KR20070007061A - High refractive index microstructure-bearing products - Google Patents

Abstract

Oligomeric urethane multi (meth) acrylates; Optional one or more other monomers selected from the group consisting of acrylic monomers, styrene-based monomers and ethylenically unsaturated nitrogen heterocycles, preferably polyol multi (meth) acrylates; And blends of nanoparticles of ethylenically unsaturated, preferably (meth) acryl-functionalized titanium or zirconium compounds are cured by ultraviolet light in contact with a photoinitiator to achieve high refractive index, haze rating of 5% or less, and desired applications. It is possible to produce optical resin products with other properties that can be tailored accordingly.

Description

MICROSTRUCTURE-BEARING ARTICLES OF HIGH REFRACTIVE INDEX}

The present invention relates to the replication of microstructure-bearing surfaces, more particularly to the class of resin-based compositions capable of such replication.

Microstructure replication at the resin surface includes the manufacture of traffic signals, the refractive index of which is provided by cube corner embossed sheeting, the manufacture of Fresnel ophthalmic lens elements and flexible video discs; And the manufacture of "brightness enhancement" or "light management" films (hereinafter, sometimes referred to briefly as "LMFs") for liquid crystal displays. For replication purposes, the resin comprises substantial transparency, a glass transition temperature (Tg) high enough for shape retention during storage and use, typically viscoelastic properties that promote molding by molding, and microstructured aspects of the molded article. It is desirable to have optimal physical properties, including long term shape retention. Suitable viscoelastic properties include modulus in the glass and rubber states within a certain range, as well as suitable transition temperatures between these states. It is also desirable that the LMF is adhesive to a substrate such as polycarbonate and has good resistance to abrasion and scratching.

Many resin compositions suitable for the replication of microstructures are disclosed in the patent literature. A comprehensive patent describing a wide variety of such compositions is US Pat. No. 4,576,850. The compositions described in this patent are characterized by "hard" and "soft" segments or residues in combination with radiation polymerizable residues. Often, all three of these types of segments are in the same molecule. A key feature of "hard" segments is the retention of cyclic (ie carbocyclic or heterocyclic) groups. Subsequent patents often cite Patent No. 4,576,850 for the disclosure of suitable polymer compositions and precursors therefor.

Suitably, the LMF may have a high refractive index, preferably at least about 1.70. If only low-cost resin materials are used, achieving this high refractive index is almost impossible. The refractive index of polymers of highly brominated monomers, such as pentabromophenyl methacrylate, is about 1.71, but such polymers sometimes have undesirable physical properties.

No. 6,291,070 discloses a highly permeable nanostructured molded article having a broad refractive index made from inorganic materials such as titanium dioxide in combination with polymerizable or condensable surface groups such as those derived from (meth) acrylic and epoxy compounds. do. Other monomer types may also be present, such as (meth) acrylic acid esters.

U. S. Patent No. 6,432, 526 discloses a high refractive index composition comprising high crystalline metal particles such as particles of titanium dioxide in combination with an organic solvent and a dispersing aid to form colloidal particles. Such particles can be combined with organic polymers such as those derived from acrylates and methacrylates to form the composition.

However, it is important to develop additional high refractive index resin LMF materials that are not disclosed in these patents or other documents. In particular, it is important to provide a means for easily fitting such materials to various property profiles.

Summary of the Invention

The present invention relates to mixed organic-inorganic compositions that can be cured by optical radiation into optical articles having high refractive index. The composition can be used to form articles having replicated microstructures. The ratio of the components of the composition can be varied to provide a broad class of property profiles.

In one aspect of the invention, the invention includes an article that can be radiation cured into an optical resin article having a surface having a replicated microstructure comprising a plurality of utility discontinuities having an optical purpose; The product can be cured on a 3.2 mm thick flat film on a bisphenol A polycarbonate substrate into a cured product having a haze rating corresponding to a value of 5% or less as measured by ASTM procedure D1003; (A) one or more oligomeric urethane multi (meth) acrylates, optionally in combination with one or more other monomers effective to reduce viscosity, improve thermomechanical properties, or increase refractive index; (B) nanoparticles of at least one ethylenically unsaturated metal compound selected from the group consisting of tetravalent titanium and tetravalent zirconium compounds; And (C) one or more photoinitiators.

Another aspect of the invention is an optical resin product prepared by radiation curing the aforementioned curable product.

1 is a schematic diagram of an LMF in a backlit liquid crystal display.

