JP7714935B2 - Color filter substrate and display device including the same - Google Patents

Description

The present invention relates to color filter substrates used in liquid crystal display devices, LED display devices using mini-LEDs or micro-LEDs, and organic EL display devices, as well as display devices equipped with color filter substrates.

Conventional LCD devices consist of a backlight unit that uses fluorescent tubes as a light source, a liquid crystal layer that controls the on/off state of the display dots, and a backplane that contains thin-film transistors (TFTs) that drive the liquid crystal molecules in the liquid crystal layer.

In recent years, attention has been focused on a technology that uses backlights in LCD displays, consisting of a matrix of white LED chips (known as mini-LEDs) measuring 50 μm to 200 μm, instead of the fluorescent tubes mentioned above.

Since the light-emitting brightness of LED chips can be adjusted individually, mini LEDs are being proposed to use a technology called local dimming, which divides the display screen into multiple sections and turns on or off multiple white LEDs within each section, allowing for more precise brightness adjustment.

A type of display device called micro LED has been proposed as a display device that does not use liquid crystal. Although not clearly defined, it mainly consists of LED chips arranged in a matrix-like area that is smaller than mini LEDs. The LED chips themselves are also approximately 2 μm to 50 μm in size, and display is achieved by driving each individual LED chip individually.

Unlike the mini-LEDs mentioned above, micro-LEDs can be broadly divided into systems that use three types of monochromatic LED chips (red, green, and blue) to achieve full color, and systems that combine LED chips that emit light in the blue to near-ultraviolet wavelength range with a wavelength conversion layer. Systems that use monochromatic LED chips can achieve full color displays by using blue LEDs that emit light in the near-ultraviolet range, or wavelength conversion layers made of materials called quantum dots that absorb ultraviolet light from UV-LEDs with emission wavelengths such as 365 nm and 385 nm and convert it into red, green, and blue wavelengths.

An organic EL display device is a display device that uses a light-emitting layer as a light source, which emits light by recombining electrons and holes injected into an organic compound as a display function layer. The light-emitting methods are broadly divided into two types: one that uses three types of light-emitting layers that emit red, green, and blue light, and one that uses a wavelength conversion layer to mix light in multiple wavelength bands to create white light, which is then separated into red, green, and blue light using color filters.

Patent No. 3941322 JP 2018-189920 A JP 2015-64391 A

In display devices using liquid crystal, the light emitted from the display function layer does not have sufficient linearity toward the pixel aperture. This results in stray light (light emitted at an angle) being emitted into adjacent pixels, resulting in a problem of reduced display contrast.

In the micro LED system, as pixel size becomes smaller, a decrease in display contrast due to stray light becomes a problem. Furthermore, when the display device is used in a bright environment, a decrease in display contrast due to external incident light entering the display device also becomes a problem.

Patent Document 1 discloses a reflective LCD device equipped with a light-scattering film. However, the components do not explicitly state how to solve the problem of reduced contrast caused by stray light originating from the scattering film.

Patent Document 2 relates to a quantum dot display device in which a color conversion material is provided inside the through-holes of the partition wall, and a color filter is further laminated on top of it. As with Patent Document 1, it does not disclose any technology related to suppressing contrast degradation. Furthermore, while the seventh embodiment is an example that includes a liquid crystal element, the light source in this example is an organic EL element common to all pixels, and does not include local dimming technology intended to reduce the number of light-emitting elements. The seventh embodiment is configured by bonding a phosphor substrate and a liquid crystal element together, which tends to result in a dark display and is prone to moire caused by alignment errors between the phosphor substrate and the liquid crystal element.

Patent Document 3, when applied to a typical liquid crystal display device in which the liquid crystal layer and color filter are in close proximity to or in contact with each other, poses a technical problem that could significantly reduce its practical applicability. A phosphor layer that fluoresces when exposed to excitation light (e.g., blue or ultraviolet light from an LED or organic EL element) is disposed between the partition walls as shown in claim 1 and Figure 1. When primary light from a light source such as an LED is wavelength-converted using phosphors or quantum dots (to become fluorescent secondary light), the secondary light has various emission angles and polarization states. In liquid crystal display devices, a polarizer is used to align the polarization, and the liquid crystal layer changes the polarization direction by 90 degrees to turn the emitted light on and off, adjusting the brightness from white to black. However, as mentioned above, the polarization of the secondary light from the phosphor layer is disrupted, resulting in a state in which contrast cannot be ensured.

Figure 9 shows a conventional example of a display device equipped with a direct-type backlight unit 50 that uses blue LEDs as light-emitting elements 51. In this conventional example, a liquid crystal panel 49 is shown as the display function part above the direct-type backlight unit 50. The liquid crystal panel 49 is provided with a color filter including a black matrix. To indicate pixel positions, pixels a, b, c, d, and e are schematically illustrated within the liquid crystal panel.

The direct-type backlight unit 50 comprises multiple light-emitting elements, a diffuser plate 52 arranged above the light-emitting elements, a wavelength conversion sheet 53, and, for example, two orthogonal prism sheets 54. The light-emitting elements are often multiple LED chips individually packaged in a metal casing. The wavelength conversion sheet converts part of the blue light emitted by the light-emitting elements into red and green, thereby obtaining the three colors red, green, and blue.

