KR20050078987A - Process for producing a wide viewing angle polarizing plate - Google Patents

Abstract

(Problem) Provided are a manufacturing method of a high contrast wide viewing angle polarizing plate, a wide viewing angle polarizing plate obtained by this method, an optical film provided with the wide viewing angle polarizing plate, and an image display device including the wide viewing angle polarizing plate or an optical film.

(Measures) The manufacturing method of the wide viewing angle polarizing plate of this invention is an optical compensation film which has a birefringence layer comprised by containing a liquid crystal polymer on at least one side of a transparency protective layer, and a manufacturing method of the wide viewing angle polarizing plate which has a polarizer. And a step of heat-treating the optical compensation film within a range of 68 ° C to 125 ° C, and bonding the polarizer and the optical compensation film through an adhesive using the transparent protective layer as an adhesive surface. do.

Description

Manufacturing method of wide viewing angle polarizer plate {PROCESS FOR PRODUCING A WIDE VIEWING ANGLE POLARIZING PLATE}

The present invention relates to a manufacturing method of a wide viewing angle polarizing plate for improving front contrast, a wide viewing angle polarizing plate obtained by the manufacturing method, an optical film having the wide viewing angle polarizing plate, and an image display device having the wide viewing angle polarizing plate or optical film. .

In recent years, the liquid crystal display device has been widely used, but the viewing angle of a good viewer is insufficient as compared to the CRT (Carhode Ray Tube), and the necessity of expanding the viewing angle is increasing. As a method of enlarging the viewing angle, a method of arranging a polarizing plate on which a birefringent layer is provided is provided in a liquid crystal cell (see Patent Document 1, for example). However, when this method is used, the viewing angle is much enlarged, but it is known that the frontal contrast falls in proportion to the polarizing plate in which the birefringence layer is not formed.

[Patent Document 1] Japanese Unexamined Patent Publication No. Hei 6-174918

The present invention has been made to solve the above problems, a method of manufacturing a wide viewing angle polarizing plate having a high front contrast, a wide viewing angle polarizing plate obtained by this manufacturing method, an optical film having the wide viewing angle polarizing plate and this wide viewing angle polarizing plate or an optical film It is an object to provide an image display device provided.

The present inventors earnestly examined to solve the above conventional problem. As a result, the inventors have found that the above object can be achieved by a method of manufacturing a wide viewing angle polarizing plate, a wide viewing angle polarizing plate, and a wide viewing angle polarizing plate described below, and have completed the present invention.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, the manufacturing method of the wide viewing angle polarizing plate which concerns on this invention is an optical compensation film which has a birefringence layer comprised by containing a liquid crystal polymer in at least one side of a transparency protective layer, and the wide viewing angle which has a polarizer. A method of manufacturing a polarizing plate, the process of heat-treating the optical compensation film in the range of 68 ° C to 125 ° C, and the step of bonding the polarizer and the optical compensation film through an adhesive using the transparent protective layer as an adhesive surface. It is characterized by having.

Moreover, it is preferable to include the process of saponifying the transparency protective layer provided with the said birefringence layer before the said heat processing.

In addition, it is preferable to use a discotic liquid crystal polymer as the liquid crystal polymer.

In addition, it is preferable to use a triacetyl cellulose film as the transparency protective layer.

Moreover, in order to solve the said subject, the wide viewing angle polarizing plate which concerns on this invention is manufactured by the manufacturing method of a wide viewing angle polarizing plate, It is characterized by the above-mentioned.

Moreover, in order to solve the said subject, the optical film which concerns on this invention is characterized in that at least 1 piece of the said wide viewing angle polarizing plate is laminated | stacked.

Moreover, in order to solve the said subject, the said wide view angle polarizing plate or the optical film is used for the image display apparatus which concerns on this invention, It is characterized by the above-mentioned.

Best Mode for Carrying Out the Invention

Embodiment of this invention is described below.

The present invention provides a method for producing an optical compensation film having a birefringence layer comprising an crystalline polymer on at least one side of a transparency protective layer, and a wide viewing angle polarizing plate having a polarizer. It has a process of heat-processing in the range, and a process of bonding the said polarizer and the said optical compensation film through an adhesive agent using the said transparent protective layer as an adhesive surface.

At this time, if the optical compensation film is formed on at least one side of the polarizer, the optical compensation film can be used as a wide viewing angle polarizing plate. On the opposite side, an appropriate layer is laminated for the purpose of protecting the polarizer and adding an optical function. It is preferable to use one optical film. Examples of the layer to be laminated include the optical compensation film, the transparent protective layer, the adhesive layer, the retardation plate, the hard coat layer, the reflective layer, the brightness enhancement film, and the like. When laminating these layers, lamination | stacking can be carried out by a suitable method, such as direct coating or indirectly using an adhesive or an adhesive.

The optical compensation film which laminated | stacked the birefringence layer on the said transparency protective layer can be produced by the conventionally well-known various methods. For example, after forming the alignment film which carried out the rubbing process on the transparency protective layer, a liquid crystal polymer etc. are coated on an alignment film, and heat processing, ultraviolet curing, etc. are performed. Thereby, the birefringence layer comprised including the liquid crystal polymer of a predetermined orientation state can be formed. Moreover, it is preferable that a transparency protective layer and a birefringence layer are in an adhesive state. The birefringence layer can also be laminated on both sides of the transparency protective layer. In this case, another transparency protective layer can be formed in the adhesive surface side with a polarizer.

The birefringence layer has a function of optical compensation for correcting the birefringence (deformation of light) generated in the process of light passing through the liquid crystal cell by the phase difference of the film. The retardation characteristics and the like of the birefringent layer are appropriately set by the control of the layer thickness. The phase difference of the birefringence layer can be controlled by the alignment state of the liquid crystal polymer in the thickness direction or the in-plane direction, the inclination angle with respect to the liquid crystal layer normal line direction in the main refractive index direction in the thickness direction, or the layer thickness.

