JP2023157234A - Organic el display - Google Patents

Abstract

To provide an organic EL display with less coloration of reflected light.SOLUTION: An organic EL display (100) comprises an organic EL element (70) having an organic light-emitting layer (75) between a pair of electrodes (73,77) and a circular polarizer (10) disposed on the first major surface of the organic EL element. The organic EL element has a reflectance spectrum for incident light from the first major surface, and the ratio of the reflectance R410 at a wavelength of 410 nm to the reflectance R510 at a wavelength of 510 nm, R410/R510, is less than 0.6. The circular polarizer includes a polarizer (11) and at least one phase difference layer (13). The polarizer has a ratio T410/T510 of orthogonal transmittance T410 at a wavelength of 410 nm to orthogonal transmittance T510 at a wavelength of 510 nm, which is 7 or greater.SELECTED DRAWING: Figure 1

Description

The present invention relates to an organic EL display device that includes a circularly polarizing plate on the surface of an organic EL element.

An organic EL display device that uses an organic EL element as a display body has a circularly polarizing plate placed on the viewing side surface of the organic EL element (organic EL cell), so that external light reflected by metal electrodes etc. is re-emitted and visually recognized. (For example, see Patent Document 1 and Patent Document 2).

JP2019-211761A Japanese Patent Application Publication No. 2020-3520

It is difficult to completely block reflected light with a circularly polarizing plate, and some of the reflected light passes through the circularly polarizing plate and is visible from the outside. Depending on the configuration of the organic EL element, reflected light that is not shielded by the circularly polarizing plate and is visible from the outside may appear colored, which causes a decrease in screen visibility and a decrease in the design of the device. In view of this problem, an object of the present invention is to provide an organic EL display device in which reflected light is less colored.

The organic EL display device of the present invention includes an organic EL element having an organic light emitting layer between a pair of electrodes, and a circularly polarizing plate disposed on a first principal surface that is a light extraction surface of the organic EL element. A circularly polarizing plate includes a polarizer and at least one retardation layer.

In the organic EL element, in the reflection spectrum for incident light from the first principal surface, the ratio R ₄₁₀ /R ₅₁₀ of the reflectance R ₄₁₀ at a wavelength of 410 nm and the reflectance R ₅₁₀ at a wavelength 510 nm is 0.6 or less. The polarizer has a ratio T 410 /T 510 of orthogonal transmittance T ₄₁₀ at a wavelength of 410 nm to orthogonal transmittance T ₅₁₀ at a wavelength of _{510 nm of} 7 or more.

In the reflection spectrum for incident light from the first principal surface, the organic EL element may have a reflectance R ₄₁₀ of 35% or less at a wavelength of 410 nm, and a reflectance R ₅₁₀ of 40% or more at a wavelength of 510 nm. good.

In the organic EL display device, the chromaticness index b ^* of the CIELAB color system of the light reflected from the circularly polarizing plate side may be -1.0 or less, and the chromaticness index a ^* of the light reflected from the circularly polarizing plate side may be 0 or more. good.

In the reflection spectrum of an organic EL element, if the reflectance of short wavelengths of visible light is low, the reflected light appears colored. When the transmittance T ₄₁₀ is relatively large, b ^* of the reflected light of the organic EL display device (reflected light that passes through the circularly polarizing plate) becomes small, and coloring is reduced.

FIG. 1 is a cross-sectional view of an organic EL display device according to an embodiment. This is an orthogonal transmission spectrum of a polarizing plate. It is a reflection spectrum of an organic EL cell. This is the reflection spectrum of the organic EL display device calculated from the product of the reflection spectrum of the organic EL cell and the orthogonal transmission spectrum of the polarizing plate.

FIG. 1 is a cross-sectional view of an image display device according to an embodiment, and shows an organic EL display device 100 in which a circularly polarizing plate 10 is disposed on the viewing side of an organic EL element 70.

[Organic EL element]
An organic EL element includes an organic light emitting layer between a pair of electrodes. In FIG. 1, a top emission type organic EL cell is shown as the organic EL element 70 (hereinafter sometimes referred to as "organic EL cell"). The top emission type organic EL cell has a structure in which a cathode 73, an organic light emitting layer 75, and an anode 77 are sequentially provided on a substrate 71, and light is extracted from the anode 77 side. A sealing material 79 is laminated on the anode 77 . Although not shown, the sealing material 79 is preferably provided so as to cover the electrodes 73 and 77 and the side surfaces of the organic light emitting layer 75.

