What Are Thermal Labels?
Thermal labels use heat to create an image. Thermal transfer uses a thermal ribbon where heat from the printhead releases the ribbon attaching it to the label surface. Direct thermal images are created when heat from the printhead causes components on the label surface to mix causing them to (usually) turn black.
A label is a label right? Wrong. Each of the thousands of different materials used in thermal printing has its own unique set of features that must be considered to ensure optimal performance in its intended application—not to mention in the specific printer in which it will be used.
Sacrificing consistency for price is risky, because unscannable barcodes must be reprinted, cancelling out the intended cost savings. Workers may have to make adjustments to the printer between rolls to account for inconsistencies in the media, make more IT calls, deal with costly downtime and risk losing productivity, efficiency and customer satisfaction. And choosing printing supplies that aren’t well suited to thermal printers can cause unnecessary wear and tear on printheads, resulting in higher replacement costs.
On the other hand, the right printing supplies will help you improve operational efficiency, keep track of all your assets and optimize the customer experience. The right printing supplies will ensure brand consistency and maintain regulatory compliance. The right printing supplies will support the growth of your business—not hinder it.
Selection of the label material depends first on whether direct thermal or thermal transfer print technology is being used.
There are two types of thermal facestocks: paper and synthetic. Understanding these facestock types and qualities will be one step in helping you to determine the right label for your application.
Paper is an economical material for indoor use and a shorter lifecycle. It is a versatile facestock that supports labeling across a wide variety of surfaces such as corrugate, paper, packaging films, (most) plastics and metal & glass.
There are different types of paper labels, first there is uncoated paper which is workhorse for business and industrial applications providing an optimal balance between performance and price. Coated paper, which is ideal for high-speed volume printing and when enhanced print quality is required.
Color is a very useful tool to provide a visual cue for highlighting important information on a label like special handling instructions or package priority. Zebra’s IQ Color technology enables you to print color on demand using your existing Zebra thermal printer. With IQ color, the customer defines the color zones on the label and the color for that particular zone. The printed image for those zones are in the defined color.
Like paper, synthetic materials also support labeling across a wide variety of surfaces. However the advantages of a synthetic label over paper is their resistance and environmental qualities such as a longer label lifecycle, the ability to withstand an outdoor environment and resistance to abrasion, moisture and chemicals.
Synthetic labels are referred to as poly and are available in four variations of poly material. The key material differentiators are outdoor durations, temperature exposure or facestock color and treatments.
Polyolefin is flexible for curved and rough surfaces and an outdoor exposure of up to 6 months.
Polypropylene is also flexible for curved surfaces and outdoor exposure of 1 to 2 years.
Polyester is used for high temperatures up to 300°F (149°C) and outdoor exposure of up to 3 years.
Polyimide is also for high temperature exposure for up to 500°F (260°C) and is often recommended for circuit board labels.
Thermal printers are designed to operate with a variety of media configurations, including die-cut, butt cut, perforated, notched, hole-punched and continuous, receipts, tags, ticket stock or pressure-sensitive labels.
Key considerations for choosing the right label solution
In order to identify the optimal print technology, material and ribbon (if thermal transfer printing), to ensure that the label remains readable during the products life, you should consider the following:
The type and the shape of surface being labeled needs to be considered to ensure that the label remains adhered to the surface. Have you ever noticed that a specific label does not adhere as well to a plastic bin as it does to a cardboard box? This is because these items have a different surface energy. The shape of the surface is also important to consider. For example, small curved surfaces are also difficult to label, since they require a flexible material with a mandrel adhesive to make sure the label does not pull away from the surface.
Materials and adhesives are also sensitive to very low and very high temperatures. There are two types of temperatures you need to consider, application temperature and service temperature:
- The application temperature is the temperature in which the label is being applied. For example, a new test tube is taken out of a box at room temperature, and a label is applied, the application temperature is 70ºF (21ºC)
- Service temperature is the temperature range in which the label will be used. For example, the same test tube is filled with a sample and cryogenically stored. Sometime later, it is thawed and sterilized with steam. The service temperature range is -112ºF (-80ºC) to 212ºF (100ºC)
Standard materials generally perform well when an application temperature is a minimum of 25°F (-4°C) and in service temperatures ranging from -65°F (-54°C) to 200°F (93°C). Labeling in conditions outside of this range requires the use of a thermal transfer solution and normally requires a specialty adhesive to insure that the label remains secured.
There are adhesives available for specific temperature ranges. The high and low temperature adhesives can maintain strong adhesion at high and low temperatures but they need to be applied to the surface at moderate temperatures. On the other hand, the all temperature adhesive is special in that the label can be applied to a surface at temperatures below freezing.
There are two kinds of high tack adhesives: high tack acrylic and high tack rubber.
High tack acrylic works well on hard-to-label surfaces and provides good resistance to chemicals and UV exposure.
High tack rubber works well on hard-to-label surfaces and provides better initial tack. In addition to permanent adhesives, there are a few types of removable adhesives: removable, multi removable, ultra-removable and security.
The key application of the removable adhesive is to provide good adhesion on the product when initially labeled while allowing a person to remove the label without damaging the label and product surface. Also being able to cleanly remove the label when the label is no longer needed.
The multi-removable adhesive is unique in that it allows the label to be applied, removed and reapplied to the surface. This enables repositioning of the label on the surface if needed.
The ultra-removable adhesive allows for clean removal from nearly all surfaces without damaging the label or the surface (including metal and glass surfaces).
Tamper proof adhesives enables you to visually see when a label is removed as an adhesive pattern remains on the surface. This type of adhesive can support warranty integrity claims when the label is removed.
Contact and rubbing will affect image and barcode readability over time. If in your application, the label will come into contact with items that could scratch it and make it unreadable, a ribbon with a higher resin content will provide improved durability.
When a label will be exposed to moderate to extreme chemicals, a thermal transfer labeling solution is required. In the case of harsh and extreme chemicals, a high-durability resin ribbon is also recommended. Below is a chart of chemical classifications:
|Weak Chemicals||Moderate Chemicals||Harsh Chemicals||Extreme Chemicals|
Indoor / Outdoor
If your product will be subjected to the elements outdoors (rain, sun, etc.), a thermal transfer synthetic material is required to survive these tough environmental factors. We offer thermal transfer labels and ribbon combinations that last up to 10 years outdoors.
Lifespan of Label
By knowing how long the label will need to be readable for in addition to the environmental factors, will help you to identify the optimal solution. For example, if the label only requires readability for six months and does not need to resist chemicals, moisture, and abrasion, a direct thermal paper label would best meet your needs. However, if the label will be subjected to moderate chemicals and be on an item that will in use for 10 years or be stored outside for over three years, a thermal transfer synthetic label would be required.
This is a key consideration, as material and ribbon selection will influence the maximum print speed. Typically, synthetic labels do not produce quality text and barcodes above 6 ips, and in order to print at 12 ips or higher, a thermal transfer paper label with a high-speed wax ribbon is required.
Increasing print darkness is necessary when printing at faster speeds to get the best barcode ANSI grades and print quality. When using resin ribbons, which require additional energy, a higher print darkness is also required.
Dots Per Inch (DPI)
Printing at 600 DPI is necessary when printing formats with detailed graphics and / or small fonts. Not all materials are compatible to print at 600dpi resulting in low print-quality and durability.
With more than 1,000 combinations of high quality and reliable labels, tags, receipt paper, wristbands, and ribbons, Zebra has a media solution for virtually any application. Whether you’re facing shipping, electronic component manufacturing, prescription labeling, or even electronic citation applications, Zebra and our certified partners can provide an in-stock or custom-made solution for you.