TW201339623A - Liquid crystal display device - Google Patents

Abstract

The present invention provides a liquid crystal display device which may correspond to the reduction in thickness of the liquid crystal display device (That is, the polarizer protective film has sufficient mechanical strength) and deterioration of visibility due to rainbow-like unevenness of colors does not occur. The liquid crystal display device is a liquid crystal display device which has backlight source and liquid crystal cells arranged between the two polarizing plates. The backlight source is a white light source having continuous emission spectrum. The polarizing plate comprises structure formed by laminating polarizer protective film on both sides of the polarizer. At least one of polarizer protective film of polarizing plate disposed on projection light side relative to the crystal cells is a polyester film having retardation value of 3000-30000nm. At least one of polarizer protective film of polarizing plate disposed on incidence light side relative to the crystal cells is cycloolefin resin film, polyolefin resin film or (meta)acrylic acid resin film.

Description

Liquid crystal display device

The present invention relates to a liquid crystal display device, a polarizing plate, and a polarizer protective film. In detail, it is a liquid crystal display device, a polarizing plate, and a polarizer protective film which are excellent in visibility and are suitable for thinning.

A polarizing plate used for a liquid crystal display device (LCD) is usually composed of two polarizing mirror protective films sandwiching a polarizing lens coated with iodine on polyvinyl alcohol (PVA) or the like, usually using triacetyl cellulose ( The TAC) film acts as a polarizer protective film. In recent years, with the thinning of LCDs, there has been a demand for thinning of polarizing plates. However, if the thickness of the TAC film used as the protective film is made thin, sufficient mechanical strength cannot be obtained, and the moisture permeability becomes high, and the polarizer is easily deteriorated. Also, TAC films are very expensive and are strongly pursuing inexpensive alternative materials.

Therefore, the thickness of the polarizing plate is reduced, and even if the thickness of the polarizer protective film is reduced, it is proposed to use a polyester film instead of the TAC film in order to maintain high durability (Patent Documents 1 to 3).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2002-116320

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2004-219620

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2004-205773

The polyester film is superior in durability to the TAC film, but has a birefringence different from that of the TAC film. When it is used as a polarizer protective film, there is a problem that image quality is lowered due to optical distortion. That is, the polyester film having birefringence has a specified optical anisotropy (hysteresis value), and when used as a polarizer protective film, if it is observed obliquely, a rainbow-like color spot will occur, and the image quality will be reduce. Therefore, in Patent Documents 1 to 3, measures for reducing the hysteresis value by using a copolyester as a polyester are carried out. However, even in this case, it is impossible to sufficiently reduce the rainbow-like stain.

The present invention has been made in order to solve the problem, and an object thereof is to provide a liquid crystal display device which can be made thinner in accordance with a liquid crystal display device (that is, a polarizer protective film has sufficient mechanical strength) and does not generate Deterioration of visual recognition due to rainbow-like stains.

As a result of intensive investigations to achieve the above-mentioned problems, the inventors have found that the above problems can be solved by adopting the following configuration, and the present invention has been completed.

That is, the present invention relates to the inventions of the following (1) to (9).

(1) A liquid crystal display device comprising a backlight source and a liquid crystal display device disposed between two polarizing plates, the backlight The source is a white light source having a continuous light emission spectrum, and the polarizing plate includes a polarizer protective film disposed on both sides of the polarizer, and is disposed on the polarizer protective film of the polarizing plate on the light exiting side with respect to the liquid crystal cell. At least one of the polyester film having a hysteresis value of 3,000 to 30,000 nm, and at least one of the polarizer protective film of the polarizing plate disposed on the incident light side with respect to the liquid crystal cell is a cycloolefin resin film or a polyolefin resin. Film or (meth)acrylic resin film.

(2) The liquid crystal display device according to the above aspect, wherein the cycloolefin resin film, the polyolefin resin film or the (meth)acrylic resin film has a hysteresis value of 200 nm or less.

(3) The liquid crystal display device according to (1) or (2), wherein the olefin-based resin film is a polypropylene film.

(4) The liquid crystal display device according to any one of (1) to (3), wherein a ratio (Re/Rth) of a retardation value to a thickness direction hysteresis value of the polyester film is 0.2 or more and 1.2 or less.

(5) The liquid crystal display device according to any one of (1) to (4) wherein the white light source having a continuous light emission spectrum is a white light emitting diode.

(6) The liquid crystal display device according to any one of (1) to (5) wherein the polyester film has an easy-adhesion layer.

The liquid crystal display device according to any one of the above aspects, wherein the polyester film contains at least three layers, and an ultraviolet absorber is contained in a layer other than the outermost layer, and light of 380 nm is worn. The penetration rate is 20% or less.

(8) The liquid crystal display device according to any one of (1) to (7), wherein the light-emitting side of the polarizing plate on the light-emitting side is disposed on the light-emitting side of the liquid crystal cell The polarizer protective film is an alignment polyester film having a hysteresis value of 3,000 to 30,000 nm, and the light-emitting side surface of the alignment polyester film has a surface selected from the group consisting of a hard coat layer, an antiglare layer, an antireflection layer, a low reflection layer, and a low One or more layers of the group of the anti-glare layer and the anti-reflection anti-glare layer are reflected.

(9) The liquid crystal display device according to any one of (3), wherein the polypropylene film is a laminated film in which an adhesion improving layer containing a polar group-containing polyolefin resin is laminated on at least one side. .

(10) The liquid crystal display device according to (9), wherein the adhesion improving layer mainly contains a polypropylene-based resin containing a polar group.

In the liquid crystal display device of the present invention, since the spectrum of the transmitted light is approximate to the spectrum of the light source at any observation angle, it can ensure good visibility of the rainbow-free color spot, and can correspond to a thin type. Chemical.

[Formation of the Invention]

(liquid crystal display device)

Generally, the liquid crystal panel has a rear module, a liquid crystal cell, and a front module in the order of the side of the display image (the visual recognition side or the emission light side) from the backlight source side. The rear module and the front module are generally composed of a transparent substrate, a transparent conductive film formed on the surface of the liquid crystal cell, and a polarizing plate disposed on the opposite side. Here, in the latter module, the polarizing plate is disposed on the backlight source side, and in the front module is configured On the display image side (visual recognition side or emission light side).

In the liquid crystal display device of the present invention, at least a backlight source and a liquid crystal cell disposed between the two polarizing plates are used as constituent members. Further, other configurations than these may include, for example, a color filter, a lens film, a diffusion sheet, an antireflection film, and the like.

The configuration of the backlight source may be an edge light method in which a light guide plate or a reflector is used as a constituent member, and may be a direct type. However, in the present invention, it is preferable to use a wide and wide spectrum of light emission. The white light source serves as a backlight source for the liquid crystal display device. The term "continuous broad-spectrum luminescence spectrum" as used herein means a luminescence spectrum having a wavelength of at least 450 nm to 650 nm, preferably in the region of visible light, without a wavelength at which the light intensity is zero. As a white light source having such a wide and wide luminescence spectrum, for example, a white light-emitting diode (white LED) can be cited. In the present invention, the white LED includes a phosphor type, that is, an element which emits white by combining a light-emitting diode and a phosphor which emits blue light or ultraviolet light using a compound semiconductor, and an organic light-emitting diode ( Organic light-emitting diode: OLED). As far as the phosphor is concerned, there is a flaw. aluminum. Garnet yellow fluorescent or enamel. aluminum. Garnet-based yellow phosphors, etc. In the white LED, a blue light-emitting diode and a germanium combined using a compound semiconductor are included. aluminum. A white light-emitting diode of a light-emitting element made of a garnet-based yellow phosphor is suitable as a backlight source of the present invention because it has not only a wide-bandwidth luminescence spectrum but also excellent light-emitting efficiency. The present invention is also effective for energy saving by using a white LED or the like that consumes less power as a light source.

Cold cathode used since it was used as a backlight source The luminescence spectrum of a fluorescent tube such as a tube or a hot cathode tube has only a discontinuous luminescence spectrum having a peak at a specific wavelength, and thus is not preferable in terms of obtaining the effects expected by the present invention.

The polarizing plate has a configuration in which two polarizing mirror protective films are sandwiched between two sides of a PVA or the like which are dyed with iodine, but in the present invention, a polyester film having a specific range of hysteresis value is used as a polarizing light. At least one of the polarizer protective film of the plate. Further, a cycloolefin resin film, a polyolefin resin film or a (meth)acrylic resin film is used as at least one of the polarizer protective films constituting the polarizing plate disposed on the incident light side.

The mechanism for suppressing the occurrence of rainbow-like stains by the above-described aspects is conceived as follows. When a polyester film having birefringence is disposed on one side of the polarizer, linear polarized light emitted from the polarizer may be scattered when passing through the polyester film. The transmitted light shows a characteristic interference color in terms of the hysteresis value of the product of the birefringence and the thickness of the polyester film. Therefore, if a discontinuous luminescence spectrum such as a cold cathode tube or a hot cathode tube is used as a light source, different penetration light intensities are displayed depending on the wavelength, and a rainbow-like color spot is generated (reference: 15th micro-optical conference (Microoptics) Conference), drafts, 30-31).

