EP1652002A1 - Ecran de retroprojection stable et son procede de production - Google Patents

Ecran de retroprojection stable et son procede de production

Info

Publication number
EP1652002A1
EP1652002A1 EP04719970A EP04719970A EP1652002A1 EP 1652002 A1 EP1652002 A1 EP 1652002A1 EP 04719970 A EP04719970 A EP 04719970A EP 04719970 A EP04719970 A EP 04719970A EP 1652002 A1 EP1652002 A1 EP 1652002A1
Authority
EP
European Patent Office
Prior art keywords
rear projection
projection screen
layer
screen according
scattering
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP04719970A
Other languages
German (de)
English (en)
Inventor
Markus Parusel
Jann Schmidt
Herbert Groothues
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Roehm GmbH Darmstadt
Original Assignee
Roehm GmbH Darmstadt
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Roehm GmbH Darmstadt filed Critical Roehm GmbH Darmstadt
Publication of EP1652002A1 publication Critical patent/EP1652002A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B21/00—Projectors or projection-type viewers; Accessories therefor
    • G03B21/54—Accessories
    • G03B21/56—Projection screens
    • G03B21/60—Projection screens characterised by the nature of the surface
    • G03B21/62—Translucent screens
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/02—Diffusing elements; Afocal elements
    • G02B5/0205—Diffusing elements; Afocal elements characterised by the diffusing properties
    • G02B5/021—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures
    • G02B5/0226—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures having particles on the surface
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/02—Diffusing elements; Afocal elements
    • G02B5/0273—Diffusing elements; Afocal elements characterized by the use
    • G02B5/0278—Diffusing elements; Afocal elements characterized by the use used in transmission

Definitions

  • the present invention relates to stable rear projection screens comprising at least one light-scattering polymethyl methacrylate layer and to processes for producing these rear projection screens.
  • Back projection technology can be used to make information accessible to a wide audience.
  • the construction of such a system consists of an imaging surface that is illuminated from the back with a projector and thus provides the information.
  • This technique takes place e.g. Use in control rooms (power plants, rail traffic) to make it easier for those responsible to keep track of the complex processes so that control errors can be avoided.
  • Another application is scoreboards in e.g. Sports stadiums and motor racing races. Here, the course and status of the event is communicated to the viewers, even if they are at a greater distance from the actual events.
  • This type of information transfer is also used in e.g. TV sets, open-plan and home cinemas, but also used as advertising media at trade fairs, in shop windows and shops.
  • BESTATIGUNGSKOPIE Furthermore, this technology is also used to transmit information in presentations and in flight simulators, where the virtual environment is mapped as realistically as possible on the cockpit panes.
  • rear projection panels and foils which have scattering media, such panels containing particles with a refractive index different from the matrix.
  • the panels and foils are also suitable for rear projection, but do not combine the entire range of the requirement profile, so that only a part of the requirements for a screen are met.
  • the projection surfaces must, for example, have a very quiet, clear and high-resolution image reproduction because the viewer has to record the information over a longer period of time (example: control room, home cinema, etc.).
  • known scattering media such as barium sulfate and titanium dioxide can be used to produce plates and foils which have a high light scattering angle
  • Umbrellas are also known which contain plastic particles as scattering media.
  • Document JP 07234304 describes a mixture of cross-linked acrylate / styrene beads (14 ⁇ m) in a transparent plastic.
  • a disadvantage of the rear projection screens set out above is that their mechanical stability depends on the thickness of the light-scattering layer, a particularly high image sharpness being improved by a relatively thin light-scattering layer.
  • multi-layer rear projection screens are also known which, in addition to the light-scattering layer, additionally have a carrier layer, so that even larger screens have sufficient mechanical stability.
  • Such umbrellas can be freely installed in a room, for example by means of ceiling fixings.
  • films or advertisements can be effectively presented by means of rear projection technology, for example at trade fairs or in exhibition rooms.
  • Multi-layer rear projection screens are known for example from JP11179856, EP-A-0 561 551, WO 98/45753 and US 6,411, 436.
  • the document WO 98/45753 describes rear projection screens which have a scattering layer, a diffusion layer and a plastic substrate. According to FIG. 6, the diffusion layer can also be arranged on the surface of the substrate that lies opposite the scattering layer.
  • the problem is that the imaging performance of such a structure is relatively poor, which is already indicated in the document itself.
  • US Pat. No. 6,411,436 describes rear projection screens which have a neutral gray layer. This is a colored layer, which according to US Pat. No. 6,411,436 should lead to an improvement in the imaging performance. However, replicas do not show such an advantage. The gloss of this neutral gray layer is not shown.
  • Japanese patent publication JP11179856 describes multilayer boards with at least one layer which comprises a polymethyl methacrylate matrix and crosslinked polymethyl methacrylate beads as scattering / matting agents, the proportion of the beads being in the range from 0.5 to 25% by weight ,
  • the document EP-A-0 561 551 describes a multilayer plate with a scattering layer made of a mixture of a transparent polymer and spherical particles (2-15 ⁇ m).
  • known rear projection screens provided with scattering media often show suboptimal imaging properties.
  • the known screens have a relatively low image sharpness or a relatively unfavorable brightness distribution.
  • many umbrellas do not meet the mechanical requirements, scratches in particular having an optically disadvantageous effect.
  • Another object of the invention was to provide rear projection screens which have a particularly uniform brightness distribution.
  • the rear projection screens should have the highest possible mechanical stability. Scratches on the screen should not be visible or only slightly. In particular, damage should have little or no influence on the imaging ability of the screen.
  • the invention was based on the object of providing rear projection screens which can be produced particularly easily. So the rear projection screens should be able to be produced in particular by extrusion.
  • Another object of the present invention was to provide rear projection screens which can be easily adapted in size and shape to the requirements.
  • the images on the rear projection screens should be particularly rich in contrast.
  • Another object of the invention was that the rear projection screens have a high durability, in particular a high resistance to UV radiation or weathering.
  • the present invention was also based on the object of providing rear projection screens which, based on their imaging properties, only reflect to a small extent.
  • the diffusion layer has an intensity half-value angle greater than or equal to 15 ° and the support layer has an intensity half-value angle less than or equal to 6.5 °, the support layer having a gloss R ⁇ o less than or equal to 70, rear projection screens comprising at least one scattering layer comprising scattering particles and at least succeed to provide a support layer which, with high stability and high image quality, enables low reflections of the projected image in space.
  • the rear projection screens of the present invention allow high definition and resolution of the projected image.
  • the rear projection screens made available according to the present invention have a particularly uniform brightness distribution.
  • the rear projection screens of the present invention show high mechanical stability. Scratches are not or only slightly visible on the screen.
  • images projected onto the rear projection screens according to the invention are very quiet. As a result, displays can be viewed without fatigue over a long period of time. D Furthermore, reflections of the projected image in space can be reduced by the present inventions.
  • the rear projection screens of the present invention show a non-glossy, matt surface profile.
  • the shape of the surface structure can be adjusted differently without affecting the optical parameters, apart from the gloss. This can reduce reflections that adversely affect the image on the screen.
  • the rear projection screens of the present invention can be manufactured particularly easily.
