JP2722074B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member comprising an amorphous silicon carbide photoconductive layer and an organic optical semiconductor layer.

[Prior art and its problems]

The photoconductive material of the electrophotographic photoreceptor includes Se, Se-Te, A
_There are inorganic materials such as _s2Se3 , ZnO, CdS, and amorphous silicon, and various organic materials. Among them, Se was first commercialized, and then ZnO, CdS, and amorphous silicon were also commercialized. On the other hand, as an organic material, PVK-TNF was first put to practical use, and thereafter, a function-separated type photoreceptor in which the functions of charge generation and charge transport were shared by different materials was proposed. The development of organic materials is developing dramatically.

On the other hand, an electrophotographic photosensitive member in which an organic optical semiconductor layer is laminated on the above-mentioned inorganic photoconductive layer has also been proposed.

For example, there is a laminated photoconductor of a Se layer and an organic optical semiconductor layer,
Although this photoreceptor has already been put to practical use, there is a disadvantage that Se itself is harmful and the sensitivity on the long wavelength side is inferior.

Therefore, Japanese Unexamined Patent Publication No. Sho 56-14241 proposes a laminated photoreceptor comprising an amorphous silicon carbide photoconductive layer and an organic photo-semiconductor layer. Pollution and high light sensitivity were obtained.

According to the electrophotographic photoreceptor of the above publication, the chemical formula Si _1-x C _x H
It has a structure in which an amorphous silicon carbide layer represented by _y (where 0 <x <1, 0.05 ≦ y ≦ 0.2) and an organic optical semiconductor layer are sequentially laminated.

However, the present inventors manufactured such an electrophotographic photoreceptor and measured its surface potential. As a result, it was found that satisfactory characteristics could not be obtained, and further improvement was required.

Accordingly, the present invention has been completed in view of the above, and an object of the present invention is to provide an electrophotographic photosensitive member having a high surface potential.

[Means for solving the problem]

According to the present invention, there is provided an electrophotographic photosensitive member in which an amorphous silicon carbide photoconductive layer (hereinafter, amorphous silicon carbide is abbreviated as a-SiC) and an organic optical semiconductor layer are sequentially laminated on a conductive substrate. The photoconductive layer has a layer structure in which a first layer region and a second layer region are sequentially formed, and the first layer region contains at least one element of oxygen or nitrogen in an amount of 0.01 to 30 atomic%. The constituent elements of the layer region of _No. 2 are Si element, C element and hydrogen or halogen. In the hydrogen, the halogen is expressed as element A, and the element ratio of the layer region is represented by a composition formula [Si _1-x C _x ] _{1- When} represented as _y A _y , x and y are respectively 0 <x <0.5, 0.2 <y <
An electrophotographic photoreceptor characterized by being set in the range of 0.5 is provided.

 Hereinafter, the present invention will be described in detail.

FIG. 1 shows the layer structure of the electrophotographic photoreceptor of the present invention. According to FIG. 1, an a-SiC photoconductive layer (2) and an organic optical semiconductor layer (3) are provided on a conductive substrate (1). Are sequentially laminated. The a-SiC photoconductive layer (2) has a function of generating charges, and the other organic optical semiconductor layer (3) has a function of transferring charges.

According to the present invention, a first layer region (2a) and a second layer region (2b) are sequentially formed inside an a-SiC photoconductive layer (2),
The first layer region (2a) contains oxygen and / or nitrogen in a predetermined range, and the element ratio of the second layer region (2b) is set in a predetermined range. It is a feature that it improved.

First, the second layer region (2b) has a substantial photocarrier generation function, and when the element ratio is set within the following range, the light sensitivity of the layer region (2b) itself is reduced. Can be significantly increased.

Composition formula: [Si _1-x C _x ] _1-y A _y (where A is hydrogen or halogen) 0 <x <0.5, preferably 0.01 <x <0.4 0.2 <y <0.5, preferably 0.25 <y <0.45 When the value x is 0.5 or more, the photoconductivity is significantly reduced, and the photocarrier excitation function is reduced.

When the y value is 0.2 or less, the dark conductivity tends to increase, and the photoconductivity tends to decrease, so that the desired photoconductivity cannot be obtained, and the y value is 0.5 or more. In the case of (1), the internal stress of the a-SiC layer increases, the adhesion to the substrate deteriorates, and the a-SiC layer easily peels off.