As the substrate 71, a glass substrate or a plastic substrate is used. In a top emission type organic EL cell, the substrate 71 does not need to be transparent, and a highly heat-resistant film such as a polyimide film may be used as the substrate 71. Cathode 73 is generally a metal electrode. The organic light emitting layer 75 may include an electron transport layer, a hole transport layer, etc. in addition to an organic layer that itself functions as a light emitting layer. The anode 77 is a metal oxide layer or a metal thin film, and transmits light from the organic light emitting layer 75. A back sheet (not shown) may be provided on the back side of the substrate 71 for the purpose of protecting and reinforcing the substrate.

The organic EL cell may be of a bottom emission type in which an anode (transparent electrode), an organic light emitting layer, and a cathode (metal electrode) are laminated in this order on a substrate. A bottom emission type organic EL cell is configured to extract light from the substrate side, and uses a transparent substrate.

As mentioned above, the cathode 73 of the organic EL cell 70 is generally a metal electrode and is light reflective. The organic light-emitting layer 75 is extremely thin, about 10 nm thick, so when external light enters the organic EL cell, it passes through the organic light-emitting layer, reaches the cathode (metallic electrode) that is the back electrode, and is reflected by the electrode. Since the external light emitted is re-emitted to the viewing side (light extraction side), the screen looks like a mirror surface. As will be described later, by arranging the circularly polarizing plate 10 on the viewing side surface of the organic EL cell 70, reflected light from the electrodes can be blocked and the visibility and design of the screen can be improved.

In the present invention, the organic EL cell 70 has a reflection spectrum when light is incident from the viewing side (the upper side of FIG. 1), which has a ratio R ₄₁₀ /R of a reflectance R ₄₁₀ at a wavelength of 410 nm and a reflectance R ₅₁₀ at a wavelength 510 nm. ₅₁₀ is 0.6 or less. The reflection spectrum is obtained by measuring the absolute reflectance of 8° reflected light in the wavelength range of 380 nm to 780 nm when light is incident at an incident angle of 8°.

In organic EL cells used in image display devices, Ag or Al is often used as the metal material for the cathode, and the R ₄₁₀ /R ₅₁₀ of reflected light is about 0.8, with little coloration and appears silver (achromatic). On the other hand, depending on the selection of the cathode material and the configuration of the element, the reflectance of short wavelength visible light may be relatively low, and R ₄₁₀ /R ₅₁₀ may be 0.6 or less. When R ₄₁₀ /R ₅₁₀ is 0.6 or less, even if white light is incident, there is little reflection of short wavelength visible light (blue and violet), so the reflected light from the organic EL cell 70 appears yellowish.

R ₄₁₀ /R ₅₁₀ of the organic EL cell may be 0.55 or less or 0.5 or less. The smaller R ₄₁₀ /R ₅₁₀ tends to be, the larger b ^* of the reflected light from the organic EL cell tends to be. R ₄₁₀ /R ₅₁₀ is generally 0.1 or more, and may be 0.2 or more, 0.25 or more, or 0.3 or more.

b ^* is the chromaticness index of the CIELAB color system; when b ^* is small, the light is colored blue and visually recognized; when b ^* is large, the light is colored yellow and visually perceived. Note that when a ^* , another chromaticness index in the CIELAB color system, is small, the light is colored green and visually perceived, and when a ^* is large, the light is colored red and visually perceived.

The reflectance R ₄₁₀ of the organic EL cell 70 at a wavelength of 410 nm may be 35% or less, 30% or less, 25% or less, or 5% or more, 10% or more, or 15% or more. good. The reflectance R ₅₁₀ of the organic EL cell 70 at a wavelength of 510 nm may be 40% or more or 45% or more, or may be 80% or less, 70% or less, or 60% or less.

[Circular polarizing plate]
A circularly polarizing plate 10 is arranged on the viewing side surface of the organic EL cell 70. The circularly polarizing plate 10 includes a retardation layer 13 on one surface of a polarizer 11, and the retardation layer 13 is arranged closer to the organic EL cell 70 than the polarizer 11 is.

