EP1894060A1

EP1894060A1 - Double-sided adhesive tapes for producing lc displays having light-reflecting and absorbing properties

Info

Publication number: EP1894060A1
Application number: EP05816278A
Authority: EP
Inventors: Marc Husemann; Reinhard Storbeck
Original assignee: Tesa SE
Current assignee: Tesa SE
Priority date: 2005-06-13
Filing date: 2005-12-02
Publication date: 2008-03-05
Also published as: WO2006133746A1; CN101198898A; KR20080027277A; US20090035563A1; JP2008545876A; TW200643520A; DE112005003571A5; DE102005027393A1

Abstract

The invention relates to an adhesive tape, especially for producing or gluing optical liquid crystal displays (LCDs). Said tape comprises an upper face and a lower face with at least one layer of an adhesive compound (c, c') and at least one support film (a) having an upper face and a lower face. The invention is characterized in that the support film has translucent properties.

Description

tesa Aktiengesellschaft Hamburg

description

Double-sided pressure-sensitive adhesive tapes for the production of LC displays with light-reflecting and absorbing properties

The invention relates to double-sided PSA tapes with multilayer carrier structures and with light-reflecting and absorbing properties for the production of liquid crystal displays (LCDs).

Pressure sensitive adhesive tapes are widely used processing aids in the age of industrialization. Especially for use in the computer industry very high demands are placed on pressure-sensitive adhesive tapes. In addition to a low outgassing behavior, the pressure-sensitive adhesive tapes should be usable over a wide temperature range and fulfill certain optical properties.

A field of application are liquid crystal displays (LCDs), which are required for computers, televisions, laptops, PDAs, mobile phones, digital cameras, etc. Fig. 1 shows the concept of a double-sided adhesive tape with a black absorption layer and a reflection layer according to the prior art; where:

1 LCD glass 8 reflection foil

2 double-sided black and white 9 LCD case

Tape 10 black absorbent

3 pressure-sensitive adhesive tape side

4 light source (LED) 11 reflective side

5 light beams 12 visible area

6 double-sided tape 13 "blind" area

7 light guides For the manufacture of LC displays, light-emitting diodes (LEDs) are glued as a light source to the LCD glass. For this purpose, black double-sided pressure-sensitive adhesive tapes are usually used. The purpose of the black coloring is to ensure that no light penetrates from the inside to the outside and vice versa in the region of the double-sided pressure-sensitive adhesive tape.

There are already many concepts to achieve such a black color. On the other hand, one would like to increase the light efficiency of the rear light module, so that preferably double-sided adhesive tapes are used which are black on one side (light-absorbing) and light-reflecting on the other side.

There are many concepts for producing the black page.

A concept for the production of black double-sided pressure-sensitive adhesive tapes consists in the coloring of the carrier material. In the electronics industry, very preferably double-sided pressure-sensitive adhesive tapes with polyester film carriers (PET) are used, since they can be punched very well. The PET supports can be dyed with carbon black or black color pigments to achieve absorption of the light. The disadvantage of this existing concept is the low absorption of the light. In very thin carrier layers, only a relatively small number of carbon black particles or other black pigment particles can be introduced, with the result that complete absorption of the light is not achieved. With the eye and also with more intense light sources (light intensity greater than 600 candela) then the lack of absorption can be determined.

Another concept for producing black double-sided pressure-sensitive adhesive tapes relates to the production of a two-layered support material by means of coextrusion. Carrier films are usually produced by extrusion. Coextrusion coextrudes, in addition to the conventional support material, a second black layer which fulfills the function of light absorption. This concept also has several disadvantages. For example, must be used for the extrusion antiblocking agents, which then lead in the product to the so-called pinholes. These pinholes are optical defects (light transmission at these holes) and negatively affect the operation in the LCD. Another problem is the layer thicknesses, since the two layers are first formed individually in the nozzle and thus can be realized in total only relatively thick carrier layers, with the result that the film is relatively thick and inflexible and thus to the surfaces to be bonded only still badly fits. In addition, the black layer must also be relatively thick, otherwise no complete absorption can be realized. Another disadvantage is the changed mechanical properties of the carrier material, since the black layer has different mechanical properties to the original carrier material (eg pure PET). Another disadvantage for the two-layer version of the carrier material is the different anchoring of the adhesive on the coextruded carrier material. In this case of the embodiment, there is always a weak spot in the double-sided adhesive tape.

In another concept, a black color coat is coated on the support material. This can be done on one or both sides of the carrier. This concept also has several disadvantages. On the one hand, there are also slight defects (pinholes) which are registered by antiblocking agents during the film extrusion process. These are not acceptable for final use in the LC display. Furthermore, the maximum absorption properties do not meet the requirements, since only relatively thin paint layers can be applied. Here, too, one is limited in the layer thicknesses upwards, since otherwise the mechanical properties of the carrier material would change.

There is a trend in the development of LC displays. On the one hand, the LC displays are to become lighter and flatter, and there is a strong demand for ever larger displays with ever higher resolution.

For this reason, the design of the displays has been changed and the light source moves accordingly closer to the LCD panel, with the consequence that the risk increases that more and more light penetrates outward into the edge zone of the LCD panel ("blind area" ) (see Figure 1). With this development, therefore, the requirements for the shading properties (black out properties) of the double-sided adhesive tape, and there is thus a need for new concepts for the production of black adhesive tapes.

On the other hand, the double sided pressure sensitive adhesive tape should be reflective. For this purpose, double-sided pressure-sensitive adhesive tapes are known which have a white or a metallic layer on one side and a black light-absorbing layer on the other side.

However, this concept also has disadvantages, since - if the viewing angle in the LCD display is about 45 ° - light diffusion is perceived, which are caused by the strong reflection of the light. To avoid this - but still increase the light output - a gray reflective layer is needed.

Some concepts for producing gray adhesive tapes are also known in the literature.

For example, e.g. the simplest method to mix gray particles of the adhesive or gray to paint a support side. However, these methods are relatively expensive, since it is difficult to hit the right color shade over the appropriate color particle composition.

The object of the invention is therefore to provide a double-sided pressure-sensitive adhesive tape, which on the one hand is able to absorb light and on the other hand to allow a reflection of light through a gray color page.

In the context of this invention, it has surprisingly been found that this can be achieved in an excellent manner by the degree of filling of the carrier film with white color particles in combination with a black-colored back.

The invention thus relates to double-sided pressure-sensitive adhesive tapes which consist of a single-layered or multilayered support material and two identical or different pressure-sensitive adhesive compositions.

The main claim therefore relates to PSA tape, in particular for the production or bonding of optical liquid crystal data displays (LCDs) comprising a top and a bottom, with at least one layer of a PSA and at least one carrier film having a top and a bottom, wherein the carrier film translucent Features.

Translucency is the translucent property (compared to transparency, which describes transparency). Translucent bodies appear cloudy but may appear clear when in contact with a substrate (clarity of contact).

For the purposes of this invention, the carrier films are referred to in particular as translucent, if they have a transmission, measured by measuring method A, in the range between a minimum of 5% and a maximum of 70%. The subclaims relate to advantageous and / or particularly suitable embodiments of the invention.

It is very advantageous if the pressure-sensitive adhesive tape is configured as a double-sided pressure-sensitive adhesive tape, that is to say is equipped with a pressure-sensitive adhesive layer on both sides.