The second layer region (2b) contains a hydrogen (H) element and a halogen element for terminating dangling bonds. Of these elements, the H element is easily taken into the terminating portion. This is desirable in that the local level density in the band gap is reduced.

The thickness of the second layer region (2b) is 0.05 to 5 μm, preferably
It may be set within the range of 0.1 to 3 μm, and within this range, high photosensitivity is obtained and the residual potential is reduced.

The other first layer region (2a) contains at least one element of oxygen or nitrogen (hereinafter abbreviated as oxygen / nitrogen element) in an amount of 0.01 to 30 atomic%, preferably 0.1 to 10 atomic%. As a result, the carrier on the substrate side is shifted to the second layer region (2
b) can be prevented from flowing into
The surface potential increases.

The content (atomic%) of the oxygen and nitrogen elements corresponds to the Z value of the composition formula (SiC) _1-z (ON) _z .

As described above, the first layer region (2a) is represented by the content of the oxygen / nitrogen element. If the content becomes non-uniform in the layer thickness direction, it is represented by the average content. .

When the oxygen and nitrogen elements are less than 0.01 atomic%, the function of preventing carrier injection from the substrate becomes small, and therefore the surface potential does not increase. Into the cell, causing an increase in the residual potential.

Further, it is desirable that the first layer region (2a) is set more specifically by the thickness thereof together with the oxygen / nitrogen element content.

That is, the thickness of the first layer region (2a) is preferably set in the range of 100 to 10,000 °, preferably 500 to 5000 °, and within this range, the surface potential can be increased and the residual potential can be increased. This is advantageous in that it can be suppressed.

Further, it is desirable to set the SiC composition ratio of the first layer region (2a) together with the oxygen / nitrogen element content and thickness as follows.

That is, when represented by the composition formula Si _1-x C _x , 0.1 <x <0.5
The surface potential can be increased, and the adhesion to the substrate can be increased within this range.

Further, when setting the C element ratio as described above, the ratio may be set to be larger than that of the second layer region (2b), which can increase the surface potential and increase the adhesion to the substrate. This is advantageous.

Further, the electrophotographic photoreceptor of the present invention can be set to a negative charge type or a positive charge type by selecting the material of the organic photo semiconductor layer (3). That is, in the case of a negatively charged electrophotographic photoreceptor, an electron donating compound is selected for the organic photoconductor layer (3), while in the case of a positively charged electrophotographic photoreceptor, an electron is supplied to the organic photoconductor layer (3). An inhalable compound is selected.

Examples of the electron donating compound include, as high molecular weight compounds, poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, pyrene-formaldehyde polycondensate, and oxadiazole, oxazole as low molecular weight compounds. There are pyrazoline, triphenylmethane, hydrazone, triarylamine, N-phenylcarbazole, stilbene, etc., and these low molecular substances are polycarbonate, polyester, methacrylic resin, polyamide, acrylic epoxy, polyethylene, phenol, polyurethane, butyral resin, It is used by being dispersed in a binder such as polyvinyl acetate or urea resin.

Examples of the electron withdrawing compound include 2.4.7-trinitrofluorenone.

The substrate (1) includes a metal conductor such as copper, brass, SUS, or Al, or an insulator such as glass or ceramic coated with a conductor thin film. In addition, it is advantageous in terms of adhesion to the a-SiC layer.

Thus, according to the present invention, the a-SiC photoconductive layer
By forming a layer region containing a nitrogen element within a predetermined range, the surface potential is improved, and the Si layer of the photoconductive layer is further improved.
The photosensitivity was improved by setting the C element ratio within a predetermined range.

Further, as shown in FIG. 12, the electrophotographic photoreceptor of the present invention contains a large amount of the C element as the third layer region between the second layer region (2b) and the organic optical semiconductor layer (3). A layer region may be formed. When the carbon (C) element-rich layer region (2c) is formed, the dark conductivity between the second layer region (2b) and the organic optical semiconductor layer (3) is reduced. The difference becomes remarkably small, so that carriers are not trapped at the interface between the two layers (2b) and (3).

