KR20160096545A - Composite polarizing plate and liquid crystal display device - Google Patents

Abstract

Provided are a composite polarizing plate and a liquid crystal display device. The composite polarizing plate includes an absorption type polarizing plate, a reflection type polarizing plate, a blue ray transmission preventing layer which prevents the transmission of a blue ray in a wavelength range of 380-500nm. The blue ray transmission preventing layer has an average transmittance of 90% or more in a wavelength range of 500-780nm and also average transmittance of 80% or more in the wavelength range of 380-500nm. So, contrast can be improved.

Description

Technical Field [0001] The present invention relates to a composite polarizer and a liquid crystal display,

The present invention relates to a composite polarizing plate including an absorption type polarizing plate and a reflection type polarizing plate, and a liquid crystal display using the same.

BACKGROUND ART [0002] Polarizing plates are widely used in liquid crystal display devices, particularly, in various mobile devices (small and medium liquid crystal display devices) such as smart phones and tablet type terminals. As the polarizing plate, an absorption type polarizing plate in which a protective film is bonded to one side or both sides of a polarizer (linearly polarizing element) in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin film is used.

With the development of a liquid crystal display device into a mobile device, a thin film of a polarizing plate is required to be reduced in weight and cost, and on the other hand, an improvement in display quality of a liquid crystal display device is also required. One of the display quality is the contrast. The contrast of the display device is represented by the following formula:

Contrast of the display device = (luminance at white display) / (luminance at black display)

. A high contrast means that a black and white image is clear and a clearer image is obtained, and is often used as one of visibility indicators in a display device. Another display quality is brightness (brightness of display screen). With the recent enhancement of the definition of liquid crystal panels, there is a high demand for higher brightness of liquid crystal display devices.

Japanese Patent No. 5147014 and Japanese Patent Laid-Open Publication No. 2001-228332 disclose patent documents relating to high contrast and high brightness of a liquid crystal display device.

As one of techniques for improving the contrast, there is a method of improving the polarization performance of the absorption type polarizing plate, that is, the simple transmittance and the polarization degree. However, when the contrast is increased by increasing the polarization degree, the single transmittance and hence the brightness are lowered. On the contrary, if the single transmittance is increased to increase the brightness, the polarization degree and hence the contrast are lowered. It has been difficult to achieve both high brightness and high contrast.

Japanese Patent No. 5147014 proposes that the emission wavelength characteristic of the backlight and the wavelength dependence of the single contrast of the polarizer of the absorption type polarizing plate have a specific relationship in order to improve the contrast of the liquid crystal display device. It was not easy to achieve high contrast.

On the other hand, as disclosed in Japanese Patent Application Laid-Open No. 2001-228332, a technique of arranging a reflection type polarizing plate (also referred to as a brightness enhancement film) between an absorbing type polarizing plate on the backlight side and a backlight for increasing the brightness of a liquid crystal display device Are conventionally known. However, when a reflective polarizer is combined with an absorbing polarizer having a high single transmittance in order to increase the brightness, there is a problem that the light leakage in the black display is increased and the contrast is lowered.

An object of the present invention is to provide a composite polarizing plate including an absorption type polarizing plate and a reflection type polarizing plate, which can realize a liquid crystal display device of high brightness and high contrast, and a liquid crystal display device using the same.

The present invention provides a composite polarizing plate and a liquid crystal display device shown below.

[1] A polarizing plate comprising an absorption type polarizing plate, a reflection type polarizing plate, and a blue light transmission inhibiting layer for suppressing transmission of blue light within a wavelength range of 380 to 500 nm,

Wherein the blue light transmission suppressing layer has an average transmittance over a wavelength range of 500 to 780 nm of 90% or more and an average transmittance over a wavelength range of 380 to 500 nm of 80% or less.

[2] The composite polarizer according to [1], wherein the absorbance-type polarizing plate has a visual sensitivity-corrected single unit transmittance of 42.6 to 44.0% and a visual sensitivity correction polarization degree of 99.5% or more.

[3] The composite polarizing plate described in [1] or [2], wherein the angle formed by the reflection axis of the reflection type polarizing plate and the absorption axis of the absorption type polarizing plate is 0 ± 4 °.

[4] The composite polarizing plate described in any one of [1] to [3], wherein the absorption type polarizing plate comprises a polarizer and a resin film laminated on at least one side thereof.

[5] The absorption type polarizing plate includes the polarizer, an acetic acid cellulose-based resin film laminated on one side thereof with an adhesive layer, and an annular polyolefin-based resin film laminated on the other side through an adhesive layer , And the complex polarizer described in [4].

[6] The absorption type polarizing plate according to any one of [1] to [6], wherein the absorption type polarizing plate comprises the polarizer and an acetic acid cellulose based resin film or a cyclic polyolefin based resin film laminated on one side thereof with an adhesive layer,

The composite polarizing plate according to [4], wherein the reflective polarizing plate is laminated on the other surface of the polarizer, or on the surface of the acetic acid cellulose based resin film or the annular polyolefin based resin film through a pressure sensitive adhesive layer.

[7] A backlight comprising a composite polarizer according to any one of [1] to [6], and a liquid crystal cell in this order,

Wherein the absorption type polarizing plate is disposed so as to be closer to the liquid crystal cell than the reflection type polarizing plate.

The luminescence intensities at the luminescence peak wavelengths of blue, green, yellow and red in the luminescence spectrum measured when the liquid crystal cell is laminated on the backlight and the backlight is turned on are expressed as L (Bmax), L (1) or the following formula (2): Lmax (Gmax), L (Ymax)

L (Bmax) / L (Ymax) > 1 (One)

L (Bmax) / L (Gmax) > 1, and L (Bmax) / L (2)

Is satisfied. ≪ / RTI >

According to the composite polarizing plate of the present invention, it is possible to realize a liquid crystal display device with high brightness and high contrast.

1 is a schematic cross-sectional view showing an example of the layer structure of a composite polarizing plate related to the present invention.
2 is a schematic sectional view showing another example of the layer structure of the complex polarizing plate related to the present invention.
3 is a schematic sectional view showing still another example of the layer structure of the complex polarizing plate related to the present invention.
4 is a schematic cross-sectional view showing an example of the layer structure of the liquid crystal display device according to the present invention.
5 is a graph showing an example of a luminescence spectrum measured by laminating a liquid crystal cell on a CCFL type backlight.
6 is a graph showing an example of a luminescence spectrum measured by laminating a liquid crystal cell on a backlight of a high color rendering type LED.
7 is a graph showing an example of a luminescence spectrum measured by laminating a liquid crystal cell on a backlight of a simulated white-type LED.

<Composite Polarizer>

The composite polarizing plate according to the present invention comprises an absorption type polarizing plate, a reflection type polarizing plate, and a blue light transmission inhibiting layer (blue light cut layer) for suppressing transmission of blue light within a wavelength range of 380 to 500 nm, The transmission suppressing layer has an average transmittance of 90% or more in a wavelength region of 500 to 780 nm and an average transmittance of 80% or less in a wavelength region of 380 to 500 nm. The composite polarizing plate exhibits brightness enhancement performance by a combination of an absorption type polarizing plate and a reflection type polarizing plate and has a high transmittance in a wavelength range of 500 to 780 nm and a blue light transmission inhibiting layer (Blue leak) of the blue light is effectively suppressed, thereby having a good luminance improving performance and a contrast improving performance. Therefore, the liquid crystal display device equipped with the complex polarizing plate according to the present invention can have high brightness and high contrast.

(1) Composition of composite polarizer

With reference to the drawings, an example of the layer structure of the complex polarizing plate related to the present invention is as follows, for example.

