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The present application is a continuation application filed under 35 U.S.C. 111(a) claiming benefit under 35 U.S.C. 120 and 365(c) of PCT International Application No. PCT/JP2005/004911, filed on Mar. 18, 2005, the entire contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to display units such as electronic paper and flat panel displays and methods of manufacturing the same.
2. Description of the Related Art
In these years, electronic paper has drawn attention as an alternative information medium to paper. Electronic paper is an electronic information medium that can be bent, rolled, and carried like paper. Display systems for electronic paper include liquid crystal systems and electrophoretic systems. There are challenges such as improvement in visibility and improvement in power efficiency in putting electronic paper to practical use.
It is known that “reflection-type” display units using reflected light in displaying are better in visibility than “transmission-type” display units using transmitted light in displaying. Further, the power efficiency of a display unit is increased by employment of a display element having a “memory characteristic” that causes the contents of a display to be maintained even when power is switched from ON to OFF. Therefore, electronic paper using a cholesteric liquid crystal, which is a reflection type and has a memory characteristic, has drawn attention (Patent Document 3).
Patent Document 1: Japanese Laid-Open Patent Application No. 2000-241828
Patent Document 2: Japanese Laid-Open Patent Application No. 2002-72244
Patent Document 3: Japanese Laid-Open Patent Application No. 2003-195261
FIG. 1 shows a conventional display unit 101 using a cholesteric liquid crystal. The display unit 101 of FIG. 1 has a stacked display panel including a red display panel 111 R, a green display panel 111 G, and a blue display panel 111 B. Each display panel 111 includes a display layer 121 , a scan electrode 122 , a signal electrode 123 , a scan electrode terminal 124 , a signal electrode terminal 125 , a scan electrode substrate 126 , a signal electrode substrate 127 , a spacer 128 , and a sealing material 129 .
FIG. 2 is a diagram illustrating the principle of displaying of the display unit 101 using a cholesteric liquid crystal. Application of a strong pulse voltage between the electrodes of the display layer 121 causes a planar state where the screw axes of liquid crystal molecules 131 of the cholesteric liquid crystal are perpendicular to the surfaces of the electrodes as shown in (A) of FIG. 2. Application of a weak pulse voltage between the electrodes of the display layer 121 causes a focal conic state where the screw axes of the liquid crystal molecules 131 of the cholesteric liquid crystal are parallel to the surfaces of the electrodes as shown in (B) of FIG. 2. A planar-state cholesteric liquid crystal has the property of reflecting incident light of a specific wavelength as from arrow I to arrow R in the drawing (selective reflection). A focal conic-state cholesteric liquid crystal has the property of transmitting incident light of various wavelengths such as from arrow I to arrow T in the drawing. The display unit 101 using a cholesteric liquid crystal realizes ON and OFF of display with reflection and transmission of incident light.
Three scanning drivers 132 and three signal drivers 133 are mounted on the display unit 101 of FIG. 1 for the three display panels 111 . The single scanning driver 132 is connected to the scan electrode terminal 124 of each display panel 111 , and the single signal driver 133 is connected to the signal electrode terminal 125 of each display panel 111 .
The signal drivers 133 and the scanning drivers 132 contribute to an increase in the cost of the display panels 111 . Therefore, while the signal driver 133 should be provided for each display panel 111 , the scanning driver 132 does not have to be provided for every display panel 111 . Accordingly, it is convenient if it is possible to reduce the number of scanning drivers 132 used by enabling two or more of the display panels 111 to share the single scanning driver 132 .
According to one aspect of the present invention, there are provided a display unit and a method of manufacturing the same in which one or more of the above-described problems may be solved or reduced.
According to one aspect of the present invention, there is provided a display unit having a stacked display panel, the display unit including a first end display panel placed at one end; a second end display panel placed at another end; and one or more internal display panels placed between the first end display panel and the second end display panel, wherein the first end display panel includes a scan electrode terminal longer than scan electrode terminals of the internal display panels, and the second end display panel includes a scan electrode terminal longer than the scan electrode terminal of the first end display panel, and a terminal surface of the scan electrode terminal in the first end display panel faces a terminal surface of the scan electrode terminal in the second end display panel; the scan electrode terminal of each of the internal display panels is joined to the scan electrode terminal of one of the first end display panel, the second end display panel, and another one of the internal display panels; the scan electrode terminal of the first end display panel is joined to the scan electrode terminal of the second end display panel; and the scan electrode terminal of the second end display panel is connected to a scanning driver circuit.
