JP6478883B2 - Liquid crystal display - Google Patents

Description

The present invention relates to a liquid crystal display device and a polarizing plate protective film used for the liquid crystal display device.

Since liquid crystal display devices have features such as power saving, light weight, and thinness, they have rapidly spread in recent years in place of conventional CRT displays.
As a general liquid crystal display device, for example, as shown in FIG. 2, a backlight light source (not shown), a backlight-side polarizing plate 25, a liquid crystal cell 21, a color filter 22, and a display-side polarizing plate 23 are provided. The structure which has is mentioned. The polarizing plates 23 and 25 are configured to selectively transmit only linearly polarized light having a vibration surface in a predetermined vibration direction, and crossed Nicols so that the respective vibration directions are perpendicular to each other. It is arranged to face each other. The liquid crystal cell 21 is disposed between the polarizing plates 23 and 25.

By the way, the polarizing plate used for the liquid crystal display device is usually provided with a polarizing plate protective film, and as the polarizing plate protective film, a film made of cellulose ester represented by triacetyl cellulose has been conventionally used. It was. This is because the cellulose ester has a low retardation value, so it has little influence on the display quality of the liquid crystal display device and has moderate water permeability. This is based on the advantage that it can be dried through the film. Moreover, the point that the cellulose ester film is comparatively cheap also contributes.

However, when such a cellulose ester film is considered as a member that supports the liquid crystal display industry that will continue to expand in the future, there are various problems. Among the most serious problems, the following have been pointed out.
First, the cellulose ester film is produced by a so-called solution casting method in which a solution in which cellulose ester is dissolved in an organic solvent is cast on a support, the solvent is dried, and then the film is peeled off. It is common to be done. However, in order to carry out such a solution casting method, it requires large-scale equipment and special techniques, including a solvent drying process, so that it can be produced only by those who possess special techniques. However, the supply and demand corresponding to the expanding liquid crystal display device market cannot be satisfied. For this reason, the reliance on cellulose ester film as a polarizing plate protective film in the future may hinder the development of the liquid crystal display industry, which is no exaggeration to say that it is the main industry in Japan.
In general, when a cellulose ester film is produced by the solution casting method described above, dichloromethane is used as a main solvent as an organic solvent used in the cellulose ester solution. However, since the dichloromethane is suspected to be dangerous to the human body, depending on the cellulose ester film in the future will increase the amount of dichloromethane used and discharged with the development of the liquid crystal display industry. It was not desirable in terms of environment.

From the problem of such a cellulose ester film, it is desired to use a versatile film that is easily available in the market or that can be produced by a simple method as a polarizing plate protective film. Attempts have been made to use a polyester film such as polyethylene terephthalate as an alternative film (see, for example, Patent Document 1).

JP 2004-205773 A

However, according to the study by the present inventors, when a polyester film such as polyethylene terephthalate (PET) is used as a cellulose ester film alternative film, the liquid crystal display device has uneven color (hereinafter also referred to as “NIJIMURA”), In particular, it has been found that there is a problem that the display quality of the liquid crystal display device is impaired when the display screen is observed from an oblique direction.

As a result of further investigation on the problem of the polarizing plate protective film using such a polyester film, a polarizing plate made of a conventional polyester film can be obtained by using a polyester film having a somewhat high retardation value as the polarizing plate protective film. It has been found that the problem of Nizimura can be improved as compared with the case where a protective film is used.
Here, as a liquid crystal display device using a polyester film having a somewhat high retardation value as a polarizing plate protective film, for example, a liquid crystal display device described in JP2011-107198A is known. In this liquid crystal display device, a polarizing plate is provided on the viewing side of the liquid crystal cell, a polymer film having a retardation of 3000 to 30000 nm is disposed on the viewing side of the polarizing plate, and the slow axis of the polymer film and the polarizing plate The liquid crystal display device has an angle formed with the absorption axis of approximately 45 degrees, and an oriented polyester film is used as the polymer film. According to this liquid crystal display device, even when the display image is viewed through a polarizing plate such as sunglasses, the occurrence of Nizimura is improved to some extent compared to the case where a conventional polyester film is used as a polarizing plate protective film. It is considered possible.
However, in recent years, the display image of the liquid crystal display device has been increasingly refined, and the quality required for the display image has become extremely high. For this reason, it has become necessary to suppress even higher levels of nitrite generated on the display screen of the liquid crystal display device.
However, the conventional polarizing plate protective film has not been able to sufficiently respond to such higher level of nitrile suppression.
As a result of further studies by the present inventors, in a liquid crystal display device using a conventional oriented polyester film having a somewhat high retardation value as a polarizing plate protective film, only with respect to the influence of backlight light that is transmitted light. Since various studies have been conducted with attention paid, the influence of light from the outside of the liquid crystal display device in an environment with external light or fluorescent light has been forgotten, and changes in wavelength uniformity due to color filters It was found that this was caused by not taking into account.
That is, even in a liquid crystal display device using a conventional oriented polyester film having a somewhat high retardation value as a polarizing plate protective film, the change in wavelength uniformity due to the color filter and the reflected light of external light or fluorescent light As a result, a problem such as generation of nidy spot and deterioration of display quality occurs, and it has not been possible to sufficiently meet the high level of suppression of yellow spot.

