WO2025173724A1 - Display device - Google Patents

Abstract

The purpose of this invention is to provide a display device capable of suppressing damage to a color filter and a microlens. A display device according to the present invention is characterized in that a light-emitting element, a color filter and/or a microlens, a resin layer, and a cover layer are laminated in this order on a substrate, and the resin layer includes a hard coat layer having a pencil hardness of H or more. In the present invention, it is preferable that the resin layer includes the hard coat layer formed by curing a resin composition containing acrylic resin, an acrylic monomer, and an initiator, 31 mass% or more of the constitutional unit of the hard coat layer is derived from the acrylic monomer, and the mass ratio of the constitutional unit derived from the acrylic monomer to the acrylic resin is 1.2 or more.

Description

display device

The present invention relates to a display device equipped with light-emitting elements.

For example, display devices equipped with organic electroluminescence (EL) elements, which are self-emitting elements, are excellent at reducing thickness and weight, and development is underway to improve their performance.

As shown in Patent Documents 1 and 2, for example, a display device has organic light-emitting elements and a color filter laminated on a substrate, and a cover layer bonded to the surface of the color filter via an adhesive layer.

Patent No. 7010279 Patent No. 6605559

However, the color filters were not sufficiently hard, and when microlenses were layered on top of the color filters, the microlenses were not sufficiently hard, which meant that the color filters and microlenses were easily scratched during the process of attaching the cover layer. This issue was not limited to organic EL microdisplays, but also arose in microLED displays.

The present invention aims to provide a display device that can prevent scratches on color filters and microlenses.

A display device according to one embodiment of the present invention is characterized in that a light-emitting element, a color filter and/or microlens, a resin layer, and a cover layer are stacked in this order on a substrate, and the resin layer includes a hard coat layer having a pencil hardness of H or higher.

Furthermore, one aspect of the present invention provides a display device in which a light-emitting element, a color filter and/or microlens, a resin layer, and a cover layer are laminated in this order on a substrate, the resin layer including a hard coat layer formed by curing a resin composition containing at least an acrylic resin, an acrylic monomer, and an initiator, the hard coat layer containing 31% by mass or more of structural units derived from the acrylic monomer, and the mass ratio of the structural units derived from the acrylic monomer to the structural units derived from the acrylic resin is 1.2 or more.

The present invention can prevent scratches on color filters and microlenses, improving display quality.

1 is a schematic cross-sectional view of a display device according to a first embodiment. FIG. 10 is a schematic cross-sectional view of a display device according to a second embodiment. FIG. 10 is a schematic cross-sectional view of a display device according to a third embodiment. 5A to 5C are schematic cross-sectional views showing a manufacturing process of the display device according to the present embodiment. 5A to 5C are schematic cross-sectional views showing a manufacturing process of the display device according to the present embodiment. FIG. 10 is a schematic cross-sectional view of a display device for explaining a problem in a conventional example. FIG. 10 is a schematic cross-sectional view of a display device for explaining a problem in a conventional example. FIG. 10 is a schematic cross-sectional view of a display device for explaining a problem in a conventional example. FIG. 10 is a schematic cross-sectional view of a display device for explaining a problem in a conventional example.

Below, one embodiment of the present invention (hereinafter abbreviated as "embodiment") will be described in detail. Note that the present invention is not limited to the embodiment below, and can be implemented in various modifications within the scope of its gist. Note that the notation "to" includes both the lower limit and upper limit (boundary value).

<Overview of the Display Device According to the Present Embodiment>
1 is a schematic cross-sectional view of a display device according to a first embodiment. The display device 1 is an organic EL microdisplay. The display device 1 includes an organic light-emitting element (organic EL element) 3, a color filter 4, a microlens 5, a hard coat layer 6, and a cover glass 7 stacked in this order on a circuit board 2.

