JP5064075B2 - Manufacturing method of polarizing film - Google Patents

Description

  The present invention relates to a method for producing a polarizing film used in an image display device such as a liquid crystal display device, an electroluminescence (EL) display device, a plasma display (PD), and a field emission display (FED), and a method for producing the same. It is related with the polarizing film obtained by these. The present invention also relates to a polarizing plate, an optical film, and an image display device using the polarizing film, the polarizing plate, or the optical film using the polarizing film.

  A polarizing film used for an image display device (particularly a liquid crystal display device) is required to have a high transmittance and a high degree of polarization in order to provide a bright image with good color reproducibility. Such a polarizing film is conventionally produced by orienting a dichroic substance such as iodine or dichroic dye having dichroism on a polyvinyl alcohol (PVA) film.

  In recent years, along with the increase in size, function, and brightness of liquid crystal display devices, the polarizing plates used therefor are also required to have improved optical properties and in-plane uniformity at the same time. However, in order to obtain a large polarizing plate, it is necessary to uniformly uniaxially stretch a wide raw film, but this is actually a very difficult process, and at the same time in-plane uniformity. Optical characteristics tend to deteriorate. If the in-plane optical characteristics are not uniform, display unevenness occurs when the image display device is formed.

  As the stretching method for orienting the dichroic substance, a wet stretching method and a dry stretching method are mainly known, but a method for obtaining a polarizing film having a high degree of orientation in a wide original film. Some have been proposed mainly in the dry drawing method. (For example, refer to Patent Document 1).

  However, the method described in Patent Document 1 has a problem that the uniaxiality of the oriented film is lowered and the in-plane uniformity is lowered, and the dry stretching method has a degree of polarization compared to the wet stretching method. There is a problem that becomes low. Therefore, in Patent Document 2 below, the ratio (L ′ / W ′) between the distance between stretching (L ′) and the initial raw film width (W ′) during the stretching treatment is set to 0.5 or more and 30 or less. This makes it possible to produce a polarizing film having a uniform in-plane optical characteristic and a high degree of orientation even in a wide original film.

  However, this manufacturing method has a problem that the film shrinks uniformly after stretching, resulting in an increase in film thickness and a decrease in width.

JP 2002-326278 A JP 2004-341515 A

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a polarizing film manufacturing method having a uniform thickness and capable of manufacturing a wide polarizing film, and a polarizing film obtained by the manufacturing method. It is to provide. Moreover, this invention is providing the image display apparatus using the polarizing plate, optical film, and polarizing film, polarizing plate, or optical film which used the said polarizing film.

  In order to solve the above-mentioned conventional problems, the inventors of the present application have studied a polarizing film manufacturing method and a polarizing film obtained by the method. As a result, it has been found that shrinkage in the width direction of the stretched film can be suppressed by reducing the distance between the stretches during the stretching treatment, and the present invention has been completed.

  That is, the method for producing a polarizing film according to the present invention is a method for producing a polarizing film including a wet drawing step of a film in order to solve the above-described problems, and a draw ratio R with respect to a state immediately before drawing, and in a bath The ratio (R / L) of the distance L between stretching at 8 is 8 or more.

  According to the above method, when the film is immersed in the bath and stretched, the ratio (R / L) of the stretch ratio R and the distance L between stretches in the bath is set to 8 or more. Increase the draw ratio with respect to the draw distance. Thereby, shrinkage | contraction in the width direction of the film after extending | stretching is suppressed. As a result, a wide polarizing film can be manufactured. Moreover, the thickness variation of a polarizing film can be suppressed and the polarizing film excellent in the uniformity of thickness is obtained. In addition, the distance L between extending | stretching represents the length distance of the pass line between the parts extended | stretched by applying the tensile force required for extending | stretching.

  Stretching is preferably performed in a multistage manner in each predetermined position in the bath, and R / L is preferably 8 or more in at least any one stretching stage. Even when stretching is performed in multiple stages, a wide polarizing film having sufficient optical properties as a polarizing film can be produced by setting R / L to 8 or more in at least one of the stretching stages. .

  It is preferable that the ratio (L / W) of the distance L between stretching and the film width W immediately before stretching is less than 0.5. As in the above method, the shrinkage in the width direction of the film after stretching is further suppressed by making the ratio (L / W) of the film length L to the film width W just before stretching less than 0.5. To do. As a result, a wider polarizing film can be manufactured.

  It is preferable that the film width residual ratio Z represented by the following mathematical formula (1) in the stretched film is 60% or more.

  Moreover, in order to solve the said subject, the polarizing film which concerns on this invention was obtained by the manufacturing method of the polarizing film as described above.

  The polarizing plate according to the present invention is characterized in that a transparent protective film is provided on at least one side of the polarizing film described above.

  Furthermore, the optical film according to the present invention is characterized in that at least one polarizing film or polarizing plate described above is laminated.

  Furthermore, an image display device according to the present invention is characterized by using at least one polarizing film, polarizing plate or optical film described above.

The present invention has the following effects by the means described above.
That is, according to the present invention, in the wet stretching treatment of the film, the ratio of the stretch ratio R to the film length L (R / L) is set to 8 or more, thereby suppressing the shrinkage in the width direction of the film. And uniform thickness. As a result, it is possible to produce a wide polarizing film while maintaining good optical characteristics as the polarizing film.

  An embodiment of the present invention will be described below with reference to FIGS. However, parts that are not necessary for the description are omitted, and there are parts that are illustrated in an enlarged or reduced manner for ease of explanation.

  The manufacturing method of the polarizing film which concerns on this invention includes a wet extending process, and performs ratio (R / L) of the draw ratio R at the time of an extending | stretching process, and the film length L at 8 or more in the wet extending process. Further, the R / L is more preferably 15 or more. However, R / L is preferably 200 or less, more preferably 50 or less, considering the mechanical strength against the tensile force in the longitudinal direction of the film. Here, the film length L represents the length of the film stretched by applying a tensile force required for stretching. Moreover, a guide roll etc. may be arrange | positioned between pinch rolls and the film may be bent.

  When a wet stretching process is performed as in the prior art, as shown in FIG. 1A, the stretched film shrinks in the width direction and the thickness direction, and thus it is difficult to widen the width. However, in the present invention, by setting R / L to 8 or more, shrinkage in the width direction can be suppressed as shown in FIG. As a result, a wide polarizing film can be manufactured.

  In the method for producing a polarizing film according to the present embodiment, the ratio (L / W) of the film length L during the stretching process and the film width W just before stretching is preferably less than 0.5. . Thereby, shrinkage of the film in the width direction can be further suppressed. As a result, a wider polarizing film can be manufactured. The L / W is more preferably 0.3 or less. However, L / W is preferably 0.1 or more from the viewpoint of ease of device design and management. The film width W immediately before stretching represents the film width of the polarizing film immediately before stretching, and means the film width of the original film before the stretching process is performed.

  The film length L is preferably in the range of 50 to 500 mm, and more preferably in the range of 150 to 350 mm. If L is less than 50 mm, it may be difficult to control stretching. On the other hand, when L exceeds 500 mm, the neck-in becomes large, which may not be preferable.

