GB2631234A - Compound - Google Patents

Abstract

Disclosed is a compound of formula (I), wherein the core comprises at least one aromatic, heteroaromatic or aliphatic group; each L is a linking group or a covalent bond, preferably a linking group; each SP is a spacer group, preferably selected from alkylene, alkenylene, arylene or heteroarylene, optionally interrupted by one or more heteroatoms and optionally substituted; each X is a latent cross-linkable group, preferably a cross-linkable group that is activatable by actinic radiation; and a is an integer selected from 3-20. Preferably, X is maleimide; the core is a phenyl ring or chain of phenyl rings; L is an ester; and SP is an alkyl chain of 3-20 carbon atoms. Further disclosed is a method for preparing a compound of formula (I), as well as it’s use as a component in an organic thin-film transistor (OTFT).

Description

COMPOUND

INTRODUCTION

The present invention provides a compound of formula (I), and compositions comprising a compound of formula (I), a polynorbornene and a photosensitiser which are useful for the preparation of organic electronic devices. The invention also relates to a method of making a compound of formula (I) and to a method of making compositions comprising a compound of formula (I). Additionally, the invention relates to a structure, and to a method of making a structure, wherein the structure comprises a substrate and the composition of the invention on at least one surface of the substrate. Moreover, the invention relates to an electronic device comprising the afore-mentioned structure, in particular a thin film transistor.

BACKGROUND

For a number of years, there has been a growing interest in organic electronic (OE) devices, including organic Field Effect Transistors (OFETs) such as organic Thin Film Transistors (TFTs) for use in backpanes of display devices as well as in sensors. A conventional TFT comprises a number of material layers, including a gate electrode, a gate dielectric, a semiconductor layer and source/drain electrodes.

A number of different types of polymers have been successfully employed as the dielectric in TFTs, including polycycloolefinic polymers such as polynorbornenes.

Polynorbornenes are attractive because they have the required low dielectric constants without the need to incorporate environmentally unattractive fluorine atoms in the structure, provide options to incorporate additional chemical functionality in the polymer backbone, such as cross-linking groups and solubility modifiers and also enable greater flexibility in formulating the material to process into oTFT devices which include tuning of the formulation viscosity, use of different solvents as formulation vehicles and enabling orthogonality with previous and subsequent layers in the device.

However, one of the challenges of using polynorbornene polymers as a gate dielectric is they often require the addition of a photosensitiser to increase the cross-linking rate to immobilise the polymer film by using UV-curing at 365 nm. Curing of the dielectric layer is required to complete the device structure, so it is important that curing is completed in a short-time frame to achieve acceptable processing conditions overall. A variety of suitable photosensitisers, such as CPTX, DETX and Speedcure 7010, are available and they successfully decrease the curing time of polynorbornenes to acceptable levels.

However, the disadvantage of including these photosensitisers in the dielectric composition is that it has been found to lead to low adhesion in the final organic electronic devices. More specifically, the presence of these photosensitisers in the polycycloolefinic polymer dielectric has been found to result in low adhesion of the dielectric to ITO (<0.2 N/2.5 cm) as well as to the underlying TFT stack (<1 N/2.5 cm).

This has been found to be the lowest adhesion in the stack, and is a key failure mode in electronic devices, such as backpanes during lamination, bending and shipping/handling. It is not known why the photosensitisers have this effect.

SUMMARY OF INVENTION

Viewed from a first aspect the present invention provides a compound of formula (I): L-SP-X (I) a wherein the core comprises at least one aromatic, heteroaromatic or aliphatic group; each L is a linking group or a covalent bond, preferably a linking group; each SP is a spacer group, preferably selected from alkylene, alkenylene, arylene or heteroarylene, optionally interrupted by one or more heteroatoms and optionally substituted; each X is a latent cross-linkable group, preferably a cross-linkable group that is activatable by actinic radiation; and a is an integer selected from 3-20.

Viewed from a further aspect the present invention provides a method for making a compound of formula (I) comprising: reacting a compound of formula (V) with a compound of formula (VI): CEORE) (Oa (V) Lu-SP-X (VI) wherein the core comprises at least one aromatic, heteroaromatic or aliphatic group; the reaction between each L' and L" generates L and each L is a linking group or a covalent bond, preferably a linking group; each SP is a spacer group, preferably selected from alkylene, alkenylene, arylene or heteroarylene, optionally interrupted by one or more heteroatoms and optionally substituted; each X is a latent cross-linkable group, preferably a cross-linkable group that is activatable by actinic radiation; and a is an integer selected from 3-20.

Viewed from a further aspect the present invention provides a composition comprising: a compound of formula (I) as hereinbefore described; (ii) a polycyclic olefin, preferably polynorbornene; and (iii) a photosensitiser.

Viewed from a further aspect the present invention provides a method for making a composition as hereinbefore described, comprising mixing: (i) a compound of formula (I) as hereinbefore described; (ii) a polycyclic olefin, preferably a polynorbornene; and (iii) a photosensitiser in a solvent.

Viewed from a further aspect the present invention provides a structure comprising: (i) a substrate; and 00 the composition as hereinbefore defined on at least one surface of said substrate.

Viewed from a further aspect the present invention provides a method for making a structure as hereinbefore described comprising: depositing a composition as hereinbefore described by solution processing on at least one surface of the substrate; (ii) drying said composition; and (iii) cross-linking said composition to produce said structure.

Viewed from a further aspect the present invention provides an electronic device comprising a structure as hereinbefore described, preferably a thin film transistor, as hereinbefore defined.

DEFINITIONS

As used herein the term "aromatic" refers to a cyclic, planar molecule with 4n+2 pi electrons. Aromatics are sometimes referred to as arenes As used herein the term "heteroaromatic" refers to an aromatic compound comprising one or more heteroatoms selected from N, 0 and S. As used herein the term "aliphatic" refers to an organic compound comprising carbon and hydrogen atoms, and which is non-aromatic.