The circuit board 2 includes a silicon substrate and an array section located on the upper surface of the silicon substrate. The array section includes pixel circuits and wiring that supplies signals and power to the pixel circuits. The pixel circuits include transistors that serve as drive elements and switches, capacitors, and wiring that connects them to each other. The transistors are, for example, field-effect transistors that include part of the surface area of the silicon substrate as source, channel, and drain regions.

The organic light-emitting element 3 is composed of a first electrode 8, an organic light-emitting layer (organic EL layer) 9, a partition layer 10 positioned around the organic light-emitting layer 9, and a second electrode 11. Note that insulating layers and other elements interposed between the circuit board 2 and the organic light-emitting element 3 are not shown.

The organic light-emitting layer 9 is configured to emit white light, for example, by injecting electric charges, and existing organic materials can be used for the organic light-emitting layer 9.

As shown in Figure 1, a color filter 4 is formed on the surface of the organic light-emitting element 3 via a base layer 12. The base layer 12 may be made of either an inorganic or organic material. For example, it may have a laminated structure of an inorganic layer and an organic layer. Examples of inorganic layers include oxides and nitrides, and serve as a sealing layer that covers the surface of the organic light-emitting element 3. The organic layer is made of an existing material such as acrylic resin, and serves to flatten the base of the color filter 4.

The color filter 4 is formed on the surface of the base layer 12 and has the function of transmitting light in any of the wavelength bands of the three primary colors of light: red (R), green (G), or blue (B).

Microlenses 5 are provided on the surface of each color filter 4. Microlenses 5 are so-called plano-convex lenses having a bottom surface and a lens surface. The curvature and shape of the lens surface are designed appropriately according to the refractive index of the material of the microlenses 5 at visible wavelengths. By providing microlenses 5, it is possible to suppress the spread of light emitted from the display output surface 7a, which is the surface of the display device 1, and achieve high contrast.

The hard coat layer 6 is a resin layer formed by curing a resin composition (photosensitive composition). As shown in Figure 1, the hard coat layer 6 covers the irregularities on the surface of the microlens 5 and has a substantially flat surface 6a. The surface 6a of the hard coat layer 6 is flattened relative to the surface of the microlens 5. Here, "flattened" means absorbing the irregularities on the surface of the microlens 5 and making it flatter than the surface of the microlens 5, and is not limited to being completely flat.

As shown in Figure 1, a cover glass 7 is adhered and fixed to the surface 6a of the hard coat layer 6 via an adhesive layer 13.

Although a transparent substrate resin or the like can be used instead of the cover glass 7, it is preferable to use the cover glass 7 as the cover layer when considering durability, transmittance, refractive index, etc. As shown in Figure 1, the cover glass 7 is attached by applying an adhesive to the surface 6a of the hard coat layer 6. The cover glass 7 protects the organic light-emitting element 3, color filter 4, and microlens 5 from external impacts, damage, etc.

<Regarding another embodiment>
Fig. 2 is a schematic cross-sectional view of a display device according to a second embodiment. Fig. 3 is a schematic cross-sectional view of a display device according to a third embodiment. Note that the same reference numerals as in Fig. 1 indicate the same layers as in Fig. 1, so please refer to Fig. 1 for a detailed explanation. Here, the differences from Fig. 1 will be mainly explained.

In Figure 2, unlike Figure 1, microlenses 5 are not provided. Therefore, in Figure 2, a hard coat layer 6 is formed on the color filter 4.

3, an overcoat layer 14 is formed to cover the surface of the microlens 5, and a hard coat layer 6, an adhesive layer 13, and a cover glass 7 are laminated on the overcoat layer 14 in this order. In this embodiment, the overcoat layer 14 and the hard coat layer 6 together constitute the resin layer 20. The overcoat layer 14 may have a lower pencil hardness than the hard coat layer 6. That is, the pencil hardness of the overcoat layer 14 may be H or less. On the other hand, the overcoat layer 14 has a lower thermal expansion coefficient than the hard coat layer 6, for example. By selecting a material with a low thermal expansion coefficient, the uneven surface of the microlens 5 can be appropriately filled and a flat surface 14a can be easily obtained. Furthermore, by using an overcoat layer 14 with a refractive index lower than that of the microlens 5, for example, the light-collecting effect of the microlens 5 can be enhanced, thereby improving the front brightness of the display device 1. In this way, using a material with a low refractive index for the overcoat layer 14 broadens the range of materials available for the hard coat layer 6. Existing materials such as acrylic resin and epoxy resin are used for the overcoat layer 14.

