CA2028541C

CA2028541C - Photosensitive mixture

Info

Publication number: CA2028541C
Application number: CA002028541A
Authority: CA
Inventors: Max Hunziker; Manfred Hofmann; Adrian Schulthess; Paul Bernhard; Bernd Klingert; Rolf Wiesendanger
Original assignee: Ciba Spezialitaetenchemie Holding AG
Current assignee: Huntsman Advanced Materials Switzerland GmbH
Priority date: 1989-10-27
Filing date: 1990-10-25
Publication date: 2000-05-16
Anticipated expiration: 2010-10-25
Also published as: DE59010008D1; JPH03160013A; EP0425441A3; CA2028541A1; EP0425441B1; KR0163588B1; KR910008491A; JP3243565B2; EP0425441A2

Abstract

Liquid mixtures containing a) 5-25 % by weight of a monomeric aliphatic or cycloaliphatic di(meth)acrylate having a molecular weight (MW) of not more than 800, b) 0-15 % by weight of a monomeric poly(meth)acrylate having a functionality of at least 3 and an MW of not more than 600, c) 0-20 % by weight of a mono(meth)acrylate or a mono-N-vinyl compound having an MW of not more than 500, d) 20-60 % by weight of a urethane (meth)acrylate having a functionality of 2 to 4 and an MW of 500 to 10,000, e) 10-50 % by weight of a monomeric or oligomeric di(meth)acrylate based on bisphenol A or bisphenol F, f) 0.1-10 % by weight of a photoinitiator and g) 0-5 % by weight of customary additives, the proportion of the components a) to g) together being 100 % by weight, are photosensitive mixtures which can be polymerized by means of actinic radiation and are preferentially suitable for the production of three-dimensional articles by means of the stereolithographic process.

Description

K-17809/1+2/+
Photosensitive mixture The present invention relates to a liquid, photosensitive mixture, to a process for the polymerization of this mixture by means of actinic radiation, to a process for the production of three-dimensional articles from the liquid mixtures and to the use of the mixtures according to the invention for the production of photopolymerized layers, in particular of three-dimensional articles built up from several photopolymerized layers.
As is known, radiation-sensitive, liquid resins or resin mixtures can be used in a variety of ways, for example as coating agents, adhesives or photoresists. In principle, liquid resins or resin systems should generally also be suitable for the production of three-dimensional articles by the stereolithographic process described in US Patent 4,575,330, but some resins prove to be too viscous, while others in turn are insufficiently light-sensitive or are subject to an excessive shrinking process when they are cured. The strength properties of the mouldings or articles composed of photo-cured resins also often leave something to be desired.
As is known, complicated three-dimensional articles can be produced from liquid, light-sensitive resins by means of the stereolithographic process. Articles of this type are built up in layers, each new curable layer of resin being firmly attached to the preceding pre-cured layer by preliminary curing by means of UVNIS light. The overall build-up of the three-dimensional article can, as is known, be accomplished by a computer-controlled process.
In recent years there has been no lack of attempts to develop resin systems which can be employed for the stereolithographic process. In Rev. Sci. Instrum. 52 (11) (1981), H. Kodama discloses, under the tradename "Tevista", a liquid, photo-curable resin mixture consisting of an unsaturated polyester, acrylic acid esters, styrene, a polymerization initiator and a sensitizer. For the stereolithographic process, this resin system has the disadvantage that the photosensitivity is insufficient and the so-called green strength of articles pre-cured by laser beams is relatively low.

