JPH0743501A - Microlens array sheet and liquid crystal display formed by using the same - Google Patents

Abstract

PURPOSE:To exceedingly expand the visual field angle of the liquid crystal display so that the display can be observed without any inconveniences at all even if the display is observed by plural persons or when the angle of observation is limited. CONSTITUTION:This microlens array sheet is formed by arranging, in a surface form, microunit lenses 6, each one of which is formed by holding a first material layer 1 having a rugged surface 3 at its boundary and a second material layer 2 having the refractive index smaller than the refractive index of the first layer between two planes 4, 5. The ray 9 entering from the first material layer 1 among the rays 9 which are incident from the normal direction of the plane 4 and pass the point 7 to maximize the angle of the rugged surface 3 with the plane 4 is transmitted by >=80% of its luminous flux to the second material layer 2. The ray 10 entering from the second material layer is refracted at >=10 deg. and is emitted from the plane 4 side of the first material layer 1. The liquid crystal display is constituted by providing the observation surface side of a liquid crystal cell with such first material layer 1 side on the observation surface side.

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 using the same.

[0002]

2. Description of the Related Art A microlens array in which minute unit lenses such as a convex lens and a concave lens are arranged in a plane is expected to be applied to a liquid crystal display, an optical coupling optical element, an image input device, etc., and research is being advanced.

Microlens arrays are roughly classified into two types. One is an array of controlled concavo-convex units (fine unit lenses) formed on a planar substrate by a microfabrication technique, and the other is refraction to an arbitrary minute unit portion in a planar substrate. It is a so-called flat plate microlens array having a distribution of the ratio.

A liquid crystal display utilizes an electro-optical effect of liquid crystal molecules, that is, optical anisotropy (refractive index anisotropy), orientation, fluidity, dielectric anisotropy, etc. to apply an electric field to an arbitrary display unit. Display is performed by using a liquid crystal cell in which optical shutters are arranged which are energized to change the light transmittance and reflectance. This liquid crystal display includes a direct-view type display for directly observing an image displayed in a liquid crystal cell and a projection type display for observing a displayed image by projecting it on a screen from the front or the back.

In a direct-viewing type liquid crystal display, a liquid crystal display and an optical element such as a microlens array are combined in order to reduce the change in display quality depending on the viewing direction and to widen the viewing angle at which good display quality can be obtained. Is proposed.

As a method for expanding the viewing angle by combining an optical element such as a lens for controlling the light transmission direction on the viewing surface side of a liquid crystal display, a plano-concave lens group is arranged (Japanese Patent Laid-Open No. 53-25399). , A method of arranging a polyhedral lens (Japanese Patent Laid-Open No. 56-65175), a method of arranging a prism-shaped projection transparent plate (Japanese Patent Laid-Open No. 61-148430).
Japanese Patent Laid-Open No. 62-56930 and Japanese Laid-Open Patent Publication No. 2-1.
In addition to these, in the case of a transmissive display, a means for controlling the light emission direction of the back light source is added (JP-A-58-16913).
No. 2, JP-A-60-202464, JP-A-6
3-253329).

[0007]

The liquid crystal display is
It has 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. However, it has a drawback that when it exceeds a certain angle, it exceeds the range that the observer can accept, that is, the viewing angle at which good display quality can be obtained (hereinafter, simply referred to as viewing angle) is narrow.

The disadvantage of a narrow viewing angle is that it has a relatively simple structure and is excellent in productivity and capable of displaying a large amount of data. Therefore, it has many advantages such as a super twisted nematic mode and a television image receiving apparatus, which are often used in personal word processors, personal computers and the like. This is especially noticeable in the twisted nematic mode for displaying halftones used in display devices, etc., from the direction of 10 to 50 degrees from the normal direction of the display surface (it depends on the vertical direction and the horizontal direction with respect to the display surface). When observed, the displayed contents are often almost unreadable. For this reason, it cannot be observed by a plurality of people, which hinders the application and development of the liquid crystal display.

In order to solve this drawback, it has been proposed to provide an optical element such as a microlens array on the observation surface of the liquid crystal display, but none of them is practical and has not solved the problem of the viewing angle. .

The reason for this is that, according to the study by the present inventors, the conventionally proposed method has a drawback that the effect of enlarging the viewing angle is small and the display quality of the liquid crystal display is remarkably deteriorated. Is.

