Label Release Liner Paper
A label release liner is the silicone-coated paper or film that carries a pressure-sensitive label from the coating line to the applicator, then releases it cleanly at the moment of dispensing. It is not a passive backing. The liner sets your die-cutting window, your matrix-stripping yield and the maximum speed at which your labeling line can run. WeShare supplies label release liner paper on glassine, super-calendered kraft (SCK), clay-coated kraft (CCK), PE-coated kraft (PEK) and PET film bases, with release force engineered to your adhesive system. Basis weights run from 40 to 150 gsm, coating is available single-side (C1S) or double-side (C2S), and jumbo rolls are supplied slit to your converting width up to 2,500 mm.
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Product Introduction
What a label release liner actually does
A pressure-sensitive label is a four-layer laminate: face material → adhesive → silicone release coating → liner base. The silicone layer is extremely thin - of the order of one micron - and its only job is to stop the pressure-sensitive adhesive (PSA) from permanently bonding to the base, so the label can be peeled away intact at the point of application.
Because the liner stays in the press and the applicator while the label leaves, the liner is what the converting line actually handles. It carries the web tension through printing, it is the anvil for die-cutting, and it must survive the heat of the coating and drying process without curling. Specify the liner badly and the failures appear far downstream - as label lift, web breaks, or a matrix that tears instead of stripping.
| Converting stage | What the liner must do |
|---|---|
| Silicone coating | Accept and anchor a thin, pinhole-free silicone layer |
| Lamination & printing | Hold flat (lay-flat), tolerate web tension without stretch |
| Die-cutting | Provide consistent caliper and stiffness as the cutting anvil |
| Matrix stripping | Release the waste matrix cleanly at high speed |
| Dispensing | Release each label within a narrow force window |
Choosing the liner substrate: glassine, SCK, CCK, PEK or PET
Substrate choice is driven by four properties: surface smoothness and closure (how little silicone the paper absorbs), dimensional stability (how the liner behaves through heat and moisture), mechanical strength (whether it survives coating tension and die-cutting), and cost.
Globally, glassine and super-calendered kraft together account for roughly half of all label liner substrates. Glassine dominates in Europe and Asia; SCK is the traditional choice in North America. The remaining half is split roughly equally between clay-coated kraft, PE-coated kraft and PET film.
| Substrate | Surface & silicone uptake | Dimensional stability | Die-cutting | Typical label use | Basis weight / caliper |
|---|---|---|---|---|---|
| Glassine | Very smooth, closed; low silicone consumption | Good | Excellent - uniform caliper | High-speed automatic labeling, primary labels | 40–120 gsm |
| SCK (super-calendered kraft) | Very smooth, closed | Good | Excellent | US-standard label liners | 40–120 gsm |
| CCK (clay-coated kraft) | Highly closed, excellent lay-flat; clay can complicate stain testing | Very good | Very good | Labels, tapes, colour-cutting vinyl | 30–137 gsm |
| PEK / PCK (PE-coated kraft) | Very smooth, closed; moisture barrier | Excellent | Very good | Labels, medical, self-adhesive vinyl; humid environments | 40–150 gsm |
| PET film | Extremely smooth - lowest silicone consumption; transparent | Outstanding | Excellent; hard surface resists blade deformation | No-label-look and clear-on-clear labels; precision die-cutting | 23–50 µm |
| PP film | Smooth; moisture resistant | Good | Good | Foam tape, butyl and foil tape liners | 25–140 µm |
Release force: the specification most buyers leave blank
Release force is the force required to peel a pressure-sensitive label away from the liner, measured as a peel test - normally at 180° (or 90° where the application calls for it). It is the single most important number on a liner specification, and it is almost never quoted.
It is not a fixed property of the liner alone. The measured value also reflects the adhesive type and thickness, the stiffness of the face stock, and the peel speed. That is why a liner that performs perfectly on one laminate can fail on another with the same silicone.
Typical release force reference bands
| Grade | Peel force (gf/25mm) | Where it is used |
|---|---|---|
| Easy | 5–10 | Delicate facestocks, hand application, low-tack adhesives |
| Standard | 8–15 | General-purpose primary labels |
| Medium | 10–30 | High-speed automatic labeling; firm facestocks |
| Tight | 35–50 | Small die-cut labels, aggressive adhesives, low-temperature dispensing |
| Very tight | ≥50 | Special constructions where premature lift is unacceptable |
What happens when the release force is wrong
| Symptom | Root cause | Direction of fix |
|---|---|---|
| Label stays on the liner, applicator misses | Release force too high at dispensing speed | Reduce release force; flatten the release profile |
| Label flies off before reaching the substrate | Release force too low | Increase release force |
| Matrix tears or breaks during stripping | Release force too high at converting speed | Flatten the release profile at high peel speed |
| Release force drifts upward in storage | Incomplete silicone cure | Raise cure; verify with SAS test |
Release profile - why one number is not enough：
Release force changes with peel speed. Hand application is slow; high-speed dispensing and matrix stripping are fast. The curve of release force against peel speed is the laminate's release profile. Modern label stock is progressively down-gauged and run faster, so the profile matters more than ever. Where a customer needs the same liner to convert fast and dispense reliably, the silicone is modified to flatten the profile - reducing high-speed release force without letting the label lift at low speed.
Silicone coverage, cure and subsequent adhesion
Two things decide whether a liner releases cleanly for its whole shelf life: how completely the substrate is covered by silicone, and how completely that silicone is cured.