It is preferable to exist in the range of 1-5 micrometers, and, as for the layer thickness of a birefringence layer, it is more preferable to exist in the range of 2-3 micrometers. When the layer thickness is within these ranges, a good visibility viewing angle can be enlarged due to the compensation effect for visual change or prevention of coloration due to wavelength dispersion of birefringence difference. Moreover, it is preferable to exist in the range of 10-200 nm, and, as for the phase difference of a front direction, it is more preferable to exist in the range of 15-150 nm.

Although it does not specifically limit as said liquid crystal polymer, A conventionally well-known thing can be employ | adopted, but in this invention, a discotic liquid crystal polymer is preferable. When the birefringence layer is formed of the discotic liquid crystal polymer, the birefringence layer has a structure in which the discotic liquid crystal polymer is obliquely or hybridly oriented. In addition, the discotic liquid crystal polymer changes the slow axis direction in accordance with the improvement effect of visibility, that is, the change of the visual angle from the vertical direction of the liquid crystal cell, whereby the parallel relationship of the slow axis with the transmission axis of the wide viewing angle polarizing plate is obtained. Alternatively, deviation is generated in the orthogonal relationship, and optical anisotropy (phase difference corresponding to compensation) is expressed based on the deviation amount.

Examples of the discotic liquid crystal polymers include those represented by the following chemical formulas.

[Formula 1]

Where R is nC ₇ H ₁₅ COO-

The formation of the discotic liquid crystal layer by the liquid crystal polymer on one side or both sides of the transparent protective layer is, for example, a method in which a liquid crystal polymer is developed on the transparent protective layer oriented as necessary to form a layer oriented on a predetermined discotic liquid crystal layer. It can carry out by the method according to the conventional methods, such as these. Therefore, in development of a liquid crystal polymer, it can be set as the solution by a solvent, the melt by heating, etc. as needed. Moreover, when orienting the solidified layer of a liquid crystal polymer to a discotic liquid crystal layer, you may heat-process above glass transition temperature etc. as needed.

Moreover, as an orientation process with respect to the said transparent protective layer, the orientation film which rubbed the laying film, such as polyimide, polyvinyl alcohol, polyester, polyallylate, polyamideimide, or polyetherimide, for example with rayon cloth, SiO, The method of forming an appropriate alignment film which consists of sustained-release deposition layers, such as these, the method of diagonally etching with an ion beam, etc. are mentioned.

In general, a birefringent layer made of a liquid crystal polymer is formed in a transparent protective layer in advance in terms of controllability in the slow axis direction at the time of polarizing plate formation and is then used for forming the polarizing plate. The thickness of the birefringent layer to be formed can be appropriately determined according to the retardation characteristics and the like, and the retardation is an inclination angle with respect to the liquid crystal layer normal direction in the orientation state in the thickness direction or in-plane direction of the liquid crystal polymer or the main refractive index direction in the thickness direction. It can control by layer thickness etc.

In addition, when forming a birefringent layer on both surfaces of a transparency protective layer, each birefringent layer can be made to superimpose the same kind or different kind of liquid crystal polymer.

The transparency protective layer can be appropriately formed of a plastic coating layer, a laminate of a protective film, or the like. In particular, plastics excellent in transparency, mechanical strength, thermal stability, water dispersion shielding, and isotropy are preferably used. Examples of the material for the transparent protective layer include polyester-based polymers such as polyethylene terephthalate and polyethylenetaphthalate, styrene-based polymers such as polystyrene and acrylonitrile-styrene copolymer (AS resin), diacetyl cellulose and triacetyl cellulose. And acrylic polymers such as cellulose polymers, polyether sulfone polymers, polycarbonate polymers, polyamide polymers, polyimide polymers, polyolefin polymers, and polymethyl methacrylates. Polyethylene-based polymers such as polyethylene, polypropylene, cyclo- or norbornene structures, polyolefin-based polymers such as ethylene-propylene copolymers, vinyl chloride-based polymers, amide-based polymers such as nylon and aromatic polyamides, imide-based polymers and liquors Phone polymer, polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, acrylate polymer, polyoxymethylene polymer, Epoxy-type polymer or the blend of the said polymer is mentioned. In addition, thermosetting or ultraviolet curing resins such as acrylic, urethane, acrylic urethane, epoxy, or silicone resins may be mentioned.

Further, the polymer film described in JP 2001-343529 A (WO01 / 37007), for example, (A) a thermoplastic resin having a substituted and / or unsubstituted amide group in the side chain, (B) a substituted and / or unsubstituted phenyl in the side chain, and The resin composition containing the thermoplastic resin which has a nitrile group is mentioned. As a specific example, the film of the resin composition containing the alternating copolymer which consists of isobutylene and N-methyl maleimide, and an acrylonitrile styrene copolymer is mentioned. As a film, the film which consists of a mixed extrusion product of a resin composition, etc. can be used. Since these films have a small phase difference and a small photoelastic coefficient, problems such as deviation due to deformation of the polarizing plate can be solved, and the moisture permeability is small, so the humidification durability is excellent.

As the transparent protective layer, the smaller the phase difference is, the better. In view of such viewpoints, polarization characteristics, durability, and the like, it is preferable to use a cellulose polymer. Among the cellulosic polymers, triacetyl cellulose is suitable. Moreover, the transparent protective layer whose surface is formed in the fine concavo-convex structure by containing microparticles | fine-particles can also be used.

Moreover, the thinner the transparent protective layer is, the better. This is because the phase difference is determined by the product (Δnd) of the refractive index difference (Δn: nx-ny) of the optical compensation film and the layer thickness (d). Considering the protection against a polarizer etc., the layer thickness of a transparent protective layer is generally 500 micrometers or less, Preferably it is 5-300 micrometers, More preferably, it is 10-200 micrometers.

