Optical device provided with liquid crystal screen
By introducing conductive coating and power connections into the liquid crystal screen, an electric field is formed and heated by the conductive coating, the problem of the liquid crystal screen not working at low temperatures is solved, and normal operation and simple and compact design are achieved in a low temperature environment.
Patent Information
- Application Number
- CN202380039098.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-05-10
- Filing Date
- 2023-05-05
- Publication Date
- 2024-12-17
AI Technical Summary
Existing LCD screens do not work at low temperatures, limiting their application in the automotive industry and need to be simple, compact and easy to manufacture.
An optical device including a liquid crystal layer, a first layer and a second conductive coating is designed. By arranging conductive coatings on both sides of the liquid crystal layer and connecting a power source, an electric field is formed to change the transparency of the liquid crystal layer, and through the second power source The liquid crystal layer is heated through the conductive coating to ensure normal operation at low temperatures.
The LCD screen operation at low temperatures (such as -20°C) is achieved, keeping the device simple, compact and easy to manufacture, while changing the transparency of the environment inside the vehicle as needed.
Smart Images
Figure CN119156565A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to an optical device for a motor vehicle, the optical device comprising a liquid crystal screen, in particular a polymer dispersed liquid crystal (PDLC) screen. The invention also relates to a lighting device for a motor vehicle comprising such an optical device. The invention also relates to a method for using such an optical device. Background Art
[0002] Liquid crystal screens are optical devices in which the transparency varies depending on the electric field passing through them. Liquid crystal screens are used to perform a wide variety of optical functions and are therefore of interest to operators in the automotive industry. For example, cars are known that are equipped with panoramic sunroofs provided with polymer dispersed liquid crystal (PDLC) screens. The transparency level of the panoramic sunroof can be easily controlled, allowing the environment inside the passenger compartment to be changed.
[0003] However, the liquid crystal screens known in the prior art do not work at low temperatures. This constraint limits the use of liquid crystal screens in the automotive industry, since motor vehicles must remain fully functional at low temperatures, in particular at negative temperatures, or even at -20°C, or even at -40°C.
[0004] Furthermore, LCD screens for motor vehicles must remain simple, compact and easy to manufacture.
[0005] Invention Introduction
[0006] The object of the present invention is to provide an optical device for a motor vehicle provided with a liquid crystal screen which overcomes the above-mentioned disadvantages and improves the optical devices known from the prior art.
[0007] More precisely, a first subject of the invention is a simple, compact optical device that is easy to manufacture and capable of operating at low temperatures. Summary of the invention
[0008] The present invention relates to an optical device for a motor vehicle, the optical device comprising a layer containing liquid crystals, a first layer of conductive coating, and a second layer of conductive coating, the first layer and the second layer being two separate layers arranged on both sides of the layer containing liquid crystals, the first layer comprising a first positive terminal and the second layer comprising a first negative terminal, the first positive terminal and the first negative terminal being intended to be connected to a first power source in order to generate an electric field through the layer containing liquid crystals, at least one of the first layer and the second layer comprising a second positive terminal and a second negative terminal, the second positive terminal and the second negative terminal being intended to be connected to a second power source in order to allow a current to flow through this layer between the second positive terminal and the second negative terminal.
[0009] The first positive terminal and the second positive terminal may form a single positive terminal, or the first negative terminal and the second negative terminal may form a single negative terminal.
[0010] The first positive terminal, the second positive terminal, the first negative terminal, and the second negative terminal may be four separate terminals.
[0011] The layer including liquid crystal may be a layer including liquid crystal dispersed in a polymer, and / or the first layer and / or the second layer may be an indium tin oxide layer.
[0012] The optical device may include a first power source electrically connected to the first positive terminal and the first negative terminal, and a second power source electrically connected to the second positive terminal and the second negative terminal.
[0013] The first power source may be an AC power source.
[0014] The second power source may be a DC power source or alternatively an AC power source.
