JP3761146B2 - Color EL panel and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a color EL panel composed of an electroluminescent (EL) element in which a light emitting layer is formed by juxtaposition by patterning a plurality of light emitting layer materials, and in particular, a color filter is combined with the EL element. The present invention relates to a filter type color EL panel configured as described above and a manufacturing method thereof.
[0002]
[Prior art]
A thin-film EL panel has a structure in which a lower electrode, a lower insulating layer, a light emitting layer, an upper insulating layer, and an upper electrode are sequentially stacked on a substrate made of glass, a ceramic plate, etc., and an alternating current is formed between the upper electrode and the lower electrode. Light emission is obtained by applying a voltage. The thin film EL panel that has been put into practical use is a yellow monochrome display using a ZnS: Mn thin film as a light emitting layer, a translucent conductive film as a lower electrode, a metal electrode as an upper electrode, and light from the lower electrode side. Take out.
[0003]
With the recent development of the information industry, the demand for color displays is increasing, and the application to colorization of thin-film EL panels is being actively promoted. In order to colorize thin film EL panels, many filter-type thin film EL panels in which a thin film EL element and a color filter are opposed have been developed. The filter system is a system in which a single color of light emitted from a thin film EL element is dispersed by a color filter made of a plurality of colors of organic substances to obtain a plurality of emission colors.
[0004]
Thin film EL panel colorization methods include a filter method, a side-by-side method in which light-emitting layers of different emission colors are arranged to form picture elements, a lamination method in which EL elements of different emission colors are stacked and stacked, A double substrate system in which EL elements having different emission colors are formed on a substrate and the both are superposed is mentioned as a main system.
[0005]
The filter system only has to be provided with one kind of light emitting layer in the EL element, and the manufacturing process is simplified, and it is easy to make and the manufacturing cost can be lowered. Therefore, the filter system is generally adopted as a method for coloring EL elements. Yes. However, since a monochromatic light emitting layer having a broad emission spectrum is spectrally divided into a plurality of emission colors by a color filter, there is a problem that a certain percentage of the emission spectrum is cut by the color filter and the luminance tends to be insufficient.
[0006]
In order to solve the above-mentioned problem, it is considered to use a light-emitting layer formed in a juxtaposed manner for an EL panel by patterning a plurality of light-emitting layer materials exhibiting an emission spectrum close to a desired emission color corresponding to the desired color. To do.
Currently, for the purpose of obtaining light emission of a desired luminescent color itself, a color filter system is not adopted at all due to problems such as luminance and lifetime. Considering the luminance depending on the desired emission color, the type using the juxtaposition method and the color filter method together can provide higher luminance.
[0007]
A plurality of light emitting layer materials are patterned to form a light emitting layer by a juxtaposition method, and a color filter is combined with the EL panel structure, and light emitted from the EL element is dispersed by the color filter. As a result, it becomes possible to use light emitting layer materials that emit light of colors close to each color, so that the portion of the emission spectrum that is cut by the color filter is reduced, and the light emission efficiency of the panel is apparently increased. As a result, the luminance of the color EL panel can be improved.
[0008]
Japanese Patent Application Laid-Open No. 61-13597 discloses a technique for patterning a light emitting layer and forming a color EL panel by a juxtaposition method. In the above publication, an etching technique, a photolithography method, a mask vapor deposition method, and the like are proposed as a method for patterning the light emitting layer. As a light emitting layer patterning method for a color EL panel, an etching technique is generally used due to the fact that the pixels of the panel are very small and the pixel density is high, and the material characteristics of the light emitting layer are well known. is there.
[0009]
[Problems to be solved by the invention]
In the side-by-side color EL panel that combines color filters as described above, the light emitting layer is patterned by etching. Therefore, when viewed in detail, the surface of the light emitting layer is formed by resist formation and etching solution penetration during etching. Becomes a very rough shape. When an EL element is formed by forming an upper insulating layer and an upper electrode on a rough light emitting layer, crystal defects are likely to occur in the rough portion, and there are many shallow levels of charge at the light emitting layer and insulating layer interface. As a result, the EL element starts to emit light when the electric field of the light emitting layer is low, and the EL element starts to emit light, and the luminance-applied voltage characteristic of the EL element characteristic is not steep.
[0010]
Usually, an EL element exhibits a steep luminance-applied voltage characteristic in which luminance rapidly increases at a threshold voltage that is a light emission start voltage. If the luminance-applied voltage characteristic is not steep, a large modulation voltage is required for the color EL panel, and the power consumption of the panel increases. Further, since electric charges flow when the light emission electric field is low, a strong electric field is not applied to the light emitting layer, and the energy of the electric charge flowing in the light emitting layer is reduced, resulting in a decrease in light emission luminance.
[0011]
Therefore, the power consumption of the panel caused by the deterioration of the luminance-applied voltage characteristics increase , And measures against brightness reduction due to the fixed modulation voltage of the drive circuit take There is also a need.