In view of the above-mentioned present situation, the present invention provides a liquid crystal display device capable of extremely highly suppressing the occurrence of nitrile in a display image of a liquid crystal display device, and a polarizing plate protective film used in the liquid crystal display device. Objective.

The present invention is a liquid crystal display device having a configuration in which a backlight light source, a liquid crystal cell, a color filter, a polarizing plate, and a polarizing plate protective film are arranged in this order, and used in an environment with external light. The polarizing plate protective film has a thickness of 20 μm to 500 μm (except when it is less than 65 μm) , has a retardation of 8000 nm or more, and has an absorption axis of the polarizing plate and the polarizing plate. Arranged so that the angle formed with the slow axis of the protective film is 0 ° ± 30 ° or 90 ° ± 30 ° (excluding -30 °, 30 °, 60 ° , 90 ° and 120 ° ) a liquid crystal display device comprising a Iruko is.

In the liquid crystal display device of the present invention, the backlight source is preferably a white light emitting diode.
In the liquid crystal display device of the present invention, the polarizing plate protective film has a refractive index (nx) in the slow axis direction, which is the direction having the largest refractive index in the plane, and an advance in a direction orthogonal to the slow axis direction. The difference (nx−ny) from the refractive index (ny) in the phase axis direction is preferably 0.05 or more.
The polarizing plate protective film includes polyester resin, polyolefin resin, (meth) acrylic resin, polyurethane resin, polyether sulfone resin, polycarbonate resin, polysulfone resin, polyether resin, polyether. It is preferably made of any one material selected from the group consisting of ketone-based resins, (meth) acrylonitrile-based resins, and cycloolefin-based resins.
Moreover, it is preferable that the said polarizing plate protective film has a retardation of 8000 nm or more and 9900 nm or less.
The present invention is described in detail below.
In the present invention, unless otherwise specified, curable resin precursors such as monomers, oligomers, and prepolymers are also referred to as “resins”.

As a result of intensive studies in view of the above-described conventional problems, the present inventors used a polarizing plate protective film having a predetermined retardation value, and the polarizing plate protective film has a slow axis of the polarizing plate. By arranging it so that the angle formed with respect to the absorption axis is approximately 0 ° or 90 °, even if it is used in an environment where there is external light or light from a fluorescent lamp, the display image is distorted. It was found that this can be suppressed to a very high degree.

FIG. 1 is a cross-sectional view schematically showing an example of the liquid crystal display device of the present invention.
As shown in FIG. 1, the liquid crystal display device 10 of the present invention has a configuration in which a liquid crystal cell 11, a color filter 12, a polarizing plate 13, and a polarizing plate protective film 14 are arranged in this order.
Although not shown, the liquid crystal display device 10 of the present invention has a backlight light source on the side opposite to the color filter 12 of the liquid crystal cell 11, and the liquid crystal cell 11 is sandwiched between two polarizing plates. In this case, a polarizing plate having the same configuration as that of the polarizing plate 13 is provided on the side surface opposite to the color filter 12 of the liquid crystal cell 11, but these two polarizing plates usually absorb each other. The shaft is arranged to be 90 ° (crossed Nicols).

In the liquid crystal display device of the present invention, the polarizing plate protective film is disposed on the most visible side and has a retardation of 8000 nm or more. If the retardation is less than 8000 nm, nitjira appears in the display image of the liquid crystal display device of the present invention. On the other hand, the upper limit of the retardation of the polarizing plate protective film is not particularly limited, but is preferably about 30,000 nm. If it exceeds 30,000 nm, no further improvement in the effect of improving the azimuth of the display image is observed, and the film thickness becomes considerably thick.
It is preferable that the retardation of the said polarizing plate protective film is 10,000-20,000 nm from a viewpoint of Nizimura prevention property and thin film formation.

The retardation is a refractive index (nx) in the direction having the largest refractive index (slow axis direction) in the plane of the polarizing plate protective film and a direction (fast axis direction) perpendicular to the slow axis direction. The refractive index (ny) and the thickness (d) of the polarizing plate protective film are represented by the following formula.
Retardation (Re) = (nx−ny) × d
The retardation can be measured, for example, by KOBRA-WR manufactured by Oji Scientific Instruments (measurement angle 0 °, measurement wavelength 548.2 nm).
In the present invention, the nx-ny (hereinafter also referred to as Δn) is preferably 0.05 or more. If the above Δn is less than 0.05, there may be a case where a sufficient effect of suppressing azimuth cannot be obtained. Moreover, since the film thickness required in order to obtain the retardation value mentioned above becomes thick, it is not preferable. A more preferable lower limit of the Δn is 0.07.

The material constituting the polarizing plate protective film is not particularly limited as long as it satisfies the above-mentioned retardation. For example, polyester resin, polyolefin resin, (meth) acrylic resin, polyurethane resin, polyether One kind selected from the group consisting of sulfone resin, polycarbonate resin, polysulfone resin, polyether resin, polyether ketone resin, (meth) acrylonitrile resin, and cycloolefin resin is preferably used. Used. Especially, it is preferable that the said polarizing plate protective film consists of polyethylene terephthalate (PET). This is because polyethylene terephthalate is highly versatile and easily available. In the present invention, a polarizing plate protective film capable of producing a liquid crystal display device with high display quality can be obtained even if it is a highly versatile film such as PET. Furthermore, PET is excellent in transparency, heat or mechanical properties, can control the retardation by stretching, has a large intrinsic birefringence, and can obtain a large retardation relatively easily even when the film thickness is small.

