KR20120026600A - Liquid crystal display device - Google Patents

Abstract

The present invention provides a liquid crystal display device having high brightness and contrast and excellent display characteristics. The liquid crystal display device of the present invention is a liquid crystal panel 10 including a surface light source 20 and a polarizing plate disposed on the surface light source and laminated on the surface of the liquid crystal cell 3 and the surface light source side of the liquid crystal cell. It is composed. The polarizing plate has a prism sheet 13 having a surface composed of a polarizing film 12 and a prism type projection 13a, and the prism sheet 13 is disposed so that the surface composed of the prism type projections faces the surface light source. And the light intensity distribution indicating the exit angle dependence of the light intensity of the outgoing light of the surface light source 20 satisfies the following (1) and (2):
(1) The peak of light intensity has the highest peak in the range of -80 ° ≤θ <-40 ° or 40 ° <θ≤80 °.
(2) The expression | θa-θb | <30 ° is satisfied when the angle representing the maximum value of the light intensity at the peak is θa and the angle representing the half of the maximum value of the light intensity at the peak is θb.

Description

[0001] LIQUID CRYSTAL DISPLAY DEVICE [0002]

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.

BACKGROUND ART Liquid crystal display devices are rapidly expanding in use as thin display devices used in liquid crystal televisions, liquid crystal monitors, personal computers, and the like. In particular, the market expansion of liquid crystal TVs is remarkable, and the demand for cost reduction is very high.

A normal liquid crystal display device is composed of a liquid crystal panel in which a surface light source using a cold cathode tube or LED, a light diffusion plate, one or more diffusion sheets, a light collecting sheet, and a polarizing plate are bonded to each other. In recent years, there has been a recent demand for thinning liquid crystal display devices in wall-mounted large-screen liquid crystal TV applications. In this case, thinning and reducing the number of members required for thinning of liquid crystal display devices are required.

In response to such a request, a method of directly adhering a prism sheet having light condensation to one side 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 the number of parts except for one or a plurality of members by a method of using a light-converging prism sheet as a protective film of a polarizing plate disposed on the surface light source side of the liquid crystal panel (for example, JP2008-262132-A and JP2005-17355-A). Techniques for reducing the pressure are known.

In the liquid crystal display device using the polarizing plate provided with sheet members, such as a prism sheet, as described in the said patent documents 1-3, the light condensing function anticipated by a sheet member is sufficient depending on the light emission characteristic which the surface light source used has It may not be exhibited, resulting in deterioration of display characteristics such as brightness and contrast.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof 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 comprising a surface light source and a liquid crystal panel disposed on the surface light source and including a liquid crystal cell and a polarizing plate laminated on the surface of the surface light source side of the liquid crystal cell. In the liquid crystal display device of the present invention, the polarizing plate includes a prism sheet having a polarizing film and a surface composed of a prism-type protrusion, which is laminated on the surface of the polarizing film through an adhesive layer, and the prism sheet is a prism-type protrusion. The surface which consists of these is arrange | positioned so that it may oppose a surface light source. In addition, the liquid crystal display device of the present invention has an angle of emission (θ) (the angle formed between the normal direction of the light exit surface of the surface light source and the exit direction of the exit light of the surface light source in a plane orthogonal to the ridge direction of the prism projection). However, when -90 ° ≤θ≤90 °), the light intensity distribution of the surface light source indicating the emission angle dependence of the light intensity of the emitted light satisfies the following (1) and (2):

(1) the peak of the light intensity has the highest peak within 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, Equation [1]: satisfies | θa-θb | <30 ° [1].

In the liquid crystal display device of the present invention, preferably, the surface light source includes a light guide plate and a light source device disposed on the side of the light guide plate. In addition, the light source device is a light source device including a light source device or a bar-shaped light source arranged linearly side by side the point light source, the light source device and the prism sheet is arranged so that the ridge lines of the light source device and the prism projections are parallel or approximately parallel to each other. It is preferable to be.

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

It is preferable that the vertex angle (alpha) of a prism-type protrusion is 60 degrees or more. And it is preferable that the cross-sectional shape of a prism protrusion is an isosceles triangle.

In addition to being thin, the liquid crystal display device of the present invention has high luminance and contrast, and is excellent in 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 TV, particularly a liquid crystal display device for a wall-mounted liquid crystal TV.

1 is a schematic cross-sectional view showing a preferred example of the liquid crystal display of the present invention.
2 is a schematic cross-sectional view showing a preferred example of the back side polarizing plate used in the present invention.
It is a schematic perspective view which shows an example of the surface shape of a prism sheet.
4 is a schematic perspective view for explaining the light output characteristics of the surface light source used in the present invention.
It is a schematic diagram for demonstrating the path | route of the light which injects into the prism-type protrusion which a prism sheet has.
FIG. 6 is a diagram showing the light intensity distribution of the surface light source A used in Examples 1 and 2. FIG.
FIG. 7 is a diagram showing the light intensity distribution of the surface light source B used in Comparative Examples 1 and 2. FIG.
FIG. 8 is a diagram showing the light intensity distribution (luminance distribution) of the liquid crystal display produced in Example 1. FIG.
9 is a diagram showing the light intensity distribution (luminance distribution) of the liquid crystal display device produced in Comparative Example 1. FIG.

1 is a schematic cross-sectional view showing a preferred example of the liquid crystal display of the present invention. The liquid crystal display device 100 shown in FIG. 1 according to the present invention includes a light guide plate 22 and a light source device 21 arranged along a side of the light guide plate 22 as a side of the light guide plate 22. The surface light source 20 and the liquid crystal panel 10 arrange | positioned on the surface light source 20 are comprised. The liquid crystal panel 10 is visually recognized by the liquid crystal cell 3, the polarizing plate 1 which is a back side polarizing plate laminated on the surface of the surface light source 20 side in the liquid crystal cell 3, and the liquid crystal cell 3. It consists of the polarizing plate 2 which is the front side polarizing plate laminated | stacked on the surface of the side. The polarizing plate 1 and the polarizing plate 2 are bonded to the liquid crystal cell 3 via the adhesive layer 17.

