JP2014092611A - Circularly polarizing plate for organic el display device and organic el display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circularly polarizing plate for an organic EL display device, which increases outgoing light in an organic EL display device, and thereby achieves improvement in the luminance of a displayed image, which also alleviates reduction of reflected light and improves visibility, and thereby can achieve saving of power consumption and a long service life of an organic EL element, and which can further suppress changes in hue of a displayed image, and to provide an organic EL display device using the circularly polarizing plate.SOLUTION: The circularly polarizing plate for an organic EL display device includes: a linearly polarizing plate having a single body transmittance of 46 to 70% in a visible light region (at a wavelength from 400 to 700 nm), a λ/4 retardation plate, and at least one colored adhesive layer containing a blue pigment. An organic EL display device including the circularly polarizing plate is also provided. The circularly polarizing plate for an organic EL display device can improve transmittance of light, reduce reflectance of external light and suppress changes in hue of transmitted light.

Description

  The present invention relates to a circularly polarizing plate for an organic EL display device and an organic EL display device having the circularly polarizing plate.

  An image display device (hereinafter also referred to as an organic EL display device) having an organic EL element (Organic Light Emitting Diode) (hereinafter also referred to as OLED) is easy to be thinned and has a wide viewing angle. Widely used as display devices such as type PCs. However, since the OLED includes a reflective metal electrode inside the apparatus, external light is likely to be reflected, causing a problem that the visibility of the screen is remarkably lowered.

As a method for preventing the visibility of the image display device from being deteriorated due to reflection of external light, a means for providing the image display device with a circularly polarizing plate made of a retardation plate such as a linear polarizing plate and a quarter-wave plate is known. An organic EL display device in which the antireflection performance is improved by the means has been proposed (Patent Document 1 and Patent Document 2).
By using the circularly polarizing plate, the reflected light from the outside can be considerably reduced. However, when the circularly polarizing plate is used, the emitted light from the EL element is also lowered, so that the visibility is lowered. In order to prevent a decrease in visibility, it is sufficient to increase the light emission of the organic EL element and increase the display light reaching the display screen. However, in order to increase the light emission of the organic EL element, it is necessary to increase the energization amount. There are fatal problems such as an increase in power consumption and a shortened life of the organic EL.

In Patent Document 3, for the purpose of improving the luminance and contrast ratio of an OLED, a reflective polarizing film that reflects polarized light perpendicular to the transmission axis of the linear polarizing plate between the linear polarizing plate and the quarter retardation plate And a color correction adhesive containing a light absorbent such as an adhesive resin and a black dye is used in any of the adhesive layers on the upper and lower sides of the reflective polarizing film.
Japanese Patent Laid-Open No. 8-322138 Japanese Patent Laid-Open No. 9-127858 JP 2011-512558 A

  Although the technique described in Patent Document 3 may achieve an excellent effect, it is necessary to sandwich a reflective polarizing plate between the linear polarizing plate and the λ / 4 retardation plate, and the manufacturing process is Since it becomes complicated and requires a new special polarizing plate, the manufacturing cost is considerably increased, resulting in disadvantages in terms of manufacturing and cost. The present invention uses a conventional method of manufacturing a circularly polarizing plate as it is, and reduces the reflectance of external light within a range that does not affect the visibility (preferably 20% or less), while at the same time being used in an organic EL display device. To provide a circularly polarizing plate for an organic EL display device capable of increasing the light emission, improving the visibility, and suppressing the hue change of transmitted light and reflected light, and an organic EL display device using the same. With the goal.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive research. As a result, the circularly polarizing plate is formed using a linearly polarizing plate having a higher transmittance than the linearly polarizing plate conventionally used for a normal circularly polarizing plate. When it is prepared, the amount of transmitted light can be increased, but the increase in reflectance on the long wavelength side is particularly large, and it has been found that there arises a problem that the reflected light becomes reddish. As a result of various investigations on how to make the reflected light neutral while keeping the visible light transmittance that greatly affects the visibility, the pressure-sensitive adhesive layer used for producing the circularly polarizing plate contains a blue pigment. The present inventors have found that the above problem can be solved by using a blue pressure-sensitive adhesive layer.

The present invention relates to the following 1 to 9.
1. (I) a linear polarizing plate having a single transmittance of 46 to 70% for light having a wavelength of 400 to 700 nm, (ii) a λ / 4 phase difference plate, and (iii) a blue pressure-sensitive adhesive layer containing a blue pigment. A circularly polarizing plate for an organic EL display device including the three.
2. 2. The circularly polarizing plate for an organic EL display device according to 1 above, wherein the maximum wavelength (λmax) of the absorption spectrum of the blue pigment is in the range of 550 to 700 nm.
3. The circularly polarizing plate for an organic EL display device according to 1 or 2 above, wherein the content of the blue pigment in the blue pressure-sensitive adhesive layer is 0.01 to 0.5 parts by mass with respect to 100 parts by mass of the solid content in the pressure-sensitive adhesive. .
4). The circularly polarizing plate for organic EL display devices according to any one of 1 to 3, wherein the color of the linearly polarizing plate is neutral gray.
5. Δa * and Δb * of the outgoing light with respect to the incident light based on the L * a * b * color system (CIE1976) when the light incident from the retardation plate side of the circularly polarizing plate is emitted from the linear polarizing plate side. The circularly polarizing plate for an organic EL display device according to any one of the above 1 to 4, wherein all of the values are from -5 to 0.
6). The blue pressure-sensitive adhesive layer according to any one of 1 to 5 above, which the circularly polarizing plate has on the outer surface of the λ / 4 retardation plate or at least one of the linear polarizing plate and the λ / 4 retardation plate. Circular polarizing plate for organic EL display devices.
7). 7. The circularly polarizing plate for an organic EL display device according to 6 above, wherein the blue pressure-sensitive adhesive layer has on the outer surface of the λ / 4 retardation plate in the circularly polarizing plate.
8). The transmittance of light having a wavelength of 450 nm is 42% or more, the transmittance of light having a wavelength of 550 nm is in the range of 45 to 55%, the transmittance of light having a wavelength of 650 nm is 45% or less, and a wavelength of 400 to The circularly polarizing plate for an organic EL display device according to any one of claims 1 to 7, wherein an average transmittance of light in a visible light region of 700 nm is 45% or more and a reflectance of external light is 20% or less. .
9. The organic electroluminescence display provided with the circularly-polarizing plate for organic electroluminescence displays as described in any one of said 1-7.

In the present invention, by using a linearly polarizing plate having a high transmittance, the amount of light emitted from the LED can be increased from the circularly polarizing plate, so that an improvement in the brightness of the display screen can be expected. . Moreover, the blue pigment | dye contained in a blue adhesive layer has a high light absorptivity with respect to the wavelength of 600-700 nm with little influence on visual sensitivity, and the light of the wavelength of less than 500-600 nm which has a big influence on visual sensitivity. In particular, light with a wavelength of less than 500 to 600 nm emitted from an LED, which has a large influence on the visibility, is emitted from the LED because the transmittance is low, especially for light near 500 nm. In a single pass through the blue adhesive layer, the amount of light absorbed by the blue dye is very small. On the other hand, the reflected light of the light incident from the outside is incident on the circularly polarizing plate, once while reaching the reflecting plate, and once again before being reflected by the reflecting plate and emitted from the circularly polarizing plate. Since it passes through the blue adhesive layer, the amount of reflected light absorbed by the blue adhesive layer becomes relatively large, the amount of light is greatly reduced, and the reflectance decreases.
Furthermore, the circularly polarizing plate of the present invention can suppress the hue change of transmitted light and reflected light. Therefore, the use of the circularly polarizing plate of the present invention can be expected to improve the visibility of the display image in the organic EL display device.

