JP2005266370A - Micro lens array and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a micro lens array in which conformity with other adjacent members is high and thickness can be reduced in a liquid crystal display and its manufacturing method. <P>SOLUTION: The micro lens array 13 is provided with a plurality of micro lenses 131 corresponding to pixels of the liquid crystal display and used in the liquid crystal display. Then, thickness of the micro lens array 13 is ≥2μm and ≤200μm, diameter of each micro lens 131 is ≥10μm and ≤600μm. In addition, difference between the largest refractive index and the smallest refractive index in the micro lens array 131 is ≥0.001 and ≤0.2. Furthermore, the micro lens array 13 is a refractive index distribution type micro lens array constituted by photodegradable materials such as polisilane. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a microlens array used in a liquid crystal display device and a manufacturing method thereof.

  A microlens array is used in various fields, and one of its uses is a part of a liquid crystal display device. In a liquid crystal display device, a microlens array is arranged on a rear glass substrate in order to avoid light shielding by a switching element such as a TFT element and to improve light use efficiency.

  The microlens array is manufactured by, for example, a manufacturing method described in Patent Document 1. In the manufacturing method described in Patent Document 1, first, wet etching is performed on a surface of a glass substrate serving as a mold through a mask to form a large number of minute recesses on a spherical surface or a cylindrical surface. Next, by performing wet etching again on the surface of the glass substrate without using a mask, a large number of minute concave portions are arranged densely to form a mold. And the microlens array is comprised using this shaping | molding die.

However, the conventional microlens array manufacturing method described in Patent Document 1 has various problems. First, the etching method has a problem that a manufacturing apparatus such as a film forming apparatus or an etching apparatus is increased in size and cost. Even if patterning of a large area is possible, it is difficult to suppress variations because the etching region is wide. If we try to achieve it by etching, first we make a small liquid crystal panel-size master by etching, then make a large number of replica masters by plating, etc., and then place them accurately on the large substrate in the vertical and horizontal directions. And it is necessary to arrange | position without angle shift. Furthermore, when transferring a predetermined microlens array from a small liquid crystal panel-size original placed on these large substrates to a large glass substrate using photo-curing resin, thermosetting resin, etc. If there are steps, gaps, etc. between the individual small liquid crystal panel size masters, it is difficult not only to apply the photo-curing resin and thermosetting resin, but also to make the mold release extremely difficult. In the etching method, a predetermined alignment mark cannot be formed simultaneously due to the influence of etching. If the alignment mark is separately formed after the microlens array is formed first, the alignment mark is formed while looking at the lens, so the accuracy between the alignment mark and the lens is lowered.
JP 10-39112 A

  The present applicant has proposed a method of manufacturing a microlens array using the so-called 2P method for the purpose of solving each problem of the etching method (Japanese Patent Application No. 2004-5072). According to the invention proposed in this application, although the above-described problems can be solved, there are various problems. First, since the lens portion of the microlens array has a convex shape, the accommodation of the polarizing film provided adjacently becomes worse. Moreover, in order to form a lens part on a glass substrate, a glass substrate part thickness must be increased. At this time, it is possible to form the microlens array directly on the liquid crystal glass substrate. However, since it is necessary to form a TFT element or ITO on the liquid crystal glass substrate, it must be at a high temperature of 500 ° C. or higher. The manufactured microlens array is dissolved. If the TFT element is formed of low-temperature polysilicon, such a problem can be avoided. However, the types of TFT elements that can be used are limited, resulting in problems in terms of cost and performance.

  The present invention has been made in order to solve the above-described problem, and has a high compatibility with other adjacent members in a liquid crystal display device, and a microlens array capable of reducing the thickness, and a manufacturing method thereof. The purpose is to provide.

The gradient index microlens according to the present invention is a gradient index microlens formed on a transparent substrate, and has a lens thickness Z ₀ of 0.005P <Z ₀ <0.23P (where P passes through the lens). (Meandering period of light).

