Long-life type colorful electroluminescent display panel

A long-life type colorful electroluminescent (EL) display panel is disclosed. The EL display panel comprises a luminescent laminate, two electrodes located at the two sides of the luminescent laminate, several terminals, and a display surface. One of the two electrodes includes plural separated sub-electrodes. Each sub-electrode comprises at least one branch portion and a bus bar connecting at least one branch portion to one of the terminals. Each of the branch portions in one sub-electrode is accompanied with one branch portion in a sub-electrode different from the one sub-electrode, and extends in parallel thereto in a position corresponding to a portion of the display surface which is representative of substantially the same area. By means of the above structure, the display panel will have a life span more than double the normal and can display colorfully.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 This invention relates to a long-life type colorful electroluminescent (EL)
 display panel and more particularly to an EL display panel that has an
 electrode structure capable of increasing life span and making the display
 panel colorful.
 2. Description of the Prior Art
 It is well known that the so-called electroluminescent (EL) display panel
 mainly comprises a transparent substrate, a transparent electrode formed
 on the transparent substrate, a luminescent laminate, and a biasing
 electrode formed on the luminescent laminate opposite to the transparent
 electrode. Moreover, a display surface is usually arranged on the surface
 of the transparent substrate opposite to the transparent electrode. The
 display surface is usually provided with a pattern.
 However, the EL display panel has a specific life span. In case the EL
 display panel is broken down, a replacement with a new EL display panel
 could be necessary. However, a procedure for such a replacement is more or
 less troublesome. Thus, how to increase the life span of the EL display
 panel would be a project.
 Moreover, in terms of a specific pattern in an EL display panel, usually
 only one color can be presented. Such a display with respect to the
 pattern is more or less monotonous.
 SUMMARY OF THE INVENTION
 An object of this invention is to provide an electroluminescent display
 panel having a life span longer than that of a conventional EL display
 panel.
 The other object of this invention is to provide an electroluminescent
 display panel capable of presenting a colorful pattern.
 To achieve the above objects, an electroluminescent display panel according
 to the present invention comprises a luminescent laminate, two electrodes
 located at the two sides of the luminescent laminate, several terminals
 respectively connected to the two electrodes, and a display surface at one
 side of one of the two electrodes opposite to the luminescent laminate,
 and is characterized in that one of the two electrodes includes plural
 separated sub-electrodes, each sub-electrode comprises at least one branch
 portion and a bus bar connecting at least one branch portion to one of the
 terminals, each of the branch portions of the sub-electrodes is
 accompanied with one branch portion in a different sub-electrode and
 extends in parallel thereto in a position corresponding to a portion of
 the display surface which is representative of substantially the same
 area.
 By means of the above structure, since each sub-electrode has one branch
 portion extending to a position corresponding to a portion of the display
 surface which is representative of substantially the same area, i.e.,
 substantially the same area can present light by means of the plural
 sub-electrodes, as well as their respectively corresponding luminescent
 material, which are actuated one by one, the life span of the EL display
 panel will increase. Moreover, if the plural sub-electrodes are actuated
 by electric powers at different frequencies, substantially the same area
 will present plural colors, and thus a colorful EL display panel is
 obtainable. Furthermore, if each sub-electrode is actuated one by one at a
 specific time interval, substantially the same area will present an effect
 like a neon lamp. Further, if the colors of the lights each emitted by the
 luminescent material corresponding to one of the sub-electrodes are
 different, the neon effect will be more colorful.
 The advantages and features of this invention can be easily comprehended by
 persons skilled in the art through the drawings and following detailed
 explanations.

DETAILED DESCRIPTIONS OF EMBODIMENTS
 Referring now to the drawings, preferred embodiments of the present
 invention will be explained.