The present invention will be described below.
The circularly polarizing plate for organic EL display devices of the present invention (hereinafter also simply referred to as “the circularly polarizing plate of the present invention”) has a single transmittance of 46 to 70% in the visible light region (wavelength 400 to 700 nm). A linear polarizing plate (hereinafter also simply referred to as “high transmittance polarizing plate”), (ii) a λ / 4 phase difference plate, and (iii) a blue pressure-sensitive adhesive layer containing a blue pigment. The present invention relates to a circularly polarizing plate for an organic EL display device including at least one of the three members.

<High transmittance linearly polarizing plate>
First, the high transmittance linearly polarizing plate used for the circularly polarizing plate for an organic EL display device of the present invention will be described below.
In the circularly polarizing plate of the present invention, a high transmittance linearly polarizing plate having a single transmittance of 46 to 70% in the visible light region (wavelength 400 to 700 nm) is used as described above.
The single transmittance of the high transmittance polarizing plate of the present invention is usually 46% or more in the visible light region (400 to 700 nm wavelength region), preferably 48% or more, more preferably 49% or more, most preferably 50. % Or more. The upper limit is not particularly limited as long as the effect of the present invention is achieved, but is usually 70% or less, preferably 65% or less, more preferably 60% or less, and further preferably 55% or less.
The orthogonal transmittance in the visible light region of the linearly polarizing plate is usually 30% or less, preferably 20% or less, more preferably 15% or less, and most preferably 11% or less. The lower limit of the orthogonal transmittance is preferably low, and about 0.1% is desired. However, when a high transmittance polarizing plate is used, the current technology uses a maximum of 1% or more, and strives to be 2% or more. The lower limit that can be easily achieved is 5% or more, and usually 8% or more.

In the present specification, “single transmittance” refers to the transmittance when one polarizing plate is used, and is measured by a method based on JIS Z8701: 1999. “Orthogonal transmittance” refers to the transmittance when two polarizing plates are stacked such that their absorption axes are orthogonal.
A more preferable high-transmittance linearly polarizing plate is a linearly polarizing plate having both the preferable single transmittance and the preferable orthogonal transmittance. A polarizing plate having a single transmittance of 48% to 60%, more preferably 50% to 55% and an orthogonal transmittance of 5% to 15% is most preferable.

  The high transmittance linearly polarizing plate used in the present invention (hereinafter simply referred to as the linearly polarizing plate) has a single transmittance within the above range in the dyeing treatment with a dichroic dye (hereinafter also referred to as a dyeing treatment step). The substrate film (for example, a polyvinyl alcohol-based resin film) is dyed with a dichroic dye according to a conventional method except that the orthogonal transmittance is adjusted to be in the above range as necessary. A polarizing element film is manufactured by performing a treatment, a stretching process, and a curing agent treatment with boric acid or the like as necessary, and a transparent protective film is pasted on one side or both sides of the obtained polarizing element film as necessary. By combining, it can be manufactured. Either order may be sufficient as the order of the said dyeing | staining process and extending | stretching process, and you may carry out simultaneously. Moreover, you may perform the said extending | stretching process simultaneously with a hardening | curing agent process. The curing agent treatment is usually performed simultaneously with the dyeing treatment and / or after the dyeing treatment.

As the base film used for the linear polarizing plate, any resin film that can be used as a polarizing plate can be used, and a polyvinyl alcohol-based resin film is usually used. As the polyvinyl alcohol-based resin film, a polymer alcohol skeleton having a polyvinyl alcohol skeleton in a molar ratio of at least 40%, preferably 50 to 100%, more preferably 80 to 100% in a repeating unit in the polymer. A coalesced film can be mentioned. In the polyvinyl alcohol skeleton, a part of the hydroxyl group may be an acetyl group, or may be modified with an organic acid other than acetic acid or an aldehyde.
Specifically, a polyvinyl alcohol film obtained by saponifying polyvinyl acetate, which is a polymer of vinyl acetate; vinyl acetate and other monomers copolymerizable therewith, such as unsaturated carboxylic acids, olefins , Vinyl ethers, unsaturated sulfonic acids, unsaturated amines, acrylamide, polyvinyl alcohol copolymer films obtained by saponifying a copolymer (polyvinyl acetate copolymer) with acrylic acid derivatives, etc .; and Examples thereof include polyvinyl alcohol-modified films obtained by modifying the above polymers and copolymers with olefins or unsaturated carboxylic acids. Specific examples include, for example, a polyvinyl alcohol resin film, the above copolymer resin film, a polyvinyl acetal film (ethylene vinyl acetate resin film) and the like. Among these, dichroic dye adsorptivity and orientation From the viewpoint, a polyvinyl alcohol resin film is preferable.

The degree of polymerization of the polyvinyl alcohol-based resin used for the linear polarizing plate is usually in the range of about 1000 to 10,000, preferably about 1500 to 7000, more preferably about 2000 to 7000. As the polyvinyl alcohol-based resin, a saponified polyvinyl acetate polymer or copolymer is usually used, and the degree of saponification is usually about 85 to 100 mol%, preferably 98 to 100 mol%. is there.
Although the thickness of the polyvinyl alcohol-type resin film used as a raw material is not specifically limited, Usually, about 10 micrometers-150 micrometers, Preferably it is about 20-100 micrometers.

For example, the polyvinyl alcohol resin film can be dyed as follows.
Usually, before the dyeing | staining process by a dichroic pigment | dye, the swelling process of a polyvinyl alcohol-type resin film (base film) is given (it is also called a swelling process). The swelling treatment is performed by immersing in a swelling treatment solution at 20 to 50 ° C. for 30 seconds to 10 minutes. The swelling treatment solution is preferably water. If necessary, the swelling treatment may be performed with a water-soluble organic solvent such as glycerin, ethanol, ethylene glycol, propylene glycol, or low molecular weight polyethylene glycol, or a mixed solution of water and a water-soluble organic solvent. Since the film swells even during the dyeing treatment, the swelling step can be omitted when it is desired to shorten the time required for producing the polarizing element film.

  The dyeing treatment with a dichroic dye is carried out according to a conventional method, in the base film, preferably in a dyeing solution containing a dichroic dye (usually dichroic dye and / or iodine, preferably dichroic dye). It is performed by immersing a polyvinyl alcohol resin film. You may perform the dyeing | staining process of the said base film simultaneously with the following extending process.

  Any dichroic dye used in the dyeing treatment step can be used as long as it is a dye that exhibits dichroism in the visible light region due to stretching of the base film, but a dye excellent in durability is preferred.