The polarizing plate 1 which is a back side polarizing plate is a surface which consists of a polarizing film 12 and the prism type protrusion 13a laminated | stacked through the adhesive bond layer 14 on the surface light source 20 side surface of the polarizing film 12. A prism sheet 13 having a prism face (hereinafter also referred to as a prism face) and a resin film 15 laminated through the adhesive layer 16 on the viewing side surface of the polarizing film 12 are provided. The polarizing plate 1 is bonded by the liquid crystal cell 3 at the resin film 15 side. More specifically, in the liquid crystal cell 3 and the polarizing plate 1, the surface opposite to the surface on which the prism sheet 13 is laminated in the polarizing film 12 faces the liquid crystal cell 3, that is, the prism sheet ( The prism face of 13) forms the surface light source side surface of the liquid crystal panel 10, and the prism face is joined so as to face the surface light source 20. In addition, in this invention, the back side polarizing plate may not have such a resin film, and the structure which the polarizing film 12 is bonded to the liquid crystal cell 3 directly through an adhesive layer etc. may be sufficient.

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 through an adhesive layer, as will be described later in detail. A liquid crystal display device using a rear polarizing plate having a prism sheet, characterized by applying a surface light source having a specific light output characteristic, specifically, a light distribution characteristic (in which direction, how much light is emitted). do. According to the present invention, a liquid crystal display device using a backside polarizing plate having a prism sheet can provide a liquid crystal display device having high brightness and contrast and excellent display characteristics. Further, the liquid crystal display device of the present invention has a sufficient mechanical strength while responding to thinning by providing a liquid crystal panel in which a thinned polarizing plate is bonded to the rear side of the liquid crystal cell, and at the same time, a prism sheet is disposed on the rear side of the liquid crystal panel. As a result, the adhesion between the liquid crystal panel and the surface light source is prevented, thereby improving display characteristics. EMBODIMENT OF THE INVENTION Hereinafter, the liquid crystal display device of this invention is demonstrated in detail, referring drawings suitably.

<Rear polarizer>

FIG. 2 is a schematic cross-sectional view showing a preferred example of a back side polarizing plate used in the present invention, the configuration of which is the same as that of the polarizing plate 1 of FIG. As in the example shown in FIG. 2, the back side polarizing plate used in the present invention is laminated on the polarizing film 12 and one side surface (surface light source side surface) of the polarizing film 12 via the adhesive layer 14. And at least a prism sheet 13 having a surface (prism surface) composed of a prism-shaped protrusion 13a. Like the polarizing plate 1 shown in FIG. 2, the back side polarizing plate is a resin film laminated | stacked through the adhesive bond layer 16 on the surface (surface of the liquid crystal cell side) on the opposite side to the surface on which the prism sheet 13 is laminated | stacked ( 15) may be provided.

(Polarizing film)

Specifically, the polarizing film 12 used for a back polarizing plate adsorbs and orients a dichroic dye to the uniaxially stretched polyvinyl alcohol-type resin film. As polyvinyl alcohol-type resin which comprises a polyvinyl alcohol-type resin film, what saponified polyvinyl acetate type resin can be used. As polyvinyl acetate type resin, besides polyvinyl acetate which is a homopolymer of vinyl acetate, the copolymer of vinyl acetate and the other monomer copolymerizable here, for example, ethylene-vinyl acetate copolymer, etc. are mentioned. As another monomer copolymerizable with vinyl acetate, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, acrylamide which has an ammonium group, etc. are mentioned, for example.

Saponification degree of polyvinyl alcohol-type resin is about 85-100 mol% normally, and 98 mol% or more is preferable. The polyvinyl alcohol-based resin may be modified. For example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, and the like modified with aldehydes may also be used. The polymerization degree of polyvinyl alcohol-type resin is about 1000-10000 normally, and about 1500-5000 is preferable.

What formed such a polyvinyl alcohol-type resin into a film is used as a raw film of a polarizing film. The method of forming a polyvinyl alcohol-type resin into a film is not specifically limited, It can form into a film by a conventionally well-known suitable method. Although the thickness of the raw film which consists of polyvinyl alcohol-type resin is not specifically limited, For example, it is about 10-150 micrometers.

The polarizing film is usually a step of dyeing a raw film made of the above-described polyvinyl alcohol-based resin with a dichroic dye to adsorb the dichroic dye (dyeing step), or a polyvinyl alcohol system with a dichroic dye adsorbed. It manufactures through the process of processing a resin film with boric-acid aqueous solution (boric acid treatment process), and the process of washing with water after the process by this boric-acid aqueous solution (water washing process process).

In addition, when manufacturing a polarizing film, a polyvinyl alcohol-based resin film is usually uniaxially stretched, and this uniaxial stretching may be performed before the dyeing treatment process, may be performed during the dyeing treatment process, or may be performed after the dyeing treatment process. have. In the case where uniaxial stretching is performed after the dyeing treatment step, this uniaxial stretching may be performed before the boric acid treatment step or may be performed during the boric acid treatment step. Of course, it is also possible to perform uniaxial stretching in these plural steps. Uniaxial stretching may make it uniaxially stretch between the rolls from which the circumferential speed differs, and may make it uniaxially stretch using a thermal roll. Moreover, it may be dry drawing which extends | stretches in air | atmosphere, or it may be wet drawing which extends | stretches in the state swollen with a solvent. The draw ratio is usually about 3 to 8 times.

The dyeing with the dichroic dye of the polyvinyl alcohol-based resin film in the dyeing treatment step is carried out, for example, by dipping the polyvinyl alcohol-based resin film in an aqueous solution containing the dichroic dye. As a dichroic dye, iodine, a dichroic dye, etc. are used, for example. Dichroic dyes include dichroic direct dyes made of disazo compounds such as C.I.DIRECT RED 39, dichroic direct dyes made of tris azo, tetrakis azo compounds and the like. In addition, it is preferable that the polyvinyl alcohol-based resin film be immersed in water before the dyeing treatment.

When using iodine as a dichroic dye, the method of immersing and dyeing a polyvinyl alcohol-type resin film in the aqueous solution containing iodine and potassium iodide is employ | adopted normally. 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 a dichroic dye, the temperature of the aqueous solution used for dyeing is usually 20 to 40 ° C, and the immersion time (dyeing time) in the aqueous solution is usually 20 to 1800 seconds.

On the other hand, when using a dichroic dye as a dichroic dye, the method of immersing and dyeing a polyvinyl alcohol-type resin film in the aqueous solution containing water-soluble dichroic dye is employ | adopted normally. The content of the dichroic dye in this aqueous solution is usually 1 × 10 ^-4 to 10 parts by weight, preferably 1 × 10 ^-3 to 1 part by weight, and particularly preferably 1 × 10 ^-3 to 1 part by weight of 100 parts by weight of water. X10 ^-2 parts by weight. This aqueous solution may contain inorganic salts, such as sodium sulfate, as a dyeing adjuvant. When using a dichroic dye as a dichroic dye, the temperature of the dye aqueous solution used for dyeing is 20-80 degreeC normally, and also the immersion time (dyeing time) in this aqueous solution is 10-1800 second normally.