As shown in Figure 3, the hard coat layer 6 can be formed with a constant thickness on the surface 14a of the overcoat layer 14, allowing the surface 6a of the hard coat layer 6 to be formed as a flat surface. By forming the resin layer 20 as a laminated structure of the overcoat layer 14/hard coat layer 6, the optical path length from the organic light-emitting layer 9 to the display output surface 7a can be appropriately adjusted to be within a specified range, even if the hard coat layer 6 is formed thin enough to achieve a predetermined pencil hardness.

Furthermore, rather than forming the hard coat layer 6 and then the overcoat layer 14 on the microlenses 5 in that order, it is preferable to laminate the overcoat layer 14 and then the hard coat layer 6, as in this embodiment. In particular, in a configuration including microlenses 5, it is necessary to fill the uneven surfaces of the microlenses 5 with precision. Therefore, in order to properly fill the uneven surfaces of the microlenses 5, it is preferable to first form the overcoat layer 14, and then form the hard coat layer 6, which has a high pencil hardness. Alternatively, the resin layer 20 can be formed, for example, with a laminated structure of overcoat layer/hard coat layer/overcoat layer.

In this embodiment, the structure of the resin layer 20 is not limited as long as it includes a hard coat layer 6 with a pencil hardness of H or higher.

<Technical Background and How the Display Device 1 of the Present Embodiment Was Developed>
For example, in the process of manufacturing an organic EL display device, there is a step of laminating a cover glass 7 after forming a microlens 5 on a color filter 4 as shown in FIGS. 1 and 3, or after forming a color filter 4 as shown in FIG. 2.

Here, the conventional process of attaching the cover glass 7 will be explained. As shown in Figure 5A, adhesive 15 is applied to the surface of the microlens 5, and then the cover glass 7 is attached as shown in Figure 5B. Reference numeral 16 in Figure 5B indicates the adhesive layer formed when the adhesive 15 has hardened.

However, because the microlenses 5 did not have sufficient hardness, they were damaged during the process of bonding the cover glass 7, resulting in scratches on the surface of the microlenses 5. This reduced the lens function of the microlenses 5, leading to a decrease in display quality. Figure 5B schematically shows the state in which scratch A has appeared on the surface of the microlenses 5. Note that the color filter 4 also did not have sufficient hardness, and scratches still appeared on the surface of the color filter 4 even in a configuration in which the cover glass 7 was bonded to the color filter 4 via adhesive 15 without forming the microlenses 5.

On the other hand, it is difficult to increase the hardness of the color filters 4 and microlenses 5. In other words, in organic EL display devices for microdisplays, the color filters 4 and microlenses 5 are mainly processed using an on-chip method to achieve the fine pixel formation. With the on-chip method, the color filters 4 and microlenses 5 are processed directly on the organic light-emitting layer 9. However, the organic light-emitting layer 9 has issues with heat resistance, so low-temperature processing is required. Specifically, each component needs to be processed at 100°C or below. However, such low-temperature processing makes it difficult to fully develop the hardness of each component. For this reason, as mentioned above, it is not possible to sufficiently increase the hardness of the color filters 4 and microlenses 5, and as a result, the color filters 4 and microlenses 5 are scratched during the process of bonding the cover glass 7.

Furthermore, by applying a thick layer of adhesive 15 and bonding the cover glass 7 as shown in Figure 6A, it is possible to form a thick adhesive layer 16 located between the cover glass 7 and the microlens 5 as shown in Figure 6B, which makes the color filter 4 and microlens 5 less susceptible to scratches.