In the inventive sense, it is further advantageous if one or both pressure-sensitive adhesive layers are transparent.

For a particularly advantageous variant of the adhesive tape according to the invention, at least one black layer is provided on one side of the translucent carrier film.

The black layer is preferably a primer layer, a further PSA layer or a lacquer layer. A sequence of several identical or different black layers, in particular the aforementioned embodiments, can be realized.

For use as an adhesive tape for LCD bonding, it is very advantageous if the pressure-sensitive adhesive tape has light-reflecting properties on the upper side and light-absorbing properties on the underside.

Some preferred embodiments of the pressure-sensitive adhesive tape according to the invention are presented below without wishing to be unnecessarily limited in the inventive idea by the selection of the advantageous examples.

A first preferred variant of the pressure-sensitive adhesive tape according to the invention consists of a translucent carrier film layer (a) filled with white color pigments, a black primer layer (b) and two pressure-sensitive adhesive layers (c) and (c ¹ ), wherein the pressure-sensitive adhesives can be identical or different from one another. This variant is shown in FIG.

In a further preferred embodiment of the invention, the inventive pressure-sensitive adhesive tape has the following product structure, sketched in FIG. 3. Here, the double-sided pressure-sensitive adhesive tape consists of a translucent carrier film layer (a) filled with white color pigments, a black-inked pressure-sensitive adhesive layer (d) and two pressure-sensitive adhesive layers. layers (c) and (c ¹ ), wherein the PSAs may be identical or different from each other.

For a third implementation of a pressure-sensitive adhesive tape according to the invention, this consists of a translucent carrier film layer (a) filled with white color pigments, a black lacquer layer (e) and two pressure-sensitive adhesive layers (c) and (c ¹ ), wherein the pressure-sensitive adhesives can be identical or different from one another.

The carrier film (a) is preferably between 5 and 250 microns, more preferably between 8 and 50 microns, most preferably between 12 and 36 microns thick, dyed white with different degrees of filling to achieve different shades of gray. Due to the proportion of white pigments, the light transmission can be varied and adjusted to a desired value.

It is advantageous if the black layer has a layer thickness between 1 μm and 15 μm, particularly preferably between 3 μm and 10 μm in the case of a primer layer, such as, for example, in variant 1 (FIG 100 microns in the case of a black-inked PSA layer, such as in variant 2 (Figure 3, layer (d)), and / or between 0.01 and 5 microns in the case of a lacquer layer, such as in the variant 3 (Figure 4, Layer (s)).

The pressure-sensitive adhesive layers (c) and (c ¹ ) preferably have a thickness of in each case 5 μm to 250 μm.

The individual layers (b), (c), (c '), (d) and (e) may differ within the double-sided pressure-sensitive adhesive tape with respect to the layer thickness, e.g. different thickness PSA layers are applied.

Carrier film (a)

As a film carrier, in principle, all filmic polymer support can be used, which have a light translucency and are especially colored white. For example, polyethylene, polypropylene, polyimide, polyester, polyamide, polymethacrylate, etc. can be used. In a particularly preferred procedure polyester films are used, most preferably PET films (polyethylene terephthalate). The slides can be relaxed or have one or more preferred directions. Preferred directions are achieved by stretching in one or two directions.

Furthermore, 12 μm thick PET films are particularly advantageous. These films allow very good adhesive properties for the double-sided adhesive tape, since the film is very flexible and can adapt well to the surface roughness of the substrates to be bonded. In addition, when the PET is stained, the translucency is balanced.

To improve the anchoring, it is advantageous if the films are pretreated. For example, the films may be etched (e.g., trichloroacetic acid or trifluoroacetic acid), pretreated with corona or plasma, or provided with a primer (e.g., saran).

Furthermore, the film contains bright, especially white color pigments and / or light, especially white, color-bearing particles. Thus, all light or white coloring pigments or particles known to the person skilled in the art are suitable. Examples are e.g. all common titanium dioxide particles or barium sulfate particles for whitening. The pigments or particles should preferably be smaller in diameter than the final layer thickness of the carrier film.

The degree of whitening is controlled by the film thickness and the transmission. The light transmission of the white film should preferably be at least 5% and at most at 70% in order to achieve a subsequent gray coloration of the page. Furthermore, the degree of filling with white color particles depends on the chemical composition and the total layer thickness of the film.

Optimal colorations can be achieved with 2 to 20 wt .-% of particles based on the film material.

Primer layer (b)

The primer layer (b) can perform various functions. In one embodiment of the invention, the primer layer has the function of substantially completely absorbing the light of the outside light, forming the contrast to produce the gray tone on the opposite side, and improving the anchoring of the adhesive on the substrate. Therefore, in this case, the transmission for the entire double-sided pressure-sensitive adhesive tape is very preferably in a wavelength range of 300-800 nm at <0.5%, more preferably <0.1%, most preferably <0.01%.

In a preferred procedure, this is achieved with a black primer layer. In a binder matrix, black color pigments are mixed in. As primer materials, e.g. Polyesters, polyurethanes, polyacrylates, saran, polyisocyanates, polyaziridines or polymethacrylates are used in conjunction with the paint additives known to the person skilled in the art. In a highly preferred inventive embodiment, carbon black or graphite particles are mixed into the binder matrix as color-carrying particles. In addition to complete absorption of light, this additization additionally achieves electrical conductivity at very high additive content (> 20% by weight), so that the inventive double-sided pressure-sensitive adhesive tapes likewise have antistatic properties.

Pressure Sensitive Adhesives (c) and (c ')

The pressure-sensitive adhesives (c) and (c ') are identical in a preferred embodiment on both sides of the pressure-sensitive adhesive tape. However, in a specific embodiment it may also be advantageous if the pressure-sensitive adhesives (c) and (c ¹ ) differ from one another by the layer thickness and / or the chemical composition. Thus, for example, different adhesive properties can be set in this way. As pressure-sensitive adhesive systems for the inventive double-sided pressure-sensitive adhesive tape, preference is given to using acrylate, natural rubber, synthetic rubber, silicone or EVA adhesive. In the event that the double-sided inventive pressure-sensitive adhesive tape must have a reflection on at least one side (gray side), the pressure-sensitive adhesive must preferably have a high degree of transparency on at least this side.

In principle, however, it is also possible to process all further PSAs known to the person skilled in the art. Reference may be made, for example, to the "Handbook of Pressure Sensitive Adhesive Technology" by Donatas Satas (van Nostrand, New York 1989) for the state of the art for PSAs.

For natural rubber adhesives, the natural rubber is preferably ground to a molecular weight (weight average) not less than about 100,000 daltons, more preferably not less than 500,000 daltons, and additized.

For rubber / synthetic rubber as the starting material for the adhesive wide variations are given. Natural rubbers or synthetic rubbers can be used rubbers or any blends of natural rubbers and / or synthetic rubbers, wherein the natural rubber or natural rubbers in principle from all available qualities such as Crepe, RSS, ADS, TSR or CV types, depending on the required level of purity and viscosity, and the synthetic rubber or the synthetic rubbers from the group of the statistically copolymerized styrene-butadiene rubbers (SBR), the butadiene rubbers (BR), the synthetic polyisoprenes (IR), the butyl rubbers (MR), the halogenated butyl rubbers (XIIR ), the acrylate rubbers (ACM), the ethylene-vinyl acetate copolymers (EVA) and the polyurethanes and / or their blends can be selected.