The boric acid treatment step is carried out by immersing the polyvinyl alcohol-based resin film dyed with a dichroic dye in an aqueous solution containing boric acid. The amount of boric acid in the aqueous solution containing boric acid 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 aforementioned dyeing treatment step, the boric acid-containing aqueous solution used in the boric acid treatment step preferably contains potassium iodide. In this case, the amount of potassium iodide in the aqueous solution containing boric acid is usually 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. Immersion time in boric acid containing aqueous solution is 60-1200 second normally, Preferably it is 150-600 second, More preferably, it is 200-400 second. The temperature of the boric-acid containing aqueous solution is 50 degreeC or more normally, Preferably it is 50-85 degreeC, More preferably, it is 60-80 degreeC.

In the following water washing process, the water washing process is performed by immersing the polyvinyl alcohol-type resin film after boric acid treatment mentioned above in water, for example. The temperature of water in a water washing process is 5-40 degreeC normally, and immersion time is 1-120 second normally. After the water washing treatment, a drying treatment is usually performed to obtain a polarizing film. Drying process can be performed using a hot air dryer, a far-infrared heater, etc., for example. The temperature of a drying process is 30-100 degreeC normally, Preferably it is 50-80 degreeC. The time of the drying treatment is usually 60 to 600 seconds, preferably 120 to 600 seconds.

In this manner, the polyvinyl alcohol-based resin film can be uniaxially stretched, dyed with a dichroic dye, boric acid treatment, and washed with water to obtain a polarizing film. The thickness of this polarizing film is in the range of 5-40 micrometers normally.

(Prism sheet)

The prism sheet 13 used for the back side polarizing plate has a surface (prism face) composed of prismatic protrusions (prism protrusions 13a). The prism sheet 13 is laminated on the polarizing film 12 such that the surface opposite to the prism face faces the polarizing film 12. The prism sheet 13 having a prism face is disposed on the surface of the back side polarizing plate, and the prism face 13 is opposed to a surface light source to be described later, so that the light emitted from the light exit face (the face opposite to the prism face) of the surface light source The direction can be intentionally changed (deflected). According to the present invention, an emission light from an area light source, in particular an emission light having directivity, an emission light whose main emission direction is different from the normal direction (the front direction of the liquid crystal display device) of the light exit surface of the surface light source] Can be deflected by the prism sheet in the front direction of the liquid crystal display, thereby improving the brightness and contrast of the front of the liquid crystal display. In addition, the prism sheet 13 also serves as a protective film of the polarizing film 12.

Herein, in the columnar body represented by a trajectory in which a triangular shape (which may include a substantially triangular shape including a curve and a sawtooth shape, etc.) including a curve is vertically parallel to the triangular surface, It means a portion of the side (ridge line) sandwiched between two sides that do not form the bottom surface (the trajectory of the diagonal of the bottom side of the triangle), and the prism surface refers to the surface of the columnar body with respect to the prism-shaped protrusion of the columnar body (the The triangular bottom side trajectories) are arranged in parallel and closely arranged in parallel to each other, and the plurality of prismatic protrusions are arranged in one direction (such that the ridges of each prism protrusion are parallel or approximately parallel to each other). 3 is a schematic perspective view showing an example of the surface shape of a prism sheet, wherein the cross-sectional shape of the prism-shaped protrusion is an isosceles triangle.

Although the vertex angle (angle of the vertex) of the prism-type protrusion 13a which the prism sheet 13 has can be 30-100 degrees, for example, in the present invention, the light emitted from the surface light source, in particular, the light having directivity In order to efficiently deflect to the front direction of a liquid crystal display device, it is especially preferable to set it as 60 degrees or more and 100 degrees or less, and it is more preferable to set it as 60 degrees or more and 80 degrees or less.

The height of the prismatic protrusion 13a can be 10-200 micrometers, for example. In addition, the pitch (distance between ridges of adjacent protrusions) of the prismatic protrusion 13a is appropriately determined in consideration of the vertex angle and the height of the prismatic protrusion 13a, and may be, for example, 5 to 300 μm.

The two sides constituting the protrusion on the cross-sectional triangle of the prismatic protrusion 13a may have the same length or may have different lengths, but at least the light source devices of the surface light source to be used are disposed on two opposite sides of the light guide plate. In this case, the two sides are preferably the same length, and 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 may be different from each other. In addition, the shape of the groove formed between the projections may be straight or curved.

As a material of the prism sheet 13, various well-known materials can be used. For example, polyester resins, such as polyolefin resin, such as polyethylene and a polypropylene, polyethylene terephthalate resin, and polyethylene naphthalate resin, polyvinyl chloride resin, polycarbonate resin, norbornene resin, polyurethane resin, acrylic resin, Synthetic polymers such as polymethyl methacrylate resin, polystyrene resin, methyl methacrylate-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene copolymer, cellulose acetate, Natural polymers, such as a cellulose triacetate resin, can be used. Among them, polyolefin resin, polyacrylic resin, polycarbonate resin, polyester resin, polystyrene resin, methyl methacrylate-styrene copolymer, acrylonitrile-butadiene-styrene from the viewpoint of transparency, moisture permeability and productivity Thermoplastic resins of any one of the copolymer and acrylonitrile-styrene copolymer are suitable. Moreover, these polymer materials can contain additives, such as a ultraviolet absorber, antioxidant, and a plasticizer, as needed.

The prism sheet 13 is based on the transparent polymer material, based on the photopolymer process method, release extrusion method, press molding method, injection molding method, roll transfer method, laser ablation method, mechanical cutting method, mechanical grinding method. It can manufacture by a well-known method, such as these. These methods may be used alone or in combination of two or more kinds thereof.

Although the thickness of the prism sheet 13 is not specifically limited, From a viewpoint of thickness reduction of a polarizing plate, it is preferable that it is 20 micrometers or more and about 200 micrometers or less, and it is more preferable that they are 30 micrometers or more and 100 micrometers or less.

(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 opposite to the surface on which the prism sheet is laminated in the polarizing film 12. In this case, the polarizing plate 1 is bonded to the liquid crystal cell through the pressure-sensitive adhesive layer laminated on the resin film 15. Moreover, the optical functional film mentioned later can also be laminated | stacked on the polarizing film 12, a protective film, or an optical compensation film via an adhesive bond layer or an adhesive layer.

