The present invention relates to an electroluminescent (EL) device and more particularly to an EL device having a substantially rectangular electroluminescent (EL) layer and to an EL device unit including the EL device.
A known EL device generally includes an EL layer, an anode and a cathode. The anode is connected to one surface of the EL layer, and the cathode is connected to the other surface of the EL layer. The anode has an anode terminal, which is connected to an external conductor (anode conductor). The anode conductor is further connected to a positive electrode of an external power source. Thus, the positive electrode of the external power source is electrically connected to the anode of the EL device. On the other hand, the cathode has a cathode terminal, which is connected to an external conductor (cathode conductor). The cathode conductor is further connected to a negative electrode of the external power source. Thus, the negative electrode of the external power source is electrically connected to the cathode of the EL device. As the electrodes are energized through the anode and cathode conductors, the EL layer emits light. The EL device will have a luminescent face of desired shape by changing the shape of the EL layer. In recent years EL devices having a rectangular EL layer in plan view have been employed in many fields, which is disclosed in Japanese patent application publication No. 2001-244069. In the EL device disclosed in the above publication, the elongated anode terminal and the elongated cathode terminal are aligned along the same short side of the rectangular EL layer.
The above prior art takes advantage of this arrangement to cause electric current to stably flow to an electrode near one short side of the EL layer. This is disadvantageous in that a small amount of electric current flows through an electrode near the other side of the EL layer because of the long distance from the terminals. Thus, the EL layer emits light more brightly near one short side where a large amount of electric current flows than near the other short side where a small amount of electric current flows. Specifically, as the long side of the EL layer becomes longer, a difference in brightness, that is, uneven brightness, gets more remarkable in the long side direction of the EL layer.
The present invention is directed to reducing uneven brightness in an EL layer, as compared to a prior art.
In accordance with the present invention, an electroluminescent device has an electroluminescent layer, a first electrode, a second electrode, a first terminal and a second terminal. The electroluminescent layer is substantially rectangular and has two long sides and two short sides in plan view. The first electrode is connected to a first surface of the electroluminescent layer. The second electrode connected to a second surface of the electroluminescent layer. The second surface is opposite the first surface. The first terminal is connected to the first electrode. The second terminal is connected to the second electrode. The first terminal is formed along one long side of the electroluminescent layer. The second terminal is formed along one long side or the other long side of the electroluminescent layer.
In accordance with the present invention, an electroluminescent device unit has an electroluminescent device and a conductor substrate. The electroluminescent device includes a laterally long electroluminescent layer in plan view, a first electrode connected to a first surface of the electroluminescent layer, a second electrode connected to a second surface of the electroluminescent layer and an electroluminescent device substrate. The second surface is opposite the first surface. The conductor substrate includes a first conductor electrically connected to the first electrode of the electroluminescent device and a second conductor electrically connected to the second electrode of the electroluminescent device. A breadth of the electroluminescent device substrate is larger than that of the conductor substrate.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:
Preferred embodiments have the following main technical features.
(Feature 1) An EL device has a transparent glass substrate.
(Feature 2) An anode (first electrode) is made of transparent ITO (indium tin oxide, which is indium oxide doped with tin).
(Feature 3) An anode extends almost over the entire breadth of an EL device substrate (the long side length of an EL layer).
(Feature 4) An EL layer has a larger breadth than an anode.
(Feature 5) A cathode (second electrode) extends almost over the entire breadth of an EL layer.
(Feature 6) A cathode is made of a metal layer connected to an EL layer. A cathode terminal (second terminal) is made of a material having a higher volume resistivity than the metal forming the cathode and connected to the cathode.
(Feature 7) An anode is formed on the upper surface of a glass substrate (EL device substrate). The cathode terminal of Feature 6 is also formed on the glass substrate and made of the same material as the anode.
(Feature 8) The material of an anode has a higher volume resistivity than the material of a cathode. In this case, an anode terminal has a twice or more larger breadth than a cathode terminal. More preferably, the anode terminal has a ten times or more breadth than the cathode terminal.
(Feature 9) A flexible printed circuit (FPC) is used as a conductor substrate to connect an EL device to an external power source.
