JP4198559B2 - Method for producing polarizing film, and polarizing film and optical film using the same - Google Patents

Description

  The present invention relates to a method for producing a polarizing film, and a polarizing film and an optical film using the same.

Liquid crystal display devices (LCDs) are widely used in desktop electronic computers, electronic watches, personal computers, word processors, automobile and machine instruments, and the like. Such a liquid crystal display device is usually provided with a polarizing plate for visualizing a change in orientation of the liquid crystal, and this polarizing plate has a very large influence on the display characteristics of the liquid crystal display device.

As the polarizing plate, generally, a protective film such as triacetyl cellulose is provided on both surfaces of a polarizer (polarizing film) such as a polyvinyl alcohol (PVA) film in which a dichroic substance such as iodine or an organic dye is adsorbed and oriented. In particular, a polarizer that can provide a liquid crystal display device that is bright and has excellent display characteristics with good color reproducibility is desired.

However, in the liquid crystal display device, in particular, when a backlight that emits polarized light is used, there is a problem in that display unevenness occurs and the uniformity of contrast decreases. In particular, when high contrast is realized for the image display device, display unevenness is noticeably associated therewith. For example, when the liquid crystal mode is normally black (a state in which no voltage is applied is a black display state), the display 30 is slanted. Display unevenness becomes noticeable at the time of visual recognition from directions of °, 40 °, and 60 ° or more.

On the other hand, as a method for producing a polarizer, a hydrophilic polymer film (raw material) is conveyed by a guide roll so as to be immersed in a swelling bath, the polymer film is swollen, and subsequently, a dyeing bath containing a dichroic substance. It is common to perform dyeing by dipping and further stretching while dipping in a crosslinking bath. So far, the hydrophilic polymer film has been disclosed in which the uniformity of the thickness of the PVA film is improved. However, even when such a film is used, the produced polarizer has a retardation difference. There is a risk that it may occur or the content of the dichroic substance may be uneven.
JP 2002-28939 A JP 2002-31720 A

  For the reasons described above, an object of the present invention is to provide a polarizing film for use in various display devices that exhibits even display unevenness and exhibits uniform display characteristics.

  In order to achieve the object, examples of the method for producing the polarizing film of the present invention include the following first and second production methods.

That is, the first manufacturing method of the present invention, immersed in an aqueous solvent in the swelling bath by conveying a polyvinyl alcohol film by the guide roll, the swelling step of swelling the polyvinyl alcohol film, the polyvinyl alcohol film A method for producing a polarizing film comprising a dyeing step for dyeing with a dichroic substance, and a drawing step for drawing the polyvinyl alcohol film ,
In the swelling step, at least a first guide roll is disposed in the swelling bath,
The immersing the polyvinyl alcohol film in said aqueous solvent and said when moving the aqueous solvent, wherein the polyvinyl alcohol film, polyvinyl alcohol film is the first guide before causing rapid swelling Contact the roll ,
The time (a) required for the polyvinyl alcohol film to contact the first guide roll after contacting the aqueous solvent is 0.6 to 12 seconds .

The second production method of the present invention, the swelling process was immersed in a swelling bath of an aqueous solvent, swells the polyvinyl alcohol film in the solvent by conveying a polyvinyl alcohol film by the guide roll, said polyvinyl A method for producing a polarizing film comprising a dyeing step of dyeing an alcohol film with a dichroic material, and a drawing step of drawing the polyvinyl alcohol film ,
In the swelling step, at least a first guide roll is disposed in the swelling bath,
The polyvinyl alcohol film was immersed in the aqueous medium, and, when moving the aqueous solvent, the polyvinyl alcohol film, after the polyvinyl alcohol film has caused a rapid swelling, the first Contact the guide roll ,
The time (c) required for the polyvinyl alcohol film to contact the first guide roll after contacting the aqueous solvent is 25 to 180 seconds .

  In order to achieve the above object, the present inventors have conducted intensive research on the production of a polarizing film. As a result, when the PVA film, which is a hydrophilic polymer film, is immersed in the aqueous solvent of the swelling bath, usually, abrupt swelling occurs between 15 seconds to 25 seconds, and when the PVA film contacts the guide roll at that time, It was found that wrinkles were generated in the film on the surface of the guide roll, and this caused the retardation of the PVA film and also the unevenness of the content of the dichroic substance. Then, by controlling the contact point with the guide roll according to the swelling state of the polymer film, specifically, after the hydrophilic polymer film is in contact with the aqueous solvent of the swelling bath, The first and second polarizing films as described above have been found by controlling the time until contact with the guide roll, thereby reducing the unevenness in retardation and the unevenness in the content of the dichroic material as described above. I came up with this manufacturing method. In addition, the generation of wrinkles is considered to be caused by the slack that occurs because the thin part of the polymer film has a larger elongation due to swelling than the other parts in the swelling process. The stretching process was performed. However, if wrinkles are eliminated by stretching, for example, the amount of dichroic substance adsorbed may be reduced, or the dichroic substance may be detached in a subsequent process (such as a crosslinking process). There was a problem that unevenness became remarkable. However, according to the method of the present invention, the stretching process is not performed for the purpose of eliminating wrinkles, but the generation of wrinkles itself is reduced, so that the conventional problems can be avoided. In addition, the present inventors have found for the first time that the relationship between the film and the guide roll in the swelling bath has a great influence on the generation of wrinkles and uneven coloring in the produced polarizing film.

  According to the first and second manufacturing methods of the present invention, the obtained polarizing film has suppressed retardation unevenness and uneven content of the dichroic substance. When applied to various image display devices, particularly large or high contrast display devices and flat panel displays, display unevenness (particularly display unevenness in black display) can be sufficiently eliminated.

First, the 1st manufacturing method of this invention is demonstrated. As described above, in the first production method of the present invention, the polyvinyl alcohol film is transported by a guide roll so as to be immersed in an aqueous solvent in a swelling bath to swell the polyvinyl alcohol film, and the polyvinyl alcohol. A method for producing a polarizing film comprising a dyeing step for dyeing a dichroic film with a dichroic material, and a drawing step for drawing the polyvinyl alcohol film ,
In the swelling step, at least a first guide roll is disposed in the swelling bath,
The polymer film was immersed in the aqueous medium, and, when moving the aqueous solvent, the polyvinyl alcohol film, the first guide roll before the polyvinyl alcohol film causes a sudden swelling Contact ,
The time (a) required for the polyvinyl alcohol film to contact the first guide roll after contacting the aqueous solvent is 0.6 to 12 seconds .

In the first production method of the present invention, the polyvinyl alcohol film only needs to be able to contact the first guide roll before sudden swelling occurs, and after the polyvinyl alcohol film contacts the aqueous solvent. time required to contact the first guide roll (a) is 0.6 seconds to 12 seconds. As mentioned above, the swelling of the polymer film generally occurs abruptly between 15 seconds and 25 seconds, so if the required time (a) is 0.6 seconds to 12 seconds, after contacting the first guide roll, since swelling of the polymer film occurs rapidly, occurrence of wrinkles is suppressed as a result. For this reason, it is because retardation unevenness and content unevenness of a dichroic substance can be suppressed about the manufactured polarizing film. The required time (a) is preferably in the range of 1.2 to 9 seconds, more preferably 2.5 to 7 seconds.

  Moreover, the said required time (a) can be suitably determined, for example according to the temperature of a swelling bath, and when the temperature of the said swelling bath is 40 to 50 degreeC, it is the range of 2.5 second-4 second. Is particularly preferable. When the temperature is 30 ° C to less than 40 ° C, the range of 2.5 seconds to 6 seconds is particularly preferable. When the temperature is 15 ° C to less than 30 ° C, the range of 2.5 seconds to 7 seconds is particularly preferable.

In the first production method of the present invention, when a second guide roll is further disposed in the swelling bath, the polyvinyl alcohol film is brought into contact with the first guide roll before sudden swelling occurs. Furthermore, it is preferable that the second guide roll is brought into contact after a rapid swelling occurs . Thus, the polyvinyl alcohol film suppresses the generation of wrinkles or the like due to contact with the first guide roll, and, after contacting the first guide roll, a sudden of the polyvinyl alcohol film This is because swelling occurs, so that even if it comes into contact with the next second guide roll, it is not affected. In addition, even if the polyvinyl alcohol film does not reach the saturation state when it comes into contact with the second guide roll, it may be after the swelling occurs abruptly.

The required time (b) from contact of the arbitrary point of the polyvinyl alcohol film with the first guide roll to contact with the second guide roll is preferably in the range of, for example, 13 seconds to 120 seconds, The range is more preferably 20 seconds to 100 seconds, and particularly preferably 33 seconds to 80 seconds. The total of the required time (a) and the required time (b) is preferably in the range of, for example, 25 seconds to 180 seconds, more preferably 30 seconds to 160 seconds, and particularly preferably 40 seconds. ~ 140 seconds.

  Moreover, the said required time (b) can be suitably determined also with the temperature of a swelling bath similarly to the said required time (a), and when the temperature of the said swelling bath is 40 to 50 degreeC, it is 15 to 80 seconds. The range of 20 seconds to 85 seconds is particularly preferable when it is 30 ° C. to less than 40 ° C., and the range of 25 seconds to 90 seconds is particularly preferable when it is 15 ° C. to less than 30 ° C.

An example of the swelling process in the 1st manufacturing method of this invention is shown in the schematic diagram of FIG. As shown in the figure, two guide rolls 41 and 42 are arranged outside the swelling bath 32, and two guide rolls 43 and 44 are arranged inside the swelling bath 32. Is filled with an aqueous solvent 33. The guide rolls are sequentially arranged in the direction of travel of the polymer film (in the direction of the arrow in the figure), and the guide roll disposed in the swelling bath 32 is the first guide roll 43 before the travel direction of the polyvinyl alcohol film. The other is the second guide roll 44. Then, when the polyvinyl alcohol film 31 is transported by the guide roll, the polyvinyl alcohol film 31 is connected to the first guide roll 43 from the portion where the polyvinyl alcohol film 31 is in contact with the aqueous solvent (that is, the water surface of the aqueous solvent). The distance to the contact part is “a”, and the time required for an arbitrary point of the polyvinyl alcohol film 31 to move the distance a is the required time (a). Further, from the site where the polyvinyl alcohol-based film 31 is in contact with the first guide roll 43, the distance to the site in contact with the second guide roll 44 is "b", any point of the polyvinyl alcohol film 31 The time required to move the distance b is the required time (b). In addition, the arrangement | positioning number in particular of a guide roll is not restrict | limited, You may arrange | position further inside and outside a swelling bath as needed.

