KR102654633B1 - Polarizing plate and method for propucing the same, and display device - Google Patents

Abstract

[Project] Provide a polarizing plate that makes it possible to make streak-shaped irregularities less noticeable regardless of color changes.
[Solution] A polarizing plate (1) including a polarizer (2) and protective films (3, 4) disposed on at least one side of the polarizer (2) through an adhesive layer, wherein the visibility correction unit is measured in an initial state. The transmittance (Ty) is 44% or more, and the orthogonal colors measured in the initial state and after the durability test do not change in sign across the a and b coordinate axes in the ab chromaticity coordinate.

Description

Polarizing plate and its manufacturing method, and display device {POLARIZING PLATE AND METHOD FOR PROPUCING THE SAME, AND DISPLAY DEVICE}

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

For example, in Patent Document 1 below, since streak-like irregularities occur due to streaks on the surface of the polarizer and are confirmed by the shade of reflected light, the height of the surface irregularities of the polarizer is set to 280 nm or less, so that the irregularities caused by the shade of reflected light are set to 280 nm or less. It has been proposed to suppress streak irregularity.

Patent Document 1: Japanese Patent No. 6166431

Recently, polarizing plates are being made highly transparent for the purpose of reducing power consumption. On the other hand, when the polarizing plate becomes highly transparent, as described in Patent Document 1, even if the surface irregularities of the polarizer are set to 280 nm or less, the stripe shape is caused by the surface irregularities of the polarizer and the light passing through the polarizer in the orthogonal Nicol state I found out that spots appear.

In addition, with respect to a high-transmission polarizer, even if the initial color is controlled and the visible streak-like irregularities are made inconspicuous by transmitting the polarizer in an orthogonal Nicol state, the color (color tone) of the polarizer while being used is reduced. Due to this change, there were cases where streak-like irregularities became noticeable.

The present invention has been proposed in consideration of such conventional circumstances, and includes a polarizing plate that makes it possible to make streak-shaped irregularities inconspicuous regardless of color changes, a method of manufacturing the same, and a display device equipped with such a polarizing plate. The purpose is to provide

As a means for solving the above problem, 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 side of the polarizer through an adhesive layer, the visibility corrected single transmittance measured in an initial state. (Ty) is 44% or more, and the orthogonal colors measured in the initial state and after the durability test do not change in sign across the a and b coordinate axes in the ab chromaticity coordinate.

In addition, in the polarizing plate, after the durability test, heating may be provided at 105° C. for 30 minutes in a dry atmosphere, at least from the initial state.

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

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

Additionally, in the polarizing plate, when the protective film is removed, the surface of the polarizer to which the adhesive is attached may have irregularities with a height difference of 80 to 250 nm.

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

Additionally, according to an aspect of the present invention, a display device including a display panel and one of the above polarizing plates is provided.

Furthermore, 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 side of the polarizer through an adhesive layer, wherein the orthogonal color measured in the initial state and after the durability test is ab A method of manufacturing a polarizing plate is provided, which includes a color adjustment process for adjusting the sign so as not to change between the a and b coordinate axes in the chromaticity coordinate.

Moreover, in the manufacturing method of the polarizing plate, the color adjustment step may be a manufacturing method that adjusts at least the color of the polarizer.

Moreover, in the manufacturing method of the polarizing plate, the color adjustment step may be a manufacturing method in which the protective film disposed on at least one side or both surfaces of the polarizing plate is selected.

As described above, according to the aspect of the present invention, it is possible to provide a polarizing plate that makes it possible to make stripe-shaped irregularities inconspicuous regardless of color changes, and a bendable display device provided with such a polarizing plate.

1 is a cross-sectional view showing the configuration of a polarizing plate according to an embodiment of the present invention.
Figure 2 is a cross-sectional view showing the configuration of a polarizing plate according to another embodiment of the present invention.
Figure 3 is a cross-sectional view showing the configuration of a polarizing plate according to another embodiment of the present invention.
FIG. 4 is a cross-sectional view showing the configuration of a display device equipped with a polarizing plate shown in FIG. 2.
Figure 5 is an ab chromaticity coordinate diagram to explain the change in orthogonal colors measured before and after the durability test of the polarizer.
Figure 6 is a schematic diagram showing the configuration of a polarizing film manufacturing apparatus.
Figure 7 is an ab chromaticity coordinate diagram showing changes in orthogonal colors measured before and after the durability test in Examples 1 and 2.
Figure 8 is an ab chromaticity coordinate diagram showing changes in orthogonal colors measured before and after the durability test in Examples 3 and 4 and Comparative Examples 1 and 2.
Figure 9 is an ab chromaticity coordinate diagram showing changes in orthogonal colors measured before and after the durability test in Reference Example 1.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Additionally, in the drawings used in the following description, the components may be schematically shown in some cases to make each component easier to see, and the dimensions may be shown at different scales depending on the components. In addition, the materials and values exemplified in the following description are examples, and the present invention is not necessarily limited to these, and may be implemented with appropriate changes without changing the gist of the invention.

(Polarizer)

First, as an embodiment of the present invention, for example, the polarizing plate 1 shown in FIG. 1 will be described.

Here, FIG. 1 is a cross-sectional view showing the schematic structure of the polarizing plate 1.

As shown in FIG. 1, the polarizing plate 1 of the present embodiment includes a polarizer 2 and protective films 3 and 4 disposed on at least one side (both sides in the present embodiment) of the polarizer 2. and has a structure in which these protective films 3 and 4 are bonded (laminated through an adhesive layer) to both sides of the polarizer 2 with an adhesive (not shown).

The polarizer 2 has the 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 direction of vibration 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 a direction perpendicular 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 on a uniaxially stretched polyvinyl alcohol (PVA)-based resin film. For this reason, the absorption axis direction of the polarizer 2 coincides with its stretching direction (MD), and the transmission axis direction of the polarizer 2 coincides with the width direction (TD).

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

The polyvinyl acetate-based resin may be, for example, polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as a copolymer of vinyl acetate and other monomers copolymerizable therewith. Other monomers that can be copolymerized include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of polymerization of polyvinyl alcohol-based resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000. These polyvinyl alcohol-based resins may be modified, and for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, etc. modified with aldehydes can also be used.

The thickness of the polarizer 2 is preferably thin from the viewpoint of thinning the polarizer 1, but is appropriately set depending on the purpose of the polarizer 1, etc. The thickness of the polarizer 2 is, for example, 25 μm or less, preferably 20 μm or less, more preferably 15 μm or less, and may be, 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 likely to occur during conveyance during processing of the PVA-based resin film, and unevenness is likely to occur in the polarizer 2, so the effect of the present invention increases. In addition, it is safe to assume that the thickness of the polarizer 2 in the polarizing plate 1 is substantially the same as the thickness of the polarizer 2 after the protective films 3 and 4 are bonded together with an adhesive and cured.

