WO2010143741A1

WO2010143741A1 - Liquid crystal display device

Info

Publication number: WO2010143741A1
Application number: PCT/JP2010/060148
Authority: WO
Inventors: 室誠治; 森美穂; 金光昭佳
Original assignee: 住友化学株式会社
Priority date: 2009-06-12
Filing date: 2010-06-09
Publication date: 2010-12-16
Also published as: CN102460285A; KR20120026600A; TW201107837A; JP2010286701A

Abstract

Provided is a liquid crystal display device with high luminance and contrast and excellent display characteristics. The liquid crystal display device is configured from a surface light source (20), and a liquid crystal panel (10) disposed above the surface light source and provided with a liquid crystal cell (3) and a polarizing plate stacked on a surface on the surface light source side of the liquid crystal cell. The polarizing plate is provided with a polarizing film (12) and a prism sheet (13) having the surface thereof configured from prism-shaped protrusions (13a), the prism sheet (13) is disposed such that the surface thereof configured from the prism-shaped protrusions faces the surface light source, and the light intensity distribution indicating the emission angle dependence of the light intensity of emitted light from the surface light source (20) satisfies the following (1) and (2). (1) The maximum value of the light intensity has the highest peak in the range of -80°≤θ<-40° or 40°<θ≤80°. (2) The following expression is satisfied: |θa-θb|<30° where θa is an angle at which the maximum value of the light intensity at the peak is shown, and θb is an angle at which a half of the maximum value of the light intensity at the peak is shown.

Description

Liquid crystal display

The present invention relates to a liquid crystal display device used for a liquid crystal television, a liquid crystal monitor, a personal computer, and the like.

The use of liquid crystal display devices is rapidly expanding as thin display devices used in liquid crystal televisions, liquid crystal monitors, personal computers, and the like. In particular, the market for liquid crystal televisions is remarkably expanding, and the demand for cost reduction is very high.

A normal liquid crystal display device includes a surface light source using a cold cathode tube or an LED, a light diffusion plate, one or more diffusion sheets, a light collecting sheet, and a liquid crystal panel on which a polarizing plate is bonded. . 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 response to such a request, a method of directly bonding a condensing prism sheet to one surface of a polarizing plate disposed between a liquid crystal cell constituting a liquid crystal panel and a surface light source (for example, JPH11-295714-A and JP2008) -262132-A) and a method using a condensing prism sheet (for example, JP2008-262132-A and JP2005-17355-A) as a protective film for a polarizing plate disposed on the surface light source side of the liquid crystal panel. Or the technique which reduces a number of parts except a some member is known.

In a liquid crystal display device using a polarizing plate provided with a sheet member such as a prism sheet as described in Patent Documents 1 to 3, the sheet member is expected depending on the light emission characteristics of the surface light source used. In some cases, the light condensing function is not fully exhibited, and display characteristics such as luminance and contrast are deteriorated.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a liquid crystal display device having high luminance and contrast and excellent display characteristics.

The present invention relates to a liquid crystal display device including a surface light source and a liquid crystal panel provided on the surface light source and including a liquid crystal cell and a polarizing plate laminated on the surface of the liquid crystal cell on the surface light source side. In the liquid crystal display device of the present invention, the polarizing plate includes a polarizing film and a prism sheet having a surface composed of prismatic protrusions laminated on the surface of the polarizing film via an adhesive layer. The sheet is disposed such that the surface formed by the prismatic protrusions faces the surface light source. Further, the liquid crystal display device of the present invention has an emission angle that is an angle formed by the normal direction of the light emission surface of the surface light source and the emission direction of the emission light of the surface light source in a plane orthogonal to the ridge line direction of the prismatic protrusion. When θ (where −90 ° ≦ θ ≦ 90 °) is satisfied, the light intensity distribution of the surface light source that shows the emission angle dependence of the light intensity of the emitted light satisfies the following (1) and (2).
(1) It has a peak having the highest light intensity maximum value in the range of −80 ° ≦ θ <−40 ° or 40 ° <θ ≦ 80 °.
(2) When the angle indicating the maximum value of the light intensity at the peak where the maximum value of the light intensity is the highest is θa, and the angle indicating 1/2 of the maximum value of the light intensity at the peak is θb, the following formula [1 ]: | Θa−θb | <30 ° [1]
Meet.

In the liquid crystal display device of the present invention, the surface light source preferably includes a light guide plate and a light source device disposed on the side of the light guide plate. The light source device is a light source device composed of a light source device in which point light sources are arranged in a line or a rod-like light source, and the light source device and the prism sheet are parallel or substantially parallel to the ridge line of the light source device and the prismatic protrusion. It is preferable to arrange so that.

In the liquid crystal display device of the present invention, the surface light source preferably has one light source device arranged on one side of the light guide plate or two light source devices arranged on two sides facing the light guide plate.

The apex angle α of the prismatic protrusion is preferably 60 ° or more. The cross-sectional shape of the prismatic protrusion is preferably an isosceles triangle.

The liquid crystal display device of the present invention is thin, has high brightness and contrast, and has excellent display characteristics. The liquid crystal display device of the present invention can be suitably applied as a liquid crystal display device for a large-screen liquid crystal television, in particular, a liquid crystal display device for a liquid crystal television that can be wall-mounted.

It is a schematic sectional drawing which shows a preferable example of the liquid crystal display device of this invention. It is a schematic sectional drawing which shows a preferable example of the back side polarizing plate used by this invention. It is a schematic perspective view which shows an example of the surface shape of a prism sheet. It is a typical perspective view for demonstrating the light emission characteristic of the surface light source used by this invention. It is a schematic diagram for demonstrating the path | route of the light which injects into the prism-shaped protrusion which a prism sheet has. It is a figure which shows the light intensity distribution of the surface light source A used in Example 1 and 2. FIG. It is a figure which shows the light intensity distribution of the surface light source B used by the comparative examples 1 and 2. FIG. 6 is a diagram illustrating a light intensity distribution (luminance distribution) of the liquid crystal display device manufactured in Example 1. FIG. 6 is a diagram showing a light intensity distribution (luminance distribution) of a liquid crystal display device manufactured in Comparative Example 1. FIG.

FIG. 1 is a schematic sectional view showing a preferred example of the liquid crystal display device of the present invention. A liquid crystal display device 100 shown in FIG. 1 according to the present invention includes a light source plate 21 and a surface light source 20 including a light source device 21 that is disposed on the side of the light guide plate 22 and along one side of the light guide plate 22. The liquid crystal panel 10 is disposed on the surface light source 20. The liquid crystal panel 10 includes a liquid crystal cell 3, a polarizing plate 1 that is a back side polarizing plate laminated on the surface of the liquid crystal cell 3 on the surface light source 20 side, and a front side polarized light laminated on the viewing side surface of the liquid crystal cell 3. The polarizing plate 2 is a plate. The polarizing plate 1 and the polarizing plate 2 are bonded to the liquid crystal cell 3 through the adhesive layer 17.