That is, in the method of arranging the single concave lens,
Since a considerable curvature is required for the lens surface, the thickness of the display becomes considerably thick considering the thickness of the lens, and the characteristic of the liquid crystal display that is thin is impaired, and the display to be observed is reduced. There is a drawback that the contents are difficult to distinguish.

[0012] Further, a plano-concave lens group which has been conventionally proposed,
With the method of exposing the uneven surface of each optical element on the observation surface of the liquid crystal display, such as the method of arranging the polyhedral lens group, the lenticular lens, and the prism plate, not only the effect of enlarging the viewing angle is small, but also the liquid crystal display. The display contrast when observing from the front (direction normal to the viewing surface) is reduced, and depending on the viewing direction, light rays incident from the outside of the liquid crystal display are strongly scattered and reflected, so normal external lighting such as indoor lighting When there is incident light, the entire screen becomes whitish, and the contrast ratio between the brightest color display and the darkest color display decreases, which makes it difficult to see the display. That is, the display quality when observing the liquid crystal display from the front is deteriorated, and as the angle formed by the normal direction of the display surface and the observation direction is increased, the deterioration of the display quality becomes more remarkable. It was unreadable, and as a result, the original viewing angle could not be expanded.

Further, in the flat plate microlens array in which the refractive index distribution region is provided inside the glass substrate or the like, the above-mentioned drawbacks are almost eliminated, but since a sufficient refractive index difference cannot be taken, the viewing angle expanding effect is obtained. Has the drawback of being small.

Since the drawback that the viewing angle of the liquid crystal display is narrow is a problem in principle of the liquid crystal display, there is a limit to expanding the viewing angle by improving the inside of the liquid crystal cell, and a sufficient effect is obtained. Absent.

It is an object of the present invention to provide a microlens array sheet which solves the above-mentioned drawbacks and can obtain a sufficient viewing angle expansion effect even in a normal use environment where there is external light. An object of the present invention is to provide a liquid crystal display which has a wide viewing angle and enables observation by a plurality of people.

[0016]

A microlens array sheet according to the present invention for this purpose comprises a first material layer and a first material layer.
It is composed of a laminated body with a second material layer having a refractive index smaller than that of the material layer, and the first material layer side surface and the second material layer side surface form planes parallel to each other, and A microlens array in which an interface with the second material layer is formed on an uneven surface, and each concave and / or convex surface of the uneven surface constitutes a minute unit lens, and the minute unit lenses are arranged in a plane shape. In the sheet, the angle which is not wider among the two angles formed by the contact surface and the surface at a point on the interface formed on the uneven surface is defined as θ, and the point on the interface where θ is maximized is defined as the point. A, where θ at that time is θmax, the θmax of the ray passing through the point A is
And the following items, which are obtained geometrically and optically from the refractive index of each substance, satisfy the following (1) and (2). (1) The transmittance of a light ray that has entered the microlens array sheet from the surface normal direction on the side of the first material layer and has reached point A to be transmitted to the second material layer is 80% or more. (2) Light rays that have entered the microlens array sheet from the surface normal direction of the second material layer side and have reached point A are transmitted through the first material layer and emitted from the surface of the first material layer side to the atmosphere. The refraction angle at that time is 10 degrees or more as an angle with respect to the normal direction of the surface.

Further, the present invention is characterized in that the microlens array sheet described above is mounted on the observation surface of the liquid crystal cell with the first substance layer side being the observation surface side. Provide a display.

Conventional microlens array sheets such as lenticular lenses and flat plate microlens arrays are
As described above, even if it is mounted on the surface of a liquid crystal display to expand the viewing angle, the viewing angle expansion effect is small, or the entire screen becomes whitish due to the reflection of external light. I can not do it.

The present inventor has made a study in view of the above-mentioned drawbacks. As a result, in order to widen the viewing angle, the observation surface has a flat surface, and the first material layer and the second material layer having a sufficient refractive index difference inside. By stacking the material layers and sandwiching both material layers in two mutually parallel planes, that is, sandwiching between the first material layer side surface and the second material layer side surface which are parallel to each other, the first material layer and the second material layer Making a minute unit lens by making the interface uneven,
It was found that the viewing angle can be expanded by arranging the minute unit lenses in a plane.

However, if the microlens array sheet is simply attached to the liquid crystal cell in such a manner, the incident light from the outside is scattered and reflected due to the reflection on the lens surface, which is especially the front face when the liquid crystal display is used. A new problem arises in that the display contrast when observed from above may decrease.

