DE102011001059A1 - Method for manufacturing flat light source, involves providing surface with translucent material with local slots, where local slots are embossed with field of rigid interconnected mandrels into surface - Google Patents

Abstract

The method involves providing a surface (8) with a translucent material (3) with local slots (10), where the local slots are embossed with field of rigid interconnected mandrels (12) into the surface. The field is a two-dimensional field. The mandrels in each dimension of the field are arranged in a fixed grid. The mandrels are parts of an embossing roller. Independent claims are also included for the following: (1) an embossing tool for carrying out a flat light source manufacturing method; and (2) a light source.

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to a method for producing a planar light source, wherein a surface of a translucent material is provided with local depressions. Furthermore, the invention relates to a tool and a device for carrying out this method and to a light source produced by the method.

Flat light sources have many applications. They are z. B. used in advertising for the back lighting of transparent posters. A more technical use find surface light sources in conjunction with LCD screens, which are also backlit to illuminate. Also for lighting farther ahead of them lying objects surface light sources are advantageous if, for example, a shadow should be avoided.

More particularly, the present invention relates to such planar light sources in which light is coupled into a substantially two-dimensional shaped body, for example a plate, of translucent material on a narrow side. This light is kept per se by total reflection on the surfaces of the shaped body in the shaped body. A targeted light emission normal to a surface of the shaped body is achieved by introduced into the surface depressions from which incident light is scattered. The shape and distribution of the depressions determine the distribution of the light normally emitted to the surface.

STATE OF THE ART

From the DE 92 17 331 U a billboard is known, which has a plane-parallel plate made of clear, colorless Plexiglas. In a visible surface of the plate by means of a laser engraving punctiform punctures is introduced. With lateral illumination of the plate, wherein the light rays enter through a narrow surface in the plate, the punctiform punctures appear as luminous dots that radiate light perpendicular to the light surfaces of the plate. In order to achieve a surface distribution of the light over the visible surface, the punctiform punctures are arranged in a grid.

Furthermore, from the DE 92 17 331 U a billboard with a two opposing viewing surfaces and one or more narrow surfaces having plate made of clear material, wherein in a viewing surface an engraving punctiform punctures is provided, the punctiform punctures are respectively arranged at the bottom of a line-shaped puncture. As a result, the grid of the punctiform punctures in unlit illuminated billboard should not be visible.

However, not every translucent material is workable with laser light in a meaningful way. In addition, a plate provided with a laser engraving must be regularly tempered to reduce material stresses introduced during laser engraving. Finally, the wells introduced into a surface by a laser based on the evaporation of material have an unfavorable spatial radiation characteristic when scattering light from the plate.

From the EP 1 335 817 B1 For example, a pin set for a V-cutter is known for efficiently introducing a plurality of V-shaped and parallel grooves into the surface of a translucent material which, in a flat light source, scatter light incident to the surface normal to the surface. The known pin set has a plurality of juxtaposed in one direction, each elastically supported on a common support structure pins with which the V-shaped grooves are scored by moving the support structure over the surface of the translucent material in the surface. In this case, the pins can be arranged differently close to one another and / or be of different lengths in order to introduce the V-shaped grooves, for example, in a primary luminous flux direction through the translucent material with increasing depth and / or density. In this way, a decrease in the luminous flux can be compensated for by already normally scattered away to the surface portions to achieve a uniform intensity distribution of the normal to the surface radiated light across the surface. However, it proves difficult in practice to produce surface light sources with uniform distribution of the light intensity over the entire surface of the translucent material in a cost-effective manner with the known pin set. In addition, the structure of the known pin set is mechanically complex and introduced with him in the surface grooves lead to a mechanical weakening of the translucent material.

OBJECT OF THE INVENTION

The invention has for its object to provide a method, a tool and a device with which surface light sources with a defined light intensity distribution over a surface are inexpensive to produce. Furthermore, an advantageous light source produced in this way should be pointed out.

The object of the invention is achieved by a method having the feature of the independent Patent claim 1, an embossing tool with the feature of the independent claim 16, an embossing device with the features of the independent claim 19 and a light source with the features of the independent claim 20 solved. The dependent claims relate to preferred embodiments of the new method and the new embossing tool.

SOLUTION

The object of the invention is achieved with the features of the independent claims.

Further preferred embodiments according to the invention can be found in the dependent claims.