The optical resin article of the present invention features a surface having a replicated microstructure comprising a number of practical discontinuities, such as protrusions and depressions, which can be easily released from the mold after radiation curing without loss of detail of the mold. Can be retained and copies of these details are retained under various conditions during use. The product has a variety of desired properties such as toughness, flexibility, optical transparency and homogeneity, and resistance to common solvents. The microstructure of such a product has high thermal dimensional stability, wear resistance, impact resistance, and integrity even when the product is bent at an angle as large as 180 °.

As used herein, the term “microstructure” is used as defined and described in US Pat. No. 4,576,850, which is incorporated herein by reference. Thus, the term refers to the construction of a surface that describes and characterizes any desired practical purpose or function of a product having a microstructure. Discontinuities, such as protrusions and indentations, on the surface of the product will deviate from the profile from the mean centerline drawn through the microstructure (the center line is the sum of the areas covered by the surface profile above it). Drawn to be identical and essentially parallel to the nominal surface (having the microstructure) of the product). The height of the deviation will typically be about ± 0.005 to about ± 750 microns as measured by optical or electron microscopy through a representative specific length of the surface, for example 1-30 cm. The average centerline can be planar, concave, convex, aspherical or a combination thereof. If the degree of deviation is low (eg, up to ± 0.005 to ± 0.1, or preferably up to ± 0.05 microns) and if the deviation occurs rarely or minimally, i.e. if the surface is not markedly discontinuous, the product may Products where the structure-bearing surface is essentially "flat" or "smooth" are useful for example in precision optical elements, such as ophthalmic lenses, with a precise optical interface. Although the degree of deviation is low, common products include those having a refractory microstructure. Products resulting from microstructures having a high degree of deviation (e.g., ± 0.1 to ± 750 microns) and comprising a plurality of practical discontinuities that are spaced apart or adjacent in the same, different, random or ordered manner are retroreflective Products such as cube corner seating, linear framing lenses, video discs and LMFs. The microstructure-bearing surface may contain both low and high degree of practical discontinuities as described above. Microstructure-bearing surfaces may contain exogenous or impractical discontinuities so long as their type or amount does not significantly counteract or adversely affect any desired utility of the product. It is necessary or desirable to select certain oligomeric compositions, for example compositions in which only 2 to 6% shrink when shrinkage upon curing does not produce this exogenous discontinuity point.

Details of LMF configuration and configuration are provided, for example, in US Pat. No. 5,900,287, which is incorporated herein by reference. Referring to the drawings, the backlight liquid crystal display 10 includes an LMF 11 that is typically disposed between the diffuser 12 and the liquid crystal display panel 14. The backlight liquid crystal display includes a light source 16 such as a fluorescent lamp; A light guide 18 for transporting reflective light toward the liquid crystal display panel 14; And a white reflector 20 that reflects light toward the liquid crystal display panel. The LMF 11 aims at the light emitted from the light guide 18 to increase the brightness of the liquid crystal display panel 14, to produce a more precise image by the liquid crystal display panel, and to reduce the power of the light source 16. To generate the selected luminance. LMF 11 in a backlit liquid crystal display is useful for devices such as computers, personal televisions, video recorders, mobile communication devices, and automotive and aviation instrument displays.

Component A of the product of the present invention is at least one oligomeric urethane multi (meth) acrylate. The term "(meth) acrylate" is used to denote esters of acrylic acid and methacrylic acid; "Multi (meth) acrylate" refers to a molecule containing one or more (meth) acryl groups, in contrast to "poly (meth) acrylates" which typically refer to a (meth) acrylate polymer. Often, multi (meth) acrylates are di (meth) acrylates, but it is also contemplated to use tri (meth) acrylates, tetra (meth) acrylates and the like.

Oligomeric urethane multi (meth) acrylates are commercially available, for example, from Sartomer Co. It can also be prepared by the initial reaction of a polyol with alkylene diisocyanates of the formula OCN-R ³ -NCO, wherein R ³ is a C _2-100 alkylene or arylene group. Often the polyol is a diol of the formula HO-R ⁴ -OH, wherein R ⁴ is a C _2-100 alkylene group. The intermediate product is then urethane diol diisocyanate, which can subsequently be subjected to the reaction with hydroxyalkyl (meth) acrylates. Suitable diisocyanates include 2,2,4-trimethylhexylene diisocyanate and toluene diisocyanate; Alkylene diisocyanates are generally preferred. Particularly preferred compounds of this type can be prepared from 2,2,4-trimethylhexylene diisocyanate, poly (caprolactone) diol and 2-hydroxyethyl methacrylate.