  • the rear projection screens can be produced in particular by extrusion.
  • the rear projection panels according to the invention show a high resistance to weathering, in particular to UV radiation.
  • the size and shape of the rear projection screens can be adapted to the needs.
  • the rear projection screen comprises a carrier layer which generally has plastics with optically outstanding properties.
  • plastics include, in particular, polycarbonates, cycloolefinic polymers and poly (meth) acrylates, poly (meth) acrylates being preferred.
  • Polycarbonates are known in the art. Polycarbonates can be considered formally as polyesters from carbonic acid and aliphatic or aromatic dihydroxy compounds. They are easily accessible through implementation of diglycols or bisphenols with phosgene or carbonic acid diesters in polycondensation or transesterification reactions.
  • bisphenols include, in particular, 2,2-bis (4-hydroxyphenyl) propane (bisphenol A), 2,2-bis (4-hydroxyphenyl) butane (bisphenol B), 1,1-bis (4-hydroxyphenyl ) cyclohexane (bisphenol C), 2,2'-methylenediphenol (bisphenol F), 2,2-bis (3,5-dibromo-4-hydroxyphenyl) propane (tetrabromobisphenol A) and 2,2-bis (3,5- dimethyl-4-hydroxyphenyl) propane (tetramethylbisphenol A).
  • bisphenol A 2,2-bis (4-hydroxyphenyl) propane
  • bisphenol B 2,2-bis (4-hydroxyphenyl) butane
  • bisphenol C 1,1-bis (4-hydroxyphenyl ) cyclohexane
  • bisphenol F 2,2'-methylenediphenol
  • 2,2-bis (3,5-dibromo-4-hydroxyphenyl) propane tetrabromobisphenol A
  • Such aromatic polycarbonates are usually produced by interfacial polycondensation or transesterification, details of which are given in Encycl. Polym. Be. Engng. 11, 648-718.
  • the bisphenols are emulsified as an aqueous, alkaline solution in inert organic solvents, such as, for example, methylene chloride, chlorobenzene or tetrahydrofuran, and reacted with phosgene in a step reaction.
  • organic solvents such as, for example, methylene chloride, chlorobenzene or tetrahydrofuran
  • Amines are used as catalysts, and phase transfer catalysts are also used for sterically hindered bisphenols.
  • the resulting polymers are soluble in the organic solvents used.
  • the properties of the polymers can be varied widely by the choice of the bisphenols. If different bisphenols are used at the same time, block polymers can also be built up in multi-stage polycondensation.
  • Cycloolefinic polymers are polymers that can be obtained using cyclic olefins, in particular polycyclic olefins.
  • Cyclic olefins include, for example, monocyclic olefins, such as cyclopentene, cyclopentadiene, cyclohexene, cycloheptene, cyclooctene and alkyl derivatives of these monocyclic olefins having 1 to 3 carbon atoms, such as methyl, ethyl or propyl, such as methylcyclohexene or dimethylcyclohexene, and acrylate and / or methacrylate derivatives of these Links.
  • cycloalkanes with olefinic side chains can also be used as cyclic olefins, such as, for example, cyclopentyl methacrylate.
  • Bridged polycyclic olefin compounds are preferred. These polycyclic olefin compounds can have the double bond both in the ring, these are bridged polycyclic cycloalkenes, and in side chains. These are vinyl derivatives, allyloxycarboxy derivatives and (meth) acryloxy derivatives of polycyclic cycloalkane compounds. These compounds may also have alkyl, aryl or aralkyl substituents.
  • Exemplary polycyclic compounds are, without being restricted thereby, bicyclo [2.2.1] hept-2-ene (norbomene), bicyclo [2.2.1] hept-2,5-diene (2,5-norbomadiene), ethyl -bicyclo [2.2.1] hept-2-ene (ethyl norbornene), ethylidene bicyclo [2.2.1] hept-2-ene (ethyliden-2-norbornene), phenylbicyclo [2.2.1] hept-2-ene, bicyclo [4.3 .0] nona-3,8-diene, tricyclo [4.3.0.1 2 ' 5 ] -3-decene, tricyclo [4.3.0.1 2.5 ] -3,8-decen- (3,8-dihydrodicyclopentadiene), tricyclo [4.4.0.1 2 ' 5 ] -3-undecene, tetracyclo [4.4.
  • the cycloolefinic polymers are produced using at least one of the cycloolefinic compounds described above, in particular the polycyclic hydrocarbon compounds.
  • other olefins which can be copolymerized with the aforementioned cycloolefinic monomers can be used in the preparation of the cycloolefinic polymers. These include Ethylene, propylene, isoprene, butadiene, methylpentene, styrene and vinyl toluene.
  • olefins especially the cycloolefins and polycycloolefins, can be obtained commercially.
  • many cyclic and polycyclic olefins are available through Diels-Alder addition reactions.
  • the cycloolefinic polymers can be prepared in a known manner, as described in Japanese Patents 11818/1972, 43412/1983, 1442/1986 and 19761/1987 and Japanese Patent Laid-Open Nos. 75700/1975, 129434/1980, 127728/1983, 168708/1985, 271308/1986, 221118/1988 and 180976 / 1990 and in European patent applications EP-A-0 6 610 851, EP-A-0 6 485 893, EP-A-0 6 407 870 and EP-A-0 6 688 801.
  • the cycloolefinic polymers can be polymerized in a solvent, for example, using aluminum compounds, vanadium compounds, tungsten compounds or boron compounds as a catalyst. It is believed that, depending on the conditions, in particular the catalyst used, the polymerization can take place with ring opening or with opening of the double bond.
  • cycloolefinic polymers by radical polymerization, using light or an initiator as a radical generator.
  • This type of polymerization can take place both in solution and in bulk.
  • Another preferred plastic comprises poly (meth) acrylates. These polymers are generally obtained by free-radical polymerization of mixtures which contain (meth) acrylates.
  • the term (meth) acrylates encompasses methacrylates and acrylates and mixtures of the two.
  • Aryl (meth) acrylates such as benzyl (meth) acrylate or
  • Phenyl (meth) acrylate where the aryl radicals can in each case be unsubstituted or substituted up to four times;
  • Cycloalkyl (meth) acrylates such as 3-vinylcyclohexyl (meth) acrylate,
  • Hydroxylalkyl (meth) acrylates such as 3-hydroxypropyl (meth) acrylate,
  • Glycol di (meth) acrylates such as 1,4-butanediol di (meth) acrylate,
  • Pentaeryth rittri (meth) acrylate
  • these mixtures contain at least 40% by weight, preferably at least 60% by weight and particularly preferably at least 80% by weight, based on the weight of the monomers, of methyl methacrylate.
  • compositions to be polymerized can also have further unsaturated monomers which are associated with Methyl methacrylate and the aforementioned (meth) acrylates are copolymerizable.
