TWI796362B - Polarizing plate, manufacturing method thereof, and display device - Google Patents

Abstract

An objective of the present invention is to provide a polarizing plate capable of making streaky unevenness inconspicuous regardless of a change in hue.

The polarizing plate 1 of the present invention includes a polarizer 2, and protective films 3 and 4 disposed on at least one surface of the polarizer 2 via an adhesive layer; wherein, the visibility correction monoaxial transmittance (Ty) measured in the initial state is 44% or more, the orthogonal hue measured in the initial state and after the durability test does not change sign with the a coordinate axis and the b coordinate axis between the ab chromaticity coordinates interposed there between.

Description

Polarizing plate, manufacturing method thereof, and display device

The present invention relates to a polarizing plate, a manufacturing method thereof, and a display device.

For example, in the following patent document 1, it is proposed that since the stripes originating from the surface of the polarizer will produce stripe-like unevenness that can be confirmed by the intensity of reflected light, by setting the height of the unevenness on the surface of the polarizer to 280nm Next, to suppress streaky unevenness caused by the intensity of reflected light.

[Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Patent No. 6166431

In recent years, for the purpose of reducing power consumption, etc., polarizer systems have been developed toward high transmittance. On the other hand, when the polarizer becomes high transmittance, as described in Patent Document 1, it is known that even if the unevenness on the surface of the polarizer is set to be 280 nm or less, the unevenness originating from the surface of the polarizer will still cause the orthogonal The light in the crossed nicols state passes through the polarizer to produce non-uniform fringes.

In addition, regarding the high-transmittance polarizer, even if the color tone of the initial state is adjusted to make the stripe-like unevenness that can be seen through the polarizer in the crossed polarized state less conspicuous, but during the use of the polarizer, there will be Striped unevenness may become conspicuous due to a change in the hue (color) of the polarizing plate.

The present invention is proposed in view of such a conventional situation, and an object thereof is to provide a polarizing plate capable of making streak-like unevenness inconspicuous regardless of changes in color tone, a method of manufacturing the same, and a display provided with such a polarizing plate. device.

In terms of means for solving the above-mentioned problems, according to the aspects of the present invention, a polarizing plate can be provided, which includes: a polarizing plate, and a protective film disposed on at least one side of the polarizing plate via an adhesive layer; Among them, the photometrically corrected monomer transmittance (Ty) measured in the initial state is above 44%, and the orthogonal hue measured in the initial state and after the durability test is determined by the a-coordinate axis and b-coordinate axis of the ab chromaticity coordinates There is no changer in the signed area of the pinch.

In addition, in the above-mentioned polarizing plate, after the durability test, the structure may be "at least starting from the above-mentioned initial state, supplying it in a dry gas environment, and heating at 105° C. for 30 minutes".

In addition, in the aforementioned polarizing plate, the aforementioned polarizing plate may have a structure of "a polarizing film in which a dichroic dye is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol-based resin film".

In addition, in the aforementioned polarizing plate, the thickness of the aforementioned polarizing plate may be a structure of 3 to 15 μm.

In addition, in the polarizing plate, when the protective film is removed, unevenness with a height difference of 80 to 250 nm may exist on the surface of the polarizing plate to which the adhesive is attached.

Also, in the aforementioned polarizing plate, the aforementioned polarizing plate may be an iodine-based polarizing plate.

Furthermore, according to an aspect of the present invention, it is possible to provide a display device comprising a display panel and any one of the aforementioned polarizing plates.

Moreover, according to the aspects of the present invention, a method for manufacturing a polarizing plate can be provided, which includes: a polarizing plate, and a protective film disposed on at least one side of the polarizing plate via an adhesive layer; the production of the polarizing plate The method includes a hue adjustment step of adjusting the orthogonal hue measured in the initial state and after the durability test in such a way that the symbol area enclosed by the a-coordinate axis and the b-coordinate axis does not change in the ab chromaticity coordinates.

In addition, the aforementioned method for producing a polarizing plate may be one in which the aforementioned step of adjusting the color tone adjusts at least the color tone of the aforementioned polarizing plate.

In addition, the method for manufacturing the polarizing plate may be a method in which the color tone adjustment step is to select the protective film disposed on at least one side or both sides of the polarizing plate.

As described above, according to the aspect of the present invention, a polarizing plate and a flexible display device having such a polarizing plate can be provided; wherein, the polarizing plate can make stripes uneven regardless of the color tone. become inconspicuous.

1, 1A, 1B‧‧‧polarizer

2‧‧‧Polarizer

3.4‧‧‧Protective film

5‧‧‧Adhesive layer

10‧‧‧display device

11‧‧‧display panel

30 to 41‧‧‧guide roller

50 to 55‧‧‧roll

100‧‧‧Manufacturing device

101‧‧‧raw material volume

102‧‧‧Swelling bath

103‧‧‧dye bath

104‧‧‧Crosslinking bath

105‧‧‧Cleansing bath

106‧‧‧Drying furnace

F‧‧‧film

Fig. 1 is a cross-sectional view showing the structure of a polarizing plate according to an embodiment of the present invention.

Fig. 2 is a cross-sectional view showing the structure of a polarizing plate according to another embodiment of the present invention.

Fig. 3 is a cross-sectional view showing the structure of a polarizing plate according to another embodiment of the present invention.

Fig. 4 is a cross-sectional view showing the structure of a display device including the polarizing plate shown in Fig. 2 .

Fig. 5 is an ab chromaticity coordinate diagram illustrating the change in orthogonal tone measured before and after the durability test of the polarizing plate.

Fig. 6 is a schematic view showing the structure of a polarizing film manufacturing apparatus.

Fig. 7 shows an ab chromaticity coordinate diagram of the orthogonal tone change measured before and after the durability test in Examples 1 and 2.

Fig. 8 shows an ab chromaticity coordinate diagram of the orthogonal tone change measured before and after the durability test in Examples 3 and 4 and Comparative Examples 1 and 2.

Fig. 9 shows an ab chromaticity coordinate diagram of the orthogonal tone change 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.

In addition, the drawings used in the following description are for easy viewing of each component, and sometimes the component is schematically shown, and the scaling ratio of the displayed size may vary depending on the component. In addition, the material, numerical value, etc. which are illustrated in the following description are an example, and this invention is not limited to these examples, In the range which does not change the summary, it can change suitably and can implement.

(polarizer)

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

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

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

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 penetration axis of the polarizer 2 is the vibration direction of the penetrating light when natural light penetrates the polarizer 2 . On the other hand, the absorption axis of the polarizer 2 is a direction perpendicular to the transmission axis of the polarizer 2 .

In general, the polarizer 2 is formed by adsorbing and aligning a polarizing film having dichroic pigments such as iodine and a dichroic dye on a uniaxially stretched polyvinyl alcohol (PVA) resin film. Therefore, the direction of the absorption axis of the polarizer 2 is consistent with its extending direction (MD; machine direction), and the direction of the transmission axis of the polarizer 2 is consistent with its width direction (TD; transverse direction).