  The film width W of the film 9 is, for example, 60% or more with respect to the film width immediately before stretching when the film is stretched within a range of a stretch ratio of 4.5 to 7.0 times with respect to the film immediately before the wet stretching step. It is preferable that the residual rate is 70% or more. If the residual ratio is less than 60%, it may be difficult to produce a large polarizing plate, and the yield may be reduced. In addition, when extending | stretching in multiple steps like the after-mentioned, the said residual rate is represented by the film width after finishing the final wet extending process with respect to the film width of the film 9 just before a wet extending process. .

  Considering the residual ratio of the film width, the film width (in the unstretched state) of the polymer film used in the present embodiment is preferably in the range of 1000 to 10000 mm, preferably 3000 to 8000 mm. More preferably within the range. When the film width is less than 1000 mm, when the film 9 is uniaxially stretched, it becomes easy to be affected by neck-in even near the center of the film 9, and a wide polarizing film with uniform optical performance is obtained. You may not be able to get it. On the other hand, when it exceeds 10,000 mm, it may be difficult to uniformly uniaxially stretch the PVA film.

  The thickness of the film 9 is preferably 20 to 200 μm, and more preferably 50 to 100 μm. If the thickness of the film 9 is less than 20 μm, the mechanical strength of the film 9 is too low to perform uniform stretching, and color spots are likely to occur in the polarizing film. On the other hand, if the thickness of the film 9 exceeds 200 μm, when the film 9 is uniaxially stretched, the thickness of the film 9 is likely to fluctuate due to neck-in at the end, and the color spots of the polarizing film are easily emphasized. It is not preferable.

  The wet stretching of the present invention may be performed in multiple stages in one bath, for example, as shown in FIG. The film 9 shown in the figure is conveyed in a direction indicated by an arrow by a pair of pinch rolls 1 and 7, and stretched between the pinch rolls by the pinch rolls 2 to 6 arranged at predetermined positions in the bath 8. Is called. As shown in FIG. 2, when stretching is performed two or more times in a multistage manner, R / L ≧ 8 only needs to be satisfied in at least one of the stages. R / L ≧ 8 may be satisfied at a plurality of locations, but for example, it is preferable to set one side to a value larger than 10 and the other to a value smaller than 10 than to set R / L to 10 at two locations. Further, the R / L in each stretching step may be the same and may vary depending on various conditions, but is preferably different. Furthermore, each stretching may be performed by continuously providing stretching steps or intermittently.

  When performing longitudinal uniaxial stretching using the apparatus shown in FIG. 2, it is preferable to set the rotational speed of the pinch rolls 2 to 6 so as to increase stepwise as the conveyance proceeds. Thereby, an extending | stretching step can be provided continuously. The rotational speed of the pinch rolls 2 to 6 can be appropriately set in consideration of the draw ratio and the like in each drawing stage. However, when stretching is not performed between the pinch rolls 1 and 2 and the pinch rolls 6 and 7, the rotational speed of the pinch roll 1 is set to be the same as that of the pinch roll 2, and the rotational speed of the pinch roll 7 is set to be the same as that of the pinch roll 6. Is preferred.

  Although it does not specifically limit as a draw ratio with respect to an unstretched state, Usually, it is preferable that it is 1.5-3 times. Moreover, when extending | stretching by multistep as shown in FIG. 2, it is preferable that the total draw ratio accumulate | stored for every extending | stretching step will be 3-8 times, and it is still more preferable that it will be 4-7 times. Thereby, it becomes possible to further improve the uniformity of the film.

  The method for producing a polarizing film according to the present invention can use an appropriate method according to the required optical properties of the polarizing film. For example, a polymer film as an initial raw film is swelled, dyed, crosslinked, A method of manufacturing by a series of manufacturing steps consisting of stretching, water washing and drying treatment steps is common. In each of these treatment steps except the drying treatment step, each treatment is performed while being immersed in a bath made of various solutions. The order, number of times, and presence / absence of each treatment of swelling, dyeing, crosslinking, stretching, rinsing and drying in each treatment step are not particularly limited, and several treatments are performed in one treatment step. It may be performed simultaneously or some processes may not be performed. For example, the stretching process may be performed after the dyeing process, may be performed simultaneously with the swelling or the dyeing process, or may be performed after the stretching process. Among these steps, the present invention can be suitably applied to swelling, dyeing, crosslinking, stretching, washing steps, and the like. Further, the water washing treatment may be performed after all the treatments or only after the specific treatment.

  There is no limitation on the stretching treatment, and any appropriate method can be used. For example, in the case of roll stretching, a method is used in which stretching is performed based on a difference in peripheral speed between rolls. Furthermore, additives such as boric acid, borax or potassium iodide may be added to each treatment as appropriate. Therefore, the polarizing film according to the present invention may contain boric acid, zinc sulfate, zinc chloride, potassium iodide and the like as necessary. Furthermore, in some of these processes, the film may be stretched in the flow direction or the width direction as appropriate, and a water washing process may be performed for each process.

  As the swelling step, for example, it is immersed in a swelling bath filled with water. As a result, the polymer film is washed with water, and the surface of the polymer film can be cleaned of stains and anti-blocking agents, and the effect of preventing unevenness such as uneven dyeing can be expected by swelling the polymer film. In this swelling bath, glycerin, potassium iodide or the like may be appropriately added, and the concentration to be added is preferably 5% by weight or less for glycerin and 10% by weight or less for potassium iodide. The temperature of the swelling bath is preferably in the range of 20 to 45 ° C, more preferably 25 to 40 ° C. The immersion time in the swelling bath is preferably 2 to 180 seconds, more preferably 10 to 150 seconds, and particularly preferably 60 to 120 seconds. Further, the polymer film may be stretched in this swelling bath, and the stretching ratio at that time is about 1.1 to 3.5 times that of the unstretched film, including stretching due to swelling.

  In the dyeing step, for example, the dichroic substance is adsorbed on the polymer film by immersing the polymer film in a dyeing bath containing a dichroic substance such as iodine.

  A conventionally known substance can be used as the dichroic substance, and examples thereof include iodine and organic dyes. Organic dyes include, for example, Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Spura Blue G, Spura Blue GL, Spura Orange GL, Direct Sky Blue, Direct First orange S, first black, etc. can be used.

  One kind of these dichroic substances may be used, or two or more kinds may be used in combination. When using the said organic dye, it is preferable to combine 2 or more types from the point which aims at neutralization of the visible region, for example. Specific examples include combinations of Congo Red and Supra Blue G, Supra Orange GL and Direct Sky Blue, or Direct Sky Blue and First Black.

  As the dye bath solution, a solution in which the dichroic substance is dissolved in a solvent can be used. As the solvent, water is generally used, but an organic solvent compatible with water may be further added. The concentration of the dichroic substance is preferably in the range of 0.010 to 10% by weight, more preferably in the range of 0.020 to 7% by weight, and 0.025 to 5% by weight. Is particularly preferred.

  Further, when iodine is used as the dichroic substance, it is preferable to further add an iodide because the dyeing efficiency can be further improved. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Examples include titanium. The addition ratio of these iodides is preferably 0.010 to 10% by weight and more preferably 0.10 to 5% by weight in the dyeing bath. Among these, it is preferable to add potassium iodide, and the ratio (weight ratio) of iodine to potassium iodide is preferably in the range of 1: 5 to 1: 100, and 1: 6 to 1:80. More preferably, it is in the range of 1: 7 to 1:70.