The stereolithographic process is described in more detail in US Patent 4,575,330, in which the liquid resin employed is a modified acrylate defined in the description as "Potting Compound 363". Resin mixtures of this type are disclosed in US Patent 4,100,141. They too have the disadvantage that they are insufficiently photosensitive and require long times for the production of three-dimensional articles by the stereolithographic process.
It is therefore understandable that exacting requirements are set for resins which are to be employed in stereolithographic processes. For example, they must have a viscosity suitable for the apparatus in which they are processed. The photosensitivity of the resin system should be so constituted that the ratio between radiation energy used and depth of penetration achieved into the liquid photosensitive resin mixture, in the course of which the components concerned solidify, is within reasonable limits. This means that, in the case of a resin or resin mixture suitable for the stereolithographic process, the highest possible depth of curing should be obtained by means of little radiation energy, together with, at the same time, a high degree of polymerization and a good green strength.
In the process of successive polymerization of thin layers, such as is used in the stereolithographic process, usually none of these layers is completely cured.
The incompletely cured article is described as a green product, and the modulus of elasticity and the tensile strength of this green product are also described as green strength.
Normally, the green product is then cured by means of UV/VIS light, for example by means of a mercury vapour or xenon arc lamp. The green strength of a component is therefore an important parameter, since articles having a low green strength can undergo deformation under their own weight or they can sag or subside during curing. A
further requirement for resin systems which are to be employed in stereolithographic processes is as small as possible a volume shrinkage in the transition from the liquid state into the laser-cured state. In the technology of stereolithography, the so-called "curl factor" is quoted as a process-specific measure of shrinkage-induced deformation. A curl factor of 1 indicates that no shrinkage-caused deformation occurs. In practice, curl factors up to values of about 4 are measured, but only resins having a curl factor of 1-1.5 are suitable for a stereolithographic process.
It has now been found that a liquid resin mixture consisting of several mono(meth)acrylates and di(meth)acrylates differing from one another, which additionally contains a urethane (meth)acrylate and a monomeric or oligomeric di(meth)acrylate based on bisphenol A or bisphenol F can be employed for the stereolithographic process and produces, in the course of preliminary curing by means of laser beams, green products distinguished by a high green strength and a low curl factor. The articles obtained by complete curing have good mechanical properties, are rigid-elastic and thereby permit after-treatment of the article, such as grinding of the surface, incorporation of special components, for example plug-in connections, or even further processing by machining.
The present invention therefore relates to a liquid, photosensitive mixture containing a) 5-25 % by weight of a monomeric aliphatic or cycloaliphadc di(meth)acrylate having a molecular weight (MW) of not more than 800, b) 0-15 % by weight of a monomeric poly(meth)acrylate having a functionality of at least 3 and an MW of not more, than 600, c) 0-20 % by weighs of a mono(meth)acrylate or a mono-N-vinyl compound having an MW of not more than 500, d) 20-60 % by weight of a urethane (meth)acrylate having a functionality of 2 to 4 and an MW of 500 to 10,000, e) 10-50 % by weight of a monomeric or oligomeric di(meth)acrylate based on bisphenol A or bisphenol F, f) 0.1-10 % by weight of a photoinitiator and g) 0-5 % by weight of customary additives, the proportion of the components a) to g) together being 100 % by weight.