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

The polyvinyl acetate-based resin may be, for example, a copolymer of vinyl acetate and other monomers that can be copolymerized with vinyl acetate, in addition to polyvinyl acetate that may be a homopolymer of vinyl acetate. Examples of other monomers that can be copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of polymerization of the 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 also be modified, for example, polyvinyl formal modified with aldehydes, polyvinyl acetal, polyvinyl butyral, etc. may be used.

From the viewpoint of thinning the polarizing plate 1, the thickness of the polarizing plate 2 is preferably thinner, but can be appropriately set depending on the use of the polarizing plate 1 and the like. The thickness of the polarizer 2 is, for example, 25 μm or less, preferably 20 μm or less, more preferably 15 μm or less; 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 handling of the PVA-based resin film, and unevenness is likely to occur on the polarizer 2 , so the effect of the present invention increases. In addition, it can be considered that the thickness of the polarizer 2 in the polarizing plate 1 is substantially equal to the thickness of the polarizer 2 after the protective films 3 and 4 are attached via an adhesive and cured.

As for the protective films 3 and 4, for example, films made of acetyl cellulose-based resins such as triacetyl cellulose or diacetyl cellulose; films made of acetyl cellulose resins such as polyethylene terephthalate Polyester, polyethylene naphthalate and polybutylene terephthalate polyester resin film; polycarbonate resin film; cycloolefin resin film; acrylic resin film; A film made of chain olefin-based resins.

When the protective films 3, 4 are arranged on both surfaces of the polarizer 2, the protective films 3, 4 may be formed of the same type of resin, or may be formed of different types of resin.

From the viewpoint of reducing the thickness of the polarizing plate 1 , the thicknesses of the protective films 3 and 4 are preferably thinner, but can be 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, more preferably 30 μm or less.

On the other hand, from the viewpoint of workability, the thickness of the protective films 3 and 4 is preferably a thickness capable of securing a certain degree of strength, 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. The water-based adhesive can be, for example, an aqueous solution of polyvinyl alcohol-based resin, or an aqueous solution prepared with a cross-linking agent in an aqueous solution of polyvinyl alcohol-based resin, or a water-based adhesive such as urethane-based latex adhesive.

The active energy ray-curable adhesive means an adhesive that is cured by irradiating active energy rays such as ultraviolet rays or electron rays. When the active energy ray-curable adhesives are classified according to their hardening forms, they include: cationic polymerizable adhesives containing a cationically polymerizable compound that becomes a curable compound, and cationic polymerizable adhesives that contain a radically polymerizable compound that becomes a curable compound. Adhesives for free radical polymerization, curable adhesives containing both cationic polymerizable compounds and free radical polymerizable compounds, etc. Examples of the cationically polymerizable compound include epoxy compounds, oxetane compounds, and the like. 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 water-based adhesive may be, for example, not less than 20 nm, preferably not less than 40 nm. On the other hand, from the standpoint of production cost, etc., the thickness of the adhesive should be more than necessary but not too thick. For example, it may be 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 at least 0.1 μm, more preferably at most 10 μm, more preferably at most 5 μm, and more preferably at most 3 μm .

Other embodiments of the present invention may have, for example, the polarizing plate 1A shown in FIG. 2 or the polarizing plate 1B shown in FIG. 3 . In addition, FIG. 2 is a cross-sectional view showing a schematic structure of the polarizing plate 1A. Fig. 3 is a cross-sectional view showing a schematic structure of the polarizing plate 1B.

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

The adhesive layer 5 can adhere the polarizer 2 and the protective films 3 and 4 by virtue of its own adhesiveness. As for the adhesive forming the adhesive layer 5, conventionally known materials may be appropriately selected, as long as it has adhesiveness to the extent that no peeling or the like occurs in an environment where the polarizing plates 1A and 1B are exposed. . Specifically, examples include: acrylic adhesives, polysiloxane adhesives, rubber adhesives, etc. In terms of transparency, weather resistance, heat resistance, and processability, acrylic adhesives are the most prominent. good. The thickness of the adhesive layer 5 is usually about 3 to 100 μm, preferably 5 to 50 μm.

Moreover, in the adhesive, it can be properly formulated as needed: tackifier, plasticizer, glass fiber, glass beads (glass beads), metal powder, fillers made of other inorganic powders, pigments, colorants, etc. Agents, fillers, antioxidants, UV absorbers, antistatic agents, silane coupling agents and other additives.

The adhesive layer 5 is used for bonding the polarizing plates 1A, 1B to other members. A release film (not shown in the figure) may be provided on the surface of the adhesive layer 5 in advance. When there is a release film on the surface of the adhesive layer 5 , the adhesive layer 5 can be bonded (laminated) to the polarizer 2 or the protective films 3 and 4 by peeling off the release film from one side. After peeling off the release film from the other side, it can be attached to other components through the adhesive layer 5 .

Also, the structure of the polarizing plate to which the present invention can be applied is not necessarily limited to the structures of the polarizing plates 1, 1A, and 1B shown in FIGS. 1 to 3 above. That is to say, the polarizing plate to which the present invention can be applied should have a structure including a polarizing plate and a protective film arranged on at least one side or both sides of the polarizing plate, and can be appropriately added with a structure other than this structure. change.

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

Also, when the above-mentioned polarizing plates 1, 1A, and 1B are used as circular polarizing plates, they may have a structure including a 1/4 wavelength (λ/4) plate in addition to the above-mentioned structure. The λ/4 plate has the function of converting linearly polarized light of a specific wavelength into circularly polarized light (or converting 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 adhesive layer 5 .

In addition, when the above-mentioned polarizing plates 1, 1A, and 1B are used as circular polarizing plates, they may have a structure including a positive C-plate (positive C-plate) in addition to the λ/4 plate. The positive type C plate can reduce the variation of the reflection tone (color) of the polarizing plates 1, 1A, 1B. When the positive type C plate is included, the λ/4 plate is preferably the reverse wavelength dispersion λ/4 plate. The positive type C plate is disposed on the surface (another surface) opposite to the polarizer 2 of the λ/4 plate via an adhesive layer or an adhesive layer. Therefore, for example, the above polarizing plate 1 has a laminated structure of the above polarizing plate 1, adhesive layer 5, λ/4 plate, adhesive layer or adhesive layer, and positive C plate.

Furthermore, when the above-mentioned polarizing plates 1, 1A, and 1B are used as circular polarizing plates, they may have a structure including a 1/2 wavelength (λ/2) plate in addition to a λ/4 plate. The λ/2 plate is capable of imparting a phase difference of π (=λ/2) in the electric field vibration direction (polarization plane) of incident light, and has the function of changing the direction of linearly polarized light (polarized light orientation). Also, when circularly polarized light is incident, the rotation direction of the circularly polarized light can be reversed. The λ/2 plate is arranged on the side (the other side) opposite to the polarizer 2 of the λ/4 plate via an adhesive layer or an adhesive layer. Therefore, for example, the above polarizing plate 1 has a laminated structure of the above polarizing plate 1, adhesive layer 5, λ/4 plate, adhesive layer or adhesive layer, and λ/2 plate.