Specific examples of the dichroic dye used in the dyeing process include C.I. I. Direct Yellow 12, C.I. I. Direct Yellow 28, C.I. I. Direct Yellow 44, C.I. I. Direct yellow 142; I. Direct Orange 26, C.I. I. Direct Orange 39, C.I. I. Direct Orange 71, C.I. I. Direct orange 107; I. Direct Red 2, C.I. I. Direct Red 31, C.I. I. Direct Red 79, C.I. I. Direct Red 81, C.I. I. Direct Red 117, C.I. I. Direct Red 247; C.I. I. Direct Green 80, C.I. I. Direct Green 59; C.I. I. Direct Blue 1, C.I. I. Direct Blue 71, C.I. I. Direct Blue 78, C.I. I. Direct Blue 168, C.I. I. Direct Blue 202; C.I. I. Direct violet 9, C.I. I. Direct violet 51; I. Direct Brown 106, C.I. I. Direct brown 223 etc. can be illustrated.
Further, depending on the purpose, a dye developed for a polarizing plate as disclosed in WO2009 / 057676A1, WO2007 / 145210A1, WO2006 / 057214A1, and JP-A-2004-251963 can also be used. These dyes are used as free acids or alkali metal salts (for example, Na salt, K salt, Li salt), ammonium salts, and salts of amines.

When the linear polarizing plate is prepared using a dichroic dye, one or a plurality of dichroic dyes may be used, and usually a plurality of dichroic dyes are preferably used. By using at least one dye selected from the following dyes (1) to (3), more preferably at least one of the following dyes (1) to (3), the hue is neutral gray. Since the polarizing plate which is can be produced, it is preferable.
(1) a dichroic dye having a maximum absorption wavelength (λmax) at 400 nm or more and less than 500 nm,
(2) A dichroic dye having a maximum absorption wavelength (λmax) at 500 nm or more and less than 600 nm, and (3) a dichroic dye having a maximum absorption wavelength (λmax) at 600 nm or more and 700 nm or less.

Examples of the dichroic dye (1) having λmax of 400 nm or more and less than 500 nm include dichroic dyes having a λmax of 400 nm or more and less than 500 nm among yellow or orange dyes. Examples of the dichroic dye (2) having λmax of 500 nm or more and less than 600 nm include dichroic dyes having a λmax of 500 nm or more and less than 600 nm among Red or Violet dyes. Examples of the dichroic dye (3) having λmax of 600 nm to 700 nm include dichroic dyes having a λmax of 600 nm to 700 nm among Blue and Green dyes.
Even if the dichroic dye used when producing the neutral gray polarizing plate is a dye included in the same group of any one of the dichroic dyes (1) to (3), it is absorbed by the individual dyes. Since the wavelengths are different, a plurality of dyes included in the same group may be used if necessary. For example, 4 to 5 kinds of dyes in the above dichroic dyes (1) to (3) group, or The above dichroic dyes may be used. As one preferred embodiment, one type of orange dichroic dye, one type of red dichroic dye, and a mode of using two types of blue and green as the dichroic dye (3) are used. Can be mentioned.

  The content ratio of each dye in the staining liquid is not particularly limited as long as the hue of the obtained polarizing element film can be neutral gray. When using at least one of each of the above dyes (1) to (3), for example, dichroic dye (1): dichroic dye based on the dichroic dye (1) in mass ratio (2): Dichroic dye (3) = 1: 0.1-3: 1-8, more preferably in a ratio of about 1: 0.2-2: 2-7. By appropriately adjusting the content ratio of each dye in the dyeing liquid within the above range, a polarizing plate having more preferable hue and optical performance as a neutral gray polarizing plate can be obtained.

The dichroic dye used for the linear polarizing plate is a dichroic dye having a dichroic ratio defined by the following formula (3) in the range of 20 to 50, preferably in the range of 25 to 45. preferable.
In this specification, the “dichroic ratio” in the dichroic dye is defined as follows. A polarizing plate using only the dye as a dichroic dye is prepared, and the transmittance when the single polarizing plate is used is the single transmittance Ts, and the absorption axis direction of the two polarizing plates is the same. The transmittance when the two polarizing plates are stacked so that the absorption axes are orthogonal to each other is defined as the orthogonal transmittance Tc. Each transmittance is calculated by the following formula (1) by obtaining a spectral transmittance τλ at predetermined wavelength intervals dλ (here, 5 nm) in a wavelength region of 380 to 700 nm.

In the formula, Pλ represents a spectral distribution of standard light (C light source), yλ represents a 2 ° visual field color matching function, and τλ represents a spectral transmittance. The degree of polarization Py is obtained from the parallel transmission Tp and the orthogonal transmission Tc by the following formula (2).
Py = {(Tp−Tc) / (Tp + Tc)} ^1/2 × 100 Formula (2)
From the degree of polarization Py and the single transmittance Ts, the dichroic ratio Rd is obtained by the following formula (3).
Rd = log {Ts / 100 * (1-Py / 100)} / log {Ts / 100 * (1 + Py / 100)} Formula (3)

Water is preferred as a solvent for the dyeing solution containing the dichroic dye. The dye concentration in the dye solution of the dichroic dye varies depending on the dyeing conditions and cannot be generally stated, but is usually about 0.01 to 5 g / L, preferably about 0.01 to 2 g / L with respect to the dye solution. More preferably, it is about 0.02 to 1 g / L, and most preferably about 0.02 to 0.9 g / L. When a plurality of dichroic dyes are used, the total concentration of the dichroic dyes used is preferably in the above range.
When performing the dyeing | staining process using a dichroic dye, the temperature of the dyeing | staining liquid is about 20-60 degreeC normally, Preferably it is about 30-55 degreeC. There is no problem as long as the immersion time can be dyed to the above-mentioned concentration, and is usually about 10 to 500 seconds, preferably about 30 to 400 seconds.

When the dyeing treatment is performed using iodine as a dichroic dye, the substrate film, preferably a PVA film may be dyed using a dyeing solution containing iodine and iodide. As the iodide, for example, an alkali metal iodide compound such as potassium iodide, ammonium iodide, cobalt iodide, or zinc iodide can be used. Usually, an alkali metal iodide compound is preferable, and potassium iodide is more preferable.
The concentration of iodine in the staining solution at this time cannot be generally described because it varies depending on the staining conditions, but is usually about 0.01 to 5 g / L, preferably about 0.01 to 4 g / L. The iodide concentration is usually about 0.001 to 1 g / L, preferably about 0.005 to 0.5 g / L. The temperature of the staining solution containing iodine and iodide is usually about 5 to 50 ° C, preferably about 5 to 40 ° C, and particularly preferably about 10 to 30 ° C. The treatment time is appropriately adjusted depending on the concentration of iodine and iodide adsorbed, but is preferably about 30 seconds to 6 minutes, more preferably about 1 to 5 minutes.
When dyeing with a dyeing solution containing iodine and iodide, a crosslinking agent and / or a water-resistant agent may be added to the dyeing solution. Although it does not specifically limit as a crosslinking agent, Usually boric acid is preferable. About 1-50 g / L is preferable and, as for the density | concentration which adds a crosslinking agent, for example, boric acid, about 10-40 g / L is more preferable.

  In the base film dyeing process, a dye solution containing both the dichroic dye and iodine may be used as the dichroic dye. In that case, it is preferable that the density | concentration of the total amount of the dichroic dye and iodine to be used is about 0.01-5 g / L with respect to a dyeing | staining liquid.

  The dyeing liquid in the dyeing treatment using a dichroic dye may contain an auxiliary agent such as a dyeing auxiliary agent as necessary. Examples of the dyeing aid include inorganic salts such as mirabilite and sodium tripolyphosphate. The density | concentration of the dyeing adjuvant at that time is about 0.01-10 g / L with respect to the total amount of the dyeing | staining liquid, Preferably it is about 0.05-5 g / L. When a plurality of dyeing assistants are used, the concentration of the total amount of dyeing assistants is preferably in the above range.