On the other hand, in the white light-emitting diode, it is usually at least in the wavelength region of 450 nm to 650 nm, and it is preferable to have a wide and wide luminescence spectrum in the visible light region. Therefore, since the interference color spectrum of the transmitted light penetrating the birefringent becomes an envelope curve shape, a spectrum similar to the light emission spectrum of the light source can be obtained by controlling the hysteresis value of the polyester film. As mentioned above, it is considered that due to the luminescence spectrum of the light source and the penetrating birefringence The shape of the envelope curve of the interference color spectrum caused by the transmitted light becomes a similar shape, so that the rainbow-like color spot does not occur and the visibility is remarkably improved.

Based on the above principle, it is considered that in the present invention, by using a white light-emitting diode having a wide light-emitting spectrum for a light source, the shape of the envelope curve of the transmitted light can be approximated to the light source with only a relatively simple configuration. The luminescence spectrum, as a result, suppresses rainbow spots on the liquid crystal display.

The polyester film having a specific range of hysteresis value is preferably used as a polarizer protective film disposed on the light-emitting side of the polarizing plate on the light-emitting side with respect to the liquid crystal cell. When the polyester film is used for a polarizer protective film disposed on the incident light side of the polarizing plate on the light-emitting side with respect to the liquid crystal cell, the polarizing characteristics of the liquid crystal cell may be changed. In a preferred embodiment, the polarizer protective film disposed on the incident light side of the polarizing plate on the incident light side with respect to the liquid crystal cell is a cycloolefin resin film, a polyolefin resin film or a (meth)acrylic resin film. In this case, a film containing the same polymer material in the front and back may be used for the other polarizer protective film of the polarizing plate on the incident light side, but it is preferable to use a film such as a TAC film, an acrylic film, or a decylene film. A film that represents no double refraction.

The liquid crystal cell can be used not only on the light-emitting side but also on the polarizer protective film disposed on the incident light side of the polarizing plate. The polyester film having the hysteresis value in the above-mentioned specific range can be used, and it can be extremely light depending on the angle. The rainbow spot is also determined depending on the case, and therefore a cycloolefin resin film, a polyolefin resin film or a (meth)acrylic resin film is preferably used. In this way, the rainbow spot is eliminated, and in particular, as long as it is a polypropylene film, the moisture resistance, the dimensional stability, and the mechanical strength are excellent, and the correspondence of the thickness reduction of the liquid crystal display device is more effective.

For the purpose of antireflection, glare suppression, damage suppression, etc., it is also preferred to apply a functional layer such as various hard coats to the surface of the polarizing plate of the present invention. Further, it is preferable to provide an antiglare layer, an antireflection layer, a low reflection layer, a low reflection antiglare layer, and an antireflection antiglare layer on the surface from the viewpoint of preventing reflection from external light. Preferably, the layers are disposed on the surface of the polyester film via an easy adhesion layer or directly. It is particularly preferable that the alignment polyester film is used for a polarizer protective film disposed on the light-emitting side of the polarizing plate on the light-emitting side with respect to the liquid crystal cell, and is provided on the side of the light emitted from the alignment polyester film to be selected from the group consisting of hard coats. One or more layers of the group of the layer, the antiglare layer, the antireflection layer, the low reflection layer, the low reflection antiglare layer, and the antireflection antiglare layer. This is because the aforementioned polarizer protective film is located closest to the external light. In addition, it is also expected to reduce the rainbow color by laminating a layer selected from the group consisting of a hard coat layer, an anti-glare layer, an anti-reflection layer, a low-reflection layer, a low-reflection anti-glare layer, and an anti-reflection anti-glare layer. Spot effect.

(Polyester film)

In order to exert the above effects, the alignment polyester film used for the polarizer protective film preferably has a hysteresis value of 3,000 to 30,000 nm. When the hysteresis value is less than 3000 nm, when it is used as a polarizer protective film, since it exhibits a strong interference color when viewed obliquely, the shape of the envelope curve is different from that of the light source, and good visibility cannot be ensured. Preferably, the lower limit value of the hysteresis value is 4500 nm or more, and secondly, it is preferably 5000 nm or more. More preferably, it is 6000 nm or more, further preferably 8000 nm or more, and still more preferably 10000 nm or more.

On the other hand, the upper limit of the hysteresis value is 30000 nm. Even if a polyester film having a hysteresis value exceeding the hysteresis value is used, not only the improvement effect of further visibility is substantially not obtained, but also the thickness of the film becomes relatively thick, and the workability as an industrial material is lowered, which is not preferable.

In addition, the hysteresis value can be obtained by measuring the refractive index and the thickness in the biaxial direction, and a commercially available automatic birefringence measuring device of RETS100 (manufactured by Otsuka Electronics Co., Ltd.) or KOBRA-21ADH (Oji Scientific Instruments Co., Ltd.) can be used. Seek. In the present specification, the hysteresis value means the in-plane hysteresis value.

The alignment polyester film used in the present invention can be obtained by condensing a dibasic acid with a glycol. The dibasic acid component used for the production of the polyester film may, for example, be terephthalic acid, isophthalic acid, phthalic acid, 2,5-naphthalene dicarboxylic acid or 2,6-naphthalene. Carboxylic acid, 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, diphenylcarboxylic acid, diphenoxyethane dicarboxylic acid, diphenylphosphonium carboxylic acid, stilbene dicarboxylic acid, 1 , 3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, Dimethylmalonic acid, succinic acid, 3,3-diethyl succinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, three Methyl adipate, pimelic acid, sebacic acid, dimer acid, sebacic acid, suberic acid, dodecanedioic acid, and the like.

The glycol component used for the production of the polyester film may, for example, be ethylene glycol, propylene glycol, hexamethylene glycol or neopentyl Alcohol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, decanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1, 6-hexanediol, 2,2-bis(4-hydroxyphenyl)propane, bis(4-hydroxyphenyl)anthracene, and the like.

One type or two or more types of the dibasic acid component and the diol component which are constituting the polyester film can be used. Specific examples of the polyester resin constituting the polyester film include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. And the like, preferably ethylene terephthalate or polyethylene naphthalate. These resins are excellent in transparency and excellent in heat and mechanical properties, and the hysteresis value can be easily controlled by extension processing. In particular, polyethylene terephthalate is the most suitable material because of its large intrinsic birefringence, and even if the thickness of the film is thin, it is relatively easy to obtain a high hysteresis value.

In addition, for the purpose of suppressing deterioration of an optical functional dye such as an iodine dye, the light transmittance of the polyester film at a wavelength of 380 nm is preferably 20% or less. The light transmittance at 380 nm is more preferably 15% or less, further preferably 10% or less, and particularly preferably 5% or less. When the light transmittance is 20% or less, deterioration of the optical functional dye due to ultraviolet rays can be suppressed. Further, the transmittance in the present invention is measured by a method in which the plane of the film is perpendicular, and can be measured using a spectrophotometer (for example, Hitachi U-3500 type).

When the transmittance of the alignment polyester film at a wavelength of 380 nm is 20% or less, the ultraviolet absorber can be added to the film, and the coating liquid containing the ultraviolet absorber can be applied to the surface of the film to appropriately adjust the type and concentration of the ultraviolet absorber. And the thickness of the film and the like are achieved. The ultraviolet absorber used in the present invention is a well-known substance. UV absorber In addition, an organic ultraviolet absorber and an inorganic ultraviolet absorber are preferable, and an organic ultraviolet absorber is preferable from a viewpoint of transparency.

Examples of the organic ultraviolet absorber include a benzotriazole-based, a diphenylketone-based, a cyclic imido ester-based, and the like, and a combination thereof is not particularly limited as long as it is within the range of the absorbance specified in the present invention. . From the viewpoint of durability, a benzotriazole-based or cyclic imido ester-based system is particularly preferred. When two or more types of ultraviolet absorbers are used in combination, since ultraviolet rays of respective wavelengths can be simultaneously absorbed, the ultraviolet absorption effect can be further improved.

Examples of the diphenylketone-based ultraviolet absorber, the benzotriazole-based ultraviolet absorber, and the acrylonitrile-based ultraviolet absorber include, for example, 2-[2'-hydroxy-5'-(methacryloxyl group A). Phenyl]-2H-benzotriazole, 2-[2'-hydroxy-5'-(methacryloxyethyl)phenyl]-2H-benzotriazole, 2-[2'-hydroxy-5'-(methacryloxypropyl)phenyl]-2H-benzotriazole,2,2'-dihydroxy-4,4'-dimethoxydiphenyl ketone, 2 , 2',4,4'-tetrahydroxydiphenyl ketone, 2,4-di-t-butyl-6-(5-chlorobenzotriazol-2-yl)phenol, 2-(2'- Hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(5-chloro(2H)-benzotriazol-2-yl)-4-methyl -6-(t-butyl)phenol, 2,2'-methylenebis(4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazole- 2-yl)phenol, etc. Examples of the cyclic imido ester-based ultraviolet absorber include 2,2'-(1,4-phenylene)bis(4H-3,1-benzo). Keto-4-one), 2-methyl-3,1-benzo 4-ketone, 2-butyl-3,1-benzo 4-ketone, 2-phenyl-3,1-benzo 4-ketone and the like. However, it is not particularly limited to this.

