1. A liquid crystal display, comprising:
a first and a second transparent substrates facing to each other;
a liquid crystal layer interposed between the first and the second transparent substrates;
a first polarizer positioned next to the first transparent substrate and opposite the liquid crystal layer;
a second polarizer positioned next to the second transparent substrate and opposite the liquid crystal layer; and
a first half wave plate provided between the first transparent substrate and the first polarizer to enable the liquid crystal display to have a normally black mode, wherein the normally black mode is obtained when the following equation is satisfied:
2\u03b1\u22122r+p1\u2212p2=90\xb0+N*180\xb0,
where N is an integer, p1 is the transmission-axis azimuth of the first polarizer, r is the slow-axis azimuth of the first half wave plate, \u03b1 is the oriented viewing angle of the liquid crystal display, and p2 is the transmission-axis azimuth of the second polarizer.
2. The liquid crystal display as claimed in claim 1, wherein a tolerance of \xb15 degrees for each angle solution of the equation is permitted to form the normally black mode.
3. The liquid crystal display as claimed in claim 1, wherein the phase retardation of the first half wave plate is larger than 200 nm and smaller than 360 nm.
4. The liquid crystal display as claimed in claim 1, wherein the liquid crystal layer interposed between the first and the second transparent substrates forms a dual-cell-gap liquid crystal (LC) cell having a reflective region and a transmissive region, and the cell-gap thickness of the reflective region being different to the cell-gap thickness of the transmissive region.
5. The liquid crystal display as claimed in claim 4, wherein a tolerance of \xb15 degrees for each angle solution of the equation is permitted to form the normally black mode.
6. The liquid crystal display as claimed in claim 4, wherein the phase retardation of the first half wave plate is larger than 200 nm and smaller than 360 nm.
7. The liquid crystal display as claimed in claim 4, wherein the phase retardation for the transmissive region of the dual-cell-gap LC cell is larger than the phase retardation of the first half wave plate, and the difference value between them is smaller than 30 nm.
8. A liquid crystal display, comprising:
a first and a second transparent substrates facing to each other;
a liquid crystal layer interposed between the first and the second transparent substrates;
a first polarizer positioned next to the first transparent substrate and opposite the liquid crystal layer;
a second polarizer positioned next to the second transparent substrate and opposite the liquid crystal layer; and
a first half wave plate provided between the first transparent substrate and the first polarizer to enable the liquid crystal display to have a normally black mode, wherein the phase retardation of the liquid crystal layer is larger than the phase retardation of the first half wave plate, and the difference value between the phase retardation of the liquid crystal layer and the phase retardation of the first half wave plate is smaller than 30 nm.
9. A liquid crystal display, comprising:
a first and a second transparent substrates facing to each other;
a liquid crystal layer interposed between the first and the second transparent substrates;
a first polarizer positioned next to the first transparent substrate and opposite the liquid crystal layer;
a second polarizer positioned next to the second transparent substrate and opposite the liquid crystal layer;
a first half wave plate provided between the first transparent substrate and the first polarizer to enable the liquid crystal display to have a normally black mode; and
a second half wave plate provided between the second transparent substrate and the second polarizer, wherein the normally black mode is obtained when the following equation is satisfied:
2r2\u22122\u03b1+2r1\u2212p1\u2212p2=90\xb0+N*180\xb0,
where N is an integer, p1 is the transmission-axis azimuth of the first polarizer, r1 is the slow-axis azimuth of the first half wave plate, \u03b1 is the oriented viewing angle of the liquid crystal display, p2 is the transmission-axis azimuth of the second polarizer, and r2 is the slow-axis azimuth of the second half wave plate.
10. The liquid crystal display as claimed in claim 9, wherein a tolerance of \xb15 degrees for each angle solution of the equation is permitted to form the normally black mode.
11. The liquid crystal display as claimed in claim 9, wherein the phase retardation of the first half wave plate or the second half wave plate is larger than 200 nm and smaller than 360 nm.
12. The liquid crystal display as claimed in claim 9, wherein the phase retardation of the liquid crystal layer is larger than the phase retardation of the first half wave plate or the second half wave plate, the difference value between the phase retardation of the liquid crystal layer and the phase retardation of the first half wave plate is smaller than 30 nm, and the difference value between the phase retardation of the liquid crystal layer and the phase retardation of the second half wave plate is smaller than 30 nm.
13. The liquid crystal display as claimed in claim 9, wherein the liquid crystal layer interposed between the first and the second transparent substrates forms a dual-cell-gap liquid crystal (LC) cell having a reflective region and a transmissive region, and the cell-gap thickness of the reflective region being different to the cell-gap thickness of the transmissive region.
