JP2008098033A - Organic el display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL display device which can prevent short circuit at a tapered part and a tapered edge part of an element isolation film and has no unlit pixels. <P>SOLUTION: A plurality of organic EL elements composed of an organic light-emitting layer pinched between a pair of electrodes are provided on a substrate as pixels, and the plurality of the pixels, in an organic EL display device which is divided by an element isolation structure formed on one of the electrodes, have a curvature radius of a corner of each pixel divided by the element isolation structure to satisfy 0<r≤0.3×Ax, wherein r denotes a curvature radius of the corner of the pixel and Ax, a pixel aperture width of a pixel pitch on a widthwise side or a shorter side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an organic EL display device used for a flat panel display or the like.

  In recent years, organic EL display devices, which are self-luminous devices, have attracted attention as flat panel displays.

  The organic EL display device has an organic EL element in which an organic light emitting layer is sandwiched between a pair of electrodes composed of an anode and a cathode facing each other on a substrate (for example, glass or film), and the organic EL element is mounted. The sealing layer is provided on the outer surface of the organic EL element substrate. In order to be able to extract the light from the organic light emitting layer to the outside, a transparent electrode such as ITO (Indium Tin Oxide) is used for the electrode on the light extraction side, and a current is applied by applying a voltage by an external drive circuit. Emits light.

  By the way, since the organic EL element has a structure in which an organic layer is sandwiched between the cathode and the anode, a short circuit may occur between the anode and the cathode. As a result, there is a problem that current is concentrated at the shorted portion and sufficient current cannot be supplied to the organic EL element, resulting in a non-lighted pixel.

  For example, a short circuit occurs when the film thickness of the taper edge portion (hereinafter referred to as the taper edge portion) of the cathode or the anode, which is in contact with the electrode disposed under the element isolation film, is extremely thin. To do. Further, since at least a part of the tapered edge portion is inversely tapered, the organic layer is not sufficiently formed, and a short circuit occurs between the cathode and the anode.

  As countermeasures against a short circuit caused by an extremely thin film thickness of the taper edge portion, proposals have been made to increase the thickness of the organic layer described above and to control the taper angle of the side wall portion of the element isolation film (Patent Document). 1).

  In addition, as a countermeasure against a short circuit due to the reverse taper of the element isolation film, the element isolation film has a two-layer structure, and the first element isolation is provided on either the anode or the cathode disposed below the element isolation film. There has been a proposal to form a sufficiently thin film (see Patent Document 2).

JP 2005-63870 A JP 2004-319119 A

  The present invention has been made in view of the problem of non-lighting pixels of an organic EL element, and provides an organic EL display device having no non-lighting pixels by preventing a short circuit at the taper portion and the taper edge portion of the element isolation film. For the purpose.

As means for solving the problems of the background art, an organic EL display device according to the invention described in claim 1 is:
An organic EL element having a plurality of organic EL elements each having an organic light emitting layer sandwiched between a pair of electrodes as a pixel on a substrate, the plurality of pixels being partitioned by an element isolation structure formed on one electrode In the display device,
The radius of curvature of the corner of each pixel partitioned by the element isolation structure is
<Formula 1>
0 <r ≦ 0.3 ・ Ax
(Where r is the radius of curvature of the corner of the pixel, Ax is the pixel aperture width of the pixel pitch in the horizontal direction or the short side)
It is characterized by satisfying the relationship.

  The organic EL display device according to the present invention is configured such that the radius of curvature r of the corner of each pixel satisfies the relationship of the above <Expression 1>. Therefore, it is possible to prevent a short circuit between the electrodes at the tapered portion and the tapered edge of the corner of each pixel, and it is possible to prevent the occurrence of non-lighting pixels.

  First, the background of the inventor's achievement of the invention will be described.

  A short circuit occurring in the taper portion of the element isolation film (structure) does not occur in a region corresponding to a side of the pixel formed by the element isolation film, but occurs in a corner region of the pixel. As a result of observing in detail the short portion of the corner region of the pixel, as shown in FIG. 2, the taper angle B ′ of the element isolation film in the region B corresponding to the corner portion of the pixel is equal to the taper angle of the region A corresponding to the pixel side. It was found to be steeper than A ′. From this, it is considered that when the taper angle of the corner portion of the pixel is steep, the thickness of the organic layer formed at the corner portion of the pixel becomes thin, and a short circuit occurs between the cathode and the anode.

  Therefore, in order to prevent such a short circuit occurring in the corner region of the pixel, it is necessary to make the taper angle of the corner portion of the pixel moderate. Thus, as a result of examining the relationship between the taper angle and the radius of curvature r of the corner of each pixel, the present invention has been achieved.