The mixture according to the invention preferably contains a) 5-15 % by weight of a monomeric aliphatic or cycloaliphatic di(meth)acrylate, b) 5-10 % by weight of a monomeric poly(meth)acrylate, c) 1-15 % by weight of a mono(meth)acrylate, d) 30-50 % by weight of a urethane (meth)acrylate, e) 30-50 % by weight of a di(meth)acrylate based on bisphenol A or bisphenol F, f) 0.5-7 % by weight of a photoinitiator and g) 0.01-3 % by weight of an additive.
Examples of suitable compounds of the component (a) are the diacrylate and dimethacrylate esters of aliphatic or cycloaliphatic diols, such as 1,3-butylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, diethylene glycol, triethylene glycol, ~~~ ~4~
-4_ tetraethylene glycol, polyethylene glycol 400, polyethylene glycol 600, tripropylene glycol, ethoxylated or propoxylated neopentyl glycol, 1,4-dihydroxymethylcyclohexane, 2,2-bis-(4-hydroxycyclohexyl)-propane or bis-(4-hydroxycyclohexyl)-methane.
It is preferable to use aliphatic di(meth)acrylates, in particular those having an MW of 200 to 500, as the compound of the component (a).
Examples of suitable compounds of the component (b) are tri-, tetra- and penta-acrylates or tri-, tetra- and penta-methacrylates of the formulae I, II and III
Rt -CH2-C--ECH2 -R2)3 (I)~
CH2- ~ -~CH2-RZ)2 (II) and CHz--CF-I3 2 R2-~'~H2-R2)2 (~I)9 in which Rt is a hydrogen atom, methyl, hydroxyl or a radical of the formula IV
-O CH2 ~ --(CH2-R2)2 (IV) CH~-OH
and R2 is a radical of the formula V
O Ra _° p~~2 ~- ~ ~---C~H
2 () in which n is zero or a number from 1 to 3 and R3 and R4 independently of one another are each a hydrogen atom or methyl.
Compounds of the formulae I to III which are particularly preferred are those of the formula I in which Rt is a methyl group or a radical of the formula IV and R2 is a radical of the formula V in which n is zero.
The following are examples of compounds of the component (b) which can be employed:
1,1,1-trimethylolpropane triacrylate or methacrylate, ethoxylated 1,1,1-trimethylolpropane triacrylate or trimethacrylate, pentaerythritol tetraacrylate, monohydroxypentaerythritol triacrylate or methacrylate or monohydroxydipentaerythritol pentaacrylate or methacrylate. Compounds of this type are known and some are obtainable commercially, for example from the SARTOMER Company under the product names SR-295, SR-350, SR-351, SR-367, SR-399, SR-444 and SR-454.
In particular, the compounds of the component (b) have an MW of 250 to 500.
The following compounds can be present for example as the component (c) in the mixtures according to the invention: allyl acrylate, allyl methacrylate, methyl, ethyl, n-propyl, n-butyl, isobutyl, n-hexyl, 2-ethylhexyl, n-octyl, n-decyl and n-dodecyl acrylate, methyl, ethyl, n-propyl, n-butyl, isobutyl, n-hexyl, 2-ethylhexyl, n-octyl, n-decyl and n-dodecyl methacrylate, 2-hydroxyethyl, 2-hydroxypropyl and 3-hydroxypropyl acrylate, 2-hydroxyethyl, 2-hydroxypropyl and 3-hydroxypropyl methacrylate, 2-methoxyethyl, 2-ethoxyethyl, 2-ethoxypropyl and 3-ethoxypropyl acrylate, tetrahydrofurfuryl methacrylate, 2-(2-ethoxyethoxy)-ethyl acrylate, cyclohexyl methacrylate, 2-phenoxyethyl acrylaie, glycidyl acrylate and isodecyl acrylate and also, as a mono-N-vinyl compound, N-vinylpyrrolidone or N-vinylcaprolactam. Products of this type are also known and some are available commercially, for example from the SARTOMER Company.
The compounds of the component (c) preferably have an MW of 50-300.
The urethane acrylates used as the component (d) in the mixtures according to the invention are known to those skilled in the art and can be prepared in a known manner, for example by reacting a hydroxyl-terminated polyurethane with acrylic acid or methacrylic acid to give the corresponding urethane acrylate, or by reacting an isocyanate-terminated grepolymer with hydroxyalkyl acrylates or methacrylates to give the urethane acrylate.
Appropriate processes are disclosed, for example, in the published EP Patent Applications ~'~~~ ~~.