The method for obtaining the polarizing plate protective film is not particularly limited as long as it satisfies the above-mentioned retardation. For example, in the case of the polyester such as PET, the material polyester is melted and extruded into a sheet shape. A method of subjecting the unstretched polyester to a heat treatment after transverse stretching using a tenter or the like at a temperature equal to or higher than the glass transition temperature.
The transverse stretching temperature is preferably 80 to 130 ° C, more preferably 90 to 120 ° C. Further, the transverse draw ratio is preferably 2.5 to 6.0 times, more preferably 3.0 to 5.5 times. When the transverse draw ratio exceeds 6.0 times, the transparency of the polarizing plate protective film made of the resulting polyester tends to be lowered, and when the draw ratio is less than 2.5 times, the draw tension becomes small. The birefringence of the obtained polarizing plate protective film becomes small, and retardation may not be 8000 nm or more.
In the present invention, the unstretched polyester is subjected to transverse stretching under the above conditions using a biaxial stretching test apparatus, and then stretched in the flow direction with respect to the transverse stretching (hereinafter also referred to as longitudinal stretching). Also good. In this case, the longitudinal stretching preferably has a stretching ratio of 2 times or less. When the draw ratio of the above-mentioned longitudinal stretching exceeds twice, the value of Δn may not be within the preferred range described above.
The treatment temperature during the heat treatment is preferably 100 to 250 ° C, more preferably 180 to 245 ° C.

Examples of the method for controlling the retardation of the polarizing plate protective film produced by the above-described method to 8000 nm or more include a method of appropriately setting the stretching ratio, the stretching temperature, and the thickness of the polarizing plate protective film to be produced. Specifically, for example, the higher the stretching ratio, the lower the stretching temperature, and the thicker the film, the easier it is to obtain high retardation. The lower the stretching ratio, the higher the stretching temperature, and the film thickness. The thinner, the easier it is to obtain low retardation.

The thickness of the polarizing plate protective film is appropriately determined according to the constituent material and the like, but is preferably in the range of 20 to 500 μm. If the thickness is less than 20 μm, the retardation of the polarizing plate protective film may not be 8000 nm or more, and the anisotropy of the mechanical properties becomes remarkable, and it is easy to cause tearing, tearing, etc. May decrease significantly. On the other hand, if it exceeds 500 μm, the polarizing plate protective film is very rigid, the flexibility specific to the polymer film is lowered, and the practicality as an industrial material is also lowered, which is not preferable. The minimum with more preferable thickness of the said polarizing plate protective film is 30 micrometers, a more preferable upper limit is 400 micrometers, and a still more preferable upper limit is 300 micrometers.

The polarizing plate protective film preferably has a transmittance in the visible light region of 80% or more, more preferably 84% or more. In addition, the said transmittance | permeability can be measured by JISK7361-1 (The test method of the total light transmittance of a plastic-transparent material).
Such a polarizing plate protective film used in the liquid crystal display device of the present invention is also one aspect of the present invention.

In the liquid crystal display device of the present invention, the polarizing plate protective film has an angle formed by a slow axis of the polarizing plate protective film and an absorption axis of a polarizing plate (a polarizing plate disposed on the viewing side of the liquid crystal cell) described later. , 0 ° ± 30 ° or 90 ° ± 30 °. The angle formed by the slow axis of the polarizing plate protective film and the absorption axis of the polarizing plate is within the above range, so that it is possible to extremely highly suppress the occurrence of nitrimla in the display image of the liquid crystal display device of the present invention. it can. The reason for this is not clear, but is thought to be due to the following reasons.
That is, in an environment free from outside light or fluorescent light (hereinafter, this environment is also referred to as “dark place”), the slow axis of the polarizing plate protective film of the liquid crystal display device of the present invention and the polarizing plate It is possible to suppress the occurrence of azimuth unevenness regardless of the angle formed with the absorption axis. However, in an environment where there is ambient light or fluorescent light (hereinafter, this environment is also referred to as “light place”), external light or fluorescent light has only a continuous wide spectrum. Therefore, if the angle formed between the slow axis of the polarizing plate protective film and the absorption axis of the polarizing plate is not within the above range, nitrite occurs and the display quality deteriorates.
Furthermore, since the backlight light transmitted through the color filter is not limited to having a continuous wide spectrum, the angle formed between the slow axis of the polarizing plate protective film and the absorption axis of the polarizing plate is not within the above range. As a result, it is presumed that the display quality will deteriorate due to the occurrence of Nizimura.

In the liquid crystal display device of the present invention, the backlight light source is not particularly limited, but is preferably a white light emitting diode (white LED).
The white LED is an element that emits white by combining a phosphor with a phosphor system, that is, a light emitting diode that emits blue light or ultraviolet light using a compound semiconductor. Above all, white light-emitting diodes, which consist of light-emitting elements that combine blue light-emitting diodes using compound semiconductors with yttrium, aluminum, and garnet yellow phosphors, have a continuous and broad emission spectrum. Therefore, it is suitable for the backlight light source in the present invention. Further, since white LEDs with low power consumption can be widely used, it is possible to achieve an energy saving effect.