Examples of the protective films 3 and 4 include films made of acetylcellulose-based resins such as triacetylcellulose and diacetylcellulose; Films made of polyester resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; polycarbonate-based resin film; Cycloolefin-based resin film; Acrylic resin film; A film made of chain olefin resin of polypropylene resin can be mentioned.

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

The thickness of the protective films 3 and 4 is preferably thin from the viewpoint of thinning the polarizing plate 1, but is appropriately set depending on the purpose of the polarizing plate 1, etc. 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 secure a certain level of strength from the viewpoint of processability, 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 water-based adhesives include water-based adhesives such as an aqueous solution of a polyvinyl alcohol-based resin or an aqueous solution mixed with a cross-linking agent, and a urethane-based emulsion adhesive.

An active energy ray-curable adhesive refers to an adhesive that is cured by irradiating active energy rays such as ultraviolet rays or electron beams. Active energy ray curable adhesives are classified by their curing mode into cationic polymerizable adhesives containing a cationically polymerizable compound as a curable compound, radically polymerizable adhesives containing a radically polymerizable compound as a curable compound, cationically polymerizable compounds and radicals. and curable adhesives containing both polymerizable compounds. Examples of cationically polymerizable compounds include epoxy compounds and oxetane compounds. Examples of the radically polymerizable compound include (meth)acrylic compounds having one or more (meth)acryloyl groups in the molecule.

The thickness of the adhesive layer formed by the water-based adhesive may be, for example, 20 nm or more, preferably 40 nm or more. On the other hand, the thickness of the adhesive should not be too large than necessary from the viewpoint of production costs, etc., and may be, for example, 1000 nm or less, preferably 500 nm or less, and 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, preferably 5 μm or less, and more preferably 3 μm or less.

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. Here, FIG. 2 is a cross-sectional view showing the schematic structure of the polarizing plate 1A. Fig. 2 is a cross-sectional view showing the schematic structure of the polarizing plate 1B.

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

The adhesive layer 5 can be bonded to the polarizer 2 and the protective films 3 and 4 due to its own adhesiveness. As the adhesive forming the adhesive layer 5, a conventionally known adhesive may be appropriately selected, and any adhesive that has sufficient adhesiveness to prevent peeling, etc., in an environment where the polarizing plates 1A, 1B may be exposed. Specifically, acrylic adhesives, silicone adhesives, rubber adhesives, etc. can be mentioned, and acrylic adhesives are particularly preferable in terms of transparency, weather resistance, heat resistance, and processability. The thickness of the adhesive layer 5 is usually about 3 to 100 μm, and is preferably 5 to 50 μm.

Additionally, the adhesive may, if necessary, contain fillers such as tackifiers, plasticizers, glass fibers, glass beads, metal powders, and other inorganic powders, pigments, colorants, fillers, antioxidants, ultraviolet absorbers, antistatic agents, and silane coupling agents. etc., various additives may be appropriately mixed.

The adhesive layer 5 is used to bond the polarizing plates 1A and 1B to other members. The surface of the adhesive layer 5 may have a peeling film (not shown) in advance. When a release film is present on the surface of the adhesive layer 5, the release film is peeled off from one side, and this adhesive layer 5 is bonded (laminated) to the polarizer 2 or the protective films 3 and 4. )can do. In addition, after peeling off the release film from the other side, it can be bonded to another member through this adhesive layer 5.

Additionally, the configuration of the polarizing plate to which the present invention is applied is not necessarily limited to the configuration of the polarizing plates 1, 1A, and 1B shown in FIGS. 1 to 3 above. That is, the polarizing plate to which the present invention is applied may have a structure including a polarizer and a protective film disposed on at least one side or both sides of the polarizer, and other configurations may be appropriately changed.

For example, in the polarizing plates 1 and 1A, other functional layers such as a retardation film or a brightness enhancing film may be applied instead of the protective film 4.

In addition, when the polarizing plates 1, 1A, 1B are used as circularly polarizing plates, they may be configured to include a 1/4 wavelength (λ/4) plate in addition to the above configuration. The λ/4 plate has the function of converting linearly polarized light of a certain wavelength into circularly polarized light (or circularly polarized light into linearly polarized light). The λ/4 plate is disposed on the side of the protective film 4 opposite to the polarizer 2 through the adhesive layer 5.

In addition, when the polarizing plates 1, 1A, and 1B are used as circularly polarizing plates, they may be configured to include a positive C plate in addition to the λ/4 plate. The positive C plate can reduce changes in the reflection color (color) of the polarizers 1, 1A, and 1B. When a positive C plate is included, the λ/4 plate is preferably an inverse wavelength dispersion λ/4 plate. The positive C plate is disposed on the side opposite to the polarizer 2 (the other side) of the λ/4 plate through an adhesive layer or adhesive layer. Therefore, for example, in the case of the polarizing plate 1, it has a stacked structure of the polarizing plate 1, the adhesive layer 5, the λ/4 plate, the adhesive layer or adhesive layer, and the positive C plate.

In addition, when the polarizing plates 1, 1A, and 1B are used as circularly polarizing plates, they may be configured to include a 1/2 wavelength (λ/2) plate in addition to the λ/4 plate. The λ/2 plate has the function of changing the direction (polarization direction) of linearly polarized light by providing a phase difference of π (=λ/2) in the direction of electric field vibration (polarization plane) of incident light. Additionally, when circularly polarized light is incident, the rotation direction of the circularly polarized light can be changed to the opposite rotation direction. The λ/2 plate is disposed on the side opposite to the polarizer 2 (the other side) of the λ/4 plate through an adhesive layer or an adhesive layer. Therefore, for example, in the case of the polarizing plate 1, it has a stacked structure of the polarizing plate 1, the adhesive layer 5, the λ/4 plate, the adhesive layer or adhesive layer, and the λ/2 plate.

(display device)

Next, the display device of this embodiment will be described with reference to FIG. 4.

Additionally, FIG. 4 is a cross-sectional view showing the configuration of the display device 10 equipped with the polarizing plate 1A shown in FIG. 2.

As shown in FIG. 4, the display device 10 of this embodiment includes a display panel 11 and a polarizing plate 1A disposed on the viewer side of the display panel 11. The polarizing plate 1A is bonded to the display panel 11 through the adhesive layer 5.

The display panel 11 is not particularly limited, but may be, for example, a liquid crystal display element, an organic electroluminescence (EL) display element, or the like. 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 the display device 10 uses an organic EL display element as the display panel 11, it is called an organic EL display device.

Additionally, 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. 4 above. That is, the display device to which the present invention is applied can make appropriate changes to the structure of the display panel as long as it is provided with the polarizing plate to which the present invention described above is applied. Meanwhile, the use of the polarizing plate to which the present invention is applied is not limited to the above-described display device, and can be used for various optical purposes.

