JPH09159805A - Microlens array sheet and liquid crystal display device formed by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a microlens array sheet with which the reflection of external light is suppressed while a high effect of expanding a visual field angle is maintained by providing the microlens array sheet with light shielding layers which include the projecting peak parts of first material layers and have a height in the thickness direction of the microlens array sheet. SOLUTION: Semicircular unit lenses 3 are arranged by transparent plastic on a transparent plastic substrate 1. The unit lenses 3 are provided with the striped light shielding layers having the height in the thickness direction of the microlens array sheet from the projecting peak parts. In such a case, the surface arranged with the unit lenses is the front surface 4 of the plastic substrate 1 and the rugged surfaces are the front surfaces 5 of the semicircular lens groups. The first material layers are the plastic layers 6 forming the semicircular lenses and the second material layers are air layers above the semicircular lenses. The front surface 4 of the plastic substrate 1 and the surface 8 opposite thereto are parallel. The microlens array sheet is thus provided with the light shielding layers 2 which include the projecting parts of the first material layers and have the height in the thickness direction of the microlens array sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention 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 Liquid crystal display devices have the drawback that the display quality changes depending on the viewing direction. Generally, it is set so that the best display quality can be obtained when observing from the normal direction of the display surface, so the display quality deteriorates as the angle between the normal direction of the display surface and the observation direction increases. , It has a drawback that if it exceeds a certain angle, it will exceed the range that the observer can accept, that is, the viewing angle at which good display quality can be obtained is small (hereinafter, it may be simply referred to as "the viewing angle is narrow"). ing.

In order to widen the viewing angle of a direct-viewing type liquid crystal display device, it has been proposed to combine a liquid crystal display device with a microlens array sheet such as a microlens array.

As a method for expanding the viewing angle by combining a microlens array sheet for controlling the light transmission direction of a microlens array or the like on the viewing surface side of a liquid crystal display device, the present inventor has already disclosed in JP-A-5-249453. is suggesting.

[0005]

However, the conventional method has the following drawbacks.

The reason for this is that, according to the study by the present inventor, the conventionally proposed method has a drawback that the display quality of the liquid crystal display is significantly lowered. That is, in the conventionally proposed method, since a light ray incident from the outside of the liquid crystal display device is strongly reflected, an incident light from the outside such as normal room lighting (hereinafter, may be simply referred to as “external light”). This is because, in some cases, the entire screen becomes whitish, and the contrast ratio between the brightest color display portion and the darkest color display portion decreases, making it difficult to see the display. There is a correlation that this defect becomes more remarkable as the effect of enlarging the viewing angle of the microlens array increases,
Expanding the viewing angle of liquid crystal displays has become even more difficult.

To solve this problem, Japanese Patent Laid-Open No. 6-27454 proposes to provide a light-shielding layer on the side of each unit lens which is the observation surface side. Also, JP-A-7-72
In Japanese Patent Publication No. 809, an example in which the shape of the same light-shielding layer is devised is shown, but depending on the lens shape, a sufficient external light antireflection function cannot be imparted, or most of the image light from the liquid crystal cell is blocked. However, there is a drawback that the efficiency of light utilization is large and the following may occur.

Accordingly, the present invention provides a microlens array sheet which eliminates the above-mentioned drawbacks and suppresses reflection of external light while maintaining a large effect of enlarging the viewing angle, and a liquid crystal display device using the same.

[0009]

The present invention has the following arrangement to solve the above-mentioned problems.

First, the microlens array sheet of the present invention comprises a first material layer and a second material layer having a refractive index smaller than that of the first material layer.
A microlens array sheet in which unit lenses are arrayed on an array surface by forming an interface with a material layer into a regular uneven surface shape, the microlens array sheet including at least a first material layer convex top portion in a thickness direction. A microlens array sheet characterized by having a light-shielding layer having a height.