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

Examples of the cellulose resin constituting the cellulose resin film include partial esterified or full esterified cellulose, and examples thereof include acetic acid ester, propionic acid ester, butyric acid ester, and mixed esters of cellulose. . More specifically, triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, cellulose acetate butyrate, etc. are mentioned. When forming such a cellulose resin into a film, well-known methods, such as the solvent casting method and the melt-extrusion method, are used suitably. As a commercial item of a cellulose ester-type resin film, "FUJITAC TD80" (made by Fuji Film Co., Ltd.), "Fujitaek TD80UF" (made by Fuji Film Co., Ltd.), "Fujitaek TD80UZ" (Fuji Film) KK8UX2M "(made by Konica Minolta Opto Co., Ltd.)," KC8UY "(made by Konica Minolta Opto Co., Ltd.), etc. are mentioned.

Moreover, as an optical compensation film which consists of a cellulose resin film, For example, the film which made the said cellulose resin film contain the compound which has a phase difference adjustment function; A film coated with a compound having a phase difference adjusting function on a surface of a cellulose resin film; The film etc. which are obtained by uniaxial stretching or biaxial stretching of a cellulose resin film are mentioned.

As an optical compensation film which consists of a commercially available cellulose resin film, "WV BZ 438" by the Fujifilm Co., Ltd. "WV EA", "KC4FR-1" by Konica Minolta Opto Co., Ltd., and "KC4HR" -1 ", etc. are mentioned.

Although the thickness of the protective film or optical compensation film which consists of a cellulose resin film is not specifically limited, It is preferable to exist in the range of 20-90 micrometers, and it is more preferable to exist in the range of 30-90 micrometers. When the thickness is less than 20 µm, handling of the film is difficult. 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 polarizing plate obtained.

As an optical compensation film which consists of said polyolefin resin film, the uniaxially stretched or biaxially stretched cycloolefin resin film is mentioned, for example. When applying to the liquid crystal panel for large liquid crystal TV, especially the liquid crystal panel provided with the liquid crystal cell of a vertical alignment (VA) mode, as said optical compensation film, the extending | stretching product of a cycloolefin resin film is an optical characteristic and durability point, Suitable. Here, a cycloolefin resin film is a film which consists of thermoplastic resin which has a unit of the monomer which consists of cyclic olefins (cycloolefin), such as a norbornene and a polycyclic norbornene-type monomer, for example. 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, an aromatic compound having a cycloolefin, a chain olefin and / or a vinyl group, or the like. It may be an addition copolymer of. It is also effective that a polar group is introduced into the main chain or the side chain.

Commercially available thermoplastic cycloolefin-based resins include "Topas" sold by TOPAS ADVANCED POLYMERS GmbH of Germany, "ARTON" sold by JSR, and "Zeo sold by Nihon Xeon". "ZEONOR" and "ZEONEX", "Apel" (all brand names) sold by Mitsui Chemicals Co., Ltd., etc. can be used suitably.

A cycloolefin resin film can be obtained by forming such a cycloolefin resin into a film. As a film forming method, well-known methods, such as a solvent casting method and a melt extrusion method, are used suitably. For example, "Esshina" and "SCA40" sold by Sekisui Chemical Industry Co., Ltd., "Zeonor Film" sold by Nihon Xeon Co., Ltd., "Aton Film sold by JSR Co., Ltd." Filmed cycloolefin resin films, such as "(all brand names), are also commercially available, and these can also be used suitably.

When the thickness of the optical compensation film which consists of an extended cycloolefin resin film is too thick, workability will be inferior, In addition, since transparency falls or it is disadvantageous in thickness reduction and weight reduction of a polarizing plate, it is preferable that it is about 20-80 micrometers.

The back side polarizing plate used in the present invention can be obtained by bonding the prism sheet to one surface of the polarizing film described above using an adhesive. Thereby, with reference to FIG. 2, the polarizing plate in which the prism sheet 13 was laminated | stacked on the surface of the polarizing film 12 through the adhesive bond layer 14 can be obtained. When laminating | stacking the resin film 15 on the other side surface of the polarizing film 12, the bonding of the polarizing film 12 and the resin film 15 is similarly performed using an adhesive agent. 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 kind of adhesive, or different kinds of adhesives. It may be. As an adhesive agent used for bonding these films, an aqueous adhesive, ie, the adhesive agent which melt | dissolved or disperse | distributed the adhesive component in water, and a photocurable adhesive agent are mentioned.

The said water-based adhesive agent is used preferably at the point which can make an adhesive bond layer thin. As an aqueous adhesive agent, the aqueous adhesive which used polyvinyl alcohol-type resin or a urethane resin as an adhesive component is mentioned, for example.

When polyvinyl alcohol-based resin is used as the adhesive component, the polyvinyl alcohol-based resin may be modified in addition to partially saponified polyvinyl alcohol and fully saponified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetacetyl group-modified polyvinyl alcohol, and methylol group-modified. It may be a modified polyvinyl alcohol-based resin such as polyvinyl alcohol, amino group-modified polyvinyl alcohol. Usually, the aqueous adhesive which uses polyvinyl alcohol-type resin as an adhesive component is prepared as an aqueous solution of polyvinyl alcohol-type resin. The concentration of the polyvinyl alcohol-based resin in the adhesive is usually about 1 to 10 parts by weight, preferably about 1 to 5 parts by weight based on 100 parts by weight of water.

In order to improve adhesiveness, it is preferable to add curable components, such as glyoxal and a water-soluble epoxy resin, or a crosslinking agent to the adhesive agent which uses polyvinyl alcohol-type resin as an adhesive component. As a water-soluble epoxy resin, the polyobtained by making epichlorohydrin react with the polyamide polyamine obtained by reaction of polyalkylene polyamines, such as diethylene triamine and triethylene tetramine, and dicarboxylic acids, such as adipic acid, for example. Amide polyamine epoxy resin can be used suitably. Commercially available products of such polyamide polyamine epoxy resins include "Semi-Resins 650" and "Semi-Resins 675" sold by Sumika Chemtex Company, Limited, and Japan PMC Co., Ltd. "WS-525", and the like. The addition amount of these curable components or a crosslinking agent (when added together, the total amount) is usually 1 to 100 parts by weight, preferably 1 to 50 parts by weight based on 100 parts by weight of the polyvinyl alcohol-based 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 resin, the effect of improving the adhesion tends to be small, and the addition amount of the curable component and the crosslinking agent is polyvinyl alcohol resin When it exceeds 100 weight part with respect to 100 weight part, there exists a tendency for an adhesive bond layer to become weak.

