KR101120282B1 - Iodine type polarizing film and process for producing the same - Google Patents

Abstract

When two polarizing plates are arrange | positioned in a liquid crystal display device so that these light transmission axes may mutually orthogonally cross, an iodine type polarizing film which can prevent generation | occurrence | production of the light leakage in the long wavelength range of visible light, and can suppress discoloration of a display screen. And a method for producing the same. The iodine type polarizing film of this invention is an iodine type polarizing film which adsorbed and oriented iodine to a polyvinyl alcohol film, and is characterized by containing a group 2 element.

Iodine, adsorption orientation, iodine polarizing film, group 2 element, polyvinyl alcohol, transparent protective film

Description

Iodine polarizing film and its manufacturing method {IODINE TYPE POLARIZING FILM AND PROCESS FOR PRODUCING THE SAME}

INDUSTRIAL APPLICABILITY The present invention relates to an iodine polarizing film for use in an image display device such as a liquid crystal display device, an electroluminescence (EL) display device, a plasma display (PD), and a field emission display (FED: field emission display), and a method of manufacturing the same. It is about. Moreover, this invention relates to the polarizing plate using the said iodine type polarizing film.

The polarizing film used for an image display apparatus (especially a liquid crystal display device) is required to have a high transmittance and a polarization degree in order to provide the image which is bright and has good color reproducibility. Such a polarizing film is conventionally manufactured by adsorbing a dichroic substance such as iodine or dichroic dye having dichroism to a polyvinyl alcohol (PVA) film.

The iodine type polarizing film which adsorb | sucked iodine among these polarizing films has the characteristic that high transmittance and high polarization, ie, high contrast, are obtained compared with a dye type polarizing film. For this reason, an iodine type polarizing film is used widely as a member of a liquid crystal display device.

However, in the liquid crystal display device in which two polarizing plates to which the iodine polarizing film is applied are arranged such that their light transmission axes are perpendicular to each other, there is a problem that light leakage of visible light occurs and the display screen is discolored. In particular, in the iodine-based polarizing film in which iodine is adsorbed on a polyvinyl alcohol film, the light absorption in the short wavelength region (360 to 410 nm) and the long wavelength region (700 to 830 nm) is small in the visible light region (360 to 830 nm). The improvement is called for.

[Patent Document 1] Japanese Patent Application No. 56-207374

The present invention has been made in view of the above problems, and its object is to prevent occurrence of light leakage in a long wavelength region of visible light when two polarizing plates are arranged in a liquid crystal display such that their light transmission axes are perpendicular to each other. It is providing the iodine type polarizing film which can suppress discoloration of a display screen, and its manufacturing method.

MEANS TO SOLVE THE PROBLEM The present inventors discovered that the light absorption in the long wavelength region or the short wavelength region of visible light improved by the iodine type polarizing film containing the Group 2 element, and came to complete this invention.

That is, the iodine type polarizing film which concerns on this invention is an iodine type polarizing film which adsorbed and oriented iodine to a polyvinyl alcohol film, and is characterized by containing a group 2 element.

The iodine polarizing film composed of polyvinyl alcohol is considered to be absorbing light in the long wavelength region (700 to 830 nm) of visible light (360 to 830 nm) by a complex formed by polyvinyl alcohol and iodine. On the other hand, it is believed that the cation of the Group 2 element causes the formation of iodine adsorption sites on the film surface. Therefore, in the iodine type polarizing film containing a group 2 element like the said structure, an iodine adsorption site is formed in the said film surface, and adsorption of iodine is promoted further. As a result, light absorption in the long wavelength region or the short wavelength region of visible light can be increased, and light leakage can be prevented. In addition, since the Group 2 element has a lower standard electrode potential than other polyvalent transition metals, the Group 2 element does not contribute to the redox reaction of iodine even when the iodine polarizing film of the present invention is used under excessive conditions. As a result, since the performance of light absorption in the long wavelength region of visible light does not fall, it is excellent also in optical reliability.

In the above configuration, the amount of the Group 2 element is preferably in the range of 5.6 × 10 ⁻⁵ to 9.7 × 10 ⁻⁵ mol / g. When the amount of the Group 2 element is within the above numerical range, the balance of the orthogonal transmittance in the short wavelength region and the long wavelength region of visible light can be made good. If the amount present is less than 5.6 × 10 ⁻⁵ mol / g, the orthogonal transmittance of the short wavelength region 360 to 410 nm of visible light may be too high, resulting in light leakage in the short wavelength region. On the other hand, when the amount present is larger than 9.7 × 10 ⁻⁵ mol / g, the orthogonal transmittance in the long wavelength region of visible light may be too high, resulting in light leakage in the long wavelength region.

The manufacturing method of the iodine type polarizing film which concerns on this invention is a manufacturing method of the iodine type polarizing film which adsorbed and oriented iodine to a polyvinyl alcohol film, The salt of a group 2 element to the polyvinyl alcohol film after carrying out the adsorption orientation of the said iodine. It characterized in that it comprises a step of contacting an aqueous solution comprising a.

