Color-absorbing adhesive composition

Abstract

The color absorbing adhesive composition includes an optically clear pressure sensitive adhesive and at least one light absorbing component dispersed within the pressure sensitive adhesive. The light absorbing component is a dye having a peak absorption at 555 nm to 600 nm and having a full width at half maximum (FWHM) of no more than 70 nm. The article has a color-absorbing adhesive layer on an optical substrate.

Description

Summary of the invention

[0001] Disclosed herein are color absorbing adhesive compositions and articles made from these color absorbing adhesive compositions. In some embodiments, the adhesive composition comprises an optically clear pressure sensitive adhesive and at least one light absorbing component dispersed within the pressure sensitive adhesive. The at least one light absorbing component comprises a dye having a peak absorption at 555 nanometers to 600 nanometers and having a full width at half maximum (FWHM) of no more than 70 nanometers.

[0002] Also disclosed are articles containing the color absorbing adhesive composition. In some embodiments, the article includes an optical substrate having a first major surface and a second major surface; and an adhesive layer disposed on at least a portion of the first major surface of the optical substrate, wherein the adhesive layer comprises the above-described adhesive composition. BRIEF DESCRIPTION OF THE DRAWINGS

[0003] The present application can be more fully understood with reference to the accompanying drawings.

[0004] Figure 1 is a graph showing the reflectance reduction of the CIE standard illuminant D65 spectrum weighted by the photopic sensitivity of the human eye.

[0005] Figure 2 is a graph showing a tabulated reduction of an OLED white spectrum consisting of a blue emission band, a green emission band, and a red emission band. DETAILED DESCRIPTION

[0006] A wide range of optical articles are being developed for a wide range of uses. Among the optical articles are optical filters. Optical filters can be used in a variety of applications, such as optical communication systems, sensors, imaging, scientific and industrial optical equipment, and display systems. Optical filters may include optical layers that manage the transmission of incident electromagnetic radiation (including light). Optical filters may reflect or absorb a portion of the incident light and transmit another portion of the incident light. The optical layers within an optical filter may differ in wavelength selectivity, optical transmittance, optical transparency, optical haze, and refractive index. The optical layers may be films, including multilayer films and adhesive layers.

[0007] Optically clear adhesives (optical grade PSA, hereinafter referred to as "OCA") are widely used in a variety of articles and have increasingly stringent performance requirements. These adhesives must not only have the desired optical properties and maintain these properties under a variety of environmental conditions, but they must also fulfill the role of adhesives, that is, to adhere substituents together.

[0008] The requirements for optical products have become more stringent. For example, many products (such as display devices) include circular polarizers to control reflections from the surface of the product. In conventional OLEDs, since a circular polarizer is usually required in front of the OLED panel to prevent ambient light from reflecting from the metal electrode, only half of the light extracted from the OLED panel reaches the eye. Therefore, the use of a circular polarizer can reduce the brightness of the product, especially in a display device. In addition, as devices become foldable, flexible multilayer optical products are needed. Circular polarizers are typically rigid multilayer polymer films with a thickness of more than 50 microns, and often do not have the appropriate flexibility for use in products that require flexibility. Therefore, there is still a need for optical products that are flexible and have low surface reflectivity without the use of a circular polarizer.

[0009] Adhesive compositions are disclosed herein that are optically clear and contain narrow-band color absorbing dyes. The adhesive layer has a desired combination of adhesive and optical characteristics. The adhesive not only adheres adjacent layers together, but also has high visible light transmittance and can be used in optical articles that do not contain circular polarizers to reduce surface reflectivity without substantially reducing the visible light transmittance of the optical article.

[0010] As used herein, the term "adhesive" refers to a polymer composition that can be used to adhere two adherends together. An example of an adhesive is a pressure sensitive adhesive.

[0011] Those of ordinary skill in the art are well aware that pressure-sensitive adhesive compositions have properties including: (1) strong and lasting tack, (2) adhesion with finger pressure, (3) sufficient ability to remain on an adherend, and (4) sufficient cohesive strength to cleanly remove from an adherend. It has been found that materials that work well as pressure-sensitive adhesives are polymers that are designed and formulated to exhibit the desired viscoelastic properties, thereby achieving a desired balance of tack, peel adhesion, and shear holding power. Achieving the proper balance of properties is not a simple approach.