When such a swelling bath is used, first, the polyvinyl alcohol film 31 is conveyed from the outside of the swelling bath 32 (left side in the figure) into the swelling bath by a guide roll and immersed in the aqueous solvent 33. Then, the distance “a” is moved before the polyvinyl alcohol film 31 suddenly swells, and the polyvinyl alcohol film 31 is swollen before reaching the second guide roll 44 from the first guide roll 43 . . The required time (a) and required time (b) are as described above.

The distance a of the polyvinyl alcohol film is the portion thereof in contact with an aqueous solvent 33 in the swelling bath 32 to the site in contact with the first guide roll 43 is not particularly limited, for example, in the range of 4～2400Mm, polyvinyl The distance “b” from the portion where the alcoholic film 31 is in contact with the first guide roll 43 to the portion where the alcohol film 31 is in contact with the second guide roll 44, that is, the distance between the first guide roll 43 and the second guide roll 44. The distance is not particularly limited, but is, for example, in the range of 80 to 36000 mm. Moreover, the conveyance speed of a film is 6-200 mm / sec, for example.

The type of the guide roll is not particularly limited, and a conventionally known one can be used, and examples thereof include those shown in the schematic diagram of FIG. In the figure, (a) is a flat roll having no irregularities on the surface, (b) is a crown roll having an effect of stretching wrinkles, (c) is an expander roll, (d) is an ear height roll, and (e) is a spiral. It is a roll. In addition to these, a vent roll or the like can also be used. Among these, the spiral roll is preferably used in addition to the first guide roll, as shown in Japanese Patent Application Laid-Open No. 2000-147252, because the polyvinyl alcohol film may have a trace. The same applies to the manufacturing method. Moreover, it is preferable that the said guide roll shows the effect which extends a wrinkle, However, It is preferable not to extend further in the horizontal direction rather than the elongation by the swelling in the width direction of a film, for example. Specifically, when the length in the width direction of the film in which elongation occurs due to swelling is 100%, the ratio of stretching by the guide roll is preferably 20% or less, more preferably 10%, for example. Below, more preferably 5% or less.

  The material of the various rolls is not particularly limited, and examples thereof include metals and polymers. For example, the expander roll and at least the ear height part of the ear height roll, and the spiral roll are processed in a swelling bath, for example. The surface energy is preferably close to the surface energy of the film in the state.

Next, the second manufacturing method of the present invention will be described. As described above, the second production method of the present invention includes a swelling step of swelling the film in the solvent by immersing the polyvinyl alcohol film in a swelling bath of an aqueous solvent by conveying it with a guide roll, and the film A method for producing a polarizing film comprising a dyeing step for dyeing a dichroic substance, and a drawing step for drawing the film,
In the swelling step, at least a first guide roll is disposed in the swelling bath,
And immersing the film in the aqueous solvent, and, when moving the aqueous solvent, the polyvinyl alcohol film, after the polyvinyl alcohol film has caused a rapid swelling, the first guide roll Contact ,
The time (c) required for the polyvinyl alcohol film to contact the first guide roll after contacting the aqueous solvent is 25 to 180 seconds .

In the second production method of the present invention, the polyvinyl alcohol film only needs to be able to come into contact with the first guide roll after rapid swelling has occurred, and after any point of the film comes into contact with the aqueous solvent. time required to contact the first guide roll (c) is a 25 to 180 seconds. As described above, since the swelling of the polymer film generally occurs suddenly in 15 to 25 seconds, if the required time (a) is 25 seconds or more, the film suddenly comes into contact with the first guide roll. since such swelling occurs, the resulting generation of wrinkles suppression, whereas not more than 180 seconds, sagging of the polyvinyl alcohol film is further prevented, conveyance of the film also is because the more stable. As a result, retardation unevenness and content unevenness of the dichroic substance can be further suppressed in the manufactured polarizing film. The required time (c) is preferably in the range of 30 seconds to 160 seconds, more preferably 40 seconds to 140 seconds. In the second production method, when the polyvinyl alcohol film comes into contact with the first guide roll, even if the swelling does not reach a saturated state, it may be after the abrupt swelling.

  Moreover, the said required time (c) can be suitably determined also with the temperature of a swelling bath similarly to the said required time (a) (b), and when the temperature of the said swelling bath is 40 to 50 degreeC, it is 40 ~ The range of 140 seconds is particularly preferred, the range of 45 to 140 seconds is particularly preferred when it is 30 ° C. to less than 40 ° C., and the range of 50 to 140 seconds is particularly preferred when it is 15 ° C. to less than 30 ° C.

An example of the swelling process in the 2nd manufacturing method of this invention is shown in the schematic diagram of FIG. As shown in the figure, two guide rolls 41 and 42 are arranged outside the swelling bath 32, and inside the swelling bath 32, one guide roll (first guide roll) 45 is arranged, The inside of the swelling bath 32 is filled with an aqueous solvent 33. Each said guide roll is arrange | positioned in order toward the advancing direction (arrow direction in a figure) of a polyvinyl alcohol-type film . Then, a polyvinyl alcohol film 31 when conveyed by guide rolls, the distance from the site where the polyvinyl alcohol-based film 31 is in contact with an aqueous solvent 33, to the site of the polyvinyl alcohol-based film 31 contacts the first guide roll 45 Is “c”, and the time required for an arbitrary point of the polyvinyl alcohol film to move the distance c is the required time (c). In addition, the arrangement | positioning number in particular of a guide roll is not restrict | limited, You may arrange | position further inside and outside a swelling bath as needed.

When such a swelling bath is used, first, the polyvinyl alcohol film 31 is conveyed from the outside of the swelling bath 32 (left side in the figure) into the swelling bath by a guide roll and immersed in the aqueous solvent 33. Then, while moving the polyvinyl alcohol film 31 to swell, causing rapid swelling of the polyvinyl alcohol film 31 to reach the second guide roll 44. The required time (c) is as described above.

The distance “c” from the portion where the polyvinyl alcohol film contacts the aqueous solvent of the swelling bath 32 to the portion where the polyvinyl alcohol film contacts the first guide roll is not particularly limited, but is, for example, in the range of 150 to 36000 mm. Moreover, the conveyance speed of a film is 6-200 mm / sec, for example.

Next, an example of a series of manufacturing steps will be described for the first and second manufacturing methods of the present invention. Specifically, a polarizing film (polarized light) is obtained by swelling a polyvinyl alcohol film under the conditions described above, dyeing a dichroic substance in a dyeing bath, stretching in a crosslinking bath, washing with water and drying. Child).

(1) The polyvinyl alcohol film <br/> the polyvinyl alcohol-based film, for example, PVA-based film, partially formalized PVA-based Fi Lum and the like. Also, in addition to these, oriented polyene films such as dehydrated products of PVA can be used. Among these, since it is excellent in the dyeability by the iodine which is the said dichroic substance, a PVA-type polymer film is preferable. In the polymer film, the length in the stretching direction is hereinafter referred to as “length”, and the length in the direction perpendicular to the stretching direction is referred to as “width”.

  The average degree of polymerization of the PVA film is not particularly limited, but is preferably in the range of 100 to 5000, more preferably 1000 to 4000, from the viewpoint of the solubility of the film in water. The degree of saponification is, for example, preferably 75 mol% or more, more preferably 98 to 100 mol%.

The thickness of the polyvinyl alcohol film is not particularly limited, but is, for example, 110 μm or less, preferably in the range of 38 to 110 μm, more preferably 50 to 100 μm, and particularly preferably 60 to 80 μm. If the thickness is 110 μm or less, the color change of the display panel can be sufficiently suppressed when the manufactured polarizer is mounted on an image display device. Further, if the thickness is in the range of 60 to 80 μm, it is easy to perform a stretching process. Because.

The polyvinyl alcohol-based film preferably includes, for example, a plastic material in the polyvinyl alcohol-based film , for example, in order to suppress retardation unevenness of the produced polarizing film and uneven content of the dichroic substance. . The content of the plastic material in the polyvinyl alcohol film is not particularly limited as long as the effect of the present invention can be achieved, but for example, 1 to 17% by mass is included with respect to the total amount of the film (100% by mass). Preferably it is. If it is the said range, it is excellent also in the handleability of a polyvinyl alcohol-type film , can prevent a fracture | rupture further, and can fully avoid the influence on film formation.

The plastic material is not particularly limited as long as it can plasticize the polyvinyl alcohol film , and conventionally known materials can be used. Specifically, a water-soluble plastic material is preferable, for example, glycols such as ethylene glycol, diethylene glycol, propylene glycol, and low molecular weight polyethylene glycol (Mw: 200 to 400); glycerin derivatives such as glycerin, diglycerin, and triglycerin. Etc. Among these, a glycerin derivative is preferable because of strong interaction with PVA and high compatibility, and glycerin is particularly preferable. Thus, when the polyvinyl alcohol film is a PVA film and the water-soluble plastic material is glycerin, the glycerin content in the total amount of the film (100% by mass) is preferably 3 to 16% by mass, more preferably 5 to 5%. It is in the range of 15% by mass.

As the polyvinyl alcohol-based film , for example, in the swelling process which is the next step, it is preferable to use a film with less swelling variation, that is, less thickness variation due to swelling. This is because variations in the retardation of the polarizer, the content of the dichroic substance, the transmittance, and the like can be further reduced. For this reason, for example, it is preferable to use a polymer film with less crystallinity unevenness, thickness unevenness, and moisture content variation. A polymer film having no variation in glycerin content is also preferred. Even if there are variations in thickness, the thickness of the thin part is large and the swelling is small. Is possible.