However, the polarizing plate 1 of the present embodiment is characterized in that the orthogonal colors measured in the initial state and after the durability test are adjusted so that the sign does not change across the a coordinate axis and the b coordinate axis in the ab chromaticity coordinate. do. That is, the change in orthogonal color measured before and after the durability test of the polarizing plate 1 is set to a value that does not span the a coordinate axis and the b coordinate axis. Accordingly, even if the orthogonal color of the polarizing plate 1 changes before and after the durability test, it is possible to make the streak-shaped unevenness generated in the polarizing plate 1 inconspicuous regardless of the change in color.

Specifically, the change in orthogonal color measured before and after the durability test of the polarizer 1 will be described with reference to FIG. 5. Here, FIG. 5 is an ab chromaticity coordinate diagram for explaining the change in orthogonal colors measured before and after the durability test of the polarizer 1.

The change in orthogonal color measured before and after the durability test of the polarizer 1 can be measured using a spectrophotometer or the like.

Additionally, in this embodiment, the transmitted color is measured using a spectrophotometer. Thereafter, after heating at 105° C. for 30 minutes in a dry atmosphere, the transmitted color is again measured by a spectrophotometer. In addition, it was confirmed that the transmitted color measured after the initial state and durability test of the polarizer 1 did not change in sign across the a and b coordinate axes.

Additionally, streak-shaped irregularities occurring on the polarizer 1 can be observed using orthogonal Nicole transmitted light on the backlight. Specifically, the intensity of the spotting can be observed by attaching a polarizing plate to the illumination surface of a white backlight, placing the polarizing plate 1 on it so that the absorption axes are perpendicular to it, and visually checking.

Even in the case where the protective films 3 and 4 of the polarizer 1 include retardation plates such as a λ/4 plate, positive C plate, and λ/2 plate, the backlight is set so that these retardation plates are on the opposite side (viewing side) of the backlight. Just install it on the table and observe. In addition, when both protective films 3 and 4 of the polarizer 1 are composed of retardation plates, the retardation plate is installed on the backlight with the polarizer bonded to the illumination surface, and the polarizer 1 is installed on it so that it is orthogonal to the nicol. This can be observed.

In this embodiment, with respect to the orthogonal colors measured before and after the durability test of the polarizing plate 1, the case where the sign does not change across the a coordinate axis and the b coordinate axis means, for example, in the ab chromaticity coordinate diagram shown in FIG. 5. This means that there is no upper limit between the a and b coordinate axes. In this case, even if the orthogonal color of the polarizing plate 1 changes before and after the durability test, the streak-shaped unevenness occurring in the polarizing plate 1 can be made inconspicuous regardless of the change in color. On the other hand, if the upper limit is placed between the a coordinate axis and the b coordinate axis, streak-like irregularities generated in the polarizing plate 1 due to changes in orthogonal colors become easily visible.

Regarding the stripe-shaped unevenness occurring on the polarizing plate 1, it is preferable that the height difference (ΔH) of the stripe-shaped unevenness on the surface of the polarizing plate 1 is 80 to 250 nm. The height difference (ΔH) of the stripe-shaped unevenness is obtained by measuring the surface of the polarizer 2 with the adhesive attached to the surface of the polarizer 1 in a direction perpendicular to the extension direction of the stripe when the protective films 3 and 4 are removed. While scanning, the uneven shape of the surface is measured along the line. From this measurement result, as shown in equation (1) below, the height (H1) at the apex of the highest convexity with respect to the average line of the surface and the height (H1) of the two concave portions adjacent to the highest convexity are , is obtained by the sum of the depth H2 at the bottom of the deeper concave portion. Additionally, the extension direction of the string is usually a direction that coincides with the stretching direction (MD).

80 nm≤ΔH=H1+H2≤250 nm···(1)

In the polarizing plate 1 of this embodiment, the orthogonal colors measured in the initial state and after the durability test are adjusted so that the sign does not change across the a coordinate axis and the b coordinate axis in the ab chromaticity coordinate, so that the polarizing plate 1 Stripe-shaped irregularities that occur can be made inconspicuous regardless of color changes.

Additionally, in the polarizing plate 1 of this embodiment, the orthogonal colors are adjusted by adjusting the color of the polarizer 2 or by selecting the protective films 4 and 5 disposed on at least one side or both sides of the polarizing plate 1. can be adjusted.

In the polarizing plate 1 of this embodiment, the visibility corrected single transmittance (Ty) is preferably 44.0% or more, more preferably 44.3% or more, and even more preferably 44.5% or more. Moreover, in the polarizing plate 1 of this 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 using, for example, a spectrophotometer.

In addition to the polarizing plate 1, the present invention also provides for polarizing plates including retardation films such as the above-described polarizing plates 1A and 1B, λ/4 plates, positive C plates, and λ/2 plates, with respect to the initial state and durability. By adjusting the orthogonal color measured after the test so that its sign does not change across the a and b coordinate axes in the ab chromaticity coordinate, the line produced by the light passing through the polarizer (2) in the orthogonal Nicol state generated in the polarizer Shape irregularities can be made inconspicuous regardless of color changes.

(Method of manufacturing polarizer)

Next, the manufacturing method of the polarizing plate of this embodiment is explained with reference to FIG. 6.

In addition, FIG. 6 is a schematic diagram showing a manufacturing apparatus 100 of a polarizing film that becomes the polarizer 2. In addition, the arrow shown in FIG. 6 represents the conveyance direction of the film F used as a polarizing film.

In this embodiment, first, a polarizing film that becomes the polarizer 2 of the polarizing plate 1 is produced using the manufacturing apparatus 100 shown in FIG. 6. Specifically, using a long unstretched PVA-based resin film (fabric film) F as a starting material, this film F is continuously conveyed along the film conveyance path of the manufacturing device 100 and subjected to a predetermined processing step. A long polarizing film is continuously manufactured through this process.

The predetermined treatment process includes a swelling treatment process in which the film F is immersed in the swelling bath 102, a dyeing treatment process in which the film F after the swelling treatment process is immersed in the dyeing bath 103, and a dyeing treatment process in which the film F is immersed in the dyeing bath 103. A crosslinking treatment step in which the film (F) is immersed in the crosslinking bath 104, a cleaning treatment step in which the film (F) after the crosslinking treatment is immersed in the cleaning bath 105, and a uniaxial stretching treatment is performed on the film (F) being transported. It may include a stretching process to be performed and a drying process to dry the film F after the cleaning process in the drying furnace 106. Additionally, other treatment steps may be added as needed.

The polarizing film manufacturing apparatus 100 shown in FIG. 6 continuously unwraps the film F from the fabric roll 101 and transports it along the film transport path, while swelling bath 102 provided on the film transport path. ), 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, for example, be conveyed as is to the next manufacturing process of the polarizing plate 1 (a process of bonding a protective film to one or both sides of the polarizing film).