[0012]
An object of the present invention is to provide a color EL panel having good display quality by preventing an increase in power consumption and a decrease in light emission luminance in a juxtaposed color EL panel for patterning a light emitting layer of an EL element, and a method for manufacturing the same. It is.
[0013]
[Means for Solving the Problems]
The present invention comprises a substrate;
Upper and lower electrodes disposed on one side of the substrate;
Two insulating layers disposed between the upper and lower electrodes;
A light emitting layer in which a plurality of light emitting layer materials are patterned and arranged in parallel on the insulating layer on the substrate side in contact with the insulating layer; and
In contact with the light-emitting layer on the light-emitting layer, and crystalline compatibility with the light-emitting layer material Is good and does not include the emission center material so , By the film-forming method without etching The film thickness should be over 50nm and below 200nm A color EL panel having an electroluminescent element including a film surface improving layer formed and covering a light emitting layer portion to be emitted.
[0014]
According to the present invention, in the color EL panel configured by the juxtaposition method of patterning the light emitting layer of the EL element, the light emitting layer material has a crystal structure close to the entire surface of the light emitting layer where light emission is desired. Since the film surface improvement layer is formed using a material that is easily combined with the crystal, the continuity of the crystal of the light emitting layer is improved at the patterning portion of the light emitting layer. Because the surface of the film surface improvement layer formed by various deposition methods such as vapor deposition and sputtering, which do not include the etching process, has better crystallinity than the light emitting layer damaged by the etching process and deteriorated in crystallinity. Between the insulating layer and the film quality improvement layer, a shallow level of charge cannot be formed due to crystal defects, and a deep level of charge is formed. As a result, the luminance-applied voltage characteristics of the EL element can be kept steep, so that a color EL panel with good display quality that can prevent an increase in panel power consumption and a decrease in light emission luminance can be configured.
[0015]
The present invention is characterized in that a color filter formed on a translucent substrate is provided so as to face the electroluminescent element.
[0016]
According to the present invention, by emitting light from an EL element in which a plurality of light emitting layer materials are patterned using a color filter, light emitting layer materials exhibiting light emission close to each color can be used. Therefore, the portion where the emission spectrum is cut by the color filter is reduced, the efficiency of the panel emission is apparently increased, the luminance of the color EL panel can be improved, and a color EL panel with a better display quality is configured. It is possible.
[0017]
In the present invention, the film thickness dm (m) of the film surface improvement layer is determined by the relative dielectric constant εm of the film surface improvement layer, the amplitude value of the applied voltage waveform to be started to be determined, which is determined by the driving circuit of the color EL panel. Va (V), the relative dielectric constant of the light emitting layer is εp, the threshold electric field of the light emitting layer where the light emitting layer starts to light is Eth (V / m), the film thickness of the light emitting layer is dp (m), and the two insulating layers When the sum of the film thicknesses is di (m) and the sum of the apparent dielectric constants of the two insulating layers is εi,
dm ≦ (εm × Va) / (εp × Eth) −εm × dp / εp-εm × di / εi
It is selected so as to satisfy the relationship.
[0018]
According to the present invention, by setting the film surface improvement layer to a certain film thickness or less, the voltage required for causing the EL element to emit light as in the case where the film thickness exceeds the certain film thickness becomes higher than the designed voltage. In addition, since the modulation voltage of the driving circuit of the color EL panel is fixed, the modulation voltage cannot be taken and the luminance is lowered, and the EL element does not emit light even when the maximum voltage applied by the driving circuit is applied. Absent. When the light emitting layer is formed by juxtaposing a plurality of different materials, dm is calculated from the above formula for each material portion, and the smallest dm among them is defined as the upper limit of dm of the entire EL element. do it.
[0019]
The present invention includes a step of forming a lower electrode and an insulating layer on one surface of a substrate;
Forming a light emitting layer on the insulating layer by patterning a plurality of light emitting layer materials by etching and juxtaposing them;
Crystalline compatibility with the light emitting layer material on the light emitting layer Is good and does not include the emission center Using a material, cover the light emitting layer part that you want to emit light, and apply a film surface improvement layer by a film formation method that does not include etching. The film thickness should be over 50nm and below 200nm Forming, and
Forming another insulating layer on the film surface improving layer and then heat-treating the layer formed;
And a step of forming an upper electrode on the heat-treated insulating layer.
[0020]
According to the present invention, in the color EL panel configured by the juxtaposition method of patterning the light emitting layer of the EL element, the light emitting layer material has a crystal structure close to the entire surface of the light emitting layer where light emission is desired. Since the film surface improvement layer is formed using a material that is easily combined with the crystal, the continuity of the crystal of the light emitting layer is improved at the patterning portion of the light emitting layer. Because the surface of the film surface improvement layer formed by various deposition methods such as vapor deposition and sputtering, which do not include the etching process, has better crystallinity than the light emitting layer damaged by the etching process and deteriorated in crystallinity. Between the insulating layer and the film quality improvement layer, a shallow level of charge cannot be formed due to crystal defects, and a deep level of charge is formed. In addition, the heat treatment improves the interface state between the patterning surface of the light emitting layer of the EL element and the film surface improvement layer, and improves the crystallinity at the interface portion and reduces crystal defects. It is possible to manufacture a color EL panel with good display quality that can be kept sharp and prevent an increase in power consumption of the panel and a decrease in light emission luminance.