(2) Swelling treatment The polyvinyl alcohol-based film is immersed in a swelling bath and moved in the swelling bath so as to satisfy the conditions as described above, and a swelling treatment is performed. In this swelling step, for example, the polyvinyl alcohol film is preferably stretched while being swollen. This is because the stretching process further advances the swelling, and even if a slight wrinkle is generated on the guide roll, this can be eliminated.

Examples of the aqueous solvent for the swelling bath include an aqueous solution for swelling treatment containing water, acid, alkali, electrolyte and the like. The type and concentration of the acid, alkali, and electrolyte are not particularly limited as long as they do not affect the retardation unevenness of the polarizer to be produced and the unevenness of the content of the dichroic substance, and conventionally known ones can be used. . Specific examples include electrolytic substances such as potassium and sodium, glycerin, and the like. In particular, when the polyvinyl alcohol film is a PVA film, it is preferable to include glycerin.

  The temperature of the aqueous solvent in the swelling bath is preferably 15 to 50 ° C., for example. If it is 15 degreeC or more, since processing time can be shortened, productivity will improve further, and if it is 50 degreeC or less, what was excellent in the optical characteristic will be obtained.

The stretch ratio of the polyvinyl alcohol film in the swelling treatment is preferably 1.5 to 4.0 times the length of the polyvinyl alcohol film (raw material) before the swelling treatment, for example. Preferably it is 1.7-3.8 times, More preferably, it is 1.9-3.6 times. This is because with such a magnification, the dyeability of the dichroic dye in the next dyeing step is sufficiently improved, and the optical characteristics are sufficiently maintained. In particular, as the draw ratio is lower, dyeing unevenness in the dyeing process described later can be further reduced, and when it is 4 times or less, the occurrence of uneven stripes can be further suppressed.

In the swelling step, the time for immersing the polyvinyl alcohol film in the swelling bath is preferably 100 seconds or more in total. If it is 100 seconds or more, the swelling is saturated or approaches the saturated state. For example, the draw ratio can be reduced to about 1.1 to 1.5 times, and the uneven dyeing can be further improved. Because. On the other hand, even when the total immersion time is less than 100 seconds, the unevenness in dyeing can be reduced by performing the stretching treatment as described above.

(2) Dyeing process The said polyvinyl alcohol-type film is pulled up from the said swelling bath, for example, it is immersed in the dyeing bath containing a dichroic substance, and is further extended | stretched in a uniaxial direction in the said dyeing bath. That is, the dichroic substance is adsorbed on the polyvinyl alcohol film by the immersion, and the dichroic substance is oriented in one direction by stretching.

  A conventionally known substance can be used as the dichroic substance, and examples thereof include iodine and organic dyes. When using the said organic dye, it is preferable to combine 2 or more types from the point which aims at neutralization of visible region, for example.

As the dye bath solution, an aqueous solution in which the dichroic substance is dissolved in a solvent can be used. As the solvent, for example, water can be used, but an organic solvent compatible with water may be further added. Although the density | concentration of the dichroic substance in the said solution is not restrict | limited in particular, Usually, it is the range of 0.1-10.0 mass parts with respect to 100 mass parts of solvents (for example, water). The solution may further contain an auxiliary agent such as potassium iodide.

The immersion conditions of the polyvinyl alcohol film in the dyeing bath are not particularly limited, but the temperature of the dyeing bath is, for example, in the range of 20 to 70 ° C., and the immersion time is in the range of, for example, 5 to 20 minutes. . Moreover, it is preferable that the draw ratio in a dyeing | staining process is the range of 2 to 4 times with respect to the length of the polyvinyl-alcohol-type film (original fabric) before swelling, for example.

(3) Crosslinking treatment The polyvinyl alcohol film is pulled up from the dyeing bath, immersed in a crosslinking bath containing a crosslinking agent, and further stretched in this crosslinking bath. The running stability is maintained by performing the crosslinking treatment.

  As the crosslinking agent, conventionally known substances can be used, and examples thereof include boron compounds such as boric acid, borax, glyoxal, and glutaraldehyde. One kind of these may be used, or two or more kinds may be used in combination. As the solution of the crosslinking bath, an aqueous solution in which the crosslinking agent is dissolved in a solvent can be used. As the solvent, for example, water can be used, but an organic solvent compatible with water may be further included.

  The concentration of the crosslinking agent in the solution is not particularly limited, but is usually preferably in the range of 0.1 to 10% by mass with respect to 100% by mass of the solvent (for example, water). When the crosslinking agent is boric acid, for example, it is in the range of 1.5 to 8% by weight, preferably 2 to 6% by weight.

  In addition to the boric acid compound, the aqueous solution may be, for example, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, iodine, etc. An assistant such as iodide such as lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide and titanium iodide may be included. Among these, a combination of boric acid and potassium iodide is preferable. The content of the auxiliary agent in the solution is usually in the range of 0.05 to 15% by mass.

  Although the temperature of the said crosslinking bath is not specifically limited, Usually, it is the range of 20-70 degreeC, Preferably it is the range of 40-60 degreeC. The immersion time of the polymer film is not particularly limited, but is usually 1 second to 15 minutes.

The stretching ratio in this crosslinking treatment is preferably stretched 5 to 7 times, for example, with respect to the length of the original fabric. When stretching a polyvinyl alcohol-based film , the stretching method, the number of stretching, and the like are not particularly limited, and may be performed in each step of the dyeing step and the crosslinking step as described above, or may be performed in any one step. Alternatively, it may be performed a plurality of times in the same process.

(4) Washing and drying treatment A polarizing film is obtained by pulling up the polyvinyl alcohol film from the stretching bath, washing with water and drying. Drying is not particularly limited, for example, natural drying, air drying, heat drying, etc. In the case of heat drying, the temperature is usually 20 to 80 ° C., and the treatment time is usually in the range of 1 to 10 minutes. .

  Although the thickness of the polarizing film of this invention finally obtained is not restrict | limited, For example, the range of 1-80 micrometers is common, More preferably, it is 2-45 micrometers. If the thickness is 1 μm or more, for example, it shows a further excellent mechanical strength, and if it is 80 μm or less, for example, when mounted on a liquid crystal display device, the color change of the display panel can be sufficiently suppressed, And thinning becomes easy.

  Next, the polarizing film of the present invention is a polarizing film obtained by the first and second manufacturing methods of the present invention, and can be used as a polarizer, for example.

  The optical film of the present invention includes the polarizing film of the present invention. Examples of such optical films are shown below.

  As a first example of the optical film of the present invention, for example, a polarizing plate comprising the polarizing film of the present invention and a transparent protective layer, wherein the transparent protective layer is disposed on at least one surface of the polarizing film. . The said transparent protective layer may be arrange | positioned only at the single side | surface of the said polarizing film, and may be arrange | positioned at both surfaces. When laminating on both surfaces, for example, the same type of transparent protective layer may be used, or different types of transparent protective layers may be used.

  FIG. 4 shows a cross-sectional view of an example of the polarizing plate. As illustrated, the polarizing plate 10 includes a polarizing film 1 and two transparent protective layers 2, and the transparent protective layers 2 are disposed on both surfaces of the polarizing film 1, respectively.

  The transparent protective layer 2 is not particularly limited, and a conventionally known transparent protective film can be used. For example, a layer having excellent transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, and the like is preferable. . Specific examples of the material for such a transparent protective layer include cellulose resins such as triacetyl cellulose, polyester, polycarbonate, polyamide, polyimide, polyethersulfone, polysulfone, polystyrene, and acrylic. And transparent resins such as acetates and polyolefins. Further, examples thereof include thermosetting resins such as acrylic, urethane, acrylic urethane, epoxy, and silicone, or ultraviolet curable resins. In addition, a low photoelastic coefficient such as polynobornene resin is also preferable.

In addition, for example, an alternating copolymer composed of, for example, isobutene and N-methylmaleimide as described in JP-A No. 2001-343529 (WO 01/37007) and JP-A No. 2002-328233 A film made of a mixed extrudate of a resin composition containing acrylonitrile / styrene copolymer can also be used. Such a film can be manufactured as follows, for example. First, the alternating copolymer (100 parts by weight) having an N-methylmaleimide content of 50 mol% and 67 parts by weight of the copolymer having a tolyl content of 27% by weight and a styrene content of 73% by weight were melt-kneaded with acrylic. The pellets are supplied to a melt extruder equipped with a T die to produce a raw film. This film is subjected to free end longitudinal uniaxial stretching under conditions of a stretching speed of 100 cm / min, a stretching ratio of 1.45 times, and a stretching temperature of 162 ° C. Furthermore, a stretched film having a thickness of 49 μm is obtained by performing free end uniaxial stretching in the direction orthogonal to the previous stretching direction under the same conditions. This stretched film has nx = 1548028, ny = 1.485005, nz = 1.547970, in-plane retardation 1.1 nm, thickness direction retardation 2.8 nm, absolute value of photoelastic coefficient 1.9 × 10 −13 cm ² / dye.

  Furthermore, the surface of these transparent protective films may be saponified with an alkali or the like, for example. Among these, a TAC film is preferable from the viewpoints of polarization characteristics and durability, and more preferably a TAC film whose surface is saponified.

For example, the transparent protective layer preferably has no color. Specifically, the retardation value (Rth) in the film thickness direction represented by the following formula is preferably in the range of −90 nm to +75 nm, more preferably −80 nm to +60 nm, and particularly preferably −70 nm. It is in the range of ˜ + 45 nm. When the retardation value is in the range of −90 nm to +75 nm, the coloring (optical coloring) of the polarizing plate due to the protective film can be sufficiently eliminated.
Rth = [{(nx + ny) / 2} -nz] · d
In the above formula, d is the thickness of the transparent protective layer, and nx, ny, and nz respectively indicate the refractive indexes of the X-axis, Y-axis, and Z-axis in the transparent protective layer. The X-axis is an axial direction showing the maximum refractive index in the transparent protective layer surface, the Y-axis is an axial direction perpendicular to the X-axis in the surface, and the Z-axis is the X-axis. The thickness direction perpendicular to the axis and the Y axis is shown.

