DE102019201647A1 - Optical unit for the background lighting of a display - Google Patents

Abstract

In the method according to the invention for producing an optical unit for the backlighting of a display, the optical unit comprises a plurality of optical films (F). A film stack (FB) comprising at least two films is formed with a first contour and folded over on at least one edge (S4). At least one further film (R) is formed with a second contour that is adapted to the first contour (S5). The further film is introduced into the folded part of the film stack (S6).

Description

The present invention relates to a method for producing an optical unit for the backlighting of a display. The invention further relates to an optical unit produced using the method for the background lighting of a display and a display with such a background lighting.

Liquid crystal displays (LCDs) are used in many areas of technology, for example in entertainment electronics, for displaying images on mobile phones or in vehicle technology for instrument clusters, for displaying in an infotainment system or as an imaging unit for head-up displays .

The display is based on mutually independent segments with liquid crystals, which change their alignment when an electrical voltage is applied and thus influence the polarization direction of incident light. In this way, the permeability of polarized light that is generated with a backlight and another polarization filter changes on a polarization filter.

In the background lighting for LCDs that is common today, light-emitting diodes (LED) are used. These can be attached to the side of a light guide and scattered forward through it. In this case, several separate, stacked optical foils are usually provided between the light guide and the liquid crystal layer in order to ensure the most homogeneous possible illumination of the display surface by scattering and deflecting the light. A reflector is often provided on the opposite side of the light guide in order to deflect light, which does not initially propagate from the light guide in the direction of the liquid crystal layer, in this direction and thus to increase the brightness and the efficiency of the display.

The film stack of the optical films used for homogeneous illumination of the display surface is currently usually produced by superimposing several prefabricated films in the final assembly of the background lighting, for example by successively positioning the individual films on the light guide, aligning them and fixing them in a holding frame.

For this purpose, the individual optical foils are procured and processed to measure. Technically, logistically and in terms of costs, this is not the best solution and is very complex. Furthermore, the individual foils can generate tinsel through friction with one another, which can interfere with the image generated by the display. Each of the individual foils must also be fixed separately in order to prevent, for example, any noise that might otherwise occur in the event of vibrations.

Furthermore describes the WO 2005/024473 A2 to hold a stack of two or more optical foils together before inserting them into the display frame by gluing them to one another by means of an adhesive positioned outside the visual range of the foils.

It is an object of the present invention to provide an improved method for producing an optical unit for the background lighting of a display, as well as a corresponding optical unit for the background lighting of a display and a display with such a background lighting.

This object is achieved by a method for producing an optical unit for the backlighting of a display having the features of claim 1, an optical unit according to claim 8 and a display according to claim 9. Preferred embodiments of the invention are the subject of the dependent claims.

In the method according to the invention for producing an optical unit for the background lighting of a display, the optical unit comprises several optical films. A stack of foils comprising at least two foils is formed with a first contour and bent at at least one edge. At least one further film is formed with a second contour adapted to the first contour. The further film is introduced into the folded part of the film stack.

This creates a mechanically stable arrangement which prevents the foils from slipping against one another or with respect to a light guide located in between. Furthermore, the ingress of dirt can be prevented or at least reduced.

According to an advantageous embodiment, film material for the at least two films of the film stack is arranged one above the other. A film stack comprising the at least two films is separated from the film material arranged one above the other. The individual foils in the foil stack are then connected to one another at the edges.

This significantly simplifies the final assembly, since only a single component is handled instead of several foils. Furthermore, the Friction of the foils with one another is excluded, so that the formation of tinsel and the resulting image disturbances are avoided. Finally, measures to reduce noise by handling only one component instead of several individual foils are easier to implement.

The individual foils in the foil stack are advantageously pressed together and thereby thermally fused to one another at the edges.

Likewise, the individual foils can advantageously also be connected to one another at the edges in the foil stack by means of an adhesive process.

In this case, the individual foils are preferably punched out in the shape and size required for the display lighting and connected in the foil stack after the punching by the adhesive process.

Likewise, the individual foils can also be cut out in the shape and size required for the display lighting by means of a thermal fusion cutting process and connected by the cutting process by melting the edge phase in the foil stack.

The thermal fusion cutting process is advantageously a laser cutting process or an ultrasonic cutting process.

• -ein mindestens zwei Folien aufweisender Folienstapel mit einer ersten Kontur geformt und an mindestens einer Kante abgekantet ist; und
• - mindestens eine weitere Folie mit einer an der ersten Kontur angepassten zweiten Kontur geformt ist; und
• - die weitere Folie in den abgekanteten Teil des Folienstapels eingebracht ist.

Correspondingly, an optical unit according to the invention for the background lighting of a display comprises a stack of foils having at least two foils, wherein

• a stack of foils comprising at least two foils is shaped with a first contour and folded at at least one edge; and
• - At least one further film is formed with a second contour adapted to the first contour; and
• - The further film is introduced into the folded part of the film stack.

A display according to the invention has a backlight with an optical unit according to the invention.

The background lighting of the display preferably has a light guide and a reflector, which is designed as a reflector film, the reflector film being introduced into the beveled part of the film stack and the light conductor being arranged between the reflector film and the film stack.

Further features of the present invention will become apparent from the following description and the appended claims in conjunction with the figures.

Figure list

• 1 shows a flow chart for the method according to the invention for producing an optical unit for the background lighting of a display;
• 2 shows schematically the production of an optical unit according to the invention consisting of a folded foil stack comprising several connected foils and a reflector foil inserted therein; and
• 3 shows schematically a backlight with an optical unit according to the invention.

Figure description

For a better understanding of the principles of the present invention, embodiments of the invention are explained in more detail below with reference to the figures. The same reference symbols are used in the figures for elements that are the same or have the same effect and are not necessarily described again for each figure. It goes without saying that the invention is not limited to the illustrated embodiments and that the features described can also be combined or modified without departing from the scope of protection of the invention as defined in the appended claims.

1 shows a flow chart of a method according to the invention for producing an optical unit for the background lighting of a display.

No individual, pre-assembled foils are used here. Instead, foil material is used in a first process step S1 Stacked on top of each other in large sheet format for the various foils. The sheet format is typically rectangular and is preferably selected so that several of the required foils can be produced from one sheet. Depending on the material properties of the respective film material, however, instead of being in large-format sheets, it may also be present on a roll and unrolled from it.

In a second process step S2 a stack of foils containing the foils is separated from the stacked foil material ( S2 ). Different methods can be used for this become. In this way, the foils can be punched out with the desired contour and size in punching processes with punching tools corresponding to the desired shape. Laser, ultrasonic, water jet or plasma cutting processes can also be used, for example.

The individual foils in the foil stack are then in a third process step S3 connected to one another at the edges by thermal fusing or by an additional gluing process, e.g. after punching. The film composite produced in this way can then be assembled in one piece as part of the final assembly of the backlight.

The connection of the individual foils can also take place during the cutting process, if the edge phase of the foil stack is melted using a suitable cutting process, for example a laser or ultrasonic cutting process. Finally, it is also conceivable to first connect the film material and only then to separate it.

The stack of foils produced has, for example, two or three foils stacked one on top of the other. The foils used can have different optical properties.

For example, so-called diffusion foils or diffuser foils are used for the background lighting, which ensure a homogeneous scattering of the light that is emitted directly by LEDs or a light guide used as a light source. Diffusion films of this kind are typically translucent with high transmission values for the incident light, but are not completely transparent and appear cloudy. For example, depending on the configuration, between zero and three diffusion foils can be used.

Likewise, prism films can be used, for example, which are highly transparent and can be used with a microprismatic surface to optimize the illumination. For example, a prism film or two prism films with prism structures arranged perpendicular to one another can be used here.

A combination of different types of film, for example two prismatic films with one diffusion film, can also be used.

In a fourth process step S4 the foil stack is then bent at the edges by hot forming, so that the restoring force of the foils is eliminated and the foil stack then permanently has a lid-like shape. This can also be done using a punching and bending process, in which the stack of foils is punched into a suitable contour and then folded over.

Furthermore, in a fifth process step S5 , which is independent of the previous process steps and can therefore take place after, during or before these other process steps, at least one further film with a smaller contour adapted to the dimensions of the lid-shaped film stack is formed. In particular, this further film can be a reflector film.

This is done in a sixth step S6 pushed into the lid-shaped stack of foils, so that the foils cannot slip against each other. In particular, a reflector foil can be introduced into the folded part of the foil stack, a light guide arranged between the reflector foil and the foil stack also becoming part of this arrangement, so that a mechanically stable optical unit is created for the background lighting of a display. In this case, the ingress of dirt can be prevented by the circumferential edge.

The folding of the stack of foils can also be done on just one, two or three sides, depending on the overall structure. Thus, when the light originating from the LEDs is coupled into the light guide from the side, the area of the coupling point can be left out of the fold.

2 shows schematically the production of an optical unit according to the invention consisting of a folded foil stack comprising three connected foils and a reflector foil inserted therein.

Foil sheets with foil material FM for the three foils is arranged one above the other, the foil material initially still being present separately. After the separation from the stacked film material, there are three films F with the dimensions required for the background lighting of the display, which are then sent for further processing. From the excess FR Further foils can be produced from the foil material as long as the size of the rest allows this. After fusing or gluing, there is then a film composite consisting of the three films FB before, this being initially plane-parallel in the example shown. By folding the edges of the stack of foils, a lid-shaped foil composite is then formed FD generated. After introducing the reflector film R into this lid-shaped film stack FD Then there is a mechanically stable optical unit OE before, where between the reflector film and the folded film stack, further optical elements, not shown here, can be arranged.

3 shows schematically a background lighting with such an optical unit according to the invention, which can be used for an electronic display element, in particular in the form of a liquid crystal display. The liquid crystals are typically arranged between two glass layers, with polarizers being arranged above and below the glass layers. This structure is familiar to the person skilled in the art and is therefore not shown in the figure.

In the embodiment shown, the background lighting has a light source L, a plate-shaped light guide LL and a cover-shaped film composite FD with two optical foils F to optimize the illumination and a reflector foil R. However, this is only an exemplary embodiment; more than two foils and several reflector foils can also be present, for example.

The light source L preferably generates white light and can in particular have an arrangement with a multiplicity of light-emitting diodes (LEDs), but other designs, for example with one or more fluorescent tubes, are also possible. Particularly in the case of display systems in which a small overall thickness is desired, the light source is positioned laterally as shown and the light from the light source is deflected by the light guide LL onto the actual display element. The cover-shaped film composite is used to enable the light from the LEDs to be coupled into the light guide FD not bevelled on the LEDs.

The composite film FD contains optical foils F to optimize the illumination, whereby various optical properties of the background light can be influenced. One or more diffuser foils, additional polarizer foils or prism foils, each having a series of prism-shaped ribs on their surface, can be provided. On the film composite FD On the opposite side of the light guide LL, a reflector sheet R is provided, which deflects light, which does not initially propagate from the light guide in the direction of the liquid crystal layer, in this direction and thus increases the brightness of the display.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was 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.

Patent literature cited

• WO 2005/024473 A2 [0007]

Claims (10)

A method for producing an optical unit for the backlighting of a display, the optical unit comprising a plurality of optical foils, characterized in that a foil stack (FB) comprising at least two foils is formed with a first contour and bent at at least one edge (S4) ; and - at least one further film (R) with a second contour adapted to the first contour is formed (S5); and - the further film is introduced into the folded part of the film stack (S6). Procedure according to Claim 1 wherein - film material (FM) for the at least two films (F) of the film stack (FB) is arranged one above the other (S1); - A film stack (FB) comprising at least two films is separated (S2) from the film material arranged one above the other; and - the individual foils in the foil stack (FB) are connected to one another at the edges (S3). Procedure according to Claim 2 , whereby the individual foils in the foil stack (FB) are pressed together and thereby thermally fused together at the edges. Procedure according to Claim 2 , whereby the individual foils in the foil stack (FB) are connected to one another at the edges by means of an adhesive process. Procedure according to Claim 4 , whereby the individual foils are punched out in the shape and size required for the display lighting and are connected in the foil stack (FB) after the punching by the adhesive process. Procedure according to Claim 5 , whereby the individual foils are cut out in the shape and size required for the display lighting by means of a thermal fusion cutting process and are connected by the cutting process by melting the edge phase in the foil stack (FB). Procedure according to Claim 6 , wherein the thermal fusion cutting process is a laser cutting process or an ultrasonic cutting process. Optical unit for the backlighting of a display, comprising several optical foils, characterized in that - a foil stack (FD) comprising at least two foils (F) is shaped with a first contour and bent at at least one edge; and - at least one further film (R) is formed with a second contour adapted to the first contour; and - the further film is introduced into the folded part of the film stack (FD). Display that has a backlight with an optical unit according to Claim 8 having. Display according to Claim 9 , wherein the backlight has a light guide (LL) and a reflector, which is designed as a reflector film (R), the reflector film is inserted into the folded part of the film stack and the light guide is arranged between the reflector film and the film stack.

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