[0015] The second positive terminal and the second negative terminal may be spaced apart from each other by a distance greater than or equal to 50% of a maximum dimension of a layer of the conductive coating including the second positive terminal and the second negative terminal.
[0016] The layer including the second positive terminal and the second negative terminal may include a rectangular shape, the second positive terminal and / or the second negative terminal extending along at least 50% of a short side of the rectangular shape.
[0017] The invention also relates to a lighting device for a motor vehicle, the lighting device comprising a light source and an optical device as defined above, the optical device being arranged to receive light from the light source.
[0018] The invention also relates to a method for controlling an optical device as defined above or a light emitting device as defined above, the control method comprising:
[0019] - detects that the temperature is less than or equal to the threshold, then
[0020] - causing an electric current to flow between the second positive terminal and the second negative terminal to heat a layer of conductive coating including the second positive terminal and the second negative terminal. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] These objects, features and advantages of the invention will be explained in detail in the following description of specific embodiments given by way of non-limiting examples in conjunction with the accompanying drawings, in which:
[0022] [ Figure 1 ] is a cross-sectional schematic diagram of a light-emitting device according to an embodiment of the present invention.
[0023] [ Figure 2 ]yes[ Figure 1 ] is a schematic cross-sectional view of an optical device of a light-emitting device.
[0024] [ Figure 3 ]yes[ Figure 2 ] is a schematic top view of the optical device in.
[0025] [ Figure 4 ] is a cross-sectional schematic diagram of an optical device according to a variant embodiment of the present invention.
[0026] [ Figure 5 ]yes[ Figure 4 ] is a schematic top view of the optical device in. DETAILED DESCRIPTION
[0027] [ Figure 1 ] schematically illustrates a lighting device 1 for a motor vehicle according to an embodiment of the invention. The lighting device 1 can be positioned anywhere on the vehicle, for example at the front or rear of the vehicle. The lighting device 1 can participate in the lighting features of the vehicle. The lighting device 1 comprises a light source 2 according to an embodiment of the invention and an optical device 3. The light source 2 can, for example, comprise one or more light emitting diodes and / or one or more incandescent bulbs. The optical device 3 is arranged to receive light rays R from the light source 2. These light rays R can form a light beam centered on an optical axis X. The light rays R can be emitted in any region of the visible spectrum.
[0028] The optical device 3 comprises a layer 4 containing liquid crystals, a first layer of conductive coating 5 and a second layer of conductive coating 6. The layer 4 containing liquid crystals (hereinafter referred to as the liquid crystal layer 4) is a screen that generally extends in a plane. This plane may be substantially perpendicular to the optical axis X. The first layer 5 and the second layer 6 are two separate layers arranged on both sides of the liquid crystal layer 4. Therefore, the first layer 5 and the second layer 6 extend on two opposite sides of the liquid crystal layer 4, respectively. In particular, the two opposite sides of the liquid crystal layer 4 are completely covered by the first layer 5 and the second layer 6, respectively. The first layer 5 may face the light source 2, and the second layer 6 may be arranged on the side opposite to the light source 2. In a variant, the positioning of the first layer and the second layer may be reversed.
[0029] The liquid crystal layer 4 is capable of changing the trajectory of light passing through the liquid crystal layer according to the electric field applied thereto. In particular, the liquid crystal layer 4 is capable of changing the transparency of the liquid crystal layer according to the electric field applied thereto. The liquid crystal layer 4 may include a crystallized liquid, wherein the elongated molecules present an ordered orientation when the liquid crystal layer is subjected to a given electric field. The ordered orientation of the molecules makes the crystallized liquid transparent. Conversely, when the liquid crystal layer is not subjected to an electric field, the molecules may be oriented according to a nematic, cholesteric or smectic configuration, which makes the crystallized liquid opaque or translucent. These characteristics of the liquid crystal layer 4 can only be obtained from a given temperature, for example when the liquid crystal layer 4 is at a temperature greater than or equal to 0°C. According to a preferred embodiment, the liquid crystal layer 4 is a layer of liquid crystal, optionally in the form of birefringent droplets, dispersed in a polymer matrix, commonly referred to as polymer dispersed liquid crystal (PDLC). The thickness of the liquid crystal layer 4 may typically be between 15 μm and 30 μm.