The light-emitting portion of these LED chips is generally filled with phosphors and light-scattering particles along with silicone resin. Because LED light is highly linear and emitted from the center of the LED chip, one of the roles of these phosphors and light-scattering particles is to scatter the light in order to expand the field of view. However, when packaged LED chips are arranged in a backlight unit in this way, the light emitted from the LED chip is scattered, and is diffused before it reaches the color filters installed in the pixel apertures, reducing contrast and making it difficult to achieve sufficient effect when applying local dimming.

The diffuser plate 52 and wavelength conversion sheet both diffuse light. For example, light emitted from a c-LED (blue LED) located directly below pixel c will not only reach pixel c, but will also be reflected in neighboring pixels a, b, d, and e, further reducing the effectiveness of local dimming. This phenomenon occurs not only in micro LED displays, but also in LED displays known as micro LEDs, where contrast reduction due to light scattering or stray light reaching neighboring pixels is a problem. The present application aims to provide an LED display with minimal contrast reduction due to stray light.

According to claim 1 of the present invention, a color filter substrate includes a first transparent substrate, a color filter layer formed on the first transparent substrate and consisting of red, green, and blue filters, a semi-transparent film, a first partition wall, and a light-scattering layer, wherein the first partition wall has a lattice shape and is made of a light-absorbing material. This prevents stray light from entering adjacent pixels, improving display contrast.

According to claim 2 of the present invention, the semi-transparent film contains either carbon or transparent fine particles, or both. By using the color filter substrate described in claim 1, stray light is prevented from entering adjacent pixels, improving display contrast.

According to claim 3 of the present invention, by using the color filter substrate described in claim 1, in which the light scattering layer is adjacent to the semi-transparent film or the first partition wall, stray light is prevented from entering adjacent pixels, thereby improving display contrast.

According to claim 4 of the present invention, by using the color filter substrate described in claim 1, which has the light scattering layer, second partition wall, and transparent resin layer in this order, stray light is prevented from entering adjacent pixels, thereby improving display contrast.

According to claim 5 of the present invention, by using the color filter substrate described in claim 1, characterized in that the film thickness of the first partition is 0.5 μm or more and 50 μm or less, stray light is prevented from entering adjacent pixels, thereby improving display contrast.

According to claim 6 of the present invention, a display device characterized by bonding together the surface of the color filter substrate described in claims 1 to 5 on which the color filter is formed and the surface of an optical module having a plurality of light-emitting elements arranged on one surface of a second transparent substrate so that they face each other prevents stray light from entering adjacent pixels, improving display contrast.

According to claim 7 of the present invention, in the display device described in claim 6, a display device having at least a liquid crystal layer and an array substrate of thin-film transistors that drive the liquid crystal layer between the first transparent substrate and the optical module prevents stray light from entering adjacent pixels, improving display contrast.

According to claim 8 of the present invention, the display device described in claims 6 and 7, in which the light-emitting element is a light-emitting diode, prevents stray light from entering adjacent pixels, improving display contrast.

This invention makes it possible to provide a display device that suppresses the influence of stray light on adjacent pixels, improves contrast, and provides good visibility.

1 is a partial cross-sectional view of a color filter substrate according to a first embodiment of the present invention. FIG. 10 is a partial cross-sectional view of a color filter substrate according to a second embodiment of the present invention. FIG. 2 is a partial plan view showing an arrangement of color filters according to the present invention. FIG. 2 is a partial plan view of the color filter as viewed from the direction of the first partition wall. FIG. 10 is a partial cross-sectional view of a display device according to a third embodiment of the present invention. FIG. 10 is a partial cross-sectional view of a display device according to a fourth embodiment of the present invention. FIG. 7 is an enlarged view of part A shown in FIG. 6, focusing on the first partition wall, the light scattering layer, and the second partition wall. FIG. 7 is an enlarged view of part B shown in FIG. 6, and is a partial cross-sectional view illustrating a light-emitting element (LED) and a thin-film transistor. 10 is a cross-sectional view of a conventional liquid crystal display device equipped with a direct-type backlight unit including a wavelength conversion sheet 53 and the like. 1 is a partial cross-sectional view of a conventional color filter in which a red filter R', a green filter G', and a blue filter B' are laminated on a black matrix 10. FIG.

Embodiments of the present invention will be described below with reference to the drawings. In the following description, identical or substantially identical functions and components will be designated by the same reference numerals, and their description will be omitted or simplified, or will be described only when necessary.

In each figure, the dimensions and proportions of each component have been appropriately altered from their actual size so that each component can be recognized on the drawing. The illustrations may be exaggerated for explanatory purposes, and the size and length of the components shown are not fixed. Furthermore, as necessary, elements that are difficult to illustrate, such as the configuration of thin-film transistors, the multi-layer structure that makes up conductive layers, wiring connections to circuit sections, and switching elements (thin-film transistors), have been omitted or partially omitted.

In each of the embodiments described below, we will explain the distinctive features, and will omit explanations of parts that are the same as those used in ordinary display devices and the display device according to this embodiment.