(display device)

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

4 is a cross-sectional view showing the configuration of a display device 10 including the polarizing plate 1A shown in FIG. 2 above.

The display device 10 of the present embodiment includes a display panel 11 and a polarizing plate 1A disposed on the viewing side of the display panel 11 as shown in FIG. 4 . The polarizing plate 1A is bonded on 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, an organic electroluminescent (EL) display element, or the like. When the display device 10 uses a liquid crystal display panel as the display panel 11, it 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.

Also, the structure of the display device to which the present invention can be applied is not necessarily limited to the structure of the display device 10 shown in FIG. 4 above. That is, the display device to which the present invention can be applied can appropriately change the structure of the display panel as long as it includes the above-mentioned polarizing plate to which the present invention can be applied. On the other hand, the applications to which the polarizing plate of the present invention can be applied are not limited to the above-mentioned display devices, and can be used in various optical applications.

By the way, in the polarizing plate 1 of this embodiment, the orthogonal color tone measured in the initial state and after the durability test is adjusted so that the symbol area enclosed by the a-coordinate axis and the b-coordinate axis in the ab chromaticity coordinates does not change. . That is, the change in the cross-color tone measured before and after the durability test of the polarizing plate 1 is set so that the a-coordinate axis and the b-coordinate axis do not cross the quadrant. Thereby, even if the cross-color tone of the polarizing plate 1 changes before and after the durability test, the streak-like unevenness generated in the polarizing plate 1 can be made inconspicuous regardless of the change in the color tone.

Specifically, changes in the cross-color tone measured before and after the durability test of the polarizing plate 1 will be described with reference to FIG. 5 . In addition, FIG. 5 is an ab chromaticity coordinate diagram for explaining the change of the orthogonal|vertical color tone measured before and after the durability test of the polarizing plate 1.

The cross-color tone change measured before and after the durability test of the polarizing plate 1 can be measured using a spectrophotometer or the like.

In addition, in this embodiment, the measurement of the through color tone is performed with a spectrophotometer. Then, after heating at 105° C. for 30 minutes in a dry gas environment, the penetration color tone was measured again by a spectrophotometer. Then, it was confirmed that the color tone of the transmission measured in the initial state of the polarizing plate 1 and after the durability test does not change in the sign region sandwiched between the a-coordinate axis and the b-coordinate axis.

In addition, the stripe-shaped unevenness generated in the polarizing plate 1 can be observed by passing through the cross-polarized light on the backlight. Specifically, a polarizing plate may be bonded to the lighting surface of a white backlight, and the polarizing plate 1 may be placed thereon so that the absorption axis may be perpendicular to it, and uneven intensity may be visually observed.

In the case of including retardation plates such as λ/4 plates, positive C plates, and λ/2 plates as the protective films 3 and 4 of the polarizing plate 1, if these retardation plates can be used as the opposite side of the backlight (visual recognition side) way to set it on the backlight and observe it. Also, when both the protective films 3 and 4 of the polarizing plate 1 are of the structure of a retardation plate, a retardation plate can be set on the backlight on which the polarizing plate is pasted on the illuminating surface, and the polarizing plate 1 can be formed on it. Crossed polarizers were set for observation.

In the present embodiment, regarding the orthogonal color tone measured before and after the durability test of the polarizing plate 1, the meaning of "the symbol area enclosed by the a-coordinate axis and the b-coordinate axis does not change" means, for example, "the In the ab chromaticity diagram shown in Figure 5, the area enclosed between the a-coordinate axis and the b-coordinate axis is the same as those that do not cross quadrants. In this case, even if the orthogonal color tone of the polarizing plate 1 changes before and after the durability test, the stripe-like unevenness generated in the polarizing plate 1 can be made inconspicuous regardless of the change in color tone. On the other hand, if the region between the a-coordinate axis and the b-coordinate axis spans across quadrants, the stripe-shaped unevenness generated in the polarizing plate 1 becomes easy to be seen due to the change of the orthogonal tone.

Regarding the stripe-like unevenness generated by the polarizing plate 1 , ideally, the height difference of the stripe-like unevenness on the surface of the polarizing plate 1 is 80 to 250 nm. Striped uneven height difference, when the protective film 3 and 4 have been removed, the attached The surface of the polarizer 2 coated with the adhesive was scanned in a direction perpendicular to the extending direction of the stripes on the surface of the polarizer 1 , and the unevenness of the surface was linearly measured. And, from the measurement results, the height of the apex of the highest convex portion with respect to the average line of the surface can be calculated by the following formula (1), and among the two concave portions adjacent to the highest convex portion, respectively, The sum of the depths of the bottoms of the deeper recesses is obtained. Also, the extending direction of the stripes is usually the same as the extending direction (MD).

80nm≦height difference=(the height of the apex of the highest raised part with respect to the average line of the surface)+(the depth of the bottom of the deeper recessed part among the two recesses adjacent to the highest raised part respectively)≦250nm‧‧ ‧(1)

In the polarizing plate 1 of the present embodiment, the orthogonal hue measured in the initial state and after the durability test is adjusted in such a way that the symbol area enclosed by the a-coordinate axis and the b-coordinate axis in the ab chromaticity coordinates does not change, and Striped unevenness generated in such a polarizing plate 1 can be made inconspicuous regardless of the change in color tone.

In addition, the polarizing plate 1 of the present embodiment can adjust the orthogonal color tone by adjusting the color tone of the polarizing plate 2 and selecting the protective films 4 and 5 arranged on at least one side or both sides of the polarizing plate 1 .

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

Also, regarding the present invention, in addition to the above-mentioned polarizing plate 1, for the above-mentioned polarizing plates 1A, 1B, or polarizing plates containing retardation films such as a λ/4 plate, a positive type C plate, and a λ/2 plate, it is also possible to borrow In the ab chromaticity coordinates, the orthogonal hue measured in the initial state and after the durability test is adjusted in such a way that the symbol area enclosed by the a-coordinate axis and the b-coordinate axis does not change, regardless of the change in hue, it can be used in polarized light Striped unevenness caused by light passing through the polarizer 2 in the crossed polarization state generated by the plate becomes inconspicuous.

(Manufacturing method of polarizing plate)

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

In addition, FIG. 6 is a schematic diagram showing a manufacturing apparatus 100 of a polarizing film to be the above-mentioned polarizing plate 2 . Moreover, the arrow shown in FIG. 6 shows the conveyance direction of the film F used as a polarizing film.