The circularly polarizing plate 10 emits external light incident from the viewing side (upper side in FIG. 1) as circularly polarized light to the organic EL cell 70 side (lower side in FIG. 1). Specifically, when external light passes through the polarizer 11 , the light vibrating in the direction of the absorption axis of the polarizer 11 is absorbed, so it becomes linearly polarized light and enters the retardation layer 13 . The retardation layer 13 is typically a quarter-wave plate, and when transmitted through the retardation layer 13, the phase of light vibrating in the slow axis direction of the retardation layer 13 is changed to vibrate in the fast axis direction. The phase of the light is delayed by π/2. Therefore, when the angle between the absorption axis direction of the polarizer 11 and the slow axis direction of the retardation layer 13 (quarter wave plate) is 45°, the linearly polarized light from the polarizer 11 is converted into circularly polarized light.

The external light converted into circularly polarized light by the circularly polarizing plate 10 enters the organic EL cell 70 . The reflected light from the organic EL cell reaches the circularly polarizing plate 10 again, and the retardation layer 13 converts the circularly polarized light into linearly polarized light. The reflected light from the organic EL cell (mainly the light reflected from the cathode 73, which is the back electrode) has a phase inverted by π at the time of reflection, so that it becomes circularly polarized light in the opposite direction to that at the time of incidence. Therefore, when the reflected light is converted from circularly polarized light to linearly polarized light by the retardation layer 13, it becomes linearly polarized light whose vibration direction is perpendicular to that at the time of incidence, and is absorbed by the polarizer 11. In this way, by arranging the circularly polarizing plate 10 on the viewing side surface of the organic EL cell 70, the reflected light from the organic EL cell 70 is blocked by the circularly polarizing plate 10, thereby improving the visibility of the screen of the display device. The design quality is improved.

<Polarizer>
As the polarizer 11, for example, a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or a partially saponified ethylene/vinyl acetate copolymer film is coated with a dichroic dye such as iodine or a dichroic dye. Examples include polyene-based oriented films such as those obtained by adsorbing a color substance and uniaxially stretched, and polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochloric acid-treated products. Among these, a polarizer in which iodine is adsorbed on a polyvinyl alcohol film is preferred because it can achieve a high degree of polarization.

In the manufacturing process of the polarizer, treatments such as water washing, swelling, crosslinking, etc. may be performed as necessary. Stretching may be performed either before or after iodine dyeing, or may be performed while dyeing. The stretching may be done in air (dry stretching) or in water or in an aqueous solution containing boric acid, potassium iodide, etc., or these may be used in combination. The thickness of the polarizer is not particularly limited, but is generally about 1 to 50 μm.

The polarizer 11 may be a thin polarizer with a thickness of 10 μm or less. Examples of thin polarizers include those described in JP-A-51-069644, JP-A-2000-338329, WO2010/100917, Patent No. 4691205, Patent No. 4751481, and JP-A No. 2012-73580. An example of this is a polarizer. A thin polarizer can be obtained, for example, by iodine dyeing and stretching a laminate in which a polyvinyl alcohol resin layer is formed on a stretching resin base material. In this manufacturing method, even if the polyvinyl alcohol resin layer is thin, it is supported by the stretching resin base material, so it can be stretched without problems such as breakage due to stretching.

In the polarizer 11, the ratio T 410 /T _{510 of} the orthogonal transmittance T ₄₁₀ at a wavelength of 410 nm and the orthogonal transmittance T ₅₁₀ at a wavelength of 510 nm is 7 or more. The orthogonal transmittance is the light transmittance when two identical polarizers are arranged in crossed nicols, and the smaller the orthogonal transmittance, the higher the degree of polarization. If it is difficult to handle the polarizer as a single film (for example, if the polarizer is small), use a crossed Nicol polarizer with a polarizer protective film (transparent film) attached to one or both sides of the polarizer. The transmission spectrum (orthogonal transmittance) can be measured by placing the

In general, a polarizer is required to have a small orthogonal transmittance over a wide wavelength range of visible light and a neutral hue of transmitted light, so it is preferable that T ₄₁₀ /T ₅₁₀ be small. On the other hand, in the embodiment of the present invention, the polarizer 11 of the circularly polarizing plate 10 disposed on the viewing side of the organic EL cell 70 has a large orthogonal transmittance T ₄₁₀ at a wavelength of 410 nm, and T ₄₁₀ /T ₅₁₀ of 7 or more. use something.