[0012] The term "(meth)acrylate" refers to monomeric acrylate or methacrylate esters of alcohols. Acrylate and methacrylate monomers or oligomers are collectively referred to herein as "(meth)acrylates." Materials referred to as "(meth)acrylate-functional" are materials that contain one or more (meth)acrylate groups.

[0013] The terms "room temperature" and "ambient temperature" are used interchangeably and refer to temperatures in the range of 20°C to 25°C.

[0014] As used herein, the terms "polymer" and "macromolecule" are consistent with their common usage in chemistry. Polymers and macromolecules are composed of many repeating subunits. As used herein, the term "macromolecule" is used to describe a group attached to a monomer that has multiple repeating units. The term "polymer" is used to describe the resulting material formed by a polymerization reaction.

[0015] The term "alkyl" refers to a monovalent group that is an alkane radical, which is a saturated hydrocarbon. The alkyl group may be linear, branched, cyclic, or a combination thereof, and typically has 1 to 20 carbon atoms. In some embodiments, the alkyl group contains 1 to 18, 1 to 12, 1 to 10, 1 to 8, 1 to 6, or 1 to 4 carbon atoms. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and ethylhexyl.

[0016] Unless otherwise indicated, the terms "optically clear" and "visibly transmissive" are used interchangeably and refer to articles, films or adhesives that have high light transmittance over at least a portion of the visible light spectrum (about 400 nm to about 700 nm). Typically, optically clear articles have a visible light transmittance of at least 90% and a haze of less than 10%.

[0017] Unless otherwise indicated, "optically clear" refers to an adhesive or article that has high light transmittance over at least a portion of the visible light spectrum (about 400 nm to about 700 nm) and exhibits low haze (typically less than about 5%, or even less than about 2%). In some embodiments, an optically clear article exhibits a haze of less than 1% at a thickness of 50 microns or even 0.5% at a thickness of 50 microns. Typically, an optically clear article has a visible light transmittance of at least 95%, typically higher such as 97%, 98%, or even 99% or higher.

[0018] Adhesive compositions are disclosed herein. The adhesive compositions include an optically clear pressure-sensitive adhesive and at least one light-absorbing component dispersed within the pressure-sensitive adhesive. The at least one light-absorbing component includes a dye having a peak absorption at 555 nanometers to 600 nanometers and having a full width at half maximum (FWHM) of no more than 70 nanometers.

[0019] The adhesive composition comprises an optically clear pressure sensitive adhesive.The pressure sensitive adhesive comprises at least one polymer component and may further comprise additional components such as tackifying resins, plasticizing resins, etc., as long as the additives do not interfere with the optical properties of the adhesive composition.

[0020] Pressure-sensitive adhesives include (meth) acrylate pressure-sensitive adhesives, (meth) acrylate pressure-sensitive adhesives, polyolefin pressure-sensitive adhesives, polyurethane pressure-sensitive adhesives, or combinations thereof. Each of these types of polymer pressure-sensitive adhesives is well known in the adhesive field. Polyolefin pressure-sensitive adhesives, also known as poly(1-olefin) pressure-sensitive adhesives, are polymers or copolymers prepared from olefin monomers. The polymer may also include radiation-activated functional groups grafted thereon, as described in U.S. Patent No. 5,209,971 (Babu et al.). Polyurethane pressure-sensitive adhesives that can be used in the present disclosure include, for example, those disclosed in U.S. Patent Nos. 3,718,712 (Tushaus); 3,437,622 (Dahl) and 5,591,820 (Kydonieus et al.).

[0021] In some embodiments, the pressure-sensitive adhesive includes a (meth) acrylate pressure-sensitive adhesive or a (meth) acrylate-based pressure-sensitive adhesive, which includes: one or more (meth) alkyl acrylate monomers having 2 to 18 carbon atoms, and the one or more (meth) alkyl acrylate monomers may contain one or more hydroxyl groups; and at least one reinforcing monomer. Such pressure-sensitive adhesives typically have a glass transition temperature of about -20°C or less. Examples of suitable (meth) alkyl acrylate monomers include, for example, isooctyl acrylate, 2-ethylhexyl acrylate, n-butyl acrylate, HEA (hydroxyethyl acrylate) and HEMA (hydroxyethyl methacrylate). Examples of reinforcing monomers include, for example, (meth) acrylic acid, (meth) acrylamide, ethylene-vinyl acetate, N-vinyl pyrrolidone and styrene macromonomers.