In addition, when forming a transparent protective layer on both surfaces of a polarizer, the transparent protective layer which consists of the same polymer material may be formed in the front and back, and the transparent protective layer which consists of another polymer material etc. can also be used.

The manufacturing method of the wide viewing angle polarizing plate of this invention can perform saponification process of the transparency protective layer provided with a birefringence layer before the process of the said heat processing. A saponification process is performed by the method of immersing a transparent protective layer in aqueous alkali solution, for example. Thereby, a hydroxyl group can be introduce | transduced into the surface of a transparency protective layer, and the adhesive effect can be improved by adhesion | attachment with the polarizer using the adhesive mentioned later. It does not specifically limit as alkali to be used, For example, it is preferable to use potassium hydroxide, sodium hydroxide, etc. In this step, washing with water or neutralization with acid can be performed as necessary.

The step of heat-treating the transparent protective layer provided with the birefringent layer, that is, the optical compensation film, is carried out for the first purpose of lowering the frontal phase difference Δnd of the birefringent layer. In other words, it is considered that the heat treatment rearranges the liquid crystal polymer in the birefringent layer. Therefore, rearrangement of the liquid crystal polymer reduces the disturbance of the arrangement, and makes the arrangement state more regular compared to before the heat treatment. For this reason, the refractive index difference of a birefringent layer falls, and the phase difference in a front direction is reduced. For example, after obliquely passing through the optical compensation film, the first light traveling in the front direction of the display screen by scattering and the second light proceeding in the front direction of the display screen as it is even after passing the optical compensation film vertically. The difference of the value of (phase difference with respect to a front direction) is made small. As a result, the first light can be compensated with the optical compensation film as much as possible to suppress the emission to the outside. As a result, the wide viewing angle polarizing plate which reduced generation | occurrence | production of light leakage and suppressed the fall of contrast of a front direction can be obtained.

Moreover, this process can be performed also for the purpose of drying the aqueous alkali solution after a saponification process. As a result, the heat treatment of the birefringent layer can be performed without increasing the number of steps, and a decrease in production efficiency can be suppressed.

It is preferable to perform the temperature of heat processing within the range of 68 degreeC-125 degreeC, The inside of the range of 90 degreeC-110 degreeC is more preferable, The inside of the range of 95 degreeC-105 degreeC is especially preferable. If the temperature of the heat treatment is less than 68 ° C., there is a problem that the reduction of the front phase difference is insufficient, and the contrast cannot be improved. On the other hand, when it exceeds 125 degreeC, the thermal contraction of an optical compensation film will become large. As a result, after bonding a transparency protective layer and a polarizer to produce a wide viewing angle polarizing plate, when processing this to arbitrary size, the cross section of a wide viewing angle polarizing plate will be destroyed, and it will become a bad display. If the heat treatment time is a long time, display defects occur for the same reason as described above, so it is necessary to set it to a suitable time. Preferably it is 1 to 300 second, More preferably, it exists in the range of 10 to 120 second. When the heat treatment is performed under the above heat treatment conditions, the phase difference value? Nd in the front direction of the optical compensation film can be reduced by about 20 to 40%. For example, when the phase difference in the front direction is initially 30 nm, it becomes 20-25 nm after heat processing.

The bonding process of the said polarizer and the transparent protective layer provided with the said birefringence layer is performed using an adhesive agent using a transparent protective layer as an adhesive surface. This is because it is necessary to adhere and fix in order to prevent misalignment between the slow axis of the birefringent layer and the transmission axis of the polarizer. The bonding is performed so that the slow axis of the birefringent layer and the transmission axis of the polarizer are substantially parallel or orthogonal. At this time, the application of the adhesive may be performed on either the polarizer side or the transparent protective layer side, or may be performed on both sides.

It is preferable to perform this process immediately after heat processing. More specifically, it is preferable to carry out within 2 hours after the heat treatment, and more preferably, within 1 minute. This is because if the process is carried out after 2 hours have elapsed after heat treatment, the effect of heat treatment is lost due to the effect of moisture absorption by the optical compensation film or the like. However, as long as moisture absorption by the optical compensation film can be prevented, the optical compensation film subjected to the heat treatment may be wound once and then bonded to the polarizer.

It does not specifically limit as said adhesive agent, Specifically, For example, the appropriate adhesive agent, such as the transparent pressure-sensitive adhesive which consists of acryl type, silicone type, polyester type, polyurethane type, polyether type, rubber type, etc. can be used. Among these adhesives, in order to prevent the optical properties of the polarizer and the optical compensation film from changing, it is preferable that the curing process or drying at the time of high temperature does not require a curing process or drying for a long time. . Moreover, the adhesive agent which does not generate | occur | produce peeling under heating or humidification conditions is also preferable.

From the above point of view, an acrylic pressure-sensitive adhesive is particularly preferable. Moreover, since an acrylic pressure-sensitive adhesive agent is excellent in the point of transparency, weather resistance, heat resistance, etc. compared with another adhesive agent, it is also preferable at these points. Such acrylic pressure-sensitive adhesive is not particularly limited, and includes, for example, monomers such as butyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, and (meth) acrylic acid, and has a weight average molecular weight of 100,000. As mentioned above, what makes an acrylic polymer whose glass transition temperature is 0 degrees C or less into a base polymer can be illustrated. In the case where the refractive indices of the birefringence layer and the transparent protective layer are different from each other, from the viewpoint of suppression of the reflection loss and the like, it is preferable that the adhesive agent exhibits the median value of both refractive indices.

As said polarizer, the suitable thing from which the light of a predetermined polarization state is obtained can be used. In particular, the polarizer from which the transmitted light of a linearly polarized state is obtained is preferable. Such a polarizer is not particularly limited, and iodine and / or dichroic dyes are adsorbed onto hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymerized partial saponified films. And a polyene oriented film such as a polyvinyl alcohol-based dehydration product or a polyvinyl chloride dehydrochlorination product. Among these polarizers, the polarizer which consists of dichroic substances, such as a stretched polyvinyl alcohol-type film of iodine adsorption and a dichroic dye, is especially preferable. This is because linearly polarized light having a high degree of polarization is obtained.

