JP2013214396A - Method of forming functional film, method of manufacturing organic el panel, display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of forming a functional film capable of forming a functional film of uniform thickness over a plurality of discharged areas, and to provide a method of manufacturing an organic EL panel by using the method of forming a functional film, and a display device having excellent display quality.SOLUTION: For a plurality of discharged areas partitioned by partition walls provided on a substrate, a predetermined amount of functional fluid containing a first solvent is discharged and then dried. Subsequently, a second solvent for dissolving a functional material within a range of predetermined amount is discharged while increasing the amount gradually, from a discharged area in the center of the substrate toward a discharged area on the periphery of the substrate, and then dried. As a result, film thickness irregularity between discharged areas can be suppressed.

Description

  The present invention relates to a method for forming a functional film, a method for manufacturing an organic electroluminescence (EL) panel, and a display device including the organic EL panel.

  In recent years, an organic EL panel using an organic EL element as a display element has been widely used as a display device. An organic EL element obtains light of a desired brightness and color by passing a current through a light emitting layer containing a light emitting material. As a method for forming the light emitting layer, for example, a liquid containing a light emitting material is applied to each of a plurality of discharge regions partitioned by a partition on a substrate from a head including a nozzle for discharging the liquid. A predetermined amount is discharged, and then the solvent component contained in the liquid is evaporated and solidified by a drying process such as reduced pressure drying or heat drying.

  By the way, in the case of a display device using an organic EL element as a display element, it is necessary to pass a current through the light emitting layer as described above. By adjusting the amount of current, the brightness and color emitted by the organic EL element are controlled to provide a display device. The light emitting layer is a functional film containing a light emitting material, and this functional film has an overwhelmingly higher electrical resistance than metal. Therefore, when manufacturing a display device using an organic EL element, it is possible to control the brightness and color of light emission of the display device to a desired state by forming the functional film so that the thickness of the functional film is uniform within the panel surface. This can improve the display quality of the display device.

  On the other hand, in the drying process, it is difficult to make the evaporation rate of the solvent component contained in the liquid material discharged to the discharge area uniform over a plurality of discharge areas in the panel surface. For example, during the drying process, the solvent evaporation is slower in the discharge area in the center of the panel and the discharge area in the center of the panel because the solvent is disposed more in the periphery of the discharge area in the center of the panel. Become. As described above, when the evaporation rate is non-uniform, the film shape of the functional film obtained by drying the liquid material varies between the discharge regions, and the film thickness between the discharge regions becomes non-uniform. The nonuniformity of the film thickness between the discharged regions causes the nonuniformity of the brightness and the color emitted from the light emitting layer, thereby degrading the display quality of the display device.

  Therefore, for example, Patent Document 1 discloses a drying speed in a drying process using two kinds of liquid materials, that is, a functional liquid containing a solute in a discharge region formed on a substrate and a solvent liquid containing no solute. There has been proposed a method for making the thickness of the functional film uniform.

JP 2009-247933 A

  However, in the liquid material discharge method proposed in Patent Document 1, the discharge amount of the functional liquid (liquid material) discharged for each discharge region is changed. The film formation start position (end latching position at which the functional film begins to form as the liquid material progresses drying; pinning position) varies for each discharge area. When the formation start position of the functional film varies, there is a problem that the film shape of the functional film varies and a functional film having a uniform film thickness is not necessarily formed. Moreover, there exists a possibility of reducing the display quality of the display apparatus provided with the organic electroluminescent panel manufactured using this method.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 A functional film forming method according to this application example is obtained by discharging a functional liquid containing a functional material to a plurality of discharge target areas partitioned by a partition provided on a substrate. A functional film forming method for forming a functional film, comprising: a first discharge step of discharging a predetermined amount of the functional liquid including a first solvent for each of the discharge target areas; and the functional liquid discharged to the discharge target areas. A first drying step for drying and a second solvent for dissolving the functional material stepwise from the discharge region at the center of the substrate to the discharge region at the periphery of the substrate within the predetermined amount or less. And a second drying step for drying the second solvent in the region to be ejected, and a second drying step for drying the second solvent in the region to be ejected.