However, this increases the amount of adhesive 15 used, resulting in higher costs, and also increases the optical path length from the organic light-emitting layer 9 to the display output surface, making it more likely that light from adjacent pixels will mix colors.

Patent Documents 1 and 2 do not address the problem of scratches on the color filter 4 or microlens 5 during the process of bonding the cover glass 7, and do not provide any detailed explanation about the hardness of the cured resin layer (expressed as an adhesive or overcoat layer) used between the cover glass 7 and the color filter 4. Moreover, the curing temperature of the resin composition used in the resin layer is usually above 100°C, and the resin composition cannot be sufficiently cured at temperatures below 100°C.
The above-mentioned problems arise not only when the display device is an organic EL display device, but also when the display device is a micro LED display device.

As a result of extensive research, the inventors focused on the pencil hardness of the resin layer located between the color filter 4 and/or microlens 5 and the cover glass 7, and were able to prevent scratches on the color filter 4 and microlens 5 during the process of bonding the cover glass 7.

<Detailed Description of Hard Coat Layer 6 According to the Present Embodiment>
(1. Pencil hardness)
In the display device 1 according to the present embodiment, a hard coat layer 6 having a pencil hardness of H or more is provided on a resin layer located between the color filter 4 and/or the microlens 5 and the cover glass 7. Here, the "pencil hardness" is measured by the method specified in JIS K 5600-5-4.

The pencil hardness is preferably 2H or higher, more preferably 3H or higher, even more preferably 4H or higher, and most preferably 5H or higher.

By adjusting the pencil hardness to H or higher, scratches on the microlenses 5 and color filters 4 can be prevented during the process of bonding the cover glass 7. While the reason for this is unclear, it is presumed that a pencil hardness of H or higher makes it less susceptible to plastic deformation and cohesive failure, effectively reducing the pressure applied to the color filters and microlenses when the cover glass 7 is bonded. Note that "scratches" refer to scratches, dents, or linear marks. As mentioned above, a pencil hardness of 2H or higher is preferable, and experiments described below have shown that the pencil hardness can be increased to 4H or higher, or even 5H or higher. In this way, in this embodiment, the pencil hardness of the hard coat layer 6 can be adjusted to higher values in stages. The upper limit of the pencil hardness is not limited, and the upper limit can be set to the hardest value of 9H.

(2. Resin Material Used in Hard Coat Layer 6)
The hard coat layer 6 of the present embodiment is a cured film obtained by curing a resin composition (photosensitive composition) containing at least an acrylic resin, an acrylic monomer, and an initiator in a solvent, and the cured film contains at least, as solid components, a structural unit derived from the acrylic resin, a structural unit derived from the acrylic monomer, and the initiator.

In this embodiment, the hard coat layer 6 contains 31% by mass or more of structural units derived from acrylic monomers.

In addition, in this embodiment, the weight ratio of structural units derived from acrylic monomers to structural units derived from acrylic resins is 1.2 or greater.

Here, "derived structural unit" refers to the structural unit from which it is derived, and refers to the chemical structure remaining in the polymer after the relevant component has undergone a polymerization reaction, or, if the original state (state in the resin composition) can be inferred from that chemical structure, the chemical structure in the state before polymerization. Monomer-derived and resin (polymer)-derived units can be observed by NMR spectroscopy or IR spectroscopy, and the mass can be calculated based on the spectrum. Alternatively, if the amounts of the constituent components of the resin composition (photosensitive composition) are known, these values can be used to substitute the mass percentage of acrylic monomer in the solid components and the mass ratio of acrylic monomer/acrylic resin.

Acrylic resins are polymers of acrylic esters or methacrylic esters. The acrylic monomers can be selected from one or more of the following: methyl acrylate, ethyl acrylate, butyl acrylate, propyl acrylate, pentyl acrylate, hexyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, dodecyl acrylate, lauryl acrylate, acrylamide, vinyl acetate, acrylonitrile, methyl methacrylate, ethyl methacrylate, butyl methacrylate, propyl methacrylate, pentyl methacrylate, hexyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, dodecyl methacrylate, lauryl methacrylate, etc.

