Semiconductor device manufacturing: process – Making device or circuit emissive of nonelectrical signal – Including integrally formed optical element
Reexamination Certificate
2001-09-21
2003-09-09
Elms, Richard (Department: 2824)
Semiconductor device manufacturing: process
Making device or circuit emissive of nonelectrical signal
Including integrally formed optical element
C438S034000, C438S035000, C438S099000, C438S690000, C438S706000
Reexamination Certificate
active
06617186
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing an electroluminescent element (may be referred to as an abbreviation of EL) in which a pattern is formed.
EL elements attract attention as spontaneously emitting flat panel display elements in which positive holes and electrons, which have been poured into from opposed electrodes, are combined in a luminous layer to generate energy, and the energy excites fluorescent material in luminous layer to emit light of a color corresponding to the fluorescent material. Among them, an organic thin film EL display using an organic material as a luminescent material has such a high luminous efficiency that high intensity luminescence can be realized even if applied voltage is a little less than 10 V, is possible to emit light with a simple element structure, and is expected to be applied to low-cost simple expression displays such as advertisements and the like in which specific patterns are emitted and displayed.
In the production of a display using such an EL element, patterning on an electrode layer and an organic EL layer is usually put into practice. Methods of EL element patterning include a vapor deposition method of a luminescent material via a shadow mask, a method of separately painting through inkjet, a method of destroying specific luminescent pigment through ultraviolet irradiation, a screen printing method, and others. However, these methods could not provide an EL element being possible to realize all of the high luminous efficiency, the high light takeout efficiency, the simplicity of the production process, and the formation of highly fine patterns.
The present invention has been achieved in order to solve the above-mentioned problems. It is a main object of this invention to provide a method for producing an EL element for realizing the high luminous efficiency, the high light takeout efficiency, the simplicity of the production process, and the formation of highly fine patterns.
SUMMARY OF THE INVENTION
In order to achieve the object mentioned above, the present invention provides a method for producing an EL element, wherein at least one organic EL layer constituting the EL element is patterned by the use of a photolithography method.
According to a method for producing an EL element in the present invention, because the EL element is obtained by patterning at least one organic EL layer within the EL element by the use of a photolithography method, when compared to the conventional vapor deposition patterning method, the EL element can be produced relatively easily and in low cost because no vacuum equipment with high precision alignment mechanism and others are needed. On the other hand, when compared to the patterning method by the use of an inkjet system, the production method of the present invention is preferable in the point of no need of carrying out preprocessing to constructions and substrates aiding patterning, and further the production method can be considered to be preferable to higher precision pattern forming because of the relationship to the discharge accuracy of an inkjet head. Thus, according to the EL element production method of the present invention, a highly fine EL element can be obtained relatively easily and in low cost.
In the above-mentioned invention, it is preferable that an organic EL layer made by patterning with the use of the above-mentioned photolithography method is a luminous layer. Because in an EL element, a luminous layer is an indispensable layer and can obtain a highly fine pattern that is needed in case of light emission.
Further, in the above-mentioned invention, it is preferable that the above-mentioned luminous layer is insoluble in a photoresist solvent, a photoresist developing solution, and a photoresist peeling liquid, and a photoresist is insoluble in a solvent that is used in forming the above-mentioned luminous layer. Although depending on the kinds of photolithography methods such as, for example, a method of using dry etching, a method of using a dry film and the like, in case where the general wet photolithography method is used, it is preferable to use a luminous layer and a photoresist that satisfy such requirements.
In addition, in the above-mentioned invention, it is preferable that the above-mentioned luminous layer is a luminous layer in which different types of luminous layers are formed by the use of the photolithography method in plural times. Because when the luminous layer is formed in different types of plural luminous layers, full coloring is possible, for example, by selecting red, green, blue and the like.
In this case, it is preferable that a solvent used for forming a luminous layer in the above-mentioned luminous layers, which are formed in two times and after, is a poor solvent to the previously formed luminous layer. Because a solvent for forming a luminous layer that is used in a luminous layer to be newly formed is a poor solvent to the previously formed luminous layer, so no mixed color will be caused when a luminous layer is further formed on the previously formed luminous layer.
In this case, it is preferable that the solubility of the previously formed luminous layer to the solvent used for forming luminous layers formed in two times and after is 0.1 g or less/g of solvent at 25° C. under 1 atmospheric pressure. This is the reason that, if the solubility is in this degree, even when a new luminous layer is formed on the previously formed luminous layer, the previously formed layer will not be dissolved in a solvent to cause mixed color.
Furthermore, it is also preferable that the above-mentioned luminous layers to be formed in plural times are formed in the order of the short wavelength of light obtained from them.
Generally, when two kinds of a luminescent material emitting light of high energy short wavelength and a luminescent material emitting light of low energy long wavelength are mixed, the light emission from the luminescent material emitting light of long wavelength becomes to be main. In the present invention, since luminous layers are planned to be formed in the order of the short wavelength of light emitted from them, a luminescent material for a luminous layer to be formed later becomes to be a luminescent material emitting light of a long wavelength, and even if the luminescent material used for forming the previously formed luminous layer is mixed in a luminous layer to be formed later, the short wavelength luminescent material in the previously farmed luminous layer that mixed in will hardly emit light, resulting In extremely lowering the possibility of causing problems like mixed color and others.
Like this, in case where luminous layers are formed in plural times, it is preferable that the above-mentioned luminous layers are three types of luminous layers emitting red, green and blue light. Because in order to make light emit in full color, it is generally preferable to make light emit in the three primary colors of red, green and blue.
Moreover, in the present invention, the above-mentioned organic EL layer that is made by patterning with the use of a photolithography method may be a buffer layer. In the present invention, it is preferable to use a photolithography method as mentioned above when a luminous layer is patterned, however the use of a photolithography method is not limited to this, the buffer layer may be patterned with the use of a photolithography. In particular, in an EL element in which a luminous layer is comprised of an organic polymer, it is preferable to combine a buffer layer and a luminous layer from the aspect of luminous efficiency, and on this occasion, through both layers are patterned with the use of a photolithography method, a cheap and high quality EL element can be produced.
In this case, it is preferable that the above-mentioned buffer layer is insoluble in a photoresist solvent and a photoresist peeling liquid, and a photoresist is insoluble in a solvent used for forming the above-mentioned buffer layer. This is the reason that, similarly to the case of
Dai Nippon Printing Co. Ltd.
Elms Richard
Ladas & Parry
Luhrs Michael K.
LandOfFree
Method for producing electroluminescent element does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for producing electroluminescent element, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for producing electroluminescent element will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3105744