JPH1039109A - Microlens array sheet, and liquid crystal display device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microlens array sheet capable of remarkably enlarging its angle of visual field and holding excellent display quality without lowering display picture quality provided in a liquid crystal cell if it is used in a liquid crystal display device, and the liquid crystal display device. SOLUTION: The microlens array sheet arranges minute unit lenses in a surface shape, and a light diffusion degree when luminous flux is made incident from the normal direction of at least one side surface is 20 deg. or below, and further, the microlens array sheet is provided with a layer that a first material layer 1 and a second material layer 2 with a refractive index smaller than the first material layer 1 are held between two parallel planes and the unit lenses with an optically projective shape are arranged by making a boundary between the first material layer 1 and the second material layer 2 a periodical rugged shape, and light shielding layers 6 are provided on respective unit lenses in the first material layer 1 side from the rugged surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a microlens array sheet and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art A liquid crystal display device uses an electro-optical effect of liquid crystal molecules, that is, optical anisotropy (refractive index anisotropy), orientation, fluidity, dielectric anisotropy, and the like, and can be used as an arbitrary display unit. Observes images displayed using an array of liquid crystal optical shutters that change the light transmittance and reflectivity by changing the alignment state of the liquid crystal by applying or applying an electric field. Devices, portable electronic devices, game machines, in-vehicle information display devices, and various information display devices.

As a display principle of a liquid crystal display device, a twisted nematic liquid crystal that performs display by controlling a voltage applied to a nematic liquid crystal layer twisted by about 90 degrees and combining a change in the optical rotation of the liquid crystal layer with a polarizing element is known. It is widely used because of its high display performance.

However, the liquid crystal display device has a viewing angle dependency in which the display quality changes depending on the viewing direction. In particular, in the case of a twisted nematic liquid crystal, the problem that the display brightness is inverted or the color tone changes, that is, the viewing angle is narrow. There was a disadvantage.

It has been proposed in Japanese Patent Application Laid-Open No. Hei 5-249453 or the like that this disadvantage can be solved by providing an optical element such as a microlens array sheet on the observation surface of a liquid crystal display device.

In Japanese Patent Application Laid-Open No. Hei 6-27454,
There has been proposed a method of obtaining good display quality without being affected by an observation environment by combining a light shielding layer with a unit lens of a microlens array sheet.

[0007]

However, in such prior art, although the viewing angle is enlarged, the display contrast is reduced due to the diffusion effect of the microlens array sheet, and in particular, in a high-definition display device having small display pixels, an image is not displayed. There are drawbacks related to display quality such as blurring.

According to the present invention, when such a disadvantage is solved and a liquid crystal display device is formed, the viewing angle can be greatly expanded, and good display quality can be maintained without deteriorating the display quality of the liquid crystal cell. And a liquid crystal display device having a high image quality and a wide viewing angle.

[0009]

The present invention employs the following means in order to solve the above-mentioned problems. That is, the microlens array sheet of the present invention is a microlens array sheet in which minute unit lenses are arranged in a plane, and has a light diffusion degree of 20 degrees when a light beam is incident from at least one surface normal direction. It is characterized by the following.

In the microlens array sheet according to the present invention, the first material layer and the second material layer having a smaller refractive index than the first material layer are sandwiched between two parallel planes. And a microlens array sheet having a layer in which unit lenses having an optically convex shape are arranged by periodically forming an interface between the second material layer and the second material layer. The light shielding layer is provided on the first material layer side from the surface, and the light shielding layer is provided on the unit lens array surface when the microlens array sheet is viewed from the first material layer side in the normal direction of the unit lens array surface. When a light ray parallel to the normal direction and incident from the second material layer travels inside the first material layer, it is determined based on the difference between the refractive index of the first material layer and the second material layer and the angle between the light traveling direction and the uneven surface. The direction of travel changes due to refraction on uneven surfaces. Angle, in which the region exceeding 20 degrees is characterized in that arranged so as to be covered by the light shielding layer.

[0011] Microlens array sheet.

Further, the liquid crystal display device of the present invention is characterized in that such a microlens array sheet is mounted on a liquid crystal cell observation surface.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As a result of a detailed study of the drawbacks of the prior art, the present invention shows that the degree of light diffusion when measured in a specific direction of a microlens array sheet is lower than that of a liquid crystal display. I found that there was a strong correlation,
In addition, a light-shielding layer corresponding to the unit lens array of the microlens array sheet is provided to control this light diffusion degree,
It has been found that such a disadvantage can be solved by controlling the arrangement position and shape of the light shielding layer.

In the present invention, the liquid crystal display device utilizes the electro-optical effect of liquid crystal molecules, ie, optical anisotropy (refractive index anisotropy), alignment, fluidity, dielectric anisotropy, and the like.
A display is performed using a liquid crystal cell which is an array of optical shutters that changes the alignment state of liquid crystal by applying or applying an electric field to an arbitrary display unit to change the light transmittance or the reflectance.

In the present invention, the terms “light beam”, “luminous flux”, and “refractive index” simply refer to a 550 nm light beam, a luminous flux, or a refractive index at 550 nm, respectively, unless otherwise specified.

The microlens array sheet of the present invention comprises:
The micro unit lenses are arranged in a plane. Here, the minute unit lens refers to a lens, a prism, a non-cylindrical light pipe, a refractive index distribution body, a scattering element, or the like that changes the traveling direction of a transmitted light beam.

