KR20060031590A - Organic el display and method of manufacturing the same - Google Patents

Abstract

An organic EL display being produced by sealing and bonding an organic light emitting element constituted by stacking a thin film transistor, an anode, an emission layer, a cathode and a protective layer on a substrate and a color conversion filter layer formed on a transparent substrate while aligning, wherein the substrate is sealed from the transparent substrate by means of an outer circumferential sealing layer and an inner circumferential sealing layer. The organic EL emission layer and the color conversion filter layer can be aligned accurately and secured in a short time while preventing intrusion of moisture, or the like, from the outer environment by means of the outer circumferential sealing layer, and light can be transmitted effectively to the color conversion filter while preventing reflection of light from the organic EL emission layer by means of the inner circumferential sealing layer. Furthermore, stripping due to shrinkage can be prevented at the time of hardening, stripping due to thermal stress caused by the environmental temperature can be lessened while preventing intrusion of moisture, or the like, from the outer environment and stabilized emission characteristics can be sustained over a long term.

Description

Organic EL display and its manufacturing method {ORGANIC EL DISPLAY AND METHOD OF MANUFACTURING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent (EL) display, which is highly precise, has excellent environmental resistance and productivity, and can be applied to a wide range of applications such as display of portable terminals and industrial measuring instruments. An organic EL display and a method of manufacturing the same.

Recently, the speed of information communication and the expansion of the application range are rapidly progressing. Among them, display devices have been invented in various ways with respect to high-precision display devices having low power consumption and high-speed responsiveness that can meet the demands of portability and moving image display.

Among them, a color display device of a driving method using a thin film transistor (hereinafter also referred to as TFT) for the colorization method is considered. In this case, in the configuration in which light is extracted toward the substrate on which the TFT is formed, since the aperture ratio does not increase due to the light shielding effect of the light in the wiring portion, in recent years, the configuration is extracting light on the opposite side to the substrate on which the TFT is formed, That is, a top emission type display device has been developed.

Even in the case of the top emission type, in a configuration in which red, blue, and green primary light emitters are arranged in a matrix form, the light emitting materials for RGB must be arranged in a matrix shape with high precision, thus producing them efficiently and inexpensively. It is difficult to do this, and since the luminance change characteristics and the driving conditions of the three kinds of light emitting materials are different, defects such as difficulty in ensuring color reproducibility for a long time remain.

In addition, even in a configuration in which three primary colors are transmitted and separated by using a color filter on a back light emitting white light, there is a problem of high efficiency of the backlight.

In the color conversion type that absorbs fluorescence of many colors from each phosphor by being absorbed by the separated phosphors, adopting the top emission type using the TFT driving method has the possibility of providing an organic EL display with high precision and high brightness. This kind of configuration is disclosed in Japanese Patent Laid-Open No. 11 (1999) -251059 and Japanese Patent Laid-Open No. 2000-77191.

An example of a conventional top emission type organic EL display is shown in FIG. 2 as a schematic sectional view.

The TFT 2, the anode 3, the organic EL light emitting layer 4, and the cathode 5 are formed on the substrate 1. Subsequently, the color filter 12 and the black mask 13 are formed on the transparent substrate 11. Next, the sealing layer 31 is formed around the substrate 1 using, for example, a room temperature curing type two-component epoxy adhesive, and bonded to the transparent substrate 11. At this time, an internal space 32 is formed between the two substrates. The curing time of the seal layer 31 is required for quite a long time at room temperature to 24 hours. When the organic EL light emitting layer 4 and the color filter 12 are aligned, they are fixed while curing at room temperature so as not to be displaced. There is a need.

In the display shown in Fig. 2, it is necessary to have a detailed color display function and at the same time the EL element has a long-term stability including color reproducibility and can be manufactured in a short time.

In the organic EL display as shown in FIG. 2, it is necessary to precisely match the positions of the organic EL light emitting layer 4 and the color filter 12, and until the alignment is completed, the adhesive used in the seal layer 31 has a viscosity. Alignment adjustment should be made freely without causing any change in properties such as change or gelation. On the other hand, when the alignment is completed, the opposite hardening characteristic that the hardening must be completed early is required.