Further, it is preferable to add to the rubbers, for the purpose of improving the processability, thermoplastic elastomers having a weight proportion of 10 to 50% by weight, based on the total elastomer content. Representative may be mentioned at this point especially the most compatible styrene-isoprene-styrene (SIS) and styrene-butadiene-styrene (SBS) types.

In an inventive preferred procedure (meth) acrylate PSAs are used.

(Meth) acrylate PSAs used according to the invention, which are obtainable by free-radical polymerization, preferably contain at least 50% by weight of at least one acrylic monomer from the group of compounds of the following general formula:

O

R ₁

In this case, the radical R ₁ = H or CH ₃ ; the radical is R ₂ = H or CH ₃ or is selected from the group of branched or unbranched, saturated alkyl groups having 1 to 30 carbon atoms.

The monomers are preferably selected such that the resulting polymers can be used as pressure-sensitive adhesives at room temperature or higher temperatures, in particular in such a way that the resulting polymers have pressure-sensitive adhesive properties. Shanks according to the "Handbook of Pressure Sensitive Adhesive Technology" by Donatas Satas (van Nostrand, New York 1989) own.

In a further inventive embodiment, the (co) monomer composition is selected such that the PSAs can be used as heat-activable PSAs.

The polymers can preferably be obtained by polymerization of a monomer mixture which is composed of acrylic esters and / or methacrylic acid esters and / or their free acids with the formula CH ₂ CHCH (R ₁ ) (COOR ₂ ), where R ₁ = H or CH ₃ and R _{2 is} an alkyl chain of 1-20 C atoms or H.

The molar masses M _w (weight average) of the polyacrylates used are preferably M _w > 200,000 g / mol.

In a very preferred manner, acrylic or methacrylic monomers are used which consist of acrylic and methacrylic acid esters having alkyl groups of 4 to 14 carbon atoms, preferably 4 to 9 carbon atoms. Specific examples, without wishing to be limited by this list, are methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, n-octyl methacrylate, n-nonyl acrylate, lauryl acrylate, stearyl acrylate, behenyl acrylate, and their branched isomers, such as Isobutyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate, isooctyl methacrylate.

Further classes of compounds to be used are monofunctional acrylates or methacrylates of bridged cycloalkyl alcohols, consisting of at least 6 C atoms. The cycloalkyl alcohols may also be substituted, e.g. by C 1-6 -alkyl groups, halogen atoms or cyano groups. Specific examples are cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate and 3,5-dimethyl adamantyl acrylate.

In an advantageous procedure, monomers are used which contain polar groups such as carboxyl radicals, sulfonic and phosphonic acids, hydroxyl radicals, lactam and lactone, N-substituted amide, N-substituted amine, carbamate, epoxy, thiol, alkoxy. Cyan radicals, ethers or the like wear.

Moderate basic monomers are N, N-dialkyl-substituted amides, such as N ₁ N-dimethylacrylamide, N, N-Dimethylmethylmethacrylamid, N-tert-butylacrylamide, N-vinyl pyrrolidone, N-vinyllactam, dimethylanninoethylnethacrylate, dimethylanninoethylacrylate, diethylaminoethylmethacrylate, diethylaminoethylacrylate, N-methylolmethacrylamide, N- (butoxymethyl) methacrylannide, N-methylolacrylamide, N- (ethoxymethyl) acrylamide _J N-isopropylacrylamide, but this list is not exhaustive.

Further preferred examples are hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, allyl alcohol, maleic anhydride, itaconic anhydride, itaconic acid, glyceridyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, 2-butoxyethyl methacrylate, 2-butoxyethyl acrylate, cyanoethyl methacrylate, cyanoethyl acrylate, glyceryl methacrylate, 6-hydroxyhexyl methacrylate, Vinylacetic acid, tetrahydrofurfuryl acrylate, β-acryloyloxypropionic acid, trichloroacrylic acid, fumaric acid, crotonic acid, aconitic acid, dimethylacrylic acid, but this list is not exhaustive.

In a further very preferred procedure, the monomers used are vinyl esters, vinyl ethers, vinyl halides, vinylidene halides, vinyl compounds having aromatic rings and heterocycles in the α-position. Here again, not only a few examples are mentioned: vinyl acetate, vinyl formamide, vinyl pyridine, ethyl vinyl ether, vinyl chloride, vinylidene chloride and acrylonitrile.

Furthermore, photoinitiators with a copolymerizable double bond are used in a further procedure. Suitable photoinitiators are Norrish I and II photoinitiators. Examples include benzoin and an acrylated benzophenone of Fa. UCB (Ebecryl ^® P 36). In principle, all photoinitiators known to those skilled in the art can be copolymerized, which can crosslink the polymer by UV irradiation via a free-radical mechanism. An overview of possible usable photoinitiators which can be functionalized with a double bond is given in Fouassier: "Photoinitiation, Photopolymerization and Photocuring: Fundamentals and Applications", Hanser Verlag, Munich 1995. In addition, Carroy et al., In "Chemistry and Technology of UV and EB Formulation for Coatings, Inks and Paints ", Oldring (ed.), 1994, SITA, London.

In a further preferred procedure, monomers which have a high static glass transition temperature are added to the comonomers described. Suitable components include aromatic vinyl compounds such as styrene, in which the aromatic nuclei preferably from C ₄ - to C consist _δ building blocks and also May contain heteroatoms. Particularly preferable examples are 4-vinylpyridine, N-vinylphthalimide, methylstyrene, 3,4-dimethoxystyrene, 4-vinylbenzoic acid, benzylacrylate, benzylmethacrylate, phenylacrylate, phenylmethacrylate, t-butylphenylacrylate, t-butylphenylmethacrylate, 4-biphenylacrylate and -methacrylate, 2 Naphthyl acrylate and methacrylate and mixtures of those monomers, this list is not exhaustive.

By increasing the aromatic content, the refractive index of the PSA increases and the scattering between the LCD glass and the PSA by e.g. Ambient light is minimized.

For further development, the PSAs may be mixed with resins. Suitable tackifying resins to be added are the previously known adhesive resins described in the literature. Mention may be made representative of the pinene, indene and rosin resins, their disproportionated, hydrogenated, polymerized, esterified derivatives and salts, the aliphatic and aromatic hydrocarbon resins, terpene resins and terpene phenolic resins and C5, C9 and other hydrocarbon resins. Any combination of these and other resins can be used to adjust the properties of the resulting adhesive as desired. In general, all compatible with the corresponding polyacrylate (soluble) resins can be used, in particular reference is made to all aliphatic, aromatic, alkylaromatic hydrocarbon resins, hydrocarbon resins based on pure monomers, hydrogenated hydrocarbon resins, functional hydrocarbon resins and natural resins. The presentation of the state of knowledge in the "Handbook of Pressure Sensitive Adhesive Technology" by Donatas Satas (van Nostrand, 1989) should be noted.

Here, too, transparent and very well compatible with the polymer resins are preferably used to improve the transparency. Hydrogenated or partially hydrogenated resins often have these properties.