  According to this application example, in the first discharge step, the functional liquid containing the first solvent is discharged to a discharge region formed on the substrate by a predetermined amount, thereby forming the functional film on the sidewall of the partition wall during the first drying step. The variation in the start position is smaller than when the functional liquid discharge amount is changed for each discharge target region. By reducing the difference in the formation start position of the functional film, variation in the film shape of the functional film in the discharge target region is reduced.

  In the second discharge step, the second solvent is discharged within a range of a predetermined amount or less of the functional liquid at the time of the first discharge step, thereby promoting re-dissolution or re-dispersion of the functional film formed at the first drying step. Even so, the formation start position is unlikely to change. Conversely, the functional film obtained in the first drying step is re-dissolved or re-dispersed in the second discharge step, so that the functional film shape of each functional region formed in the first drying step is obtained. Can be reset and changed. Furthermore, in the second discharge step, by changing the filling amount discharged into the discharge region, the difference in the evaporation rate of the second solvent from each discharge region in the second drying step is reduced, Thereby, the difference in film thickness between the discharged regions can be reduced. In other words, it is possible to provide a method for forming a functional film that can reduce variations in film thickness between discharge target regions.

  Application Example 2 In the method for forming a functional film according to the application example, the viscosity of the second solvent is equal to or lower than the viscosity of the functional liquid.

  According to this application example, even if the second solvent discharged in the second discharge step is smaller in discharge amount than the first solvent discharged in the first discharge step, the entire area to be discharged can be wetted and spread. I can do it.

  Application Example 3 In the method for forming a functional film according to the application example described above, the liquid repellent treatment is performed so that at least a part of the side wall of the partition wall has liquid repellency.

  According to this application example, when the functional liquid and the second solvent containing the first solvent are discharged to the discharge target area in the first discharge process and the second discharge process, respectively, the functional liquid and the second solvent are discharged from the discharge target area. It is possible to avoid defects overflowing from the inside and defects in which the functional liquid and the second solvent are disposed across adjacent discharge target areas.

  Application Example 4 A method for manufacturing an organic EL panel according to this application example is a method for manufacturing an organic EL panel having a structure in which a plurality of functional films including at least a light emitting layer are sandwiched between an anode and a cathode. Using the functional film forming method, at least one of the plurality of functional films is formed.

  According to this application example, for example, the film thickness of the light emitting layer formed by the functional liquid after the drying process becomes substantially uniform, and the luminance unevenness of the organic EL panel is suppressed.

  Application Example 5 A display device according to this application example includes an organic EL panel manufactured by the method for manufacturing an organic EL panel.

  According to this application example, it is possible to provide a display device including an organic EL panel in which luminance unevenness is suppressed.

FIG. 2 is a schematic diagram of a discharge situation according to the first embodiment. FIG. 6 is a schematic diagram showing a wiring structure of an organic EL panel according to Embodiment 2. FIG. 5 is a plan view schematically showing a configuration of an organic EL panel according to Embodiment 2. (A) And (b) is sectional drawing in the manufacturing process of the organic electroluminescent panel which concerns on Embodiment 2. FIG. (A) And (b) is sectional drawing in the manufacturing process of the organic electroluminescent panel which concerns on Embodiment 2. FIG. (A) And (b) is sectional drawing in the manufacturing process of the organic electroluminescent panel which concerns on Embodiment 2. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the scale of each layer and each member is made different from the actual scale so that each layer and each member can be recognized.

(Embodiment 1)
First, an outline of a method for forming a functional film of the present embodiment will be described with reference to FIG. In FIG. 1, four colors are arranged in the Y-axis direction (vertical direction in the drawing) on the substrate P and six pixels are arranged in the X-axis direction (horizontal direction in the drawing). It is a schematic diagram which shows a mode that the functional liquid containing the luminescent material and solvent corresponding to a layer are discharged. Each pixel is partitioned on the substrate P by partition walls, and the partitioned area is called a discharge target area. In other words, the illustrated pixel may be referred to as an ejection area. In the present embodiment, the direction in which pixels of different colors are repeatedly arranged is referred to as an X-axis direction, and the direction in which pixels of the same color are arranged is described as a Y-axis direction hereinafter.