According to the method, by contacting an aqueous solution containing a salt of the Group 2 element to the polyvinyl alcohol film surface, the cations of the Group 2 element cause the formation of iodine adsorption sites on the film surface. Thereby, an iodine adsorption site is formed in a film surface, and adsorption of iodine is promoted further. As a result, light absorption in the long wavelength region of visible light can be increased, and the iodine type polarizing film which can prevent generation of light leakage can be manufactured. Moreover, since the group 2 element to contain does not contribute to the redox reaction of iodine, the polarizing film obtained by the said method can suppress the fall of the adsorption amount of iodine even if it uses under excessive conditions. Thereby, the fall of the light absorption in the long wavelength region of visible light can be suppressed, and the iodine type polarizing film excellent in optical reliability is obtained.

The said process WHEREIN: The said process contains the process of extending | stretching a polyvinyl alcohol film, the process of dyeing the said polyvinyl alcohol film in the aqueous solution containing iodine and potassium iodide, and the polyvinyl alcohol film after dyeing containing boric acid. It is preferable to carry out after the process of immersion treatment in the aqueous solution to make.

In the above method, it is preferable to use an aqueous solution of the iodide of the Group 2 element as the aqueous solution containing the salt of the Group 2 element.

Moreover, the polarizing plate which concerns on this invention was provided with the transparent protective film in at least one surface of the iodine type polarizing film as described above. It is characterized by the above-mentioned.

This invention has the effect as demonstrated below by the means demonstrated above.

That is, according to the iodine polarizing film according to the present invention, the polyvinyl alcohol film is brought into contact with an aqueous solution containing a salt of the Group 2 element to contain the Group 2 element, thereby causing the formation of iodine adsorption sites on the surface thereof. It is to increase the adsorption. As a result, light absorption in the long wavelength region of visible light can be increased to prevent the occurrence of light leakage. In addition, since Group 2 elements do not contribute to the redox reaction of iodine in comparison with other polyvalent transition metals, even when used under excessive conditions, the performance of light absorption in the long wavelength region of visible light does not deteriorate. . As a result, the optical reliability is also excellent.

Moreover, according to the manufacturing method of the iodine type polarizing film which concerns on this invention, since only the aqueous solution containing the salt of a Group 2 element is made to contact a polyvinyl alcohol film surface, it causes formation of an iodine adsorption site on the said film surface, Thereby, the iodine type polarizing film to which iodine was adsorb | sucked can be manufactured. As a result, the iodine type polarizing film which prevents generation | occurrence | production of light leakage and is excellent also in optical reliability is obtained.

The iodine polarizing film (henceforth "polarizing film") which concerns on this embodiment is immersed in the aqueous solution containing the salt of a Group 2 element by immersing a polyvinyl alcohol film (henceforth "PVA film"), It is the structure which contained the group 2 element.

The said PVA film consists of polyvinyl alcohol-type resin, For example, it is obtained by saponifying a polyvinyl acetate type resin. As polyvinyl acetate type resin, the copolymer etc. of vinyl acetate and the other monomer copolymerizable with this besides the polyvinyl acetate which is a homopolymer of vinyl acetate are mentioned. As another monomer copolymerized with vinyl acetate, unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, vinyl ethers, etc. are mentioned, for example.

The degree of polymerization of the polyvinyl alcohol-based resin is generally 500 to 10,000, preferably in the range of 1,000 to 8,000, and more preferably in the range of 1,400 to 7,000. In the case of saponification, the saponification degree is preferably 75 mol% or more, for example, from the point of solubility in water, more preferably 98 mol% or more, and more preferably in the range of 98.3 mol% or more. .

As a manufacturing method of the PVA film which consists of polyvinyl alcohol-type resin, the film formed by arbitrary methods, such as the casting method, the casting method, and the extrusion method which cast-forms the stock solution melt | dissolved in water or an organic solvent, can be used suitably. The retardation value at this time is preferably 5 nm to 100 nm. Moreover, in order to obtain an in-plane uniform polarizing film, it is preferable that the in-plane phase difference deviation in PVA film surface is as small as possible, and it is preferable that the in-plane phase difference deviation of the PVA film as a raw film is 10 nm or less in 1000 nm of measurement wavelengths, and is 5 nm or less It is more preferable.

Specifically, the Group 2 element refers to any one or more selected from the group consisting of beryllium, magnesium, calcium, strontium, barium and radium. Among these Group 2 elements, magnesium and calcium are preferable from the viewpoint of safety and ease of handling. These group 2 elements can be used individually or in combination of 2 or more types. It is thought that the cation of the Group 2 element (that is, the divalent cation) causes the formation of an iodine adsorption site on the surface of the PVA film. Therefore, when the film is brought into contact with an aqueous solution containing a salt of a group 2 element as in the above configuration, an iodine adsorption site is formed on the surface of the film. As a result, adsorption of iodine on the surface of the PVA film is further promoted. In addition, the ionic strength of the polyvalent ions is proportional to the square of the valence of the ions. For this reason, the divalent cation has a higher ionic strength than the monovalent cation, and as a result, the divalent cation has a higher cause of forming an iodine adsorption site. In addition, in other polyvalent transition metals, since the standard electrode potential is high compared with the Group 2 element, when the polarizing film containing such a polyvalent transition metal is used under excessive conditions, the polyvalent transition metal contributes to the redox reaction of iodine. , The adsorption amount of iodine decreases. As a result, the performance of light absorption in the long wavelength region (700 to 830 nm) of visible light (360 to 830 nm) is lowered, resulting in light leakage, and optical reliability is lowered.

