Toshiba HDD Capacity Doubling: TDK (6762.T), HOYA, NHK Spring Read-Through

Toshiba plans to double its hard disk drive (HDD) capacity, Tom's Hardware and others reported on October 2, 2026, and Seagate and Western Digital each fell about 10% that day. Toshiba's Japanese suppliers of heads, glass substrates and suspensions could ship more over the next two years.[1][2]

Toshiba plans to invest about ¥60 billion to double its HDD capacity by 2027.[3] The company also said 30TB-class drives are imminent, and 65TB and 100TB drives are on its roadmap for 2030 and beyond.[1]

On the day of the report, Seagate (STX) closed at $848.99, down 10.21%, and Western Digital (WDC) closed at $415.29, down 10.22%.[4] The same day TDK (6762.T) fell 0.06%, HOYA (7741.T) fell 0.86% and NHK Spring (5991.T) fell 0.97%.[4]

How the HDD industry works

Data centers store most bulk data, including much of what AI training and inference produce, on high-capacity HDDs.

Only three companies build complete HDDs: Seagate, Western Digital and Toshiba. Toshiba holds about 17% of global units.[5]

Drives are in short supply: Nikkei reported HDD contract prices rose 15% q/q in July-September 2026, a sixth straight quarterly increase and a record high.[6]

Key drive components:

• Platters: the data-holding disks, about ten per high-capacity drive. Their base, the substrate, is moving from aluminum to thinner glass.
• Heads: the parts that read and write data, two per platter.
• Suspensions: small metal parts holding each head near the platter.

Seagate and Western Digital make their own heads and media. Toshiba relies on outside suppliers. Toshiba has said its high-capacity drives came from years of work with head maker TDK.[7]

From Toshiba's expansion to Japanese component orders

First, new industry drive units come mainly from Toshiba. Seagate's strategy is to keep its unit count flat and grow capacity through areal density.[8] Based on Toshiba's roughly 17% unit share, its doubling adds about 15-20% to industry unit capacity.[5]

Second, incumbent pricing may suffer. Most of Seagate's nearline capacity is allocated through calendar 2028,[8] so pressure is likelier in post-2028 contracts.

Third, every extra Toshiba drive means another purchase of heads, substrates and suspensions.

Fourth, more platters amplify demand. Toshiba's new high-capacity drive uses 11 glass platters,[9] and a 12-platter 40TB-class product is planned. A 12-platter drive needs 24 heads and matching suspensions, so component demand could grow faster than drive units.

Companies that could be affected

TDK (6762.T) is a Japanese electronic components maker whose largest business is batteries. HDD heads and suspensions sit in its Magnetic Application Products segment, which had revenue of about ¥262.9 billion in the fiscal year ended March 2026, 10.5% of company revenue.[10]

In April-June 2026, TDK's HDD head shipments rose 36% year over year.[11] The company expects head unit sales to grow about 50% in the fiscal year ending March 2027.[12] If Toshiba's added head orders go mainly to TDK, segment revenue and profit could benefit, depending on whether this is already inside the 50% plan.

HOYA (7741.T) is mainly an eyeglass-lens and semiconductor mask-blank company. It is also the only supplier of glass HDD substrates, with a 100% share.[13]

HOYA does not disclose HDD substrate revenue. Based on its sales to Seagate, the business is about 11% of revenue.[14] HOYA expects revenue contributions from a second 3.5-inch nearline customer beginning in FY26.[15] If Toshiba's glass platforms ramp, substrate revenue could benefit, but HOYA's roughly ¥50 billion Vietnam plant does not begin operations until 2028,[16] so shipments are capacity-limited until then.

NHK Spring (5991.T) mainly makes car seats and springs. It is also one of two global HDD suspension suppliers, with about 60% of the world market.[17]

Its suspension business had revenue of about ¥126.8 billion in the fiscal year ended March 2026, 15.5% of company revenue.[10] In the company's plan, the business accounts for more than half of group operating profit.[18] More drives mean more suspensions, which could leverage its profit, depending on its undisclosed share of Toshiba's suspensions.