  More specifically, if the radius of curvature r of the corner of each pixel satisfies the relationship of 0 <r, the taper angle of the corner of the pixel becomes gradual and prevents a short circuit that occurs in the corner area of the pixel. can do.

  However, if the radius of curvature r of the corner of each pixel exceeds 0.3 · Ax, the ratio of the light emitting portion in one pixel region (so-called aperture ratio) decreases, which is not preferable.

From the above, the range of the radius of curvature r of the corner of each pixel in the present invention is
<Formula 1>
0 <r ≦ 0.3 ・ Ax
It was decided to stipulate.

Also, when considering application to R, G, B pixels or R, G, B, W pixels, the pixel aperture width Ax of the pixel pitch on the horizontal direction or the short side and the vertical direction or the long side The relationship between the pixel pitch and the pixel aperture width Ay is
<Formula 2>
Ax ≧ 1 / 4.5 ・ Ay
It is preferable to satisfy the relationship.

Further, the pixel opening width of the pixel pitch in the horizontal direction or the short side is <Formula 3>
18 μm ≦ Ax ≦ 75 μm
In the case of the range, the radius of curvature of the corner of each pixel is
<Formula 4>
0.05 ・ Ax ≦ r ≦ 0.3 ・ Ax
It is preferable to satisfy the relationship.

When the organic EL element is used for a display or the like, the pixel aperture width for setting the resolution within a range of about 100 ppi or more and about 300 ppi or less, which is particularly preferably applied at present,
<Formula 5>
8μm ≦ Ax ≦ 75μm
It is.

  In the range of the pixel opening width, if the opening width is smaller than 0.05 · Ax, the taper angle of the corner portion of the pixel becomes too steep and a short circuit is likely to occur. For this reason, it is preferable that the radius of curvature of the corner of each pixel be equal to or greater than the above lower limit value.

  Next, embodiments of the present invention will be described with reference to the drawings.

<Embodiment 1>
FIG. 1A schematically shows a cross-sectional view of the left side of the organic EL display device according to the present invention, and FIG. 1B schematically shows a top view of pixels arranged in the organic EL display device according to the present invention. Indicate. Here, in FIG. 1A, 1 is a glass substrate, 2 is a TFT (thin film transistor), 3 is an insulating layer, 4 is a planarizing film, and 5 is an anode electrode (anode). Furthermore, 6 is an organic light emitting layer, 6 ′ is an electron transport layer and an electron injection layer, 7 is a cathode electrode (cathode), 8 is a hygroscopic material, 9 is an inert gas, 10 is an element isolation film, 11 is a sealing glass, Reference numeral 12 denotes an adhesive, and a denotes one pixel region. In FIG. 1B, reference numeral 10 'denotes a device isolation film taper portion.

  The organic EL display device shown in the figure is sandwiched between a pair of electrodes consisting of an anode electrode 5 and a cathode electrode 7 facing each other on a glass substrate 1 in substantially the same manner as a conventional organic EL display device. A plurality of organic EL elements each having the organic light emitting layer 6 are provided as pixels. The plurality of pixels are configured to be partitioned by an element isolation film 10 formed on the anode electrode 5.

The feature of this organic EL display device is that the radius of curvature of the corner of each pixel partitioned by the element isolation film 10 is
<Formula 1>
0 <r ≦ 0.3 ・ Ax

(Where r: radius of curvature of the corner of the pixel, Ax (= Px−Wx): pixel aperture width of the pixel pitch on the horizontal direction or short side, Px: pixel pitch on the horizontal direction or short side of each pixel, Wx: width of the region where the element isolation film 10 is formed within the pixel pitch)
It is characterized by satisfying the relationship. As described above, it is possible to prevent a short circuit between the electrodes at the tapered portion and the tapered edge of the corner portion of each pixel, and it is possible to prevent the occurrence of non-lighting pixels. Moreover, since it can be realized by changing the r shape at the time of mask pattern production or by changing the process conditions at the time of pattern formation, it can be produced simply and without increasing the cost.

In particular, when the organic EL display device is an R / G / B pixel or an R / G / B / W pixel, the pixel aperture width in the horizontal or short side pixel pitch and the vertical or long side pixel pitch. The relationship with the pixel aperture width is
<Formula 2>
Ax ≧ 1 / 4.5 ・ Ay
(However, Ay: pixel opening width of the pixel pitch in the vertical direction or long side)
It is characterized by satisfying the relationship.