The ordinal numbers "first" and "second" used in terms such as first partition, second partition, first substrate, second substrate, and third substrate are used to avoid confusion between components and do not limit the quantity. Furthermore, a matrix arrangement of light-emitting elements refers to an arrangement in which light-emitting units, each containing one or more light-emitting elements (LEDs), are arranged in a matrix at a fixed pitch in a planar view. A substrate on which light-emitting elements are arranged in a matrix, or a substrate on which light-emitting units are arranged in a matrix at a fixed pitch, may be referred to as an optical module in the following descriptions. Thin-film transistors that drive the light-emitting elements and light-emitting units are preferably also arranged on the substrate. When the display function layer is a liquid crystal layer, this optical module is called a direct-type backlight. The light-emitting units may be surrounded by partitions in a grid pattern in a planar view when assembled into a display device.

In an embodiment of the present invention, the "display function layer" of the display device can be made up of either a plurality of light-emitting diode elements known as LEDs (Light Emitting Diodes) or a liquid crystal layer. In the following description, LEDs, LED chips, and light-emitting diode elements may be simply referred to as light-emitting elements.

LEDs are light-emitting diodes, and compounds such as aluminum gallium arsenide (AlGaAs), gallium arsenide phosphide (GaAsP), indium gallium nitride (InGaN)/gallium nitride (GaN)/aluminum gallium nitride (AlGaN), gallium phosphide (GaP), zinc selenide (ZnSe), and aluminum indium gallium phosphide (AlGaInP) are used in LEDs.

Three types of light-emitting elements (LEDs) can be used: red, green, and blue. Blue and ultraviolet LEDs are primarily made of gallium nitride (GaN). Mini LEDs can use LED chips with sizes ranging from 50 μm to 200 μm, for example. Micro LEDs can use LED chips with sizes ranging from 2 μm to 50 μm, for example.

The LED chip structure may be a horizontal LED in which the n-side electrode and p-side electrode are on the same side, or a vertical LED in which the n-side electrode and p-side electrode are on different surfaces (facing parallel surfaces) in the thickness direction of the LED. In the following description, the upper electrode and lower electrode refer to either the n-side electrode or the p-side electrode of a vertical LED. Note that the pixel openings of the first or second partition, or some of the light-emitting elements (light-emitting diodes), overlap along the center lines of their respective central positions in a planar view. The pixel openings of the first partition and the pixel openings of the second partition are positioned to overlap in a planar view.

A first embodiment of the present invention will be described below.
[Transparent substrate]
The first transparent substrate 100 applicable to the display device of the present invention may be made of a transparent substrate such as a glass substrate, a quartz substrate, a sapphire substrate, or a plastic substrate containing a polyimide film. The second transparent substrate 300, 500 on which multiple light-emitting elements are arranged in a matrix may be made of the same material as the transparent substrate 100, or may be colored black or another color. The second transparent substrate 300, 500 may be a silicon substrate on which CMOS elements (transistors, etc.) are arranged. It may also be a silicon substrate on which crystal-grown LEDs (light-emitting elements) are arranged via a buffer layer. The light-emitting elements 24 (blue or purple LEDs) may be mounted by flip-chip mounting using a low-melting-point alloy, mounting using an anisotropic conductive film, or wire bonding using gold wires. Multiple thin-film transistors for driving the light-emitting elements or the liquid crystal layer may be arranged on the second transparent substrate.

[Bulkhead]
The first and second partitions (sometimes simply referred to as partitions) according to the present invention can be made of a resin in which a black color material having a visible light absorbing function, such as carbon, is dispersed. The planar shape of the partitions is substantially the same as that of what is commonly called a black matrix, but the partitions according to the present invention are called "partitions" because they have the additional function of suppressing stray light, such as oblique light, diffused from an LED light source from entering unintended pixel openings, for example, openings of adjacent pixels.

As will be explained in the examples below, thick barrier ribs and barrier ribs with a two-layer structure are proposed, so the first barrier ribs of the present invention do not need to have high light-blocking properties. An optical density ΔOD of, for example, 2 or more and 3 or less is sufficient. By setting the concentration of the black colorant lower, it is possible to create first barrier ribs with a thickness of, for example, 10 μm or more. An optical density of 4 or more is also possible, but this would increase the process load, such as exposure time. If the optical density is 1 or less, external light reflection from reflective electrodes (LED electrodes) such as aluminum is easily visible, which may lead to a decrease in image quality of the display device. The concentration and film thickness of the black colorant, such as carbon, can be set to a black colorant concentration that allows it to be set within the above optical density range.

The film thickness of the first partition wall, as viewed from the normal direction of the first transparent substrate 100, can be 0.5 μm or more and 50 μm or less. When a first partition wall and a second partition wall are configured as in Example 2 described below, the film thickness of each of these partition walls can be thin, for example, 0.5 μm or more and 2.5 μm or less. When only the first partition wall is used as in Example 1, it is desirable to form it with a thick film thickness, for example, 2.5 μm or more and 50 μm or less, in order to mitigate the adverse effects of stray light (e.g., L1 and L2 in Figure 5) on adjacent pixels.

In addition to carbon, other light-absorbing black pigments that can be used include carbon fiber, carbon nanotubes, carbon nanohorns, and carbon nanobrushes. Organic pigments such as blue pigments can also be added. Metal oxides such as titanium black can also be added. Carbon-based materials with high thermal conductivity, such as carbon nanotubes, carbon nanohorns, graphene, and graphite, can also be added.