[0021]
The present invention is characterized in that, when ZnS: Mn and SrS: Ce are used as the light emitting layer material and ZnS is used as the material of the film surface improving layer, the temperature is set to 400 ° C. or higher in the heat treatment step. To do.
[0022]
According to the present invention, heat treatment is performed at 400 ° C. or more using ZnS: Mn and SrS: Ce as the light emitting layer material and ZnS as the film surface improving layer, so that the crystallinity near the interface between the film surface improving layer and the light emitting layer is improved. Since crystal defects are reduced, a color EL panel with high luminance and luminous efficiency can be obtained.
[0023]
The present invention is characterized in that, in the heat treatment step, the temperature is set to a temperature lower than the lower one of the deformation temperature and the alteration temperature of the substrate.
[0024]
According to the present invention, since the heat treatment is performed at a temperature lower than the temperature at which the substrate is deformed and deteriorated, the yield of the panel can be improved and the panel cost can be reduced without causing the deformation of the panel during and after the production of the color EL panel. At the same time, display quality deterioration due to panel distortion can be prevented.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
First embodiment
FIG. 1 is a cross-sectional perspective view of a color EL panel according to an embodiment of the present invention. The color EL panel includes an EL panel substrate 123, a color filter substrate 120, and a resin adhesive 115. The EL panel substrate 123 includes an EL element substrate 119, an insulating liquid 20, a sealing plate 18, an injection hole 19, a sealing plate 110, and a sealing resin 117.
[0026]
The EL element substrate 119 is formed by forming an EL element 118 on a substrate 11 which is a glass substrate having a plate thickness of 1.1 mm and a glass size of 150 mm × 110 mm, for example. The EL element 118 includes, for example, a translucent lower electrode 12 in which ITO (Indium-tin-oxide) is formed in a thickness of 50 to 500 nm, Si _Three N _Four / SiO ₂ The lower insulating layer 13 having a laminated film thickness of 200 to 500 nm, the light emitting layer 14 patterned in a stripe shape with ZnS: Mn and SrS: Ce with a thickness of 300 to 1000 nm, and the same crystal structure as ZnS: Mn Film surface improvement layer 15 formed to a film thickness of 150 nm using a certain ZnS, SiO ₂ / Si _Three N _Four The upper insulating layer 16 having a laminated film thickness of 50 to 500 nm and the translucent upper electrode 17 having an ITO thickness of 100 to 800 nm are laminated.
[0027]
For the film surface improvement layer 15, a material having good crystallinity with the light emitting layer, such as ZnS, which is the same as the ZnS: Mn base material of the light emitting layer, is used. Although ZnS has a crystal structure different from that of SrS, it has a good crystallinity and is often used as a charge accelerating layer in blue-green light-emitting EL devices having SrS: Ce as a light-emitting layer. Therefore, there is no problem even if a ZnS layer is used on SrS: Ce in the sense that the charge flows smoothly in the light emitting layer.
[0028]
If the film surface improving layer 15 is a substance that emits light, the meaning of patterning the light emitting layer is lost. If the film surface improving layer 15 emits light, the emission color of the EL element changes and the display quality of the panel deteriorates. For the surface improvement layer 15, an additive-free (non-doped) light emitting layer material having no emission center is used. The film thickness of the film surface improvement layer 15 is set to a certain film thickness or less as will be described later.
[0029]
The color filter substrate 120 has a red, green and blue color filter 112 with a film thickness of 1.2 μm formed in parallel in a stripe pattern on one surface of a translucent substrate 111 such as a glass plate having a thickness of 1.1 mm. A region where the color filters 112 are overlapped is a black mask 113.
[0030]
The EL element substrate 119 and the color filter substrate 120 are bonded to each other by the resin adhesive 115 on the EL element 118 side so that the EL element 118 and the color filter 112 are in a very close distance of about 20 μm without contacting each other. Yes. The resin adhesive 115 is not applied to the entire circumference of the color filter substrate 120 but is applied to four corners or a part of one side of the color filter substrate 120.
[0031]
An EL element substrate 119 and a seal plate 18 provided with an injection hole 19 with one surface of glass having a thickness of 1.8 mm, for example, dug to a depth of 0.7 mm leaving a frame portion, are arranged around the display unit. Are bonded together by a sealing resin 117 such as an epoxy resin. When the insulating liquid 20 is injected into the gap between the EL element substrate 119 and the seal plate 18 from the injection hole 19, the resin adhesive 115 is applied to the four corners and part of one side of the color filter substrate 120 as described above. Therefore, the space between the EL element 118 and the color filter 112 is also filled with the insulating liquid 20. The injection hole 19 is sealed by a sealing plate 110 to form an EL panel substrate 123.