A polarizing plate 1 which is a back side polarizing plate is a surface (hereinafter referred to as a prism surface) composed of a polarizing film 12 and a prism-shaped protrusion 13a laminated on the surface light source 20 side surface of the polarizing film 12 with an adhesive layer 14 interposed therebetween. And a resin film 15 laminated on the surface of the polarizing film 12 via the adhesive layer 16. The polarizing plate 1 is bonded to the liquid crystal cell 3 on the resin film 15 side. More specifically, the liquid crystal cell 3 and the polarizing plate 1 are arranged such that the surface of the polarizing film 12 opposite to the surface on which the prism sheet 13 is laminated faces the liquid crystal cell 3, that is, the prism sheet 13 The prism surface forms a surface light source side surface of the liquid crystal panel 10 and is bonded so that the prism surface faces the surface light source 20. In addition, in this invention, the back side polarizing plate does not need to have such a resin film, and is the structure by which the polarizing film 12 is directly bonded to the liquid crystal cell 3 through an adhesive layer etc. Also good.

As shown in FIG. 1, the liquid crystal display device of the present invention is a liquid crystal display device using a back-side polarizing plate having a prism sheet laminated on the surface of a polarizing film via an adhesive layer. In the liquid crystal display device using the back-side polarizing plate having such a prism sheet, specific light emission characteristics, specifically light distribution characteristics (how much light is emitted in which direction and how much light is emitted) A surface light source having the above is applied. ADVANTAGE OF THE INVENTION According to this invention, it is a liquid crystal display device using the back side polarizing plate which has a prism sheet, Comprising: A brightness | luminance and contrast are high, and the liquid crystal display device which is excellent in the display characteristic can be provided. In addition, the liquid crystal display device of the present invention includes a liquid crystal panel in which a thinned polarizing plate is bonded to the back side of the liquid crystal cell, and thus has sufficient mechanical strength while supporting thinning. Since the prism sheet is disposed on the back side of the liquid crystal panel, the liquid crystal panel and the surface light source are prevented from coming into close contact with each other, thereby improving the display characteristics. Hereinafter, the liquid crystal display device of the present invention will be described in detail with reference to the drawings as appropriate.

<Back side polarizing plate>
FIG. 2 is a schematic cross-sectional view showing a preferred example of the back-side polarizing plate used in the present invention, and the configuration thereof is the same as that of the polarizing plate 1 in FIG. 1 (reference numerals are also the same). As in the example shown in FIG. 2, the back side polarizing plate used in the present invention was laminated on the polarizing film 12 and one surface (surface light source side surface) of the polarizing film 12 via the adhesive layer 14. And a prism sheet 13 having a surface (prism surface) composed of the prismatic protrusions 13a. The back-side polarizing plate was laminated on the surface opposite to the surface on which the prism sheet 13 was laminated (surface on the liquid crystal cell side) via the adhesive layer 16 like the polarizing plate 1 shown in FIG. A resin film 15 may be provided.

(Polarizing film)
Specifically, the polarizing film 12 used for the back polarizing plate is obtained by adsorbing and orienting a dichroic dye on a uniaxially stretched polyvinyl alcohol resin film. As the polyvinyl alcohol resin constituting the polyvinyl alcohol resin film, a saponified polyvinyl acetate resin can be used. Polyvinyl acetate resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith, such as ethylene-vinyl acetate copolymers. Etc. 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-based resin may be modified, for example, polyvinyl formal modified with aldehydes, polyvinyl acetal, polyvinyl butyral, and the like can be used. The degree of polymerization of the polyvinyl alcohol-based resin is usually about 1000 to 10000, and preferably about 1500 to 5000.

A film obtained by forming such a polyvinyl alcohol resin is used as an original film of a polarizing film. The method for forming the polyvinyl alcohol-based resin is not particularly limited, and can be formed by a conventionally known appropriate method. The film thickness of the raw film made of the polyvinyl alcohol resin is not particularly limited, but is, for example, about 10 to 150 μm.

A polarizing film is usually a process of dyeing an original film made of polyvinyl alcohol resin as described above with a dichroic dye and adsorbing the dichroic dye (dyeing process), and the dichroic dye is adsorbed. The polyvinyl alcohol-based resin film is produced through a step of treating with a boric acid aqueous solution (boric acid treatment step) and a step of washing with water after the treatment with the boric acid aqueous solution (water washing treatment step).

Further, in the production of the polarizing film, the polyvinyl alcohol-based resin film is usually uniaxially stretched, but this uniaxial stretching may be performed before the dyeing treatment step or during the dyeing treatment step, It may be performed after the dyeing process. When uniaxial stretching is performed after the dyeing treatment step, this uniaxial stretching may be performed before the boric acid treatment step or during the boric acid treatment step. Of course, it is also possible to perform uniaxial stretching in these plural stages. Uniaxial stretching may be performed uniaxially between rolls having different peripheral speeds, or may be performed uniaxially using a hot roll. Moreover, the dry-type extending | stretching which extends | stretches in air | atmosphere may be sufficient, and the wet extending | stretching which extends | stretches in the state swollen with the solvent may be sufficient. The draw ratio is usually about 3 to 8 times.

The dyeing of the polyvinyl alcohol-based resin film with the dichroic dye in the dyeing process is performed, for example, by immersing the polyvinyl alcohol-based resin film in an aqueous solution containing the dichroic dye. As the dichroic dye, for example, iodine, a dichroic dye or the like is used. Examples of dichroic dyes include C.I. I. Dichroic direct dyes composed of disazo compounds such as DIRECT RED 39, dichroic direct dyes composed of trisazo, tetrakisazo compounds and the like are included. In addition, it is preferable that the polyvinyl alcohol-type resin film performs the immersion process to 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 0.01 to 1 part by weight per 100 parts by weight of water, and the content of potassium iodide is usually 0.5 to 20 parts by weight per 100 parts by weight of water. . When iodine is used as the dichroic dye, the temperature of the aqueous solution used for dyeing is usually 20 to 40 ° C., and the immersion time (dyeing time) in this aqueous solution is usually 20 to 1800 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, usually, 1 × ^{10 -4} ~ ¹⁰ parts by weight per 100 parts by weight of water, preferably 1 × ^{10 -3} ~ 1 parts by weight, particularly preferably 1 × 10 ^{- 3} to 1 × 10 ⁻² parts by weight. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. When a dichroic dye is used as the dichroic dye, the temperature of the dye aqueous solution used for dyeing is usually 20 to 80 ° C., and the immersion time (dyeing time) in this aqueous solution is usually 10 to 1800 seconds. is there.