Then, as a result of a more detailed study, by optimizing the shape and configuration of the minute unit lens,
The inventors have completed the present invention by discovering that the viewing angle of a liquid crystal display can be expanded with almost no deterioration in display quality.

In the present invention, the microlens array sheet (hereinafter sometimes abbreviated as MLA) is a unit array of minute unit lenses, that is, minute unit portions having a lens function. This includes a one-dimensional MLA in which one side surface is a flat surface such as a semi-cylindrical column, and the one side surface is aligned with the array surface in one direction, and a solid body having a planar bottom surface such as a rectangle, triangle, or hexagon. There is a two-dimensional MLA in which is arranged vertically and horizontally.

Here, the "minute" unit portion means that the array body (MLA) is sufficiently large with respect to the size of the unit portion (unit lens). When, it is assumed that the unit portion is minute. Further, "having a lens function" as used herein does not need to have a fixed focus like a normal single-convex lens or a single-concave lens, but has a function of refracting an incident light beam in an arbitrary controlled direction. Good.

In the unit lens of the present invention, the interface between the first substance layer sandwiched between two parallel planes and the second substance layer having a smaller refractive index than the first substance layer has a concave and / or convex surface. By functioning as a lens, it functions as a lens.

Here, each of the first substance and the second substance is a substantially transparent substance. A glass material, a transparent plastic material, or the like is preferably used as the first substance. As the second substance, a substance having a smaller refractive index than the first substance may be used, and in addition to a glass material, a transparent plastic material, a liquid such as water or a gas such as air can be used.

Such layers of first and second material are sandwiched between two parallel planes. The interface is concave and / or convex. With such a shape, it is possible to obtain a viewing angle widening effect when used as a liquid crystal display.

1 to 10 show an MLA according to the present invention.
The shape of is schematically shown. FIG. 1 and FIG. 2 show an example of a one-dimensional MLA in which semi-cylindrical columnar solids are arranged in one direction. 3 to 5 show an example of a two-dimensional MLA in which dome-shaped solids having a hexagonal bottom surface are arranged vertically and horizontally. Further, FIGS. 6 and 7 and FIGS. 8 to 10 show a one-dimensional and two-dimensional structure in which the interface between the first material layer and the second material layer is a continuous curved surface.
It is an example of dimension MLA. In the case of such an interface of continuous curved surfaces, the interface between the first material layer and the second material layer of the unit lens has both concave and convex surfaces. 1 to 10, the surfaces 4 and 5 of the first material layer 1 and the second material layer 2 which are different from the interface 3 with each other, that is, the surface 4 on the first material layer 1 side and the second material layer 2 side The surface 5 is a plane parallel to each other.

Here, the term "planar" means that the surface is substantially flat as compared with the uneven surface that functions as a lens. Here, the average roughness Ra is 5 minutes with respect to the height of the uneven surface. When it is 1 or less, it is assumed to be a plane. Similarly, being parallel means being substantially parallel to the size of the unevenness.

The characteristic of the minute unit lens constituting the MLA of the present invention is that the angle which is not wide (of the two formed angles) between the contact surface of a point on the uneven surface and the surface is θ. When the point on the interface where θ is the maximum is point A and θ at that time is θmax, the following items obtained geometrically from the θmax and the refractive index of each substance for the ray passing through the point A: The following (1) and (2) are satisfied. (1) Transmittance when light rays that have entered the microlens array sheet from the surface normal direction on the side of the first material layer and reach point A are transmitted to the second material layer (hereinafter, this is referred to as Te)
Is 80% or more. (2) Light rays that have entered the microlens array sheet from the surface normal direction of the second material layer side and have reached point A are transmitted through the first material layer and emitted from the surface of the first material layer side to the atmosphere. The refraction angle at this time (hereinafter referred to as α) is 10 degrees or more in terms of the angle with respect to the normal line direction of the surface.

Here, the refractive index of the first material layer is n ₁ , and the second material layer is
When the transmittance Te and the refraction angle α are obtained geometrically when the refractive index of the material layer is n ₂ , the following expressions (1) and (2) can be used. Shall be used.

[0031]

[Equation 1]

[0032]

[Equation 2]

From the above equation, in order to provide the unit lens with such characteristics, the refractive indexes of the first material layer and the second material layer, and the first material layer and the second material layer which become the uneven surface, It can be seen that this can be obtained by optimizing the combination of the interface shapes.