You may perform the extending | stretching process for orienting a dichroic dye with a dyeing | staining process. In addition, the stretching process may be performed in a plurality of times. In some cases, the stretching treatment may be performed after swelling and before the dyeing treatment.
In the present invention, the polarizing element film is preferably stretched by stretching (preferably uniaxially stretching) a dyed substrate film, preferably a polyvinyl alcohol-based resin film, at a predetermined magnification. The stretching method in the stretching treatment may be either a dry stretching method or a wet stretching method, but a wet stretching method is preferred. The wet stretching method is usually a method in which a solution composed of water, a water-soluble organic solvent, or a mixed solution thereof is heated and stretched while immersing a polyvinyl alcohol-based resin film in the heated solution. The stretching ratio cannot be generally specified depending on the thickness of the original film, but is usually about 2 to 20 times, preferably about 3 to 10 times that of the base film.
By containing a curing agent in the stretching treatment solution, the curing agent treatment may be performed simultaneously with the stretching treatment. As the curing agent at that time, the curing agent exemplified in the section of the curing agent treatment below can be used, a boron compound is preferable, and boric acid is more preferable. Although content of the hardening | curing agent in the extending | stretching process solution at this time changes with kinds of hardening | curing agent, it cannot say unconditionally, It is about 0.1-10.0 mass%, Preferably it is 0.5-5.0 mass. %.
As the stretching method, a method of uniaxial stretching between two rolls having different speeds is preferable. The total draw ratio of the film obtained by the drawing treatment with respect to the raw film is about 2.0 to 10.0 times, preferably 4.0 to 7.0 times. The temperature of the treatment solution in the stretching treatment is about 30 to 60 ° C.

It is preferable to perform a curing agent treatment after the dyeing treatment. Curing agent treatment refers to treating the film with a solution containing a curing agent simultaneously with and / or after the dyeing treatment. As the curing agent treatment, a method of immersing a film subjected to a dyeing treatment in the solution is preferable, but a method of applying or applying the solution to a film subjected to the dyeing treatment may be used.
Examples of the curing agent used in the curing agent treatment include boron compounds such as boric acid or salts thereof (alkali metal salts such as borax, borax ammonium, etc.), polyvalent aldehydes such as glyoxal or glutaraldehyde, biuret types, Polyisocyanate compounds such as isocyanurate type or block type, titanium compounds such as titanium oxysulfate, ethylene glycol glycidyl ether, polyamide epichlorohydrin, and the like can be used. Usually, boron compounds are preferred, and boric acid is more preferred. As the solvent for the curing agent treatment solution, water, a water-soluble organic solvent, a mixed solvent thereof or the like can be used, and water is preferable.
The curing agent concentration of the curing agent treatment solution varies depending on the type of the curing agent and cannot be generally specified, but is usually about 0.1 to 10% by mass, preferably about 1 to 6% by mass. About 1-6.0 mass% is preferable. 10-60 degreeC is preferable and the processing temperature of a hardening | curing agent process has more preferable 30-60 degreeC. The treatment time is preferably 30 seconds to 6 minutes, and more preferably 1 to 5 minutes.

In the preferable aspect of this invention, since a hardening | curing agent process and extending | stretching process are performed in boric-acid aqueous solution, boric acid is contained in a polyvinyl alcohol-type resin film. The content of boric acid in the polarizing element film at this time is obtained by heating the obtained polarizing element film in pure water to completely dissolve it, adding a phenolphthalein indicator, and performing neutralization titration with an aqueous sodium hydroxide solution. Can be determined by
The boric acid content in the polarizing element film of the present invention is 5 to 40% by mass, more preferably 10 to 25% by mass. The boric acid content in the polarizing element film can be adjusted by changing the concentration of the solution, the immersion time, the solution temperature, and the stretching ratio in the stretching treatment or the curing agent treatment.

When iodine is used as the dichroic dye in the dyeing process, the base film is subjected to a complementary color process as necessary after the dyeing process and the stretching process. Performing complementary color processing stabilizes the state of iodine ions in the polarizing element film and has the effect of making it difficult for hue changes to occur, so when using iodine as a dichroic dye, complementary color processing is performed in the production of the polarizing element film. It is preferable to apply.
The complementary color treatment is performed by immersing the base film that has been dyed and stretched in an aqueous potassium iodide solution. As the potassium iodide aqueous solution used for the complementary color treatment, an aqueous solution containing potassium iodide at a concentration of 0.1 to 10% by mass, preferably 1.0 to 6.0% by mass is used. The temperature of the potassium iodide aqueous solution during the complementary color treatment is usually about 10 to 70 ° C, preferably about 20 to 40 ° C, and the immersion time is about 5 to 300 seconds, preferably about 5 to 100 seconds.

  After each step of these dyeing treatment, stretching treatment, curing agent treatment and complementary color treatment applied as necessary, for the purpose of removing the dyes and curing agents deposited on the film surface, or adhered foreign matters, if necessary. The film surface may be cleaned. Usually, it is preferable to wash with water, the temperature of the cleaning solution is about 10 to 60 ° C, and the cleaning time is about 1 second to 5 minutes. Washing may be performed once or multiple times as necessary.

The polarizing element film that has been subjected to the stretching treatment is washed as necessary and then dried. The drying temperature in a drying process is about 30-70 degreeC normally, Preferably it is about 40-65 degreeC. The drying time is about 10 to 500 seconds, preferably about 60 to 350 seconds.
The thickness of the obtained polarizing element film is preferably about 10 to 40 μm, and more preferably 15 to 30 μm.

The polarizing element film thus obtained can be made into a polarizing plate by laminating a transparent protective film excellent in optical transparency, mechanical strength, and isotropy on one surface or both surfaces thereof. Examples of the compound that forms the protective film include cellulose acetate films, acrylic films, fluorine films such as tetrafluoroethylene / hexafluoropropylene copolymers, polyester resins, polyolefin resins, and polyamide resins. A film or the like is used. Preferably, a triacetyl cellulose film (TAC film) or a cycloolefin film is used. The thickness of the protective film is usually 40 to 200 μm.
Examples of adhesives that can be used to bond the polarizing element film and the protective film include polyvinyl alcohol adhesives, urethane emulsion adhesives, acrylic adhesives, polyester-isocyanate adhesives, and polyvinyl alcohol adhesives. Agents are preferred.

  A transparent protective layer may be further provided on the surface of the obtained high transmittance linearly polarizing plate on the side opposite to the side on which the λ / 4 retardation plate is bonded. Examples of the protective layer include a hard coat layer made of an acrylic resin or a polysiloxane resin, and a protective layer made of a urethane resin. Further, an AR layer (antireflection layer) may be provided on the protective layer. The AR layer can be formed, for example, by depositing or sputtering a material such as silicon dioxide or titanium oxide, or by thinly applying a fluorine-based material.