Moreover, when using urethane resin as an adhesive component, the mixture of the polyester-type ionomer type urethane resin and the compound which has glycidyloxy group is mentioned as an example of a suitable adhesive composition. Here, polyester ionomer type urethane resin is a urethane resin which has a polyester frame | skeleton, and a small amount of ionic component (hydrophilic component) is introduce | transduced into this frame | skeleton. Such ionomer-type urethane resins are suitable as an aqueous adhesive because they are emulsified directly in water without using an emulsifier to form an emulsion.

The polyester-ionomer-type urethane resin itself is known, for example, Japanese Patent Laid-Open No. 7-97504 discloses an example of a polymer dispersant for dispersing a phenolic resin in an aqueous medium, and also Japanese Patent Laid-Open No. 2005- Japanese Patent Application Laid-Open No. 070140 and Japanese Patent Laid-Open No. 2005-181817 disclose a cycloolefin-based resin film on a polarizing film made of polyvinyl alcohol-based resin as an adhesive by using a mixture of a polyester ionomer-type urethane resin and a compound having glycidyloxy group. Joining is disclosed.

As a method of apply | coating an adhesive agent to a polarizing film and / or a member bonded to it (prism sheet, a protective film, or an optical compensation film), what is generally known may be sufficient, For example, the casting method, the Mayer bar coating method, the gravure coating A method, a comma coater method, a doctor blade method, a die coating method, a dip coating method, a spraying method and the like. The casting method is a method of spreading and spreading an adhesive on a surface thereof while moving a film to be coated in a substantially vertical direction, a substantially horizontal direction, or an oblique direction between them.

After apply | coating an adhesive agent, the polarizing film and the member joined to it are superimposed on each other, and the film bonding is performed by sandwiching in between with a nip roll etc. Bonding of a film using a nip roll is, for example, a method of applying pressure with a roll or the like and then spreading uniformly after applying the adhesive, a method of passing through a roll between the rolls and applying pressure and diffusion after applying the adhesive, and the like. It can be adopted. In the former case, it is possible to use a metal, rubber | gum, etc. as a material of a roll. In the latter case, the plurality of rolls may be the same material or different materials.

The polarizing plate can be obtained by drying after the said bonding and hardening an adhesive bond layer. This drying treatment is performed, for example, by spraying hot air, and the temperature is usually in the range of 40 to 100 ° C, preferably in the range of 60 to 100 ° C. Moreover, drying time is 20 to 1200 second normally.

The thickness of the adhesive bond layer after drying is 0.001-5 micrometers normally, Preferably it is 0.01-2 micrometers, More preferably, it is 0.01-1 micrometer. When the thickness of the adhesive bond layer after drying is less than 0.001 micrometer, adhesion may become inadequate, and when the thickness of the adhesive bond layer after drying exceeds 5 micrometers, there exists a possibility that the appearance defect of a polarizing plate may arise. Moreover, before drying and hardening, it is preferable that the thickness of the adhesive bond layer after bonding using the said nip roll etc. is 5 micrometers or less, and it is preferable that it is 0.01 micrometers or more.

After the drying treatment, curing at least half a day, usually one or more days at a temperature of room temperature or more, may be sufficient to obtain sufficient adhesive strength. Such curing is typically carried out in a rolled state. Preferable curing temperature is the range of 30-50 degreeC, More preferably, it is 35-45 degreeC. When the curing temperature exceeds 50 ° C, so-called "tight-winding" easily occurs in the roll winding state. In addition, the humidity at the time of curing is not particularly limited, but is preferably selected so that the relative humidity is in the range of about 0% RH to about 70% RH. The curing time is usually about 1 day to 10 days, preferably 2 days to 7 days.

Moreover, as said photocurable adhesive agent, the mixture of a photocurable epoxy resin and a photocationic polymerization initiator, etc. are mentioned, for example. As a photocurable epoxy resin, an alicyclic epoxy resin, the epoxy resin which does not have an alicyclic structure, a mixture thereof, etc. are mentioned, for example. The photocurable adhesive may contain, in addition to the photocurable epoxy resin, an acrylic resin, an octacene resin, a urethane resin, a polyvinyl alcohol resin, and the like together with the photocationic polymerization initiator or in place of the photocationic polymerization initiator. Therefore, the radical photopolymerization initiator may be included.

When using a photocurable adhesive agent, after apply | coating a photocurable adhesive agent to a polarizing film and / or a member bonded to it (prism sheet, a protective film, or an optical compensation film), after bonding a polarizing film and a member bonded to this, The photocurable adhesive is cured by irradiating active energy rays. The coating method of a photocurable adhesive agent and the bonding method of a film can be made the same as an aqueous adhesive agent. The light source of the active energy ray is not particularly limited, but an active energy ray having a luminescence distribution at a wavelength of 400 nm or less is preferable, and specifically, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a chemical lamp, a black light lamp, a microwave A mercury lamp, a metal halide lamp, etc. are used preferably here.

Light irradiation intensity to a photocurable adhesive agent is suitably determined by the composition of the said photocurable adhesive agent, Although it does not specifically limit, It is preferable that irradiation intensity of the wavelength range effective for activation of a polymerization initiator is 0.1-6000 mW / cm <^2> . When the irradiation intensity is 0.1 mW / cm ² or more, the reaction time is not excessively long and 6000 mW / cm ² When it is below, there is little possibility that the yellowing of an epoxy resin and deterioration of a polarizing film by the heat radiated | emitted from a light source and the heat | fever at the time of hardening of a photocurable adhesive agent will be produced. The irradiation time to the photocurable adhesive is not particularly limited as long as it is controlled for each photocurable adhesive to be cured, but the amount of accumulated light expressed by the product of the irradiation intensity and the irradiation time is set to 10 to 10000 mJ / m ^2. desirable. When the accumulated light amount to the photocurable adhesive agent is 10 mJ / m ² or more, a sufficient amount of active species derived from a polymerization initiator can be generated to reliably advance the curing reaction, and when the amount is less than 10000 mJ / m ² , the irradiation time is excessive. Good productivity can be maintained since it is not long.

In the case of curing the photocurable adhesive by irradiation of active energy rays, curing is performed under conditions in which the polarizing plate, such as polarization degree, transmittance and color of the polarizing film, and transparency of the prism sheet, protective film, and optical compensation film, does not deteriorate. It is desirable to.

In addition, prior to the bonding of the prism sheet and the protective film or the optical compensation film to the polarizing film, in order to improve the adhesiveness to the adhesive surface of the polarizing film and / or the member bonded thereto, plasma treatment, corona treatment, ultraviolet irradiation Surface treatment, such as a process, flame (flame) process, and saponification process, can also be performed. As a saponification process, the method of immersing in aqueous alkali solution, such as sodium hydroxide and potassium hydroxide, is mentioned.