In this embodiment, first, a polarizing film serving as the polarizer 2 among the polarizing plates 1 is produced using the manufacturing apparatus 100 shown in FIG. 6 . Specifically, a long unstretched PVA-based resin film (raw material film) F is used as a starting material, and the film F is continuously conveyed along the film conveyance path of the manufacturing apparatus 100, and simultaneously passes through predetermined processing steps. , while continuously manufacturing elongated polarizing films.

In terms of predetermined treatment steps, it may include: a swelling treatment step of immersing the membrane F in the swelling bath 102, a dyeing treatment step of immersing the membrane F after the swelling treatment step in the dyeing bath 103, and a dyeing treatment step of immersing the membrane F after the swelling treatment step. A cross-linking treatment step of immersing the film F in the cross-linking bath 104, a washing treatment step of immersing the cross-linked film F in the cleaning bath 105, a stretching treatment step of performing a uniaxial stretching treatment on the transported film F . A drying treatment step of drying the film F after the washing treatment step by using the drying oven 106 . It is also possible to further add other processing steps as needed.

The polarizing film manufacturing device 100 shown in FIG. 6 is configured in such a way that the film F is continuously unwound from the raw material roll 101, conveyed along the film conveyance path, and the film F is sequentially passed through here. Swelling bath 102 , dyeing bath 103 , crosslinking bath 104 , and cleaning bath 105 on the film conveying path, and finally make the film F pass through drying oven 106 . The obtained polarizing film can be directly transported, for example, to the next step of producing the polarizing plate 1 (step of attaching a protective film to one side or both sides of the polarizing film).

Also, in the manufacturing apparatus 100 shown in FIG. 6 , although the swelling bath 102, the dyeing bath 103, the cross-linking bath 104, and the cleaning bath 105 are each provided with one tank as an example to accommodate the treatment of the membrane F In the case of the treatment bath for liquid, however, it can also be a structure in which more than one treatment bath is provided as two or more tanks as required.

The manufacturing apparatus 100 shown in Fig. 6 is attached to the film conveyance path, and in addition to disposing the above-mentioned treatment baths 102 to 105, it is also suitably configured to support the conveyed film F and change the conveyed film F as necessary. Guide rolls (guide roll) 30 to 41 in the conveying direction of the film F; press/clamp the conveyed film F, transmit the driving force caused by its rotation to the film F, and change the conveyance of the conveyed film F as necessary The direction of the roll (nip roll) 50 to 55 and constitute.

The guide rolls 30 to 41 and the rolls 50 to 55 can be arranged before and after each of the treatment baths 102 to 105 , or in the treatment baths 102 to 105 . Thereby, the introduction/immersion of the membrane F to each treatment bath 102 to 105 and the derivation from the treatment baths 102 to 105 can be performed. For example, one or more guide rollers 30 to 41 are provided in each treatment bath 102 to 105, and the film F is conveyed along these guide rollers 30 to 41, whereby the film F can be immersed in each treatment bath 102 to 1055. .

In the manufacturing apparatus 100 shown in FIG. 6 , rolls 50 to 55 are arranged before and after each treatment bath 102 to 105 . Thereby, in any one or more of the treatment baths 102 to 105, the rolls 50 to 55 disposed before and after the treatment baths can be provided with a rotational speed difference, so that the film F can be uniaxially stretched longitudinally and stretched between rolls.

Hereinafter, various processing steps performed on the film F when producing a polarizing film will be described.

<Swelling treatment step>

The purpose of the swelling treatment step is to remove impurities existing on the surface of the film F used as a raw material film, to remove plasticizers present in the film F, to impart easy dyeability, to plasticize the film F, and the like. The treatment conditions are determined within the range within which the object can be achieved, and within a range in which defects such as extreme dissolution and loss of transparency of the film F do not occur.

As the raw material 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 (reel) of an elongated unstretched PVA-based resin film. However, the raw material film may be a stretched film that has been subjected to uniaxial stretching in gas beforehand before the swelling treatment step.

In the swelling treatment step, when the film (raw film) F continuously rolled out from the raw material roll 101 passes through the nip roll 50 and the guide rolls 30 to 32 sequentially, it is immersed in the treatment solution contained in the swelling bath 102 for a predetermined time. Thereby, the membrane F is subjected to swelling treatment. In addition, the film F may be subjected to uniaxial stretching in the swelling bath 102 using the difference in rotation speed between the rolls 50 and 51 as the stretching step.

In the treatment solution of the swelling bath 102, in addition to pure water, boric acid (refer to Japanese Patent Application Laid-Open No. 10-153709 ), chloride (refer to Japanese Patent Application Laid-Open No. 06-281816 ) can be used in the range of about 0.01 to 10% by weight. Publication No.), inorganic acids, inorganic salts, water-soluble organic solvents, alcohols and other aqueous solutions.

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, 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, 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, a problem of what is called "the film F is swollen in the width direction and wrinkles are formed on the film F" is likely to occur. As a means for removing such wrinkles and carrying the film F, guide rolls 30, 31 and/or guide roll 32 are used such as expander rolls, spiral rolls, convex rolls ( crown roll), or use other expanding devices such as cross guider, bend bar, tenter clip. On the other hand, stretching treatments may be implemented as an additional means to suppress the development of wrinkles.

In the swelling treatment, since the film F will also swell and expand in the conveying direction of the film F, when the film F is not actively stretched, in order to eliminate the slack of the film F in the conveying direction, it is better to control and configure it in the swelling bath, for example. Means such as the speed of roll 50,51 before and after 102. Also, for the purpose of stabilizing the transfer of the film F in the swelling bath 102, the water flow in the swelling bath 102 is controlled by showering in water, or an EPC device [Edge Position Control device: inspecting the film The end of the film, the device that prevents the membrane from meandering], etc. are also useful.

The film F drawn out from the swelling bath 102 is conveyed to the dyeing bath 103 side through the guide roll 32 and the nip roll 51 in this order.

<Dyeing treatment procedure>

The dyeing treatment step is performed for the purpose of adsorbing a dichroic dye, orienting the film F after the swelling treatment step, and the like. The processing conditions are determined within the range in which the object is achieved, and the film F does not cause defects such as extreme dissolution and loss of transparency.

In the dyeing treatment step, the film F after the swelling treatment step is immersed in the treatment liquid contained in the dyeing bath 103 for a predetermined time while passing through the nip roll 51 and the guide rolls 33 to 35 in sequence. Thereby, the membrane F can be dyed. In addition, the film F may be uniaxially stretched in the dyeing bath 103 by utilizing the difference in rotational speed between the roll 51 and the roll 52 as a stretching step.

The film F to be subjected to the dyeing treatment step is preferably a film F that has been subjected to at least a certain degree of uniaxial stretching treatment in order to improve the dyeability of the dichroic pigment, and may be subjected to uniaxial stretching treatment before the dyeing treatment, or In addition to the uniaxial stretching treatment before the dyeing treatment, it is preferable to perform the uniaxial stretching treatment during the dyeing treatment.