The above partition-related features are common to both the first and second partitions. The first and second partitions each have a grid pattern in a plan view, and overlap with the same line width center in both the first direction (X direction) and the second direction (Y direction). In other words, the center positions of the respective pixel openings also overlap in a plan view.

The color filters described below are, for example, stripe patterns of red, green, and blue filters extending in a first direction (X direction), and arranged adjacent to each other in the first direction (X direction). In this case, by forming the first partitions into a grid pattern as described above, the effect of stray light on adjacent pixels in both the first direction (X direction) and the second direction (Y direction) can be reduced, improving display quality.

In the color filter substrate configuration of the present invention, a color filter and semi-transparent film are first disposed on a first substrate, and then a first partition wall is laminated thereon, and in later embodiments, a second partition wall is also laminated thereon. This minimizes the impact of stray light on adjacent pixels. The reasons for this will be explained in detail in later embodiments.

[Color filter]
Color filters (red filter R, green filter G, blue filter B) and a first partition wall can be laminated in this order on a first transparent substrate 100. The red filter R, green filter G, and blue filter B are each disposed in a pixel opening in a plan view. However, the color filters and components such as a semi-transparent film 3 and a first partition wall 2, which will be described later, can be formed together on the first transparent substrate 100. The color filters, typified by the red filter R, green filter G, and blue filter B, are formed by dispersing an organic pigment, described below, in a resin such as acrylic.

Red organic pigments that can be used in the present invention include, for example, C.I. Pigment Red 7, 14, 41, 48:2, 48:3, 48:4, 81:1, 81:2, 81:3, 81:4, 146, 168, 177, 178, 179, 184, 185, 187, 200, 202, 208, 210, 246, 254, 255, 264, 270, 272, and 279. Yellow and orange pigments can also be used in combination with the red filter R.

Yellow organic pigments that can be used in the present invention include C.I. Pigment Yellow 1, 2, 3, 4, 5, 6, 10, 12, 13, 14, 15, 16, 17, 18, 24, 31, 32, 34, 35, 35:1, 36, 36:1, 37, 37:1, 40, 42, 43, 53, 55, 60, 61, 62, 63, 65, 73, 74, 77, 81, 83, 93, 94, 95, 97, 98, 100, 101, 104, 106, 108, 109, 110, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168 6, 117, 118, 119, 120, 123, 126, 127, 128, 129, 147, 151, 152, 153, 154, 155, 156, 161, 162, 164, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 179, 180, 181, 182, 187, 188, 193, 194, 199, 198, 213, 214, etc.

Green organic pigments such as C.I. Pigment Green 7, 10, 36, and 37 can be used, and yellow pigments can also be used in combination. Suitable green pigments include halogenated zinc phthalocyanine and halogenated aluminum phthalocyanine.

Blue organic pigments include, for example, C.I. Pigment Blue 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22, 60, and 64, and can also be used in combination with violet pigments. Examples of violet pigments include C.I. Pigment Violet 1, 19, 23, 27, 29, 30, 32, 37, 40, 42, and 50.

These organic pigments are dispersed in a transparent resin along with an organic solvent and dispersant. The transparent resin preferably has a visible transmittance of 90% or more, and is preferably an alkali-soluble photosensitive resin containing a resin precursor. The pigment can be contained in the resin in an amount ranging from 15% to 45% by weight.

The photosensitive resin used is a resin in which a linear polymer having reactive substituents such as hydroxyl groups, carboxyl groups, or amino groups is reacted with a (meth)acrylic compound or cinnamic acid having reactive substituents such as isocyanate groups, aldehyde groups, or epoxy groups, to introduce photocrosslinkable groups such as (meth)acryloyl groups or styryl groups into the linear polymer.

Monomers and oligomers that serve as precursors to transparent resins include various acrylic acid esters and methacrylic acid esters such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, cyclohexyl (meth)acrylate, polyethylene glycol di(meth)acrylate, pentaerythritol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tricyclodecanyl (meth)acrylate, melamine (meth)acrylate, and epoxy (meth)acrylate, as well as (meth)acrylic acid, styrene, vinyl acetate, (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, and acrylonitrile. These can be used alone or in combination. When curing by exposure to ultraviolet light at a wavelength of 365 nm or greater, a photopolymerization initiator or the like is further added.

[Light scattering layer]
As shown in Figures 1 and 2, the color filter substrate according to the present invention can be provided with a light-scattering layer 4. The light-scattering layer 4 can basically be a dispersion of transparent resin and transparent particles. Furthermore, as will be described later, a light-absorbing black coloring material such as carbon can be added to the layer to prevent scattered light from reaching adjacent pixels.

Transparent particles having an average particle size of 1 μm or more and 3.0 μm or less can be used. Optically isotropic transparent particles can be used. "Optically isotropic" means that the transparent particles used in embodiments of the present invention have a crystal structure in which the a-axis, b-axis, and c-axis are all equal, or are amorphous, and light propagation is isotropic and not affected by the crystal axis or crystal structure. Silica particles have a non-crystalline structure (amorphous).

Resin particles such as resin beads are known to have various properties, including refractive index, and these particles can be used in combination. Resin particles such as acrylic, styrene, urethane, nylon, melamine, and benzoguanamine may also be used in combination. For the light-scattering layer 10, it is preferable to use light-scattering particles (transparent particles) with an average particle size of, for example, microns, of 1.0 μm to 3.0 μm. In other words, by using particles with a particle diameter larger than the wavelength of visible light, it is easier to obtain appropriate light-scattering properties for the light-scattering layer 4.