The initiator may be present in an amount sufficient to promote polymerization of the monomers, and the effects of this embodiment can be achieved regardless of its type. The initiator may be selected from, but is not limited to, oxime ester initiators, acetophenone compounds, benzoin compounds, benzophenone compounds, thioxanthone compounds, triazine compounds, phosphine compounds, quinone compounds, borate compounds, carbazole compounds, imidazole compounds, or titanocene compounds.

It is preferable that the content of structural units derived from acrylic monomers is 35% by mass or more, and more preferably 38% by mass or more.

Furthermore, the weight ratio of structural units derived from acrylic monomers to structural units derived from acrylic resins is preferably 1.5 or greater, more preferably 2.0 or greater, and even more preferably 2.5 or greater.

In this way, by adjusting the composition ratio and mass ratio of the acrylic monomers, the degree of polymerization in the cured film increases, and the pencil hardness can be adjusted to H or higher, preferably 2H or higher, and more preferably 5H or higher, effectively preventing scratches on the microlenses 5 and color filters 4 during the process of bonding the cover glass 7.

In this embodiment, the hard coat layer 6 may contain components other than the acrylic resin, acrylic monomer, and initiator as solid components. For example, it may contain a pigment. In this embodiment, this can be selected from known pigments and dyes depending on the color of the desired pixel. The amount of pigment contained is not limited, but may be the same as or greater than the amount of structural units derived from the acrylic monomer.

Here, the content of the structural units derived from the acrylic monomers listed above (31% by mass or more, preferably 35% by mass or more, more preferably 38% by mass or more) is within a range regardless of whether or not a pigment is present, but if no pigment is present, the content of structural units derived from the acrylic monomers can be 70% by mass or more.

Furthermore, in a configuration in which the hard coat layer 6 does not contain a pigment, the mass ratio of structural units derived from acrylic monomers to structural units derived from acrylic resins can be 4.0 or more, and even 4.5 or more.

Note that the above numerical ranges include measurement error. Also, deviations from the numerical ranges may occur depending on how the values are rounded. For this reason, in this embodiment, a tolerance of approximately ±10% of the analytical value, and preferably approximately ±5%, is included.

(3. Film Thickness of Hard Coat Layer 6)
The thickness of the hard coat layer 6 is preferably 0.5 μm or more and 10.0 μm or less. The thickness is more preferably 0.8 μm or more, and even more preferably 1.0 μm or more. Furthermore, the thickness is more preferably 7.0 μm or less, and even more preferably 5.0 μm or less. This allows for accurate pencil hardness of H or more, preferably 2H or more, and more preferably 5H or more. Furthermore, the optical path length from the organic light-emitting layer 9 to the display light-emitting surface 7a can be adjusted to an appropriate length, effectively suppressing color mixing between adjacent pixels. Note that the "thickness of the hard coat layer 6" in this embodiment refers to the minimum value. For example, if the hard coat layer 6 is on a microlens 5, it refers to the vertical thickness from the top of the microlens 5 to the top surface of the hard coat layer 6.

(4. Other)
The hard coat layer 6 preferably has an average transmittance of 95% or more for wavelengths of 400 nm to 800 nm, which can increase the light extraction efficiency of the hard coat layer 6 and improve the brightness of the display.

The refractive index of the hard coat layer 6 is preferably lower than that of the microlenses 5 and color filters 4 that are in contact with the lower layer side (organic light-emitting element 3 side) of the hard coat layer 6, and higher than that of the adhesive layer 13 that is in contact with the upper layer side (cover glass 7 side) of the hard coat layer 6. In the embodiment shown in Figure 1, the refractive index of the hard coat layer 6 is preferably lower than that of the microlenses 5 and higher than that of the adhesive layer 13. In addition, in the embodiment shown in Figure 2, the refractive index of the hard coat layer 6 is preferably lower than that of the color filters 4 and higher than that of the adhesive layer 13.