DESCRIPTION OF THE INVENTION

In the new method for producing a planar light source, in which a surface of a translucent material is provided with local depressions, the local depressions are embossed into the surface with a field of rigidly interconnected spikes. The impressing of the depressions leads to a defined shape of the depressions. By embossing with individual mandrels, there is no continuous mechanical weakening of the material. By not a single mandrel but a field of rigidly interconnected thorns is used when impressing the depressions in the surface, any speed penalty of mechanical impressions are compensated. In addition, a field of rigidly interconnected thorns can be provided in a very cost effective in precise form.

Not only the shape of the recesses can be specified by the shape of the mandrels used for embossing, but also the surface quality of the recesses. Thus, when using thorns with a smooth surface, the surface also remains smooth in the area of the embossed depressions. Even relatively large depressions are therefore hardly visible in the non-illuminated state. The impressing of the recesses is also possible with a wide variety of translucent materials. Prerequisite is only a certain ductility.

It is particularly preferred if the field of rigidly connected mandrels is a two-dimensional field. As a result, the speed of the new method can be further accelerated.

Preferably, the mandrels are arranged in any dimension of the field in a fixed grid. This makes it easy to continue the pattern of the wells beyond the boundaries of the field evenly over the entire surface of the translucent material. In addition, a fixed grid ensures a uniformity of light emission from the surface of the finished light source.

In the new method, the recesses may be arranged in a large distance from each other in comparison to their diameter. Thus, a grid dimension in the respective dimension of the field of the mandrels may be at least twice as large, preferably at least three times as large and even more preferably at least four times as large as a diameter of the depressions embossed into the surface in this dimension.

In a particularly preferred embodiment of the new method, the mandrels are parts of an embossing roller that is rolled over the surface of the translucent material. This embodiment of the new method is characterized by an extremely high speed in the defined introduction of the depressions over very large areas of the surface of the translucent material.

Preferably, the recesses are impressed in a rectangular pattern in the surface, wherein an edge direction of the pattern in a primary luminous flux direction passes through the material. The primary luminous flux direction through the material is determined by the arrangement of illuminants at an edge of the translucent material. By aligning the rectangular pattern with a longitudinal edge on the primary luminous flux direction always diverging only slightly to the primary luminous flux direction portions of the luminous flux to the wells. As a result, the luminous flux has a long reach along the surface, which is advantageous for homogeneous light emission from large surfaces in the case of the final planar light source.

Nevertheless, it may also be useful in the new method to impress the recesses with increasing depth and / or density in the primary luminous flux direction through the material, in order to compensate for attenuation of the luminous flux in this direction.

As favorable for the emission characteristics of the light from the individual wells, it turns out, when the wells are impressed with stamping surfaces on the spikes in the surface, at least in a primary luminous flux through the material an angle of 30 ° to 60 °, preferably from 40 ° to 45 °, ie from about 45 ° to the surface normal of the surface. These surfaces do not have to be flat, but can also have a curvature have, as far as said angular ranges are at least substantially maintained.

Point-shaped depressions, which are hereby meant recesses having at least in their two main directions of extension along the surface approximately the same dimensions, are preferably embossed with a diameter of 0.1 mm to 1.5 mm in the surface. However, stretched depressions which have a stretch ratio between their maximum and their minimum diameter of not more than 6: 1, and preferably from 3: 1 to 5: 1, d., Prove particularly favorable for the radiation behavior of the respective surface. H. of about 4: 1. These elongated depressions may also be made larger in the direction of their maximum diameter than the punctiform depressions described in the last paragraph and have a maximum diameter of at most 5 mm and preferably from 2 mm to 4 mm, d. H. about 3 mm. With this maximum diameter, the elongated recesses transverse to the primary luminous flux direction through the material are to be impressed into the surface to take advantage of their particular shape for the light radiated from the surface.

The concrete form of impressed into the surface depressions is variable in the new method. You can z. B. lenticular, conical or pyramidal, these basic shapes are distorted accordingly in elongated depressions. But there are also wells with even more or less edges than pyramids possible.

In a particularly preferred embodiment of the new method, the edges of the depressions are pressed on impressing the depressions to the surface. Due to the impressing of the depressions, there is generally a tendency for the material around the depressions to form a crater-shaped protrusion projecting over the surface. However, this survey is preferably pressed in the new method to the surface, d. H. at least rounded.

The new method proves to be particularly tolerant of tolerances in the thickness of the translucent material normal to the surface into which the recesses are inserted when the mandrels are pressed into the surface with a predetermined embossing force. Tolerances in the thickness direction of the material are often present in cast translucent materials. However, these are usually tolerances with a relatively large wavelength, so that in the new method rigid relative arrangement of the mandrels within the field is not a problem, because the tolerances occurring over the dimensions of the field away are negligible in most cases.