The polarizing plate is not particularly limited as long as it has desired polarization characteristics, and those generally used for polarizing plates of liquid crystal display devices can be used. Specifically, for example, a polyvinyl alcohol film is stretched, and a polarizing plate containing iodine is preferably used.

The liquid crystal cell is not particularly limited, and for example, a generally known liquid crystal cell for a liquid crystal display device can be used. In addition, as liquid crystal cells for liquid crystal display devices, display types such as TN, STN, VA, IPS, and OCB are known. In the present invention, any of these display types is used. Can also be used.

Moreover, it does not specifically limit as said color filter, For example, generally what is known as a color filter of a liquid crystal display device can be used. Such a color filter is usually composed of transparent colored patterns of red, green and blue, and each transparent colored pattern is made of a resin composition in which a colorant is dissolved or dispersed, preferably pigment fine particles are dispersed. Composed. The color filter may be formed by preparing an ink composition colored in a predetermined color and printing it for each colored pattern. However, a paint-type photosensitive material containing a colorant of a predetermined color may be used. It is more preferable to carry out by a photolithography method using a conductive resin composition.
The display image of the liquid crystal display device of the present invention is displayed in color as the light emitted from the backlight light source passes through the color filter. However, when the light transmitted through the color filter is controlled so as to display in a single color, if a conventional oriented polyester film is used as the polarizing plate protective film, there is a case where Nizimura becomes stronger. On the other hand, since the liquid crystal display device of the present invention has the polarizing plate protective film described above, even when such a monochromatic display is used, it is possible to suitably suppress the occurrence of nitrile.

In the liquid crystal display device of the present invention, another polarizing plate protective film may be provided on the opposite side surface of the polarizing plate provided with the polarizing plate protective film. By providing such another polarizing plate protective film, it is possible to prevent the polarizing plate from being exposed to moisture or the like in the air, or to prevent dimensional change of the polarizing plate.

Although it will not specifically limit if it has transparency as said another polarizing plate protective film, The thing in which the transmittance | permeability in visible region is 80% or more is preferable, and what is 90% or more is more preferable. Here, the said transmittance | permeability can be measured by JISK7361-1 (the test method of the total light transmittance of a plastic-transparent material).

Examples of the material constituting the other polarizing plate protective film include cellulose derivatives, cycloolefin resins, polymethyl methacrylate, polyvinyl alcohol, polyimide, polyarylate, polyethylene terephthalate, polysulfone, polyethersulfone, amorphous polyolefin, and modified acrylic. Examples thereof include resin materials such as polymer, polystyrene, epoxy resin, polycarbonate and polyester. Among these, cellulose derivatives or cycloolefin polymers are preferably used as the resin material.

The cellulose derivative is not particularly limited as long as it has desired transparency, moisture permeability, etc. Among them, cellulose acetate can be particularly preferably used.
As the cellulose acetate, triacetyl cellulose having an average acetylation degree of 57.5 to 62.5% (substitution degree: 2.6 to 3.0) is most preferably used. Here, the degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation can be determined by measurement and calculation of the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate and the like).

The cycloolefin polymer is not particularly limited as long as it is a resin having a monomer unit composed of a cyclic olefin (cycloolefin). Examples of such a monomer comprising a cyclic olefin include norbornene and polycyclic norbornene monomers.
In addition, as said cycloolefin type polymer, any of a cycloolefin polymer (COP) or a cycloolefin copolymer (COC) can be used conveniently. The cycloolefin-based polymer may be a homopolymer of a monomer composed of the cyclic olefin or a copolymer.

In addition, the cycloolefin polymer preferably has a saturated water absorption at 23 ° C. of 1% by mass or less, and particularly preferably within a range of 0.1% by mass to 0.7% by mass. By using such a cycloolefin-based polymer, it is possible to make the other polarizing plate protective film less susceptible to changes in optical properties and dimensions due to water absorption.
Here, the said saturated water absorption is calculated | required by immersing in 23 degreeC water for 1 week based on ASTMD570, and measuring an increase weight.

Further, the cycloolefin-based polymer preferably has a glass transition point in the range of 100 to 200 ° C, more preferably in the range of 100 to 180 ° C, and in the range of 100 to 150 ° C. Is more preferable. When the glass transition point is within the above range, the other polarizing plate protective film can be made more excellent in heat resistance and processability.

Specific examples of another polarizing plate protective film made of the above cycloolefin-based resin include, for example, Topas manufactured by Ticona, Arton manufactured by JSR, ZEONOR, ZEONEX manufactured by Nippon Zeon, and Appel manufactured by Mitsui Chemicals. Is mentioned.

Said another polarizing plate protective film may consist of a single layer, or may have a configuration in which a plurality of layers are laminated. Here, the configuration in which a plurality of layers are stacked may be a configuration in which a plurality of layers having the same composition are stacked, or a configuration in which layers having different compositions are stacked.