As a polyvinyl alcohol-type film, what was film-formed by arbitrary methods, such as the casting | flow_spreading method, the casting method, the extrusion method, etc. which cast a polyvinyl alcohol-type resin in water or the organic solvent, and cast-formed can be suitably used. . About 100-5000 are preferable and, as for the polymerization degree of polyvinyl alcohol-type resin, 1400-4000 are more preferable.

Moreover, the process which forms a hard coat layer, the anti-reflective process, the sticking prevention, and the process for the purpose of diffused or antiglare can also be performed to the surface which did not adhere the polarizer of the said transparent protective layer.

The hard coat treatment is performed for the purpose of preventing scratches on the surface of the polarizing plate. For example, it can be formed by a method of adding a cured film excellent in hardness, sliding properties, etc., by suitable ultraviolet curable resins such as acrylic or silicone, to the surface of the transparent protective layer. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the prior art. In addition, the sticking prevention treatment is performed for the purpose of preventing the adhesion with the adjacent layer.

Moreover, antiglare process is performed in order to prevent external light from reflecting off the surface of a polarizing plate, and to impair visibility of the polarizing plate transmitted light. For example, it can form by providing a fine uneven | corrugated structure to the surface of a transparent protective layer by a suitable method, such as a roughening method by a sandblast system, the embossing system, and the compounding method of a transparent fine particle. Examples of the fine particles to be included in the formation of the surface fine uneven structure include inorganic fine particles having conductivity such as silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide and the like having an average particle diameter of 0.5 to 20 µm. And transparent fine particles such as organic fine particles made of a crosslinked or uncrosslinked polymer or the like. When forming a surface fine uneven structure, the usage-amount of microparticles | fine-particles is generally about 2-70 weight part with respect to 100 weight part of transparent resin which forms a surface fine uneven structure, and 5-50 weight part is preferable. The antiglare layer may also serve as a diffusion layer (visual magnification function, etc.) for diffusing the transmitted light of the polarizing plate to enlarge vision.

The antireflection layer, the anti-sticking layer, the diffusion layer, the antiglare layer, and the like may be formed on the transparent protective layer itself, or may be formed separately from the transparent protective layer as an optical layer.

In the above aspect, the wide viewing angle polarizing plate which concerns on this invention can be used as what is a transmission type. However, this invention is not limited to this, It can use with the optical film laminated | stacked with the other optical layer according to a use, etc .. Although it does not specifically limit about an optical layer, For example, an optical layer which may be used for a liquid crystal display device etc., such as a reflecting plate, a semi-transmissive plate, or a retardation plate (including wavelength plates, such as 1/2 or 1/4), is used for one layer or Two or more layers can be used. In more detail, a reflecting plate or a semi-transmissive reflector is laminated on the wide viewing angle polarizing plate of the present invention, and can be used as a reflective polarizing plate or a semi-transmissive polarizing plate. Moreover, the retardation plate is laminated on the wide viewing angle polarizing plate of the present invention, and can be used as an elliptical polarizing plate or circular polarizing plate. Moreover, it can also be used as a polarizing plate which laminated | stacked the brightness enhancement film on the wide viewing angle polarizing plate of this invention.

The reflection type polarizing plate is a reflection layer formed on a wide viewing angle polarizing plate, and is applied to a reflection type liquid crystal display device which reflects and displays incident light from the viewing side (display side). Formation of a reflective polarizing plate can be performed by a suitable method, such as providing a reflective layer made of metal or the like on the transparent protective layer on the side opposite to the side on which the birefringent layer is laminated. In more detail, the thing which provided the foil and vapor deposition film which consist of reflective metals, such as aluminum, on the single side | surface of transparent protective layers, such as the protective film which carried out the mat process as needed, for example. Moreover, what provided the metal reflection layer by the appropriate method, such as a vapor deposition method and a plating system, on the surface fine uneven structure by microparticles | fine-particles of the said transparent protective layer, etc. are mentioned. The reflection layer of the fine uneven structure has the advantage of preventing incident light reflection by diffusing the incident light by diffuse reflection to prevent projection and diffuse reflection, and the like. Moreover, the transparent protective layer containing microparticles | fine-particles also has the advantage that it can spread | diffuse when incident light and its reflected light transmit it, and can suppress a deviation of contrast more. Formation of the reflective layer having a fine uneven structure reflecting the surface fine uneven structure of the transparent protective layer may be performed by forming a metal into the transparent protective layer by an appropriate method such as a deposition method such as a vacuum deposition method, an ion plating method, a sputtering method, or a plating method. This can be done by a method of directly laying on the surface.

Moreover, the reflective polarizing plate can also be used as a reflection sheet formed by changing to the aspect directly formed in the transparent protective layer of the said wide viewing angle polarizing plate, and forming a reflective layer in the appropriate film according to the transparency protective layer. In addition, since the reflective layer is usually made of a metal, the use mode in which the reflective surface is covered with a transparent protective layer, a wide viewing angle polarizing plate, or the like prevents a decrease in reflectance due to oxidation. In addition, it is also possible to keep the initial reflectance over a long period and to separately deposit a protective layer on the reflective layer.

A semi-transmissive polarizing plate can be obtained by making it a semi-transmissive reflective layer, such as a half mirror which reflects light in the reflective layer and permeate | transmits in the above. The semi-transmissive polarizing plate is usually formed on the back side of the liquid crystal cell. When the transflective liquid crystal display device having such a transflective polarizing plate is used in a bright environment, external light incident from the viewing side (display surface side) is used as the display light, and when used in a dark environment, Use light as display light. Therefore, the power consumption can be reduced.