In addition, as mentioned above, the back side polarizing plate may have the optical functional film laminated | stacked on the surface on the opposite side to the surface where the prism sheet 13 is laminated | stacked in the polarizing film 12. As shown in FIG. As an optical functional film, For example, the optical compensation film by which the liquid crystalline compound is apply | coated and orientated on the surface of a base material; Reflective polarizing film which transmits some kind of polarized light and reflects the polarized light which shows the opposite property; Retardation film made of polycarbonate resin; Retardation film which consists of cycloolefin resin film; A film having an antiglare function having an uneven shape on the surface; Films with surface antireflection; A reflective film having a reflective function on a surface thereof; And a semi-transmissive reflective film having both a reflection function and a transmission function. As a commercial item corresponding to the optical compensation film with which the liquid crystalline compound is apply | coated and oriented on the base material surface, "WV film" (Fuji Film Co., Ltd. product), "NH film" (New Nippon Petroleum Co., Ltd. product), " NR film "(New Nippon Petroleum Co., Ltd. product) etc. are mentioned. As a commercial item which corresponds to the reflective polarizing film which transmits some kind of polarized light and reflects the polarized light which shows the opposite property, it is obtained from "DBEF" (3M company make, Sumitomo 3M Co., Ltd. in Japan), for example. And the like). Moreover, as a commercial item corresponding to the retardation film which consists of a cycloolefin resin film, "Aton film" (made by JSR Corporation), "Esshina" (made by Sekisui Chemical Industries, Ltd.), "Zeonor film" "(Nihon Xeon Co., Ltd.) etc. are mentioned.

It is preferable that a back polarizing plate has an adhesive layer for bonding to a liquid crystal cell on the surface on the opposite side to a prism sheet. As an adhesive used for such an adhesive layer, a conventionally well-known suitable adhesive can be used, For example, an acrylic adhesive, a urethane type adhesive, a silicone type adhesive etc. are mentioned. Especially, an acrylic adhesive is used preferably from a viewpoint of transparency, adhesive force, reliability, rework property, etc. The pressure-sensitive adhesive layer can be provided by a method of applying such a pressure-sensitive adhesive to an organic solvent solution, for example, by applying a die coater, a gravure coater, or the like on a base film (such as a polarizing film) and drying. Moreover, it can also install by the method of transferring the sheet-like adhesive formed on the plastic film (it is called a separate film) to which the mold release process was performed to the base film. Although the thickness in particular of an adhesive layer is not restrict | limited, It is preferable to exist in the range of 2-40 micrometers.

<Front side polarizer>

The front side polarizing plate (polarizing plate 2 of Fig. 1) is a polarizing plate disposed on the side opposite to the surface light source (viewing side) on the basis of the liquid crystal cell. As a front side polarizing plate, a conventionally well-known suitable polarizing plate can be used. For example, in addition to the polarizing plate which laminated | stacked the protective film which consists of triacetyl cellulose etc. on one or both surfaces of a polarizing film, the polarizing plate etc. in which the anti-glare process, the hard-coating process, and the anti-reflective process were given can be used. Moreover, the polarizing plate in which the protective film which consists of a polyethylene terephthalate film, an acryl film, a polypropylene film, etc. or an optical compensation film was laminated | stacked on one side of a polarizing film may be sufficient.

<Surface light source>

The liquid crystal display of the present invention includes a surface light source 20 for uniformly illuminating the liquid crystal panel. In the present invention, in order to maximize the function of the prism sheet (the function of deflecting the emitted light from the surface light source and correcting the direction of the emitted light from the prism-type projection in the front direction of the liquid crystal display device) as the surface light source 20. A surface light source having a specific light output characteristic (light distribution characteristic) is used.

More specifically, referring to FIG. 4, in the plane light source used in the present invention, in the plane W orthogonal to the ridge direction of the prism-shaped protrusion of the prism sheet, the normal direction of the light exit surface of the plane light source When the angle formed by (T) and the emission direction M of the exit light of the surface light source is referred to as the exit angle θ (wherein -90 ° ≤θ≤90 °), it indicates the emission angle dependency of the light intensity of the exit light. The light intensity distribution of the surface light source satisfies the following (1) and (2):

(1) the peak of the light intensity has the highest peak within 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 the half of the maximum value of the light intensity at the peak is θb, Equation [1]: | θa satisfies-[theta] b | <30 ° [1].

Moreover, the range which the emission angle (theta) can employ | adopt is -90 degrees <= (theta) <= 90 degrees. θ = 0 ° means that the direction M of the emitted light from the surface light source is the same direction as the normal direction T of the light exit surface of the surface light source. θ = -90 ° means that the direction M of the emitted light from the surface light source forms an angle of 90 ° counterclockwise (or clockwise) with respect to the normal direction T in the plane W. Θ = 90 ° means that in the plane W, the direction M of the emitted light from the surface light source forms an angle of 90 ° clockwise (or counterclockwise) with respect to the normal direction T It means to be.

Light having an emission direction M that is relatively far from the normal direction T of the light exit surface of the surface light source (relatively large in absolute value of the exit angle θ) is incident on the prism-like protrusion 13a of the prism sheet. In this case, the incident light reaches the hypotenuse P of the prism-shaped protrusion 13a and is reflected by the hypotenuse P, as shown schematically in FIG. It may be focused in the normal direction (T) of the light exit surface of the light source. That is, in the liquid crystal display device using the back side polarizing plate provided with a prism sheet, the absolute value of the emission angle (theta) which has the emission direction M far larger than the normal direction T of the light emission surface of such a surface light source. Relatively large) contributes greatly to the improvement of the brightness and contrast in the front direction of the liquid crystal display device.

In the plane W, the present inventors have a range of -80 ° ≤θ <-40 ° or 40 ° <θ≤80 ° (that is, the absolute value | θ | of the exit angle θ is 40 ° <). The surface light source (which satisfies the condition (1)) exhibiting the light intensity distribution characteristic having the highest peak of the light intensity within the range of | θ | ≤80 °) is satisfied by the prism sheet. Since the light is effectively focused in the front direction of the liquid crystal display (normal direction T of the light exit surface of the surface light source), it has been found to be very effective for improving the brightness and contrast in the front direction of the liquid crystal display. The lower limit and the upper limit of the emission angle θ considered under the condition (1) are -80 ° and 80 °, respectively, so that it is difficult to accurately measure the light intensity at an angle exceeding the lower limit and the upper limit. Because it is difficult and not practical.