<High transmittance circularly polarizing plate>
A circularly polarizing plate is produced by laminating a λ / 4 retardation plate to the high transmittance linearly polarizing plate obtained above. At this time, the lamination is performed so that the angle between the slow axis of the λ / 4 retardation plate (the direction in which the refractive index becomes maximum in the plane) and the absorption axis of the linear polarizing plate is 45 °. The circularly polarizing plate composed of the high transmittance linearly polarizing plate and the λ / 4 retardation plate used in the present invention is hereinafter simply referred to as “high transmittance circularly polarizing plate”.
The material of the λ / 4 retardation plate used for manufacturing the high transmittance circularly polarizing plate is not particularly limited, and a known material such as a polymer film, a liquid crystal film, or a film in which a liquid crystal compound is oriented can be used. . The λ / 4 phase difference plate may be a narrow band λ / 4 phase difference plate, but is preferably a broadband λ / 4 phase difference plate that generates a quarter wavelength phase difference in the entire visible light region. It is preferable to produce a broadband circularly polarizing plate using the broadband λ / 4 retardation plate.
It does not specifically limit as an adhesive used for bonding of the said linearly-polarizing plate and (lambda) / 4 phase difference plate, The well-known adhesive with high transparency used for preparation of a normal circularly-polarizing plate can be used. An embodiment in which the following blue pressure-sensitive adhesive is used as the pressure-sensitive adhesive used for bonding the high transmittance linearly polarizing plate and the λ / 4 retardation plate is one of the preferred embodiments of the present invention.

<Blue adhesive>
The circularly polarizing plate of the present invention is also characterized in that at least one of the pressure-sensitive adhesive layers is composed of a blue pressure-sensitive adhesive layer containing a blue pigment.
As the blue pigment used in the blue pressure-sensitive adhesive of the present invention, any conventionally known blue pigment can be used. The blue dye preferably absorbs visible light having a wavelength longer than 550 nm and does not absorb visible light having a wavelength shorter than 550 nm. The blue dye is more preferably a dye having an absorption spectrum maximum wavelength (λmax) in the range of 550 to 700 nm, more preferably a dye having an absorption spectrum maximum wavelength (λmax) in the range of 600 to 700 nm, and an absorption spectrum. Particularly preferred is a dye having a maximum wavelength (λmax) of 650 to 700 nm. The absorption spectrum of the dye can be measured by a conventionally known method in which the dye is dissolved in water or an organic medium and the absorbance at each wavelength is measured with a spectrophotometer.

The blue pigment used in the blue pressure-sensitive adhesive of the present invention may be selected from conventionally known blue organic dyes, blue organic pigments and blue inorganic pigments. Specific examples thereof include phthalocyanine dyes, anthraquinone dyes, Organic dyes such as azo dyes, triphenylmethane dyes, quinoneimine dyes, oil dyes, lake dyes; cyan pigments such as phthalocyanine pigments and lake pigments; titania, alumina, silica, zirconia, ceria, zinc oxide, etc. Examples thereof include inorganic pigments such as metal oxide powders and complex oxide pigments such as cobalt aluminate. As the blue pigment used in the blue pressure-sensitive adhesive of the present invention, the above-mentioned blue organic dye is preferable. For example, a metal-containing copper phthalocyanine complex dye or the like can be used.
Examples of the blue pigment used in the blue pressure-sensitive adhesive of the present invention include Kayaset (registered trademark, the same applies hereinafter) Blue K-FL, Kayaset Blue N, Kayaset Blue A2R (all manufactured by Nippon Kayaku Co., Ltd.) and the like. Can be obtained from the market. Λmax of these blue pigments is in the range of 650 to 700 nm for Kayaset Blue K-FL, 600 to 650 nm for Kayaset Blue N, and 550 to 600 nm for Kayaset Blue A2R.

The said blue pigment | dye can be used 1 type or in mixture of 2 or more types by arbitrary ratios. When using the blue adhesive of this invention in a some adhesive layer, the blue pigment | dye to be used may differ for every adhesive layer, and may be the same.
As for content of the blue pigment | dye in a blue adhesive, about 0.01-0.5 mass part is preferable with respect to 100 mass parts of solid content in an adhesive, More preferably, it is about 0.02-0.2 mass part. More preferably, it is about 0.04 to 0.2 parts by mass. If the content of the blue pigment is too small, the light absorption ability may be insufficient. If the content is too large, the purpose of increasing the amount of light from the LED may not be achieved. When using 2 or more types of blue pigment | dyes, what is necessary is just to adjust so that content of the total amount of a blue pigment | dye may become the said range. In addition, solid content in an adhesive means the component which remains after removing the solvent contained in an adhesive by evaporation etc.

The adhesive used for the blue adhesive of this invention is not specifically limited, What is necessary is just to use the well-known adhesive or commercially available adhesive used for bonding of an optical base material.
Examples of the pressure-sensitive adhesive include acrylic pressure-sensitive adhesive, urethane pressure-sensitive adhesive, rubber pressure-sensitive adhesive (polyisobutylene pressure-sensitive adhesive, SBR (styrene-butadiene copolymer rubber) pressure-sensitive adhesive), polyvinyl ether pressure-sensitive adhesive, epoxy pressure-sensitive adhesive, and oxetane pressure-sensitive adhesive. A melamine adhesive, a polyester adhesive, a phenol adhesive, a silicon adhesive, or the like can be used.
Among these, since it is excellent in transparency and durability, acrylic adhesive, epoxy adhesive, oxetane adhesive containing (meth) acrylic acid ester copolymer, epoxy resin, oxetane resin or polyester resin as an adhesive component An adhesive or a polyester pressure-sensitive adhesive is preferably used, and an acrylic pressure-sensitive adhesive is particularly preferable. A commercial item can be used for this acrylic adhesive. The acrylic pressure-sensitive adhesive is a pressure-sensitive adhesive having poly (meth) acrylate {(meth) acrylic acid ester polymer or copolymer} as an adhesive component, and the poly (meth) acrylate has a hydroxyl group, a carboxyl group, It may have a functional group such as an amide group, an amino group, or an epoxy group. In the present invention, “(meth) acrylate” is used in the meaning of at least one of methacrylate and / or acrylate, and the same expression is used in the same meaning.
Only 1 type may be used for the adhesive used for the blue adhesive of this invention, and 2 or more types may be mixed and used for it in arbitrary ratios.

The blue pressure-sensitive adhesive of the present invention is a curing agent, curing catalyst, crosslinking agent, color correction dye, leveling agent, antistatic agent, as long as the effects of the present invention are not impaired in addition to the blue pigment and the pressure-sensitive adhesive component. Further, additives such as a heat stabilizer, an antioxidant, a dispersant, a flame retardant, a lubricant, a plasticizer, or an ultraviolet absorber may be contained.
The blue pressure-sensitive adhesive of the present invention preferably contains a curing agent. Examples of the curing agent include isocyanate compounds, aluminum chelates, aziridinyl compounds, and epoxy compounds. It is preferable that content of a hardening | curing agent is 0.01-10 mass parts with respect to 100 mass parts of adhesives total amount.

The method for producing the blue pressure-sensitive adhesive of the present invention is not particularly limited, and the blue pigment, the pressure-sensitive adhesive, and additives such as a curing agent to be added as necessary may be mixed by a conventional method.
A solvent may be added to the blue pressure-sensitive adhesive of the present invention for the purpose of facilitating the above mixing and adjusting the viscosity at the time of coating. Any solvent can be used as long as it can dissolve the pressure-sensitive adhesive. Examples thereof include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone.