The refractive index decreases in the order of organic light-emitting layer 9, color filter 4, microlens 5, hard coat layer 6, adhesive layer 13, and cover glass 7, thereby achieving excellent light-collecting properties and increasing brightness.

<Regarding the manufacturing method of the display device according to the present embodiment>
The lamination from the hard coat layer 6 to the cover glass 7 will be mainly described.

As shown in Figure 4B, after the microlenses 5 have been formed on-chip, a photosensitive composition is applied to the surface of the microlenses 5. The photosensitive composition contains an acrylic monomer, an acrylic resin, and an initiator in a solvent. A pigment may also be added. In this case, the acrylic monomer content in the solid components is adjusted to 31% by mass or more, and the acrylic monomer/acrylic resin weight ratio is adjusted to 1.2 or more.

In the case of the display device of Figure 2, the photosensitive composition is applied to the surface of the color filter 4, and in the case of the display device of Figure 3, the photosensitive composition is applied to the surface of the overcoat layer 14. Any existing method can be used for the application method. The photosensitive resin is then dried on a hot plate. Although not limited, the drying temperature is approximately 50°C or higher and 70°C. The drying time is approximately several tens of seconds to several minutes. This causes the solvent contained in the photosensitive resin to evaporate.

Next, an exposure step is carried out. Although not limited thereto, the composition is cured by exposure to an exposure dose of several thousand J/ ^m2 using i-rays with an illuminance of approximately tens of thousands of W/ ^m2 . The composition is then further cured on a hot plate, for example, at a heating temperature of 80°C or higher and 100°C or lower for a heating time of several tens of minutes. Although not limited thereto, for example, an exposure dose of approximately 1000 J/ ^m2 to 5000 J/ ^m2 generally allows the initiator to react sufficiently, and a pencil hardness of H or higher, preferably a pencil hardness of 2H or higher, and more preferably a pencil hardness of 5H or higher can be appropriately and reliably obtained.

As a result of the above, a hard coat layer 6 with a pencil hardness of H or higher can be formed at a temperature of 100°C or less. As shown in Figure 4A, the hard coat layer 6 fills in the irregularities on the surface of the microlens 5. Furthermore, the surface 6a of the hard coat layer 6 becomes a flat surface.

Next, as shown in Figure 4A, adhesive 15 is applied to the surface 6a of the hard coat layer 6, and as shown in Figure 4B, a cover glass 7 is attached. Any existing adhesive can be used as adhesive 15. For example, a light-curing adhesive, a UV-curing adhesive, or a heat-curing adhesive can be used for adhesive 15. This allows the cover glass to be adhered and fixed to the surface 6a of the hard coat layer 6 via the adhesive layer 13.

As shown in Figure 3, if the resin layer 20 is not a single layer of the hard coat layer 6 but also includes other resin layers such as an overcoat layer 14, the other resin layers are also formed at a temperature of 100°C or less. In this case, the pencil hardness of the other resin layers may be H or less.

<Effects of the Display Device According to the Present Embodiment>
In this embodiment, as shown in Fig. 4A, a hard coat layer 6 having a pencil hardness of H or more is formed on the surface of the microlens 5, an adhesive 15 is applied to the surface 6a of the hard coat layer 6, and a cover glass 7 is attached as shown in Fig. 4B. Therefore, compared to the conventional example shown in Figs. 5A and 5B in which the hard coat layer 6 is not formed and the adhesive 15 is applied directly to the surface of the microlens 5, and the cover glass 7 is attached, in this embodiment, the surface of the microlens 5 is protected by the hard hard coat layer 6, so that it is possible to prevent scratches A from being caused on the microlens 5 in the process of attaching the cover glass 7, as in the conventional example.