  As shown in FIG. 1, in the present embodiment, the substrate P and the nozzle head 20 having nozzles are arranged to face each other and move from the nozzles to R, G, and B during the main scanning in which they are relatively moved in the Y-axis direction. The R functional liquid, the G functional liquid, and the B functional liquid are discharged to the corresponding pixels, respectively. Furthermore, R solvent liquid, G solvent liquid, and B solvent liquid are respectively applied to the pixels corresponding to R, G, and B from the nozzle provided in the nozzle head 30 that moves relative to the substrate P together with the nozzle head 20. Discharge. In addition, each solvent solution may be the same solvent as the solvent contained in each functional solution, or may be different.

  In the present embodiment, the functional liquid is discharged by so-called scan scanning of the nozzle head 20 with respect to three pixels continuous in the X-axis direction by one main scanning. That is, for all the pixels formed on the substrate P, first, the functional liquid is discharged to the pixels included in the main scanning area indicated by the broken line in the drawing by the first main scanning (first discharging step). Thereafter, vacuum drying is performed for the purpose of removing the solvent from the functional liquid (first drying step). Next, the solvent liquid is ejected by performing so-called scan scanning of the nozzle head 30 with respect to three pixels continuous in the X-axis direction by two main scans (second ejection step). However, the solvent liquid discharged for the second time is discharged by controlling the discharge amount so as to be equal to or less than the discharge amount (volume amount) of the functional liquid discharged for the first time. Then, the solvent liquid discharged to each pixel is dried under reduced pressure (second drying step).

  Here, in this embodiment, in order to simplify the description, it is assumed that each nozzle block 20R, 20G, 20B and each nozzle block 30R, 30G, 30B has one nozzle. Usually, the nozzle head 20 is formed with a large number of nozzles, and it goes without saying that the functional liquid and the solvent liquid are discharged from the corresponding nozzles to the large number of discharged areas partitioned on the substrate P, respectively.

  When the functional liquid is discharged to all the pixels in this way, the R functional liquid is in the order of pixels R1 to R8, the G functional liquid is in the order of pixels G1 to G8, and the B functional liquid is Functional liquids are discharged in the order of the pixels B1 to B8. As a result, for example, with respect to all the R pixels, the amount of the functional liquid discharged to each pixel decreases by natural drying during the time until the functional liquid is discharged to the last pixel R8. The number of discharged pixels R1 is the largest, and the number decreases in the order in which the R functional liquid is discharged, such as the next pixel R2, the next pixel R3,. Further, when the solvent is dried under reduced pressure for the purpose of removing the solvent of the functional liquid thereafter, the amount of solvent per unit area arranged around each pixel is different. ) Occurs. Similarly, when other G function liquids or B function liquids are ejected, uneven evaporation of the solvent occurs.

  Therefore, in this embodiment, when discharging the solvent liquid, for example, if the pixel is around the substrate, the amount of the solvent liquid to be discharged is increased, and if the pixel is at the center of the substrate, the amount of the solvent liquid to be discharged is decreased. The time required for the solvent to evaporate during drying under reduced pressure is set to be the same for the pixels on the entire substrate. In other words, the solvent amount is discharged for each pixel by adjusting the discharge amount so as to reduce the unevenness of the evaporation rate of the solvent between the pixels of the substrate P.

  As described above, according to the present embodiment, by setting the liquid amount (discharge amount) of the functional liquid discharged first to the same amount for all the discharge target regions on the substrate, each discharge target region The formation start position (pinning position) of the functional film on the side wall of the partition wall that divides is substantially the same in all the discharge target regions. Then, by changing the discharge amount of the solvent liquid to be discharged (discharge amount) from the central portion of the substrate to the peripheral portion within a predetermined amount, the time required for evaporation of the solvent can be reduced. To equalize. Further, in order to keep the formation start position of the functional film on the side wall of the partition wall at the same position in all the discharge target regions, the discharge amount of the solvent liquid is set to be equal to or less than the discharge amount (predetermined amount) of the functional liquid. By doing so, since the formation start position of the functional film obtained in the first drying step does not change, film unevenness is suppressed.

(Embodiment 2)
The organic EL panel according to the present embodiment will be described with reference to FIGS. FIG. 2 is a schematic view showing a wiring structure of the organic EL panel according to the second embodiment, and FIG. 3 is a plan view schematically showing a configuration of the organic EL panel according to the second embodiment.