As used herein the term "linking group" refers to any group which acts to indirectly bond two or more components of a molecule together. When two components of a molecule are bonded together without a linking group the two parts of the molecule are directly bonded to one another, i.e. without any intervening atoms. When two components of a molecule are connected by a linking group there are intervening atoms between the two components.

As used herein the term spacer group refers to any group which acts to separate two or more components of a molecule. Its function is to increase the distance between the two or more components of the molecule.

As used herein the term "alkyl" refers to any group comprising carbon and hydrogen. The group may be saturated, straight chained, branched or cyclic. Alkyl groups may be substituted or unsubstituted.

As used herein the term "alkylene" refers to a bivalent group derived from an alkyl that has had two hydrogen atoms removed. The group may be substituted or unsubstituted. An example of an alkylene group is ethylene which has the formula -C2H4.

As used herein the term "alkenylene" refers to a bivalent group derived from an alkene that has had two hydrogen atoms removed. The group may be substituted or unsubstituted. An example of an alkenylene group is ethenylene which has the formula -CH=CH-.

As used herein the term "arylene" refers to a bivalent group derived from an aromatic hydrocarbon that has had a hydrogen atom removed from each of two carbon atoms. An example of an arylene group is phenylene (C6H4) which is derived from benzene.

As used herein the term "heteroarylene" refers to an arylene group containing at least one heteroatom. Examples of "heteroatoms" include N, S or 0. A heteroarylene is derived from an aromatic heterocycle that has had a hydrogen atom removed from two carbon atoms.

As used herein the term "polynorbornene" refers to a polymer comprising at least one repeating unit which is derived from norbornene, substituted norbornene or cyclic derivatives of norbornene. Preferably at least 55 %wt, more preferably at least 70 wt%, and still more preferably at least 95 %wt of the repeating units present in polynorbornene are derived from the afore-mentioned norbornene monomers. Other monomer units that may be present include, for example, alkenes, acrylics, acrylates, styrene, vinyl, and combinations thereof.

As used herein the term "hydrocarbyl" refers to a radical or group that contains a carbon backbone where each carbon is appropriately substituted with one or more hydrogen atoms. Representative examples of hydrocarbyls C1_25 alkyl, C2-24 alkenyl, C224 alkynyl, 05-25 cycloalkyl, C6_24 aryl or 07-24 aralkyl. Specific examples of alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl and dodecyl. Specific examples of alkenyl groups include vinyl, propenyl, butenyl and hexenyl. Specific examples of alkynyl groups include ethynyl, 1-propynyl, 2-propynyl, 1 butynyl, and 2-butynyl. Specific examples of cycloalkyl groups include cyclopentyl, cyclohexyl, and cyclooctyl. Specific examples of aryl groups include phenyl, biphenyl, naphthyl, and anthracenyl. Specific examples of aralkyl groups include benzyl, phenethyl and phenbutyl.

As used herein the term "halohydrocarbyl" refers to a hydrocarbyl group where one or more of the hydrogen atoms, but not all, have been replaced by a halogen (F, CI, Br, or I).

As used herein the term "perhalocarbyl" refers to a hydrocarbyl group where each hydrogen has been replaced by a halogen.

In addition, the definition of the terms "hydrocarbyl", "halohydrocarbyl", and "perhalohydrocarbyl", as used herein are inclusive of moieties where one or more of the carbons atoms is replaced by a heteroatom selected independently from 0, N, P, or Si.

Such heteroatom containing moieties include, for example, ethers, epoxies, glycidyl ethers, alcohols, carboxylic acids, esters, maleimides, amines, imines, amides, phenols, amido-phenols, silanes, siloxanes, phosphines, phosphine oxides, phosphinites, phosphonites, phosphites, phosphonates, phosphinates, and phosphates.

As used herein, the phrase "latent cross-linkable group" refers to a group that does not cross-link under ambient conditions or during the initial formation of the compound per se and instead only cross-links when it is specifically initiated.

As used herein, the phrase "cross-linkable group that is activatable by actinic radiation" refers to a group that is reactive to actinic radiation and as a result of that reactivity enters into a cross-linking reaction. Such groups are an example of a latent cross-linkable group.

As used herein the term photosensitiser refers to a compound that absorbs light and transfers the energy to reactants to facilitate a chemical reaction. In the present case, the chemical reaction is curing.

As used herein the term "total dry weight" refers to the total weight of the dry ingredients, i.e. excluding solvents.

DETAILED DESCRIPTION OF INVENTION

The present invention provides a compound of formula (I): 1 (I)

L-SP-X a

wherein the core comprises at least one aromatic, heteroaromatic or aliphatic group; each L is a linking group or a covalent bond, preferably a linking group; each SP is a spacer group, preferably selected from alkylene, alkenylene, arylene or heteroarylene, optionally interrupted by one or more heteroatoms and optionally substituted; each X is a latent cross-linkable group, preferably a cross-linkable group that is activatable by actinic radiation; and a is an integer selected from 3-20.

Advantageously, the compound of formula (I) can be incorporated into a composition comprising a polycyclic olefin, preferably a polynorbornene, and a photosensitiser, and applied to a substrate to form a dielectric layer. The presence of the compound of formula (I) in the composition improves the adhesion of the dielectric layer to adjacent layers, e.g. ITO and/or semiconducting layer. The composition comprising formula (I) is therefore particularly useful in organic electronic devices such as TFTs, which require a dielectric, and where the improved adhesion to the remainder of the TFT stack is highly beneficial during lamination, bending, shipping and handling.

