KR101828213B1 - Polarizing plate and method for propucing the same and image display device - Google Patents

Abstract

The present invention relates to a polarizing plate comprising a polarizer and a protective film bonded to at least one surface of the polarizer by an adhesive, the polarizing plate comprising: a novel polarizing plate capable of effectively suppressing the appearance of a stripe- And to provide the above objects.
A polarizing plate comprising a polarizer and a protective film bonded to at least one surface of the polarizer by an adhesive, wherein a height difference at the surface of the polarizer to which the adhesive is attached when the protective film is removed is 280 nm or less.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing plate,

The present invention relates to a polarizing plate which can be used for various optical applications and a manufacturing method thereof. The present invention also relates to an image display apparatus having such a polarizing plate.

The polarizing plate is widely used as a polarizing light supply element or the like in an image display apparatus. For such a polarizing plate, for example, a polarizer obtained by subjecting a polyvinyl alcohol-based resin film to stretching, dyeing, crosslinking, drying and the like is suitably employed. Generally, the polarizing plate has a structure in which a protective film is bonded to one or both surfaces of a polarizer using an adhesive.

Conventionally, in a polarizing plate, a stripe-shaped unevenness that is confirmed by the shade of reflected light occurs in some cases. When such a polarizing plate is used in an image display apparatus, image quality is impaired. Therefore, in order to prevent occurrence of stripe- (See Patent Documents 1 to 4). For example, in a polarizing plate in which a protective film is bonded to one or both surfaces of a polarizer (polarizing film) through an adhesive layer, it has been proposed to make the thickness of the adhesive layer 52 nm or less (Patent Document 1). Particularly, in order to prevent wrinkles occurring in the stretching axis direction of the polarizer, the thickness of the polyvinyl alcohol film before stretching is set to 85 占 퐉 or more and the surface roughness in the direction perpendicular to the stretching axis of the polarizer (polarizing film) (Paragraphs 0011 to 0012 of Patent Document 2) or a drying process performed on a polyvinyl alcohol film is carried out in multiple stages based on the roughness, so that the tension of the film at each stage of the drying process Is controlled to be substantially constant, and the tension at the rear end is made to be equal to or smaller than the tension at the front end (Patent Document 3). Further, the neck ratio (= B / A) defined by the width B of the polarizer at the time of bonding the protective film to the width A of the polarizer in the final bath is adjusted to 0.80 or more and 0.95 or less (Paragraph 0019 of Patent Document 4) is also known.

[Patent Document 1] Japanese Patent Application Laid-Open No. 2006-221158 [Patent Document 2] Japanese Unexamined Patent Publication No. 2000-249832 [Patent Document 3] Japanese Unexamined Patent Application Publication No. 2006-189560 [Patent Document 4] JP-A-2002-40247 [Patent Document 5] JP-A-2015-114536

In recent years, the polarizing plate has been made thinner, and it is required to make the polarizer and the protective film constituting the polarizing plate thinner. When the protective film is thinned, occurrence of streaks in the form of streaks is remarkably confirmed. In the above-described conventional method, it is difficult to sufficiently suppress the influence of the stripe-shaped streak on the appearance of the polarizing plate. Under such circumstances, it has been proposed to reduce the shrinkage force when the adhesive layer is hardened (or dried) by making the thickness of the adhesive layer relatively small, thereby suppressing irregularities that may occur on the surface of the protective film Literature 5). However, such a method can reduce the shrinkage force when the adhesive layer is cured, but the line-shaped unevenness may be caused by other factors, and it is more preferable to solve it by other methods.

An object of the present invention is to provide a polarizing plate that includes a polarizer and a protective film bonded to at least one surface of the polarizer by an adhesive and which is capable of effectively suppressing the influence of the stripe- And to provide a polarizing plate and a manufacturing method thereof.

The inventors of the present invention have focused on the problem of the surface irregularities of the polarizer, taking into consideration that the appearance of the polarizer is susceptible to the surface irregularities of the polarizer through a thin protective film, especially when the protective film is thin. As a result of intensive studies, the inventors of the present invention have found that, in the polarizing plate, by making the height difference on the surface of the polarizer having the adhesive attached small, specifically by setting it to 280 nm or less, The inventors of the present invention have obtained the knowledge of the inventor that the present invention can be effectively suppressed.

The present invention includes the following [1] to [5].

[1] A polarizing plate comprising a polarizer and a protective film bonded to at least one surface of the polarizer by an adhesive, wherein a height difference at a surface of the polarizer to which the adhesive is attached when the protective film is removed is 280 nm or less.

[2] The polarizer according to [1], wherein the thickness of the protective film is 85 μm or less.

[3] A method for producing a polarizing plate, comprising a polarizer and a protective film bonded to at least one surface of the polarizer by an adhesive,

A protective film is bonded to at least one surface of the polarizer by an adhesive,

Curing the polarizer to which the protective film is bonded

And a height difference on a surface of the polarizer having the adhesive attached thereto is 280 nm or less after the protective film is bonded and cured by an adhesive.

[4] The method for producing a polarizing plate according to [3], wherein the protective film has a thickness of 85 탆 or less after the protective film is bonded and cured by an adhesive.

[5] An image display device comprising a liquid crystal cell or an organic electroluminescence element and a polarizing plate according to [1] or [2].

According to the present invention, there is provided a polarizing plate comprising a polarizer and a protective film bonded to at least one surface of the polarizer by an adhesive, wherein the polarizing plate is a novel polarizing plate capable of effectively suppressing the influence of the stripe- A polarizing plate and a manufacturing method thereof are provided. Further, according to the present invention, an image display apparatus having such a polarizing plate is provided.

Fig. 1 (a) is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention, and Fig. 1 (b) is a schematic cross-sectional view of a polarizer having an adhesive attached thereto when a protective film is removed from the polarizing plate c) is a conceptual diagram for deriving the elevation difference (undulation magnitude? H) from the result of removing the protective film from the polarizing plate and line-measuring the surface irregularities of the polarizer having the adhesive obtained therefrom. The average line of the surface is indicated by a dotted line , And a horizontal or vertical auxiliary line is indicated by a dot-dash line.
Fig. 2 shows a schematic sectional view of a polarizing plate according to still another embodiment of the present invention.
3 is a schematic cross-sectional view of a polarizing plate according to another embodiment of the present invention.
4 is a schematic cross-sectional view of an image display apparatus according to an embodiment of the present invention.
5 is a schematic sectional view of an apparatus for explaining a method of producing a polarizing film usable in a polarizer in the polarizing plate of the present invention.
6 shows the results of line measurement of the surface unevenness of the front side of the polarizer having the adhesive after the first protective film and the second protective film were removed from the polarizer obtained in Example 1. Fig.
7 shows the results of line measurement of the surface unevenness on the front side of the polarizer with the adhesive after removing the first protective film and the second protective film from the polarizer obtained in Example 2. Fig.
8 shows the results of line measurement of the surface irregularities on the front side of the polarizer having the adhesive after the first protective film and the second protective film were removed from the polarizing plate obtained in Example 3. Fig.
Fig. 9 shows the results of line measurement of the surface irregularities on the front side of the polarizer having the adhesive after the first protective film and the second protective film were removed from the polarizer obtained in Example 4. Fig.
10 shows the results of line measurement of the surface unevenness on the front side of the polarizer having the adhesive after removing the first protective film and the second protective film from the polarizing plate obtained in Comparative Example 1. Fig.
11 shows the results of line measurement of surface unevenness on the front side of a polarizer having an adhesive after removing the first protective film and the second protective film from the polarizing plate obtained in Comparative Example 2. Fig.