114,982 and 133,908. The molecular weight of such acrylates is generally within the range from 400 to 10,000, preferably between 500 and 7000.
Urethane acrylates are also available commercially and are offered, for example, under the name EBECRYL~ by UCB, under the name Uvithane~ by Morton Thiokol or under the product names SR 9504, SR 9600, SR 9610, SR 9620, SR 9630, SR 9640 and SR 9650 by the SARTOMER Company.
It is preferable to employ, as urethane acrylates, those which have an MW of and have been prepared from aliphatic starting materials.
Diacrylates based on bisphenol A and bisphenol F which can be employed as the component (e) are both the bisphenol A diacrylates and dimethacrylates and bisphenol F
diacrylates and dimethacrylates and the diacrylates or dimethacrylates of alkoxylated, preferably ethoxylated or propoxylated, bisphenol A or F. The acrylates obtainable by reacting bisphenol A or bisphenol F diglycidyl ether with (meth)acrylic acid are also suitable. Monomeric or oligomeric di(meth)acrylates of this type are also known and some are available commercially, for example from the SARTOMER Company under the product name SR-348 for ethoxylated bisphenol A dimethacrylate and under the product name SR-349 for ethoxylated bisphenol A diacrylate. It is preferable to use the di(meth)acrylates of bisphenol A or F and of ethoxylated bisphenol A or of ethoxylated bisphenol F as the component (e).
In particular, the compounds of the component (e) have an MW of 300-1000.
Any type of photoinitiator which forms free radicals when irradiated suitably can be employed as the component F in the mixtures according to the invention.
Typical compounds of known photoinitiators are benzoins, benzoin ethers, such as benzoin, benzoin methyl ether, benzoin ethyl ether and benzoin isopropyl ether, benzoin phenyl ether and benzoin acetate, acetophenones, such as acetophenone, 2,2-dimethoxyacetophenone and 1,1-dichloroacetophenone, benzil, benzil ketals, such as benzil dimethyl ketal and benzil diethyl ketal, anthraquinones, such as 2-methylanthraquinone, 2-ethylanthraquinone, 2-tent-butylanthraquinone, 1-chloroanthraquinone and 2-amylanthraquinone, triphenylphosphine, benzoylphosphine oxides, for example 2,4,6-trimethylbenzoyldiphenylphosphine oxide {Luzirin TPO), benzophenones, such as benzophenone and 4,4'-bis-(N,1V'-dimethylamino)-benzophenone, thioxanthones and xanthones, acridine derivatives, phenazine derivatives, quirioxaline derivatives or 1-phenyl-1,2-propanedione 2-O-benzayl oxime, 1-aminophenyl ketones or 1-hydroxyphenyl ketones, such as 1-hydroxycyclohexyl phenyl ketone, phenyl 1-hydroxyisopropyl ketone and 4-isopropylphenyl 1-hydroxyisopropyl ketone, all of which constitute known compounds.
Particularly suitable photoinitiators, which are generally used in combination with a HeCd laser as the radiation source, are acetophenones, such as 2,2-dialkoxybenzophenones, and «-hydroxyphenyl ketones, for example 1-hydroxycyclohexyl phenyl ketone or 2-hydroxyisopropyl phenyl ketone (= 2-hydroxy-2,2-dimethylacetophenane).
Another class of photoinitiators (f), which are usually employed when argon ion lasers are used, are the benzil ketals, for example benzil dimethyl ketal. In particular, an «-hydroxyphenyl ketone, benzil dimethyl ketal or 2,4,6-trimethylbenzoyldiphenylphosphine oxide is used as the photoinitiator.
Another class of suitable photoinitiators (f) is constituted by the ionic dye-counter ion compounds which are capable of absorbing actinic radiation and producing free radicals which initiate the polymerization of the acrylates (a) to (e) or the mono-N-vinyl compound (c). The mixtures according to the invention containing ionic dye-counter ion compounds can be cured in a fairly variable manner in this way with visible light within the adjustable wavelength range of 400-700 nm. Ionic dye-counter ion compounds and their mode of action are known, for example from EP-A-0,223,587 and US Patents 4,751,102;
4,772,530 and 4,772,541. Examples of suitable ionic dye-counter ion compounds which may be mentioned are the anionic dye-iodonium ion complexes, the anionic dye-pyrylium ion complexes and, especially, the cationic dye-borate anion,compounds of the formula VI
RS\ / R7 B~ X c~n~