[0022] The adhesive composition also includes at least one light absorbing dye. Suitable dyes are those having peak absorption in the range of 555 nanometers to 600 nanometers and having a relatively narrow half-height full width (FWHM) of no more than 70 nanometers. In some embodiments, the dye has peak absorption in the range of 555 nanometers to 580 nanometers and has a relatively narrow half-height full width (FWHM) of no more than 40 nanometers.

[0023] Examples of suitable light-absorbing dyes include coordination complex dyes. Commercially available dyes include VIS589A and VIS591A from QCR Solution Corp.; EPOLIGHT 5699 from Epolin LLC, Newark, NJ; FDG-007 from Yamada Chemical Co. Ltd. Kyoto, Japan: Other useful materials may include those coordination complex dyes that have absorption in the range of 480 nm to 510 nm, such as DSL500B from Crysta-Lyn, Binghampton, NY and FDB-007 from Yamada Chemical Co. Ltd. Kyoto, Japan:

[0024] The amount of dye present in the adhesive composition can vary as desired, but generally only a very small amount of dye is needed to provide the desired result. In some embodiments, the dye comprises 0.05 wt % to 0.50 wt %, or even 0.05 wt % to 0.2 wt % of the total weight of the adhesive composition.

[0025] The adhesive composition has the characteristic of multiple expectations. The adhesive composition has peak absorption at 555 nanometers to 600 nanometers and has a half-height full width (FWHM) that is no more than 70 nanometers. In some embodiments, the adhesive composition has peak absorption at 555 nanometers to 580 nanometers and has a half-height full width (FWHM) that is no more than 40 nanometers.

[0026] The fact that the adhesive composition has the same peak absorption curve as the added dye indicates that the dye has excellent compatibility with the pressure-sensitive adhesive and is therefore substantially completely dissolved in the pressure-sensitive adhesive matrix. This compatibility helps prevent the dye from agglomerating into particles that do not function well as a light absorber and can inhibit the transmission of light.

[0027] The adhesive composition can form a 15-200 micrometer pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer has a peak absorption at 555-600 nanometers and a full width at half maximum (FWHM) of no more than 70 nanometers.

[0028] Optical articles are also disclosed herein. In some embodiments, the article includes: an optical substrate having a first major surface and a second major surface; and an adhesive layer disposed on at least a portion of the first major surface of the optical substrate. The adhesive layer comprises an adhesive composition as described above. Thus, the adhesive layer comprises an adhesive composition comprising an optically clear pressure-sensitive adhesive and at least one light-absorbing component dispersed within the pressure-sensitive adhesive. The at least one light-absorbing component comprises a dye having a peak absorption at 555 nanometers to 600 nanometers and having a full width at half maximum (FWHM) of no more than 70 nanometers.

[0029] A wide range of optical substrates are suitable. In some embodiments, the optical substrate is an optical film substrate. The optical film substrate can be a single-layer film substrate or a multi-layer film substrate. Typically, the film substrate is optically clear. In some embodiments, the film substrate provides a flexible cover layer.

[0030] In many embodiments, the optical substrate includes an optical device. Examples of suitable optical devices include display devices. Examples of suitable display devices include organic light emitting diodes (OLEDs). Optical devices typically include additional layers. Examples of suitable layers include cover layers and touch sensor layers.

[0031] In some embodiments, the optical device includes an OLED and a cover layer with an adhesive layer therebetween. In other embodiments, the device is more complex, wherein a multilayer optical stack is disposed on a cover plate of the OLED. The multilayer stack may be adhered to the multilayer stack by an adhesive layer of the present disclosure. Additional layers of the multilayer optical stack may include layers such as a touch sensor layer, a cover layer, and one or more additional adhesive layers.

[0032] As described above, one advantage of the adhesive layers of the present disclosure is that they can be used in optical multilayer articles, where the multilayer article does not include a circular polarizer. Circular polarizers are typically included to reduce the reflectivity of the optical article. It has been found that current adhesive layers reduce the reflectivity of the optical article by filtering a narrow absorbance between green and red emission light of a display device (such as an OLED device).