  • 1-alkenes such as 1-hexene, 1-heptene
  • branched alkenes such as vinylcyclohexane, 3,3-dimethyl-1-propene, 3-methyl-1-diisobutylene, 4-methylpentene-1;
  • Styrene substituted styrenes with an alkyl substituent in the side chain, such as. B. ⁇ -methylstyrene and ethylstyrene, substituted styrenes with an alkyl substituent on the ring, such as vinyltoluene and p-methylstyrene, halogenated styrenes such as monochlorostyrenes, dichlorostyrenes, tribromostyrenes and tetrabromostyrenes;
  • Heterocyclic vinyl compounds such as 2-vinylpyridine, 3-vinylpyridine, 2-methyl-5-vinylpyridine, 3-ethyl-4-vinylpyridine, 2,3-dimethyl-5-vinylpyridine, vinylpyrimidine, vinylpiperidine, 9-vinylcarbazole, 3-vinylcarbazole, 4-vinylcarbazole, 1-vinylimidazole, 2-methyl-1-vinylimidazole, N-vinylpyrrolidone, 2-vinylpyrrolidone, N-vinylpyrrolidine, 3-vinylpyrrolidine, N-vinylcaprolactam, N-vinylbutyrolactam, vinyloxolane, vinylfuran, vinylthiophene, vinylthiophene, vinylthiolthene hydrogenated vinyl thiazoles, vinyl oxazoles and hydrogenated vinyl oxazoles;
  • Maleic acid derivatives such as maleic anhydride, methyl maleic anhydride, maleimide, methyl maleimide; and dienes such as divinylbenzene.
  • these comonomers are used in an amount of 0 to 60% by weight, preferably 0 to 40% by weight and particularly preferably 0 to 20% by weight, based on the weight of the monomers, the compounds being used individually or can be used as a mixture.
  • the polymerization is generally started with known radical initiators.
  • the preferred initiators include the azo initiators well known in the art, such as AIBN and 1, 1-azobiscyclohexane carbonitrile, and peroxy compounds, such as methyl ethyl ketone peroxide, acetylacetone peroxide, dilauryl peroxide, tert-butyl per-2-ethylhexanoate, ketone peroxide, methyl isobutyl ketone peroxide, and peroxide compounds , tert-butyl peroxybenzoate, tert-butyl peroxyisopropyl carbonate, 2,5-bis (2-ethylhexanoyl-peroxy) -2,5-dimethylhexane, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxy-3,5,5-trimethylhexanoate, Dicumyl peroxide, 1, 1-bis (tert-butylperoxy) cyclohe
  • These compounds are often used in an amount of 0.01 to 3% by weight, preferably 0.05 to 1% by weight, based on the weight of the monomers.
  • the aforementioned polymers can be used individually or as a mixture.
  • Various polycarbonates, poly (meth) acrylates or cycloolefinic polymers can also be used here, which differ, for example, in molecular weight or in the monomer composition.
  • the carrier layers according to the invention can be produced, for example, from molding compositions of the aforementioned polymers.
  • Thermoplastic molding processes such as extrusion or injection molding, are generally used here.
  • the weight average molecular weight M w of the homopolymers and / or copolymers to be used according to the invention as a molding composition for the production of the support layers can vary within wide limits, the molecular weight usually being matched to the intended use and the processing mode of the molding composition. In general, however, it is in the range between 20,000 and 1,000,000 g / mol, preferably 50,000 to 500,000 g / mol and particularly preferably 80,000 to 300,000 g / mol, without any intention that this should impose a restriction.
  • This size can be determined, for example, by means of gel permeation chromatography.
  • the carrier layer can be produced by casting chamber processes.
  • suitable (meth) acrylic mixtures are given in a mold and polymerized.
  • Such (meth) acrylic mixtures generally have the (meth) acrylates set out above, in particular methyl methacrylate.
  • the (meth) acrylic mixtures can contain the copolymers set out above and, in particular for adjusting the viscosity, polymers, in particular poly (meth) acrylates.
  • the weight average molecular weight M w of the polymers produced by casting chamber processes is generally higher than the molecular weight of polymers used in molding compositions. This results in a number of known advantages. In general, the weight average molecular weight of polymers which are produced by casting chamber processes is in the range from 500,000 to 10,000,000 g / mol, without any intention that this should impose any restriction.
  • Preferred backing layers produced by the casting chamber process can be obtained commercially from Röhm GmbH & Co. KG.
  • the molding compositions to be used for the production of the carrier layers and the acrylic resins may contain all kinds of conventional additives. These include antistatic agents, antioxidants, mold release agents, flame retardants, lubricants, dyes, flow improvers, fillers, light stabilizers and organic phosphorus compounds such as phosphites, phosphorinanes, phospholanes or phosphonates, pigments, weathering protection agents and plasticizers.
  • additives include antistatic agents, antioxidants, mold release agents, flame retardants, lubricants, dyes, flow improvers, fillers, light stabilizers and organic phosphorus compounds such as phosphites, phosphorinanes, phospholanes or phosphonates, pigments, weathering protection agents and plasticizers.
  • the amount of additives is limited to the application.
  • molding compositions comprising poly (meth) acrylates are commercially available from Cyros Inc. USA under the trade name Acrylite®.
  • Preferred molding compositions comprising cycloolefinic polymers can be obtained under the trade names ⁇ Topas from Ticona and ⁇ Zeonex from Nippon Zeon.
  • Polycarbonate molding compositions are available, for example, under the trade name ®Makrolon from Bayer or ®Lexan from General Electric.
  • the carrier layer particularly preferably comprises at least 80% by weight, in particular at least 90% by weight, based on the total weight of the carrier layer, of poly (meth) acrylates, polycarbonates and / or cycloolefinic polymers.
  • the carrier layer particularly preferably consists of polymethyl methacrylate, it being possible for the polymethyl methacrylate to contain customary additives.
  • the carrier layer has a gloss R 6 ° measured at an angle of 60 ° less than or equal to 70, preferably less than or equal to 60, in particular less than or equal to 40, particularly preferably less than or equal to 30 and very particularly preferably less than or equal to 15.
  • This low gloss of the carrier layer can be created by various methods.
  • a textured glass plate can be used. Such glass plates can be created by etching. As a result, the cast plate produced has a low gloss, which decreases with increasing etching of the glass plate.
  • a roller can be used which comprises a structured surface. Furthermore, a structured paper can be arranged between the smoothing roller and the extruded plate. The stronger the structure of the roller or of the paper, the less the gloss of the surface produced thereby.
  • a film can be laminated onto a smooth plastic plate to create a corresponding surface structure.
  • the carrier layer can have a multilayer structure.
  • the carrier layer can contain plastic particles with a size in the range from 20 to 100 ⁇ m, which have no or only a slight refractive index difference to the plastic of the carrier layer. The higher the proportion of these plastic particles, the lower the gloss.
  • a relatively thin layer to reduce the gloss can be applied to the carrier layer, for example by coextrusion or lamination, which has a relatively high proportion of scattering particles.
  • concentration of the scattering particles in the relatively thin layer to reduce the gloss is preferably in the range from 0.5 to 20% by weight, preferably in the range from 0.5 to 10% by weight and particularly preferably in the range from 0.5 up to 6% by weight, the mean particle size V 50 of the scattering particles used being preferably less than or equal to 150 ⁇ m, in particular less than or equal to 100 ⁇ m, particularly preferably less than or equal to 50 ⁇ m and very particularly preferably less than or equal to 30 ⁇ m.
