KR100445215B1 - Optical diffuser plates - Google Patents

Abstract

The present invention relates to a light guide plate made of a transparent plastic such as polycarbonate or polymethacrylate. A number of thin strips of plastic B are inserted into a plate made of plastic A, where plastics A and B are not combined and strips made of plastic B are later removed. Cavities formed in plates made of plastic A are used to deflect light.

Description

Optical diffuser plates

One of the top priorities in the field of technical science is energy conservation or resource conservation, and related research aims to save underground resources and reduce electrical energy consumption.

The present invention relates to a transparent plastic light guide plate used for better room lighting by daylight.

1 shows a typical interior space.

Figure 2 is a view showing the installation of a light guide plate according to the invention in a portion of the window in the space shown in Figure

3 shows a plurality of thin strips of plastic B inserted in a plate made of plastic A;

4 shows that light is directed according to each situation.

The problem when illuminating a space deeply laid in daylight is that the rear part far from the window cannot be adequately illuminated, especially in the case of daylight steep slopes (see Figure 1). This situation means that the subspace of the room should always be illuminated by artificial lighting, even during the day, which is undesirable in terms of energy saving and ergonomics. FIG. 1 shows a typical internal space and the reference numerals of FIG. 1 mean the following.

S = incident daylight H = relatively bright area

F = window D = relatively dark area

T = statement

The object of the present invention is to find a solution and use a so-called photoguide plate to solve the problem. This light guide plate collects daylight-through a portion of the glass pane-and directs it to the dark side of the space or to the ceiling (FIG. 2). That is, the light guide plate deflects the daylight incident on the steep slope from the outside deeply in the room. FIG. 2 is a view showing that the light guide plate according to the present invention is installed in one window in the space shown in FIG. 1. Reference numeral LLP denotes a light guide plate. The remaining numerals correspond to those in FIG. 1. In order to achieve the desired deflection, the light guide plate LLP has the following configuration (Fig. 3). A thin strip of transparent plastic B having a refractive index n _B is inserted into a generally flat plate of transparent plastic A having a refractive index n _A , Preferably, the plastic A is not compounded with plastic B and plastic A is separated from plastic B. The separation is better done if there is an apparent yield point in plastic B. With plastic B, for example, the plastics described below are contemplated.

Fluoropolymers, for example thermoplastic fluoropolymers such as THV 500G from 3M

Polypropylene type, for example Luporene form of BASF AG

Polyethylene type,

Polyamide type, for example Vestamid type from Wheels AG

Two kinds of unique properties can lead to the induction of light. The separation surface of this material or the transition portion of the material can only be observed due to the difference in refractive index or in the case where a separation gap is formed, the difference can be seen very clearly as a reflective surface. Extruded plastic B strips can be separated from the plastic A plate and easily withdrawn from the plate during or after cooling. This can be done manually or via a winding device. The strips of plastic B are arranged perpendicular to the surface of the plate or at an angle γ <90 ^o with respect to the surface of the plate. Light rays hit the photoguide plate LLP in the manner described above. On the other hand, the law of total reflection is applied at the boundary layer between plastic A and the air gap, and the boundary angle α _G depends only on the refractive index of both plastics.

The following law applies when plastic B is separated from plastic A, thereby creating a gap between the strips and the matrix surrounding the strip.