(Feature 10) When an anode terminal and a cathode terminal are aligned along one long side of an EL layer, a gap is formed between the anode terminal and the cathode terminal. This gap has a smaller breadth than the anode terminal and the cathode terminal.
(Feature 11) An auxiliary electrode extends in the long side direction of an EL layer.
Note that an electrode formed separately from a terminal or formed integrally with a terminal is regarded that “an electrode is connected to a terminal” in the preferred embodiments. The term “long side direction” and the term “short side direction” mean “long side direction of an EL layer” and “short side direction of an EL layer”, respectively unless otherwise stated. The wording “terminals (a first terminal and a second terminal) are aligned along the long side of an EL layer” not only includes that the terminals extend continuously without any gap in between but also includes that the terminals are aligned discontinuously along the long side of an EL layer with a gap in between. “An area of a first electrode to which an EL layer is connected” is an area where a first electrode and an EL layer are overlapped in plan view.
The following will describe a first preferred embodiment of an EL device unit 700 according to the present invention with reference to
Referring to
The anode 30 is formed on the upper surface of the glass substrate 20. Note that in the preferred embodiment, the term “upper surface” means a near-side surface with respect to the direction of normal of the sheet of
The EL layer 40 is mainly formed on the upper surface of the anode 30. The EL layer 40 (For example, right and left end portions) is partially formed on the upper surface of the glass substrate 20, as best seen in
The cathode 50 made of metal is mainly formed on the upper surface of the EL layer 40, but the cathode 50 is partially formed on the upper surface of the glass substrate 20 and on the upper surface of a connection 60, as best shown in
As shown in
The connection 60 is formed on the glass substrate 20, as shown in
The size of the above-described EL device 100 will now be described.
The EL layer 40 has a breadth L1 of approximately 100 mm, which is larger than those of the anode 30 and the cathode 50. The clearance between the right side of the EL layer 40 and the right side of the glass substrate 20 is approximately 1 mm. The clearance between the left side of the EL layer 40 and the left side of the glass substrate 20 is approximately 1 mm. Thus, the glass substrate 20 has a breadth L0 of approximately 102 mm. The anode terminal 34 has a breadth L2 of approximately 97 mm. The cathode terminal 64 has a breadth L3 of approximately 2 mm. The gap L4 between the anode terminal 34 and the cathode terminal 64 is approximately 1 mm.
In the first preferred embodiment, the breadth L2 of the anode terminal 34 is much larger than breadth L3 of the cathode terminal 64. The anode 30 made of ITO has a higher volume resistivity than the cathode 50, so that the breadth L2 of the anode terminal 34 is formed larger. This makes a voltage to be applied uniformly in the long side direction of the anode 30. The narrow cathode terminal 64 is applicable for the cathode 50 due to the low volume resistivity of the cathode 50. Thus, when the material of the anode 30 has a higher volume resistivity than the cathode 50, the long side length of the EL layer 40 along (on or adjacent to) the anode terminal 34 is larger than that of the EL layer 40 along (on or adjacent to) the cathode terminal 64. The glass substrate 20 has a width L0′ of approximately 6 mm. The EL layer 40 has a width L1′ of approximately 2 mm. In the first preferred embodiment, the EL layer 40 has a very narrow width, formed in a substantially rectangular shape having a long side and a short side with a ratio of approximately 50 to 1. Therefore, the EL layer 40 is almost linear. The anode 30, the EL layer 40 and the cathode 50 each are extremely thin on the order of nanometer. The glass substrate 20 is thicker than these layers 30, 40, 50.
The FPC 600 will now be described.
