METHOD FOR MANUFACTURING A MULTILAYER PLASTIC LENS

Abstract

To form a multilayer plastic lens, a plurality of intermediate layers of a plastic material are injected one after another onto a basic part in an injection molding device in different cavities, wherein at least some of the cavities have a common first runner system with a common material feed. At least its [sic—“one”—“seine” is an obvious typo for “eine” meaning “one”—Tr.Ed.] outer layer consisting of a plastic material is then injected in a cavity by means of a second runner system, the second runner system having a material feed of its own and a control of its own.

Claims

1. A method for manufacturing a multilayer plastic lens, the method comprising the steps of: injecting a plurality of intermediate layers of a plastic material onto a basic part in an injection molding device in different cavities; providing at least some of the different cavities with a common first runner system with a common material feed subsequently injecting at least one outer layer with a plastic material, in another cavity with a second runner system; providing an injection channel, through which the plastic material is injected into the respective cavity, with each respective cavity; providing the second runner system with a material feed that is different from the common material feed; providing the second runner system with a control that is different from one or more control of the first runner system; and controlling pressures and the temperatures of the plastic material independently from one another in at least some of the injection channels.

2. A method in accordance with claim 1, wherein the control of the second runner system has a temperature control device or a pressure control device or both a temperature control device and a pressure control device.

3. A method in accordance with claim 1, wherein only the outer layer of the plastic lens is injected by means of the second runner system.

4. A method in accordance with claim 1, wherein the outer layer and at least one intermediate layer of the plastic lens, which at least one intermediate layer is located under the outer layer, are injected by means of the second runner system.

5. A method in accordance with claim 1, wherein the basic part is manufactured in a first step in the injection molding device in another cavity.

6. A method in accordance with claim 5, wherein the other cavity forming the basic part is a part of the first runner system.

7. A method in accordance with claim 1, wherein the basic part and the intermediate layers consist of the same plastic material.

8. A method in accordance with claim 1, wherein the outer layer consists of the same plastic material as the intermediate layers.

9. A method in accordance with claim 1, wherein at least some of the intermediate layers or the outer layer are injected in the form of two partial layers on opposite sides of the basic part or of a blank comprising the basic part and at least one intermediate layer.

10. (canceled)

11. A method in accordance with claim 1, wherein the masses of the plastic material inserted into the individual cavities of the first runner system differ from one another by a maximum of ±10%.

12. A method in accordance with claim 11, wherein the masses of the plastic material inserted into the individual cavities differ one another by a maximum of ±5%.

13. A method in accordance with claim 12, wherein the masses of the plastic material inserted into the individual cavities differ from one another by a maximum of ±1%.

14. A method in accordance with claim 1, wherein the pressures are controlled independently from one another in all injection channels.

15. A method in accordance with claim 1, wherein the individual intermediate layers of the plastic lens are formed with different layer thicknesses, wherein the layer thickness of an (n+1)th layer formed is smaller than a layer thickness of an nth layer formed previously.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In the drawings:

[0023] FIG. 1 is a schematic cross sectional view through a plastic lens composed layer by layer according to a first exemplary embodiment;

[0024] FIG. 2 is a schematic cross sectional view through a plastic lens composed layer by layer according to a second exemplary embodiment;

[0025] FIG. 3 is a schematic view of an injection molding device for manufacturing a multilayer plastic lens according to the method according to the present invention; and

[0026] FIG. 4 is a variant of the injection molding device according to FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Referring to the drawings, FIG. 1 shows a cross section through a multilayer plastic lens 10 according to a first exemplary embodiment. The plastic lens 10 has a carrier-like basic part 11, on which a plurality of layers arranged one on top of another are applied. A first intermediate layer 12 is injected on one side onto the basic part 11. A second intermediate layer 13, which is covered by a third intermediate layer, is applied to the first intermediate layer 12. A fourth intermediate layer is, in turn, applied to this third intermediate layer. An outer layer 14, which covers all intermediate layers 12, 13, etc. and which passes smoothly over into the basic part 11, is finally applied. All layers consist of the same plastic material, so that a monolithic body consisting of a uniform material, which body was composed layer by layer, is formed.