Hereinafter, a polarizing plate, a manufacturing method thereof, and an image display apparatus according to the present invention are described in detail, but the present invention is not limited to these embodiments.

The polarizing plate of the present invention comprises a polarizer and a protective film bonded to at least one side of the polarizer by an adhesive (or laminated via an adhesive). For example, in one embodiment of the present invention, as shown in Fig. 1A, the polarizing plate 110 includes a polarizer 1, a first protective film (first protective film) 3 and the second protective film 5 may be included. However, the constitution (stacking order and the like) of the polarizing plate of the present invention is not limited to these embodiments and can be any structure as long as it includes a polarizer and a protective film bonded to at least one surface of the polarizer by an adhesive have.

The "polarizer" in the present invention is a member having a function of converting light such as natural light into linearly polarized light and has a transmission axis and an absorption axis. The transmission axis direction of the polarizer is understood as a vibration direction of the transmitted light when natural light is transmitted through the polarizer. On the other hand, the absorption axis of the polarizer is orthogonal to the transmission axis of the polarizer. In general, the polarizer may be a stretched film, the absorption axis direction of the polarizer may coincide with the stretching direction MD, and the transmission axis direction of the polarizer may coincide with the width direction TD.

The polarizing plate of the present invention has a height difference (? H, hereinafter simply referred to as " undulation depth ") of 280 nm or less on the surface of the polarizer having the adhesive when the protective film is removed. More specifically, the degree of undulation (DELTA H) is determined by scanning the surface of the polarizer having the adhesive attached thereto in the direction perpendicular to the line direction when the protective film is removed from the polarizing plate, (H ₁ ) at the vertex of the highest convex portion with respect to the average line (indicated by a dotted line in the figure) of the surface as shown in Fig. 1 (c) And the depth (H ₂ ) at the bottom of the concave portion on the deeper side among the two concave portions adjacent to the highest convex portion, and satisfies the following expression (1).

? H = H ₁ + H _2? 280 nm (1)

H ₁ : height of vertex of highest convex portion (nm)

H ₂ : the depth (nm) at the bottom of the concave portion on the deeper side among the two concave portions adjacent to the highest convex portion,

The term " line direction " in the present invention means a direction parallel to the strip-shaped surface unevenness of the polarizer to which the adhesive is attached, and is generally a direction coinciding with the stretching direction MD.

In the present invention, it is important not to evaluate the surface state of the polarizer before bonding the protective film, but to evaluate the surface state of the polarizer after bonding and curing the protective film with an adhesive. Therefore, when the protective film is removed from the polarizing plate (Undulation amount) on the surface of the polarizer having the adhesive attached thereto. The method of removing the protective film from the polarizing plate may be any appropriate method as long as the level difference on the surface of the polarizer to which the adhesive is adhered can be held substantially in the state in which the polarizing plate is formed. More specifically, although the protective film can be dissolved, a solvent in which the adhesive and the polarizer are not substantially dissolved can be used to immerse the polarizing plate in such a solvent, perform ultrasonic treatment and / or agitation, etc., The film may be dissolved and removed to expose the surface of the polarizer having the adhesive.

In the present invention, the height difference (the size of undulation) on the surface of the polarizer having the adhesive is 280 nm or less, so that the stripe-shaped unevenness appearing in the polarizing plate as a shade of the reflected light is not easily visible, And this good polarizing plate can be obtained. The size of the undulations may be 280 nm or less, for example, 250 nm or less, preferably 230 nm or less. The lower limit of the size of the undulation is not particularly limited, but the size of the undulation can be, for example, 10 nm or more, and typically 50 nm or more. The present invention is not limited to this, but from the in-plane distance between the convex portion and the concave portion adjacent to each other on the surface of the polarizer having the adhesive, typically from the measurement results described above, Between the vertex of the highest convex portion and the bottom portion of the concave portion on the deeper side among the two concave portions adjacent to the highest convex portion with respect to the average line of the surface (indicated by a dotted line in the figure) (Hereinafter, simply referred to as " inter-irregularity distance ") in a direction parallel to the average line of the cross-sectional area may be, for example, 300 to 800 m.

The reason for setting the size of the undulation to 280 nm or less is to reduce the surface irregularities of the polarizer itself (the polarizer before bonding the protective foams by the adhesive) by controlling the conditions (in particular, drying conditions) , And then the amount of the adhesive applied to the surface of the polarizer is increased to increase the inflow of the adhesive (see Fig. 1 (b)) to the concave portion of the surface irregularities of the polarizer itself, Can be achieved. Fig. 1 (b) schematically shows the introduction of an adhesive into the concave portion of the surface irregularities of the polarizer itself (Fig. 1 (a) and Figs. 2 to 4 Note that the adhesive is omitted.

When the first protective film 3 and the second protective film 5 are laminated (bonded) on both surfaces of the polarizer 1 as shown in Fig. 1A, the polarizing plate of the present invention has the front , The polarizer having the adhesive disposed thereon when the protective film located on at least one of the side (on the viewer side in the case of applying to the image display apparatus) and the rear side (on the display apparatus side in the case of applying to the image display apparatus) (The size of the undulation) on the surface of the substrate W may be within the above range. Although it is not essential to the present invention, in the case where the protective film is removed on both the front side and the rear side, the height difference (the size of the undulation) on the surface of the polarizer with the adhesive placed thereunder is within the above range Is more preferable.