  Here, the refractive index in the thickness direction of the microlens is preferably substantially constant. The gradient index microlens is preferably made of a photodegradable material, and in particular, the photodegradable material is preferably polysilane.

A microlens array for a liquid crystal display panel according to the present invention comprises a refractive index distribution type microlens for a liquid crystal panel, characterized in that a refractive index distribution type microlens is arrayed and attached to a backlight side or a display side of a liquid crystal panel substrate. The lens array is characterized in that the lens thickness Z ₀ is 0.005P <Z ₀ <0.20P (where P is a meandering period of light passing through the lens).

  Here, it is desirable that a lens diameter of the gradient index microlens is 10 μm or more and 800 μm or less. The refractive index in the thickness direction of the microlens is preferably substantially constant. The gradient index microlens is preferably made of a photodegradable material, and in particular, the photodegradable material is preferably polysilane.

  The microlens array may be a gradient index lens formed on a transparent substrate, and a lens surface facing a surface where the transparent substrate and the lens are in contact may be in contact with an optical base material or air.

The manufacturing method of the microlens array according to the present invention is based on a gradient index lens having a lens thickness Z ₀ of 0.005P <Z ₀ <0.20P (where P is a meandering period of light passing through the lens). The substrate is formed in advance, and the lens surface is adhered to the liquid crystal display panel substrate, and then the substrate is removed.

Here, it is desirable that the substrate is a film having 10,000 N / mm ² . The substrate may be an aramid film.

  Another method of manufacturing a microlens array according to the present invention includes a step of applying silver chloride to a transparent substrate, and performing laser drawing on the transparent substrate to which the silver chloride is applied. A step of manufacturing a mask, a step of applying a photodegradable material to the substrate, and a photodegradable material to the substrate coated with the photodegradable material via the gray scale mask. Irradiating with light that causes a reaction.

  Here, the gray scale mask preferably has a gradation line resolution of 450 nm or less.

  According to the method for manufacturing a microlens array and the method for manufacturing the same according to the present invention, the microlens array having high compatibility with other adjacent members in the liquid crystal display device and capable of reducing the thickness, and the method for manufacturing the microlens array Can be provided.

Embodiment 1 of the Invention
In describing the microlens array according to the present invention, first, the configuration of a liquid crystal display device in which the microlens array is mainly used will be briefly described together with the function of the microlens array.

  FIG. 1 is a cross-sectional view of a liquid crystal display device. In this liquid crystal display device, a liquid crystal 7 is sandwiched between two glass substrates 2 and 12. A polarizing film 1 is provided on the front side (observer side) of the glass substrate 2. A black matrix 3, a color filter layer 4, a transparent electrode 5, and an alignment film 6 are formed on the side (back side) of the glass substrate 2 on which the liquid crystal layer 7 is provided. A spacer 8 is provided between the glass substrate 2 and the glass substrate 12. On the front side of the glass substrate 12, a TFT element 11, which is a switching element, a transparent electrode 10, and an alignment film 9 are formed.

  In the liquid crystal display device shown in FIG. 1, a microlens array 13 is formed on the back side of the glass substrate 12. The microlens array 13 is provided with a microlens for each pixel. That is, the same number of pixels is provided. For example, in the case of a liquid crystal display device for a portable terminal, a set of microlens array 13 is configured by about 200,000 microlenses 131. Here, the microlens array 13 is a refractive index distribution type microlens array, and is preferably formed of polysilane which is a photodegradable material (photodegradable photopolymer). When this photodegradable polymer is irradiated with light having a specific wavelength such as ultraviolet rays, the contained polymer is decomposed to lower the degree of polymerization. The degree of decrease in the degree of polymerization can be changed according to the amount of light applied, and the refractive index changes according to the degree of polymerization, so that the refractive index can be changed by changing the amount of light. .

  Unlike the microlens array formed by the 2P method, the microlens array 13 is a flat lens array having a smooth surface, that is, a flat surface. Therefore, the compatibility with the polarizing film 14 provided adjacently is high, and both can be positioned accurately.