 FIG. 1 illustrates a schematic plan view of one of the electrodes of an EL
 display panel according to the first embodiment of this invention. One of
 the electrodes can be either a biasing electrode or a transparent
 electrode. As shown in FIG. 1, the electrode 1 comprises a first
 sub-electrode 10 and a second sub-electrode 20. The first sub-electrode 10
 includes a group of separated branch portions 11 in parallel formation
 extending in a specific area and a bus bar 19 connecting each branch
 portion 11 to a first terminal (no shown). The second sub-electrode 20
 includes a group of branch portions 21, parallel to each other, extending
 in an area substantially identical to the aforesaid specific area and a
 bus bar 29 connecting each branch portion 21 to a second terminal (not
 shown). Each pair of the branch portions 11 in the first sub-electrode 10
 are interleaved with one branch portion 21 in the second sub-electrode 20.
 All the branch portions 11 in the first sub-electrode 10 are combined by
 the bus bar 19 on one side opposite to the bus bar 29 by which the branch
 portions 21 of the second sub-electrode 20 are combined.
 According to the configuration shown in FIG. 1, since the first
 sub-electrode 10 and the second sub-electrode 20 spread over substantially
 the same area via a plurality of separate strip-like branch portions and
 since each pair of the branch portions of the first sub-electrode 10 are
 interleaved with one branch portion of the second sub-electrode 20, the
 two sub-electrodes 10 and 20 could be deemed to be located at
 substantially the same lighting area. Thus, if the portion of the
 luminescent laminate corresponding to the first sub-electrode 10 is
 expired, the second sub-electrode 20 which is located in substantially the
 same lighting area could be actuated so as to excite substantially the
 same lighting area. Consequently, the life span of the EL display panel
 could double and the display panel is still available.
 Moreover, as an application example of the electrode structure shown in
 FIG. 1, the first sub-electrode 10 can be biased by an electric power at a
 first frequency while the second sub-electrode 20 can be biased by an
 electric power at a second frequency different to the first frequency. In
 such a case, since the luminescent laminate can luminesce with different
 colors based upon the frequencies of the electric powers to be applied,
 the luminescing light of the EL display panel will be colorful if the two
 sub-electrodes 10 and 20 are simultaneously or succeedingly biased by the
 two electric powers of different frequencies. For example, the light of a
 yellow color or of a red color can be simultaneously or succeedingly
 generated. Therefore, by means of the electrode structure of this
 invention, a colorful EL display panel would be obtainable. However, if
 the two sub-electrodes 10 and 20 are biased by the same electric power
 with the same frequency, while the areas of the luminescent laminate
 respectively corresponding to the first and the second sub-electrodes 10
 and 20 are constructed by different luminescent material respectively
 emitting lights of different colors, a colorful EL display panel is also
 obtainable. Furthermore, each of the first and the second sub-electrodes
 10 and 20 has only one branch portion so as to present a line pattern
 represented in substantially the same area.
 FIG. 2 illustrates a schematic plan view of the electrode structure shown
 in FIG. 1 incorporated with a display surface having two patterns in
 substantially the same area. According to the embodiment in FIG. 2,
 substantially the same area of the display surface 2 of the EL display
 panel contains a first pattern A (shown as "A") and a second pattern B
 (shown as "a") which overlap in terms of substantially the same area but
 offset in terms of each pattern element thereof. In detail, each of the
 first pattern A and the second pattern B is composed of a group of
 separated longitudinal pattern segments in parallel, and each pair of the
 pattern segments in one group are interleaved with one pattern segment in
 the other group. Moreover, the branch portions 11 of the first
 sub-electrode 10 respectively correspond to the pattern segments of the
 first pattern A while the branch portions 21 of the second sub-electrode
 20 respectively correspond to the pattern segments of the second pattern
 B. By means of the above arrangement, the place corresponding to the first
 pattern A, which presents the pattern of "A", will light when the first
 sub-electrode 10 is actuated, and the place corresponding to the second
 pattern B, which presents the pattern of "a", will light if the second
 sub-electrode 20 is actuated. However, it is comprehensible that the
 patterns A and B could be any proper patterns such as "welcome" and "thank
 you" respectively. Thus, different indicators could be displayed in
 substantially the same area based upon different situations.