According to one aspect of the present invention, there is provided a method of manufacturing a display unit having a stacked display panel, the display unit including a first end display panel placed at one end; a second end display panel placed at another end; and one or more internal display panels placed between the first end display panel and the second end display panel, the first end display panel including a scan electrode terminal longer than scan electrode terminals of the internal display panels, the second end display panel including a scan electrode terminal longer than the scan electrode terminal of the first end display panel, the method including causing a terminal surface of the scan electrode terminal in the first end display panel to face a terminal surface of the scan electrode terminal in the second end display panel; joining the scan electrode terminal of each of the internal display panels to the scan electrode terminal of one of the first end display panel, the second end display panel, and another one of the internal display panels; joining the scan electrode terminal of the first end display panel to the scan electrode terminal of the second end display panel; and connecting the scan electrode terminal of the second end display panel to a scanning driver circuit.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings, in which:
FIG. 1 shows a conventional display unit using a cholesteric liquid crystal;
FIG. 2 is a diagram illustrating the principle of displaying of the display unit using the cholesteric liquid crystal;
FIG. 3 shows an embodiment of a display unit using a cholesteric liquid crystal;
FIG. 4 shows matrix-driving electrodes and segment-driving electrodes;
FIG. 5 is a front view of a display panel;
FIG. 6 is a perspective view of a laminated structure of the display panels;
FIG. 7 is a diagram for illustrating input images and output images of signal drivers;
FIG. 8 shows a variant embodiment of the display unit using the cholesteric liquid crystal;
FIG. 9 shows a variant embodiment of the display unit using the cholesteric liquid crystal;
FIG. 10 shows a variant embodiment of the display unit using the cholesteric liquid crystal;
FIG. 11 is a diagram illustrating a method of manufacturing the display unit having the display panels in three layers;
FIG. 12A is a diagram illustrating a method of manufacturing the display unit having the display panels in four layers;
FIG. 12B is a diagram illustrating the method of manufacturing the display unit having the display panels in four layers;
FIG. 13A is a diagram illustrating a method of manufacturing the display unit having the display panels in five layers;
FIG. 13B is a diagram illustrating the method of manufacturing the display unit having the display panels in five layers;
FIG. 14A is a diagram illustrating a method of manufacturing the display unit having the display panels in six layers;
FIG. 14B is a diagram illustrating the method of manufacturing the display unit having the display panels in six layers; and
FIG. 15 is a flowchart for illustrating the methods of manufacturing the display unit using the cholesteric liquid crystal.
A description is given, with reference to the accompanying drawings, of embodiments of the present invention.
FIG. 3 shows an embodiment of a display unit 101 using a cholesteric liquid crystal. The display unit 101 of FIG. 3 has a stacked display panel including a red display panel 111 R, a green display panel 111 G, and a blue display panel 111 B. Each display panel 111 includes a display layer 121 , a scan electrode 122 , a signal electrode 123 , a scan electrode terminal 124 , a signal electrode terminal 125 , a scan electrode substrate 126 , a signal electrode substrate 127 , a spacer 128 , and a sealing material 129 .
The display layer 121 is a liquid crystal layer formed of a liquid crystal forming a cholesteric phase. The display layer 121 may be a liquid crystal layer formed principally of a cholesteric liquid crystal or a liquid crystal layer formed of a nematic liquid crystal containing a cholesteric liquid crystal (a chiral dopant). As a result, a reflection-type display layer (display unit) having a memory characteristic is realized, so that improvement in the visibility and improvement in the power efficiency of electronic paper are realized.