Further, in addition to the ultraviolet absorber, it is preferable to contain various additives within a range that does not impair the effects of the present invention. on Examples of the additive include inorganic particles, heat-resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, light stabilizers, flame retardants, heat stabilizers, antioxidants, and anti-gelation. Agent, surfactant, etc. Further, in order to exhibit high transparency, it is preferred that the polyester film contains substantially no particles. The term "substantially free of particles" means, for example, inorganic particles. When the inorganic element is quantified by fluorescent X-ray analysis, the weight is 50 ppm or less, preferably 10 ppm or less, and particularly preferably the detection limit. The following content.

Further, in order to improve the adhesion to the polarizer, the polyester film may be subjected to corona treatment, coating treatment, flame treatment, or the like.

In the present invention, in order to improve the adhesion to the polarizer, it is preferred to have at least one of a polyester resin, a polyurethane resin or a polyacrylic resin as a main component on at least one side of the polyester film. Easy to adhere layer. Here, the "main component" means a component of 50% by mass or more of the solid component constituting the easy-adhesion layer. The coating liquid used for the formation of the easy-adhesion layer is preferably an aqueous coating liquid containing at least one of a water-soluble or water-dispersible copolymerized polyester resin, an acrylic resin, and a polyurethane resin. Examples of the coating liquids include those disclosed in, for example, Japanese Patent No. 3567927, Japanese Patent No. 3589232, Japanese Patent No. 3589233, Japanese Patent No. 3900191, Japanese Patent No. 4150982, and the like. A water-soluble or water-dispersible copolyester resin solution, an acrylic resin solution, a polyurethane resin solution, or the like.

The easy-adhesion layer is obtained by coating the coating liquid on one or both sides of the unstretched or longitudinal uniaxially stretched film, drying at 100 to 150 ° C, and extending in the lateral direction. The coating amount of the final easy-adhesion layer is preferably managed at 0.05 to 0.20 g/m ² . When the coating amount is less than 0.05 g/m ² , the adhesion to the obtained polarizer may be insufficient. On the other hand, when the coating amount exceeds 0.20 g/m ² , the anti-blocking property may be lowered. When the easy-adhesion layer is provided on both sides of the polyester film, the coating amounts of the easy-adhesion layers on both sides may be the same or different, and may be independently set within the above range.

In order to impart slipperiness to the easy-adhesion layer, it is preferred to add particles. It is preferred to use particles having an average particle diameter of 2 μm or less of fine particles. When the average particle diameter of the particles exceeds 2 μm, the particles are likely to fall off from the easy-adhesion layer. Examples of the particles contained in the easy-adhesion layer include titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, vermiculite, alumina, talc, kaolin, clay, calcium phosphate, mica, lithium bentonite, and zirconia. Inorganic particles such as tungsten oxide, lithium fluoride or calcium fluoride, or organic polymer particles such as styrene, acrylic, melamine, benzoguanamine or polyoxyn. These may be added separately to the easy-adhesion layer, or two or more types may be combined and added.

Further, as a method of applying the coating liquid, a well-known method can be used. For example, a reverse roll coating method, a gravure roll coating method, a roll coating method, a roll brush method, a spray coating method, an air knife coating method, a wire rod coating method, a tube scraping method, etc. may be mentioned, and these methods may be used alone or in combination. get on.

Further, the measurement of the average particle diameter of the above particles was carried out by the following method. A photograph of the particles was taken by a scanning electron microscope (SEM), and the size of one of the smallest particles was 2 to 5 mm, and 300 was measured. The maximum diameter of the ~500 particles (the distance between the two most distant points), and the average value thereof is taken as the average particle diameter.

The oriented polyester film can be produced by following the manufacturing method of a general polyester film. For example, an unaligned polyester obtained by melting a polyester resin and extruding it into a sheet shape may be used, and at a temperature equal to or higher than the glass transition temperature, the speed difference in the longitudinal direction of the roll is extended in the longitudinal direction, and then the width of the machine is extended. The method of laterally extending and applying heat treatment.

The aligning polyester film is a uniaxially stretched film, and it is also possible to use a biaxially stretched film. However, when a biaxially stretched film is used as the polarizing film protective film, even if it is observed from directly above the film surface, no rainbow color is observed. Spot, but since the rainbow-like stain is observed when viewed from an oblique direction, care must be taken.

This phenomenon is due to the fact that the biaxially stretched film contains refractive index ellipsoids having different refractive indices in the traveling direction, the width direction, and the thickness direction, and has a hysteresis value of zero (refraction) as the direction of light penetration inside the film is different. The direction of the ellipsoid looks like a true circle. Therefore, if the liquid crystal display screen is viewed from a specific direction in the oblique direction, there is a case where the hysteresis value becomes zero, and the rainbow-like color spots are concentrically formed around the point. Further, if the angle from the directly above (normal direction) of the film surface to the position of the rainbow-colored stain is set to θ, the larger the birefringence in the film plane, the larger the angle θ becomes. The rainbow-like stains will become more difficult to see. In the case of the biaxially stretched film, since the angle θ tends to be small, it is preferable that the uniaxially stretched film becomes difficult to see a rainbow-like color patch.

However, in terms of a completely uniaxial (uniaxial symmetry) film Since the mechanical strength in the direction orthogonal to the alignment direction is remarkably lowered, it is not preferable. The present invention preferably has biaxiality (biaxial symmetry) in a range in which a rainbow-like color patch does not substantially occur or in a range in which a rainbow-like color patch does not occur in a viewing angle range required for a liquid crystal display screen. .

The inventors of the present invention have found that the mechanical strength of the alignment-oriented polyester film is controlled such that the ratio of the hysteresis value (in-plane hysteresis value) of the alignment polyester film to the hysteresis value (Rth) in the thickness direction converges within a specific range. At the same time, it inhibits the occurrence of rainbow spots. The phase difference in the thickness direction means an average of the phase differences obtained by multiplying the two birefringences ΔNxz and ΔNyz of the film by the film thickness d from the thickness direction cross section. Since the difference between the in-plane hysteresis value and the thickness direction hysteresis value is smaller, the effect of birefringence caused by the different observation angles will increase the isotropic direction more and more, so the change of the hysteresis value due to the difference in the observation angle is smaller. Therefore, it is considered that rainbow-like stains caused by different viewing angles may become difficult to produce.

The ratio (Re/Rth) of the retardation value to the thickness direction hysteresis value of the alignment polyester film is preferably 0.2 or more, more preferably 0.5 or more, still more preferably 0.6 or more. The greater the contrast between the hysteresis value and the thickness direction hysteresis value (Re/Rth), the more the birefringence will increase the isotropic direction, and the generation of rainbow-like color spots caused by the different observation angles will become more difficult. Further, in the case of a completely uniaxial (uniaxial symmetry) film, the ratio of the hysteresis value to the thickness direction hysteresis value (Re/Rth) is 2. However, as described above, with an approximately completely uniaxial (uniaxial symmetry) film, the mechanical strength in a direction orthogonal to the alignment direction is remarkably lowered.

On the other hand, the hysteresis value and thickness of the alignment polyester film The ratio of the hysteresis value (Re/Rth) is preferably 1.2 or less, more preferably 1 or less. In order to completely suppress the generation of rainbow-like color spots caused by the difference in observation angle, the ratio of the retardation value to the thickness direction phase difference (Re/Rth) need not be 2, and it is sufficient to be 1.2 or less. Moreover, even if the ratio is 1.0 or less, the viewing angle characteristics (about 180 degrees left and right and 120 degrees above and below) required for the liquid crystal display device can be sufficiently satisfied.

When the film forming conditions of the alignment polyester film are specifically described, the longitudinal stretching temperature and the lateral stretching temperature are preferably 80 to 130 ° C, particularly preferably 90 to 120 ° C. The longitudinal stretching ratio is preferably 1.0 to 3.5 times, and particularly preferably 1.0 to 3.0 times. Further, the lateral stretching ratio is preferably 2.5 to 6.0 times, and particularly preferably 3.0 to 5.5 times. In order to control the hysteresis value within the above range, it is more preferable to control the ratio of the longitudinal stretching ratio to the lateral stretching ratio. If the difference between the vertical and horizontal stretching ratios is too small, it becomes difficult to increase the hysteresis value. Further, in terms of increasing the hysteresis value, setting a low extension temperature is also a preferable correspondence. In the subsequent heat treatment, the treatment temperature is preferably from 100 to 250 ° C, particularly preferably from 180 to 245 ° C.