1 is a schematic cross-sectional view showing an example of the layer structure of a composite polarizing plate related to the present invention. 1 includes an absorption type polarizing plate 100, a reflection type polarizing plate 200 laminated on the absorption type polarizing plate 100, and a blue light transmission inhibiting layer (blue light cut layer) 300 laminated thereon In this order. In the composite polarizing plate 1, the absorption type polarizing plate 100 comprises a polarizer 5, a first protective film 10 laminated on one side thereof with a first adhesive layer 15, And a second protective film (20) laminated via a second adhesive layer (25) on the second adhesive layer (25). The reflection type polarizing plate 200 can be laminated on the absorption type polarizing plate 100 through the first pressure-sensitive adhesive layer 41. [ In the complex polarizing plate 1, the blue light transmission suppressing layer 300 is formed directly on the outer surface of the reflective polarizing plate 200.

2 is a schematic sectional view showing another example of the layer structure of the complex polarizing plate related to the present invention. The composite polarizing plate 2 shown in Fig. 2 uses a blue light transmission suppressing film (blue light cut film) 350 having a blue light transmission suppressing layer 300 on one side of the base film 301, Sensitive adhesive layer 42 on the outer surface of the reflection-type polarizing plate 200 in the same manner as the composite polarizing plate 1 shown in Fig. By using the blue light transmission suppressing film 350 and bonding it to the reflective polarizing plate 200 through the adhesive layer (or the adhesive layer or the like) in this way, the composite polarizing plate is provided with the contrast enhancing performance (blue leak suppressing function) It is possible.

As shown in Figs. 3 (a) and 3 (b), the absorption type polarizing plate may be a polarizing plate with a single side protective film. That is, in the composite polarizing plate 3 shown in FIG. 3A, the absorption type polarizing plate 110 includes a polarizer 5 and a first adhesive layer 15 laminated on one side thereof with a first adhesive layer 15 And a protective film (10). The reflection type polarizing plate 200 is laminated on the surface of the polarizer 5 opposite to the first protective film 10 with the first pressure sensitive adhesive layer 41 interposed therebetween. The blue light transmission suppressing layer 300 is formed directly on the outer surface of the reflection type polarizing plate 200.

On the other hand, the absorption type polarizing plate 120 constituting the composite polarizing plate 4 shown in FIG. 3 (b) also has a polarizer 5 and a first adhesive layer 15 laminated on one side thereof The reflection type polarizing plate 200 is laminated on the outer surface of the first protective film 10 through the first pressure sensitive adhesive layer 41, The blue light transmission suppressing layer 300 is formed directly on the outer surface of the reflection type polarizing plate 200. The blue light transmission suppressing film 350 may be used in place of the blue light transmission suppressing layer 300 in the composite polarizing plates 3 and 4 shown in Figs. 3A and 3B.

The composite polarizers 1, 2, 3 and 4 may be formed of another optical functional layer (or film) laminated on the outer surface of the first protective film 10, the polarizer 5 and / or the blue light transmission suppressing layer 300 A separator film (also referred to as a &quot; release film &quot;) laminated on the outer surface of the pressure-sensitive adhesive layer, and a protective film. The optically functional layer (or film) may be interposed inside the outermost surface of the composite polarizing plate, not inside the outermost surface.

(2) Optical characteristics of absorption type polarizing plate

From the viewpoint of achieving both brightness enhancement performance and contrast enhancement performance, the absorbance-type polarizers 100, 110, and 120 preferably have a visible light-transmissive unity transmittance Ty of 42.6 to 44.0%, more preferably 42.9 to 44.0% , And more preferably 42.9 to 43.5%. If Ty is less than 42.6%, the transmittance is too low and a sufficiently high luminance is hardly obtained. If the Ty exceeds 44.0%, the contrast tends to decrease.

From the viewpoint of improving the contrast, the absorption type polarizers 100, 110, and 120 preferably have a visibility correction polarization degree Py of 99.5% or more, more preferably 99.9% or more, and still more preferably 99.95% or more. The method of measuring the visibility-sensitive corrected single-beam transmittance (Ty) and the visual sensitivity correction polarization degree (Py) is as described in the following embodiments.

(3) Polarizer

The polarizer 5 is an absorption type polarizer that absorbs linearly polarized light having a vibration plane parallel to its absorption axis and transmits linearly polarized light having a vibration plane perpendicular to the absorption axis (parallel to the transmission axis) A polarizing film in which a dichromatic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film can be suitably used. The polarizer 5 is, for example, a step of uniaxially stretching a polyvinyl alcohol-based resin film; A step of adsorbing a dichroic dye by staining a polyvinyl alcohol resin film with a dichroic dye; A step of treating a polyvinyl alcohol resin film adsorbed with a dichroic dye with an aqueous solution of boric acid; And a step of washing with water after treatment with an aqueous boric acid solution.

As the polyvinyl alcohol-based resin, a saponified polyvinyl acetate-based resin can be used. As the polyvinyl acetate resin, a copolymer of vinyl acetate, which is a homopolymer of vinyl acetate, and other monomers copolymerizable with vinyl acetate, and the like can be given. Examples of other monomers copolymerizable with vinyl acetate include (meth) acrylamides having unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids and ammonium groups, and the like. In the present specification, "(meth) acryl" means at least one selected from acrylic and methacrylic. Quot ;, &quot; (meth) acryloyl &quot;, and the like.

The degree of saponification of the polyvinyl alcohol resin is generally about 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol resin may be modified. For example, polyvinyl formal or polyvinyl acetal modified with aldehyde may be used. The average degree of polymerization of the polyvinyl alcohol resin is usually about 1000 to 10000, preferably about 1500 to 5000. The average polymerization degree of the polyvinyl alcohol resin can be determined in accordance with JIS K 6726.

Such a polyvinyl alcohol resin film is used as the original film of the polarizer 5. The method of forming the polyvinyl alcohol resin is not particularly limited, and a known method is employed. The thickness of the polyvinyl alcohol original film is, for example, 150 占 퐉 or less, and preferably 100 占 퐉 or less (for example, 50 占 퐉 or less).

The uniaxial stretching of the polyvinyl alcohol resin film can be performed before, simultaneously with, or after dyeing the dichroic dye. In the case where uniaxial stretching is carried out after dyeing, this uniaxial stretching may be carried out before the boric acid treatment or during the boric acid treatment. In addition, uniaxial stretching may be performed in these plural stages.

In the uniaxial stretching, the uniaxial stretching may be performed between rolls different in the main speed, or may be uniaxially stretched using a heat roll. The uniaxial stretching may be dry stretching in which drawing is performed in the air, or wet stretching in which stretching is performed in a state in which a polyvinyl alcohol resin film is swollen with a solvent or water. The stretching magnification is usually about 3 to 8 times.

As a method for dyeing a polyvinyl alcohol resin film with a dichroic dye, for example, a method of immersing the film in an aqueous solution containing a dichroic dye is employed. As the dichroic dye, iodine or a dichroic organic dye is used. It is preferable that the polyvinyl alcohol resin film is subjected to immersion treatment in water before the dyeing treatment.

As a dyeing treatment by iodine, a method of immersing a polyvinyl alcohol resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The content of iodine in the aqueous solution may be about 0.01 to 1 part by weight per 100 parts by weight of water. The content of potassium iodide may be about 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution may be about 20 to 40 캜. On the other hand, as a dyeing treatment with a dichroic organic dye, a method of immersing a polyvinyl alcohol resin film in an aqueous solution containing a dichroic organic dye is usually employed. The aqueous solution containing the dichroic organic dye may contain an inorganic salt such as sodium sulfate as a dyeing aid. The content of the dichroic organic dye in this aqueous solution may be about 1 × 10 ^-4 to 10 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution may be about 20 to 80 캜.

