JP2012037683A - Optical member, liquid crystal panel including the same, and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical member that causes less deformation in a prism shape and lens shape after bonding a light collection film and another optical film, and hardly causes brightness unevenness in an obtained liquid crystal panel and liquid crystal display device, and to provide the liquid crystal panel including the same and the liquid crystal display device.SOLUTION: In a polarizing plate 20, the light collection film 25 having a prism shape or lens shape on its surface and a polarizing film 21 are laminated with pasting pressure. In a thickness distribution of the light collection film 25 after the lamination, the difference (H) between the maximum film thickness (H) and the minimum film thickness (H) is 5% or less in terms of the average film thickness (H). By controlling the thickness distribution to 5% or less, the brightness ratio is made less than 10%, and the brightness unevenness is significantly reduced.

Description

  The present invention relates to an optical member, a liquid crystal panel including the same, and a liquid crystal display device, and more particularly, to an optical member including a prism-like or lens-shaped condensing film, a liquid crystal panel including the same, and a liquid crystal display device.

  A liquid crystal display device has features such as low power consumption, operation at a low voltage, and light weight and thinness. Therefore, the liquid crystal display device is used in various display devices by taking advantage of these features. In particular, the market for liquid crystal televisions is remarkably expanding, and the demand for cost reduction is also significant.

  A normal liquid crystal display device includes a surface light source element using a cold cathode tube or an LED, a light diffusion plate, one or a plurality of diffusion sheets, a light collecting sheet, a liquid crystal panel in which a polarizing plate is bonded to a liquid crystal cell, and the like. Has been. In recent years, the demand for thin liquid crystal display devices has become apparent in applications such as wall-mounted large-screen liquid crystal televisions. In this case, in response to the thinning of liquid crystal display devices, the thickness of the members used therefor has been reduced. Therefore, it is necessary to reduce the number of members.

  In a general liquid crystal display device, a prism sheet (also referred to as a “light condensing sheet”) is disposed between a polarizing plate and a backlight so that light from the backlight is directed toward the liquid crystal cell to improve luminance. Yes. However, when a prism sheet is provided between the polarizing plate and the backlight, it is necessary to provide a certain space between these members in order to prevent contact between the prism sheet and the polarizing plate. For this reason, there is a disadvantage that the liquid crystal panel and the liquid crystal display device including the liquid crystal panel are thick.

  Therefore, conventionally, a technique is known in which a protective film having a condensing prism structure (hereinafter referred to as “condensing film”) is provided on the surface of the polarizing plate on the backlight side (see, for example, Patent Document 1). According to this technology, it is not necessary to provide a prism sheet separately from the polarizing plate, or to provide a space between the polarizing plate and the prism sheet, thereby reducing the number of components or reducing the thickness of the liquid crystal display device. Is possible.

  By the way, when manufacturing a polarizing plate in which a resin film such as a protective film is bonded to a polarizing film, sheet-to-sheet bonding, sheet-to-roll bonding (also called roll-to-sheet bonding), etc. This method is used. The sheet-to-sheet bonding method is a method in which both a polarizing film and a resin film are chip-cut and bonded to a sheet. On the other hand, the sheet-to-roll bonding method is a method in which one of the polarizing film and the resin film is a roll film, and the other film is chip-cut into a sheet and bonded to this roll film. .

  As another method, a roll-to-roll bonding method of bonding a roll-shaped polarizing film and a roll-shaped resin film is also known. The inventors of the present invention have also previously described a roll-shaped linearly polarizing plate and a roll-shaped optical compensation film coated with a coating material that exhibits an optical compensation function. The technique of laminating by the roll bonding method is developed (for example, refer patent document 2).

  With this roll-to-roll bonding method, problems such as air bubbles entering the bonded portion and lowering adhesion are likely to occur. Therefore, a technique is known in which the thickness distribution is intentionally non-uniform so that the thickness of the central region in the width direction of the long optical film is larger than the thickness of the regions at both ends in the width direction (for example, patents). Reference 3). By making the thickness distribution non-uniform in this way, it becomes possible to provide a resin film with good adhesion between optical films, which is less likely to cause air bubbles in the bonded portion when roll-to-roll bonding is performed. Become.

JP 2005-17355 A JP 2007-155970 A JP 2006-175616 A

  When laminating a polarizing film or a retardation film by the roll-to-roll laminating method as described above, generally, the laminating pressure is narrowed by two laminating rolls in a state where a plurality of optical films are laminated. By adding, two films are adhered.

  However, in the case of the condensing film having the prism shape as described above, since the surface has prism-like or lens-like irregularities, the prism shape and the lens shape are crushed when a bonding pressure is applied with a bonding roll. There is an inconvenience. In particular, as in Patent Document 3 described above, when a technique for imparting a non-uniform thickness distribution to a long optical film is applied to a light collecting film as it is, a thick portion of the light collecting film has a high bonding pressure. The prism shape and the lens shape are apt to be crushed too much. On the other hand, the portion having a small thickness is less crushed because the bonding pressure is low. For this reason, there is a problem in that light is lost in a region where the prism shape or lens shape is crushed and deformed, the portion becomes dark, the other portion becomes bright, and luminance unevenness occurs.

  The objective of this invention is an optical member provided with the condensing film which has a prism-shaped or lens-shaped surface shape, Comprising: It is providing the optical member which a brightness nonuniformity does not produce easily.

  Furthermore, another object of the present invention is to provide a liquid crystal panel and a liquid crystal display device having such a favorable optical characteristic that uneven luminance is not generated using such an optical member.

  As a result of intensive studies to solve the above problems, the inventors have a correlation between the thickness distribution of the light collecting film and the luminance unevenness, and make the thickness distribution of the light collecting film smaller than a specific value. As a result, it was found that the luminance unevenness can be greatly reduced, and the present invention has been completed.

  That is, according to the optical member of the present invention, the above-described problem is an optical member obtained by laminating a light-collecting film having a prism shape or a lens shape on the surface and another optical film by applying a bonding pressure, In the thickness distribution of the condensing film after the lamination, the difference between the maximum film thickness and the minimum film thickness is 5% or less with respect to the average film thickness.

  Further, the prism shape or the lens shape of the condensing film is such that the distance from the end point of one prism or the slope of the lens to the start point of the next prism or the slope of the lens is relative to the pitch interval of the ridge line. It is preferably formed so as to be 30% or less.

  The condensing film is preferably made of a thermoplastic resin.

  In this case, the thermoplastic resin is preferably made of a polypropylene resin.

  Further, in this case, it is preferable that the polypropylene resin is substantially composed of a homopolymer of propylene.

  Alternatively, the polypropylene resin may be made of a copolymer of propylene and ethylene containing 10% by weight or less of ethylene units.

  Moreover, when the said condensing film is comprised with active energy ray hardening resin, it is suitable.

  Furthermore, it is preferable that an optical compensation film or a protective film is laminated on the surface of the optical member opposite to the surface on the light collecting film side.

  In addition, it is preferable that a protective film is provided on the surface of the condensing film having the prism shape or the lens shape.

  Furthermore, it is preferable that the other optical film is a polarizing film and the optical member is a polarizing plate.

  Further, it is preferable that the liquid crystal display device is used by being disposed between a liquid crystal cell and a backlight.

  According to the liquid crystal panel of the present invention, the above problem is a liquid crystal panel in which a liquid crystal cell and the optical member according to any one of the above are laminated, the liquid crystal cell, the other optical film, This is solved by stacking the light collecting film in this order.

  According to the liquid crystal display device of the present invention, the above problem is a liquid crystal display device in which a backlight and the liquid crystal panel described above are arranged to face each other. This is solved by arranging the prism shape or the lens shape so as to face the backlight.

  In this case, it is preferable that the front luminance distribution is within 10% of the maximum luminance.

  According to the optical member of the present invention, the thickness distribution of the condensing film after bonding is set to 5% or less, thereby reducing the deformation of the prism shape and the lens shape of the condensing film and suppressing luminance unevenness. It becomes possible. In addition, according to the liquid crystal panel and the liquid crystal display device of the present invention, it is possible to provide a liquid crystal panel and a liquid crystal display device with excellent optical characteristics by including an optical member with little luminance unevenness.

It is the cross-sectional schematic diagram which showed the condensing film from which thickness distribution differs. It is a cross-sectional schematic diagram of the polarizing plate in one Embodiment of this invention. It is a cross-sectional schematic diagram of a liquid crystal panel using a polarizing plate and a liquid crystal display device. It is a perspective fragmentary sectional view of a condensing film. It is a cross-sectional schematic diagram of a condensing film. It is the cross-sectional schematic diagram which showed the process of bonding a condensing film to a polarizing film. It is the photograph which imaged the single wafer sample used in the Example. It is the graph which showed the thickness distribution and brightness ratio value of the sheet sample in the shape of a contour line. It is the graph which showed the relationship between the thickness distribution of a single wafer sample, and a luminance ratio.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In addition, this invention is not limited by the member, arrangement | positioning, etc. which are demonstrated below, These members etc. can be suitably changed in accordance with the meaning of this invention. Hereinafter, a polarizing plate will be described as an example of the optical member of the present invention.

The optical member of the present invention is obtained by laminating a condensing film and another optical film by applying a bonding pressure using a bonding roll or the like. As will be described later, the present invention is characterized in that the thickness distribution of the condensing film after the lamination is 5% or less. That is, the difference (H _dif ) between the maximum film thickness (H _max ) and the minimum film thickness (H _min ) shown in FIG. 1 is 5% or less with respect to the average film thickness (H _ave ). Thereby, it is possible to reduce the luminance ratio of the optical member and reduce the luminance unevenness.