Further, the liquid crystal display device of the present invention is closer to the observation surface side than the liquid crystal cell, the first material layer side of the microlens array sheet described above is the observation surface side, and the second material layer side is the liquid crystal cell side. The liquid crystal display device is characterized by being provided as described above.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the liquid crystal display means the electro-optical effect of liquid crystal molecules, that is, optical anisotropy (refractive index anisotropy), orientation, fluidity, dielectric anisotropy and the like. A liquid crystal cell that is an array of optical shutters that changes the light transmittance or reflectance by applying an electric field or energizing an arbitrary display unit to change the alignment state of liquid crystal. . Further, here, a so-called direct-view liquid crystal display device of a type in which a display image displayed on the liquid crystal cell is directly observed is referred to.

The microlens array sheet of the present invention comprises:
It has a first material layer and a second material layer having a smaller refractive index than the first material layer. 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.

As the shape of the uneven surface, a one-dimensional lens array sheet in which curved surfaces, which are represented by loci of parallel movement of curved lines such as arcs like a lenticular lens, are arranged in one direction, and rectangular, triangular, hexagonal, etc. There is a two-dimensional lens array sheet in which dome-shaped curved surfaces having a low surface are arranged vertically and horizontally. There is also a polyhedron in which planes having various angles are combined.

In the present invention, any of these shapes can be selected, but it is an optically convex shape, that is, the uneven surface shape of the unit lens is a unit on the side of the first material layer which is a high refractive index material. As the angle between the lens array surface and the contact surface at a certain point on the uneven surface increases, the uneven surface is preferably located closer to the unit lens array surface on the first substance layer side.

Here, the unit lens array surface means a reference surface of the uneven surface which is the interface between the first material layer and the second material layer, and as a geometrical definition, it intersects with the uneven surface. Of the planes that are not in contact with the concave and convex surface, the plane parallel to the surface of the liquid crystal cell on which the microlens array sheet of the present invention is mounted is meant.

Further, the unit lens array surface on the side of the first material layer means the unit lens array surface on the side of the first material layer of the two unit lens array surfaces on both sides of the uneven surface.

However, in practice, the unit lens array surface is not limited to the position defined by the above-mentioned geometrical strictness due to the limitation of the actual manufacturing method, etc., and within a range not exceeding 1/2 of the unit lens array pitch. It may be separated from the uneven surface.

With the conventional lenticular lens and the microlens array alone, even if it is mounted on the surface of the liquid crystal display device to expand the viewing angle as described above, the effect of expanding the viewing angle is small, or the external light is reflected. There was a defect that the whole screen became whitish. The present inventor has studied in detail the relationship between the configuration of the lens array sheet, the viewing angle expansion effect of the liquid crystal display device, and the display quality, and as a result, a lens array having an uneven surface including a portion having a large angle with respect to the plane of the observation surface. It was discovered that a large viewing angle widening effect can be obtained by mounting the sheet on the observation surface side of the liquid crystal cell with the high refractive index material layer side facing the observation surface side. However, in this case, there is a problem that the reflection of external light becomes strong at the same time and the display quality (contrast) is deteriorated. In other words, there is a trade-off relationship between the effect of enlarging the viewing angle and the strength of external light reflection only by controlling the shape of the uneven surface. Therefore, when trying to obtain a sufficient effect of enlarging the viewing angle, the display quality is inevitably degraded to some extent. It was

When the cause of this is examined, the main cause of the diplomatic reflection is that the external light incident on the lens array sheet from the high refractive index material layer side has an uneven surface, and both of the interfaces with the low refractive index material layer are present. The light is totally reflected at a portion having an angle equal to or greater than the critical reflection angle based on the difference in the refractive index of the substance, and the reflected light beam is emitted from the re-incident surface by repeating reflection on the same principle. It was found that the portion having a large angle with respect to the observation surface that causes the first total reflection exhibits a large effect of enlarging the viewing angle when mounted on a liquid crystal display device.

In particular, when a microlens array sheet having a unit lens showing a large maximum angle of refraction of 30 degrees or more which can obtain a large viewing angle widening effect in combination with a liquid crystal cell, this drawback becomes remarkable. I understood.