As a boric acid treatment after dyeing with a dichroic dye, a method of immersing a dyed polyvinyl alcohol resin film in an aqueous solution containing boric acid is usually employed. When iodine is used as the dichroic dye, it is preferable that the aqueous solution containing boric acid contains potassium iodide. The amount of boric acid in the aqueous solution containing boric acid may be about 2 to 15 parts by weight per 100 parts by weight of water. The amount of potassium iodide in this aqueous solution may be about 0.1 to 15 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution may be 50 ° C or higher, for example, 50 to 85 ° C.

The polyvinyl alcohol resin film after boric acid treatment is usually subjected to water washing treatment. The water washing treatment can be carried out, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. The water temperature in the water washing treatment is usually about 5 to 40 캜. After washing with water, a drying treatment is carried out to obtain a polarizer 5. The drying treatment can be performed using a hot-air dryer or a far-infrared heater.

As another example of the production method of the polarizer 5, there may be mentioned, for example, the methods described in JP-A-2000-338329 and JP-A-2012-159778. In this method, a solution containing a polyvinyl alcohol-based resin is applied to the surface of a base film to form a resin layer, and then a laminated film comprising a base film and a resin layer is stretched, followed by dyeing treatment and crosslinking treatment Thereby forming a polarizer layer from the resin layer. The polarizing laminated film comprising the base film and the polarizer layer is obtained by bonding a protective film or the like to the polarizer layer surface and then peeling off the base film to obtain a polarizing plate 5 having a protective film or the like on one surface thereof, . When the protective film is further bonded to the surface of the polarizer layer exposed by the peeling of the base film, it becomes a polarizing plate with a double-side protective film.

The thickness of the polarizer 5 may be 40 占 퐉 or less, preferably 30 占 퐉 or less (for example, 20 占 퐉 or less, further 15 占 퐉 or less, further 10 占 퐉 or less). According to the method described in Japanese Patent Application Laid-Open Nos. 2000-338329 and 2012-159778, a thin film polarizer 5 can be manufactured more easily, and the thickness of the polarizer 5 is set to, for example, 20 Mu m or less, more preferably 15 mu m or less, and further more, 10 mu m or less. The thickness of the polarizer 5 is usually 2 占 퐉 or more. Reducing the thickness of the polarizer 5 is advantageous for reducing the thickness of the composite polarizing plate, and furthermore, the liquid crystal display device.

As a specific method for adjusting the visual sensitivity-corrected single transmittance Ty and the visual sensitivity correction polarity Py in the above-described preferred numerical range in the polarizer 5 obtained by the above-described method, for example, The dyeing temperature and the dyeing time, or adjusting the temperature and time in the drying process.

(4) The first and second protective films

Each of the first and second protective films 10 and 20 may be a resin film. Specifically, the first and second protective films 10 and 20 may be made of a transparent (preferably optically transparent) resin such as a polyolefin resin And the like), a polyolefin-based resin such as a cyclic polyolefin-based resin (norbornene-based resin and the like); Cellulose acetate resins such as triacetylcellulose and diacetylcellulose; Polyester-based resin; Polycarbonate resin; (Meth) acrylic resins; Polystyrene type resin; Or a mixture or copolymer thereof, or a film made of a thermoplastic resin. In the absorption type polarizing plate 100 with a double-sided protective film, the first protective film 10 and the second protective film 20 may be either a protective film made of the same kind of resin or a protective film made of different kinds of resins .

The first and / or second protective films 10 and 20 may be protective films having an optical function such as a retardation film. For example, a phase difference film having an arbitrary retardation value can be obtained by stretching the film (uniaxial stretching or biaxial stretching) of the thermoplastic resin or forming a liquid crystal layer or the like on the film.

Examples of the chain type polyolefin type resin include a homopolymer of a chain type olefin such as a polyethylene resin and a polypropylene resin, and a copolymer comprising two or more kinds of chain type olefins.

The cyclic polyolefin-based resin is a generic name of a resin that is polymerized using a cyclic olefin as a polymerization unit. Specific examples of the cyclic polyolefin-based resin include ring-opened (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and chain olefins such as ethylene and propylene (typically, random copolymers ), Graft polymers obtained by modifying these with an unsaturated carboxylic acid or a derivative thereof, and hydrides thereof. Of these, norbornene-based resins using norbornene monomers such as norbornene and polycyclic norbornene-based monomers as the cyclic olefins are preferably used.

Acetic acid cellulose-based resin is partly or completely acetic acid esterified product of cellulose, and examples thereof include triacetyl cellulose (TAC), diacetyl cellulose, cellulose acetate propionate and the like.

The polyester-based resin is a resin other than the above-mentioned cellulose acetate-based resin having an ester bond, and is generally composed of a polycondensation product of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. As the polycarboxylic acid or its derivative, a dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethylterephthalate, and dimethyl naphthalenedicarboxylate. Examples of polyhydric alcohols include diols such as ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol.

Specific examples of the polyester-based resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexanedimethyl terephthalate, polycyclohexane Dimethyl naphthalate.

The polycarbonate resin is composed of a polymer to which a monomer unit is bonded through a carbonate group. The polycarbonate resin may be a resin called a modified polycarbonate such as a modified polymer skeleton, or a copolymerized polycarbonate.

The (meth) acrylic resin is a resin mainly composed of a compound having a (meth) acryloyl group. Specific examples of the (meth) acrylic resin include poly (meth) acrylic acid esters such as polymethyl methacrylate; Methyl methacrylate- (meth) acrylic acid copolymer; Methyl methacrylate- (meth) acrylic acid ester copolymer; Methyl methacrylate-acrylic acid ester- (meth) acrylic acid copolymer; (Meth) acrylate-styrene copolymer (MS resin and the like); A copolymer of a compound having an alicyclic hydrocarbon group and a methyl methacrylate (e.g., a methyl methacrylate-cyclohexyl copolymer, a methacrylic acid methyl- (meth) acrylate norbornyl copolymer, etc.). Preferably, a polymer mainly composed of a poly (meth) acrylate C _1-6 alkyl ester such as poly (meth) acrylate is used, more preferably methyl methacrylate as a main component (50 to 100 wt% By weight, preferably 70 to 100% by weight) is used.

A surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer is formed on the surface of the first and / or second protective films 10 and 20 opposite to the polarizer 5 You may.

The thickness of the first and second protective films 10 and 20 is preferably not more than 90 占 퐉, more preferably not more than 50 占 퐉, still more preferably not more than 40 占 퐉, from the viewpoint of thinning of the composite polarizing plate and the liquid crystal display device to be. The thickness is usually 5 占 퐉 or more from the viewpoints of strength and handling property.

For example, when the first protective film 10 is a cyclic polyolefin resin film (norbornene resin film or the like) and the second protective film 20 is a cellulose acetate resin The absorbing polarizer 100 with a double-sided protective film as a film (TAC film or the like) and the first protective film 10 are laminated on a cyclic polyolefin resin film (norbornene resin film or the like) or an acetic acid cellulose resin film A TAC film or the like), and the like. In these embodiments, the first protective film 10 may be a retardation film having an in-plane retardation value and / or a thickness retardation value in accordance with the type or the like of the liquid crystal cell.

It is also a preferred embodiment that at least one protective film to be bonded to the polarizer 5 is a resin film having a low moisture permeability. This makes it possible to suppress the deterioration of the optical characteristics of the polarizer 5 under a high humidity environment or a high temperature and high humidity environment. The moisture permeability of the protective film is preferably 400 g / m ² · 24 hr or less, more preferably 300 g / m ² · 24 hr or less, and more preferably 100 g / m ² · 24 hr or less, and particularly preferably 50 g / m ² · 24 hr or less.

(5) The first and second adhesive layers

As the adhesive forming the first and second adhesive layers 15 and 25, an aqueous adhesive or an active energy ray-curable adhesive may be used. The adhesive forming the first adhesive layer 15 and the adhesive forming the second adhesive layer 25 may be the same or different.