  As shown in FIG. 2, the microlens 131 is formed of a regular hexagonal region, and the refractive index distribution is adjusted in each lens to constitute an optical lens. The microlens array 13 refracts light so that light from the back side does not strike the TFT element 11. As a result, the light utilization efficiency is increased, and high-luminance display is possible.

  FIG. 3 shows a sectional view of the microlens 131 and a change distribution of the refractive index. As shown in the figure, the microlens 131 is adjusted so that the refractive index n is the highest in the central portion, and the refractive index n decreases as it approaches the outer periphery.

When the lens thickness Z ₀ is 0.005P <Z ₀ <0.23P, and preferably 0.005P <Z ₀ <0.20P, the light from the backlight side is favorably focused on the liquid crystal panel substrate side (almost liquid crystal substrate It is possible to collect light with a thickness of about). In other words, a refractive index distribution type lens is formed by decreasing the refractive index from the lens center toward the outer periphery, and an appropriate back focus surface is set by setting the lens thickness Z ₀ in the above range. In other words, the light can be condensed on the liquid crystal panel substrate side with a back focus comparable to the thickness of the liquid crystal panel substrate.

When Z ₀ is in the range of 0.23P or more and 0.25P or less, the light from the backlight condenses rapidly after passing through the lens and becomes a very short back focus, and in order to obtain the effect of the lens on the liquid crystal panel, The thickness of the liquid crystal panel substrate must be reduced, which causes a problem in strength. For example, Z ₀ = 0.23P, lens thickness Z0 = 210 μm, lens diameter 100 μm, back focus = 26 μm, and glass substrate thickness = 40 μm. In addition, even if the same Z ₀ = 0.23P, when trying to obtain the glass substrate thickness = 380 μm, the lens thickness Z ₀ becomes 4.8 mm, and the lens thickness becomes very thick.

  Further, although it becomes possible to obtain a focal point with an appropriate back focus surface even at 0.25P or more, the lens thickness is increased, and the thickness of the liquid crystal panel substrate is effectively increased. In addition, this gradient index lens is manufactured by applying a photodegradable material to the substrate.In this case, a coating thickness of 500 μm or more is required, which may cause uneven thickness, etc. It becomes difficult to form the lens itself.

FIG. 9 shows a ray tracing diagram when the lens thickness Z ₀ = 0.06P, and FIG. 10 shows a ray tracing diagram when the lens thickness Z ₀ = 0.60P. As is clear from this figure, when Z ₀ = 0.06P, the lens thickness is thin and good back focus can be obtained. On the other hand, in the case of Z ₀ = 0.60P, the back focus can obtain the same distance, but the condensing characteristic is deteriorated, and the lens thickness itself becomes 10 times. In this case, the refractive index distribution is deliberately excluded from the ideal distribution curve.

Also, at 0.005P or less, the back focus becomes long (for example, the lens diameter is 50 μm, the refractive index difference is 0.2, Z ₀ = 0.004P, the back focus is 2000 μm or more, and the focused spot size is about 50 μm). It becomes impossible to obtain a light spot (for example, when the lens diameter is 50 μm, the refractive index difference is 0.2, Z ₀ = 0.004P, the back focus is 2000 μm or more, and the converging spot size is about 50 μm).

  For a microlens array for a liquid crystal panel, the lens diameter is desirably 10 μm or more and 800 μm or less.

In FIG. 12, when the maximum refractive index n _max = n ₀ = 1.70, for each lens diameter 10 μm to 2000 μm, the refractive index difference is changed within the range of 0.01 to 0.2, and the lens thickness Z (P) is changed. The calculation result of back focus was shown. However, the lens thickness Z (P) is expressed as N (0.001 to 0.25) times the meandering period P of light passing through the lens.

  It can be seen that when the lens diameter is 10 μm to 2000 μm and the refractive index difference is 0.01 to 0.2, there is a region where the lens thickness Z (P) is 0.005P or more and 0.23P or less, and the back focus is 0.1 mm to 2 mm. Displayed with shading in the table).

