KR20170138497A - A polarizing element in which a film having a high retardation and a layer containing a dichroic dye are laminated, and a display device - Google Patents

Abstract

An object of the present invention is to provide a polarizing element having excellent polarizing performance which can be easily manufactured, and a display device provided with the polarizing element.
Wherein a stretched film having retardation of 3000 to 50000 nm and a layer containing at least one dichroic dye are laminated and the thickness of the stretched film is 20 to 500 mu m. The polarizing element of the present invention using such a specific stretched film exhibits a high degree of polarization, particularly a polarization degree of 85% or more, a high dichroism property, particularly a dichroism property of 5 or more.

Description

A polarizing element in which a film having a high retardation and a layer containing a dichroic dye are laminated, and a display device

The present invention relates to a polarizing element in which a film having a high retardation and a layer containing a dichroic dye are laminated. The present invention also relates to a display device provided with the polarizing element.

Polarizing elements used in liquid crystal displays, sunglasses, goggles and the like are generally made by adsorbing a dichroic dye such as iodine or dichroic dye to a film produced from a polymer material such as polyvinyl alcohol, , And orienting the dichroic dye molecules in a certain direction, or uniaxially stretching the polymer film, and then adsorbing the dichroic dye. However, since the polarizing axis and the absorption axis of the polarizing element obtained by these methods are perpendicular to each other, the shape of the polarizing element is usually limited to a flat plate shape. In order to manufacture such a polarizing element, a polyvinyl alcohol film is swollen and dyed, followed by stretching in an aqueous boric acid solution, followed by washing with water and drying, and then applying a protective film to the obtained film using an adhesive A complicated process was required. In addition, it is required to provide a polarizing element at a desired portion in a simpler manner.

In view of the problems of such a conventional polarizing element, Non-Patent Document 1 discloses a method of producing a polarizing element by orienting dichroic dye molecules in a certain direction by rubbing treatment. However, the coating ability of the dye solution on the substrate is lowered due to scratches and dust on the substrate caused by the rubbing process in the rubbing process, and furthermore, electrical scratches caused by static electricity. As a result, there was a portion not coated (poor coating) on the obtained dye film, and as a result, the quality of the polarization performance in the polarizing element having the dye film was unsatisfactory.

Patent Document 1 discloses a technique of obtaining a polarizing element having a high polarization performance by orienting a dichroic dye molecule in contact with a corresponding photo alignment layer in an arbitrary direction using a photo alignment layer. However, when the surface of the dye film of the polarizing element is observed with an atomic force microscope (AFM), there exists a portion where the dichroic dye is uniformly oriented and a portion where no dichroic dye is mostly present and an unoriented portion (crater) . Therefore, the polarization performance of the obtained polarizing element did not meet a sufficient demand as a practical level in the polarizing element for a display element.

Patent Document 2 discloses a method for reducing the occurrence of a crator to a minimum and increasing the orientation of a dichroic dye compound as a whole in order to improve the uniformity of the dichroic dye molecule orientation and the polarization performance of the obtained polarizing element, A method for manufacturing a polarizing element at a low level is disclosed. The polarizing element can be obtained by using a liquid crystalline polymer thin film having a photoactive group as an alignment film, irradiating the thin film with linearly polarized light, aligning the molecular axis of the photoactive group of the polarized light irradiation region in a predetermined direction, And then applying a dichroic dye solution on the thin film with a roll coater such that a pressure in a specific range is applied perpendicularly to the substrate. However, in the production of the polarizing element, it is necessary to apply a specific pressure between the roll and the substrate, and the compression pressure must be strictly controlled. Therefore, it is required to develop a polarizing element having excellent polarizing performance that can be manufactured more easily, without requiring such strict pressure control.

Patent Document 1: JP-A-7-261024 Patent Document 2: Japanese Patent No. 4175455

Non-Patent Document 1: "The Institute of Electronics, Information and Communication Engineers", 1988, JJ71-C, p. 1188

A conventional polarizing element having a dye film obtained by applying a composition containing a dichroic dye could not obtain sufficiently satisfactory polarization performance due to the influence of rubbing treatment or the like. Therefore, it is necessary to further improve the polarization performance. It is also preferable to more easily manufacture a polarizing element having such a high polarization performance.

Accordingly, an object of the present invention is to provide a polarizing element which is easily producible with excellent polarization performance, and a display device provided with the polarizing element.

Means for Solving the Problems As a result of a study to solve the above problems, the present inventors have found that a polarizing plate having a stretched film having retardation of 3,000 to 50,000 nm and a layer containing a dichroic dye laminated thereon, It has been found for the first time that a polarizing element having excellent polarizing performance that can be easily manufactured can be obtained by using the device.

That is, the main structure of the present invention is as follows.

(1) A polarizing element characterized in that a stretched film having retardation of 3000 nm to 50000 nm and a layer containing at least one dichroic dye are laminated and the thickness of the stretched film is 20 to 500 μm.

(2) The polarizing element according to (1), wherein the stretched film is made of polyethylene terephthalate.

