WO2005006066A1

WO2005006066A1 - A liquid crystal display (lcd) adapted to control the amount of transmitted light

Info

Publication number: WO2005006066A1
Application number: PCT/SE2004/001128
Authority: WO
Inventors: Kent Skarp; Gustav Franklin; Christian ADÅS
Original assignee: Conoptix Ab
Priority date: 2003-07-14
Filing date: 2004-07-12
Publication date: 2005-01-20
Also published as: SE0302067L; SE526836C2; SE0302067D0

Abstract

The present invention relates to an LCD (1) adapted to control the transmission of light for both the visible wavelength interval and the ultra violet wavelength interval. The LCD comprises a polarizer (2a, 2b) adapted to achieve polarised light, an optical filter (3) adapted to absorb light in the wavelength interval where the contrast ratio is not according to requirements, and a substrate (4a, 4b) and electrodes (5a, 5b) adapted to high light transmission for both visible light and UV-light.

Description

A liquid crystal display (LCD) adapted to control the

_ . amount of transmitted light

Field of invention The present invention relates to a liquid crystal display (LCD) adapted to control the amount of transmitted light. The invention also relates to different kinds of shutters, each comprising an inventive LCD.

Description of the background art It is known to control the amount of transmitted light through different kinds of shutters in various applications. Visible light is the light in the wavelength interval of approximately 400 to 700 nm, while ultra violet light (UV-light) covers a wide wavelength interval normally divided into UVA (315-400 nm), UVB (280-315 nm), UVC (100-280 nm) and extreme UV (1-10 nm). It may in different applications be desirable to control the light from these wavelength intervals separately. In the field of vehicle headlights it is known that under certain weather conditions, such as in heavy fog or rain, visible light is reflected, thus making the sight range unacceptably short. A new type of headlights emits light in both the visible light interval and the UV-light interval, with the purpose of providing UV-light in poor weather conditions. UV-light is transmitted through fog and rain and can be made visible through fluorescing material on road markings, road signs, navigation marks etc., thus providing a longer sight range than with visible light. In the field of non-destructive testing of material defects a fluorescing paint can be applied to the surface of the material, which later can be removed. The paint will remain in the defects, and as the material is irradiated with UV-light the remaining paint will emit visible light, making it possible to easily detect the defects. In production facilities with clean rooms, the amount of particles, bacteria and other contaminations have to be controlled in order to keep a sufficient level of quality in the production. In these environments UV-light may be used to detect such undesired substances. In photolithography applications a mask made out of a glass substrate is used to control the exposure of UV light on a material. The mask will allow exposure in certain areas and prevent exposure of other areas, thus forming a pattern of exposable area. Each mask has to be manufactured separately. It should also be mentioned that known LCDs are designed to modulate visible light, meaning that it is possible to control the transmission or absorption of light in the visible wavelength interval.

Summary of the present invention

Problems It is a problem to control or modulate light from the two mentioned wavelength intervals, visible light and UV-light, separately by means of one shutter. With vehicle headlights it is a problem to modulate or adjust the amount of visible light, where a very small amount of visible light is wanted during poor weather conditions, and a large amount of visible light is wanted during good weather conditions, and at the same time keeping a constant amount of UV-light with one shutter. With the non-destructive testing of material deficiencies it is a problem to adjust or modulate both the amount of visible light and the amount of UV-light with one shutter. With the inspection of contamination in clean rooms it is a problem to modulate or control the transmission of UV-light and always absorb visible light with one shutter. It is a time consuming and complex process to produce a new mask for every pattern in a photolithography application, where in some applications several masks with different patterns are required.

