Method for producing a film having luminescent particles

Abstract

A method for producing a film having luminescent particles is described. The method has steps a) mixing a thermoplastic and a luminescent pigment containing a hydroxyalkyl terephthalate of the formulate: R.sub.1—COO—P(OH)x-COO—R.sub.2 and obtaining a thermoplastic mixture; and b) homogenizing the thermoplastic mixture to 150° C. to 200° C. in an extruder, by way of an extrusion nozzle, and obtaining a thermoplastic film.

Claims

1. A method for producing a film having luminescent particles, comprising: a. mixing a thermoplastic and a luminescent pigment containing a hydroxyalkyl terephthalate of the formula R.sub.1—COO—P(OH)x-COO—R.sub.2, thereby obtaining a thermoplastic mixture without a solvent, wherein the thermoplastic mixture contains 0.5 g to 8 g of luminescent pigment per kg of the thermoplastic, wherein R.sub.1, R.sub.2 is an alkyl, aryl, or allyl radical having 1 C to 10 C atoms, P is a phenyl ring, OH is a hydroxyl group bound to the phenyl ring, and x is an integer from 1 to 4, and b. homogenizing the thermoplastic mixture in an extruder at 150° C. to 200° C., and obtaining a thermoplastic film via an extrusion nozzle of the extruder, wherein the extruder is heated in an extruder intake comprising a first 20% of the length of the extruder screw to a temperature of 135° C. to 150° C., wherein the extruder is heated in an extruder middle to temperature of 150° C. to 170° C., wherein the extruder is heated in an extruder discharge comprising a last 20% of the length of the extruder screw to a temperature of 160° C. to 180° C., and wherein the thermoplastic film is conveyed with an extrusion rate of 10 mm/s to 20 mm/s.

2. The method according to claim 1, wherein the luminescent pigment contains diethyl 2,5-dihydroxyterephtalate.

3. The method according to claim 1, wherein the luminescent pigment has an excitation maximum in a range from 380 nm to 420 nm and/or an emission maximum in a range from 430 nm to 500 nm.

4. The method according to claim 1, wherein the luminescent pigment comprises benzopyranes, naphthopyranes, 2H-naphthopyranes, 3H-naphthopyranes, 2H-phenanthropyranes, 3H-phenanthropyranes, photochromic resins, coumarins, xanthines, naphthalinic acid derivatives, oxazoles, stilbenes, styryls, perylenes, lanthanides, preferably Y.sub.2O.sub.3:Eu, YVO.sub.4:Tm, Y.sub.2O.sub.2S:Pr, Gd.sub.2O.sub.2S:Tb, and/or mixtures thereof.

5. The method according to claim 1, wherein the thermoplastic film is conveyed in the extruder via a single extruder screw.

6. The method according to claim 1, wherein the thermoplastic film is conveyed in a thickness of 0.3 mm to 1 mm.

7. The method according to claim 6, wherein the thickness is 0.76 mm.

Description

(1) In the following, the invention is explained in detail with reference to drawings. The drawings are purely schematic representations and are not to scale. They in no way restrict the invention.

(2) They depict:

(3) FIG. 1 a cross-section of the device according to the invention,

(4) FIG. 2 a cross-section of the extruder used in the method according to the invention, and

(5) FIG. 3 a flowchart of the method according to the invention.

(6) FIG. 1 depicts a cross-section of the device according to the invention. The composite glass pane (6) made of inner pane (6b), intermediate layer (thermoplastic film) (5), and outer pane (6a) is illuminated by a light source (9), preferably a diode laser. The luminescent pigments (2) situated in the intermediate layer (5) emit light that is perceived by the viewer (8) as a signal or pictogram.

(7) FIG. 2 depicts a cross-section of the extruder (4) used in the method according to the invention, which comprises the above-described regions extruder intake (4a) comprising a first 20% of the length of the extruder screw, extruder middle (4b), and extruder discharge (4c) comprising a last 20% of the length of the extruder screw. The extruder (4) has, from the extruder intake (4a) comprising a first 20% of the length of the extruder screw to the extruder discharge (4c) comprising a last 20% of the length of the extruder screw, a temperature gradient from 130° C. to 190° C., preferably from 140° C. to 170° C. The extruder screw (11) installed in the extruder housing (7) comprises a screw thread (11a) and a screw shaft (11b). The thermoplastic mixture (3) made of a thermoplastic granulate (1) and a luminescent pigment (2) with a local excitation maximum in the range from 350 nm to 450 nm and a local emission maximum in the range from 400 nm to 800 nm arrives in the extruder (6) via the extruder feeder (10). The thermoplastic mixture (3) melted and homogenized in the extruder (4) is conveyed as a thermoplastic film (5) at a preferred rate of 14 mm/s.

(8) FIG. 3 depicts a flowchart of the method according to the invention. In a first step, the mixing of the thermoplastic granulate (1) with a luminescent pigment (2) takes place. The thermoplastic granulate preferably includes PVB (polyvinyl butyral). The luminescent pigment (2) used has a local excitation maximum in the range from 350 nm to 450 nm and a local emission maximum in the range from 400 nm to 800 nm. The thermoplastic mixture (3) obtained is then filled into an extruder (4). In the next step, the thermoplastic mixture (3) is homogenized in the extruder (4) at 150° C. to 200° C. and, then, a thermoplastic film (5) is obtained. In a subsequent step, the thermoplastic film (5) is cooled. This can take place using air or by quenching with water.

(9) With the method according to the invention, a thermoplastic film (5) is obtained that has, in contrast to known films, no solvent residues since production takes place without solvents.

LIST OF REFERENCE CHARACTERS

(10) (1) thermoplastic/thermoplastic granulate (2) luminescent pigment (3) thermoplastic mixture (4) extruder (4a) extruder intake (4b) extruder middle (4c) extruder discharge (5) thermoplastic film (6) composite glass pane (6a) outer pane (6b) inner pane (7) extruder housing (8) viewer (9) light source (10) extruder feeder (11) extruder screw (11a) screw thread (12a) screw shaft (12) extruder nozzle