The scan electrode 122 is a transparent electrode for applying a scan voltage to the display layer 121 . The signal electrode 123 is a transparent electrode for applying a signal voltage (data voltage) to the display layer 121 . Here, the scan electrode 122 and the signal electrode 123 are matrix-driving electrodes ((A) of FIG. 4), but may also be segment-driving electrodes ((B) of FIG. 4). The scan electrode 122 and the signal electrode 123 are IZO (Indium-Zinc-Oxide) electrodes, but may also be ITO (Indium-Tin-Oxide) electrodes.
The scan electrode terminal 124 is a terminal for connecting the scan electrode 122 and the scanning driver 132 . The signal electrode terminal 125 is a terminal for connecting the signal electrode 123 and the signal driver 133 . The scan electrode terminal 124 and the signal electrode terminal 125 are IZO electrodes, but may also be ITO electrodes.
The scan electrode substrate 126 is a transparent, flexible substrate on which the scan electrode 122 and the scan electrode terminal 124 are formed. The signal electrode substrate 127 is a transparent, flexible substrate on which the signal electrode 123 and the signal electrode terminal 125 are formed. The scan electrode substrate 126 and the signal electrode substrate 127 are flexible substrates that can be bent and rolled, thereby realizing flexible electronic paper that can be bent and rolled. Here, the scan electrode substrate 126 and the signal electrode substrate 127 are polycarbonate printed boards.
The scanning driver 132 and the signal drivers 133 are mounted on the display unit 101 of FIG. 3. The scanning driver 132 is a driver circuit for supplying scan voltage to the display panels 111 (display layers 121 ). The signal drivers 133 are driver circuits for supplying signal voltage to the display panels 111 (display layers 121 ). The scanning driver 132 and the signal drivers 133 are IC chips that are contained in IC packages by a surface mounting format such as a TCP (Tape Carrier Package) format. As a result, the scanning driver 132 and the signal drivers 133 are reduced in thickness, so that electronic paper is reduced in thickness.
The single scanning driver 132 and the three signal drivers 133 are mounted on the display unit 101 . The scanning driver 132 is common to all the display panels 111 , while the signal drivers 133 are provided individually for the corresponding display panels 111 .
A description is given below of the laminated structure of the display panels 111 .
In the display unit 101 of FIG. 3, the red (R) display panel 111 R, the green (G) display panel 111 G, and the blue (B) display panel 111 B are stacked. The display panel 111 R is placed at a “lower layer,” which defines one end; the display panel 111 B is placed at an “upper layer,” which defines another end; and the display panel 111 G is placed at the “intermediate layer” between the display panel 111 R and the display panel 111 B.
In the display unit 101 of FIG. 3, a terminal surface SR of the scan electrode terminal 124 R in the lower-layer display panel 111 R faces a terminal surface SB of the scan electrode terminal 124 B in the upper-layer display panel 111 B. This is for bonding the scan electrode terminal 124 R of the lower-layer display panel 111 R to the scan electrode terminal 124 B of the upper-layer display panel 111 B with an anisotropic conductive adhesive agent 134 as shown in FIG. 3. Therefore, a length LR of the scan electrode terminal 124 R in the lower-layer display panel 111 R and a length LB of the scan electrode terminal 124 B in the upper-layer display panel 111 B are both greater than a length LG of the scan electrode terminal 124 G in the intermediate-layer display panel 111 G.
In the display unit 101 of FIG. 3, a terminal surface SG of the scan electrode terminal 124 G in the intermediate-layer display panel 111 G may be caused to face the terminal surface SR of the scan electrode terminal 124 R in the lower-layer display panel 111 R or be caused to face the terminal surface SB of the scan electrode terminal 124 B in the upper-layer display panel 111 B. In the former case, the scan electrode terminal 124 G of the intermediate-layer display panel 111 G is joined to the opposing scan electrode terminal 124 R of the lower-layer display panel 111 R with the anisotropic conductive adhesive agent 134 . In the latter case, the scan electrode terminal 124 G of the intermediate-layer display panel 111 G is joined to the opposing scan electrode terminal 124 B of the upper-layer display panel 111 B with the anisotropic conductive adhesive agent 134 .