The microlens array sheet of the present invention comprises:
A first material layer and a second material layer having a lower refractive index than the first material layer are sandwiched between two parallel surfaces.
A unit lens array is formed by periodically forming an interface (hereinafter, simply referred to as an “irregular surface”) of a substance into an irregular shape. A microlens array sheet having an uneven surface "). Preferably, both substances are substantially colorless and transparent, but they may be colored to improve the application and the display quality of the liquid crystal display device. As the first substance, a transparent plastic material is preferably used in terms of workability and handling properties. As the second substance, a gas such as air and a liquid such as water are used in addition to such a transparent plastic. Can also.

The difference in refractive index between the first substance and the second substance is 0.2
Above, more preferably 0.3 or more in that it is easy to obtain a large viewing angle enlarging effect.

As the shape of the uneven surface, a one-dimensional lens array sheet in which curved surfaces represented by trajectories obtained by translating a curve such as an arc like a lenticular lens are arranged in one direction, a rectangular shape, a triangle shape, a hexagon shape, etc. A two-dimensional lens array sheet in which dome-shaped curved surfaces having a low surface are arranged vertically and horizontally can be used. Also, a polyhedron in which planes having various angles are combined can be used.

In the present invention, any of these shapes can be used.
That is, as the angle between the unit lens array surface on the first material layer side, which is a high-refractive index material, and the contact surface at a certain point on the uneven surface increases, the uneven surface shape of the unit lens increases. The shape is preferably such that it is located near the unit lens array surface on the side.

However, for the purpose of suppressing the generation of stray light due to light scattering on an optically discontinuous surface, a unit lens period of 2
If the width is less than 0%, it is preferable that the optically concave or flat region is an uneven surface formed continuously with the optically convex region.

The characteristics of the microlens array sheet of the present invention are most exhibited when the unit lens is mounted on a liquid crystal cell, and the maximum final refraction angle of the unit lens is preferably 30 degrees or more, more preferably 40 degrees or more. This is the case when the corner is set.

Here, the maximum final refraction angle of the unit lens is
When a light beam enters from the normal direction of the microlens array sheet and exits from the unit lens, it is defined as the angle between the incident direction and the exit direction for the light beam whose traveling direction changes most greatly and exits.

When the unit lens has a concave-convex surface, the smaller of the angles formed by the contact surface of a point on the concave-convex surface and the lens array surface is α, and α is the maximum value αmax. When a point on the interface is point A, a light beam incident on the microlens array sheet from the normal direction of the unit lens array surface on the second material layer side and reaching point A passes through the first material layer and becomes first light. It is defined as the angle between the direction of travel when emitted from the surface on the material layer side to the atmosphere and the normal direction of the unit lens array surface.

In a first aspect of the microlens array sheet of the present invention, the degree of light diffusion when a light beam is incident from the normal direction of at least one surface of the microlens array sheet is 20 degrees or less. This is a first mode. In particular, when the microlens array sheet of the present invention is a microlens array sheet having an uneven surface, a microlens array in which a unit lens receives a light beam from the first material layer side in a direction normal to the arrangement surface of the unit lenses. It is preferable that the light diffusion degree by the sheet (hereinafter, referred to as “reverse light diffusion degree”) is 20 degrees or less.

In the present invention, the “unit lens array surface” is defined as two parallel surfaces on both sides of an uneven surface which is in contact with at least one point and does not intersect with the uneven surface which is an interface between the first material layer and the second material layer. When it is necessary to distinguish between the two planes, the unit lens array surface on the first material layer side and the unit lens array surface on the second material layer side are respectively the first material layer side unit. The lens arrangement surface is referred to as a second material layer side unit lens arrangement surface. When air is used as the second substance, the unit lens array surface on the second substance layer side is a virtual plane in the atmosphere.

In the present invention, the "light diffusivity by the microlens array sheet" means that a luminous flux having a directivity angle of full width at half maximum of 6 degrees is incident on the microlens array sheet, and the incident light direction is opposite to the incident surface. , The luminance observed from various directions is measured by scanning the observation angle, and at a certain observation angle χ (degree), 輝 度 -10 (degree), χ-5
(Degree), χ (degree), χ + 5 (degree), χ + 10 (degree)
When the average luminance of a point is the diffused light luminance at the observation angle χ,
Among the observation angles at which the diffused light luminance equal to or more than 最大 of the measured maximum diffused light luminance is observed, the maximum value is indicated by the absolute value of the difference from the observation angle at which the maximum diffused light luminance is obtained. .

The present invention is effective as long as the degree of light diffusion is 20 degrees or less in any direction within the plane of the microlens array sheet, but is preferably 20 degrees or less in any direction. When a microlens array sheet is used, image quality can be maintained almost completely. However, this is not always the case depending on the arrangement of the liquid crystal cell pixels to be combined.

In order to obtain such a microlens array sheet, there is a method of controlling a lens shape to reduce a component refracted at a large angle. However, this method has an effect of enlarging a viewing angle in a liquid crystal display device. It is not preferable because it tends to be small. That is, in this method, the degree of light diffusion when a light beam is incident from the normal direction of the unit lens array surface on the first material layer side of the microlens array sheet and the normal line of the unit lens array surface on the second material layer side The degree of light diffusion when a light beam is incident from the direction (hereinafter, this is referred to as “positive direction light diffusion degree”) substantially coincides. Since the forward direction light diffusivity has a large effect on the viewing angle widening effect, the viewing angle widening effect is also reduced at the same time as the backward direction light diffusivity is reduced.