  By satisfying the above relational expression, when the organic EL display device is an R / G / B pixel or an R / G / B / W pixel, the pixel aperture width of the pixel pitch on the horizontal direction or the short side, and the vertical direction or The pixel opening width of the pixel pitch on the long side does not change extremely. As a result, substantially the same shape can be obtained even if the taper portion at each corner and the taper edge process conditions in each pixel are constant.

Further, the pixel opening width of the pixel pitch in the horizontal direction or the short side is <Formula 3>
18 μm ≦ Ax ≦ 75 μm
In the case of the range, the radius of curvature of the corner of each pixel is
<Formula 4>
0.05 ・ Ax ≦ r ≦ 0.3 ・ Ax
It is characterized by satisfying the relationship. As described above, when the organic EL element is used for a display or the like, it is possible to prevent occurrence of a short circuit.

  The configuration of the organic EL display device will be described along the manufacturing method.

  A TFT 2 was formed on the glass substrate 1 and an insulating layer 3 was formed to protect the TFT 2. At this time, the pitch on each scanning line side formed by the TFT backplane is 126 μm, and the pitch on the signal line side is 42 μm.

  An organic planarization layer 4 was formed in order to planarize the unevenness caused by the formation of the TFT backplane.

  In order to make electrical contact with each drain terminal formed in the TFT backplane, a contact hole is formed in the insulating layer 3 and the organic planarization layer 4, and then a Cr electrode is formed to a thickness of 100 nm, and an anode is formed. An electrode 5 was formed.

  After the anode electrode 5 was formed, the substrate was cleaned. Then, a PI (polyimide) material is spin-coated as the element isolation film 10, and the element isolation film 10 is exposed using a mask having a radius of curvature r = 2 μm at the corner of the pixel as shown in FIG. Thereafter, development processing was performed to form an element isolation film 10.

  In FIG. 3, the horizontal pixel pitch Px corresponding to the short side is 42 μm, and the mask dimension corresponding to the width Wx of the element isolation film 10 disposed on the short side in the one pixel a (see FIG. 1). Wx ′ is 15 μm.

  DL-1000 (manufactured by Toray Industries, Inc.) was used as the PI material of the element isolation film 10, and Microposit Developer CD26 (manufactured by Rohm and Haas) was used as the developer.

  The spin condition is increased from 500 rpm to 1000 rpm stepwise, kept for 10 seconds, and then set to 700 rpm / 10 seconds. Post-pake conditions were performed in an oven at 230 ° C./30 min.

After UV / ozone cleaning, vacuum baking was performed at 1 × 10 ⁻² Pa and 50 ° C. for 7 hours.

  The substrate was transferred to an organic EL vapor deposition apparatus and evacuated, and 50 W RF power was applied to a ring electrode provided in the pretreatment chamber to perform an oxygen plasma cleaning process. The oxygen pressure is 0.6 Pa and the treatment time is 40 seconds.

The substrate was transferred from the pretreatment chamber to the film formation chamber, and after the vacuum degree in the film formation chamber was evacuated to 1 × 10 ⁻⁴ Pa, αNPD having hole transportability was formed by resistance heating vapor deposition. The film formation rate was 0.2 nm / sec, and a hole transport layer having a thickness of 35 nm was formed. Note that the hole transport layer was deposited using a lattice-shaped metal mask so as to be deposited on all the pixels.

  Subsequently, Alq3, which is an alkylate complex, is formed on the hole transport layer by a resistance heating vapor deposition method with a thickness of 15 nm under the same film formation conditions as the hole transport layer, thereby forming the organic light emitting layer 6. did.

  In addition, since it is not necessary to apply the organic light emitting layer 6 to each of R, G, and B at this time, the organic light emitting layer 6 is formed in a lattice-shaped metal mask so as to be deposited on all the pixels in the same manner as the hole transport layer. Vapor deposition was performed. At this time, as shown in FIG. 1, the metal mask openings were deposited at the same pitch as the display area up to the area where the element isolation film 10 was formed.

  When coating each R, G, and B separately, each organic light emitting layer 6 may be formed using a metal mask corresponding to each R, G, and B arrangement.

On the organic light emitting layer 6, Alq3 and cesium carbonate (Cs ₂ CO ₃ ) are mixed at a film thickness ratio of 9: 1 by a resistance overheating co-evaporation method, and the deposition rate becomes 0.3 nm / sec. As described above, an electron injection layer having a film thickness of 35 nm was formed by adjusting the respective vapor deposition rates.

  In order to form the cathode electrode, the substrate is transferred to a sputtering chamber for electrode formation, and a metal mask film is formed on the electron injection layer so that the film thickness becomes 130 nm by a DC magnetron sputtering method using an ITO target. Thus, a cathode electrode 7 as a transparent electrode was formed.