Definition of X In preferred compounds of formula (I), each X is a cross-linkable group via a [2rr+2rr] photo-cycloaddition reaction. Preferred cross-linkable groups have a degree of latency. This means that the group does not cross-link under ambient conditions or during the initial formation of the compound per se and instead only cross-links when they are specifically initiated, preferably by actinic radiation.

Preferably the cross-linkable group comprises a maleimide, an epoxy, a vinyl, an acetyl, an indenyl, a cinnamate or a coumarin group. More preferably the cross-linkable group comprises a maleimide group, e.g. a 3-monoalkylmaleimide or 3,4-dialkylmaleimide.

Representative examples of suitable cross-linkable groups are those shown below:

O

0 C6H40Me-p In the above structures, the wavy line depicts where the cross-linkable group is attached to the remainder of the compound of formula (I).

In preferred compounds of formula (I), each X is a cross-linkable group of formula wherein R1 is selected from H, and C1_6 alkyl, preferably C1.6 alkyl, and more preferably methyl; R2 is selected from H, and C1_6 alkyl, preferably C1_6 alkyl, and more preferably methyl; or R1 and R2, together with the carbon atoms to which they are attached form a ring, wherein said ring is optionally fused to a further ring.

In the above depiction of formula (II), the wavy bond shows where the group is attached to the remainder of the molecule.

In preferred compounds of formula (II), R1 is selected from H and C1_6 alkyl. In further preferred compounds of formula (II), R2 is selected from H and C1_6 alkyl. In yet further preferred compounds of formula (II), R1 and 52 are each selected from H and C1_ 6 alkyl.

In further preferred compounds of formula (II), R1 is Ci_6 alkyl. For example, R1 may be methyl, ethyl, propyl, butyl, pentyl or hexyl. Preferably, however, R1 is methyl.

In further preferred compounds of formula (II), R2 is Ci_6 alkyl. For example, 52 may be methyl, ethyl, propyl, butyl, pentyl or hexyl. Preferably, however, 52 is methyl. In particularly preferred compounds of formula (I), R1 and R2 are methyl. Preferred compounds of the invention are those of formula (la): SP la R2 (la) wherein the core, L, SP, and a are as hereinbefore defined in relation to formula (I); and 51 and R2 are each selected from 01_6 alkyl, preferably methyl.

In compounds of formula (I) and (la), the letter "a" represents the number of arms that extend from the core of the compound. In preferred compounds of formula (I) and (la), a is 3-12, more preferably 3-6, and still more preferably 3 or 4. Preferred compounds of formula (I) and (la) therefore have 3 arms, or 4 arms. The presence of multiple arms increases the number of cross-links per molecule, which results in a more highly cross-linked film. Typically this leads to a more robust film with lower solubility and better resistance to process chemicals such as solvents, etchants etc. Definition of core group In compounds of formula (I), the core may comprise one or more, preferably one, aliphatic group. Preferred aliphatic groups derive from polycarboxylic acids and polyols.

Preferred polycarboxylic acids comprise a C4-8 dicarboxylic acid backbone, e.g. 1,5-dipentanoic acid, 1,6-dihexanoic acid, and so on. Further preferred polycarboxylic acids are substituted by one or more COON groups, e.g. along their backbone. Thus preferred polycarboxylic acids comprise 3-6 and more preferably 3-4 COOH groups in total. The presence of multiple COOH groups enable multiple arms to be formed, and for the arms to remain separated in space. Examples of suitable aliphatic cores may be formed from polycarboxylic acids selected from tricarballyic acid, 1,2,4- butanetricarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid, and aconitic acid.

Preferred polyols comprise a C3-12 backbone, e.g. 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, and so on. Further preferred polyols are substituted by one or more OH groups, e.g. along their backbone. Thus preferred polyols comprise 3-8 OH groups and more preferably 3-6 OH groups in total. The presence of multiple OH groups enables multiple arms to be formed, and for the arms to remain separated in space. Examples of suitable aliphatic cores may be formed from polyols selected from glycerol, 1,2,4-butanetriol, erythritol, threitol, 1,2,6-hexanetriol, 1,2,10-decanetriol, 1,2,3-hexanetriol, sorbitol, mannitol and inositol.

In preferred compounds of formula (I) and (la), the core comprises at least one aromatic or heteroaromatic group, preferably an aromatic group. Aromatic or heteroaromatic groups are generally preferred because they enable the "arms" of the compound to be spatially separated, which avoids any steric hindrance issues. The presence of an aromatic or heteroaromatic core also tends to improve the compatibility of the compounds with the types of solvents with which they are preferred used.

In preferred compounds of formula (I) and (la), the core comprises 1 to 6, more preferably 1 to 4 and still more preferably 1, 2, or 3 aromatic or heteroaromatic groups, preferably aromatic groups.

Preferably the core comprises 6-24 atoms, preferably C atoms. More preferably the core comprises 6-18 atoms, preferably C atoms. Particularly preferable the core comprises 6, 12 or 18 atoms, preferably C atoms.

Preferably the core is not fused. Preferably the core is not substituted by any group (e.g. C1_6 alkyl, halo, NO2, etc) other than by the "arms" as hereinbefore described.

In preferred compounds of formula (I) and (la) the core is selected from the group consisting of: (ii) Preferably the core is (i) or (ii), and most preferably (i).

In preferred compounds of formula (I) or (la) the core is selected from the group consisting of: wherein the bonds terminating in wavy lines show the positions at which SP is connected to said core. Preferably the "arms" are distributed around the core so they are separated from one another.

Particularly preferred compounds of the invention are those of formula (Ib), (lc) or (Id), and especially those of formula (Ib): (lb) (lc) (Id) wherein L, SP, a, R1 and R2 are as hereinbefore defined in relation to formula (la); and k+I = a as hereinbefore defined.

