JP2007027043A - Organic el display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL display device sufficiently restrained from deterioration caused by irradiation of external light. <P>SOLUTION: The organic EL display device has organic EL element OLEDs and a ultraviolet-ray shielding layer MFL of which transmissivity of visible light at wave length of 418 nm or shorter is not more than 3%, and that from 450 nm to 770 nm is not less than 40%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an organic electroluminescence (EL) display device.

  In an electronic device equipped with an organic EL display device, a polarizing plate may be disposed on the front side of the display panel. Many of these polarizing plates have an ultraviolet blocking function, and therefore play a role of suppressing deterioration of the organic EL element due to ultraviolet irradiation. However, even if such a polarizing plate is disposed on the front side of the organic EL display panel, deterioration of the organic EL element due to external light irradiation cannot be sufficiently suppressed.

  An object of the present invention is to sufficiently suppress deterioration of an organic EL element due to external light irradiation.

  According to the first aspect of the present invention, the organic EL element is disposed on the front side thereof, and the transmittance for visible light is 3% or less at each wavelength of 418 nm or less and 40% at each wavelength of 450 nm to 770 nm. An organic EL display device comprising the ultraviolet blocking layer as described above is provided.

According to a second aspect of the present invention, an organic EL element, the ratio between the transmittance T ₄₅₀ for light transmittance T ₄₁₈ and wavelength 450nm for the light wavelength of 418nm while being disposed on the front surface side T ₄₁₈ An organic EL display device comprising an ultraviolet blocking layer having / T ₄₅₀ of 0.1 or less is provided.

According to the third aspect of the present invention, the organic EL element and the light that is disposed on the front side thereof and has a maximum transmittance T _max and a wavelength in the range of 450 nm to 770 nm for visible light having a wavelength of 418 nm or less. There is provided an organic EL display device comprising an ultraviolet blocking layer having a ratio T _max / T _min of 0.1 or less to the minimum value T _min of the transmittance for the above.

  According to the present invention, it is possible to sufficiently suppress deterioration of an organic EL element due to external light irradiation.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same referential mark is attached | subjected to the component which exhibits the same or similar function, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a plan view schematically showing a display device according to one embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing an example of a structure that can be employed in the display device of FIG. In FIG. 2, the display device is drawn such that its display surface, that is, the front surface or the light emitting surface faces downward, and the back surface faces upward.

  The display device in FIGS. 1 and 2 is a bottom emission organic EL display device that employs an active matrix drive system. This organic EL display device includes a display panel DP, a video signal line driver XDR, a scanning signal line driver YDR, and a multilayer film MLF.

  The display panel DP includes an array substrate AS, a sealing substrate CS, and a seal layer SS interposed therebetween. The array substrate AS and the sealing substrate CS face each other. The seal layer SS has a frame shape, and forms a sealed space between the array substrate AS and the sealing substrate CS. This sealed space is filled with an inert gas.

The array substrate AS includes, for example, an insulating substrate SUB such as a glass substrate.
On the substrate SUB, as shown in FIG. 2, for example, a SiN _x layer and a SiO _x layer are sequentially stacked as the undercoat layer UC.

  On the undercoat layer UC, for example, a semiconductor layer SC which is a polysilicon layer in which a channel and a source / drain are formed, a gate insulating film GI which can be formed using, for example, TEOS (tetraethyl orthosilicate), and a MoW, for example, The gates G are sequentially stacked, and they constitute a top gate type thin film transistor which is a field effect transistor. In this example, these thin film transistors are p-channel thin film transistors and are used as the drive control element DR and the switches SWa to SWc in FIG.

  On the gate insulating film GI, scanning signal lines SL1 and SL2 shown in FIG. 1 and a lower electrode (not shown) are further arranged. The scanning signal lines SL1 and SL2 and the lower electrode can be formed in the same process as the gate G.

  As shown in FIG. 1, the scanning signal lines SL1 and SL2 each extend in the row direction (X direction) of the pixels PX, and are alternately arranged in the column direction (Y direction) of the pixels PX. These scanning signal lines SL1 and SL2 are connected to the scanning signal line driver YDR.

  The lower electrode is connected to the gate of the drive control element DR. The lower electrode is used as one electrode of a capacitor C described later.