  Although the immersion time of the polymer film in the said dyeing bath is not specifically limited to this, It is preferable that it is the range for 1 to 20 minutes, and it is more preferable that it is 2 to 10 minutes. Moreover, it is preferable that the temperature of a dyeing bath exists in the range of 5-42 degreeC, and it is more preferable that it exists in the range of 10-35 degreeC. In addition, the polymer film may be stretched in this dye bath, and the total stretch ratio accumulated at this time is about 1.1 to 4.0 times.

  In addition to the method of immersing in a dyeing bath as described above, the dyeing treatment may be, for example, a method of applying or spraying an aqueous solution containing a dichroic substance onto the polymer film, and the polymer film A dichroic substance may be mixed in advance at the time of film formation.

  As the crosslinking step, for example, the polymer film is immersed in a bath containing a crosslinking agent to be crosslinked. A conventionally known substance can be used as the crosslinking agent. Examples thereof include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. One kind of these may be used, or two or more kinds may be used in combination. When two or more types are used in combination, for example, a combination of boric acid and borax is preferable, and the addition ratio (molar ratio) is preferably in the range of 4: 6 to 9: 1. The range of 5: 4.5 to 7: 3 is more preferable, and 6: 4 is most preferable.

  As the solution of the crosslinking bath, a 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 limited to this, but is preferably in the range of 1 to 10% by weight, and more preferably 2 to 6% by weight.

  In the crosslinking bath, an iodide may be added from the viewpoint of obtaining in-plane uniform characteristics of the polarizing film. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Examples thereof include titanium, and the content is 0.05 to 15% by weight, more preferably 0.5 to 8% by weight. Among these, a combination of boric acid and potassium iodide is preferable, and the ratio (weight ratio) of boric acid and potassium iodide is preferably in the range of 1: 0.1 to 1: 3.5, and 1: 0 More preferably, it is in the range of 5 to 1: 2.5.

  The temperature of the crosslinking bath is usually in the range of 20 to 70 ° C., and the immersion time of the polymer film is usually in the range of 1 second to 15 minutes, preferably 5 seconds to 10 minutes. Further, the crosslinking treatment may use a method of applying or spraying a solution containing a crosslinking agent in the same manner as the dyeing treatment, and the polymer film may be stretched in this crosslinking bath. 1.1 to 4.0 times.

  As the stretching step, for example, in the wet stretching method, stretching is performed so that the accumulated total stretching ratio is about 2 to 7 times in a state of being immersed in a bath.

  The stretching bath solution is not particularly limited to this, but for example, a solution to which various metal salts or a compound of iodine, boron or zinc is added can be used. As a solvent of this solution, water, ethanol or various organic solvents are appropriately used. Especially, it is preferable to use the solution which added about 2-18 weight% of boric acid and / or potassium iodide, respectively. When boric acid and potassium iodide are used at the same time, the content ratio (weight ratio) is about 1: 0.1 to 1: 4, more preferably about 1: 0.5 to 1: 3. It is preferable to use in.

  The temperature of the stretching bath is, for example, preferably in the range of 40 to 67 ° C, and more preferably 50 to 62 ° C.

  In the water washing step, for example, by immersing the polymer film in an aqueous solution of a water washing bath, unnecessary residues such as boric acid attached in the previous treatment can be washed away. Iodide may be added to the aqueous solution. For example, sodium iodide or potassium iodide is preferably used. When potassium iodide is added to the washing bath, the concentration is usually 0.1 to 10% by weight, and preferably 3 to 8% by weight. Furthermore, the temperature of the washing bath is preferably 10 to 60 ° C, more preferably 15 to 40 ° C. Moreover, the frequency | count of a washing process may be implemented in multiple times, without being specifically limited, You may change the kind and density | concentration of an additive in each washing bath.

  In addition, when pulling up the polymer film from each treatment bath, in order to prevent the occurrence of dripping, a conventionally known liquid cutting roll such as a pinch roll may be used, or the liquid is scraped off by an air knife, etc. Excess water may be removed by this method.

  As the drying step, an appropriate method such as natural drying, air drying, heat drying or the like can be used, but heat drying is usually preferably used. In heat drying, for example, the heating temperature is preferably about 20 to 80 ° C., and the drying time is preferably about 1 to 10 minutes. Furthermore, the drying temperature is preferably as low as possible for the purpose of preventing the deterioration of the polarizing film regardless of the above method. More preferably, it is 60 degrees C or less, and it is especially preferable that it is 45 degrees C or less.

  The final total draw ratio of the polarizing film produced through the above steps is preferably 3.0 to 7.0 times that of the polymer film before the treatment, and 5.5 to 6. More preferably, it is in the range of 2 times. If the final total draw ratio is less than 3.0 times, it is difficult to obtain a polarizing film having a high degree of polarization, and if it exceeds 7.0 times, the film tends to break.

  As a polymer film which forms the said film 9, various things can be used without being specifically limited. For example, PVA films, polyethylene terephthalate (PET) films, ethylene / vinyl acetate copolymer films, partially saponified films, cellulose films and other hydrophilic polymer films, PVA dehydrated products and poly Examples include polyene-based oriented films such as a dehydrochlorinated product of vinyl chloride. Among these, it is preferable to use a PVA film because it is excellent in dyeability with iodine as a polarizing film and has a high effect of improving in-plane uniformity according to the present invention.

  The degree of polymerization of the polymer film material is generally 500 to 10,000, preferably in the range of 1000 to 6000, and more preferably in the range of 1400 to 4000. Furthermore, in the case of a saponified film, the saponification degree is preferably 75 mol% or more, more preferably 98 mol% or more, for example, from the viewpoint of solubility in water, and 98.3 to 99.8 mol. % Is more preferable.

  When a PVA-based film is used as the polymer film, the PVA-based film can be formed by any method such as a casting method in which a stock solution dissolved in water or an organic solvent is cast, a casting method, an extrusion method, or the like. Can be used as appropriate. The phase difference value at this time is preferably 5 nm to 100 nm. Further, in order to obtain a polarizing film having a uniform in-plane, it is preferable that the retardation variation in the PVA film is as small as possible. The in-plane retardation of the PVA film as the raw film is at a measurement wavelength of 1000 nm. The thickness is preferably 10 nm or less, and more preferably 5 nm or less.

  As for the polarizing film by this invention, it is preferable that the single-piece | unit transmittance | permeability when measured with a polarizing film single-piece is 41.5% or more, and it is more preferable that it exists in the range of 41.5-44.5%. Moreover, it is preferable that the parallel transmittance measured by superimposing two polarizing films so that the absorption axes of the two polarizing films are parallel to each other is 35% or more, and 35% to 40%. It is more preferable that The practical degree of polarization is preferably 99.97% to 100%, more preferably 99.99% to 100%. The transmittance and the degree of polarization can be measured by the method shown in the examples described later.

  A transparent protective film may be provided on at least one surface of the polarizing film. As a material constituting the transparent protective film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like is used. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth) acrylic resins, cyclic Examples thereof include polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. A transparent protective film is bonded to one side of the polarizer with an adhesive layer. On the other side, as a transparent protective film, (meth) acrylic, urethane, acrylurethane, epoxy, silicone A thermosetting resin such as a system or an ultraviolet curable resin can be used. One or more kinds of arbitrary appropriate additives may be contained in the transparent protective film. Examples of the additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a mold release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a coloring agent. The content of the thermoplastic resin in the transparent protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. . When content of the said thermoplastic resin in a transparent protective film is 50 weight% or less, there exists a possibility that the high transparency etc. which a thermoplastic resin originally has cannot fully be expressed.