When the treatment solution of the dyeing bath 103 uses iodine as a dichroic pigment, for example, an aqueous solution with a weight ratio of iodine/potassium iodide/water=about 0.003 to 0.3/about 0.1 to 10/100 can be used. Instead of potassium iodide, other iodides such as zinc iodide may be used, or potassium iodide may be used in combination with other iodides. In addition, compounds other than iodide may coexist with, for example, boric acid, zinc chloride, cobalt chloride, and the like. When boric acid is added, it is different from the cross-linking treatment described later in that it contains iodine. If the aqueous solution contains about 0.003 parts by weight or more of iodine with respect to 100 parts by weight of water, it can be regarded as the dyeing bath 103 .

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

On the other hand, when the treatment solution of the dyeing bath 103 is to use a water-soluble dichroic dye as the dichroic pigment, for example, the dichroic dye/water=about 0.001 to 0.1/100 (preferably about 0.003 to 0.03/about 0.1 to 10/100) in aqueous solution. At this time, dyeing auxiliaries and the like may coexist in the treatment liquid in the dyeing bath 103, and for example, inorganic salts such as sodium sulfate and surfactants may be contained. One type of dichroic dye may be used alone, or two or more types of dichroic dye may be used in combination.

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 seconds. to about 300 seconds.

The dyeing treatment is the same as the above-mentioned swelling treatment. As a means to remove the wrinkles of the film F and carry the film F, it can be used as a telescopic roll, a spiral roll, etc. at the guide rolls 33, 34 and/or guide rolls 35. Rolls, convex rolls that have the function of expanding, and other expanding devices such as cross guide rollers, bending rods, and tenter clips can also be used. On the other hand, as another means for suppressing the generation of wrinkles, stretching treatment can be performed in the same way as the above-mentioned swelling treatment.

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

<Crosslinking treatment step>

The crosslinking treatment step is a treatment performed for the purpose of making water resistance or adjusting color tone by crosslinking. In the cross-linking treatment step, the film F after the dyeing treatment step is immersed in the treatment liquid contained in the cross-linking bath 104 for a predetermined time while passing through the nip roll 52 and the guide rolls 36 to 38 sequentially. Thereby, the film F is subjected to a crosslinking treatment. Also, the film F may be uniaxially stretched in the crosslinking bath 104 by utilizing the difference in rotational speed between the rolls 52 and 53 as the stretching step.

As the treatment solution of the crosslinking bath 104, an aqueous solution containing, for example, about 1 to 10 parts by weight of boric acid per 100 parts by weight of water can be used. The treatment solution of the crosslinking bath 104 is preferably one containing iodide in addition to boric acid when the dichroic pigment used in the dyeing treatment is iodine, and the amount thereof can be set to, for example, 100 parts by weight relative to water. to 30 parts by weight. The iodide may, for example, be potassium iodide or zinc iodide. In addition, compounds other than iodide may coexist, for example, with zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate, and the like.

In the cross-linking treatment, the concentrations of the cross-linking agent (boric acid, etc.) and iodide, and the temperature of the cross-linking bath can be appropriately changed according to the purpose. For example, when the purpose of the cross-linking treatment is to increase water resistance by cross-linking, and the unstretched polyvinyl alcohol-based resin film is sequentially subjected to swelling treatment, dyeing treatment, and cross-linking treatment, the cross-linking bath contains For the liquid of the agent, it can be an aqueous solution whose concentration is boric acid/iodide/water=3 to 10/1 to 20/100 in weight ratio. Moreover, other crosslinking agents, such as glyoxal and glutaraldehyde, may be used instead of boric acid as needed, and boric acid and another crosslinking agent 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, more preferably 20 to 200 seconds. On the other hand, when dyeing and crosslinking are performed sequentially on the pre-stretched membrane F, the temperature of the crosslinking bath 104 is usually about 50 to 85°C, preferably 55 to 80°C.

In the cross-linking treatment for the purpose of adjusting the color tone, for example, when using iodine as a dichroic pigment, a cross-linking concentration of boric acid/iodide/water = 1 to 5/3 to 30/100 can be used in terms of weight ratio. bath. The temperature of the crosslinking bath 104 at the time of immersing the membrane 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 cross-linking treatment may be performed plural times, usually 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-mentioned range. As for the crosslinking treatment for water resistance by crosslinking and the crosslinking treatment for adjusting the color tone, a plurality of steps may be performed separately.

When the cross-linking treatment is the same as the above-mentioned swelling treatment, as a means for removing the wrinkles of the film F and transporting the film F, it is possible to use such as stretching rolls on the guide rolls 36, 37 and/or guide rolls 38. , helical rolls, convex rolls with the function of expanding, and other expanding devices such as cross guide rolls, bending rods, and tenter clips can also be used. On the other hand, as another means for suppressing the generation of wrinkles, stretching treatment can be performed in the same way as the above-mentioned swelling treatment.

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

<Cleaning treatment procedure>

The cleaning treatment step is performed for the purpose of removing excess chemicals such as boric acid and iodine adhering to the membrane F. In the cleaning step, for example, when the film F after the crosslinking step passes through the nip roll 53 and the guide rolls 39 to 41 sequentially, it is immersed in the cleaning solution (water) contained in the cleaning bath 105 for a predetermined time. Alternatively, the film F after the crosslinking treatment step is sprayed with water as a shower. Alternatively, these cleaning treatments may be used in combination.

The manufacturing apparatus 100 shown in FIG. 6 exemplifies a case where the film F is immersed in a cleaning bath 105 to perform cleaning treatment. The temperature of the cleaning bath 105 is usually about 2 to 40°C. The immersion time of the membrane F is usually about 2 to 120 seconds.

The cleaning treatment is the same as the case of the above-mentioned swelling treatment. In terms of a means for removing the wrinkles of the film F and transporting the film F, the guide rollers 39, 40 and/or the guide rollers 41 can be used such as telescopic rollers. , helical rolls, and convex rolls have the function of expanding, and can also use other expanding devices such as cross guide rolls, bending rods, and tenter clips. On the other hand, as another means for suppressing the generation of wrinkles, stretching treatment may be performed as in the case of swelling treatment described above.

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

<Drying treatment procedure>

In the drying treatment step, drying treatment is performed on the membrane F after the washing treatment step. The drying process of the film F is not particularly limited, and may be performed using a drying oven 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, 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.

<Extended processing steps>

The stretching treatment step is to perform wet or dry uniaxial stretching treatment on the film F between the above-mentioned series of treatment steps (that is, before and after any one or more treatment steps and/or during any one or more treatment steps). .

As a specific method of uniaxial stretching treatment, for example, it is possible to adopt a method of performing longitudinal uniaxial stretching by applying a rotational speed difference between two rolls constituting a film conveyance path (for example, two rolls arranged in front of and behind a treatment bath). Stretching between rolls; or hot roll stretching, tenter stretching, etc. as described in Japanese Patent No. 2731813, preferably stretching between rolls.