What to watch

The first signal comes in late October. Seagate reports on October 28 and Western Digital on October 29.[19] Watch for comments on rival capacity and any renegotiation of 2028 long-term agreement pricing.

The second signal is supplier results. TDK reports on October 30.[19] Watch whether head shipments beat guidance and whether the roughly 50% full-year growth plan is raised. HOYA reports interim results in late October or early November and NHK Spring in mid-November; watch whether HDD substrate revenue and suspension volumes exceed plan.

Volumes should show gradually through 2027 as Toshiba's lines come online.

The chain breaks if Toshiba only expands assembly while suppliers add no capacity, so it cannot double before 2028; if HOYA's second customer turns out to be Seagate or Western Digital, or Toshiba qualifies a second glass substrate supplier; if HDD contract prices turn down in Q4 2026 or Q1 2027 so Toshiba only takes share from rivals; or if Toshiba's added output is mostly low-platter-count drives.

This only helps you find transmission chains that may be overlooked. It is not a stock recommendation.

Sources

[1] Tom's Hardware · 2026-10-02 · Toshiba to double HDD capacity · https://www.tomshardware.com/pc-components/hdds/toshiba-to-double-hdd-production-capacity-as-30tb-class-loom-65tb-100tb-drives-on-the-roadmap-for-2030-and-beyond [2] Invezz · 2026-10-02 · Seagate and WD fall on Toshiba report · https://invezz.com/news/2026/10/02/why-are-seagate-technology-and-western-digital-stocks-tanking-on-friday/ [3] Drillr event data · 2026-10-02 · Toshiba ¥60bn plan to double HDD capacity by 2027 [4] Drillr price data · 2026-10-02 · Daily closes for STX, WDC, 6762.T, 7741.T, 5991.T [5] M Report · 2026-02-03 · Toshiba to Mass-Produce 40TB HAMR HDDs Starting in 2028 · https://www.mreport.co.th/en/news/industry-movement/102-toshiba-hamr-hdd-40tb-mass-production-2028 [6] Nikkei · 2026-09-08 · HDD contract prices rose 15% q/q in July-September 2026 · https://www.nikkei.com/article/DGXZQOUB314U30R30C26A8000000/ [7] Toshiba · 2024-05-14 · Press release: 30TB+ nearline HDDs · https://toshiba.semicon-storage.com/ap-en/company/news/news-topics/2024/05/storage-20240514-1.html [8] Drillr call summary · 2026-07-28 · Seagate FY2026 Q4 call [9] Blocks & Files · 2026-03-31 · Toshiba goes glassy-eyed with 11-platter 34TB SMR drive · https://www.blocksandfiles.com/disk/2026/03/31/toshiba-goes-glassy-eyed-with-11-platter-34tb-smr-drive/5213568 [10] Drillr segment data · FY ended 2026-03-31 · segment revenue [11] Drillr call summary · 2026-07-31 · TDK FY2027 Q1 call [12] XenoSpectrum · 2026-07-23 · AI nearline HDD demand and Japanese component makers · https://xenospectrum.com/en/ai-nearline-hdd-japan-components/ [13] HOYA · 2026 · Integrated Report: Information Technology · https://www.hoya.com/ir/2026/en/review/it.html [14] Drillr customer relationship data · 2026-10-02 · Seagate at 10.71% of HOYA revenue [15] HOYA · 2026 · Integrated Report summary (10min read) · https://www.hoya.com/ir/2026/en/common/files/10min_read.pdf [16] TrendForce · 2026-07-22 · Japanese HDD component makers expand capacity · https://www.trendforce.com/news/2026/07/22/news-ai-data-center-demand-revives-hdd-demand-japanese-component-makers-tdk-hoya-resonac-expand-capacity/ [17] The Shashi · 2026-10-02 · NHK Spring (TSE 5991) company history · https://the-shashi.com/en/tse/5991/ [18] NHK Spring · 2025-11-28 · FY3/2026 interim results presentation · https://www.nhkspg.co.jp/news/20251128_01 [19] Drillr earnings calendar · 2026-10-02 · STX Oct 28, WDC Oct 29, TDK Oct 30