For example, in one embodiment of the present invention, as shown in Fig. 1 (b), at least one of the first protective film 3 located on the front side and the second protective film 5 located on the rear side A difference in height at the surface of the polarizer 1 to which the adhesive 2 is adhered and a difference in the adhesive 4 between the adhesive 4 and the adhesive 2 are shown in Fig. 1 (b) At least one of the height differences on the surface of the polarizer 1 may be within the above range. It is preferable that the height difference on the surface of the polarizer 1 on which the adhesive 2 is adhered is in the above range when the first protective film 3 located on the front side which is the viewer side is removed, The difference in level difference on the surface of the polarizer 1 on which the adhesive 4 is adhered when the second protective film 5 located on the rear side is removed is also within the above range And the high level difference on both surfaces of the polarizer 1 to which the polarizing plate 4 is attached is in the above range).

In order to reduce the size of the finally obtained relief (that is, the height difference on the surface of the polarizer with the adhesive), it is preferable that the height difference on the surface of the polarizer itself is smaller. The difference in height on the surface of the polarizer itself may be considered to be substantially equal to the height difference on the surface of the polarizer before bonding the protective film with the adhesive, and is, for example, 400 nm or less, preferably 350 nm or less . The lower limit of the height difference on the surface of the polarizer is not particularly limited, but may be 5 nm or more, for example. The height difference on the surface of the polarizer itself is determined by scanning the surface of the polarizer in the direction perpendicular to the line direction as in the case of the difference in height (undulations) on the surface of the polarizer with the adhesive attached thereto, From the measurement results, it was found from the measurement results that the height at the vertex of the highest convex portion and the height at the bottom portion of the concave portion deeper than the two concave portions adjacent to the highest convex portion, And the depth of the light-shielding film.

The thickness of the polarizer is preferably thin from the viewpoint of thinning of the polarizing plate, but it can be appropriately set in accordance with the use of the polarizing plate and the like. The thickness of the polarizer may be, for example, not more than 35 占 퐉, particularly not more than 20 占 퐉, particularly not more than 15 占 퐉, for example, not less than 1 占 퐉, particularly not less than 3 占 퐉. The thickness of the polarizer in the polarizing plate may be considered to be substantially equal to the thickness of the polarizer after the protective film is bonded and cured by an adhesive.

The thickness of the protective film is preferably thin from the viewpoint of thinning of the polarizing plate, but may be suitably set in accordance with the use of the polarizing plate or the like. The thickness of the protective film may be, for example, 85 占 퐉 or less, particularly 50 占 퐉 or less, particularly 30 占 퐉 or less. INDUSTRIAL APPLICABILITY According to the present invention, even when a relatively thin protective film is applied, it is possible to effectively suppress the influence on the appearance due to the stripe-shaped unevenness. On the other hand, the thickness of such a protective film is preferably such that a certain degree of strength can be ensured from the viewpoint of workability, and for example, it may be 5 占 퐉 or more, particularly 10 占 퐉 or more. The thickness of the protective film in the polarizing plate may be considered to be substantially the same as the thickness of the protective film after curing the protective film by bonding with an adhesive.

The thickness of the adhesive (or adhesive layer) is set such that the adhesive flows into the recesses of the surface irregularities of the polarizer itself, and the size of the undulation (which can be understood as the total apparent surface irregularities of the polarizer and the adhesive) It is preferable that the size is as small as possible. The thickness of the adhesive may be 20 nm or more, for example, 40 nm or more. On the other hand, the thickness of such an adhesive may be such that it is not excessively large in terms of production cost or the like, and may be, for example, 1000 nm or less, particularly 500 nm or less, particularly 300 nm or less. The thickness of the adhesive (adhesive layer) in the polarizing plate may be considered to be substantially equal to the thickness of the adhesive (adhesive layer) after the protective film is bonded and cured by the adhesive.

The polarizing plate of the present invention is also characterized in that a polarizer 1 of at least one protective film (second protective film 5 in the illustrated embodiment), for example, the polarizing plate 111 shown in Fig. 2, , The pressure-sensitive adhesive layer 7 may be laminated on the surface opposite to the pressure-sensitive adhesive layer 7, and the pressure-sensitive adhesive layer 7 may or may not have a release layer (not shown) on the outermost surface. The second protective film 5 is not essential, but other functional layers such as a retardation film and a brightness enhancement film may be applied instead of the second protective film 5, for example. 3, the polarizing plate 112 includes a polarizer 1, a protective film 3 bonded to one surface of the polarizer 1 with an adhesive, And a pressure-sensitive adhesive layer (7) laminated on the other surface. The thickness of the pressure-sensitive adhesive layer is usually about 3 to 100 占 퐉, and preferably 5 to 50 占 퐉.

As shown in Figs. 2 and 3, the pressure-sensitive adhesive layer 7 (which may be included in the polarizing plate of the present invention) is not essential to the present invention (if the release layer is present on the surface thereof, ), And polarizing plates 111 and 112 to other members.

For example, the polarizing plate 111 can be bonded to the other member 115 through the pressure-sensitive adhesive layer 7 as shown in Fig. 4 to constitute the image display apparatus 120. [ The other member is not particularly limited, but may be, for example, a liquid crystal cell, an organic electroluminescence element, or the like. Typically, a polarizing plate may be bonded to a glass plate constituting these members through an adhesive layer. An image display apparatus is called a liquid crystal display apparatus in the case of a liquid crystal cell and an organic electroluminescence display apparatus in the case of an organic electroluminescence element. However, the image display device of the present invention is not limited to such an embodiment, but may have any suitable configuration as long as it includes a liquid crystal cell or an organic electroluminescence element and the polarizing plate of the present invention.

Hereinafter, the polarizing plate and the image display apparatus of the present invention will be described in more detail with reference to their manufacturing methods.

<Polarizer>

The polarizer may be a polyvinyl alcohol polarizing film in which a dichroic dye (iodine or a dichroic dye) is adsorbed and aligned on a uniaxially stretched polyvinyl alcohol resin film.

The polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin film is usually obtained by saponifying a polyvinyl acetate-based resin. The degree of saponification is usually about 85 mol% or more, preferably about 90 mol% or more, and more preferably about 99 mol% or more. The polyvinyl acetate resin may be, for example, a polyvinyl acetate which is a homopolymer of vinyl acetate, a copolymer of vinyl acetate and other monomers copolymerizable therewith, and the like. Examples of other copolymerizable monomers include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of polymerization of the polyvinyl alcohol-based resin is usually about 1000 to 10000, and preferably about 1500 to 5000. These polyvinyl alcohol resins may be modified, and examples thereof include polyvinyl formal modified with aldehydes, polyvinyl acetal, polyvinyl butyral, and the like.

&Lt; Polarizing Film Production Method >

The polarizing film may be formed by the following steps:

A swelling treatment step of immersing the polyvinyl alcohol-based resin film in a swelling bath,

A dyeing treatment step of immersing the film after the swelling treatment step in a dyeing bath,

A crosslinking treatment step in which the film after the dyeing treatment step is immersed in a crosslinking bath,

A stretching treatment step of subjecting the film to uniaxial stretching treatment and

Drying process for drying film

And the like.