  As shown in FIG. 2, the organic EL panel 1 of the present embodiment is of an active matrix type using a thin film transistor (hereinafter referred to as TFT) as a switching element, and includes a plurality of scanning lines 101, The wiring structure includes a plurality of signal lines 102 extending in a direction perpendicular to the scanning line 101 and a plurality of power supply lines 103 extending in parallel to each signal line 102. A pixel (sub pixel 40) is provided in the vicinity of each intersection.

  A data line driving circuit 100 including a shift register, a level shifter, a video line, and an analog switch is connected to the signal line 102. Further, a scanning line driving circuit 80 having a shift register and a level shifter is connected to the scanning line 101.

  Each of the sub-pixels 40 holds a switching TFT 122 in which a scanning signal is supplied to the gate electrode through the scanning line 101 and a pixel signal supplied from the signal line 102 through the switching TFT 122. A driving current is applied from the power source line 103 when the capacitor 113, the driving TFT 123 to which the pixel signal held by the holding capacitor 113 is supplied to the gate electrode, and the power source line 103 through the TFT 123 are electrically connected. Light-emitting function sandwiched between the pixel electrode (anode) 23, the counter electrode (cathode) 50 at a position facing the pixel electrode (anode) 23, and the pixel electrode (anode) 23 and the counter electrode (cathode) 50 And an organic EL element 17 (R, G, B) (R (red), G (green), B (blue)) provided with a functional layer.

Next, a specific aspect of the organic EL panel 1 of the present embodiment will be described with reference to FIG.
As shown in FIG. 3, in the actual display area 4 on the substrate 20A, subpixels 40 provided corresponding to R, G, and B are regularly arranged in a matrix. Here, the substrate 20 </ b> A includes a substrate body 20 and, for example, TFTs 122 and 123 provided on the substrate body 20.

  The sub-pixels 40 (R, G, B) of R, G, and B colors constitute a display unit pixel 41 as one basic unit. Each of the sub-pixels 40 (R, G, B) emits light corresponding to red (R), green (G), and blue (B) as the TFTs 122 and 123 operate. (R, G, B). Thus, the display unit pixel 41 has a configuration for performing full color display by mixing R, G, and B light emission.

  In the present embodiment, the pixel unit 3 includes an actual display area 4 in the center (within the two-dot chain line in the figure) and a dummy area 5 (one-dot chain line and two-dot chain line) arranged around the actual display area 4. Between the two areas). Further, scanning line driving circuits 80 are arranged on both sides of the actual display area 4 in FIG. The scanning line driving circuit 80 is provided on the lower layer side of the dummy region 5.

  Further, an inspection circuit 90 is disposed above the actual display area 4 in FIG. 3, and the inspection circuit 90 is disposed on the lower layer side of the dummy area 5. This inspection circuit 90 is a circuit for inspecting the operating state of the organic EL panel 1, and includes, for example, inspection information output means for outputting inspection results to the outside, and the quality of the organic EL panel 1 during manufacture or at the time of shipment. It is configured to be able to inspect for defects. A relay substrate (FPC) 36 on which a driver IC (data line driving circuit) 100 for driving the organic EL panel 1 is mounted is electrically connected to the terminal portion of the organic EL panel 1.

  A method for manufacturing the organic EL panel 1 according to the present embodiment will be described with reference to FIGS.

  4 (a) and 4 (b), 5 (a) and 5 (b), 6 (a) and 6 (b) are process cross-sectional views for explaining a method for manufacturing the organic EL panel shown in the present embodiment. It is. In addition, as a manufacturing method of an organic EL panel, a manufacturing method of one organic EL element 17 among R, G, and B will be described. Hereinafter, description will be made along this drawing.

  First, as step 1, a substrate 20A formed by forming TFTs 122, 123, etc. on a substrate body 20 using a transparent member such as glass is washed, and a silicon nitride layer to be an interlayer insulating layer 202 is formed by a CVD method (chemical vapor phase). About 400 nm is deposited using a deposition method or the like.

  Next, as process 2, ITO is laminated | stacked using a sputtering method so that it may become a thickness of about 50 nm. Then, the anode 204 having light transmittance is formed by etching away unnecessary portions.