in which X+ is a cationic dye and R5, R6, R~ and R8 independently of one another are each an alkyl, aryl, alkaryl, allyl, aralkyl, alkenyl or alkinyl group, an alieyclic group or a saturated or unsaturated hetexocyclic group.

_g_ As is known, the photoinitiators are added in effective amounts, ie. in amounts of about 0.1 to about 10 % by weight, relative to the total amount of the mixture. If the mixtures according to the invention are used for stereolithographic processes in which laser radiation is normally employed, it in essential that the absorption capacity of the mixtures is so adjusted by means of the type and concentration of the photoinitiator that the depth of curing at normal laser speed is approximately 0.1 to 2.5 mm.
The mixtures according to the invention can also also contain different photoinitiators which have a different radiation sensitivity in relation to the radiation of emission lines of different wavelengths. This achieves, for example, better utilization of a UV/VIS light source which radiates emission lines of different wavelengths. It is advantageous in this case if the various photoinitiators are so chosen and employed in such a concentration that a uniform optical absorption is produced in the case of the emission lines used.
If desired, the customary additives, for example stabilizers, such as UV
stabilizers, polymerization inhibitors, mould release agents, wetting agents, flow control agents, sensitizers, anti-sedimentation agents, surface-active agents, dyes, pigments or fillers can be added to the mixtures according to the invention.
The mixtures according to the invention can be prepared in a known manner, for example by premixing individual components and subsequently mixing these premixes or by mixing all the components by means of customary devices, such as stirred vessels, in the absence of light and, if appropriate, at a slightly elevated temperature.
The photosensitive mixtures according to the invention can be polymerized by irradiation with actinic light, for example by means of electron or X-ray beams or UV or VIS light, ie. by means of radiation within the wavelength range from 280 to 650 nm.
Laser radiation from HeCd, argon ions or nitrogen ions and also metal vapour and NdYAG Iasers of multiplied frequency are particularly suitable. It is known to those skilled in the art that the suitable photoinitiator must be selected and, if appropriate, sensitized for each light source selected. It has been found that the depth of penetration of the radiation into the composition to be polymerized and the rate of working are directly correlated with the absorption coefficient and the concentration of the photoinitiator. In stereolithography it is preferable to employ photoinitiators which induce the highest number of free radicals formed and make possible the greatest depth of penetration of radiation into the compositions to be polymerized.
The invention therefore also relates to a process for polymerizing the mixtures according to the invention by irradiating them with actinic light.
The mixtures according to the invention are liquids having a viscosity of about 300 to about 10,000 mPa.s at 30°C, preferably 500 to 5000 mPa.s and particularly 500 to 2500 mPa.s. Surprisingly, the mixtures according to the invention have, for a high light sensitivity, a low curl factor and a high green strength after precuring by means of laser radiation, which is particularly important in the case of stereolithographic processes. After complete curing, the shaped articles prepared from the mixtures according to the invention have a high strength at an adequate elasticity and are therefore rigid-elastic.
The invention also relates to a process for the production of three-dimensional articles from the liquid mixtures according to the invention by means of stereolithographic processes in which the surface of a layer of the liquid mixture according to the invention is irradiated either as the whole surface or in a predetermined pattern, by means of a ~JVV/VIS
light source, so that a layer is solidified in a desired layer thickness in the irradiated areas, then a new layer of the mixtures according to the invention is foixned on the solidified layer, and this is also irradiated either as the whole surface or in a predetermined pattern, and, by repeated coating and irradiation, three-dimensional articles composed of several solidified layers adhering to one another are obtained.
It is preferable to use a laser beam which is preferably computer-controlled as the radiation source in this process.
If the mixtures according to the invention are employed as coating agents, clear and hard coatings are obtained on wood, paper, metal, ceramics or other surfaces. The coating thickness can be varied very much and can be from about 1 wan to about 1 mm.
Relief images for printed circuits or printing plates can be produced direct from the mixtures according to the invention by izradiating the mixtures, for example by means of a computer-controlled laser beam of suitable wavelength or using a photomask and a corresponding light source.
It is preferable to use the mixtures according to the invention for the production of photopolymerized layers, particularly in the form of three-dimensionai articles built up - to -from several solidified layers adhering to one another.
The curl factor is determined on test specimens produced by stereolithographic processes, the deformation of a self supporting part of the test specimen being determined by shrinkage. The curl factor is the xatio of the height of a deformed, fixed segment of the test specimen to the height of the non-deformed segment. A ratio of 1 thus means that no shrinkage has taken place, and values of up to 1.5 represent acceptable properties in respect of shrinkage and deformation.
The mechanical properties of the article cured by means of laser radiation (green strength) and of the article obtained by after-curing are measured on an Instron 1112 tensile test machine, using ribbons 45.7 mm in length and having a cross-section of 0.38 x 0.51 mm as test specimens.
Example 1: 39.75 g of ethoxylated bisphenol A diacrylate (MW = 424, product SR-349 of the SARTOMER Company) are mixed at 40°C with 40.02 g of urethane acrylate (MW =
1700, product SR 9504 of the SARTOMER Company), 3.25 g of 1,1,1-trimethylolpropane triacrylate (MW = 408), 12.99 g of 1,4-butanediol diacrylate (MW = 198) and 4 g of 1-hydroxycyclohexyl phenyl ketone. The resulting homogeneous liquid mixture has a viscosity of 1510 mPa.s at 30°C. The curl factor of a three-dimensional shaped article built up from individual layers (layer thickness = 0.305 mm) and prepared with an HeCd laser is 1.05. The so-called green shaped article, cured by means of laser radiation, has an elastic modulus of 20 N/mm2, a tensile strength of 2.4 N/mm2 and an elongation at break of 13 %. After the green shaped article has been cured for 30 minutes under UV/VIS light by means of an Hg lamp, the green strength is 1500 N/mm2, the tensile strength is 40 N/mm2 and the elongation at break is 7 to 19 %.
Examples 2-7: Mixtures are prepared as in Example 1 by mixing the components indicated in Table 1 below and are processed to give three-dimensional shaped articles under the conditions indicated in Example 1. The properties of the shaped articles obtained are also shown in Table 1.