  If the back focus is shorter than the above range, it is necessary to reduce the thickness of the liquid crystal panel substrate, which causes a problem in strength. Moreover, if it becomes longer than the above range, it is necessary to increase the thickness of the liquid crystal panel substrate, resulting in problems such as an increase in the thickness of the liquid crystal panel body and an increase in weight.

In FIG. 11, when the maximum refractive index n _max = n ₀ = 1.70, for each lens diameter 10 μm to 2000 μm, the refractive index difference is changed in the range of 0.01 to 0.2, and the lens thickness Z (P) is changed. The actual lens thickness Z ₀ was shown. However, the lens thickness Z (P) is expressed as N (0.001 to 0.25) times the meandering period P of light passing through the lens.

When the lens diameter is 10 μm to 2000 μm and the refractive index difference is 0.01 to 0.2, there is a region where the lens thickness Z (P) is 0.005 P or more and 0.25 P or less and the actual lens thickness Z ₀ is 0.5 μm to 500 μm. You can see (shaded in the table). When the actual lens thickness Z ₀ is 0.5 μm or less, it becomes difficult to apply the photodegradable material to the substrate. Further, even when the thickness is 500 μm or more, coating unevenness easily occurs, and coating becomes extremely difficult.

FIG. 13 shows that when the maximum refractive index n _max = n ₀ = 1.70, the photodegradable material can be satisfactorily applied to the substrate (0.5 μm to 500 μm) and the thickness of the liquid crystal panel substrate The range of the lens thickness Z ₀ that can obtain a suitable back focus of 0.1 mm to 2 mm is shown (indicated by a square in the table). As a result, the value of Z ₀ that satisfies both was 0.005P <Z ₀ <0.18P. At this time, a lens diameter of 10 μm to 800 μm showed good light-collecting characteristics.

Similarly, FIG. 14 and FIG. 15 show the values when the maximum refractive index n _max = n ₀ = 1.50. The actual lens thickness Z ₀ is the same as in FIG.

  Similarly, in this case, it can be seen that there is a region where the back focus is 0.1 mm to 2 mm in the region of 0.005P or more and 0.23P or less (displayed by shading in the table).

Further, it can be seen that the value of Z ₀ that satisfies both the optimum back focus value and the optimum lens thickness is 0.005P <Z ₀ <0.20P. Here, the lens diameter means the maximum length in the surface of the formed lens, for example, the diagonal length in the case of a square lens.

As described above, the lens diameter is in the range of 10 μm or more and 800 μm or less, and the lens thickness Z ₀ is in the range of 0.005P <Z ₀ <0.23P, preferably 0.005P <Z ₀ <0.20P. By setting the thickness, the light can be focused without diverging, and the lens thickness can be reduced, so that the thickness of the liquid crystal panel body can be prevented from increasing, Since the coating thickness of the photodegradable material can be reduced, stable production can be achieved. If this gradient index microlens array is used, a good back focus, that is, an optimum glass substrate thickness can be used, and a liquid crystal panel excellent in luminance characteristics can be provided.

  The refractive index difference used here is 0.01 or more and 0.2 or less, and the refractive index difference in this range was obtained by variously examining the UV irradiation intensity and baking conditions.

Further, it was confirmed that the back focus value with respect to Z ₀ has a good range as described above in the range of n ₀ = 1.4 to 1.8.

  The present gradient index lens has a characteristic that the refractive index is substantially constant in the lens thickness direction, although the refractive index varies in the lens in-plane direction. Conventionally, a planar refractive index distribution lens known by an ion exchange method has a refractive index that changes in the lens thickness direction. This is because a refractive index difference is generated by ion exchange from a patterning opening in advance by patterning on a glass substrate or the like. However, in such a method, since ion exchange is performed by diffusion from the opening, only a substantially isotropic shape can be obtained. Therefore, for example, it is difficult to obtain a rectangular lens shape of length: width = 3: 1 corresponding to the liquid crystal element.