 Moreover, the patterns A and B could be two related patterns such as those
 shown in FIG. 3 which show dog heads of facing different directions
 respectively. In this case, if the first sub-electrode 10 and the second
 sub-electrode 20 are alternatively actuated, the display surface 2' will
 present a swing action of the dog head. Furthermore, based upon the
 aforesaid case, if there are many sets of the patterns including the
 patterns A and B in the display surface as well as their corresponding
 sub-electrodes, a continuously changing effect like animation could be
 obtainable if such sub-electrodes are actuated in sequence.
 In the above case in which the two patterns are alternatively displayed, a
 diffusion plate (not shown) can be disposed on the display surface 2 or 2'
 so as to smooth the lines in each pattern.
 The above structure relates to a situation where the branch portions and
 the bus bar of each sub-electrode are located at a same laminating level.
 However, the branch portions and the bus bar can be disposed at different
 laminating levels as illustrated in the following embodiment in which the
 quantity of the sub-electrodes could be more than two.
 FIG. 4 shows an exploded schematic view of the EL display panel according
 to the second embodiment of this invention. As shown in FIG. 4, the EL
 display panel 30 according to the second embodiment of this invention
 mainly comprises a transparent laminate 31 including a transparent
 substrate and a transparent electrode, a luminescent laminate 32, a
 biasing electrode laminate including a branch layer 33, an insulating
 layer 34, and a bus bar layer 35, and a protecting layer 36, all of them
 being laminated in sequence.
 The luminescent laminate 32 is constructed by three kinds of materials 32a,
 32b, and 32c, each being capable of emitting a specific color under bias.
 Each kind of luminescent material is divided into a plurality of pattern
 segments parallel to each other. Each pair of pattern segments in the same
 kind of luminescent material, for example 32a, are interleaved with one
 pattern segment of the other two kinds of luminescent materials, for
 example 32b and 32c. The biasing electrode laminate includes three
 sub-electrodes. The three sub-electrodes respectively comprise plural
 branch portions 33a, 33b, 33c located in the branch layer 33, plural vias
 34a, 34b, 34c located in the insulating layer 34, and a bus bar 35a, 35b,
 35c located in the bus bar layer 35. Like the arrangement of the three
 kinds of luminescent materials in this embodiment, each pair of branch
 portions of each sub-electrode, for example 33a, are interleaved with one
 branch portion of the other two sub-electrodes such as 33b and 33c such
 that all branch portions respectively belonging to the three
 sub-electrodes are distributed at substantially the same area of the
 display surface, such as the pattern of "S" and that each branch portion
 corresponds to one pattern segment.
 Moreover, the insulating layer 34 is formed with many vias which are
 separated into three sets 34a, 34b, and 34c. Each via corresponds to one
 branch portion that belongs to the sub-electrode corresponding to the set
 of the via.
 The bus bar layer 35 is laminated on the insulating layer 34 and includes
 three bus bars 35a, 35b, and 35c constructed by silver glue, each
 belonging to one sub-electrode and being connected to one terminal (not
 shown). Each bus bar, for example 35a, can be connected to its
 corresponding branch portion, for example 33a, belonging to a same
 sub-electrode, through the corresponding via, for example 34a, so as to
 supply electric power to each branch portion, for example 33a. Moreover,
 the bus bar layer 35 can be constructed by any proper conductive material
 in addition to the silver glue. The protecting layer 36 is laminated over
 the whole biasing electrode laminate so as to protect the biasing
 electrode. However, it is optional.
 By means of the above structure in the second embodiment of this invention,
 substantially the same area could contain an arbitrary number of
 sub-electrodes, and such sub-electrodes can be biased by any measure
 illustrated in the above.
 Furthermore, it is comprehensible that each of the branch portions
 illustrated in the second embodiment can be of a circle shape or a dot.
 They can be supplied with electric power group by group by the bus bars
 respectively. Thus, by virtue of the arrangement of such dots, the
 presented pattern would be more smooth and colorful.
 From the embodiments of this invention thus described, it will be obvious
 that the present invention may be varied in many ways. Such variations are
 not to be regarded as a departure from the spirit and scope of the
 invention, and all such modifications as would be obvious to one skilled
 in the art are intended for inclusion within the scope of the following
 claims.