WO1996014594A1

WO1996014594A1 - High refractive index lenses

Info

Publication number: WO1996014594A1
Application number: PCT/EP1995/004329
Authority: WO
Inventors: Robert Winston Van De Graaf
Original assignee: Akzo Nobel N.V.
Priority date: 1994-11-08
Filing date: 1995-11-03
Publication date: 1996-05-17
Also published as: AU3846695A; IL115877A0

Abstract

The invention relates to a lens having a refractive index of at least 1.60 which comprises the cured product of a composition comprising an unsaturated compound and a thiol compound comprising at least three thiol groups. Also covered is a process for the manufacture of these lenses either by thermal curing or by photocuring. The lenses have a glass transition temperature of more than 70 °C and a satisfactory Barcol hardness and Abbe number.

Description

HIGH REFRACTIVE INDEX LENSES

The invention relates to high refractive index lenses and a process for the manufacture of high refractive index lenses.

Recently, organic glass has begun to replace inorganic glass in optical elements, such as windows, prisms, cameras, television screens, telescopes, and ophthalmic lenses. Organic glass possesses several favourable characteristics, including a lighter weight and better safety because of a higher impact resistance than inorganic glass.

Conventional materials used in organic glass include for example diethylene glycol bisallyl carbonate, polycarbonate, and polymethyl methacrylate resin. However, these conventional materials have the disadvantage of a maximum refractive index of approximately 1.58, whereas inorganic glass has a refractive index of 1.80. The refractive index is a factor in the thickness of an ophthalmic lens. More particularly, ophthalmic lenses made from materials having a high refractive index are thinner than lenses with the same diopter made from materials having a low refractive index.

The first attempts to prepare high refractive index lenses were made with aromatic compounds. These did indeed increase the refractive index, but also lowered the Abbe number to an unacceptably low level (< 35). A lot of research has also been carried out on halogen- containing materials. A major disadvantage of these materials, however, is a low UV-resistance, i.e., the lenses prepared therefrom discolour rapidly when subjected to UV-light. Metal-containing compositions suffer the drawback of an increase in specific gravity. Over the last few years optical research has moved in the direction of phosphorus- and, especially, sulphur-containing compounds for the preparation of high refractive index lenses. The introduction of sulphur into a polymer leads to an increase in refractive index without there being a dramatic fall of the Abbe number. Japanese patent application 03 084 031, for example, discloses lenses made from triallyl isocyanurate (TAIC) and

1,2-bis[(2-mercaptoethyl )thio] -3-mercaptopropane. Another publication is European patent application 0 528 590 disclosing a sulphur-containing polyurethane resin obtained by reacting 2-(2-mercaptoethylthio)-l,3-dimercaptopropane with a cyanate compound. The resin is used in lenses. European patent application 0 598 551 discloses a composition comprising an aromatic olefin monomer and a polythiol compound. This composition is also used in the preparation of lenses. Other publications in this field are US 3,338,810 and JP 61 157 529.

However, sulphur-containing polymers of the prior art show a low glass transition temperature. This is particularly disadvantageous when lenses are coated to improve their scratch resistance. During such a coating procedure the lenses have to endure high temperatures without permanent damage, such as change of the curvature of the lenses. Sulphur-containing lenses of the prior art having a low glass transition temperature have difficulties to withstand a coating procedure using high temperatures.

Accordingly, there is a need in the optical industry for monomer compositions which as lenses have a high refractive index and a glass transition temperature above 70°C, preferably above 90°C, without other properties, such as Barcol hardness and Abbe number, being detoriated. Preferably, the Abbe number of the lens of the present invention is above 35 and its Barcol hardness is more than 20. Accordingly, it is the primary object of the present invention to provide a high refractive index lens which has a glass transition temperature above 70°C. It is another object of the present invention to provide a high refractive index lens with a satisfactory Abbe number and Barcol hardness.