[0032]
FIG. 2 is a plan view of the color EL panel of FIG. When viewed from the normal direction 21, the lower electrode 12 and the upper electrode 17 are orthogonal to each other to form a lattice shape, and a pixel 216 is formed by the intersection of the lower electrode 12 and the upper electrode 17. A black mask 113 is formed between the color filters 112 formed in a stripe shape, and a color filter substrate 120 is formed by the translucent substrate 111, the color filter 112, and the black mask 113.
[0033]
FIG. 3 is a graph showing the luminance-applied voltage characteristics of an EL element having a light emitting layer of ZnS: Mn using the film surface improvement layer. FIG. 4 is a graph showing the luminance-applied voltage characteristics of an EL element having no film surface improvement layer and having ZnS: Mn as a light emitting layer. The element structure of the EL element used in FIG. 3 is the same as that in FIG. 1 except that the light emitting layer 14 is not patterned and the color filter substrate 120 is not present, and the film surface improving layer uses ZnS. The crystal compatibility with the light emitting layer is very good.
[0034]
The element structure of the EL element used in FIG. 4 is the same as the element structure of the EL element in FIG. 3 except that there is no film surface improvement layer. 3 and 4, the same lot of ZnS: Mn was used for the light emitting layer, and measurement was performed with the same AC pulse voltage waveform having a frequency of 100 Hz and a pulse width of 35 μm.
[0035]
The EL element determines the light emission / non-light emission state of the pixel based on the modulation voltage during driving. The modulation voltage is a difference between a voltage having a luminance of 1 ft-L or less and a voltage L50 at the time of light emission that can sufficiently obtain a necessary luminance higher than that, and the maximum value is practically determined by the performance of the drive circuit. , About 50V is taken. The voltage L50 at the time of light emission is assumed to be a threshold voltage that represents a luminance of 1 ft-L.
L50 = threshold voltage + modulation voltage
It is represented by When the panel brightness is 1 ft-L or higher, the pixels appear to emit light to the human eye, and the contrast with the light emission is lowered and the display quality of the panel is lowered. Therefore, the voltage value at the time of non-light emission is usually slightly higher than 1 ft-L. A low value is chosen. Since the maximum value of the voltage that can be applied during light emission is a fixed value, the luminance-applied voltage characteristic of the panel needs to be steep.
[0036]
In FIG. 3, since the vicinity of 1 ft-L is steep, when the threshold voltage is about 170 V and the modulation voltage is 50 V, the voltage L50 at the time of light emission is about 220 V, and a luminance of about 100 ft-L is obtained. It is done. In FIG. 4, light emission starts from a low voltage, the vicinity of 1 ft-L is gentle, the threshold voltage is about 155 V, and when the modulation voltage is 50 V, the voltage L50 at the time of light emission is 205 V and the luminance is about 55 ft-L. It is quite low. As a result, when a conventional EL element having no film surface improvement layer is used in a color EL panel, the display quality is deteriorated. On the other hand, in the color EL panel of the present invention using an EL element having a film surface improvement layer. Thus, it can be seen that the brightness-applied voltage characteristics of the EL element can be kept steep to prevent an increase in power consumption of the panel, and a decrease in light emission brightness can be prevented to improve display quality.
[0037]
The EL element emits light when charges flowing in the light emitting layer excite the light emission center in the light emitting layer. The additive in the light emitting layer mainly becomes the light emission center. This excitation requires a high electric field of 1 MV / cm or more, and it is necessary to allow the electric charge to flow smoothly in the light emitting layer in order to make the EL element emit light efficiently and with higher luminance. For this purpose, it is necessary to allow the charge flowing between the insulating layer and the light emitting layer to flow when a high electric field is applied to the light emitting layer, and the charge stored between the light emitting layer and the insulating layer is trapped in a deep level. It is essential.
[0038]
In a conventional EL element having no film surface improvement layer, the charge trapped between the light emitting layer and the insulating layer tends to become a shallow level, whereas in an EL element having a film surface improvement layer, a deep level is formed. Therefore, a color EL panel with high luminance can be formed efficiently.
[0039]
In the color EL panel, it is necessary to set the film thickness of the film surface improvement layer 15 to be equal to or less than a certain thickness in order not to cause the problem that the luminance is lowered or the light is not emitted.
[0040]
When the light emitting layer thickness is dp (m), the threshold electric field of the light emitting layer where the light emitting layer starts to light is Eth (V / m), and the voltage applied to the light emitting layer is Vp (V), the light emitting layer emits light ,
dp × Eth ≦ Vp (1)
If it is. From an electrical viewpoint, an EL element having a film surface improvement layer is equivalent to a series connection of three types of capacitors, that is, a film surface improvement layer capacitance Cm, a light emitting layer capacitance Cp, and a total capacitance Ci combining the upper and lower insulating layers. It can be seen as a series connection of three capacitors. The total capacitance when Cm, Cp, and Ci are connected in series is the total capacitance C of the EL element, the voltage applied to the film surface improvement layer is Vm, and the voltage applied to the insulating layer is Vi. When applied, the amount of charge stored in each capacitor is from the formula that shows the electrical relationship,
C x Va = Cm x Vm = Cp x Vp = Ci x Vi (2)
Va = Vm + Vp + Vi (3)
It becomes. From equation (2)
Vm = C * Va / Cm, Vp = C * Va / Cp, Vi = C * Va / Ci (4)
It becomes. Substituting equation (4) into equation (3) and rearranging,
C = 1 / (1 / Cm + 1 / Cp + 1 / Ci) (5)
It becomes. The voltage Vp applied to the light emitting layer from the equations (2) and (5) is
Vp = Cm x Ci x Va / (Cm x Cp + Cp x Ci + Cm x Cp) (6)
It becomes.