Furthermore, in order to prevent scratches on the microlenses 5, the amount of adhesive 15 applied is increased in Figure 6A, making the adhesive layer 16 considerably thicker as shown in Figure 6B. However, increasing the amount of adhesive 15 used increases costs and prevents the display device from being made thinner. In contrast, in this embodiment, the amount of adhesive 15 used can be reduced by providing a hard coat layer 6 with a pencil hardness of H or higher that covers the surface side of the microlenses 5 and color filters 4. Furthermore, in this embodiment, the film thickness of the hard coat layer 6 can be reduced to approximately 0.5 μm to 10.0 μm, which facilitates the thinning of the display device 1. In this way, by reducing the thickness of the hard coat layer 6, the optical path length from the organic light-emitting layer 9 to the display output surface 7a can be made appropriate, effectively preventing color mixing between adjacent pixels.

Furthermore, in this embodiment, by reducing the amount of adhesive 15 used, it becomes easier to adhere the cover glass 7 parallel to the substrate 2, and quality variations due to misalignment of the cover glass 7 can be suppressed.

Furthermore, in this embodiment, the hard coat layer 6 is formed by curing a resin composition containing at least an acrylic resin, an acrylic monomer, and an initiator, and the content of structural units derived from the acrylic monomer in the hard coat layer 6 is 31% by mass or more, and the mass ratio of structural units derived from the acrylic monomer/structural units derived from the acrylic resin is 1.2 or more. By forming a hard coat layer 6 with such a composition, the pencil hardness of the hard coat layer 6 can be adjusted to H or higher, even if the curing temperature is set to 100°C or lower, and the thermal impact on the organic light-emitting layer 9 can be reduced.

The above describes in detail one embodiment of the present invention, but the present invention is not limited to that specific embodiment and includes structural modifications and combinations that do not deviate from the gist of the present invention. For example, while the above description uses an organic EL microdisplay as an example, the organic light-emitting element 3 may be an LED (light-emitting diode), and therefore the display device may be a microLED display. For example, the LED may be a combination of a blue light-emitting element and quantum dots, making it an element that can convert blue to red or green wavelengths. MicroLED displays can also achieve the effects of the display device described above by having a resin layer that includes a hard coat layer with a pencil hardness of H or higher.

The present invention will be explained in detail below using examples that were carried out to clarify the effects of the present invention. However, the present invention is not limited in any way by the following examples.

<Composition of the Photosensitive Composition>
A photosensitive composition was obtained by mixing and stirring the pigment, acrylic monomer (M), acrylic resin (P), and oxytacene initiator (I) in a PGMEA solvent.

Photosensitive compositions were prepared for Experimental Examples 1 to 6. The composition ratios for each experiment are shown in Table 1.

<Formation of hard coat layer>
Each of the photosensitive compositions of Experimental Examples 1 to 6 was applied onto a color filter by spin coating, and then dried by heating on a hot plate at 70° C. for 1 minute.

Subsequently, the film was cured by exposure to i-rays with an illuminance of 20,000 W/m ² at an exposure dose of 1,000 J/m ² , 3,000 J/m ² , or 5,000 J/m ² , and then heated on a hot plate at 100°C for 15 minutes to promote curing.

In addition, in each experimental example, hard coat layers with thicknesses of 0.6 μm, 1.0 μm, and 2.0 μm were prepared.

<Pencil hardness test>
The pencil hardness of the hard coat layer was measured under the following conditions in accordance with JIS K5600-5-4.
Test method: ISO pencil scratch hardness tester used Load on pencil tip: 750g
・Pencil used: Mitsubishi Uni (6B-9H)
- Adjusting the pencil lead: Sharpen only the wood, leaving the lead cylindrical. The tip should have a smooth, circular cross section at a 90-degree angle.
- Definition of pencil hardness: Use the hardest pencil scale that does not leave a mark and continue measuring until the same result is obtained both times.
The presence of scratches on the hard coat layer was confirmed using a microscope (reflection magnification: 50 times).
The experimental results are shown below.

As shown in Table 1, it was found that Experimental Examples 1 and 2 were able to achieve a pencil hardness of H or higher regardless of the film thickness of the hard coat layer. On the other hand, Experimental Examples 3 to 6 had pencil hardness below H, falling to B or lower.