The thickness of the transparent protective layer is not particularly limited, but is, for example, 500 μm or less, preferably 1 to 300 μm, more preferably 5 to 300 μm, for the purpose of thinning the polarizing plate, for example. .

  The transparent protective layer may be further subjected to, for example, a hard coat treatment, an antireflection treatment, an antisticking treatment, a treatment for diffusion, antiglare, or the like. The hard coat treatment is for the purpose of preventing scratches on the surface of the polarizing plate, for example, a treatment for forming a cured film having excellent hardness and slipperiness composed of a curable resin on the surface of the transparent protective layer. It is. As the curable resin, for example, a silicone-based, urethane-based, acrylic-based, or epoxy-based ultraviolet curable resin can be used, and the treatment can be performed by a conventionally known method.

  The antireflection treatment is intended to prevent reflection of external light on the surface of the polarizing plate, and can be performed by forming a conventionally known antireflection film or the like. The purpose of the anti-sticking treatment is to prevent adhesion between adjacent layers.

  The anti-glare treatment is intended to prevent visual interference of the light transmitted through the polarizing plate by reflecting external light on the surface of the polarizing plate. For example, the surface of the transparent protective layer may be finely coated by a conventionally known method. This can be done by forming an uneven structure. Examples of a method for forming such a concavo-convex structure include a roughening method by sandblasting or embossing, a method of forming the transparent protective layer by blending transparent fine particles in the transparent resin as described above, and the like. It is done.

  Examples of the transparent fine particles include silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, and the like, and solid solutions thereof. The average particle size of the transparent fine particles is not particularly limited, but is, for example, in the range of 0.5 to 50 μm. In addition, conductive inorganic fine particles, organic fine particles composed of crosslinked or uncrosslinked polymer particles, and the like can also be used. The blending ratio of the transparent fine particles is not particularly limited, but is generally preferably in the range of 2 to 50 parts by mass, more preferably in the range of 5 to 25 parts by mass as described above for 100 parts by mass of the transparent resin.

  The antiglare layer containing the transparent fine particles can be used as, for example, the transparent protective layer itself, or may be formed as a coating layer on the surface of the transparent protective layer. Furthermore, the antiglare layer may also serve as a diffusion layer for diffusing the light transmitted through the polarizing plate to expand the viewing angle.

  Note that the antireflection film, the diffusion layer, the antiglare layer, and the like can be provided on the polarizing plate separately from the transparent protective layer, for example, as an optical layer composed of a sheet or the like provided with these layers.

  The adhesion method between the polarizer and the transparent protective layer is not particularly limited, and can be performed by a conventionally known method. In general, a pressure-sensitive adhesive or other adhesive is used, and the type thereof can be appropriately determined depending on the type of the polarizing film and the transparent protective layer. Specific examples include adhesives and pressure-sensitive adhesives composed of PVA-based, modified PVA-based, and urethane-based polymers. In order to improve durability, these adhesives and the like are made of vinyl alcohol polymers such as boric acid, borax, glutaraldehyde, melamine, oxalic acid, chitin, chitosan, metal salts, alcohol solvents, etc. A water-soluble crosslinking agent for crosslinking may be added. In the case where the polarizer is, for example, a PVA film, a PVA adhesive is preferable from the viewpoint of the stability of the adhesive treatment. The thickness of such an adhesive layer is not particularly limited, but is, for example, 1 nm to 500 nm, preferably 10 nm to 300 nm, and more preferably 20 nm to 100 nm.

  When the polarizer and the transparent protective layer are bonded with the adhesive, for example, in order to prevent peeling due to the influence of humidity and heat and to obtain a polarizing plate excellent in light transmittance and polarization degree, a drying treatment is performed. It is preferable to apply. It does not restrict | limit especially as drying temperature, According to the kind etc. of used adhesive agent or an adhesive, it can determine suitably. When the pre-adhesive is a water-soluble adhesive such as PVA, modified PVA, or urethane as described above, for example, the drying temperature is preferably 60 to 70 ° C, more preferably 60 to 75 ° C, The drying time is preferably about 1 to 10 minutes.

  Moreover, since the polarizing plate of this invention becomes easy to laminate | stack to a liquid crystal cell etc., for example, it is preferable to have an adhesive layer in the outermost layer further. FIG. 5 shows a cross-sectional view of a polarizing plate having an adhesive layer as described above. As illustrated, the polarizing plate 20 includes the polarizing plate 10 and the pressure-sensitive adhesive layer 3 shown in FIG. 4, and the pressure-sensitive adhesive layer 3 is further disposed on the surface of one transparent protective layer 2 of the polarizing plate 10. .

  The pressure-sensitive adhesive layer is formed on the surface of the transparent protective layer by, for example, adding a solution or a melt of the pressure-sensitive adhesive directly to a predetermined surface of the transparent protective layer by a developing method such as casting or coating. It can be performed by a method of forming a layer, a method of forming a pressure-sensitive adhesive layer on a separator, which will be described later, and transferring it to a predetermined surface of the transparent protective layer. In addition, although such an adhesive layer may be formed in any one surface of a polarizing plate like the said FIG. 5, it is not limited to this, You may arrange | position on both surfaces as needed. .

  The pressure-sensitive adhesive layer can be formed by appropriately using, for example, a conventionally known pressure-sensitive adhesive such as acrylic, silicone, polyester, polyurethane, polyether, or rubber. In particular, the moisture absorption rate is low in terms of preventing foaming and peeling due to moisture absorption, reducing optical characteristics due to thermal expansion differences, preventing warping of liquid crystal cells, and forming liquid crystal display devices with high quality and durability. It is preferable to use a low pressure-sensitive adhesive having excellent heat resistance. Examples of such an adhesive include acrylic, silicone, acrylic silicone, polyester, and heat resistant rubber adhesives. Moreover, the adhesion layer etc. which show the light diffusibility containing microparticles | fine-particles etc. may be sufficient.

  Moreover, when the surface of the adhesive layer provided in the polarizing plate is exposed, it is preferable to cover the surface with a separator for the purpose of preventing contamination until the adhesive layer is put to practical use. This separator is formed by a method in which an appropriate thin layer film such as the transparent protective film is provided with a release coat with a release agent such as silicone, long chain alkyl, fluorine, molybdenum sulfide, etc. Can be formed.

  Although the thickness of the said adhesive layer is not specifically limited, For example, it is preferable that it is 5-35 micrometers, More preferably, it is 10-25 micrometers, Most preferably, it is 15-25 micrometers. This is because, if set in such a range, for example, even if the size of the polarizing plate changes, the stress generated at that time can be relaxed.

  In addition, the polarizing plate of the present invention can be used for forming a liquid crystal cell, a liquid crystal display device, and the like. For example, in a state where a transparent protective layer is laminated on the polarizer, the polarizing plate is cut according to the size of the liquid crystal cell ( (Chip cutting), or the transparent protective layer may be bonded together after cutting the polarizer in advance.

  Next, a second example of the optical film of the present invention is a laminate including the polarizer of the present invention or the polarizing plate of the first example, and at least one of a polarization conversion element and a retardation film.

  The polarization conversion element is not particularly limited, and examples thereof include those generally used for forming a liquid crystal display device, such as an anisotropic reflection polarization element and an anisotropic scattering polarization element. These polarization conversion elements may be, for example, a single layer or a stack of two or more layers. Moreover, when using two or more layers, the same kind may be sufficient and a different kind of layer may be used.

  Among the polarization conversion elements, the anisotropic reflection type polarization element is, for example, a composite of a cholesteric liquid crystal layer and a phase difference plate, and the phase difference plate is a reflection that the anisotropic reflection polarizer has. It is preferable that the phase difference is 0.2 to 0.3 times the wavelength included in the band. More preferably, it is 0.25 times. As the cholesteric liquid crystal layer, in particular, the cholesteric liquid crystal polymer alignment film or the circularly polarized light of either the left-handed or the right-handed is reflected, such as the one in which the oriented liquid crystal layer is supported on the film substrate. Thus, it is preferable that other light has a characteristic of transmitting. As such an anisotropic reflective polarizing element, for example, a product name PCF series manufactured by Nitto Denko can be used. The wavelength may be any wavelength as long as it is included in the reflection band of the anisotropic reflective polarizer. Also, the cholesteric liquid crystal layer transmits linearly polarized light with a predetermined polarization axis and reflects other light, such as a multilayer thin film of dielectric or a multilayer laminate of thin film having different refractive index anisotropy. It may show the characteristic to do. As such an anisotropic reflective polarizing element, for example, a product name DBEF series manufactured by 3M Corporation can be used.

  In addition, as the anisotropic reflection type polarizing element, a reflection type grid polarizer is also preferable. As a specific example, trade name Micro Wires manufactured by Maxtek and the like can be used.

  On the other hand, as the anisotropic scattering type polarizing element, for example, trade name DRPF manufactured by 3M Company can be used.

  Next, the third example of the optical film of the present invention includes, for example, the polarizer of the present invention, the polarizing plate in the first example, or the laminate in the second example, and various optical layers. Various polarizing plates which are laminates are listed. The optical layer is not particularly limited. For example, as shown below, a retardation plate including a reflection plate, a transflective plate, a λ plate such as a half-wave plate, a quarter-wave plate, etc. Examples thereof include an optical layer used for forming a liquid crystal display device such as a compensation film and a brightness enhancement film. And these optical layers may be one kind, and may use two or more kinds together. As the polarizing plate including such an optical layer, a reflective polarizing plate, a transflective polarizing plate, an elliptical polarizing plate, a circular polarizing plate, a polarizing plate on which a viewing angle compensation film or a brightness enhancement film is laminated, and the like are particularly preferable. .