For the purpose of suppressing this phenomenon, the present inventors have studied in detail the optical path when external light enters the microlens array sheet and again exits from the incident surface, and the external light traveling path The present invention has been completed by finding a method of forming a light-shielding layer for blocking the above.

That is, the microlens array sheet of the present invention has a light-shielding layer having a height in the thickness direction of the microlens array sheet, which includes at least a convex top portion of the first material layer, and the light-shielding layer is a protrusion of the first material layer. The essence is to provide so as to shield the light rays traveling in the interior of the part in parallel with the unit lens array direction.

The structure of the microlens array sheet of the present invention will be described with reference to the drawings.

FIG. 1 is a view for explaining an example of the structure of the microlens array sheet of the present invention, in which the semi-cylindrical unit lenses 3 are arranged on the transparent plastic substrate 1 by the transparent plastic. The unit lens is provided with a stripe-shaped light shielding layer 2 having a height from the top of the convex portion in the thickness direction of the microlens array sheet. In this case, the unit lens array surface is the surface 4 of the plastic substrate 1, the uneven surface is the surface 5 of the semi-cylindrical lens group, and the first material layer is the plastic layer 6 forming the semi-cylindrical lens, The second material layer becomes an air layer (not shown here) above the semicylindrical lens. The surface 4 of the plastic substrate 1 and the opposite surface 8 are parallel to each other.

FIG. 2 is a sectional view of a plane perpendicular to the surface 4 of the microlens array sheet shown in FIG. 1 and parallel to the unit lens array direction. Irregular surface shape 5 formed by the unit lens 3
To explain the relationship. FIG. 3 is a cross-sectional view of a so-called normal lenticular lens, which has the same shape as that shown in FIG. 1 but has no light-shielding layer, as an example of a conventional microlens array sheet.

The function of the light-shielding layer will be described below by comparing FIGS. 2 and 3.

In FIG. 3, among the incident light from the side of the first material layer, which is external light, that is, the incident light from the substrate side, for example, the light ray 101 incident from the substrate surface is 3 on the uneven surface.
The light is totally reflected and emitted again from the substrate surface. In addition, the light ray 102 which is incident from the normal direction of the substrate surface is
The light is totally reflected twice and emitted from the substrate surface. in this way,
A light beam emitted from the same surface as the incident surface by repeating total reflection has been a main cause of external light reflection when using the conventional microlens array sheet.

As is well known, the condition under which total reflection occurs is that when a light ray reaches an interface between a high refractive index material and a low refractive index material, the angle θ formed by the traveling direction of the light ray and the normal line of the interface. Occurs at or above the critical reflection angle θc represented by the following formula (1).

Sin (θc) = n2 / n1 (1) where n2 is the refractive index of the low refractive index substance and n1 is the refractive index of the high refractive index substance.

2 and 3, assuming that the refractive index of the lens material layer 6 which is a high refractive index material is 1.5 and the refractive index of the air layer which is a low refractive index material layer is 1.0, The critical reflection angle θc is about 41.8 degrees, and all light rays that reach the uneven surface 5 at an angle of more than this are reflected.

The external light is incident not only from the normal direction to the unit lens array surface but also at various angles, but the present inventor satisfies the above-mentioned conditions and repeats total reflection. The light rays emitted again from the incident surface all proceed in the direction near the convex portion of the unit lens in a direction parallel to or close to the unit lens array direction.
In this portion, it was found that the incident light from the side of the second material layer, which should be transmitted by the microlens array sheet, travels in a direction nearly perpendicular to the unit lens array surface.

Therefore, in the microlens array sheet of the present invention, as shown in FIG. 2, a light shielding layer 2 having a height in the thickness direction of the microlens array sheet is provided, which includes the convex tops of the first material layer.

The light-shielding layer includes at least the top of the convex portion, and its height varies depending on the shape of the lens to be combined. Generally, this height is 4 times the uneven height of the uneven surface.
If it is not more than one-third, sufficient external light reflection cannot be prevented. On the other hand, if it exceeds three-fourths of the height of the unevenness, the luminous flux to be transmitted is also blocked and the efficiency is lowered, which is not preferable.