[0033] The article includes an adhesive layer, which is an optically clear pressure-sensitive adhesive having at least one light-absorbing dye as described above. In some embodiments, the adhesive layer has a peak absorption at 555 nanometers to 600 nanometers and has a half-maximum full width (FWHM) of no more than 70 nanometers. In other embodiments, the adhesive layer has a peak absorption at 555 nanometers to 580 nanometers and has a half-maximum full width (FWHM) of no more than 40 nanometers.

[0034] In some embodiments, when comparing with the goods without adhesive composition layer, adhesive layer causes the surface reflectivity of goods to reduce by up to 80%, and wherein visible light transmittance keeps at least 70%.In other embodiments, when comparing with the goods without adhesive composition layer, adhesive layer causes the surface reflectivity of goods to reduce by up to 50%, and wherein visible light transmittance keeps at least 80%.In these embodiments, reflectivity is defined as the reflectivity of the relative reduction compared to the equivalent goods without the adhesive layer containing dye.Visible light transmittance is measured by the light emission through goods, and is defined as the relative reduction compared to the light emission of the equivalent goods without the adhesive layer containing dye.

[0035] The adhesive layer has a thickness of 15 microns to 200 microns. The adhesive layer comprises an optically clear pressure-sensitive adhesive and a light-absorbing dye. In some embodiments, the dye accounts for 0.05 wt % to 0.50 wt %, or even 0.05 wt % to 0.20 wt % of the total weight of the adhesive composition.

[0036] Example

[0037] These examples are for illustrative purposes only and are not intended to limit the scope of the appended claims. Unless otherwise indicated, all parts, percentages, ratios, etc. in the examples and the remainder of the specification are by weight. The following abbreviations are used: nm = nanometer; ppm = parts per million; g = gram; mol = mole; IV = intrinsic viscosity; dL = deciliter; min = minute. The terms "weight %", "%wt" and "wt%" are used interchangeably.

[0038] Abbreviations

[0039]

[0040] Test Method

[0041] Transmission spectra of selected dye solutions

[0042] The transmission spectra of the selected dyes were measured using Lambda 1050. First, dye-1, dye-2 and dye-3 were dissolved in methyl ethyl ketone to a concentration of about 100 ppm. Dye-4 was dissolved in methanol to a concentration of about 100 ppm. For dye-1, dye-2 and dye-3, MEK solvent was used as a reference, whereas for dye-4, methanol was used as a reference during the T% measurement using Lambda 1050. The diluted dye absorptions are listed in Table 1.

[0043] Table 1: Transmission spectra of selected dyes in solvents

[0044]

[0045] Sample preparation

[0046] 1. Preparation of Adhesive Polymer

[0047] 936.6g 2-EHA, 187.5g IBOA, 125g 2-HEA, 1.88g AEBP (50% EA solution) and 1870g EA were added to the reactor. The monomer solution was mixed for 10 minutes and the reactor temperature was raised to 65°C. At the same time, 1.25g Iniator-1 was pre-dissolved in 5g EA. Initiator-1 solution was added to the reactor. Afterwards, oxygen in the reactor and solution was removed by purging N2 several times at 65°C to start polymerization. The reaction was maintained at 65°C for 24 hours. The polymer solution was discharged from the reactor as a clear and viscous solution with a solid content of 40%. The IV of the polymer was measured to be 0.85dL / g (Mw was about 500,000g / mol).

[0048] 2. Color Filter OCA Preparation: Examples 1-3

[0049] Preparation of color filter OCA solution

[0050] Example 1: Color filter OCA solution 1 :

[0051] In a 4 oz brown jar, 0.03 g of Dye-1, 22.5 g of MEK, 30.1 g of the base OCA solution prepared above (47.2 wt%) and 0.45 g of Initiator-2 were mixed together. The mixture was placed on a drum mixer overnight.

[0052] Examples 2 and 3: Color filter OCA solutions 2 and 3

[0053] Binder solutions were prepared as described above, but using Dye-2 (Example 2) and Dye-3 (Example 3) instead of Dye-1.