It is preferable that the peak with the highest maximum value of the light intensity is located in the range of 50 ° ≤ | θ | ≤80 °, and more preferably located in the range of 60 ° ≤ | θ | ≤80 °.

On the other hand, it has been discovered by the present inventors that the width (spread) of the peak having the highest maximum light intensity also affects the brightness and contrast in the front direction of the liquid crystal display. That is, in the light intensity distribution of the surface light source in the plane W, the angle indicating the maximum value of the light intensity at the highest peak of the maximum light intensity is θa and represents 1/2 of the maximum value of the light intensity at the peak. When the angle is θb, if the half-width half (| θa-θb |) is less than 30 ° (if the above condition (2) is satisfied), the absolute value of the emission angle θ is not largely affected by the adverse effects of light with a relatively small value, By condensing the light having the exit angle of the exit light in the vicinity of θa, the luminance and contrast in the front direction of the liquid crystal display can be improved. On the other hand, when the half-width (| θa-θb |) is 30 degrees or more or θb does not exist (for example, the peak is a very gentle peak, the maximum value is in the range of -80 ° ≤θ≤80 °). The point where 1/2 is not present on the peak), the light component with a relatively small absolute value of the emission angle θ constituting the vicinity of the bottom of the peak where the maximum value of the light intensity is highest increases, and as a result The prism sheet increases the light component which is bent in a direction other than the front direction of the liquid crystal display (normal direction T of the light exit surface of the surface light source), thereby sufficiently improving the luminance and contrast in the front direction of the liquid crystal display. Tend not to. It is preferable that the half width (| θa -θb |) is 25 degrees or less.

The light intensity distribution of the surface light source in the plane W may have any light distribution characteristic as long as it satisfies the above (1) and (2), but does not have a significant peak in the emission angle of -40 to 40 °. It is preferable. This is because such peaks tend not to be properly focused in the front direction of the liquid crystal display by the prism sheet.

Here, a plurality of planes can be employed as the plane W orthogonal to the ridge direction of the prism-shaped protrusion, but in the present invention, in the at least one plane W, the above (1) and (2) You just need to meet. However, in order to achieve a sufficiently high brightness and contrast over the entire surface of the liquid crystal display device, it is preferable to satisfy the above (1) and (2) in any two or more planes (W) orthogonal to the ridge direction of the prismatic protrusion. Do.

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

As the surface light source, a direct type light source using a diffusion plate, an edge type light source using a light guide plate, or the like may be used. In order to realize the light distribution characteristics as described above, the light guide plate 22 and the light guide plate 22 are illustrated in FIG. 1. It is preferable to use the edge type light source (surface light source 20) provided with the light source device 21 arrange | positioned at the side of. As the light guide plate 22, a flat or wedge-shaped member made of transparent resin such as acrylic resin can be used, for example. Patterns are added to the back or both surfaces of the light guide plate by screen printing or etching using an ink and processing of blasts. Moreover, the micro reflective element, micro refractive element, etc. which have a reflection function in the back surface or both surfaces of a light guide plate may be comprised. Desired light distribution characteristics can be obtained by appropriately adjusting the shape or elements on the back or both surfaces of these light guide plates. More specifically, for example, "the latest technology of liquid crystal backlight, Chapter 4" published by Toray Research Center, Inc., and "backlit technology for liquid crystal display, Chapter 2, Part 1, Part 1," published by CMC Publishing Co., Ltd. The light source device described in Chapter "can be used suitably.

As the light source device 21, a light source device including a light source device in which point light sources such as LEDs are linearly arranged side by side and a bar 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 disposed on one side of the light guide plate, or may have two light source devices disposed on two sides facing each other.

It is preferable that the light source device including the point light source or the light source device including a rod-shaped light source provided in the edge light source is arranged in parallel or substantially parallel to the ridge line of the prism protrusion of the prism sheet. By arranging in this way, the light radiated by 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 well-known suitable structure can be adopted about the structure other than what was demonstrated above. For example, the liquid crystal display of the present invention may further include a light diffusion plate, a light diffusion sheet, a reflecting plate, and the like.

Example

Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited by these examples.

(Manufacture example 1: preparation of a polarizing film)

A polyvinyl alcohol film having an average degree of polymerization of about 2400 and a saponification degree of 99.9 mol% or more and a thickness of 75 μm was immersed in 30 ° C. pure water, and then immersed at 30 ° C. in an aqueous solution having a weight ratio of iodide / potassium iodide / water of 0.02 / 2/100. . Then, it was immersed at 56.5 degreeC in the aqueous solution whose weight ratio of potassium iodide / boric acid / water is 12/5/100. Subsequently, after wash | cleaning with the pure water of 8 degreeC, it dried at 65 degreeC and obtained the polarizing film in which iodine adsorption-orientated to polyvinyl alcohol. Stretching was mainly performed in the process of iodine dyeing and boric acid treatment, and the total draw ratio was 5.3 times.

(Manufacture example 2: preparation of an ultraviolet curable adhesive)

10.0 g of Nippon Soda Co., Ltd. brand name "Epicoat YX8000" which is a hydrogenation epoxy resin by Japan Epoxy Resin Co., Ltd. 4.0 g of the name "CI5102", a photocationic polymerization initiator manufactured by (Nippon Soda Co., Ltd.) and 1.0 g, the name "CS7001", a photosensitizer manufactured by Nippon Soda Co., Ltd., were taken out in a 100 ml disposable cup, The ultraviolet curable adhesive was prepared by mixing and defoaming.

(Manufacture example 3: production of prism sheet 1)

The molten polypropylene resin was apply | coated to the previously designed metal mold | die so that the pitch of the prism-shaped protrusion (cross-section shape may be an isosceles triangle) and a vertex angle after shaping | molding was pressurized, heating. Subsequently, it cooled to 60 degreeC immediately after peeling from the metal mold | die, and obtained the prism sheet 1 which consists of polypropylene resins. One prism-shaped protrusion had a shape as designed. The refractive index of the prism sheet 1 was 1.49.