The gate insulating film GI, the gate G, the scanning signal lines SL1 and SL2, and the lower electrode are covered with an interlayer insulating film II shown in FIG. The interlayer insulating film II is made of, for example, SiO _x formed by a plasma CVD method or the like. A portion of the interlayer insulating film II on the lower electrode is used as a dielectric layer of the capacitor C.

  On the interlayer insulating film II, the source electrode SE and the drain electrode DE shown in FIG. 2, the video signal line DL and the power supply line PSL shown in FIG. 1, and an upper electrode (not shown) are arranged. These can be formed in the same process and have, for example, a three-layer structure of Mo / Al / Mo.

  The source electrode SE and drain electrode DE are electrically connected to the source and drain of the thin film transistor through contact holes provided in the interlayer insulating film II.

  As shown in FIG. 1, each video signal line DL extends in the Y direction and is arranged in the X direction. One end of each of the video signal lines DL is connected to the video signal line driver XDR.

  In this example, the power supply lines PSL extend in the Y direction and are arranged in the X direction. In this example, the power supply line PSL is connected to the video signal line driver XDR.

  The upper electrode is connected to the power supply line PSL. The upper electrode is used as the other electrode of the capacitor C.

The source electrode SE, the drain electrode DE, the video signal line DL, the power supply line PSL, and the upper electrode are covered with a passivation film PS. The passivation film PS is made of, for example, SiN _x .

  On the passivation film PS, a light transmissive pixel electrode PE is formed as a front electrode. The pixel electrode PE is connected to the drain electrode DE of the switch SWa through a through hole provided in the passivation film PS.

  The pixel electrode PE is an anode in this example. As a material of the pixel electrode PE, for example, a transparent conductive oxide such as ITO (indium tin oxide) can be used.

  A partition insulating layer PI shown in FIG. 2 is further formed on the passivation film PS. In the partition insulating layer PI, a through hole is provided at a position corresponding to the pixel electrode PE, or a slit is provided at a position corresponding to a column or row formed by the pixel electrode PE. Here, as an example, the partition insulating layer PI is provided with a through hole at a position corresponding to the pixel electrode PE.

  The partition insulating layer PI is, for example, an organic insulating layer. The partition insulating layer PI can be formed using, for example, a photolithography technique.

  On the pixel electrode PE, an organic layer ORG including a light emitting layer as an active layer is disposed. A light emitting layer is a thin film containing the luminescent organic compound whose luminescent color is blue, green, or red, for example. The organic layer ORG can further include a hole injection layer, a hole transport layer, a hole blocking layer, an electron transport layer, an electron injection layer, and the like in addition to the light emitting layer.

  As shown in FIG. 2, the partition insulating layer PI and the organic layer ORG are covered with a counter electrode CE which is a back electrode. The counter electrode CE is a common electrode connected to each other between the pixels PX. In this example, the counter electrode CE is a light reflective cathode made of aluminum, for example. The counter electrode CE is electrically connected to an electrode wiring (not shown) formed on the same layer as the video signal line DL through, for example, a contact hole provided in the passivation film PS and the partition insulating layer PI. It is connected. Each organic EL element OLED includes a pixel electrode PE, an organic layer ORG, and a counter electrode CE.

  In this example, the pixel circuit included in each pixel PX includes a drive control element (drive transistor) DR, an output control switch SWa, a video signal supply control switch SWb, a diode connection switch SWc, and a capacitor C. Yes. As described above, in this example, the drive control element DR and the switches SWa to SWc are p-channel thin film transistors. In this example, the video signal supply control switch SWb and the diode connection switch SWc are connected to each other in the connection state between the drain of the drive control element DR, the video signal line DL, and the gate of the drive control element DR. The switch group which switches between a 1st state and the 2nd state from which they were interrupted | blocked from each other is comprised.

  The drive control element DR, the output control switch SWa, and the organic EL element OLED are connected in series in this order between the first power supply terminal ND1 and the second power supply terminal ND2. In this example, the first power supply terminal ND1 is a high potential power supply terminal, and the second power supply terminal ND2 is a low potential power supply terminal.

  The gate of the output control switch SWa is connected to the scanning signal line SL1. The video signal supply control switch SWb is connected between the video signal line DL and the drain of the drive control element DR, and its gate is connected to the scanning signal line SL2. The diode connection switch SWc is connected between the gate and the drain of the drive control element DR, and the gate is connected to the scanning signal line SL2.

  The capacitor C is connected between the gate of the drive control element DR and the constant potential terminal ND1 '. The constant potential terminal ND1 'is connected to the first power supply terminal ND1, for example.

