KR101853446B1 - Organic light emitting display and sealing method threrof - Google Patents

Abstract

An organic light emitting diode (OLED) display device includes a display substrate, an encapsulation substrate disposed opposite the display substrate, an organic light emitting diode And a sealing member for bonding the display substrate and the encapsulation substrate with the display unit interposed therebetween. Here, the sealing member is formed of crystallized glass, minimizing the thermal expansion coefficient difference with the glass substrate, minimizing the thermal stress on the bonding surface, and preventing cracks from propagating to the external impact, The impact resistance can be improved.

Description

TECHNICAL FIELD [0001] The present invention relates to an organic light emitting display, and more particularly,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting display and a sealing method thereof, and more particularly, to an organic light emitting display including a sealing member made of crystallized glass and a sealing method thereof.

The OLED display is a self-emission type display that emits light by electrically exciting an organic compound. The OLED display can be driven at a low voltage, has a fast response speed, has a wide viewing angle and excellent contrast, and can be made thinner and lighter , Is currently being commercialized, and the research and development thereof is continuously being carried out.

In general, an OLED display includes a display substrate having a display unit and an encapsulating substrate facing the encapsulation substrate. The display unit includes an organic light emitting diode to function as a display unit. do.

In such an organic light emitting display, deterioration due to internal factors such as deterioration of the light emitting layer due to oxygen derived from a transparent conductive oxide or the like used for forming electrodes of the display portion or deterioration due to reaction between the light emitting layer and the interface may occur. In addition, deterioration may also be caused by external influences of moisture, oxygen, ultraviolet rays, and external factors generated during the manufacturing process of the apparatus. In particular, since external oxygen and moisture have a critical impact on the lifetime of the organic light emitting device, sealing during the manufacture of the organic light emitting display device is very important.

Generally, the joining material joining the substrates functions as a sealing member that seals from the external environment, and such a sealing member is vulnerable to damage by external impact or pressure. Therefore, there is still a need for an improved method for preventing damage to the sealing member in order to completely seal the organic light emitting element constituting the display unit to eliminate external influences.

Disclosure of the Invention The present invention has been made to solve the above problems of the prior art, and it is an object of the present invention to provide an organic light emitting display device for improving the strength of a sealing member for bonding between substrates and shielding an organic light emitting diode from the outside, And to provide a sealing method therefor.

An organic light emitting display according to an embodiment of the present invention includes a display substrate, an encapsulation substrate disposed opposite the display substrate, a display unit formed on the display substrate and including an organic light emitting element, And a sealing member for bonding the substrate. Here, the sealing member is formed of crystallized glass.

According to the present embodiment, the display substrate is formed of glass, and a chemical bond can be formed through the oxygen atom at the boundary between the display substrate and the sealing member.

In addition, the organic light emitting diode display according to the present embodiment may further include a polarizer attached to the encapsulation substrate on the encapsulation substrate not facing the display substrate.

Further, according to this embodiment, the crystallized glass of the sealing member may include at least one of Zn ₂ V ₂ O ₇ and α-Zn ₂ V ₂ O ₇ .

A sealing method of an OLED display according to an embodiment of the present invention includes the steps of preparing a display substrate including a display substrate including a sealing substrate and an organic light emitting diode, Applying a sealing paste containing a sealing agent to the sealing substrate, heating the sealing paste to a crystallization temperature such that the glassy substance of the applied sealing paste becomes crystalline, arranging the display substrate by aligning the sealing substrate with the sealing substrate, And a step of bonding the display substrate and the sealing substrate by curing the sealing paste by irradiating laser light.

According to this embodiment, the laser to be irradiated for curing the sealing paste can be irradiated onto the region corresponding to the end of the sealing paste on the display substrate.

The sealing method of the organic light emitting diode display according to the present embodiment may further include the step of attaching a polarizer on the encapsulation substrate not facing the display substrate.