Also, due to the influence of the internal space 32 formed between the two substrates, there is a problem that the light emission from the organic EL light emitting layer 4 is reflected at the air layer interface having a large refractive index. In order to solve this problem, a method of filling the internal space 32 with a material having a high refractive index and curing is considered. However, if the elastic modulus of the material to be filled is high, for example, there is a serious problem that peeling occurs from the organic EL light emitting layer or the color filter layer due to the thermal stress generated by the temperature change of the use environment.

By the way, Japanese Patent Laid-Open No. 3 (1991) -190084 discloses that two substrates are bonded using an epoxy resin at an adhesive portion, and an internal space is filled with an insulating material. However, the invention described in Japanese Patent Laid-Open No. 3 (1991) -190084 does not solve the problems unique to the organic EL display of the top emission type. First, according to the necessity of precisely aligning the position of the organic EL light emitting layer and the color filter, curing of the adhesive should not be initiated during the alignment, and the adhesive should be cured in a short time in the outer peripheral layer when the alignment is completed. to be. Second, as a function of effectively transmitting light to the color filter without reflecting light from the organic EL light emitting layer, a material having a high refractive index and a function of alleviating peeling due to thermal stress is required for the inner seal layer.

An object of the present invention is to accurately position the organic EL light emitting layer and the color filter, to configure the outer seal which can be cured in a short time, to effectively transmit the light to the color filter without reflecting light from the organic EL light emitting layer, The present invention provides an organic EL display and a method of manufacturing the same, which can prevent the intrusion of pneumonia and maintain stable light emission characteristics for a long time.

According to the present invention to achieve the above object,

A thin film transistor having a source and a drain formed on the substrate, a first electrode made of a conductive thin film material connected to the source or drain on the thin film transistor, an organic EL light emitting layer, and a second electrode made of at least a transparent conductive material And an organic EL light emitting element configured by stacking a protective layer, and driven by the thin film transistor;

A laminate having a transparent substrate and a color conversion filter layer formed on the transparent substrate,

In an organic EL display in which the positions of the organic EL light emitting layer and the color conversion filter layer are sealed and bonded together,

An outer circumferential seal layer for sealing and bonding the substrate and the transparent substrate and an inner seal layer filled inside the outer circumferential seal layer to prevent the light emission of the organic EL light emitting layer from being reflected at the inner space interface.

Here, it is preferable to use an ultraviolet curable adhesive or a visible light curable adhesive for the outer seal layer, and to use an elastic transparent sealing agent having a refractive index of 1.3 to 2.5 for the inner seal layer. It is preferable to use a transparent silicone rubber material or a transparent silicone gel material as the elastic transparent sealing agent.

On the other hand, the manufacturing method of this invention is a thin film transistor which has a source and a drain formed on the board | substrate, the 1st electrode which consists of a conductive thin film material connected to the said source or drain on the said thin film transistor, an organic electroluminescent layer, and at least transparent A second electrode comprising a conductive material, a protective layer, and a step of forming an organic EL light emitting device driven by the thin film transistor, a transparent substrate, and a color conversion filter layer formed on the transparent substrate. Forming a laminate;

Attaching the outer periphery of the substrate and the transparent substrate precisely in position by means of a sealing agent that forms an outer periphery seal layer having an uncoated portion at a portion thereof, and

A step of filling a sealing agent forming an inner seal layer from the uncoated portion to a space surrounded by a substrate, a transparent substrate, and an outer seal layer;

It has a process of blocking the uncoated part of the said outer periphery seal layer.

Since the outer peripheral seal layer requires a function of accurately aligning the position of the color filter of the organic EL light emitting layer and the color conversion filter layer and curing it in a short time, and a function of preventing moisture from invading from the external environment after curing, the above materials are suitable. .

In order to transfer light from the organic EL light emitting layer to the color filter, the inner seal layer is required to have a high refractive index, to prevent peeling due to curing shrinkage during curing, and to relieve peeling due to thermal stress from environmental temperature, Suitable materials are refractive indexes of 1.3 to 2.5 and compressive modulus of 50 kg / mm 2 (490 MPa) or less. Since the refractive index is in the range of the refractive index of the other component of the organic light emitting element (for example, the cathode) is 1.3 to 2.5, filling the material in the above range, that is, making the difference in the refractive index small leads to the reduction of the light loss. In addition, the range of the above-mentioned compressive modulus is the value calculated | required empirically.

