JP2011138144A - Electroluminescent (el) display device with touch panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EL display device with a touch panel capable of performing good display even under external light. <P>SOLUTION: The display device using an EL element is constituted by laminating a polarizing plate 111, wavelength plates 112, 113, a touch panel 120 and an EL display unit 130, in this order from the outside. The wavelength plates 112, 113 are composed of layers of a half-wavelength plate 112 and a quarter-wavelength plate 113. The touch panel 120 is constituted of transparent electrodes opposing through a space. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an EL (electroluminescence) display device having a touch panel as an input device.

  The EL element is a self-luminous element and is expected as a surface light source because the light emitting layer is thin. It has high visibility and has been put to practical use in backlights such as display elements and liquid crystal display devices.

  An organic EL element using an organic compound as a light-emitting material has been actively studied because of a significant decrease in applied voltage and a high degree of freedom in material design compared to an inorganic EL element using an inorganic compound as a light-emitting material. Various improvements have been made to use the organic EL element as a surface light source. Color display has become a practical stage due to the development of blue light emitting elements. For example, C.I. Adachi, S .; Tokyo, T .; Tsutsui, S .; Saito. , Jpn. J. et al. App1. Phy. , Vol. 27, L269 (1988) (Non-patent Document 1) reported a method of installing an electron transport layer such as phenylbiphenyloxadiazole between a light emitting layer and a cathode. Patent Document 1) proposes a method of obtaining white light by emitting three colors of RGB.

  P.P. Dyrek1ev et a1, Adv. Mater. , 8, 146 (1995), J. et al. H. Wendorff et al, Liquid Crystal 1, Vo 1.21, No. 1; 6,903 (1996) (Non-Patent Document 2) and the like have also proposed a method of obtaining polarized light emission by aligning an electroluminescent layer in one direction.

JP-A-7-90260

C. Adachi, S .; Tokyo, T .; Tsutsui, S .; Saito. , Jpn. J. et al. App1. Phy. , Vol. 27, L269 (1988) P. Dyrek1ev et a1, Adv. Mater. , 8, 146 (1995), J. et al. H. Wendorff et al, Liquid Crystal 1, Vo 1.21, No. 1; 6,903 (1996)

  Recently, a display device using the EL element is combined with a touch panel as an input / output device. The touch panel as the input / output device is generally formed by forming a transparent electrode on one side of a pair of transparent substrates and facing the transparent electrode inside. At this time, a transparent spacer for preventing adhesion may be formed between the transparent electrodes. In this case, a transparent conductive thin film such as indium tin oxide (ITO) is usually used as the transparent electrode, but its refractive index is about 2.0 or more. However, these transparent conductive films function as a touch panel and detect the position by contact, so that they are provided in direct contact with air. For example, the light reflectance is very large compared to the surface of the EL element panel. In addition, since it is used on the front surface of an EL display device, the number of interfaces is simply increased, and there is a problem that the display contrast of the EL element panel is greatly reduced by the light reflection.

  FIG. 3 is a cross-sectional view of a conventional EL display device with a touch panel. In the drawing, the touch panel portion 320 is formed of an upper touch panel transparent electrode 321, a lower touch panel transparent electrode 322, a spacer 323, an upper glass plate 324, and a lower glass plate 325. Further, the middle layer portion 310 is formed of a polarizing plate 311, a half-wave plate 312, and a quarter-wave plate 313. Further, the EL display unit 330 is formed of a glass transparent substrate 331, an ITO electrode 332, a hole transport layer 333, a fluorescent layer 334, a back electrode 335, and a moisture-proof film 336. The touch panel unit 320, the middle layer unit 310, and the EL display unit 330 constitute an EL display device 300 with a touch panel. In this conventional EL display device with a touch panel, since the touch panel portion 320 is on the surface layer portion, the external light α is strongly reflected as α1 and α2 by the touch panel portion 320 and strongly affects the display light β, making the display remarkably difficult to see. .

  Thus, attempts have been made to suppress surface reflection by applying antireflection treatment to the surface of the substrate or providing a low refractive index layer with a predetermined thickness under the transparent electrode, but it is possible to effectively suppress reflection. This led to an increase in cost.

  An object of the present invention is to provide an EL display device with a touch panel that realizes an easy-to-see display by suppressing glare and contrast reduction due to surface reflection that is light reflection of the touch panel.

  In order to solve the above-described problems, the EL display device with a touch panel of the present invention is a display device using an EL element, in which a polarizing plate, a wavelength plate, a touch panel, and an EL display unit are stacked in order from the outside. It is characterized by.