Further, according to this embodiment, the crystal of vitreous of the sealing paste may include at least one of Zn ₂ V ₂ O ₇ and α-Zn ₂ V ₂ O ₇ .

According to an embodiment of the present invention, the use of the crystallized glass as the sealing member sealing the organic light emitting element by bonding between the substrates of the organic light emitting display device can prevent the breakage of the crack due to the external impact. Further, the bonding strength between the substrate and the sealing member can be improved through crystallization of the sealing member.

1 is a side sectional view of an organic light emitting display according to an embodiment of the present invention.
2 is an enlarged cross-sectional view of a display unit of an OLED display according to an exemplary embodiment of the present invention.
3 is a view illustrating a process of sealing an OLED display according to an exemplary embodiment of the present invention.
Figs. 4 to 6 are graphs showing the results of XRD measurement at different primary heating temperatures of the glass frit. Fig.
7 is an enlarged view of a boundary of a sealing member in the OLED display according to an embodiment of the present invention.
8 is a diagram illustrating crack formation in a sealing member according to a comparative example of the present invention and an embodiment, respectively.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily carry out the present invention. In order to clearly illustrate the present invention, parts that are not related to the present invention are omitted, and the same components are denoted by the same reference numerals throughout the specification.

Where an element is referred to herein as being "above" another element, it includes the case where it is located "directly on" another element, as well as the presence of another element therebetween. The sizes and the like of the respective components shown in the drawings are arbitrarily shown for convenience of explanation, and the present invention is not necessarily limited to those shown in the drawings.

That is, the specific shapes, structures, and characteristics described in the specification can be implemented by changing from one embodiment to another embodiment without departing from the spirit and scope of the present invention. It is to be understood that changes may be made without departing from the scope. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of the present invention should be construed as encompassing the scope of the appended claims and all equivalents thereof.

1 is a side sectional view of an organic light emitting display according to an embodiment of the present invention. 1, the OLED display 100 includes a display substrate 110 and an encapsulating substrate 120 facing each other, a display unit 130 formed on a display substrate, a polarizing plate And a sealing member 150 for bonding the sealing substrate 140 and the sealing substrate 120 to the display substrate 110.

In an embodiment of the present invention, the display substrate 110 may be formed of an insulating substrate made of glass or the like. In an embodiment of the present invention, the sealing substrate 120 faces the display substrate 110 with the display unit 130 interposed therebetween to protect the display unit 130. In this embodiment, the sealing substrate 120 may be formed of an insulating substrate made of transparent material such as glass so that light generated from the display unit 130 may be emitted through the sealing substrate 120.

In an exemplary embodiment of the present invention, the display unit 130 includes an organic light emitting diode and emits light when a voltage is applied.

FIG. 2 is an enlarged cross-sectional view of a display unit of an OLED display according to an exemplary embodiment of the present invention. Referring to FIG. 2, a display unit 130 includes a buffer layer 131, The driving semiconductor layer 132, the gate trimming film 133, the interlayer insulating film 134, the driving thin film transistor 135 and the planarization film 137 are successively positioned and the organic light emitting element 138 is formed on the planarization film 137. [ Can be formed.

The organic light emitting device 138 may include a pixel electrode 138p, an organic light emitting layer 138e formed on the pixel electrode 138p, and a common electrode 138c formed on the organic light emitting layer 138e. Here, the pixel electrode 138p may be a positive electrode which is a positive hole purchase electrode, and in this case, the common electrode 138c may be a negative (-) electrode which is an electron injection electrode. Alternatively, the pixel electrode may be a cathode and the common electrode may be an anode according to a driving method of an organic light emitting display device. When holes and electrons are injected into the organic light emitting layer 138e from the pixel electrode 138p and the common electrode 138c, light is emitted when the excitons formed by the injected holes and electrons fall from the excited state to the ground state . The organic light emitting layer 138e may include a red light emitting layer, a green light emitting layer, and a blue light emitting layer to realize full colorization of the OLED display. For example, the light emitting layer of the same color may be formed in the column direction, and the red light emitting layer, the green light emitting layer, and the blue light emitting layer may be sequentially formed in the row direction, or may be embodied in various other different forms .

