Display assembly with contrast inversion including two superposed display devices

• US 6,903,784 B1
• Filed: 02/15/2001
• Issued: 06/07/2005
• Est. Priority Date: 02/22/2000
• Status: Expired due to Fees

• Current Assignee: Asulab SA (The Swatch Group AG)
• Original Assignee: Asulab SA (The Swatch Group AG)
• Inventors: Basturk, Naci
• Primary Examiner(s): Chowdhury, Tarifur R.
• Assistant Examiner(s): QI, ZHI QIANG
• Application Number:
  US09/783,286
• Time in Patent Office: 1,573 Days
• Field of Search: 349/2, 349/73, 349/74, 368/30, 368/242, 368/327
• US Class Current: 349/2
• CPC Class Codes: G02F 1/133533 Colour selective polarisers G02F1/1347 takes precedence
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/13471 in which all the liquid crystal cells or layers remain transparent, e.g. FLC, ECB, DAP, HAN, TN, STN, SBE-LC cells G02F1/13475 takes precedence
• CPC Class Codes: G04G 9/0082 by building-up characters using a combination of indicating elements and by selecting desired characters out of a number of characters or by selecting indicating elements the positions of which represents the time, i.e. combinations of G04G9/02 and G04G9/08

Abstract

A second device (24) is mounted on a first device (22) formed of a liquid crystal (27) display cell (26) at the front of which is arranged a first linear polarizer (40), of a liquid crystal (29) optical valve (28) at the back of which is arranged a second polarizer (44) and means (23) for controlling the valve (28) and the cell (26) from a switched state to a non switched state. When the cell (26) is switched to display a data item, by associating a first light or dark device (22) with a second absorbent or reflective polarizer (44), an inversion of the contrast in said data is obtained by switching the valve (28).

Claims

1. A display assembly with two superposed contrast inversion display devices, the assembly including:

a first display device; and

a second active display device having a double structure, one structure being formed by a first contrast inversion display device provided by a twisted nematic liquid crystal dot matrix display cell or by a digit twisted nematic liquid crystal display cell, the liquid crystals of the one structure being confined in a space delimited by two transparent substrates and having two switching states, and the other structure being formed by a second contrast inversion display device provided by a twisted nematic liquid crystal optical valve, the liquid crystals of the other structure being confined in a space delimited by two transparent substrates and having at least two switching states and control means allowing an appropriate voltage to be selectively applied to the display cell and optionally to all or part of the valve to cause each liquid crystal to switch from one state to another, wherein the second active display includes only two polarisers such that a first absorbent or reflective front polariser is arranged at the front of the display cell and in that a second back polariser, crossed with the front polariser or parallel thereto, is arranged at the back of the valve so that when the display cell is switched to display at least one item of data, the total or partial switching of the valve, from one state to another, inverts the contrast of the data displayed from a light appearance to a dark appearance or vice versa, wherein the first display device has a dark shade and the back polariser is a reflective polariser, and wherein the first contrast inversion display device and the second contrast inversion display device are superposed;

wherein

the back polariser is crossed with the front polariser, the display cell and the optical valve both have positive anisotropy or both have negative anisotropy, and wherein the at least two switching states comprise;

a first switching state wherein the display cell is switched OFF and the optical valve is switched OFF, and the first display device is hidden by a mirror mask;

a second switching state wherein the display cell is switched ON and the optical valve is switched OFF so a portion of the first display device is seen through a transparent window and the display cell shows data in the dark shade on a light background;

a third switching state wherein the display cell is switched OFF and the optical valve is switched ON so that only the first display device is seen; and

a fourth switching state wherein the display cell is switched ON and the optical valve is switched ON so the first display device is seen and the display cell shows data in a light color on a dark background.

2. A display assembly according to claim 1, wherein the switching of the valve from one state to another also allows either the first display only to be made visible, or for the first display to be totally hidden by a mirror mask or by a black mask when the display cell is not switched.

3. A display assembly according to claim 1, wherein the first display device is selected from among an analogue device, a digital device, a combination of an analogue device and a digital device, and a decorative element.