The present invention relates to a lens having a refractive index of at least 1.60 which comprises the cured product of a composition comprising a) at least one thiol compound, comprising at least three thiol groups, of the following general formula I

wherein n and m are integers being either 0 or 1; y, p, and z are integers ranging from 0 to 20;

are independently selected from a single valency bond, a C_j-C_β alkylene group, a 2-C8 alkenylene group, a C2-Cg alkynylene group, a C3-C20 cycloalkylene group, a C6-C20 arylene group, a C7-C20 aralkylene group, and a C7-C20 alkarylene group, which groups may be lineair or branched and may optionally contain one or more atoms or groups selected from oxygen, nitrogen, sulphur, sulphone, or sulphoxy, and may optionally be substituted with epoxy, cyano, amino, thiol, hydroxy, halogen, nitro, phosphorus, sulphoxy, amido, ester, and ether groups;

R , R3 and R4 are independently selected from hydrogen, epoxy, cyano, amino, thiol, hydroxy, halogen, nitro, phosphorus, sulphoxy, amido, ester, and ether groups, C1-C20 alkyl groups, C2-C20 alkenyl groups, 2-C20 alkynyl groups, C3-C20 cycloalkyl groups, ^c6^_c20 ^apy^ groups, C7-C20 aralkyl groups and C7-C 0 alkaryl groups, which groups may be linear or branched, may optionally contain one or more oxygen, nitrogen, sulphur, sulphoxy, sulphone, -0-C0-, or -C0-0-, and may optionally be substituted with epoxy, 0 cyano, amino, thiol, hydroxy, halogen, nitro, phosphorus, sulphoxy, amido, ester, and ether groups, and R₂ and R3, R3 and R4, and R4 and R2 may combine to form a ring whereby R , R3, and R4 may be a single valency bond;

X , X3, and X4 are independently selected from a single valency bond, oxygen, nitrogen, sulphur, a 1-C20 alkylene group, a C -C20 alkenylene group, a 2-C20 alkynylene group, a C3-C20 cycloalkylene group, a C6-C20 arylene group, a C7-C 0 aralkylene group, and a C7-C20 alkarylene group, which groups may be lineair or branched and may optionally contain one or more of oxygen, o nitrogen, sulphur, sulphone, sulphoxy, -0-C0-, or -0-C0-, and may optionally be substituted with epoxy, cyano, amino, thiol, hydroxy, halogen, nitro, phosphorus, sulphoxy, amido, ester, and ether groups; with the proviso that the thiol compound may not be _ς l,2-bis[(2-mercaptoethyl)thio]-3-mercaptopropane or 1,2,3-tri [(2-mercaptoethyl )thio]propane; and

0 b) an unsaturated compound of the formula II

wherein R5, Rβ, and R7 are independently chosen from groups with a chain length of at most 5 atoms, each chain comprising at least one unsaturated group and being build of atoms selected from carbon atoms, oxygen atoms, nitrogen atoms, sulphur atoms, and carboxy groups, each chain may be linear or branched and optionally substituted with epoxy, cyano, amino, thiol, hydroxy, halogen, nitro, phosphorus, sulphoxy, amido, ester, ether, and acetate groups;

X5, X5, and X7 are independently selected from nitrogen and carbon atoms and C-H groups; and

Yj, Y2, and Y3 are independently selected from oxygen and sulphur atoms.

With regard to X2, X3, and X4 in the formula I as defined above the following has to be said. When, for example, y is chosen to be an integer more than 1, then there is more than one X2 group present in the chain. In such case the X2 groups are independently from each other chosen from the definition provided for X2. The same counts for z and X3 and for p and X4.

When X5, X_β, and/or X7 is a carbon atom, it means that one or more of X5, X_β, and X7 are linked with a double bond to R5, Rβ, or R7, respectively. High refractive index lenses according to the present invention have a high glass transition temperature without deterioration of such properties as Abbe number or Barcol hardness. It should be noted that if the Abbe number or the Barcol hardness of a lens is not satisfactory, the lens cannot be used. Accordingly, a high refractive index lens according to the present invention has to apply to the two criteria given above, apart from having a high glass transition temperature.

It has been observed that lenses prepared according to the disclosure of JP-A-03 084031, i.e. triallylisocyanurate and l,2-bis[(2-mercaptoethyl)thio]-3-mercaptopropane, have a Barcol hardness and a glass transition temperature which are both too low for the lenses to be employable. This will also be the case for lenses prepared from triallyl isocyanurate and 1,2,3-tri [(2-mercaptoethyl)thio]propane.