The organic light emitting display 100 according to the present embodiment may be a front emission type in which the display unit 130 emits light in the direction of the sealing substrate 120. For this purpose, An electrode is used, and as the common electrode 138c, a transmissive or semi-transmissive electrode can be used. However, the present invention is not limited to this, and the organic light emitting display device may be configured as a back light emitting type or a both surface light emitting type.

On the other hand, the buffer layer 131 serves to prevent penetration of impurity elements and planarize the surface, and any one of a silicon nitride (SiNx) film, a silicon oxide (SiOx) film and a silicon oxynitride (SiOxNy) film can be used. The driving semiconductor layer 132 formed on the buffer layer 131 may be formed of a polycrystalline silicon film and may include a channel region 132c that is not doped with impurities and a p + And a source region 132s and a drain region 132d formed in the semiconductor substrate. The gate insulating film 133 may be formed of silicon nitride (SiNx), silicon oxide (SiOx), or the like, and a gate wiring including a driving gate electrode (not shown) may be formed thereon. An interlayer insulating film 134 that may be formed of silicon nitride (SiNx), silicon oxide (SiOx), or the like may be formed on the gate insulating film 133 in the same manner as the gate insulating film 133. [ The gate insulating film 133 and the interlayer insulating film 134 may be formed with through holes for exposing the source region 132s and the drain region 132d of the driving semiconductor layer 132. [ A data line including the driving source electrode 135s and the driving drain electrode 135d is formed on the interlayer insulating film 134 so that the driving source electrode 135s and the driving drain electrode 135d are electrically connected to the driving semiconductor And may be connected to the source region 132s and the drain region 132d of the layer 132. [ The driving thin film transistor 135 including the driving semiconductor layer 132, the driving gate electrode, the driving source electrode 135s, and the driving drain electrode 135d may be formed. On the other hand, the data line may further include a data line 136d, a common power line 136c, and the like.

The planarizing layer 137 may be formed on the interlayer insulating layer 134 to remove the step and planarize the organic light emitting diode 137 to increase the luminous efficiency of the organic light emitting diode 137. The planarization film 137 may be formed to cover the data line on the interlayer insulating film 134 and may be formed with a contact hole 137h exposing a part of the drain electrode 135d. It is preferable to use an epoxy resin, a phenolic resin, a polyamide resin, a polyimide resin, an unsaturated polyesters resin, a polyphenylenethers resin, polyphenylene sulfide resin, benzocyclobutene (BCB), and the like. A pixel defining layer 139 having a plurality of openings for exposing the respective pixel electrodes 138p may be formed on the planarization layer 137. The portion where the pixel defining layer 139 is formed is substantially a non- And the portion where the opening of the pixel defining layer 139 is formed can be substantially a light emitting region.

The structure of the display unit 130 including the organic light emitting element 138 described above is illustrative, and the present invention is not limited thereto, and the structure thereof may be changed as is known to those skilled in the art. For example, either the flattening film or the interlayer insulating film may be omitted, and the material constituting each layer may be changed to another known material.

Referring to FIG. 1 again, the polarizer 140 may be formed on the encapsulation substrate 120 to enhance the visibility of the OLED display 100 in one embodiment of the present invention. The polarizing plate 140 may be configured to include, for example, a retardation film positioned on the sealing substrate 120 and a polarizing film positioned on the retardation film.

The sealing member 150 may be formed by bonding the display substrate 110 and the encapsulation substrate 120 to each other while the display unit 130 including the organic light emitting elements between the display substrate 110 and the encapsulation substrate 120 is exposed to moisture, Oxygen, ultraviolet rays or the like. Referring to a schematic enlarged sectional view of the sealing member 150 in FIG. 1, the sealing member 150 according to the present embodiment may be made of crystalline glass. That is, the sealing member 150 may be formed in a form in which crystals 153 are contained in the vitreous (amorphous) 151.