The film formation conditions are room temperature film formation without substrate heating, the film formation pressure is 1.0 Pa, Ar, H ₂ O, and O ₂ gas are used, and the respective flow rates are 500, 1.5, 5.0 sccm, The input power applied to the target was ITO: 500 W. The transmittance is 85% (at 450 nm), and the specific resistance value is 8 × 10 ⁻⁴ Ω · cm.

  As described above, after forming a TFT backplane on the substrate, an anode, a hole transport layer, an organic light emitting layer, an electron injection layer, and a cathode were provided to produce an organic EL element substrate.

  On the other hand, the hygroscopic material 8 was affixed to the sealing glass 11 in the glove box at a position where it does not interfere with the display area. In the present embodiment, etching glass is used as the sealing glass 11, and a sheet-like getter material mainly composed of Ca is used as the hygroscopic material 8. The main purpose of using the hygroscopic material 8 is to remove moisture entering from the bonded portion between the organic EL element substrate and the sealing glass 11.

  In order to seal the sealing glass 11 obtained in the above step and the organic EL element substrate, the sealing glass 11 is disposed at a predetermined position of the organic EL element substrate, and then conveyed to a glove box, and the sealing glass 11 and the organic EL element substrate were sealed with an adhesive 12. More specifically, the adhesive 12 was poured into a dispenser syringe, and after the injection, the organic EL element substrate having the sealing glass 11 disposed at a predetermined position was conveyed to a glove box. And the adhesive agent 12 was apply | coated to the peripheral part of the sealing glass 11 by width 0.5mm and thickness 35micrometer using the dispensing robot. As the adhesive 12, a photocationic polymerization type liquid resin (KR695 / Asahi Denka) was used.

The ultraviolet irradiation intensity at that time was 100 mW / cm ² and the amount of light was 3,000 mJ / cm ^{2. The} sealing process described above was performed by controlling the moisture concentration in the glove box to 10 ppm or less. .

  The element evaluation of the organic EL display device obtained in the above process was performed.

  First, as a result of measuring the radius of curvature of the corner portion of each pixel formed at the contact portion between the anode electrode and the element isolation film using an optical microscope with a length measuring function, the radius of curvature was about 6.5 μm.

  Since the pixel pitch Px on the short side is 42 μm and the measured value of the width Wx of the element isolation film disposed on the short side is 13 μm, Ax = 29 μm. Substituting into the above <Formula 4>, 1.45 ≦ r ≦ 8.7, which satisfied the present invention.

  Further, since the pixel pitch Py on the long side is 126 μm and the actual measurement value of the width Wy of the element isolation film disposed on the long side is 30 μm, Ay (= Py−Wy) = 96 μm. Substituting into the above <Equation 2>, 29 ≧ 21.3, which satisfied the present invention.

  Next, the organic EL display device was caused to emit light, the number of non-lighted pixels was counted, and non-lighted pixels due to foreign matters or obvious patterning defects were classified in the non-lighted pixels. As a result, the number of non-illuminated pixels in the entire display device was 96 pixels, but it was confirmed that all the non-illuminated pixels had foreign matters.

  That is, no short circuit between the electrodes at the tapered portion and the tapered edge portion of the element isolation film at the corner portion of the pixel, which was a problem, was observed.

<Embodiment 2>
In the present embodiment, adjustment of the curvature radius r of the corner portion of the pixel is realized by manufacturing process conditions.

  Also in the present embodiment, since the anode electrode 5 is formed in the same procedure as in the first embodiment, detailed description until the anode electrode 5 is formed is omitted.

  After the anode electrode 5 is formed, the substrate is cleaned, an acrylic material is spin-coated as the element isolation film 10, and the element isolation film 10 is exposed using a mask having a shape in which the corners of the pixels do not have a curvature radius in particular. Thereafter, development processing was performed to form an element isolation film 10.

  The horizontal pixel pitch Px corresponding to the short side was set to 42 μm, and the mask dimension W ′ corresponding to the width Wx of the element isolation film disposed on the short side was set to 15 μm.

  Optmer PC415G (manufactured by JSR Corporation) was used as the acrylic material of the element isolation film 10, and NMD-3 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) was used as the developer.

  Spin conditions were kept at 1500 rpm for 20 seconds, and then set to 1100 rpm / 10 seconds. The prebake condition was 90 ° / 2 min.

  Post-pake conditions were set to 220 ° C./60 min, and performed in a clean oven manufactured by Tabai.