However, according to this method, the refractive index in the lens thickness direction is made substantially constant, and the lens is formed by changing the refractive index only in the in-plane direction. A lens can also be easily manufactured. In addition, the present gradient index lens array can be applied to a different substrate with a film thickness set in advance so as to obtain a predetermined back focus, and the lens diameter for the back focus can be collectively formed using a gray scale mask. . Further, the gray scale mask gradation can be set so that the refractive index distribution at that time has a refractive index distribution represented by the following equation, for example.
n (a) = n0 {1- (A 2 a 2/2)}
Here, a is the distance between any location and the center of the microlens 131, A is the refractive index distribution constant, n ₀ is the maximum value of the refractive index, i.e. a refractive index at the central point.

  The gray scale mask gradation can be generated by applying intensity modulation of, for example, 16 to 128 gradations to the silver chloride coated on the transparent substrate using a laser direct drawing device.

  At this time, it is desirable that the gray scale mask has a gradation line width resolution of 450 nanometers or less. For forming a lens using a gray scale mask, as is generally known, for example, a normal positive resist or a negative resist is applied to a substrate, exposed through a gray scale mask, and then an alkali is formed. Although it can be formed by a method of developing with a liquid, in this case, the resolution of the gray scale mask does not need to be much concerned. This is because, in the resist development process, the resist is smoothed by the alkaline solution, so that a smooth shape appears.

  On the other hand, when a photodegradable material is used, a refractive index difference corresponding to the density of the gray scale mask is generated by exposure and subsequent heat treatment (for example, 200 ° C. for 30 minutes). In other words, since the development process with the alkaline solution is not performed, the lens faithfully reproduces the gray scale light and shade of the gray scale mask. In this case, in the laser drawing of the silver chloride substrate for forming the gray scale mask, if the line width gradation resolution is 450 nanometers or more, a discontinuous point is generated, and therefore, on the short wavelength side of the backlight light source of the liquid crystal panel. It causes diffraction and is not preferable. For the above reasons, it is preferable that the laser direct drawing of a silver chloride substrate for producing a gray scale mask has a line width gradation resolution of 450 nanometers or less.

  Of course, as a method of providing this line width resolution, electron beam drawing is also possible, but in this case, drawing of a metric silver chloride substrate is difficult, and the advantage of performing batch exposure over a large area is lost.

  The gradient index microlens array on another substrate obtained by the above method can be removed by attaching the lens surface to the liquid crystal panel substrate and then peeling the substrate.

  A substrate having transparency, such as a glass substrate or a transparent film substrate, is convenient. This is because an alignment mark is formed on the liquid crystal panel substrate in advance, and the alignment mark is also formed on the refractive index distribution type microlens array side at the same time when the microlens array is formed, and is aligned and pasted with the alignment mark on the liquid crystal panel side. In addition, a gradient index microlens array can be attached together with the liquid crystal pixels. Originally, the refractive index distribution type micro lens array has a flat surface, so it is necessary to fill the concave portions of the lens or the concave portions between the lenses with a different refractive index as in the case of the micro lens array using the 2P method. Is very convenient.

The transparent film substrate does not need to be completely colorless and transparent as long as the alignment mark can be recognized. Rather, since a tension is applied at the time of bonding, a film having a high elastic modulus is preferable in order to prevent a lens pitch shift due to elongation. A film having a modulus of elasticity of at least 10,000 N / mm ² is desirable.

  In addition, the gradient index microlens array is subjected to heat treatment at 150 ° C. or higher after exposure. However, when the film is thermally contracted, it is not preferable because the lens pitch shifts.

For the reasons described above, an aramid film having a high elastic modulus (15000 N / mm ² ), a heat shrinkage of 200 ° C. or less and 0.1% or less is preferable for the transparent film substrate.

  After the refractive index distribution microlens array formed on a separate substrate is bonded to the liquid crystal panel substrate, a separate release agent is applied to the separate substrate in advance or by sputtering, vapor deposition, CVD, etc. to easily peel off the separate substrate. You may keep it. The release agent may be a fluorine-based material (fluorine-based lubricant such as perfluorocarbon or Teflon (registered trademark)) that reduces surface energy, nitrocellulose, or the like.