The preferable range of Te is 85%.
Above, and the preferable range of α is 15
It is not less than 20 degrees, more preferably not less than 20 degrees. For this purpose, the refractive index n ₁ of the first material layer is preferably 1.50 or more, and the refractive index n ₂ of the second material layer is preferably 1.30 or more.

By making each unit lens have such a characteristic, it is possible to suppress the reflection of external light while sufficiently maintaining the effect of enlarging the viewing angle, and the display quality is degraded when the liquid crystal display (LCD) is mounted. The problem goes away. 80% or more of the light rays incident from the first material layer side are the second
If the light does not pass through the material layer, the scattering reflection of external light becomes strong, so that the display quality is deteriorated when the LCD is mounted, and if the light ray incident from the second material layer side is not refracted by 10 degrees or more, a sufficient viewing angle is obtained. No expansion effect can be obtained.

The structure and function of this unit lens will be described with reference to FIG. 11 in which a part of the cross section of the MLA shown in FIG. 7 is enlarged. The unit lens 6 is configured such that the interface 3 between the first material layer 1 and the second material layer 2 sandwiched between the two parallel planes 4 and 5 forms a continuous uneven curved surface. In this unit lens 6, the planes 4 and 5 and the uneven surface 3
The point on the uneven surface where the angle formed by
However, a ray 9 that is incident from the normal direction of the plane 4 on the first substance layer side and passes through the point 7 is partially reflected at the point 7 but 80% or more of the light flux is refracted and the second substance Penetrate to layers.
On the other hand, the light ray 10 which is incident from the normal direction of the plane 5 on the second material layer side and passes through the point 7 is refracted at the point 7 and further refracted at the point 8 on the plane 4 to be emitted into the atmosphere. However, at this time, the angle 11 formed by the direction of incidence on the second material layer and the direction of emission is 10 degrees or more.

If the above conditions are satisfied, the shape and function of each unit lens portion can be designed according to the characteristics of the liquid crystal display to be applied, the operating environment, etc. as will be described later.

The substrate on which the MLA is formed can be selected according to the method of use. The most versatile method is a method using an MLA sheet formed on glass or a transparent plastic film. In this case, it is preferable to use a transparent plastic film as the base material because it is easy to handle and the lens surface is relatively easy to form.

When used in a liquid crystal display,
It can be directly formed on the liquid crystal display surface,
MLA can also be built into the polarizing film attached to the liquid crystal display. In particular, in the case of a polarizing film having a structure in which a protective film is superposed on a polarizer, the protective film on which MLA is formed in advance is used.
It is preferable to use it as an attached polarizing film because a liquid crystal display equipped with the MLA of the present invention can be manufactured without any modification to the conventional liquid crystal display manufacturing process.

The microlens array of the present invention can be obtained by applying a conventional lenticular lens or Fresnel lens manufacturing method.

That is, in order to obtain the first material layer or the second material layer, a female mold in which a desired lens shape is engraved is prepared, and a resin or the like is filled and transferred onto the sheet surface. A method of simultaneously preparing a mold and injecting resin to mold the base material part and the lens group part, and evenly applying a photo-curing resin such as an ultraviolet-curing resin onto a base material such as a plastic film and applying light rays only to the desired part. After curing by irradiating with, a method of removing unnecessary portions, a method of mechanically cutting the surface of a substrate such as plastic or glass to create a lens shape, and a method combining these, It is not limited to these.

Of these, from the viewpoint of continuous production, good productivity, and precise processing, the mold is filled with an ultraviolet curable resin and is transferred onto a plastic film substrate while being irradiated with ultraviolet rays to be cured. The method is preferred.

After the first substance layer or the second substance layer is thus obtained, when a substance other than air is used as the second substance layer, the material for the substance layer is filled to fill the microlens of the present invention. An array sheet can be obtained.

Next, the liquid crystal display of the present invention will be described. The liquid crystal display of the present invention is characterized in that the first substance layer (high refractive index substance layer) of the microlens array described above is attached to the observation face side of the liquid crystal cell with the observation face side. FIG. 12 is a schematic diagram illustrating an example of the configuration. In FIG. 12, 12 is the above-mentioned MLA, and in this case, MLA is the transparent substrate 1, 2.
Interface (that is, the interface between the first material layer 1 and the second material layer 2)
To form an MLA sheet. This MLA
The sheet is mounted on the observation surface of the liquid crystal cell 13 with the first substance layer 1, which is a high refractive index substance, facing the observation face.