[0041]
The dielectric constant of vacuum is εo, the relative dielectric constants of the film surface improvement layer, the light emitting layer and the insulating layer are εm, εp and εi, respectively. Since all three capacitors of the same EL element have the same area, the area of Cm, Cp or Ci To S (m ² ), And when the film thickness of the film surface improvement layer, the light emitting layer, and the insulating film are represented by dm (m), dp (m), and di (m), respectively,
Cm = εo × εm × S / dm, Cp = εo × εp × S / dp, Ci = εo × εi × S / di (7) Substituting equation (7) into equation (6) and rearranging,
Vp = dp × εm × εi × Va / (dp × εm × εi + dm × εp × εi + di × εm × εp) (8) Substituting equation (8) into equation (1) and rearranging,
dm ≦ (εm × Va) / (εp × Eth) −εm × dp / εp−εm × di / εi (9)
[0042]
If the film thickness dm of the film surface improvement layer exceeds the condition of the formula (9), the voltage required for causing the EL element to emit light becomes higher than the designed voltage, and the modulation voltage cannot be taken and the luminance decreases. The EL element may not emit light even when the maximum voltage applied by the drive circuit is applied. The maximum value of the modulation voltage is practically determined depending on the performance of the drive circuit, and is currently technically possible up to about 250V.
[0043]
Next, a method for manufacturing a color EL panel according to an embodiment of the present invention will be described in detail with reference to FIG.
[0044]
First, a glass substrate (1737: manufactured by Corning Japan Co., Ltd.) having a plate thickness of 1.1 mm and a glass size of 150 mm × 110 mm is used as a substrate 11, and a transparent conductive film such as ITO is formed on the substrate 11 by, for example, sputtering, electron beam evaporation, After forming the film to a thickness of 50 to 500 nm by various thin film forming methods such as a spray method, the light-transmitting lower electrode 12 is formed by forming it in a stripe shape by a photoetching process.
[0045]
Next, Si is formed on the lower electrode 12. _Three N _Four / SiO ₂ A lower insulating layer 13 was formed by forming a light-transmitting insulating film such as a laminated film to a thickness of 200 to 500 nm by sputtering, for example.
[0046]
Next, the substrate temperature is maintained at 200 to 300 ° C. on the lower insulating layer 13, ZnS: Mn pellets in which 0.2 to 0.6 wt% of Mn is added to ZnS is used as an evaporation source, and 300 to 300 by an electron beam evaporation method. A ZnS: Mn layer having a thickness of 1000 nm was formed. The formed ZnS: Mn layer was etched into a stripe pattern orthogonal to the lower electrode 12.
[0047]
Specifically, a photoresist (OFPR8600: manufactured by Fuji Film Orin Co., Ltd.) was applied on the ZnS: Mn layer by a spin coat method, and exposed to a predetermined stripe pattern with a photomask and an ultraviolet exposure machine. After developing with a developing solution diluted 5 times (FH2130: manufactured by Fuji Film Orin), the substrate was washed with water. ZnS: Mn was etched with 35% hydrochloric acid at room temperature for 20 seconds and washed with water, and the photoresist was removed with acetone to form striped ZnS: Mn.
[0048]
Furthermore, the substrate temperature is maintained at 500 to 650 ° C., and SrS: Ce having a thickness of 300 to 1000 nm is formed by an electron beam evaporation method using SrS: Ce pellets in which 0.05 to 0.5 wt% of Ce is added to SrS as an evaporation source. A Ce layer was formed. The formed SrS: Ce layer was etched into a striped pattern at a portion perpendicular to the lower electrode 12 and free of ZnS: Mn.
[0049]
Specifically, a photoresist (OFPR8600: manufactured by Fuji Film Orin Co., Ltd.) is applied onto the SrS: Ce layer by a spin coat method, and a photomask is used on the layer without ZnS: Mn and striped by an ultraviolet exposure machine. The pattern was exposed. After developing with a developing solution diluted 5 times (FH2130: manufactured by Fuji Film Orin), the substrate was washed with water. SrS: Ce was etched with 5% phosphoric acid at room temperature for 5 seconds and washed with water, and the photoresist was removed with acetone to form a light emitting layer 14 patterned with ZnS: Mn and SrS: Ce.