An elliptical polarizing plate or circular polarizing plate in which a retardation plate is further laminated on the wide viewing angle polarizing plate will be described. A retardation plate or the like is used to change linearly polarized light into elliptical polarization or circularly polarized light, to change elliptical polarization or circularly polarized light into linearly polarized light, or to change the polarization direction of linearly polarized light. In particular, a so-called quarter wave plate (also referred to as λ / 4 plate) is used as the phase difference plate which changes linearly polarized light into circularly polarized light or changes circularly polarized light into linearly polarized light. A half wave plate (also called a λ / 2 plate) is usually used when changing the polarization direction of linearly polarized light.

The elliptical polarizing plate is effectively used for, for example, compensating (preventing) coloration (blue or yellow) caused by birefringence of the liquid crystal layer of the liquid crystal display device of the STN (Super Twisted Nematic) mode to produce black and white display without the coloration. . In addition, controlling the three-dimensional refractive index is preferable because it can compensate (prevent) the coloration generated when the screen of the liquid crystal display device is viewed in the oblique direction. The circularly polarizing plate is effectively used, for example, when adjusting the image color tone of a reflective liquid crystal display device in which an image is displayed in color, and also has an antireflection function. Specific examples of the retardation plate include a birefringent film formed by stretching a film made of a suitable polymer such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene or other polyolefin, polyallylate, polyamide, The thing which supported the orientation film of a liquid crystal polymer, the orientation layer of a liquid crystal polymer with a film, etc. are mentioned. The retardation plate may have a suitable retardation according to the purpose of use, for example, for the purpose of compensating coloring or vision due to birefringence of various wavelength plates and the liquid crystal layer, or by laminating two or more kinds of retardation plates to provide retardation. It may be the one that controlled the optical characteristics of the.

The elliptical polarizing plate and the reflective elliptical polarizing plate are obtained by laminating a wide viewing angle polarizing plate or a reflective polarizing plate and a phase difference plate in an appropriate combination. Such an elliptical polarizing plate may be formed by sequentially laminating them in the manufacturing process of the liquid crystal display device so as to be a combination of the (reflective type) polarizing plate and the retardation plate. However, as described above, the elliptical polarizing plate may be formed of an optical film such as an elliptical polarizing plate in advance. One of them is that the quality stability, lamination workability and the like are excellent, so that the manufacturing efficiency of the liquid crystal display device and the like can be improved.

The polarizing plate which bonded together the wide viewing angle polarizing plate and the brightness enhancement film is normally used in the back surface side of a liquid crystal cell. The luminance enhancing film is characterized by reflecting linearly polarized light on a predetermined polarization axis or circularly polarized light in a predetermined direction when natural light is incident due to a backlight such as a liquid crystal display device or reflection from the back side, and transmitting other light. The polarizing plate laminated with the wide viewing angle polarizing plate receives light from a light source such as a backlight to obtain transmitted light in a predetermined polarization state, and light other than the predetermined polarization state is reflected without being transmitted. The light reflected from the luminance-enhancing film surface is again inverted through a reflecting layer or the like formed on the rear side thereof, and re-injected into the luminance-enhancing film, and part or all of the light is transmitted as light in a predetermined polarization state to increase the amount of light passing through the luminance-enhancing film. In addition, the luminance can be improved by supplying polarized light that is hardly absorbed by the polarizer and increasing the amount of light that can be used for liquid crystal display. That is, in the case where light is incident through the polarizer from the back side of the liquid crystal cell with the backlight or the like without using the luminance enhancing film, most of the light having a polarization direction that does not coincide with the polarization axis of the polarizer is absorbed by the polarizer, Does not transmit polarizer. That is, although it depends on the characteristic of the polarizer used, about 50% of light is absorbed by the polarizer, and the quantity of light which can be used for a liquid crystal image display etc. decreases by that amount, and an image becomes dark. The brightness enhancement film repeats the reflection of light having a polarization direction absorbed by the polarizer once in the brightness enhancement film without incident on the polarizer, inverted through a reflective layer formed on the rear side thereof, and then reincident to the brightness enhancement film. Since only the polarization direction in which the polarization direction of the light reflected and inverted between the two polarization directions is allowed to pass through the polarizer is transmitted through the luminance enhancement film, the polarization enhancement film is transmitted to the polarizer, so that light such as a backlight can be efficiently displayed in the image of the liquid crystal display device. Can be used to brighten the screen.

A diffusion plate may be formed between the luminance enhancing film and the reflective layer. The light in the polarization state reflected by the brightness enhancement film proceeds to the reflective layer or the like, but the diffuser plate is uniformly diffused the light passing therethrough and at the same time resolves the polarization state to become a non-polarization state. In other words, the diffusion plate returns the polarized light to the original natural light state. The light in this non-polarized state, that is, in the natural light state, is reflected through the reflecting layer toward the reflecting layer or the like, and passes through the diffuser plate again and is reincident to the luminance enhancing film. Thus, by forming a diffuser plate that returns the polarized light to the original natural light state between the luminance enhancing film and the reflective layer, the display screen can be maintained at the same time while reducing the display deviation of the display screen. Can be provided. By forming such a diffuser plate, it is considered that the first incident light can increase the number of times of reflection repetition moderately, and can provide a uniform bright display screen with the diffuser function of the diffuser plate.

The luminance enhancing film, for example, exhibits a property of transmitting a linearly polarized light of a predetermined polarization axis and reflecting other light, such as a multilayered thin film of a dielectric material or a multilayered film of a thin film having different refractive index anisotropy, and the orientation of a cholesteric liquid crystal polymer. As the film or the alignment liquid crystal layer is supported on the film base material, an appropriate one such as showing a characteristic of reflecting either circularly polarized light in one of the left rotation and the right rotation and transmitting the other light can be used.

