CH714306B1 - Liquid crystal display. - Google Patents

Abstract

The invention relates to a transflective liquid crystal screen which comprises a set of superimposed layers, namely a first outer layer (1) comprising a polarizing filter, a second layer (2) comprising electrodes, a third layer (3) comprising crystals liquids, a fourth layer (4) comprising electrodes, a fifth layer (5) comprising a polarizing filter, and a sixth layer (6) in the form of a backlight display including an electroluminescent panel element. The screen comprises a seventh additional transparent layer (7), arranged between the fifth layer (5) and the sixth layer (6), this seventh additional transparent layer (7) comprising a phosphorescent material. The invention also relates to an electronic device and a timepiece comprising such a screen.

Description

The present invention relates to a liquid crystal screen, in particular monochrome LCD screens.

Liquid crystal displays called LCD (Liquid Crystal Display) are used for countless applications today. From mobile phones to televisions to scientific industrial controllers. Historically, these screens have been and still are today implanted in watches in various endings. The LCD screen allows a very precise reading of the time, and offers the possibility of expressing various pre-programmed functions in the CPU.

[0003] An LCD screen operates by the principle of superimposing several filters. This operating principle captures the ambient light and the crossing of the polarizing filters associated with the sending of current in the electrodes allows the display of information by an optical effect.

The limits of this system are precisely the capture of ambient light. Indeed, beyond a certain brightness, the system continues to operate according to the same principle, however, the eye is no longer able to discern the resolution of the screen. An impression of non-operation then appears and the screen must be illuminated by an external source to restore correct operation.

[0005] To overcome this effect, a backlighting system has been developed. This system, by the electrical ignition of a generally LED bulb, therefore allows the reading of information when the ambient light is insufficient.

[0006] The major drawback of this principle is twofold:

[0007] Firstly, with regard to devices operating on the battery principle (rechargeable or replaceable), the consumption is considerably increased and therefore the autonomy is significantly reduced.

[0008] Secondly, the user is obliged to activate the switching on of the light by generally pressing a button that is not necessarily easily accessible in the dark.

The object of the present invention is to provide a transflective liquid crystal screen comprising a set of superimposed layers, i.e. a first outer layer comprising a polarizing filter, a second layer comprising electrodes, a third layer comprising liquid crystals, a fourth layer comprising electrodes, a fifth layer comprising a polarizing filter, and a sixth layer in the form of a backlight display including an electroluminescent panel element. The screen comprises a seventh additional transparent layer, arranged between the fifth and the sixth layer, this seventh additional transparent layer comprising a phosphorescent material. The invention also relates to an electronic device or a timepiece comprising such a screen.

In one embodiment, the other additional transparent layer comprises a phosphorescent phosphor pigment emitting light in the visible spectrum.

[0011] Preferably, the other transparent layer comprises a phosphorescent material storing light, to then restore it in low light conditions.

In one embodiment, the phosphor material comprises a compound expressed by Mal2O4 as a matrix, in which M consists of strontium (Sr) and barium (Ba), europium (Eu) doped in said matrix as an activator and dysprosium (Dy) doped in said matrix as a coactivator.

In another embodiment, the phosphorescent material comprises a compound expressed by Mal2O4 as a matrix, in which M consists of strontium (Sr) and calcium (Ca), europium (Eu) doped in said matrix as an activator and dysprosium (Dy) doped in said matrix as a coactivator.

[0014] In yet another embodiment, the phosphorescent material comprises a compound expressed by Mal2O4 as a matrix, in which M consists of strontium (Sr) and barium (Ba) and calcium (Ca), europium (Eu) doped in said matrix as activator and dysprosium (Dy) doped in said matrix as coactivator.

[0015] In one embodiment, the phosphorescent material of the additional transparent layer stores the light produced by the sixth layer in the form of a backlight screen.

[0016] Preferably, the transparent additional layer transmits at least 80% of the light emitted by the sixth layer in the form of a backlight screen, in particular by its transparency on the one hand and by its reactivation of somewhere else.