[0050]
Next, ZnS having the same crystal structure as ZnS: Mn was formed as the film surface improvement layer 15 on the light emitting layer 14 by electron beam evaporation using the ZnS pellets as an evaporation source while maintaining the substrate temperature at 200 to 300 ° C. . The film thickness dm of the film surface improvement layer 15 was set to satisfy the condition of the formula (9) as described above. For example, in the light emitting layer 14 portion patterned with ZnS: Mn, εm = 8, Va = 200 (V), εp = 8, Eth = 1.0 (MV / cm), dp = 1 (μm), di = 0 For devices fabricated to be .5 (μm) and εi = 5,
dm ≦ (8 × 200) / (8 × 1.0 × 10 ⁶ /1.0×10 ^-2 ) −8 × 1.0 × 10 ^-6 /8−8×0.5×10 ^-6 /Five
dm ≦ 0.2 × 10 ^-6 (M)
Thus, in the light emitting layer 14 portion patterned with SrS: Ce, εm = 8, Va = 200 (V), εp = 10, εth = 0.8 (MV / cm), dp = 1 (μm), di = In the case of an element created so that 0.5 (μm) and εi = 5, when calculated in the same manner from Equation (9),
dm ≦ 0.4 × 10 ^-6 (M)
However, since ZnS: Mn has a smaller dm, in this embodiment, dm may be 0.2 (μm) or less, and the film thickness of the film surface improvement layer 15 is set to 0.15 μm. .
[0051]
Then SiO ₂ / Si _Three N _Four An insulating film such as a laminated film is formed in the same manner as the lower insulating layer 13 and sequentially laminated as the upper insulating layer 16.
[0052]
Thus, the board | substrate with which each layer was formed was heat-processed at 450-650 degreeC for 1 to 6 hours in the vacuum in order to improve crystallinity.
[0053]
In order to emit light efficiently and with high brightness, it is necessary for the EL element to smoothly flow electric charges in the light emitting layer. For this reason, the crystallinity of the light emitting layer is required to be better. As described above, since the film surface improving layer is formed using a material that is close in crystallinity to the light emitting layer, the light emitting layer and the film surface improving layer can be considered as an integral light emitting layer. Even if crystal defects exist between the light emitting layer and the film surface improving layer, it can be reduced by heat treatment, so that the flow of electric charges can be smoothed and the luminance and efficiency of the EL panel can be improved. .
[0054]
It is known that ZnS: Mn and SrS: Ce employed as the light emitting layer material are heat-treated at 400 ° C. or higher and the crystallinity is sufficiently improved as shown in FIG. Because.
[0055]
FIG. 5 shows the luminance at L50 of the color EL panel produced by setting the annealing temperature of the color EL panel according to the configuration of this example to 300 ° C., 350 ° C., 400 ° C., 500 ° C., and 650 ° C. From FIG. 5, the luminance is greatly improved at an annealing temperature of 400 ° C. or higher. When heat treatment is performed at less than 400 ° C., only a color EL panel with low luminance and efficiency can be formed.
[0056]
Since the upper limit of the heat treatment temperature is set to 650 ° C. which is lower than the deformation change temperature of the glass substrate (1737: manufactured by Corning Japan Co., Ltd.) used for the substrate, the yield and display quality are deteriorated due to the distortion of the substrate. Absent. Since the crystallinity was improved in the light emitting layer 14 and the film surface improving layer 15, the electric charge flowed smoothly, and the luminance and the light emission efficiency were improved.
[0057]
Finally, after ITO is formed into a film thickness of 100 to 800 nm by various film forming methods as in the case of the lower electrode 12, the upper electrode 17 is formed in stripes so as to be orthogonal to the lower electrode 12 by a photoetching process. .
[0058]
The EL element 118 formed in this manner uses a translucent electrode for the lower electrode 12 and a translucent electrode for the upper electrode 17, and the light extraction direction from the light emitting layer is opposite to that of a conventional monochrome thin film EL panel. In addition, the surface of the substrate 11 on the EL element 118 formation side, that is, the upper side in FIG. Further, the light in the lower direction in FIG. 1 from the light emitting layer 14 can be taken out upward using a metal electrode or a reflective material such as Au-based material for the lower electrode 12. The lower electrode 12 needs to have heat resistance to withstand heat treatment. Therefore, refractory metals such as Mo, W and Ta may be used.
[0059]
The light emitting layer 14 may contain Mg for improving the emission spectrum. ZnS: Tb, SrAl to improve the emission spectrum of the light emitting layer ₂ S _Four : Eu may be contained in the light emitting layer. There may be more than two types of substances constituting the light emitting layer.
[0060]
Next, separately from the EL element, a red filter (CR, in which a red pigment, a green pigment, and a blue pigment are dispersed in a photosensitive resin on one surface of a translucent substrate 111 such as a glass plate having a thickness of 1.1 mm. -7001: Fuji Film Orin Co., Ltd.), green filter (CG-7001: Fuji Film Orin Co., Ltd.) and blue filter (CB-7001: Fuji Film Orin Co., Ltd.) are used for red, green and blue by photolithography. The color filter substrate 120 was formed by sequentially arranging the color filters 112 in parallel in a stripe shape with a film thickness of 1.2 μm. At the time of formation, a green color filter is slightly overlapped with the previously formed red color filter, and a blue color filter is slightly overlapped with the green color filter, and then formed on the previously formed color filter. A region where the color filter to be slightly overlapped outside the pixel 216 region was used as a black mask 113.