Therefore, since the forward light diffusivity is closely related to the viewing angle widening effect, when the microlens array sheet has the forward light diffusivity larger than the backward light diffusing degree, a large viewing angle widening effect is obtained. While maintaining
It is possible to prevent the image quality from deteriorating.

That is, the present invention satisfies the first aspect by adopting a method of blocking unnecessary light beams by using a light shielding layer in a microlens array sheet having a large viewing angle expanding effect.

As a method for blocking unnecessary light beams by the light-shielding layer, a light-shielding layer having an opening at least at the top of the unit lens convex portion is provided on the first material layer side from the uneven surface of the microlens array sheet. Are preferred.

Here, the "light-shielding layer" means a layer having a function of absorbing and / or reflecting light rays passing therethrough.

According to a second aspect of the microlens array sheet of the present invention, the first material layer and the second material layer having a smaller refractive index than the first material layer are sandwiched between two parallel planes. A microlens array sheet having a layer in which unit lenses having an optically convex shape are arranged by forming an interface between a layer and the second material layer into a periodic uneven shape, and a light shielding layer is provided on each unit lens. The light shielding layer is provided on the first material layer side from the uneven surface, and the light-shielding layer has a refraction angle on the uneven surface when the microlens array sheet is viewed from the first material layer side in the normal direction of the unit lens array surface. This is a microlens array sheet provided so that a region exceeding 20 degrees is covered with a light shielding layer.

More preferably, the light-shielding layer has a shape in which at least a portion corresponding to the top of the convex portion of the unit lens is opened in the inner surface direction of the microlens array sheet, so that the light-shielding layer is formed in the normal direction of the unit lens array surface. The light-shielding layer does not block light rays that are parallel and incident from the second material layer side and have a refraction of 20 degrees or less in the convex portion region of the unit lens.

Hereinafter, these requirements will be described as condition (1) and condition (2). Again, conditions (1) and (2) are as follows.

Condition (1): When the microlens array sheet is viewed from the first material layer side in the normal direction of the unit lens array surface, a region where the refraction angle on the uneven surface exceeds 20 degrees is covered with a light shielding layer. Being done.

Condition (2): Of the light rays parallel to the normal direction of the unit lens array surface and incident from the second material layer side, the light rays whose refraction on the concave and convex surface of the unit lens is 20 degrees or less pass through the light shielding layer. Don't do it. These conditions prescribe the arrangement position of the light-shielding layer in order to control the “forward light diffusivity” and “reverse light diffusivity” described above.

Hereinafter, these conditions will be described step by step with reference to the drawings. FIG. 1 shows an example of a cross section of the microlens array sheet of the present invention. First, condition (1)
Means that when the microlens array sheet is viewed from the first material layer side in the normal direction of the unit lens arrangement surface, a region where the refraction angle on the uneven surface exceeds 20 degrees is covered with a light shielding layer. .

Here, the "refraction angle on the concave and convex surface" means that when a light ray parallel to the normal direction of the unit lens array surface and incident from the second material layer advances into the first material layer, the first material The angle at which the traveling direction changes due to refraction on the uneven surface based on the refractive index difference between the layer and the second material layer and the angle between the light traveling direction and the uneven surface.

FIG. 2 shows an example of one preferable shape of the unit lens used in the microlens array sheet of the present invention, wherein the first material layer 1 and the second material layer 2 are two parallel materials. The first material layer-side unit lens array surface 3 and the second material layer-side unit lens array surface 4 which are flat surfaces are sandwiched between them, and the interface between them is a convex-concave surface 5.

When this unit lens is viewed from the direction of the normal line 10 of the unit lens array surface on the first material layer side, the region where the refraction angle of the uneven surface exceeds 20 degrees is the light beam traveling from the second material layer side. When the refraction proceeds on the uneven surface, the angle between the normal 10 and the traveling direction, that is, the refraction angle 30 on the uneven surface is 2
The regions 20 and 20 ′ on the uneven surface having an angle of 0 ° or more are obtained.

According to the condition (1), in the microlens array sheet of the present invention, it is preferable that the regions 20 and 20 'are covered with a light shielding layer. That is, a light-shielding band is preferably provided so as to cross each of the hatched regions 21 and 21 'in FIG.

Here, an area where the uneven surface is optically concave or flat (hereinafter referred to as a "unit lens boundary area").
However, in the case of an uneven surface which is continuously formed in an optically convex region, the unit lens boundary region is also covered with a light-shielding layer, which is a display when a liquid crystal display device is used. This is preferable in suppressing the “smearing”.

A more preferable aspect of the condition (1) is that a region where the refraction angle 30 on the uneven surface exceeds 15 degrees is covered with a light shielding layer. However, covering a region having a refraction angle 30 of 5 degrees or less with a light-shielding layer on an uneven surface is not preferable because it has no effect in terms of image quality when a display device is used, but lowers light flux utilization efficiency.

Next, condition (2) will be described. FIG. 3 shows FIG.
This is the same unit lens. A ray incident on the unit lens from the second material layer side in parallel with the normal direction of the unit lens array surface 4 and having a refraction angle 31 of 20 degrees on the uneven surface 5 passes through a point 51 on the uneven surface. And the light beam 13 passing through the point 52. Light rays that have passed through the uneven surface between the points 51 and 52 have a refraction angle of 20 degrees or less,
The area through which these light beams pass is the area 22. From condition (2), these rays must not pass through the light-shielding layer, so that the area 23 must not be part of the light-shielding layer.