Definition of Spacer group In preferred compounds of formula (I), (la), (Ib), (Ic) and (Id) each spacer group is the same. The purpose of the spacer group is to separate the core from the cross-linkable group and cross-linkable groups from each other and to increase the degree of freedom to the cross-linkable group, thereby increasing the likelihood that cross-linking occurs. The nature of the spacer may also be used to modify the solubility of the compound and/or to tune its interaction with polymers with which the compound is mixed.

In preferred compounds each spacer group is selected from C3_20 alkylene, and C3_20 alkenylene, and even more preferably 03-20 alkylene. In preferred compounds of formula (I), (la), (Ib), (Ic) and (Id) each spacer group is C3_20 alkylene, more preferably C4_18 alkylene, still more preferably C5_16 alkylene and yet more preferably C5_14 alkylene.

Optionally the spacer group is substituted, but is preferably unsubstituted. Particularly preferred compounds of the invention are those of formula (Ibi): wherein L, a, R1 and R2 are as hereinbefore defined in relation to formulae (la) and (Ib); and n is an integer selected from 3-20, preferably 4-16, more preferably 4-10 and still more preferably 6-8.

Definition of linking group In preferred compounds of formula (I), (la), (Ib), (Ibi), (Ic) and (Id) each L is a linking group.

In some preferred compounds of formula (I), (la), (Ib), (Ibi), (Ic) and (Id) the linking group comprises C(0)0, C(0), OC(0)O, C(0)NH, 0, S, SO2, SO2NH, NH, and NMe. In some particularly preferred compounds of the invention the linking group consists of C(0)0.

In some preferred compounds of formula (I), (la), (Ib), (Ibi), (Ic) and (Id) the linking group comprises an aromatic or heteroaromatic group, preferably an aromatic group. In such compounds, preferably each L is a linking group of formula (III): R3)72._ "\R3 R3..."1"? (III) wherein each R3 is selected from C(0)0, OC(0), C(0), 00(0)0, C(0)NH, 0, S, 302, SO2NH, NH, and NMe, and preferably C(0)0 and OC(0).

Particularly preferred compounds of the invention are those of formula (I bii) and a °bhp wherein a, n, R1 and R2 are as hereinbefore defined in relation to formulae (la), (lb) and (Ibi). Especially preferred compounds of the invention are selected from the compounds shown below: The present invention also relates to a method for making a compound of formula (I) comprising: reacting a compound of formula (V) with a compound of formula (VI): CORE (L')a (V) L"-SP-X (VI) wherein the core comprises at least one aromatic, heteroaromatic or aliphatic group; the reaction between each L' and L" generates L and each L is a linking group or a covalent bond, preferably a linking group; each SF' is a spacer group, preferably selected from alkylene, alkenylene, arylene or heteroarylene, optionally interrupted by one or more heteroatoms and optionally each X is a latent cross-linkable group, preferably a cross-linkable group that is activatable by actinic radiation; and a is an integer selected from 3-20.

Preferably L' is CO-LG, wherein LG is a leaving group, such as halo e.g. Cl.

Preferably L" is OH. The linking group formed then comprises ester (COO).

The skilled person will readily be able to choose appropriate L' and L" depending on the L desired. Similarly, the conditions for carrying out the identified reaction can be readily determined by a synthetic chemist using their knowledge of synthetic chemistry.

The present invention also relates to a composition comprising: (i) a compound of formula (I) as hereinbefore described; (ii) a polycyclic olefin, preferably a polynorbornene; and (iii) a photosensitiser. During device fabrication, the composition further preferably comprises a solvent to facilitate solution processing. The majority of the solvent subsequently evaporates during drying, hence the final composition present in the device is substantially solvent free. In devices of the present invention, the composition preferably consists of (Da compound of formula (I) as hereinbefore described; (ii) a polycyclic olefin, preferably a polynorbornene; and (iii) a photosensitiser.

Preferred compositions of the invention comprise 1-30 wt% compound of formula (I), more preferably 2-20 wt% compound of formula (I) and still more preferably 5-10 wt% compound of formula (I), based on the total dry weight of the composition.

Preferred compositions of the invention comprise 55-98.5 wt% polycyclic olefin, preferably polynorbornene, more preferably 70-97.5 wt% polycyclic olefin, preferably polynorbornene and still more preferably 75-90 wt% polycyclic olefin, preferably polynorbornene, based on the total dry weight of the composition.

Preferred compositions of the invention comprise 0.5-15 wt% photosensitiser, more preferably 1-10 wt% photosensitiser and still more preferably 5-10 wt% photosensitiser, based on the total dry weight of the composition.

Polycyclic olefin The polycyclic olefin present in the compositions of the present invention is preferably a polynorbornene, and more preferably a polynorbornene derived from norbornene monomers of formula (X): (X) wherein Z is selected from -CH2-, -CH2-CH2-or -0-; z is 0 or an integer from 1 to 5; and each of 513, Rii, R12 and R13 are independently selected from H, 01_26 hydrocarbyl, 01-25 halohydrocarbyl or 01_26 perhalocarbyl.

Thus a preferred polynorbene present in the compositions of the present invention comprises a repeating unit of formula (XI): (XI) wherein Z is selected from -CH2-, -CH2-CH2-or -0-; z is 0 or an integer from 1 to 5; and each of 513, Rii, R12 and R13 are independently selected from H, 01_26 hydrocarbyl, C1-25 halohydrocarbyl or 01_26 perhalocarbyl.

In preferred monomers of formula (X) and repeating units of formula (XI) Z is - CH2-In other preferred monomers of formula (X) and repeating units of formula (XI) z is 0, 1 or 2, still more preferably 0 or 1 and especially preferably 0.