The stretching treatment may be performed several times between the film F and the polarizing film obtained. In addition, the stretching treatment is also advantageous in suppressing the occurrence of wrinkles in the film F described above.

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

<Other processing steps>

In the production process of the polarizing film, other processing steps other than the above-mentioned processing steps may be added. Examples of the additional treatment step include, for example, after the cross-linking treatment step, the immersion treatment step (color supplementation treatment step) in an iodide aqueous solution not containing boric acid, or the method containing zinc chloride without boric acid. A immersion treatment step of an aqueous solution (zinc treatment step) and the like.

The polarizer 2 can be obtained by appropriately cutting the prepared polarizing film. In addition, the polarizer 2 may be in the shape of a square, or may be an elongated film. As mentioned above, although the manufacturing steps of the polarizing film used as the polarizer 2 have been described, the polarizing film used as the polarizer 2 may also be manufactured by other methods.

Next, after making the above-mentioned polarizer 2, the above-mentioned polarizer 1 can be manufactured through the following steps: a preliminary processing step of performing pretreatment on the bonding surface of the polarizer 2 and/or the protective film 3, 4; The step of laminating the protective films 3 and 4 on both sides of the polarizer 2 through an adhesive; the curing step of curing the polarizer 2 bonded with the protective films 3 and 4 .

<Preliminary processing steps>

The preparatory treatment step is to implement corona treatment and flame treatment on the bonding surface of the polarizer 2 and/or the protective film 3, 4 in order to improve the adhesion between the polarizer 2 and the protective film 3, 4 before the lamination process step. , plasma treatment, ultraviolet irradiation, primer coating treatment, saponification treatment and other surface treatments.

<Laying process steps>

The bonding process step is to bond the protective films 3 and 4 on 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 condition is to set a larger amount than the amount of the adhesive applied to the surface of the polarizer 2 .

<Hardening treatment procedure>

The hardening treatment step is to harden the polarizer 2 bonded with the protective films 3 and 4 . When using a water-based adhesive, after bonding the protective films 3 and 4, the adhesive layer is dried to harden. 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, aging can also be carried out at room temperature or a temperature slightly higher than room temperature, for example, at a temperature of 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, it is cured by irradiating active energy rays (ultraviolet rays, electron rays, X-rays, etc.). The light irradiation time is controlled by various active energy ray-curing adhesives and is not particularly limited, but it is preferably set so that the cumulative light amount represented by the product of the irradiation intensity and the irradiation time is 10 to 2,500 mJ/cm ² .

Like the polarizer 2, the polarizing plate 1 may be a square or elongated film. The square polarizing plate 1 can be obtained, for example, by cutting a long polarizing plate 1 . Also, the elongated polarizing plate 1 may be a roll of the polarizing plate 1 (spool).

The manufacturing method of the polarizing plate 1 of the present embodiment includes: a color tone adjustment step, which is adjusted in the initial state and after the durability test in such a way that the symbol area enclosed by the a-coordinate axis and the b-coordinate axis in the ab chromaticity coordinates does not change. The measured ortho-hue.

As far as the specific tone adjustment step is concerned, by adjusting the tone of the polarizer 2 , the initial state of the polarizer 1 and the orthogonal tone measured after the durability test can be adjusted. Again, the color tone of the polarizer 2 can be determined by the concentration of the above-mentioned treatment solution (such as potassium iodide concentration or dye concentration in the dyeing bath 103, boric acid concentration in the cross-linking bath 104, potassium iodide concentration, etc.), the temperature of the treatment solution, and water washing. Intensity (time, temperature), thickness of the film F and its elongation ratio are adjusted. Among them, in terms of the adjustment of the orthogonal tone, it is also useful to control the intensity of washing.

Also, in terms of the tone adjustment step, it is possible to adjust the initial state of the polarizer 1 and the orthogonal tone measured after the durability test by selecting the protective films 3 and 4 disposed on at least one side or both sides of the polarizer 2. . That is, the initial state of the polarizing plate 1 and the cross-color tone measured after the durability test can also be adjusted by the type of the protective films 3 and 4 selected.

From the point of view of adjustment of the orthogonal tone change, the protective films 3 and 4 are preferably films formed of cycloolefin resin, cellulose resin, polyester resin, or acrylic resin. In addition, the protective film 3 positioned on the outermost surface may be provided with a hard coat layer.

In addition, in the color tone adjustment step, the orthogonal color tone measured in the initial state of the polarizing plate 1 and after the durability test is adjusted in a manner that is farther away from the a coordinate axis and the b coordinate axis in the ab chromaticity coordinates. good. In this way, even if the orthogonal hue of the polarizing plate 1 changes before and after the durability test, since the a-coordinate axis and the b-coordinate axis of the ab chromaticity coordinates do not cross the quadrant, no matter how the hue changes, the polarizing plate can be made The streak-like unevenness generated in 1 becomes inconspicuous.

Also, the present invention is not only in the case of manufacturing the above-mentioned polarizing plate 1, but also in the initial state and durable The orthogonal hue measured after the test is also adjusted by setting the hue adjustment step of "the symbol area enclosed by the a-coordinate axis and the b-coordinate axis in the ab chromaticity coordinates does not change", regardless of how the hue changes , can make the streak-like unevenness generated in the manufactured polarizing plate inconspicuous.

[Example]

The effect of the present invention is illustrated by the following examples. In addition, this invention is not limited to the following Example, In the range which does not change the gist of this invention, it can change suitably and implement.

<Example 1>

In embodiment 1, except that the manufacturing device 100 of the polarizing film shown in the 6th figure is to use two cross-linking baths 104 (in order to distinguish, the first one is set as the cross-linking bath 104a, and the second is set as the cross-linking bath 104a, and the second is set as the cross-linking bath 104a. Except for the combined bath 104b), the same manufacturing apparatus as the above-mentioned manufacturing apparatus 100 was used to manufacture a polarizing film, and a protective film was attached to both sides of the obtained polarizing film to manufacture a polarizing plate.

(1) Swelling treatment steps

First, a polyvinyl alcohol film (raw material film) with a thickness of 30 μm (trade name "Kuraray Poval Film VF-PE #3000" manufactured by Kuraray Co., Ltd., average degree of polymerization 2400, degree of saponification 99.9 mol%) was continuously rolled from a raw material roll It was carried while unwinding, and immersed for 30 seconds in a swelling bath added with pure water at 20°C. In this swelling treatment step, the roll-to-roll stretching (longitudinal uniaxial stretching) is carried out by applying a rotational speed difference between the rolls 50 and 51 . The elongation ratio based on the raw material film is 2.5 times.