(3) The polarizing element according to (1) or (2), wherein the dichroic ratio is 5 or more.

(4) The polarizing plate according to any one of (1) to (3), wherein a molecular anisotropy greater than the molecular anisotropy imparted to the surface of the stretched film is imparted in the same direction as the stretching axis of the stretched film. device.

(5) The film according to any one of (1) to (4), further comprising a phase difference film having a retardation phase or a phase-advance axis of retardation at an angle of 10 DEG to 100 DEG with respect to the major axis direction of the film, The polarizing element described in any one of < 1 >

(6) The polarizing element according to any one of (1) to (5), wherein at least one of the dichroic dyes is a compound represented by the following formula 1 or a salt thereof.

[Formula 1]

(In the formula 1,

X ₁ represents a phenyl group or a naphthyl group having one or two sulfonic acid groups and a hydroxyl group or an alkoxy group having a carbon number of 1 to 3,

X ₂ and X ₃ each independently represent a phenylene group or a naphthylene group, and the phenylene group or naphthylene group is preferably an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a hydroxyl group, and a sulfonic acid group Or one or two substituents selected from the group consisting of hydrogen,

R ₁ represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an acetyl group, a benzoyl group, an unsubstituted phenyl group or an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, A substituted phenyl group,

m is 0 or 1, and

n is 1 or 2,

(7) The polarizing element according to (6), wherein X ₁ is a compound represented by the following formula 3 as a substituent or a salt thereof.

[Formula 3]

(In the above formula 3, j is 1 or 2)

(8) The image forming method as described in any one of (1) to (7), wherein the layer containing the dichroic dye further contains a polyoxyethylene polyoxypropylene alkyl ether or a polyoxyethylene polyoxypropylene block polymer Polarized light.

(9) A display device provided with the polarizing element according to any one of (1) to (8).

The polarizing element of the present invention, which is characterized in that a film having retardation of 3000 to 50000 nm and a layer containing a dichroic dye are laminated, is characterized in that a stretched film having a high retardation thickness of 20 to 500 μm use. The polarizing element of the present invention using such a specific stretched film exhibits a high degree of polarization, particularly a polarization degree of 85% or more, a high dichroism property, particularly a dichroism property of 5 or more. Therefore, by using the specific stretched film of the present invention as a substrate, a polarizing element having excellent polarization performance can be obtained. Further, the polarizing element of the present invention is a laminate of a specific base material and a layer containing a dichroic dye. Therefore, by the constitution of the present invention, it is possible to obtain a high-performance polarizing element which is excellent in polarization performance and can be easily manufactured.

Hereinafter, the present invention will be described in detail. In the following description, the numerical range indicated by "~" means a range including numerical values before and after "~" as a lower limit value and an upper limit value. Unless otherwise stated, the compounds (substituents) represented by the formulas 1 to 3 are represented in the form of the free acid, and the salt of the free acid means, for example, a salt of a sulfonic acid group or a hydroxyl group. In the following description, unless otherwise stated, in order to avoid troublesomeness, the term " compound represented by formula 1 or salt thereof ", " compound represented by formula 2 or salt thereof ", " The salt thereof "are respectively referred to as" compound represented by formula 1 "," compound represented by formula 2 "and" compound represented by formula 3 as a substituent "for convenience.

First, a polarizing element constituting the present invention will be described. The polarizing element of the present invention is a polarizing element in which a stretched film having retardation of 3000 to 50000 nm and a layer containing a dichroic dye are laminated and the stretched film has a thickness of 20 to 500 μm.

(Stretched film)

The polarizing element of the present invention uses a stretched film having retardation of 3,000 to 50,000 nm as a substrate. The material of the stretched film is not particularly limited. Examples of the material of the stretched film include resins such as polyesters such as polyethylene terephthalate and polyethylene naphthalate, polycarbonate, polystyrene, polyether ether ketone, polyphenylene sulfide, cycloolefin polymer and the like . Among them, polycarbonate or polyester is particularly preferable. These resins are excellent in transparency as well as in thermal and mechanical properties and can easily control the retardation of the film by stretching and also have a high degree of crystallinity after stretching. The dimensional change such as heat shrinkage after stretching is smaller than that of the vinyl alcohol film and therefore the dimensional change can be extremely reduced as compared with the conventional polarizing element using the polyvinyl alcohol film. Further, the stretched film used in the present invention has such a high retardation even though it is a relatively thin thickness of 20 to 500 탆. As the material of such a stretched film, particularly, a polyester typified by polyethylene terephthalate is the most preferable material because it has a high intrinsic birefringence and a comparatively low thickness of the stretched film and relatively high retardation can be obtained.