1 is a cross-sectional view showing the structure of an organic EL display of the present invention.

2 is a cross-sectional view showing the structure of a conventional organic EL display.

The organic EL display of the present invention will be described below. Brief Description of Drawings [Fig. 1] Fig. 1 is a sectional view showing the structure of an organic EL display showing an embodiment of the present invention. In the following description, the case where the first electrode is the anode 3 will be described, but the first electrode may be the cathode.

A. Organic EL Light Emitting Device

The organic EL light emitting device of the present invention includes a substrate 1, a TFT 2 formed on the substrate 1, a planarization insulating film (not shown), an anode 3, an organic EL light emitting layer 4, and a cathode ( 5) and a protective layer 6.

1: TFT part

The TFT portion of the organic EL display according to the present invention includes a substrate 1, a TFT 2, a planarization insulating film, and an anode 3.

The TFTs 2 are arranged in a matrix on an insulating substrate made of glass or plastic, or a substrate 1 on which an insulating thin film is formed on a semi-conductive or conductive substrate, and a source electrode is connected to an anode 3 corresponding to each pixel. do.

An insulating film having a planarization is formed on the TFT 2. The insulating film is provided in addition to the portions necessary for the connection between the source electrode and the anode 3 and other circuits, and the surface of the substrate 1 is planarized to facilitate formation of a high precision pattern of the next layer. The source electrode and the anode 3 may be connected by a conductive plug filled in a contact hole formed in the planarization insulating film.

The anode 3 is formed on the planarization insulating film formed on the TFT 2. In order to perform hole injection efficiently, a material having a large work function is used for the anode 3. In the case of the top emission method of the present invention, the anode 3 need not be transparent, but a conductive metal oxide such as ITO or IZO can be used. In addition, when using a conductive metal oxide such as ITO, it is preferable to use a metal electrode (aluminum, silver, molybdenum, tungsten, etc.) having a high reflectance thereunder. Since the metal electrode has a lower resistivity than the conductive metal oxide, the metal electrode functions as an auxiliary electrode and at the same time reflects the light emitted from the organic EL light emitting layer 4 toward the color filter 12, thereby enabling effective use of the light.

When using a 1st electrode as a cathode, it is connected with the drain of TFT2. An electron-injectable metal or other metal composed of an alkali metal such as lithium or sodium, which is a material having a small work function, and an alkaline earth metal such as potassium, calcium, magnesium, or strontium, or a fluoride thereof, instead of the conductive metal oxide Alloys and compounds with

2: organic EL light emitting layer and cathode

The organic EL light emitting layer 4 and the cathode 5 are provided on the TFT 2 portion where the TFT 2 and the anode 3 are patterned. In the case of using the color conversion method, light in the visible region in the near ultraviolet region emitted from the organic EL light emitting layer 4, preferably light in the blue to blue green region is incident on the color conversion filter layer to emit visible light representing a desired color.

The organic EL light emitting layer 4 has a structure in which a hole injection layer, a hole transport layer, and / or an electron injection layer are interposed, when expressed by combining the anode 3 and the cathode 5. As the layer structure, the following layer structure is adopted.

Anode, organic EL light emitting layer, cathode

Anode, hole injection layer, organic EL light emitting layer, cathode

Anode, organic EL light emitting layer, electron injection layer, cathode

Anode, hole injection layer, organic EL light emitting layer, electron injection layer, cathode

Anode, hole injection layer, hole transport layer, organic EL light emitting layer, electron injection layer, cathode

As a material of each layer mentioned above, a well-known thing is used. In order to obtain blue-blue-green light emission, fluorescent brighteners, such as a benzothiazole type, a metal chelating oxonium compound, etc. are used suitably in the organic EL light emitting layer 4, for example.