  In the following description, the overall configuration and individual configurations of the polarizing plate (optical member) and the liquid crystal panel will be described first, and then the manufacturing methods thereof will be described. In the latter half of the description, the relationship between the thickness distribution of the light-collecting film after lamination, which is a feature of the present invention, and luminance unevenness will be described. First, a polarizing plate which is an example of an optical member and a liquid crystal panel using the same will be described.

<Polarizing plate (optical member)>
FIG. 2 is a drawing showing a polarizing plate in one embodiment of the present invention, and shows a schematic cross-sectional view of the polarizing plate. As shown in this figure, the polarizing plate 20 includes at least a polarizing film 21 and a condensing film 25 laminated on one surface of the polarizing film 21 and having a prism shape or a lens shape on the surface. The polarizing plate 20 corresponds to the optical member of the present invention, and the polarizing film 21 corresponds to another optical film.

  Furthermore, in this embodiment, it has the layer structure by which the transparent resin film 23 was laminated | stacked on the surface on the opposite side to the side where the condensing film 25 is laminated | stacked among the surfaces of the polarizing film 21. FIG. In the present invention, the transparent resin film 23 is not an essential component.

<Liquid crystal panel and liquid crystal display device>
FIG. 3 is a schematic sectional view showing an example of a basic layer configuration of the liquid crystal panel 2 of the present invention and the liquid crystal display device 1 to which the liquid crystal panel 2 is applied. As shown in this figure, the polarizing plate 20 is bonded to the liquid crystal cell 40 and used as a component of the liquid crystal panel 2. The liquid crystal panel 2 is a constituent member of the liquid crystal display device 1. The liquid crystal panel 2 includes a liquid crystal cell 40, a polarizing plate 20 bonded to the back side of the liquid crystal cell 40, and a polarizing plate 30 bonded to the viewing side of the liquid crystal cell 40. The liquid crystal display device 1 includes a liquid crystal panel 2, a backlight 10, and a light diffusion plate 50. In the liquid crystal display device 1, the liquid crystal panel 2 is disposed such that the polarizing plate 20 is on the backlight 10 side, that is, the light collecting film 25 faces the light diffusion plate 50. The polarizing plate 20 and the polarizing plate 30 are bonded to the liquid crystal cell 40 through the adhesive layer 27, respectively. Here, the back side means the backlight 10 side when the liquid crystal panel 2 is mounted on the liquid crystal display device 1. The viewing side means the side opposite to the backlight 10 when the liquid crystal panel 2 is mounted on the liquid crystal display device 1.

  The light diffusing plate 50 is an optical member having a function of diffusing light from the backlight 10, for example, a material in which particles as a light diffusing agent are dispersed in a thermoplastic resin to impart light diffusibility, thermoplasticity The surface of the resin film may be uneven to provide light diffusibility, or the resin film may be provided with a coating layer of a resin composition in which particles are dispersed on the surface of the thermoplastic resin film. . The thickness can be about 0.1-5 mm.

  Between the light diffusing plate 50 and the liquid crystal panel 2, a sheet or film exhibiting other optical functionality such as a brightness enhancement sheet (a reflective polarizing film (such as “DBEF”)) or a light diffusing sheet is disposed. You can also Two or more sheets or films exhibiting other optical functionalities can be arranged as needed. Below, each film which comprises the polarizing plate 20 of the back side is demonstrated.

(1) Polarizing film The polarizing film 21 is a member having a function of converting natural light into linearly polarized light. As the polarizing film 21, a film obtained by adsorbing and orienting a dichroic dye on a uniaxially stretched polyvinyl alcohol resin film can be used. As the polyvinyl alcohol resin, a saponified polyvinyl acetate resin can be used. As the polyvinyl acetate resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, polyvinyl acetate and Examples thereof include copolymers with other copolymerizable monomers. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

  The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol resin may be modified. For example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The degree of polymerization of the polyvinyl alcohol resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000.

  A film obtained by forming such a polyvinyl alcohol resin is used as a raw film of the polarizing film 21. The method for forming a polyvinyl alcohol-based resin is not particularly limited, and can be formed by a known method. Although the thickness of a polyvinyl alcohol-type raw film is not specifically limited, For example, it is about 10-150 micrometers.

  The polarizing film 21 usually has a step of uniaxially stretching such a polyvinyl alcohol resin film, a step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol resin film with a dichroic dye, and a dichroic dye It is manufactured through a step of treating the adsorbed polyvinyl alcohol-based resin film with a boric acid aqueous solution and a step of washing with water after the treatment with the boric acid aqueous solution.

  Uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before dyeing with the dichroic dye, simultaneously with dyeing, or after dyeing. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Of course, uniaxial stretching can also be performed in a plurality of stages shown here. For uniaxial stretching, a method of stretching uniaxially between rolls having different peripheral speeds, a method of stretching uniaxially using a hot roll, or the like can be adopted. The uniaxial stretching may be dry stretching in which stretching is performed in the air, or may be wet stretching in which a polyvinyl alcohol-based resin film is swollen using a solvent such as water. The draw ratio is usually about 3 to 8 times.

  The stretching direction of the polyvinyl alcohol-based resin film is a direction parallel to the longitudinal direction of the long polarizing film 21. For this reason, the absorption axis of the polarizing film 21 is a direction parallel to the stretching direction of the polyvinyl alcohol-based resin film, that is, the longitudinal direction of the long polarizing film 21.

  The polyvinyl alcohol resin film can be dyed with a dichroic dye by, for example, a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye. Specifically, iodine or a dichroic dye is used as the dichroic dye. In addition, it is preferable to perform the process which a polyvinyl alcohol-type resin film swells by immersing in water before a dyeing process.

  When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The content of iodine in this aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water, and the content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. It is. The temperature of the aqueous solution used for dyeing is usually about 20 to 40 ° C. Moreover, the immersion time (dyeing time) in this aqueous solution is usually about 20 to 1,800 seconds.

On the other hand, when a dichroic dye is used as the dichroic dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic dye is usually employed. The content of the dichroic dye in this aqueous solution is usually about 1 × 10 ⁻⁴ to 10 parts by weight, preferably about 1 × 10 ⁻³ to 1 part by weight per 100 parts by weight of water. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The temperature of the aqueous dichroic dye solution used for dyeing is usually about 20 to 80 ° C. Moreover, the immersion time (dyeing time) in this aqueous solution is usually about 10 to 1,800 seconds.

  The boric acid treatment after dyeing with a dichroic dye can be performed by immersing the dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution. The boric acid content in the boric acid-containing aqueous solution is usually about 2 to 15 parts by weight, preferably about 5 to 12 parts by weight per 100 parts by weight of water. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide. The content of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by weight, preferably about 5 to 12 parts by weight per 100 parts by weight of water. The immersion time in the boric acid-containing aqueous solution is usually about 60 to 1,200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C., more preferably 60 to 80 ° C.

  The polyvinyl alcohol resin film after the boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. The temperature of water in the water washing treatment is usually about 5 to 40 ° C., and the immersion time is usually about 1 to 120 seconds.

  After washing with water, a drying process is performed to obtain the polarizing film 21. The drying process can be performed using a hot air dryer or a far infrared heater. The temperature of a drying process is about 30-100 degreeC normally, Preferably it is 50-80 degreeC. The drying time is usually about 60 to 600 seconds, preferably 120 to 600 seconds.

  In this way, the polyvinyl alcohol-based resin film is subjected to uniaxial stretching, dyeing with a dichroic dye, and boric acid treatment, and the polarizing film 21 is obtained. The thickness of the polarizing film 21 can be about 2-40 micrometers, for example.

(2) Condensing film The condensing film 25 is a member that has a function of improving the luminance of condensing light emitted from the backlight 10 to be described later onto the liquid crystal cell 40 and also has a protective function of protecting the polarizing film 21. . One surface of the condensing film 25 has a prism-like or lens-like surface shape. The light collecting film 25 is focused on the liquid crystal cell 40 by changing the angle of the light emitted obliquely from the backlight 10 at the slope portion of the prism shape or the lens shape and reflecting the light toward the liquid crystal cell 40. .

  As shown in FIGS. 2 and 3, the condensing film 25 is usually placed on the polarizing film 21 so that the surface opposite to the surface having a prism-like or lens-like surface shape faces the polarizing film 21. Stacked so-called “downward prisms” are used. On the other hand, an “upward prism” in which a surface having a prism-like or lens-like surface shape is arranged to face the polarizing film 21 can also be used.

  In such an upward prism, the prism-shaped or lens-shaped ridge line R (the line formed by the apex portion having the highest height h of the prism-shaped or lens-shaped) is adhered to the polarizing film 21 using an adhesive or the like. In order to contact the plane of the film 21 with a line, it is preferable to use an adhesive having a certain degree of adhesive strength. In addition, it is possible to make the top end of the prism shape or lens shape flat and easily adhere to the polarizing film 21. However, if the flat portion becomes too wide, the flat portion becomes dark and the liquid crystal panel 2 becomes dark. Since a striped stripe pattern is formed and visibility is deteriorated, it is preferable to make contact with a line as much as possible.

  In the present invention, the “prism shape” refers to a line-shaped protrusion indicated by a locus obtained by translating a triangular shape as shown in FIG. 4A (which may include a curve in part). It means a shape in which a plurality are arranged in parallel or substantially in parallel. In addition, the “lens shape” is a locus obtained by translating a convex shape formed from a curved surface such as a semicircular arc shape as shown in FIG. Means a shape in which a plurality of line-shaped protrusions shown in FIG.