In addition, plasticizers (plasticizers), further fillers (such as, for example, fibers, carbon black, zinc oxide, chalk, solid or hollow glass spheres, microspheres of other materials, silicic acid, silicates), nucleating agents, electrically conductive materials, such as, for example, conjugated polymers, may optionally be used , doped conjugated polymers, metal pigments, metal particles, metal salts, graphite, etc., blowing agents, compounding agents and / or anti-aging agents, for example in the form of primary and secondary antioxidants or in the form of light However, protection agents should be added, but then should not affect the reflection on the gray side.

In a further advantageous variant of the invention, the pressure-sensitive adhesive (c ') applied on the black side contains light-absorbing particles, e.g. black color pigments or carbon black or graphite particles as filler.

In addition, crosslinkers and promoters can be mixed for crosslinking. Suitable crosslinkers for electron beam crosslinking and UV crosslinking are, for example, difunctional or polyfunctional acrylates, difunctional or polyfunctional isocyanates (also in blocked form) or difunctional or polyfunctional epoxides. Furthermore, thermally activatable crosslinkers, such as e.g. Lewis acid, metal chelates or multifunctional isocyanates may be added.

For optional crosslinking with UV light, UV-absorbing photoinitiators can be added to the PSAs. Useful photoinitiators which are very useful are benzoin ethers, such as benzoin ethers. B. benzoin methyl ether and benzoin isopropyl ether, substituted acetophenones, such as. For example, 2,2-diethoxyacetophenone (available as Irgacure 651 ^® from. Ciba Geigy ^® ), 2,2-dimethoxy-2-phenyl-1-phenylethanone, Dimeth- oxyhydroxyacetophenone, substituted α-ketols, such as. B. 2-methoxy-2-hydroxypropiophe- non, aromatic sulfonyl chlorides, such as. For example, 2-naphthyl sulfonyl chloride, and photoactive oximes, such as. B. 1-phenyl-1,2-propanedione-2- (O-ethoxycarbonyl) oxime.

The above-mentioned and other usable photoinitiators and others of the type Norrish-I or Norrish-II may contain the following radicals: benzophenone, acetophenone, benzil, benzoin, hydroxyalkylphenone, phenylcyclohexylketone, anthraquinone, trimethylbenzoylphosphine oxide, methylthiophenylmorpholine ketone -, aminoketone, azobenzoin, thioxanthone, Hexarylbisimidazol-, triazine, or fluorenone, wherein each of these radicals additionally with one or more halogen atoms and / or one or more alkoxy groups and / or one or more amino groups or hydroxy groups substituted can. A representative overview is given by Fouassier: "Photoinitiation, Photopolymerization and Photocuring: Fundamentals and Applications", Hanser-Verlag, Munich 1995. In addition, Carroy et al., Chemistry and Technology of UV and EB Formulation for Coatings, Inks and Paints ", Oldring (ed.), 1994, SITA, London. PSA layer (d)

The PSA layer (d) can advantageously fulfill various functions according to the invention. In a preferred embodiment of the invention, layer (d) has the function of substantially completely absorbing the outside light and forming the contrast to produce the gray tone on the opposite side. Therefore, it is advantageous if - especially in the aforementioned case - the transmission of the double-sided pressure-sensitive adhesive tape in a wavelength range of 300 - 800 nm at <0.5%, more preferably at <0.1%, most preferably at <0.01% lies. In the context of this invention, this is preferably achieved with a black PSA layer.

In a highly preferred inventive embodiment, carbon black or graphite particles are mixed into the pressure-sensitive adhesive matrix as black-carrying particles. By means of this additivation, in addition to the (substantially) complete absorption of light, electrical conductivity is additionally achieved with a very high additive content (> 20% by weight), so that the inventive double-sided pressure-sensitive adhesive tapes likewise have antistatic properties.

Advantageously, the pressure-sensitive adhesive composition (c) contains between 2 and 30% by weight of carbon black, more preferably between 5 and 20% by weight of carbon black and most preferably between 8 and 15% by weight of carbon black. The soot has a light-absorbing function. In a preferred embodiment, carbon black powders from Degussa are used. These are commercially available under the trade name Printex ™. For better dispersibility into the PSA it is particularly preferred to use oxidatively after-treated blacks. Furthermore, it may be advantageous for the pressure-sensitive adhesive (c) if, in addition to carbon black, color pigments are added. Thus, as additives, e.g. Blue pigments, e.g. Aniline Black BS890 from Degussa. Furthermore, matting agents can be used as additives.

As pressure-sensitive adhesive matrix, it is possible to use all PSA systems known to the person skilled in the art. Examples of suitable PSA systems are acrylate, natural rubber, synthetic rubber, silicone or EVA compositions. However, it is possible to process the further PSAs known to the person skilled in the art, as listed, for example, in the "Handbook of Pressure Sensitive Adhesive Technology" by Donatas Satas (van Nostrand, New York 1989). For natural rubber adhesives, the natural rubber is preferably ground to a molecular weight (weight average) not less than about 100,000 daltons, preferably not less than 500,000 daltons, and additized.

For rubber / synthetic rubber as the starting material for the adhesive wide variations are given. Natural rubbers or synthetic rubbers or any blends of natural rubbers and / or synthetic rubbers can be used, the natural rubber or the natural rubbers in principle from all available qualities such as Crepe, RSS, ADS, TSR or CV types, depending on the required purity and viscosity level, and the synthetic rubber or synthetic rubbers from the group of random copolymerized styrene-butadiene rubbers (SBR), the butadiene rubbers (BR), the synthetic polyisoprenes (IR), the butyl rubbers (MR), the halogenated Butyl rubbers (XIIR), the acrylate rubbers (ACM), the ethylene-vinyl acetate copolymers (EVA) and the polyurethanes and / or their blends can be selected.

In an inventive preferred embodiment, (meth) acrylate PSAs are used.

(Meth) acrylate PSAs used according to the invention, which are obtainable by free-radical polymerization, preferably contain at least 50% by weight of at least one acrylic monomer selected from the group of compounds of the following general formula:

O

R ₁ In this case, the radical R ₁ = H or CH ₃ ; the radical is R ₂ = H or CH ₃ or is selected from the group of branched or unbranched, saturated alkyl groups having 1 to 30 carbon atoms.

The monomers are preferably chosen such that the resulting polymers can be used as pressure-sensitive adhesives at room temperature or higher temperatures, in particular such that the resulting polymers have pressure-sensitive adhesive properties according to the Handbook of Pressure Sensitive Adhesive Technology by Donatas Satas (van Nostrand, New York 1989).

For the inventive embodiment, it is of particular advantage if the pressure-sensitive adhesive matrix from (d) is identical to the PSA (c) or (c ¹ ). The use of the same pressure-sensitive adhesive strengthens the viscoelastic profile of the layers (d) and (c) or (c ¹ ), which in turn leads to a significant improvement in the adhesive properties (a particular advantage over black lacquer-coated adhesive tapes or black lacquers thick straps equipped adhesive tapes). This can be achieved for acrylate PSAs by a preferred glass transition temperature T _{G of} the polymers of T _G <25 ° C. Accordingly, the monomers are very preferably selected in such a way and the quantitative composition of the monomer mixture is advantageously chosen such that according to the Fox equation (G1) (see TG Fox, Bull. Am. Phys. Soc., 1 (1956) 123) T _G value for the polymer.