Examples of the method for applying the blue pressure-sensitive adhesive of the present invention include a method of applying to an optical substrate with a coating machine such as a roll coater, a reverse coater, a comma coater, a lip coater, and a die coater. When applying the blue pressure-sensitive adhesive of the present invention, it is preferable to use a coating solution obtained by adding the solvent to the composition.
Although the viscosity of the coating solution varies depending on the coating method used, it cannot be generally stated, but usually, the viscosity measured with a viscometer is preferably about 500 to 3000 mPa · s, preferably about 1000 to 2000 mPa · s. Is more preferable.
The thickness of the blue pressure-sensitive adhesive layer in the circularly polarizing plate of the present invention may be the same as the conventionally known pressure-sensitive adhesive layer as long as the effect of the present invention is achieved, but the film thickness after drying is 10 to 100 μm. Is more preferable, and 20 to 50 μm is more preferable.

<Circularly polarizing plate for organic EL display>
A circularly polarizing plate for an organic EL display device according to the present invention comprises (i) the high transmittance linearly polarizing plate, (ii) a λ / 4 phase difference plate, and (iii) at least one blue pressure-sensitive adhesive layer. It is a circularly-polarizing plate containing a person.
Specifically, the blue pressure-sensitive adhesive layer may be located between the high-transmittance linearly polarizing plate and the λ / 4 retardation plate, or / and the λ / 4 position of the circularly polarizing plate on which the both are bonded. It may be on the outer surface on the phase difference plate side. The blue pressure-sensitive adhesive layer formed on the outer surface of the λ / 4 retardation plate is a pressure-sensitive adhesive layer used for bonding to an LED or the like.
Even if the blue pressure-sensitive adhesive layer is between the polarizing plate and the λ / 4 retardation plate or on the outer surface of the laminated λ / 4 retardation plate, there is no difference in effect. From the viewpoint of easiness, a circularly polarizing plate (blue adhesive) having a blue adhesive layer on the outer surface of the pasted λ / 4 retardation plate (outer surface of the circularly polarizing plate on the λ / 4 retardation plate side) A circularly polarizing plate with an agent layer) is preferred.
The circularly polarizing plate of the present invention includes an optical layer other than the linearly polarizing plate and the λ / 4 retardation plate as long as the visibility improving effect, antireflection effect and hue adjusting effect of the circularly polarizing plate are not lost. May be. For example, the circularly polarizing plate of the present invention includes a protective layer (hard coat layer), an AR layer (antireflection layer), a retardation plate other than a λ / 4 retardation plate, etc. described in the section of the high transmittance polarizing plate. You may have.

The circularly polarizing plate of the present invention can be produced by the following method.
For example, when the circularly polarizing plate of the present invention has a blue pressure-sensitive adhesive layer on the outer surface of the circularly polarizing plate on the λ / 4 retardation plate side, blue is applied on the outer surface of the circularly polarizing plate on the λ / 4 retardation plate side. A blue pressure-sensitive adhesive layer is formed by a means such as applying a pressure-sensitive adhesive so that the thickness after drying becomes the above-mentioned thickness, or a blue pressure-sensitive adhesive layer previously formed on a release film is It can be bonded to the outer surface of the circularly polarizing plate on the side of the λ / 4 retardation plate to form a blue pressure-sensitive adhesive layer, thereby making the circularly polarizing plate of the present invention. In any case, the circularly polarizing plate with the blue pressure-sensitive adhesive layer preferably protects the outer surface of the blue pressure-sensitive adhesive layer with a release film or the like.
The blue pressure-sensitive adhesive layer is formed on the release film by applying a blue pressure-sensitive adhesive to the release surface of a film that has been subjected to a release treatment on one side (hereinafter also simply referred to as “release film”), The second release film can be adhered to the outer surface of the formed blue pressure-sensitive adhesive layer so that the release surfaces face each other and then dried. The obtained blue pressure-sensitive adhesive layer with a double-sided release film is peeled off from the single-sided release film and bonded to the outer surface of the circularly polarizing plate on the side of the λ / 4 retardation plate, whereby the blue pressure-sensitive adhesive of the present invention. It can be set as the circularly-polarizing plate which has a layer.
When the blue pressure-sensitive adhesive layer is between the linearly polarizing plate and the λ / 4 phase difference plate, the blue pressure-sensitive adhesive is bonded to the surface on the bonding side of the linear polarizing plate or the surface on the bonding side of the λ / 4 phase difference plate. The two may be applied to each other and bonded together, and if necessary, dried or cured to form a circularly polarizing plate. In this case, if necessary, an adhesive layer for adhering to the LED or the like is provided on the outer surface of the obtained circularly polarizing plate on the λ / 4 retardation plate side, and the circularly polarizing plate with the adhesive layer is provided. It is good. Usually, a circularly polarizing plate with an adhesive layer is preferred. In this case, the adhesive described in the section of blue adhesive can be used.
In the case of having a blue pressure-sensitive adhesive layer having a release film on both sides, which has been prepared in advance, the release film on one side is peeled off, and then the outer surface on the λ / 4 retardation plate side of the circularly polarizing plate is used. The method of laminating to the circular polarizing plate of the present invention (circular polarizing plate with a blue pressure-sensitive adhesive layer) has an adverse effect on the optical substrate (the linear polarizing plate or the λ / 4 retardation plate) due to the heat generated during drying. It is preferable at the point which can form a blue adhesive layer, without giving.

  As the release film, a known release film can be used. For example, a known release agent coating film such as a silicone film is formed on one surface of a plastic film such as polyethylene terephthalate (PET). Or the like.

Although the circularly polarizing plate of the present invention depends on the purpose of use, the light transmittance in the visible light region (wavelength 400 to 700 nm) is preferably 46% or more, and more preferably 47% or more. In addition, external light incident on the circularly polarizing plate of the present invention from the linearly polarizing plate side passes through the circularly polarizing plate of the present invention and is reflected by a reflecting plate placed on the opposite surface, and the reflected light is reflected. The ratio (reflectance) of the amount of reflected light emitted again from the linearly polarizing plate with respect to the amount of incident light on the course opposite to that when incident again is preferably 20% or less, and more preferably 15% or less. When the circularly polarizing plate for an organic EL display device is used in a conventional application, it can be allowed if the reflectance is 20% or less.
Here, the “light transmittance” means that the light enters the circularly polarizing plate from the λ / 4 retardation plate side, passes through the circularly polarizing plate, and exits from the linearly polarizing plate side. The ratio of the amount of emitted light to the amount of incident light on a circularly polarizing plate. In addition, the “reflectance of external light” means that external light enters the circularly polarizing plate from the linearly polarizing plate side, passes through the circularly polarizing plate, and exits from the λ / 4 retardation plate side. When all the light is reflected by the reflecting plate, and the reflected light is transmitted through the circularly polarizing plate from the λ / 4 retardation plate side and emitted from the linearly polarizing plate side in a course opposite to the incident light. The ratio of the last emitted light quantity with respect to the first incident light quantity of external light.

In the circularly polarizing plate used in the organic EL display device of the present invention, the light transmittance at a wavelength of 450 nm is preferably 40% or more, more preferably 42% or more, and further preferably 45% or more. Further, the transmittance at a wavelength of 550 nm is preferably in the range of 40 to 55%, and more preferably in the range of 45 to 55%. Further, the transmittance at a wavelength of 650 nm is preferably 50% or less, and more preferably 45% or less. A circularly polarizing plate in which the transmittances at wavelengths of 450 nm, 550 nm, and 650 nm are all in the above preferable range or more preferable range is particularly preferable. For example, the light transmittance at a wavelength of 450 nm is preferably 42% or more, more preferably 45% or more, the transmittance at a wavelength of 550 nm is in the range of 45 to 55%, and the transmittance at a wavelength of 650 nm is A circularly polarizing plate having 45% or less is particularly preferable.
In the organic EL display device of the present invention, it is preferable that the reflectance of light at wavelengths of 450 nm, 550 nm, and 650 nm is 20% or less among the reflectance of external light by the cathode electrode of the OLED.