  FIG. 4A is a perspective partial sectional view showing an example of a light collecting film 25 having a prism shape on the surface (hereinafter also referred to as a prism sheet). 5A and 5B are schematic cross-sectional views of the light collecting film 25 having a prism shape on the surface. The pitch interval P of the prism-shaped ridge lines R (the shortest distance between the ridge lines R of adjacent line-shaped protrusions) is preferably 1 μm or more and 70 μm or less, and more preferably 10 μm or more and 50 μm. When the pitch interval P exceeds 70 μm, strong moire occurs due to interference with the regular matrix structure of the color filter of the liquid crystal cell 40, and visibility is deteriorated. On the other hand, when the pitch interval P exceeds 70 μm, the height h of the line-shaped protrusions is relatively high, which increases the thickness of the sheet member and is not preferable from the viewpoint of reducing the thickness of the polarizing plate 20. On the other hand, when the pitch interval P is less than 1 μm, light diffraction occurs, which may adversely affect the visibility of the liquid crystal display device 1. Also, a prism sheet having a pitch interval P of less than 1 μm is not preferable from the viewpoint of manufacturing because it is difficult to form a prism shape.

  In the line-shaped protrusions of the prism sheet, the apex angle (vertical angle θa) in the triangular cross-sectional shape can be in the range of 10 to 120 ° or less, preferably 30 to 100 °. The height h of the line-shaped protrusion having a triangular cross section can be set to, for example, 10 to 200 μm, and preferably 15 to 100 μm. The two sides in the cross-sectional triangle shape may have the same length or may have different lengths. Further, the heights h of the line-shaped protrusions of the prism sheet may all be the same or different.

  Further, the plurality of line-shaped protrusions of the prism sheet may be arranged continuously as shown in FIG. 5A, and arranged with a constant interval as shown in FIG. 5B. Also good. When the prism shapes are arranged with a certain interval as shown in FIG. 5B, the distance L from the end point of the slope of one prism to the start point of the slope of the next adjacent prism is equal to the ridge line R of the prism shape. It is preferably 30% or less with respect to the pitch interval P. When the distance L exceeds 30% with respect to the pitch interval P, the interval between the prisms becomes too large, so that the amount of light passing between the prisms increases, and conversely, the liquid crystal cell is reflected by the prism-shaped or lens-shaped slope. Less light goes to 40. For this reason, the brightness enhancement function is lowered by the light collecting film 25, and a bright and dark stripe pattern is generated between the region between the prisms and the prism portion. The plurality of line-shaped protrusions are preferably arranged at the same pitch interval P.

  FIG. 4B is a schematic perspective view showing an example of a condensing film 25 having a lens shape on the surface (hereinafter also referred to as a lens sheet). Moreover, FIG.5 (c) is a cross-sectional schematic diagram of the condensing film 25 which has a lens shape on the surface. The lens shape having the lens sheet shown in these drawings is called a lenticular lens. Also in such a lens sheet, for the same reason as described above, the pitch interval P between the lens-shaped ridge lines R (the shortest distance between the ridge lines R of adjacent line-shaped protrusions) is preferably 1 μm or more and 70 μm or less, and 10 μm or more and 50 μm. Is more preferable.

  The height h of the line-shaped protrusions of the lens sheet can be set to 5 to 100 μm, for example. The heights h of the line-shaped protrusions may all be the same or different. Further, the plurality of line-shaped protrusions included in the lens sheet may be continuously arranged or may be arranged with a certain interval. The plurality of line-shaped protrusions are preferably arranged at the same pitch interval P.

  The thickness H of the light collecting film 25 is not particularly limited, but can be, for example, about 20 μm to 200 μm, and preferably 30 μm to 100 μm. The thickness H of the condensing film 25 here is from the flat surface (the surface opposite to the surface having the line-shaped protrusions) constituting one surface of the condensing film 25 to the apex in the prism shape or lens shape. It means the shortest distance.

  In addition, the condensing film 25 preferably has a Gurley bending resistance measured in accordance with JIS L 1096 of 300 mgf or less, and more preferably 250 mgf or less. Thus, since the rigidity of the polarizing plate 20 obtained by using the condensing film 25 with small bending resistance is reduced, the handleability at the time of bonding to the liquid crystal cell 40 can be improved.

  The condensing film 25 having a prism shape or a lens shape on the surface is a manufacturing method in which a prism shape or a lens shape is thermally transferred to a thermoplastic resin, or an active energy ray curable resin that is cured by ultraviolet rays or the like into a resin film. The manufacturing method etc. which shape a lens shape are mentioned.

  Examples of the production method for thermal transfer to the former thermoplastic resin include the following methods. First, a thermoplastic resin is melt-kneaded and discharged from a T die into a film. Subsequently, the film-like sheet is sandwiched between a roll (hereinafter also referred to as a transfer roll) having a transfer mold in which a prismatic or lens-like shape is engraved and a roll having a flat surface, and is cooled and solidified. A prism shape or a lens shape is formed on the surface of the film-like sheet. According to this manufacturing method, it is possible to manufacture a sheet member whose projection shape is precisely controlled, such as the pitch interval P between the prism-shaped or lens-shaped ridge lines R, with high productivity.

  Examples of such thermoplastic resins include olefin resins such as polypropylene resins, polyacrylic resins, polycarbonate resins, polyester resins, polystyrene resins, and methyl methacrylate from the viewpoint of transparency, moisture permeability, and productivity. It is preferable to use a styrene copolymer, an acrylonitrile-butadiene-styrene copolymer or an acrylonitrile-styrene copolymer. Among these, in particular, the polypropylene resin includes a resin substantially composed of a propylene homopolymer and a resin composed of a copolymer of propylene and ethylene containing 10% by weight or less of ethylene units. The thermoplastic resin can contain additives such as an ultraviolet absorber, an antioxidant, and a plasticizer as necessary.

  Moreover, as a manufacturing method by shaping using the latter active energy ray curable resin, the following method is mentioned, for example. First, a sheet-like base material such as a polyester film is prepared, and a transfer mold having a prism-like or lens-like pattern formed on the surface of the sheet-like base material and active energy ray curing between the sheet-like base material. Pour in a functional resin. And a prism shape or a lens shape is formed in the surface of a sheet-like base material by irradiating an active energy ray from the sheet-like base material side, and hardening a resin composition, conveying a sheet-like base material.

  Such active energy ray-curable resins include acrylate compounds such as urethane (meth) acrylate, epoxy (meth) acrylate, and ester (meth) acrylate, enethiol compounds composed of polyene and polythiol, radicals, and the like. And a resin composition containing a cationic photopolymerization initiator, and a resin composition containing an epoxy compound, an oxetane compound, a vinyl ether compound, and a cationic photopolymerization initiator. Among these, a resin composition containing a urethane (meth) acrylate compound, an ester (meth) acrylate compound, and a radical photopolymerization initiator is particularly preferable.

  The condensing film 25 as described above can be easily obtained as a commercial product. Examples of such a commercial product of the condensing film 25 include 3M's “BEF” and Mitsubishi Rayon's “Diaart”.

  A protective film 26 may be laminated on the surface of the condensing film 25 opposite to the polarizing film 21 for the purpose of protecting the prism-like or lens-like surface shape. The protective film 26 is a protective film for preventing the surface shape of the light collecting film 25 from being damaged in the process of storage and transportation. When the polarizing film 21 is bonded to the liquid crystal cell 40 to manufacture the liquid crystal panel 2, the protect film 26 is peeled from the light collecting film 25.

  Examples of the resin material that forms the protective film 26 include polyethylene terephthalate, polyethylene, polypropylene, and an ethylene-vinyl acetate copolymer. Among these, polyethylene terephthalate having a small fish eye and a good yield is particularly preferable.

[Protect film]
When the condensing film 25 is wound in a roll shape, it is preferable that a protective film 26 is bonded to the prism-like or lens-like surface to protect the prism-like or lens-like surface until use. The protective film 26 used for this purpose is generally one in which a pressure-sensitive adhesive layer 26b is formed on the surface of a base film 26a, and the pressure-sensitive adhesive layer 26b is connected to the prism-like or lens-like surface of the light collecting film 25. Bonded to contact.

  The base film 26a constituting the protect film 26 is not particularly limited as long as it is made of a transparent resin. Examples of such transparent resins include acrylic resins typified by polymethyl methacrylate, olefin resins typified by polypropylene and polyethylene, and polyester resins typified by polybutylene terephthalate and polyethylene terephthalate. Can be mentioned. In particular, from the viewpoint of adhesion with a rubber-based pressure-sensitive adhesive described later, it is preferable to use an olefin-based resin as the base film 26a.

  The thickness of the base film 26a is not particularly limited, but is preferably in the range of 10 μm to 200 μm from the viewpoint of workability, more preferably in the range of 15 μm to 100 μm, and particularly preferably in the range of 20 μm to 70 μm. If the thickness of the base film 26a is too small, the surface protection property and the strength when the protective film 26 is peeled off from the light collecting film 25 tend to be insufficient. On the other hand, if the thickness is too large, it tends to be disadvantageous in terms of handling and cost.

[Adhesive that forms the protective film]
The pressure-sensitive adhesive layer 26b constituting the protect film 26 can be a known re-peeling pressure-sensitive adhesive such as a rubber-based pressure-sensitive adhesive or an acrylic pressure-sensitive adhesive. In particular, it is preferable to employ a rubber-based adhesive from the viewpoint of adhesion to the prism surface. Since the acrylic adhesive has weak adhesion to the prism surface, when the protective film 26 is bonded to the prism-like or lens-like surface of the condensing film 25, the protective film 26 may be lifted off. .

  Examples of rubber-based pressure-sensitive adhesives include natural rubber or synthetic rubber as a pressure-sensitive adhesive component, modified rubber in which an acrylic component such as methyl methacrylate is graft-polymerized on natural rubber or synthetic rubber having a double bond And those having a rubber elasticity copolymer such as a styrene / butadiene / styrene block copolymer or a hydrogenated product thereof as the adhesive component.