Here n represents the number of runs via the monomers used, W _n the mass fraction of the respective monomer n (wt .-%) and T _G , _n the respective glass transition temperature of the homopolymer of the respective monomers n in K.

A further advantage of this invention is that no color-bearing black particles can migrate onto the substrate to be bonded, since the transparent pressure-sensitive adhesive layers lie on the outer sides of the pressure-sensitive adhesive tape. This is a particularly important aspect of the repositionability, since in extreme cases, if incorrectly glued, black residues remain on the LCD film when peeled off accordingly would be, and the entire part would be useless. Within the scope of this invention, this is again achieved in a particularly preferred embodiment in that (d) and (c) or (c ¹ ) have the same pressure-sensitive adhesive matrix.

A further advantage of the identical pressure-sensitive adhesive matrix is the reduced tendency of the dyes or color-bearing particles to migrate into the adhesive layers (c) or (c ¹ ). There is no danger here that the color-bearing particles - for example due to a different polarity - are more soluble in a matrix and migrate there.

Furthermore, the two-layer structure also allows additional functions to be implemented. Thus, in layer (d) it is also possible to add blowing agents which may increase the vibration properties, or further fillers which reduce the production price of the adhesive tape without the adhesive pressure-sensitive adhesive layer (c) or (c ¹ ) being affected thereby.

Color layer (s)

The color layer (e) can fulfill various functions. In one embodiment of the invention, the color layer has the function of substantially completely absorbing the light of the outside light and forming the contrast to produce the gray tone on the opposite side. Therefore, it is advantageous if, especially in this case, the transmission of the entire double-sided pressure-sensitive adhesive tape in a wavelength range of 300-800 nm at <0.5%, more preferably at <0.1%, most preferably at <0.01 % lies. In a preferred embodiment, this is achieved with a black lacquer layer. In a curing binder matrix (preferably thermosetting system, but also radiation-curing system possible) black color pigments are mixed into the paint matrix. As paint materials, for example, polyesters, polyurethanes, polyacrylates or polymethacrylates may be used, especially in conjunction with the paint additives known to the person skilled in the art. In a highly preferred inventive embodiment, carbon black or graphite particles are mixed into the binder matrix as color-carrying particles. By means of this additivation, in addition to the substantially complete absorption of light, electrical conductivity is additionally achieved with a very high additive content (> 20% by weight), so that the inventive double-sided pressure-sensitive adhesive tapes likewise have antistatic properties. Production process for the acrylic PSAs

For the polymerization, the monomers are chosen such that the resulting polymers can be used as PSAs at room temperature or higher temperatures, in particular such that the resulting polymers have pressure-sensitive adhesive properties according to the Handbook of Pressure Sensitive Adhesive Technology by Donatas Satas (van Nostrand, New In order to obtain a preferred glass transition temperature T _{G of} the polymers of T _G <25 ° C., the monomers are very preferably selected in accordance with the above and the quantitative composition of the monomer mixture is advantageously chosen such that the following formula is used Fox equation (G1) (see TG Fox, Bull. Am. Phys Soc., 1 (1956) 123) gives the desired T _G value for the polymer.

Y w _n

4- τ _G , _n (G1)

Here n represents the number of runs via the monomers used, W _n the mass fraction of the respective monomer n (wt .-%) and T _{G n} the respective glass transition temperature of the homopolymer of the respective monomers n in K.

To prepare the poly (meth) acrylate PSAs, conventional free-radical polymerizations are advantageously carried out. Initiator systems which additionally comprise further free-radical initiators for the polymerization, in particular thermally decomposing radical-forming azo or peroxo initiators, are preferably used for the free-radical polymerizations. In principle, however, all acrylates customary to the person skilled in the art are suitable. The production of C-centered radicals is described in Houben Weyl, Methods of Organic Chemistry, Vol. E 19a, pp. 60-147. These methods are preferably applied by analogy. Examples of free radical sources are peroxides, hydroperoxides and azo compounds, as some non-exclusive examples of typical free-radical initiators are potassium peroxodisulfate, dibenzoyl peroxide, cumene hydroperoxide, cyclohexanone peroxide, di-tert-butyl peroxide, Azodiisosäurebutyronitril, Cyclohexylsulfonylacetylperoxid, diisopropyl percarbonate, tert-butyl peroctoate, Benzpinacol , In a very preferred embodiment, the radical initiator used is 1, 1'-azobis (cyclohexanecarboxylic acid nitrile) (Vazo 88 ™ from DuPont) or azoisobutyronitrile (AIBN). The average molecular weights M _w (weight average) of the PSAs formed in the free-radical polymerization are very preferably selected such that they are in a range from 200,000 to 4,000,000 g / mol; PSAs of average molecular weights M _{w of} from 400,000 to 1,400,000 g / mol are produced especially for further use as electrically conductive hotmelt PSAs with resilience. The determination of the average molecular weight is carried out by size exclusion chromatography (GPC) or matrix-assisted laser desorption / ionization mass spectrometry (MALDI-MS).

The polymerization may be carried out neat, in the presence of one or more organic solvents, in the presence of water or in mixtures of organic solvents and water. The aim is to keep the amount of solvent used as low as possible. Suitable organic solvents are pure alkanes (eg hexane, heptane, octane, isooctane), aromatic hydrocarbons (eg benzene, toluene, xylene), esters (eg ethyl acetate, propyl, butyl or hexyl acetate), halogenated hydrocarbons (eg chlorobenzene) , Alkanols (eg, methanol, ethanol, ethylene glycol, ethylene glycol monomethyl ether) and ethers (eg, diethyl ether, dibutyl ether) or mixtures thereof. The aqueous polymerization reactions can be treated with a water-miscible or hydrophilic cosolvent to ensure that the reaction mixture is in the form of a homogeneous phase during the monomer conversion. Advantageously used cosolvents for the present invention are selected from the following group consisting of aliphatic alcohols, glycols, ethers, glycol ethers, pyrrolidines, N-alkylpyrrolidinones, N-alkylpyrrolidones, polyethylene glycols, polypropylene glycols, amides, carboxylic acids and salts thereof, esters, Organosulfides, sulfoxides, sulfones, alcohol derivatives, hydroxy ether derivatives, aminoalcohols, ketones and the like, as well as derivatives and mixtures thereof.

The polymerization time is - depending on the conversion and temperature - between 2 and 72 hours. The higher the reaction temperature can be selected, that is, the higher the thermal stability of the reaction mixture, the lower the reaction time can be selected. To initiate the polymerization, the entry of heat is essential for the thermally decomposing initiators. The polymerization can be initiated for the thermally decomposing initiators by heating to 50 to 160 ° C, depending on the type of initiator.

For the preparation, it may also be advantageous to polymerize the (meth) acrylate PSAs in substance. In particular, the Präpolymerisationstechnik is suitable here. The polymerization is initiated with UV light, but only led to a low conversion about 10 - 30%. Subsequently, this polymer syrup may e.g. are shrink-wrapped in films (in the simplest case, ice cubes) and then polymerized in water to high conversion. These pellets can then be used as acrylate hotmelt adhesive, with film materials which are compatible with the polyacrilate being particularly preferably used for the melting process. Also for this preparation method, the thermally conductive material additives can be added before or after the polymerization.