In addition, transparent fine particles with an average particle size of approximately 0.2 μm or 0.1 μm or less may be used in combination as a dispersion aid. The transparent particles 8 or transparent fine particles can be dispersed in a transparent resin or a resin containing an ultraviolet absorber to form the light-scattering layer 10.

Transparent particles or transparent microparticles of zinc oxide that are transparent in the visible range and can absorb ultraviolet light of 390 nm or less can also be used. In this description of the present invention, transparent particles are defined as particles with an average primary particle size of 1 μm or more, and transparent microparticles are defined as particles with an average primary particle size of 0.2 μm or less.

The thickness of the light-scattering layer 4 is a dispersion of transparent particles larger than the wavelength of light, and as such, can be between 2.5 μm and 50 μm. It can be made thicker than 50 μm, but increasing the thickness beyond 50 μm does not improve scattering properties much. In fact, making the layer thicker increases process loads, such as wasted work time during coating and drying. A light-scattering layer with a thickness of less than 2.5 μm, or even 2.0 μm or less, makes it difficult to achieve a scattering effect sufficient for visibility.

Light scattering does not have to be limited to the dispersion of transparent particles in a transparent resin. For example, it is possible to apply and dry a dispersion of two resins with different refractive indices dissolved in an organic solvent, thereby causing phase separation between the two resins and imparting light scattering properties.

In display devices that do not use circular polarizers or polarizers, the transparent particles do not need to be optically isotropic, allowing for a wider range of choices for the transparent particles 8. For example, zinc oxide particles can be used as transparent particles that can be added to the light scattering layer 4. Zinc oxide has high transmittance in the visible range of 400 nm to 700 nm and can absorb ultraviolet light of 390 nm or less. From this perspective, it makes sense to use transparent particles or transparent microparticles of zinc oxide in display devices that do not use circular polarizers.

[Semi-permeable membrane]
The semi-transmitting film adjusts and combines transmittance to improve visibility, and when assembled into a display device, it plays a major role in suppressing external light reflection toward the viewing side from the light scattering layer 4 and the wavelength conversion layer (a wavelength conversion sheet is often used in mini LEDs that use a liquid crystal layer).The semi-transmitting film can also suppress external light reflection from the interface with the first partition.In display devices that include a reflective electrode, such as micro LEDs, the semi-transmitting film can suppress external light reflection from the reflective electrode.

The semi-transparent film is a dispersion of at least carbon and resin. In addition to carbon, an ultraviolet absorber may also be added. The semi-transparent film is a resin dispersion containing carbon as the main pigment. It is preferable that the semi-transparent film have a visible light transmittance in the range of 70% to 99.7%. The amount of carbon added to the resin dispersion is adjusted from the perspective of this transmittance. In addition to carbon, transparent fine particles or organic pigments such as blue may also be added. The transmittance of such semi-transparent films can be easily adjusted by adding carbon, a black pigment, in an amount ranging from 0.2 wt% to 5 wt% of the resin solids, for example. Adding carbon in an amount exceeding 6 wt%, or even 7 wt%, results in excessively low transmittance of the transmittance adjustment layer.

Assuming that external light is incident on the display surface, the external light passes through the semi-transmitting film once, is reflected by the light-reflective electrode, and then passes through the semi-transmitting film again to be emitted toward the viewer. This double passage of light can rapidly reduce the reflection of external light. If the semi-transmitting film has a visible light transmittance of 70% or more, the display device provided by the present invention will be brighter than a display device that uses a circular polarizer. Note that the display device of the present invention can also be made using a semi-transmitting film in a high transmittance region and a circular polarizer.

Moreover, many LCD displays use two polarizing plates in a crossed Nicol configuration (with orthogonal polarization axes). When using such a circular polarizing plate or polarizing plate, it is possible to add optically isotropic, transparent particles in the visible range that do not cause polarization distortion to the semi-transparent film in order to improve dispersion or reduce the refractive index of the semi-transparent film.

For example, if the semi-transparent film is a transparent inorganic film or a resin film with nearly 100% transmittance for visible light, ripples due to interference in the light reflection at the interface with the first partition wall may occur, causing the first partition wall to appear slightly colored. This slight coloration caused by reflected light is easily observed when the display device is turned off and in black.

In addition, in such cases, the image may appear rainbow-colored when viewed from an oblique angle by an observer, which can easily reduce visibility.

In contrast, forming a semi-transparent film using a combination of silica microparticles and carbon can reduce the size of these ripples. From the above perspective, semi-transparent films containing microparticles that are transparent in the visible range are useful. A similar effect can be achieved by not including silica microparticles but including a low concentration of carbon.

The particle size of the transparent particles, such as silica microparticles, is not specified, but for example, transparent particles with an average primary particle size of 3 nm to 100 nm can be used. The thickness of the semi-transparent film is preferably in the range of 0.1 μm to 2 μm, but may be 2 μm or more.

If the semi-transparent film does not use carbon and is formed primarily with organic pigments, external light reflected at the interface with the first partition wall may appear yellow. In contrast, a semi-transparent film containing carbon as its primary pigment component has a nearly flat reflected light, with almost no coloring. "Flat reflected light" means that within the visible range of light wavelengths from 400 nm to 700 nm, there are no irregularities (fluctuations) in transmittance of 2% or more over a small range, such as 50 nm, and a nearly linear transmittance curve is obtained.