The boric acid treatment step is performed by immersing a polyvinyl alcohol resin film dyed with a dichroic dye in a boric acid-containing aqueous solution. The amount of boric acid in the boric acid-containing aqueous solution is usually 2 to 15 parts by weight, preferably 5 to 12 parts by weight per 100 parts by weight of water. When iodine is used as the dichroic dye in the dyeing process described above, the boric acid-containing aqueous solution used in this boric acid treatment process preferably contains potassium iodide. In this case, the amount of potassium iodide in the boric acid-containing aqueous solution is usually 0.1 to 15 parts by weight, preferably 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 60 to 1200 seconds, preferably 150 to 600 seconds, and more preferably 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.

In the subsequent washing process, the polyvinyl alcohol-based resin film after the boric acid treatment described above is washed with water, for example, by immersing it in water. The temperature of water in the water washing treatment is usually 5 to 40 ° C., and the immersion time is usually 1 to 120 seconds. After the water washing treatment, a drying treatment is usually performed to obtain a polarizing film. The drying process can be performed using, for example, a hot air dryer or a far infrared heater. The temperature for the drying treatment is usually 30 to 100 ° C., preferably 50 to 80 ° C. The time for the drying treatment is usually 60 to 600 seconds, preferably 120 to 600 seconds.

Thus, a polarizing film is obtained by subjecting the polyvinyl alcohol-based resin film to uniaxial stretching, dyeing with a dichroic dye, boric acid treatment and water washing treatment. The thickness of this polarizing film is usually in the range of 5 to 40 μm.

(Prism sheet)
The prism sheet 13 used for the back-side polarizing plate has a surface (prism surface) composed of prism-shaped protrusions (prism-shaped protrusions 13a). The prism sheet 13 is laminated on the polarizing film 12 so that the surface opposite to the prism surface faces the polarizing film 12. A prism sheet 13 having a prism surface is disposed on the surface of the back-side polarizing plate, and the prism surface is opposed to a surface light source to be described later, thereby exiting from the light emitting surface of the surface light source (surface facing the prism surface). The direction of the emitted light can be changed intentionally (deflected). According to the present invention, the outgoing light from the surface light source, particularly the outgoing light having directivity [the main outgoing direction is different from the normal direction of the light outgoing surface of the surface light source (the front direction of the liquid crystal display device). The emission direction of the emitted light can be deflected in the front direction of the liquid crystal display device by the prism sheet, thereby improving the brightness and contrast of the front surface of the liquid crystal display device. The prism sheet 13 also serves as a protective film for the polarizing film 12.

Here, the “prism-like protrusion” is a columnar shape indicated by a locus obtained by translating a triangular shape (which may include a substantially triangular shape including a curve in part, a sawtooth shape, etc.) perpendicularly to the triangular surface. This means the part of the side (ridgeline) sandwiched between two side surfaces that do not form the bottom surface (the trajectory of the diagonal of the triangular base) in the body, and the prism surface refers to the prismatic protrusion on the columnar body. A plurality of prismatic protrusions are arranged in close contact in parallel with the surface (the locus of the base of the triangular shape) as the bottom surface, and the plurality of prismatic protrusions are in one direction (so that the ridgelines of each prismatic protrusion are parallel or substantially parallel) It is arranged. FIG. 3 is a schematic perspective view showing an example of the surface shape of the prism sheet, and the cross-sectional shape of the prism-shaped protrusion is an isosceles triangle.

The apex angle (vertex angle) of the prismatic protrusion 13a of the prism sheet 13 can be set to, for example, 30 to 100 °. In the present invention, the emitted light from the surface light source, particularly the emitted light having directivity. Is more preferably 60 ° or more and 100 ° or less, and more preferably 60 ° or more and 80 ° or less in order to more efficiently deflect the light in the front direction of the liquid crystal display device.

The height of the prismatic protrusion 13a can be set to 10 to 200 μm, for example. Further, the pitch of the prismatic protrusions 13a (the distance between the ridge lines of adjacent protrusions) is appropriately determined in consideration of the apex angle and height of the prismatic protrusions 13a, for example, 5 to 300 μm. it can.

The two sides constituting the projection in the triangular cross section of the prismatic projection 13a may have the same length or different lengths, but at least the light source device of the surface light source used is When arranged on two sides facing each other of the light guide plate, it is preferable that the two sides have the same length. Therefore, the cross-sectional shape of the prismatic protrusion 13a is preferably an isosceles triangle. The heights of the plurality of prismatic protrusions 13a may all be the same or different. The shape of the groove formed between the protrusions may be a straight line or a curved line.

As the material of the prism sheet 13, various known materials can be used. For example, polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate resin and polyethylene naphthalate resin, polyvinyl chloride resins, polycarbonate resins, norbornene resins, polyurethane resins, acrylic resins, polymethyl methacrylate resins , Synthetic polymers such as polystyrene resin, methyl methacrylate-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene copolymer, natural diacetate resin, cellulose triacetate resin, etc. Polymers can be used. Among them, from the viewpoint of transparency, moisture permeability and productivity, polyolefin resin, polyacrylic resin, polycarbonate resin, polyester resin, polystyrene resin, methyl methacrylate-styrene copolymer, acrylonitrile-butadiene-styrene Any one of a thermoplastic copolymer and an acrylonitrile-styrene copolymer is suitable. These polymer materials can contain additives such as ultraviolet absorbers, antioxidants, and plasticizers as necessary.

The prism sheet 13 is a known material such as a photopolymer process method, a profile extrusion method, a press molding method, an injection molding method, a roll transfer method, a laser ablation method, a mechanical cutting method, or a mechanical grinding method using the transparent polymer material as a base material. It can be manufactured by the method. Each of these methods may be used alone, or two or more methods may be combined.

The thickness of the prism sheet 13 is not particularly limited, but is preferably about 20 μm or more and 200 μm or less, and more preferably 30 μm or more and 100 μm or less from the viewpoint of thinning the polarizing plate.

(Resin film)
As in the example shown in FIG. 2, a resin film 15 such as a protective film or an optical compensation film may be laminated on the surface of the polarizing film 12 opposite to the surface on which the prism sheet is laminated. In this case, the polarizing plate 1 is bonded to the liquid crystal cell via the adhesive layer laminated on the resin film 15. Moreover, the optical functional film mentioned later can also be laminated | stacked through the adhesive bond layer or an adhesive layer on the polarizing film 12, a protective film, or an optical compensation film.

