What Is Diazonaphthoquinone? The Complete Guide to DNQ Chemistry
The photoactive chemistry behind UV CtCP plates and positive photoresists.
What is diazonaphthoquinone (DNQ)? Photosensitive chemistry for UV CtCP plates and positive photoresists — mechanism, grades, applications. Orion manufactures in Karad, India.
Diazonaphthoquinone (DNQ) is the photoactive chemistry behind two industries that rarely share a supplier: UV CtCP offset printing plates and g-line/i-line electronic photoresists. The same chemical family — diazo ketones esterified onto resin backbones — changes solubility on ultraviolet exposure. Formulation determines whether exposed areas develop away or stay on the substrate.
This guide covers DNQ chemistry from first principles through to procurement: how photosensitivity works, where DNQ is used, which Orion grades supply each step of the value chain, and what buyers should verify before qualifying a supplier.
DNQ in one paragraph
Diazonaphthoquinone derivatives are organic photosensitisers that undergo a Wolff rearrangement on UV exposure, converting diazo ketones into ketenes that react with trace water to form indene carboxylic acids. The exposed areas change solubility — becoming more soluble in alkaline developer (positive mode) or remaining insoluble depending on formulation.
In offset printing, DNQ-based coatings on aluminium substrates form the image layer of UV computer-to-conventional-plate (CtCP) systems. In electronics, DNQ esters blended with novolac resins are the photoactive component of positive photoresists used to pattern circuits on silicon wafers.
Orion manufactures the sodium salt intermediate (CAS 64173-96-2), the esterified one-pack resin (CAS 3770-97-6), DNQ-THBP building blocks, and a ready-to-use developer-free CtCP coating — covering the DNQ value chain from building block to finished plate chemistry at its works in Karad, Maharashtra, India.
How DNQ photosensitivity works
| Mode | What happens on exposure | Typical application |
|---|---|---|
| Positive-working | Exposed areas become soluble and develop away | Photoresists (g-line/i-line), conventional positive UV CtCP |
| Negative-working | Exposed areas remain on substrate; unexposed areas remove | Developer-free UV CtCP (Orion Next) |
The Wolff rearrangement
Unexposed DNQ compounds are dissolution inhibitors. When UV photons strike the diazo ketone group, a Wolff rearrangement occurs:
- UV absorption by the diazo ketone (n→π* transition)
- Loss of nitrogen gas (N₂)
- Formation of a reactive ketene intermediate
- Reaction with trace water to produce an indene carboxylic acid
The carboxylic acid product is substantially more soluble in alkaline developer than the parent DNQ compound. This solubility switch is the basis of positive-working photoresist behaviour.
Positive vs negative working
The same DNQ chemistry family serves both modes. Formulation — resin choice, DNQ loading, developer chemistry, and coating architecture — determines the outcome:
This distinction matters for procurement. A photoresist formulator and a plate coater both buy DNQ chemistry, but they need different grades and opposite working modes. See Positive vs Negative Working Plates for the full comparison.
Spectral sensitivity
DNQ sensitivity is tuned by esterification and resin choice:
- UV CtCP offset plates: 360–375 nm (standard UV laser plate setters)
- G-line photoresists: 436 nm
- I-line photoresists: 365 nm
Esterification with different phenolic resins (cresol novolak, THBP, cresol novolac) shifts absorption and bleaching characteristics. The DNQ novolak resist mechanism explains how resin and PAC interact during exposure and development.
Where DNQ is used: two industries
UV CtCP offset printing plates
Plate manufacturers coat anodised aluminium with DNQ-based lacquers and image them on UV laser plate setters. The diazo polymer forms the photosensitive layer that defines ink-receptive and non-image areas.
Two coating paths exist within UV CtCP:
Conventional positive UV CtCP — esterified DNQ-cresol resin (such as Orion Freedom Plus One Pack) coated at 1.7–1.8 g/m², imaged at 365–405 nm, developed in alkaline developer.
Developer-free negative UV CtCP — Orion Next multi-polymer coating, same coat weight and UV range, developed in plain tap water. No alkaline developer chemistry.
For the complete offset-plate coating guide, see The Complete Guide to UV CtCP Plate Coatings.
Electronic photoresists (g-line and i-line)
Positive photoresists for circuit patterning use DNQ derivatives blended with novolac or cresol-formaldehyde resins. On UV exposure through a photomask or stepper, DNQ PACs photobleach in exposed areas, increasing solubility in alkaline developer.
Orion supplies DNQ chemistry at multiple integration points:
- Orion Freedom 2-1-4 — water-soluble sodium salt (CAS 64173-96-2) for in-house synthesis
- DNQ-THBP building block — industry-standard PAC for g-line and i-line
- Orion P-1403, P-1610, P-3101, P-0711 — application-ready grades
For wavelength-specific formulation guidance, see g-Line vs i-Line Photoresist.