Table 1:
Example 2 3 4 5 6 7 Pentaerythritol tetraacrylate (M5V = 352; SR-295) 3.60 2.88 3.61 2.89 - -[g]

Trimethylol propane triacrylate (MW = 296; SR-351) - - - - 4.06 3.25 [g]

1,4-Butanediol diacrylate (MW =198; SR-213) [g] 12.1512.97- - 12.1712.99 Diethylene glycol diacrylate (MW = 214; SR-230) - - 13,1814,07- -[g]

Urethane acrylate (MW =1700; SR-9504) 40.5040.4039.4539.2840.0240.02 [g]

Ethoxylated bisphenol A diacrylate (MW = 424; SR-349) 39.7539.7539.7539.7539.7539.75 [g]

1-Hydroxycyclohexyl 4.00 4.00 4.00 4.00 4.00 4.00 phenyl ketone [g]

Viscosity at 30C [mPa 1720 1650 1870 1750 1650 1510 ~ s]

Mechanical properties after laser curing:

Elastic modulus [N/mm2]30 25 50 50 15 18 Tensile strength [N/mm2]3.5 3.3 7.3 7.3 2.8 2.4 Elongation at break 14 12 15 15 12 13 [%]

curl factor ~ x) 1.01 x) ~ x) 1.0 1.0 Mechanical properties after UV/VIS curing:

Elastic modulus [N/mm2]1500 1500 1700 1400 1400 1400 Tensile strength [N/mm2]55 50 50 35 40 40 Elongation at break 10-1510-1514-2010-225-15 5-10 [%]

x) not measured Examples ~-13: Mixtures are prepared as in Example 1 by mixing the components indicated in Table 2 below and are processed to give three-dimensional shaped articles under the conditions indicated in Example 1. The properties of the shaped articles obtained are also shown in Table 2.