The screen according to the present invention can be arranged in various electronic devices comprising a transflective screen.

[0018] In particular, a timepiece may include a screen according to one of the preceding claims.

The characteristics of the invention will appear more clearly on reading the description of several embodiments given solely by way of example, in no way limiting with reference to the schematic figures, in which: FIG. 1 represents an exploded view of a transflective screen comprising an additional phosphorescent layer; and FIG. 2 represents a comparison of two watches, one comprising a conventional transflective screen and the other comprising a transflective screen according to the present invention.

As illustrated in Figure 1, a transflective liquid crystal screen according to the present invention comprises a set of superimposed layers, namely: A first outer layer 1 comprising a polarizing filter, A second layer 2 comprising electrodes, A third layer 3 comprising liquid crystals, A fourth layer 4 comprising electrodes, A fifth layer 5 comprising a polarizing filter, and A sixth layer 6 in the form of a backlight screen including an electroluminescent panel element.

The screen further comprises another additional transparent layer 7, arranged between the fifth layer 5 and the sixth layer 6, this additional transparent layer 7 comprising a phosphorescent material.

In the comparison illustrated in Figure 2, a first watch 8, the left has a transflective screen according to the present invention while the second watch 9, the right has a conventional transflective screen.

More specifically, the screen of the first watch 8 comprises on its additional transparent layer 7 of Super-Luminova®, a luminescent substance which makes it possible to read the time in the dark. Super-Luminova® stores light, then releases it in low light conditions, as shown.

[0024] In particular, in this example, the color of the Super-Luminova® used is green and its reference is G1X.

[0025] Thanks to the present invention, the Super-Luminova® pigments recover ambient light and retransmit it in the dark as they do for analog watches, thus considerably reducing the need to switch on the LED bulb diffusing the light in front of the reflector.

The Super-Luminova® stores the light produced by the sixth layer (6) in the form of a backlight screen. According to the present invention, the backlight screen operates in a conventional manner.

Thus, the backlight screen is used between 30 and 35% less compared to a conventional transflective liquid crystal screen. In addition, the capacity of an accumulator is saved by at least 20%.

Another advantage of the present invention is that in the dark, the brightness of the screen, without using the backlight, is improved by at least 15%.

Claims (8)

1. Transflective liquid crystal screen comprising a set of superimposed layers, namely: – A first outer layer (1) comprising a polarizing filter, – A second layer (2) comprising electrodes, – A third layer (3) comprising liquid crystals, – A fourth layer (4) comprising electrodes, – A fifth layer (5) comprising a polarizing filter, and – A sixth layer (6) in the form of a backlit screen including an electroluminescent panel element, Characterized in that it comprises a seventh additional transparent layer (7), arranged between the fifth layer (5) and the sixth layer (6), this seventh additional transparent layer (7) comprising a phosphorescent material. 2. Screen according to claim 1, in which the seventh additional transparent layer (7) comprises a phosphorescent phosphor pigment emitting light in the visible spectrum. 3. Screen according to one of claims 1 or 2, in which the phosphorescent material of the seventh additional transparent layer (7) is arranged to store the light, to then restore it in low light conditions, in particular in the dark. . 4. Screen according to one of the preceding claims wherein the phosphorescent material of the seventh additional transparent layer (7) is arranged to store the light produced by the sixth layer (6). 5. Screen according to one of the preceding claims, wherein the seventh transparent additional layer (7) transmits at least 80% of the light emitted by the sixth layer (6). 6. Screen according to one of the preceding claims, in which the phosphorescent material comprises a compound expressed by Mal2O4 as matrix, in which M consists of strontium Sr and barium Ba and/or calcium Ca, europium Eu doped in said matrix as an activator and dysprosium Dy doped in said matrix as a coactivator. 7. Electronic device comprising a screen according to one of the preceding claims. 8. Timepiece comprising a screen according to claims 1 to 6.