  • the thickness of the thin layer for reducing the gloss can in particular be in the range from 10 ⁇ m to 500 ⁇ m, preferably in the range from 20 ⁇ m to 250 ⁇ m and very particularly preferably in the range from 50 ⁇ m to 150 ⁇ m.
  • the surface of the carrier layer preferably has an average surface roughness Rz in the range from preferably 2 ⁇ m to 45 ⁇ m, in particular 3 to 40 ⁇ m, preferably 5 to 35 ⁇ m. These values are measured on the surface of the carrier layer that lies opposite the scattering layer.
  • the average surface roughness Rz can be determined in accordance with DIN 4768 using a Talysurf 50 measuring device from Taylor Hobson, where R z is the average roughness depth that results from the mean values of the individual roughness depths of five successive individual measuring sections in the roughness profile.
  • the carrier layer exhibits an intensity half-value angle of less than or equal to 6.5 °, in particular less than or equal to 6 °, preferably less than or equal to 5 ° and particularly preferably less than or equal to 3 °. These values are measured by separating the scattering layer from the rear projection screen, the previously described surface with a low gloss R ⁇ or the carrier layer being covered by the measurement. This low scatter is achieved, inter alia, by the fact that the carrier layer contains no or only a small amount of scattering media, this information relating to the entire carrier layer, so that part of the carrier layer, for example a thin layer laminated or coextruded thereon, has a relatively high level Can have proportion of scattering particles.
  • the thickness of the support layer can be in a wide range, depending on the stability requirements for the rear projection screen.
  • the thickness of the carrier layer is in the range from 0.5 mm to 100 mm, preferably 1 mm to 10 mm, particularly preferably 1.5 mm to 6 mm and very particularly preferably 2 mm to 4 mm.
  • the carrier layer has a transmission of greater than 85%, preferably greater than 88% and very particularly preferably greater than 90%. These values are measured without the scatter layer.
  • the carrier layer shows a yellowness index of less than 2 and preferably less than 1. These values are measured without the scattering layer.
  • the scattering layer has an intensity half-value angle greater than or equal to 15 °, in particular greater than or equal to 25 °, the scattering being generated in particular by particles contained in the scattering layer.
  • the scattering layer of the rear projection screen according to the present invention preferably has 2 to 60% by weight, in particular 3 to 55% by weight and particularly preferably 6 to 48% by weight, based on the weight of the scattering layer, of scattering particles, which preferably are spherical.
  • the term spherical denotes that the scattering particles preferably have a spherical shape, it being obvious to the person skilled in the art that, due to the production methods, scattering particles with a different shape may also be present, or that the shape of the scattering particles may deviate from the ideal spherical shape ,
  • the term spherical means that the ratio of the largest dimension of the scattering particles to the smallest dimension is a maximum of 4, preferably a maximum of 2, these dimensions being measured in each case by the center of gravity of the scattering particles. At least 70%, particularly preferably at least 90%, based on the number of scattering particles, is preferably spherical.
  • Such scattering particles are known per se and can be obtained commercially, the light refraction taking place at the phase boundary of the scattering particles with the matrix plastic of the scattering layer.
  • the refractive index of the scattering particles has a refractive index n 0 measured at the Na-D line (589 nm) and at 20 ° C., which differs by 0.02 to 0.2 units from the refractive index n 0 of the matrix plastic of the scattering layer.
  • the scattering particles can, for example, have an average diameter (weight average) in the range from 0.1 to 40 ⁇ m, in particular from 5 to 30 ⁇ m.
  • plastic particles and particles made of inorganic materials such as aluminum hydroxide, aluminum-potassium silicate (mica), aluminum silicate (kaolin), barium sulfate (BaSO 4 ), Calcium carbonate, magnesium silicate (talc).
  • inorganic materials such as aluminum hydroxide, aluminum-potassium silicate (mica), aluminum silicate (kaolin), barium sulfate (BaSO 4 ), Calcium carbonate, magnesium silicate (talc).
  • plastic particles are particularly preferred.
  • the plastic particles that can be used according to the invention are not particularly limited.
  • the type of plastic from which the plastic particles are produced is largely uncritical.
  • Preferred plastic particles have an average diameter (weight average) in the range from 5 to 35 ⁇ m, preferably in the range from 8 to 25 ⁇ m. 75% of the plastic particles are advantageously in the range from 5 to 35 ⁇ m.
  • the particle size and the particle size distribution can be determined using a laser extinction method.
  • a Galai-CIS-1 from L.O.T. GmbH are used, the measurement method for determining the particle size is included in the user manual.
  • the plastic particles that can be used according to the invention are not particularly limited.
  • the type of plastic from which the plastic particles are produced is largely uncritical, with the light refraction taking place at the phase boundary of the plastic beads with the matrix plastic.
  • the spherical plastic particles preferably comprise crosslinked polystyrene, polysilicon and / or crosslinked poly (meth) acrylates.
  • Preferred plastic particles that are used as scattering agents contain silicones. Such particles are obtained, for example, by hydrolysis and polycondensation of organotrialkoxysilanes and / or tetraalkoxysilanes, which have the formulas R 1 Si (OR 2 ) 3 and Si (OR 2 ) 4
  • R 1 represents, for example, a substituted or unsubstituted alkyl group, an alkenyl group or a phenyl group
  • R 2 of the hydrolyzable alkoxy group represents an alkyl group such as methyl, ethyl or butyl or an alkoxy-substituted hydrocarbon group such as 2-methoxyethyl or 2 Represents ethoxyethyl.
  • Exemplary organotrialkoxysilanes are methyltrimethoxysilane, methyltriethoxysilane, methyl-n-propoxysilane, methyltriisopropoxysilane and methyltris (2-methoxyethoxy) silane.
  • Spreading agents made of silicone that are particularly preferably used in the present invention are available from GE Bayer Silicones under the trade names TOSPEARL® 120 and TOSPEARL® 3120.
  • Preferred plastic particles are composed of: b1) 25 to 99.9 parts by weight of monomers which have aromatic groups as substituents, such as styrene, ⁇ -methylstyrene, ring-substituted styrenes, phenyl (meth) acrylate, benzyl (meth) acrylate, 2-phenylethyl (meth) acrylate, 3-phenylpropyl (meth) acrylate or vinyl benzoate; and b2) 0 to 60 parts by weight of an acrylic and / or methacrylic acid ester with 1 to 12 carbon atoms in the aliphatic ester radical, which can be copolymerized with the monomers b1), examples of which are: methyl (meth) acrylate, ethyl ( meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate,
  • Mixtures from which the plastic particles are produced particularly preferably have at least 80% by weight of styrene and at least 0.5% by weight of divinylbenzene.
  • the scattering particles can be produced by emulsion polymerization, as described, for example, in EP-A 342 283 or EP-A 269 324, very particularly preferably by polymerization in the organic phase, as described, for example, in German patent application P 43 27 464.1, with the latter Polymerization technology particularly narrow particle size distributions or, in other words, particularly small deviations of the particle diameter from the average particle diameter occur.
  • Plastic particles are particularly preferably used which have a temperature resistance of at least 200 ° C., in particular of at least 250 ° C., without this being intended to impose a restriction.