An embossing tool for carrying out the new method according to the invention is characterized in that it comprises a two-dimensional array of rigidly interconnected spikes which are arranged in a fixed grid in each dimension of the field, wherein a grid of the solid grid in the respective dimension at least twice large, preferably at least three times as large and even more preferably at least four times as large as a diameter of impressed with the spikes in a surface depressions in this dimension.

Preferably, the mandrels are part of an embossing roll, which is freely rotatably mounted in a rotary bearing, and so can be rolled over a surface to be provided with depressions.

To produce the embossing tool, the mandrels can be machined out of a material surface of a continuous body. This represents a cost-effective approach to the formation of very precise mandrels with high surface quality.

In an embossing device according to the invention for carrying out the new method with a new embossing tool embossing tool, z. B. with a traversing device for the embossing tool, acted upon by a predeterminable embossing force against a workpiece support.

A light source according to the invention, which was produced according to the new method and in which a surface of a translucent material is provided with local depressions, is characterized in that the depressions are embossed in a rectangular pattern in the surface, wherein an edge direction of the pattern in a primary Luminous flux direction through the translucent material, wherein a pitch of the rectangular pattern in each edge direction is at least twice, preferably at least three times and more preferably at least four times as large as a diameter of the recess in this edge direction and wherein the recess with an aspect ratio are stretched between their maximum and their minimum diameter of at most 6: 1 and preferably from 3: 1 to 5: 1 and with their maximum diameter of at most 5 mm and preferably 2 mm to 4 mm in the transverse direction of the primary luminous flux direction through the mat are aligned erial.

Advantageous developments of the invention will become apparent from the claims, the description and the drawings. The advantages of features and combinations of several features mentioned in the introduction to the description are merely exemplary and may be alternative or cumulatively come into effect, without the advantages necessarily having to be achieved by embodiments of the invention. Further features are the drawings - in particular the illustrated geometries and the relative dimensions of several components to each other and their relative arrangement and operative connection - refer. The combination of features of different embodiments of the invention or of features of different claims is also possible deviating from the chosen relationships of the claims and is hereby stimulated. This also applies to those features which are shown in separate drawings or are mentioned in their description. These features can also be combined with features of different claims. Likewise, in the claims listed features for further embodiments of the invention can be omitted.

BRIEF DESCRIPTION OF THE FIGURES

The invention is explained in more detail below with reference to preferred embodiments with reference to the accompanying drawings and described.

1 is a longitudinal section through a flat light source.

2 is a plan view of a planar light source.

3 is a plan view of an enlarged section of the surface of a translucent material of the light source according to 1 and 2 with recesses introduced into the surface.

4 shows an embossing tool with a two-dimensional array of thorns for inserting the wells according to 3 ,

5 illustrates the use of the embossing tool according to FIG 4 ,

6 illustrates the use of an embossing roller with a two-dimensional array of spikes for inserting the indentations according to FIG 3 ,

7 illustrates an alternative use of an embossing roller provided with a two-dimensional array of spikes for introducing indentations into a surface.

8th is a plot of an embossing force across the extent of a surface into which recesses are introduced, in a primary luminous flux direction, and the resulting distribution of the depth of the recesses.

9 shows a first embodiment of punctiform depressions in a plan view of the surface.

10 showed one of the wells according to 9 in a section through the surface.

11 to 13 show other punctiform depressions looking towards the surface.

14 shows an embodiment of elongated depressions looking towards the surface.

15 shows an alternative embodiment of an elongated depression with a view towards the surface.

16 shows the recess according to 15 in a section through the surface.

17 shows yet another embodiment of an elongated depression facing the surface into which it is introduced.

DESCRIPTION OF THE FIGURES

The in the 1 and 2 schematically illustrated planar light source 1 builds on a plate 2 from a translucent material 3 on. On a narrow side 4 the plate 2 is a series of light emitting diodes 5 with integrated reflectors 6 arranged as a primary light source. The light emitted by these bulbs light is on the narrow side 4 in the plate 2 coupled and then spreads in a primary luminous flux direction 7 out. Due to the special education of one of in 1 overhead and in 2 surface facing the viewer 8th the plate 2 that will be in the plate 2 coupled light over the entire surface 8th distributed radiated and not only in the in 1 marked directions 9 the surface normal but also at other angles to the surface 8th ,

The special, in the 1 and 2 not reproduced design of the surface 8th to the radiation of the in the plate 2 coupled light, without this special design of the surface 8th by total reflection in the plate 2 would be based on the surface 8th embossed depressions 10 , in the 3 are reproduced. The wells 10 are arranged here in a square pattern whose one edge direction is parallel to the primary luminous flux direction 7 through the plate 2 runs.