More specifically, the polarizing film is made of, for example, an elongated unstretched polyvinyl alcohol based resin film (original film) as a starting material, and continuously transporting the polarizing film along a film transport path of the polarizing film producing apparatus It can be continuously produced as a long polarizing film.

The predetermined treatment step includes a swelling treatment step of immersing the original film in a swelling bath, a dyeing treatment step of immersing the film after the swelling treatment step in a dyeing bath, and a crosslinking treatment step of immersing the film after the dyeing treatment step in a crosslinking bath can do. In addition, the uniaxial stretching treatment is carried out either wet or dry during these series of treatment steps (that is, before and / or after any one or more treatment steps). Thereafter, the obtained film is subjected to a drying treatment. If necessary, other treatment steps may be added.

Hereinafter, a method for producing a polarizing film usable in the polarizer will be described in more detail with reference to FIG. The polarizing film producing apparatus shown in Fig. 5 is a device in which a disc (unstretched) film 20 made of a polyvinyl alcohol-based resin is successively unwound from a disc roll 11 and conveyed along a film conveying path, The dyeing bath 14, the crosslinking bath 17 and the cleansing bath 19 provided on the surface of the drying furnace 21 and then passing through the drying furnace 21. The obtained polarizing film 10 can be transported, for example, as it is in the next polarizing plate producing step (a step of bonding a protective film to one side or both sides of the polarizing film 10). The arrows in Fig. 5 indicate the transport direction of the film.

5 shows an example in which a set of each of the swelling bath 13, the dye bath 14, the crosslinking bath 17 and the cleansing bath 19 is provided. However, if necessary, any one of the treatment baths The bath containing the treatment liquid for treating the polyvinyl alcohol based resin film provided on the film transport path, such as the dyeing bath 14, the crosslinking bath 17 and the cleansing bath 19, Two or more sets may also be provided.

The film transport path of the polarizing film producing apparatus includes, in addition to the above treatment bath, guide rolls 30 to 41 for supporting the film to be transported or capable of further changing the film transport direction, or for pressing and holding the transported film, Or by arranging the nip rolls 50 to 55 capable of further changing the film transport direction at appropriate positions. The guide roll and the nip roll can be disposed before and after each treatment bath and in the treatment bath, whereby the introduction and immersion of the film in the treatment bath and the withdrawal from the treatment bath can be performed (see Fig. 5). For example, by providing at least one guide roll in each treatment bath and transporting the film along these guide rolls, the film can be immersed in each treatment bath.

5, the nip rolls (nip rolls 50 to 54) are arranged in front of and behind the respective processing baths, and accordingly, in the at least one processing bath, A difference in peripheral speed) between the rolls of the rolls, thereby performing roll-to-roll stretching in which longitudinal uniaxial stretching is performed. Hereinafter, each processing step will be described.

(Swelling treatment)

The swelling process is performed for removing foreign substances on the surface of the original film 20, removing the plasticizer in the original film 20, imparting easiness of dyeing, and plasticizing the original film 20. The processing conditions are determined within a range that can achieve the above object and within a range that does not cause problems such as extreme melting or devitrification of the original film 20.

The original film 20 may be an unoriented polyvinyl alcohol based resin film having a thickness of 65 占 퐉 or less, preferably about 10 to 50 占 퐉, and more preferably about 10 to 35 占 퐉. The original film 20 is normally prepared as a roll (wound product) of a long unoriented polyvinyl alcohol based resin film. However, the original film 20 may be a stretched film obtained by previously performing uniaxial stretching treatment in a gas before the swelling treatment step.

5, the swelling process is carried out by conveying the original film 20 along the film conveyance path constructed by the guide rolls 30 to 32 and the nip roll 50 while continuously unwinding the original roll 20 from the original roll 11 , And immersing the original film 20 in the swelling bath 13 (treatment liquid accommodated in the swelling bath) for a predetermined time and withdrawing it continuously. It is also possible to perform the uniaxial stretching process in the swirl bath 13 by using the peripheral speed difference between the nip roll 50 and the nip roll 51. [

In addition to pure water, boric acid (Japanese Unexamined Patent Publication No. 10-153709), chloride (Japanese Unexamined Patent Publication No. 06-281816), inorganic acid, inorganic salt, water-soluble organic solvent, It is also possible to use an aqueous solution added in the range of 0.01 to 10% by weight.

When the original film 20 is an unstretched film, the temperature of the swelling bath 13 is, for example, about 10 to 50 占 폚, preferably about 10 to 40 占 폚, and more preferably about 15 to 30 占 폚. The immersion time of the original film 10 is preferably about 10 to 300 seconds, more preferably about 20 to 200 seconds. When the polyvinyl alcohol based resin film stretched in advance in the gas is swelled, the temperature of the swelling bath 13 is, for example, about 20 to 70 캜, preferably about 30 to 60 캜. The immersion time of the film is preferably about 30 to 300 seconds, more preferably about 60 to 240 seconds.

In the swelling process, there is a problem that the original film 20 swells in the width direction and wrinkles occur in the film. As a means for transporting the film while removing the wrinkles, a roll having a widening function such as an expander roll, a spiral roll, and a crown roll may be used for the guide rolls 30, 31 and / or 32, Or using other widening devices such as bars, tenter clips, and the like. Another means for suppressing the occurrence of wrinkles is to perform stretching treatment.

In the swelling process, since the film swells and expands even in the transport direction of the film, when the film is not actively stretched, in order to eliminate the looseness of the film in the transport direction, for example, It is preferable to take measures such as controlling the speed of the first and second motors 50 and 51. Further, in order to stabilize the film transportation in the swelling bath 13, the water flow in the swelling bath 13 may be controlled by an underwater shower, an EPC apparatus (Edge Position Control apparatus: detecting the end of the film, Or the like) may be used in combination.

5, the film drawn out from the swelling bath 13 passes through the guide roll 32 and the nip roll 51 in turn, and is introduced into the dyeing bath 14. In the example shown in Fig.

(Dyeing treatment)

The dyeing treatment is carried out for the purpose of adsorbing and orienting the dichroic dye to the polyvinyl alcohol-based resin film after the swelling treatment. The treatment conditions are determined within a range in which the above object can be achieved, and within a range in which problems such as extreme melting or disintegration of the film do not occur. 5, the dyeing process is carried out along the film transport path established by the guide rolls 33 to 35 and the nip roll 51, and the film after the swelling process is transferred to the dyeing bath 14 ) For a predetermined period of time, and subsequently withdrawing it. In order to enhance the dyeability of the dichroic dye, the film provided in the dyeing treatment step is preferably a film subjected to uniaxial stretching treatment at least to some extent, or in place of uniaxial stretching treatment before dyeing treatment or uniaxial stretching treatment before dyeing treatment In addition, it is preferable to perform uniaxial stretching treatment at the time of dyeing treatment.