The FPC 600 includes a substrate material 610, terminals (first conductors) 630, 632, 634, 636, 638, 640 for connection with the anode terminal 34 and terminals (second conductors) 620, 622, 624 for connection with the cathode terminal 64. The substrate material 610 is made of electrically insulating material. The illustration of the lower side of the FPC 600 is omitted in
The terminals 630, 632, 634, 636, 638, 640 are formed at the lower surface of the substrate material 610. The terminal 630 is made of electrically conductive material extending vertically in
The EL device 100 and the FPC 600 are connected together to form the EL device unit 700. The breadth L5 of the FPC 600 is slightly smaller than the breadth LO of the glass substrate 20 of the EL device 100. When the EL device 100 is connected to the FPC 600, the FPC 600 fits within the breadth of the glass substrate 20 of the EL device 100. The EL device unit 700 in which the FPC 600 fits within the breadth of the glass substrate 20 is very compact in its breadth direction. A high electric potential will be applied to the anode terminal 34 through the terminals 630 through 640 of the FPC 600. On the other hand, a low electric potential will be applied to the cathode terminal 64. Then, a potential difference arises between the anode 30 and the cathode 50. Thus, the EL layer 40 is supplied with electric power to emit light. Since the anode 30 and the glass substrate 20 are transparent and colorless, light emitted from the EL layer 40 directly transmits the anode 30 and the glass substrate 20 or transmits them after being reflected on the cathode 50. Emitted light exits from the lower surface of the glass substrate 20. The anode terminal 34 extends laterally, so that a potential difference is small in the lateral direction of the anode 30. The cathode terminal 64 has a smaller breadth than the anode terminal 34, but a potential difference is small in the lateral direction of the cathode 50 due to the low volume resistivity of metal forming the cathode 50. This causes a voltage applied to the EL layer 40 to be small in difference as measured in the lateral direction, with the result that electric current flowing through the EL layer 40 is small in difference as measured in the lateral direction. Thus, uneven brightness is reduced in the lateral direction.
As described above, according to the EL device 100 in the first preferred embodiment, uneven brightness is reduced at any positions of the EL layer 40. Furthermore, the anode terminal 34 and the cathode terminal 64 are all formed at the lower side in
The EL device unit 700 has a larger long side length of the EL layer 40 along the glass substrate 20 than the long side length of the EL layer 40 along the FPC 600. Thus, the EL device unit 700 including the FPC 600 is very compact. The EL device unit 700 according to the first preferred embodiment is applicable to a light source for optical readers, such as copiers, facsimiles and scanners. Since the FPC 600 does not extend in the long side direction of the EL device unit 700, an optical reader and a copier, a facsimile and a scanner using it will be compact, especially in the longitudinal direction of the EL device unit.
The following will describe a second preferred embodiment of an EL device 200 with reference to
Referring to
The cathode 150 made of metal is mainly formed on the upper surface of the EL layer 140. The cathode 150 is substantially U-shaped in plan view. Specifically, the cathode 150 has a portion 150c extending almost over the entire breadth of the EL layer 140, a portion 150d extending downward in
A first connection 160 is rectangular in plan view. The portion 150d of the cathode 150 is connected to the upper surface of the connection 160 on the upper side in
A second connection 166 is also rectangular in plan view. The second connection 166 has the same breadth as the first connection 160. The portion 150e of the cathode 150 is connected to the upper surface of the second connection 166 on the upper side in
The FPC (not shown) has terminals for connection with the cathode terminals 163, 169 and terminals for connection with the anode terminal 134. When the FPC is connected to the EL device 200, the FPC will fit within the breadth of the glass substrate 20. The anode terminal 134 extends laterally, so that a potential difference is small in the lateral direction of the anode 130. The sum of the breadths of the cathode terminals 163, 169 is smaller than that of the anode terminal 134, but a potential difference is small in the lateral direction of the cathode 150 due to a low volume resistivity of metal forming the cathode 150. This causes a voltage applied to the EL layer 140 to be small in difference as measured in the lateral direction, with the result that electric current flowing through the EL layer 140 is small in difference as measured in the lateral direction. Thus, uneven brightness is reduced in the lateral direction.
As described above, according to the EL device 200 in the second preferred embodiment, uneven brightness is reduced at any positions of the EL layer 140. Furthermore, the anode terminal 134 and the cathode terminals 163, 169 are all formed at the lower side in
In the second preferred embodiment, the long side length of the EL layer 140 along the glass substrate 20 is larger than the long side length of the EL layer 140 along the FPC. Thus, the EL device unit including the FPC is very compact. The EL device unit according to the second preferred embodiment is applicable to a light source for optical readers, such as copiers, facsimiles and scanners. Since the FPC does not extend in the long side direction of the EL device unit, an optical reader and a copier, a facsimile and a scanner using it will be compact, especially in the longitudinal direction of the EL device unit.