In this embodiment, by forming the sealing member with the crystallized glass, breakage of the sealing member can be suppressed even when there is an external impact and the bonding strength between the substrates can be improved, which will be described later in detail.

FIG. 3 is a view sequentially illustrating a process of sealing an organic light emitting display according to an exemplary embodiment of the present invention. Hereinafter, a sealing method of the organic light emitting display will be described in detail with reference to FIG.

3 (a), a sealing substrate 120 having a polarizing plate 140 on one side thereof is prepared, and a sealing paste is applied along the edge of the side to which the polarizing plate 140 is not attached. As described above, the sealing substrate 120 may be formed of a transparent insulating substrate such as glass, and the polarizing plate 140 may include a retardation film and a polarizing film sequentially attached on the sealing substrate 120 . Although the sealing substrate 120 with the polarizing plate 140 is used in this embodiment, the polarizing plate 140 may be attached after the sealing substrate 120 and the display substrate 110 are bonded to each other, and the polarizing plate 140 It is also possible not to adhere.

The sealing paste may be a paste in which the glass frit is dispersed in an organic vehicle, wherein the organic vehicle may be in the form of an organic solvent in an organic binder that imparts a liquid phase property to the paste composition. As the organic binder, one or more kinds of cellulose-based polymers may be used in addition to the acrylic polymer. The organic solvent may be a glycol ether-based material, but it may be any conventional one that is compatible with the organic binder, Can be used. The glass frit of the sealing paste may include zinc oxide (ZnO), vanadium pentoxide (V ₂ O ₅ ), tellurium dioxide (TeO ₂ ), or the like. However, the constituent components of the sealing paste described above are not limited to those illustrated and may be modified by those skilled in the art within the scope of the present invention.

After the sealing paste is applied and dried, the glass frit is dried and then calcined (primary heating) to crystallize the glass frit as shown in Fig. 3 (b). That is, the glass frit of the sealing paste is firstly dried after being dried to be crystallized glass. At this time, organic binders and organic solvents contained in the sealing paste can be volatilized and removed by heat during drying and primary heating.

Table 1 below exemplarily shows the constituent elements contained in the glass frit, and the heating temperature necessary for crystallization of the glass frit can be determined depending on the constituent elements.

division ZnO V ₂ O ₅ TeO ₂ Sample 1 30 mol% 34 mol% 18 mol% Sample 2 43 mol% 20 mol% 8 mol%

FIG. 4 is a graph showing the X-ray diffraction measurement results of the glass frit of sample 2 at different primary heating temperatures. Specifically, FIGS. 4 (a) to 4 (c) XRD results are shown when the heating temperatures are set at 400 ° C, 430 ° C and 450 ° C.

Referring to FIG. 4, in the case of the first heating at 400 ° C. (FIG. 4 (a)), no crystallization was observed and no peak point was observed as a result of XRD measurement. 4 (b) and (c)), crystallization is carried out. As a result, XRD measurement shows a peak point. That is, it is determined whether or not it is crystallized according to the primary heating temperature.

5 and 6 are graphs showing X-ray diffraction measurement results when the glass frit of sample 2 is first heated at 430 ° C. and 450 ° C., respectively, as shown in FIG. When the glass frit of the sample 2 is heated to 430 ° C, crystals of Zn ₂ V ₂ O ₇ (refer to FIG. 5B) are mainly formed, whereby the XRD measurement result as shown in FIG. 5A is obtained . Also, referring to Figure 6, when the glass frit of the sample 2 was heated to 430 ℃ crystals of Zn ₂ V ₂ O ₇ (refer to (c) in Fig. 6) in addition to the determination of _{α-Zn 2 V 2 O 7} ( Fig. 6 (b)) is formed. Thus, an XRD measurement result as shown in Fig. 6 (a) is obtained.