The another polarizing plate protective film may have an optical compensation function by having refractive index anisotropy.
That is, in the present invention, an optical compensation film (retardation film) for a liquid crystal surface device can be used as the other polarizing plate protective film. As an aspect in which the other polarizing plate protective film has an optical compensation function, an aspect in which a compound having refractive index anisotropy is contained in a film made of the material as described above, or a refractive index on the film. Examples include a mode in which a layer containing a compound having anisotropy is formed.
In the present invention, any of these embodiments can be preferably used, but the latter embodiment is preferably used in that it is easy to arbitrarily adjust the refractive index anisotropy according to the application. It is done.

Examples of the compound having refractive index anisotropy include rod-shaped compounds, discotic compounds, and liquid crystal compounds. In addition, these compounds having refractive index anisotropy are compounds that have a polymerizable functional group from the viewpoint of alignment stability because they can exhibit an excellent optical compensation function by regular alignment. Is preferably used.

Such a polarizing plate protective film, another polarizing plate protective film, and a polarizing plate can be arrange | positioned through an adhesive bond layer.
It does not specifically limit as an adhesive used for the said adhesive bond layer, For example, hydrophilic adhesives, such as polyvinyl alcohol and polyvinylpyrrolidone, an acrylic adhesive, a urethane type adhesive, an epoxy-type adhesive, etc. are mentioned. Especially, in the polarizing plate protective film which is hydrophobic like PET, it is preferable that it is an ultraviolet curable adhesive layer.
In addition, in the polarizing plate protective film having a high ultraviolet transmittance, it is also a preferable aspect that an ultraviolet absorber is contained in the adhesive layer.

The liquid crystal display device of the present invention may have a configuration in which an arbitrary layer is formed as a single layer and / or multiple layers on the polarizing plate protective film.
The arbitrary layer is not particularly limited, and examples thereof include a hard coat layer, an antistatic layer, a low refractive layer, a high refractive index layer, an antiglare layer, and an antifouling layer.

The hard coat layer is a layer that ensures the hard coat properties of the surface of the liquid crystal display device of the present invention. For example, an ionizing radiation curable resin that is a resin curable by ultraviolet rays or an electron beam and a photopolymerization initiator. It is preferably formed using the hard coat layer-forming composition that it contains.

Examples of the ionizing radiation curable resin include compounds having one or more unsaturated bonds such as compounds having an acrylate functional group. Examples of the compound having one unsaturated bond include ethyl (meth) acrylate, ethylhexyl (meth) acrylate, styrene, methylstyrene, N-vinylpyrrolidone and the like. Examples of the compound having two or more unsaturated bonds include polymethylolpropane tri (meth) acrylate, hexanediol (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, pentaerythritol tri ( Polyfunctional compounds such as (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, or the above polyfunctional compound and (meth) acrylate And the like (eg, poly (meth) acrylate esters of polyhydric alcohols). In the present specification, “(meth) acrylate” refers to methacrylate and acrylate.

In addition to the above compounds, relatively low molecular weight polyester resins having unsaturated double bonds, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiol polyene resins, etc. It can be used as an ionizing radiation curable resin.

The ionizing radiation curable resin is used in combination with a solvent-drying resin (a thermoplastic resin or the like, which is a resin that forms a film only by drying the solvent added to adjust the solid content during coating). You can also. By using a solvent-drying resin in combination, coating defects on the coated surface can be effectively prevented. The solvent-drying resin that can be used in combination with the ionizing radiation curable resin is not particularly limited, and a thermoplastic resin can be generally used.
The thermoplastic resin is not particularly limited. For example, a styrene resin, a (meth) acrylic resin, a vinyl acetate resin, a vinyl ether resin, a halogen-containing resin, an alicyclic olefin resin, a polycarbonate resin, or a polyester resin. Examples thereof include resins, polyamide-based resins, cellulose derivatives, silicone-based resins, rubbers, and elastomers. The thermoplastic resin is preferably amorphous and soluble in an organic solvent (particularly a common solvent capable of dissolving a plurality of polymers and curable compounds). In particular, from the viewpoints of film forming properties, transparency, and weather resistance, styrene resins, (meth) acrylic resins, alicyclic olefin resins, polyester resins, cellulose derivatives (cellulose esters, etc.) and the like are preferable.

Moreover, the said composition for hard-coat layer formation may contain the thermosetting resin.
The thermosetting resin is not particularly limited. For example, phenol resin, urea resin, diallyl phthalate resin, melamine resin, guanamine resin, unsaturated polyester resin, polyurethane resin, epoxy resin, aminoalkyd resin, melamine-urea cocondensation Examples thereof include resins, silicon resins, polysiloxane resins, and the like.

The photopolymerization initiator is not particularly limited, and known ones can be used. For example, specific examples of the photopolymerization initiator include acetophenones, benzophenones, Michler benzoylbenzoate, α-amylo. Examples include oxime esters, thioxanthones, propiophenones, benzyls, benzoins, and acylphosphine oxides. In addition, it is preferable to use a mixture of photosensitizers, and specific examples thereof include n-butylamine, triethylamine, poly-n-butylphosphine, and the like.

As the photopolymerization initiator, when the ionizing radiation curable resin is a resin system having a radical polymerizable unsaturated group, acetophenones, benzophenones, thioxanthones, benzoin, benzoin methyl ether, etc. may be used alone or in combination. It is preferable to use it. When the ionizing radiation curable resin is a resin system having a cationic polymerizable functional group, the photopolymerization initiator may be an aromatic diazonium salt, aromatic sulfonium salt, aromatic iodonium salt, metallocene compound, benzoin sulfone. It is preferable to use acid esters alone or as a mixture.