The radiation curable compositions forming the articles of the invention may also include one or more other monomers that are effective to reduce viscosity, improve thermomechanical properties, or increase refractive index. Monomers having these properties include acrylic monomers (ie, acrylate and methacrylate esters, acrylamides and methacrylamides), styrene-based monomers and ethylenically unsaturated nitrogen heterocycles.

Suitable acrylic monomers include monomeric (meth) acrylate esters. These include alkyl (meth) acrylates such as methyl acrylate, ethyl acrylate, 1-propyl acrylate, methyl methacrylate and t-butyl acrylate.

Also included are (meth) acrylate esters having other functionality. Compounds of this type include 2- (N-butylcarbamoyl) ethyl (meth) acrylate, 2,4-dichlorophenyl acrylate, 2,4,6-tribromophenyl acrylate, t-butylphenyl acrylate , Phenyl acrylate, phenyl thioacrylate, phenylthioethyl acrylate, alkoxylated phenyl acrylate, isobornyl acrylate and phenoxyethyl acrylate.

The other monomer may also be monomeric N-substituted or N, N-disubstituted (meth) acrylamide, in particular acrylamide. These include N-alkylacrylamides and N, N-dialkylacrylamides, especially those containing C _1-4 alkyl groups. Examples are N-isopropylacrylamide, Nt-butylacrylamide, N, N-dimethylacrylamide and N, N-diethylacrylamide.

The other monomer may further be a polyol multi (meth) acrylate. Such compounds are typically prepared from aliphatic diols, triols and / or tetraols containing 2 to 10 carbon atoms. Examples of suitable poly (meth) acrylates are ethylene glycol diacrylate, 1,6-hexanediol diacrylate, 2-ethyl-2-hydroxymethyl-1,3-propanediol triacrylic Rate (trimethylolpropane triacrylate), di (trimethylolpropane) tetraacrylate, pentaerythritol tetraacrylate, corresponding methacrylates and alkoxylated (usually ethoxylated) derivatives of the polyols It is (meth) acrylate of.

Styrene-based compounds suitable for use as other monomers include styrene, dichlorostyrene, 2,4,6-trichlorostyrene, 2,4,6-tribromosstyrene, 4-methylstyrene and 4-phenoxy Contains cystyrenes. Ethylenically unsaturated nitrogen heterocycles include N-vinylpyrrolidone and vinylpyridine.

Component B is at least one ethylenically unsaturated metal compound selected from the group consisting of tetravalent titanium and tetravalent zirconium compounds, and titanium compounds are generally preferred because of their low cost and their particular suitability. Because of its unsaturated functionality inside, it is possible to incorporate metal compounds into polymers formed upon radiation curing.

In making the products of the present invention, it is important to minimize light scattering. Thus, component B is in the shape of nanoparticles. "Nanoparticle" means a particle having an average diameter of 200 nm or less. Preferably, the particle diameter is in the range of 100 nm or less, more preferably 70 nm or less, most preferably about 5-50 nm. Particles of this size are recognized in the prior art, including flame pyrolysis, plasma methods, condensation methods in the gas phase, colloidal methods, precipitation methods, sol-gel methods, controlled nuclear reaction and growth methods, MOCVD methods and (micro) emulsion methods. Can be prepared by any technique. Particularly suitable in many instances is the sol-gel process starting with the corresponding alkoxide (ie titanium or zirconium tetraalkoxide).

The functionalization of the metal-containing nanoparticles can be carried out simultaneously or following its formation by contacting ethylenically unsaturated compounds, typically unsaturated trialkoxysilanes with alkoxides or particles prepared. Frequently, the compounds are often (meth) acrylic compounds which are preferably (meth) acryloxyalkyltrialkoxysilanes, such as 3-methacryloxypropyltrimethoxysilane (hereinafter sometimes referred to as "MPTMS"). MPTMS functionalization is a free radical scavin, such as a free radical that is stable as exemplified by 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxy (hereinafter often "4-OH TEMPO"). It is preferably carried out in the presence of a reservoir. Although the present invention does not depend on any arbitrary theory in manipulation, it is believed that this functionalization mainly affects the surface of the nanoparticles.

For the purpose of this functionalization, molar ratios of titanium and / or zirconium to (meth) acrylic compounds in the range of about 5-10: 1 are commonly used. The ratio of free radical compounds is a catalyst ratio that is effective for catalyzing the reaction. The reaction temperature is typically in the range of about 30 to 80 ° C. Solvents such as alkanols may also be present if removed by vacuum stripping or the like prior to formation of the curable product. It is often convenient to formulate nanoparticles as sol in a suitable suspending agent such as propylene glycol methyl ether acetate.