The material used for the cathode 5 is desired to have a small work function in order to efficiently inject electrons. Moreover, in the top emission color conversion system of the present embodiment, since the light from the organic EL light emitting layer 4 is emitted through the cathode 5, it must be transparent in the wavelength region of the light. In order to make these two characteristics compatible, it is preferable that the cathode 5 in this invention is a laminated structure which consists of multiple layers. This is because a material having a small work function is generally low in transparency. That is, an alloy or compound with an electron-injectable metal or other metal composed of an alkali metal such as lithium, sodium, alkaline earth metal such as potassium, calcium, magnesium, strontium, or the like, or a fluoride thereof in a portion in contact with the organic EL light emitting layer A thin film of is used. By using materials having a small work function, efficient electron injection is possible, and further, by forming a thin film, it is possible to minimize the decrease in transparency due to these materials. On this thin film, a transparent conductive film such as ITO or IZO is formed. These conductive films function as auxiliary films, and the resistance value of the entire cathode 5 can be reduced to supply sufficient current to the organic EL light emitting layer.

When the second electrode is used as the anode, it is necessary to use a material having a large work function in order to increase the hole injection efficiency. In addition, in order for light emission from the organic EL light emitting layer 4 to pass through the second electrode, it is necessary to use a material having high transmittance. ITO or IZO are preferable.

3: protective layer 6

The protective layer 6 is provided covering each layer below the 2nd electrode formed as mentioned above. The protective layer 6 is effective in preventing oxygen, low molecular weight components, and moisture from permeating from the external environment, thereby preventing the functional degradation of the organic EL light emitting layer 4 by these. It is preferable that the protective layer 6 has a suitable hardness so that it is easy to form another layer thereon.

In order to satisfy this requirement, the protective layer 6 has high transparency in the visible region (50% or more transmittance in the range of 400 to 700 nm), electrical insulation, and barrier property against moisture, oxygen, and the like. It is preferably formed of a material having a film hardness of 2H or more. For example, materials such as inorganic oxides and inorganic nitrides such as SiOx, SiNx, AlOx, TiOx, TaOx, and ZnOx may be used. The protective layer is formed by a sputtering method, a vapor deposition method, an immersion method, a CVD method, or the like.

In addition, various polymer materials can be used as the protective layer 6. The material which disperse | distributed inorganic metal compounds, such as imide modified silicone resin and titanium oxide, in acrylic, polyimide, silicone resin, etc. can be used.

Although the protective layer 6 mentioned above may be a single | mono layer, the effect becomes large when laminating a some layer. It is preferable that the thickness of the protective layer 6 is 0.1-10 micrometers.

B: color conversion filter

The color conversion filter of the present invention is laminated on a transparent substrate 11, which is a second substrate, and has a color filter 12 corresponding to each desired color, or a stack of color filters 12 and a fluorescent conversion layer (not shown), And a black mask 13. In the following description, a transparent substrate is described.

1: transparent substrate

As the transparent substrate 11, a plastic material having a film shape is preferable. As for thickness, 20 micrometers-500 micrometers are suitable. When plastics having a film shape as the substrate are used, the organic EL display of the present invention can be reduced in weight and stronger against bending stress as compared with the case of using glass. However, in the present invention, glass is not excluded as a transparent substrate.

In addition, in this specification, "transparent" means what transmits visible light 10 to 100%. The visible light transmittance also depends on the conversion performance of the fluorescent dye used in the fluorescent conversion layer, preferably about 40 to 80%.

2: color conversion filter layer

In the present specification, the color conversion filter layer includes the color filter 12 or the laminate of the color filter 12 and the fluorescent conversion layer (not shown) and the black mask 13 as described above. The fluorescence conversion layer absorbs light in the near-ultraviolet region to the visible region, particularly in the blue to blue-green region, emitted from the organic EL light-emitting layer to emit visible light having a different wavelength as fluorescence. In order to enable full color display, separate layers for emitting light in at least the blue region, the green region, and the red region are provided.

The red color may be formed only by the fluorescent conversion layer. However, when sufficient color purity is not obtained only by conversion by fluorescent dye, it can also be set as a laminated body of a fluorescent conversion layer and a color filter. Green is the same as red.

On the other hand, in the case of blue, when blue light is emitted from the organic EL light emitting layer, it can be formed only by the color filter. As for the thickness, 1-10 micrometers is preferable.

As is known, the shape of the color conversion filter layer may be a stripe pattern separated for each color, or may have a structure separated for each subpixel of each pixel.                 

It is preferable to form the black mask 13 in the color conversion filter interlayer region corresponding to each color. By providing the black mask 13, light is prevented from leaking to the color conversion filter of the adjacent sub-pixel, and only the desired fluorescent conversion color which does not spread can be obtained. It is preferable that the thickness of the black mask 13 is 1-6 micrometers.