Therefore, in the luminance improvement film of the type which transmits the linearly polarized light of the predetermined polarization axis, the transmitted light can be efficiently transmitted while suppressing the absorption loss caused by the wide viewing angle polarizing plate by allowing the transmitted light to enter the wide viewing angle polarizing plate as it is. On the other hand, in a luminance enhancement film of a type that transmits circularly polarized light such as a cholesteric liquid crystal layer, the polarized light may be incident on a polarizer as it is, but in view of suppressing absorption loss, the circularly polarized light is linearly polarized through a retardation plate to obtain a wide viewing angle. It is preferable to make it incident on a polarizing plate. In addition, by using a quarter wave plate as the retardation plate, circularly polarized light can be converted into linearly polarized light.

A retardation plate functioning as a quarter wave plate in the wide wavelength range of the visible light region is a retardation layer exhibiting retardation characteristics different from a retardation layer functioning as a quarter wave plate for light color light having a wavelength of 550 nm, for example, 1 / It can obtain by the method of superimposing the retardation layer which functions as two wavelength plates. Therefore, the retardation plate disposed between the wide viewing angle polarizing plate and the brightness enhancement film may be made of one or two or more retardation layers.

In addition, the cholesteric liquid crystal layer can also be obtained by reflecting circularly polarized light in a wide wavelength range such as a visible light region by using a combination structure in which the reflected wavelengths are different and having two or more layers. As a result, transmission circularly polarized light in a wide wavelength range is obtained.

In addition, the wide viewing angle polarizing plate may be formed by laminating a wide viewing angle polarizing plate and two or three or more optical layers like the polarization splitting polarizing plate. Therefore, it may be a reflective elliptical polarizing plate or a semi-transparent elliptical polarizing plate in which the reflective polarizing plate, the transflective polarizing plate and the phase difference plate are combined.

The optical film in which the optical layer is laminated on the wide viewing angle polarizer may be formed by sequentially stacking the optical films in a manufacturing process of a liquid crystal display device or the like. However, an optical film laminated in advance has an advantage of improving the stability of quality, assembly workability, and the like and improving productivity of a liquid crystal display device and the like. Suitable lamination means such as an adhesive layer can be used for lamination. At the time of adhering the wide viewing angle polarizing plate or the other optical film, these optical axes can be set to an appropriate placement angle in accordance with a desired phase difference characteristic or the like.

The adhesive layer for adhering with other members, such as a liquid crystal cell, can also be formed in the optical film which has laminated | stacked at least one wide viewing angle polarizing plate and at least 1 wide viewing angle polarizing plate mentioned above. The pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine rubber-based polymer, or the like may be appropriately selected and used as the base polymer. In particular, an acrylic adhesive has excellent optical transparency, exhibits proper wettability, cohesiveness, and adhesive adhesion characteristics, and is excellent in weather resistance, heat resistance, and the like, and can be preferably used.

In addition to the above, in view of prevention of foaming or peeling phenomenon due to moisture absorption, reduction of optical characteristics due to thermal expansion difference, prevention of warping of liquid crystal cell, and furthermore, formation of high quality and durable liquid crystal display device, etc. The adhesive layer which is low and excellent in heat resistance is preferable.

The pressure-sensitive adhesive layer may contain an additive. Examples of the additives include fillers, pigments, colorants, antioxidants, etc., which are made of natural or synthetic resins, particularly tackifying resins, glass fibers, glass beads, metal powders, other inorganic powders, and the like. Moreover, microparticles | fine-particles can be contained and light diffusivity can also be provided to an adhesive layer.

Laying an adhesive layer on one side or both sides of a wide viewing angle polarizing plate or an optical film can be performed by a suitable method. As an example, about 10 to 40 weight% of the adhesive solution which melt | dissolved or disperse | distributed or disperse | distributed a base polymer or its composition in the solvent which consists of a single substance or mixture of suitable solvents, such as toluene and ethyl acetate, is prepared, and it is a casting method or a coating method. The method of directly laying on a wide viewing angle polarizing plate or an optical film by suitable development methods, such as these, is mentioned. Moreover, the method of forming an adhesion layer on a separator according to the above, and attaching it to a wide viewing angle polarizing plate or an optical film, etc. are mentioned.

The pressure-sensitive adhesive layer may be formed on one side or both sides of a wide viewing angle polarizing plate or an optical film as an overlapping layer of another composition or kind. Moreover, when formed in both surfaces, it can also be set as adhesive layers, such as a composition, a kind, thickness, etc. which differ in the front and back of a wide viewing angle polarizing plate or an optical film. The thickness of an adhesion layer can be suitably determined according to a purpose of use, adhesive force, etc. Generally, it is 1-500 micrometers, 5-200 micrometers is preferable, and 10-100 micrometers is especially preferable.

The exposed surface of the pressure-sensitive adhesive layer is temporarily covered with a separator for the purpose of preventing contamination thereof until it is practically provided. As a result, the adhesive layer can be prevented from coming into contact with foreign matter or the like in the usual handling state. As the separator, except for the above thickness conditions, for example, a plastic film, a rubber sheet, a paper, a cloth, a nonwoven fabric, a net, a foam sheet, a metal foil, a suitable thin body such as a laminate thereof, or a silicone-based or long-chain alkyl-based compound may be necessary. And a conventional one such as those coated with an appropriate release agent such as fluorine or molybdenum sulfide can be used.

Moreover, in this invention, what provided the ultraviolet absorbing power to each layer, such as the polarizer, transparency protective layer, or optical layer which comprise said wide viewing angle polarizing plate, or an adhesion layer, etc. may be sufficient. The ultraviolet absorber, such as a salicylic acid ester compound, a benzophenol type compound, a benzotriazole type compound, a cyanoacrylate type compound, and a nickel complex salt type compound, can be used for provision of an ultraviolet absorbing ability.

The wide viewing angle polarizing plate or optical film of this invention can be applied to various image display apparatuses, such as a liquid crystal display device and an electroluminescent (EL) display device.