The light-shielding layer inevitably has a width in the unit lens array direction, but since this width affects the light transmission efficiency of the microlens array sheet, it is preferable that it be as small as possible. Therefore, as a preferable shape of the light shielding layer,
It has a film shape as shown in FIG.

When the light-shielding layer has a film shape, it is most preferable that the light-shielding layer is perpendicular to the unit lens array surface.

As a method of forming such a light-shielding layer, the following method can be mentioned.

A method in which a unit lens is formed and then a groove is cut in a portion serving as a light-shielding layer, and the groove is filled with a light-shielding substance. A method of implanting a light shielding layer after forming a unit lens. A method of forming a portion of the unit lens to be a light-shielding layer in advance with a dyeable substance or with a color-changing substance and then dyeing or changing the color. A method of forming a unitary lens and a light shielding layer integrally by arranging a light shielding layer in a mold or the like for forming the unitary lens and filling a resin or the like to be the unit lens.

The feature of the microlens array sheet of the present invention is most exerted when it is used as a microlens array sheet capable of obtaining a large viewing angle expansion effect when mounted on a liquid crystal cell, that is, the maximum refraction angle of a unit lens is Thirty
More than once.

Here, the maximum refraction angle of the unit lens is defined as θ which is the wider angle between the contact surface of a certain point on the uneven surface and the lens array surface, and θ is the maximum value on the interface. When point A is point A, it is incident on the microlens array sheet from the direction normal to the lens array surface on the side of the second material layer and point A
Is defined as the angle between the traveling direction and the normal direction of the lens array surface when the light ray that has reached the point is transmitted through the first material layer and emitted from the surface on the first material layer side into the atmosphere.

In order to efficiently obtain a good display contrast and a wide viewing angle by mounting the microlens array sheet of the present invention on a liquid crystal cell, in order to efficiently obtain a good display contrast and a wide viewing angle, the light rays incident from the unit lens array surface on the second substance layer side are Of the light rays incident at an angle of ± 10 degrees with respect to the normal direction of the unit lens array surface as a center, 80% of the light rays having any incident angle are averaged over the entire surface of the microlens array sheet.
The above is preferably a microlens array sheet that is transparent to the unit lens array surface on the side of the first material layer.

In order to satisfy this characteristic, it is sufficient to control the refractive index and shape of the substance forming each unit lens, the shape of the light shielding layer, the transmittance, the disposition position and the like.

FIGS. 1 and 2 show an example in which a light-shielding layer is efficiently provided in a one-dimensional lens array sheet in which unit lenses are arranged in one direction, but a two-dimensional lens array sheet in which unit lenses are arranged vertically and horizontally. In this case, the light-shielding layer can be provided in the same way.

Although FIGS. 1 to 3 show examples in which the lens array is formed on the transparent plastic substrate 1, the transparent plastic substrate 1 is not essential in the microlens array sheet of the present invention.

Of the microlens array sheet of the present invention,
A surface to be an observation surface when mounted on a liquid crystal display device, for example, a transparent plastic substrate 1 in the case of the configuration shown in FIG.
On the surface 8 opposite to the surface 4 provided with the light-shielding layer, surface hardening treatment, antireflection treatment, antiglare treatment, which may be performed on the surface of the observation surface of the conventional liquid crystal display device, is performed as necessary. (Non-glare) processing can be performed.

Next, the liquid crystal display device of the present invention will be described.

The liquid crystal display device of the present invention (hereinafter sometimes 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 optical shutters that change the optical characteristics by the electro-optical effect of liquid crystal molecules are arranged, and the liquid crystal display device is arranged on the observation surface side of the liquid crystal cell as described above. A liquid crystal display device, wherein the first material layer side of the microlens array sheet for a liquid crystal display device of the present invention is provided on the observation surface side, and the second material layer side is provided on the liquid crystal cell side. It was done.