  In this example, the video signal line driver XDR and the scanning signal line driver YDR are arranged on the array substrate AS. That is, in this example, the video signal line driver XDR and the scanning signal line driver YDR are mounted on a COG (chip on glass). The video signal line driver XDR and the scanning signal line driver YDR may be mounted by TCP (tape carrier package) instead of COG mounting.

  The multilayer film MLF is attached to the front surface of the display panel DP. The multilayer film MLF is an ultraviolet blocking layer having a function as a polarizing filter.

  FIG. 3 is a cross-sectional view schematically showing an example of a multilayer film that can be used in the organic EL display device of FIGS. 1 and 2. The multilayer film MLF includes a retardation film RTD, an adhesive layer AD1, a polarizing plate PLZ, a hard resin layer HR, an ultraviolet absorption layer UVA, and an antireflection layer AR. The multilayer film MLF is disposed so that the retardation plate RTD faces the substrate SUB, and is attached to the array substrate AS via the adhesive layer AD2. The polarizing plate PLZ and the ultraviolet absorbing layer UVA may be laminated in the reverse order shown in FIG.

  The multilayer film MLF blocks not only ultraviolet rays but also rays having a short wavelength among visible rays. Typically, this optical property is mainly provided by the UV absorbing layer UVA.

  As the ultraviolet absorption layer UVA, for example, an organic polymer film in which ultrafine particles made of a metal oxide are supported can be used. For example, as the ultraviolet absorbing layer UVA, a polyethylene terephthalate film in which ultra fine particles made of ATO (antimony tin oxide) or ITO (indium tin oxide) are dispersed can be used. Further, instead of the ultraviolet absorption layer UVA, an interference filter made of a dielectric multilayer film can be used.

  When an image is displayed on this organic EL display device, for example, each of the scanning signal lines SL1 and SL2 is line-sequentially driven. In the writing period in which the video signal is written to the pixels PX in a certain row, first, the scanning signal line driver YDR opens the switch SWa to the scanning signal line SL1 to which the previous pixel PX is connected (OFF). A voltage signal is output, and subsequently, a scan signal that closes the switches SWb and SWc (ON) is output as a voltage signal to the scan signal line SL2 to which the previous pixel PX is connected. In this state, the video signal line driver XDR outputs the video signal as a current signal to the video signal line DL to which the previous pixel PX is connected, and the gate-source voltage of the drive control element DR is changed to the previous video signal. Set to a size corresponding to. Thereafter, the scanning signal line driver YDR outputs a scanning signal as a voltage signal that opens (OFF) the switches SWb and SWc to the scanning signal line SL2 to which the previous pixel PX is connected, and then the previous pixel PX is connected. The scanning signal line SL1 closes the switch SWa (ON) and outputs a scanning signal as a voltage signal.

  In the effective display period in which the switch SWa is closed (ON), a drive current having a magnitude corresponding to the gate-source voltage of the drive control element DR flows through the organic EL element OLED. The organic EL element OLED emits light with a luminance corresponding to the magnitude of the drive current.

  Now, the multilayer film MLF used in this organic EL display device blocks not only ultraviolet rays but also rays having a short wavelength among visible rays. For this reason, it is possible to sufficiently suppress the deterioration of the organic EL element OLED due to irradiation with external light such as sunlight. This will be described in detail below.

FIG. 4 is a graph illustrating an example of the optical characteristics of the organic layer included in the organic EL element. In the figure, the horizontal axis indicates the wavelength, and the vertical axis indicates the refractive index and the extinction coefficient. A curve C _n indicates the refractive index of the organic layer ORG, and a curve C _k indicates the extinction coefficient of the organic layer ORG.

  As shown in FIG. 4, the organic material layer ORG of the organic EL element OLED has an absorption peak in the ultraviolet region having a wavelength of 400 nm or less. However, the organic layer ORG does not absorb only ultraviolet rays but also absorbs light rays having a short wavelength among visible rays having a wavelength longer than 400 nm. Therefore, even if only ultraviolet rays are blocked, deterioration due to external light irradiation of the organic EL element OLED cannot be sufficiently suppressed.

  On the other hand, as described above, the multilayer film MLF blocks not only ultraviolet rays but also rays having a short wavelength among visible rays. Therefore, deterioration due to external light irradiation of the organic EL element OLED can be sufficiently suppressed.