The liquid crystal display displays arbitrary information by a liquid crystal cell in which display units of arbitrary shapes are combined, and displays one information by one pictogram or the like. There are various display formats, including the dot matrix type that can display a large amount of information by the liquid crystal cells arranged in the. The liquid crystal display of the present invention may be of any type, but the effect obtained by enabling observation by a plurality of people by enlarging the viewing angle is large. Is.

Here, the liquid crystal cell means an electro-optical effect of liquid crystal molecules, that is, a voltage is applied by changing the alignment state of liquid crystal molecules by applying or energizing liquid crystal molecules having a refractive index and a dielectric anisotropy. It is an arrangement in which an optical shutter mechanism for controlling the light transmittance is utilized as a display unit by utilizing the difference in optical properties between the portion and the non-applied portion.

As examples of 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 for driving each display unit of the liquid crystal cell, segment drive for independently driving each liquid crystal cell, simple matrix drive for time-divisionally driving each display unit, transistor, diode, etc. for each display unit are used. There is an active matrix drive in which active elements are arranged.

As a method for 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 also a combination of both.

The liquid crystal display of the present invention can be constructed by appropriately combining some of the above display modes, driving methods, and observation methods, and among these, a transmission type simple matrix driving method. The effect of the present invention is great in a liquid crystal display of a super twisted nematic mode, a transmissive active matrix driving twisted nematic mode, and a reflective simple matrix driving super twisted nematic mode.

By providing the above-mentioned MLA on the observation surface side of the liquid crystal cell, it is possible to eliminate the drawback of a narrow viewing angle without degrading the display quality of the conventional liquid crystal display.

In general, a change in display quality depending on the viewing direction of a liquid crystal cell is caused by rotating the viewing direction about the normal line even if the angle formed by the viewing direction and the normal line direction of the cell viewing surface is constant. Also occurs. That is, the viewing angle is generally different depending on the direction in which the observation direction moves from the front of the cell (left direction when viewed from the display surface, right direction, upward direction, downward direction, etc.). Alternatively, depending on the purpose of use of the liquid crystal display, there is a case in which the viewing angle in one direction should be preferentially expanded, for example, the viewing angle in the left and right directions should be expanded. In such a case, with respect to the viewing angle characteristics of each direction of the liquid crystal cell or the desired viewing angle expansion direction, by designing the lens function to have different scattering angles depending on each direction, a liquid crystal display with higher display quality Can be

That is, in the two-dimensional MLA as shown in FIGS. 3 to 5 and FIGS. 8 to 10, when mounted on a liquid crystal display, the viewing angle is enlarged in the up, down, left and right directions. 2 and the one-dimensional MLA as shown in FIGS. 6 and 7, the viewing angle can be expanded only in the arrangement direction (the left and right direction of the paper surface in FIGS. 1 and 6).

In the case of a one-dimensional MLA, two or more MLAs may be laminated by making the arrangement directions of the minute unit lenses orthogonal to each other. In that case, the viewing angle is expanded in each of the up, down, left and right directions.

The size and position of the unit lens of the MLA used in the present invention can be selected according to the size of the display unit of the liquid crystal cell. When the liquid crystal display is a dot matrix type, there are two preferable modes for the correspondence between one display unit and the unit lens. One is that one unit lens exactly corresponds to one display unit of the liquid crystal cell, and the other is for one display unit,
Two or more lenses are compatible. As a result, it is possible to suppress the occurrence of moire fringes due to the interference between the lens array pitch of the MLA and the cell display unit pitch.
Of these, the latter mode is preferable from the viewpoint that productivity is improved because precise alignment is unnecessary and the same MLA can be used for cells having several kinds of dot sizes. More preferably, four or more unit lenses correspond to one dot,
Further, it is preferable that 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 (3) in the case of one-dimensional MLA and by the following equation (4) in the case of two-dimensional MLA. n = N / (L / l) (3) n = N / (A / a) (4)

Here, N is the total number of unit lenses on the LCD display surface, L is the length of the liquid crystal cell in the one-dimensional MLA unit lens arrangement direction, and 1 is the portion 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, and a is the area of a portion of one display unit of the liquid crystal cell that contributes to display. These expressions 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 present invention, the MLA is preferably mounted as close as possible to the liquid crystal cell in that the display quality such as resolution and contrast does not deteriorate. Specifically, the distance at the closest point between the cell surface and the MLA is preferably 1.0 mm or less, more preferably 0.5 mm or less, still more preferably 0.1 mm or less.