A more preferred embodiment of the condition (2) is that the refraction on the concave / convex surface of the unit lens is 25 among rays incident from the second material layer side parallel to the normal direction of the unit lens arrangement surface.
The light rays of the degree or less do not pass through the light shielding layer. This makes it possible to provide a microlens array sheet that can substantially completely eliminate the viewing angle dependence of the liquid crystal display device in the arrangement direction of the unit lenses.

The condition shown in FIG. 1 is adopted as the condition that satisfies the conditions (1) and (2) at the same time. FIG. 1 shows an arrangement in which unit lenses having the same concavo-convex surface shape and refractive index as those of the unit lenses shown in FIGS. 2 and 3 are arranged on a transparent plastic substrate 7.
And does not enter the portion corresponding to the region 22, and is incident on the unit material lens from the second material layer side in a direction parallel to the normal direction of the unit lens array surface. Light rays having a refraction of 28 degrees or less on the uneven surface do not pass through the light shielding layer. In the case of the microlens array sheet shown in FIG. 1, since air is used as the second material layer, the unit lens array surface on the second material layer side is a virtual plane 4 in the atmosphere.

The position of the light-shielding layer in the thickness direction of the microlens array sheet is a distance of 0.5F to 2.0F from the unit lens array surface on the first material layer side when the focal point distance of the unit lens is F. It is preferable that Further, it is preferable that the focal point distance F is 0.5 times or more and 1.3 times or less of the unit lens width.

Here, the focal point distance means the distance between the unit lens array surface and the focal point assuming that the microlens array sheet has a sufficient thickness.

Here, the “condensing point” means that the light beam incident on the unit lens from the normal direction on the second material layer side of the microlens array sheet is condensed by the unit lens, and the light beam density is the highest. (In the case of a one-dimensional lens array, it is a “line”, but here, according to a custom, this is also referred to as a “focus point”).

Further, in order to exhibit a large viewing angle expanding effect and a function of maintaining image quality, the focal point distance is set to 1.0 times or less of the unit lens width, and the width of the opening of the light shielding layer is set to １ ／ of the unit lens width. It is preferable to set the following.

The end of the light-shielding layer is a light ray that is parallel to the normal direction of the unit lens array surface and is incident from the second material layer side and is most refracted at or near the edge of the unit lens. It is preferable to be on the side of the uneven surface from the intersection of the two light beams. Thus, when the liquid crystal display device is used, a light beam can be emitted in a deeper viewing angle direction.

The microlens array sheet of the present invention
Since unit lenses having an optically convex shape are arrayed, the inclination of the irregularities becomes stronger toward the edge of the unit lens, and is incident from the second material layer side in parallel with the normal direction of the unit lens arrangement surface. That light is ideally refracted most at the edges. Further, in actual practice, the light beam may be refracted most a little inside from the edge portion due to a limitation in the manufacturing method. (Hereinafter, the “most refracted light beam” is referred to as the “maximally refracted light beam.”) At this time, the maximum refracted light beam travels toward the inside of the unit lens after passing through the uneven surface, and intersects at a certain point P. .

It is preferable that the edge of the light-shielding layer of the microlens array sheet of the present invention is on the uneven surface side from the intersection P. More preferably, the entire light-shielding layer is on the uneven surface side of the intersection P.

Here, "being on the uneven surface side from the intersection point P" means that it is in a space between the plane including the intersection point P and parallel to the unit lens array surface and the uneven surface.

When the unit lens is symmetric,
The angle at which the maximum refracted ray at one edge is refracted at the uneven surface and the angle at which the refraction is refracted at the other edge have the same value, and the intersection P is on the center line of the unit lens, but the unit lens is asymmetric. In some cases, the angle of refraction of the maximum refraction ray at one edge may be different from the angle of refraction at the other end. In this case, the intersection point P does not coincide with the center line of the unit lens.

Next, in the case where the microlens array sheet of the present invention has a light-shielding layer, the preferred light-shielding layer common to exhibit the characteristics of the first and second embodiments will be described. explain.

In the present invention, the term "light-shielding layer" means a layer having a function of absorbing and / or reflecting a light beam passing therethrough. It is preferable that

Such a light-shielding layer can be made of a known material such as a metal film and its oxide, and a resin composition to which a pigment or a dye is added. It is preferable that the liquid crystal display device absorbs visible light from the viewpoint of the appearance of the liquid crystal display device.

The color tone of the light-shielding layer is preferably substantially achromatic, that is, black. In order to obtain such a color tone, a pigment obtained by adding a pigment such as carbon black or titanium black or a black dye to a resin composition is preferably used. Further, when a dye is used here, it is preferable to use a black dye having a light fastness of 5 or more from the viewpoint of light resistance and the like, and further, dispersibility, solubility,
It is most preferable to use an azo black dye from the viewpoint of versatility and the like.

As the shape of the light shielding layer, any of a flat film shape and a three-dimensional shape proposed in JP-A-7-72809 can be used.

The light-shielding ability of the light-shielding layer is expressed as an average of the entire light-shielding band and expressed as an average visible light transmittance after visibility correction from the viewpoint of efficient use of the light flux from the liquid crystal cell to be combined. It is preferably at least 0.5%, and also preferably at most 20%, more preferably at most 10% from the viewpoint of suppressing external light reflection.

This light shielding layer is provided on the first material layer side from the uneven surface. The cross-section of the light-shielding layer is not flat but triangular or inverted T
In the case of a three-dimensional irregular cross section such as a letter shape, a part of the light shielding layer may be in contact with the uneven surface or protrude toward the second material layer side, but at least the widest part is the first material layer. It is necessary to be on the material layer side, and it is preferable that the light-shielding layer and the uneven surface are not in contact with each other.