(3) Transparent resin film The transparent resin film 23 is a film that is bonded to the surface of the polarizing film 21, and employs films having various properties depending on the characteristics required for the liquid crystal panel 2 and the liquid crystal display device 1. can do. As an example of the transparent resin film 23, for example, a protective film for protecting the surface of the polarizing film 21, a retardation film for solving the problem of viewing angle characteristics of the liquid crystal display device 1, and the like can be employed. As the protective film, for example, a non-oriented film having a haze value of 0.5% or less and an in-plane retardation value of less than 30 nm can be employed. As the retardation film, a biaxial retardation film having an in-plane retardation value in the range of 30 to 200 nm and a thickness direction retardation value in the range of 30 to 350 nm can be employed. The in-plane retardation value R ₀ and the thickness direction retardation value R _th here are values at a wavelength of 590 nm, and so on.

  The transparent resin film 23 preferably has a Gurley method bending resistance measured in accordance with JIS L 1096 of 350 mgf or less, more preferably 200 mgf or less, and even more preferably 150 mgf or less. Thus, since the rigidity of the obtained polarizing plate 20 is reduced by using the transparent resin film 23 with a low bending resistance, the handling property at the time of bonding to the liquid crystal cell 40 can be improved.

  The resin material which comprises the transparent resin film 23 is not specifically limited. Examples of such resin materials include (meth) acrylic resins such as methyl methacrylate resins ((meth) acrylic resins mean methacrylic resins or acrylic resins), olefin resins, poly Vinyl chloride resin, cellulose resin, styrene resin, acrylonitrile / butadiene / styrene copolymer resin, acrylonitrile / styrene copolymer resin, polyvinyl acetate resin, polyvinylidene chloride resin, polyamide resin, polyacetal resin Polycarbonate resin, modified polyphenylene ether resin, polyester resin (for example, polybutylene terephthalate resin, polyethylene terephthalate resin, etc.), polysulfone resin, polyethersulfone resin, polyarylate resin, polyamideimide resin, Polyimide resins, epoxy resins, and oxetane-based resin. These resins can contain additives as long as transparency and adhesiveness with the polarizing film 21 are not impaired.

(3-1) Biaxial retardation film As the transparent resin film 23, a retardation film can be adopted as described above. Examples of such a retardation film include a film obtained by stretching the unstretched film made of the resin material described above to develop a retardation, thereby forming a transparent resin film 23. In addition, there is a method of forming a retardation film by applying an orientation material such as liquid crystal to a base material and orienting it to develop a phase difference and fixing it (for example, JP-A-2004-272202). A method for forming an optically anisotropic layer containing a rod-like liquid crystalline compound on a transparent support, as described in Example 4 of the publication or Example 3 of JP-A-2004-233872. In particular, those in which biaxial birefringence is expressed by successive biaxial stretching are preferred. The stretching ratio at this time is approximately 1.1 to 10 times in the direction in which the optical axis is expressed (the direction in which the stretching ratio is large and the slow axis) among the longitudinal direction and the transverse direction, and is orthogonal to that. What is necessary is just to select suitably from the range of about 1.1-7 times by the direction (direction where a draw ratio is small, and becomes a fast axis) according to the required phase difference value. The optical axis may be developed in the lateral direction of the film, or the optical axis may be developed in the longitudinal direction. Examples of commercially available cellulose acetate-based resin films imparted with such retardation characteristics include KC4FR-1 (manufactured by Konica Minolta Opto) and KC4HR-1 (manufactured by Konica Minolta Opto).

Next, the retardation value of the transparent resin film 23 will be described. The refractive index of in-plane slow axis direction n _x of the _film, the refractive index n _y in-plane fast axis direction (direction orthogonal with the slow axis and the _plane), the refractive index in the thickness direction n _z, thickness Where d is the in-plane retardation value R ₀ and the thickness direction retardation value R _th are defined by the following equations (I) and (II), respectively.
_{R 0 = (n x -n y} ) × d (I)
R _th = [(n _x + _ny ) / 2−n _z ] × d (II)

Further, the transparent resin film 23 has the following formula (III):
_nx > _ny > _nz (III)
It satisfies the relationship.

In the present invention, the transparent resin film 23 having an in-plane retardation value R ₀ in the range of 30 to 200 nm and a thickness direction retardation value R _th in the range of 30 to 350 nm is used. The phase difference value may be appropriately selected according to the characteristics required for the applied liquid crystal display device 1. The in-plane retardation value R ₀ is preferably 100 nm or less, and the thickness direction retardation value R _th is preferably 80 nm or more and 200 nm or less.

The accuracy of the in-plane retardation value R ₀ is within the center value ± 7 nm, preferably within the center value ± 5 nm, and the accuracy of the thickness direction retardation value R _th is within the center value ± 15 nm, preferably the center value ± 10 nm. Is within. If the accuracy of these values exceeds the above range, the visual characteristics of the applied liquid crystal display device 1 tend to deteriorate.

  The slow axis angle in the film plane of the transparent resin film 23 is substantially 0 ° or 90 °. If the slow axis deviates from this angle, light leakage occurs when the polarizing plate 20 and the polarizing plate 30 are in a crossed Nicol state, and when applied to the liquid crystal display device 1, visual characteristics such as front contrast are greatly increased. It tends to decrease. The accuracy of the slow axis is preferably within the center value ± 0.7 °, and more preferably within the center value ± 0.5 °. Here, the light leakage means that when the axial accuracy of the polarizing film 21 with respect to the biaxial retardation film 23 or the axial accuracy of the polarizing plate 20 with respect to the liquid crystal cell 40 is poor, the liquid crystal display device 1 starts from the entire display area when displaying black. A phenomenon in which light leaks. As described above, the shift of the slow axis in the transparent resin film 23 is reduced, and accordingly, the shift of the angle between the slow axis and the absorption axis of the polarizing film 21 is also reduced. Light leakage can be reduced by increasing the axial accuracy of the polarizing plates to be bonded (polarizing plate 20 and polarizing plate 30) and by reducing the deviation from 90 ° of the angle formed by the absorption axes of both polarizing plates. .

  In adhering the transparent resin film 23 to the polarizing film 21, the optimum axial relationship between them may be selected in consideration of the viewing angle characteristics and color change characteristics of the target liquid crystal display device 1. In large liquid crystal television applications where front contrast is important, the slow axis of the transparent resin film 23 and the absorption axis of the polarizing film 21 are often arranged in a substantially parallel or substantially orthogonal relationship. Here, “substantially parallel or substantially orthogonal” includes not only the case of being completely parallel or orthogonal but also the case of deviation from the parallel or orthogonal relationship within a range of about ± 10 °. The angle deviation is preferably within ± 5 °, more preferably within ± 2 °. The slow axis of the transparent resin film 23 and the absorption axis of the polarizing film 21 are preferably in a completely parallel or orthogonal relationship.

(3-2) Non-orientable film As the transparent resin film 23, a protective film can be employed as described above. As such a protective film, a non-oriented film having substantially no retardation in the plane or thickness direction can be employed. The non-oriented film means an unstretched resin film (unstretched film) obtained by forming a resin material into a film.

  Since the non-oriented film has no retardation, it does not have the function of widening the viewing angle of the liquid crystal display device 1 like the biaxial retardation film. However, the non-oriented film is stretched like the biaxial retardation film. The manufacturing cost is low because it is not necessary to do so. Therefore, the manufacturing cost of the liquid crystal display device 1 can be further reduced as compared with the case where two biaxial retardation films described later are employed.

  Moreover, since a non-oriented film does not perform a extending | stretching process and a film thickness becomes thick, the handleability of the transparent resin film 23 becomes favorable. Such a transparent resin film 23 can be obtained from an unstretched film (raw film) obtained by forming the resin composition.

  The resin material mentioned above is formed into an unstretched film by any method. This unstretched film is preferably transparent and substantially free of in-plane retardation. Examples of the film forming method include an extrusion method in which a molten resin is extruded to form a film, and a solvent cast method in which a solvent dissolved in an organic solvent is cast on a flat plate and then the solvent is removed to form a film. Etc. can be adopted.

From the viewpoint of the retardation value _{Rth in} the thickness direction, it is preferable that the transparent resin film 23 is thinner because the retardation value can be reduced. Specifically, the transparent resin film 23 preferably has a thickness of 15 to 45 μm. Considering not only the handling property of the polarizing plate 20 but also the handling property of the transparent resin film 23 itself, a film having a thickness of 35 to 45 μm is more preferable.

(4) Adhesive Layer The condensing film 25 and the transparent resin film 23 to the polarizing film 21 are usually bonded and laminated through an adhesive layer (not shown). The adhesive that forms the adhesive layer provided on both surfaces of the polarizing film 21 may be the same or different.

  From the viewpoint of rapid curing and productivity improvement of the polarizing plate 20 associated therewith, as an example of a preferable adhesive for forming the adhesive layer, an active energy ray-curable adhesive that is cured by irradiation with active energy rays can be mentioned. it can. As an example of such an active energy ray-curable adhesive, for example, a photo-curable adhesive that is cured by light energy such as ultraviolet light and visible light can be cited. As a photocurable adhesive agent, the curable composition containing a photocurable epoxy resin and a photocationic polymerization initiator etc. can be mentioned, for example. In particular, when a polypropylene resin is used as the light condensing film 25, the polypropylene resin film has a low moisture permeability as described above. Therefore, when a water-based adhesive described later is used, drainage is bad, and the moisture of the adhesive In some cases, the polarizing film 21 may be damaged or the polarizing performance may be deteriorated. Therefore, when bonding such a resin film with low moisture permeability, a photocurable resin is preferable.