When the LCD of the present invention is a transmissive LCD having a back light source, it is preferable that the back light source emits 80% or more of the luminous flux within the effective viewing angle range of the liquid crystal cell with which it is combined. .

Here, the effective viewing angle range of the liquid crystal cell means 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 light flux emitted from the light source body such as the fluorescent tube can be effectively used. That is, in the liquid crystal display of the present invention, the individual unit lenses of the lens array sheet refract the light flux transmitted in the direction of poor display quality of the liquid crystal cell so as not to affect the observation, and at the same time show a good display. Since the light flux that has been transmitted in all directions can be observed from various directions, the back light source that has not been used in general and has been conventionally used emits light at a large angle with respect to the normal direction of the display surface. The luminous flux is not used. Therefore, by giving directivity to the light flux emitted from the back light source,
The light flux emitted from the light source can be effectively used.

Another advantage is that it is possible to prevent bleeding of the displayed image. The liquid crystal display of the present invention is equipped with a lens array sheet on the observation surface, and it is preferable that the lens array sheet is provided as close to the liquid crystal cell as possible. However, the display unit of the liquid crystal layer of the liquid crystal cell and the unevenness of the lens array sheet Since there is a distance between the surfaces, which is generally equivalent to the thickness of the substrate for enclosing the liquid crystal or the polarizing element, it is often impossible to sufficiently bring them close to each other. Therefore, the light flux transmitted through one display unit of the liquid crystal cell reaches not only the unit lens portion corresponding to the display unit portion but also the unit lens located at a slightly distant position, and the effect of the unit lens causes the liquid crystal cell to move. The outline of one display unit is observed as if it is enlarged while being blurred, so that the display image is observed as if it is blurred.

On the other hand, when the back light source having directivity is used, even if there is a slight distance between the display unit portion of the liquid crystal layer and the uneven surface of the lens array sheet, the light flux transmitted through the display unit portion is Has a directivity, and mainly reaches only the corresponding unit lens portion, so that the display image does not bleed as described above. However, depending on the application of the liquid crystal display, it may be preferable to blur the displayed image to some extent. In this case, it is possible to deal with this by controlling the directivity of the back light source.

In order to provide a back light source having such a directivity, a method of using a Fresnel lens, a Fresnel prism, or other means for the light flux emitted from a light source such as a fluorescent tube, or a minute reflecting surface as a reflecting mirror is combined. There are means for using a multi-reflector, means for absorbing unnecessary light flux by an optical fiber sheet, louver, and the like. Although not limited to these, a Fresnel sheet in which microlenses and microprisms are arranged in a sheet shape is effective in that the light emitted from a light source such as a fluorescent tube is effectively used and it is easy to reduce the thickness and weight. It is preferable to provide it on the light emitting surface close to the liquid crystal cell of the back light source.

As a method of mounting the MLA on the liquid crystal cell, as described above, a method of separately preparing and mounting the MLA sheet provided on the transparent plastic film, a method of directly forming the MLA on the liquid crystal display, There is a method of using a polarizing film with MLA.

When the MLA sheet is used, it is preferable that the MLA formation surface is provided on the liquid crystal cell side in order to bring the MLA as close as possible to the liquid crystal cell. As a result, the effect of enlarging the viewing angle can be great. Furthermore, since the surface opposite to the MLA formation surface becomes the observation surface, the observation surface can be subjected to the non-glare treatment or the like which is formed on the conventional liquid crystal display surface.

The method of fixing the MLA sheet to the liquid crystal cell may be a method of superposing the MLA sheet on the liquid crystal cell and fixing it at several points at the edge portions, or by applying an adhesive to the entire surface of the display or the MLA sheet. A method of bonding may be used. Further, the second substance layer of the MLA sheet may be made of a material having an adhesive property or a curability property in advance and mounted on the liquid crystal cell.

The liquid crystal display of the present invention requires the liquid crystal cell and MLA as essential requirements, and the manufacturing method is as follows.
There is no particular question. That is, since the liquid crystal cell uses the electro-optical effect of liquid crystal molecules as in the conventional liquid crystal display, all the conventional liquid crystal display manufacturing methods can be used as they are.

FIG. 12 shows an example of the structure of the liquid crystal display of the present invention. The microlens array sheet 12 of the present invention, which comprises the first material layer 1 and the second material layer 2 having a smaller refractive index than the first material layer, has the liquid crystal cell 13 with the first material layer side as the observation surface side. It is attached to the observation surface.