In other words, if the visible range of 400 nm to 700 nm is divided into 50 nm increments, the magnitude of the reflectance fluctuation (ripple) within each 50 nm increment can be kept to 1.0% or less. Furthermore, within the visible range of light wavelengths from 400 nm to 700 nm, the reflectance at the interface with the first partition can be kept within the range of 0.01% to 1.0%.

Note that reflectance fluctuation (ripple) is the difference between the peaks and valleys of the reflectance spectral curve within 50 nm increments as described above, when measured in the visible range of light wavelengths from 400 nm to 700 nm. However, for a simpler evaluation, the reflectance peak value within 50 nm increments may also be used. With the latter simple evaluation, the apparent reflectance fluctuation value will be larger.

The reflectance here is the reflectance measured through the transparent substrate and semi-transparent film, with the reflectance of the aluminum film as the reference (100%). Measurements can be easily made using, for example, a microspectrophotometer. Note that the optically isotropic transparent fine particles play an important role in suppressing reflectance fluctuations. To further suppress reflectance fluctuations and achieve lower reflectance, a semi-transparent film can be made by incorporating trace amounts of carbon or blue pigment into the resin along with the transparent particles.

In the color filter substrate configuration of the present invention, the semi-transparent film 3 also serves as a planarizing film for the color filters (red filter R, green filter G, and blue filter B). As described above, the semi-transparent film 3 suppresses external light reflection from light-scattering films and the like, improving visibility, and can also improve the planarization of the color filters. The improvement in planarization of the semi-transparent film 3 can be further improved by adding transparent particles such as the above-mentioned carbon and silica fine particles. Here, the average primary particle diameter of the transparent particles such as silica fine particles is preferably 100 nm or less, as described above. An average primary particle diameter significantly exceeding 100 nm tends to result in unevenness due to the particle size of the transparent particles, which can have an adverse effect.

Example 1 will be described using Figures 1, 3, 4, and 10. Figure 1 is a cross-sectional view of a color filter substrate 110 according to the present invention. Figure 3 is a partial plan view showing only the color filters (red filter R, green filter G, and blue filter B). Figure 4 is a partial plan view of Figure 1 as seen from the Zo direction. In Figure 4, the light scattering layer is omitted. Figure 10 is a partial cross-sectional view of a conventional color filter configuration in which red filter R', green filter G', and blue filter B' are stacked on a black matrix 10.

A semi-transparent film 3, a light-scattering layer 3, a first partition wall, a transparent resin layer 11, and other layers are laminated on a color filter 5, which is made up of adjacent red filters R, green filters G, and blue filters B. In Example 1, the light-scattering layer 3 is disposed so as to fill the gaps between the first partition walls, which are thick in the normal direction of the first transparent substrate 100. The transparent resin layer 11 may be omitted. The film thickness of each of the red filters R, green filters G, and blue filters B is, for example, 2.2 μm.

In the first embodiment, the film thickness of the first partition wall (from the normal direction of the first transparent substrate 100) is limited by the film thickness required for the light scattering layer 4 in terms of the particle size of the transparent particles. As described above, the light scattering layer 4 is to have a thickness of 2.5 μm to 50 μm, so the film thickness of the first partition wall in the first embodiment is desirably 2.5 μm to 50 μm. (In the second embodiment described below, the first partition wall may be formed with a thickness as thin as 0.5 μm.) The light scattering layer 4 can be formed, for example, by injecting a dispersion of transparent particles, resin, and organic solvent between the first partition walls using an inkjet or microneedle.

As shown in FIG. 3, the color filters 5 included in the color filter substrate 110 of the present invention have overlapping portions Wrg, where red filter R overlaps green filter G, Wgb, where green filter G overlaps blue filter B, and Wbr, where blue filter B overlaps red filter. The color filter configuration proposed by the present invention stacks the color filters (red filter R, green filter G, and blue filter B) directly on the first transparent substrate 100. The heights of the overlapping portions Wrg, Wgb, and Wbr are small, ranging from approximately +0.4 μm to -0.5 μm. When a semi-transparent film 3 is stacked on these color filters 5, the unevenness of the overlapping portions is further reduced, falling within a range of approximately +0.2 μm to -0.3 μm. As mentioned above, the semi-transparent film 3 has the dual effects of suppressing external light reflection and improving surface flatness.

However, as shown in Figure 10, the unevenness of the overlapping portions of conventional color filters (red filter R', green filter G', blue filter B') stacked on a black matrix 10 is quite large. The height H2 of the raised portion of each overlapping portion is quite large, for example, 1.7 μm for Wrg, 1.3 μm for Wbr, and 1.5 μm for Wbg. The reason for the large height H2 is that a thick black matrix 10 (e.g., 1.2 μm) is formed underneath the color filters. Since the difference in unevenness of the overlapping portions is directly related to the variation and precision of the first partition walls that are stacked in a subsequent process, the configuration proposed by this invention can be considered superior. The effects of the light-scattering layer 4 and the thick first partition walls will be explained in the examples below.