In addition, in the manufacturing apparatus 100 shown in FIG. 6, as a processing bath containing a processing liquid for processing the film F, a swelling bath 102, a dyeing bath 103, a crosslinking bath 104, and Although the case in which one set of washing baths 105 is installed is shown as an example, a configuration in which two or more sets of one or more treatment baths are installed may be used as needed.

The manufacturing apparatus 100 shown in FIG. 6 supports the conveyed film F in addition to the above-described processing baths 102 to 105 on the film conveyance path, and also supports the conveyed film F as needed. ) and guide rolls 30 to 41 that change the conveyance direction of the conveyed film F, which press and hold the conveyed film F, and provide a driving force due to rotation to the film F, and the conveyed film as necessary. It is configured by appropriately arranging nip rolls 50 to 55 that change the conveyance direction of (F).

The guide rolls 30 to 41 and nip rolls 50 to 55 can be disposed before or after each of the treatment baths 102 to 105 or in the treatment baths 102 to 105. Accordingly, the film F can be introduced and immersed in each of the treatment baths 102 to 105, and taken out from the treatment baths 102 to 105. For example, by installing one or more guide rolls 30 to 41 in each of the treatment baths 102 to 105 and transporting the film F along these guide rolls 30 to 41, each of the treatment baths 102 to 105 The film (F) can be immersed in .

In the manufacturing apparatus 100 shown in FIG. 6, nip rolls 50 to 55 are arranged before and after each treatment bath 102 to 105. Accordingly, in one or more of the treatment baths 102 to 105, a difference in peripheral speed is provided between the nip rolls 50 to 55 disposed before and after them, and inter-roll stretching is performed to perform longitudinal uniaxial stretching of the film F. It is possible to do so.

Hereinafter, each treatment process performed on the film F when producing a polarizing film will be described.

<Swelling treatment process>

The swelling treatment process includes removal of foreign substances present on the surface of the film (F) that becomes the fabric film, removal of the plasticizer present in the film (F), provision of discoloration, and plasticization of the film (F). It is carried out for purposes such as anger. Processing conditions are determined within a range that can achieve the purpose and do not cause problems such as extreme dissolution or loss of transparency of the film F.

As the raw film, an unstretched PVA-based resin film having a thickness of 65 μm or less, preferably about 10 to 50 μm, and more preferably about 10 to 35 μm, can be used. The raw film is usually prepared as a roll of a long unstretched PVA-based resin film. However, the raw film may be a stretched film that has previously been subjected to uniaxial stretching treatment in a gas before the swelling treatment process.

In the swelling treatment process, while passing the film (fabric film) F continuously unwound from the fabric roll 101 through the nip roll 50 and the guide rolls 30 to 32 in that order, the swelling bath 102 It is immersed in the treatment liquid contained in the process for a predetermined period of time. Accordingly, a swelling treatment is performed on the film F. In addition, as a stretching process, the film F may be subjected to uniaxial stretching in the swelling bath 102 using the difference in peripheral speed between the nip rolls 50 and 51.

The treatment liquid in the swelling bath 102 contains, in addition to pure water, boric acid (see JP-A-10-153709), chloride (see JP-A-06-281816), inorganic acid, inorganic salt, and water-soluble organic. An aqueous solution containing solvents, alcohols, etc. added in the 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, 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, and preferably about 30 to 60°C. The immersion time of the film (F) is preferably about 30 to 300 seconds, more preferably about 60 to 240 seconds.

In the swelling treatment, the film F is swollen in the width direction, and problems such as wrinkles forming in the film F are likely to occur. As a means for conveying the film F while eliminating the wrinkles, the guide rolls 30, 31 and/or the guide roll 32 are provided with a roll having a widening function such as an expander roll, spiral roll, or crown roll. You can use , or you can use other widening devices such as cloth guiders, bend bars, and tenter clips. On the other hand, stretching treatment can be performed as another means to suppress the occurrence of wrinkles.

In the swelling treatment, the swelling and expansion of the film F also occurs in the transport direction of the film F. Therefore, when the film F is not actively stretched, in order to eliminate relaxation of the film F in the transport direction, for example, It is desirable to take measures such as controlling the speed of the nip rolls 50 and 51 disposed before and after the swelling bath 102. In addition, for the purpose of stabilizing the transport of the film F in the swelling bath 102, the water flow in the swelling bath 102 is controlled by an underwater shower, or an EPC device (edge position control device: controls the end of the film). It is also useful to use a device that detects and prevents the film from meandering.

The film F taken out from the swelling bath 102 sequentially passes through the guide roll 32 and the nip roll 51 and is conveyed to the dyeing bath 103 side.

<Dyeing treatment process>

The dyeing treatment process is performed for the purpose of adsorbing and orienting the dichroic dye to the film (F) after the swelling treatment process. Processing conditions are determined within a range that can achieve the above-mentioned purpose and do not cause problems such as extreme dissolution or loss of transparency of the film F.

In the dyeing treatment process, the film F after the swelling treatment process is immersed in the treatment liquid contained in the dyeing bath 103 for a predetermined period of time while passing the film F in that order through the nip roll 51 and the guide rolls 33 to 35. Accordingly, dyeing treatment is performed on the film F. In addition, for the film F, as a stretching process, it is also possible to perform uniaxial stretching treatment in the dye bath 103 by utilizing the difference in peripheral speed between the nip roll 51 and the nip roll 52. .

The film (F) used in the dyeing process is preferably a film (F) that has undergone at least a certain degree of uniaxial stretching in order to increase the dyeability of the dichroic dye, and uniaxial stretching is added or dyeing is performed before the dyeing. In addition to the previous uniaxial stretching treatment, it is preferable to perform uniaxial stretching treatment during the dyeing treatment.

When iodine is used as a dichroic dye, the treatment liquid of the dyeing bath 103 can be, for example, an aqueous solution with a concentration of iodine/potassium iodide/water = about 0.003 to 0.3/about 0.1 to 10/100 in weight ratio. Instead of potassium iodide, other iodides such as zinc iodide may be used, and potassium iodide and other iodides may be used together. Additionally, compounds other than iodide, such as boric acid, zinc chloride, cobalt chloride, etc., may be coexisted. The addition of boric acid is different from the crosslinking treatment described later in that it contains iodine. If the aqueous solution contains about 0.003 parts by weight or more of iodine based on 100 parts by weight of water, it can be regarded as the dyeing bath 103. You can.

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 dichroic dye as a dichroic dye, the treatment liquid of the dyeing bath 103 has, for example, a concentration by weight of dichroic dye/water = about 0.001 to 0.1/100 (preferably about 0.003 to 0.03/100). An aqueous solution of about 0.1 to 10/100 can be used. In this case, the treatment liquid of the dyeing bath 103 may contain a dyeing aid or the like, and may contain, for example, an inorganic salt such as sodium sulfate or a surfactant. One type of dichroic dye may be used individually, and two or more types of dichroic dyes may be used together.