The micro lens array sheet of the present invention
A surface serving as an observation surface when mounted on a liquid crystal display device, for example, a transparent plastic substrate 7 in the configuration shown in FIG.
The surface 8 opposite to the surface 3 on which the light-shielding layer 6 is provided may have a surface hardening treatment, an anti-reflection treatment, or an anti-reflection treatment as required on the observation surface of a conventional liquid crystal display device. A glare (non-glare) treatment or the like can be performed.

In order to easily mount the microlens array sheet on the liquid crystal cell, the second material layer or
The top of the convex portion of the first material layer penetrating the second material layer may be formed of an adhesive or adhesive material, or the surface of the second material or the top of the convex portion of the first material layer may be provided with tack or adhesive. It is also possible to add a material layer to have.

In the microlens array sheet of the present invention, when the light shielding layer is embedded in the microlens array sheet, the mechanical strength of the microlens array sheet can be increased, and the microlens array sheet is excellent in handleability. It is preferable in that it becomes. For this purpose, a method of embedding a light-shielding layer inside the first material layer and a method of forming each layer in the order of a light-shielding layer / first material layer / second material layer on a separately prepared transparent substrate are adopted. Can be.

The microlens array sheet of the present invention
It can also be made using a transparent sheet or film as a substrate. At this time, it is preferable to use a flexible plastic film as the substrate from the viewpoint of handleability and impact resistance when the liquid crystal display device is used. As such a plastic film, a polyethylene terephthalate film, a polycarbonate film, a polyarylate film, a polysulfone film, an acrylic resin film and the like are preferably used.

The microlens array sheet of the present invention
The present invention can be applied not only to a liquid crystal display device described in detail below, but also to various devices using a screen of a projection type image display device or a function of transmitting light rays to only one side.

Next, the liquid crystal display of the present invention will be described. Liquid crystal display device of the present invention (hereinafter referred to as LCD)
Is a liquid crystal display device using the above-described microlens array sheet of the present invention and having a wide viewing angle. That is, a liquid crystal display device that displays an arbitrary image by a liquid crystal cell in which an optical shutter that changes optical characteristics by an electro-optical effect of liquid crystal molecules is arranged, and the liquid crystal display device is described above on the observation surface side of the liquid crystal cell. In the case of the microlens array sheet of the first embodiment, the surface on which the light diffusivity is 20 degrees or less when a light beam is incident from the normal direction is set to the observation surface side, and the other surface is set to the liquid crystal cell side. In the case of the microlens array sheet of the second embodiment, which is mounted on the liquid crystal cell observation surface, the first material layer side is on the observation surface side, and the second material layer side is on the liquid crystal cell side. A liquid crystal display device characterized by being provided.

Here, the liquid crystal cell is generated when the alignment state of the liquid crystal molecules is changed by applying an electric field or applying an electric current to the liquid crystal molecules having an electro-optical effect, that is, a refractive index and a dielectric anisotropy. It refers to an array of optical shutter mechanisms that control the light transmittance by utilizing the difference in optical properties.

Examples of the mode of the optical shutter mechanism include a dynamic scattering mode (DS), a guest host mode (GH), a phase transition mode, a twisted nematic mode (TN), a ferroelectric mode, and a super twisted nematic mode (STN). ), Polymer dispersion mode, homeotropic mode and the like.

As a method of driving each display unit of the liquid crystal cell, a segment drive for independently driving each display unit, a simple matrix drive for time-divisionally driving each display unit, a transistor, a diode, and a plasma for each display unit There is an active matrix drive in which an active element such as a gas chamber is arranged.

As a method of observing the LCD, a reflective layer having a light reflecting ability is provided on the back surface of the LCD, and a reflection type in which light incident from the front surface of the LCD is reflected and observed, and a light source is provided on the back surface of the LCD and emitted from the light source. There is a transmissive LCD for observing transmitted light through an LCD. In addition, there is a type that uses both of them.

The liquid crystal display device of the present invention can be constructed by appropriately combining several display modes, drive modes, and observation modes as described above in accordance with the required characteristics. Matrix drive super twisted nematic mode, transmission type active matrix drive twisted nematic mode, reflection type simple matrix drive super twisted nematic mode liquid crystal display device, the effect of the present invention is great, furthermore, transmission type simple matrix drive super twisted nematic mode, transmission type The effect is great when the liquid crystal cell is in the active matrix driven twisted nematic mode.

By providing the above-described microlens array sheet of the present invention on the observation surface side of the liquid crystal cell, the disadvantage that the viewing angle is narrow can be efficiently reduced without substantially deteriorating the display quality of the conventional liquid crystal display device. Can be eliminated.

In general, the viewing angle characteristics of a liquid crystal cell, that is, the change in display quality depending on the observation direction, can be determined even if the angle between the observation direction and the normal direction of the cell observation surface is constant. It is also caused by rotation. That is, the viewing angle is generally different depending on the direction in which the observation direction is moved from the front of the cell (left direction, right direction, upward direction, downward direction, etc., with respect to the display surface). Or,
Depending on the purpose of use of the liquid crystal display device, there is a case where the viewing angle in one direction should be preferentially expanded, such as to increase the viewing angle in the left-right direction. In such a case, the function of the lens of the microlens array sheet is changed to the viewing angle characteristics in each direction of the liquid crystal cell,
Alternatively, a liquid crystal display device with higher display quality can be provided by giving different characteristics to the desired viewing angle enlargement direction in each direction.