Solution With the purpose of solving one or more of the above identified problems, and from the standpoint of an LCD adapted to control the amount of transmitted light, the present invention teaches that the LCD is adapted to control the transmission of light for both the visible wavelength interval and the ultra violet wave- length interval. Such an LCD comprises a polarizer adapted to achieve polarised light, an optical filter adapted to absorb light in the wavelength interval where the contrast ratio is not according to requirements, and a substrate and electrodes adapted to high light transmission for both visible light and UV-light. With the purpose of providing an LCD adapted to a constant transmission of UV-light and a modulation of visible light, the present invention teaches that the polarizer is adapted to polarisation for visible light and minimal polarisation for UV- light, and that the optical filter is adapted to light absorption for UV-light. With the purpose of providing an LCD adapted to modulation of visible light and UV-light, the present invention teaches that the polarizer is adapted to polarisation for both visible light and for UV-light, and that the optical filter is adapted to light absorption in the wavelength interval where the contrast ratio is too low. With the purpose of providing an LCD adapted to modulation of UV-light and absorption of visible light, the present invention teaches that the polarizer is adapted to polarisation for both visible light and for UV-light, and that the optical filter is adapted to light absorption of visible light. All three above described embodiments may use a polarizer of different kinds and there are different commercially available polarizers that could be used. In the first described embodiment, with a constant transmission of UV-light and a modulation of visible light, it is proposed that a thin film polarizer, such as blue or violet TCF®, is used. It is also possible to use conventional polarizer Pro Flux®. The thin film polarizer black TCF® may also be used, even if this will not provide an optimal result. In the latter two embodiments, with modulation of visible light and UV-light and the modulation of UV-light and absorption of visible light, it is proposed that a thin film polarizer, such as black TCF®, is used. It is also possible to use a conventional polarizer such as Pro Flux® or a UV polarizer. An example of suitable UV polarizer is the HNP'B from 3M. The thin film polarizer blue or violet TCF® may also be used, even if this will not provide an optimal result. The present invention teaches that a substrate with required features could be made out of quartz, High quality Soda Lime glass or Borosilicate glass. With the purpose of providing a flexible LCD the present invention teaches that used electrodes are divided into separately electrically controllable segments. This makes it possible to use an inventive electrode as a mask in a photolithography application, which mask may be dynamically adapted to every required pattern. The present invention proposes that used electrodes comprise active electronic circuits or that used electrodes are adapted to passive electric driving. Polarisation may be realised in various ways. The polarizer may thus be made out of an external polarizer, or, in embodiments with a thin film polarizer, an internal polarizer. An inventive LCD comprises LC-alignment layers. These may be conven- tional separate LC-alignment layers or they may be made out of the thin film polarizers of an internal polarizer. In the latter embodiment, the present invention teaches that a protective layer is positioned between each LC-alignment layer and the LC to prevent the contamination of the LC from the thin film polarizer. The present invention is not restricted to the working phase of the LC, thus the present invention teaches that the LC may be adapted to work in its nematic phase, its smectic phase or its cholesteric phase, which LC-phase can be of the following types; low molecular weight LC, polymer stabilized LC, polymer dispersed LC (PDLC) or polymer LC. The LCD may also be adapted to work in bistable mode. The present invention also relates to a first shutter adapted to modulate the amount of transmitted visible light and to transmit a constant amount of UV- light, which first shutter comprises an inventive LCD with required features. The present invention also relates to a second shutter adapted to modulate the amount of transmitted visible light and the amount of transmitted UV- light, which second shutter comprises an inventive LCD with required features. The present invention also relates to a third shutter adapted to modulate the amount of transmitted UV-light and to absorb visible light, which third shutter comprises an inventive LCD with required features. The present invention also relates to a fourth shutter adapted to modulate the amount of transmitted UV light, which fourth shutter comprises an inventive LCD with required features. The present invention specifically teaches that the fourth shutter is adapted to function as a mask in a photolithography application.

Advantages The advantages of an LCD or a shutter according to the present invention are that such an LCD or shutter will provide the possibilities of controlling light from the two wavelength intervals visible light and UV-light according to the requirements of its practical implementation. Brief description of the drawings. An LCD and shutters according to the present invention will now be described in detail with reference to the accompanying drawings, in which: Figure 1 is a schematic and simplified illustration of an inventive LCD, Figures 2a and 2b are schematic illustrations of an LCD with segmented electrodes and a fourth embodiment of an inventive shutter, Figure 3 is a schematic illustration of an LCD with an internal polarizer, Figure 4 is a schematic illustration of an LCD with an internal polarizer, this internal polarizer also forming LC-alignment layers, and Figure 5 is a schematic illustration of the function of a first embodiment of an inventive shutter.