[0054] Preparation of adhesive layer

[0055] Examples 1-3 :

[0056] On a laboratory coater, adhesive solutions 1-3 were coated on liner-1 using a blade coater, and the coating thickness was controlled by the gap between the blade and the release liner. The dried coating thickness was controlled at 25 microns. The coated film was then placed in a 70°C drying oven for 20 minutes. The sample was removed from the oven and liner-2 was laminated on the dried adhesive surface. The adhesive sample between the liner-1 liner and the liner-2 liner was finally cured for 1 minute using a laboratory benchtop UV-LED light system that operated at a wavelength of 365nm with an input light intensity of 2 amps.

[0057] Measurement of Optical Properties of Color Filter OCA

[0058] The spectra of the three color filter OCAs were measured using a Lambda 1050. The results are shown in Table 2 below:

[0059] Table 2: Optical properties of color filter OCA

[0060] Example dye λMax(nm) T% at λMax FWHM(nm) %T at 520nm I Dye-1 590 18.9 26 91.8 2 Dye-2 594 19.1 27 92.2 3 Dye-3 592 13.6 28 90.2

[0061] Comparing the spectra of the dye in the OCA matrix (Table 2) and the solvent (Table 1), the dye absorption peak is slightly red-shifted, but the full width at half maximum (FWHM) is also only slightly broadened, indicating that the dye is well dispersed in the OCA matrix without aggregation.

[0062] Modeling studies

[0063] Effect of absorption spectrum characteristics on emissivity and reflectivity

[0064] To examine the performance space that can be achieved with this concept, we implemented an optical model to predict the effect of dye design on the emissivity and reflectivity of OLED displays. To reduce ambient light, we tabulate the reflectivity reduction of the CIE standard illuminant D65 spectra weighted by the photopic sensitivity of the human eye. These spectra can be seen in Figure 1 middle:

[0065] For potential degradation of OLED displays, we tabulate the degradation of an example OLED white spectrum consisting of a blue emission band, a green emission band, and a red emission band, such as Figure 2 As shown:

[0066] First, the performance space for prototype dyes with absorption spectra defined by Gaussian distributions was understood. The dye absorption peaks were then parameterized by their peak position, peak full width at half maximum (FWHM), and their peak absorbance when measured as stand-alone films. Absorbance (A) is defined via the following formula, where I0 is the initial intensity of the light source, I is the final intensity of the light source after traversing the film, and λ is the wavelength of the light source.

[0067] I[λ]=I0[λ]10 -A[λ]

[0068] Reflectivity is defined as the relative reflectivity compared to an equivalent display without the color filter material. Emissivity is defined as the relative emissivity compared to an equivalent display without the color filter material. Generally speaking, the goal is to minimize reflectivity while maximizing emissivity.

[0069] In the first review, we varied the peak position of the dye absorption between the green and red emission peaks of the white OLED spectrum. Table 3 summarizes the results of the optical model, where the absorbance was systematically varied to target specific levels of device reflectance (25%, 50%, 75%, and 90%). For a target device reflectance of 25%, we observed an optimal dye peak wavelength of 565nm. For a target device reflectance of 50%, we observed an optimal dye peak wavelength of 575nm. For a target device reflectance of 75%, we observed an optimal dye peak wavelength of 575nm. For a target device reflectance of 90%, we observed an optimal dye peak wavelength of 575nm.

[0070] Table 3

[0071]

[0072] In the second review, we varied the peak FWHM of the dye absorption spectrum when the dye peak position was 575 nm. Again, Table 4 summarizes the results of the optical model as the film absorbance was varied to achieve several levels of reflectivity reduction. For a target device reflectivity of 25%, we observed an optimal dye peak FWHM of 80 nm. For a target device reflectivity of 50%, we observed an optimal dye peak FWHM of 30 nm. For a target device reflectivity of 75%, we observed an optimal dye peak FWHM of 30 nm. For a target device reflectivity of 90%, we observed an optimal dye peak FWHM of less than 30 nm.

[0073] Table 4

[0074]

[0075]

[0076] In the third review, we co-optimized the peak position, peak FWHM, and absorbance of the dye film to achieve several different reflectance reductions. The results are summarized in Table 5.