In preferred monomers of formula (X) and repeating units of formula (XI), at least one of R10, R11, R12 and rcn13 is H, more preferably at least two of R10, R11, R12 and R13 is H and still more preferably at least three of R10, R11, R12 and R13 is H. Optionally, each of R10, Rii, R12 and 513 is H. In some preferred monomers of formula (X) and repeating units of formula (XI), one of R13,R11 R12 and R13 is C1_26 alkyl or C7-24 aralkyl. Preferred 01.25 alkyl groups include 04-20 alkyl groups, and more preferably C6-18 alkyl groups. Preferred aralkyl groups are -(CH2)2_6-Phenyl.

In some preferred monomers of formula (X) and repeating units of formula (XI), one of R10, R11, r,12 and R13 comprises a cross-linkable group. Representative examples of cross-linkable groups include a maleimide, an epoxy, a vinyl, an acetyl, an indenyl, a cinnamate or a coumarin group. More preferably the cross-linkable group present is a maleimide group, e.g. a 3-monoalkylmaleimide or 3,4-dialkylmaleimide. Preferably the cross-linkable group is connected to the norbornene core via an alkylene linker, e.g. a 01_12 alkylene linker.

In some preferred monomers of formula (X) and repeating units of formula (XI), one of 510, R11, R12 and 513 is a hydrocarbyl group comprising a terminal hydroxyl, carboxy or oligoethyleneoxy group. Representative examples include a terminal hydroxyalkyl, alkylcarbonyloxy (e.g. acetyl), hydroxyoligoethyleneoxy, alkyloxyoligoethyleneoxy or alkylcarbonyloxyoligoethyleneoxy moiety, where "oligoethyleneoxy" is -(CH2CH20)s-wherein s is 1, 2 or 3 Particularly preferred monomers of formula (X) are shown below. The corresponding repeating units of formula (XI) are also preferred.

Structure Acronym le NB le Me MeNB le Bu BuNB 0 Hexyi HexNB 0 Octyl OctNB 0 Decyl PENS 100) TD OAc 4) e0AcNB M0 4) OH NBXOH 0 o,..cH2cH2oAc NBCH2GIyOAc 0 o,cH2cH2oH NBCH2GIyOH 0 0.--(cH20F12)2me NBTON 0 00-(cF120F12)3me NBTODD le* DCPD 0 0 DMMIMeNB 0 4.___ le 01.$_ DMMIEtNB N 0 0 0 DMMIPrNB le 0 DMMIBuNB

N

le y4_ DMMIHxNB

N

0 0114_ EtPhDMMINB o 0 0 MMIMeNB

N

0 N 0 MINE le 0 \ MIENS

N

le ON O DHNMINB at Preferred polynorbenes present in the compositions of the present invention may comprise one or more repeating units of formula (XI). For instance, the polycyclic olefin, preferably polynorbornene, may comprise 2 or 3 different repeating units of formula (XI) and preferably 2 different repeating units of formula (XI). When more than one type of repeating unit is present in a polymer, the skilled person will be able to readily determine suitable ratios depending on the precise properties desired for a given application. Preferred copolymers are random copolymers.

Preferred polynorbenes present in the compositions of the present invention have a Mw of 5,000 to 500,000, more preferably 30,000 to 400,000 and still more preferably 60,000 to 250,000.

Suitable polynorbornenes may be synthesised using methods known in the art. Alternatively, suitable polynorbornenes for use in the present invention are commercially available, e.g. from Sumitomo Bakelite.

Photosensitiser The photosensitiser present in the compositions of the present invention is preferably a Type II photosensitiser and still more preferably a thioxanthone derivative. These photosensitisers have been found to be the most efficient at reducing the curing time of, e.g. polynorbornenes. This is thought to be due to the excited sensitiser molecule efficiently activating the DMMI group by triplet-triplet energy transfer. Preferably the thioxanthone derivative comprises the moiety of formula (XII): wherein each R is independently selected from H, halogen, and hydrocarbyl; and r is 0 or an integer from 1 to 4. Preferably R is an integer from 1 to 4.

Optionally, each R may be C1_25 alkyl, C2_25 alkenyl or C2_25 alkynyl, optionally interrupted by one or more heteroatoms, preferably 0.

Representative examples of suitable photosensitisers include 1-chloro-4-propoxythioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone (DETX) (CAS 82799-44-8), 2-isopropylthioxanthone (CAS 5495-84-1), thioxanthone, CPTX (CAS 142770-42-1) and mixtures thereof.

Suitable photosensitisers for incorporation into the compositions of the invention are commercially available. Examples include: Speedcure 7010 from Arkema, and Omnipol-TX from IGM resins.

Solvent To facilitate solution processing, the composition of the invention further comprises a single solvent or mixture of two or more solvents. A wide range of solvents may be used, e.g. toluene, 3-methylthiophene, cyclopentanone, chlorobenzene, ethylcyclohexane, p-xylene, cyclopentanol, o-xylene, 2-heptanone (MAK), anisole, cumene, cyclohexanone, alpha-pinene, bromobenzene, n-propylbenzene, cyclohexanol, 3-methylcyclohexanol, p-ethyltoluene, mesitylene, 1,2,4-trimethylbenzene, tbutylbenzene, diisobutyl ketone, phenetole, 3-methylcyclohexanone, 4-methylcyclohexanone, t-butylcyclohexane, 1,3-benzodioxole, 4-methylanisole, 3-methylanisole, indane, 1,2,3-trimethylbenzene, p-cymene, o-dichlorobenzene, diethylbenzene (mix.), 2,6-dimethylanisole, n-butylbenzene, decalin (mix.), ethyl heptanoate, 2,3-dihydrobenzofuran, 2,5-dimethylanisole, 2,4-dimethylanisole, 3,5-dimethylanisole, (-)-fenchone, phenyl acetate, 1,2,3,5-tetramethylbenzene, 1,2,4,5-tetramethylbenzene, methyl benzoate, 3,4-dimethylanisole, NMP, acetophenone, 1,3-diisopropylbenzene, g-butyrolactone, benzyl alcohol, benzyl acetate, tetralin, veratrole, ethyl benzoate, isophorone, propiophenone, alpha-terpineol, methyl phenylacetate, n-hexylbenzene, n-propyl benzoate, 4-phenyl-2-butanone, 2-phenoxyethanol, bicyclohexyl, cyclohexylbenzene, 1-methylnaphthalene, 1,4-benzodioxane, ethyl hydrocinnamate, butyl benzoate, 2-pyrrolidinone, 4-methoxybenzyl alcohol, 1-methoxynaphthalene, ethyl cinnamate, N-cyclohexyl-pyrrolidinone, diisopropyl naphthalenes, dodecylbenzene and mixtures thereof.