That is, the dark conductivity of the second layer region (2b) is about 10 ^-11 to 10
^-13 (Ω · cm) ^-1 and the other organic optical semiconductor layer (3)
Has a dark conductivity of about 10 ⁻¹⁴ to 10 ⁻¹⁵ (Ω · cm) ⁻¹ , so that the carriers generated in the second layer region (2b) have a large difference in dark conductivity, so that the organic optical semiconductor layer ( It does not flow smoothly to 3). Therefore, the present inventors have formed the C element-rich layer region (2c), thereby reducing the dark conductivity of the layer region (2c) and the dark conductivity between the two layers (2b) and (3). It has been found that the difference in rate can be reduced, and as a result, both characteristics of photosensitivity and residual potential are improved.

Such a C element high content layer region (2c) is as follows:
It is represented by the element content ratio and thickness.

The C element content ratio may be set in the range of 0.2 <x <0.5, preferably 0.3 <x <0.5, as the x value of Si _1-x C _x ,
If it is less than 0.2, the difference in the dark conductivity between the two layers (2b) and (3) cannot be reduced as required, thereby failing to improve the respective characteristics of photosensitivity and residual potential. When the value of x is 0.5 or more, carriers are easily trapped in the a-SiC photoconductive layer, and the photosensitivity is deteriorated.

Further, the thickness is preferably set in the range of 10 to 2000 mm, preferably 500 to 1000 mm.If the thickness is less than 10 mm, the characteristics of the photosensitivity and the residual potential cannot be improved.
If it exceeds 00 °, the residual potential tends to increase.

The C element content of each of the second layer region (2b) and the C element high-content layer region (2c) may be changed in the layer thickness direction. For example, there are examples shown in FIGS. 6 to 11, in which the horizontal axis is the layer thickness direction, and a
Is the interface between the first layer region (2a) and the second layer region (2b), b
Represents an interface between the second layer region (2b) and the C element-rich layer region (2c), and C represents an interface between the C element-rich layer region (2c) and the organic optical semiconductor layer (3). The vertical axis represents the C element content.

In addition, the second layer region (2b) or the C element-rich layer region (2
When the C element content is changed in the layer thickness direction inside c), the C element content ratio (x value) corresponds to the average C element content ratio in the entire layer region (2b) (2c). I do.

Furthermore, in the electrophotographic photoreceptor of the present invention, the second
The layer region (2b) may contain a Group IIIa element in an amount of 1 to 300 ppm, whereby the mobility of holes is increased and an electrophotographic photosensitive member suitable for negative charging is obtained.

When the group IIIa element is contained in the second layer region (2b), the doping distribution may be uniform or non-uniform in the layer thickness direction. In the case of non-uniform doping, a part of the layer region (2b) may include a layer region containing no Group IIIa element. The average content of the Group IIIa element in the entire a-SiC layer including both the a-SiC layer region containing no group element must be 1 to 300 ppm.

This IIIa group element includes B, Al, Ga, In, etc., but B has excellent covalent properties and can change semiconductor characteristics sensitively, and furthermore, excellent charging ability and photosensitivity are obtained. This is desirable.

 Next, a method for producing the electrophotographic photoreceptor of the present invention will be described.

For forming the a-SiC layer, there are a thin film forming method such as a glow discharge decomposition method, an ion plating method, a reactive sputtering method, a vacuum evaporation method, and a CVD method.

When glow discharge decomposition is used, the gas containing Si element and C
Element-containing gases are combined, and this mixed gas is plasma-decomposed to form a film. The Si element-containing gas includes SiH ₄ , Si ₂ H ₆ , S
_{i 3 H 8, SiF 4,} SiCl 4, SiHCl 3 has etc., _{also, CH 4, C 2 H 4} , C 2 H 2, C 3 H 8 have so the C element-containing gas, especially, C ₂ H ₂ is desirable in that high-speed film forming properties can be obtained.

The glow discharge decomposition apparatus used in this embodiment will be described with reference to FIG.

In the figure, the first tank (4), the second tank (5), the third tank (6), and the fourth tank (7) are respectively SiH ₄ , C ₂ H ₂ ,
H ₂ and NO is sealed, first these gases corresponding respectively
The gas is released by opening the regulating valve (8), the second regulating valve (9), the third regulating valve (10) and the fourth regulating valve (11), and the flow rate of the released gas is controlled by the mass flow controller (12) ( 13) Controlled by (14) and (15). And
The respective gases of SiH ₄ , C ₂ H ₂ and H ₂ are mixed to form the first main pipe (16)
And the NO gas is sent to the second main pipe (17). still,
(18) and (19) are stop valves.