The amount present in the polarizing film of the Group 2 element is preferably in the range of 5.6 × 10 ⁻⁵ to 9.7 × 10 ⁻⁵ mol / g, and is in the range of 6.4 × 10 ⁻⁵ to 7.3 × 10 ⁻⁵ mol / g It is more preferable to be inside. 5.6 × 10 is within a range of ^-5 to 9.7 × 10 ^-5 mol / g, it can be improved the balance of the short-wavelength region (360 to 410nm) and perpendicular transmittance in a long wavelength region of the visible light. When the amount present is less than 5.6 × 10 ⁻⁵ mol / g, the orthogonal transmittance of the short wavelength region may be too high, and light leakage may occur in the short wavelength region. On the other hand, when larger than 9.7x10 <^-5> mol / g, the orthogonal transmittance | permeability of a long wavelength region may be too high, and light leakage may arise in a long wavelength region.

Although the thickness of a polarizing film is not specifically limited, Generally, it is about 5-80 micrometers. By laminating a transparent protective film on one side or both sides of this polarizing film, it becomes a polarizing plate (it mentions later for details).

The polarizing film which concerns on this embodiment is manufactured by making the polyvinyl alcohol film after adsorption-orientation of iodine contact the aqueous solution containing the salt of a group 2 element. It is preferable to perform the said process after a series of processes, such as swelling, dyeing, crosslinking, and extending | stretching a polyvinyl alcohol film as an initial raw film. Moreover, the polarizing film which concerns on this embodiment can be manufactured by performing a drying process after the said process. In each of these steps except the drying step, it is preferable to perform each treatment while immersing in a bath containing various solutions. The order, number of times and the presence or absence of each process at this time are not specifically limited, A some process may be performed simultaneously in one process process, and some processes do not need to be performed. For example, an extending | stretching process may be performed after a dyeing process, may be performed simultaneously with a swelling and a dyeing process, and may be dye | stained after extending | stretching process. In addition, you may perform a washing | cleaning process after all processes, and may carry out only after a specific process.

As said swelling process, it is immersed in the swelling bath filled with water, for example. Thereby, a PVA film is washed with water, the contamination of a PVA film surface and an antiblocking agent can be wash | cleaned, and an effect which prevents nonuniformity, such as a dyeing nonuniformity, can be expected by swelling a PVA film. In this swelling bath, you may add glycerin, potassium iodide, etc. suitably, It is preferable that the density | concentration to add is 5 weight% or less for glycerin and 10 weight% or less for potassium iodide. It is preferable that it is the range of 20-45 degreeC, and, as for the temperature of a swelling bath, it is more preferable that it is 25-40 degreeC. The immersion time in the swelling bath is preferably 2 to 180 seconds, more preferably 10 to 150 seconds, and particularly preferably 60 to 120 seconds. Moreover, you may extend | stretch a PVA film in this swelling bath, and the draw ratio at that time is about 1.1 to 3.5 times with respect to the film of an unstretched state also including the extension by swelling.

As the dyeing step, for example, the dichroic substance is adsorbed onto the PVA film by immersing the PVA film in a dye bath containing a dichroic substance such as iodine.

As said dichroic substance, a conventionally well-known substance can be used, For example, iodine, an organic dye, etc. are mentioned. As an organic dye, for example, red BR, red LR, red R, pink LB, rubin BL, Bordeaux GS, sky blue LG, lemon yellow, blue BR, blue 2R, navy RY, green LG, violet LB, violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congored, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, Direct Sky Blue, Direct Fast Orange S, Fast Black and the like can be used.

One type of these dichroic substances may be used, and two or more types may be used together. When using the said organic dye, it is preferable to combine two or more types from the point which neutralizes a visible light region, for example. As a specific example, the combination of Congo red, supra blue G, supra orange GL, direct sky blue, or direct sky blue and fast black is mentioned.

As a solution of the said dyeing bath, the solution which melt | dissolved the said dichroic substance in the solvent can be used. As the solvent, water is generally used, but an organic solvent compatible with water may be further added. The concentration of the dichroic substance is preferably in the range of 0.010 to 10% by weight, more preferably in the range of 0.020 to 7% by weight, and particularly preferably in the range of 0.025 to 5% by weight.

In addition, when iodine is used as the dichroic substance, it is preferable to further add iodide, since the dyeing efficiency can be further improved. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide and the like. It is preferable that it is 0.010 to 10 weight% in the said dyeing bath, and, as for the addition ratio of these iodide, it is more preferable that it is 0.10 to 5 weight%. It is preferable to add potassium iodide among these, It is preferable that ratio (weight ratio) of iodine and potassium iodide exists in the range of 1: 5-1: 100, and it exists in the range of 1: 6-1: 80. More preferably, it is especially preferable to exist in the range of 1: 7-1: 70.