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

In the dyeing treatment, as in the case of the swelling treatment described above, guide rolls 33, 34 and/or guide rolls 35 are used as a means for conveying the film F while eliminating wrinkles in the film F. Alternatively, rolls with a widening function such as expander rolls, spiral rolls, and crown rolls can be used, or other widening devices such as cloth guiders, bend bars, and tenter clips can be used. On the other hand, as another means for suppressing the occurrence of wrinkles, stretching treatment can be performed similarly to the swelling treatment described above.

The film F taken out from the dyeing bath 103 sequentially passes through the guide roll 35 and the nip roll 52 and is introduced into the crosslinking bath 104.

<Cross-linking treatment process>

The crosslinking treatment process is a treatment performed for purposes such as water resistance or color adjustment by crosslinking. In the crosslinking treatment process, the film F after the dyeing treatment process is immersed in the treatment liquid contained in the crosslinking bath 104 for a predetermined period of time while passing the film F in that order through the nip roll 52 and the guide rolls 36 to 38. Accordingly, crosslinking treatment is performed on the film (F). In addition, as a stretching process, the film F may be subjected to uniaxial stretching in the crosslinking bath 104 using the difference in peripheral speed between the nip rolls 52 and 53.

The treatment liquid of the crosslinking bath 104 can be an aqueous solution containing, for example, about 1 to 10 parts by weight of boric acid per 100 parts by weight of water. When the dichroic dye used in the dyeing treatment is iodine, the treatment liquid in the crosslinking bath 104 preferably contains iodide in addition to boric acid, and the amount is, for example, 1 to 30 parts by weight based on 100 parts by weight of water. You can. Examples of iodide include potassium iodide and zinc iodide. Additionally, compounds other than iodide, such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, and sodium sulfate, may be coexisted.

In the crosslinking treatment, the concentrations of the crosslinking agent (boric acid, etc.) and iodide, and the temperature of the crosslinking bath can be appropriately changed depending on the purpose. For example, when the purpose of the crosslinking treatment is water resistance by crosslinking, and the swelling treatment, dyeing treatment, and crosslinking treatment are performed in this order on an unstretched polyvinyl alcohol-based resin film, the crosslinking agent-containing liquid in the crosslinking bath has a concentration of It may be an aqueous solution with a weight ratio of boric acid/iodide/water = 3 to 10/1 to 20/100. Additionally, if necessary, other cross-linking agents such as glyoxal or glutaraldehyde may be used instead of boric acid, and boric acid and other cross-linking agents may be used together.

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, when the dyeing treatment and crosslinking treatment are performed on the pre-stretched film (F) in this order, the temperature of the crosslinking bath 104 is usually about 50 to 85°C, preferably 55 to 80°C.

In crosslinking treatment for the purpose of color adjustment, for example, when iodine is used as a dichroic dye, a crosslinking bath with a concentration of boric acid/iodide/water = 1 to 5/3 to 30/100 by weight ratio can be used. The temperature of the crosslinking bath 104 when immersing the film F 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 used may be the same or different as long as they are within the above range. Crosslinking treatment for water resistance by crosslinking and crosslinking treatment for color adjustment may each be performed in multiple processes.

In the crosslinking treatment, as in the case of the swelling treatment described above, guide rolls 36, 37 and/or guide rolls 38 are used as a means for conveying the film F while eliminating wrinkles in the film F. Alternatively, rolls with a widening function such as expander rolls, spiral rolls, and crown rolls can be used, or other widening devices such as cloth guiders, bend bars, and tenter clips can be used. On the other hand, as another means for suppressing the occurrence of wrinkles, stretching treatment can be performed similarly to the swelling treatment described above.

The film F taken out from the crosslinking bath 104 passes through the guide roll 38 and the nip roll 53 in that order and is introduced into the washing bath 105 side.

<Cleaning treatment process>

The washing treatment process is performed for the purpose of removing excess chemicals such as boric acid and iodine attached to the film F. In the washing treatment process, for example, the film F after the crosslinking treatment process is immersed in a washing liquid (water) contained in the washing bath 105 for a predetermined period of time while passing the film F in that order through the nip roll 53 and the guide rolls 39 to 41. do. Alternatively, water is sprayed as a shower on the film (F) after the crosslinking treatment process. Alternatively, it can be performed by using these washing treatments together.

The manufacturing apparatus 100 shown in FIG. 6 illustrates a case in which the film F is immersed in the cleaning bath 105 to perform a cleaning treatment. 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 cleaning treatment, as in the case of the swelling treatment described above, as a means for conveying the film F while eliminating wrinkles in the film F, the guide rolls 39, 40 and/or the guide roll 41 are used. Alternatively, rolls with a widening function such as expander rolls, spiral rolls, and crown rolls can be used, or other widening devices such as cloth guiders, bend bars, and tenter clips can be used. On the other hand, as another means for suppressing the occurrence of wrinkles, stretching treatment can be performed similarly to the swelling treatment described above.

The film F taken out from the washing bath 105 passes through the guide roll 41 and the nip roll 54 in that order and is introduced into the drying furnace 106 side.

<Drying treatment process>

In the drying treatment process, a drying treatment is performed on the film F after the washing treatment process. The drying process for the film F is not particularly limited, and can be performed using the drying furnace 106 in the manufacturing apparatus 100 shown in FIG. 6. More specifically, the film F can be dried using, for example, a hot air dryer or a far-infrared heater.

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 treatment process>

In the stretching treatment process, a uniaxial stretching treatment is performed on the film F in a wet or dry manner during the above-described series of treatment processes (i.e., before and after and/or during one or more treatment processes). .

A specific method of uniaxial stretching treatment is, for example, inter-roll stretching in which longitudinal uniaxial stretching is performed with a difference in peripheral speed between two nip rolls (e.g., two nip rolls disposed before and after the treatment bath) constituting the film transport path, Hot roll stretching, tenter stretching, etc., such as those described in Japanese Patent No. 2731813, can be used, and inter-roll stretching is preferred.

Stretching treatment can be performed several times until a polarizing film is obtained from the film (F). In addition, stretching treatment is also advantageous for suppressing wrinkles occurring in the above-mentioned film (F).

The final cumulative draw 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 treatment processes>

In the production process of the polarizing film, it is also possible to add treatment processes other than the above treatment processes. Examples of additional treatment processes include, for example, a immersion treatment process (complementary color treatment process) in an iodide aqueous solution not containing boric acid, which is performed after the crosslinking treatment process, or immersion in an aqueous solution containing zinc chloride, etc., but not boric acid. A treatment process (zinc treatment process) etc. are mentioned.