Gas flowing through the first main pipe (16) and the second main pipe (17) flows into the reaction tube (20), and a capacitively coupled discharge electrode (21) is installed inside the reaction tube (20). Also,
The cylindrical film-forming substrate (22) is placed on the substrate support (23), and the substrate support (23) is driven to rotate by the motor (24), and the substrate (22) is rotated accordingly. You. A high frequency power of 50 W to 3 kW and a frequency of 1 to 50 MHz is applied to the electrode (21), and the substrate (22) is heated to about 200 to 400 ° C., preferably about 200 to 350 ° C. by a suitable heating means. Heated to temperature. The reaction tube (20) is connected to a rotary pump (25) and a diffusion pump (26).
(0.1-2.0 Torr) is maintained.

When the a-SiC layer is formed on the substrate (22) using the glow discharge decomposition device having such a configuration, the first regulating valve (8), the second regulating valve (9), and the third regulating valve (10) are used. ) And fourth
Open the control valve (11) to release each gas of SiH ₄ , C ₂ H ₂ , H ₂ , NO, and determine the release amount by mass flow controller (12)
(13) Controlled by (14) and (15), the respective gases are mixed and flow into the reaction tube (20) via the first main pipe (16) and the second main pipe (17). And the vacuum state inside the reaction tube,
When the substrate temperature and the high-frequency power for electrode application are set to predetermined conditions, glow discharge occurs, and an a-SiC film containing N element and 0 element is formed on the substrate at high speed with the decomposition of the gas.

When the a-SiC layer is formed by the thin film forming method as described above, an organic optical semiconductor layer is formed next.

The organic optical semiconductor layer is formed by a dip coating method or a coating method. The former is immersed in a coating liquid in which a photosensitive material is dispersed in a solvent, then pulled up at a constant speed, and is naturally dried and heated. Aging (about 150 ° C, about 1 hour)
According to the latter coating method, a photosensitive material dispersed in a solvent is applied using a coater (coating machine), and then hot-air drying is performed.

〔Example〕

 Next, examples of the present invention will be described.

(Example 1) using a glow discharge decomposition apparatus of FIG. 2, a SiH ₄ gas 20
At a flow rate of 0 sccm, H ₂ gas was flowed at a flow rate of 270 sccm and C ₂
The flow rate of the H ₂ gas was changed, the gas pressure was set to 0.6 Torr, the high frequency power was set to 150 W, the substrate temperature was set to 250 ° C., and an a-SiC film (thickness: about 1 μm) was formed by glow discharge.

Thus, the carbon content ratio of the a-SiC film was changed, and the amount of carbon in the film was measured by the XMA method.
Further, when the photoconductivity and the dark conductivity were measured, the results as shown in FIG. 3 were obtained. In FIG. 3, the horizontal axis is the carbon content ratio, that is, the x value of Si _1-x C _x . , The vertical axis represents the conductivity, and the circle represents the emission wavelength of 55.
It is a plot of the photoconductivity with respect to light of 0 nm (light quantity 50 μW / cm ² ).
Are the respective characteristic curves.

Further, the hydrogen content of each of the a-SiC films was determined by infrared absorption measurement, and the results shown in FIG. 4 were obtained.

In Figure 4, the horizontal axis is the x value of the Si _1-x C _x, vertical axis hydrogen content, is namely [Si _1-x C _x] y value of _1-y H _y, ○ mark Si
It is a plot of the amount of hydrogen bonded to the atom, the mark ● is a plot of the amount of hydrogen bonded to the C atom, and c and d are the respective characteristic curves.

As is clear from FIG. 4, it can be seen that the a-SiC films of this example all have y values in the range of 0.3 to 0.4.

As is clear from FIG. 3, the carbon content ratio x
Is within the range of 0 <x <0.5, a high photoconductivity is obtained, and the ratio of the photoconductivity to the dark conductivity is remarkably increased, so that excellent photosensitivity is obtained.