The higher the molecular orientation of the stretched film, and eventually the higher the retardation, the better the orientation of the dichroic dye molecules applied on the stretched film. Therefore, in order to obtain a polarizing element having a high degree of polarization, it is preferable to use a stretched film having a high retardation. As described above, the range of the retardation of the stretched film used as the polarizing element of the present invention is 3000 to 50000 nm. The polymer film having retardation exceeding 50000 nm is liable to be stiff and the thickness of the film becomes correspondingly thick, and as a result, the handling property as an industrial material is lowered, which is not preferable. On the other hand, from the viewpoint of visibility, it is preferable to use a stretched film having a retardation range of 3000 to 30000 nm. It is known that when a display screen is viewed through a polarizing plate such as a polarizing sunglass, it has a specifically good performance exhibiting a strong interference color. On the other hand, if the retardation is in the range of 3000 to 30000 nm, such interference does not occur and good visibility can be ensured. However, when the retardation is less than 3000 nm, when the display screen is viewed through a polarizing plate such as a polarizing sunglass, a strong interference color is exhibited, so that the envelope shape differs from the light emission spectrum of the light source. As a result, , The performance of the polarizing element is deteriorated. Therefore, the retardation of the stretched film used as the polarizing element of the present invention is in the range of 3000 to 50000 nm, the lower limit of the retardation is preferably 4500 nm, more preferably the lower limit is 6000 nm, more preferably the lower limit is 8000 nm The lower limit value is preferably 10000 nm, and the upper limit value of the retardation is preferably 30000 nm.

The method for producing a stretched film used in the polarizing element of the present invention is not particularly limited as long as it satisfies the properties of the stretched film specified in the present invention. Examples of the stretched film to be used include a film described in Japanese Unexamined Patent Publication No. 2012-230390 and Japanese Unexamined Patent Publication No. 2012-256014, and a film made of a cosmetic material such as a cosmetic shoe made of polyethylene terephthalate film (SRF film)). By using such a stretched film, molecular anisotropy is expressed on the film surface, and the dichroic dye molecule can be oriented. The state in which the film is stretched means that anisotropy is expressed with respect to the orientation of the dichroic dye molecules on the surface of the film to indicate that the retardation is expressed. The expression of this anisotropy can be measured by diffraction measurement by X-ray measurement, phase difference measurement, anisotropic IR absorption analysis and the like. In particular, Alexxander, L. E. Diffraction Methods in Polymer Science New York, 1969, Chapter 4, p. 241-252, the fc may be 0.3 or more, preferably 0.5 or more, more preferably 0.7 or more, and particularly preferably 0.9 or more. The method of stretching the film is not particularly limited as far as anisotropy is exhibited. Particularly, by using a uniaxially stretched film, in the application of the solution containing the dichroic dye, the dichroic dye molecule has a high Orientation, and as a result, a polarizing element exhibiting a high degree of polarization can be obtained.

In the present invention, the retardation (retardation value) is a parameter defined by a product of the anisotropy of the refractive index of the film-form biaxial film and the film thickness, and is a measure of optical isotropy and anisotropy. Therefore, this retardation can be obtained by measuring the refractive index and thickness in the biaxial direction and can be obtained, for example, by using a commercially available automatic birefringence measuring device such as KOBRA-21ADH (manufactured by Prince Instruments).

By subjecting the stretched film as a base material to corona discharge treatment or ultraviolet irradiation, the dichroism of the polarizing element described later can be improved, and the polarizing characteristic of the obtained polarizing element can be enhanced. The corona discharge treatment is applicable to corona discharge treatment using various commercially available corona discharge processors, and it is particularly preferable to use a corona discharge treatment machine having an aluminum head. The conditions of the corona discharge treatment are about 20 to 400 W · min / m ² , preferably about 50 to 300 W · min / m ² , as energy density in the corona discharge treatment per one time. In addition, when the corona discharge treatment is insufficient for one time, the corona discharge treatment may be performed twice or more. The ultraviolet ray irradiation is similarly applicable by using various commercially available ultraviolet ray irradiation apparatuses. The wavelength of the ultraviolet ray to be used is not particularly limited, and for example, far ultraviolet ray of 300 nm or less is preferable. The ultraviolet ray irradiation is preferably carried out under an oxygen flow, and the ultraviolet ray irradiation time is long enough to be several minutes.

(Dichroic dye)

The polarizing element of the present invention has a layer containing a dichroic dye to form a dye film as an element exhibiting a polarization function. A dichroic dye is used as a material for forming a layer containing a dichroic dye, and the dichroic dye is a compound that exhibits a polarizing property by being arranged in a certain direction by itself or as an aggregate. Examples of such a dichroic dye include a dye compound such as an azo dye, a stilbene dye, a pyrazolone dye, a triphenylmethane dye, a quinoline dye, an oxazine dye, a thiazine dye and an anthraquinone dye And the like. The dichroic dye used in the present invention is a compound exhibiting lyotropic liquid crystallinity under a constant solvent composition, colorant concentration, and temperature condition, and includes, for example, Irie Masahiro, "Application of Functional Dyes" , CMC Corporation, June 2002, p. And dichroic dyes described in 102-104. As the dichroic dye, it is preferable to use a water-soluble azo dye, and among these, a compound having an aromatic ring structure is more preferable. Examples of the aromatic ring structure include benzene, naphthalene, anthracene and phenanthrene, as well as heterocyclic rings such as thiazole, pyridine, pyrimidine, pyridazine, pyrazine and quinoline or quaternary salts thereof, Talline and the like. Particularly, a hydrophilic substituent such as a sulfonic acid group, a carboxyl group, an amino group or a hydroxyl group, or a salt of a sulfonic acid group or a carboxyl group is preferably introduced into the aromatic ring.