  When visible light having a wavelength of 450 nm or more is blocked, deterioration of the organic EL element OLED due to external light irradiation can be almost completely prevented by blocking light having a wavelength of about 500 nm or less. However, in this case, the color reproducibility becomes insufficient. Therefore, the multilayer film MLF is designed to transmit visible light having a wavelength of 450 nm or more, and is designed to transmit visible light having a wavelength of 430 nm or more when higher color reproducibility is required.

  FIG. 5 is a graph showing an example of optical characteristics of a multilayer film that can be used in the organic EL display device of FIGS. 1 and 2. FIG. 6 is an enlarged graph showing a part of FIG. 5 and 6, the horizontal axis indicates the wavelength, and the vertical axis indicates the transmittance.

5 and 6, a curve C ₁ shows the transmittance of the multilayer film MLF having the structure of FIG. Here, a polycarbonate layer is used as the hard resin layer HR, an ultra-fine particle composed of ATO is dispersed on a polyethylene terephthalate film as the ultraviolet absorbing layer UVA, and an SiO ₂ layer and TiO ₂ are used as the antireflection layer AR. A laminate with layers is used. A curve C ₂ indicates the transmittance of the multilayer film MLF from which the ultraviolet absorbing layer UVA is omitted. Curve C ₃ shows the transmittance of the multilayer film MLF from which the ultraviolet absorbing layer UVA and the antireflection layer AR are omitted.

As indicated by the curve C ₁ , this multilayer film MLF has a transmittance for ultraviolet rays of 0%, and a transmittance for visible light of 0% at each wavelength of 418 nm or less. Considering that the maximum measurement error is 2 to 3%, this multilayer film MLF has a transmittance for ultraviolet rays of 3% or less and a transmittance for visible light of 418 nm or less at each wavelength. 3% or less. The multilayer film MLF has a visible light transmittance of 10% or more at each wavelength of 420 nm or more, and 40% or more at each wavelength of 450 nm to 770 nm.

That is, this multilayer film MLF has a small ratio between the transmittance for visible light having a wavelength close to that of ultraviolet light and the transmittance for visible light having other wavelengths. For example, the multilayer film MLF, the ratio T ₄₁₈ / T ₄₅₀ between the transmittance T ₄₅₀ for light transmittance T ₄₁₈ and wavelength 450nm for the light having a wavelength of 418nm is 0.1 or less. Further, the multilayer film MLF, the ratio T _max between the minimum value T _min of the transmittance for light maximum value T _max and the wavelength of the transmittance of the wavelength for the following visible light 418nm is within the range of 450nm to 770nm / T _min is 0.1 or less.

On the other hand, if the ultraviolet absorbing layer UVA or the like is omitted from the multilayer film MLF, the transmittance for visible light exceeds 10% at each wavelength of 410 nm or more, as is apparent from the curves C ₂ and C _3. . Thus, if the ultraviolet absorbing layer UVA is omitted from the previous multilayer film MLF, the transmittance as shown by the curve C ₁ cannot be realized.

The following light resistance test was performed in order to investigate the influence of the difference in optical characteristics on the light resistance characteristics of the organic EL display device. That is, the organic EL display device was continuously lit while irradiating the display surface with light, and the luminance was measured at regular intervals. Here, a sunshine carbon arc was used as the light source, the temperature was controlled at about 63 ° C., and the relative humidity was controlled at about 30 to about 70%. Further, the irradiation illuminance with respect to light having a wavelength of 300 to 700 nm was set to 255 W / m ² . Under this condition, continuing the test for 360 hours corresponds to the fact that 15 years have passed since the display device was installed in the car.

  7 to 10 are graphs showing the light resistance characteristics of the organic EL display device. FIG. 7 shows data obtained when a white image is displayed on the organic EL display device. FIG. 8 shows data obtained when a blue image is displayed on the organic EL display device. FIG. 9 shows data obtained when a green image is displayed on the organic EL display device. FIG. 10 shows data obtained when a red image is displayed on the organic EL display device.

7 to 10, the horizontal axis represents the elapsed time from the start of the light resistance test, and the vertical axis represents the relative luminance with reference to the initial luminance. Curve C _A shows data in the case of using the multilayer film MLF having optical properties represented by the curve C ₁ in FIGS. On the other hand, the curve C _B, instead of the multilayer film MLF, shows data in the case of using the film having optical properties represented by the curve C ₂ in FIGS.