When iodine is used as the dichroic dye, an aqueous solution having iodine / potassium iodide / water = about 0.003 to 0.3 / about 0.1 to 10/100 at a concentration of, for example, a weight ratio can be used for the dyeing bath 14. Instead of potassium iodide, other iodides such as zinc iodide may be used, or potassium iodide and other iodides may be used in combination. Further, compounds other than iodide such as boric acid, zinc chloride, cobalt chloride, etc. may be coexistent. When boric acid is added, it is distinguished from a crosslinking treatment to be described later in that it contains iodine. If the aqueous solution contains about 0.003 part by weight or more of iodine with respect to 100 parts by weight of water, it is regarded as a dyeing bath 14 . The temperature of the dyeing bath 14 at the time of immersing the film is usually about 10 to 45 占 폚, preferably 10 to 40 占 폚, more preferably 20 to 35 占 폚, 600 seconds, preferably 60 to 300 seconds.

When a water-soluble dichroic dye is used as the dichroic dye, for example, an aqueous solution having a dichroic dye / water concentration of about 0.001 to 0.1 / 100 in a concentration by weight ratio can be used for the dyeing bath 14. The dyeing bath 14 may be coexisted with a dyeing aid or the like, and may contain an inorganic salt such as sodium sulfate or a surfactant. The dichroic dye may be used alone, or two or more dichroic dyes may be used in combination. The temperature of the dyeing bath 14 at the time of immersing the film is, for example, about 20 to 80 캜, preferably 30 to 70 캜, and the immersion time of the film is usually about 30 to 600 seconds, preferably 60 to 300 Seconds.

As described above, in the dyeing treatment step, uniaxial stretching of the film can be performed in the dyeing bath 14. The uniaxial stretching of the film can be performed by a method such that the main speed difference is provided between the nip roll 51 and the nip roll 52 arranged before and after the dyeing bath 14.

In the dyeing process, as in the swelling process, the guide rolls 33, 34 and / or 35 are provided with widening functions such as an expander roll, a spiral roll, and a crown roll in order to transport the polyvinyl alcohol- Or other widening devices such as cross guiders, bend bars, tenter clips or the like. Another means for suppressing the generation of wrinkles is to perform the stretching treatment in the same manner as the swelling treatment.

In the example shown in Fig. 5, the film drawn out from the dyeing bath 14 is introduced into the crosslinking bath 17 through the guide roll 35 and the nip roll 52 in order.

(Crosslinking treatment)

The crosslinking treatment is a treatment for the purpose of, for example, water resistance by cross-linking or color adjustment (to prevent the film from becoming blue). 5, the cross-linking treatment is carried out along the film transport path established by the guide rolls 36 to 38 and the nip roll 52, and the cross-linking treatment is carried out in the cross-linking bath 17 (treatment liquid accommodated in the cross- The film can be immersed for a predetermined time, and subsequently taken out.

The crosslinking bath 17 may 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 crosslinking bath 17 preferably contains iodide in addition to boric acid, and the amount thereof may be, for example, 1 to 30 parts by weight relative to 100 parts by weight of water . Examples of the iodide include potassium iodide and zinc iodide. Further, compounds other than iodide such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate and the like may be coexistent.

In the crosslinking treatment, the concentration of the crosslinking agent (such as boric acid) and the iodide and the temperature of the crosslinking bath can be appropriately changed depending on the purpose. For example, in the case where the purpose of the crosslinking treatment is water resistance by crosslinking, and the swell treatment, the dyeing treatment and the crosslinking treatment are performed in this order on the unstretched polyvinyl alcohol resin film, the crosslinking agent- And may be an aqueous solution of boric acid / iodide / water = 3 to 10/1 to 20/100 by weight. If necessary, other crosslinking agents such as glyoxal or glutaraldehyde may be used instead of boric acid, or boric acid and another crosslinking agent may be used in combination. The temperature of the crosslinking bath at the time of immersing the film is usually about 50 to 70 DEG C, preferably 53 to 65 DEG C, and the immersion time of the film is usually about 10 to 600 seconds, preferably 20 to 300 seconds, Preferably 20 to 200 seconds. On the other hand, when the polyvinyl alcohol-based resin film that has been stretched in advance is subjected to the dyeing treatment and the crosslinking treatment in this order, the temperature of the crosslinking bath is usually about 50 to 85 캜, preferably 55 to 80 캜.

In the crosslinking treatment for the purpose of color adjustment, for example, when iodine is used as the dichroic dye, a crosslinking bath having a concentration of boric acid / iodide / water = 1 to 5/3 to 30/100 in terms of the weight ratio can be used. The temperature of the crosslinking bath at the time of immersing the film is usually about 10 to 45 DEG C, and the immersing time of the film is usually about 1 to 300 seconds, preferably 2 to 100 seconds.

The crosslinking treatment may be carried out plural times, usually 2 to 5 times. In this case, the composition and temperature of each crosslinking bath to be used may be the same or different if they are within the above-mentioned range. The cross-linking treatment for water resistance by cross-linking and the cross-linking treatment for color adjustment may be performed in a plurality of steps, respectively. However, the crosslinking treatment for the purpose of color adjustment is optional and may be omitted.

It is also possible to perform the uniaxial stretching process in the crosslinking bath 17 by using the peripheral speed difference between the nip roll 52 and the nip roll 53. [

In the crosslinking treatment, as in the case of the swelling treatment, a widening function such as an expander roll, a spiral roll, and a crown roll is applied to the guide rolls 36, 37 and / or 38 in order to transport the polyvinyl alcohol- Or other widening devices such as cross guiders, bend bars, tenter clips or the like. Another means for suppressing the generation of wrinkles is to perform the stretching treatment in the same manner as the swelling treatment.

In the example shown in Fig. 5, the film drawn out from the crosslinking bath 17 passes through the guide roll 38 and the nip roll 53 in order, and is introduced into the cleansing bath 19.

(Cleaning treatment)

And a cleaning treatment step after the crosslinking treatment step. The cleaning treatment is carried out for the purpose of removing excess boric acid or iodine adhered to the polyvinyl alcohol-based resin film. The cleaning treatment can be carried out, for example, by immersing a crosslinked polyvinyl alcohol resin film in a cleansing bath 19 (water), spraying water to the film as a shower, or using them in combination.