4. A timepiece including a case closed by a crystal and a back cover in which a clockwork movement associated with at least one display device is housed, characterized in that said display device is formed by a display assembly according to claim 1, said first display device essentially displaying time related data and said second display device displaying time related data complementary to the preceding data or non time related data of sensor systems, or alphanumerical processing systems, integrated in the case of the timepiece.

5. A timepiece according to claim 4, wherein said first display device includes a dial above which move an hour hand, a minute hand and a second hand.

6. A timepiece according to claim 4, wherein the second display is combined with the crystal.

7. A display assembly with two superposed contrast inversion display devices, the display assembly including:

a first display device; and

a second active display device having a double structure, one structure being formed by a first contrast inversion display device provided by a twisted nematic liquid crystal dot matrix display cell or by a twisted nematic digit liquid crystal display cell, the liquid crystals of the one structure being confined in a space delimited by two transparent substrates and having two switching states, and the other structure being formed by a second contrast inversion display device provided by a twisted nematic liquid crystal optical valve, the liquid crystals of the other structure being confined in a space delimited by two transparent substrates and having at least two switching states and control means allowing an appropriate voltage to be selectively applied to the display cell and optionally to all or part of the valve to cause each liquid crystal to switch from one state to another, wherein the second active display includes only two polarisers such that a first absorbent or reflective front polariser is arranged at the front of the display cell and in that a second back polariser, crossed with the front polariser or parallel thereto, is arranged at the back of the valve so that when the display cell is switched to display at least one item of data, the total or partial switching of the valve, from one state to another, inverts the contrast of the data displayed from a light appearance to a dark appearance or vice versa, wherein the first display device has a light shade and the back polariser is an absorbent polariser, and wherein the first contrast inversion display device and the second contrast inversion display device are superposed;

wherein

the back polariser is crossed with the front polariser, the display cell and the optical valve both have positive anisotropy or both have negative anisotropy, and wherein the at least two switching states comprise;

a first switching state wherein the display cell is switched OFF and the optical valve is switched OFF, and the first display device is hidden by a black mask;

a second switching state wherein the display cell is switched ON and the optical valve is switched OFF so a portion of the first display device is seen through a transparent window and the display cell shows data in the light shade on a dark background;

a third switching state wherein the display cell is switched OFF and the optical valve is switched ON so that only the first display device is seen; and

a fourth switching state wherein the display cell is switched ON and the optical valve is switched ON so the first display device is seen and the display cell shows data in a dark color on a light background.

8. A display assembly according to claim 7, wherein the switching of the valve from one state to another also allows either the first display only to be made visible, or for the first display to be totally hidden by a mirror mask or by a black mask when the display cell is not switched.

9. A display assembly according to claim 7, wherein the first display device is selected from among an analogue device, a digital device, a combination of an analogue device and a digital device, and a decorative element.

10. A display assembly with two superposed contrast inversion display devices, the assembly including:

a first display device; and

a second active display device having a double structure, one structure being formed by a first contrast inversion display device provided by a twisted nematic liquid crystal dot matrix display cell or by a digit twisted nematic liquid crystal display cell, the liquid crystals of the one structure being confined in a space delimited by two transparent substrates and having two switching states, and the other structure being formed by a second contrast inversion display device provided by a twisted nematic liquid crystal optical valve, the liquid crystals of the other structure being confined in a space delimited by two transparent substrates and having at least two switching states and control means allowing an appropriate voltage to be selectively applied to the display cell and optionally to all or part of the valve to cause each liquid crystal to switch from one state to another, wherein the second active display includes only two polarisers such that a first absorbent or reflective front polariser is arranged at the front of the display cell and in that a second back polariser, crossed with the front polariser or parallel thereto, is arranged at the back of the valve so that when the display cell is switched to display at least one item of data, the total or partial switching of the valve, from one state to another, inverts the contrast of the data displayed from a light appearance to a dark appearance or vice versa, wherein the first display device has a dark shade and the back polariser is a reflective polariser, and wherein the first contrast inversion display device and the second contrast inversion display device are superposed;

wherein

the back polariser is parallel to the front polariser, the display cell and the optical valve both have positive anisotropy or both have negative anisotropy, and wherein the at least two switching states comprise;

a first switching state wherein the display cell is switched OFF and the optical valve is switched OFF so that only the first display device is seen;

a second switching state wherein the display cell is switched ON and the optical valve is switched OFF so the first display device is seen and the display cell shows data in a light color on a dark background;

a third switching state wherein the display cell is switched OFF and the optical valve is switched ON, and the first display device is hidden by a mirror mask; and

a fourth switching state wherein the display cell is switched ON and the optical valve is switched ON so a portion of the first display device is seen through a transparent window and the display cell shows data in the dark shade on a light background.