Although the immersion time of the PVA film in the said dyeing bath is not specifically limited to this, It is preferable that it is the range of 1 to 20 minutes, and it is more preferable that it is 2 to 10 minutes. Moreover, it is preferable to exist in the range of 5-42 degreeC, and, as for the temperature of a dyeing bath, it is more preferable to exist in the range which is 10-35 degreeC. Moreover, you may extend | stretch a PVA film in this dyeing bath, and the cumulative total draw ratio at this time is about 1.1 to 4.0 times.

The dyeing treatment may be a method of applying or spraying an aqueous solution containing a dichroic substance to the PVA film, for example, in addition to the method of immersing it in the dyeing bath as described above. The materials may be mixed beforehand.

As the crosslinking step, for example, the PVA film is immersed in a bath containing a crosslinking agent and crosslinked. As said crosslinking agent, a conventionally well-known substance can be used. For example, boron compounds, such as boric acid and borax, glyoxal, glutaraldehyde, etc. are mentioned. One type may be sufficient as these and they may use two or more types together. When using two or more types together, the combination of boric acid and a borax is preferable, for example, Moreover, it is preferable that the addition ratio (molar ratio) exists in the range of 4: 6-9: 1, and is 5.5: 4.5-7 The range of: 3 is more preferable, and it is most preferable that it is 6: 4.

As a solution of the said crosslinking bath, the solution which melt | dissolved the said crosslinking agent in the solvent can be used. As the solvent, for example, water may be used, but an organic solvent compatible with water may also be included. Although the density | concentration of the crosslinking agent in the said solution is not limited to this, It is preferable to exist in the range of 1 to 10 weight%, and it is more preferable that it is 2 to 6 weight%.

You may add iodide in the said crosslinking bath from the point which the in-plane uniform characteristic of a polarizing film is obtained. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide, and the content thereof is 0.05 to iodide. 15 weight%, More preferably, it is 0.5-8 weight%. Especially, the combination of boric acid and potassium iodide is preferable, It is preferable that the ratio (weight ratio) of boric acid and potassium iodide exists in the range of 1: 0.1-1: 3.5, and it exists in the range of 1: 0.5-1: 2.5. More preferred.

The temperature of the said crosslinking bath is the range of 20-70 degreeC normally, and the immersion time of a PVA film is the range of 1 second-15 minutes normally, Preferably it is 5 second-10 minutes. In addition, the crosslinking treatment may also be performed by applying or spraying a crosslinking agent-containing solution in the same manner as the dyeing treatment, or stretching the PVA film in the crosslinking bath, and the cumulative total draw ratio at this time is 1.1 to 4.0. About twice as much.

As the stretching step, for example, in the wet stretching method, stretching is performed so that the cumulative total stretching ratio is about 2 to 7 times in a state immersed in the bath.

Although it does not specifically limit as a solution of an extending | stretching bath, For example, the solution which added various metal salts, the compound of iodine, boron, or zinc can be used. As a solvent of this solution, water, ethanol or various organic solvents are suitably used. Especially, it is preferable to use the solution which added about 2 to 18 weight% of boric acid and / or potassium iodide, respectively. When using this boric acid and potassium iodide simultaneously, it is preferable to use the content rate (weight ratio) in the ratio of about 1: 0.1-1: 4, More preferably, it is about 1: 0.5-1: 3.

It is preferable that it is the range of 40-67 degreeC, for example, and, as for the temperature of the said stretching bath, it is more preferable that it is 50-62 degreeC.

The step of bringing the PVA film into contact with the aqueous solution containing the salt of the Group 2 element is performed by immersing the PVA film in the aqueous solution, for example. Thereby, formation of an iodine adsorption site on the surface of a PVA film becomes possible. As an aqueous solution containing the salt of a group 2 element, the aqueous solution of any 1 or more types of iodide selected from the group which consists of beryllium, magnesium, calcium, strontium, barium, and radium is mentioned. Moreover, it is preferable that it is 2.2-3.8 weight%, and, as for the density | concentration of the salt of a group 2 element, it is more preferable that it is 2.7-3.3 weight%. When the said concentration is less than 2.2 weight%, absorption of the light in the short wavelength region of visible light may become inadequate. On the other hand, when the said concentration exceeds 3.8 weight%, absorption of the light in the long wavelength region of visible light may become inadequate. Moreover, it is preferable that it is 3 to 25 second, and, as for immersion time, it is more preferable that it is 5 to 15 second. Moreover, it is preferable that it is 10-60 degreeC, and, as for the temperature of a bath, it is more preferable that it is 15-40 degreeC. In addition, the number of the immersion processes in the said process is not specifically limited, You may carry out in multiple times. Moreover, you may change suitably the kind and density | concentration of the additive in a bath according to the frequency | count.

As the washing step, for example, by immersing the PVA film in an aqueous solution of the washing bath, the unnecessary residue such as boric acid attached in the previous treatment can be washed away. You may add the salt of the said group 2 element to the said aqueous solution, As said salt, the iodide of the said group 2 element is used preferably, for example. When the salt of group 2 element is added to a washing bath, the density | concentration is 2.2-3.8 weight% normally, and it is preferable that it is 2.7-3.3 weight%. Moreover, it is preferable that it is 10-60 degreeC, and, as for the temperature of a washing bath, it is more preferable that it is 15-40 degreeC. In addition, the frequency | count of a washing | cleaning process is not specifically limited, You may carry out multiple times, such as performing after each said process. Moreover, you may change the kind and density | concentration of the additive in each washing bath.