  • temperature-resistant means that the particles are essentially not subject to thermal degradation. Thermal degradation leads to undesirably cause discoloration, so that the plastic material becomes unusable.
  • Particularly preferred particles are available, among others, from Sekisui under the trade names ⁇ Techpolymer SBX-6, ⁇ Techpolymer SBX-8 and ⁇ Techpolymer SBX-12.
  • the spherical particles have a size in the range from 15 ⁇ m to 35 ⁇ m.
  • at least 60% of the spherical particles particularly preferably have a diameter of at least 15 ⁇ m and at most 30% of the scattering beads have a diameter of more than 25 ⁇ m.
  • at most 80% of these spherical particles have a size in the range from 15 ⁇ m to 25 ⁇ m.
  • these particles are present in the plastic matrix in a uniformly distributed manner without any significant aggregation or aggregation of the particles occurring. Evenly distributed means that the concentration of particles within the plastic matrix is essentially constant.
  • the scattering layer of the rear projection screens has at least two particles (A) and (B), which differ in size, without any intention that this should impose a restriction.
  • the particles (A) generally have an average diameter (weight average) in the range from 0.1 to 40 ⁇ m, preferably 1 to 35 ⁇ m, preferably 2 to 30 ⁇ m, in particular 3 to 25 ⁇ m, particularly preferably 4 to 20 ⁇ m and entirely particularly preferably 5 to 15 ⁇ m and a refractive index difference to the plastic matrix in the range of 0.02 to 0.2
  • the particles (B) generally having an average diameter (weight average) in the range from 10 to 150 ⁇ m, preferably 15 to 70 ⁇ m and particularly preferably 30 to 50 ⁇ m and a refractive index difference to the plastic matrix in the range from 0 to 0.2.
  • the weight ratio of the scattering particles (A) to the particles (B) is preferably in the range from 1:10 to 10: 1, in particular 1: 5 to 5: 1, particularly preferably 1: 3 to 3: 1 and very particularly preferably 1: 2 to 2: 1.
  • the difference between the mean particle size V 50 of the scattering particles (A) and the particles (B) is preferably at least 5 ⁇ m, in particular at least 10 ⁇ m, the particles (B) being larger than the scattering particles (A).
  • the particle size and the particle size distribution can be determined using a laser extinction method.
  • a Galay-CIS from LOT GmbH can be used for this, the measurement method for determining the particle size and the particle size distribution being contained in the user manual.
  • the average particle size of 5 V o is derived from the weight of the Mediän agent, wherein 50 wt .-% of the particles less than or equal to 50 wt .-% of the particles are greater than or equal to this value.
  • the light-scattering layer includes a plastic matrix in addition to the spherical particles.
  • Plastics for producing the matrix of the scattering layer are generally known. These include in particular polycarbonates, cycloolefinic polymers and poly (meth) acrylates, poly (meth) acrylates being preferred. These plastics have previously been described in detail.
  • the scattering layer particularly preferably has polymethyl methacrylate (PMMA).
  • PMMA polymethyl methacrylate
  • the light-scattering polymethyl methacrylate layer comprises at least 30% by weight, based on the weight of the light-scattering layer, of polymethyl methacrylate.
  • Polymethyl methacrylates are generally obtained by radical polymerization of mixtures containing methyl methacrylate.
  • these mixtures contain at least 40% by weight, preferably at least 60% by weight and particularly preferably at least 80% by weight, based on the weight of the monomers, of methyl methacrylate.
  • these mixtures for the production of polymethyl methacrylates can contain further (meth) acrylates which can be copolymerized with methyl methacrylate. These monomers have been set out above.
  • the matrix of the light-scattering layer can contain further polymers in order to modify the properties.
  • these include polyacrylonitriles, polystyrenes, polyethers, polyesters, polycarbonates and polyvinyl chlorides. These polymers can be used individually or as a mixture, copolymers also being derivable from the aforementioned polymers.
  • the matrix of the scattering layer has at least 70, preferably at least 80 and particularly preferably at least 90% by weight, based on the weight of the matrix of the light-scattering layer, of polymethyl methacrylate.
  • the poly (meth) acrylates of the matrix of the light-scattering layer have a refractive index measured at the Na-D line (589 nm) and at 20 ° C in the range from 1.46 to 1.54.
  • the thickness of the light-scattering layer is generally in the range from 0.05 to 4 mm, preferably 0.05 to 2 mm, preferably 0.1 to 1 mm, in particular 0.2 to 0.8 mm, without any intention that this should impose a restriction ,
  • the concentration of the spherical particles Cp, the thickness of the scattering layer ds and the particle size of the spherical particles D P can be chosen such that the ratio of the product of the concentration of the spherical particles Cp and the thickness of the scattering layer to the third Potency of the particle size of the spherical particles c P * d s / D P 3 is in the range from 0.001 to 0.015% by weight * mm / ⁇ m 3 , preferably 0.0025 to 0.009% by weight * mm / ⁇ m 3
  • the ratio of the square of average surface roughness of the polymethyl methacrylate layer Rz to the third power of the particle size of the spherical particles Rz 2 / Dp 3 can preferably be in the range from 0.0002 ⁇ m "1 to 0.1300 ⁇ m " 1 , in particular 0.0009 ⁇ m “1 to 0.0900 ⁇ m " 1 and preferably 0.00025 ⁇ m "1 to 0.0600 ⁇ m “ 1 and particularly preferably 0.0025 ⁇ m "1 to 0.0600 ⁇ m " 1 .
  • the ratio of the concentration of the spherical particles c to the thickness of the scattering layer ds Cp / ds is greater than or equal to 2.5% by weight / mm, in particular greater than or equal to 4% by weight / mm.
  • the scattering layer preferably has a gloss R 85 ° of less than or equal to 60, in particular less than or equal to 50.
  • the ratio of the thickness of the scattering layer ds to the particle size of the spherical particles D P ds / Dp is preferably in the range from 1 to 500, in particular 1 to 250, preferably 2.5 to 250 and particularly preferably 2.5 to 150, without this resulting in a Restriction should take place.
  • the average surface roughness Rz of the scattering layer is preferably in the range from 5 ⁇ m to 50 ⁇ m, in particular 5 to 25 ⁇ m, preferably 6 to 35 ⁇ m, in particular 15 ⁇ m to 50 ⁇ m, particularly preferably 6 ⁇ m to 30 ⁇ m ,
  • This scratch resistance can be determined in accordance with DIN 53799 and DIN EN 438 by a visual assessment of a damaged surface, the damage being caused by a diamond which acts on the surface with different forces.
  • the scattering layer can be produced by known processes, thermoplastic molding processes being preferred. After the addition of the particles, light-scattering layers can be produced from the molding compositions described above by conventional thermoplastic molding processes.
  • a twin-screw extruder is used for the extrusion or for the production of molding compound granules containing scattering pearls.
  • the plastic particles are preferably transferred to the melt in the extruder.
  • the spreading layer can be produced in a two-stage process in which a sidefeeder compounding according to the invention is followed by extrusion of the film or plate on a single-screw extruder and intermediate granulation.
  • the granules obtained via the twin-screw extruder can contain particularly high proportions of scattering pearls, so that projection screens with different scattering pearls content can be produced in a simple manner by mixing with molding compositions without scattering pearls.