In order to suppress the variation of the hysteresis value, it is preferred that the thickness of the polyester film is small. Since the stretching temperature and the stretching ratio have a large influence on the thickness unevenness of the film, it is necessary to optimize the film forming conditions from the viewpoint of thickness unevenness. In particular, if the longitudinal stretching ratio is lowered in order to increase the hysteresis value, the value of the longitudinal thickness unevenness may become high. Since there is a region in which the value of the longitudinal thickness unevenness becomes extremely high in a certain range of the stretching ratio, it is preferable to set the film forming conditions outside the range.

The thickness unevenness of the polyester film is preferably 5.0% or less, more preferably It is 4.5% or less, further preferably 4.0% or less, and particularly preferably 3.0% or less. The thickness unevenness of the film can be measured by any means, for example, taking a continuous strip sample (length 3 m) in the flow direction of the film, using SEIKO. Measuring machine such as an EM (Millitron 1240) electronic measuring instrument, measuring the thickness of 100 points at intervals of 1 cm, and obtaining the maximum thickness (dmax), the minimum value (dmin), and the average value (d). The thickness can be calculated as the thickness unevenness (%).

Uneven thickness (%) = ((dmax-dmin) / d) × 100

As described above, in order to control the hysteresis value of the film to a specific range, it can be carried out by appropriately setting the stretching ratio or the stretching temperature and the thickness of the film. For example, the higher the difference in stretch ratio between the longitudinal extension and the lateral extension, the lower the extension temperature, and the thicker the thickness of the film, the easier it is to obtain a high hysteresis value. On the contrary, the lower the difference between the stretching ratio of the longitudinal extension and the lateral extension, the higher the extension temperature, and the thinner the thickness of the film, the easier it is to obtain a low hysteresis value. Further, the higher the elongation temperature and the lower the total stretching ratio, the easier it is to obtain a film having a low ratio of hysteresis value to retardation value (Re/Rth). On the contrary, the lower the extension temperature is, the higher the total stretching ratio is, the easier it is to obtain a film having a higher ratio of hysteresis value to the retardation value in the thickness direction (Re/Rth). Further, in addition to the control of the hysteresis value, the final film forming conditions must be set in consideration of physical properties required for processing.

The polyester film has an arbitrary thickness, but preferably has a range of 15 to 300 μm, more preferably 15 to 200 μm. Even in the case of a film having a thickness of less than 15 μm, a hysteresis value of 3000 nm or more can be obtained in principle. However, in this case, the directionality of the mechanical properties of the film is remarkable, and cracks, breakage, and the like are likely to occur, and the practicality as an industrial material is remarkably lowered. A particularly preferred lower limit of thickness is 25 μm. On the other hand, partial If the upper limit of the thickness of the light shielding film exceeds 300 μm, the thickness of the polarizing plate may become too thick. The upper limit of the thickness is preferably 200 μm from the viewpoint of practicality as a polarizer protective film. The upper limit of the particularly preferable thickness is 100 μm which is equivalent to that of a general TAC film. In the above thickness range, in order to control the hysteresis value within the scope of the present invention, polyethylene terephthalate which is used as a film substrate is also suitable.

Further, in the method of blending the ultraviolet absorber in the polyester film, a well-known method may be used in combination, for example, by mixing a dried ultraviolet absorber and a polymer raw material by using a kneading extruder in advance. The master batch is prepared, and a predetermined method of mixing the master batch with the polymer material at the time of film formation is blended. The addition weight of the ultraviolet absorber added to the film is preferably from 0.3 to 1.5%, more preferably from 0.4 to 1.0%.

In order to uniformly disperse the ultraviolet absorber and economically blend, it is preferable to set the concentration of the ultraviolet absorber of the master batch to a concentration of 5 to 30% by mass. The conditions for producing the master batch are preferably from 1 to 15 minutes at a temperature at which the extrusion temperature is 290 ° C or more above the melting point of the polyester material, using a kneading extruder. At 290 ° C or higher, the amount of reduction of the ultraviolet absorber becomes large, and the viscosity of the master batch decreases. When the residence time is 1 minute or less, uniform mixing of the ultraviolet absorber becomes difficult. At this time, a stabilizer, a color tone adjuster, and an antistatic agent may be added as needed.

Further, in the present invention, it is preferred that the alignment polyester film has a multilayer structure of at least three or more layers, and an ultraviolet absorber is added to the intermediate layer of the film. The film having a three-layer structure containing an ultraviolet absorber in the intermediate layer can be specifically produced as follows. Mix the outer layer with the specified ratio The individual polyester pellets, the masterbatch containing the ultraviolet absorber for the intermediate layer, and the pellets of the polyester are dried, and then supplied to a known melt laminating extruder, and extruded from a slit-shaped die. The sheet was formed into a sheet and cooled and solidified on a casting roll to produce an unstretched film. That is, two or more extruders, three-layer collecting tubes, or confluent sections (for example, confluent sections having rectangular confluences) are used, and a thin film layer constituting the two outer layers and a thin film layer constituting the intermediate layer are laminated, and the metal nozzle is used. Three sheets of the sheet were extruded and cooled on a casting roll to produce an unstretched film. Further, in the present invention, in order to remove foreign matter contained in the polyester of the raw material which causes optical defects, it is preferred to perform high-precision filtration at the time of melt extrusion. The filter particle size (initial filtration efficiency: 95%) of the filter medium used for high-precision filtration of the molten resin is preferably 15 μm or less. When the filter particle size of the filter medium exceeds 15 μm, the removal of foreign matter of 20 μm or more is likely to be insufficient.

(cycloolefin type resin film, polyolefin type resin film or (meth)acrylic resin film)

A cycloolefin resin film, a polyolefin resin film or a (meth)acrylic resin film is used as at least one of the polarizer protective films constituting the polarizing plate disposed on the incident light side.

The cycloolefin resin film is a film containing a cycloolefin resin. The cycloolefin-based resin is a general term for a resin in which a cyclic olefin is used as a polymerization monomer, and the like, for example, Japanese Patent Laid-Open No. Hei. 1-240517, Japanese Patent Application Laid-Open No. Hei No. Hei No. Hei No. Hei No. Hei No. Hei. The resin is described. More specifically, a ring-opening (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, a copolymer of a cyclic olefin, and an alpha olefin such as ethylene or propylene (represented by a random copolymer) ) and these substances are not A graft copolymer obtained by upgrading a saturated carboxylic acid or a derivative thereof, and a hydride or the like.

Various products such as a decene-based resin are sold on the market of a cycloolefin-based resin. For the specific example, the product name "ZEONEX" manufactured by Japan ZEON Co., Ltd., "ZEONOR", the product name "ARTON" manufactured by JSR Co., Ltd., the product name "TOPAS" manufactured by TICONA, and the Mitsui Chemicals Co., Ltd. The product name "APEL" manufactured by the company and the product name "ESSINA" manufactured by Sekisui Chemical Industry Co., Ltd.

The polyolefin resin film is a film containing a polyolefin resin. The polyolefin resin may be selected from the group consisting of low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, ethylene-alpha olefin copolymer, ethylene-ethyl acrylate copolymer, ethylene- One or two of ethyl acetate copolymer, ethylene-methyl acrylate copolymer, ethylene-n-butyl acrylate copolymer, and polypropylene (homopolymer, random copolymer or block copolymer) a mixture of the above. Among them, the polypropylene film is more effective in reducing the thickness of the liquid crystal display device based on moisture resistance, dimensional stability, and mechanical strength.

The (meth)acrylic resin film is a film containing a (meth)acrylic resin. The (meth)acrylic resin described in [0017] to [0043] of JP-A-2010-055062 can be mentioned. Further, the (meth)acrylic resin is a methacrylic resin and an acrylic resin.

The Tg (glass transition temperature) of the (meth)acrylic resin is preferably 115 ° C or higher, more preferably 120 ° C or higher, and still more preferably 125 ° C. Above, it is particularly preferably 130 ° C or more. By having a Tg of 115 ° C or more, a polarizing plate excellent in durability can be obtained. The upper limit of the Tg of the (meth)acrylic resin is not particularly limited, and is preferably 170 ° C or less from the viewpoint of moldability and the like.

Any suitable (meth)acrylic resin can be used as the (meth)acrylic resin. For example, poly(meth)acrylate such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymer, methyl methacrylate-(meth) acrylate copolymer, methyl group Methyl acrylate-acrylate-(meth)acrylic acid copolymer, methyl (meth)acrylate-styrene copolymer (MS resin, etc.) and polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-A) A cyclohexyl acrylate copolymer, a methyl methacrylate-(meth)acrylic acid norbornyl ester copolymer, etc.). Preferable examples thereof include poly(meth)acrylic acid C1-6 alkyl esters such as poly(methyl) acrylate. More preferably, a methyl methacrylate-based resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight) is used.

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

A (meth)acrylic resin having a lactone ring structure can be used as the (meth)acrylic resin. It is due to its high heat resistance, high transparency, and high mechanical strength due to biaxial stretching.