Table 2:
Example 8 9 10 11 12 13 Pentaerythritol tetraacrylate (MW = 352; SR-295) 5.89 5.43 3.76 3.64 6.04 3.92 [g]

1,4-Butanediol diacrylate (MW = 198; SR-213 [g] 9.94 9.16 12.6812.2710.196.61 Ethoxylated bisphenol A diacrylate (MW = 424; SR-349) 39.7539.7539.7539.7539.7539.75 [g]

1-Hydroxycyclohexylphenyl4.00 4.00 4.00 4.00 4,00 4.00 ketone [gl SR-9503 40.42 SR-9505 41.66 U-782 39.81 U-892 40.34 PM-6162 40.03 PM6184 45.72 Viscosity at 30C [mPa 4600 5400 6700 3400 3000 6450 ~ s]

Mechanical properties after laser curing:

Elastic modulus (N/mm2]20 43 9 14 9 58 Tensile strength [N/mm2]5 6 2 4 2 8 Elongation at break 50 33 33 38 28 43 [%]

Mechanical properries after UV/VIS curing:

Elastic modulus [N/rnm2]340 560 215 270 196 625 Tensile strength [N/mm~]41 55 32 32 22 57 Elongation at break 46 16 41 37 19 15 [%]

~02~~~:~

SR-9503: Linear urethane acrylate made by SARTOMER;
MW = 2000, viscosity = 2000 Pa.s at 21C.

SR-9505: Urethane acrylate made by SARTOMER; MW =1250, viscosity: 145 Pa.s at 38C.

U-782: Uvithane 782, a urethane acrylate made by Morton Thiokol Inc., double bond equivalent = 2400, viscosity =
800-1600 Pa.s at 49C.

U-892: Uvithane 892, a urethane acryilate made by Morton Thiokol Inc., double bond equivalent = 1800, viscosity 410 Pa.s at 49C.

PM-6162: Photomer 6162, a linear urethane acrylate made by Lanla~o, MW =

5000.

PM-6184: Photomer 6184, a trifunctional urethane acrylate made by Lankro, MW = 1800.

Examples 14-25: Mixtures are prepared as in Example 1 by mixing the components indicated in Table 3 below and are processed to give three-dimensional shaped articles under the conditions indicated in Example 1. The properties of the shaped articles obtained are also shown in Table 3.

_ o_ Cr~ N 00 ~

~lyT~ ~ M d' N

M

M N ~ ~ ~ N

~t ~ i~ 'n N
G~ O O ~ct N

M .--i.-r M

M N ~ ~

M '~ t~ ~ N

O a ~ M N

~ ~O ~O ~ ~ ~O Ov N ~ C~M N
' ~ O w ' N Q, O v"~ N

M

~ ~D ~D O 00 00 V t~;M N O O M

N CT~ O N ~t ~ ~ ,..., M ~ M

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d' ~ W u'~4 M

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M N ~ O I~ N

M

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dr' I~M N d ~ ~ N

00 . O Ci d'v7 !n t~

M ~ ~ M N

t M N

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M .-, M .-r M l~ N ~ M M

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m N ~ a ~ N

,~ t~ ' ,~ O c n -r Ov O N d .--i N

M ~ M

'd t~M N y 0 N

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M

N

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~D ~ ~Dv C~V1 ' ' ~

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- is -~D N d' ~n N N

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M O N N

N

N

N N

s , -~ n o0 r ~ N V
N

h N

O o o ~ N N

v~

N N N

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t~ N

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z z a a O O U tn .D
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__ SC-961: Aliphatic urethane diacrylate made by SARTOMER;
MG = 1850, viscosity = 81 Pas at 60°C.
SC-964: Aliphatic urethane diacrylate made by SARTOMER;
MG = 1300, viscosity = 21 Pas at 60°C.
SC-965: Aliphatic urethane diacrylate made by SARTOMER;
MG = 1500, viscosity =12 Pas at 60°C.
SR-9504: Aliphatic urethane diacrylate made by SARTOMER;
MG = 1700, viscosity =167 Pas at 21°C.
LR-8765: Diacrylate of butanediol diglycidylether made by BASF;
11~IG = 346.
CL-959: Monofunctional acrylate made by SNPE;
MG = 185.
SR-209: Tetraethylene glycol dimethacrylate made by SARTOMER;
MG = 330.
SR-348: Ethoxylated bisphenol A dimethacrylate made by SARTOMER;
MG = 452.
SR-349: Ethoxylated bisphenol A diacrylate made by SARTOMER;
MG = 424.