C: seal floor

1: inner seal layer

The inner seal layer 22 is filled with a sealing agent in the inner space 32 formed in the display of the conventional method, thereby suppressing the light emission of the organic EL light emitting layer 4 from being reflected at the inner space interface, and suppressing light emission from the color filter ( 12) is installed for efficient transmission. The inner seal layer 22 is formed of a material having a visible light transmittance of 10 to 100%, preferably 50% or more, and a refractive index of 1.3 to 2.5 to light having a wavelength of 400 to 800 nm. Examples of such materials include organic materials such as transparent silicone rubber and transparent silicone gel.

The filler may be filled between the substrates through an injection port formed in the outer circumferential seal layer 21 after the two substrates are joined by the outer circumferential seal layer 21.

By using such a filler, the refractive index difference of the transmission path of the light emission from the organic EL light emitting layer 4 can be made small, and the reflection at each interface can be suppressed so that light can be transmitted to the color filter 12 more efficiently. do.

2: Outsourced floor

The outer circumferential seal layer 21 is attached to the outer circumference of the substrate and adheres the substrate 1 to the transparent substrate 11 and protects the internal components from oxygen, moisture, and the like in the external environment. The outer seal layer 21 is formed of a visible light curable adhesive or an ultraviolet curable adhesive, and may include beads having a diameter of 3 to 50 μm therein. In this case, the distance between the substrates is defined by the beads, and at the same time, the pressure applied for bonding can be applied. Furthermore, the stress generated at the time of driving the display is also burdened to prevent the display from deteriorating due to the stress.

When the inner seal layer 22 is formed by injection after the bonding of the substrate 1 and the transparent substrate 11, an uncoated portion is formed on a part of the outer seal layer 21 to seal the uncoated portion. It can be used as an injection port of the layer. The injection port may be closed by attaching and curing an outer circumferential seal layer material after the completion of injection.

Hereinafter, embodiments of the present invention will be described in detail.

(Example 1)

As shown in Fig. 1, a TFT 2, an anode 3, an organic EL light emitting layer 4, a cathode 5, and a protective layer 6 are sequentially formed on a substrate (a glass substrate in this embodiment). do. Next, the color filter 12 and the black mask 13 are sequentially formed on the transparent substrate 11 (in this embodiment, the transparent glass substrate). The two substrates thus formed are subjected to the following steps under a dry nitrogen atmosphere (both oxygen and water concentration of 1 ppm or less) in a glove box.

Ultraviolet curable adhesive (Three Bond product, trade name: 30Y-437), which is an epoxy-based material by a dispenser robot (driven by an XY robot as a coating device for an adhesive) on the outer peripheral portion of the organic EL light emitting layer side glass substrate 1 An outer circumferential seal layer 21 is formed to bond the transparent glass substrate 11 toward the color filter 12.

At this time, the coating shape of the outer circumferential seal layer 21 is applied in a shape having an uncoated portion (not shown) in part (in this embodiment, an uncoated portion is placed in a portion of the rectangular display outer circumference). The coated portion is later used as a material injection port of the inner seal layer 22.

Thereafter, the organic EL light emitting layer 4 and the color filter 12 are aligned so as to correspond to each other, and the outer seal layer 21 is irradiated with ultraviolet light for 30 seconds with an illuminance of a wavelength of 365 nm and 100 mW / cm 2 as an ultraviolet curing condition. Harden.

Next, a transparent silicone rubber material (Shin-Etsu Chemical Co., Ltd., product name: KE103) having a refractive index of approximately 1.45 and a compressive modulus of 0.5 kg / mm 2 or less is injected by a dispenser from an injection port formed in a portion of the outer seal layer 21. And cured at 80 ° C. for 60 minutes to form an inner seal layer 22. Thereafter, the material injection port formed in the outer seal layer 21 is sealed using the same ultraviolet curable adhesive as the outer seal layer 21 to complete the organic EL display.

In the present embodiment, blue light is emitted from the organic EL light emitting layer. Accordingly, B of the color filter 12 is composed of only a filter, but G and R of the color filter 12 are laminated with a filter (not shown) for performing wavelength conversion. The thickness of the inner seal layer is 3 to 5 µm (about 10 µm maximum), and the thickness of the outer seal layer is 5 to 30 µm (about 100 µm maximum).