Specific examples of such dichroic dyes include, for example, CIDirect Orange 39, CIDirect Orange 41, CIDirect Orange 49, CIDirect Orange 72, CIDirect Red 2, CIDirect Red 28, CIDirect Red 39, CIDirect Red 79, CIDirect Red 81, CIDirect Red 89, CIDirect Violet 9, CIDirect Violet 35, CIDirect Violet 48, CIDirect Violet 57, CIDirect Blue 1, CIDirect Blue 15, Blue 67, CIDirect Blue 78, CIDirect Blue 83, CIDirect Blue 90, CIDirect Blue 98, CIDirect Blue 151, CIDirect Blue 168, CIDirect Blue 202, CIDirect Green 42, 59, CIDirect Green 85, CIDirect Yellow 4, CIDirect Yellow 12, CIDirect Yellow 26, CIDirect Yellow 44, CIDirect Yellow 50, Mordant Yellow 26, CINo.27865, CINo.27915, CINo. 27920, CINo.29058, CINo.29060, and the like. Further, Japanese Patent Application Laid-Open Nos. 1-161202, 1-172906, 1-172907 There may be mentioned a dichroic dye disclosed in, Japanese Patent Application Laid-Open No. 1-183602 discloses, Japanese Patent Application Laid-Open No. 1-248105 discloses, Japanese Patent Application Laid-Open No. 1-265205 discloses, Japanese Patent Application Laid-Open No. 9-230142, etc. Each publication No..

Among the dichroic dyes shown in the above specific examples, the compounds represented by the following formula 1 or 2 are particularly preferable, and the compounds represented by the formula 1 are particularly preferable. The compounds represented by the formulas (1) and (2) are present as free acids or salts thereof. The salt of the free acid is not particularly limited and may be, for example, an alkali metal salt such as Li, Na, K or an optional salt such as a quaternary ammonium salt. By using such a dichroic dye, the polarization performance of the obtained polarizing element can be improved.

(In the formula 1,

X ₁ represents a phenyl group or a naphthyl group having one or two sulfonic acid groups and a hydroxyl group or an alkoxy group having a carbon number of 1 to 3,

X ₂ and X ₃ each independently represent a phenylene group or a naphthylene group, and the phenylene group or naphthylene group is preferably an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a hydroxyl group, and a sulfonic acid group Or one or two substituents selected from the group consisting of hydrogen,

R ₁ represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an acetyl group, a benzoyl group, an unsubstituted phenyl group or an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, A substituted phenyl group,

m is 0 or 1, and

n is 1 or 2.)

[Formula 2]

(In the formula 2,

Y ₁ represents one or two sulfonic acid groups and also represents a hydroxyl group or a naphthyl group which may have an alkoxy group having 1 to 3 carbon atoms,

Y ₂ and Y ₃ each independently represent a phenylene group or a naphthylene group, and the phenylene group or naphthylene group is preferably an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a hydroxyl group, and a sulfonic acid group Or one or two substituents selected from the group consisting of hydrogen,

R ₂ represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an acetyl group, a benzoyl group, an unsubstituted phenyl group or an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, A substituted phenyl group,

As the phenyl azo group

는, 말단 나프틸기의 5위, 6위, 7위 또는 8위 중 어느 하나의 위치에서 치환되며,

Is substituted at any position of the 5th, 6th, 7th or 8th position of the terminal naphthyl group,

R ₃ and R ₄ each independently represent a hydrogen atom, a hydroxyl group, a sulfonic acid group, an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms,

q is 0 or 1,

p is 1 or 2.)

Specific examples of the compound represented by the above-mentioned formula (1) include, for example, the following compounds:

.

.

Specific examples of the compound represented by the formula 2 include, for example, the following compounds:

.

.

Among the compounds represented by Formula 1 or Formula 2, when X _{1 in} Formula ₁ or Y _{1 in} Formula 2 has a compound represented by Formula 3 as a substituent, it is possible to further improve the polarization performance, and in particular, , It is preferable to use the compound represented by the formula 1 having the compound represented by the following formula 3 as a substituent. The substituent also exists as a free acid or a salt thereof, like the compound represented by the formula 1 and the formula 2. The salt of the free acid is not particularly limited and may be, for example, an alkali metal salt such as Li, Na, K or an optional salt such as a quaternary ammonium salt.

[Formula 3]

(In the formula 3, j is 1 or 2.)

The dichroic dye used in the present invention may be used singly or in combination of two or more. The combination of two or more kinds of dichroic dyes is not particularly limited, but the dichroic ratio of the dichroic dyes can be further improved by using the added dichroic dyes.