Incorporated are the wells 2 according to 3 for example with an in 4 illustrated embossing tool 11 that a variety of thorns 12 in a two-dimensional field with a pattern of wells 10 according to 3 corresponding grid has.

5 shows how the stamping tool 11 with a stamping force 13 against the plate 2 is applied to the spines 12 in the translucent material 3 the plate 2 push in. This is the embossing tool 11 in connection already in the plate 2 existing depressions 10 set to the pattern of the wells 10 evenly over the surface 8th to train away.

For the production of the embossing tool 11 according to the 4 and 5 can the spines 12 Materialabnehmend from a surface of a continuous body, ie machined and / or abrasive and / or on by spark erosion, be worked out. This surface may also be the surface of a roll body. Then results as a stamping tool in 6 shown embossing roll 14 , This embossing roll 14 is about a rotation axis 15 rotatably mounted and is here with the stamping force 13 against a about a parallel axis of rotation 16 rotatably mounted counter roll 17 acted upon when the plate 2 from the translucent material 3 between these two rollers 14 and 17 is passed through with the thorns 12 the embossing roll 14 the wells 10 in the surface 8th imprinted.

7 illustrates the possibility of relative movement between the plate 2 and the embossing roll 14 also by unrolling the embossing roller 14 over the surface 8th of the arrested plate 2 to realize.

In 8th is about the length of the plate 2 in the primary luminous flux direction 7 according to the 1 to 3 the embossing force F and the resulting depth T of the recesses in the plate applied. As the distance to the primary light sources increases, the depth T increases, which is achieved by an increasing embossing force F in order to compensate for the light flux decreasing in the same direction.

9 and 10 sketch conical depressions 10 in the surface 8th , wherein the opening angle of the recesses is a right angle.

However, this is only one way of forming the wells 10 represents. 11 shows a pyramid-shaped depression 10 , 12 shows a depression 10 with hexagonal circumference and corresponding six in the translucent material 8th running edges. 13 outlines a recess 10 whose circumference is octagonal and which eight accordingly in the material 3 has running edges.

While in the 9 to 13 sketched depressions 10 are substantially punctate points 14 elongated depressions 10 with their maximum diameter transverse to the primary luminous flux direction 7 are aligned compared to the extent of the recesses 10 towards the surface 8th more light from the surface 8th away from the plate 2 to reflect out. The aspect ratio of the pit 10 between its maximum diameter and its minimum diameter is 4: 1. The shape of the depressions 10 is that of a deformed pyramid with a rhombic base corresponding to that in 14 To see the extent of the wells 10 ,

15 shows a likewise elongated depression 10 , which has a kind of lens shape here. The surfaces of the depression 10 but are like 16 showing a section in the primary luminous flux direction, ie across the depression 10 is not concave, but convexly curved, although a concave curvature would be possible.

17 shows a stretched recess 10 which has the shape of a deformed cone. Even more forms are in the wells 10 possible. More important than the exact shape of the wells 10 are their dimensions and the quality of the surface 8th in the area of the depression. This depends on the quality of the surface of the spines, with which the indentations 10 in the surface 8th be introduced. If the surface 8th in the area of the depressions 10 is just as smooth as before impressing the wells 10 is the depression 10 in the unlit condition of the respective plate 2 barely visible.

LIST OF REFERENCE NUMBERS

1

light source

2

plate

3

translucent material

4

narrow surface

5

led

6

reflector

7

primary luminous flux direction

8th

surface

9

Direction normal to the surface 8th

10

deepening

11

embossing tool

12

mandrel

13

embossing force

14

embossing roller

15

axis of rotation

16

axis of rotation

17

backing roll

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 9217331 U [0004, 0005]
• EP 1335817 B1 [0007]

Claims (20)

