产品系列： <span>光变/OVI系列</span>

Color-shifting ink: daylight-change and OVI are a tier apart

Both products in this series are loosely called “color-shifting”, but their mechanisms and security levels differ by an order of magnitude — and the market routinely conflates them. Daylight-change (photochromic) ink works through a reversible chemical change under UV: colourless or pale indoors, colour appearing within seconds in sunlight, fading back when the light goes. OVI relies on physical interference in multilayer metal-oxide flakes: no special light source at all, just a change of viewing angle producing a clear hue shift.

The dividing line is whether the inspector needs a tool. Daylight-change ink is still condition-triggered — it needs sunlight or a UV lamp. OVI needs nothing: tilt the print in ordinary light and green turns blue. Photocopies and scans cannot reproduce it, which is why it appears on banknotes and passports. The trade-off is pigment cost and minimum order — both far above photochromic — so OVI is used for markings or accent areas rather than large areas of low-cost packaging.

The real barrier to copying OVI is the pigment itself. Many products sold as “color-shifting ink” are only pearlescent or metallic effects: the angle change alters brightness, not hue. Testing is simple — tilt the print slowly in daylight. Genuine OVI changes colour (green to blue, gold to green, purple to brown); imitations only change brightness. Several colour pairs are available, and we recommend requesting a printed proof for a side-by-side tilt test.