Next, a method of manufacturing the polarizing element of the present invention will be described. The polarizing element of the present invention is produced by applying a solution containing the dichroic dye to the stretched film as the base material described above and subsequently drying it to form a layer containing a dichroic dye on the stretched film. In order to exhibit a polarization function, the layer containing the formed dichroic dye may use a laminate composed of a substrate and a layer containing a dichroic dye as a polarizing element, A protective layer or the like may be laminated on the polarizing element.

A solution (coating liquid) containing a dichroic dye is prepared in order to orient a dichroic dye molecule on a stretched film as a base material. The solvent as the coating liquid is not particularly limited as long as it can dissolve the dichroic dye to be used. Examples of the solvent include water, alcohols, ethers, pyridine, dimethylformamide (DMF), dimethylsulfoxide (DMSO) , N-methylpyrrolidinone (NMP), dimethylacetamide (DMAC) and dimethylimidazoline (DMI). Of these, only one solvent may be included, or plural solvents may be included It is possible. Particularly, when a water-soluble dichroic dye is used, a mixed solvent with water or an organic solvent mainly containing water is preferable as the solvent. The amount of the organic solvent to water mixed with water is arbitrary, but it is preferably 0 to 50 mass%, particularly 0 to 20 mass% with respect to water. The concentration of the dichroic dye in the coating liquid is preferably 0.1 to 25% by mass, more preferably 0.3 to 10% by mass, still more preferably 0.5 to 5% by mass.

In addition, the polarizing element of the present invention has a layer containing a dichroic dye formed by using a coating liquid which further contains a compound comprising a polyoxyethylene polyoxypropylene alkyl ether or a polyoxyethylene polyoxypropylene block polymer, The polarization performance can be further improved. The layer containing the dichroic dye further contains such a compound, so that it is possible to improve the coating defects caused by the coating in the production of the dye film on the substrate. These compounds may be used singly or in combination of two or more. The concentration of these compounds in the coating liquid is preferably 0.001 mass% to 5 mass%, more preferably 0.01 mass% to 2 mass%, still more preferably 0.05 mass% to 1.0 mass%.

Subsequently, the solution containing the dichroic dye is dropped on the surface of the stretched film of the present invention as a substrate, and a layer containing a dichroic dye having a uniform thickness on the stretched film, that is, A coating film is provided. The method of providing the coating film is not particularly limited as long as the solution containing the dichroic dye can be applied. For example, a method of immersing the stretched film of the present invention in a solution containing a dichroic dye A method of coating the solution with a bar coater or the like, a method of applying with an applicator of an ink jet printer such as a piezo system, a thermal system or a bubble jet (registered trademark) system used for home or commercial use, A roll coater application method, a flexo printing method, a screen printing method, a gravure printing method, a curtain coater application method, a spray coater application method, and the like are preferable. In particular, a roller coating application method, a curtain coater application method and a spray coating method are preferable .

Furthermore, a layer containing the dichroic dye of the present invention can be obtained by drying a substrate coated with a solution of a dichroic dye, and forming a layer of a dichroic dye in a solid state. The drying conditions vary depending on the kind of the solvent, the type of the dichroic dye, the amount of the solution containing the applied dichroic dye, the concentration of the dichroic dye, and the like, but the drying temperature is 5 to 100 ° C, preferably 10 to 50 ° C , And the humidity is preferably about 20 to 95% RH, and preferably about 30 to 90% RH.

The thickness of the dye film of the present invention is preferably thin, for example, from 0.001 to 10 탆, particularly preferably from 0.05 to 2 탆, from the viewpoint of improvement of polarizing characteristics. In order to form the dye film of the present invention within the range of such a thickness, the thickness of the coated film coated with the solution containing the dichroic dye is preferably 2 to 10 mu m, more preferably 3 to 5 mu m.

Further, the stretched film of the present invention coated with the solution containing a dichroic dye may be further subjected to heat treatment and / or humidification treatment. By performing the heat treatment and / or the humidifying treatment, the adhesion of the layer containing the dichroic dye to the stretched film of the present invention, the polarization performance of the obtained polarizing element, dichroism and durability can be improved. The temperature of the heat treatment is from room temperature to 110 캜, preferably from 60 to 90 캜, and the humidity of the humidifying treatment is preferably from 40 to 95% RH, and more preferably from 50 to 90% RH.

The polarizing element of the present invention thus obtained has a dichroic ratio (Rd). The dichroic ratio is generally defined as the ratio of the absorbance along the absorption axis to the absorbance along the transmission axis. The dichroic ratio of the polarizing element of the present invention is calculated by the following formula (4), and when the dichroic ratio is 5 or more, it means that the polarizing function is exerted. The dichroic ratio of the polarizing element of the present invention is 5 or more, preferably 10 or more, more preferably 15 or more, still more preferably 20 or more. When the dichroic ratio becomes less than 5, the degree of polarization becomes less than 65%, and the function as a polarizing element is not sufficient. The polarization degree of the polarizing element is usually 65% or more, preferably 70% or more, and more preferably 80% or more. The degree of polarization refers to the ratio of the optical intensity of the polarized component to the total optical intensity, which means that the higher the polarization degree, the higher the polarization performance. In the following expression (4), Ky is the transmittance of the axis that transmits the most light when polarized light is incident, and Kz is the transmittance of the axis that absorbs the most light when polarized light is incident.