  Hereinafter, these polarizing plates will be described.

  First, an example of the reflective polarizing plate or transflective polarizing plate of the present invention will be described. For example, the reflection type polarizing plate further includes a reflection plate laminated on the polarizing plate of the first example as described above, and the transflective polarizing plate further includes a semi transmission reflection plate on the polarizing plate. Are stacked.

  The reflective polarizing plate is usually disposed on the back side of a liquid crystal cell, and can be used for a liquid crystal display device (reflective liquid crystal display device) of a type that reflects incident light from the viewing side (display side). Such a reflective polarizing plate, for example, has an advantage that the liquid crystal display device can be thinned because the built-in light source such as a backlight can be omitted.

  The reflective polarizing plate can be produced by a conventionally known method such as a method of forming a reflective plate made of metal or the like on one surface of the polarizing plate after the heat treatment. Specifically, for example, one surface (exposed surface) of the transparent protective layer in the polarizing plate is mat-treated as necessary, and a metal foil or a vapor deposition film made of a reflective metal such as aluminum is formed on the surface as a reflection plate. The reflective polarizing plate formed as follows.

  In addition, as described above, a reflective polarizing plate or the like in which a reflecting plate reflecting the fine uneven structure is formed on a transparent protective layer containing fine particles in various transparent resins and having a fine uneven structure on the surface. It is done. A reflector having a fine concavo-convex structure on its surface has an advantage that, for example, incident light can be diffused by irregular reflection to prevent directivity and glaring appearance and to suppress uneven brightness. Such a reflector is, for example, directly on the uneven surface of the transparent protective layer by a conventionally known method such as a vacuum deposition method, an ion plating method, a sputtering method, or a plating method. It can form as a metal vapor deposition film.

  In addition, instead of the method of directly forming the reflective plate on the transparent protective layer of the polarizing plate as described above, a reflective sheet having a reflective layer provided on a suitable film such as the transparent protective film is used as the reflective plate. May be. Since the reflective layer in the reflective plate is usually composed of metal, for example, from the viewpoint of preventing the decrease in reflectance due to oxidation, and thus the long-term persistence of the initial reflectance, and the separate formation of a transparent protective layer, etc. The usage form is preferably a state in which the reflective surface of the reflective layer is covered with the film, a polarizing plate or the like.

  On the other hand, the transflective polarizing plate has a transflective reflective plate instead of the reflective plate in the reflective polarizing plate. Examples of the transflective reflector include a half mirror that reflects light through a reflective layer and transmits light.

  The transflective polarizing plate is usually provided on the back side of a liquid crystal cell. When a liquid crystal display device or the like is used in a relatively bright atmosphere, the incident light from the viewing side (display side) is reflected to display an image. In a relatively dark atmosphere, it can be used for a liquid crystal display device of a type that displays an image using a built-in light source such as a backlight built in the back side of the transflective polarizing plate. That is, the transflective polarizing plate can save the energy of using a light source such as a backlight in a bright atmosphere, and can be used with the built-in light source in a relatively dark atmosphere. It is useful for the formation of etc.

  Next, an example of the elliptically polarizing plate or the circularly polarizing plate of the present invention will be described. In these polarizing plates, for example, a retardation plate or a λ plate is further laminated on the polarizing plate of the first example as described above.

  The elliptically polarizing plate compensates (prevents) coloring (blue or yellow) caused by birefringence of a liquid crystal layer of a super twist nematic (STN) type liquid crystal display device, for example, to obtain a monochrome display without the coloring. It is used effectively. Furthermore, an elliptically polarizing plate having a controlled three-dimensional refractive index is preferable because it can compensate (prevent) coloring that occurs when the screen of a liquid crystal display device is viewed from an oblique direction, for example. On the other hand, the circularly polarizing plate is effective in, for example, adjusting the color tone of an image of a reflection type liquid crystal display device in which an image is displayed in color, and also has an antireflection function.

  The retardation plate is used when linearly polarized light is converted into elliptically polarized light or circularly polarized light, elliptically polarized light or circularly polarized light is converted into linearly polarized light, or the polarization direction of linearly polarized light is polarized. In particular, as a retardation plate that converts linearly polarized light into elliptically polarized light or circularly polarized light, and elliptically polarized light or circularly polarized light into linearly polarized light, respectively, for example, a ¼ wavelength plate (also referred to as “λ / 4 plate”) or the like. When a polarization direction of linearly polarized light is used, a half-wave plate (also referred to as “λ / 2 plate”) is usually used.

  Examples of the material of the retardation plate include polycarbonate, PVA, polystyrene, polymethyl methacrylate, polypropylene and other polyolefins, polyarylate, polyamide, polynorbornene, and other birefringent films, liquid crystal polymer Examples include an alignment film, a laminate in which an alignment layer of a liquid crystal polymer is supported by a film, and the like.

  The type of the retardation plate is, for example, various wavelength plates such as ½ or ¼, those for the purpose of compensating the viewing angle such as coloration compensation due to birefringence of the liquid crystal layer and viewing angle expansion, etc. The film may have a phase difference according to the purpose, or may be a tilted alignment film in which the refractive index in the thickness direction is controlled. Further, a laminate or the like in which two or more kinds of retardation plates are laminated and optical characteristics such as retardation are controlled may be used.

  The tilted orientation film is, for example, a method in which a heat-shrinkable film is bonded to a polymer film, and the polymer film is subjected to stretching treatment or shrinkage treatment under the action of the shrinkage force by heating, or a liquid crystal polymer is obliquely oriented. It can obtain by the method of making it.

  Next, an example of a polarizing plate in which a viewing angle compensation film is further laminated on the polarizing plate of the first example will be described.

  The viewing angle compensation film is, for example, a film for widening the viewing angle so that the image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from an oblique direction rather than perpendicular to the screen. As such a viewing angle compensation film, for example, a film obtained by applying a discotic liquid crystal to a triacetyl cellulose film or the like, or a retardation plate is used. As a normal retardation plate, for example, a polymer film having birefringence that is uniaxially stretched in the plane direction is used, whereas as the viewing angle compensation film, for example, biaxially stretched in the plane direction. Retardation of bi-directionally stretched films, such as polymer films having birefringence, and uniaxially stretched in the plane direction and also in the thickness direction, such as a tilted oriented polymer film with a controlled refractive index in the thickness direction A board is used. Examples of the tilted orientation film include a heat shrinkable film adhered to a polymer film, and the polymer film stretched or shrunk under the action of the shrinkage force by heating, or a liquid crystal polymer obliquely oriented. Etc. In addition, as a raw material material of the polymer film, the same material as the polymer material of the retardation plate previously extended can be used.

  Next, an example of a polarizing plate in which a brightness enhancement film is further laminated on the polarizing plate of the first example will be described.

  This polarizing plate is usually used by being disposed on the back side of the liquid crystal cell. The brightness enhancement film reflects linearly polarized light with a predetermined polarization axis or circularly polarized light in a predetermined direction when natural light is incident, for example, by a backlight of a liquid crystal display device, reflection from the back side, or the like, and transmits other light. It shows the characteristic to do. Light from a light source such as a backlight is incident to obtain transmitted light in a predetermined polarization state, and light other than the predetermined polarization state is reflected without being transmitted. The light reflected on the surface of the brightness enhancement film is further inverted via a reflector or the like provided behind the brightness enhancement film, and is incident again on the brightness enhancement film, and part or all of the light is transmitted as light having a predetermined polarization state. In addition to increasing the amount of light transmitted through the brightness enhancement film, the polarized light film (polarizer) is supplied with polarized light that is not easily absorbed to increase the amount of light that can be used for liquid crystal image display and the like, thereby improving the brightness. Is. When light is incident through the polarizer from the back side of the liquid crystal cell without using the brightness enhancement film, light having a polarization direction that does not coincide with the polarization axis of the polarizer is almost absorbed by the polarizer. As a result, the light does not pass through the polarizer. That is, although depending on the characteristics of the polarizer used, approximately 50% of the light is absorbed by the polarizer, and the amount of light that can be used for liquid crystal image display or the like is reduced accordingly, and the image becomes dark. The brightness enhancement film reflects light having a polarization direction that is absorbed by the polarizer without being incident on the polarizer, and is reflected once by the brightness enhancement film, and further provided on the rear side of the reflector. Etc., and re-incident on the brightness enhancement film. Then, since the polarization direction of the light reflected and inverted between the two passes only through the polarization direction that can pass through the polarizer, it transmits the polarized light and supplies it to the polarizer. Light can be efficiently used to display an image on the liquid crystal display device, and the screen can be brightened.

  A diffusion plate may be provided between the brightness enhancement film and the reflective layer. In this case, the polarized light reflected by the brightness enhancement film is directed to the reflective layer, but the installed diffusion plate uniformly diffuses the light passing therethrough, and at the same time, cancels the polarization state and unpolarizes the light. And That is, the original natural light state is restored. The light in the non-polarized state, that is, the light in the natural light state is directed to the reflection layer and the like, reflected through the reflection layer, passes through the diffusion plate again, and reenters the brightness enhancement film. In this way, by providing the diffuser plate for returning to the original natural light state, for example, while maintaining the brightness of the display screen, at the same time, reducing unevenness in the brightness of the display screen and providing a uniform bright screen Can do. In addition, it is considered that the diffuser plate appropriately increases the number of repetitions of reflection of the first incident light, and it is possible to provide a uniform bright display screen in combination with the diffusion function of the diffuser plate.

  The brightness enhancement film is not particularly limited, and for example, a linear multi-layer thin film of dielectric material or a multi-layer laminate of thin film films having different refractive index anisotropy transmits linearly polarized light having a predetermined polarization axis, Other light can be used that reflects light. Specifically, for example, trade name D-BEF manufactured by 3M Company can be used. Also, it reflects the circularly polarized light on the left and right sides and transmits other light, such as a cholesteric liquid crystal layer, especially an oriented film of a cholesteric liquid crystal polymer, and a film substrate that supports the oriented liquid crystal layer. May be shown. As such a film, for example, the product name “PCF350” manufactured by Nitto Denko Corporation, the product name Transmax manufactured by Merck Co., etc. can be used.