By having a pencil hardness of H or higher, as in Experimental Examples 1 and 2, cohesive failure does not occur during the process of bonding a cover glass onto the hard coat layer via an adhesive layer, effectively preventing scratches on the color filter and microlenses.

Comparing Experimental Examples 1 and 2 with Experimental Examples 3 to 6, differences were observed in the content of acrylic monomer in the hard coat layer. Specifically, in Experimental Examples 1 and 2, the content of acrylic monomer in the solid components was 31% by mass or more. Furthermore, in Experimental Examples 1 and 2, the mass ratio of acrylic monomer to acrylic resin (M/P) was 1.2 or more. Note that all of these values were calculated from the constituent components contained in the resin composition.

Experimental Example 1 contains a pigment, while Experimental Example 2 does not. It was found that when no pigment is contained, the acrylic monomer content in the solid components can be increased to 70% by mass or more.

Furthermore, with regard to pencil hardness, when the hard coat layer has a thickness of 1.0 μm, a pencil hardness of H or higher can be distinguished as an Example, and a pencil hardness below H can be distinguished as a Comparative Example. However, pencil hardness tends to decrease as the thickness of the hard coat layer becomes thinner, and it is preferable that the pencil hardness be H or higher even when the thickness is around 0.5 μm.

Furthermore, the upper limit of the film thickness of the hard coat layer was set to 10 μm. Although the pencil hardness of the hard coat layer in Experimental Examples 1 and 2 was able to be maintained at H or higher, if the film thickness was too thick, there was concern that the display quality would be reduced due to the increased optical path length from the organic light-emitting layer to the display output surface. Therefore, a film thickness of 7 μm or less was more preferable, and 5 μm or less was even more preferable.

It was also found that an exposure dose of about 1000 J/m ² to 5000 J/m ² when forming the hard coat layer was sufficient to obtain a pencil hardness of H or higher.
It was also confirmed that the hard coat layers in Experimental Examples 1 and 2 had an average transmittance of 95% or more for wavelengths of 400 nm to 800 nm.
Based on the above, Experimental Examples 1 and 2 were set as working examples, and Experimental Examples 3 to 6 were set as comparative examples.

According to the present invention, cover glass can be attached without damaging the color filter or microlens, making it possible to use it in organic EL microdisplays and micro LED displays, which have excellent display quality.

This application is based on Japanese Patent Application No. 2024-021592, filed February 16, 2024, the contents of which are incorporated herein in their entirety.

Claims (8)

a light-emitting element, a color filter and/or a microlens, a resin layer, and a cover layer are laminated in this order on a substrate;
The resin layer includes a hard coat layer having a pencil hardness of H or more.
A display device characterized by: a light-emitting element, a color filter and/or a microlens, a resin layer, and a cover layer are laminated in this order on a substrate;
the resin layer includes a hard coat layer formed by curing a resin composition containing at least an acrylic resin, an acrylic monomer, and an initiator;
the hard coat layer contains 31% by mass or more of the structural unit derived from the acrylic monomer,
a mass ratio of the structural units derived from the acrylic monomer to the structural units derived from the acrylic resin is 1.2 or more;
A display device characterized by: The display device described in claim 2, characterized in that the hard coat layer has a pencil hardness of H or higher. The display device described in claim 1 or 2, characterized in that the film thickness of the hard coat layer is 0.5 μm or more and 10.0 μm or less. The display device described in claim 1 or 2, characterized in that the hard coat layer has an average transmittance of 95% or more for wavelengths between 400 nm and 800 nm. The display device described in claim 1 or 2, characterized in that the refractive index of the hard coat layer is lower than that of the layer on the color filter side that is in contact with the hard coat layer, and higher than that of the layer on the cover layer side that is in contact with the hard coat layer. The display device described in claim 1 or claim 2, characterized in that the cover layer is bonded to the surface of the resin layer via an adhesive layer. 3. The display device according to claim 1, wherein the light-emitting element is an organic light-emitting element.