The following will describe a third preferred embodiment of an EL device 300 with reference to
Referring to
The cathode 250 made of metal is mainly formed on the upper surface of the EL layer 240. The cathode 250 is substantially T-shaped in plan view. Specifically, the cathode 250 has a portion 250b extending almost over the entire breadth of the EL layer 240 and a portion 250c extending downward in
The FPC (not shown) has terminals for connection with the cathode terminal 264 and terminals for connection with the anode terminals 234a, 234b. When the FPC is connected to the EL device 300, the FPC will fit within the breadth of the glass substrate 20. In the third preferred embodiment, the anode terminals 234a, 234b extend laterally, so that a potential difference is small in the lateral direction of the anode 230. The breadth of the cathode terminal 264 is smaller than that of the anode terminals 234a, 234b, but a potential difference is small in the lateral direction of the cathode 250 due to a low volume resistivity of metal forming the cathode 250. This causes a voltage applied to the EL layer 240 to be small in difference as measured in the lateral direction, with the result that electric current flowing through the EL layer 240 is small in difference as measured in the lateral direction. Thus, uneven brightness is reduced in the lateral direction.
As described above, according to the EL device 300 in this embodiment, uneven brightness is reduced at any positions of the EL layer 240. Furthermore, the anode terminals 234a, 234b and the cathode terminal 264 are all formed at the lower side in
In the third preferred embodiment, the long side length of the EL layer 240 along the glass substrate 20 is larger than the long side length of the EL layer 240 along the FPC. Thus, the EL device unit including the FPC is very compact. The EL device unit according to the third preferred embodiment is applicable to a light source for optical readers, such as copiers, facsimiles and scanners. Since the FPC does not extend in the long side direction of the EL device unit, an optical reader and a copier, a facsimile and a scanner using it will be compact, especially in the longitudinal direction of the EL device unit.
The following will describe a fourth preferred embodiment of an EL device 400 with reference to
Referring to
The cathode 350 made of metal is mainly formed on the upper surface of the EL layer 340. The cathode 350 is substantially L-shaped in plan view. Specifically, the cathode 350 has a portion 350b extending almost over the entire breadth of the EL layer 340 and a portion 350c extending upward in
The FPC (not shown) has a first substrate (not shown) having terminals for connection with the cathode terminal 364 and a second substrate (not shown) having terminals for connection with the anode terminal 334. The first substrate and the second substrate may be integrated or separated. When the FPC is connected to the EL device 400, the FPC will fit within the breadth of the glass substrate 20.
In the fourth preferred embodiment, the anode terminals 334 extend laterally, so that a potential difference is small in the lateral direction of the anode 330. The breadth of the cathode terminal 364 is smaller than that of the anode terminal 334, but a potential difference is small in the lateral direction of the cathode 350 due to a low volume resistivity of metal forming the cathode 350. This causes a voltage applied to the EL layer 340 to be small in difference as measured in the lateral direction, with the result that electric current flowing through the EL layer 340 is small in difference as measured in the lateral direction. Thus, uneven brightness is reduced in the lateral direction.
As described above, according to the EL device 400 in this embodiment, uneven brightness is reduced at any positions of the EL layer 340. In the fourth preferred embodiment, the long side length of the EL layer 340 along the glass substrate 20 is larger than the long side length of the EL layer 340 along the FPC. Thus, the EL device unit including the FPC is very compact. The EL device unit according to the fourth preferred embodiment is applicable to a light source for optical readers, such as copiers, facsimiles and scanners. Since the FPC does not extend in the long side direction of the EL device unit, an optical reader and a copier, a facsimile and a scanner using it will be compact, especially in the longitudinal direction of the EL device unit.