  Further, from the viewpoint of thinning the adhesive layer, an aqueous adhesive, that is, an adhesive in which an adhesive component is dissolved in water or an adhesive component is dispersed in water can also be used as the adhesive. For example, an aqueous composition using a polyvinyl alcohol resin or a urethane resin as a main component can be mentioned as a preferred aqueous adhesive.

  Polyvinyl alcohol resins as the main component of the adhesive include partially saponified polyvinyl alcohol and fully saponified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, methylol group-modified polyvinyl alcohol, amino group-modified polyvinyl alcohol. It may be a modified polyvinyl alcohol resin such as alcohol. An aqueous adhesive whose main component is an polyvinyl alcohol resin is often prepared as an aqueous solution of a polyvinyl alcohol resin. The density | concentration of the polyvinyl alcohol-type resin in a water-system adhesive agent is about 1-10 weight part normally with respect to 100 weight part of water, Preferably it is 1-5 weight part.

  In order to improve the adhesiveness, it is preferable to add a curable component such as glyoxal or a water-soluble epoxy resin or a crosslinking agent to an aqueous adhesive containing a polyvinyl alcohol resin as a main component. Examples of water-soluble epoxy resins include polyamides obtained by reacting epichlorohydrin with polyamide polyamines obtained by reacting polyalkylene polyamines such as diethylenetriamine and triethylenetetramine with dicarboxylic acids such as adipic acid. Mention may be made of polyamine epoxy resins. Commercially available products of such polyamide polyamine epoxy resins include “Smiles Resin 650” and “Smiles Resin 675” sold by Sumika Chemtex Co., Ltd., and “WS-525” sold by Japan PMC Co., Ltd. Etc., and these can be preferably used. The addition amount of these curable components or crosslinking agents is usually 1 to 100 parts by weight, preferably 1 to 50 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin. If the amount added is small, the effect of improving the adhesiveness is reduced, while if the amount added is large, the adhesive layer tends to be brittle.

  When a urethane resin is used as the main component of the adhesive, examples of suitable water-based adhesives include a mixture of a polyester ionomer type urethane resin and a compound having a glycidyloxy group. The polyester-based ionomer type urethane resin here is a urethane resin having a polyester skeleton, into which a small amount of an ionic component (hydrophilic component) is introduced. Such an ionomer-type urethane resin is suitable as a water-based adhesive because it is emulsified directly into water without using an emulsifier and becomes an emulsion. Polyester ionomer urethane resins are known per se. For example, Japanese Patent Application Laid-Open No. 7-97504 describes a polyester ionomer type urethane resin as an example of a polymer dispersant for dispersing a phenolic resin in an aqueous medium, and Japanese Patent Application Laid-Open No. 2005-070140. In JP-A-2005-181817, a cycloolefin-based resin film is bonded to a polarizing film made of a polyvinyl alcohol-based resin using a mixture of a polyester-based ionomer-type urethane resin and a compound having a glycidyloxy group as an adhesive. The form is shown.

  As a method for bonding the light collecting film 25 and the transparent resin film 23 to the surface of the polarizing film 21 using an adhesive, a conventionally known method can be used. For example, the polarizing film 21 and / or the film to be bonded to it by the casting method, Meyer bar coating method, gravure coating method, comma coater method, doctor plate method, die coating method, dip coating method, spraying method, etc. The method of apply | coating an adhesive agent to a surface and superimposing both is mentioned. The casting method is a method of spreading and spreading an adhesive on the surface of a film to be coated while moving the film in a substantially vertical direction, a substantially horizontal direction, or an oblique direction between the two.

  After apply | coating an adhesive agent by the said method, both are joined by pinching | interposing the polarizing film 21 and the film bonded by it with a nip roll. Moreover, after dripping an adhesive agent between the polarizing film 21 and the film bonded to it, the method of pressing this laminated body with a roll etc. and spreading it uniformly can also be used suitably. In this case, a metal, rubber, or the like can be used as the material of the roll. Furthermore, after dropping an adhesive agent between the polarizing film 21 and the film bonded thereto, a method of passing the laminate between the rolls and pressurizing and spreading is preferably employed. In this case, these rolls may be made of the same material or different materials.

  Note that the thickness of the adhesive layer after being bonded using a nip roll or the like before drying or curing is preferably 5 μm or less, and more preferably 0.01 μm or more.

  In order to improve the adhesiveness, the polarizing film 21 and / or the adhesive surface of the film bonded thereto are subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, saponification treatment, etc. You may give suitably. Examples of the saponification treatment include a method of immersing in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide.

  The laminated body joined through the water-based adhesive is usually subjected to a drying treatment, and the adhesive layer is dried and cured. The drying process can be performed, for example, by blowing hot air. A drying temperature is normally selected from the range of about 40-100 degreeC, Preferably it is 60-100 degreeC. The drying time is, for example, about 20 to 1,200 seconds. The thickness of the adhesive layer after drying is usually about 0.001 to 5 μm, preferably 0.01 μm or more, preferably 2 μm or less, more preferably 1 μm or less. If the thickness of the adhesive layer becomes too large, the appearance of the polarizing plate 20 tends to be poor.

  After the drying treatment, sufficient adhesive strength may be obtained by performing curing at a temperature of room temperature or higher for at least half a day, usually 1 day or longer. Such curing is typically performed in a state of being wound into a roll. The preferable curing temperature is in the range of 30 to 50 ° C, more preferably 35 ° C or more and 45 ° C or less. When the curing temperature exceeds 50 ° C., so-called “roll tightening” is likely to occur in the roll winding state. The humidity during curing is not particularly limited, but is preferably selected so that the relative humidity is in the range of about 0% RH to 70% RH. The curing time is preferably about 1 to 10 days, more preferably about 2 to 7 days.

  On the other hand, when the polarizing film 21 and the film bonded thereto are bonded using a photocurable adhesive, the photocurable adhesive is cured by irradiating active energy rays after these films are bonded. Let The light source of the active energy ray is not particularly limited, but an active energy ray having a light emission distribution at a wavelength of 400 nm or less is preferable. Specifically, the low-pressure mercury lamp, the medium-pressure mercury lamp, the high-pressure mercury lamp, the ultrahigh-pressure mercury lamp, the chemical lamp, and the black light lamp A microwave excited mercury lamp, a metal halide lamp, or the like is preferably used.

The light irradiation intensity to the photocurable adhesive is appropriately determined depending on the composition of the photocurable adhesive and is not particularly limited, but the irradiation intensity in the wavelength region effective for activating the polymerization initiator is 0.1 to 6000 mW. / Cm ² is preferable. When the irradiation intensity is 0.1 mW / cm ² or more, the reaction time does not become too long, and when it is 6000 mW / cm ² or less, the heat is radiated from the light source and the heat generated when the photocurable adhesive is cured. There is little possibility of causing yellowing of the photocurable epoxy resin and deterioration of the polarizing film 21. The light irradiation time to the photocurable adhesive is controlled for each photocurable adhesive to be cured and is not particularly limited, but the integrated light amount expressed as the product of the irradiation intensity and the irradiation time is It is preferably set to be 10 to 10,000 mJ / cm ² . When the cumulative amount of light to the photocurable adhesive is 10 mJ / cm ² or more, a sufficient amount of active species derived from the polymerization initiator can be generated to allow the curing reaction to proceed more reliably, and at 10,000 mJ / cm ² or less. In some cases, irradiation time does not become too long and good productivity can be maintained. In addition, the thickness of the adhesive bond layer after active energy ray irradiation is about 0.001-5 micrometers normally, Preferably it is 0.01 micrometer or more, More preferably, it is 0.1 micrometer or more.

  When the photocurable adhesive is cured by irradiation with active energy rays, various functions of the polarizing plate 20 such as the degree of polarization, the transmittance and the hue of the polarizing film 21 and the transparency of the transparent resin film 23 and the light collecting film 25 are provided. It is preferable to perform the curing under conditions that do not decrease.

<Production method of polarizing plate>
Hereinafter, an embodiment of a method for manufacturing the polarizing plate 20 will be described in detail with reference to FIG. In this manufacturing method, the condensing film 25 is bonded to one surface of the polarizing film 21 via an adhesive, and the transparent resin film 23 is bonded to the other surface of the polarizing film 21 via an adhesive. Thus, the polarizing plate 20 is manufactured. The manufacturing method of the polarizing plate 20 includes a raw material film conveyance step (A), a bonding step (B), and a curing step (C).

  In the raw material film transporting step (A), the polarizing film 21 is transported in a certain direction, the condensing film 25 is supplied to one surface thereof, and the transparent resin film 23 is supplied to the other surface. In the middle of the raw material film conveying step (A), the adhesive is applied to the surface of the light collecting film 25 to be bonded to the polarizing film 21 by the adhesive application device 12, and the other adhesive application device 13 is used. An adhesive can be applied to the surface of the transparent resin film 23 to be bonded to the polarizing film 21.

  A pasting process (B) is the 1st pasting roll 15 which contacts the outside (surface side which has prism shape or lens shape) of condensing film 25, and the 2nd pasting which contacts the outside of polarizing film 21. It is performed while sandwiching the laminated body of the light collecting film 25 / the polarizing film 21 / the transparent resin film 23 with the roll 16. The 1st bonding roll 15 and the 2nd bonding roll 16 are rotating in the conveyance direction of the film which each contacts, and the curve arrow in a figure has shown the rotation direction.

  In the curing step (C), energy for curing the adhesive is supplied from the curing device 18 to the laminate obtained in the pasting step (B), and between the polarizing film 21 and the light collecting film 25, And a step for curing the adhesive between the polarizing film 21 and the transparent resin film 23. Each of these steps will be described in order.