  • a one-step process can also be carried out, in which the spherical plastic particles are compounded into the melt as described on a twin-screw extruder, which may be followed by a pressure-increasing unit (e.g. melt pump), to which the extrusion nozzle is directly connected, with which a flat product is formed.
  • a pressure-increasing unit e.g. melt pump
  • rear projection screens with a particularly low yellow index can be obtained by the measures described above.
  • the screens can also be produced by injection molding, but the process parameters or the mold must be selected such that a surface roughness is achieved in the area according to the invention.
  • the matrix is preferably compounded with the scattering particles by means of a twin-screw extruder; a single-screw extruder can also be used in the actual plate extrusion, without any intention that this should impose a restriction.
  • the surface roughness R z of the scattering layer can be influenced by varying various parameters which are dependent on the type of production. These include the temperature of the melt during extrusion, whereby a higher temperature of the melt leads to a rougher surface. However, it should be noted that the temperature of the melt depends on the exact composition of the molding compound. The temperature of the melt is generally in the range from 150 to 300 ° C., preferably in the range from 200 to 290 ° C. These temperatures refer to the temperatures of the melt at the nozzle outlet.
  • the surface roughness can be influenced via the gap between the rollers used to smooth the plates.
  • a calender comprises, for example, 3 rolls in an L arrangement, the molding compound being guided from the nozzle onto the nip between roll 1 and roll 2 and looping around the roll 2 by 60-180 °, the gap between roll 2 and roll 3 smoothes the surfaces. If the gap between roller 2 and roller 3 is set to plate thickness, the scattering particles on the plate surface are pressed into the matrix, which makes the surface appear smoother.
  • this gap is set somewhat larger than the plate thickness of the plate to be produced in order to achieve a rougher surface, this value being in the range from 0.1 to 2 mm above plate thickness, preferably 0.1 to 1.5 mm above plate thickness, without this there should be a restriction.
  • the surface roughness is influenced by the particle size and the plate thickness, the exemplary embodiments setting out the dependencies.
  • the scattering layer can be connected to the carrier layer by known methods. These include, for example, gluing or laminating.
  • both layers can be obtained in one step via coextrusion.
  • the scattering layer can serve as a boundary of the casting chamber, as a result of which the carrier layer is polymerized onto the scattering layer.
  • the quotient of the thickness of the carrier layer and the thickness of the scattering layer is preferably in the range from 1: 2 to 100: 1, in particular 1: 1 to 50: 1 and preferably 3: 1 to 10: 1.
  • the plastics for producing the carrier layer and / or the scattering layer can optionally be given a mechanically more stable finish by means of an impact modifier.
  • the impact modifiers of this type are well known, for example the production and construction of impact-modified polymethacrylate molding compositions are described, inter alia, in EP-A 0 113 924, EP-A 0 522 351, EP-A 0 465 049 and EP-A 0 683 028 described. Corresponding modifiers are also known for other plastics.
  • Preferred impact-resistant molding compositions which can be used to produce the matrix generally have 50-99% by weight, in particular 70-98% by weight, of polymethyl methacrylates. These polymethyl methacrylates have been previously described.
  • the polymethyl methacrylates used to produce impact-modified molding compositions are obtained by radical polymerization of mixtures which contain 80 to 100% by weight, preferably 90 to 98% by weight, methyl methacrylate and optionally 0 to 20% by weight. %, preferably 2-10% by weight of further free-radically polymerizable comonomers, which were also listed above.
  • Particularly preferred comonomers are among other C to C4-alkyl (meth) acrylates, especially methyl acrylate, ethyl acrylate or butyl methacrylate.
  • the average molecular weight M w of the polymethyl methacrylates which can be used to produce the impact-modified matrix is preferably in the range from 90,000 g / mol to 200,000 g / mol, in particular 100,000 g / mol to 150,000 g / mol.
  • Preferred impact-resistant molding compositions which can be used to prepare the matrix contain 0.5 to 55, preferably 1 to 45, particularly preferably 2 to 40, in particular 3 to 35% by weight of an impact modifier which is an elastomer phase composed of crosslinked polymer particles.
  • the impact modifier can be obtained in a manner known per se by bead polymerization or by emulsion polymerization.
  • Preferred impact modifiers are crosslinked particles with an average particle size in the range from 50 to 1000 nm, preferably 60 to 500 nm and particularly preferably 80 to 120 nm.
  • Such particles can be obtained, for example, by the radical polymerization of mixtures which generally have at least 40% by weight, preferably 50 to 70% by weight, of methyl methacrylate,
  • a crosslinking monomer e.g. B. a multifunctional (meth) acrylate, such as. B. allyl methacrylate and
  • Comonomers that can be copolymerized with the aforementioned vinyl compounds.
  • the preferred comonomers include C 1 -C 4 alkyl (meth) acrylates, such as ethyl acrylate or butyl methacrylate, preferably methyl acrylate, or other vinyl-polymerizable monomers such as, for example, B. styrene.
  • the mixtures for producing the abovementioned particles can preferably comprise 0 to 10, preferably 0.5 to 5% by weight of comonomers.
  • Particularly preferred impact modifiers are polymer particles which have a two, particularly preferably a three-layer core-shell structure.
  • core-shell polymers are described, inter alia, in EP-A 0 113 924, EP-A 0 522 351, EP-A 0 465 049 and EP-A 0 683 028.
  • Particularly preferred impact modifiers based on acrylate rubber have the following structure, among others:
  • Core polymer with a methyl methacrylate content of at least 90% by weight, based on the weight of the core.
  • Shell 1 polymer with a butyl acrylate content of at least 80% by weight, based on the weight of the first shell.
  • Shell 2 polymer with a methyl methacrylate content of at least 90% by weight, based on the weight of the second shell.
  • the core and the shells can each contain other monomers in addition to the monomers mentioned. These were set out above, with particularly preferred comonomers having a crosslinking effect.
  • a preferred acrylate rubber modifier can have the following structure: Core: copolymer of methyl methacrylate (95.7% by weight), ethyl acrylate (4% by weight) and allyl methacrylate (0.3% by weight) S1: copolymer of butyl acrylate (81.2% by weight), styrene (17.5% by weight) and allyl methacrylate (1.3% by weight) S2: copolymer of methyl methacrylate (96% by weight) and ethyl acrylate (4% by weight)
  • the ratio of core to shell (s) of the acrylate rubber modifiers can vary within wide ranges.
  • the weight ratio core to shell K / S is preferably in the range from 20:80 to 80:20, preferably from 30:70 to 70:30 to modifiers with one shell or the ratio of core to shell 1 to shell 2 K / S1 / S2 in the range from 10:80:10 to 40:20:40, particularly preferably from 20:60:20 to 30:40:30 for modifiers with two shells.
  • the particle size of the core-shell modifiers is usually in the range from 50 to 1000 nm, preferably 100 to 500 nm and particularly preferably from 150 to 450 nm, without any intention that this should impose a restriction.
  • Such impact modifiers are commercially available from Mitsubishi under the trade name METABLEN® IR 441.
  • impact-modified molding compounds can also be obtained.