[Formula 4]

Rd = Log (Kz / 100) / Log (Ky / 100)

As a method of further improving the dichroic ratio of the polarizing element of the present invention, a method of increasing the dichroic ratio of the polarizing element of the present invention is preferably a method in which, in the same direction as the stretching axis of the stretched film, By further imparting anisotropy, the dichroic ratio can be further improved. As a method for expressing the molecular anisotropy larger than the stretched film, for example, a method of rubbing the stretched film can be mentioned. Such rubbing is exemplified in, for example, Japanese Patent Application Laid-Open No. H06-110059 and Japanese Patent Application Laid-Open No. 2002-90743. The measurement of the molecular anisotropy of the stretched film surface is not particularly limited, but it is measured by a measuring method used for anchoring measurement of the alignment film for liquid crystal, for example. The apparatus for measuring the molecular anisotropy is not particularly limited. For example, Lay Scan of MARITEX SCOTT can be used.

On the stretched film of the present invention, a retardation film exhibiting molecular anisotropy in the major axis direction is formed on the surface of the film having the slow axis or the fast axis in phase different from the long axis direction of the film, preferably 10 DEG to 100 DEG, It is also possible to manufacture a polarizing element that is further laminated. Such a retardation film can be obtained by imparting molecular anisotropy to the surface of a retardation film having a retardation phase or a retardation axis of a retardation at an arbitrary angle by rubbing or the like in the long axis direction to thereby arbitrarily control the polarization axis or absorption axis of the polarizing element can do. That is, by using a new retardation film having a retardation axis or a retardation axis with a phase difference at an angle different from that of the long axis direction of the film and exhibiting molecular anisotropy on the surface in the long axis direction on the stretched film of the present invention, It becomes possible to manufacture a polarizing element having an absorption axis or a polarization axis at an angle different from that of the phase axis or the slow axis as the axle. It is most preferable that the angle between the phase axis of the phase difference film and the absorption axis or the polarization axis of the polarizing element is 15 °, 45 °, 75 °, or 90 °. When the linearly polarized light is to be controlled to be circularly polarized light, a film having a phase difference of 1/4 with respect to the length of a wavelength to be controlled is preferably set at 45 degrees with respect to the absorption axis of the polarizing element It is known to install. As a method of reversing the polarization axis of linearly polarized light, it is known to provide a film having a phase difference of 1/2 with respect to the length of a wavelength to be controlled at 90 degrees. The reason why the film is provided at an angle of 15 DEG or 75 DEG with respect to the absorption axis or polarization axis of the polarizing element is that the angle is a prescription showing a retardation of 1/4 with respect to a wide wavelength (generally referred to also as a wide band acromatic retardation plate ). This makes it possible to arbitrarily control the polarization axis or the absorption axis of the polarizing element.

The layer containing the dichroic dye of the present invention thus prepared is in a solid state such as an amphus or a crystal. However, since the layer containing the dichroic dye typically has a low mechanical strength, A rake treatment, a crosslinking treatment with a silane coupling agent, or a protective layer. Lake is to electrically bind a metal ion or the like to a dichroic dye showing water solubility. It is also called rake or insolubility to make a dichroic pigment into rake. Examples of suitable compounds for rake include aluminum chloride, iron chloride, calcium chloride, barium chloride, nickel chloride, magnesium chloride, copper chloride, barium acetate and nickel acetate. And is not particularly limited as long as the dichroic dye can be insolubilized in water. The crosslinking treatment by the silane coupling agent is not particularly limited. For example, a crosslinking treatment is carried out by heating using a silane coupling agent described in JP-A No. 2011-53234, and a dye containing a dichroic dye Can be immobilized. The protective layer is usually formed by coating a layer containing a dichroic dye with a transparent polymer film having ultraviolet curing properties or thermosetting properties or a coating method such as laminating with a transparent polymer film such as a polyester film or a cellulose acetate film Respectively. The protective layer can be provided as a coating layer of a polymer or as a laminate layer of a film. As the transparent polymer or film forming the transparent protective layer, a transparent polymer or film having high mechanical strength and good thermal stability is preferable. As the material used as the transparent protective layer, for example, a cellulose acetate resin or a film thereof such as triacetylcellulose or diacetylcellulose, an acrylic resin or a film thereof, a polyvinyl chloride resin or a film thereof, a nylon resin or a film thereof, A resin or a film thereof, a polyarylate resin or a film thereof, a cyclic polyolefin resin having a cyclic olefin such as norbornene as a monomer or a film thereof, a polyolefin having a polyethylene, a polypropylene, a cyclo- or norbornene skeleton, A copolymer or a resin or polymer of imide and / or amide of the main chain or side chain, or a film thereof. As the transparent protective layer, a resin having liquid crystallinity or a film thereof may be provided. The thickness of the protective layer is, for example, about 0.5 to 200 mu m. One or more layers of a resin or film as a protective layer may be provided on one side or both sides of the polarizing element. When a plurality of protective layers are used, these protective layers may be the same or different.