  Moreover, as a transparent protective film, the polymer film as described in Unexamined-Japanese-Patent No. 2001-343529 (WO01 / 37007), for example, (A) thermoplastic resin which has a substituted and / or unsubstituted imide group in a side chain, ( B) Resin compositions containing a thermoplastic resin having substituted and / or unsubstituted phenyl and nitrile groups in the side chain. Specific examples include a film of a resin composition containing an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile / styrene copolymer. As the film, a film made of a mixed extruded product of the resin composition or the like can be used. Since these films have a small phase difference and a small photoelastic coefficient, problems such as unevenness due to the distortion of the polarizing plate can be eliminated, and since the moisture permeability is small, the humidification durability is excellent.

  Although the thickness of a transparent protective film can be determined suitably, generally it is about 1-500 micrometers from points, such as workability | operativity, such as intensity | strength and handleability, and thin-layer property. 1-300 micrometers is especially preferable, and 5-200 micrometers is more preferable. The transparent protective film is particularly suitable when the thickness is 5 to 150 μm.

  In addition, when providing a transparent protective film on both sides of a polarizer, the protective film which consists of the same polymer material may be used by the front and back, and the protective film which consists of a different polymer material etc. may be used.

  As the transparent protective film of the present invention, it is preferable to use at least one selected from a cellulose resin, a polycarbonate resin, a cyclic polyolefin resin, and a (meth) acrylic resin.

  Cellulose resin is an ester of cellulose and fatty acid. Specific examples of the cellulose ester resin include triacetyl cellulose, diacetyl cellulose, tripropyl cellulose, dipropyl cellulose, and the like. Among these, triacetyl cellulose is particularly preferable. Many products of triacetylcellulose are commercially available, which is advantageous in terms of availability and cost. Examples of commercially available products of triacetyl cellulose include trade names “UV-50”, “UV-80”, “SH-80”, “TD-80U”, “TD-TAC”, “Fuji Photo Film Co., Ltd.” UZ-TAC "," KC series "manufactured by Konica, and the like. In general, these triacetyl celluloses have an in-plane retardation (Re) of almost zero, but a thickness direction retardation (Rth) of about 60 nm.

  In addition, the cellulose resin film with a small thickness direction retardation is obtained by processing the said cellulose resin, for example. For example, a base film made of polyethylene terephthalate, polypropylene, stainless steel or the like coated with a solvent such as cyclopentanone or methyl ethyl ketone is bonded to a general cellulose film and dried by heating (for example, at 80 to 150 ° C. for about 3 to 10 minutes). ) And then peeling the substrate film; a solution obtained by dissolving norbornene resin, (meth) acrylic resin, etc. in a solvent such as cyclopentanone, methyl ethyl ketone, etc. is applied to a general cellulose resin film and dried by heating ( For example, a method of peeling the coated film after 80 to 150 ° C. for about 3 to 10 minutes is mentioned.

  Moreover, as a cellulose resin film with a small thickness direction retardation, the fatty acid cellulose resin film which controlled the fat substitution degree can be used. Generally used triacetyl cellulose has an acetic acid substitution degree of about 2.8, but preferably the acetic acid substitution degree is controlled to 1.8 to 2.7, more preferably the propion substitution degree is controlled to 0.1 to 1. As a result, Rth can be reduced. By adding a plasticizer such as dibutyl phthalate, p-toluenesulfonanilide, acetyltriethyl citrate to the fatty acid-substituted cellulose resin, Rth can be controlled to be small. The addition amount of the plasticizer is preferably 40 parts by weight or less, more preferably 1 to 20 parts by weight, still more preferably 1 to 15 parts by weight with respect to 100 parts by weight of the fatty acid cellulose resin.

  Specific examples of the cyclic polyolefin resin are preferably norbornene resins. The cyclic olefin-based resin is a general term for resins that are polymerized using a cyclic olefin as a polymerization unit, and is described in, for example, JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, and the like. Resin. Specific examples include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, cyclic olefins and α-olefins such as ethylene and propylene (typically random copolymers), And the graft polymer which modified these with unsaturated carboxylic acid or its derivative (s), and those hydrides, etc. are mentioned. Specific examples of the cyclic olefin include norbornene monomers.

  Various products are commercially available as the cyclic polyolefin resin. Specific examples include the product names “ZEONEX” and “ZEONOR” manufactured by ZEON CORPORATION, the product name “ARTON” manufactured by JSR Corporation, the product name “TOPAS” manufactured by TICONA, and the product rules manufactured by Mitsui Chemicals, Inc. “APEL” may be mentioned.

  The (meth) acrylic resin preferably has a Tg (glass transition temperature) of 115 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 125 ° C. or higher, and particularly preferably 130 ° C. or higher. When Tg is 115 ° C. or higher, the polarizing plate can be excellent in durability. Although the upper limit of Tg of the (meth) acrylic resin is not particularly limited, it is preferably 170 ° C. or less from the viewpoint of moldability. From (meth) acrylic resin, a film having in-plane retardation (Re) and thickness direction retardation (Rth) of almost zero can be obtained.

  As the (meth) acrylic resin, any appropriate (meth) acrylic resin can be adopted as long as the effects of the present invention are not impaired. For example, poly (meth) acrylic acid ester such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester- (Meth) acrylic acid copolymer, (meth) methyl acrylate-styrene copolymer (MS resin, etc.), a polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, Methyl methacrylate- (meth) acrylate norbornyl copolymer, etc.). Preferably, poly (meth) acrylic acid C1-6 alkyl such as poly (meth) acrylate methyl is used. More preferred is a methyl methacrylate-based resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight).

  Specific examples of (meth) acrylic resins include (meth) acrylic resins having a ring structure in the molecule described in, for example, Acrypet VH and Acrypet VRL20A manufactured by Mitsubishi Rayon Co., Ltd., and JP-A-2004-70296. And a high Tg (meth) acrylic resin system obtained by intramolecular crosslinking or intramolecular cyclization reaction.

  As the (meth) acrylic resin, a (meth) acrylic resin having a lactone ring structure can also be used. It is because it has high mechanical strength by high heat resistance, high transparency, and biaxial stretching.

  Examples of the (meth) acrylic resin having a lactone ring structure include JP 2000-230016, JP 2001-151814, JP 2002-120326, JP 2002-254544, and JP 2005. Examples thereof include (meth) acrylic resins having a lactone ring structure described in Japanese Patent No. 146084.

  The (meth) acrylic resin having a lactone ring structure preferably has a ring pseudo structure represented by the following general formula (Formula 1).

^Wherein, R 1, ^{R 2} and ^{R 3} each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom.

  The content ratio of the lactone ring structure represented by the general formula (Formula 1) in the structure of the (meth) acrylic resin having a lactone ring structure is preferably 5 to 90% by weight, more preferably 10 to 70% by weight, More preferably, it is 10 to 60% by weight, and particularly preferably 10 to 50% by weight. When the content of the lactone ring structure represented by the general formula (Chemical Formula 1) in the structure of the (meth) acrylic resin having a lactone ring structure is less than 5% by weight, the heat resistance, solvent resistance, and surface hardness are low. May be insufficient. If the content of the lactone ring structure represented by the general formula (Chemical Formula 1) in the structure of the (meth) acrylic resin having a lactone ring structure is more than 90% by weight, molding processability may be poor.