The content of the photopolymerization initiator in the hard coat layer forming composition is preferably 1 to 10 parts by mass with respect to 100 parts by mass of the ionizing radiation curable resin. When the amount is less than 1 part by mass, the hardness of the hard coat layer in the optical laminate of the present invention may not be within the above-described range. When the amount exceeds 10 parts by mass, ionizing radiation is transmitted to the deep part of the coated film. This is because it does not reach and internal curing is not promoted, and there is a possibility that the target pencil hardness of 3H or higher on the surface of the hard coat layer may not be obtained.
The minimum with more preferable content of the said photoinitiator is 2 mass parts, and a more preferable upper limit is 8 mass parts. When the content of the photopolymerization initiator is in this range, a hardness distribution does not occur in the film thickness direction, and uniform hardness is likely to occur.

The composition for forming a hard coat layer may contain a solvent.
As said solvent, it can select and use according to the kind and solubility of the resin component to be used, for example, ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, diacetone alcohol etc.), ethers ( Dioxane, tetrahydrofuran, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, etc.), aliphatic hydrocarbons (hexane, etc.), alicyclic hydrocarbons (cyclohexane, etc.), aromatic hydrocarbons (toluene, xylene, etc.), Halogenated carbons (dichloromethane, dichloroethane, etc.), esters (methyl acetate, ethyl acetate, butyl acetate, etc.), water, alcohols (ethanol, isopropanol, butanol, cyclohexanol, etc.), cellosolves (methyl cello) Lube, ethyl cellosolve), cellosolve acetates, sulfoxides (dimethyl sulfoxide), amides (dimethylformamide, dimethylacetamide, etc.) and the like can be exemplified, it may be a mixed solvent thereof.

Although it does not specifically limit as a content rate (solid content) of the raw material in the said composition for hard-coat layer formation, Usually, it is preferable to set it as 5-70 mass%, especially 25-60 mass%.

According to the purpose of increasing the hardness of the hard coat layer, suppressing curing shrinkage, controlling the refractive index, imparting antiglare properties, etc., the hard coat layer forming composition, Surfactant, antistatic agent, silane coupling agent, thickener, anti-coloring agent, coloring agent (pigment, dye), antifoaming agent, leveling agent, flame retardant, ultraviolet absorber, adhesion promoter, polymerization inhibitor In addition, an antioxidant, a surface modifier, a lubricant and the like may be added.

Moreover, the said composition for hard-coat layer formation may mix and use a photosensitizer, As a specific example, n-butylamine, a triethylamine, poly-n-butylphosphine etc. are mentioned, for example. .

The method for preparing the composition for forming a hard coat layer is not particularly limited as long as each component can be uniformly mixed. For example, the composition can be performed using a known apparatus such as a paint shaker, a bead mill, a kneader, or a mixer.

In addition, the method for coating the hard coat layer forming composition on the polarizing plate protective film is not particularly limited, for example, spin coating method, dipping method, spray method, die coating method, bar coating method, roll coater method, Well-known methods such as meniscus coater method, flexographic printing method, screen printing method and peade coater method can be mentioned.

The coating film formed by applying the composition for forming a hard coat layer on the polarizing plate protective film is preferably heated and / or dried as necessary and cured by irradiation with active energy rays.

Examples of the active energy ray irradiation include irradiation with ultraviolet rays or electron beams. Specific examples of the ultraviolet light source include light sources such as an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc lamp, a black light fluorescent lamp, and a metal halide lamp. Moreover, as a wavelength of an ultraviolet-ray, the wavelength range of 190-380 nm can be used. Specific examples of the electron beam source include various electron beam accelerators such as a cockcroft-wald type, a bandegraft type, a resonant transformer type, an insulated core transformer type, a linear type, a dynamitron type, and a high frequency type.

In addition, the film thickness (at the time of hardening) of the said hard-coat layer is 0.1-100 micrometers, Preferably it is the range of 0.8-20 micrometers. The film thickness of the hard coat layer is a value measured by observing the cross section with an electron microscope (SEM, TEM, STEM).

The antistatic agent can be formed, for example, by incorporating an antistatic agent into the hard coat layer forming composition.
As the antistatic agent, conventionally known ones can be used. For example, a cationic antistatic agent such as a quaternary ammonium salt, fine particles such as tin-doped indium oxide (ITO), a conductive polymer, or the like can be used. Can do.
When using the said antistatic agent, it is preferable that the content is 1-30 mass% with respect to the total mass of all the solid content.

Moreover, the said glare-proof layer can be formed by containing an anti-glare agent in the said composition for hard-coat layer formation, for example.
The antiglare agent is not particularly limited, and various known inorganic or organic fine particles can be used.
The average particle size of the fine particles is not particularly limited, but generally may be about 0.01 to 20 μm.
Further, the shape of the fine particles may be any of a spherical shape, an elliptical shape, etc., and preferably a spherical shape.

The fine particles exhibit antiglare properties and are preferably transparent fine particles. Specific examples of such fine particles include silica beads if they are inorganic, and plastic beads if they are organic.
Specific examples of the plastic beads include, for example, styrene beads (refractive index 1.60), melamine beads (refractive index 1.57), acrylic beads (refractive index 1.49), and acrylic-styrene beads (refractive index 1. 54), polycarbonate beads, polyethylene beads and the like.