(Example 2) Next, in this example, SiH ₄ gas was supplied at a flow rate of 200 sccm and C
₂ H ₂ gas is introduced at a flow rate of 20 sccm, H ₂ gas is introduced at a flow rate of 0 to 1000 sccm, and high frequency power is 50 to 300 W and gas pressure is increased.
The pressure was set to 0.3 to 1.2 Torr, and an a-SiC film (thickness: about 1 μm) was formed by glow discharge.

Thus, various a-SiC films were formed in which the carbon content ratio x was set to 0.3 and the hydrogen content y was changed, and the photoconductivity and dark conductivity of each film were measured. The result as shown in the figure was obtained.

In FIG. 5, the horizontal axis is the hydrogen content, that is, [Si _1-x C _x ] _1-y
The y value of H _y , the vertical axis represents the conductivity, the mark 印 is a plot of photoconductivity with respect to light having an emission wavelength of 550 nm (light quantity 50 μW / cm ² ), and the mark ● is a plot of dark conductivity. ,Also,
e and f are respective characteristic curves.

As is clear from FIG. 5, when the y value exceeds 0.2,
It can be seen that high photoconductivity as well as low dark conductivity are obtained.

(Example 3) Next, the present inventors sequentially laminated a first layer region and a second layer region on an aluminum substrate under the film forming conditions shown in Table 1, and then dispersed a hydrazone-based compound in polycarbonate. An organic photo-semiconductor layer (thickness: about 15 μm) was formed to obtain an electrophotographic photosensitive member.

The first layer region (2a) and the second
For each layer region (2b), the respective carbon contents were measured by the XMA method, and the respective contents of oxygen and nitrogen in the first layer region (2a) were measured by a secondary ion mass spectrometer.
When the total amount was determined, the results as shown in Table 2 were obtained.

The properties of the thus obtained electrophotographic photosensitive member were measured by an electrophotographic property measuring apparatus. As a result, excellent photosensitivity and surface potential were obtained, and a low residual potential was obtained.

(Example 4) In manufacturing the electrophotographic photoreceptor of the above (Example 3), NO gas was not introduced at the time of forming the first layer region, and the other film formation conditions were set to be exactly the same. An electrophotographic photoreceptor provided with a first layer region containing no.

When the surface potential of this electrophotographic photosensitive member was measured,
It was reduced by about 20% as compared with the electrophotographic photosensitive member of (Example 3).

(Example 5) In manufacturing the electrophotographic photoreceptor of the above (Example 3), B ₂ H ₆ diluted with hydrogen gas was used when forming the second layer region (2b).
Gas (B ₂ H ₆ concentration 40 ppm) was released at a flow rate of 90 sccm, and setting the other manufacturing conditions to the same, thereby, and the B element in the second layer region about 15ppm is contained.

When the characteristics of the electrophotographic photoreceptor thus obtained were evaluated, the photosensitivity was about 15 times that of the electrophotographic photoreceptor of (Example 3).
% Increased.

(Example 6) In producing the electrophotographic photoreceptor of (Example 3), the present inventors changed the flow rate of NO gas, whereby the N.O. of the first layer region was changed as shown in Table 3. Eight types of electrophotographic photoconductors (photoconductors A to H) having different element contents were manufactured.

When the photosensitivity, surface potential, and residual potential of these electrophotographic photosensitive members were measured, the results shown in Table 3 were obtained.

In the same table, the light sensitivity is classified into three stages of ◎, △ and △ by relative evaluation, ◎ indicates the case where the best light sensitivity was obtained, and ○ indicates a somewhat superior light sensitivity. Is obtained, and the symbol △ indicates that the light sensitivity is slightly inferior to the others.

The characteristic evaluation of the surface potential was also classified into three stages of ◎, ○ and Δ, ◎ indicates the case where the highest surface potential was obtained, and ○ indicates the case where a somewhat higher potential was obtained. And △ indicate cases where no higher surface potential was observed than the others.

In addition, the residual potential was also relatively evaluated in three stages, and ◎ indicates the case where the residual potential was the smallest, and
The mark indicates a case where a rise in the residual potential was slightly recognized, and the mark Δ indicates a case where a rise in the residual potential was recognized as compared with the others, which had a practical problem.