  The (meth) acrylic resin having a lactone ring structure has a mass average molecular weight (sometimes referred to as a weight average molecular weight) of preferably 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, still more preferably 10,000 to 500,000, particularly preferably. Is 50,000 to 500,000. If the mass average molecular weight is out of the above range, it is not preferable from the viewpoint of molding processability.

  The (meth) acrylic resin having a lactone ring structure has a Tg of preferably 115 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 125 ° C. or higher, and particularly preferably 130 ° C. or higher. Since Tg is 115 ° C. or higher, for example, when incorporated into a polarizing plate as a transparent protective film, it has excellent durability. The upper limit value of Tg of the (meth) acrylic resin having the lactone ring structure is not particularly limited, but is preferably 170 ° C. or less from the viewpoint of moldability and the like.

  The (meth) acrylic resin having a lactone ring structure is preferably as the total light transmittance of a molded product obtained by injection molding measured by a method according to ASTM-D-1003 is higher, preferably 85. % Or more, more preferably 88% or more, still more preferably 90% or more. The total light transmittance is a measure of transparency. If the total light transmittance is less than 85%, the transparency may be lowered.

  As the transparent protective film, one having a front phase difference of less than 40 nm and a thickness direction retardation of less than 80 nm is usually used. The front phase difference Re is represented by Re = (nx−ny) × d. The thickness direction retardation Rth is represented by Rth = (nx−nz) × d. The Nz coefficient is represented by Nz = (nx−nz) / (nx−ny). [However, the refractive indexes in the slow axis direction, the fast axis direction, and the thickness direction of the film are nx, ny, and nz, respectively, and d (nm) is the thickness of the film. The slow axis direction is the direction that maximizes the refractive index in the film plane. ]. The transparent protective film preferably has as little color as possible. A protective film having a thickness direction retardation value of −90 nm to +75 nm is preferably used. By using a film having a thickness direction retardation value (Rth) of −90 nm to +75 nm, the coloring (optical coloring) of the polarizing plate caused by the transparent protective film can be almost eliminated. The thickness direction retardation value (Rth) is more preferably −80 nm to +60 nm, and particularly preferably −70 nm to +45 nm.

  On the other hand, as the transparent protective film, a retardation plate having a retardation with a front retardation of 40 nm or more and / or a thickness direction retardation of 80 nm or more can be used. The front phase difference is usually controlled in the range of 40 to 200 nm, and the thickness direction phase difference is usually controlled in the range of 80 to 300 nm. When a retardation plate is used as the transparent protective film, the retardation plate functions also as a transparent protective film, so that the thickness can be reduced.

  Examples of the retardation plate include a birefringent film formed by uniaxially or biaxially stretching a polymer material, a liquid crystal polymer alignment film, and a liquid crystal polymer alignment layer supported by a film. The thickness of the retardation plate is not particularly limited, but is generally about 20 to 150 μm.

  Examples of the polymer material include polyvinyl alcohol, polyvinyl butyral, polymethyl vinyl ether, polyhydroxyethyl acrylate, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, polycarbonate, polyarylate, polysulfone, polyethylene terephthalate, polyethylene naphthalate, polyether sulfone, Polyphenylene sulfide, polyphenylene oxide, polyallylsulfone, polyamide, polyimide, polyolefin, polyvinyl chloride, cellulose resin, cyclic polyolefin resin (norbornene resin), or their binary, ternary copolymers, graft copolymers Examples thereof include polymers and blends. These polymer materials become an oriented product (stretched film) by stretching or the like.

  Examples of the liquid crystal polymer include various main chain types and side chain types in which a conjugated linear atomic group (mesogen) imparting liquid crystal alignment is introduced into the main chain or side chain of the polymer. . Specific examples of the main chain type liquid crystal polymer include a nematic alignment polyester liquid crystal polymer, a discotic polymer, and a cholesteric polymer having a structure in which a mesogen group is bonded at a spacer portion that imparts flexibility. Specific examples of the side chain type liquid crystal polymer include polysiloxane, polyacrylate, polymethacrylate, or polymalonate as a main chain skeleton, and a nematic alignment-providing para-substitution through a spacer portion composed of a conjugated atomic group as a side chain. The thing etc. which have a mesogen part which consists of a cyclic compound unit are mentioned. These liquid crystal polymers are prepared by, for example, applying a solution of a liquid crystalline polymer on an alignment treatment surface such as a surface of a thin film such as polyimide or polyvinyl alcohol formed on a glass plate, or an oblique deposition of silicon oxide. This is done by developing and heat treatment.

  The retardation plate may have an appropriate retardation according to the purpose of use, such as those for the purpose of compensating for coloring, viewing angle, etc. due to birefringence of various wavelength plates and liquid crystal layers. What laminated | stacked the phase difference plate and controlled optical characteristics, such as phase difference, etc. may be used.

  The retardation plate has a relationship of nx = ny> nz, nx> ny> nz, nx> ny = nz, nx> nz> ny, nz = nx> ny, nz> nx> ny, nz> nx = ny. What is satisfactory is selected and used according to various applications. Note that ny = nz includes not only the case where ny and nz are completely the same, but also the case where ny and nz are substantially the same.

  For example, in a phase difference plate that satisfies nx> ny> nz, a surface plate having a front phase difference of 40 to 100 nm, a thickness direction phase difference of 100 to 320 nm, and an Nz coefficient of 1.8 to 4.5 is used. Is preferred. For example, in a retardation plate (positive A plate) that satisfies nx> ny = nz, it is preferable to use a retardation plate that satisfies a front phase difference of 100 to 200 nm. For example, for a retardation plate (negative A plate) that satisfies nz = nx> ny, it is preferable to use a retardation plate that satisfies a front phase difference of 100 to 200 nm. For example, in a phase difference plate that satisfies nx> nz> ny, it is preferable to use one that satisfies a front phase difference of 150 to 300 nm and an Nz coefficient of more than 0 to 0.7. As described above, for example, a material satisfying nx = ny> nz, nz> nx> ny, or nz> nx = ny can be used.

  The transparent protective film can be appropriately selected according to the applied liquid crystal display device. For example, in the case of VA (including Vertical Alignment, MVA, and PVA), it is desirable that at least one of the polarizing plates (cell side) has a retardation. As specific phase differences, it is desirable that Re = 0 to 240 nm and Rth = 0 to 500 nm. In terms of the three-dimensional refractive index, nx> ny = nz, nx> ny> nz, nx> nz> ny, nx = ny> nz (positive A plate, biaxial, negative C-plate) is desirable. When polarizing plates are used above and below the liquid crystal cell, both the upper and lower sides of the liquid crystal cell have a phase difference, or any one of the upper and lower transparent protective films may have a phase difference.

  For example, in the case of IPS (including In-Plane Switching, FFS), both cases where the transparent protective film on one side of the polarizing plate has a phase difference and does not have a phase difference can be used. For example, when there is no phase difference, it is desirable that the liquid crystal cell does not have a phase difference both above and below (cell side). When the liquid crystal cell has a phase difference, it is desirable that the liquid crystal cell has a phase difference in both the upper and lower sides, and the upper and lower sides have a phase difference (for example, nx> nz> nyZ on the upper side). Biaxial film satisfying the above relationship, when there is no phase difference on the lower side, or when the positive A-plate is on the upper side and the positive C-plate is on the lower side). When it has a phase difference, it is desirable that Re = −500 to 500 nm and Rth = −500 to 500 nm. In terms of the three-dimensional refractive index, nx> ny = nz, nx> nz> ny, nz> nx = ny, nz> nx> ny (positive A-plate, positive C-plate) are desirable.