As it is apparent from a comparison between curves C _A and the curve C _B, in the case of using the multilayer film MLF containing the ultraviolet absorbing layer UVA could be sufficiently suppressed a decrease in relative brightness. That is, when the multilayer film MLF including the ultraviolet absorbing layer UVA is used, excellent light resistance can be realized.

  In addition, by disposing the ultraviolet shielding layer UVA on the outside of the panel, it is possible to suppress the influence of heat absorbed in the ultraviolet shielding layer UVA on the organic EL element OLED. Therefore, it is possible to realize a display device having a longer life compared to the case where the ultraviolet shielding layer UVA is provided inside the panel.

  In this embodiment, the present invention is applied to a bottom emission type organic EL display device, but the present invention is also applicable to a top emission type organic EL display device. Further, in this aspect, the configuration in which the current signal is written as the video signal in the pixel circuit is adopted, but the configuration in which the voltage signal is written in the pixel circuit as the video signal may be employed.

The top view which shows schematically the display apparatus which concerns on 1 aspect of this invention of this invention. FIG. 2 is a cross-sectional view schematically illustrating an example of a structure that can be employed in the display device of FIG. 1. Sectional drawing which shows roughly an example of the multilayer film which can be used with the organic electroluminescence display of FIG.1 and FIG.2. The graph which shows an example of the optical characteristic of the organic substance layer which an organic EL element contains. The graph which shows an example of the optical characteristic of the multilayer film which can be used with the organic electroluminescence display of FIG.1 and FIG.2. The graph which expands and shows a part of FIG. The graph which shows the light resistance characteristic of an organic electroluminescence display. The graph which shows the light resistance characteristic of an organic electroluminescence display. The graph which shows the light resistance characteristic of an organic electroluminescence display. The graph which shows the light resistance characteristic of an organic electroluminescence display.

Explanation of symbols

AD1 ... adhesive layer, AD2 ... adhesive layer, AR ... antireflection layer, AS ... array substrate, C ... capacitors, C ₁ ... transmittance, C ₂ ... transmittance, C ₃ ... transmittance, C _A ... relative luminance C _B ... Relative luminance, C _k ... extinction coefficient, C _n ... refractive index, CE ... counter electrode, CS ... sealing substrate, DE ... drain electrode, DL ... video signal line, DP ... display panel, DR ... drive Control element, G ... gate, GI ... gate insulating film, HR ... hard resin layer, II ... interlayer insulating film, MLF ... multilayer film, ND1 ... power supply terminal, ND1 '... constant potential terminal, ND2 ... power supply terminal, OLED ... organic EL element, ORG ... organic layer, PE ... pixel electrode, PI ... partition insulating layer, PLZ ... polarizing plate, PS ... passivation film, PSL ... power line, PX ... pixel, RTD ... retardation plate, SC ... semiconductor layer, SE ... Source electrode, SL1 ... Scanning signal line, S L2 ... Scanning signal line, SS ... Sealing layer, SUB ... Insulating substrate, SWa ... Output control switch, SWb ... Video signal supply control switch, SWc ... Diode connection switch, UC ... Undercoat layer, UVA ... UV absorbing layer, XDR ... Video signal line driver, YDR... Scanning signal line driver.

Claims (5)

  An organic EL element and an ultraviolet blocking layer that is disposed on the front surface side thereof and has a visible light transmittance of 3% or less at each wavelength of 418 nm or less and 40% or more at each wavelength of 450 nm to 770 nm. An organic EL display device characterized by that.   2. The organic EL display device according to claim 1, wherein the ultraviolet blocking layer has a visible light transmittance of 10% or more at each wavelength of 420 nm or more. In the organic EL element, the wavelength while being disposed on the front surface side of the ratio T ₄₁₈ / T ₄₅₀ between the transmittance T ₄₅₀ for transmission T ₄₁₈ and the wavelength of 450nm light for the light of 418nm is 0.1 or less An organic EL display device comprising an ultraviolet blocking layer. The maximum value T _max of the transmittance for visible light having a wavelength of 418 nm or less and the minimum value T _min of the transmittance for light having a wavelength in the range of 450 nm to 770 nm, disposed on the front side of the organic EL element. And an ultraviolet blocking layer having a ratio T _max / T _min of 0.1 or less.   The organic EL display device according to claim 1, wherein the ultraviolet blocking layer includes a polarizing plate.

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