  As described above, since the microlens array can be directly formed on the liquid crystal panel substrate without using another substrate, the microlens array can be formed on the liquid crystal panel substrate while positioning the microlens array without increasing the thickness of the liquid crystal panel.

  Next, an example of a method for manufacturing a microlens array according to an embodiment of the present invention will be described with reference to FIG. FIG. 4 is a partial cross-sectional view for each process.

  First, as shown in FIG. 4A, silver chloride 102 is applied on a glass substrate 101 (dry plate), which is a transparent plate member, by spin coating, slider coating, roller coating, or the like. Next, as shown in FIG. 4B, laser light is irradiated to the silver chloride 102. At this time, utilizing the fact that the reaction of the silver chloride 102 varies depending on the intensity of the laser light emitted from the laser device, the laser light is sequentially emitted so that a concentration distribution corresponding to the shape of the microlens array 13 is formed. The silver chloride 102 is scanned while adjusting the intensity. Examples of usable lasers include a KrF laser, a YAG laser, and a HeCd laser having a line width resolution of 0.5 μm. In the case of a YAG laser, for example, it has a wavelength of 266 nm. These lasers are metal vapor lasers and solid-state lasers, and continuous oscillation control is performed. The diameter of the laser beam is about 1.5 μm, and is narrowed down to 0.5 μm by the objective lens. When laser processing is performed, the laser beam may be scanned by moving an XY table on which the glass substrate 101 is fixed. In this case, the XY table is positioned by interference control, for example. The intensity of the laser beam can be adjusted, for example, in 32 gradations or 128 gradations. The adjustment of the intensity of the laser beam may be performed by an acousto-optic modulator or may be performed by controlling the power of the laser itself. In this way, a gray scale mask is formed.

  On the other hand, as shown in the lower part of FIG. 4C, a photodegradable polymer 104 is applied on a glass substrate 103, which is a transparent plate member, by a spin coat method, a slider coat method, a roller coat method, or the like. To do. The photodegradable polymer 102 is, for example, polysilane. More preferably, it is network-like polysilane.

  As shown in the upper part of FIG. 4C, the gray scale mask is disposed above the glass substrate 103 with the silver chloride 102 portion positioned below. In such a state, ultraviolet (UV) exposure is performed. The amount of ultraviolet light changes according to the density of silver chloride 102 of the gray mask, and is irradiated to the photodegradable polymer 104. The photodegradable polymer 104 changes its refractive index in response to the irradiated ultraviolet rays, and the microlens array 13 having a plurality of microlenses 131 is formed (see FIG. 4D).

  Next, liquid crystal display elements such as transparent electrodes and color filter layers are formed on the glass substrate 12. Thereafter, the microlens array 13 fixed to the glass substrate 103 is bonded to the glass substrate 12 (FIG. 5A). And the glass substrate 120 grade | etc., Is cut | disconnected after a sealing process and a liquid-crystal sealing process. After cutting, the glass substrate 103 is separated (see FIG. 5B).

  As described above, according to the method for manufacturing a microlens array according to the embodiment of the present invention, since the laser device is used for forming the gray scale, it can be formed with high accuracy. In the embodiment of the present invention, since the glass substrate 103 is finally separated and removed, the thickness can be reduced. In addition, since the microlens array 13 is a flat lens sheet, the polarizing film 14 can be accommodated well.

Other embodiments.
FIG. 6 shows another configuration example of a liquid crystal display device having a microlens array. In the liquid crystal display device shown in FIG. 6, the microlens array 13 is provided on the front surface of the front glass substrate 2. Thus, by providing the microlens array 13 on the front surface of the glass substrate 2 on the front surface side, the viewing angle can be widened.