Another advantageous preparation process for the poly (meth) acrylate PSAs is anionic polymerization. Here, inert solvents are preferably used as the reaction medium, e.g. aliphatic and cycloaliphatic hydrocarbons, or aromatic hydrocarbons.

The living polymer in this case is generally represented by the structure P _L (A) -Me, where Me is a Group I metal such as lithium, sodium or potassium, and P _L (A) is a growing polymer of the acrylate monomers , The molecular weight of the polymer to be produced is controlled by the ratio of initiator concentration to monomer concentration. Suitable polymerization initiators are, for. As n-propyllithium, n-butyllithium, sec-butyllithium, 2-naphthyllithium, cyclohexyllithium or octyllithium, this list is not exhaustive. Furthermore, initiators based on samarium complexes for the polymerization of acrylates are known (Macromolecules, 1995, 28, 7886) and can be used here.

Furthermore, it is also possible to use difunctional initiators, for example 1,1,1,4,4-tetraphenyl-1,4-dilithiobutane or 1,1,1,4,4-tetraphenyl-1,4-dilithioisobutane. Coordinators can also be used. Suitable coinitiators include lithium halides, alkali metal alkoxides or alkylaluminum compounds. In a very preferred version, the ligands and coinitiators are selected so that acrylate monomers, such as n-butyl acrylate and 2-ethylhexyl acrylate, can be polymerized directly and need not be generated in the polymer by transesterification with the corresponding alcohol.

For the preparation of poly (meth) acrylate PSAs having a narrow molecular weight distribution, controlled radical polymerization methods are also suitable. For the polymerization, a control reagent of the general formula is then preferably used:

(I) (II)

wherein R and R ^{1 are} independently selected or the same

- branched and unbranched d- to Ci ₈ -alkyl radicals; C ₃ to C ₈ alkenyl radicals; C ₃ to Cis alkynyl radicals;

Cr to cis alkoxy residues

by Cr to Cis-alkyl radicals substituted by at least one OH group or a halogen atom or a silyl ether; C ₃ to C ₈ alkenyl radicals; C ₃ - to C ₈ -alkynyl radicals; C ₂ -C ₈ -Hetero-alkyl radicals having at least one O atom and / or one NR * group in the carbon chain, where R * may be any (in particular organic) radical,

with at least one ester group, amine group, carbonate group, cyano group, isocyano group and / or epoxy group and / or sulfur-substituted C _r Cis-alkyl radicals, C ₃ -C ₈ -alkenyl radicals, C ₃ -C ₈ -alkynyl radicals; C ₃ -C ₂ -cycloalkyl radicals

- C ₆ -C ₈ - aryl or benzyl radicals

- Represent hydrogen.

Control reagents of type (I) preferably consist of the following further restricted compounds:

Halogen atoms are in this case preferably F, Cl, Br or I, more preferably Cl and Br. Suitable alkyl, alkenyl and alkynyl radicals in the various substituents are both linear and branched chains. Examples of alkyl radicals which contain 1 to 18 carbon atoms are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, 2-pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, t-octyl, Nonyl, decyl, undecyl, tridecyl, tetradecyl, hexadecyl and octadecyl. Examples of alkenyl radicals having 3 to 18 carbon atoms are propenyl, 2-butenyl, 3-butenyl, isobutenyl, n-2,4-pentadienyl, 3-methyl-2-butenyl, n-2-octenyl, n-2-dodecenyl, isododecenyl and oleyl.

Examples of alkynyl radicals having 3 to 18 carbon atoms are propynyl, 2-butynyl, 3-butynyl, n-2-octynyl and n-2-octadecynyl.

Examples of hydroxy-substituted alkyl radicals are hydroxypropyl, hydroxybutyl or hydroxyhexyl.

Examples of halogen-substituted alkyl radicals are dichlorobutyl, monobromobutyl or trichlorohexyl.

A suitable C ₂ -C ₈ -Hetero-alkyl radical having at least one O atom in the carbon chain is, for example, -CH ₂ -CH ₂ -O-CH ₂ -CH ₃ .

As C ₃ -C ₂ cycloalkyl radicals, for example, cyclopropyl, cyclopentyl, cyclohexyl or trimethylcyclohexyl serve.

The C ₆ -C ₈ -aryl radicals used are, for example, phenyl, naphthyl, benzyl, 4-tert-butylbenzyl or further substituted phenyl, such as, for example, ethyl, toluene, xylene, mesitylene, isopropylbenzene, dichlorobenzene or bromotoluene.

The above listings serve only as examples of the respective connection groups and are not exhaustive.

Furthermore, compounds of the following types can also be used as control reagents

(IM) (IV)

where R ^{2 can} also be selected independently of R and R ¹ from the above-mentioned group for these radicals. In the conventional 'RAFT process', polymerisation is usually carried out only to low conversions (WO 98/01478 A1) in order to realize the narrowest possible molecular weight distributions. Due to the low conversions, however, these polymers can not be used as pressure-sensitive adhesives and in particular not as hotmelt PSAs, since the high proportion of residual monomers adversely affects the adhesive properties, the residual monomers in the concentration process contaminate the solvent recycled and the corresponding self-adhesive tapes show a very high outgassing behavior , In order to avoid this disadvantage of lower conversions, in a particularly preferred procedure the polymerization is initiated several times.

As a further controlled radical polymerization method, nitroxide-controlled polymerizations can be carried out. For radical stabilization nitroxides of the type (Va) or (Vb) are used in a favorable procedure:

(Va) (Vb)

where R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ independently of one another are the following compounds or

Atoms are: i) halides, e.g. Chlorine, bromine or iodine ii) linear, branched, cyclic and heterocyclic hydrocarbons having 1 to 20

Carbon atoms which may be saturated, unsaturated or aromatic, iii) esters -COOR ¹¹ , alkoxides -OR ¹² and / or phosphonates -PO (OR ¹³ J ₂ , where R ¹¹ , R ¹² or R ^{13 are} radicals from group ii) stand.

Compounds of the formulas (Va) or (Vb) may also be bound to polymer chains of any kind (primarily in the sense that at least one of the abovementioned radicals represents such a polymer chain) and thus be used for the construction of polyacrylate PSAs. More preferably, controlled regulators are used for the polymerization of compounds of the type:

• 2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (PROXYL), 3-carbamoyl-PROXYL, 2 _J 2 _J-dimethyl-4 5-cyclohexyl-PROXYL _J 3-oxo-PROXYL, 3-Hydroxylimine-PROXYL, 3-aminomethyl-PROXYL, 3-methoxy-PROXYL, 3-t-butyl-PROXYL, 3,4-di-t-butyl-PROXYL

2,2,6,6-tetramethyl-i-piperidinyloxy (TEMPO), 4-benzoyloxy-TEMPO, 4-methoxy-TEMPO, 4-chloro-TEMPO, 4-hydroxy-TEMPO, 4-oxo-TEMPO, 4- Amino-TEMPO, 2,2,6,6, -tetraethyl-i-piperidinyloxy, 2,2,6-trimethyl-6-ethyl-1-piperidinyloxy