[Raw material film transport process (A)]
In the raw film transporting step (A), the long polarizing film 21 is fed out from the polarizing film 21 wound in a roll shape. On one surface side of the polarizing film 21, a long condensing film 25 fed out from the condensing film 25 which is also wound in a roll shape is supplied, and on the other surface side, it is wound in a roll shape. A long transparent resin film 23 fed out from the transparent resin film 23 is supplied.

  The conveyance speed of the condensing film 25 and the transparent resin film 23 may be set to a value suitable for the production apparatus, and is not particularly limited. Usually, the conveyance of the polarizing film 21 produced and conveyed in the previous step is usually performed. The speed is adjusted to the speed. Unless the type and quality of the polarizing plate 20 are restricted, the pressure applied to the film per unit time in the bonding step (B) becomes smaller as the conveying speed is higher. For this reason, the prism shape or lens shape of the condensing film 25 is not easily crushed, and the optical characteristics are good. A higher conveying speed is preferable from the viewpoint of productivity because the tact time becomes faster. Specifically, the conveyance speed can be set to about 1 to 100 m / min, for example.

  The direction in which each film is conveyed may be such that the polarizing film 21 is sandwiched between the condensing film 25 and the transparent resin film 23 at the end of the conveying step. In the middle stage, for example, there may be a portion where the condensing film 25 and / or the transparent resin film 23 is transported in a direction perpendicular to the transport direction of the polarizing film 21, There may be a portion in which the condensing film 25 and / or the transparent resin film 23 is conveyed in parallel to the conveying direction of the polarizing film 21. Further, when there is a restriction on the arrangement of the manufacturing apparatus, the condensing film 25 and / or the transparent resin film 23 is once fed out in the direction opposite to the conveying direction of the polarizing film 21 and then the polarizing film 21 by an appropriate roll. The direction may be changed so as to be directed to one side of the polarizing film 21, or the polarizing film 21 is fed out at an appropriate angle including the vertical direction from the transverse direction in which the polarizing film 21 is conveyed, and then is applied to one side of the polarizing film 21 by an appropriate roll. The direction may be changed so as to be directed.

[Protect film pasting process]
Although illustration is abbreviate | omitted, the condensing film 25 can use for a raw material film conveyance process (A) in the state in which the protective film was laminated | stacked on the opposite side to the surface bonded by the polarizing film 21. FIG. Since the condensing film 25 is easily damaged or damaged in the prism shape or lens shape on the surface, it is effective to supply such a protective film in a layered manner for the purpose of protecting the surface shape. In this case, after the condensing film 25 passes through the protect film bonding process which bonds a protect film, it is provided to a raw material film conveyance process (A).

  The condensing film 25 to which the protective film is bonded is preferably a positive curl that is slightly convex on the condensing film 25 side and has a curl amount of 10 mm or less. Here, the curl amount means the height at which the corners or sides of the film rise from the surface when the convex surface is placed on a flat surface. When the curling amount of the condensing film 25 to which the protective film is bonded is within this range, the curling amount of the obtained polarizing plate 20 can be adjusted to a more preferable range.

[Adhesive application process]
Bonding of the polarizing film 21 and the light collecting film 25 is performed via an adhesive. An adhesive agent can be apply | coated to at least one of the bonding surfaces of the polarizing film 21 and the condensing film 25 in the arbitrary steps in a raw material film conveyance process (A). In FIG. 6, the adhesive is applied to the bonding surface of the condensing film 25, but the adhesive can also be applied to the bonding surface of the polarizing film 21, for example.

  In addition, an adhesive may be applied to the bonding surface of the polarizing film 21 or the light collecting film 25 immediately before the light collecting film 25 and the polarizing film 21 are bonded by the bonding rolls 15 and 16. However, from the viewpoint of operability and the like, as shown in FIG. 6, it is preferable to apply an adhesive in advance to the bonding surface of the light collecting film 25 instead of just before the bonding. That is, in the raw material film conveying step (A), there is a portion where the condensing film 25 and the polarizing film 21 are conveyed with a certain gap in preparation for the subsequent bonding step (B). It is preferable to apply an agent.

  Then, Preferably, an adhesive agent coating process is provided in the middle of a raw material film conveyance process (A). An adhesive agent is apply | coated to the surface bonded to the polarizing film 21 among the condensing films 25 in this adhesive agent application process. FIG. 6 shows an example in which the adhesive is applied to the bonding surface of the light collecting film 25 by the adhesive application device 12.

  The bonding surfaces of the light collecting film 25 and the polarizing film 21 may be subjected to a surface activation treatment such as corona treatment, plasma treatment, ultraviolet irradiation treatment, or electron beam irradiation treatment before the adhesive is applied. Good. In addition, each film may be subjected to washing and drying treatment as necessary, or may be subjected to application of an easy adhesion treatment agent, a surface modifier, etc. and subsequent drying treatment.

  The structure and application method of the adhesive application device 12 are not particularly limited, and an apparatus and method that can uniformly apply a required amount of adhesive may be employed. For example, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be adopted.

[Bonding process (B)]
In the raw film transporting step (A), the condensing film 25 supplied from both sides so as to sandwich the polarizing film 21 is the first pasting which contacts the outside of the condensing film 25 in the subsequent bonding step (B). It is bonded by the bonding roll 15 and the second bonding roll 16 that contacts the outside of the polarizing film 21.

  In this bonding step, the bonding pressure by the first bonding roll 15 and the second bonding roll 16 is preferably in the range of 0.3 MPa to 5.0 MPa or less. If the bonding pressure is too high, the prism shape or lens shape of the light-collecting film 25 is crushed and the shape tends to collapse during bonding, which is not preferable. On the other hand, when the bonding pressure is too low, the films are not sufficiently bonded to each other and are easily peeled off, which is not preferable.

  In this bonding step (B), it is preferable to perform the bonding by making the peripheral speed of the second bonding roll 16 faster than the peripheral speed of the first bonding roll 15. By doing in this way, the obtained polarizing plate 20 becomes a so-called positive curl shape in which the polarizing film 21 side is slightly convex and the condensing film 25 side is slightly concave. Since the polarizing film 20 having such a positive curl shape has a convex shape on the side of the polarizing film 21, air bubbles are formed on the bonding surface when bonding to another film such as a retardation film or the liquid crystal cell 40. It is preferable because it becomes difficult to enter.

On the other hand, if the convex shape on the polarizing film 21 side is too large, that is, if the curl amount of the positive curl is too large, the four corners of the polarizing plate 20 are likely to be lifted. Since the polarizing plate 20 is bonded to the film or the liquid crystal cell 40, it is not preferable because it tends to peel off from the end side. Therefore, specifically, the peripheral speed is differentiated so that the ratio of the peripheral speed of the second bonding roll 16 to the peripheral speed of the first bonding roll 15 is 1.0105 or more and 1.0118 or less. Preferably, it is done. The relationship between the peripheral speeds is that the peripheral speed of the first bonding roll 15 that contacts the outside of the light collecting film 25 is R ₁ , and the peripheral speed of the second bonding roll 16 that contacts the outside of the polarizing film 21 is R. ₂ , the following expression (1) is satisfied.
1.0105 ≦ R ₂ / R ₁ ≦ 1.0118 (1)

Due to the difference in the peripheral speeds of the bonding rolls 15 and 16 defined by the ratio of the peripheral speeds, the condensing stress is applied to the light collecting film 25 and the tensile stress is applied to the polarizing film 21, respectively. To the curing step (C), and the adhesive is cured. After the curing, the polarizing plate 20 is distorted and curls with each stress release. The circumferential speed R2 of the _second laminating roll 16 that contacts the outside of the polarizing film 21 is slightly larger than the circumferential speed R1 of the _1st laminating roll 15 that contacts the outside of the condensing film 25. By setting the ratio to be in the above range, the curl amount of the obtained polarizing plate 20 is appropriately controlled.

  Surface materials constituting the bonding rolls 15 and 16 are metals such as stainless steel, copper alloy, and chrome-plated products; rubbers such as polyurethane, polyfluoroethylene, and silicone; chromium oxide, silicon oxide Further, ceramics obtained by spraying zirconium oxide or aluminum oxide may be used. Especially, it is preferable that the 1st bonding roll 15 which contacts the outer side of the condensing film 25 is a rubber roll, and the 2nd bonding roll 16 which contacts the outer side of the polarizing film 21 is a metal roll. That is, a polarizing film having surface irregularities in a prism shape or a lens shape, a relatively thin and weak rigidity, and a rubber roll having elasticity on the surface is generally applied, and the rigidity is generally higher than that of the light collecting film 25. A metal roll is applied to the 21 side. By doing in this way, the stress which arises by the difference of both peripheral speed can be given to a film effectively and uniformly.

[Curing step (C)]
In the curing step (C), the above-mentioned adhesive is used for the laminate bonded in the order of the condensing film 25 / adhesive (not shown) / polarizing film 21 conveyed from the bonding step (B). The cured film 25 is bonded to the polarizing film 21 and becomes the polarizing plate 20. In FIG. 6, the laminated body bonded by the bonding rolls 15 and 16 is sent into the hardening apparatus 18, and a hardening process is given there. The curing treatment can be performed by irradiation with active energy rays, heating, or drying depending on the type of adhesive.

  As the adhesive, it is preferable to use an adhesive composition that cures upon irradiation with the above-described active energy rays, particularly one containing an epoxy compound and a cationic polymerization initiator. In this case, the curing step (C) is performed by irradiation with active energy rays. The active energy rays used for curing the adhesive may be, for example, X-rays having a wavelength of 1 pm to 10 nm, ultraviolet rays having a wavelength of 10 to 400 nm, visible rays having a wavelength of 400 to 800 nm, and the like. Among these, ultraviolet rays are preferably used from the viewpoints of ease of handling, ease of preparation of the curable adhesive composition and its stability, and its curing performance. As an ultraviolet light source, for example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, a metal halide lamp or the like having a light emission distribution at a wavelength of 400 nm or less may be used. it can.

