DE7706895U1 - Partly transparent reflector for liquid crystal displays - Google Patents

Description

10/77

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BBC Aktiengesellschaft Brown, Boveri & Cie,., Baden (Switzerland)

Partly transparent reflector for liquid crystal display ti-rn ffir ·.

The invention relates to a partially transparent reflector for liquid crystal displays with a translucent

between the cell with the liquid crystal and a lighting element.

5 According to the technology used up to now, a translucent Foil used, which has a depolarizing effect; in case of

“When it comes to daylight, the display is often too dark.

The lighting element is either a thin sheet of plexiglass with a micro lamp or a beta light ampoule.

The invention is based on the object of finding a reflector which has the following properties:

1. a good scattering characteristic for incident light for use of the display during the day,

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2. a permeability of about 10 - 30 % for using the display at night with integrated rear lighting,

3. It must not depolarize incident light.

This object is achieved in that the aforementioned translucent foil is designed as a thin aluminum foil, the surface of which has a scattering effect and which contains a number of holes or pores which are designed so that the permeability is optionally 10-30 % .

It should also be noted that from the German Offenlegungsschrift 2,264,702 a partially transparent reflector inside a Plussig crystal cell is known, which is either designed as a semitransparent mirror or as a vapor-deposited metal layer that is provided with holes through an etching process.

The invention will now be explained in more detail with reference to FIGS. Fig. 1 shows the usual arrangement with the translucent sheet 3, which generally depolarizes incident light; the film 3 is between the cell with the liquid crystal 1 and the lighting element 2.

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In Fig. 2, the translucent film 3 is according to the invention educated. 3 is a thin sheet of aluminum whose

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The surface has a scattering effect and contains "dXe \ number of holes or pores (4), which are designed so that the permeability is optionally 10 - 30 % . This aluminum foil can be glued directly to the lower polarizer.

In order to improve the effectiveness of the lighting, the lighting element can also have one on its underside reflective layer 5, e.g. Aluminum.

3 shows a method for the production of the semitransparent reflector proposed according to the invention. A piece of thin aluminum foil about 15 to 20 μm thick is used, which is etched for 2-3 minutes, for example in a mixture of one part H0 and one part 38 to 40 % HF. It is then rinsed with distilled water. The etching effect is not uniform because of the presence of foreign elements in the aluminum or because of other inhomogeneities in the surface layer, so that a large number of small holes are formed in a random distribution. After this chemical treatment, the thickness of the aluminum foil is about 10 µm. The size of the etched holes is 5 to 200 µm, their density is between 10 and 1000 / mm ² . ■ ··; ···:, - ·,, ··, ··. . ··. : ··.

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The permeability achieved is practically determined by the duration of the treatment certainly.

In the detailed embodiment of FIG. 3, one begins with a roll 6 of thin aluminum foil.

The aluminum passes through the bath 15 , in which the chemical treatment takes place. With the help of the guide rollers 7, 8 and 8 ', the film passes a bath 16 which is filled with constantly renewed, distilled water. The aluminum foil must not come into contact with air between bath 15 and bath 16. With the help of the guide roller 9, the aluminum foil leaves the bath, is dried and then runs between the lamp 13 and the photocell 14, where the permeability can be checked and the speed of the foil through the etching bath can be controlled.

With the help of the guide roller 10, the aluminum foil is brought to the polarizer coming from the roller 11, glued to it, and then the laminate is wound onto roll 12.

Instead of a \ einzelnenFolie of aluminum which is etched and then laminated to the polarizer, it is also possible to etch a laminated aluminum foil already with a polarizer sheet according to the method described above (which already provided with adhesive layer polarizer Reflektortosnib.i'na 'bi.p'n, i will not get from the caustic solution

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attacked). This eliminates the critical lamination of the aluminum foil mechanically weakened by the etching process. Also, no creases or gaps can form in the etching process. To increase the wear resistance of the etched polysite this can be protected with a thin, transparent layer of varnish.

The process is relatively cheap; since it is a continuous process, it can be used on an industrial scale.
The reflector produced in this way has a metallic brilliance
on. The transmittance can be selected in a wide range (2 - 30 %). Finally it takes place at the reflector
no depolarization.

Claims (4)

BBC Baden:: ϊ-, J:. ' . ♦. ' 10/77 ^ ••• I ·· »«. ». S.c hat for claims 1. Partially transparent reflector for liquid crystal displays with a translucent film between the cell with the liquid crystal and a lighting element, characterized in that the translucent film I is designed as a thin aluminum foil (3), the upper surface acts scattering and which contains a number of holes or pores (4), which are such that the ^ permeability is optionally 10-30 % . 2. Reflector according to claim 1, characterized in that the aluminum foil (3) directly to the lower polarizer the liquid crystal cell is glued ·. 3. Reflector according to claim 1 or 2, characterized in that the lighting element (2) still on its underside has a reflective layer (5). 4. Reflector according to claim 3, characterized in that the reflective layer (5) consists of vapor-deposited aluminum. BBC Public Company Brown, Boveri & Cie.