In addition, when pulling up a PVA film from each process bath, in order to prevent generation | occurrence | production of liquid slack, you may use conventionally well-known liquid cutting rolls, such as a pinch roll, and a method, such as shaving off a liquid with an air knife, etc. By this, excess moisture may be removed.

As said drying process, although suitable methods, such as natural drying, air drying, and heat drying, can be used, normally, heat drying is used preferably. In heat drying, heating temperature is about 20-80 degreeC, for example, and it is preferable that drying time is about 1 to 10 minutes.

It is preferable that it is 3.0-7.0 times with respect to the PVA film before the said process, and, as for the final total draw ratio of the polarizing film produced through each said process, it is more preferable to exist in the range of 5.5-6.2 times. If the final total draw ratio is less than 3.0 times, it is difficult to obtain a high polarization polarizing film, and if it exceeds 7.0 times, the film will easily break.

As for the polarizing film which concerns on this embodiment obtained by the said manufacturing method, it is preferable that the single transmittance | permeability when it measures by the polarizing film single thing is 40% or more, and it is more preferable to exist in 42.0 to 45.0% of range.

You may form a transparent protective film on at least single side | surface of the said polarizing film. As a material which comprises this transparent protective film, the thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, etc. is used, for example. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins, polyether sulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth) acrylic resins, cyclic Polyolefin resin (norbornene-based resin), polyarylate resin, polystyrene resin, polyvinyl alcohol resin and mixtures thereof. In addition, although a transparent protective film is bonded by one side of a polarizing film by an adhesive bond layer, thermosetting resins, such as (meth) acrylic-type, a urethane type, an acrylic urethane type, an epoxy type, a silicone type, or ultraviolet type resin, are used as a transparent protective film on the other side. Can be used. One or more types of arbitrary appropriate additives may be contained in the transparent protective film. As an additive, a ultraviolet absorber, antioxidant, a lubricating agent, a plasticizer, a mold release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment, a coloring agent, etc. are mentioned, for example. Content of the said thermoplastic resin in a transparent protective film becomes like this. Preferably it is 50-100 weight%, More preferably, it is 50-99 weight%, More preferably, it is 60-98 weight%, Especially preferably, it is 70-97 weight% . When content of the said thermoplastic resin in a transparent protective film is 50 weight% or less, there exists a possibility that the high transparency etc. which a thermoplastic resin originally has may not fully be expressed.

Moreover, as a transparent protective film, the polymer film of Unexamined-Japanese-Patent No. 2001-343529 (WO01 / 37007), for example, the thermoplastic resin which has a substituted and / or unsubstituted imide group in (A) side chain, and (B The resin composition containing the thermoplastic resin which has a substituted and / or unsubstituted phenyl and a nitrile group in a side chain) is mentioned. As a specific example, the film of the resin composition containing the alternating copolymer containing 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 unevenness due to distortion of the polarizing plate can be solved, and since the moisture permeability is small, the humidification durability is excellent.

Although the thickness of a transparent protective film can be suitably determined, it is generally 1-500 micrometers from the points of workability, thinness, etc., such as strength and handleability. 1-300 micrometers is especially preferable, and 5-200 micrometers is more preferable. The transparent protective film is particularly suitable in the case of 5 to 150 mu m.

In addition, when forming a transparent protective film on both sides of a polarizing film, you may use the protective film which consists of the same polymer material in the front and back, and may use the protective film which consists of other polymer materials.

As a transparent protective film which concerns on this embodiment, it is preferable to use any 1 or more types chosen from a cellulose resin, a polycarbonate resin, a cyclic polyolefin resin, and a (meth) acrylic resin.

Cellulose resins are esters of cellulose and fatty acids. Specific examples of such cellulose ester-based resins include triacetyl cellulose, diacetyl cellulose, tripropyl cellulose, dipropyl cellulose and the like. Among these, triacetyl cellulose is particularly preferable. Triacetyl cellulose is commercially available in many products, and is advantageous in terms of availability and cost. As an example of the commercial item of triacetyl cellulose, brand names "UV-50", "UV-80", "SH-80", "TD-80U", "TD-TAC" and "UZ-TAC" made by Fuji-Shashin Film Co., Ltd. And "KC series" manufactured by Konica Corporation. In general, these triacetyl cellulose has almost zero in-plane retardation Re, but the thickness retardation Rth has a thickness of about 60 nm.

As a specific example of cyclic polyolefin resin, Preferably it is norbornene-type resin. Cyclic olefin resin is a general term for resin which superpose | polymerizes a cyclic olefin as a polymerization unit, For example, Unexamined-Japanese-Patent No. 1-240517, Unexamined-Japanese-Patent No. 3-14882, and Unexamined-Japanese-Patent No. 3-122137 The resin described in the publication etc. can be mentioned. Specific examples include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, cyclic olefins and α-olefins such as ethylene and propylene, copolymers thereof (typically random copolymers), and unsaturated carboxylic acids and derivatives thereof. The graft polymer modified | denatured by these, those hydrides, etc. are mentioned. A norbornene-type monomer is mentioned as a specific example of cyclic olefin.