[0028] According to FIG. 1, all layers are applied to the basic part 11 on one side only, so that the plastic lens 10 is defined in its finished state by the basic part 11, on the one hand, and by the outer layer 14, on the other hand. FIG. 2 shows a modified exemplary embodiment, in which the layers are applied to the basic part 11 on both sides. As in the first exemplary embodiment, a carrier-like basic part 11, which is provided with the plastic material of the first intermediate layer 12 on both sides in a first step, is provided in the exemplary embodiment of the plastic lens 10, which exemplary embodiment is shown in FIG. 2. These partial layers of the first intermediate layer 12, which are arranged on opposite sides of the basic part 11, are covered with respective corresponding partial layers of the second intermediate layer 13. The partial layers of the third intermediate layer and of the intermediate layer are subsequently applied on both sides. The outer layer 14 is finally injected onto both sides of the blank formed from the basic part 11 and the intermediate layers, so that the plastic lens 10 is provided on both sides of the basic part 11 by a layer comprising four intermediate layers 12, 13, etc. and an outer layer 14 covering it on the outside.

[0029] FIG. 3 shows a schematic view of an injection molding device 20, with which a plastic lens 10 according to FIG. 1 and FIG. 2 can be manufactured according to the method according to the present invention. The injection molding device 20 comprises a mold part 21, in which a plurality of cavities, namely, a first cavity 22, a second cavity 23, a third cavity 24, a fourth cavity 24 and a fifth cavity 26, are formed. The cavities are arranged in a row next to one another in the exemplary embodiment shown, but it is also possible and even preferred to arrange the cavities distributed over the circumference of a rotatable mold part.

[0030] To manufacture plastic lenses, the cavities are closed by means of an additional mold part, not shown, in the usual manner, and the same plastic material is inserted simultaneously in a so-called shot into all cavities 22, 23, 24, 25, 26. The injection molding device 20 comprises a first runner system 33 and a second runner system 34, which is fully independent therefrom, the runner systems preferably being so-called hot runner systems. The first runner system 33 comprises the cavities 22, 23, 24, 25 and 26 of the mold part 21.

[0031] The plastic material is located in a plastic supply 29, which is also suggested, and from which a common feed channel 35 leads to the cavities 22, 23, 24, 25, 26. A separate injection channel 36 branches off to each cavity from the feed channel 35. A pressure control device 32 in the form of an adjustable throttle point is arranged in each injection channel 36. In addition, a temperature control device 31, with which the temperature of the plastic material in the respective injection channel 36 can be controlled, is arranged in each injection channel 36.

[0032] The injection molding device 20 further comprises the second runner system 34, which has a sixth cavity 27, which is formed in a mold part 28 and into which the plastic material can be inserted from a plastic supply 30 via an injection channel 36. A temperature control device 31 and a pressure control device 32 are likewise arranged in the injection channel 36.

[0033] The first runner system 33 and the second runner system 34 may be configured in a common injection mold, but it is also possible to provide a separate injection mold for each runner system, but it is essential that the runner systems 33 and 34 be able to be actuated and operated independently from one another.

[0034] The method according to the present invention for manufacturing a plastic lens will be explained below in detail on the basis of FIG. 3.

[0035] The plastic material is injected during a starting phase of the manufacturing process into the first cavity 22 of the first runner system 23 only, while the other cavities are still closed. The carrier-like basic part 11 is formed in the first cavity 22. The mold is then opened and the mold parts are adjusted relative to one another such that the basic part 11 formed previously in the first cavity 22 is now located in the second cavity 23. After closing the mold parts, the plastic material is injected into the second cavity 23, as a result of which the first intermediate layer 12 is injected (on one side or on two sides) onto the basic part 11, as a result of which a so-called first blank is formed. At the same time, the plastic material is also injected, in turn, into the first cavity 22, as a result of which an another basic part 11 is formed. The other cavities are still closed now.