The polarizing element of the present invention can be used for polarized sunglasses, goggles and the like. Further, in the polarizing element of the present invention, in the case of using a stretched film produced from the above material as the base material, in the production of the polarizing element of the present invention, the dichroic property required when using a conventional polyvinyl alcohol- The adsorption of the dye and the stretching treatment in the boric acid solution are not required. Therefore, a polarizing element free from any dimensional change of the substrate and free from shrinkage can be obtained. Particularly, it is effective for a display in which a polarizing element is required to be provided on one side of a display device such as a flexible display or an organic electroluminescence display (commonly referred to as OLED). Therefore, the polarizing element of the present invention can be installed in a display device such as a flexible display or an organic electroluminescence display. Further, unlike the conventional method of producing a polarizing element, there is no application of strict conditions required for coating a dichroic dye, and a solution containing a dichroic dye is applied to the stretched film of the present invention as a substrate, It is very simple and easy to manufacture the polarizing element of the present invention in that a polarizing element can be easily obtained by simply drying and providing a layer containing a dichroic dye on a substrate.

Hereinafter, the present invention will be described in further detail with reference to examples, but the present invention is not limited thereto. The transmittance shown in the examples was evaluated as follows.

The transmittance and dichroism ratio (Rd) of each wavelength were measured using a spectrophotometer (V-7100, manufactured by Nippon Bunko K.K.). At this time, when the transmittance Ts of each wavelength when the layer containing the dichroic dye is measured in one layer and the layer containing two dichroic dyes are overlapped so as to have the same absorption axis direction Transmittance was defined as the flat actuation transmittance Tp, and the transmittance in the case where the layers including two dichroic dyes were overlapped such that their absorption axes were perpendicular to each other was taken as the perpendicular transmittance Tc.

The polarization degree ρ was obtained from Equation 5 from the flat actuation transmittance Tp and the orthogonality transmittance Tc.

[Formula 5]

Example  One

4 parts by mass of CIDirect Blue 67 as a dichroic dye, 4 parts by mass of polyoxyethylene polyoxypropylene (hereinafter referred to as " CI Direct Blue 67 ") as a dichroic dye, A solution containing 0.15 parts by mass of an alkyl ether (Margens MS-110 by Kao Corporation) and 100 parts by mass of water was applied by using a coating machine equipped with a glass rod set to have an interval of 3 占 퐉 from the stretched film. The obtained coating film was allowed to stand in an environment of 25 캜 and 70% humidity for 1 minute, and the solvent was dried. The dried coating film was subjected to heat treatment and humidification treatment in an environment of 60 占 폚 and 90% humidity for 5 minutes to obtain a layer containing a dichroic dye having a thickness of 0.15 占 퐉. An acrylic resin-based ultraviolet curable resin composition (SPC-920C, manufactured by Nippon Kayaku Co., Ltd.) was coated on the layer containing the obtained dichroic dye by a spin coater so as to have a protective layer thickness of 3 占 퐉 after curing, The resin composition was cured, and a protective layer was provided on the layer containing the dichroic dye. The polarizing element thus obtained was used as a measurement sample.

Example  2

A rubbing cloth (MK0012 manufactured by TANAKAFILE TEXTILE CO., LTD.) Was wound on a non-stretch-bonded surface of the stretched film having a retardation of 10500 nm used in Example 1 along the direction of 0 DEG with respect to the slow axis of the stretched film A test sample was prepared in the same manner as in Example 1 except that the rubbing treatment was further carried out under the conditions of a speed of 100 rpm and a load of 5 kgf. At this time, the angle of the stretched film with respect to the slow axis was measured by KOBRA-21 ADH (manufactured by Prince Instruments).

Example  3

Except that the non-stretch-bonded surface of the stretched film having the retardation of 10500 nm used in Example 1 was subjected to a rubbing treatment with a roll covered with a rubbing cloth along the direction of 45 DEG to the slow axis of the stretched film A measurement sample was prepared in the same manner as in Example 2.

Example  4

Except that rubbing treatment was performed on a non-stretch-bonded surface of a stretched film having a retardation of 10500 nm used in Example 1 with a roll covered with a rubbing cloth along the direction of 90 DEG to the slow axis of the stretched film A measurement sample was prepared in the same manner as in Example 2.

Example  5

As a substrate, a stretched film of polyethylene terephthalate (SKYGREEN PETG K2012 (manufactured by Mitsubishi Chemical Corporation) having a retardation of 35000 nm was dissolved at 230 占 폚 in place of the stretched film having a retardation of 10500 nm used in Example 1 And a non-stretched PET film molded to have a thickness of 100 탆 was stretched by about 4 times uniaxially stretched).

Example  6

As a substrate, a stretched film of polyethylene terephthalate (SKYGREEN PETG K2012 (manufactured by Mitsubishi Heavy Industries, Ltd.) having a retardation of 3500 nm was dissolved at 230 占 폚 in place of the film having retardation of 10500 nm used in Example 1, Of a PET film obtained by stretching the unstretched PET film to a film thickness of about 2.1 times the uniaxially stretched film) was used in place of the non-stretched PET film.