For example, when applied to a transmissive liquid crystal display device, the liquid crystal display device is formed by forming a liquid crystal cell between a pair of transmissive polarizing plates (or optical films). The transmissive polarizing plate and the liquid crystal cell are adhered by a conventionally known pressure-sensitive adhesive or the like. The front polarizing plate on the display surface side and the rear polarizing plate on the back side of the liquid crystal cell may be of the same kind or of different kinds. In addition, when applied to a reflective liquid crystal display device or a transflective liquid crystal display device, a reflective polarizing plate or a transflective polarizing plate is formed on the back side of the liquid crystal cell and applied. In manufacturing a liquid crystal display device, for example, a diffuser plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusion plate, a backlight, or the like may be incorporated in one or two or more layers at appropriate positions. can do.

As the display mode of the liquid crystal display device, it is applicable to TN (Twisted Nematic) mode, STN mode, VA mode (Vertical Aligned) mode, or OCB (Optically self-Compensated Birefringence) mode, but the optical compensation film according to the present invention It is especially preferable to use the TN mode and the STN mode. In the OCB mode among these display modes, the decrease in contrast due to light leakage at the time of black display is particularly remarkable, but the liquid crystal display device having the wide viewing angle polarizing plate exhibits the effect of the present invention.

Fabrication of the liquid crystal display device can be carried out according to a conventionally known method. That is, a liquid crystal display device is generally manufactured by appropriately assembling components such as a liquid crystal cell, a wide viewing angle polarizing plate or an optical film, and an illumination system, if necessary, and mounting a driving circuit. However, in this invention, it does not specifically limit except the point which uses the wide viewing angle polarizing plate or optical film by this invention, and can follow conventionally.

Moreover, the wide viewing angle polarizing plate or optical film of this invention can be applied also to an organic electroluminescence display. In general, an organic EL display device forms a light emitting body (organic electro luminescent light emitting body) by sequentially stacking a transparent electrode, an organic light emitting layer, and a metal electrode on a transparent substrate. Here, an organic light emitting layer is a laminated body of various organic thin films, For example, the laminated body of the hole main pressure layer which consists of triphenylamine derivatives, etc., and the light emitting layer which consists of fluorescent organic solids, such as anthracene, or such a light emitting layer and a perylene derivative The structure which has various combinations, such as the laminated body of the electron injection layer which consists of these etc., or these laminated bodies of a hole injection layer, a light emitting layer, and an electron injection layer is known.

In the organic EL display device, by applying a voltage to the transparent electrode and the metal electrode, holes and electrons are injected into the organic light emitting layer, and energy generated by recombination of these holes and electrons excites the fluorescent material, and the excited fluorescent material is It emits light on the principle of emitting light when returning to the ground state. The mechanism of intermediate recombination is the same as that of a general diode, and as can be expected from this, the current and the light emission intensity show strong nonlinearity accompanied by rectification with respect to the applied voltage.

In the organic EL display device, at least one electrode must be transparent in order to induce light emission from the organic light emitting layer, and a transparent electrode formed of indium tin oxide (ITO) or the like is usually used as an anode. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and metal electrodes such as Mg-Ag and Al-Li are usually used.

In the organic EL display device having such a configuration, the organic light emitting layer is formed of a very thin film having a thickness of about 10 nm. For this reason, the organic light emitting layer also transmits light almost completely like the transparent electrode. As a result, light incident on the surface of the transparent substrate during non-emission, and transmitted through the transparent electrode and the organic light emitting layer and reflected by the metal electrode again comes out to the surface side of the transparent substrate, and thus, when viewed from the outside, the organic EL display device The display surface of looks like a mirror.

An organic EL display device comprising an organic electroluminescent light emitting body comprising a transparent electrode on the front side of an organic light emitting layer that emits light by application of a voltage and a metal electrode on the back side of the organic light emitting layer, wherein the organic EL display device is transparent. While providing a wide viewing angle polarizing plate on the surface side of an electrode, a phase difference plate can be formed between these transparent electrodes and a wide viewing angle polarizing plate.

Since the retardation plate and the wide viewing angle polarizing plate have a function of polarizing light incident from the outside and reflected from the metal electrode, there is an effect that the mirror surface of the metal electrode is not viewed from the outside by the polarization action. In particular, when the phase difference plate is constituted by a quarter wave plate and the angle formed by the polarization direction between the wide viewing angle polarizing plate and the phase difference plate is adjusted to π / 4, the mirror surface of the metal electrode can be completely shielded.

That is, only the linearly polarized light component is transmitted to the external light incident on the organic EL display device by the wide viewing angle polarizer. This linearly polarized light generally becomes elliptical polarized light by the retardation plate. In particular, when the phase difference plate is a quarter wave plate and the angle between the wide viewing angle polarizer and the polarization direction between the phase difference plate is π / 4, circular polarization becomes.

The circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, reflected by the metal electrode, and then transmitted through the organic thin film, the transparent electrode, and the transparent substrate, and becomes linearly polarized again on the retardation plate. And since this linearly polarized light is orthogonal to the polarization direction of the wide viewing angle polarizing plate, it cannot transmit through a wide viewing angle polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded.

Example

(Example 1)

Optical compensation film (Fuji Photo Film Co., Ltd. make, product name: WVA12B, layer thickness 108 micrometers) in which the discotic liquid crystal layer (birefringence layer) of a liquid crystal polymer was closely attached to the single side | surface of a triacetyl cellulose film (transparent protective layer, 80 micrometers in thickness). The solution was immersed in a 60 ° C NaOH aqueous solution for 30 seconds to saponify. Then, it heat-dried for 40 second at 100 degreeC. At this time, the front phase difference value ((DELTA) nd) of before and after heating of the optical compensation film measured using the automatic birefringence measuring apparatus (KOBRA21ADH, the product made from OH clock side) was 31.7 nm before a heating, and 23.3 nm after heating.

On the other hand, after extending | stretching a polyvinyl alcohol film with a thickness of 75 micrometers in iodine aqueous solution, it dried and produced the polarizer.