Examples of the water-based adhesive include an adhesive comprising an aqueous solution of a polyvinyl alcohol resin, an aqueous two-component type urethane emulsion adhesive, and the like. Among them, an aqueous adhesive comprising a polyvinyl alcohol resin aqueous solution is suitably used.

Examples of the polyvinyl alcohol resin include a polyvinyl alcohol copolymer obtained by saponifying a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate which is a homopolymer of vinyl acetate, as well as a copolymer of vinyl acetate and another monomer copolymerizable therewith , Or a modified polyvinyl alcohol polymer obtained by partially modifying the hydroxyl group of these polymers. The water-based adhesive may include additives such as polyvalent aldehyde, water-soluble epoxy compound, melamine compound, zirconia compound, and zinc compound.

When an aqueous adhesive is used, it is preferable to carry out a drying step in which the polarizer 5 is bonded to the protective film and then dried to remove water contained in the aqueous adhesive. After the drying step, a curing step may be provided for curing at a temperature of, for example, 20 to 45 ° C.

The active energy ray-curable adhesive refers to an adhesive that cures by irradiating active energy rays such as ultraviolet rays. Examples thereof include those containing a polymerizable compound and a photopolymerization initiator, those containing a photoreactive resin, a binder resin and a photoreactive crosslinking agent And the like. Examples of the polymerizable compound include photopolymerizable monomers such as a photocurable epoxy monomer, a photocurable (meth) acrylic monomer, a photocurable urethane monomer, and an oligomer derived from a photopolymerizable monomer. Examples of the photopolymerization initiator include materials that generate active species such as neutral radicals, anion radicals, and cation radicals upon irradiation with active energy rays such as ultraviolet rays. As the active energy ray-curable adhesive containing a polymerizable compound and a photopolymerization initiator, those containing a photocurable epoxy-based monomer and a photocationic polymerization initiator can be preferably used.

In the case of using an active energy ray-curable adhesive, a curing step of curing the active energy ray-curable adhesive is carried out by bonding the polarizer 5 and the protective film, then performing a drying step if necessary, and then irradiating with an active energy ray. Although a light source of an active energy ray is not particularly limited, ultraviolet rays having a light emission distribution at a wavelength of 400 nm or less are preferable, and specifically, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, a high pressure mercury lamp, A mercury lamp, a metal halide lamp, or the like can be used.

Prior to bonding of the polarizer 5 and the protective film using the adhesive, surface activation treatment such as plasma treatment, corona treatment, ultraviolet ray irradiation treatment, flame treatment may be performed on the bonding surface of the polarizer 5 and / (Flame) treatment, saponification treatment or the like may be carried out.

(6) Pressure-sensitive adhesive layer and other layers

The composite polarizing plate is applied to the other surface of the first protective film 10 in the absorption type polarizing plates 100 and 110 or the outer surface of the polarizing plate 5 in the absorption type polarizing plate 120 (For example, a liquid crystal cell or another optical film in the case of a liquid crystal cell) or the like (see Fig. 4, for example). The pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer generally comprises a pressure-sensitive adhesive composition in which a base polymer is a (meth) acrylic resin, a styrene-based resin, a silicone resin or the like and a crosslinking agent such as an isocyanate compound, an epoxy compound or an aziridine compound is added thereto . It is also possible to use a pressure-sensitive adhesive layer containing fine particles and exhibiting light scattering properties. The thickness of the pressure-sensitive adhesive layer may be 1 to 40 占 퐉, but it is preferable that the pressure-sensitive adhesive layer is formed thinly within a range not deteriorating the workability and durability characteristics, and specifically, it is preferably 3 to 25 占 퐉.

The method of forming the pressure-sensitive adhesive layer is not particularly limited, and a pressure-sensitive adhesive composition (pressure-sensitive adhesive solution) containing each component including the base polymer described above may be coated on the surface of a protective film or the like and dried to form a pressure- After the pressure-sensitive adhesive layer is formed on the film (release film), the pressure-sensitive adhesive layer may be transferred onto the surface of a protective film or the like. When the pressure-sensitive adhesive layer is formed on the surface of a protective film or the like, surface activation treatment such as plasma treatment, corona treatment, or the like may be performed on the bonding surface of the protective film and / or the bonding surface of the pressure-

The above description of the pressure-sensitive adhesive layer can be applied to the first pressure-sensitive adhesive layer 41 shown in Figs. 1 and 3 and the second pressure-sensitive adhesive layer 42 shown in Fig.

The polarizing plate may include a separate film laminated on the outer surface of the pressure-sensitive adhesive layer. The separator film may be a film made of a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, or a polyester-based resin such as polyethylene terephthalate. Among them, a stretched film of polyethylene terephthalate is preferable.

The absorption type polarizing plate 120 is bonded to the outer surface of the first protective film 10 in the absorption type polarizing plates 100 and 110 or the outer surface of the polarizing plate 5 in the absorption type polarizing plate 120 through an adhesive layer or a pressure- An optical film having an optical function may be laminated. Examples of such an optical film include an optical compensation film on which a liquid crystal compound is applied and oriented on the surface of a substrate; And a retardation film made of a polycarbonate resin or a cyclic polyolefin resin.

(7) Manufacturing method of absorption type polarizing plate

The first protective film 10 is bonded to one side of the polarizer 5 according to a conventional method through the first adhesive layer 15 to form the protective film 10 with the one side protective film shown in Figs. Absorption type polarizing plates 110 and 120 can be obtained. When the second protective film 20 is bonded to the other surface of the polarizer 5 through the second adhesive layer 25, the absorption type polarizing plate 100 with the double-sided protective film shown in Figs. 1 and 2 . In the case of obtaining the absorption type polarizing plate 100, the first and second protective films 10 and 20 may be bonded at the same time or sequentially.

The present invention is not limited to a method of bonding a protective film to a polarizer 5 made of a single (single) film, but it is also possible to use a base film for supporting a polyvinyl alcohol- A polarizing plate may be produced. In this case, the absorption type polarizing plates 110 and 120 having a one-side protective film are formed by, for example,

A resin layer forming step of forming a polyvinyl alcohol resin layer by coating a coating solution containing a polyvinyl alcohol resin on at least one surface of a base film and then drying the resin film to obtain a laminated film,

A stretching step of uniaxially stretching the laminated film to obtain a stretched film,

A dyeing step of dying a polyvinyl alcohol resin layer of a stretched film with a dichroic dye to form a polarizer 5 to obtain a polarizing laminated film,

A first bonding step of bonding the first protective film 10 to the polarizer 5 of the polarizing laminated film to obtain a bonded film,

A peeling process for peeling off the base film from the bonding film to obtain the absorption type polarizing plates 110 and 120 with a one side protective film

In this order.

In the case of manufacturing the absorption type polarizing plate 100 having the double-sided protective film shown in Figs. 1 and 2, the method of manufacturing the absorption type polarizing plate is such that after the peeling step,

A second bonding step of bonding the second protective film 20 to the surface of the absorption type polarizing plates 110 and 120 on the side of the polarizer 5

.

(8) Reflection-type polarizing plate and lamination of reflection type polarizing plate to absorption type polarizing plate

The reflection type polarizing plate 200 is a polarization conversion element having a function of separating backlight light into transmission polarized light and reflected polarized light or scattered polarized light. By arranging the reflection type polarizing plate 200 on the absorption type polarizing plates 100, 110, and 120, the utilization efficiency of the backlight can be improved, so that the brightness of the liquid crystal display can be improved. As the reflection type polarizing plate 200, a commercially available one may be used. The reflective polarizing plate 200 is disposed on the side opposite to the liquid crystal cell in the absorbing polarizers 100, 110, and 120 when the liquid crystal display is constructed by laminating the composite polarizing plate on the liquid crystal cell.