The irradiation intensity of ultraviolet rays is determined by the type of adhesive and the irradiation time, and is not particularly limited. For example, the irradiation intensity in the wavelength region effective for activating the initiator is 0.1 to 300 mW / cm ^2. It is preferable to set so as to be, and it is more preferable to set so as to be 1 to 200 mW / cm ² . When the light irradiation intensity to the curable adhesive composition is less than 0.1 mW / cm ² , the curing reaction time becomes long, and it becomes difficult to cure unless the irradiation time is lengthened, which is disadvantageous in terms of productivity. . On the other hand, when the light irradiation intensity exceeds 300 mW / cm ² , yellowing of the curable adhesive composition or deterioration of the polarizing film 21 is caused by heat radiated from the lamp and heat generated during polymerization of the curable adhesive composition. May occur.

The irradiation time of ultraviolet rays is also determined by the type of adhesive and the irradiation intensity and is not particularly limited. For example, the integrated light amount represented by the product of the irradiation intensity and the irradiation time is 10 to 5,000 mJ / cm ^2. It is preferable to set so that it may become, and it is more preferable to set so that it may become 50-1,000 mJ / cm < ² > further. When the cumulative amount of light to the curable adhesive composition is less than 10 mJ / cm ² , active species derived from the initiator are not sufficiently generated, and the resulting adhesive layer tends to be insufficiently cured. On the other hand, if the integrated light quantity exceeds 5,000 mJ / cm ² , the irradiation time becomes very long, which is disadvantageous in terms of productivity.

  When the curing step (C) is performed by irradiation with active energy rays, the thickness of the cured adhesive layer is usually 1 μm or more and 50 μm or less, but the viewpoint of thinning the polarizing plate 20 while maintaining an appropriate adhesive force Therefore, it is preferably 20 μm or less, and more preferably 10 μm or less.

  In the manufacturing method mentioned above, the method of laminating | stacking two films of the polarizing film 21 and the condensing film 25 is demonstrated. When manufacturing the polarizing plate 20 provided with the transparent resin film 23 like FIG. 2, you may make it bond three films with the bonding rolls 15 and 16 simultaneously.

  Hereinafter, this manufacturing method will be specifically described. First, in the bonding apparatus in FIG. 6, a roll-shaped transparent resin film 23 is provided on the surface of the polarizing film 21 opposite to the surface on which the light collecting film 25 is bonded. Place. Then, the long transparent resin film 23 is drawn out from the roll-shaped transparent resin film 23, and an adhesive application device (not shown) or the like is applied to any of the surfaces to which the transparent resin film 23 and the polarizing film 21 are bonded. Apply the adhesive using. An adhesive agent is apply | coated to the surface of an other side using the adhesive agent coating apparatus 12 in either of the surfaces where the condensing film 25 and the polarizing film 21 are bonded similarly to embodiment mentioned above. After the application, the first pressure roll 15 and the second pressure roll 16 are applied to the laminated body of the light collecting film 25 / the polarizing film 21 / the transparent resin film 23 to apply the pressure. . The adhesive is cured by the curing device 18 with respect to the laminated body after pasting to produce a polarizing plate (three-layer structure).

<Thickness distribution and luminance ratio after lamination>
Hereinafter, the thickness distribution of the condensing film 25 which is a feature of the present invention will be described with reference to FIG. This figure is a schematic cross-sectional view of the light collecting film 25 and schematically shows variations in film thickness. The present invention is characterized in that the thickness distribution of the light collecting film 25 represented by the following formula is 5% or less. That is, the average film thickness (H _dif ) between the maximum film thickness (H _max ) with the largest thickness of the polarizing plate 20 and the minimum film thickness (H _min ) with the smallest film thickness is an average value of the film thickness ( H _ave ) is 5% or less. Here, the thickness distribution of the condensing film 25 indicates the thickness distribution of the condensing film 25 after lamination after being bonded to the polarizing film 21.

Thus, if the thickness distribution of the condensing film 25 after lamination | stacking is 5% or less, a brightness nonuniformity can be reduced significantly. Specifically, the luminance ratio when the liquid crystal panel 2 is viewed from the front can be kept within about 10%. Here, the luminance ratio is an index representing the contrast of light and darkness of the polarizing plate 20. When the polarizing plate 20 is viewed from the front, the luminance at the brightest place (maximum luminance: (B _max )) and the arbitrary place are used. It means the ratio of the maximum luminance (B _max ) to the difference from the luminance (B). The luminance ratio can be expressed by the following formula.

  This means that the smaller the luminance ratio is, the smaller the luminance region (dark region) is with respect to the region showing the maximum luminance (bright region), and the lower the contrast ratio and the less the luminance unevenness. On the contrary, it means that as the luminance ratio is larger, there are more dark regions than bright regions, and it can be said that the contrast ratio is large and the luminance unevenness is large.

  Empirically, when the luminance ratio exceeds 10%, the luminance unevenness of the polarizing plate 20 is visually increased, and is recognized as the display unevenness of the liquid crystal panel 2, and the visibility deteriorates. The inventors can suppress the luminance ratio to 10% or less by suppressing the above-described thickness distribution to 5% or less, thereby reducing luminance unevenness. Conversely, if the thickness distribution exceeds 5%, the luminance ratio is reduced. The present invention was completed by experimentally confirming that the brightness suddenly increased and the luminance unevenness increased.

  Next, the reason why the luminance unevenness can be reduced by setting the thickness distribution of the light collecting film 25 after lamination to 5% or less will be considered. The polarizing plate 20 is manufactured by laminating the polarizing film 21 and the condensing film 25 using two laminating rolls 15, 16 and the like. A large bonding pressure is applied to the shape or the lens shape, and the prism shape and the lens shape are easily crushed. The condensing film 25 emits light emitted obliquely from a light source such as the backlight 10 toward the liquid crystal cell 40 by changing the angle on the inclined surface of the prism shape or the lens shape, but the prism shape or the lens shape is crushed and deformed. Then, a phenomenon in which the light from the light source goes straight without changing its angle, that is, so-called light leakage is likely to occur.

  On the other hand, in the thin part, since the bonding pressure applied at the time of bonding is small, the prism shape or the lens shape is not easily crushed. For this reason, the thick part is displayed dark due to light loss, and the thin part is displayed brightly, which is considered to cause uneven brightness.

  The region where the thickness distribution of the light collecting film 25 after lamination exceeds 5% is considered to be a region where the film thickness of the light collecting film 25 is originally thick from the stage before bonding. For this reason, when giving and laminating | stacking the bonding pressure to the condensing film 25 and the polarizing film 21, a big bonding pressure is applied and a prism shape or a lens shape tends to deform | transform. On the contrary, the region where the thickness distribution of the light collecting film 25 after lamination is 5% or less is considered to be a region where the film thickness of the light collecting film 25 is originally thin. For this reason, it is considered that an excessive bonding pressure is not applied when applying and laminating the condensing film 25 and the polarizing film 21 and the prism shape or the lens shape is hardly deformed.

  As described above, when the thickness distribution of the light collecting film 25 after lamination is 5% or less, the film thickness of the light collecting film 25 is substantially uniform, and the difference between the thick and thin portions is reduced. For this reason, it is considered that the prism shape or the lens shape is not easily crushed at the thick part, and as a result, the obtained polarizing plate 20 has less luminance unevenness and good visibility. On the other hand, as shown in experimental data in Examples described later, when the thickness distribution of the light collecting film 25 exceeds 5%, the luminance ratio increases rapidly, and the luminance unevenness becomes remarkable. The reason why the luminance ratio suddenly increases with 5% as a boundary is not clear, but it is clear from the examples that the luminance unevenness greatly changes with 5% as a boundary. From this, it can be said that the thickness distribution of 5% is a numerical value having critical significance.

  The thickness distribution may be 5% or less (that is, 0 to 5.0%). However, the thickness distribution is preferably closer to zero from the viewpoint of reducing luminance unevenness. Actually, since the light distribution film 25 having a thickness distribution of zero, that is, a completely uniform thickness is difficult to manufacture, the thickness distribution is preferably 4.0% or less, more preferably 3.0% or less. is there.

  Next, a method for obtaining an optical member (polarizing plate 20) having a thickness distribution of 5% or less will be described. When the polarizing plate obtained in the production process includes a region having a thickness distribution exceeding 5%, it is preferable to cut a region having a thickness distribution exceeding 5% and use the remaining region as the polarizing plate 20. In this remaining region, since the thickness distribution is 5% or less in any part, the luminance ratio is 10% or less, and the polarizing plate 20 exhibits good optical characteristics with little luminance unevenness.

  Specifically, the film thickness at a plurality of locations is measured with respect to the laminated polarizing plate 20 using a film thickness measuring device. Specifically, for example, the thickness distribution is measured by dividing a plurality of vertical and horizontal portions into a matrix. As a result of the thickness distribution measurement, the region where the thickness distribution exceeds 5% is cut as a region with high luminance unevenness, and the other regions are used as regions with low luminance unevenness.

  In embodiment mentioned above, the example using the polarizing film 21 as another optical film was demonstrated. However, other optical films are not limited to the polarizing film 21 as long as they are laminated by applying a bonding pressure. For example, a protective film such as a triacetyl cellulose-based resin film or a retardation film may be used as another optical film, and a condensing film may be bonded and laminated thereon.

  Moreover, in embodiment mentioned above, the example of the polarizing plate 20 was mentioned and demonstrated as an optical member. However, the optical member is not limited to the polarizing plate, and may be a member having another optical function. For example, the optical member which laminated | stacked the diffusion film on the condensing film, the optical member which laminated | stacked the condensing film on the light guide, etc. may be sufficient.