Coverage. Wherever silicone is missing, the adhesive touches bare paper and bonds. On a paper liner the adhesive can even migrate into the sheet and bond from within - at which point the laminate will not release at all. This is why substrates for liners are specified with a smooth, closed surface: a closed sheet keeps the silicone on the surface, so less coating is needed and coverage is easier to hold. Coverage is verified with a stain/dye test on glassine and SCK, and with polarised-light optical measurement on films and PE-coated papers.
Cure. Silicone must be cross-linked into an elastomer. Cure is expressed as a percentage of the completed reaction; a properly cured coating typically reaches 95% or higher. Under-cured silicone stays mobile and migrates - into the adhesive, where it kills tack, and onto the label face, where it damages printability. Two checks are standard:
Direct: solvent extraction (MIBK). An extractable fraction below about 5% indicates a stable, well-cured coating.
Indirect: the Subsequent Adhesive Strength (SAS) test. A strip of PSA tape is left in contact with the liner, peeled off, then applied to a standard surface (glass, steel or PET) and peeled again. The measured adhesion is compared with a fresh, uncontaminated strip. An SAS value below about 85% means unreacted silicone has migrated into the adhesive.
Caliper, GSM and stiffness: what decides your die-cutting
A liner specification that quotes only GSM is incomplete. Three measurements govern whether a liner runs on your press:
| Measurement | Why it matters | Typical control |
|---|---|---|
| Caliper (thickness) | Die-cutting depth. Inconsistent caliper means some labels are cut through and some are not. | Held to a tight tolerance across the web |
| Stiffness | A liner that is too soft lets the cutting blade deform the paper instead of cleanly cutting the face material. | Grade-dependent; PEK and PET are stiffer than unsized paper grades |
| GSM / basis weight | Related to caliper but not interchangeable - the same GSM can be calendered to different thicknesses. | Quoted as a target with tolerance |
Matching the liner to your labeling line
| Your process | What to specify |
|---|---|
| Hand application, low volume | Standard release; glassine base; no special profile |
| Semi-automatic labeling | Standard to Medium release; glassine or SCK |
| High-speed automatic labeling (>200 labels/min) | Medium to Tight release; flat release profile; consistent caliper |
| Humid or unconditioned plant | PEK (PE-coated) base for dimensional stability; CCK for lay-flat |
| Clear-on-clear / no-label look | PET film liner, transparent |
| Small die-cut labels on aggressive adhesive | Tight to Very tight release; PET or high-stiffness paper |
| In-line die-cutting on a narrow-web press | PET liner or a liner with proven matrix-stripping behaviour |
How to write a liner specification (10 fields)
Sending us these ten fields turns a sample request into a usable recommendation:
Face material and thickness
Adhesive type and coat weight (water-based, hot-melt, solvent)
Label size and die-cut geometry (including corner radius)
Press type and line speed
Dispensing speed and applicator type
Required release force, or the failure you are trying to fix
Shelf life and storage conditions
Liner preference, if any (paper vs film; glassine / CCK / PEK / PET)
Roll width, core diameter and maximum roll diameter
Number of splices permitted per roll
FAQ
Q1. What is the difference between a release liner and a release paper?
"Release paper" is the general term for any silicone-coated paper that protects an adhesive. A "release liner" is the same material in its functional role - the carrier on a pressure-sensitive label, tape or film. A liner can also be a film.
Q2. Is your label release liner coated on one side or both?
Standard label liners are single-side coated (C1S), because only the face that touches the adhesive needs to release. Double-side coating (C2S) is available for double-sided tape carriers, self-wound tapes and protective films.
Q3. What release force should I specify?
It depends on three things: your adhesive, your facestock stiffness and your peel speed. Tell us the applicator speed and the adhesive type and we will recommend a band. If you currently have a failure - labels not dispensing, matrix breaking - describe it and we will work back to the likely release force target.
Q4. What is the Subsequent Adhesive Strength (SAS) test and why does it matter?
It measures how much adhesion your adhesive loses after contact with the liner, which reveals whether uncured silicone has migrated into the adhesive. A value below roughly 85% of the reference indicates contamination. It is the fastest way to catch a cure problem before it reaches your customer.
Q5. Will the liner work with hot-melt adhesives?
Yes - hot-melt, water-based and solvent-based adhesives are all common on our liners. Hot-melt and solvent systems place more demand on adhesive-compatibility and release stability, so we match the silicone formulation accordingly.
Q6. Can you supply a liner for high-speed automatic labeling?
Yes. High-speed dispensing needs a Medium-to-Tight release with a flat release profile, plus consistent caliper for reliable die-cutting. Give us your line speed and label geometry.
Q7. What is your minimum order quantity and lead time?
MOQ 1,000 kg; lead time typically 15–21 days after deposit.
Q8. Do you provide samples?
Yes. Free samples within 1–2 kg; you cover the courier cost. Send your specification and we will match the closest grade.
Q9. Which base paper is best for humid conditions?
PE-coated kraft (PEK) adds a moisture barrier and improves dimensional stability compared with plain paper, which is why it is common in unconditioned plants and in medical and vinyl applications. CCK offers excellent lay-flat and is a good middle option.
Q10. Can the liner be printed?
Yes - up to two colours, register-printed on the liner, for branding or for functional registration marks.
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