Some preferred solvents include organic ketones such as methyl ethyl ketone (MEK), 2-heptanone (MAK), cyclohexanone, cyclopentanone, esters such as ethyl benzoate, ethers such as butyl-phenyl ether, 4-methylanisole and propylene glycol methyl ether actetate and aromatic hydrocarbons such as cyclohexylbenzene, or mixtures thereof.

Preferably, the total concentration of the polycyclic olefin, preferably polynorbornene, in the solution is from 3-30 wt%, based on the total weight of the composition.

Preferably, the total concentration of the compound of formula (I) in the solution is from 0.15-3 wt%, based on the total weight of the composition.

Preferably, the total concentration of the photosensitiser in the solution is from 0.3-3 wt%, based on the total weight of the composition.

The present invention also relates to a method for making a composition as hereinbefore described, comprising mixing (i) a compound of formula (I) as hereinbefore described; (ii) a polycyclic olefin, preferably a polynorbornene, as hereinbefore described; and (iii) a photosensitiser as hereinbefore described in a solvent. Preferred solvents are described above. Any conventional mixing technique may be employed.

Structures and devices The compound of formula (I) and compositions comprising the compound of formula (I) are ideal for the preparation of structures present in electronic devices and therefore electronic devices. The present invention therefore also relates to a structure comprising: (i) a substrate; and (ii) the composition as hereinbefore defined on at least one surface of said substrate.

Preferably the composition is present as a layer on the substrate.

Preferably the substrate is selected from an electrode material, such as Al, Ag, Au, Cr, Ni, Mo ITO or another material patterned with ITO. The present invention is particularly advantageous when the electrode material is ITO or another material patterned with ITO.

Preferably the substrate is a semiconducting layer. It may be any conventional semiconducting layer. Preferably the semiconducting layer comprises a semiconducting polymer.

A significant advantage of the compositions of the invention comprising a compound of formula (I) is that adhesion of the composition to a substrate such as ITO is significantly improved. Preferably the adhesion of a composition of the invention, e.g. a cured composition, to ITO is at least 5 N/cm, and more preferably at least 5 N/cm as determined by the test method set out in the examples herein.

Deposition and/or forming of a layer of the composition of the invention on a substrate is preferably carried out by solution processing. Preferred techniques include dip coating, spin coating, slot die or slit coating, ink jet printing, letter-press printing, screen printing, doctor blade coating, roller printing, reverse-roller printing, offset lithography printing, flexographic printing, web printing, spray coating, brush coating, or pad printing. Spin coating, flexographic printing, inkjet printing and slot die coating are preferred. In each technique, deposition is followed by evaporation of the solvent to result in formation of the composition, e.g. in the form of a layer, on the substrate.

The composition of the invention should be applied to an appropriate thickness, which will depend on the device being fabricated and the materials used. The person skilled in the art will readily be able to determine a suitable dry film thickness for the layer formed by the composition of the invention.

Crosslinking of composition of the invention is preferably carried out by exposing the composition to electromagnetic (actinic) radiation such as X-ray, UV or visible radiation. For example, actinic radiation with a wavelength of from 11 nm to 700 nm, such as from 200 to 700 nm, may be employed. A dose of actinic radiation for exposure is generally from 25 to 15,000 mJ/cm. Suitable radiation sources include mercury, mercury/xenon, mercury/halogen and xenon lamps, argon or xenon laser sources, or X-ray. Such exposure to actinic radiation causes crosslinking in the polynorbornene, in the compound of formula (I) and between such compounds. Advantageously these reactions occur with few, if any, side products.

Optionally baking is carried out. In some cases, heating the structure, e.g. to a temperature of 70-130 °C, can further promote cross-linking.

The present invention also relates to a method for making a structure as hereinbefore defined comprising: depositing a composition as hereinbefore defined by solution processing on at least one surface of a substrate; (ii) drying said composition; and (iii) cross-linking said composition to produce said structure.

Typically the structure of the present invention is incorporated into an electronic device. Thus the present invention also relates to an electronic device comprising a structure as hereinbefore described. The electronic device is preferably an organic electronic device. Preferred devices include Organic Field Effect Transistors (OFETs), such as Organic Thin Film Transistors (OTFTs), Organic Photovoltaic (OPV) devices, Bio sensors and other Organic Sensors. Particularly preferred devices are OFETs, especially electrolyte gated TFTs, OTFTs. OFETs and OTFTs may be top gate or bottom gate devices.

The other components or functional layers of the electronic device, such as the substrate, the gate and source and drain electrodes, and organic semiconductor layer, can be selected from standard materials, and can be manufactured and applied to the device by standard methods. Suitable materials and manufacturing methods for these components and layers are known to a person skilled in the art and are described in the literature. Exemplary deposition methods include the liquid coating methods previously described as well as chemical vapor deposition (CVD) or physical vapor deposition methodologies.