  Therefore, in the case of a brightness enhancement film of a type that transmits linearly polarized light with a predetermined polarization axis, for example, the transmitted light is directly incident on the polarizing plate with the polarization axis aligned, thereby suppressing absorption loss due to the polarizing plate. While being able to permeate efficiently. On the other hand, in the case of a brightness enhancement film of a type that transmits circularly polarized light such as a cholesteric liquid crystal layer, it can be directly incident on a polarizer, but from the point of suppressing absorption loss, the transmitted circularly polarized light is converted into a retardation plate. It is preferable that the light is linearly polarized through the light and incident on the polarizing plate. Note that circularly polarized light can be converted to linearly polarized light by using, for example, a quarter wave plate as the retardation plate.

  A retardation plate that functions as a quarter-wave plate in a wide wavelength range such as a visible light region includes, for example, a retardation layer that functions as a quarter-wave plate for monochromatic light such as light having a wavelength of 550 nm, and other positions. It is obtained by laminating a retardation layer (for example, a retardation layer functioning as a half-wave plate) showing a retardation characteristic. Accordingly, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be a laminate composed of one or more retardation layers. Note that the cholesteric liquid crystal layer can also have a laminated structure in which two or more layers are laminated by combining those having different reflection wavelengths. Accordingly, a polarizing plate that reflects circularly polarized light in a wide wavelength range such as a visible light region can be obtained, and based on this, transmitted circularly polarized light in a wide wavelength range can be obtained.

  The various polarizing plates in the third example as described above may be, for example, an optical film obtained by laminating the polarizing plate and two or more optical layers. Specifically, for example, a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate, which is a combination of the reflective polarizing plate or transflective polarizing plate and a retardation plate, may be mentioned.

  As described above, an optical film in which two or more optical layers are laminated can be formed, for example, by a method of sequentially laminating them in the manufacturing process of a liquid crystal display device or the like. For example, there is an advantage that the quality stability and assembly workability are excellent, and the manufacturing efficiency of the liquid crystal display device and the like can be improved. For the lamination, various adhesive means such as an adhesive layer can be used as described above.

  Each layer such as a polarizing film, a transparent protective layer, an optical layer, and a pressure-sensitive adhesive layer forming the optical film of the present invention as described above includes, for example, salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, and cyanoacrylate compounds. Further, it may be provided with ultraviolet absorbing ability by appropriately treating with an ultraviolet absorber such as a nickel complex compound.

  Next, the liquid crystal panel of the present invention includes at least one of the polarizer and the optical film of the present invention (hereinafter also referred to as “optical film”), which is disposed on at least one surface of the liquid crystal cell.

The type of the liquid crystal cell is not particularly limited, and a conventionally known liquid crystal cell can be used as appropriate. The polarizer of the present invention is useful for a liquid crystal display device that displays light by making light in a polarized state incident on the liquid crystal cell. Therefore, among them, for example, a liquid crystal cell using TN (Twisted Nematic) liquid crystal or STN (Super Twisted Nematic) liquid crystal is preferable. In addition to these, IPS (In-Plane Switching), VA (Vertical Aligned), OCB (Optically Compensated Birefringence) mode liquid crystal cells using non-twisted liquid crystal, and the dichroic dye dispersed in the liquid crystal It can also be used for a liquid crystal cell using a guest-host liquid crystal or a ferroelectric liquid crystal. The liquid crystal driving method is not particularly limited.

  The optical film such as the polarizing plate may be disposed only on one surface of the liquid crystal cell, or may be disposed on both surfaces. When arrange | positioning on the said both surfaces, the kind of optical film may be the same and may differ. Moreover, when providing a polarizing plate and an optical member in the both sides of a liquid crystal cell, they may be the same and may differ.

  Furthermore, normal parts such as a prism array sheet, a lens array sheet, and a light diffusion plate may be provided at appropriate positions, and one or two or more of these parts may be arranged.

  The example of the liquid crystal panel which has arrange | positioned the optical film of this invention to FIGS. These figures are cross-sectional views showing the laminated state of the liquid crystal cell and the optical film, and hatching is provided to distinguish the components. Moreover, the same code | symbol is attached | subjected to the same location in each figure. The liquid crystal panel of the present invention is not limited to these.

  The liquid crystal panel of FIG. 6 includes a liquid crystal cell 12 and a polarizing plate 11, and the polarizing plates 11 are disposed on both surfaces of the liquid crystal cell 12. The structure of the liquid crystal cell (not shown) is not particularly limited, and is generally a structure in which liquid crystal is held between the array substrate and the filter substrate.

  7 includes a liquid crystal cell 12, a polarizing plate 11, and a retardation plate 13, and the polarizing plate 11 is laminated on both surfaces of the liquid crystal cell 12 with the retardation plate 13 interposed therebetween. In addition, the phase difference plate 13 and the polarizing plate 11 may be arrange | positioned on both surfaces of the liquid crystal cell 12 as an integrated optical film of this invention.

  The liquid crystal panel of FIG. 8A includes a liquid crystal cell 12, a polarizing plate 11, and a polarization conversion element 14, and the polarizing plate 11 is laminated on both surfaces of the liquid crystal cell 12, and further polarization conversion is performed on one side of one polarizing plate. Elements 14 are stacked. As the polarization conversion element 14, the element as described above can be used. For example, as shown in FIG. 5B, a composite of the quarter wavelength plate 15 and the cholesteric liquid crystal 16, or the same figure (C). An anisotropic multiple thin film reflective polarizing element 17 as shown in FIG. The polarizing plate 11 and the polarization conversion element 14 may be arranged on one side of the liquid crystal cell 12 as an integrated optical film of the present invention.

  Next, the liquid crystal display device of the present invention is a liquid crystal display device including a liquid crystal panel, and the liquid crystal panel is the liquid crystal panel of the present invention.

  The liquid crystal display device may further include a light source. Although it does not restrict | limit especially as said light source, For example, since the energy of light can be used effectively, it is preferable that it is a plane light source which radiate | emits polarized light, for example.

  In the liquid display device of the present invention, for example, a diffusion plate, an antiglare layer, an antireflection film, a protective layer and a protective plate are further arranged on the optical film (polarizing plate) on the viewing side, or a liquid crystal cell in a liquid crystal panel A compensation retardation plate or the like may be appropriately disposed between the polarizing plate and the polarizing plate.

  Next, the electroluminescence (EL) display device of the present invention is a display device having at least one of the polarizer of the present invention and the optical film of the present invention. This EL device may be either organic EL or inorganic EL.

  In recent years, it has been proposed to use, for example, an optical film such as a polarizer or a polarizing plate together with a λ / 4 plate in an EL display device as an antireflection from an electrode in a black state. The polarizer or optical film of the present invention is slanted even when linearly polarized light, circularly polarized light or elliptically polarized light is emitted from the EL layer or when natural light is emitted in the front direction. This is very useful when the emitted light in the direction is partially polarized.

  First, a general organic EL display device will be described here. The organic EL display device generally has a light emitter (organic EL light emitter) in which a transparent electrode, an organic light emitting layer, and a metal electrode are laminated in this order on a transparent substrate. The organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative or the like and a light emitting layer made of a fluorescent organic solid such as anthracene, or the like. Various combinations such as a laminate of a light-emitting layer and an electron injection layer made of a perylene derivative, or a laminate of the hole injection layer, the light-emitting layer, and the electron injection layer can be given.

  In such an organic EL display device, by applying a voltage to the anode and the cathode, holes and electrons are injected into the organic light emitting layer, and the holes and electrons are recombined. The generated energy emits light on the principle that it excites the phosphor and emits light when the excited phosphor returns to the ground state. The mechanism of recombination of holes and electrons is the same as that of a general diode, and current and emission intensity show strong nonlinearity with rectification with respect to applied voltage.

  In the organic EL display device, in order to extract light emitted from the organic light emitting layer, at least one of the electrodes needs to be transparent. Therefore, the organic EL display device is usually formed of a transparent conductor such as indium tin oxide (ITO). A transparent electrode is used as the anode. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.

  In the organic EL display device having such a configuration, the organic light emitting layer is preferably formed of an extremely thin film having a thickness of about 10 nm, for example. This is because the organic light-emitting layer transmits light almost completely as in the transparent electrode. As a result, at the time of non-light emission, the light incident from the surface of the transparent substrate, transmitted through the transparent electrode and the organic light emitting layer, and reflected by the metal electrode again returns to the surface side of the transparent substrate. For this reason, when viewed from the outside, the display surface of the organic EL display device looks like a mirror surface.

  The organic EL display device of the present invention is, for example, an organic EL display device including the organic EL light emitting device including a transparent electrode on a front surface side of the organic light emitting layer and a metal electrode on a back surface side of the organic light emitting layer. The optical film (polarizing plate or the like) of the present invention is preferably disposed on the surface of the transparent electrode, and a λ / 4 plate is preferably disposed between the polarizing plate and the EL element. Thus, by arranging the optical film of the present invention, it becomes an organic EL display device that has the effect of suppressing reflection from the outside and improving the visibility. Moreover, it is preferable that a phase difference plate is further disposed between the transparent electrode and the optical film.

  For example, the retardation film and the optical film (polarizing plate, etc.) have a function of polarizing the light incident from the outside and reflected by the metal electrode, so that the mirror surface of the metal electrode is visually recognized from the outside by the polarization action. There is an effect of not letting it. In particular, if a quarter-wave plate is used as a retardation plate and the angle formed by the polarization direction of the polarizing plate and the retardation plate is adjusted to π / 4, the mirror surface of the metal electrode is completely shielded. can do. That is, only the linearly polarized component of the external light incident on the organic EL display device is transmitted by the polarizing plate. The linearly polarized light becomes generally elliptically polarized light by the retardation plate, but becomes circularly polarized light particularly when the retardation plate is a quarter wavelength plate and the angle is π / 4.