Description of embodiments as presently preferred The present invention will be described with reference to Figure 1 showing a liquid crystal display (LCD) 1 adapted to control the amount of transmitted light A2. The figure shows a light source A adapted to emit light A1 in both the visible and UV interval. The LCD 1 is characterised by it being adapted to control the transmission of light A2 for both the visible wavelength interval and the ultra violet wavelength interval. It should be understood that the present invention might be used with light sources emitting light in other wavelength intervals, or only the UV wavelength interval, depending on the practical implementation of the invention. An inventive LCD 1 comprises a polarizer 2a, 2b adapted to achieve pola- rised light, an optical filter 3 adapted to absorb light in the wavelength interval where the contrast ratio is not according to requirements, and a substrate 4a, 4b and electrodes 5a, 5b adapted to high light transmission for both visible light and UV-light. It is advantageous, but not required, that the LCD comprises liquid crystal (LC) 6 with a constant optical anisotropy for both visible light and UV-light. The figure also shows conventional LC-alignment layers 7a, 7b. A first proposed embodiment presents an inventive LCD 1 adapted to a constant transmission of UV-light and a modulation of visible light. According to this first embodiment is the polarizer 2a, 2b adapted to polarisation for visible light and minimal polarisation for UV-light, and the optical filter 3 is adapted to light absorption for UV-light. The invention proposes that the optical filter 3 is adapted to light absorp- tion for light in the wavelength range of approximately 380 to 430 nm. A polarizer 2a, 2b used in an LCD 1 according to this first proposed embodiment may be made out of a thin film polarizer, such as a blue or violet TCF®. A black TCF® may also be used even if this will not provide an optimal result. The polarizer 2a, 2b may also be made out of the conventional polarizer Pro Flux®. A second proposed embodiment presents an inventive LCD 1 adapted to modulation of visible light and UV-light. According to this second embodiment is the polarizer 2a, 2b adapted to polarisation for both visible light and for UV-light, and the optical filter 3 is adapted to light absorption in the wavelength interval where the contrast ratio is too low. A third proposed embodiment presents an inventive LCD 1 adapted to modulation of UV-light and absorption of visible light. According to this third embodiment is the polarizer 2a, 2b adapted to polarisation for both visible light and for UV-light, and the optical filter 3 is adapted to light absorption of visible light. A polarizer 2a, 2b used in an LCD according to this second or third embodiment may be made out of a thin film polarizer, such as a black TCF®. A blue or violet TCF® may also be used even if this will not provide an optimal result. The polarizer 2a, 2b may also be made out of the conventional polarizer Pro Flux® or a UV polarizer, such as the HNP'B from 3M. Used substrate 4a, 4b in an inventive LCD 1 may be made out of quartz, High quality Soda Lime glass or Borosilicate glass, regardless of embodiment. The present invention teaches that used electrodes 5a, 5b may be divided into separately electrically controllable segments. Figure 2a shows an embodiment where the electrodes belonging to an inventive LCD 1^* are segmented into separately controllable segments forming a matrix 51 , in this case a very simplified 9x9 matrix. Figure 2b shows schematically that the segmented electrode forming the matrix 51 is activated to form a pattern 81 , in this case the figure 8, of not exposed area on a surface 8. Used electrodes 5a, 5b may, regardless of embodiment, comprise active electronic circuits or they may be adapted to passive electric driving. Figure 1 shows an external polarizer 2a, 2b. Figure 3 shows that in em- bodiments with a thin film polarizer, the polarizer 2c, 2d may be made out of an internal polarizer. Other components belonging to the LCD 1" are given the same reference figures as in figure 1 including the separate LC-alignment layers 7a, 7b. Figure 4 shows that it is also possible to let the thin film polarizer 2c, 2d form the LC-alignment layers 7a, 7b. With the purpose of preventing contamination of the LC 6 from the thin film polarizer 2c, 2d, the present invention teaches that a protective layer 7c, 7d is positioned between each LC-alignment layer 7, 7b and the LC 6. Regardless of embodiment, the LC 6 may be adapted to work in its nematic phase, in its smectic phase, or in its cholesteric phase, where the LC- phase can be of the following types; low molecular weight LC, polymer stabilized LC, polymer dispersed LC (PDLC) or polymer LC. The LCD 1 may also be adapted to work in bistable mode. The present invention also relates to different shutters. Figure 5 shows a first inventive shutter 91 used on the headlights of a vehicle 911. The first shutter 91 is adapted to modulate the amount of transmitted visible light and to transmit a constant amount of UV-light A2. The headlights A of the vehicle emits both visible and UV light. The first shutter 91 comprises an inventive LCD 1. The figure shows a mode where the first shutter 91 is absorbing visible light so that transmitted light A2 is UV light. This transmitted light irradiates a fluorescing road sign 912, which thus reflects A21 visible light. This is done without the disadvantageous reflection of direct visible light in the fog 913. A second inventive shutter is adapted to modulate the amount of transmitted visible light and the amount of transmitted UV-light, which second shutter comprises an inventive LCD, and a third inventive shutter is adapted to modulate the amount of transmitted UV-light and to absorb visible light, which third shutter comprises an inventive LCD, these embodiments not being illustrated in any specific figures. Figure 2b shows a fourth inventive shutter 94 adapted to modulate the amount of transmitted UV light A2, which fourth shutter 94 comprises an inventive LCD 1', where this fourth shutter 94 is adapted to function as a mask in a photolithography application. It will be understood that the invention is not restricted to the aforede- scribed and illustrated exemplifying embodiments thereof and that modifications can be made within the scope of the inventive concept as illustrated in the accompanying Claims.