As cyclic polyolefin resin, various products are marketed. As a specific example, the brand name "Xeonex", the product made by Nippon Xeon Kabushiki Kaisha, "Zeonoa", the brand name "Aton" made by JSR Kabushiki Kaisha, the brand name "Topus" made by Ticona (TICONA), Mitsui Kagaku Kabushiki The brand name "APEL" made by Kaisha is mentioned.

As (meth) acrylic-type resin, Tg (glass transition temperature) becomes like this. Preferably it is 115 degreeC or more, More preferably, it is 120 degreeC or more, More preferably, it is 125 degreeC or more, Especially preferably, it is 130 degreeC or more. When Tg is 115 degreeC or more, it can become the thing excellent in the durability of a polarizing plate. Although the upper limit of Tg of the said (meth) acrylic-type resin is not specifically limited, From a moldability viewpoint, Preferably it is 170 degrees C or less. From (meth) acrylic-type resin, the film whose in-plane phase difference Re and thickness direction phase difference Rth are almost zero can be obtained.

As (meth) acrylic-type resin, arbitrary appropriate (meth) acrylic-type resin can be employ | adopted within the range which does not impair the effect of this invention. For example, poly (meth) acrylic acid esters, such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer, methyl methacrylate-methyl ester- (Meth) acrylic acid copolymer, (meth) acrylic acid methyl-styrene copolymer (MS resin etc.), a polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl copolymer, methyl methacrylate) -(Meth) acrylic acid norbornyl copolymer, etc.) are mentioned. Preferably, poly (meth) acrylic-acid C1-6 alkyl, such as methyl poly (meth) acrylate, is mentioned. More preferably, methyl methacrylate resin which has methyl methacrylate as a main component (50-100 weight%, Preferably 70-100 weight%) is mentioned.

As a specific example of (meth) acrylic-type resin, For example, (meth) which has a ring structure in the molecule | numerator of Mitsubishi Rayon Co., Ltd. Acripet VH, Acripet VRL20A, and Unexamined-Japanese-Patent No. 2004-70296. And high Tg (meth) acrylic resins obtained by acrylic resins, intramolecular crosslinking or intramolecular cyclization reactions.

As (meth) acrylic-type resin, you may use (meth) acrylic-type resin which has a lactone ring structure. It is because it has high mechanical strength by high heat resistance, high transparency, and biaxial stretching.

As (meth) acrylic-type resin which has a lactone ring structure, Unexamined-Japanese-Patent No. 2000-230016, Unexamined-Japanese-Patent No. 2001-151814, Unexamined-Japanese-Patent No. 2002-120326, Unexamined-Japanese-Patent No. 2002-254544 (Meth) acrylic-type resin which has a lactone ring structure as described in Unexamined-Japanese-Patent No. 2005-146084, etc. is mentioned.

As for the said transparent protective film, a thing whose frontal phase difference is less than 40 nm and thickness direction phase difference is less than 80 nm is normally used. Front phase difference Re is represented by Re = (nx-ny) xd. Thickness direction phase difference Rth is represented by Rth = (nx-nz) xd. In addition, Nz coefficient is represented by Nz = (nx-nz) / (nx-ny) (However, the refractive index of the slow axis direction, the fast axis direction, and the thickness direction of a film is set to nx, ny, nz, respectively. d (nm) is taken as the thickness of a film. The slow axis direction is a direction in which the refractive index in the film plane is maximized. Moreover, it is preferable that a transparent protective film does not have coloring as much as possible. The protective film whose retardation value of the thickness direction is -90 nm-+75 nm is used preferably. By using the thing whose phase difference value Rth of such a thickness direction is -90 nm-+75 nm, the coloring (optical coloring) of the polarizing plate resulting from a transparent protective film can be almost eliminated. The thickness direction retardation value Rth is more preferably -80 nm to +60 nm, particularly -70 nm to +45 nm.

On the other hand, as said transparent protective film, the phase difference plate which has a phase difference whose front phase difference is 40 nm or more and / or thickness direction phase difference is 80 nm or more can be used. The front phase difference is usually controlled in the range of 40 to 200 nm, and the thickness direction phase difference is usually controlled in the range of 80 to 300 nm. When using a retardation plate as a transparent protective film, since the said retardation plate also functions as a transparent protective film, thickness can be aimed at.

The transparent protective film may perform a surface modification process before coating an adhesive agent. Specific treatments include corona treatment, plasma treatment, primer treatment, saponification treatment, and the like.

The surface which does not adhere | attach the polarizing film of the said transparent protective film may be the thing which performed the process for the purpose of a hard-coat layer, an anti-reflective process, sticking prevention, and diffused or antiglare.

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

The polarizing plate of this invention is manufactured by bonding a transparent protective film and a polarizing film using the said adhesive agent. The said manufacturing method is a process of coating the said adhesive agent on the surface which forms the said adhesive bond layer of a polarizing film, and / or the surface which forms the said adhesive bond layer of a transparent protective film; It has a process of bonding a polarizing film and a transparent protective film through the said adhesive agent for polarizing plates.