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

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

Further, 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 active elements such as a gas chamber are arranged.

As a method of observing an LCD, a reflective layer having a light-reflecting ability is provided on the back surface of the LCD and a reflection type for reflecting and observing light incident from the front surface of the LCD, and a light source provided on the back surface of the LCD and emitted from the light source. There is a transmissive LCD that observes the emitted light through the 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 the above-mentioned display modes, driving methods, and observation methods according to the required characteristics. Matrix driving super twisted nematic mode, transmissive active matrix driving twisted nematic mode, reflection type simple matrix driving super twisted nematic mode liquid crystal display device, the effect of the present invention is great, and further transmission type simple matrix driving super twisted nematic mode, transmission type The effect is large in the liquid crystal cell of the active matrix drive twisted nematic mode.

By providing the above-mentioned microlens array sheet of the present invention on the observation surface side of the liquid crystal cell, the disadvantage of narrow viewing angle is eliminated without substantially lowering the display quality of the conventional liquid crystal display device. be able to.

In general, the viewing angle characteristic of a liquid crystal cell, that is, the change in display quality depending on the viewing direction is such that the viewing direction is about the normal line even if the angle between the viewing direction and the normal line direction of the cell viewing surface is constant. It is also generated by rotating. 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 expand the viewing angle characteristics in only one direction such as the up-down direction or the left-right direction, a one-dimensional lens array sheet is used, and the arrangement direction of the unit lenses is fitted so that the viewing angle is widened. 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.

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 number n of unit lenses for one display unit is defined by the following equation (2) in the case of a one-dimensional lens array sheet and by the following equation (3) in the case of a two-dimensional lens array sheet.

N = N / (L / l) (2) n = N / (A / a) (3) Here, 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, the microlens array sheet is preferably mounted as close to the liquid crystal cell as possible because it does not deteriorate the 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.

When the LCD of the present invention is a transmissive LCD having a rear light source, the rear light source emits 80% or more of the total luminous flux emitted from the rear light source within the effective viewing angle range of the liquid crystal cell. It is preferable to use a light source.

Here, the effective viewing angle range of the liquid crystal cell refers to a viewing angle range in which a good display quality is obtained when the liquid crystal cell is observed, and here, the maximum viewing angle range in which the best display quality is obtained. A contrast ratio of 1/5 is obtained as a range in the observing direction.

There are two effects obtained by using the back light source having such a directivity, and one is that the luminous flux emitted from the light source body such as the fluorescent tube can be effectively used. That is, in the liquid crystal display device of the present invention, the individual unit lenses of the lens array sheet refract the light flux transmitted in the direction in which the display quality of the liquid crystal cell is inferior, so that the observation is not affected and, at the same time, a good display is achieved. Since the luminous flux transmitted in the indicated direction can be observed from various directions, the back light source without directivity, which has been generally used conventionally, is emitted at a large angle with respect to the normal direction of the display surface. No luminous flux is 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.

Another advantage is that it is possible to prevent bleeding of the displayed image. In the liquid crystal display device of the present invention, a lens array sheet is mounted on an observation surface, and it is preferable that the lens array sheet is provided as close to the liquid crystal cell as possible. In general, there is a distance corresponding to the thickness of the substrate or the polarizing element for enclosing the liquid crystal between the concave and convex surfaces, so that it is often impossible to bring the liquid crystal sufficiently close. Therefore, the luminous flux transmitted through one display unit of the liquid crystal cell is
Not only the unit lens part corresponding to the display unit part,
The image reaches the unit lens at a slightly distant position, and the effect of the unit lens causes the outline of one display unit of the liquid crystal cell to be observed as blurred and enlarged, so that the displayed image is observed as blurred. On the other hand, when a directional back light source is used, even if there is some distance between the display unit portion of the liquid crystal layer and the uneven surface of the lens array sheet, the luminous flux transmitted through the display unit portion has directivity. Therefore, since the light reaches only the corresponding unit lens portion, the displayed image does not blur as described above. However, depending on the application of the liquid crystal display device, it may be preferable to blur the displayed image to some extent. In this case, it is possible to cope by controlling the directivity of the back light source.