For the (meth)acrylic resin having a lactone ring structure, JP-A-2000-230016, JP-A-2001-151814, JP-A-2002-120326, and JP-A-2002 A (meth)acrylic resin having a lactone ring structure described in JP-A-2005-146084, and the like.

One or more optional additives may be contained in the cycloolefin resin film, the polyolefin resin film or the (meth)acrylic resin film. Examples of the additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-staining agents, fire retardants, nucleating agents, antistatic agents, pigments, and color formers. The content of the aforementioned additive in the film is preferably from 0 to 50% by weight, more preferably from 1 to 50% by weight, still more preferably from 2 to 40% by weight, particularly preferably from 3 to 30% by weight. When the content of the above-mentioned additive in the film is more than 50% by weight, the high transparency which the thermoplastic resin originally has cannot be sufficiently exhibited. These films can also be extended.

The thickness of the cycloolefin-based resin film, the polyolefin-based resin film, or the (meth)acrylic resin film can be appropriately set, but it is generally about 1 to 500 μm from the viewpoints of workability such as strength and handling, and thin layer properties. about. It is preferably 5 to 500 μm, more preferably 10 to 300 μm, still more preferably 20 to 200 μm.

The cycloolefin resin film, the polyolefin resin film or the (meth)acrylic resin film is preferably transparent and has a hysteresis value of 200 nm or less. More preferably, it is 150 nm or less, and further more preferably 100 nm or less. A particularly good hysteresis value is 50 nm or less. When the hysteresis value exceeds 200 nm, the rainbow spot is sometimes observed to be poor. From the viewpoint of rainbow spot observation, since the hysteresis value is preferably small, the lower limit value is 0 or more.

(polypropylene film)

At least one of the polarizer protective films disposed on the incident light side of the polarizing plate with respect to the liquid crystal cell is preferably a polypropylene film. In particular, as long as it is a polypropylene film, it is excellent in moisture resistance, dimensional stability, mechanical strength, workability, and workability, and it is more effective in reducing the thickness of the liquid crystal display device. The polypropylene film used in the present invention contains a polypropylene resin. Here, the polypropylene-based resin mainly contains a resin of a polypropylene unit, and is generally a crystalline one, and may be a copolymer of a propylene unit and a comonomer copolymerizable therewith in addition to a homopolymer of propylene.

The polypropylene film used in the present invention is preferably transparent and has a hysteresis value of 200 nm or less. More preferably, it is 150 nm or less, More preferably, it is 100 nm or less. The hysteresis value is particularly preferably 50 nm or less. When the hysteresis value exceeds 200 nm, it is sometimes observed that the rainbow spot is not good. From the viewpoint of rainbow spot suppression, the hysteresis value is preferably small, and the lower limit is not particularly limited, but is actually 1 nm or more.

As the comonomer copolymerized with propylene, a comonomer known in the art can be appropriately selected, and for example, it can be ethylene or an α-olefin having 4 to 20 carbon atoms. The α-olefin in this case may specifically be as follows.

1-butene, 2-methyl-1-propene (above C ₄ ); 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene (above C ₅ ); -hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl 1-pentene, 3,3-dimethyl-1-butene (above C ₆ ); 1-heptene, 2-methyl-1-hexene, 2,3-dimethyl-1- Pentene, 2-ethyl-1-pentene, 2-methyl-3-ethyl-1-butene (above C ₇ ); 1-octene, 5-methyl-1-heptene, 2- Ethyl-1-hexene, 3,3-dimethyl-1-hexene, 2-methyl-3-ethyl-1-pentene, 2,3,4-trimethyl-1-pentene , 2-propyl-1-pentene, 2,3-diethyl-1-butene (above C ₈ ); 1-decene (C ₉ ); 1-decene (C ₁₀ ); 1-ten Monocarbene (C ₁₁ ); 1-dodecene (C ₁₂ ); 1-tridecene (C ₁₃ ); 1-tetradecene (C ₁₄ ); 1-pentadecene (C _{15 )} 1-hexadecene (C ₁₆ ); 1-heptadecene (C ₁₇ ); 1-octadecene (C ₁₈ ); 1-nonadecene (C ₁₉ ) and the like.

The copolymer may be a random copolymer or a block copolymer.

The propylene-based resin can be polymerized by using, for example, an inert solvent represented by a hydrocarbon such as hexane, heptane, octane, decane, cyclohexane, methylcyclohexane, benzene, toluene or xylene. The method is produced by a bulk polymerization method using a liquid monomer as a solvent, a gas phase polymerization method in which a gas monomer is directly polymerized, or the like. The polymerization by these methods can be carried out batchwise or continuously.

The stereoregularity of the propylene resin may be any of isotactic, syndiotactic, and random.

The propylene-based resin to be used in the present invention has a melt flow rate (MFR) measured in accordance with JIS-K7210 at a temperature of 230 ° C and a load of 21.18 N of 0.1 to 200 g/10 min, particularly preferably 0.5 to 50 g/10 min. By using a propylene-based resin having an MFR in this range, a bulk load is not applied to the extruder and a uniform film can be obtained.

The propylene-based resin can be blended with a known additive without departing from the effects of the present invention. Examples of the additive include an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, a nucleating agent, an antifogging agent, an anti-caking agent, and the like. For antioxidants, for example, phenolic antioxidants A compounding agent, a phosphorus-based antioxidant, a sulfur-based antioxidant, a hindered amine-based light stabilizer, or the like, and a composite antioxidant having a unit having both a phenolic antioxidant mechanism and a phosphorus-based antioxidant mechanism in one molecule. . Examples of the ultraviolet absorber include a 2-hydroxydiphenylketone-based, hydroxyphenylbenzotriazole-based ultraviolet absorber, and a benzoate-based ultraviolet blocking agent. The antistatic agent may be any of a polymer type, an oligomer type, and a monomer type. The lubricant may, for example, be a higher fatty acid guanamine such as mannosamine or ceramide, a higher fatty acid such as stearic acid or a salt thereof. Examples of the nucleating agent include, for example, a glucose alcohol nucleating agent, an organic phosphate nucleating agent, and a polymer nucleating agent for polyethylene naphthe. In the case of the anti-caking agent, the spherical or nearly spherical shape of the fine particles can be used regardless of the inorganic or organic type. These additives may also be used in combination.

The polypropylene film preferably has an adhesion improving layer containing a polar group-containing polyolefin resin on at least one side thereof from the viewpoint of adhesion improvement with a polarizer or a polyvinyl alcohol-based adhesive.

The above-mentioned adhesion improving layer will be described below. The polar group-containing polyolefin resin contains an olefin such as ethylene, propylene, butene, hexene, octene, methylpentene or a cyclic olefin in the skeleton. The polyolefin resin containing a polar group is preferably a polypropylene resin containing a propylene monomer as a skeleton, based on the adhesion to the propylene resin. The polyolefin resin may be a homopolymer using one of the above monomers, or a copolymer using two or more kinds of monomers.

The polar group-containing polyolefin resin preferably contains at least one polar group. Examples of the polar group include a carboxylic acid group, a sulfonic acid group, a phosphonic acid group, a hydroxyl group, a glycidyl group, an isocyanate group, an amine group, an imido group, An oxazoline group, an ester group, an ether group, a metal carboxylate group, a metal sulfonate group, a metal phosphonate group, a tertiary amine group or a 4- to amine group. The polyolefin resin may contain only one kind of polar group, and may contain two or more types. Among these polar groups, the polyolefin resin preferably contains a carboxylic acid group.

The polar group-containing polyolefin resin may be introduced into the polymer chain of the polyolefin resin as it is, or may be introduced, added, or mixed to another resin. Further, the polyolefin resin may be used by reacting a polar group (for example, a carboxylic acid group or a hydroxyl group) introduced into the terminal or the inside of the molecular chain with a compound capable of reacting.

The introduction of the polar group into the olefin resin can introduce the carboxylic acid group into the olefin resin by acid denaturation using, for example, maleic anhydride. The amount of acid denaturation is preferably 0.1% by weight or more based on the viewpoint of adhesion improvement. The amount of acid denaturation is more preferably 0.2% by weight or more, still more preferably 0.3% by weight or more. The amount of acid denaturation is preferably 5% by weight or less. Further, the acid denaturation can be measured in accordance with the measurement method shown in the examples described later.

The polar group-containing polyolefin resin contained in the adhesion improving layer may be one type or a mixture of two or more types. Further, the adhesion improving layer may further contain a polyolefin resin having no polar group or other kinds of resins. The total solid content of the adhesion-improving layer is preferably 10% by mass or more of the polar group-containing polyolefin resin, and more preferably 30% by mass or more.

The adhesion improving layer may be disposed on one side of the polypropylene film or on both sides. The thickness of the polypropylene film including the adhesion improving layer is not particularly limited, but is preferably 2 to 200 μm. The thickness of the adhesion improving layer provided on one side of the polypropylene film is not particularly limited, but is preferably 1~. 100 μm. Further, the ratio of the thickness of the polypropylene film to the adhesion improving layer (polypropylene film/adhesive modified layer) is preferably from 100/1 to 3/1, more preferably from 20/1 to 4/1. By doing so, the balance between the reduction in brightness and the improvement in adhesion can be improved.