Preferably, in the formula I as defined above the groups R2, R3, and R4 are not thiol and the groups R\ , R , R3, R4, X]_., X2, X3 and X4 are not substituted with thiol groups. More preferably, in the formula I as defined above y and p are 1; z is 0; R2, R3, and R4 are hydrogen; X2 and X4 are single valency bonds; m is 1; and the other groups are as defined above. Most preferably, the thiol compound of formula I is selected from propane trithiol or 2-(2-mercaptoethylthio)-l,3-dimercaptopropane.

With regard to the unsaturated compound of the formula II X5, Xβ, and X7 are preferably independently selected from nitrogen atoms and C-H groups and R5, R_β, and R7 are preferably C2-C5 alkenyl groups. More preferably, the unsaturated compound of the formula II is trial1ylisocyanurate. The composition comprises the thiol compound of the formula I and the unsaturated compound of the formula II preferably in a molar ratio of from 70:30 to 30:70. More preferably, the molar ratio ranges from 55:45 to 35:65.

Comonomers may optionally be present in the curable composition, preferably in a quantity up to 20 wt%. These comonomers may be acrylic, vinylic or allylic or may be thiol compounds. Examples include methyl (meth)acrylate, phenyl (meth)acrylate, vinyl acetate, vinyl benzoate, diallyl isophthalate, diallyl terephthalate, diallyl adipate, triallyl cyanurate, pentaerythritol tetrakis (3-mercaptopropionate) , trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis (3-mercaptoacetate) , tris(2-hydroxyethyl)isocyanurate triacrylate, trimethylolpropane tris(3-mercaptoacetate), 2-mercaptoethylsulfide,

4,4'-thiodibenzenethiol , benzenedithiol , and glycol dimercaptoacetate, and mixtures thereof.

The composition may also contain one or more conventional additives to act as ultraviolet light absorbers, release agents, dyes, pigments, infrared light absorbers, etc., preferably in quantities not higher than 1 wt%.

The present invention also relates to a process for the preparation of high refractive index lenses comprising polymerization casting into a mould of the above-described composition. The composition may be polymerized either thermally using a radical initiator or by UV-light using a photoinitiator.

With regard to the thermal polymerization process, the process is initiated by free radicals produced by the decomposition of a radical initiator at a working temperature which generally ranges from 30° to 150°C. Under these conditions the time necessary for complete polymerization ranges from 0.5 to 100 hours. The radical initiator may be present in quantities ranging from 0.01 to 10 wt%. Some non-limitative examples of such radical initiators are tert.butyl peroxyneodecanoate, tert.butyl peroxy-2-ethylhexanoate, tert.butyl peroxydiethylacetate, l,l-bis(tert.butylperoxy)-3,3,5-trimethyl cyclohexane, 1,1-bis(tert.butylperoxy)cyclohexane, tert.butylperoxy-3,5,5-trimethylhexanoate, tert.butylperoxyisopropyl carbonate, dicumylperoxide, 2,2-bis(tert.butylperoxy)butane, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, dibenzoyl peroxide, tert.butyl perbenzoate, 2,2'-azobis(isobutyronitrile) , 2,2'-azobis(2-methylbutyronitrile) , 2,2'-azobis(2,4-dimethylvaleronitrile) , dimethyl-2,2 '-azobisisobutyrate, l,l-azobis(l-cyclohexanecarbonitrile) , and mixtures thereof. For the purpose of the present invention, it is preferable for the polymerization initiator to be present in the process in quantities from 0.01 to 3 wt%.

With regard to the UV polymerization process, the process is initiated by photoinitiators. The cast composition comprising 0.001 to 1 wt% of photoinitiator is subjected at least once to UV-light to polymerize the composition. The time necessary to complete polymerization ranges from 30 sec. to 5 hours. Some non-limitative examples of the photoinitiators' are methylphenyl glyoxylate, n-butylbenzoinether, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2,2-dimethylacetophenone, 1-benzoylcyclohexan-l-ol , benzophenone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide and mixtures thereof.

The lens can be subjected to further physical or chemical treatment such as surface polishing, antistatic treatment, hard coating, non- reflective coating, dyeing or photochromic treatment as needed in order to prevent reflection, impart high hardness, improve its abrasion resistance, improve its chemical resistance, impart anti-mist properties or impart fashionability.

The invention will be further illustrated by the following examples, which are not to be construed as limiting the invention in any way. The scope of the invention is to be determined from the claims appended hereto.

