare a polarizing plate. The thickness of the adhesive layer in the obtained polarizing plate was about 50 nm.

  Then, the same method as in Example 1 was applied to the visual sensitivity correction single transmittance (Ty) of the obtained polarizing plate, the surface unevenness of the polarizer, the hue change before and after the endurance test, and the change of streaky unevenness before and after the endurance test. It measured by. The measurement results are shown in Table 1 below. Further, in Example 3, the hue change before and after the endurance test is illustrated in the ab chromaticity coordinate diagram in FIG.

Example 4
In Example 4, a polarizing plate was produced in the same manner as in Example 3 except that the type of protective film was changed to the protective film shown in Table 1 below. Then, the visual sensitivity correction single transmittance (Ty) of the polarizing plate 4 thus obtained, the surface unevenness of the polarizer, the hue change before and after the endurance test, and the change in streaky unevenness before and after the endurance test are the same as those in Example 1 above. It measured by the method. The measurement results are shown in Table 1 below. Further, FIG. 8 shows the hue change before and after the endurance test in the ab chromaticity coordinate diagram in Example 4.

Comparative Example 1
Comparative Example 1 was the same as Example 3 except that only the washing conditions for the polarizing film were changed (specifically, the immersion time was 3 seconds) in order to adjust the hue of the polarizing film. Made. The same method as in Example 1 was used for the visual sensitivity correction single transmittance (Ty) of the obtained polarizing plate, the surface unevenness of the polarizer, the hue change before and after the endurance test, and the change in streak unevenness before and after the endurance test. It measured by. The measurement results are shown in Table 1 below. Further, for Comparative Example 1, the hue change before and after the endurance test is illustrated in the ab chromaticity coordinate diagram in FIG.

Comparative Example 2
Comparative Example 2 was the same as Example 4 except that only the washing conditions for the polarizing film were changed (specifically, the immersion time was 3 seconds) in order to adjust the hue of the polarizing film. Made. The same method as in Example 1 was used for the visual sensitivity correction single transmittance (Ty) of the obtained polarizing plate, the surface unevenness of the polarizer, the hue change before and after the endurance test, and the change in streak unevenness before and after the endurance test. It measured by. The measurement results are shown in Table 1 below. Further, for Comparative Example 2, the hue change before and after the endurance test is illustrated in the ab chromaticity coordinate diagram in FIG.

Reference Example 1
As Reference Example 1, the procedure of Example 1 was repeated except that the pure water / potassium iodide / iodine / boric acid / (mass ratio) was 100/2 / 0.03 / 0.3 in the dyeing process. A polarizing plate was produced. The same method as in Example 1 was used for the visual sensitivity correction single transmittance (Ty) of the obtained polarizing plate, the surface unevenness of the polarizer, the hue change before and after the endurance test, and the change in streak unevenness before and after the endurance test. It measured by. The measurement results are shown in Table 1 below. Further, for reference example 1, the hue change before and after the endurance test is illustrated in the ab chromaticity coordinate diagram in FIG.

In addition, the protective film in Table 1 is as showing below.
Protective film A: Ultraviolet curable hard coat layer provided diagonally stretched cyclic polyolefin resin film, thickness 29 μm
Protective film B: triacetyl cellulose film, thickness 25 μm
Protective film C: UV-curable hard coat layer-containing triacetyl cellulose film, thickness 32 μm
Protective film D: UV curable hard coat layer-containing triacetyl cellulose film (however, protective film C differs from UV absorbing ability) thickness 32 μm

  Further, in Table 1, the hue axis “o” is defined as that whose orthogonal hue does not change sign across the ab chromaticity coordinate axis before and after the endurance test. On the other hand, the hue axis “x” is defined as that whose orthogonal hue changes its sign across the ab chromaticity coordinate axis before and after the endurance test.

  As shown in Table 1 and FIGS. 7 to 9, in Examples 1 to 4, the orthogonal hue does not change the sign across the ab chromaticity coordinate axis before and after the endurance test, and the streak-like unevenness is small and the endurance is small. Even after the test, the streak unevenness was good without increasing significantly.

  On the other hand, in Comparative Examples 1 and 2, the orthogonal hue changes the sign across the ab chromaticity coordinate axis before and after the endurance test, and even after the endurance test, the unevenness of streaks increases significantly. Moreover, in the reference example 1, the stripe-like unevenness was not visually recognized in the polarizing film whose visibility correction single transmittance (Ty) is less than 44%.

  1, 1A, 1B: Polarizing plate 2: Polarizer 3, 4: Protective film 5: Adhesive layer 10: Display device 11: Display panel 30-41: Guide roll 50-55: Nip roll 100: Manufacturing device 101: Original roll Roll 102 Swelling bath 103 Dyeing bath 104 Crosslinking bath 105 Cleaning bath 106 Drying oven F Film

Claims (10)

A polarizing plate comprising: a polarizer; and a protective film disposed on at least one surface of the polarizer via an adhesive layer,
The visibility corrected single transmittance (Ty) measured in the initial state is 44% or more,
A polarizing plate characterized in that the orthogonal hues measured in the initial state and after the endurance test do not change in sign across the a coordinate axis and the b coordinate axis in the ab chromaticity coordinates.   The polarizing plate according to claim 1, wherein after the endurance test, the polarizing plate is at least after being subjected to heating at 105 ° C for 30 minutes in a dry atmosphere from at least the initial state.   The polarizing plate according to claim 1 or 2, wherein the polarizer is a polarizing film in which a dichroic dye is adsorbed and oriented to a uniaxially stretched polyvinyl alcohol-based resin film.   The thickness of the said polarizer is 3-15 micrometers, The polarizing plate as described in any one of Claims 1-3 characterized by the above-mentioned.   The unevenness | corrugation which becomes 80-250 nm of height differences exists in the surface of the said polarizer to which the adhesive agent adhered, when the said protective film is removed, The characteristics in any one of Claims 1-4 characterized by the above-mentioned. Polarizer.   The polarizing plate according to any one of claims 1 to 5, wherein the polarizer is an iodine-based polarizer. Display panel,
The display apparatus provided with the polarizing plate as described in any one of Claims 1-6. A method for producing a polarizing plate, comprising: a polarizer; and a protective film disposed on at least one surface of the polarizer via an adhesive layer,
A method of manufacturing a polarizing plate, comprising: a hue adjustment step of adjusting orthogonal hues measured in the initial state and after the endurance test so that the sign does not change across the a coordinate axis and the b coordinate axis in ab chromaticity coordinates .   9. The method of manufacturing a polarizing plate according to claim 8, wherein the hue adjustment step adjusts at least the hue of the polarizer.   The method for producing a polarizing plate according to claim 8 or 9, wherein the protective film disposed on at least one surface or both surfaces of the polarizing plate is selected as the hue adjusting step.

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