The following will describe a fifth preferred embodiment of an EL device 500 with reference to
Referring to
The cathode 450 made of metal is mainly formed on the upper surface of the EL layer 440. The cathode 450 is substantially L-shaped in plan view. Specifically, the cathode 450 has a portion 450b extending almost over the entire breadth of the EL layer 440 and a portion 450c extending downward in
In the fifth preferred embodiment, the anode terminal 434 has a smaller breadth than the above described preferred embodiments. An auxiliary electrode 438 is provided for supplying power constantly over the anode 430 in the lateral direction. The auxiliary electrode 438 is formed on the upper surface of the portion 430b of the anode 430. The auxiliary electrode 438 extends laterally, having a larger breadth (lateral length) than the anode terminal 434. The auxiliary electrode 438 is made of the same material as the cathode 450, so that the auxiliary electrode 438 has a very low volume resistivity (much smaller than ITO).
The FPC (not shown) has terminals for connection with the cathode terminal 464 and terminals for connection with the anode terminal 434. When the FPC is connected to the EL device 500, the FPC will fit within the breadth of the glass substrate 20. In the fifth preferred embodiment, the anode terminal 434 has a small breadth but the auxiliary electrode 438 extends laterally, so that a potential difference is small in the lateral direction of the anode 430. The cathode terminal 464 has a smaller breadth than the portion 430b of the anode 430, but a potential difference is small in the lateral direction of the cathode 450 due to a low volume resistivity of metal forming the cathode 450. This causes a voltage applied to the EL layer 440 to be small in difference as measured in the lateral direction, with the result that electric current flowing through the EL layer 440 is small in difference as measured in the lateral direction. Thus, uneven brightness is reduced in the lateral direction.
As described above, according to the EL device 500 in the fifth preferred embodiment, uneven brightness is reduced at any positions of the EL layer 440. Furthermore, the anode terminal 434 and the cathode terminals 464 are all formed at the lower side in
In the fifth preferred embodiment, the long side length of the EL layer 440 along the glass substrate 20 is larger than the long side length of the EL layer 440 along the FPC. Thus, the EL device unit including the FPC is very compact. The EL device unit according to the second preferred embodiment is applicable to a light source for optical readers, such as copiers, facsimiles and scanners. Since the FPC does not extend in the longitudinal direction of the EL device unit, an optical reader and a copier, a facsimile and a scanner using it will be compact, especially in the longitudinal direction of the EL device unit. In the fifth preferred embodiment, the anode terminal 434 will be small, so that the number of terminals for the FPC may be smaller. Thus, the structure of the FPC will be simple.
The present invention is not limited to the embodiments described above but may be modified into the following alternative embodiments.
(1) In the first preferred embodiment, the breadth L1 of the EL layer 40 is substantially equal to the sum of the breadth L2 of the anode terminal 34 and the breadth L3 of the cathode terminal 64. However, the breadth L2 or L3 may be smaller than the gap L4. The breadth L2, the breadth L3 and the gap L4 may be substantially equal. Alternatively, the breadth L2 is substantially equal to the breadth L3, and the sum of the breadths L2 and L3 is half or larger than the breadth L1.
As far as the anode terminal (such as the anode terminal 34) and the cathode terminal (such as the cathode terminal 64) fit within the breadth L1 of the EL layer (such as the EL layer 40) on the glass substrate 20, they may be formed on any positions in the width L1′ direction of the EL layer (the short side direction of the EL layer). Furthermore, as far as the anode terminal (such as the anode terminal 34) and the cathode terminal (such as the cathode terminal 64) are formed along the long side direction of the EL layer (such as the EL layer 40) within the breadth L1, the breadth L2 and the breadth L3 may be smaller than the breadth L1.
(2) In the above-preferred embodiments, three terminals 620 through 624 (as shown in
(3) Shapes of various types may be employed for the EL layer. The rectangular shape as shown in
Alternatively, the side 654 and the side 656 may be regarded as one long side. One electrode terminal is formed along the side 654 and the other electrode terminal is formed along the side 656. An elliptical EL layer as shown in
(4) An anode having a shape as shown in
Furthermore, the auxiliary electrode 538 having a much smaller volume resistivity than ITO may be formed as shown in
Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims.
Number | Date | Country | Kind |
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2005-209514 | Jul 2005 | JP | national |