[0030] The first layer 5 and the second layer 6 are configured to apply an electric field to the liquid crystal layer 4. The first layer 5 and the second layer 6 are capable of conducting electricity, but still have an intrinsic resistance. The first layer 5 and the second layer 6 can be substantially transparent. These layers can optionally include a slight coloring. In particular, the first layer 5 and the second layer 6 can be an indium tin oxide (ITO) layer, commonly referred to as ITO. The thickness of the first layer 5 and / or the second layer 6 can typically be between 30nm and 50nm.
[0031] The first layer 5 and the second layer 6 can each be covered on their free faces with a layer 7, 8 of a transparent and electrically insulating material, in particular a layer of a thermoplastic saturated polyester, in particular a layer of polyethylene terephthalate (commonly known as PET). These layers can be obtained by a thermally induced phase separation process or a polymerization induced phase separation (PIPS) process. The thermoplastic saturated polyester layers 7, 8 can form a protective envelope encapsulating the liquid crystal layer 4, the first layer 5 and the second layer 6. The layers 7 and 8 can also constitute a support on which the first layer 5 and the second layer 6 are respectively deposited. Incidentally, Figure 1 , Figure 2 and Figure 4 The various layers shown in are shown schematically, and their apparent thicknesses may be not to scale.
[0032] The second layer 6 comprises a first positive terminal P1 and the first layer 5 comprises a first negative terminal N1. The first positive terminal P1 and the first negative terminal N1 are connected to a first power source 9 in order to generate an electric field across the liquid crystal layer 4, in particular to orient the molecules constituting the liquid crystal layer. The electric field thus obtained may be oriented substantially parallel to the optical axis X. This electric field is Figure 1 , Figure 2 and Figure 4Indicated by arrow F1. Preferably, the first power source 9 may be an AC power source. When the electric field is established, the peak-to-peak potential difference between the first positive terminal P1 and the first negative terminal N1 may be between 70V and 120V.
[0033] In addition, as Figure 1 ], the second layer 6 includes a second positive terminal P2 and a second negative terminal N2. In this case, the first positive terminal P1 and the second positive terminal P2 form a single positive terminal. The second positive terminal P2 and the second negative terminal N2 are connected to a second power supply 10, which is configured so that a current flows through the second layer 6 between the second positive terminal P2 and the second negative terminal N2. This current Figure 1 , Figure 2 and Figure 4 Indicated by arrow F2. Preferably, the second power supply 10 can be a DC power supply. The potential difference between the second positive terminal P2 and the second negative terminal N2 can be determined according to the size of the liquid crystal layer. When current flows between the second positive terminal P2 and the second negative terminal N2, the potential difference can, for example, reach about ten volts or even more.
[0034] Thus, the positive terminals P1 and P2 and the negative terminals N1 and N2 are three separate electrical terminals electrically connected to the first layer 5 or the second layer 6. These electrical terminals may be obtained, for example, by welding wires or by using an adhesive.
[0035] The dimensions of the first layer 5 and / or the second layer 6 along at least one axis perpendicular to the optical axis X may be strictly greater than the dimensions of the liquid crystal layer 4 along this same axis. This provides portions 11, 12 of the first layer 5 and the second layer 6, respectively, which are offset relative to the liquid crystal layer 4. These portions 11, 12 provide contact surfaces on which the electrical terminals P1, P2, N1, N2 can be arranged. In a variant or in addition, the layers 7 and / or 8 of transparent and electrically insulating material may be locally perforated so as to expose portions 13 of the first layer 5 and / or the second layer 6 where the electrical terminals are arranged.