The polarizer 2 can be obtained by appropriately cutting the produced polarizing film. Additionally, the polarizer 2 may have a rectangular shape or may be a long film. As described above, the production process for the polarizing film that becomes the polarizer 2 has been described, but it is also possible to produce the polarizing film that becomes the polarizer 2 using another method.

Subsequently, after manufacturing the polarizer 2, a preliminary treatment process is performed to apply preliminary treatment to the bonding surfaces of the polarizer 2 and/or the protective films 3 and 4, and a protective film is applied to both sides of the polarizer 2. The polarizing plate 1 can be manufactured by going through a bonding process of bonding (3, 4) with an adhesive and a curing process of curing the polarizer (2) to which the protective films (3, 4) are bonded.

<Preliminary treatment process>

In the preliminary treatment process, before the bonding treatment process, corona treatment is applied to 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 treatments such as flame treatment, plasma treatment, ultraviolet irradiation, primer application treatment, and saponification treatment are performed.

<Joining treatment process>

In the bonding process, 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 so that the amount of adhesive applied to the surface of the polarizer 2 is relatively large.

<Harding treatment process>

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

When an active energy ray-curable adhesive is used, after bonding the polarizer 2 and the protective films 3 and 4, the adhesive is cured by irradiating active energy rays (ultraviolet rays, electron rays, X-rays, etc.). The light irradiation time is controlled for each active energy ray-curable adhesive and is not particularly limited, but is preferably set so that the accumulated light amount expressed as the product of the irradiation intensity and the irradiation time is 10 to 2,500 mJ/cm2.

Like the polarizer 2, the polarizing plate 1 may have a rectangular shape or may be a long film. The square-shaped polarizing plate 1 may be obtained, for example, by cutting a long polarizing plate 1. Additionally, the long polarizing plate 1 may be a roll of the polarizing plate 1.

The manufacturing method of the polarizing plate 1 of this embodiment is a color adjustment process in which the orthogonal colors measured in the initial state and after the durability test are adjusted so that their signs do not change across the a coordinate axis and the b coordinate axis in the ab chromaticity coordinate. It is characterized by including.

As a specific color adjustment process, it is possible to adjust the orthogonal color measured in the initial state of the polarizer 1 and after the durability test by adjusting the color of the polarizer 2. In addition, the color of the polarizer 2 is determined by the concentration of the above-mentioned processing liquid (e.g., potassium iodide concentration or dye concentration in the dyeing bath 103, boric acid concentration, potassium iodide concentration, etc. in the crosslinking bath 104), the processing liquid It is possible to adjust it by the temperature, the strength of water (time and temperature), the thickness of the film (F) and its stretching ratio, etc. Among them, it is useful to control the strength of the water force when adjusting orthogonal colors.

In addition, as a color adjustment process, the orthogonal color measured in the initial state and after the durability test of the polarizer 1 is adjusted by selecting the protective films 3 and 4 disposed on at least one side or both sides of the polarizer 2. It is possible. In other words, it is possible to adjust the orthogonal colors measured in the initial state of the polarizer 1 and after the durability test also depending on the type of protective films 3 and 4 selected.

The protective films 3 and 4 are preferably films made of cycloolefin resin, cellulose resin, polyester resin, or acrylic resin from the viewpoint of orthogonal color change adjustment. Additionally, the protective film 3 closest to the surface may be provided with a hard coat layer.

In addition, in the color adjustment process, it is preferable to adjust the orthogonal color measured in the initial state of the polarizer 1 and after the durability test to change in a direction away from the a coordinate axis and the b coordinate axis in the ab chromaticity coordinate. Accordingly, even if the orthogonal color of the polarizer 1 changes before and after the durability test, the a coordinate axis and the b coordinate axis in the ab chromaticity coordinates are not crossed, so the stripe-shaped irregularities generated in the polarizer 1 are changed in color. Regardless, you can make it inconspicuous.

In addition, in addition to the case of manufacturing the polarizer 1, the present invention also applies to the case of manufacturing a polarizer including polarizers 1A, 1B, λ/4 plate, positive C plate, λ/2 plate, etc. By applying a color adjustment process to adjust the orthogonal color measured after the condition and durability test so that the sign does not change across the a and b coordinate axes in the ab chromaticity coordinate, streak-like irregularities occurring in the manufactured polarizer are eliminated. It can be made inconspicuous regardless of the color change.

[Example]

Hereinafter, the effect of the present invention will be made more clear through examples. In addition, the present invention is not limited to the following examples, and can be implemented with appropriate modifications without changing the gist of the present invention.

<Example 1>

In Example 1, in the polarizing film manufacturing apparatus 100 shown in FIG. 6, two crosslinking baths 104 (the first is a crosslinking bath 104a, and the second is a crosslinking bath 104b) A polarizing film was manufactured using the same manufacturing apparatus as the above-mentioned manufacturing apparatus 100, except that a polarizing film was used, and a polarizing plate was produced in which a protective film was bonded to both sides of the obtained polarizing film.

(1) Swelling treatment process

First, a 30 ㎛ thick polyvinyl alcohol film (fabric film) (trade name “Kurarepobal Film VF-PE#3000” manufactured by Shakurare Corporation, average degree of polymerization 2400, degree of saponification 99.9 mol%) is continuously rolled from the fabric roll. It was conveyed while loosening and immersed in a swelling bath containing pure water at 20°C for 30 seconds. In this swelling treatment step, inter-roll stretching (vertical uniaxial stretching) was performed with a difference in peripheral speed between the nip rolls 50 and 51. The stretching ratio based on the fabric film was set to 2.5 times.

(2) Dyeing treatment process

Next, the film that passed through the nip roll 51 was immersed in a dyeing bath at 30°C with a pure water/potassium iodide/iodine/boric acid (mass ratio) of 100/2/0.01/0.3 for 120 seconds. Also in this dyeing treatment, a difference in peripheral speed was provided between the nip rolls 51 and 52, and inter-roll stretching (vertical uniaxial stretching) was performed. The stretching ratio based on the film after the swelling treatment process was set to 1.1 times.

(3) Cross-linking treatment process

Next, the film that passed through the nip roll 52 was immersed in a crosslinking bath 104a at 56°C with a pure water/potassium iodide/boric acid (mass ratio) of 100/12/4 for 70 seconds. Roll-to-roll stretching (vertical uniaxial stretching) was performed with a difference in peripheral speed between the nip rolls and the nip rolls 52 and 53 provided between the first crosslinking bath 104a and the second crosslinking bath 104b. The stretching ratio based on the film after the dyeing process was set to 1.9 times.

(4) Complementary color processing process

Next, the film after the first crosslinking treatment was immersed in a crosslinking bath 104b at 40°C with a potassium iodide/boric acid/pure water (mass ratio) of 9/2.9/100 for 10 seconds.

(5) Cleaning treatment process

Next, the film after the second crosslinking treatment was immersed in a washing bath 105 containing pure water at 5°C for 5 seconds.