  For example, this circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, reflected by the metal electrode, again transmitted through the organic thin film, the transparent electrode, and the transparent substrate, and again by the retardation plate. Become. And since this linearly polarized light is orthogonal to the polarization direction of the polarizing plate, it cannot pass through the polarizing plate, and as a result, the mirror surface of the metal electrode can be completely shielded as described above. .

  Moreover, the in-house manufacturing method of the liquid crystal display device and EL display device of the present invention comprises the polarizer of the present invention comprising a surface protective film on the display surface side, and an adhesive layer and a release layer on the opposite surface, and It is a manufacturing method including a step of bonding at least one of the optical films of the present invention to the display device immediately after being chip-cut.

  In this way, according to the in-house manufacturing method in which the polarizer and the optical film are cut and bonded to a liquid crystal cell or the like is consistently produced to produce various display devices, for example, to detect a defective area Immediate measurement is required, and marking must be determined by setting a limit sample or measuring inline. According to the manufacturing method of the present invention, the polarizer or the optical film of the present invention is marked on a portion that does not satisfy the condition (1), and immediately after punching, it is bonded to a liquid crystal panel or an EL display element for various displays. The device can be manufactured. In this way, the process from punching out the polarizer and optical film to sorting and bonding can be performed consistently, and the inspection time can be simplified, which simplifies manufacturing and reduces costs. You can also plan. In-house generally refers to an integrated line from punching and inspecting the roll of the polarizing plate to inspection and bonding to the LCD.

  Next, the present invention will be further described using the following examples and comparative examples. In addition, this invention is not limited only to these Examples. Unless otherwise specified, “%” means “mass%”.

(Example 1)
As shown in FIG. 1, two guide rolls (flat rolls) were placed in the swelling bath in advance, and pure water was placed in the bath as a swelling solvent and maintained at 25 ° C. A PVA film (trade name: VF-PS # 7500; manufactured by Kuraray Co., Ltd.) having a thickness of 75 μm is conveyed to the swelling bath by a guide roll, and the film is swollen in the swelling bath, and the length of the original fabric is further increased. On the other hand, it extended | stretched so that it might become 2.5 times. The time (a) from when the film comes into contact with the solvent in the swelling bath until it comes into contact with the first guide roll by conveyance is set to 3.5 seconds, and further after the second contact with the first guide roll. The time (b) until contact with the guide roll was 60 seconds. The total time during which any point of the film was immersed in the swelling bath was 92 seconds.

This film is immersed in a mixed solution of 0.04% iodine and 0.4% potassium iodide (dyeing bath, the same applies hereinafter) so that the film becomes three times the length of the original fabric in the dyeing bath. The film was dyed while stretching. This film was further immersed in a 3.5% boric acid aqueous solution (stretching bath) and stretched so as to be 6 times as much as the original fabric, thereby producing a polarizing film (thickness 27 μm). And after saponifying the TAC film (trade name TD-80U; manufactured by Fuji Photo Film Co., Ltd.) having a thickness of 80 μm, the polarizing film was bonded to both surfaces of the polarizing film with a 1% PVA aqueous solution and dried. .

(Example 2)
In the swelling treatment, the time (a) from the contact of the film with the solvent in the swelling bath to the contact with the first guide roll by conveyance is 2 seconds, and the second guide after the contact with the first guide roll. A polarizing film and a polarizing plate were produced in the same manner as in Example 1 except that the time (b) until contact with the roll was 35 seconds. The total time during which any point of the film was immersed in the swelling bath was 63 seconds.

(Example 3)
In the swelling treatment, the time (a) from the contact of the film with the solvent in the swelling bath to the contact with the first guide roll by conveyance is 11 seconds, and the second guide after the contact with the first guide roll. A polarizing film and a polarizing plate were produced in the same manner as in Example 1 except that the time (b) until contact with the roll was 110 seconds. The total time during which any point of the film was immersed in the swelling bath was 130 seconds.

Example 4
As shown in FIG. 2, one guide roll is arranged in the swelling bath, and the time (c) from when the film comes into contact with the solvent in the swelling bath until it comes into contact with the first guide roll by conveyance is 70 seconds. A polarizing film and a polarizing plate were produced in the same manner as in Example 1 except that. The total time during which any point of the film was immersed in the swelling bath was 75 seconds.

(Example 5)
As shown in FIG. 1, two guide rolls were previously placed in the swelling bath, and water was placed in the bath as a swelling solvent and kept at 32 ° C. 75 μm thick PVA film (trade name OPL-M;
Nippon Synthetic Chemical Co., Ltd.) The raw fabric is conveyed to the swelling bath by a guide roll, the film is swollen in the swelling bath, and further stretched to 1.9 times the length of the raw fabric. went. The time (a) from when the film comes into contact with the solvent in the swelling bath until it comes into contact with the first guide roll by conveyance is set to 5 seconds, and after the contact with the first guide roll, the second guide roll. The time (b) until contact with was 77 seconds. The total time that any point on the film was immersed in the swelling bath was 121 seconds.

  This film is immersed in a mixed solution (dye bath) of 0.04% iodine and 0.4% potassium iodide so as to be 2.8 times the length of the original fabric in the dye bath. The film was dyed while stretching. This film was further immersed in a 3.5% boric acid aqueous solution (stretching bath) and stretched so as to be 6 times the length of the original fabric, thereby producing a polarizing film (thickness 30 μm). And the polarizing plate was produced by bonding the saponified TAC film on both surfaces of the polarizing film with a 1% PVA aqueous solution and drying.

(Example 6)
Using the same PVA film as in Example 5, replacing the guide roll with a spiral roll, the time (a) from contact of the film with the solvent of the swelling bath to contact with the first guide roll by conveyance is 11 seconds, Further, a polarizing film and a polarizing plate were produced in the same manner as in Example 1 except that the time (b) from contact with the first guide roll to contact with the second guide roll was 110 seconds. The spiral roll had a groove (indentation) width of 1 cm and a groove depth of 1 cm. The total time during which any point of the film was immersed in the swelling bath was 128 seconds.

(Example 7)
Using the same PVA film as in Example 5, replacing the guide roll with a crown roll, the stretching ratio in the swelling bath is 2.1 times the length of the original fabric, and the stretching ratio in the dyeing bath is the length of the original fabric The time (a) from contact of the film with the solvent in the swelling bath to contact with the first guide roll by conveyance for 2.9 times is 2 seconds, and after the contact with the first guide roll, A polarizing film and a polarizing plate were produced in the same manner as in Example 1 except that the time (b) until contact with the guide roll No. 2 was 35 seconds. The total time during which any point of the film was immersed in the swelling bath was 63 seconds.

(Example 8)
The same PVA film as in Example 5 was used, the swelling bath temperature was 42 ° C., and in the swelling treatment, the time from contact of the film with the solvent of the swelling bath to contact with the first guide roll by conveyance was 6 seconds ( a) Further, the polarizing film and the polarizing plate were prepared in the same manner as in Example 1 except that the time (b) from contact with the first guide roll to contact with the second guide roll was 60 seconds. Produced. The total time during which any point of the film was immersed in the swelling bath was 95 seconds.

Example 9
As shown in FIG. 2, one guide roll (crown roll) is arranged in the swelling bath, the same PVA film as in Example 5 is used, and after the film comes into contact with the solvent in the swelling bath, the first is conveyed. A polarizing film and a polarizing plate were produced in the same manner as in Example 4 except that the time (c) until contact with the guide roll was 170 seconds. The total time during which any point of the film was immersed in the swelling bath was 173 seconds.

(Comparative Example 1)
In the swelling treatment, the time (a) from the contact of the film with the solvent in the swelling bath to the contact with the first guide roll by conveyance is set to 14 seconds, and the second contact after the contact with the first guide roll. A polarizing film and a polarizing plate were produced in the same manner as in Example 1 except that the time (b) until contact with the guide roll was 75 seconds. The total time during which any point of the film was immersed in the swelling bath was 94 seconds.

(Comparative Example 2)
In the swelling treatment, the time (a) from the contact of the film with the solvent in the swelling bath to the contact with the first guide roll by conveyance is set to 0.3 seconds, and the contact with the first guide roll is performed after the contact with the first guide roll. A polarizing film and a polarizing plate were produced in the same manner as in Example 1 except that the time (b) until contact with the guide roll No. 2 was 4 seconds. The total time during which any point of the film was immersed in the swelling bath was 15 seconds.

(Comparative Example 3)
In the swelling treatment, the polarizing film and the polarizing film were obtained in the same manner as in Example 4 except that the time (c) from contact of the film to the solvent of the swelling bath to contact with the first guide roll by conveyance was set to 22 seconds. A polarizing plate was produced. The total time during which any point of the film was immersed in the swelling bath was 24 seconds.

(Comparative Example 4)
The same PVA film as in Example 5 was used, the guide roll was replaced with a spiral roll (same as in Example 6), the swelling temperature was 38 ° C., and the draw ratio in the swelling bath was 2.5 times the original length. The draw ratio in the dyeing bath was 3.2 times the length of the original fabric, and the time (c) from the contact of the film with the solvent of the swelling bath to the contact with the first guide roll was 188 seconds. A polarizing film was produced in the same manner as in Example 4 except for the above. The total time during which any point of the film was immersed in the swelling bath was 191 seconds. However, in Comparative Example 4, the traveling property of the film was poor and a polarizing film could not be produced.

(Comparative Example 5)
The same PVA film as in Example 5 was used, the swelling bath temperature was 32 ° C., the stretching ratio in the swelling bath was 2.8 times the length of the original fabric, and the stretching ratio in the dyeing bath was based on the length of the original fabric. 3.5 times, the time (a) from contact of the film to the solvent of the swelling bath to contact with the first guide roll by conveyance is set to 15 seconds. A polarizing film and a polarizing plate were produced in the same manner as in Example 1 except that the time (b) until contact with the guide roll No. 2 was 5 seconds. The total time during which any point of the film was immersed in the swelling bath was 21 seconds.