Examples of the resin film 15 include cellulose resin films such as a triacetyl cellulose film (TAC film), polyolefin resin films, acrylic resin films, and polyester resin films such as polyethylene terephthalate.

Examples of the cellulose-based resin constituting the cellulose-based resin film include a partially esterified product or a completely esterified product of cellulose, such as cellulose acetate ester, propionate ester, butyrate ester, and mixed esters thereof. Can be mentioned. More specifically, triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, cellulose acetate butyrate and the like can be mentioned. When such a cellulose resin is formed into a film, a known method such as a solvent casting method or a melt extrusion method is appropriately used. Examples of commercially available cellulose ester resin films include “Fujitac TD80” (manufactured by Fuji Film Co., Ltd.), “Fujitac TD80UF” (manufactured by Fuji Film Co., Ltd.), and “Fujitac TD80UZ” (manufactured by Fuji Film Co., Ltd.). , “KC8UX2M” (manufactured by Konica Minolta Opto), “KC8UY” (manufactured by Konica Minolta Opto), and the like.

Moreover, as an optical compensation film comprising a cellulose resin film, for example, a film containing a compound having a retardation adjusting function in the cellulose resin film; a compound having a retardation adjusting function is applied to the surface of the cellulose resin film. And a film obtained by uniaxially or biaxially stretching a cellulose resin film.
Examples of the optical compensation film made of a commercially available cellulose resin film include “WV BZ 438” and “WV EA” manufactured by Fuji Film Co., Ltd., “KC4FR-1” and “KC4HR” manufactured by Konica Minolta Opto Co., Ltd. -1 "and the like.

The thickness of the protective film or optical compensation film made of a cellulose resin film is not particularly limited, but is preferably in the range of 20 to 90 μm, and more preferably in the range of 30 to 90 μm. When the thickness is less than 20 μm, it is difficult to handle the film. On the other hand, when the thickness exceeds 90 μm, the workability is inferior, and it is disadvantageous in reducing the thickness and weight of the resulting polarizing plate. .

Examples of the optical compensation film made of the polyolefin resin film include a uniaxially stretched or biaxially stretched cycloolefin resin film. When applied to a liquid crystal panel for a large-sized liquid crystal television, particularly a liquid crystal panel having a vertical alignment (VA) mode liquid crystal cell, as the optical compensation film, a stretched product of a cycloolefin-based resin film has optical characteristics and durability. It is suitable also from this point. Here, the cycloolefin resin film is a film made of a thermoplastic resin having a unit of a monomer made of a cyclic olefin (cycloolefin) such as norbornene or a polycyclic norbornene monomer. The cycloolefin-based resin film may be a hydrogenated product of a ring-opening polymer using a single cycloolefin or a hydrogenated product of a ring-opening copolymer using two or more cycloolefins. And an addition copolymer of a chain olefin and / or an aromatic compound having a vinyl group. Further, those having a polar group introduced into the main chain or side chain are also effective.

Commercially available thermoplastic cycloolefin-based resins are “Topas” sold by TOPAS ADVANCED POLYMERS GmbH in Germany, “Arton” sold by JSR Corporation, and Nippon Zeon Corporation. There are “ZEONOR” and “ZEONEX”, “APEL” (both trade names) sold by Mitsui Chemicals, Inc., and the like, which can be preferably used.
A cycloolefin resin film can be obtained by forming such a cycloolefin resin. As a film forming method, a known method such as a solvent casting method or a melt extrusion method is appropriately used. In addition, for example, “Essina” and “SCA40” sold by Sekisui Chemical Co., Ltd., “Zeonor Film” sold by Nippon Zeon Co., Ltd., “Arton Film” sold by JSR Co., Ltd. (All are trade names) and the like are also commercially available, and these can also be used suitably.

If the thickness of the optical compensation film made of the stretched cycloolefin-based resin film is too thick, the workability will be inferior, and the transparency will be lowered, and it will be disadvantageous in reducing the thickness and weight of the polarizing plate. Therefore, the thickness is preferably about 20 to 80 μm.

The back side polarizing plate used in the present invention can be obtained by laminating the prism sheet on one surface of the polarizing film described above using an adhesive. Thereby, with reference to FIG. 2, the polarizing plate by which the prism sheet 13 was laminated | stacked through the adhesive bond layer 14 on the surface of the polarizing film 12 is obtained. When the resin film 15 is laminated on the other surface of the polarizing film 12, the polarizing film 12 and the resin film 15 are similarly bonded using an adhesive. This adhesive forms the adhesive layer 16. When the resin film 15 is bonded to the polarizing film 12, the adhesive used for bonding the prism sheet 13 and the adhesive used for bonding the resin film 15 may be the same type of adhesive, Different types of adhesives may be used. Examples of the adhesive used for laminating these films include a water-based adhesive, that is, an adhesive in which an adhesive component is dissolved or dispersed in water and a photocurable adhesive.

The aqueous adhesive is preferably used in that the adhesive layer can be thinned. Examples of the water-based adhesive include a water-based adhesive using a polyvinyl alcohol resin or a urethane resin as an adhesive component.

When a polyvinyl alcohol resin is used as the adhesive component, the polyvinyl alcohol resin is not only partially saponified polyvinyl alcohol and completely saponified polyvinyl alcohol, but also carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, and methylol group-modified polyvinyl. It may be a modified polyvinyl alcohol resin such as alcohol and amino group-modified polyvinyl alcohol. Usually, the water-based adhesive having a polyvinyl alcohol resin as an adhesive component is prepared as an aqueous solution of a polyvinyl alcohol resin. The concentration of the polyvinyl alcohol resin in the adhesive is usually about 1 to 10 parts by weight, preferably about 1 to 5 parts by weight with respect to 100 parts by weight of water.

It is preferable to add a curable component such as glyoxal or a water-soluble epoxy resin or a cross-linking agent to an adhesive having a polyvinyl alcohol resin as an adhesive component in order to improve adhesiveness. Examples of water-soluble epoxy resins include polyamide polyamine epoxy resins obtained by reacting epichlorohydrin with polyamide polyamines obtained by reaction of polyalkylene polyamines such as diethylenetriamine and triethylenetetramine with dicarboxylic acids such as adipic acid. Can be suitably used. 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. Or the like. The addition amount of these curable components or crosslinking agents (the total amount when added together) 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. . When the addition amount of the curable component and the crosslinking agent is less than 1 part by weight with respect to 100 parts by weight of the polyvinyl alcohol-based resin, the effect of improving adhesiveness tends to be reduced, and the curable component, When the addition amount of the crosslinking agent exceeds 100 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin, the adhesive layer tends to become brittle.