Fig. 5 shows an example in which the polyvinyl alcohol-based resin film is immersed in a cleansing bath 19 to perform a cleaning treatment. The temperature of the cleansing bath 19 in the cleansing treatment is usually about 2 to 40 DEG C, and the immersion time of the film is usually about 2 to 120 seconds.

Also in the cleaning process, the rolls having the widening function such as the expander roll, the spiral roll, and the crown roll may be provided on the guide rolls 39, 40 and / or 41 for the purpose of transporting the polyvinyl alcohol- Or using other widening devices such as cross guiders, bend bars, tenter clips or the like. Further, in the cleaning treatment, a stretching treatment may be performed to suppress the occurrence of wrinkles.

(Drawing process)

As described above, the original film 20 is uniaxially stretched in a wet or dry manner during the series of processing steps (that is, before and / or after any one or more processing steps). A specific method of the uniaxial stretching treatment is, for example, a roll-to-roll stretching in which longitudinal uniaxial stretching is carried out with a main speed difference between two nip rolls constituting the film transport path (for example, two nip rolls arranged before and after the treatment bath) The thermal roll drawing, the tenter stretching, and the like described in JP-A-2731813, and is preferably a roll-to-roll stretching. The uniaxial stretching process can be performed a plurality of times until the polarizing film 10 is obtained from the original film 20. As described above, the stretching treatment is also advantageous in suppressing the occurrence of wrinkles of the film.

The final cumulative stretching magnification of the polarizing film 10 based on the original film 20 (polyvinyl alcohol based resin film not drawn) is usually about 4.5 to 7 times, preferably 5 to 6.5 times.

(Dry treatment)

After the cleaning treatment, the polyvinyl alcohol based resin film is dried. The drying of the film is not particularly limited, but can be carried out using the drying furnace 21 as in the example shown in Fig. 5, and more specifically, for example, using a hot-air drier or a far-infrared heater. In the present invention, the drying conditions are important because they influence the finally obtained undulation size (i.e., the height difference on the surface of the polarizer to which the adhesive is attached). The drying temperature is, for example, 20 to 100 DEG C, particularly 20 to 80 DEG C, and the drying time is 10 to 600 seconds, particularly 30 to 300 seconds.

(Other processing steps)

Processing other than the above-described processing may be added. Examples of the treatment that can be added include an immersion treatment (complementary treatment) in an iodide aqueous solution containing no boric acid, which is performed after the crosslinking treatment, an immersion treatment in an aqueous solution containing zinc chloride or the like without containing boric acid Processing).

The polarizer can be obtained by appropriately cutting the polarizing film 10, and may be a rectangular shape or a long film. As described above, the method of manufacturing the polarizing film 10 usable in the polarizer has been described, but it is also possible to manufacture the polarizing film or the polarizer by other methods.

The difference in height on the surface of the polarizer before bonding the protective film with an adhesive is, for example, 400 nm or less, preferably 350 nm or less, and is not limited to the present invention, but may be 5 nm or more, for example.

&Lt; Polarizing plate production method >

The polarizing plate according to the present invention can be obtained by, for example, obtaining a polarizer by the above-mentioned method,

A bonding treatment step of bonding a protective film to at least one surface of the polarizer by an adhesive, and

A curing treatment process for curing the polarizer to which the protective film is bonded

And the like.

As the protective film, for example, a film made of an acetylcellulose-based resin such as triacetylcellulose or diacetylcellulose; Films made of a polyester resin such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; Polycarbonate resin film, cycloolefin resin film; Acrylic resin film; And a film made of a chain olefin resin of a polypropylene type resin. When the polarizing plate has the first protective film and the second protective film, they may be a film made of the same kind of resin or a film made of different kinds of resins.

(Preliminary processing)

In order to improve the adhesiveness between the polarizer (polarizing film) and the protective film (the first protective film and the second protective film in the case where it is present, hereinafter the same), before the bonding, , A corona treatment, a flame treatment, a plasma treatment, an ultraviolet irradiation, a primer coating treatment, a saponification treatment and the like.

(Joining process)

A protective film is bonded to at least one surface of the polarizer by an adhesive. Examples of the adhesive used for bonding the polarizer and the protective film include an aqueous solution of a polyvinyl alcohol resin or an aqueous adhesive to which a crosslinking agent is blended and an aqueous adhesive such as a urethane emulsion adhesive.

In the present invention, the bonding condition is important because it affects the finally obtained undulation size (i.e., the height difference on the surface of the polarizer to which the adhesive is attached). The bonding conditions are set so that the amount of the adhesive applied to the surface of the polarizer is relatively large. When an aqueous adhesive is used, the main component concentration of the adhesive is about 0.5 to 20 parts by weight based on 100 parts by weight of water.

(Curing treatment)

Thereafter, the polarizer attached to at least one surface of the protective film is cured. In the case of using an aqueous adhesive, after the film is bonded, the adhesive layer is cured by drying treatment. The drying temperature is, for example, 30 to 100 占 폚, particularly 40 to 90 占 폚, and the drying time is 30 to 1200 seconds, particularly 60 to 900 seconds. After drying, it may be cured at a room temperature or a slightly higher temperature, for example, at a temperature of about 20 to 45 캜.

The polarizing plate is manufactured through the above process. Like the polarizer, the polarizing plate may have a rectangular shape or a long film. The quadrangular polarizer may be obtained, for example, by cutting a long polarizer. The long polarizing plate according to the present invention may be a polarizing plate roll (wound product).

The thickness of the polarizer may be, for example, 35 mu m or less, particularly 20 mu m or less, particularly 15 mu m or less, for example, 1 mu m or more, particularly 3 mu m or more after bonding and curing the protective film with an adhesive.

The thickness of the protective film may be, for example, 85 占 퐉 or less, particularly 50 占 퐉 or less, particularly 30 占 퐉 or less, for example, 5 占 퐉 or more, particularly 10 占 퐉 or more after the protective film is bonded and cured by an adhesive.

The thickness of the adhesive (adhesive layer) may be, for example, 20 nm or more, particularly 40 nm or more, such as 1000 nm or less, particularly 500 nm or less, especially 300 nm or less after bonding and curing the protective film with an adhesive.

As shown in Figs. 2 and 3, when a pressure-sensitive adhesive layer is used, it can be laminated to a protective film or a polarizer by its own adhesiveness. More specifically, when a release layer is present on the laminate surface of the pressure-sensitive adhesive layer, the release layer may be peeled off, and the pressure-sensitive adhesive layer may be laminated to the protective film or polarizer.