Component C of the radiation curable article of the present invention is one or more photoinitiators effective to promote polymerization of the article upon exposure to ultraviolet light. Suitable materials for use as photoinitiators are described in the above-mentioned US Pat. No. 4,576,850 and in the reference Encyclopedia of Polymer Technology. Examples are benzoin ether, hydroxy- and alkoxyalkyl phenyl ketones, thioalkylphenyl morpholinoalkyl ketones and acylphosphine oxides. Commercially available materials represented by "Darocure 4265" comprising a mixture of 2-hydroxy-2-propyl phenyl ketone and (2,4,6-trimethylbenzoyl) diphenylphosphine oxide are particularly useful in many instances.

The component ratios in the radiation curable articles of the invention vary widely. Generally, component A is about 30 to 100% by weight oligomeric urethane multi (meth) acrylate, with the remainder being other (meth) acrylate monomers. Component B often comprises about 5 to 90 weight percent of the total weight of components A and B (all percentages are weight percent). Component C, a photoinitiator, is generally present in the range of about 0.005 to 3.0% by weight, preferably about 0.005 to 1.0% by weight, based on the total weight of the polymerizable component, in a minimum amount effective to promote the polymerization upon exposure to ultraviolet light. .

An important property of the cured product of the present invention is a haze rating corresponding to a value of 5% or less as measured by ASTM procedure D1003 on a 3.2 mm thick flat film on a bisphenol A polycarbonate substrate. Other desirable properties include a bisphenol A poly of 5B as measured by the falling sand abrasion test (ASTM procedure D968) of 20 or less, preferably 10 or less, and a crosshatch adhesion test (ASTM procedure D3359). Adhesion grade of carbonate.

Radiation curable articles of the invention can be prepared by simply mixing their ingredients effectively to produce a simple homogeneous mixture, and then removing any solvent used in the preparation of the ingredients. If the mixture is viscous, it is often desirable to remove air bubbles by application of a vacuum or the like, with mild heating, and to produce a film of the blend produced on the casting or otherwise desired surface. The film is then filled into a mold containing the microstructures to be replicated and polymerized by UV exposure to produce a cured optical resin product of the present invention having the aforementioned characteristics. When polymerized on a surface other than the surface used, the optical resin product may be transferred to another surface.

This polymerization process is suitable for rapid mass production of products without adversely affecting the environment because no or only small amounts of solvents or other volatiles are included and the polymerization is carried out at ambient temperature and pressure. In addition, the process allows the optical resin article of the present invention to have a microstructure that includes practical discontinuities such as protrusions and depressions and is easily released from the mold without loss of detail of the mold and retains the replication of such details under various conditions during use. Suitable for duplication of products. The product can be made to have a variety of required properties such as toughness, flexibility, optical transparency and homogeneity, and resistance to common solvents, and the microstructure of such products provides high thermal dimensional stability, even when the product is bent. Wear resistance, impact resistance, and integrity.

The invention is illustrated by the following examples. All parts and percentages are parts by weight and weight percent unless otherwise indicated. The percentage of monomer components, including component B and the photoinitiator, is based on the weight of the total monomer components.

Example 1

A three neck flask equipped with an addition funnel, temperature probe and mechanical stirrer was charged with 31.2 ml of 2,2,4-trimethylhexane 1,6-diisocyanate and 50 mg of dibutyltin dilaurate. The addition funnel was charged with 39.75 g of warmed polycaprolactone diol (Mn. 530) and added to the contents of the flask at 55-60 ° C. The mixture was then stirred at 65 ° C. for 14 hours. The flask was then cooled to 55 ° C. and a mixture of 18.7 mL 2-hydroxyethyl methacrylate and 100 mg hydroquinone monomethyl ether was added while maintaining a temperature of 54 to 58 ° C. The mixture was stirred at 55 ° C. for 10-12 hours until completion of reaction was confirmed by infrared spectroscopy. The product was the desired oligomeric urethane dimethacrylate, sometimes referred to herein as "oligomeric dimethacrylate".

Example 2

105 g of titanium tetraisopropoxide was added to a mixture of 1000 g 2-propanol, 49.05 g concentrated hydrochloric acid and 5.25 g distilled water with stirring. The resulting mixture was stirred at rt for 72 h, then 0.23 g of a 33% solution of 4-OH TEMPO in 1-methoxy-2-propanol and 13.75 g of 3-methacryloxypropyltrimethoxysilane were added. After heating the solution at 50 ° C. for 6.5 hours, 447 g of the solution was transferred to a round bottom flask and stripped of most volatiles using a rotary evaporator. 140 g of propylene glycol methyl ether acetate was added and stripping was continued at 55 ° C. and full vacuum. Stripping was stopped when the solution weighed 171 g and 137 g additional propylene glycol methyl ether acetate was added to the flask. Stripping was continued until the weight of the solution was 236 g. The solids content of the resulting titanium-containing nanoparticle dispersion was determined by weight analysis by stripping all volatiles and found to be 17.4% by weight.