[0061]
Next, the light emitting layer 14 and the color filter 112 are aligned so that ZnS: Mn is red and green and SrS: Ce is blue, and the color filter substrate 120 is bonded to the resin adhesive 115 (X-9318: Mitsui Chemicals). The EL element substrate 119 was bonded to the substrate through a company-made product. X-9318 is a modified epoxy resin having fluidity and low viscosity before curing.
[0062]
Specifically, plastic beads having a diameter of 20 μm (Micropearl SP-220: manufactured by Sekisui Fine Chemical Co., Ltd.) are sprayed on the EL element substrate 119 in advance so that about several pieces are provided in 1 mmφ. The EL element substrate 119 on which is sprayed is bonded to the color filter substrate 120 in which a very small amount of X-9318 is attached to the four corners of the substrate with a toothpick or the like. As a result, the distance between the EL element 118 and the color filter 112 is constant, and the bonding can be performed with a thickness of 20 μm which is close enough to prevent the viewing angle problem from occurring.
[0063]
Next, the seal plate 18 was bonded to an EL element substrate 119 to which the color filter substrate 120 was bonded via a seal resin 117 such as an epoxy resin. The sealing plate 18 was prepared in advance by using a grindstone to dig one surface of glass having a thickness of 1.8 mm to a depth of 0.7 mm, leaving a frame portion, and also providing an injection hole 19. The substrate on which the EL element substrate 119 with the color filter substrate 120 bonded and the seal plate was bonded was placed in a vacuum chamber, and the gap between the EL element substrate 119 and the seal plate 18 was sufficiently evacuated through the injection hole 19.
[0064]
After the injection hole 19 is immersed in an insulating liquid 20 composed of silicone oil mixed with 25% by weight of silica gel, the insulating liquid 20 is colored from the injection hole 19 by leaking the inside of the vacuum chamber with nitrogen. Injection was performed in the gap between the EL element substrate 119 and the seal plate 18 to which the filter substrate 120 was bonded, and in the gap between the EL element 118 and the color filter 112. Since the resin adhesive 115 is applied to the four corners of the color filter substrate 120 as described above, when the insulating liquid 20 is injected into the gap between the EL element substrate 119 and the seal plate 18 from the injection hole 19, the EL The space between the element 118 and the color filter 112 is also filled with the insulating liquid 20. However, the silica gel in the silicone oil has a particle size sufficiently smaller than the distance of 20 μm between the EL element 118 and the color filter 112, for example, about 5 μm.
[0065]
After the gap was filled with the insulating liquid 20, the sealing plate 110 was adhered to the injection hole 19 with an epoxy resin or the like, thereby sealing the injection hole 19 to form an EL panel substrate 123 that was a color EL panel. . The insulating liquid 20 plays a role of protecting the EL element 118 that is extremely sensitive to moisture.
[0066]
As described above, according to one embodiment of the present invention, a film surface using a material having a crystal structure close to that of the light emitting layer material or easily associated with a crystal of the light emitting layer material is formed on the entire surface of the light emitting layer where light emission is desired. By forming the improvement layer, the crystal continuity of the light emitting layer is improved at the patterning portion of the light emitting layer.
[0067]
Also, the surface of the film surface improvement layer formed by various deposition methods such as vapor deposition and sputtering, which do not include an etching process, has better crystallinity than the light emitting layer damaged by the etching process and deteriorated in crystallinity. Between the insulating layer and the film quality improving layer, a shallow level of charge is not formed due to crystal defects, and a deep level of charge is formed, and the brightness-applied voltage characteristic of the EL element is kept sharp, and the panel consumption An increase in power and a decrease in light emission luminance can be prevented.
[0068]
Furthermore, the heat treatment improves the interface state between the patterning surface of the light emitting layer of the EL element and the film surface improvement layer, and also improves the crystallinity at the interface part and reduces crystal defects. It is possible to provide a color EL panel with good display quality that can be kept sharp and prevent an increase in power consumption of the panel and a decrease in light emission luminance.
[0069]
【The invention's effect】
According to the present invention, the continuity of the crystal of the light emitting layer is improved at the patterning portion of the light emitting layer, and there is no shallow level of charge due to crystal defects between the insulating layer and the film quality improving layer, and the deep level of the charge is not obtained. Since the brightness and applied voltage characteristics of the EL element can be kept steep, a color EL panel with good display quality that can prevent an increase in power consumption of the panel and a decrease in light emission brightness can be configured.
[0070]
According to the present invention, the luminance of a color EL panel can be improved by dispersing light emitted from an EL element in which a plurality of light emitting layer materials are patterned using a color filter, and the color EL panel has a better display quality. Can be configured.