In the display unit 101 of FIG. 3, the scan electrode terminal 124 B of the upper-layer display panel 111 B is joined to the terminal of the scanning driver 132 with the anisotropic conductive adhesive agent 134 , so that the scan electrode terminal 124 B of the upper-layer display panel 111 B is connected to the scanning driver 132 . Therefore, the length LB of the scan electrode terminal 124 B in the upper-layer display panel 111 B is greater than the length LR of the scan electrode terminal 124 R in the lower-layer display panel 111 R. In the case of bonding the terminal of the scanning driver 132 to the lower-layer scan electrode terminal 124 R in place of the upper-layer scan electrode terminal 124 B, the length LB of the upper-layer scan electrode terminal 124 B and the length LR of the lower-layer scan electrode terminal 124 R are reversed.
In the display unit 101 of FIG. 3, the number of scanning drivers 132 used can be reduced to one in this manner. According to this method, there is no need to go through the scan electrode 122 or the dedicated flexible printed board 141 as in the methods disclosed in Patent Document 1 and Patent Document 2 in order to supply scan voltage from the scanning driver 132 to the display panels 111 . This eliminates the burden of setting a rather high scan voltage in consideration of a voltage drop due to the electric resistance of from the scanning driver 132 to the display panels 111 . Further, it is also possible to eliminate the cost of preparing the dedicated flexible printed board 141 . In the case of using segment-driving electrodes instead of matrix-driving electrodes for the scan electrodes 122 and the signal electrodes 123 in this method, an adhesive agent without anisotropic conductivity may be used in place of an anisotropic conductive adhesive agent as an adhesive agent for bonding the scan electrode terminals 124 .
FIG. 5 is a front view of the display panel 111 .
The display panel 111 has a substantially rectangular shape. One set of scan electrode terminals 124 is formed on one short side A of the four sides of the display panel 111 . Two sets of signal electrode terminals 125 are formed on one long side B of the four sides of the display panel 111 . The display panel 111 has substantially the same shape except for the length of the scan electrode terminal 124 in each layer. The length of the scan electrode terminal 124 is 4 mm in the lower-layer display panel 111 R, 2 mm in the intermediate-layer display panel 111 G, and 6 mm in the upper-layer display panel 111 B, including a margin.
FIG. 6 is a perspective view of a laminated structure of the display panels 111 .
The top-bottom orientation in the lower-layer display panel 111 R and the top-bottom orientation in the upper-layer display panel 111 B are opposite to each other. As a result, it is possible to cause the terminal surface SR of the scan electrode terminal 124 R in the lower-layer display panel 111 R and the terminal surface SB of the scan electrode terminal 124 B in the upper-layer display panel 111 B to face each other.
The three display panels 111 are stacked so that the scan electrode terminals 124 of the display panels 111 are on the sides of the display panels 111 on the same side. The four sides of each display panel 111 are positioned on the right side, the left side, the front side, and the bottom side in the drawing, and the scan electrode terminals 124 of the display panels 111 are on the sides on the right side in the drawing. This makes it possible to bond the scan electrode terminals 124 of the display panels 111 to each other.
The scanning driver 132 is placed opposite to the sides of the display panels 111 on which the respective scan electrode terminals 124 are provided. That is, the scanning driver 132 is placed opposite to the right-side one of the four sides of each display panel 111 in the drawing. This makes it possible to place the scanning driver 132 in the vicinity of the sides of the display panels 111 on which the respective scan electrode terminals 124 are provided, and to bond a terminal TM of the scanning driver 132 and the scan electrode terminal 124 R of the upper-layer display panel 111 R to each other. Here, the term “vicinity” means a range of distances within which it is possible to bond the terminal TM of the scanning driver 132 and the scan electrode terminal 124 R of the upper-layer display panel 111 R to each other.
In order to make it possible to realize these, the arrangement of the scan electrode terminals 124 of the display panel 111 is axisymmetric with respect to a long axis X of the screen of the display panel 111 (FIG. 5). Further, although not related in particular to making it possible to realize these, the arrangement of the signal electrode terminals 125 of the display panel 111 is axisymmetric with respect to a short axis Y of the screen of the display panel 111 (FIG. 5).
FIG. 7 is a diagram for illustrating input images and output images of the signal drivers 133 .