  In addition, the film which has the said phase difference can be separately bonded to the transparent protective film which does not have a phase difference, and the said function can be provided.

  The transparent protective film may be subjected to a surface modification treatment before coating with an adhesive. Specific examples of the treatment include corona treatment, plasma treatment, primer treatment, and saponification treatment.

  The surface of the transparent protective film to which the polarizer is not adhered may be subjected to a hard coat layer, an antireflection treatment, an antisticking treatment, or a treatment for diffusion or antiglare.

  The hard coat treatment is performed for the purpose of preventing scratches on the surface of the polarizing plate. For example, a transparent protective film with a cured film excellent in hardness, sliding properties, etc. by an appropriate ultraviolet curable resin such as acrylic or silicone is used. It can be formed by a method of adding to the surface of the film. The antireflection treatment is performed for the purpose of preventing the reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the prior art. In addition, the sticking prevention treatment is performed for the purpose of preventing adhesion with an adjacent layer (for example, a backlight-side diffusion plate).

  The anti-glare treatment is applied for the purpose of preventing the outside light from being reflected on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, the surface is roughened by a sandblasting method or an embossing method. Or by applying a fine concavo-convex structure to the surface of the transparent protective film by an appropriate method such as a blending method of transparent fine particles. Examples of the fine particles to be included in the formation of the surface fine concavo-convex structure include conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, and the like having an average particle diameter of 0.5 to 20 μm. In some cases, transparent fine particles such as inorganic fine particles, organic fine particles composed of a crosslinked or uncrosslinked polymer, and the like are used. When forming the surface fine uneven structure, the amount of fine particles used is generally about 2 to 70 parts by weight, preferably 5 to 50 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle or the like.

  The antireflection layer, antisticking layer, diffusion layer, antiglare layer, and the like can be provided on the transparent protective film itself, or can be provided separately from the transparent protective film as an optical layer.

  The polarizing plate of the present invention is produced by laminating a transparent protective film and a polarizer using the adhesive. In the production method, the adhesive is applied to the surface of the polarizer on which the adhesive layer is formed and / or the surface of the transparent protective film on which the adhesive layer is formed; the polarizer and the transparent protective film; A step of bonding them through the polarizing plate adhesive.

  The adhesive coating method is appropriately selected depending on the viscosity of the adhesive and the target thickness. Examples of coating methods include reverse coaters, gravure coaters (direct, reverse and offset), bar reverse coaters, roll coaters, die coaters, bar coaters, rod coaters and the like. In addition, for coating, a method such as a dapping method can be appropriately used.

  The polarizer and the transparent protective film are bonded together through the adhesive applied as described above. The polarizer and the transparent protective film can be bonded together using a roll laminator or the like.

  The thickness of the adhesive layer formed by the production method is preferably 0.1 to 20 μm, more preferably 0.2 to 10 μm, and still more preferably 0.3 to 8 μm. When the thickness is small, the cohesive force of the adhesive force itself cannot be obtained, and the adhesive strength may not be obtained. When the thickness of the adhesive layer exceeds 20 μm, the cost increases and the effect of curing shrinkage of the adhesive itself appears, which may adversely affect the optical properties of the polarizing plate.

  When performing the said manufacturing method by a continuous line, although it depends on the hardening time of an adhesive agent, Preferably it is 1-500 m / min, More preferably, it is 5-300 m / min, More preferably, it is 10-100 m / min. When the line speed is too low, productivity is poor, or damage to the transparent protective film is too great, and a polarizing plate that can withstand a durability test or the like cannot be produced. When the line speed is too high, the adhesive is not sufficiently cured, and the target adhesiveness may not be obtained.

  The polarizing plate of the present invention can be used as an optical film laminated with another optical layer in practical use. The optical layer is not particularly limited. For example, it is used for forming a liquid crystal display device such as a reflection plate, a semi-transmission plate, a retardation plate (including wavelength plates such as 1/2 and 1/4), and a viewing angle compensation film. One or two or more optical layers that may be used can be used. In particular, a reflective polarizing plate or a semi-transmissive polarizing plate in which a polarizing plate or a semi-transmissive reflecting plate is further laminated on the polarizing plate of the present invention, an elliptical polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on the polarizing plate. A wide viewing angle polarizing plate obtained by further laminating a viewing angle compensation film on a plate or a polarizing plate, or a polarizing plate obtained by further laminating a brightness enhancement film on the polarizing plate is preferable.

  The reflective polarizing plate is a polarizing plate provided with a reflective layer, and is used to form a liquid crystal display device or the like that reflects incident light from the viewing side (display side). Such a light source can be omitted, and the liquid crystal display device can be easily thinned. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of a metal or the like is attached to one surface of the polarizing plate via a transparent protective layer or the like as necessary.

  Specific examples of the reflective polarizing plate include those in which a reflective layer is formed by attaching a foil or a vapor deposition film made of a reflective metal such as aluminum on one surface of a transparent protective film matted as necessary. Moreover, the transparent protective film contains fine particles to form a surface fine concavo-convex structure, and a reflective layer having a fine concavo-convex structure thereon. The reflective layer having the fine concavo-convex structure has an advantage that incident light is diffused by irregular reflection to prevent directivity and glaring appearance, and to suppress unevenness in brightness and darkness. Moreover, the transparent protective film containing fine particles also has an advantage that incident light and its reflected light are diffused when passing through it and light and dark unevenness can be further suppressed. The reflective layer with a fine concavo-convex structure reflecting the surface fine concavo-convex structure of the transparent protective film can be formed by, for example, transparent metal by an appropriate method such as a vapor deposition method such as a vacuum deposition method, an ion plating method, a sputtering method, or a plating method. It can be performed by a method of directly attaching to the surface of the protective layer.

  The reflecting plate can be used as a reflecting sheet or the like in which a reflecting layer is provided on an appropriate film according to the transparent film instead of directly applying to the transparent protective film of the polarizing plate. Since the reflective layer is usually made of metal, the usage form in which the reflective surface is covered with a transparent protective film, a polarizing plate or the like is used to prevent the reflectance from being lowered due to oxidation, and thus to maintain the initial reflectance for a long time. In addition, it is preferable from the viewpoint of avoiding the additional attachment of the protective layer.

  The transflective polarizing plate can be obtained by using a transflective reflective layer such as a half mirror that reflects and transmits light in the reflective layer described above. A transflective polarizing plate is usually provided on the back side of a liquid crystal cell, and displays an image by reflecting incident light from the viewing side (display side) when a liquid crystal display device is used in a relatively bright atmosphere. In a relatively dark atmosphere, it is possible to form a liquid crystal display device or the like that displays an image using a built-in light source such as a backlight built in the back side of the transflective polarizing plate. In other words, the transflective polarizing plate can save energy for using a light source such as a backlight in a bright atmosphere, and can be used with a built-in light source even in a relatively dark atmosphere. Useful for.