Example 3

Vacuum stripping of the product of Example 2 and a mixture of 49.5 parts by weight of oligomeric polyester urethane diacrylate sold under the trade name "CN-985B88" in the Sartomer company in an amount to provide 50 parts by weight of titanium, and 0.5 parts by weight of " Darcure 4265 "(in the form of a 10% solution in 1-methoxy-2-propanol) was added. The resulting composition was spin coated from 1-methoxy-2-propanol onto bisphenol A polycarbonate plaques and cured by exposure to ultraviolet radiation emitted by a single “H” bulb. The resulting coating has a haze value of 0.43%, abrasion rating of 25.7 and adhesion rating of 0B. As measured by simple experiments, it is anticipated that adhesion can be improved by addition of small amounts of multifunctional (meth) acrylate monomers.

Examples 4-10

The seven compositions, the curable product and the cured product were prepared using the oligomer dimethacrylate of Example 1, the nanoparticle dispersion of Example 2, “Darocure 4265” (0.5%) and photoinitiators as photoinitiators and Examples 5, 6, 8 and Prepared in propylene glycol methyl ether acetate from hexanediol diacrylate (“HDDA”) at 10.

The relevant parameters and properties of the resulting composition are shown in Table 1 below. In three samples, the refractive index was measured by ellipsometry at 589.878 nm, which also provides the result.

It is clear from the table that the cured product of the present invention has a refractive index approaching a preferred range (particularly Example 9), a haze rating of 5 or less, and a wear rating within the required range. Except for the product of Example 8, the products also have a suitable adhesive grade. For the product of Example 3, it is expected that the adhesion of the product of Example 8 can be improved by small addition of the multifunctional (meth) acrylate monomer as measured by simple experiments.

While typical embodiments have been disclosed for purposes of illustration, the foregoing description and examples are not intended to limit the scope of the invention. Accordingly, those skilled in the art can make various modifications, adaptations, and alternatives without departing from the spirit and scope of the present invention.

Claims (10)

A radiation curable product with an optical resin product having a surface of a replicated microstructure comprising a plurality of practical discontinuities with an optical purpose, The product can be cured into a cured product having a haze rating corresponding to a value of 5% or less as measured by ASTM procedure D1003 on a 3.2 mm thick flat film on a bisphenol A polycarbonate substrate, (A) reducing viscosity One or more oligomeric urethane multi (meth) acrylates, optionally in combination with one or more other monomers, which are effective to increase or improve thermomechanical properties or increase refractive index; (B) nanoparticles of at least one ethylenically unsaturated metal compound selected from the group consisting of tetravalent titanium and tetravalent zirconium compounds; And (C) at least one photoinitiator. The method of claim 1, A product in which component B is a titanium compound. The method of claim 2, An article wherein component B is a (meth) acryloxyalkyltrialkoxysilane-functionalized compound. The method of claim 3, wherein An article wherein component B is 3-methacryloxypropyltrimethoxysilane-functionalized. The method of claim 2, A product wherein component A is the reaction product of 2,2,4-trimethylhexane 1,6-diisocyanate, polycaprolactone diol and 2-hydroxyethyl methacrylate. The method of claim 2, A product in which said other monomer is present. The method of claim 6, Wherein said other monomer is an acrylic monomer, a styrene monomer or an ethylenically unsaturated nitrogen heterocycle. The method of claim 6, Wherein said other monomer is a polyol multi (meth) acrylate. The method of claim 8, Wherein said polyol (meth) acrylate is hexanediol diacrylate. A radiation-curable article with an optical resin article having a surface of a replicated microstructure comprising a plurality of practical discontinuities with an optical purpose, The product has a haze rating corresponding to a value of 5% or less when measured by ASTM procedure D1003 on a 3.2 mm thick flat film on a bisphenol A polycarbonate substrate, and a wear rating of 20 or less when measured by ASTM procedure D968. And a reaction product of (A) 2,2,4-trimethylhexane 1,6-diisocyanate, polycaprolactone diol and 2-hydroxyethyl methacrylate ; (B) nanoparticles of at least one 3-methacryloxypropyltrimethoxysilane-functionalized titanium compound; And (C) at least one photoinitiator.

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