When a urethane resin is used as the adhesive component, examples of suitable adhesive compositions include a mixture of a polyester ionomer type urethane resin and a compound having a glycidyloxy group. Here, the polyester ionomer type urethane resin is a urethane resin having a polyester skeleton, and a small amount of an ionic component (hydrophilic component) is introduced into the skeleton. Such an ionomer-type urethane resin is suitable as a water-based adhesive because it is emulsified directly in water without using an emulsifier to form an emulsion.
Polyester-based ionomer urethane resins are known per se. For example, JP-A-7-97504 describes an example of a polymer dispersant for dispersing a phenol-based resin in an aqueous medium. In JP-A-2005-070140 and JP-A-2005-181817, a mixture of a polyester ionomer type urethane resin and a compound having a glycidyloxy group is used as an adhesive, and a polarizing film made of a polyvinyl alcohol resin is used as a cycloolefin resin. It is shown that a resin film is bonded.

As a method of applying an adhesive to the polarizing film and / or a member (prism sheet, protective film or optical compensation film) bonded to the polarizing film, a generally known method may be used. For example, a casting method, a Meyer bar may be used. Examples thereof include a coating method, a gravure coating method, a comma coater method, a doctor blade method, a die coating method, a dip coating method, and a spraying method. The casting method is a method of spreading and spreading an adhesive on the surface of a film to be coated while moving it in a substantially vertical direction, a substantially horizontal direction, or an oblique direction between the two.
After apply | coating an adhesive agent, a polarizing film and the member bonded by this are piled up, and it bonds by a nip roll etc. and bonds a film. Film bonding using nip rolls is, for example, a method in which an adhesive is applied and then pressurized with a roll or the like to spread uniformly, and after applying an adhesive, it is passed between the rolls and pressed. A method of spreading out can be employed. In the former case, it is possible to use metal or rubber as the material of the roll. In the latter case, the plurality of rolls may be made of the same material or different materials.

After the above bonding, the polarizing plate can be obtained by drying and curing the adhesive layer. This drying treatment is performed, for example, by blowing hot air, and the temperature is usually in the range of 40 to 100 ° C., and preferably in the range of 60 to 100 ° C. The drying time is usually 20 to 1200 seconds.

The thickness of the adhesive layer after drying is usually 0.001 to 5 μm, preferably 0.01 to 2 μm, more preferably 0.01 to 1 μm. If the thickness of the adhesive layer after drying is less than 0.001 μm, the adhesion may be insufficient, and if the thickness of the adhesive layer after drying exceeds 5 μm, the appearance of the polarizing plate is poor. May occur. In addition, it is preferable that the thickness of the adhesive bond layer after bonding using the said nip roll etc. before drying and hardening is 5 micrometers or less, and it is preferable that it is 0.01 micrometers or more.

After the drying treatment, sufficient adhesive strength may be obtained by curing at 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 in a roll. The preferable curing temperature is in the range of 30 to 50 ° C, more preferably 35 to 45 ° C. 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 usually about 1 to 10 days, preferably about 2 to 7 days.

Further, examples of the photocurable adhesive include a mixture of a photocurable epoxy resin and a photocationic polymerization initiator. Examples of the photocurable epoxy resin include alicyclic epoxy resins, epoxy resins having no alicyclic structure, and mixtures thereof. The photocurable adhesive may contain an acrylic resin, an okitacene resin, a urethane resin, a polyvinyl alcohol resin, etc. in addition to the photocurable epoxy resin, and together with the photocationic polymerization initiator or the photocationic polymerization initiator. Instead of this, a radical photopolymerization initiator may be included.

When using a photocurable adhesive, a photocurable adhesive is applied to the polarizing film and / or a member (prism sheet, protective film, or optical compensation film) to be bonded to the polarizing film and the polarizing film and the same. After bonding the members to be combined, the photocurable adhesive is cured by irradiating active energy rays. The application method of a photocurable adhesive and the bonding method of a film can be made the same as that of an aqueous adhesive. 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 excitation mercury lamp, a metal halide lamp and the like are 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, it is caused by heat radiated from the light source and heat generated during curing of the photocurable adhesive. There is little risk of yellowing of the epoxy resin and deterioration of the polarizing film. The light irradiation time to the photocurable adhesive is controlled for each photocurable adhesive to be cured and is not particularly limited. However, the integrated light amount expressed as the product of the irradiation intensity and the irradiation time is 10. It is preferably set to be ˜10000 mJ / m ² . When the cumulative amount of light to the photocurable adhesive is 10 mJ / m 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 10,000 mJ / m ^2. In the case of the following, the irradiation time does not become too long, and good productivity can be maintained.

When curing a photo-curable adhesive by irradiation with active energy rays, the polarizing film functions such as the degree of polarization, transmittance and hue of the polarizing film, and transparency of the prism sheet, protective film and optical compensation film do not deteriorate. It is preferable to perform curing under conditions.

Prior to the bonding of the prism sheet and the protective film or the optical compensation film to the polarizing film, the plasma treatment, corona, and the like are performed on the bonding surface of the polarizing film and / or a member bonded to the polarizing film. Surface treatment such as treatment, ultraviolet irradiation treatment, flame (flame) treatment, and saponification treatment may be performed. Examples of the saponification treatment include a method of immersing in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide.

Further, as described above, the back side polarizing plate may have an optical functional film laminated on the surface of the polarizing film 12 opposite to the surface on which the prism sheet 13 is laminated. As an optical functional film, for example, an optical compensation film in which a liquid crystal compound is coated on a substrate surface and oriented; a reflection type that transmits polarized light of some kind and reflects polarized light that shows the opposite property Polarizing film; Retardation film made of polycarbonate-based resin; Retardation film made of cycloolefin-based resin film; Film with anti-glare function having uneven shape on surface; Film with surface anti-reflection function; Reflecting film having reflection function on surface And a transflective film having both a reflection function and a transmission function. Commercially available products corresponding to an optical compensation film coated with a liquid crystal compound on the surface of the base material are “WV film” (Fuji Film Co., Ltd.), “NH film” (Shin Nippon Oil Co., Ltd.) And “NR Film” (manufactured by Nippon Oil Corporation). For example, “DBEF” (manufactured by 3M, available from Sumitomo 3M Co., Ltd. in Japan) is a commercially available product corresponding to a reflective polarizing film that transmits certain types of polarized light and reflects polarized light that exhibits the opposite properties. Can be). Moreover, as a commercial item corresponding to the retardation film which consists of a cycloolefin type resin film, for example, "Arton film" (made by JSR Corporation), "Essina" (made by Sekisui Chemical Co., Ltd.), "Zeonor film" (Nippon ZEON Co., Ltd.).