  In the EL display device with a touch panel of the present invention, it is preferable that the wavelength plate is a laminate of a half-wave plate and a quarter-wave plate.

  The EL display device with a touch panel according to the present invention provides a touch panel function by using a polarizing plate and a wave plate that are used for the EL display device to perform black display, such as a transparent electrode used for the touch panel. The reflection at the interface can be remarkably reduced by the combination of the polarizing plate and the two kinds of wave plates, and the resulting reduction in contrast and glare does not occur, thereby eliminating the deterioration in display quality. Further, since no special component is used for the component of the present invention, the weight can be reduced and the thickness can be reduced at the same time.

  In the EL display device with a touch panel of the present invention, it is preferable that the touch panel is formed of transparent electrodes facing each other through a space portion.

  The upper electrode of the touch panel of the present invention may be directly formed on the wave plate, or may be an optically isotropic film formed on a film having a retardation value of 30 nm or less and bonded with an adhesive or an adhesive. good. Also, the lower electrode is not particularly limited, but a conductive thin film is formed on a glass plate or a plastic plate used for an EL substrate, or a glass plate or an electrode is formed on another film. It may be bonded to a plastic substrate with an adhesive or the like.

  In the EL display device with a touch panel of the present invention, the wavelength plate is formed by laminating a half-wave plate and a quarter-wave plate in order from the outside, and the optical axis of the polarizing plate and the half wavelength Assuming that the angle of the slow axis of the plate is θ, θ is 15 ° ± 5 °, and the angle of the optical axis of the polarizing plate and the slow axis of the quarter wave plate is (2θ + 45 °) ± 10 °. Preferably there is.

  In the EL display device with a touch panel of the present invention, the wavelength plate is formed by laminating a quarter-wave plate and a half-wave plate in order from the outside, and the optical axis and the quarter wavelength of the polarizing plate. If the angle of the slow axis of the plate is θ, θ is 45 ° ± 5 °, and the angle of the slow axis of the quarter-wave plate and the slow axis of the half-wave plate is 90 ° ± 10 °. It is preferable that

  The material of the half-wave plate and the quarter-wave plate of the present invention is not particularly limited and is preferably excellent in transparency. For example, a polycarbonate polymer, a polyester polymer, a polysulfone polymer, a polysulfone polymer, Examples include ether polymers, polystyrene polymers, polyolefin polymers, polyvinyl alcohol polymers, cellulose acetate polymers, polyvinyl chloride polymers, polymethyl methacrylate polymers, norbornene polymers.

However, when the wave plate is formed by laminating a polarizing plate, a quarter wave plate, and a half wave plate in order from the outside, the thickness of the wave plate is d, and the wavelength of light λ = 550 nm. Where the refractive index of the half-wave plate is n ₅₅₀ and the refractive index of the light wavelength λ = 400 nm is n ₄₀₀ , the phase difference ratio Δn ₄₀₀ d / Δn ₅₅₀ d of the half-wave plate is It is preferable that the phase difference ratio is smaller than Δn ₄₀₀ d / Δn ₅₅₀ d. That is, the half-wave plate is preferably low in wavelength dispersion (small refractive index difference at each wavelength), and the quarter-wave plate is preferably high in wavelength dispersion.

Specifically, when the thickness of the wave plate is d, the refractive index at the light wavelength λ = 550 nm is n ₅₅₀ , and the refractive index at the light wavelength λ = 400 nm is n ₄₀₀ , The ratio Δn ₄₀₀ d / Δn ₅₅₀ d of the phase difference is preferably 1.1 or less. For example, in the case of a norbornene polymer, a product having a ratio of 1.03 is commercially available. The phase difference ratio Δn ₄₀₀ d / Δn ₅₅₀ d of the quarter-wave plate is preferably 1.1 or more. For example, a polycarbonate-based product of 1.16 and a polysulfone-based product of 1.2 are commercially available. . In this way, when the polarizing plate, the quarter wavelength plate, and the half wavelength plate are sequentially formed from the outside, the phase difference at each wavelength is obtained by laminating the slow axes having different phase differences. Can be superimposed or adjusted, and a predetermined phase difference can be obtained over a wide wavelength range, so that ideal circularly polarized light can be created.

  There is no particular limitation on the stretching of the quarter-wave plate and the half-wave plate, but free-end uniaxial stretching, fixed-end uniaxial stretching, biaxial stretching, for example, the thickness direction stretching described in Japanese Patent No. 2818983 is used. Can do. Further, the half-wave plate and the quarter-wave plate may not be a stretched film, but may be a substrate coated with an alignment film such as a polymer liquid crystal. Further, an inorganic crystal may be used.