[0036] By a surprising effect, the current generated by the second power source 10 heats the second layer 6. By heat conduction, the liquid crystal layer 4 can thus reach a temperature sufficient to ensure its correct operation. The second layer 6 thus forms means for heating the liquid crystal layer 4. Advantageously, this heating means is formed by a layer of conductive coating required to generate the electric field through the thickness of the liquid crystal layer 4. It is therefore sufficient to provide only at least one additional electrical terminal and a second power source to form this heating means.
[0037] The first power source 9, the second power source 10 and the temperature sensor 14 are electrically connected to the electronic control unit 15. Incidentally, the first power source 9, the second power source 10 and the electronic control unit 15 may optionally be built into a single housing. The electronic control unit 15 is configured to control the second power source 10 according to the temperature detected by the temperature sensor 14. The method of controlling the optical device 3 may be implemented as follows: First, a temperature less than or equal to a threshold value, such as 0°C, -10°C or even -20°C, is detected using the temperature sensor 14. Then, the electronic control unit 15 commands the second power source 10 to deliver current. This current flows between the second positive terminal P2 and the second negative terminal N2 to heat the second layer 6.
[0038] Advantageously, the second positive terminal P2 and the second negative terminal N2 are positioned substantially at two opposite ends of the second layer 6. The distance between the second positive terminal and the second negative terminal can be greater than or equal to at least 50% of the maximum dimension of the second layer or at least 75% of the maximum dimension of the second layer. Therefore, the generated heat is well distributed over the entire length of the second layer 6.
[0039] like Figure 2 and Figure 3 As shown, a first embodiment of the optical device 3 is shown, and the second layer 6 includes a first positive terminal P1, a second positive terminal P2 and a second negative terminal N2. The first positive terminal P1 and the second positive terminal P2 form a single positive terminal. The first layer 5 includes only the first negative terminal N1. The first layer and the second layer 6 may include a generally rectangular shape. Advantageously, the second positive terminal P2 and the second negative terminal N2 extend along two opposite short sides of the rectangular shape, respectively. This maximizes the distance between the terminals P2 and N2 and optimizes the heating obtained. Preferably, the second positive terminal and / or the second negative terminal extend along at least 50% of the short sides of the rectangular shape, preferably at least 75% of the short sides of the rectangular shape, or even the entire short sides of the rectangular shape, respectively. Increasing the surface area of the second positive terminal P2 and / or the second negative terminal N2 improves the distribution of the electron flux in the second layer 6, thereby producing stronger heating.
[0040] According to a variant embodiment (not shown), the positive terminal will be converted into a negative terminal and the negative terminal will be converted into a positive terminal. This provides an optical device in which the first negative terminal and the second negative terminal form the same electrical terminal. According to another variant embodiment, the second positive terminal and the second negative terminal can be arranged on the first layer 5.
[0041] Figure 4 and Figure 5Another variant embodiment of the optical device 3 is shown. For the description of this embodiment, the reference numerals used in the description of the first embodiment are also used to designate the same objects. In addition, only the differences relative to the first embodiment are described. This second embodiment differs from the first embodiment described in that the first positive terminal P1 is separated from the second positive terminal P2. Therefore, the optical device includes four separate electrical terminals P1, P2, N1 and N2. An advantage of this second embodiment can be that an electric field can be established between the first positive terminal P1 and the first negative terminal N1, while a current flows between the second positive terminal P2 and the second negative terminal N2. This will enable the liquid crystal layer to be heated while generating an electric field intended to make the liquid crystal layer transparent. On the other hand, relative to the first embodiment, this embodiment requires the use of additional electrical terminals. Advantageously, the first positive terminal P1 is not positioned between the second positive terminal P2 and the second negative terminal N2. Therefore, the flow of current between the second positive terminal P2 and the second negative terminal N2 does not interfere with the electric field between the first layer 5 and the second layer 6. As previously mentioned, and according to another variant embodiment (not shown), the positive and negative terminals can be inverted.