Example 2 will be described using Figures 2, 3, 4, and 10. Figure 2 is a cross-sectional view of a color filter substrate 210 according to the present invention. Figure 3 is a partial plan view showing only the color filters (red filter R, green filter G, and blue filter B). Figure 4 is a partial plan view of Figure 1 as seen from the Zo direction. In Figure 4, the light scattering layer is omitted. Figure 10 is a partial cross-sectional view of a conventional color filter configuration in which red filter R', green filter G', and blue filter B' are stacked on a black matrix 10.

A semi-transparent film 3, a first partition, a light-scattering layer 4, a second partition 2, a transparent resin layer 11, and other layers are laminated on a color filter 5 consisting of adjacent red filters R, green filters G, and blue filters B. The major difference between Example 1 and Example 2 is that the light-scattering layer 4 is a single layer, and the second partition is laminated on top of this light-scattering layer 4. The two-layer structure of the first partition and the second partition further reduces the adverse effects of stray light on adjacent pixels.

Unlike Example 1, the first and second barrier ribs, each of which is a thin film (e.g., 1 μm), have the advantage of being easily formed using a photolithography process, and the light-scattering layer 4 in Example 2 has the advantage of being easily formed using a common coating device such as a slit coater. The effects of the first barrier ribs, light-scattering layer 4, and second barrier ribs 2 will be explained in later examples.

Example 3 is an example of a display device according to embodiment 2 of the present invention. Example 3 will be explained using Figure 5. Figure 5 is a partial cross-sectional view of a display device according to the present invention, and is a display device 101 in which the color filter substrate 110 of Example 1 and an array substrate 310 on which light-emitting elements D1, D2, and D3 are arranged are bonded together so that they face each other.

The display device 101 shown in Figure 5 has light-emitting units 38 separated by third partitions 33 arranged in a matrix, and light-emitting elements D1 in each light-emitting unit 38 are driven by one or more thin-film transistors. The number of light-emitting elements in each light-emitting unit 38 separated by third partitions 33 may be one or more, and is not limited to one.

Light-emitting element D1 shown in Figure 5 is located below blue filter B (in the Z direction in the illustration) and is a blue-emitting LED (light-emitting diode). To improve the uniformity of the display screen and reduce unevenness, for example, multiple light-emitting elements may be arranged within the light-emitting unit at random angles of 90° in plan view. Light-emitting element D2 located below red filter R is a red-emitting light-emitting element, and light-emitting element D3 located below green filter G is a green-emitting LED.

Emission from light-emitting element D2 is shown as emitted light L1, L2, L3, L4, and L5. Obliquely emitted light L1 and L5 from the end of light-emitting element D2 are cut off by the thick first partition, making it possible to suppress stray light from reaching adjacent pixels. If the first partition is thin, oblique light is more likely to enter adjacent pixels, which can cause problems.

LED elements that do not incorporate scattering particles or wavelength-converting particles within the LED chip emit light that is highly directional, making it difficult to ensure a wide viewing angle. The light-scattering layer 4 shown in Figure 5 has the effect of scattering the light emitted from light-emitting elements D1, D2, and D3, thereby widening the viewing angle. The main role of the semi-transparent film 3 in this Example 3 is to suppress external light reflection from the light-scattering layer 4 and from the interface between the first partition and the semi-transparent film 3. It is desirable that the LED chips used in the display devices proposed in this invention are LED chips that do not incorporate scattering particles or wavelength-converting particles. Figure 5 shows an LED display (μLED) that does not use a circular polarizer; however, if necessary, a circular polarizer may be attached to the viewing-side surface of the display device.

Example 4 will be described using Figures 6, 7, and 8. Figure 6 is a partial cross-sectional view of a display device according to a second embodiment of the present invention. This is a liquid crystal display device (mini-LED) in which the display function layer is liquid crystal 30. Figure 7 is an enlarged view of part A in Figure 6, including the first partition wall, the second partition wall 2, and the light scattering layer 4. Figure 8 is an enlarged view of part B in Figure 6, including the thin-film transistor 60 that drives the light-emitting element D5. In Example 4, an optical module 510 in which light-emitting elements are arranged serves as a direct-type backlight unit and is driven by local dimming.

In Figure 8, only one thin-film transistor 60 is shown, but there are two or more thin-film transistors that drive one light-emitting element (LED) or one set of light-emitting units 39, and these are not shown. When a gate signal is input to the gate electrode 56, current from the thin-film transistor 60 power line 67 flows into the drain electrode 57 via the source electrode and semiconductor layer 55, causing the light-emitting element 70 to emit light.

The lower electrode 74 of the light-emitting element 70 is electrically connected to a light-reflective reflective electrode 65 via a connection layer 75 made of a low-melting-point alloy containing, for example, indium. The reflective electrode 65 is connected to the drain electrode 57 of the thin-film transistor 60 via a contact hole 66. The connection layer 75 may be made of other connection means, such as an anisotropic conductive film. The upper electrode 71 may be made of a transparent conductive film such as ITO, which serves as the common electrode for the light-emitting element 70. A highly conductive metal thin film may be laminated on part of the common electrode as an auxiliary conductor.

Emitting elements D4, D5, and D6 are arranged in three or more units within the light-emitting unit 39, and include red, green, and blue light-emitting elements. There are roughly two ways to drive the light-emitting elements: a local dimming method in which the red, green, and blue light-emitting elements are uniformly illuminated to produce white light and adjust the brightness of the white light; and a local dimming drive method that adjusts the light-emitting intensity of specific light-emitting elements, including color adjustment. The orientation angle, density, and number of the light-emitting elements can be adjusted to ensure even light emission.