  Moreover, the polarizing plate used for this invention is not specifically limited. For example, a polarizing film obtained by stretching and orienting a normal dichroic substance-containing polyvinyl alcohol film is preferably used. Moreover, what uses the polarizing element by a liquid crystal polymer may be used. Higher transmittance is preferable because a brighter display can be obtained.

  In the present invention, the polarizing plate, the wave plate, the touch panel, and the EL display unit are laminated in order from the outside as described below. Further, an EL display device with a touch panel that can perform good display even when there is external light can be provided, and its industrial value is great.

It is sectional drawing of Embodiment 1 of EL display apparatus with a touch panel of this invention. It is sectional drawing of Embodiment 2 of EL display apparatus with a touchscreen of this invention. It is sectional drawing of the conventional EL display apparatus with a touch panel.

  Embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 shows a cross-sectional view of Embodiment 1 of an EL display device with a touch panel according to the present invention. FIG. 1 shows an example of an organic EL display device. In FIG. 1, reference numeral 100 denotes an EL display device with a touch panel of the present invention. In the figure, 111 is a polarizing plate, 112 is a half-wave plate, and 113 is a quarter-wave plate from the outermost surface, and these are laminated to form the surface layer portion 110. Next, 121 is an upper touch panel transparent electrode made of an ITO conductive film, 122 is a lower touch panel transparent electrode made of an ITO conductive film, and a touch panel portion 120 is formed by arranging a spacer 123 therebetween. . Further, 131 is a transparent glass substrate, 132 is an ITO electrode, 133 is N, N′-diphenyl-N, N′-bis- (3-methylphenyl)-(1,1′-biphenyl) -4,4 ′. A hole transport layer composed of diamine (hereinafter referred to as TPD), 134 a fluorescent layer composed of tris (8-quinolinol) aluminum (hereinafter referred to as A1q), 135 a back electrode, 136 a moisture-proof film, A display unit 130 is formed. The EL display device 100 with a touch panel is formed by combining the surface layer part 110, the touch panel part 120, and the EL display part 130. As the back electrode 135, a metal thin film layer such as a silver magnesium alloy is preferably used.

  Since a metal thin film having a high reflectance is generally used for the back electrode, it is difficult to obtain a good black display by strongly reflecting external light other than during light emission. Therefore, by combining a polarizing plate, a half-wave plate, and a quarter-wave plate and installing them on the surface of the EL display device in this order from the outside, this external light reflection can be remarkably prevented.

  In FIG. 1, when external light α is incident on the EL display device 100, the external light α becomes linearly polarized light due to absorption by the outer polarizing plate 111 and passes through the half-wave plate 112 and the quarter-wave plate 113. It is converted into almost perfect circularly polarized light. Since the back electrode 135 of the EL display device functions as a light reflection layer, the circularly polarized light is inverted by the reflection, and is reflected as circularly polarized light having the opposite phase. At that time, when the light passes through the quarter-wave plate 113 and the half-wave plate 112, it becomes linearly polarized light in a direction orthogonal to the transmission direction of the polarizing plate 111, so that most of the reflected light α3 is absorbed by the polarizing plate 111. Is done. Moreover, the reflected lights α1 and α2 from the electrode surface of the touch panel unit 120 are already circularly polarized light by the polarizing plate and the two wave plates. Therefore, similarly, the reflected light α1 and α2 that have reached the two wave plates and the polarizing plate are linearly polarized light, but are absorbed by the polarizing plate 111 because the optical axis of the polarizing plate 111 has a 90 ° phase. Will be. Accordingly, the reflected lights α1 and α2 are hardly observed from the outside. Thus, since the external light α is not generated except for reflection on the surface of the polarizing plate 111, a good black state can be formed. Therefore, only the EL element light emitting portion can be substantially used as the display light β. As for the polarization inversion on the reflection surface of the circularly polarized light, the better the circularly polarized light, the more effective. In general, the phase difference of a quarter-wave plate has wavelength dispersion that can be approximated by Cauchy's dispersion formula, so that it does not become good circularly polarized light at all wavelengths. In order to improve this, as shown in Japanese Patent Laid-Open No. 5-100114, by providing a combination of a quarter wavelength plate and a half wavelength plate, good circularly polarized light can be obtained in most visible light wavelength regions. it can. In this case, there are a method of providing the slow axis of the quarter-wave plate at a different angle, a method of using a film having a different wavelength dispersion, or a method of using these in combination.