As the pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer, any conventionally known pressure-sensitive adhesive may be appropriately selected, and any adhesive may be used so long as it does not cause peeling or the like under an environment in which the polarizing plate can be exposed. Specific examples include an acrylic pressure-sensitive adhesive, a silicone pressure-sensitive adhesive, and a rubber pressure-sensitive adhesive. From the viewpoints of transparency, weather resistance, heat resistance and workability, an acrylic pressure-sensitive adhesive is particularly preferable.

The pressure-sensitive adhesive may contain a filler, a pigment, a colorant, a filler, an antioxidant, an ultraviolet absorber, an antistatic agent, a silane coupling agent, and the like, which are composed of a tackifier, plasticizer, glass fiber, glass bead, metal powder, Various additives may be appropriately blended.

The polarizing plate of the present invention has a visibility-corrected transmittance of usually 42.0% or more, preferably 42.5% or more, and more preferably 43.0% or more. The visual sensitivity correction polarization degree is usually 99.8% or more, preferably 99.9% or more, and more preferably 99.99% or more. The visibility-corrected transmittance and visibility-correcting polarization degree can be measured using, for example, a spectrophotometer or the like.

&Lt; Fabrication of Image Display Device >

An image display device can be obtained by bonding the polarizing plate produced as described above to another member (optical member) through the pressure-sensitive adhesive layer. More specifically, when a peeling layer is present on the bonding surface of the pressure-sensitive adhesive layer, the peeling layer may be peeled off and the polarizing plate may be bonded to another member by adhesiveness of the pressure-sensitive adhesive layer. For example, a liquid crystal display device can be obtained by bonding a polarizing plate to a liquid crystal cell, and an organic electroluminescence display device can be obtained by bonding to an organic electroluminescence device. A known liquid crystal cell or an organic electroluminescence device to which a polarizing plate is bonded may be applied. Among the liquid crystal cell or the organic electroluminescence device, the component to which the polarizing plate is directly bonded is typically a glass plate.

However, it should be noted that the use of the polarizing plate of the present invention is not limited to the image display apparatus, but can be used for various optical applications.

Example

The present invention has been described in more detail with reference to the following examples, but the present invention is not limited by these examples.

&Lt; Example 1 >

Except that three crosslinking baths 17 (hereinafter referred to as first crosslinking bath 17a, second crosslinking bath 17b, and third crosslinking bath 17c) were used, A polarizing film was produced using the same apparatus as that of the apparatus, and a polarizing plate having a protective film bonded to both surfaces of the polarizing film 10 was produced using the obtained polarizing film. All the guide rolls 30 to 41 in Fig. 5 use flat rolls.

(1) swelling treatment process

(Trade name: &quot; Kurarupo Foot Film VF-PE # 3000 &quot;, manufactured by Kuraray Co., Ltd., degree of polymerization: 2400, degree of saponification: 99.9 mol% or more) having a thickness of 30 탆 and a width of 450 mm Was continuously unwound from the disk roll 11 and transported, and immersed in a swelling bath 13 containing pure water at 20 DEG C for 30 seconds. In this swelling treatment, roll stretching (longitudinal uniaxial stretching) is performed in such a manner that the film width immediately after being drawn out from the swelling bath 13 is equal to or smaller than the film width before the swelling bath 13 is immersed, ). The stretching ratio based on the original film 10 was 2.5 times.

(2) Dyeing process

Next, the film having passed through the nip roll 51 was immersed in a dyeing bath 14 at 30 占 폚 for 120 seconds with iodine / potassium iodide / water (weight ratio) of 0.05 / 2/100. In this dyeing treatment, too, the longitudinal speed difference is provided between the nip rolls 51 and 52 so that the film width immediately after being drawn out from the dyeing bath 14 is equal to or smaller than the film width before the dyeing bath 14 is immersed, Stretching) was performed. The cumulative stretching magnification in the swelling treatment and dyeing treatment based on the original film 10 was set at 2.7 times.

(3) Crosslinking treatment process

Next, in order to carry out the first crosslinking treatment for the purpose of water resistance, the film passed through the nip rolls 52 is subjected to a first crosslinking treatment at 55 占 폚 at a potassium / iodobenzene / water (weight ratio) of 12 / 4.4 / And immersed in the bath 17a for 30 seconds. The nip roll 52 and the first crosslinking bath 17a are formed so that the film width immediately after being drawn out from the first crosslinking bath 17a becomes equal to or smaller than the film width before the first crosslinking bath 17a is immersed in the first crosslinking bath 17a, And the nip rolls 53 provided between the second crosslinking bath 17b and the second crosslinking bath 17b. The cumulative stretching magnification in the swelling treatment, dyeing treatment and first crosslinking treatment based on the original film 10 was 5.0 times.

Subsequently, the film after the first crosslinking treatment is immersed in a second crosslinking bath 17b at 59 deg. C having the same composition as that of the first crosslinking bath 17a for 30 seconds (second crosslinking treatment) (Third crosslinking treatment) for 15 seconds in a third crosslinking bath 17c at 40 占 폚 in which potassium iodide / boric acid / water (weight ratio) is 9 / 2.9 / 100.

(4) Drying process

Thereafter, the film after the third crosslinking treatment was immersed in a cleansing bath 19 containing pure water at 5 캜 and then dried at 80 캜 for 3 minutes by passing through the drying furnace 21 to remove the polarizing film 10 Respectively.

The obtained polarizing film 10 had a thickness of about 12 탆. In addition, the surface of the polarizing film 10 was scanned in the direction perpendicular to the stretching direction (line direction), and the surface irregularities of the polarizing film 10 were line-measured. The difference in height was about 320 nm.

The surface irregularities were measured under the following conditions.

Measuring device: VertScan (registered trademark) (R5500G manufactured by Rikoka System Co., Ltd.)

Objective lens (magnification): 2.5 times

Measuring range: 3700 × 2800 μm

Resolution: 640 × 480 pixels

Measurement mode: Wave mode

Face correction: fourth-order processing

(5) Bonding process

As the adhesive, an aqueous adhesive containing 5 parts by weight of polyvinyl alcohol (PVA) relative to 100 parts by weight of water was prepared.

While continuously feeding the elongated polarizing film 10 obtained above and supplying the adhesive prepared above to both surfaces thereof, a triacetyl cellulose film having a thickness of about 20 mu m as a first protective film (front side) A triacetylcellulose film having a thickness of about 25 占 퐉 as the film (rear side) was bonded to both surfaces of the polarizing film 10 using a pair of bonding rolls. The bonding conditions were as follows.

Transporting speed: 4 m / min

Bonding roll: hardness 72.5 °, made of rubber (material), diameter 100 mm

Bonding pressure: 0.45 MPa

Adhesive feed rate (per side): 15 ml / min

Subsequently, the polarizing plate with the first protective film and the second protective film bonded thereto was continuously conveyed and passed through a drying furnace to dry at 80 DEG C for 5 minutes (thereby curing the adhesive) to prepare a polarizing plate.