As described above, the gap (gap) between the substrate 1 and the transparent substrate 11 is fixed at an interval of 5 to 100 μm, and intrusion of moisture from the external environment is prevented, resulting in a reliable organic EL display for a long time.

Here, according to the present invention, by forming the display as in the above embodiment, the position of the organic EL light emitting layer 4 and the color filter 12 can be accurately matched. That is, the position is aligned by a marker (not shown) attached to each of the substrate 1 and the transparent substrate 11, and at this time, the following two characteristics are required for the adhesive used for the outer circumferential seal layer 21. That is, the coated adhesive needs to be able to be freely aligned (microscopic movement) without curing until both substrates are combined and the alignment by the marker is completed, and the alignment is cured in a short time. The above two characteristics can be satisfied by using the above UV-curable adhesive and the visible light-curable adhesive described below.

Example 2

The basic configuration of this embodiment is the same as that of the first embodiment. However, a visible light curable adhesive was used for the outer seal layer 21 and a transparent silicone gel material was used for the inner seal layer 22. The visible light curable adhesive is, for example, trade name Luxtrak LCR0275 manufactured by Toagosei Co., Ltd., and is an acrylic material. Curing conditions are wavelength 400nm, illuminance 100mW / ㎠ and irradiation time is 30 seconds. Visible light curable adhesives are cheaper than the ultraviolet curable adhesives and advantageous in terms of equipment cost. The transparent silicone gel material is KE104Gel, manufactured by Shin-Etsu Chemical Co., Ltd., having a refractive index of approximately 1.45 and a compressive modulus of 0.5 kg / mm 2 or less.

According to the present invention, as a result of adopting the above-described configuration, the outer peripheral seal layer allows the organic EL light emitting layer and the color filter to be precisely positioned and fixed in a short time, thereby preventing intrusion of moisture and the like from the external environment. It became.

Moreover, the inner seal layer prevents light from being reflected from the organic EL light emitting layer, thereby effectively transferring the light to the color filter, and also prevents peeling due to curing shrinkage during curing, and prevents thermal stress from environmental temperature. It is possible to alleviate the peeling, and to prevent the intrusion of moisture and the like from the external environment it is possible to maintain a stable light emission characteristics for a long time.

Claims (5)

A thin film transistor having a source and a drain formed on the substrate, a first electrode made of a conductive thin film material connected to the source or drain on the thin film transistor, an organic EL light emitting layer, and a second electrode made of at least a transparent conductive material And an organic EL light emitting element configured by stacking a protective layer, and driven by the thin film transistor; A laminate having a transparent substrate and a color conversion filter layer formed on the transparent substrate, In an organic EL display in which the positions of the organic EL light emitting layer and the color conversion filter layer are sealed and bonded together, An outer circumferential seal layer for sealing and bonding the substrate and the transparent substrate, and an inner seal layer filled inside the outer circumferential seal layer to prevent light emission of the organic EL light emitting layer from being reflected at the inner space interface. Organic EL display. The method of claim 1, An organic EL display using an ultraviolet curable adhesive or a visible light curable adhesive for the outer seal layer. The method according to claim 1 or 2, An organic EL display characterized by using an elastic transparent sealing agent having a refractive index of 1.3 to 2.5 for the inner seal layer. The method of claim 3, wherein An organic EL display using a transparent silicone rubber material or a transparent silicone gel material as an elastic transparent sealing agent. A thin film transistor having a source and a drain formed on the substrate, a first electrode made of a conductive thin film material connected to the source or drain on the thin film transistor, an organic EL light emitting layer, and a second electrode made of at least a transparent conductive material And a step of forming an organic EL light emitting element which is formed by laminating a protective layer and driven by the thin film transistor, Forming a laminate having a transparent substrate and a color conversion filter layer formed on the transparent substrate; A step of precisely positioning and bonding the outer periphery of the substrate and the transparent substrate with a sealing agent to form an outer seal layer having an uncoated portion in part; A step of filling a sealing agent forming an inner seal layer from the uncoated portion to a space surrounded by the substrate, the transparent substrate, and the outer seal layer; Closing the uncoated portion of the outer seal layer; The manufacturing method of the organic electroluminescent display characterized by having.

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