[0069]

In the microlens array sheet of the present invention described in detail above, when the interface between the first substance layer and the second substance layer having a smaller refractive index than the first substance layer is formed on the uneven surface, Since the uneven surface is specified as the optimum shape range so that 80% or more of the light rays that are incident from the surface normal direction of the one material layer and pass through the point A are transmitted to the second material layer, the light from the surface side is Total reflection is effectively suppressed by the uneven surface, and scattering of external light is suppressed.

When a light ray incident from the surface normal to the surface of the second material layer is emitted from the surface (observation surface) of the first material layer into the atmosphere, it is at an angle of 10 with respect to the surface normal direction.
Since it is refracted by more than °, when it is mounted on a liquid crystal display, even when the liquid crystal display element is observed from an angle exceeding the critical viewing angle of the cell, the observed light is actually the critical viewing angle of the display cell. It is considered that the viewing angle is expanded as a result because the light ray is transmitted at an angle that does not exceed the range.

In the liquid crystal cell of the liquid crystal display, the light transmittance and the display color change depending on the viewing direction, and if it exceeds a certain angle (critical viewing angle of the cell) from the normal line direction of the display surface, it exceeds the range that the observer can accept. I will end up. In the conventional method of enlarging the viewing angle of a liquid crystal display using a microlens array, the uneven surface of the lens is exposed and the refraction effect of the lens is small, so the effect of enlarging the viewing angle is small or the diffuse reflection of incident light from the outside. However, the microlens array of the present invention has no unevenness of the lens on the surface of the observation surface, the reflection on the lens surface is small, and the refraction effect of the lens is large. , When the liquid crystal display is used, the decrease in the contrast ratio is minimized, and even when the liquid crystal display element is observed from an angle exceeding the critical viewing angle of the cell, the light rays observed at that time are the light rays observed in each unit of the microlens array. Due to the refraction in the lens, the transmitted light ray is observed in the display cell portion at an angle within the range not exceeding the critical viewing angle of the cell. Because, good display quality can be considered that the viewing angle of the obtained liquid crystal display element is to be expanded.

[0072]

EXAMPLES The present invention will be specifically described below with reference to examples. EXAMPLES, COMPARATIVE EXAMPLES (1) Preparation of Microlens Array Sheet (MLA) Prepared dies having some corrugated plate surfaces imprinted thereon, and UV-cured resin (refractive index after curing 1. 46)
, A transparent polyester film (manufactured by Toray Industries, Inc., thickness: 188 μm) was superposed thereon, and ultraviolet rays were irradiated by a high pressure mercury lamp to temporarily cure the resin, and then the resin was removed from the mold, and again, Several one-dimensional MLAs (MLA1 to 4) as shown in Table 1 were prepared by the method of irradiating ultraviolet rays from the lens forming surface to the main curing. These uneven surface shapes of MLA are shown in FIGS.
1) Arrange a part of the side surface of the cylinder in one direction as shown in
The dimension is MLA, and the arrangement pitch is 50 μm in each case, but the heights of the peaks of the irregularities are different from each other.

In this case, the ultraviolet curable resin layer is the first substance layer which is a high refractive index substance, and the air around the first substance layer is the second substance layer which is a low refractive index substance. In addition, a plane which is an interface between the polyester film which is the base material and the ultraviolet curable resin layer, and a plane of the surface of the liquid crystal cell on which the MLA is mounted (in the state before being mounted on the liquid crystal cell, an imaginary plane in the air is used. Are two parallel planes that sandwich the first and second material layers. Table 1 also shows the minimum external light transmittance and the maximum refraction angle as the characteristics of the minute unit lenses constituting these MLAs.

(2) Preparation and evaluation of liquid crystal display Super twisted liquid crystal monochrome display mounted on a commercially available personal computer (display color blue mode, screen size diagonal about 10 inches, number of pixels vertical 400 ×)
Various microlens array sheets prepared in (1) are attached to the observation surface side of 640 width, 290 μm dot pitch, with backlight, with the lens forming surface inside (the liquid crystal cell side), and the MLA is the observation surface of the liquid crystal cell. A liquid crystal display mounted on the side was created. In addition, a conventional liquid crystal display with nothing attached was prepared for comparison. Here, the array direction of the unit lenses of the microlens array sheet was made to coincide with the horizontal direction of the screen.