[0042] According to yet another variant (not shown), the first layer may comprise a first positive terminal and a first negative terminal, and the second layer may comprise a second positive terminal and a second negative terminal. The first layer may form a first heating device by causing a current to flow between the first positive terminal and the first negative terminal. The second layer may form a second heating device by causing a current to flow between the second positive terminal and the second negative terminal. The electric field through the thickness of the liquid crystal layer 4 may be obtained by means of a power supply connected to the first positive terminal and / or the first negative terminal on the one hand and to the second positive terminal and / or the second negative terminal on the other hand.
[0043] Finally, each of the embodiments presented provides an optical device 3 that can operate at low temperatures, in particular at a temperature less than or equal to -20°C. The heating device built into the optical device is partly based on existing components. Therefore, the optical device 3 remains simple, compact and easy to manufacture. When built into a light-emitting device, the optical device enables the light characteristics of the vehicle to be changed according to different situations, in particular according to the external light level. The optical device 3 described above can also be built into a motor vehicle independently of any light source. The optical device 3 can, for example, be used to make the glazed surface of the vehicle opaque or transparent.
Claims
1. An optical device (3) for a motor vehicle, the optical device comprising a layer (4) containing liquid crystals, a first layer of conductive coating (5), and a second layer of conductive coating (6), the first layer and the second layer being two separate layers arranged on both sides of the layer containing liquid crystals, the first layer comprising a first positive terminal (P1) and the second layer comprising a first negative terminal (N1), the first positive terminal and the first negative terminal being intended to be connected to a first power source (9) in order to generate an electric field through the layer containing liquid crystals, It is characterized in that At least one of the first and second layers comprises a second positive terminal (P2) and a second negative terminal (N2), the second positive terminal and the second negative terminal being intended to be connected to a second power source (10) so that a current flows through the layer between the second positive terminal and the second negative terminal.
2. An optical device (3) as claimed in the preceding claim, It is characterized in that The first positive terminal (P1) and the second positive terminal (P2) form a single positive terminal, or the first negative terminal (N1) and the second negative terminal (N2) form a single negative terminal.
3. The optical device according to claim 1, It is characterized in that The first positive terminal (P1), the second positive terminal (P2), the first negative terminal (N1), and the second negative terminal (N2) are four separate terminals.
4. The optical device (3) as claimed in one of the preceding claims, It is characterized in that The layer (4) containing liquid crystal is a layer containing liquid crystal dispersed in a polymer, and / or the first layer (5) and / or the second layer (6) is an indium tin oxide layer.
5. An optical device according to any one of the preceding claims, It is characterized in that The optical device comprises a first power source (9) and a second power source (10), the first power source being electrically connected to the first positive terminal (P1) and the first negative terminal (N1), the second power source being electrically connected to the second positive terminal (P2) and the second negative terminal (N2).
6. The optical device (3) as claimed in the preceding claim, It is characterized in that The first power source (9) is an AC power source, and / or the second power source (10) is a DC power source.
7. The optical device (3) as claimed in one of the preceding claims, It is characterized in that The second positive terminal (P2) and the second negative terminal (N2) are spaced apart from each other by a distance greater than or equal to 50% of a maximum dimension of a layer of conductive coating including the second positive terminal and the second negative terminal.
8. The optical device (3) as claimed in one of the preceding claims, It is characterized in that The layer comprising the second positive terminal (P2) and the second negative terminal (N2) comprises a rectangular shape, the second positive terminal (P2) and / or the second negative terminal (N2) extending along at least 50% of a short side of the rectangular shape.
9. A lighting device (1) for a motor vehicle, It is characterized in that The lighting device comprises a light source (2) and an optical device (3) as claimed in one of the preceding claims, the optical device being arranged to receive light (R) from the light source.
10. A method for controlling an optical device (3) as claimed in one of claims 1 to 8 or a lighting device (1) as claimed in the preceding claim, It is characterized in that The method comprises: - detects that the temperature is less than or equal to the threshold, then - causing an electric current to flow between the second positive terminal (P2) and the second negative terminal (N2) to heat a layer of conductive coating comprising the second positive terminal and the second negative terminal.