Method for producing a flat light source ( 1 ), whereby a surface ( 8th ) of a translucent material ( 3 ) with local pits ( 10 ), characterized in that the local depressions ( 10 ) with a field of rigidly connected spines ( 12 ) into the surface ( 8th ). A method according to claim 1, characterized in that the field is a two-dimensional field. Method according to claim 1 or 2, characterized in that the mandrels ( 12 ) are arranged in a fixed grid in each dimension of the field. A method according to claim 3, characterized in that a grid of the solid grid in the respective dimension at least twice as large, preferably at least three times as large and even more preferably at least four times as large as a diameter of the in the surface ( 8th ) embossed depressions ( 10 ) in this dimension. Method according to one of the preceding claims, characterized in that the mandrels ( 12 ) Parts of an embossing roll ( 14 ), which are above the surface ( 8th ) is rolled. Method according to one of the preceding claims, characterized in that the depressions ( 10 ) in a rectangular pattern in the surface ( 8th ). Method according to claim 6, characterized in that the depressions ( 10 ) in the rectangular pattern in the surface ( 8th ) are impressed such that an edge direction of the pattern is parallel to a primary luminous flux direction ( 7 ) through the material ( 3 ) runs. Method according to one of the preceding claims, characterized in that the depressions ( 10 ) transversely to a primary luminous flux direction through the material ( 3 ) constant depth into the surface ( 8th ). Method according to one of the preceding claims, characterized in that the depressions ( 10 ) in a primary luminous flux direction ( 7 ) through the material ( 3 ) increasing depth and / or density in the surface ( 8th ). Method according to one of the preceding claims, characterized in that the depressions ( 10 ) predominantly with embossing surfaces on the thorns ( 12 ) into the surface ( 8th ), which are at least in a primary luminous flux direction ( 7 ) through the material ( 3 ) an angle of 30 ° to 60 °, preferably from 40 ° to 50 ° to the surface normal of the surface ( 8th ) exhibit. Method according to one of the preceding claims, characterized in that punctiform depressions ( 10 ) with a diameter of 0.1 mm to 1.5 mm into the surface ( 8th ). Method according to one of the preceding claims, characterized in that elongated depressions ( 10 ) having a stretch ratio between their maximum and minimum diameter of at most 6: 1, and preferably from 3: 1 to 5: 1, with their maximum diameter of at most 5 mm, and preferably from 2 mm to 4 mm in the transverse direction to a primary one Luminous flux direction ( 7 ) through the material ( 3 ) into the surface ( 8th ). Method according to one of the preceding claims, characterized in that the depressions ( 10 ) lenticular, conical or pyramidal in the surface ( 8th ). Method according to one of the preceding claims, characterized in that the edges of the recesses ( 10 ) when impressing the depressions ( 10 ) into the surface ( 10 ) are pressed. Method according to one of the preceding claims, characterized in that the mandrels ( 12 ) with a predetermined embossing force into the surface ( 8th ). Embossing tool ( 11 ) for carrying out the method according to any one of the preceding claims, characterized by a two-dimensional array of rigidly connected thorns ( 12 ) which are arranged in a fixed grid in each dimension of the field, wherein a grid of the fixed grid in the respective dimension is at least twice as large, preferably at least three times and more preferably at least four times as large as a diameter of the Thorns ( 12 ) into a surface ( 8th ) embossed depressions ( 10 ) in this dimension. Embossing tool ( 11 ) according to claim 16, characterized in that the mandrels ( 12 ) Part of an embossing roll ( 14 ), which are about a rotation axis ( 15 ) is rotatably mounted. Embossing tool ( 11 ) according to claim 16 or 17, characterized in that the mandrels ( 12 ) are machined material removal from a surface of a continuous body. Embossing device for carrying out the method according to one of claims 1 to 15 with an embossing tool ( 11 ) according to one of claims 16 to 18, wherein one of the embossing tool ( 11 ) against a workpiece support acting on embossing force ( 13 ) can be specified. Light source ( 1 ) prepared by the method according to any one of claims 1 to 15, wherein a surface ( 8th ) of a translucent material ( 3 ) with local pits ( 10 ), characterized in that the depressions ( 10 ) in a rectangular pattern in the surface ( 8th ), wherein an edge direction of the pattern in a primary luminous flux direction ( 7 ) through the material ( 3 ), wherein a pitch of the rectangular pattern in each edge direction is at least twice as large, preferably at least three times as large and even more preferably at least four times as large as a diameter of the depressions ( 10 ) in this edge direction and wherein the depressions ( 10 ) are stretched at a stretch ratio between their maximum and minimum diameters of at most 6: 1 and preferably from 3: 1 to 5: 1 and with their maximum diameter of at most 5 mm and preferably from 2 mm to 4 mm in the transverse direction to the primary Luminous flux direction ( 7 ) through the material ( 3 ) are aligned.

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