(Evaluation method of display unevenness)
The polarizing plates obtained in Examples 1 to 9 and Comparative Examples 1 to 3 and 5 were each cut into a 25 cm length × 20 cm square, and the adhesive was applied to the surface (light source side) of the high contrast type IPS liquid crystal cell. The product name SEG1425DU (manufactured by Nitto Denko) was bonded to the other surface (viewing side) of the liquid crystal cell. The obtained liquid crystal panel was placed on various backlights (A to D) described later such that the light source side polarizing plate (produced polarizing plate) was on the bottom. Then, on the viewing side of the liquid crystal panel, observation was performed from the front direction and the oblique direction (30 °, 45 °, 60 °), and unevenness during black display was evaluated based on the following evaluation criteria. In addition, in the following evaluation criteria, 7-6 shows the outstanding effect, 5-3 can be used practically, and it can be judged that 2-1 is impractical.

(Evaluation criteria)
7: Unevenness is not seen at all.
6: Unevenness is slightly visible in the dark room, but no unevenness is visible under the fluorescent lamp.
5: Unevenness is visible in the dark room, but no unevenness is visible under the fluorescent lamp.
4: Unevenness is clearly visible in the dark room, but no unevenness is visible under fluorescent lamps.
3: Unevenness is slightly visible under fluorescent light.
2: Unevenness is visible under fluorescent light.
1: Unevenness is clearly visible under fluorescent light.

(Backlight A)
FIG. 9 is a cross-sectional view schematically showing the backlight A. As shown, the backlight 6 includes a wedge-shaped light guide plate 22 printed on the back surface, a cold cathode tube 26 and a lamp house 27, a diffuser plate 21 on the upper surface, and a diffuse reflector on the lower surface. 23 were arranged respectively.

(Backlight B)
FIG. 10 is a cross-sectional view schematically showing the backlight B. As shown in the figure, in the backlight 7, a laminate of a cholesteric layer and a λ / 4 plate layer is disposed on the backlight 6 shown in FIG. At this time, the laminate was disposed such that the cholesteric surface (16) was on the backlight 6 side and the λ / 4 plate (15) was on the viewing side. When the liquid crystal cell is disposed on the backlight 7 as described above, the amount of transmitted light is maximized. In addition, as a laminate of the cholesteric layer and the λ / 4 plate layer, a product obtained by removing only the polarizing plate portion from the product name PCF400TEG manufactured by Nitto Denko Corporation was used.

(Backlight C)
FIG. 11 is a cross-sectional view schematically showing the backlight C. As shown in the figure, in the backlight 8, an anisotropic multiple thin film reflective polarizer (trade name DBEF; manufactured by 3M) 17 is disposed on the backlight 6 shown in FIG. 9. When the liquid crystal cell is disposed on the backlight 8 as described above, the amount of transmitted light is maximized.

(Backlight D)
FIG. 12A is a cross-sectional view showing an outline of the backlight D, and FIG. 12B is a view showing a partial outline of the above-described (A). As shown in the figure, this backlight 9 is provided with a cold cathode tube 26 and a lamp house 27 on a wedge-shaped light guide plate 25 in which a prism is formed on a light emitting surface, and a diffuse reflector 23 on the lower surface of the light guide plate 25. A prism sheet 24 is disposed on the upper surface of the light guide plate 25. The prism sheet 24 was disposed so that the prism surface thereof faces the prism surface of the light guide plate 25 as shown in a partially enlarged view (B) of FIG. A diffusion plate 21 is further disposed on the upper surface of the prism sheet 24.

表１から明らかなように、実施例１〜９の偏光板は、比較例１〜３および５の偏光板と比べて、正面および斜めから視認した際の表示ムラが少ないという優れた結果となった。以上の結果から、本発明の製造方法によれば、優れた偏光フィルムが製造できるため、表示ムラが抑制された各種画像表示装置を得ることができる。

As is clear from Table 1, the polarizing plates of Examples 1 to 9 have excellent results in that display unevenness when viewed from the front and oblique directions is less than the polarizing plates of Comparative Examples 1 to 3 and 5. It was. From the above results, according to the production method of the present invention, since an excellent polarizing film can be produced, various image display devices in which display unevenness is suppressed can be obtained.

  As described above, if the polarizer obtained by the production method of the present invention is used as an optical film such as a polarizing plate in a liquid crystal panel, a liquid crystal display device, etc., there is no display unevenness and excellent display characteristics. Can be achieved. In addition, according to the present invention, since a polarizer, a polarizing plate, and the like can be marked by in-line measurement, for example, an off-line process such as appearance inspection and packaging immediately after chip-cutting the polarizer is unnecessary, and a liquid crystal display device or In-house manufacturing to be bonded to an EL display device is possible. Thereby, for example, the cost of the display device can be reduced, and the manufacturing process can be easily managed. Therefore, the industrial value is great.

It is the schematic which shows an example of the swelling process in the manufacturing method of the optical film of this invention. It is the schematic which shows the other example of the swelling process in the manufacturing method of the optical film of this invention. It is the schematic which shows the example of the guide roll used for the manufacturing method of this invention. It is sectional drawing which shows an example of the optical film of this invention. It is sectional drawing which shows the other example of the optical film of this invention. It is sectional drawing which shows the example of the liquid crystal panel of this invention. It is sectional drawing which shows the other example of the liquid crystal panel of this invention. (A) is sectional drawing which shows the further another example of the liquid crystal panel of this invention, (B) and (C) are partial sectional drawings of said (A). It is sectional drawing of an example of the backlight in the Example of this invention. It is sectional drawing of the other example of the backlight in the Example of this invention. It is sectional drawing of the further another example of the backlight in the said Example. (A) is sectional drawing of the further another example of the backlight in the said Example, (B) is the partial schematic of said (A).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polarizing film 2 Transparent protective layer 3 Adhesive layer 10, 11, 20 Polarizing plate 12 Liquid crystal cell 13 Phase difference plate 14 Polarization conversion element 15 1/4 wavelength plate 16 Cholesteric liquid crystal layer 17 Anisotropic multiple thin film reflective polarizing element 21 Diffusion plate 22 Light guide plate 23 Reflector plate 24 Prism sheet 25 Light guide plate 31 with prism 31 Polyvinyl alcohol film 32 Swelling bath 33 Aqueous solvent 41, 42, 43, 44, 45 Guide roll

Claims (15)

A swelling step of swelling the polyvinyl alcohol film by immersing it in an aqueous solvent in a swelling bath by conveying the polyvinyl alcohol film with a guide roll, a dyeing step of dyeing the polyvinyl alcohol film with a dichroic substance, A method for producing a polarizing film comprising a stretching step of stretching a polyvinyl alcohol film ,
In the swelling step, at least a first guide roll is disposed in the swelling bath,
The immersing the polyvinyl alcohol film in said aqueous solvent and said when moving the aqueous solvent, wherein the polyvinyl alcohol film, polyvinyl alcohol film is the first guide before causing rapid swelling Contact the roll ,
The time required for the polyvinyl alcohol film to contact the first guide roll after contacting the aqueous solvent (a) is 0.6 to 12 seconds. . A second guide roll is further disposed in the swelling bath,
The polyvinyl alcohol film is brought into contact with the first guide roll before the polyvinyl alcohol film undergoes rapid swelling , and further, the second guide roll after the polyvinyl alcohol film undergoes rapid swelling. The manufacturing method of Claim 1 made to contact. The manufacturing method of Claim 1 or 2 which makes the required time (b) until it contacts the 2nd guide roll after the said polyvinyl alcohol-type film contacts the said 1st guide roll to 13 to 120 seconds. The manufacturing method according to claim 3 , wherein the total of the required time (a) and the required time (b) is in the range of 25 to 180 seconds. The polyvinyl alcohol film was immersed in a swelling bath of aqueous solvent by conveying the guide roll, and stained with the solvent swelling step of swelling the polyvinyl alcohol film, the polyvinyl alcohol film with a dichroic substance staining A process for producing a polarizing film comprising a stretching step of stretching the polyvinyl alcohol film ,
In the swelling step, at least a first guide roll is disposed in the swelling bath,
The polyvinyl alcohol film was immersed in the aqueous medium, and, when moving the aqueous solvent, the polyvinyl alcohol film, after the polyvinyl alcohol film has caused a rapid swelling, the first Contact the guide roll ,
The production method characterized in that the time (c) required for the polyvinyl alcohol film to contact the first guide roll after contacting the aqueous solvent is 25 to 180 seconds . The manufacturing method according to any one of claims 1 to 5 , wherein a time for immersing the material in the swelling bath is 100 seconds or more. The manufacturing method according to any one of claims 1 to 6 , wherein a thickness of the polyvinyl alcohol-based film before the swelling treatment is 110 µm or less. The manufacturing method as described in any one of Claims 1-7 in which the said polyvinyl alcohol-type film contains 1 to 17 weight% of plastic materials. The manufacturing method according to claim 1 , wherein the guide roll is at least one roll selected from a crown roll, a vent roll, and an ear height roll. The manufacturing method as described in any one of Claims 1-9 in which guide rolls other than a 1st guide roll contain a spiral roll. The temperature of the said swelling bath is the range of 15-50 degreeC, The manufacturing method as described in any one of Claims 1-10 . The manufacturing method according to any one of claims 1 to 11 , wherein in the swelling step, the polyvinyl alcohol film is further subjected to stretching treatment in the swelling bath. Stretch ratio in the stretching process, according to any one of claims 1 to 12 in the range of 1.5 to 4.0 times the length before the polyvinyl alcohol-based film subjected to swelling process Production method. The method according to any one of claims 1 to 13 , wherein the dichroic substance is at least one of iodine and an organic dye. The method according to claim 14 , wherein the dichroic substance is two or more kinds of organic dyes.

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