As described above, the organic EL cell 70 has a low reflectance of short wavelength visible light, and the reflected light is colored yellow. Due to the relatively large T ₄₁₀ of the polarizer 11, the shielding rate of short-wavelength visible light reflected by the circularly polarizing plate 10 is low, so the hue of the reflected light that is not shielded by the circularly polarizing plate 10 and leaks to the outside is reduced. becomes neutral. Furthermore, since T ₅₁₀ is relatively small and the shielding rate of reflected light in a wavelength range with high specific luminous efficiency is high, the organic EL display device has a low luminous reflectance of reflected light and excellent visibility.

T ₄₁₀ /T ₅₁₀ of the polarizer 11 may be 8 or more, 9 or more, or 10 or more. The larger T ₄₁₀ /T ₅₁₀ tends to be, the smaller b ^* of the reflected light from the organic EL display device tends to be. On the other hand, if T ₄₁₀ /T ₅₁₀ of the polarizer 11 is excessively large, the reflected light is strongly colored in blue and is visually perceived, resulting in poor visibility. Therefore, T ₄₁₀ /T ₅₁₀ of the polarizer 11 is preferably 30 or less, more preferably 25 or less, and may be 20 or less, 17 or less, or 15 or less.

The ratio T ₄₁₀ /T ₅₁₀ of the orthogonal transmittance of the polarizer 11 at a wavelength of 410 nm and a wavelength of 510 nm can be set within the above range by adjusting the manufacturing conditions of the polarizer. For example, in a polarizer in which iodine is adsorbed to a polyvinyl alcohol film, T ₄₁₀ /T ₅₁₀ changes depending on the ratio of polyiodine ions forming a complex with the polyvinyl alcohol molecular chain.

In the polarizer, iodine exists in the form of iodine ions (I ⁻ ), iodine molecules (I ₂ ), polyiodine ions (I ₃ ⁻ and I ₅ ⁻ ), and the like. Among these, polyiodine ions I ₃ ^- and I ₅ ^- form a complex with the polymer chain of polyvinyl alcohol (PVA) and contribute to the expression of dichroism.

The complex of PVA and triiodide ion I ₃ ^- has an absorption peak around 470 nm, and the complex of PVA and pentaiodide ion I ₅ ^- has an absorption peak around 600 nm. Therefore, the polarizer exhibits dichroism in a wide wavelength range of visible light, but the orthogonal transmission spectrum has maximum transmittance (minimum absorbance) near 410 nm and 510 nm. The spectral shape of the orthogonal transmittance changes depending on the ratio of I ₃ ^- to I ₅ ^- in the polarizer, and as the ratio of I ₃ ^- becomes relatively large, the orthogonal transmittance on the shorter wavelength side of visible light becomes smaller. Therefore, T ₄₁₀ /T ₅₁₀ of the polarizer tends to become smaller. When the ratio of I ₅ ^- becomes relatively large, the orthogonal transmittance on the long wavelength side of visible light becomes small, and T ₄₁₀ /T ₅₁₀ of the polarizer tends to become large.

As methods for adjusting the ratio of I ₃ ^- to I ₅ ^- in a polarizer, adjustment of iodine dyeing conditions, adjustment of stretching conditions, reduction treatment, heat treatment, etc. are known. 341503, JP 2010-91811, JP 2010-117516, JP 2013-101301, JP 2013-210516, JP 2016-148830, WO 2016/117659, You can refer to JP-A No. 2017-167517, JP-A No. 2019-53279, etc.

In the polarizer 11, the ratio T ₄₇₀ /T ₆₀₀ of the orthogonal transmittance T ₄₇₀ at a wavelength of 470 nm and the orthogonal transmittance T ₆₀₀ at a wavelength of 600 nm may be 23 or less, 20 or less, or 18 or less. As mentioned above, the wavelength of 470 nm is the maximum absorption (minimum transmittance) of the complex of PVA and I ₃ ^- , and the wavelength of 600 nm is the maximum absorption of the complex of PVA and I ₅ ^- . Therefore, when the ratio of I ₅ ^- is relatively large, T ₄₇₀ /T ₆₀₀ tends to become large.