Comparative Example  One

Except that SKYGREEN PETG K2012 (manufactured by Mitsubishi Heavy Industries, Ltd.) was dissolved at 230 占 폚 and molded into a film thickness of 100 占 퐉, instead of the stretched PET film of Example 1, A measurement sample was prepared in the same manner as in Example 1.

Comparative Example  2

A measurement sample was prepared in the same manner as in Example 1 except that the unstretched PET film of Comparative Example 1 was uniaxially stretched to 1.5 times to obtain a film having a retardation of 1000 nm.

Table 1 shows Ts, Tp, Tc, r, and Rd at the wavelength with the highest degree of polarization obtained by measuring the samples obtained in Examples 1 to 6 and Comparative Examples 1 and 2.

[Table 1]

As is clear from the results of Table 1, the polarizing element of the present invention using the stretched film having retardation values in Examples 1 to 6 exhibited a high degree of polarization (rho) and a high dichroic ratio (Rd) .

On the other hand, in Comparative Example 1 in which an unstretched film having no retardation was used and in Comparative Example 2 in which the retardation value was outside the stipulation of the present invention, the degree of polarization (rho) was less than 65% and the dichroic ratio (Rd) 5, it can be seen that the function as a polarizing element is not sufficient.

From the above results, the polarizing element of the present invention exhibits a high polarization degree of 85% or more and a high dichroism of 5 or more. Further, in the production of the polarizing element of the present invention, the adsorption of a dichroic dye required when using a conventional polyvinyl alcohol-based film substrate and the stretching treatment in a boric acid solution are not required, It is possible to manufacture a polarizing element without any dimensional change or shrinkage. That is, the polarizing element of the present invention is only a laminate of a specific base material and a layer containing a dichroic dye. From this, it can be seen that the polarizing element of the present invention is a polarizing element which is excellent in polarization performance and can be easily manufactured.

The polarizing element of the present invention is not a polarizing element using a polyvinyl alcohol resin film such as a conventional polarizing element but a polarizing element can be manufactured by applying a solution containing a dichroic dye to a stretched substrate having a specific retardation Therefore, a process such as swelling, dyeing, stretching, and the like required in the conventional process is not required, and the polarizing element can be manufactured simply and easily. In addition, since a film of a polarizing element can be produced only by a dichroic dye as a component exhibiting a polarizing function, it is possible to form a polarizing element that is an ultrathin film. Further, since the polarizing element can be produced by applying a solution containing a dichroic dye, it is not limited to the shape of the flat plate-shaped polarizing element such as the conventional polarizing plate, and the shape of the polarizing element may be a curved surface or a spherical polarizing It is also possible to form a device. Particularly, in the conventional stretched film, only the polarizing plate that allows the polarized light perpendicular to the stretching direction to pass can be formed. However, since the polarizing element of the present invention can arbitrarily set the orientation direction with respect to the rubbed base material, It is possible to form a polarizing element provided with polarizability in any direction.

Claims (9)

Characterized in that a stretched film having retardation of 3000 nm to 50000 nm and a layer containing at least one dichroic dye are laminated, and the stretched film has a thickness of 20 탆 to 500 탆.
The polarizing element according to claim 1, wherein the stretched film is made of polyethylene terephthalate.
The polarizing element according to claim 1 or 2, wherein the dichroic ratio is 5 or more.
4. The polarizing element according to any one of claims 1 to 3, further imparting molecular anisotropy larger than molecular anisotropy imparted to the surface of the stretched film in the same direction as the stretching axis of the stretched film.
The polarizing element according to any one of claims 1 to 4, further comprising a retardation film having a slow axis or a fast axis of the retardation at an angle of 10 ° to 100 ° with respect to the major axis direction of the film.
The polarizing element according to any one of claims 1 to 5, wherein at least one of the dichroic dyes is a compound represented by the following formula 1 or a salt thereof:
[Formula 1]

In the above formula 1,
X ₁ represents a phenyl group or a naphthyl group having one or two sulfonic acid groups and a hydroxyl group or an alkoxy group having a carbon number of 1 to 3,
X ₂ and X ₃ each independently represent a phenylene group or a naphthylene group, and the phenylene group or naphthylene group is preferably an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a hydroxyl group, and a sulfonic acid group Or one or two substituents selected from the group consisting of hydrogen,
R ₁ represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an acetyl group, a benzoyl group, an unsubstituted phenyl group or an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, A substituted phenyl group,
m is 0 or 1, and
n is 1 or 2;
The polarizing element according to claim 6, wherein X ₁ is a compound represented by the following formula 3 as a substituent or a salt thereof:
[Formula 3]

In the above formula 3, j is 1 or 2.
The polarizing element according to any one of claims 1 to 7, wherein the layer containing a dichroic dye further contains a polyoxyethylene polyoxypropylene alkyl ether or a polyoxyethylene polyoxypropylene block polymer.
A display device provided with the polarizing element according to any one of claims 1 to 8.