11. A display assembly with two superposed contrast inversion display devices, the display assembly including:

a first display device; and

a second active display device having a double structure, one structure being formed by a first contrast inversion display device provided by a twisted nematic liquid crystal dot matrix display cell or by a twisted nematic digit liquid crystal display cell, the liquid crystals of the one structure being confined in a space delimited by two transparent substrates and having two switching states, and the other structure being formed by a second contrast inversion display device provided by a twisted nematic liquid crystal optical valve, the liquid crystals of the other structure being confined in a space delimited by two transparent substrates and having at least two switching states and control means allowing an appropriate voltage to be selectively applied to the display cell and optionally to all or part of the valve to cause each liquid crystal to switch from one state to another, wherein the second active display includes only two polarisers such that a first absorbent or reflective front polariser is arranged at the front of the display cell and in that a second back polariser, crossed with the front polariser or parallel thereto, is arranged at the back of the valve so that when the display cell is switched to display at least one item of data, the total or partial switching of the valve, from one state to another, inverts the contrast of the data displayed from a light appearance to a dark appearance or vice versa, wherein the first display device has a light shade and the back polariser is an absorbent polariser, and wherein the first contrast inversion display device and the second contrast inversion display device are superposed;

wherein

the back polariser is parallel to the front polariser, the display cell and the optical valve both have positive anisotropy or both have negative anisotropy, and wherein the at least two switching states comprise;

a first switching state wherein the display cell is switched OFF and the optical valve is switched OFF so that only the first display device is seen;

a second switching state wherein the display cell is switched ON and the optical valve is switched OFF so the first display device is seen and the display cell shows data in a dark color on a light background;

a third switching state wherein the display cell is switched OFF and the optical valve is switched ON, and the first display device is hidden by a black mask; and

a fourth switching state wherein the display cell is switched ON and the optical valve is switched ON so a portion of the first display device is seen through a transparent window and the display cell shows data in the light shade on a dark background.

12. A display assembly with two superposed contrast inversion display devices, the assembly including:

a first display device; and

a second active display device having a double structure, one structure being formed by a first contrast inversion display device provided by a twisted nematic liquid crystal dot matrix display cell or by a digit twisted nematic liquid crystal display cell, the liquid crystals of the one structure being confined in a space delimited by two transparent substrates and having two switching states, and the other structure being formed by a second contrast inversion display device provided by a twisted nematic liquid crystal optical valve, the liquid crystals of the other structure being confined in a space delimited by two transparent substrates and having at least two switching states and control means allowing an appropriate voltage to be selectively applied to the display cell and optionally to all or part of the valve to cause each liquid crystal to switch from one state to another, wherein the second active display includes only two polarisers such that a first absorbent or reflective front polariser is arranged at the front of the display cell and in that a second back polariser, crossed with the front polariser or parallel thereto, is arranged at the back of the valve so that when the display cell is switched to display at least one item of data, the total or partial switching of the valve, from one state to another, inverts the contrast of the data displayed from a light appearance to a dark appearance or vice versa, wherein the first display device has a dark shade and the back polariser is a reflective polariser, and wherein the first contrast inversion display device and the second contrast inversion display device are superposed;

wherein

the back polariser is crossed with the front polariser, the display cell has negative anisotropy and the optical valve has positive anisotropy, and wherein the at least two switching states comprise;

a first switching state wherein the display cell is switched OFF and the optical valve is switched OFF so that only the first display device is seen;

a second switching state wherein the display cell is switched ON and the optical valve is switched OFF so the first display device is seen and the display cell shows data in a light color on a dark background;

a third switching state wherein the display cell is switched OFF and the optical valve is switched ON, and the first display device is hidden by a mirror mask; and

a fourth switching state wherein the display cell is switched ON and the optical valve is switched ON so a portion of the first display device is seen through a transparent window and the display cell shows data in the dark shade on a light background.