[0071]
According to the present invention, by setting the film surface improvement layer to a certain film thickness or less, the voltage required for causing the EL element to emit light as in the case of exceeding the certain film thickness becomes higher than the designed voltage. In addition, since the modulation voltage of the driving circuit of the color EL panel is fixed, the modulation voltage cannot be taken and the luminance is lowered, and the EL element does not emit light even when the maximum voltage applied by the driving circuit is applied. Absent.
[0072]
According to the present invention, the continuity of the crystal of the light emitting layer is improved at the patterning portion of the light emitting layer, and there is no shallow level of charge due to crystal defects between the insulating layer and the film quality improving layer, and the deep level of the charge is not obtained. A position is formed. In addition, the heat treatment improves the interface state between the patterning surface of the light emitting layer of the EL element and the film surface improvement layer, and improves the crystallinity at the interface portion and reduces crystal defects. It is possible to manufacture a color EL panel with good display quality that can be kept sharp and prevent an increase in power consumption of the panel and a decrease in light emission luminance.
[0073]
According to the present invention, since heat treatment is performed at 400 ° C. or higher using ZnS: Mn and SrS: Ce as the light emitting layer material and ZnS as the film surface improving layer, a color EL panel having high luminance and high luminous efficiency can be obtained.
[0074]
According to the present invention, since the heat treatment is performed at a temperature lower than the temperature at which the substrate is deformed and deteriorated, the yield of the panel can be improved and the panel cost can be reduced without causing the deformation of the panel during and after the production of the color EL panel. At the same time, display quality deterioration due to panel distortion can be prevented.
[Brief description of the drawings]
FIG. 1 is a perspective view of a color EL panel according to an embodiment of the present invention.
2 is a plan view of the color EL panel of FIG. 1 as viewed from the normal direction 21. FIG.
FIG. 3 is a graph showing luminance-applied voltage characteristics of an EL element using a film surface improvement layer and having ZnS: Mn as a light emitting layer.
FIG. 4 is a graph showing luminance-applied voltage characteristics of an EL element having no film surface improvement layer and using ZnS: Mn as a light emitting layer.
FIG. 5 is a graph showing the luminance of the color EL panel at L50 when the annealing temperature of the color EL panel according to the embodiment of the present invention is 300 to 650 ° C.
[Explanation of symbols]
11 Substrate
12 Lower electrode
13 parts insulation layer
14 Light emitting layer
15 Film surface improvement layer
16 Upper insulation layer
17 Upper electrode
111 Translucent substrate
112 Color filter
113 black mask

Claims (6)

A substrate,
Upper and lower electrodes disposed on one side of the substrate;
Two insulating layers disposed between the upper and lower electrodes;
A light emitting layer in which a plurality of light emitting layer materials are patterned and arranged in parallel on the insulating layer on the substrate side in contact with the insulating layer; and
Contact with the luminescent layer on the light emitting layer, the luminescent layer material and the sexual compatibility is good crystal, a material that does not contain an emission center, formed as a film thickness by a film forming method which does not include the etching becomes less 200nm exceed 50nm A color EL panel comprising: an electroluminescent element including a film surface improvement layer covering a light emitting layer portion to be emitted. The color EL panel according to claim 1, further comprising a color filter formed on a light-transmitting substrate so as to face the electroluminescent element. The film thickness dm (m) of the film surface improvement layer is expressed by Va (V), which is an amplitude value of an applied voltage waveform desired to start light emission determined by a relative dielectric constant εm of the film surface improvement layer and a color EL panel drive circuit. The dielectric constant of the light emitting layer is εp, the threshold electric field of the light emitting layer where the light emitting layer begins to light is Eth (V / m), the film thickness of the light emitting layer is dp (m), and the film thickness of the two insulating layers is When the sum is di (m) and the sum of the apparent dielectric constants of the two insulating layers is εi,
dm ≦ (εm × Va) / (εp × Eth) −εm × dp / εp-εm × di / εi
2. The color EL panel according to claim 1, wherein the color EL panel is selected so as to satisfy the following relationship. Forming a lower electrode and an insulating layer on one side of the substrate;
Forming a light emitting layer on the insulating layer by patterning a plurality of light emitting layer materials by etching and juxtaposing them;
On the light emitting layer, the luminescent layer material and the sexual compatibility is good crystal, a material that does not contain an emission center, covering the light emitting layer portion to emit light, the membrane film surface improving layer by a film forming method which does not include the etching Forming a thickness of more than 50 nm and not more than 200 nm ;
Forming another insulating layer on the film surface improving layer and then heat-treating the layer formed;
And a step of forming an upper electrode on the heat-treated insulating layer. 5. The temperature of the heat treatment step is set to 400 ° C. or higher when ZnS: Mn and SrS: Ce are used as the light emitting layer material and ZnS is used as the material of the film surface improvement layer. The manufacturing method of the color EL panel of description. 5. The method of manufacturing a color EL panel according to claim 4, wherein, in the heat treatment step, the temperature is set to a temperature lower than the lower one of the deformation temperature and the alteration temperature of the substrate.

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