  The microlens array according to the present invention can be used for a liquid crystal using a striped color pattern as used in a liquid crystal display device such as a large screen television. FIG. 7 shows a microlens array having a lens shape corresponding to a striped color pattern. Each microlens 131 is a rectangular lens corresponding to the color pattern, and its cross section has a spherical shape both vertically and horizontally. In this embodiment, one having an aspect ratio of approximately 1: 3 is used, but it can also be applied to one having a different aspect ratio. Even in the form of stripe-shaped color patterns, it is possible to form a lens with a rectangular bottom, which was impossible to achieve with the etching method, thereby forming a dense structure and a microlens with a very high light utilization efficiency. An array can be manufactured.

  In the above example, the microlens array has been described for a liquid crystal display panel. However, the present invention is not limited to this, and the microlens array can also be used for optical communication.

  When the back focus was 2000 μm, the relationship between the lens thickness and the refractive index difference of the gradient index microlens array having 20 lens diameters from 50 μm to 600 μm was obtained by computer simulation. Here, the back focus is a distance from the exit surface of the microlens to the focal point. In this example, the back focus is calculated on the assumption that there is a glass medium between the exit surface and the focal point. FIG. 8 shows the simulation result. The back focus can be set to 2000 μm at any point.

  Polysilane, a photodegradable material, uses “Gracia” (registered trademark) made by Nippon Paint, an organic solvent in which polysilane is dissolved, a spin coater on a quartz substrate, and the thickness of the polysilane layer after drying the organic solvent. Is then dried in an oven to evaporate the organic solvent to form a polysilane layer having a thickness of 50 μm.

  A gray scale photomask for a microlens array is placed on the polysilane layer so that the silver chloride portion is facing down, and ultraviolet exposure is performed.

  A gray scale photomask for a microlens array is a photomask for forming a microlens array in which regular hexagonal microlenses each having a side of 50 μm are densely arranged.

  The gray scale photomask density for microlens array is based on the relationship between the amount of exposure and the refractive index change obtained by conducting an experimental investigation in advance. That is, it is the apex of a regular hexagon, its distance is 100 μm, the refractive index at that position is the lowest 1.57, and silver chloride is achieved so as to achieve an exposure amount that goes away from the center and goes down on a quadratic curve. Creating shades of.

  After the exposure to ultraviolet rays, heating was further performed to form a regular hexagonal dense microlens array having a thickness of 50 μm, a maximum refractive index of 1.65, a refractive index difference of 0.08, and a side of 50 μm.

  In the case of the above conditions, the meandering period P is 908 μm, and the thickness Z = 50 μm corresponds to 0.06P.

  In the case of the above conditions, the result of calculating the back focus in the air by solving the differential equation was 302 μm. In this case, when the glass used for the liquid crystal was borosilicate glass having a refractive index of 1.52, light was most efficiently used when the glass thickness was 450 μm.

  Similarly, a polysilane layer having a thickness of 18 μm is formed to produce a microlens. The meandering period P is 908 μm, and the thickness Z = 18 μm corresponds to 0.016P. In the case of the above conditions, the back focus in the air was calculated by solving the differential equation, and the result was 864 μm. In this case, when the glass used for the liquid crystal is borosilicate glass having a refractive index of 1.52, light was most efficiently used when the glass thickness was 1300 μm, and the condensing spot size was 13 μm.

Comparative Example 1
Similarly, a 4 μm-thick polysilane layer is formed to produce a microlens. The meandering period P is 908 μm, and the thickness Z = 4 μm corresponds to 0.004P. In the case of the above conditions, the back focus in air was calculated by solving a differential equation, and the result was 3905 μm. In this case, when the glass used for the liquid crystal is a borosilicate glass having a refractive index of 1.52, a glass thickness of 5900 μm is necessary to efficiently use light, and the condensing spot size is 55 μm.

Comparative Example 2
Similarly, a 210 μm-thick polysilane layer is formed to produce a microlens. The meandering period P is 908 μm, and the thickness Z = 210 μm corresponds to 0.23P.

  In the case of the above conditions, the result of calculating the back focus in the air by solving the differential equation was 26 μm. In this case, when the glass used for the liquid crystal is a borosilicate glass having a refractive index of 1.52, a glass thickness of 40 μm is necessary to efficiently use light.