After UV / ozone cleaning, vacuum baking was performed at 1 × 10 ⁻² Pa and 50 ° C. for 7 hours.

  The substrate was transferred to an organic EL vapor deposition apparatus and evacuated, and 50 W RF power was applied to a ring electrode provided in the pretreatment chamber to perform an oxygen plasma cleaning process. The oxygen pressure is 0.6 Pa and the treatment time is 40 seconds.

The substrate was transferred from the pretreatment chamber to the film formation chamber, the degree of vacuum in the film formation chamber was evacuated to 1 × 10 ⁻⁴ Pa, and αNPD having a hole transporting property was formed by resistance heating vapor deposition. The film formation rate was 0.2 nm / sec, and a hole transport layer having a thickness of 35 nm was formed. Note that the hole transport layer was deposited using a lattice-shaped metal mask so as to be deposited on all the pixels.

  Subsequently, Alq3, which is an alkylate complex, was formed on the hole transport layer by a resistance heating vapor deposition method with a thickness of 15 nm under the same film formation conditions as the hole transport layer, and the organic light emitting layer 6 was formed. .

  Finally, the sealing step was performed after forming the electron injection layer and the cathode electrode 7 in the same procedure as in the first embodiment.

  The element evaluation of the organic EL display device obtained in the above process was performed.

  First, as a result of measuring the radius of curvature r of the corner portion of each pixel formed at the contact portion between the anode electrode 5 and the element isolation film 10 using an optical microscope with a length measuring function, the radius of curvature was about 5.5 μm. It was.

  Since the pixel pitch Px on the short side is 42 μm and the measured value of the width Wx of the element isolation film disposed on the short side is 12 μm, Ax = 30 μm. When substituting into the above <Expression 4>, 1.5 ≦ r ≦ 9, which satisfied the present invention.

  Next, the organic EL display device was caused to emit light, the number of non-lighted pixels was counted, and non-lighted pixels due to foreign matters or obvious patterning defects were classified in the non-lighted pixels. As a result, the number of non-illuminated pixels in the entire display device was 28 pixels, but it was confirmed that all the non-illuminated pixels had foreign matters.

  In other words, the short circuit between the electrodes generated at the tapered portion and the tapered edge portion of the element isolation film at the corner portion of the pixel, which was a problem in this embodiment, was not observed.

  In the above embodiment, a mask pattern having no curvature is used. However, there is no problem even if the mask pattern has a radius of curvature and the curvature radius r of the corner of the pixel obtained by the element isolation film 10 is adjusted in combination with the adjustment according to the process conditions.

(A) is a schematic diagram which shows the cross section of the left side of the organic electroluminescence display which concerns on Embodiment 1 of this invention. (B) is a schematic diagram showing an upper surface of a pixel region. (A) is a schematic diagram which shows the upper surface of the pixel area | region of the conventional organic electroluminescence display. (B) is a schematic diagram which shows a cross section. It is a schematic diagram which shows the mask for formation of an element isolation film.

Explanation of symbols

1 Glass substrate 2 TFT (Thin Film Transistor)
3 Insulating film 4 Planarizing film 5 Anode electrode 6 Organic light emitting layer 7 Cathode electrode 8 Hygroscopic material 9 Inert gas 10 Element isolation film 11 Sealing glass 12 Adhesive

Claims (3)

An organic EL element having a plurality of organic EL elements each having an organic light emitting layer sandwiched between a pair of electrodes as a pixel on a substrate, the plurality of pixels being partitioned by an element isolation structure formed on one electrode In the display device,
The radius of curvature of the corner of each pixel partitioned by the element isolation structure is
<Formula 1>
0 <r ≦ 0.3 ・ Ax
(Where r is the radius of curvature of the corner of the pixel, Ax is the pixel aperture width of the pixel pitch in the horizontal direction or the short side)
An organic EL display device satisfying the following relationship: The pixel opening width of the pixel pitch in the horizontal direction or the short side and the pixel opening width of the pixel pitch in the vertical direction or the long side are:
<Formula 2>
Ax ≧ 1 / 4.5 ・ Ay
(However, Ay: pixel opening width of the pixel pitch in the vertical direction or long side)
The organic EL display device according to claim 1, wherein the relationship is satisfied. The pixel aperture width of the pixel pitch in the horizontal direction or the short side is
<Formula 3>
18 μm ≦ Ax ≦ 75 μm
The radius of curvature of the corner of each pixel is
<Formula 4>
0.05 ・ Ax ≦ r ≦ 0.3 ・ Ax
The organic EL display device according to claim 1, wherein the relationship is satisfied.

Images