The method for producing the polypropylene film is not particularly limited as long as it satisfies the above-described optical characteristics, and is preferably a method of forming a film by melt extrusion molding from the viewpoint of economy.

The film forming method by the melt extrusion molding method is not particularly limited, and may be, for example, any of a T-die method and an expansion method. Further, the film may be in an unstretched state, and may be subjected to stretching treatment. However, since the polypropylene film is preferably unaligned, it is preferably a film which is not stretched.

In the above melt extrusion molding method, a molten resin is generally extruded from a die into a sheet shape by an extruder, and the sheet is adhered to a cooling roll to be cooled and solidified to form a film. The method of adhering the cooling rolls is not particularly limited, but it is preferably a method in which the molten resin is extruded from a die into a sheet shape by an extruder, and the pressing method is performed by a pressing roller, and the gas is used. The film is formed by a pressing method and/or a pumping method and/or an electrostatic sealing method, and the sheet is densely cooled and solidified to form a film. By this method, a film having high transparency and a small hysteresis value can be obtained.

The method of adhering the aforementioned sheet to the cooling roll and cooling and solidifying is not particularly limited. For example, the pressing method by the gas pressure may be, for example, a method of pressing with a gas pressure such as air, a method such as an air knife method, or a vacuum chamber method in which a vacuum nozzle is used to evacuate the air pressure. Electrostatic sealing, which is made by electrostatic force. This method can be made separately Use, you can also use the plural method. The latter is implemented as a preferred embodiment in terms of improving the thickness accuracy of the obtained film.

Further, the polypropylene film may have a two-layer structure and may have a multilayer structure of three or more layers. An adhesion improving layer may also be provided on one or both sides of the polypropylene film. In the case of the above-described multilayer constitution, it may be produced by a multilayer coextrusion method, or may be carried out by an extrusion lamination method or a dry lamination method.

Further, the film may be subjected to surface activation treatment such as corona discharge treatment, glow discharge treatment, flame treatment, ultraviolet irradiation treatment, electron beam irradiation treatment, ozone treatment, etc., within a range not impairing the object of the present invention.

The thickness of the polypropylene film is preferably from 5 to 500 μm, more preferably from 10 to 300 μm, still more preferably from 20 to 200 μm.

The heat shrinkage ratio in the width direction and the longitudinal direction of the polypropylene film is preferably 1.0% or less, more preferably 0.8% or less at 120 ° C for 30 minutes. When the value of the heat shrinkage ratio exceeds 1.0%, when the heat treatment process is performed in the post-processing step or when it is used as a member for display or the like at a high temperature for a long period of time, the film is largely contracted to produce optical. Deterioration of properties, or deterioration in planarity, collapse, bending, etc., is not good.

The variation of the hysteresis value of the polypropylene film in the film width direction is preferably 100 nm/m or less. As long as the variation of the hysteresis value is 100 nm/m or less, even in a wide film corresponding to a large screen, the hysteresis value on the film plane is stabilized, and generation of color spots can be suppressed. The variation of the hysteresis value in the film width direction is more preferably 80 nm/m or less, still more preferably 50 nm/m or less, and particularly preferably 20 nm/m or less.

[Examples]

The present invention is not limited by the following examples, but the present invention is not limited by the following examples, and may be appropriately modified and implemented within the scope of the present invention. The technical scope of the present invention. Further, the evaluation methods of the physical properties in the following examples are as follows.

(1) Hysteresis value (Re)

The so-called hysteresis value is defined by the product of the anisotropy (ΔNxy=| Nx-Ny |) of the orthogonal biaxial refractive index on the film and the film thickness d (nm) (ΔNxy × d). A parameter that displays the scale of optical isotropy and anisotropy. The anisotropy (ΔNxy) of the biaxial refractive index of the polyester film was obtained by the following method. Using two polarizing plates, the direction of the alignment axis of the film was determined, and the direction of the alignment axis was orthogonal, and a rectangle of 4 cm × 2 cm was cut out and used as a sample for measurement. With respect to this sample, an orthogonal biaxial refractive index (Nx, Ny) and a refractive index (Nz) in the thickness direction were obtained by an Abbe refractometer (NAR-4T, manufactured by ATAGO Co., Ltd., measuring wavelength: 589 nm). The absolute value (|Nx-Ny|) of the above-described biaxial refractive index difference is taken as the anisotropy (ΔNxy) of the refractive index. The thickness d (nm) of the film was measured using an electric micrometer (manufactured by FEINPRUF, Millitron 1245D), and the unit was converted into nm. The hysteresis value (Re) of the polyester film was determined by the product of the anisotropy of the refractive index (ΔNxy) and the thickness d (nm) of the film (ΔNxy × d).

In addition, the cycloolefin resin film, the polyolefin resin film, and the (meth)acrylic resin film were measured using RETS100 (manufactured by Otsuka Electronics Co., Ltd.). Cut to make the sample size 10 cm × 10 cm, and arranged perpendicular to the incident light, and measured at 400 nm to 800 nm. The measuring point diameter is 2 mm, and the light source uses a 100 W halogen lamp. The measurement stage uses an automatic tilt rotation stage, and the measurement mode is measured by one point measurement, and the hysteresis value at a wavelength of 589 nm is obtained.

(2) Thickness direction hysteresis value (Rth)

The thickness direction hysteresis value is obtained by observing the two birefringences ΔNxz (=|Nx-Nz |) and ΔNyz (=|Ny-Nz |) when viewed from the cross section of the film thickness direction by the film thickness d. The average parameter of the hysteresis value obtained. Nx, Ny, Nz and film thickness d (nm) were obtained by the same method as the measurement of hysteresis value, and the average value of (ΔNxz × d) and (ΔNyz × d) was calculated to obtain the thickness direction hysteresis value. (Rth).

(3) Light transmittance at a wavelength of 380 nm

Using a spectrophotometer (manufactured by Hitachi, Ltd., model U-3500), the transmittance of light in the region of 300 to 500 nm of each PET film was measured in the atmosphere layer to determine the light transmittance at a wavelength of 380 nm.

(4) Rainbow spot observation

From the front side and the oblique direction of the polarizing plate of the liquid crystal display device, the presence or absence of rainbow spots was judged as follows. Further, in Comparative Example 3, a backlight source using a cold cathode tube as a light source was used instead of the white LED.

◎: There is no rainbow spot in any direction.

○: When viewed obliquely, a partially pale rainbow spot was observed.

×: When observed from an oblique direction, a rainbow spot is clearly observed.

(5) tear strength

Using Elmendorf tearing made by Toyo Seiki Co., Ltd. The test machine was used to measure the tear strength of each PET film in accordance with JIS P-8116. The tearing direction was performed in parallel with the direction of the main axis of the film, and was determined as follows. In addition, the measurement of the direction of the alignment axis was measured by a molecular alignment meter (manufactured by Oji Scientific Instruments Co., Ltd., MOA-6004 molecular alignment meter).

○: tear strength is 50mN or more

×: tear strength is less than 50mN

(6) Adhesion

On the surface of the adhesion-improving layer of the polypropylene film, the saponification degree adjusted to a solid content concentration of 5 mass% was 100 mol% by the wire rod coating so that the thickness of the dried polyvinyl alcohol polymer layer was 2 μm. An aqueous solution of polyvinyl alcohol polymer was dried at 70 ° C for 5 minutes. In order to make the determination easy, it is used for adding a blue dye to an aqueous solution of a polyvinyl alcohol polymer. The prepared evaluation sample was adhered to a glass plate having a thickness of 5 mm adhered to a double-sided tape, and the opposite surface of the surface of the prepared evaluation sample on which the polyvinyl alcohol polymer layer was formed was adhered to the double-sided tape. Next, 100 square-shaped cuts penetrating the polyvinyl alcohol polymer layer and reaching the base film were applied using a cutter rail having a gap of 2 mm. Next, a tape (Cellotape (registered trademark) CT-24; 24 mm wide manufactured by NICHIBAN Co., Ltd.) was adhered to a square cut surface. When the adhesive is used to squeeze the air remaining in the interface to make it completely adhered, the operation of peeling off the tape vertically and vigorously is performed five times. The number of squares in which the polyvinyl alcohol polymer layer was not peeled off was counted, and the adhesion was evaluated. The case where the number of squares in which the polyvinyl alcohol polymer layer was not peeled off was more than 70, and the case where 70 or less was used was set to "poor".

(acid degeneration amount)

The sheet (10 to 17 mg/cm ² ) of the resin was prepared by superheating (230 ° C), and the sheet was extracted with acetone for 5 hours, and then air-dried, and the absorbance was measured by an infrared spectrometer, and was determined by the following formula.