(Manufacture example 4: production of prism sheet 2)

The UV curable resin composition having the composition shown below was applied to a mold previously designed such that the pitch of the prism-like protrusions (cross section is an isosceles triangle) and the prism vertex angle was 65 ° after molding, and the surface was smoothed, followed by A 188 μm-thick polyethylene terephthalate film was deposited on the layer made of the curable resin composition. Subsequently, ultraviolet rays having a wavelength of 320 to 390 nm were irradiated so that the accumulated irradiation amount was 1000 mJ / cm ² to cure the ultraviolet curable resin composition. Then, the prism sheet 2 in which the hardened | cured material layer of the ultraviolet curable resin composition which has a prism-type protrusion was laminated on the polyethylene terephthalate film was obtained by peeling from a metal mold | die. One prism-shaped protrusion had a shape as designed. The refractive index of the prism-shaped protrusion of the prism sheet 2 was 1.54.

[Composition of UV Curable Resin Composition Used in Production Example 4]

45 parts by weight of panryl FA-321M (ethylene oxide modified bisphenol A methacrylate manufactured by Hitachi Kasei Co., Ltd.)

25 parts by weight of NK ester A-BPE-4 (ethylene oxide modified bisphenol A diacrylate manufactured by Shin-Nakamura Chemical Co., Ltd.)

Satomer 285 (tetrahydrofurfuryl acrylate manufactured by Satomer)

30 parts by weight

Dalocure 1173 (2-hydroxy-2-methyl-1-phenylpropan-1-one manufactured by Chiba)

3 parts by weight.

&Lt; Example 1 >

(a) Preparation of Polarizing Plate

The prism sheet 1 obtained in manufacture example 3 was bonded to the one side surface of the polarizing film obtained in manufacture example 1 through the ultraviolet curable adhesive obtained in manufacture example 2 using the surface on the opposite side as the prism face as a bonding surface. Moreover, the triacetyl cellulose film (80 micrometers, the Konica Minolta Opto company make) was bonded to the other side of the polarizing film through the ultraviolet curable adhesive obtained in the manufacture example 2. Next, a good appearance was obtained by passing once at a line speed of 1.0 m / min in an ultraviolet irradiation device manufactured by GS Yuasa Corporation (ultraviolet lamp uses “HAL400NL” at 80 W and irradiation distance at 50 cm). A polarizing plate having a was obtained. Curability of the ultraviolet curable adhesive which is an epoxy resin composition was favorable. Moreover, when the adhesiveness of the prism sheet 1 was evaluated by the check method of JISK5400, the number of the non-peeling check eyes with respect to the number of the formed check eyes showed 100-100 favorable adhesiveness. The 25-micrometer-thick acrylic adhesive layer was provided in the outer surface of the triacetyl cellulose film of this polarizing plate.

(b) Fabrication of liquid crystal display device

The said polarizing plate was arrange | positioned at the back side of a liquid crystal cell through an acrylic adhesive layer, and the commercially available polarizing plate was arrange | positioned at the front side of a liquid crystal cell, and the liquid crystal panel was assembled. This liquid crystal panel was combined with the surface light source A (what is used by Sony Corporation VAIO VGN-FE32B / W) of the light-guide plate system (edge type light source), and produced the liquid crystal display device. When the display of the liquid crystal display device was visually confirmed, a bright image was obtained from the front, and visibility was good. The light intensity distribution of the surface light source A measured using EZContrast (LX88W by ELDIM) 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 visibility was good.

Comparative Example 1

A liquid crystal display device was manufactured in the same manner as in Example 1 except that the surface light source B (the one used in Flexscan EV2411W-H manufactured by Nanao Corporation) of the light guide plate method (edge type light source) was used instead of the surface light source A. 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. The light intensity distribution of the surface light source B measured using EZContrast (LX88W by ELDIM) is shown in FIG.

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 | determined from the light intensity distribution of the surface light source used in the examples and comparative examples, and the results of the visibility evaluation of the produced liquid crystal display device. The brightness | luminance and contrast of the liquid crystal display device were measured using EZContrast (LX88W made from ELDIM) from the front of the center part of a liquid crystal display device in a dark room. 8 and 9 show light intensity distribution (luminance distribution) of the liquid crystal display devices produced in Example 1 and Comparative Example 1. FIG. In addition, in the column of "θb" of Table 1, "-" means that the point which becomes 1/2 of the maximum value does not exist in the range of -80 degrees <= <= 80 degrees in the highest peak of light intensity. .

It is to be understood that the embodiments and examples disclosed herein are in all respects illustrative and not restrictive. The scope of the present invention is disclosed by the claims rather than the foregoing description, and is intended to include any modifications within the scope and meaning equivalent to the claims.

1, 2: polarizer,
3: liquid crystal cell,
10: liquid crystal panel,
12: polarizing film,
13: prism sheet,
13a: prism turning,
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,
W: plane orthogonal to the ridge direction of the prismatic protrusion,
T: normal direction of the light exit surface of the surface light source,
M: the emission direction of the exit light of the surface light source,
θ: the angle between the normal direction of the light exit surface of the surface light source and the exit direction of the exit light of the surface light source (emission angle),
P: hypotenuse of prismatic protrusion,
apex angle of α prism type projection.

Claims (5)

Surface Light Source,
A liquid crystal panel disposed on the surface light source and including a liquid crystal cell and a polarizing plate laminated on a surface of the surface light source side of the liquid crystal cell;
A liquid crystal display device composed of
The polarizing plate is provided with a prism sheet having a surface composed of a polarizing film and a prism-shaped protrusion laminated on the surface of the polarizing film through an adhesive layer,
The prism sheet is disposed such that a surface composed of the prism-shaped protrusions faces the surface light source,
The angle formed between the normal direction of the light exit surface of the surface light source and the exit direction of the exit light of the surface light source in a plane orthogonal to the ridge line direction of the prism-shaped protrusion is the output angle θ (wherein -90 ° ≤θ≤ 90 °), wherein the light intensity distribution of the surface light source showing the emission angle dependence of the light intensity of the emitted light satisfies the following (1) and (2):
(1) the peak of the light intensity has the highest peak within the range of −80 ° ≦ θ <-40 ° or 40 ° <θ ≦ 80 °,
(2) When the angle representing the maximum value of the light intensity at the peak is θa and the angle representing the half of the maximum value of the light intensity at the peak is θb, the expression | θa-θb | <30 ° [1] is satisfied. Sikkim. The liquid crystal display device of 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 of claim 2, wherein the light source device is a light source device including a point light source or a linear light source device, or a light source device including a bar light source.
And the light source device and the prism sheet are arranged such that the ridge lines of the light source device and the prism-shaped protrusion are parallel or approximately parallel to each other. The liquid crystal display device of claim 1, wherein the light source device is disposed on one side or two opposite sides of the light guide plate. The liquid crystal display device according to any one of claims 1 to 4, wherein the vertex angle (α) of the prismatic protrusions is 60 ° or more.

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