The display quality thus obtained was evaluated by observing the display from the direction normal to the display surface of the display (front) and left 60 degrees. The evaluation was performed under room lighting, which is a normal use environment. The results are summarized in Table 1.

[0076]

[Table 1]

As described above, the microlens array sheet of the present invention can widen the viewing angle without deteriorating the display quality of the liquid crystal display, and the liquid crystal display of the present invention has a wide viewing angle which has never existed before. You can see that it has a liquid crystal display.

[0078]

With the microlens array of the present invention, the angle at which a good display of a liquid crystal display is observed, that is, the viewing angle is dramatically expanded. In other words, with a very simple structure in which only a microlens array is provided on the viewing surface side of the liquid crystal cell, the drawback of the liquid crystal display having a narrow viewing angle is eliminated, and a good display in a wide range of viewing directions is achieved. The quality can be obtained and the display can be observed without any inconvenience even when the display is observed by a plurality of people or the observation angle is limited. It is possible to obtain a display quality that is comparable to the display method of.

As a result, the excellent advantages of the liquid crystal display such as thinness, light weight and low power consumption can be further utilized, and the dissatisfaction and inconvenience with respect to the display quality, which has been a problem in the past, can be solved. At the same time, it will be possible to develop new applications that were previously impossible.

[Brief description of drawings]

FIG. 1 is an enlarged schematic plan view of a part of a one-dimensional MLA according to an embodiment of the present invention.

2 is a II arrow view of the MLA shown in FIG. 1. FIG.

FIG. 3 is an enlarged schematic plan view of a part of a two-dimensional MLA according to an embodiment of the present invention.

FIG. 4 is a view on arrow IV of the MLA shown in FIG.

5 is a V arrow view of the MLA shown in FIG. 3. FIG.

FIG. 6 is an enlarged schematic plan view of a part of a one-dimensional MLA having an interface as a continuous curved surface according to an embodiment of the present invention.

7 is a VII arrow view of the MLA shown in FIG. 6. FIG.

FIG. 8 is an enlarged schematic plan view of a part of a two-dimensional MLA having an interface as a continuous curved surface according to an embodiment of the present invention.

9 is a view on arrow IX of the MLA shown in FIG.

10 is a view on arrow X of the MLA shown in FIG.

FIG. 11 is an explanatory diagram illustrating functions of the MLA of the present invention.

FIG. 12 is a schematic perspective view illustrating an example of the configuration of the liquid crystal display of the present invention.

[Explanation of symbols]

1 1st material layer 2 2nd material layer 3 Uneven surface 4 Surface of 1st material layer 5 Surface of 2nd material layer 6 Unit lens 7 Plane 4 and the point where the angle between the plane 5 and the uneven surface 3 becomes maximum 8 Plane 4 Point 9 Light ray incident from plane 4 normal direction 10 Ray incident from plane 5 normal direction 11 Refraction angle α 12 Microlens array sheet 13 Liquid crystal cell

Claims (2)

[Claims] 1. A laminated body of a first material layer and a second material layer having a refractive index smaller than that of the first material layer, wherein a surface on the first material layer side and a surface on the second material layer side are While forming flat surfaces parallel to each other, the interface between the first material layer and the second material layer is formed into an uneven surface, and each concave and / or convex surface of the uneven surface constitutes a minute unit lens that functions as a lens,
In the microlens array sheet in which the minute unit lenses are arranged in a plane, the lesser of the two angles formed by the contact surface of a point on the interface formed on the uneven surface and the surface is θ. When the point on the interface where θ is the maximum is point A and θ at that time is θmax, the light ray passing through the point A can be geometrically obtained from θmax and the refractive index of each substance. A microlens array sheet characterized by satisfying the following (1) and (2) for the following items. (1) The transmittance of a light ray that has entered the microlens array sheet from the surface normal direction on the side of the first material layer and has reached point A to be transmitted to the second material layer is 80% or more. (2) Light rays that have entered the microlens array sheet from the surface normal direction of the second material layer side and have reached point A are transmitted through the first material layer and emitted from the surface of the first material layer side to the atmosphere. The refraction angle at that time is 10 degrees or more as an angle with respect to the normal direction of the surface. 2. A liquid crystal display, wherein the first material layer side of the microlens array sheet according to claim 1 is used as an observation surface side and the microlens array sheet is mounted on the observation surface of a liquid crystal cell. .