The degree of polarization of the polarizer 11 is preferably 95% or more, more preferably 98% or more, even more preferably 99% or more, and may be 99.9% or more. The degree of polarization P is determined from the parallel transmittance Tp and the orthogonal transmittance Tc using the following formula. Note that the parallel transmittance Tp and the orthogonal transmittance Tc here are Y values obtained by performing visibility correction based on the 2-degree field of view (C light source) of JIS Z8701 from the parallel transmission spectrum and the orthogonal transmission spectrum.
P (%) = 100 x {(Tp-Tc)/(Tp+Tc)}/2

<Retardation layer>
As described above, the circularly polarizing plate 10 is configured by arranging the retardation layer 13 on one surface of the polarizer 11. The retardation layer 13 may consist of one layer of retardation layer, or may consist of two or more layers.

The retardation layer 13 is preferably a quarter wavelength plate. The quarter-wave plate has a front retardation Re (550) of 100 to 180 nm at a wavelength of 550 nm. Re(550) of the quarter-wave plate is preferably 110 nm to 165 nm, more preferably 120 nm to 155 nm, even more preferably 127.5 nm to 147.5 nm.

The retardation layer 13 may have a characteristic in which the longer the wavelength, the larger the retardation (so-called "reverse wavelength dispersion"). When the retardation layer 13 has reverse wavelength dispersion, the difference between the front retardation of the retardation layer and 1/4 wavelength is small over a wide wavelength range of visible light, so the circularly polarizing plate has a wide band and provides excellent reflection. Prevention properties can be achieved.

In the retardation layer having reverse wavelength dispersion characteristics, the ratio Re(450)/Re(550) of the front retardation Re(450) at a wavelength of 450 nm to the front retardation Re(550) at a wavelength of 550 nm is less than 1. Re(450)/Re(550) is preferably 0.65 to 0.99, more preferably 0.70 to 0.95, even more preferably 0.75 to 0.90, and 0.80 to 0.85. It may be.

In particular, when Re(450)/Re(550) is 0.80 to 0.85, the difference between Re(λ) and λ/4 is small in the wavelength λ range of 450 to 550 nm (ideal 1 /4 wavelength), so there is little light leakage in this wavelength range. Therefore, the organic EL display device has a low reflectance in the wavelength range of 450 to 550 nm where the relative luminous efficiency is high, and the luminous reflectance of reflected light is low, resulting in excellent visibility. On the other hand, in a range where the wavelength λ is shorter than 450 nm, Re(λ)<λ/4, and light leakage in this wavelength range is likely to occur. Therefore, together with the large T ₄₁₀ /T ₅₁₀ of the polarizer 11, b ^* of the reflected light of the organic EL display device tends to become small. Re(450)/Re(550) of the retardation layer 13 may be 0.80 to 0.84, or 0.81 to 0.83.

The retardation layer is, for example, a stretched film. The resin materials for the film include polycarbonate resin, cyclic olefin resin, cellulose resin, polyester resin, polyvinyl alcohol resin, polyamide resin, polyimide resin, polyether resin, polystyrene resin, acrylic resin, Examples include phenylmaleimide resin. The retardation layer may be an oriented liquid crystal layer in which a liquid crystal compound is oriented in a predetermined direction. The thickness of the retardation layer is, for example, about 1 to 300 μm.

As described above, the retardation layer 13 may be configured as a laminate of two or more retardation layers. For example, by laminating a plurality of retardation layers, the wavelength dispersion of the retardation of the quarter-wave plate can be adjusted to make the circularly polarizing plate broadband. Further, by stacking a plurality of retardation layers and adjusting the three-dimensional refractive index anisotropy (refractive index ellipsoid), it is also possible to reduce changes in retardation depending on the viewing direction.

The stacking form of the polarizer 11 and the retardation layer 13 is not particularly limited. A polarizer protective film may be bonded to the surface of the polarizer 11, and the retardation layer 13 may be laminated via the polarizer protective film. Furthermore, the retardation layer 13 may also function as a polarizer protective film. The polarizer 11 and the retardation layer 13 do not necessarily have to be integrally laminated, and may be spaced apart from each other.

The angle between the absorption axis direction of the polarizer 11 and the slow axis direction of the quarter-wave plate as the retardation layer 13 is, for example, 35° to 55°, preferably 40° to 50°, more preferably is 43° to 47°, more preferably 44° to 46°. Note that when adjusting the wavelength dispersion of the retardation of a quarter-wave plate by stacking multiple retardation layers (for example, stacking a quarter-wave plate and a half-wave plate at an angle that is neither parallel nor perpendicular) ), a fixed slow axis cannot be assumed, so the arrangement angle of the polarizer and retardation layer is not limited to the above, and the laminate of the polarizer and retardation layer can function as a circularly polarizing plate. The arrangement angle of each optical layer may be set as follows.