The polarizing plate which concerns on this embodiment can be used as an optical film laminated | stacked with the other optical layer at the time of practical use. Although there is no limitation in particular about the optical layer, For example, in formation of a liquid crystal display device, such as a reflecting plate, a semi-transmissive plate, a retardation plate (including wavelength plates, such as 1/2 or a quarter), a visual compensation film, etc. One or two or more optical layers that have been used may be used.

Although the optical film which laminated | stacked the said optical layer on the polarizing plate can also be formed also by the method of laminating | stacking separately sequentially in manufacturing processes, such as a liquid crystal display device, what laminated | stacked previously and made into the optical film is quality stability, an assembly work, etc. It is excellent in this and there exists an advantage which can improve manufacturing processes, such as a liquid crystal display device. Appropriate adhesion means, such as an adhesion layer, can be used for lamination. At the time of adhering the above-mentioned polarizing plate and other optical films, these optical axes can be made into an appropriate arrangement angle according to the target retardation characteristic etc.

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

On the exposed surface of the adhesive layer, the separator is temporarily bonded and covered for the purpose of preventing contamination thereof until it is provided for practical use. Thereby, contact with an adhesion layer can be prevented in a 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.

The polarizing plate which concerns on this embodiment can be used suitably for various image display apparatuses, such as a liquid crystal display device and an organic electroluminescent device. When it applies to a liquid crystal display device, the polarizing plate which concerns on this embodiment is arrange | positioned so that a light transmission axis may orthogonally cross a surface and a back surface of a liquid crystal cell, respectively. Thereby, the liquid leakage in the wavelength range of visible light is reduced and the liquid crystal display device which prevented discoloration from occurring on a display screen is obtained. It does not specifically limit as said liquid crystal cell, For example, arbitrary types, such as TN type, STN type, (pi) type, VA type, IPS type, can be applied.

<Examples>

In the following, preferred embodiments of the present invention will be described in detail by way of example. However, unless otherwise indicated, the material, compounding quantity, etc. which are described in this Example are not the meaning which limits the range of this invention only to them, and are only a mere illustrative example.

&Lt; Example 1 >

Using the polyvinyl alcohol (PVA) film of 75 micrometers in thickness, film width 50mm, polymerization degree 2400, and saponification degree 99.9% or more, each process was performed in the following procedures, and the iodine type polarizing film which concerns on a present Example was produced.

<Swelling process>

The PVA film was conveyed to the swelling bath filled with pure water, and it swelled by immersing for 30 seconds in 30 degreeC pure water. Moreover, uniaxial stretching was performed until the draw ratio became 2.2 times.

<Dyeing process>

PVA film is conveyed to the dye bath filled with the iodine dyeing solution containing 0.035 weight% of iodine, and immersed in 30 degreeC iodine dyeing solution for 27 second, uniaxially stretching until the draw ratio becomes 3.3 times with respect to the initial PVA film. By staining.

<Crosslinking process>

The PVA film was conveyed to a crosslinking bath filled with an aqueous boric acid solution containing 3.0% by weight of potassium iodide and 3.0% by weight of boric acid and immersed in an aqueous solution of 30 ° C. for 28 seconds, while the draw ratio was 3.6 relative to the initial PVA film. It uniaxially stretched and bridge | crosslinked until it became double.

<Stretching process>

In the stretching bath filled with an aqueous boric acid solution containing 5.0% by weight of potassium iodide and 4.0% by weight of boric acid, the PVA film subjected to the treatment was conveyed, and the drawing ratio was initially immersed in an aqueous solution of boric acid at 60 ° C. for about 58 seconds. It uniaxially stretched until it became 5.9 times with respect to PVA film.

<Group 2 element introduction process>

The PVA film in the bath filled with an aqueous solution containing MgI ₂ of 0.093mol / ℓ was conveyed and immersed into the aqueous solution of 30 ℃ 10 seconds.

Thereafter, the PVA film was dried using an oven. As drying conditions, the passing time in 60 degreeC of drying temperature and oven was made into 4 minutes.

<Examples 2 and 3>

In Examples 2 and 3, as shown in Table 2 below, except that CaI ₂ and BaI ₂ were used instead of MgI ₂ in the Group 2 element introduction step, the same procedure as in Example 1 above, Each iodine type polarizing film was produced.

<Comparative Examples 1 to 3>

In Comparative Examples 1 to 3, as shown in Table 3 below, Example 1 except for using 0.186 mol / L of LiI, NaI, and KI instead of MgI ₂ in the Group 2 element introduction step, In the same manner as in the above, each iodine polarizing film was produced.

<Examples 4 to 10>

Example 4 In a to 10, Group 2 to be, the same as in Example 1 except that changed as shown, the concentration of MgI ₂ of the element introduced into the process in the following Table 4, produce a respective iodine-based polarizing film It was. In addition, the amount of Mg in each polarizing film is the value measured by the chelate titration using the EDTA (ethylenediamine tetraacetic acid) standard liquid and EBT (eryochrome black T) indicator.

<Comparative Example 4>

In Comparative Example 4, an iodine-based polarizing film was produced in the same manner as in Example 1 except that 0.093 mol / L ZnI ₂ was used instead of MgI ₂ in the group 2 element introduction step.