(6) Drying treatment process

Next, the film after the washing treatment process was passed through a drying furnace and heated and dried at 80°C for 190 seconds to produce a polarizing film. The thickness of the obtained polarizing film was about 12 μm.

(7) Bonding treatment process

Next, as an adhesive, a water-based adhesive containing 5 parts by mass of polyvinyl alcohol per 100 parts by mass of water was prepared. The protective films shown in Table 1 below were laminated on both sides of the polarizing film prepared above using the prepared water-based adhesive. The obtained laminate was heated and dried, the adhesive was dried, and a polarizing plate was produced. Additionally, the thickness of the adhesive layer in the obtained polarizing plate was about 50 nm.

<Measurement of visibility correction single transmittance>

The visibility-corrected single transmittance (Ty) of the obtained polarizing plate was measured in accordance with “JIS Z 8729” using a spectrophotometer equipped with an integrating sphere (“V7100” manufactured by Nippon Bunko Co., Ltd.).

The measurement results are shown in Table 1 below.

<Measurement of surface irregularities of polarizer>

The obtained polarizing plate was cut into small pieces of 10 cm x 5 cm, immersed in 600 mL of methylene dichloride, and ultrasonicated at room temperature for 30 minutes to dissolve and remove the bonded first and second protective films.

Regarding the polarizing film from which these protective films have been removed, the surface of the polarizer on the front side (the side to which the first protective film was bonded), to which the adhesive is attached, is scanned in a direction perpendicular to the stretching direction, and the adhesive is The surface irregularities of the attached polarizer were line measured. And, from this measurement result, the size of the undulations (difference in elevation of unevenness) and the spacing of unevenness were calculated. The calculation results are shown in Table 1 below.

Here, the uneven elevation difference and uneven spacing are values calculated as follows.

Uneven elevation difference: The height (H1) at the apex of the highest convexity with respect to the average line of the surface, and the depth (H1) at the bottom of the deeper concave of the two concavities adjacent to the highest convexity ( Sum with H2).

Convex-convex spacing: Distance in a direction parallel to the average line of the surface between the vertex of the highest convexity and the bottom of the deeper concave of the two concavities each adjacent to the highest convexity.

In addition, the measurement of surface irregularities was performed under the following conditions.

Measuring device: VertScan (registered trademark) (model R5500G manufactured by Ryoka Systems Co., Ltd.)

Objective lens (magnification): 2.5x

Measuring range: 3700×2800 ㎛

Resolution: 640×480 pixels

Measurement mode: wave mode

Face correction: 4th processing

<Measurement of color>

The orthogonal a value and orthogonal b value of the manufactured polarizing plate were measured using a spectrophotometer equipped with an integrating sphere (“V7100” manufactured by Nippon Bunko Co., Ltd.). The measurement results are shown in Table 1 below.

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

<Measurement of streak shape irregularity>

Polarizer A, which has a visibility-corrected single transmittance (Ty) of 41.6% and a visibility-corrected polarization (Py) of 99.997, was bonded to the illumination surface of a white backlight module with a luminance of 20000 cd/m2, and a polarizer was placed thereon.

In addition, at this time, the first protective film shown in Table 1 below was placed on top of the polarizing plate, and the transmission axis of the polarizing plate A was placed so that the transmission axis of the polarizing plate was orthogonal (orthogonal Nicol state). In this state, streak-shaped irregularities were confirmed visually on the first protective film side of the polarizing plate. The unevenness of the streak shape was evaluated in the following four stages. The evaluation results are shown in Table 1 below.

0: Irregularity of the line shape is not recognized.

1: Stripe-like irregularities are hardly recognized.

2: Irregularities in the shape of lines can be slightly recognized.

3: Irregularity of the line shape is clearly recognized.

After that, the manufactured polarizing plate was subjected to heating at 105°C for 30 minutes in a dry atmosphere. The polarizing plate after heating was checked for stripe-shaped unevenness in the same manner as above, and was evaluated in the same manner as above. The evaluation results are shown in Table 1 below. Additionally, regarding Example 1, the color change before and after the durability test is shown in the ab chromaticity coordinate diagram in FIG. 7.

<Example 2>

In Example 2, in order to adjust the color of the polarizing film, polarizing plate 2 was produced in the same manner as Example 1, except that only the cleaning conditions for the polarizing film were changed (specifically, the immersion time was set to 3 seconds). Then, the visibility corrected single transmittance (Ty) of the obtained polarizing plate, the surface irregularities of the polarizer, the color change before and after the durability test, and the change in streak shape irregularity before and after the durability test were measured by the same method as Example 1 above. The measurement results are shown in Table 1 below. Additionally, with respect to Example 2, the color change before and after the durability test is shown in the ab chromaticity coordinate diagram in Figure 7.

<Example 3>

(1) Swelling treatment process

First, a 30 ㎛ thick polyvinyl alcohol film (fabric film) (trade name “Kurarepobal Film VF-PE#3000” manufactured by Shakurare Corporation, average degree of polymerization 2400, degree of saponification 99.9 mol%) is continuously rolled from the fabric roll. It was conveyed while loosening and immersed in a swelling bath containing pure water at 20°C for 30 seconds. In this swelling treatment step, inter-roll stretching (vertical uniaxial stretching) was performed with a difference in peripheral speed between the nip rolls 50 and 51. The stretching ratio based on the fabric film was set to 2.2 times.

(2) Dyeing treatment process

Next, the film that passed through the nip roll 51 was immersed in a dyeing bath at 30°C with a pure water/potassium iodide/iodine/boric acid (mass ratio) of 100/1.4/0.01/0.3 for 120 seconds. Also in this dyeing treatment, a difference in peripheral speed was provided between the nip rolls 51 and 52, and inter-roll stretching (vertical uniaxial stretching) was performed. The stretching ratio based on the film after the swelling treatment process was set to 1.2 times.

(3) Cross-linking treatment process

Next, the film that passed through the nip roll 52 was immersed in a crosslinking bath 104a at 53°C with a pure water/potassium iodide/boric acid (mass ratio) of 100/9/4 for 70 seconds. Roll-to-roll stretching (vertical uniaxial stretching) was performed with a difference in peripheral speed between the nip rolls and the nip rolls 52 and 53 provided between the first crosslinking bath 104a and the second crosslinking bath 104b. The stretching ratio based on the film after the dyeing process was set to 2.1 times.

(4) Complementary color processing process

Next, the film after the first crosslinking treatment was immersed in a crosslinking bath (104b) at 50°C with a pure water/potassium iodide/boric acid (mass ratio) of 100/9/3.9 for 10 seconds.

(5) Cleaning treatment process

Next, the film after the second crosslinking treatment was immersed in a washing bath 105 containing pure water at 13°C for 5 seconds.