Claims

1. A liquid crystal display (LCD) adapted to control the amount of transmitted light, characterised in, that said LCD is adapted to control the transmission of light for both the visible wavelength interval and the ultra violet wavelength interval, that said LCD comprises a polarizer adapted to achieve polarised light, and that said LCD comprises a substrate and electrodes adapted to high light transmission for both visible light and UV-light.

2. An LCD according to Claim 1 , characterised in, that said LCD is adapted to a constant transmission of UV-light and a modulation of visible light.

3. An LCD according to Claim 2, characterised in, that said polarizer is adapted to polarisation for visible light and minimal polarisation for UV-light, and that said LCD comprises an optical filter adapted to light absorption for UV-light.

4. An LCD according to Claim 3, characterised in, that said optical filter is adapted to light absorption for light in the wavelength range of approximately 380 to 430 nm.

5. An LCD according to Claim 2, 3 or 4, characterised in, that said polarizer is made out of a thin film polarizer.

6. An LCD according to Claim 5, characterised in, that said thin film polari- zer is a blue or violet TCF®.

7. An LCD according to Claim 5, characterised in, that said thin film polarizer is a black TCF®.

8. An LCD according to Claim 2, 3 or 4, characterised in, that said polarizer is made out of Pro Flux®.

9. An LCD according to Claim 1 , characterised in, that said LCD is adapted to modulation of visible light and UV-light.

10. An LCD according to Claim 9, characterised in, that said polarizer is adapted to polarisation for both visible light and for UV-light, and that said LCD comprises an optical filter adapted to light absorption in the wavelength interval where said contrast ratio is too low.

11. An LCD according to Claim 1 , characterised in, that said LCD is adapted to modulation of UV-light and absorption of visible light.

12. An LCD according to Claim 11 , characterised in, that said polarizer is adapted to polarisation for both visible light and for UV-light, and that said LCD comprises an optical filter adapted to light absorption of visible light.

13. An LCD according to any one of Claims 8 to 12, characterised in, that said polarizer is made out of a thin film polarizer.

14. An LCD according to any one of Claims 13, characterised in, that said thin film polarizer is a black TCF®.

15. An LCD according to Claim 13, characterised in, that said thin film polarizer is a blue or violet TCF®.

16. An LCD according to any one of Claims 8 to 12, characterised in, that said polarizer is made out of Pro Flux®.

17. An LCD according to any one of Claims 8 to 12, characterised in, that said polarizer is a UV polarizer.

18. An LCD according to Claim 17, characterised in, that said UV polarizer is made out of HNP'B from 3M.

19. An LCD according to any preceding Claim, characterised in, that said substrate is made out of quartz.

20. An LCD according to any one of Claims 1 to 18, characterised in, that said substrate is made out of High quality Soda Lime glass.

21. An LCD according to any one of Claims 1 to 18, characterised in, that said substrate is made out of Borosilicate glass.

22. An LCD according to any preceding Claim, characterised in, that said electrodes are divided into separately electrically controllable segments.

23. An LCD according to any preceding Claim, characterised in, that said electrodes comprises active electronic circuits.

24. An LCD according to any one of Claims 1 to 22, characterised in, that said electrodes are adapted to passive electric driving.

25. An LCD according to any preceding Claim, characterised in, that said polarizer is made out of an external polarizer.

26. An LCD according to Claim 5 or 13, characterised in, that said polarizer is made out of an internal polarizer.

27. An LCD according to any preceding Claim, characterised in, that said LCD comprises separate LC-alignment layers.

28. An LCD according to Claim 5 and 26, or Claim 13 and 26, characterised in, that said LCD comprises LC-alignment layers that are made out of said thin film polarizer.

29. An LCD according to Claim 28, characterised in, that a protective layer is positioned between each LC-alignment layer and said LC.

30. An LCD according to any preceding Claim, characterised in, that said LC is adapted to work in its nematic phase.

31. An LCD according to any one of Claims 1 to 29, characterised in, that said LC is adapted to work in its smectic phase.

32. An LCD according to any one of Claims 1 to 29, characterised in, that said LC is adapted to work in its cholesteric phase.

33. An LCD according to any preceding Claim, characterised in, that said LCD is adapted to work in bistable mode.

34. An LCD according to any one of Claims 30 to 32, characterised in, that said LC-phase can be of the following types; low molecular weight LC, polymer stabilized LC, polymer dispersed LC (PDLC) or polymer LC.