The back side polarizing plate preferably has an adhesive layer for bonding to the liquid crystal cell on the surface opposite to the prism sheet. As the pressure-sensitive adhesive used for such a pressure-sensitive adhesive layer, conventionally known appropriate pressure-sensitive adhesives can be used, and examples thereof include acrylic pressure-sensitive adhesives, urethane pressure-sensitive adhesives, and silicone-based pressure-sensitive adhesives. Among these, an acrylic pressure-sensitive adhesive is preferably used from the viewpoints of transparency, adhesive strength, reliability, reworkability, and the like. The pressure-sensitive adhesive layer can be provided by a method in which such a pressure-sensitive adhesive is, for example, an organic solvent solution, which is applied on a base film (for example, a polarizing film) by a die coater or a gravure coater and dried. Moreover, it can provide also by the method of transcribe | transferring the sheet-like adhesive formed on the plastic film (it is called a separate film) to which the mold release process was given to a base film. The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is preferably in the range of 2 to 40 μm.

<Front side polarizing plate>
The front side polarizing plate (polarizing plate 2 in FIG. 1) is a polarizing plate disposed on the opposite side (viewing side) from the surface light source with reference to the liquid crystal cell. A conventionally well-known appropriate polarizing plate can be used as the front side polarizing plate. For example, in addition to a polarizing plate in which a protective film made of triacetyl cellulose or the like is laminated on one side or both sides of a polarizing film, a polarizing plate subjected to an antiglare treatment, a hard coat treatment, or an antireflection treatment can be used. Moreover, the polarizing plate by which the protective film or optical compensation film which consists of a polyethylene terephthalate film, an acrylic film, a polypropylene film etc. on the single side | surface of the polarizing film may be laminated | stacked.

<Surface light source>
The liquid crystal display device of the present invention includes a surface light source 20 for uniformly illuminating a liquid crystal panel. In the present invention, as the surface light source 20, the function of the prism sheet (the function of deflecting the light emitted from the surface light source and correcting the direction of the light emitted from the prism-shaped protrusion to the front direction of the liquid crystal display device) is maximized. In order to achieve this, a surface light source having specific light emission characteristics (light distribution characteristics) is used.
More specifically, referring to FIG. 4, the surface light source used in the present invention is the normal direction of the light emitting surface of the surface light source in the plane W orthogonal to the ridge line direction of the prismatic protrusions of the prism sheet. A surface showing the output angle dependency of the light intensity of the emitted light when the angle formed by T and the emission direction M of the emitted light from the surface light source is an outgoing angle θ (where −90 ° ≦ θ ≦ 90 °). The light intensity distribution of the light source satisfies the following (1) and (2).
(1) It has a peak having the highest light intensity maximum value in the range of −80 ° ≦ θ <−40 ° or 40 ° <θ ≦ 80 °.
(2) When the angle indicating the maximum value of the light intensity at the peak having the highest light intensity maximum value is θa and the angle indicating 1/2 of the maximum value of the light intensity at the peak is θb, the following formula [1 ]:
| Θa−θb | <30 ° [1]
Meet.

Note that the range in which the emission angle θ can be taken is −90 ° ≦ θ ≦ 90 °. θ = 0 ° means that the direction M of the emitted light from the surface light source is the same as the normal direction T of the light emitting surface of the surface light source. θ = −90 ° means that in the plane W, the direction M of the light emitted from the surface light source forms an angle of 90 ° counterclockwise (or clockwise) with respect to the normal direction T. Θ = 90 ° means that the direction M of the light emitted from the surface light source is 90 ° clockwise (or counterclockwise) with respect to the normal direction T in the plane W. Means that

When light having an emission direction M that is relatively far away from the normal direction T of the light emission surface of the surface light source (the absolute value of the emission angle θ is relatively large) is incident on the prismatic protrusion 13a of the prism sheet, As schematically shown in FIG. 5, the incident light reaches the oblique side P of the prism-shaped protrusion 13 a and is reflected by the oblique side P, thereby causing the front direction of the liquid crystal display device (the light emitting surface of the surface light source to It can be condensed in the normal direction T). That is, in a liquid crystal display device using a back-side polarizing plate including a prism sheet, the liquid crystal display device has an emission direction M that is relatively far from the normal direction T of the light emission surface of such a surface light source (the absolute value of the emission angle θ). The light having a relatively large value greatly contributes to the improvement of the brightness and contrast in the front direction of the liquid crystal display device.
In particular, the present inventors have a range of −80 ° ≦ θ <−40 ° or 40 ° <θ ≦ 80 ° in the plane W (that is, the absolute value | θ | of the emission angle θ is 40 ° <| θ | ≦ 80 °), a surface light source exhibiting a light intensity distribution characteristic having a peak with the highest light intensity maximum value (satisfying the above condition (1)), the light constituting the peak is reflected by the prism sheet It is found that it is extremely effective in improving the brightness and contrast in the front direction of the liquid crystal display device because the light is effectively focused in the front direction of the liquid crystal display device (normal direction T of the light emitting surface of the surface light source). It was. The lower and upper limits of the emission angle θ considered in the above condition (1) are set to −80 ° and 80 °, respectively, and it is difficult to accurately measure the light intensity at an angle exceeding the lower and upper limits. This is because it is not practical.

The peak having the highest light intensity maximum value is preferably located within the range of 50 ° ≦ | θ | ≦ 80 °, and is located within the range of 60 ° ≦ | θ | ≦ 80 °. It is more preferable.

On the other hand, the present inventors have found that the width (broadening) of the peak having the highest maximum value of the light intensity also affects the luminance and contrast in the front direction of the liquid crystal display device. That is, in the light intensity distribution of the surface light source on the plane W, the angle indicating the maximum value of the light intensity at the peak where the maximum value of the light intensity is the highest is θa, and 1/2 of the maximum value of the light intensity at the peak. When the angle is θb, when the half-value width | θa−θb | is less than 30 ° (satisfies the above condition (2)), the absolute value of the emission angle θ is not significantly affected by light, By condensing light whose emission angle, which is the main emitted light, is in the vicinity of θa, the luminance and contrast in the front direction of the liquid crystal display device can be improved. On the other hand, when the half-value width | θa−θb | is 30 ° or more or θb does not exist (for example, the peak is an extremely gentle peak, and is maximal in the range of −80 ° ≦ θ ≦ 80 °). The point where the value becomes ½ of the peak does not exist on the peak), the light component having a relatively small absolute value of the emission angle θ constituting the vicinity of the base of the peak where the maximum value of the light intensity is highest increases. As a result, the light component bent in a direction other than the front direction of the liquid crystal display device (normal direction T of the light emitting surface of the surface light source) is increased by the prism sheet, so that the brightness and contrast in the front direction of the liquid crystal display device are sufficient. There is a tendency that cannot be improved. The half-value width | θa−θb | is preferably 25 ° or less.