(2) Dyeing treatment steps

Next, the film passing through the nip roll 51 was immersed for 120 seconds in a 30° C. dyeing bath of pure water/potassium iodide/iodine/boric acid (mass ratio) 100/2/0.01/0.3. Also in this dyeing process, roll-to-roll stretching (longitudinal uniaxial stretching) is performed by applying a rotational speed difference between the rolls 51 and 52 . The stretching ratio based on the film after the swelling treatment step was 1.1 times.

(3) Cross-linking treatment steps

Next, the film passed through the nip roll 52 was immersed for 70 seconds in a 56° C. crosslinking bath 104 a in which pure water/potassium iodide/boric acid (mass ratio) was 100/12/4. Roll-to-roll stretching (longitudinal uniaxial stretching) is performed by applying a rotational speed difference between the rolls and the rolls 52 and 53 provided between the first crosslinking bath 104a and the second crosslinking bath 104b. The elongation ratio based on the film after the dyeing treatment step was 1.9 times.

(4) Complementary color processing steps

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

(5) Washing treatment steps

Next, the film after the second cross-linking treatment was immersed for 5 seconds in the cleaning bath 105 filled with pure water at 5°C.

(6) Drying process step

Next, a polarizing film was produced by passing the film after the cleaning treatment step through a drying oven and heating and drying at 80° C. for 190 seconds. The thickness of the obtained polarizing film was about 12 μm.

(7) Bonding process steps

Next, a water-based adhesive containing 5 parts by mass of polyvinyl alcohol with respect to 100 parts by mass of water was prepared as an adhesive. The protective films shown in Table 1 below were laminated on both sides of the polarizing film produced above using the prepared water-based adhesive. Heat drying was performed in the obtained laminated body, and the adhesive agent was dried, and the polarizing plate was produced. Moreover, the thickness of the adhesive agent layer in the obtained polarizing plate was about 50 nm.

<Measurement of photometrically corrected monomer transmittance>

The photometric correction monomer transmittance (Ty) of the obtained polarizing plate was measured in accordance with "JIS Z 8729" using a spectrophotometer ("V7100" manufactured by JASCO Corporation) with an integrating sphere.

The measurement results are shown in Table 1 below.

<Measurement of surface roughness of polarizer>

Cut the obtained polarizer into small pieces of 10cm×5cm, dip them in 600mL of dichloromethane, and perform ultrasonic treatment at room temperature for 30 minutes, dissolve and remove the pasted first protective film and second protective film .

With respect to the polarizing film from which these protective films have been removed, the surface of the polarizer to which the adhesive is attached is the surface belonging to the front side (the side to which the first protective film is bonded), which is perpendicular to the direction in which it extends. Direction scanning, linear measurement of the surface unevenness of the polarizer attached with the adhesive. Then, from the measurement results, the size of the undulations (height difference between unevennesses) and the interval between unevennesses were calculated. The calculation results are shown in Table 1 below.

Here, the uneven height difference and the uneven interval refer to values calculated as follows.

Concave-convex height difference: Relative to the average line of the surface, the total value of the height of the apex of the highest convex part and the depth of the bottom of the deeper concave part among the two concave parts adjacent to the highest convex part .

Concave-convex interval: the distance between the apex of the highest convex part and the bottom of the deeper concave part among the two concave parts adjacent to the highest convex part, in the parallel direction with respect to the surface average line.

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

Measuring device: Vert Scan (registered trademark) (Model R5500G manufactured by Ryoka System Co., Ltd.)

Objective lens (magnification): 2.5 times

Measuring range: 3700×2800μm

Resolution: 640×480 pixels (pixel)

Measurement mode: wave mode (wave mode)

Surface modification: 4 treatments

<Measurement of hue>

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

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

<Measurement of streaky unevenness>

On the lighting surface of a white backlight module with a brightness of 20000cd/ ^m2 , a polarizing plate A with a photometrically corrected monomer transmittance (Ty) of 41.6% and a photometrically corrected polarization degree (Py) of 99.997 was attached, and placed on it Place a polarizer on it.

In addition, at this time, the first protective film shown in the following Table 1 of the polarizing plate is used as the upper surface, and the transmission axis of the polarizing plate A and the transmission axis of the polarizing plate are perpendicularly intersecting (orthogonal polarization state) place. In this state, stripe-like unevenness was confirmed visually from the first protective film side of the polarizing plate. Streak unevenness was evaluated in the following four steps. The results of this evaluation are shown in Table 1 below.

0: Striped unevenness is not recognized.

1: Streak-like unevenness is hardly recognized.

2: Streak-like unevenness can be slightly recognized.

3: Streak-like unevenness is clearly recognized.

Thereafter, the manufactured polarizing plate was heated at 105° C. for 30 minutes in a dry gas atmosphere. The polarizing plate after heating was confirmed in the same manner as above for streak-like unevenness, and evaluated in the same manner as above. The evaluation results are shown in Table 1 below. In addition, in relation to Example 1, the change in color tone before and after the durability test is shown on the ab chromaticity coordinate diagram in Fig. 7 .

<Example 2>

In Example 2, except that in order to adjust the color tone of the polarizing film, only the cleaning conditions for the polarizing film were changed (specifically, the immersion time was set to 3 seconds), and the rest were produced in the same manner as in Example 1. Polarizer 2. Then, by the same method as in Example 1 above, the photometrically corrected monomer transmittance (Ty) of the obtained polarizing plate, the surface irregularities of the polarizing plate, the color tone change before and after the durability test, and the stripe shape before and after the durability test were measured. Uneven changes. The measurement results are shown in Table 1 below. In addition, about Example 2, what showed the color tone change before and after the endurance test with an ab chromaticity coordinate diagram is shown in FIG. 7.

<Example 3>

(1) Swelling treatment steps

First, a polyvinyl alcohol film (raw material film) with a thickness of 30 μm (trade name "Kuraray Poval Film VF-PE #3000" manufactured by Kuraray Co., Ltd., average degree of polymerization 2400, degree of saponification 99.9 mol%) was continuously rolled from a raw material roll It was conveyed while unwinding, and immersed for 30 seconds in a swelling bath to which 20° C. pure water was added. In this swelling treatment step, the roll-to-roll stretching (longitudinal uniaxial stretching) is performed by applying a rotational speed difference between the rolls 50 and 51 . The elongation ratio based on the raw material film is 2.2 times.

(2) Dyeing treatment steps

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

(3) Cross-linking treatment steps

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

(4) Complementary color processing steps

Next, the membrane after the first cross-linking treatment was immersed for 10 seconds in a 50° C. cross-linking bath 104 b in which pure water/potassium iodide/boric acid (mass ratio) was 100/9/3.9.

(5) Washing treatment steps

Next, the film after the second crosslinking treatment was immersed for 5 seconds in the cleaning bath 105 filled with pure water at 13°C.

(6) Drying process step

Next, a polarizing film was produced by passing the film after the cleaning treatment step through a drying oven and heating and drying at 80° C. for 190 seconds. The thickness of the obtained polarizing film was about 12 μm.