Maleic anhydride modified mass (ppm) = (A1790cm - ^{1 /} (8.5 × t) + (A1710cm ^-1 / (10.0 × t)) × 10 ⁶

A1790cm ^-1 and A1710cm ^-1 : Absorbance value (absorbance)

t = thickness of the sheet (μg/cm ² )

(Manufacturing Example 1 - Polyester A)

The temperature of the esterification reactor was raised, and 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were charged at a time point of reaching 200 ° C, and 0.017 parts by mass of antimony trioxide and 0.064 parts by mass were charged while stirring. Magnesium acetate tetrahydrate and 0.16 parts by mass of triethylamine were used as a catalyst. Subsequently, the temperature was raised under pressure, and the pressure esterification reaction was carried out under the conditions of a gauge pressure of 0.34 MPa and 240 ° C. Thereafter, the esterification reaction tank was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. Further, the temperature was raised to 260 ° C over 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added. Then, after 15 minutes, the dispersion treatment was carried out in a high-pressure disperser, and after 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reaction tank, and a polycondensation reaction was carried out at 280 ° C under reduced pressure.

After completion of the polycondensation reaction, the filter was treated with a 95%-blocking filter of NASLON filter having a diameter of 5 μm, extruded into a strand shape from a nozzle, and cooled by using a cooling water previously subjected to filtration treatment (pore diameter: 1 μm or less). Cured and cut into pellets. The obtained polyethylene terephthalate resin (A) had an intrinsic viscosity of 0.62 dl/g and contained substantially no inert particles and internal precipitated particles (hereinafter abbreviated as PET (A)).

(Manufacturing Example 2 - Polyester B)

Mix 10 parts by mass of dried UV absorber (2,2'-(1,4-phenylene) bis(4H-3,1-benzo) Keto-4-ketone), 90 parts by mass of PET-free (A) (inherent viscosity: 0.62 dl/g), using a kneading extruder to obtain polyethylene terephthalate containing a UV absorber Resin (B) (hereinafter abbreviated as PET (B)).

(Production Example 3 - Preparation of Adhesive Modification Coating Liquid)

The transesterification reaction and the polycondensation reaction were carried out by a usual method to prepare 46 mol% of terephthalic acid, 46 mol% of isophthalic acid, and 8 mol of dibasic acid component (for the entire dibasic acid component). Water-dispersible sulfonic acid metal salt of sodium 5-sulfonate isophthalate, 50 mol% ethylene glycol and 50 mol% neopentyl glycol as a diol component (for the entire diol component) Base copolyester resin. Next, 51.4 parts by mass of water, 38 parts by mass of isopropyl alcohol, 5 parts by mass of n-butyl cellosolve, and 0.06 parts by mass of a nonionic surfactant were mixed, and then heated and stirred. When 77 ° C was reached, 5 was added. The above-mentioned copolymerized polyester resin containing a water-dispersible sulfonic acid metal salt group is further stirred until the resin agglomerates disappear, and the aqueous resin dispersion liquid is cooled to normal temperature to obtain uniform water dispersibility of a solid content concentration of 5.0% by mass. Copolymerized polyester resin solution. Further, after dispersing 3 parts by mass of the aggregated ceria particles (manufactured by FUJI SILYSIA Co., Ltd., Sylysia 310) in 50 parts by mass of water, 0.54 by mass of the above water-dispersible copolymerized polyester resin liquid is added to 99.46 parts by mass. The aqueous dispersion of Sylysia 310 was added with 20 parts by mass of water while stirring to prepare an adhesive modified coating liquid.

(Manufacturing Example 4 - Production of Polypropylene Film)

Polypropylene resin FLX80E4 (Sumitomo) was supplied to the first extruder (PCM30 extruder: Ikebike Iron Works Co., Ltd.) and the second extruder (PCM45 extruder: Ikebe Iron Works Co., Ltd.) using two melt extruders. Chemical company, Sumitomo NOBRENE, melt flow rate: 7g/10min (230 ° C)) as a base layer, melt-co-extruded in a T-die at a resin temperature of 250 ° C, and then cooled by a mirror cooling roll. Polarized mirror protective film. The thickness was 69 μm. At the time of the above cooling, the adhesion to the polypropylene film of the cooling roll was performed by electrostatic sealing. The surface temperature of the cooling roll was set to 20 °C. The film was taken up at a speed of 5 m/min.

(Manufacturing Example 5 - Production of Polypropylene Film Having Adhesive Modified Layer)

Polypropylene resin FLX80E4 was supplied to the first extruder (PCM30 extruder: manufactured by Ikebike Iron Works Co., Ltd.) and the second extruder (PCM45 extruder: manufactured by Chiba Iron Works Co., Ltd.) using three melt extruders. (Sumitomo Chemical Co., Ltd., Sumitomo NOBRENE, melt flow rate: 7g/10 minutes (230 °C)) as a base layer, the third extruder (PCM30 extruder: Ikei Iron Works Co., Ltd.) is supplied with polypropylene-based adhesion. Resin (Admer QF551, manufactured by Mitsui Chemicals Co., Ltd., melt flow rate: 5.7 g/10 min (230 ° C), acid denaturation amount: 0.365 wt%) was used as a surface layer on the side of the cooling roll, and was melted by a T-die at a resin temperature of 250 ° C. After co-extrusion, a polarizer protective film was obtained by cooling with a mirror-finished cooling roll. The thickness composition ratio (adhesive modified layer/polypropylene film) was 11/69 μm. At the time of the above cooling, the film is adhered to the cooling roll by electrostatic sealing. The surface temperature of the cooling roll was set to 20 °C. The film was taken up at a speed of 5 m/min.

(Production Example 6 - Polypropylene film having an adhesion improving layer) Manufacturing)

A polypropylene-based adhesive resin (Mitsubishi Chemical Co., Ltd., Modic AP P504, melt flow rate: 5 g/10 min (230 ° C)) was supplied to a third extruder (PCM 30 extruder: manufactured by Chiba Iron Works Co., Ltd.). A polarizer protective film was obtained by the same method as in Production Example 5 except that the amount of acid denaturation was 0.4% by weight. It is known that the adhesion to PVA is good.

(Example 1)

90 parts by mass of the PET (A) resin pellets containing no particles and 10 parts by mass of the PET (B) resin pellet containing the ultraviolet absorber were used as a base material for the intermediate layer of the base film at 135 ° C under reduced pressure (1 Torr). After 6 hours, it is supplied to the extruder 2 (for the intermediate layer II layer), and the PET (A) is dried by the usual method and supplied to the extruder 1 (for the outer layer I and the outer layer III). Melt at 285 °C. Each of the two kinds of polymers was filtered with a filter medium of a stainless steel sintered body (95% cut-off of a nominal filtration accuracy of 10 μm particles), laminated by two kinds of three-layer bus bars, extruded into a sheet shape from a metal nozzle, and then cast using static electricity. The film was rolled and applied to a casting barrel having a surface temperature of 30 ° C to be cooled and solidified to produce an unstretched film. At this time, the discharge amount of each extruder was adjusted so that the ratio of the thickness of the I layer, the II layer, and the III layer became 10:80:10.

Next, the above-mentioned adhesive modified coating liquid was applied onto both surfaces of the unstretched PET film by a reverse roll method so that the coating amount after drying became 0.08 g/m ² , and then dried at 80 ° C for 20 seconds.

The unstretched film on which the coating layer was formed was guided to a stenter, and while holding the end portion of the film with a jig, it was guided to a hot air region at a temperature of 125 ° C and extended 4.0 times in the width direction. Next, in a state where the width extending in the width direction is maintained, the temperature is 225 ° C. After sec processing, further 3% relaxation treatment was carried out in the width direction to obtain a uniaxially oriented PET film having a film thickness of about 50 μm.

On one side of the polarizer including PVA and iodine, the uniaxially oriented polyester film is adhered to the perpendicular axis of the absorption axis of the polarizer, and the TAC film is adhered on the opposite side (FUJIFILM ( The polarizing plate A was produced by a thickness of 80 μm. Further, on one side of the polarizer including PVA and iodine, the polypropylene film obtained in Production Example 4 was adhered so that the absorption axis of the polarizer was perpendicular to the alignment main axis of the film, and TAC was adhered on the opposite side. A film (manufactured by FUJIFILM Co., Ltd., thickness: 80 μm) was used to prepare a polarizing plate B.

Will contain a combination of blue light-emitting diodes and enamel. aluminum. A white LED having a light-emitting element made of a garnet-based yellow phosphor is used as a light source (a Nissan Chemical, NSPW500CS) on the light-emitting side of the liquid crystal display device, and a polarizing plate is provided so that the polyester film becomes a visual recognition side. A. Further, on the incident light side of the liquid crystal display device, the obtained polarizing plate B was placed so that the polypropylene film was on the light source side, and a liquid crystal display device was produced.