  Next, as step 3, a silicon oxide layer is formed to a thickness of about 50 nm, and a region where the light emitting region 211 is formed is removed by etching to form a first partition 205.

  Next, as step 4, a photosensitive acrylic resin is applied to a thickness of about 2 μm, and exposed and developed to form the second partition 206. The planar dimension of the discharge target region 117 inside the second partition 206 has a substantially rectangular shape having a shape of about 150 μm × 50 μm, for example.

  Next, as step 5, oxygen plasma treatment, plasma treatment with carbon tetrafluoride gas, or the like is performed to impart lyophilicity to the anode 204 and the first partition 205, and to impart lyophobicity to the second partition 206.

  Next, as Step 6, the PEDOT / PSS dispersion is discharged into the second partition 206 using a droplet discharge method. In this case, since the second partition wall 206 is given liquid repellency, the PEDOT / PSS dispersion liquid is repelled in the second partition wall 206 and flows onto the first partition wall 205 and the anode 204, so Some deviation is corrected, and the droplets are arranged on the first partition 205 and the anode 204 with high reproducibility.

  Next, as a process 7, a hole injection layer 207 as a carrier injection layer using PEDOT / PSS is formed by performing a drying process or the like. FIG. 4A shows a cross-sectional view after the process is completed. The thickness of the hole injection layer 207 is preferably about 20 nm, for example.

  Next, as step 8, the functional liquid 220 including the first solvent 222 is discharged into the second partition 206 using a droplet discharge method. In this case, as the first solvent 222 constituting the functional liquid 220, it is preferable to use a solvent having a boiling point of 170 ° C. or higher and 300 ° C. or lower, such as cyclohexylbenzene or tetramethylbenzene. Further, as a material constituting the functional layer 224 functioning as a light emitting layer (see FIG. 6A), a polyfluorene polymer derivative is added with a perylene dye, a coumarin dye, a rhodamine dye, rubrene, perylene, 9, 10 -It is possible to use substances doped with diphenylanthracene, tetraphenylbutadiene, Nile red, coumarin 6, quinacridone, etc., and to obtain three colors of RGB by using one or a mixture of these dopants Is possible.

  At this time, it is not always necessary to obtain a state in which injection unevenness caused by evaporation of the solvent in the vicinity of the ejection head is suppressed.

  The concentration of the material added to form the functional layer 224 in the first solvent 222 is preferably about 3 wt%. By using such a concentration, the layer thickness of the functional layer 224 can be secured, and the viscosity can be suppressed to such an extent that ejection can be easily performed.

  Next, as step 9, drying under reduced pressure is performed. By performing the reduced pressure drying process, the first solvent 222 is evaporated and the functional layer 221 is formed. FIG. 5A shows a cross-sectional view after this process is completed.

  Next, as step 10, the discharge of the functional liquid 220 containing the first solvent 222 into the second partition 206 with the second solvent 223 having a viscosity of the first solvent 222 or less and a boiling point of 170 ° C. or more and 300 ° C. or less. The discharge is performed so that the discharge amount decreases stepwise from the peripheral partition to the central partition. As the second solvent 223 used here, for example, tetralin, tetralone, cyclohexylbenzene, or tetramethylbenzene is preferably used. In this discharging step, the functional layer 221 is dissolved or dispersed again, and once becomes liquid, spreads in the second partition 206 in a film shape. FIG. 5B shows a cross-sectional view after this process is completed.

  Then, vacuum drying is performed. By performing the reduced pressure drying process, the second solvent 223 evaporates and the functional layer 224 is formed.

  Here, the effect obtained for the step 10 will be described in more detail. Although the functional liquid 220 containing the first solvent 222 is discharged to all the discharge target regions 117 at a constant amount, the functional layer 221 formed by the uneven evaporation rate of the first solvent 222 has uneven film shape in the surface. It has occurred. However, since the second solvent 223 has a lower viscosity than the functional liquid 220 including the first solvent 222 and is smaller than the discharge amount of the functional liquid 220, the second solvent 223 of the functional layer 221 formed by the functional liquid 220 is used. The functional layer 221 can be redissolved or dispersed by the second solvent 223 while maintaining the pinning position formed in the partition wall 206. Therefore, by changing the discharge amount of the second solvent 223 in the surface, it becomes possible to make the film shape in the discharge target region 117 on the entire panel surface the same, and the organic EL panel 1 with high uniformity of light emission luminance can be obtained. It can be manufactured.