The circularly polarizing plate used in the organic EL display device preferably has almost no change in hue in both transmitted light and reflected light. About the change of the hue of the transmitted light and reflected light of a circularly-polarizing plate, it can evaluate by the value of (DELTA) a * and (DELTA) b * based on a L * a * b * color system (CIE1976). In the L * a * b * color system (CIE 1976), L * represents the lightness of the color, and a * and b * represent the hue.
As for the transmitted light of the circularly polarizing plate, the wavelength spectrum of the incident light and the outgoing light when the light incident from the retardation plate side is emitted from the linearly polarizing plate side is measured, and L * a * b * is calculated for each. The hue change of the transmitted light can be evaluated based on the difference (Δa * and Δb *) between the a * and b * of the emitted light with respect to the incident light. Similarly, with respect to the reflected light, the light incident from the linear polarizing plate side is emitted from the phase difference plate side, reflected, incident again from the phase difference plate side, and emitted from the linear polarizing plate side. By calculating the difference (Δa * and Δb *) between the a * and b * of the light emitted from the linearly polarizing plate side, the hue change of the reflected light can be evaluated.
As a circularly polarizing plate used for an organic EL display device, the value of Δb * is preferably in the range of −10 to 5 and in the range of −5 to 0 for each of transmitted light and reflected light. More preferably. Further, the value of Δa * is not particularly limited, but it is preferable that the value of Δa * is in a range of −5 to 5 for each of transmitted light and reflected light. The transmitted light is particularly preferably in the above range from the viewpoint that as the hue is closer to zero, the light emitted from the OLED is emitted in the same hue and the hue of the display image does not change. In addition, the reflected light is preferably in the above range because it is possible to prevent black display from being tinted by reflected light from outside light.

<Organic EL display device>
The organic EL display device of the present invention is an organic EL display device including the circularly polarizing plate of the present invention, and λ / 4 of the circularly polarizing plate of the present invention on the surface from which the light of the organic EL element (OLED) is emitted. It has a structure in which the outer surface of the retardation plate is bonded with an adhesive layer. Specifically, the organic EL element and the circularly polarizing plate are bonded together so that the image display surface (anode side) of the organic EL element and the λ / 4 retardation plate side of the circularly polarizing plate face each other. A display device is obtained.
For the bonding of the organic EL element and the circularly polarizing plate of the present invention, an adhesive or a pressure-sensitive adhesive usually used for the bonding can be used. As a preferable aspect, the aspect using the blue adhesive of this invention can be mentioned. When the circularly polarizing plate of the present invention is the circularly polarizing plate with a blue adhesive layer having a release film, the release film is peeled off from the blue adhesive layer, and the blue adhesive layer of the circularly polarizing plate is used as it is as an organic EL element. The organic EL display device of the present invention can be obtained by bonding to the image display surface (anode side).

In the blue adhesive layer of the organic EL display device of the present invention, external light passes through one blue adhesive layer twice in addition to the antireflection effect by the circularly polarizing plate. It has the effect of preventing reflection. On the other hand, since the light (display light) emitted from the OLED passes through the high transmittance circularly polarizing plate and the blue pressure-sensitive adhesive layer only once, it is emitted from the display screen. Therefore, the amount absorbed by the blue pressure-sensitive adhesive layer is reflected. Less than light.
In the organic EL display device of the present invention, by improving the transmittance of emitted light, the visibility of an image is improved, and the power consumption of the OLED can be reduced and the lifetime can be increased. In the organic EL display device of the present invention, the hue of the display image of the OLED is hardly influenced by the circularly polarizing plate.

  The organic EL display device having the circularly polarizing plate of the present invention is used for any application, for example, portable devices such as notebook computers, tablet computers, mobile phones and portable game machines, video cameras, monitors for car navigation systems, etc. Can be preferably used.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited only to the following Example.

Example 1
(1) Production of high transmittance linear polarizing plate A polyvinyl alcohol resin film (manufactured by Kuraray Co., Ltd., VF-PS, thickness 75 μm) was washed with water and then swollen in water at 35 ° C. As a dichroic dye, Orange dichroic dye (λmax = 460 nm, dichroic ratio 39.4) is 0.105 g / L [mass / volume], Red dichroic dye (λmax = 520 nm, dichroic) 38.8) 0.062 g / L [mass / volume], Blue dichroic dye (λmax = 600 nm, dichroism ratio 40.8) 0.19 g / L [mass / volume], Green System dichroic dye (λmax = 660 nm, dichroic ratio 29.7), 0.10 g / L [mass / volume], respectively, and mirabilite and sodium tripolyphosphate each 0.25 g / L The swollen film was immersed in the contained 46 ° C. dyeing solution for 2 minutes for dyeing treatment. The dyed film is washed in a 2.6% by mass boric acid aqueous solution and then uniaxially stretched in a 3.7% by mass boric acid aqueous solution at 54 ° C. so that the draw ratio is 6.2 times. The dichroic dye in the film was oriented. The obtained stretched film was washed with water at 25 ° C. and then dried in air at 60 ° C. to obtain a polarizing element film. The thickness of the obtained polarizing element film was 23 μm. When the boric acid concentration in the polarizing element film was determined by neutralization titration, the boric acid content in the polarizing element film was 17.0% by mass.
A TAC film (manufactured by Fuji Film Co., Ltd.) having a thickness of 80 μm was laminated on both sides of the obtained polarizing element film using a polyvinyl alcohol adhesive, and then dried at 70 ° C. to produce a high transmittance linear polarizing plate. .
Regarding the transmittance in the wavelength region of 400 to 700 nm of the obtained polarizing plate, the single transmittance was 50.29% and the orthogonal transmittance was 9.92%.

  The transmittance of the polarizing plate was measured as follows. The transmittance when one polarizing plate was used was the single transmittance Ts, and the transmittance when the two polarizing plates were stacked so that the absorption axes were orthogonal to each other was defined as the orthogonal transmittance Tc. Each transmittance was calculated by the following formula (1) by obtaining a spectral transmittance τλ every predetermined wavelength interval dλ (5 nm in this embodiment) in a wavelength region of 400 to 700 nm.

In the equation, Pλ represents a spectral distribution of standard light (C light source), and yλ represents a 2 ° visual field color matching function. Spectral transmittance τλ was measured using a spectrophotometer (manufactured by Hitachi High-Technologies Corporation, product name U-4100).

(2) Production of Circular Polarizing Plate To the obtained high transmittance polarizing plate, a polycarbonate wide-band quarter-wave retardation plate (manufactured by Teijin Ltd., W-147) is used. The absorption axis of the polarizing plate and the retardation plate Bonding was performed using an acrylic pressure-sensitive adhesive (manufactured by Soken Chemical Co., Ltd., product name: SK Dyne 1885) so that the angle with respect to the slow axis was 45 degrees, and a high transmittance circularly polarizing plate was produced.