<Polarizer protective film>
A transparent film 15 may be bonded to the viewing side surface of the polarizer 11 (the surface opposite to the surface on which the retardation layer 13 is disposed) as a polarizer protective film. The thickness of the transparent film 15 is approximately 1 to 300 μm. Examples of the resin material for the transparent film 15 include those mentioned above as the resin material for the retardation layer 13.

[Organic EL display device]
By arranging the circularly polarizing plate 10 on the viewing side surface of the organic EL cell 70, an organic EL display device 100 is formed. As shown in FIG. 1, the organic EL cell 70 and the circularly polarizing plate 10 may be bonded together via a suitable adhesive layer 21. As the adhesive layer 21, a curable adhesive or adhesive (pressure sensitive adhesive) is used. The thickness of the adhesive layer is, for example, about 0.1 to 500 μm.

From the viewpoint of handleability and the like, the adhesive layer 21 is preferably an adhesive. As the adhesive, those having base polymers such as acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyethers, fluorine polymers, rubber polymers, etc. can be appropriately selected and used. In particular, adhesives such as acrylic adhesives and rubber adhesives that have excellent transparency, exhibit appropriate wettability, cohesiveness, and adhesive properties, and are excellent in weather resistance, heat resistance, etc. are preferred. The thickness of the adhesive layer is, for example, about 5 to 500 μm.

In the organic EL display device 100, external light reflected by the electrodes and the like of the organic EL cell 70 is blocked by the circularly polarizing plate 10, so that the screen has excellent visibility and the screen can be viewed as if it were a mirror surface. It has excellent design. However, even if a circularly polarizing plate is placed on the viewing side surface of the organic EL cell, the reflected light cannot be completely blocked by the circularly polarizing plate, so some of the reflected light passes through the circularly polarizing plate.

Since the ratio R ₄₁₀ /R ₅₁₀ of the reflectance R ₄₁₀ at a wavelength of 410 nm and the reflectance R ₅₁₀ at a wavelength 510 nm is 0.6 or less, the organic EL cell 70 can be used without a circularly polarizing plate. When external light (white light) enters the cell 70, the reflected light appears yellowish. As described above, the circularly polarizing plate 10 including the polarizer 11 with a large cross-transmittance T ₄₁₀ at a wavelength of 410 nm (that is, large light leakage at short wavelengths of visible light) is placed on the viewing side of the organic EL cell 70, By intentionally increasing the light leakage of the short-wavelength visible light, b ^* of the reflected light from the organic EL display device 100 is reduced, and the hue is neutralized.

From the viewpoint of neutralizing the hue, it is ideal that the reflected light of the organic EL display device has chromaticness indices a ^* and b ^* close to 0. On the other hand, when the reflected light from the front is a ^* ≒ 0, b ^* ≒ 0, the change in color due to the color shift of the reflected light in the diagonal direction is complicated, especially when a ^* < 0, b ^* > 0. In this case, the green coloring is strongly visible and visual perception is likely to be impaired.

In order to reduce the change in color (visual perception) even when a hue change occurs due to a color shift of reflected light in an oblique direction, the organic EL display device 100 includes a circularly polarizing plate 10 on the organic EL cell 70. The b ^* of the reflected light (reflected light from the front) is preferably −1.0 or less. b ^* of the reflected light of the organic EL display device may be -1.1 or less or -1.2 or less. If the b ^* of the reflected light is too small, the blue coloring will be strong and the visibility will be impaired, so the b ^* of the reflected light of the organic EL display device is preferably -3.0 or more, and -2.5 or more. More preferably, it may be -2.2 or more, -2.1 or more, or -2.0 or more. As described above, the larger T ₄₁₀ /T ₅₁₀ of the polarizer 11, the smaller the b ^* of the reflected light from the organic EL display device 100 tends to be.

From the viewpoint of suppressing green coloration of reflected light due to color shift, a ^* of reflected light of an organic EL display device is preferably 0 or more, and more preferably larger than 0. The a ^* of the reflected light may be 0.1 or more, 0.3 or more, 0.4 or more, or 0.5 or more. If the a ^* of the reflected light is too large, the red coloring will be strong and the visibility will be impaired, so the a ^* of the reflected light of the organic EL display device is preferably 2.5 or less, more preferably 2.2 or less. , 2.0 or less is more preferable, and may be 1.8 or less or 1.6 or less.