  Moreover, the method of bonding the condensing film 25 and another optical film is not limited to the method by the bonding roll mentioned above. If it is the method of giving bonding pressure and bonding, the method of spraying air on a film from an air cylinder etc., for example, and laminating | stacking will be mentioned.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these examples. In the examples, “%” and “part” representing the content or amount used are based on weight unless otherwise specified.

[Example 1]
(A) Preparation of light condensing film Polypropylene (substantially a homopolymer of propylene) is melt-extruded and sandwiched between a shaping roll arranged below the discharge port of the T-die and a touch roll with a flat surface. By cooling and solidifying and further bringing the flat surface into contact with the cooling roll, a prism film (light collecting film) having a thickness of 100 μm having a prism shape formed on the surface in contact with the shaping roll was produced. The shaping roll used here has a triangular V-shaped groove in parallel with the circumferential direction of the roll, and when the shape is directly transferred to the resin film, as shown in FIG. The portion corresponding to the portion has a flat portion, the pitch interval P of the prism is 33 μm, the height h of the linear protrusion of the prism is 21 μm, and the apex angle θa of the prism is 65 °.

(B) Preparation of single wafer sample The condensing film prepared in the above (a) was placed on an inverted prism, and a single wafer sample was cut out. The size of the single-wafer sample was A4 size, and was used after being cut in half (200 mm × 100 mm) in the longitudinal direction. The obtained single wafer sample was passed through a bonding roll at a bonding pressure of 2.0 MPa and a bonding speed of 1 m / min. A PET (polyethylene terephthalate) film was used as the lead film when the sheet sample was passed through the bonding roll. The bonding apparatus used a metal roll having a diameter of 305 mm and a metal roll having a diameter of 305 mm (both surface roughness is Ra 0.1 or less). The sample after passing through the bonding roll was observed through a liquid crystal cell of a notebook personal computer “VAIO” (manufactured by Sony Corporation). FIG. 7 is a photograph of a state in which the single wafer sample was observed through the liquid crystal cell.

(C) Thickness measurement of single-wafer sample As shown in FIG. 7, the single-wafer sample after passing through the bonding roll is formed into a matrix of 4 vertical positions (S1 to S4) and 6 horizontal positions (1 to 6) at 20 mm vertical and horizontal intervals. The thickness was measured at 24 points of intersections (S1-1 to S4-6). Thickness measurement was performed using DIGIMICRO STAND MS-5C (manufactured by Nikon).

The results of this thickness measurement are shown in Table 1 below. The numerical values in this table indicate the actual film thickness at each intersection, and the unit is μm.

Based on the results in Table 1, the thickness distribution was calculated using the following formula. The minimum value of the thickness distribution = the minimum film thickness (H _min ) is 101.3 μm (value of the intersection S4-3), and the average film thickness (H _ave ) is 106.4 μm.

Table 2 shows the thickness distribution obtained as a result of the calculation.

(D) Measurement of brightness of single-wafer sample The single-wafer sample after thickness measurement was bonded to a liquid crystal cell of a notebook personal computer “VAIO” (manufactured by Sony Corporation) and mounted on a liquid crystal display device. Luminance measurement was performed at each intersection point of the single wafer sample after mounting. For the luminance measurement, a spectral radiance meter: SR-UL1R (manufactured by Topcon Technohouse) was used.

The results of this luminance measurement are shown in Table 3 below. The numerical values in this table indicate the actual luminance at each intersection, and the unit is cd / m ² .

Based on the results in Table 3, the brightness ratio was calculated using the following equation. Note that the maximum luminance (B _max ) is 5105 cd / m ² (value of the intersection S3-4).

The brightness ratio obtained as a result of the calculation is shown in Table 4.

  FIG. 8 is a graph showing the thickness distribution and the luminance ratio with contour lines. FIG. 8A shows the thickness distribution shown in Table 2, and FIG. 8B shows the luminance ratio shown in Table 4. The two circles in this figure correspond to the circles S2-2 and S3-2 in FIG. The lower side of FIG. 8A is a region with a small thickness distribution, and the upper side is a region with a large thickness distribution. On the other hand, the lower side of FIG. 8B is a region with a small luminance ratio, and the upper side is a region with a large luminance ratio. Thus, it can be seen that there is a correlation between the thickness distribution and the luminance ratio. The larger the thickness distribution, the larger the luminance ratio, and the smaller the thickness distribution, the smaller the luminance ratio.

  FIG. 9 is a graph in which the intersections are plotted with the thickness distribution on the horizontal axis and the luminance ratio on the vertical axis. As described above, there is a correlation between the thickness distribution and the luminance ratio, and the thickness distribution becomes smaller and the luminance ratio becomes smaller toward the lower left of the graph. Conversely, the thickness distribution increases and the luminance ratio increases toward the upper right of the graph. The arrows in the figure are approximate curves obtained from the values of the respective intersections. Further, the thickness distribution at the intersection of this approximate curve and the luminance ratio of 10% is 5%. That is, when the thickness distribution is 5% or less, the luminance ratio is 10% or less and the luminance unevenness is small. Conversely, when the thickness distribution exceeds 5%, the luminance ratio exceeds 10% and the luminance unevenness increases. Further, it can be seen from this approximate curve that when the thickness distribution exceeds 5%, the luminance ratio increases rapidly and the luminance unevenness increases.

  This is apparent from the specific values of the thickness distribution in Table 2 and the luminance ratio in Table 4. That is, from Table 4, the brightness ratio is as small as 10% or less in S3-2 to S3-6 and S4-1 to S4-6, but from Table 2, the thickness distribution values corresponding to these regions are almost equal. 5% or less. On the contrary, the luminance ratio greatly exceeds 10% in Table 4 from Table 4, and is approximately 20 to 50%. However, from Table 2, the thickness distribution exceeds 5% in that region, which is approximately 7%. It is ~ 8%. That is, when the thickness distribution slightly exceeds 5%, the luminance ratio greatly exceeds 10%, and the luminance unevenness increases rapidly. Thus, since the luminance ratio changes abruptly at the thickness distribution of 5%, it can be said that the value of the thickness distribution of 5% has a critical significance.

Next, the single wafer sample is cut into a square connecting the four intersections S3-3, S3-4, S4-3, and S4-4. In this region, the maximum value of the thickness distribution = the maximum film thickness (H _max ) is 105.2 μm (S3-3), and the minimum value of the thickness distribution = the minimum film thickness (H _min ) is 101.3 μm (S4-3). The difference (H _dif ) is 3.9 μm, and the average film thickness (H _ave ) is 103.5 μm. Based on this result, when the thickness distribution is calculated at all four intersections, 3.8 μm (S3-2), 3.6 μm (S3-23), 0 μm (S4-2), 1.1 μm (S4- 3). That is, the thickness distribution of the cut sheet sample is 3.8% (S3-2) at the maximum, and is 5% or less in any region.

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device, 2 Liquid crystal panel, 10 Backlight, 12 Adhesive coating device, 15 1st bonding roll, 16 2nd bonding roll, 18 Curing apparatus, 20 Polarizing plate (optical member), 21 Polarizing film (Other optical film), 23 Transparent resin film, 25 Condensing film, 26 Protective film, 26a Base film, 26b Adhesive layer, 27 Adhesive layer, 30 Polarizer, 40 Liquid crystal cell, 50 Light diffusion plate, R Condensation film ridge line, θa apex angle, h height of line-shaped protrusion, P pitch interval, L Distance from the end point of one prism slope to the start point of the next prism slope, H thickness of the light gathering film , H _max maximum film thickness, H _min minimum film thickness, H _ave average film thickness, difference between H _dif maximum film thickness and minimum film thickness

Claims (14)

An optical member in which a condensing film having a prism shape or a lens shape on the surface and another optical film are laminated by applying a bonding pressure,
In the thickness distribution of the condensing film after the lamination, the difference between the maximum film thickness and the minimum film thickness is 5% or less with respect to the average film thickness.   The prism shape or the lens shape of the condensing film is such that the distance from the end point of the slope of one prism or lens to the start point of the next prism or the slope of the lens is 30% with respect to the pitch interval of the ridge line. The optical member according to claim 1, wherein the optical member is formed as follows.   The optical member according to claim 1, wherein the light collecting film is made of a thermoplastic resin.   The optical member according to claim 1, wherein the thermoplastic resin is made of a polypropylene resin.   The optical member according to any one of claims 1 to 4, wherein the polypropylene resin is substantially composed of a homopolymer of propylene.   The optical member according to any one of claims 1 to 5, wherein the polypropylene resin is made of a copolymer of propylene and ethylene containing 10% by weight or less of ethylene units.   The optical member according to claim 1, wherein the light collecting film is made of an active energy ray curable resin.   The optical member in any one of Claims 1-7 by which the optical compensation film or the protective film is laminated | stacked on the surface on the opposite side to the surface at the said condensing film side among the said optical members.   The optical member in any one of Claims 1-8 which has a protection film in the surface which has the said prism shape or the said lens shape of the said condensing film.   The optical member according to claim 1, wherein the other optical film is a polarizing film, and the optical member is a polarizing plate.   The optical member according to claim 1, wherein the optical member is used by being disposed between a liquid crystal cell of a liquid crystal display device and a backlight. A liquid crystal panel in which a liquid crystal cell and the optical member according to claim 1 are laminated,
The liquid crystal panel, wherein the liquid crystal cell, the other optical film, and the light collecting film are laminated in this order. A liquid crystal display device arranged so that the backlight and the liquid crystal panel according to claim 12 face each other,
The liquid crystal panel is arranged such that the prism shape or the lens shape of the condensing film is opposed to the backlight.   The liquid crystal display device according to claim 13, wherein the front luminance distribution is within 10% of the maximum luminance.

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