FIG. 7 shows an “ABC” image displayed on the display unit 101 . Displayed images 153 R, 153 G, and 153 B of the display panels 111 R, 111 G, and 111 B of their respective colors are “ABC”s of the corresponding colors. Here, it should be noted that the display panel 111 R is face-up, the display panel 111 G is face-up, and the display panel 111 B is face-down. Accordingly, output images 152 R, 152 G, and 152 B output from the signal drivers 133 R, 133 G, and 133 B to the display panels 111 R, 111 G, and 111 B should be face-up, face-up, and face-down in order to make all of the display images 153 R, 153 G, and 153 B face up. This further requires input images 151 R, 151 G, and 151 B input to the signal drivers 133 R, 133 G, and 1333 to be face-up, face-up, and face-down.
Accordingly, the display unit 101 of this embodiment corrects the orientations of the input images 151 input to the signal drivers 133 with image processing ICs 161 so that the output images 152 output from the signal drivers 133 to the display panels 111 are oriented so as to match the orientation of the display image 153 in the face-up display panel 111 with the orientation of the display image 153 in the face-down display panel 111 . In FIG. 7, when the orientations of the output images 152 R, 152 G, and 152 B are face-up, face-up, and face-down, the orientations of the display images 153 R, 153 G, and 1533 match one another. Accordingly, the orientations of the input images 151 R, 151 G, and 151 B are corrected to be face-up, face-up, and face-down so that the output images 152 R, 152 G, and 152 B are oriented face-up, face-up, and face-down.
In the above, a three-layer laminated structure is taken as an embodiment of the present invention. In the following, multilayer laminated structures having three or more layers ate taken as variant embodiments of the present invention.
In the display units 101 of FIGS. 8, 9, and 10 , the red (R) display panel 111 R, a green (G) display panel 111 Ga, a green (G) display panel 111 Gb, and the blue (B) display panel 111 B are stacked. The display panel 111 R is placed at a “lower layer,” which defines one end; the display panel 111 B is placed at an “upper layer,” which defines another end; and the display panels 111 Ga and 111 Gb are placed at the “intermediate layer” between the display panel 111 R and the display panel 111 B.
In the display unit 101 of each drawing, the terminal surface SR of the scanning electrode terminal 124 R in the lower-layer display panel 111 R faces the terminal surface SB of the scanning electrode terminal 124 B in the upper-layer display panel 111 B. This is for bonding the scan electrode terminal 124 R of the lower-layer display panel 111 R to the scan electrode terminal 124 B of the upper-layer display panel 111 B with the anisotropic conductive adhesive agent 134 as shown in each drawing. Therefore, the length LR of the scan electrode terminal 124 R in the lower-layer display panel 111 R and the length LB of the scan electrode terminal 124 B in the upper-layer display panel 111 B are both greater than lengths LGa and LGb of scan electrode terminals 124 Ga and 124 Gb in the intermediate-layer display panels 111 Ga and 111 Gb.
In the display unit 101 of each drawing, terminal surfaces SGa and SGb of the scan electrode terminals 124 Ga and 124 Gb in the intermediate-layer display panels 111 Ga and 111 Gb may be caused to face the terminal surface SR of the scan electrode terminal 124 R in the lower-layer display panel 111 R or be caused to face the terminal surface SB of the scan electrode terminal 124 B in the upper-layer display panel 111 B. In the former case, the scan electrode terminals 124 Ga and 124 Gb of the intermediate-layer display panels 111 Ga and 111 Gh are joined to the opposing scan electrode terminal 124 R, 124 Gb, or 124 Ga of the lower-layer or other intermediate display panel 111 R, 111 Gb, or 111 Ga with the anisotropic conductive adhesive agent 134 . In the latter case, the scan electrode terminals 124 Ga and 124 Gb of the intermediate-layer display panels 111 Ga and 111 Gb are joined to the opposing scan electrode terminal 124 B, 124 Gb, or 124 Ga of the upper-layer or other intermediate-layer display panel 111 B, 111 Gb, or 111 Ga with the anisotropic conductive adhesive agent 134 .