The low refractive index layer is a layer that plays a role of reducing the reflectance when external light (for example, a fluorescent lamp, natural light, etc.) is reflected on the surface of the polarizing plate protective film.
The low refractive index layer has a refractive index smaller than that of the polarizing plate protective film and larger than air.

The low refractive index layer preferably has a refractive index with respect to light transmitted through the polarizing plate protective film within a range of 1.1 to 2.0, and within a range of 1.2 to 1.8. Is more preferable, and it is further preferable to be within the range of 1.3 to 1.6. When the refractive index of the low refractive index layer is within the above range, the liquid crystal display device of the present invention can have higher display quality.

The refractive index of the low refractive index layer may be one in which the refractive index gradually changes toward the refractive index of air from the polarizing plate protective film side to the air side in the low refractive index layer. .

The material used for the low refractive index layer is not particularly limited as long as the low refractive index layer having the above-described refractive index can be formed. For example, the resin material described in the hard coat layer forming composition described above It is preferable to contain.
In addition to the resin material, the low refractive index layer can adjust the refractive index by containing a silicone-containing copolymer, a fluorine-containing copolymer, and fine particles.
Examples of the silicone-containing copolymer include a silicone-containing vinylidene copolymer. Specific examples of the fluorine-containing copolymer include a copolymer obtained by copolymerizing a monomer composition containing vinylidene fluoride and hexafluoropropylene.
Examples of the fine particles include silica fine particles, acrylic fine particles, styrene fine particles, acrylic styrene copolymer fine particles, and fine particles having voids. In the present invention, “fine particles having voids” means a structure in which fine particles are filled with gas and / or a porous structure containing gas, and the gas in the fine particles is compared with the original refractive index of the fine particles. It means a fine particle whose refractive index decreases in inverse proportion to the occupation ratio.

The antifouling layer has a role that dirt (fingerprints, water-based or oil-based inks, pencils, etc.) is not easily attached to the outermost surface of the liquid crystal display device of the present invention, or can be easily wiped even when it adheres. It is a layer to bear. Further, by forming the antifouling layer, it is possible to improve the antifouling property and scratch resistance of the liquid crystal display device of the present invention.

The antifouling layer can be formed of a composition containing an antifouling agent and a resin, for example.
The antifouling agent is mainly intended to prevent contamination of the outermost surface of the liquid crystal display device of the present invention, and can also impart scratch resistance to the liquid crystal display device of the present invention.
Examples of the antifouling agent include fluorine compounds, silicon compounds, and mixed compounds thereof. More specifically, silane coupling agents having a fluoroalkyl group, such as 2-perfluorooctylethyltriaminosilane, and the like can be mentioned, and those having an amino group can be preferably used.
It does not specifically limit as said resin, The resin material illustrated with the above-mentioned composition for hard-coat layer formation is mentioned.

The antifouling layer can be formed, for example, on the hard coat layer described above. In particular, it is preferable to form the antifouling layer so as to be the outermost surface.
The antifouling layer can be replaced by imparting antifouling performance to the hard coat layer itself, for example.

In the liquid crystal display device of the present invention, the above-mentioned arbitrary layer is usually provided on the viewing side (outermost surface side) of the polarizing plate protective film, but for example, also on the color filter side of the polarizing plate protective film. It may be provided.

Since the present invention has the above-described configuration, it is possible to provide a liquid crystal display device that can extremely highly suppress the occurrence of nitrile in the display image.

It is sectional drawing which shows typically an example of the liquid crystal display device of this invention. It is sectional drawing which shows an example of the conventional liquid crystal display device typically.

The contents of the present invention will be described with reference to the following examples, but the contents of the present invention should not be construed as being limited to these embodiments. Unless otherwise specified, “part” and “%” are based on mass.

Example 1
The polyethylene terephthalate material was melted at 290 ° C., extruded through a film-forming die, into a sheet form, closely adhered onto a water-cooled and cooled rotating quenching drum, and cooled to produce an unstretched film. This unstretched film was preheated at 120 ° C. for 1 minute with a biaxial stretching test apparatus (manufactured by Toyo Seiki Co., Ltd.), and then stretched at 120 ° C. at a stretch ratio of 4.5 times. The film was stretched at a stretching ratio of 1.5 times in the direction of degree to obtain a polarizing plate protective film having retardation = 9900 nm, film thickness = 100 μm, and Δn = 0.099.
Next, the obtained polarizing plate protective film was placed on the polarizing plate on the observer side of the liquid crystal monitor (FLATRON IPS 226V (manufactured by LG Electronics Japan)) to produce a liquid crystal display device. The polarizing plate protective film was arranged so that the angle formed by the slow axis of the polarizing plate protective film and the absorption axis of the polarizing plate on the observer side of the liquid crystal monitor was 0 °.

( Reference Example A )
A liquid crystal display device was produced in the same manner as in Example 1 except that the angle formed by the slow axis of the polarizing plate protective film and the absorption axis of the polarizing plate on the observer side of the liquid crystal monitor was 30 °.