The gate, source and drain electrodes of the electronic device of the present invention may be deposited or formed by liquid coating, such as spray-, dip-, web-or spin-coating, or by vacuum deposition methods, such as physical vapor deposition (PVD), chemical vapor deposition (CVD) or thermal evaporation. Suitable electrode materials and deposition methods are known to the person skilled in the art. However the compound of formula (I) and compositions comprising this compound are particularly suitable for use with metal oxides such as indium tin oxide (ITO), F-doped ITO or Al-doped ZnO, in particular ITO.

The invention will now be described with reference to the following non-limiting examples.

EXAMPLES

Synthesis of compounds 1 and 2 Preparation of intermediate 2,3-Dimethylmaleimide was reacted with a small excess of 6-amino-1-hexanol (1.05 eq) in toluene. The reaction mixture was heated at reflux until the reaction was completed.

The reaction mixture was evaporated in vacuo to yield a colourless oil product (101 wt% yield). 1H N MR showed the presence of 1.2 wt% toluene, thus the adjusted yield was 99 wt%. The product was used without further purification.

Preparation of compound 1 0 + H2N

O COCI O

Et3N N JCI)

CIOC COCI DMAP

THE

compound 1 The intermediate DMMI-C6-OH was dissolved in THE and trimethylamine (1.4 eq.) Trimesoyl chloride (0.4 eq) was added dropwise at 0-10 °C then the reaction mixture was allowed to warm to room temperature. The reaction completed after 2 hrs. The reaction mixture was then filtered to remove Et3N-HCI and then evaporated. The resulting residue was redissolved in DCM, and washed with dilute acid to remove residual base. The resulting DCM solution was filtered through silica using 6% ethylacetate in DCM and was then evaporated to an oil. The product, compound 1, was obtained in 99.7 wt% purity, m.p. 76-80 °C.

Preparation of compound 2 Step (1) CO3H CO2H

HO

HO

5-Hydroxyphthalic acid was heated in reflux with 2.5 eq. of the intermediate DMMI-C6-OH in toluene with 5 mol% pTSA in a Dean-Stark apparatus for 72 hrs. The resulting mixture was filtered to remove a white solid, which was unreacted 5-hydroxyphthalic acid. The resulting solution contained the product with a purity of 98.6 % (by HPLC).

Step (2)

OCI

O

RO2C 02R

M R=

M

COCI

CIOC

E13N, DMAP

THF Me

compound 2 The product from step (1) was dissolved in THF, along with benzene-1, 3, 5-tricarbonyl trichloride (0.3 eq), trimethylamine (1.5 eq.) and DMAP. The reaction completed after 2 hrs. The reaction mixture was then filtered to remove Et3N-HCI and the resulting solution was filtered through silica and then evaporated to a viscous, colourless oil. The product, compound 2, was obtained (88 wt% yield).

The other compounds and polymers used in the examples are set out in the table below. They were all commercially available.

Component Type Function Polyolefin Polynorbornene Dielectric Speedcure 7010 Thioxanthone-based Photosensitiser CPTX Thioxanthone-based Photosensitiser PGMEA Solvent

Table 1

Test methods * Solubility was tested by visual observation. The solutions were mixed using a magnetic stirrer for 12 hrs. Solutions with a cloudy appearance or undissolved particles were considered insoluble.

* Coating was tested by visual observation. The coating quality was assessed by checking for de-wetting and colour changes relating to coating thickness. Film thickness tests across a substrate were also used using a stylus profilometer.

* Adhesion tests were carried out analogously to ASTM D6862-11 (2021).

Different substances were carried out using a Mecmesin Imperial 1000 adhesion tester fitted with a 50 N load cell and compliance value set at 20 N (equivalent to 8 N/cm). Adhesion was determined using a 90° peel test and 25 mm width Tesa 4965 tape. A scalpel was used to make both an initiation cut at the start of the peel and along the sides of the tape to eliminate the effects of the wider film adhesion/cohesion.

Preparation and testing of compositions of the invention The components of the composition, as shown in table 2 below, were mixed in sealed amber glass bottles either on laboratory rollers or a stirrer plate at room temperature for 12 hours to produce a homogenous, stable formulation. In Table 2, the numerical values for the components are all in weight percent.

The compositions were coated at thicknesses of 0.5 -1 pm using spin-coating or bar coating on TAC substrates coated with either SU8 (Nippon Kayaku Co.), Indium tin-oxide (ITO) or SU8 with a patterned ITO layer applied (this is referred to as "mixed adhesion in Table 2 below). All substrates were first treated with a 500 W oxygen plasma for 30 seconds in a plasma chamber.

Coated films were dried on a hotplate at 80 °C for 5 minutes and then allowed to cool to room temperature. Next, the films were cross-linked using a 365 nm LED lamp with a total UV dose of 2 -10 J/cm2.

Adhesion testing was carried out as described above and the results are shown in Table 2 below, wherein CE represents comparative example. CE1 lacks any adhesion additive.

# Component Function CE1 1 2 3 4 5 6 1 Polyolefin Dielectric 10 10 10 10 10 9.3 11 2 Speedcure Photosensitiser 0.5 0.5 0.5 0.47 0.55 3 CPTX Photosensitiser 0.05 0.05 4 Compound 1 1.0 Compound 2 0.5 1.5 1.25 0.93 1.1 6 PGMEA Solvent 89.5 89.45 89.45 88 88.75 89.3 87.35 Evaluation Results 7 Solubility Visual check / - / V / / / 8 Coating Test Visual check / / V V V / V 9 ITO N/cm 0.1 8 8 8 8 8 8 Adhesion SU8 N/cm 8 2.8 8 8 8 8 Adhesion 11 Mixed N/cm 0.4 - 4 8 8 8 8 Adhesion Table 2: Solubility: V = soluble and stable formulation -= soluble but unstable formulation, x = poor solubility. Adhesion values in N/cm.