  • the screen has a transmission greater than or equal to 25%, in particular greater than or equal to 40% and particularly preferably greater than or equal to 55%, these values being achieved in particular by screens without contrast-enhancing dyes.
  • the molding composition or the resin for producing the carrier layer and / or Scatter layer can be colored.
  • This measure can surprisingly improve the contrast.
  • Dyes and / or soot known per se are particularly suitable for coloring.
  • Particularly preferred dyes are commercially available. These include, among others, ⁇ Sandoplast Rot G and ⁇ Sandoplast Gelb 2G each from Clariant and ⁇ Macrolex Grün 5B and ⁇ Macrolex Violett 3R each from Bayer. The concentration of these dyes depends on the desired color impression and the thickness of the plate.
  • this concentration per dye is generally in the range from 0 to 0.8% by weight, preferably 0.000001 to 0.4% by weight, based on the total weight of the colored molding composition without scattering beads .
  • the sum of the dye concentrations is preferably in the range from 0 to 1% by weight, preferably 0.0001 to 0.6% by weight, based on the total weight of the colored molding composition without scattering beads.
  • the loss of transmission can at least partially be compensated for by stronger projectors.
  • the screen preferably shows a yellowness index of less than or equal to 12, in particular less than or equal to 10, without this being intended to impose a restriction.
  • the screen has a scattering power greater than or equal to 0.15, in particular greater than or equal to 0.35, without this being intended to impose a restriction.
  • the surface of the polymethyl methacrylate plates according to the invention have a matt appearance when reflected on the lens.
  • the characterization can be carried out by measuring the gloss with a reflectometer according to DIN 67530.
  • the gloss of the plates is preferably at an angle of 85 ° below 50, particularly preferably below 40 and very particularly preferably below 30.
  • the size and shape of the rear projection screen of the present invention is not limited. In general, however, the screen has a rectangular, tabular shape, since images are usually displayed in this format.
  • Such a rear projection screen preferably has a length in the range from 25 mm to 10000 mm, preferably from 50 to 3000 mm and particularly preferably from 200 to 2000 mm.
  • the width of this particular embodiment is generally in the range from 25 to 10000 mm, preferably from 50 to 3000 mm and particularly preferably from 200 to 2000 mm. In order to provide a particularly large projection area, several of these screens can be combined.
  • the screen has a particularly high weather resistance in accordance with DIN EN ISO 4892, Part 2 -Artificial weathering or irradiation in devices, filtered xenon arc radiation.
  • the average roughness Rz was determined in accordance with DIN 4768 using a Talysurf 50 measuring device from Taylor Hobson.
  • the transmission ⁇ 06 5/2 ° was determined in accordance with DIN 5036 using a Lambda 19 measuring device from Perkin Elmer.
  • the yellowness index ⁇ D65 / - ⁇ o ° was determined in accordance with DIN 6167 with a Lambda 19 measuring device from Perkin Elmer.
  • the gloss R85 ° was measured at 85 ° according to DIN 67530 with a Dr. Long laboratory reflectometer from Dr. For a long time.
  • the scattering power and the intensity half-value angle were determined in accordance with DIN 5036 using an LMT goniometer measuring station GO-T-1500 from LMT.
  • Projection system dichroic mirror and lens system
  • picture elements 2359296 pixels (1024x768) * 3
  • brightness 1200 ANSI lumens
  • contrast 400: 1
  • image illumination 85%
  • color rendering 24 bit with 16.7 million colors
  • H 15-92 kHz
  • V 50-85 Hz
  • lamp 150 watt UHE
  • video resolution 750 TV lines
  • Table 1
  • An aluminum hydroxide Pickering stabilizer was used to produce spherical plastic particles, which was prepared by precipitation from aluminum sulfate and soda solution immediately before the actual polymerization started.
  • 16 g Al2 (SO 4 ) 3, 0.032 g complexing agent (Trilon A) and 0.16 g emulsifier (emulsifier K 30 available from Bayer AG; sodium salt of a cis-paraffin sulfonate) were first dissolved in 0.81 distilled water , A 1 N sodium carbonate solution was then added to the aluminum sulfate dissolved in water with stirring at a temperature of about 40 ° C., the pH then being in the range from 5 to 5.5. This procedure resulted in a colloidal distribution of the stabilizer in the water.
  • the aqueous phase was transferred to a beaker. 110 g of methyl methacrylate, 80 g of benzyl methacrylate and 10 g of allyl methacrylate, 4 g of dilauryl peroxide and 0.4 g of tert-butyl per-2-ethylhexanoate were added. This mixture was dispersed for 15 minutes at 7000 rpm using a disperser (Ultra-Turrax S50N-G45MF, from Janke and Kunkel, Staufen).
  • the reaction mixture was poured into the reactor, which was preheated to the appropriate reaction temperature of 80 ° C., and polymerized at about 80 ° C. (polymerization temperature) for 45 minutes (polymerization time) with stirring (600 rpm). This was followed by a post-reaction phase of 1 hour at an internal temperature of approx. 85 ° C. After cooling to 45 ° C., the stabilizer was converted into water-soluble aluminum sulfate by adding 50% sulfuric acid. To work up the beads, the suspension obtained was filtered through a commercially available filter cloth and dried in a heating cabinet at 50 ° C. for 24 hours. The size distribution was examined by laser extinction methods. The particles had an average size V50 of 18.6 ⁇ m. The beads had a spherical shape, with no fibers being found. Coagulation did not occur. The particles obtained in this way are referred to below as plastic particles B1.
  • An aluminum hydroxide Pickering stabilizer was used to produce spherical plastic particles, which was prepared by precipitation from aluminum sulfate and soda solution (sodium carbonate solution) immediately before the actual polymerization started. For this purpose, 38 ions were initially used. Water, 400 g of aluminum sulfate and 8 g of complexing agent (Trilon A) were introduced with stirring (330 rpm) using an impeller stirrer in a 100 L V4A vessel flushed with N 2 with breakwater, Ni-Cr-Ni thermocouple and circulation heating.
  • Trilon A complexing agent
  • a monomer mixture consisting of 6900 g of methyl methacrylate, 3000 g of styrene, 100 g of glycol dimethacrylate, 200 g of dilauroyl peroxide, 20 g of tert-butyl per-2-ethylhexanoate and 50 g of 2-ethylhexylthioglycolate is then also added at room temperature.
  • the heating phase takes place up to a temperature of 80 ° C., the reactor being sealed pressure-tight at an internal boiler temperature of 40 ° C. and the N 2 introduction being shut off. Over the next 115 minutes the internal temperature rises to approx. 87 ° C and the pressure increases from 0.70 to 0.92 bar.
  • the reaction mixture was heated to about 87-88 ° C. and stirred at this temperature for about an hour, the stirring speed being reduced to 200 rpm.
  • the kettle was let down at a temperature of 46 ° C. and then 400 ml of 50% strength sulfuric acid were added, as a result of which the aluminum hydroxide is converted into the soluble aluminum sulfate and the suspension polymer thereby precipitates out.
  • the suspension obtained was filtered through a stoneware filter with a filter cloth, washed neutral and dried at 50 ° C. in an oven for about 20 hours.
  • the size distribution was examined by laser extinction methods.
  • the particles had an average size V 50 of 40.5 ⁇ m.