(Embodiment 2)
FIG. 2 shows a cross-sectional view of Embodiment 2 of the EL display device with a touch panel of the present invention. FIG. 2 also shows an example of an organic EL display device. In FIG. 2, reference numeral 200 denotes an EL display device with a touch panel according to the present invention. In the figure, 211 is a polarizing plate, 214 is a quarter-wave plate, and 212 is a half-wave plate from the outermost surface, and these are laminated to form the surface layer portion 210. Next, 221 is an upper touch panel transparent electrode made of an ITO conductive film, 222 is a lower touch panel transparent electrode made of an ITO conductive film, and a touch panel portion 220 is formed by arranging a spacer 223 therebetween. . Further, 231 is a glass transparent substrate, 232 is an ITO electrode, 233 is a hole transport layer made of TPD, 234 is a fluorescent layer made of A1q, 235 is a back electrode, 236 is a moisture-proof film, and these are the EL display unit 230. Is formed. An EL display device 200 with a touch panel is formed by combining the surface layer part 210, the touch panel part 220, and the EL display part 230. As the back electrode 235, a metal thin film layer such as a silver magnesium alloy is preferably used.

(Example 1)
A 75 μm-thick polyvinyl alcohol film was treated with iodine, and uniaxially stretched under conditions of a stretching temperature of 60 ° C. and a stretching ratio of 6.0 times to obtain a polarizing plate. Next, a norbornene-based polymer film having a thickness of 100 μm is uniaxially stretched at a stretching temperature of 170 ° C. and a stretching ratio of 1.7 times, and a phase difference of ½ wavelength is obtained for light having a wavelength of 550 nm based on birefringent light. A half-wave plate was obtained. Further, a 1/4 wavelength plate that gives a phase difference of 1/4 wavelength to light having a wavelength of 550 nm by subjecting a norbornene-based polymer film having a thickness of 50 μm to a uniaxial stretching process at a stretching temperature of 170 ° C. and a draw ratio of 1.7 times. Got.

  The quarter-wave plate obtained above was subjected to plasma treatment in an Ar atmosphere, an ITO thin film was formed by sputtering, and a transparent electrode substrate for the upper touch panel was produced.

  Next, after cutting out the glass substrate into a predetermined shape, plasma treatment was performed in an Ar atmosphere, and an ITO thin film having a thickness of 100 nm was formed by sputtering to produce an EL panel substrate. In advance, the transparent electrode of one substrate is divided into two by etching.

Similarly, a 25 nm thick ITO thin film was formed by sputtering on the opposite surface of the glass substrate as a transparent electrode for the lower touch panel. After this glass substrate was subjected to ultrasonic cleaning and ultraviolet ozone cleaning, it was placed in a resistance heating type vacuum vapor deposition device, TPD was placed in a molybdenum heating boat disposed in the device, and Alqq was placed in another molybdenum resistance heating boat. And the pressure inside the vacuum chamber was reduced to 1 × 10 ⁻⁴ Pa.

Next, a TPD resistance heating boat was heated to 220 ° C. and deposited on a 100 μm ITO thin film on the glass substrate to form a 60 nm-thick hole transport layer. Subsequently, the resistance heating boat containing Alq was heated to 275 ° C., and Alq was deposited on the hole transport layer to form an Alq layer having a thickness of 60 nm. Next, put magnesium in a resistance heating boat made of molybdenum, put silver in another resistance heating boat made of molybdenum, depressurize the inside of the vacuum chamber to 2 × 10 ^-4 Pa, and simultaneously use magnesium and silver alloy electrodes in two elements A back electrode was formed by vapor deposition to a film thickness of 140 nm by a vapor deposition method. The atomic ratio of magnesium and silver was 9: 1. All depositions were held such that the substrate temperature was room temperature. Further, this deposited film is divided into two in advance by masking.

  In this way, an EL display unit was created. The obtained EL display portion emitted green light (main wavelength 513 nm).

  Next, after printing the silver electrode on the ITO surface of the transparent electrode for the upper and lower touch panels, the electrode side of the transparent conductive film is arranged facing the spacer through the spacer, and the half-wave plate is delayed with respect to the optical axis of the polarizing plate. A bonded touch panel was prepared so that the phase axis was 15 ° and the slow axis of the quarter-wave plate was 75 °, and an EL display device with a touch panel was prepared.