As described above, it can be confirmed that the degree of crystallization and the crystallization phase are also changed according to the first heating temperature.

Table 2 shows the values of the coefficient of thermal expansion (CTE) measured before and after crystallization, and it can be confirmed that the coefficient of thermal expansion becomes smaller than that before crystallization when crystallized.

division ZnO V ₂ O ₅ TeO ₂ Before Crystallization CTE
(ppm / DEG C) After crystallization, CTE
(ppm / DEG C) Sample 1 30 mol% 34 mol% 18 mol% 5.7 5.3 Sample 2 43 mol% 20 mol% 8 mol% 4.6 4.3

When the glass frit is crystallized by the primary heating in this manner, the densification, that is, the density becomes high, and the coefficient of thermal expansion becomes low. Therefore, the thermal expansion coefficient of the glass frit to be bonded to the display substrate 110 (thermal expansion coefficient: 40 x 10 < ^-7 > / DEG C) can be approximated to the display substrate 110 and the stress with the display substrate 110 at the time of sealing becomes low The bonding strength can be improved.

Table 3 shows the results of a drop test for determining whether breakage occurs while increasing the drop height in order to test the strength before and after the crystal. Specifically, the drop test prior to crystallization shows that two drops of drop test were performed in the case of the first heating at 400 ° C, and the falling drops after crystallization were subjected to drop test in the case of first heating at 430 ° C and 450 ° C, respectively . Referring to Table 3, breakage occurs when falling at a height of 95 cm or 87 cm before crystallization, but breakage occurs when falling at a height of 118 cm when it is determined by first heating at 430 ° C., It can be confirmed that breakage occurs only when it is dropped at a height of 162 cm. That is, it can be seen that the strength after crystallization is improved, and the strength varies depending on the degree of crystallization and the phase of crystallization.

division Drop test before crystallization (cm) Drop test after crystallization (cm) Primary Secondary Primary Secondary Sample 2 95 87 118 162

3 (c), the display substrate 110 on which the display unit 130 is formed after the sealing paste is firstly heated is prepared and aligned to be adhered to the sealing substrate 120. Next, as shown in FIG. As described above, the display substrate 110 may be formed of an insulating substrate such as glass, and the display unit 130 may include an organic light emitting device to emit light by an electrical signal.

Referring to FIG. 3 (d), the display substrate 110 and the sealing substrate 120 are aligned with the crystallized glass frit of the sealing paste interposed therebetween, and the glass frit is softened and flowed by irradiating a laser. Accordingly, the display substrate 110 and the sealing substrate 120 are bonded together through the sealing member 150, so that the display unit 130 is sealed between the two substrates so as not to be influenced by the external environment.

In this embodiment, as shown in FIG. 3 (d), by irradiating a laser beam to a region corresponding to the end portion of the sealing paste applied on the upper portion of the display substrate 110, the energy is directly transmitted to the glass frit It can be melted and then cooled again to keep it in the crystallized glass state. Alternatively, the sealing substrate 120 may be cured by irradiating a laser on the sealing substrate 120 in the same manner.

The laser irradiation in this embodiment can use an infrared laser, for example, an infrared ray in a wavelength range of 800 to 820 nm. The glass frit crystallized in accordance with the laser irradiation is melted and cured again, and is adhered between the display substrate 110 and the sealing substrate 120. Specifically, the crystals 151 in the glass frit formed by the first heating in the laser irradiation process are maintained as they are, and only the glassy material 153 is softened and adhered to the display substrate 110 while maintaining the crystallized state.

As described above, in the present embodiment, since the sealing is performed by the low-temperature local heating using the infrared laser, the organic light emitting elements spaced apart from the sealing portion receive less thermal influence, and deterioration of the device can be prevented.