The organic EL display device may include any optical member in addition to the organic EL cell 70 and the circularly polarizing plate 10. For example, a hard coat layer, an antireflection layer, an antifouling layer, a surface protection layer (cover window), etc. may be provided on the viewing side surface of the circularly polarizing plate 10. Further, the organic EL display device may include a touch panel sensor. The touch panel sensor may be placed on the back surface of the organic EL cell 70, inside the organic EL cell 70, between the organic EL cell 70 and the circularly polarizing plate 10, or on the viewing side of the circularly polarizing plate 10.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these specific examples.

[Preparation of polarizing plate]
<Polarizing plate A>
One side of a 100 μm thick amorphous polyester film (polyethylene terephthalate/isophthalate; glass transition temperature 75° C.) was subjected to corona treatment. Polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified polyvinyl alcohol (Nippon Gosei Kagaku Kogyo "Gosefaimer Z410") were mixed at a weight ratio of 9:1 to 100 parts by weight of a resin. , and 13 parts by weight of potassium iodide were added to prepare a PVA aqueous solution. This aqueous solution was applied to the corona-treated surface of the amorphous polyester film and dried at 60° C. to produce a laminate in which a 13 μm thick PVA resin layer was provided on the amorphous polyester film base material.

This laminate was uniaxially stretched at the free end to 3.0 times in the longitudinal direction by aerial auxiliary stretching in an oven at 130°C, and then immersed in a 4% boric acid aqueous solution at 40°C for 30 seconds at 40°C while being conveyed by rolls. The specimens were sequentially immersed in a staining solution (0.2% iodine, 1.4% potassium iodide aqueous solution) for 60 seconds. Next, the laminate was immersed in a crosslinking solution (3% potassium iodide, 5% boric acid aqueous solution) at 40°C for 30 seconds while being conveyed by rolls for crosslinking treatment. While immersed in a 5% aqueous solution, the free end was uniaxially stretched in the longitudinal direction so that the total stretching ratio was 5.5 times. Thereafter, the laminate was immersed in a cleaning solution (4% potassium iodide aqueous solution) at 20°C.

The laminate was transported in an oven at 60° C. for 1 minute to dry. During this time, it was brought into contact with a SUS heating roll placed in an oven and having a surface temperature of 75° C. for about 2 seconds. Through the above steps, a laminate in which a PVA polarizer with a thickness of about 5 μm was provided on an amorphous polyester film base material was obtained.

The non-hard coat layer side of a triacetyl cellulose film (thickness: 32 μm), which had a hard coat layer formed on one side, was bonded to the polarizer side of the above laminate via an ultraviolet curable adhesive. Thereafter, the amorphous polyester film base material was peeled off from the polarizer to obtain a polarizing plate A in which a hard coat film was bonded to one side of the polarizer.

<Polarizing plate B>
The oven temperature when drying the polarizer (laminate) was changed from 60°C to 80°C. Other than that, a polarizing plate B in which a hard coat film was bonded to one side of a polarizer was obtained in the same manner as in the production of polarizing plate A.

[Orthogonal transmission spectrum of polarizing plate]
The orthogonal transmission spectra of the above polarizing plate A and polarizing plate B were measured using an ultraviolet-visible spectrophotometer ("V-7100" manufactured by JASCO Corporation). The spectrum is shown in Figure 2. The orthogonal transmittances T ₄₁₀ , T 470 , T 510 and T 600 of polarizing plate A and polarizing plate B at wavelengths of 410 nm, 470 _nm , _{510 nm} and _{600 nm} and their ratios were as shown in Table 1.

[Organic EL cell]
<Organic EL cell A>
As a reference example organic EL cell, a circularly polarizing plate attached to the surface of an organic EL cell of a Samsung smartphone (GALAXY S5) was removed.

<Organic EL cell B>
A decorative film in which a metal oxide thin film was formed on a hard coat film was prepared as a sample that simulated the reflected light of an organic EL cell. A polyethylene terephthalate (PET) film having a thickness of 50 μm and having a hard coat layer formed by UV curing of urethane acrylate resin on one side was set in a sputtering film forming apparatus. A Nb target (manufactured by Daido Steel Co., Ltd.) was attached to a sputtering film forming apparatus, and while introducing Ar gas and O ₂ gas, a 60 nm thick layer was deposited on the hard coat layer forming surface of the hard coat film by alternating current sputtering (AC: 40 Hz). A decorated film was obtained by forming a niobium oxide thin film.