(7) Bonding process steps

Next, protective films shown in the following Table 1 were laminated on both sides of the manufactured 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, and the adhesive was dried to produce a polarizing plate. Moreover, the thickness of the adhesive agent layer in the obtained polarizing plate was about 50 nm.

Then, by the same method as in Example 1 above, the photometrically corrected monomer transmittance (Ty) of the obtained polarizing plate, the surface irregularities of the polarizing plate, the color tone change before and after the durability test, and the stripe shape before and after the durability test were measured. Uneven changes. The measurement results are shown in Table 1 below. In addition, regarding Example 3, those in which color tone changes before and after the durability test are shown on an ab chromaticity coordinate diagram are shown in Fig. 8 .

<Example 4>

In Example 4, a polarizing plate was produced in the same manner as in Example 3 except that the type of the protective film was changed to those shown in Table 1 below. Then, by the same method as in Example 1 above, the photometrically corrected single transmittance (Ty) of the obtained polarizing plate 4, the surface irregularities of the polarizing plate, the color tone change before and after the durability test, and the streaks before and after the durability test were measured. Uneven shape changes. The measurement results are shown in Table 1 below. In addition, regarding Example 4, those in which the change in color tone before and after the durability test is shown on an ab chromaticity coordinate diagram are shown in Fig. 8 .

<Comparative example 1>

In Comparative Example 1, except that in order to adjust the color tone of the polarizing film, only the cleaning conditions for the polarizing film were changed (specifically, the immersion time was set to 3 seconds), and the rest were produced in the same manner as in Example 3. polarizer. Then, by the same method as in Example 1 above, the photometrically corrected monomer transmittance (Ty) of the obtained polarizing plate, the surface irregularities of the polarizing plate, the color tone change before and after the durability test, and the stripe shape before and after the durability test were measured. uneven variation. The measurement results are shown in Table 1 below. In addition, regarding Comparative Example 1, those showing the change in color tone before and after the durability test with an ab chromaticity coordinate diagram are shown in Fig. 8 .

<Comparative example 2>

In Comparative Example 2, except that in order to adjust the color tone of the polarizing film, only the cleaning conditions for the polarizing film were changed (specifically, the immersion time was set to 3 seconds), and the remaining systems were produced in the same manner as in Example 4. plate. Then, by the same method as in Example 1 above, the photometrically corrected monomer transmittance (Ty) of the obtained polarizing plate, the surface irregularities of the polarizing plate, the color tone change before and after the durability test, and the stripe shape before and after the durability test were measured. uneven variation. The measurement results are shown in Table 1 below. In addition, regarding Comparative Example 2, those in which color tone changes before and after the durability test are shown on an ab chromaticity coordinate diagram are shown in Fig. 8 .

<Reference example 1>

As reference example 1, except that in the dyeing process step, the pure water/potassium iodide/iodine/boric acid (mass ratio) is set to 100/2/0.03/0.3, the rest are made in the same way as in Example 1. plate. Then, by the same method as in Example 1 above, the photometrically corrected monomer transmittance (Ty) of the obtained polarizing plate, the surface irregularities of the polarizing plate, the color tone change before and after the durability test, and the stripe shape before and after the durability test were measured. The change in unevenness was measured by the same method as in Example 1 above. The measurement results are shown in Table 1 below. In addition, regarding Reference Example 1, those in which color tone changes before and after the durability test are shown on an ab chromaticity coordinate diagram are shown in Fig. 9 .

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

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

Protective film B: triacetyl cellulose film, thickness 25 μm

Protective film C: Triacetyl cellulose film with UV-curable hard coat, thickness 32μm

Protective film D: Triacetyl cellulose film with UV-curable hard coat (but the UV absorption capacity is different from that of protective film C), thickness 32μm

In addition, in Table 1, the axis where the orthogonal color tone before and after the durability test is the color tone in which the sign area on the ab chromaticity coordinate axis does not change is set to "◯". On the other hand, the orthogonal color tone before and after the durability test is set to "x" on the axis of the color tone in which the symbol area on the ab chromaticity coordinate axis changes.

As shown in Table 1 and Figures 7 to 9, the orthogonal hue of Examples 1 to 4 before and after the durability test is the same as the symbol area enclosed by the ab chromaticity coordinate axis, and the stripes are less uneven. After the durability test, the streaky unevenness does not greatly increase and is good.

On the other hand, in Comparative Examples 1 and 2, the symbol area enclosed by the ab chromaticity coordinate axes of the orthogonal hue system before and after the durability test changed, and after the durability test, the striped unevenness also increased significantly. Also, in Reference Example 1, the polarizing film system having a photometrically corrected single transmittance (Ty) of less than 44% did not visually recognize streaky unevenness.

1‧‧‧Polarizer

2‧‧‧Polarizer

3.4‧‧‧Protective film

Claims (9)

A polarizing plate comprising: a polarizing plate, and a protective film disposed on at least one side of the polarizing plate via an adhesive layer, wherein the transmittance (Ty) of a photometric correction monomer measured in an initial state is 44% or more , the orthogonal hue measured in the initial state and after the durability test is in the ab chromaticity coordinates, and the area between the a coordinate axis and the b coordinate axis does not cross the quadrant. After the aforementioned durability test, it starts at least from the aforementioned initial state , supplied into a dry gas environment, after heating at 105° C. for 30 minutes. The polarizing plate described in claim 1, wherein the polarizing film is a polarizing film having a dichroic pigment adsorbed and oriented on a uniaxially stretched polyvinyl alcohol-based resin film. The polarizing plate as described in claim 1 or 2 of the patent claims, wherein the thickness of the polarizing plate is 3 to 15 μm. The polarizing plate as described in claim 1 or 2 of the patent claims, wherein, when the protective film is removed, the surface of the polarizing plate to which the adhesive is attached has unevenness with a height difference of 80 to 250 nm. The polarizing plate as described in claim 1 or 2 of the patent application, wherein the aforementioned polarizer is an iodine-based polarizer. A display device comprising: a display panel, and the polarizing plate described in any one of items 1 to 5 of the scope of the patent application. A method of manufacturing a polarizing plate, comprising a polarizing plate, and a protective film disposed on at least one side of the polarizing plate via an adhesive layer The manufacturing method of the present invention, which includes: a step of adjusting the color tone, which is to adjust the orthogonality measured in the initial state and after the durability test in such a way that the area between the a-coordinate axis and the b-coordinate axis does not cross the quadrant in the ab chromaticity coordinates. Color tone, after the aforementioned durability test, is at least from the aforementioned initial state, supplied in a dry gas environment, and heated at 105° C. for 30 minutes. The method of manufacturing a polarizing plate according to claim 7 of the patent application, wherein the step of adjusting the color tone is at least adjusting the color tone of the polarizing plate. The method of manufacturing a polarizing plate as described in claim 7 or 8 of the patent claims, wherein the color tone adjustment step is to select the protective film disposed on at least one or both sides of the polarizing plate.

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