(3) Preparation of blue pressure-sensitive adhesive layer with double-sided release film Acrylic pressure-sensitive adhesive (manufactured by Soken Chemical Co., Ltd., product name AS-513) 500 g (solid content: 17% by mass) with a curing agent (manufactured by Soken Chemical Co., Ltd., E -AX) 0.34 g was added, and methyl ethyl ketone was added as a solvent so that the viscosity was in the range of 1000 to 2000 mPa · s. The viscosity at this time was measured using a viscosity cup (C-1). To this adhesive solution, 0.06 g of a blue pigment (manufactured by Nippon Kayaku Co., Ltd., product name Kayaset Blue K-FL, metal-containing copper phthalocyanine complex dye) was added to color the adhesive.
The obtained blue pressure-sensitive adhesive was applied onto a PET film with a release agent using a comma coater. At this time, at a coating speed of 1.5 m / min, the coating amount was adjusted so that the thickness of the pressure-sensitive adhesive layer after drying was 25 ± 5 μm, and the blue pressure-sensitive adhesive was applied. Subsequently, the blue adhesive layer with a double-sided release film was obtained by drying at 60 degreeC for 1 minute, and 80 degreeC for 2 minutes.

(4) Preparation of circularly polarizing plate for organic EL display device One release film is peeled off from the blue adhesive layer with a release film obtained above, and the blue adhesive layer surface of the high transmittance circularly polarizing plate is removed. The laminate was bonded to the outer surface of the λ / 4 retardation plate to obtain a circularly polarizing plate for an organic EL display device (high transmittance circularly polarizing plate with a blue adhesive layer) of the present invention.

Comparative Example 1
Instead of the high transmittance linear polarizing plate in Example 1 (1), a commercially available dye-based polarizing plate (neutral gray, manufactured by Polatechno Co., Ltd., product name SHC-115U) was used. In Example 1 (3), Except not adding a blue pigment | dye to an adhesive solution, it carried out similarly to the said Example 1, and obtained the organic EL display apparatus circularly-polarizing plate (circularly-polarizing plate with an adhesive layer) of the comparative example 1.

Test Example 1 (Measurement of transmittance, reflectance and hue)
The transmittance and reflectance of the circularly polarizing plate obtained in each of Example 1 and Comparative Example 1 were measured with a spectrophotometer (manufactured by Hitachi High-Technologies Corporation, product name U-4100).
Here, the transmittance was determined by measuring the transmittance of light having a wavelength of 400 to 700 nm when the high transmittance circularly polarizing plate of Example 1 or the circularly polarizing plate of Comparative Example 1 was used. The reflectance is such that light is incident from the linearly polarizing plate side of the high transmittance circularly polarizing plate of Example 1 or the circularly polarizing plate of Comparative Example 1, and all of the transmitted light transmitted from the phase difference plate side is reflected again. The light incident on the phase difference plate and again transmitted through the linear polarizing plate was measured, and the reflectance at a wavelength of 400 to 700 nm was measured.
The measurement results of transmittance are shown in Table 1 below, and the measurement results of reflectance are shown in Table 2 below.

Also, a * and b * based on the L * a * b * color system (CIE 1976) are calculated based on the wavelength spectrum data of the transmitted light and reflected light of each circularly polarizing plate, and the phase difference of the circularly polarizing plate is calculated. The values of Δa * and Δb * of the emitted light with respect to the incident light when the light incident from the plate side transmitted through the circularly polarizing plate and emitted from the circularly polarizing plate side were calculated. In addition, the light incident from the linearly polarizing plate side of the circularly polarizing plate is emitted from the phase difference plate side, reflected, incident again from the phase difference plate side, and the incident light when exiting from the linear polarizing plate side. The values of Δa * and Δb * of the emitted light from the linear polarizing plate side were calculated.
Changes in the hues of transmitted light and reflected light of the circularly polarizing plates obtained in Example 1 and Comparative Example 1 were evaluated based on the obtained Δa * and Δb * values.
Changes in hues of transmitted light and reflected light (Δa * and Δb *) are shown in Table 3 below.

As is clear from Table 1 and Table 2, the circularly polarizing plate of the present invention is inferior in reflectance as compared with the conventional circularly polarizing plate, but has a transmittance of 6% or more at a wavelength between 450 nm and 550 nm. The average transmittance of visible light is 3% or higher, and the light emitted from the OLED can be increased compared to the circularly polarizing plate of Comparative Example 1 using a conventional linearly polarizing plate. It was found to have an effect of improving brightness.
Further, as is apparent from the results in Table 3, the values of Δa * and Δb * are in the range of −5 to 0 for each of the transmitted light and reflected light of the circularly polarizing plate of the present invention. This circular polarizing plate was found to be an excellent circular polarizing plate in which the hue of the image displayed by the OLED does not change.

  The circularly polarizing plate for an organic EL display device of the present invention can be easily manufactured by using the conventional manufacturing method of a circularly polarizing plate as it is, has a high transmittance in the visible light region, and emits light from an OLED. Can be increased. Therefore, it is possible to extend the lifetime of the OLED by suppressing the power consumption of the OLED while maintaining the brightness of the display image. In addition, since the adhesive layer contains a blue pigment, the reflectance can be lowered and the hue change of transmitted light can be suppressed, so that it is useful as a circularly polarizing plate for organic EL display devices.

Claims (9)

  (I) a linear polarizing plate having a single transmittance of 46 to 70% for light having a wavelength of 400 to 700 nm, (ii) a λ / 4 phase difference plate, and (iii) a blue pressure-sensitive adhesive layer containing a blue pigment. A circularly polarizing plate for an organic EL display device including the three.   The circularly polarizing plate for an organic EL display device according to claim 1, wherein a maximum wavelength (λmax) of an absorption spectrum of the blue pigment is in a range of 550 to 700 nm.   3. The circularly polarizing plate for an organic EL display device according to claim 1, wherein the content of the blue pigment in the blue adhesive is 0.01 to 0.5 parts by mass with respect to 100 parts by mass of the solid content in the adhesive. .   The circularly polarizing plate for an organic EL display device according to any one of claims 1 to 3, wherein the linear polarizing plate has a hue of neutral gray.   When the light incident from the retardation plate side of the circularly polarizing plate is emitted from the linear polarizing plate side, the value of Δb * of the outgoing light with respect to the incident light based on the L * a * b * color system (CIE1976) is It is -5-0, The circularly-polarizing plate for organic EL display apparatuses as described in any one of Claims 1-4.   The blue pressure-sensitive adhesive layer has at least one of the outer surface of the λ / 4 retardation plate in the circularly polarizing plate or between the linearly polarizing plate and the λ / 4 retardation plate. The circularly-polarizing plate for organic electroluminescent display of description.   The circularly-polarizing plate for organic EL display devices of Claim 6 which a blue adhesive layer has in the outer surface of (lambda) / 4 phase difference plate in a circularly-polarizing plate.   The transmittance of light having a wavelength of 450 nm is 42% or more, the transmittance of light having a wavelength of 550 nm is in the range of 45 to 55%, the transmittance of light having a wavelength of 650 nm is 45% or less, and a wavelength of 400 to 8. The circularly polarized light for an organic EL display device according to claim 1, wherein an average single transmittance of light in a visible light region of 700 nm is 45% or more and a reflectance of external light is 20% or less. Board.   The organic electroluminescence display provided with the circularly-polarizing plate for organic electroluminescence displays as described in any one of Claims 1-7.