In the display unit 101 of each drawing, the scan electrode terminal 124 B of the upper-layer display panel 111 B is joined to the terminal of the scanning driver 132 with the anisotropic conductive adhesive agent 134 , so that the scan electrode terminal 124 B of the upper-layer display panel 111 B is connected to the scanning driver 132 . Therefore, the length LB of the scan electrode terminal 124 B in the upper-layer display panel 111 B is greater than the length LR of the scan electrode terminal 124 R in the lower-layer display panel 111 R. In the case of bonding the terminal of the scanning driver 132 to the lower-layer scan electrode terminal 124 R in place of the upper-layer scan electrode terminal 124 B, the length LB of the upper-layer scan electrode terminal 124 B and the length LR of the lower-layer scan electrode terminal 124 R are reversed.
FIG. 11, FIGS. 12A and 12B, FIGS. 13A and 13B, and FIGS. 14A and 14B are diagrams illustrating methods of manufacturing the display units 101 having the display panels 101 in three layers, four layers, five layers, and six layers, respectively. FIG. 15 shows a flow of these manufacturing methods.
In each manufacturing method, the display panels 111 having the scan electrode terminals 124 whose lengths increase in the order of “each intermediate layer, the lower layer, and the upper layer” are prepared (FIG. 15, S 10 ), the scan electrode terminals 124 of the display panels 111 are bonded to each other in the order of the numbers in arrows (FIG. 15, S 30 ), and finally, the terminal of the scanning driver 132 is bonded (FIG. 15, S 50 ). At the time of bonding, it is necessary to bend the scan electrode substrate 126 of the display panel 111 . Since the scan electrode substrate 126 of the display panel 111 is a flexible substrate, it is possible to bend it. The particulars described with reference to FIG. 6 are applied to the top-bottom orientations and the orientations of the four sides of the display panels 111 at the time of their stacking (FIG. 15, S 20 ) and to the placement of the scanning driver 132 at the time of its installation (FIG. 15, S 40 ).
In the process of S 30 , the scan electrode terminal 124 of the intermediate-layer display panel 111 is bonded to the scan electrode terminal 124 of the lower-layer, upper-layer, or other intermediate-layer display panel 111 (S 30 - 1 ), and finally, the scan electrode terminal 124 of the lower-layer display panel 111 is bonded to the scan electrode terminal 124 of the upper-layer display panel 111 (S 30 - 2 ).
According to one aspect of the present invention, there is provided a display unit having a stacked display panel, the display unit including a first end display panel placed at one end; a second end display panel placed at another end; and one or more internal display panels placed between the first end display panel and the second end display panel, wherein the first end display panel includes a scan electrode terminal longer than scan electrode terminals of the internal display panels, and the second end display panel includes a scan electrode terminal longer than the scan electrode terminal of the first end display panel, and a terminal surface of the scan electrode terminal in the first end display panel faces a terminal surface of the scan electrode terminal in the second end display panel; the scan electrode terminal of each of the internal display panels is joined to the scan electrode terminal of one of the first end display panel, the second end display panel, and another one of the internal display panels; the scan electrode terminal of the first end display panel is joined to the scan electrode terminal of the second end display panel; and the scan electrode terminal of the second end display panel is connected to a scanning driver circuit.
According to one aspect of the present invention, there is provided a method of manufacturing a display unit having a stacked display panel, the display unit including a first end display panel placed at one end; a second end display panel placed at another end; and one or more internal display panels placed between the first end display panel and the second end display panel, the first end display panel including a scan electrode terminal longer than scan electrode terminals of the internal display panels, the second end display panel including a scan electrode terminal longer than the scan electrode terminal of the first end display panel, the method including causing a terminal surface of the scan electrode terminal in the first end display panel to face a terminal surface of the scan electrode terminal in the second end display panel; joining the scan electrode terminal of each of the internal display panels to the scan electrode terminal of one of the first end display panel, the second end display panel, and another one of the internal display panels; joining the scan electrode terminal of the first end display panel to the scan electrode terminal of the second end display panel; and connecting the scan electrode terminal of the second end display panel to a scanning driver circuit.
Thus, according one aspect of the present invention, there are provided a non-conventional, novel method for reducing the number of scanning driver circuits used with respect to a display unit having a stacked display panel and a method of manufacturing the same.
The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention.