DE102012112386A1 - Process for the transparent bonding of transparent layers - Google Patents

Abstract

The invention relates to a bonding of transparent layers, in which a curable, transparent adhesive (1) is provided, wherein in a first step, the transparent adhesive (1) in still liquid or viscous phase on a predetermined adhesive region (52) of a bearing surface ( 51) is applied to an input unit (5); in a next step, a display unit (3) having a side edge (32) is placed on the adhesive layer at a predeterminable tilt angle (53) to the support surface (51) of the input unit (5) on the input unit (5); in a next step, the display unit (3) is tilted down about this side edge (32), as a tilting axis, in the direction of the input unit (5), whereby the tilting movement between the input unit (5) and the display unit (3) arranged transparent adhesive (1) in the form of a propagation wave air bubbles on the predetermined adhesive area (52) of the input unit (5) distributed.

Description

The invention relates to a method for transparent bonding of transparent layers and resulting products, in particular displays for mobile phones.

The term »optical bonding« means »transparent liquid bonding« and stands for an adhesive technology that combines optical components such as display units, input units, such as touch carriers or front glass, with a particularly high optical quality. "Transparent" means that such a material for electromagnetic radiation, in particular in the visible range of the wavelength spectrum, at least 80%, preferably more than 90%, is permeable.

Optically bonded displays are well-known in military equipment, especially in onboard instruments of airplanes and ships. Good readability of the instruments in sunlight, reduction of unwanted glare and reflections and prevention of condensation in the display elements in changing environmental conditions are the most important criteria for the application here.

In particular, the introduction of ever more powerful, industrial-grade display units with multi-touch PCT (Projected Capacitive Touch) technology has helped optical bonding to its current level of popularity: mention the iPhone effect. Here, an air gap (present in other devices) is "filled in" by optical bonding.

The special feature is that highly transparent, index-adapted adhesives (refractive index glass: 1.51, refractive index air: 1.0, refractive index adhesive system = glass) are used to achieve the clearest possible representation of the display elements even in unfavorable lighting conditions. In addition, the bonding is specially designed to meet the requirements of new, ever-better-resolution display units. The optical losses caused by reflections at the interfaces are reduced so much by index-adapted adhesives that the contrast ratio and luminous efficacy can be measurably improved. Another advantage is the high brilliance, which is achieved especially in connection with new, high-intensity LED backlight displays. The use of LEDs allows a higher maximum contrast ratio; Colors look more intense and realistic.

Filling in the air gap ensures that there are no air pockets between the display element and the front glass or touch support, so that even possible condensation effects are completely eliminated.

In addition to the optical advantages, optical bonding enables a more robust overall design. The firmly interconnected glass components act as laminated safety glass and are therefore very resistant to vibration, thermal stresses and shock loads.

Optical bonding is considered a well-established technology because of its long-term use in military products. Meanwhile, a wide range of related materials has been adequately tested and commercially available. The know-how of process engineering distinguishes the few suppliers.

Process-reliable optical bonding processes, for which HMI touch panels, for example, can be manufactured without air bubbles and consequently with a particularly high optical quality, have so far been too costly for standard applications in industry due to the high staff workload and usually necessary joining steps in a vacuum.

Today's problems result both from the adhesive material, as well as from the process engineering. One of the biggest challenges is the bubble-free bonding of optical materials. Depending on the viscosity and surface tension of the adhesive, the air bubbles dissolve on the surface. When joining the glass plates, however, again air bubbles can be trapped, which can then escape in the course of the bonding process and remain trapped between the workpieces to be joined, such as between a display surface and a touch screen or between touch screen and front glass. A single bubble disrupts a bonded display. For this reason, many display manufacturers currently refrain from the optical bonding process and offer their products without the aforementioned optical advantages. Alternatively, solutions with a bonded touch on the front glass and air gap between the display and the touch are also available. Resistive touch structures can not be completely optically bonded anyway - for technical reasons, an air gap is always required between the actuating and contact surfaces. However, as long as an air layer is still included in the overall structure, disturbing reflections due to the transitions glass / air are installed and not eliminated.

Accordingly, the present invention has for its object to provide a method for transparent bonding of transparent layers and products resulting therefrom, in which a bubble-free bonding of optical materials is possible, as well as a cost-effective application of such a method and production of the resulting products is made possible. It is also an object of the invention to improve by such a method and the resulting products, the optical properties of a display with a transparent touch unit. It is also an object of the invention to improve the image quality of such products, in particular electronic devices having a display, when the display is provided with a transparent touch unit.

In order to provide a method for transparent bonding of transparent layers, in which a curable, transparent adhesive is distributed free of air bubbles on a predeterminable adhesive area of the input unit, the present invention makes use, inter alia, of the idea, in a first step, the transparent adhesive in even liquid or viscous phase to apply to a predetermined adhesive area of a bearing surface of an input unit. In a next step, the display unit is placed with a side edge on the adhesive layer at a predefinable tilt angle to the support surface of the input unit on the input unit. In a next step, the display unit is tilted down around this side edge, as a tilting axis, in the direction of the input unit, wherein through and during the tilting movement of the arranged between the input unit and the display unit transparent adhesive is free of air bubbles in the form of a propagation wave on the predetermined adhesive area of the input unit distributed. Preferably, the transparent adhesive is distributed starting from the side edge of the display unit in the form of a propagation wave.

In other words, such a spread of the transparent adhesive of the uncured transparent adhesive allows any air bubbles resulting during the assembly to be forced out of the adhesive and / or pressed out by such an expansion of the adhesive. Such assembly therefore acts as an automatic bubble removal step by which the formation of any air bubbles can be precluded. A resulting display device is therefore a device of particularly high optical brilliance and can be produced at the same time by the method described here in a particularly simple and cost-effective manner.

The display unit is preferably of the liquid crystal display (LCD) type, organic light emitting diode (OLED) type or electronic paper type (e-paper). There are basically two types of LCD displays commercially available: Variant 1 consists of a back lighting unit, the LCD unit and a frame that encloses both components. Variant 2, unlike Variant 1, has no frame. The transparent touch unit is preferably of the type analog-resistive, projective-capacitive or ultrasound-based.

The entire structure of the display is made by the professional introduction of a transparent adhesive material, such as liquid adhesive material, between the transparent blocks display unit and touch unit. In this way disturbing reflections are largely reduced. Compared to the prior art, the image quality is significantly improved.

The process enables reliable bubble-free optical bonding for common industrial HMI applications, especially for small and medium sized series. Automation in the manufacture of the display structures described herein is e.g. today absolutely necessary for nationwide use in the automotive industry. Future automobiles will be equipped with optically bonded display units. The advantages such as optical improvements, higher contrast of the display and improved mechanical stability (shock, shock and vibration) make optical bonding more and more popular.

In accordance with at least one embodiment, a curable, transparent adhesive is first provided in the method described here. In a next step, the transparent adhesive is applied in a still liquid or viscous phase to a predeterminable adhesive area of a contact surface of an input unit. In a next step, the display unit is placed with a side edge on the adhesive layer at a predefinable tilt angle to the support surface of the input unit on the input unit. In a next step, the display unit is tilted down about this side edge, as a tilting axis, in the direction of the input unit, wherein through and during the tilting movement of the arranged between the input unit and the display unit transparent adhesive in the form of a propagation wave air bubbles on the predetermined adhesive area of the input unit distributed. Preferably, the transparent adhesive is distributed starting from the side edge of the display unit in the form of a propagation wave.

In accordance with at least one embodiment, the curable, transparent adhesive is formed with an additive cross-linking of two-component silicone and / or a UV-curable acrylate. In particular, this two-component silicone may be formed with a UV-curable silicone and an additive-crosslinking silicone. It has surprisingly been found that such a Silicone leads to a particularly simple elimination of air bubbles during assembly and at the same time this silicone is particularly easy, for example by means of a temperature-setting curable. Alternatively or additionally, the curable, transparent adhesive is formed with the UV-curable acrylate, the acrylate allows a particularly rapid curing by irradiation of electromagnetic radiation in the ultraviolet wavelength range. If both the silicone and the acrylate are contained in the adhesive, both advantageous effects can complement each other, so that such an adhesive is a particularly easily and quickly hardenable adhesive.

In accordance with at least one embodiment, the curable, transparent adhesive in the liquid or viscous state has a viscosity of at least 300 mPas and at most 10,000 mPas. With a claimed in such a range viscosity and thus directly associated surface tension of the adhesive applied to the support surface, for example, enclosed air bubbles on the surface particularly easy to solve. Such viscosity also ensures that the still liquid or viscous adhesive neither dissolves too quickly nor is formed too tough on the support surface.

For example, the adhesive consists of equal parts of components A + B. For example, component A has a viscosity of 1,000 mPas. Component B is commercially available, for example, in viscosities of from 150 to 20,000 mPas. This makes it possible to set an overall viscosity of the overall system between about 300 and 10,000 mPas. This is of crucial importance for the course of the adhesive material, in particular after the joining of the components.

In accordance with at least one embodiment, in the cured state, the transparent adhesive layer has a layer thickness of at least 0.2 mm and at most 1.5 mm. In particular, such a layer thickness can be achieved with a viscosity of at least 300 mPas and at most 10,000 mPas described here. In other words, such a layer thickness allows the lowest possible refractive losses during the transition of the electromagnetic radiation from the display unit through the adhesive layer and the input unit.

In accordance with at least one embodiment, transparent fillers are introduced into the curable, transparent adhesive or these are arranged on the adhesive area after or before the application of the transparent adhesive, wherein the fillers have an edge length of at least 0.2 mm and at most 0.5 mm. For this purpose, the filler can be mixed into the material of the transparent adhesive and applied simultaneously with the material of the adhesive on the connecting surface of the display unit. In particular, the transparent fillers may be formed with the same material as the curable, transparent adhesive. In other words, the transparent fillers form spacers for the input unit that are integrated into the material of the transparent adhesive. The transparent fillers are therefore arranged after the application of the adhesive between the input unit and the display unit and therefore both spaced from each other. In this respect, it is particularly easy to set a layer thickness by means of such fillers integrated in the transparent adhesive. In particular, the transparent filler can be cube-shaped and / or parallelepiped-shaped. The fillers, which are spacers in the present embodiment, can be achieved simply by casting the material of the later filler in a desired layer thickness between two non-adhesive glass or plastic plates. With the same aim of ensuring the adhesive layer thickness, film sections of already cured adhesive material in the desired layer thickness can be used.

According to at least one embodiment, the sealing surface is sealed by means of a UV-curable sealant before the application of the transparent adhesive to the support surface. Advantageously, it is thus avoided that the transparent adhesive can, for example, undesirably penetrate into the input unit in any existing openings or cavities on the support surface during application. As such, the sealant can otherwise avoid structural damage caused by the transparent adhesive.

According to at least one embodiment, after the assembly of the display unit and the input unit, the transparent adhesive layer is cured by means of temperature radiation and / or UV irradiation. Such a curing process is particularly time-saving and cost feasible, since, for example, can be dispensed with additional curing agent for curing the transparent adhesive.

In accordance with at least one embodiment, at least one sealing means is arranged on the connecting surface of the display unit and / or on the support surface of the input unit, which laterally limits the adhesive region at least in places in the horizontal direction after assembly. "Horizontal direction" in this context means a direction in the main extension direction of the display unit and / or the input unit. If the display unit and the input unit are joined, the liquid or even viscous adhesive between these two Units pressed together and squeezed out in the horizontal direction. In order for the squeezed adhesive not to emerge laterally from the input unit and / or the display unit during assembly, the sealing means may limit propagation of the adhesive in that direction in the horizontal direction. In addition, this sealing means may act as a spacer for spacing the input unit and the display unit. It is conceivable that in this case the sealing means has a vertical extension, that is to say an extension in the direction perpendicular to a main extension plane of the input unit and / or the display unit, which corresponds to the desired layer thickness of the subsequent adhesive layer. Such a sealing means can therefore serve as a shaping device for the expansion and the layer thickness of the subsequent adhesive layer. In particular, the sealing means and the adhesive may each be formed with an optically identical material. "Optically identical material" means that these materials, unless they are identical materials, are the same in terms of their optical properties.

In at least one embodiment, the sealing means is a UV-curable spacer dam. In particular, the spacer dam and the adhesive layer may be formed with the same material. The spacer dam can then be arranged in the form of a frame around the adhesive area in the horizontal direction on, for example, the contact surface of the input unit.

In accordance with at least one embodiment, the sealing means is a spacer frame or the sealing means is mechanically fixedly connected to a spacer frame arranged on the connection surface of the display unit or on the support surface of the input unit, wherein the spacer frame completely surrounds the adhesive region after assembly in the horizontal direction. Such a spacer frame can therefore be a hermetic protection, which is arranged, for example, airtight after assembly between the display unit and the input unit.

Now, if the spacer frame is fixed, for example, arranged on the connection surface of the display unit, it has been customary to feed the display unit from above the input unit and perform the trapping of later visible air bubbles in the step of joining with the help of a sometimes complex vacuum step. By means of the method described here, however, can be advantageously dispensed with such a complex vacuum step, since air bubbles are already completely avoided by the claimed here specific spread of the adhesive on the support surface.

In addition, a display device is specified. For example, by means of the method described here, as described in connection with one or more of the abovementioned embodiments, a display device described here can be produced. That is, the features listed for the method described here are also disclosed for the display device described here and vice versa.

According to at least one embodiment, the display device comprises a display unit and an input unit, wherein in the vertical direction between the display unit and the input unit at least one transparent, cured adhesive layer is arranged. The transparent, cured adhesive layer is free of air bubbles. Such a display device has the advantages already described at the outset.

In the following, the method described here and the display device described here will be explained in more detail by means of exemplary embodiments and the associated figures.

The 1A to 1D show in schematic top and side views of a display described here as well as an input unit described here.

The 2A to 2C show individual process steps for producing a display device described here.

In the embodiments and in the figures, the same or equivalent components are each provided with the same reference numerals. The illustrated elements are not to be considered as true to scale, but individual elements may be exaggerated to better understand.

In the 1A is a schematic plan view of an embodiment of a display unit described here 3 having a connection surface 31 shown.

In the 1B is shown in a schematic plan view, as on a support surface 51 an input unit 5 first a UV curable sealant 33 is arranged to the bearing surface 51 in front of you on the support surface 51 to be applied, transparent adhesive 1 seal. On the sealant 33 is a frame element 35 arranged, which in the horizontal direction H an adhesive area 52 Are defined. Alternatively or additionally it can with the sealant 32 to act, for example, a condensation-crosslinking curable agent (one-component).

The 1C and 1D show in schematic side views respectively in the 1A and 1B shown display unit 3 or input unit 5 and that on the frame element 35 and on this mechanically fixed sealing means 4 , which in the present case in the form of a spacer frame 42 is trained. Alternatively, the sealing means 4 in the form of a distance dam 41 be educated.

In the 2A is shown a process step in which initially a transparent adhesive 1 on the specifiable adhesive area 52 the input unit 5 is applied.

In a next step is in the 2A shown as the display unit 3 initially within the gluing area 52 with a side edge 32 in a predefinable tilt angle 53 to the support surface 51 the input unit 5 on the input unit 5 is placed.

In the 2A is further shown as the display unit 3 around this side edge 32 as a tilting axis in the direction of the input unit 5 is tilted down, wherein by and during the tilting movement of the between the input unit 5 and the display unit 3 arranged transparent glue 1 in the form of a propagation wave air bubbles, starting from the side edge 32 , on the specifiable adhesive area 52 the input unit 5 distributed.

After assembling the display unit 3 with the input unit 5 spreads the liquid or even viscous, transparent adhesive 1 bubble-free until it passes through the spacer frame 42 in the horizontal direction H and through the display unit 3 and the input unit 5 in the vertical direction V is limited in its extent (see 2 B ). Here is the display unit 3 from the input unit 5 through in the transparent glue 1 introduced, transparent packing 12 objected. In particular, a predefinable layer thickness of at least 0.2 mm to at most 1.5 mm, for example of 0.8 mm, can thus be easily set. In the present case, both the transparent filler 12 , the transparent adhesive layer 11 and the spacer frame 42 formed with the same material.

In the 2C is a display device made by the method described herein 100 shown in a schematic plan view. Recognizable is again between the display unit 3 and the input unit 5 arranged adhesive layer 11 that of the sealant 4 in the present embodiment in the form of the spacer frame 42 is formed in the horizontal direction H is bounded.

The illustrated method allows bubble-free joining of the components without transferring the assembly into a vacuum chamber. In addition, the procedure according to the method shown here prevents the unwanted bending of the display unit by the action of the weight of the adhesive.

• 1) Abdichtung des TFT-Displays mit Hilfe eines UV-aushärtbaren Silikons (wie es beispielsweise von der Firma Momentive angeboten wird), das nach Aufbringen (maschinellem Dosieren) desselben per UV-Licht oder per Raumtemperatur beispielsweise innerhalb von 24 Stunden ausgehärtet wird oder aushärtbar ist.
• 2) Maschinelles Dosieren des Klebesystems 2-Komponenten Silikon vorzugsweise auf das Display (andere Erfinder beschreiben das Aufbringen auf die Gegenseite) nach einem speziellen Muster
• 3) Maschinelles Fügen der zu verbindenden Teile mit der Maßgabe, dass das Display „oben“ liegt.
• 4) Aushärtung (bei erhöhter Temperatur bzw. durch Kombination von UV-Strahlung/Aktivierung und Temperatur)

In this respect, method steps for bonding, for example, a TFT display with a protective glass or the combination of a touch carrier and a protective glass of the following dimensions can be summarized:

• 1) sealing of the TFT display with the aid of a UV-curable silicone (such as that offered by the company Momentive), which is cured after application (mechanical dosing) of the same by UV light or at room temperature, for example within 24 hours or curable is.
• 2) Machine dosing of the adhesive system 2-component silicone preferably on the display (other inventors describe the application to the opposite side) according to a special pattern
• 3) Mechanical joining of the parts to be connected with the proviso that the display is "up".
• 4) Curing (at elevated temperature or by combination of UV radiation / activation and temperature)

Also inventive is the combination of two different adhesive systems (1. UV-curing silicone system, 2nd additive crosslinking silicone system), which allows a good yield and short cycle times in the automatic process. The compatibility of the two systems (curing of both systems in direct contact) is given in this invention.

In addition, the layer thickness of the bond can be achieved by precise adjustment of the viscosity of the 2-component adhesive system (for example at least 0.2 and at most 1.5 mm adhesive layer thickness at a viscosity of at least 300 and at most 10,000 mPas)

Advantageously, a desired layer thickness can also be achieved by introducing cube-shaped or cuboid-shaped, cured adhesive moldings, ie the transparent fillers, from the (silicone) adhesive in the dosing step instead of glass or polymer beads (see also prior art). This excludes a difference between refractive indices solid / adhesive.

The production of the display unit according to the method described above allows a significantly improved screen quality without the need for an expensive and expensive production line.

• a) UV-härtbares Acryl-basiertes System: Unregelmäßigkeiten wie Luftblasen im Verklebeprozess müssen jedoch hier vor dem Schritt der UV-Härtung erkannt und ausgeschleust werden, um die teuren Ausgangsmaterialien zu retten.
• b) Additiv (wärme-)vernetzendes Silikon-Klebesystem: auch beim Einsatz dieser Klebesysteme empfiehlt sich eine Kontrolle und ein Ausschleusen fehlerhafter Aufbauten vor der Aushärtung. Jedoch sind die mechanischen Eigenschaften dieser Klebesysteme so eingestellt, dass eine Aufarbeitung der Ausgangsmaterialien durch mechanisches Trennen auch nach der Aushärtung möglich ist. Dieser Vorteil spielt auch im Falle von Reklamationen eine große Rolle.

In particular, a selection of a suitable adhesive system of a UV-curable acrylic-based system or an additive (heat) crosslinking silicone adhesive system, the following should be noted:

• a) UV-curable acrylic-based system: However, irregularities such as air bubbles in the bonding process must be detected and removed here before the UV curing step in order to save the expensive starting materials.
• b) Additive (heat) crosslinking silicone adhesive system: even when using these adhesive systems, it is advisable to check and remove defective structures before curing. However, the mechanical properties of these adhesive systems are adjusted so that a processing of the starting materials by mechanical separation is possible even after curing. This advantage also plays a major role in the case of complaints.

The invention is not limited by the description with reference to the embodiments. Rather, the invention encompasses any novel feature as well as any combination of features, including in particular any combination of features in the claims, even if this feature or combination itself is not explicitly stated in the claims or exemplary embodiments.

This patent application claims the internal priority of German first application with application number 10 2012 015 458.5 , the disclosure of which is hereby fully incorporated by reference.

LIST OF REFERENCE NUMBERS

H

Horizontal direction H

V

Vertical direction V

1

Glue

2

layer thickness

3

display unit

4

sealant

5

input unit

11

adhesive layer

12

packing

31

Top / joint surface

32

top

33

UV curable sealant

41

distance dam

42

spacer frames

51

bearing surface

52

adhesive area

100

display device

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 102012015458 [0051]

Claims (12)

Process for the transparent bonding of transparent layers, in which a curable, transparent adhesive ( 1 ), characterized in that in a first step the transparent adhesive ( 1 ) in still liquid or viscous phase on a predefinable adhesive area ( 52 ) a bearing surface ( 51 ) an input unit ( 5 ) is applied; in a next step, a display unit ( 3 ) with a side edge ( 32 ) on the adhesive layer in a predefinable tilt angle ( 53 ) to the support surface ( 51 ) of the input unit ( 5 ) on the input unit ( 5 ) is placed; in a next step the display unit ( 3 ) around this side edge ( 32 ), as a tilting axis, in the direction of the input unit ( 5 ) is tilted down, wherein by and during the tilting movement of the between the input unit ( 5 ) and the display unit ( 3 ) arranged transparent adhesive ( 1 ) in the form of a propagation wave air bubbles on the predetermined adhesive area ( 52 ) of the input unit ( 5 ). A method according to claim 1, characterized in that the curable, transparent adhesive ( 1 ) is formed with an additive cross-linking two-component silicone and / or a UV-curable acrylate. A method according to claim 1 or 2, characterized in that the curable, transparent adhesive ( 1 ) has a viscosity of at least 300 mPas and at most 10000 mPas in the liquid or viscous state. Method according to one of the preceding claims, characterized in that in the cured state, the transparent adhesive layer ( 11 ) a layer thickness ( 2 ) of at least 0.2 mm and at most 1.5 mm. Method according to one of the preceding claims, characterized in that in the curable, transparent adhesive ( 1 ) transparent fillers ( 12 ) or these are applied after or before the application of the transparent adhesive to the adhesive area ( 52 ), wherein the transparent filler ( 12 ) have an edge length of at least 0.2 mm and at most 0.5 mm. Method according to one of the preceding claims, characterized in that before the application of the transparent adhesive ( 1 ) on the support surface ( 51 ), the bearing surface ( 51 ) by means of a UV-curable sealant ( 33 ) is sealed. Method according to one of the preceding claims, characterized in that after assembly of the display unit ( 3 ) and the input unit ( 5 ) the transparent adhesive layer ( 11 ) is cured by means of temperature radiation and / or UV irradiation. Method according to one of the preceding claims, characterized in that on the connection surface ( 31 ) of the display unit ( 3 ) and / or on the support surface ( 51 ) of the input unit ( 5 ) at least one sealing means ( 4 ), which in the horizontal direction (H), after assembly, the adhesive area ( 51 ) At least in places laterally limited. Method according to claim 8, characterized in that the sealing means ( 4 ) around a UV-curable spacer dam ( 41 ). Method according to claim 8, characterized in that the sealing means ( 4 ) by a spacer frame ( 42 ) or the sealing agent ( 4 ) with a spacer frame ( 42 ) at the connection surface ( 31 ) of the display unit ( 3 ) or on the support surface ( 51 ) of the input unit ( 5 ) is mechanically firmly connected, wherein the spacer frame ( 42 ) the gluing area ( 51 ), after joining, in the horizontal direction (H), completely outlined. Display device ( 100 ) comprising a display unit ( 3 ) as well as an input unit ( 5 ), wherein in the vertical direction (V) between the display unit ( 3 ) and the input unit ( 5 ) at least one transparent, cured adhesive layer ( 11 ), characterized in that the transparent, cured adhesive layer ( 11 ) is free of air bubbles. Display device ( 100 ) according to claim 11, which is produced by means of a method according to at least one of the embodiments claimed here.

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