14. The liquid crystal display as claimed in claim 13, wherein a tolerance of \xb15 degrees for each angle solution of the equation is permitted to form the normally black mode.
15. The liquid crystal display as claimed in claim 13, wherein the phase retardation of the first half wave plate or the second half wave plate is larger than 200 nm and smaller than 360 nm.
16. The liquid crystal display as claimed in claim 13, wherein the phase retardation for the transmissive region of the dual-cell-gap LC cell is larger than the phase retardation of the first half wave plate or the second half wave plate, the difference value between the phase retardation for the transmissive region of the liquid crystal layer and the phase retardation of the first half wave plate is smaller than 30 nm, and the difference value between the phase retardation for the transmissive region of the liquid crystal layer and the phase retardation of the second half wave plate is smaller than 30 nm.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An automatic document feeder, comprising:
a document tray on which a document to be read is placed;
an output tray on which the document for which image reading is finished is placed;
a movable ejection flap configured to be movable between a first position where the document for which the image reading is finished is sunk into a position between the output tray and a bottom of a stacked document already staked on the output tray and a second position where the document is ejected on the output tray without being sunk into the position between the output tray and the bottom of the stacked document;
a setting unit configured to set the movable flap to one of the first position and the second position;
a change unit configured to change a position of the movable flap to the second position in response to a fact that a predetermined condition is satisfied in a state where the position of the movable flap has been set to the first position through the setting unit.
2. The automatic document feeder according to claim 1,
further comprising a reversing mechanism configured to reverse a carrying direction of the document which has passed a reading portion to carry again the document to the reading portion,
wherein the setting unit sets the movable flap to one of the first position and the second position in accordance with whether the reversing mechanism is activated.
3. The automatic document feeder according to claim 1,
further comprising an accepting unit configured to accept a user input,
wherein if a user command for changing the position of the movable flap to the second position is accepted through the accepting unit, the change unit judges that the predetermined condition is satisfied, and changes the position of the movable flap to the second position.
4. The automatic document feeder according to claim 1,
further comprising a first judgment unit configured to judge whether total weight of documents placed on the document tray exceeds a predetermined value,
wherein if it is judged by the first judgment unit that the total weight of the documents placed on the document tray exceeds the predetermined value, the change unit judges that the predetermined condition is satisfied, and changes the position of the movable flap to the second position.
5. The automatic document feeder according to claim 1,
further comprising a second judgment unit configured to detect whether a curl is produced on the document being carried,
wherein if it is judged by the second judgment unit that a curl is produced on the document being carried, the change unit judges that the predetermined condition is satisfied, and changes the position of the movable flap to the second position.
6. An image reading device, comprising:
an automatic document feeder; and
a reading portion configured to read a document carried to the reading portion,
the automatic document feeder comprising:
a document tray on which a document to be read is placed;
an output tray on which the document for which image reading is finished is placed;
a movable ejection flap configured to be movable between a first position where the document for which the image reading is finished is sunk into a position between the output tray and a bottom of a stacked document already staked on the output tray and a second position where the document is ejected on the output tray without being sunk into the position between the output tray and the bottom of the stacked document;
a setting unit configured to set the movable flap to one of the first position and the second position;
a change unit configured to change a position of the movable flap to the second position in response to a fact that a predetermined condition is satisfied in a state where the position of the movable flap has been set to the first position through the setting unit.
7. The image reading device according to claim 6,
further comprising a reversing mechanism configured to reverse a carrying direction of the document which has passed the reading portion to carry again the document to the reading portion,
wherein the setting unit sets the movable flap to one of the first position and the second position in accordance with whether the reversing mechanism is activated.
8. The image reading device according to claim 6,
further comprising an accepting unit configured to accept a user input,
wherein if a user command for changing the position of the movable flap to the second position is accepted through the accepting unit, the change unit judges that the predetermined condition is satisfied, and changes the position of the movable flap to the second position.
9. The image reading device according to claim 6,
further comprising a first judgment unit configured to judge whether total weight of documents placed on the document tray exceeds a predetermined value,
wherein if it is judged by the first judgment unit that the total weight of the documents placed on the document tray exceeds the predetermined value, the change unit judges that the predetermined condition is satisfied, and changes the position of the movable flap to the second position.
10. The image reading device according to claim 6,
further comprising a second judgment unit configured to detect whether a curl is produced on the document being carried,
wherein if it is judged by the second judgment unit that a curl is produced on the document being carried, the change unit judges that the predetermined condition is satisfied, and changes the position of the movable flap to the second position.