Company history

The company began in April 1936 as Tokyo Ohka Laboratory, a one-man venture by Mukai Shigemasa. Mukai had joined the Tokyo Industrial Testing Laboratory around 1920 and spent his career in applied chemistry at a time when Japan’s young chemical industry still depended on German imports; his ambition was to make at home what the country was buying abroad. What he set out to make was not a photographic material but purified potassium hydroxide — caustic potash — the electrolyte for the alkaline batteries in the safety lamps used underground in coal mines. In October 1940 the laboratory was reorganized into Tokyo Ohka Kogyo Co., Ltd. in Kawasaki with capital of ¥180,000. The name Ohka is a contraction of the Japanese for “applied chemistry”; the company started life as a basic-chemicals specialist.

Through the war years purified potassium and sodium hydroxide were treated as strategic goods — alkaline cells outperformed the older sulphuric-acid batteries that lit the mines. After the defeat the mines pressed for supply again, but potassium chloride was scarce and a process that took twenty hours collapsed with every power cut, until the company persuaded GHQ to give it a dedicated line. At the same time it restarted chloronaphthalene, a heat-resistant insulator, and supplied it as a filler for the capacitors in the C4 field telephones the occupying US forces brought with them — its first working contact with electronics.

In the reconstruction years Mukai recruited chemists and pushed into organic synthesis: benzyl chloride and benzyl acetate for the fragrance trade, and cinnamic acid, which would later be the raw material of the company’s first photoresist. From May 1955 it succeeded with Ohka Seal, the phosphor binder for black-and-white television tubes — the point at which fine chemicals began working directly for electronics. When the 1964 Tokyo Olympics pulled colour television into the mass market, the company researched the photosensitive chemistry used to etch shadow masks together with NHK and three other firms, and developed TPR (Tokyo Ohka Photo Resist) jointly with the Tokyo Industrial Testing Laboratory. The chemistry learned for lamps and perfumes had turned into the chemistry of screens.

The Sagami plant, opened in January 1967 and today the group’s technology innovation centre, put volume production and research on one site. The company went to the over-the-counter market in June 1968, and in 1972 commercialized Japan’s first positive photoresist for semiconductors. The logic that would carry it for the next half century was already visible: the denser the integration, the more the resolution and uniformity of the light-sensitive film decided a chipmaker’s yield, so the accumulated know-how of a specialist became something its customers could not easily replace.

The narrowness was deliberate, and it was defensive. Asked why it would not enter PVC and the other large-volume markets of the day, the company answered that a maker of its size “would not last a moment” there. With capital in the ¥500 million range and some 700 employees, the very smallness of a photoresist market worth about $25.3M (¥6bn) a year was the point — it was a shelter, not a prize. Nor was it ever a pure single-product house: in FY1983 electronic materials were a little under half of sales, process equipment about a fifth and printing materials about a tenth, and photoresist alone was still 36% of sales in 1986. What it narrowed was not the number of businesses but where, year after year, it sent its cash and its engineers.

From the late 1970s the plants followed the customers’ capital-spending cycle inland and then south: Utsunomiya in June 1981, Kumagaya Ohka in September 1983 and the Kumagaya plant that December, and the Aso plant in Kyushu in December 1984. Front-end semiconductor lines cannot be allowed to run dry, so being able to make identical material at several sites was the condition of taking on more customers — the supply structure, as much as the chemistry, was the product.

Tokyo Ohka listed on the second section of the Tokyo Stock Exchange in July 1986, forty-six years after incorporation, and moved up to the first section in September 1990. President Ito Takeo did not present the listing as a fundraising: what he named was the responsibility that came with holding more than 70% of the photoresist market and over 90% of purified potassium hydroxide. Still, the money mattered. Capital spending that had been financed out of retained earnings and bank credit now had an equity market behind it — the Gotemba plant followed in June 1987, TOK Engineering in October 1992 to build the coating and developing equipment in-house, and the Koriyama plant in February 1994.

Abroad, the company did not so much export as relocate. When OHKA AMERICA was set up in March 1987, exports were only about 3% of total sales; what crossed the Pacific was a supply doctrine already proved at home — that a material which degrades in transit has to be held close to the customer’s line, with stock and engineers alongside it. TOK INTERNATIONAL followed in Oregon in April 1989, and in December 1992 the two were merged back into a single OHKA AMERICA. It took ten years from the first American base before semiconductor photoresist could actually be made in Oregon.

The same logic took the company to Taiwan, where the foundry model was becoming the centre of world chip manufacturing: a Taiwanese subsidiary was established in January 1998 to supply the island’s fabs directly, and it became the engine of overseas sales. A new head office was completed in Kawasaki in July 2000, a distribution centre at Ebina in November 2003, and in January 2006 OHKA AMERICA was renamed TOKYO OHKA KOGYO AMERICA — the group’s geography, and its brand, settled into the shape it still has.

In August 2012 the company carved its leading-edge work out into a separate subsidiary, TOK Advanced Materials, to develop and produce resists for advanced logic and memory. As geometries moved toward a few nanometres, small differences in purity and resolving power began to decide a customer’s yield outright, and that work needed to run at a different speed from the general line. The subsidiary gave the company a way into the fine-geometry demands of Korea and Taiwan.

Leadership changed character alongside it. Akutsu Ikuo, a semiconductor-materials technologist who had run the Taiwanese operation, handed the presidency in 2019 to Taneichi Yoriaki, a career insider from sales and new-business development, and moved up to chairman — a shift in the kind of person the top job was thought to require. Under Taneichi the earnings base moved up a full range: FY2021 set records at $1.3B (¥140bn) of sales and ¥20.7bn of operating profit, FY2022 went further, and FY2023 dipped with the semiconductor correction.

The AI build-out then took it higher again — FY2024 at ¥201.0bn of sales, and FY2025 at $1.6B (¥237bn) (+18%) with operating profit of $316.6M (¥47bn) (+43%), holding an operating margin above 20%. Eighty-five years after it was founded, the company has still never diversified out of light-sensitive chemistry. The narrowness that was a hiding place in 1984 now works as a moat: at the leading edge, materials knowledge accumulated by a specialist is the barrier that keeps others out — and the same narrowness means the semiconductor cycle passes straight through to the bottom line, with nothing else to absorb it.