When the liquid crystal display device of the present invention is particularly required to suppress the bleeding of the display image, the light emission directivity of the back light source and the arrangement of the display units in the minute unit lens arrangement direction of the display units of the liquid crystal cell. It is preferable that the following expression (4) is satisfied in relation to the pitch.

P ≧ dtan χ (4) Here, p (mm) represents the length of the display unit of the liquid crystal cell in the arrangement direction of the minute unit lenses, that is, the arrangement pitch of the display units. However, when a liquid crystal cell forms one dot with a plurality of pixels for the purpose of performing color display or the like, one dot is used as a display unit. Further, d (mm) is the distance from the liquid crystal layer to the minute unit lens, and Δ is when a certain point on the back light source is inclined from the direction showing the maximum luminance to the minute unit lens arrangement direction. Represents an angle until the luminance becomes half of the maximum luminance.

In order to obtain a back light source having such a directivity, a method of using a Fresnel lens, a Fresnel prism, or other means for a light beam emitted from a light source such as a fluorescent tube, or a micro-reflecting surface as a reflecting mirror is combined. There is a means of using a multi-reflector, a means of absorbing an unnecessary light flux by an optical fiber sheet, a louver, etc., but it is not limited to these, but among them, the light emitted from a light source such as a fluorescent tube is effectively used. It is preferable to provide a Fresnel sheet in which microlenses and microprisms are arranged in a sheet shape on the light emitting surface in the vicinity of the liquid crystal cell of the back light source from the viewpoint of easy thinning and weight reduction.

FIG. 4 shows 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 1 is provided on the observation surface side of the liquid crystal cell 12.
1 is provided, and a back light source 13 is provided on the back surface 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 13.

[0067]

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

(1) Preparation of Microlens Array Sheet Prepare a mold having chamfered grooves at a pitch of 40 μm, and fill this mold with an ultraviolet curable resin (refractive index 1.51 after curing). Then, superimpose a polyester film (thickness 100 μm) on it, irradiate UV rays from the film surface to cure the UV curable resin, remove it from the mold, and then expose it again to UV ray from the UV curable resin layer side After curing, a one-dimensional microlens array sheet whose cross-sectional shape is shown in FIG. 3 was obtained. This microlens array sheet was used in Comparative Example 1.

(2) Preparation of light-shielding layer Aluminum was vapor-deposited to a thickness of 0.2 μm on the surface of the uneven surface of the microlens array sheet obtained in (1) above,
By rubbing the vapor deposition surface side with a cloth, the vapor deposition film only on the tops of the convex portions was peeled off.

Then, a groove was formed in the ultraviolet curable resin layer from the opening at the top of the convex portion by dry etching.

On the uneven surface side of the grooved microlens array sheet thus obtained, a black paint prepared by adding and dispersing carbon black in an acrylic acid copolymerization methacrylate resin solution was applied, and an alkaline aqueous solution was applied to the parts other than the groove part. The adhered black paint and aluminum vapor deposition film were peeled off to obtain the microlens array sheet of the present invention having the cross-sectional shape shown in FIG. 2 and used in the examples.

This microlens array sheet has a lens unevenness height of 19 μm and a maximum refraction angle of a unit lens of about 4 μm.
The light-shielding layer had a width of 4 μm and a height of 14 μm.

Further, when light rays were made incident at various angles in the range of −10 degrees to +10 degrees centering on the normal direction of the unit lens array surface on the side of the second material layer, the entire surface of the microlens array sheet was averaged. The transmittance was 83% or more in all cases.

In such a microlens array sheet, the first material layer is a layer of ultraviolet curable resin, the uneven surface is the surface to which the mold shape of the ultraviolet curable resin layer is transferred, and the second material layer is the upper portion of the ultraviolet curable resin layer. The air layer and the unit lens array surface are virtual planes in the polyester film surface and in the air layer parallel to and in contact with the uneven surface.

