Louis le Brocquy's new exhibition illustrates the way the renowned painter's style has developed over five decades, writes Aidan Dunne

In 1939, while he was living for a time in France, Louis le Brocquy received a letter from Ireland, together with a newspaper photograph of a group of schoolgirls taking part in an Easter procession from Adam and Eve's Church on Merchants Quay in Dublin. The photograph was dated June 16th, which is now, of course, Bloomsday. Having, as he said once, "a slow-moving mind", le Brocquy put the photograph aside and only considerably later, in 1962, returned to it.

By then he was making paintings of single, isolated human presences emergent against bleached, white textured grounds. Oddly, these human images are both spectral and extremely corporeal, even visceral. On the one hand they verge on complete dissolution, on the other they retain a sense of inner, pulsing life. Often the central vertical line of the spinal column is the armature that supports the picture.

It was, he says, seeing figures exposed to powerful sunlight against the whitewashed walls of buildings in La Mancha, in Spain, that partly inspired these works. "The bodies themselves seemed completely insubstantial, and only the shadows remained tangible. I've never regarded the human presence in quite the same way ever since."

In his Procession studies he turns to multiple individuals, a communal moment. It is a moment of intense, bustling vitality. Yet while he retains its sense of vitality, le Brocquy also explodes the image, radically fragmenting it, suggesting myriad perspectives. This rather deconstructs the communal nature of the original image, as the artist readily assents. "I wasn't painting from the point of view of a crowd. To my mind each girl has her own individuality; each one is as much alone as the subjects of any of the presence or head paintings."

He returned again to the Procession series in the 1980s. All of these works, together with a roughly comparable series inspired by a 17th-century painting by Cornelis Bisschop of a group of young boys playing with a goat in a wood, were gathered for exhibition at Crawford Municipal Art Gallery, in Cork, and now the Taylor Galleries, in Dublin. The two sets of work have slightly different overtones in his mind.

The Processions "are geared to the whole idea of time", he says. "The moment had long slipped into oblivion, and there was something poignant about that. So I regard the paintings as successive attempts to try to capture this reality, something of the emotional experience, to make real something that is gone, rather along the lines of Joyce's 'succession of present moments'."

With Children In A Wood, on the other hand, "I didn't have this preoccupation with time, though the works do have certain things in common, such as their sense of correlated movement. But when I was working on Children In A Wood it came to me that the image recalled the games we played as children under a giant thuja tree - it was like a great tent - in Co Roscommon. I now think these memories have a lot to do with why I was drawn to this curious little painting."

Le Brocquy is best known for his portrait images of Yeats, Joyce and Beckett, "imaginative reconstructions" that are not so much portraits in the conventional sense of the term as attempts at "an archaeology of the spirit". The head images, he notes, "are in a way a continuum from the presences, with just a change of subject matter. If you look at the torsos, they very seldom have much of the head."

Triggered by seeing ancient Polynesian decorated skulls at the Musée de l'Homme, in Paris, and subsequently informed by the Celtic head cults that envisaged "the head as a magic box that held the spirit prisoner", le Brocquy set about making a series of ancestral heads. Initially, he was "groping for my own human ancestry". But it was a commission in the mid-1970s from Per-Olov Borjeson, a Swedish gallery director, that focused his attention on literary figures. Borjeson was putting together an international show based on images of Nobel prize-winners. He asked le Brocquy to select an Irish laureate.

"There were several possibilities," he recalls. "But I was drawn to Yeats because he was the one I knew best in every sense" - not least because he had been a family friend. In the process of making a number of studies, "I gradually realised that you couldn't any longer do a single effigy, as Ingres did, for example, as a definitive account of an individual. Many factors, including film, photography and psychology, had firmly established the idea that we are multifaceted beings."

So although all of his images of Yeats are recognisably Yeats, they are all different, and they all suggest the depths and complexity of the inner life of the imagination. When the Musée d'Art Moderne in Paris organised a show of the Yeats heads in 1976, le Brocquy found himself alone there one day before the opening. He fell into conversation with a man who came in. "He told me he was the art critic of Le Monde, and he said, look, I don't understand, these are supposedly all Yeats, but they are all different. All I could say was, well, it worries me too. One day I try to do Yeats and he looks a bit like Roosevelt, the next and he looks a bit like Brando. I was, I said, pretty mystified." He was delighted, however, when Anne Yeats wrote that in his studies she saw her father very much as he was.

His most recent head is of a contemporary iconic figure, Bono, commissioned by the National Gallery of Ireland. "Bono worried me, for this reason. When I paint someone, I'm not trying for a likeness. Of course I am attentive to the features, but now and again I look at an image and don't myself recognise that it is Beckett or whoever. And Bono is so universally known that I thought it would be of no use to either his many fans, or indeed to the gallery, if I produced my own internalised image of him." In the event, he's "not displeased with it now". In fact he has known Bono for about 20 years.

The commission to paint a rock star not only indicates le Brocquy's sustained energy and reputation - he celebrated his 87th birthday recently - but also contrasts with his departure from Ireland in 1946. The family business was the Greenmount Oil Company, and he initially studied chemistry and went to work for the firm. But he was drawn to painting and set about educating himself in that direction. Apart from his sympathy for the classical tradition in Western art, he had a tremendous grasp of, and flair for, modernist ideas in his work, which set him at odds with the artistic orthodoxy in Ireland. He was instinctively aligned with the modernist wing of the art world here, but possibilities were limited.

"It was virtually impossible to live as a painter in Ireland unless you had a private income. I painted murals on pub walls in Tullamore and sets for Jimmy O'Dea - in fact set painting was relatively lucrative."

When the dealer Charles Gimpel took him on he was encouraged to try London, where he settled. Although a great deal of this thematic material is Irish, he has apparently worked happily in Ireland, in London and in France, where he was based for many years with his partner, the painter Anne Madden.

"I've always been able to work anywhere. I'm not that influenced by place. Of course I very much appreciated the good light in the south of France, but it never entered into my work in the way that it did Anne's. Place doesn't matter that much to me."

Despite remarkable antipathy towards his work in official art circles here during the early days - the Hugh Lane turned down one of his most famous paintings, the RHA consistently rejected his work - he maintained and developed a presence in Ireland.

He is philosophical about the question of reputation. "I became quite well established in London. It was a very welcoming place. The Arts Council, the British Council bought work and so forth."

Then he and Anne moved to France, in 1958, and he built up a presence in Paris. "I thought things would go on in the same kind of way, but not at all. Any painter can come to Paris and, once there, be accepted. But if you leave, you're gone: you will be instantly forgotten." Which is why he was delighted to renew contacts with Paris recently.

His most recent body of work, shown by Gimpel Fils at the International Contemporary Art Fair in Paris, returns to the theme of the isolated human presence. These paintings, 21 in all, and on a large scale, will be shown in Dublin at some stage in the future. "I'm very keen that they will be seen here, because in a sense I see them as a last thrust, if you know what I mean."

Rather than coalescing from a radiant white ground, as in the earlier Presences, these figures emerge "from a textured grey matrix, as though from particles, rhythmic forms distantly related to cubism", he says.

"It is as though each image establishes its own rhythm and becomes concentrated into a figure, while from the centre the figure correspondingly sheds outwards its inner reality into this rhythmic context."

He was intrigued and gratified when, walking on a beach in the west of Ireland with Anne, "I recognised the same kind of natural rhythm impressed into the sand by the outgoing tide. It pleased me because, you know, I don't govern it, I obey it."

• Procession is at the Taylor Galleries, Dublin, until December 13th