(Example 2)
The order in which the wave plates of Example 1 are laminated is changed from the outside to a quarter wave plate and a half wave plate, and the quarter wave plate is formed from a polycarbonate film having a thickness of 50 μm at a drawing temperature of 150 ° C. and a draw ratio. The film was stretched at a magnification of 1.05, and changed to give a phase difference of ¼ wavelength with respect to light having a wavelength of 550 nm based on birefringent light. At that time, the slow axis of the quarter wavelength plate is 45 ° with respect to the optical axis of the polarizing plate, and the slow axis of the half wavelength plate is 90 ° with respect to the slow axis of the quarter wavelength plate. Adjust as follows. In Example 1, the transparent electrode for the upper touch panel was formed by sputtering an ITO thin film on a quarter-wave plate, but in Example 2, it was formed in the same manner on the half-wave plate. Otherwise, an EL display device with a touch panel was prepared in the same manner as in Example 1.

(Comparative Example 1)
In the same manner as in Example 1, a polarizing plate, a wave plate, and an EL display unit were sequentially laminated from the outside. A transparent electrode made of an ITO thin film printed with a silver paste and a polyethylene terephthalate (PET) film is attached to the glass plate via an adhesive from the outside, and the two glass plates are transparent via a spacer. A touch panel was created by placing the electrodes facing each other, and an EL display device with a touch panel was created.

(Evaluation test)
As a light source, one fluorescent lamp was arranged at an interval of 1 m from the panel so as to be 20 ° from the front of the panel. An electric field was applied to one of the two divided electrodes to display half of the green light emitting portion, and the display state was observed and compared.

  First, when the touch panel part was removed and observed, all of Examples 1, 2 and Comparative Example 1 were able to perform good display at a level that would not be a problem.

  Next, the touch panel part was attached and observed. As a result, in Example 1 and Example 2, the display state did not change at all and was good. However, in Comparative Example 1, the reflection of the fluorescent lamp on the touch panel was particularly large in the vicinity of regular reflection, and the black light was particularly disturbed by the reflected light, which was very difficult to see. Even when the viewpoint was removed from the specular reflection direction, it was very difficult to see because of the reflection of the observer's face. In Examples 1 and 2, the light emitting part was very good because a green display was observed very clearly. Further, in Examples 1 and 2, reflected light that was thought to be caused by the touch panel could be effectively prevented, and even with regular reflection, only the reflection of the antireflection film on the panel surface was visible, and the display quality was good.

  The touch panel functioned without any problem in all of Example 1, Example 2, and Comparative Example 1.

DESCRIPTION OF SYMBOLS 100 EL display device with a touch panel 110 Surface layer part 111 Polarizing plate 112 1/2 wavelength plate 113 1/4 wavelength plate 120 Touch panel part 121 Transparent electrode for upper touch panel 122 Transparent electrode for lower touch panel 123 Spacer 130 EL display part 131 Glass transparent base Material 132 ITO electrode 133 Hole transport layer 134 Fluorescent layer 135 Back electrode 136 Moisture-proof film

Claims (6)

  An EL display device with a touch panel, comprising an EL element, wherein a polarizing plate, a wavelength plate, a touch panel, and an EL display unit are stacked in order from the outside.   The touch panel-equipped EL display device according to claim 1, wherein the wave plate is a laminate of a half-wave plate and a quarter-wave plate.   An EL display device with a touch panel, wherein the touch panel is formed of transparent electrodes facing each other through a space.   The wave plate is formed by laminating a half-wave plate and a quarter-wave plate in order from the outside, and the angle between the optical axis of the polarizing plate and the slow axis of the half-wave plate is θ, 2. The EL display device with a touch panel according to claim 1, wherein θ is 15 ° ± 5 °, and an angle between an optical axis of the polarizing plate and a slow axis of the quarter-wave plate is (2θ + 45 °) ± 10 °. .   The wave plate is formed by laminating a quarter wave plate and a half wave plate in order from the outside, and the angle between the optical axis of the polarizing plate and the slow axis of the quarter wave plate is θ, 2. The EL display with a touch panel according to claim 1, wherein θ is 45 ° ± 5 °, and an angle between a slow axis of the quarter-wave plate and a slow axis of the half-wave plate is 90 ° ± 10 °. apparatus. When the thickness of the wave plate is d, the refractive index of the light wavelength λ = 550 nm is n ₅₅₀ , and the refractive index of the light wavelength λ = 400 nm is n ₄₀₀ , the phase difference ratio Δn of the half-wave plate ₄₀₀ d / △ n ₅₅₀ d is 1/4-wave plate retardation ratio _{△ n 400 d / △ n 550} d less than with a touch EL display device according to claim 5.

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