  Next, as step 11, a cathode 225 using calcium having a thickness of about 5 nm is formed. Then, an organic EL element 17 (R, G, B) shown in FIG. 6B is formed by forming a light reflection layer 226 using aluminum having a layer thickness of 200 nm or more so as to cover the cathode 225. Is done.

  Here, the manufacturing method of the bottom emission type organic EL element 17 (R, G, B) for extracting light through the transparent substrate 20A has been described, but this is easily changed to the top emission type manufacturing process. It is possible. That is, by adding a step of forming a reflective layer such as aluminum having a thickness of, for example, 200 nm or more between the transparent substrate 20A and the interlayer insulating layer 202, the reflectance on the substrate 20A side is increased, and light transmittance is achieved. If the cathode 225 is formed using Mg / Ag which is resistant to oxidation, a step of obtaining a top emission type structure can be obtained. In addition, by omitting the step of forming the light reflection layer 226 and not performing the step of forming the reflection layer, it is possible to obtain a structure that can be viewed on both sides.

As described above, according to the method for manufacturing the organic EL panel 1 according to the present embodiment, it is possible to manufacture the organic EL panel 1 with high uniformity of light emission luminance.
Note that the hole injection layer 207 is not limited to the formation of the functional layer 224 functioning as a light emitting layer, and the functional film formation method of Embodiment 1 can be applied.
Further, the organic EL element 17 is not limited to the one having the hole injection layer 207 and the functional layer 224 between the anode 204 and the cathode 225. For example, a hole transport layer may be provided between the hole injection layer 207 and the functional layer 224, or an intermediate layer, an electron transport layer, or the like may be provided between the functional layer 224 and the cathode 225. These hole transport layer, intermediate layer, and electron transport layer can also be formed by applying the functional film forming method of the first embodiment.

(Embodiment 3)
The display apparatus of this embodiment is provided with the organic EL panel 1 manufactured using the manufacturing method of the organic EL panel 1 of the said embodiment. The display device including the organic EL panel 1 can be suitably used for a display unit in an electronic device such as a notebook personal computer, a portable information terminal, a mobile phone, a video camera, a digital camera, or a navigation system.

  DESCRIPTION OF SYMBOLS 1 ... Organic EL panel, 17 ... Organic EL element, 20A ... Substrate, 23, 204 ... Anode (pixel electrode), 40 ... Pixel, 50, 225 ... Cathode, 117 ... Discharge area, 206 ... Second partition as a partition 220, functional liquid, 221, 224, functional layer (light emitting layer), 222, first solvent, 223, second solvent.

Claims (5)

A functional film forming method for forming a functional film by discharging a functional liquid containing a functional material to a plurality of discharge target areas partitioned by a partition provided on a substrate,
A first discharge step of discharging a predetermined amount of the functional liquid containing a first solvent for each of the discharged regions;
A first drying step of drying the functional liquid discharged to the discharged region;
A second discharge that discharges the second solvent that dissolves the functional material while increasing stepwise within a range of the predetermined amount or less as the second solvent moves from the discharge region at the center of the substrate to the discharge region at the periphery of the substrate. Process,
And a second drying step of drying the second solvent in the discharge region. A method for forming a functional film according to claim 1,
The method for forming a functional film, wherein the viscosity of the second solvent is equal to or lower than the viscosity of the functional liquid. A method for forming a functional film according to claim 1 or 2,
A method for forming a functional film, comprising performing a liquid repellent treatment so that at least a part of the side wall of the partition wall has liquid repellency. A method for producing an organic EL panel having a structure in which a plurality of functional films including at least a light emitting layer are sandwiched between an anode and a cathode,
A method for producing an organic EL panel, wherein at least one of the plurality of functional films is formed using the method for forming a functional film according to claim 1.   A display device comprising the organic EL panel manufactured by the method for manufacturing an organic EL panel according to claim 4.

Images