(Example 2)

A uniaxially oriented PET film was produced in the same manner as in Example 1 except that the thickness of the unstretched film was changed to a thickness of about 100 μm. Further, on both sides of the polarizer including PVA and iodine, the polypropylene film obtained in Production Example 4 was adhered so that the absorption axis of the polarizer was perpendicular to the alignment main axis of the film, and the polarizing plate C was produced. The polarizing plate C was used for the polarizing plate on the incident light side of the liquid crystal cell, and the same as in the first embodiment except that the above-described uniaxially oriented polyester film having a thickness of 100 μm was used. , manufacturing a liquid crystal display device.

(Example 3)

The unstretched film produced by the same method as in Example 1 was heated to 105 ° C using a heated roll group and an infrared heater, and then extended by 1.5 times in the traveling direction by a roll group having a peripheral speed difference. A biaxially oriented PET film having a film thickness of about 50 μm was obtained by stretching 4.0 times in the width direction in the same manner as in Example 1. A liquid crystal display device was produced in the same manner as in Example 1 except that the biaxially oriented PET film was used.

(Example 4)

In the same manner as in Example 3, a biaxially oriented PET film having a film thickness of about 50 μm was obtained by extending 2.0 times in the traveling direction and 4.0 times in the width direction. A liquid crystal display device was produced in the same manner as in Example 1 except that the biaxially oriented PET film was used.

(Example 5)

In the same manner as in Example 3, a biaxially oriented PET film having a film thickness of about 75 μm was obtained by extending 3.3 times in the traveling direction and 4.0 times in the width direction. A liquid crystal display device was produced in the same manner as in Example 1 except that the biaxially oriented PET film was used.

(Example 6)

In the same manner as in Example 1, the PET resin (B) containing the ultraviolet absorber was not used in the intermediate layer, and a uniaxially oriented PET film having a film thickness of 50 μm was obtained. The obtained PET film has a high light transmittance of 380 nm and has a problem of deteriorating the optical functional pigment. A liquid crystal display device was produced in the same manner as in Example 1 except that this uniaxially oriented PET film was used.

(Example 7)

In the same manner as in Example 3, a uniaxially oriented PET film having a film thickness of about 100 μm was obtained by extending 4.0 times in the traveling direction and 1.0 times in the width direction. A liquid crystal display device was produced in the same manner as in Example 1 except that this uniaxially oriented PET film was used.

(Example 8)

In the same manner as in Example 3, a biaxially oriented PET film having a film thickness of about 250 μm was obtained by extending 3.5 times in the traveling direction and 3.7 times in the width direction. A liquid crystal display device was produced in the same manner as in Example 1 except that the biaxially oriented PET film was used. Although the Re of the polyester film is 4,500 nm or more, the Re/Rth ratio is less than 0.2, and the extremely weak rainbow spot is recognizable in the oblique direction.

(Example 9)

In the same manner as in Example 1, a uniaxially oriented PET film having a film thickness of about 75 μm was obtained by extending 1.0 times in the traveling direction and 3.5 times in the width direction. A liquid crystal display device was produced in the same manner as in Example 1 except that this uniaxially oriented PET film was used.

(Embodiment 10)

In the same manner as in Example 1, a uniaxially oriented PET film having a film thickness of about 275 μm was obtained by changing the thickness of the unstretched film. A liquid crystal display device was produced in the same manner as in Example 1 except that this uniaxially oriented PET film was used.

(Example 11)

The same procedure as in Example 1 was carried out except that the polypropylene film of Production Example 4 was used instead of the polypropylene film of Production Example 5. In addition, it is thin with polypropylene A polarizer is produced in such a manner that the surface of the film having the adhesive modified layer becomes the polarizer side. As a result of evaluation of the adhesion, it was found that the number of squares in which the polyvinyl alcohol polymer layer was not peeled off was 80, and the adhesion to PVA was good.

(Embodiment 12)

The same procedure as in Example 11 was carried out, except that the polypropylene film of Production Example 5 was replaced with the polypropylene film of Production Example 6. As a result of evaluation of the adhesion, it was found that the number of squares in which the polyvinyl alcohol polymer layer was not peeled off was 75, and the adhesion to PVA was good.

(Example 13)

In the same manner as in Example 1, except that a biaxially stretched film of a decene-based resin (manufactured by Nippon Zeon Co., Ltd., trade name: ZEONOR) having a thickness of 40 μm was used instead of the polypropylene film of Production Example 4, the hysteresis value was 55 nm. That is, a liquid crystal display device is manufactured.

(Example 14)

A liquid crystal was produced in the same manner as in Example 1 except that a lactone-based polymethyl methacrylate film (having a lactonization ratio of 20%, a thickness of 30 μm, and a hysteresis value of 0 nm) was used instead of the polypropylene film of Production Example 4. Display device.

(Comparative Example 1)

In the same manner as in Example 3, a biaxially oriented PET film having a film thickness of about 38 μm was obtained by extending 3.6 times in the traveling direction and 4.0 times in the width direction. A liquid crystal display device was produced in the same manner as in Example 1 except that the biaxially oriented PET film was used. The hysteresis value of the polyester film was low, and a rainbow-like stain was observed when observed obliquely.

(Comparative Example 2)

In the same manner as in Example 1, by changing the thickness of the unstretched film A uniaxially oriented PET film having a film thickness of about 10 μm was obtained. A liquid crystal display device was produced in the same manner as in Example 1 except that this uniaxially oriented PET film was used. The hysteresis value was also low, and a rainbow-like stain was observed.

(Comparative Example 3)

The same procedure as in the first embodiment was carried out except that the cold cathode tube was used as a light source of the liquid crystal display device to perform rainbow spot observation.

In the liquid crystal display devices of Examples 1 to 14 and Comparative Examples 1 to 3, the results of measurement of the rainbow spot and the physical properties of each film are shown in Table 1 below.

As shown in Table 1, the liquid crystal display devices of Examples 1 to 14 were subjected to rainbow spot observation, and when observed from the front direction, the generation of rainbow spots was greatly reduced in any of the examples. Regarding the liquid crystal display devices of Examples 3 to 5 and 8, a part of the rainbow spots were sometimes observed when viewed obliquely, but with respect to Examples 1, 2, 6, 7, 9, 10, 13 and 14 In the liquid crystal display device, when viewed obliquely, the rainbow spot is not observed at all. On the other hand, in the liquid crystal display devices of Comparative Examples 1 to 3, a clear rainbow spot was observed when observed from an oblique direction.

Further, it was confirmed that the polyester film used in Example 7 and Comparative Example 2 had insufficient tear strength. It is considered that the polyester film of Example 7 is too large in Re/Rth, and the polyester film of Comparative Example 2 is too thin in film thickness.

[Industrial availability]

By using the liquid crystal display device of the present invention, the visibility is not deteriorated by the rainbow-colored color spots, and the LCD can be made thinner and lower in cost, and the industrial use possibility is extremely high.

Claims (10)

A liquid crystal display device comprising a backlight source and a liquid crystal cell disposed between two polarizing plates, the backlight source being a white light source having a continuous luminescence spectrum, the polarizing plate being included in two of the polarizers In the configuration of the laminated polarizer protective film, at least one of the polarizer protective films disposed on the polarizing plate on the light-emitting side of the liquid crystal cell has an alignment polyester film having a hysteresis value of 3,000 to 30,000 nm. At least one of the polarizer protective films of the polarizing plate disposed on the incident light side of the liquid crystal cell is a cycloolefin resin film, a polyolefin resin film, or a (meth)acrylic resin film. The liquid crystal display device according to claim 1, wherein the cycloolefin resin film, the polyolefin resin film or the (meth)acrylic resin film has a hysteresis value of 200 nm or less. A liquid crystal display device according to claim 1 or 2, wherein the olefin resin film is a polypropylene film. The liquid crystal display device according to any one of claims 1 to 3, wherein a ratio (Re/Rth) of the retardation value to the thickness direction hysteresis value of the alignment polyester film is 0.2 or more and 1.2 or less. A liquid crystal display device according to any one of claims 1 to 4, wherein the white light source having a continuous luminescence spectrum is a white light-emitting diode. The liquid crystal display device of any one of claims 1 to 5, wherein the alignment polyester film has an easy adhesion layer. The liquid crystal display device according to any one of claims 1 to 6, wherein the alignment polyester film contains at least three layers or more, outside the outermost layer. The layer contains an ultraviolet absorber, and the light transmittance at 380 nm is 20% or less. The liquid crystal display device according to any one of claims 1 to 7, wherein the polarizer protective film disposed on the light-emitting side of the polarizing plate on the light-emitting side with respect to the liquid crystal cell has a hysteresis value of 3,000 to 30,000 nm. The alignment polyester film has a group selected from the group consisting of a hard coat layer, an anti-glare layer, an anti-reflection layer, a low-reflection layer, a low-reflection anti-glare layer, and an anti-reflection anti-glare layer on the light-emitting side of the alignment polyester film. One or more layers. The liquid crystal display device according to any one of claims 3 to 8, wherein at least one surface of the polypropylene film is laminated with an adhesion improving layer containing a polyolefin resin, and the polyolefin resin contains a polar group. The liquid crystal display device of claim 9, wherein the polyolefin resin is a polypropylene resin.