In the laminate after the first protective film and the second protective film are bonded to the polarizing film by an adhesive and dried (cured), the thickness of the first protective film is about 20 탆 and the thickness of the second protective film is about 25 mu m, the thickness of the adhesive (adhesive layer) was about 50 nm, and the thickness of the polarizing film (polarizer) was about 12 mu m.

The presence or absence of a line-shaped unevenness (hereinafter simply referred to as "line") appearing as a shade of reflected light on the front side (first protective film side) of the obtained polarizing plate was checked visually. It was not. The transmittance (visibility-corrected transmittance) of this polarizing plate was 43.3% and the degree of polarization (visual sensitivity correction polarization degree) was 99.97%. Visibility Sensitivity The transmittance and visual sensitivity correction polarity were measured in accordance with JIS Z 8729 using a spectrophotometer ("V7100" manufactured by Nihon Bunko Co., Ltd.). These results are shown in Table 1. In Table 1, in the appearance of the polarizing plate, the occurrence of streaks was identified as &quot;? &Quot;

The polarizing plate thus obtained was cut into small pieces of 10 cm x 5 cm, immersed in 600 ml of methylene dichloride, and subjected to ultrasonic treatment at room temperature for 30 minutes to dissolve the first protective film and the second protective film Respectively. With respect to the polarizing film from which these protective films have been removed, the surface of the polarizer on which the adhesive is adhered is scanned in the direction perpendicular to the stretching direction as the surface of the front side (the side where the first protective film is bonded) The surface unevenness of the attached polarizer was measured in a line. The results are shown in Fig. From the measurement results, the magnitude of the undulation (the difference in height on the surface of the polarizer to which the adhesive was adhered) was 276 nm. Further, the distance between the irregularities was found from this measurement result, and it was 791 탆. The results are shown in Table 1.

The surface irregularities were measured under the following conditions.

Measuring device: VertScan (registered trademark) (R5500G manufactured by Rikoka System Co., Ltd.)

Objective lens (magnification): 2.5 times

Measuring range: 3700 × 2800 μm

Resolution: 640 × 480 pixels

Measurement mode: Wave mode

Face correction: fourth-order processing

&Lt; Example 2 >

Of the operations described in Example 1, (5) in the bonding step, an aqueous adhesive containing 6 parts by weight of polyvinyl alcohol (PVA) relative to 100 parts by weight of water as an adhesive was prepared and used in Examples 1, a polarizing plate was produced. The obtained polarizing plate was measured and evaluated in the same manner as in Example 1 for the occurrence of streaks (visually confirmed), the transmittance, the degree of polarization, the amount of undulation, and the distance between irregularities. The results are shown in Table 1 and Fig.

&Lt; Example 3 and Comparative Example 1 >

(5) In the bonding step, a water-based adhesive in which the content concentration of polyvinyl alcohol was changed as shown in Table 1 was prepared as an adhesive and was used, In the same manner, a polarizing plate was produced. The obtained polarizing plate was measured and evaluated in the same manner as in Example 1 for the occurrence of streaks (visually confirmed), the transmittance, the degree of polarization, the amount of undulation, and the distance between irregularities. The results are shown in Table 1, Fig. 8 (Example 3) and Fig. 10 (Comparative Example).

&Lt; Example 4 and Comparative Example 2 >

(4) the drying temperature was changed as shown in Table 1, (5) the content concentration of polyvinyl alcohol (PVA) was changed to A polarizing plate was prepared in the same manner as in Example 1 except that the modified water-based adhesive agent was prepared as shown in Table 1 and used. The obtained polarizing plate was measured and evaluated in the same manner as in Example 1 for the occurrence of streaks (visually confirmed), the transmittance, the degree of polarization, the amount of undulation, and the distance between irregularities. The results are shown in Table 1, Fig. 9 (Example 4), and Fig. 11 (Comparative Example 2).

As can be understood from Table 1, in Examples 1 to 4 in which the size of the undulation (the height difference on the surface of the polarizer with the adhesive) is 280 nm or less, the appearance of the polarizing plate, the line ) Was not confirmed. On the other hand, in Comparative Examples 1 and 2 in which the undulation depth was 280 nm or more, occurrence of streaks in the appearance of the polarizing plate was confirmed. Although the present invention is not limited, in particular, in Embodiments 1 and 2, a very high degree of polarization can be obtained.

The polarizing plate of the present invention can be used for various optical applications, and can be widely used, for example, as a polarizing light supplying element in an image display apparatus and also as a polarizing light detecting element.

1: polarizer (polarizing film)
2, 4: Adhesive
3, 5: Protective film
7: Pressure-sensitive adhesive layer
10: polarizing film
11: disk roll
13: swelling bath
14: Dyeing bath
17: Bridging bath
19: Three lusts
20: original film made of polyvinyl alcohol-based resin
21: drying furnace
30 to 41: guide roll
50 to 55: Nip roll
110, 111, 112: polarizer
115: other member (for example, liquid crystal cell, organic electroluminescence element, etc.)
120: Image display device

Claims (5)

A polarizing plate comprising a polarizer and a protective film bonded to at least one surface of the polarizer by an adhesive, wherein when the protective film is removed, the surface of the polarizer having the adhesive attached thereto is scanned in a direction perpendicular to the absorption axis direction of the polarizer , The surface irregularities of the polarizer having the adhesive attached thereto were measured in a line. From the measured results, it was found that the height at the vertex of the highest convex portion relative to the average line of the surface and the height And the depth of the concave portion at the bottom of the concave portion is 280 nm or less. The polarizing plate according to claim 1, wherein the thickness of the protective film is 85 占 퐉 or less. A method for producing a polarizing plate comprising a polarizer and a protective film bonded to at least one surface of the polarizer by an adhesive,
A protective film is bonded to at least one surface of the polarizer by an adhesive,
Curing the polarizer to which the protective film is bonded
Wherein a surface of the polarizer having the adhesive is scanned in a direction perpendicular to the absorption axis direction of the polarizer when the protective film is cured by bonding with an adhesive and then the protective film is removed, And the measurement result shows that the height at the vertex of the highest convex portion relative to the average line of the surface and the height of the bottom portion of the concave portion on the deeper side among the two concave portions adjacent to the highest convex portion, And the depth of the undulation of the polarizing plate is 280 nm or less. The method of producing a polarizing plate according to claim 3, wherein the protective film has a thickness of 85 占 퐉 or less after the protective film is bonded and cured by an adhesive. An image display device comprising a liquid crystal cell or an organic electroluminescence element and the polarizing plate according to claim 1 or 2.

Images