The reflection-type polarizing plate 200 may be, for example, an anisotropic reflection polarizer. An example of the anisotropic reflective polarizer is an anisotropic multi-layer film which transmits linearly polarized light in one vibration direction and reflects linearly polarized light in the other vibration direction, and specific examples thereof are &quot; DBEF &quot; -268505, etc.) and "APF" (available from 3M, available from Sumitomo 3M Ltd.). Another example of the anisotropic reflective polarizer is a composite of a cholesteric liquid crystal layer and a? / 4 plate, and a specific example thereof is "PCF" manufactured by Nitto Denko (Japanese Patent Laid-Open Publication No. 11-231130). Another example of the anisotropic reflective polarizer is a reflective grid polarizer. Specific examples thereof include metal lattice reflective polarizers (such as U.S. Patent No. 6288840) such as those in which fine processing of metal is performed to emit reflected polarized light even in the visible light region, (Japanese Patent Application Laid-Open No. 184701/1990) which is obtained by adding metal fine particles to a polymer matrix.

The thickness of the reflection type polarizing plate 200 may be about 10 to 100 占 퐉, but is preferably 10 to 50 占 퐉, from the viewpoint of thinning of the composite polarizing plate and the liquid crystal display device. The reflection type polarizing plate 200 can be laminated on the absorption type polarizing plates 100, 110 and 120 through the first pressure sensitive adhesive layer 41 as shown in FIGS. However, bonding may be performed using an adhesive. 1 and 2, the reflection type polarizing plate 200 is laminated on the second protective film 20 through the first pressure sensitive adhesive layer 41. In FIG. 3 (a), the reflection type polarizing plate 200 The reflection type polarizing plate 200 is laminated on the polarizer 5 through the first pressure sensitive adhesive layer 41 and the reflection type polarizing plate 200 is bonded to the first pressure sensitive adhesive layer 41 through the first pressure sensitive adhesive layer 41, Is laminated on the film (10). An optical functional layer such as a hard coat layer, an antiglare layer, a light diffusion layer, and a retardation layer (retardation film) having a retardation value of 1/4 wavelength is formed on the surface of the reflective polarizing plate 200 opposite to the pressure- . Further, a protective film, a retardation film, or the like may be disposed between the reflective polarizer 200 and the blue light transmission suppressing layer 300.

The reflection type polarizing plate 200 is arranged on the absorption type polarizing plates 100, 110, and 120 so that the angle? Between the reflection axis thereof and the absorption axis of the absorption type polarizing plates 100, . Parallel "or" substantially parallel "means that the angle α is 0 ± 4 °. The angle? Within the above range is advantageous from the viewpoint of suppressing light leakage during black display and further improving the contrast of the liquid crystal display device. The method of measuring the angle? Is described in the description of the following embodiments.

(9) Blue light transmission inhibiting layer

The blue light transmission suppressing layer 300 is a layer for suppressing transmission of blue light within a wavelength range of 380 to 500 nm and is preferably a layer for suppressing the transmission of blue light over the entire wavelength range. The blue light transmission suppressing layer 300 preferably has an average transmittance T (500-780) over a wavelength range of 500 to 780 nm of 90% or more, preferably 95% or more to be. In order to impart good contrast enhancement performance to the composite polarizing plate, the blue light transmission suppressing layer 300 preferably has an average transmittance T (380-500) of 80% or less, and preferably 75 % Or less. The average transmittance T (500-780) of the blue light transmission suppressing layer 300 over a wavelength range of 500 to 780 nm is measured by measuring the transmittance at each wavelength (5 nm pitch) using a spectrophotometer, nm &lt; / RTI &gt; The same applies to the average transmittance T (380 to 500) over the wavelength range of 380 to 500 nm.

2, the blue light transmission suppressing layer 300 is introduced into the complex polarizing plate in the form of a blue light transmission suppressing film 350 having a blue light transmission suppressing layer 300 on one side of the base film 301 You may. The blue light transmission suppressing layer 300 need not be laminated on the surface of the base film 301. For example, the blue light transmission suppressing layer 300 may be a three-layer structure film having the blue light transmission suppressing layer 300 as an inner layer, Alternatively, the blue light transmission suppressing layer 300 may be the base film 301 itself having a blue light transmission suppressing function.

The base film 301 may be made of a thermoplastic resin having light transmittance (preferably optically transparent), and the specific examples of the above-mentioned protective film are cited. Among them, the base film 301 is preferably composed of a resin selected from the group consisting of a cyclic polyolefin resin, a polycarbonate resin, a cellulose ester resin, a polyester resin, and a (meth) acrylic resin .

The base film 301 may have a retardation property, or may be a retardation film (retardation film) such as a? / 2 plate or a? / 4 plate. / 4 plate. Retardation properties are imparted to the base film 301 and the base film 301 (preferably a? / 4 plate) is laminated on the outer side of the reflection type polarizing plate 200 (the liquid crystal display is constructed by laminating the composite polarizing plate on the liquid crystal cell (On the side opposite to the liquid crystal cell (and the absorption type polarizing plates 100, 110, and 120) in the reflection type polarizing plate 200), it is possible to give a better luminance improving performance to the composite polarizing plate.

When the base film 301 is a lambda / 4 plate, the blue light transmission suppressing film 350 is formed so that the slow axis direction of the base film 301 is approximately coincident with the reflection axis direction of the reflective polarizer 200 Lt; RTI ID = 0.0 &gt; 135 &lt; / RTI &gt; About 45 ° means 45 ° ± 20 °, and about 135 ° means 135 ° ± 20 °. If the angle? ₁ of the slow axis of the base film 301 with respect to the direction of the reflection axis of the reflection type polarizing plate 200 is out of the above range, the effect of improving the brightness tends to become insufficient. The angle? ₁ (reference axis of the reflection axis of the reflection type polarizing plate 200, counterclockwise) is preferably 45 ± 10 ° or 135 ± 10 °, more preferably 45 ± 5 ° or 135 ± 5 °. The base film 301 as a phase difference plate is a stretched film made of a resin selected from the group consisting of a cyclic polyolefin resin, a polycarbonate resin, a cellulose ester resin, a polyester resin, and a (meth) .

The thickness of the blue light transmission suppressing layer 300 is 0.1 to 100 占 퐉 and the thickness of the blue light transmission suppressing film 350 composed of the blue light transmission suppressing layer 300 and the base film 301 is 5 to 300 占 퐉 to be. As the blue light transmission suppressing layer 300 and the blue light transmission suppressing film 350, those having a conventionally known structure may be used, or a commercially available product may be used.

The blue light transmission suppression film 300 and the blue light transmission suppression film 350 for suppressing the transmission of blue light are formed by suppressing transmission (absorbing type) by absorbing the blue light and suppressing transmission by reflecting the blue light Reflection type). In the present invention, any type can be used.

The arrangement position of the blue light transmission suppressing layer 300 or the blue light transmission suppressing film 350 in the composite polarizing plate is not particularly limited. The absorption type polarizing plates 100, 110 and 120, the reflection type polarizing plate 200 and the blue light transmission suppressing layer 300 or the blue light transmission suppressing film 350 are arranged in this order The blue light transmission suppressing layer 300 or the blue light transmission suppressing film 350 may be disposed on the side opposite to the absorption type polarizing plates 100, 110 and 120 in the reflection type polarizing plate 200, (For example, between the absorption type polarizing plates 100, 110 and 120 and the reflection type polarizing plate 200 on the side opposite to the reflection type polarizing plate 200 in the absorption type polarizing plates 100, 110 and 120).

When the blue light transmission suppressing layer 300 or the blue light transmission suppressing film 350 is of a reflective type, when the liquid crystal display device is constructed by laminating the complex polarizing plate on the liquid crystal cell, the blue light transmission suppressing film 300, When the liquid crystal cell 350 is disposed between the liquid crystal cell and the absorption type polarizing plates 100, 110 and 120 or between the absorption type polarizing plates 100, 110 and 120 and the reflection type polarizing plate 200, The blue light transmission suppression film 350 may be a polarization dissipation element. Therefore, in the case of the reflection type, it is preferable that the blue light transmission suppressing layer 300 or the blue light transmission suppressing film 350 is disposed on the side opposite to the absorption type polarizing plates 100, 110, and 120 in the reflection type polarizing plate 200 .

(10) Properties of composite polarizer

According to the composite polarizing plate of the present invention, the luminance and contrast of the liquid crystal display device to which the present invention is applied can be increased. The luminance of the liquid crystal display can be measured by a commercially available luminance meter or spectroscopic radiation meter. The luminance values measured by these measuring apparatuses are those for which visibility is corrected.

On the other hand, the luminance and contrast of a liquid crystal display can be evaluated by actually constructing a liquid crystal display device and directly measuring its luminance and contrast. However, the transmittance (T _x (?) Or T _y (L) (= expression (3)) obtained by white display in which the luminosity correction is performed by multiplying the luminous intensity P (?) of each wavelength? in the "combination of liquid crystal cell and backlight" And the contrast (S _CR ) defined by the ratio of the luminance (L) at the time of white display to the luminance at the time of black display (= denominator of the following formula (3)). The luminance (L) and contrast (S _CR ) as these indicators can be values in the wavelength range of 380 to 780 nm and are respectively referred to as L (380-780) and S _CR (380-780). The larger the L (380-780) and the S _CR (380-780), the higher the luminance and contrast of the liquid crystal display device.

S _CR (380-780) is represented by the following formula (3):

. The numerator of the right side in the formula (3) is the cumulative value of P (?) - y (?) - T _X (?) At a wavelength of 380 to 780 nm and the denominator is an integrated value of P (? ), Y (?), And T _Y (?). In the present invention, respectively, P at a wavelength of 380~780 nm The accumulated value in the actual measurement of the _{S CR (380-780) (λ)} · y (λ) · T X (λ), P (λ) · y (?) - T _Y (?) is measured at a pitch of 5 nm.

In the above formula (3), P (?) Is the luminescence intensity measured when the liquid crystal cell is stacked on the backlight and the backlight is lit, and y (?) Is the 2-degree viewing- Is a function of the non-viscous sensitivity in the visual sense). Further, T _x (?) And T _y (?) Satisfy the following equations (4) and (5)

T _X (λ) = 0.5 × [Tp (λ) ² + Tc (λ) ² ] / 100 (4)

T _Y (?) = Tp (?) Tc (?) / 100 (5)

.

Tp (?) In the formulas (4) and (5) is the transmittance (%) of the composite polarizing plate measured by the relationship between the linearly polarized light of incident wavelength? Nm and the parallel Nicol, and Tc Is the transmittance (%) of the composite polarizing plate measured by the relationship between linearly polarized light of wavelength? Nm and Cross-Nicol. A spectrophotometer is used as a measuring device for Tp (?) And Tc (?). In order to more accurately evaluate the Tc (?) Value, it is necessary to use a spectrophotometer capable of measuring up to a higher absorbance region, specifically, a spectrophotometer capable of measuring an absorbance of about 7 to 8 is used. Examples of such a spectrophotometer include a spectrophotometer &quot; V7100 &quot; manufactured by Nihon Spectroscopy. As a method for introducing linearly polarized light, a method using a polarizing prism made of calcite or the like is generally known, and the extinction ratio of the polarizing prism is set to 10 ^-5 or less.

When the constituent layers (for example, the protective film of the absorption type polarizing plate or the base film of the blue light transmission suppressing film) included in the composite polarizing plate do not substantially have the retardation characteristics (specifically, the retardation of the phase difference at the wavelength of 590 nm R _e) and the thickness direction phase aside (R _th) is 10 nm or less), or even if they have the retardation characteristics, in the case that the slow axis is that the absorption axis of the polarizer is parallel or perpendicular, as the composite polarizer S _CR (380-780). On the other hand, in the case where layers having retardation characteristics are disposed on both surfaces of the polarizer and their slow axes are neither parallel nor orthogonal to the absorption axis of the polarizer, Tp (?) And Tc If the protective film of the absorption type polarizing plate has a retardation property, the protective film may be peeled off from the absorption type polarizing plate to form a laminate of the reflection type polarizing plate and the blue light transmission suppressing layer, Type polarizing plate and the reflection type polarizing plate and the blue light transmission suppressing layer are laminated on the same polarizer as that contained in the polarizing plate.

The in-plane phase difference value (R _e ) and the thickness direction phase difference value (R _th )

R _e = (n _x -n _y ) x d

_{R th = [(n x +} n y) / 2-n z] × d

. Wherein, n _x is a refractive index of the refractive index and, n _y is a (y-axis direction orthogonal to the x axis within the plane), the fast axis direction in the film plane of the slow axis direction (x axis direction) in the film plane, n _z is Is the refractive index in the film thickness direction (z-axis direction perpendicular to the film surface), and d is the thickness of the film.

From the viewpoint of the contrast of the liquid crystal display device, the complex polarizer according to the present invention preferably has S _CR (380-780) of 30,000 or more, more preferably 40,000 or more.

<Liquid Crystal Display Device>

4 showing a layer structure of a liquid crystal display device according to the present invention, a liquid crystal display device according to the present invention includes a backlight 60, a complex polarizing plate related to the present invention, and a liquid crystal cell 50, In order. Fig. 4 shows an example using the composite polarizing plate 1 shown in Fig. 1 as a composite polarizing plate. The composite polarizers 1, 2, 3 and 4 are generally used as a polarizer on the back side (backlight side) and the absorption type polarizers 100, 110 and 120 are disposed on the liquid crystal cell 50 side . When the composite polarizers 1, 2, 3 and 4 include the absorption type polarizing plates 100, 110 and 120, the reflection type polarizing plate 200 and the blue light transmission suppressing layer 300 in this order, The transmissive suppression layer 300 becomes the backlight 60 side. The composite polarizers 1, 2, 3 and 4 can be laminated on the liquid crystal cell 50 through the third pressure-sensitive adhesive layer 43. [ The driving method of the liquid crystal cell 50 may be any conventionally known method, but is preferably an in-plane switching (IPS) mode or a vertically aligned (VA) mode.

The liquid crystal display further includes a front side (viewing side) polarizing plate 70 laminated on a surface opposite to the side on which the back side polarizing plate (a composite polarizing plate related to the present invention) in the liquid crystal cell 50 is stacked . The front-side polarizing plate 70 can also be laminated on the liquid crystal cell 50 through the pressure-sensitive adhesive layer. The front-side polarizing plate 70, the liquid crystal cell 50, and the rear-side polarizing plate constitute a liquid crystal panel.

The spectrum of the light emitted through the liquid crystal cell 50 when the liquid crystal cell 50 is laminated without the composite polarizing plate laminated on the backlight 60 and the backlight 60 is lit is not the same in the propagation field, Strength exists. This intensity is determined by the emission spectrum from the backlight and the design of the color filter of the liquid crystal cell 50.

Figs. 5 to 7 show examples of luminescence spectra measured when a liquid crystal cell is stacked on a backlight and the backlight is turned on. FIG. 5 shows an example using a cold cathode fluorescent lamp (CCFL) as a backlight, FIG. 6 shows an example using a light emitting diode (LED) of a high color rendering type, This is an example used. Since the design of the color filter of the liquid crystal cell is important for the color production of the liquid crystal display device, the design of the color filter is different for each color, and the color filter of three colors, red (R), green many. The shape of the luminescence spectrum when the liquid crystal cell is laminated on the backlight is also somewhat characteristic in that the principle of light emission differs depending on the type of backlight.

The shape of the luminescence spectrum when the liquid crystal cell is laminated on the backlight is roughly divided into two types. One type is a type including three emission peaks of blue (B), green (G) and red (R) (hereinafter also referred to as BGR type) as shown in Figs. 5 and 6. One other type is a type including two emission peaks of blue (B) and sulfur (Y) (hereinafter also referred to as BY type) as shown in Fig.

According to the complex polarizing plate of the present invention, it is possible to realize a liquid crystal display device having a high luminance and a high contrast at any type of luminescence spectrum, but the present invention is particularly effective in a luminescence spectrum in which the luminescence intensity in the blue region is high. That is, in order to obtain a high luminance by relatively increasing the visible light transmittance corrected Ty of the absorption type polarizing plate of the composite polarizing plate, the absorbance of the blue region in the absorption type polarizing plate is generally lowered, (Blue leak) in the blue light transmission suppressing layer, the composite polarizer according to the present invention including the blue light transmission suppressing layer can effectively suppress light leakage in the blue light region having a high light emission intensity, It is possible to provide a liquid crystal display device of high brightness and high contrast.

The luminescence spectrum having a high light emission intensity in the blue region in the luminescence spectrum measured when the liquid crystal cell is laminated on the backlight and the backlight is lit refers specifically to the BY type in the following formula (1): &

L (Bmax) / L (Ymax) &gt; 1 (One)

(2): &quot; (2) &quot;

L (Bmax) / L (Gmax) &gt; 1, and L (Bmax) / L (2)

.

L (Bmax), L (Gmax), L (Ymax), and L (Ymax) represent the emission peak wavelengths of blue, green, yellow and red, respectively, in the above formulas (1) and (Rmax) indicate the light emission intensities at the luminescence peak wavelengths Bmax, Gmax, Ymax and Rmax, respectively.

For example, in the case of a backlight of the LED backlight type such as a liquid crystal display of a mobile phone, the peak is clear as shown in Figs. 6 and 7 and is very easy to understand. However, in a CCFL type backlight shown in a large liquid crystal television or the like, And may be composed of a plurality of fine peaks. Therefore, Bmax is an emission peak wavelength of a peak at which the integral area becomes the maximum among emission peaks in which the emission peak wavelength is between 380 and 500 nm. The peak wavelength is determined by performing a fitting method such as appropriate normal distribution approximation, as necessary, without counting fine peaks and the like such as noise. Likewise, Gmax and Ymax are the emission peak wavelengths of the peaks at which the integral area is the maximum among the emission peaks having the emission peak wavelengths of 500 to 570 nm, and Rmax is the emission peak wavelength at the emission peak wavelengths of 570 to 700 nm, And is an emission peak wavelength of the peak at which the integral area becomes the maximum.

Generally, the luminescence spectrum measured in a state in which the liquid crystal cell is laminated on the backlight and the backlight is lit is represented by the following formula (6) in the BY type:

(Ymax-550) &lt; (550-Bmax) (6)

(7): &quot; (7) &quot;

(Rmax-550) &lt; (550-Bmax) (7)

.

550 &quot; in the above equations (6) and (7) considers light with a wavelength of approximately 550 nm, which is the highest sensitivity of human eyes, and these expressions show that when the luminance subjected to visibility correction is measured, Compared with light, blue light means that light is measured weakly. (1) and (6), or (2) or (3) because a peak in the long wavelength side is restricted in principle in a liquid crystal display device for mobile use such as a mobile phone or a PDA in which a white LED is used for a backlight, ) And (7). However, even in a large TV using CCFL type backlight, it is preferable to satisfy the above expression from the viewpoint of color production or the like.

Example

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

(Thickness of polarizer, protective film, and reflective polarizer)

MH-15M &quot; manufactured by Nikon Corporation.

(Average transmittance of blue light cut film)

Spectrophotometer equipped with an integrating sphere ("V7100" manufactured by Nihon Spectroscope, Ltd., 2 degree field of view; C light source], the transmittance at each wavelength (5 nm pitch) was measured. An average of these values over the wavelength range of 380 to 500 nm was obtained, and the average transmittance T (380 to 500) over the wavelength range of 380 to 500 nm was obtained, and the average thereof over the wavelength range of 500 to 780 nm , And this was regarded as an average transmittance T (500-780) over a wavelength range of 500 to 780 nm. It can be said that the average transmittance of the blue light cut film is substantially equal to the average transmittance of the blue light transmittance suppressing layer.

(Visibility Sensitivity Corrected Uniform Transmissivity and Visibility Correction Polarization of Absorption Type Polarizer)

The mass transmittance and the degree of polarization are respectively represented by the following formulas:

(?) = 0.5 x (Tp (?) + Tc (?))

(?) = 100 × (Tp (?) - Tc (?)) / (Tp (?) + Tc

. Tp (?) Is the transmittance (%) of the absorption type polarizing plate measured in relation to the incident linearly polarized light of wavelength? Nm and parallel Nicol, Tc (?) Is the transmittance of the linearly polarized light of incident wavelength? Is the transmittance (%) of the absorption type polarizing plate measured in relation to each other.

The visibility-corrected corrected single-beam transmittance Ty and the visibility-corrected polarization degree Py can be expressed by the two-view visual field (C light source) of JIS Z 8701 for the simplex transmittance lambda and the polarization degree lambda, , And a spectrophotometer equipped with an integrating sphere ("V7100" manufactured by Nihon Spectroscope, Ltd., 2 degrees viewing angle; C light source]. The measurement was carried out by a single absorption type polarizing plate. In the measurement, incident light was set to be incident on the side opposite to the side bonded to the reflection type polarizing plate. Ty and Py were measured at a pitch of 5 nm in a wavelength range of 380 to 780 nm.

(The angle formed between the reflection axis of the reflection type polarizing plate and the absorption axis of the absorption type polarizing plate)

The angle? Between the reflection axis of the reflection type polarizing plate and the absorption axis of the absorption type polarizing plate is obtained by separating the reflection type polarizing plate and the absorption type polarizing plate from the composite polarizing plate and setting the reflection axis of the reflection type polarizing plate, And the absorption axis of the absorption type polarizing plate were measured by a rotation analyzer method using an automatic birefringence system "KOBRA-WPR" manufactured by Oji Measurement Instruments Co.,

? = (angle of reflection axis of reflection type polarizing plate) - (absorption axis angle of absorption type polarizing plate) (8)

Respectively.

&Lt; Example 1 >

(1) Production of polarizer

A polyvinyl alcohol film having a thickness of 30 占 퐉 (average degree of polymerization of about 2400, degree of saponification of 99.9 mol% or more) was uniaxially stretched by about 4 times by dry stretching and kept at 40 占 폚 for 40 seconds And dipped in a dyeing aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.044 / 5.7 / 100 at 28 ° C for 30 seconds to perform dyeing treatment. Thereafter, it was immersed in an aqueous solution of boric acid having a weight ratio of potassium iodide / boric acid / water of 11.0 / 6.2 / 100 at 70 ° C for 120 seconds. Subsequently, the film was washed with pure water at 8 캜 for 15 seconds, then dried at 60 캜 for 50 seconds and then at 75 캜 for 20 seconds while maintaining the tension at 300 N / m, and the polyvinyl alcohol film was subjected to adsorption And a polarizer having a thickness of 12 占 퐉 was aligned.

