Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
  • G02B26/004—Optical devices or arrangements for the control of light using movable or deformable optical elements based on a displacement or a deformation of a fluid
  • G02B26/005—Optical devices or arrangements for the control of light using movable or deformable optical elements based on a displacement or a deformation of a fluid based on electrowetting
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
  • G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
  • G09F9/30—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements
  • G09F9/37—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements being movable elements
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
  • G09F13/00—Illuminated signs; Luminous advertising
  • G09F13/24—Illuminated signs; Luminous advertising using tubes or the like filled with liquid, e.g. bubbling liquid

Definitions

• the invention relates to a display device comprising picture elements having at least one first fluid and a second fluid immiscible with each other within a space between a first transparent support plate and a second support plate, the second fluid being electroconductive or polar.
• Display devices like TFT-LCDs are used in laptop computers and in organizers, but also find an increasingly wider application in GSM telephones. Instead of LCDs, for example, (polymer) LED display devices are also being used.
• the display device comprises an intermediate substrate between the first support plate and the second support plate, the intermediate substrate having a reflective surface at the side of the first support plate and being provided with at least one passage between spaces at both sides of the intermediate substrate, the device comprising means for introducing flow of the first fluid through said passage.
• the invention is based on a principle called electro-wetting.
• the invention provides new ways of using this principle.
• a two layer system which comprises a water layer on top of the oil layer.
• a voltage is applied between the water layer and an electrode on a wall or a support plate, the stack of fluid layers is perturbed due to electrostatic forces. Since parts of the water now displace the oil layer the picture element becomes partly transparent.
• the contrast is limited by the fraction of area occupied by (first) fluid ((colored) oil).
• a further limitation is that a color display with a high brightness cannot be realized without special measures since each area of the display can only reflect one of the three colors desired to obtain the proper color performance.
• Fig. 1 is a diagrammatic cross-section of a part of a display device in which the principle of electrowetting is explained
• Fig. 2 is a diagrammatic cross-section of a part of a display device according to the invention
• Fig. 3 is a diagrammatic cross-section of a part of a color display device according to the invention.
• Fig. 1 shows a diagrammatic cross-section of a part of a display device 1.
• a first fluid 5 and a second fluid 6 are provided, which are immiscible with each other.
• the first fluid 5 is for instance an alkane like hexadecane or as in this example a (silicone) oil.
• the second fluid 6 is electroconductive or polar, for instance water or a salt solution (e.g. a solution of KC1 in a mixture of water and ethyl alcohol).
• the fluids 5, 6 adjoin the first and second transparent support plates 3, 4 of e.g. glass or plastic.
• a transparent electrode 7 for example indium (tin) oxide is provided and a hydrophobic insulator layer 8, in this example an amorphous fluoropolymer (AF1600).
• the device further comprises a white reflector 10 When a voltage is applied (voltage source 9) between the fluid layer 6 and the transparent electrode 7 via interconnections 21, 20, displacement of the layer 5 occurs due to a phenomenon called electrowetting.
• Fig. la shows a diagrammatic cross-section of a part of a display device viz. a display cell 1 according to the invention.
• one or more flow channels or passage 13 are provided between spaces 15, 16 at both sides of the white reflector 14 (intermediate substrate).
• one pixel wall could be hydrophilic, whereas the opposite pixel wall could be hydrophobic.
• a full-color display could be realized by stacking three of such display cells, whereby each of the individual cells absorbs a particular part of the spectrum of the light. This can be done for both cells shown in Fig. 1 and Fig. 2.
• FIG. 3 shows a further embodiment in which a subtractive color display has been realized.
• a display cell of a display device comprises a sub- cell for each of the colors cyan, magenta and yellow having spaces 15C, 15M, 15Y and 16C, 16M, 16Y at both sides of the white reflector 14.
• Spaces 15C, 15M, and 15Y are separated physically from each other by transparent substrates 24. Also the spaces 16C, 16M and 16Y should be fabricated such that no mixing of the differently colored oils will occur.
• the walls separating these spaces do not necessarily have to extend the full space 16 between the intermediate reflector 14 and the second supporting plate 3 throughout the entire cell. In fact, leaving a part of the walls high enough to contain the oils and low enough such that the second polar fluid 6 is continuous through the sub-cells will facilitate the driving of the system.
• the spaces 15, 16 related to one specific color are interconnected to each other via channels or passages 13C, 13M, 13Y ( Figures 3a). When no voltage is applied the spaces 15C, 15M, 15Y remain filled with the transparent polar fluid 6 and the display cell reflects (white) light (arrows 12).
• switches 23 C, 23M, 23 Y are controlled as shown schematically by control line 25 by driving apparatus 22 to supply driving voltages via interconnections 21, 20. If the voltage is sufficiently high the spaces 15C, 15M, 15Y are completely filled and the display reflects no light, resulting in a black state (Fig. 3b). By applying intermediate voltages, intermediate filling and therefore grey-scales can be obtained as shown schematically in Figure 3c.
• the electrode under space 16Y is activated by an intermediate voltage, partly filling space 15Y with liquid 6Y and the display cell partly reflects (white) light (arrows 12) and partly absorbs blue light, resulting in a light yellow color.
• the three subtractive colors can be independently pumped due to the separated flow channels. Based on the color strength of the currently available oils suitable for electrowetting, good color rendition can be obtained for a flow channel thickness of less than 25 microns and therefore a total pixel thickness including the sub pixel reservoirs of less than 200 microns (not including the thickness of the active electrode layer and substrate).
• the invention is not limited to the embodiments as shown.
• the transparent substrates 24 may be deleted. Due to the difference in mobility a stacking of the fluid layers may be introduced then by the driving scheme.
• the invention resides in each and every novel characteristic feature and each and every combination of characteristic features. Reference numerals in the claims do not limit their protective scope. Use of the verb "to comprise” and its conjugations does not exclude the presence of elements other than those stated in the claims. Use of the article "a” or “an” preceding an element does not exclude the presence of a plurality of such elements.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Theoretical Computer Science (AREA)
• Optics & Photonics (AREA)
• Electrochromic Elements, Electrophoresis, Or Variable Reflection Or Absorption Elements (AREA)
• Devices For Indicating Variable Information By Combining Individual Elements (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (7)

Cited By (26)

Families Citing this family (70)

Citations (2)

Family Cites Families (9)

• 2004
  • 2004-01-12 CN CNB2004800028711A patent/CN100380167C/zh not_active Expired - Fee Related
  • 2004-01-12 EP EP04701419A patent/EP1599751A1/en not_active Withdrawn
  • 2004-01-12 KR KR1020057013768A patent/KR20050092786A/ko not_active Withdrawn
  • 2004-01-12 WO PCT/IB2004/050008 patent/WO2004068208A1/en not_active Ceased
  • 2004-01-12 US US10/543,204 patent/US7359108B2/en not_active Expired - Fee Related
  • 2004-01-12 JP JP2006502513A patent/JP2006516755A/ja active Pending
  • 2004-01-20 TW TW093201101U patent/TWM256504U/zh not_active IP Right Cessation

Patent Citations (2)

Non-Patent Citations (2)

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