The light intensity distribution of the surface light source on the plane W may have any light distribution characteristic as long as the above (1) and (2) are satisfied, but within an emission angle range of −40 to 40 °. It is preferred not to have a significant peak. This is because such a peak tends not to be properly collected in the front direction of the liquid crystal display device by the prism sheet.

Here, as the plane W orthogonal to the ridge line direction of the prism-like projection, a plurality of planes can be adopted. However, in the present invention, at least one of the planes W (1) and (2 ). However, in order to achieve sufficiently high luminance and contrast over the entire surface of the liquid crystal display device, the above (1) and (2) must be satisfied in any two or more planes W orthogonal to the ridge line direction of the prism-shaped protrusions. preferable.

The light intensity distribution of the surface light source can be obtained by measuring the brightness of the surface light source using a commercially available brightness measuring device.

As the surface light source, a direct light source using a diffusing plate, an edge light source using a light guide plate, or the like can be used. In order to realize the above light distribution characteristics, as shown in FIG. It is preferable to use an edge-type light source (surface light source 20) including the light guide plate 22 and the light source device 21 disposed on the side of the light guide plate 22. As the light guide plate 22, for example, a flat plate or wedge-shaped member made of a transparent resin such as an acrylic resin can be used. A pattern is added to the back surface or both surfaces of the light guide plate by screen printing using ink, etching, or blasting. In addition, a minute reflection element or a minute refraction element having a reflection function may be formed on the back surface or both surfaces of the light guide plate. Desired light distribution characteristics can be obtained by appropriately adjusting the shapes or elements of the back surface or both surfaces of these light guide plates. More specifically, for example, “Latest Liquid Crystal Backlight Technology Chapter 4” published by Toray Research Center Co., Ltd., and “LCD Backlight Technology, Volume 2, Chapter 1, Chapter 4” published by CM Publishing Co., Ltd. The light source device described in “Chapter 1” can be suitably used.

As the light source device 21, a light source device in which point light sources such as LEDs are arranged in a line or a light source device composed of a rod-like light source such as a cold cathode tube can be used. In the liquid crystal display device of the present invention, the surface light source may have one light source device arranged on one side of the light guide plate, or two light source devices arranged on two sides facing the light guide plate. You may do it.

It is preferable that the edge type light source, which includes a light source device in which point light sources are arranged in a line or a light source device including a rod-like light source, is arranged in parallel or substantially in parallel with the ridge line of the prism-shaped protrusions of the prism sheet. By arranging in this way, the light emitted from the edge type light source is most efficiently collected by the prism sheet.

In the liquid crystal display device of the present invention, a conventionally known appropriate configuration can be adopted for configurations other than those described above. For example, the liquid crystal display device of the present invention may further include a light diffusing plate, a light diffusing sheet, a reflecting plate, and the like.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

(Production Example 1: Production of polarizing film)
A polyvinyl alcohol film having an average polymerization degree of about 2400 and a saponification degree of 99.9 mol% or more and a thickness of 75 μm was immersed in pure water at 30 ° C., and then the weight ratio of iodine / potassium iodide / water was 0.02 / 2. / 100 aqueous solution at 30 ° C. Then, it was immersed at 56.5 ° C. in an aqueous solution having a potassium iodide / boric acid / water weight ratio of 12/5/100. Subsequently, after washing with pure water at 8 ° C., it was dried at 65 ° C. to obtain a polarizing film in which iodine was adsorbed and oriented on polyvinyl alcohol. Stretching was mainly performed in the iodine staining and boric acid treatment steps, and the total stretching ratio was 5.3 times.

(Production Example 2: Preparation of UV-curable adhesive)
10.0 g of Nippon Epoxy Resin Co., Ltd. product name “Epicoat YX8000” (diglycidyl ether of hydrogenated bisphenol A having an epoxy equivalent of about 205 g / equivalent), Nippon Soda A 100 ml disposable cup of 4.0 g of trade name “CI5102”, which is a photocationic polymerization initiator manufactured by Co., Ltd., and 1.0 g of trade name “CS7001,” which is a photosensitizer, manufactured by Nippon Soda Co., Ltd. The ultraviolet curable adhesive was prepared by weighing out, mixing and defoaming.

(Production Example 3: Preparation of prism sheet 1)
Applying molten polypropylene resin to a mold that has been designed in advance so that the pitch of prism-shaped protrusions after molding (the cross-sectional shape is an isosceles triangle) is 50 μm and the apex angle is 65 °, while heating Pressurized. Then, immediately after peeling from the mold, it was cooled to 60 ° C. to obtain a prism sheet 1 made of polypropylene resin. All the prismatic protrusions had the shape as designed. The refractive index of the prism sheet 1 was 1.49.

(Production Example 4: Production of Prism Sheet 2)
A UV curable mold having the composition shown below in a mold preliminarily designed so that the pitch of the prism-shaped projections after molding (the cross-sectional shape is an isosceles triangle) is 50 μm and the prism apex angle is 65 ° After applying the resin composition and smoothing the surface, a polyethylene terephthalate film having a thickness of 188 μm was overlaid on the layer made of the ultraviolet curable resin composition. Subsequently, ultraviolet rays having a wavelength of 320 to 390 nm were irradiated so that the integrated irradiation amount was 1000 mJ / cm ² to cure the ultraviolet curable resin composition. Then, the prism sheet 2 by which the hardened | cured material layer of the ultraviolet curable resin composition which has a prism-shaped protrusion was laminated | stacked on the polyethylene terephthalate film was obtained by peeling from a metal mold | die. All the prismatic protrusions had the shape as designed. The refractive index of the prismatic protrusions of the prism sheet 2 was 1.54.

[Composition of UV curable resin composition used in Production Example 4]
45 parts by weight of NK ester A-BPE-4 (Shin Nakamura Chemical Co., Ltd., ethylene oxide-modified bisphenol A diacrylate) 25 parts by weight Sartomer 285 (tetrahydroful manufactured by Sartomer) Furyl acrylate)
30 parts by weight Darocur 1173 (2-hydroxy-2-methyl-1-phenylpropan-1-one manufactured by Ciba) 3 parts by weight.