Total reflection occurs when the angle α _E at which the light beam strikes the interface is smaller than the boundary angle α _G (I in FIG. 4). Light rays incident at steep slopes are deflected in a plane or upwards. Replacing the plastic strips of plastic B described in DE 195 43 687 with air gives the maximum difference in refractive index. When the angle α _E is larger than the angle α _G (case II in FIG. 4), the incident light beams pass through the boundary surface. Since the preferred method of manufacturing the photoguide plate LLP is to co-extrude the plates together with the inserted thin strips, a transparent thermoplastic resin which is not compatible with the plastic A of the plates and which is co-extruded is provided. The larger the difference in the refractive indices, the higher the boundary angle α _G and thus the efficiency of the system. If the plastic strips are arranged at an angle (γ <90 ^° ), sufficient system efficiency is obtained even when the limit angle α _G is small. The angle of incidence to the interface α _E decreases due to the inclined position of the strip (case II in FIG. 4). As plastic A, for example, polymethylmethacrylate (copolymer with PMMA) or polycarbonate (PC), and As the plastic B, the polymers already mentioned above are used. In tests for the production of photoinductive plates as described above, the light inducing effect was exhibited by additional properties. If the plastic B is not compatible with the plastic A, that is, a thin strip of plastic B is separated from the plastic A by the thin gap without bonding with the matrix, i.e., the plastic A, the induction efficiency of light increases. The separation of the matrix polymer A from the plastic strip of plastic B is optically easy to recognize: the plastic strip appears to have a single reflective surface, which means that a thin gap causes a pronounced total reflection along the surface of the strip. It is an indication. The difference in refractive index between air and matrix plastic A is significantly larger than the difference in refractive index between plastic B and matrix plastic A according to the above formula, which means higher total reflection. So far, whether the gap will be initially filled with air, or somewhat aired out, Was not determined. Then assume that the gap is filled with air by the diffusion of air through plastic A over time after plastic B has been separated from plastic A. The separation of plastics A and B is facilitated by different coefficients of thermal expansion. This is well done when cooling the extrudate. In this case, the strip must shrink faster than the matrix. In other words, plastic B should have a higher coefficient of thermal expansion than plastic A. The difference according to the present invention is also obtained by the difference of the minute coefficient of thermal expansion, i.e. by the minute coefficient of thermal expansion of not less than 0.001%. It does not matter whether or not there is a difference. The refractive index of plastic A is advantageously higher than the refractive index of plastic B, but may be the same or smaller. Total reflection resulting from the formation of splitting points is always sufficient to produce a strong light induction effect. The width of the separation gap should be greater than 1 μm.

The thickness of the light guide plate LLP is generally in the range of 2 to 20 mm. Inserted, preferably extruded strips made of plastic B generally have a thickness of 0.05 to 0.5 mm and a width of 50 to 95% of the thickness of the plate made of plastic A. In general, strips made of plastic B are arranged on plastic sheet A with a regular interval of 2 to 40 mm. The remaining dimensions of the light guide plate LLP are adjusted according to the mounting glass window, in particular the shape of the glass window or door frame. There is generally no dimensional limitation by the extrusion technique applied. The production technique using extrusion in an extrusion machine with a multi-material nozzle corresponds to the prior art (DE-A 4 326 232). The light guide plate LLP according to the invention is shown in FIG. It is explained according to 3. Reference numerals have the following meanings.

(1) = light guide plate LLP of plastic A

(2) = inserted thin strips of plastic B

(3) = spacing between cavities made through plastic drawing

(4) = cavity

In order to fix the light guide plate according to the present invention, a plate fixing frame made of a known organic glass can be used.

The light guide plate according to the invention can be installed for improved lighting in spaces, in particular in factories, auditoriums, basements, domed ceilings, vertical shafts, optionally cars or ships, and the like. Its use not only saves energy but also contributes to better ergonomic design of the workplace.

Claims (13)

Into a sheet of transparent plastic A with a refractive index n _A , a number of thin strips of plastic B with a refractive index n _B are inserted, where plastic A and plastic B are not compatible with each other and the plastic B strips are separated from the plate. Transparent plastic light guide plate, characterized in that. The light guide plate of claim 1 wherein the strips of plastic B are arranged perpendicular to the plate surface. The light guide plate of claim 1 wherein the strips of plastic B are arranged at an angle γ <90 ^° with respect to the plate surface. The light guide plate according to claim 1, wherein the plastics A and B are made of a thermoplastic material. The light guide plate according to claim 1, wherein the light guide plate is manufactured by a coextrusion method. The light guide plate of claim 1 wherein the light guide plate has a thickness in the range of 2 to 30 mm. The light guide plate of claim 1 wherein the strip-shaped cavity has a thickness of 0.05 to 0.5 mm. The light guide plate according to any one of claims 1 to 7, wherein the size of the light guide plate is adjusted according to the existing glass window shape. A glass window comprising the light guide plate according to any one of claims 1 to 7. 8. A method according to any one of claims 1 to 7, wherein the thin strips made of plastic B are separated from the matrix of plastic A after coextrusion of the light guide plate. The light guide plate according to any one of claims 1 to 7, wherein the plastic A is polymethacrylate or polycarbonate. The light guide plate according to any one of claims 1 to 7, wherein the plastic B is a plastic which is incompatible with polycarbonate or polymethacrylate. The light guide plate according to any one of claims 1 to 7, wherein the plastic B is a thermoplastic fluoropolymer, polypropylene, polyethylene, or polyamide.