<Orthogonal band>

The single transmittance and orthogonal transmittance of the polarizing film were measured with a spectrophotometer (V7100 manufactured by Nippon Bunko Co., Ltd.) having an integrating sphere. The transmittance | permeability with respect to each linearly polarized light was measured making 100% the complete polarization obtained through the Grantera-prism polarizing film. The measurement wavelength of orthogonal transmittance was performed at wavelength 410nm and 700nm. In addition, single transmittance | permeability was shown by the Y value correct | amended visibility by the 2-degree field of view (C light source) of JIS Z8701 based on the measurement result of the measurement wavelength 380nm-780nm. The results are shown in Tables 2 to 5.

(Production of polarizing plate)

As a transparent protective film, the triacetyl cellulose film of thickness 80micrometer was used. In addition, the adhesive agent used for the bonding of the iodine type polarizing film and transparent protective film obtained by each Example and the comparative example was manufactured as follows. That is, with respect to 100 weight part of polyvinyl alcohol resins containing an acetoacetyl group (average degree of polymerization 1200, 98.5 mol% of saponification degree, 5 mol% of acetoacetylation degree), 32 weight part of methylol melamine is pure under the temperature conditions of 30 degreeC. It melt | dissolved in water and adjusted the adhesive aqueous solution so that it might become solid content concentration 3.2%.

Using the said adhesive agent, after bonding said transparent protective film to the both surfaces of the iodine type polarizing film produced in Example 1 and the comparative example 4 on 24 degreeC temperature conditions with a roll bonding machine, it dried at 60 degreeC for 12 minutes, and polarizing plate Got. The polarization degree was evaluated about each obtained polarizing plate.

(Polarization)

The obtained polarizing plate was left to stand on heating conditions of the temperature of 80 degreeC for 120 hours, and the polarization degree in back and front was measured. The results are shown in Table 5. In addition, the polarization degree used the spectrophotometer (The Nippon Bunker, V7100) which has an integrating sphere, and the measurement wavelength was performed at 380 nm-780 nm. In addition, the polarization degree refers to the transmittance (parallel transmittance: H ₀ ) when two identical polarizing plates are overlapped so that their light transmission axes are orthogonal to each other, and the transmittance (orthogonal transmittance: H ₉₀ ) when the transmission axes of both are overlapped so as to be perpendicular to each other. It calculated | required by applying to the following formula.

Polarization degree (%) = {(H ₀ -H ₉₀ ) / (H ₀ + H ₉₀ )} ^1/2 × 100

Each transmittance | permeability is represented by the Y value which corrected visibility by the 2-degree visual field (C light source) of JIS Z8701 as 100% of the fully polarized light obtained through the Granterra prism polarizing film.

(result)

As is clear from Tables 2 to 4 above, the iodine-based polarizing films of the present invention according to Examples 1 to 10 can suppress the orthogonal transmittance at a wavelength of 700 nm low, and the light leakage in the long wavelength region of visible light It was confirmed that prevention was planned. On the other hand, in the polarizing films concerning Comparative Examples 1-3, the orthogonal transmittance was large and it was confirmed that light leakage generate | occur | produces.

In addition, as apparent from Table 4, the iodine-based polarizing films of Examples 5 to 9 in which the amount of Mg per 1 g of the polarizing film is in the range of 5.6 × 10 ⁻⁵ to 9.7 × 10 ⁻⁵ mol / g are present at 410 nm and 700 nm. The balance of the orthogonal transmittance | permeability in it was good and it was confirmed that generation | occurrence | production of light leakage in both wavelength ranges can be prevented.

Moreover, when the polarization degree was investigated after the endurance test which left to stand at 80 degreeC for 120 hours about the polarizing plate using the polarizing film of Example 1 and the polarizing film of Comparative Example 4, the polarizing plate side using the polarizing film of Example 1 It turned out that this fall of polarization degree is few. By this, it was confirmed that the polarizing plate according to the present invention was excellent in optical reliability even when used under excessive conditions.

Claims (6)

An iodine-based polarizing film obtained by adsorption-orienting iodine on a polyvinyl alcohol film, and containing a Group 2 element, and the amount of the Group 2 element present in the range of 5.6 × 10 ⁻⁵ to 9.7 × 10 ⁻⁵ mol / g Polarizing film. delete It is a manufacturing method of the iodine type polarizing film which adsorption-oriented iodine to the polyvinyl alcohol film, Including the process of contacting the polyvinyl alcohol film after adsorption-orientation of the said iodine, the aqueous solution containing the salt of a group 2 element, The manufacturing method of the iodine type polarizing film whose amount of group 2 elements exists in the range of 5.6 * 10 <^-5> -9.7 * 10 <^-5> mol / g. The said process is a process of extending | stretching a polyvinyl alcohol film, the process of dyeing the said polyvinyl alcohol film in the aqueous solution containing iodine and potassium iodide, the polyvinyl alcohol film after dyeing, boric acid The manufacturing method of the iodine type polarizing film performed after the process of immersion in the aqueous solution to contain. The manufacturing method of the iodine type polarizing film of Claim 3 which uses the aqueous solution of the iodide of a Group 2 element as an aqueous solution containing the salt of the said Group 2 element. A transparent protective film is provided on at least one side of the iodine type polarizing film of Claim 1 Formed polarizer.