The properties of the materials indicated in the examples were determined as follows:

- the index of refraction (ΠQ) and the Abbe value with the use of a Zeiss refractometer;

- the Barcol hardness with a Barber-Colman impressor (model GYZJ 934-1);

- the glass temperature Tg with a Zwick Torsiometer;

Examples 1-7

8 g of propane trithiol (PTT) and triallylisocyanurate (TAIC) were mixed with various amounts of 2,2-bis(tert.butylperoxybutane) , Trigonox^® D (TxD) , as detailed in Table 1. These mixtures were placed in glass moulds having a 4 mm thick moulding cavity and were polymerized in an air curing oven using the following temperature programme: 4 hours at 90°C, a linear temperature rise program over 14 hours from 90°C to 120°C, and 4 hours at 120°C. After this cycle, the oven was cooled to 60°C over 1 hour and the lenses were removed from the mould.

The glass temperature of polymer prepared from a composition containing 50 mole PTT and 50 mole% TAIC was 104°C, that of a composition containing 45 mole PTT and 55 mole% TAIC was 120°C. Comparati ve Exampl es A-B

The procedure of Example 2 was repeated, except that triallyl cyanurate (TAC) or tris(2-hydroxyethyl)isocyanurate triacrylate (TRIS) was employed instead of TAIC. The results are given in Table 1. As can be seen from the results in Table 1, the lens made from the composition of Comparative Example A has a too low Barcol hardness to obtain an employable lens. The composition of Comparative Example B results in a lens which refractive index is too low and with a glass transition temperature of 39°C.

TABLE 1

Examples 8-12

8 g of propane trithiol (PTT) and TAIC were mixed with various amounts of a photoinitiator, i.e., 2,4,6-trimethylbenzoyl diphenylphosphine oxide (TPO) or methylphenyl glyoxylate, Vicure^® 55 (VC), as detailed in Table 2. These mixtures were placed in glass moulds having a 4 mm thick moulding cavity and were polymerized under Philips HOK high pressure mercury lamps. Polymerization procedure was to pass the mould 4 to 6 times under the UV light for a total period of time ranging from 1 to 2 minutes. The intensity was 50mW/cm².

TABLE 2

Examples 13-18

2-(2-mercaptoethylthio)-l,3-dimercaptopropane (TTS) and TAIC were cured in the same manner as in Examples 1-7. The results are listed in Table 3.

The glass temperature of polymer prepared from a composition containing 50 mole% TTS and 50 mole% TAIC was 73°C, that of a composition containing 40 mole% TTS and 60 mole% TAIC was 83°C.

Comparative Examples C-D

The procedure of Example 14 was repeated, except that triallyl cyanurate (TAC) or tris(2-hydroxyethyl)isocyanurate triacrylate (TRIS) was employed instead of TAIC. The results are given in Table 3. Again it can be seen from the listed results that the refractive index and/or the Barcol hardness are too low to obtain lenses with satisfactory properties. Accordingly, the glass transition temperature was not measured.

TABLE 3

Comparative Example E

The procedure of Example 2 was repeated with 1,3-dimercaptopropane and TAIC. The refractive index of the lens obtained was 1.58, the Abbe number was 46 and the Barcol hardness was smaller than 1. Accordingly, the lens obtained by this comparative example was not employable.

Comparative Examples F

50 mole% TAIC and 50 mole% l,2-bis[(2-mercaptoethyl)thio]-3-mercaptopropane was thermally cured with 2% by weight of dicumylperoxide, Perkadox^® BC. The mixture was placed in a glass mould having a 4 mm thick moulding cavity and was polymerized in an air curing oven using the following temperature programme: 4 hours at 70°C, a linear temperature rise program over 20 hours from 70°C to 130°C, and 2 hours at 130°C. After this cycle, the oven was cooled to 60°C over 1 hour and the lens was removed from the mould.

The refractive index of the lens was 1,62, the Abbe number was 42, and the Barcol hardness was 10. The glass transition temperature was measured as being lower than 70°C. Accordingly, the lens fails entirely in its properties.