  • the beads had a spherical shape, with no fibers being found. Coagulation did not occur.
  • the particles obtained in this way are referred to below as plastic particles B2.
  • a diffusion layer was made by extrusion.
  • a scattering bead compound composed of 6% by weight of plastic particles B2, 6% by weight of plastic particles based on styrene with a particle size V 50 of approximately 8.4 ⁇ m, sold under the trade name ⁇ Techpolymer SBX-8 by Sekisui are commercially available, and 88% by weight of one from Röhm GmbH & Co.
  • KG extruded PMMA molding compound (copolymer of 97 wt .-% methyl methacrylate and 3 wt .-% methyl acrylate) extruded to a plastic plate with a thickness of 0.5 mm.
  • An extruder 060 mm from BREYER was used.
  • the temperature of the melt at the nozzle outlet was generally 270 ° C.
  • the smoothing unit was adjusted so that the surface was as rough as possible.
  • the surface roughness Rz was 15.0 ⁇ m.
  • the carrier layer 1 was produced by extrusion of a PMMA molding compound (copolymer of 97% by weight methyl methacrylate and 3% by weight methyl acrylate) available from Röhm GmbH & Co. KG.
  • the thickness of the carrier layer 1 was 3 mm.
  • An embossing roller was used here.
  • the support layers 2 to 5 were produced by coextrusion.
  • a 2 mm layer of a PMMA molding compound (copolymer of 97% by weight methyl methacrylate and 3% by weight methyl acrylate) available from Röhm GmbH & Co. KG was coextruded with an approx. 100 ⁇ m layer which, in addition to a PMMA molding compound (copolymer of 97% by weight methyl methacrylate and 3% by weight methyl acrylate) available from Röhm GmbH & Co. KG had different proportions of plastic particles B1.
  • the thickness of the carrier layer was 2 mm.
  • the different proportions of the 100 ⁇ m thick coextrusion layer of plastic particles B1 are shown in Table 2. Table 2
  • the support layers 6 to 9 were produced by coextrusion.
  • a 2 mm layer of a PMMA molding compound (copolymer of 97% by weight methyl methacrylate and 3% by weight methyl acrylate) available from Röhm GmbH & Co. KG was coextruded with an approx. 100 ⁇ m layer which, in addition to a PMMA molding compound (copolymer of 97% by weight methyl methacrylate and 3% by weight methyl acrylate) available from Röhm GmbH & Co. KG had different proportions of plastic particles B2.
  • the thickness of the Backing layers were 2 mm.
  • the different proportions of the 100 ⁇ m thick coextrusion layer of plastic particles B2 are shown in Table 3.
  • the carrier layer 10 was produced in the same way as the carrier layer 1, although a conventional smooth roller without embossing was used.
  • the carrier layers 11 to 14 were produced in accordance with the carrier layers 2 and 3, the thickness of the carrier layers being varied. The details can be found in Table 4. Table 4
  • the carrier layers 15 to 18 were produced in accordance with the carrier layers 6 and 7, the thickness of the carrier layers being varied. The details can be found in Table 5. Table 5
  • the properties of the carrier layers produced are shown in Table 6, the roughness Rz and the gloss at 60 ° R60 ° being determined in each case on the rougher surface provided with an embossing or 100 ⁇ m plastic particles B1 or B2 comprising coextrusion layer. The opposite surface was smooth. Table 6
  • the roughness Rz and the gloss of the support layers 11 and 12 corresponded to the values of the support layer 2.
  • the roughness Rz and the gloss of the support layers 13 and 14 corresponded to the values of the support layer 3.
  • the roughness Rz and the gloss of the support layers 15 and 16 corresponded to the values of the carrier layer 6.
  • the roughness Rz and the gloss of the carrier layers 17 and 18 corresponded to the values of the carrier layer 7.
  • Rear projection screens were produced by joining the scattering layer with the various carrier layers 1 to 10.
  • the rear projection screen according to the invention can also be used for the 3D projection of images or films.
  • two projections are superimposed as image sources, which in principle transmit the same image content, but which is at a certain distance, e.g. B. were added at eye relief.
  • a commonly used principle is e.g. B. the polarization process.
  • the viewer views the image through glasses which are each equipped with appropriate polarization filters for the right and left eyes.
  • the human brain processes the two different image impressions into a three-dimensional image perception.
  • the rear projection screens according to the invention can be made in the form of a plate or film, comprising the carrier layer and the light-scattering layer, preferably from coextruded polymethyl methacrylate plastic, the path difference due to the optical birefringence altogether at most 25 nm, preferably at most 15 , particularly preferably at most 5 nm.
  • extrusion process always causes a certain orientation of the molecular chains in the extrusion direction. This alignment leads to birefringence properties which partially depolarize the polarized light of the two projections, which is of course undesirable.
  • the extruded polymethyl methacrylate plastic for rear projection screens intended for 3D projection is therefore particularly preferably subjected to a thermal aftertreatment after the extrusion. During thermal aftertreatment, shrinkage occurs, which largely negates the alignment of the polymer molecules. The result is that the birefringence property originally present in the material is greatly reduced.
  • the thermal aftertreatment of extruded polymethyl methacrylate plastic in the form of foils or plates which are provided for rear projection screens for 3D projection can, for. B. in the range of 110 to 190, preferably 120 to 160 ° C for 5 minutes to 24 hours, preferably 10 minutes to 2 hours, depending on the material composition and material thickness.
  • the thermally induced shrinking process can be carried out with material lying or preferably hanging.
  • the path difference can e.g. B. be measured using a polarization microscope in combination with an Ehringhaus tilt compensator.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Elements Other Than Lenses (AREA)
  • Overhead Projectors And Projection Screens (AREA)
  • Laminated Bodies (AREA)
  • Compositions Of Macromolecular Compounds (AREA)

Abstract

La présente invention concerne des écrans de rétroprojection présentant au moins une couche de dispersion contenant des particules de dispersion et au moins une couche de support. Ces écrans de rétroprojection se caractérisent en ce que la couche de dispersion présente un angle de demi-valeur d'intensité >/= 15 DEG et la couche de support présente un angle de demi-valeur d'intensité </= 6,5 DEG , la couche de support présentant une brillance R60 DEG </= 70.
EP04719970A 2003-08-04 2004-03-12 Ecran de retroprojection stable et son procede de production Withdrawn EP1652002A1 (fr)

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DE10336131A DE10336131A1 (de) 2003-08-04 2003-08-04 Stabiler Rückprojektionsschirm sowie Verfahren zu dessen Herstellung
PCT/EP2004/002627 WO2005022254A1 (fr) 2003-08-04 2004-03-12 Ecran de retroprojection stable et son procede de production

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WO2005022254A1 (fr) 2005-03-10
JP2007501424A (ja) 2007-01-25
CN1829943A (zh) 2006-09-06
DE10336131A1 (de) 2005-02-24
RU2006106614A (ru) 2006-09-10
CN100529959C (zh) 2009-08-19
CA2534539A1 (fr) 2005-03-10
RU2378674C2 (ru) 2010-01-10
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US20080158670A1 (en) 2008-07-03
TWI344059B (en) 2011-06-21

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