<Example 1>
(A) Production of Polarizing Plate Production Example 2 with the prism sheet 1 obtained in Production Example 3 on one surface of the polarizing film obtained in Production Example 1 and the surface opposite to the prism surface as the bonding surface It bonded together through the ultraviolet curable adhesive obtained in above. A triacetyl cellulose film (80 μm, manufactured by Konica Minolta Opto) was bonded to the other surface of the polarizing film via the ultraviolet curable adhesive obtained in Production Example 2. Next, it was passed once at a line speed of 1.0 m / min through a UV irradiation device manufactured by Nippon Batteries Co., Ltd. (UV lamp uses “HAL400NL” at 80 W and irradiation distance was 50 cm). A polarizing plate having an excellent appearance was obtained. The curability of the ultraviolet curable adhesive which is an epoxy resin composition was good. Moreover, when the adhesiveness of the prism sheet 1 was evaluated by the cross cut method described in JIS K 5400, the number of non-peeling cross cuts with respect to the number of formed cross cuts was 100/100, indicating good adhesion. An acrylic pressure-sensitive adhesive layer having a thickness of 25 μm was provided on the outer surface of the triacetyl cellulose film of the polarizing plate.

(B) Production of liquid crystal display device The above polarizing plate was disposed on the back surface of the liquid crystal cell via an acrylic pressure-sensitive adhesive layer, and a commercially available polarizing plate was disposed on the front surface of the liquid crystal cell to assemble a liquid crystal panel. This liquid crystal panel was combined with a light source plate type (edge type light source) surface light source A (used in Sony VAIO VGN-FE32B / W) to produce a liquid crystal display device. When the display of the liquid crystal display device was visually observed, a bright image was obtained when viewed from the front, and the visibility was good. The light intensity distribution of the surface light source A measured using EZContrast (ELXIM LX88W) is shown in FIG.

<Example 2>
A polarizing plate was produced in the same manner as in Example 1 except that the prism sheet 2 obtained in Production Example 4 was used instead of the prism sheet 1 obtained in Production Example 3, and then a liquid crystal display device was produced.
When the display of the liquid crystal display device was visually observed, a bright image was obtained when viewed from the front, and the visibility was good.

<Comparative Example 1>
In the same manner as in Example 1, except that the surface light source A (edge-type light source) surface light source B (used in the Flexscan EV2411W-H manufactured by Nanao Corporation) was used instead of the surface light source A, the liquid crystal was used. A display device was produced. When the display of the liquid crystal display device was visually observed, the image viewed from the front was dark, the contrast was low, and the visibility was poor. FIG. 7 shows a light intensity distribution of the surface light source B measured using EZContrast (ELXIM LX88W).

<Comparative Example 2>
A liquid crystal display device was produced in the same manner as in Comparative Example 1 except that the prism sheet 2 obtained in Production Example 4 was used instead of the prism sheet 1 obtained in Production Example 3. When the display of the liquid crystal display device was visually observed, the image viewed from the front was dark, the contrast was low, and the visibility was poor.

Table 1 summarizes the values of θa, θb and | θa−θb | obtained from the light intensity distributions of the surface light sources used in the examples and comparative examples, and the visibility evaluation results of the manufactured liquid crystal display device. The brightness and contrast of the liquid crystal display device were measured using EZContrast (ELXIM LX88W) from the front of the center of the liquid crystal display device in a dark room. 8 and 9 show the light intensity distribution (luminance distribution) of the liquid crystal display devices manufactured in Example 1 and Comparative Example 1. FIG. In addition, “−” in the column of “θb” in Table 1 has a point that is ½ of the maximum value in the range of −80 ° ≦ θ ≦ 80 ° at the peak with the highest light intensity maximum value. It means not.

It should be considered that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1, 2: Polarizing plate 3: Liquid crystal cell 10: Liquid crystal panel,
12: Polarizing film,
13: Prism sheet,
13a: prism protrusion,
14, 16: adhesive layer,
15: Resin film,
17: adhesive layer
20: surface light source,
21: Light source device,
22: Light guide plate,
100: Liquid crystal display device,
W: a plane perpendicular to the ridge line direction of the prismatic protrusion,
T: normal direction of the light emitting surface of the surface light source,
M: the emission direction of the emitted light from the surface light source,
θ: angle formed by the normal direction of the light emission surface of the surface light source and the emission direction of the emitted light of the surface light source (output angle),
P: hypotenuse of prismatic protrusion,
α The apex angle of the prismatic protrusion.

Claims

[Supplement under rule 26 12.11.2010]
A surface light source;
A liquid crystal panel comprising a polarizing plate disposed on the surface light source and laminated on a surface of the liquid crystal cell and the surface light source side of the liquid crystal cell;
A liquid crystal display device comprising:
The polarizing plate includes a polarizing film and a prism sheet having a surface composed of prismatic protrusions laminated on the surface of the polarizing film via an adhesive layer,
The prism sheet is arranged such that a surface constituted by the prism-shaped projections faces the surface light source,
The angle formed by the normal direction of the light emitting surface of the surface light source and the emitting direction of the emitted light of the surface light source in a plane orthogonal to the ridge line direction of the prism-shaped protrusion is an emission angle θ (however, −90 ° ≦ θ ≦ 90 °), a liquid crystal display device in which the light intensity distribution of the surface light source, which shows the emission angle dependence of the light intensity of the emitted light, satisfies the following (1) and (2).
(1) It has a peak having the highest light intensity maximum value in the range of −80 ° ≦ θ <−40 ° or 40 ° <θ ≦ 80 °.
(2) When the angle indicating the maximum value of the light intensity at the peak is θa and the angle indicating 1/2 of the maximum value of the light intensity at the peak is θb, the following formula [1]:
| Θa−θb | <30 ° [1]
Meet.
The liquid crystal display device according to claim 1, wherein the surface light source includes a light guide plate and a light source device disposed on a side of the light guide plate.
The light source device is a light source device composed of a light source device or a rod-like light source in which point light sources are arranged in a line,
The liquid crystal display device according to claim 2, wherein the light source device and the prism sheet are arranged such that ridge lines of the light source device and the prismatic protrusion are parallel or substantially parallel.
4. The liquid crystal display device according to claim 1, wherein the light source device is disposed on one side of the light guide plate or on two sides facing each other.
5. The liquid crystal display device according to claim 1, wherein an apex angle α of the prismatic protrusion is 60 ° or more.