[0077] Table 5

[0078]

[0079] The combined results of these three studies allow us to determine a set of general parameters that can be used to identify and select the best dyes based on their absorption spectra. It should be noted that the optimal set of values ​​will depend on the specific emission spectrum of the OLED, the spectrum of the ambient light, and the sensitivity of the observation.

Claims

1. An adhesive composition comprising: Optically clear pressure sensitive adhesive; and At least one light absorbing component is dispersed in the pressure sensitive adhesive, wherein the at least one light absorbing component comprises a dye having a peak absorption at 555 nm to 600 nm and having a full width at half maximum (FWHM) of no more than 70 nm. 2 . The adhesive composition according to claim 1 , wherein the adhesive composition has a peak absorption at 555 nm to 600 nm and has a full width at half maximum (FWHM) of no more than 70 nm. 3 . The adhesive composition of claim 1 , wherein the adhesive composition has a peak absorption at 555 nm to 580 nm and has a full width at half maximum (FWHM) of no more than 40 nm. 4 . The adhesive composition according to claim 1 , wherein the pressure-sensitive adhesive comprises a (meth)acrylate pressure-sensitive adhesive, a (meth)acrylate-based pressure-sensitive adhesive, a polyolefin pressure-sensitive adhesive, a polyurethane pressure-sensitive adhesive, or a combination thereof.

5. The adhesive composition according to claim 1, wherein the pressure-sensitive adhesive comprises a (meth)acrylate pressure-sensitive adhesive or a (meth)acrylate-based pressure-sensitive adhesive, wherein the (meth)acrylate pressure-sensitive adhesive or the (meth)acrylate-based pressure-sensitive adhesive comprises: One or more alkyl (meth)acrylate monomers having 2 to 18 carbon atoms, and the one or more alkyl (meth)acrylate monomers may contain one or more hydroxyl groups; and At least one reinforcing monomer.

6. The adhesive composition of claim 1, wherein the light absorbing dye comprises a coordination complex. 7 . The adhesive composition of claim 1 , wherein the dye accounts for 0.05 wt % to 0.50 wt % of the total weight of the adhesive composition.

8. The adhesive composition according to claim 1, wherein the adhesive composition is capable of forming a 15 to 200 micrometer pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer has a peak absorption at 555 to 600 nanometers and a full width at half maximum (FWHM) of no more than 70 nanometers.

9. A product comprising: an optical substrate having a first major surface and a second major surface; as well as an adhesive layer disposed on at least a portion of the first major surface of the optical substrate, wherein the adhesive layer comprises an adhesive composition comprising: Optically clear pressure-sensitive adhesive; and At least one light absorbing component is dispersed in the pressure sensitive adhesive, wherein the at least one light absorbing component comprises a dye having a peak absorption at 555 nm to 600 nm and having a full width at half maximum (FWHM) of no more than 70 nm.

10. The article of claim 9, wherein the adhesive layer has a peak absorption at 555 nm to 600 nm and has a full width at half maximum (FWHM) of no more than 70 nm.

11. The article of claim 9, wherein the adhesive layer has a peak absorption at 555 nm to 580 nm and has a full width at half maximum (FWHM) of no more than 40 nm.

12. The article of claim 9, wherein the optical substrate comprises an optical device.

13. The article of claim 12, wherein the optical device comprises an organic light emitting diode (OLED).

14. The article of claim 13, wherein the article further comprises a cover layer.

15. The article of claim 9, wherein the article comprises a multilayer article, wherein the optical substrate comprises an organic light emitting diode (OLED) panel; and further comprising a cover layer; and touch sensors.

16. The article of claim 15, wherein the multilayer article does not include a circular polarizer.

17. The article of claim 9, wherein the adhesive layer causes the surface reflectance of the article to be reduced by up to 80% when compared to an article without the adhesive composition layer, wherein visible light transmission is maintained at least 70%.

18. The article of claim 9, wherein the adhesive layer causes the surface reflectance of the article to be reduced by up to 50% when compared to an article without the adhesive composition layer, wherein visible light transmission is maintained at least 80%.

19. The article of claim 9, wherein the adhesive layer has a thickness of 15 micrometers to 200 micrometers.

20. The article of claim 9, wherein the dye comprises 0.05 wt% to 0.50 wt% of the total weight of the adhesive composition.

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