Orion DNQ grades mapped to the value chain
Level 1: Sodium salt (CAS 64173-96-2)
↓ in-house conversion
Level 2: Sulphonyl chloride / custom esterification
↓ resin blending
Level 3: One-pack ester (CAS 3770-97-6) or DNQ-THBP PAC
↓ dissolve, coat, image
Level 4: Ready coating system (Orion Next)Buyers enter the DNQ supply chain at one of four points:
For the salt vs ester decision, see DNQ Sodium Salt vs DNQ-Cresol Ester.
| Entry point | Orion grade | CAS | Buyer profile |
|---|---|---|---|
| Salt / synthesis | Freedom 2-1-4 | 64173-96-2 | Formulators with in-house DNQ chemistry |
| One-pack ester | Freedom Plus 1413 | 3770-97-6 | Plate coaters, resist formulators |
| DNQ-THBP PAC | P-1403 / P-1610 / P-3101 / P-0711 | Complex polymer | Photoresist coaters (g-line/i-line) |
| Ready CtCP coating | Orion Next | Multi-polymer | Plate coaters wanting developer-free |
Key specifications buyers verify
| Parameter | Freedom 2-1-4 | Freedom Plus 1413 | Orion Next | DNQ-THBP grades |
|---|---|---|---|---|
| Assay | 98.0% min | Per batch COA | N/A (coating system) | Per batch COA |
| Moisture | 2.5% max | Per batch COA | N/A | Per batch COA |
| Form | Yellow powder | Powder or solution | Ready liquid | Powder or liquid |
| Sensitivity | N/A (intermediate) | 365–405 nm | 360–375 nm | G-line / I-line |
| Coat weight | N/A | 1.7–1.8 g/m² | 1.7–1.8 g/m² | Spin-coat per grade |
| Documentation | COA, MSDS, TDS | COA, MSDS, TDS, method of use | Method of use PDF | Product info PDF per grade |
Storage, handling, and safe light
DNQ compounds are light-sensitive. Decomposition from white light or UV exposure before intentional imaging ruins batch quality and coating performance.
Storage (all grades): Cool, dry place; protect from direct light and moisture; keep containers sealed between use.
Safe light: Handle undeveloped coatings and plates under yellow safe light only. Do not expose unexposed or undeveloped material to daylight or white light before development is complete.
For operational detail, see DNQ Storage, Shelf Life and Safe-Light Handling.
Qualifying a DNQ supplier
Procurement teams should request:
- Certificate of analysis (COA) per batch — not generic product-line documents
- MSDS and TDS for the exact grade and CAS number
- Trial quantity (10 kg minimum at Orion) for coating or dissolution testing
- Method-of-use guidance for your specific application
- Export documentation if importing
Use the full DNQ supplier qualification checklist for a step-by-step workflow. For sourcing from India specifically, see Sourcing DNQ Actives From India.
Regulatory questions buyers ask
DNQ chemicals raise compliance questions that vary by destination market:
- REACH (EU): What registration status does the supplier hold for this CAS number? See REACH and DNQ Chemicals.
- GHS labelling: What hazard classification appears on the MSDS for this specific grade? See GHS Classification for DNQ Actives.
- Export from India: What documentation accompanies the shipment? See Exporting DNQ Chemicals From India.
Ask these questions of any supplier. Verify answers with documentation, not marketing claims.
What procurement teams verify first
Common questions.
What is diazonaphthoquinone used for?
Diazonaphthoquinone (DNQ) is used as the photoactive component in UV CtCP offset printing plate coatings and in positive-tone g-line/i-line electronic photoresists. On UV exposure, DNQ undergoes a Wolff rearrangement that changes solubility in developer.
What is the difference between DNQ salt and DNQ ester?
DNQ sodium salt (CAS 64173-96-2) is a water-soluble building block for in-house synthesis and coating formulation. DNQ ester (CAS 3770-97-6) is DNQ pre-esterified with cresol resin — a ready photoactive resin for plate-coating lacquers and photoresists.
Does Orion manufacture DNQ in India?
Yes. Orion Photosensitive Systems manufactures diazonaphthoquinone actives at its works in Banawadi, Karad, Maharashtra, India. The company has produced photosensitive chemicals since 1988 and supplies DNQ grades for offset plate and electronics applications worldwide.
What is the minimum order for DNQ actives from Orion?
Minimum order quantity is 10 kg across active grades. Pack sizes extend to full container load depending on grade and destination. COA, MSDS, and TDS are provided per batch. Contact sales@orionppp.com for pricing and lead time.