[Reflection spectrum of organic EL cell]
For the above organic EL cell A and organic EL cell B, the reflection spectra were determined by making light incident at an incident angle of 8° and measuring the absolute reflectance in the wavelength range of 380 nm to 780 nm. The reflection spectrum is shown in Figure 3. The reflectances R ₄₁₀ and R 510 of organic EL cell A and organic EL cell B at wavelengths of 410 nm and ₅₁₀ nm and their ratios were as shown in Table 2.

[Reflection spectrum of organic EL display device]
The reflectance of each wavelength in the reflection spectrum of organic EL cell A was multiplied by the transmittance of each wavelength in the orthogonal transmission spectrum of polarizing plate A to obtain a reflection spectrum. This reflection spectrum corresponds to a pseudo reflection spectrum of an organic EL display device in which a circularly polarizing plate including the polarizing plate A is disposed on the surface of the organic EL cell A. Similarly, for the combination of organic EL cell B and polarizing plate A, and the combination of organic EL cell B and polarizing plate B, the pseudo reflection spectra were obtained by multiplying the reflectance of the organic EL cell by the orthogonal transmittance of the polarizing plate. . The respective pseudo reflection spectra are shown in FIG. For each organic EL cell and polarizing plate combination, the reflectances R ₄₁₀ and R ₅₁₀ at wavelengths of 410 nm and 510 nm, and their ratios were as shown in Table 3.

From FIG. 3 and Table 2, organic EL cell B has lower reflectance than organic EL cell A, and in particular, the decrease in reflectance in the wavelength region shorter than 500 nm is remarkable, so R ₄₁₀ /R ₅₁₀ is small, and the reflected light is colored yellow.

In this combination of organic EL cell B and polarizing plate A, R ₄₁₀ /R ₅₁₀ in the reflection spectrum was less than 2. In the combination of organic EL cell B and polarizing plate B with large T ₄₁₀ /T ₅₁₀ , R ₄₁₀ /R ₅₁₀ in the reflection spectrum is 4 or more, similar to the combination of organic EL cell A and polarizing plate A, and the reflected light It can be seen that b ^* has become smaller. In addition, as shown in Figure 4, the combination of organic EL cell B and polarizing plate B has a lower reflectance over a wide wavelength range of visible light than the combination of organic EL cell A and polarizing plate A, and the screen It can be seen that visibility is excellent.

10 circularly polarizing plate 11 polarizer 13 retardation layer 15 transparent film 21 adhesive layer 70 organic EL element (organic EL cell)
71 Substrate 73 Cathode (metal electrode)
75 Organic light emitting layer 77 Anode (transparent electrode)
79 Sealing material

Claims (5)

An organic EL display device comprising an organic EL element having an organic light emitting layer between a pair of electrodes, and a circularly polarizing plate disposed on a first principal surface of the organic EL element,
The circularly polarizing plate includes a polarizer and at least one retardation layer,
In the organic EL element, in the reflection spectrum for incident light from the first principal surface, a ratio R ₄₁₀ /R ₅₁₀ of a reflectance R ₄₁₀ at a wavelength of 410 nm to a reflectance R ₅₁₀ at a wavelength 510 nm is 0.6 or less,
The polarizer has a ratio T 410 /T 510 of an orthogonal transmittance T ₄₁₀ at a wavelength of 410 nm and an orthogonal transmittance T ₅₁₀ at a wavelength _{510 nm of} 7 or more.
Organic EL display device. The organic EL display device according to claim 1, wherein the organic EL element has a reflectance R ₄₁₀ of 35% or less at a wavelength of 410 nm in a reflection spectrum for incident light from the first principal surface. 3. The organic EL display device according to claim 1, wherein the organic EL element has a reflectance _R510 of 40% or more at a wavelength of 510 nm in a reflection spectrum for incident light from the first principal surface. 3. The organic EL display device according to claim 1, wherein a chromaticness index b ^* of the CIELAB color system of the reflected light from the circularly polarizing plate side is -1.0 or less. 3. The organic EL display device according to claim 1, wherein the chromaticness index a ^* of the CIELAB color system of the reflected light from the circularly polarizing plate side is 0 or more.

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