  An elliptically polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on a polarizing plate will be described. A phase difference plate or the like is used when changing linearly polarized light to elliptically polarized light or circularly polarized light, changing elliptically polarized light or circularly polarized light to linearly polarized light, or changing the polarization direction of linearly polarized light. In particular, a so-called quarter-wave plate (also referred to as a λ / 4 plate) is used as a retardation plate that changes linearly polarized light into circularly polarized light or changes circularly polarized light into linearly polarized light. A half-wave plate (also referred to as a λ / 2 plate) is usually used when changing the polarization direction of linearly polarized light.

  The elliptically polarizing plate is effectively used to compensate (prevent) the coloration (blue or yellow) caused by the birefringence of the liquid crystal layer of the super twist nematic (STN) type liquid crystal display device, and to display black and white without the color. It is done. Further, the one in which the three-dimensional refractive index is controlled is preferable because it can compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed from an oblique direction. The circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflective liquid crystal display device in which the image is displayed in color, and also has an antireflection function. Specific examples of the retardation plate described above include a birefringent film obtained by stretching a film made of an appropriate polymer such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, other polyolefins, polyarylate, and polyamide. And a liquid crystal polymer alignment film, a liquid crystal polymer alignment layer supported by a film, and the like. The retardation plate may have an appropriate retardation according to the purpose of use, such as those for the purpose of compensating for various wavelength plates and birefringence of liquid crystal layers, viewing angle, and the like. What laminated | stacked the phase difference plate and controlled optical characteristics, such as phase difference, etc. may be used.

  The elliptically polarizing plate and the reflective elliptical polarizing plate are obtained by laminating a polarizing plate or a reflective polarizing plate and a retardation plate in an appropriate combination. Such an elliptically polarizing plate or the like can also be formed by sequentially laminating them sequentially in the manufacturing process of the liquid crystal display device so as to be a combination of a (reflection type) polarizing plate and a retardation plate. What was used as optical films, such as a polarizing plate, is excellent in quality stability, lamination workability, etc., and has the advantage which can improve manufacturing efficiency, such as a liquid crystal display device.

  The viewing angle compensation film is a film for widening the viewing angle so that an image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly oblique direction rather than perpendicular to the screen. Such a viewing angle compensation retardation plate is made of, for example, an alignment film such as a retardation film or a liquid crystal polymer, or a support in which an alignment layer such as a liquid crystal polymer is supported on a transparent substrate. A normal retardation plate uses a birefringent polymer film uniaxially stretched in the plane direction, whereas a retardation plate used as a viewing angle compensation film stretches biaxially in the plane direction. Birefringent polymer film, biaxially stretched film such as polymer with birefringence with controlled refractive index in the thickness direction that is uniaxially stretched in the plane direction and stretched in the thickness direction, and tilted orientation film, etc. Used. Examples of the inclined alignment film include a film obtained by bonding a heat shrink film to a polymer film and stretching or / and shrinking the polymer film under the action of the contraction force by heating, or a film obtained by obliquely aligning a liquid crystal polymer. Can be mentioned. The raw material polymer for the phase difference plate is the same as the polymer described in the previous phase difference plate, preventing coloration due to a change in the viewing angle based on the phase difference by the liquid crystal cell and expanding the viewing angle for good visual recognition. An appropriate one for the purpose can be used.

  In addition, from the viewpoint of achieving a wide viewing angle with good visibility, an optically compensated phase difference in which an alignment layer of a liquid crystal polymer, particularly an optically anisotropic layer composed of a tilted alignment layer of a discotic liquid crystal polymer, is supported by a triacetyl cellulose film. A plate can be preferably used.

  The brightness enhancement film has a characteristic of transmitting linearly polarized light having a predetermined polarization axis and reflecting other light, such as a multilayer thin film of dielectric material or a multilayer laminate of thin film films having different refractive index anisotropies. Such as an alignment film of a cholesteric liquid crystal polymer or an alignment liquid crystal layer supported on a film substrate, which reflects either left-handed or right-handed circularly polarized light and transmits other light. Appropriate things, such as a thing, can be used.

  The brightness enhancement film has a characteristic of transmitting linearly polarized light having a predetermined polarization axis and reflecting other light, such as a multilayer thin film of dielectric material or a multilayer laminate of thin film films having different refractive index anisotropies. Such as an alignment film of a cholesteric liquid crystal polymer or an alignment liquid crystal layer supported on a film substrate, which reflects either left-handed or right-handed circularly polarized light and transmits other light. Appropriate things, such as a thing, can be used.

  Therefore, in the brightness enhancement film of the type that transmits linearly polarized light having the predetermined polarization axis as described above, the transmitted light is incident on the polarizing plate with the polarization axis aligned as it is, thereby efficiently transmitting while suppressing absorption loss due to the polarizing plate. Can be made. On the other hand, in 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 circularly polarized light is linearly polarized through a retardation plate. It is preferable to make it enter into a polarizing plate. In addition, circularly polarized light can be converted into linearly polarized light by using a quarter wave plate as the retardation plate.

  An optical film in which the optical layer is laminated on a polarizing plate can be formed by a method of sequentially laminating separately in the manufacturing process of a liquid crystal display device or the like. There is an advantage that the manufacturing process of a liquid crystal display device or the like can be improved because of excellent stability and assembly work. For the lamination, an appropriate adhesive means such as an adhesive layer can be used. When adhering the polarizing plate and other optical films, their optical axes can be set at an appropriate arrangement angle in accordance with the target retardation characteristics and the like.

  An adhesive layer for adhering to other members such as a liquid crystal cell may be provided on the polarizing plate described above or an optical film in which at least one polarizing plate is laminated. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, silicone-based polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer is appropriately selected. Can be used. In particular, those having excellent optical transparency, such as an acrylic pressure-sensitive adhesive, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and having excellent weather resistance, heat resistance and the like can be preferably used.

  In addition to the above, from the viewpoints of prevention of foaming phenomenon and peeling phenomenon due to moisture absorption, deterioration of optical characteristics due to thermal expansion difference and the like, prevention of warpage of liquid crystal cell, and formation of liquid crystal display device with high quality and durability. An adhesive layer having a low moisture absorption rate and excellent heat resistance is preferred.

  The adhesive layer is, for example, natural or synthetic resins, in particular, tackifier resins, fillers or pigments made of glass fibers, glass beads, metal powders, other inorganic powders, colorants, antioxidants, etc. It may contain an additive to be added to the adhesive layer. Moreover, the adhesion layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient.

  Attachment of the adhesive layer to one or both sides of the polarizing plate or the optical film can be performed by an appropriate method. For example, a pressure sensitive adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of an appropriate solvent alone or a mixture such as toluene and ethyl acetate is prepared. A method in which it is directly attached on a polarizing plate or an optical film by an appropriate development method such as a casting method or a coating method, or an adhesive layer is formed on a separator according to the above, and this is applied to a polarizing plate or an optical film. The method of moving up is mentioned.

  The pressure-sensitive adhesive layer can be provided on one side or both sides of a polarizing plate or an optical film as a superimposed layer of different compositions or types. Moreover, when providing in both surfaces, it can also be set as the adhesion layers of a different composition, a kind, thickness, etc. in the front and back of a polarizing plate or an optical film. The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is generally 1 to 40 μm, preferably 5 to 30 μm, particularly preferably 10 to 25 μm. If it is thinner than 1 μm, the durability will be poor, and if it is thicker than 40 μm, it will be liable to float or peel off due to foaming, resulting in poor appearance.