N-tert-butyl-1-phenyl-2-methylpropyl nitroxide

N-tert-butyl-1- (2-naphthyl) -2-methylpropyl nitroxide

N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide

N-tert-butyl-1-dibenzylphosphono-2,2-dimethylpropyl nitroxide

N- (1-phenyl-2-methylpropyl) -1-diethylphosphono-1-methylethyl nitroxide

• Di-tert-butyl nitroxide

• diphenyl nitroxide

Tert-butyl tert-amyl nitroxide

A number of other polymerization methods, according to which the PSAs can be prepared in an alternative procedure, can be selected from the prior art:

No. 4,581,429 A discloses a controlled-free radical polymerization process which uses as initiator a compound of the formula R'R "N-O-Y, wherein Y is a free radical species which can polymerize unsaturated monomers, but the reactions generally have low conversions WO 98/13392 A1 describes open-chain alkoxyamine compounds which have a symmetrical substitution pattern EP 735 052 A1 discloses a process for the preparation of thermoplastic elastomers having narrow molecular weight distributions 96/24620 A1 describes a polymerization process in which very specific free-radical compounds, such as, for example, phosphorous-containing nitroxides based on imidazolidine, are used, WO 98/44008 A1 discloses specific nitroxyls which are based on morpholines, piperazinones and piperazinediones 199 49 352 A1 describes heterocyclic Alkoxyamines as regulators in controlled radical polymerizations. Corresponding developments of the Alkoxyamines or the corresponding free nitroxides improve the efficiency for the preparation of polyacrylates.

As a further controlled polymerization method can be used advantageously for the synthesis of the polyacrylate PSA atom transfer radical polymerization (ATRP), wherein as initiator preferably monofunctional or difunctional secondary or tertiary halides and for the abstraction of the (r) halide (s) Cu, Ni , Fe, Pd, Pt, Ru, Os, Rh, Co, Ir, Ag or Au complexes (EP 0 824 111 A1, EP 826 698 A1, EP 824 110 A1, EP 841 346 A1, EP 850 957 A1). The different possibilities of ATRP are further described in US Pat. Nos. 5,945,491, 5,854,364 and 5,789,487.

Coating process, equipment of the carrier material

To prepare the PSA is coated in a preferred procedure from solution to the substrate. To increase the anchoring of the pressure-sensitive adhesive, it is optionally possible to pretreat the layers (a) and / or (e). Thus, e.g. pretreated with corona or with plasma, it can be applied from the melt or from solution, a primer or it can be chemically etched. Especially with a black lacquer layer but the corona power should be minimized, since otherwise pinholes are burned into the film. For the coating of the PSA from solution, heat is applied via e.g. in a drying channel, the solvent is removed and optionally initiated the crosslinking reaction.

The polymers described above can furthermore also be coated as hotmelt systems (ie from the melt). For the production process, it may therefore be necessary to remove the solvent from the PSA. In principle, all methods known to those skilled in the art can be used here. A very preferred method is concentration over a single or twin screw extruder. The twin-screw extruder can be operated in the same direction or in opposite directions. The solvent or water is preferably distilled off over several vacuum stages. In addition, depending on the distillation temperature of the solvent is heated counter. The residual solvent contents are preferably <1%, more preferably <0.5% and very preferably <0.2%. The hotmelt is processed from the melt. For coating as a hotmelt different coating methods can be used. In one embodiment, the PSAs are coated by a roll coating process. Different roll coating processes are described in the Handbook of Pressure Sensitive Adhesive Technology by Donatas Satas (van Nostrand, New York 1989), in another embodiment, a melt die is coated, in another preferred process, extrusion is coated Extrusion coating is preferably carried out with an extrusion die The extrusion dies used can advantageously come from one of the following three categories: T die, fishtail die and stirrup die The individual types differ in the shape of their flow channel also get an orientation.

Furthermore, it may be necessary for the PSA to be crosslinked. In a preferred embodiment is crosslinked with UV and / or electron radiation.

For UV crosslinking is irradiated by short-wave ultraviolet irradiation in a wavelength range of 200 to 400 nm, depending on the UV photoinitiator used, in particular using high-pressure or medium-pressure mercury lamps at a power of 80 to 240 W / cm , The irradiation intensity is adapted to the respective quantum yield of the UV photoinitiator and the degree of crosslinking to be set.

Furthermore, the PSA are crosslinked in an advantageous embodiment with electron beams. Typical irradiation devices which are advantageously used are linear cathode systems, scanner systems or segment cathode systems, if they are electron beam accelerators. A detailed description of the state of the art and the most important process parameters can be found in Skelhome, Electron Beam Processing, in Chemistry and Technology of UV and EB Formulation for Coatings, Inks and Paints, Vol. 1, 1991, SITA, London. The typical acceleration voltages are in the range between 50 kV and 500 kV, preferably 80 kV and 300 kV. The applied waste cans range between 5 to 150 kGy, in particular between 20 and 100 kGy.

Both crosslinking methods or other methods enabling high-energy irradiation can also be used. Furthermore, the invention relates to the use of the inventive double-sided pressure-sensitive adhesive tapes for bonding or production of LC displays. For use as pressure-sensitive adhesive tape, the double-sided pressure-sensitive adhesive tapes may be covered with one or two release films or release papers. In a preferred embodiment, siliconized or fluorinated films or papers, such as glassine, HPDE or LDPE coated papers are used, which in turn are provided with a release layer based on silicones or fluorinated polymers.

In a particularly preferred embodiment, siliconized PET films are used for covering.

Particularly advantageous are the pressure-sensitive adhesive tapes according to the invention for bonding light-emitting diodes (LED) as a light source with the LCD module.

Examples

The invention will be described below without wishing to be unnecessarily limited by the choice of examples.

The following test methods were used.

Test Methods

A .X.ra.OsMssjon

The transmission was measured in the wavelength range from 190 to 900 nm using a Uvikon 923 from the company Biotek Kontron. The measurement is carried out at 23 ⁰ C. Absolute transmission is reported as the value at 550 nm in%, based on the total light absorption (transmission 0% = no light transmission, transmission 100% = complete light transmission).

B ,. RefJektipn.

The reflection test is carried out according to DIN standard 5036 part 3, DIN 5033 part 3 and DIN 5033 part 4. The measuring instrument used was an integrating sphere type LMT (diameter 50 cm) in combination with a digital indicator TYP LMT Tau-p-Meter. The integral measurements are made with a light source according to standard light A and V (A) - matched Si photoelement. It was measured against a glass reference sample. The reflectance is given as the sum of directed and scattered light fractions in%.

Ppjymer.1

A conventional 200 L reactor for free-radical polymerizations was charged with 2400 g of acrylic acid, 64 kg of 2-ethylhexyl acrylate, 6.4 kg of N-isopropylacrylamide and 53.3 kg of acetone / isopropanol (95: 5). After 45 minutes, passing nitrogen gas while stirring, the reactor was heated to 58 ⁰ C and added 40 g of 2,2'-azoisobutyronitrile (AIBN). Subsequently, the outer heating bath was heated to 75 ° C and the reaction was carried out constantly at this external temperature. After 1 h reaction time again 40 g of AIBN was added. After 5 h and 10 h each was diluted with 15 kg acetone / isopropanol (95: 5). After 6 and 8 h 100 g of dicyclohexyl peroxydicarbonate (Perkadox ^® 16, Fa. Akzo Nobel) were each dissolved in 800 g of acetone was added respectively. The reaction was stopped after 24 h reaction time and cooled to room temperature.