(2) Fabrication of absorption type polarizing plate

3 parts by weight of a carboxyl group-modified polyvinyl alcohol (trade name "KL-318", available from Kuraray Co., Ltd.) was dissolved in 100 parts by weight of water. To the aqueous solution was added a polyamide epoxy additive 1.5 parts by weight of "Sumireze Resin 650 (30)", an aqueous solution having a solid content concentration of 30% by weight, obtained from Kagaku Kogyo Co., Ltd.) was added to prepare an aqueous adhesive. The water-based adhesive was coated on one surface of the polarizer obtained in the above (1), and a triacetylcellulose (TAC) film (trade name &quot; KC2UA &quot;, no retardation characteristic) was bonded to the other side via an adhesive layer made of the same water-based adhesive, and a norbornene resin film having an in-plane phase difference of 10 nm and a thickness of 23 mu m Trade name &quot; ZEONOR &quot;, manufactured by Zeon Corporation). The bonded product was dried at 60 캜 for 220 seconds and then at 80 캜 for 125 seconds after 5 seconds from the bonding while maintaining the tension at 280 N / m to obtain the visual sensitivity-corrected single unit transmittance (Ty) of 43.0% Whereby an absorption type polarizing plate having a correction polarity Py of 99.99% was obtained. Thereafter, a sheet-type pressure-sensitive adhesive (trade name &quot;# 7 &quot;, manufactured by Lintec Corporation) having a thickness of 25 占 퐉 was bonded to the outer surface of the norbornene resin film.

(3) Fabrication of composite polarizer

(Trade name: &quot;# 7 &quot; manufactured by Lintec Co., Ltd.) having a thickness of 25 占 퐉 and a reflection type polarizing plate having a thickness of 26 占 퐉 (manufactured by 3M Corporation) on the TAC film side of the absorption type polarizing plate obtained in (2) APF &quot;, obtained from Sumitomo 3M Ltd.) was bonded such that the angle (alpha) formed by the reflection axis of the reflection type polarizing plate with respect to the absorption axis of the absorption type polarizing plate was 4 DEG in the counterclockwise direction.

Subsequently, a blue polarized light cut film A (trade name "EF-FLBL series" manufactured by ELECOM, Reflective type) was bonded to the outer surface of the reflection polarizing plate to obtain a composite polarizing plate. The T (380-500) and T (500-780) of the blue light cut film A were 78.9% and 95.0%, respectively.

&Lt; Comparative Example 1 &

A composite polarizing plate was obtained in the same manner as in Example 1 except that Blue Light Curtain Film B (trade name "LCD-140WBC", manufactured by Sanwa Supply Co., Ltd., absorption type) was used in place of Blue Light Curtain Film A. The T (380-500) and T (500-780) of the blue light cut film B were 73.8% and 79.7%, respectively.

&Lt; Comparative Example 2 &

A composite polarizing plate was obtained in the same manner as in Example 1 except that the blue light cut film A was not bonded.

&Lt; Example 2 >

A composite polarizing plate was obtained in the same manner as in Example 1 except that a dye aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.04 / 5.7 / 100 was used in the dyeing treatment of the polyvinyl alcohol film. The visual sensitivity-corrected single transmission (Ty) and visual sensitivity correction polarization degree (Py) of the obtained absorption type polarizing plate were 43.5% and 99.97%, respectively.

&Lt; Comparative Example 3 &

A composite polarizing plate was obtained in the same manner as in Example 2 except that the blue light cut film B was used in place of the blue light cut film A. [

&Lt; Comparative Example 4 &

A composite polarizing plate was obtained in the same manner as in Example 2 except that the blue light cut film A was not bonded.

[Evaluation of display quality of liquid crystal display device]

(1) Brightness

As described above, the luminance of the liquid crystal display device can be evaluated by the luminance L (380-780). The larger the L (380-780), the higher the luminance of the liquid crystal display device. L (380-780) has the same meaning as the molecule on the right side in the formula (3), and Tp (?) And Tc (?) At a pitch of 5 nm (d? = 5 nm) in the wavelength range of 380-780 nm, Was measured according to the method described above and calculated according to the above-mentioned equations (3) and (4). The emission spectrum (FIG. 7) in which the following VA type liquid crystal cell was laminated on the following backlight 1 was used for P (?). The results are shown in Table 2.

(2) Contrast

Contrast of a liquid crystal display device as described above can be evaluated by contrast _CR S (380-780). The larger the S _CR (380-780), the higher the contrast of the liquid crystal display device. Tp (lambda) and Tc (lambda) were measured at a pitch of 5 nm (d? = 5 nm) in a wavelength range of 380 to 780 nm by the method described above and S _CR (? 380-780). The emission spectrum (Fig. 7) obtained by laminating the following VA type liquid crystal cell on the following backlight 1 was used for P (?) In the above formula (3). The results are shown in Table 2.

Further, L '(380-780) and S _CR ' (380-780) were obtained in the same manner as above except that the emission spectrum (FIG. 6) obtained by laminating the following VA type liquid crystal cell to the following backlight 2 in P 780) was obtained. The results are shown in Table 2.

Backlight 1 is a simulated white type LED backlight. Fig. 7 shows a luminescence spectrum of the VA type liquid crystal cell laminated thereon and measured with the backlight 1 lit. The backlight 2 is a high color rendering type LED backlight. FIG. 6 shows a luminescence spectrum measured with the VA type liquid crystal cell laminated thereon and the backlight 2 lit. For measurement of the emission spectrum, the spectroscopic radiation system "SR-UL1" manufactured by TOPCON was used. The luminescence spectrum characteristics obtained from these luminescence spectra are summarized in Table 1 below.

Claims (8)

An absorption type polarizing plate, a reflection type polarizing plate, and a blue light transmission suppressing layer for suppressing transmission of blue light within a wavelength range of 380 to 500 nm,
Wherein the blue light transmission suppressing layer has an average transmittance over a wavelength range of 500 to 780 nm of 90% or more and an average transmittance over a wavelength range of 380 to 500 nm of 80% or less. The composite polarizing plate according to claim 1, wherein the absorption type polarizing plate has a visual sensitivity-corrected single transmission of 42.6 to 44.0% and a visual sensitivity correction polarization degree of 99.5% or more. The composite polarizing plate according to claim 1, wherein an angle formed by the reflection axis of the reflection type polarizing plate and the absorption axis of the absorption type polarizing plate is 0 +/- 4 degrees. The composite polarizer according to claim 1, wherein the absorption type polarizing plate comprises a polarizer and a resin film laminated on at least one side thereof. The absorbent polarizing plate according to claim 4, wherein the absorption type polarizing plate comprises a polarizer, a cellulose acetate resin film laminated on one side thereof with an adhesive layer, and a cyclic polyolefin resin laminated on the other side through an adhesive layer A composite polarizer comprising a film. The absorption type polarizing plate according to claim 4, wherein the absorption type polarizing plate comprises the polarizer, and a cellulose acetate based resin film or a cyclic polyolefin based resin film laminated on one side thereof with an adhesive layer,
Wherein the reflective polarizing plate is laminated on the other surface of the polarizer or on the surface of the acetic acid cellulose based resin film or the annular polyolefin based resin film through a pressure sensitive adhesive layer. A backlight, a composite polarizing plate according to any one of claims 1 to 6, and a liquid crystal cell in this order,
Wherein the absorption type polarizing plate is disposed so as to be closer to the liquid crystal cell than the reflection type polarizing plate. 8. The liquid crystal display device according to claim 7, wherein the liquid crystal cell is laminated on the backlight, and the luminescence intensities at the luminescence peak wavelengths of blue, green, yellow and red in the luminescence spectrum measured with the backlight turned on are expressed as L (Bmax ), L (Gmax), L (Ymax) and L (Rmax)
L (Bmax) / L (Ymax) &gt; 1 (1)
L (Bmax) / L (Rmax) &gt; 1 (2)
Is satisfied.

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