The results show that the compositions of the invention, comprising the compound 1 or 2, achieves much stronger adhesion to the substrate, in particular ITO and SU8 with a patterned ITO layer applied. CE1 lacks any compound of the invention and does not adhere to ITO or SU8 with a patterned ITO layer applied whereas in examples 1 the composition of the invention comprising compound 1 significantly increases the level of adhesion achieved. Similarly examples 2-6, comprising compound 2, achieve adhesion to both ITO and SU8 with a patterned ITO layer, despite the presence of UV-photosensitisers (CPTX or Speedcure 7010). A range of concentrations of compound 2 are shown to be effective at improving adhesion.

Films comprising 0-1.5 wt% of the compounds of the present invention were also tested to ensure curing could still be carried out. The films achieved the same level of curing (tested by solvent resistance) with a test UV dose of 4 J/cm2 as films lacking the compounds of the invention.

Claims (25)

1. CLAIMS: A compound of formula (I): 1 (I)L-SP-X awherein the core comprises at least one aromatic, heteroaromatic or aliphatic group; each L is a linking group or a covalent bond, preferably a linking group; each SP is a spacer group, preferably selected from alkylene, alkenylene, arylene or heteroarylene, optionally interrupted by one or more heteroatoms and optionally each X is a latent cross-linkable group, preferably a cross-linkable group that is activatable by actinic radiation; and a is an integer selected from 3-20.
2. 2. A compound as claimed in claim 1, wherein each X is a cross-linkable group via a [27c+27c] photo-cycloaddition reaction.
3. 3. A compound as claimed in claim 1 or 2, wherein each X is a cross-linkable group of formula (II): wherein R1 is selected from H, and C1_6 alkyl, preferably methyl; R2 is selected from H, and 01_6 alkyl, preferably methyl; or R1 and R2, together with the carbon atoms to which they are attached form a ring, wherein said ring is optionally fused to a further ring.
4. A compound as claimed in claim 3, wherein R1 and R2 are methyl.
5. A compound as claimed in any preceding claim of formula (la):
6. 6. A compound as claimed in any preceding claim, wherein each a is 3-12, more preferably 3-6, and still more preferably 3 or 4.
7. 7. A compound as claimed in any preceding claim wherein the core comprises at least one aromatic or heteroaromatic group, preferably an aromatic group.
8. 8. A compound as claimed in any preceding claim, wherein the core is selected from the group consisting of: wherein the bonds terminating in wavy lines show the positions at which SP is connected to said core.
9. A compound as claimed in any preceding claim of formula (lb), (lc) or (Id): laSP R2wherein the core, L, SP, and a are as defined in claim 1; and R1 and R2 are as defined in claim 3 or 4. (la) (lc) (Id)wherein L, and SP are as defined in claim 1; R1 and R2 are as defined in claim 3 or 4; and k+I = a as defined in claim 1, i.e. 3-20, more preferably 3-6, and still more preferably 3 or 4.
10. 10. A compound as claimed in claim 9 of formula (lb).
11. 11. A compound as claimed in any preceding claim, wherein each spacer group is selected from C3-2o alkylene, and C3-2o alkenylene. (lb)
12. 12. A compound as claimed in any preceding claim of formula (Ibi): wherein L, and a are as defined in claim 1; R1 and R2 are as defined in claim 3 or 4; and n is an integer selected from 3-20
13. 13. A compound as claimed in any preceding claim, wherein each Lisa linking group consisting of C(0)O.
14. 14. A compound as claimed in any one of claims 1 to 13, wherein each L is a linking group comprising an aromatic or heteroaromatic group, preferably an aromatic group.
15. 15. A compound as claimed in any preceding claim, wherein each Lisa linking group of formula (Ill): ".\ s3 R3)11 (Ill) wherein each R3 is selected from C(0)O, OC(0), C(0), 00(0)0, C(0)NH, 0, S, SO2, SO2NH, NH, and NMe, and preferably C(0)0 and OC(0).
16. 16. A compound as claimed in any preceding claim selected from the structures shown below:
17. 17. A method for making a compound of formula (I) as claimed in any one of claims 1 to 16 comprising: reacting a compound of formula (V) with a compound of formula (VI): C-CORE) (Oa (V) 12 -SP -X (VI) wherein the core comprises at least one aromatic, heteroaromatic or aliphatic group; the reaction between U and L" generates L and each L is a linking group or a covalent bond, preferably a linking group; each SP is a spacer group, preferably selected from alkylene, alkenylene, arylene or heteroarylene, optionally interrupted by one or more heteroatoms and optionally substituted; each X is a latent cross-linkable group, preferably a cross-linkable group that is activatable by actinic radiation; and a is an integer selected from 3-20.
18. 18. A composition comprising: a compound of formula (I) as claimed in any one of claims 1 to 16; (ii) a polycyclic olefin, preferably a polynorbornene; (iii) a photosensitiser; and (iv) optionally a solvent.
19. 19. A method for making a composition as claimed in claim 18, comprising mixing (i) a compound of formula (I) as claimed in any one of claims 1 to 16; (ii) a polycyclic olefin, preferably a polynorbornene; and (iii) a photosensitiser in a solvent.
20. 20. A structure comprising: (i) a substrate; and (ii) the composition as defined in claim 18 on at least one surface of said substrate.
21. 21. A structure as claimed in claim 20, wherein said composition is present as a layer on said substrate.
22. 22. A structure as claimed in claim 20 or 21, wherein said substrate is selected from ITO or another substrate patterned with ITO.
23. 23. A method for making a structure as claimed in any one of claims 20 to 22 comprising: (i) depositing a composition as claimed in claim 18 by solution processing on at least one surface of the substrate; (ii) drying said composition; and (iii) cross-linking said composition to produce said structure.
24. 24. An electronic device comprising a structure as claimed in any one of claims 20 to 22.
25. 25. An electronic device as claimed in claim 24, which is a thin film transistor.