RußmasseJ.

In a drum, polymer 1 is diluted with petroleum spirit to a solids content of 30%. Subsequently, with vigorous stirring, 8% by weight of carbon black (Printex ™ 25, Degussa AG), based on the polymer 1, is mixed in. For homogenization, the solution is homogenized for 10 minutes with a homogenizer (Ultraturrax).

Networking

The PSAs are coated from solution onto a siliconized release paper (PE-coated release paper from. Loparex), dried for 10 minutes in a drying oven at 100 ⁰ C and then crosslinked at 25 kGy dose at an accelerating voltage of 200 kV. The mass application was in each case 50 g / m ²

White film production:

Slide a):

A polyethylene terephthalate copolymer (Advansa Melinar ™ B60) was used at 15% by weight.

Titanium dioxide (average diameter 0.25 microns) mixed in a kneader for 2 h at 180 ° C and dried under vacuum. Subsequently, in a single-screw Extruder the film material through a slot die (T-shape, 300 micron slot gap) extruded at 280 ° C. The film is applied to a mirrored chill roll. It is then stretched by tempering to 90 to 95 ⁰ C 3.5 times in the longitudinal direction. Then the film moved into a jig. There is stretched by means of brackets at temperatures between 100 ⁰ C and 110 ⁰ C ^4- fold in the transverse direction. The mixture is then postcured again for 10 s at 210.degree. The white PET film has a total thickness of 36 μm. The absolute transmission lies after measurement according to test method A at 8%.

Slide b):

A polyethylene terephthalate copolymer (Advansa Melinar ™ B60) was blended with 20% by weight.

Titanium dioxide (average diameter 0.25 microns) mixed in a kneader for 2 h at 180 ° C and dried under vacuum. Subsequently, in a single-screw extruder, the film material was extruded through a slot die (T-shape, 300 μm slot gap) at 280 ^° C. The film is applied to a mirrored chill roll. It is then stretched by tempering to 90 to 95 ° C 3.5 times in the longitudinal direction. Then the film moved into a jig. There is stretched by means of brackets at temperatures between 100 ° C and 110 ° C 4-fold in the transverse direction. The mixture is then postcured again for 10 s at 210.degree. The white PET film has a total thickness of 36 μm. The absolute transmission lies after measurement according to test method A at 5%.

Slide c):

A polyethylene terephthalate copolymer (Advansa Melinar ™ B60) was used at 12% by weight.

Titanium dioxide (average diameter 0.25 microns) mixed in a kneader for 2 h at 180 ° C and dried under vacuum. Subsequently, in a single-screw extruder, the film material was extruded through a slot die (T-shape, 300 μm slot gap) at 280 ° C. The film is applied to a mirrored chill roll. It is then stretched by tempering to 90 to 95 ⁰ C 3.5 times in the longitudinal direction. Then the film moved into a jig. There is stretched by means of brackets at temperatures between 100 ° C and 110 ° C 4-fold in the transverse direction. The mixture is then postcured again for 10 s at 210.degree. The white PET film has a total thickness of 23 μm. The absolute transmission is 17% after measurement according to test method A. Foil (color painting):

Production of the black color:

The black paint was made from 4 parts Hardener CVL no. 10 (from Dainippon Ink and Chemicals, Inc.) and 35 parts Daireducer ™ V No. 20 (from Dainippon Ink and Chemicals, Inc.) and 100 parts Panacea ™ CVL-SPR805 paint (from Dainippon Ink and Chemicals, Inc., a vinyl chloride / vinyl acetate based paint).

Slide 1 (black / white):

On film a), the black color is applied flat and dried for 48 hours at 45 ° C. The black lacquer-coated side is full-surface and evenly black. The application is about 2 g / m ² .

example 1

The film 1 is coated in the lamination process with the polymer 1 on both sides with 50 g / m ² .

Example 2

The film b) is coated in the lamination process with the polymer 1 on one side with 50 g / m ² , on the opposite side first with carbon black 1 (50 g / m ² ) and then with the polymer 1 again with 50 g / m ² ,

Example 3

The film c) is coated in the lamination process with the polymer 1 on one side at 50 g / m ² and on the opposite side with soot mass 1 (50 g / m ² ).

Results

Examples 1 to 3 were tested according to test methods A and B. The test method A provides information about the total transmission of the double-sided adhesive tape and thus information about the degree of blackness of the light-absorbing side. In contrast, the reflection (test B) must not exceed values of 65%, otherwise the gray side is too reflective and the gray side would appear white. The results for the inventive examples are shown in Table 1.

From the results of Table 1, it can be seen that Examples 1 to 3 have excellent light absorption properties. Furthermore, Examples 1 to 3 show that the reflection and thus the gradation of the white / black shading can be controlled by the filler content. The white film with the lowest filler content and the thinnest layer thickness reflects the least and has the grayest color. In contrast, Example 2 demonstrates that the film b) with the highest white particle content has the lowest gray color.

Claims

claims

1. pressure-sensitive adhesive tape, in particular for the production or bonding of optical liquid crystal data displays (LCDs), comprising a top and a bottom, with at least one layer of a pressure-sensitive adhesive and at least one carrier film having a top and a bottom, characterized in that the carrier film has translucent properties.

2. Pressure-sensitive adhesive tape according to claim 1, characterized in that the pressure-sensitive adhesive tape is provided on both sides with a pressure-sensitive adhesive layer.

3. Pressure-sensitive adhesive tape according to at least one of claims 1 or 2, characterized in that one or both pressure-sensitive adhesive layers are transparent.

4. Pressure-sensitive adhesive according to at least one of the preceding claims, characterized in that the carrier film has a thickness of between 5 and 250 μm, preferably between 8 and 50 μm, very preferably between 12 and 36 μm, in particular has a thickness of 12 μm.

5. Pressure-sensitive adhesive tape according to at least one of the preceding claims, characterized in that a black layer is provided on one side of the translucent carrier film.

6. Pressure-sensitive adhesive tape according to at least one of the preceding claims, characterized in that the black layer is a primer layer, a further PSA layer or a lacquer layer.

7. Pressure-sensitive adhesive tape according to at least one of the preceding claims, characterized in that it has light-reflecting properties on the upper side and light-absorbing properties on the underside.

8. pressure-sensitive adhesive tape according to at least one of the preceding claims, characterized in that the translucency is effected by the presence of white color pigments in the carrier film, in particular to a proportion of 2 to 20 wt .-%.

9. Pressure-sensitive adhesive tape according to claim 6, characterized in that the black layer has a layer thickness between a) 1 and 15, especially between 3 and 10 μm in the case of a primer layer, b) 10 and 100 μm in the case of a PSA layer, c) 0.01 and 5 microns in the case of a lacquer layer.

10. Use of a pressure-sensitive adhesive tape according to at least one of the preceding claims for the production or bonding of optical liquid crystal data displays (LCDs).

11. Use according to claim 10 for the bonding of LCD glasses.

12. Liquid crystal data display device comprising a pressure-sensitive adhesive tape according to at least one of claims 1 to 9.