That is, when it is desired to increase the viewing angle characteristics in only one direction, such as the vertical direction or the horizontal direction, a one-dimensional lens array sheet is used, and the unit lenses are mounted so that the arrangement direction matches the direction in which the viewing angle is to be expanded. Can be achieved by: When it is desired to enlarge the viewing angle characteristics in two directions, there is a method in which two one-dimensional lens array sheets are superposed with an angle in the unit lens array direction, and a method using a two-dimensional lens array sheet. The lens shape can be controlled and designed so that the viewing angle in each direction is desired to be increased.

In the liquid crystal display device of the present invention, the preferred relationship between the shape of the unit lenses, the arrangement direction, and the mounting direction to the liquid crystal cell is such that the microlens array sheet is a one-dimensional micro array in which streak-like unit lenses are arranged in one direction. A lens array is used, and the unit lens arrangement direction of the lens array coincides with the liquid crystal alignment direction of the liquid crystal cell. This virtually eliminates the problem of viewing angles in all directions.

Here, “the liquid crystal alignment direction of the liquid crystal cell” means
When the liquid crystal cell to which no voltage is applied is observed from the normal direction of the observation surface, this is the direction in which the long-axis alignment directions of each liquid crystal molecule are averaged. In other words, the liquid crystal layer is regarded as one birefringent body. This is the major axis direction of the refractive index ellipse. In the case of a twisted nematic liquid crystal, this direction coincides with the average alignment direction of liquid crystal molecules equidistant from both substrates in a liquid crystal layer sandwiched between two substrates. Also here, "Match"
This means that in actual implementation, it is not necessary to exactly match the geometrically defined unique directions, and a deviation of ± 10 degrees is acceptable. This method is particularly effective when the liquid crystal cell uses a twisted nematic liquid crystal.

The size and position of the unit lens of the lens array sheet used in the LCD of the present invention can be selected according to the size of the display unit of the liquid crystal cell. When the liquid crystal display device is of a dot matrix type, there are two preferable modes for the correspondence between one display unit and a unit lens. One is that one unit lens corresponds exactly to one display unit of the liquid crystal cell, and the other is that two or more lenses correspond on average to one display unit. is there. As a result, it is possible to suppress the occurrence of moire due to interference between the unit lens array pitch of the lens array sheet and the display unit pitch of the cells. Among these, the latter aspect does not require precise alignment, and improves productivity because the same microlens array sheet can be used for cells having several types of dot sizes. preferable. More preferably, four or more unit lenses correspond to one dot, and more preferably, eight or more unit lenses correspond to one display unit. Here, the definition of the number n of unit lenses for one display unit is defined by the following equation (1) for a one-dimensional lens array sheet, and defined by the following equation (2) for a two-dimensional lens array sheet.

N = N / (L / l) (1) n = N / (A / a) (2) where N is on the LCD display surface Total number of unit lenses,
L is the length of the liquid crystal cell in the one-dimensional MLA unit lens array direction, l is the length of one display unit of the liquid crystal cell that contributes to display in the lens array direction, A is the area of the LCD display surface,
a is the area of a portion contributing to display in one display unit of the liquid crystal cell. These equations show the average number of lenses corresponding to the display unit portion excluding the portion that does not directly contribute to the display such as the wiring space on the LCD display surface.

In the LCD of the present invention, it is preferable to mount the microlens array sheet as close as possible to the liquid crystal cell, since there is no reduction in display quality such as resolution and contrast. More specifically, it is preferably 1.0 mm or less, more preferably 0.5 mm or less, and still more preferably 0.1 mm or less, as the distance at the point where the cell surface and the uneven surface of the lens array sheet are closest to each other. It is.

The method of mounting the microlens array sheet on the liquid crystal cell is not particularly limited, but a method of forming the microlens array sheet on a transparent substrate having high bending rigidity and mounting the microlens array sheet on the liquid crystal cell, and The second material layer of the microlens array sheet or the top of the convex portion of the first material layer penetrating the second material layer is formed of a material having tackiness or adhesiveness, or the surface of the second material or the first material A method in which a material layer having tackiness or adhesiveness is added to the top of the convex portion of the layer, and the layer is attached to a liquid crystal cell using the tackiness or adhesiveness is preferably used.

When the LCD of the present invention is a transmissive LCD having a back light source, it is preferable that the back light source has directivity in the normal direction of the light emitting surface. Thereby, a light beam emitted from a light source such as a fluorescent tube can be effectively used.

That is, in the liquid crystal display device of the present invention, the individual unit lens of the lens array sheet refracts the light flux transmitted in the direction of poor display quality of the liquid crystal cell so as not to affect the observation, or to shield the light beam. At the same time as being absorbed or reflected by the layer, the luminous flux transmitted in the direction showing good display can be observed from various directions. The light flux emitted at a large angle with respect to the normal direction of the display surface is not used. Therefore, by giving directivity to the light beam emitted from the rear light source, the light beam emitted from the light source can be used effectively.

Therefore, the directivity of the back light source is 30
Degree or less. On the other hand, when the directivity is set to 5 degrees or less, the structure of the back light source becomes complicated, but the above-mentioned effect is practically lost, and a high degree of uniformity is required for the microlens array. Absent.

Here, the “directivity” means that when a certain point on the back light source is tilted from the direction showing the maximum brightness to the direction of arrangement of the minute unit lenses, the brightness becomes half of the maximum brightness. Indicates the angle up to.