1 is a partial cross-sectional view of a liquid crystal display device having a microlens array according to the present invention. It is a top view of the micro lens array concerning this invention. It is sectional drawing and refractive index distribution figure of the micro lens concerning this invention. It is a flowchart which shows the manufacturing method of the micro lens array concerning this invention. It is a flowchart which shows the manufacturing method of the micro lens array concerning this invention. 1 is a partial cross-sectional view of a liquid crystal display device having a microlens array according to the present invention. It is sectional drawing which shows the mode of one process in the manufacturing method of the micro lens array concerning this invention. It is a figure which shows the simulation result concerning the Example of the microlens concerning this invention. It is a ray tracing figure of a micro lens. It is a ray tracing figure of a micro lens. It is a table | surface which shows the calculation result of the back focus of a micro lens. It is a table | surface which shows the calculation result of the lens thickness of a microlens. It is a table | surface which shows the calculation result of the back focus of a micro lens. It is a table | surface which shows the calculation result of the back focus of a micro lens. It is a table | surface which shows the calculation result of the back focus of a micro lens.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polarizing film 2 Glass substrate 3 Black matrix 4 Color filter layer 5 Transparent electrode 6 Alignment film 7 Liquid crystal 8 Spacer 9 Alignment film 10 Transparent electrode 11 Switching element 12 Glass substrate 13 Microlens array 131 Microlens 14 Polarizing film

Claims (15)

A gradient index microlens formed on a transparent substrate, wherein the lens thickness Z ₀ is 0.005P <Z ₀ <0.23P (where P is a meandering period of light passing through the lens). Gradient index microlens.   2. The gradient index microlens according to claim 1, wherein the refractive index in the thickness direction of the microlens is substantially constant.   3. The gradient index microlens according to claim 1, wherein the gradient index microlens is made of a photodegradable material.   4. The gradient index microlens according to claim 3, wherein the photodegradable material is polysilane. A gradient index microlens array for liquid crystal panels, characterized in that a gradient index microlens is arrayed and attached to the backlight side or display side of the liquid crystal panel substrate, and the lens thickness Z ₀ is 0.005P <Z ₀ <0.20P (where P is a meandering period of light passing through the lens), and a microlens array for a liquid crystal display panel.   6. The microlens array for a liquid crystal display panel according to claim 5, wherein a lens diameter of the gradient index microlens is 10 μm or more and 800 μm or less.   The microlens array for a liquid crystal display panel according to claim 5 or 6, wherein the refractive index in the thickness direction of the microlens is substantially constant.   The microlens array for a liquid crystal display panel according to claim 5, wherein the gradient index microlens is made of a photodegradable material.   9. The microlens array for a liquid crystal display panel according to claim 8, wherein the photodegradable material is polysilane.   The gradient index microlens array is a gradient index lens formed on a transparent substrate, and a lens surface facing a surface where the transparent substrate and the lens are in contact is in contact with an optical substrate or air. 10. The microlens array for a liquid crystal display panel according to claim 5, wherein the microlens array is a liquid crystal display panel. A refractive index distribution type lens having a lens thickness Z ₀ of 0.005P <Z ₀ <0.20P (where P is a meandering period of light passing through the lens) is formed in advance on a substrate, and is applied to a liquid crystal display panel substrate. A method of manufacturing a microlens array, wherein the substrate is removed after bonding the lens surfaces. 12. The method of manufacturing a microlens array according to claim 11, wherein the substrate is a film having 10,000 N / mm < ² >.   The method for manufacturing a microlens array according to claim 11, wherein the substrate is an aramid film.   Applying silver chloride to the transparent substrate; producing a gray scale mask by performing laser drawing on the transparent substrate coated with the silver chloride; and photodegradable to the substrate. A step of applying a material; and a step of irradiating the substrate coated with the photodegradable material with light that causes a photodecomposition reaction to the photodegradable material via the gray scale mask. A method of manufacturing a lens array. 14. The method of manufacturing a microlens array according to claim 13, wherein the gray scale mask has a gradation line resolution of 450 nm or less.

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