Claims

1. A lens having a refractive index of at least 1.60 which comprises the cured product of a composition comprising

a) at least one thiol compound, comprising at least three thiol groups, of the following general formula I

R₂(-

wherein n and m are integers being either 0 or 1; y, p, and z are integers ranging from 0 to 20; Xl and R are independently selected from a single valency bond, a Ci-Cg alkylene group, a C2-C8 alkenylene group, a C2-C8 alkynylene group, a C3-C20 cycloalkylene group, a Cβ-C20 arylene group, a C7-C₂Q aralkylene group, and a C7-C20 alkarylene group, which groups may be lineair or branched and may optionally contain one or more atoms or groups selected from oxygen, nitrogen, sulphur, sulphone, or sulphoxy, and may optionally be substituted with epoxy, cyano, amino, thiol, hydroxy, halogen, nitro, phosphorus, sulphoxy, amido, ester, and ether groups; R2, R3 and R4 are independently selected from hydrogen, epoxy, 15

cyano, amino, thiol, hydroxy, halogen, nitro, phosphorus, sulphoxy, amido, ester, and ether groups, Cι-C₂o alkyl groups, C₂-C₂o alkenyl groups, C -C₂o alkynyl groups, C3-C20 cycloalkyl groups, Cβ-C20 aryl groups, C7-C20 aralkyl groups and C7-C20 alkaryl groups, which groups may be linear or branched, may optionally contain one or more oxygen, nitrogen, sulphur, sulphoxy, sulphone, -0-C0-, or -C0-0-, and may optionally be substituted with epoxy, cyano, amino, thiol, hydroxy, halogen, nitro, phosphorus, sulphoxy, amido, ester, and ether groups, and R2 and R3, R3 and R4, and R4 and R₂ may combine to form a ring whereby R , R3, and R4 may be a single valency bond; X₂, X3, and X4 are independently selected from a single valency bond, oxygen, nitrogen, sulphur, a I-C Q alkylene group, a C2-C20 alkenylene group, a C2-C20 alkynylene group, a C3-C20 cycloalkylene group, a β-C 0 arylene group, a C7-C20 aralkylene group, and a C7-C20 alkarylene group, which groups may be lineair or branched and may optionally contain one or more of oxygen, nitrogen, sulphur, sulphone, sulphoxy, -0-C0-, or -0-C0-, and may optionally be substituted with epoxy, cyano, amino, thiol, hydroxy, halogen, nitro, phosphorus, sulphoxy, amido, ester, and ether groups; with the proviso that the thiol compound may not be 1,2-bis[(2-mercaptoethyl)thio]-3-mercaptopropane or 1,2,3-tri [(2-mercaptoethyl)thio]propane; and

b) an unsaturated compound of the formula II

X5, X_β, and X7 are independently selected from nitrogen and carbon atoms and C-H groups; and

Y-_, Y2, and Y3 are independently selected from oxygen and sulphur atoms.

A lens according to claim 1, characterized in that the groups R2, R3, and R4 are not thiol and the groups R , R2, R3, R4, Xi, X2- X3, and X4 are not substituted with thiol groups.

A lens according to claim 2, characterized in that y and p are 1; z is 0;

R₂, R3, and R4 are hydrogen;

X₂ and X4 are single valency bonds; m is 1; and the other groups are as defined in claim 2.

A lens according to claim 3, characterized in that the thiol compound of formula I is selected from propane trithiol or 2-(2-mercaptoethylthio)-l,3-dimercaptopropane.

A lens according to any of the preceding claims, characterized in that X5, X_β, and X7 are independently selected from nitrogen atoms and C-H groups and R5, Rβ, and R7 are C2-C5 alkenyl groups. 6. A lens according to claim 5, characterized in that the compound of the formula II is tπallyl isocyanurate.

7. A lens according to any of the preceding claims, characterized in that the composition comprises the thiol compound of the formula I and the unsaturated compound of the formula II in a molar ratio of from 70:30 to 30:70.

8. A lens according to claim 7, characterized in that the molar ratio ranges from 55:45 to 35:65.

9. A process for the production of a lens according to any one of the preceding claims, comprising the steps of mixing a compound of the formula I as defined in claim 1 and a compound of the formula II as defined in claim 1, and a radical initiator, casting the resulting mixture into a mould and heating the mould for a certain period of time.

10. A process for the production of a lens according to claims 1 to 8, comprising the steps of mixing a compound of the formula I as defined in claim 1 and a compound of the formula II as defined in claim 1, and a photoimtiator, casting the resulting mixture into a mould and subjecting the mixture at least once to UV-light.