Next, the optical compensation film and the polarizer were bonded with an acrylic adhesive so that the transparent protective layer side of the optical compensation film was an adhesive surface. Bonding was performed 1 minute after the optical compensation film was produced. Moreover, the transparent protective layer which consists of a triacetyl cellulose film (made by Fuji Photographic Film, product name: TD80UF) of thickness 80micrometer was also adhere | attached on the other surface side of a polarizer using acrylic adhesive, and was dried.

This obtained the wide viewing angle polarizing plate which concerns on this Example 1. Moreover, adhesion | attachment of a polarizer and a transparency protective layer was performed so that the transparent axis of a birefringent layer might become a substantially parallel relationship with the transmission axis of a polarizer.

(Example 2)

In Example 2, a wide viewing angle polarizing plate according to Example 2 was prepared in the same manner as in Example 1 except that the heat drying after the saponification treatment performed at 100 ° C. was carried out at 70 ° C. Produced.

(Example 3)

In Example 3, the wide viewing angle polarizing plate which concerns on Example 3 is carried out similarly to Example 1 except having performed the heat drying after the saponification process performed at 100 degreeC in Example 1 at 120 degreeC. Produced.

(Comparative Example 1)

In Comparative Example 1, a wide viewing angle polarizing plate according to Comparative Example 1 was produced in the same manner as in Example 1 except that the heat drying after the saponification treatment performed at 100 ° C. was performed at 65 ° C. in Example 1. It was. At this time, the front retardation plate (Δnd) before and after heating of the optical compensation film was measured in the same manner as in Example 1, and the heating transition was 31.6 nm and the heating was 31.4 nm.

(Comparative Example 2)

In Comparative Example 2, a wide viewing angle polarizing plate according to Comparative Example 2 was produced in the same manner as in Comparative Example 1 except that the heat drying after the saponification treatment performed at 65 ° C. was carried out at 130 ° C. in Example 1. It was.

(Contrast)

Evaluation of contrast was performed by placing the wide viewing angle polarizing plate produced by the said Example or the comparative example on both sides of TFT type liquid crystal cell (TN mode), and measuring white brightness and black brightness, respectively. A luminance meter (brand name: BM-5A, manufactured by TOPCON) was used for the measurement of the luminance. The contrast (white luminance / black luminance) in the front direction of the display screen was calculated from the luminance value thus obtained. These results are shown in Table 1. As apparent from the table, good contrast was obtained for the wide viewing angle polarizing plates according to the first to third embodiments.

(Section observation)

Cross-sectional observation was performed by punching out the wide viewing angle polarizing plate produced in the said Example or the comparative example in A4 size, and observing the cross section. Evaluation was made into (circle) when there was not one point of fracture | rupture surface in cross section, and it was set as x when there was even one point. The results are shown in Table 1. As is clear from the table, no fracture surfaces such as cracks were observed in the wide viewing angle polarizing plates according to the first to third embodiments. On the other hand, in the wide viewing angle polarizing plate which concerns on the comparative example 2, the fracture surface by a crack was observed.

Heat treatment temperature (℃) Contrast The presence of cracks Example 1 100 453 ○ Example 2 70 438 ○ Example 3 120 432 ○ Comparative Example 1 65 412 ○ Comparative Example 2 130 432 ×

In the manufacturing method of the wide viewing angle polarizing plate which concerns on this invention, the refractive index difference of a birefringence layer falls by heat-processing the transparency protective layer (henceforth an optical compensation film) which provided the birefringence layer within the range of 68 degreeC-125 degreeC. This reduces the phase difference in the front direction. As a result, the wide viewing angle polarizing plate which reduced generation | occurrence | production of light leakage and suppressed the fall of contrast of a front direction can be obtained.

Moreover, a hydroxyl group is introduce | transduced into the surface of a transparent protective layer by performing the process of saponifying the transparent protective layer provided with the said birefringence layer whole the heat processing. In the case where the transparent protective layer is, for example, triacetyl cellulose or the like, by introducing a hydroxyl group on the surface thereof, when bonding the transparent protective layer and the polarizer with an adhesive, a hydrogen bond can be made to a hydroxyl group of the hydroxyl group and the adhesive on the surface of the transparent protective layer. . Thereby, the adhesive effect by an adhesive agent is further improved. In addition, by performing the heat treatment step, it is possible to omit the drying step that usually needs to be performed after the saponification process. As a result, production efficiency is improved.

Moreover, the liquid crystal display device provided with the wide viewing angle polarizing plate obtained by the said manufacturing method is excellent in display characteristics, such as showing a high contrast also in the front direction of a display screen at a wide viewing angle.

Claims (7)

In the manufacturing method of the optical compensation film which has a birefringence layer comprised by containing a liquid crystal polymer on the at least single side | surface side of a transparency protective layer, and the wide viewing angle polarizing plate which has a polarizer, Heat-treating the optical compensation film within a range of 68 ° C to 125 ° C; And a step of bonding the polarizer and the optical compensation film to the transparent protective layer as an adhesive surface and bonding the adhesive through an adhesive. The method of manufacturing a wide viewing angle polarizing plate according to claim 1, further comprising a step of saponifying a transparent protective layer having the birefringence layer before the heat treatment. The method for producing a wide viewing angle polarizing plate according to claim 1 or 2, wherein a discotic liquid crystal polymer is used as said liquid crystal polymer. The method of manufacturing a wide viewing angle polarizing plate according to any one of claims 1 to 3, wherein a triacetyl cellulose film is used as the transparency protective layer. The wide viewing angle polarizing plate manufactured by the manufacturing method in any one of Claims 1-4. At least one wide viewing angle polarizing plate of Claim 5 is laminated | stacked, The optical film characterized by the above-mentioned. The wide viewing angle polarizing plate of Claim 5, or the optical film of Claim 6 is used, The image display apparatus characterized by the above-mentioned.