( Reference Example B )
A liquid crystal display device was produced in the same manner as in Example 1 except that the angle formed between the slow axis of the polarizing plate protective film and the absorption axis of the polarizing plate on the observer side of the liquid crystal monitor was 60 °.

( Reference Example 1 )
A liquid crystal display device was produced in the same manner as in Example 1 except that the angle formed by the slow axis of the polarizing plate protective film and the absorption axis of the polarizing plate on the observer side of the liquid crystal monitor was 90 °.

(Example 5)
The stretching ratio of the unstretched film obtained in the same manner as in Example 1 was adjusted to obtain a polarizing plate protective film having retardation = 8200 nm, film thickness = 92 μm, and Δn = 0.089. A liquid crystal display device was produced in the same manner as in Example 1 except that the obtained polarizing plate protective film was used.

(Example 6)
The draw ratio of the unstretched film obtained in the same manner as in Example 1 was adjusted to obtain a polarizing plate protective film having retardation = 19000 nm, film thickness = 190 μm, and Δn = 0.10. A liquid crystal display device was produced in the same manner as in Example 1 except that the obtained polarizing plate protective film was used.

(Comparative Example 1)
A liquid crystal display device was produced in the same manner as in Example 1 except that the angle formed between the slow axis of the polarizing plate protective film and the absorption axis of the polarizing plate on the viewer side of the liquid crystal monitor was 45 °.

(Comparative Example 2)
A liquid crystal display device was produced in the same manner as in Example 1 except that PET film A4100 manufactured by Toyobo Co., Ltd. having retardation = 6200 nm, film thickness = 188 μm, Δn = 0.033 was used as the polarizing plate protective film.

(Comparative Example 3)
The draw ratio of the unstretched film obtained in the same manner as in Example 1 was adjusted to obtain a polarizing plate protective film having retardation = 7500 nm, film thickness = 188 μm, and Δn = 0.040.
A liquid crystal display device was produced in the same manner as in Example 1 except that the obtained polarizing plate protective film was used.

(Nijimura evaluation)
The liquid crystal display devices manufactured in Examples 1 , 5 and 6, Comparative Examples 1 to 3, Reference Examples A and B, and Reference Example 1 were used in a dark place and a bright place (liquid crystal monitor peripheral illumination 400 lux). Of humans observed the displayed image visually and through polarized sunglasses from the front and oblique directions (about 50 degrees), and evaluated the presence or absence of nidimra according to the following criteria.
A: Nijimura is not observed.
○: Nizimura is observed, but it is thin and there is no problem in practical use.
Δ: Nizimura is observed.
X: Nizimura is strongly observed.

As shown in Table 1, the retardation of the polarizing plate protective film is 8000 nm or more, and the slow axis of the polarizing plate protective film and the absorption axis of the polarizing plate are 0 ° ± 30 ° or 90 ° ± 30 °. The liquid crystal display device according to the example in the range was excellent in the evaluation of any of the visible and dark areas through the polarized sunglasses.
On the other hand, the liquid crystal display device according to Comparative Example 1 in which the angle formed between the slow axis of the polarizing plate protective film and the absorption axis of the polarizing plate was 45 ° had a good evaluation of NDIMRA in the dark. However, it was inferior to the Nizimura evaluation through polarized sunglasses in the light place. Moreover, the liquid crystal display device which concerns on the comparative examples 2 and 3 whose retardation is less than 8000 nm was inferior to any nitrile evaluation of a bright place and a dark place.

The liquid crystal display device of the present invention can be applied to a liquid crystal display device provided with a polarizing plate protective film having a high retardation value, and it is possible to extremely highly suppress the occurrence of nitrimla in a display image.

10, 20 Liquid crystal display device 11, 21 Liquid crystal cell 12, 22 Color filter 13, 23, 25 Polarizing plate 14 Polarizing plate protective film

Claims (5)

A backlight source, a liquid crystal cell, a color filter, a polarizing plate and a polarizing plate protective film have a configuration arranged in this order, and is a liquid crystal display device used in an environment with light from the outside ,
The polarizing plate protective film has a thickness of 20 μm to 500 μm (except when it is less than 65 μm) , has a retardation of 8000 nm or more, and the absorption axis of the polarizing plate and the polarizing plate protective film It is arranged so that the angle formed with the slow axis is 0 ° ± 30 ° or 90 ° ± 30 ° (except -30 °, 30 °, 60 ° , 90 ° and 120 ° ) Have
A liquid crystal display device comprising a call. The liquid crystal display device according to claim 1, wherein the backlight light source is a white light emitting diode. The polarizing plate protective film has a refractive index (nx) in the slow axis direction which is the direction having the largest refractive index in the plane, and a refractive index (ny) in the fast axis direction which is a direction orthogonal to the slow axis direction. 3. The liquid crystal display device according to claim 1, wherein a difference (nx−ny) with respect to is 0.05 or more. Polarizing plate protective film is polyester resin, polyolefin resin, (meth) acrylic resin, polyurethane resin, polyether sulfone resin, polycarbonate resin, polysulfone resin, polyether resin, polyether ketone resin. 4. The liquid crystal display device according to claim 1, comprising a material selected from the group consisting of: a (meth) acrylonitrile-based resin, and a cycloolefin-based resin. The liquid crystal display device according to claim 1, wherein the polarizing plate protective film has a retardation of from 8000 nm to 9900 nm.

Images