The two-layer barrier ribs shown in Figure 7, the first and second barrier ribs 2, play a role in improving contrast by suppressing stray light, similar to the thick first barrier ribs shown in Example 3. In other words, oblique light 44, 45 from a light source such as an LED is cut by the second barrier ribs, reducing the adverse effects on adjacent pixels.

In addition to transparent particles, it is desirable to add a light-absorbing black material such as carbon to the light-scattering layer 4. The amount of black material added can be, for example, 0.2 at% to 5 at% in terms of the resin solid ratio (weight ratio). Adding such a black material suppresses diffused light that crosses the light-scattering film 4 in the direction of adjacent pixels (see Figure 7), thereby preventing a decrease in contrast and color purity. In this case, the partition width Tw (common to the first partition and second partition 2) is preferably at least twice the thickness Th of the light-scattering layer 4. The suppression effect can be expected to be the square of the ratio of the light-scattering layer Th to the partition width Tw. If the black material is carbon, it can prevent coloring of the light 41 emitted from the pixel opening.

Display devices equipped with color filter substrates according to the above-described embodiments can be used in a variety of applications. Electronic devices to which the display devices according to the above-described embodiments can be applied include mobile phones, portable game devices, personal digital assistants, personal computers, e-books, video cameras, digital still cameras, head-mounted displays, navigation systems, audio playback devices (car audio, digital audio players, etc.), copiers, facsimiles, printers, multi-function printers, vending machines, automated teller machines (ATMs), personal authentication devices, optical communication devices, and IC cards. The above-described embodiments can be freely combined and used. Electronic devices incorporating display devices according to the embodiments of the present invention preferably further include an antenna for communication and contactless power reception and supply.

While preferred embodiments of the present invention have been described and illustrated above, it should be understood that these are illustrative of the present invention and should not be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the scope of the present invention. Accordingly, the present invention should not be considered as limited by the foregoing description, but is defined by the claims.

The present invention can be used in semiconductor devices that include a wiring board and a wiring board on which a semiconductor element is mounted.

1, 6: First partition wall 2: Second partition wall 3: Semi-transparent film 4: Light scattering layer 5: Color filter 8: Pixel electrode 9: Common electrode 10: Black matrix 11: Transparent resin layer 12: Adhesive layer 17: First insulating layer 18: Second insulating layer 19: Third insulating layer 23: Light control sheet (prism sheet)
24: Wavelength conversion layer 25, 26: Polarizing plate 30: Liquid crystal layer 33, 37: Third partition 38, 39: Light-emitting unit 41: Linear light 44, 45: Oblique light 49: Liquid crystal panel 50: Backlight unit 51: Light-emitting element (LED light-emitting element filled with scattering particles)
52: Diffusion plate 53: Wavelength conversion sheet 54: Prism sheet 55: Semiconductor layer 56: Gate electrode 57: Drain electrode 58: Source electrode 59: Light-shielding film 60: Thin film transistor 61: Fourth insulating layer 62: Fifth insulating layer 63: Sixth insulating layer 64: Gate insulating film 65: Reflection electrode 66: Contact hole 67: Power supply line 69: Upper electrode (common electrode)
70: Light emitting element (LED)
71: First semiconductor layer 72: Light-emitting layer 73: Second semiconductor layer 74: Lower electrode 75: Connection layer 100, 200: First transparent substrate 110, 210: Color filter substrate 101, 102: Display device 300, 500: Second transparent substrate 310, 510: Optical module (on which light-emitting elements are arranged) 400: Third transparent substrate 410: Array substrate (on which thin-film transistors that drive liquid crystal are arranged) D1, D2, D3, D4, D5, D6...light-emitting elements (LEDs)
R, R': Red filter G, G': Green filter B, B': Blue filter

Claims (7)

A color filter substrate comprising: a first transparent substrate; a color filter layer formed on the first transparent substrate and including a red filter, a green filter, and a blue filter; a semi-transparent film; a first partition wall; a light scattering layer ; a second partition wall; and a transparent resin layer, in this order ;
the first partition wall and the second partition wall have a lattice shape in which openings of the first partition wall and the second partition wall overlap each other in a plan view , and are made of a light-absorbing material;
a width of the first partition wall and the second partition wall being at least twice the thickness of the light scattering layer ; The color filter substrate of claim 1, wherein the semi-transparent film contains either carbon or transparent fine particles, or both. The color filter substrate of claim 1, wherein the light scattering layer is adjacent to the semi-transparent film or the first partition wall. The color filter substrate of claim 1, wherein the film thickness of the first partition wall is 0.5 μm or more and 50 μm or less. A display device characterized in that the surface on which the color filter of the color filter substrate according to any one of claims 1 to 4 is formed and the surface of an optical module having a plurality of light-emitting elements arranged on one surface of a second transparent substrate are bonded together so as to face each other. 6. The display device according to claim 5 , further comprising at least a liquid crystal layer and an array substrate of thin film transistors for driving the liquid crystal layer between the first transparent substrate and the optical module. 7. The display device according to claim 5 , wherein the light-emitting element is a light-emitting diode.