(6) Drying treatment process

Next, the film after the washing treatment process was passed through a drying furnace and heated and dried at 80°C for 190 seconds to produce a polarizing film. The thickness of the obtained polarizing film was about 12 μm.

(7) Bonding treatment process

Next, the protective films shown in Table 1 below were laminated on both sides of the produced polarizing film using a water-based adhesive containing 5 parts by mass of polyvinyl alcohol with respect to 100 parts by mass of water. The obtained laminate was heated and dried, the adhesive was dried, and a polarizing plate was produced. Additionally, the thickness of the adhesive layer in the obtained polarizing plate was about 50 nm.

Then, the visibility corrected single transmittance (Ty) of the obtained polarizing plate, the surface irregularities of the polarizer, the color change before and after the durability test, and the change in streak shape irregularity before and after the durability test were measured by the same method as Example 1 above. The measurement results are shown in Table 1 below. Additionally, regarding Example 3, the color change before and after the durability test is shown in the ab chromaticity coordinate diagram in FIG. 8.

<Example 4>

In Example 4, a polarizing plate was produced in the same manner as Example 3, except that the type of protective film was changed to the protective film shown in Table 1 below. Then, the visibility corrected single transmittance (Ty) of the obtained polarizer 4, the surface unevenness of the polarizer, the change in color before and after the durability test, and the change in streak shape irregularity before and after the durability test were measured by the same method as Example 1 above. The measurement results are shown in Table 1 below. Additionally, regarding Example 4, the color change before and after the durability test is shown in the ab chromaticity coordinate diagram in FIG. 8.

<Comparative Example 1>

In Comparative Example 1, in order to adjust the color of the polarizing film, a polarizing plate was produced in the same manner as Example 3, except that only the cleaning conditions for the polarizing film were changed (specifically, the immersion time was set to 3 seconds). Then, the visibility corrected single transmittance (Ty) of the obtained polarizing plate, the surface irregularities of the polarizer, the color change before and after the durability test, and the change in streak shape irregularity before and after the durability test were measured by the same method as Example 1 above. The measurement results are shown in Table 1 below. Additionally, regarding Comparative Example 1, FIG. 8 shows the color change before and after the durability test in an ab chromaticity coordinate diagram.

<Comparative Example 2>

In Comparative Example 2, in order to adjust the color of the polarizing film, a polarizing plate was produced in the same manner as Example 4, except that only the cleaning conditions for the polarizing film were changed (specifically, the immersion time was set to 3 seconds). Then, the visibility corrected single transmittance (Ty) of the obtained polarizing plate, the surface irregularities of the polarizer, the color change before and after the durability test, and the change in streak shape irregularity before and after the durability test were measured by the same method as Example 1 above. The measurement results are shown in Table 1 below. Additionally, with respect to Comparative Example 2, the color change before and after the durability test is shown in the ab chromaticity coordinate diagram in FIG. 8 .

<Reference Example 1>

As Reference Example 1, in the dyeing treatment process, a polarizing plate was produced in the same manner as in Example 1, except that the pure water/potassium iodide/iodine/boric acid (mass ratio) was set to 100/2/0.03/0.3. Then, the visibility corrected single transmittance (Ty) of the obtained polarizing plate, the surface irregularities of the polarizer, the color change before and after the durability test, and the change in streak shape irregularity before and after the durability test were measured by the same method as Example 1 above. The measurement results are shown in Table 1 below. Additionally, regarding Reference Example 1, the color change before and after the durability test is shown in the ab chromaticity coordinate diagram in FIG. 9.

In addition, the protective films in Table 1 are as described below.

Protective film A: Obliquely stretched cyclic polyolefin-based resin film with a UV-curable hard coat layer, thickness 29 ㎛

Protective film B: triacetylcellulose film, thickness 25 ㎛

Protective film C: Triacetylcellulose film with UV-curable hard coat layer, thickness 32 ㎛

Protective film D: Triacetylcellulose film with UV-curable hard coat layer (however, UV absorption capacity is different from protective film C), thickness 32 ㎛

In addition, in Table 1, the sign of the orthogonal hue that did not change across the ab chromaticity coordinate axis before and after the durability test was designated as "○" on the hue axis. On the other hand, the sign of the orthogonal color changing across the ab chromaticity coordinate axis before and after the durability test was designated as the color axis "×".

As shown in Table 1 and Figures 7 to 9, in Examples 1 to 4, the signs of the orthogonal colors across the ab chromaticity coordinate axis did not change before and after the durability test, and there was little streak-like irregularity, and even after the durability test. It was good, with no significant increase in streak-shaped unevenness.

On the other hand, in Comparative Examples 1 and 2, the signs of the orthogonal colors were changing across the ab chromaticity coordinate axis before and after the durability test, and the streak-shaped unevenness greatly increased even after the durability test. Additionally, in Reference Example 1, streak-like irregularities were not recognized in the polarizing film with a visibility-corrected single transmittance (Ty) of less than 44%.

1, 1A, 1B: Polarizer, 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 apparatus, 101: fabric roll, 102: swelling bath, 103: dyeing bath, 104: crosslinking bath, 105: washing bath, 106: drying furnace, F: film

Claims (10)

A polarizing plate including a polarizer and a protective film disposed on at least one side of the polarizer through an adhesive layer,
The visibility corrected single transmittance (Ty) measured in the initial state is 44% or more,
The orthogonal color measured in the initial state and after the durability test does not change sign across the a and b coordinate axes in the ab chromaticity coordinate,
A polarizing plate characterized in that, after the durability test, it is after heating at 105° C. for 30 minutes in a dry atmosphere from at least the initial state. delete The polarizing plate according to claim 1, wherein the polarizer is a polarizing film in which a dichroic dye is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol-based resin film. The polarizing plate according to claim 1 or 3, wherein the polarizer has a thickness of 3 to 15 ㎛. The polarizing plate according to claim 1 or 3, wherein when the protective film is removed, irregularities having a height difference of 80 to 250 nm are present on the surface of the polarizer to which the adhesive is attached. The polarizing plate according to claim 1 or 3, wherein the polarizer is an iodine-based polarizer. a display panel,
A display device comprising the polarizing plate according to claim 1 or 3. A method of manufacturing a polarizing plate including a polarizer and a protective film disposed on at least one side of the polarizer through an adhesive layer,
It includes a color adjustment process in which the orthogonal color measured in the initial state and after the durability test is adjusted so that the sign does not change across the a and b coordinate axes in the ab chromaticity coordinate,
A method of manufacturing a polarizing plate, characterized in that after the durability test, heating is provided at 105° C. for 30 minutes in a dry atmosphere from at least the initial state. The method of manufacturing a polarizing plate according to claim 8, wherein in the color adjustment step, at least the color of the polarizer is adjusted. The method of manufacturing a polarizing plate according to claim 8 or 9, wherein in the color adjustment step, the protective film disposed on at least one side or both surfaces of the polarizing plate is selected.