(3) Preparation of Liquid Crystal Display Device Observation of twisted nematic liquid crystal TFT color display (screen diagonal 10.4 inches, number of pixels vertical 480 dots × horizontal 640 dots, with backlight) mounted on a commercially available personal computer. On the surface side, the lens forming surface of the microlens array sheet prepared in the above (2) was placed on the liquid crystal cell side so as to be pressed by an acrylic plate (thickness 3 mm) to obtain a liquid crystal display device of the present invention. At this time, the unit lens array direction of the microlens array sheet was the screen vertical direction.

For comparison, a conventional liquid crystal display device without a microlens array sheet was also prepared.

(4) Evaluation The liquid crystal display device thus obtained was applied with white, 75% gray,
A test pattern composed of five colors of 50% gray, 25% gray, and black was displayed, and the display quality was evaluated by observing from the display surface normal direction (front), the upper 40 degree direction, and the lower 40 degree direction. The evaluation was performed under room lighting, which is a normal use environment.
The results are shown in Table 1.

As can be seen from the table, the liquid crystal display device of the present invention equipped with the microlens array sheet of the present invention is:
It can be seen that a good image can be observed from any direction and the viewing angle is expanded.

[0079]

[Table 1]

[0080]

By the simple operation of mounting the microlens array sheet on the observation surface, the disadvantage of the conventional liquid crystal display device having a narrow viewing angle can be efficiently eliminated.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional schematic view showing an example of the structure of a microlens array sheet of the present invention.

FIG. 2 is a sectional view of an example of a microlens array sheet of the present invention.

FIG. 3 is a cross-sectional view of an example of a conventional microlens array sheet.

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

[Explanation of symbols]

1 ・ ・ Transparent plastic substrate 2 ・ ・ ・ ・ ・ ・ Light-shielding layer 3 ・ ・ ・ ・ Unit lens 4 ・ ・ ・ ・ ・ ・ Unit lens array surface 5 ・ ・ ・ ・ Rough surface 6 ・・ ・ ・ First material layer 8 ・ ・ ・ ・ ・ Surface of substrate 1 ・ ・ ・ Microlens array sheet 12 ・ ・ ・ ・ ・ Liquid crystal cell 13 ・ ・ ・ ・ ・ Back light source 101 --- Rays that enter from the substrate surface and repeatedly undergo total internal reflection within the lens and then exit from the substrate surface again 102 ... --- Rays incident from the substrate surface and repeatedly undergo total internal reflection within the lens and exit from the substrate surface again Another ray

Claims (5)

[Claims] 1. A microlens in which unit lenses are arrayed on an array surface by forming an interface between a first material layer and a second material layer having a smaller refractive index than the first material layer into a regular uneven surface shape. A microlens array sheet comprising an array sheet having a light-shielding layer having a height in a thickness direction of the microlens array sheet, the light-shielding layer including at least a convex top portion of the first material layer. 2. The microlens array sheet according to claim 1, wherein light rays incident from the unit lens array surface on the second material layer side are within ± 10 degrees about the normal direction of the unit lens array surface. The light rays incident at an angle are 80% or more of the light rays having any incident angle, which are averaged over the entire surface of the microlens array sheet and are transmitted to the unit lens array surface on the first substance layer side. Lens array sheet. 3. The microlens array sheet according to claim 1, wherein the maximum refraction angle of the unit lens is 30 degrees or more. 4. The microlens array sheet according to claim 1, wherein the light shielding layer has a film shape perpendicular to the unit lens array surface. 5. A liquid crystal display device for displaying an arbitrary image by a liquid crystal cell in which display units for changing optical characteristics by an electro-optical effect of liquid crystal molecules are arranged, the liquid crystal display device being closer to an observation surface side than the liquid crystal cell. 5. The microlens array sheet according to claim 1, wherein the first material layer side is the observation surface side and the second material layer side is the liquid crystal cell side. Liquid crystal display device.