[0036] The mold parts are then opened again and adjusted relative to one another, so that the first blank comprising the basic part 11 and the first intermediate layer 12 is arranged now in the third cavity and the basic part 11 formed previously in the first cavity 22 is arranged now in the second cavity 23. The mold parts are closed again, and the plastic material is injected into the first, second and third cavities 22, 23 and 24. Another basic part 11 is formed now in the first cavity 22. A first intermediate layer 12 is injected in the second cavity 23 onto the basic part 11 formed previously, and a second intermediate layer 13 is injected in the third cavity onto the first blank having the basic part 11 and the first intermediate layer 12, as a result of which a so-called second blank is formed. The fourth cavity 25 and the fifth cavity 26 are still closed now.

[0037] The mold parts are subsequently opened again and adjusted relative to one another, so that the second blank comprising the basic part 11, the first intermediate layer 12 and the second intermediate layer 13 is then arranged in the fourth cavity 25. At the same time, a first blank, which was manufactured before in the cavity 23 and which comprises the basic part 11 and the first intermediate layer 12, is located in the third cavity 24. A basic part 11 formed previously in the first cavity 22 is located in the second cavity 23. The mold parts are closed again and the plastic material is injected into the cavities. The method is continued correspondingly.

[0038] A blank is formed in this manner within five method steps in the first runner system 33, said blank having the carrier-like basic part 11, on which four intermediate layers 12, 13, etc. are arranged one on top of another and overlapping each other on one side according to FIG. 1 or on both sides according to FIG. 2, the part 11 and all intermediate layers 12, 13, etc. consisting of the same plastic material. In a next method step, this blank is removed from the first runner system 33 and inserted into the sixth cavity 27 of the second runner system 34 and an outer layer 14 is injected over it either on one side according to FIG. 1 or on both sides according to FIG. 2, the plastic material used for the outer layer 16 being taken from the plastic supply 30 of the runner system 34. The plastic material may be the same plastic material as that of the first runner system 33 or also a plastic material that is different therefrom.

[0039] After application of the outer layer, the injection process is concluded and the plastic lens is manufactured layer by layer, and possible finishing operations may be performed in the usual manner.

[0040] The layers forming the plastic lens are bonded into a monolithic, one-piece body, on which no boundary surfaces can be seen between the layers.

[0041] Since the outer layer 16 is manufactured in a separate second runner system 34, the process parameters effective for the manufacture of the outer layer 16 can be optimally adapted to the requirements of the outer layer 16, while the basic part 11 and the intermediate layers are manufactured in the first runner system 33 with a constellation of parameters that makes possible the rapid manufacture of the blank with good quality.

[0042] FIG. 4 shows an injection molding device 20 in the form of a variant of the injection molding device according to FIG. 3. The injection molding device 20 according to FIG. 4 differs from the injection molding device according to FIG. 3 in that both the last intermediate layer and the outer layer 14 are formed one after another in the second runner system 34, while only the basic part 11 and the three intermediate layers 12, 13, etc are formed in the first runner system 33. Both the fifth cavity 26 and the sixth cavity 27, which can be supplied with plastic material from the plastic supply 30 via a feed channel 37 and an injection channel 36 each, are formed for this purpose in the mold part 28 of the second runner system 34. A temperature control device 31 and a pressure control device 32 are provided in each injection channel 36 in the manner mentioned. The blank to be transferred between the first runner system 33 and the second runner system 34 comprises in this case the carrier-side basic part 11 as well as three intermediate layers 12, 13, etc. applied on one side according to FIG. 1 or on two sides according to FIG. 2. After the transfer of the blank into the second runner system 34, the last intermediate layer is injected there in the fifth cavity, after which the outer layer 14 is injected in the sixth cavity 27 in another method step.

[0043] While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.