As is clear from Table 1, the photoconductors B to G exhibited excellent photosensitivity, and had high surface potential and little increase in residual potential.

However, it can be seen that the photoreceptor A is not improved in the photosensitivity and the surface potential, and that the photoreceptor H is deteriorated in both the photosensitivity and the residual potential.

(Example 7) Further, in producing the electrophotographic photoreceptor of (Example 3), the present inventors used N ₂ gas or O ₂ gas instead of NO gas, and N ₂ gas contained in the first layer region. The amount of element or O element
It was set to 4.0 atomic%, and it was confirmed that the electrophotographic photoreceptor thus obtained also had excellent photosensitivity, high surface potential and low residual potential. Then, with respect to such an electrophotographic photoreceptor, the N
Element or O element content is 0.05, 0.3, 1.2, 7.
When the content is 0,15.0,25.0 at%, both the light sensitivity and the surface potential are improved, and when the content of the N element or the O element is 0.005 at%, the light sensitivity and the surface potential are improved. Was not observed, and it was confirmed that when the content of the N element or the O element was 40.0 atomic%, the photosensitivity was reduced and the residual potential was increased.

Thus, the electrophotographic photoreceptor of the present invention is improved in both characteristics of photosensitivity and surface potential. According to experiments by the present inventors, oxygen and nitrogen elements are contained in the first layer region.
It has been found that when the content is 0.01 to 30 atomic%, the adhesion of the a-SiC layer to the substrate is significantly increased.

(Example 8) In producing the electrophotographic photoreceptor of the above (Example 3), C was deposited on the second layer region under the film forming conditions shown in Table 4.
An element-rich layer region (third layer region) was laminated, and the other was formed with an organic optical semiconductor layer as shown in (Example 3) to obtain an electrophotographic photosensitive member.

When the amount of carbon was measured for the third layer region, the X value of Si _1-x C _x was 0.4, and the dark conductivity was 2.5 × 10
^-14 . When the characteristics of the electrophotographic photosensitive member were evaluated, the photosensitivity was increased by about 5% and the residual potential was decreased by about 10%, as compared with the electrophotographic photosensitive member of (Example 3).
Further, the surface potential increased by about 5%.

〔The invention's effect〕

As described above, according to the electrophotographic photoreceptor of the present invention, a-
By forming a layer region containing oxygen and nitrogen elements within a predetermined range inside the SiC photoconductive layer, excellent photosensitivity can be obtained, surface potential can be increased, and increase in residual potential can be suppressed. did it.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the layer structure of the electrophotographic photoreceptor of the present invention, FIG. 2 is a schematic view of a glow discharge decomposition apparatus used in Examples, and FIG. 3 is a line showing the relationship between the carbon content ratio and the conductivity. FIG. 4 is a diagram showing the relationship between the carbon content ratio and the hydrogen content, FIG. 5 is a diagram showing the relationship between the hydrogen content and the conductivity, and FIG. 6, FIG. 8, FIG. 9,
FIG. 10 and FIG. 11 are diagrams showing the carbon content in the thickness direction of the amorphous silicon carbide photoconductive layer. FIG. 12 is a sectional view showing another layer constitution of the electrophotographic photosensitive member of the present invention. DESCRIPTION OF SYMBOLS 1 ... Conductive substrate 2 ... Amorphous silicon carbide photoconductive layer 2a ... 1st layer area 2b ... 2nd layer area 3 ... Organic optical semiconductor layer

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-275844 (JP, A) JP-A-60-67950 (JP, A) JP-A-59-224847 (JP, A)

Claims (1)

(57) [Claims] 1. An electrophotographic photoreceptor having an amorphous silicon carbide photoconductive layer and an organic optical semiconductor layer sequentially laminated on a conductive substrate, wherein the amorphous silicon carbide photoconductive layer has the following first layer region, Layer area and third
An electrophotographic photoreceptor, wherein the following layer regions are sequentially formed. First layer region: At least one element of oxygen or nitrogen
Second layer region containing 0.01 to 30 atomic%: when represented by a composition formula [Si _1-x C _X ] _1-y A _y (A: hydrogen or halogen), x and y are each 0 <x <
0.5, 0.2 <y <0.5 Third layer area: 0.2 <x <0.5, thickness: 10 to 2000 mm