In order to provide a rear light source having such directivity, a light beam emitted from a light source such as a fluorescent tube is converted to a method using a Fresnel lens, a Fresnel prism, or the like, or a combination of a minute reflecting surface as a reflecting mirror. There are, but not limited to, means using a multi-reflector, and among these, a micro lens or a lens is used because the light emitted from a light source such as a fluorescent tube is effectively used and the thin and light weight is easily achieved. It is preferable to provide a Fresnel sheet in which micro prisms are arranged in a sheet shape on a light emitting surface close to a liquid crystal cell of a back light source.

FIG. 4 is a schematic sectional view of a liquid crystal display device for explaining an example of the structure of the liquid crystal display device of the present invention. The microlens array sheet 6 is provided on the observation surface side of the liquid crystal cell 60.
1 is provided, and a back light source 62 is provided on the back of the liquid crystal cell. When the liquid crystal display device of the present invention does not use a back light source, a reflector (not shown) is provided instead of the back light source 62.

[0091]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments, but is not limited thereto.

(A) Preparation of Microlens Array Sheet A mold in which a large number of curved grooves are marked in parallel (the pattern pitch is 43 μm, the groove depth is 6.5 μm, and the groove depth is 10.5 μm).
4 types of m, 13.5 μm, 19.5 μm, and the size of the engraved part is 300 mm × 500 mm flat stamper)
Is filled with an ultraviolet curable resin (refractive index of 1.50 after curing), and a transparent polyester film "Lumirror" (manufactured by Toray Industries, Inc., having a thickness of 6 μm) is further formed thereon as a flat transparent substrate.
m, 25 μm, 38 μm, width 300 mm) and thickness 2
After laminating the film coated with the μm easy-to-adhesive coating agent, the excess UV curable resin is squeezed out from above the polyester film with a rubber roller so that the ridge of the mold contacts the polyester film, and the film is removed. It was adhered to the mold.

A commercially available carbon black-added black resist (manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied to the film surface of the obtained mold / ultraviolet effect resin layer / film laminate using a spin coater and dried. Ultraviolet light was exposed by a high-pressure mercury lamp through a photomask having a striped pattern (pattern pitch: 43 μm), and an uncured portion was dissolved and removed by a developer.

At this time, the mold and the alignment mark written on the photomask are overlapped so that the center line of the opening of the light-shielding layer coincides with the ridge line of each unit lens. 10 μm width, 13 μm, 2
A light-shielding layer having a thickness of 3 μm was formed and removed from the mold to produce various microlens array sheets.

Further, a microlens array sheet partially having no light-shielding layer was prepared.

Next, on the light shielding layer side of the microlens array sheet obtained here (for those without the light shielding layer,
The film side) was bonded to a 0.8 mm thick acrylic flat plate (transparent plastic substrate).

Table 1 summarizes the characteristics of the various microlens array sheets thus obtained. Table 1
In the above, the "gap" of the "position of the light shielding layer" indicates the distance between the unit lens array surface on the first material layer side and the light shielding layer forming surface. Similarly, in Table 1, “correspondence to conditions” means “○” when the formed light-shielding layer satisfies the above-described conditions (1) and (2), and “x” when the formed light-shielding layer does not satisfy the above conditions (1) and (2), respectively. Indicated by.

The microlens array sheet used in Example 3 has the concavo-convex surface shape and the light-shielding layer disposing position shown in FIG. 1 in which the light rays incident from the normal direction of the microlens array sheet become one straight line. This is a one-dimensional microlens array in which a part of a non-cylindrical side surface having a cross section expressed by a 6th order equation is arranged in one direction so as to condense light. The focal point distance of the unit lens of this microlens array sheet is 2
9 μm.

(B) Preparation of Liquid Crystal Display Device A twisted nematic liquid crystal TFT color display (11.3 inches diagonal, 600 pixels vertically 800 pixels horizontally, equipped with a backlight) mounted on a commercially available personal computer is a liquid crystal display. The microlens array sheet prepared in (1) was mounted on the observation surface side of the liquid crystal cell with the lens forming surface facing the liquid crystal cell to obtain a liquid crystal display device. At this time, the unit lens arrangement direction of the microlens array sheet was the screen vertical direction which is the liquid crystal alignment direction of the liquid crystal cell. As a comparison object,
A conventional liquid crystal display device without a microlens array sheet was also prepared.

(C) Evaluation A test pattern composed of three colors “white”, “50% gray”, and “black” was displayed on the liquid crystal display device thus obtained, and observed from the viewing angle and from the front. The image quality at the time was evaluated according to the following criteria. The evaluation was performed in a dark room. The results are shown in Table 1.

[Characteristic Evaluation Method] (a) Viewing Angle When the luminance of the display surface was measured by scanning the viewing direction in the vertical direction of the screen from the normal direction of the observation surface of the liquid crystal display device,
The brightness of the area where “50% gray” is displayed is “white”
The viewing angle range in the range of 20% to 80% with respect to the luminance of the region where is displayed was defined as the viewing angle. This indicates a viewing angle range in which the display of “halftone” is observed as “halftone”.

At this time, if the luminance of the “white” display area is 5% or less of the luminance in the normal direction, the viewing angle up to the observation angle is set.

(B) Image quality When observed from the front (normal direction) of the observation surface of the liquid crystal display device, the contrast ratio (the luminance of the “white” display area relative to the luminance of the “black” display area) is 50 or more; The image quality was evaluated as “O” when both of the above and that each pixel can be independently observed with respect to the adjacent pixels were evaluated as “、”, and when none of them was satisfied, it was evaluated as “×”.