Claims

1. A liquid, photosensitive mixture containing a) 5-25 % by weight of a monomeric aliphatic or cycloaliphatic di(meth)acrylate having a molecular weight (MW) of not more than 800, b) 0-15 % by weight of a monomeric poly(meth)acrylate having a functionality of at least 3 and an MW of not more than 600, c) 0-20 % by weight of a mono(meth)acrylate or a mono-N-vinyl compound having an MW of not more than 500, d) 20-60 % by weight of a urethane (meth)acrylate having a functionality of 2 to 4 and an MW of 500 to 10,000, e) 10-50 % by weight of a monomeric or oligomeric di(meth)acrylate based on bisphenol A or bisphenol F, f) 0.1-10 % by weight of a photoinitiator and g) 0-5 % by weight of customary additives, the proportion of the components a) to g) together being 100 % by weight.

2. A mixture according to claim 1, containing a) 5-15 % by weight of a monomeric aliphatic or cycloaliphatic di(meth)acrylate, b) 5-10 % by weight of a monomeric poly(meth)acrylate, c) 1-15 % by weight of a mono(meth)acrylate, d) 30-50 % by weight of a urethane (meth)acrylate, e) 30-50 % by weight of a di(meth)acrylate based on bisphenol A or bisphenol F, f) 0.5-7 % by weight of a photoinitiator and g) 0.01-3 % by weight of an additive.

3. A mixture according to claim 1, in which the MW of the component (a) is 200-500, of the component (b) is 250-500, of the component (c) is 50-300, of the component (d) is 500-7000 and of the component (e) is 300-1000.

4. A mixture according to claim 1, containing aliphatic di(meth)acrylates as the component (a).

5. A mixture according to claim 1, containing, as the component (b), a tri-, tetra- or penta-acrylate or tri-, tetra- ox penta-methacrylate of the formula I, II or III

in which R1 is a hydrogen atom, methyl, hydroxyl or a radical of the formula IV
and R2 is a radical of the formula V
in which n is zero or a number from Z to 3 and R3 and R4 independently of one another are each a hydrogen atom or methyl.

6. A mixture according to claim 5, containing, as the component (b), a compound of the formula I in which R2 is a methyl group or a radical of the formula IV and R2 is a radical of the formula V in which n is zero.

7. A mixture according to claim 1, containing, as the component (e), the di(meth)acrylates of ethoxylated bisphenol A or of ethoxylated bisphenol F.

8. A mixture according to claim 1, containing, as the photoinitiator, an a-hydroxyphenyl ketone, a benzil dimethyl ketal or 2,4,6-trimethylbenzoyldiphenylphosphine oxide.

9. The use of a mixture according to claim 1 for the production of photopolymerized layers, particularly in the form of three-dimensional articles built up from several solidified layers adhering to one another.

10. A process for the production of three-dimensional articles from a liquid photosensitive mixture according to claim 1 by means of stereolithographic processes in which the surface of a layer of the liquid mixture according to the invention is irradiated either as the whole surface or in a predetermined pattern, by means of a UV/VIS light source, so that a layer is solidified in a desired layer thickness in the irradiated areas, then a new layer of the mixtures according to the invention is formed on the solidified layer, and this is also irradiated either as the whole surface or in a predetermined pattern, and, by repeated coating and irradiation, three-dimensional articles composed of several solidified layers adhering to one another are obtained.

11. A process according to claim 10, in which the radiation source used is a laser beam, preferably a computer-controlled laser beam.