  On the exposed surface of the adhesive layer, a separator is temporarily attached and covered for the purpose of preventing contamination until it is put to practical use. Thereby, it can prevent contacting an adhesion layer in the usual handling state. As the separator, except for the above thickness conditions, for example, a suitable thin leaf body such as a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foamed sheet or metal foil, or a laminate thereof, silicone type or Appropriate conventional ones such as those coated with an appropriate release agent such as long-chain alkyl, fluorine-based, or molybdenum sulfide can be used.

  In the present invention, the polarizer, the transparent protective film, the optical film, and the like that form the polarizing plate described above, and each layer such as the adhesive layer include, for example, salicylic acid ester compounds, benzophenol compounds, benzotriazole compounds, It may be one having a UV absorbing ability by a method such as a method of treating with a UV absorber such as a cyanoacrylate compound or a nickel complex salt compound.

  The polarizing plate or optical film of the present invention can be preferably used for forming various devices such as a liquid crystal display device. The liquid crystal display device can be formed according to the conventional method. That is, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, a polarizing plate or an optical film, and an illumination system as necessary, and incorporating a drive circuit. Is not particularly limited except that the polarizing plate or the optical film according to the present invention is used, and can be based on the conventional method. As the liquid crystal cell, any type such as a TN type, STN type, π type, VA type, IPS type, or the like can be used.

  An appropriate liquid crystal display device such as a liquid crystal display device in which a polarizing plate or an optical film is disposed on one side or both sides of a liquid crystal cell, or a backlight or a reflecting plate used in an illumination system can be formed. In that case, the polarizing plate or optical film by this invention can be installed in the one side or both sides of a liquid crystal cell. When providing a polarizing plate or an optical film on both sides, they may be the same or different. Furthermore, when forming the liquid crystal display device, for example, a single layer or a suitable layer of a diffusion plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusion plate, a backlight, etc. Two or more layers can be arranged.

  Next, an organic electroluminescence device (organic EL display device) will be described. Generally, in an organic EL display device, a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light emitter (organic electroluminescent light emitter). Here, 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 and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Alternatively, a structure having various combinations such as a laminate of such a light-emitting layer and an electron injection layer composed of a perylene derivative or the like, or a laminate of these hole injection layer, light-emitting layer, and electron injection layer is known. It has been.

  In organic EL display devices, holes and electrons are injected into the organic light-emitting layer by applying a voltage to the transparent electrode and the metal electrode, and the energy generated by recombination of these holes and electrons excites the phosphor material. Then, light is emitted on the principle that the excited fluorescent material emits light when returning to the ground state. The mechanism of recombination in the middle is the same as that of a general diode, and as can be predicted from this, the current and the emission intensity show strong nonlinearity with rectification with respect to the applied voltage.

  Since the retardation plate and the polarizing plate have a function of polarizing light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized by the polarization action. In particular, the mirror surface of the metal electrode can be completely shielded by configuring the retardation plate with a quarter-wave plate and adjusting the angle formed by the polarization direction of the polarizing plate and the retardation plate to π / 4. .

  Hereinafter, preferred embodiments of the present invention will be described in detail by way of example. However, the materials, blending amounts, and the like described in the examples are not intended to limit the scope of the present invention only to them, but are merely illustrative examples, unless otherwise specified.

Example 1
In this example, wet stretching of a polyvinyl alcohol (PVA) film (VF-PS # 7500) was performed using a multistage nip roll using the stretching apparatus shown in FIG. A PVA film having a thickness of 75 μm and a film width of 400 mm was used. The film lengths between the pinch rolls 2 to 6 were all the same and 0.235 m. The film length between the pinch roll 1 and the pinch roll 2 was 0.65 m, and the film length between the pinch roll 7 and the pinch roll 6 was 0.8 m. The rotational speeds of the pinch rolls 2 to 6 are R2 = 0.22 m / min, R3 = 0.90 m / min, R4 = 0.95 m / min, R5 = 0.98 m / min, R6 = 1. It was set to 0 m / min. The rotational speeds of the pinch roll 1 and the pinch roll 7 were R1 = 0.20 m / min and R7 = 1.00 m / min, respectively. Table 1, using the multi-stage stretching machine, shows the rotational speed of each pinch roll.

The dimensions of the bath 8 are as follows.
Length: 200mm
Width: 100cm
Height: 70cm

The bath conditions are as follows.
Iodine stock solution: 2% (water; 92 wt%, KI; 7 _{wt%, I} 2; 1 wt%)
KI: 3%
Boric acid: 0.5%
Mixture temperature: 21 ° C

  After stretching, the PVA film was dried using an oven. As drying conditions, the drying temperature was 70 ° C., the passage time in the oven was 5 minutes, and the results are shown in Table 1 below.

(Examples 2 to 6)
In Examples 2 to 6, the PVA film was stretched and dried in the same manner as in Example 1 except that the rotational speed of each pinch roll 1 to 7 was changed as shown in Table 1 below. . The results are shown in Table 1 below.

(Comparative Examples 1-3)
In Comparative Examples 1 to 3, the PVA film was stretched and dried in the same manner as in Example 1 except that the rotational speed of each pinch roll 1 to 7 was changed as shown in Table 1 below. . The results are shown in Table 1 below.

(Measurement of remaining film width)
The measurement of the film width residual ratio was calculated using the following formula after measuring the film width of the PVA film in an unstretched state and the film width after stretching and drying.

(Measurement of film thickness)
The thickness of the stretched film was measured using a carry package. The average value of thickness was measured at 10 points in the TD direction, and the average value and standard deviation were calculated.

In the embodiment of the present invention, it is a schematic diagram showing the state of shrinkage of the film after stretching, wherein FIG. (A) shows the case of the conventional stretching process, FIG. (B) is the stretching of the present invention. Indicates the case of processing. It is a schematic diagram which shows the manufacturing process of the polarizing film in the said embodiment.

Explanation of symbols

1-7 pinch rolls 8 baths

Claims (8)

A method for producing a polarizing film including a wet stretching process for a film, wherein stretching is performed continuously and in multiple stages at predetermined positions in a bath, and at least in any one stretching stage with respect to a state immediately before stretching. A method for producing a polarizing film, wherein a ratio (R / L [m] ) of a draw ratio R and a distance L [m] between draws in a bath is 8 or more and 17.41 or less . 2. The polarized light according to claim 1, wherein a ratio (L [mm] / W [mm] ) between the distance L [mm] between stretching and the film width W [mm] immediately before stretching is less than 0.5. A method for producing a film. The method for producing a polarizing film according to claim 1 or 2 , wherein the film width remaining rate Z represented by the following formula (1) in the stretched film is 60% or more.

It has a swelling, dyeing | staining, bridge | crosslinking, extending | stretching, and a drying process, The manufacturing method of the polarizing film in any one of Claims 1-3 characterized by the above-mentioned .   A polarizing film obtained by the method for producing a polarizing film according to claim 1.   The polarizing plate which provided the transparent protective film in the at least single side | surface of the polarizing film of Claim 5.   An optical film, wherein at least one polarizing film according to claim 5 or at least one polarizing plate according to claim 6 is laminated.   An image display device using at least one polarizing film according to claim 5, a polarizing plate according to claim 6, or an optical film according to claim 7.

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