On the other hand, a chemical bond can be formed at the boundary portion while the glass frit is bonded to the display substrate 110 by laser irradiation.

FIG. 7 is an enlarged view of a boundary of a sealing member in an OLED display according to an embodiment of the present invention. Referring to FIG. 7, at a boundary between a display substrate 110 and a sealing member 150, The glassy material 153 of the sealing member 150 is melted and can be chemically bonded during the curing process. For example, if the glass frit contains ZnO and the display substrate 110 comprises SiO ₂ , they can be chemically bonded via an oxygen atom. In this way, chemical bonding can occur at the interface between the display substrate 110 and the sealing member 150 during laser irradiation, thereby improving the bonding strength between the display substrate 110 and the sealing member 150.

As described above, according to one embodiment of the present invention, the sealing substrate 120 is bonded to the display substrate 110 of the organic light emitting diode display 100, and the seal 130 for sealing the display unit 130 including the organic light emitting device The member 150 is formed of a crystallized glass, whereby the bonding strength between the substrates can be improved. According to the present embodiment, the presence of the crystal in the sealing member 151 can suppress breakage due to an external impact as follows.

Fig. 8 is a view schematically showing crack formation in a sealing member according to Comparative Example (a) and Example (b) of the present invention, respectively. Referring to FIG. 8A, when the sealing member is made of amorphous material as shown in FIG. 8A, cracks can easily occur around the defective portion when an external force equal to or greater than a critical point is applied. On the other hand, when the sealing member is formed of crystalline glass as shown in FIG. 8 (b), an external force equal to or greater than the critical point acts to stop the crack if the crystal reaches the crystalline portion even if the crack progresses around the defective portion.

In this way, even when an external force greater than a critical point is applied due to the presence of crystals in the sealing member, the crack can be minimized and breakage can be suppressed.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limited to the embodiments set forth herein. It can be understood that It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

100: organic light emitting display
110: Display substrate
120: sealing substrate
130:
131: buffer layer
132: driving semiconductor layer
133: Gate insulating film
134: interlayer insulating film
135: driving thin film transistor
137: planarization film
138: Organic light emitting device
139: pixel definition film
140: polarizer
150: sealing member
151: Decision
153: vitreous

Claims (8)

The display substrate,
An encapsulation substrate disposed opposite the display substrate,
A display unit formed on the display substrate and including an organic light emitting element;
A sealing member for bonding the display substrate and the encapsulation substrate with the display unit interposed therebetween;
Lt; / RTI >
Wherein the sealing member is formed of crystallized glass,
Wherein the crystallization glass of the sealing member includes both Zn ₂ V ₂ O ₇ and? -Zn ₂ V ₂ O ₇ . The method according to claim 1,
Wherein the display substrate is formed of glass, and a chemical bond is formed at the boundary between the display substrate and the sealing member via oxygen atoms. The method according to claim 1,
And a polarizer attached to the encapsulation substrate at a side not facing the display substrate in the encapsulation substrate. delete Preparing a display substrate including a sealing substrate and a display portion including an organic light emitting element,
Applying a sealing paste containing glassy material along a side of one surface of the encapsulation substrate facing the display substrate,
Heating the coated sealing paste to a crystallization temperature such that the vitreous of the sealing paste becomes crystalline,
Arranging the display substrate in alignment with the encapsulation substrate with the sealing paste interposed therebetween;
A step of bonding the sealing substrate with the display substrate by irradiating the sealing paste with laser to cure the sealing substrate
Lt; / RTI >
Wherein the glassy crystal of the sealing paste contains both Zn ₂ V ₂ O ₇ and? -Zn ₂ V ₂ O ₇ . 6. The method of claim 5,
Wherein a laser irradiating for curing the sealing paste is irradiated onto an area corresponding to an end of the sealing paste on the display substrate. 6. The method of claim 5,
Further comprising the step of attaching a polarizer on the sealing substrate not facing the display substrate. delete

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