[0104]

[Table 1] As can be seen from the table, it is understood that the liquid crystal display device of the present invention equipped with the microlens array sheet of the present invention has a wide viewing angle while maintaining image quality. In particular, it can be seen that when the light-shielding layer is appropriately arranged, a good image can be observed from virtually any direction, and a wide viewing angle and good image quality can be obtained.

[0105]

According to the present invention, the disadvantage that the viewing angle of the conventional liquid crystal display device is narrow by the simple operation of mounting the microlens array sheet on the observation surface is obtained.
The display can be efficiently eliminated without deteriorating the display quality.

[Brief description of the drawings]

FIG. 1 shows an example of a cross section of a microlens array sheet of the present invention.

FIG. 2 is a diagram illustrating a condition (1).

FIG. 3 is a diagram illustrating a condition (2).

FIG. 4 is a diagram illustrating an example of a configuration of a liquid crystal display device of the present invention.

[Explanation of symbols]

 1: 1st material layer 2: 2nd material layer 3: 1st material layer side unit lens arrangement surface 4: 2nd material layer side unit lens arrangement surface 5: uneven surface 6: light shielding layer 7: transparent plastic substrate 8: transparent Surface of the plastic substrate 10: normal to the unit lens array surface 11: normal to the uneven surface 12: light beam with a refraction angle of 20 degrees 13: another light beam with a refraction angle of 20 degrees 14: refraction angle of less than 20 degrees 21, 21 ': Area satisfying condition (1) 22: Area satisfying condition (2) 30: Refraction angle on uneven surface 50: Point on uneven surface 51: Point on uneven surface 52: Light shielding layer End 60: liquid crystal cell 61: microlens array sheet 62: back light source

Claims (13)

[Claims] 1. A microlens array sheet in which minute unit lenses are arranged in a plane, wherein a light diffusion degree when a light beam is incident from at least one surface normal direction is 20 degrees or less. Microlens array sheet. 2. The micro unit lens according to claim 1, wherein the first material layer and a second material layer having a smaller refractive index are sandwiched between two parallel planes, and the first material layer side and the second material layer are sandwiched between the first material layer and the second material layer. 2. The microlens array sheet according to claim 1, wherein the microlens array sheet is a micro-optical element formed by forming an interface of a layer into a periodic uneven shape. 3. The microlens array sheet according to claim 2, wherein said minute unit lens is an optically convex unit lens. 4. The microlens array sheet according to claim 2, wherein a light diffusion degree when a light beam is incident from a normal direction of the surface on the first material layer side is 20 degrees or less. 5. A light diffusing degree when a light beam is incident from a normal direction of one surface is smaller than a light diffusing degree when a light beam is incident from a normal direction of the other surface. The microlens array sheet according to any one of claims 1 to 4. 6. The microlens array sheet according to claim 2, wherein the microlens array sheet has a light-shielding layer on the first material layer side from the uneven surface. 7. The microlens array sheet according to claim 6, wherein the light-shielding layer has a shape in which at least a portion corresponding to the top of the convex portion of the unit lens is opened in the in-plane direction of the microlens array sheet. . 8. A first material layer and a second material layer having a smaller refractive index than the first material layer are sandwiched between two parallel planes, and an interface between the first material layer and the second material layer is provided. A microlens array sheet having a layer in which unity lenses having an optically convex shape are arranged by forming a periodic uneven shape, wherein each unit lens has a light-shielding layer that shields light from the uneven surface to the first material layer side. The light-shielding layer is provided on the microlens array sheet in a direction normal to the unit lens arrangement surface from the first material layer side, and is parallel to the normal direction of the unit lens arrangement surface. When a light beam incident from the layer side travels inside the first material layer, the traveling direction is changed by the refractive index difference between the first material layer and the second material layer and the refraction on the uneven surface based on the angle between the light traveling direction and the uneven surface. The area where the changed angle exceeds 20 degrees is covered with the light shielding layer. Microlens array sheet, characterized in that arranged as. 9. The light-shielding layer has a shape in which at least a portion corresponding to the top of the convex portion of the unit lens is opened in the inner surface direction of the microlens array sheet, so that the light-shielding layer is parallel to the normal direction of the unit lens array surface. 9. The microlens array sheet according to claim 8, wherein the light-shielding layer does not block rays of light having a refraction of 20 degrees or less in the convex portion area of the unit lens among rays incident from the two material layers. The light-shielding layer covers a region where the refraction angle on the uneven surface exceeds 20 degrees when the microlens array sheet is viewed from the first material layer side in a direction normal to the unit lens array surface. The microlens array sheet according to any one of claims 4 to 5, wherein 10. The microlens array sheet according to claim 8, wherein a light beam diffusing degree when light is incident from a normal direction of the surface on the first material layer side is 20 degrees or less. 11. The degree of light diffusion when a light beam is incident from the normal direction of the surface on the first material layer side is different from that when the light beam is incident from the normal direction of the surface on the second material layer side. The microlens array sheet according to any one of claims 8 to 10, wherein the microlens array sheet is smaller than a light diffusion degree. 12. Observation of the microlens array sheet according to any one of claims 1 to 7, wherein the degree of light diffusion is 20 degrees or less when light is incident from the normal direction of the microlens array sheet. A liquid crystal display device comprising: a surface side; and the other surface mounted on a liquid crystal cell observation surface. 13. The microlens array sheet according to claim 8, wherein the first material layer side of the microlens array sheet is the observation surface side and the second material layer side is the liquid crystal cell side. A liquid crystal display device mounted on a liquid crystal cell observation surface.